A method for recovering heavy metals from metal waste

Abstract

The present invention relates to the technical field of heavy metal recovery, and more particularly to a method for recovering heavy metals from metal waste. The method comprises the following steps: preparing a silicotungstate composite; preparing a heteropolyacid powder; preparing a resin heteropolyacid composite material; and recovering heavy metals from metal waste using a resin adsorption method. The present invention prepares the silicotungstate composite under relatively mild conditions by reacting sodium metasilicate, sodium tungstate, and potassium chloride. The operation is simple and the conditions are easy to control. The silicotungstate composite has abundant active sites and a large specific surface area. The surface of the silicotungstate composite carries a negative charge and can adsorb positively charged heavy metal ions through electrostatic action. Furthermore, compared with traditional chemical precipitation methods, the extraction of heavy metals using the silicotungstate composite does not require the addition of a large amount of chemical reagents, thereby reducing secondary pollution.

Description

Technical Field

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

[0002] Metal waste refers to waste materials such as used and discarded metal products, obsolete machinery, and solid waste. These wastes typically originate from industrial production, building demolition, and discarded electronic products. Because they contain reusable metal components, they are considered "renewable resources." However, the rapid development of electronic technology and the frequent replacement of electronic products have led to the rapid obsolescence of a large number of electronic devices, generating significant amounts of electronic waste. Furthermore, strong consumer demand for newer electronic products has shortened the average lifespan of these products, further increasing the generation of electronic waste.

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

[0004] Among them, wet leaching is the extraction of metals by leaching with chemical solutions. Generally, copper and nickel are dissolved from waste by acid leaching, and then separated and recovered by electrolysis or precipitation. The metal recovery rate of wet 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 amount of other metal ions in addition to copper and nickel. Therefore, the solid matter directly precipitated by electrolysis and precipitation also contains other metals, resulting in poor recovery of copper and nickel. Therefore, a method for recovering heavy metals from metal waste is needed to improve the recovery rate of copper and nickel to address the shortcomings of the above-mentioned prior art. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention aims to provide a method for recovering heavy metals from metal waste.

[0006] A method for recovering heavy metals from metal waste comprises the following steps:

[0007] S1: Preparation of silicotungstate complex

[0008] Prepare sodium metasilicate solution and sodium tungstate solution, mix the two solutions, and then add potassium chloride to prepare silicotungstate;

[0009] S2: Preparation of heteropolyacid powder

[0010] Silicate tungstate and potassium acetate are added to deionized water, and then hexadecyltrimethylammonium bromide and tetrabutylammonium bromide are dissolved in chloroform, and the two solutions are mixed to prepare heteropolyacid powder;

[0011] S3: Preparation of resin heteropolyacid composites

[0012] The D201 resin was soaked in a sodium chloride solution, then rinsed, soaked in a hydrochloric acid solution, washed, and then soaked in a sodium hydroxide solution, washed to obtain a treated resin, the heteropoly acid powder was dissolved in deionized water, and then added to the treated resin to prepare a resin heteropoly acid composite material;

[0013] S4: Resin adsorption method for recovery of heavy metals from metal waste

[0014] The metal waste is crushed and immersed in water, and then soaked in concentrated sulfuric acid to prepare a mixed solution containing heavy metals. A resin heteropolyacid composite material is added to the mixed solution containing heavy metals, and then an acetic acid-ammonium acetate buffer is added, shaken, and washed. The washed resin is then desorbed to obtain a heavy metal filtrate. Sodium hydroxide is added to the heavy metal filtrate until a precipitate is generated to obtain a heavy metal hydroxide product.

[0015] Furthermore, step S1 of preparing silicotungstate composite comprises the following steps:

[0016] S1.1: Dissolve 10-15 parts by weight of sodium metasilicate in 100-110 parts by weight of deionized water and stir magnetically for 10-15 minutes to obtain a sodium metasilicate solution;

[0017] 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 maintain 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 maintain the solution temperature at 100-105°C for 1-1.5 hours, then cool to room temperature, filter, and then add 50-60 parts by mass of potassium chloride, filter and retain the filter residue, wash and dry to obtain silicotungstate.

