A process for the recovery of precious metals from refinery wastewater

Abstract

This application relates to the field of metal refining, specifically disclosing a process for recovering precious metals from refining wastewater. The process includes the following steps: S1. Adsorption: Adjusting the pH of the refining wastewater to 2-3, then introducing a temperature-sensitive resin for adsorption at an adsorption temperature of 20-28℃; S2. Desorption: Heating the system to a desorption temperature of 42-50℃ and collecting the desorbed liquid; S3. Recovery: Concentrating the desorbed liquid, adding a precipitant and stirring, filtering, and calcining to purify, obtaining elemental precious metals; the temperature-sensitive resin is prepared from N-isopropylacrylamide monomer and organic acid. The process of this application exhibits excellent adsorption performance of precious metal ions even at low temperatures, and automatic desorption can be achieved by controlling the temperature. It has high selectivity for the adsorption of precious metal ions, and the obtained elemental precious metals have higher purity and greater recovery rates, which is of great significance to the field of metal refining.

Description

Technical Field

[0001] This application relates to the technical field of metal refining, and in particular to a process for recovering precious metals from refining wastewater. Background Technology

[0002] Precious metals are scarce strategic metals and key materials for sustainable development, possessing numerous advantages such as high density, high melting point, corrosion resistance, and high stability. Therefore, they are widely used in various fields including electronics, aerospace, chemicals, and medicine. However, the reliance on and widespread use of precious metals inevitably leads to resource scarcity. Natural reserves of precious metals (gold, silver, platinum, palladium, etc.) are limited, and mining costs are high. Therefore, simply relying on mineral resources can no longer meet the demand for precious metals. Researchers have proposed that recovering precious metals from industrial wastewater can effectively solve the problem of precious metal resource scarcity. Although the concentration of residual precious metals in smelting wastewater is low (trace to micro levels), the total amount accumulated over a long period is considerable. Therefore, recycling this portion of precious metals can replace approximately 30% of the demand for raw ore, significantly reducing the pressure on precious metal mining.

[0003] Currently, commonly used processes for recovering precious metals include electrodeposition, resin adsorption, coagulation and flocculation, and solvent extraction. Among these, resin adsorption has superior capture capabilities for precious metal ions, effectively treating concentrations as low as 0.1 mg / L, and the adsorption unit can be automated without complex equipment, making it a popular choice in the field of precious metal recovery. However, traditional resins widely used in industrial wastewater treatment suffer from low regeneration efficiency, are prone to causing secondary pollution, and exhibit significantly reduced adsorption kinetics at low temperatures.

[0004] Existing solutions attempt to enhance resin performance through physical or chemical modification, but the effects are limited, failing to achieve the multiple advantages of high selective adsorption, low-temperature adsorption capacity, and efficient regeneration. Furthermore, with increasing environmental protection requirements and emphasis on resource recycling, developing a novel and efficient process for recovering precious metals from refining wastewater is of great significance to the field of metal refining. Summary of the Invention

[0005] To address the aforementioned technical problems, this application provides a process for recovering precious metals from refining wastewater.

[0006] This application provides a process for recovering precious metals from refining wastewater, comprising the following steps:

[0007] S1. Adsorption: Adjust the pH of the refining wastewater to 2-3, and then pass it through the temperature-sensitive resin at a flow rate of 0.8-1.2 BV / h for adsorption. The adsorption temperature is 20-28℃.

[0008] S2. Desorption: Heat the system to the desorption temperature of 42-50℃ and collect the desorbed solution;

[0009] S3. Recovery: Concentrate the desorption solution, add a precipitant and stir, filter, and calcine to purify and obtain the noble metal element;

[0010] The thermosensitive resin is prepared from N-isopropylacrylamide monomer and organic acid.

[0011] By adopting the above technical solution, this application utilizes a thermosensitive resin prepared from N-isopropylacrylamide monomer and organic acid to adsorb noble metal ions in refining wastewater. The noble metal ions are adsorbed from the water into the resin skeleton. During the adsorption process, the adsorption temperature is controlled at 20-28℃, which is lower than the low critical dissolution temperature of the thermosensitive resin. At this temperature, the pore structure in the resin skeleton is very stable, enabling the noble metal ions to be rapidly adsorbed by the thermosensitive resin. After the water influent is discharged, the temperature of the system is raised to 42-50℃. At this temperature, the system temperature reaches the desorption temperature, which is higher than the low critical dissolution temperature of the thermosensitive resin. The hydrophobicity increases, the volume of the thermosensitive resin begins to shrink, and the pores inside the skeleton are squeezed, forcing the adsorbed noble metal ions to dissociate from the ligand grafted specific ligands, forming dissolved ions or small molecule complexes and dispersing them in the desorption liquid. Finally, the desorption liquid is concentrated, a precipitant is added and stirred, filtered, and calcined for purification to obtain the noble metal element.

[0012] This application also adjusts the pH of the refining wastewater before adsorption. A strongly acidic environment inhibits hydrolysis, maintains metal ions in an adsorbable free state, and ensures that the temperature-sensitive resin retains its molecular state under acidic conditions, enabling it to better form stable grafted specific ligands with noble metal ions and base metal ions (Fe). 3+ Al 3+ Al(II) and other similar compounds will be inhibited in adsorption due to the formation of hydrated ions; furthermore, at pH > 4, Al(II) and other similar compounds will be desorbed. 3+ and Zn 2+ Amphoteric metals can generate colloidal hydroxides, which can easily clog the pores of temperature-sensitive resins. Lowering the pH can dissolve the colloids and inhibit clogging.

[0013] In summary, the process for recovering precious metals from refining wastewater in this application fully utilizes the temperature-sensitive properties of the temperature-sensitive resin, which still exhibits excellent adsorption of precious metal ions at low temperatures. Furthermore, it eliminates the need for additional chemical substances for elution; automatic desorption can be achieved simply by controlling the temperature. The process also demonstrates high selectivity for the adsorption of precious metal ions. Therefore, the precious metals obtained using this application's process have higher purity and greater recovery rates, which is of great significance to the field of metal refining.

