SEPARATION OF ELECTROLYTE-SOLUTIONS BY REVERSE-OSMOSIS

The paper presented is subdivided into two parts. The first one includ es a survey of current notions concerning the physico-chemical nature of interaction potential PHI between dissolved molecules or ions and w ater with a membrane material. Special attention is paid to the struct ural potential and the potential of image forces. The main conclusion is that the potential of interaction PHI determines the major part of phenomena which are relevant for reverse osmosis (RO) separation. In t he second part the distribution coefficient gamma = exp (PHI) is suppo sed to be known and a survey of theoretical investigations of RO proce sses is undertaken. The so called homogeneous model of RO membranes is employed and concentration polarization is taken into account. Two ma in points in this investigation should be emphasized, that is, taking into account concentration polarization and a theory of RO separation of electrolyte mixtures. The maximum value of rejection coefficient an d corresponding optimum velocity of filtration are calculated. Negativ e rejection of some ions from the mixture is explained, as well as a c hange in pH of filtrate. The streaming potential is calculated as a fu nction of Peclet number, distribution coefficients, membrane charge an d so on in all cases. The suggested theory gives the possibility to ex plain a number of phenomena in RO separation of electrolyte solutions.