Magnetic separation of hematite-coated Fe3O4 particles used as arsenic adsorbents

Ball-milling of magnetite powder is studied as a potential method to produce large quantities of nanostructured particles for As(III) and As(V) adsorption. Surfactant-assisted milling resulted in 30 nm isolated nanoparticles with high specific surface area but limited adsorption capacity. On the opposite, when no surfactant is added, large aggregates (300 nm) surrounded by a thick α-Fe2O3 shell were formed. Hematite-coated particles appear to be very effective in the removal of As(III) and As(V) from aqueous solutions being able to adsorb around 1.0 and 2.1 μg/mg, respectively, while keeping the residual arsenic below the regulation limits for drinking water. In addition, the existence of a magnetic core facilitates their application in a magnetic separation system.