Red mud artificial soil reconstruction method based on biomass and fly ash

Abstract

The invention discloses a red mud artificial soil reconstruction method based on biomass and fly ash, which is used for performing soil treatment on red mud and comprises the following steps: pretreating the red mud; the method comprises the following steps: mixing biomass and an inorganic material to serve as an additive material, and performing pretreatment; adding materials into the red mud and then culturing. According to the method, the biomass and the inorganic material are mixed to serve as the additive material, pretreatment is conducted, and therefore the red mud can be effectively treated, and vegetation reconstruction and ecological restoration of the red mud storage yard are achieved.

Description

Technical Field

[0001] The present invention belongs to the field of soil treatment, and particularly relates to a method capable of effectively treating red mud and realizing vegetation reconstruction and ecological restoration of a red mud yard. Background Art

[0002] Red mud is a strongly alkaline solid waste generated in the alumina industrial production process. Due to its strong alkalinity and high salt content, it is difficult to comprehensively utilize red mud, and it is mainly stored in piles. The environmental safety problems caused by the large-scale storage of red mud are threatening the sustainable development of the alumina industry.

[0003] The regulation of red mud alkalinity is the main direction to solve the problem of red mud storage and is also the key link to realize the soil treatment of red mud. At present, the research on alkalinity regulation based on the soil treatment of red mud by domestic and foreign scholars mainly includes gypsum improvement method, carbonization method, biological remediation method, etc. Among them, the research on using biological methods to regulate the alkalinity of red mud at home and abroad mainly focuses on microbial screening and metabolic acid production for alkalinity regulation. This method can better improve the physical and chemical properties of red mud, reduce the alkalinity and pH of red mud, and is of great significance for realizing large-scale in-situ restoration of red mud. However, due to the high salt content, strong alkalinity and low organic matter content of red mud, the types and numbers of viable bacteria in it are less. Therefore, establishing an environment suitable for the growth of microorganisms and improving the metabolic acid production activity of in-situ microorganisms in red mud are the current research focuses of the biological alkalinity regulation method.

[0004] Secondly, compared with ordinary soil, red mud has a fine particle size and poor physical structure, which seriously affects the growth of plant roots. How to improve the physical structure of red mud and transform it into a growth matrix similar to soil is another key factor for realizing the ecological system reconstruction of a red mud yard.

[0005] Therefore, how to effectively treat red mud and realize vegetation reconstruction and ecological restoration of a red mud yard is a technical problem that needs to be solved urgently at present. Summary of the Invention

[0006] A main object of the present invention is to provide a method for reconstructing artificial soil of red mud based on biomass and fly ash, which can effectively treat red mud and realize vegetation reconstruction and ecological restoration of a red mud yard.

[0007] To achieve the above-mentioned invention object, the present invention adopts the following technical solutions:

[0008] As one aspect of the present invention, there is provided a method for reconstructing artificial soil of red mud based on biomass and fly ash for soil treatment of red mud, including the following steps:

[0009] Pretreatment of red mud;

[0010] Mix biomass with inorganic materials as additive materials and conduct pretreatment;

[0011] Cultivate after adding materials to the red mud.

[0012] As an embodiment of the present invention, the pretreatment of the red mud includes coarse crushing treatment of the red mud.

[0013] As an embodiment of the present invention, in the pretreatment of the red mud, the moisture content of the red mud matrix is reduced to less than 30%.

[0014] As an embodiment of the present invention, mechanical crushing is performed on the biomass raw material during the pretreatment of the added materials.

[0015] As an embodiment of the present invention, the fineness of the crushed biomass raw material is less than 5 mm.

[0016] As an embodiment of the present invention, in the added materials, the addition ratio of the biomass raw material is less than or equal to 2%.

[0017] As an embodiment of the present invention, the inorganic materials include fly ash and / or vermiculite.

[0018] As an embodiment of the present invention, the addition ratio of the fly ash is less than or equal to 10%, and the addition ratio of the vermiculite is less than or equal to 0.5%.

[0019] As an embodiment of the present invention, during the cultivation, each treatment is filled into flower pots and placed under outdoor natural conditions for cultivation, and watered regularly to maintain a stable matrix humidity at 75 ± 2% of the maximum water holding capacity of the soil.

