CN109433213B - Method for selectively dealkalizing red mud and enriching iron - Google Patents
Method for selectively dealkalizing red mud and enriching iron Download PDFInfo
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Abstract
The invention relates to a method for selectively dealkalizing red mud and enriching iron, belonging to the field of environmental protection and solid waste recycling. The alkaline substances contained in the red mud react with the acid as far as possible by controlling parameters such as reaction acid amount, liquid-solid ratio, stirring time, temperature and the like, and the alkaline substances are transferred into the solution in a filtering mode, so that the iron oxide component basically keeps the original content in the whole reaction process, and the aim of relative enrichment is fulfilled. The iron content in the obtained red mud is higher by controlling the reaction process, and metal elements such as Al, Ti and the like with proper compositions are reserved.
Description
Technical Field
The invention belongs to the fields of environmental protection and solid waste recycling, and particularly relates to a method for selectively dealkalizing red mud and enriching iron.
Background
Red mud is solid waste generated in the industrial production process of alumina, the cumulative stacking quantity of red mud all over the world currently exceeds 40 million tons, the generation quantity of China increases at a speed of more than 7000 million tons per year, and the cumulative stacking quantity exceeds 5 million tons. At present, the comprehensive utilization rate of the red mud in the global range is not more than 10%, the red mud can be only stacked in large-area yards for treatment, and the resource waste also poses potential serious threats to the ecological environment.The red mud contains rich valuable metal element resources, and the main chemical component comprises Fe2O3、SiO2、Al2O3、TiO2、Na2O, CaO, etc., is an important secondary resource with potential application value. However, the characteristics of high alkalinity and strong salinity of the red mud cause metal elements in the red mud not to be comprehensively utilized, thereby restricting the resource development of the red mud. The alkaline adjustment of red mud is the main direction for solving the comprehensive application of red mud. The red mud contains about 20-50% of iron oxide, the content of the iron oxide in the high-iron red mud is even up to more than 65%, if alkaline substances in the red mud can be removed, hematite components are reserved, and the obtained substances can be used as iron-making raw materials, iron-based carriers or catalysts. At present, the dealkalization method of red mud mostly adopts a water washing method, a limestone method, an ion replacement method, a salt leaching method, an acid leaching method and the like, but the methods also cause the loss of a large amount of valuable elements including Fe while removing alkaline substances, thereby forming secondary pollution and resource waste.
The comprehensive utilization of the red mud is a great problem in the recycling of the red mud by fully utilizing the effective components of the red mud.
Disclosure of Invention
In view of the problems in the prior art, the present invention aims to provide a method for selectively dealkalizing red mud and enriching iron. Alkaline substances contained in the red mud are selectively removed, so that the alkaline substances are basically and completely removed, and the ferric oxide components are basically and completely reserved, thereby achieving the effect of enriching iron. The alkaline substances contained in the red mud react with the acid as far as possible by controlling parameters such as reaction acid amount, liquid-solid ratio, stirring time, temperature and the like, and the alkaline substances are transferred into the solution in a filtering mode, so that the iron oxide component basically keeps the original content in the whole reaction process, and the aim of relative enrichment is fulfilled.
In order to solve the technical problems, the technical scheme of the invention is as follows:
a method for selectively dealkalizing red mud and enriching iron comprises the following specific steps:
1) analyzing the content of each element contained in the red mud, calculating the consumption of acid required by the complete reaction of the red mud according to the common chemical valence state under the selected acid system, and calculating the consumption of acid required by alkaline substances contained in the red mud;
2) drying and crushing the red mud, and mixing the crushed red mud with acid;
the acid amount is 30-80% of theoretical acid amount required to be consumed by the complete reaction of the red mud, the acid amount is controlled to be 200-600% of the acid amount consumed by the complete reaction of the red mud alkaline substances, and the solid-to-liquid ratio is controlled to be 3-15: 1.
3) The mixed solution of the red mud and the acid is filtered, washed to be neutral and dried to obtain the red mud filter cake.
The dosage of the acid refers to molar weight, the complete reaction of the red mud refers to the complete reaction of elements such as Fe, Al, Ca, Na, Ti, K and the like in the red mud, and the alkaline substance is a compound mainly containing elements such as Na, Ca and the like and mainly comprises sodalite, cancrinite, hydrated garnet and the like.
