Green synthesis of recyclable MgFeCrO4 spinel nanoparticles for rapid photodegradation of direct black 122 dye

[Display omitted] •Green synthesis of MgFeCrO4 spinel nanoparticles by Tragacanth gel.•Direct black 122 dye was completely degraded in 60 s.•Synthesized photocatalyst has a band gap of 1.57 eV and is active photocatalyst in a visible-light region.•MgFeCrO4 MNPs were effective and reusable for photodegradation of direct black 122 in four runs. In this work, MgFeCrO4 magnetic nanoparticles were prepared in spinel structure via the green sol-gel method. The high photocatalytic activity of MgFeCrO4 MNPs was studied for the fast degradation of organic dye in water solution at room condition and natural pH. Tragacanth gel was used for providing comfortable, nature, and an inexpensive sol-gel method. The MgFeCrO4 MNPs were fully characterized by FTIR, XRD, BET, FESEM, EDX, VSM, TEM, DRS, and percent of dyes degradation was followed by UV–vis spectroscopy. The XRD pattern confirmed the formation of spinel cubic MgFeCrO4 magnetic nanoparticles. Direct black 122 (DB122) was chosen as an example of pollution to investigate the photodegradation via as-prepared magnetic nanoparticle. The results indicated that 96 % of DB122 dye were degraded in only 60 s. The kinetics of degradation of DB122 is consistent with the pseudo-first-order kinetics model. MgFeCrO4 magnetic nanoparticles show excellent reusability for degradation DB122 dye because the photocatalyst did not exhibit a significant decrease in its activity even after four runs.