Ionic Transport in Cation-Exchange Membranes MK-40 Modified with Zirconium Phosphate

Abstract

The synthesis of a composite membrane material on the basis of cation-exchange membrane MK-40 with inserted particles of acid zirconium phosphate is realized. It is shown that zirconium phosphate in the membrane's matrix takes on the form of small amorphous particles and is uniformly distributed. The obtained membrane is characterized by large values of conductance and diffusion coefficients for cations and anions, as well as by a lower selectivity when compared with the initial analogue. It is shown that the basic reason for this is the increase in the size of pores and channels, which are filled in the course of experiment by a solution of an electrolyte.

Water uptake and salt transport through Nafion cation-exchange membranes with different thicknesses

“…From this membrane ionic permeability the diffusion coefficient for the anion may be estimated directly. As the solution is very dilute, the membrane is very selective and therefore the diffusion penetrability is defined by the magnitude of the diffusion coefficient for the anion, D salt $ 2D iÀ (Novikova et al, 2005). Thus, in these conditions, from the diffusion coefficient for the coions it is possible to estimate the membrane salt diffusion coefficient.…”

Improvement of Selectivity of RALEX-CM Membranes via Modification by Ceria with a Functionalized Surface

“…Since the transport numbers t + of the modified membranes are higher than those of the pristine membrane ( Table 1 ), an increase in the limiting current density may be attributed to an enhancement of electro-convection on the surface of the modified membranes. Moreover, according to [ 45 , 53 , 54 ], the presence of phosphate groups in the modified membranes can catalyze water dissociation.…”

“…RALEX-solutions leads to an increase in the water uptake of the R_Ce_HPM membranes based on a copolymer of sulfonated styrene and divinylbenzene (Mega a.s., Straz pod Ralskem, Czech Republic) were preliminarily conditioned according to the standard procedure [ 45 ] in aqueous NaCl solutions of various concentrations (decreasing from 2 M to 0.01 M) to let membranes swell and in 5% HCl aqueous solution to convert membranes into H + -form. For asymmetric modification (on only one side of a membrane) by in situ method, conditioned RALEX-CM membranes were placed for 10 min in a two-compartment cell, one compartment of which was filled with 0.01 M Ce(NO 3 ) 3 solution, and the other was filled with deionized water.…”

“…For comparison, the dopant content of heterogeneous membranes bulk-modified with zirconia was much higher (up to 20 wt %) [ 46 ]. Ion exchange capacity (IEC) was determined by direct titration [ 45 ] of the membranes in the H + -form. IEC is given per 1 g of swollen membrane…”