Using a microheterogeneous model to assess the applicability of ion-exchange membranes in the process of reverse electrodialysis

Abstract

This paper shows the possibility of using a microheterogeneous model to describe the properties of ion-exchange membranes and calculate the characteristics of a reverse electrodialyzer from the data obtained. We studied the properties of eight samples of heterogeneous cation exchange membranes (two samples of each type of membrane). The samples differed in the year of issue and storage conditions. It is shown that for heterogeneous ion-exchange membranes MK-40 and MA-41, the samples' properties can differ significantly. The counterions transport numbers calculated within the framework of the microheterogeneous model for Ralex membranes differ insignificantly. The counterion transport number in 1 mol/L sodium chloride solution is 0.96 for Ralex CM and 0.98 ± 0.01 for Ralex AMH. For the MK-40 membrane, the transport number in the same solution is 0.94 ± 0.04, and for the MA-41 membrane, it is 0.85 ± 0.1. The possibility of calculating the transport numbers and predicting the open-circuit voltage based on simple physicochemical measurements allows selecting the best membrane pairs for the reverse electrodialysis process. Comparison of the open-circuit potential value calculated using the obtained transfer numbers with experimental data showed that in the case of using Ralex membranes, the difference between the experimental and calculated values is 2%. The calculated value of the open circuit potential was 0.19 V/membrane pair or 1.69 V for the investigated reverse electrodialyzer with nine pair chambers.

A Cell Model of an Ion-Exchange Membrane. Capillary-Osmosis and Reverse-Osmosis Coefficients

“…At interface , the conditions for equality between the radial components of ion fluxes must be fulfilled, with these conditions leading to the following set of equations relative to the unknown constants (see Eq. (43a) in [2]): (10) Here, taking into account the form of the general solution for radial velocity component , the following denotation has been introduced: (11) Cell pressure gradient was previously determined as…”

“…Substituting Eqs. ( 17), ( 18), (20), and (21) into set (10), we find explicit expressions for constants :…”

“…Such models are known and have been published in, e.g., [7,8]. It should be noted that there are other models of an ion-exchange membrane, e.g., microheterogeneous one [9,10], which is actively developed by the researchers of the Kuban scientific school of membrane electrochemistry. The author intends to compare the microheterogeneous and cell models of an ion-exchange membrane in subsequent works.…”

Microstructural description of ion exchange membranes: The effect of PPy-based modification

“…From the microscopic point of view, membranes may differ structurally and chemically when performing modifications and that affects the processes that are taking place at the inner. Therefore, the importance of inquire about the membrane microstructure is fundamental to foresee the benefits of this materials in pursuits of a potential application [27,28].…”