Synthesis of a novel bifunctional hybrid molecularly imprinted poly (methacrylic acid-phenyltrimetoxysilane) for highly effective adsorption of diuron from aqueous medium

摘要

This paper describes the synthesis of a bifunctional hybrid molecularly imprinted poly(methacrylic acid-phenyltrimetoxysilane) (BHMIP) exploring the sol-gel process and free radical polymerization and its applica-tion for highly adsorption of diuron in aqueous medium. The polymer was characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), nitrogen adsorption/ desorption measurements and measurements of the wettability through contact angle. Equilibrium time of diuron adsorption onto BHMIP was reached in 130 min, which was described by pseudo-first order model, while the adsorption isotherm was described as a dual-site Langmuir-Freundlich model. From this model, the maximum adsorption capacities, determined at pH 4, were found to be 145.04 mg g-1 for BHMIP and 23.84 mg g-1 for BHNIP (non-imprinted polymer). Diuron adsorption onto polymers suggests an exothermic and spontaneous process with Delta Ho values of-22.99 and-9.94 kJ mol-1 K-1; Delta Go values of-21.89 and-17.20 kJ mol-1 K-1 for BHMIP and BHNIP, respectively. Selectivity of BHMIP was evaluated from binary solutions containing diuron and tebuthiuron, hexazinone, ametryn or imazapic, giving rise to relative selectivity coefficients (k)' higher than one unit, which demonstrates the formation of imprinting cavities in the polymer. The new proposed adsorbent has substantial higher adsorption capacity towards diuron compared to previously molecularly imprinted organic polymers and many carbonaceous adsorbents reported in the literature.