The permeability and solubility for water and ethanol in PTFEP membranes were determined experimentally, and the data were analyzed by the solution-diffusion model. The permeability for water and ethanol ranged from s...
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The permeability and solubility for water and ethanol in PTFEP membranes were determined experimentally, and the data were analyzed by the solution-diffusion model. The permeability for water and ethanol ranged from several hundreds to several thousands Barrers, and they increased exponentially with the vapor activity and increased with temperature. At the same temperature and vapor activity, the permeability ratio between water and ethanol ranged from 5.7 to 2.3, and it decreased as the vapor activity increased. The sorption isotherms for water and ethanol were fitted by the Henry's law relationship. The solubility decreased as the temperature increased so that the heat of sorption for both water and ethanol was negative. The solubility for water was more than twice the solubility for ethanol. The solubility seems to be inversely proportional to the molecular size of the penetrants in such a system. The solubility ratio between water and ethanol is smaller than their molecular volume ratio possibly due to the slightly stronger nonpolar interaction and the higher degree of plasticization in the ethanol-polymer system. The diffusivity for water and ethanol ranged from 10(-8) to 10(-7) cm(2)/s, and the values for water were larger than those for ethanol at the same temperature and vapor activity. The diffusivity for water and ethanol also increased exponentially with the vapor activity. The diffusivities for water and ethanol increased with temperature and their activation energies of diffusion were very similar possibly due to the same energy characteristic of polymer main chain movement.
In the field of reverse osmosis (RO) there are several theories from which mathematical models have been developed, allowing for the simulation of processes and the prediction of results. This study used the model dev...
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In the field of reverse osmosis (RO) there are several theories from which mathematical models have been developed, allowing for the simulation of processes and the prediction of results. This study used the model developed by Slater and Col, based on the solution-diffusion model for the simulation of RO processes. It was developed with an M20 RO Lab Unit made by DOW DANMARK SEPARATION SYSTEMS and uses a pair of flat membranes of HR 98 PP type, also made by DOW DANMARK A/S SEPARATION SYSTEMS. The results obtained are within the expected range for the volume flows and permeate concentrations under study. All the relevant constants in the model were determined, and were found to be in agreement with the expected results. The solute used was potassium chloride (KCI) and the dissolvent was distilled water, with concentrations ranging between 200 and 3000 ppm. Feed flows were in the range of 4.80 y 8.18 L/min, while the working pressure varied between 5 and 20 bar.
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