A method for preparing artificial soil by combining iron tailings conditioned sludge compost with plant colonization

Abstract

The present invention provides a method for preparing artificial soil by conditioning sludge compost with iron tailings and coordinating plant colonization. First, municipal sludge, straw and iron tailings are mixed evenly and then placed in a closed composting reactor for aerobic composting. After the internal temperature of the compost reaches a peak, the compost product is collected as a high-temperature compost product; the high-temperature compost product is then mixed evenly with the iron tailings and inoculated with an inoculum containing soil microorganisms; the inoculated artificial soil matrix is ​​placed in a container for sufficient static cultivation; plant seedlings are planted in the cultivated artificial soil matrix for plant colonization, and artificial soil is obtained after the plant colonization is completed. The present invention uses iron tailings as a conditioning agent to promote the humification of organic matter and the formation of aggregates during the sludge composting process, and further plants are colonized in the compost product to stabilize the artificial soil structure, thereby improving the structural stability and land utilization efficiency of the sludge-based artificial soil.

Description

Technical Field

[0001] The present invention relates to a method for improving sludge composting efficiency by conditioning iron tailings and preparing artificial soil by planting plants on the compost product, belonging to the technical field of organic solid waste resource utilization. Background Art

[0002] With the rapid development of industrialization and urbanization, the amount of solid waste generated is increasing. Among them, excess sludge and iron tailings are two typical types of solid waste. Excess sludge is the main by-product of sewage treatment plants and is usually rich in nutrients such as organic matter, nitrogen, and phosphorus. Iron tailings are the solid residues in the iron ore beneficiation process. They are mainly composed of silicate minerals and iron oxides. They have high physical stability but low chemical activity. The large-scale accumulation of these two types of solid waste not only occupies a large amount of land resources, but may also cause pollution to the soil, water bodies and atmospheric environment. Therefore, the rational and efficient resource utilization of sludge and iron tailings and the realization of their synergistic transformation have become important research directions in the field of solid waste management and soil remediation.

[0003] Aerobic composting of sewage sludge is a biological treatment process that, under aerobic conditions, decomposes organic matter in sewage sludge and converts it into stable humified substances through the metabolic activity of aerobic microorganisms. This process not only effectively removes pathogenic microorganisms and reduces heavy metal activity, but also allows the final product to be used as a fertilizer or soil conditioner, with widespread applications in landscaping, agricultural production, and mining area ecological restoration. However, the physical structure of traditional sewage sludge compost products is relatively loose, lacking stable soil aggregates, which affects their water and fertilizer retention capacity and long-term soil fertility. Recent studies have demonstrated the potential of iron-based materials in sewage sludge composting. They promote organic matter stabilization through adsorption and organic-mineral complexation, and regulate pH and the redox environment, thereby maintaining microbial activity and promoting humification. Furthermore, iron-based minerals have strong surface activity and readily form stable complexes with organic matter, which helps improve the structural stability and agglomeration of the compost product, enhancing its performance in soil application. Iron tailings, a typical solid waste byproduct, offer advantages such as abundant resources and low cost, making them an ideal material for synergistic composting and mineral processing.

[0004] In recent years, technicians in this field have developed a variety of methods for preparing artificial soil using waste, mainly including: (1) organic solid waste matrix improvement, that is, improving the organic matter content and nutrient supply capacity of artificial soil through composting or fermentation of organic waste such as sludge, livestock and poultry manure, and straw; (2) mineral waste compounding, that is, using mineral materials such as fly ash, coal gangue, and construction waste to improve soil structure and physical and chemical stability. For example, Zhu Wen applied for patent CN202210441510.7, a method for producing artificial soil. This patent utilizes fermentation of organic waste (such as livestock and poultry manure, urban sediment, and plant waste), and adds specially treated wood ash during the composting stage to produce artificial soil, thereby increasing the organic matter content and nitrogen fixation capacity. Fu Yao et al. applied for patent CN202410334575.0, a method for preparing and applying coal-based artificial soil. This patent combines composted organic matter with soil, zeolite, a water-retaining agent, and crushed coal gangue to create artificial soil, effectively increasing its nutrient content and enabling its use in mining area land remediation. However, most of these methods focus on nutrient enrichment while neglecting the formation and long-term stability of soil aggregates, resulting in poor water and fertilizer retention. Furthermore, existing auxiliary materials (coal-based) are simply added after composting / fermentation, without sufficient microbial-driven reaction. This leaves room for improvement in the structural formation and long-term ecological adaptability of the artificial soil. Summary of the Invention

