BACKGROUNDIn 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 ReO4- (a chemical analogue for radioactive TcO4-) from acidic solutions.RESULTSThe diffusion, mass transfer and recovery for ReO4- could be significantly improved by the large specific surface area (SBET, 2412 m2 g-1) and high total volume (Vtot, 1.26 cm3 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 ReO4- was systematically investigated. BC-PH exhibited high adsorption capacity and selectivity for ReO4- with a maximal sorption capacity (qm) 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 ReO4- and the multilayer adsorption process occurred on the heterogeneous surface of BC-PH. Besides, the recovery of ReO4- 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 ReO4-.CONCLUSIONThese results suggest that BC-PH has great potential for the application of TcO4- separation in consideration of its high adsorption capacity and selectivity. (c) 2024 Society of Chemical Industry (SCI).
