Background technology
Along with information technology fast development, electron wastes (Waste Electric and Electronic equipment, WEEE) output constantly rises, discarded printed circuit boards (Printed Circuit Boards, PCBs) as WEEE important component, usually contain the metal of about 40%, wherein metallic copper is main composition, and content is up to 20% ~ 30%.According to estimates, China needs process PCBs greatly about more than 500,000 tons and with 22% speed increment every year.If realize discarded PCB Treatment and recovery, can problem of environmental pollution be solved, metal efficient recovery can be realized again, by the Sustainable development important in inhibiting to China PCBs industry.
The method extracting copper at present from discarded printed circuit boards mainly contains Physical, chemical method and biological process.Physical evaluation index in renewable resource effect, environment friendliness, industrial application rate is higher, but the mechanical means used investment is large, energy-output ratio is high, maintenance cost is high, and thus economic feasibility is relatively poor; And be difficult between metal in product be separated.Chemical method is mainly divided into pyrogenic process and wet method, although the advantage that pyrogenic process has simply, convenient and the rate of recovery is high, can produce obnoxious flavour simultaneously, discharge the shortcomings such as a large amount of scum silica frost; Wet method have exhaust gas emission few, extract the advantages such as the residue after copper is easy to process and technique is simple, but copper leaching rate is low and leach liquor and residue have toxicity.Therefore the biological process polluted less, cost is low, reaction conditions is gentle is applied in discarded printed circuit boards metal recovery and there is unique advantage.
Copper in bioleaching PCBs has the features such as safe, clean, efficient, has become domestic and international study hotspot.The most general microorganism of current application be Acidithiobacillus thiooxidans (
a.t) and thiobacillus ferrooxidant (
a. f).
Such as Zhou Peiguo etc. (Zhou Peiguo, Zheng Zheng, Peng Xiaocheng etc. the Changeement of iron in copper leaching from printed circuit board by Thiobacillus ferrooxidans and process. " Environmental Pollution and Control "; 2007(02): 119 ~ 122) utilize the copper in thiobacillus ferrooxidant leaching waste printed circuit board powder (Copper mass fraction is 10.4%), when waste printed circuit board powder addition is 100 g/L, about 15d copper leaching rate is about 90%.
Chinese patent literature CN 1948524 A(application number 200610097382.X) disclose a kind of waste printed circuit board comprehensive resources treatment method, in culture medium solution, inoculate the thiobacillus ferrooxidant through taming, the micro-spirillum of iron protoxide or sulfolobus solfataricus bacterium liquid cultivate, after the circuit board substrate eliminating various components and parts is pulverized, add the bacterium liquid cultivated and obtain wherein, agitation leach 10 ~ 15 days under the speed of 120 ~ 160r/min, separating liquid and solid; Liquid copper extractant extracts, then carries out stripping and electrolytic deposition obtains metallic copper.
Aforesaid method is all use single microorganism to carry out bioleaching, and its metal extraction time is long, and leaching efficiency is low.
Research shows, in mixed bacterium leaching PCBs, copper is current most effective means.
Such as (the Sadia I such as SADIA; Munir AA; Shahida BN, Afzal Ghauri M. Bioleaching of metals from electronic scrap by moderately thermophilic acidophilic bacteria. Hydrometallurgy 2007; 88:180 – 8.) utilize in temperature addicted to the metal in sour mixed bacterium leaching waste printed circuit board powder (Copper mass fraction is 8.5%), when waste printed circuit board powder addition is 10g/L, after 18d, the leaching rate of copper is 89%.But although this mixed bacterium leaching method employs mixed bacterium, leaching time is long, leaching rate is high not as a kind of efficiency of bacterial leaching.When this is due to multi strain co cultivation, provide which type of nutritional substrate and ambient conditions to make mixed bacterium energy uniform growth, thus there will not be a kind of excessive multiplication and the suppressed phenomenon of another kind of bacterium is most important.In addition, bacterial leaching copper ability and himself growth metabolism closely related, understand bacteria growing inhibiting in PCBs adding procedure and then cause copper leaching power to decline, thus how optimizing PCBs addition manner is one of another key factor realizing copper in mixed bacterium efficient leaching PCBs.
