A process for separating and recovering precious metals using photocatalytic coupling technology

Abstract

The invention discloses a process for separating and recovering precious metals by applying photocatalytic coupling technology, which belongs to the technical field of resource recovery and comprises the following steps: filtering electroplating wastewater and adjusting the pH value to 6.0-6.8 to obtain primary electroplating wastewater; adding a composite adsorption material and an auxiliary agent to the primary electroplating wastewater, stirring and reacting for 1-1.5 hours at room temperature under the irradiation of a xenon lamp, filtering after the reaction is completed, washing the filter cake and drying to obtain an adsorption material adsorbed with the precious metal; ashing the adsorption material adsorbed with the precious metal, grinding the ashing components, mixing with dilute hydrochloric acid, stirring for 30-60min and filtering to obtain a solid product; calcining the solid product under a hydrogen atmosphere to obtain a recovered precious metal mixture. The invention can realize efficient separation and recovery of precious metals and avoid the environmental pollution problems that may be caused by traditional chemical methods.

Description

Technical Field

[0001] The invention belongs to the technical field of resource recovery, and in particular relates to a process for separating and recovering precious metals by applying photocatalytic coupling technology. Background Art

[0002] Due to their excellent physical and chemical properties, precious metals play an important role in various fields of industry, national economy, and national defense construction. However, it is reported that precious metal resources are limited in reserves, difficult to mine, and their prices remain high. Therefore, precious metal resource recovery is a very important way to develop precious metals. Among them, the recovery of platinum, palladium, gold, and silver precious metal elements is particularly important.

[0003] There are many sources of secondary resources of precious metals, among which electroplating wastewater contains more precious metals, such as platinum, palladium, gold, and silver. The recovery of precious metal elements in electroplating wastewater currently mainly includes metal replacement, extraction, adsorption, and electrolysis. While the metal replacement method enriches and recovers precious metals, it will also be contaminated by various reagents because the recovered slag is contaminated, resulting in a low recovery rate of precious metals. Although ion exchange resin adsorption has the advantages of simple operation and low labor, the ion exchange resin has limited loading capacity and the resin is expensive. The extraction method will produce a large amount of organic waste liquid, causing secondary pollution to the environment. The electrolysis method has the problems of high energy consumption, long processing time, and poor effluent quality. Therefore, providing a precious metal recovery method with high recovery rate, low energy consumption, and simple operation is a technical problem that needs to be solved at present. Summary of the invention

[0004] The purpose of the present invention is to provide a process for separating and recovering precious metals using photocatalytic coupling technology, combining photocatalytic reduction, chemical adsorption and molecular imprinting to obtain a composite adsorption material, which is applied to selectively separate precious metals from electroplating wastewater, and has the characteristics of simple process, high precious metal recovery rate and high purity of recovered precious metals.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A process for separating and recovering precious metals using photocatalytic coupling technology comprises the following steps:

[0007] S1, filtering the electroplating wastewater and adjusting the pH value to 6.0-6.8 to obtain primary electroplating wastewater;

[0008] S2, adding composite adsorption material and auxiliary agent to the primary electroplating wastewater, stirring and reacting for 1-1.5h at room temperature under xenon lamp irradiation, filtering after the reaction is completed, washing the filter cake and drying it to obtain an adsorption material adsorbed with precious metals;

[0009] S3, ashing the adsorption material adsorbed with the precious metal, grinding the ashing components and mixing with dilute hydrochloric acid, stirring for 30-60 minutes and then filtering to obtain a solid product;

[0010] S4. calcining the solid product under a hydrogen atmosphere to obtain a recovered precious metal mixture.

[0011] Furthermore, in step S2, the composite adsorption material is prepared by the following steps:

[0012] Potassium chloroplatinite, potassium tetrachloropalladate, silver nitrate and chloroauric acid trihydrate are added to deionized water, stirred evenly, and then a mixed solution a consisting of functional monomer, modified polyethyleneimine, methacrylic acid and methanol is added, stirred at room temperature at 600-800rpm for 3h, ethylene glycol dimethacrylate, modified nano titanium dioxide and azobisisobutyronitrile are added, ultrasonically dispersed for 5-10min, stirred at 200-300rpm at 60°C for 24h under nitrogen protection, filtered, the filter cake is washed with deionized water for 3-5 times, and dried to obtain a semi-finished product, and the semi-finished product is eluted with an eluent to remove platinum, palladium, gold and silver ions in the semi-finished product until no Pt is detected in the eluent. 2+ , Pd 2+ 、Au 3+ 、Ag + , and finally dried in an oven at 50°C to constant weight to obtain a composite adsorption material.

