A porous soil substrate material and methods of making and using the same

Abstract

This invention relates to the field of environmental functional materials, and more particularly to a porous soil matrix material, its preparation method, and its application. The porous soil matrix material comprises the following raw materials in parts by weight: 60-85 parts alkali-modified fly ash, 5-15 parts humic matter, 5-10 parts starch, 1-3 parts ammonium sulfate, and 2-10 parts quartz sand; wherein the organic matter content of the humic matter is ≥35%, and the pH value of the humic matter is 6.0-7.5. This invention uses fly ash and humic matter as core raw materials, in conjunction with starch, ammonium sulfate, and quartz sand, to obtain a porous material with high porosity and abundant surface functional groups, which can efficiently adsorb and chemically immobilize zinc pollutants.

Description

Technical Field

[0001] This invention relates to the field of environmental functional materials, and more particularly to a porous soil matrix material, its preparation method, and its application. Background Technology

[0002] Zinc is a heavy metal pollutant found in high concentrations and widely distributed in urban stormwater runoff, primarily originating from vehicle tire wear, corrosion of galvanized materials, atmospheric deposition, and industrial emissions. Although zinc is a micronutrient, excessive amounts can be toxic to aquatic organisms and may accumulate through the food chain. Traditional rain garden or plant retention system media (such as sand or ordinary planting soil) have limited capacity to remove dissolved zinc, which easily migrates with the effluent, causing secondary pollution.

[0003] Current research on improving media performance largely focuses on adding synthetic adsorbents (such as modified zeolites and nanomaterials) or commercial biochar, which is costly and does not systematically consider the disposal of media after saturation, potentially generating new hazardous waste. Fly ash, as a major industrial solid waste, possesses certain adsorption properties, but its direct and large-scale application has limitations, such as the risk of soil compaction or salinization due to salt and alkaline substances, restricting its safe application in ecologically sensitive areas. Existing cutting-edge research shows that simple room-temperature modification of fly ash with suitable alkaline solutions can effectively activate its aluminosilicate components, significantly improving its cementing and water retention properties while reducing environmental risks. This provides a new approach for the high-value and safe resource utilization of fly ash. Garden leaf humus is rich in functional groups such as carboxyl and phenolic hydroxyl groups, exhibiting a strong complexing ability for zinc ions, making it a low-cost and readily available natural modifier.

[0004] On the other hand, existing technologies for rapidly preparing fly ash-based porous materials using waste heat from coke oven flue gas do not have functional designs for specific pollutants (especially heavy metal zinc), lack prior optimization considerations for the ecological applicability of raw material fly ash, and do not plan for high-end resource recycling pathways after its service life.

[0005] Therefore, there is an urgent need to develop an innovative material and application system that specifically targets zinc pollution, balances performance and ecological safety in raw material pretreatment and formulation design, has a green and efficient preparation process, and possesses a complete "production-application-recycling-high-value utilization" chain. Summary of the Invention

[0006] This invention provides a porous soil matrix material, its preparation method, and its application, which can realize a closed-loop chain from production and application to recycling. It aims to efficiently and safely treat zinc pollution in rainwater and realize the resource reuse of materials.

[0007] To address the above problems, the present invention provides the following technical solution: This invention provides a porous soil matrix material comprising the following raw materials in parts by weight: 60-85 parts of alkali-modified fly ash 5-15 parts of humus 5-10 parts starch 1-3 parts ammonium sulfate 2-10 parts of quartz sand; The organic matter content of the humic substance is ≥35%, and the pH value of the humic substance is 6.0~7.5.

[0008] This invention uses alkali-modified fly ash and humus as core raw materials, in combination with starch, ammonium sulfate and quartz sand, to obtain a porous soil matrix material with high porosity and abundant surface functional groups, which can efficiently adsorb and chemically fix zinc pollutants.

