Preparation method of red mud-based artificial soil

Abstract

The invention discloses a preparation method of red-mud-based artificial soil, which comprises the following steps: A, mixing and stirring red mud, calcium-based solid waste, industrial ferric salt, manganese slag and water according to a mass ratio, and fully stirring to fully react to obtain dealkalized red mud; wherein the mass ratio of the red mud to the calcium-based solid waste to the industrial ferric salt to the manganese slag to the water is 100: (1-5): (0.1-1): (0.1-1): (10-50); b, mixing the dealkalized red mud with the fly ash, the biomass and the stable organic solid waste, and fully and uniformly stirring to obtain a mixture; and C, naturally stacking the mixture and fertilizing. The method can accelerate the red mud harmlessness and soil treatment process, and reduces the environmental pollution risk of the storage yard.

Description

Technical Field

[0001] The invention relates to the technical field of harmless disposal of bulk solid waste and environmental protection, and in particular to a method for preparing red mud-based artificial soil. Background Art

[0002] Red mud is a strongly alkaline solid waste discharged during the production of alumina. It usually has strong alkalinity and complex chemical composition, which makes it face many challenges in resource utilization and harmless disposal. Traditional dry storage methods not only occupy land resources, but also may cause pollution to the surrounding soil, water and air. Using physical, chemical, biological and other methods to transform red mud into a soil-like matrix for plant growth is one of the effective strategies to achieve large-scale disposal of red mud and reduce environmental risks of landfills. The key to red mud soil formation is harmless treatment and nutrient input. Commonly used calcium-based solid wastes such as desulfurized gypsum and phosphogypsum can react with free alkali in red mud by continuously releasing calcium ions to reduce pH. Industrial iron salts such as ferrous sulfate, ferrous sulfate, and polyferric sulfate can hydrolyze to produce hydrogen ions that quickly react with free alkali in red mud. The combination of heavy metals in red mud with iron and manganese oxides is conducive to reducing its biological effectiveness. In addition, calcium or iron-containing phases such as calcium carbonate, iron hydroxide, and manganese oxide have been found to enhance soil carbon retention capacity. Adding calcium / iron ions to red mud can increase the total organic carbon content. Calcium / iron / manganese all show excellent red mud harmlessness and fertilization capabilities. The combined use of the three is expected to achieve rapid soil formation of red mud and coordinated large-scale disposal of multiple solid wastes.

[0003] Therefore, in order to better utilize red mud to regenerate soil and reduce the potential environmental hazards caused by red mud storage, in-depth research is needed. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing red mud-based artificial soil. The method rationally configures the dosage of the modifier, optimizes the modification process, and proposes a red mud soil-forming idea that synergizes the advantages of calcium-based solid waste and industrial iron salts, which can accelerate the harmless and soil-forming process of red mud and reduce the risk of environmental pollution in the storage yard.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] The method for preparing red mud-based artificial soil comprises the following steps:

[0007] A. Mix red mud with calcium-based solid waste, industrial iron salt, and manganese slag in a mass ratio and stir evenly, then add water under stirring, stir evenly, and let stand to obtain dealkalized red mud; wherein the mass ratio of red mud, calcium-based solid waste, industrial iron salt, manganese slag, and water is 100:1-5:0.1-1:0.1-1:10-50;

[0008] B. mixing the dealkalized red mud with fly ash, biomass, and stabilized organic solid waste, and stirring evenly to obtain a mixture;

[0009] C. Pile the mixture up naturally to fertilize it.

[0010] In the step A, the calcium-based solid waste includes at least one of desulfurized gypsum, phosphogypsum, and hydrated calcium sulfate; the industrial iron salt includes at least one of hydrated ferric sulfate, ferrous sulfate, and polyferric sulfate; and the manganese slag is solid waste generated by the electrolytic manganese industry.

[0011] In the step A, the initial moisture content of the red mud is 10-30%.

[0012] In the step A, the standing time is 5-20 minutes.

[0013] In the step A, the temperature at which the calcium-based solid waste, industrial iron salt, manganese slag and red mud are mixed and stirred is room temperature.

[0014] In the step B, the mass ratio of dealkalized red mud, fly ash, biomass and stabilized organic solid waste is 100:0.5-2.5:1-10:0.5-2.5.

[0015] In the step B, the temperature at which the dealkalized red mud is mixed with fly ash, biomass and stabilized organic solid waste is room temperature.

