Comparison of biomaterials produced from carbonatization, hydrothermal reaction and chemical activation: Characterization, CO2 capture and mechanism

Abstract

This study examines the development of carbon-based materials as an affordable bio-sorbent for low-temperature CO₂ adsorption. Therefore, pea peel (BM) was suggested as a lignocellulosic precursor for the synthesis of activated carbon (AC), activated hydrochar (AHC), biochar (BC) and hydrochar (HC) through various techniques such as hydrothermal carbonization, direct carbonization, and chemical activation. Hydrothermal carbonization was performed to produce HC in a Teflon-lined autoclave at 210 °C for 24 h. HC and BM were impregnated with KOH to produce AHC and AC, respectively. Following the impregnation step, the materials were adjusted to the carbonization process at 500 °C for an hour. BC was produced by direct carbonization of BM without hydrothermal treatment and KOH activation. To obtain BC, the carbonization of BM was carried out at the same conditions as AC and AHC.

The N₂ adsorption/desorption results of BM and the as-obtained carbonaceous materials demonstrated that AC exhibited the largest surface area and the smallest pore diameter of 693.67 m²/g and 0.9 nm, respectively, whereas the pore volume was nearly 90 times more than that of BC which was in accordance with the CO₂ capture capacity. AC achieved the highest CO₂ adsorption performance with a capacity of 3 mmol/g. A significantly high carbon content of activated carbon (66.26 %) was obtained via the carbonization process of biomass. The results suggested that the chemical activation and carbonization steps provided advanced textural properties, which are favorable for efficient adsorbents to be utilized in the CO₂ adsorption process.