A method, apparatus and application for recovering precious metals from electroplating wastewater

Abstract

This invention relates to a method, apparatus, and application for recovering precious metals from electroplating wastewater. The method includes the following steps: contacting the electroplating wastewater with hydrogen and a functional membrane module, causing precious metal II in the wastewater to deposit on the surface of the functional membrane module, resulting in a functional membrane module deposited with precious metal II; wherein the functional membrane module comprises a hollow fiber membrane, and the surface of the hollow fiber membrane is pre-loaded with precious metal I nanoparticles. This method overcomes the limitation of traditional processes that only obtain crude metals. By using a "seed catalyst" pre-loaded on the membrane module under mild conditions to induce selective reduction and deposition of precious metal II ions in the wastewater, highly catalytically active precious metal I nanoparticles are grown in situ on the membrane surface. The recovered membrane module requires no complex post-processing and can be used as a ready-to-use, high-efficiency catalytic module, simultaneously completing the preparation of high-value-added catalytic materials.

Description

Technical Field

[0001] This invention relates to the field of precious metal wastewater recycling and treatment technology, and in particular to a method, apparatus and application for recovering precious metals from electroplating wastewater. Background Technology

[0002] With the rapid development of industries such as electronics and information, high-end equipment manufacturing, and jewelry processing, precious metals (such as gold, silver, palladium, and platinum) are widely used in electroplating and electroless plating processes due to their excellent conductivity, stability, and catalytic activity. During production, a large amount of wastewater rich in precious metal ions is generated, mainly including rinsing water, aging solutions, and stripping solutions. This type of electroplating wastewater is characterized by "large volume, low concentration of precious metals, but high total value." According to industry statistics, a medium-sized electronic electroplating company can generate hundreds to thousands of tons of rinsing water containing precious metals daily, with precious metal concentrations generally between 1 mg / L and 100 mg / L, and concentrations of metals such as gold and palladium even below 0.5 mg / L. Although the precious metals in the wastewater are dispersed, the annual cumulative loss is staggering. Furthermore, due to the biotoxicity and environmental accumulation of precious metal ions, their efficient recovery not only has significant economic value but also substantial environmental benefits.

[0003] Currently, the industry and research fields mainly use the following types of technologies for the recovery of precious metals from electroplating wastewater: 1. Chemical precipitation method This method is the most traditional, which involves adding reducing agents (such as sodium borohydride, hydrazine hydrate, etc.) or precipitating agents (such as sulfides) to the wastewater to convert noble metal ions into elements or precipitate them. Although the operation is simple and the cost is low, there are also obvious shortcomings: (1) poor selectivity, as a large number of base metal ions such as copper, nickel, and zinc coexist in the wastewater and compete for precipitation, resulting in low product purity. The noble metal grade is usually less than 10%, requiring subsequent complex refining; (2) large consumption of reagents and large sludge production, which can easily cause secondary pollution; (3) low recovery efficiency for low concentration (<5-10 mg / L) wastewater, resulting in poor economic efficiency.

[0004] 2. Adsorption method This method utilizes ion exchange resins or specific adsorbent materials (such as activated carbon, functionalized polymers, and biomass materials) to selectively adsorb noble metal ions. Its advantages include continuous operation, but it also suffers from limitations such as limited adsorption capacity, slow adsorption rate, high material costs (especially for specialized resins), and complex desorption steps. The enriched solution after desorption still requires further treatment to obtain pure metals, and the adsorbent materials are easily contaminated by organic matter and suspended solids in wastewater, leading to their degradation.

[0005] 3. Electrolytic recovery method This method is suitable for wastewater with high concentrations of precious metals (e.g., >500 mg / L), where the metal is recovered directly by electrochemical reduction and deposition at the cathode. Its advantage is the ability to obtain high-purity metals. However, for low-concentration, high-flow-rate electroplating rinse water, the current efficiency is extremely low, energy consumption is enormous, and it is economically infeasible. Furthermore, the cathode surface is easily contaminated by co-deposited base metals, affecting product purity.

[0006] 4. Membrane separation technologies (such as reverse osmosis and nanofiltration) Membrane technology can be used for the concentration of precious metals, but it faces challenges such as severe membrane fouling, high operating pressure, limited concentration ratio, short membrane life, and high investment costs. The concentrate still requires other methods to ultimately recover the metal; therefore, this technology is mostly used as a pretreatment or concentration step.

