posted on 2019-05-22, 00:00authored byMohammad
I. Hossain, T. Grant Glover
The
diffusion mechanism and the concentration dependence of the
mass transfer rate of water vapor adsorbing in the zirconium-based
metal organic framework (MOF) UiO-66 has been determined using a concentration
swing frequency response (CSFR) apparatus. The mechanism that best
describes the adsorption of water in UiO-66 is micropore diffusion
and the rate is dependent on the gas phase concentration of the water.
Moreover, the results show that as the gas phase water concentration
increases, a minimum in the water adsorption rate occurs near 4 mol/kg
of water loading. Although the Darken relationship is unable to predict
the concentration dependence, it agreed qualitatively with the experimental
diffusivity data extracted from the CSFR analysis. The results demonstrate
the ability of the concentration-swing frequency response technique
to accurately determine adsorption rate mechanisms and quantify the
adsorption kinetics of a slow to moderately fast diffusing component
in MOFs.