Method for in-situ synthesis of organic modified porous functional material by using coal gangue

Abstract

The invention relates to the technical field of coal gangue utilization, and provides a method for in-situ synthesis of an organic modified porous functional material by using coal gangue, which comprises the following steps: crushing and sieving coal gangue, and calcining the powder at 100-1000 DEG C to obtain layered silicate minerals; the preparation method comprises the following steps: mixing 1-10g of layered silicate minerals, 5-50g of soluble silicate and / or soluble silicic acid, 3-30g of a metal compound and 40-400ml of deionized water, stirring, and carrying out ultrasonic treatment reaction to obtain a suspension A; adding a complexing agent, stirring to obtain a precursor solution, transferring the precursor solution into a closed reactor, and reacting at the temperature of 50-400 DEG C and the pressure of 5-30 MPa to obtain a mixed product containing solid and liquid; performing solid-liquid separation to obtain a solid organic modified porous functional material; and spraying 1-3wt% of potassium permanganate aqueous solution through a nozzle. The pore is small, the average control reaches the nanoscale, metal elements, carbon and other components are effectively utilized, waste of valuable metal and carbon is avoided to a great extent, and the method is suitable for industrial production.

Description

Technical Field

[0001] This application relates to the technical field of coal gangue utilization, and specifically relates to a method for in-situ synthesizing an organically modified porous functional material using coal gangue. Background Art

[0002] After multiple coal washing processes, a large amount of solid waste such as coal gangue is generated. Coal gangue is a black-gray rock with a low carbon content (10%-30%) and harder than coal, usually accounting for about 10-20% of coal production. Coal gangue solid waste has become the bulk solid waste with the largest output and the lowest comprehensive utilization rate in China at present. The accumulation of a large amount of solid waste will not only pollute the air and water, but also cause safety problems, which has attracted great attention from society.

[0003] Coal gangue mainly consists of kaolinite, quartz, calcite, pyrite and illite, and contains a certain amount of organic matter and a small amount of mica. Its main elements include Si, Al, C, Ca, Fe, Mg, K, etc. In the past few decades, a large amount of research has been carried out on the utilization of coal gangue, mainly focusing on landfilling, building material production, energy industry and agriculture, etc. Nevertheless, achieving high-value utilization of coal gangue remains a challenge. In the current context of carbon peaking and carbon neutrality, it is crucial to achieve efficient and green utilization of coal gangue with low-carbon economy.

[0004] The results of mineral composition analysis show that the components of coal gangue vary with its geographical location. However, most coal gangue is mainly composed of a hydrated aluminosilicate clay mineral, kaolinite (Al2O3·2SiO2·2H2O), in which SiO2 and Al2O3 usually account for more than 80% of the overall composition. Clay minerals such as kaolinite are 1:1 or 1:2 type nanolayered silicate minerals composed of silicon-oxygen tetrahedra and metal-oxygen octahedra. The silicon-oxygen tetrahedra and metal-oxygen octahedra are connected by Si-O-Si and Si-O-M (M: Al, Fe, Mg) bonds to form a nanosheet structure. For example, Chinese Patent CN115196640A discloses a method for preparing a mesoporous silica material using coal gangue and its preparation method. The coal gangue-based silicon source, organic carboxylic acid, anhydrous organic alcohol, and surfactant are mixed and reacted, and a mesoporous material is prepared through a series of steps such as self-assembly treatment, centrifugation, drying, activation with an inorganic strong acid solution, and calcination. However, this method uses the silicon species extraction solution obtained after the coal gangue, a solid waste, is subjected to acid washing for dealumination treatment under stirring and reflux, activation treatment under high temperature and high pressure (subcritical) conditions with an inorganic strong base solution, and dissolution treatment with an inorganic strong acid solution as the silicon source. That is, the coal gangue needs to be subjected to processes such as acid washing and alkali treatment before being used as a raw material. With the selective and appropriate introduction of organic alcohol and organic carboxylic acid, combined with solvothermal self-assembly, the hydrolysis-polymerization degree of silicon species and its surface hydroxyl content are regulated, promoting its cooperative self-assembly with a block copolymer nonionic surfactant, and through high-temperature hydrothermal polymerization treatment under conditions where the pH value in the strong acid solution is close to the isoelectric point of silica, a mesoporous silica material with a highly uniform mesoporous channel structure and high hydrothermal stability is prepared; it is modified repeatedly with strong acids, strong bases, and other additives, the process is complex, the cross-use of acids and bases leads to a significant increase in consumption, and it is only utilized from the perspective of the raw material composition substances, without being utilized from the perspective of the composition of coal gangue such as carbon-containing substances and layered crystal structures.

