Facile synthesis of TiO₂/Chitosan nanohybrid for adsorption-assisted rapid photodegradation of an azo dye in water

A series of bifunctional nanohybrids containing different proportions of chitosan and titanium dioxide (TiO₂) were prepared through precipitation technique and applied for removal of a model anionic azo dye, Remazol Orange 3R (RO), from aqueous solution. This study reveals the dual benefit of adsorption and photocatalytic degradation of RO by TiO₂/Chitosan nanohybrids. Nanohybrid fabricated from 80% TiO₂ (w/w) and 20% chitosan (w/w) termed as T_0.80CS_0.20 removed ∼98.8% RO within only 8 min at pH 2.0 under sunlight irradiation from 60 mg L⁻¹ dye solution. This was mainly due to the simultaneous role of adsorption and photodegradation activities of nanohybrids. The adsorption performance of T_0.80CS_0.20 was investigated in terms of the Langmuir isotherm under dark and the maximum adsorption capacity of T_0.80CS_0.20 for RO was found to be 243.9 mg g⁻¹. Electrostatic interaction was suggested as a plausible mechanism for RO adsorption whereas photogenerated holes controlled photocatalytic degradation of RO by producing sufficient quantities of different radical species. In addition, T_0.80CS_0.20 can be regenerated for removal of RO by simple alkali washing. Therefore, T_0.80CS_0.20 is recommended as a promising photocatalyst for the removal of RO dye from water.