[0014] In the specific embodiments of this application, the refining wastewater is potassium gold cyanide wastewater with a concentration of 420 mg / L. This is only an example and should not be used to limit the scope of protection of this application.

[0015] Preferably, the temperature-sensitive resin in S1 is prepared by the following method:

[0016] (1) Under inert gas protection, N-isopropylacrylamide monomer, crosslinking agent and initiator with a molar ratio of 100:(2-4):(0.24-0.48) are dispersed in water to obtain a mixture with an N-isopropylacrylamide concentration of 15-20wt%. The mixture is reacted at 65-70℃ for 3-4h, filtered to obtain a gel substance, washed with alcohol and dried to obtain a resin skeleton;

[0017] (2) The resin skeleton obtained in (1) is immersed in an organic acid solution with a concentration of 10-20wt% at a solid-liquid ratio of (5-8):100, a catalyst is added, the mixture is stirred for 18-24h, filtered, washed, and dried to obtain a thermosensitive resin.

[0018] By adopting the above technical solution, this application utilizes the blending reaction of N-isopropylacrylamide monomer, crosslinking agent and initiator to obtain a resin skeleton with temperature-sensitive properties and a porous structure. Subsequently, the resin skeleton is immersed in an organic acid solution with a concentration of 10-20wt% at a solid-liquid ratio of (5-8):100. Under the condition of adding a catalyst, stirring is carried out to achieve amide bond grafting, thereby obtaining a temperature-sensitive resin with high adsorption capacity, good adsorption selectivity and temperature-sensitive ability. This application also controls the molar ratio of N-isopropylacrylamide monomer, crosslinking agent, and initiator. The amount of crosslinking agent ensures that the crosslinking degree of the resin skeleton is moderate. Too high a crosslinking density will result in too small a pore size in the resin skeleton, hindering the diffusion of subsequent organic acids into the skeleton and reducing the ligand grafting rate. Too low a crosslinking density will cause the resin to disintegrate during swelling and cannot be recycled after regeneration. The amount of initiator can make the resin more stable. Too high an initiator amount will cause chain transfer, resulting in branched structure and weakening the uniformity of organic acid grafting sites. Too low an initiator amount will lead to accelerated chain termination, a wider molecular weight distribution, and affect recyclability.

[0019] Preferably, in (2), the organic acid is thiomalic acid.

[0020] By adopting the above technical solution, this application utilizes thiomalic acid as an organic acid. The thiol groups in thiomalic acid form grafted specific ligands with noble metal ions (such as gold ions, platinum ions, and palladium ions), thereby adsorbing noble metal ions from water into the resin framework. It still has excellent adsorption effect on noble metal ions at low temperatures. Compared with other organic acids with metal chelating ability, the binding of thiomalic acid to the temperature-sensitive framework is more stable. According to experimental data, the temperature-sensitive resin with thiomalic acid as the organic acid can more efficiently adsorb gold ions in refining wastewater, and the recovery rate is significantly improved.

[0021] Preferably, in step (1), the amount of water is adjusted to obtain a mixture with an N-isopropylacrylamide concentration of 18 wt%.

[0022] By adopting the above technical solution, this application further controls the N-isopropylacrylamide concentration to 18 wt%. At this concentration, the resin skeleton has the most suitable swelling degree, providing a good channel for the penetration of organic acid solution. If the N-isopropylacrylamide concentration is too high, it will lead to low viscosity of the reaction system, loose cross-linking network, insufficient resin specific surface area after drying, and decreased adsorption capacity. If the N-isopropylacrylamide concentration is too low, it will lead to excessively high viscosity of the reaction system, hindering heat dissipation, local overheating causing explosive polymerization, forming a heterogeneous gel, and failing to form a resin skeleton with porous channels.

[0023] Preferably, in step (2), the resin skeleton is immersed in an organic acid solution with a concentration of 15wt% at a solid-liquid ratio of 6:100.

[0024] By adopting the above technical solution, this application further controls the solid-liquid ratio of the resin skeleton immersed in the organic acid solution, ensuring sufficient swelling and diffusion balance of the resin. At this time, the organic acid molecules can occupy about 80% of the active sites on the resin surface, achieving a higher grafting density and realizing efficient and uniform grafting of organic acid on the temperature-sensitive resin. At the same time, the solid-liquid ratio of 6:100 ensures that there is a suitable gap between the resin particles, the flow resistance of the solution is minimized during stirring, and the organic acid molecules can penetrate evenly into the interior of the resin.

[0025] Preferably, the temperature-sensitive resin in S1 is further modified with titanium carbide nanosheets, specifically through the following steps:

[0026] A dispersion of titanium carbide nanosheets with a concentration of 4-6 g / L was ultrasonically treated to obtain a colloid. Thermosensitive resin was then immersed in the colloid under negative pressure, cured, and dried to obtain a thermosensitive resin modified with titanium carbide nanosheets with a loading of 2-4 wt%.

[0027] By adopting the above technical solution, this application utilizes ultrasonic-assisted dispersion to uniformly embed titanium carbide nanosheets into the interior of the thermosensitive resin. Negative pressure impregnation ensures that the titanium carbide nanosheets penetrate into the internal pores of the thermosensitive resin, filling the micropore defects generated during resin curing, isolating diffusion channels, and enhancing adsorption stability. More importantly, the titanium carbide nanosheet-modified thermosensitive resin has a micro / nano structure with a larger specific surface area and therefore a higher density of active sites, resulting in a stronger adsorption capacity for noble metal ions. Experimental data show that the modified thermosensitive resin can increase the recovery rate to over 99.5%.

[0028] Preferably, by adjusting the solid-liquid ratio when the thermosensitive resin is immersed in the colloid, a titanium carbide nanosheet modified thermosensitive resin with a loading of 3wt% is obtained.

