CN103484680B - Method for leaching copper in waste printed circuit board by using mixed bacteria - Google Patents

Abstract

The invention discloses a method for leaching copper in waste printed circuit boards by mixed bacteria. The waste printed circuit boards (PCBs) are pretreated for use, and acidophilic Thiobacillus ferrooxidans and acidophilic Thiobacillus thiooxidans are respectively subjected to After the copper acclimatization culture, mixed culture in the mixed bacteria culture solution; when the culture time reaches 40h ~ 55h, start to add PCBs powder, and then add PCBs powder point by point at other time points for bioleaching. When the mixed bacteria of the present invention is cultivated, the two bacteria can grow in a balanced manner without adjusting the pH value of the culture solution. At the same time, when the two bacteria grow, a large amount of sulfuric acid and Fe ³⁺ are generated for the leaching of copper in the waste PCBs powder in the later stage, and the efficiency of the whole process is high. High, save energy. By adopting the method of adding low at the front and then high at multiple points, on the basis of increasing the amount of waste PCBs powder added, the copper leaching rate was significantly increased while the growth of bacteria was relatively less inhibited.

Description

Method for leaching copper from waste printed circuit boards by mixed bacteria

technical field

The invention relates to a method for recovering copper from waste printed circuit boards, in particular to a method for leaching copper from waste printed circuit boards with mixed bacteria.

Background technique

With the rapid development of information technology, the output of waste electric and electronic equipment (WEEE) continues to increase. As an important component of WEEE, waste printed circuit boards (PCBs) usually contain about 40% of metals, of which metal Copper is the main component, with a content as high as 20% to 30%. It is estimated that my country needs to process more than 500,000 tons of PCBs every year and it is growing at a rate of 22%. If the disposal and recycling of waste PCBs can be realized, it can not only solve the problem of environmental pollution, but also realize the effective recovery of metals, which will be of great significance to the sustainable development of my country's PCBs industry.

At present, the methods for extracting copper from waste printed circuit boards mainly include physical, chemical and biological methods. The physical method has relatively high evaluation indicators in terms of renewable resource effect, environmental friendliness, and industrial application rate, but the investment in mechanical equipment used is large, energy consumption is high, and maintenance costs are high, so the economic feasibility is relatively poor; and the metal in the product difficult to separate. The chemical method is mainly divided into fire method and wet method. Although the fire method has the advantages of simplicity, convenience and high recovery rate, it will produce harmful gases and discharge a large amount of scum at the same time; The residue is easy to handle and the process is simple, but the copper leaching rate is low and the leaching solution and residue are toxic. Therefore, it has unique advantages to apply the biological method with less pollution, low cost and mild reaction conditions to the metal recycling of waste printed circuit boards.

Bioleaching of copper from PCBs has the characteristics of safety, cleanliness, and high efficiency, and has become a research hotspot at home and abroad. At present, the most commonly used microorganisms are acidophilus Thiobacillus thiooxidans ( At ) and Thiobacillus ferrooxidans ( A.f ).

For example, Zhou Peiguo et al. (Zhou Peiguo, Zheng Zheng, Peng Xiaocheng, etc. Research on the change of iron in the copper and iron in the process of leaching circuit boards by Thiobacillus ferrooxidans. "Environmental Pollution and Prevention"; 2007 (02): 119～122) using ferrous sulfur oxide Bacteria leached copper from waste circuit board powder (copper mass fraction 10.4%). When the amount of waste circuit board powder added was 100 g/L, the copper leaching rate was about 90% in about 15 days.

Chinese patent document CN 1948524 A (application number 200610097382.X) discloses a comprehensive resource treatment method for waste circuit boards, inoculating domesticated Thiobacillus ferrooxidans, Microspiral ferrooxidans or vulcanized leaves into the culture medium solution. Bacteria liquid is cultivated, after the circuit board substrate with various components removed is crushed, the cultured bacterial liquid is added to it, stirred and leached at a speed of 120-160r/min for 10-15 days, and the liquid and solid are separated; The liquid is extracted with a copper extractant, and then back-extracted and electrolytically deposited to obtain metallic copper.

