LAUSR

Abstract A novel heterogeneous photocatalyst Ca x H 4-x Si 4 W 12 O 40 /Ca 2 Ta 2 O 7 was prepared by planting silicotungstic acid on the surface of calcium tantalate. The materials are characterized by X-ray diffraction (XRD), scanning electron microspectroscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transformation infrared spectroscopy (FTIR), UV–vis diffuse reflectance spectroscopy (UV–vis), Energy-dispersive X-ray spectroscopy (EDS), BET surface area, and Malvern ZEN3690 Particle Analyzer (ZP). The results recovered Ca 2 Ta 2 O 7 presented regular octahedron morphology with the cubic phase structure, and H 4 Si 4 W 12 O 40 uniformly grew on the surface of Ca 2 Ta 2 O 7 with the form of Ca x H 4-x Si 4 W 12 O 40 . The primary Keggin structures of H 4 Si 4 W 12 O 40 was found to remain intact as noticed by XRD and FTIR. The modification of H 4 Si 4 W 12 O 40 on Ca 2 Ta 2 O 7 surface contributed the increase in negative zeta potential and red shifts. The as-prepared catalyst exhibited greatly enhanced UV photocatalytic efficiency in the reduction of Cr(VI) ions as high as 94.6% under the optimum conditions (Ca 2 Ta 2 O 7 to H 4 Si 4 W 12 O 40 was 1:2). Moreover, the composite presented an excellent reusability, which was mainly ascribed to the locally formation of water-insoluble Ca x H 4-x Si 4 W 12 O 40 . A probable mechanism involved in the enhanced reducible activity and well recycled performance via Ca O binding linkage of H 4 Si 4 W 12 O 40 and Ca 2 Ta 2 O 7 is proposed by DFT simulation. This work will be significant in the design of heteropoly acid as stable heterogeneous photocatalyst applied to heavy metal ions reduction.