An Ecological Restoration Method Based on Phosphorus Fixation and Dewatering Stabilized Substrate of River and Lake Sludge

Abstract

This invention discloses an ecological restoration method based on a phosphorus fixation and dewatering stabilizing substrate made from river and lake sludge. Using dredged sludge as the core raw material, it synergistically regulates the sludge using a solid waste-based composite passivation material and a lanthanum-cerium bimetallic modified phosphorus-locking material. Combined with a two-stage stirring maturation process and a high-pressure diaphragm elastic pressing dewatering process, it simultaneously achieves stable consolidation of heavy metals and steady-state mineralization of phosphorus in the sludge, resulting in a high-strength, low-environmental-risk phosphorus fixation and dewatering stabilizing substrate. Using this substrate as the core framework, this invention can be used to prepare ecologically structured planting soil, gradient porous catalytic ceramsite, and self-healing mine pit filling cementitious materials according to the differentiated needs of mine ecological restoration, thereby constructing a three-dimensional ecological restoration system for mines. This invention achieves deep harmlessness and high-value resource utilization of river and lake sludge, synergistically promoting the restoration of degraded mine ecosystems. It features low material costs, strong engineering adaptability, and is suitable for the restoration and management of various types of degraded ecosystems.

Description

Technical Field

[0001] This invention belongs to the fields of environmental engineering, solid waste resource utilization and mine ecological restoration technology. Specifically, it relates to a systematic method for preparing phosphorus-fixing and dehydrating stable substrates by using river and lake dredging sludge as the core raw material and through harmless stabilization treatment, and for preparing functional materials based on the substrates and carrying out the restoration of degraded mine ecosystems. Background Technology

[0002] Endogenous pollution of river and lake sediments and ecological degradation caused by mining are two typical complex environmental problems restricting regional sustainable development. River and lake sediments accumulate nutrients such as nitrogen and phosphorus, as well as various heavy metal pollutants, which are easily released again under external disturbances, leading to eutrophication and exacerbating ecological risks. Current treatment and disposal methods for dredged sediments mainly include landfill and incineration, but these methods generally suffer from limitations such as high disposal costs, low resource utilization rates, and the risk of secondary pollution. On the other hand, mining activities cause large-scale vegetation destruction, soil erosion, and slope instability. In some areas, acidic drainage and heavy metal migration also occur, making ecological restoration difficult. Currently, mine remediation projects mostly rely on topsoil covering, chemical fertilizers, and commercial engineering materials, which are not only costly but also lack sufficient environmental adaptability and long-term sustainability.

[0003] While existing research has focused on the resource utilization of river and lake sludge, it has largely been limited to single pathways such as brick making and roadbed soil application. These approaches suffer from drawbacks including a high risk of pollutant reactivation, limited product functionality, and difficulty in meeting the demands of complex ecological restoration scenarios. In particular, there is a lack of systematic technical solutions that can organically integrate water source remediation with terrestrial ecological restoration to achieve stable solidification and functional transformation of pollutants.

[0004] In summary, to overcome the shortcomings of existing technologies, it is necessary to provide a complete, multifunctional, environmentally friendly, and economically feasible method for constructing an ecological restoration system based on river and lake sludge. Furthermore, it is essential to develop an integrated technology capable of simultaneously achieving deep harmlessness treatment and multi-path resource utilization of river and lake sludge, applicable to the restoration of degraded ecosystems such as mines, to meet the comprehensive requirements of ecological restoration projects for environmental safety, material functionality, and long-term stability. Summary of the Invention