[0007] In summary, existing single technologies often struggle to achieve an ideal balance between recovery efficiency, product purity, operating costs, ease of operation, and environmental friendliness when treating electroplating wastewater with complex composition and low, fluctuating precious metal concentrations. This is particularly true when treating low-concentration precious metal wastewater, where the following limitations are commonly observed: 1. The contradiction between efficiency and cost: High-efficiency recycling often relies on high energy consumption or high reagent consumption, resulting in poor economic efficiency; 2. Risk of secondary pollution: The use of chemical agents or the generation of low-grade sludge may bring new environmental problems; 3. The value of recycled products is not maximized: the precious metals obtained by traditional processes are mostly crude products (such as low-grade sludge or spongy metals), which need to be returned to large refineries for complex purification and reprocessing. The process is long and costly, and it fails to form synergistic benefits with the wastewater treatment process.

[0008] Therefore, there is an urgent need to develop a new integrated process that is simple, highly selective, efficient, cost-effective, and environmentally friendly, in order to achieve efficient and high-value recycling of electroplating wastewater, especially low-concentration precious metal wastewater, and truly achieve the goals of "turning waste into treasure" and clean production. Summary of the Invention

[0009] To address the above technical problems, this invention provides a method for recovering precious metals from electroplating wastewater. This method enables in-situ recovery of precious metals and allows the recovered highly active precious metal materials to be directly used for catalytic purification of water.

[0010] The present invention also provides an apparatus for implementing the above method.

[0011] The present invention also provides applications for implementing the above-described methods and apparatus.

[0012] In some embodiments of the present invention, a method for recovering precious metals from electroplating wastewater is proposed, comprising the following steps: Electroplating wastewater is brought into contact with hydrogen and a functional membrane module, causing precious metal II in the electroplating wastewater to be deposited on the surface of the functional membrane module, thereby obtaining a functional membrane module with precious metal II deposited on it; wherein, the functional membrane module includes a hollow fiber membrane, the surface of which is preloaded with precious metal I nanoparticles, and the precious metal II may be the same as or different from precious metal I.

[0013] In some embodiments of the present invention, the concentration of precious metal II ions in the electroplating wastewater to be treated is less than 10 mg / L. This method is applicable to the recovery of extremely low concentrations of precious metal ions, overcoming the bottleneck of low efficiency or poor economy of traditional methods at extremely low concentrations.

[0014] In some embodiments of the present invention, the concentration of precious metal II ions in the electroplating wastewater to be treated is 1~10 mg / L.

[0015] In some embodiments of the present invention, the noble metal II and noble metal I each independently include at least one of Ru, Rh, Pt or Pd.

[0016] In some embodiments of the present invention, the particle size of the noble metal I nanoparticles is 3-100 nm.

[0017] In some embodiments of the present invention, the loading of the noble metal I nanoparticles is 0.01~0.07 g / m³. 2 .

[0018] In some embodiments of the present invention, the reaction temperature during the deposition process is 10~35°C.

[0019] In some embodiments of the present invention, the reaction temperature during the deposition process is 20~25°C.

[0020] In some embodiments of the present invention, the absolute pressure of the environment during the deposition process is 1-2 atm. In a low-pressure hydrogen atmosphere, using a noble metal seed layer immobilized on a support as a catalyst, the target noble metal ions in wastewater can be selectively reduced and deposited without pressurization, resulting in high economic benefits.

[0021] In some embodiments of the present invention, the method further includes a step of preparing the functional membrane module: placing the membrane module in a precursor solution containing noble metal I, adjusting the hydrogen pressure of the system to 3-30 psig, so that noble metal I nanoparticles are loaded on the surface of the membrane module. The noble metal ions are reduced in situ to metal nanoparticles and firmly adhere to the membrane surface, forming a highly active "seed catalyst" layer. Under these reduction conditions, it is more conducive to obtaining catalytic active sites with small particle size and uniform distribution.

[0022] In some embodiments of the present invention, the precursor solution containing noble metal I includes at least one of sodium tetrachloropalladium, palladium chloride, or palladium acetate.

