Sorption of phenolics and carboxylic acids on polybenzimidazole

Abstract

The sorption of phenolics and carboxylic acids on the new ion-exchange resin polybenzimidazole (PBI) has been measured using aqueous solutions of the sorbates and compared with the sorption on another weak-base resin, poly(4-vinyl pyridine) (PVP). The phenolics used include phenol, p-cresol, p-chlorophenol and m-aminophenol, while the carboxylic acids chosen are formic, acetic, propionic and butyric acids. For aminophenol and phenol, the equilibrium sorption capacities of PBI and PVP are comparable, while for more acidic p-cresol and p-chlorophenol, PVP has significantly higher equilibrium sorption than PBI. On the other hand, for carboxylic acids at low concentrations, PBI exhibits considerably higher sorption capacity than PVP, the difference being more pronounced for acids with smaller acidity. At low concentrations, formic acid has several-fold higher sorption than phenol on PBI, which thus offers a simple method for separation of formic acid from phenol in dilute solutions. PBI has fast sorption kinetics for both phenols and carboxylic acids and a fast rate of stripping and regeneration with dilute NaOH, being much superior to PVP in both these respects.