Metal tailing soil improvement method based on high-order granulation technology

Abstract

The invention belongs to the technical field of planting soil preparation, and particularly provides a metal tailing soil improvement method based on a high-order granulation technology, metal tailings are treated through a'serpentine-organic matter-mycorrhizal fungi 'ternary composite cementing system, and improved soil is formed after high-order granulation treatment. According to the technical scheme, gradient magnetic separation is adopted to separate tailing components, extracted tailings, organic compost and a ternary composite cementing agent are mixed in proportion, and a stable aggregate structure is formed through a high-order aggregate process. The method has the advantages that the water-stable aggregate content reaches 70% and is increased by 2-3 times compared with that of a traditional method; the soil erosion modulus is reduced to 1200 t / km.a, and the 3-year survival rate of plants reaches 92%; the organic matter content is increased to 3.5%, maintenance-free long-acting improvement is achieved, and an economical and feasible technical path is provided for ecological restoration of the metal tailings.

Description

Technical Field

[0001] This invention belongs to the field of planting soil preparation technology, and specifically provides a method for improving metal tailings soil based on high-order granulation technology. Background Technology

[0002] Tailings waste generated from metal mining is a core challenge in the ecological governance of the mining industry. my country's cumulative metal tailings stockpile exceeds 20 billion tons, with an annual increase of over 1.5 billion tons. Some metal mines containing specific substances discharge millions of tons of tailings annually. Traditional tailings storage occupies land and easily leads to environmental problems and safety hazards, making the resource utilization and ecological restoration of tailings an urgent priority.

[0003] Higher soil aggregates are the core physical basis of soil fertility and a key indicator for tailings soil remediation. Currently, tailings soil remediation technologies are divided into four categories. While they improve the physicochemical properties of tailings, all have technical shortcomings, making it difficult to efficiently, stably, and ecologically remediate tailings. Chemical improvement method: Adding regulators to adjust pH value and solidify heavy metals, but only focusing on a single indicator, without solving the problem of lack of cementing substances, unable to form a stable granular structure, and the improved tailings have problems such as acidification and rebound, and are prone to secondary pollution, low plant survival rate, and serious soil degradation in the later stage.

[0004] Simple organic fertilization method: Adding organic materials increases the organic matter content, but the organic materials lack decomposition treatment, the organic matter is easily lost, and no cementing system is introduced, so water-stable aggregates cannot be formed. The soil has poor erosion resistance and is prone to heavy metal activation, which poses ecological risks.

[0005] The method of importing topsoil involves transporting topsoil from other locations and mixing it with tailings to improve planting performance. This method can quickly enhance planting performance, but it consumes high-quality arable soil, is costly, does not address the structural defects of tailings, cannot fully utilize tailings, and does not meet the requirements of ecological governance.

[0006] Conventional granulation technology: mostly used for hydroseeding restoration of mine slopes, but it has not formed a systematic granulation cultivation system, has not adapted to the composition characteristics of metal tailings, ignores the role of microorganisms, and the improved soil lacks ecological self-sustaining capacity and has high maintenance costs. Summary of the Invention

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for improving metal tailings soil based on high-order granulation technology, the specific steps of which include: Step 1: Tailings pretreatment and component blending; Step 1.1: Perform cascade magnetic separation on the re-selection tailings to separate them into magnetic, non-magnetic, and extracted tailings. The magnetic portion is returned to the smelting system; the non-magnetic portion is used as a cementing material; and the extracted tailings are used as a basic material for planting soil substrate. Step 1.2: Mix the extracted tailings with organic materials and auxiliary materials according to the following mass ratio: Step 2, preparation and composting of organic compost; Crop straw is mixed with rural kitchen waste, the moisture content is adjusted, and a high-temperature fermentation agent is added for aerobic fermentation. Step 3, preparation of ternary composite binder; Step 3.1, serpentine activation treatment; Serpentine concentrate was subjected to acid activation, thermal activation, and nano-sizing treatment. Step 3.2, propagation of mycorrhizal fungi; A mixed strain of arbuscular mycorrhizal fungi was used; Step 3.3, preparation of composite binder; Step 4, high-order granulation cultivation; Step 4.1, mix the ingredients; Add the matrix material prepared in step 1 and the composite binder prepared in step 3 to a horizontal ribbon mixer; Step 4.2, granulation and molding; Granulation is performed using a disc granulator, with AMF bacterial solution sprayed during granulation; Step 4.3, combined biochemical ripening; Step 5: Quality inspection and shipment; The testing indicators include mechanical stability, water-stable floc content, biological activity, and physicochemical properties.

