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

Abstract

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 a 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 ºC 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 behavior 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.