Patent Application
20230071700
Pursuant to 35 U.S.C.§ 119 and the Paris Convention Treaty, this application claims foreign priority to Chinese Patent Application No. 202111035860.5 filed Sep. 6, 2021, the contents of which, including any intervening amendments thereto, are incorporated herein by reference. Inquiries from the public to applicants or assignees concerning this document or the related applications should be directed to: Matthias Scholl P. C., Attn.: Dr. Matthias Scholl Esq., 245 First Street, 18th Floor, Cambridge, Mass. 02142.
The disclosure relates to the field of electrochemical oxidation and water treatment, and more particularly, to an electrode comprising a catalyst layer comprising magnetic SnO2—Sb particles, a preparation method and uses thereof.
Wastewater usually contains toxic and persistent organic compounds which cannot be degraded in natural ways or by conventional biochemical treatment. The wastewater is discharged into natural environment, which causes damage to the ecological environment. In recent years, a conductive separation membrane electrode has attracted widespread attention for wastewater treatment because it outcompetes a conventional flat plate electrode in mass transfer and thus improves the removal efficiency of pollutants. A conventional Ti/SnO2—Sb membrane electrode assembly exhibits excellent catalytic activity and high oxygen evolution potentials. However, the thermal distortion and crystal structure difference between the catalytic layer and the substrate leads to an unstable binding and a relatively short service life of the Ti/SnO2—Sb membrane electrode assembly.
The disclosure provides an electrode comprising a microporous titanium substrate coated with a catalytic layer. Specifically, SnO2—Sb xerogel powders and iron tetroxide nanoparticles are mixed, calcined, and ground into microparticles; the microparticles are magnetically bound to a microporous titanium substrate to form an electrode comprising a catalyst layer comprising magnetic SnO2—Sb particles. The following advantages are associated with the electrode: (1) the microporous titanium substrate is loaded with the microparticles and the space between the microparticles and the pores of the microporous titanium substrate improves the filtering efficiency of the electrode on the pollutants; (2) the microparticles preferentially absorb the pollutants thus reducing chances of the pollutants to block the membrane pores; (3) the thickness of the catalyst layer is adjustable, and the catalyst layer is dynamically replaceable, thus overcoming the disadvantages of a conventional Ti/SnO2—Sb electrode, such as low catalyst loading and unstable binding.
The first objective of the disclosure is to provide an electrode; the electrode comprises a microporous titanium substrate coated with a catalytic layer, and the catalytic layer comprising magnetic SnO2—Sb particles; the magnetic SnO2—Sb particles are attached to the microporous titanium substrate through an external magnetic field; and the microporous titanium substrate comprises a plurality of membrane pores having a pore size of 5-50 μm that is smaller than a particle size of the magnetic SnO2—Sb particles. The catalytic layer comprising the magnetic SnO2—Sb particles is dynamically attached to the microporous titanium substrate through external force, so that the catalytic layer acts as a secondary membrane on the substrate, which can be separated from the substrate through backwashing and can be recycled.
In a class of this embodiment, the particle size of the magnetic SnO2—Sb particles is 1.2-2.5 times the pore size of the membrane pores. The magnetic SnO2—Sb particles are attached to the outer surface of the microporous titanium substrate and the space between the microparticles and the pores of the microporous titanium substrate improves the filtering efficiency of the electrode on the pollutants.
In a class of this embodiment, the particle size of the magnetic SnO2—Sb particles is 1.5-2.0 times the pore size of the membrane pores.
In a class of this embodiment, the magnetic SnO2—Sb particles are composite particles comprising SnO2—Sb xerogel powders and magnetic nanoparticles; the capacity of the magnetic nanoparticles on the microporous titanium substrate is 5-75 mg/cm2; and the magnetic property of the magnetic SnO2—Sb particles is produced by the iron tetroxide particles in the size of 50-200 nm.
The second objective of the disclosure is to provide a method for preparing the electrode, the method comprising: filtering and loading the magnetic SnO2—Sb particles onto the microporous titanium substrate to form a catalyst layer; and fixing the catalyst layer on the microporous titanium substrate through a magnetic field to form the electrode comprising the catalyst layer comprising the magnetic SnO2—Sb particles.
In a class of this embodiment, operations for preparing the magnetic SnO2—Sb particles comprise:
S1. preparation of SnO2—Sb xerogel powders;
S2. preparation of a Sn—Sb precursor solution;
S3. dispersing the SnO2—Sb xerogel powders and the iron tetroxide nanoparticles in the Sn—Sb precursor solution to form a mixture; heating, calcining, and grinding the mixture to form the magnetic SnO2—Sb particles.
