The ferromagnetic Fe3O4 nanoparticles with the average particle size of about 10 nm were used to adsorb chromium (VI) in aqueous solution. The equilibrium of Cr(VI) adsorption can be achieved at the pH value of 2.5, in the contact time of 120 minutes. The mechanisms of Cr(VI) adsorption were evaluated by 4 isothermal adsorption models Langmuir, Freundlich, Redlich-Peterson, and Temkin. The results showed that all four models are satisfied; especially, Redlich-Peterson is the most suitable model to describe the adsorption kinetic of Cr(VI) on ferromagnetic Fe3O4 nanoparticles.

A highly ordered mesoporous bio-glass has been successfully prepared by the sol-gel method, in which copolymer pluronic P123 was used as a structure-creating template. The obtained material has the mesoporous structure with the high value of specific surface area (395.6 m2 /g) and the 2D hexagonal pore architecture with the pore sizes from 5.5 to 7 nm. The ‘‘in vitro’’ experiment was effectuated by soaking the bio-glass powder in the simulated body fluid (SBF). The obtained results confirmed the bioactivity of the synthetic biomaterial through the quick formation of a hydroxyapatite layer after 1 day of immersion. Keywords: Bio-glass, pore size, mesoporous, bioactivity, ‘‘in vitro’’.