K2CO3 supported on activated carbon (K2CO3/AC) is a promising means to remove low-concentration CO2 from confined spaces. In this removal process, physical adsorption plays an important role but it is difficult to quantify the amount of CO2 adsorbed when both H2O and CO2 are present. The linear driving force mass transfer model is adopted to study the CO2 adsorption kinetic characteristics of K2CO3/AC by analyzing the experimental data. The effect of K2CO3 and H2O on the adsorption of CO2 in K2CO3/AC was also evaluated. K2CO3 loaded on the support is found to increase the mass transfer resistance but decrease the activation energy required for the physical adsorption process. The presence of water vapor is disadvantageous to achieve high physical adsorption capacity since it enhances the chemical sorption in the competitive dynamic sorption process.