A leaching agent for waste electronic and electrical equipment recycling, a preparation method and a silver leaching recovery method

Abstract

The application belongs to the technical field of silver-containing waste electronic and electrical equipment recycling, and particularly relates to a leaching agent for waste electronic and electrical equipment recycling, a preparation method and a silver leaching and recycling method. The leaching agent is trioctylmethylammonium triiodide [N 1888 ][I3], the trioctylmethylammonium triiodide [N 1888 ][I3] has good stability and low viscosity, does not need to be diluted by toxic organic solvents, the leaching agent recycles metals through oxidation and reduction, realizes high leaching efficiency under low-temperature stirring conditions, and avoids the use of acid or corrosive reagents and high energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of silver-containing waste electronic and electrical appliance recycling technology. Specifically, it relates to a leaching agent for waste electronic and electrical appliance recycling, its preparation method, and a silver leaching and recycling method. Background Technology

[0002] Silver, as a precious metal, is widely used in electronics, machinery, and jewelry due to its unique physical and chemical properties. However, with the rapid development of global technology and the limited reserves in the Earth's crust, a series of silver supply crises have emerged. In 2020, silver consumption in electronic products was approximately 6,350 tons, and demand is projected to grow by 10% to 7,000 tons by 2025. In 2021, the U.S. Geological Survey reported that global silver reserves were approximately 500,000 tons, with 32% of consumed silver used in the production of electronic appliances. Furthermore, recycling silver from electronic appliances is economically feasible, as the silver content in these appliances is approximately 1300 g / t. -1 Silver levels are much higher than in ore. Therefore, recovering silver from electronic and electrical appliances is an inevitable trend. However, due to immature recycling technology, the effective silver recovery rate from waste electronic and electrical appliances is only 20%.

[0003] To date, hydrometallurgy is the primary technology for recovering silver from electronic appliances. Hydrometallurgy mainly includes two processes: leaching and extraction. In general, hydrometallurgy has the advantages of relatively simple equipment and low energy consumption, but it still requires the use of highly toxic or highly corrosive chemicals such as NaCN, HCl, and HNO3, making safety and environmental protection issues prominent. Traditional hydrometallurgical methods for recovering silver face unavoidable challenges: (1) the use of highly toxic and corrosive reagents; (2) the separation of leaching and extraction processes, increasing process complexity. If these problems can be avoided, hydrometallurgy will be more competitive.

[0004] Trihalide ionic liquids (ILs) are a unique class of ionic liquids whose anions consist of a cluster of negatively charged halogen atoms, such as [I3]. - These trihalomethane ionic liquids possess excellent potential for safe halogen storage and high metal oxidation capacity. They combine the ability to leach precious metals with the advantages of safety and environmental friendliness, showing potential to replace aqua regia and sodium cyanide in achieving green precious metal recovery processes. Furthermore, trihalomethane ionic liquids function as both leaching and extraction agents, simplifying the process flow. They avoid the aforementioned problems associated with conventional hydrometallurgy. Therefore, as a novel green leaching agent for recovering silver from waste electronic and electrical appliances, they will demonstrate superior performance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a leaching agent, a preparation method, and a silver leaching and recovery method for the recycling of waste electronic and electrical appliances.

[0006] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a leaching agent for the recycling of waste electronic and electrical appliances, wherein the leaching agent is trioctylmethylammonium triiodide ([N... 1888 [I3]), the structure is shown in Equation I below: Formula I.

[0007] Based on the above scheme, the extractant further has high thermal stability, reaching 223℃ without decomposition; low viscosity, with a viscosity of 49 cP at 55℃; and low water solubility, with a solubility of 0.032 mg / L.

