This study was aimed at investigating the leaching behavior of Cu2O (cuprite) powder, in sulfuric acid solution, obtained in waste printed circuit boards (WPCBs) recycling process. Some conventional studies about Cu2O leaching reported that cuprous ions changed into metallic copper and cupric ion by disproportionation reaction during Cu2O leaching in oxyacid solution without oxidant such as oxygen and ferric ion. Therefore, leaching tests using Cu2O reagent were carried out with air introduction to prevent the suppression of further leaching by metallic copper formed on the Cu2O particle.
The effects of N2/air/O2 introduction, air flow rate, pulp density, agitation speed, sulfuric acid concentration, and temperature were investigated in details. Consequently, leaching efficiency of Cu increased with increasing air flow rate and agitation speed whereas it decreased with increasing pulp density. The precipitates of CuSO4·3Cu(OH)2 were observed in 0.5M H2SO4 solution due to increase of pH value over 4.0. The leaching rate decreased with increase concentration of H2SO4 from 1 M to 5 M, and the precipitates of CuSO4·5H2O was observed in 5.0M H2SO4 because Cu2+ ion reacted with high concentration of HSO4- and SO42-. The effect of temperature was found that leaching rate was proportional to temperature.
A kinetics study was conducted based on shrinking particle model about leaching of Cu2O, the rate determining step was determined to be film diffusion than chemical reaction and the activation energy (Ea) was calculated to be 2.7kJ/mol.