Metal concentrates of printed circuit boards (PCBs) are the residue valuable metals from which nonmetallic components are removed. The non-metallic components show bacterial toxicity in bioleaching process and can be recycled as well. In this study, the effects of initial pH, initial Fe(II) concentration, metal concentrate dosage, particle size, and inoculation quantity on the bioleaching were investigated so as to determine the optimum conditions and evaluate the feasibility of bioleaching of metal concentrates of PCBs by mixed culture of acidophilic bacteria (MCAB). The results showed that the initial pH and Fe(II) concentration played an important role in copper extraction and precipitate formation. Under the optimized conditions of initial pH 2.00, 12 g/L initial Fe(II), 12 g/L metal concentrate dosage, 10% inoculation quantity, and 60-80 mesh particle size. 96.8% the copper leaching efficiency was achieved in 45 h, and aluminum and zinc 88.2% and 91.6% in 98 h. respectively. All findings demonstrated that metals could be efficiently leached from metal concentrates of waste PCBs by using the MCAB, and the leaching period was shorten from about 8 days to 45 h. (C) 2011 Elsevier B.V. All rights reserved.