MECHANISM OF POLYMER-BASED SEPARATIONS. I. COMPARISON OF PHOSPHINIC ACID WITH SULFONIC ACID ION EXCHANGE RESINS

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Abstract
The metal ion complexing ability of the phosphinic acid polymeric extractant has been compared with that for the sulfonic acid ion exchange resin. Based on the performance of the extractants with Fe(III), Hg(II), and Mn(II) under dilute solution/ high acid conditions, both with and without the presence of a large excess of sodium ions, it is concluded that the phosphinic resin operates through an entropy-driven coordination for hard trivalent ions such as Fe(III), an enthalpy -driven coordination for soft ions such as Hg(II) and only ion exchange for hard divalent ions such as Mn(II). The sulfonic resin operates non-selectively through the ion exchange mechanism.