Superparamagnetic Dy modified ZnFe₂O₄ magnetic nanophotocatalysts for the photocatalytic degradation of crystal violet pollutant

This study focuses on the development of superparamagnetic and multifunctional Dy doped ZnDy_xFe_2-xO₄ (x = 0.0, 0.01, 0.02, 0.03) ferrite using sol–gel auto-combustion (SG) technique to remove the crystal violet pollutant found in textile industry wastewater using the adsorption and photocatalysis processes. The pure phased spinel cubic crystal structure was achieved for the prepared ferrite nanoparticles, as confirmed through the XRD results. The calculated crystallite size employing the Scherrer formula by taking the high intensity (311) peak was in the range of 26–35 nm. FESEM pictures confirm the presence of spherically shaped grains with definite grain boundaries. With the increasing doping content of Dy, the band gap for the produced photocatalysts was decreased from 1.47 to 1.11 eV. We demonstrated that our prepared Dy doped zinc ferrite nanoparticles behave as a soft magnetic material based on the magnetic measurement data by exhibiting the hysteresis behaviour with low rentivity and coercivity. This indicates the tendency of zinc nanoparticles to exhibit superparamagnetic behaviour at ambient temperature under an external magnetic field. ZnDy_0.03Fe_1.97O₄ (x = 0.03) sample exhibits greater reactivity with a discolouring rate of 92.30% as compared to the ZnFe₂O₄ degradation rate of 83.07% during 120 min of irradiation under the natural sunlight. Furthermore, the adsorption/photocatalytic activities are amplified as the content of the dopant (Dy) rises, suggesting that the dopants are crucial to the photocatalytic breakdown and the adsorption of crystal violet (CV) dye. Using the antibacterial analysis, it was noted that ZnFe₂O₄ (x = 0.00) shows the zone of inhibition (ZOI) for both the strains, Bacillus subtilis and Salmonella typhi. With all the excellent magnetic, adsorption, photocatalytic, and antibacterial behaviours, the multifunctional magnetic nanomaterials will be highly beneficial for environmental and biological usages.