The above methods all use a single microorganism for bioleaching, and the metal leaching time is long and the leaching efficiency is low.

Studies have shown that the leaching of copper in PCBs by mixed bacteria is currently the most effective method.

For example, SADIA et al. ( Sadia I, Munir AA, Shahida BN, Afzal Ghauri M. Bioleaching of metals from electronic scrap by moderately thermophilic acidophilic bacteria. Hydrometallurgy 2007;88:180–8.) use mesophilic acidophilic mixed bacteria to leach waste circuit boards For the metal in the powder (the mass fraction of copper is 8.5%), when the amount of waste circuit board powder added is 10g/L, the leaching rate of copper is 89% after 18 days. But although this mixed bacteria leaching method has used mixed bacteria, the leaching time is long, and the leaching rate is not as high as that of a kind of bacterium leaching. This is because when the mixed bacteria are cultivated, what kind of nutrient substrate and external conditions are provided so that the mixed bacteria can grow in a balanced manner, so that one kind of overgrowth and the other kind of bacteria will not be inhibited is very important. In addition, the ability of bacteria to leach copper is closely related to their own growth and metabolism. The addition of PCBs will inhibit the growth of bacteria and lead to a decrease in copper leaching ability. Therefore, how to optimize the way of adding PCBs is another key to achieve efficient leaching of copper in PCBs by mixed bacteria. one of the factors.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for cultivating mixed bacteria and using it to efficiently extract copper from waste printed circuit boards.

The technical solution for realizing the object of the present invention is a method for leaching copper in waste printed circuit boards by mixed bacteria, comprising the following steps:

① Pretreatment of waste printed circuit boards: crush and grind the waste printed circuit boards PCBs from which electronic components have been removed into powder, sieve the waste printed circuit board powder obtained through grinding, and collect the waste printed circuit board powder that passes through the sieve holes for processing .

②Aclimation of strains: acidophilus A.ferrooxidans ^and acidophilus A.thiooxidans were respectively domesticated and cultivated for resistance to Cu ²⁺ . A. ferrooxidans and A. thiooxidans from the environment were used.

③Cultivation of mixed bacteria: A. ferrooxidans and A.thiooxidans obtained after step ② domestication and cultivation are carried out in the mixed bacteria culture solution according to the inoculum size of 1:1.5-2.5. The initial pH of the culture is 1.5-1.8, and mixed The amount of bacterial inoculum is 10% to 20% of the volume of the mixed bacterial culture solution.

④ Addition of waste printed circuit board powder; after step ③ the mixed bacteria culture time reaches 40-55 hours, add the waste PCBs powder obtained in step ① pretreatment to the mixed bacteria culture system cultivated for 40-55 hours for the first time, and then Every 20 to 25 hours, add the waste PCBs powder obtained in step ① to the mixed bacteria culture system again. The total mass of the discarded PCBs powder is 28g-36g; when the waste PCBs powder is added and the culture time of the mixed bacteria reaches 175h-200h, the leaching reaction of the mixed bacteria is completed; the mixed material after the reaction is centrifuged and the upper leachate is collected.

⑤ post-processing; the leach solution obtained in step ④ is extracted with a copper extractant, and the obtained copper-containing extract is stripped with a stripping agent; then the obtained copper-containing stripping solution is transferred into an electrolytic cell for electrowinning Get copper and complete the recovery of copper from waste printed circuit boards.

In the above step ③ when the mixed bacteria are cultured, the content of each component in the mixed bacteria culture solution used is: elemental sulfur 4.0-6.5g/L, ammonium sulfate 3.5-4.5g/L, dipotassium hydrogen phosphate 0.45-0.65 g/L , magnesium sulfate heptahydrate 0.45～0.65 g/L, potassium chloride 0.1～0.15 g/L, calcium nitrate 0.008～0.015 g/L, ferrous sulfate heptahydrate 15～18g/L, calcium chloride 0.10～0.18 g/L L; the solute of the mixed bacteria culture solution is water.