[0029] By adopting the above technical solution, this application controls the loading of titanium carbide nanosheets to 3 wt%, ensuring that the swelling degree of the resin remains at an optimal value and balancing the adsorption performance. If the amount of titanium carbide nanosheets is too large, it will cause stacking and agglomeration, and may also cause stress concentration leading to resin brittleness; if the amount of titanium carbide nanosheets is too small, it will not be able to effectively optimize the temperature-sensitive resin.

[0030] Preferably, the pressure of the negative pressure impregnation is -0.1 MPa.

[0031] By adopting the above technical solution, this application controls the negative pressure impregnation pressure to -0.1 MPa, making it easier for the nanosheet dispersion to penetrate into the resin pores, breaking down the van der Waals aggregates of the nanosheets, improving colloidal stability, removing trapped air bubbles from the resin pores, and making the nanosheet-resin interface more tightly bonded. If the negative pressure is too high, it will cause the flexible resin skeleton to collapse; if the negative pressure is too low, it will not be able to fully remove trapped air bubbles from the resin pores, nor will it be able to effectively promote the penetration of the nanosheet dispersion into the resin pores.

[0032] Preferably, in step S1, the adsorption temperature is 25°C, and in step S2, the desorption temperature is 45°C.

[0033] By adopting the above technical solution, this application controls the adsorption temperature and desorption temperature in the process. This temperature control and temperature difference can further improve the adsorption and desorption effect of precious metal ions in this process and increase the recovery rate.

[0034] Preferably, in step S2, the desorbed temperature-sensitive resin is acid-washed and regenerated. The acid-washing substance is a 0.5-1 wt% HCl solution, and the acid-washing and regeneration temperature is controlled at 20-30℃.

[0035] By adopting the above technical solution, the thermosensitive resin of this application can be regenerated at a temperature of 20-30℃ using a 0.5-1wt% HCl solution. The regenerated thermosensitive resin can be recycled in this process and still has good adsorption capacity and large adsorption capacity. At the same time, the adsorption-desorption process is almost unaffected by the regeneration operation. After multiple uses, it can still adsorb a large number of noble metal ions, which has the great advantage of efficient regeneration.

[0036] In summary, this application has the following beneficial technical effects:

[0037] 1. The process for recovering precious metals from refining wastewater in this application fully utilizes the temperature-sensitive properties of the temperature-sensitive resin, which still has excellent adsorption effect on precious metal ions at low temperatures. At the same time, no additional chemical substances are needed for elution, and automatic desorption can be achieved by controlling the temperature. The adsorption selectivity for precious metal ions is also high. Therefore, the precious metal elements obtained by the process of this application have higher purity and greater recovery amount, which is of great significance to the field of metal refining.

[0038] 2. This application utilizes ultrasonic-assisted dispersion to uniformly embed titanium carbide nanosheets into the interior of a thermosensitive resin. Negative pressure impregnation ensures that the titanium carbide nanosheets penetrate into the internal pores of the thermosensitive resin, which can fill the micropore defects generated during resin curing, improve density and integrity, isolate diffusion channels, enhance adsorption stability, increase specific surface area through micro / nano structures, and improve the density of active sites.

[0039] 3. The thermosensitive resin of this application still has good adsorption capacity and large adsorption capacity after regeneration. At the same time, the adsorption-desorption process is almost unaffected by the regeneration operation. It can still adsorb a large number of noble metal ions after multiple uses, which has the great advantage of efficient regeneration. Detailed Implementation

[0040] Material source

[0041] Strongly basic anion exchange resin A, purchased from Duolite, brand name A-21S;

[0042] Weakly basic macroporous resin, purchased from Duolite, brand name A-654;

[0043] Strongly basic anion exchange resin B was purchased from Zhejiang Zhengguang Industrial Co., Ltd., with the brand name ZGA304.

[0044] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0045] Preparation Example 1.1

[0046] The preparation method of thermosensitive resin includes the following steps:

[0047] (1) In an inert atmosphere reactor, add 150g of N-isopropylacrylamide monomer, 4.09g of crosslinking agent N,N'-methylenebisacrylamide, and 6mg of initiator ammonium persulfate. Use 0.85L of deionized water as solvent, purge with nitrogen for 10min, heat to 70°C and react for 3h. Filter to obtain gel material, wash with ethanol 3 times to remove unreacted monomers, and vacuum dry at 40°C for 12h to obtain resin skeleton;

[0048] (2) 120g of resin skeleton was immersed in 1.5L of 20wt% thiomalic acid aqueous solution, and catalyst (575g 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and 346g N-hydroxysuccinimide) was added. The mixture was stirred at room temperature for 24h, filtered, washed with deionized water until neutral, and dried at 60℃ for 6h to obtain thermosensitive resin.

[0049] Preparation Example 1.2

[0050] The preparation method of thermosensitive resin includes the following steps:

[0051] (1) In an inert atmosphere reactor, add 150g of N-isopropylacrylamide monomer, 8.18g of crosslinking agent N,N'-methylenebisacrylamide, and 3mg of initiator ammonium persulfate. Use 0.6L of deionized water as solvent, purge with nitrogen for 10min, heat to 65°C and react for 4h. Filter to obtain gel material, wash with ethanol 3 times to remove unreacted monomers, and vacuum dry at 40°C for 12h to obtain resin skeleton;

[0052] (2) 120g of resin skeleton was immersed in 2.4L of 10wt% thiomalic acid aqueous solution, and catalyst (460g 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and 277g N-hydroxysuccinimide) was added. The mixture was stirred at room temperature for 18h, filtered, washed with deionized water until neutral, and dried at 60℃ for 6h to obtain thermosensitive resin.

[0053] Preparation Example 2.1

[0054] The method for preparing the thermosensitive resin differs from that in Preparation Example 1.1 in that 1.5 L of a 20 wt% aqueous solution of thiomalic acid is replaced with 1.5 L of a 20 wt% aqueous solution of N-hydroxyethyl ethylenediamine triacetic acid; all other steps are the same as in Preparation Example 1.1.

