Synthesis and application of ion imprinted polymers for selective extraction of metal ions from different matrices

Abstract

Exposure to toxic metal ions such as Zn2+ and Pb2+ can lead to several diseases including cancer on human being. This study aims to synthesize Zn2+and Pb2+ ion imprinted polymers (IIPs) for removal of Zn2+ and Pb2+ from various sample matrixes. Polymerization was achieved by mixing the methacrylic acid (MAA) as a functional monomer, ethylene glycol di-methacrylate (EGDMA) as a cross-linker, azobis (isobutyronitrile) (AIBN) as initiator and methanol as a progen. The temperature was increased to 80 oC while stirring for 7 h. The identical procedure was used to make non- imprinted polymer (NIP), but no template was used. Imprinted polymers were extracted with 2 M HCl for the removal of templates. The point of zero, or pHPZC, was determined and infrared spectroscopy was used to characterize the final products. The results of the Fourier-transform infrared (FTIR) analysis demonstrated the removal of ion templates by broad O-H peak at a wavelength of 3500 cm-1 and pHPZC results revealed that, at acidic solution, the imprinted polymers carried positive charges, and at basic solution pH, the imprinted polymers carried negative charges the PHPZC was found 6.98 and pH level was 7.0. The maximum percentage of Zn2+ removal using the Zn-IIP was found to be 80% when the solution pH of 7.0, adsorbent dose was 5 mg, contact time at 15 min at shaking speed of 100 rpm and initial metal ion concentration of 25 mg/L were used. The adsorption kinetic data corresponded to pseudo-second order reaction kinetics with R2 = 0.99, indicating that the process occurred by chemisorption. The Langmuir isotherm showed an excellent fit with an adsorption capacity of up to 9.03 mg g-1 and R2 = 0.99, implying that adsorption was on a monolayer surface. This study shows that zinc ion imprinted polymer has higher efficiency towards Zn2+ in the solution. The finding indicates that zinc ion imprinted polymer has high adsorption efficiency of 94.00 (mg/g) in removing zinc ion from the honey sample. The removal of Pb (II) from wastewater using Pb (II) IIP was found to be 90%. Further the re-usability study was evaluated 7 times and the adsorption efficiency was high at 90%, for this study the waste material can be beneficial for reused. The functional groups of both the imprinted polymer and the non-imprinted polymer were characterized by FTIR, and the point of zero charge was determined using the optimum conditions of 50 mg adsorbent dose, initial solution pH 9, and 15 min contact time. The adsorptive nature of the IIP and NIP was evaluated by means of Langmuir and Freundlich isotherms. The Langmuir adsorption isotherm modelled the data better, as shown by the Langmuir and Freundlich correlation coefficients of 0.999 and 0.975, respectively. An inventive answer has evolved in the form of ion-imprinted polymer, which was produced using the molecular imprinting approach as a basis. Higher selectivity coefficients have been demonstrated by IIPs compared to non-imprinted polymers.