[0013] Pt 2+ , Pd 2+ 、Au 3+ 、Ag + The target ions are functional monomers, modified polyethyleneimine and methacrylic acid are polymerization monomers, ethylene glycol dimethacrylate is a cross-linking agent, modified nano-titanium dioxide is a photocatalytic component, and azobisisobutyronitrile is an initiator. The surface imprinting polymerization method is used to polymerize the imprinting layer on the surface of nano-titanium dioxide through grafting technology, and then the template ions are eluted to remove them to obtain a composite adsorption material.

[0014] Furthermore, the dosage ratio of potassium chloroplatinite, potassium tetrachloropalladate, silver nitrate, chloroauric acid trihydrate, deionized water, functional monomer, modified polyethyleneimine, methacrylic acid, methanol, ethylene glycol dimethacrylate, modified nano titanium dioxide and azobisisobutyronitrile is 5mmo l: 5mmo l: 5mmo l: 5mmo l: 60-80mL: 0.7-1.1g: 1.7-2.1g: 2mmo l: 40-50mL: 10-15mmo l: 0.6-0.8g: 30mg.

[0015] Furthermore, the eluent is composed of methanol and hydrochloric acid solution in a volume ratio of 8:2, and the concentration of the hydrochloric acid solution is 2 mol / L.

[0016] Furthermore, the modified nano titanium dioxide is 3-(methacryloyloxy)propyltrimethoxysilane-modified anatase nano titanium dioxide.

[0017] Further, the functional monomer is prepared by the following steps:

[0018] At room temperature, 2-aminomethyl-15-crown-5 and anhydrous ethanol were added to a flask, and after stirring at 200-400 rpm for 5-10 minutes, dibutyltin dilaurate was added dropwise. After the addition was completed, allyl isothiocyanate was added dropwise. After the addition was completed, the mixture was stirred at 50° C. for 4-6 hours, and then the temperature was lowered to room temperature and the reaction was continued for 48 hours. After the reaction was completed, the mixture was cooled to 5° C. and filtered. The filtrate was evaporated to remove anhydrous ethanol to obtain a functional monomer;

[0019] The amount ratio of the above-mentioned 2-aminomethyl-15-crown-5, anhydrous ethanol, dibutyltin dilaurate and allyl isothiocyanate is 14.96g:60mL:0.06g:6.1-6.3g. The amino functional group of 2-aminomethyl-15-crown-5 and the isosulfate functional group of allyl isothiocyanate are reacted to obtain a functional monomer containing a crown ether structure, an allyl group and a thiourea structure.

[0020] Further, the modified polyethyleneimine is prepared by the following steps:

[0021] Acrylic acid was added to deionized water, and EDC·HCl and NHS were added after stirring, and the mixture was stirred at 800 rpm for 2 h. Hyperbranched polyethyleneimine was then added, and the mixture was stirred at 800 rpm for 24 h at room temperature. The reaction product was placed in a dialysis bag, and dialyzed in deionized water for 2 d. The dialyzed product was dried to obtain modified polyethyleneimine.

[0022] The usage ratio of the acrylic acid, deionized water, EDC·HCl, NHS and hyperbranched polyethyleneimine is 1g:70-100mL:2g:2g:3-5g, EDC·HCl is 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, NHS is N-hydroxysuccinimide, and the number average molecular weight of the hyperbranched polyethyleneimine is 600-3000. The carboxyl functional group of acrylic acid and the amino functional group on the hyperbranched polyethyleneimine skeleton undergo amide reaction to obtain a modified polyethyleneimine with unsaturated double bonds.

[0023] Furthermore, in step S1, the pH adjuster is dilute hydrochloric acid or sodium hydroxide.

[0024] Furthermore, in step S2, the dosage ratio of the primary electroplating wastewater, the composite adsorption material and the auxiliary agent is 1L: 0.3-0.5g: 0.05-0.1g, and the power of the xenon lamp is 300W.

[0025] Furthermore, in step S2, the auxiliary agent is one or more of methanol, ethanol, formic acid, acetic acid, oxalic acid and ethylenediaminetetraacetic acid.

