Composite adsorption material for recovering palladium and platinum in acidic wastewater and preparation method thereof

Abstract

The invention relates to the technical field of precious metal recovery, in particular to a composite adsorption material for recovering palladium and platinum in acid wastewater and a preparation method of the composite adsorption material. The preparation method comprises the following steps: taking ferric chloride, pentacarbonyl iron and N, N-dimethylformamide as raw materials to prepare a special-shaped core material with a spiny structure on the surface; mixing and dispersing the special-shaped core material with N-methyl pyrrolidone, polyvinylpyrrolidone and modified polyvinylidene fluoride resin powder, and treating to obtain a core-shell adsorption base material; dispersing the core-shell adsorption base material in a chitosan solution, reacting with polyethyleneimine under the activation action of EDC.HCl and NHS, and performing subsequent treatment to obtain the composite adsorption material. The prepared composite adsorption material has the advantages of being large in specific surface area and high in acid resistance, and through the synergistic effect of the core-shell base material, chitosan and polyethyleneimine, the composite adsorption material has excellent adsorption performance on palladium and platinum in acid wastewater; meanwhile, good magnetism is achieved, and convenient magnetic separation and recovery can be achieved.

Description

Technical Field

[0001] This invention relates to the field of precious metal recycling technology, specifically to a composite adsorbent material for recovering palladium and platinum from acidic wastewater and its preparation method. Background Technology

[0002] Palladium and platinum, as rare and precious metals, possess excellent catalytic activity, chemical stability, and electrical properties, and are widely used in many fields such as electronics manufacturing, chemical catalysis, jewelry, and automotive exhaust purification. However, rare and precious metal resources are scarce and difficult to mine, and with the continuous growth of industrial demand, their resource shortage problem is becoming increasingly prominent. At the same time, industrial production processes such as precious metal smelting, electronic component processing, and electroplating generate large amounts of acidic wastewater containing palladium and platinum ions. This type of wastewater not only seriously pollutes aquatic ecosystems, threatening the survival of animals and plants and human health, but also wastes valuable precious metal resources. Therefore, the efficient recovery of palladium and platinum from acidic wastewater has significant environmental and economic value.

[0003] Currently, methods for recovering palladium and platinum from acidic wastewater mainly include chemical precipitation, solvent extraction, ion exchange, and adsorption. Among these, adsorption is one of the most promising methods due to its simple operation, low cost, high adsorption efficiency, and minimal secondary pollution. The core of adsorption lies in the performance of the adsorbent material, which currently includes activated carbon, zeolite, resin, and magnetic nanomaterials. However, traditional adsorbent materials generally suffer from poor acid resistance, limited specific surface area, insufficient selective adsorption capacity for palladium and platinum ions, and low adsorption capacity. For example, conventional activated carbon is prone to structural damage under strongly acidic conditions, leading to a decline in adsorption performance; ordinary magnetic nanomaterials have few surface active groups, resulting in limited adsorption capacity for palladium and platinum ions, and are prone to aggregation in acidic environments, affecting adsorption efficiency. Furthermore, some adsorbent materials are difficult to separate and recover after adsorption, limiting their recycling.

[0004] Based on the above, the present invention provides a composite adsorbent material for recovering palladium and platinum from acidic wastewater and its preparation method, so as to solve the technical problems mentioned above. Summary of the Invention

[0005] The purpose of this invention is to provide a composite adsorbent material for recovering palladium and platinum from acidic wastewater and its preparation method. The composite adsorbent material prepared by this invention has the advantages of large specific surface area and strong acid resistance. Through the synergistic effect of the core-shell substrate, chitosan and polyethyleneimine, it has excellent adsorption performance for palladium and platinum in acidic wastewater. At the same time, it has good magnetic properties, which can realize convenient magnetic separation and recovery.

