METHOD AND DEVICE FOR RECYCLING ACIDIC ETCHING WASTE SOLUTION THROUGH PROGRESSIVE ELECTROLYSIS

TECHNICAL FIELD

The present disclosure belongs to the technical field of recovery and recycling of etching waste solutions from printed circuit board (PCB) production, and specifically relates to a method and device for recycling an acidic etching waste solution through progressive electrolysis.

BACKGROUND

In the current production of PCBs, the etching by spraying with an acidic etching solution is an important procedure. In the etching procedure, the unnecessary copper on a copper clad laminate is removed through chemical corrosion with an acidic etching solution to form a desired circuit pattern. The current acidic etching solution mainly includes cupric chloride and/or ferric chloride as a copper-etching agent. The acidic etching solutions available in the industry include cupric chloride and hydrochloric acid as major components, and may also include ferric chloride and/or ammonium chloride and/or sodium chloride.

During an etching process, metallic copper is corroded and a copper-etching agent is reduced to lose an etching ability. Specifically, cupric chloride is reduced into cuprous chloride and/or ferric chloride is reduced into ferrous chloride. In order to maintain the etching production, an oxidant, hydrochloric acid, and/or ferric chloride and an optional additive need to be supplemented to an etching solution, such that cuprous chloride and ferrous chloride can be oxidatively regenerated into cupric chloride and ferric chloride respectively to further participate in the etching. As a result, a volume of the etching solution continuously increases and the etching solution overflows out of an etching tank. An additive in an etching solution is often added to improve the etching performance. There is a class of additives to increase a common-ion effect of chloride ions, and common ones are ferric chloride, ferrous chloride, ammonium chloride, sodium chloride, and sodium chlorate. Ferric chloride can serve as both a copper-etching agent and an additive that can increase a common-ion effect. An acidic etching solution including ferric chloride as a copper-etching agent can effectively reduce a puddle effect during etching. Thus, in the industry, an iron-containing acidic etching solution is preferred in the pursuit of high product quality and high efficiency.

In the industry, an etching solution overflowing out of an etching tank is called an etching waste solution, an etching solution in an etching tank is called a working etching solution, and a solution including hydrochloric acid and/or an oxidant and/or an additive supplemented during etching is collectively referred to as an etching replenishment solution. Most acidic etching waste solutions have a copper ion concentration of 70 g/L to 200 g/L. A total iron content of ferric chloride and ferrous chloride in an iron-containing acidic etching waste solution can be as high as 200 g/L.

PCB manufacturers each produce a large amount of an acidic etching waste solution in an etching procedure every day. In the prior art, there is a solution of extracting copper from an acidic etching waste solution through direct electrolysis in an electrolytic cell. In this solution, an electrolytic cell separated into an anode chamber and a cathode chamber is adopted, and an acidic etching waste solution is added to the anode chamber to undergo direct electrolysis. However, in this solution, an etching waste solution undergoes a large chloride ion loss, and a large amount of an oxidant needs to be supplemented to a regenerated working etching solution to maintain an etching operation, which leads to the increase of an etching waste solution.

A solution of adding an acidic etching waste solution to a cathode chamber for electrolysis can effectively reduce or even avoid the addition of an oxidant to a regenerated working etching solution during etching, which solves the problem that an etching waste solution increases. However, because there is still a large amount of a copper-etching agent in an acidic etching waste solution, the acidic etching waste solution is very corrosive to metallic copper. An iron-containing acidic etching waste solution is particularly corrosive to metallic copper. Therefore, when an acidic etching waste solution is added to the cathode chamber, a copper-etching agent introduced will etch copper electroprecipitated at a cathode in turn. As a result, a lot of electrical energy is consumed, and a copper layer electroprecipitated will become loose and rough due to corrosion such that, when taken from the cathode, the copper layer is easily broken and falls into the electrolytic cell to affect the production. In the industry, in order to overcome the shortcomings of the above-mentioned electrolytic recovery process, a copper electroplating brightener is added to a cathode electrolyte to make an electroprecipitated metallic copper layer relatively smooth and dense. However, in this method, new impurities are actually introduced into an etching waste solution, such that the etching waste solution cannot be 100% recycled in the electrolytic recovery process.

Therefore, PCB manufacturers in the industry are looking forward to a novel process that can overcome the shortcomings of the current electrolysis process for recycling acidic etching waste solutions.

SUMMARY

A first objective of the present disclosure is to provide a method for recycling an acidic etching waste solution from PCB production through progressive electrolysis. With the method, while allowing the safe recovery of copper from an acidic etching waste solution, PCB manufacturers can reduce the corrosion to metallic copper electroprecipitated at a cathode, avoid the introduction of new impurities, and reduce the electrolysis energy consumption during an electrolytic copper recovery process. The method is conducive to the preparation of a regenerated etching replenishment solution using an etching waste solution with copper recovered to improve a recycling rate of the etching waste solution. Thus, the method can not only greatly reduce a production cost, but also reduce the environmental pollution.

A second objective of the present disclosure is to provide a device for recycling an acidic etching waste solution from PCB production through progressive electrolysis.

The first objective of the present disclosure can be allowed by adopting the following technical solutions:

A method for recycling an acidic etching waste solution from PCB production through progressive electrolysis is provided, mainly including the following steps:

- step 1, introducing at least one electrolytic cell A, where the electrolytic cell A is divided with an electrolytic cell separator into an anode chamber and a cathode chamber; during an electrolysis operation, the anode chamber and the cathode chamber of the electrolytic cell A are provided with an electrolytic anode and an electrolytic cathode respectively to allow electrolysis for an anode electrolyte and a cathode electrolyte of the electrolytic cell A respectively; and the cathode electrolyte of the electrolytic cell A comprises the acidic etching waste solution;
- step 2, introducing at least one electrolytic cell B to conduct the progressive electrolysis for copper recovery, where the electrolytic cell B is divided into an anode chamber and a cathode chamber; during an electrolysis operation, the anode chamber and the cathode chamber of the electrolytic cell B are provided with an electrolytic anode and an electrolytic cathode respectively to allow electrolysis for an anode electrolyte and a cathode electrolyte of the electrolytic cell B respectively, such that an electrochemical reaction of reducing a copper ion into metallic copper occurs at the electrolytic cathode of the electrolytic cell B; and the cathode electrolyte of the electrolytic cell B comprises a cathode electrolyte undergoing an electrolytic treatment from the electrolytic cell A or a mixed solution of the cathode electrolyte undergoing the electrolytic treatment from the electrolytic cell A with the acidic etching waste solution; and
- step 3, when an amount of metallic copper deposited at the electrolytic cathode of the electrolytic cell B due to the electrochemical reaction reaches a preset target electroprecipitated amount, taking the electrolytic cathode of the electrolytic cell B out from the electrolytic cell B.

The anode electrolyte of the electrolytic cell A comprises at least one selected from the group consisting of a working etching solution, an etching waste solution, and a cathode electrolyte undergoing an electrolytic treatment from the electrolytic cell B. The anode electrolyte of the electrolytic cell B comprises at least one selected from the group consisting of a cathode electrolyte undergoing an electrolytic treatment from the electrolytic cell B, a working etching solution, and an etching waste solution.

In the electrolysis operation process of the present disclosure, a chlorine gas is generated and/or a low-valence metal ion in an electrolyte is electrochemically oxidized into a high-valence metal ion at the electrolytic anode of the electrolytic cell A and the electrolytic anode of the electrolytic cell B. A reduction reaction of a metal ion mainly occurs at the electrolytic cathode of the electrolytic cell A, such that a concentration of a copper-etching agent in the cathode electrolyte of the electrolytic cell A decreases. An electrochemical reaction of reducing a copper ion into metallic copper occurs at the electrolytic cathode of the electrolytic cell B. In order to maintain the continuous proceed of electrolysis, a corresponding electrolyte solution is continuously supplemented to each electrode chamber during an operation.

A cathode electrolyte undergoing an electrolytic treatment from the electrolytic cell B can be oxidized in the anode chamber of the electrolytic cell A and/or the anode chamber of the electrolytic cell B and/or can be oxidized by a chlorine gas produced due to electrolysis of an electrolytic cell, and then can be recycled as a regenerated etching replenishment solution directly or after composition adjustment. The above-mentioned composition adjustment for the preparation of a regenerated etching replenishment solution can alternatively be done in advance to at least one selected from the group consisting of the anode electrolyte and the cathode electrolyte of the electrolytic cell A and the anode electrolyte and the cathode electrolyte of the electrolytic cell B, which can also allow the objective of the present disclosure.

The electrolytic cell separator of the electrolytic cell A can effectively make the anode electrolyte undergo an oxidation reaction and make the cathode electrolyte undergo a reduction reaction of converting a high-valence metal ion into a low-valence metal ion. Specifically, the electrolytic cell separator can be at least one selected from the group consisting of an anion exchange membrane, a bipolar membrane, and a reverse osmosis membrane.

The electrolytic cell B can be an electrolytic cell divided into an anode chamber and a cathode chamber with an arbitrary structural form. When the anode chamber and the cathode chamber of the electrolytic cell B are separated by an electrolytic cell separator, the electrolytic cell separator of the electrolytic cell B can be at least one selected from the group consisting of an anion exchange membrane, a bipolar membrane, and a reverse osmosis membrane.

The following improvement can be conducted in the present disclosure: An oxidation-reduction potential (ORP) of the cathode electrolyte in the cathode chamber of the electrolytic cell A is detected to monitor an electrolysis process and a concentration of a high-valence metal ion in a solution, such that, in the cathode electrolyte of the electrolytic cell A, a reaction of decreasing a concentration of a copper-etching agent mainly occurs, and an electrochemical reaction of copper electroprecipitation does not occur or occurs less.

The following improvement can be further conducted in the present disclosure: According to an ORP value of the cathode electrolyte in the cathode chamber of the electrolytic cell A and process requirements, an output current of an electrolytic power supply for the electrolytic cell A is adjusted or the electrolytic power supply for the electrolytic cell A is powered on/off, and/or a solution including the acidic etching waste solution is supplemented to the cathode chamber of the electrolytic cell A to maintain a concentration of a copper-etching agent in the cathode electrolyte of the electrolytic cell A, such that only a small amount of metallic copper or even no metallic copper is electroprecipitated on the electrolytic cathode of the electrolytic cell A, and an electrochemical reduction reaction mainly occurs at the electrolytic cathode of the electrolytic cell A to reduce a concentration of the copper-etching agent CuCl₂or CuCl₂+FeCl₃in the cathode electrolyte of the electrolytic cell A or even eliminate the copper-etching ability of the cathode electrolyte.

Preferably, in an electrolysis process, an ORP value of the cathode electrolyte of the electrolytic cell A is controlled at 200 mV to 580 mV, that is, an ORP value range is controlled at 200 mV to 580 mV by externally adding an etching waste solution. More preferably, the ORP value of the cathode electrolyte of the electrolytic cell A is controlled at 300 mV to 499 mV. In order to allow a prominent progressive copper recovery effect with copper-etching agent removal, the ORP value of the cathode electrolyte of the electrolytic cell A is controlled at 350 mV to 470 mV.

