Method for converting secondary aluminum ash into soil

Abstract

The invention discloses a method for treating secondary aluminum ash residues into soil. The method comprises the following steps: S1, carrying out acid leaching treatment on the secondary aluminum ash residues for 2-10 hours; s2, adding an adsorption column prepared by taking oyster shells as a raw material, standing for 20-30 minutes, stirring for 2-3 minutes, standing, stirring, and repeatedly circulating for 3-5 times; s3, filtering for the first time, recovering the adsorption column, and filtering for the second time to obtain filter residues; s4, adjusting the pH value of the filter residues to 6.8-7.2 to obtain a mixture B which can be directly used for planting green plants or crops. The secondary aluminum ash soil treatment method is simple, easy to operate and suitable for large-scale use, heavy metal elements in the secondary aluminum ash can be efficiently removed by adding the adsorption column with high adsorbability in the process of extracting the oxyaluminide from the secondary aluminum ash through acid leaching, and the secondary aluminum ash soil treatment effect is improved. The problems that in the prior art, the secondary aluminum ash resource utilization efficiency is low, and the technical level is not advanced enough can be solved.

Description

Technical Field

[0001] The invention relates to the technical field of soil utilization of secondary aluminum ash, and in particular to a method for soil utilization of secondary aluminum ash slag. Background Art

[0002] At present, most production enterprises only recycle primary aluminum ash with high aluminum content, and the remaining aluminum slag, secondary aluminum ash, etc. (aluminum exists mainly in the form of alumina) after recycling are mostly piled up or landfilled in the form of waste slag. Secondary aluminum ash is the waste after the extraction of aluminum from primary aluminum ash or aluminum-containing waste slag produced in the aluminum refining process. The aluminum content is low, usually between 10% and 20%, and it also contains fluoride salts, chlorides and other toxic and harmful substances. This not only causes a huge waste of aluminum resources, but also the aluminum nitride contained in it is easy to hydrolyze when it comes into contact with water or is affected by a humid environment, releasing ammonia and nitrogen, etc., which pollutes the atmosphere and forms a safety hazard, causing serious pollution to the surrounding environment. Because aluminum ash contains aluminum nitride, fluoride and heavy metal substances such as manganese, zinc, chromium, and nickel that are harmful to human health and the environment, and it contains a certain amount of salt, its comprehensive and effective utilization in industry and agriculture is limited.

[0003] The currently developed secondary aluminum ash aluminum extraction processes can be roughly divided into three categories: electric heating method, acid leaching method, and alkali fusion method. All of them can produce qualified alumina products, but they all face the problems of large aluminum extraction emissions and insoluble absorption to varying degrees. In addition, due to the problems of difficult separation, high cost, and easy generation of secondary hazardous waste, it is difficult to achieve industrialization. There are also other methods. For example, the patent (application number: 201911330007.9) discloses a soil water retainer produced using aluminum ash and its preparation method. This method includes: adding dilute nitric acid and sodium sulfide solution to the aluminum ash respectively to remove heavy metals in the aluminum ash, and the content reaches the agricultural heavy metal limit standard; secondly, mixing and grinding the aluminum ash with heavy metals removed with calcium-based compounds; after high-temperature activation of the fully mixed materials, a material with calcium sulfoaluminate as the main mineral component is obtained; finally, under hydration conditions, a soil water retainer with weak alkaline characteristics and calcium sulfonate as the main mineral component is obtained. Although the patent has certain positive significance for the resource recycling and environmental protection of aluminum ash, the method: (1) has many steps in the process and high cost, which is not conducive to mass production and use; (2) is not advanced enough in terms of technical level. The above method relies on chemical balance and reaction conditions (such as pH value, temperature, etc.), and may require a long reaction time and complex operating conditions to ensure the effective removal of heavy metals. It is inefficient and difficult to guarantee the removal effect. (3) In terms of application scope, the application scenario is relatively single. The weak alkaline characteristics of the above soil water retaining agent are not suitable for certain acidic soils, which has certain limitations. Summary of the invention

[0004] In order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide a method for soilification of secondary aluminum ash slag, so as to solve the problems of low efficiency in resource utilization of secondary aluminum ash and insufficient technical level in the prior art.

