Performance of Bamboo-Based Activated Carbon in Enhancing CO₂ Absorption by Aqueous Diethanolamine Solution

Abstract

The large diffusion resistance of CO₂ in aqueous diethanolamine (DEA) solution is the primary factor resulting in its slow absorption rate. By introducing a small amount of bamboo-based activated carbon (BAC), the diffusion resistance of CO₂ in 30% DEA-H₂O is significantly reduced, thereby effectively enhancing the CO₂ absorption rate. In this study, five types of BAC with different pore size distributions were prepared by adjusting the mass ratio of bamboo charcoal (BC) to the activator of potassium hydroxide (KOH). The hybrid sorbent of 30% DEA-BAC-H₂O for CO₂ absorption (adsorption) was developed. CO₂ absorption (adsorption) capacity, rate, and desorption enthalpy of the hybrid sorbent were systematically measured, calculated as well as compared with the commercial absorbents. The results showed that when the mass ratio of BC to KOH was 1:2 (denoted as BAC₁:₂), BAC₁:₂ exhibited a well-developed specific surface area and micropore volume (pore size ≤1 nm). Under this condition, the CO₂ absorption (adsorption) rate in 30% DEA-1% BAC₁:₂-H₂O was 7 times and 3.5 times those of 30% DEA-H₂O and 25.5% DEA-4.5% piperazine (PZ)-H₂O (a commercial absorbent), respectively. Meanwhile, CO₂ absorption (adsorption) capacity of 30% DEA-1% BAC₁:₂-H₂O was moderate, and the CO₂ desorption enthalpy was reduced by 25% compared with that of 25.5% DEA-4.5% PZ-H₂O, demonstrating its potential for industrial application.