Method for recovering platinum group metal from copper anode slime treatment wastewater, modified resin and preparation method

Abstract

The invention discloses a method for recovering platinum group metal from copper anode slime treatment wastewater, which comprises the following steps: synthesizing modified resin containing amino and sulfydryl at the same time, and sequentially carrying out the steps of wastewater filtration, pH regulation, adsorption, elution, concentration, precipitation and firing or smelting. According to the method, high selectivity and high adsorption capacity of the resin to the platinum group metal chloride complex anions are utilized, efficient enrichment and recovery of low-concentration platinum group metal are achieved, and the method has the advantages that the process is simple, the cost is controllable, the resin can be recycled, and secondary pollution is avoided.

Description

Technical Field

[0001] This invention relates to the field of resource recycling technology, specifically to a method for recovering platinum group metals from wastewater from copper anode mud treatment, as well as the resin and preparation method used in this method. Background Technology

[0002] In the copper electrolytic refining process, anode mud, as a byproduct, is rich in various valuable metals, among which platinum group metals (such as platinum, palladium, and rhodium) have extremely high economic value. However, in the process of recovering valuable metals through wet or pyrometallurgical treatment of copper anode mud, the resulting wastewater still contains a certain concentration of platinum group metal ions.

[0003] Currently, the treatment of copper anode sludge wastewater and the recovery of platinum group metals face numerous challenges. Traditional recovery methods, such as precipitation and extraction, suffer from low recovery rates, high costs, and the potential for secondary pollution. For example, precipitation often fails to completely separate platinum group metals, resulting in low recovery efficiency; extraction requires large amounts of organic solvents, which are not only costly but also cause serious environmental pollution due to the volatilization and residues of these solvents.

[0004] Ion exchange resins, as an emerging recycling technology, offer advantages such as ease of operation, high selectivity, and reusability. However, existing ion exchange resins have limited adsorption capacity for platinum group metals (PGMs), making it difficult to meet the practical requirements for efficient PGM recovery. Therefore, developing a novel resin with high adsorption capacity and selectivity for PGMs and establishing a corresponding efficient recovery method are of great significance for realizing the resource utilization and environmental protection of PGMs in copper anode sludge wastewater. Summary of the Invention

[0005] This invention provides a method for recovering platinum group metals from copper anode sludge treatment wastewater. The method is based on a modified resin containing both amino and thiol active groups. Through a two-step chemical modification process, coordination functional sites with high selectivity and high adsorption capacity are constructed on a polystyrene-divinylbenzene copolymer matrix. Combined with optimized wastewater pretreatment, adsorption, elution and metal recovery process steps, the method achieves efficient enrichment and recovery of low concentrations of platinum group metal ions from copper anode sludge wastewater.

[0006] In a first aspect, the present invention provides a modified resin with polystyrene-divinylbenzene copolymer as the backbone, and two functional groups, amino and thiol, grafted onto the surface, wherein the amino content is 0.5-1.5 mmol / g dry resin and the thiol content is 0.6-1.6 mmol / g dry resin.

[0007] Using polystyrene-divinylbenzene (PS-DVB) copolymer as the resin matrix provides excellent physicochemical stability, mechanical strength, and a large specific surface area, offering a robust supporting structure for subsequent modification. Amino and mercapto groups are the main active groups. Amino groups possess strong electron-donating capabilities, with the lone pair of electrons on their nitrogen atom forming coordinate bonds with platinum group metal ions. Platinum group metal ions typically have empty d orbitals, allowing them to accept electron pairs donated by the amino group, thus forming stable coordination compounds. Furthermore, the presence of amino groups can alter the charge distribution on the resin surface, imparting a positive charge and enhancing the electrostatic attraction between the resin and the negatively charged platinum group metal complexes. Mercapto groups exhibit a unique affinity for platinum group metal ions due to the relatively low electronegativity of sulfur atoms and their loose outer electron cloud, facilitating the formation of stable metal-sulfur bonds. The high bond energy of these metal-sulfur bonds results in a very strong bond between the mercapto groups and the platinum group metal ions, thereby improving the resin's adsorption capacity and selectivity for platinum group metal ions.

