Activation and β-FeOOH modification of sepiolite in one-step hydrothermal reaction and its simulated solar light catalytic reduction of Cr(VI)

A simple one-step hydrothermal reaction was used to successfully activate and modify original sepiolite. The as-prepared sepiolite/β-FeOOH composites were characterized by X-ray diffractions, Fourier transform infrared spectrum, specific surface area, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities were evaluated by the Cr(VI) reduction efficiency in the presence of tartaric acid under simulated solar light illumination. The results show that the most optimal amount of iron modification on the surface of sepiolite was 2.8 mmol Fe3 +/g sepiolite in the reaction dispersion. The developed sepiolite/20β-FeOOH catalyst exhibited outstanding photocatalytic performance with complete Cr(VI) reduction of after irradiation of 10 min under the test condition of c (Cr(VI)) = 100 mM, catalyst dosage = 400 mg/L, c (tartaric acid) = 40 mM and initial pH = 5. The XPS analysis verified that Cr(VI) adsorption also contributed to the Cr(VI) removal from the aqueous solution. The effects of test parameters, such as initial pH of suspension, catalyst dosage and tartaric acid concentration on Cr(VI) photocatalytic reduction rates were investigated. It has to be noted that the synthesized sepiolite/20β-FeOOH catalyst can be effective in a wide range of pH with quite good catalytic performance.