[0023] In some embodiments of the present invention, the membrane module is a hollow fiber membrane (preferably, with an outer diameter of 100-400 μm and an inner diameter of 50-150 μm). A hollow fiber membrane with a high specific surface area is preferred. A dense, non-porous, breathable membrane is also preferred.

[0024] In some embodiments of the present invention, the membrane component is made of a modified or unmodified polymer.

[0025] In some embodiments of the present invention, the modification includes hydrophilization or the introduction of amino or thiol groups. The immobilization capacity of the seed catalyst can be enhanced by hydrophilization or modification with functional groups such as amino or neck groups.

[0026] In some embodiments of the present invention, the polymer comprises at least one of polyethylene (PE), polypropylene (PP), polyvinylidene fluoride (PVDF), or polyethersulfone (PES).

[0027] In some embodiments of the present invention, the polymer is one or a combination of two of the following materials: polyethylene (PE), polypropylene (PP), polyvinylidene fluoride (PVDF), or polyethersulfone (PES).

[0028] In some embodiments of the present invention, the preparation process of the functional membrane module further includes at least one of the following conditions: 1) the concentration of noble metal ions in the precursor solution containing noble metal I is 5~20 mg / L; 2) the system temperature is 5~60℃, preferably 20~25℃.

[0029] In some embodiments of the present invention, the pH of the electroplating wastewater to be treated is 1-5. It can be pre-adjusted to an acidic range of 1-5 to stabilize the noble metal ions.

[0030] In some embodiments of the present invention, the deposition process includes the following conditions: maintaining the hydrogen pressure inside the hollow fiber membrane at 3 to 30 psig.

[0031] In some embodiments of the present invention, the hydrogen pressure inside the hollow fiber membrane is maintained at 5 to 10 psig.

[0032] In some embodiments of the present invention, the hydraulic retention time (HRT) of the electroplating wastewater to be treated in the hollow fiber membrane cavity is 6-24 h. Under the induction of the "seed catalyst" and the reduction of hydrogen, the target noble metal II ions (such as Pd) in the wastewater... 2+ ,Rh 3+ Ru 3+ Pt 4+Base metal ions (such as Fe) are preferentially and selectively reduced to metal atoms and continuously deposited on the seed particles, achieving "autocatalytic" growth of the particles. Coexisting base metal ions (such as Fe) 3+ Ni 2+ Zn 2+ K + Na + Mg 2+ Ca 2+ Al 3+ Due to their high reduction potential, these metals do not react under these mild conditions, thus achieving highly selective recovery of precious metals.

[0033] In some embodiments of the present invention, the hydraulic residence time is 6 to 12 hours.

[0034] In some embodiments of the present invention, the electroplating wastewater to be treated is circulated on the surface of the functional membrane module at a circulation rate of 50~300 mL / min.

[0035] In some embodiments of the present invention, the circulation flow rate is 80~200 mL / min.

[0036] In some embodiments of the present invention, the hydraulic retention time is 6–24 h, the hydrogen pressure (HRT) inside the hollow fiber membrane is 3–30 psig, and the circulation flow rate is 50–300 mL / min. By precisely controlling the system's hydrogen pressure, HRT, and circulation flow rate, the process window is better suited for the recovery of noble metal ions of different concentrations. These parameters are better suited for the enrichment and reduction of noble metal ions at low concentrations, thus better overcoming the bottlenecks in efficiency or economy of traditional methods at extremely low concentrations.

[0037] In some embodiments of the present invention, the hydraulic retention time is 6-12 h, the hydrogen pressure inside the hollow fiber membrane is 5-10 psig, and the circulation flow rate is 80-200 mL / min. The recovery efficiency can be further optimized synergistically by adjusting the HRT, hydrogen pressure, and circulation flow rate.

[0038] In some embodiments of the present invention, the deposition amount of noble metal II on the functional membrane module reaches 0.03~4.00 g / m³. 2 Stop feeding the electroplating wastewater to be treated. Loading rate is 0.03~4.00 g / m³. 2 It can be directly used as a structured catalyst to treat wastewater containing organic pollutants.

[0039] In some embodiments of the present invention, the amount of noble metal II deposited on the functional membrane module is 0.2~1.00 g / m³. 2 At this point, the catalytic activity is even better, making its application in water purification more effective.