[0006] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a method for preparing a composite adsorbent material for recovering palladium and platinum from acidic wastewater, comprising the following steps: Step 1: Mix ferric chloride, ferric pentacarbonyl, and N,N-dimethylformamide in air at a ratio of 1-3 mmol: 1 mL: 50-300 mL, stir until homogeneous, and then transfer to a reaction vessel. React at 180-210℃ for 10-25 h, and then allow to cool naturally to room temperature. Finally, filter, wash, and vacuum dry the reaction solution to obtain the shaped core material. Step 2: Disperse the shaped core material, N-methylpyrrolidone, and polyvinylpyrrolidone at high speed and uniformly according to a mass ratio of 10-30:150-200:0.5-2. Then add 8-15wt% of modified polyvinylidene fluoride resin powder to the shaped core material. After it is uniformly dispersed, slowly add deionized water and continue high-speed dispersion for 2-3 hours. Then discharge the material. The resulting mixture is then centrifuged, washed with ethanol 3-5 times, and vacuum dried to obtain the core-shell adsorption substrate. Step 3: Disperse the core-shell adsorbent substrate uniformly in chitosan solution to prepare a core-shell adsorbent substrate dispersion of 20-50 g / L. Then add EDC·HCl, mix and stir for 20-30 min, and then add NHS. Stir and react at room temperature for 2-5 h, then add polyethyleneimine, and react at 50-70℃ for 3-10 h. Separate the reaction solution into solid and liquid, wash and vacuum dry to obtain the composite adsorbent material. The molecular weight of polyethyleneimine is 10,000-20,000, and the mass ratio of the core-shell adsorbent substrate, polyethyleneimine, EDC·HCl and NHS is 1:3-6:2-3:2-3.

[0007] Furthermore, in step one, the mixing and stirring rate is 800-1200 r / min, and the mixing and stirring time is 30-80 min.

[0008] Furthermore, in step one, the vacuum drying temperature is 40-60℃, and the vacuum drying time is 5-8 hours.

[0009] Furthermore, in step two, the high-speed dispersion speed is 5000-8000 r / min, and the high-speed dispersion time is 2-4 h.

[0010] According to claim 1, the method for preparing a composite adsorbent material for recovering palladium and platinum from acidic wastewater is characterized in that, in step two, the amount of deionized water added is 40-65 wt% of N-methylpyrrolidone, and the dropping rate of the deionized water is 10-20 g / min.

[0011] Furthermore, the preparation method of the modified polyvinylidene fluoride resin powder in step two is as follows: dissolve the polyvinylidene fluoride resin powder in acetone to prepare a 5-8 wt% polyvinylidene fluoride solution, then slowly add an alkaline solution containing a catalyst, react at 40-60℃ for 10-15 h, and then dry. The resulting solid powder is the modified polyvinylidene fluoride resin powder.

[0012] Furthermore, the alkaline solution is selected from sodium hydroxide aqueous solution or potassium hydroxide aqueous solution, and its concentration is 1-1.5 mol / L, and the amount used is 10-15% of the volume of polyvinylidene fluoride solution.

[0013] Furthermore, the catalyst is any one of tetrabutylammonium bromide, tetrabutylammonium chloride, and benzyltributylammonium bromide, and the concentration of the catalyst in the alkaline solution is 3-5 g / L.

[0014] Furthermore, the preparation method of the chitosan solution in step three is as follows: chitosan is added to an acetic acid solution with a volume concentration of 2-5%, and the mixture is stirred until it is completely dissolved to obtain a chitosan solution with a concentration of 2-3 wt%; the molecular weight of the chitosan is 1500-3200, and the degree of deacetylation is 80-95%.

[0015] Secondly, the present invention provides a composite adsorbent material for recovering palladium and platinum from acidic wastewater, which is prepared by the preparation method described above.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention uses ferric chloride, ferric pentacarbonyl, and N,N-dimethylformamide as raw materials to prepare a heteromorphic core material with a densely protruding, spiky structure on its surface. Due to its unique morphology, the prepared heteromorphic core material possesses a large specific surface area, excellent adsorption performance, and high adsorption capacity. The prepared heteromorphic core material is uniformly mixed with N-methylpyrrolidone, polyvinylpyrrolidone, and modified polyvinylidene fluoride resin powder. After centrifugation, washing, and vacuum drying, a modified polyvinylidene fluoride film is coated onto the surface of the heteromorphic core material, resulting in a core-shell adsorption substrate with a distinct core-shell structure, an uneven surface, and excellent adsorption performance. Furthermore, this invention uses alkali and a catalyst to treat polyvinylidene fluoride, preparing modified polyvinylidene fluoride resin powder with carboxyl groups at the ends, introducing active groups and laying a theoretical foundation for the subsequent preparation of composite substrates. Simultaneously, the presence of the modified polyvinylidene fluoride film also enhances the acid resistance of the prepared core-shell adsorption substrate.