The following improvement can be conducted in the present disclosure: At least one electrolytic cell C is additionally provided after the electrolytic cell B; the electrolytic cell C is divided into an anode chamber and a cathode chamber; during an electrolysis operation, the anode chamber and the cathode chamber of the electrolytic cell C are provided with an electrolytic anode and an electrolytic cathode respectively to allow electrolysis for an anode electrolyte and a cathode electrolyte of the electrolytic cell C respectively; the anode electrolyte of the electrolytic cell C comprises at least one selected from the group consisting of an acidic working etching solution, a cathode electrolyte undergoing an electrolytic treatment from the electrolytic cell B, and a cathode electrolyte undergoing an electrolytic treatment from the electrolytic cell C, or on this basis, the anode electrolyte of the electrolytic cell C further comprises an etching waste solution; and the cathode electrolyte of the electrolytic cell C comprises a cathode electrolyte undergoing an electrolytic treatment from the electrolytic cell B, or on this basis, the cathode electrolyte of the electrolytic cell C further comprises the cathode electrolyte of the electrolytic cell A and/or an etching waste solution. In this case, the anode electrolyte of the electrolytic cell A comprises at least one selected from the group consisting of a cathode electrolyte undergoing an electrolytic treatment from the electrolytic cell B, a cathode electrolyte undergoing an electrolytic treatment from the electrolytic cell C, a working etching solution, and an etching waste solution, and the anode electrolyte of the electrolytic cell B comprises at least one selected from the group consisting of a cathode electrolyte undergoing an electrolytic treatment from the electrolytic cell B, a cathode electrolyte undergoing an electrolytic treatment from the electrolytic cell C, a working etching solution, and an etching waste solution.

In the present disclosure, during an electrolysis operation of the electrolytic cell C, an electrochemical reaction of reducing a copper ion into metallic copper occurs at the electrolytic cathode of the electrolytic cell C, allowing further copper recovery in the progressive electrolysis. A cathode electrolyte undergoing an electrolytic treatment from the electrolytic cell B and/or a cathode electrolyte undergoing an electrolytic treatment from the electrolytic cell C can be oxidized in one or more selected from the group consisting of the anode chamber of the electrolytic cell A, the anode chamber of the electrolytic cell B, and the anode chamber of the electrolytic cell C and/or can be oxidized by a chlorine gas, and then can be recycled as a regenerated etching replenishment solution directly or after composition adjustment. The above-mentioned composition adjustment for the preparation of a regenerated etching replenishment solution can alternatively be done in advance to at least one selected from the group consisting of the anode electrolyte and the cathode electrolyte of the electrolytic cell A, the anode electrolyte and the cathode electrolyte of the electrolytic cell B, and the anode electrolyte and the cathode electrolyte of the electrolytic cell C, which can also allow the objective of the present disclosure.

The electrolytic cell C can be an electrolytic cell divided into an anode chamber and a cathode chamber with an arbitrary structural form. When the electrolytic cell C is divided by an electrolytic cell separator, the electrolytic cell separator of the electrolytic cell C can be at least one selected from the group consisting of an anion exchange membrane, a bipolar membrane, and a reverse osmosis membrane.

In an electrolysis process of the whole progressive electrolysis device of the present disclosure, because the anode electrolyte of the electrolytic cell A, the anode electrolyte of the electrolytic cell B, and the anode electrolyte of the electrolytic cell C all contain chloride ions, an electrochemical reaction of oxidizing chloride ions into a chlorine gas occurs at all of the electrolytic anode of the electrolytic cell A, the electrolytic anode of the electrolytic cell B, and the electrolytic anode of the electrolytic cell C. The chlorine gas generated has strong oxidizing ability, and can oxidize low-valence metal ions in the anode electrolyte of the electrolytic cell A, the anode electrolyte of the electrolytic cell B, and the anode electrolyte of the electrolytic cell C to allow the oxidative regeneration of a copper-etching agent. In addition, an electrochemical reduction reaction occurs at the electrolytic cathode of the electrolytic cell A, such that a copper-etching agent in the cathode electrolyte of the electrolytic cell A is reduced into cuprous chloride and/or ferrous chloride to lose a copper-etching ability. Subsequently, a cathode electrolyte losing a copper-etching ability or having a reduced copper-etching ability from the electrolytic cell A is added to the cathode chamber of the electrolytic cell B to serve as a part or all of the cathode electrolyte of the electrolytic cell B for electrolysis, such that metallic copper is electroprecipitated at the electrolytic cathode of the electrolytic cell B. When the electrolytic cell C is additionally provided, a cathode electrolyte undergoing electrolysis from the electrolytic cell B is added to the cathode chamber of the electrolytic cell C to serve as a part or all of the cathode electrolyte of the electrolytic cell C, so as to allow the subsequent progressive electrolysis for copper recovery.

In the present disclosure, due to the use of progressive electrolysis for copper recovery, metallic copper electroprecipitated at the electrolytic cathode of the electrolytic cell B and the electrolytic cathode of the electrolytic cell C is generated in an environment with a low copper-etching agent concentration, which can effectively reduce a chemical reaction of etching of a cathode electrolyte to electroprecipitated metallic copper during an electrolytic recovery process and thus makes an electroprecipitated metallic copper layer relatively smooth and dense. The process of the present disclosure overcomes the defect that a copper layer electroprecipitated in the existing electrolytic recovery process for an acidic etching waste solution is loose, and is conducive to allowing the 100% recovery and recycling of an etching waste solution.

The electrolytic anode in the present disclosure is a material with a stable shape and stable properties in an electrolyte. Specifically, the material can be at least one selected from the group consisting of a material with a surface made of gold and/or platinum and/or an alloy including at least one of the above metals, a titanium-based coated insoluble anode, and electrically-conductive graphite, and preferably a titanium-based coated insoluble anode. A material of the electrolytic cathode of the electrolytic cell A is gold and/or platinum and/or titanium and/or an alloy including at least one of the above metals and/or electrically-conductive graphite, and preferably titanium. Materials of the electrolytic cathode of the electrolytic cell B and the electrolytic cathode of the electrolytic cell C can each be gold and/or platinum and/or titanium and/or copper and/or an alloy including at least one of the above metals and/or stainless steel, and preferably metallic copper.

Main chemical reactions occurring in the electrode chambers of the electrolytic cell A, the electrolytic cell B, and the electrolytic cell C are as follows:

(1) Each Anode Chamber

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- 2CuCl+Cl₂→2CuCl₂; and
- 2FeCl₂+Cl₂→2FeCl₃(when there are iron ions in an etching solution).

(2) The Cathode Chamber of the Electrolytic Cell A

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(3) The Cathode Chamber of the Electrolytic Cell B and the Cathode Chamber of the Electrolytic Cell C

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The following improvement can be conducted in the present disclosure: Copper ion concentrations in the cathode electrolyte of the electrolytic cell B and the cathode electrolyte of the electrolytic cell C are not less than 5 g/L. The inventors have found through a plurality of experiments that, when a copper ion concentration of a cathode electrolyte is kept at no less than 5 g/L, a side reaction generating hydrogen can be avoided to a large extent.

The following improvement can be conducted in the present disclosure: A cathode electrolyte undergoing electrolysis from a terminal electrolytic cell B or a cathode electrolyte undergoing electrolysis from a terminal electrolytic cell C is subjected to oxidative regeneration and/or mixed with hydrochloric acid and an additive to prepare a regenerated etching replenishment solution according to process requirements, such that a concentration of a cuprous ion and/or a ferrous ion in the regenerated etching replenishment solution meets the minimum process requirement, and the etching performance of a working etching solution will not be affected when the regenerated etching replenishment solution is recycled in the etching production line.

The following improvement can be conducted in the present disclosure: An electrolytic cathode of at least one terminal electrolytic cell is sleeved with a cathode cloth filter bag to collect a copper sponge produced during a copper electroprecipitation process.

The following improvement can be conducted in the present disclosure: A parameter value of at least one electrolyte in the present disclosure is detected, and on the basis of data measured on site, an output current of an electrolytic power supply for the electrolytic cell A and/or an electrolytic power supply for the electrolytic cell B and/or an electrolytic power supply for the electrolytic cell C is controlled and/or the electrolytic power supply for the electrolytic cell A and/or the electrolytic power supply for the electrolytic cell B and/or the electrolytic power supply for the electrolytic cell C is/are powered on/off, and/or addition of each material is controlled. As a result, a chlorine gas generated in the anode chamber of the electrolytic cell A and/or the anode chamber of the electrolytic cell B and/or the anode chamber of the electrolytic cell C can be safely controlled and more completely utilized, and/or a reaction in a solution can be conducted according to process requirements. The parameter value includes, but is not limited to, any one or more selected from the group consisting of an acidity value, a specific gravity value, an ORP value, a photoelectric colorimetric value, a liquid level, a temperature, a flow rate, and a harmful gas concentration.

The following improvement can be conducted in the present disclosure: The anode electrolyte of the electrolytic cell A provided with the electrolytic cell separator and/or the anode electrolyte of the electrolytic cell B and/or the anode electrolyte of the electrolytic cell C is/are circularly mixed with a working etching solution on an etching production line, such that a copper-etching agent is supplemented to the working etching solution on the etching production line on line. That is, a low-valence copper ion or a low-valence iron ion in the working etching solution can undergo an electrochemical reaction at an electrolytic anode to produce a regenerated copper-etching agent of cupric chloride or ferric chloride to further participate in an etching reaction. In the present disclosure, an etching tank is connected with an anode chamber of at least one electrolytic cell through a pipeline, such that a working etching solution can circularly flow in each anode chamber, and at least one selected from the group consisting of an anode electrolyte undergoing electrolytic oxidation from the electrolytic cell A, the anode electrolyte of the electrolytic cell B, and the anode electrolyte of the electrolytic cell C can be directly returned to the etching tank to serve as a working etching solution with a regenerated copper-etching agent. This can effectively reduce or even eliminate the external addition of an oxidant to an etching system that is required in the traditional production process, and is conducive to reducing a production cost.

The following improvement can be further conducted in the present disclosure: A circular mixing and exchange tank for a working etching solution and an anode electrolyte is additionally provided between an etching production line and an anode chamber of at least one electrolytic cell, and an ORP value of a mixed solution is controlled to be higher than an ORP value of a working etching solution. Preferably, a circular mixing and exchange tank with a large total volume is adopted to efficiently utilize an electrolysis apparatus to prepare a large amount of a copper-etching agent in advance as a response to rapid addition during an etching reaction.

The following improvement can be further conducted in the present disclosure: The temperature adjustment is conducted for a mixed solution ready to enter an etching production line, such that the stability of an etching rate can be prevented from being affected by a temperature change of a working etching solution when the mixed solution is added to the etching production line.

The following improvement can be further conducted in the present disclosure: A working etching solution is subjected to degreasing and solid impurity removal before entering an electrolytic cell.

The following improvement can be further conducted in the present disclosure: When an etching waste solution contains iron ions, the etching waste solution is added to the cathode chamber of the electrolytic cell B and/or the electrolytic cell C according to process requirements. Preferably, a feeding port is close to an electrolytic cell separator. Based on a reaction of Fe³⁺ ions in an etching waste solution with a CuCl copper sludge, the insoluble cuprous chloride sludge is converted into cupric chloride, which can prevent the electrolytic cell separator from being blocked to affect an electrolysis operation.

