Enhanced performance of a novel superparamagnetic g-C3N4/NiO/ZnO/Fe3O4 nanohybrid photocatalyst for removal of esomeprazole: Effects of reaction parameters, co-existing substances and water matrices

Abstract

In this work, a hydrothermal route was adopted for the construction of a nanohybrid of g-C3N4/NiO/ZnO/Fe3O4. For determination of the structure, morphology and composition, the nanohybrid photocatalyst was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray (EDX). UV–visible (UV–vis) spectrophotometry and photoluminescence spectroscopy were performed on the nanohybrid sample for proper assessment of its optical properties. The superparamagnetic nature of the nanocomposite was evaluated with vibrating sample magnetometer (VSM) techniques. XRD, TEM, HRTEM, XPS and EDX data revealed the formation of the intended nanocomposite. The band gap of the nanohybrid using Tauc plot was determined to be ~ 2.8 eV. This confirmed a modification of the band edges of the individual moieties- ZnO, NiO and g-C3N4. A remarkable reduction in the rate of electron-hole recombination was thus induced via enhanced charge separation as evident from photoluminescence studies of the nanocomposite. An efficient photocatalytic activity of the heterojunction that had originated from the synergistic effects of the individual moieties was therefore observed. The hybrid photocatalyst was found to cause ~ 95.05% degradation of esomeprazole, an emerging organic water pollutant, under visible light irradiation within 70 min. The photodegradation followed pseudo-first order kinetics with a specific reaction rate of 0.06616 min−1. Additionally, the effects of various reaction parameters, other species and water matrices were studied. The current work fulfills its objective of designing a hybrid nano-photocatalyst that is active in the visible region of electromagnetic spectrum, demonstrates the ability to cause disintegration of emerging, non-biodegradable organic water pollutant, has superior photostability, and is magnetically retrievable.