Defining water flux in electro-membrane processes

Abstract

IUPAC recommendations on the terminology for membranes and membrane processes have been made on the understanding that new definitions are augmented as evolution of the field occurs. With increasing interest being taken in the determination of water transport through ion exchange membranes, it is time to codify definitions which can be used as a basis for the comparison of performances. This paper sets out the definitions of (i) superficial water flux, (ii) water transport number, and (iii) specific water transport number. It focuses on the water transport measures, their definition and physical meaning. Experimental techniques, therefore, are not discussed in detail. The importance of understanding measurement limitations is highlighted, along with the necessity to report complete sets of performance data.