Visible light-induced degradation of organic pollutant using a novel g-C₃N₄/Fe-Mg LDH/ZIF-67 ternary photocatalyst

Malachite green (MG) is a persistent organic contaminant that poses serious ecological and environmental hazards, underscoring the need for effective, long-term remediation techniques. In this study, a g-C₃N₄/Fe-Mg LDH/ZIF-67 photocatalyst was successfully synthesized via co-precipitation. Structural, optical and morphological analysis of the materials synthesized was done using XRD, FTIR, UV-DRS, BET, FESEM-EDX, XPS, PL, EIS and Mott-Schottky. A pseudo-first-order model adequately represented the dyes' degradation dynamics. The effects of irradiation duration and catalyst dosage on the photocatalytic degradation of MG were thoroughly examined. Under visible-light irradiation, the g-C₃N₄/Fe-Mg LDH/ZIF-67 composite achieved a substantial degradation efficiency of 94.74%. Scavenger experiments suggest that photogenerated electrons play the predominant role in MG degradation, while holes and superoxide radicals also contribute to the photocatalytic process. The positive slope values acquired through the Mott Schottky plot suggested the existence of n-type semiconductor in the sample. The EIS analysis revealed that charge transfer occurs at the interface. The results of electrochemical and optical analyses supported the formation of a successful heterojunction and the charge transfer process. Although the individual Fe-Mg LDH and ZIF-67 materials exhibited slightly higher degradation efficiencies, the g-C₃N₄/Fe-Mg LDH/ZIF-67 composite demonstrated high photocatalytic activity and provides a versatile heterostructure platform for further optimization and wastewater treatment applications. Moreover, the photocatalyst showed fair reusability by maintaining photocatalytic ability during three consecutive reuses although it gradually declined in degradation performance.