[0026] Furthermore, in step S3, the ashing temperature is 600-800° C. and the time is 1-2 h.

[0027] Furthermore, in step S3, the mass ratio of the hydrochloric acid solution to the components after ashing is 100:5-10, and the mass fraction of the dilute hydrochloric acid is 10-20%.

[0028] Furthermore, in step S4, the calcination temperature is 380-420° C. and the calcination time is 0.5-1 h.

[0029] Beneficial effects of the present invention:

[0030] 1. The present invention provides a process for separating and recovering precious metals by using photocatalytic coupling technology. The recovery method is simple. By using a composite adsorption material and an auxiliary agent in combination, photocatalytic reduction, chemical adsorption and molecular imprinting are combined. The adsorption material adsorbed with precious metals is subjected to simple ashing, impurity dissolution and reduction treatment to obtain a mixture with a high content of precious metals. This photocatalytic coupling technology can achieve efficient separation and recovery of precious metals, while avoiding the environmental pollution problems that may be caused by traditional chemical methods.

[0031] 2. The composite adsorption material in the present invention is a multi-template ion imprinted polymer, and the template ion is Pt 2+ , Pd 2+ 、Au 3+ 、Ag + There are holes in the structure that completely match the template molecules in terms of spatial position and binding sites. It has a high selective recognition characteristic for template ions and can effectively adsorb precious metal ions in electroplating wastewater. In addition, the composite adsorbent material also contains nano-titanium dioxide. Under light conditions, it can exert a coupled synergistic effect of metal reduction and organic oxidation with electron donor additives, accelerate the reduction of precious metal ions, thereby improving the adsorption efficiency of the composite adsorbent material for precious metal ions, and then improve the recovery efficiency of precious metals.

[0032] 3. The composite adsorbent material of the present invention contains a functional monomer prepared with 2-aminomethyl-15-crown-5 and allyl isothiocyanate as raw materials, which can not only participate in the cross-linking reaction, but also contains crown ether and thiourea structure, and has excellent complexing ability for precious metal ions, and can provide the composite adsorbent material with an adsorption capacity for precious metal ions, facilitate the transfer of electrons from the conduction band of Ti to metal ions, reduce the interference of oxygen, and generate new capture sites on the surface of titanium dioxide, thereby increasing the photocatalytic reduction rate and thus improving the recovery efficiency of precious metals.

[0033] 4. The composite adsorbent material of the present invention contains modified polyethyleneimine, which can not only participate in the cross-linking reaction, but also has a highly branched structure and rich nitrogen-containing functional groups. The spatial branched structure can increase the specific surface area and pore capacity of the composite adsorbent material. The nitrogen-containing functional groups form more precious metal adsorption sites, which is beneficial to the migration of precious metal ions to the composite adsorbent material, accelerates the adsorption process, and improves the recovery efficiency of precious metals.

[0034] 5. The present invention accurately controls the pH value of primary electroplating wastewater to provide favorable adsorption conditions for the composite adsorption material. When the pH value is low, the cavities in the composite adsorption material are filled with more H + The binding ability of the noble metal ions with the composite adsorption material is greatly reduced. When the pH value is too high, the noble metals will produce oxides, which are difficult to selectively separate. Therefore, the present invention controls the pH value of the primary electroplating wastewater to 6.0-6.8. DETAILED DESCRIPTION

[0035] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Example 1

[0037] This embodiment provides a modified nano titanium dioxide, and the preparation process is as follows:

[0038] Anhydrous ethanol and deionized water were prepared into 50 mL of a mixed solution in a volume ratio of 1:1, 28 wt% ammonia water was added dropwise to adjust the pH to 9, 10 g of dry nano titanium dioxide (industrial grade rutile type powder, Chongqing Xinhua Chemical Plant) was added, ultrasonic dispersion was performed for 10 min, and stirring was performed at 400 rpm for 20 min under a constant temperature water bath at 80 ° C. An anhydrous ethanol solution containing 0.15 g of 3-(methacryloyloxy)propyltrimethoxysilane was added dropwise. After the addition was completed, the reaction was stirred at 80 ° C for 2 h, and the filter cake was filtered, and after deionized water was washed 5 times, it was dried in an oven at 80 ° C to constant weight to obtain modified nano titanium dioxide.

