preface electromembr processes

Preface For the last forty years, electromembrane processes have experienced a steady growth for the industrial scale applications. They have been used in water processing, preparation of ultrapure water, in the management of effluents from mining industry, hydrometallurgical industry, pulp and paper industry or pharmaceutical industry. Recently, they have been applied for blue energy production, fuel cells, diary applications , chromic acid recovery, organic acid separation and recovery, synthesis of chemical (like ionic liquids), extraction of water-soluble organic acids, salt separation from mixtures in organic solutions, separation of valuable ions from wastewater, demineralization of sugar and amino acids and so on. The modern industries like pharmaceutical or chemical one, biotechnology and energy-related sectors use the electromembrane processes widely. However, the early euphoria of their applications has turned to more maturated and rational way of thinking. Available ion exchange membranes and electromembrane processes have still severe technical and commercial limitations. The main reason for this phenomenon is the shortage of knowledge on the processes and not completely satisfactory properties of available materials — poor selectivity at high ion concentration, deterioration of membrane properties, high costs and problems with mechanical and chemical stabilities of membranes. Taking into account the above reasons , we have decided to prepare a special issue of Desalination and dedicate it to the Electromembrane Processes. We have asked to the group of the well-recognized experts to show their opinion on the above mentioned subject. As the result of their work, the special issue was prepared. It contains 18 contributions dealing with one or more of the following topics: Fundamental • One paper presents the application of the computer program for evaluation of desalination extent when membrane properties , process parameters and electrodialyzer configuration are well known. That approach allows us to estimate the efficiency of an ED system before its assembling. • The second paper deals with evaluation of desalination run in the over-limiting current density mode. It gives an answer to the general question on the place of the process under the high current density — the profits and contras of such approach. • To avoid the membrane scaling during electrodialytic desalination of sparingly soluble salt solutions, the electrodialysis should be performed in a way that the vast majority of growing clusters is washed out an electrodialyzer before their crystalli-zation. Such method requires determination of residence time distribution in the electrodialyzer. It was a subject of another paper that focused on determination of residence time distribution in the electrodialyzer under electric field conditions. • Modeling the transport phenomenon of sulfuric acid and its sulfates through an anion-exchange membrane by electrodia-lytic method was the topic of another paper. The acid perme-ation was described using a transport model based on the Nernst–Planck equation and Donnan equilibria. Materials • In a review paper, the up-to-date synthetic strategies in the development of new ion-exchange materials were explained. The main focus was put on the introduction of functional groups into an existing polymer backbone. • Bipolar membranes occupy a special place among ion exchange membranes due to their ability to produce acid and alkali from corresponding salt. These properties allow designing a number of unique electromembrane processes having a great industrial impact. Electrochemical properties of heterogeneous bipolar membranes, methods for their investigation, some theories developed for description of water dissociation and ion transfer mechanism are discussed in another paper. Some of the novel electromembrane processes for application of heterogeneous bipolar membranes are presented. • In another paper, the use of inorganic–organic hybrid ion exchangers in the electrodeionization system for separation of Ni(II) ions from the a multicomponent solution was reported. • Modification of ceramic membranes with inorganic sorbents and their application for separation of Cr(VI) from a multicom-ponent solution were presented in another paper. It was mentioned that electrochemical behavior of the composite membranes was close to that for polymer ion exchange membranes. Moreover, the reported modification minimized the concentration polarization on the membrane surface. Applications • Electrodialysis can be used to concentrate NaCl for industrial applications. In one paper, the results obtained in an electrodi-alysis pilot plant established to concentrate the seawater reverse osmosis (SWRO) brine were discussed. According to the obtained data, it was possible to concentrate SWRO brine from 70 to 245 g/L NaCl using electrodialysis. • The concept of an integrated membrane system for boron removal, concentration and boric acid recovery was presented in the next paper. In such system boron and polyol containing Desalination 342 (2014) 1–2