Thermodynamic factors in partitioning and rejection of organic compounds by polyamide composite membranes.

The paper analyzes the mechanism of partitioning and rejection of organic solutes by polyamide membranes for reverse osmosis and nanofiltration. The partitioning of homologous series of alcohols and polyols, in which polarity changes with size in opposite ways, was measured using attenuated total reflection IR spectroscopy. The results show that the partitioning of polyols monotonously decreases with size, whereas for alcohols it is not monotonous and slightly decreases for small C1-C3 alcohols followed by a sharp increase for larger alcohols.

Use of attenuated total reflection infrared spectroscopy for analysis of partitioning of solutes between thin films and solution.

The paper examines attenuated total reflection (ATR) spectroscopy as a tool for quantifying the partitioning of small molecular species between a solution and a thin film, while the film is directly exposed to the solution for equilibration. For the case of a thin film having a thickness substantially smaller than the decay length of the evanescent wave, we developed suitable linear relationships that relate the measured absorption of the characteristic band to the concentration of the species under study in the film and in solution. In the application of ATR-Fourier transform infrared spectroscopy, the method is particularly suitable for films a few tens to hundreds of nanometers thick and for solutes that preferentially partition into the film.