Coal gangue-based porous material as well as preparation method and application thereof in ecological restoration

Abstract

The embodiment of the invention provides a coal gangue-based porous material as well as a preparation method and application thereof in ecological restoration, and belongs to the technical field of resource utilization and ecological restoration. According to the preparation method, coal gangue powder is taken as a raw material and mixed with an adhesive and a foaming agent, and the coal gangue-based porous material with different pore structures is obtained by adding different porous additives and adjusting preset sintering conditions through sintering; wherein different pore channels are formed inside the coal gangue-based porous material through any one or any combination of a high-temperature decomposition reaction, an oxidative combustion reaction, a catalytic reaction and a phase change reaction in the sintering process, and different pore structures are constructed inside and outside the coal gangue-based porous material. The coal gangue-based porous material can be suitable for reconstruction and improvement of soil of various structures by adjusting the pore structure, the porosity of the soil is increased, and the ecological performance of the soil is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of resource utilization and ecological restoration, and particularly relates to a gangue-based porous material and a preparation method thereof and application of the material in ecological restoration. Background Art

[0002] During the construction of ecological civilization in my country, we have entered a strategic direction with carbon reduction as the focus, and a critical period for promoting the synergy and efficiency of pollution reduction and carbon reduction. While the construction of open-pit coal mines in my country has experienced rapid development, ecological and environmental problems have become increasingly prominent. If the coal-based solid waste generated during coal mining cannot be properly treated, it will not only cause a waste of resources, but also have a negative impact on the surrounding ecological environment. For example, acid mine water pollution, land destruction, surface soil peeling, water and soil pollution, etc., will affect the sustainable development of the economy, society and environment and the protection of biodiversity.

[0003] In the process of ecological restoration planning, soil matrix improvement is the key to land reclamation and ecological reconstruction in open-pit coal mining areas. How to fully recycle and reuse solid waste (such as waste slag, crushed stone, tailings, etc.) generated by mining to achieve soil matrix improvement has become a key issue in technical research.

[0004] Domestic and foreign studies have shown that solid waste can be transformed into substances suitable for improving sandy soils in semi-arid areas through microbial digestion. Such substances can increase soil organic matter content, improve degraded soils, and promote plant growth. For example, the unique ecological matrix made by mixing coal gangue with different organic raw materials can significantly increase soil nutrient content and permeability, thereby achieving better water and fertilizer retention. However, most of these studies remain at the experimental accumulation stage, and have not yet made significant progress in the internal mechanism of solid waste modification or the key technologies for effectively controlling its modification.

[0005] In view of this, it is necessary to propose new porous materials using solid waste, such as coal gangue, as raw materials and their preparation methods and apply them to ecological restoration to solve the problems of recycling and reuse of solid waste and effectively improve ecological soil. Summary of the invention

[0006] In order to solve at least one aspect of the above problems and defects in the prior art, the embodiments of the present invention provide a gangue-based porous material and a preparation method thereof and application in ecological restoration. By using different porous additives under different sintering conditions, the gangue-based porous material obtains a pore structure suitable for different soils, thereby achieving soil reconstruction and improvement and increasing soil porosity. The technical solution is as follows:

[0007] According to one aspect of an embodiment of the present invention, a method for preparing a gangue-based porous material is provided.

[0008] The preparation method uses coal gangue powder as raw material and mixes a binder and a foaming agent, and obtains a coal gangue-based porous material with different pore structures by adding different porous additives and adjusting preset sintering conditions. The porous additive undergoes any one of high-temperature decomposition reaction, oxidation combustion reaction, catalytic reaction, phase change reaction or any combination thereof during the sintering process to form different pore channels inside the coal gangue-based porous material and construct different pore structures inside and outside the coal gangue-based porous material.

[0009] In some embodiments, specifically, the porosity aid generates volatile gas through high temperature decomposition reaction during sintering. When the volatile gas escapes, a channel effect is generated inside the gangue-based porous material to form different pore channels, and different pore structures are formed through the different pore channels.

[0010] In some embodiments, further, when pore channels are formed inside the gangue-based porous material, three-dimensional internal pores are formed inside the gangue-based porous material through the pore channels.

[0011] In some embodiments, further, when the pore channel penetrates the gangue-based porous material, surface pores are formed on the outside of the gangue-based porous material through the pore channel.

[0012] In some embodiments, optionally, the different pore structures are any one of a microporous structure, a mesoporous structure, a macroporous structure, or any combination thereof.

[0013] In some embodiments, specifically, the porosity aid generates thermodynamic and material exclusion effects through oxidation combustion reaction during the sintering process, and the thermodynamic and material exclusion effects are used to increase the distribution density and distribution uniformity of the surface pores.

[0014] In some embodiments, specifically, the minerals remaining from the porosity aid during the sintering process are embedded in the interior and / or surface of the coal gangue-based porous material to form a reinforcement structure for supporting different pore structures.

[0015] In some embodiments, specifically, the porosity aid produces a chemical expansion effect through a catalytic reaction or a phase change reaction during the sintering process, and forms a mesoporous structure, a macroporous structure, or a combination thereof inside the gangue-based porous material through the chemical expansion effect.

[0016] In some embodiments, further, as the particle size of the porous additive decreases, more pores with a microporous structure are formed inside and / or outside the gangue-based porous material; as the particle size of the porous additive increases, the connectivity of the pore channels is enhanced, and more pores with a mesoporous structure or a macroporous structure are formed inside and / or outside the gangue-based porous material.

[0017] In some embodiments, specifically, the preset sintering conditions include sintering temperature, sintering time and sintering pressure.

[0018] In some embodiments, further, the sintering temperature affects the firmness of the pore space of the gangue-based porous material by affecting the water evaporation rate during the sintering process; the sintering time affects the uniform distribution of the pore structure of the gangue-based porous material by affecting the melting degree during the sintering process; the connectivity of the pore channels and the formation path of the pore structure are adjusted by adjusting the sintering temperature and sintering time.

[0019] In some embodiments, further, the sintering pressure affects the specific surface area and the porosity of the surface pores of the gangue-based porous material.

[0020] In some embodiments, specifically, the steps of the preparation method include:

[0021] Mixing coal gangue powder, a binder and a foaming agent, wherein the mass percentage of the coal gangue powder is in the range of 50% to 90%, the mass percentage of the binder is in the range of 5% to 30%, and the mass percentage of the foaming agent is in the range of 5% to 20%;

[0022] Mixing coal gangue powder, a binder and a foaming agent with water at a preset solid-liquid ratio to obtain a mixture, wherein the preset solid-liquid ratio ranges from 0.4 to 0.7;

[0023] Adding a porous additive to the mixture in a preset amount to obtain a matrix, wherein the preset amount is the percentage of the mass of the porous additive to the mass of the mixture, and the range of the preset amount is 5% to 50%;

[0024] The matrix is ​​sintered under preset sintering conditions, and a gangue-based porous material is obtained after cooling, wherein the sintering temperature ranges from 600 to 800°C, the sintering time ranges from 100 to 300 minutes, and the sintering pressure ranges from 1.1 to 1.5 times of the atmospheric pressure.

