La-doped Al2O3/g-C3N4 /agarose aerogel for removal of As(III) via simultaneous photocatalytic oxidation and adsorption

Abstract

Attributing to its ubiquitous nature, arsenic (As) is frequently detected in various waterbodies across the globe, at concentrations often exceeding the permissible limits. In view of the acute and chronic toxicity of the arsenite species (As(III)), it is highly recommended to remove As(III) from aqueous matrices. Herein, we propose a agarose-based La-doped Al2O3/g-C3N4 (LAC) aerogel as a novel adsorptive photocatalyst for removal of As(III) via the synergistic effect of adsorption and photocatalysis. While g-C3N4 could transform As(III) to As(V) through photocatalytic oxidation, La-doped Al2O3 provided strong adsorption sites for the resulting As(V). Accordingly, the combination of adsorption and photocatalytic transformation of highly toxic As(III) into less toxic As(V), followed by subsequent adsorption of the latter can be considered as a promising technique to treat arsenic-contaminated water. The as-prepared aerogel was successfully characterized via a range of state-of-the-art microscopy, spectroscopy, and surface-specific analytical techniques. The optimized aerogel demonstrated a removal efficiency of 66.5% after 300 min of UV light irradiation. Furthermore, evaluating the effects of various reactive oxygen species via free-radical quenching experiments revealed that superoxide radicles (•O2−), singlet oxygen (1O2), and holes (h+) played a role key in the photocatalytic oxidation of As(III). More importantly, the LAC aerogel was structurally resilient and can be reused over multiple cycles, without any significant loss of the desired functionalities. Based on these deliberations, the integration of g-C3N4 with La-Al2O3 in the form of aerogel can be considered as a prospective strategy for the removal of arsenic from aqueous phase.