Method for leaching electronic waste mixed powder by using lactobacillus plantarum

Abstract

The invention relates to a method for leaching electronic waste mixed powder by using lactobacillus plantarum, and belongs to the technical field of resource recovery. The leaching method comprises the following steps: preparing electronic waste mixed powder, preparing a culture medium, domesticating bacteria and leaching. According to the method, lactobacillus plantarum is applied to biological leaching of the mixed material of the waste lithium iron phosphate battery and the waste printed circuit board, and extraction of lithium and iron in the waste lithium iron phosphate battery and extraction of copper in the waste printed circuit board are achieved at the same time. Compared with traditional biological leaching of single electronic waste, the method has the advantages that strong acidophilic bacteria are not used, strong acid wastewater is not generated, additional chemical reagents are not added, the problem of water and soil acidification caused by the traditional strong acidophilic bacteria is greatly relieved, and the method can be used for recycling the electronic waste under the condition that a large amount of strong acid harmful to the environment is not generated. And efficient biological leaching of the mixed material of the waste lithium iron phosphate battery and the waste printed circuit board is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of resource recovery, and in particular relates to a leaching method for leaching mixed powder of electronic waste using Lactobacillus plantarum. Background Art

[0002] With the rapid development of the electronics industry, the amount of electronic waste generated has also risen sharply. Electronic waste comes from a wide range of sources and is of many types. Common ones include lithium-ion batteries, liquid crystal displays, tantalum capacitors, printed circuit boards, light-emitting diodes, etc. These electronic wastes are composed of ceramics, organic materials and many metals. Electronic waste not only contains a large amount of valuable metals such as lithium, copper, aluminum, silver, gold, palladium, iron, etc., but also contains many heavy metals such as mercury, cadmium, lead and brominated flame retardants, which are substances that are harmful to the environment. Therefore, the resource recovery of these electronic wastes is not only of economic value, but also of great significance to environmental protection. Among the many electronic waste metal recovery technologies, pyrometallurgy and hydrometallurgy are two more mainstream methods.

[0003] Pyrometallurgical technology mainly uses high-temperature means to separate and recycle metal components in electronic waste. The steps involved include pretreatment (crushing, sorting, etc.), pyrolysis and smelting. In this process, organic matter is decomposed by high temperature and the metal components are melted, thereby achieving efficient separation of metals and non-metals. In the process of recycling electronic waste, the use of pyrometallurgical technology will produce a variety of harmful gases including dioxins, sulfur oxides and nitrogen oxides. These gases will not only seriously affect the air quality, but also cause harm to human health. In addition, pyrometallurgical technology needs to be carried out under high temperature conditions, which not only consumes a lot of energy, but also leads to an increase in carbon emissions.

[0004] Hydrometallurgical technology includes chemical leaching and bioleaching. Chemical leaching is the process of leaching metals from electronic waste using chemical reagents. As a special hydrometallurgical technology, bioleaching mainly uses the biochemical action of microorganisms to recover valuable metals from electronic waste. This process mainly relies on the reaction between substances produced by microbial metabolism (such as acidic substances) and metal ions to promote the dissolution of metals, and then achieves the concentration and recovery of metals through subsequent processes such as precipitation and adsorption. Bioleaching technology is favored for its mild operating conditions and small environmental impact.

[0005] Chemical leaching usually relies on chemical agents such as strong acids or strong bases, while traditional biological leaching mainly uses strong acidophilic microorganisms such as Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. These methods produce a large amount of strongly acidic or alkaline wastewater during the leaching process, which will cause serious damage to the water and soil environment if not properly treated. Therefore, it is particularly urgent to develop an environmentally friendly and effective biotechnology to recover valuable metals from electronic waste. Summary of the invention

[0006] The purpose of the present invention is to provide an efficient and environmentally friendly method for simultaneously recovering valuable metals in waste lithium iron phosphate batteries and waste printed circuit boards using Lactobacillus plantarum, so as to achieve efficient recovery of valuable metals in electronic waste without adding other chemical substances.

