Adsorption of chitosan combined with nicotinamide-modified eupatorium adenophorum biochar to Sb3+: Application of DFT calculation

The pollution and harm of Sb 3+ to aquatic systems is a global problem, so Sb 3+ removal from the water environment to make sure environment safety and human beings wellbeing is of urgency. This study explored the effect of chitosan combined with nicotinamide-modified eupatorium adenophorum biochar (CEBC) on adsorbing Sb 3+ through batch adsorption experiments. The experiments indicated CEBC's maximum adsorption capacity to Sb 3+ is 170.15 mg·g −1 . Meanwhile, the capacity of the original biochar (EBC) is only 9.97 mg·g −1 . Compared with EBC, CEBC contains more functional groups, such as C O, -OH and -NH 2 . In addition, the pseudo-second-order kinetic model and the Langmuir model are fit to describe the kinetics and isotherms of adsorption of CEBC to Sb 3+ , which suggests that the adsorption of CEBC to Sb 3+ is dominated by monolayer chemisorption. Density functional theory (DFT) calculations confirmed that the chelation between –NH 2 and Sb 3+ is of significance in the adsorption process of CEBC. DFT calculations also found that the newly added –OH and C O in EBC have a synergistic enhancement effect on the absorption of Sb 3+ . The mechanism of CEBC absorbing Sb 3+ includes electrostatic interactions, pore filling, Л–Л interactions, hydrogen bonding, functional group complexation, chelation, and oxidation . CEBC has an excellent anti-interference ability for inorganic anions (NO 3 − , SO 4 2− and Cl − ) and can also use the coexisting HA to improve its adsorption performance. In addition, CEBC has better mitigation of Sb 3+ on the performance of Sb 3+ about its secondary release and good reproducibility, which indicates that CEBC is a viable Sb 3+ adsorbent.