[0018] Furthermore, step S2 of preparing heteropolyacid powder comprises the following steps:

[0019] 0.5-1 parts by mass of silicotungstate and 0.1-0.3 parts by mass of potassium acetate are added to 80-85 parts by mass of deionized water, and the pH value is adjusted to 6.5. Then, 0.3-0.5 parts by mass of hexadecyltrimethylammonium bromide and 0.2-0.4 parts by mass of tetrabutylammonium bromide are dissolved in 60-65 parts by mass of chloroform. The two solutions are mixed and stirred at a speed of 6000-7000 r / min for 1-1.5 hours, and then centrifuged at a speed of 10000-11000 r / min for 5-8 minutes. Then, the liquid is extracted and separated, the aqueous phase is removed, the organic phase is retained, and the organic phase is distilled and dried at 80-85°C for 4-5 hours to obtain a heteropolyacid powder.

[0020] Furthermore, step S3 of preparing the resin heteropolyacid composite material comprises the following steps:

[0021] S3.1: Soak D201 resin in three volumes of saturated sodium chloride solution and stir at 500-600 rpm for 12-13 hours. Rinse with deionized water three times, soak in three volumes of hydrochloric acid solution for 8-8.5 hours, wash with deionized water until neutral, soak in sodium hydroxide solution for 8-8.5 hours, wash with deionized water until neutral, and dry to obtain the treated resin.

[0022] S3.2: Dissolve 20-25 parts by mass of heteropolyacid powder in 100-105 parts by mass of deionized water and ultrasonically treat for 20-25 minutes. Then add 2-3 parts by mass of treated resin, place in a constant temperature water bath at 50-60°C, and keep stirring to react for 24-25 hours. Then remove the filtrate by suction, wash with deionized water 3 times, and then dry at 60-65°C for 3-4 hours to obtain a resin heteropolyacid composite material.

[0023] Furthermore, step S4, the resin adsorption method for recovering heavy metals from metal waste, comprises the following steps:

[0024] S4.1: Crush the metal waste and immerse it in water. Stir for 2-3 hours. Then add concentrated sulfuric acid three times the mass of the system and soak for 12-13 hours. Then filter to remove the precipitate. Then add sodium hydroxide solution to adjust the pH to 5-6 to obtain a mixed solution containing heavy metals.

[0025] S4.2: Add 1-2 parts by mass of a resin heteropolyacid composite material to 5-10 parts by mass of a mixed solution containing heavy metals, and then add 1-2 parts by mass of an acetic acid-ammonium acetate buffer solution. Set the water bath temperature to 60-65°C and the oscillation speed to 600-650 r / min for 50-70 min using a constant temperature water bath oscillator. After the oscillation is completed, filter out the filtrate, wash the resin three times with acetic acid-ammonium acetate buffer, then transfer the washed resin to a conical flask, add 50-60 parts by mass of a nitric acid solution, seal and oscillate for 50-70 min, and heat in a water bath to 60-65°C for desorption. After desorption, filter with a filter membrane to obtain a heavy metal filtrate;

[0026] S4.3: Add sodium hydroxide to the heavy metal filtrate until a precipitate is formed to obtain a heavy metal hydroxide product.

[0027] Furthermore, the mass fraction of the hydrochloric acid solution is 5-6%.

[0028] Furthermore, the mass fraction of the sodium hydroxide solution is 2-4%.

[0029] Furthermore, 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 then adjusting the pH value to 4.8-5.2 with acetic acid.

[0030] Furthermore, the concentration of concentrated sulfuric acid is 85 wt %.

[0031] Compared with the prior art, the present invention has at least the following beneficial effects:

[0032] 1. The present invention can prepare silicotungsten composite salts under relatively mild conditions through the reaction of sodium metasilicate, sodium tungstate and potassium chloride. The operation is simple and the conditions are easy to control. The silicotungsten composite salts have abundant active sites and a large specific surface area. The surface of the silicotungsten composite salts has a negative charge and can adsorb positively charged heavy metal ions through electrostatic action. At the same time, the oxygen atoms in the silicotungsten composite salts can form stable complexes with copper and nickel ions, thereby achieving specific adsorption of copper and nickel in heavy metal ions. The silicotungsten composite salts can remain stable under acidic conditions and are suitable for use under environmental conditions after acid leaching. Moreover, compared with the traditional chemical precipitation method, the extraction of heavy metals using silicotungsten composite salts does not require the addition of a large amount of chemical reagents, thereby reducing secondary pollution.