[0007] A method for leaching mixed powder of electronic waste using Lactobacillus plantarum, comprising the following steps:

[0008] Step 1: preparing electronic waste mixed powder;

[0009] The electronic waste is waste lithium iron phosphate batteries and waste printed circuit boards;

[0010] After disassembling, discharging and drying the waste lithium iron phosphate battery, the positive electrode is separated and cut into small square pieces, the square pieces of waste lithium iron phosphate battery are immersed in an organic solvent to dissolve the binder, and the waste lithium iron phosphate battery powder is obtained after washing, drying, crushing and screening;

[0011] Dismantle the waste printed circuit boards, remove the electronic components and plastic parts on the surface of the waste printed circuit boards, cut them into small square pieces, crush them through a sieve, and then ball mill them, and sieve them again to obtain waste printed circuit board powder;

[0012] Step 2: Prepare the culture medium;

[0013] Step 3: domesticate bacteria;

[0014] Add Lactobacillus plantarum and the mixed powder of electronic waste to the culture medium prepared in step 2 and culture until the cell concentration is 10 8 cells / mL, subculture is performed to obtain domesticated Lactobacillus plantarum;

[0015] Step 4: Leaching;

[0016] The two-step method and the spent culture medium method are used for leaching respectively. After sampling the leachate, the pH value, ORP value and bacterial concentration are monitored, and then the filtrate is filtered to obtain the filtrate, and the concentrations of lithium, iron and copper in the filtrate are measured; the filtrate is diluted with 1% dilute nitric acid, and the concentrations of lithium, iron and copper are measured using an inductively coupled plasma optical emission spectrometer ICP-OES to calculate the leaching percentage.

[0017] Furthermore, the discharge in step 1 is discharged in a 20% (w / w) NaCl solution for 24 hours, the drying temperature is 54°C to 56°C, and the drying is performed to constant weight; the length and width of the square pieces of waste lithium iron phosphate batteries and waste printed circuit boards are 1 cm; the square pieces of waste lithium iron phosphate batteries are crushed and passed through a 100-mesh sieve; the square pieces of waste printed circuit boards are crushed and passed through a 100-mesh sieve, then ball-milled for 3 minutes, and then passed through a 200-mesh sieve again.

[0018] Furthermore, the organic solvent in step 1 is N-methylpyrrolidone solution, the square pieces of waste lithium iron phosphate batteries are immersed in the organic solvent and dissolved at 60° C. for 2 hours, and the cleaning is to wash the dissolved square pieces three times with distilled water.

[0019] Furthermore, the culture medium described in step 2 is configured as: MRS culture medium containing 10.0 g / L peptone, 5.0 g / L beef extract powder, 4.0 g / L yeast extract powder, 20.0 g / L glucose, 2.0 g / L KH2PO4, 2.0 g / L C6H5O7(NH4)3, 5.0 g / L CH3COONa, 0.2 g / L MgSO4, 0.05 g / L MnSO4, and 1.0 g / L Tween-80.

[0020] Furthermore, in step 3, the initial pH value of the culture medium is 6, and the initial bacterial concentration is 10 7 cells / mL, the initial concentrations of waste lithium iron phosphate powder and waste printed circuit board powder were 1.0 g / L respectively; the culture temperature was 36°C-38°C.

[0021] Further, the subculture step described in step 3 is: taking the subcultured bacterial solution, waste lithium iron phosphate powder and waste printed circuit board powder, and adding them to the culture medium described in step 2 at the same time, each 5 mL of the subcultured bacterial solution corresponds to 100 mL of the culture medium described in step 2, the concentrations of the waste lithium iron phosphate powder and the waste printed circuit board powder are 1.0 g / L respectively, and culturing until the bacterial concentration is 10 8 cells / mL, take the subcultured bacterial solution at this time and repeat the above steps; the same waste lithium iron phosphate powder and waste printed circuit board powder concentrations are subcultured twice, that is, every two cultures, the waste lithium iron phosphate powder and waste printed circuit board powder concentrations are increased by 0.5g / L, and so on, until the waste lithium iron phosphate powder and waste printed circuit board powder concentrations are 50.0g / L respectively, and the cell concentration reaches and stabilizes at 10 8 cells / mL, the domestication process is completed and the domesticated Lactobacillus plantarum is obtained.

[0022] Furthermore, the two-step leaching method described in step 4 is as follows: adding waste printed circuit board powder into a conical flask for high-pressure sterilization, inoculating the domesticated plant lactobacillus into the culture medium, and making the initial bacterial concentration be 10 7 cells / mL, and cultured to the logarithmic growth phase to obtain an extract containing Lactobacillus plantarum and its metabolites. The extract and waste lithium iron phosphate powder were added to a sterilized conical flask to start the leaching experiment, which was recorded as 0h.