[0025] According to another aspect of the embodiments of the present invention, a gangue-based porous material is provided.

[0026] The gangue-based porous material is obtained by using the preparation method of the gangue-based porous material described in the above aspects. The gangue-based porous material has adjustable pore channels and three-dimensional internal pores inside; the gangue-based porous material has adjustable surface pores outside; the pore structure of the three-dimensional internal pores and the surface pores is any one of a microporous structure, a mesoporous structure, and a macroporous structure, or any combination thereof.

[0027] According to another aspect of the embodiments of the present invention, there is provided an application of a gangue-based porous material in ecological restoration, wherein the gangue-based porous material is a gangue-based porous material obtained according to the preparation method of the gangue-based porous material described in the above aspects.

[0028] In some embodiments, the gangue-based porous material has different pore structures corresponding to different soil properties, and is used to reconstruct the soil structure, increase soil porosity, water holding capacity and microbial growth space.

[0029] The gangue-based porous material and the preparation method thereof and the application thereof in ecological restoration provided by the embodiments of the present invention have at least one or part of the following advantages:

[0030] (1) The gangue-based porous material and its preparation method and application in ecological restoration provided by the embodiments of the present invention use different porous additives to make the sintered gangue-based porous material have different pore structures, and the gangue-based porous materials with different pore structures are used in soils with different ecological requirements to achieve soil reconstruction and improvement, thereby increasing soil porosity;

[0031] (2) The gangue-based porous material and its preparation method and application in ecological restoration provided by the embodiments of the present invention use porous additives of different components or different types. Through the different chemical and physical reactions of these porous additives during the sintering process, different pore channels are formed inside the gangue-based porous material. These pore channels in turn form different pore structures inside and outside the gangue-based porous material.

[0032] (3) The gangue-based porous material and its preparation method and application in ecological restoration provided by the embodiments of the present invention can adjust the pore structure and pore parameters of the gangue-based porous material by controlling the sintering conditions during the sintering process, thereby obtaining a variety of pore structures and improving the chemical stability of the gangue-based porous material, thereby extending its service life and realizing effective recycling and reuse of solid waste;

[0033] (4) The gangue-based porous material provided by the embodiments of the present invention, its preparation method and application in ecological restoration can obtain microporous structure, mesoporous structure and macroporous structure by selecting the type and amount of the porous additive and controlling the sintering conditions, and can be applied to, for example, contaminated soil, sandy soil and sandy soil;

[0034] (5) The gangue-based porous material and its preparation method and application in ecological restoration provided by the embodiments of the present invention can reconstruct and improve the soil structure by returning the prepared gangue-based porous material with different pore structures to the original soil, thereby improving the pore structure of the original soil, effectively making up for the weak resistance to stress in ecologically fragile areas, and contributing to the restoration of vegetation in the original soil;

[0035] (6) The gangue-based porous material and its preparation method and application in ecological restoration provided by the embodiments of the present invention use the prepared gangue-based porous materials with different pore structures for soil structure reconstruction and improvement, thereby improving the pore structure of the original soil, helping to improve and optimize the breeding space of microorganisms in the soil and improving the ecological performance of the soil;

[0036] (7) The gangue-based porous material and its preparation method and application in ecological restoration provided by the embodiments of the present invention use scanning electron microscopy or specific surface area detection to monitor the formation state of the pore structure during the preparation process, and adjust the preparation conditions such as the solid-liquid ratio of the mixture, the type and amount of porous additives, and sintering conditions in real time, thereby effectively ensuring that the pore structure of the prepared gangue-based porous material meets the corresponding soil improvement requirements;

[0037] (8) The gangue-based porous material and its preparation method and application in ecological restoration provided by the embodiments of the present invention remove impurities on the surface of the gangue-based porous material through acid washing or alkali washing to make the pore size of the pore structure smooth and evenly distributed, and control the pH value of the gangue-based porous material, thereby adjusting the soil and microbial properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] These and / or other aspects and advantages of the present invention will become apparent and readily understood from the following description of preferred embodiments in conjunction with the accompanying drawings, in which:

[0039] Figure 1A A schematic diagram of a photograph of the surface of coal gangue powder used according to an embodiment of the present invention;

[0040] Figure 1B According to the embodiment 1 of the present invention and using Figure 1A A schematic diagram of a surface of a gangue-based porous material prepared from gangue powder;

[0041] Figure 2A for Figure 1A SEM microstructure of coal gangue powder;

[0042] Figure 2B According to Example 1 of the present invention, Figure 1B Scanning electron microscope microstructure of coal gangue-based porous materials;

[0043] Figure 3 According to Example 2 of the present invention and using Figure 1A A curve diagram showing the pore volume change rate of the pore structure of the gangue-based porous material prepared from gangue powder as a function of pore size. DETAILED DESCRIPTION

[0044] The technical solution of the present invention is further specifically described below by examples and in conjunction with the accompanying drawings. In the specification, the same or similar reference numerals indicate the same or similar components. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the overall inventive concept of the present invention and should not be construed as a limitation of the present invention.

[0045] By using the solid waste associated with open-pit mines to prepare porous ecological materials and reusing them in spoil dumps, we can effectively improve soil structure, enhance soil activity, and promote the replacement of ecosystems, thereby achieving coordinated development of ecology and economy.

[0046] Theoretically, for different types of soil, the pore structure of gangue-based porous materials can be designed to adapt to the characteristics of various types of soil to the greatest extent. For example, for sandy soil, due to its large particles and strong water permeability, it is suitable to use gangue-based porous materials with larger pores to improve water retention and nutrient storage capacity. For another example, for clay, although it has good water retention capacity, it has poor air permeability. Therefore, it is suitable to use gangue-based porous materials with medium or small pores to improve air permeability, prevent water accumulation, and promote plant root growth. For another example, for loam, its soil characteristics are between sandy soil and clay. It is usually necessary to take into account good water retention and air permeability. It is suitable to use gangue-based porous materials with medium pores to take into account water retention and air permeability to promote plant root development.

[0047] Based on the above theoretical analysis, an embodiment of the present invention provides a method for preparing a gangue-based porous material, which controls the design of the pore structure, pore distribution, pore channels and other parameters of the gangue-based porous material, and obtains a gangue-based porous material with specific pore structure, pore distribution, pore channels and other parameters by controlling the preparation conditions. Gangue-based porous materials with suitable pore structures are used for different soil characteristics, and the gangue solid waste is effectively recycled. By returning the gangue-based porous materials to the original soil, it is beneficial to the reconstruction and improvement of soil structure, improve soil porosity and microbial level, promote plant growth, and maintain sustainable soil utilization.

