Extent and mechanism of metal ion incorporation into precipitated ferrites

The ability of many noniron metals to be incorporated into the structure of ferrites is being utilized in numerous industrial and environmental applications. The incorporation of some of these metals during Fe(II) oxidation-induced precipitation at moderate temperatures (80–100 °C) appears to be limited, for reasons not fully understood, and to extents not always agreed (e.g., Ni2+, Cr3+). In this paper, the incorporation maxima of six metals into the structure of precipitated ferrites (in terms of x in MexFe3−xO4, Me represents a noniron metal) were concluded to be 1.0, 1.0, 0.78, 0.49, 0.35, and 0.0 for Zn2+, Co2+, Ni2+, Al3+, Cd2+ and Cr3+, respectively. With the exception of the much larger Cd2+, these values were associated with kinetic considerations controlled by the H2O exchange rate between the hydration shells surrounding the dissolved metal ion.

Graphical abstractThe incorporation extent of a dissolved metal ion into a precipitated ferrite seems to relate predominately to the water exchange rate between its surrounding hydration shells.Figure optionsDownload full-size imageDownload high-quality image (29 K)Download as PowerPoint slideHighlights► Zn and Co can be fully incorporated. Ni, Al, and Cd incorporation is limited. ► Cr does not enter the ferrite structure. ► Cr and Ni form amorphous solid phases resistant to dissolution at pH 2.0. ► The incorporation extent is affected predominantly by the water exchange rate.