Adsorption of Zn(II) on activated red mud: Neutralized by CO2

In this study, caustic red mud was neutralized using CO2 sequestration. Batch adsorption study was conducted to investigate the ability of activated CO2-neutralized red mud (ANRM) for the adsorption of Zn(II) ions from the aqueous solutions. The experiments were carried out with respect to adsorbent dose, pH, contact time, initial Zn(II) concentrations, kinetics, Langmuir and Freundlich isotherms. The characterization of CO2 neutralized red mud and mechanisms of Zn(II) adsorption on ANRM were studied by using TG-DSC, SEM/EDX, BET, AAS and chemical methods. Adsorption kinetic studies revealed that the adsorption process followed pseudo-second-order kinetics. The adsorption data were fitted to linearly transformed Langmuir isotherm with R2 (correlation coefficient) > 0.98.

Research Highlights► The red mud was neutralized by using carbon dioxide. ► Activated carbon dioxide- neutralized red mud was used for removal of Zn(II). ► The maximum adsorption capacity of ANRM was found to be 14.92 mg g-1. ► The adsorption process follows pseudo- second order rate equation.