Hydrothermally Synthesized CuVO/g‑CN Nanocomposite for Efficient Co(II) Removal: RSM Optimization, Adsorption Mechanism, and Reusability Study.

Co-(II)-ion-polluted water has become a significant global environmental issue recently. This study synthesized a CuVO/g-CN 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 HNO 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 CuVO/g-CN nanocomposite in addressing water pollution challenges.