Enhanced bioleaching efficiency of copper from waste printed circuit board driven by nitrogen-doped carbon nanotubes modified electrode

To improve the copper bioleaching efficiency from waste printed circuit board (WPCB) by Acidithiobacillus ferrooxidans (A. ferrooxidans), a novel simplified material (nitrogen-doped carbon nanotubes (NCNTs) modified electrode) was used in this paper. Experiments mainly including the exploration of NCNTs optimal concentration and recycling effect of NCNTs modified electrode were investigated. The variations of pH, ORP, Fe2+ concentration and Cu2+ concentration were studied in detail, and the mechanism of the modified electrode was also analyzed in this study. Conclusions were obtained that the optimal experimental conditions were: bacteria inoculation 10%, initial pH 2.0, WPCB powder 1 g, solid/liquid (w/v) ratio 1/50, temperature 28 °C, rotational speed 125 r/min and modified electrode 2.5 mg/cm2. The copper bioleaching rate reached 99% after 9 days reaction, and it was 20% higher than that of the group which was only added A. ferrooxidans. With the analysis of XRD, the precipitate formed (NH4)Fe3(SO4)2(OH)6 at the end of the reaction, and the modified electrode didn't affect the formation of the yellow precipitate. Meanwhile, the modified electrode could be recycled, and the positive effect wasn't weakened obviously on these processes. The results may provide a reference for enhancing the copper bioleaching efficiency from WPCBs and expand the application of NCNTs in hydrometallurgy field.