As preferred, when step ③ mixed bacteria culture, the content of each component in the mixed bacteria culture solution used is: elemental sulfur 5.2 ~ 5.6g/L, ammonium sulfate 3.5 ~ 4.5g/L, dipotassium hydrogen phosphate 0.45 ~ 0.65 g/L, magnesium sulfate heptahydrate 0.45～0.65 g/L, potassium chloride 0.1～0.15 g/L, calcium nitrate 0.008～0.015 g/L, ferrous sulfate heptahydrate 17～17.5g/L, calcium chloride 0.10 ~0.18 g/L; the solute of the mixed bacterial culture solution is water.

When adding the waste PCBs powder in the above step ④, after the mixed bacteria culture time in step ③ reaches 40-55 hours, add the waste PCBs powder obtained in step ① pretreatment to the mixed bacteria culture system that has been cultivated for 40-55 hours. Add 4g to 6g of waste PCBs powder to the culture system, and the added waste PCBs powder starts the mixed bacteria leaching reaction; after the mixed bacteria continue to culture for 20 to 25 hours, add the waste PCBs obtained in step ① pretreatment to the culture system for the second time. For PCBs powder, add 6g-8g of waste PCBs powder to every 1L of mixed bacteria culture system, and the added waste PCBs powder will start the mixed bacteria leaching reaction; after the mixed bacteria continue to culture for 20-25 hours, add it to the culture system for the third time Step ① Add 8g-10g of waste PCBs powder to each 1L of mixed bacteria culture system for the waste PCBs powder obtained from pretreatment, and the added waste PCBs powder will start the mixed bacteria leaching reaction; after the mixed bacteria continue to be cultivated for 20-25 hours, add to The fourth addition step in the culture system: ① Pretreatment waste PCBs powder, add 10g ~ 12g waste PCBs powder to each 1L mixed bacteria culture system, and the waste PCBs powder is added.

When the above step ② A.ferrooxidans is domesticated and cultivated, the sludge extracted from the aeration tank of the urban sewage treatment plant is enriched and cultivated, and then separated and purified to obtain A.ferrooxidans ; A.ferrooxidans is cultivated in 9K culture solution until Logarithmic phase; according to the inoculum amount of the strain is 10% to 20% (volume ratio v/v), absorb the above bacterial solution and transfer it to the culture medium with a Cu ²⁺ concentration of 10mmol/L; after cultivating to the logarithmic phase, According to the inoculum amount of the bacteria is 10% to 20% (volume ratio v/v), absorb the above bacterial solution and transfer it to the culture solution with a Cu ²⁺ concentration of 20mmol/L to cultivate to the logarithmic phase; repeat the above operation, each increase For the domestication of the first-generation strain, the concentration of Cu ²⁺ in the culture medium used was increased by 10mmol/L compared with the previous generation, so as to obtain A.ferrooxidans cultured to the logarithmic phase in an environment of 100-200mmol/L Cu ²⁺ .

When the above step ② A.thiooxidans is domesticated and cultivated, the sludge extracted from the aeration tank of the urban sewage treatment plant is enriched and cultivated, and then separated and purified to obtain A.thiooxidans ; A.thiooxidans is cultivated in the culture medium until the Several phases; according to the inoculum amount of the bacteria is 10% to 20% (volume ratio v/v), absorb the above bacterial solution and transfer it to the culture solution with a Cu ²⁺ concentration of 10mmol/L; after cultivating to the logarithmic phase, follow the The inoculum amount of the bacteria is 10%-20% (volume ratio v/v), absorb the above-mentioned bacterial solution and transfer it to the culture solution with a Cu ²⁺ concentration of 20mmol/L to cultivate to the logarithmic phase; repeat the above operation, each additional generation For the acclimatization of the strain, the concentration of Cu ²⁺ in the culture medium used was increased by 10mmol/L compared with the previous generation, so as to obtain A.thiooxidans cultured to the logarithmic phase in an environment of 100-200mmol/L Cu ²⁺ .

