Isoelectric points of fresh and aged Fe(OH)2

Gray-green precipitates obtained from FeCl2 solutions in basic medium in anaerobic conditions were studied in wet state. The results obtained by X-ray diffraction and Mossbauer spectroscopy suggest that Fe(OH)2 is their main component. It is accompanied by wüstite, goethite, and Fe(OH)3. The isoelectric point (IEP) of such precipitates falls at pH 10, which is a higher value than the IEP of iron (III) (hydr)oxides reported in the literature. Aging (for several days) had rather insignificant effect on the IEP.