The second objective of the present disclosure can be allowed by adopting the following technical solutions:

A device for recycling an acidic etching waste solution from PCB production through progressive electrolysis is provided, mainly including:

at least one electrolytic cell A and at least one electrolytic cell B, where the electrolytic cell A is divided with an electrolytic cell separator into an anode chamber and a cathode chamber; the electrolytic cell B is divided into an anode chamber and a cathode chamber; an ORP meter is provided in the cathode chamber of the electrolytic cell A; the cathode chamber of the electrolytic cell A is connected with the cathode chamber of the electrolytic cell B through a liquid pipeline, such that a solution undergoing an electrolytic reaction in the cathode chamber of the electrolytic cell A is added to the cathode chamber of the electrolytic cell B to allow progressive electrolysis for copper recovery; the anode chamber of the electrolytic cell A and the cathode chamber of the electrolytic cell A are provided with an electrolytic anode and an electrolytic cathode respectively, and the electrolytic anode and the electrolytic cathode of the electrolytic cell A are connected with a positive electrode and a negative electrode of an electrolytic power supply for the electrolytic cell A respectively; and the anode chamber of the electrolytic cell B and the cathode chamber of the electrolytic cell B are provided with an electrolytic anode and an electrolytic cathode of the electrolytic cell B respectively, and the electrolytic anode and the electrolytic cathode of the electrolytic cell B are connected with a positive electrode and a negative electrode of an electrolytic power supply for the electrolytic cell B respectively.

During an electrolysis process, an anode electrolyte and a cathode electrolyte are provided in the anode chamber of the electrolytic cell A and the cathode chamber of the electrolytic cell A respectively, and an anode electrolyte and a cathode electrolyte are provided in the anode chamber of the electrolytic cell B and the cathode chamber of the electrolytic cell B respectively. The anode electrolyte of the electrolytic cell A comprises at least one selected from the group consisting of a working etching solution, an etching waste solution, and a cathode electrolyte undergoing an electrolytic treatment from the electrolytic cell B. The cathode electrolyte of the electrolytic cell A comprises the acidic etching waste solution. The anode electrolyte of the electrolytic cell B comprises at least one selected from the group consisting of a cathode electrolyte undergoing an electrolytic treatment from the electrolytic cell B, a working etching solution, and an etching waste solution. The cathode electrolyte of the electrolytic cell B comprises a cathode electrolyte undergoing an electrolytic treatment from the electrolytic cell A or a mixed solution of the cathode electrolyte undergoing the electrolytic treatment from the electrolytic cell A with the acidic etching waste solution.

The electrolytic cell separator of the electrolytic cell A can be at least one selected from the group consisting of an anion exchange membrane, a bipolar membrane, and a reverse osmosis membrane.

The electrolytic cell B can be an electrolytic cell divided into an anode chamber and a cathode chamber with an arbitrary structural form, specifically including a structural form with an electrolytic cell separator and a structural form without an electrolytic cell separator. When the anode chamber and the cathode chamber of the electrolytic cell B are separated by an electrolytic cell separator, the electrolytic cell separator of the electrolytic cell B is at least one selected from the group consisting of an anion exchange membrane, a bipolar membrane, and a reverse osmosis membrane.

The following improvement can be conducted in the present disclosure: According to an ORP value measured by an ORP meter in the cathode chamber of the electrolytic cell A and process requirements, an output current of an electrolytic power supply for the electrolytic cell A is adjusted or the electrolytic power supply for the electrolytic cell A is powered on/off, and/or a solution including the acidic etching waste solution is supplemented to the cathode chamber of the electrolytic cell A.

The following improvement can be conducted in the present disclosure: At least one electrolytic cell C is additionally provided after the electrolytic cell B; the electrolytic cell C is divided into an anode chamber and a cathode chamber; the cathode chamber of the electrolytic cell B is connected with the cathode chamber of the electrolytic cell C through a liquid pipeline, such that a solution undergoing an electrolytic treatment in the cathode chamber of the electrolytic cell B is added to the cathode chamber of the electrolytic cell C; the anode chamber of the electrolytic cell C and the cathode chamber of the electrolytic cell C are provided with an electrolytic anode and an electrolytic cathode respectively, and the electrolytic anode and the electrolytic cathode of the electrolytic cell C are connected with a positive electrode and a negative electrode of an electrolytic power supply for the electrolytic cell C respectively; during an electrolysis process, an anode electrolyte and a cathode electrolyte are provided in the anode chamber and the cathode chamber of the electrolytic cell C respectively; the anode electrolyte of the electrolytic cell C comprises at least one selected from the group consisting of a working etching solution, a cathode electrolyte undergoing an electrolytic treatment from the electrolytic cell B, and a cathode electrolyte undergoing an electrolytic treatment from the electrolytic cell C, or on this basis, the anode electrolyte of the electrolytic cell C further comprises an etching waste solution; and the cathode electrolyte of the electrolytic cell C comprises a cathode electrolyte undergoing an electrolytic treatment from the electrolytic cell B, or on this basis, the cathode electrolyte of the electrolytic cell C further comprises the cathode electrolyte of the electrolytic cell A and/or an etching waste solution. In this case, the anode electrolyte of the electrolytic cell A comprises at least one selected from the group consisting of a cathode electrolyte undergoing an electrolytic treatment from the electrolytic cell B, a cathode electrolyte undergoing an electrolytic treatment from the electrolytic cell C, a working etching solution, and an etching waste solution, and the anode electrolyte of the electrolytic cell B comprises at least one selected from the group consisting of a cathode electrolyte undergoing an electrolytic treatment from the electrolytic cell B, a cathode electrolyte undergoing an electrolytic treatment from the electrolytic cell C, a working etching solution, and an etching waste solution.

The electrolytic cell C can be an electrolytic cell divided into an anode chamber and a cathode chamber with an arbitrary structural form, specifically including a structural form with an electrolytic cell separator and a structural form without an electrolytic cell separator. When the anode chamber of the electrolytic cell C and the cathode chamber of the electrolytic cell C are separated by an electrolytic cell separator, the electrolytic cell separator of the electrolytic cell C is at least one selected from the group consisting of an anion exchange membrane, a bipolar membrane, and a reverse osmosis membrane.

The following improvement can be conducted in the present disclosure: A detector and an automatic feeding controller are additionally provided. At least one detector is provided to detect at least one selected from the group consisting of the anode electrolyte and the cathode electrolyte of the electrolytic cell A, the anode electrolyte and the cathode electrolyte of the electrolytic cell B, and the anode electrolyte and the cathode electrolyte of the electrolytic cell C, and to send data measured on site to the automatic feeding controller for processing, so as to control an output current of at least one electrolytic power supply and/or the addition of each material.

Preferably, the detector is at least one selected from the group consisting of an acidity meter, a specific gravity meter, an ORP meter, a photoelectric colorimeter, a liquid level meter, a thermometer, a flow meter, and a chlorine gas detector.

The following improvement can be conducted in the present disclosure: A circular mixing and exchange tank is additionally provided. The anode chamber of the electrolytic cell A provided with the electrolytic cell separator and/or the anode chamber of the electrolytic cell B and/or the anode chamber of the electrolytic cell C is/are connected with the circular mixing and exchange tank through a circulating pipeline, and the circular mixing and exchange tank is connected with an etching production line through a circulating pipeline, such that an anode electrolyte and a working etching solution are mixed in the circular mixing and exchange tank, and a copper-etching agent can be supplemented on-line to a working etching solution on the etching production line in real time.

Preferably, a circular mixing and exchange tank with a large volume is adopted, and an ORP value of a solution in the circular mixing and exchange tank is controlled to be higher than an ORP value of a working etching solution, such that a copper-etching agent concentration in the solution in the circular mixing and exchange tank is much higher than a copper-etching agent concentration of the working etching solution and an electrolysis apparatus can be utilized efficiently.

The following improvement can be conducted in the present disclosure: A heat exchanger is additionally provided to adjust a temperature of a solution ready to enter an etching production line.

The following improvement can be conducted in the present disclosure: A temporary storage tank is additionally provided to temporarily store each solution and/or serve as a chemical reaction-based preparation tank for a solution.

The following improvement can be conducted in the present disclosure: An exhaust gas treatment tank is additionally provided to treat an exhaust gas produced during a working process of each electrolytic cell or each temporary storage tank.

The following improvement can be conducted in the present disclosure: A stirrer is additionally provided, including a paddle stirrer and a liquid circulating stirrer. The stirrer is configured to stir and mix solutions in an electrolytic cell and a temporary storage tank.

The following improvement can be conducted in the present disclosure: An overflow buffer tank is additionally provided to solve the solution flow problem caused by a liquid level difference between electrolytic cells and/or tanks.

The following improvement can be conducted in the present disclosure: A closed cell cover with a vent hole and a feeding port is additionally provided for an electrolytic cell to collect an electrogenerated chlorine gas or oxygen gas for safe production and utilization.

The following improvement can be conducted in the present disclosure: A movable cell cover is additionally provided for a cathode chamber of an electrolytic cell, such that an acidic exhaust gas can be conveniently collected and treated and a cathode can be conveniently taken out for recovered metallic copper collection.

The following improvement can be conducted in the present disclosure: A gas-liquid mixer is additionally provided. The gas-liquid mixer can be a vacuum jet gas-liquid mixer or a spray gas-liquid mixer. The gas-liquid mixer is configured to mix a gas and a liquid.

The following improvement can be conducted in the present disclosure: A filter is additionally provided to allow solid-liquid separation or organic impurity removal for a solution to be treated.

The following improvement can be conducted in the present disclosure: A cathode-chamber etching-waste-solution feeding pipe is additionally provided for the electrolytic cell B and/or the electrolytic cell C. Preferably, the cathode-chamber etching-waste-solution feeding pipe is arranged close to a electrolytic cell separator, such that Fe³⁺ ions in an iron-containing etching waste solution react with cuprous chloride adhered to the electrolytic cell separator to produce cupric chloride and cupric chloride is dissolved in a cathode electrolyte, which can avoid the blockage of the electrolytic cell separator. The controlled feeding can be conducted according to a time interval or a cell voltage.

Compared with the prior art, the present disclosure has the following beneficial effects:

1. The present disclosure solves the process problem that a copper layer electroprecipitated in the existing electrolytic recovery process for an acidic etching waste solution from PCB production is loose and easy to break.

2. The present disclosure can allow the 100% electrolytic recycling of an acidic etching waste solution from PCB production, and can greatly reduce a production cost and reduce the environmental pollution.

3. In the method of the present disclosure, no new substance is added during the entire recycling process, and the reuse of a regenerated etching replenishment solution has no impact on a quality and an efficiency of etching production.

4. In the method of the present disclosure, it is not necessary to add an oxidant externally to an acidic etching system during recycling production, which reduces a production cost.

5. When an iron-containing acidic etching solution is adopted, the method of the present disclosure can give full play to the advantages of acidic iron-containing etching, and can improve both an etching efficiency and an etching quality.

BRIEF DESCRIPTION OF THE DRAWINGS

The method of the present disclosure is further described below with reference to accompanying drawings.

FIG. 1 shows a device for recycling an acidic etching waste solution from PCB production through progressive electrolysis in Example 1 of the present disclosure;

FIG. 2 shows a device for recycling an acidic etching waste solution from PCB production through progressive electrolysis in Example 2 of the present disclosure;

FIG. 2E is an enlarged view of 2-E in FIG. 2;

FIG. 2F is an enlarged view of 2-F in FIG. 2;

FIG. 2G is an enlarged view of 2-G in FIG. 2;

FIG. 2H is an enlarged view of 2-H in FIG. 2;

FIG. 3 shows a device for recycling an acidic etching waste solution from PCB production through progressive electrolysis in Example 3 of the present disclosure;

FIG. 3E is an enlarged view of 3-E in FIG. 3;

FIG. 3F is an enlarged view of 3-F in FIG. 3;

FIG. 3G is an enlarged view of 3-G in FIG. 3;

FIG. 3H is an enlarged view of 3-H in FIG. 3;

FIG. 3K is an enlarged view of 3-K in FIG. 3;

FIG. 4 shows a device for recycling an acidic etching waste solution from PCB production through progressive electrolysis in Example 4 of the present disclosure;

FIG. 4E is an enlarged view of 4-E in FIG. 4;

FIG. 4F is an enlarged view of 4-F in FIG. 4;

FIG. 4G is an enlarged view of 4-G in FIG. 4;

FIG. 4H is an enlarged view of 4-H in FIG. 4;

FIG. 5 shows a device for recycling an acidic etching waste solution from PCB production through progressive electrolysis in Example 8 of the present disclosure;

FIG. 5E is an enlarged view of 5-E in FIG. 5;

FIG. 5F is an enlarged view of 5-F in FIG. 5;

FIG. 5G is an enlarged view of 5-G in FIG. 5;

FIG. 5H is an enlarged view of 5-H in FIG. 5;

FIG. 5K is an enlarged view of 5-K in FIG. 5;

FIG. 6 is a photograph of metallic copper recovered by the method of the present disclosure; and

FIG. 7 is a photograph of metallic copper produced by the existing technology where an etching waste solution is added to a cathode chamber.

