Abstract:Two-step bioleaching process was applied to extract metal from waste printed circuit board (PCB). In the first step, copper in waste PCB was extracted by Acidithiobacillus ferrooxidans and its influencing factors were discussed. In the second step, gold was extracted from residue of first step with Chromobacterium violaceum by single factor experiment. Taking gold leaching rate as response value, Box-Behnken (BB) design was adopted to improve gold leaching rate, and response value was analyzed by multiple quadratic regression analysis of 4 factors and 3 levels with Design-Expert software. The results show that 99% of copper can be extracted by Acidithiobacillus ferrooxidans at pH value of 2.0, Fe2+ concentration of 44.3 g/L, particle size of 75~147 μm, and pulp density of 0.5 g for 4 days. Gold leaching rate is 72.58% under the optimum conditions including pH value of 10.5, glycine concentration of 4.02 g/L, MgSO4 concentration of 5.67 mg/L, and temperature of 31.0 ℃.