Photocatalytic Degradation Properties of Li-Cr Ions Substituted CoFe2O4 Nanoparticles for Wastewater Treatment Application

Herein, the dual substitution of Li/Cr in CoFe2O4 ferrite nanoparticles synthesized through the sol-gel auto combustion method is reported. X-ray diffraction confirms mixed cubic spinel structure, while as dense morphology with well-defined grain boundaries with the minimum grain size of 20 nm is obtained using FE-TEM analysis. The thermal stability of the sample improves with an increase in dopant concentration. XPS study shows that Fe and Co exhibit +2 and +3 oxidation states with lower concentrations of oxygen vacancies. Raman spectroscopy confirms the substitution of Li/Cr ions at octahedral and tetrahedral sites, and the direct bandgap increases monotonously with doping. Saturation magnetization increases for x = 0.01, but it decreases for higher dopant concentration due to the spin canting effect, and the coercivity decreases for all the doping concentrations. The photodegradation studies show the enhanced activity against crystal violet (CV) dye when exposed to sunlight for 60 min but easily recoverable using a magnet. The increased activity by the doped nanoparticles is because of the decreased coercivity, particle size, and magnetic anisotropy. A 90.4% photocatalytic degradation is obtained for the composition, x = 0.03, which suggests that it can be an effective candidate for wastewater treatment.

Automated summary

This study reports the dual substitution of Li/Cr in CoFe2O4 ferrite nanoparticles synthesized through the sol-gel auto combustion method. The analysis shows that the substituted nanoparticles have mixed cubic spinel structure and dense morphology with well-defined grain boundaries. The thermal stability and photocatalytic activity of the sample increase with an increase in dopant concentration. XPS and Raman spectroscopy confirm the substitution of Li/Cr ions at specific sites and the changes in oxidation states. The magnetic properties of the doped nanoparticles show an increase in saturation magnetization for a certain dopant concentration, but a decrease in higher concentrations.