%0 Journal Article
%T Measurement of Membrane Characteristics Using the Phenomenological Equation and the Overall Mass Transport Equation in Ion-Exchange Membrane Electrodialysis of Saline Water
%A Yoshinobu Tanaka
%J International Journal of Chemical Engineering
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/148147
%X The overall membrane pair characteristics included in the overall mass transport equation are understandable using the phenomenological equations expressed in the irreversible thermodynamics. In this investigation, the overall membrane pair characteristics (overall transport number , overall solute permeability , overall electro-osmotic permeability and overall hydraulic permeability ) were measured by seawater electrodialysis changing current density, temperature and salt concentration, and it was found that occasionally takes minus value. For understanding the above phenomenon, new concept of the overall concentration reflection coefficient is introduced from the phenomenological equation. This is the aim of this investigation. is defined for describing the permselectivity between solutes and water molecules in the electrodialysis system just after an electric current interruption. is expressed by the function of and . is generally larger than 1 and is positive, but occasionally becomes less than 1 and becomes negative. Negative means that ions are transferred with water molecules (solvent) from desalting cells toward concentrating cells just after an electric current interruption, indicating up-hill transport or coupled transport between water molecules and solutes. 1. Introduction Mass transport across the membrane must be discussed fundamentally on the basis of the thermodynamics because the thermodynamics describes the rule of energy changes inevitably generating in the mass transport. However, the classical thermodynamics discusses only reversible phenomena and it does not treat transport rate. The irreversible thermodynamics came to succeed in discussing the transport rate by introducing the concept of ¡°time¡± in its system [1¨C4]. Basic theory of the irreversible thermodynamics is established on the assumption of ¡°microscopic irreversibility¡± [5¨C7]. This assumption holds more strictly in the circumstance being more close to equilibrium states. The actual electrodialysis process is not formed in the equilibrium states, so that the irreversible thermodynamics is assumed to exhibit only approximated meaning in the electrodialysis system. However, the irreversible thermodynamics is considered to be applicable in the circumstances being apart to some extent from equilibrium states [8, 9]. The irreversible thermodynamics is the fundamental rule of mass transport and it is expressed by the functions including phenomenological coefficients. On the other hand, the performance of an electrodialyzer is expressed by the functions including parameters such as
%U http://www.hindawi.com/journals/ijce/2012/148147/