Method for removing alkali from red mud by microorganisms

Abstract

This invention relates to the field of sludge treatment technology and discloses a method for dealkalizing red mud using microorganisms, comprising the following steps: (1) adding anaerobic granular sludge and nutrient solution to a reaction vessel containing red mud slurry; (2) continuing to add nutrient solution to the reaction vessel, mixing and stirring, and allowing it to stand and separate into layers to obtain a supernatant, and measuring the pH value of the supernatant; wherein, the solute of the nutrient solution is a carbon source, and the solvent is effluent from the anaerobic reactor; (3) taking the supernatant and returning the taken-out supernatant to the anaerobic reactor; (4) repeating steps (2)-(3) until the pH value of the supernatant is stable. This invention utilizes the organic acids released during the degradation of organic matter by anaerobic microorganisms of a complex bacterial community to neutralize the alkali in red mud, reduce the pH of the red mud, simplify the microbial dealkalization process of red mud, and the red mud dealkalized by this method has a near-neutral pH and remains stable.

Description

Technical Field

[0001] This invention relates to the field of sludge treatment technology, and in particular to a method for dealkalizing red mud using microorganisms. Background Technology

[0002] Red mud is a solid waste generated during alumina production. In 2023, my country's red mud production reached 107 million tons. Although resource utilization methods such as extracting metal elements, environmentally friendly materials, and building materials can reduce red mud inventory, the utilization rate is only 9.8%. Red mud has specific pH requirements when used as a structural material for roadbeds, river embankments, etc., but its high pH (still above 11.0 even after 10 times dilution) limits its application as a building material, necessitating dealkalization pretreatment. Currently, red mud dealkalization methods include water washing, acid washing, chemical neutralization, and microbial methods. In the study "Research on Water Washing Dealkalization Process of Bayer Process Red Mud" published by Zhang Guoli et al., under a liquid-to-solid ratio of 5:1, after soaking red mud for one day and washing it eight times, the slurry pH decreased from 11.9 to approximately 9.6. The dealkalization efficiency of the water washing method is limited, and the water consumption is 40 times the volume of red mud. Khaitan et al. neutralized the alkalinity of red mud by titration with hydrochloric acid, and the pH dropped from 13.0 to about 6.0. Although the acid washing method has a high dealkali removal efficiency, the waste acid is prone to secondary pollution and requires subsequent treatment. The chemical neutralization method also has the same secondary pollution problem.

[0003] In recent years, microbial red mud dealkali removal has attracted widespread attention. Microbial red mud dealkali removal has mild reaction conditions and high dealkali removal efficiency, but the microbial species are limited, and it is susceptible to contamination by other microorganisms during the preservation, cultivation, inoculation and dealkali removal processes. The process requires high precision and is complex to operate.

[0004] Therefore, how to provide a simple and efficient method for the microbial dealkali treatment of red mud is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a method for dealkalizing red mud by microorganisms, in order to solve the problems that existing methods for dealkalizing red mud by microorganisms are complicated, difficult to preserve strains, and easily affected by contamination, which can easily affect the dealkalization efficiency.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A method for dealkalizing red mud using microorganisms includes the following steps:

[0008] (1) Add the anaerobic granular sludge and nutrient solution to the reaction vessel containing the red mud slurry;

[0009] (2) Continue to add nutrient solution to the reaction vessel, mix and stir, and let stand to separate into layers to obtain supernatant. Measure the pH value of the supernatant. The solute in the nutrient solution is a carbon source, and the solvent is the effluent from the anaerobic reactor.

[0010] (3) Take the supernatant and return the supernatant to the anaerobic reactor;

[0011] (4) Repeat steps (2)-(3) until the pH of the supernatant is stable.

[0012] Preferably, the pH value of the red mud slurry is 10.0-14.0.

[0013] Preferably, the red mud slurry includes one or more of the following: raw red mud ore, middlings red mud ore, and tailings red mud.

[0014] Preferably, the mixing volume ratio of the red mud slurry, the anaerobic granular sludge, and the nutrient solution is 1:(0.25-2.0):(0.25-2.0).

[0015] Preferably, the particle diameter of the anaerobic granular sludge is 2.0-4.0 mm.

[0016] Preferably, the settling time is 12-36 hours.

[0017] Preferably, the carbon source includes one or more of sodium acetate, glucose, and sucrose.

