Biopolymer-based hydrogels for encapsulation of photocatalytic TiO2 nanoparticles prepared by the freezing/thawing method

We report a method of making biopolymer-based photocatalytic composite materials. The method is based on encapsulation of TiO2 nanoparticles into a porous polymer matrix by mixing the nanoparticles with a biopolymer, iota-carrageenan (CRG), and polyvinyl alcohol (PVA) followed by freezing/thawing cycles; the resulting material makes a stable hydrogel upon mixing with water. CRG-PVA and CRG-PVA-TiO2 hydrogels were characterized by X-ray diffraction, STEM, swelling capacity, TGA and FTIR. Mechanical properties of the gels were evaluated with use of tensile testing machine. The photocatalytic activity of the composites with concentrations of TiO2 0.25%, 0.5%, 0.75% was investigated by oxidative decomposition of organic dye, methyl orange.