Evaluation of CO2 adsorption with eucalyptus wood based activated carbon modified by ammonia solution through heat treatment

• Activated carbon was prepared from eucalyptus wood with H3PO4 and modified by NH3.
• AC surface chemistry and micropore structure improved by ammonia modification.
• AC modified by ammonia showed enhanced CO2 loading relative to the untreated AC.
• Incorporation of nitrogen group in ACs increased their adsorption capacities.
• Adsorption isotherm, kinetic and thermodynamics of ammonia-treated AC were studied.

Eucalyptus wood was used to produce activated carbon by chemical activation with H3PO4 as an adsorbent for adsorption of CO2. It was subjected to thermal treatment with the ammonia solution at 400 and 800 °C in order to improve CO2 capture. The textural and surface characteristics of the prepared activated carbons were determined from the analysis of N2 adsorption isotherms, elemental analysis, Fourier Transform Infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM), acid–base Boehm titration and X-ray photoelectron spectroscopy (XPS). The results show that the modification of activated carbon at high temperature enhanced BET surface area and micropore volume. The results indicate that the physical parameters such as surface area, lower pore diameter, and larger micropore volume of carbon samples show influence on the adsorbed amount of CO2. The adsorption behavior of CO2 onto carbon samples was experimentally evaluated by volumetric method at temperatures ranging from 288 to 348 K and pressure range of 0–16 bar. The CO2 adsorption capacity achieved by modified carbon was 3.22 mmol/g at 1 bar and 303 K which became more than the virgin carbon (2.9 mmol/g). The equilibrium CO2 adsorption data were fitted by Langmuir and Freundlich isotherms models. The thermodynamic parameters were investigated and indicated that the adsorption process was spontaneous and exothermic in nature and physisorption was the dominant mechanism for CO2 adsorption.