Method for recovering heavy metals from metal wastes

Abstract

The invention relates to the technical field of heavy metal recovery, in particular to a method for recovering heavy metal from metal waste. Comprising the following steps: preparing silicon-tungsten composite acid salt; preparing heteropolyacid powder; preparing a resin heteropolyacid composite material; heavy metals are recovered from metal wastes by a resin adsorption method. The silicon-tungsten composite acid salt is prepared under mild conditions through reaction of sodium metasilicate, sodium tungstate and potassium chloride, the operation is simple, the conditions are easy to control, the silicon-tungsten composite acid salt has rich active sites and a large specific surface area, the surface of the silicon-tungsten composite acid salt carries negative charges, and the surface of the silicon-tungsten composite acid salt is not prone to damage. Compared with a traditional chemical precipitation method, the method for extracting the heavy metal by using the silicon-tungsten composite acid salt does not need to add a large number of chemical reagents, and secondary pollution is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of heavy metal recovery, and particularly relates to a method for recovering heavy metals from metal waste. Background Art

[0002] Metal waste refers to the waste composed of used and scrapped metal products, waste machinery, solid waste, etc. These wastes usually come from industrial production, building demolition, electronic product scrapping and other fields. Because they contain reusable metal components, they are regarded as "recyclable resources". Due to the rapid development of electronic technology and the frequent replacement of electronic products, a large number of electronic devices are eliminated in a short period of time, generating a large amount of electronic waste. And because consumers have a strong demand for the replacement of electronic products, the average service life of electronic products is shortened, which further increases the generation of electronic waste.

[0003] A large number of circuit boards are included in electronic and electrical product waste. Copper and nickel are widely used in the circuit boards, wires and cables, and electroplating layers of electronic devices due to their excellent electrical conductivity and corrosion resistance. Copper and nickel are important strategic resources. Recycling can reduce the dependence on primary mineral resources. Recovering copper and nickel from metal waste in electronic waste has significant economic benefits, and its recovery cost is usually lower than the mining cost of primary minerals. Therefore, pyrometallurgy or hydrometallurgical leaching methods are often used to recover heavy metals from these wastes.

[0004] Among them, hydrometallurgical leaching extracts metals by chemical solution leaching. Generally, copper and nickel are dissolved from waste by acid leaching, and then separated and recovered by electrolysis or precipitation methods. The metal recovery rate of hydrometallurgical leaching is high and it is suitable for treating low-grade waste containing metals such as copper and nickel. However, after acid leaching, the acid leaching solution contains a large number of other metal ions in addition to copper and nickel. Therefore, the solid substances directly precipitated by electrolysis and precipitation methods also contain other metals, resulting in poor recovery rates of copper and nickel. Therefore, a method for recovering heavy metals from metal waste is needed to improve the recovery rates of copper and nickel to solve the deficiencies of the above-mentioned existing technologies. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a method for recovering heavy metals from metal waste.

[0006] A method for recovering heavy metals from metal waste includes the following steps: S1: Prepare silicotungstate Prepare sodium metasilicate solution and sodium tungstate solution. After mixing the two solutions, add potassium chloride to prepare silicotungstate; S2: Prepare heteropolyacid powder Add the silicon tungstate composite salt and potassium acetate to deionized water. Then dissolve cetyltrimethylammonium bromide and tetrabutylammonium bromide in chloroform. Mix the two solutions to prepare the heteropolyacid powder. S3: Prepare the resin heteropolyacid composite material Soak the D201 resin in a sodium chloride solution, then rinse it. Next, soak it in a hydrochloric acid solution, wash it, then soak it in a sodium hydroxide solution, and wash it to obtain the treated resin. Dissolve the heteropolyacid powder in deionized water, and then add the treated resin to prepare the resin heteropolyacid composite material. S4: Recover heavy metals from metal waste by the resin adsorption method Crush the metal waste and soak it in water. Then soak it in concentrated sulfuric acid to prepare a mixed solution containing heavy metals. Add the resin heteropolyacid composite material to the mixed solution containing heavy metals, then add an acetic acid-ammonium acetate buffer solution, shake it, and wash it. Then desorb the washed resin to obtain a heavy metal filtrate. Add sodium hydroxide to the heavy metal filtrate until a precipitate is formed to obtain the hydroxide product of the heavy metal.