[0008] The adsorption performance of resins is closely related to the type, quantity, and distribution of active groups. Different amino and thiol modifiers, due to their differences in molecular structure, introduce active groups with different spatial structures and electronic properties. The quantity of active groups also significantly affects the adsorption performance of resins. Increasing the amount of amino or thiol modifiers can introduce more active groups onto the resin surface, thereby increasing the binding sites between the resin and platinum group metal ions and improving the resin's adsorption capacity. However, excessive active groups may lead to overcrowding of the resin surface, affecting the effective binding of active groups with platinum group metal ions, and may even reduce the resin's selectivity. Furthermore, the uniformity of the distribution of active groups on the resin surface is also crucial. Uniformly distributed active groups allow the resin to fully exert its adsorption effect at all points when in contact with copper anode sludge wastewater, improving adsorption efficiency and uniformity. If the distribution of active groups is uneven, it may lead to excessively strong or weak local adsorption capacity of the resin, affecting the overall adsorption effect.

[0009] The amino and thiol groups of this resin are distributed adjacently at the molecular scale, forming a multidentate coordination microenvironment. This results in a significantly higher adsorption capacity and selectivity for platinum group metal chloride complex anions compared to resins with single functional groups. Experiments show that in simulated wastewater containing 5 g / L copper and 10 mg / L platinum, the resin of this invention exhibits an adsorption capacity of 45-60 mg / g for platinum, while its adsorption capacity for copper is less than 2 mg / g, with a selectivity coefficient (K_Pt / Cu) greater than 20.

[0010] Furthermore, the resin has a specific surface area of ​​20-80 square meters per gram, an average pore size of 15-40 nanometers, and a pore volume of 0.4-0.8 cubic centimeters per gram.

[0011] In some embodiments, the amino group is introduced by N-β(aminoethyl)-γ-aminopropyltriethoxysilane, and the thiol group is introduced by dimercaptoadiic acid. The two are stably linked to the resin backbone via covalent bonds, as indicated by infrared spectroscopy at 1560 cm⁻¹. -1 (NH bending vibration), 2550 cm -1 A characteristic absorption peak appeared at the (SH stretching vibration) position, and X-ray photoelectron spectroscopy showed that the N 1s binding energy was 399.2 to 399.8 eV, confirming that the functional group was successfully grafted.

[0012] The second invention provides a method for preparing a modified resin, comprising the following steps:

[0013] S1 uses polystyrene-divinylbenzene (PS-DVB) copolymer as the resin matrix;

[0014] S2, Amino Modification: PS-DVB resin is added to an appropriate amount of toluene and swelled at a certain temperature for a period of time to allow the resin to fully absorb the solvent, increasing its internal porosity and facilitating the entry of subsequent modifiers; then, an amino modifier is added to the swollen resin, along with an appropriate amount of the catalyst dibutyltin dilaurate, and the reaction is carried out at 80-120℃ for 6-12 hours, so that the amino modifier reacts chemically with the active groups on the surface of PS-DVB resin, thereby introducing amino groups onto the resin surface;

[0015] S3, Thiol Modification: After completing the amino modification, the resin is separated from the reaction system and repeatedly washed with deionized water until neutral to remove unreacted amino modifiers and catalysts; then, the washed resin is added to an alkaline solution containing thiol modifiers and reacted at 50-80℃ for 4-8 hours to allow the thiol modifiers to react with the existing amino groups or other active sites on the resin surface, thereby introducing thiol groups onto the resin surface;

[0016] S4, after the above two steps of modification, a modified resin containing both amino and thiol active groups is obtained.

[0017] Further, the amino modifier is one or more combinations of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β(aminoethyl)-γ-aminopropyltriethoxysilane, and N-β(aminoethyl)-γ-aminopropylmethyldiethoxysilane.

[0018] Furthermore, the thiol modifier may be selected from one or more of mercaptoacetic acid, dimercaptosuccinic acid, dimercaptoadiic acid, and dithiol dihydroxyacetic acid.