[0039] Example 2

[0040] This embodiment provides a composite adsorption material, which is prepared by the following steps:

[0041] 5 mmol potassium chloroplatinite, 5 mmol potassium tetrachloropalladate, 5 mmol silver nitrate and 5 mmol chloroauric acid trihydrate were added to 60 mL deionized water, stirred evenly, and then a mixed solution a consisting of 0.7 g functional monomer, 1.7 g modified polyethyleneimine, 2 mmol methacrylic acid and 40 mL methanol was added, stirred and reacted at room temperature at 600 rpm for 3 h, 10 mmol ethylene glycol dimethacrylate, 0.6 g modified nano titanium dioxide of Example 1 and 30 mg azobisisobutyronitrile were added, ultrasonically dispersed for 5 min, stirred and reacted at 200 rpm at 60 ° C for 24 h under nitrogen protection, filtered, the filter cake was washed with deionized water 3 times, and dried to obtain a semi-finished product, and the semi-finished product was eluted with an eluent to remove platinum, palladium, gold and silver ions in the semi-finished product until no Pt was detected in the eluent. 2+ , Pd 2+ 、Au 3 + 、Ag + , and finally dried in an oven at 50°C to constant weight to obtain a composite adsorption material.

[0042] The eluent is composed of methanol and hydrochloric acid solution in a volume ratio of 8:2, and the concentration of the hydrochloric acid solution is 2 mol / L.

[0043] Functional monomers are made by the following steps:

[0044] At room temperature, 14.96 g of 2-aminomethyl-15-crown-5 and 60 mL of anhydrous ethanol were added to a flask, stirred at 200 rpm for 5 min, and then 0.06 g of dibutyltin dilaurate was added dropwise. After the addition was completed, 6.1 g of allyl isothiocyanate was added dropwise. After the addition was completed, the reaction was stirred at 50 ° C for 4 h, then cooled to room temperature and continued to react for 48 h. After the reaction was completed, the temperature was cooled to 5 ° C and filtered, and the filtrate was evaporated to remove anhydrous ethanol to obtain a functional monomer.

[0045] Modified polyethyleneimine is prepared by the following steps:

[0046] 1 g of acrylic acid was added to 70 mL of deionized water, and after stirring, 2 g of EDC·HCl and 2 g of NHS were added, and the mixture was stirred at 800 rpm for 2 h. Then, 3 g of hyperbranched polyethyleneimine was added, and the mixture was stirred at 800 rpm at room temperature for 24 h. The reaction product was placed in a dialysis bag and dialyzed in deionized water for 2 d. The dialyzed product was dried to obtain modified polyethyleneimine, and the number average molecular weight of the hyperbranched polyethyleneimine was 600.

[0047] Example 3

[0048] This embodiment provides a composite adsorption material, which is prepared by the following steps:

[0049] 5 mmol potassium chloroplatinite, 5 mmol potassium tetrachloropalladate, 5 mmol silver nitrate and 5 mmol chloroauric acid trihydrate were added to 80 mL deionized water, stirred evenly, and then a mixed solution a consisting of 1.1 g functional monomer, 2.1 g modified polyethyleneimine, 2 mmol methacrylic acid and 50 mL methanol was added, stirred at room temperature at 800 rpm for 3 h, 15 mmol ethylene glycol dimethacrylate, 0.8 g modified nano titanium dioxide of Example 1 and 30 mg azobisisobutyronitrile were added, ultrasonically dispersed for 10 min, stirred at 300 rpm at 60 ° C for 24 h under nitrogen protection, filtered, the filter cake was washed with deionized water 5 times, and dried to obtain a semi-finished product, and the semi-finished product was eluted with an eluent to remove platinum, palladium, gold and silver ions in the semi-finished product until no Pt was detected in the eluent. 2+ , Pd 2+ 、Au 3 + 、Ag + , and finally dried in an oven at 50°C to constant weight to obtain a composite adsorption material.

[0050] The eluent is composed of methanol and hydrochloric acid solution in a volume ratio of 8:2, and the concentration of the hydrochloric acid solution is 2 mol / L.