[0007] Furthermore, the preparation of the silicon tungstate composite salt in step S1 includes the following steps: S1.1: Dissolve 10 - 15 parts by mass of sodium metasilicate in 100 - 110 parts by mass of deionized water, and stir magnetically for 10 - 15 min to obtain a sodium metasilicate solution. S1.2: Heat 100 - 110 parts by mass of deionized water to 90 - 100 °C, add 60 - 65 parts by mass of sodium tungstate to obtain a sodium tungstate solution, and keep the temperature of the sodium tungstate solution at 90 - 100 °C. Dropwise add 50 - 60 parts by mass of hydrochloric acid solution, then add the prepared sodium metasilicate solution. Adjust the pH value to 5 - 6 with hydrochloric acid solution, and keep the solution temperature at 100 - 105 °C for reaction for 1 - 1.5 h. Then cool to room temperature, filter, add 50 - 60 parts by mass of potassium chloride, perform suction filtration to retain the filter residue, wash it, and dry it to obtain the silicon tungstate composite salt.

[0008] Furthermore, the preparation of the heteropolyacid powder in step S2 includes the following steps: Add 0.5 - 1 part by mass of the silicon tungstate composite salt and 0.1 - 0.3 part by mass of potassium acetate to 80 - 85 parts by mass of deionized water, and adjust the pH value to 6.5. Then dissolve 0.3 - 0.5 part by mass of cetyltrimethylammonium bromide and 0.2 - 0.4 part by mass of tetrabutylammonium bromide in 60 - 65 parts by mass of chloroform. Mix the two solutions completely and stir at a speed of 6000 - 7000 r / min for 1 - 1.5 h. Then centrifuge at a speed of 10000 - 11000 r / min for 5 - 8 min. Then perform extraction and liquid separation, remove the aqueous phase, retain the organic phase, and distill the organic phase. Dry it at 80 - 85 °C for 4 - 5 h to obtain the heteropolyacid powder.

[0009] Further, the preparation of the resin heteropolyacid composite material in step S3 includes the following steps: S3.1: Immerse the D201 resin in a saturated sodium chloride solution with three times the volume, stir at a speed of 500 - 600 r / min for 12 - 13 h, then rinse it with deionized water three times, soak it in a hydrochloric acid solution with three times the volume for 8 - 8.5 h, wash it with deionized water until neutral, then soak it in a sodium hydroxide solution for 8 - 8.5 h, wash it with deionized water until neutral, and dry it to obtain the treated resin; S3.2: Dissolve 20 - 25 parts by mass of heteropolyacid powder in 100 - 105 parts by mass of deionized water, and ultrasonically treat it for 20 - 25 min. Then add 2 - 3 parts by mass of the treated resin, keep it in a constant temperature water bath at 50 - 60 °C, and maintain stirring for reaction for 24 - 25 h. Then filter to remove the filtrate, wash it with deionized water three times, and then dry it at 60 - 65 °C for 3 - 4 h to obtain the resin heteropolyacid composite material.

[0010] Further, the recovery of heavy metals from metal waste by the resin adsorption method in step S4 includes the following steps: S4.1: Crush the metal waste and immerse it in water, stir for 2 - 3 h, then add concentrated sulfuric acid with three times the mass of the system, soak for 12 - 13 h, then filter to remove the precipitate, and then add a sodium hydroxide solution to adjust the pH value to 5 - 6 to obtain a heavy metal-containing mixed solution; S4.2: Add 1 - 2 parts by mass of the resin heteropolyacid composite material to 5 - 10 parts by mass of the heavy metal-containing mixed solution, then add 1 - 2 parts by mass of the acetic acid - ammonium acetate buffer solution, and set the water bath temperature to 60 - 65 °C and the oscillation speed to 600 - 650 r / min for 50 - 70 min through a constant temperature water bath oscillator. After the oscillation ends, filter to remove the filtrate, wash the resin three times with the acetic acid - ammonium acetate buffer solution, then transfer the washed resin to a conical flask, add 50 - 60 parts by mass of nitric acid solution, seal it and oscillate for 50 - 70 min, and at the same time heat it in a water bath to 60 - 65 °C for desorption. After desorption, filter it with a filter membrane to obtain a heavy metal filtrate; S4.3: Add sodium hydroxide to the heavy metal filtrate until a precipitate is formed to obtain a heavy metal hydroxide product.

