Mesoporous magnetic nanocomposites: a promising adsorbent for the removal of dyes from aqueous solutions

Abstract

Water pollution by synthetic organic dyes is mainly regarded as environmental and ecological issues worldwide and requires feasible solutions in face of the short-term risk to human health and stability of eco-systems. Therefore, in this paper, the magnetic mesoporous composites (MMC) were synthesized by surfactant template sol–gel method, using cetyl-trimethylammonium bromide (CTAB) as mesoporous structure generator and investigated for anionic and cationic dyes removal from aqueous solutions. The magnetic iron oxide nanoparticles were obtained by reverse co-precipitation, followed by mesoporous silica coating through modified sol–gel method. The obtained materials were characterized by FT-IR spectroscopy, X-ray diffraction, transmission electron microscopy, Mossbauer spectroscopy, nitrogen adsorption, small-angle X-ray scattering and magnetization measurements. The influence of CTAB amount on the morpho-textural and structural properties of nanocomposites was studied. XRD and Mossbauer spectroscopy showed that the obtained nanocomposites were composed of pure maghemite nanoparticles, and TEM images revealed particles size around 10 nm, embedded in silica matrix. The combination of magnetic properties and high surface area values, up to 695 m2/g, made suitable the obtained nanocomposites to be used as adsorbents. The dye removal efficiency was higher than 90% after the first adsorption and remained above 65% after four adsorption–desorption cycles, indicating that the as-prepared magnetic mesoporous nanocomposites can be considered excellent adsorbent materials for the removal of both anionic and cationic dyes from wastewaters, and the recycling performance revealed the stability of MMC.