Synthesis Of Ultra-fine Iron Oxide Red From Ferrous Salt By Photocatalytic Air Oxidiation In Solution

Iron oxides, widely used in different fields, are the second largest inorganic paints in production and sales, merely below Titanium dioxide pigment (TiO2). Iron oxide paints mainly refers to Iron oxide red, Iron oxide black, Iron oxide yellow and Iron oxide brown, in which Iron oxide red in the most used production.Because of its chemical stability, high catalytic ability, its fine sunlight resistance, heat resistance and ultraviolet proof ability, Iron oxide paints have millions of years history. In ancient times, people began to use natural Iron oxide paints such as limonite, brown and yellow earth. And now Iron oxides still are the second most used inorganic colored paints. Iron oxides paints are ever-green trees in inorganic colored paints, owing to its own nontoxic, impervious, tending to form different colors property and low production cost. At present, the hematite synthesizing pathway, using sheet iron as raw material, through direct air oxidation, is still widely used, for its low cost and high quality of its product. It uses crystal seeds prepared with HNO3, which causes serious pollution problem, Furthermore, there is no report on its mechanism. The green pathway using ferrihydrite andδ-FeOOH as crystal seeds, iron sheet as raw material is greatly influenced by the high price of ferric salt and iron sheet when it is put into mass production. In this article, a new industrialized pathway of synthesizing hematite was found. This pathway uses FeSO4 from Titanium dioxide pigment production as raw material. First, the reactantγ-FeOOH is prepared, and then through its phase transformation mechanism, hematite is prepared. This pathway is characterized by its low cost, high reactant concentration, easily-controlled reaction conditions and high reaction rate.In this paper, using FeSO4 from Titanium dioxide pigment production as raw material, FeSO4 solution of a certain concentration can be prepared, in which 30% NaOH solution is added and control its pH and temperature. The above solution then is oxidated under light and EDTA with air. The change of pH in the reaction presents a characterized form. The color of the above system changes from gray at the beginning to dark green. Then red or brown substance is prepared under certain conditions. At last, nano-sized hematite particle is prepared under the condition of boiling reflux and certain pH.The synopsis of the paper is as follows:1 The study on the oxidation of Fe(OH)2 with air.2 The preparation ofγ-FeOOH and its transformation to hematite.Using FeSO4 from Titanium dioxide pigment production as raw material,γ-FeOOH is prepared through air oxidation under the presence of EDTA and light. The influences onγ-FeOOH formation are studied, such as FeSO4,EDTA concentration, pH and temperature. The results show,γ-FeOOH can be prepared under CFeSO4=0. 50mol/L,CEDTA =4.5mmol/L,pH=8.6,T=293K conditions. In the following solution transformation process, nano-sized hematite particle of different sizes(ranging from 200 to 300nm) is prepared. XRD,TEM and IR are used to identify the product. The mechanism of light in the oxidation process of Fe(OH)2 is stated.