Utilizing a polymer containing squaramide-based ion pair receptors for salt extraction

Herein, we report a novel polymer containing synthetic squaramide-based ion pair receptors, which effectively capture and remove sulfate salts from aqueous source phases during liquid–liquid extraction. The monomer M1 was synthesized in a modular fashion, assuring acidity of the anion binding domain and allowing the receptor to be incorporated into the polymer chain and then tested in ion pair binding studies using UV–vis and NMR spectroscopy. After the incorporation of the monomer M1 into the polystyrene polymer chain, its solubility was improved, and a system was developed to selectively remove sulfate ions from systems similar to those naturally occurring in the environment, i.e. among mixtures with other salts. To identify the polymer's salt binding mechanism, additional solid–liquid extractions (SLE) were carried out, which were characterized using 1H NMR, thermal analyses (DSC and TGA) and Scanning Electron Microscopy (SEM).