[0016] In the step B, fly ash is solid waste generated by coal-fired power plants; stable organic solid waste includes at least one of pig manure, cow manure, sheep manure, chicken manure and other poultry manure; biomass includes at least one of straw, bagasse and wheat bran.

[0017] In the step C, the process of natural stacking and fertilization is: stacking at room temperature for 7-30 days.

[0018] The present invention provides a method for preparing red mud-based artificial soil with synergistic harmlessness of calcium, iron and manganese. The free alkali is neutralized and the bound alkali is stabilized through the synergistic effect of calcium, iron and manganese, thereby reducing environmental risks. Meanwhile, dissolved organic carbon is enriched, and energy is continuously supplied to exogenous microorganisms, thereby ensuring the normal metabolic behavior of plants and microorganisms, and facilitating the reconstruction of vegetation in red mud dumps.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1) In the method of the present invention, the calcium-based solid waste, industrial iron salt, manganese slag and other improvers used are mostly derived from industrial waste, which are low in price and wide in source, have low energy consumption and short cycle in the treatment process, and are easy to realize large-scale production.

[0021] 2) In the method of the present invention, it is preferred to use industrial iron salts with sulfate as anionic ligands, and avoid using nitrate and chloride ions such as ferric nitrate and ferric chloride, so as to reduce the corrosion of industrial equipment during large-scale application.

[0022] 3) In the method of the present invention, a combination of calcium-based solid waste and industrial iron salts is used to improve red mud. On the one hand, the free alkali in the red mud can be neutralized by the hydrolysis of iron ions to produce hydrogen ions. On the other hand, it can also wrap the alkaline minerals through co-precipitation with calcium ions to inhibit the alkaline rebound caused by the continuous dissolution of alkaline minerals. At the same time, after the calcium-based solid waste, industrial iron salts and red mud are evenly mixed and then water is added, the micro-region low pH environment formed around the iron ions is conducive to the dissolution of gypsum to produce calcium ions, promoting the co-precipitation of calcium and iron ions.

[0023] 5) In the method of the present invention, calcium and iron ions are co-precipitated to form weakly crystalline minerals. Compared with the original iron minerals and alkaline minerals in red mud, weakly crystalline calcium, iron and manganese oxides have higher specific surface areas and are easier to stabilize heavy metals and fix dissolved organic carbon.

[0024] 6) In the method of the present invention, manganese slag is added. The main component of manganese slag is manganese oxide, which has a large specific surface area. When calcium and iron ions are co-precipitated, the generated iron oxide cooperates with manganese oxide, has a strong adsorption capacity for heavy metal ions, and can bind and fix heavy metals such as As, Cr, Cd, etc. into their structure or adsorb on their surface to form an iron-manganese oxide binding state. Compared with the single use of iron oxide to adsorb heavy metals, the iron-manganese binding state is more stable and more difficult to resolve. At the same time, the heavy metals in the iron-manganese binding state will slowly transform into a residual state. This process reduces the migration ability of heavy metals and their environmental risks. In addition, the addition of manganese oxide is also beneficial to the fixation of organic carbon. By forming an organic-mineral complex, the organic molecules are at least temporarily stabilized, the mineralization rate in the soil is reduced, and a slow-release carbon source is formed. The synergistic effect of iron and manganese is used to reduce the environmental risks of red mud, and the resource utilization of manganese slag can also be achieved.

[0025] 7) In the method of the present invention, the added nutrient source is mainly long-rod biomass rich in lignin and cellulose, and spherical or block-shaped stable organic solid waste rich in nitrogen and phosphorus, which can not only provide nutrients but also improve the pore structure of red mud and form a physical structure that is easier for plant roots to grow.

[0026] Moreover, after the dealkalized red mud is fully mixed with fly ash, biomass and stabilized organic solid waste, it can be piled in the red mud yard for a period of time to obtain red mud-based artificial soil, which does not require an additional composting process and greatly simplifies the production process of red mud artificial soil.

[0027] 8) In the method of the present invention, the selected manure and biomass correspond to the quick-acting carbon source and the slow-release carbon source, respectively. The weak crystalline iron generated by stirring the calcium iron modifier with red mud will absorb a large amount of organic carbon that is rapidly dissolved in the manure, which can effectively reduce the amount of carbon lost by red mud adsorbed or leached with rainwater. Moreover, the neutral environment formed by the calcium iron dealkalized red mud is more conducive to the decomposition of biomass and the continuous supply of organic carbon. In addition, the weak crystalline iron will also slowly desorb organic carbon under sunlight, further providing nutrients for plants and microorganisms. DETAILED DESCRIPTION

[0028] In order to facilitate a better understanding of the present invention, the following examples are used to illustrate the present invention. These examples belong to the protection scope of the present invention, but do not limit the protection scope of the present invention.