[0018] Preferably, the concentration of the nutrient solution is 0.5-1.0 g / L.

[0019] Preferably, the method further includes: after the pH value of the supernatant has stabilized, separating the material in the reaction vessel, and returning the resulting anaerobic granular sludge to the anaerobic reactor.

[0020] This invention provides a method for dealkalizing red mud using microorganisms, which has the following advantages compared with existing technologies:

[0021] In the red mud microbial dealkali removal process of the present invention, anaerobic granular sludge containing a complex microbial community is used. The microorganisms are diverse and have strong resistance to adverse environments. After being returned to the original anaerobic reactor, the activity of the anaerobic granular sludge is restored. Furthermore, the effluent from the anaerobic reactor is used to prepare nutrient solution, and the liquid products are directly returned to the original anaerobic reactor, resulting in less waste liquid.

[0022] In the red mud microbial dealkali removal process of the present invention, the organic acids released by the anaerobic microorganisms of the composite bacterial community during the degradation of organic matter are used to neutralize the red mud alkali. The particle size of the anaerobic granular sludge is much larger than that of the red mud, and the anaerobic granular sludge and red mud can be separated by screening. The red mud microbial dealkali removal process involves a simple structure, is easy to operate, and has high dealkali removal efficiency. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the pH changes of the supernatant in Example 1 and Comparative Example 1 of the present invention;

[0025] Figure 2 This is a schematic diagram of the pH change of the supernatant in Example 2 and Comparative Example 2 of the present invention;

[0026] Figure 3 This is a schematic diagram of pH changes in the supernatant of Examples 3-5 of the present invention. Detailed Implementation

[0027] The embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in the art or in accordance with the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0028] This invention provides a method for dealkalizing red mud using microorganisms, comprising the following steps:

[0029] Step S100. Add anaerobic granular sludge and nutrient solution to a reaction vessel containing red mud slurry, mix and stir, and then let stand to separate into layers to obtain new red mud slurry and supernatant. Measure the pH value of the supernatant. The solute in the nutrient solution is a carbon source, and the solvent is the effluent from the anaerobic reactor.

[0030] In this step, the red mud slurry includes, but is not limited to, one or more of the following: raw red mud ore, middlings red mud, and tailings red mud. It can be high-iron or low-iron red mud, and the pH value of the red mud slurry is 10.0-14.0, for example, 10.0, 11.0, 12.0, 13.0, 14.0, etc. Because red mud itself contains high alkaline substances and has a high pH, ​​no pretreatment of the red mud slurry is required.

[0031] Optionally, the mixing volume ratio of the red mud slurry, the anaerobic granular sludge, and the nutrient solution is 1:(0.25-2.0):(0.25-2.0), for example, it can be 1:0.25:0.25, 1:0.5:0.5, 1:1:1, 1:2.0:2.0, 1:0.25:0.5, 1:2:1, etc.

[0032] Optionally, the particle diameter of the anaerobic granular sludge is 2.0-4.0 mm. This invention uses anaerobic granular sludge containing a complex microbial community, which has a wide variety of microorganisms and strong resistance to adverse environments. It should be noted that if the diameter of the anaerobic granular sludge used is too small, the anaerobic sludge may be immature and have poor activity, affecting the dealkalization efficiency. If the diameter is too large, the anaerobic sludge may expand and disintegrate, affecting the separation of sludge and red mud. This invention preferably uses anaerobic granular sludge with a particle diameter of 2.0-4.0 mm.

[0033] Optionally, the settling time is 12-36 hours, for example, 12 hours, 24 hours, 30 hours, 36 hours, etc. There is no special limitation on this. As long as a clear separation of supernatant and precipitate is observed, subsequent operations can be carried out.

[0034] Optionally, the carbon source includes, but is not limited to, one or more of sodium acetate, glucose, and sucrose, and optionally, the concentration of the nutrient solution is 0.5-1.0 g / L, for example, 0.5 g / L, 0.8 g / L, 1.0 g / L, etc.

[0035] It is important to note that if the nutrient solution concentration is too low, the anaerobic sludge will have insufficient nutrients and poor activity. Conversely, the higher the concentration, the more nutrients the anaerobic sludge contains, the stronger its activity, and the higher the dealkalization efficiency. However, within the limited reaction time, if the nutrient solution concentration is too high, most of the nutrients will not be degraded and may adhere to the red mud particles. This wastes reagents and may affect the subsequent resource utilization of the red mud. Therefore, the preferred nutrient solution concentration in this invention is 0.5-1.0 g / L, which satisfies the sludge's nutritional needs without leaving too much residue on the red mud.