[0040] In some embodiments of the present invention, the method further includes the step of removing the functional membrane module on which noble metal II is deposited and separating the noble metal II. The noble metal II can be detached by ultrasound and then separated by centrifugation.

[0041] In other embodiments of the present invention, an apparatus for implementing the above method is provided, comprising a sealed reaction vessel, a hydrogen supply assembly, and a circulation assembly, wherein a functional membrane assembly is longitudinally installed inside the reaction vessel, the circulation assembly is connected to the reaction vessel to form an internal circulation loop, the hydrogen supply assembly is connected to the top and bottom of the reaction vessel, and the reaction vessel has an inlet on one side and an outlet on the other side; the electroplating wastewater to be treated enters through the inlet, and the treated electroplating wastewater is discharged through the outlet.

[0042] In some embodiments of the present invention, the hydrogen supply assembly includes a hydrogen cylinder, a pressure reducing valve, an exhaust device, and a safety device, wherein the hydrogen cylinder is connected to the top and bottom of the reaction vessel via the pressure reducing valve, and the exhaust device and the safety device are mounted on the reaction vessel.

[0043] In some further embodiments of the present invention, the application of the functional membrane module deposited with precious metal II obtained by the above method or the above-described recovery device is also proposed in wastewater treatment, wherein the wastewater contains organic pollutants and / or reducible oxygen-containing anionic pollutants.

[0044] In some other embodiments of the present invention, a wastewater treatment apparatus is also proposed, comprising a functional membrane module deposited with precious metal II obtained by the above method or the above-described recovery device, wherein the wastewater contains organic pollutants and / or reducible oxygen-containing anionic pollutants.

[0045] In some embodiments of the present invention, the organic pollutants include halogenated organic pollutants, persistent organic pollutants (POPs), and / or novel pollutants.

[0046] In some embodiments of the present invention, the halogenated organic pollutant includes at least one of trichloroethane or trichloroethylene.

[0047] In some embodiments of the present invention, the novel contaminants include antibiotics, perfluorinated compounds (PFAS), etc.

[0048] In some embodiments of the present invention, the reducible oxygen-containing anionic pollutant includes NO2. - NO3 - ClO4 - ClO3 - BrO3 - CrO42- wait.

[0049] The functional membrane modules with deposited precious metal II recovered by the above method can be used directly as structured catalysts or the entire recovery unit can be used as a water treatment reactor to treat wastewater containing organic pollutants and / or reducible oxygen-containing anionic pollutants. It can be used for the catalytic degradation of organic pollutants (such as halogenated pollutants like trichloroethane and trichloroethylene, and new pollutants like PFAS and antibiotics) or the reduction of toxic heavy metals (such as NO2) in wastewater. - NO3 - ClO4 - CrO4 2- (containing oxygen-containing anions), to achieve "waste treatment with waste".

[0050] Compared with the prior art, the above-mentioned technical solution of the present invention has the following advantages: The present invention provides a method and apparatus for recovering precious metals from electroplating wastewater and directly converting them into catalytic materials. This method overcomes the limitation of traditional processes that only obtain crude metals. Under mild conditions (room temperature and pressure, low-pressure hydrogen atmosphere), a "seed catalyst (precious metal I nanoparticles)" pre-loaded on a membrane module induces selective, autocatalytic chemical reduction and deposition of precious metal II ions in the wastewater, thereby growing highly catalytically active precious metal I nanoparticles in situ on the membrane surface. The recovered membrane module requires no complex post-processing and can be used as a ready-to-use, high-efficiency catalytic module for direct application in advanced water treatment processes such as the catalytic degradation of organic pollutants, realizing a closed loop of "recovering resources from wastewater and then using those resources for wastewater treatment." This method simultaneously achieves efficient and high-purity recovery of precious metals while simultaneously preparing high-value-added catalytic materials. The present invention combines high efficiency with low environmental impact, overcoming the problems of high energy consumption, low efficiency, and easy secondary pollution commonly found in existing precious metal recovery technologies, providing an integrated solution for the resource utilization and deep purification of electroplating wastewater. Attached Figure Description

[0051] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein... Figure 1 This is a schematic diagram of the recycling device in an embodiment of the present invention.

