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Diatomite-based recyclable photocatalysts containing single lanthanide doped TiO 2 nanoparticles (NPs) were synthesized by using simple sol–gel method. Photocatalytic activities of the prepared Ce- or La- single doped TiO 2 /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 TiO 2 for the un-doped and Ce-doped samples. The TEM images revealed uniform distribution of TiO 2 NPs on the matrix, indicating that diatomite played an important role to prevent the agglomeration of TiO 2 NPs. Ce-TiO 2 /diatomite showed a red shift in UV–visible light absorption edge with enhanced absorption intensity than un-doped sample, whereas La-TiO 2 /diatomite showed a blue shift. The bandgap energy of 1.5%-Ce doped sample is as low as 2.75 eV. The XPS spectra showed the presence of both Ce 3 + and Ce 4 + 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 Ce 4 + /Ce 3 + pairs acting as electron scavengers and localized unoccupied Ce 4 f level narrowing the band gap. The incorporation with diatomite as support of TiO 2 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. [ABSTRACT FROM AUTHOR]

Abstract: Natural porous mineral supported (TiO2/diatomite) photocatalyst was prepared via a modified sol–gel method using titanium (IV) butoxide (TBOT) and diatomite. The effect of TBOT dosage on adsorption capacity and photocatalytic activity for Rhodamine B (RhB) solution was investigated. The morphology and elemental distribution were determined by scanning electron microscopy with attached energy-dispersive X-ray detector. The porous and crystalline structures were characterized using nitrogen adsorption–desorption and X-ray diffraction techniques, respectively. The prepared TiO2/diatomite hybrid catalyst has shown relatively even porous structure and dispersion of TiO2 over the surface. This suggests that the diatomite matrix prevented the agglomeration of TiO2 particles. Initially, the surface area and pore volume of the hybrid catalyst were increased by adding TBOT then decreased for dosages higher than 1.0ml. The crystalline size of TiO2 immobilized on diatomite matrix by sol–gel method was around 20nm. When the experiments were carried out in the absence of diatomite, this value was increased to 33.73nm. The use of diatomite also promoted an increase of the transformation temperature of the crystalline phase anatase to rutile for the TiO2. The as-prepared TiO2/diatomite composite exhibited high photocatalytic activity (96.0% for 0.5h UV-light irradiation) for the degradation of RhB from wastewater as a result of its unique porous structure and optimum TiO2 loading. In addition, it can be easily separated from suspension and possess a good durability. This hybrid material holds great promise in the engineering field for the environmental remediation. [Copyright &y& Elsevier]