Insight into the performance of molecularly imprinted poly(methacrylic acid) and polyvinylimidazole for extraction of imazethapyr in aqueous medium

The present paper describes the synthesis, characterization, and evaluation of two cross-linked molecularly imprinted poly(methacrylic acid) and polyvinylimidazole towards selective extraction of imazethapyr in aqueous medium. Characterization of materials was performed by FT-IR, TGA, SEM, TEM, elemental analysis and nitrogen adsorption/desorption measurements. Based on relative selectivity coefficients (k'), the molecularly imprinted polyvinylimidazole showed higher selectivity towards imazethapyr and some similar structurally compounds belonging to imidalizones families, imazapic and imazapyr, when compared with poly(methacrylic acid). The kinetics and isotherms of sorption as well as the thermodynamic parameters were then obtained by using the polyvinylimidazole. It was observed that the pseudo-first and second-order models provided the best fit for imazethapyr sorption. Regarding the sorption isotherm, the dual-site Langmuir-Freundlich model presented the best fit for the experimental data, thereby suggesting the existence of sorption sites with different affinities. The maximum sorption capacities obtained for the imprinted and non-imprinted polymers were found to be 27.1 and 24.4 mg g(-1), respectively. According to the obtained thermodynamic parameters, Delta G (0.96 kJ mol(-1)), Delta H (-22.81 kJ mol(-1)) and Delta S (-79.73 J mol(-1) K-1), it might be suggested that the sorption process is not too much favorable, exothermic and provides increase of order at the solid-solution interface. In this case, the low temperature is favorable for the sorption of imazethapyr, typical of physisorption, which match with low sorption activation energy (20.25 kJ mol(-1)) determined from Arrhenius equation. The molecularly imprinted polyvinylimidazole exhibited higher sorption capacity when compared with previously reported commercial sorbents for imazethapyr.