[0052] Figure 2 This is a graph showing the concentration changes of palladium and nickel ions during the recovery process in Example 1 of this invention.

[0053] Figure 3These are STEM (scanning transmission electron microscopy) and EDS (energy-dispersive X-ray spectroscopy) images of palladium recovered in Example 1 of this invention; wherein, Figure A) shows the recovered palladium nanoparticles distributed on the membrane carrier, Figure B) is a partial magnified view of Figure A), and Figure C) is the EDS image of Figure B).

[0054] Figure 4 These are the XRD (X-ray diffraction) patterns and XRD standard cards of the palladium recovered in Example 1 of this invention.

[0055] Figure 5 This is the XPS (X-ray photoelectron spectroscopy) spectrum of the palladium recovered in Example 1 of this invention. Detailed Implementation

[0056] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0057] This invention provides an apparatus and method for recovering precious metals from electroplating wastewater, specifically including the following steps: Step S1: Construction of the recycling device Prepare a membrane module (preferably a hollow fiber membrane with a high specific surface area), a sealed glass reaction vessel, a hydrogen supply line (equipped with a precision pressure reducing valve and flow meter), a circulation pump, a water inlet pump, and necessary pipelines and valves. Connect and construct the recovery device in the following order: fix the membrane module inside the glass reaction vessel, and form an internal circulation loop through the pump pipes connected to the upper and lower ends of the vessel side by the circulation pump; connect one side of the vessel to the electroplating wastewater raw water tank through the water inlet pump, and install a drain valve on the other side to drain the water tank; the hydrogen gas line is connected to the top and bottom of the vessel (upper and lower ends of the membrane module) through the pressure reducing valve, and venting and safety devices are installed.

[0058] Step S2: Preparation and loading of seed catalyst Prepare a precursor solution containing noble metal I ions (such as platinum, palladium, rhodium, etc.) at a concentration of 5-20 mg / L. Fill a glass container with the precursor solution and adjust the hydrogen pressure to 3-30 psig. At 10-35℃ (20-25℃ is better), the noble metal ions are reduced in situ to metal nanoparticles, which firmly adhere to the membrane surface, forming a highly active "seed catalyst" layer, resulting in a structure as shown. Figure 1 The diagram shows a recovery device. By controlling the reduction conditions, it is easier to obtain catalytically active sites with fine particle size and uniform distribution.

[0059] Step S3: Continuous treatment of electroplating wastewater and recovery of precious metals The electroplating wastewater to be treated (with a pH value pre-adjusted to an acidic range of 1-5 to stabilize precious metal ions) is continuously pumped into the reaction vessel of the recovery unit via an influent pump for a set hydraulic retention time (HRT of 6-24 hours). The hydrogen pressure within the system is maintained at approximately 3-30 psig, and a circulation pump is started to circulate the wastewater across the membrane module surface at a flow rate of 50-300 mL / min. Under the induction of the "seed catalyst" and the reduction effect of hydrogen, the target precious metal ions (such as Pd) in the wastewater... 2+ ,Rh 3+ Ru 3+ Pt 4+ Base metal ions (such as Fe) are preferentially and selectively reduced to metal atoms and continuously deposited on the seed particles, achieving "autocatalytic" growth of the particles. Coexisting base metal ions (such as Fe) 3+ Ni 2+ Zn 2+ K + Na + Mg 2+ Ca 2+ Al 3+ Due to their high reduction potential, these materials exhibit minimal reaction under these mild conditions, thus achieving highly selective recovery of precious metals. The treated effluent is discharged through an overflow port or control valve. Once the desired precious metal loading on the membrane module is achieved, the feed water can be stopped. The membrane module loaded with high-purity precious metals is then removed, sonicated for 2 hours to detach the precious metal particles, and centrifuged to recover the precious metals.

[0060] Step S4: Harvesting and Functional Applications of Precious Metals When the noble metal loading on the membrane module reaches 0.03-4.00 g / m 2 When necessary, the water intake can be stopped. Membrane modules loaded with high-purity precious metals can be directly used as structured catalyst modules, transforming the entire recovery unit into a water treatment reactor. This reactor is used for the catalytic degradation of organic pollutants in wastewater (such as halogenated pollutants like trichloroethane and trichloroethylene, and new pollutants like PFAS and antibiotics) or the reduction of toxic heavy metals (such as NO2). - NO3 - ClO4 - CrO4 2- (containing oxygen-containing anions), to achieve "waste treatment with waste".