[0048] Specifically, the preparation method uses coal gangue powder as raw material and mixes a binder and a foaming agent, and obtains coal gangue-based porous materials with different pore structures by adding different porous additives and adjusting preset sintering conditions. The porous additives undergo any one of high-temperature decomposition reaction, oxidation combustion reaction, catalytic reaction, phase change reaction or any combination thereof during the sintering process to form different pore channels inside the coal gangue-based porous material and construct different pore structures inside and outside the coal gangue-based porous material.

[0049] In one example, the process of preparing the gangue-based porous material includes a basic preparation process and a control preparation process. The basic preparation process refers to the preparation steps that must be experienced to complete the preparation of the gangue-based porous material. The control preparation process is a preparation step in the basic preparation process that controls and adjusts the steps that directly or indirectly affect the pore structure, pore distribution, pore channels and other parameters of the gangue-based porous material.

[0050] In one example, the basic preparation process in the process of preparing the coal gangue-based porous material mainly includes the following steps:

[0051] Step S100: crushing and activating the coal gangue to obtain coal gangue powder as a raw material. Preferably, the coal gangue powder is sieved through a 20-mesh sieve to control the particle diameter of the coal gangue powder to be less than or equal to 1 mm;

[0052] Step S200: Mixing coal gangue powder with a binder, a foaming agent, and water in a preset ratio; wherein the ratio of coal gangue powder to the binder and the foaming agent, and the ratio of solid to liquid after addition can affect the formation of the final pore structure by affecting the sintering process (e.g., sintering time, water evaporation during the sintering process, etc.);

[0053] Step S300: adding a porous additive to the mixture obtained in step S200 to obtain a base material of a gangue-based porous material. By adding the porous additive, the fluidity and pore formation process of the mixture can be changed to adjust the pore structure, pore distribution, pore channels and other parameters of the gangue-based porous material finally obtained;

[0054] Step S400: sintering the gangue-based porous material substrate obtained in step S300, wherein the sintering temperature, heating rate, sintering time, sintering pressure, etc. will have different degrees of influence on the melting degree, gas release, high temperature decomposition, combustion of specific components, etc. of the gangue-based porous material substrate during the sintering process, so as to control the pore formation process and the final pore structure;

[0055] Step S500: performing an acid wash treatment or an alkali wash treatment on the sintered coal gangue-based porous material to remove impurities on the surface of the coal gangue-based porous material and in the pores thereof;

[0056] Step S600: During and after the preparation of the gangue-based porous material, the pore structure of the gangue-based porous material is monitored and characterized using scanning electron microscopy (SEM), specific surface area measurement (BET) and other methods to ensure that the pore structure meets the requirements.

[0057] In one example, alternatively, the binder is selected from any one of silica sol, cement, gypsum, epoxy resin, bentonite, lime, or any combination thereof. For example, one material can be used as the binder, preferably cement. For another example, two or more materials can be mixed as the binder, preferably cement and lime are mixed or epoxy resin and bentonite are mixed.

[0058] In one example, alternatively, the foaming agent is selected from any one of hydrogen peroxide, aluminum powder, sodium perborate, sulfobetaine, or any combination thereof. For example, one material can be used as the foaming agent, preferably hydrogen peroxide. For another example, two or more materials can be mixed as the foaming agent, preferably a mixed foaming agent of hydrogen peroxide and aluminum powder.

[0059] In one example, after selecting suitable binders and foaming agents, it is necessary to mix the gangue powder with the binder and foaming agent with water according to a preset ratio to obtain a raw material mixture. Alternatively, in the raw material mixture, taking mass fraction calculation as an example, the content of gangue powder ranges from 50% to 90%, the content of binder ranges from 5% to 30%, and the content of foaming agent ranges from 5% to 20%. At the same time, in the process of adding water and mixing, the solid-liquid ratio is controlled to be in the range of 0.5 to 0.9, where the solid-liquid ratio refers to the ratio of the total mass of gangue powder, binder and foaming agent (when the binder and foaming agent are both solid) to the mass of the added water, or the ratio of the total mass of the solid mixture with gangue powder as the main component to the total mass of the liquid mixture (when there is liquid in the binder and / or foaming agent).

[0060] In one example, further, the adjustment and determination of the solid-liquid ratio belongs to one of the steps in the regulation and preparation process, and the change of the solid-liquid ratio can directly or indirectly affect the changes in parameters such as the pore structure, pore distribution, and pore channels of the gangue-based porous material. In some cases, for example, if the solid-liquid ratio is too high (higher than 0.9), the viscosity of the substrate during the sintering process will be very high, which is not conducive to the formation of pores and pore channels. For another example, if the solid-liquid ratio is too low (lower than 0.5 or lower), the insufficient proportion of solids will make it difficult to form pores. Therefore, by regulating the appropriate solid-liquid ratio, the substrate is presented as a wet slurry with moderate viscosity before sintering, which helps to promote the formation of a uniform pore structure that meets the requirements at different levels, as a whole or on the surface of the substrate. At the same time, the solid-liquid ratio will also affect the drying process after sintering (usually natural drying or drying in a drying equipment with preset drying conditions is required after sintering and acid-base treatment). For example, the solid-liquid ratio of the initial substrate affects the water evaporation and material shrinkage during the final drying, which in turn affects the pore structure eventually formed inside or outside the gangue-based porous material to a certain extent. For example, when the solid-liquid ratio is too low, water evaporation may cause cracks inside the material, thereby changing the pore structure preset during the preparation process or causing the pore structure to be incomplete and uneven.

[0061] In one example, how to add the porous additive, such as the selection of its type, the selection of the reaction mechanism, the mixing of the porous additive of non-single substance and its total dosage, is one of the most critical steps in the regulation and preparation process. Alternatively, the porous additive is generally derived from organic additives, porous small molecule mixtures, reactive minerals, phase change materials, etc. Specifically, the porous additive can be selected from any one of clay, activated carbon, straw, sawdust, expanded graphite or any combination thereof. In the process of preparing coal gangue-based porous materials, the addition process of the porous additive is the most important step affecting the formation of the pore structure of the substrate. Adding different types of porous additives and coordinating the regulation of sintering parameters during the sintering process can effectively control the formation process of the pore channels and the final pores inside the substrate, thereby obtaining coal gangue-based porous materials with different pore structure parameters.