[0033] 2. The present invention combines silicon tungsten composite with resin to prepare resin heteropolyacid composite material. The resin heteropolyacid composite material combines the high adsorption performance of silicon tungsten composite and the high specific surface area of ​​resin. The resin acts as a carrier, which can firmly load silicon tungsten composite on its surface and pores, increase the exposure of adsorption sites, and improve adsorption efficiency, thereby significantly improving the adsorption capacity of heavy metal ions. At the same time, quaternary ammonium cations are formed on the D201 resin used in the present invention under the protonation conditions of heteropolyacid, which can play an auxiliary coordination role in the adsorption process. The quaternary ammonium cations can form weaker 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 synergistically acts with the coordination effect of heteropolyacid to improve the adsorption capacity of copper and nickel, thereby improving the recovery rate of copper and nickel heavy metals. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a flow chart of a method for recovering heavy metals from metal waste adopted in an embodiment of the present invention. DETAILED DESCRIPTION

[0035] 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 used to limit the scope of the present invention.

[0036] The following describes in detail a method for recovering heavy metals from metal waste provided by the present invention, with reference to the accompanying drawings and specific embodiments. It is also noted that, for the sake of completeness, the following embodiments are best and preferred embodiments, and those skilled in the art may employ alternative methods for implementing known techniques. Furthermore, the accompanying drawings are intended only to provide a more detailed description of the embodiments and are not intended to limit the present invention.

[0037] Example 1:

[0038] A method for recovering heavy metals from metal waste, such as Figure 1 As shown, the following steps are included:

[0039] S1: Preparation of silicotungstate complex

[0040] S1.1: Dissolve 10 parts by mass of sodium metasilicate in 100 parts by mass of deionized water and stir magnetically for 10 minutes to obtain a sodium metasilicate solution;

[0041] 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 maintain 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 maintain the solution temperature at 100°C for 1 hour, then cool to room temperature, filter, and add 50 parts by mass of potassium chloride. Filter and retain the filter residue, wash and dry to obtain tungsten silicotungstate.

[0042] S2: Preparation of heteropolyacid powder

[0043] 0.5 parts by mass of silicotungstate and 0.1 parts by mass of potassium acetate were added to 80 parts by mass of deionized water, and the pH value was adjusted to 6.5. Then, 0.3 parts by mass of hexadecyltrimethylammonium bromide and 0.2 parts by mass of tetrabutylammonium bromide were dissolved in 60 parts by mass of chloroform. The two solutions were mixed and stirred at a speed of 6000 r / min for 1 hour, and then centrifuged at a speed of 10000 r / min for 5 minutes. The solution was then extracted and separated, the aqueous phase was removed, the organic phase was retained, and the organic phase was distilled and dried at 80°C for 4 hours to obtain a heteropolyacid powder.

[0044] S3: Preparation of resin heteropolyacid composites

[0045] S3.1: Soak D201 resin in three volumes of saturated sodium chloride solution and stir at 500 r / min for 12 hours. Rinse with deionized water three times, soak in three volumes of 5% hydrochloric acid solution for 8 hours, wash with deionized water until neutral, soak in 2% sodium hydroxide solution for 8 hours, wash with deionized water until neutral, and dry to obtain the treated resin.

[0046] S3.2: Dissolve 20 parts by mass of heteropolyacid powder in 100 parts by mass of deionized water and ultrasonically treat for 20 minutes. Then add 2 parts by mass of treated resin, keep stirring in a constant temperature water bath at 50°C and react for 24 hours. Then remove the filtrate by suction, wash with deionized water three times, and then dry at 60°C for 3 hours to obtain a resin heteropolyacid composite material.

[0047] S4: Resin adsorption method for recovery of heavy metals from metal waste

[0048] S4.1: Crush the metal waste and immerse it in water. Stir for 2 hours. Then, add 85 wt% concentrated sulfuric acid (three times the mass of the system) and soak for 12 hours. Then, filter to remove the precipitate. Then, add sodium hydroxide solution to adjust the pH to 5 to obtain a mixed solution containing heavy metals.

[0049] S4.2: To 5 parts by mass of the mixed solution containing heavy metals, 1 part by mass of a resin heteropolyacid composite material was added, followed by the addition of 1 part by mass of an acetic acid-ammonium acetate buffer solution, and the water bath temperature was set to 60°C and the oscillation speed was set to 600 r / min for 50 min using a constant temperature water bath oscillator. After the oscillation, the filtrate was removed by filtration, and the resin was washed three times with the acetic acid-ammonium acetate buffer solution. The washed resin was then transferred to a conical flask, 50 parts by mass of a nitric acid solution was added, and the flask was sealed and oscillated for 50 min. At the same time, the flask was heated in a water bath to 60°C for desorption. After desorption, the filtrate was filtered using a filter membrane to obtain a heavy metal filtrate;

[0050] The acetic acid-ammonium acetate buffer solution was 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.