[0055] Preparation Example 2.2

[0056] The method for preparing the thermosensitive resin differs from that in Preparation Example 1.1 in that 1.5 L of 20 wt% aqueous solution of thiomalic acid is replaced with 1.5 L of 20 wt% aqueous solution of N,N-dihydroxyethylglycine; all other steps are the same as in Preparation Example 1.1.

[0057] Preparation Example 2.3

[0058] The method for preparing the thermosensitive resin differs from that in Preparation Example 1.1 in that 1.5 L of 20 wt% aqueous solution of thiomalic acid is replaced with 1.5 L of 20 wt% aqueous solution of 2-hydroxyphosphonoacetic acid; all other steps are the same as in Preparation Example 1.1.

[0059] Preparation Example 3.1

[0060] The method for preparing the thermosensitive resin differs from that in Preparation Example 1.1 in that (1) the amount of deionized water used is 0.68L, while the rest is the same as in Preparation Example 1.1.

[0061] Preparation Example 3.2

[0062] The method for preparing the thermosensitive resin differs from that in Preparation Example 1.1 in that (1) the amount of deionized water used is 0.73L, while the rest is the same as in Preparation Example 1.1.

[0063] Preparation Example 3.3

[0064] The method for preparing the thermosensitive resin differs from that in Preparation Example 1.1 in that (1) the amount of deionized water used is 0.5L, while the rest is the same as in Preparation Example 1.1.

[0065] Preparation Example 3.4

[0066] The method for preparing the thermosensitive resin differs from that in Preparation Example 1.1 in that (1) the amount of deionized water used is 1L, while the rest is the same as in Preparation Example 1.1.

[0067] Preparation Example 4.1

[0068] The method for preparing the thermosensitive resin differs from that in Preparation Example 1.1 in that (2) 120g of resin skeleton is immersed in 2L of 15wt% aqueous solution of thiomalic acid, and catalysts (575g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and 346g of N-hydroxysuccinimide) are added. The rest is the same as in Preparation Example 1.1.

[0069] Preparation Example 4.2

[0070] The method for preparing the thermosensitive resin differs from that in Preparation Example 1.1 in that (2) 120g of resin skeleton is immersed in 1.7L of 18wt% aqueous solution of thiomalic acid, and catalysts (586g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and 353g of N-hydroxysuccinimide) are added. The rest is the same as in Preparation Example 1.1.

[0071] Preparation Example 5.1

[0072] The preparation method of titanium carbide nanosheet modified thermosensitive resin includes the following steps:

[0073] A dispersion of titanium carbide nanosheets with a concentration of 6 g / L was ultrasonically treated at a power of 400 W and a frequency of 40 kHz to obtain a colloid. The amount of thermosensitive resin was calculated based on a loading of 2 wt%, and then the amount of thermosensitive resin was immersed in the colloid. The mixture was impregnated under negative pressure at a pressure of -0.1 MPa, cured at room temperature for 12 h, and then dried at 60 °C for 8 h to obtain a thermosensitive resin modified with titanium carbide nanosheets with a loading of 2 wt%.

[0074] Preparation Example 5.2

[0075] The preparation method of titanium carbide nanosheet modified thermosensitive resin includes the following steps:

[0076] A dispersion of titanium carbide nanosheets with a concentration of 4 g / L was ultrasonically treated at a power of 400 W and a frequency of 40 kHz to obtain a colloid. The amount of thermosensitive resin was calculated based on a loading of 4 wt%, and then the amount of thermosensitive resin was immersed in the colloid. The mixture was impregnated under negative pressure at a pressure of -0.1 MPa, cured at room temperature for 12 h, and then dried at 60 °C for 8 h to obtain a thermosensitive resin modified with titanium carbide nanosheets with a loading of 4 wt%.

[0077] Preparation Example 6.1

[0078] The preparation method of the titanium carbide nanosheet modified thermosensitive resin differs from that of Preparation Example 5.1 in that the solid-liquid ratio when the thermosensitive resin is immersed in the colloid is adjusted to obtain a titanium carbide nanosheet modified thermosensitive resin with a loading of 3wt%. The rest are the same as those in Preparation Example 5.1.

[0079] Preparation Example 6.2

[0080] The preparation method of the titanium carbide nanosheet modified thermosensitive resin differs from that of Preparation Example 5.1 in that the solid-liquid ratio when the thermosensitive resin is immersed in the colloid is adjusted to obtain a titanium carbide nanosheet modified thermosensitive resin with a loading of 1 wt%. The rest are the same as those in Preparation Example 5.1.

[0081] Preparation Example 6.3

[0082] The preparation method of the titanium carbide nanosheet modified thermosensitive resin differs from that of Preparation Example 5.1 in that the solid-liquid ratio when the thermosensitive resin is immersed in the colloid is adjusted to obtain a titanium carbide nanosheet modified thermosensitive resin with a loading of 5 wt%. The rest are the same as those in Preparation Example 5.1.

[0083] Preparation Example 7.1

[0084] The preparation method of the titanium carbide nanosheet modified thermosensitive resin differs from that of Preparation Example 5.1 in that the negative pressure impregnation pressure is -0.2 MPa, while the rest is the same as that of Preparation Example 5.1.

[0085] Preparation Example 7.2

[0086] The preparation method of the titanium carbide nanosheet modified thermosensitive resin differs from that of Preparation Example 5.1 in that the negative pressure impregnation pressure is -0.05 MPa, while the rest is the same as that of Preparation Example 5.1.

[0087] Example 1.1

[0088] A process for recovering precious metals from refining wastewater includes the following steps:

[0089] S0. Filling: The resin obtained in Preparation Example 1.1 is added into a vertically fixed column, while the column wall is gently tapped to allow the resin to settle evenly. The filling height is 8 times the inner diameter of the column to obtain a temperature-sensitive resin column.

[0090] S1. Adsorption: The pH of 500 mL of potassium gold cyanide wastewater with a concentration of 420 mg / L was adjusted to 2, and then the solution was passed into the temperature-sensitive resin column obtained by S0 at a flow rate of 1.2 BV / h for adsorption. The adsorption temperature was 28℃.

