Synergistic photocatalytic and adsorption capabilities of ZnO/chitosan/CMC for organic dye degradation under sunlight irradiation

The bionanomaterial for wastewater treatment attracts interest due to it is nontoxic and biodegradable. However, it has limitations cause of the weak chemical interaction, narrow surface area, and reusability of this material. In this study, a novel bionanomaterial for wastewater treatment was developed using a nontoxic and biodegradable carboxymethyl cellulose (CMC) base. To overcome the limitations of weak chemical interactions affecting its adsorption capacity and reusability, chitosan (CS) and ZnO nanoparticles with photocatalytic properties were incorporated. The resulting ZnO/CS/CMC nanocomposite exhibits dual functionality as a photocatalyst and adsorbent, enhancing the removal of methylene blue (MB) from wastewater. The material's morphology and physicochemical properties were thoroughly characterized using SEM, TEM, FTIR, XRD, BET, and DLS techniques. The molar ratio of ZnO (0.5–1.5) significantly influenced the nanocomposite's characteristics, with higher ZnO ratios producing a highly homogeneous spherical morphology and increased surface area. At a ZnO ratio of 1.5, the nanocomposite achieved outstanding photocatalytic performance, degrading 99.5 % of MB in just 60 min under sunlight irradiation. Additionally, the highest adsorption capacity of 4.66 mg g⁻¹ followed the Langmuir isotherm model. This study highlights the enhanced MB removal efficiency due to the synergistic effect of ZnO particles and the supportive matrix. The developed material offers an eco-friendly, efficient, and sustainable solution for wastewater treatment, combining high performance with the benefits of biodegradability and reusability.