Formation of nickel and nickel, zinc-bearing ferrite in aqueous suspensionby air oxidation

Stoichiometric Ni-bearing ferrite was formed by air oxidation of an iron(II ) hydroxide suspension at an initial Ni : Fe-tot mol ratio (r(Ni)) of 0.20: 2.80 at pH 10.0 and 65 degrees C. Most of products formed at r(Ni) = 0.40:2 .60 and 0.60:2.40 were Ni-bearing ferrites, of which vacancies of Fe3+ ion on the lattice points may be considered. Only Ni, Zn-bearing ferrites were formed in the suspensions at initial (Ni + Zn) : Fe-tot mol ratios (r(Ni) ( +) (Zn)) of 0.20 : 2.80-0.60 : 2.40 at pH 10.0 and 65 degrees C. At higher r(Ni) or r(Ni) (+ Zn) by-products containing Ni, Fe and O-4(2-) were formed . The formation of the by-products was depressed in the suspensions contain ing chloride ions in the place of sulfate ions. (C) 1998 Elsevier Science B .V. All rights reserved.