Efficient removal of composite organic micro-pollutants by amphiphilic modified magnetic biochar.

Waterborne organic micro-pollutants threaten both ecological integrity and human health. However, the simultaneous elimination of these contaminants remains challenging. We synthesized a magnetic biochar (CD/Fe3O4-BC) with amphiphilic and magnetic properties via a coprecipitation method using humic acid, iron compounds, and β-cyclodextrin as raw materials, followed by optimization of the preparation conditions. Surface and bulk properties of the modified biochar were probed by multiple analytical techniques, including SEM, BET, FT-IR, XRD, and XPS. The results showed that decorating the biochar surface with Fe3O4 nanoparticles and β-cyclodextrin substantially expanded its specific surface area and generated new active sites for pollutant adsorption. Adsorption experiments demonstrated that CD/ Fe3O4-BC efficiently removed both hydrophobic 2,4-dichlorophenol (2,4-DCP) and hydrophilic tetracycline hydrochloride (TCH), achieving removal rates of 86.38% and 85.45%, respectively. Under the optimal adsorption conditions, CD/ Fe3O4-BC achieved equilibrium adsorption capacities reaching approximately 105.71 mg g-1 toward 2,4-DCP and 35.44 mg g-1 toward TCH in the binary mixed system. The adsorption process involved multiple mechanisms, including pore filling, hydrogen bonding, π-π stacking, and electrostatic attraction. Furthermore, surface complexation contributed specifically to TCH adsorption. The Fe3O4 loading enables rapid magnetic separation of the spent adsorbent, and reusability tests showed that the material maintained elevated removal efficiency over five successive reuse cycles. This work provides a promising strategy for treating composite organic micropollutants in water.