Summary of the invention
Technical problem to be solved by this invention is to provide a kind of multi strain co cultivation method and efficiently leaches the method for copper in discarded printed circuit boards with it.
The technical scheme realizing the object of the invention is the method for copper in a kind of mixed bacterium leaching discarded printed circuit boards, comprises the following steps:
1. the pre-treatment of discarded printed circuit boards; The discarded printed circuit boards PCBs having removed electronic component is crushed and grind into powder, grinds the discarded printed circuit boards powder obtained and sieve, collect by the discarded printed circuit boards powder of sieve aperture pending.
2. tamed strain; By Acidithiobacillus ferrooxidans strain GF
a.ferrooxidansand Acidithiobacillus thiooxidans
a.thiooxidanscarry out resistance to Cu respectively
2+domestication cultivate, domestication terminate obtain resistance to 100 ~ 200mmol/L Cu respectively
2+environment
a.ferrooxidanswith
a.thiooxidansstand-by.
3. multi strain co cultivation; Obtain after 2. step is tamed cultivation
a.ferrooxidanswith
a.thiooxidansaccording to inoculum size is 1: 1.5 ~ 2.5 in multi strain co cultivation liquid, carry out multi strain co cultivation, and cultivating initial pH is 1.5 ~ 1.8, mixed bacterium inoculum size be multi strain co cultivation liquid long-pending 10% ~ 20%.
4. the interpolation of discarded printed circuit boards powder; Treat that 3. the multi strain co cultivation time arrives 40 ~ 55 hours to step, first time adds the step 1. discarded PCBs powder that obtains of pre-treatment in the multi strain co cultivation system of having cultivated 40 ~ 55 hours, then in multi strain co cultivation system, the step 1. discarded PCBs powder that obtains of pre-treatment was again added every 20 ~ 25 hours, after the discarded PCBs powder that once adds compare before once increase by 1 ~ 3g/L, the total mass of the discarded PCBs powder added in 1L multi strain co cultivation system is 28g ~ 36g; When discarded PCBs powder finishes bacterium incubation time to be mixed arrival 175h ~ 200h, mixed bacterium leaching reaction terminates; Centrifugation is carried out to reacted mixture, collects upper strata leach liquor.
5. aftertreatment; Leach liquor copper extractant step 4. obtained extracts, and for the cupric extraction liquid obtained, strips with strippant; Then the cupric strip liquor obtained is transferred in electrolyzer and carries out electrodeposition and obtain copper, complete the recovery of copper in discarded printed circuit boards.
Above-mentioned steps 3. multi strain co cultivation time, in multi strain co cultivation liquid used, the content of each component is: elemental sulfur 4.0 ~ 6.5g/L, ammonium sulfate 3.5 ~ 4.5g/L, dipotassium hydrogen phosphate 0.45 ~ 0.65 g/L, bitter salt 0.45 ~ 0.65 g/L, Repone K 0.1 ~ 0.15 g/L, nitrocalcite 0.008 ~ 0.015 g/L, ferrous sulfate 15 ~ 18g/L, calcium chloride 0.10 ~ 0.18 g/L; Multi strain co cultivation liquid solute is water.
As preferably, step 3. multi strain co cultivation time, in multi strain co cultivation liquid used, the content of each component is: elemental sulfur 5.2 ~ 5.6g/L, ammonium sulfate 3.5 ~ 4.5g/L, dipotassium hydrogen phosphate 0.45 ~ 0.65 g/L, bitter salt 0.45 ~ 0.65 g/L, Repone K 0.1 ~ 0.15 g/L, nitrocalcite 0.008 ~ 0.015 g/L, ferrous sulfate 17 ~ 17.5g/L, calcium chloride 0.10 ~ 0.18 g/L; Multi strain co cultivation liquid solute is water.