[0008] Furthermore, in step 1.2, the lower layer of planting base soil and the upper layer of cultivated planting soil are prepared respectively; Substrate planting soil formula: After extraction, the composition is: tailings 25-35%, clay material 30-45%, organic compost material 6-12%, serpentine concentrate 15-25%, and fly ash 5-10%. Topsoil formula: After extraction, the composition is as follows: tailings 35-45%, soil 20-30%, organic compost material 10-15%, serpentine concentrate 10-15%, fly ash 5-10%; The lower layer of serpentine powder has a D50 of less than 0.074 mm, while the upper layer of serpentine powder is nano-sized with a D50 of less than 10 μm.

[0009] Furthermore, in step 2, the ratio of crop straw to rural kitchen waste is 3:2, with a moisture content of 55-60%. The high-temperature fermentation agent uses Bacillus subtilis and thermophilic actinomycetes, with an inoculum size of 0.5%.

[0010] Further, in step 3.1, acid activation: 20% hydrochloric acid solution, liquid-to-solid ratio 3:1, stirred at 80℃ for 2 hours, dissolving some Mg²⁺.+ Increase the surface hydroxyl density; Thermal activation: Calcination at 600℃ for 2 hours removes structural water, forming amorphous MgO-SiO2 and improving reactivity; Nanoparticles: air-jet milling to D50: 5-10μm, specific surface area >100m² / g.

[0011] Furthermore, in step 3.2, the microbial composition includes *Glomus radiata*, *Glomus moses*, and *Glomus terrestrialis*. Further, in step 3.3, the mass ratio of the composite binder is: 60% activated serpentine powder, 25% humic acid, 10% AMF bacterial agent, and 5% water-retaining agent, mixed evenly to obtain a ternary composite binder.

[0012] Furthermore, in step 4.1, the mixing time for the ingredients is 8-10 minutes, and the mixing uniformity (CV) is less than 5%.

[0013] Further, in step 4.3, the wet pellets are transferred to the maturation chamber and maturated under controlled conditions.

[0014] Furthermore, the maturation mechanism includes chemical bonding, biological bonding, and physical consolidation.

[0015] The beneficial effects of using this invention are: This invention employs a ternary composite cementing system of "serpentine-organic matter-mycorrhizal fungi" to overcome the bottleneck of lack of cementing materials in metal tailings, forming a stable high-order aggregate structure (>0.25mm aggregate content>65%), reaching the level of natural topsoil. Full utilization of resources: 100% utilization rate of tailings after reprocessing; serpentine transformed from "impurity separation" to "functional material"; co-processing of organic waste (straw, kitchen waste) to achieve the goal of "zero solid waste"; Ecological self-sustaining: The AMF mycorrhizal network endows the soil with biological activity, forming a "plant-mycorrhizal-soil" positive feedback system. After 3-5 years, it can be freed from artificial management and achieve self-succession of the ecosystem. Economic feasibility: Compared with the topsoil method, the present invention eliminates long-distance transportation costs, reduces overall costs by 40%, and avoids the ecological cost of damaging the topsoil. Regional adaptability: It is particularly suitable for metal mines in the arid Northwest region, where serpentine resources are abundant and the high evaporation rate is conducive to the cultivation of pellets through alternating dry and wet conditions. Detailed Implementation

