Facile synthesis of ZnO/RGO/Fe2O3 using macroalgae Caulerpa taxifolia as green reductor and its application as malachite green removal

This study presents the synthesis of a novel ZnO/rGO/Fe₂O₃ composite using Caulerpa taxifolia as a green reductant for the effective removal of Malachite Green from aqueous solutions. Characterization techniques, including FTIR, SEM, and XRD, confirmed the successful incorporation of ZnO and Fe₂O₃ onto the rGO matrix, enhancing its adsorption properties. The composite achieved an exceptional maximum adsorption capacity of 454.5 mg/g at pH 9, significantly outperforming rGO alone and other adsorbents. The adsorption kinetics followed a pseudo-second-order model, indicating chemisorption as the dominant mechanism, with a high correlation coefficient (R² = 0.999). The adsorption isotherms were best described by the Langmuir model, suggesting monolayer adsorption. Thermodynamic parameters revealed that the process was spontaneous and exothermic, with a Gibbs free energy (ΔGo) of -10.93 kJ/mol at 25 °C. The composite's high adsorption capacity, rapid kinetics, and favorable thermodynamics highlight its potential as an efficient and sustainable adsorbent for dye removal. This research offers a promising approach to water treatment, aligning with environmentally friendly practices and providing a viable solution for mitigating water pollution caused by organic dyes. KEY WORDS: Reduced graphene oxide, Water treatment, Caulerpa taxifolia, Isothermal and kinetic studies, Malachite Green Bull. Chem. Soc. Ethiop. 2025, 39(1), 29-47. DOI: https://dx.doi.org/10.4314/bcse.v39i1.3