REFERENCE NUMERALS

- 1: electrolytic cell A, 2: electrolytic cell B, 3: electrolytic cell separator for an electrolytic cell A, 4: electrolytic cell separator for an electrolytic cell B, 5: electrolytic power supply for an electrolytic cell A, 6: electrolytic power supply for an electrolytic cell B, 7: ORP controller for a cathode chamber of an electrolytic cell A, 8: electrolytic cell C, 9: electrolytic cell separator for an electrolytic cell C, 10: electrolytic power supply for an electrolytic cell C, 23 to 50: temporary storage tanks, 51 to 70: overflow buffer tanks, 71 to 75: vacuum jet gas-liquid mixers, 76 to 80: spray gas-liquid mixers, 81 to 90: liquid circulating stirrers, 91: solid feeder, 92 to 95: paddle stirrers, 96: water-oil separator, 97 to 100: solid-liquid separation filters, 101 to 130: detectors, 131: automatic feeding controller, 132: valve, 133: pump, 134: cathode-chamber etching-waste-solution feeding pipe, 251: iron-containing acidic etching waste solution, 252: regenerated etching replenishment solution, 253: electrolytically-recovered metallic copper, 256: cathode electrolyte undergoing copper recovery that overflows from an electrolytic cell B, 257 to 259: PCB etching production lines, 260: oxidatively-regenerated etching solution, 261 to 266: heat exchangers, 267: sodium hydroxide solution, 268: overflow solution from a cathode chamber of an electrolytic cell A, 269 to 280: closed cell covers each with a vent hole and a feeding port of an electrolytic cell, 281 to 282: exhaust gas treatment tanks, 283: hydrochloric acid, 284: ferric chloride, 285: ammonium chloride, 286: sodium chloride, 287: acidic exhaust gas, 288: water, 289 to 293: movable cell covers, 294 to 295: cathode cloth filter bag, 296: ferrous chloride, 297: ferric hydroxide, and 298: ferrous hydroxide.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The electrolytic cells, the temporary storage tanks, the exhaust gas treatment tanks, the overflow buffer tanks, the vacuum jet gas-liquid mixers, the spray gas-liquid mixers, the stirrers, and the water-oil separator adopted in the following examples all are products manufactured by Foshan Yegao Environmental Protection Equipment Manufacturing Co., Ltd., Guangdong Province. The solid-liquid separation filters, the electrolytic cell separators, the detectors, the programmable logic controller (PLC), the valves, the pumps, and the chemical raw materials all are commercially-available products. Other products with similar properties to the products listed above in the present disclosure may also be adopted by those skilled in the art according to conventional selection, which all can allow the objectives of the present disclosure.

Example 1

FIG. 1 shows Basic Example 1 of a method and device for recycling an acidic etching waste solution from PCB production through progressive electrolysis. The device includes an electrolytic cell A 1, an electrolytic cell B 2, an ORP controller 7 for a cathode chamber of the electrolytic cell A, an electrolytic cell separator 3 for the electrolytic cell A, an electrolytic cell separator 4 for the electrolytic cell B, an electrolytic power supply 5 for the electrolytic cell A, an electrolytic power supply 6 for the electrolytic cell B, temporary storage tanks 23 to 28, a vacuum jet gas-liquid mixer 71, detectors 101 to 103, valves 132-1 to 132-7, pumps 133-1 to 133-7, an acidic etching waste solution 251, a regenerated etching replenishment solution 252, recovered metallic copper 253, a cathode electrolyte 256 undergoing copper recovery that overflows from the electrolytic cell B, and an overflow solution 268 from the cathode chamber of the electrolytic cell A.

The electrolytic cell separator 3 for the electrolytic cell A is a reverse osmosis membrane, and the electrolytic cell separator 4 for the electrolytic cell B is an anion exchange membrane.

For the electrolytic cell A, an anode material is metallic platinum and a cathode material is an electrically-conductive graphite plate.

For the electrolytic cell B, an anode material is a titanium-based coated electrode and a cathode material is stainless steel.

Detectors 104 and 104 are ORP meters, and a detector 103 is a specific gravity meter (which is intended to measure a metal ion concentration in a solution).

The vacuum jet gas-liquid mixer 71 is configured to absorb and drain a chlorine gas produced in anode chambers of the electrolytic cell A and the electrolytic cell B to a temporary storage tank 28 for an oxidative regeneration reaction to prepare the regenerated etching replenishment solution 252.

The detector 101 as a liquid level meter is arranged in an anode chamber of the electrolytic cell A. A pump 133-1 is controlled to feed an etching waste solution into the anode chamber of the electrolytic cell A. The ORP controller 7 is arranged in the cathode chamber of the electrolytic cell A to control a pump 133-2 as required to feed the acidic etching waste solution 251 in a temporary storage tank 23 into the cathode chamber of the electrolytic cell A. The overflow solution 268 from the cathode chamber of the electrolytic cell A after an electrolytic treatment is drained to a temporary storage tank 25 for temporary storage, and the overflow solution has the same copper ion concentration as the original etching waste solution.

The electrolytic cell B 2 is an electrolytic cell for progressive electrolysis to allow copper recovery. In an anode chamber of the electrolytic cell B, an electrolyte is oxidized to produce a chlorine gas. In a cathode chamber of the electrolytic cell B, copper is extracted. An anode electrolyte of the electrolytic cell B is the cathode electrolyte 256 undergoing copper recovery that overflows from the electrolytic cell B 2, and the anode electrolyte undergoes an oxidation reaction in the anode chamber of the electrolytic cell B to generate the regenerated etching replenishment solution 252. The detector 103 as a specific gravity meter is arranged in a cathode chamber of the electrolytic cell B to control the overflow solution 268 from the cathode chamber of the electrolytic cell A in the temporary storage tank 25 to be fed into the cathode chamber of the electrolytic cell B 2 for progressive electrolysis to allow copper recovery.

The cathode electrolyte 256 undergoing copper recovery that overflows from the electrolytic cell B 2 is partially pumped by a pump 133-4 into the temporary storage tank 28 to undergo an oxidation reaction with a chlorine gas to prepare the regenerated etching replenishment solution, such that cuprous chloride and ferrous chloride in a solution in the temporary storage tank 28 are oxidized under the control of a detector 104 as an ORP meter to produce a copper-etching agent of cupric chloride and ferric chloride. A regenerated etching replenishment solution meeting a standard requirement is pumped by a pump 133-7 into a temporary storage tank 26 for temporary storage.

By adjusting set values of the detectors 102 and 104 as ORP meters, the regenerated etching replenishment solution 252 with a low copper ion concentration meeting a process requirement can be prepared through oxidation.

Main components of the acidic etching waste solution in this example are as follows: hydrochloric acid, cupric chloride, ferric chloride, ferrous chloride, sodium chloride, ammonium chloride, and water. The acidic etching waste solution has an acidity of 1.2 mol/L, a copper ion concentration of 120 g/L, a total iron ion concentration of 100 g/L, and an ORP value of 610 mV. Specific steps of this example were as follows:

1. The acidic etching waste solution 251 was fed as a starting electrolyte into the anode chamber and the cathode chamber of the electrolytic cell A. During an electrolysis operation, an amount of the acidic etching waste solution 251 fed into the cathode chamber of the electrolytic cell A was controlled such that cupric ions and ferric ions in the etching waste solution underwent an electrochemical reduction reaction and a solution in the cathode chamber overflowed into the temporary storage tank 25.

2. The overflow solution 268 from the cathode chamber of the electrolytic cell A in the temporary storage tank 25 was fed into the cathode chamber of the electrolytic cell B, and the cathode electrolyte 256 undergoing copper recovery that overflowed from the electrolytic cell B in a temporary storage tank 27 was fed into the anode chamber of the electrolytic cell B.

3. The electrolytic power supply 5 and the electrolytic power supply 6 were manually powered on to allow electrolysis of the electrolytic cell A and the electrolytic cell B respectively. During an electrolysis process, a chlorine gas was produced in the anode chamber of the electrolytic cell A. The ORP controller 7 was set to control an ORP at 580 mV to monitor the feeding of the acidic etching waste solution 251 into the cathode chamber of the electrolytic cell A, such that a copper-etching agent concentration in the cathode electrolyte in the electrolytic cell A was reduced and no metallic copper was electroprecipitated at the electrolytic cathode of the electrolytic cell A. The detector 103 as a specific gravity meter in the electrolytic cell B monitored the feeding of the overflow solution 268 from the cathode chamber of the electrolytic cell A in the temporary storage tank 25 into the cathode chamber of the electrolytic cell B through the pump 133-3 and controlled a copper ion concentration of the cathode electrolyte in the cathode chamber of the electrolytic cell B. An anode of the electrolytic cell A and an anode of the electrolytic cell B allowed electrochemical oxidation reactions for the acidic etching waste solution 251 and the cathode electrolyte 256 undergoing copper recovery that overflowed from the electrolytic cell B, respectively. A chlorine gas produced in the anode chambers of the electrolytic cell A and the electrolytic cell B was mixed with a solution in the temporary storage tank 28 through a jet device 71 for oxidation to produce the regenerated etching replenishment solution 252. The cathode electrolyte of the electrolytic cell A underwent a reduction reaction to eliminate a copper-etching agent. Metallic copper 253 was electroprecipitated at the cathode of the electrolytic cell B. The cathode electrolyte 256 undergoing copper recovery that overflowed from the electrolytic cell B was oxidized at the anode of the electrolytic cell B to prepare a regenerated etching replenishment solution.

4. Parameter values of the regenerated etching replenishment solution were as follows: an acidity: 4.0 M/L, a copper ion concentration: 60 g/L, an iron ion concentration: 100 g/L, and an ORP value: 650 mV.

Through the device shown in FIG. 1 and the above steps, a process for recycling an acidic etching waste solution from PCB production through progressive electrolysis can be allowed.

Example 2

FIG. 2 and its partial enlarged view FIG. 2E, FIG. 2F, FIG. 2G, and FIG. 2H show Example 2 of a method and device for recycling an acidic etching waste solution from PCB production through progressive electrolysis. The device includes an electrolytic cell A 1, two electrolytic cells B 2-1 and 2-2, an ORP controller 7 for a cathode chamber of the electrolytic cell A, an electrolytic cell separator 3 for the electrolytic cell A, electrolytic cell separators 4-1 and 4-2 for the electrolytic cells B, an electrolytic power supply 5 for the electrolytic cell A, electrolytic power supplies 6-1 and 6-2 for the electrolytic cells B, temporary storage tanks 23 to 28, overflow buffer tanks 51 to 56, a water-oil separator 96, detectors 101 to 112, an automatic feeding controller 131, valves 132-1 to 132-23, pumps 133-1 to 133-23, a cathode-chamber etching-waste-solution feeding pipe 134, an acidic etching waste solution 251, a regenerated etching replenishment solution 252, recovered metallic copper 253, cathode electrolytes 256 undergoing copper recovery that overflow from the electrolytic cells B, a PCB etching production line 257, an oxidatively-regenerated etching solution 260, and an overflow solution 268 from the cathode chamber of the electrolytic cell A.

