Adsorption characteristics of the tri-iodide and iodide forms of an anion-exchange resin

Abstract

Adsorption characteristics of the tri-iodide and iodide forms of an anion-exchange resin (R—I^–₃ and R—I^–) have been probed by microcalorimetry, dynamic adsorption of vapour-phase mercury and organic compounds, and the oxidation of naphthalenediol.

At first, a transformation of the nature of the R—I^– surface from hydrophilic to hydrophobic by the exchange of I^– with I^–₃ was seen. This transformation is complete when two thirds of the I^– in the resin is exchanged with I^–₃. The hydrophobic nature of I₂ in I^–₃ ions screens the hydrophilic I^– ions. The I^–₃ content in the resin is decreased by evacuation, after which only stable I^–₃ ions remain on the surface.

Secondly, vaporized organic compounds such as benzene, stryrene and n-hexane were adsorbed on R—I^–; their adsorbed amounts on R—I^–₃ decreased according to the degree of exchange of I^– with I^–₃.

Thirdly, it was found that mercury vapour is adsorbed on the surface of the resin. Mercury was sensitive to all I^–₃ ions, both stable and unstable. However, 1,4-naphthalenediol was sensitive only to some of the stable I^–₃ ions by which it was oxidized to 1,4-naphthoquinone in a buffer solution at pH 10.

These results imply that the R—I^–₃ resin has a chemically active surface with both hydrophilic and hydrophobic sites.