C₃B₂ Quantum Dot: A Potential Candidate for Heavy Metal Ion Detection and Removal in Wastewater Treatment

Heavy metal (HM) toxicity has become one of the major issues nowadays. In this research, we have studied the adsorption approach for HM ion (HMI) detection and removal applications from wastewater. A novel quantum dot (QD) of tricarbon diboride (C₃B₂) is designed and geometrically relaxed using density functional theory (DFT) calculations. The QD possesses a cohesive energy of -4.41 eV with a 2.44 eV energy gap. No imaginary vibrational frequencies are observed, making C₃B₂ QD (CBQD) thermodynamically stable geometry. CBQD demonstrates physisorption of Cd(ii) and Hg(ii) ions, whereas it shows strong chemisorption of Ni(ii), As(iii), and Pb(ii) ions. The adsorption energy ranges from -0.15 to -10.27 eV. The optical response varies excessively due to HMI adsorption, making CBQD suitable for differentiating HMIs. All of the adsorption processes are exothermic and thermodynamically ordered, where HMIs interact with CBQD using van der Waals and strong attractive force. A significant change in the energy gap is observed due to HMI adsorption, resulting in high sensitivity (over 80%) for all the HMIs.