DEFINING WATER FLUX IN ELECTROMEMBRANE PROCESSES

IUPAC recommendations on the terminology for membranes and membrane pr ocesses have been made on the understanding that new definitions are a ugmented as evolution of the field occurs. With increasing interest be ing taken in the determination of water transport through ion exchange membranes, it is time to codify definitions which can be used as a ba sis for the comparison of performances. This paper sets out the defini tions of (i) superficial water flux, (ii) water transport number, and (iii) specific water transport number. It focuses on the water transpo rt measures, their definition and physical meaning. Experimental techn iques, therefore, are not discussed in detail. The importance of under standing measurement limitations is highlighted, along with the necess ity to report complete sets of performance data.