When 4. above-mentioned steps discards the interpolation of PCBs powder, treat that 3. the multi strain co cultivation time arrives 40 ~ 55 hours to step, the step 1. discarded PCBs powder that obtains of pre-treatment is added in the multi strain co cultivation system of having cultivated 40 ~ 55 hours, add 4g ~ 6g in every 1L multi strain co cultivation system and discard PCBs powder, the discarded PCBs powder added starts to carry out mixed bacterium leaching reaction; Bacterium to be mixed continued cultivation after 20 ~ 25 hours, in culture system, second time adds the step 1. discarded PCBs powder that obtains of pre-treatment, add 6g ~ 8g in every 1L multi strain co cultivation system and discard PCBs powder, the discarded PCBs powder added starts to carry out mixed bacterium leaching reaction; Bacterium to be mixed continued cultivation after 20 ~ 25 hours, in culture system, third time adds the step 1. discarded PCBs powder that obtains of pre-treatment, add 8g ~ 10g in every 1L multi strain co cultivation system and discard PCBs powder, the discarded PCBs powder added starts to carry out mixed bacterium leaching reaction; Bacterium to be mixed continued cultivation after 20 ~ 25 hours, and in culture system, add the step 1. discarded PCBs powder that obtains of pre-treatment for the 4th time, add 10g ~ 12g in every 1L multi strain co cultivation system and discard PCBs powder, discarded PCBs powder adds complete.
Above-mentioned steps 2.
a.ferrooxidanscarry out domestication when cultivating, by the mud enrichment culture extracted from the aeration tank of municipal sewage plant, then separation and purification and obtaining
a.ferrooxidans; Will
a.ferrooxidanslogarithmic phase is cultured in 9K nutrient solution; Be 10% ~ 20%(volume ratio v/v according to strain inoculation amount), draw above-mentioned bacterium liquid and transfer to Cu
2+concentration be in the nutrient solution of 10mmol/L; After being cultured to logarithmic phase, be 10% ~ 20%(volume ratio v/v according to strain inoculation amount), draw above-mentioned bacterium liquid and transfer to Cu
2+concentration be cultured to logarithmic phase in the nutrient solution of 20mmol/L; Repeat aforesaid operations, often increase the domestication of generation bacterial strain, Cu in nutrient solution used
2+concentration compare previous generation and increase 10mmol/L, thus to obtain at 100 ~ 200mmol/L Cu
2+logarithmic phase is cultured in environment
a.ferrooxidans.
Above-mentioned steps 2.
a.thiooxidanscarry out domestication when cultivating, by the mud enrichment culture extracted from the aeration tank of municipal sewage plant, then separation and purification and obtaining
a.thiooxidans; Will
a.thiooxidanslogarithmic phase is cultured in nutrient solution; Be 10% ~ 20%(volume ratio v/v according to strain inoculation amount), draw above-mentioned bacterium liquid and transfer to Cu
2+concentration be in the nutrient solution of 10mmol/L; After being cultured to logarithmic phase, be 10% ~ 20%(volume ratio v/v according to strain inoculation amount), draw above-mentioned bacterium liquid and transfer to Cu
2+concentration be cultured to logarithmic phase in the nutrient solution of 20mmol/L; Repeat aforesaid operations, often increase the domestication of generation bacterial strain, Cu in nutrient solution used
2+concentration compare previous generation and increase 10mmol/L, thus to obtain at 100 ~ 200mmol/L Cu
2+logarithmic phase is cultured in environment
a.thiooxidans.
The present invention has positive effect:
(1) nutritional substrate provided when the present invention carries out multi strain co cultivation and culture condition make Acidithiobacillus ferrooxidans strain GF (
acidithiobacillus.ferrooxidans, A.ferrooxidans) and Acidithiobacillus thiooxidans (
acidithiobacillus. thiooxidans, A.thiooxidans) two kinds of bacterium energy uniform growth, there is not a kind of bacterium excessive multiplication and the suppressed phenomenon of another kind of bacterium.In addition, present invention optimizes the addition manner of discarded PCBs powder, adopt the mode that low early and high after multiple spot adds, on the basis of improving discarded PCBs addition, copper leaching rate significantly improves and the suppressed degree of thalli growth is relatively little.
