ABSTRACT
Novel ternary ZnO/Fe3O4-sepiolite nanostructured materials were developed in a two-step procedure based on the incorporation of ZnO nanoparticles on a substrate composed by magnetite nanoparticles previously assembled to the sepiolite fibrous silicate (Fe3O4-sepiolite). The structural and morphological characterization shows that both, ZnO and Fe3O4 nanoparticles, were homogeneously dispersed on the surface of sepiolite. Therefore, the resulting material is characterized as a multifunctional nanoplatform simultaneously providing magnetic and photoactive properties. ZnO/Fe3O4-sepiolite materials exhibit superparamagnetic properties at room temperature, which is one of the sought properties in view to facilitate their recovery from the reaction medium after application as heterogeneous catalysts. ZnO/Fe3O4-sepiolite materials were tested as photocatalysts using methylene blue dye in water as model of a pollutant molecule, showing full decolorization after 2h of UV irradiation. Moreover, the photocatalytic activity of this nanoplataform may be maintained after reuse in several consecutive cycles of treatment. Remarkably, the ZnO/magnetite-sepiolite nanostructured material displays a similar activity as ZnO/sepiolite materials, but shows the additional advantage of easier recovery by means of a magnet which facilitates its reuse.
ABSTRACT
The present paper is focused on the theoretical and experimental study of the kinetics of field-induced aggregation of magnetic nanoparticles of a size range of 20-100 nm. Our results demonstrate that (a) in polydisperse suspensions, the largest particles could play a role of the centers of nucleation for smaller particles during the earliest heterogeneous nucleation stage; (b) an intermediate stage of the aggregate growth (due to diffusion and migration of individual nanoparticles towards the aggregates) is weakly influenced by the magnetic field strength, at least at high supersaturation;