[0005] To address the shortcomings of the prior art, the present invention provides a method for preparing artificial soil by conditioning sludge compost with iron tailings and coordinating plant colonization. The method innovatively utilizes iron tailings as a conditioning agent to promote the humification of organic matter and the formation of aggregates during the sludge composting process. Plant colonization is then performed on the compost product to stabilize the artificial soil structure, thereby improving the structural stability and land utilization efficiency of the sludge-based artificial soil.

[0006] The technical solutions adopted to achieve the above-mentioned purpose of the present invention are:

[0007] A method for preparing artificial soil by combining iron tailings conditioned sludge compost with plant colonization, comprising the following steps:

[0008] (1) Municipal sludge, straw and iron tailings were mixed evenly in a mass ratio of 3.5-4:3.5-4:2-3, and then placed in a closed composting reactor for aerobic composting. The temperature of the compost was controlled between 40 and 50 °C, and intermittent aeration was used to maintain an aerobic environment. The compost product was collected as the high-temperature compost product after the internal temperature of the compost reached its peak;

[0009] (2) adding iron tailings accounting for 25-35% of the total weight of the thermophilic compost product to the thermophilic compost product and mixing them evenly to obtain an artificial soil matrix;

[0010] (3) inoculating an inoculum containing soil microorganisms into the artificial soil matrix;

[0011] (4) Place the inoculated artificial soil matrix in a container and incubate it at room temperature. During the incubation period, the moisture content is controlled at 55% to 60%.

[0012] (5) Planting plant seedlings in the cultured artificial soil matrix, and carrying out plant colonization under outdoor light conditions. The plant colonization period is 90 to 95 days, and the moisture content is maintained at 55 to 60% during the plant colonization period. After the plant colonization is completed, the artificial soil is obtained.

[0013] Furthermore, the water content of the municipal sludge in step (1) is 80%; the straw is crushed to a particle size of less than 2 mm after drying; and the main components of the iron tailings are gypsum, silicate minerals and iron-containing minerals.

[0014] Furthermore, in step (1), the temperature of the pile is controlled by a water bath thermostat; the specific steps of intermittent aeration are: each aeration is 10 minutes, the interval is 50 minutes, and the aeration rate is 0.2 L·min⁻¹.

[0015] Furthermore, the internal temperature of the pile in step (1) reaches a peak value of 47-50°C after 4-5 days of composting, and the high-temperature compost product is collected on the first day of cooling after the temperature reaches the peak value.

[0016] Furthermore, the preparation method of the inoculum solution in step (3) is as follows: collecting topsoil from a natural vegetation area, removing gravel, dead leaves, and roots from the topsoil, mixing the topsoil with deionized water, and pre-culturing overnight at room temperature under stirring conditions. After the pre-culturing is completed, the soil is allowed to stand, and then the upper layer of the suspension containing microorganisms is taken as the inoculum solution.

[0017] Furthermore, in the preparation method of the inoculum, the inoculum was pre-cultured at 25°C and 80 rpm for 24 h, and then allowed to stand for 1 h.

[0018] Furthermore, in step (3), the artificial soil matrix and the inoculation solution are evenly mixed at a ratio of 4:3 (Kg / L).

[0019] Furthermore, in step (4), the mixture is placed in a static culture at 25° C. and a moisture content of 55% to 60% for one month.

[0020] Furthermore, the plant seedlings in step (5) are selected from alfalfa seeds that have been hydroponically cultivated for 2 to 3 days and have uniform growth.

[0021] Furthermore, in step (5), the plant planting period is 90 to 95 days, and the plants are watered once every 3 days during the planting period.

