Preparation of renewable porous TiO2/PVA composite sphere as photocatalyst for methyl orange degradation.

Firstly, preparation of porous polyvinyl alcohol (PVA) spheres were investigated in detail by phase inversion method using N,N-dimethylacetamide (DMAc) and polyvinylpyrrolidone (PVP) as pore-forming additives. The morphology and pore structure of PVA spheres were characterized by SEM and BET measurements. It was found that the addition of DMAc and PVP increased the pore volume and the surface pore size of PVA sphere respectively. The maximum surface area of the porous PVA sphere reached 220 m²/g. Secondly; the synthesis of photoactive TiO₂ NPs (anatase type) at the low temperature was developed by controlling the aging process of the TiO₂ precursors. The crystallinity and photoactivity of TiO₂ NPs increased with the aging time. Finally, TiO₂ NPs/PVA composite spheres were prepared by immersing PVA sphere into TiO₂ precursor solution. Their structures were characterized by XRD pattern, TEM and TGA measurement. It was found that TiO₂ NPs were successfully immobilized into PVA spheres. The photodegradation of methyl orange (MO) under UV light by TiO₂/PVA spheres showed a good photocatalytic efficiency. Moreover, TiO₂/PVA spheres can be easily regenerated by the repeated immersion process. Overall, the porous TiO₂/PVA sphere displays a good photoactive property and an advantage of easier recovery, which facilitates its application in large-scale wastewater treatment. [ABSTRACT FROM AUTHOR]