Nanomaterials and Nanocomposites

Surface design of magnetite/silica adsorbents
Melnyk I.1,2, Bespalko O.2, Stolyarchuk N.2, Tomina V.2, Vaclavikova M.1
1 Institute of Geotechnics SAS, Kosice 04001, Slovak Republic
E-mail: in.melnyk@gmail.com
2 Chuiko Institute of Surface Chemistry NASU, Kyiv 03164, Ukraine.

Current report deals with the advantages of functionalized magnetic silica adsorbents, their synthesis routes, texture, morphology, surface layer structure, and sorption properties. We developed a single-step technique of producing magnetite/silica functional composites, during which it is possible to change the size of the obtained particles, porosity of the polysiloxane layer, the amount and nature of functional groups. So, the composites Fe3O4/SiO2/-(CH2)3NH2, Fe3O4/SiO2/=[(CH2)3]2NH, Fe3O4/SiO2/-(CH2)3NH2/-CH3, Fe3O4/SiO2/-(CH2)3NH2/-C3H7, Fe3O4/SiO2/-(CH2)3SH, Fe3O4/SiO2/-(CH2)3SH/-CH3, Fe3O4/SiO2/-(CH2)3SH/-C3H7, Fe3O4/SiO2/-(CH2)3NH-C(S)-NH-C2H5 were obtained and studied. The data of physico-chemical methods assume that the amounts of functional groups introduced during the syntheses coincide with those expected basing on the ratios of reacting components, and the use of the ammonium fluoride as catalyst provides almost complete proceeding of the reaction of hydrolytic polycondensation.
Adsorption experiments showed that the amino-containing samples had high sorption capacity to Ni(II), Cu(II), Pd(II) ions and albumine, while the mercapto-containing magnetite/silica nanoparticles could be used as effective solid phase extractive agents for Ag(I), Cd(II), Hg(II), and Pb (II) ions from aqueous solutions. The samples functionalized with ethylthiocarbamidepropyl groups could selectively adsorb and concentrate Au(III) ions from metal ions mixtures at pH=2. In addition, the adsorbents with mercaptopropyl groups were employed to treat real wastewater from Ruskov region (Slovakia) with excessive concentrations of Fe, As, Sb, and Cr. After treatment with the sorbents, the concentrations of these metals in such water decreased to acceptable limits. Thus, the described approach opens wide opportunities for the controlled surface design of magnetic materials for their sustainable use in water purification.
This work has received funding from the People Programme (Marie Curie Actions) of the EU's 7th Framework Programme under REA grant agreement No. 609427 co-funded by the Slovak Academy of Sciences (SASPRO grant n°1298/03/01)