[0008] Secondly, the present invention provides a method for preparing a leaching agent for the recycling of waste electronic and electrical appliances, comprising the following steps: S1. Iodomethane, trioctylamine, and an appropriate amount of acetonitrile were mixed in a round-bottom flask and stirred at room temperature for 15 hours. After the reaction was completed, the acetonitrile was removed by rotary evaporation, and benzene was added. The mixture was washed three times each with 0.1 M NaOH solution, 1.0 M sodium chloride solution, and water. The benzene was removed by rotary evaporation to obtain a pale yellow oily substance, which was washed twice with petroleum ether to remove the trioctylamine. Finally, the mixture was dried to obtain the intermediate product trioctylmethylammonium iodide ([N... 1888 ]I); S2, the intermediate product [N] 1888 I and elemental iodine reacted under light-protected heating conditions for 2 hours to obtain the product triiodide ion liquid leaching agent trioctylmethyltriiodammonium ([N 1888 [I3]).

[0009] Based on the above scheme, the molar ratio of iodomethane to trioctylamine in step S1 is further: 1:(0.9-1.2).

[0010] Based on the above scheme, further, in step S1, the molar volume ratio of iodomethane to acetonitrile is 0.1:(40-60), in mol / mL; the molar volume ratio of iodomethane to benzene is 0.1:(80-150), in mol / mL; and the molar volume ratio of iodomethane to petroleum ether is 0.1:(70-110), in mol / mL.

[0011] Based on the above scheme, further, in step S2, the intermediate product [N] 1888 The molar ratio of I to iodine is 1:1.

[0012] Based on the above scheme, further, in step S2, the reaction temperature is 40-60℃.

[0013] Thirdly, the application of the leaching agent used for the recycling of waste electronic and electrical appliances in the silver leaching and recycling.

[0014] Fourthly, the present invention provides a method for silver leaching and recovery using the leaching agent for waste electronic and electrical appliance recycling, specifically comprising the following steps: (1) Place [N] 1888 [I3] The leaching agent is used as an ionic liquid phase; (2) Alloy powder from the dismantling of waste electronic and electrical appliances with a size of about 400 mesh is used as the solid phase; (3) The ionic liquid phase and the solid phase are heated and stirred to leach; (4) After leaching, add ethanol to the ionic liquid phase. The leached silver will precipitate to the bottom in the form of silver iodide nanoparticles. Filter and recover the silver iodide nanoparticles. (5) Rotary evaporation to remove the upper layer [N] 1888 [I3] Ethanol in ethanol solution, recover the remaining [N] 1888 [I3] Leaching agent, and add an appropriate amount of [N] consumed in the synthesis of elemental iodine. 1888 [I3] is used for the next round of recycling.

[0015] Based on the above scheme, in step (2), the alloy powder solid phase of the waste electronic and electrical appliances dismantled also includes Cu and Ni metals.

[0016] Based on the above scheme, further, the immersion temperature in step (3) is 35-75℃, the stirring speed is 300 rpm, the mass ratio of ionic liquid phase to solid phase is 10-60:1, and the immersion time is 0.2-8 hours.

[0017] Based on the above scheme, further, in step (4), the volume ratio of the ionic liquid phase to ethanol is 1:4.

[0018] Based on the above scheme, the molar ratio of added iodine to silver is further 1:2.

[0019] Compared with the prior art, the beneficial effects of the present invention are: (1) This invention provides a method for preparing a leaching agent that combines leaching and extraction, and develops a simple, environmentally friendly, and recyclable silver leaching and recovery method. The leaching agent, triiodine ionic liquid, can achieve acid-free, one-step recovery of silver from waste electronic appliances, and therefore has broad application prospects.

[0020] (2) The triiodine leaching agent of the present invention [N 1888 [I3] It has good stability and low viscosity, and does not require dilution with toxic organic solvents, which protects the environment and saves costs significantly.

[0021] (3) [N] 1888 [I3] itself acts as a leaching agent, recovering metals through oxidation-reduction and achieving high leaching efficiency under low-temperature stirring conditions, while avoiding the use of acid or corrosive reagents and high energy consumption.

