Pervaporation of UDMH–water mixtures using hydrophilic zeolite NaA membranes: Mechanisms and experimental results

Zeolite membranes are thus well suited for separating liquid-phase mixtures by pervaporation. In this study, experiments were conducted with various UDMH–water mixtures at temperature 25 C o and UDMH concentrations (1–20 wt. %). The total flux for UDMH–water mixture was found to vary from 0.329 to 0.215 kg/m2/h at 25 C o as the feed solvent concentration was increased from 1 to 20 wt.%. The ionic sites in the NaA zeolite matrix play a very important role in the water transport through the membrane. These sites act both as water sorption and transport sites. The surface diffusion of water occurs in an activated fashion on these sites. The precise micropore structure of the zeolite cage helps in a partial molecular sieving of the large solvent molecules leading to high separation factors. One of the reasons for the high hydrophilic of zeolite NaA is the strong electrostatic interaction between ionic sites and the water molecule (due to its highly polar nature). A comparison between experimental flux and calculated flux by Stephan Maxwell correlation was be carried out. A linear correlation was found to exist for the water flux through the membrane and UDMH concentration.

Keywords:

Pervaporation , UDMH separation , NaA , Zeolite , Membrane