Lanthanum substituted Ni-Zn ferrite (Ni0.75Zn0.25Fe2O4) nanomaterial and its composite with rGO for degradation of binary dyes under visible light irradiation

Magnetically separable lanthanum modified Ni-Zn spinel ferrite nanoparticles (Ni0.75Zn0.25La0.06Fe1.94O4) and Ni0.75Zn0.25La0.06Fe1.94O4@rGO nanocomposites were successfully synthesized by the sol-gel auto-combustion and sonication methods respectively, for the degradation of binary organic pollutants. The results of x-ray Diffraction (XRD) analysis confirmed the formation of the face centered cubic (FCC) ferrites with the crystallite sizes ranging between 29.74 and 44.94 nm. The optical bandgap of the nano-composite was found to be 1.691 eV as revealed by the diffused reflectance spectral (DRS) study. The formation of the desired composition nanoparticles with a nearly spherical shape and their homogeneous distribution on sheets of rGO were verified by the scanning electron microscopy (SEM) coupled with energy dispersive x-ray (EDAX) instrument. The HR-TEM/SEAD analysis also revealed the formation of spherical polycrystalline nanoparticles and their uniform dispensability with a little agglomeration on the sheet of rGO. The degradation studies were conducted using binary dyes (MB and MO) under the irradiation of visible light in the presence of peroxide. The effects of catalyst dose, irradiation time, initial dye concentration, pH value, and recyclability of nanocomposites have been systematically studied. The findings showed that as compared to La3+ substituted Ni-Zn ferrite nanoparticles (78% for MB and 85 % for MO), the magnetic Ni0.75Zn0. 25La0.06Fe1.94O4@rGO nanocomposite exhibited as a potential photocatalyst towards the simultaneous degradation of both dyes (95% for MB and 98% MO) within 40 min under the optimized conditions. The hydroxyl radical (·OH) play a key role for Ni0.75Zn0.25La0.06Fe1.94O4@rGO nanocomposite photocatalyst for photocatalytical degradation of the binary dyes (methyl orange and methylene blue)