Activated carbon-based CO2 uptake evaluation at different temperatures: The correlation analysis and coupling effects of the preparation conditions

As potential CO2 adsorbents, carbon materials have recently gained attention because of their low energy penalty, abundant sources and good stability. In this study, the response surface methodology (RSM) was used to guide the pitch-based activated carbon preparation and CO2 adsorption at different temperatures. Based on this experimental design, the correlations of CO2 uptakes at different temperatures, as well as the coupling effects of the preparation conditions on CO2 uptake, were analyzed by mathematical modelling. The obtained optimal carbon sample AC650-1.25-2.5 showed a high atmospheric CO2 uptake of 3.15( +/- 0.14), 2.05( +/- 0.02), and 1.37( +/- 0.11) mmol/g at 25 degrees C, 50 degrees C, and 75 degrees C, respectively. Furthermore, the analysis of variance confirmed that the key factor to determine CO2 uptake at 25 degrees C was the activator ratio, contributing to 77.8 % of the total variance; however, it gradually shifted to the activation temperature and its coupling effect with other factors for CO2 uptake at 75 degrees C. The linear regression and significance test of CO2 uptakes showed that using CO2 uptake at 25 degrees C to predict the uptake at 50 degrees C was feasible; however, it failed to work when predicting the CO2 uptake at 75 degrees C. The good linear relationship of CO(2 )uptakes at similar adsorption temperatures benefited from the existence of sharable effective pore width. It was also concluded that the strict requirement for extremely narrow ultra-micropores led to the non-coincidence of suitable preparation conditions, corresponding to a good CO2 uptake at different adsorption temperatures; this further led to the bad predictability when the adsorption temperature varied greatly.