The present invention has positive effect:

(1) The nutrient substrate and culture conditions provided by the present invention when carrying out mixed bacterial culture make Acidithiobacillus ferrooxidans ( Acidithiobacillus.ferrooxidans, A.ferrooxidans ) and Acidithiobacillus. ) The two bacteria can grow in a balanced manner, and there is no phenomenon that one kind of bacteria is excessively multiplied while the other is inhibited. In addition, the present invention optimizes the way of adding waste PCBs powder, and adopts the way of low front and high multi-point addition. On the basis of increasing the amount of waste PCBs added, the copper leaching rate is significantly improved while the growth of bacteria is relatively inhibited. Small.

(2) The present invention adopts mixed bacteria culture, and the two bacteria can grow in a balanced manner without adjusting the pH of the culture solution during culture, and at the same time, when the two bacteria grow, a large amount of sulfuric acid and Fe ³⁺ are produced for leaching copper from waste PCBs powder in the later stage , the whole process has high efficiency and saves energy.

(3) In the present invention, before bioleaching, A. ferrooxidans and A. thiooxidans are treated with copper resistance, which significantly improves the copper resistance of the two bacteria and promotes the leaching of copper in waste PCBs powder.

(4) The entire process of the present invention is simple, economical and environmentally friendly, meets the needs of the development of circular economy, and has good industrial application prospects.

Detailed ways

(Example 1)

The method for the mixed bacteria of the present embodiment to extract copper in waste printed circuit boards may further comprise the steps:

① Pretreatment of waste printed circuit boards. The waste printed circuit board PCBs from which electronic components have been removed are crushed and ground into powder, and the ground waste PCBs powder passes through a sieve of 100 μm to 200 μm (in this example, the waste printed circuit board powder obtained through grinding passes through a 100 μm sieve) , to collect the waste PCBs powder passing through the sieve for processing.

After the discarded PCBs processed in this embodiment were ground and sieved, their main metal content was analyzed.

The main metal content is shown in Table 1 below:

Table 1 Main metal content in waste printed circuit board powder

② Domestication of strains.

(1) Domestication of acidophilic Thiobacillus ferrooxidans ( A.ferrooxidans ). The sludge extracted from the aeration tank of the urban sewage treatment plant is enriched and cultured, and then separated and purified to obtain A.ferrooxidans ; A.ferrooxidans is cultivated in the 9K culture solution to the logarithmic phase, and the bacterial concentration in the bacterial solution is now rise to 10 ⁷ cells/mL.

The 9K culture medium used per 1L includes: 44.7g FeSO ₄ 7H ₂ O, 3.0g (NH ₄ ) ₂ SO ₄ , 0.5g K ₂ HPO ₄ , 0.5g MgSO ₄ 7H ₂ O, 0.1g KCl, 0.01g Ca(NO ₃ ) ₂ , the pH of the culture solution is 2.00.

According to the inoculum amount of the strain is 10%-20% (volume ratio v/v), transfer the above-mentioned bacterial solution to a 250mL conical flask with 100mL fresh culture solution added, at a temperature of 32°C and a shaker speed of 120-200r /min (150 r/min in this example) to the logarithmic phase to complete the first generation of domestication. The rest of the Af culture medium used for the first-generation domestication is the same as the above 9K culture medium, except that Cu ²⁺ is added to the culture medium, and the concentration of Cu ²⁺ in the culture medium is 10mmol/L.

According to the inoculum amount of the strain is 10%-20% (volume ratio v/v), absorb the above-mentioned first-generation domesticated bacteria liquid into the fresh culture medium for cultivation to the logarithmic phase, Cu ²⁺ in the culture medium used this time The concentration rose to 20mmol/L.