In a class of this embodiment, the operations for preparing the magnetic SnO2—Sb particles comprise:
S1. preparation of the SnO2—Sb xerogel powders:
mixing an ethanol solution of SnCl4.5H2O, a NH4F aqueous solution, and a hydrochloric acid solution of SbCl3 to form a mixed solution; dissolving an ethanol solution of propylene oxide in the mixed solution and heating to form a white gel; adding an ethanol solution of tetraethyl orthosilicate to the white gel, resting, sonicating, washing the white gel with n-hexane, air drying, and heating in a muffle furnace, to yield a SnO2—Sb gel; and grinding the gel, sieving through a mesh sieve, thus obtaining the SnO2—Sb xerogel powders;
S2. preparation of the Sn—Sb precursor solution:
mixing citric acid, ethylene glycol, SnCl4.5H2O, and SbCl3 to form the Sn—Sb precursor solution;
S3. preparation of the magnetic SnO2—Sb particles:
mixing the SnO2—Sb xerogel powders with the iron tetroxide nanoparticles to form a powder mixture; adding the Sn—Sb precursor solution to the powder mixture to form a solution; heating the solution to evaporate solvents, thus obtaining a black solid block; calcining the black solid block in the muffle furnace; grinding and sieving the black solid block, immersing in an acid, and drying to obtain the magnetic SnO2—Sb particles.
In a class of this embodiment, in S2, a molar ratio of citric acid to ethylene glycol to SnCl4.5H2O to SbCl3 is 140:30:9:1.
In a class of this embodiment, in S3, the iron tetroxide nanoparticles have a particle size of 50-200 nm, and the SnO2—Sb xerogel powders have a particle size of 10-50 μm; and/or
in S3, a mass ratio of the iron tetroxide nanoparticles to the SnO2—Sb xerogel powders is between 1:1 and 1:3; and/or
in S3, every 10 mL of the Sn—Sb precursor solution is added to 10 g of the powder mixture; and/or
in S3, the black solid block is calcined in the muffle furnace at a temperature of 350-550° C. with a heating rate of 1.5-5° C./min for 0.5-2 h; and/or
in S3, the mesh sieve is a 200-800 mesh sieve; and the acid is 5-10 wt. % sulfuric acid, hydrochloric acid, or nitric acid.
The third objective of the disclosure is to provide an electrochemical device that comprises the electrode comprising a catalyst layer comprising magnetic SnO2—Sb particles, and the electrode is used an anode.
The fourth objective of the disclosure is to provide a method for treatment of wastewater comprising humic substances, the method comprising horizontally placing the electrochemical device of claim 10 on ground, the electrochemical device comprising the electrode as an anode, and perforated stainless steel as a cathode; and allowing the wastewater comprising humic substances to pass through the electrochemical device.
In a class of this embodiment, a current density is 5-30 mA/cm2 during electrochemical oxidation.
The following advantages are associated with the electrode, the preparation method and uses thereof:
1. Magnetic nanoparticles bind to SnO2—Sb to form a catalyst layer in the form of particles; the catalyst layer is attached to the microporous titanium substrate through an external magnetic field to form an electrode; the microporous titanium substrate is loaded with the particles with space left between the particles and the micropores, so that the electrode can filter pollutants out of wastewater; and the particles preferentially absorb the pollutants thus reducing chances of the pollutants to block the membrane pores.
2. The size of the magnetic SnO2—Sb particles is 1.2-2.5 times the size of the membrane pores. The particles are attached to the outer surface of the microporous titanium substrate and the space between the microparticles and the pores of the microporous titanium substrate is formed; the space prevents the pollutants from blocking the membrane pores and filters the pollutants out of the wastewater. Experimental results show that the size of the magnetic SnO2—Sb particles is preferably 1.2-2.0 times the total volume of the membrane pores.
3. The magnetic SnO2—Sb particles are composite particles formed by embedding the SnO2—Sb particles with the iron tetroxide nanoparticles. Compared with the core-shell type particles, the microporous titanium substrate and the catalyst layer comprise the same material capable of being melted into a stable whole structure during high-temperature calcination, and no surface cracks are observed. The magnetic SnO2—Sb particles have catalyst activities and can be fixedly loaded onto the microporous titanium substrate with a magnetic field strength. The thickness of the catalyst layer is adjustable, and the catalyst layer is dynamically replaceable, thus overcoming the disadvantages of a conventional Ti/SnO2—Sb electrode, such as low catalyst loading and unstable binding.
To further illustrate the disclosure, examples detailing an electrode comprising a catalyst layer comprising magnetic SnO2—Sb particles, a preparation method and uses thereof are described below. It should be noted that the following embodiments are intended to describe and not to limit the disclosure.
