Selective Leaching of Zinc from Carbonate Source Using Glycine As an Ecofriendly Lixiviant

In the present study, a selective leaching process of zinc from a low-grade carbonate source is proposed by the use of a green lixiviant, namely glycine. Response surface methodology (RSM) coupled with central composite design (CCD), was applied to optimize the levels of glycine concentration, pH and temperature and to quantify the significance of the factors and the interactions among them. Under optimum conditions, glycine concentration = 1.5 M, pH = 9.5 and temperature = 70 ?, more than 90% of zinc was leached while the leaching percentages of main impurities were negligible. Finally, zinc was removed from the leaching solution through the precipitation process by Na2S solution in the form of ZnS. The thermodynamic aspect of the leaching process was elucidated and it was attempted to justify the results obtained from statistical modeling.