Method for the Removal and Recovery of Metals and Precious Metals from Substrates

Abstract

A method for removing metal and/or precious metal-containing depositions from substrates, wherein said substrate is subjected to treatment with an organo amine protectant component P and an inorganic active component A. Component P may be formed in situ by reaction with component R. Component P is an organic amine and/or organic amine hydrohalide and/or organic ammonium halide (preferably diisopropylamine hydrochloride), component A is an inorganic compound (preferably inorganic acid or a mixture thereof) and component R is an organic compound that can be split along the C—N bond by the component A into an organic amine (preferably dimethylformamide or N-methyl pyrrolidone). The metals in the form of organo-metallic complexes and/or metalorganic compounds are isolated and/or separated by means of different chemical reactions (preferably reduction reactions) and/or biosorption (preferably with seaweed or yeast). The isolated and/or separated organo-metallic complexes and/or metalorganic compounds are subjected to refinement process to form pure metals and/or pure precious metals. The substrates remain intact after the treatment.

Description

FIELD OF THE INVENTION

Traditionally it has been a challenge to remove thick and or multiple layers of depositions of metals and precious metals from various types of substrates. Current methods typically involve manually or mechanically removing depositions, including precious metal layers, which can damage substrates. Other methods can include the use of aggressive or poisonous chemicals to remove the precious metals that can also damage or destroy the substrate or that may not remove the entire deposition from the substrate. Therefore, it was desirable to develop a chemical method to remove layers of depositions, including precious metals, form various types of substrates.

Traditionally, separating different precious metals and metals has been a challenging if not impossible task. This has led to the loss of precious metals due to the lack of a viable method to separate then once they have been chemically changed from a metal to a compound in solution. Therefore, it was desirable to develop a chemical method to selectively remove metals and precious metals from a solution. Selective biomass sorption of metals and precious metals has been studied in the prior art. Hydrometallurgy 2010, 103, 180-189. Nilanjana, D.; Recovery of Precious Metals Through Biosorption, deals with biosorption in recovery of precious metals from aqueous solutions. The metal binding mechanism, as well as the parameters influencing the uptake of precious metals and isotherm modeling, is presented. Biotechnology Advances 2007, 25, 264-271, Mack, C.: Wilhelmi, B. Duncan, J. R., Burgess, J. E.; Biosorption of Precious Metals, reviews recent research regarding the biosorption of some precious metals, with emphasis on the effects of the biosorption environment and the biosorption mechanism identified. Biotechnology Advances 2006, 24, 427-451. Wang, J., Chen, C.; Biosorption of Heavy Metals by Saccharomyces cerevisae: A Review, elucidates the mechanism of metal uptake. Various mechanism assumptions of metal uptake by S. cerevisiae are summarized. Kvasinky, Bachelor's thesis, Marketa Novakova, 2010, deals with Saccharomyces cerevisiae, and summarizes cell biological study, and its genome, reproduction, growth conditions, and metabolism.

STATEMENT OF THE INVENTION

This invention concerns use of organo amines, to protect a substrate from damage during the removal of a deposition consisting of one or more layers of metal and/or precious metals adhered to the substrate. Once in solution, it is disclosed in this invention to use certain types of reduction methods and/or biomass materials to extract and separate the different types of metals and/or precious metals. The use of inorganic nitrogen compounds is also contemplated for use with the present invention.

The invention provides a method to remove depositions, including metals and precious metals such as gold and/or platinum and/or silver and/or palladium and/or indium, from a substrate without damaging the substrate and/or efficiently extract it from different substrates.

The invention would be a suitable replacement for aqua regia, a known powerful acid traditionally used to recovery gold and platinum. Additionally, the invention provides a method for the removal/extraction/separation of metals and precious metals from different abrasive blasting media and from solutions of mixtures of metals and precious metals, from ores, and from other sources.