[0036] This invention utilizes the organic acids released during the degradation of organic matter by anaerobic microorganisms in a complex microbial community to neutralize the alkali in red mud. The operation is simple, the dealkali removal efficiency is high, and there is no secondary pollution.

[0037] Step S200. Take the supernatant and return the supernatant to the anaerobic reactor.

[0038] In this step, the supernatant is returned to the anaerobic reactor, which reduces the generation of waste liquid, and the nutrient solution contains residual carbon sources, which can provide energy for the microorganisms in the anaerobic reactor.

[0039] Step S300. Repeat steps S100 and S200 until the pH value of the supernatant is stable.

[0040] In this step, it is important to note that during the repetition of step S100, no new anaerobic granular sludge is added. Instead, new nutrient solution is added, mixed, and then the cycle is repeated. This allows the complex microbial community in the anaerobic granular sludge to continue to function.

[0041] Step S400. After the pH value of the supernatant stabilizes, the material in the reaction vessel is separated, and the anaerobic granular sludge obtained after separation is returned to the anaerobic reactor.

[0042] In this step, the material in the reaction vessel is sieved through a stainless steel sieve with a 1.0 mm aperture. Since the particle size of anaerobic granular sludge is larger than the sieve aperture and the particle size of red mud is smaller than the sieve aperture, the sieving method can be used to separate the anaerobic granular sludge and red mud. The operation is simple. Furthermore, the activity of the anaerobic granular sludge can be restored after it is returned to the original anaerobic reactor.

[0043] The present invention will be described below through specific embodiments. Those skilled in the art will understand that the specific embodiments below are merely illustrative and do not limit the scope of the invention in any way. Furthermore, in the following embodiments, unless otherwise specified, the reagents and equipment used are commercially available. If specific processing conditions and methods are not explicitly described in the later embodiments, conditions and methods known in the art can be used for processing.

[0044] Example 1

[0045] (1) Weigh 5.0 mL of red mud tailings with a pH of 13.0 and set aside for later use;

[0046] (2) Take 1.25 mL of anaerobic granular sludge from the anaerobic digester and set aside for later use;

[0047] (3) Using the effluent from the anaerobic reactor as a solvent and sodium acetate as a solute, a nutrient solution with a concentration of 1.0 g / L was prepared.

[0048] (4) Add the anaerobic granular sludge from (2) and 1.25 mL of nutrient solution from (3) to a reaction vessel containing red mud tailings. Stir with a glass rod for 3 min and let stand at room temperature for 24 h to obtain the supernatant. Measure the pH value of the supernatant.

[0049] (5) Take out 1.25 mL of supernatant and let it flow back into the anaerobic reactor through the inlet;

[0050] (6) Add 1.25 mL of the nutrient solution from (3) to the reaction vessel containing the red mud tailings again;

[0051] (7) Repeat steps (5) and (6);

[0052] (8) Performance test: After the pH value of the supernatant stabilizes, a alkali return test is performed without replacing the supernatant;

[0053] (9) Pass the mixture in the reaction vessel through a stainless steel sieve with a pore size of 1.0 mm to separate the anaerobic granular sludge and red mud. After separation, add the anaerobic granular sludge back into the anaerobic reactor.

[0054] Example 2

[0055] (1) Weigh 5.0 mL of red mud tailings with a pH of 13.0 and set aside for later use;

[0056] (2) Take 10.0 mL of anaerobic granular sludge from the anaerobic digester and set aside for later use;

[0057] (3) Using the effluent from the anaerobic reactor as a solvent and sodium acetate as a solute, a nutrient solution with a concentration of 1.0 g / L was prepared.

[0058] (4) Add the anaerobic granular sludge from (2) and 10.0 mL of nutrient solution from (3) to a reaction vessel containing red mud tailings. Stir with a glass rod for 3 min and let stand at room temperature for 24 h to obtain the supernatant. Measure the pH value of the supernatant.