[0020] As an embodiment of the present invention, samples are taken at 0, 1, 3, 6, 9, and 12 months after the cultivation of each experimental treatment group to analyze indicators such as the pH, EC, content of each exchangeable cation, and alkalinity ESP of the red mud soil. After the cultivation is completed, the basic physical and chemical properties, salinity and alkalinity indicators, and nutrient indicators such as organic matter, soluble organic matter, available nitrogen, and available phosphorus of each treatment group are measured respectively.

[0021] As can be seen from the above technical solutions, the advantages and positive effects of the method for reconstructing red mud artificial soil based on biomass and fly ash of the present invention are as follows:

[0022] In the present invention, biomass and inorganic materials are mixed as added materials and pretreated, so as to effectively treat the red mud and realize the vegetation reconstruction and ecological restoration of the red mud yard. Description of the Drawings

[0023] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments recorded in the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained as these drawings.

[0024] Figure 1 It is a comparative diagram of the water-stable aggregate composition of each improved treatment substrate.

[0025] Figure 2 It is a comparative diagram of the heavy metal element content in each treatment.

[0026] Figure 3 It is a comparative diagram of the difference in the composition of soluble organic compounds in each treatment.

[0027] Figure 4 It is a comparative diagram of the abundance of soil microorganisms.

[0028] Figure 5 It is a comparative diagram of the microbial community composition in each treatment. Detailed implementation manners

[0029] Now, the exemplary embodiments will be described more fully with reference to the accompanying drawings. However, the exemplary embodiments can be implemented in various forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this invention will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the figures denote the same or similar structures, and thus their detailed descriptions will be omitted.

[0030] In the following description of different examples of the present invention, reference is made to the accompanying drawings, which form a part of the present invention, and in which different exemplary structures, systems, and steps that can implement various aspects of the present invention are shown by way of example. It should be understood that other specific solutions of components, structures, exemplary devices, systems, and steps can be used, and structural and functional modifications can be made without departing from the scope of the present invention. Moreover, although terms such as "top", "bottom", "front", "rear", "side" etc. may be used in this specification to describe different exemplary features and elements of the present invention, these terms are used herein only for convenience, for example, the direction of the examples as shown in the accompanying drawings. Nothing in this specification should be construed as requiring a specific three-dimensional direction of the structure to fall within the scope of the present invention.

[0031] As one aspect of the present invention, a method for reconstructing red mud artificial soil based on biomass and fly ash is provided for soil treatment of red mud, including the following steps:

[0032] Red mud pretreatment;

[0033] Mix biomass with inorganic materials as an additive material and perform pretreatment.

[0034] Cultivate after adding the additive material to the red mud.

[0035] As an embodiment of the present invention, the pretreatment of the red mud includes coarse crushing treatment of the red mud.

[0036] As an embodiment of the present invention, the moisture content of the red mud matrix is reduced to less than 30% during the pretreatment of the red mud.

[0037] As an embodiment of the present invention, mechanical crushing is performed on the biomass raw material during the pretreatment of the additive material.

[0038] As an embodiment of the present invention, the fineness of the crushed biomass raw material is less than 5 mm.

[0039] As an embodiment of the present invention, in the additive material, the addition ratio of the biomass raw material is less than or equal to 2%.

[0040] As an embodiment of the present invention, the inorganic material includes fly ash and / or vermiculite.

[0041] As an embodiment of the present invention, the addition ratio of the fly ash is less than or equal to 10%, and the addition ratio of the vermiculite is less than or equal to 0.5%.

[0042] As an embodiment of the present invention, during the cultivation, each treatment is loaded into flower pots and placed outdoors under natural conditions for cultivation, and watered regularly to maintain a stable substrate humidity at 75 ± 2% of the maximum water holding capacity of the soil.

[0043] As an embodiment of the present invention, samples are taken at 0, 1, 3, 6, 9, and 12 months after the cultivation of each experimental treatment group to analyze indicators such as the pH, EC, content of each exchangeable cation, and alkalinity ESP of the red mud soil. After the cultivation is completed, the basic physical and chemical properties, salinity and alkalinity indicators, and nutrient indicators such as organic matter, soluble organic matter, available nitrogen, and available phosphorus of each treatment group are measured respectively.

