TY - JOUR
T1 - Dia-nanofiltration-electrodialysis hybrid process for selective removal of monovalent ions from Mg2+ rich brines
AU - Nativ, Paz
AU - Fridman-Bishop, Noga
AU - Nir, Oded
AU - Lahav, Ori
N1 - Publisher Copyright:
© 2020 Elsevier B.V.
Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2020/5/1
Y1 - 2020/5/1
N2 - A hybrid nanofiltration-electrodialysis process was developed and tested for highly-selective separation of MgSO4 from seawater. The magnesium-rich solution was produced primarily for replenishing Mg2+ into desalinated water within the post-treatment step in seawater desalination plants. The new three-step process consists of: (1) seawater nanofiltration (NF) for generation of a magnesium-rich retentate; (2) a Dia-NF step in which the NF retentate is used as feed, which is aimed at minimizing unwanted solutes (primarily B, Na+ and Cl−); and (3) a selective electrodialysis (ED) step on the retentate from step 2, aimed at further lowering the Cl−:Mg2+ mass ratio to below 0.2, to produce a high-purity MgSO4-rich product solution. Results are presented with an emphasis on the ED step, for which the effects of flow velocity, current density and two operation modes (constant-current and constant-potential) were assessed. The results show a highly-dependent selectivity of the monovalent-selective ion-exchange membrane to the cell potential, suggesting that it can serve as a fine-tuning tool for selective ED processes. The cost of adding 20 mgMg/L to one m3 of desalinated water was estimated at ~$0.014/m3, which is competitive compared to other separation techniques, and certainly versus the alternative of direct dosage of food-grade magnesium salts.
AB - A hybrid nanofiltration-electrodialysis process was developed and tested for highly-selective separation of MgSO4 from seawater. The magnesium-rich solution was produced primarily for replenishing Mg2+ into desalinated water within the post-treatment step in seawater desalination plants. The new three-step process consists of: (1) seawater nanofiltration (NF) for generation of a magnesium-rich retentate; (2) a Dia-NF step in which the NF retentate is used as feed, which is aimed at minimizing unwanted solutes (primarily B, Na+ and Cl−); and (3) a selective electrodialysis (ED) step on the retentate from step 2, aimed at further lowering the Cl−:Mg2+ mass ratio to below 0.2, to produce a high-purity MgSO4-rich product solution. Results are presented with an emphasis on the ED step, for which the effects of flow velocity, current density and two operation modes (constant-current and constant-potential) were assessed. The results show a highly-dependent selectivity of the monovalent-selective ion-exchange membrane to the cell potential, suggesting that it can serve as a fine-tuning tool for selective ED processes. The cost of adding 20 mgMg/L to one m3 of desalinated water was estimated at ~$0.014/m3, which is competitive compared to other separation techniques, and certainly versus the alternative of direct dosage of food-grade magnesium salts.
KW - Desalinated water
KW - Electrodialysis
KW - Ion exchange membranes
KW - Mg replenishment
UR - http://www.scopus.com/inward/record.url?scp=85079234293&partnerID=8YFLogxK
U2 - 10.1016/j.desal.2020.114357
DO - 10.1016/j.desal.2020.114357
M3 - 文章
AN - SCOPUS:85079234293
VL - 481
JO - Desalination
JF - Desalination
SN - 0011-9164
M1 - 114357
ER -