Modified TiO₂/chitosan-based hydrogel beads for the photocatalytic degradation of dyes and heavy metals for water treatment

Photocatalytic degradation has gained significant attention in treating water as an eco-friendly method and cost-effective solution. Titanium dioxide (TiO₂) is one of the most efficient and non-toxic photocatalysts used in water treatment. The main obstacle facing TiO₂ being applied on a large scale is requiring high light energy, mainly in the ultraviolet region (only 5% of sunlight), to activate the photocatalysts. Lowering the band gap of TiO₂ nanoparticles makes them easily activated by sunlight. Oxygen vacancies (OVs) or Ti³⁺-rich TiO₂ can have a lower band gap and enhance performance. Titanium hydroxide was calcinated in a vacuum to obtain modified TiO₂ and then immobilized in chitosan hydrogel as a great self-healable supporter with high availability and antimicrobial behavior. Characterization was done by using XRD and UV–visible absorbance spectroscopy. Photocatalytic studies were constructed on C.I. Acid Blue 324 as a model for dyes and on Pb, Cu, Cd, and Ni as models for heavy metals using modified-TiO₂ and white-TiO₂ encapsulated in chitosan beads separately under sunlight. The modified TiO₂\chitosan composite has a higher degrading ability than the white one. The study is considered a first step toward making a lifelong solution for water treatment with no power consumption.