Statistical Modeling of Oxalic Acid Adsorption on Rice Bran Using Response Surface Methodology–Box–Behnken Design

This study investigates the adsorption of oxalic acid by rice bran, a low-cost bioresource. Fifteen adsorption experiments were conducted under conditions specified by Response Surface Methodology (RSM) using the Box–Behnken Design (BBD). A three-level Box-Behnken experimental design incorporating three factors (temperature, biosorbent mass, and contact time) was applied. A quadratic mathematical model was developed to predict the responses. Analysis of variance (ANOVA) indicated that temperature significantly affects oxalic acid adsorption. A decrease in temperature corresponded with an increased oxalic acid removal rate. The best conditions for removing oxalic acid were determined, achieving a maximum removal rate of 100% at a temperature of 301.15 K with 5 grams of biosorbent and a contact time of 45 minutes. Kinetic analysis showed that the adsorption of oxalic acid on rice bran follows the pseudo-second-order kinetic model, demonstrating rice bran's effectiveness as a biosorbent in this process.