Enhanced photocatalytic properties of reusable TiO2-loaded natural porous minerals in dye wastewater purification

Abstract

Diatomite-based recyclable photocatalysts containing single lanthanide doped TiO2 nanoparticles (NPs) were synthesized by using simple sol–gel method. Photocatalytic activities of the prepared Ce- or La- single doped TiO2/diatomite catalysts were estimated by the degradation of Rhodamine B (RhB) under simulated sunlight irradiation. The XRD and Raman spectra shown only anatase phase of TiO2 for the un-doped and Ce-doped samples. The TEM images revealed uniform distribution of TiO2 NPs on the matrix, indicating that diatomite played an important role to prevent the agglomeration of TiO2 NPs. Ce-TiO2/diatomite showed a red shift in UV–visible light absorption edge with enhanced absorption intensity than un-doped sample, whereas La-TiO2/diatomite showed a blue shift. The bandgap energy of 1.5%-Ce doped sample is as low as 2.75eV. The XPS spectra showed the presence of both Ce3+ and Ce4+ oxidation states for Ce dopant. The photoluminescence spectra of the Ce-doped samples showed first decrease in the recombination centers with the maximum decrease for 1.5%-Ce doped sample and then started increase with the increasing Ce in the samples. As compared to the La-doped samples, a desired behavior was observed for the Ce-doped hybrid due to the redox Ce4+/Ce3+ pairs acting as electron scavengers and localized unoccupied Ce 4f level narrowing the band gap. The incorporation with diatomite as support of TiO2 nanoparticles is contributed for the improved reusability and also gives a promising strategy to enable the application of nano-photocatalysts in a real wastewater remediation treatment.