Synergistic regulation of pore structure and oxygen functionalities in EtOH-KOH Co-activated biochar for I2 capture

Ethanol evaporation and KOH were firstly applied to co-activated biochar for Iodine Capture. • The obtained EKBC-200 had a high-surface-area and carboxyl-rich architecture. • I₂ capture of 2300 mg g⁻¹ with high stability was achieved at 200 ℃. • DFT analysis confirmed the key role of -COOH in stabilizing iodine molecules. In this study, a synergistic ethanol impregnation-KOH activation strategy was proposed to fabricate hierarchically porous biochar from pine cones, applied for the efficient capture of gaseous radioactive iodine. Systematic optimization of ethanol evaporation temperature as well as the KOH ratio revealed that EKBC-200 exhibited the highest surface area of 1285 m 2 g −1 with a micropore volume of 0.51 cm 3 g −1 , achieving an excellent I 2 uptake of 2300 mg g −1 . The desorption rate remained as low as 13%, and the capacity exceeded 1500 mg g −1 after five regeneration cycles, outperforming most reported sorbents. FTIR spectral changes (e.g., peak shifts or broadening) may provide supportive evidence for interactions such as hydrogen bonding. Characterization and density functional theory (DFT) calculations revealed that ethanol pretreatment could effectively open blocked pores and introduce oxygen-containing functional groups (e.g., -OH and -COOH). Subsequently, KOH activation generated abundant micro/mesopores and stabilized these oxygenated sites, resulting in a high-surface-area, carboxyl-rich structure favorable for I 2 adsorption. The grey relational analysis revealed that higher total and micropore volumes enhanced I 2 uptake, while the oxygenated surface groups strengthened I 2 retention. This work could offer an efficient and safe sorbent for radioactive I 2 capture from nuclear off-gas and provide a promising pathway for the high-value utilization of biomass. Download: Download high-res image (121KB) Download: Download full-size image