[0017] 2. In this invention, a core-shell adsorption substrate is uniformly dispersed in a chitosan solution, allowing chitosan to be uniformly dispersed and adsorbed onto the surface of the substrate. The raised, spiky structure on the substrate surface significantly increases its specific surface area and adsorption capacity, enabling it to adsorb more chitosan molecules. Then, under the action of EDC·HCl (1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride) and NHS (N-hydroxysuccinimide), the carboxyl groups on the surface of the core-shell adsorption substrate and the carboxyl groups on the chitosan molecular chains react chemically with polyethyleneimine to form bonds. This ultimately forms a dense three-dimensional envelope layer on the surface of the substrate. This envelope layer not only bonds to the chitosan molecules but also, in conjunction with the raised, spiky structure, firmly "anchors" the chitosan molecules to the surface of the substrate, greatly reducing the probability of chitosan migration. Ultimately, the synergistic effect of the core-shell adsorbent substrate, chitosan, and polyethyleneimine results in a composite adsorbent material exhibiting excellent adsorption performance for palladium and platinum in acidic wastewater. Furthermore, the composite adsorbent material prepared in this invention possesses strong magnetic properties, facilitating magnetic separation and reuse, thus reducing application costs.

[0018] In summary, the composite adsorbent material prepared by this invention has the advantages of large specific surface area and strong acid resistance. Through the synergistic effect of the core-shell substrate, chitosan and polyethyleneimine, it has excellent adsorption performance for palladium and platinum in acidic wastewater. At the same time, it has good magnetic properties, which can realize convenient magnetic separation and recovery. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] In the following examples and comparative examples, EDC·HCl represents 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and NHS represents N-hydroxysuccinimide.

[0021] Example 1 A method for preparing a composite adsorbent material for recovering palladium and platinum from acidic wastewater includes the following steps: Step 1: Mix ferric chloride, ferric pentacarbonyl and N,N-dimethylformamide in air at a ratio of 1 mmol:1 mL:50 mL, stir evenly, and then transfer to a reaction vessel. React at 180°C for 25 h, and then allow to cool naturally to room temperature. The reaction solution is then filtered, washed and vacuum dried to obtain the shaped core material. The mixing speed was 800 r / min, and the mixing time was 30 min; the vacuum drying temperature was 40℃, and the vacuum drying time was 8 h. Step 2: Disperse the shaped core material, N-methylpyrrolidone, and polyvinylpyrrolidone at high speed and uniformly according to a mass ratio of 10:150:0.5, then add 8 wt% of modified polyvinylidene fluoride resin powder of the shaped core material. After it is uniformly dispersed, slowly add deionized water and continue high-speed dispersion for 2 hours before discharging. The resulting mixture is then subjected to centrifugation, washing with ethanol three times, and vacuum drying to obtain the core-shell adsorption substrate. The high-speed dispersion speed was 5000 r / min, and the high-speed dispersion time was 4 h; the amount of deionized water added was 40 wt% of N-methylpyrrolidone, and the dropping rate of deionized water was 10 g / min. Step 3: Disperse the core-shell adsorbent substrate uniformly in chitosan solution to prepare a 20 g / L core-shell adsorbent substrate dispersion. Then add EDC·HCl, mix and stir for 20 min, and then add NHS. After stirring and reacting at room temperature for 2 h, add polyethyleneimine, and then react at 50 °C for 10 h. Separate the reaction solution into solid and liquid, wash and vacuum dry to obtain the composite adsorbent material. The molecular weight of polyethyleneimine is 10,000, and the mass ratio of the core-shell adsorbent substrate, polyethyleneimine, EDC·HCl and NHS is 1:3:2:2. The chitosan solution is prepared by adding chitosan to a 2% (v / v) acetic acid solution, mixing and stirring until completely dissolved to obtain a 2 wt% chitosan solution; the molecular weight of chitosan is 1500 and the degree of deacetylation is 80%.