[0019] By employing a sequential modification strategy of first introducing amino groups and then thiol groups, the effective loading of both functional groups onto the resin backbone was ensured. The amino group, acting as a nucleophilic ligand, allows its nitrogen atom's lone pair electrons to interact with platinum group metal ions (such as Pt). 4+ Pd 2 + ,Rh 3+ The empty d orbitals of the [amino group] form coordinate bonds; the sulfur atom in the mercapto group, due to its low electronegativity and high electron cloud density, can form strong covalent metal-sulfur bonds with platinum group metal ions. The two groups work synergistically in space, not only enhancing the binding strength to platinum group metal ions but also through electrostatic attraction (the protonated amino group becomes positively charged, allowing it to adsorb negatively charged chloride complex anions such as [PtCl6]). 2- It enhances the selective adsorption capacity in strong acid and high chlorine environments.

[0020] In some embodiments, the amino modifier is N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, which contains two primary amino groups in its molecular structure, and can introduce a higher density of coordination sites on the resin surface.

[0021] In some embodiments, the thiol modifier is dimercaptoadiic acid, which has a long molecular chain and contains two thiol groups, which helps to form a multidentate coordination structure on the resin surface and enhances the chelation ability for multivalent platinum group metal ions.

[0022] Thirdly, the present invention provides a method for recovering platinum group metals from copper anode sludge treatment wastewater, comprising the following steps: T10: filtering the copper anode sludge treatment wastewater through a filter membrane with a pore size of 0.22-0.45 micrometers to remove suspended solid particles; T20: adding hydrochloric acid or sulfuric acid to the filtered wastewater to adjust the pH value to 2-5; T30: mixing the modified resin prepared by the method according to any one of claims 3 to 5 with the wastewater obtained in step T20 at a solid-liquid ratio of 1g:10-50ml, and adsorbing for 1-3 hours under a stirring speed of 100-300 rpm; T40: after adsorption, separating the resin from the wastewater by filtration or centrifugation, and washing the resin with deionized water until the washing liquid is colorless and transparent; T50: adding the washed resin to an eluent and eluting at 40-60°C for 1-2 hours; wherein the eluent is a mixed aqueous solution of thiourea and hydrochloric acid, wherein the mass concentration of thiourea is 5-15% and the mass concentration of hydrochloric acid is 3-8%; T60: Heat the eluent to 70-90℃ for evaporation and concentration, or distill under reduced pressure at 40-60℃ and 10-30 kPa to concentrate to one-quarter to one-third of the original volume; T70: Add a precipitant, namely an aqueous solution of ammonium chloride or sodium sulfide, to the concentrated eluent and stir for 30-60 minutes; T80: Filter the precipitate, wash it 3-5 times with deionized water, and then calcine it at 500-700℃ for 2-4 hours in air, or melt it at 900-1100℃ for 1-2 hours in an inert atmosphere to obtain platinum group metals or compounds.

[0023] The pH of the wastewater is controlled within the range of 2-5. This ensures that platinum group metals exist in a stable chloride complex anionic form, while avoiding the corrosion of the resin skeleton by excessively high acidity and the erosion of other heavy metal ions (such as Fe) by excessively low pH. 3+ Cu 2+ Competitive adsorption. The elution stage employs a thiourea-hydrochloric acid system, where the sulfur and nitrogen atoms in the thiourea molecule can form more stable five-membered cyclic complexes with platinum group metals (such as [Pd(SC(NH2)2)4)). 2+ Its stability constant is higher than the binding constant of amino / thiol groups on the resin with metals, thus achieving efficient desorption. In the precipitation step, ammonium chloride can selectively precipitate platinum as (NH4)2PtCl6, while sodium sulfide can cause palladium, rhodium, etc. to form sulfide precipitates, which facilitates subsequent stepwise refining.

[0024] Furthermore, in step T70, the mass concentration of the ammonium chloride aqueous solution is 10-20%, and the amount added is 1-2 times the volume of the concentrated solution; the mass concentration of the sodium sulfide aqueous solution is 5-15%, and the amount added is 0.8-1.5 times the volume of the concentrated solution.

[0025] Furthermore, in step T80, the calcination temperature is 550-650℃ and the calcination time is 2.5-3.5 hours.

[0026] Furthermore, the copper anode sludge treatment wastewater originates from the waste liquid generated after copper electrolytic refining through sulfation roasting-leaching or chlorination leaching processes, wherein the total concentration of platinum group metals is 1-50 mg / L, and the coexisting ions include copper 5-50 g / L, arsenic 0.1-2 g / L, antimony 0.05-1 g / L, and bismuth 0.01-0.5 g / L.

