Mechanical activation of anatase as a way to improve hexavalent chromium removal from solutions by the photoreduction and adsorption under near visible LED irradiation

Abstract

Bifunctional as a photocatalyst and a sorbent material was obtained by easily accessible mechanical activation of commercially available anatase powder. The resulting powders were characterized by SEM, HRTEM, Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ESR. The material made it possible to eliminate completely both chromium (VI) and total chromium from its 10 mg/L aqueous solutions under the illumination with 400 nm LED for 15–60 min, depending on the dose. It is shown that the mechanical activation by the selected mode, in contrast to some literature data, improves both the adsorption and photocatalytic properties of TiO2. Cr(VI) photoreduction rate constant increased by 8 times. There is also a change in its physicochemical properties: a 5-fold reduction in the average crystallites size, a 3.7-fold increase in the specific surface area, a change in the phase composition, and a rise of a visible light absorbance.