[0022] Compared with the prior art, the method for preparing artificial soil by combining iron tailings conditioned sludge compost with plant colonization provided by the present invention has the following advantages:

[0023] (1) In the present invention, iron tailings are added during the sludge composting process. Iron tailings can promote the degradation of dissolved organic matter (DOM) and the conversion of humus, enabling organic waste to be more effectively converted into nutrient-rich, stable humified products. Iron tailings particles can serve as the core of aggregates, combining with organic colloids and humus formed during the composting process to form a stable aggregate structure, thereby improving the physical and chemical properties of the artificial soil.

[0024] (2) Unlike the compost products collected in the prior art, the present invention innovatively collects compost products in the high-temperature period and combines them with iron tailings for microbial culture. Due to the high content of biodegradable organic matter in the high-temperature compost products, the secretion of polysaccharides by plant roots, and the strong cementation effect of organic matter and iron tailings, during the soil formation process, microorganisms decompose the abundant biodegradable organic matter in the high-temperature compost and synthesize humus. At the same time, cementing substances such as polysaccharides, proteins, and lipids are produced during the metabolism process. These substances can adhere to the surface of soil particles and promote the formation of microaggregates. Subsequently, microorganisms further adhere the microaggregates by secreting extracellular polymers, entanglement of hyphae networks, decomposition and transformation of organic matter, and cementation of metabolites, thus constructing large aggregates, thereby significantly improving the mechanical strength and stability of the aggregates.

[0025] (3) The present invention innovatively adopts the treatment step of plant colonization, which also plays an important role in the construction of soil aggregates and the accumulation of organic matter. Plant root secretions can not only serve as a carbon source for microorganisms and activate the diversity of soil microorganisms, but also promote the bonding of organic-inorganic interfaces and enhance the stability of soil structure and ecological functions. Through the synergistic effect of plants, microorganisms and minerals, the compost product can be transformed from a "loose matrix" to a "stable soil-like" structure. Plant root secretions and the physical effects of the roots further strengthen the stability of soil aggregates and improve the soil's anti-erosion ability and ecological adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a process flow chart in an embodiment of the present invention;

[0027] Figure 2 These are photos of the artificial soils prepared in different treatment groups in the examples;

[0028] Figure 3 Graph showing the distribution of water-stable aggregates of various levels in the artificial soils prepared in different treatment groups in the examples and the proportion of aggregates in the soil used for wet screening;

[0029] Figure 4This is a distribution diagram of the average weight diameter of water-stable aggregates in the artificial soil prepared from different treatment groups in the examples;

[0030] Figure 5 Figure 2 is a diagram showing the morphology and elemental composition of iron-containing minerals in the artificial soils prepared from different treatment groups in the examples;

[0031] Figure 6 This is a graph showing the particle size distribution curves of the artificial soil samples prepared in different treatment groups in the embodiment after laser testing;

[0032] Figure 7 This is a comparison chart of key particle size parameters of artificial soil samples prepared from different treatment groups in the examples after laser testing;

[0033] Figure 8 Figure 2 is a graph showing the physical and chemical properties of artificial soils prepared in different treatment groups in the examples. DETAILED DESCRIPTION

[0034] The present invention is described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments. In order to analyze the mechanism of action of each process step in the present invention, a plurality of comparative examples are provided simultaneously.

[0035] The specific process flow of this embodiment is as follows Figure 1 As shown below, combined Figure 1 Provide a detailed explanation.

[0036] Preparation of S1 Iron Tailings Co-composted Sludge: Sludge samples were collected from a wastewater treatment plant in Nanjing. They were dehydrated municipal sludge with a moisture content of approximately 80%. Iron tailings (IT) samples were obtained from an iron mine in Wuhan and were primarily composed of gypsum, silicate minerals (quartz, microcline, and phlogopite), and iron-containing minerals (magnetite, pyrite, and andradite). Straw was dried and pulverized to a particle size of less than 2 mm. After being mixed uniformly at a mass ratio of 4:4:2 (sludge: straw: iron tailings, w / w / w), the mixture was placed in a closed composting reactor for aerobic composting. The compost was maintained at a temperature between 40 and 50°C using a water bath thermostat. Intermittent aeration was used to maintain an aerobic environment: 10-minute intervals, 50-minute intervals, and an aeration rate of 0.2 L min⁻¹. Composting temperatures were measured and recorded daily in the morning and evening. The compost reaches its high-temperature phase (47-50°C) around day 4-5 of composting. Compost samples are collected on the first day after the temperature peaks and begins to cool, and are recorded as the high-temperature compost (TC). Composting continues until the 28th day, when the compost reaches maturity, at which point samples are collected and recorded as the mature compost (MC).

