Fabrication of ZnFe-layered double hydroxides with graphene oxide for efficient visible light photocatalytic performance

In this study, ZnFe-layered double hydroxides were synthesized by a chemical co-precipitation method with different intercalated anions, including chloride and sulfate. They were then modified with graphene oxide to obtain ZnFe[sbnd]Cl-LDH/GO and ZnFe[sbnd]SO₄-LDH/GO photocatalysts. The as-synthesized samples were characterized by XRD, SEM, EDX, TEM, FTIR, BET, UV-Vis DRS, XPS, and PL analyses and evaluated for the decomposition of ofloxacin (OFX) under visible light irradiation. OFX is a persistent and resistant emerging pollutant in an aqueous solution. Among the photocatalysts synthesized, the photocatalytic activity of ZnFe[sbnd]SO₄-LDH/GO was highest (71.19% after 150 min irradiation) under optimum conditions. This observation is ascribed to the synergistic impact of swift separation rates of the photo-generated electrons that extend the longevity of charge carriers resulting from the heterostructures created between pure ZnFe[sbnd]SO₄-LDH and GO. The results indicate that a pseudo-first-order kinetic model can determine the kinetics of the OFX-degrading system. Based on the results of scavengers, ^•OH radicals and h⁺ were the major species for OFX degradation. Moreover, a possible photocatalytic mechanism is proposed for the degradation of OFX. Gas chromatography–mass spectrometry (GC–MS) was employed to recognize the by-products formed in solution by the dissociation of OFX. The chemical oxygen demand (COD) was analyzed to evaluate the mineralization of the OFX solution. Furthermore, the reusability and photostability of the photocatalyst were examined. The leaching zinc and iron concentrations in the aqueous phase were measured within five consecutive examinations.