[0005] The technical solution adopted by the present invention is as follows: The method for soilification of secondary aluminum ash comprises the following steps: S1, subjecting the secondary aluminum ash to acid leaching for 2-10 hours; S2, adding an adsorption column prepared with oyster shells as raw materials, standing for 20-30 minutes, stirring for 2-3 minutes, standing again, stirring, and repeating the cycle 3-5 times; S3, performing a first filtration, recovering the adsorption column, and then performing a second filtration to obtain a filter residue; S4, washing the filter residue with water for 2-4 times, adjusting the pH value to 6.8-7.2, and obtaining a mixture B, which can be directly used to plant green plants or crops.

[0006] Principle of the present invention: During the acid leaching process of secondary aluminum ash, the metal aluminum, aluminum nitride, aluminum carbide, etc. in the secondary aluminum ash react with acid to obtain an aluminum compound solution, such as an aluminum nitrate solution. The aluminum element in the secondary aluminum ash can be recovered by recovering the filtrate. However, the secondary aluminum ash contains trace amounts of heavy metals. During the acid leaching process, these heavy metals are dissolved under acidic conditions and become pollutants that need to be removed. For this reason, the present invention adds an adsorption column during the acid leaching process of the secondary aluminum ash, and uses physical adsorption to fix the heavy metal elements to the adsorption column. Through the first filtration, the adsorption column adsorbed with heavy metals is removed, and then the second filtration is performed to obtain filter residues and aluminum compound solutions. Since a small amount of salts such as fluoride salts and other harmful substances are still adhered to the filter residue, the filter residue is washed with water for 2-4 times to obtain harmless aluminum ash. The harmless aluminum ash is mainly a mixture of aluminum oxide, silicate, iron oxide, calcium oxide, magnesium oxide, etc., that is, mixture B. After adjusting the pH of mixture B to be close to neutral, it is directly applied to different soils to increase soil nutrients.

[0007] Beneficial effects of the present invention: The secondary aluminum ash soilification method adopted by the present invention is simple and easy to operate. By adding an adsorption column during the acid leaching process of the secondary aluminum ash, the heavy metal elements in the secondary aluminum ash are efficiently removed by physical adsorption without introducing other chemical substances, which can avoid the risk of secondary pollution and achieve efficient treatment, and is more suitable for large-scale use. In addition, the adsorption column of the present invention is prepared with oyster shells as raw materials. Oyster shells are easy to obtain and have low costs. Natural oyster shells have larger pores than other shells, and the specific surface area of ​​the macroporous structure is larger, and the effect of adsorbing heavy metals is better.

[0008] As a preferred embodiment of the present invention, the preparation method of the adsorption column includes the following steps: a. crushing the oyster shell and sieving it to obtain oyster shell powder; b. mixing the oyster shell powder and nano titanium dioxide, adding a pore-forming agent and fully burning it to obtain a mixture A; c. crushing the mixture A and activated carbon and stirring them evenly, and using them as raw materials to make a porous adsorption column with a density of 40%-60%, and the length of the adsorption column is 1 cm; the addition ratio of oyster shell powder, nano titanium dioxide and activated carbon is 10-20:0.5-2:1-5.

[0009] Beneficial effects: The adsorption column of the present invention is mainly composed of oyster shell powder, supplemented by nano titanium dioxide and activated carbon powder, and is made into a porous adsorption column with a density of 40%-60%. It has extremely strong adsorption capacity, which is 4-5 times that of general adsorbents. The pore radius of natural oyster shell powder is within 2nm, and the pore radius after high-temperature calcination at 750°C is about 10nm. Its microscopic morphology is basically a regular circle under a scanning electron microscope. The present invention adds a pore-forming agent during high-temperature calcination, and the pore radius of the oyster shell powder can reach about 30nm, which can double its adsorption effect. At the same time, the oyster shell powder also introduces hydroxyl (-OH) or carboxyl (-COOH) after thermal modification. The hydroxyl (-OH) and carboxyl (-COOH) can make the heavy metal adsorption more stable through hydrogen bonding, electrostatic interaction or chemical coordination.

[0010] As a preferred embodiment of the present invention, in step c, the addition ratio of oyster shell powder, nano-titanium dioxide and activated carbon is 15:1.5:3.

[0011] As a preferred embodiment of the present invention, it also includes an adsorption ball, which is filled with an adsorption column. The adsorption ball includes an outer filter ball and an inner filter ball. The inner filter ball is installed in the outer filter ball, and the inner filter ball is filled with the adsorption column. The adsorption ball filled with the adsorption column is put into the secondary aluminum ash acid leaching solution to adsorb heavy metals.

