ZnO /Gelatin Hydrogel Composite via a Green Approach for Dye‐Contaminated Wastewater Treatment

Hydrogels were prepared using the biodegradable polymers gelatin and poly(vinyl alcohol) (PVA) to substitute up to 80 wt% of polyacrylamide. Scanning electron microscopy revealed that the addition of gelatin altered the network structure. The pore size strongly affected absorption capacity. The hydrogel (G30) containing 60 wt% of gelatin and PVA absorbed 2000% of its dry weight in water due to the excellent hydrophilicity of the polymers. Dye adsorption was favorable towards cationic dyes. Adsorption occurred via chemical interactions between polymer functional groups and dyes, with a maximum adsorption capacity for methylene blue (MB) of 381 mg/g. The hydrogel could also adsorb Zn 2+ ions, which were transformed into a ZnO photocatalyst using an aqueous wood ash extract. X‐ray diffractometry indicated a hexagonal wurtzite ZnO structure in the G30 matrix. The ZnO particles enhanced the thermal stability of the polymer matrix and introduced photocatalytic functionality. Under UV irradiation, 81% of MB adsorbed in the hydrogel was decolorized, indicating photodegradation. The hydrogel composite was reusable for at least five cycles while maintaining its structural stability due to strong interactions between the polymers and inorganic particles. The proposed material integrates synergistic adsorption and photocatalytic degradation properties suitable for wastewater treatment, while reducing secondary waste generation.