摘要： The development of highly efficient photocatalyst for oxidizing and further removing toxic As(III) from water environment remains a big challenge. Herein, mesoporous Ti0.5Sn0.5O2 (TSO-0.5) solid solution microspheres are synthesized by a facile solvothermal method and followed by annealing. The mesoporous TSO-0.5 microspheres are systematically characterized in terms of the crystalline phases, morphological, optical, photoelectric and photocatalytic properties using X-ray diffraction, scanning electron microscopy, N2 sorption-desorption, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, and electrochemical analysis. The characterizations show the TSO-0.5 are of well crystallinity, hierarchical mesoporosity, broad-light responsive capacity, large surface area, and excellent photoelectric features. Under irradiation, the mesoporous TSO-0.5 microspheres exhibit ultrahigh photocatalytic activity for methyl orange degradation (0.537 min-1?m-2, ~8 times that of TiO2) and As(III) removal (up to 98.4%). The photogenerated holes are determined to be the primary active species in the photocatalysis process of MO-degradation and As(III)-oxidation. Based the results, a possible mechanism of photo-induced charge transfer and subsequent reaction processes over the TSO-0.5 is proposed.