[0027] Furthermore, after completing one adsorption-elution cycle, the modified resin is regenerated with 0.5 mol / L hydrochloric acid solution for 30 minutes, and then washed with deionized water until neutral, and can be reused at least 10 times.

[0028] In summary, this invention, by designing and synthesizing a modified resin possessing both amino and thiol groups, and providing a complete wastewater treatment-adsorption-elution-recovery process chain, solves the problems of low recovery rate, poor selectivity, and severe secondary pollution faced by existing technologies in treating copper anode mud wastewater. This method operates at ambient temperature and pressure, requires no organic solvents, allows for resin recycling, and enables closed-loop treatment of the eluent. The overall process is simple, cost-controllable, and suitable for industrial-scale applications. Detailed Implementation

[0029] The various embodiments or implementation schemes in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments.

[0030] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0031] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0032] As described in the background section, wastewater from copper anode sludge treatment contains low concentrations of platinum group metal ions, along with high concentrations of coexisting ions such as copper, arsenic, antimony, and bismuth. Traditional adsorption materials struggle to selectively enrich platinum group metals. Existing technologies often employ resins with single functional groups, which have limited adsorption capacity and selectivity for platinum group metals, along with low elution efficiency and poor regeneration performance, resulting in low overall recovery rates. Therefore, this application provides a method for recovering platinum group metals from copper anode sludge treatment wastewater. By designing and synthesizing a modified resin containing both amino and thiol groups, and integrating it with a complete wastewater pretreatment, adsorption, elution, and metal recovery process, efficient and selective recovery of low-concentration platinum group metals can be achieved.

[0033] In one aspect, this application provides a modified resin for recovering platinum group metals from copper anode sludge treatment wastewater, with polystyrene-divinylbenzene copolymer as the backbone and two functional groups, amino and thiol, grafted onto the surface, wherein the amino content is 0.5-1.5 mmol / g dry resin and the thiol content is 0.6-1.6 mmol / g dry resin.

[0034] The resin has a specific surface area of ​​20-80 m² / g, an average pore size of 15-40 nm, and a pore volume of 0.4-0.8 m³ / g. Its infrared spectrum is at 1560 cm⁻¹. -1 An absorption peak for the NH bending vibration appears at 2550 cm⁻¹. -1 An absorption peak of SH stretching vibration was observed at the point; X-ray photoelectron spectroscopy showed that the N 1s binding energy was 399.2 to 399.8 eV, confirming that the functional group was successfully grafted.

[0035] Secondly, this application provides a method for synthesizing a modified resin for recovering platinum group metals from copper anode sludge treatment wastewater, comprising the following steps:

[0036] 1) Add polystyrene-divinylbenzene (PS-DVB) copolymer resin to toluene and swell at 80-100℃ for 2-4 hours to fully expand the internal pores of the resin.

[0037] 2) Add an amino modifier and a catalyst, dibutyltin dilaurate, to the swollen resin system, and react at 80-120℃ for 6-12 hours to allow the amino modifier to be grafted onto the resin backbone via silicon-oxygen bonds, forming an amino-functionalized resin; the amino modifier is selected from one or more combinations of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β(aminoethyl)-γ-aminopropyltriethoxysilane, and N-β(aminoethyl)-γ-aminopropylmethyldiethoxysilane.

[0038] 3) Filter and separate the amino-functionalized resin obtained in step 2), wash with toluene until no unreacted amino modifier can be detected in the washing solution, and then wash repeatedly with deionized water until neutral.

[0039] 4) The washed amino-functionalized resin is added to a 4-8% sodium hydroxide aqueous solution, and then a thiol modifier is added. The mixture is reacted at 50-80°C for 4-8 hours, so that the thiol groups are linked to the existing amino groups or other active sites on the resin surface through amide bonds or thioether bonds, forming a modified resin containing both amino and thiol groups. The thiol modifier is selected from one or more combinations of thioglycolic acid, dimercaptosuccinic acid, dimercaptoadipic acid, and dithiol dihydroxyacetic acid.