[0005] Chinese Patent CN115057458A discloses a method for preparing nano-aluminum oxide from coal gangue. The coal gangue loaded with inorganic salts of alkali metal K, inorganic salts of Na or biomass is gasified or burned at high temperature to achieve the activation of coal gangue at high temperature. The obtained aluminum hydroxide precursor is subjected to high-temperature roasting, water washing, acid washing, and filtration to obtain flaky aluminum oxide. The temperature of gasification or combustion is 600-1000 °C. The alkali metal is used as an activator. Using inorganic salts or biomass containing alkali metal as an activator can improve the aluminum extraction efficiency and effectively reduce the temperature of thermal activation. According to the characteristics of the solution after acid dissolution and combining with the traditional molten salt method (MSS) for preparing flaky aluminum oxide, adding a mixed solution of KOH and NaOH to the acidic crude liquid can achieve the purpose of adjusting the pH and form molten salts K2SO4 and Na2SO4. The recycled molten salt can be used again as an activator for coal gangue. The coal gangue loaded with inorganic salts of alkali metal K, inorganic salts of Na or biomass is gasified or burned at high temperature to achieve the activation of coal gangue, and this process can also consume the carbon element in the coal gangue. However, in this method, the carbon element in the coal gangue is mainly consumed by combustion, and the carbon is only used for combustion. Flaky aluminum oxide is obtained through acid leaching and alkali solution coordination, resulting in low utilization rate of the components in coal gangue, only one component, aluminum oxide, can be effectively used, and complex processes such as impurity removal are required.

[0006] Chinese Patent CN112316924B discloses a coal gangue-based porous composite material, its preparation method and application. By crushing, foaming, and modifying coal gangue, a coal gangue-based porous composite material with a large specific surface area, strong heavy metal adsorption ability, and good solid particle removal effect is obtained. Among them, after heat treatment at 600 °C for 4 h, it is taken out and cooled at 25 °C. After demolding, the green body is heated to 1100 °C at a programmed rate in an air atmosphere and held for 2 h to obtain a coal gangue-based porous framework. That is, this method obtains a porous composite material through multiple heat treatments and intermediate foaming using an external foaming aid. It is difficult to ensure the pores inside the composite material, and it is difficult to obtain an efficient porous adsorption material.

[0007] As can be seen from the above, although the existing methods can endow coal gangue with adsorption properties, the preparation process is relatively complex, a large amount of acid-base coordination is used, external aids are used to create pores, it is difficult to increase the pores inside the material, the utilization of coal gangue components is single, impurity removal and other processes further complicate the process, and it is difficult to effectively utilize components such as carbon in coal gangue. Therefore, the present invention provides a new technology for in-situ synthesizing organically modified porous functional materials using coal gangue. There is no literature report and technical application precedent for this technology at present. Summary of the Invention

[0008] Overcoming the deficiencies of the prior art, the present application provides a method for in-situ synthesizing an organically modified porous functional material using coal gangue, achieving small pores with an average control reaching the nanoscale, high pore volume, large specific surface area, and capable of efficiently removing pollutants such as organic dyes, heavy metals, antibiotics, and phosphorus. It in-situ converts the mineral components in coal gangue into a porous functional material, effectively utilizes components such as metal elements and carbon, and largely avoids the waste of valuable metals and carbon, being suitable for industrial production.