The dealkalized red mud preparation method controls the proportion of acid and red mud according to the common chemical valence state of a selected acid system and the following formula: mn++Ab-＝MAn/b(wherein, Mn+Represents a metal ion, Ab-Representing the selected acid radical ions), firstly crushing the red mud to a proper mesh number to ensure that the components in the red mud are fully dissolved, and then obtaining a proper acid amount under the crushed mesh number of the red mud through continuous tests, wherein the selected acid amount is determined according to the contents of Fe, Al, Ca, Na and Ti elements in the obtained dealkalized red mud, so that the iron is retained to the maximum extent, and meanwhile, a proper amount of Al and Ti are retained.
Preferably, the types and contents of the elements before dealkalization of the red mud in the step 1) are determined by X-Ray Fluorescence spectroscopy (X Ray Fluorescence) analysis.
Preferably, the red mud in the step 2) is dried and then crushed into 60-200 meshes.
The purpose of crushing is to increase the contact area of the red mud and the acid liquor.
Preferably, the acid amount in the step 2) is 30% -50% of the theoretical acid amount required to be consumed by the complete reaction of the red mud, and the acid amount is controlled to be 300% -500% of the acid amount consumed by the complete reaction of the red mud alkaline substances.
Preferably, the solid-liquid ratio in the step 2) is controlled to be 8: 1.
The liquid-solid ratio is controlled to ensure that the red mud is fully dissolved, thereby being beneficial to stirring and uniformly reacting.
Preferably, the mixing reaction temperature in the step 2) is 30-100 ℃; preferably 70-80 deg.C.
The temperature is controlled to stabilize the neutralization reaction speed of acid and alkali and control the whole reaction process, and higher temperature can properly promote the reaction and reduce the reaction time.
Preferably, the stirring time in the step 2) is 20-300 minutes; preferably 100-.
Preferably, the time for drying the red mud filter cake in the step 3) is 6-10 h.
The red mud after dealkalization is obtained by the preparation method.
The invention has the beneficial effects that:
compared with the red mud dealkalization method in the prior art, the method removes useless components in the red mud, reserves red mud components with better catalytic activity, reasonably controls the relation between the acid dosage and the red mud quantity, obtains dealkalized red mud enriched with iron to the maximum extent by controlling the proportion of added acid, and simultaneously contains metal elements such as Al, Ti and the like with proper components;
the obtained red mud matrix has a loose pore structure and a large specific surface area, and is beneficial to the adsorption reaction and the heat and mass transfer.
Differences between controlling acid amount and controlling Ph: the Ph of the solution is controlled during the reaction of the acid with the components in the red mud, and the amount of acid involved in the reaction is related to the final solution amount, and the absolute amount of acid used cannot be controlled. The method comprises the steps of firstly analyzing the content of components in the red mud, and calculating the acid amount required by the red mud, wherein the method is selected according to a reaction principle, and the catalyst prepared by the method contains a large amount of iron oxide because of Fe2O3Basically does not participate in the reaction under weak acid, so the control of the acid amount is the control of the reaction process of each component and the acid, and the reaction process is differentThe content of the residual components in the red mud is influenced; on the other hand, the amount of acid used takes into account a balance in the dealkalization process, and if the amount of acid is higher, although more Ca and Na can be removed, the iron content in the remaining residue will be lost, so the amount of acid needs to be controlled within a range to obtain as much iron element as possible.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application.
FIG. 1 is a flow chart of red mud dealkalization treatment process;
FIG. 2 shows the pore size comparison of acid-washed red mud with virgin red mud.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
The invention will be further illustrated by the following examples
The sources of materials and instruments in the following examples are as follows:
bayer process red mud, which is collected from Shandong GmbH of aluminum industry in China;
hydrochloric acid, analytical grade, Tianjin Kemi Euro Chemicals Co., Ltd;
sulfuric acid, analytical grade, Tianjin Kemi Euro Chemicals Co., Ltd;
nitric acid, analytical grade, Tianjin Kemi Euro Chemicals Co., Ltd;
citric acid, analytically pure, tianjinke miou chemical reagents ltd;
magnetic stirring water bath, DF-110S, shanghai dynasty instruments ltd;
a blast type drying oven, GZX-9070MBE, Shanghai Bingmai industries, Ltd;
circulating water vacuum pump, SHZ-D (III), Shanghai Li Chen apparatus Co.
