Magnetic Molecularly Imprinted Polymers for Selective Adsorption of Quinoline: Theoretical and Experimental Studies

Abstract

For the synthesis of magnetic molecularly imprinted polymers (MMIPs), quinoline was used as a template molecule, methacrylic acid (MAA) as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as a cross-linking agent and toluene as porogenic solvent, adding magnetic character with nanoparticles of maghemite (γ-Fe2O3). The solvents for extraction of the template were cyclohexane (EC) or a mixture of methanol/acetic acid (9:1 v/v) (EM), obtaining the materials MMIP-EC and MMIP-EM nomenclatures corresponding to the respective extractions. The materials were characterized by thermogravimetric analysis (TGA), infrared with Fourier transform (FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and specific area (BET). The adsorption capacity of the materials was evaluated through kinetic tests and adsorption isotherms at different temperatures. 288.15, 298.15, 308.15 and 318.15 K. The adsorption process was evaluated with thermodynamic parameters ∆adsG°, ∆adsH°, and ∆adsS°. In order to shed some light on the interaction between monomer and template, theoretical calculations were carried out. Results indicate 3-hour balance time. For MMIP-EM, more efficient adsorption was shown with the temperature increase, with an adsorption capacity qmax in 318.15 K of 36.66 mg g−1. Negative values of ∆adsG° and positives of ΔadsH° indicate spontaneous, favorable, endothermic and physical adsorption processes. The printing factor (IF) of quinoline over MMIP-EM was 1.086 indicating better adsorption effectiveness in the selective process.