Development of a magnetic ion-imprinted polymer with selective adsorption performance and solid state colourimetric detection of lead ions

In this research, a novel chemosensor based on magnetic ion-imprinted polymer was developed for the colourimetric detection and selective removal of lead ions. In this regard, magnetic and non-magnetic ion-imprinted polymers were prepared as well as magnetic and non-magnetic non-imprinted polymers. In the magnetic form, Fe₃O₄@SiO₂-NH₂ was synthesised and applied as a substrate. Lead (II), sodium rhodisonate, 2-hydroxyethyl methacrylate, sodium formaldehyde sulfoxylate/ethylene glycol dimethacrylate and tert-butyl hydroperoxide were applied to prepare the IIP-based sensor. Fe₃O₄@SiO₂@NIP and related non-magnetic NIP were prepared in the absence of lead ions. The characterisation of chemosensor was carried out using Scanning Electron Microscopy, Thermal Gravimetric Analysis, Fourier Transform Infrared Spectroscopy, Energy Dispersive X-Ray Analysis, and X-Ray Diffraction Analysis. The obtained results indicated the appropriate imprinting factor by comparing the adsorptive capability of Fe₃O₄@SiO₂@IIP (192.308 mg g⁻¹) and Fe₃O₄@SiO₂@NIP (107.527 mg g⁻¹). The adsorption data for both Fe₃O₄@SiO₂@NIP and Fe₃O₄@SiO₂@IIP fitted well to the Langmuir isotherm (R² ≥ 0.9871) and pseudo-second-order kinetic model (R² ≥ 0.9998). Also, adsorption selectivity of magnetic IIP and NIP for Pb²⁺ were determined against interfering ions indicating the proper relative selectivity coefficient for the adsorption of lead ions versus all investigated interfering ions. In addition, colourimetric analyses were performed by evaluating CIE Lab parameters (L*, a*, b*, C* and h°), for the IIP, NIP, the magnetic composite and the extracted samples, demonstrating clear differences that support the successful identification and visible change in the colour of the chemosensor in the exposure of lead ions.