CO2 capture over steam and KOH activated biochar: effect of relative humidity

Carbon dioxide (CO2) capture is critical for emission reduction. Biochar is a promising adsorbent for CO2 capture. In this work, the effect of relative humidity and biochar activation with steam or KOH treatment on CO2 capture was investigated. The results demonstrate that the biochar sample activated by KOH has a high CO2 capture capacity (50.73 mg g−1). In addition, the biochar after 1.0 h of steam treatment showed a carbon capture capacity of 38.84 mg g−1. The results also show that the capture ability of biochar decreased as CO2 concentration decreased from 100% to 15%. The relative humidity had a negative impact on CO2 capture over biochar. The CO2 capture capability of biochar materials treated by steam decreased by a range of 31.38%–62.89% as the relative humidity rose from 8.8% to 87.9%. Furthermore, the lifetime of biochar samples at various relative humidity shows that increased relative humidity had a negative impact on CO2 adsorption due to water molecules occupying active sites.