This paper focuses on the successful synthesis of Zn0.5Ni0.5AlFeO4 magnetic nanoparticles applying tragacanth gel through the sol-gel technique, as an environmentally-friendly, economical and simple method for the first time. The prepared magnetic nanoparticles were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDX), and vibrating sample magnetometer (VSM). Based on the XRD result, the conformation of single phase cubic spinel structure with the average crystallite size of 10 nm was confirmed. The VSM result exhibited that the nanoparticles have the saturation magnetization of 33.82 emu/g and coercive field of 56 Oe. The organic dye degradation of reactive blue 21 (RB21) was specified utilizing the synthesized magnetic nanoparticles under visible light irradiation. The toxicity of the by-products derived from dye degradation was studied using phytotoxicity test and total organic carbon (TOC) analysis. The photocatalytic activity of the catalyst was measured with changing factors including photocatalyst dosage, initial dye concentration, pH, and contact time. The results presented that Zn0.5Ni0.5AlFeO4 MNPs could degrade 94% of the reactive blue 21.
