Dephosphorization of nickel powder by leaching with sulphuric acid

Abstract

Nickel powder is the sludge after extracting Mo and V from spent catalyst from oil refineries. Ni grade of in the nickel powder is around 5.5% by mass and it can be a nickel source for nickel smelters. However, P grade of nickel powder is around 0.61%. Since P is one of the major impurites of steel, this is a limitation of nickel powder in use for nickel smelters. In this study, selective removal of P (Dephosphorization) by sulfuric acid leaching was investigated to increase usability of nickel powder. Five key parameters, namely acidity, leaching time, liquid/solid ratio, rpm of a magnetic agitator and temperature were examined to find out an optimal acid leaching condition. Optimal acid leaching conditions were determined as 0.1 mol/L acidity, 10 min leaching time, 10 mL/g liquid/solid, 200 rpm and room temperature. Under optimal acid leaching condition, 91.7% dephosphorization, 4.3% Ni loss and 2.6% leached fraction of Al were achieved and acid consumption was determined as 100 kg/t nickel powder. The experimental data was analyzed by the unreacted shrinking core model and rate controlling step was found to be chemical reaction control up to 10 min of leaching time. Additionally, the reason for low Ni leached fraction of nickel powder was verified through calcination experiments.