title: Chemical stability and extent of isomorphous substitution in ferrites precipitated under ambient temperatures.
abstract: The ferrite process is an established method for treating wastewaters containing dissolved toxic metals, using precipitation at temperatures above 65 °C. Various ambient-temperature operation methodologies have also been proposed, but the effects of temperature reduction on product stability, and on the extent of isomorphous substitution (in terms of x in Me(x)Fe(3-x)O(4), Me representing a non-iron metal), have not been adequately quantified. At ambient temperature precipitation, maximal x of Zn(2+), Co(2+), Ni(2+) and Cd(2+) was found in the current study to be approximately 0.73, 0.67, 0.39 and 0.17, respectively. These values are 73% to 50% of the corresponding values attained by precipitation at 90 °C. The chemical stability of the ferrites produced under ambient temperatures was found to deteriorate upon high Me(2+) incorporation levels, in stark contrast with the trend observed in ferrites precipitated at 90 °C. Both observations were ascribed to the increased importance of Fe(2+)-Fe(3+) interaction under ambient conditions in driving spinel ordering. In the presence of high Me to Fe ratio in the initial solution, this interaction is weaker, resulting in impeded dehydration.
authors.affiliation: Faculty of Civil and Environmental Engineering, Technion, Haifa 32000, Israel. sivan.klas@gmail.com
authors.forename: Sivan
authors.initials: S
authors.lastname: Klas
authors.forename: Yael
authors.initials: Y
authors.lastname: Dubowski
authors.forename: Ori
authors.initials: O
authors.lastname: Lahav
mesh_terms: D005290:Ferric Compounds / Q000737:chemistry*; D013696:Temperature
chemical_list: D005290:Ferric Compounds; C001215:ferrite