[0009] The embodiments of the present application are implemented as follows: The present application example provides a method for in-situ synthesizing an organically modified porous functional material using coal gangue, including: (1) Crushing the coal gangue, sieving it, and calcining the powder at 100 - 1000 °C for 2 - 24 h to obtain a layered silicate mineral; (2) Mixing 1 - 10 g of the layered silicate mineral, 5 - 50 g of soluble silicate and / or soluble silicic acid, 3 - 30 g of metal compound, and 40 - 400 ml of deionized water, stirring, and then subjecting the reaction mixture to ultrasonic treatment using a cell crusher to obtain suspension A; (3) Adding 0.05 - 5 g of a complexing agent to suspension A, and then stirring to obtain a homogeneous precursor solution; (4) Transferring the obtained precursor solution into a closed reactor, reacting at a temperature of 50 - 400 °C and a pressure of 5 - 30 MPa for 1 - 30 h to obtain a mixed product containing solids and liquids; (5) Separating the solid and liquid of the obtained mixed product to obtain a solid organically modified porous functional material; Among them, during the process of crushing, sieving, and subjecting the coal gangue powder to low-temperature calcination in step (1), an aqueous solution of potassium permanganate with a concentration of 1 - 3 wt% is sprayed in through a nozzle, the spraying mass accounts for 0.1 - 0.2 wt% of the mass of the coal gangue, and the spraying time is 0.5 - 1 h.

[0010] Optionally, in step (1), the coal gangue is crushed, sieved, and the powder is calcined at a temperature of 195 - 296 °C.

[0011] Optionally, before subjecting the coal gangue to low-temperature calcination in step (1), it is subjected to high-temperature calcination for 5 - 10 min at a calcination temperature of 850 - 945 °C with microwave-assisted heating.

[0012] Optionally, the content of kaolinite in the layered silicate mineral obtained after calcining the coal gangue is not less than 40%; the particle size of the powder after crushing the coal gangue is in the range of 48 - 200 μm.

[0013] Optionally, the soluble silicate is one or any combination of lithium silicate, sodium silicate, ammonium silicate, and potassium silicate, and the soluble silicic acid is orthosilicic acid. The addition amount is such that the mass ratio of coal gangue to soluble silicate and / or soluble silicic acid is 1:(4.5 - 5.5); the metal compound is one or any combination of magnesium chloride, magnesium oxide, basic magnesium carbonate, zinc chloride, zinc sulfate, zinc nitrate, zinc dihydrogen phosphate, calcium oxide, calcium chloride, magnesium sulfate, magnesium nitrate, magnesium acetate, calcium halide, calcium carbonate, calcium nitrate, calcium chlorate, and calcium perchlorate. The addition amount is such that the mass ratio of coal gangue to the metal compound is 1:2.5 - 3.5; the complexing agent is one or any combination of nitrilotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, and diethyltriacetic acid, and the mass concentration is 0.1 - 30%.

[0014] Optionally, the soluble silicate is lithium silicate, sodium silicate, and potassium silicate. Based on the total mass of the soluble silicate, the ratio of lithium silicate:sodium silicate:potassium silicate is 1:(12 - 13):(13 - 14).

[0015] Optionally, the metal compound is magnesium oxide, zinc chloride, and calcium oxide. Based on the total mass of the metal compound, the ratio of magnesium oxide:zinc chloride:calcium oxide is 1:(0.2 - 0.3):(1.3 - 1.5).

[0016] Optionally, the complexing agent is ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid. Based on the total mass of the complexing agent, the ratio of ethylenediaminetetraacetic acid:diethylenetriaminepentaacetic acid is 1:(0.3 - 0.4).

[0017] Optionally, the amount of deionized water added is such that the mass ratio of coal gangue to deionized water is 1:35 - 45.

[0018] Optionally, the pH value of the suspension A is between 5 and 12. To adjust the pH, an alkaline metal compound can be added.

