Adsorptive removal of bis(2-ethylhexyl) phthalate using an imprinted polymer: isotherm and kinetic modelling

An adsorbent material specifically designed to capture bis(2-ethylhexyl) phthalate (DEHP) was successfully prepared by molecular imprinting technology. The molecularly imprinted polymer (MIP) was fabricated using methacrylic acid as a functional monomer and was crosslinked by ethylene glycol dimethacrylate via a bulk polymerisation method. The corresponding nonimprinted polymer (NIP) was synthesised as a control sample. The polymers were characterised by Fourier transform infrared spectroscopy, scanning electron microscopy, and porosity analysis by N2 adsorption–desorption. The binding performances of the MIP and NIP were evaluated through rebinding of DEHP in prepared solutions. The experiment was conducted by quantifying the amount of unbound template via the kinetic spectrophotometric method performed with a UV–Vis spectrophotometer. The effects of the initial concentration of the template and the adsorption time were revealed through an adsorption isotherm study. The obtained MIP showed a greater efficiency towards the removal of DEHP from solution (92%) than the NIP (34%). Therefore, the MIP exhibited preferential adsorption of DEHP molecules. The adsorption isotherm experiments showed good linearity and higher correlation coefficients for the Freundlich isotherm model than for the Langmuir model, and the pseudo-second-order equation provided the best fit describing the kinetic sorption behaviour of the polymers. Under optimised conditions, the MIP exhibited high selectivity towards DEHP over a competitive molecule; in addition, good recovery was achieved, resulting in a high distribution coefficient.