Synergistic photocatalytic and adsorptive removal of organic dyes using ZnO-Fe2O3 nanoparticles incorporated into guar gum-carboxymethyl cellulose biopolymer matrix.

A novel GGCMC@ZnO-Fe2O3 nanocomposite was green-synthesized using Murraya koenigii leaf extract and incorporated into a guar gum-carboxymethyl cellulose (GGCMC) biopolymer matrix for efficient photocatalytic degradation of organic dyes under natural sunlight. Structural and morphological analysis confirmed nanoscale crystallinity and homogeneous dispersion of metal oxides within the hydrogel framework. Optical characterization revealed enhanced visible-light absorption and reduced electron-hole (e-- h+ pairs) recombination. The effects of key operational parameters- including pollutant concentration, catalyst dosage, solution pH, and irradiation source- were systematically examined. Optimal conditions yielded degradation efficiencies of 95 % for methylene blue (MB) and 92 % for crystal Violet (CV) within 120 min. Kinetic modeling showed that the degradation followed first-order kinetics (R2 > 0.98), whereas, adsorption isotherm studies revealed a strong fit to the Langmuir model, indicating monolayer adsorption prior to photocatalysis. Radical scavenging experiments indicated that hydroxyl radicals (·OH) played a dominant role in the degradation of MB, while superoxide radicals (O2·-) played a dominant role in the degradation of CV. The nanocomposite demonstrated excellent reusability, maintaining photocatalytic performance over six consecutive cycles with minimal loss in activity. These findings suggest that the GGCMC@ZnO-Fe2O3 nanocomposite is a sustainable and efficient photocatalyst with significant potential for environmental remediation of dye-contaminated wastewater.