Repeat the above operation, transfer the bacterial solution to the culture medium containing 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190 and 200mmol/L ^{Cu2 +} in fresh culture medium, after the culture, centrifuge to remove the supernatant, collect the cells that can withstand the concentration of 200 mmol/L Cu ²⁺ and put them in the refrigerator for later use.

During the above-mentioned acclimation process, the concentration of Cu ²⁺ in the culture solution used increased by 10mmol/L for each additional generation of strain acclimatization compared with the previous generation. As the concentration of Cu ²⁺ increases, the time required for culturing to the logarithmic phase (bacterial concentration of 10 ⁷ cells/mL) will be longer and longer. According to the treated powder, acidophilic Thiobacillus ferrooxidans can be cultured to the logarithmic phase at a concentration of 100 mmol/L Cu ²⁺ to stop acclimatization, so as to obtain a concentration resistant to 100 mmol/L Cu ²⁺ A. ferrooxidans .

(2) Domestication of Acidophilus Thiobacillus Thiooxidans ( A.thiooxidans ). The sludge extracted from the aeration tank of the urban sewage treatment plant is enriched and cultivated (the sewage plant uses A2/O to treat sewage), and then separated and purified to obtain A.thiooxidans ; A.thiooxidans are cultivated in the culture medium to logarithmic At this time, the bacterial concentration in the bacterial solution rose to 10 ⁷ cells/mL.

Each 1L of culture medium used includes: 10.0g S ⁰ , 0.5g (NH ₄ ) ₂ SO ₄ , 0.25g K ₂ HPO ₄ , 0.25g MgSO ₄ ·7H ₂ O, 0.02g CaCl ₂ ·2H ₂ O; The pH value is 4.00.

According to the inoculum amount of the strain is 10%-20% (volume ratio v/v), transfer the above-mentioned bacterial solution to a 250mL conical flask with 100mL fresh culture solution added, at a temperature of 32°C, and a shaker speed of 120-200r /min (150 r/min in this example) was cultivated to the logarithmic phase to obtain the first generation of domesticated acidophilic Thiobacillus thiooxidans.

The rest of the At culture medium used for the first-generation domestication is the same as the above-mentioned culture medium, except that Cu ²⁺ is added to the At culture medium used for the first-generation domestication, and the concentration of Cu ²⁺ in the culture medium is 10 mmol/L.

According to the acclimation method of acidophilic Thiobacillus ferrooxidans ( Af ) in (1), the bacterial liquid was successively transferred into the 140, 150, 160, 170, 180, 190 and 200mmol/L Cu ²⁺ in the fresh culture medium to acclimatize and cultivate to the logarithmic phase. After the cultivation, centrifuge to remove the supernatant, and collect Cu ²⁺ that can withstand 200 mmol/L The concentration of bacteria was stored in the refrigerator for later use.

According to the treated powder, A.thiooxidans can be cultured to the logarithmic phase at a concentration of 100 mmol/L Cu ²⁺ to stop acclimatization, so as to obtain A.thiooxidans resistant to a concentration of 100 mmol/L Cu ²⁺ .

That is, during the above domestication process, the concentration of Cu ²⁺ in the culture solution used increased by 10mmol/L for each additional generation of strain acclimatization compared with the previous generation. As the concentration of Cu ²⁺ increases, the time required for culturing to the logarithmic phase (bacterial concentration of 10 ⁷ cells/mL) will be longer and longer.

③Cultivation of mixed bacteria. The A.ferrooxidans and A.thiooxidans obtained after the step ② domestication culture are carried out in the mixed bacteria culture solution according to the inoculum size of 1:1.5-2.5 (1:2 in this example), and the initial pH of the culture is 1.5 to 1.8 (1.6 in this embodiment), the inoculum amount of the mixed bacteria is 10% to 20% of the volume of the mixed bacteria culture solution. When cultivating mixed bacteria, the temperature was controlled at 32°C, and the rotation speed of the shaker was 120-200 r/min (150 r/min in this example).

