Pervaporation membranes that are highly selective for acetic acid over water

Supported liquid membrane pervaporation (SLMPV) is a pervaporation process for separating volatile organic compounds (VOCs) from their dilute aqueous solution. It simultaneously integrates extraction of the VOCs from the aqueous solution with flash distillation of the VOCs from the organic phase. By using a liquid membrane consisting of reactive extractants, pervaporation of primarily acetic acid from its aqueous solutions was studied. Limited studies of butyric acid were also done. Among various extractants tested, trioctylamine (TOA) and tridodecylamine demonstrated better performances. The SLM is permselective for acetic acid and butyric acid. The acetic acid selectivity can be as high as 33 for a feed of 1 M at 60°C, an order of magnitude higher than that obtained by any solid polymeric membrane reported in the literature. The simple SLM system demonstrated long-term stability; for example, decreases of about 30% in both pervaporation flux and selectivity were observed over an operational period of 500 h. A new technique of continuous on-line regeneration of the LM during operation maintains completely stable operational performance.