(2) the present invention adopts multi strain co cultivation, without the need to regulating pH two kinds of bacterium just energy uniform growth of nutrient solution during cultivation, generates a large amount of sulfuric acid and Fe during two kinds of bacteria growings simultaneously
3+discard the leaching of copper in PCBs powder for the later stage, whole process efficiency is high, save the energy.
(3) the present invention is before carrying out bioleaching, right
a.ferrooxidanswith
a.thiooxidanscarry out resistance to Copper treatment, significantly improved the resistance to copper of two kinds of bacterium, facilitate the leaching of copper in discarded PCBs powder.
(4)) simple, the economy of whole process of the present invention, environmental protection, meet the needs of recycling economy development, have good prospects for commercial application.
Embodiment
(embodiment 1)
In the mixed bacterium leaching discarded printed circuit boards of the present embodiment, the method for copper comprises the following steps:
1. the pre-treatment of discarded printed circuit boards.The discarded printed circuit boards PCBs having removed electronic component is crushed and grind into powder, grind the sieve aperture (grinding the sieve aperture that the discarded printed circuit boards powder obtained crosses 100 μm in the present embodiment) that the discarded PCBs powder obtained crosses 100 μm ~ 200 μm, collect by the discarded PCBs powder of sieve aperture pending.
The discarded PCBs of the present embodiment process, after grinding is sieved, analyzes its major metal content,
Major metal content is as shown in table 1 below:
Major metal content in table 1 discarded printed circuit boards powder
2. tamed strain.
(1) Acidithiobacillus ferrooxidans strain GF (
a.ferrooxidans) domestication.By the mud enrichment culture extracted from the aeration tank of municipal sewage plant, then separation and purification and obtaining
a.ferrooxidans; Will
a.ferrooxidansin 9K nutrient solution, be cultured to logarithmic phase, now in bacterium liquid, bacteria concentration rises to 10
7cell/mL.
The every 1L of 9K nutrient solution used comprises: 44.7g FeSO
47H
2o, 3.0g (NH
4)
2sO
4, 0.5g K
2hPO
4, 0.5g MgSO
47H
2o, 0.1g KCl, 0.01g Ca (NO
3)
2, the pH value of nutrient solution is 2.00.
Be 10% ~ 20%(volume ratio v/v according to strain inoculation amount), draw above-mentioned bacterium liquid and transfer to and add in the 250mL Erlenmeyer flask of 100mL fresh medium, in temperature 32 DEG C, shaking speed is be 150 r/min in 120 ~ 200r/min(the present embodiment) be cultured to logarithmic phase under condition and complete first-generation domestication.First-generation domestication is used
a.fall the other are identical with above-mentioned 9K nutrient solution for nutrient solution, and difference is to add Cu in nutrient solution
2+, Cu in nutrient solution
2+concentration be 10mmol/L.
Be 10% ~ 20%(volume ratio v/v according to strain inoculation amount), draw the domestication of the above-mentioned first-generation after bacterium liquid carry out being cultured to logarithmic phase to fresh medium, Cu in this nutrient solution used
2+concentration rise to 20mmol/L.
Repeat aforesaid operations, bacterium liquid is proceeded to successively containing 30,40,50,60,70,80,90,100,110,120,130,140,150,160,170,180,190 and 200mmol/L Cu
2+fresh medium in domestication cultivate, cultivate after terminating, centrifugal segregation supernatant liquor, collect the Cu of ability 200 mmol/L
2+the thalline of concentration to put refrigerator stand-by.
In above-mentioned domestication process, often increase the domestication of generation bacterial strain, Cu in nutrient solution used
2+concentration compare previous generation and increase 10mmol/L.Due to Cu
2+concentration raises, so be cultured to logarithmic phase, (bacteria concentration is 10
7cell/mL) required time can be more and more longer.According to the powder situation of process, by the Cu of Acidithiobacillus ferrooxidans strain GF at 100 mmol/L
2+concentration under be cultured to logarithmic phase after also can stop domestication, thus obtain the Cu of resistance to 100 mmol/L
2+concentration
a.ferrooxidans.