[0051] S4.3: Add sodium hydroxide to the heavy metal filtrate until a precipitate is formed to obtain a heavy metal hydroxide product.

[0052] Example 2:

[0053] A method for recovering heavy metals from metal waste, such as Figure 1 As shown, the following steps are included:

[0054] S1: Preparation of silicotungstate complex

[0055] S1.1: Dissolve 15 parts by mass of sodium metasilicate in 110 parts by mass of deionized water and stir magnetically for 10 minutes to obtain a sodium metasilicate solution;

[0056] 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 maintain the temperature of the sodium tungstate solution at 90°C, add 60 parts by mass of hydrochloric acid solution dropwise, and then add the prepared sodium metasilicate solution, adjust the pH value to 5 with hydrochloric acid solution, and maintain the solution temperature at 100°C for 1 hour, then cool to room temperature, filter, and add 50 parts by mass of potassium chloride. Filter and retain the filter residue, wash and dry to obtain silicotungstate.

[0057] S2: Preparation of heteropolyacid powder

[0058] 1 part by mass of silicotungstate and 0.3 part by mass of potassium acetate were added to 85 parts by mass of deionized water, and the pH value was adjusted to 6.5. Then, 0.5 parts by mass of hexadecyltrimethylammonium bromide and 0.4 parts by mass of tetrabutylammonium bromide were dissolved in 65 parts by mass of chloroform. The two solutions were mixed and stirred at a speed of 6000 r / min for 1 hour, and then centrifuged at a speed of 10000 r / min for 5 minutes. The liquid was then extracted and separated, the aqueous phase was removed, the organic phase was retained, and the organic phase was distilled and dried at 80°C for 4 hours to obtain a heteropolyacid powder.

[0059] S3: Preparation of resin heteropolyacid composites

[0060] S3.1: Soak D201 resin in three volumes of saturated sodium chloride solution and stir at 500 r / min for 12 hours. Rinse with deionized water three times, soak in three volumes of 5% hydrochloric acid solution for 8 hours, wash with deionized water until neutral, soak in 2% sodium hydroxide solution for 8 hours, wash with deionized water until neutral, and dry to obtain the treated resin.

[0061] S3.2: Dissolve 25 parts by mass of heteropolyacid powder in 105 parts by mass of deionized water and ultrasonically treat for 20 minutes. Then add 3 parts by mass of treated resin, keep in a constant temperature water bath at 50°C, and keep stirring for 24 hours. Then remove the filtrate by suction, wash with deionized water 3 times, and then dry at 60°C for 3 hours to obtain a resin heteropolyacid composite material.

[0062] S4: Resin adsorption method for recovery of heavy metals from metal waste

[0063] S4.1: Crush the metal waste and immerse it in water. Stir for 2 hours. Then, add 85 wt% concentrated sulfuric acid (three times the mass of the system) and soak for 12 hours. Then, filter to remove the precipitate. Then, add sodium hydroxide solution to adjust the pH to 5 to obtain a mixed solution containing heavy metals.

[0064] S4.2: Add 2 parts by mass of a resin heteropolyacid composite material to 10 parts by mass of a mixed solution containing heavy metals, and then add 2 parts by mass of an acetic acid-ammonium acetate buffer solution. Set the water bath temperature to 60°C and the oscillation speed to 600 r / min for 50 minutes using a constant temperature water bath oscillator. After the oscillation is completed, filter out 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 60 parts by mass of a nitric acid solution, seal and oscillate for 50 minutes, and heat in a water bath to 60°C for desorption. After desorption, filter with a filter membrane to obtain a heavy metal filtrate;

[0065] The acetic acid-ammonium acetate buffer solution was 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.

[0066] S4.3: Add sodium hydroxide to the heavy metal filtrate until a precipitate is formed to obtain a heavy metal hydroxide product.

