1,2-Bis(o-aminophenoxy)ethane-N,N,N′,N ′-tetraacetic Acid (BAPTA) Covalently Bound to a Polysulfone and to an Insoluble Polystyrene: Synthesis and Applications to the Selective Adsorption of Ca2+ from Mg2+ in Water

The synthesis of polymeric analogues of 1,2-bis(o-aminophenoxy)ethane-N,N,N ′,N ′-tetraacetic acid (BAPTA) is described. Aminomethyl-polysulfone, an organic-soluble polymer, was used first to develop the synthetic procedure. The insoluble aminomethyl-polystyrene (macroporous Amberlite XE-305) and an ε-aminoalkyl spaced Amberlite XE-305 are used as the bead shaped insoluble-matrix counterparts to which BAPTA units are directly linked through a 2-atom or a 9-atom spacer arm. The BAPTA linked polystyrenes show a higher affinity for calcium over magnesium ions (eight fold) and significantly high distribution values (up to 175) from very dilute aqueous (pH 7) mixtures of these ions. However, in the presence of transition metals ions these resins show the highest binding affinity for Cu2+ ions.