de . Dac CO, in the gas phase within the porous adsorbent (mol CO2/cm (cm' gas/cm' adsorbent). The experiment is conducted as an gas pore space), and K is the apparent CO, adsorption constant unsteady-state process where the total amount of CO, captured within the adsorbent is measured after a given time. Initially, there is no CO2 adsorbed on the solid or in the pore space, and the process is considered dilute with respect to CO2 in the gas phase. The diffusion process is modeled as a semi-infinite sink for Co, with the CO2 flux given by D Nakao = CAS where DAC E+R and CA, is the molar concentration of CO2 at the outer surface of the slab. In the above equation, DA is the apparent diffusion coefficient of CO2 within the adsorbent material under conditions where the solute adsorbs onto the surface of the pores, which includes the following terms: apparent CO2 adsorption constant (K"), the void fraction of the porous adsorbent (e), and the effective diffusion coefficient of Co, within the solid under non-CO, adsorbing conditions (DA). In the present system, X = 1776.2 cmcm. =0.60, and Ds = 0.018 cm/s. After a total contact time of 60 min, what was the total mass of CO2 captured by the slab? Consider that the slab acts as a semi-infinite sink for CO2, and that convective mass-transfer resistances are eliminated so that CA = Case 10 mol% CO2, 90 mol% Nz 200C, 15 atm Z=0 CA = CA. Microporous material (e = 0.60) adsorbs CO from gas (semi-infinite slab) 12 As society searches for technical solutions to global warm- ing, one approach to sequester carbon-dioxide-rich greenhouse gases is to capture the CO2 within an adsorbent material at high pressure. An experiment designed to evaluate a candidate adsorbent material is presented in the figure below, which consists of a 10 cm x 10 cm slab with 100 cm? of exposed surface. A gas mixture of 10 mole% CO2 (species A) and 90 mole% N2 (species B) at 15.0 atm total system pressure and temperature of 200C is contacted with a microporous material designed to selectively adsorb the CO2 from the gas mixture. The partitioning of CO2 gas within the adsorbent is described by QA = K'CA = where QA is the amount of CO2 adsorbed per unit volume of porous adsorbent (mol CO2/cm adsorbent), CA is the concentration of