Selectrodialysis with bipolar membrane for the reclamation of concentrated brine from RO plant

Abstract

Reverse osmosis (RO) is increasingly becoming the dominant strategy for seawater desalination owing to its excellent desalination performance over the past few decades. It produces a considerable amount of concentrated brine, which is a threat to marine ecosystems accompanying freshwater production. Electrodialysis has been demonstrated to be a feasible process for brine treatment. In this work, a novel process called Selectrodialysis with Bipolar Membranes (BMSED) was firstly proposed for treating concentrated brine. BMSED uses bipolar membranes and monovalent selective ion exchange membranes inside the ED stack and thus combines the selectrodialysis (SED) and bipolar membrane electrodialysis (BMED) processes into a single step. BMSED can desalinate concentrated brine, selectively regenerate monovalent ions and produce acids/bases in a single route. The feasibility of the process was investigated by using different commercial membranes. The factors, including the current density and brine concentrations, were investigated. The results indicated that brine was successfully treated by using BMSED and that a HCl and NaOH solution (up to an approximate 2 mol/L concentration) with high purity was eventually produced. Therefore, BMSED is a pertinent environmentally and economically friendly process for RO concentrated brine management.