[0091] S2. Desorption: After heating the system to the desorption temperature of 50°C, start collecting the desorbate;

[0092] S3. Recovery: The desorption solution obtained in S2 is concentrated, and then sodium sulfite is slowly added at a temperature of 25℃ and pH=2.0 to reduce gold ions to elemental form. After filtration, the resulting precipitate is washed three times with dilute hydrochloric acid and purified by calcination to obtain elemental gold.

[0093] Example 1.2

[0094] A process for recovering precious metals from refining wastewater includes the following steps:

[0095] S0. Filling: The resin obtained in Preparation Example 1.2 is added into a vertically fixed column, while the column wall is gently tapped to allow the resin to settle evenly. The filling height is 8 times the inner diameter of the column to obtain a temperature-sensitive resin column.

[0096] S1. Adsorption: The pH of 500 mL of potassium gold cyanide wastewater with a concentration of 420 mg / L was adjusted to 3, and then the solution was passed into the temperature-sensitive resin column obtained by S0 at a flow rate of 0.8 BV / h for adsorption. The adsorption temperature was 20℃.

[0097] S2. Desorption: After heating the system to the desorption temperature of 42℃, start collecting the desorbed solution;

[0098] S3. Recovery: The desorption solution obtained in S2 is concentrated, and then sodium sulfite is slowly added at a temperature of 25℃ and pH=2.0 to reduce gold ions to elemental form. After filtration, the resulting precipitate is washed three times with dilute hydrochloric acid and purified by calcination to obtain elemental gold.

[0099] Example 1.3

[0100] A process for recovering precious metals from refining wastewater includes the following steps:

[0101] S0. Filling: The resin obtained in Preparation Example 1.1 is added into a vertically fixed column, while the column wall is gently tapped to allow the resin to settle evenly. The filling height is 8 times the inner diameter of the column to obtain a temperature-sensitive resin column.

[0102] S1. Adsorption: The pH of 500 mL of potassium gold cyanide wastewater with a concentration of 420 mg / L was adjusted to 2.5, and then the solution was passed into the temperature-sensitive resin column obtained by S0 at a flow rate of 1.0 BV / h for adsorption. The adsorption temperature was 22℃.

[0103] S2. Desorption: After heating the system to the desorption temperature of 44℃, start collecting the desorbed solution;

[0104] S3. Recovery: The desorption solution obtained in S2 is concentrated, and then sodium sulfite is slowly added at a temperature of 25℃ and pH=2.0 to reduce gold ions to elemental form. After filtration, the resulting precipitate is washed three times with dilute hydrochloric acid and purified by calcination to obtain elemental gold.

[0105] Example 1.4

[0106] A process for recovering precious metals from refining wastewater includes the following steps:

[0107] S0. Filling: The resin obtained in Preparation Example 1.1 is added into a vertically fixed column, while the column wall is gently tapped to allow the resin to settle evenly. The filling height is 8 times the inner diameter of the column to obtain a temperature-sensitive resin column.

[0108] S1. Adsorption: The pH of 500 mL of potassium gold cyanide wastewater with a concentration of 420 mg / L was adjusted to 2.5, and then the solution was passed into the temperature-sensitive resin column obtained by S0 at a flow rate of 1.0 BV / h for adsorption. The adsorption temperature was 25℃.

[0109] S2. Desorption: After heating the system to the desorption temperature of 45°C, start collecting the desorbate;

[0110] S3. Recovery: The desorption solution obtained in S2 is concentrated, and then sodium sulfite is slowly added at a temperature of 25℃ and pH=2.0 to reduce gold ions to elemental form. After filtration, the resulting precipitate is washed three times with dilute hydrochloric acid and purified by calcination to obtain elemental gold.

[0111] Example 1.5

[0112] A process for recovering precious metals from refining wastewater includes the following steps:

[0113] S0. Filling: The resin obtained in Preparation Example 1.1 is added into a vertically fixed column, while the column wall is gently tapped to allow the resin to settle evenly. The filling height is 8 times the inner diameter of the column to obtain a temperature-sensitive resin column.

[0114] S1. Adsorption: The pH of 500 mL of potassium gold cyanide wastewater with a concentration of 420 mg / L was adjusted to 2.5, and then the solution was passed into the temperature-sensitive resin column obtained by S0 at a flow rate of 1.0 BV / h for adsorption. The adsorption temperature was 27℃.

[0115] S2. Desorption: After heating the system to the desorption temperature of 48°C, start collecting the desorbate;

[0116] S3. Recovery: The desorption solution obtained in S2 is concentrated, and then sodium sulfite is slowly added at a temperature of 25℃ and pH=2.0 to reduce gold ions to elemental form. After filtration, the resulting precipitate is washed three times with dilute hydrochloric acid and purified by calcination to obtain elemental gold.

[0117] Examples 2.1-2.3

[0118] A process for recovering precious metals from refining wastewater differs from Example 1.4 in that, in S0, the thermosensitive resin obtained in Preparation Example 1.1 is replaced with the thermosensitive resin obtained in Preparation Examples 2.1-2.3, while the rest is the same as in Example 1.4.

[0119] Examples 3.1-3.4

[0120] A process for recovering precious metals from refining wastewater differs from Example 1.4 in that, in S0, the thermosensitive resin obtained in Preparation Example 1.1 is replaced with the thermosensitive resin obtained in Preparation Examples 3.1-3.4, while the rest is the same as in Example 1.4.

[0121] Examples 4.1-4.2

[0122] A process for recovering precious metals from refining wastewater differs from Example 1.4 in that, in S0, the thermosensitive resin obtained in Preparation Example 1.1 is replaced with the thermosensitive resin obtained in Preparation Examples 4.1-4.2, while the rest is the same as in Example 1.4.

[0123] Examples 5.1-5.2

[0124] A process for recovering precious metals from refining wastewater differs from Example 1.4 in that, in S0, the thermosensitive resin obtained in Preparation Example 1.1 is replaced with the thermosensitive resin obtained in Preparation Examples 5.1-5.2, while the rest is the same as in Example 1.4.

