A comparative study on metal ion uptake behavior of chelating resins derived from the formaldehyde-condensed phenolic Schiff bases of 4,4′-diaminodiphenylsulfone and hydroxybenzaldehydes

Abstract

Abstract Three reactive and functional polymers were synthesized by reacting formaldehyde with the phenolic Schiff bases derived from 4,4′-diaminodiphenylsulfone and o-, m-, and p-hydroxybenzaldehydes, respectively. The metal ion uptake behavior of these resins towards Cu2+, Ni2+, Co2+, and UO2 2+ ions in dilute aqueous media was studied. The optimum conditions for the absorption of metal ions were determined by varying the various parameters like contact time, size of the sorbents, concentration of the metal ion solutions, and the pH of the reaction medium. Suitable conditions were ascertained for preferential adsorption of the above metal ions from the salt solutions containing other interfering ions such as Na+, K+, and Mg2+. Presence of these alkali and alkaline earth metal ions in the salt solutions did not affect the adsorption behavior of the resins. It was observed that the structural features of the resins have a profound effect on the uptake characteristics. The position of the OH group present in the meta position with respect to the imine nitrogen atom in the resin, demonstrated a significant influence on the extent of metal ion adsorption by the resin. Out of the three resins reported here, the resin derived from the Schiff base of m-hydroxybenzaldehyde-4,4′-diaminodiphenylsulfone showed higher efficiency in uptake of metal ions from the solutions than the corresponding resins derived from the Schiff bases of o- and p-hydroxybenzaldehyde-4,4′-diaminodiphenylsulfone. Keywords: Chelating resinsMetal ion uptakeSeparation Acknowledgments We are thankful to the central libraries of IIT, Kharagpur, IIT Delhi, and the library of Regional Research Laboratory, Bhubaneswar, India for literature survey.