Activated biochar derived from pomelo peel as a high-capacity sorbent for removal of carbamazepine from aqueous solution

Abstract

In recent years, the application of biochar to remove contaminants from aqueous solutions has become interesting due to favorable physical/chemical properties and abundant feedstocks. Herein, activated biochar was prepared by carbonization and further KOH activation using pomelo peel as a precursor. A series of characterization methods indicated that activation temperature can significantly influence the pore structure and surface chemistry of the obtained activated biochar. When used as a sorbent, the results showed that the adsorption isotherms of carbamazepine (CBZ) onto these activated biochars could be described well by Langmuir models. In addition, the kinetics of CBZ adsorption onto activated biochars were fitted well by pseudo-second-order kinetics and controlled by the intra-particle diffusion. The pore structure and surface functional groups could affect the adsorption of CBZ, resulting in the activated biochar of AB-700 delivering a higher adsorption capacity of CBZ up to 286.5 mg g⁻¹. Furthermore, different factors in the sorption process of CBZ on AB-700, such as temperature, pH, ionic strength and reusability, were studied in detail. The effects of solution temperature revealed that the adsorption processes were spontaneous and exothermic, and mainly physisorption. The presence of Na⁺ ions in solution showed almost no effect on the adsorption of CBZ. The reuse studies demonstrated that AB-700 showed 58.5% capacity retention at the 4^th cycle for the adsorption of CBZ. The effect of solution pH and surface analysis of biochar indicated that the adsorption of CBZ onto the activated biochar was mainly controlled by π–π electron donor–acceptor interaction.