Enhanced Photocatalytic Degradation of Malachite Green Dye Using Novel, Visible-Light-Active Ternary Magnetic Cellulose Nanofiber/Graphene Oxide Nanocatalyst: RSM Optimization

Herein, a visible light-active, facile, ternary magnetic MCNFs/GO nanocatalyst comprising enzyme-extracted-cellulose nanofibers, graphene oxide, and iron oxide nanoparticles for effective degradation of malachite green (MG) dye is reported. The nanocatalyst was characterized using Fourier transform infrared spectroscopy, X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, dynamic light scattering, thermogravimetric analysis, vibrating sample magnetometry, Brunauer-Emmett-Teller analysis, and UV-diffuse reflectance spectroscopy. The nanocatalyst exhibited an average diameter of 19.93 ± 0.94 nm, a high surface area of 212.39 m² g^-1, paramagnetic properties, and a band gap energy of 1.8 eV. The nanocatalyst was successfully demonstrated to photodegrade MG dye from the aqueous solution with a maximum 99.01% removal percentage at a nanocatalyst dose of 122.93 mg, MG dye concentration of 11.06 mg/L, pH = 6.37, irradiation time of 32 min, and constant agitation at room temperature using the central composite design approach of response surface methodology. The equilibrium data were best characterized by the Langmuir isotherm model, and the pseudo-second-order kinetic model was found to describe the degradation kinetics. Liquid chromatography-mass spectrometry analysis confirmed complete mineralization of dye, with the degradation pathways identified. The nanocatalyst also demonstrated high MG dye degradation in real wastewater samples, with more than 96% recyclability during seven consecutive degradation cycles, indicating its stability and reusability. The augmented photodegradation efficiency of the MCNFs/GO nanocatalyst may be attributed to synergistic interactions of three components, resulting in a highly efficient photocatalyst for real-world wastewater treatment.