Supported liquid membrane-based pervaporation for VOC removal from water

Supported liquid membrane pervaporation (SLMPV) is a pervaporation process for separating volatile organic compounds (VOCs) from their dilute aqueous solutions through a supported liquid membrane. It integrates simultaneous extraction of the VOCs from the aqueous solution with vacuum stripping of the VOCs from the organic phase in one membrane module. Using a liquid membrane consisting of nonvolatile hydrocarbons immobilized in the micropores of hydrophobic porous polypropylene hollow fibers with or without a plasma-polymerized ultrathin silicone membrane on the outside diameter of the fibers, trichloroethylene (TCE) was separated and concentrated from its aqueous solution at 25°C and essentially atmospheric pressure. The feed TCE concentration was varied between 50 and 950 ppm; the permeate pressure range was 0.6-70 mmHg. A 78-fiber, 30-33-cm-long module can achieve as much as 98% removal of TCE. The hexadecane SLM is permselective for TCE: the experimental selectivity was 30 000, and the intrinsic selectivity could be as high as 2 × 10⁵, much higher than the values reportedly obtained by any solid membrane. The hexadecane SLM performance indicated long-term stability: about 30% decreases in both pervaporation flux and selectivity were observed in a run lasting 4 months. A mathematical model has been proposed to predict the exit concentration, permeation flux, and selectivity from the properties of the membrane and VOCs and the operating conditions.