Search

A reinforcing fabric is an integral part of heterogeneous ion exchange membranes (IEMs). It guarantees the mechanical resistance of IEMs. Thermal fixation of the fabric is one of the most important refining operations, which is also reflected in the production of IEMs during lamination on heated cylinders. The influence of the fixation temperature (grey variant, 120, 160 and 215°C) of the Ulester 31HDA polyester fabric with a twill weave on the production of IEMs was studied. DSC, iodine sorption value measurement and dimensional stability during the additional heat load were studied for commercially supplied fabrics Ulester 31HDA. The values were compared with a model series of fabrics prepared in laboratory drying under precisely defined conditions (temperature and time). The principle of fixation is the rearrangement of the internal fiber structure associated with the change of the crystalline phase. The reinforcing fabric is dimensionally stable up to the fixation temperature. Iodine sorption value decreased with the increasing temperature of fixation. No changes were seen from SEM images or density measurements. DSC analysis did not show the predicted dependence for the model series of fabric. Dimensional changes after temperature loading increased with temperature. [ABSTRACT FROM AUTHOR]

Drinking water quality has been a global problem in recent years. With the growing specific industry, groundwater and surface water are contaminated with certain substances, so drinking water concentration limits for these substances must be defined. Fortunately, with the evolving industry, there is a range of methods that can be used to treat water dedicated to potable purposes. Among them, an electromembrane process with anion exchange membranes can be found. These membranes can be used approximately to remove perchlorate ions from purified water. The paper deals with regeneration and long-term stability of anion exchange membranes in 3% perchloric acid solution. For anion exchange membranes, electrochemical properties such as an areal resistance and a permselectivity were observed for 5 months. At the same time, a change in the mechanical and optical properties of the reinforcing fabrics used in the anion exchange membranes was monitored. Long-term exposure did not have a major effect on the anion exchange membrane permselectivity, and the mechanical properties of the reinforcing fabric did not show significant changes. Differences were determined only for the areal resistance, which grew slightly with the increasing exposure time. [ABSTRACT FROM AUTHOR]

Mechanical, physical and electrochemical characteristics are one of the important properties of ion exchange membranes. These parameters are required for a next operation and for an application in an electrodialysis (as tightness of a stack, energy consumption, capacity of electrodialysis). The goal of this article is comparison of the influence of the different reinforcing fabric on the properties of ion exchange membranes. Six types of ion exchange membranes with the nonwoven fabric, the monofilament knit, the multifilament knit, the monofilament woven fabric, the multifilament woven fabric, and for comparison non-reinforcing ion exchange membranes were chosen. The most important properties of a fabric in this application are thickness, free area related to the warp and the weft, mechanical strength, the material (shrinkage), type of fabric (plain or twill weave, a knit, monofilament, multifilament) and of course price. Electrochemical, physical and mechanical properties of ion exchange membranes were studied. Non-reinforcing ion exchange membranes have lower mechanical strength, but the best elongation. These ion exchange membranes report big relative dimension changes after swelling in demineralized water and the lowest value of the areal resistance. The most appropriate ion exchange membrane is with woven fabric from monofilaments after comparison with other ion exchange membranes in terms of the quality of the lamination and other electrochemical, physical and mechanical parameters. [ABSTRACT FROM AUTHOR]

The goal of this article is focused on the preparation and the basic characterization of heterogeneous weak acid cation exchange membranes. The six weak cation exchange resins were chosen for the preparation of the membranes. The strong acid cation exchange membrane was prepared for the comparison of properties and preparation parameters. Heterogeneous membranes were prepared in the several steps. The last operations were the extrusion and hydraulic hot-pressing. The torque and pressure in the extrusion head were observed while the extrusion of heterogeneous membranes. According to the type of the ion exchange resin, parameters varied greatly. The strong acid cation exchange membrane and weak acid cation exchange membranes with carboxylic groups had the lowest values of the torque and pressure while the homogenization and extrusion. All membranes were characterized. Electrochemical (permselectivity, ion exchange capacity, resistance), physical (relative water content, swelling in the different solutions), and mechanical properties were measured. Properties varied distinctly according to the type of the ion exchange resins. Swelling dimensional changes of ion exchange membranes in sodium hydroxide and water were bigger than changes in hydrochloric acid. Ion exchange capacity of membranes related with ion exchange capacity of used ion exchange resins. Weak acid cation exchange membranes with carboxylic functional groups compared to the strong membrane had the best specific and areal resistance. [ABSTRACT FROM AUTHOR]

This article focuses on the preparation of the heterogeneous ion exchange membrane with a special surface structure made with three types of knitted fabric. The special surface structure of ion exchange membranes can be useful for the intensification of mass transfer processes in electrodialysis. Three types of structured ion exchange membranes were prepared together with a membrane with a flat surface to compare the influence of geometrical structures on the behaviour of ion exchange membrane properties. Electrochemical, mechanical and physical properties were determined. Structured membranes exhibited comparable electrochemical and physical properties to the flat ion exchange membrane. Some transport parameters were measured in an electrodialysis stack with two concentrations of solution. Two electrodialysis stacks with different sizes of active area were used for comparison. Improving efficiency and mass flux was not confirmed. It was not demonstrated that structured IEMs were not better than IEMs with the flat surface. [ABSTRACT FROM AUTHOR]

Copyright of Waste Forum is the property of Czech Environment Management Center (CEMC) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Waste Forum is the property of Czech Environment Management Center (CEMC) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The heterogeneous ion-exchange membranes consist of polymer matrix and ion-exchange resin powder. The goal of this work was to compare two types of the heterogeneous bipolar membranes made of powdered ion-exchange resin with different water content. The water content influences the resistance of layers and the kinetics of water dissociation. The properties of heterogeneous bipolar ion-exchange membranes were compared due to the current–voltage curve. The evaluated parameters are the limiting current density, the efficiency of the water dissociation, and the resistance below the potential for water splitting. Finally, the bipolar membranes were tested in the electrodialysis stack. The membranes with higher water content had about 25% higher performance at the stack. [ABSTRACT FROM PUBLISHER]