[0019] The beneficial effects include: The method for in-situ synthesizing an organically modified porous functional material using coal gangue provided by the present invention prepares a layered silicate mineral from coal gangue, directly mixes it with soluble silicate and / or soluble silicic acid, metal compound, organic complexing agent, and water, and then undergoes a heating and pressurization reaction to obtain a solid organically modified porous functional material. This is conducive to the formation of a hierarchical pore structure and the increase in the generation of carbon pores. There is no need for acid or alkali treatment, avoiding problems such as impurity dissolution and large consumption of acids and alkalis during acid-base treatment, simplifying the process, and in one-pot synthesizing an organically modified porous functional material from the mineral components and metals in coal gangue, endowing it with characteristics such as a high specific surface area and a porous structure.

[0020] Through low-temperature calcination, it is mainly used to reduce the combustion loss of carbon, which will be beneficial to the retention of carbon and the formation of porous carbon such as activated carbon, improving porosity and making the layered silicate minerals become fine nano-scale pore structures with rich porous silica and porous carbon composite (i.e., the pore structure of the silica-C composite structure). At the same time, the layered silicate has a more abundant Si-O-Al skeleton, increasing the loading capacity and loading stability, thus facilitating the improvement of adsorption and metal loading capacity. The value of carbon combustion is obviously lower than the value of being a component of the adsorption material, greatly improving the application value of coal gangue and reducing carbon emissions.

[0021] During the low-temperature calcination of coal gangue powder, an aqueous solution of potassium permanganate with a concentration of 1-3 wt% is sprayed in. The water reacts with the carbon in the coal gangue through the water-gas reaction to generate hydrogen, CO, and accompanying water vapor, which can effectively improve the gas circulation within the layered structure of the coal gangue, facilitating the formation of mesopores with moderate pore sizes and enhancing the generation of carbonaceous pores. At the same time, the long-term spraying of a low content of potassium permanganate on the surface of the coal gangue decomposes into MnO2 when heated and is accompanied during the formation of pores, realizing the loading of MnO2 on the surface and inside of the coal gangue, thereby improving its loading dispersion uniformity and loading rate. The generated oxygen reacts with carbon, and the water reacts with the carbon in the coal gangue through the water-gas reaction, which is more conducive to the partial consumption of carbon in the coal gangue, generating gas to promote the formation of pores and facilitating the improvement of adsorption performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required in the embodiments. It should be understood that the following drawings only show some embodiments of the present application and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0023] Figure 1 SEM image of the organically modified porous functional material of Example 1; Figure 2 TEM image of the organically modified porous functional material of Example 1; Figure 3 N2 adsorption-desorption isotherm of the organically modified porous functional material of Example 1; Figure 4 Pore size distribution curve of the organically modified porous functional material of Example 1; Figure 5 XRD curve of the organically modified porous functional material of Example 1.

[0024] DESCRIPTION OF THE APPENDIX TABLES: Table 1 shows the pore structure parameters of the organically modified porous functional material; Table 2 shows the adsorption performance of the organically modified porous functional material for organic dyes, heavy metals, tetracycline hydrochloride, and phosphorus. Specific embodiments

[0025] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0026] Those skilled in the art of the present technology can understand that, unless otherwise defined, all terms used herein (including technical terms and scientific terms) have the same meaning as commonly understood by those of ordinary skill in the field to which the present invention belongs. It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted in an idealized or overly formal sense unless specifically defined as here.

[0027] Those skilled in the art of the present technology can understand that, unless specifically stated, the singular forms "a", "an", "the", and "said" used herein may also include the plural forms. It should be further understood that the term "including" used in the description of the present invention means the presence of the described features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or their groups. The term "and / or" used herein includes all or any unit and all combinations of one or more of the associated listed items. The raw materials used hereinafter, unless otherwise specified, are all commercially available products. The performance detection refers to national standards or industry standards.

[0028] Regarding the preparation process of coal gangue recycling, it is relatively complex, with a large amount of acid-base cooperation, additional additives for pore formation, it is difficult to increase the internal pores of the material, the utilization of coal gangue components is single, impurity removal, etc. lead to further complexity of the process, and it is difficult to effectively utilize components such as carbon in coal gangue. Therefore, the embodiments of the present invention provide a method for in-situ synthesizing an organically modified porous functional material using coal gangue.