[0017] A method for soil improvement of metal tailings based on high-order agglomeration technology, the target tailings being metal tailings containing nickel, copper, and serpentine (magnesium silicate); The specific steps include: Step 1: Tailings pretreatment and component blending; Step 1.1: Perform cascade magnetic separation on the re-selection tailings to separate them into magnetic, non-magnetic, and extracted tailings. The magnetic portion is returned to the smelting system; the non-magnetic portion is used as a cementing material; and the extracted tailings are used as a basic material for planting soil substrate. Step 1.2: Mix the extracted tailings with organic materials and auxiliary materials according to the following mass ratio: Substrate planting soil formula: After extraction, the composition is: tailings 25-35%, clay material 30-45%, organic compost material 6-12%, serpentine concentrate 15-25%, and fly ash 5-10%. Topsoil formula: After extraction, the composition is 35-45% tailings, 20-30% loam, 10-15% organic compost material, 10-15% serpentine concentrate, and 5-10% fly ash.

[0018] Preferably, the clay material is sand washing pool mud or loess; The lower layer of serpentine powder has a D50 of less than 0.074 mm, while the upper layer of serpentine powder is nano-sized with a D50 of less than 10 μm.

[0019] Step 2, preparation and composting of organic compost; Crop straw is mixed with rural kitchen waste, the moisture content is adjusted, and a high-temperature fermentation agent is added for aerobic fermentation.

[0020] Preferably, the crop straw is crushed to a particle size of less than 5 cm; The ratio of crop straw to rural kitchen waste is 3:2, with a moisture content of 55-60%. The high-temperature fermentation agent uses Bacillus subtilis and thermophilic actinomycetes, with an inoculum size of 0.5%.

[0021] Step 3, preparation of ternary composite binder; Step 3.1, serpentine activation treatment; Serpentine concentrate was subjected to acid activation, thermal activation, and nano-sizing treatment.

[0022] in, Acid activation: 20% hydrochloric acid solution, liquid-to-solid ratio 3:1, stirred at 80℃ for 2 hours, dissolving some Mg²⁺. + Increase the surface hydroxyl density; Thermal activation: Calcination at 600℃ for 2 hours removes structural water, forming amorphous MgO-SiO2 and improving reactivity; Nanoparticles: air-jet milling to D50: 5-10μm, specific surface area >100m² / g.

[0023] Step 3.2, propagation of mycorrhizal fungi; A mixed strain of arbuscular mycorrhizal fungi (AMF) was used.

[0024] The fungal species consist of: Glomus intraradices, G. mosseae, and G. versiforme. Propagation substrate: a mixture of sterilized river sand and zeolite, used to inoculate host plants; Harvesting criteria: spore density greater than 100 spores / g dry soil, mycelial density greater than 5m / g dry soil.

[0025] Step 3.3, preparation of composite binder; The following components are mixed evenly by mass ratio: 60% activated serpentine powder, 25% humic acid, 10% AMF bacterial agent, and 5% water-retaining agent to obtain a ternary composite binder.

[0026] Step 4, high-order granulation cultivation; Step 4.1, mix the ingredients; Add the matrix material prepared in step 1 and the composite binder prepared in step 3 to a horizontal ribbon mixer and mix for 8-10 minutes. The mixing uniformity CV is less than 5%.

[0027] Step 4.2, granulation and molding; Granulation was performed using a disc granulator, with AMF bacterial solution (spore suspension, 10) sprayed on simultaneously during granulation. 6 (Spores / mL), inoculation amount 50mL / kg dry material.

[0028] Step 4.3, combined biochemical ripening; The wet pellets are transferred to the maturation chamber under controlled conditions.

[0029] ripening mechanism: Chemical bonding: Mg-OH and Si-OH groups on the serpentine surface form hydrogen bonds and coordination bonds with the carboxyl and phenolic hydroxyl groups of organic matter; Biobinding: AMF hyphae penetrate the interior of the particles, forming a three-dimensional entangled network and secreting globulin-associated soil protein (GRSP). Physical consolidation: alternating wet and dry conditions promotes the shrinkage and expansion of aggregates, enhancing water stability.

[0030] Step 5: Quality inspection and shipment; The testing indicators include mechanical stability, water-stable floc content, biological activity, and physicochemical properties.