[0061] In step S1, the membrane module material is polyethylene (PE), polypropylene (PP), polyvinylidene fluoride (PVDF), polyethersulfone (PES), or any combination of two materials. Its surface may be modified by hydrophilization or functional groups such as amino and thiol groups to enhance the immobilization capacity of the seed catalyst. Polypropylene is preferred.

[0062] In step S2, the precursor solution containing noble metals can be selected from sodium tetrachloropalladium, palladium chloride, palladium acetate, etc., preferably sodium tetrachloropalladium.

[0063] In step S3, the recovery endpoint can be determined in real time by monitoring the concentration of precious metal ions in the water online, and the recovery efficiency can be optimized by adjusting the HRT, hydrogen pressure or circulation flow rate. Preferably, the HRT is 6-12 hours, the hydrogen pressure is 5-10 psig, and the circulation flow rate is 80-200 mL / min.

[0064] In step S4, the optimal noble metal loading for catalytic activity is 0.2-1.00 g / m³. 2 .

[0065] This invention ingeniously employs a selective reduction mechanism of "room temperature and pressure seed catalytic induction," distinguishing it from traditional high-energy-consuming electrolysis or non-selective chemical precipitation. This invention creatively utilizes trace amounts of noble metals (concentration of 5-20 mg / L) pre-immobilized on the surface of the membrane module as a "seed catalyst" within a hydrogen pressure range of 3-20 psig, inducing a surface-catalyzed hydrogenation reduction reaction of the target noble metal ions, thereby achieving highly selective deposition of noble metals from complex electroplating wastewater. Under a low-pressure hydrogen atmosphere (e.g., 1-2 atm absolute pressure), a noble metal seed layer immobilized on a support is used as a catalyst (concentration of 5-20 mg / L, corresponding loading of 0.01-0.07 g / m³). 2 This induces the selective reduction and deposition of target precious metal ions in wastewater.

[0066] This scheme is designed with an integrated "recycling-reuse" function in mind. It goes beyond simply obtaining crude metals; instead, by controlling the reduction deposition process, it allows precious metals to be directly grown onto the membrane surface as highly catalytically active nanoparticles. This enables the loaded membrane module to function as a ready-made, highly efficient catalyst module without complex post-processing, directly used in advanced water treatment processes such as the catalytic degradation of organic pollutants, achieving a closed loop of "recovery from wastewater and reuse for wastewater treatment." The membrane module loaded with precious metals (precious metal loading of 0.03-4.00 g / m³) is recovered using the aforementioned method or apparatus. 2 It can be directly used as a structured catalyst to treat wastewater containing organic pollutants.

[0067] Furthermore, by precisely controlling the hydrogen pressure (3-30 psig), HRT (6-24 hours), and circulation flow rate (50-300 mL / min) of the reaction system, the process window is optimized to the most suitable state for the enrichment and reduction of low-concentration precious metal ions. This breaks through the bottleneck of low efficiency or uneconomical use of traditional methods at extremely low concentrations and can be well applied to low-concentration precious metal wastewater (such as 1-10 mg / L).

[0068] Example 1

[0069] This example demonstrates a method for recovering metals from electroplating wastewater, the specific steps of which are as follows: Set up the recycling unit according to the following steps: Prepare the membrane module (using a 24000 m³ / h membrane). 2 / m 3 The system consists of a dense, non-porous hollow fiber membrane made of polypropylene material with a specific surface area of ​​approximately 200 μm outer diameter and 100 μm inner diameter, a sealed glass reaction vessel, a hydrogen supply line (equipped with a precision pressure reducing valve and flow meter), a circulation pump, a water inlet pump, and necessary piping and valves. The recovery unit is constructed by connecting the following components in sequence: the functional membrane module is fixed inside the glass reaction vessel, and an internal circulation loop is formed by connecting the circulation pump to the pump pipes connected to the upper and lower ends of the vessel side; one side of the vessel is connected to the electroplating wastewater raw water tank via the water inlet pump, and the other side is equipped with a drain valve to drain the water tank; the hydrogen supply line is connected to the top and bottom of the vessel (upper and lower ends of the membrane module) via a pressure reducing valve, and venting and safety devices are installed.