[0062] In one example, specifically, different types of porous additives have different physical and chemical properties. For example, the porous additive itself is usually also a porous material. In terms of physical properties, it has a large specific surface area, a pore distribution with an inherent pore size inside or on its surface, an inherent pore shape, an inherent pore channel morphology, etc. Due to the composition of the porous additive and its porous physical properties, it forms different chemical reactions or physicochemical reactions during the sintering process, such as high-temperature decomposition reaction, oxidation combustion reaction, catalytic reaction, phase change reaction, etc. Therefore, the coal gangue powder mixture (coal gangue powder, binder, foaming agent and water) with different types of porous additives added will produce specific physical and / or chemical reactions during the sintering process, which will cause the substrate to have different pores, pore channels, etc. The formation process and the final pore structure.

[0063] In one example, further, the porous additive will undergo specific physical and / or chemical reactions when participating in the sintering process, and then the substrate will be sintered to form a specific pore structure under the action of the specific physical and / or chemical reactions. For porous materials, they are usually divided into microporous structure (pore diameter <2nm), mesoporous structure (2nm≤pore diameter≤50nm) and macroporous structure (pore diameter>50nm) according to the pore structure, especially the pore size, and by regulating the specific components or specific combination components and dosage of the porous additive, the porous additive can be controlled to produce specific physical and / or chemical reactions during the sintering process of the substrate to form a microporous structure, a mesoporous structure, a macroporous structure or any combination of these three pore structures. For example, the interior of the gangue-based porous material has a pore structure of microporous structure, mesoporous structure, and macroporous structure, and the surface has one of the above three pore structures different from the internal pores. For another example, one of the above three pore structures is formed in layers inside the gangue-based porous material.

[0064] In one example, specifically, the porous additive generates volatile gas through high-temperature decomposition reaction during sintering, and when the volatile gas escapes, a channel effect is generated inside the gangue-based porous material to form different pore channels, and different pore structures are formed through different pore channels. Some organic porous additives, especially small molecule organic porous materials, release gases during high-temperature decomposition that generate a channel effect inside the matrix of the gangue-based porous material, forming fully or partially connected pore channels.

[0065] Furthermore, when the pore channel is formed inside the gangue-based porous material, that is, when the pore channel only partially penetrates the inside of the substrate, three-dimensional internal pores can be formed inside the gangue-based porous material through the pore channel. The particles of the porous additive are dispersed and filled inside the substrate, and are decomposed at high temperature after sintering. With the decomposition of the components and the volatilization of the decomposed gas, it leaves the substrate at high temperature, leaving a certain pore structure or a combination of more than one pore structure inside the substrate, thereby constructing a three-dimensional pore network inside the gangue-based porous material.

[0066] Furthermore, when the pore channel penetrates the gangue-based porous material, surface pores are formed on the outside of the gangue-based porous material through the pore channel. Some organic porous additives (such as sawdust, straw, etc.) undergo high-temperature decomposition during the sintering process, and volatile gases (such as CO 2 , CH 4 When volatile gases escape, they will leave pore structures on the surface of the substrate of the gangue-based porous material. As the volatile gases continue to escape, a large number of regular or irregular surface pores will be formed on the surface of the substrate. This type of surface pore is an adsorptive pore with a high specific surface area, which is generally used to quickly adsorb harmful components or pollutants in the soil in the early stage of mixing soil.

[0067] During the high-temperature decomposition process of the porous additive, by adjusting the type and chemical composition of the porous additive, especially by screening based on the particle size of the porous additive itself, a pore structure of microporous structure, mesoporous structure, macroporous structure or any combination of these three pore structures can be obtained.

[0068] In one example, specifically, the porous additive generates thermodynamic and material exclusion effects through oxidation combustion reaction during the sintering process, and the thermodynamic and material exclusion effects are used to improve the distribution density and uniformity of surface pores. This thermodynamic and material exclusion effect guides the change of the surface pores of the substrate during sintering, so that the substrate gradually forms dense and uniform pores on its surface, which is used to adjust and control the distribution of surface pores to adapt to soils with different characteristics and soils with different modification requirements.

[0069] In one example, specifically, the minerals remaining in the porous additive during the sintering process are embedded in the interior and / or surface of the coal gangue-based porous material to form a reinforcing structure for supporting different pore structures. During the sintering process, as part of the components in the porous additive undergo high-temperature decomposition or oxidative combustion to generate gas escaping, the substances that do not participate in the reaction or the residual substances in the reaction will remain in the substrate. The minerals in the porous additive, such as silicates or carbonates in clay, will eventually remain in the substrate, and a part of the mineral residues will be embedded in the surface of the substrate, a certain layer inside the substrate, or in the pore channels formed inside the substrate. The embedding of such mineral residues forms a reinforcing structure at the position of the pore channel and / or pore structure, providing strength support for the pore channel and pore structure, and preventing the pore channel from breaking or collapsing and the pore structure from breaking.

[0070] In one example, specifically, the porous additive produces a chemical expansion effect through a catalytic reaction or a phase change reaction during the sintering process, and forms one of a mesoporous structure and a macroporous structure or a combination thereof inside the gangue-based porous material through the chemical expansion effect. The gangue raw material itself has some active oxides (such as silicon oxide, aluminum oxide, etc.), and this active oxide can react chemically with some components in the porous additive (such as silicates in clay). This type of chemical reaction is prone to produce a chemical expansion effect, which is accompanied by the expansion effect and helps to promote the formation and development of the pore structure inside the substrate. Further controlling the reaction components and the reaction rate can adjust the specific pore size of the pore structure finally formed inside the gangue-based porous material and the distribution form of the pore structure with different pore sizes. For example, the process of the expansion reaction or phase change reaction is adjusted by coordinating the control of the sintering parameters and the control of the sintering process, so that internal pores with different pore sizes (microporous structure, mesoporous structure or macroporous structure) are formed at different levels inside the gangue-based porous material.

[0071] In one example, specifically, as the particle size of the porous additive decreases, more pores with a microporous structure are formed inside and / or outside the gangue-based porous material; as the particle size of the porous additive increases, the connectivity of the pore channels is enhanced, and more pores with a mesoporous structure or a macroporous structure are formed inside and / or outside the gangue-based porous material. The particle size of the porous additive has a certain influence on the distribution and size of the pores. Porous additives with small particle sizes help to produce more pores with a microporous structure, while porous additives with large particle sizes help to expand the pore size and connect or communicate between pore channels, thereby being more conducive to forming pores with a mesoporous structure or a macroporous structure.

[0072] In one example, when the gangue-based porous material is required to have a microporous structure. Preferably, the porous additive is a porous small molecule mixture, such as any one of clay, straw, sawdust or any combination thereof. The porous small molecule mixture is easily decomposed rapidly by high temperature during the sintering process due to its short molecular chain and small molecular cluster. This allows the substrate to quickly construct microporous channels inside it during the sintering process, and then construct a microporous structure on the surface of the substrate, ultimately forming a gangue-based porous material with a uniform microporous structure.