[0011] Further, the mass fraction of the hydrochloric acid solution is 5 - 6%.

[0012] Further, the mass fraction of the sodium hydroxide solution is 2 - 4%.

[0013] Further, the acetic acid - ammonium acetate buffer solution is prepared by mixing acetic acid and ammonium acetate in a mass ratio of 5:7 - 8 and adjusting the pH value to 4.8 - 5.2 with acetic acid.

[0014] Further, the concentration of concentrated sulfuric acid is 85 wt%.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: 1. Through the reaction of sodium metasilicate, sodium tungstate and potassium chloride, the present invention can prepare the silicon-tungsten composite salt under relatively mild conditions. The operation is simple and the conditions are easy to control. The silicon-tungsten composite salt has rich active sites and a large specific surface area. The surface of the silicon-tungsten composite salt is negatively charged and can adsorb positively charged heavy metal ions through electrostatic interaction. At the same time, the oxygen atoms in the silicon-tungsten composite salt can form stable complexes with copper and nickel ions, so as to realize the specific adsorption of copper and nickel in heavy metal ions. Moreover, the silicon-tungsten composite salt can remain stable under acidic conditions and is suitable for use under the environmental conditions after acid leaching. And, compared with the traditional chemical precipitation method, using the silicon-tungsten composite salt to extract heavy metals does not require adding a large amount of chemical reagents, reducing secondary pollution.

[0016] 2. The present invention combines the silicon-tungsten composite salt with resin to prepare a resin heteropolyacid composite material. The resin heteropolyacid composite material combines the high adsorption performance of the silicon-tungsten composite salt and the high specific surface area of the resin. As a carrier, the resin can firmly load the silicon-tungsten composite salt on its surface and pores, increasing the exposure of adsorption sites and improving the adsorption efficiency, thus significantly increasing the adsorption capacity for heavy metal ions. At the same time, the D201 resin used in the present invention forms quaternary ammonium cations under the protonation conditions of the heteropolyacid, which can play an auxiliary coordination role during the adsorption process. The quaternary ammonium cations can form weak coordination bonds with copper and nickel metal ions, further enhancing the binding ability of copper and nickel metal ions with the D201 resin. This coordination effect and the coordination effect of the heteropolyacid work together to improve the adsorption ability for copper and nickel, thereby increasing the recovery rate of copper and nickel heavy metals. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a flowchart of a method for recovering heavy metals from metal waste adopted in the embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0019] The method for recovering heavy metals from metal waste provided by the present invention is described in detail below with reference to the accompanying drawings and specific embodiments. At the same time, it should be noted here that in order to make the embodiments more detailed, the following embodiments are the best and preferred embodiments. For some well-known technologies, those skilled in the art can also adopt other alternative methods for implementation; and the drawings are only for more specifically describing the embodiments and are not intended to specifically limit the present invention.

[0020] Example 1: A method for recovering heavy metals from metal waste, as Figure 1 shown, includes the following steps: S1: Prepare silicotungstic composite salt S1.1: Dissolve 10 parts by mass of sodium metasilicate in 100 parts by mass of deionized water, and stir magnetically for 10 min to obtain a sodium metasilicate solution; S1.2: Heat 100 parts by mass of deionized water to 90 °C, add 60 parts by mass of sodium tungstate to obtain a sodium tungstate solution, and keep the temperature of the sodium tungstate solution at 90 °C. Dropwise add 50 parts by mass of hydrochloric acid solution, then add the prepared sodium metasilicate solution, adjust the pH value to 5 with hydrochloric acid solution, and keep the solution temperature at 100 °C for reaction for 1 h. Then cool to room temperature, filter, add 50 parts by mass of potassium chloride, filter by suction to retain the filter residue, wash and then dry to obtain silicotungstic composite salt.

[0021] S2: Prepare heteropolyacid powder Add 0.5 part by mass of silicotungstic composite salt and 0.1 part by mass of potassium acetate to 80 parts by mass of deionized water, and adjust the pH value to 6.5. Then dissolve 0.3 part by mass of cetyltrimethylammonium bromide and 0.2 part by mass of tetrabutylammonium bromide in 60 parts by mass of chloroform. Mix the two solutions and stir at a speed of 6000 r / min for 1 h, then centrifuge at a speed of 10000 r / min for 5 min, then extract and separate the liquid, remove the aqueous phase, retain the organic phase, and then distill the organic phase and dry at 80 °C for 4 h to obtain heteropolyacid powder.