Example 1
Taking 20g of red mud, taking hydrochloric acid with the amount of 30% of the theoretical consumption of the complete reaction of the red mud and acid with the amount of 310% of the acid consumption of the complete reaction of the alkaline substances of the red mud, diluting the red mud with deionized water to a liquid-solid ratio of 7:1, dissolving the red mud in a solution, setting the water bath temperature of a magnetic stirring water bath kettle to be 80 ℃, continuously stirring the red mud solution in the water bath kettle for 1 hour, taking out the red mud, performing vacuum filtration and solid-liquid separation to obtain a red mud filter cake, and drying the red mud filter cake in a blast type drying box for 12 hours at 100 ℃. And detecting the content of the substance components in the filtrate by ICP-AES, and calculating the residual quantity of each substance component in the red mud.
Example 2
Taking 20g of red mud, taking 30% of nitric acid and 310% of acid, diluting the nitric acid with deionized water until the liquid-solid ratio is 7:1, dissolving the red mud in a solution, setting the water bath temperature of a magnetic stirring water bath kettle to be 80 ℃, continuously stirring the red mud solution in the water bath kettle for 2 hours, taking out the red mud, performing vacuum filtration and solid-liquid separation to obtain a red mud filter cake, and drying the red mud filter cake in a blast type drying box for 12 hours at 100 ℃ to obtain a sample B. And detecting the content of the substance components in the filtrate by ICP-AES, and calculating the residual quantity of each substance component in the red mud.
Example 3
Taking 20g of red mud, taking 30% of sulfuric acid and 310% of acid, diluting the sulfuric acid to a liquid-solid ratio of 8:1, dissolving the red mud in a solution, setting the water bath temperature of a magnetic stirring water bath kettle to be 90 ℃, continuously stirring the red mud solution in the water bath kettle for 1 hour, taking out the red mud, performing vacuum filtration, performing solid-liquid separation to obtain a red mud filter cake, and drying the red mud filter cake in a blast type drying box for 12 hours at 100 ℃ to obtain a sample C. And detecting the content of the substance components in the filtrate by ICP-AES, and calculating the residual quantity of each substance component in the red mud.
Example 4
Taking 20g of red mud, taking hydrochloric acid with the amount of 40% of the theoretical consumption of the complete reaction of the red mud, taking acid with the amount of 440% of the acid consumption of the complete reaction of the alkaline substances of the red mud, diluting the red mud to a liquid-solid ratio of 10:1 by deionized water, dissolving the red mud in a solution, setting the water bath temperature of a magnetic stirring water bath kettle to be 80 ℃, continuously stirring the red mud solution in the water bath kettle for 1 hour, taking out the red mud, performing vacuum filtration and solid-liquid separation to obtain a red mud filter cake, and drying the red mud filter cake in a blast type drying box for 12 hours at 100. And detecting the content of the substance components in the filtrate by ICP-AES, and calculating the residual quantity of each substance component in the red mud.
Example 5
Taking 20g of red mud, taking hydrochloric acid with the amount of 50% of the theoretical consumption of the complete reaction of the red mud, taking acid with the amount of 560% of the acid consumption of the complete reaction of the alkaline substances of the red mud, diluting the red mud with deionized water to a liquid-solid ratio of 15:1, dissolving the red mud in a solution, setting the water bath temperature of a magnetic stirring water bath kettle to be 60 ℃, continuously stirring the red mud solution in the water bath kettle for 1 hour, taking out the red mud, performing vacuum filtration and solid-liquid separation to obtain a red mud filter cake, and drying the red mud filter cake in a blast type drying box for 12 hours at 100. And detecting the content of the substance components in the filtrate by ICP-AES, and calculating the residual quantity of each substance component in the red mud.
Example 6
Taking 20g of red mud, taking 40% of sulfuric acid and 460% of acid, diluting the sulfuric acid with deionized water until the liquid-solid ratio is 10:1, dissolving the red mud in a solution, setting the water bath temperature of a magnetic stirring water bath to be 40 ℃, continuously stirring the red mud solution in the water bath for 1 hour, taking out the red mud, carrying out vacuum filtration, carrying out solid-liquid separation, and drying the obtained red mud filter cake in a blast type drying box for 12 hours at the temperature of 100 ℃ to obtain a sample F. And detecting the content of the substance components in the filtrate by ICP-AES, and calculating the residual quantity of each substance component in the red mud.