The invention will allow for the recovery of gold, platinum, silver, palladium, indium and other metals and precious metals utilizing a chemical method of stripping, separation, and purification from different substrates that results in high yields and purity while preserving the substrates. The invention may be used either in a batch process for treatment of discrete materials with coatings or in a continuous process for materials in long rolls. The invention has the potential to offer “green technology” by allowing the recovery and recycling of substrates, especially polymeric substrates that are normally destroyed when recovering precious metals and by avoiding the use of poisonous chemicals (cyanides for instance) while extracting gold and platinum from ores.

The invention consists of two chemical constituents: a PROTECTANT “P” and an ACTIVE chemical “A” that function to remove a layer and/or multiple layers of depositions, including metals and/or precious metals, from various types of substrates while not damaging the substrate. PROTECTANT agent “P” functions in the reaction as a surface protectant for the substrate. Additionally, PROTECTANT agent “P” can function as a COMPLEXING agent “C” with metals that are oxidized and/or form other metal compounds. The PROTECTANT agent “P” may be added to the reaction directly or created in situ by the chemical reaction between REAGENT “R” and the ACTIVE chemical “A”. Since the PROTECTANT agent “P” protects the surface of the substrate, it allows the ACTIVE chemical “A” to be a chemical or mixture of chemicals (such as aqua regia) that would otherwise damage the substrate while dissolving or separating the precious metals from the substrate.

It has turned out that the protectant function according to the invention is best performed by mono-, di-, tri-substituted amines and/or their hydrohalides and/or tetra-substituted ammonium halides, wherein each substituent is independently an alkyl, a cycloalkyl or a substituted alkyl. The term “alkyl” as used herein means an aliphatic linear or branched group having 1 to 18 carbon atoms. The term “cycloalkyl” herein means a cyclic aliphatic group having 3 to 8 carbon atoms. The term “substituted alkyl” as used herein means an aliphatic linear or branched group having 1 to 18 carbon atoms substituted by different functional groups, such as hydroxy-group and/or carboxy-group and/or hydroxy and carboxy group,

Examples of surface PROTECTANT “P”/COMPLEXING agent “C” chemical include the organo-amines such as trimethylamine hydrochloride ((CH₃)₃N.HCl), dimethylamine hydrochloride ((CH₃)₂NH.HCl), methylamine hydrochloride (CH₃NH₂.HCl), triethylamine hydrochloride ((CH₃CH₂)₃N.HCl), dimethylamine hydrochloride ((CH₃CH₂)₂NH.HCl), methylamine hydrochloride (CH₃CH₂NH₂.HCl), cyclohexylamine hydrochloride (C₆H₁₁NH₂.HCl), dicyclohexylamine hydrochloride ((C₆H₁₁)₂NH.HCl), N,N-dimethylcyclohexylamine hydrochloride (C₆H₁₁N(CH₃)₂.HCl), diisopropylamine hydrochloride ((CH₃)₂CHNHCH(CH₃)₂.HCl), N-ethylcyclohexylamine hydrochloride (C₆H₁₁NC₂H₅.HCl), N-methylcyclohexylamine hydrochloride (C₆H₁₁NCH₃.HCl), glycine betaine hydrochloride (CH₃)₃N⁺CH₂COOH.Cl⁻, choline chloride [(CH₃)₃NCH₂CH₂OH]Cl, carnitine hydrochloride (CH₃)₃N(Cl)CH₂CH(OH)CH₂COOH, tetraethylammonium bromide [(CH₃CH₂)₄N]Br, tetra-n-butylammonium fluoride (CH₃CH₂CH₂CH₂)₄NF, methylamine hydroiodide (CH₃NH₂.HI), etc.

Examples of REACTIVE “R” surface protectant/COMPLEXING “C” agents that can form amines in situ include dimethylformamide (DMF)-C₃H₇NO) and N-methyl pyrrolidone (NMP)-C₅H₉NO, and other organic compounds (such as amides and/or lactams) that can be split along the C—N bond into an amine and other organic compound (such as dimethylamine and formic acid in case of DMF).