[0023] Furthermore, the waste culture medium method leaching in step 4 is as follows: waste printed circuit board powder is added to a conical flask for high pressure sterilization, and the domesticated plant lactobacillus is inoculated into the culture medium to make the initial bacterial concentration be 10 7 cells / mL, and cultured to a stable period to obtain a stable period bacterial solution containing Lactobacillus plantarum and its metabolites. The stable period bacterial solution was centrifuged and filtered to obtain an extract containing Lactobacillus plantarum metabolites. The extract and waste lithium iron phosphate powder were added to a sterilized conical flask to start a leaching experiment, which was recorded as 0h.

[0024] Furthermore, the leaching temperature in the two-step method and the waste culture medium method described in step 4 is 36°C to 38°C, and the stirring speed is 150rpm; the temperature of the high-pressure sterilization is 120°C to 122°C, the pressure is 99kPa to 101kPa, and the sterilization time is 15min to 25min; the centrifugal speed in the waste culture medium method is 4500rpm / min, the time is 8min to 12min, and the filtration adopts a 0.22μm water system membrane.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention creatively applies Lactobacillus plantarum to the biological leaching of waste lithium iron phosphate batteries and waste printed circuit board mixed materials. The bacteria grows well in an environment with a pH value of 4-6. The present invention uses Lactobacillus plantarum to leach lithium and iron from waste lithium iron phosphate batteries. After the iron element is leached, it is converted into Fe 3+ The present in the form of in the leachate can be used as an oxidant to promote the biological leaching of copper in waste printed circuit boards. The present invention can simultaneously realize the extraction of lithium and iron in waste lithium iron phosphate batteries and the extraction of copper in waste printed circuit boards. The present invention does not require the addition of additional auxiliary substances (such as chemical reagents, extracellular polymers, biochar, etc.), and has a good extraction effect in a relatively large solid-liquid ratio and a relatively short time. Compared with the traditional biological leaching of single electronic waste, this method does not use strong acidophilic bacteria, does not produce strong acidic wastewater, and does not add additional chemical reagents, which greatly reduces the water and soil acidification problem caused by traditional strong acidophilic bacteria. It can achieve efficient biological leaching of mixed materials of waste lithium iron phosphate batteries and waste printed circuit boards without producing a large amount of strong acid that is harmful to the environment.

[0027] The present invention adopts different leaching methods, wherein when the concentration of waste lithium iron phosphate battery powder and waste printed circuit board powder is 15.0 g / L respectively, the leaching percentages of lithium, iron and copper within 5 days are 87.3%, 44.3% and 99.8% respectively. While ensuring the efficient leaching of lithium and copper, plant lactobacillus also shows good leaching selectivity.

[0028] No additional chemical reagents are added during the leaching process of the present invention, and the pH value is basically maintained in the range of 3 to 6, which is relatively mild. Compared with traditional chemical and biological leaching, it is safer and can reduce secondary pollution to the environment.

[0029] The acidic wastewater generated by the bioleaching method of the present invention has little impact on the environment, meets the requirements of green and sustainable development, and helps to promote the development of green recycling technology.

[0030] The present invention provides an efficient, environmentally friendly, economical, safe method capable of simultaneously recovering valuable metals in waste lithium iron phosphate batteries and waste printed circuit boards, providing a new solution for the treatment of electronic waste. The present invention not only reduces the environmental pollution and resource waste problems existing in traditional methods, but also provides new ideas and technical support for the resource recycling of electronic waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The present invention is a flowchart of a leaching method for using plant lactobacillus to extract mixed powder of electronic waste. DETAILED DESCRIPTION

[0032] like Figure 1 As shown, the scheme in the present invention is further described by examples, which are not intended to limit the present invention. Unless otherwise specified, the experimental operations in the examples are all based on mature prior art in the biological or chemical fields, and the raw materials and reagents used can be obtained commercially.

[0033] The waste lithium iron phosphate batteries and waste printed circuit boards used in this embodiment were purchased from the waste market.

