Optimization of combined microwave pretreatment–magnetic separation parameters of ilmenite using response surface methodology

The paper addresses the effect of three major influencing parameters, microwave power, time and mass of sample on the combined microwave pretreatment and magnetic separation of ilmenite through application of process optimization technique response surface methodology. The experimental data obtained were fitted into a quadratic polynomial model using multiple regression analysis and were analyzed by the method of least squares. It was found that microwave power and time were the most significant factors affecting the recovery ratio while the mass of sample was found to be an insignificant parameter. The optimum process conditions were determined by analyzing response surface plots and by solving the regression model equation. Based on the analysis of variance (ANOVA) and the coefficient of determination (R2 = 0.9410), the model was found to be in good agreement with the experimental data. The optimum experiment conditions were found to be 2400 W of microwave power, 30.11 min of time and 44.80 g of sample mass, resulting in an experimental recovery ratio of 68.73%, as compared to the model prediction of 69.15%. The crystal structures of the samples were characterized before and after microwave pretreatment using X-ray diffraction (XRD).