Selective permeation through hydrophobic–hydrophilic membranes

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Abstract
Hydrophobic–hydrophilic composite membranes, containing polystyrene as the dispersed phase and polyacrylamide as the continuous phase, have been prepared by the concentrated emulsion polymerization method. They are highly absorptive for methyl chloride, benzene, and toluene, but poorly absorptive for cyclohexane. The absorption from toluene–cyclohexane mixtures was found to increse with increasing temperature and toluene concentration and to decrease with increasing fraction of polyacrylamide in the composite. The absorption is controlled by diffusion. The permeation rate through the membrane, which was determined by the pervaporation method, exhibits similar trends with respect to temperature, concentration, and fraction of polyacrylamide as absorption does. Higher permeation was obtained by increasing the temperature and by increasing the toluene concentration or by decreasing the fraction of polyacrylamide. The selectivity which was in the range of 4–8 varies inversely with the permeation rate through the membrane which was in the range of 2 × 103−1.0 × 104 g/m2 h.