[0073] In one example, when the gangue-based porous material is required to have a mesoporous structure. Preferably, the porous additive is selected from any one of organic additives, porous materials, reactive minerals, phase change materials, or any combination thereof. Among them, organic additives or phase change materials are more likely to undergo phase change under the influence of high temperature during sintering, and porous materials are more likely to decompose at high temperature during sintering (since porous materials are usually macromolecular organic matter or organic mixtures with complex components, the high temperature decomposition mechanism of porous materials is different from the high temperature decomposition mechanism of small molecule mixtures), and reactive minerals help to improve the efficiency of their catalytic reactions due to high temperature conditions during sintering. Whether it is a phase change reaction, high temperature decomposition of macromolecular organic matter or a catalytic reaction, a large number of bubbles will be rapidly generated inside and on the surface of the substrate, and these bubbles will allow the substrate to quickly construct mesoporous channels inside it during the sintering process, and then construct a mesoporous structure on the surface of the substrate, and finally form a gangue-based porous material with a uniform mesoporous structure.

[0074] In one example, when the gangue-based porous material is required to have a macroporous structure, preferably, the porous additive is a phase change material or an expansion material, and more preferably, expanded graphite can be selected. Expanded graphite will rapidly produce an expansion reaction under the influence of high temperature during the sintering process, and under its expansion, a larger pore space can be formed to construct a macroporous channel inside the substrate, and then a macroporous structure is constructed on the surface of the substrate, and finally a gangue-based porous material with a uniform macroporous structure is formed.

[0075] In one example, further, the amount of the porosity aid used will also affect the formation of pores and pore channels of the substrate during sintering. The appropriate use of the porosity aid can promote the formation of an ideal pore structure and pore channels that meet the requirements of the substrate during the sintering process. If the amount of the porosity aid is excessive or insufficient, it may cause the substrate to have an uneven pore structure, deform or block the pore channels, and the pore size cannot grow as expected or produce a dense structure during the sintering process.

[0076] By adjusting the type and amount of the porous additive, the formation process of pores and pore channels in the substrate during sintering can be effectively adjusted, thereby controlling the substrate to ultimately form parameters such as pore structure, pore distribution, and porosity that meet the requirements.

[0077] In one example, alternatively, mechanical force can be used, for example, by uniformly dispersing the porous additive in the base material through mechanical stirring when mixing the raw materials and adding the porous additive, and by selectively controlling the particle size of the porous additive, the distribution state of the pore structure inside and on the surface of the finally obtained coal gangue-based porous material can be further improved.

[0078] Furthermore, in practical applications, the gangue-based porous material may be an ecological restoration material having only one type of pore structure, such as the single microporous structure, mesoporous structure or macroporous structure mentioned above. At the same time, the gangue-based porous material may also be an ecological restoration material having a mixed pore structure. For example, the same gangue-based porous material has different porous layers and different pore structures at different porous layers, that is, the pore channels formed inside it may be uneven, which may allow it to have a pore distribution such as a microporous structure at a certain porous layer, while at the same time having a mesoporous structure with a controllable pore size distribution at other porous layers.

[0079] In one example, the control of the sintering process is another most critical step in the preparation process. Mechanistically, the preset sintering conditions, such as sintering temperature, heating or heating rate, sintering equipment, sintering pressure and other factors, will have an important influence on the final pore structure of the substrate.

[0080] Specifically, the sintering temperature affects the firmness of the pore space of the gangue-based porous material by affecting the evaporation rate of water during the sintering process; the sintering time affects the uniform distribution of the pore structure of the gangue-based porous material by affecting the melting degree during the sintering process; the connectivity of the pore channels and the formation path of the pore structure are adjusted by adjusting the sintering temperature and sintering time. Furthermore, the sintering pressure affects the specific surface area and the porosity of the surface pores of the gangue-based porous material.

[0081] For example, if the sintering temperature is too high, it will accelerate the evaporation of water, resulting in the formation of cracks inside the substrate, which will affect the stable generation of pore channels according to the preset shape. For another example, if the sintering temperature is too low, it will prolong the time for the pore space to form. If the pore space is formed slowly, the final pore structure will be weak. For another example, quickly increasing the sintering temperature may cause the surface of the substrate particles to melt rapidly, thereby affecting the formation of pore channels and pores inside. At the same time, by adjusting the sintering temperature and sintering time, the pore formation path and the connectivity between the pore channels can be adjusted more accurately, so as to obtain pores with specific structures at specific positions of the substrate.

[0082] After a lot of experimental verification and analysis, it is known that appropriately reducing the heating or temperature rise rate can promote a more complete reaction between the components in the substrate (coal gangue powder, binder, foaming agent and porous additive). This can effectively promote the diffusion and rearrangement between the substrate particles, thereby forming a more uniform pore structure. Different sintering parameters and sintering conditions can be controlled by different sintering equipment. In addition, if a certain pressure is applied during the sintering process, it will also help to form a denser pore distribution.

[0083] In one example, alternatively, controlling the temperature gradient change during the sintering process, combined with controlling the cooling rate of the cooling process after sintering, can also control the pore structure morphology, pore channel distribution, and pore distribution state of the gangue-based porous material. For example, by adjusting the heating rate of the sintering process, the volatilization of gas and the dispersion of water vapor in the substrate can be controlled, thereby affecting the formation path of the pores. For another example, when cooling after sintering, increasing the cooling rate can promote the quenching effect inside the gangue-based porous material to a certain extent, thereby helping to form a small and uniform pore structure inside it. On the contrary, slow cooling at a reduced cooling rate helps to form a larger mesoporous structure or a macroporous structure.

[0084] In one example, alternatively, the sintering temperature in the preset sintering conditions ranges from 600 to 1500°C, the sintering time ranges from 60 to 300 min, and the sintering pressure ranges from 1.1 to 1.5 times the atmospheric pressure. Within the above parameter range, a gangue-based porous material that meets most soil remediation requirements can usually be obtained. Further, when preparing targeted gangue-based porous materials for a certain type of soil characteristics, optimization adjustments can be made within the above parameter range, and pore characterization monitoring can be performed through detection equipment during the preparation process. Through the mutual adjustment of each parameter range and experimental verification, a gangue-based porous material with a specific pore structure that can repair a specific soil structure or meet specific remediation needs can be obtained.