[0022] The preparation method of modified polyvinylidene fluoride resin powder is as follows: dissolve polyvinylidene fluoride resin powder in acetone to prepare a 5wt% polyvinylidene fluoride solution, then slowly add an alkaline solution containing a catalyst, react at 40°C for 15 hours and then dry. The resulting solid powder is the modified polyvinylidene fluoride resin powder. The alkaline solution is selected from sodium hydroxide aqueous solution or potassium hydroxide aqueous solution, with a concentration of 1 mol / L and a dosage of 10% of the volume of polyvinylidene fluoride solution; the catalyst is tetrabutylammonium bromide, and the concentration of the catalyst in the alkaline solution is 3 g / L.

[0023] Example 2 A method for preparing a composite adsorbent material for recovering palladium and platinum from acidic wastewater includes the following steps: Step 1: Mix ferric chloride, ferric pentacarbonyl and N,N-dimethylformamide in air at a ratio of 2mmol:1mL:150mL until homogeneous, then transfer the mixture to a reaction vessel. React at 200℃ for 15 h, then allow it to cool naturally to room temperature. Finally, filter, wash and vacuum dry the reaction solution to obtain the shaped core material. The mixing speed was 1000 r / min, and the mixing time was 50 min; the vacuum drying temperature was 50℃, and the vacuum drying time was 6 h. Step 2: Disperse the shaped core material, N-methylpyrrolidone, and polyvinylpyrrolidone at high speed and uniformly according to a mass ratio of 20:150:1. Then add 10wt% of the modified polyvinylidene fluoride resin powder of the shaped core material. After it is uniformly dispersed, slowly add deionized water and continue high-speed dispersion for 3 hours before discharging. The resulting mixture is then centrifuged, washed with ethanol 4 times, and vacuum dried to obtain the core-shell adsorption substrate. The high-speed dispersion speed was 6000 r / min, and the high-speed dispersion time was 3 h; the amount of deionized water added was 50 wt% of N-methylpyrrolidone, and the dropping rate of deionized water was 15 g / min. Step 3: The core-shell adsorbent substrate is uniformly dispersed in chitosan solution to prepare a 40 g / L core-shell adsorbent substrate dispersion. Then, EDC·HCl is added and the mixture is stirred for 25 min before NHS is added. After stirring and reacting at room temperature for 3 h, polyethyleneimine is added, and the mixture is reacted at 60 °C for 5 h. The reaction solution is then subjected to solid-liquid separation, washing, and vacuum drying to obtain the composite adsorbent material. The molecular weight of polyethyleneimine is 20,000, and the mass ratio of the core-shell adsorbent substrate, polyethyleneimine, EDC·HCl and NHS is 1:5:3:3. The chitosan solution is prepared by adding chitosan to a 3% (v / v) acetic acid solution, mixing and stirring until completely dissolved to obtain a 3 wt% chitosan solution; the molecular weight of chitosan is 2000 and the degree of deacetylation is 95%.

[0024] The preparation method of modified polyvinylidene fluoride resin powder is as follows: dissolve polyvinylidene fluoride resin powder in acetone to prepare a 6wt% polyvinylidene fluoride solution, then slowly add an alkaline solution containing a catalyst, react at 50°C for 15 hours and then dry. The resulting solid powder is the modified polyvinylidene fluoride resin powder. The alkaline solution is selected from sodium hydroxide aqueous solution or potassium hydroxide aqueous solution, with a concentration of 1.5 mol / L and a dosage of 15% of the volume of polyvinylidene fluoride solution; the catalyst is tetrabutylammonium chloride, and the concentration of the catalyst in the alkaline solution is 5 g / L.