[0044] From the above technical solutions, the advantages and positive effects of the method for reconstructing artificial red mud soil based on biomass and fly ash of the present invention are as follows:

[0045] In the present invention, biomass is mixed with inorganic materials as an additive material and pretreated, so as to effectively treat red mud and realize the vegetation reconstruction and ecological restoration of red mud dumps.

[0046] Next, based on the analysis of the physical and chemical indexes, fertility levels, and microbial community drivers of the red mud matrix, the improvement effects of biomass, fly ash, and vermiculite on the soilization of the red mud matrix were studied and compared, and a red mud artificial soil reconstruction technology based on the utilization of biomass and fly ash was invented. Among them, BR is red mud; BRM is 2% straw biomass improvement; BRFM is 2% biomass and 10% fly ash combined improvement; BRVM is 2% straw biomass and 0.5% vermiculite combined improvement.

[0047] Each treatment was placed in flowerpots and cultured under outdoor natural conditions, and watered regularly to maintain a stable matrix humidity of about 75% of the maximum water holding capacity of the soil. Samples were taken at 0, 1, 3, 6, 9, and 12 months after the cultivation of each experimental treatment group to analyze the pH, EC, exchangeable cation contents, and alkalinity ESP and other indexes of the red mud soil. After the cultivation was completed, the basic physical and chemical properties, salinity and alkalinity indexes, and nutrient indexes such as organic matter, soluble organic matter, available nitrogen, and available phosphorus of each treatment group were measured respectively.

[0048] As shown in Table 1, from the pH changes of the BRFM, BRVM, and BRM treatments, it can be seen that the use of biomass alone or in combination with fly ash can significantly neutralize the alkalinity of red mud. Specifically, the pH of the BRFM treatment decreased from nearly 11.0 (red mud treatment group BR) to about 8.5. At the same time, the electrical conductivity (EC), alkalization degree (ESP), and sodium adsorption ratio (SAR) also decreased significantly. The decrease in pH value may be attributed to the neutralization effect of organic acids produced by microbial decomposition of organic matter. In addition, the decrease in alkalinity should also be related to the adsorption and leaching of sodium in the red mud matrix after being improved by organic matter or combined with vermiculite / fly ash, which can be seen from the significant increase in soil organic matter (SOM) and porosity and the decrease in bulk density in the matrix (Table 1). Among these four treatment methods, the combined use of organic matter and fly ash (BRFM) has a better improvement effect on the alkalinity of red mud. This may be because fly ash can provide more abundant calcium ions (Ca 2 +), and previous studies have shown that Ca 2 + can promote the loss of sodium ions (Na+) through ion exchange (add reference). Compared with the combination with fly ash, although the combined use of organic matter and vermiculite (BRFM) significantly increased the porosity of the red mud matrix (Table 1), it did not cause a significant decrease in the alkalinity of red mud. This may be due to the different decomposition characteristics of organic matter when combined with vermiculite and fly ash in red mud.

[0049]

[0050] Table 1 Basic physical and chemical properties of the red mud matrix after 1 year of soilization improvement

[0051] As can be seen from Table 2, in the control treatment of red mud (BR), the contents of nutrient elements are all relatively low. Specifically, the content of dissolved organic matter (DOM) is 3.56 mg / L, and the contents of available nitrogen and available phosphorus are also very low, being 30.17 mg / kg and 2.66 mg / kg respectively. However, the addition of biomass and its combination with fly ash (BRFM) or vermiculite (BRVM) increases the contents of various nutrient elements in the red mud soil. Among them, the content of dissolved organic carbon (DOC) increases by more than 3 times, and the highest content of DOC reaches 19.05 mg / L. At the same time, the improved treatments such as BRFM, BRVM, and BRM also increase the contents of available nitrogen and available phosphorus in the red mud soil. Among them, the available nitrogen content in the BRVM group is the highest, with a value of 133.31 mg / kg, while the available phosphorus content in the BRM group is the highest, being 11.92 mg / kg.

[0052] That is, after one year of improvement, the typical fertility indexes in the red mud are all close to those of natural soil.