[0059] (5) Take out 10.0 mL of supernatant and let it flow back into the anaerobic reactor through the inlet;

[0060] (6) Add 10.0 mL of the nutrient solution from (3) to the reaction vessel containing the red mud tailings again;

[0061] (7) Repeat steps (5) and (6);

[0062] (8) Performance test: After the pH value of the supernatant stabilizes, a alkali return test is performed without replacing the supernatant;

[0063] (9) Pass the mixture in the reaction vessel through a stainless steel sieve with a pore size of 1.0 mm to separate the anaerobic granular sludge and red mud. After separation, add the anaerobic granular sludge back into the anaerobic reactor.

[0064] Example 3

[0065] (1) Weigh 5.0 mL of red mud tailings with a pH of 13.0 and set aside for later use;

[0066] (2) Take 5.0 mL of anaerobic granular sludge from the anaerobic digester and set aside for later use;

[0067] (3) Using the effluent from the anaerobic reactor as a solvent and sodium acetate as a solute, a nutrient solution with a concentration of 1.0 g / L was prepared.

[0068] (4) Add the anaerobic granular sludge from (2) and 5.0 mL of nutrient solution from (3) to a reaction vessel containing red mud tailings. Stir with a glass rod for 3 min, let stand at room temperature for 24 h to obtain supernatant, and measure the pH value of supernatant.

[0069] (5) Take out 5.0 mL of supernatant and let it flow back into the anaerobic reactor through the inlet;

[0070] (6) Add 5.0 mL of the nutrient solution from (3) to the reaction vessel containing the red mud tailings again;

[0071] (7) Repeat steps (5) and (6);

[0072] (8) Performance test: After the pH value of the supernatant stabilizes, a alkali return test is performed without replacing the supernatant;

[0073] (9) Pass the mixture in the reaction vessel through a stainless steel sieve with a pore size of 1.0 mm to separate the anaerobic granular sludge and red mud. After separation, add the anaerobic granular sludge back into the anaerobic reactor.

[0074] Example 4

[0075] (1) Weigh 5.0 mL of raw red mud ore, pH 12.1, and set aside for later use;

[0076] (2) Take 5.0 mL of anaerobic granular sludge from the anaerobic digester and set aside for later use;

[0077] (3) Using the effluent from the anaerobic reactor as a solvent and sodium acetate as a solute, a nutrient solution with a concentration of 1.0 g / L was prepared.

[0078] (4) Add the anaerobic granular sludge from (2) and 5.0 mL of nutrient solution from (3) to a reaction vessel containing red mud ore. Stir with a glass rod for 3 min, let stand at room temperature for 24 h to obtain supernatant, and measure the pH value of supernatant.

[0079] (5) Take out 5.0 mL of supernatant and let it flow back into the anaerobic reactor through the inlet;

[0080] (6) Add 5.0 mL of the nutrient solution from (3) to the reaction vessel containing the raw red mud ore again;

[0081] (7) Repeat steps (5) and (6);

[0082] (8) Performance test: After the pH value of the supernatant stabilizes, a alkali return test is performed without replacing the supernatant;

[0083] (9) Pass the mixture in the reaction vessel through a stainless steel sieve with a pore size of 1.0 mm to separate the anaerobic granular sludge and red mud. After separation, add the anaerobic granular sludge back into the anaerobic reactor.

[0084] Example 5

[0085] (1) Weigh 5.0g of red mud minerals, add 6.0mL of tap water, pH 11.1, and set aside;

[0086] (2) Take 5.0 mL of anaerobic granular sludge from the anaerobic digester and set aside for later use;

[0087] (3) Using the effluent from the anaerobic reactor as a solvent and sodium acetate as a solute, a nutrient solution with a concentration of 1.0 g / L was prepared.

[0088] (4) Add the anaerobic granular sludge from (2) and 5.0 mL of nutrient solution from (3) to a reaction vessel containing red mud tailings. Stir with a glass rod for 3 min, let stand at room temperature for 24 h to obtain supernatant, and measure the pH value of supernatant.

[0089] (5) Take out 5.0 mL of supernatant and let it flow back into the anaerobic reactor through the inlet;

[0090] (6) Add 5.0 mL of the nutrient solution from (3) to the reaction vessel containing the red mud tailings again;

[0091] (7) Repeat steps (5) and (6);

[0092] (8) Performance test: After the pH value of the supernatant stabilizes, a alkali return test is performed without replacing the supernatant;

[0093] (9) Pass the mixture in the reaction vessel through a stainless steel sieve with a pore size of 1.0 mm to separate the anaerobic granular sludge and red mud. After separation, add the anaerobic granular sludge back into the anaerobic reactor.