[0005] To address the shortcomings of existing technologies, such as difficulties in the disposal of river and lake sludge, low added value of resource utilization, high risk of secondary release of pollutants, and high cost, poor adaptability, and lack of systematic solutions for mine ecological restoration materials, the present invention aims to provide an ecological restoration method based on phosphorus fixation and dehydration stabilizing substrate of river and lake sludge. This method achieves deep harmlessness and high-value utilization of river and lake sludge in multiple scenarios, while constructing a three-dimensional ecological restoration system adaptable to all mining scenarios, taking into account environmental safety, technological innovation, and engineering economy.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: Step S1: Preparation of phosphorus fixation and dehydration stabilized substrate a. Raw material pretreatment: Solid waste-based composite passivating material and lanthanum-cerium bimetallic modified phosphorus-locking material are sequentially added to river and lake sludge; b. Conditioning reaction: After two stages of stirring and ripening reaction, mechanical dehydration is carried out; c. Substrate molding: A high-strength, low-permeability phosphorus-fixed dehydration stabilized substrate is obtained; Step S2: Preparation of functionalized ecological restoration materials. Using the phosphorus-fixed dehydration and stabilized substrate obtained in step S1 as the core framework, at least one of the following is prepared by compounding functional additives according to the differentiated scenario requirements of mine ecological restoration: ecological structured planting soil, gradient porous catalytic ceramsite, and self-healing mine pit filling cementitious material. Step S3: Systematic application of ecological restoration engineering. The functional ecological restoration materials prepared in step S2 are applied to mine ecological restoration scenarios such as habitat reconstruction on mine slopes, hydrological regulation and ecological purification of slopes, and three-dimensional restoration of mining goaf areas.

[0007] In a preferred embodiment, in step S1a, the solid waste-based composite passivation material is prepared by mixing steel slag micro powder, electrolytic manganese slag calcined modified material, waste concrete ultrafine powder and red mud-based geological polymer precursor in a mass ratio of (3-5):(2-4):(1-2):(0.5-1.5), followed by chemical mechanical activation and grinding to a particle size D90≤0.05mm; the lanthanum-cerium bimetallic modified phosphorus-locking material is prepared by loading lanthanum and cerium elements using multi-level porous zeolite or organic modified bentonite as a carrier and a co-impregnation-gradient calcination method, wherein the molar ratio of La to Ce is (1:1) to (3:1), and the total rare earth element loading is 5% to 10% of the dry weight of the carrier.

[0008] In a preferred embodiment, in step S1a, the amount of the solid waste-based composite passivation material added is 6% to 12% of the dry weight of the river and lake sludge, and the amount of the lanthanum-cerium bimetallic modified phosphorus-locking material added is 2.5% to 6% of the dry weight of the river and lake sludge.

[0009] In a preferred embodiment, the specific process of the two-stage stirring in step S1b is as follows: first, solid waste-based composite passivation material is added with low-speed stirring at 20-40 rpm for 15-20 minutes; then, lanthanum-cerium bimetallic modified phosphorus-locking material is added with medium-speed stirring at 40-60 rpm for 20-30 minutes; after stirring, the mixture is allowed to stand and mature for 1-2 hours; the mechanical dewatering is performed using a high-pressure diaphragm elastic filter press with an operating pressure of 1.8-2.5 MPa and a pressing time of 60-90 minutes.

[0010] In a preferred embodiment, in step S1c, the obtained phosphorus-fixing and dehydration-stabilized substrate has a moisture content of ≤55%, an unconfined compressive strength of ≥50kPa, a heavy metal leaching concentration lower than the Class IV limit of the "Groundwater Quality Standard" (GB / T14848), and a phosphorus fixation efficiency of ≥95%.

[0011] In a preferred embodiment, in step S2, the raw materials of the ecologically structured planting soil include, by weight, 50-70 parts of phosphorus-fixing dehydrated and stabilized substrate, 10-20 parts of silicon-potassium type rice husk ash, 10-20 parts of humified mushroom residue, 5-10 parts of magnetic biochar, and 0.1-0.5 parts of rhizosphere growth-promoting bacteria agent; after homogenization and mixing, the ecologically structured planting soil has a water-stable aggregate content ≥40% and an effective water-holding porosity ≥25%.

[0012] In a preferred embodiment, in step S2, the raw materials for the gradient porous catalytic ceramic particles include, by weight, 40-60 parts of phosphorus-fixing and dehydrating stabilizing substrate, 20-30 parts of catalytically modified dehydrating sludge, 10-20 parts of activated coal gangue powder, 5-10 parts of composite pore-forming agent, and 1-3 parts of transition metal oxide coating precursor. The gradient porous catalytic ceramic particles are obtained by rotary granulation, segmented drying, and controlled atmosphere sintering at 1000-1150℃, with a finished product porosity of 45%-65% and a particle size of 10-25mm.

