Enhancing Degradation of Methyl Orange Dye Using Green Zinc Oxide Nanoparticles Synthesized with Exopolysaccharides (EPS) Extracted from Cyanobacterial Mats

Abstract In response to growing global concern regarding the environmental impacts of organic dye contamination in surface water, we present a novel approach utilizes zinc oxide nanoparticles (ZnO NPs) doped with exopolysaccharides (EPS) derived from cyanobacterial biomass to degrade the methyl orange (MO) dye. Our study demonstrates that incorporation of EPS extracted from cyanobacteria enhances the photodegradation efficiency of ZnO NPs. The physical characterization of the prepared catalyst NPs involved comprehensive analysis of their structural, morphological, and compositional properties through scanning and transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and UV‒Vis spectrophotometry to understand the synergistic effects of ZnO and EPS in enhancing the photocatalytic performance against methyl orange dye. MO dye more strongly degraded (q max = 49.1 mg/g) by ZnO@EPS NPs than pure ZnO NPs (q max = 40.9 mg/g) under optimal conditions (pH = 7, catalyst dose = 0.25 g/L, initial MO concentration = 100 mg/L and contact time = 90 min). Isothermal studies indicated that the Freundlich isotherm model (R 2 > 0.99) fit better than the Langmuir model (R 2 = 0.88). Kinetically, the photodegradation of MO dye adhered to pseudo-second-order models, exhibiting C e values between 40.9 and 49.1 mg/g and R 2 > 0.99.