Sol-gel synthesis of new ZnFe2O4/Na-bentonite composites for simultaneous oxidation of RhB and reduction of Cr(VI) under visible light irradiation

To improve the photogenerated charge carrier separation and stability of ZnFe2O4, we prepared new ZnFe2O4/Na-bentonite composites using Na-bentonite as the carrier via a sol-gel method. The composition, surface morphology and optical properties of samples were characterized by XRD, TEM, XPS, FTIR and UV-vis DRS analysis. The results of TEM and XPS show that the ZnFe2O4 nanoparticles spread on the thin layers of Na-bentonite due to intercalation with Na-bentonite. The simultaneous effect of the Cr(VI)-RhB wastewater system was investigated by ZnFe2O4/Na-bentonite composites, the removal rate are 88.6% for Cr(VI) and 94.2% for RhB in 120 min, which is 1.3-fold higher of Cr(VI) reduction than that of the individual ones. Based on experimental results of PL and reactive species involved in the removal of RhB and Cr(VI), the enhanced photocatalytic activity of the new ZnFe2O4/Na-bentonite composite could be due to visible-light adsorption ability, larger interfacial area, as well as effective transfer and prolonged charge-hole separation. (C) 2018 Elsevier B.V. All rights reserved.