A method for dealkalization of red mud

Abstract

The invention discloses a red mud dealkalization method. Specifically, high-concentration bottom water collected from the bottom of a Maotai-flavor liquor brewing pit is used as a dealkalization agent. Specifically, the steps are as follows: first, the filter press red mud produced by an alumina plant is crushed and sieved, and then the dealkalization agent is evenly mixed with the red mud under the sieve, and after reacting at 20-50 DEG C for a certain time, an appropriate amount of a decolorizing agent is added, stirred evenly, and then the dealkalization red mud is obtained by filter pressing. The method can effectively remove alkali from the red mud and promote the agglomeration of red mud particles. The dealkalized red mud can be applied to the fields of soil, building materials, water treatment agents, etc. The entire dealkalization process of the method is green, low-carbon, environmentally friendly, and low-cost, and has a prospect for industrial application.

Description

Technical Field

[0001] The invention relates to a method for dealkalizing red mud, a strongly alkaline solid waste residue discharged during the production of aluminum oxide, in particular to a low-cost dealkalizing method for red mud. Background Art

[0002] Red mud is a strongly alkaline solid waste discharged during the production of alumina, which contains a large amount of iron oxide, aluminum oxide and various alkaline substances. The chemical composition of red mud varies due to different production processes and bauxite raw materials, but it is strongly alkaline (pH11~13) and contains radioactive trace elements such as potassium, thorium, and radium. At present, most red mud is mainly stored in piles. The large-scale stacking of red mud not only occupies land and farmland, but also pollutes soil, water resources and the atmosphere, corrodes buildings and building surfaces, and has a huge impact on people's health. How to solve the global problem of comprehensive utilization of alumina red mud has long attracted the attention of countries around the world. The key to large-scale resource utilization of red mud lies in how to reduce its alkalinity at low cost.

[0003] During the brewing process in pits, the brewing enterprises of Maotai-flavor liquor will produce a large amount of high-concentration pit bottom wastewater that is difficult to treat and seriously polluted. The wastewater mainly contains high concentrations of dissolved organic matter, including polysaccharides, organic acids, ethanol, glycerol and other organic matter, with physical and chemical properties such as high COD, high BOD, high biological activity, high chroma, acidity, low dissolved oxygen, high nitrogen concentration and high phosphorus concentration. The treatment cost of pit bottom wastewater is extremely high. If the pit bottom wastewater infiltrates into the soil, it will reduce the alkalinity and bioavailability of manganese in the soil, inhibit the germination and growth of seeds, lead to vegetation failure, and cause a certain degree of damage to terrestrial plants and animals; if it is directly discharged into rivers and lakes, it will cause the rapid consumption of dissolved oxygen in the water, eutrophication of the water, and cause the water to become black and smelly.

[0004] The key point of large-scale resource utilization of red mud lies in how to reduce its alkalinity at low cost. At present, the methods for dealkalization of red mud include water washing, acid leaching, lime method, salt leaching method, CO2 method, biological method, etc. However, the above methods have the problems of cumbersome operation and high dealkalization cost, and are still difficult to promote and utilize. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the existing problems and provide a low-cost red mud dealkalization method, that is, using acidic pit bottom wastewater to dealkalize red mud, which not only solves the problem of high alkalinity of red mud, but also realizes the resource utilization of pit bottom wastewater, achieves the purpose of "treating waste with waste and turning waste into treasure", and can effectively solve the problems existing in the current technology.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] The present invention provides a low-cost red mud dealkalization method, which comprises the following detailed steps:

[0008] S1) Red mud pretreatment: Grind and sieve the red mud from the aluminum plant filter press;

[0009] S2) Dealkalizing agent treatment: filtering the dealkalizing agent to remove suspended particles therein;

[0010] S3) dealkalization treatment: the raw materials treated in steps S1 and S2 are mixed evenly at a certain solid-liquid ratio, and reacted at a certain temperature for a certain time;

[0011] S4) Decolorization of the dealkalized liquid: a certain amount of decolorizing agent is added to the red mud after the reaction, and the mixture is stirred evenly, and then filtered to obtain the dealkalized red mud.

[0012] As a preferred technical solution of the present invention, the filter press red mud described in S1 is a high-alkali solid residue produced by smelting alumina by the Bayer process, the sintering process or the combined process, with a pH value of ≥10 and sieved with a 40-mesh sieve.

[0013] As a preferred technical solution of the present invention, the dealkalizing agent described in S2 is high-concentration bottom water collected from the bottom of the Maotai-flavor liquor brewing pit, which is filtered through a 100-mesh filter.

[0014] As a preferred technical solution of the present invention, the solid-to-liquid ratio described in S3 is 5:1 to 1:2.

[0015] As a preferred technical solution of the present invention, the dealkalization temperature in S3 is 20°C to 80°C, and the reaction time is 10h to 100h.

[0016] As a preferred technical solution of the present invention, the decolorizing agent in S4 is one or more of activated carbon powder, polyacrylamide, polyaluminum chloride, thiourea dioxide, and calcined red mud.

[0017] As a preferred technical solution of the present invention, the filtration pressure described in S4 is the filtration pressure provided by a belt filter press or a plate and frame filter press.

[0018] As a preferred technical solution of the present invention, the pH value of the dealkalized red mud in S4 is 7.3-8.6.

