Fluoride removal from drinking water using regenerated aluminum oxide coated media

• Potential readily available and low cost fluoride removal adsorbents have been developed.
• Aluminium oxide coated charcoal has higher fluoride removal potential than aluminium oxide coated bauxite.
• Regenerated aluminium oxide coated charcoal has shown improved fluoride removal capacity.
• Regeneration of exhausted potential adsorbents still remains a grey area to investigate.
• The study showcases a functional protocol to regenerate a potential adsorbent and its capacity.
• The stabilization of the toxic exhausted adsorbent has been investigated and the probability of leaching upon disposal has been determined.

Studies conducted in the past have shown aluminum oxide coated bauxite (AOCB) and aluminum oxide coated charcoal (AOCC) as versatile and potential fluoride adsorbents. This study focused on the feasibility of regenerating AOCB and AOCC by recoating and stabilizing the exhausted media. Using bench scale and short column experiments the adsorption capacities, kinetics and filter run times of the fluoride removal process were determined. The toxicity and leaching of the adsorbed fluoride from exhausted adsorbents were also investigated. Recoating of exhausted AOCC and AOCB in order to regenerate them was feasible empirically with three regeneration cycles. The fluoride adsorption capacities of the AOCC and AOCB were restored and even increased after the first episode of regeneration. The adsorption capacity of the AOCC was 1.5 times greater than that of the AOCB. In the column experiments AOCC1 and AOCB1 showcased longer filter run times. The aluminum oxide coated onto all exhausted media was stable and did not leach into solution.