Preparation Of Nano-Fe₂O₃ Powders By The Reversed Micelle Method

Nano-ferric oxide is one kind of multi-functional materials, and can be used as paint, catalyst for organic synthesis and magnetic recording material. Solvent extraction and reversed micelle microemulsion method were used to prepare nano-ferric oxide with iron ore as rude material in the paper.Methyl isobutyle ketone (MIBK) is used to exact Fe³⁺ for its high selectivity for Fe³⁺. Iron ore was first dissolved and oxidized by 6 mol·L-1 HCl and H2O2. Fe³⁺ in the resulting solution after filtration was extracted with MIBK. Orthogonal experiments were carried out to investigate the influences of time, temperature, the concentration of HCl, the concentration of Fe³⁺ and the ratio of oil to water on the extraction efficiency. Influencing regulations of factors and the optimum conditions for extraction are obtained, and the correspongding optimum extraction percentage for Fe³⁺ is 99.99%. The back-extraction is complete by using dual-distilled water as back-extractant to extract Fe³⁺ with the ratio of water to oil of 1 with the result that MIBK and HCl solution can be reused. The purity of Fe2O3 meets the standard of the excellent grade by the original Chemical Engineering Adminstration.Reversed micelle microemulsions were prepared with cyclohexane as solvent, and iso-pentyl alcohol as co-surfactant. Solubilization of water in the microemulsion of single surfactanct of Span-80 was firstly discussed. Influences of solubilization of water and 0.1 mol·L-1 Fe³⁺ solution on the stability of microemulsion were investigated by absorbency method. Structural parameters were obtained from the proposed modified particle model. Results from experiments and calculations show that single surfactant of Span-80 was not applicable for the solubilization of water or Fe³⁺ solution. Based on the results from single surfactant of Span-80 the solubilization of water in the composite systems of surfactants of Span series and Tween series, that is, Span-80+Tween-80, Span-80+Tween-60, Span-40+Tween-80, and Span-40+Tween-60 was examined, respectively. The microemulsion system of Tween-60+Span-80/iso-pentyl alcohol/cyclohexane has the maximum solubilization of water and the stable region is the most wide. The optimum composition for the micromulsion system is 10ml cyclohexane, 2ml iso-pentyl alcohol, the ratio of Tween-80/(Tween-80+Span-80) of 0.88, and the content of whole surfactant of 33.9% with the corresponding solubilization of water of between 0.8ml and 3.0ml.The optimum microemulsion system of 33.9%(88%Tween-60+12%Span-80)/iso-pentyl alcohol/cyclohexane was used to prepare nano ferric oxide. Ferric hydroxide microemulsion was first prepared by the uniform mixing of one microemusion with solubilization of ammonia and the other with Fe³⁺ solution. After the breaching of the microemulsion the ferrite was obtained. A sintering system was established by the TGA-DTA of the ferrite. XRD pictures show that the phase of ferric oxide is alpha after sintering at 600℃. AFM pictures show that the powders of ferric oxide are uniform and sphere, and its particle size becomes larger with the increasing w of [Fe³⁺]/[Tween-60+Span-80].Both surfactants and organic solvent were recovered by dual-distillation from the breached emulsion. The reprepared ferric oxide has the same particle size as that of the first prepared one by using the reused surfactants, co-surfactant and solvent.