The conditions not stated in examples follow traditional or manufacturer instructions. The reagents or instruments without manufacturer's indication are common products available on the market.
Various examples of the disclosure may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 4.5 should be considered to have specifically disclosed subranges such as from 1 to 3, from 2 to 4, etc., as well as individual numbers within that range, for example, 1, 2, 3, and 4. This applies regardless of the breadth of the range.
1. Preparation of magnetic SnO2—Sb particles.
S1. Preparation of SnO2—Sb xerogel powders.
17.5 g of SnCl4.5H2O was added to 83.5 mL of ethanol and heated at 60° C. for 5 hours. 1.85 mg of NH4F was dissolved in 7.15 mL of water. 1.71 g of SbCl3 was dissolved in 3.75 mL of HCl. A mixture was formed by mixing all of the above solutions together and then was placed on an ice bath. 38.5 mL of propylene oxide was dissolved in 60 mL of ethanol, added to the mixture, and heated at 40° C. for 48 hours to form a white gel. 150 mL of ethanol containing 5% (v/v) of tetraethyl orthosilicate was added to the white gel and allowed to rest for three days with daily ten-minute-sonication. The sonicated gel was washed with n-hexane, air dried, and heated in a muffle furnace at 450° C., ground to pass through a 200-500 mesh sieve, thus forming SnO2—Sb xerogel powders in the size of micron.
S2. Preparation of a Sn—Sb precursor solution.
Citric acid: ethylene glycol: SnCl4.5H2O: SbCl3 were mixed in a ratio to form a Sn—Sb precursor solution.
S3. Preparation of magnetic SnO2—Sb particles.
5 g of SnO2—Sb xerogel powders was mixed with 5 g of iron tetroxide nanoparticles with a particle size of 50-200 nm. 20 mL of the Sn—Sb precursor solution was added, mixed, and heated until the solvent evaporated to obtain a black solid block. The black solid block was placed in the muffle furnace at 450° C. for 30 minutes, and the heat was increased at a rate of 1.5° C./min. The heated black solid block was ground to pass through a 200-500 mesh sieve, immersed in 5% sulfuric acid for 24 hours, and dried to obtain magnetic SnO2—Sb particles with a size of 30-50 μm. Referring to
2. Preparation of an electrode comprising a catalyst layer comprising magnetic SnO2—Sb particles.
The magnetic SnO2—Sb particles were passed through a 300 mesh sieve to obtain fine particles. 0.5 g of the fine particles was ultrasonically dispersed in deionized water, captured on the surface of a microporous titanium substrate by filtration, and fixed on the microporous titanium substrate with a strong magnetic strength to obtain an electrode comprising a catalyst layer comprising magnetic SnO2—Sb particles, as shown in
An electrochemical device comprised an anode and a cathode. The cathode was a perforated stainless steel, and the anode was the electrode in Example 1. The electrode was the microporous titanium substrate loaded with 10 mg/m2 magnetic SnO2—Sb particles. Electricity was generated to degrade pollutants as water flows downhill.
500 mL of leachate was collected from a waste landfill and used for degradation analysis. The leachate contained 640 mg/L COD produced by humus and microbial metabolites. The leachate was degraded under conditions below: the current density was 20 mA/cm2, the flow rate was 50 mL/min, and the degradation time was 4 hours. 3D fluorescence spectrum analysis (EEM) was conducted to evaluate the degradation of the leachate at 0 h, 2 h, 3 h, and 4 h. Referring to
0 g, 0.5 g, 1.0 g, and 1.5 g of the fine particles in Example 1 were ultrasonically dispersed in deionized water, captured on the surface of a microporous titanium substrate by filtration, and fixed on the microporous titanium substrate with a strong magnetic strength to obtain an electrode comprising a catalyst layer comprising magnetic SnO2—Sb particles. The microporous titanium substrate has an effective area of 20 cm2.