The content of each component in the mixed bacterial culture solution is: elemental sulfur 4.0-6.5g/L, ammonium sulfate 3.5-4.5g/L, dipotassium hydrogen phosphate 0.45-0.65 g/L, magnesium sulfate heptahydrate 0.45-0.65 g/L L, potassium chloride 0.1～0.15 g/L, calcium nitrate 0.008～0.015 g/L, ferrous sulfate heptahydrate 15～18g/L, calcium chloride 0.10～0.18 g/L; the solute of the mixed bacteria culture solution is water, The pH is 1.5-1.8.

The content of each component in the mixed bacterial culture solution used in the present embodiment is: elemental sulfur 5.5g/L, ammonium sulfate 4.0 g/L, dipotassium hydrogen phosphate 0.5 g/L, magnesium sulfate heptahydrate 0.5 g/L, Potassium chloride 0.1 g/L, calcium nitrate 0.01 g/L, ferrous sulfate heptahydrate 17.2 g/L, calcium chloride 0.13 g/L, pH 1.6.

④ Addition of waste printed circuit board powder. After step ③ the mixed bacteria culture time reaches 48 hours, add the waste PCBs powder obtained in step ① pretreatment to the mixed bacteria culture system cultivated for 48 hours, add 4g waste PCBs powder to each 1L mixed bacteria culture system, and add waste PCBs The powder begins to undergo mixed bacterial leaching reaction.

When the mixed bacteria culture reaches 72 hours, continue to add the waste PCBs powder obtained in step ① pretreatment to the culture system, add 6g of waste PCBs powder to each 1L mixed bacteria culture system, and the added waste PCBs powder starts the mixed bacteria leaching reaction .

When the mixed bacteria culture reaches 96 hours, continue to add the waste PCBs powder obtained in step ① pretreatment to the culture system, add 8g of waste PCBs powder to each 1L of the mixed bacteria culture system, and the added waste PCBs powder starts the mixed bacteria leaching reaction .

When the mixed bacteria culture reaches 120 hours, continue to add the waste PCBs powder obtained in step ① pretreatment to the culture system, add 10g of waste PCBs powder to each 1L mixed bacteria culture system, and the added waste PCBs powder starts the mixed bacteria leaching reaction .

When the mixed bacteria continued to be cultivated for 175h to 200h (180h in this example), the leaching reaction of the mixed bacteria was completed; the leaching rates of Cu, Ni, Zn, and Pb in the waste printed circuit board powder were measured to be 97.3% and 92.5% respectively. , 93.4%, 89.6%.

Centrifuge the reacted mixed material and collect the leachate from the upper layer. The solids in the lower layer can be used as building materials after treatment.

⑤ post-processing. Extract the leaching solution obtained in step ④ with a copper extractant, and carry out back extraction with a stripping agent for the obtained copper-containing extraction solution; then transfer the obtained copper-containing stripping solution into an electrolytic cell for electrowinning to obtain copper, and complete Copper recovery from scrap printed circuit boards.

During electrowinning, a titanium plate is used as the anode, and a copper plate is used as the cathode. The control voltage is 2.0V, the current density is 350A/m ² , the pH value is 3, the pole distance is 1cm, the time is 3h, and the temperature is 10°C.

The copper extraction agent used is 2-hydroxyl-5-dodecylbenzophenone oxime, and the stripping agent is copper electrolysis waste liquid.

The recovery rate of electrodeposited copper is 99%. Recycled copper can meet the national GB/T 6516-1997 standard.

In order to keep the electrowinning conditions basically stable, the electrowinning solution should be continuously circulated. In this embodiment, the titanium plate is used as the anode, which can efficiently transfer current to the electrolyte solution and provide anion discharge, so that the electrowinning efficiency is improved. In addition, the sulfuric acid produced during the copper electrodeposition process can be recycled and reused.

