New insight into the synergy of nitrogen-related sites on biochar surface for sulfamethoxazole adsorption from water
Chuanbin Wang, Lingchao Kong, Yanshan Wang, Xiaoqiang Cui, Ning Li, Beibei Yan, Guanyi Chen
Abstract
In-depth exploration of the relationship among different adsorption sites is conducive to design of efficient adsorbents for target pollutants removal from water. In this study, the experiments, multivariate non-linear regression and density functional theory calculations are applied to explore the possible synergistic effects of three nitrogen (N)-containing sites on cow dung biochar surface for sulfamethoxazole (SMX) adsorption. Notably, a strong synergistic effect between pyridinic N and pyrrolic N sites was found for sulfamethoxazole adsorption. The adsorption energies of SMX on four pyrrolic N-coupled pyridinic N structures were −1.02, −0.41, −0.49 and −0.72 eV, much higher than the sum of adsorption energies (−0.31 eV) on pyrrolic N and pyridinic N. Besides, the alteration of Mulliken charge revealed that the simultaneous presence of pyridinic N and pyrrolic N improved the electron transfer remarkably from −0.459 e and 0.094 e to −0.649 e and 0.186 e, benefiting for SMX adsorption. This work firstly explored the possible synergies of adsorption sites on biochar surface for organic contaminants removal from water, which shed new lights on the adsorption mechanism and provided valuable information to design efficient adsorbents in the field of water treatment.