Iron hydroxides as magnetic scavengers

In the application of magnetic separation procedures, ferrous and ferric hydroxide gels are proposed as magnetic seeding materials to remove many metal ions from waste water. Ferric hydroxide gel, which has been well known as an excellent scavenger, has been found to be strongly magnetic and almost amorphous. Inspection of Mössbauer spectra suggests that, in addition to adsorption, occlusion is responsible for the excellent scavenging effect of ferric hydroxide gel. Ferrous hydroxide has been found to be especially efficient for removing mercury from solution. A redox reaction occurs between mercuric and ferrous ions on the surface of ferrous hydroxide gel, resulting in the formation of metallic mercury and magnetite. Metallic mercury, adsorbed on the surface of the magnetite, is easily removed by magnetic separation.