[0022] (4) [N] 1888 [I3] It acts as both a leaching agent and an extraction agent, combining the leaching and extraction processes into one, eliminating the need for expensive extraction agents. Furthermore, the entire process requires no back-extraction, achieving recovery in one step, overcoming the complex steps of multiple leaching-extraction-back-extraction processes in traditional methods, and simplifying the process flow.

[0023] (5) After the leaching agent of the present invention has finished leaching the metal, the metal and the ionic liquid can be separated by precipitation filtration, thereby realizing the recycling of the ionic liquid and the metal. Attached Figure Description

[0024] Figure 1 The NMR spectrum of the leaching agent; Figure 2 Raman spectra of the leaching agent; Figure 3 The effect of leaching time on the leaching of silver, copper and nickel is shown on the horizontal axis, with leaching time on the horizontal axis and leaching rate on the vertical axis. Figure 4 The flowchart for leaching and recovering silver with leaching agent; Figure 5 SEM image of silver iodide nanoparticles obtained by leaching with the leaching agent. Detailed Implementation

[0025] To facilitate understanding of the present invention by those skilled in the art, specific embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the following text is merely used to describe one or more specific embodiments of the present invention and does not strictly limit the scope of protection specifically claimed by the present invention.

[0026] Unless otherwise specified, the methods described in the following embodiments are conventional methods.

[0027] After leaching, 100 mg of triiodine ionic liquid was first digested with concentrated nitric acid, and then the content of silver and other metal ions in the triiodine ionic liquid phase was determined by inductively coupled plasma optical emission spectrometry (ICP-OES). This acid digestion method was only used for determination and had no effect on the leaching experiment.

[0028] The extraction rate is calculated using the following formula: m0 and m E These represent the mass of metal in the alloy of disassembled waste electronic and electrical appliances before leaching and the mass of metal in the ionic liquid phase, respectively.

[0029] Example 1 [N 1888 Synthesis of [I3] Leaching Agent: 0.08 mol iodomethane and 0.088 mol trioctylamine were weighed into a round-bottom flask, and 50 mL acetonitrile was added and stirred for 15 hours. After the reaction was completed, the acetonitrile was removed by rotary evaporation, and 115 mL benzene was added. The mixture was washed three times each with 200 mL 0.1 M NaOH solution, 1.0 M NaCl solution, and water. Then, the organic phase benzene was removed by rotary evaporation, yielding a pale yellow oily substance. 100 mL petroleum ether was added to the oil, and the mixture was washed twice to remove trioctylamine. The mixture was then dried to obtain the intermediate product [N]. 1888 ]I.

[0030] 0.05 mol of intermediate product [N 1888 I and 0.05 mol of elemental iodine were placed in a 100 mL round-bottom flask and then stirred at 50 °C in the dark for 2 hours to obtain the final leaching agent [N]. 1888 [I3], [N] 1888 The NMR and Raman spectra of [I3] are as follows: Figure 1 As shown in Figure 2.

[0031] Example 2 [N 1888 Synthesis of [I3] Leaching Agent: 0.08 mol iodomethane and 0.072 mol trioctylamine were weighed into a round-bottom flask, and 40 mL acetonitrile was added and stirred for 15 hours. After the reaction was completed, the acetonitrile was removed by rotary evaporation, and 80 mL benzene was added. The mixture was washed three times each with 200 mL 0.1 M NaOH solution, 1.0 NaCl solution, and water. Then, the organic phase benzene was removed by rotary evaporation, yielding a pale yellow oily substance. 70 mL petroleum ether was added to the oil, and the mixture was washed twice to remove trioctylamine. The mixture was then dried to obtain the intermediate product [N]. 1888 ]I.

[0032] 0.05 mol of intermediate product [N 1888 I and 0.05 mol of elemental iodine were placed in a 100 mL round-bottom flask and then stirred in the dark at 40 °C for 2 hours to obtain the final leaching agent [N]. 1888 [I3].

