Removal of arsenic from drinking water by photo‐catalytic oxidation on MoOx/TiO2 and adsorption on γ‐Al2O3

BACKGROUND: A typical approach for removing As from drinking water includes a pre‐oxidation step to transform the more toxic As(III) to As(V) and a subsequent separation process for As(V) removal. Unfortunately, typical oxidants result in the formation of toxic oxidation by‐products, so alternative options, such as TiO₂ photocatalysis, have been investigated. But As(V) produced by oxidation of As (III) remains adsorbed on the catalyst surface, thus limiting process efficiency. In this work a new catalyst based on molybdenum oxide supported on titania (MoOₓ/TiO₂) was investigated to overcome this drawback. RESULTS: The complete photocatalytic oxidation of As(III) (5 mg L⁻¹) to As(V) took place after 120 min exposure to UV‐A light. Moreover, the removal of As(V) by adsorption treatment downstream of the photocatalytic process was more effective (90% by γ‐Al₂O₃ after 10 min) compared with the combined photocatalysis–adsorption process. Finally, the experimental set‐up with UV LED irradiation was found to be more effective (96% As(III) converted) than the UV‐A light system (75% As(III) converted). CONCLUSION: Photocatalytst did not adsorb As(V) which was completely released into the solution, thus preserving its surface activity and, consequently, drastically reducing operating costs related to catalyst reactivation. © 2014 Society of Chemical Industry