[0067] Example 3:

[0068] A method for recovering heavy metals from metal waste, such as Figure 1 As shown, the following steps are included:

[0069] S1: Preparation of silicotungstate complex

[0070] S1.1: Dissolve 10 parts by mass of sodium metasilicate in 100 parts by mass of deionized water and stir magnetically for 15 minutes to obtain a sodium metasilicate solution;

[0071] 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 maintain 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 maintain the solution temperature at 105°C for 1.5 hours, then cool to room temperature, filter, add 50 parts by mass of potassium chloride, filter and retain the filter residue, wash and dry to obtain silicotungstate.

[0072] S2: Preparation of heteropolyacid powder

[0073] 0.5 parts by mass of silicotungstate and 0.1 parts by mass of potassium acetate were added to 80 parts by mass of deionized water, and the pH value was adjusted to 6.5. Then, 0.3 parts by mass of hexadecyltrimethylammonium bromide and 0.2 parts by mass of tetrabutylammonium bromide were dissolved in 60 parts by mass of chloroform. The two solutions were mixed and stirred at a speed of 6000 r / min for 1.5 hours, and then centrifuged at a speed of 11000 r / min for 8 minutes. The solution was then extracted and separated, the aqueous phase was removed, the organic phase was retained, and the organic phase was distilled and dried at 85°C for 5 hours to obtain a heteropolyacid powder.

[0074] S3: Preparation of resin heteropolyacid composites

[0075] S3.1: Soak D201 resin in three volumes of saturated sodium chloride solution and stir at 600 r / min for 13 hours. Rinse with deionized water three times, soak in three volumes of 5% hydrochloric acid solution for 8.5 hours, wash with deionized water until neutral, soak in 2% sodium hydroxide solution for 8 hours, wash with deionized water until neutral, and dry to obtain the treated resin.

[0076] S3.2: Dissolve 20 parts by mass of heteropolyacid powder in 100 parts by mass of deionized water and ultrasonically treat for 20 minutes. Then add 2 parts by mass of treated resin, keep stirring in a constant temperature water bath at 60°C for 25 hours, remove the filtrate by suction, wash with deionized water three times, and then dry at 65°C for 4 hours to obtain a resin heteropolyacid composite material.

[0077] S4: Resin adsorption method for recovery of heavy metals from metal waste

[0078] S4.1: Crush the metal waste and immerse it in water with stirring for 3 hours. Then, add 85 wt% concentrated sulfuric acid (three times the mass of the system) and soak for 13 hours. Then, filter to remove the precipitate and add sodium hydroxide solution to adjust the pH to 6 to obtain a mixed solution containing heavy metals.

[0079] S4.2: To 5 parts by mass of the mixed solution containing heavy metals, 1 part by mass of a resin heteropolyacid composite material was added, followed by the addition of 1 part by mass of an acetic acid-ammonium acetate buffer solution, and the water bath temperature was set to 65°C and the oscillation speed was set to 650 r / min for 70 min using a constant temperature water bath oscillator. After the oscillation, the filtrate was removed by filtration, and the resin was washed three times with acetic acid-ammonium acetate buffer solution. The washed resin was then transferred to a conical flask, 50 parts by mass of a nitric acid solution was added, and the flask was sealed and oscillated for 70 min. At the same time, the flask was heated in a water bath to 65°C for desorption. After desorption, the filtrate was filtered using a filter membrane to obtain a heavy metal filtrate;

[0080] The acetic acid-ammonium acetate buffer solution was 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.

[0081] S4.3: Add sodium hydroxide to the heavy metal filtrate until a precipitate is formed to obtain a heavy metal hydroxide product.

[0082] Comparative Example 1:

[0083] Compared with Example 1, the difference of Comparative Example 1 is that no sodium metasilicate solution is added in step S1.2, specifically "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 maintain the temperature of the sodium tungstate solution at 90°C, add 50 parts by mass of hydrochloric acid solution, adjust the pH value to 5 with hydrochloric acid solution, and maintain the solution temperature at 100°C for 1h, then cool to room temperature, filter, add 50 parts by mass of potassium chloride, filter and retain the filter residue, wash and dry to obtain tungstate", tungstate is used instead of silicotungstate, and the other steps remain unchanged, which is recorded as Comparative Example 1.

