Catalytic effect of graphene in bioleaching copper from waste printed circuit boards by Acidithiobacillus ferrooxidans

Exploration of enhancing bioleaching percent of copper from waste printed circuit board (WPCB) has received an increasing attention in recent years. This research explored the catalytic effect of graphene in bioleaching copper from WPCB by Acidithiobacillus ferrooxidans (A. ferrooxidans). Series of experiments were investigated, such as compatibility test between A. ferrooxidans and graphene, optimal dosage test of graphene, test of orthogonal experiment design, mechanism analysis of graphene, and recycling experiment of used graphene. Conclusions were obtained that graphene had a good compatibility with A. ferrooxidans, and it could catalyze the bioleaching reaction when added with appropriate dosage of graphene. The optimal dosage of graphene was 0.04 gin 50 ml culture solution, and 84% of copper was leached after five days bioleaching, while only 74% of copper was leached without adding graphene. The optimal condition of bioleaching copper was WPCB 10 g L-1, initial pH 2.5, bacterial activation time 4 days, and FeSO4 center dot 7H(2)O 40 g L-1, about 91.8% of copper was leached. The mechanism analysis of graphene indicated that the transformation between Fe2+ and Fe3+ was actuated by A. ferrooxidans and graphene in these reactions, and both of FeCI3 center dot 6H(2)O and KFe(SO4)(2)(OH)(6) were generated in bioleaching process. The catalytic ability of bioleaching copper wasn't weakened by treating with 40% HNO3, and graphene could recycle and reuse in these reactions. Our experimental results shows that the catalysis of graphene in bioleaching copper from WPCB by A. ferrooxidans is promising.