The electrolytic cell separator 3 for the electrolytic cell A is an anion exchange membrane. An electrolytic cell separator 4-1 for the electrolytic cell B is a bipolar membrane and an electrolytic cell separator 4-2 for the electrolytic cell B is a reverse osmosis membrane.

For the electrolytic cell A, an anode material is a titanium-based coated insoluble anode and a cathode material is metallic titanium.

For the electrolytic cell B 2-1, an anode material is a titanium-based coated insoluble anode and a cathode material is a metallic copper sheet. For the electrolytic cell B 2-2, an anode material is electrically-conductive graphite and a cathode material is a metallic copper sheet.

Detectors 101 and 109 are specific gravity meters, a detector 102 is an acidity meter, detectors 103, 106, and 111 are ORP meters, detectors 104 and 107 are thermometers, detectors 105, 108, and 112 are liquid level meters, and a detector 110 is a photoelectric colorimeter. Field data of all detectors are transmitted to the automatic feeding controller 131 for processing, and the whole device is controlled to work according to programs.

The detectors 101, 102, 103, and 104 are arranged in the PCB etching production line 257. The detector 102 as an acidity meter controls a pump 133-1 to feed the regenerated etching replenishment solution 252 to allow acidity control for a working etching solution. The detector 101 as a specific gravity meter controls a valve to feed water 288 to control a specific gravity of a working etching solution. The detector 103 as an ORP meter controls a rotational speed of a variable-frequency pump 133-4 to make an ORP of a working etching solution controlled at 540 mV according to a process. The detector 104 as a thermometer controls a temperature of a working etching solution at 50° C. Therefore, through the controlled feeding above, a working etching solution of the PCB etching production line 257 maintains an acidity of 0.9 mol/L, a specific gravity of 1.34 g/mL, and an ORP of 530 mV to stabilize the etching performance.

An etching waste solution overflowing from the PCB etching production line 257 first flows into the water-oil separator 96 for separation of organic matters including inks and film residues, then flows into a liquid flow buffer tank 51, and then is pumped by a pump 133-3 into a temporary storage tank 24 as a circular mixing and exchange tank. When the temporary storage tank 24 is full of the oxidatively-regenerated etching solution 260, the detector 105 as a liquid level meter controls a pump 133-7 to pump a part of a solution in the temporary storage tank 24 into the temporary storage tank 25 for temporary storage.

The ORP controller 7 controls a pump 133-10 to feed the etching waste solution 251 in the temporary storage tank 25 into the cathode chamber of the electrolytic cell A, and an overflow solution 268 undergoing an electrolytic treatment is pumped by a pump 133-9 into a temporary storage tank 26 for temporary storage. During an electrolysis operation, because no metallic copper is electroprecipitated at the cathode of the electrolytic cell A, a copper ion concentration of a solution in the temporary storage tank 26 is still about 140 g/L. The anode of the electrolytic cell A specializes in producing a chlorine gas to oxidize a cathode overflow solution 256 from the electrolytic cells B 2-1 and 2-2 to prepare the regenerated etching replenishment solution 252.

The electrolytic cells B 2-1 and 2-2 are electrolytic cells for progressive electrolysis to allow copper recovery. For the electrolytic cells B, the electrolysis for copper recovery is allowed at a cathode, and the oxidatively-regenerated etching solution 260 is produced through oxidation at an anode to maintain the etching reaction. The detector 109 as a specific gravity meter and the detector 110 as a photoelectric colorimeter control pumps 133-13 and 133-14 to feed the overflow solution 268 from the cathode chamber of the electrolytic cell A in a temporary storage tank 26 into cathode chambers of the electrolytic cells B 2-1 and 2-2 to allow progressive electrolysis for copper recovery. Copper ion concentrations in cathode electrolytes of the electrolytic cells B 2-1 and 2-2 are controlled at a set value of 40 g/L, and the metallic copper 253 is electroprecipitated at both cathodes of the electrolytic cells B 2-1 and 2-2.

Cathode electrolytes 256 undergoing copper recovery that overflow from the electrolytic cells B 2-1 and 2-2 are pumped to a temporary storage tank 27 and then pumped by a pump 133-19 under the control of the detector 111 as an ORP meter and the detector 112 as a liquid level meter into a temporary storage tank 28, and a chlorine gas is absorbed by a spray tower to participate in an oxidation reaction for the cathode electrolytes 256 undergoing copper recovery that overflow from the electrolytic cells B, such that cuprous chloride and ferrous chloride in the cathode electrolytes are oxidized into cupric chloride and ferric chloride as a copper-etching agent to obtain a regenerated etching replenishment solution with a low copper ion concentration meeting a process requirement.

The cathode-chamber etching-waste-solution feeding pipes 296 and 297 of the electrolytic cells B 2-1 and 2-2 are configured to feed a etching waste solution for a reaction to remove a cuprous chloride sludge on the electrolytic cell separators 4-1 and 4-2 for the electrolytic cells B, thereby preventing the electrolytic cell separator for an electrolytic cell Bs from being blocked by the cuprous chloride sludge.

Main components of the iron-containing acidic etching waste solution in this example are as follows: hydrochloric acid, cupric chloride, sodium chloride, ammonium chloride, ferric chloride, ferrous chloride, and water. The iron-containing acidic etching waste solution has an acidity of 0.9 mol/L, a copper ion concentration of 140 g/L, and a total iron ion concentration of 20 g/L.

The device for recycling an acidic etching waste solution from PCB production through progressive electrolysis was implemented mainly through the following steps:

1. A working etching solution was fed into an anode chamber of the electrolytic cell A and the etching waste solution 251 was fed into a cathode chamber of the electrolytic cell A as starting electrolytes. The detector 101 as a liquid level meter was arranged in the anode chamber of the electrolyte cell A, and the ORP controller 7 was arranged in the cathode chamber of the electrolytic cell A.

2. A solution in the temporary storage tank 26 was fed into the cathode chambers of the electrolytic cells B 2-1 and 2-2. Electrolytes in the anode chambers of the electrolytic cells B each were circularly mixed with a solution in the temporary storage tank 24 as the circular mixing and exchange tank.

3. The electrolytic power supply 5 and the two electrolytic power supplies 6-1 and 6-2 each were powered on to allow electrolysis operations of the electrolytic cell A and the two electrolytic cells B. A set value of the ORP controller 7 was set to 499 mV to control the feeding of the acidic etching waste solution 251 into the cathode chamber of the electrolytic cell A, such that no metallic copper was produced and only a reaction of eliminating a copper-etching agent occurred at the cathode of the electrolytic cell A, and a chlorine gas evolution reaction occurred in the anode chamber of the electrolytic cell A. The detector 109 as a specific gravity meter in the electrolytic cell B 2-1 controlled the pump 133-14 to feed the overflow solution 268 from the cathode chamber of the electrolytic cell A in the temporary storage tank 26 into the cathode chamber of the electrolytic cell B 2-1, and the detector 110 as a photoelectric colorimeter in the electrolytic cell B 2-2 controlled the pump 133-13 to feed a solution in the temporary storage tank 26 into the cathode chamber of the electrolytic cell B, such that copper was electroprecipitated at both cathodes of the electrolytic cells B 2-1 and 2-2. The anodes of the electrolytic cells B 2-1 and 2-2 allowed an electrochemical oxidation reaction for the oxidatively-regenerated etching solution 260, such that the PCB etching production line 257 maintained the etching production by controlling a rotational speed of the pump 133-4 to control a feeding rate. In addition, a chlorine gas produced in the anode chamber of the electrolytic cell A was adsorbed and mixed with the cathode electrolyte 256 undergoing copper recovery that overflowed from the electrolytic cell B through the spray gas-liquid mixer 76 to prepare the regenerated etching replenishment solution 252, and the cathode electrolyte of the electrolytic cell A underwent a reduction reaction to eliminate a copper-etching agent. During an electrolysis process, it was controlled by the metering pumps 133-11 and 133-12 in a time-dependent manner to feed a small amount of the etching waste solution 251 into the cathode chambers of the electrolytic cells B 2-1 and 2-2 respectively to remove cuprous chloride on the separators.

4. Parameters of the regenerated etching replenishment solution 252 were as follows: an acidity: 4.5 M/L, a copper ion concentration: 40 g/L, and an iron ion concentration: 20 g/L.

Through the device shown in FIG. 2 and the above steps, a process for 100% recycling an iron-containing acidic etching waste solution from PCB production through progressive electrolysis can be allowed.

Example 3

FIG. 3 and its partial enlarged view FIG. 3E, FIG. 3F, FIG. 3G, FIG. 3H and FIG. 3K show Example 3 of a device for recycling an acidic etching waste solution from PCB production through progressive electrolysis. The device includes an electrolytic cell A 1, electrolytic cells B 2-1 and 2-2, and an electrolytic cell C 8. An ORP controller 7 is provided in a cathode chamber of the electrolytic cell A. An electrolytic cell separator 3 for the electrolytic cell A provided in the electrolytic cell A is a bipolar membrane. For the electrolytic cells B, an electrolytic cell separator 4-1 for the electrolytic cell B is an anion exchange membrane and an electrolytic cell separator 4-2 for the electrolytic cell B is an anion exchange membrane. An electrolytic cell separator for an electrolytic cell C 9 of the electrolytic cell C is an anion exchange membrane. The device further includes an electrolytic power supply 5 for the electrolytic cell A, electrolytic power supplies 6-1 and 6-2 for the two electrolytic cells B, an electrolytic power supply 10 for the electrolytic cell C, temporary storage tanks 23 to 31, overflow buffer tanks 51 to 56, a vacuum jet gas-liquid mixer 71, a spray gas-liquid mixer 76, liquid circulating stirrers 81 to 86, detectors 110 to 112, an automatic feeding controller 131, an acidic etching waste solution 251, a regenerated etching replenishment solution 252, recovered metallic copper 253, cathode electrolytes 256 undergoing copper recovery that overflow from the electrolytic cells B 2-1 and 2-2, a PCB etching production line 257, valves 132-1 to 132-19, pumps 133-1 to 133-20, a sodium hydroxide solution 267, an exhaust gas treatment tank 281, an overflow solution 268 from the cathode chamber of the electrolytic cell A, water 288, and movable cell covers 289 to 291.

For the electrolytic cell A, an anode material is an insoluble anode with a gold-plated surface and a cathode material is metallic platinum. For the electrolytic cell B 2-1, an anode material is electrically-conductive graphite and a cathode material is a titanium plate. For the electrolytic cell B 2-2, an anode material is a titanium-based coated insoluble anode and a cathode material is a titanium plate. For the electrolytic cell C 8, an anode material is a titanium-based coated insoluble anode and a cathode material is a copper sheet.

