Thermodynamic analysis and application for preparing FePO4 from nitric acid pressure leach laterite residue by selective leaching in phosphoric acid and induced precipitation

Currently, with the increasing demand of nickel and cobalt, more and more attention has been placed on hydrometallurgical processing to treat laterite ore. The nitric acid pressure leaching (NAPL) has several advantages. In order to solve the problems of environmental pollution and resource wastage caused by the NAPL residue, this work proposes a novel and green process for treating laterite residue to prepare high-purity iron phosphate. The laterite residue was subjected to selective leaching by 6.0 mol L −1 phosphoric acid . The pregnant leach solution (PLS) was used to prepare iron phosphate by induced precipitation. The selective leaching was conducted using 6.0 mol L −1 H 3 PO 4 of to obtain high extraction of iron. After leaching and clarification of PLS iron phosphate was precipitated in two steps by controlling temperature and pH, to yield more than 94% iron phosphate. The reaction mechanism of the induced precipitation was analyzed, which illustrated that intermediate products were first formed from the leach liquor and then transformed to FePO 4(s) . Characterization of the iron phosphate showed that the product displayed flowerlike morphology with high purity and dispersion. This process not only solves the serious environmental damage by accumulation and landfill of laterite residue, but also improve the efficiency of resource utilization for the hydrometallurgical nickel laterite industry.