PERVAPORATION OF LOW VOLATILITY AROMATICS FROM WATER

Pervaporative enrichment of high boiling aromatic hydrocarbons from dilute aqueous solution through elastomeric polymer membranes is investigated. Selectivity in favor of the organic solution component, in addition to preferential membrane permeability, requires the aqueous-organic feed solution to be non-ideal with positive deviation from Raoult's law. The observed effects of downstream pressure and membrane thickness on pervaporation performance are rationalized by a transport model picturing the membrane as freely permeable to the organics while typically posing a resistance to water. The model predicts organic flux density and enrichment to be proportional to the activity coefficient of the organic solutes in water, and inversely proportional to downstream pressure in pervaporation. © 1990.