[0084] Comparative Example 2:

[0085] Compared with Example 1, the difference of Comparative Example 2 is that no sodium tungstate solution is added in step S1.2. Specifically, "S1.2: adjust the pH value of the prepared sodium metasilicate solution to 5 with hydrochloric acid solution, maintain the solution temperature at 100°C for 1 hour, then cool to room temperature, filter, add 50 parts by mass of potassium chloride, filter and retain the filter residue, wash and dry to obtain silicate". Silicate is used instead of tungsten silicotungstate, and the other steps remain unchanged, which is recorded as Comparative Example 2.

[0086] Comparative Example 3:

[0087] Compared with Example 1, the difference of Comparative Example 3 is that, in step S4, no resin heteropolyacid composite material is added but heteropolyacid powder is directly added, specifically "S4.2: 1 part by mass of heteropolyacid powder is added to 5 parts by mass of a mixed solution containing heavy metals, and then 1 part by mass of acetic acid-ammonium acetate buffer is added, and the water bath temperature is set to 60°C and the oscillation speed is 600r / min through a constant temperature water bath oscillator, and the time is 50min. After the oscillation is completed, the filtrate is filtered out, and the filter residue is added to sodium hydroxide to react to obtain a heavy metal hydroxide product", which is recorded as Comparative Example 3.

[0088] The copper and nickel contents in the mixed solution containing heavy metals in step S4.1 were detected, and the copper and nickel contents in the heavy metal hydroxide products were then tested, thereby calculating the copper and nickel recovery rates, as shown in Table 1.

[0089] Copper recovery rate = (copper content in heavy metal hydroxide * weight of heavy metal hydroxide) / (copper content in mixed solution containing heavy metals * weight of mixed solution containing heavy metals) * 100%.

[0090] Nickel recovery rate = (nickel content in heavy metal hydroxide * weight of heavy metal hydroxide) / (nickel content in mixed solution containing heavy metals * weight of mixed solution containing heavy metals) * 100%.

[0091] Table 1 Recovery rate statistics

[0092]

[0093] As can be seen from Table 1, the copper recovery rate of Examples 1-3 is 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%, respectively. This indicates that the acidic salts formed by using sodium metasilicate or sodium tungstate alone have fewer active sites and are not as effective in adsorbing heavy metal ions as the combination of the two. After the combination of the two, the contact with heavy metal ions can be further enhanced by using a resin load. Therefore, the copper recovery rate of Comparative Example 3 is 84%, and the nickel recovery rate is 79%, which are higher than those of Comparative Examples 1-2, but not as good as those of Examples 1-3.

[0094] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A method for recovering heavy metals from metal waste, characterized in that: The steps include: S1: Preparation of silicotungstate complex Dissolve 10-15 parts by mass of sodium metasilicate in 100-110 parts by mass of deionized water to prepare a sodium metasilicate solution, 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 maintain 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, and maintain the solution temperature at 100-105° C. for reaction, then cool to room temperature, and then add 50-60 parts by mass of potassium chloride to prepare a silicotungstate; S2: Preparation of heteropolyacid powder 0.5-1 parts by mass of silicotungstate and 0.1-0.3 parts by mass of potassium acetate are added to 80-85 parts by mass of deionized water, and the pH value is adjusted. Then, 0.3-0.5 parts by mass of hexadecyltrimethylammonium bromide and 0.2-0.4 parts by mass of tetrabutylammonium bromide are dissolved in 60-65 parts by mass of chloroform. The two solutions are mixed and stirred, and then centrifuged, extracted and separated, the aqueous phase is removed, the organic phase is retained, and the organic phase is distilled and dried at 80-85° C. to obtain a heteropolyacid powder; S3: Preparation of resin heteropolyacid composites The D201 resin was immersed in three times the volume of saturated sodium chloride solution, stirred, rinsed, then immersed in three times the volume of hydrochloric acid solution, washed, then immersed in sodium hydroxide solution, washed, and dried to obtain a treated resin; 20-25 parts by mass of heteropoly acid powder was dissolved in 100-105 parts by mass of deionized water, ultrasonically treated, and then 2-3 parts by mass of the treated resin was added, and the mixture was reacted in a constant temperature water bath at 50-60°C, the filtrate was removed by suction, washed, and then dried at 60-65°C to obtain a resin heteropoly acid composite material; S4: Resin adsorption method for recovery of heavy metals from metal waste The metal waste is crushed and immersed in water, stirred, and then concentrated sulfuric acid three times the mass of the system is added for soaking. The precipitate is then filtered to remove, and the pH value is adjusted to obtain a mixed solution containing heavy metals. 1-2 parts by mass of a resin heteropolyacid composite material is added to 5-10 parts by mass of the mixed solution containing heavy metals, and then 1-2 parts by mass of an acetic acid-ammonium acetate buffer solution is added. The temperature is set to 60-65°C for oscillation. After the end, the filtrate is filtered out, the resin is washed with an acetic acid-ammonium acetate buffer solution, and the washed resin is then transferred to a triangular flask. 50-60 parts by mass of a nitric acid solution is added, the flask is sealed and shaken, and the precipitate is heated to 60-65°C for desorption. After desorption, the filtrate is filtered using a filter membrane to obtain a heavy metal filtrate. Sodium hydroxide is added to the heavy metal filtrate until a precipitate is generated 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 prepares silicotungstate composite, comprising the following steps: S1.1: Dissolve 10-15 parts by weight of sodium metasilicate in 100-110 parts by weight of deionized water and stir magnetically for 10-15 minutes 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 maintain 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 maintain the solution temperature at 100-105°C for 1-1.5 hours, then cool to room temperature, filter, and then add 50-60 parts by mass of potassium chloride, filter and retain the filter residue, wash and dry to obtain silicotungstate.

