Leaching of copper and zinc from the tailings sample obtained from a porcelain stone mine: feasibility, modeling, and optimization

This research was aimed to investigate the leaching behavior of zinc and copper from a porcelain stone tailings sample using RSM-CCD modeling. The synergetic and individual effects of five main factors including liquid/solid ratio, sulfuric acid concentration, agitation speed, leaching time, and temperature were examined on the recoveries of zinc and copper. For this purpose, two 2F1 models with R2 values of 0.9341 and 0.8693 were developed for the relationship between the leaching efficiencies of copper and zinc and effective terms, respectively. The results indicated that the leaching process was significantly influenced by the interactive effects between factors. The leaching recoveries increased by increasing all factors in the range studied. However, the recoveries were nearly independent of the agitation rate, indicating surface chemical reaction as the leaching kinetics controlling step. It was also found that the linear effect of temperature, the interaction effect of leaching time with liquid/solid ratio, and the interactive effect between sulfuric acid concentration and agitation rate had the greatest impact on the leaching rate of copper. Additionally, the linear effect of temperature and the interactive effect of temperature with agitation speed and liquid/solid ratio were distinguished to be the most effective factors on the recoveries of zinc. Moreover, the optimization was performed using desirability function approach, and the highest recoveries of copper (73.95%) and zinc (81.02%) were obtained at an acid concentration of 10%, 300 rpm agitation rate, 10 mL/g liquid/solid ratio, 35 °C temperature, and 75 min leaching time.