[0031] Example 1

[0032] The sample was taken from reprocessed tailings containing 30-40% serpentine. Tailings further processed: 2.94 million tons (15% water content), containing 30% serpentine, 50% quartz, and 20% feldspar; Sand washing pond sludge: 2 million tons (20% water content); Straw: 150,000 tons (dry basis); Kitchen waste: 100,000 tons (60% water content).

[0033] The specific process of soil improvement using a method for remediating metal tailings based on high-order granulation technology is as follows: Step 1: Tailings pretreatment and component blending; After stepwise magnetic separation, the magnetic fraction (yield 4-5%) is obtained as: iron minerals; Non-magnetic fraction (yield 30-35%): serpentine concentrate (MgO>42%); Tailings after extraction (yield 56-60%).

[0034] Tailings pretreatment results: 1.38 million tons of serpentine concentrate (MgO 42%) were obtained by cascade magnetic separation, and 2.94 million tons of tailings were extracted.

[0035] Step 2: Preparation and composting of organic compost; Crop straw (crushed to <5cm) is mixed with rural kitchen waste at a mass ratio of 3:2, and the moisture content is adjusted to 55-60%. A high-temperature fermentation agent (Bacillus subtilis + thermophilic actinomycetes, inoculation amount 0.5%) is added, and a trough-type aerobic fermentation is carried out. During the warming period (days 1-3): when the temperature rises to 60-65℃, turn the pile once a day; High temperature period (days 4-12): Maintain temperature at 60-65℃, turn the pile twice a day; Cooling period (days 13-20): When the temperature drops below 40℃, turn the pile once every 2 days; Aging period (days 21-35): Static aging to obtain well-rotted organic fertilizer with an organic matter content ≥45% and a humic acid content ≥15%.

[0036] Step 3, preparation of ternary composite binder; Step 3.1, serpentine activation treatment; Serpentine concentrate was subjected to acid activation, thermal activation, and nano-sizing treatment.

[0037] in, Acid activation: 20% hydrochloric acid solution, liquid-to-solid ratio 3:1, stirred at 80℃ for 2 hours, dissolving some Mg²⁺. + Increase the surface hydroxyl density; Thermal activation: Calcination at 600℃ for 2 hours removes structural water, forming amorphous MgO-SiO2 and improving reactivity; Nanoparticles: air-jet milling to D50: 5-10μm, specific surface area >100m² / g.

[0038] Step 3.2, propagation of mycorrhizal fungi; A mixed strain of arbuscular mycorrhizal fungi (AMF) was used.

[0039] The fungal composition was as follows: Glomus intraradices 40%, G. mosseae 35%, and G. versiforme 25%. Propagation substrate: Sterilized river sand and zeolite mixture, with a mixing ratio of 3:1, inoculated with host plants (clover / corn). Culture conditions: 14h / d light, 25-28℃ temperature, 60-70% humidity, culture for 60 days. Harvesting criteria: spore density > 100 spores / g dry soil, mycelial density > 5m / g dry soil.

[0040] Step 3.3, preparation of composite binder; The following components are mixed evenly by mass ratio: 60% activated serpentine powder, 25% humic acid (extracted from compost), 10% AMF microbial agent, and 5% water-retaining agent (polyacrylamide, molecular weight 3 million) to obtain a ternary composite binder.

[0041] Step 4, high-order granulation cultivation; Step 4.1, mix the ingredients; Add the matrix material prepared in step 1 and the composite binder prepared in step 3 to a horizontal ribbon mixer at a mass ratio of 100:(3-5). Mix for 8-10 minutes, and the mixing uniformity CV<5%.

[0042] Step 4.2, granulation and molding; Disc granulator parameters: Disk diameter: 3.0-3.5m; Inclination angle: 45-50°; Speed: 12-15 rpm; Spray intensity: mist water, moisture content adjusted to 18-22%. Step 5: Quality inspection and shipment; Mechanical stability: Drop strength greater than 90%; Water-stable aggregate content: >65% for aggregates >0.25mm, >30% for aggregates >2mm; Bioactivity: AMF spore count > 50 spores / g dry soil, dehydrogenase activity > 100 μg TF / g·h; Physicochemical properties: pH 6.5-7.5, lower layer organic matter greater than 5% or upper layer organic matter >8%, bulk density 1.0-1.3 g / cm³.

