Design of experiments to study the extraction of nickel from lateritic ore by sulphatization using sulphuric acid

Experiments were designed to optimize the sulphatization of a mechanical mixture of chemically pure nickel and iron oxide and a lateritic ore using sulphuric acid. The significance of various parameters and their selectivity for nickel extraction over iron have been established. The interaction among the operating parameters has been studied using statistically designed experiments and the data, thus obtained for the pure system, was correlated with that for the lateritic ore. Regression equations were formulated for both systems and the extraction was represented as a function of response variables. The accuracy of the equation has been verified by Fisherʹs adequacy test. It was observed that the coefficient of temperature was the most dominant, followed by acid concentration. Interestingly, the time factor induces a small effect on extraction. The process has been further optimised using the steepest ascent method.