Examples of ACTIVE chemical “A” include inorganic acids and mixtures thereof from the group consisting of nitric acid (HNO₃) and/or hydrofluoric acid (HF), and/or hydrochloric acid (HCl) and/or phosphoric acid (H₃PO₄), and/or fluorosilicic acid (H₂SiF₆), and/or ammonium peroxydisulfate ((NH₄)₂S₂O₈), and/or sulfuric acid (H₂SO₄), and other inorganic compounds that can cause splitting organic compounds (such as amides and/or lactams) along the C—N bond into organic amine(s) and other organic compounds and/or can dissociate any amine hydrochloride into the PROTECTANT “P” and COMPLEXING agent “C” to allow its dual action (protecting and complexing).

Examples of substrates include aluminum, copper, steel, stainless steel, glass, titanium, their alloys, graphite, carbon fibre, ceramic, fused silica, quartz, blasting media (such as corundum, sand, corn cob, plastic abrasives, silicon carbide, pumice, steel grit, steel shot, walnut shells, soda, and glass beads), polymers (such as PEEK, PET, polyimide, polyether, etc.) and ores.

The following equations illustrate the two chemical reaction mechanisms:

[Deposition on Substrate]+P/C+A→Deposition (in solution) or Deposition-C (in solution)+Substrate-P+Solution[Deposition on Substrate]+R/C+A→Deposition (in solution) or Deposition-C (in solution)+Substrate-P+Solutionwhere Deposition=one or more selected from Be, Mg, Ca, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, In, Tl, C, Si, Sn, N, P, As, S, Se, Te, and their mixtures, and/or their chemical compounds.

Once the depositions have been separated from the substrate and dissolved and/or extracted into solution, separating the different precious metals has traditionally been a challenging if not impossible task. One method to remove metals from solution is the use of biomass materials to selectively biosorb reaction products that were originated in situ by chemical reactions between the deposition and/or “P” and/or “R” and/or “A”. The use of biomass materials allows one to reclaim metals and/or precious metals that would have otherwise been difficult and/or unsafe to separate. Specifically, certain types of biomass materials are able to bind and concentrate metals from aqueous solutions. A biosorption-based process offers a number of advantages including low cost, selective metal reclamation, high efficiency in metal complexation and high purity of the final metal.

This invention consists of using selected biosorbants to recover metals and/or precious metals and/or their chemical compounds. Examples of selective biosorbants include seaweed (ie Spirulina platensis) and yeast (i.e. Saccharomyces cerevisiae).

The following equations illustrate the selective chemical reaction mechanisms:

[Mixture of M's (X,Y,Z)] (in solution)+Bioadsorbant (I)→[M (X)+Bioadsorbant]+[Mixture of M's (Y,Z)] (in solution[Mixture of M (X,Y,Z)] (in solution)+Bioadsorbant (II)→[M (Y)+Bioadsorbant]+[Mixture of M's (X,Z)] (in solution)where M=Metals and/or Precious Metals and/or their chemical compoundsX,Y,Z=Mixture of Metals and/or Precious Metals and/or their chemical compounds

BRIEF DESCRIPTION OF FIGURES

FIG. 1 depicts an apparatus for recovering gold from a PET substrate. The PET substrate is provided in spooled rolls.

FIGS. 2 and 3, the gold-hued PET is fed from the roll to a first station where it is soaked in a cleaning solution that was made in accordance with the teachings of the present invention.

FIG. 4, the substrate is passed from the first station to a second station that is filled with water. By passing the substrate through the second station, the majority of the solution from the first station is removed.

FIG. 5, the substrate is passed through a series of rollers to remove the rest of the cleaning solution and subsequently passed through a water mist. The liquids from all stations are subjected to a gold recovery process including reduction.

FIG. 6, the illustrated rolls are 425 meters long and two such rolls can be processed in approximately 90 minutes in the illustrated continuous process.

FIG. 7, approximately 187 g of gold are recovered for every 100 kg of the PET substrate.

FIG. 8 illustrates a batch process for cleaning a substrate and recovering the gold plating. Gold-plated substrates are soaked in a cleaning solution that was made in accordance with the teachings of the present invention. Before submersions, the sheets have a metallic hue.

FIG. 9, after briefly soaking the substrate, the metallic hue is gone and the substrate is white.