[0022] S3: Prepare resin heteropolyacid composite material S3.1: Immerse D201 resin in a saturated sodium chloride solution with three times the volume, stir at a speed of 500 r / min for 12 h, then rinse with deionized water 3 times, then immerse in a hydrochloric acid solution with three times the volume for 8 h, the mass fraction of the hydrochloric acid solution is 5%, wash with deionized water until neutral, then immerse in a sodium hydroxide solution for 8 h, the mass fraction of the sodium hydroxide solution is 2%, wash with deionized water until neutral, and dry to obtain the treated resin; S3.2: Dissolve 20 parts by mass of heteropolyacid powder in 100 parts by mass of deionized water, and perform ultrasonic treatment for 20 min. Then add 2 parts by mass of the treated resin, keep it in a constant temperature water bath at 50 °C, and keep stirring and reacting for 24 h. Then filter to remove the filtrate, wash with deionized water 3 times, and then dry at 60 °C for 3 h to obtain the resin heteropolyacid composite material.

[0023] S4: Recover heavy metals from metal waste by resin adsorption method S4.1: Crush the metal waste and soak it in water, stir for 2 h, then add concentrated sulfuric acid accounting for three times the mass of the system and with a concentration of 85 wt%, soak for 12 h, then filter to remove the precipitate, and add sodium hydroxide solution to adjust the pH value to 5 to obtain a heavy metal-containing mixed solution; S4.2: Add 1 part by mass of the resin heteropolyacid composite material to 5 parts by mass of the heavy metal-containing mixed solution, then add 1 part by mass of the acetic acid-ammonium acetate buffer solution, and set the water bath temperature to 60 °C, the oscillation speed to 600 r / min, and the time to 50 min through a constant temperature water bath oscillator. After the oscillation ends, filter to remove the filtrate, wash the resin 3 times with the acetic acid-ammonium acetate buffer solution, then transfer the washed resin to a triangular flask, add 50 parts by mass of nitric acid solution, seal and oscillate for 50 min, while heating in a water bath to 60 °C for desorption. After desorption, filter with a filter membrane to obtain a heavy metal filtrate; Among them, the acetic acid-ammonium acetate buffer solution is prepared by mixing acetic acid and ammonium acetate in a mass ratio of 5:7 and adjusting the pH value to 4.8 with acetic acid; S4.3: Add sodium hydroxide to the heavy metal filtrate until a precipitate is formed to obtain a heavy metal hydroxide product.

[0024] Example 2: A method for recovering heavy metals from metal waste, as Figure 1 shown, includes the following steps: S1: Prepare silicotungstate S1.1: Dissolve 15 parts by mass of sodium metasilicate in 110 parts by mass of deionized water, stir magnetically for 10 min to obtain a sodium metasilicate solution; S1.2: Heat 110 parts by mass of deionized water to 90 °C, add 65 parts by mass of sodium tungstate to obtain a sodium tungstate solution, and keep the temperature of the sodium tungstate solution at 90 °C. Dropwise add 60 parts by mass of hydrochloric acid solution, then add the prepared sodium metasilicate solution, adjust the pH value to 5 with hydrochloric acid solution, and keep the solution temperature at 100 °C for reaction for 1 h. Then cool to room temperature, filter, add 50 parts by mass of potassium chloride, filter by suction to retain the filter residue, wash and dry to obtain silicotungstate.

[0025] S2: Prepare heteropolyacid powder Add 1 part by mass of silicotungstate and 0.3 part by mass of potassium acetate to 85 parts by mass of deionized water, and adjust the pH value to 6.5. Then dissolve 0.5 part by mass of cetyltrimethylammonium bromide and 0.4 part by mass of tetrabutylammonium bromide in 65 parts by mass of chloroform. Mix the two solutions and stir at a speed of 6000 r / min for 1 h, then centrifuge at a speed of 10000 r / min for 5 min, then extract and separate, remove the aqueous phase, retain the organic phase, and then distill the organic phase and dry at 80 °C for 4 h to obtain heteropolyacid powder.