[0043] The ingredients (by weight) for cultivating the lower planting substrate soil are as follows: Tailings after extraction: 35% (1.03 million tons); Sand washing pond sludge: 38% (1.12 million tons); Well-rotted organic fertilizer: 9% (260,000 tons, made from straw and kitchen waste compost). Serpentine concentrate (-0.074mm): 15% (440,000 tons); Fly ash: 3% (90,000 tons).

[0044] Preparation results of ternary composite binder: Serpentine powder was thermally activated at 600℃ for 2 hours; Prepare according to the ratio of serpentine: humic acid: AMF inoculant: PAM = 60:25:10:5; Addition amount: 4% (based on dry substrate mass); Higher-order agglomeration: Disc granulation, particle size 5-10mm; Cure for 10 days, alternating between dry and wet conditions 3 times; 1.68 million tons of subsoil were obtained for planting. Product performance: Water-stable aggregates (>0.25mm): 68%; Water-stable large aggregates (>2mm): 35%; Saturated water conductivity: 3.5 mm / h (moderate); Field water holding capacity: 28%; pH: 7.2; Organic matter: 6.5%.

[0045] Application: In the reclamation of hillside dumps, a 60cm thick layer of soil was laid and alfalfa was planted. The survival rate was >95%. After 3 years, the soil organic matter increased to 3.5%, which is close to the level of natural soil.

[0046] Ingredients (by weight) for cultivating topsoil: Tailings after extraction: 40% (450,000 tons); Soil: 22% (250,000 tons); Well-rotted organic fertilizer: 13% (150,000 tons, high fertility ratio); Nano serpentine powder (D50=8μm): 15% (170,000 tons); Fly ash: 10% (110,000 tons); Ternary composite binder: 5% addition amount, with the proportion of nano serpentine increased to 70%.

[0047] High-order granulation: granulation particle size 2-5mm, maturation for 7 days, yielding 1.12 million tons of topsoil.

[0048] Product performance: Water-stable aggregates (>0.25mm): 72%; Organic matter: 9.2%; Total nitrogen: 0.18%; Available phosphorus: 22 mg / kg; Available potassium: 145 mg / kg; Mycorrhizal infection rate: 65% (clover seedlings).

[0049] Application: Reclaiming the top 30cm layer of soil and planting potatoes yields up to 85% of the local farmland level, with heavy metal content meeting the screening values ​​of GB15618-2018.

[0050] Comparative test Comparative Example 1: Conventional Chemical Modification Method (CN201910234567.8) Ingredients: 60% tailings + 30% loess + 10% organic fertilizer, with 2% gypsum added to adjust pH and 1% lime added for neutralization.

[0051] result: Initially, the pH was 7.0, but it dropped to 6.2 after 3 months (acidification). Poor aggregate structure leads to surface crusting after rain, resulting in a 90% decrease in permeability. The plant survival rate was 60%, but it deteriorated severely after 2 years. Comparative Example 2: Simple Organic Fertilization.

[0052] Ingredients: 50% tailings + 30% silt + 20% cow dung, no binder added.

[0053] result: Organic matter decomposes rapidly, with 60% loss after one year. It has no granular structure, and its corrosion resistance index is only 1 / 5 of that of the present invention; Risk of heavy metal activation; excessive heavy metal levels in plants.

[0054] .

[0055] The above content is only a preferred embodiment of the present invention. For those skilled in the art, many changes can be made in the specific implementation and application scope based on the concept of the present invention. As long as these changes do not depart from the concept of the present invention, they all fall within the protection scope of the present invention.

