Fe3O4 and r-Fe2O3 nanoparticles for the adsorption of Co2+ from aqueous solution Abdusalam Uheida,German Salazar-Alvarez, Eva Bjorkman, Zhang Yu, Mamoun Muhammed Journal of Colloid and Interface Science Volume 298, Issue 2, 15 June 2006, Pages 501-507 http://dx.doi.org/10.1016/j.jcis.2005.12.057 Thanks a lot.