[0026] S3: Prepare the resin heteropolyacid composite material S3.1: Immerse the D201 resin in saturated sodium chloride solution with three times the volume, stir at a speed of 500 r / min for 12 h, then rinse with deionized water three times, and then immerse in hydrochloric acid solution with three times the volume for 8 h. The mass fraction of the hydrochloric acid solution is 5%. Wash with deionized water until neutral, then immerse in sodium hydroxide solution for 8 h. The mass fraction of the sodium hydroxide solution is 2%. Wash with deionized water until neutral and dry to obtain the treated resin; S3.2: Dissolve 25 parts by mass of heteropolyacid powder in 105 parts by mass of deionized water, and perform ultrasonic treatment for 20 min. Then add 3 parts by mass of the treated resin, keep it in a constant temperature water bath at 50 °C, and maintain stirring and reaction for 24 h. Then remove the filtrate by suction filtration, wash with deionized water three times, and then dry at 60 °C for 3 h to obtain the resin heteropolyacid composite material.

[0027] S4: Recover heavy metals from metal waste by resin adsorption method S4.1: Crush the metal waste and immerse it in water, stir for 2 h, then add concentrated sulfuric acid with 85 wt% of three times the mass of the system, soak for 12 h, then filter to remove the precipitate, and then add sodium hydroxide solution to adjust the pH value to 5 to obtain a heavy metal-containing mixed solution; S4.2: Add 2 parts by mass of the resin heteropolyacid composite material to 10 parts by mass of the heavy metal-containing mixed solution, then add 2 parts by mass of acetic acid-ammonium acetate buffer solution, and set the water bath temperature to 60 °C, the oscillation speed to 600 r / min, and the time to 50 min through a constant temperature water bath oscillator. After the oscillation ends, filter to remove the filtrate, wash the resin three times with acetic acid-ammonium acetate buffer solution, then transfer the washed resin to a conical flask, add 60 parts by mass of nitric acid solution, seal and oscillate for 50 min, and simultaneously heat in a water bath to 60 °C for desorption. After desorption, filter with a filter membrane to obtain a heavy metal filtrate; Among them, the acetic acid-ammonium acetate buffer solution is prepared by mixing acetic acid and ammonium acetate in a mass ratio of 5:8 and adjusting the pH value to 4.8 with acetic acid; S4.3: Add sodium hydroxide to the heavy metal filtrate until precipitation occurs to obtain a heavy metal hydroxide product.

[0028] Example 3: A method for recovering heavy metals from metal waste, as Figure 1 shown, includes the following steps: S1: Prepare silicotungstate S1.1: Dissolve 10 parts by mass of sodium metasilicate in 100 parts by mass of deionized water, and stir magnetically for 15 min to obtain a sodium metasilicate solution; S1.2: Heat 100 parts by mass of deionized water to 100 °C, add 60 parts by mass of sodium tungstate to obtain a sodium tungstate solution, and keep the temperature of the sodium tungstate solution at 100 °C. Dropwise add 50 parts by mass of hydrochloric acid solution, then add the prepared sodium metasilicate solution. Adjust the pH value to 6 with hydrochloric acid solution, and keep the solution temperature at 105 °C for reaction for 1.5 h. Then cool to room temperature, filter, add another 50 parts by mass of potassium chloride, perform suction filtration to retain the filter residue, wash and then dry to obtain the silicon-tungsten composite salt.

[0029] S2: Prepare heteropolyacid powder Add 0.5 part by mass of the silicon-tungsten composite salt and 0.1 part by mass of potassium acetate to 80 parts by mass of deionized water, and adjust the pH value to 6.5. Then dissolve 0.3 part by mass of cetyltrimethylammonium bromide and 0.2 part by mass of tetrabutylammonium bromide in 60 parts by mass of chloroform. Mix the two solutions completely and stir at a speed of 6000 r / min for 1.5 h, then centrifuge at a speed of 11000 r / min for 8 min. Then perform extraction and liquid separation, remove the aqueous phase, retain the organic phase, and then distill the organic phase and dry at 85 °C for 5 h to obtain the heteropolyacid powder.

