Department of Chemical Engineering, The University of Melbourne, Victoria, 3010, Australia.
State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, 100084, PR China.
Water Res. 2020 May 15;175:115681. doi: 10.1016/j.watres.2020.115681. Epub 2020 Mar 4.
The co-ion and counter-ion sorption of monovalent (Na, K, Cl and NO) and divalent ions (Ca and SO) in commercial Neosepta ion exchange membranes were systemically studied in both single and binary salt systems. The new generation of Neosepta cation exchange membrane (CSE) showed a significant difference in water uptake and co-ion sorption compared to the earlier generation (CMX). Use of the Manning model confirmed that there were significant differences between these membranes, with the estimated value of the Manning parameter changing from 1.0 ± 0.1 for CMX to 2.8 ± 0.5 for CSE. There were fewer differences between the two Neosepta anion exchange membranes, AMX and ASE. In single salt solutions, potassium sorbed most strongly into the cation exchange membranes, but in binary salt mixtures, calcium dominated due to Donnan exclusion at low concentrations. While these trends were expected, the sorption behaviour in the anion exchange membranes was more complex. The water uptake of both AMX and ASE was shown to be the greatest in NaSO solutions. This strong water uptake was reflected in strong sorption of sulphate ions in a single salt solution. Conversely, in a binary salt mixture with NaCl, sulphate sorption fell significantly at higher concentrations. This was possibly caused by ion pairing within the solution, as well as the strongly hydrophobic nature of styrene in the charged polymer. Water uptake was lowest in NaNO solutions, even though sorption of the nitrate ion was comparable to that of chloride in these single salt solutions. In the binary mixture, nitrate was absorbed more strongly than chloride. These results could be due to the low surface charge density of this ion allowing it to bond more strongly with the hydrophobic polymeric backbone at the exclusion of water and other ions.
在单盐和双盐体系中系统地研究了单价（Na、K、Cl 和 NO）和二价离子（Ca 和 SO）在商业 Neosepta 离子交换膜中的共离子和反离子吸附。与早期的一代（CMX）相比，新一代的 Neosepta 阳离子交换膜（CSE）在水摄取和共离子吸附方面表现出显著差异。使用 Manning 模型证实了这些膜之间存在显著差异，估计的 Manning 参数值从 CMX 的 1.0 ± 0.1 变为 CSE 的 2.8 ± 0.5。两种 Neosepta 阴离子交换膜 AMX 和 ASE 之间的差异较小。在单盐溶液中，钾最强地吸附到阳离子交换膜中，但在双盐混合物中，由于低浓度下的 Donnan 排斥，钙占主导地位。虽然这些趋势是可以预期的，但阴离子交换膜中的吸附行为更为复杂。在 AMX 和 ASE 中，水摄取在 NaSO 溶液中最大。这种强烈的水摄取反映在单一盐溶液中对硫酸盐离子的强烈吸附。相反，在含有 NaCl 的二元盐混合物中，硫酸盐的吸附在较高浓度下显著下降。这可能是由于溶液中的离子对以及带电荷聚合物中苯乙烯的强疏水性所致。在 NaNO 溶液中，水摄取最低，尽管在这些单盐溶液中，硝酸盐离子的吸附与氯离子相当。在二元混合物中，硝酸盐的吸附比氯离子更强。这些结果可能是由于该离子的表面电荷密度低，使其能够与疏水性聚合物主链更牢固地结合，排斥水和其他离子。
