Characterization of Polymer Inclusion Membranes (PIMs) Containing Phosphonium Ionic Liquids as Zn(II) Carriers

Phosphonium ionic liquids (IL), i.e., trihexyl(tetradecyl)phosphonium chloride (Cyphos IL 101), trihexyl(tetradecyl)phosphonium bis-(2,4,4-trimethylpentyl)phosphinate (Cyphos IL 104), and tributyl(tetradecyl)phosphonium chloride (Cyphos IL 167), were used as ion carriers in CTA or PVC-based polymer inclusion membranes (PIM). Up to now, the morphology and structure of PIMs with phosphonium ILs have not been characterized in detail. Thus, the following techniques were proposed in this paper-contact angle measurements, FT-IR, XRD, DSC, AFM, and SEM-to analyze the influence of PIM morphology on the efficiency of Zn(II) transport. CTA-based membranes appeared to be more hydrophilic, with a more expanded and rough surface that allowed better accessibility of the metal ions to the membrane. PVC-based PIMs were more hydrophobic and completely amorphous, and their surface showed less diversity, resulting in worse accessibility. Also, PIM stability after five cycles of transport processes was examined.