[0125] Examples 6.1-6.3

[0126] A process for recovering precious metals from refining wastewater differs from Example 5.1 in that, in S0, the thermosensitive resin obtained in Preparation Example 1.1 is replaced with the thermosensitive resin obtained in Preparation Examples 6.1-6.3, while the rest is the same as in Example 5.1.

[0127] Examples 7.1-7.2

[0128] A process for recovering precious metals from refining wastewater differs from Example 5.1 in that, in S0, the thermosensitive resin obtained in Preparation Example 1.1 is replaced with the thermosensitive resin obtained in Preparation Examples 7.1-7.2, while the rest is the same as in Example 5.1.

[0129] Example 8.1

[0130] A process for recovering precious metals from refining wastewater differs from Example 1.4 in that, in S2, the desorbed temperature-sensitive resin is acid-washed and regenerated. The acid-washing substance is a 1wt% HCl solution, and the acid-washing and regeneration temperature is controlled at 20°C. The regenerated temperature-sensitive resin is then used to continue the operation in S1. The above operation is repeated a total of 5 times, and the rest is the same as in Example 1.4.

[0131] Example 8.2

[0132] A process for recovering precious metals from refining wastewater differs from Example 1.4 in that, in S2, the desorbed temperature-sensitive resin is acid-washed and regenerated. The acid-washing substance is a 0.5wt% HCl solution, and the acid-washing and regeneration temperature is controlled at 30°C. The regenerated temperature-sensitive resin is then used to continue the operation in S1. The above operation is repeated a total of 5 times, and the rest is the same as in Example 1.4.

[0133] Example 9.1

[0134] A process for recovering precious metals from refining wastewater differs from Example 2.1 in that, in S2, the desorbed temperature-sensitive resin is acid-washed and regenerated. The acid-washing substance is a 0.75wt% HCl solution, and the acid-washing and regeneration temperature is controlled at 25°C. The regenerated temperature-sensitive resin is then used to continue the operation in S1. The above operation is repeated a total of 5 times, and the rest is the same as in Example 2.1.

[0135] Example 9.2

[0136] A process for recovering precious metals from refining wastewater differs from Example 2.2 in that, in S2, the desorbed temperature-sensitive resin is acid-washed and regenerated. The acid-washing substance is a 0.75wt% HCl solution, and the acid-washing and regeneration temperature is controlled at 25°C. The regenerated temperature-sensitive resin is then used to continue the operation in S1. The above operation is repeated a total of 5 times, and the rest is the same as in Example 2.2.

[0137] Example 9.3

[0138] A process for recovering precious metals from refining wastewater differs from Example 2.3 in that, in S2, the desorbed temperature-sensitive resin is acid-washed and regenerated. The acid-washing substance is a 0.75wt% HCl solution, and the acid-washing and regeneration temperature is controlled at 25°C. The regenerated temperature-sensitive resin is then used to continue the operation in S1. The above operation is repeated a total of 5 times, and the rest is the same as in Example 2.3.

[0139] Comparative Example 1.1

[0140] S0. Packing: Backwash the strong base anion exchange resin A with clean water until the effluent is clear, then soak it in 4wt% HCl solution and 4wt% sodium hydroxide solution for 20 hours in sequence, and finally rinse it with clean water until neutral. Then add it into a vertically fixed column, while gently tapping the column wall to make the resin settle evenly. The packing height is 8 times the inner diameter of the column to obtain the strong base anion exchange resin column A.

[0141] S1. Adsorption: The pH of 500 mL of potassium gold cyanide wastewater with a concentration of 420 mg / L was adjusted to 2, and then the solution was passed into the strongly basic anion exchange resin column A obtained from S0 at a flow rate of 1.2 BV / h for adsorption. The adsorption temperature was 25℃.

[0142] S2. Desorption: Elute with a mixture of 3 wt% HCl solution and 5 wt% thiourea solution at a flow rate of 1.8 BV / h, and collect the eluent;

[0143] S3. Recovery: The desorption solution obtained in S2 is concentrated, and then sodium sulfite is slowly added at a temperature of 25℃ and pH=2.0 to reduce gold ions to elemental form. After filtration, the resulting precipitate is washed three times with dilute hydrochloric acid and purified by calcination to obtain elemental gold.

[0144] Comparative Example 1.2

[0145] S0. Filling: Backwash the weakly basic macroporous resin with clean water until the effluent is clear, then soak it in 4wt% HCl solution and 4wt% sodium hydroxide solution for 20 hours in sequence, and finally rinse it with clean water until neutral. Then add it into a vertically fixed column, while gently tapping the column wall to make the resin settle evenly. The filling height is 8 times the inner diameter of the column to obtain a weakly basic macroporous resin column.

[0146] S1. Adsorption: The pH of 500 mL of potassium gold cyanide wastewater with a concentration of 420 mg / L was adjusted to 2, and then the water was passed into the weakly basic macroporous resin column obtained by S0 at a flow rate of 1.2 BV / h for adsorption. The adsorption temperature was 25℃.

[0147] S2. Desorption: Elute with a mixture of 3 wt% HCl solution and 5 wt% thiourea solution at a flow rate of 1.8 BV / h, and collect the eluent;

[0148] S3. Recovery: The desorption solution obtained in S2 is concentrated, and then sodium sulfite is slowly added at a temperature of 25℃ and pH=2.0 to reduce gold ions to elemental form. After filtration, the resulting precipitate is washed three times with dilute hydrochloric acid and purified by calcination to obtain elemental gold.

[0149] Comparative Example 1.3

[0150] S0. Packing: Backwash the strong base anion exchange resin B with clean water until the effluent is clear, then soak it in 4wt% HCl solution and 4wt% sodium hydroxide solution for 20 hours in sequence, and finally rinse it with clean water until neutral. Then add it into a vertically fixed column, while gently tapping the column wall to make the resin settle evenly. The packing height is 8 times the inner diameter of the column to obtain the strong base anion exchange resin column B.