[0013] In a preferred embodiment, in step S2, the raw materials of the self-healing mine filling cementitious material include, by weight: 50-70 parts of phosphorus-fixing dehydration stabilized substrate, 10-20 parts of ultrafine desulfurized gypsum, 10-20 parts of highly active carbide slag, 10-20 parts of alkali-activated coal gangue geopolymer cementitious agent, 1-3 parts of microencapsulated shrinkage-reducing and toughening agent, and 0.2-0.8 parts of retarded polycarboxylate superplasticizer; the hardened body of the self-healing mine filling cementitious material has a 28-day compressive strength ≥ 5.0 MPa, a drying shrinkage rate ≤ 0.03%, and possesses the ability to self-heal microcracks.

[0014] In a preferred embodiment, the specific implementation method of the mine slope habitat reconstruction in step S3 is as follows: using hydraulic spraying to spray ecologically structured planting soil onto the mine slope anchored by the wire mesh, forming an ecological restoration layer with a thickness of 60-100mm.

[0015] In a preferred embodiment, in step S3, the specific implementation method of slope hydrological regulation and ecological purification is as follows: gradient porous catalytic ceramsite is graded according to particle size and then filled into biodegradable ecological fiber bags, and multi-layer ecological interception and purification units are constructed on the slope in combination with geocells; the specific implementation method of three-dimensional restoration of mining goaf is as follows: self-healing mine pit filling cementitious material is injected into the mining goaf using a layered alternating injection method, and the micro-expansion characteristics of the material are used to achieve top filling.

[0016] The beneficial effects of this invention are: (1) This invention achieves stable solidification of heavy metals and steady-state mineralization of phosphorus in river and lake sludge through the synergistic conditioning of a dual system of "solid waste-based composite passivation material + lanthanum-cerium bimetallic modified phosphorus-locking material". Among them, the passivation material of multi-source industrial solid waste achieves adsorption, complexation and lattice solidification of heavy metals through mechanochemical activation, and the lanthanum-cerium bimetallic modified material converts free phosphorus into stable rare earth phosphate mineral phase through specific coordination. The combination of the two achieves phosphorus fixation efficiency ≥95% and heavy metal leaching concentration is far below the national standard limit. It cuts off the migration and release pathway of pollutants in the process of sludge resource utilization from the source and solves the core pain point of high secondary pollution risk in sludge resource utilization in the prior art. (2) Based on the same harmless phosphorus-fixing and dehydration stabilizing substrate, this invention derives three major categories of functional materials suitable for different mine restoration scenarios through targeted regulation of "material compounding - structural design - performance imparting": ecological structured planting soil suitable for slope vegetation restoration, gradient porous catalytic ceramsite suitable for slope runoff purification, and self-healing filling cementitious material suitable for geological stability of mining goaf. This innovative design of "core substrate + functional module" breaks the limitations of the existing single sludge resource utilization path and low added value, realizes the high-value transformation of sludge from "hazardous waste" to "ecological restoration functional material", and perfectly matches the differentiated needs of multiple mine ecological restoration scenarios. (3) The core conditioning materials and functional compound raw materials of this invention are all derived from bulk industrial solid wastes such as steel slag, electrolytic manganese slag, waste concrete, red mud, coal gangue, desulfurized gypsum, and carbide slag, as well as agricultural and forestry wastes such as mushroom residue and rice husk ash. This not only realizes the synergistic resource utilization of multiple types of solid waste, reduces the consumption of natural resources and the environmental burden of solid waste disposal, but also significantly reduces the raw material cost of ecological restoration materials. According to engineering calculations, the comprehensive cost of the restoration materials prepared by this invention is more than 30% lower than that of traditional mine restoration materials. At the same time, it solves the two major solid waste disposal problems of river and lake sludge and industrial solid waste, and has environmental, economic and social benefits. (4) This invention integrates three types of functional materials through scientific ecological engineering design to construct a three-dimensional mine restoration system consisting of “slope vegetation restoration layer (planting soil) - slope runoff interception and purification zone (ceramsite unit) - underground goaf area stabilization support body (filling cementitious material)”. This system can not only realize the rapid reconstruction of mine slope vegetation and soil and water conservation, but also simultaneously purify nitrogen, phosphorus and suspended matter in slope runoff, stabilize the geological structure of the mine goaf area, and achieve the synergistic improvement of ecological benefits, hydrological benefits and engineering safety benefits, thus solving the problems of single function and insufficient system of existing mine restoration technology. Attached Figure Description

