Sustainable and easy recoverable magnetic TiO2-Lignocellulosic Biomass@Fe3O4 for solar photocatalytic water remediation

This work was undertaken to design a magnetic TiO2 hybridized with lignocellulosic biomass (olive pits: OP) for dyes and Cr(VI) photocatalytic removal from water. Firstly, TiO2-OP was synthetized by ultrasonic-assisted sol-gel process, and then TiO2-OP@Fe3O4 was obtained via hydrothermal magnetization at 180 degrees C. Materials were characterized by XRD, BET, UV-DRS and XPS. The as-prepared photocatalysts showed a visible light responsive, wherein, Eg values are 3.20, 3.02, 3.00 and 2.55 eV for TiO2, TiO2@Fe3O4, TiO2-OP and TiO2-OP@Fe3O4, respectively. While the specific surface area values were as follows: 22.94, 15, 55.1 and 104.7 m(2)/g for TiO2, TiO2@Fe3O4, TiO2-OP and TiO2-OP@Fe3O4, respectively. Photocatalytic activities of TiO2@Fe3O4, TiO2-OP and TiO2-OP@Fe3O4 were tested for the photocatalytic removal of three dyes (Rhodamine B (RhB), Methylene blue (MB) and Congo Red (CR)) and hexavalent chromium under visible light. It was found that TiO2-OP@Fe3O4 composite exhibited higher adsorption and photocatalytic abilities compared with TiO2@Fe3O4 and TiO2-OP. The oxidation rates using TiO2-OP@Fe3O4 were 100, 75 and 81% within 1 h for MB, RhB and CR, respectively, at a dye concentration of 10 ppm and photocatalyst mass of 0.25 g/L. While the photocatalytic reduction rates of Cr(VI) (10 ppm, pH 3) were 64% (within 60 min), 70% (within 60 min) and 100% (within 40 min) by TiO2@Fe2O3, TiO2-OP and TiO2-OP@Fe3O4, respectively. The effect of pH, MB concentration, photocatalyst dose, co-presence of metallic cations and Tert-butyl alcohol concentration (as (OH)-O-center dot scavenger) on the MB oxidation was studied. Since the composite showed an excellent magnetic recoverability and high photocatalytic efficiency, it could be a potential candidate in industrial wastewater treatment. (C) 2019 Elsevier Ltd. All rights reserved.