CO2 Adsorption and Storage on Ca-Modified Biochar Derived from Coconut Endocarp.

Carbon capture and storage are technologies capable of reducing atmospheric CO2 levels, contributing to mitigating the problems caused by global warming and climate change. Biochar has been widely investigated as an adsorbent for CO2 capture due to its low cost and wide availability. However, research on CO2 capture followed by storage using biochar is still limited. Therefore, this work aimed to investigate the capture and storage of CO2 in physically activated and Ca-modified biochars derived from coconut endocarp. The adsorption and carbonation performances were evaluated at different temperatures and moisture conditions. The maximum adsorption capacity was observed at 30 °C and among the Ca-modified samples, the biochar with the lowest Ca content (3.5 wt %) exhibited the highest specific surface area (577 m2/g) and adsorption capacity (46.1 mg/g). The adsorption kinetics were evaluated using three kinetic models, with the Avrami model showing the best fit to the experimental data. Thermal treatment at 510 °C led to the formation of CaCO3 particles deposited throughout the porous carbon structure; the sample with the highest Ca content (23.9 wt %) and the lowest specific surface area (242 m2/g) showed the highest carbonation capacity (104.6 mg/g). Carbonation of the Ca-modified biochars was also affected by moisture, being significantly faster in humid environments as compared to dry ones at room temperature. The results of this study demonstrated that Ca-modified biochars are environmentally friendly hybrid adsorbents capable of adsorbing and storing CO2 in the form of carbonates, potentially serving as a sustainable alternative to help achieving the goals set by the Paris Agreement.