Sustainable Cu@CoFe₂O₄/SGCN Heterojunction Photocatalysts for Solar-Driven Degradation of Methylene Blue and Antifungal Potential

Ecosystems and people are in danger from organic dye contamination in water bodies, which calls for creative approaches to water purification. Using a straightforward co-precipitation technique, we synthesized a new copper-doped cobalt ferrite composite with sulfur-doped graphitic carbon nitride (Cu@CoFe₂O₄/S-g-C₃N₄) heterojunction nanocomposite in this work. The composite was systematically characterized using XRD, FTIR, BET surface area analysis, SEM, TEM, UV-Vis DRS, and PL spectroscopy to reveal its structural and optical properties. BET analysis confirmed a surface area of 85.4 m²/g, contributing to improved photocatalytic action. The photocatalytic efficiency was assessed using methylene blue (MB) as a model pollutant under solar radiation. Among the synthesized materials, the optimized Cu@CoFe₂O₄/S-g-C₃N₄ NC demonstrated outstanding performance, achieving 97% degradation of MB within 120 min, with a degradation rate constant of 0.032 min⁻¹, approximately 3.5 times higher than pristine g-C₃N₄ (0.009 min⁻¹) and 2.8 times higher than Cu@CoFe₂O₄ (0.011 min⁻¹). The effective charge carrier separation made possible by the heterojunction interface and the enhanced light absorption brought about by the combined effects of Cu doping and the integration of CoFe₂O₄ and S-g-C₃N₄ are responsible for this astonishing improvement. Stability and reusability tests confirmed the Nanocomposite retained 91.6% of its photocatalytic efficiency after five cycles, highlighting its robustness and potential for long-term application. The cost-effectiveness, environmental compatibility, and scalability of the Cu@CoFe₂O₄ /S-g-C₃N₄ make it a favorable intranet for industrial wastewater treatment. The highest antifungal activities of Cu@CoFe₂O₄ /S-g-C₃N₄ were estimated to be 36.7 mm, 39.4 mm, and 43.3 mm versus C. gloeosporioides, E. salmonicolor and C. albicans, respectively. This study underscores the potential of heterojunction-based photocatalysts in sustainable water purification, providing a pathway for tackling organic dye pollution. Future research will focus on extending this approach to address other emerging organic contaminants, further advancing global efforts in environmental remediation.