[0017] Figure 1The image shows the phosphorus-fixed dehydration stabilized substrate obtained in Example 1.

[0018] Figure 2 These are before, during, and after (from left to right) comparison images of the phosphorus-fixed dehydration stabilized substrate used for slope planting in Example 2.

[0019] Figure 3 The images shown are small schematic diagrams of Example 2, where the left image shows a substrate treated in the manner of Example 2 for planting, and the right image shows untreated sludge for planting.

[0020] Figure 4 The images show the finished product of the phosphorus-fixed dehydration stabilized substrate used in Example 3 to produce ceramsite. The left image shows the finished ceramsite, and the right image shows the ceramsite after use.

[0021] Figure 5 The image shows the phosphorus-fixed dehydration stabilized substrate used for filling mine pits in Example 4. Detailed Implementation

[0022] The present invention will be further described in detail and completely below with reference to specific embodiments. It should be understood that the embodiments described below are only for explaining the present invention and are not intended to limit the scope of protection of the present invention. All modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the present invention.

[0023] In the following embodiments, the raw materials and equipment used are all commercially available products in the field, and the detection and testing methods used are all conventional methods in the field. Specifically, the river and lake sludge was taken from the bottom sediment of the eutrophic lake dredging project in the ecological environment restoration and management project of Junshan Mining Area, Caidian District, Wuhan City, Hubei Province, and the industrial solid waste raw materials were taken from bulk solid waste by-products of relevant enterprises. All materials comply with relevant environmental protection and engineering application standards.

[0024] Example 1 This embodiment prepares a phosphorus-fixed dehydration stabilized substrate, including the following steps: (1) Raw material pretreatment The sediment from the bottom of a severely eutrophic lake was taken from a dredging project. The initial water content was 85%, the pH was 6.8, and the total Pb content was 280 mg / kg, the total Cd content was 2.5 mg / kg, the total Cu content was 150 mg / kg, and the total phosphorus content was 1200 mg / kg.

[0025] The solid waste-based composite passivation material was prepared by mixing steel slag (specific surface area 420 m² / kg), electrolytic manganese slag activated by calcination at 600℃, waste concrete ultrafine powder (D50=8μm), and red mud-based polymer precursor in a mass ratio of 4.5:3.0:1.5:1.0. The red mud-based polymer precursor was obtained by reacting red mud with a sodium silicate solution with a modulus of 1.2. The mixture was dry-milled in a planetary ball mill at 450 rpm for 2 hours to obtain a composite powder with a D90 of 45μm.

[0026] Lanthanum-cerium bimetallic modified phosphorus-locking material uses hierarchical porous zeolite particles with a particle size of 1-2 mm as a carrier. The particles are impregnated in a mixed solution of La(NO3)3 and Ce(NO3)3, where the molar ratio of La:Ce is 2:1. After impregnation for 24 hours, the material is filtered, dried at 110℃, and then calcined in a muffle furnace at 550℃ for 3 hours to obtain a modified phosphorus-locking material with a total rare earth loading of about 7.5%.

[0027] (2) Preparation of substrate Take 10 tons of wet sludge (with an oven-dry solids content of approximately 1.5 tons) and place it in a conditioning reaction tank. First, add 150 kg of solid waste-based composite passivation material at 10% of the oven-dry sludge mass and stir at 30 rpm for 20 minutes. Then, add 60 kg of lanthanum-cerium bimetallic modified phosphorus-locking material at 4% of the oven-dry sludge mass, increase the stirring speed to 50 rpm, and continue stirring for 25 minutes. After stirring is complete, stop the operation and let it stand for 1.5 hours to mature.