FIG. 10 provides a depiction of one submerged substrate (white) and one pre-treated substrate (metallic).

FIG. 11, after soaking, the residual cleaning solution is removed from the substrate by rising with water.

FIG. 12 depicts the cleaned, white substrate. The gold layer was removed without damaging the substrate, including notes that were written on the substrate.

FIG. 13 provides another depiction of the metallic substrate prior to treatment.

FIG. 14 depicts an aqua regia solution dissolving a copper substrate. The copper wire gets dissolved within 40 minutes.

FIGS. 15 and 16 illustrates the addition of DMF to the aqua regia solution and the subsequent inability of the DMF solution to rapidly dissolve the copper wire (FIG. 16). The copper wire stays intact long enough until the aqua regia dissolves a possible deposition.

FIG. 17 depicts a copper part plated with gold, platinum and titanium. After two days of soaking in the inventive cleaning solution followed by brush cleaning, the majority of the metal layer was removed without damaging the copper.

FIGS. 18 and 19, the copper part is intact, i.e. the aqua regia selectively etched the deposition only, while DMF served as surface protectant.

FIG. 20 depicts an aluminum part plated with SiOx deposits. In order to etch the SiO_x the aluminum part was treated with DMF and a mixture of phosphoric acid and hydrofluoric acid (where the organo-amine is formed in-situ).

FIG. 21, a layer of black material was visible on the surface of the aluminum which was rinsed away with water.

FIG. 22 depicts the aluminum part undamaged from this treatment method. Without wishing to be bound to any particular theory, applicant believes this black material is a protective layer that prevents damage to the aluminum part.

FIGS. 23-27 depict that a multilayer deposition of gold, platinum, titanium, and aluminum has been dissolved and removed from a stainless steel substrate using an organo-amine and nitric acid. FIG. 23 depicts parts feeding into the reaction mixture (etching solution). The ratio of chemicals stays the same every time a fresh solution is prepared. All 4 of the metals were successfully dissolved/removed from the stainless steel substrate without damage to the substrate (FIG. 27).

FIG, subsequently, the gold was separated from the platinum, titanium, and aluminum using gold reduction methods; addition of the reducing agent;

FIG. 29 shows filtration of the solution with gold powder;

FIG. 30-31 shows cleaning the melted gold's surface from residues), and purified to 99.99% minimum purity;

FIGS. 31-34 show the platinum was separated from the titanium/aluminum solution using a biosorption method (for example, using yeast, FIGS. 32 through 34).

EXAMPLES

Example 1—Comparative

A sample of nitric acid (50%) and hydrochloric acid (31%) was prepared (1:1 volume ratio). Several pieces of copper wire were added to this solution. The copper wire completely dissolved within 40 minutes.

Example 2

A 20 mL sample of nitric acid (50%) and 20 mL hydrochloric acid (31%) was prepared in 200 mL N,N-dimethylformamide (DMF). Several pieces of copper wire were added to this solution. The copper wire showed no signs of dissolving within 40 minutes.

Example 3

A sample of 100 mL nitric acid (50%) and 300 mL hydrochloric acid (31%) was prepared in 4 L N,N-dimethylformamide (DMF). A solid piece of copper was coated with an alloy of gold, platinum and titanium. The copper was soaked in the sample solution for fourteen days at room temperature. The copper was removed from the solution and rinsed and manually washed to remove residual protective coating. The resulting copper appeared free of gold, platinum and titanium. There was no visible damage to the copper.

Example 4—Comparative

A sample of phosphoric acid (50%) and hydrofluoric acid (50%) was prepared. A piece of aluminum foil was added to this solution. The aluminum completely dissolved within 20 minutes.

Example 5

A sample of 25 mL phosphoric acid (50%) and 25 mL hydrofluoric acid (50%) was prepared in 400 mL N,N-dimethylformamide (DMF). A piece of aluminum foil was added to this solution. The aluminum showed no signs of dissolving within 20 minutes.