[0025] Example 3 A method for preparing a composite adsorbent material for recovering palladium and platinum from acidic wastewater includes the following steps: Step 1: Mix ferric chloride, ferric pentacarbonyl and N,N-dimethylformamide in air at a ratio of 3mmol:1mL:300mL until homogeneous, then transfer the mixture to a reaction vessel. React at 210℃ for 10 h, then allow it to cool naturally to room temperature. Finally, filter, wash and vacuum dry the reaction solution to obtain the shaped core material. The mixing speed was 1200 r / min, and the mixing time was 30 min; the vacuum drying temperature was 60℃, and the vacuum drying time was 5 h. Step 2: Disperse the irregularly shaped core material, N-methylpyrrolidone, and polyvinylpyrrolidone at high speed and uniformly according to a mass ratio of 30:200:2. Then add 15wt% of the modified polyvinylidene fluoride resin powder of the irregularly shaped core material. After it is uniformly dispersed, slowly add deionized water and continue high-speed dispersion for 3 hours before discharging. The resulting mixture is then centrifuged, washed with ethanol 5 times, and vacuum dried to obtain the core-shell adsorption substrate. The high-speed dispersion speed was 8000 r / min, and the high-speed dispersion time was 2 h; the amount of deionized water added was 65 wt% of N-methylpyrrolidone, and the dropping rate of deionized water was 20 g / min. Step 3: The core-shell adsorbent substrate is uniformly dispersed in chitosan solution to prepare a 50 g / L core-shell adsorbent substrate dispersion. Then, EDC·HCl is added and the mixture is stirred for 30 min before NHS is added. After stirring and reacting at room temperature for 5 h, polyethyleneimine is added, and the mixture is reacted at 70 °C for 3 h. The reaction solution is then subjected to solid-liquid separation, washing, and vacuum drying to obtain the composite adsorbent material. The molecular weight of polyethyleneimine is 20,000, and the mass ratio of the core-shell adsorbent substrate, polyethyleneimine, EDC·HCl and NHS is 1:6:3:3. The chitosan solution is prepared by adding chitosan to a 5% (v / v) acetic acid solution, mixing and stirring until completely dissolved to obtain a 3 wt% chitosan solution; the molecular weight of chitosan is 3200 and the degree of deacetylation is 95%.

[0026] The preparation method of modified polyvinylidene fluoride resin powder is as follows: dissolve polyvinylidene fluoride resin powder in acetone to prepare an 8wt% polyvinylidene fluoride solution, then slowly add an alkaline solution containing a catalyst, react at 60°C for 10 hours, and then dry. The resulting solid powder is the modified polyvinylidene fluoride resin powder. The alkaline solution is selected from sodium hydroxide aqueous solution or potassium hydroxide aqueous solution, with a concentration of 1.5 mol / L and a dosage of 15% of the volume of polyvinylidene fluoride solution; the catalyst is benzyltributylammonium bromide, and the concentration of the catalyst in the alkaline solution is 5 g / L.

[0027] Comparative Example 1: The difference from Example 1 is that chitosan was not used in the preparation of the composite adsorbent material in this comparative example, and an equal amount of deionized water was used instead of chitosan solution.

[0028] Comparative Example 2: The difference from Example 1 is that the magnetic microspheres prepared in Example 1 of the invention patent with application number "CN202311769363.7" entitled "A core-shell structured adsorbent and its preparation method and kit, and a method for detecting the concentration of styrene metabolites in plasma" are used instead of the irregular core material in this application, and composite adsorbent materials are prepared using them as raw materials.

[0029] Adsorption performance test 1. Test method: Prepare simulated acidic wastewater containing multiple metal ions, including Pd. 2+ Pt 4+ Cu 2+ Ni 2+ Fe 3+ The initial concentration of each adsorbent was 50 mg / L, and the pH of the solution was adjusted to 2.0 with nitric acid. 20 mg of each of the composite adsorbents prepared in Examples 1-3 and Comparative Examples 1-2 were weighed and added to 50 mL of the simulated wastewater. The adsorption was carried out in a constant-temperature shaker at 25°C and 200 rpm for 12 h to ensure adsorption equilibrium was reached. After adsorption, the adsorbents were quickly separated using a magnet, and the supernatant was filtered through a 0.45 μm filter membrane. The residual concentration of each metal ion in the solution was determined using inductively coupled plasma optical emission spectrometry (ICP-OES).

[0030] 2. Calculation of Adsorption Capacity and Removal Rate: Calculate the adsorption capacity (Q) according to the formula. e (mg / g) and removal rate (R, %).

[0031] Q e = (C0-C e )×V / m R = (C0 - C) e ) / C0×100% Among them, C0 and C e The initial and equilibrium concentrations of the metal ions are (mg / L), respectively; V is the solution volume (L); and m is the adsorbent mass (g).