When the mixed bacteria of the present invention is cultivated, the two bacteria can grow in a balanced manner without adjusting the pH of the culture solution. At the same time, when the two bacteria grow, a large amount of sulfuric acid and Fe ³⁺ are generated for the leaching of copper in the waste PCBs powder in the later stage. The whole process has high efficiency and save energy. In addition, the present invention optimizes the way of adding waste PCBs powder, and adopts the way of low front and high multi-point addition. On the basis of increasing the amount of waste PCBs powder added, the copper leaching rate is significantly improved while the growth of bacteria is relatively inhibited. smaller.

(Example 2 to Example 6)

The mixed bacteria of embodiment 2 to the method of embodiment 6 leaching copper in the waste printed circuit board all the other are the same as embodiment 1, difference is: the content of each component in the mixed bacteria culture solution used when step 3. mixed bacteria culture As well as the addition time and amount of waste printed circuit board powder in step ④, see Table 2 and Table 3 below for details.

Table 2 The content of each component in the mixed bacteria culture solution used in step ③ mixed bacteria culture

Table 3 Step ④ Addition time and amount of waste printed circuit board powder

Note: The addition time mentioned in the above table refers to the time for powder addition after the start of the mixed bacteria culture in step ③; the added amount refers to the weight of waste printed circuit board powder added per 1L of mixed bacteria culture system , the unit is grams.

Claims (6)