[0051] Functional monomers are made by the following steps:

[0052] At room temperature, 14.96 g of 2-aminomethyl-15-crown-5 and 60 mL of anhydrous ethanol were added to a flask, and the mixture was stirred at 400 rpm for 10 min, followed by dropwise addition of 0.06 g of dibutyltin dilaurate. After the addition was completed, 6.3 g of allyl isothiocyanate was continued to be added. After the addition was completed, the mixture was stirred at 50 ° C for 6 h, then cooled to room temperature and continued to react for 48 h. After the reaction was completed, the mixture was cooled to 5 ° C and filtered. The filtrate was evaporated to remove anhydrous ethanol to obtain a functional monomer.

[0053] Modified polyethyleneimine is prepared by the following steps:

[0054] 1 g of acrylic acid was added to 100 mL of deionized water, and after stirring, 2 g of EDC·HCl and 2 g of NHS were added, and the mixture was stirred at 800 rpm for 2 h. Then, 5 g of hyperbranched polyethyleneimine was added, and the mixture was stirred at 800 rpm at room temperature for 24 h. The reaction product was placed in a dialysis bag and dialyzed in deionized water for 2 d. The dialyzed product was dried to obtain modified polyethyleneimine, and the number average molecular weight of the hyperbranched polyethyleneimine was 3000.

[0055] Comparative Example 1

[0056] This embodiment provides a composite adsorption material. Compared with the embodiment 2, the functional monomer in the embodiment 3 is removed, and the remaining raw materials and preparation process are the same as the embodiment 2.

[0057] Comparative Example 2

[0058] This embodiment provides a composite adsorption material. Compared with Example 2, the modified polyethyleneimine in Example 3 is removed, and the remaining raw materials and preparation process are the same as Example 2.

[0059] Comparative Example 3

[0060] This embodiment provides a composite adsorption material. Compared with the embodiment 2, the modified nano titanium dioxide in the embodiment 3 is removed, and the other raw materials and preparation process are the same as the embodiment 2.

[0061] Example 4

[0062] A process for separating and recovering precious metals using photocatalytic coupling technology comprises the following steps:

[0063] S1, filtering the electroplating wastewater and adjusting the pH value to 6.0 with a 5wt% hydrochloric acid solution to obtain primary electroplating wastewater;

[0064] S2. Add the composite adsorption material and the auxiliary agent of Example 2 to the primary electroplating wastewater, add 0.3g of the composite adsorption material and 0.05g of methanol to each 1L of the primary electroplating wastewater, stir and react at room temperature for 1h under irradiation with a 300W xenon lamp, filter after the reaction is completed, wash the filter cake and dry it to obtain an adsorption material adsorbed with precious metals;

[0065] S3, ashing the adsorbent material adsorbed with precious metals at 600°C for 2h, grinding the ashing components and mixing them with a 10wt% hydrochloric acid solution, wherein the mass ratio of the hydrochloric acid solution to the ashing components is 100:5, stirring for 30min and then filtering to obtain a solid product;

[0066] S4. calcining the solid product in a hydrogen atmosphere at a temperature of 380° C. for 1 h to obtain a recovered precious metal mixture.

[0067] Example 5

[0068] A process for separating and recovering precious metals using photocatalytic coupling technology comprises the following steps:

[0069] S1, filtering the electroplating wastewater and adjusting the pH value to 6.5 with a 5wt% hydrochloric acid solution to obtain primary electroplating wastewater;

[0070] S2. Add the composite adsorption material and the auxiliary agent of Example 2 to the primary electroplating wastewater, add 0.4 g of the composite adsorption material and 0.08 g of formic acid to each 1 L of the primary electroplating wastewater, and stir and react for 1.2 h at room temperature under irradiation with a 300 W xenon lamp. After the reaction is completed, filter, wash the filter cake and dry it to obtain an adsorption material adsorbed with precious metals;

[0071] S3, ashing the adsorbent material adsorbed with the precious metal at 800° C. for 1 h, grinding the ashing component and mixing it with a 15 wt % hydrochloric acid solution, wherein the mass ratio of the hydrochloric acid solution to the ashing component is 100:8, stirring for 40 min and then filtering to obtain a solid product;

[0072] S4. calcining the solid product in a hydrogen atmosphere at a temperature of 400° C. for 0.8 h to obtain a recovered precious metal mixture.

