The synthesis of a dual-template surface molecularly imprinted polymer based on silica gel and its application in the removal of pesticides from tea polyphenols

Abstract

Imidacloprid and acetamiprid are poisonous insecticides that are used in tea plants; however, their residues remain in the tea after use. In the process of extracting tea polyphenols by a solvent, the pesticides dissolved in the solvent will be enriched in tea polyphenols, which affects the quality and safety of products. In order to selectively remove the pesticides, a dual-template surface molecularly imprinted polymer (MIP) supported on silica gel was prepared by precipitation polymerization using imidacloprid and acetamidine as templates, methacrylic acid (MAA) as the functional monomer, and ethylene glycol dimethylacrylate (EGDMA) as the cross-linker. The morphology, structure, and thermal stability of the prepared polymers were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Furthermore, the investigation of the adsorption behavior of MIP showed excellent adsorption capacities of 33.01 mg g⁻¹ (imidacloprid) and 25.62 mg g⁻¹ (acetamiprid) as well as good selectivity towards imidacloprid and acetamiprid compared with that for a non-imprinted polymer. The adsorption process of the two pesticides on MIP fitted the Langmuir isotherms well. On MIP, the removal rates of imidacloprid and acetamiprid in tea polyphenols reached 95.8% and 94.8%, respectively. The adsorption rate of tea polyphenols was 2.7%. Thus, this new polymer shows potential applications to remove imidacloprid and acetamiprid from tea polyphenols and improve the quality and safety of tea.