[0034] Example 1

[0035] A method for leaching mixed powder of electronic waste using Lactobacillus plantarum, comprising the following steps:

[0036] Step 1: preparing electronic waste mixed powder;

[0037] The electronic waste is waste lithium iron phosphate batteries and waste printed circuit boards;

[0038] The waste lithium iron phosphate battery is pretreated as follows: first, the metal shell is cut open with a battery angle grinder and disassembled into individual batteries, and then discharged in a 20% (w / w) NaCl solution for 24 hours, and dried at 55°C for further disassembly of the battery; second, the shell and the plastic separator inside are peeled off, leaving the positive electrode, and then the positive electrode is cut into square pieces with a length and width of about 1 cm, and immersed in an N-methylpyrrolidone solution to dissolve the binder (polyvinylidene fluoride) of the positive electrode, and after dissolving at 60°C for 2 hours, the dissolved waste lithium iron phosphate battery powder is washed three times with distilled water; finally, the dissolved waste lithium iron phosphate battery powder is dried at 60°C, crushed with a universal grinder, and finally the powder is passed through a 100-mesh sieve to obtain waste lithium iron phosphate battery powder for bioleaching;

[0039] The obtained battery positive electrode powder was digested using a chemical digestion method (HNO3:HClO4:HF=2:1:2, v / v), and the concentrations of lithium and iron in the digestion solution were determined using ICP-OES, which were calculated to be 37.9 mg / g and 308.9 mg / g, respectively.

[0040] The waste printed circuit boards are pretreated as follows: first, the waste printed circuit boards are disassembled, and the electronic components (such as resistors, capacitors, inductors, etc.) and plastic parts on the surface of the waste printed circuit boards are removed using wire strippers; second, the waste printed circuit boards are cut into small square pieces with a length and width of about 1 cm using pliers; finally, a universal grinder is used for preliminary crushing, and the crushed products are passed through a 100-mesh sieve and ball-milled for 3 minutes to obtain waste printed circuit board powder. Finally, the obtained waste printed circuit board powder is passed through a 200-mesh sieve to obtain waste printed circuit board powder for bioleaching;

[0041] The obtained waste printed circuit board powder was digested using a chemical digestion method (HNO3:HCl=1:3, v / v), and the copper concentration in the digestion solution was measured using ICP-OES, which was calculated to be 191.9 mg / g.

[0042] Step 2: Prepare the culture medium;

[0043] Prepare MRS medium with 10.0 g / L peptone, 5.0 g / L beef extract powder, 4.0 g / L yeast extract powder, 20.0 g / L glucose, 2.0 g / L KH2PO4, 2.0 g / L C6H5O7(NH4)3, 5.0 g / L CH3COONa, 0.2 g / L MgSO4, 0.05 g / L MnSO4, and 1.0 g / L Tween-80.

[0044] Step 3: domesticate bacteria;

[0045] Add Lactobacillus plantarum and leaching powder to the prepared culture medium, the initial pH value of the culture medium is 6, the bacterial concentration is 10 7 cells / mL, the concentrations of waste lithium iron phosphate powder and waste printed circuit board powder were 1.0 g / L, respectively, and cultured at 37°C until the bacterial concentration was 10 8 When the cells / mL is 10, take the subcultured bacterial solution and the new leached powder and add them to the new culture medium at the same time. Every 5mL of subcultured bacterial solution corresponds to 100mL of new culture medium. The concentrations of waste lithium iron phosphate powder and waste printed circuit board powder are 1.0g / L respectively. Cultivate until the bacterial concentration is 10 8 cells / mL, the bacterial solution of the subculture was taken to repeat the above steps, except that the concentrations of waste lithium iron phosphate powder and waste printed circuit board powder were 1.5 g / L, that is, the concentration of leached powder increased by 0.5 g / L each time the culture was repeated twice, and so on, until the concentrations of waste lithium iron phosphate powder and waste printed circuit board powder were 50.0 g / L, and the cell concentration reached and stabilized at 10 8 cells / mL, the domestication process is completed and the domesticated Lactobacillus plantarum is obtained.