[0040] 5) Filter the resin obtained in step S40, wash it repeatedly with deionized water until neutral, and vacuum dry it at 50-70℃ for 12-24 hours to obtain the final modified resin.

[0041] In some embodiments, 1) the mass-to-volume ratio of PS-DVB resin to toluene is 1g:4-6ml, preferably 1g:5ml. The swelling temperature is controlled at 90°C for 3 hours, which allows the resin microspheres to fully swell, facilitating the diffusion of subsequent modifier molecules into the internal pores.

[0042] In some embodiments, 2) the amount of amino modifier added is 10-25% of the mass of PS-DVB resin, preferably 15-20%; the amount of catalyst dibutyltin dilaurate added is 3-8% of the mass of amino modifier, preferably 5%. The reaction temperature is preferably 90-110°C, and the reaction time is preferably 7-10 hours. Under these conditions, the alkoxysilane groups in the amino modifier undergo hydrolytic condensation, forming stable Si-OC or Si-O-Si bonds with the benzene rings or crosslinking points on the resin backbone, thereby achieving covalent grafting of amino groups.

[0043] In some embodiments, 3) the washing with toluene is performed at least three times, each time using five times the volume of the resin, until gas chromatography detects no amino modifier residue in the washing solution. The solution is then washed with deionized water until the pH reaches 6.5-7.5.

[0044] In some embodiments, 4) the volume of the sodium hydroxide solution is 3-5 times (in milliliters) the mass of the PS-DVB resin, preferably 4 times. The amount of the thiol modifier added is 8-20% of the mass of the PS-DVB resin, preferably 12-18%. The reaction temperature is controlled at 60-75°C, and the reaction time is 5-7 hours. Under these alkaline conditions, the carboxyl groups in the thiol modifier are activated and undergo a condensation reaction with the amino groups on the resin surface to form amide bonds; if the thiol modifier is a thiol-containing dicarboxylic acid, some thiol groups may also combine with unsaturated sites on the resin backbone through Michael addition or nucleophilic substitution to form thioether bonds.

[0045] In some embodiments, 5) the vacuum drying conditions are 60°C, 10 kPa absolute pressure, and 18 hours to ensure that moisture and residual solvent in the resin are completely removed.

[0046] In some embodiments, the amino modifier is N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, which contains two primary amino groups in its molecular structure, thereby introducing a higher density of coordination sites on the resin surface. During the reaction, this compound first hydrolyzes to form a silanol, which then condenses with the resin backbone, exposing both amino groups on the resin surface and enhancing its coordination ability.

[0047] In some embodiments, the thiol modifier is dimercaptoadiic acid, containing two thiol groups and one carboxyl group. Under alkaline conditions, the carboxyl group deprotonates and condenses with the amino group, while the two thiol groups face the solution phase, forming a multidentate coordination structure, which is beneficial for Pt. 4+ Pd 2+ They form stable chelates with metal ions of various valence states.

[0048] Thirdly, this application provides a method for recovering platinum group metals from copper anode sludge treatment wastewater, comprising the following steps:

[0049] T10: The wastewater from the copper anode mud treatment is filtered through a filter membrane with a pore size of 0.22-0.45 micrometers to remove suspended solid particles;

[0050] T20: Add hydrochloric acid or sulfuric acid to the filtered wastewater to adjust the pH value to 2-5;

[0051] T30: The modified resin obtained in any embodiment of the first aspect is mixed with the wastewater obtained in step T20 at a solid-liquid ratio of 1g:10-50ml, and adsorbed for 1-3 hours under a stirring speed of 100-300 rpm.

[0052] T40: After adsorption is complete, the resin is separated from the wastewater by filtration or centrifugation, and the resin is washed with deionized water until the washing liquid is colorless and transparent.

[0053] T50: Add the washed resin to the eluent and elute at 40-60℃ for 1-2 hours; the eluent is a mixed aqueous solution of thiourea and hydrochloric acid, wherein the mass concentration of thiourea is 5-15% and the mass concentration of hydrochloric acid is 3-8%;

[0054] T60: Heat the eluent to 70-90℃ to evaporate and concentrate it, or distill it under reduced pressure at 40-60℃ and 10-30 kPa to concentrate it to one-quarter to one-third of its original volume.

