Development of zinc ferrite nanoparticles with enhanced photocatalytic performance for remediation of environmentally toxic pharmaceutical waste diclofenac sodium from wastewater

Diclofenac sodium is an anti-inflammatory drug commonly used to cure pain in various treatments. The remarkable potential of this pain-killer leads to its excessive use and, therefore, a persistent water contaminant. Its presence in aqueous bodies is hazardous for both humans and the environment because it causes the growth of harmful drug-resistant bacteria in water. Herein, we present a comparative study of the ZnO and ZnFe2O4 as photocatalysts for the degradation of diclofenac sodium, along with their structural and morphological studies. A simple co-precipitation method was used for the synthesis of ZnO and ZnFe2O4 and characterized by various analytical techniques. For instance, the UV-Vis study revealed the absorption maxima of ZnO at 320 nm, which was shifted to a longer wavelength region at 365 nm for zinc ferrite. The optical band gaps obtained from the Tauc plot indicated that the incorporation of iron has led to a decreased band gap of zinc ferrite (2.89 eV) than pure ZnO (3.14 eV). The metal-oxygen linkages shown by FTIR indicated the formation of desired ZnO and ZnFe2O4, which was further confirmed by XRD. It elucidated the typical hexagonal structure for ZnO and spinel cubic structure for ZnFe2O4 with an average crystallite of 31 nm and 44 nm for ZnO and ZnFe2O4, respectively. The micrographs obtained by SEM showed rough spherical particles of ZnO, whereas for ZnFe2O4 flower-like clustered particles were observed. The photocatalytic investigation against diclofenac sodium revealed the higher degradation efficiency of ZnFe2O4 (61.4%) in only 120 min, whereas ZnO degraded only 48.9% of the drug. Moreover, zinc ferrite has shown good recyclability and was stable up to five runs of photodegradation with a small loss (3.9%) of photocatalytic activity. The comparison of two catalysts has suggested the promising role of zinc ferrite in wastewater remediation to eliminate hazardous pharmaceuticals.