Chitosan-based ion-imprinted polymer for selective extraction of Zn(II) in aqueous samples

Abstract

ABSTRACT In this study, a new strategy for novel chitosan-based ion-imprinted polymer (IIP) preparation was adopted for selective separation and recovery of Zn(II) ions from aqueous environmental samples using batch extraction experiments. The Zn(II) ion-imprinted polymer was prepared by precipitation copolymerisation of methacrylamide and 2,2- azobisisobutyronitrile along with Zn(II) ions and toluene as a functional complexing monomer, initiator, template ion, and porogenic solvent, respectively, in the presence of chitosan. The ethylene glycol dimethacrylate and tetraethyl orthosilicate were used as cross-linking agents. The prepared Zn(II) ion-imprinted polymer was characterised by Fourier transform infrared spectroscopy, field emission scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy, X-ray diffraction, thermogravimetric analysis, and inductively coupled plasma-optical emission spectroscopy to determine the structural and functional IIP variations before and after Zn(II) adsorption. Characterisation results suggested the formation of Zn(II) ion-imprinted polymer with excellent thermal stability and also have the potential for selective Zn(II) extraction. Further, the Zn(II) sorption using IIP sorbent was also evaluated as a function of pH, IIP sorbent dosages, Zn(II) ion concentration, sorption time, and IIP sorbent reusability. The Zn(II) sorption equilibrium was studied using various isotherm and kinetic models, and the result suggested that the Langmuir and pseudo-second-order model as the best to explain the sorption process. Sorption capacity was calculated using Langmuir isotherm linear equation and its value was found to be 3.06 mg/g. The method detection limit (MDL) and limit of quantification (LOQ) of sorbent were calculated as 0.1 and 0.3 mg/L, respectively. Finally, the developed sorbent Zn(II) IIP was found to be effective in the selective extraction of Zn(II) from the tap and river water samples.