Water electrotransport in membrane systems. Experiment and model description☆

Electrokinetic Phenomena in Sulfonated Cation-Exchange Membranes with Tetraalkylammonium Ions

“…In accordance with this model, structural elements of a swollen membrane are assembled into the conducting phases by the mechanism of current transfer. The applicability of such model also to perfluorinated membranes, whose structure significantly differs from that of heterogeneous membranes, was demonstrated in [11][12][13]. In spite of the fact that MF-4SK films are homogeneous according to their preparation, probably, there are cavities in their structure containing internal solution that does not constitute the composition of water cluster phase.…”

“…In MK-40 membrane, in addition to the gel fragments of a resin, there is a pore space filled with water or equilibrium solution. The volume fraction of this "pseudo-phase" determined within the framework of two-phase model of conductivity, on average, is equal to 0.2 [9,11]. In accordance with this model, structural elements of a swollen membrane are assembled into the conducting phases by the mechanism of current transfer.…”

“…In spite of the fact that MF-4SK films are homogeneous according to their preparation, probably, there are cavities in their structure containing internal solution that does not constitute the composition of water cluster phase. The determination of the volume fraction of this "pseudo-phase" demonstrated for a number of MF-4SK and Nafion membranes that, on average, its contribution is approximately twofold lower than for heterogeneous membranes [6,[11][12][13].…”

“…Conductivity κ m was calculated based on the measurements of electrical resistance of a sample by hydrogen contact method at the ac frequency of 200 kHz. Electroosmotic permeability D i (m 3 A -1 s -1 ) of membranes was determined by volumetric method in a two-chamber cell with unpolar-SO 3 -ized silver chloride electrodes [11]. The transport number of water as a number of water moles transferred with 1 F of electricity ( t w , mol ç 2 é/ F ) was calculated by the formula (1) where F is Faraday's number and is the molar volume of water.…”

Hybrid electrodialysis reverse osmosis system design and its optimization for treatment of highly saline brines

“…However, where the salinity of the concentrate is high, the effective concentration of this volume transported can be similar in value. The modelling of electro-osmotic transport through membranes is complex and depends upon the degree of crosslinking of the membrane (related to pore and channel size and distributions) and also the concentration of the diluate and concentrated solutions [15]. To some extent, in particular at high concentrations, the water transport number is related to the hydration number of the ion in a concentrated solution [15].…”