INFLUENCE OF TEMPERATURE POLARIZATION ON SEPARATION BY MEMBRANE DISTILLATION

Nonisothermal mass transport through three PTFE membranes has been studied. Aqueous solutions (0.1, 0.2, and 0.3 M) of sodium chloride were employed. The experiments were carried out under a temperature difference of 30 K and at mean temperatures of 25 and 45-degrees-C. The initial concentration and the stirring rate were changed independently. The stirring rate was varied among 0, 75, 150, 250 and 350 rpm. The results were interpreted on the basis of the membrane distillation theory. A separation between the two components increasing with time was obtained, and a model has been developed which permits us 1) to obtain concentration values from volume values, 2) to define a separation coefficient, and 3) to quantify the influence of stirring rate on the separation. The model has been applied to the experimental results and the agreement may be considered good.