[0085] In one example, alternatively, the gangue-based porous material obtained by sintering and cooling usually needs to be cleaned for the pores or pore channels. For the acid wash treatment, diluted hydrochloric acid or sulfuric acid can be selected, and for the alkaline wash treatment, diluted sodium hydroxide or calcium hydroxide can be selected. On the one hand, the acid wash treatment or the alkaline wash treatment is mainly to clean the pores in the gangue-based porous material. For example, the impurities in the pores can be removed by dissolving with diluted acid or alkali so that the pores or pore channels present a smooth and uniform shape as a whole. On the other hand, the pH value of the gangue-based porous material can be further controlled by acid wash or alkaline wash, so as to be suitable for soil improvement with requirements for pH value.

[0086] In one example, alternatively, in each embodiment of the present invention, gangue in an open-air dump is used as a raw material to prepare a gangue-based porous material, and then the gangue-based porous material is reused as an ecological restoration material in the open-air dump to reconstruct the soil structure of the open-air dump, so as to improve the pore structure, pore distribution and porosity of the soil in the open-air dump, and promote the growth and reproduction of microorganisms in the soil. The specific regulation and preparation process and the key regulation steps and parameters therein are described in more detail below through Examples 1 and 2.

[0087] In one example, preferably, the main chemical components of the coal gangue in the open-air dump and the proportions of each chemical component are shown in Table 1. Figure 1A , showing the surface morphology of the gangue powder after the gangue is activated and crushed (obtained by photographing with a high-resolution camera device). The following Examples 1 and 2 all use the gangue as a raw material for preparing the gangue-based porous material.

[0088] Table 1 Main chemical components and their proportions of coal gangue

[0089] chemical composition <![CDATA[Al 2 THE 3 ]]> <![CDATA[SiO 2 ]]> CaO <![CDATA[Fe 2 THE 3 ]]> MgO Component mass fraction About 20.43% About 61.35% About 2.32% About 4.28% About 2.52%

[0090] Example 1

[0091] Example 1 A gangue-based porous material with a microporous structure is obtained by adjusting and controlling the important parameters and important conditions in the preparation process. Gangue-based porous materials with microporous structures are generally suitable for the restoration of some heavy metal-contaminated soils. The contaminated soil has a dense structure and high pollution, resulting in low biological activity. Because the microporous structure has a large specific surface area, its adsorption performance is improved. After the gangue-based porous material with a microporous structure adsorbs heavy metals, various functional groups (such as hydroxyl groups, alcohol groups, etc.) on its surface can form coordination or ion exchange with heavy metal ions, thereby reducing the heavy metal concentration in the soil. In heavy metal-contaminated soils, the permeability, water retention rate and nutrient status of the soil can be improved, which is conducive to plant growth. At the same time, the microporous structure can also provide a suitable living space for microorganisms, which is conducive to improving microbial activity. For the complete basic preparation process, refer to the aforementioned steps S100 to S600, and only the regulation preparation process is described in detail here.

[0092] In one example, in a mixture of coal gangue powder, a binder and a foaming agent, the mass percentage of coal gangue powder ranges from 80% to 90%, the binder is cement and the mass percentage of cement ranges from 5% to 10%, the foaming agent is hydrogen peroxide and the mass percentage of hydrogen peroxide ranges from 5% to 10%; water is added and mixed according to a first solid-liquid ratio to form a mixture, and the first solid-liquid ratio ranges from 0.5 to 0.7; clay is selected as the porous additive, and the amount of clay added ranges from 5% to 10% of the mass of the mixture; the sintering temperature ranges from 650 to 800°C, and the sintering time ranges from 100 to 150 minutes.

[0093] In one example, preferably, the mass percentage of coal gangue powder is 82%, the mass percentage of cement is 10%, and the mass percentage of hydrogen peroxide is 8%; the first solid-liquid ratio is 0.6; the amount of clay added is 8% of the mass of the mixture; the sintering temperature is 700°C, and the sintering time is 120 minutes; and after the sintering process is completed, alkaline washing treatment is performed using sodium hydroxide solution.

[0094] See also Figure 1B , showing the use of Figure 1A The surface morphology of the gangue-based porous material prepared by the gangue powder of Example 1 is shown in the photograph (obtained by taking pictures with a high-resolution camera). Figure 2A and Figure 2B , respectively show the obtained by scanning electron microscope (SEM) equipment Figure 1A The microstructure of coal gangue powder and Figure 1B Use Figure 1AThe microstructure of the gangue-based porous material prepared by the gangue powder in Example 1. The pore structure of the gangue-based porous material is monitored and characterized by scanning electron microscopy (SEM), specific surface area detection (BET) and other methods. It can be determined that the gangue-based porous material obtained in Example 1 has a uniform microporous structure, especially a dense microporous structure on its surface, wherein the micropore diameter is less than 2nm. The overall porosity of the gangue-based porous material reaches 70%, and the water holding rate reaches 40%.

[0095] Furthermore, combined with Figure 1A-Figure 2B It can be seen that the gangue-based porous material prepared in Example 1 has more and more obvious pore structures, and the pore distribution and pore morphology of the pore structure show more obvious regularity and uniformity. The gangue-based porous material is reused in the originally damaged or polluted soil to reconstruct its soil structure, which helps to improve the soil moisture retention capacity and enhance the soil permeability, thereby maintaining the moisture and nutrients of the soil to a greater extent, and further contributes to the growth of plants and the survival and reproduction of soil microorganisms.

[0096] Example 2

[0097] Example 2 A gangue-based porous material with a mesoporous structure is obtained by adjusting and controlling the preparation process and the key parameters and key conditions in the preparation process. Gangue-based porous materials with a mesoporous structure are generally suitable for soil reconstruction of sandy loam, and sandy soil generally leaks water and fertilizer and has low biological activity. The use of mesoporous gangue-based porous materials for sandy soil can effectively retain organic matter, water, etc. in the soil, while increasing the habitat space of microorganisms, thereby promoting plant growth and accelerating ecological recovery. For the complete basic preparation process, please refer to the aforementioned steps S100 to S600, and only the regulation and preparation process is described in detail here.

[0098] In one example, in a mixture of coal gangue powder, a binder and a foaming agent, the mass percentage of coal gangue powder ranges from 70% to 90%, the binder is cement and the mass percentage of cement ranges from 5% to 20%, the foaming agent is hydrogen peroxide and the mass percentage of hydrogen peroxide ranges from 5% to 10%; water is added and mixed according to a second solid-liquid ratio to form a mixture, and the second solid-liquid ratio ranges from 0.4 to 0.6; activated carbon is selected as a porous additive, and the amount of activated carbon added ranges from 20% to 40% of the mass of the mixture; the sintering temperature ranges from 600 to 700°C, and the sintering time ranges from 150 to 250 min.

[0099] In one example, preferably, the mass percentage of coal gangue powder is 80%, the mass percentage of cement is 14%, and the mass percentage of hydrogen peroxide is 6%; the first solid-liquid ratio is 0.5; the amount of activated carbon added is 30% of the mass of the mixture; the sintering temperature is 650°C, and the sintering time is 200min; and after the sintering process is completed, a hydrochloric acid solution is used for pickling.

