AWWA MTC53726

The general objective of the study is to extend the widely accepted solution-diffusion model to predict the differential rejection of various electrolytesthrough reverse osmosis (RO) membranes. The central theme of the model rests onthe premise that ions diffuse through the RO membrane as electrically neutralsolutes and their effective diffusivities (i.e., salt permeability coefficients)are strongly correlated to the hydrated ionic radii of individual ions. It isknown that the affinity of an ion towards a polymeric ion exchanger is stronglycorrelated to its hydrated ionic radius. Thus, more easily obtained ion exchangeselectivity data may serve as the basis in determining the difference inpermeation rates of different electrolytes. According to information in the openliterature to date, ion exchange selectivity data have not been used as yet formodeling solute permeation through RO membrane. Of particular importance is theability of this new approach to predict differential permeation (or rejection)among ions of the same valance. Theoretical approaches as well as experimentalresults to this effect are included in this paper. Includes 19 references, table, figures.