SEAWATER REVERSE OSMOSIS BRINES AS A NEW SALT SOURCE FOR THE CHLOR-ALKALI INDUSTRY: INTEGRATION OF NaCl CONCENTRATION BY ELECTRODIALYSIS

Seawater RO brines have been identified as an alternative to common NaCl sources for the chlor-alkali industry. Electrodialysis (ED) has been evaluated as a preliminary step of NaCl concentration for these brines. Experimental results showed that ED was an effective concentration technology, where values up to 252 g(NaCl) L-1 were reached at 0.3-0.4 kA m(-2) with a power consumption of approx. 0.20-0.30 kWh kg(-1) NaCl. As the membranes used (Neosepta CIMS and ACS) were mainly selective for univalent ions, polyvalent ions were partially removed from the brine, benefiting its reuse. NaCl concentrated solutions are to be used as feed brine in the chlor-alkali industry after a purification step.