[0100] In one example, specifically, as described above, the main feature of the porous additive is that it has a high porosity, uniform pore size, and certain chemical stability. The activated carbon selected for use in Example 2 is mainly because it has a high-quality pore structure, and sintering with the substrate can effectively help the substrate to form a pore network or pore channel with a mesoporous morphology. This pore network or pore channel with a mesoporous morphology can effectively promote the connectivity between the pores of the substrate, and can also effectively adjust the pore size and the shape of the hole. In addition, activated carbon will form a large amount of cavities and gases during sintering, which effectively promotes the rapid improvement of the porosity of the substrate.

[0101] Furthermore, activated carbon itself has both mesoporous and microporous structures. The mesoporous structure of activated carbon helps to increase the air permeability and water retention of the soil, and also increases the soil's ability to adsorb fertilizers. The microporous structure of activated carbon can adsorb harmful substances in the soil and is conducive to the activity and reproduction of soil microorganisms.

[0102] Furthermore, controlling the amount of activated carbon can also effectively control the final formation of a mesoporous structure of the substrate. For example, if the amount of activated carbon added increases, the porosity of the gangue-based porous material will increase, and its pore size will shrink to become a microporous structure. Therefore, when adding a porous additive, it is necessary to perform experimental optimization and monitoring with the help of equipment such as a scanning electron microscope to determine the optimal amount of the porous additive, so as to ensure that the pore structure parameters that meet the requirements are obtained.

[0103] The pore structure of the gangue-based porous material was monitored and characterized by scanning electron microscopy (SEM), specific surface area measurement (BET), etc. It can be determined that the gangue-based porous material obtained in Example 2 has a uniform mesoporous structure, wherein the pore size of the mesopores ranges from 3 to 4 nm. The overall porosity of the gangue-based porous material reaches 70%, and the water holding rate reaches 10%.

[0104] See also Figure 3 , shows that Example 2 uses Figure 1A The pore size distribution diagram of the pore structure of the gangue-based porous material prepared from the gangue powder. Specifically, Figure 3 The horizontal axis represents the pore size of the gangue-based porous material, and the vertical axis represents the rate of change of the pore volume within the logarithmic pore size interval, where the logarithmic pore size interval is expressed by “dV / dlogW” (cm3 ·g -1 ·nm -1 ) is determined, and the curve in the figure is the pore volume change rate curve of the adsorptive pores on the surface of the coal gangue-based porous material. Generally, pore size refers to the size of the pores, pore volume refers to the total volume of all pores, and porosity refers to the ratio of pore volume to total solid volume. Analysis Figure 3 It can be seen that the pore volume is larger when the pore diameter is 2 to 4 nm, that is, the gangue-based porous material forms a mesoporous structure on the surface.

[0105] In the actual soil reconstruction process, specifically, the pore size determines the mobility of water and nutrients. Large pore size (mesoporous structure or macroporous structure) can quickly drain water and has good air circulation. Therefore, for clay soils and soils with poor water and air circulation, coal gangue-based porous materials with mesoporous or macroporous structures are mainly prepared as ecological restoration materials. Small pore size is conducive to the retention of nutrients and water. For soils with severe water and fertilizer loss, coal gangue-based porous materials with smaller pore size and microporous structure are mainly prepared as ecological restoration materials.

[0106] Furthermore, pore volume is mainly an overall parameter about the pore state of porous materials. Pores of different sizes and pore size distribution will affect the pore volume. At the same time, a higher porosity means that the material has more pores inside and has a suitable pore size distribution, which effectively promotes the formation of porous materials with higher processing efficiency.

[0107] The present invention also regulates the pore structure of the gangue-based porous material through some other examples of preparation experiments. Referring to Table 2, the average values ​​of the pore properties of the gangue raw materials and the gangue-based porous materials under microporous structure, mesoporous structure and macroporous structure are summarized.

[0108] Table 2 Porosity properties of gangue raw materials and gangue-based porous materials with different pore structures

[0109]

[0110] Compared with the initial gangue powder raw material, the pore structure is improved and the parameters of the pore structure are controlled by regulating the preparation process, so that a gangue-based porous material with a controllable pore structure suitable for a variety of soil remediation can be obtained. In particular, the porosity and water holding capacity have been significantly improved, which has a good water retention effect on soil remediation.

[0111] In addition, it should be noted that the changes in important parameters during the preparation process will directly affect whether the substrate can eventually form a pore structure that meets the requirements. For example, the first solid-liquid ratio, the composition and dosage of the porous additive, the sintering conditions, etc. in Example 1 can only ensure that the pore structure within the microporous structure range of Example 1 is obtained. When it is necessary to adjust the specific pore size range, pore distribution, and pore channels, it is necessary to conduct repeated experiments and use equipment such as scanning electron microscopes to monitor and characterize during the basic preparation process until a pore structure that meets the requirements is obtained.

[0112] Another aspect of the embodiments of the present invention further provides a gangue-based porous material, which is obtained using the method for preparing the gangue-based porous material of the above aspects and embodiments thereof. The gangue-based porous material has an adjustable pore channel and / or pore structure inside, and an adjustable surface pore structure on the surface of the gangue-based porous material. The specific pore structure adjustment method, adjustment mechanism, and specific implementation process for specific conditions that may affect the formation of the pore structure can be referred to the previous content, and will not be repeated here.

[0113] Another aspect of the embodiments of the present invention also provides an application of a gangue-based porous material in ecological restoration. The gangue-based porous material is obtained according to the above aspects and the preparation methods of each embodiment. Specifically, the gangue-based porous material has different pore structures corresponding to different soil properties, and is used to reconstruct the soil structure, increase soil porosity, water holding capacity and microbial growth space.

[0114] The gangue-based porous material and the preparation method thereof and the application thereof in ecological restoration provided by the embodiments of the present invention have at least one or part of the following advantages:

[0115] (1) The gangue-based porous material and its preparation method and application in ecological restoration provided by the embodiments of the present invention use different porous additives to make the sintered gangue-based porous material have different pore structures, and the gangue-based porous materials with different pore structures are used in soils with different ecological requirements to achieve soil reconstruction and improvement, thereby increasing soil porosity;

[0116] (2) The gangue-based porous material and its preparation method and application in ecological restoration provided by the embodiments of the present invention use porous additives of different components or different types. Through the different chemical and physical reactions of these porous additives during the sintering process, different pore channels are formed inside the gangue-based porous material. These pore channels in turn form different pore structures inside and outside the gangue-based porous material.