[0151] S1. Adsorption: The pH of 500 mL of potassium gold cyanide wastewater with a concentration of 420 mg / L was adjusted to 2, and then the solution was passed into the strongly basic anion exchange resin column B obtained from S0 at a flow rate of 1.2 BV / h for adsorption. The adsorption temperature was 25℃.

[0152] S2. Desorption: Elute with a mixture of 3 wt% HCl solution and 5 wt% thiourea solution at a flow rate of 1.8 BV / h, and collect the eluent;

[0153] S3. Recovery: The desorption solution obtained in S2 is concentrated, and then sodium sulfite is slowly added at a temperature of 25℃ and pH=2.0 to reduce gold ions to elemental form. After filtration, the resulting precipitate is washed three times with dilute hydrochloric acid and purified by calcination to obtain elemental gold.

[0154] Comparative Example 2.1

[0155] The difference from Comparative Example 1.1 is that in S2, the desorbed strong basic anion exchange resin A is acid-washed and regenerated. The acid-washing substance is a 1wt% HCl solution, and the acid-washing and regeneration temperature is controlled at 20°C. The regenerated strong basic anion exchange resin A is used to continue the operation of S1. The above operation is repeated a total of 5 times, and the rest is the same as in Example 1.1.

[0156] Comparative Example 2.2

[0157] The difference from Comparative Example 1.2 is that in S2, the desorbed weakly basic macroporous resin is acid-washed and regenerated. The acid-washing substance is a 1wt% HCl solution, and the acid-washing and regeneration temperature is controlled at 20°C. The regenerated weakly basic macroporous resin is used to continue the operation of S1. The above operation is repeated a total of 5 times. The rest is the same as in Example 2.2.

[0158] Comparative Example 2.3

[0159] The difference from Comparative Example 1.3 is that in S2, the desorbed strong basic anion exchange resin B is acid-washed and regenerated. The acid-washing substance is a 1wt% HCl solution, and the acid-washing and regeneration temperature is controlled at 20°C. The regenerated strong basic anion exchange resin B is used to continue the operation of S1. The above operation is repeated a total of 5 times. The rest is the same as in Example 2.3.

[0160] Performance testing

[0161] Recovery rate detection: The concentration of potassium gold cyanide in the effluent of S1 was determined (for Examples 8.1-9.3 and Comparative Examples 2.1-2.3, only the concentration of potassium gold cyanide in the last effluent was determined), and the gold recovery rate was calculated (%).

[0162] Purity testing: The purity of the gold obtained in S3 was tested.

[0163] Table 1 Data Records

[0164]

[0165] Data Analysis:

[0166] As shown in Table 1, in the processes of Examples 1.1-1.5 of this application, the gold recovery rate reached 99.20-99.28%, and the purity of the elemental substance was higher than 98.7%. It can be seen that the process for recovering precious metals from refining wastewater of this application has excellent adsorption effect on precious metal ions, and the obtained precious metal elemental substance has higher purity and greater recovery amount. In Examples 8.1-8.2, the temperature-sensitive resin of this application was acid-washed and regenerated. The results showed that after five cycles, the temperature-sensitive resin could still maintain a recovery rate of 99.23-99.24%, and the cycle decline rate was 0.04-0.05%. It can be seen that it has good regenerability and regeneration adsorption stability, which is of great significance to the field of metal refining.

[0167] In Examples 2.1-2.3, the type of organic acid was adjusted, and the results showed that the gold recovery rate decreased to 99.02-99.06%. This demonstrates that the application utilizes thiomalic acid as the organic acid to adsorb precious metal ions from water into the resin framework, maintaining excellent adsorption performance even at low temperatures. Compared to other organic acids with metal chelating capabilities, thiomalic acid exhibits more stable binding to the temperature-sensitive framework. Experimental data shows that the temperature-sensitive resin using thiomalic acid as the organic acid can more efficiently adsorb gold ions from refining wastewater, significantly improving the recovery rate. In Examples 9.1-9.3, the temperature-sensitive resin from Examples 2.1-2.3 was acid-washed and regenerated. The results showed that the recovery rate after five cycles was 98.94-98.95%, with a cycle decrease rate of 0.08-0.11%.

[0168] In Examples 3.1-3.4, the concentration of N-isopropylacrylamide in the mixture was adjusted. The recovery rate in Example 3.1 reached 99.41%, indicating that the resin skeleton has the most suitable swelling degree when the N-isopropylacrylamide concentration is 18wt%, which can provide a good channel for the permeation of thiomalic acid solution. The recovery rate in Examples 3.3-3.4 was significantly reduced. It can be seen that if the N-isopropylacrylamide concentration is too high, the viscosity of the reaction system will be low, the cross-linking network will be loose, the specific surface area of ​​the resin after drying will be insufficient, and the adsorption capacity will decrease. If the N-isopropylacrylamide concentration is too low, the viscosity of the reaction system will be too high, which will hinder heat dissipation, cause local overheating and burst polymerization, form a heterogeneous gel, and fail to form a resin skeleton with porous channels.

[0169] In Examples 4.1-4.2, this application adjusted the solid-liquid ratio of the resin skeleton and the aqueous solution of thiomalic acid, as well as the concentration of the aqueous solution of thiomalic acid. The results showed that the recovery rate of Example 4.1 was significantly improved. It can be seen that further controlling the solid-liquid ratio of the resin skeleton immersed in the thiomalic acid solution can ensure sufficient swelling and diffusion balance of the resin. At this time, thiomalic acid molecules can occupy about 80% of the active sites on the resin surface, achieving a higher grafting density and realizing efficient and uniform grafting of thiomalic acid on the temperature-sensitive resin. At the same time, the solid-liquid ratio of 6:100 ensures that there is a suitable gap between the resin particles, and the flow resistance of the solution is minimized during stirring, so that thiomalic acid molecules can penetrate evenly into the interior of the resin.