[0033] Example 3 [N 1888 Synthesis of [I3] Leaching Agent: 0.08 mol iodomethane and 0.096 mol trioctylamine were weighed into a round-bottom flask, and 60 mL acetonitrile was added and stirred for 15 hours. After the reaction was completed, the acetonitrile was removed by rotary evaporation, and 150 mL benzene was added. The mixture was washed three times each with 200 mL 0.1 M NaOH solution, 1.0 M NaCl solution, and water. Then, the organic phase benzene was removed by rotary evaporation, yielding a pale yellow oily substance. 110 mL petroleum ether was added to the oil, and the mixture was washed twice to remove trioctylamine. The mixture was then dried to obtain the intermediate product [N]. 1888 ]I.

[0034] 0.05 mol of intermediate product [N 1888 I and 0.05 mol of elemental iodine were placed in a 100 mL round-bottom flask and then stirred at 60 °C in the dark for 2 hours to obtain the final leaching agent [N]. 1888 [I3] Composition analysis of alloy powder from dismantled waste electronic and electrical appliances: The alloys from the dismantled waste electronic and electrical appliances were pulverized, ground in a mortar and pestle, and then passed through a 400-mesh sieve. Their chemical composition was determined using X-ray diffraction. The alloy powder was then leached with concentrated nitric acid and aqua regia for 6 hours each, followed by ICP-OES analysis to determine the content of silver, copper, nickel, etc. This acid dissolution process was only used for the determination and had no effect on subsequent leaching and recovery experiments. The specific values ​​for each metal are shown in Table 1.

[0035] Table 1 Main Chemical Composition of Alloy Powder from Waste Electronic and Electrical Appliance Dismantling Example 4 [N 1888 [I3] Application of leaching agents in the recovery of precious metal silver: The leaching was carried out in a 7 mL plastic tube, to which 1.00 g [N] was added. 1888 [I3] The leaching agent and 30 mg of waste electronic and electrical dismantling alloy powder were heated at 55°C and stirred at 300 rpm for 0.2-8 hours. After leaching, 100 mg of [N] 1888 [I3] The leaching agent was digested by heating with concentrated nitric acid, then diluted and measured. The metal content in the ionic liquid phase was then determined using inductively coupled plasma atomic emission spectrometry (ICP-MS). This acid digestion method was used only for the determination and had no effect on the leaching experiment. The above [N] 1888 [I3] During the leaching process, the leaching rates of silver, copper, and nickel at different leaching times are as follows: Figure 3 As shown.

[0036] pass Figure 3 It can be seen that as the leaching time continues to extend, the leaching rate of silver and copper increases first and then reaches equilibrium, while the leaching rate of nickel has little effect.

[0037] Example 5 [N 1888 [I3] The synthesis process of the extractant was carried out according to Example 1.

[0038] The composition analysis of alloy powder from the dismantled waste electronic and electrical appliances was carried out according to Example 1.

[0039] [N 1888 [I3] Application of leaching agents for precious metal silver: The leaching was carried out in a 7 mL plastic tube, to which 1.00 g [N] was added. 1888 [I3] Leaching agent and different masses of waste electronic and electrical appliance dismantling alloy powder were heated at 55°C and stirred for 3 hours at 300 rpm. After leaching, 100 mg of [N] was taken. 1888 [I3] The leaching agent was digested by heating with concentrated nitric acid, then diluted and measured. The metal content of the leaching agent phase was determined by inductively coupled plasma atomic emission spectrometry (ICP-MS).

[0040] The above [N] 1888 [I3] During the leaching process, the leaching rates of silver, copper, and nickel from different masses of waste electronic and electrical appliance dismantling alloy powders are shown in Table 2. It can be seen that [N] 1888 [I3] The leaching rate of the leaching agent for nickel is <1.0%, the maximum leaching rate for silver is 97.2% at 30 g / kg, and the maximum leaching rate for copper is 99.2% at 40 g / kg.