Example 7
Taking 20G of red mud, taking 30% of citric acid and 280% of acid, diluting the citric acid with deionized water until the liquid-solid ratio is 15:1, dissolving the red mud in a solution, setting the water bath temperature of a magnetic stirring water bath to be 40 ℃, continuously stirring the red mud solution in the water bath for 2 hours, taking out the red mud, carrying out vacuum filtration, carrying out solid-liquid separation, and drying the obtained red mud filter cake in a blast type drying box for 12 hours at the temperature of 100 ℃ to obtain a sample G. And detecting the content of the substance components in the filtrate by ICP-AES, and calculating the residual quantity of each substance component in the red mud.
TABLE 1 residual amount of each component in red mud samples prepared in examples 1 to 7 (ICP-AES reverse calculation)
TABLE 2 comparison of the components contained before and after dealkalization of Red mud (XRF analysis)
TABLE 3 comparison of specific surface area before and after dealkalization of Red mud (BET analysis)
Tables 1 and 2 are mutually testified, the alkaline substances contained in the red mud are basically completely transferred into the filtrate in the acid cleaning process, and the iron compounds are basically not influenced by the acid cleaning, so that the Fe in the red mud filter cake obtained by filtering2O3The content is relatively increased, the increase range is more than 40 percent, and the aim of selectively dealkalizing and relatively enriching iron is achieved. In the red mud filter cake, oxides of 4 elements such as Fe, Al, Ti, Si and the like exist as main elements, and good conditions are created for the utilization of the red mud in the aspect of catalysts. Fe2O3Is a high-efficiency and environment-friendly denitration catalystActive ingredient, and Al2O3、TiO2With SiO2Are good support materials. As can be seen from fig. 2, the acid washing does not have a fundamental influence on the pore size distribution of the red mud, and still belongs to a macroporous material, but in the acid washing process, the pores of the red mud are dredged while the alkaline substances are removed, and the specific surface area is greatly increased.
Example 8
Taking 20g of the sample A obtained in the example 1, taking 1.2 times of the amount of the acid used in the example 1, diluting the sample A to an acid solution with a liquid-solid ratio of 5:1, adding the red mud, and uniformly stirring; adding 1/6 red mud into chromium nitrate with the molar weight of iron element, keeping the temperature at 50 ℃, and stirring for 4 hours; titrating the solution by using ammonia water until the pH value is 9, then filtering, and washing to be neutral to obtain the chromium element doped composite red mud; and placing the dried composite red mud filter cake in a muffle furnace, keeping the atmosphere of air, calcining for 3 hours at 550 ℃, taking out after cooling to room temperature, grinding and crushing, and sieving catalyst particles to 40 meshes to obtain a red mud nitre-removing catalyst sample J.
Example 9
Taking the sample D obtained in the example 4, diluting the sample D to an acid solution with the liquid-solid ratio of 5:1 by taking 1.5 times of the acid used in the example 4, adding the red mud, and uniformly stirring; adding 1/8 chromium nitrate with the molar weight of iron element contained in the red mud, keeping the temperature at 60 ℃, and stirring for 3 hours; titrating the solution by using ammonia water until the pH value is 9, then filtering, and washing to be neutral to obtain the chromium element doped composite red mud; and placing the dried composite red mud filter cake in a muffle furnace, keeping the atmosphere of air, calcining for 5 hours at 530 ℃, taking out after the temperature is reduced to room temperature, grinding and crushing, and sieving catalyst particles to 60 meshes to obtain a red mud denitration catalyst sample K.
Comparative example 1
Diluting 20g of red mud with deionized water until the liquid-solid ratio is 7:1, dissolving the red mud in a solution, setting the water bath temperature of a magnetic stirring water bath kettle to 80 ℃, dripping hydrochloric acid into the red mud solution, keeping the pH value of the final solution at 4, placing the solution in the water bath kettle for continuous stirring for 1 hour, taking out the solution, carrying out vacuum filtration, carrying out solid-liquid separation to obtain a red mud filter cake, and placing the red mud filter cake in a blast type drying oven for drying for 12 hours at 100 ℃ to obtain a sample L. The residual contents of the main components in sample L were (Fe: 64.25%, Al: 60.73%, Ca: 15.68%, Na: 4.62%).
Controlling the PH may result in excessive total acid in the solution being reacted, which, although still sufficient dealkalization results, results in a large loss of iron.