[0019] Compared with the prior art, the present invention has the following positive and beneficial effects: the pH value of red mud can be effectively reduced by dealkalizing red mud with brewing acid wastewater. The dealkalized red mud can be applied to the fields of soil, building materials, water treatment agents, etc., which solves the two major problems of red mud and brewing wastewater at one stroke and has high economic and social value. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1This is a scanning electron microscope photograph of the dealkalized red mud agglomerates of Example 1 of the present invention;

[0021] Figure 2 The X-ray diffraction patterns of the red mud before and after dealkalization in Example 2 of the present invention;

[0022] Figure 3 This is a scanning electron microscope photograph of the dealkalized red mud agglomerates of Example 3 of the present invention;

[0023] Figure 4 This is a scanning electron microscope photograph of the dealkalized red mud agglomerates of Example 4 of the present invention. Specific implementation methods

[0024] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] The present invention provides the following technical solutions

[0026] The red mud is put into a shearing mill, ground and crushed, and passed through a 40-mesh sieve, and the sample is stored for later use; the brewing wastewater is filtered to remove suspended particles therein, and stored for later use; Embodiment 1:

[0027] 100 parts of red mud and 20 parts of fermentation pit water of Maotai-flavor liquor were placed in a reaction container and stirred to obtain red mud slurry. The mixture was reacted for 48 hours at room temperature. Then, 0.1 parts of cationic polyacrylamide was added to the slurry and mixed evenly. The mixed slurry was pumped into a plate-and-frame filter press for pressure filtration to obtain de-alkalized red mud with a pH value of 8.6. The scanning electron microscope photo of red mud agglomerates is shown in FIG. Figure 1 The chemical composition of red mud before and after dealkalization is shown in Table 1. Embodiment 2:

[0028] 100 parts of red mud and 100 parts of fermentation pit water of Maotai-flavor liquor were placed in a reaction container, stirred evenly to obtain red mud slurry, and reacted at room temperature for 24 hours. Then, 0.2 parts of polyaluminium chloride and 0.5 parts of activated carbon were added to the slurry and mixed evenly. The mixed slurry was pumped into a plate-and-frame filter press for pressure filtration to obtain dealkalized red mud with a pH value of 7.5. The X-ray diffraction patterns of the red mud before and after dealkalization are shown in FIG. Figure 2 The chemical composition of red mud before and after dealkalization is shown in Table 1. Embodiment 3:

[0029] 100 parts of red mud and 80 parts of fermentation pit water of Maotai-flavor liquor were placed in a reaction vessel and stirred evenly to obtain red mud slurry. The mixture was reacted at room temperature for 72 hours. Then, 1 part of activated carbon, 2 parts of calcined red mud and 0.2 parts of thiourea dioxide were added to the slurry and mixed evenly. The mixed slurry was pumped into a plate and frame filter press for pressure filtration to obtain dealkalized red mud with a pH value of 7.8. The chemical composition of the red mud before and after dealkalization is shown in Table 1. Embodiment 4:

[0030] 100 parts of red mud and 200 parts of fermentation pit water of Maotai-flavor liquor were placed in a reaction container and stirred to obtain red mud slurry. The mixture was reacted at room temperature for 96 hours. Then, 1 part of activated carbon, 1 part of calcined red mud and 0.01 part of cationic polyacrylamide were added to the slurry and mixed evenly. The mixed slurry was pumped into a plate and frame filter press for pressure filtration to obtain dealkalized red mud with a pH value of 7.3. The scanning electron microscope photo of red mud agglomerates is shown in FIG. Figure 4 The chemical composition of red mud before and after dealkalization is shown in Table 1.

[0031] Table 1 Changes in the main chemical components of red mud before and after dealkalization (mass fraction / %)

[0032]

[0033] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A red mud dealkalization method, characterized in that: The method comprises the following steps: S1) Red mud pretreatment: grinding and sieving the red mud from the aluminum plant; S2) de-alkali agent treatment: filtering the de-alkali agent to remove suspended particles therein; S3) dealkalization treatment: the raw materials treated in steps S1 and S2 are mixed evenly at a certain solid-liquid ratio, and reacted at a certain temperature for a certain time; S4) adding a certain amount of decolorizing agent to the reacted red mud and continuing to stir evenly, and then performing filter pressing to obtain dealkalized red mud; Wherein, the filter press red mud in S1) is a high-alkali solid residue produced by smelting alumina by the Bayer process, the sintering process or the combined process, with a pH value of ≥10 and sieved with a 40-mesh sieve; Wherein, the dealkalizing agent in S2) is high-concentration pit bottom water collected from the bottom of the Maotai-flavor liquor brewing pit, which is filtered through a 100-mesh filter; Wherein, the method comprises: 100 parts of red mud and 100 parts of fermentation pit water of Maotai-flavor liquor are placed in a reaction container, stirred evenly to obtain red mud slurry, reacted at room temperature for 24 hours, and then a decolorant is added to the slurry and mixed evenly, wherein the decolorant is 0.2 parts of polyaluminium chloride and 0.5 parts of activated carbon, and the mixed slurry is pumped into a plate and frame filter press for pressure filtration to obtain dealkalized red mud with a pH value of 7.5; or 100 parts of red mud and 80 parts of fermentation pit water of Maotai-flavor liquor are placed in a reaction container, stirred evenly to obtain red mud slurry, reacted at room temperature for 72 hours, and then a decolorant is added to the slurry and mixed evenly, wherein the decolorant is 1 part of activated carbon, 2 parts of calcined red mud and 0.2 parts of thiourea dioxide, and the mixed slurry is pumped into a plate and frame filter press for pressure filtration to obtain dealkalized red mud with a pH value of 7.8; or 100 parts of red mud and 200 parts of fermentation pit water of Maotai-flavor liquor are placed in a reaction container, stirred evenly to obtain red mud slurry, reacted at room temperature for 96 hours, and then a decolorizer is added to the slurry and mixed evenly. The decolorizer is 1 part of activated carbon, 1 part of calcined red mud and 0.01 part of cationic polyacrylamide. The mixed slurry is pumped into a plate and frame filter press for pressure filtration to obtain dealkalized red mud with a pH value of 7.3.

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