[0041] Table 2. Solid-liquid ratios at different rates [N] 1888 [I3] Effect on the leaching rates of silver, copper and nickel Example 6 [N 1888 [I3] The synthesis process of the extractant was carried out according to Example 1.

[0042] The composition analysis of alloy powder from the dismantled waste electronic and electrical appliances was carried out according to Example 1.

[0043] [N 1888 [I3] Application of leaching agents in the recovery of precious metal silver: The leaching was carried out in a 7 mL plastic tube, to which 1.00 g [N] was added. 1888 [I3] The leaching agent and 30 mg of waste electronic and electrical dismantling alloy powder were stirred at 300 rpm for 3 hours. After leaching, 100 mg of [N] was taken. 1888 [I3] The leaching agent was digested by heating with concentrated nitric acid, then diluted and measured. The metal content of the leaching agent phase was determined by inductively coupled plasma atomic emission spectrometry (ICP-MS).

[0044] The above [N]1888 [I3] The leaching process, the leaching rates of silver, copper and nickel under different temperature conditions are shown in Table 3. It can be seen that as the temperature increases, the leaching rates of silver and copper first increase and then stabilize, while the leaching rate of nickel hardly changes.

[0045] Table 3 Temperature versus [N] 1888 [I3] Effects of leaching silver, copper and nickel Example 7 This embodiment studies the separation of silver, copper, and nickel after leaching. [N 1888 [I3] The synthesis process of the extractant was carried out according to Example 1.

[0046] [N 1888 [I3] Application of leaching agents in the recovery of precious metal silver: The leaching was carried out in a 7 mL plastic tube, to which 1.00 g [N] was added. 1888 [I3]] The leaching agent and 30 mg of waste electronic and electrical dismantling alloy powder were heated at 55°C and stirred for 3 hours at a speed of 300 rpm.

[0047] Separation of the three metals: silver, copper, and nickel: The whole process is as follows Figure 4 As shown, after leaching, under the condition that the volume ratio of ethanol to ionic liquid phase is 4, [N] 1888 [I3] Ethanol was added to the leaching agent. The leached silver and copper formed silver iodide and cuprous iodide, respectively, and precipitated to the bottom. Elemental nickel also precipitated to the bottom. The mixture of the three metals was filtered to obtain a mixture. After drying, the magnetic nickel was removed using a magnet. 1.0 M NaI solution was added to the remaining mixture of silver iodide and cuprous iodide, and the cuprous iodide was converted to [CuI2]. - The solution was used to remove it, leaving silver iodide nanoparticles with the following morphology: Figure 5 As shown. Towards [CuI2] - Diluting the solution with water yielded a new precipitate of cuprous iodide.

[0048] Example 8 This embodiment studies [N] 1888 [I3] Recycling of Leaching Agent [N 1888 [I3] The synthesis process of the extractant was carried out according to Example 1.

[0049] [N 1888 [I3] Recycling of Leaching Agent: After leaching, under the condition that the volume ratio of ethanol to leaching agent is 4, [N] 1888[I3] When ethanol is added to the leaching agent, the metal will sink to the bottom, and the mixture of the three metals can be obtained by filtration.

[0050] Recover the upper layer of ethanol [N] 1888 [I3] solution, rotary evaporation to remove ethanol and recover the remaining [N] 1888 [I3] Leaching agent. The [N] consumed in the synthesis of iodine is added to the recovered ionic liquid phase. 1888 [I3]. The molar ratio of added iodine to the silver content in the leached waste electronic and electrical appliance dismantling alloy powder is 1:2. [N] 1888 [I3] The leaching agent will proceed to the next leaching round. Table 4 shows the number of cycles and [N]. 1888 The silver leaching rate of [I3] after 6 leaching-recovery cycles, [N] 1888 The extraction rate of [I3] can reach over 97%, therefore, [N] 1888 [I3] is a recyclable and highly efficient leaching agent.