Example 6

A sample of 30 L phosphoric acid (50%) and 30 L hydrofluoric acid (50%) was prepared in 200 L N,N-dimethylformamide (DMF). A sheet of aluminum was coated with a SiOx deposition. The aluminum was soaked in the sample solution for ten days at room temperature. The aluminum was removed from the solution and rinsed and manually washed to remove residual protective coating. The resulting aluminum appeared free of the SiOx deposits. There was no visible damage to the aluminum.

Example 7

A gold-coated polyethylene terephthalate (PET) substrate (57.6 kg) was provided as a rolled thin-film. The film was sequentially rolled through the solution 50 L of nitric acid (50% diluted) and 3.5 kg of trimethylamine hydrochloride at a rate of about 9 meters per minute. The film was rinsed under a stream of water to remove trace acid. After processing, the gold-color was no longer visible on the film and the cleaning agents were gold-colored. There was no visible damage to the PET substrate.

Example 8

A provided stainless steel substrate coated with gold, platinum, titanium and aluminum (44 parts of different weights and sizes) was submerged into an etching mixture of 240 L of nitric acid (50%) and 16 kg of trimethylamine hydrochloride. All layers of gold, platinum, titanium, and aluminum dissolved in the etching mixture within 3 hours to 30 days depending on the thickness of the layers. There was no visible damage to the stainless steel parts. The solution was subsequently subjected to a reduction and refinement process that separated the gold from the other metals and refined the gold to 99.99% minimum purity. To the remaining solution containing platinum, titanium, and aluminum yeast (Saccharomyces cerevisiae) was added in the ratio of 1 kg of yeast per 200 liters of the solution. The organo-platinum complex and/or metalorganic compound of platinum was left to selectively bioadsorb onto the yeast for one day to successfully separate the platinum from the other metals. Then yeast/organo-platinum adsorbate mix was then filtered off and burned at 1500° C. The remaining platinum oxide was isolated, pressed into pellets, and vacuum melted into platinum metal.

Example 9

The gold containing solutions of example 7 and 8 were subjected to a reduction and refinement protocol to provide 99.99% minimum purity gold—107.75 g of gold (187 g Au per 100 kg of the PET strip). The following describes the reduction and refinement protocol.

Example 10—Comparative

Three pieces of gold of similar shape, each 30 grams, were submerged into three etching mixtures. Each mixture consisted of 15 liters of nitric acid (50%) and (1) 1 kg of trimethylamine hydrochloride, (2) 1 kg of dimethylamine hydrochloride, (3) 1 kg of methylamine hydrochloride. The speed of gold dissolutions were measured over the period of two weeks and compared. The experiments suggested that the amine hydrochloride ability to dissolve and/or etch gold decreases in the trimethylamine hydrochloride>dimethylamine hydrochloride>methylamine hydrochloride order. The speeds were: 0.81 g>0.65 g>0.52 g of gold weight loss per day (room temperature, no stirring).

Example 11—Comparative

Five pieces of gold of similar shape, each 30 grams, were submerged into five etching mixtures. Each mixture consisted of 15 liters of nitric acid (50%) and (1) 1 kg of triethylamine hydrochloride, (2) 1 kg of diisopropylamine hydrochloride, (3) 1 kg of N-ethylcyclohexylamine hydrochloride, (4) 1 kg of dibutylamine hydrochloride and (5) 1 kg of trimethylamine hydrochloride. The speed of gold dissolutions were measured over the period of two weeks and compared. The experiments suggested that the amine hydrochloride ability to dissolve and/or etch gold decreases in the diisopropylamine hydrochloride>dibutylamine hydrochloride>triethylamine hydrochloride>N-ethylcyclohexylamine hydrochloride>trimethylamine hydrochloride order. The speeds were: 2.03 g>1.78 g>1.53 g>1.51 g>0.81 g of gold weight loss per day (room temperature, no stirring).

