Synthesis of anatase titanium dioxide nanostructures via chitosan-polyvinyl alcohol templating for effective reduction of hexavalent chromium

Hexavalent chromium (Cr(VI)) is a serious environmental and health problem due to its high toxicity, carcinogenicity, and mobility in aquatic systems.This study presented a new sol-gel synthesis of porous anatase titanium dioxide (TiO₂) nanostructures using chitosan and polyvinyl alcohol (PVA) as templating agents, which enhance surface area and accessibility for Cr(VI) remediation.The organic templates allow for homogenous dispersion of the titanium precursor, resulting in a gel network.Calcination at 400°C provides mesoporous TiO₂ with a BET surface area of 70 m²/g and predominant pore sizes of 2-5 nm.Raman spectroscopy identified anatase peaks at 145 cm⁻¹ and 390-640 cm⁻¹.Post-treatment spectra showed high fluorescence, indicating Cr(III) inclusion after Cr(VI) reduction.FTIR examination revealed increased hydroxyl groups and Cr-O bonds following treatment, with a shift in zeta potential from -57.2 mV to -48.1 mV, indicating Cr(III) surface adsorption and suspension stability.Under visible light, the material effectively reduces Cr(VI) to less harmful Cr(III) or other Cr-containing compounds that remain on the surface of the material.This strategy provides a low-cost, environmentally friendly option for wastewater treatment, balancing high adsorption capacity with photocatalytic effectiveness, and demonstrates the promise of biopolymer-templated nanomaterials for heavy metal remediation.