Removal of chlorinated compounds by pervaporation for the reuse of surfactant

Abstract

Recently pervaporation has been studied for the separation of volatile organic compounds from waste flushing solutions for surfactant recovery. Surfactant reuse is the key factor in surfactant-enhanced remediation (SER) because the cost of surfactants is high. Volatile compounds in waste solution sorb on the membrane, penetrate through it and evaporate into vapor phase. As a result, surfactant is recovered without foaming phenomenon and surfactant loss. This study focused on the simultaneous removal of contaminants and feasibility for application into field. Trichloroethylene (TCE) and tetrachloroethylene (PCE) were selected as representative contaminants. Tween 80, surfactant commonly used in groundwater remediation, and polydimethylsiloxane (PDMS), widely used hydrophobic material in pervaporation, were used. The effects of process parameters on pervaporation process were investigated. Membrane thickness between 200 and 300 μm did not affect the pervaporation performance. Organic flux did not increase above flow rate of 100 mL/min even though flow rate increased. The increase of feed concentration and temperature led to large organic flux. Selectivity reduced significantly with temperature due to the increase of molecular mobility and membrane swelling. The reduction of flux was small below 1.0 wt% Tween 80 in feed solution. Flux and selectivity of TCE were higher than those of PCE because extramicellar portion of TCE was higher than that of PCE. Pervaporation process was investigated for the simultaneous removal of TCE and PCE from surfactant solution. The competitive sorption by flux and selectivity decline was observed. However, the reduction percentage was less than 10% with 1:1 ratio of TCE/PCE. 4.0 wt% isopropyl alcohol (IPA) as flushing additive was added in feed solution. IPA flux was small as 2 g/ ㎡h and organic flux and selectivity did not change. With long-term operation, over 95% of TCE and 90% of PCE were removed fro...