Efficient and selective separation of Re(VII), an analogue of Tc(VII), by a defective biochar with honeycomb‐like porous structure

Abstract BACKGROUND In this study, a defective biochar with honeycomb‐like porous structure (BC‐PH) was successfully prepared by the activation of pristine biochar derived from bamboo shoot shell with the chemical reagent KOH, and was applied to selectively separate ReO 4 − (a chemical analogue for radioactive TcO 4 − ) from acidic solutions. RESULTS The diffusion, mass transfer and recovery for ReO 4 − could be significantly improved by the large specific surface area ( S BET , 2412 m 2 g −1 ) and high total volume ( V tot , 1.26 cm 3 g −1 ) of BC‐PH. The influence of adsorbent dosage, system pH and coexisting ions with different valence states on the adsorption capability and selectivity of BC‐PH toward ReO 4 − was systematically investigated. BC‐PH exhibited high adsorption capacity and selectivity for ReO 4 − with a maximal sorption capacity ( q m ) of 73.11 mg g −1 at initial pH 2. By applying an analysis of kinetics and isotherm adsorption studies, the liquid film diffusion was verified to be the primary rate‐controlling step for the sorption of ReO 4 − and the multilayer adsorption process occurred on the heterogeneous surface of BC‐PH. Besides, the recovery of ReO 4 − using BC‐PH occurred in an exothermic and spontaneous manner according to thermodynamic analysis. Furthermore, an investigation of the adsorption mechanism suggested that pore filling and electron donor–acceptor interaction were mainly related to the removal of ReO 4 − . CONCLUSION These results suggest that BC‐PH has great potential for the application of TcO 4 − separation in consideration of its high adsorption capacity and selectivity. © 2024 Society of Chemical Industry (SCI).