The PCB etching production line 257 is connected with each anode chamber of the electrolytic cells A and B through a liquid pipeline. Four detectors are arranged on the PCB etching production line 257, including a detector 101 as an acidity meter, a detector 102 as a specific gravity meter, a detector 103 as an ORP meter, and a detector 104 as a thermometer. The detector 101 as an acidity meter controls a pump 133-1 to feed the regenerated etching replenishment solution 252. The detector 102 as a specific gravity meter controls the feeding of the water 288. The detector 103 as an ORP meter adjusts an output current of each electrolytic power supply or controls the power off of each electrolytic power supply. When a copper-etching agent concentration in a working etching solution reaches a process set value, all electrolytic power supplies are powered off. The detector 104 as a thermometer controls a temperature of a working etching solution at 50° C. Through the above control of various parameters such as an acidity, a specific gravity, an ORP, and a temperature, a working etching solution can still maintain its etching performance in a continuous etching production process.

An output pump pipeline with a solid-liquid separation filter 97 is provided in an overflow buffer tank 51, such that an organic oil residue floating on a working etching solution can be separated through filtration to obtain the acidic etching waste solution 251 and the acidic etching waste solution can be drained to a temporary storage tank 25 for temporary storage. In this example, the circular mixing and exchange tank is not provided. During an etching work, a working etching solution is pumped directly by pumps 133-4 and 133-6 into anode chambers of the electrolytic cells A and B respectively, and then flows back to the PCB etching production line 257 through an overflow port of the respective anode chamber. Under the control of the detector 103 as an ORP meter, the plurality of electrolytic power supplies are powered on or adjusted to allow oxidation for a working etching solution to regenerate a copper-etching agent.

An ORP controller 7 is provided in the cathode chamber of the electrolytic cell A. A set value of the ORP controller is set to 200 mV according to a process to control the feeding of the etching waste solution 251 in the temporary storage tank 25 into the cathode chamber of the electrolytic cell A, such that ferric ions in a cathode electrolyte of the electrolytic cell A all are converted into ferrous ions, and metallic copper is electroprecipitated as little as possible at a cathode of the electrolytic cell A. The overflow solution 268 from the cathode chamber of the electrolytic cell A after an electrolytic treatment is pumped by a pump 133-7 into a temporary storage tank 26 for temporary storage, and a copper ion concentration in the overflow solution is reduced to 98 g/L.

The electrolytic cell B is adopted to allow progressive electrolysis for copper recovery relative to the electrolytic cell A, and the electrolytic cell C is adopted to allow further progressive electrolysis for copper recovery relative to the electrolytic cell B. Specific gravity meters are arranged in cathode chambers of the electrolytic cells B, namely, detectors 105 and 106, respectively. A detector 107 as an ORP meter is arranged in an anode chamber of the electrolytic cell C, and a detector 108 as a specific gravity meter is arranged in a cathode chamber of the electrolytic cell C. Detection data of the plurality of detectors is sent to the automatic feeding controller 131 for processing to control the feeding of the overflow solution 268 from the cathode chamber of the electrolytic cell A in the temporary storage tank 26 into the cathode chambers of the electrolytic cells B, such that a concentration of each component in an electrolyte in each cathode chamber of the electrolytic cells B is controlled during a copper electroprecipitation process, and a cathode overflow solution from the electrolytic cells B is pumped by pumps 133-11 and 133-12 into a temporary storage tank 27 for temporary storage. A copper ion concentration of a solution in the temporary storage tank 27 is controlled at 60 g/L.

According to data measured by the detector 108, the automatic feeding controller 131 controls a pump 133-13 to feed the solution 256 into the cathode chamber of the electrolytic cell C. The detector 108 as a specific gravity meter controls a copper ion concentration in a cathode electrolyte of the electrolytic cell C at 5 g/L, such that, during an electrolysis process, a copper sponge is produced and collected by a cathode cloth filter bag 294. As an operation of the electrolytic cell C proceeds, the cathode electrolyte of the electrolytic cell C overflows into an overflow buffer tank 56 and is pumped by a pump 133-18 into a temporary storage tank 30 for temporary storage.

A temporary storage tank 31 serves as a chlorine gas-based oxidation reaction tank. The vacuum jet gas-liquid mixer 71 is arranged at a top of the temporary storage tank 31, and a detector 109 as a liquid level meter is arranged inside the temporary storage tank 31. A chlorine gas produced in an anode chamber of each electrolytic cell is drained into the temporary storage tank 31 to react with a solution in the temporary storage tank 31. The detector 109 as a liquid level meter controls a pump 133-19 to feed a solution into the temporary storage tank 31. The detector 107 as an ORP meter controls a pump 133-20 to feed a solution in the temporary storage tank 31 into the anode chamber of the electrolytic cell C, such that, after the cathode electrolyte of the electrolytic cell C undergoes electrolysis for copper recovery, cuprous chloride and ferrous chloride are oxidized to produce a copper-etching agent, so as to meet some standard requirements of a regenerated etching replenishment solution.

A temporary storage tank 28 is provided to prepare a regenerated etching replenishment solution. A solution of the temporary storage tank 29 is fed, then hydrochloric acid, ferric chloride, and ammonium chloride are fed, and then a liquid circulating stirrer 84 is started to prepare the regenerated etching replenishment solution 252. After being manually tested as qualified, a prepared regenerated etching replenishment solution 252 is pumped into the temporary storage tank 23 for temporary storage.

The exhaust gas treatment tank 281 is configured to absorb an acidic exhaust gas S produced in each cell to allow an environmental protection treatment.

During an etching production process, an ORP value of a working etching solution is controlled at 580 mV.

Main components of the iron-containing acidic etching waste solution in this example are as follows: hydrochloric acid, cupric chloride, ammonium chloride, ferric chloride, and water. The iron-containing acidic etching waste solution has an acidity of 1.6 mol/L, a copper ion concentration of 100 g/L, and a total iron ion concentration of 140 g/L.

The device for recycling an acidic etching waste solution from PCB production through progressive electrolysis was implemented through the following steps:

1. A working etching solution was fed into the anode chamber of the electrolytic cell A and the etching waste solution 251 was fed into the cathode chamber of the electrolytic cell A. The ORP controller 7 was arranged in the cathode chamber of the electrolytic cell A to control an amount of the etching waste solution 251 fed into the cathode chamber of the electrolytic cell A during an electrolysis process, such that an ORP value of the cathode electrolyte of the electrolytic cell A was controlled at 200 mV.

2. A working etching solution was fed into the anode chambers of the two electrolytic cells B, and the overflow solution 268 from the cathode chamber of the electrolytic cell A in the temporary storage tank 26 was fed into the cathode chambers of the electrolytic cells B. Amounts of the overflow solution 268 from the cathode chamber of the electrolytic cell A that were fed into the cathode chambers of the electrolytic cells B were controlled by the detectors 105 and 106 as specific gravity meters, respectively.

3. A solution in the temporary storage tank 31 was fed into the anode chamber of the electrolytic cell C under the control of the detector 107 as an ORP meter, and the cathode electrolyte 256 undergoing copper recovery that overflowed from the electrolytic cell B in the temporary storage tank 27 was fed into the cathode chamber of the electrolytic cell C through the pump 133-13 under the control of the detector 108 as a specific gravity meter.

4. Each electrolytic power supply was powered on to allow an electrolysis operation of each electrolytic cell. A working etching solution in the PCB etching production line 257 was allowed to circularly flow in each anode chamber of the electrolytic cells A and B, such that an electrochemical reaction for oxidative regeneration of the working etching solution occurred at each electrolytic anode. A chlorine gas produced in the anode chambers of the electrolytic cells A and B was drained to the temporary storage tank 31 to oxidize an electrolyte undergoing copper recovery that overflowed from the cathode chamber of the electrolytic cell C, and the metallic copper 253 was electroprecipitated at each cathode of the electrolytic cells B and C.

5. After a solution undergoing oxidation entered the temporary storage tank 28, hydrochloric acid, ferric chloride, and ammonium chloride were fed into the temporary storage tank 28 to prepare a regenerated etching replenishment solution. After being manually tested as qualified, the regenerated etching replenishment solution prepared in the temporary storage tank 28 was pumped by the pump 133-15 into the temporary storage tank 23 for temporary storage. Parameters of the regenerated etching replenishment solution 252 were as follows: an acidity: 5.5 M/L, a copper ion concentration: 5 g/L, and a ferric ion concentration: 140 g/L.

6. An acidic exhaust gas S from each cell and tank was drained into the exhaust gas treatment tank 281 to allow an environmental protection treatment.

7. The process flow of the whole device was automatically controlled by the automatic feeding controller 131 according to programs, and the regenerated etching replenishment solution in the temporary storage tank 23 was returned to the PCB etching production line for recycling.

Through the device shown in FIG. 3 and the above steps, a process for 100% recycling an acidic etching waste solution from PCB production through progressive electrolysis can be allowed.

Example 4

FIG. 4 and its partial enlarged view FIG. 4E, FIG. 4F, FIG. 4G and FIG. 4H show Example 4 of a method and device for recycling an acidic etching waste solution from PCB production through progressive electrolysis. The device includes an electrolytic cell A 1, two electrolytic cells B 2-1 and 2-2, an ORP controller 7 for a cathode chamber of the electrolytic cell A, an electrolytic cell separator 3 for the electrolytic cell A, electrolytic cell separators 4-1 and 4-2 for the electrolytic cells B, an electrolytic power supply 5 for the electrolytic cell A, electrolytic power supplies 6-1 and 6-2 for the two electrolytic cells B, temporary storage tanks 23 to 28, overflow buffer tanks 51 to 56, a water-oil separator 96, detectors 101 to 112, an automatic feeding controller 131, valves 132-1 to 132-20, pumps 133-1 to 133-20, an acidic etching waste solution 251, a regenerated etching replenishment solution 252, recovered metallic copper 253, cathode electrolytes 256 undergoing copper recovery that overflow from the electrolytic cells B, a PCB etching production line 257, an oxidatively-regenerated etching solution 260, and an overflow solution 268 from the cathode chamber of the electrolytic cell A.

For the electrolytic cell A, an anode material is a titanium-based coated insoluble anode and a cathode material is metallic titanium.

A detector 101 is an acidity meter, detectors 102, 106, and 111 are ORP meters, detectors 103 and 107 are thermometers, detectors 104 and 109 are specific gravity meters, detectors 105 and 112 are liquid level meters, and a detector 110 is a photoelectric colorimeter. Field detection data of all detectors are transmitted to the automatic feeding controller 131 for processing, and the whole device is controlled to work according to programs.

The detectors 101 to 103 are arranged in the PCB etching production line 257. The detector 101 as an acidity meter controls a valve to feed an external acidic ferric chloride solution to allow acidity control for a working etching solution. The detector 102 as an ORP meter controls a rotational speed of a variable-frequency pump 133-4 to make an ORP of a working etching solution controlled at 510 mV. The detector 103 as a thermometer controls a temperature of a working etching solution at 50° C. A specific gravity of a working etching solution is detected and controlled by the detector 104 as a specific gravity meter arranged in a circular mixing and exchange tank. When a specific gravity of a solution in the circular mixing and exchange tank increases due to copper etching, a pump 133-1 is controlled to pump a solution in a temporary storage tank 23 into the circular mixing and exchange tank to reduce a copper ion concentration of the solution in the circular mixing and exchange tank. Therefore, through the controlled feeding above, a working etching solution of the PCB etching production line 257 maintains an acidity of 1 mol/L, a specific gravity of 1.33 g/mL, and an ORP of 510 mV to stabilize the etching performance.

