Entropy-driven selective ion exchange for aromatic ions and the role of cosolvents

This study investigates favorable sorption of several environmentally significant aromatic anions, such as pentachlorophenate, benzene and naphthalene sulfonates, onto polymeric anion exchangers. Such favorable sorption processes are unique because they are all endothermic and entropy driven. The sorption behaviors of these aromatic anions are greatly influenced by both hydrophobic and ionic properties. The sorption of the aromatic anions onto the anion exchanger follows ion exchange stoichiometry, but the ion exchange selectivity is determined by concurrent hydrophobic interactions. The ion exchange selectivity in favor of the aromatic anions can be reduced and reversed in cosolvents. The cosolvent effects on the ion exchange selectivity are correlated to Lewis acidity and basicity of cosolvents.