[0053] Treatment DOM (mg / L) Available nitrogen (mg / kg) Available phosphorus (mg / kg) BR 3.56 30.17 2.66 BRFM 14.17 63.53 7.16 BRVM 16.33 133.31 9.33 BRM 19.05 98.72 11.92 Natural soil 22.65 189.54 17.91

[0054] Analysis of the fertility levels of each treatment group in Table 2 (taking natural soil as a reference)

[0055] Figure 1 It is a comparison chart of the water-stable aggregate composition of the substrates for each improved treatment

[0056] From Figure 1 it can be seen that in each improved treatment such as BRFM, BRVM, and BRM, although the proportion of water-stable aggregates with a particle size > 2 mm does not increase significantly; the content of water-stable aggregates with a particle size > 0.25 mm increases to more than 80%. Among them, in the BRFM treatment, the content of water-stable aggregates with a particle size of 2 - 1 mm increases most significantly. However, in comparison, the improvement effects of the two improved treatments of BRFM and BRVM on the aggregate structure of red mud are better than that of the BRM treatment.

[0057] Figure 2 It is a comparison chart of the heavy metal element contents in each treatment.

[0058] From Figure 2 it can be seen that the main heavy metal element in the red mud substrate is V, followed by As. And in the improved treatments such as BRFM, BRVM, and BRM, the content levels of various heavy metals in the substrate all decrease significantly. Among them, except for the heavy metals Cd, Hg, Pb, Cu, Zn, etc. that are not detected, As, Ni, Cr, and V are all within the limit values of the second-class land use standards, and the Cr concentration is close to 0 mg / kg. This indicates that the heavy metal pollution risk of the reconstructed red mud artificial soil in this study is low.

[0059] Figure 3 It is a comparison chart of the differences in the composition of soluble organic compounds in each treatment.

[0060] FromFigure 3 It can be seen that BRFM or BRVM treatment can significantly change the components of organic compounds in the red mud matrix, significantly increasing the abundances of nitrogen-containing organic compounds (CHNO) and nitrogen- and sulfur-containing organic compounds (CHNOS), indicating that the co-application of biomass with the two can promote the degradation and transformation of organic matter and the colonization and reproduction of microbial communities in the red mud matrix. This result was also verified by the following microbial community analysis.

[0061] Figure 4 It is a comparison chart of the abundances of soil microorganisms. Among them, on the left: bacteria; on the right: fungi.

[0062] From Figure 4 It can be seen that in the improved treatments such as BRFM, BRVM, and BRM, the abundances of bacteria and fungi in the red mud matrix have all increased significantly. Especially in the BRFM treatment, followed by the BRVM treatment group. In the treatment with biomass alone (BRM), the abundances of the two types of microorganisms have also increased significantly, but significantly lower than the other two improved treatments, indicating that improving the physical structure of the red mud matrix based on mineral materials can significantly enhance the improvement effect of biomass addition on the soilization of red mud. This result is more significant in the subsequent microbial community analysis.

[0063] Figure 5 It is a comparison chart of the microbial community compositions in each treatment. Among them, on the top: bacteria; on the bottom: fungi.

[0064] From Figure 5 It can be seen that compared with the BR treatment, the BRM treatment, especially the BRFM and BRVM treatments, significantly enriched the species composition of microorganisms in the red mud. Specifically, after improvement, the relative abundances of halophilic and alkaliphilic bacteria and fungi with population advantages in the red mud decreased significantly. At the same time, some new populations appeared, that is, the diversity of the population increased significantly, indicating that in the improvement treatments, especially the BRFM and BRVM treatments, promoted the construction of the microbial community structure in the red mud, which is also an important indicator for realizing the soilization improvement of red mud.

[0065] The following is the specific factual process:

[0066] 1) Red mud pretreatment: The moisture content of the red mud matrix is less than 30%, and it meets the limit requirements of relevant pollutants in GB18599-2020. If it is severely caked, coarse crushing treatment should be carried out, and the proportion of particles with a diameter less than 5 mm is more than 90%.

[0067] 2) Pretreatment of improvement materials: The biomass raw materials used for the reconstruction of artificial red mud soil should be subjected to pre-mechanical crushing treatment, and the crushing fineness is less than 5 mm; the addition ratio is not higher than 5%.

[0068] 3) Requirements for adding modifiers: The addition ratio of fly ash applied to the reconstruction of red mud artificial soil shall not exceed 10%, the addition ratio of vermiculite shall not exceed 0.5%, and the addition ratio of biomass shall not exceed 2%.