[0028] The matured sludge is transported to a high-pressure diaphragm elastic filter press and pressed for 60 minutes at an operating pressure of 2.0 MPa to complete the mechanical dewatering process.

[0029] (3) Obtain the target substrate After the above treatment, a phosphorus-fixed, dehydrated, and stabilized substrate was obtained with a moisture content of 52% and an unconfined compressive strength of 68 kPa. TCLP leaching toxicity testing showed that the leaching concentrations of Pb, Cd, and Cu were 0.08 mg / L, 0.005 mg / L, and 0.25 mg / L, respectively, all significantly lower than the limits specified in the "Hazardous Waste Identification Standard"; the phosphorus fixation rate (in PO4³⁺) was [not specified in the original text]. - The leaching concentration (calculated) is not less than 97%, and the leaching concentration remains stable and at a low level under long-term soaking conditions of 30 days.

[0030] The resulting phosphorus-fixed dehydration stabilized substrate has high environmental safety and its mechanical properties meet the requirements for transportation, storage and subsequent functional processing.

[0031] Example 2 The specific implementation process of preparing planting soil using the substrate obtained in Example 1 and applying it to the ecological restoration of a steep slope in a limestone mine is as follows: (1) Substrate pretreatment Weigh out the following by weight: 65 parts of phosphorus-fixed dehydration stabilized substrate (moisture content 52%), 15 parts of silicon-potassium type rice husk ash (effective SiO2+K2O=38%), 12 parts of humified mushroom residue (humic acid content 18%), 7 parts of magnetic biochar (specific surface area 320m² / g), and 0.3 parts of commercial rhizosphere growth-promoting bacteria agent (containing gelatinous Bacillus and Bacillus megaterium).

[0032] (2) Preparation of required materials The mixture was thoroughly mixed using a twin-shaft paddle mixer, with the final moisture content controlled between 25% and 30%. The content of water-stable agglomerates (>0.25 mm) was found to be 45%.

[0033] (3) Application of planting soil First, slope repair work is carried out: loose rocks are removed, 8m long anchor rods are drilled and installed (1.5m × 1.5m spacing), three-dimensional geonet is laid and fixed to the anchor rods with wire.

[0034] Substrate hydroseeding is then carried out: A high-power hydraulic hydroseeder is used to mix the prepared planting soil with composite plant seeds (tall fescue, bermudagrass, amorpha fruticosa, lespedeza, and local Pioneer herb seeds) at a ratio of 100:1 (by volume) in the hydroseeder, with the addition of appropriate amounts of binder and water-retaining agent. The mixture is then sprayed evenly onto the slope to a designed thickness of 80mm.

[0035] Further maintenance is required: after hydroseeding, cover with biodegradable non-woven fabric and install an automatic drip irrigation system. Keep the substrate moist in the early stages.

[0036] The final results showed that 20 days after hydroseeding, herbaceous plants generally sprouted, with a coverage of 30%. After 60 days, the coverage exceeded 80%, and shrubs began to grow. After 180 days, the vegetation community stabilized, with a coverage of over 95%. The root system penetrated deep into the substrate and rock crevices, and the activity of soil microorganisms was significantly higher than that of the control area with imported soil. There was no obvious soil erosion on the slope.

[0037] Example 3 The specific implementation process for preparing functional ceramsite using the substrate obtained in Example 1 and constructing a slope runoff purification system is as follows: (1) Substrate pretreatment Raw materials: 50 parts of phosphorus-fixed dehydration stabilized substrate (Example 1); Fenton's reagent (Fe²⁺) + 25 parts of dewatered municipal sludge (75% moisture content) pretreated with H2O2; 15 parts of coal gangue powder activated by calcination at 750℃; 8 parts of composite pore-forming agent (pine sawdust: food-grade ammonium bicarbonate = 2:1); 2 parts of 10% manganese nitrate solution (for surface coating).