[0046] Step 4: Leaching;

[0047] Two-step experiment of waste lithium iron phosphate battery and waste printed circuit board mixed materials under different solid-liquid ratio leaching conditions:

[0048] 1.5 g of waste printed circuit board powder was added to a 250 mL conical flask and sterilized by high pressure at a temperature of 121 ° C, a sterilization time of 20 minutes, and a pressure of 100 kPa; Lactobacillus plantarum was added to 100 mL of sterilization medium to an initial bacterial concentration of 10 7 cells / mL, culture to the logarithmic growth phase, and obtain the leaching solution of Lactobacillus plantarum and its metabolites. Add 1.5g of waste lithium iron phosphate battery powder and 100mL of the leaching solution to the sterilized conical flask, and ensure that the waste lithium iron phosphate battery powder and the waste printed circuit board powder are completely immersed in the above-mentioned leaching solution. Repeat the above operation, only changing the addition amount of waste lithium iron phosphate battery powder to 1.0g, 2.0g, 2.5g and 5.0g, respectively, and the addition amount of waste printed circuit boards to 1.0g, 2.0g, 2.5g and 5.0g, respectively.

[0049] The start of the leaching experiment was recorded as 0 hours, the leaching temperature was controlled at 37 °C, the stirring speed was 150 rpm, the leaching time was 5 days, and samples were taken at 24 hours, 48 ​​hours, 72 hours, 96 hours, and 120 hours;

[0050] After sampling, the pH value, ORP value and bacterial concentration of the system should be monitored. The pH value fluctuates within the range of 4.0 to 5.0, the ORP value fluctuates within the range of 100mV to 250mV, and the bacterial concentration is within the range of 2.5×10 8 cells / mL~1.1×10 9 cells / mL, and it is also necessary to filter with a 0.22μm water filter to obtain the filtrate and measure the concentrations of lithium, iron, and copper in the filtrate;

[0051] The filtrate obtained above was diluted with 1% dilute nitric acid, and the concentrations of lithium, iron and copper were measured by ICP-OES and the leaching percentages were calculated. After 5 days, the leaching percentages of lithium, iron and copper at solid-to-liquid ratios of 10.0 g / L, 15.0 g / L, 20.0 g / L, 25.0 g / L and 50.0 g / L were shown in Table 1.

[0052]

[0053] Table 1

[0054] Example 2

[0055] A method for leaching mixed powder of electronic waste using Lactobacillus plantarum is different from that in Example 1 in that:

[0056] Step 4: Leaching;

[0057] Waste culture medium method experiment of waste lithium iron phosphate battery and waste printed circuit board mixed materials under different solid-liquid ratio leaching conditions:

[0058] 1.5 g of waste printed circuit board powder was added to a 250 mL conical flask and sterilized by high pressure at a temperature of 121 ° C, a sterilization time of 20 minutes, and a pressure of 100 kPa; Lactobacillus plantarum was added to 100 mL of sterilization medium to an initial bacterial concentration of 10 7 cells / mL, and culture to the stable phase. Then, the obtained stable phase bacterial solution was divided into 50mL centrifuge tubes, placed in a centrifuge, and centrifuged at a speed of 4500rpm / min for ten minutes. Subsequently, the centrifuged liquid was filtered with a 0.22μm aqueous membrane to obtain an extract containing plant lactobacillus metabolites. 1.5g of waste lithium iron phosphate battery powder and 100mL of the extract were added to the sterilized conical flask, and it was ensured that the waste lithium iron phosphate battery powder and the waste printed circuit board powder were completely immersed in the above-mentioned extract. Repeat the above operation, only changing the amount of waste lithium iron phosphate battery powder added to 1.0g, 2.0g, 2.5g and 5.0g, respectively, and the amount of waste printed circuit boards added to 1.0g, 2.0g, 2.5g and 5.0g, respectively.

[0059] The start of the leaching experiment was recorded as 0 hours, the leaching temperature was controlled at 37 °C, the stirring speed was 150 rpm, the leaching time was 5 days, and samples were taken at 24 hours, 48 ​​hours, 72 hours, 96 hours, and 120 hours;

[0060] After sampling, the changes in the system pH and ORP values ​​should be monitored. The pH value fluctuates within the range of 4.0 to 5.0, and the ORP fluctuates within the range of 150 mV to 220 mV. It is also necessary to filter the filtrate with a 0.22 μm water filter to measure the concentrations of lithium, iron, and copper in the filtrate.

[0061] The filtrate obtained above was diluted with 1% dilute nitric acid, and the concentrations of lithium, iron and copper were measured using ICP-OES and the leaching percentages were calculated. After 5 days, the leaching percentages of lithium, iron and copper at solid-to-liquid ratios of 10.0 g / L, 15.0 g / L, 20.0 g / L, 25.0 g / L and 50.0 g / L were shown in Table 2.

