Solar Light Assisted Photocatalytic Degradation of Malachite Green Dye using CoO/BiVO4 Nanocomposite: Kinetics and Mechanism Studies

Abstract

Water pollution caused by dye discharge is a critical environmental concern, driving the exploration of efficient wastewater treatment methods using nanocomposites. This study presents the synthesis of a CoO/BiVO₄ nanocomposite, with CoO and BiVO₄ prepared through the co-precipitation process. The structural, morphological and optical properties of the synthesized catalyst were characterized using XRD, FESEM and UV-DRS analyses. The band gap energies, determined from Tauc’s plot, were found to be 2.9 eV for pristine BiVO₄ and 2.5 eV for the CoO/BiVO₄ nanocomposite, indicating enhanced light absorption. The photocatalytic performance of the nanocomposite was evaluated by degrading malachite green dye under solar irradiation. Various parameters, including pH, catalyst dosage, dye concentration and irradiation time, were optimized to maximize degradation efficiency. The nanocomposite achieved 84% dye degradation at pH ~ 7 using 40 mg of catalyst on a 40 ppm dye solution within 80 min of solar exposure. Kinetic analysis revealed that the degradation followed a pseudo-first-order kinetic model. Moreover, the reusability of the catalyst was confirmed, showing stable performance even after five consecutive cycles. The findings highlight the potential of the CoO/BiVO₄ nanocomposite as a sustainable photocatalyst for effective dye degradation in wastewater treatment applications under solar light.