Ligand sorption of aromatic amines on resin-bound ferrous ion

Abstract

The sorption of aromatic amines as ligands on polymer-bound ferrous ion has been measured, using the sulfonic polystyrene resin Dowex 50W-X8 to bind the Fe 2+ ion. The sorption is compared with that on the corresponding Fe 3+-form resin and on a weakly acidic cation exchanger, Amberlite IRC-50. The amines used include aniline, m-hydroxyaniline, p-hydroxyaniline, m-nitroaniline, p-nitroaniline and p-carboxyaniline. Unlike the Fe 3+-form resin which oxidizes some of these amines, such as aniline and hydroxyanilines, to insoluble products, thereby fouling the resin irreversibly, the Fe 2+-form resin affords complete recovery of the sorbed species by acid stripping. The Fe 2+-form resin also has higher sorption capacity (on dry basis) than the weak-acid cation exchanger. The stability constant of ligand sorption on the Fe 2+-form resin increases markedly with the increasing basicity of the aromatic amines. The level of pH of the aqueous medium has a large influence on sorption capacity, sorption kinetics, and stability constant. While both the sorption capacity and sorption rate on the Fe 2+-form resin increase markedly at lower pH, the stability constant, however, decreases. The ligand sorption kinetics at lower pH are well described by the unreacted-core model for unchanging particle size.