3. The method for recovering heavy metals from metal waste according to claim 2, characterized in that: Step S2 prepares heteropolyacid powder, comprising the following steps: 0.5-1 parts by mass of silicotungstate and 0.1-0.3 parts by mass of potassium acetate are added to 80-85 parts by mass of deionized water, and the pH value is adjusted to 6.

5. Then, 0.3-0.5 parts by mass of hexadecyltrimethylammonium bromide and 0.2-0.4 parts by mass of tetrabutylammonium bromide are dissolved in 60-65 parts by mass of chloroform. The two solutions are mixed and stirred at a speed of 6000-7000 r / min for 1-1.5 hours, and then centrifuged at a speed of 10000-11000 r / min for 5-8 minutes. Then, the liquid is extracted and separated, the aqueous phase is removed, the organic phase is retained, and the organic phase is distilled and dried at 80-85°C for 4-5 hours to obtain a heteropolyacid powder.

4. The method for recovering heavy metals from metal waste according to claim 3, characterized in that: Step S3 is to prepare a resin heteropolyacid composite material, comprising the following steps: S3.1: Soak D201 resin in three volumes of saturated sodium chloride solution and stir at 500-600 rpm for 12-13 hours. Rinse with deionized water three times, soak in three volumes of hydrochloric acid solution for 8-8.5 hours, wash with deionized water until neutral, soak in sodium hydroxide solution for 8-8.5 hours, wash with deionized water until neutral, and dry 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 for 20-25 minutes. Then add 2-3 parts by mass of treated resin, place in a constant temperature water bath at 50-60°C, and keep stirring to react for 24-25 hours. Then remove the filtrate by suction, wash with deionized water 3 times, and then dry at 60-65°C for 3-4 hours to obtain a resin heteropolyacid composite material.

5. The method for recovering heavy metals from metal waste according to claim 4, characterized in that: Step S4: Resin adsorption method is used to recover heavy metals from metal waste, comprising the following steps: S4.1: Crush the metal waste and immerse it in water. Stir for 2-3 hours. Then add concentrated sulfuric acid three times the mass of the system and soak for 12-13 hours. Then filter to remove the precipitate. Then add sodium hydroxide solution to adjust the pH to 5-6 to obtain a mixed solution containing heavy metals. S4.2: Add 1-2 parts by mass of a resin heteropolyacid composite material to 5-10 parts by mass of a mixed solution containing heavy metals, and then add 1-2 parts by mass of an acetic acid-ammonium acetate buffer solution. Set the water bath temperature to 60-65°C and the oscillation speed to 600-650 r / min for 50-70 min using a constant temperature water bath oscillator. After the oscillation is completed, filter out the filtrate, wash the resin three times with acetic acid-ammonium acetate buffer, then transfer the washed resin to a conical flask, add 50-60 parts by mass of a nitric acid solution, seal and oscillate for 50-70 min, and heat in a water bath to 60-65°C for desorption. After desorption, filter 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. The 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. The method for recovering heavy metals from metal waste according to claim 5, characterized in that: The mass fraction of sodium hydroxide solution is 2-4%.

8. The 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 then adjusting the pH value to 4.8-5.2 with acetic acid.

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

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