Pervaporation of water, hydrazine and monomethylhydrazine using ethylcellulose membranes

Ethylcellulose membrane has been selected on the basis of Hansen's solubili ty parameter and Flory-Huggins interaction parameter for the enrichment of hydrazine and monomethylhydrazine (MMH) liquid propellants by pervaporation . An extensive study of the overall mass transfer resistance experienced by the permeants has been conducted. The resistance values were quantitativel y estimated by changing the membrane thickness and calculating the correspo nding flux. Due to its lower sorption, and fewer interactions, the membrane showed least desorption resistance towards water and thus it is permselect ive with respect to water. Results of pervaporation selectivity obtained in separation of water-hydrazine and water-MMH mixtures at azeotropic composi tions have been correlated. Higher sorption of MMH and hydrazine did not re sult in preferential separation inspite of lower membrane resistance. Exper imental results clearly showed that desorption resistance and diffusivity w ere predominant over the respective solubilities. To confirm the reasons fo r these phenomena, FTIR and DSC spectra of membranes soaked in pure hydrazi ne, MMH, water and hydrazine hydrate were compared. (C) 2000 Elsevier Scien ce Ltd. All rights reserved.