[0070] A noble metal precursor (sodium tetrachloropalladium) solution with a palladium ion concentration of 5 mg / L was prepared (pH adjusted to 6 using PBS (phosphate buffer)). This precursor solution was added to the recovery device constructed as described above, and the hydrogen pressure was adjusted to 5 psig (absolute pressure 19.69 psia). After reacting at 25°C for 24 hours, the reaction solution was discharged. The surface of the functional membrane module was loaded with Pd particles with a particle size of approximately 3-7 nm, at a loading rate of approximately 0.04 g / m². 2 .

[0071] Then the electroplating wastewater to be treated (containing Pd) 2+ Approximately 10 mg / L, Ni 2+ Approximately 6.5 mg / L (pH 2) was pumped in using a circulating pump. The hydrogen pressure was set to 5 psig, the HRT to 12 h, the temperature to 25℃, and the circulation rate to 50 mL / min, thus recovering precious metals from the wastewater. The palladium and nickel concentrations at the inlet and outlet were monitored, and the concentration changes were recorded as follows: Figure 2 As shown in the figure, selective recovery of Pd was successfully achieved. For comparison, the average concentrations of Ni and Pd at the inlet and outlet were recorded, and the recovery rates were calculated, as shown in Table 1 below.

[0072] Example 2

[0073] This example provides a method for recovering metals from electroplating wastewater. The difference between this method and Example 1 lies in the slight differences in the recovery process parameters and the concentrations of palladium and nickel in the influent, as detailed in Table 1 below. The concentrations of palladium and nickel at the influent and effluent were measured, and the average concentrations of Ni and Pd at the influent and effluent were recorded. The recovery rate was calculated, and the results are shown in Table 1 below.

[0074] Example 3

[0075] This example provides a method for recovering metals from electroplating wastewater. The difference between this method and Example 1 lies in the slight differences in the recovery process parameters and the concentrations of palladium and nickel in the influent, as detailed in Table 1 below. The concentrations of palladium and nickel at the influent and effluent were measured, and the average concentrations of Ni and Pd at the influent and effluent were recorded. The recovery rate was calculated, and the results are shown in Table 1 below.

[0076] Table 1

[0077] As can be seen from the table above, the method provided in this embodiment of the invention can efficiently recover palladium from electroplating palladium-nickel wastewater, with a palladium recovery rate of over 98.5% throughout the entire recovery process. Compared with existing technologies, this invention not only features mild reaction conditions, low energy consumption, and low operating costs, but also achieves high palladium recovery rate and purity, simple post-processing, and is easy to implement for industrial production.

[0078] The recovered Pd particles were characterized in terms of morphology, structure, and composition. The results of STEM-EDS characterization of the Pd particles recovered in Example 1 are as follows: Figure 3 As shown. From Figure 3 As can be seen from the data, the particle size recovered in Example 1 is approximately 300 nm, and the purity is 100%.

[0079] The results of XRD characterization of the Pd particles recovered in Example 1 are as follows: Figure 4 As shown in the figure, the particles recovered in Example 1 are elemental palladium, mainly with the (111) crystal plane.

[0080] The results of XPS characterization of the Pd particles recovered in Example 1 are as follows: Figure 5 As shown in the figure, the particles recovered in Example 1 are elemental palladium, and the recovered product contains only palladium, indicating high recovery selectivity.

[0081] The characterization results of Examples 2 and 3 are basically the same as those of Example 1, and are not shown one by one to avoid redundancy.

[0082] In summary, compared with the prior art, the recycling method and apparatus of the present invention have the following advantages: 1) High recovery efficiency and selectivity: Under optimized low-pressure hydrogen reduction and seed catalysis conditions, even for precious metals such as palladium and platinum with concentrations below 10 mg / L, the recovery rate can be consistently above 99%. Based on the unique selective reduction mechanism, the purity of precious metals in the recovered products can reach over 95%, far exceeding that of traditional chemical precipitation methods (usually <10%), thus significantly reducing the difficulty and cost of subsequent refining.

