Arsenic contamination in groundwater and soil has become a serious health risk to human body. Among different arsenic oxidation states, arsenite (As(III)) is more toxic than arsenate (As(V)) due to its high mobility and low affinity for adsorbents, which brings about high persistence during water treatment. Therefore, the development for efficient conversion of As(III) into As(V) has been highly required to reduce toxicity and enhance immobilization into adsorbents. In this respects, TiO2-based photocatalytic oxidation of As(III) has some advantages for practical utilization in that i) any chemical oxidants are not required, ii) true catalytic driving force comes from continuous light irradiation, iii) materials are not expensive, and iv) it is environmentally benign process. Herein, the hybridization of reduced graphene oxide (rGO) with TiO2 significantly enhances the photocatalytic arsenic oxidation under UV irradiation. Similar to the role of Pt cocatalyst on TiO2, the presence of rGO accelerates electron transfer from TiO2 conduction band to dissolved oxygen and effectively prohibits an As(III) mediated recombination cycle. Although the photocatalytic As(III) oxidation mechanism is still controversial what reactive oxygen species (ROS) are directly involved, this report clearly demonstrates that not only superoxide but also hydroxyl radicals (or hole) are involved in As(III) photo-oxidation in the presence of rGO as a cocatalyst. The result is completely different with bare TiO2 system in that the superoxide radical is the sole As(III) oxidant, which implies that the photocatalytic mechanism for As(III) oxidation can be changed via the modification of TiO2. The cost-effective and eco-friendly synthesis of rGO-based composites in combination with their efficient photocatalytic performance provides a practical alternative for development of solar-assisted arsenic treatment technologies.

Highly enhanced photocatalytic oxidation of arsenite (As(III)) to arsenate (As(V)) via hybridization of reduced graphene oxide with TiO<sub>2</sub> nanoparticles and its mechanistic investigation

246th National Meeting (2013)

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Highly enhanced photocatalytic oxidation of arsenite (As(III)) to arsenate (As(V)) via hybridization of reduced graphene oxide with TiO2 nanoparticles and its mechanistic investigation

Highly enhanced photocatalytic oxidation of arsenite (As(III)) to arsenate (As(V)) via hybridization of reduced graphene oxide with TiO₂ nanoparticles and its mechanistic investigation