Abstract
A comprehensive study of the polyaniline influence on mineral scaling on the surface of the heterogeneous MK-40 sulfocationite membrane under electrodialysis has been conducted. Current-voltage curves and chronopotentiograms have been obtained and analyzed for the pristine MK-40 membrane and the MK-40 membrane which is surface-modified by polyaniline. The study of the electrochemical behavior of membranes has been accompanied by the simultaneous control of the pH of the solution outcoming from the desalination compartment. The mixture of Na2CO3, KCl, CaCl2, and MgCl2 is used as a model salt solution. Two limiting states are observed on the current-voltage curve of the surface-modified membrane. There is the first pseudo-limiting state in the range of small values of the potential drop. The second limiting current is comparable with that of the limiting current for the pristine membrane. It is shown that chronopotentiometry cannot be used as a self-sufficient method for membrane scaling identification on the surface-modified membrane at high currents. A mineral scale on the surfaces of the studied membranes has been found by scanning electron microscopy. The amount of precipitate is higher in the case of the surface-modified membrane compared with the pristine one.
Highlights
To date, methods of electromembrane technology are effective, environmentally cleanest, and cost-effective [1,2]
ED is based on the selective migration of ions through ion-exchange membranes (IEMs) under the action of applied electric field as the driving force
Mineral scaling on IEMs happens when salts from the solution precipitate and settle on the membrane surface and inside the ion-conductive pathways of the membrane [10]
Summary
Methods of electromembrane technology are effective, environmentally cleanest, and cost-effective [1,2]. Electrodialysis (ED) processes are widely implemented for brine concentrations in sea-salt production [2], the food industry [3,4], the extraction of precious or toxic substances, such as organic acids [5,6], wastewater treatment, especially for the removal of heavy metals [7,8], and production of acids and bases [9]. ED is based on the selective migration of ions through ion-exchange membranes (IEMs) under the action of applied electric field as the driving force. Despite the efforts of many other researchers to optimize ED performance for various applications, there are several weaknesses that restrict ED usefulness, involving selectivity, membrane fouling, and mineral scaling. Mineral scaling on IEMs happens when salts from the solution precipitate and settle on the membrane surface and inside the ion-conductive pathways (pores) of the membrane [10]. Scaling is Membranes 2020, 10, 145; doi:10.3390/membranes10070145 www.mdpi.com/journal/membranes
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