[0055] T70: Add a precipitant, which is an aqueous solution of ammonium chloride or sodium sulfide, to the concentrated eluent and stir for 30-60 minutes to convert platinum group metal ions into insoluble precipitates.

[0056] T80: Filter the precipitate, wash it 3-5 times with deionized water, and then calcine it at 500-700℃ for 2-4 hours in air, or melt it at 900-1100℃ for 1-2 hours in an inert atmosphere to obtain high-purity platinum group metal elements or compounds.

[0057] According to this application, in step T10, the filter membrane material is polytetrafluoroethylene or polyethersulfone, the filtration pressure is 0.1-0.3 MPa, and the filtration time is 10-30 minutes, ensuring that the suspended solids removal rate is greater than 99%.

[0058] In step T20, hydrochloric acid is preferred for adjusting the pH value because it can maintain a chlorine complexation environment, which is beneficial for platinum group metals to react with [PtCl6]. 2- [PdCl4] 2- It exists stably in various forms. The pH value is preferably controlled between 3 and 4; this range can inhibit Fe. 3+ Cu 2+ Plasma hydrolysis precipitation avoids the degradation of the resin skeleton by strong acids.

[0059] In step T30, the preferred solid-liquid ratio is 1g:20-40ml, the stirring speed is 180-250 rpm, and the adsorption time is 1.5-2.5 hours. Under these conditions, mass transfer resistance is low, and adsorption reaches equilibrium.

[0060] In step T40, the centrifugation conditions are 3000 rpm for 10 minutes, or Buchner funnel filtration is used. The washing water volume is 10 times the resin volume and is added in 3 portions.

[0061] In step T50, the preferred concentration of thiourea in the eluent is 8-12%, the concentration of hydrochloric acid is 4-7%, the elution temperature is 45-55℃, and the elution time is 1.2-1.8 hours. Thiourea and hydrochloric acid work synergistically to break the metal-resin coordination bonds, forming a soluble thiourea complex.

[0062] In step T60, the vacuum distillation conditions are 50°C and 20 kPa, which result in high concentration efficiency and avoid decomposition of metal complexes.

[0063] In step T70, if the target metal is platinum, add 10-20% ammonium chloride aqueous solution, the amount of which is 1-2 times the volume of the concentrated solution, to generate a yellow precipitate of (NH4)2PtCl6; if the target is palladium or rhodium, add 5-15% sodium sulfide aqueous solution, the amount of which is 0.8-1.5 times the volume of the concentrated solution, to generate a black precipitate of PdS or Rh2S3.

[0064] In step T80, calcination is carried out in a muffle furnace at a heating rate of 5°C per minute and held for 3 hours, resulting in a platinum sponge with a purity of up to 97.5%. Melting is carried out in a graphite crucible under argon protection and held at 1000°C for 1.5 hours to obtain a metal ingot.

[0065] In some embodiments, the copper anode mud treatment wastewater originates from the waste liquid generated after copper electrolytic refining through a sulfation roasting-leaching process, wherein the concentration of platinum is 8 mg / L, palladium is 3 mg / L, rhodium is 1 mg / L, copper is 35 g / L, arsenic is 1.2 g / L, antimony is 0.6 g / L, and bismuth is 0.3 g / L.

[0066] In some embodiments, after completing one adsorption-elution cycle, the modified resin is regenerated with 0.5 mol / L hydrochloric acid solution for 30 minutes, and then washed with deionized water until neutral. It can be reused at least 10 times, and its equilibrium adsorption capacity for platinum is not less than 85% of the initial value.

[0067] Example 1

[0068] Synthesis of modified resins:

[0069] 1) Take 10 grams of PS-DVB resin (crosslinking degree 8%, particle size 0.3-1.2 mm) and add it to 50 ml of toluene, and swell at 90℃ for 3 hours;

[0070] 2) Add 1.8 g of N-β(aminoethyl)-γ-aminopropyltrimethoxysilane and 0.09 g of dibutyltin dilaurate, and react at 100 °C for 8 hours;

[0071] 3) Filter, wash three times with 50 ml of toluene, then wash with deionized water until pH=7.0;

[0072] 4) Add the resin to 40 ml of 6% sodium hydroxide solution, then add 1.5 g of dimercaptoadiic acid, and react at 70°C for 6 hours;

[0073] 5) Filter, wash with deionized water until neutral, and vacuum dry at 60°C for 18 hours to obtain bifunctional resin A.

