Double acting liberation of Ni and Co in the pre-treatment process to increase recovery of nickel from low-grade nickel laterite

Abstract

This study highlights the effectiveness of employing double-acting liberation to release Ni and Co from the complex phases of the low-grade nickel laterite. It includes the addition of concentrated sulphuric acid and NaF as well as the heat treatment prior to roasting and leaching processes to improve the destruction of the complex phases contained. The finding describes that dehydration of iron sulfate and decomposition of the lizardite at a lower temperature, 270 °C, were occurred in the pre-treatment process, followed by hematite formation in the roasting process. It subsequently accelerated Ni and Co extraction in the pregnant solution and omitted Fe as the water-insoluble hematite in the residue when the leaching process was employed. The optimum leaching percentages of nickel and cobalt are 71.3% and 98.8%, serially and were obtained at a roasting temperature of 700°C for 30 min with the addition of 3 wt.% sodium fluoride. This research provides essential contributions to the optimization of decomposition process for complex phases in the low-grade nickel laterite at a lower temperature and to upsurge leaching percentage of Ni and Co by strictly suppressing Fe dissolution.