[0073] Example 6

[0074] A process for separating and recovering precious metals using photocatalytic coupling technology comprises the following steps:

[0075] S1, filtering the electroplating wastewater and adjusting the pH value to 6.8 with a 5wt% hydrochloric acid solution to obtain primary electroplating wastewater;

[0076] S2, adding the composite adsorption material and auxiliary agent of Example 3 to the primary electroplating wastewater, adding 0.5g of the composite adsorption material and 0.1g of ethylenediaminetetraacetic acid to each 1L of the primary electroplating wastewater, stirring and reacting at room temperature for 1.5h under irradiation of a 300W xenon lamp, filtering after the reaction is completed, washing the filter cake and drying it to obtain an adsorption material adsorbed with precious metals;

[0077] S3, ashing the adsorbent material adsorbed with the precious metal at 800° C. for 2 h, grinding the ashing component and mixing it with a 20 wt % hydrochloric acid solution, wherein the mass ratio of the hydrochloric acid solution to the ashing component is 100:10, stirring for 60 min and then filtering to obtain a solid product;

[0078] S4. calcining the solid product in a hydrogen atmosphere at a temperature of 420° C. for 1 h to obtain a recovered precious metal mixture.

[0079] Comparative Example 4

[0080] A process for separating and recovering precious metals using photocatalytic coupling technology. Compared with Example 4, the composite adsorption material in Example 4 is replaced by the product prepared in Comparative Example 1, and the remaining raw materials and steps are the same as Example 4.

[0081] Comparative Example 5

[0082] A process for separating and recovering precious metals using photocatalytic coupling technology. Compared with Example 4, the composite adsorption material in Example 4 is replaced by the product prepared in Comparative Example 2, and the remaining raw materials and steps are the same as Example 4.

[0083] Comparative Example 6

[0084] A process for separating and recovering precious metals using photocatalytic coupling technology. Compared with Example 4, the composite adsorption material in Example 4 is replaced with the product prepared in Comparative Example 3, and the remaining raw materials and steps are the same as Example 4.

[0085] Comparative Example 7

[0086] A process for separating and recovering precious metals using photocatalytic coupling technology. Compared with Example 4, the step "filtering the electroplating wastewater and adjusting the pH value to 6.0 with a 5wt% hydrochloric acid solution" in Example 4 is modified to "filtering the electroplating wastewater and adjusting the pH value to 5.0 with a 5wt% hydrochloric acid solution", and the remaining raw materials and steps are the same as Example 4.

[0087] Comparative Example 8

[0088] A process for separating and recovering precious metals using photocatalytic coupling technology. Compared with Example 4, the step "filtering the electroplating wastewater and adjusting the pH value to 6.0 with a 5wt% hydrochloric acid solution" in Example 4 is modified to "filtering the electroplating wastewater and adjusting the pH value to 8.0 with sodium hydroxide", and the remaining raw materials and steps are the same as Example 4.

[0089] Comparative Example 9

[0090] A process for separating and recovering precious metals using photocatalytic coupling technology. Compared with Example 4, methanol in Example 4 is removed, and the remaining raw materials and steps are the same as Example 4.

[0091] The precious metal recovery process provided by Example 4 to Example 6 and Comparative Example 4 to Comparative Example 9 was used to treat electroplating wastewater from a factory in Anhui Province. The pH of the electroplating wastewater was 7.1. The electroplating wastewater contained precious metals such as platinum, palladium, gold, silver ions, and other metal ions. The filtrate obtained in each group of step S2 was tested for precious metal ion content. The results are shown in Table 1. The recovered precious metal mixture obtained in each group of step S4 was weighed and tested for content. The results are shown in Table 2.

[0092] Table 1

[0093]

[0094] It can be seen from Table 1 that the process provided by Examples 4-6 has a higher precious metal extraction rate, specifically, the Pd(II) recovery rate is 97.6-99.8%, the Pt(II) recovery rate is 97.4-99.8%, the Au(III) recovery rate is 98.0-99.3%, and the Ag(I) recovery rate is 98.8-99.6%, which are all better than Comparative Examples 4-9, indicating that the recovery method provided by the present invention has a good recovery effect and a fast recovery rate for precious metal waste liquid with extremely low precious metal content.

[0095] Table 2

[0096]

[0097]

[0098] It can be seen from the data recorded in Table 2 that the process provided in Example 4 obtains a higher precious metal content in the mixture, specifically 96.78%, which is better than Comparative Examples 4-9. This shows that the recovery method provided by the present invention has a good recovery effect and a fast recovery rate for precious metal waste liquid with extremely low precious metal content.