[0029] Example 1

[0030] The preparation method of red mud-based artificial soil comprises the following steps:

[0031] A. 100 kg of red mud with a moisture content of 10% was stirred evenly with calcium-based solid waste, industrial iron salt and manganese slag at room temperature, and then water was added under stirring, and after stirring and mixing evenly, the mixture was allowed to stand for 5 minutes to allow the reaction to fully react, thereby obtaining dealkalized red mud;

[0032] The mass ratio of red mud, calcium-based solid waste, industrial iron salt, manganese slag, and water is 100:1:0.1:0.1:10;

[0033] The calcium-based solid waste is a 1:1 mixture of desulfurized gypsum and phosphogypsum;

[0034] Industrial iron salt is hydrated iron sulfate;

[0035] Manganese slag is solid waste generated by the electrolytic manganese industry.

[0036] B. mixing the dealkalized red mud with fly ash, biomass, and stabilized organic solid waste, and stirring the mixture at room temperature to obtain a mixture;

[0037] The mass ratio of dealkalized red mud, fly ash, biomass and stabilized organic solid waste is 100:0.5:1:0.5.

[0038] Fly ash is a solid waste generated by coal-fired power plants;

[0039] Stabilize organic solid waste into a mixture of pig manure and cow manure;

[0040] The biomass was a 1:1 mixture of straw and bagasse.

[0041] C. Leave the mixture to stand at room temperature for 7 days.

[0042] Example 2

[0043] The preparation method of red mud-based artificial soil comprises the following steps:

[0044] A. 100 kg of red mud with a moisture content of 30% was stirred evenly with calcium-based solid waste, industrial iron salt and manganese slag at room temperature, and then water was added under stirring, and after stirring and mixing evenly, it was allowed to stand for 20 minutes to allow the reaction to fully react, thereby obtaining dealkalized red mud;

[0045] The mass ratio of red mud, calcium-based solid waste, industrial iron salt, manganese slag, and water is 100:5:1:1:50;

[0046] Calcium-based solid waste is hydrated calcium sulfate;

[0047] Industrial iron salt is polyferric sulfate;

[0048] Manganese slag is solid waste generated by the electrolytic manganese industry.

[0049] B. mixing the dealkalized red mud with fly ash, biomass, and stabilized organic solid waste, and stirring the mixture at room temperature to obtain a mixture;

[0050] The mass ratio of dealkalized red mud, fly ash, biomass and stabilized organic solid waste is 100:2.5:10:2.5.

[0051] Fly ash is a solid waste generated by coal-fired power plants;

[0052] Stabilize organic solid waste into chicken manure;

[0053] The biomass is wheat bran.

[0054] C. Leave the mixture to stand at room temperature for 30 days.

[0055] Example 3

[0056] The preparation method of red mud-based artificial soil comprises the following steps:

[0057] A. 100 kg of red mud with a moisture content of 20% was stirred evenly with calcium-based solid waste, industrial iron salt and manganese slag at room temperature, and then water was added under stirring, and after stirring and mixing evenly, the mixture was allowed to stand for 10 minutes to allow the reaction to fully react, thereby obtaining dealkalized red mud;

[0058] The mass ratio of red mud, calcium-based solid waste, industrial iron salt, manganese slag, and water is 100:3:0.5:0.3:30;

[0059] The calcium-based solid waste is a 2:1:1 mixture of desulfurized gypsum, phosphogypsum, and hydrated calcium sulfate;

[0060] Industrial iron salts are a 1:1:1 mixture of hydrated ferric sulfate, ferrous sulfate, and polyferric sulfate;

[0061] Manganese slag is solid waste generated by the electrolytic manganese industry.

[0062] B. mixing the dealkalized red mud with fly ash, biomass, and stabilized organic solid waste, and stirring the mixture at room temperature to obtain a mixture;

[0063] The mass ratio of dealkalized red mud, fly ash, biomass and stabilized organic solid waste is 100:1.5:5:1.5.

[0064] Fly ash is a solid waste generated by coal-fired power plants;

[0065] Stabilize organic solid waste into a mixture of pig manure, cow manure, and sheep manure;

[0066] The biomass was a 1:1:1 mixture of straw, bagasse, and wheat bran.