[0037] S2 Secondary addition of iron tailings: Mix TC or MC compost products with iron tailings at a dry weight ratio of 3:7 (iron tailings: compost) and use it as a substrate for subsequent inoculation and plant planting.

[0038] S3 Soil Microbial Inoculation: Collect topsoil from a naturally vegetated area and remove surface gravel, dead leaves, and roots. Mix the topsoil with deionized water at a solid-to-liquid ratio of 1:3 (w / v). Pre-incubate at 25°C and 80 rpm for 24 hours. After 1 hour of stagnation, collect the microbial suspension from the top layer as the inoculum. Mix the inoculum with the artificial soil matrix obtained in S2 at a ratio of 4:3 (w / v) for soil microbial inoculation.

[0039] S4 Artificial Soil Stable Cultivation: Fill the inoculated artificial soil matrix into the flower pot and place it in a static culture at 25°C and a moisture content of about 55% for one month to promote organic-mineral bonding and the establishment of microbial homeostasis. Two experimental groups were set up in this stage:

[0040] The thermophilic iron tailings composting group (TC-IT) consisted of the TC product obtained in S1 and then subjected to treatments S2-S4. The mature iron tailings composting group (MC-IT) consisted of the MC product obtained in S1 and then subjected to treatments S2-S4. Each experimental group had six replicates: three replicates for the TC-IT and MC-IT groups, and three replicates for the subsequent thermophilic iron tailings composting plus plant colonization (TC-ITP) and mature iron tailings composting plus plant colonization (MC-ITP) groups.

[0041] S5 Planting: After two days of hydroponic cultivation of alfalfa seeds, select seedlings with consistent growth and transplant them into the TC-IT / MC-IT pots from S4, planting a consistent number of seeds per pot. Cure under natural light and water every three days to maintain a moisture content of 55-60%. The planting period lasts for three months. Two experimental groups were set up during this phase:

[0042] High-temperature iron tailings composting plus plant colonization (TC-ITP): The TC product obtained in S1 was treated with S2-S5. Mature-stage iron tailings composting plus plant colonization (MC-ITP): The MC product obtained in S1 was treated with S2-S5. Each experimental group had three replicates.

[0043] S6 Artificial Soil Collection: After three months, the matrix in the pots of the four experimental groups was collected as the final stabilized artificial soil samples for analysis of indicators such as structural stability, proportion of water-stable aggregates, organic matter content, and mineral binding characteristics, to verify the effects of different treatments on the artificial soil construction effect.

[0044] S7 Separation of Water-Stable Aggregates: 50.0 g of air-dried soil sample from each experimental group was evenly spread on a stack of 2 mm, 0.25 mm, and 0.053 mm sieves. The sieves were placed in deionized water for 1 hour. The sieves were manually shaken up and down 50 times with an amplitude of 5 cm. Aggregates remaining on the 2 mm, 0.25 mm, and 0.053 mm sieves were collected and dried in a 40°C oven to constant weight. The dry weight of each aggregate fraction was weighed and recorded. Aggregates remaining on the 2 mm sieve were labeled as oversized aggregates (>2 mm), those remaining on the 0.25 mm sieve were labeled as large aggregates (0.25 mm to 2 mm), and those remaining on the 0.053 mm sieve were labeled as microaggregates (<0.25 mm). The mean weight diameter (MWD) of the aggregates was calculated using the following formula:

[0045]

[0046] in, r k is the aperture of the sieve; m k is the mass ratio of each aggregate part; n is the number of sieves (3 in this embodiment).

[0047] S8 Result Analysis: To evaluate the potential of artificial soil as a soil-like matrix, the present invention systematically measured key aggregate-related indicators, including the distribution characteristics and particle size composition of water-stable aggregates, as well as the morphology and elemental composition of iron-containing minerals in the aggregates.