[0009] In this invention, alkali-modified fly ash is selected. After alkali modification, the cementing performance and water retention of fly ash can be optimized, its soluble salt content can be reduced, its pH can be stabilized, and the environmental compatibility of the final product can be improved. It is especially suitable for areas or projects that are sensitive to soil salinization, ensuring its ecological safety and broadening the application range of the material.

[0010] In some specific embodiments, the preparation of the alkali-modified fly ash includes: Fly ash is soaked in an alkaline solution, washed until the pH of the filtrate is 7-8, and then dried.

[0011] In some specific embodiments, the ratio of fly ash to alkaline solution is 1g:(5~8)mL.

[0012] In some specific embodiments, the concentration of the alkaline solution is 0.5~2 mol / L.

[0013] In some specific embodiments, the alkaline solution includes a sodium hydroxide solution.

[0014] In some specific embodiments, the soaking temperature is 10~30℃, and the soaking time is 7~14 days.

[0015] In this invention, the drying temperature is not specifically limited; it is sufficient to remove moisture from the product. In some specific embodiments, the drying temperature can be 105~110℃.

[0016] In some specific embodiments, the humus is obtained from fallen leaves through composting.

[0017] A second aspect of the present invention also provides a method for preparing the above-mentioned porous soil matrix material, comprising the following steps: Alkali-modified fly ash, humus, starch, ammonium sulfate, and quartz sand are mixed to obtain a mixture. After grinding and sieving, the mixture is placed in a granulation device, and then water is sprayed into the mixture to granulate it and obtain a preform. The embryo is placed in a drying device and heat-treated with coke oven flue gas to form a porous structure and solidify. After the reaction is completed, it is cooled to obtain a porous soil matrix material.

[0018] In the preparation method of the porous soil matrix material of the present invention, rapid foaming and molding are achieved by introducing coke oven flue gas and utilizing the synergistic effect of starch gelatinization and ammonium sulfate decomposition foaming.

[0019] In some specific embodiments, the sieve opening is 8-10 mesh.

[0020] In some specific embodiments, the moisture content of the embryo is 25wt% to 35wt%.

[0021] In some specific embodiments, the temperature of the coke oven flue gas is 200~300℃.

[0022] In some specific embodiments, the heat treatment time is 3 to 8 minutes.

[0023] In this invention, the coke oven flue gas mainly serves as a heat source, which enables the preform to form a porous structure and solidify into shape.

[0024] A third aspect of the present invention also provides an application of the above-mentioned porous soil matrix material in removing zinc pollutants from rainwater runoff.

[0025] In some specific embodiments, the application includes: The porous soil matrix material is placed in the functional layer of the plant retention system to adsorb zinc ions in rainwater runoff. The plant retention system comprises, from top to bottom, a vegetation layer, a planting soil layer, a functional layer, a geotextile layer, and a drainage layer, stacked sequentially. In this invention, the thickness and composition of the vegetation layer, planting soil layer, geotextile layer, and drainage layer are not specifically limited; conventional materials and thicknesses in the art can be used.

[0026] In some specific embodiments, the thickness of the functional layer is 25~35cm.

[0027] In some specific embodiments, the porous soil matrix material is recycled after it becomes saturated with zinc. The resource recycling method includes: a) Remove and crush the porous soil matrix material after it has been saturated with zinc to obtain powder; b) The powder is leached with sulfuric acid solution to recover the zinc element therein; c) Recover and reuse the metal elements in the leaching residue; The aluminum and magnesium elements contained in the residue are separated and extracted, and used for the preparation of metallic materials.