500 mL of leachate was collected from a waste landfill and used for degradation analysis. A microporous Ti/SnO2—Sb electrode (disclosed in Example 2 of Chinese Patent Application CN106186205A) was used as a control. The leachate contained 716 mg/L COD produced by humus, proteins, and microbial metabolites. The leachate was degraded under conditions below: the current density was 20 mA/cm2, the flow rate was 50 mL/min, and the degradation time was 4 hours. Referring to
The fourth example of the disclosure is similar to the Example 1, except for the following differences: the magnetic SnO2—Sb particles were passed through different mesh sieves to obtain the particles of different particle sizes. The ratio of the particle size to the substrate pore size was 1-1.2:1, 1.2-1.5:1, 1.5-2.0:1, 2.0-2.5:1, 3-5:1. 1.0 g of the magnetic SnO2—Sb particles of different particle sizes was ultrasonically dispersed in deionized water, captured on the surface of a microporous titanium substrate by filtration, and fixed on the microporous titanium substrate with a strong magnetic strength to obtain an electrode comprising a catalyst layer comprising magnetic SnO2—Sb particles. The microporous titanium substrate had an effective area of 20 cm2. 500 mL of leachate was collected from a waste landfill and used for degradation analysis. The leachate contained 716 mg/L COD produced by humus, proteins, and microbial metabolites. The leachate was degraded under conditions below: the current density was 20 mA/cm2, the flow rate was 50 mL/min, and the degradation time was 4 hours. Referring to
The fifth example of the disclosure is similar to the Example 1, except for the following differences: in 3), the magnetic SnO2—Sb particles were prepared by mixing 2 g and 3 g of the SnO2—Sb xerogel powders with 6 g of iron tetroxide nanoparticles with a particle size of 50-200 nm. 1.0 g of the magnetic SnO2—Sb particles were ultrasonically dispersed in deionized water, captured on the surface of a microporous titanium substrate by filtration, and fixed on the microporous titanium substrate with a strong magnetic strength to obtain an electrode comprising a catalyst layer comprising magnetic SnO2—Sb particles. The microporous titanium substrate has an effective area of 20 cm2. 500 mL of leachate was collected from a waste landfill and used for degradation analysis. The leachate contained 716 mg/L COD produced by humus, proteins, and microbial metabolites. The degradation of the leachate was performed under conditions below: the current density was 20 mA/cm2, the flow rate was 50 mL/min, and the degradation time was 4 hours. Referring to
0.5 g of the magnetic SnO2—Sb particles in Example 1 was ultrasonically dispersed in deionized water, captured on the surface of a microporous titanium substrate by filtration, and fixed on the microporous titanium substrate with a strong magnetic strength to obtain an electrode comprising a catalyst layer comprising magnetic SnO2—Sb particles. The microporous titanium substrate has an effective area of 20 cm2 (i.e. 25 mg/cm2). 500 mL of leachate was collected from a waste landfill and used for degradation analysis. The leachate contained 716 mg/L COD produced by humus, proteins, and microbial metabolites. The degradation of the leachate was performed under conditions below: the current density was 5 mA/cm2, 10 mA/cm2, 20 mA/cm2, 30 mA/cm2, and 40 mA/cm2, the flow rate was 50 mL/min, and the degradation time was 4 hours. Referring to
In certain examples, the microporous titanium substrate with a membrane pore of 5 μm was loaded with the magnetic SnO2—Sb particles of about 10 μm; the leachate was collected from a waste landfill and used for degradation analysis; and the leachate was degraded under conditions as described in Example 1 so that the pollutants can be removed from the leachate.
In certain examples, the microporous titanium substrate with a membrane pore of 10 μm was loaded with the magnetic SnO2—Sb particles of about 20-25 μm; the leachate was collected from a waste landfill and used for degradation analysis; and the leachate was degraded under conditions as described in Example 1 so that the pollutants can be removed from the leachate.
In certain examples, the microporous titanium substrate with a membrane pore of 50 μm was loaded with the magnetic SnO2—Sb particles of about 70-100 μm; the leachate was collected from a waste landfill and used for degradation analysis; and the leachate was degraded under conditions as described in Example 1 so that the pollutants can be removed from the leachate.
The disclosure provides a method for removing pollutants from wastewater by using a membrane electrode assembly based on electrochemical oxidation. The membrane can also intercept the pollutants. Humic acid is a compound with a large molecular weight and a complex structure, which carries a large number of charged groups. In addition to being oxidized in water, part of humic acid is intercepted and trapped on the surface of the membrane due to the repulsion of the magnetic field. The smaller the membrane pore, the better the interception effect. But a smaller membrane pore may cause high transmembrane pressure. The larger membrane pore may result in the poor interception effect. The larger the particle size of the same loading amount of the magnetic particles, the poorer the covering effect on the substrate membrane and the less active sites, which inhibits the electrochemical reaction and effects the removal of the pollutants in water. Therefore, a reduction in the membrane pore size is beneficial to the removal effect while requiring strict operating conditions; but an increase in the membrane pore size may affect the removal of the pollutants in water.
It will be obvious to those skilled in the art that changes and modifications may be made, and therefore, the aim in the appended claims is to cover all such changes and modifications.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202111035860.5 | Sep 2021 | CN | national |
