Application of HPAL to the extraction of Ni from FeNi alloy

Abstract

Ni has been used as a principal element especially in steel making process for decades. There are many movements to replace fuel engines with electrical machines, the demand for Ni is expected to increase and the price of it is also expected to rise. To measure up the demand, various resources of Ni are needed. In this study, the materials used were FeNi alloy with unproper size to use in industry. Among typical three processes to extract Ni from its raw materials, the high pressure acid leaching(HPAL) is adopted to get a high purity of Ni which can be used in EV market. In HPAL of FeNi alloy the optimal condition of temperature to be 250 ℃, acidity to be 1.75 mol/l with 14 liquid/solid (w/w) ratio and the addition of hydrogen peroxide to the system showed better selectivity based on [Ni+Co]/[Fe]. Shrinking core model was applied to the results to determine the rate controlling step and to evaluate the activation energy. The activation energy was evaluated based on the model which showed a high R^2 value over 0.95. It was 60.80 kJ/mol for the chemical reaction model of cylinder with k_0value of 3.812×〖10〗^5/s and 69.60 kJ/mol for the chemical reaction model of shrinking sphere with k_0 value of 6.804×〖10〗^6/s.