Preparation of Fe3O4 nanoparticles and their application to composite biosorbent

Magnetite (Fe3O4) nanoparticles were fabricated by hydrolyzing Fe2+ and Fe3+ ions with NaOH diffusing through a half-permeable membrane. The Fe3O4 nanoparticles, about 15 nm in diameter, showed ferrimagnetisim with very small coercivity and remanent magnetization. The nanoparticles were combined with Sphaerotillus natans, a Gram negative bacterium used in biosorption of heavy metal ions in water, to prepare a composite biosorbent. The composite biosorbent showed excellent sorption properties to Phi(2+) ion in a pH range between 6 and 8, and to Cr2O72- ion in a pH range below 4. The combination of Fe3O4 nanoparticles made it easy to separate the composite biosorbent from water by the use of a magnetic field and improved the sorption properties. It was also shown that the composite biosorbent was reusable after being rinsed with a dilute hydrochloric acid solution.