Exploring the photocatalytic degradation of Direct Black 122 dye using Ni-doped magnesium ferrichromite nanoparticles synthesized by sol–gel method

Abstract

Water dye contamination has been increasing recently, which has serious toxicological repercussions for human health and the ecosystem. In this study, we synthesized a series of spinel ferrite nanomaterials with the composition Mg1-xNixFeCrO4 (0.0 ≤ x ≤ 1.0) using a cost-effective sol–gel method. The structural, morphological, compositional, thermal, and optical properties of the synthesized samples were systematically investigated using XRD, FTIR, SEM, EDX, TGA, and UV-DRS. XRD results confirmed the formation of single-phase spinel structures, with crystallite size influenced by the Ni substitution level. FTIR analysis verified the characteristic vibrational modes of spinel ferrites. SEM images revealed uniform morphology with particle agglomeration, while EDX confirmed the elemental composition and homogeneity. TGA demonstrated good thermal stability of the materials. UV-DRS analysis revealed that increasing Ni content systematically tuned the band gap energy, thereby influencing the photocatalytic activity. Among the series, the MgFeCrO₄ (x = 0.0) sample exhibited the highest photocatalytic efficiency, achieving 96% degradation of Direct Black 122 dye within just 15 min under UV–visible light irradiation. The improved performance is ascribed to its suitable band gap, efficient charge carrier separation, and surface characteristics. These findings demonstrate the strong potential of MgFeCrO₄ as an efficient photocatalyst for wastewater treatment.