SiO2 based nanocomposite for simultaneous magnetic removal and discrimination of small pollutants in water

A nanocomposite adsorbent material was synthetized in order to obtain an efficient system able to remove, by means of chemical adsorption, mainly aromatic analytes dissolved in aqueous phase. The adsorbing substrate is composed by a magnetic responsive iron oxide (γ-Fe2O3) core coated by a shell of SiO2. The adsorption process is mediated by the chemical interaction among amine and silanol groups on the surface of the nanocomposite adsorbent and the analyte π cloud. The paramagnetic core allows to remove the formed nanosystem-analyte adduct quickly and completely, representing a huge improvement in comparison of the most used gravimetric separation. The removal efficiency obtained using the proposed nanocomposite reaches about 93% for the dangerous pollutant 1,2-phenylenediamine in water solution, 70% for dinitrophenol, 60% for aniline. Further, the nano-adsorbent was decorated with plasmonic Ag nanoparticles without significantly affecting the ability to adsorb the aromatic compounds. The presence of the plasmonic nanoparticles on the SiO2 surface allows to obtain surface enhanced Raman scattering (SERS) of the signals of the adsorbed aniline and 1,2-phenylenediamine proposing this approach to remove and, concomitantly, discriminate the retrieved pollutants from water.