Production of Acids and Bases for Ion Exchange Regeneration from Dilute Salt Solutions Using Bipolar Membrane Electrodialysis

Abstract

The acids and bases used for ion exchange regeneration contribute significantly to the increasing salinity of potable water supplies. This research investigated the use of bipolar membrane electrodialysis (BMED) for producing acids and bases from dilute salt solutions that are produced during reverse osmosis or evaporative cooling. Using single pass BMED, acids and bases were produced with concentrations equal to ∼75% of the feed salt concentration with current utilizations >75%. Current utilization increased with increasing feed salt concentrations due to decreased leakage current through the monopolar membranes. The maximum current density at which the BMED stack could be operated depended on the feed salt concentration and the flow velocity and was limited by water dissociation at the interface between the diluate solutions and the monopolar membranes. The stack resistance was dominated by the bipolar membranes, even for the most dilute feed solutions. The energy required per mole of acid or base produced increased linearly with increasing current density. The energy costs for producing acids and bases were significantly less than costs for purchasing bulk HCl and NaOH, and the process is scalable to large systems.

Microbial electrochemical separation of CO2 for biogas upgrading

“…A bipolar membrane is made of an anion-exchange layer, a cation-exchange layer and a hydrophilic interface at their junction (Bazinet et al, 1998). Research has suggested that the production of acids and bases with application of BMED can be considered as costeffective and be applied in large-scale systems (Davis et al, 2015). Thus, BMED has potential for an innovative biogas upgrading method.…”

Valorization of desalination brines by electrodialysis with bipolar membranes using nanocomposite anion exchange membranes

“…Thus, EDBM simultaneously deals with desalination brines, lowering its salt content, and does valorize this salt into hydrochloric acid and sodium hydroxide. Several works in the literature deals with the modeling [12,13] and laboratory experimental work [14][15][16][17][18][19][20] of EDBM for treatment and valorization of brines, mainly focusing on the feasibility and optimization of operation conditions for the treatment. However, there are still some technical and economic challenges to overcome before this approach can develop its full potential.…”

Electrodialysis with Bipolar Membranes for Valorization of Brines

“…Figure 1 shows a possible configuration of the EDBM stack used in order to produce acids and bases from desalination brines. There are several inorganic sodium salts such as Na 2 CO 3 , NaNO 3 , Na 2 SO 4 , Na 3 PO 4 and NaCl that are reported to generate acids and bases by EDBM, with NaCl as the main pursued salt (55).Several publications reported the use of EDBM for the generation of HCl and NaOH from desalination brines and industrial wastewaters(56)(57)(58)(59)(60)(61)(62)(63)(64)(65)(66). Some of the treated salty streams were…”

“…A c c e p t e d M a n u s c r i p t 11 desalination retentates from RO plants producing drinking water(56,57) or industrial wastewaters with a high content of NaCl(58)(59)(60)(61)(62)(63)(64)(65)(66).…”