[0032] The calculated data obtained above are recorded in the table below:

[0033] By comparing and analyzing the data in the table, it can be seen that the composite adsorbent material prepared by this invention has the advantages of large specific surface area and strong acid resistance. Through the synergistic effect of the core-shell substrate, chitosan, and polyethyleneimine, it exhibits excellent adsorption performance for palladium and platinum in acidic wastewater. Simultaneously, it possesses good magnetic properties, enabling convenient magnetic separation and recovery. Therefore, this invention provides a composite adsorbent material for recovering palladium and platinum from acidic wastewater, along with its preparation method, which has a broader market prospect and is more suitable for widespread application.

[0034] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0035] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a composite adsorbent material for recovering palladium and platinum from acidic wastewater, characterized in that, It comprises the following steps: Step one: mix the iron chloride, iron pentacarbonyl and N, N-dimethylformamide in the air at the ratio of 1-3 mmol: 1 mL: 50-300 mL, stir them evenly and then transfer them into a reaction kettle, react at 180-210℃ for 10-25 hours, then cool them to room temperature naturally, filter, wash and dry them in vacuum to obtain the heteromorphic nucleating agent; Step two: mix the heteromorphic nucleating agent, N-methyl pyrrolidone and polyvinylpyrrolidone at the ratio of 10-30: 150-200: 0.5-2, disperse them evenly at high speed, then add the modified polyvinylidene fluoride resin powder which accounts for 8-15wt% of the heteromorphic nucleating agent, disperse them evenly, then slowly add deionized water, continue to disperse them at high speed for 2-3 hours, then discharge, centrifuge, wash them with ethanol for 3-5 times and dry them in vacuum to obtain the core-shell adsorption base material; Step three: disperse the core-shell adsorption base material in the chitosan solution to prepare a 20-50g / L core-shell adsorption base material dispersion liquid, then add EDC·HCl, mix and stir them for 20-30 minutes, then add NHS, stir and react them at room temperature for 2-5 hours, then add polyethyleneimine, react them at 50-70℃ for 3-10 hours, then separate them, wash them and dry them in vacuum to obtain the composite adsorption material. The molecular weight of the polyethyleneimine is 10000-20000, and the mass ratio of the core-shell adsorption base material, polyethyleneimine, EDC·HCl and NHS is 1: 3-6: 2-3: 2-3.

2. The method according to claim 1, wherein the method is characterized by, The mixing and stirring rate in step one is 800-1200r / min, and the mixing and stirring time is 30-80 minutes.

3. The method according to claim 1, wherein the method is characterized by, The vacuum drying temperature in step one is 40-60℃, and the vacuum drying time is 5-8 hours.

4. The method according to claim 1, wherein the method is characterized by, The high-speed dispersion speed in step two is 5000-8000r / min, and the high-speed dispersion time is 2-4 hours.

5. The method according to claim 1, wherein the method is characterized by, The amount of deionized water added in step two is 40-65wt% of the N-methyl pyrrolidone, and the dropping speed of the deionized water is 10-20g / min.

6. The method according to claim 1, wherein the method is characterized by, The preparation method of the modified polyvinylidene fluoride resin powder in step two is as follows: dissolve the polyvinylidene fluoride resin powder in acetone to prepare a 5-8wt% polyvinylidene fluoride solution, then slowly add the lye containing a catalyst, react them at 40-60℃ for 10-15 hours, then dry them, and the obtained solid powder is the modified polyvinylidene fluoride resin powder.

7. The method according to claim 6, wherein the method is characterized by, The lye is sodium hydroxide aqueous solution or potassium hydroxide aqueous solution, and its concentration is 1-1.5mol / L, and its amount is 10-15% of the volume of the polyvinylidene fluoride solution.

8. The method according to claim 6, wherein the method is characterized by, The catalyst is any one of tetrabutylammonium bromide, tetrabutylammonium chloride and benzyltributylammonium bromide, and the concentration of the catalyst in the lye is 3-5g / L.

9. The method according to claim 1, wherein the method is characterized by, The preparation method of the chitosan solution in step three is as follows: add chitosan into a 2-5% acetic acid solution, mix and stir them to make the chitosan completely dissolved, and then obtain a 2-3wt% chitosan solution; the molecular weight of the chitosan is 1500-3200, and the deacetylation degree is 80-95%.

10. A composite adsorption material for recovering palladium platinum in acidic waste water, characterized by, The preparation method according to any one of claims 1-9 is adopted.

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