Hydrothermally Synthesized CuV2O6/g-C3N4 Nanocomposite for Efficient Co(II) Removal: RSM Optimization, Adsorption Mechanism, and Reusability Study

Abstract

Co(II)-ion-polluted water has become a significant global environmental issue recently. This study synthesized a CuV₂O₆/g-C₃N₄ nanocomposite through a hydrothermal method. The nanocomposite was analyzed using various techniques, including X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), scanning electron microscopy (SEM), and the Brunauer–Emmet–Teller (BET) method. RSM-CCD was utilized to model and optimize the adsorption of Co(II) in aqueous solutions, subsequently examining the isotherm and kinetic models. The maximum adsorption (905.22) was achieved at an initial Co(II) concentration of 65.144 mg/L, a solution pH of 6.02, an adsorbent dosage of 1.058 g/L, and a contact time of 47.958 min. The removal efficiency was obtained to be 96.356%. The kinetic adsorption results were accurately fitted using the pseudo-second-order model, and the equilibrium data were well described using the Freundlich isotherm behavior. The adsorbent exhibited excellent reusability, maintaining high recovery efficiencies of 97.86% in KOH and 89.7% in HNO₃ during the first cycle. The adsorption of Co(II) is governed by electrostatic attraction, hydrogen bonding, ion exchange, and surface complexation with a functional group on the nanocomposite surface. This study highlights the potential of the CuV₂O₆/g-C₃N₄ nanocomposite in addressing water pollution challenges.