The CO2 adsorption behavior study on activated carbon synthesized from olive waste

Abstract

Abstract In the present framework, we have studied the relationship between the activated carbon surface characteristics and the CO2 adsorption behavior. The two activated carbon series were synthesized from olive waste as a precursor employing ZnCl2 and H3PO4 as chemical activation agents; their yield of production reaches 34.2 % and 47.3 % respectively. Adsorption isotherms were carried out at 20 °C, 30 °C, 40 °C and 50 °C and pressured up to 1.48 MPa via manometric measurement. Activation agent and post-synthesis heat treatment effects have been investigated. The CO2 maximum amount uptake was equal to 10.96 mmol. g−1 and was achieved on the activated sample with ZnCl2 having a specific surface area about 1399 m2. g-1. Although, the synthesized activated carbon through the H3PO4 activation agent has less surface area, their adsorption per unit area is in the same range as the activated sample with ZnCl2. Four adsorption models were applied to modulate the CO2 adsorption behavior on the activated carbon surface (Langmuir, dual Langmuir, Sips and Toth isotherms). Models considering surface heterogeneity lead to a good correlation with adsorption data. Furthermore, the adsorption heats are measured and compared to the isosteric heats estimated from the isotherm model equation as well as the calculated ones using the Clausius − Clapeyron equation. The Langmuir model provides the nearest values to the measured adsorption heat, these value are about 24.64 ± 0.2 k J . m o l - 1 .