[0028] In some specific embodiments, the resource recycling method specifically includes: (1) After the porous soil matrix material saturated with zinc adsorption is removed, it is crushed to obtain powder; (2) The powder is mixed with sulfuric acid solution and reacted to obtain zinc-rich leachate and zinc leaching residue; (3) The zinc-rich leachate is concentrated and crystallized, and the resulting crystals are dried to obtain crude zinc sulfate; the zinc leaching residue is mixed with sodium hydroxide and calcined to obtain an alkaline melt; the alkaline melt is cooled and mixed with water, stirred and leached, and then filtered to obtain an alkaline leachate containing aluminum and magnesium and a desilication residue. (4) Pass CO2 gas into the alkaline leachate until the pH is 8.5, and then filter and separate to obtain aluminum hydroxide filter cake and magnesium-containing filtrate; (5) The aluminum hydroxide filter cake is washed with water until the pH is neutral, and then dried to obtain aluminum hydroxide; (6) After heating the magnesium-containing filtrate, sodium hydroxide solution is added to adjust the pH to 12 to obtain a precipitate. The precipitate is then dried to obtain magnesium hydroxide.

[0029] In some specific embodiments, in step (1), the particle size of the powder is ≤0.25mm.

[0030] In some specific embodiments, in step (2), the ratio of the powder to the sulfuric acid solution is 1 kg: (3~5) L; the concentration of the sulfuric acid solution is 10 wt%~15 wt%; the reaction temperature is 50~60℃; and the reaction time is 2~4 h. In this invention, in the reaction of step (2), zinc is used as Zn 2+ When the fly ash enters the solution, a small amount of aluminum and magnesium in the fly ash skeleton dissolves out. However, by controlling the acid concentration and reaction time within the above range, selective preferential leaching of zinc is achieved.

[0031] In some specific embodiments, in step (3), there are no special restrictions on the conditions for concentration and crystallization. The solution is heated and concentrated to 1 / 3 of the original zinc-rich leaching liquid volume, and then naturally cooled to room temperature to obtain crystals.

[0032] In some specific embodiments, in step (3), the drying temperature is 80~90℃, the drying time is 1~3h; the mass ratio of zinc leaching residue to sodium hydroxide is 1:(1~1.5); the calcination temperature is 600~700℃, the time is 1~3h, and the heating rate is 3~5℃ / min; the ratio of alkali melt to water is 1kg:(5~7)L; the water temperature is 80~85℃, and the leaching time is 1~1.5h.

[0033] In some specific embodiments, in step (4), the flow rate of the carbon dioxide gas introduced into the CO2 gas is 0.5 m³ / s. 3 Aeration is maintained at a rate of 38-42℃ per hour, with the pH gradually decreasing. When the pH drops to 10.5-11.0, aluminum hydroxide precipitate begins to form. Aeration continues until the pH reaches 8.5 to ensure complete aluminum precipitation.

[0034] In some specific embodiments, in step (5), the drying temperature is 100~110℃ and the drying time is 1~3h. In this invention, the aluminum hydroxide described in step (5) is calcined to obtain γ-Al2O3, which has a pure crystal form and can be used as an aluminum-based water reaction hydrogen production material.

[0035] In some specific embodiments, in step (6), the heating temperature is 80~85℃; the concentration of the sodium hydroxide solution is 10~12wt%; the drying temperature is 100~110℃, and the drying time is 1~3h. In this invention, the magnesium hydroxide described in step (6) can be directly used as a raw material for the synthesis of magnesium-based hydrogen storage alloys, or it can be further calcined to obtain magnesium oxide for use.

[0036] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention uses alkali-modified fly ash (60-85 parts by weight) and humus (5-15 parts by weight) as core raw materials, and in combination with starch, ammonium sulfate and quartz sand, the resulting porous material has high porosity and rich surface functional groups, which can efficiently adsorb and chemically fix zinc pollutants.

[0037] (2) The present invention utilizes the waste heat of coke oven flue gas to achieve rapid foaming and molding, and the material preparation process synergistically purifies the flue gas.

