Response surface design for nickel recovery from laterite by sulfation-roasting-leaching process

The present study deals with the nickel extraction and iron dissolution from nickeliferous laterite by a process of sulfation-roasting-leaching. To optimize the roasting process, response surface methodology (RSM) was utilized which employed two-level and two-factor full factorial central composite design (CCD). The factors of roasting temperature and time were studied. Experiments were carried out for fitting two non-linear regression models of nickel extraction and iron dissolution. Predicted values obtained were close to experimental values, indicating the suitability of the models. Three-dimensional surface plots and contour plot were helpful to predicting the results by performing only limited set of experiments. An area of nickel extraction from 75% to 78% and iron dissolution from 5% to 10% is obtained by an overlaid contour plot. The samples roasted at different temperatures and for different durations were characterized by XRD, which show a good agreement to iron dissolution analysis.