Comparative example 2-technical scheme for comparing that the acid content is 180%, and then adding calcium oxide for dealkalization
Diluting 20g of red mud with deionized water until the liquid-solid ratio is 7:1, dissolving the red mud in a solution, setting the water bath temperature of a magnetic stirring water bath kettle to be 80 ℃, taking the hydrochloric acid amount to be 20% of the theoretical consumption amount of the complete reaction of the red mud, taking the acid amount to be 180% of the acid amount consumed by the complete reaction of the alkaline substances of the red mud, then adding calcium oxide for dealkalization, placing the red mud solution in the water bath kettle for continuous stirring for 1 hour, then taking out the red mud solution, carrying out vacuum filtration and solid-liquid separation to obtain a red mud filter cake, placing the red mud filter cake in a blast type drying box, and. The content of the substance components in the filtrate is detected by ICP-AES, and the residue of each substance component of the red mud is calculated (Fe: 85.79%, Al: 71.48%, Ca: 213.24%, Na: 5.73%).
After the calcium oxide is added, partial calcium oxide can not fully react, and part of the calcium oxide remains after being washed by deionized water, so that the proportion of alkali-containing substances in the red mud is increased.
Comparative example 3
The difference from the comparative example 1 is that the filter cake of the sample L obtained in the comparative example 1 is placed in a muffle furnace, air atmosphere is maintained, the sample L is calcined for 4 hours at 550 ℃, and is taken out after being cooled to room temperature, ground and crushed, and catalyst particles are sieved to 60 meshes to obtain a red mud denitration catalyst sample.
Catalytic test
Flue gas denitration rates obtained by denitration of flue gas by the red mud denitration catalysts of example 8 and example 9
Table 4 evaluation of nitrogen oxide removal results of catalyst samples
As can be obtained in fig. 2, the pore size distribution of the original red mud before dealkalization is mainly macroporous distribution, and the specific surface area is low; the pore size distribution of the red mud after the acid washing is basically the same as that of the original red mud, macropores are taken as the main part, and the specific surface area of the red mud after the acid washing is improved. According to the flue gas denitration reaction principle, the pore size distribution of the composite red mud is more favorable for the reduction reaction, so that the denitration efficiency is improved, and the temperature window is widened.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (9)
1. A method for selectively dealkalizing red mud and enriching iron is characterized in that: the method comprises the following specific steps:
1) analyzing the content of each element contained in the red mud, calculating the consumption of acid required by the complete reaction of the red mud according to the common chemical valence state under the selected acid system, and calculating the consumption of acid required by alkaline substances contained in the red mud;
2) drying and crushing the red mud, mixing and stirring the crushed red mud and acid;
the acid amount is 30-80% of theoretical acid amount required to be consumed by the complete reaction of the red mud, the acid amount is controlled to be 200-600% of the acid amount consumed by the complete reaction of the red mud alkaline substances, and the liquid-solid ratio is controlled to be 3-15: 1;
3) filtering, washing to neutrality and drying the mixed solution of the red mud and the acid to obtain a red mud filter cake;
in the step 2), the mixing reaction temperature is 30-100 ℃, and the stirring time is 20-300 minutes.
2. The method for selective dealkalization and iron enrichment of red mud according to claim 1, characterized in that: the content of each element before dealkalization of the red mud in the step 1) is analyzed and determined by X-ray fluorescence spectrum analysis.
3. The method for selective dealkalization and iron enrichment of red mud according to claim 1, characterized in that: the red mud in the step 2) is dried and then crushed into 60-200 meshes.
4. The method for selective dealkalization and iron enrichment of red mud according to claim 1, characterized in that: in the step 2), the acid amount is 30% -50% of the theoretical acid amount required to be consumed by the complete reaction of the red mud, and the acid amount is controlled to be 300% -500% of the acid amount consumed by the complete reaction of the red mud alkaline substances.
5. The method for selective dealkalization and iron enrichment of red mud according to claim 1, characterized in that: and in the step 2), the liquid-solid ratio is controlled to be 8: 1.
6. The method for selective dealkalization and iron enrichment of red mud according to claim 1, characterized in that: the mixing reaction temperature in the step 2) is 70-80 ℃.
7. The method for selective dealkalization and iron enrichment of red mud according to claim 1, characterized in that: the stirring time in the step 2) is 100-150 minutes.
8. The method for selective dealkalization and iron enrichment of red mud according to claim 1, characterized in that: the time for drying the red mud filter cake in the step 3) is 6-10 h.
9. The red mud filter cake after dealkalization is prepared by the method for selectively dealkalizing and enriching iron of red mud according to any one of claims 1 to 8.
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| CN110496591A (en) * | 2019-08-23 | 2019-11-26 | 河南长兴实业有限公司 | A kind of red mud preparation method of extra specific surface area |
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