[0029] The features and performance of the present application will be further described in detail below in conjunction with the embodiments: The embodiments of the present invention provide a method for in-situ synthesizing an organically modified porous functional material using coal gangue, including: (1)Crush the coal gangue, sieve it, and calcine the powder at 100 - 1000 °C (selectable as 100 °C, 105 °C, 134 °C, 146 °C, 157 °C, 166 °C, 173 °C, 184 °C, 196 °C, 211 °C, 234 °C, 246 °C, 271 °C, 286 °C, 291 °C, 351 °C, 378 °C, 394 °C, 411 °C, 423 °C, 567 °C, 678 °C, 689 °C, 723 °C, 754 °C, 768 °C, 778 °C, 798 °C, 854 °C, 873 °C, 946 °C, 967 °C, 971 °C, 985 °C, 1000 °C, etc.) for 2 - 24 h to obtain layered silicate minerals.

[0030] (2)Mix 1 - 10 g (selectable as 1 g, 2 g, 3 g, 4 g, 5 g, 6 g, 7 g, 8 g, 9 g, 10 g, etc.) of layered silicate minerals, 5 - 50 g (selectable as 5 g, 8 g, 11 g, 13 g, 16 g, 28 g, 35 g, 42 g, 47 g, 50 g, etc.) of soluble silicate and / or soluble silicic acid, 3 - 30 g (selectable as 3 g, 8 g, 11 g, 13 g, 16 g, 22 g, 24 g, 26 g, 28 g, 30 g, etc.) of metal compounds and 40 - 400 ml of deionized water, stir, and then ultrasonically treat the reaction mixture with a cell disruptor to obtain suspension A.

[0031] (3)Add 0.05 - 5 g (selectable as 0.05 g, 0.17 g, 0.29 g, 0.38 g, 0.74 g, 1.1 g, 1.7 g, 2.1 g, 2.4 g, 2.7 g, 3.3 g, 3.6 g, 3.9 g, 4.1 g, 4.5 g, 4.6 g, 4.9 g, 5 g, etc.) of complexing agent to suspension A, and then stir to obtain a homogeneous precursor solution.

[0032] (4)Transfer the above - obtained precursor solution into a closed reactor, and react it at a temperature of 50 - 400 °C (selectable as 50 °C, 53 °C, 57 °C, 64 °C, 69 °C, 74 °C, 75 °C, 78 °C, 86 °C, 89 °C, 93 °C, 96 °C, 98 °C, 107 °C, 115 °C, 143 °C, 152 °C, 161 °C, 178 °C, 183 °C, 194 °C, 204 °C, 235 °C, 252 °C, 264 °C, 284 °C, 304 °C, 325 °C, 338 °C, 385 °C, 392 °C, 400 °C, etc.) and a pressure of 5 - 30 MPa (selectable as 5 MPa, 6 MPa, 8 MPa, 9 MPa, 11 MPa, 14 MPa, 16 MPa, 18 MPa, 21 MPa, 22 MPa, 25 MPa, 28 MPa, 30 MPa, etc.) for 1 - 30 h to obtain a mixed product containing solids and liquids. Preferably, react it at a temperature of 83 - 97 °C and a pressure of 27 - 30 MPa.

[0033] (5) Solid-liquid separation is carried out on the obtained mixed product above to obtain a solid organically modified porous functional material.

[0034] Layered silicate minerals are prepared by calcining coal gangue and directly mixed with soluble silicate and / or soluble silicic acid, metal compounds, organic complexing agents and water, and then heated and pressurized to react to obtain a solid organically modified porous functional material. There is no need to add acid or alkali treatment, avoiding problems such as impurity dissolution and large consumption of acid and alkali in acid-base treatment, simplifying the process. The mineral components and metals in coal gangue are in-situ synthesized into an organically modified porous functional material by a one-pot method, making it have characteristics such as a high specific surface area and a porous structure. The added complexing agent can quickly complex with metal ions, and the adsorption performance can be increased to dozens of times that of the original coal gangue ore, and the removal efficiency of pollutants in wastewater is more efficient. At the same time, it can effectively repair soil seriously polluted by heavy metals.

