Dissolution kinetics of manganese during nickel recovery from high iron grade laterite by acid leaching combined NaOH-assisted mechanochemical technology

This study investigates the effect of the process involving a combination of sodium-based reagent-assisted mechanochemical conversion (NaOH-MC) and leaching, which was developed to provide highly efficient nickel recovery, on the amount of dissolved manganese during nickel recovery. For this purpose, firstly laterite was treated with NaOH as reagent and then leaching performed in sulphuric acid medium. Response Surface Methodology (RSM) was successfully used as a statistical approach to determine the effect of parameters for both processes and to optimize processes conditions in terms of dissolved manganese. In optimum conditions determined as 0.5 M H2SO4, 55 mL/g liquid to solid ratio, 75 °C and 30 min; dissolution amount of manganese from NaOH-MC treated laterite was achieved as 97.54% ± 1.06 (N = 2) with standard deviation. In addition, the dissolution behaviour of manganese was defined by a control mechanism, a combination of chemical reaction and diffusion based on the shrinking core kinetic model. The activation energy of manganese dissolution was found as 35.42 kJ/mol. According to the results, the mechanochemistry contributed positively to the dissolution of manganese due to the increased leachability of laterite at low temperature and in a short time with low acid consumption.