Facile synthesis of eggshell-stabilized erythromycin-based imprinted composites for recognition and separation applications

Abstract

In this work, eggshell particles, an abundant source of waste and a natural inorganic–organic composite material, were found to be well suited to stabilize O/W Pickering emulsions, because the small amount of organic components in eggshell results in a near 90 degree contact angle θ (81.03°). Erythromycin-based molecularly imprinted polymers (EM-MIPs) whose surfaces were covered in eggshell particles were successfully synthesized through developing an eggshell-stabilized Pickering emulsion methodology, and interestingly and importantly in this work, the discarded eggshell particles were employed solely to stabilize an oil-in-water emulsion for the first time. The imprinting process was conducted through radical polymerization between the functional and polymeric monomers in the presence of template molecules (EM) and initiators. Various analytical approaches including Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and specific surface and pore size analysis were used to characterize the synthesized EM-MIPs, and the results sufficiently demonstrated the formation of approximately spherical and wrinkled imprinted polymer which showed thermal stability (especially below 250 °C) and a specific surface area of 81.3 m² g⁻¹. Attributed to the formation of the eggshell-stabilized Pickering emulsion structure, the as-prepared EM-MIPs not only exhibited outstanding adsorption capacities, but also showed an excellent selective adsorption effect toward EM molecules. The Langmuir isotherm model and pseudo-second-order kinetic model also strongly suggested that the chemical process was the rate-limiting step in the adsorption of EM. Moreover, we envision that the EM-MIPs and the synthesis strategy employed in this work could be utilized in a broad range of applications.