Example 12—Comparative

Two pieces of gold of similar shape, each 30 grams, were submerged into two etching mixtures. Each mixture consisted of 15 liters of nitric acid (50%) and (1) 1 kg of N-ethylcyclohexylamine hydrochloride, purchased commercially, and (2) 1 kg of N-ethylcyclohexylamine hydrochloride, prepared in situ by mixing appropriate amounts of N-ethylcyclohexylamine and hydrochloric acid, followed by adding the nitric acid. The speed of gold dissolutions were measured over the period of two weeks and compared. The speeds were: 1.51 g/1.50 g per day (room temperature, no stirring). The experiments suggested that there is no difference in ability to dissolve and/or etch gold between the commercial and in situ prepared chemical.

Example 13

A gold-, silver-, indium-coated ethylene vinyl acetate (EVA) substrate (30 kg) was provided as a rolled thin-film. The film was sequentially rolled through the solution 25 L of nitric acid (50% diluted) and 1.5 kg of carnitine chloride at a rate of about 6 meters per minute. The film was rinsed under a stream of water to remove trace acid. After processing, there was no visible damage to the EVA substrate. The dark-color was no longer visible on the EVA film and the etching agents were yellow-colored and there was a visible precipitate of a silver salt. The silver salt was removed from the solution, rinsed, washed and subjected to refinement process to deliver silver in 99.9 minimum purity. The remaining solution containing indium and gold was subsequently subjected to a reduction and refinement process that separated the gold from indium and refined the gold to 99.99% minimum purity. The remaining solution containing indium was subsequently subjected to a treatment with sodium hydroxide (NaOH) and formic acid (HCOOH). The precipitate of an indium complex and/or metalorganic compound of indium was subsequently subjected to refinement process to obtain the indium in 99.9% minimum purity. The yields of silver, gold and indium were quantitative.

Example 14

A provided stainless steel substrate coated with gold, platinum, palladium, nickel, copper, and zinc was submerged into an etching mixture 6 L of nitric acid (50% diluted) and 0.5 kg of glycine betaine hydrochloride. All layers of gold, platinum, palladium, nickel, copper, and zinc dissolved in the etching mixture within 3 hours. There was no visible damage to the stainless steel substrate. The solution was subsequently subjected to a reduction and refinement process that separated the gold from platinum and palladium and from nickel, copper, and zinc, and refined the gold to 99.99% minimum purity. To the remaining solution containing platinum, palladium, nickel, copper, and zinc yeast (Saccharomyces cerevisiae) was added in the ratio of 0.05 kg of yeast per 10 liters of the solution. The organo-platinum complex and/or metalorganic compound of platinum was left to selectively bioadsorb onto the yeast for one day to successfully separate the platinum from the other metals. The yeast/organo-platinum adsorbate was then filtered off and burned at 1500° C. The remaining platinum oxide was isolated, pressed into pellets, and vacuum melted into platinum metal. The remaining solution containing palladium, nickel, copper, and zinc was subsequently subjected to a treatment with sodium hydroxide (NaOH) and acetic acid (CH₃COOH). The precipitate of a palladium complex and/or metalorganic compound of palladium was subsequently subjected to refinement process to obtain the palladium in 99.9% minimum purity. The yields of gold, platinum and palladium were quantitative.

Example 15

A provided ceramic substrate coated with indium, iron, arsenate vanadium, magnesium, calcium, chromium, yttrium, thallium and manganese, was submerged into an etching mixture 6 L of nitric acid (50% diluted) and 0.5 kg of tetraethylammonium bromide. All layers of indium, iron, arsenate, vanadium, magnesium, calcium, chromium, yttrium, thallium and manganese, dissolved in the etching mixture within 3 hours. There was no visible damage to the ceramic substrate. The solution containing indium, iron, arsenate vanadium, magnesium, calcium, chromium, yttrium, thallium and manganese was subsequently subjected to a treatment with sodium hydroxide (NaOH) and formic acid (HCOOH). The precipitate of an indium complex and/or metalorganic compound of indium was subsequently subjected to refinement process to obtain the indium in 99.9% minimum purity. The yield of indium was quantitative.

