The BRISA process as a path for efficient copper recovery from waste PCBs

Abstract

In the present work, a two-stage biohydrometallurgical process for copper extraction from waste PCBs is developed. The main goal of this study is to check whether to separate the chemical leaching of copper with ferric iron from the regeneration of the leaching agent by bacterial oxidation of the ferrous iron is an efficient route for copper recovery from waste PCBs. To test this proposal, large waste PCBs pieces were retained in a stirred tank reactor (STR) in contact with a leaching liquor circulating at a high flow rate between this STR and a bioreactor. The kinetics of leaching of large PCB pieces, when ferric iron is added in excess over the stoichiometric requirements, is limited by the rate of mass transfer of the leaching agent. A heterogeneous kinetic model was proposed to fit the experimental data. It was also found that by increasing the ferric iron concentration the leaching rate was increased. Process separation has proven to be a promising configuration in which the productivity of the bioreactor has fulfilled the leaching agent demand and 90% of copper extraction was achieved in 48 h for large waste PCBs.