[0030] S3: Prepare the resin-heteropolyacid composite material S3.1: Immerse the D201 resin in a saturated sodium chloride solution with three times the volume, stir at a speed of 600 r / min for 13 h, then rinse with deionized water 3 times, and then immerse in a hydrochloric acid solution with three times the volume for 8.5 h. The mass fraction of the hydrochloric acid solution is 5%. Wash with deionized water until neutral, then immerse in a sodium hydroxide solution for 8 h. The mass fraction of the sodium hydroxide solution is 2%. Wash with deionized water until neutral and dry to obtain the treated resin; S3.2: Dissolve 20 parts by mass of the heteropolyacid powder in 100 parts by mass of deionized water, and perform ultrasonic treatment for 20 min. Then add 2 parts by mass of the treated resin, keep it in a constant temperature water bath at 60 °C, and keep stirring and reacting for 25 h. Then remove the filtrate by suction filtration, wash with deionized water 3 times, and then dry at 65 °C for 4 h to obtain the resin-heteropolyacid composite material.

[0031] S4: Recover heavy metals from metal waste by resin adsorption method S4.1: Crush the metal waste and immerse it in water, stir for 3 h, then add concentrated sulfuric acid with 85 wt% of three times the mass of the system, soak for 13 h, then filter to remove the precipitate, and then add sodium hydroxide solution to adjust the pH value to 6 to obtain a heavy metal-containing mixed solution; S4.2: Add 1 part by mass of the resin heteropolyacid composite material to 5 parts by mass of the heavy metal-containing mixed solution, then add 1 part by mass of the acetic acid-ammonium acetate buffer solution, and set the water bath temperature to 65 °C, the oscillation speed to 650 r / min, and the time to 70 min using a constant temperature water bath oscillator. After the oscillation ends, filter to remove the filtrate, wash the resin 3 times with the acetic acid-ammonium acetate buffer solution, then transfer the washed resin to a conical flask, add 50 parts by mass of the nitric acid solution, seal and oscillate for 70 min, and simultaneously heat in a water bath to 65 °C for desorption. After desorption, filter with a filter membrane to obtain the heavy metal filtrate; Among them, the acetic acid-ammonium acetate buffer solution is prepared by mixing acetic acid and ammonium acetate in a mass ratio of 5:7 and adjusting the pH value to 5.2 with acetic acid; S4.3: Add sodium hydroxide to the heavy metal filtrate until a precipitate is formed to obtain the heavy metal hydroxide product.

[0032] Comparative Example 1: Compared with Example 1, the difference in Comparative Example 1 is that in step S1.2, no sodium metasilicate solution is added. Specifically, it is “S1.2: Heat 100 parts by mass of deionized water to 90 °C, add 60 parts by mass of sodium tungstate to obtain a sodium tungstate solution, and keep the temperature of the sodium tungstate solution at 90 °C. Dropwise add 50 parts by mass of hydrochloric acid solution, adjust the pH value to 5 with the hydrochloric acid solution, and keep the solution temperature at 100 °C for reaction for 1 h. Then cool to room temperature, filter, add another 50 parts by mass of potassium chloride, filter with suction and retain the filter residue, wash and dry to obtain tungstate”. Use tungstate instead of the silicon-tungsten composite salt, and the remaining steps remain unchanged, denoted as Comparative Example 1.

[0033] Comparative Example 2: Compared with Example 1, the difference in Comparative Example 2 is that in step S1.2, no sodium tungstate solution is added. Specifically, it is “S1.2: Adjust the pH value of the prepared sodium metasilicate solution to 5 with hydrochloric acid solution, and keep the solution temperature at 100 °C for reaction for 1 h. Then cool to room temperature, filter, add another 50 parts by mass of potassium chloride, filter with suction and retain the filter residue, wash and dry to obtain silicate”. Use silicate instead of the silicon-tungsten composite salt, and the remaining steps remain unchanged, denoted as Comparative Example 2.

[0034] Comparative Example 3: Compared with Example 1, the difference in Comparative Example 3 is that in step S4, instead of adding the resin heteropolyacid composite material, heteropolyacid powder is directly added. Specifically, it is "S4.2: Add 1 part by mass of heteropolyacid powder to 5 parts by mass of the heavy metal-containing mixed solution, then add 1 part by mass of acetic acid-ammonium acetate buffer solution, and set the water bath temperature to 60 °C, the oscillation speed to 600 r / min, and the time to 50 min through a constant temperature water bath oscillator. After the oscillation ends, filter to remove the filtrate, and react the filter residue with sodium hydroxide to obtain the heavy metal hydroxide product", which is recorded as Comparative Example 3.