[0067] C. Leave the mixture to stand at room temperature for 20 days.

[0068] Example 4

[0069] The preparation method of red mud-based artificial soil comprises the following steps:

[0070] A. 100 kg of red mud with a moisture content of 15% was stirred evenly with calcium-based solid waste, industrial iron salt and manganese slag at room temperature, and then water was added under stirring, and after stirring and mixing evenly, the mixture was allowed to stand for 12 minutes to allow the reaction to fully react, thereby obtaining dealkalized red mud;

[0071] The mass ratio of red mud, calcium-based solid waste, industrial iron salt, manganese slag, and water is 100:2:0.7:0.4:20;

[0072] The calcium-based solid waste is phosphogypsum;

[0073] The industrial iron salt is ferrous sulfate;

[0074] Manganese slag is solid waste generated by the electrolytic manganese industry.

[0075] B. mixing the dealkalized red mud with fly ash, biomass, and stabilized organic solid waste, and stirring the mixture at room temperature to obtain a mixture;

[0076] The mass ratio of dealkalized red mud, fly ash, biomass and stabilized organic solid waste is 100:2:3:1.

[0077] Fly ash is a solid waste generated by coal-fired power plants;

[0078] Stabilize organic solid waste into pig manure;

[0079] The biomass is sugarcane bagasse.

[0080] C. Leave the mixture to stand at room temperature for 15 days.

[0081] Example 5

[0082] The effects of different addition amounts of calcium-based solid waste, industrial iron salts, and manganese slag on red mud pH, conductivity, and arsenic and chromium leaching concentrations were investigated, including the following steps:

[0083] The red mud was fully mixed with 1-5 parts of desulfurized gypsum (phosphogypsum), 0.1-1 parts of ferrous sulfate (ferrous sulfate, polyferric sulfate), and 0.1-1 parts of manganese slag for 20 minutes, and then 30 parts of water were added and stirred at 9r / min for 20 minutes. After stacking for 7 days, it was dried at 105°C for 48 hours, and the pH and conductivity were measured. The specific grouping and results are shown in Table 1. The results show that when the amount of industrial iron salt added exceeds 1 part, the conductivity in the system will increase significantly, which is not conducive to plant growth. The continuous dissolution of calcium ions in calcium-based solid waste is conducive to alkaline stability, and the introduction of an appropriate amount of industrial iron salt can reduce the amount of desulfurized gypsum. Avoid the introduction of excessive new pollutants. When 2.5 parts of calcium-based solid waste, 0.5 parts of industrial iron salt, and 0.5 parts of manganese slag are added, the pH and conductivity values ​​of red mud-based artificial soil are more suitable for plant growth.

[0084] Table 1-1 Effect of desulfurization gypsum addition on red mud pH, conductivity and arsenic and chromium leaching concentrations under fixed iron sulfate and manganese slag addition

[0085]

[0086] Table 1-2 Effect of iron sulfate addition on red mud pH, conductivity and arsenic and chromium leaching concentrations under fixed desulfurization gypsum and manganese slag addition

[0087]

[0088]

[0089] Table 1-3 Effect of manganese slag addition on red mud pH, conductivity and arsenic and chromium leaching concentrations under fixed desulfurization gypsum and iron sulfate addition

[0090]

[0091] Example 6

[0092] The effects of different water addition amounts on red mud pH and conductivity were investigated, including the following steps:

[0093] Red mud was thoroughly mixed with 2.5 parts of desulfurized gypsum, 0.5 parts of ferric chloride, and 0.5 parts of manganese slag and stirred for 20 minutes, then 10-50 parts of water were added and stirred continuously at 9r / min for 20 minutes. After stacking for 7 days, it was dried at 105°C for 48 hours, and the pH and conductivity were measured. The specific grouping and results are shown in Table 2. The results show that when the amount of water added is 10 parts, the reaction of red mud with calcium ions and iron ions is insufficient, and the iron ions are quickly passivated, which is not conducive to the dealkalization reaction. When the amount of water added is greater than or equal to 60 parts, excess water will increase the solid-liquid interface reaction of alkaline minerals, and a large amount of sodium ions will dissolve, resulting in increased conductivity. When the amount of water added is 30 parts, the pH and conductivity values ​​of red mud-based artificial soil are more suitable for plant growth

[0094] Table 2 Effect of different water addition amounts on red mud pH and conductivity

[0095]

[0096]

