Coal gangue is coal production process in the garbage, solid waste is a major coal, many mines around there are mountains of coal waste, not only pollute the environment, but also occupy large tracts of land, the country's total coal waste dumps about 4.5 billion t[ 1-2] , the environment is polluted and the resources are wasted. There is a large amount of aluminum in coal gangue, and the content of alumina accounts for about 25%. It is a resource that can be utilized [3-4] . After utilization, it solves the problem of land occupation and environmental pollution in coal gangue. It has turned waste into treasure to create more economic benefits [2,6-8] . The gangue is leached by sulfuric acid to prepare aluminum sulfate, which is a commonly used flocculant and is mostly used for sewage treatment. In this experiment, a coal gangue in Zhengzhou mining area was analyzed and studied. After many experiments, under the best conditions, the aluminum dissolution rate can be stable to 89.6%, and the prepared aluminum sulfate purity can reach 95%, which is coal gangue. Development and utilization provide new ideas. First, the experimental part (1) Materials A coal-like coal gangue in Zhengzhou is pulverized to 40 mesh, and its composition is shown in Table 1. (2) Instruments and equipment Muffle furnace, acidity meter, electronic balance, pulverizer, mixer. (three) reagent Leaching reagent: 1:1 hydrochloric acid (diluted hydrochloric acid diluted twice by distilled water), 1:2 sulfuric acid (diluted sulfuric acid diluted twice by distilled water), reverse aqua regia (concentrated nitric acid: concentrated hydrochloric acid = 3:1); aluminum determination reagent : 10% sulfosalicylic acid, 0.02mol/L CuSO 4 , 0.02mol/L ethylenediaminetetraacetic acid (EDTA), l:l hydrochloric acid, l:1 ammonia water, pH 5.0 acetic acid-sodium acetate buffer solution , PAN indicator. (4) Experimental methods Weigh a proper amount of the gangue sample after drying, and place it in a muffle furnace at a certain temperature for high-temperature roasting. The sinter is leached with a certain amount of sulfuric acid at a certain temperature to test the calcination temperature, roasting time, acidity, and dip. Taking the influence of temperature, leaching time and other factors on the leaching rate of aluminum, the optimal leaching conditions for aluminum in coal gangue were determined. Method for the determination of aluminum: EDTA continuous measurement. Second, the experimental results and analysis (1) Effect of activation temperature The coal gangue is directly immersed in concentrated sulphuric acid and anti-aqua regia for 2h without activation treatment, and its dissolution rate is very low, only 3.6%. 50 g of 40-mesh coal gangue was placed in a magnetic evaporating dish at 400 ° C, 600 ° C, 800 ° C, 1000 ° C, 1200 ° C high temperature furnace for 5 h, after cooling, 10 g was added to 1:2 sulfuric acid leaching for 5 h, the results see Table 2. According to the data in Table 2, a dissolution rate and temperature relationship diagram is shown, as shown in Fig. 1. When the calcination temperature exceeds 500 °C, the A1 2 O 3 •2SiO 2 •2H 2 O component in the coal gangue begins to take off part of the hydroxyl group, which changes from a crystalline state to an amorphous state; the activity reaches the highest at 700 °C. After 1000 ° C, the new phase γ-A12O3 and the mullite phase are formed, and the amount of aluminum eluted rapidly decreases. (2) Impact of leaching time Weigh 30 g of coal gangue ore after calcination at 800 ° C, add 150 mL of 1:1 hydrochloric acid, and control the temperature at 85 ° C. Pipette 1 mL of leachate for analysis. The results are shown in Table 3. According to the data in Table 3, the dissolution rate-leaching time chart is shown in Fig. 2. Experiments show that the leaching time is 5h, the dissolution rate is too slow, the time is too short, and the dissolution rate is low, which can not achieve the production purpose. (3) The influence of acid type The strong acids used for acid leaching are HNO 3 , HCl, H 2 SO 4 . Based on the technically feasible and economically sound principle, the acid used should be selected from HCl and H 2 SO 4 . 10 g of the ore sample was immersed at 1200 ° C with 1:1 hydrochloric acid and 1:2 sulfuric acid, respectively, to prepare 100 mL (the weight loss rate of the ore sample was 11.3%). The results showed that the dissolution rate of hydrochloric acid was 68.78%; the dissolution rate of sulfuric acid was 89.6%. It can be seen that under the conditions of the same amount of acid and the same leaching time, the dissolution rate of sulfuric acid is much larger than that of hydrochloric acid, and the concentration of sulfuric acid for industrial use is quite large, and the price is much cheaper than hydrochloric acid. Therefore, leaching of coal gangue by sulfuric acid is used. Have good economic benefits. (4) Selection of leaching temperature A sample of 800 g of 800 ° C was leached with 1.5 times the acid amount of sulfuric acid for 5 hours. They were leached at different temperatures, and the results are shown in Table 4. And as a temperature-dissolution rate