Impurity partitioning in Nafion and ceramic separators used for purification of spent chromium plating solutions

Cationic partitioning (Cu(II), Ni(II), and Fe(III)) into Nafion and ceramic membranes equilibrated with different salt solutions was investigated in this study. Both single-ion and multicomponent partitioning in a Nafion-117 membrane in a 2.12 M chromic acid solution was well characterized with the Freundlich isotherm. The affinity for the Nafion membrane was Fe(III)>Ni(II)>Cu(II). The partition coefficients of the divalent cations in multicomponent partitioning experiments were similar to those in single-ion experiments whereas the partition coefficients of the trivalent cation decreased. Among the factors investigated, pH had the most significant influence on the partition coefficients, especially in the pH range of about 0.5–1.5. In contrast, temperature in the range of 25–55 °C had an insignificant effect. The ceramic diaphragm had partition coefficients equal to the porosity (0.4) of the ceramic for all of the species implying that cations were not adsorbed to its surface.