[0035] Detect the contents of copper and nickel in the heavy metal-containing mixed solution in step S4.1, and then test the contents of copper and nickel in the heavy metal hydroxide product, so as to calculate the recovery rates of copper and nickel, as shown in Table 1.

[0036] Copper recovery rate = (content of copper in heavy metal hydroxide * weight of heavy metal hydroxide) / (content of copper in heavy metal-containing mixed solution * weight of heavy metal-containing mixed solution) * 100%.

[0037] Nickel recovery rate = (content of nickel in heavy metal hydroxide * weight of heavy metal hydroxide) / (content of nickel in heavy metal-containing mixed solution * weight of heavy metal-containing mixed solution) * 100%.

[0038] Table 1 Recovery rate statistical table

[0039] It can be seen from Table 1 that the copper recovery rates of Examples 1-3 are above 93%, and the nickel recovery rate is 90%. While the copper recovery rates of Comparative Examples 1 and 2 are only 78% and 76%, and the nickel recovery rates are only 72% and 70%. This shows that the acidic salts formed by using sodium metasilicate or sodium tungstate alone have fewer active sites, and the adsorption effect on heavy metal ions is not as good as when the two are used in combination. After the two are used in combination, loading with resin can further improve the contact with heavy metal ions. Therefore, the copper recovery rate of Comparative Example 3 is 84%, and the nickel recovery rate is 79%, which is higher than that of Comparative Examples 1-2, but lower than that of Examples 1-3.

[0040] The above examples only illustrate the principle and its effects of the present invention by way of example, and are not used to limit the present invention. Any person familiar with this technology can modify or change the above examples without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A method for recovering heavy metals from metal waste, characterized in that, It includes the following steps: S1: Prepare silicotungstic composite salt Prepare sodium metasilicate solution and sodium tungstate solution. After mixing the two solutions, add potassium chloride to prepare silicotungstic composite salt; S2: Prepare heteropolyacid powder Add silicotungstic composite salt and potassium acetate to deionized water, then dissolve cetyltrimethylammonium bromide and tetrabutylammonium bromide in chloroform. Mix the two solutions to prepare heteropolyacid powder; S3: Prepare resin heteropolyacid composite material Immerse D201 resin in sodium chloride solution, then rinse, soak in hydrochloric acid solution, wash, then soak in sodium hydroxide solution, wash to obtain treated resin. Dissolve heteropolyacid powder in deionized water, then add treated resin to prepare resin heteropolyacid composite material; S4: Recover heavy metals from metal waste by resin adsorption method Crush metal waste and immerse it in water, then soak it in concentrated sulfuric acid to prepare a heavy metal-containing mixed solution. Add resin heteropolyacid composite material to the heavy metal-containing mixed solution, then add acetic acid-ammonium acetate buffer solution, shake, wash, then desorb the washed resin to obtain a heavy metal filtrate. Add sodium hydroxide to the heavy metal filtrate until precipitation occurs to obtain a heavy metal hydroxide product.

2. The method for recovering heavy metals from metal waste according to claim 1, characterized in that, Step S1 for preparing silicotungstic composite salt includes the following steps: S1.1: Dissolve 10 - 15 parts by mass of sodium metasilicate in 100 - 110 parts by mass of deionized water, and stir magnetically for 10 - 15 min to obtain sodium metasilicate solution; S1.2: Heat 100 - 110 parts by mass of deionized water to 90 - 100 °C, add 60 - 65 parts by mass of sodium tungstate to obtain sodium tungstate solution, and keep the temperature of the sodium tungstate solution at 90 - 100 °C. Dropwise add 50 - 60 parts by mass of hydrochloric acid solution, then add the prepared sodium metasilicate solution, adjust the pH value to 5 - 6 with hydrochloric acid solution, and keep the solution temperature at 100 - 105 °C for reaction for 1 - 1.5 h. Then cool to room temperature, filter, add 50 - 60 parts by mass of potassium chloride, filter by suction to retain the filter residue, wash and dry to obtain silicotungstic composite salt.

