Study On Isolation And Purification Of Acid Litter From

Coal gangue is a kind of solid waste generated in coal mining and coal dressing.its emissions equivalent to 10%-25% of coal production, and account for 1/4 of the industrial waste emissions. At present, the utilization rate of coal gangue is less than 30%. The majority of coal gangue is given priority to with storage. A large number of stockpiling of coal gangue not only wastes the resources, but also causes serious environmental pollution problems. How to achieve efficient and clean utilization of coal gangue, has became a major technical problems of China’s current in coal gangue comprehensive utilization.Coal gangue containing silicon, aluminum, iron, titanium and other useful elements that can be utilized. In this paper, a extraction technology of valuable elements from coal gangue was adopted by using concentrated sulfuric acid as medium. Which not only solve the problem of covering and pollution, but also save the iron ore, titanium ore and bauxite, meeting the dual requirements of our country to build a resource-saving and environment-friendly society. The economic and effective separation process of the acid leaching solution to prepare chemical products with high additional value, will have a positive impact on the sustainable development of the coal industry.Coal gangue in this paper obtained from a coal mine located Liu Pan-shui, Guizhou province. The acid leaching liquid of coal gangue was prepared by acid leaching and neutralizing. Using sodium carbonate as pH adjusting agent, aluminum, titanium and iron were separated to prepare aluminum hydroxide, titanium-rich material and iron oxide red by step hydrolysis method. The following conclusions are obtained through the experimental research.(1) The effect factors on preliminary separation of aluminum, titanium and iron were examined by single factor experiment, such as reaction temperature, terminal pH value, Na2CO3 concentration and reaction time. The basic parameters of the separation are following:reaction temperature 80℃, terminal pH of 4.5, concentration of sodium carbonate 15%, the reaction time 3h.(2) XRD analysis of the hydrolysis product after calcining at 1200℃, crystal phases are mainly aluminum titanate and a small amount of mullite and alumina. EDS and X ray fluorescence analysis showed that the main compositions of the hydrolysate were oxygen, aluminum, titanium, and a small amount of other impurities, such as carbon, silicon, calcium, iron and sulfur.(3) The influence factors of aluminum and titanium separation were searched through single factor and orthogonal experiments, such as temperature, dosage of NaOH, reaction time, concentration of NaOH. The optimal conditions as follows:reaction temperature is 80℃, the dosage of NaOH is 2.5 times of the theoretical amount, mass fraction of NaOH is 50%, reaction time is 3h.(4) Desilication agent was synthesized for deep desilication in sodium aluminate solution. The technical parameters of desilication were obtained:the temperature 80℃, the effective calcium oxide content of 68g/L, the reaction time 2h.(5)The process conditions used for carbonate decomposition of sodium aluminate to prepare aluminum hydroxide are following:the end pH of reaction at 9.0, reaction temperature 80℃, seed coefficient of 10%, the ventilation rate of 100 mL/min, stirring speed of 300 rpm. Analysis results of XRD, SEM and chemical composition showed that aluminum hydroxide as spherical particles, crystal phase of β’-gibbsite type, performance indicators reached the requirements of GB/T4294-2010.(6)The pickling conditions of hydrated titanium dioxide were reserched, with 2% H2SO4 stirring 2h, aluminum and magnesium reduced obviously. titanium dioxide as anatase phase, content of titanium dioxide in rich-titanium material reached 90.50% after calcining at 800℃.(7) The appropriate technological conditions for preparation iron oxide red using ferrous sulfate solution are following:maintaining pH of the solution in 6.0～8.0, the reaction temperature of 25℃, Na2CO3 concentration of 30%, calcining temperature of 800℃. Analysis results of XRD, SEM and performance indicators showed that iron oxide red as spherical particles, crystal phase of hematite type a-Fe2O3, performance indicators meet the requirements of GB/T1863-2008 qualified goods.(8) Production process of iron oxide red, aluminum hydroxide and titanium-rich material by the acid leaching liquid of coal gangue, under the optimal conditions, the yields of iron oxide, aluminum oxide and titanium dioxide were 98.82%,88.97% and 95.22%, respectively.