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.