3. A method for recovering heavy metals from metal waste according to claim 2, characterized in that, Step S2 for preparing heteropolyacid powder includes the following steps: Add 0.5 - 1 part by mass of silicotungstic composite salt and 0.1 - 0.3 part by mass of potassium acetate to 80 - 85 parts by mass of deionized water, and adjust the pH value to 6.

5. Then dissolve 0.3 - 0.5 part by mass of cetyltrimethylammonium bromide and 0.2 - 0.4 part by mass of tetrabutylammonium bromide in 60 - 65 parts by mass of chloroform. Mix the two solutions and stir at a speed of 6000 - 7000 r / min for 1 - 1.5 h, then centrifuge at a speed of 10000 - 11000 r / min for 5 - 8 min. Then extract and separate the liquid, remove the aqueous phase, retain the organic phase, and distill the organic phase, dry at 80 - 85 °C for 4 - 5 h to obtain heteropolyacid powder.

4. A method for recovering heavy metals from metal waste according to claim 3, characterized in that, Step S3 for preparing resin heteropolyacid composite material includes the following steps: S3.1: Immerse the D201 resin in a saturated sodium chloride solution with three times the volume, stir at a speed of 500 - 600 r / min for 12 - 13 h, then rinse it with deionized water three times, soak it in a hydrochloric acid solution with three times the volume for 8 - 8.5 h, wash it with deionized water until neutral, then soak it in a sodium hydroxide solution for 8 - 8.5 h, wash it with deionized water until neutral, and dry it to obtain the treated resin; S3.2: Dissolve 20 - 25 parts by mass of heteropolyacid powder in 100 - 105 parts by mass of deionized water, and ultrasonically treat it for 20 - 25 min. Then add 2 - 3 parts by mass of the treated resin, keep it in a constant temperature water bath at 50 - 60 °C, and keep stirring and reacting for 24 - 25 h. Then filter to remove the filtrate, wash it with deionized water three times, and then dry it at 60 - 65 °C for 3 - 4 h to obtain the resin heteropolyacid composite material.

5. A method for recovering heavy metals from metal waste according to claim 4, characterized in that, Step S4 The method for recovering heavy metals from metal waste by resin adsorption method includes the following steps: S4.1: Crush the metal waste and immerse it in water, stir for 2 - 3 h, then add concentrated sulfuric acid with three times the mass of the system, soak for 12 - 13 h, then filter to remove the precipitate, and then add sodium hydroxide solution to adjust the pH value to 5 - 6 to obtain a heavy metal-containing mixed solution; S4.2: Add 1 - 2 parts by mass of the resin heteropolyacid composite material to 5 - 10 parts by mass of the heavy metal-containing mixed solution, then add 1 - 2 parts by mass of acetic acid - ammonium acetate buffer solution, and set the water bath temperature to 60 - 65 °C and the oscillation speed to 600 - 650 r / min for 50 - 70 min through a constant temperature water bath oscillator. After the oscillation ends, filter to remove the filtrate, wash the resin three times with acetic acid - ammonium acetate buffer solution, then transfer the washed resin to a triangular flask, add 50 - 60 parts by mass of nitric acid solution, seal it and oscillate for 50 - 70 min, and simultaneously heat it in a water bath to 60 - 65 °C for desorption. After desorption, filter it with a filter membrane to obtain a heavy metal filtrate; S4.3: Add sodium hydroxide to the heavy metal filtrate until a precipitate is formed to obtain a heavy metal hydroxide product.

6. A method for recovering heavy metals from metal waste according to claim 5, characterized in that, The mass fraction of the hydrochloric acid solution is 5 - 6%.

7. A method for recovering heavy metals from metal waste according to claim 5, characterized in that, The mass fraction of the sodium hydroxide solution is 2 - 4%.

8. A method for recovering heavy metals from metal waste according to claim 5, characterized in that, The acetic acid - ammonium acetate buffer solution is prepared by mixing acetic acid and ammonium acetate in a mass ratio of 5:(7 - 8) and adjusting the pH value to 4.8 - 5.2 with acetic acid.

9. A method for recovering heavy metals from metal waste according to claim 5, characterized in that, The concentration of the concentrated sulfuric acid is 85 wt%.

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