Functionalization of Molecularly Imprinted Polymer Microspheres for the Highly Selective Removal of Contaminants from Aqueous Solutions and the Analysis of Food-Grade Fish Samples

The proliferation of pollution in aquatic environments has become a growing concern and calls for the development of novel adsorbents capable of selectively removing notorious and recalcitrant pollutants from these ecosystems. Herein, a general strategy was developed for the synthesis and functionalization of molecularly imprinted polymer microspheres (MIPs) that could be optimized to possess a significant adsorption selectivity to an organic pollutant in aqueous media, in addition to a high adsorption capacity. Considering that the molecular imprinting alone was far from satisfactory to produce a high-performance MIPs-based adsorbent, further structural engineering and surface functionalization were performed in this study. Although the more carboxyl groups on the surfaces of the MIPs enhanced the adsorption rate and capacity toward an organic pollutant through electrostatic interactions, they did not strengthen the adsorption selectivity in a proportional manner. Through a systematic study, the optimized sample exhibiting both impressive selectivity and capacity for the adsorption of the organic pollutant was found to possess a small particle size, a high specific surface area, a large total pore volume, and an appropriate amount of surface carboxyl groups. While the pseudo-second-order kinetic model was found to better describe the process of the adsorption onto the surface of MIPs as compared to the pseudo-first-order kinetic model, neither Langmuir nor Freundlich isothermal model could be used to well fit the isothermal adsorption data. Increased temperature facilitated the adsorption of the organic pollutant onto the MIPs, as an endothermic process. Furthermore, the optimized MIPs were also successfully employed as a stationary phase for the fabrication of a molecularly imprinted solid phase extraction column, with which purchased food-grade fish samples were effectively examined.