Heterostructured γ-FeO/FeTiO magnetic nanocomposite: An efficient visible-light-driven photocatalyst for the degradation of organic dye.

The catalyst recovery is the major concern in commercialization of photocatalysts for the industrial effluent treatment process. To overcome this major issue, FeO based magnetic photocatalytic heterostructure ɣ-FeO/FeTiO nanocomposite was synthesized by hydrothermal method. FeO is the cheapest visible active magnetic photocatalytic material, but it has the limitation of fast e/h + recombination. Titanium (Ti) was loaded on γ-FeO to overcome this issue. The loaded Ti has grown as FeTiO on the surface of ɣ-FeO nanocrystals and emerged as heterostructure ɣ- FeO/FeTiO nanocomposites, which was confirmed by XRD and TEM results. The loading concentration of Ti on γ-FeO was optimized to achieve the maximum photocatalytic efficiency without compromising the magnetic property of γ-FeO to facilitate the magnetic separation. DRS-UV spectra revealed the strong visible light response of γ- FeO/FeTiO nanocomposite. The photocatalytic efficiencies of the synthesized materials were evaluated using methylene blue (MB) as a model pollutant under sunlight. The built-in electric field between p-n junction between FeTiO and FeO and type II charge transfer mechanism extended the lifetime of the charge carriers at the heterojunction of γ- FeO/FeTiO, which was confirmed by PL spectra. The vibrating sample magnetometer (VSM) study revealed the decreasing magnetization, coercivity (Hc), and retentivity (Mr) of γ-FeO with increasing concentration of Ti. 92% of the used-up 20 wt% Ti loaded γ-FeO/FeTiO magnetic nanocomposite was recovered from the treated wastewater using an electromagnet. Both magnetic properties and efficiency of the nanocomposite increased up to 20 wt% of Ti loading, beyond that decreased due to the increasing composition of antiferromagnetic FeTiO and the increasing number of defect sites as recombination centers. Hence, 20 wt% loading of Ti was concluded as the optimum to enhance the efficiency and to retain the magnetic properties. This work aims the commercialization of magnetic photocatalytic materials for the industrial effluent treatment.