Claims

1. A method for soil improvement of metal tailings based on high-order agglomeration technology, characterized in that, The specific steps include: Step 1: Tailings pretreatment and component blending; Step 1.1: Perform cascade magnetic separation on the re-selection tailings to separate them into magnetic, non-magnetic, and extracted tailings. The magnetic portion is returned to the smelting system; the non-magnetic portion is used as a cementing material; and the extracted tailings are used as a basic material for planting soil substrate. Step 1.2: Mix the extracted tailings with organic materials and auxiliary materials according to the following mass ratio: Step 2, preparation and composting of organic compost; Crop straw is mixed with rural kitchen waste, the moisture content is adjusted, and a high-temperature fermentation agent is added for aerobic fermentation. Step 3, preparation of ternary composite binder; Step 3.1, serpentine activation treatment; Serpentine concentrate was subjected to acid activation, thermal activation, and nano-sizing treatment. Step 3.2, propagation of mycorrhizal fungi; A mixed strain of arbuscular mycorrhizal fungi was used; Step 3.3, preparation of composite binder; Step 4, high-order granulation cultivation; Step 4.1, mix the ingredients; Add the matrix material prepared in step 1 and the composite binder prepared in step 3 to a horizontal ribbon mixer; Step 4.2, granulation and molding; Granulation is performed using a disc granulator, with AMF bacterial solution sprayed during granulation; Step 4.3, combined biochemical ripening; Step 5: Quality inspection and shipment; The testing indicators include mechanical stability, water-stable floc content, biological activity, and physicochemical properties.

2. The method for improving metal tailings soil based on high-order granulation technology as described in claim 1, characterized in that: In step 1.2, the lower layer of planting base soil and the upper layer of cultivated planting soil are prepared respectively; Substrate planting soil formula: After extraction, the composition is: tailings 25-35%, clay material 30-45%, organic compost material 6-12%, serpentine concentrate 15-25%, and fly ash 5-10%. Topsoil formula: After extraction, the composition is as follows: tailings 35-45%, soil 20-30%, organic compost material 10-15%, serpentine concentrate 10-15%, fly ash 5-10%; The lower layer of serpentine powder has a D50 of less than 0.074 mm, while the upper layer of serpentine powder is nano-sized with a D50 of less than 10 μm.

3. The method for improving metal tailings soil based on high-order granulation technology as described in claim 1, characterized in that: In step 2, the ratio of crop straw to rural kitchen waste is 3:2, with a moisture content of 55-60%. The high-temperature fermentation agent uses Bacillus subtilis and thermophilic actinomycetes, with an inoculum size of 0.5%.

4. The method for improving metal tailings soil based on high-order agglomeration technology as described in claim 1, characterized in that: In step 3.1, acid activation: 20% hydrochloric acid solution, liquid-to-solid ratio 3:1, stirred at 80℃ for 2 hours, dissolving some Mg²⁺. + Increase the surface hydroxyl density; Thermal activation: Calcination at 600℃ for 2 hours removes structural water, forming amorphous MgO-SiO2 and improving reactivity; Nanoparticles: air-jet milling to D50: 5-10μm, specific surface area >100m² / g.

5. The method for improving metal tailings soil based on high-order agglomeration technology as described in claim 1, characterized in that: In step 3.2, the fungal species composition includes Root Gastropoda, Moses Gastropoda, and Surface Gastropoda.

6. The method for improving metal tailings soil based on high-order agglomeration technology as described in claim 1, characterized in that: In step 3.3, the mass ratio of the composite binder is: 60% activated serpentine powder, 25% humic acid, 10% AMF bacterial agent, and 5% water-retaining agent. The mixture is stirred evenly to obtain a ternary composite binder.

7. The method for improving metal tailings soil based on high-order granulation technology as described in claim 1, characterized in that: In step 4.1, the mixing time for the ingredients is 8-10 minutes, and the mixing uniformity (CV) is less than 5%.

8. A method for improving metal tailings soil based on high-order granulation technology as described in claim 1, characterized in that: In step 4.3, the wet pellets are transferred to the maturation chamber and maturated under controlled conditions.

9. A method for improving metal tailings soil based on high-order agglomeration technology as described in claim 1, characterized in that: The maturation mechanism includes chemical bonding, biological bonding, and physical consolidation.