[0012] Beneficial effects: Since stirring is required during the heavy metal adsorption process, if the adsorption column is directly put into the adsorption column during the stirring process, the adsorption column may be mechanically damaged by mutual collision, resulting in slag falling, which is not only inconvenient to recover but also part of it will be mixed into the filter residue, and heavy metals will also be mixed into the filter residue. The present invention fills the adsorption column in the adsorption ball, and the double-layer filter screen of the adsorption ball can be used to effectively solve the problem of the adsorption column mixing into the filter residue, and it is also more convenient for recovery.

[0013] As a preferred embodiment of the present invention, the outer filter ball has a diameter of 6-10 cm, a mesh size of 1-10 μm, and the inner filter ball has a diameter of 2-4 cm, a mesh size of 0.05-0.2 cm.

[0014] Beneficial effects: 1. Heavy metals are adsorbed on the surface or pores of the adsorption column through electrostatic action or complex reaction. When the adsorption sites are saturated, metal ions may aggregate. With continued stirring, the adsorption columns collide with each other, the inner and outer filter balls collide with each other, and large aggregate structures may fall off. In the present invention, the mesh size of the inner filter ball is 0.05-0.2 cm, and the mesh size of the outer filter ball is 1-10 μm. Under a scanning electron microscope, large aggregate structures will fall out of the inner filter ball and be intercepted in the outer filter ball, thereby being collected between the inner and outer balls to achieve heavy metal separation.

[0015] 2. When the clustered structure falls off, the adsorption sites on the adsorption column are exposed again and can continue to adsorb, thereby greatly increasing the adsorption capacity of each adsorption ball and achieving efficient utilization of the adsorption material.

[0016] 3. There may be foreign matter in the mesh of the outer filter ball, but because the inner filter ball moves in the outer filter ball, when the inner filter ball hits the outer filter ball, the foreign matter in the mesh of the outer filter ball will be shaken off under the action of vibration, which can clean the filter.

[0017] As a preferred embodiment of the present invention, the filling density of the adsorption column in the inner filter ball is 70%-90%.

[0018] As a preferred embodiment of the present invention, the weight ratio of the adsorption column to the secondary aluminum ash slag is 1-2:1-5.

[0019] As a preferred embodiment of the present invention, the weight ratio of the adsorption column to the secondary aluminum ash slag is 1.5:2.

[0020] As a preferred embodiment of the present invention, diatomaceous earth and humus are added to the mixture B to obtain a composition suitable for improving salinized soil.

[0021] The composition obtained by mixing mixture B with diatomaceous earth and humus is suitable for improving soil salinization. Since the salinized soil structure has low air permeability and water permeability, poor water retention and biological activity, the phenomenon of compaction and warping will occur. The present invention adds diatomaceous earth and humus. Diatomaceous earth has good water retention, but poor air permeability and water permeability. By adding humus, the air permeability and water permeability problems can be improved, and the biological activity can also be improved, thereby improving the soil compaction. Diatomaceous earth and humus are mixed with mixture B again, and the various substances in mixture B can act synergistically to achieve the purpose of improving the salinized soil structure, so that it has good air permeability and water permeability while having water retention, improving biological activity, and improving compaction and warping.

[0022] As a preferred embodiment of the present invention, the weight ratio of mixture B, diatomaceous earth and humus soil is 5-10:1-2:2-5. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 4 is a cross-sectional view of an adsorption ball in an embodiment of the present invention.

[0024] Reference numerals include: Outer filter ball 1, inner filter ball 2, adsorption column 3. DETAILED DESCRIPTION

[0025] Typical embodiments that embody the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various changes in different embodiments without departing from the scope of the present invention, and the descriptions and illustrations therein are essentially used for illustration purposes rather than for limiting the present invention.