[0074] Platinum recovery process:

[0075] T10: Take 1 liter of copper anode mud wastewater (containing 10 mg / L Pt and 40 g / L Cu) and filter it through a 0.45-micron filter membrane;

[0076] T20: Add concentrated hydrochloric acid to adjust the pH to 3.5;

[0077] T30: Add 25 grams of resin A, solid-liquid ratio 1:40, stir at 200 rpm for 2 hours;

[0078] T40: Centrifuge and wash with deionized water 3 times;

[0079] T50: Add 100 ml of 10% thiourea + 5% hydrochloric acid elution buffer and elute at 50°C for 1.5 hours;

[0080] T60: Concentrate to 25 ml under reduced pressure at 50℃ and 20 kPa;

[0081] T70: Add 30 ml of 15% ammonium chloride solution and stir for 45 minutes;

[0082] T80: Filtered, washed 4 times with water, and calcined at 600℃ for 3 hours to obtain 0.098 g of sponge platinum, with a recovery rate of 98%.

[0083] Example 2

[0084] Synthesis of modified resins:

[0085] 1) Same as Example 1;

[0086] 2) Add 2.0 g of γ-aminopropyltriethoxysilane and 0.12 g of catalyst, and react at 95 °C for 9 hours;

[0087] 3) Same as Example 1;

[0088] 4) Add 1.2 g of mercaptoacetic acid and react at 65°C for 5 hours;

[0089] 5) Same as in Example 1, resin B is obtained.

[0090] Palladium recovery process:

[0091] T10-T40: Same as Example 1, wastewater contains Pd 5 mg / L;

[0092] T50: Elution conditions are the same as in Example 1;

[0093] T70: Add 20 ml of 10% sodium sulfide solution;

[0094] T80: Argon melting at 900℃ for 1.5 hours yields 0.049 g of palladium metal, with a recovery rate of 98%.

[0095] Example 3

[0096] Synthesis of modified resins:

[0097] 1) Same as Example 1;

[0098] 2) Add 1.5 g of N-β(aminoethyl)-γ-aminopropyltriethoxysilane and react at 105 °C for 7 hours;

[0099] 4) Add 1.8 g of dimercaptosuccinic acid and react at 75°C for 7 hours;

[0100] The rest is the same as in Example 1, yielding resin C.

[0101] For wastewater containing 2 mg / L Rh, sodium sulfide was added at T70 and smelted at T80 to obtain 0.019 g of rhodium, with a recovery rate of 95%.

[0102] Comparative Example 1

[0103] Commercially available D401 amino resin (amino content 1.8 mmol / g) was used, with other conditions the same as in Example 1. The platinum recovery rate was only 62%, and the copper co-adsorption capacity reached 8.5 mg / g.

[0104] Comparative Example 2

[0105] A self-made thiol-containing resin (modified with thioglycolic acid) was used, with the rest being the same as in Example 1. The platinum recovery rate was 71%, and the selectivity coefficient K_Pt / Cu = 8.3.

[0106] Comparative Example 3

[0107] The eluent used is only 5% hydrochloric acid, without thiourea, and the elution rate is only 45%.

[0108] The resins and recycling effects obtained in the above embodiments and comparative examples were tested, and the results are shown in Table 1.

[0109]

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A modified resin, characterized in that, The structure is based on polystyrene-divinylbenzene copolymer, with two functional groups, amino and thiol, grafted onto the surface. The amino content is 0.5-1.5 mmol / g dry resin, and the thiol content is 0.6-1.6 mmol / g dry resin.

2. The modified resin according to claim 1, characterized in that, The resin has a specific surface area of ​​20-80 square meters per gram, an average pore size of 15-40 nanometers, and a pore volume of 0.4-0.8 cubic centimeters per gram.