[0094] Comparative Example 1

[0095] Weigh 5.0 mL of red mud tailings with a pH of 13.0 and dealkalize the red mud by washing it with water. Do not add anaerobic granular sludge. Replace the solution with 1.25 mL of tap water each time.

[0096] Comparative Example 2

[0097] Weigh 5.0 mL of red mud tailings with a pH of 13.0 and dealkalize the red mud by washing it with water. Do not add anaerobic granular sludge. Replace the solution with 10.0 mL of tap water each time.

[0098] like Figure 1-2The diagram shows the pH changes of the supernatant in Examples 1-2 and Comparative Examples 1-2 of the present invention. The results of Examples 1-2 show that, under the condition of treating the same amount of red mud slurry, the time for the pH value of the supernatant to reach a stable value is shorter as the amount of anaerobic granular sludge and nutrient solution mixed increases, that is, the treatment efficiency is higher. However, the change in the mixing ratio of red mud slurry with anaerobic granular sludge and nutrient solution does not have a significant impact on the final pH value of the supernatant. The final pH value of the supernatant is stable below 8.5.

[0099] The results of Comparative Examples 1-2 show that, under the condition of treating the same amount of red mud slurry, if water washing is used for dealkalization, the time for the pH value of the supernatant to reach a stable value will increase, that is, the treatment efficiency will be lower, and the final pH value of the supernatant will stabilize at 10-11, that is, the treatment effect will also be worse.

[0100] like Figure 3 The diagram shown is a schematic diagram of the pH change of the supernatant in Examples 3-5 of the present invention. The results show that the method of dealkalization by mixing anaerobic granular sludge and nutrient solution is universally applicable to red mud ore, red mud middlings and red mud tailings, and the final pH value of the supernatant is stable below 8.5.

[0101] In summary, this invention provides a method for dealkalizing alumina red mud using anaerobic sludge blended microorganisms. It utilizes the organic acids released during the degradation of organic matter by the anaerobic microorganisms of the composite microbial community to neutralize the alkali in the red mud, thereby reducing the pH of the red mud and simplifying the microbial dealkalization process. The red mud dealkalized using this method has a near-neutral pH and remains stable.

[0102] In the description of this specification, the terms "one embodiment," "another embodiment," "yet another embodiment," "some embodiments," "some specific embodiments," "other specific embodiments," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment, which are included in at least one embodiment of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples, without contradiction. Additionally, it should be noted that in this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0103] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for dealkalizing red mud using microorganisms, characterized in that, Includes the following steps: (1) Add the anaerobic granular sludge and nutrient solution to the reaction vessel containing the red mud slurry; (2) Continue to add nutrient solution to the reaction vessel, mix and stir, and let stand to separate into layers to obtain supernatant. Measure the pH value of the supernatant. The solute in the nutrient solution is a carbon source, and the solvent is the effluent from the anaerobic reactor. (3) Take the supernatant and return the supernatant to the anaerobic reactor; (4) Repeat steps (2)-(3) until the pH of the supernatant is stable; The mixing volume ratio of the red mud slurry, the anaerobic granular sludge, and the nutrient solution is 1:(0.25-2.0):(0.25-2.0).

2. The red mud microbial dealkali removal method according to claim 1, characterized in that, The pH value of the red mud slurry is 10.0-14.

0.

3. The red mud microbial dealkali removal method according to claim 1, characterized in that, The red mud slurry includes one or more of the following: raw red mud ore, middlings red mud ore, and tailings red mud.

4. The red mud microbial dealkali removal method according to claim 1, characterized in that, The anaerobic granular sludge has a particle diameter of 2.0-4.0 mm.

5. The red mud microbial dealkali removal method according to claim 1, characterized in that, The settling time is 12-36 hours.

6. The red mud microbial dealkali removal method according to claim 1, characterized in that, The carbon source includes one or more of sodium acetate, glucose, and sucrose.

7. The red mud microbial dealkali removal method according to claim 1, characterized in that, The concentration of the nutrient solution is 0.5-1.0 g / L.

8. The red mud microbial dealkali removal method according to any one of claims 1-7, characterized in that, Also includes: After the pH value of the supernatant stabilizes, the material in the reaction vessel is separated, and the resulting anaerobic granular sludge is returned to the anaerobic reactor.

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