Absorptive Removal of Palm Oil Free Fatty Acids Onto Silica/smectite Composite: A Statistical Study using Box-Behnken Design in Response Surface Methodology

Abstract

Response Surface Methodology was used to evaluate the main and interactions effects of contact time (20–60 min), temperature (60–90°C) and adsorbent dosage (1–2%) of the palm oil free fatty acids (FFAs) adsorption onto a silica/smectite composite. The regression model was found to be able to predict more than 99% of the targeted response variation in the studied range (R2 = 99.31%). An ANOVA was used to evaluate the accuracy of the regression model and it was found to predict more than 99% of the response variation. The Pareto Charts of Standardized Effects showed that almost all the explanatory factors were influential. The factorial plots evidenced that time/temperature interaction was most effective and the corresponding contour and surface plots were drawn. The second-order kinetic model was better followed with the highest value of the determination coefficient (R2 = 0.996) and the lowest value of Root Mean Square Deviation of 0.555. Response Optimizer Function showed an optimum for FFAs removal of more than 90% (27.18 mg of KOH/g) at the adsorbent dosage of 2%, contact time of 60 min, and temperature of 90°C. Moreover, a good correlation between the predicted and experimental values was observed within reasonable limits.