graph, see Figure 3. As can be seen from Table 4 and Figure 3, as the temperature increases, the dissolution rate of Al also increases. However, if the temperature is too high, not only energy is wasted, but also the solution is easy to boil, so the leaching temperature is preferably 85 to 90 °C. (5) Choice of acidity The concentration of concentrated sulfuric acid is heavy, it is viscous, too thick and not suitable for stirring, and it is difficult to dissolve the ore sample; if the dilution factor is too high, the leaching effect is poor. It has been proved by experiments that the dissolution of the ore sample with 1:2 sulfuric acid is better. (6) Selection of acid amount When leaching coal gangue with acid, considering the economic benefits, it is necessary to use as little acid as possible to dip as much aluminum as possible. The experimental results are shown in Table 5 and Figure 4. The calcined coal gangue contains about 31% of A1 2 O 3 , and the best leaching effect by 1.5 times of acid is obtained by experiments, and the dissolution rate is 89.6%. As can be seen from Fig. 4, a high Al dissolution rate can be obtained by leaching the ore sample with 1.5 times the acid amount of sulfuric acid. If the amount of acid is too large, it is easy to cause waste. If the amount is too small, the dissolution rate is too low, and the remaining sulfuric acid can be recycled during the production process. (7) Stirring effect Experiments show that the same leaching time (5h), the leaching temperature is the same (85 ° C), the dissolution rate is only 52% when not fully stirred, and the dissolution rate can reach 89.6% when vigorously stirred. In summary, the best conditions for leaching coal gangue are: pulverized coal gangue is calcined in a high temperature furnace at 800 ° C for 5 h, and dilute with 1.5 times acid amount with 1:2 sulfuric acid, and the temperature is controlled at about 85 ° C. Dip for 5h, and vigorously stir to achieve Al dissolution rate of 89.6%. (VIII) Preparation of aluminum sulfate products There are two main methods for preparing aluminum sulfate: 1 The leachate is filtered and evaporated, and when the density is 1.25 to 1.30, the evaporation is stopped, and natural crystallization is performed to obtain aluminum sulfate crystals. 2 The leachate is filtered, and a part of the filtration mother liquid is added to the alkali to control the pH value to about 7, and an Al(OH) 3 precipitate is formed. The aluminum hydroxide obtained by filtration is added to another portion of the mother liquor to neutralize the sulfuric acid which is not completely reacted, the pH is adjusted to 1.0 to 2.0, and the mother liquor is evaporated to a density of 1.25 to 1.30 to cool the natural crystals. A schematic diagram of the process for preparing aluminum sulfate crystals is shown in FIG. The obtained aluminum sulfate crystals were analyzed to have a purity of more than 95%. The SiO 2 content in the leaching residue was determined by gravimetric method to be 80.88%. Third, the conclusion 1. This experiment explores in detail the various optimal conditions for the extraction of aluminum salts from coal gangue, so that the dissolution rate of aluminum is 89.6%. 2. The process is simple and easy to operate. The purity of the product aluminum sulfate crystal can reach 95%, and the waste residue in the process contains 80% SiO 2 , which can be considered for use in general silicate factories. 3. The coal gangue contains about 10% of carbon, so when activated, it can save a lot of energy, which is very beneficial with industrial mass production. references [1] Gao Menghua, Gong Mingming, Wang Jijing, et al. Activation of coal gangue and extraction of alumina[J]. China Mining Industry, 2007, 16(6): 88-90, 102. [2] Haydn H, Mttrray. Traditional and new applications for Kaolin, Smectite, and palygorskite: a general overview[J]. Applied Clay Science, 2000, 17: 207-221 [3] Cui Li, Zhang Hong, Zhang Juncai, et al. Experimental study on dissolution of alumina in coal gangue[J]. Journal of Environmental Engineering, 2007, 11(1): 99-103. [4] Yasuhito, gangue utilization rule specifically alumina and aluminum [J] light metal, 2005 (1): 64 [5] Li Yafeng, Su Yongbin.Principles, Conditions and Benefit Analysis of Preparation of Coagulant from Coal Gangue[J].Chemical Minerals and Processing,2002,31(3):29-30,21. [6] Kakali G Perraki L Tsivilis S, et a1. Thermal treatment of kaolin: The effect of mineralogy on the pozzol activity [J]. Applied Clay Science, 2001, (20): 73-80. [7] Hou Fuchun, Gu Mingchun. Preparation of Crystalline Aluminum Chloride and Polyaluminium Chloride Using Coal Gangue[J]. Journal of Changchun Institute of Optics and Fine Mechanics, 1999, 22(1): 65-67 [8] Zhang Baojun, Yang Jianguo.Study on the Production of Polyaluminium Chloride by Coal Gangue[J].Resources Research,2001(4):28-30. Mist Sprayer Drone carries a light smlog machine and use for the trees with dense leaves. Sprayer Drone,Airless Mist Drone,Farm Spray Drone,Drone For Fumigation In Agriculture shenzhen GC Electronics Co.,Ltd. , https://www.jmrdrone.com
Discussion on the process of extracting aluminum from coal gangue