Uptake of Benzene and Alkylbenzenes by Cation- and Anion-Exchange Resins from Aqueous Solutions

Abstract

We recently studied the uptake of alkanes and alcohols 1 and cycloalkanes and bicyclic aromatic compounds 2 by ionexchange resins from aqueous solutions and demonstrated that the uptake is governed by partition rather than adsorption. We showed that the hydrophobic interaction plays an important role and that the π interaction of aromatic rings with the resin matrix contributes to solute uptake by the resin. This paper deals with benzene and alkylbenzenes. These substances have been chosen because they have both aliphatic and aromatic characteristics.The octanol-water partition coefficient (Kow), which is a measure of hydrophobicity, varies over a wide range for alkylbenzenes, and hence, it is convenient to compare the Kow values and the solute distribution constant (K). The present work is also concerned with benzene. Studying this basic substance is important to understand the uptake mechanism of ion-exchange resins. Chromatographic studies have revealed that anion-exchange resins hold cyclohexane much more strongly than benzene, which makes one conclude that π-electron interactions with the resin matrix are less important than the hydrophobic interaction. 3

Uptake of Iodine and Bromine by Ion-Exchange Resins in Aqueous Solution

“…These K values fall within the line expected from Kow. 3 The Kow value of iodine was determined in this work to be 270, while that of bromine was not determined, because a denaturant of bromine occurred during shaking with the aqueous octanol phase. On the other hand, the K values of iodine for anion-exchange resins, 1.39 ¥ 10 4 for X-4 and 1.89 ¥ 10 4 for X-8, are extremely higher than expected from the Kow; even higher than those of bicyclic aromatic compounds, such as naphthalene, biphenyl and azulene, the K values of which are relatively high due to the p interaction of aromatic rings with the resin matrix.…”

“…All of the organic nonelectrolytes that we have so far studied have shown a direct proportional relationship between the amount of solute taken up by resins and the solute concentration in aqueous solutions. [1][2][3] This gives us an image of solvent extraction, the partition of a solute between the organic solvent and the aqueous phase; resin particles seem to be an organic solvent. In the present study, however, the uptake mechanism of the bromine-anion exchanger system appeared to be adsorption rather than partition.…”

“…[1][2][3] Iodine and bromine were of analytical grade, commercially available from Wako Pure Chemical Co., and were used as received.…”

“…When iodine was used as a solute, a vapor-circulation technique described in previous papers 3,8 was used to prepare aqueous solutions saturated with the solute. The iodine solute vapor was generated by bubbling air through a cylindrical separatory funnel, in which an excess amount of solid iodine was placed together with water.…”

“…Then, another technique was employed. 3 A glass test tube with a glass stopper of ca. 30 or 100 ml capacity was filled with an aqueous solution saturated or unsaturated with bromine.…”