[0097] Example 7

[0098] The study of the effects of different biomass and stabilized organic solid waste on the total organic carbon and porosity of red mud includes the following steps:

[0099] The red mud was fully mixed with 2.5 parts of desulfurized gypsum, 0.5 parts of ferric chloride, and 0.5 parts of manganese slag for 20 minutes, and then 30 parts of water were added and stirred at 9r / min for 20 minutes. After standing for 20 minutes, 0.5-2.5 parts of fly ash, 1-10 parts of bagasse, and 0.5-2.5 parts of sheep manure were added and stirred at 9r / min for 20 minutes. After stacking for 7 days, 100 ryegrass seeds were sown. After 30 days, the red mud samples were collected and dried at 105℃ for 48 hours, and the total organic carbon and porosity were measured. The germination rate was calculated according to the number of ryegrass seeds germinated. The specific grouping and results are shown in Table 5. The results show that when 1 part of fly ash, 3 parts of biomass, and 1 part of stabilized organic solid waste are added, the nutrient requirements for plant growth are basically met. When 5 parts of biomass and 1.5 parts of stabilized organic solid waste are added, the carbon-nitrogen ratio of exogenous nutrients is more conducive to plant growth.

[0100] Table 5-1 Effects of fly ash, bagasse and sheep manure addition on total organic carbon and porosity of red mud

[0101]

[0102] Table 5-2 Effects of fly ash, wheat bran and chicken manure addition on total organic carbon and porosity of red mud

[0103]

[0104]

[0105] From the above results, it can be seen that the red mud-based artificial soil prepared by the calcium, iron and manganese synergistic detoxification method provided by the present invention has a greatly reduced pH, a stable electrical conductivity, an increased total organic carbon content and porosity, and a greatly improved ryegrass germination rate compared to the original red mud, which can meet the growth needs of plants.

[0106] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing red mud-based artificial soil, characterized in that: The following steps are involved: A. Mix red mud with calcium-based solid waste, industrial iron salt, and manganese slag in a mass ratio and stir evenly, then add water under stirring, stir evenly, and let stand to obtain dealkalized red mud; wherein the mass ratio of red mud, calcium-based solid waste, industrial iron salt, manganese slag, and water is 100:1-5:0.1-1:0.1-0.5:10-50; B. mixing the dealkalized red mud with fly ash, biomass, and stabilized organic solid waste, and stirring evenly to obtain a mixture; C. Pile the mixture up naturally to fertilize it.

2. The method for preparing red mud-based artificial soil according to claim 1, characterized in that: The mass ratio of the red mud, calcium-based solid waste, industrial iron salt, manganese slag and water is 100:1-5:0.1-0.9:0.1-1:10-50.

3. The method for preparing red mud-based artificial soil according to claim 1, characterized in that: In the step A, the calcium-based solid waste includes at least one of desulfurized gypsum, phosphogypsum, and hydrated calcium sulfate; the industrial iron salt includes at least one of hydrated ferric sulfate, ferrous sulfate, and polyferric sulfate; and the manganese slag is solid waste generated by the electrolytic manganese industry.

4. The method for preparing red mud-based artificial soil according to claim 1, characterized in that: In the step A, the initial moisture content of the red mud is 10-30%.

5. The method for preparing red mud-based artificial soil according to claim 1, characterized in that: In the step A, the standing time is 5-20 min.

6. The method for preparing red mud-based artificial soil according to claim 1, characterized in that: In the step A, the temperature at which the calcium-based solid waste, industrial iron salt, manganese slag and red mud are mixed and stirred is room temperature.

7. The method for preparing red mud-based artificial soil according to claim 1, characterized in that: In the step B, the mass ratio of dealkalized red mud, fly ash, biomass and stabilized organic solid waste is 100:0.5-2.5:1-10:0.5-2.

5.

8. The method for preparing red mud-based artificial soil according to claim 1, characterized in that: In the step B, the temperature at which the dealkalized red mud is mixed with fly ash, biomass and stabilized organic solid waste is room temperature.

9. The method for preparing red mud-based artificial soil according to claim 1, characterized in that: In the step B, fly ash is solid waste generated by coal-fired power plants; stable organic solid waste includes at least one of pig manure, cow manure, sheep manure, chicken manure and other poultry manure; biomass includes at least one of straw, bagasse and wheat bran.

10. The method for preparing red mud-based artificial soil according to claim 1, characterized in that: In the step C, the process of natural stacking and fertilization is: stacking at room temperature for 7-30 days.

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