[0051] Table 4. [N] for different number of cycle cycles 1888 [I3] Effect on silver leaching rate .

Claims

1. A method for preparing a leaching agent for recycling waste electronic and electrical appliances, characterized in that: The leaching agent is trioctylmethyltriiodammonium ([N... 1888 [I3]), the structure is shown in Equation I below: ； Formula I; The extractant has high thermal stability, remaining undecomposed up to 223℃; it has low viscosity, with a viscosity of 49 cP at 55℃; and low water solubility, with a solubility of 0.032 mg / L. The preparation method includes the following steps: S1. Iodomethane, trioctylamine, and an appropriate amount of acetonitrile were mixed in a round-bottom flask and stirred at room temperature for 15 hours. After the reaction was completed, the acetonitrile was removed by rotary evaporation, and benzene was added. The mixture was washed three times each with 0.1M NaOH solution, 1.0M sodium chloride solution, and water. The benzene was removed by rotary evaporation to obtain a pale yellow oily substance, which was washed twice with petroleum ether to remove the trioctylamine. Finally, the mixture was dried to obtain the intermediate product trioctylmethylammonium iodide [N 1888 ]I; S2, the intermediate product [N] 1888 I and elemental iodine reacted under light-protected heating for 2 hours to obtain the product triiodine ions. The leaching agent was trioctylmethylammonium triiodide. 1888 [I3].

2. The method for preparing the leaching agent for waste electronic and electrical appliance recycling according to claim 1, characterized in that: The molar ratio of iodomethane to trioctylamine in step S1 is 1:(0.9-1.2).

3. The method for preparing the leaching agent for waste electronic and electrical appliance recycling according to claim 1, characterized in that: In step S1, the molar volume ratio of iodomethane to acetonitrile is 0.1:(40-60), in mol / mL; the molar volume ratio of iodomethane to benzene is 0.1:(80-150), in mol / mL; and the molar volume ratio of iodomethane to petroleum ether is 0.1:(70-110), in mol / mL.

4. The method for preparing the leaching agent for waste electronic and electrical appliance recycling according to claim 1, characterized in that: In step S2, the intermediate product [N] 1888 The molar ratio of I to iodine is 1:1, and the reaction temperature is 40-60℃.

5. A method for silver leaching and recovery using a leaching agent prepared by any one of claims 1-4, characterized in that: Specifically, the following steps are included: (1) Place [N] 1888 [I3] The leaching agent is used as an ionic liquid phase; (2) Alloy powder from the dismantling of waste electronic and electrical appliances with a size of 400 mesh was used as the solid phase; (3) The ionic liquid phase and the solid phase are heated and stirred to leach; (4) After leaching, add ethanol to the ionic liquid phase. The leached silver will precipitate to the bottom in the form of silver iodide nanoparticles. Filter and recover the silver iodide nanoparticles. (5) Rotary evaporation to remove the upper layer [N] 1888 [I3] Ethanol in ethanol solution, recover the remaining [N] 1888 [I3] Leaching agent, and add an appropriate amount of [N] consumed in the synthesis of elemental iodine. 1888 [I3] is used for the next round of recycling.

6. The method for silver leaching and recovery using a leaching agent according to claim 5, characterized in that: The immersion temperature in step (3) is 35-75℃, the stirring speed is 300 rpm, the mass ratio of ionic liquid phase to solid phase is 10-60:1, and the immersion time is 0.2-8 hours.

7. The method for silver leaching and recovery using a leaching agent according to claim 5, characterized in that: In step (4), the volume ratio of the ionic liquid phase to ethanol is 1:

4.

8. The method for silver leaching and recovery using a leaching agent according to claim 5, characterized in that: The molar ratio of iodine to silver added in step (5) is 1:2.

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