[0099] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0100] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A process for separating and recovering precious metals using photocatalytic coupling technology, characterized in that: The following steps are involved: S1, filtering the electroplating wastewater and adjusting the pH value to 6.0-6.8 to obtain primary electroplating wastewater; S2, adding potassium chloroplatinite, potassium tetrachloropalladate, silver nitrate and chloroauric acid trihydrate into deionized water, stirring evenly, adding a mixed solution a consisting of functional monomer, modified polyethyleneimine, methacrylic acid and methanol, stirring and reacting for 3 hours, adding ethylene glycol dimethacrylate, modified nano titanium dioxide and azobisisobutyronitrile, ultrasonically dispersing for 5-10 minutes, stirring and reacting at 60°C for 24 hours under nitrogen protection, filtering, washing the filter cake with deionized water, drying to obtain a semi-finished product, eluting the semi-finished product with an eluent, drying to obtain a composite adsorption material; Adding composite adsorption material and auxiliary agent to primary electroplating wastewater, stirring and reacting for 1-1.5 hours at room temperature under xenon lamp irradiation, filtering after the reaction is completed, washing the filter cake and drying to obtain adsorption material adsorbed with precious metals; S3, ashing the adsorption material adsorbed with the precious metal, grinding the ashing components and mixing with dilute hydrochloric acid, stirring for 30-60 minutes and then filtering to obtain a solid product; S4, calcining the solid product under a hydrogen atmosphere to obtain a recovered precious metal mixture; Functional monomers are made by the following steps: At room temperature, add 2-aminomethyl-15-crown-5 and anhydrous ethanol into a flask, stir for 5-10 minutes, then add dibutyltin dilaurate dropwise. After the addition is completed, continue to add allyl isothiocyanate dropwise. After the addition is completed, stir at 50°C for 4-6 hours, then cool to room temperature and continue to react for 48 hours to obtain a functional monomer.

2. A process for separating and recovering precious metals using photocatalytic coupling technology according to claim 1, characterized in that: The dosage ratio of potassium chloroplatinite, potassium tetrachloropalladate, silver nitrate, chloroauric acid trihydrate, deionized water, functional monomer, modified polyethyleneimine, methacrylic acid, methanol, ethylene glycol dimethacrylate, modified nano titanium dioxide and azobisisobutyronitrile is 5mmol:5mmol:5mmol:5mmol:60-80mL:0.7-1.1g:1.7-2.1g:2mmol:40-50mL:10-15mmol:0.6-0.8g:30mg.

3. The process for separating and recovering precious metals using photocatalytic coupling technology according to claim 1, characterized in that: The eluent is composed of methanol and hydrochloric acid solution in a volume ratio of 8:2, and the concentration of the hydrochloric acid solution is 2 mol / L.

4. The process for separating and recovering precious metals using photocatalytic coupling technology according to claim 1, characterized in that: The modified nano titanium dioxide is 3-(methacryloyloxy)propyltrimethoxysilane-modified anatase nano titanium dioxide.

5. The process for separating and recovering precious metals using photocatalytic coupling technology according to claim 1, characterized in that: The dosage ratio of 2-aminomethyl-15-crown-5, anhydrous ethanol, dibutyltin dilaurate and allyl isothiocyanate is 14.96 g: 60 mL: 0.06 g: 6.1-6.3 g.

6. The process for separating and recovering precious metals using photocatalytic coupling technology according to claim 1, characterized in that: Modified polyethyleneimine is prepared by the following steps: Acrylic acid was added to deionized water, and EDC·HCl and NHS were added after stirring. The mixture was stirred at 800 rpm for 2 hours. Then, hyperbranched polyethyleneimine was added and stirred at room temperature for 24 hours. The reaction product was dialyzed and dried to obtain modified polyethyleneimine.

7. A process for separating and recovering precious metals using photocatalytic coupling technology according to claim 6, characterized in that: The usage ratio of acrylic acid, deionized water, EDC·HCl, NHS and hyperbranched polyethyleneimine is 1 g:70-100 mL:2 g:2 g:3-5 g.

8. The process for separating and recovering precious metals using photocatalytic coupling technology according to claim 1, characterized in that: In step S2, the dosage ratio of the primary electroplating wastewater, the composite adsorption material and the auxiliary agent is 1L: 0.3-0.5g: 0.05-0.1g, and the power of the xenon lamp is 300W.

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