[0062]

[0063] Table 2

[0064] Comparative Example 1

[0065] A method for leaching mixed powder of electronic waste using Lactobacillus plantarum is different from that in Example 1 in that:

[0066] Step 4: Leaching;

[0067] Blank control experiment of waste lithium iron phosphate battery and waste printed circuit board mixed materials under different solid-liquid ratio leaching conditions:

[0068] 1.5 g of waste printed circuit board powder was added to a 250 mL conical flask and sterilized by high pressure, wherein the temperature of the high pressure sterilization was 121°C, the sterilization time was 20 minutes, and the pressure was 100 kPa; 1.5 g of waste lithium iron phosphate battery powder and 100 mL of leaching solution (sterilization medium) were added to the sterilized conical flask, and it was ensured that the waste printed circuit board powder and the waste lithium iron phosphate battery powder were completely immersed in the above-mentioned leaching solution. The above operation was repeated, only the addition amount of waste lithium iron phosphate battery powder was changed to 1.0 g, 2.0 g, 2.5 g and 5.0 g, respectively, and the addition amount of waste printed circuit boards was changed to 1.0 g, 2.0 g, 2.5 g and 5.0 g, respectively.

[0069] The start of the leaching experiment was recorded as 0 hours, the leaching temperature was controlled at 37 °C, the stirring speed was 150 rpm, the leaching time was 5 days, and samples were taken at 24 hours, 48 ​​hours, 72 hours, 96 hours, and 120 hours;

[0070] After sampling, the changes in the system pH and ORP values ​​should be monitored. The pH value fluctuates within the range of 5.9 to 7.0, and the ORP value fluctuates within the range of 90mV to 150mV. It is also necessary to filter the filtrate with a 0.22μm water filter to measure the concentrations of lithium, iron, and copper in the filtrate.

[0071] The filtrate obtained above was diluted with 1% dilute nitric acid, and the concentrations of lithium, iron and copper were measured by ICP-OES and the leaching percentages were calculated. After 5 days, the leaching percentages of lithium, iron and copper at solid-to-liquid ratios of 10.0 g / L, 15.0 g / L, 20.0 g / L, 25.0 g / L and 50.0 g / L were shown in Table 3.

[0072]

[0073] Table 3.

Claims

1. A method for leaching electronic waste mixed powder using Lactobacillus plantarum, characterized in that: The following steps are involved: Step 1: preparing electronic waste mixed powder; The electronic waste is waste lithium iron phosphate batteries and waste printed circuit boards; After disassembling, discharging and drying the waste lithium iron phosphate battery, the positive electrode is separated and cut into small square pieces, the waste lithium iron phosphate battery square pieces are immersed in an organic solvent to dissolve the binder, washed, dried, crushed and sieved to obtain waste lithium iron phosphate battery powder; The waste printed circuit boards are disassembled, the electronic components and plastic parts on the surface of the waste printed circuit boards are removed, and then the waste printed circuit boards are cut into small square pieces, crushed through a sieve, ball milled, and sieved again to obtain waste printed circuit board powder; Step 2: Prepare the culture medium; Step 3: domesticate bacteria; Add Lactobacillus plantarum and electronic waste mixed powder to the culture medium prepared in step 2 and culture until the cell concentration is 10 8 cells / mL, the culture was carried out to obtain the domesticated Lactobacillus plantarum; Step 4: Leaching; Leaching was performed using a two-step method and a spent culture medium method, respectively. After sampling the leachate, the pH value, ORP value, and bacterial concentration were monitored, and the filtrate was filtered to obtain a filtrate. The concentrations of lithium, iron, and copper in the filtrate were measured. The filtrate was diluted with 1% dilute nitric acid, and the concentrations of lithium, iron, and copper were measured using an inductively coupled plasma optical emission spectrometer (ICP-OES), and the leaching percentage was calculated.

2. A leaching method for leaching electronic waste mixed powder using Lactobacillus plantarum according to claim 1, characterized in that: The discharge in step 1 is performed in a 20% (w / w) NaCl solution for 24 hours, and the drying temperature is 54° C. to 56° C., and the drying is performed to constant weight. The length and width of the square pieces of waste lithium iron phosphate batteries and waste printed circuit boards are 1 cm. The square pieces of waste lithium iron phosphate batteries are crushed and passed through a 100-mesh sieve. The square pieces of waste printed circuit boards are crushed and passed through a 100-mesh sieve, then ball-milled for 3 minutes and passed through a 200-mesh sieve again.

