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VOC REMOVAL FROM WATER AND SURFACTANT SOLUTIONS BY PERVAPORATION: A PILOT STUDY
Citation:
Hitchens*, L, L M. Vane*, AND F R. Alvarez*. VOC REMOVAL FROM WATER AND SURFACTANT SOLUTIONS BY PERVAPORATION: A PILOT STUDY. Strathmann, H., Lien C., Teramoto, M. (ed.), SEPARATION AND PURIFICATION TECHNOLOGY. Elsevier Science Ltd, New York, NY, 24(1-2):67-84, (2001).
Description:
The removal of VOCs from aqueous solutions via pervaporation is an established technology that has been successfully demonstrated at the full scale. The purpose of this research was to measure the effect of DOWFAX 8390 surfactant addition on pervaporation system performance and the mass transfer of 1,1,1 trichloroethane (TCA) and toluene. This aqueous surfactant application of pervaporation targets the recovery and reuse of surfactant from SEAR (surfactant enhanced aquifer remediation) process fluids. In this study, a pilot scale pervaporation unit with 4 spiral wound modules was used to conduct 75 eight hour runs. Process variables included temperature (30, 40, 50, 60oC), permeate pressure (15,25, 55 torr), flow rate 0.25 - 2.0 gpm), and VOC feed concentration (17 - 265 mg/L TCA and 5 - 200 mg/l toluene). Comparable conditions were used in both surfactant and non-surfactant systems. The fraction of each VOC removed from the feed stream was calculated from feed and effluent concentration measurements. No relationship was observed between absolute VOC feed concentration and relative removal though TCA was more easily removed than toluene in both surfactant and non-surfactant systems. There was also no difference in the water flux between the two systems. Surfactant addition reduced the removal of VOCs from 0.7% to 29% depending on the system flowrate (membrane contact time), feed temperature and VOC. The reduced VOC flux resulting from the additon of surfactant was found to be attributed to an increase in the liquid viscosity due to the addition of the surfactant (10-13% increase) and the partitioning of the VOC into the micellar phase of the surfactant (0.321 - 0.372 extramicellar fraction TCA and 0.216 - 0.271 extramicellar fraction toluene) at experimental conditions. Though the addition of surfacturant causes a decrease in the removal of VOCs, this study demonstrates that pervaporation can be used to remove VOCs from surfactant solutions without affecting the surfactant, permitting surfactant recycle.