Processes Study On Magnetization Roasting Method To Strengthen Whitening Kaolin By Magnetic Separating Removal Iron Method

Currently, a series of removing iron means, including the floatation removal ironmethod, chemical bleaching removal iron method, chlorination roasting process removaliron method, microorganism removal iron method, and magnetic separating removal ironmethod, and etc., to remove iron of sandy kaolin contaminated by iron, had someshortage in industrial applications. With the rapid development of industry in China, highgrade kaolin resources in China appear to be the situation that demand exceeds supply.And there are much sandy kaolin contaminated by iron in some of kaolin mining zones inChina, but abandoned such kaolin mine, this is not only a waste of natural mineralresources but also cause serious damage to the ecological environment. The paper tookthis as research background,took Guizhou kaolin as subject investigated, studiedprocesses on magnetization roasting kaolin to strengthen whitening kaolin by magneticseparating removal iron method.By this paper, there are some research results asfollows:1. Studied on Ferriferous minerals of kaolin used in the experiment by X-raydiffraction analysis, X-ray fluorescence analysis, it shows that it exists as the form ofgoethite, and goethite and kaolinite form cementation body. And thermodynamiccalculations research and comprehensive thermal analysis to Fe（OH）₃, speculated thatgoethite would be decomposed into Fe₂O₃at the exothermic peak temperature123.7℃,when magnetic roasting above that temperature, its main reaction is reduction reaction ofFe₂O₃;2. Used magnetic roasting process, took bamboo charcoal powder that was dealtwith KOH activator as magnetic roasting reducing agent, it studied that additive（H3BO₃, KHCO₃, NaHCO₃and MgCO₃）, sintering temperature, and holding time hadsome effects on mass susceptibility of iron mineral in kaolin, and considering additiveperformance, the kaolin performance indicators and other factors, determined finally thebest solution of magnetic roasting process was that it was added2.0%boric acid and3.0%NaHCO₃, its magnetic roasting temperature was about450℃, its holding time was30minutes, and mass susceptibility of iron mineral in kaolin reached5.58×10-4m3/kg, itshowed that most of the iron mineral in kaolin was converted to magnetite Fe₃O₄whenmagnetic roasting below the decomposition temperature of kaolinite at524℃, it haveachieved target of magnetic roasting process;3. To kaolin after treament of magnetic roasting process, it had some magneticseparation technical problems with ferromagnetic magnetite Fe₃O₄in the kaolin, and itwas necessary to deal with it by wet milling. In the system of the wet milling’s slurry, it 0.2%took natrium carbonicum calcinatum and0.2%sodium hexametahposphate asgrinding aid agent, it studied that different pH values of the slurry system and differentmilling time had some effects on production rate of magnetic separation concentrate.The best solution optimized was that production rate of magnetic separation was up to84.4%when the pH value in the slurry system was about9and milling time was about30minutes;4. Did calcined whiteness test to magnetic concentrate,its calcined whiteness wasabout87.4%, were increased by22.6%than calcined whiteness71.3%of original kaolinsample, and increased by14.2%than calcined whiteness71.3%of kaolin that was dealtby chemical bleaching, which was taken rongalite as bleaching agent and takenEDTA（Ethylenediamine tetraacetic acid） as complexing agent.And magnetic concentratewas main mineral forms of kaolinite and contained a small amount of metakaolinite;5. To iron impurities of magnetic separation, after analyzed by XRD spectrum andchemical composition, it shows that existence form of its mineral was main on quartz andmagnetite. Diffraction peaks strong and higher Fe₂O₃content of magnetite in ironimpurities of magnetic separation, it shows that iron-bearing minerals of original kaolinsample was transformed into magnetite by magnetic roasting process mostly. Moreover,iron-bearing minerals of original kaolin sample existed as goethite, it shows that quartzand magnetite in iron impurities of magnetic separation existed as cementation, so it wasdifficultly to to be were peeled off by wet milling peel off and it wass pick out ascementation by magnetic separation.