[0083] 2) Low energy consumption and environmentally friendly: The entire recycling process is carried out under mild conditions of normal temperature and pressure, with extremely low energy consumption and no need to add any chemical agents, thus avoiding the large amount of toxic sludge produced by traditional sedimentation methods from the source and eliminating the risk of secondary pollution.

[0084] 3) Maximizing resource value: This invention breaks through the traditional model of "recycling crude metals and selling them externally," directly converting the recovered precious metals into high-performance, ready-to-use water treatment catalytic modules in situ. This not only opens up a high-value application path for the recovered products but also saves expensive catalyst procurement costs for subsequent deep wastewater treatment, constructing a new circular economy model of "treating waste with waste."

[0085] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for recovering precious metals from electroplating wastewater, characterized by: The method comprises the following steps: contacting the electroplating wastewater with hydrogen and a functional membrane module to deposit noble metal II in the functional membrane module surface from the electroplating wastewater, to obtain the functional membrane module deposited with noble metal II; obtaining the functional membrane module deposited with noble metal II; wherein the functional membrane module comprises a hollow fiber membrane, and the surface of the hollow fiber membrane is pre-loaded with noble metal I nanoparticles, and the noble metal II is the same as or different from the noble metal I.

2. The method for recovering precious metals from electroplating wastewater according to claim 1, characterized in that: The ion concentration of noble metal II in the electroplating wastewater to be treated is less than 10 mg / L; and / or, the reaction temperature in the deposition process is 10-35℃.

3. The method for recovering precious metals from electroplating wastewater according to claim 1, characterized in that: The noble metal II and the noble metal I each independently comprises at least one of Ru, Rh, Pt or Pd; and / or, the loading of the noble metal I nanoparticles is 0.01 to 0.07 g / m 2 .

4. The method for recovering precious metals from electroplating wastewater according to claim 1, characterized in that: The absolute pressure of the environment in the deposition process is 1-2 atm; and / or, the pH of the electroplating wastewater to be treated is 1-5.

5. The method for recovering precious metals from electroplating wastewater according to claim 1, characterized in that: The method further comprises a preparation step of the functional membrane module: placing the membrane module in a precursor solution containing noble metal I, adjusting the hydrogen pressure of the system to 3-30 psig, so that noble metal I nanoparticles are loaded on the surface of the membrane module.

6. The method for recovering precious metals from electroplating wastewater according to claim 1, characterized in that: The deposition process comprises at least one of the following conditions: 1) maintaining the hydrogen pressure in the lumen of the hollow fiber membrane in the lumen of the hollow fiber membrane at 3-30 psig; 2) the hydraulic retention time of the electroplating wastewater to be treated in the lumen of the hollow fiber membrane is 6-24 h; 3) the electroplating wastewater to be treated circulates on the surface of the functional membrane module, and the circulation flow rate is 50-300 mL / min.

7. The method for recovering precious metals from electroplating wastewater according to claim 1, characterized in that: The noble metal II deposition amount on the functional membrane assembly reaches 0.03-4.00 g / m 2 When the noble metal II deposition amount reaches 0.03-4.00 g / m2, the treatment of the electroplating wastewater is stopped.

8. An apparatus for implementing the method of any one of claims 1 to 7, characterized by: The recovery device comprises a closed reaction container, a hydrogen supply assembly and a circulating assembly, wherein the functional membrane module is longitudinally installed in the reaction container, the circulating assembly communicates with the reaction container to form an internal circulation loop, the hydrogen supply assembly is connected with the top and bottom of the reaction container, one side of the reaction container is provided with a water inlet, and the other side is provided with a water outlet; the electroplating wastewater to be treated enters through the water inlet, and the treated electroplating wastewater is discharged through the water outlet.

9. The application of the functional membrane module deposited with noble metal II obtained by the method according to any one of claims 1 to 7 or the recovery device according to claim 8 in sewage treatment, wherein the sewage contains organic pollutants and / or reducible oxygen-containing anion pollutants.

10. A sewage treatment apparatus characterised by: The application of the functional membrane module deposited with noble metal II obtained by the method according to any one of claims 1 to 7 or the recovery device according to claim 8 in sewage treatment, wherein the sewage contains organic pollutants and / or reducible oxygen-containing anion pollutants.

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