Of electrolytic manganese industry more than 40 years of development, has become the world's largest manganese production, exporting and consuming countries. In the process of electrolytic manganese production, a large amount of waste residue is inevitably produced in the anode region, and its manganese content is as high as 40% to 50%. The main component is hydrated oxide of Mn 4+ and contains significant amounts of Pb 2+ and Sn 2 . + and other heavy metal impurities. Since it cannot be directly recycled by simple machinery or beneficiation methods, most electrolytic manganese plants adopt the method of storage or low-cost sale, which not only wastes resources but also causes environmental pollution. Research and utilization of manganese anode mud have been reported, such as oxidative roasting to prepare chemical manganese dioxide, high temperature reduction and volatile removal of heavy metal impurities, etc. These methods have certain limitations in product purity or high thermal equipment investment. Based on wet reduction leaching, this study developed two practical process routes for preparing high-purity manganese sulfate from manganese anode mud. By comparing and optimizing the process conditions, it was used for the recovery and utilization of manganese anode mud in an electrolysis plant in Hubei. Try and lay the foundation for industrialization. First, the experimental part (1) Experimental materials Sulfuric acid, calcium carbonate: chemically pure; ammonium sulfide: analytically pure; manganese anode mud: taken from an electrolytic manganese plant in Hubei, the average particle size after crushing is 0.2mm, its main components (%) Mn 50.9, O 37.1, S 5.83, Pb 3.38 Ca 2.04, Si 0.03, P 0.03, K 0.15, Mg 0.26, Se 0.27, Sn 0.06, Cu 0.01; wood chips: average particle size 0.3 mm. (two) the principle of reaction The cellulose-rich cellulose (C 6 H 10 O 5 ) n used in the process expands and hydrolyzes to form reducing sugar under the action of concentrated sulfuric acid, and can undergo redox reaction with manganese dioxide to form soluble under acidic conditions. Manganese sulfate. The main reactions involved in the process are: (3) Process and operation process The process 1 process is shown in Figure 1. Since the leaching reaction is exothermic, the reaction is relatively intense. After the wood chips are hydrolyzed to a suitable degree, the manganese anode mud should be added slowly and in stages. The filtrate is subjected to purification and the like to obtain a high-purity manganese sulfate product. Figure 1 Manganese sulfate recovery from manganese anode sludge (Process 1) The process of Process 2 is shown in Figure 2. The black paste obtained after the reaction is calmed and aged at about 300 °C. After aging, the porous grayish white solid mixture is loosened, soaked in water, and filtered to obtain a manganese sulfate leaching solution. Subsequent purification treatment is similar to Process 1. Figure 2 Manganese sulfate recovery from manganese anode sludge (Process 2) (4) Process comparison analysis The manganese anode mud powder 50g was selected for testing. The amount of sulfuric acid and wood chips is 110% of the theoretical amount. Process 1 The amount of wood chips is 15g, the amount of sulfuric acid is 27.6mL, the hydrolysis time is 0.5h, the time of immersion manganese is 1.5h, and the temperature of immersion manganese is 90°C. Process 2 used 8 g of wood chips, 27.6 mL of sulfuric acid, 1.25 h of ripening time, and 300 ° C of curing temperature. Process effect: The amount of calcium carbonate consumed by Process 1 leaching solution is 3 times that of Process 2, and secondary decolorization is required; the leaching rates of manganese in the two processes are 98% and 99.7%, respectively; the recovery rates of manganese are 90% and 98%, respectively. It can be seen from the above data that the amount of wood chips in the process 2 is relatively small, the amount of slag production is also extremely small, the cost is low, and the yield is high. Because the humus and partially charred wood chips generated during the maturation process can continue to be reduced and leached, the carbon in the wood chips is fully utilized, the organic color quality is also removed, and the leaching rate and recovery rate are improved. The process 1 reacts at a low temperature, the wood chip utilization rate is low, the wood chips are consumed, the slag production amount is large, and the discoloration is troublesome. Therefore, Process 2 is selected to prepare manganese sulfate, and the corresponding process optimization is performed. Second, process optimization results and discussion The mass of fixed manganese anode mud powder is 50g, the process 2 route is selected, the leaching rate of manganese is the objective function, the amount of wood chips, the amount of sulfuric acid, the curing time, the curing temperature, etc. are selected, and the four-factor three-level orthogonal test L9(3)4 is designed. The experimental factors and levels are shown in Table 1. Table 1 Orthogonal test factors and levels The experimental results show that the order of influence of four factors on manganese leaching rate is A>B>C>D. The preferred conditions selected by the orthogonal test are: 27 mL of sulfuric acid, 7 g of wood chips, 1 h of ripening time, and 300 ° C of ripening temperature. (1) Effect of wood chip dosage on manganese leaching rate The effect of sawdust dosage on manganese leaching rate is shown by single factor. When the amount of wood chips is 7g, the manganese leaching rate has reached 99.5%. Experiments have shown that increasing the amount of wood chips will increase the excess carbon and organic matter, and correspondingly increase the curing time, increase the drug and energy consumption. Therefore, it is advisable to choose 7g/50g (wood chips/manganese anode mud). Figure 3 Effect of wood chip dosage on manganese leaching rate (2) Effect of sulfuric acid dosage on manganese leaching rate The effect of the amount of sulfuric acid on the leaching rate of manganese was investigated separately on the basis of orthogonal experiments. The results are shown in Fig. 4. The amount of sulfuric acid has a significant effect on the leaching rate of manganese. The leaching rate of manganese increases with the increase of the amount of sulfuric acid. When the amount of sulfuric acid is 107% of the theoretical amount (27mL), the leaching rate of manganese is 99.7%. Increasing the amount of sulfuric acid leads to a high acidity of the solution, an increase in the mass of calcium carbonate consumed during neutralization, and an increase in industrialization costs. Therefore, 27mL sulfuric acid is more suitable. Figure 4 Effect of sulfuric acid dosage on manganese leaching rate (III) Effect of curing time on manganese leaching rate The effect of curing time on manganese leaching rate is not very large, and the curing temperature is selected based on the principle of removing carbon and organic color. The aging time and the aging temperature were selected to be 1.25 h and 300 ° C, respectively. Third, the conclusion (1) Optimal optimization process conditions: 27mL of sulfuric acid, 7g of wood chips, 1h of curing time, 300°C of curing temperature, the manganese leaching rate is over 99.5%, and the manganese recovery rate can reach 98%; (2) After purification, the heavy metal content of the high-purity manganese sulfate product meets the requirements of GB/T 15899-1995. Frp Pultruded,Pultruded Frp Grating,Pultruded Frp Composites,Frp Pultruded Materials HEBEI DONGDING CHEMICAL TRADE CO.,LTD , https://www.hebeiopct.com
May 02, 2024