Abstract

Photocatalytic oxidation technology is one of the most efficient and green methods to convert highly toxic As(III) into lowly toxic As(V) for arsenic-polluted wastewater. However, the obtained As(V) may be reduced to As(III) again in the environment, causing secondary pollution. In order to resolve these issues, a bifunctional composite consisting of needle-like α-FeOOH-modified Sn/N-codoped TiO2 granules (SNT-FeOOH) has been synthesized. After modifying, the band gap of SNT-FeOOH narrowed from 2.94 eV (SNT) to 2.29 eV. When the composites were applied to As(III) removal, 10 mg of SNT-FeOOH could totally photocatalytically oxidize 40 mL of As(III) solution with a concentration of 10,000 μg/L within 15 min and synchronously achieve complete adsorption of the produced As(V), which is much more efficient than pure Sn/N-codoped TiO2 [21 min for As(III) photocatalytic oxidation and only 20.01% of total arsenic removal efficiency]. Based on the characterizations, α-FeOOH modification plays a significant role in the promoted performances of photocatalytic oxidation and adsorption of SNT-FeOOH, leading to arsenic removal. On one hand, the Fe-O-Ti interfacial chemical interactions formed between α-FeOOH and Sn/N-codoped TiO2 can further boost the separation rate of photogenerated carriers, hence increasing the photocatalytic oxidation efficiency. On the other hand, α-FeOOH surface hydroxyl groups adsorb the generated As(V) by forming Fe-O-As bonds. The SNT-FeOOH bifunctional composites, prepared in this paper, with dual performances of photocatalytic oxidation and adsorption provide a new strategy to achieve arsenic removal from wastewater.

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