[0048] Stabilized artificial soil samples were collected on day 90 from four experimental groups: thermophilic compost + iron tailings group (TC-IT), thermophilic compost + iron tailings + plant colonization group (TC-ITP), mature compost + iron tailings group (MC-IT), and mature compost + iron tailings + plant colonization group (MC-ITP). The resulting samples were air-dried, and equal amounts of air-dried samples were taken for aggregate observation and analysis. Figure 2 As shown, from Figure 2 Aggregate formation was observed in all treatment groups, but their structural characteristics varied significantly. Aggregates formed in the TC-IT and MC-IT groups were smaller, looser, and contained more broken particles, demonstrating weak structural stability. However, in the TC-ITP and MC-ITP groups treated with plant colonization, the number of large, densely structured aggregates increased significantly, demonstrating stronger overall cohesion and water stability. The number of broken small aggregates decreased significantly, indicating that plant root activity played a key role in promoting organic-mineral bonding and aggregate formation.

[0049] The water-stable aggregates were further separated and analyzed by wet sieving to evaluate the structural stability of the artificial soil. Based on the particle size, the aggregates were divided into super-large aggregates (>2 mm), macro-aggregates (0.25 mm to 2 mm), and micro-aggregates (<0.25 mm). Figure 3 As shown, from Figure 3 As can be seen in the figure, the total proportion of water-stable aggregates in all treatment groups exceeded 95%, indicating that the artificial soil prepared by this method has excellent overall water erosion resistance. Among them, super-large aggregates accounted for 61% to 92%, large aggregates accounted for 7% to 28%, and micro-aggregates accounted for the lowest proportion, only 0% to 11%. This distribution characteristic indicates that the artificial soil is mainly composed of large-particle aggregates with strong structural stability. The mean weight diameter (MWD) results are shown in the figure below. Figure 4 As shown, Figure 4 Aggregate size structure was further verified in the study. The results showed that the MWD values ​​of each treatment ranged from 10.04 to 14.84 mm, indicating that the method significantly promoted the formation of large aggregates. The thermophilic composting + iron tailings + plant colonization (TC-ITP) treatment performed the best, with a high proportion of very large aggregates reaching 92% and an MWD of 14.84 mm, reflecting extremely high aggregate stability. This result is related to the high content of biodegradable organic matter in the thermophilic compost, the secretion of polysaccharides by plant roots, and the strong cementation between the organic matter and the iron tailings. During soil formation, microorganisms decompose the abundant biodegradable organic matter in the thermophilic compost and synthesize humus. Simultaneously, their metabolism produces cementing substances such as polysaccharides, proteins, and lipids. These substances can adhere to the surface of soil particles and promote the formation of microaggregates. Subsequently, fungi further bind these microaggregates through their hyphal networks, forming macroaggregates, significantly enhancing the mechanical strength and stability of the aggregates. Plant colonization further enhances this process. On the one hand, the physical entanglement of roots facilitates aggregate formation. On the other hand, plant root exudates provide both additional cementing material and a nutrient source for microorganisms, promoting microbial growth and activity in the rhizosphere, thereby enhancing the efficiency of aggregate bioconstruction. In comparison, the organic matter in the mature compost treatments (MC-IT / MC-ITP) had stabilized, lacking sufficient available carbon sources to drive microbial activity. This resulted in a decrease in the rate of cementing material formation and limited the rapid formation of aggregates. Consequently, over the experimental period, the MC group exhibited smaller aggregate size and relatively poor structural stability, indicating that mature compost has limited ability to enhance soil structure in the short term.

[0050] In order to reveal the organic-mineral structural characteristics inside the aggregates, backscattered electron imaging-scanning electron microscopy-energy dispersive spectroscopy (BSE-SEM-EDS) analysis was carried out on the water-stable aggregates of different treatment groups. The analysis results are as follows: Figure 5As shown. Figure 5 The element distribution diagram shows that the distribution areas of typical elements in iron tailings such as Fe, Si, and Al overlap with those of C and O, indicating that organic matter and mineral particles form an organic-mineral composite structure. The element quantification results show that the C content of the TC-ITP treatment group is as high as 37.17%, and the Fe content is 12.34%, which are significantly higher than those of other treatment groups, once again indicating that easily degradable organic matter and plant colonization effectively enhance the binding efficiency between iron oxides and organic matter. In contrast, due to the high stability of organic matter in the MC group, there are fewer active sites for metal elements to bind, the Fe content is significantly reduced, and the density and stability of the aggregate structure are not as good as those of the TC group. This further confirms the key role of the composition of compost raw materials used for soil formation and plant colonization in regulating the organic-mineral composite mechanism.

