Synthesis and application of a highly efficient polyvinylcalix[4]arene tetraacetic acid resin for adsorptive removal of lead from aqueous solutions

Abstract

Novel polyvinylcalix[4]arene resin has been synthesized by direct polymerization of calix[4]arene through vinylic groups at upper rim and an ion-exchange resin has been developed by appending carboxylic acid groups onto the resin. Adsorption behavior of the polyvinylcalix[4]arene carboxylic acid resin towards some divalent heavy metal ions has been investigated, together with its corresponding monomeric analogue as a control, in terms of effect of pH on selectivity, equilibrium time of adsorption and maximum uptake capacity. The calixarene resin was found to be superior to the monomeric analogue for adsorption ability and separation efficiency. Pb(II) ions were highly preferred over Cu(II), Zn(II), Co(II) and Ni(II) ions by calixarene resin. Size fit complementarity effect of the host cavity and the guest species was found to be the prevailing factor for specific lead ion selectivity of the resin. Surface reactive adsorption of cation on the resin due to ion exchange with carboxyl groups was sufficiently fast and significant adsorption of Pb(II) ions on the resin was achieved within 15 min. However, the equilibrium of adsorption was achieved within 4 h. Maximum lead loading capacity of calix[4]arene resin was found to be 1.82 mmol g −1 while that of the monomeric analogue was 0.064 mmol g −1 resin. Because of the resin's sensitivity to change in pH, the loaded lead was easily eluted with dilute acid solution and the resin was regenerated without any physical and chemical damage. Separation of trace amount of lead in presence of excess of zinc ions was achieved in column chromatographic experiment.