1. a kind of mixed bacteria leaching method for copper in the waste printed circuit board is characterized in that comprising the following steps: ① Pretreatment of waste printed circuit boards: crush and grind the waste printed circuit boards PCBs from which electronic components have been removed into powder, sieve the waste printed circuit board powder obtained through grinding, and collect the waste printed circuit board powder that passes through the sieve holes for processing ; ②Aclimation of strains: acidophilus A.ferrooxidans ^and acidophilus A.thiooxidans were respectively domesticated and cultivated for resistance to Cu ²⁺ . Environmental A. ferrooxidans and A. thiooxidans for use; ③Cultivation of mixed bacteria: A. ferrooxidans and A.thiooxidans obtained after step ② domestication culture are carried out in the mixed bacteria culture solution according to the inoculum volume ratio of 1:1.5-2.5, and the initial pH of the culture is 1.5-1.8, The inoculum amount of the mixed bacteria is 10% to 20% of the volume of the mixed bacteria culture solution; ④ Addition of waste printed circuit board powder; after step ③ the mixed bacteria culture time reaches 40-55 hours, add the waste PCBs powder obtained in step ① pretreatment to the mixed bacteria culture system cultivated for 40-55 hours for the first time, and then Every 20 to 25 hours, add the waste PCBs powder obtained in step ① to the mixed bacteria culture system again. The total mass of the discarded PCBs powder is 28g-36g; after the waste PCBs powder is added and the culture time of the mixed bacteria reaches 175h-200h, the leaching reaction of the mixed bacteria is completed; the mixed material after the reaction is centrifuged and the upper leachate is collected; ⑤ post-processing; the leach solution obtained in step ④ is extracted with a copper extractant, and the obtained copper-containing extract is stripped with a stripping agent; then the obtained copper-containing stripping solution is transferred into an electrolytic cell for electrowinning Get copper and complete the recovery of copper from waste printed circuit boards. 2. the method for leaching copper in waste printed circuit boards by mixed bacteria according to claim 1, is characterized in that: step 3. when mixed bacteria are cultivated, the content of each component in the mixed bacteria culture solution used is: elemental sulfur 4.0 ～6.5g/L, ammonium sulfate 3.5～4.5g/L, dipotassium hydrogen phosphate 0.45～0.65 g/L, magnesium sulfate heptahydrate 0.45～0.65 g/L, potassium chloride 0.1～0.15 g/L, calcium nitrate 0.008 ～0.015 g/L, ferrous sulfate heptahydrate 15～18g/L, calcium chloride 0.10～0.18 g/L; the solvent of mixed bacteria culture solution is water. 3. The method for leaching copper in waste printed circuit boards by mixed bacteria according to claim 2, characterized in that: step 3. when the mixed bacteria are cultivated, the content of each component in the mixed bacteria culture solution used is: elemental sulfur 5.2 ～5.6g/L, ammonium sulfate 3.5～4.5g/L, dipotassium hydrogen phosphate 0.45～0.65 g/L, magnesium sulfate heptahydrate 0.45～0.65 g/L, potassium chloride 0.1～0.15 g/L, calcium nitrate 0.008 ～0.015 g/L, ferrous sulfate heptahydrate 17～17.5 g/L, calcium chloride 0.10～0.18 g/L; the solvent of mixed bacteria culture medium is water. 4. The method for leaching copper in waste printed circuit boards by mixed bacteria according to claim 1, characterized in that: when step ④ waste PCBs powder is added, wait until step ③ the mixed bacteria culture time reaches 40 to 55 hours, and the cultured Add the waste PCBs powder obtained in step ① to the mixed bacteria culture system for 40-55 hours, add 4g-6g waste PCBs powder to each 1L mixed bacteria culture system, and start the mixed bacteria leaching reaction for the added waste PCBs powder; After the mixed bacteria culture continues for 20 to 25 hours, add the waste PCBs powder obtained in step ① pretreatment to the culture system for the second time, add 6g to 8g of waste PCBs powder to each 1L mixed bacteria culture system, and start to process the waste PCBs powder added. Mixed bacteria leaching reaction; after the mixed bacteria continue to be cultivated for 20-25 hours, add the waste PCBs powder obtained in step ① pretreatment to the culture system for the third time, add 8g-10g waste PCBs powder to each 1L mixed bacteria culture system, The added waste PCBs powder starts the mixed bacteria leaching reaction; after the mixed bacteria continue to be cultivated for 20-25 hours, add the waste PCBs powder obtained in step ① pretreatment to the culture system for the fourth time, and add it to every 1L of the mixed bacteria culture system 10g~12g of waste PCBs powder, the waste printed circuit board powder has been added. 5. the method for mixing copper according to claim 1 leaching waste printed circuit board, it is characterized in that: step 2. when A. ferrooxidans is domesticated and cultivated, the sewage extracted from the aeration tank of urban sewage treatment plant A. ferrooxidans was obtained by enriching and culturing with mud, and then separated and purified to obtain A. ferrooxidans ; cultured A. ferrooxidans in 9K culture medium to the logarithmic phase; Transfer to the culture solution with a Cu ²⁺ concentration of 10mmol/L; after culturing to the logarithmic phase, absorb the above bacteria solution and transfer it to the Cu ²⁺ Concentration is 20mmol/L in the culture fluid cultured to logarithmic phase; Repeat ^above -mentioned operation, the acclimatization of every generation strain increases, the concentration of Cu in the culture fluid used increases 10mmol/L compared with previous generation, thus obtains in 100～ A.ferrooxidans cultured to logarithmic phase in 200mmol/L Cu ²⁺ environment. 6. the mixed bacteria leaching method for copper in waste printed circuit boards according to claim 1 is characterized in that: when step 2. A.thiooxidans is domesticated and cultivated, the sewage extracted from the aeration tank of the urban sewage treatment plant Mud enrichment culture, and then separation and purification to obtain A.thiooxidans ; A.thiooxidans is cultivated in the culture medium to the logarithmic phase; according to the bacterial inoculum volume ratio v/v is 10% to 20%, absorb the above-mentioned bacterial liquid transfer into the culture solution with a Cu ²⁺ concentration of 10mmol/L; after culturing to the logarithmic phase, according to the inoculum volume ratio v/v of 10% to 20%, absorb the above bacterial solution and transfer to the concentration of Cu ²⁺ Cultivate to the logarithmic phase in the culture fluid of 20mmol/L; Repeat above-mentioned operation, increase the acclimatization of strain ^of one generation every time, the concentration of Cu in the culture fluid used increases 10mmol/L compared with previous generation, thus obtains in 100～200mmol A.Thiooxidans cultured to logarithmic phase in /L Cu ²⁺ environment.