[0051] In summary, the synergistic composting of iron tailings and sewage sludge combined with plant colonization treatment can not only effectively improve the aggregate structure stability of artificial soil, but also significantly enhance the cementation efficiency of organic matter and minerals, providing a practical technical path and theoretical basis for the construction of artificial soil.

[0052] In order to further verify the particle size distribution characteristics of artificial soil, the present invention uses a laser particle size analyzer to quantitatively analyze the particle size composition of each treated sample. The results further confirm the excellent physical structure performance of artificial soil. Figure 6 As shown, from Figure 6 It can be seen that the main particle size of each treatment group is concentrated in the range of 100-1000 μm, showing a typical loam-like structure. Among them, the particle size in the high temperature period composting + iron tailings + plant colonization group (TC-ITP) is generally larger, and the distribution curve shifts to the coarse particle area, indicating that its structure is more dense and stable. Figure 7 As shown, Figure 7 The results show that the TC-ITP group has the largest particles, about 485 μm, which is significantly higher than that of other treatment groups; the surface area average particle size (D[3,2]) reaches about 80 μm, indicating that this treatment has good potential for microbial attachment and binding with metal elements while maintaining a larger particle size.

[0053] Notably, the TC-ITP group exhibited a significantly large particle size despite being fully dispersed, indicating a highly stable particle structure. This further reflects the formation of a robust organic-mineral composite structure between the organic matter and the metal elements in the iron tailings. This phenomenon, in line with the SEM-EDS results, suggests that the synergistic effect of plant colonization and biodegradable organic matter is the key mechanism for particle formation and structural stability in this invention.

[0054] The results of combined wet sieving and laser particle size analysis indicate that TC-ITP treatment is most effective in promoting coarse particle aggregation, effectively optimizing the particle size structure of the artificial soil. This improvement not only helps improve soil aeration and permeability, but also provides a good foundation for stabilizing the aggregate structure and building microbial ecological functions.

[0055] Finally, the soil physical and chemical properties were tested and the test results were as follows: Figure 8 The artificial soil prepared by the present invention exhibits good physical and chemical properties after stable cultivation and plant colonization, and has multiple functions of meeting the nutritional supply and environmental buffering capacity required for plant growth. Figure 8 As can be seen from the figure, the pH value of the artificial soil is in the slightly acidic to neutral range, which can provide a suitable rhizosphere environment for most plants and avoid plant growth stress caused by acid-base imbalance. The pH values ​​of the plant-inoculated treatments (TC-ITP and MC-ITP) were slightly higher than those of the uninoculated treatments (TC-IT and MC-IT), which is related to plant rhizosphere secretions.

[0056] The artificial soil's cation exchange capacity (CEC) performed well across all treatments, remaining stable between 14.25 and 16.07 cmol⁺ / kg, demonstrating strong soil buffering and nutrient adsorption capabilities. High CEC helps store cationic nutrients, reducing the risk of nutrient loss and improving the soil's overall nutrient retention capacity.

[0057] Total organic carbon (TOC) content in the artificial soil remained high across all treatments, ranging from 136.94 to 167.57 g / kg. This indicates that the artificial soil is rich in organic matter. High organic carbon content provides a sufficient carbon source for soil microorganisms, promoting their activity and metabolism. It also contributes to aggregate formation and soil structure improvement, maintaining good air permeability and water retention. Regarding major nutrients, total nitrogen (TN) content ranged from 0.95 to 1.31 g / kg, meeting the basic nitrogen needs of plants. Total phosphorus (TP) content was sufficient in all treatments. The TP content in the high-temperature treatment (8.86-9.10 g / kg) was significantly higher than that in the mature-stage treatment, indicating that phosphorus is more active and has a higher retention rate in the early stages of composting. The relatively low TP content in the mature-stage compost (4.50-5.47 g / kg) is due to mineralization and partial loss of organic phosphorus. The total potassium (TK) content of the artificial soil was maintained at a moderate level, ranging from 2.65–3.72 g / kg, which could provide a stable potassium source for plants.

