Desalination of an industrial saline water with conventional and bipolar membrane electrodialysis

Abstract

The removal of salts from industrial effluents by sustainable techniques is of great interest to many companies. In this study, an industrial saline water, mainly composed of NaCl and KCl, was treated with conventional electrodialysis (ED) and bipolar membrane electrodialysis (EDBM) on lab-scale. The saline water also contained significant amounts of sulfate and calcium, which may give rise to various types of scaling. A partial desalination (target was a removal of 50% of the chlorides) was easily achieved with both ED and EDBM. By using ED, a concentrate containing circa 2M of chlorides was obtained. The formation of scaling was avoided by using monovalent selective anion- and cation-exchange membranes, which was particularly necessary to avoid CaSO4 scaling. A further improvement was obtained by applying EDBM, which yielded an acid and a base stream with a concentration of around 2M, with a relatively good purity. From the initial lab-scale study it was concluded that both ED and EDBM are technologically feasible to desalinate the saline water. In a second phase, the ED scenario was scaled up in a pilot scale study, which demonstrated that the ED pilot plant was operated in a stable way during a long-term experiment.