3. A method for preparing a modified resin, comprising the following steps: S1 uses polystyrene-divinylbenzene (PS-DVB) copolymer as the resin matrix; S2, Amino Modification: PS-DVB resin is added to an appropriate amount of toluene and swelled at a certain temperature for a period of time to allow the resin to fully absorb the solvent, increasing its internal porosity and facilitating the entry of subsequent modifiers; then, an amino modifier is added to the swollen resin, along with an appropriate amount of the catalyst dibutyltin dilaurate, and the mixture is reacted at 80-120℃ for 6-12 hours to allow the amino modifier to chemically react with the active groups on the surface of the PS-DVB resin, thereby introducing amino groups onto the resin surface; S3, Thiol Modification: After completing the amino modification, the resin is separated from the reaction system and repeatedly washed with deionized water until neutral to remove unreacted amino modifiers and catalysts; then, the washed resin is added to an alkaline solution containing thiol modifiers and reacted at 50-80℃ for 4-8 hours to allow the thiol modifiers to react with the existing amino groups or other active sites on the resin surface, thereby introducing thiol groups onto the resin surface; S4, after the above two steps of modification, a modified resin containing both amino and thiol active groups is obtained.

4. The preparation method according to claim 3, characterized in that, The amino modifier is one or more combinations of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β(aminoethyl)-γ-aminopropyltriethoxysilane, and N-β(aminoethyl)-γ-aminopropylmethyldiethoxysilane.

5. The preparation method according to claim 3, characterized in that, The thiol modifier may be selected from one or more of thioglycolic acid, dimercaptosuccinic acid, dimercaptoadiic acid, and dithiol dihydroxyacetic acid.

6. A method for recovering platinum group metals from wastewater treated with copper anode sludge, characterized in that, The process includes the following steps: T10: Filtering the copper anode mud treatment wastewater through a filter membrane with a pore size of 0.22-0.45 micrometers to remove suspended solid particles; T20: Adding hydrochloric acid or sulfuric acid to the filtered wastewater to adjust the pH value to 2-5; T30: Mixing the modified resin prepared by the method according to any one of claims 3 to 5 with the wastewater obtained in step T20 at a solid-liquid ratio of 1g:10-50ml, and adsorbing for 1-3 hours under a stirring speed of 100-300 rpm; T40: After adsorption, separating the resin from the wastewater by filtration or centrifugation, and washing the resin with deionized water until the washing liquid is colorless and transparent; T50: Adding the washed resin to an eluent and eluting at 40-60℃ for 1-2 hours; wherein the eluent is a mixed aqueous solution of thiourea and hydrochloric acid, wherein the mass concentration of thiourea is 5-15% and the mass concentration of hydrochloric acid is 3-8%; T60: Heat the eluent to 70-90℃ for evaporation and concentration, or distill under reduced pressure at 40-60℃ and 10-30 kPa to concentrate to one-quarter to one-third of the original volume; T70: Add a precipitant, namely an aqueous solution of ammonium chloride or sodium sulfide, to the concentrated eluent and stir for 30-60 minutes; T80: Filter the precipitate, wash it 3-5 times with deionized water, and then calcine it at 500-700℃ for 2-4 hours in air, or melt it at 900-1100℃ for 1-2 hours in an inert atmosphere to obtain platinum group metals or compounds.

7. The method according to claim 6, characterized in that, In step T70, the mass concentration of the ammonium chloride aqueous solution is 10-20%, and the amount added is 1-2 times the volume of the concentrated solution; the mass concentration of the sodium sulfide aqueous solution is 5-15%, and the amount added is 0.8-1.5 times the volume of the concentrated solution.

8. The method according to claim 6, characterized in that, In step T80, the calcination temperature is 550-650℃ and the calcination time is 2.5-3.5 hours.

9. The method according to claim 6, characterized in that, The copper anode mud treatment wastewater originates from the waste liquid generated after copper electrolytic refining through sulfation roasting-leaching or chlorination leaching processes. The total concentration of platinum group metals is 1-50 mg / L, and coexisting ions include copper 5-50 g / L, arsenic 0.1-2 g / L, antimony 0.05-1 g / L, and bismuth 0.01-0.5 g / L.

10. The method according to claim 6, characterized in that, After completing one adsorption-elution cycle, the modified resin is regenerated with 0.5 mol / L hydrochloric acid solution for 30 minutes, and then washed with deionized water until neutral. It can be reused at least 10 times.

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