[0058] In summary, the artificial soils prepared in different groups in this embodiment all exhibited good physical and chemical properties, were able to provide the basic nutrients and soil environment required for plant growth, and had the foundation for constructing high-performance artificial soils.

Claims

1. A method for preparing artificial soil by composting conditioned sludge from iron tailings and coordinating plant colonization, characterized in that The following steps are involved: (1) Municipal sludge, straw and iron tailings were mixed evenly in a mass ratio of 3.5-4:3.5-4:2-3, and then placed in a closed composting reactor for aerobic composting. The temperature of the pile was controlled between 40 and 50 °C, and intermittent aeration was used to maintain an aerobic environment. The compost products were collected as high-temperature compost products after the internal temperature of the pile reached its peak. The internal temperature of the pile reached its peak after 4-5 days of composting, and the peak temperature was 47-50 °C. The high-temperature compost products were collected on the first day of cooling after the temperature reached its peak. (2) adding iron tailings accounting for 25-35% of the total weight of the thermophilic compost product to the thermophilic compost product and mixing them evenly to obtain an artificial soil matrix; (3) inoculating an inoculum containing soil microorganisms into the artificial soil matrix; (4) Place the inoculated artificial soil matrix in a container and incubate it at room temperature. During the incubation period, the moisture content is controlled at 55% to 60%. (5) Planting plant seedlings in the cultured artificial soil matrix, and carrying out plant colonization under outdoor light conditions. The plant colonization period is 90 to 95 days, and the moisture content is maintained at 55 to 60% during the plant colonization period. After the plant colonization is completed, the artificial soil is obtained.

2. The method for preparing artificial soil by combining iron tailings conditioned sludge compost with plant planting according to claim 1, characterized in that: The water content of the municipal sludge in step (1) is 80%; the straw is crushed to a particle size of less than 2 mm after drying; and the main components of the iron tailings are gypsum, silicate minerals and iron-containing minerals.

3. The method for preparing artificial soil by combining iron tailings conditioned sludge compost with plant planting according to claim 1, characterized in that: In step (1), the temperature of the pile is controlled by a water bath thermostat; the specific steps of intermittent aeration are: each aeration is 10 minutes, the interval is 50 minutes, and the aeration rate is 0.2 L·min⁻¹.

4. The method for preparing artificial soil by combining iron tailings conditioned sludge compost with plant planting according to claim 1, characterized in that: The preparation method of the inoculum solution in step (3) is as follows: collecting topsoil from a natural vegetation area, removing gravel, dead leaves, and roots from the topsoil, mixing the topsoil with deionized water, and pre-culturing overnight at room temperature under stirring conditions. After the pre-culturing is completed, the soil is allowed to stand, and then the upper layer of the suspension containing microorganisms is taken as the inoculum solution.

5. The method for preparing artificial soil by combining iron tailings conditioned sludge compost with plant planting according to claim 4, characterized in that: In the preparation method of the inoculum, the culture was pre-cultured at 25°C and 80 rpm for 24 h and allowed to stand for 1 h.

6. The method for preparing artificial soil by combining iron tailings conditioned sludge compost with plant planting according to claim 1, characterized in that: In step (3), the artificial soil matrix and the inoculum solution are mixed evenly at a ratio of 4:3 (Kg / L).

7. The method for preparing artificial soil by combining iron tailings conditioned sludge compost with plant planting according to claim 1, characterized in that: In step (4), the mixture is placed in a static culture at 25°C and a moisture content of 55% to 60% for one month.

8. The method for preparing artificial soil by combining iron tailings conditioned sludge compost with plant planting according to claim 1, characterized in that: The plant seedlings in step (5) are selected from alfalfa seeds that have been hydroponically cultivated for 2 to 3 days and have uniform growth.

9. The method for preparing artificial soil by combining iron tailings conditioned sludge compost with plant planting according to claim 1, characterized in that: The plant planting period in step (5) is 90 to 95 days, and the plants are watered once every 3 days during the planting period.

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