Abstract:
The subject of this MSc thesis is devoted to the preparation of spinel Ferrites MgFe2O4
and ZnFe2O4 nanopowders using low-cost and straightforward mechanical milling
(MM) of elemental oxides Fe2O3, MgO and ZnO followed by subsequent annealing.
The obtained milled powders were characterized and tested for application in
environmental cleaning and remediation (i.e. heavy metals ions removal from aqueous
solutions). For (Fe2O3+MgO), prolonged MM process reduced the crystallite size of
MgFe2O4 to the nanometer range as confirmed by X-ray diffraction analysis, with
the presence of α-Fe2O3 and Fe. SEM observations showed a cauliflowerlike nanostructure with narrower size distribution (≈ 75 nm. BET analysis demonstrated
flatter rather than cylindrical-shaped pores with an average pore diameter in the range
24.7–66.3 nm and decreased surface area from 13.45 to 2.23 m2
/g as a function of
temperature, consistent with the increased crystallite size obtained by XRD analysis.
The magnetic study indicated a ferromagnetic behavior with low coercivity (68.68 Oe),
remanence (0.840 emu/g), and saturation magnetization of about 6.52 emu/g. The
variation of magnetization as a function of temperature signified cations redistribution
within the spinel phase MgFe2O4. Tests of heavy metals removal from aqueous
solutions revealed improved performance by low temperature annealed nanopowder for
Ni+2 and Cd+2
. For (Fe2O3+ZnO), X-ray diffraction, confirmed the phase composition
with crystal growth from 7 to 11 nm due to annealing. SEM observations revealed
agglomerated and spherical particles that increased in size in same trend as XRD results.
The nanopowders exhibited a ferromagnetic behavior with varying magnetization from
1.45 to 0.09 emu/g as function of temperature, associated with phase transition and
allocation of atoms in A-tetrahedral and B-Octahedral sites within spinel structure. BET
analysis showed an un-patterned pore size distribution with a maximum surface area of
1.84 m2
/g after annealing at 500°C. This sample demonstrated the highest adsorption
capacity of 49.42, 54.69 and 12.34 mg/g for Ni+2, Cd+2and Cr6+
, respectively.