3. A leaching method for leaching electronic waste mixed powder using Lactobacillus plantarum according to claim 1, characterized in that: In step 1, the organic solvent is N-methylpyrrolidone solution. The square pieces of waste lithium iron phosphate batteries are immersed in the organic solvent and dissolved at 60° C. for 2 hours. The washing step is to wash the dissolved square pieces three times with distilled water.

4. A leaching method for leaching electronic waste mixed powder using Lactobacillus plantarum according to claim 1, characterized in that: The culture medium described in step 2 is configured as: MRS medium containing 10.0 g / L peptone, 5.0 g / L beef extract powder, 4.0 g / L yeast extract powder, 20.0 g / L glucose, 2.0 g / L KH2PO4, 2.0 g / L C6H5O7(NH4)3, 5.0 g / L CH3COONa, 0.2 g / L MgSO4, 0.05 g / L MnSO4, and 1.0 g / L Tween-80.

5. The method for leaching electronic waste mixed powder using Lactobacillus plantarum according to claim 1, wherein: In step 3, the initial pH value of the culture medium is 6, and the initial bacterial concentration is 10 7 cells / mL, the initial concentrations of waste lithium iron phosphate powder and waste printed circuit board powder were 1.0 g / L respectively; and the culture temperature was 36°C to 38°C.

6. The method for leaching electronic waste mixed powder using Lactobacillus plantarum according to claim 1, characterized in that: The subculture step in step 3 is as follows: take the subcultured bacterial solution and the waste lithium iron phosphate powder and the waste printed circuit board powder, and add them to the culture medium in step 2 at the same time, and each 5 mL of the subcultured bacterial solution corresponds to 100 mL of the culture medium in step 2, and the concentrations of the waste lithium iron phosphate powder and the waste printed circuit board powder are 1.0 g / L respectively, and culture until the bacterial concentration is 10 8 cells / mL, take the subcultured bacterial solution at this time and repeat the above steps; the same waste lithium iron phosphate powder and waste printed circuit board powder concentrations are subcultured twice, that is, every time the waste lithium iron phosphate powder and waste printed circuit board powder concentrations are increased by 0.5g / L, and so on, until the waste lithium iron phosphate powder and waste printed circuit board powder concentrations are 50.0g / L respectively, and the cell concentration reaches and stabilizes at 10 8 cells / mL, the acclimation process is completed and the acclimated Lactobacillus plantarum is obtained.

7. The method for leaching electronic waste mixed powder using Lactobacillus plantarum according to claim 1, wherein: The two-step leaching method described in step 4 is as follows: adding waste printed circuit board powder into a conical flask for high-pressure sterilization, inoculating the domesticated plant lactobacillus into the culture medium to make the initial bacterial concentration be 10 7 cells / mL, and cultured to the logarithmic growth phase to obtain an extract containing Lactobacillus plantarum and its metabolites. The extract and waste lithium iron phosphate powder were added to a sterilized conical flask to start the leaching experiment, which was recorded as 0 h.

8. The method for leaching electronic waste mixed powder using Lactobacillus plantarum according to claim 1, characterized in that: The waste culture medium method leaching in step 4 is as follows: waste printed circuit board powder is added to a conical flask and sterilized under high pressure, and the domesticated plant lactobacillus is inoculated into the culture medium to make the initial bacterial concentration be 10 7 cells / mL, cultured to a stable phase to obtain a stable phase bacterial solution containing Lactobacillus plantarum and its metabolites, centrifuged and filtered to obtain an extract containing Lactobacillus plantarum metabolites, and added the extract and waste lithium iron phosphate powder to a sterilized conical flask to start the leaching experiment, which was recorded as 0 h.

9. A method for leaching electronic waste mixed powder using Lactobacillus plantarum according to any one of claims 7 or 8, characterized in that: The leaching temperature in the two-step method and the spent culture medium method described in step 4 is 36°C to 38°C, and the stirring speed is 150 rpm; the temperature of the high-pressure sterilization is 120°C to 122°C, the pressure is 99 kPa to 101 kPa, and the sterilization time is 15 min to 25 min; the centrifugation speed in the spent culture medium method is 4500 rpm / min, the time is 8 min to 12 min, and the filtration uses a 0.22 μm aqueous membrane.

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