Biosorption of antimony(V) onto Fe(III)-treated aerobic granules

• Fe(III) treatment was applied to modify the surface of aerobic granules at pH 2.
• Fe-precipitate was form to bind with the amino or hydroxyl groups of the granules.
• Fe(III)-treated granules had higher adsorption capacity of Sb(V) than untreated ones.
• Intraparticle diffusion and film diffusion resistances controlled the Sb(V) adsorption.

Iron precipitate was produced with 0.1 M FeCl3 and bound with the amino or hydroxyl groups of the granules surface, accompanied with removal of Ca, Mg, K and Na from the biomass matrix. The Fe(III)-treated granules exhibited much higher adsorption capacity of antimony(V) than the untreated granules, peaked at pH 3.4 at a maximum capacity of 22.6 mg g−1 of dry mass. The intraparticle diffusion and film diffusion resistances controlled the Sb(V) adsorption onto the Fe(III)-treated granules. Fe(III) treatment is a cost-effective and easy-to-implement process to modify the surface of aerobic granules to enhance their adsorption capacity to Sb(V).