[0038] (2)Preparation of required materials Mix the first four raw materials evenly, and granulate them into green balls with a diameter of 18 - 22 mm by a disk granulator. Dry the green balls at 105°C until the moisture content is <5%. Then immerse them in a manganese nitrate solution for 5 seconds, and quickly take them out and drain. Finally, place the treated green balls in a controllable atmosphere sintering furnace, and sinter them at 1050°C for 35 minutes in a weakly reducing atmosphere with 5% N2 content, and cool them with the furnace.

[0039] (3)Application of functional ceramsite The prepared ceramsite is reddish-brown and has good sphericity. There is a dense thin shell on the surface, and the interior is a honeycomb-like pore structure that is interconnected. The average particle size is 20 mm, the bulk density is 0.95 g / cm³, the porosity is 58%, and the cylinder compressive strength is 3.8 MPa. The saturated adsorption capacity for NH4 + -N is 5.8 mg / g, and it shows catalytic degradation activity for methyl orange simulated dye wastewater in the presence of low-concentration H2O2.

[0040] First, divide the ceramsite into different-density coconut fiber mesh bags according to the particle size (15 - 20 mm, 20 - 25 mm). Secondly, on the slope of the mine waste dump that has been preliminarily leveled (with a slope of about 25°), dig shallow trenches along the contour line.

[0041] Subsequently, construct a slope ecological interception and purification unit: Place the slender bags filled with small-particle-size ceramsite at the bottom of the trench as the "purification layer", and stack the bags filled with large-particle-size ceramsite on it in a staggered manner as the "interception layer", and build them into an interception ridge unit in the shape of a "pin". The units are arranged at intervals of 5 - 8 m. And plant moisture-tolerant shrubs downstream of the interception ridge to form a plant filter belt.

[0042] Finally, obtain the system functions shown by the rainy season monitoring: This interception system can effectively retain more than 60% of the surface runoff and extend the confluence time. The removal efficiency of suspended solids (SS) in the runoff is >85%, and the removal efficiencies of total phosphorus (TP) and ammonia nitrogen (NH4 + -N) reach 65% and more than 50% respectively, significantly improving the water quality of the water body at the foot of the slope.

[0043] Example 4 The specific implementation process of using the base material obtained in Example 1 to prepare a high-performance cementitious material and use it for mine filling is as follows: (1)Base material pretreatment Formula (parts by weight): 60 parts of phosphorus-fixing dehydration stabilized substrate (dried to moisture content <5% and pulverized through a 2mm sieve); 15 parts of ultrafine desulfurized gypsum (specific surface area 550m² / kg); 15 parts of carbide slag activated by vertical mill (specific surface area 450m² / kg); 10 parts of alkali-activated coal gangue geopolymer gelling agent (coal gangue powder: water glass modulus 1.5: NaOH = 10:3:1, pre-prepared); 2 parts of commercial microencapsulated acrylate repair agent (particle size 50-100μm); 0.5 parts of retarded polycarboxylate superplasticizer.

[0044] (2) Preparation of required materials Mixing: Dry mix all dry materials except the water-reducing agent in a forced mixer for 2 minutes. Then dissolve the water-reducing agent in the total mixing water (water-to-solid ratio 0.28), add it to the mixer, and mix for another 3-5 minutes to obtain a uniform and viscous filling slurry.

[0045] (3) Application of high-performance cementitious materials First, a series of key performance tests were conducted: Workability: The initial slump of the slurry is 215mm, the spread is 550mm, and it has good fluidity. The initial setting time is 4 hours, and the final setting time is 6.5 hours, which meets the requirements for pumping and filling operations.

[0046] Mechanical properties: Under standard curing conditions, the compressive strength is 2.8 MPa at 3 days, 4.2 MPa at 7 days, and stabilizes at 5.8 MPa at 28 days.

