Removal of Sulphate from Drinking Water Sources Using H3PO4—Chakhao Rice Husk Activated Carbon (CHAC): A Comprehensive Adsorption Study

Abstract

The present study investigated the adsorption efficiency of H₃PO₄ activated Chakhao rice husk activated carbon (CHAC) to remove sulphate ions (\({\text{SO}}_{4}^{{2 - }}\)) from an aqueous solution. The study’s finding highlighted 96.62% as the removal efficiency of sulphate ions using a dosage of 4 g/L of CHAC for a 60 s retention period. Moreover, the research findings illustrate that the highest removal of sulphate ions by adsorption occurs at the pH condition of 7. The study indicates that the presence of interfering anions such as phosphate, nitrate, chloride, fluoride, and bicarbonate notably impact the adsorption phenomenon of sulphate ions by CHAC. The study of various kinetic models, including the pseudo-first-order, pseudo-second-order, intra-particle diffusion, Bangham’s pore diffusion, and Elovich’s equation, illustrated the chemical kinetics of the adsorption phenomenon of CHAC. It was observed that the pseudo-second-order model demonstrated the most accurate fit for the kinetics studies with the r² value of 0.999. The experimental study also underwent analysis using various adsorption isotherm models, and the findings of the study highlight that the adsorption aligns more effectively with the Freundlich model, offering a superior fit for the equilibrium data.