Development of Novel Nanofiltration Membranes for Separating Mg^2＋ and Ca^2＋ from Effluent in Electrodialysis

Abstract

This mini-review introduces an idea for a membrane-based recovery process of Mg^2＋ and Ca^2＋ from effluents after electrodialysis and our progress on developing novel negatively-charged and positively-charged nanofiltration (NF) membranes to be used for this purpose. As for the negatively-charged NF membranes, it was demonstrated that the incorporation of iminodiacetic acid (IDA) with piperazine (PIP) to form the polyamide layers by the interfacial polymerization with trimesoyl chloride (TMC) was promising for the separation of SO₄^2－ from Mg^2＋ and Ca^2＋. As for the positively-charged NF membranes, it was demonstrated that the modification of the piperazine-amide layer with poly ([2-methacryloyloxyethyl] trimethylammonium chloride) via plasma graft polymerization was promising for the separation of Mg^2＋ and Ca^2＋ from Na^＋. Finally, an example for concentrating Mg^2＋ with the NF membranes was successfully demonstrated. These achievements will lead to bench-scale and pilot-scale tests in the near future.