Nanosized strongly-magnetic bacterially-produced iron sulfide materials

Using sulfate-reducing bacteria and a novel bioreactor strongly magnetic ir on sulfide material has been produced. TEM studies reveal that a substantia l fraction of the material consists of particles of a few nanometres in dia meter. Normal X-ray diffraction showed no lines. Neutron scattering reveale d some Bragg peaks and peaks in the radial distribution which may be associ ated with the results from the extended X-ray absorption fine structure (EX AFS). At small angles the neutron scattering revealed that a large fraction of the sample had particle diameters of the order of 2 nm. EXAFS gave resu lts consistent with the neutron scattering. The trapped magnetisation was m onitored as the temperature was slowly increased from 4.2 K. 75% of the tra pped flux was lost between 4.2 and 20 K. Some particles remained blocked at 300 K showing hysteresis, but with an applied field greater than 1 T the m agnetisation was linear with the field. This material is an excellent adsor bent for many metal ions, (C) 1999 Elsevier Science B.V. All rights reserve d.