Study On Leaching Of Copper From Waste Printed Circuit Boards By Microbial Metabolites

The expanding information technology and ever increasing demand of the market has led to a speeding up production and replacement of electronic productions, which inevitably will bring about a dramatic increasing in electrical and electronic equipment wastes.Meanwhile,the waste Printed Circuit Boards(PCB),which is widely applied in those equipments,is increasing accordingly.Waste PCB contains a large number of recyclable heavy metals as well as some rare and noble metals, amongst which copper plays the main part.Rational treatment and recycling of them could not only make up for the keep-mounting copper scarcity,but also help in keeping a green and sustainable environment.This research aimed mainly at studying on copper leaching from pulverized waste PCB by microbial metabolites.Aspergillus niger was cultured in a 100ml liquid fermentation medium for 4 days, its metabolites were collected for leaching copper in a conical flask,then mixed with waste PCB particles(the sizeΦ＜0.2mm),the concentration of them was 50g/L.The initial leaching was completed after 2d.Subsequently,100ml of fresh metabolites was employed for leaching copper from solid residue in the conical flask after the solid-liquid separation.This operation was repeated successively for 24d,and the cumulative copper leaching rate reached 90%.The sediments of leaching liquid were may be cupric oxalate,which determined with X-ray diffraction analysis.A brand new method was employed in our research.Copper was leached from waste PCB particles(Φ＜0.2mm)by the acidizing fluid produced by indigenous sulfur-oxidizing bacteria,which was cultured in sewage sludge(of secondary clarifier) with the elemental sulfur as substrate.100ml of metabolites of indigenous sulfur-oxidizing bacteria was fed to a conical flask which contained 10g pulverized waste PCB particles.These experimental operations are the same as the previous experiments'.The cumulative copper leaching rate reached 93.69%after 24d's contact. The sediments of leaching liquid were may be cupric sulfate,basic,which determined with X-ray diffraction analysis.Meanwhile,isolated the solution from leaching liquid, which then using LIX84I extractant to extract copper.In the single-stage extraction operation,the rate of extraction of copper can reach more than 93%.The result showed that both Aspergillus niger 's and sulfur-oxidizing microbial metabolites can leach copper completely from pulverized waste PCB particles if only given enough time.Furthermore,the leaching of copper from pulverized waste PCB particles by the production of indigenous sulfur-oxidizing bacteria was characterized low-cost and high efficiency and therefore can be regarded as a new way with competency to recycle metals from waste PCB.It is a method worth further investigation.