Improved photocatalytic oxidation of arsenic (III) with WO3/TiO2 nanomaterials synthesized by the sol-gel method

Photocatalytic oxidation of arsenite (As(III)) to arsenate (As(V)) was studied in aqueous solution using a series of WO3/TiO2 semiconductors readily synthesized through sol-gel method with WO3 content in the range of 1-5 wt%. The resulting materials showed enhanced photocatalytic activity towards As(III) photo-oxidation compared to their individual counterparts under UV radiation. The amount of As(III) and As(V) species in the irradiated solution was determined using the molybdenum blue method. The efficiency of photoinduced carriers separation was further affirmed by electrical impedance spectroscopy (EIS) and photocurrent tests. The maximum catalytic efficiency was observed when the binary oxide 3%WO3/TiO2 (TW3) was used, reaching a 99% conversion of As(III) to As(V) within the first 25 min under UV irradiation. The enhanced photocatalytic performance of the heterostructures could be explained as consequent to an improved charge separation due to the migration of photoproduced holes in TW3 photocatalyst. Based on the electric band structure of WO3 and TiO2, a reasonable mechanism for the photo-oxidation of As(III) over TW3 novel catalyst has been proposed. •WO3/TiO2 nanomaterials were prepared for As(III) photo-oxidation.•Enhanced photo-oxidation of As(III) correlates to efficient transfer of generated charges at the interface of TiO2 and WO3.•Mott−Schottky experiment was performed to determine the relative positions of CB and VB edges in the materials.•A maximum of 99% oxidation efficiency of As(III) was recorded in the presence of UV light and pH = 7.•Addition of WO3 improved significantly the photo-oxidation capacity of bare TiO2.