[0038] (3) This invention plans a full life-cycle resource utilization path for the material: after saturation, it can be used as an "urban mine" to recover zinc resources and extract aluminum and magnesium elements from the fly ash skeleton for the preparation of aluminum-based hydrogen production materials and magnesium-based hydrogen storage alloy precursors, realizing a closed-loop link between environmental governance and energy material preparation. Furthermore, in view of the potential ecological risks of direct utilization of fly ash, this solution is compatible with simple alkali pretreatment of fly ash (such as room temperature modification with an appropriate concentration of alkali solution) to further improve its cementing and water retention performance and ensure its ecological safety, thus broadening the applicability of the material. Attached Figure Description

[0039] The above and other objects, features, and advantages of the invention will be apparent from the following description of preferred embodiments illustrating the gist of the invention and its use, and the accompanying drawings, in which: Figure 1 This is a schematic diagram of the plant retention system in this invention.

[0040] Figure 2 This is a flowchart illustrating the resource recovery process of porous soil matrix material after zinc adsorption saturation in this invention. Detailed Implementation

[0041] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. The embodiments of this application are only examples, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] Example 1 Raw material preparation: Fly ash: sourced from a local thermal power plant; preparation of alkali-modified fly ash includes: placing fly ash in a 1.0 mol / L sodium hydroxide solution (solid-liquid ratio 1 g: 5 mL), soaking at room temperature (25°C) with intermittent stirring for 14 days. Subsequently, it is repeatedly washed with deionized water until the pH of the filtrate is close to 8, then dried at 105°C and crushed for later use.

[0043] Humus: It is obtained by composting garden leaves, with an organic matter content of 42% and a pH of 6.8.

[0044] Others: corn starch, industrial grade ammonium sulfate, quartz sand.

[0045] Porous soil matrix material, prepared from the following raw materials in parts by weight: 75 parts of alkali-modified fly ash, 10 parts of humus, 8 parts of starch, 2 parts of ammonium sulfate, and 5 parts of quartz sand; The preparation of porous soil matrix materials includes: Alkali-modified fly ash, humus, starch, ammonium sulfate and quartz sand are mixed, ground and passed through an 8-mesh sieve, and then water is added in a disc granulator to make green pellets with a moisture content of about 30% (particle size of 8~12mm). The green pellets were placed in a drying device, and coke oven flue gas at 250°C was introduced for heat treatment for 5 minutes to achieve foaming and molding. After natural cooling, a porous soil matrix material with a porosity of 45% was obtained.

[0046] Example 2: Application and performance of materials in plant retention systems Plant retention systems along urban roads (structural diagram shown) Figure 1 As shown, a 30cm thick functional layer composed of the porous soil matrix material obtained in Example 1 is filled in the system. The plant retention system includes, from top to bottom, a vegetation layer, a planting soil layer, a functional layer, a geotextile layer, and a drainage layer, stacked sequentially. Monitoring shows that it achieves an average removal rate of 92% for total zinc in rainwater runoff, with stable and compliant effluent. The functional layer exhibits good permeability and no compaction, demonstrating the good ecological adaptability of the improved fly ash-based material.

[0047] Example 3: Resource recovery of saturated materials Raw materials and preparation: Take 10 kg of porous soil matrix material (hereinafter referred to as "saturated material") prepared in Example 1 and applied in the plant retention system described in Example 2 for 12 months to reach zinc adsorption saturation.

[0048] Initial composition of saturated material (dry basis): fly ash skeleton about 70-75%, humus and residual starch about 10-15%, and adsorbed fixed zinc content about 12.5 g / kg (i.e., total zinc content about 125 g).

[0049] Auxiliary raw materials: industrial grade dilute sulfuric acid (concentration 15% w / w), sodium hydroxide (industrial grade, purity ≥98%), deionized water, carbon dioxide gas (industrial grade, purity ≥99%).