Example 16

A provided glass substrate coated with palladium, beryllium, zirconium, niobium, tantalum and molybdenum was submerged into an etching mixture 6 L of nitric acid (50% diluted) and 0.5 kg of methylamine hydroiodide. All layers of palladium, beryllium, zirconium, niobium, tantalum and molybdenum dissolved in the etching mixture within 3 hours. There was no visible damage to the glass substrate. The solution containing palladium, beryllium, zirconium, niobium, tantalum and molybdenum was subsequently subjected to a treatment with sodium hydroxide (NaOH) and acetic acid (CH₃COOH). The precipitate of a palladium complex and/or metalorganic compound of palladium was subsequently subjected to refinement process to obtain the palladium in 99.9% minimum purity. The yield of palladium was quantitative.

Example 17

A provided blasting sand with gold, carbide, yttrium, tungsten, gallium, sulfate and selenium was submerged into an etching mixture 6 L of nitric acid (50% diluted) and 0.5 kg of tetra-n-butylammonium fluoride. Gold, carbide, yttrium, tungsten, gallium, sulfate and selenium dissolved in the etching mixture within 3 hours. The solution was subsequently subjected to a reduction and refinement process that separated the gold from the other metals and refined the gold to 99.99% minimum purity. The yield of gold was quantitative.

Example 18

A provided carbon fiber precision parts coated with silver, cadmium, borate, silicon, tin, nitride, phosphate and tellurium was submerged into an etching mixture 6 L of nitric acid (50% diluted) and 0.5 kg of choline chloride. All layers of silver, cadmium, borate, silicon, tin, nitride, phosphate and tellurium dissolved in the etching mixture within 3 hours. There was no visible damage to the carbon fibre precision parts. A precipitate of a silver salt was visible in the solution after the etching. The silver salt was removed from the solution, rinsed, washed and subjected to refinement process to deliver silver in 99.9 minimum purity.

Reduction and Refinement of Gold Recovered from a Substrate

Once the gold has been removed from a substrate and is in solution as a complex and/or metalorganic compound, it must then be reduced through chemical treatment to form elemental gold.

Reduction of the gold is accomplished as follows. Dilute the gold solution with between 60% to 80% by volume of the solution with distilled water. Then add a saturated aqueous solution of urea (H₂NCONH₂) to the diluted solution of gold (5 kg per 250 liters of solution) to destroy the nitric acid, HNO₃. Neutralization of the solution is determined by standard methods such as pH, titration, visual, or by other methods. Once the solution has been neutralized, hydroxylamine hydrochloride, NH₂OH.HCl, is added to the solution at room temperature. Addition of the hydroxylamine hydrochloride is done in 5 kg quantities until all of the gold has been precipitated from solution. Likewise, the hydroxylamine hydrochloride is added in 5 kg quantities so as to avoid any hazards in adding too much of the reducing agent too quickly. The presence of gold in the solution is tested on a small sample of solution using tin chloride, SnCl₂. If gold is still present, a dark brown/black precipitate will form with the addition of tin chloride. If no gold is present, the color of the solution will stay the same and be free of precipitate. Once all of the gold has been precipitated from solution, most of the solution is decanted from the gold precipitate, the gold is then filtered through a standard filter paper, and rinsed with distilled water during filtration. The recovered gold powder and filter paper are dried at 120-130 C for 4 hours in a standard convection oven. The gold powder is weighed after it is fully dried, and all gold is removed from the filter paper, using a wire brush if necessary to get as much gold as possible from the paper. The gold powder is now transferred to a melting crucible, mixed with anhydrous sodium tetraborate (Na₂B₄O₇), two teaspoons of borax per 200 grams of gold powder, and heated to 1180° C. for 5 to 10 minutes. The crucible is cooled in water and destroyed so as to remove the gold. The recovered gold “Roundlet” is boiled in nitric acid (12M, diluted by 50%, 2 hours minimum), rinsed with distilled water, air dried, weighed, rinsed with isopropyl alcohol, and air dried a final. The gold is now 99.99% minimum purity.

Similar results have been obtained using other alkylamine and/or cycloalkylamine and/or substituted alkylamine hydrohalides and/or alkylammonium and/or cycloalkylammonium and/or substituted alkylammonium halides as protectant and/or complexing component.

