Synthesis of Nanocrystalline Metal Tungstate NiWO4/CoWO4 Heterojunction for UV-Light-Assisted Degradation of Paracetamol

Abstract

The discharge of pharma products such as paracetamol (PCT) into water has resulted in great harm to humans and emerged as a potential threat requiring a solution. Therefore, the development of smart and efficient materials as photocatalysts has become imperative in order to treat PCT in wastewater. The present study demonstrates the synthesis of pristine NiWO4 and CoWO4 and a heterojunction nanostructure, NiWO4/CoWO4, through a hydrothermal process using a Teflon-lined autoclave at 180 °C for 18 h. Various spectroscopic techniques, such as X-ray diffraction (XRD), Fourier transform infrared (FTIR), ultraviolet–visible (UV–Vis), transmission electron microscopy (TEM), scanning electron microscopy–energy dispersive X-ray (SEM–EDX), and X-ray photoelectron spectroscopy (XPS) were utilised to determine the lattice, structural, optical, and morphological information of the solid nanomaterial upon heterojunction formation. The synthesised nanomaterials were exploited for the photocatalytic degradation of paracetamol (PCT) under UV light irradiation. Photocatalytic experiments were performed for the optimization of various reaction parameters, such as irradiation time, pH, catalyst dose, and PCT concentration at room temperature. The results obtained suggested that the heterojunction nanocomposite NiWO4/CoWO4 exhibited enhanced photocatalytic efficiency (97.42%) with PCT as compared to its precursors—96.50% for NiWO4 and 97.12% for CoWO4. The photocatalytic data were best defined by the Langmuir–Hinshelwood (L–H) model of pseudo-first-order kinetics, with apparent rates constant at 0.015 min−1 for NiWO4, 0.017 min−1 for CoWO4, and 0.019 min−1 for NiWO4/CoWO4 NC. It was observed that NiWO4/CoWO4 NC with enhanced optical properties effected a higher rate of PCT degradation due to the improved bandgap energy upon heterojunction formation. The scavenger test revealed the involvement of •OH radicals as reactive oxidant species (ROS) in PCT degradation. The material was found to be highly stable and reusable for the degradation of PCT at optimized reaction conditions.