Diffusion-controlled hysteresis

A new model of time-dependent sorption-desorption hysteresis is presented. This type of hysteresis is not related to transitions between metastable adsorption states, which are a common cause of capillary condensation hysteresis in mesoporous materials. We show that time-dependent hysteresis is a consequence of slow kinetics and failure to reach equilibrium at given experimental conditions. The model of diffusion-con trolled hysteresis (DCH) we developed is capable of predicting time-dependent experimental data. It allows one to estimate the characteristic diffusion. We show that DCH model time and the equilibrium sorption isotherms from non-equilibrium sorption/desorption measurements. The DCH model has been tested using experimental CO,) isotherms on polymeric and carbonaceous materials.