Separation of Phenylenediamines by Selective Solubilization and Adsorption on Ion-Exchange Resin

Abstract

Separation of phenylenediamines (PDAs) was attempted using a combination of selective solubilization in an organic solvent and then adsorption from nonaqueous solutions on commercial acidic ion-exchange resins. Toluene was the best solvent for selective solubilization and also for the subsequent sorption of the amines by an acidic ion-exchange resin having sulfonic acid groups on the styrene-divinylbenzene backbone. The equilibrium sorption studies showed very selective sorption of the amines with a high loading capacity on the resin. The uptake of the amines was reinforced by Lewis acid–base interaction between the lone pair of electrons on the nitrogen of the amine and the sulfonic acid group of the resin. In the sorption studies involving mixtures, p-PDA was selectively adsorbed. Molecular mechanics calculations confirm the existence of the acid–base interactions.

Keywords:

• Separation
• Selective solubilization
• Ion-exchange resin
• o-/p-/m-Phenylenediamines
• Sorption
• Adsorption
• Molecular simulation

Acknowledgments

We thank Aarti Industries Ltd & Ion Exchange (I) Ltd. for free samples of m-phenylenediamine and ion-exchange resin, respectively. We would also like to acknowledge the support to this work by Department of Science & Technology, Government of India.