Magnetic MCM-41 silica particles grafted with poly(glycidylmethacrylate) brush: Modification and application for removal of direct dyes

Abstract

Magnetic MCM-41composite particles were prepared and modified with (3-aminopropyl) triethoxysilane (APTES), then grafted with poly(glycidyl methacrylate) p(GMA) by surface-initiated atom transfer radical polymerization (SI-ATRP). The p(GMA) grafted magnetic MCM-41 particles were functionalized with tris(2-aminoethyl)amine (TAEA), and used as a cationic adsorbent for the adsorptive removal of Direct Blue 6 (DB-6) and Direct Black-38 (DB-38) from aqueous medium. The mMCM-41 and mMCM-41-p(GMA)-TAEA particles were characterized by BET, X-ray diffraction (XRD), thermogravimetric (TGA), Fourier transform infrared spectroscopy (ATR-FT-IR), Zeta potential, nitrogen adsorption desorption isotherms (BET method), scanning electron microscope (SEM) and analytical methods. VSM data shows that the mMCM-41-p(GMA)-TAEA display a paramagnetic behavior with saturation magnetization of about 19.6 emu/g. Adsorption potential of two different textile dyes (i.e., DB-6 and DB-38) was evaluated by varying experimental conditions (i.e., pH, temperature, ionic strength and initial dye concentration). Both dyes were removed from aqueous medium with high efficiency in a wide pH range of 4.0-7.0. The equilibrium adsorption data were analysed by Langmuir, and Freundlich models. The experimental equilibrium data was found to fit the Langmuir model well for adsorption of DB-6 and DB-38 dyes on the mMCM-41-g-p(GMA)-TAEA particles. The adsorption kinetic data were also analysed using pseudo-first order, and pseudo-second-order kinetic equations. It was found that the pseudo second-order model can describe the adsorption data well. The presented adsorbent can be regenerated using 0.1 M HNO3 solution and desorption efficiency was more than 96%. Hence, mMCM-41composite particles were very stable, and easily regenerated