(2) Acidithiobacillus thiooxidans (
a.thiooxidans) domestication.By the mud enrichment culture extracted from the aeration tank of municipal sewage plant (Sewage Plant adopt A2/O dispose of sewage), then separation and purification and obtaining
a.thiooxidans; Will
a.thiooxidansin nutrient solution, be cultured to logarithmic phase, now in bacterium liquid, bacteria concentration rises to 10
7cell/mL.
The every 1L of nutrient solution used comprises: 10.0g S
0, 0.5g (NH
4)
2sO
4, 0.25g K
2hPO
4, 0.25g MgSO
47H
2o, 0.02g CaCl
22H
2o; The pH value of nutrient solution is 4.00.
Be 10% ~ 20%(volume ratio v/v according to strain inoculation amount), draw above-mentioned bacterium liquid and transfer to and add in the 250mL Erlenmeyer flask of 100mL fresh medium, in temperature 32 DEG C, shaking speed is be 150 r/min in 120 ~ 200r/min(the present embodiment) be cultured to logarithmic phase under condition and obtain first-generation domestication Acidithiobacillus thiooxidans.
First-generation domestication is used
a.tall the other are identical with above-mentioned nutrient solution for nutrient solution, and difference is that first-generation domestication is used
a.tcu is added in nutrient solution
2+, Cu in nutrient solution
2+concentration be 10mmol/L.
According to Acidithiobacillus ferrooxidans strain GF in (1) (
a.f) acclimation method, bacterium liquid is proceeded to successively containing 20,30,40,50,60,70,80,90,100,110,120,130,140,150,160,170,180,190 and 200mmol/L Cu
2+fresh medium in domestication be cultured to logarithmic phase, cultivate after terminating, centrifugal segregation supernatant liquor, collect the Cu of ability 200 mmol/L
2+the thalline of concentration to put refrigerator stand-by.
According to the powder situation of process, will
a.thiooxidansat the Cu of 100 mmol/L
2+concentration under be cultured to logarithmic phase after also can stop domestication, thus obtain the Cu of resistance to 100 mmol/L
2+concentration
a.thiooxidans.
Namely, in above-mentioned domestication process, the domestication of generation bacterial strain is often increased, Cu in nutrient solution used
2+concentration compare previous generation and increase 10mmol/L.Due to Cu
2+concentration raises, so be cultured to logarithmic phase, (bacteria concentration is 10
7cell/mL) required time can be more and more longer.
3. multi strain co cultivation.Obtain after 2. step is tamed cultivation
a.ferrooxidanswith
a.thiooxidansaccording to inoculum size is be 1: 2 in 1: 1.5 ~ 2.5(the present embodiment) in multi strain co cultivation liquid, carry out multi strain co cultivation, cultivating initial pH is be 1.6 in 1.5 ~ 1.8(the present embodiment), mixed bacterium inoculum size be multi strain co cultivation liquid long-pending 10% ~ 20%.Control temperature 32 DEG C during multi strain co cultivation, shaking speed is be 150 r/min in 120 ~ 200r/min(the present embodiment).
In multi strain co cultivation liquid, the content of each component is: elemental sulfur 4.0 ~ 6.5g/L, ammonium sulfate 3.5 ~ 4.5g/L, dipotassium hydrogen phosphate 0.45 ~ 0.65 g/L, bitter salt 0.45 ~ 0.65 g/L, Repone K 0.1 ~ 0.15 g/L, nitrocalcite 0.008 ~ 0.015 g/L, ferrous sulfate 15 ~ 18g/L, calcium chloride 0.10 ~ 0.18 g/L; Multi strain co cultivation liquid solute is water, and pH is 1.5 ~ 1.8.
In multi strain co cultivation liquid used in the present embodiment, the content of each component is: elemental sulfur 5.5g/L, ammonium sulfate 4.0 g/L, dipotassium hydrogen phosphate 0.5 g/L, bitter salt 0.5 g/L, Repone K 0.1 g/L, nitrocalcite 0.01 g/L, ferrous sulfate 17.2 g/L, calcium chloride 0.13 g/L, pH are 1.6.
