Frequency-response evidence for parallel diffusion processes in the bimodal micropore system of an activated carbon

The rates of mass transport of gases such as propane, carbon dioxide, and ammonia have been studied in an activated carbon sorbent. The frequency-response (FR) method was used to measure these rates. Small-angle X-ray scattering (SAXS) and nitrogen-adsorption isotherm at 77 K showed that the activated carbon contains small micropores with diameters around 0.64 and 0.92 nm, respectively. The FR-rate spectra distinguished two parallel diffusion processes with different time constants, suggesting that the smaller and the larger micropores were not interconnected.