Sustainable selenium remediation from water using aluminium–iron mixed oxide: Batch and column adsorption studies

Abstract

Selenium contamination of water resources has become a potential health risk issue. The application of aluminium–iron (AlFe) mixed oxide for the rapid adsorption of both selenite (IV) and selenate (VI) ions from water was studied. The synthesized AlFe mixed oxide was characterized to understand the morphological and structural properties. Batch adsorption experiments were performed to understand the adsorption performance with variable parameters. AlFe mixed oxide was found as efficient for both selenite (IV) and selenate (VI) ion adsorption over a wide pH range up to pH < 9. Adsorption experiments revealed that the dose of 0.1 g L−1 with an initial selenium concentration of 500 μg L−1 is sufficient to meet the WHO guideline value within the first 30 min of contact time. Langmuir, Temkin and Dubinin-Radushkevich (DR) adsorption isotherm and pseudo–second order kinetics presented better fitting for selenite (IV) and selenate (VI) ions with maximum adsorption capacity for Se(VI) and Se(IV) as 33.1 mg g−1 and 6.188 mg g−1 respectively. Column adsorption and regeneration were also studied to understand the practical applicability of the adsorbent. The adsorbent was regenerated using mild alkali and can further be reused without any significant decrease in adsorption efficiency.