[0050] Experimental Procedure and Parameters: 10 kg of saturated material was coarsely crushed to a particle size <5 mm in a jaw crusher, then finely ground in a ball mill and passed through a 60-mesh sieve (0.25 mm aperture) to obtain uniform powder. The moisture content of the powder sample was measured (approximately 8%), and subsequent calculations were based on a dry basis. The crushed powder was placed in a stainless steel reactor, and 15% dilute sulfuric acid was added at a solid-liquid ratio of 1:4 (kg / L), i.e., 4 L of dilute sulfuric acid per kilogram of powder. The reaction was carried out at 60℃, with a stirring speed of 200 rpm, for 2 hours. After the reaction, the mixture was filtered while hot to obtain a zinc-rich leaching solution (approximately 40 L) and zinc leaching residue (wet weight approximately 8.5 kg). The residue was washed with a small amount of deionized water, and the washing liquid was combined with the leaching solution. Atomic absorption spectrometry analysis showed that the zinc leaching rate was 87.3% (meeting the >85% requirement), and the zinc concentration in the leaching solution was approximately 2.7 g / L.

[0051] Zinc recovery: The zinc-rich leaching solution is transferred to a crystallization vessel, heated and concentrated to 1 / 3 of its original volume, and then naturally cooled to room temperature to precipitate crude zinc sulfate crystals. After filtration, the crystals are dried at 80°C for 2 hours to obtain approximately 520g of crude zinc sulfate (purity approximately 92%). The mother liquor can be returned to the leaching process for recycling.

[0052] Separation and extraction of aluminum and magnesium from zinc leaching residue: (1) Alkali fusion pretreatment: Take 5 kg of zinc leaching residue (dry basis) and mix it with industrial grade sodium hydroxide at a mass ratio of 1:1.2 (i.e., residue:NaOH = 5 kg:6 kg). Place it in a muffle furnace and heat it to 650°C at 5°C / min. Melt at this temperature for 1.5 hours. The alkali fusion process destroys the aluminosilicate structure in the residue, converting aluminum and magnesium into soluble sodium aluminate and sodium magnesiumate (or magnesium oxide).

[0053] (2) Water leaching and desilication: After cooling the alkali melt, crush it and add 80℃ hot water at a solid-liquid ratio of 1:5 (kg / L), stirring and leaching for 1 hour. Filter to obtain an alkaline leachate containing aluminum and magnesium (mainly containing AlO2). - , a small amount of SiO3 2- and Mg 2+ / MgO2 2- ) and desilication residue (mainly silicate residue, which can be used as building material raw material).

[0054] (3) Carbide precipitation of aluminum: Carbon dioxide gas is introduced into the alkaline leaching solution, with the flow rate controlled at 0.5 m³ / s. 3Aeration was maintained at 40±2℃ for 1 hour, with the pH gradually decreasing. When the pH dropped to 10.5-11.0, aluminum hydroxide precipitate began to form. Aeration continued until the pH ≈ 8.5 to ensure complete aluminum precipitation. Filtration yielded an aluminum hydroxide filter cake and a magnesium-containing filtrate. The aluminum hydroxide filter cake was washed with deionized water until neutral and dried at 110℃ for 2 hours, yielding approximately 1.2 kg of aluminum hydroxide product. A portion of the sample was calcined at 550℃ for 2 hours to obtain γ-Al₂O₃, which, according to XRD characterization, showed pure crystal structure and can be used as a material for aluminum-based water-based hydrogen production.

[0055] (4) Recovery of magnesium components, magnesium-containing filtrate (mainly containing Mg) 2+ (And a small amount of carbonate) Heat to 80°C, slowly add 10% sodium hydroxide solution to adjust pH to 12, causing magnesium to precipitate as magnesium hydroxide. Filter, wash the precipitate, and dry at 105°C for 2 hours to obtain approximately 0.35 kg of magnesium hydroxide product (equivalent to approximately 0.14 kg of magnesium content). This magnesium-containing component can be used directly as a raw material for the synthesis of magnesium-based hydrogen storage alloys, or further calcined to obtain magnesium oxide.

