Photooxidation/adsorption of arsenic (III) in aqueous solution over bentonite/ chitosan/TiO2 heterostructured catalyst

Abstract

Arsenic contamination of the environment is a serious health hazard due to its toxicity and carcinogenic effects thus demanding developed and robust removal methodologies. In this study, bentonite/chitosan/titania (BT/CS-TiO₂) was developed to boost photo-oxidation/adsorption efficiency while providing a low-cost and potential heterostructured platform for arsenic removal from aqueous media. Under UV irradiation, BT/CS-TiO₂ heterostructured exhibited the desired capability (97%) of boosting oxidize toxic As^III to minor toxic As^V. Results confirmed that •OH radicals available at TiO₂ sites under UV light played a critical role in the proposed photo-oxidation process of As^III. BT/CS exhibited a high adsorption capacity (160 mg g^-1) for As^V removal due to its electrostatic interaction and surface complexation. Additionally, BT/CS-TiO₂ heterostructured showed satisfactory recyclability with no considerable interferences in the presence of coexisting anions due to the suitability of the valence band position of TiO₂ for the oxidation of As^III as well as the presence of CS into BT layers. Thereby, the findings revealed that impregnation of TiO₂ in BT/CS is a promising approach for arsenic removal.

Keywords: Adsorption; Arsenic; Bentonite/chitosan/titania; OH radicals; Photooxidation.