Optimization of Nickel Chemical Extraction from Hazardous Residue

Statistical design of experiments was used for design and analysis of nickel extraction from hazardous waste. Sulphuric acid leaching of zinc plant residue has been performed for monitoring and evaluating the effects of process factors on the nickel leaching yield. Factorial design was planned first in order to study the effect of six process factors and screen main variables. These factors were reaction time, acid concentration, solid-liquid ratio % (w/v), particle size, stirring speed and reaction temperature. The main factors and their interaction were studied by analysis of variance (ANOVA), and the results showed that the reaction time, acid concentration and solid-liquid ratio were the most significant factors. In the second set of experiments, response surface methodology (RSM) was used for modelling and optimisation of significant factors. Quadratic model was derived for the prediction of nickel extraction. The optimum values for maximum nickel was identified to be a leaching time of 30 min, acid concentration 10% (V/V) and solid liquid ratio of 10%. Using these optimum conditions, more than 94% nickel was extracted. In addition the results of model equation showed a good agreement with the experimental data.