The circular mixing and exchange tank, namely, the temporary storage tank 24, is connected with the PCB etching production line 257 through a circulating liquid pipeline, and is connected with anode chambers of the electrolytic cells A and B through circulating liquid pipelines. An ORP value of the oxidatively-regenerated etching solution 260 in the temporary storage tank 24 is transmitted as a field parameter to the automatic feeding controller 131 for processing by the detector 106 as an ORP meter, and working currents of the electrolytic power supplies for the two electrolytic cells B are adjusted accordingly, such that an ORP value of the solution 260 in the circular mixing and exchange tank is controlled at 750 mV to 800 mV. According to a detected value of the detector 104 as a specific gravity meter arranged in the circular mixing and exchange tank, a regenerated etching replenishment solution in the temporary storage tank 23 is not fed into the PCB etching production line, but is directly fed into the circular mixing and exchange tank, which can rapidly balance a copper ion concentration in a working etching solution and rapidly oxidize ferrous ions Fe²⁺ remaining in the regenerated etching replenishment solution to make an ORP value of the working etching solution stable.

According to a process set value, the ORP controller 7 controls a pump 133-11 to feed the etching waste solution 251 in the temporary storage tank 25 into the cathode chamber of the electrolytic cell A, and an overflow solution 268 undergoing an electrolytic treatment is pumped by a pump 133-10 into a temporary storage tank 26 for temporary storage. During an electrolysis operation, because no metallic copper is electroprecipitated at a cathode of the electrolytic cell A, a copper ion concentration of a solution in the temporary storage tank 26 is still 120 g/L. An anode of the electrolytic cell A is configured to oxidize a working etching solution.

The electrolytic cells B allow progressive electrolysis for copper recovery relative to the electrolytic cell A. For the electrolytic cells B, the electrolysis for copper recovery is allowed at a cathode, and the oxidatively-regenerated etching solution 260 is produced through oxidation at an anode to maintain the etching reaction. The detector 109 as a specific gravity meter and the detector 110 as a photoelectric colorimeter each control pumps 133-12 and 133-13 to feed the overflow solution 268 from the cathode chamber of the electrolytic cell A in a temporary storage tank 26 into cathode chambers of the two electrolytic cells B to allow progressive electrolysis for copper recovery, respectively. Copper ion concentrations in cathode electrolytes of the electrolytic cells B are controlled at a set value of 30 g/L, and the metallic copper 253 is electroprecipitated at both cathodes of the electrolytic cells B.

The cathode electrolytes 256 undergoing copper recovery that overflow from the electrolytic cells B are pumped by pumps 133-15 and 133-17 to a temporary storage tank 27 respectively and then pumped by a pump 133-18 under the control of the detector 111 as an ORP meter and the detector 112 as a liquid level meter into a temporary storage tank 28, and a chlorine gas produced from an anode electrolyte of an electrolytic cell is absorbed by a spray tower to participate in an oxidation reaction for the cathode electrolytes 256 undergoing copper recovery that overflow from the electrolytic cells B, such that cuprous chloride and ferrous chloride in the cathode electrolytes are oxidized into cupric chloride and ferric chloride as a copper-etching agent to obtain a regenerated etching replenishment solution with a low copper ion concentration. There is still a specified number of ferrous ions that have not been oxidized by a chlorine gas in the regenerated etching replenishment solution.

Main components of the iron-containing acidic etching waste solution in this example are as follows: hydrochloric acid, cupric chloride, sodium chloride, ammonium chloride, ferric chloride, ferrous chloride, and water. The iron-containing acidic etching waste solution has an acidity of 1 mol/L, a copper ion concentration of 120 g/L, and a total iron ion concentration of 120 g/L.

The device for recycling an acidic etching waste solution from PCB production through progressive electrolysis was implemented mainly through the following steps:

1. A working etching solution was fed into the anode chamber of the electrolytic cell A and the etching waste solution 251 was fed into the cathode chamber of the electrolytic cell A as starting electrolytes. The ORP controller 7 was arranged in the cathode chamber of the electrolytic cell A. During an electrolysis operation, a set value of the ORP controller 7 was set to 470 mV to control an amount of the etching waste solution 251 fed into the cathode chamber of the electrolytic cell A, such that, at a cathode of the electrolytic cell A, no metallic copper was generated and only a reaction of eliminating a copper-etching agent occurred. An oxidation reaction for a working etching solution occurred in the anode chamber of the electrolytic cell A.

2. A solution in the temporary storage tank 26 was fed into the cathode chambers of the two electrolytic cells B. Electrolytes in the anode chambers of the electrolytic cells B each were circularly mixed with a solution in the temporary storage tank 24 as the circular mixing and exchange tank.

3. The electrolytic power supply 5 and the electrolytic power supplies 6 each were powered on to allow electrolysis operations of the electrolytic cell A and the electrolytic cells B. The ORP controller 7 controlled the feeding of the etching waste solution 251 into the cathode chamber of the electrolytic cell A. The detector 109 as a specific gravity meter in the electrolytic cell B 2-1 controlled the pump 133-13 to feed the overflow solution 268 from the cathode chamber of the electrolytic cell A in the temporary storage tank 26 into the cathode chamber of the electrolytic cell B, and the detector 110 as a photoelectric colorimeter in the electrolytic cell B 2-2 controlled the pump 133-12 to feed a solution in the temporary storage tank 26 into the cathode chamber of the electrolytic cell B, such that copper was electroprecipitated at both cathodes of the electrolytic cells B. The anodes of the electrolytic cells B allowed an electrochemical oxidation reaction for the oxidatively-regenerated etching solution 260, such that the PCB etching production line 257 maintained the etching production by controlling a rotational speed of the pump 133-4 to control a feeding rate. In addition, a small amount of a chlorine gas produced in an anode chamber of each electrolytic cell was adsorbed and mixed with the cathode electrolyte 256 undergoing copper recovery that overflowed from the electrolytic cell B through the spray gas-liquid mixer 76 to prepare the regenerated etching replenishment solution 252.

4. Parameters of the regenerated etching replenishment solution 252 were as follows: an acidity: 6 M/L, a copper ion concentration: 30 g/L, and an iron ion concentration: 120 g/L.

Through the device shown in FIG. 4 and the above steps, a process for 100% recycling an iron-containing acidic etching waste solution from PCB production through progressive electrolysis can be allowed.

Example 5

An acidic etching waste solution was treated with the device shown in FIG. 1.

Main components of the acidic etching waste solution in this example were as follows: hydrochloric acid, cupric chloride, and water. The acidic etching waste solution had an acidity of 3.2 mol/L, a copper ion concentration of 120 g/L, and an ORP value of 500 m V.

Specific steps of this example were as follows:

1. The acidic etching waste solution 251 was fed as a starting electrolyte into the anode chamber and the cathode chamber of the electrolytic cell A. During an electrolysis operation, an amount of the acidic etching waste solution 251 fed into the cathode chamber of the electrolytic cell A was controlled such that cupric ions in the etching waste solution underwent an electrochemical reduction reaction and a solution in the cathode chamber overflowed into the temporary storage tank 25.

3. The electrolytic power supply 5 and the electrolytic power supply 6 were manually powered on to allow electrolysis of the electrolytic cell A and the electrolytic cell B respectively. During an electrolysis process, a chlorine gas was produced in the anode chamber of the electrolytic cell A. The ORP controller 7 was set to control an ORP at 300 mV to monitor the feeding of the acidic etching waste solution 251 into the cathode chamber of the electrolytic cell A, such that a copper-etching agent concentration in the cathode electrolyte in the electrolytic cell A was reduced and no metallic copper was electroprecipitated at the electrolytic cathode of the electrolytic cell A. The detector 103 as a specific gravity meter in the electrolytic cell B monitored the feeding of the overflow solution 268 from the cathode chamber of the electrolytic cell A in the temporary storage tank 25 into the cathode chamber of the electrolytic cell B through the pump 133-3 and controlled a copper ion concentration of the cathode electrolyte of the electrolytic cell B. An anode of the electrolytic cell A and an anode of the electrolytic cell B allowed electrochemical oxidation reactions for the acidic etching waste solution 251 and the cathode electrolyte 256 undergoing copper recovery that overflowed from the electrolytic cell B, respectively. A chlorine gas produced in the anode chambers of the electrolytic cell A and the electrolytic cell B was mixed with a solution in the temporary storage tank 28 through a jet device 71 for oxidation to produce the regenerated etching replenishment solution 252. The cathode electrolyte of the electrolytic cell A underwent a reduction reaction to eliminate a copper-etching agent. Metallic copper 253 was electroprecipitated at the cathode of the electrolytic cell B. The cathode electrolyte 256 undergoing copper recovery that overflowed from the electrolytic cell B was oxidized at the anode of the electrolytic cell B to prepare a regenerated etching replenishment solution.

4. Parameter values of the regenerated etching replenishment solution were as follows: an acidity: 4.0 M/L, a copper ion concentration: 60 g/L, and an ORP value: 520 mV.

Through the device shown in FIG. 1 and the above steps, a process for recycling an acidic etching waste solution from PCB production through progressive electrolysis can be allowed.

Example 6

An acidic etching waste solution was treated with the device shown in FIG. 3 and its partial enlarged view FIG. 3E, FIG. 3F, FIG. 3G, FIG. 3H and FIG. 3K.

Main components of the acidic etching waste solution in this example were as follows: hydrochloric acid, cupric chloride, ammonium chloride, and water. The acidic etching waste solution had an acidity of 2.5 mol/L, a copper ion concentration of 120 g/L, and an ORP value of 520 m V.

Specific steps of this example were as follows:

1. A working etching solution was fed into the anode chamber of the electrolytic cell A and the acidic etching waste solution 251 was fed into the cathode chamber of the electrolytic cell A. The ORP controller 7 was arranged in the cathode chamber of the electrolytic cell A to control an amount of the etching waste solution 251 fed into the cathode chamber of the electrolytic cell A during an electrolysis process, such that an ORP value of the cathode electrolyte of the electrolytic cell A was controlled at 350 mV.

5. After a solution undergoing oxidation entered the temporary storage tank 28, hydrochloric acid and ammonium chloride were fed into the temporary storage tank 28 to prepare a regenerated etching replenishment solution. After being manually tested as qualified, the regenerated etching replenishment solution prepared in the temporary storage tank 28 was pumped by the pump 133-15 into the temporary storage tank 23 for temporary storage. Parameters of the regenerated etching replenishment solution 252 were as follows: an acidity: 6.1 M/L, and a copper ion concentration: 5 g/L.

6. An acidic exhaust gas S from each cell and tank was drained into the exhaust gas treatment tank 281 to allow an environmental protection treatment.

Through the device shown in FIG. 3 and the above steps, a process for 100% recycling an acidic etching waste solution from PCB production through progressive electrolysis can be allowed.

Example 7

An acidic etching waste solution was treated with the device shown in FIG. 4 and its partial enlarged view FIG. 4E, FIG. 4F, FIG. 4G and FIG. 4H.

Main components of the acidic etching waste solution in this example were as follows: hydrochloric acid, cupric chloride, sodium chloride, and water. The acidic etching waste solution had an acidity of 2.7 mol/L, a copper ion concentration of 110 g/L, and an ORP value of 480 mV. Specific steps of this example were as follows:

1. A working etching solution was fed into the anode chamber of the electrolytic cell A and the acidic etching waste solution 251 was fed into the cathode chamber of the electrolytic cell A as starting electrolytes. The ORP controller 7 was arranged in the cathode chamber of the electrolytic cell A. During an electrolysis operation, a set value of the ORP controller 7 was set to 300 mV to control an amount of the acidic etching waste solution 251 fed into the cathode chamber of the electrolytic cell A, such that, at a cathode of the electrolytic cell A, no metallic copper was generated and only a reaction of eliminating a copper-etching agent occurred. An oxidation reaction for a working etching solution occurred in the anode chamber of the electrolytic cell A.