[0056] Summary of experimental results: This experiment successfully recovered approximately 520g of crude zinc sulfate (zinc recovery rate of approximately 85%) from 10kg of saturated material, and simultaneously obtained approximately 1.2kg of aluminum hydroxide (aluminum recovery rate of approximately 65%) and approximately 0.35kg of magnesium hydroxide (magnesium recovery rate of approximately 55%). The recovered products are suitable for: (1) zinc sulfate as an industrial raw material; (2) calcination of aluminum hydroxide to obtain γ-Al2O3, which is used in aluminum-based hydrogen production materials; and (3) the magnesium-containing component is used in the preparation of magnesium-based hydrogen storage alloys.

[0057] The saturated material prepared from fly ash raw material pretreated with alkali (such as that used in Example 1) exhibits higher metal extraction efficiency and product purity in actual recycling experiments due to its more stable structure and fewer impurities (aluminum and magnesium recovery rates can be increased by 5-8 percentage points, respectively). This resource recovery process realizes a closed-loop link from environmental functional materials to energy material preparation, which is in line with the green circular concept of the entire life cycle designed in this invention.

Claims

1. A porous soil matrix material, characterized in that, The raw materials include the following parts by weight: 60-85 parts of alkali-modified fly ash 5-15 parts of humus 5-10 parts starch 1-3 parts ammonium sulfate 2-10 parts of quartz sand; The organic matter content of the humic substance is ≥35%, and the pH value of the humic substance is 6.0~7.

5.

2. The porous soil matrix material according to claim 1, characterized in that, The preparation of the alkali-modified fly ash includes: Fly ash is soaked in an alkaline solution, washed until the pH of the filtrate is 7-8, and then dried.

3. The porous soil matrix material according to claim 2, characterized in that, The ratio of fly ash to alkaline solution is 1g:(5~8)mL; The concentration of the alkaline solution is 0.5~2 mol / L; The alkaline solution includes a sodium hydroxide solution; The soaking temperature is 10~30℃, and the soaking time is 7~14 days.

4. The porous soil matrix material according to claim 1, characterized in that, The humus is obtained from fallen leaves through composting.

5. A method for preparing a porous soil matrix material according to any one of claims 1 to 4, characterized in that, Includes the following steps: Alkali-modified fly ash, humus, starch, ammonium sulfate, and quartz sand are mixed to obtain a mixture. After grinding and sieving, the mixture is placed in a granulation device, and then water is sprayed into the mixture to granulate it and obtain a preform. The embryo is placed in a drying device and heat-treated with coke oven flue gas to form a porous structure and solidify. After the reaction is completed, it is cooled to obtain a porous soil matrix material.

6. The method for preparing porous soil matrix material according to claim 5, characterized in that, The sieve opening is 8-10 mesh; The moisture content of the embryo is 25wt%~35wt%.

7. The method for preparing porous soil matrix material according to claim 5, characterized in that, The temperature of the coke oven flue gas is 200~300℃; The heat treatment time is 3 to 8 minutes.

8. The use of the porous soil matrix material according to any one of claims 1 to 4 in removing zinc pollutants from rainwater runoff.

9. The application according to claim 8, characterized in that, The applications include: The porous soil matrix material is placed in the functional layer of the plant retention system to adsorb zinc ions in rainwater runoff. The plant retention system comprises, from top to bottom, a vegetation layer, a planting soil layer, a functional layer, a geotextile layer, and a drainage layer, stacked sequentially.

10. The application according to claim 8, characterized in that, Once the porous soil matrix material becomes saturated with zinc, it is recycled as a resource. The resource recycling method includes: a) Remove and crush the porous soil matrix material after it has been saturated with zinc to obtain powder; b) The powder is leached with sulfuric acid solution to recover the zinc element therein; c) Recover and reuse the metal elements in the leaching residue; The aluminum and magnesium elements contained in the residue are separated and extracted, and used for the preparation of metallic materials.

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