Functional polyketones for the removal of calcium and magnesium from water (Part II): cross-linking and functional characterization

Functional polyketones were chemically cross-linked for the softening of hard water, i.e. for the removal of the divalent cations Ca2+ and Mg2+. Elemental analysis, FT-IR spectroscopy, solubility- and swelling-experiments were used to demonstrate the occurrence of the cross-link reaction. Testing the different compounds for their Ca2+ and Mg2+ removal capacity assessed the structure-functionality of the polymers. The corresponding water-insoluble resins were then tested for their Ca2+ and Mg2+ removal capacity-performance being explained in terms of their chemical structure. Ion adsorption of these polymers is not based on an ion exchange, the prevailing mechanism for most currently existing adsorption resins. Rather, the amino functionalized polymers synthesized here adsorb cations as well as their accompanying anionic counterparts, possibly through a chelating mechanism. The obtained results show that functional polyketones are promising in this context as they are easily tunable with the chemical nature of the N-containing groups determining the affinity of the polymer for Ca2+ and/or Mg2+.