[0069] 4) Cultivation requirements: Put each treatment into flower pots and cultivate them under natural outdoor conditions. Water regularly to maintain a stable substrate humidity of about 75% of the maximum water holding capacity of the soil. Sampling shall be carried out at 0, 1, 3, 6, 9, and 12 months after cultivation in each experimental treatment group to analyze indicators such as the pH, EC, content of each exchangeable cation, and alkalinity ESP of the red mud soil. After the cultivation is completed, the basic physical and chemical properties, salinity and alkalinity indicators, and nutrient indicators such as organic matter, soluble organic matter, available nitrogen, and available phosphorus of each treatment group shall be measured respectively.

[0070] The reconstructed red mud artificial soil shall meet the following requirements:

[0071] 1) Salinity and alkalinity of the substrate: After the red mud is soil-improved, the pH value of the substrate generally reaches below 9.0, the EC value is lower than 16 dS / m, the ESP value is lower than 30%, and the SAR% is lower than 10%.

[0072] 2) Fertility indicators of the improved substrate: The organic matter content shall not be lower than the average level of organic matter in garden green space soil; the substrate density shall be maintained at about 1.0 - 1.3 g / cm3; the relevant fertility indicator requirements for other soil fertilities can refer to the relevant fertility indicator requirements of the third-class soil in DB11T 864-2020.

[0073] 3) Risk control: The inorganic pollutant indicators are mainly the heavy metal contents of lead, cadmium, mercury, arsenic, nickel, copper, zinc, and chromium. After the red mud substrate is improved and repaired, it shall comply with the provisions of CJ / T 340.

[0074] Those of ordinary skill in the art to which the present invention pertains should understand that the specific structures and process procedures shown in the above specific implementation part are merely exemplary, not restrictive. Moreover, those of ordinary skill in the art to which the present invention pertains can combine the various technical features shown above in various possible ways to form new technical solutions, or make other modifications, and all fall within the scope of the present invention.

Claims

1. A method for reconstructing artificial soil of red mud based on biomass and fly ash, which is used for soil treatment of red mud, is characterized in that It includes the following steps: Red mud pretreatment; Mix biomass with inorganic materials as additive materials and conduct pretreatment; Cultivate after adding the additive materials to the red mud.

2. The method for reconstructing red mud artificial soil based on biomass and fly ash according to claim 1, characterized in that: The red mud pretreatment includes coarse crushing treatment of the red mud.

3. The method for reconstructing red mud artificial soil based on biomass and fly ash according to claim 2, characterized in that: In the red mud pretreatment, the moisture content of the red mud matrix is reduced to less than 30%.

4. The method for reconstructing red mud artificial soil based on biomass and fly ash according to claim 1, wherein: During the pretreatment of the additive materials, mechanical crushing is performed on the biomass raw materials.

5. The method for reconstructing red mud artificial soil based on biomass and fly ash according to claim 4, wherein: The fineness of the crushed biomass raw materials is less than 5 mm.

6. The method for reconstructing artificial soil from red mud based on biomass and fly ash according to claim 1, wherein: In the additive materials, the addition ratio of the biomass raw materials is less than or equal to 2%.

7. The method for reconstituting bauxite residue artificial soil based on biomass and fly ash according to claim 6, characterized in that: The inorganic materials include fly ash and / or vermiculite.

8. The method for reconstructing red mud artificial soil based on biomass and fly ash according to claim 7, wherein: The addition ratio of the fly ash is less than or equal to 10%, and the addition ratio of the vermiculite is less than or equal to 0.5%.

9. The method for reconstructing red mud artificial soil based on biomass and fly ash according to claim 1, characterized in that: During the cultivation, put each treatment into flowerpots and place them under natural outdoor conditions for cultivation, and water regularly to maintain a stable matrix humidity at 75±2% of the maximum water holding capacity of the soil.

10. The method for reconstructing red mud artificial soil based on biomass and fly ash according to claim 9, characterized in that: Samples are taken at 0, 1, 3, 6, 9, and 12 months after the cultivation of each experimental treatment group to analyze indicators such as the pH, EC, content of each exchangeable cation, and alkalinity ESP of the red mud soil. After the cultivation is completed, the basic physical and chemical properties, salinity and alkalinity indicators, and nutrient indicators such as organic matter, soluble organic matter, available nitrogen, and available phosphorus of each treatment group are measured respectively.

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