Claims

1. A method for removing metal and precious metal-containing depositions from a substrate, comprising the step of (i) treating the substrate with an organo amine protectant component (“P”) and an inorganic active component (“A”) or (ii) treating with a complexing component (“C”) and an “A”, wherein said component “P” or “C” is selected from the group consisting of mono-substituted amine hydrohalides, di-substituted amine hydrohalides, tri-substituted amine hydrohalides, and tetra-substituted ammonium halides, wherein each substituent is independently an alkyl having 1 to 18 carbon atoms or a cycloalkyl having 3 to 8 carbon atoms or an alkyl having 1 to 18 carbon atoms substituted by hydroxy-group or an alkyl having 1 to 18 carbon atoms substituted by carboxy-group or an alkyl having 1 to 18 carbon atoms substituted by hydroxy and carboxy group, and wherein said component “A” is an inorganic acid, a salt of an inorganic acid, or a mixture thereof.

2. The method of claim 1, wherein said halide is chloride or fluoride or bromide or iodide.

3. The method of claim 1, wherein said organo amine protectant is prepared in situ by reaction of an organic amine and hydrochloric- or hydrofluoric- or hydrobromic- or hydroiodic-acid.

4. The method of claim 1, wherein said component “P” or “C” is selected from the group consisting of triethylamine hydrochloride, diethylamine hydrochloride, ethyl amine hydrochloride, cyclohexylamine hydrochloride, dicyclohexylamine hydrochloride, N,N dimethylcyclohexylamine hydrochloride, diisopropylamine hydrochloride, N ethylcyclohexylamine hydrochloride and N-methylcyclohexylamine hydrochloride, glycine betaine hydrochloride, choline chloride, carnitine chloride, tetra-n-butylammonium fluoride, tetraethylammonium bromide, methylamine hydroiodide.

5. The method of claim 1, wherein said component “P” or “C” is selected from the group consisting of trimethylamine hydrohalide, dimethylamine hydrohalide and methylamine hydrohalide.

6. The method of claim 1, wherein said component “P” or “C” is formed in situ by reaction of said component “A” with a reactive component “R”.

7. The method of claim 5, wherein said component “R” is selected from the group consisting of organic amides and organic lactams.

8. The method of claim 6, wherein said component “R” is dimethylformamide or N-methylpyrrolidone.

9. The method of claim 1, wherein said component “A” is aqua regia.

10. The method of claim 1, wherein said component “A” is selected from the group consisting of nitric acid, hydrofluoric acid, hydrochloric acid, phosphoric acid, hexafluorosilicic acid, ammonium peroxydisulfate and sulfuric acid and mixtures thereof.

11. The method of claim 1, wherein said deposition comprises at least one material selected from the group consisting of Be, Mg, Ca, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, In, Ti, C, Si, Sn, N, P, As, S, Se, Te, their mixtures, and their chemical compounds.

12. The method of claim 1, wherein said substrate comprises at least one material selected from the group consisting of aluminum, copper, steel, stainless steel, glass, titanium, aluminum alloys, copper alloys, steel alloys, stainless steel alloys, titanium alloys, graphite, carbon fiber, ceramic, fused silica, quartz, polymers, ores and blasting media selected from the group consisting of: corundum, sand, corn cob, plastic abrasives, silicon carbide, pumice, steel grit, steel shot, walnut shells, soda and glass beads.

13. The method of claim 1, wherein said metal is recovered from the solution resulting from said treatment.

14. The method of claim 13, wherein said recovery is carried out by means of a biosorbant.

15. The method of claim 14, wherein said biosorbant is selected from seaweed and yeast.

16. The method of claim 15, wherein the biosorbant is Spirulina platensis.

17. The method of claim 15, wherein the biosorbant is Saccharomyces cerevisiae.

18. The method of claim 13, wherein said recovery is carried out by means of a reducing agent.

19. The method of claim 18, wherein the reducing agent is hydroxylamine hydrochloride, glucose, sodium bisulfite, sulfur dioxide.

20. The method of claim 13, wherein said recovery is carried out by means of an organic acid.

21-37. (canceled)