[0026] Example 1 This embodiment discloses a method for soilification of secondary aluminum ash slag, comprising the following steps: S1. Acid leaching treatment: 30 wt% nitric acid was added to the secondary aluminum ash and stirred for 10 hours; S2, continue to add adsorption column 3 in S1 at a weight ratio of 1:1 to secondary aluminum ash slag. Specifically, adsorption column 3 is filled in adsorption balls. The structure of adsorption balls is shown in Figure 1 As shown, the adsorption ball includes an outer filter ball 1 and an inner filter ball 2. The outer filter ball 1 has a diameter of 6-10 cm and a mesh size of 1-10 μm. The inner filter ball 2 has a diameter of 2-4 cm and a mesh size of 0.05-0.2 cm. The inner filter ball 2 is installed in the outer filter ball 1. The inner filter ball 2 is filled with an adsorption column 3, and the filling density is 70%. The adsorption column 3 is put into the secondary aluminum ash acid leaching solution in the form of being filled in the adsorption ball. After the adsorption ball is put in, it is allowed to stand in the acid leaching solution for 20 minutes, and the heavy metal cluster structure is enriched on the adsorption column 3. Then, it is stirred for 3 minutes, and the heavy metal clusters are shaken off between the inner and outer filter balls and collected. Then, it is allowed to stand and stirred again. This cycle is repeated 3 times, so that the adsorption column 3 can fully capture the heavy metal elements. S3, perform the first filtration, recover the adsorption balls, perform the second filtration, and then recover the filtrate and the filter residue respectively; S4. After the filter residue is washed with water for 2-4 times, the pH value is adjusted to 6.8-7.2 to obtain a mixture B. The mixture B can be directly used to plant green plants or crops. The dosage of the mixture B is 5-10 kg / m 2 Diatomaceous earth and humus can also be added to mixture B. The weight ratio of mixture B, diatomaceous earth and humus is 5:1:2. A composition suitable for improving salinized soil is obtained. The dosage of the composition is 10-20 kg / m 2 .

[0027] The preparation method of the adsorption column 3 in this embodiment comprises the following steps: a. crushing the oyster shells and sieving them to obtain oyster shell powder; b. After mixing the oyster shell powder and nano-titanium dioxide, a pore-forming agent is added and fully burned to obtain a mixture A, wherein the pore-forming agent may be ammonia, sodium bicarbonate, etc.; c. The mixture A and activated carbon are crushed, stirred evenly, and used as raw materials to make a porous adsorption column 3 with a density of 40%. The length of the adsorption column 3 is 1 cm, wherein the addition ratio of oyster shell powder, nano titanium dioxide, and activated carbon is 10:0.5:1.

[0028] Example 2 This embodiment discloses a method for soilification of secondary aluminum ash slag, comprising the following steps: S1. Acid leaching treatment: 30 wt% nitric acid was added to the secondary aluminum ash and stirred for 2 hours; S2, continue to add adsorption column 3 in S1 at a weight ratio of 1.5:2 to secondary aluminum ash slag, fill the adsorption column 3 with the same adsorption balls as in Example 1, let it stand for 25 minutes, stir for 3 minutes, let it stand again, stir, and repeat this cycle 4 times; S3, perform the first filtration, recover the adsorption column 3, perform the second filtration, and then recover the filtrate and the filter residue respectively; S4. After the filter residue is washed with water for 2-4 times in a cycle and the pH value is adjusted to 6.8-7.2, a mixture B is obtained. The mixture B can be directly used to grow green plants or crops, or diatomaceous earth and humus can be added to the mixture B. The weight ratio of the mixture B, diatomaceous earth and humus is 8:2:3, and a composition suitable for improving salinized soil is obtained.

[0029] The difference between the adsorption column 3 added in this embodiment and that in embodiment 1 is that the addition ratio of oyster shell powder, nano-titanium dioxide and activated carbon used to prepare the adsorption column 3 is 15:1.5:3, and the density of the adsorption column 3 is 50%.

[0030] Example 3 This embodiment discloses a method for soilification of secondary aluminum ash slag, comprising the following steps: S1. Acid leaching treatment: 30 wt% nitric acid was added to the secondary aluminum ash and stirred for 5 hours; S2, continue to add adsorption column 3 in S1 at a weight ratio of 2:5 to secondary aluminum ash slag, fill the adsorption column 3 with the same adsorption balls as in Example 1, let it stand for 30 minutes, stir for 2 minutes, let it stand again, stir, and repeat this cycle 5 times; S3, perform the first filtration, recover the adsorption column 3, perform the second filtration, and then recover the filtrate and the filter residue respectively; S4. After the filter residue is washed with water for 2-4 times in a cycle and the pH value is adjusted to 6.8-7.2, a mixture B is obtained. The mixture B can be directly used to grow green plants or crops, or diatomaceous earth and humus can be added to the mixture B. The weight ratio of the mixture B, diatomaceous earth and humus is 10:2:5, and a composition suitable for improving salinized soil is obtained.

