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Abstract: Nano titanium dioxide (TiO2) photocatalyst is generally immobilized onto the matrix through the physical absorption, hydrogen bonding or chemical bonding, which is utilized for the application of wastewater treatment. In this research, TiO2 nanoparticles were immobilized in polyvinyl alcohol (PVA) matrix via solution-casting combined with heat-treatment method. Structure characterization indicated that Tih name="sbnd" />C chemical bond formed via dehydration reaction between TiO2 and PVA during the heat treatment process, and TiO2 nanoparticles had been chemically immobilized in PVA matrix. Photodegradation results of methyl orange (MO) showed that the film with 10wt% TiO2 and treated at 140°C for 2h exhibited a remarkable ultraviolet (UV) photocatalytic activity, approximately close to the TiO2 slurry system. This was mainly attributed to the fixation effect by Tih name="sbnd" />C chemical bonds, which was indirectly confirmed by the slight loss of TiO2 photocatalysts even after 25-cycle use. In addition, the good swelling ability of PVA matrix provided the MO molecules with more opportunities to fully contact with TiO2, thus benefited the photocatalysis. This route to chemically immobilize TiO2 nanoparticles is simple and cheap to prepare polymer/TiO2 hybrid materials with high photocatalytic activity for multi-cycle use, which is of significance to the practical application of TiO2 catalysts. [Copyright &y& Elsevier]

Abstract: Four types of soil clays from different sites in China have been chosen to simulate chemical remediation of soils contaminated with dyes by light-assisted Fenton-like method. X-Ray diffraction (XRD), X-ray photoelectron spectroscopic (XPS) and electron spin resonance (ESR) measurements indicated that these soil clays contain iron oxides such as magnetite and hematite, where nondistorted iron active sites (ESR spectra, g =2.3) predominate. Upon visible or UV irradiation, the soil clays were very effective for the degradation of nonbiodegradable cationic dyes such as Rhodamine B (RhB) by activating H2O2 at neutral pH. The photodegradation rates of RhB were closely related to total Fe content in clays and H2O2 dosage, indicating the mineral-catalyzed Fenton-like reactions operated. Soil organic matters (SOM) would remarkably inhibit the photodecomposition of RhB dye. The reaction products were some low-molecular-weight dicarboxylic acids and their derivatives, all of which are easily biodegradable. A possible mechanism was proposed based on the results obtained by spin-trapping ESR technique. [Copyright &y& Elsevier]