Highly porous and monodisperse magnetic silica beads prepared by a green templating method

We describe the preparation of magnetic silica nanocomposite millimetric beads using alginate as a green biopolymer template. The simple and soft method which is used here is particularly suitable since the alginate template allows a multiscale control of the structure of the material, both its morphological characteristics at the millimetric scale and its porosity at the nanometric level. These nanocomposites are characterised by a high monodispersity, a perfect spherical shape, a very large and multiscale porosity with pore diameters ranging from 2 nm to more than 50 nm, a homogeneous dispersion of the magnetic nanoparticles in the silica matrix and a high magnetic susceptibility which increases linearly with the volume fraction of the nanoparticles. These highly porous materials which can be used as magnetic adsorbents in water treatment, showed a good sorption capacity for methylene blue, chosen as a model dye.