[0031] The difference between the adsorption column 3 added in this embodiment and that in embodiment 1 is that the addition ratio of oyster shell powder, nano-titanium dioxide and activated carbon used to prepare the adsorption column 3 is 20:2:5, and the density of the adsorption column 3 is 60%.

[0032] Adsorption effect of adsorption column Activated carbon, ion exchange resin, and the adsorption column in Example 1 were used to treat the secondary aluminum ash slag respectively, and the treatment method was the method in Example 1. The following table shows the heavy metal content of the secondary aluminum ash slag before treatment and after treatment with different adsorbents. The test results are shown in Table 1.

[0033] Table 1 As shown in Table 1, the heavy metal content of the secondary aluminum ash after treatment with the adsorption column is much lower than that after treatment with activated carbon and ion exchange resin. Since the oyster shell powder itself has strong adsorption, after thermal modification, the adsorption is stronger. The adsorption column made of oyster shell powder as the main raw material has better adsorption effect. Its adsorption capacity can reach 4-5 times that of general adsorbents, and can effectively remove heavy metal elements in secondary aluminum ash.

[0034] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A method for soilification of secondary aluminum ash, characterized in that: The following steps are involved: S1. Acid leaching of secondary aluminum ash for 2-10 hours; S2, adding an adsorption column prepared with oyster shells as raw materials, letting it stand for 20-30 minutes, stirring for 2-3 minutes, letting it stand again, stirring, and repeating the cycle 3-5 times; S3, perform a first filtration, recover the adsorption column, and then perform a second filtration to obtain a filter residue; S4. After the filter residue is washed 2-4 times with water, the pH value is adjusted to 6.8-7.2 to obtain a mixture B, which can be directly used to grow green plants or crops.

2. The method for converting secondary aluminum ash into soil according to claim 1, characterized in that: The preparation method of the adsorption column comprises the following steps: a. crushing the oyster shells and sieving them to obtain oyster shell powder; b. After mixing the oyster shell powder and nano-titanium dioxide, a pore-forming agent is added and fully burned to obtain a mixture A; c. Mixture A and activated carbon are crushed and stirred evenly, and a porous adsorption column with a density of 40%-60% is prepared using the mixture as raw material. The length of the adsorption column is 1 cm; The adding ratio of oyster shell powder, nano titanium dioxide and activated carbon is 10-20:0.5-2:1-5.

3. The method for converting secondary aluminum ash into soil according to claim 2, characterized in that: In the step c, the addition ratio of oyster shell powder, nano titanium dioxide and activated carbon is 15:1.5:

3.

4. The method for converting secondary aluminum ash into soil according to claim 2, characterized in that: It also includes an adsorption ball, which is filled with an adsorption column. The adsorption ball includes an outer filter ball and an inner filter ball. The inner filter ball is installed in the outer filter ball, and the inner filter ball is filled with an adsorption column. The adsorption ball filled with the adsorption column is put into a secondary aluminum ash acid leaching solution to adsorb heavy metals.

5. The method for converting secondary aluminum ash into soil according to claim 4, characterized in that: The diameter of the outer filter ball is 6-10 cm, the mesh size of the outer filter ball is 1-10 μm, the diameter of the inner filter ball is 2-4 cm, and the mesh size of the inner filter ball is 0.05-0.2 cm.

6. The method for converting secondary aluminum ash into soil according to claim 4, characterized in that: The filling density of the adsorption column in the inner filter ball is 70%-90%.

7. The method for converting secondary aluminum ash into soil according to claim 1, characterized in that: The weight ratio of the adsorption column to the secondary aluminum ash slag is 1-2:1-5.

8. The method for converting secondary aluminum ash into soil according to claim 7, characterized in that: The weight ratio of the adsorption column to the secondary aluminum ash slag is 1.5:

2.

9. The method for converting secondary aluminum ash into soil according to claim 1, characterized in that: Diatomaceous earth and humus are added to the mixture B to obtain a composition suitable for improving salinized soil.

10. The method for converting secondary aluminum ash into soil according to claim 9, characterized in that: The weight ratio of the mixture B, diatomaceous earth and humus soil is 5-10:1-2:2-5.

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