[0047] Self-healing performance: 28-day-old specimens were preloaded to produce microcracks approximately 0.15 mm wide. They were then cured in a humid environment (relative humidity >95%). After 14 days, microscopic observation and ultrasonic testing revealed that most of the cracks were filled with a white healing product. The permeability coefficient increased from 10 after cracking. -6 The speed recovered to nearly 10 times that of a perfectly intact specimen. -8 The compressive strength recovery rate is on the order of cm / s.

[0048] Environmental safety: Long-term leaching tests (HJ / T299) were conducted on the hardened body, and the concentrations of heavy metals and phosphates in the leachate were all far below the relevant standard limits.

[0049] Finally, it was proven that the material exhibits good pumpability, sufficient support strength, excellent impermeability and unique self-healing ability, as well as long-term environmental safety, making it suitable for filling goaf areas in mines where stability and impermeability requirements are high.

[0050] The comprehensive application effect obtained by combining the above embodiments is as follows: In the demonstration project of ecological environment restoration and governance in Junshan mining area, Caidian District, Wuhan City, Hubei Province, the three materials and technologies described in this invention were integrated and applied: spraying greening was carried out on the slope of the open-pit mine. After 6 months of monitoring, the vegetation coverage rate in the project area increased from less than 10% to more than 85%, the amount of soil erosion decreased by 90%, the pollutant output load of slope runoff decreased by more than 70%, and the dust pollution in the mine was effectively controlled, realizing the overall improvement of the ecology and safety of river and lake bottom sediments and mining area environment.

Claims

1. An ecological restoration method based on a phosphorus fixation and dewatering stabilizing substrate made from river and lake sludge, characterized in that, Includes the following steps: Step S1: Preparation of phosphorus fixation and dehydration stabilized substrate a. Raw material pretreatment: Solid waste-based composite passivating material and lanthanum-cerium bimetallic modified phosphorus-locking material are sequentially added to river and lake sludge; b. Conditioning reaction: After two stages of stirring and ripening reaction, mechanical dehydration is carried out; c. Substrate molding: A high-strength, low-permeability phosphorus-fixed dehydration stabilized substrate is obtained; Step S2: Preparation of functionalized ecological restoration materials. Using the phosphorus-fixed dehydration and stabilized substrate obtained in step S1 as the core framework, at least one of the following is prepared by compounding functional additives according to the differentiated scenario requirements of mine ecological restoration: ecological structured planting soil, gradient porous catalytic ceramsite, and self-healing mine pit filling cementitious material. Step S3: Systematic application of ecological restoration engineering. The functional ecological restoration materials prepared in step S2 are applied to mine ecological restoration scenarios such as habitat reconstruction on mine slopes, hydrological regulation and ecological purification of slopes, and three-dimensional restoration of mining goaf areas.

2. The ecological restoration method based on phosphorus fixation and dewatering stabilizing substrate of river and lake sludge according to claim 1, characterized in that, In step S1a, the solid waste-based composite passivation material is prepared by mixing steel slag micro powder, electrolytic manganese slag calcined modified material, waste concrete ultrafine powder and red mud-based geological polymer precursor in a mass ratio of (3-5):(2-4):(1-2):(0.5-1.5), and then chemically and mechanically activated and ground to a particle size D90≤0.05mm; the lanthanum-cerium bimetallic modified phosphorus-locking material is prepared by loading lanthanum and cerium elements using multi-level porous zeolite or organic modified bentonite as a carrier and using a co-impregnation-gradient roasting method, wherein the molar ratio of La to Ce is (1:1) to (3:1), and the total rare earth element loading is 5% to 10% of the dry weight of the carrier.

3. The ecological restoration method based on phosphorus fixation and dewatering stabilizing substrate of river and lake sludge according to claim 1, characterized in that, In step S1a, the amount of solid waste-based composite passivation material added is 6% to 12% of the dry weight of river and lake sludge, and the amount of lanthanum-cerium bimetallic modified phosphorus-locking material added is 2.5% to 6% of the dry weight of river and lake sludge.