[0117] (3) The gangue-based porous material and its preparation method and application in ecological restoration provided by the embodiments of the present invention can adjust the pore structure and pore parameters of the gangue-based porous material by controlling the sintering conditions during the sintering process, thereby obtaining a variety of pore structures and improving the chemical stability of the gangue-based porous material, thereby extending its service life and realizing effective recycling and reuse of solid waste;

[0118] (4) The gangue-based porous material provided by the embodiments of the present invention, its preparation method and application in ecological restoration can obtain microporous structure, mesoporous structure and macroporous structure by selecting the type and amount of the porous additive and controlling the sintering conditions, and can be applied to, for example, contaminated soil, sandy soil and sandy soil;

[0119] (5) The gangue-based porous material and its preparation method and application in ecological restoration provided by the embodiments of the present invention can reconstruct and improve the soil structure by returning the prepared gangue-based porous material with different pore structures to the original soil, thereby improving the pore structure of the original soil, effectively making up for the weak resistance to stress in ecologically fragile areas, and contributing to the restoration of vegetation in the original soil;

[0120] (6) The gangue-based porous material and its preparation method and application in ecological restoration provided by the embodiments of the present invention use the prepared gangue-based porous materials with different pore structures for soil structure reconstruction and improvement, thereby improving the pore structure of the original soil, helping to improve and optimize the breeding space of microorganisms in the soil and improving the ecological performance of the soil;

[0121] (7) The gangue-based porous material and its preparation method and application in ecological restoration provided by the embodiments of the present invention use scanning electron microscopy or specific surface area detection to monitor the formation state of the pore structure during the preparation process, and adjust the preparation conditions such as the solid-liquid ratio of the mixture, the type and amount of porous additives, and sintering conditions in real time, thereby effectively ensuring that the pore structure of the prepared gangue-based porous material meets the corresponding soil improvement requirements;

[0122] (8) The gangue-based porous material and its preparation method and application in ecological restoration provided by the embodiments of the present invention remove impurities on the surface of the gangue-based porous material through acid washing or alkali washing to make the pore size of the pore structure smooth and evenly distributed, and control the pH value of the gangue-based porous material, thereby adjusting the soil and microbial properties.

[0123] Although some embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the present general inventive concept, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for preparing a coal gangue-based porous material, characterized in that: Gangue powder is used as raw material and mixed with a binder and a foaming agent, and different porous additives are added and the preset sintering conditions are adjusted to obtain gangue-based porous materials with different pore structures through sintering; Among them, the porous additive forms different pore channels inside the gangue-based porous material and constructs different pore structures inside and outside the gangue-based porous material through any one of high-temperature decomposition reaction, oxidation combustion reaction, catalytic reaction, phase change reaction or any combination thereof during the sintering process.

2. The preparation method according to claim 1, characterized in that: The porous additive generates volatile gas through high-temperature decomposition reaction during sintering. When the volatile gas escapes, a channel effect is generated inside the gangue-based porous material to form different pore channels, and the different pore structures are formed through the different pore channels. When the pore channels are formed inside the gangue-based porous material, three-dimensional internal pores are formed inside the gangue-based porous material through the pore channels; When the pore channel penetrates the gangue-based porous material, surface pores are formed on the outside of the gangue-based porous material through the pore channel; The different pore structures are any one of microporous structure, mesoporous structure and macroporous structure or any combination thereof.

3. The preparation method according to claim 2, characterized in that: The porous auxiliary agent generates thermal power and material removal effect through oxidation combustion reaction during the sintering process, and the thermal power and material removal effect are used to improve the distribution density and distribution uniformity of the surface pores.

4. The preparation method according to claim 2, characterized in that: The minerals remaining in the porosity aid during the sintering process are embedded in the interior and / or surface of the gangue-based porous material to form a reinforcement structure for supporting the different pore structures.

5. The preparation method according to claim 1, characterized in that: The porous auxiliary agent generates a chemical expansion effect through a catalytic reaction or a phase change reaction during the sintering process, and forms a mesoporous structure, a macroporous structure or a combination thereof inside the gangue-based porous material through the chemical expansion effect.

6. The preparation method according to any one of claims 1 to 5, characterized in that: As the particle size of the porous auxiliary agent decreases, more pores with a microporous structure are formed inside and / or outside the gangue-based porous material; As the particle size of the porosity aid increases, the connectivity of the pore channels is enhanced, and more pores having a mesoporous structure or a macroporous structure are formed inside and / or outside the gangue-based porous material.

7. The preparation method according to claim 6, characterized in that: The preset sintering conditions include sintering temperature, sintering time and sintering pressure; The sintering temperature affects the firmness of the pore space of the gangue-based porous material by affecting the water evaporation rate during the sintering process; The sintering time affects the uniform distribution of the pore structure of the gangue-based porous material by affecting the melting degree during the sintering process; By adjusting the sintering temperature and sintering time, the connectivity of the pore channels and the formation path of the pore structure are adjusted; The sintering pressure affects the specific surface area and the porosity of the surface pores of the gangue-based porous material.

8. The preparation method according to claim 7, characterized in that: The steps of the preparation method include: Mixing coal gangue powder, a binder and a foaming agent, wherein the mass percentage of the coal gangue powder is in the range of 50% to 90%, the mass percentage of the binder is in the range of 5% to 30%, and the mass percentage of the foaming agent is in the range of 5% to 20%; Adding water to mix the gangue powder, the binder and the foaming agent at a preset solid-liquid ratio to obtain a mixture, wherein the preset solid-liquid ratio ranges from 0.4 to 0.7; Adding a porous auxiliary agent in a preset amount to the mixture to obtain a matrix, wherein the preset amount is the percentage of the mass of the porous auxiliary agent to the mass of the mixture, and the range of the preset amount is 5% to 50%; The matrix is ​​sintered under preset sintering conditions, and a gangue-based porous material is obtained after cooling, wherein the sintering temperature ranges from 600 to 800° C., the sintering time ranges from 100 to 300 minutes, and the sintering pressure ranges from 1.1 to 1.5 times the atmospheric pressure.

9. A coal gangue-based porous material obtained by the preparation method according to any one of claims 1 to 8, characterized in that: The gangue-based porous material has adjustable pore channels and three-dimensional internal pores inside; The gangue-based porous material has adjustable surface pores on the outside; The pore structure of the three-dimensional internal pores and the surface pores is any one of a microporous structure, a mesoporous structure, and a macroporous structure, or any combination thereof.

10. Application of a gangue-based porous material in ecological restoration, wherein the gangue-based porous material is The gangue-based porous material according to claim 9 or the gangue-based porous material obtained according to the preparation method of any one of claims 1 to 8, characterized in that: The gangue-based porous material has different pore structures corresponding to different soil characteristics, and is used to reconstruct the soil structure, increase the soil porosity, water holding capacity and microbial growth space.

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