Basic Research On Preparation Of Iron Oxide Red From Coal Gangue Acid

Coal gangue is a by-product waste after coal mining,and its large stockpile will not only cause serious environmental pollution,but also take up a lot of land and waste valuable resources.It is a great significance to improve the comprehensive utilization and develop a friendly environmental technology of coal gangue resources due to the chemical composition of coal gangue.In this thesis,thermodynamic calculations of Fe2+-CO32--H2O system which used FeSO4·7H2O as raw material and Na2CO3 as precipitant were conducted to understand problems in the study of polymetallic extraction of coal gangue,such as the product purity was low and mechanism was unclear.X-ray diffractometer,Fourier transform infrared spectroscopy,canning electron microscope and thermal analyzer analysis further revealed that the formation mechanism of iron oxide red intermediate and the formation mechanism of preparing iron red ?-Fe2O3 by heat treatment of ?-FeOOH.Under the condition,the effect of Na2CO3 concentration,reaction temperature and Fe(?)concentration on the preparation of iron oxide red by the gangue leaching solution was studied.The results provided a theoretical basis for the preparation of iron oxide red by the gangue acid solution.In the Fe2+-CO32--H2O system,?-FeOOH was formed by the oxidation of Fe(OH)2 in the Fe2+-CO32--H2O system.In the process of reaction,pH had a great effect on the color,microstructure and Fe(?)oxidation rate of ?-FeOOH.When the pH was in the range of 5.0?5.5,the quality of ?-FeOOH was better.TG-DTG analysis and solid-phase reaction kinetics model of ?-FeOOH were studied.The results showed that ?-FeOOH was pyrolyzed and transformed into?-Fe2O3,and its reaction mechanism model was random nucleation growth mechanism.The pyrolysis kinetic model function was-ln(1-x),the reaction activation energy Ea=140.49kJ · mol-1,the reaction order was 0.98.?-FeOOH pyrolysis reaction was divided into two steps,the first step was to remove water of the crystal between the crystal;the second step was to remove the crystal structure of water,and finally translated into ?-Fe2O3 grains.The morphology changes of ?-FeOOH were as follows:as the temperature of the heat treatment increased,the sheet-like ?-FeOOH gradually cleaved into small pieces until the flaky form disappears to form powdered crystals,the temperature continues to rise,and the fine powder particles begin to agglomerate and crystallize of the spherical ?-Fe2O3 grains at 700 ?.The process condition of iron oxide red from gangue acid was optimized by the response surface method.The optimum conditions were as follows:Na2CO3 concentration 107g/L,reaction temperature 43 ?,and Fe(?)concentration 0.26mol/L.The amplification experiment was studied based on the optimum conditions.The result showed that the iron oxide product quality reached the standard GB/T1863-2008 " Iron Oxide Pigments " in the superior product requirements.