[0170] In Examples 5.1-5.2, the present application modified the thermosensitive resin, and the results showed that the recovery rate increased to 99.52-99.53%. It can be seen that titanium carbide nanosheets can penetrate into the internal pores of the thermosensitive resin, fill the micropore defects generated during resin curing, improve density and integrity, isolate diffusion channels, enhance adsorption stability, increase specific surface area through micro / nano structures, and improve the density of active sites.

[0171] In Examples 6.1-6.3, this application adjusted the loading of titanium carbide nanosheets in the modified thermosensitive resin. The results showed that the recovery rate of Example 6.1 increased to 99.62%, while the recovery rate of Examples 6.2-6.3 dropped to 99.26-99.33%. It can be seen that a loading of 3 wt% of titanium carbide nanosheets can ensure that the swelling degree of the resin is still at an optimal value, balancing the adsorption performance. If the amount of titanium carbide nanosheets is too large, it will cause stacking and self-agglomeration, and may also cause stress concentration leading to resin brittleness. If the amount of titanium carbide nanosheets is too small, it will not be able to effectively optimize the thermosensitive resin.

[0172] In Examples 7.1-7.2, the pressure of the negative pressure impregnation was adjusted, and the results showed a decrease in recovery rate. This indicates that a pressure of -0.1 MPa allows the nanosheet dispersion to more easily penetrate the resin pores, disrupting the van der Waals aggregates of the nanosheets, improving colloidal stability, removing trapped air bubbles from the resin pores, and resulting in a tighter bond between the nanosheets and the resin. If the negative pressure is too high, the flexible resin framework will collapse; if the negative pressure is too low, trapped air bubbles in the resin pores cannot be sufficiently removed, nor can the penetration of the nanosheet dispersion into the resin pores be effectively promoted.

[0173] In Comparative Examples 1.1-1.3, this application selected three conventional resins for recycling. The results showed that the recovery rates were all lower than those in Example 1.4. Furthermore, in the regeneration and recycling of Comparative Examples 2.1-2.3, the recovery rate even dropped below 96%. This demonstrates that the process of this application fully utilizes the temperature-sensitive properties of the temperature-sensitive resin, exhibiting excellent adsorption of precious metal ions even at low temperatures. Simultaneously, no additional chemical substances are required for elution; automatic desorption can be achieved by controlling the temperature. The adsorption selectivity for precious metal ions is also high, and the adsorption-desorption process is almost unaffected by regeneration operations. Even after multiple uses, it can still adsorb a large amount of precious metal ions. Therefore, the precious metal element obtained using the process of this application has higher purity and a greater recovery rate, and also possesses the significant advantage of efficient regeneration.

[0174] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A process for the recovery of precious metals from refinery wastewater, characterized in that, It comprises the following steps: S1. Adsorption: adjust the pH of the refining wastewater to 2-3, then pass into the temperature-sensitive resin at a flow rate of 0.8-1.2 BV / h for adsorption, and the adsorption temperature is 20-28℃; S2. Desorption: raise the temperature of the system to a desorption temperature of 42-50℃, and collect the desorption liquid; S3. Recovery: concentrate the desorption liquid, add a precipitant and stir, filter, and calcine to purify to obtain noble metal elements; The temperature-sensitive resin is prepared from N-isopropyl acrylamide monomer and organic acid, and the organic acid includes one of thiomalic acid, N-hydroxyethyl ethylenediamine triacetic acid, N,N-dihydroxyethyl glycine and 2-hydroxyphosphonoacetic acid; The temperature-sensitive resin in S1 is prepared by the following method: (1) Under the protection of inert gas, disperse N-isopropyl acrylamide monomer, crosslinking agent and initiator in a molar ratio of 100: (2-4): (0.24-0.48) in water to obtain a mixed solution with a N-isopropyl acrylamide concentration of 15-20wt%, and react at a temperature of 65-70℃ for 3-4h, filter to obtain a gel material, alcohol wash and dry to obtain a resin skeleton; (2) Submerge the resin skeleton obtained in (1) in an organic acid solution with a concentration of 10-20wt% according to a solid-liquid ratio of (5-8) g: 100mL, add a catalyst, stir for 18-24h, filter, wash and dry to obtain a temperature-sensitive resin.

2. A process for the recovery of precious metals from refinery wastewater according to claim 1, characterized in that, In (2), the organic acid is thiomalic acid.

3. A process for the recovery of precious metals from refinery wastewater according to claim 1, characterized in that, In (1), adjust the amount of water to obtain a mixed solution with a N-isopropyl acrylamide concentration of 18wt%.

4. A process for recovering precious metals from refinery wastewater according to claim 1, characterized in that, In (2), submerge the resin skeleton in an organic acid solution with a concentration of 15wt% according to a solid-liquid ratio of 6g: 100mL.

5. A process for recovering precious metals from refinery wastewater according to claim 1, characterized in that, The temperature-sensitive resin in S1 is also modified by titanium carbide nanosheets, and the specific steps are as follows: Ultrasonic treat a titanium carbide nanosheet dispersion liquid with a concentration of 4-6g / L to obtain a colloid, then submerge the temperature-sensitive resin in the colloid, perform negative pressure impregnation, solidify and dry to obtain a titanium carbide nanosheet modified temperature-sensitive resin with a loading amount of 2-4wt%.

6. A process for the recovery of precious metals from refinery wastewater according to claim 5, characterized in that, Adjust the solid-liquid ratio when submerging the temperature-sensitive resin in the colloid to obtain a titanium carbide nanosheet modified temperature-sensitive resin with a loading amount of 3wt%.

7. A process for the recovery of precious metals from refinery wastewater according to claim 5, characterized in that, The pressure of the negative pressure impregnation is -0.1MPa.

8. A process for recovering precious metals from refinery wastewater according to claim 1, characterized in that, In S1, the adsorption temperature is 25℃, and in S2, the desorption temperature is 45℃.

9. A process for recovering precious metals from refinery wastewater according to claim 1, characterized in that, In S2, perform acid pickling regeneration on the desorbed temperature-sensitive resin, and the acid pickling uses 0.5-1wt% of HCl solution, and the temperature of the acid pickling regeneration is controlled at 20-30℃.

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