Increasing the phenol adsorption capacity of neutralized red mud by application of acid activation procedure

The objective of this study was to investigate the removal of phenol from aqueous solution by using acid activated red mud in batch adsorption experiments. The study was carried out as functions of pH, contact time, activated red mud dosage and initial phenol concentration. It was found that the maximum removal was obtained at pH below 8 and the adsorption equilibrium time was 10 h. Adsorption was followed the pseudo second-order kinetic model. According to the coefficient of determination and non-linear regression analysis carried out by Chisquare test, the Langmuir isotherm better represented the adsorption data in comparison to the Freundlich isotherm. The phenol adsorption capacity of the activated red mud (8.156 mg/g) was found to be higher than that of the neutralized red mud (4.127 mg/g) at pH 6 and 25±1°C. Negative ΔG0 value (–22.692 kJ/mol) indicated that the adsorption of phenol onto the activated red mud was spontaneous and feasible process.