Mesoporous La/Mg/Si-incorporated palm shell activated carbon for the highly efficient removal of aluminum and fluoride from water

Abstract

Abstract A novel La/Mg/Si-loaded, palm shell-based activated carbon (LMSAC) for the selective removal of aluminum and fluoride from water was synthesized through various methods. FESEM/EDX, BET, XRD, and FT-IR were utilized to characterize the synthetic LMSACs and investigate the aluminum and fluoride adsorption mechanisms of LMSAC prepared by sonication followed by calcination (LMSAC8). The adsorption kinetics, isotherms, and effects of pH and competing ions on the aluminum and fluoride uptake by LMSAC8 were evaluated. The maximum aluminum and fluoride adsorption capacities of LMSAC8 were 270.3 mg Al/g and 285.7 mg F/g at pH 7.0, respectively, which are much higher than those of the various adsorbents reported in the literature. Adsorption was highly dependent on the pH, which determines the distribution of aluminum and fluoride species in the solution. When common ions were present, LMSAC8 still exhibited good selectivity for aluminum and fluoride at a neutral pH. The aluminum and fluoride adsorption capacities of the regenerated LMSAC8 approached 80.7 and 77.0% of those of the fresh LMSAC8 after the five recycles. The adsorption experiments and FT-IR analysis revealed that the uptake of aluminum and fluoride can be attributed to complicated processes, including electrostatic interaction, inner sphere complexation via a ligand–exchange, and Lewis acid–base interactions.