Permeation and thermal osmosis of water through cellulose acetate membranes

Isothermal permeation and thermal osmosis of pure water through cellulose acetate membranes have been studied. In all cases the results have been analyzed and compared with those of the literature. Two kinds of isothermal permeation experiments have been carried out, in order to find the influence of temperature and stirring rate on the phenomenon. The activation energy for permeation has been calculated.In the case of thermal osmosis two different kinds of experiments have been developed. In the first, thermoosmotic flows have been measured. In the second, evolution towards steady states has been obtained. In both cases the experiments have been performed by varying separately the temperature difference, the mean temperature and the stirring rate. The activation energy for thermal osmosis has been calculated. The influence of stirring rate on thermal osmosis has shown that “temperature polarization” cannot be avoided with the experimental setup, but its influence may be evaluated. A method is proposed to evaluate the differential thermoosmotic permeability. It is suggested that the results obtained from steady states are more reliable than those obtained from thermoosmotic flows.