Use of the desalination brines in the saturation of membrane electrolysis feed

Abstract

Seawater desalination by reverse osmosis (RO) invokes the necessity of brine disposal. On the other hand, the chlor-alkali industry requires saturated brine with a low content of calcium and magnesium contaminations. This paper describes a preliminary study exploring the possibility of the application of RO, nanofiltration–reverse osmosis, and nanofiltration–reverse osmosis–multieffect distillation seawater desalination brines as a sodium chloride source for membrane electrolysis. A concept has been proposed in which electrodialysis with univalent permselective membranes is used to enrich chlor-alkali lean brine with sodium chloride, and simultaneously desalinate discharge brine. The experiments with an electrodialyzer equipped with Neosepta® ACS and CMS membranes of 42 cm effective length have shown that the desired concentration of membrane electrolysis feed (above 300 g/L as NaCl) can be achieved. At the same time, the concentrations of both calcium and magnesium are decreased, the latter to a greater extent, that facilitates the successive brine purification step.

Keywords:

• Electrodialysis
• Chlor-alkali brines
• Brine reuse
• Membrane electrolysis feed
• Univalent permselective membranes
• Calcium and magnesium transport

Acknowledgment

This work was partially financed by Polish Ministry of Science and Higher Education, Grant No. N N2092 27738.