Photocatalytic activity of ZnxCd0.8−xMn0.2Al0.1Fe1.9O4, (X = 0, 0.3) spinel ferrite for photodegradation of Congo red dye

In this study, we investigated the photocatalytic degradation of Congo red dye using zinc-doped cadmium manganese aluminum ferrite nanoparticles (Zn_xCd_0.8−xMn_0.2Al_0.1Fe_1.9O₄, X = 0, 0.3). Ferrite catalysts were synthesized via a sol–gel method and extensively characterized to understand the impact of Zn doping on their structural, morphological, and textural properties. FTIR, SEM, EDX, and BET analyses confirmed that Zn doping modified the characteristics of the catalyst. Zn doping decreased the crystallite size and lattice parameters, increased the FWHM and density, and shifted the metal–oxygen bond vibration peaks. The SEM images showed that Zn doping refined the particle size and improved the morphology, confirming the incorporation of Zn. The BET analysis revealed that Zn doping enhanced the surface area, pore volume, and pore radius. The undoped photocatalyst possessed a bandgap of 2.8 eV, while Zn-doping led to a narrower bandgap (2.6 eV), consequently enhancing visible light absorption. The Zn-doped catalyst achieved 93.12% Congo red degradation at pH 7, 30 °C, 80 min and concentration of Congo red dye 10 ppm, significantly outperforming the undoped catalyst (62.45%). Zn doping improved charge separation and promoted the generation of reactive oxygen species (ROS), leading to enhanced photodegradation efficiency. Scavenger studies confirmed the crucial role of hydroxyl radicals in the degradation process. Furthermore, the Zn-doped catalyst maintained an 81.03% degradation efficiency even after five consecutive cycles, indicating promising recyclability. These findings highlight the potential of Zn-doped cadmium manganese aluminum ferrite as an efficient and stable photocatalyst for remediation of Congo red-contaminated wastewater.