4. The ecological restoration method based on phosphorus fixation and dewatering stabilizing substrate of river and lake sludge according to claim 1, characterized in that, In step S1b, the specific process of the two-stage stirring is as follows: first, solid waste-based composite passivation material is added with low-speed stirring at 20-40 rpm for 15-20 min; then, lanthanum-cerium bimetallic modified phosphorus-locking material is added with medium-speed stirring at 40-60 rpm for 20-30 min; after stirring, the mixture is allowed to stand and mature for 1-2 h; the operating pressure of the mechanical dehydration is 1.8-2.5 MPa, and the pressing time is 60-90 min.

5. The ecological restoration method based on phosphorus fixation and dewatering stabilizing substrate of river and lake sludge according to claim 1, characterized in that, In step S1c, the obtained phosphorus-fixing and dehydration-stabilized substrate has a moisture content of ≤55%, an unconfined compressive strength of ≥50kPa, a heavy metal leaching concentration lower than the Class IV limit of the "Groundwater Quality Standard" (GB / T14848), and a phosphorus fixation efficiency of ≥95%.

6. The ecological restoration method based on the phosphorus fixation and dewatering stabilizing substrate of river and lake sludge according to claim 1, characterized in that, In step S2, the raw materials of the ecologically structured planting soil include, by weight, 50-70 parts of phosphorus-fixing dehydrated and stabilized substrate, 10-20 parts of silicon-potassium type rice husk ash, 10-20 parts of humified mushroom residue, 5-10 parts of magnetic biochar, and 0.1-0.5 parts of rhizosphere growth-promoting bacteria agent; after homogenization and mixing, the ecologically structured planting soil has a water-stable aggregate content ≥40% and an effective water-holding porosity ≥25%.

7. The ecological restoration method based on phosphorus fixation and dewatering stabilizing substrate of river and lake sludge according to claim 1, characterized in that, In step S2, the raw materials for the gradient porous catalytic ceramic particles include, by weight, 40-60 parts of phosphorus-fixing and dehydration stabilizing substrate, 20-30 parts of catalytically modified dehydrating sludge, 10-20 parts of activated coal gangue micro powder, 5-10 parts of composite pore-forming agent, and 1-3 parts of transition metal oxide coating precursor. The gradient porous catalytic ceramic particles are obtained by rotary granulation, segmented drying, and controlled atmosphere sintering at 1000-1150℃. The finished product has a porosity of 45%-65% and a particle size of 10-25mm.

8. The ecological restoration method based on the phosphorus fixation and dewatering stabilizing substrate of river and lake sludge according to claim 1, characterized in that, In step S2, the raw materials of the self-healing mine filling cementitious material include, by weight: 50-70 parts of phosphorus-fixing dehydration stabilized base material, 10-20 parts of ultrafine desulfurized gypsum, 10-20 parts of highly active carbide slag, 10-20 parts of alkali-activated coal gangue geopolymer cementitious agent, 1-3 parts of microencapsulated shrinkage-reducing and toughening agent, and 0.2-0.8 parts of retarded polycarboxylate superplasticizer; the hardened body of the self-healing mine filling cementitious material has a 28-day compressive strength ≥5.0MPa, a drying shrinkage rate ≤0.03%, and possesses the ability to self-heal microcracks.

9. The ecological restoration method based on the phosphorus fixation and dewatering stabilizing substrate of river and lake sludge according to claim 1, characterized in that, In step S3, the specific implementation method of the mine slope habitat reconstruction is as follows: using hydraulic spraying to spray ecologically structured planting soil onto the mine slope anchored by the wire mesh, forming an ecological restoration layer with a thickness of 60-100mm.

10. The ecological restoration method based on phosphorus fixation and dewatering stabilizing substrate of river and lake sludge according to claim 1, characterized in that, In step S3, the specific implementation method of slope hydrological regulation and ecological purification is as follows: gradient porous catalytic ceramsite is graded according to particle size and then filled into biodegradable ecological fiber bags, and multi-layer ecological interception and purification units are constructed on the slope in combination with geocells; the specific implementation method of three-dimensional restoration of mining goaf is as follows: self-healing mine pit filling cementitious material is injected into the mining goaf using a layered alternating injection method, and the micro-expansion characteristics of the material are used to achieve top filling.

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