The Study On Phase Transformation And Surface Modification Of Ruthner Iron Oxide

Iron oxide industry is our traditional industries of fine chemical industry. The gap of the primary iron oxide production, level of technical and technological between foreign countries with us is not significant. However, there is a considerable gap between foreign countries with us in the iron oxide product deep-processing technology. Therefore, the Low-grade iron oxide products of thin profit primary products are exported in large numbers, but high- grade products in a large numbers have to rely on imports. The iron oxide products are widely used in the various fields of the actual production and living and there is an abroad market at home and internationals and a development prospect. The preparation of iron oxide becomes one of the hot researches of researchers and manufacturers.The steel before the cold-rolling has to go through descaling with acid to improve the quality of steel. It will generate a large number waste acid liquid. There will be a large number of iron oxide in-product when iron and steel enterprises recycle the waste acid. Most of the iron oxide is used in pigment industry. Because of its poor performance, the paint can only be used for low- grade products with less demanding. We have considered whether it could be converted to beγ-Fe₂O₃ used as magnetic materials.Thermal solution organic compounds of iron can obtain directly toγ-Fe₂O₃。Organic matter combustion is not complete at lower temperature conditions of calcinations and the product will certainly be coacervated. When calcined at higher temperatures,γ-Fe₂O₃ appeals to change into hematite that has a more stable crystal structure. It Resulted in the purity of product is not high. The method thatγ-Fe₂O₃ is prepared by organic compounds of iron often is found in literature. However the research aboutγ-Fe₂O₃ directly converted from hematite has been rare reported. There is some methods thatγ-Fe₂O₃ is prepared by hydrogen, carbon monoxide and other strong reducing agent under the protection of nitrogen. But conditions are harsh, and are difficulte to conducive to industrial production.In this paper, binding sol - gel method and Dry Preparation of technology, the steel enterprises byproduct Ruthner iron oxide red is reduced to magnetic by the organic acid, and then oxidized directly in air toγ-Fe₂O₃. The sodium carbonates can improveγ-Fe₂O₃ phase transition temperature. Finally the pure phaseγ-Fe₂O₃ was synthesized. The technological conditions of the method are easier to control than that ofγ-Fe₂O₃ synthesized by hydrogen and other strong reducing agent. The raw materials are cheaper and easier to get than those ofγ-Fe₂O₃ prepared by organic compounds of iron. This provides the basis for industrial production. In addition, papers of our predecessors in our Nano Research Institute are absorbed in this study. The surface of Ruthner iron oxide red formatted a new layer hematite that is synthesized by liquid catalytic phase transformation method. This improved some characters in the color performance like oil absorption, pH and purity. In this paper, the main research contents as follows:(1)The experiment confirmed that the pure phaseγ-Fe₂O₃ by the sol–gel method of one-step can be synthesized. The choice of organic carboxylic acids was verified by analysis of gel preparation by melt gel and aqueous gel on the preparation process. The gels of preparation with citric acid solution can obtaine the pure phaseγ-Fe₂O₃ after calcining. However, it is difficult obtaining the pure phaseγ-Fe₂O₃ after calcining with the gels of preparation by stearic acid gel melting citric acid. Methods of the preparation affect the gel coating effects, while the encapsulation efficiency affects the product composition after calcination. The calcinations'temperature is chosen according to the temperature of pyrolysis and combustion of organic carboxylic acid and iron oxide phase transformation. How do the pH value when the gel is prepared influence on the actual amount of the organic carboxylic acid is discussed. When the pH is above 7, the amount of organic acids can save and the amount of the theory organic acids is n(citric acid): n(hematite)=0.33:1.00. The actual amount of organic acids is n(citric acid): n(hematite)=1.80:1.00.This confirmed that the part of sodium carbonate by pyrolysis and combustion of organic acids played the stabilizing role. When calcinations'temperature is 450, the minimum amount that sodium carbonate can stable allγ-Fe₂O₃ is n (γ-Fe₂O₃ ): n (sodium carbonate) =0.56:1.00.When the sodium carbonate was added before the the gels was prepared, The minimum amount of organic acids is n(citric acid): n(hematite)=0.45:1.00. This is larger than the theory mass, but excess mass is only 21.6%.It is far less than the amount of citric acid when the sodium carbonate wasn't added before the the gels was prepared.(2)It is confirmed that the surface of Ruthner iron oxide red formed a new layer hematite that is synthesized by liquid catalytic phase transformation method. The particle diameter of original sample and the product coated is compared. It is discussed that the coating volume and original concentration effects on the pigment performance of oil absorption, pH and content of hematite.