(418g) CO?-Activated Cellulose Biochar for CO? Capture

Biomass-based carbon capture offers a promising pathway for reducing carbon emissions and sequestering atmospheric CO₂. Currently, it is estimated that nearly 10% of global emissions could be reduced if biomass is used for carbon capture. Improving the porous structure of biochar through activation processes plays a key role in CO₂ adsorption. The use of CO₂ as an activation agent for biochar has been recently explored and offers a cleaner and more environmentally friendly approach compared to KOH activation, which requires strong chemical agents. This research wants to investigate CO₂ as an activation gas to enhance the adsorption sites of biochar so that CO₂ can be subsequently captured in this material. We are looking at synthesizing cellulose-derived biochar using hydrothermal carbonization at 300 °C and activating it using CO₂ (at different temperatures (700–1000 °C) in an inert nitrogen atmosphere). CO₂ activation will be performed at different flow rates (25–75 mL/min) to assess its impact on micropore formation, surface area and adsorption capacity. CO₂ activation is expected to open inaccessible micropores or form new ones and increase the pore network of the activated biochar. Small-angle x-ray scattering (SAXS) will be used to analyze the micropore formation and surface area of the activated biochar, and thermogravimetric analysis (TGA) to investigate the adsorption capacity. The CO₂-activated samples will then be compared to two conventional activation methods: thermal (700–1000 °C) and/or KOH activation.

Preliminary results indicate that increasing the activation temperature from 800°C to 900 °C enhances micropore formation, significantly improving adsorption capacity. However, temperatures above 900 °C may induce partial micropore collapse, reducing the biochar’s overall effectiveness for CO₂ capture. We found that as the activation temperature increases beyond 800°C, CO₂ adsorption decreases which is consistent with observed micropore collapse at 1000 °C. Overall, at the same activation temperature, CO₂ performed better than just thermal activation. We further found that increasing the CO₂ flow rate during activation did not enhance pore development and adsorption capacity. These findings provide valuable insights into optimizing biochar activation for enhanced CO₂ sequestration.