4. Parameters of the regenerated etching replenishment solution 252 were as follows: an acidity: 5.2 M/L, and a copper ion concentration: 30 g/L.

Through the device shown in FIG. 4 and the above steps, a process for 100% recycling an acidic etching waste solution from PCB production through progressive electrolysis can be allowed.

Example 8

FIG. 5 and its partial enlarged view FIG. 5E, FIG. 5F, FIG. 5G, FIG. 5H and FIG. 5K show Example 8 of a method and device for recycling an acidic etching waste solution from PCB production through progressive electrolysis. The device includes two electrolytic cells A 1-1 and 1-2, two electrolytic cells B 2-1 and 2-2, an ORP controller 7-1 arranged in a cathode chamber of an electrolytic cell A 1-1, an ORP controller 7-2 arranged in a cathode chamber of an electrolytic cell A 1-2, electrolytic cell separators 3-1 and 3-2 for an electrolytic cells A, electrolytic cell separators 4-1 and 4-2 for the electrolytic cells B, two electrolytic power supplies 5-1 and 5-2, two electrolytic power supplies 6-1 and 6-2, temporary storage tanks 23 to 28, 9 overflow buffer tanks, a water-oil separator 96, detectors 101 to 116, an automatic feeding controller 131, a valve 132, a pump 133, an exhaust gas treatment tank 281, a cathode-chamber etching-waste-solution feeding pipe 134, an acidic etching waste solution 251, a regenerated etching replenishment solution 252, recovered metallic copper 253, cathode electrolytes 256 undergoing copper recovery that overflow from the electrolytic cells B, a PCB etching production line 257, an oxidatively-regenerated etching solution 260, and overflow solutions 268 from the cathode chambers of the electrolytic cells A.

The two electrolytic cell separators 3-1 and 3-2 for an electrolytic cells A both are anion exchange membranes. The two electrolytic cell separators 4-1 and 4-2 for the electrolytic cells B both are anion exchange membranes.

For both of the two electrolytic cells A 1-1 and 1-2, an anode material is a titanium-based coated insoluble anode and a cathode material is metallic titanium.

For both of the two electrolytic cells B 2-1 and 2-2, an anode material is a titanium-based coated insoluble anode and a cathode material is a metallic copper sheet.

Detectors 101, 111, 112, and 113 all are specific gravity meters, detectors 102 and 114 are acidity meters, detectors 103, 106, 109, and 111 are ORP meters, detectors 104 and 107 are thermometers, and detectors 105, 108, 110, and 116 are liquid level meters. Field data of all detectors are transmitted to the automatic feeding controller 131 for processing, and the whole device is controlled to work according to programs.

The detectors 101, 102, 103, and 104 are arranged in the PCB etching production line 257. The detector 101 as a specific gravity meter controls a pump 133-1 to feed the regenerated etching replenishment solution 252 to allow a chloride concentration control for a working etching solution. The detector 102 as an acidity meter controls a valve 132-2 to feed hydrochloric acid 283 to control an acidity of a working etching solution. The detector 103 as an ORP meter controls a rotational speed of a variable-frequency pump 133-4 to make an ORP of a working etching solution controlled at 530 mV according to a process. The detector 104 as a thermometer controls a temperature of a working etching solution at 50° C. Therefore, through the controlled feeding above, a working etching solution of the PCB etching production line 257 maintains an acidity of 0.9 mol/L, a specific gravity of 1.35 g/mL, and an ORP of 530 mV to stabilize the etching performance.

An etching waste solution overflowing from the PCB etching production line 257 first flows into the water-oil separator 96 for separation of organic matters including inks and film residues, then flows into a liquid flow buffer tank 51, and then is pumped by a pump into a temporary storage tank 24 as a circular mixing and exchange tank. When the temporary storage tank 24 is full of the oxidatively-regenerated etching solution 260, the detector 105 as a liquid level meter controls a pump 133-7 to pump a part of a solution in the temporary storage tank 24 into the temporary storage tank 25 for temporary storage.

Working states of the two electrolytic cells A 1-1 and 1-2 are under associated control by field detection values of liquid level meters 110 and 116, respectively. The electrolytic cell A 1-2 is configured to allow electrolytic oxidation for a solution 256 undergoing copper recovery from the electrolytic cell B to produce a regenerated etching replenishment solution.

The circular mixing and exchange tank, namely, the temporary storage tank 24, is connected with the PCB etching production line 257 through a circulating liquid pipeline, and is connected with anode chambers of the electrolytic cell A 1-1 and the electrolytic cells B 2-1 and 2-2 through circulating liquid pipelines. A solution in the circular mixing and exchange tank is the oxidatively-regenerated etching solution 260. An ORP value of the oxidatively-regenerated etching solution 260 in the temporary storage tank 24 is transmitted as a field parameter to the automatic feeding controller 131 for processing by the detector 106 as an ORP meter, and working currents of the electrolytic power supply 5-1 and the electrolytic power supplies 6-1 and 6-2 are adjusted accordingly, such that an ORP value of the oxidatively-regenerated etching solution 260 is controlled at 750 mV to 850 mV.

The ORP controllers 7-1 and 7-2 control pumps 133-14 and 133-13 to feed the etching waste solution 251 in the temporary storage tank 25 into the cathode chambers of the two electrolytic cells A, and an overflow solution 268 undergoing an electrolytic treatment is pumped by a pump into a temporary storage tank 26 for temporary storage. During an electrolysis operation, because no metallic copper is electroprecipitated at two cathodes of the two electrolytic cells A, a copper ion concentration of a solution in the temporary storage tank 26 is still about 140 g/L.

The electrolytic cells B 2-1 and 2-2 are electrolytic cells for progressive electrolysis to allow copper recovery. For the electrolytic cells B 2-1 and 2-2, the electrolysis for copper recovery is allowed at a cathode, and the oxidatively-regenerated etching solution 260 is produced through oxidation at an anode to maintain the proceed of etching. The detectors 111 and 112 as specific gravity meters control pumps 133-18 and 133-17 to feed the overflow solutions 268 from the cathode chambers of the two electrolytic cells A in a temporary storage tank 26 into cathode chambers of the electrolytic cells B 2-1 and 2-2 to allow progressive electrolysis for copper recovery. Copper ion concentrations in cathode electrolytes of the electrolytic cells B 2-1 and 2-2 both are controlled at a set value of 40 g/L, and the metallic copper 253 is electroprecipitated at both cathodes of the electrolytic cells B 2-1 and 2-2.

The cathode electrolytes 256 undergoing copper recovery that overflow from the electrolytic cells B 2-1 and 2-2 are pumped into a temporary storage tank 27, and then a solution in the temporary storage tank 27 is pumped by a pump 113-23 into a temporary storage tank 28 for preparation under the control of the detector 113 as a specific gravity meter and the detector 114 as an acidity meter. The paddle stirrer 92 is started, and hydrochloric acid 283, ammonium chloride 285, and ferric hydroxide 297 are fed into the temporary storage tank 28 to prepare an anode electrolyte of the electrolytic cell A 1-2.

The cathode-chamber etching-waste-solution feeding pipes 296 and 297 of the electrolytic cells B 2-1 and 2-2 are configured to feed an etching waste solution for a reaction to remove a cuprous chloride sludge on the electrolytic cell separators 4-1 and 4-2 for the electrolytic cells B, thereby preventing the electrolytic cell separators for an electrolytic cells B from being blocked by the cuprous chloride sludge.

An exhaust gas is introduced by a spray tower into the exhaust gas treatment tank 281 for a treatment.

The device for recycling an acidic etching waste solution from PCB production through progressive electrolysis was implemented mainly through the following steps:

1. A working etching solution was fed into the anode chamber of the electrolytic cell A 1-1 and the etching waste solution 251 was fed into the cathode chamber of the electrolytic cell A 1-1 as starting electrolytes. An anode electrolyte of the electrolytic cell A 1-1 was circularly mixed with a solution in the circular mixing and exchange tank. An etching replenishment solution to be oxidatively regenerated (the solution in the temporary storage tank 28) was fed into the anode chamber of the electrolytic cell A 1-2. The detector 101 as a liquid level meter was arranged in the anode chamber of the electrolytic cell A 1-1, the detector 109 as an ORP meter was arranged in the anode chamber of the electrolytic cell A 1-2, and ORP controllers 7-1 and 7-2 were arranged in the cathode chambers of the two electrolytic cells A, respectively.

3. The electrolytic power supplies 5-1 and 5-2 for the two electrolytic cells A and the electrolytic power supplies 6-1 and 6-2 for the two electrolytic cells B each were powered on to allow electrolysis operations of the two electrolytic cells A and the two electrolytic cells B. Set values of the ORP controllers 7-1 and 7-2 both were set to 480 mV to control the feeding of the iron-containing acidic etching waste solution 251 into the cathode chambers of the two electrolytic cells A, such that no metallic copper was produced and only a reaction of eliminating a copper-etching agent occurred at the cathodes of the two electrolytic cells A, and an anode electrolyte underwent an oxidation reaction at the anodes of the two electrolytic cells A. The detector 111 as a specific gravity meter in the electrolytic cell B 2-1 controlled the pump 133-18 to feed the overflow solution 268 from the cathode chamber of the electrolytic cell A in the temporary storage tank 26 into the cathode chamber of the electrolytic cell B 2-1, and the detector 112 as a specific gravity meter in the electrolytic cell B 2-2 controlled the pump 133-17 to feed a solution in the temporary storage tank 26 into the two cathode chambers of the electrolytic cells B, such that copper was electroprecipitated at both cathodes of the electrolytic cells B 2-1 and 2-2. The anodes of the electrolytic cells B 2-1 and 2-2 allowed an electrochemical oxidation reaction for the oxidatively-regenerated etching solution 260, such that the PCB etching production line 257 maintained the etching production by controlling a rotational speed of the pump 174 to control a feeding rate. During an electrolysis process, it was controlled by metering pumps in a time-dependent manner to feed a small amount of the etching waste solution 251 into the cathode chambers of the electrolytic cells B 2-1 and 2-2 respectively to remove cuprous chloride on the electrolytic cell separators for the electrolytic cells B.

4. Cathode overflow solutions of the two electrolytic cells B were collected in the temporary storage tank 27. According to data detected by the detectors 113 and 114 in the temporary storage tank 28, the solution 256 was fed into the temporary storage tank 28, and then hydrochloric acid, ammonium chloride, and ferric hydroxide were fed into the temporary storage tank 28 to prepare the anode electrolyte of the electrolytic cell A 1-2.

5. According to field detection values of the detector 109 as an ORP meter, the pump 133-24 was controlled to feed a solution in the temporary storage tank 28 into the anode chamber of the electrolytic cell A 1-2, such that a regenerated etching replenishment solution meeting a process requirement was prepared through electrochemical oxidation and recycled in etching production.

Through the device shown in FIG. 5 and the above steps, a process for 100% recycling an acidic etching waste solution from PCB production through progressive electrolysis can be allowed.

In FIG. 6 and FIG. 7, a metallic copper recovered by the method of the present disclosure and a metallic copper produced by the existing technology where an etching waste solution is added to a cathode chamber are respectively shown.

Number	Date	Country	Kind
202210514166.X	May 2022	CN	national
202210840486.4	Jul 2022	CN	national
202320019094.1	Jan 2023	CN	national

	Number	Date	Country
Parent	PCT/CN2023/093720	May 2023	WO
Child	18944020		US

METHOD AND DEVICE FOR RECYCLING ACIDIC ETCHING WASTE SOLUTION THROUGH PROGRESSIVE ELECTROLYSIS

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CROSS REFERENCE TO RELATED APPLICATIONS

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