Synthesis, characterization, and photocatalytic performance of ZnFe 2 O 4 -g-C 3 N 4 composites for tetracycline removal from contaminated water

Abstract

The presence of emerging contaminants in wastewater like tetracycline poses a significant challenge in water reuse worldwide. The implementation of a p-n heterojunction and dye-sensitized techniques in the enhancement of graphite carbon nitride provides a promising alternative for visible light-driven degradation of emerging contaminants present in wastewater. Te present study investigated dye-sensitized and plain composites in degrading tetracycline using natural sunlight in a parabolic trough reactor. Te study synthesized four composites of ZnFe2 O 4-g-C 3 N 4 at 5, 15, and 25 wt% loading of the ferrite by direct annealing of melamine, followed by thermal and ultrasonic exfoliation of bulk graphite carbon nitride and in situ precipitation with zinc ferrites to yield a composite photocatalyst. Te photocatalysts were characterized using X-ray difraction (XRD) analyses which confrmed that all the spinel ferrite phases of ZnFe 2 O4 were well bonded with g-C 3 N4 nanosheets to form a composite. Te crystallite sizes were calculated by the Debye–Scherrer equation indicating crystal sizes of between 4.63 and 8.61 nm confrming the nanostructures. Te scanning electron microscope-energy dispersive spectroscopy (SEM-EDX) tests verifed that the spherical globules of ZnFe 2 O4 were well attached to the mesoporous layers of g-C 3 N4 and absence of contaminant phases. Te UV-Vis analysis for 25% ZF-GCN revealed a band gap reduction from 2.67 eV to 2.03 eV. Te PL intensity for all the composites decreased at excitation of 266 nm and 550 nm which was evidence for suppressed charge recombination. A 25% ferrite loading resulted in the best photocatalytic performance with tetracycline degradation of 93.64% and total organic carbon (TOC) removal of 51.89%. Te sensitization of the 25% ZF-GCN composite with Eosin Y further improved its performance for degradation of tetracycline to 94.62% and TOC removal to 68.29%. Terefore, dye sensitization is an efcient way of improving the photocatalytic activity of a multicomponent photocatalyst for the removal of emerging pollutants.