Efficient adsorption of antibiotics in aqueous solution through ZnCl2-activated biochar derived from Spartina alterniflora

In recent years, Spartina alterniflora as an invasive species has seriously threatened the native coastal ecosystem of China. There is a lack of effective management and utilization methods towards Spartina alterniflora at present. To realize the ecological remediation and resource utilization of Spartina alterniflora, the functional biochar (BC) materials were successfully prepared using Spartina alterniflora as the substrates via the high temperature calcination method, which were utilized for efficient removal of antibiotics. The biochar was further activated by ZnCl2 (ZnBC) and optimized under different calcination temperatures and ZnCl2 dosages to improve the adsorption ability. Among these biochar materials, the ZnCl2-activated biochar obtained under the mass ratio of Spartina alterniflora to ZnCl2 of 1:5 and calcination temperature of 600 °C (ZnBC-600) exhibited the strongest adsorption performance towards sulfadiazine (SDZ) and ciprofloxacin (CIP), which can be attributed to the larger specific surface area, richer pore structure and more abundant surface oxygen-containing functional groups. Additionally, the adsorption kinetics and isotherms demonstrated that the adsorption of both SDZ and CIP onto ZnBC-600 (1:5) followed the pseudo-second-order kinetic model and Freundlich model. At the same time, the performances of Spartina alterniflora biochar derived from different biomass were compared under the condition of activation with ZnCl2, presenting the superior performance of ZnCl2 activated Spartina alterniflora biochar. Moreover, the adsorption mechanism of ZnBC-600 (1:5) was proposed, illustrating the crucial roles of effects of electrostatic attraction, pore filling, oxygen-containing groups complexation, π-π stacking and hydrogen bonding in the adsorption of antibiotics. Above all, this study not only provides a feasible strategy for the preparation of functional biochar derived from Spartina alterniflora for removing organic pollutants, but also opens up a new pathway for resource utilization of Spartina alterniflora. [Display omitted]