4. the interpolation of discarded printed circuit boards powder.Treat that 3. the multi strain co cultivation time arrives 48 hours to step, the step 1. discarded PCBs powder that obtains of pre-treatment is added in the multi strain co cultivation system of having cultivated 48 hours, add 4g in every 1L multi strain co cultivation system and discard PCBs powder, the discarded PCBs powder added starts to carry out mixed bacterium leaching reaction.
Bacterium to be mixed is cultured to 72 constantly little, and continue to add the step 1. discarded PCBs powder that obtains of pre-treatment in culture system, add 6g in every 1L multi strain co cultivation system and discard PCBs powder, the discarded PCBs powder added starts to carry out mixed bacterium leaching reaction.
Bacterium to be mixed is cultured to 96 constantly little, and continue to add the step 1. discarded PCBs powder that obtains of pre-treatment in culture system, add 8g in every 1L multi strain co cultivation system and discard PCBs powder, the discarded PCBs powder added starts to carry out mixed bacterium leaching reaction.
Bacterium to be mixed is cultured to 120 constantly little, and continue to add the step 1. discarded PCBs powder that obtains of pre-treatment in culture system, add 10g in every 1L multi strain co cultivation system and discard PCBs powder, the discarded PCBs powder added starts to carry out mixed bacterium leaching reaction.
It is 180h that bacterium to be mixed continues to be cultured in 175h ~ 200h(the present embodiment) time, mixed bacterium leaching reaction terminates; Record Cu, Ni, Zn, Pb leaching yield in discarded printed circuit boards powder and be respectively 97.3%, 92.5%, 93.4%, 89.6%.
Centrifugation is carried out to reacted mixture, collects upper strata leach liquor.Lower floor's solid can be used as material of construction after treatment.
5. aftertreatment.Leach liquor copper extractant step 4. obtained extracts, and for the cupric extraction liquid obtained, strips with strippant; Then the cupric strip liquor obtained is transferred in electrolyzer and carries out electrodeposition and obtain copper, complete the recovery of copper in discarded printed circuit boards.
Use titanium plate to do anode during electrodeposition, copper coin does negative electrode.Control voltage is 2.0V, and current density is 350A/m
2, pH value is 3, and pole span is 1cm, and the time is 3h, and temperature is 10 DEG C.
Copper extractant used is 2-hydroxyl-5-dodecyl diphenylketoxime, and strippant is waste solution of copper electrolysis.
The rate of recovery of electro deposited copper is 99%.Reclaim copper and can reach national GB/T 6516-1997 standard.
In order to keep the basicly stable of electrodeposition condition, electrodeposition solution will constantly circulate.The present embodiment use titanium plate does anode and can current delivery be discharged to electrolytic solution and for negatively charged ion expeditiously, and electrodeposition efficiency is improved.In addition, the sulfuric acid produced in the process of electro deposited copper, recyclable recycling.
Without the need to regulating pH two kinds of bacterium just energy uniform growth of nutrient solution during multi strain co cultivation of the present invention, generate a large amount of sulfuric acid and Fe during two kinds of bacteria growings simultaneously
3+discard the leaching of copper in PCBs powder for the later stage, whole process efficiency is high, save the energy.In addition, present invention optimizes the addition manner of discarded PCBs powder, adopt the mode that low early and high after multiple spot adds, on the basis of improving discarded PCBs powder addition, copper leaching rate significantly improves and the suppressed degree of thalli growth is relatively little.
(embodiment 2 to embodiment 6)
In the mixed bacterium leaching discarded printed circuit boards of embodiment 2 to embodiment 6, all the other are identical with embodiment 1 for the method for copper, difference is: step 3. multi strain co cultivation time multi strain co cultivation liquid used in the content of each component and step 4. interpolation time of discarded printed circuit boards powder and addition, specifically see the following form 2 and table 3.
Table 2 step 3. multi strain co cultivation time multi strain co cultivation liquid used in the content of each component
Table 3 step is interpolation time of discarded printed circuit boards powder and addition 4.
Note: above show the described interpolation time refer to from step 3. mixed bacterium after starting to cultivate how many hours time carry out time of powder interpolation; Described addition refers to the weight of the discarded printed circuit boards powder added in every 1L multi strain co cultivation system, and unit is gram.