TY - JOUR
T1 - Permeation selectivity in the electro-dialysis of mono- and divalent cations using supported liquid membranes
AU - Qian, Zexin
AU - Miedema, Henk
AU - de Smet, Louis C.P.M.
AU - Sudhölter, Ernst J.R.
PY - 2022
Y1 - 2022
N2 - We investigated in detail the permeation selectivity in the electro-dialysis of Na+, K+, Mg2+ and Ca2+ in both binary and quaternary mixtures using a supported liquid membrane (SLM). The SLM consisted of the organic liquid 2-nitrophenyl octyl ether (NPOE) containing a lipophilic anion, i.e. tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, as the cation-exchanging site, which was used to fill the pores of the supporting membrane AccurelR. We first determined the electro-phoretic mobilities of the migrating cations in single salt solutions, yielding: Na+ > K+ > Mg2+ > Ca2+. This order reflects the different size of the migrating cations. The monovalent cations Na+ and K+ migrate in the dehydrated state and the divalent cations Ca2+ and Mg2+ migrate in a (partly) hydrated state, a conclusion was supported by Karl Fisher titrations. Both binary and quaternary salt experiments showed a permeation selectivity in the following order: K+ > Na+ > Ca2+ > Mg2+. Since this order does not correlate with the order of electro-phoretic mobilities, we have determined the ion-exchange selectivity constant (Kex) and found: K+ > Ca2+ > Mg2+ ≈ Na+. We conclude that the overall permeation selectivity is determined by the combination of ion-exchange selectivity and electro-phoretic mobility of the cations present in the membrane.
AB - We investigated in detail the permeation selectivity in the electro-dialysis of Na+, K+, Mg2+ and Ca2+ in both binary and quaternary mixtures using a supported liquid membrane (SLM). The SLM consisted of the organic liquid 2-nitrophenyl octyl ether (NPOE) containing a lipophilic anion, i.e. tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, as the cation-exchanging site, which was used to fill the pores of the supporting membrane AccurelR. We first determined the electro-phoretic mobilities of the migrating cations in single salt solutions, yielding: Na+ > K+ > Mg2+ > Ca2+. This order reflects the different size of the migrating cations. The monovalent cations Na+ and K+ migrate in the dehydrated state and the divalent cations Ca2+ and Mg2+ migrate in a (partly) hydrated state, a conclusion was supported by Karl Fisher titrations. Both binary and quaternary salt experiments showed a permeation selectivity in the following order: K+ > Na+ > Ca2+ > Mg2+. Since this order does not correlate with the order of electro-phoretic mobilities, we have determined the ion-exchange selectivity constant (Kex) and found: K+ > Ca2+ > Mg2+ ≈ Na+. We conclude that the overall permeation selectivity is determined by the combination of ion-exchange selectivity and electro-phoretic mobility of the cations present in the membrane.
KW - Electro-dialysis
KW - Ion dehydration
KW - Ion electro-phoretic mobility
KW - Ion exchange
KW - Ion selectivity
KW - Supported liquid membrane
UR - http://www.scopus.com/inward/record.url?scp=85118606536&partnerID=8YFLogxK
U2 - 10.1016/j.desal.2021.115398
DO - 10.1016/j.desal.2021.115398
M3 - Article
AN - SCOPUS:85118606536
SN - 0011-9164
VL - 521
JO - Desalination
JF - Desalination
M1 - 115398
ER -