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.