[0035] Preferably, the calcination temperature is 195 - 296 °C. By calcining at a relatively low temperature, the main minerals in coal gangue, such as crystalline aluminum-containing minerals like kaolinite, are transformed into semi-crystalline or even amorphous metakaolinite and other minerals. Their structure is in a thermodynamically metastable state. It mainly removes the hydroxyl groups (-OH) in the structure, resulting in the breakage of the interlayer hydrogen bonds in the layered silicate, the loosening of the layered structure, and the exposure of more surface active sites (a large number of broken Si-O and Al-O bonds, forming surface hydroxyl groups (Si-OH, Al-OH) and defect sites, etc., which are conducive to direct reaction and combination with soluble silicate and / or soluble silicic acid, metal compounds, organic complexing agents, etc.), generating more amorphous phases (such as amorphous silica), which is conducive to subsequent mixing and reaction with soluble silicate and / or soluble silicic acid, metal compounds, organic complexing agents and water. Calcining at a low temperature overcomes the deficiency that the layered structure cannot be fully changed into a loose structure and the reaction activity cannot be greatly improved by direct high-temperature sintering. The low-temperature calcination does not completely destroy its layered aluminosilicate framework, avoiding the melting and collapse of internal pores caused by high-temperature calcination, and still maintaining a two-dimensional sheet structure with an expanded layer spacing, providing an insertion channel for soluble silicate and metal ions. The low-temperature calcination greatly reduces the energy consumption. The main purpose of previous calcination was to remove carbon and activate it. The low-temperature calcination in this application has a different purpose. By low-temperature calcination, it is mainly used to reduce the combustion loss of carbon, which will be beneficial to the retention of carbon and the formation of porous carbon such as activated carbon, improving the porosity, making the layered silicate minerals become a fine nano-scale pore structure with abundant porous silica and porous carbon composite (i.e., the pore structure of the silica-C composite structure). At the same time, the layered silicate has a more abundant Si-O-Al framework, increasing the loading capacity and loading stability, thus facilitating the improvement of adsorption and metal loading ability. The value of carbon combustion is obviously lower than the value of being a component of the adsorption material, and it also greatly improves the application value of coal gangue and reduces carbon emissions.

[0036] Soluble silicates (such as sodium silicate, etc.) and / or orthosilicic acid are hydrolyzed to form silicate (SiO4 4- ) or oligomeric silicic acid, by connecting with the active sites of layered silicates, for example, connecting with the Si-O-Al skeleton of layered silicates through a condensation reaction, and the layered open structure of layered silicates can effectively block and separate and insert soluble silicates and / or orthosilicic acid, and silicate ions penetrate into the interlayers, filling the interlayer gaps to form a three-dimensional interpenetrating network, thereby enhancing the mechanical strength of the material. The silicate gel shrinks during the pressurized drying process to produce mesopores (2-30nm) (which are conducive to the diffusion of large molecular pollutants), which together with the mesopores and macropores (>30nm) in the layered silicate mineral structure (reducing mass transfer resistance and providing a stable channel for material migration) form a multi-level pore system, which greatly enriches the pore type and pore density, significantly increases the specific surface area of the material, and improves the adsorption capacity.

[0037] The addition of metal compounds and complexes, such as metal ions (Mg 2+ 、Zn 2+ , Ca 2+ etc.) coordinate with the oxygen atoms of silicates to form a "metal-silicon-oxygen" cross-linked network, which enhances the mechanical strength of the material and is conducive to the stable formation of a small pore structure; and some metal (such as Zn, Ca) oxides have catalytic oxidation ability, which can promote the degradation of organic pollutants; at the same time, the surface of metal oxides is positively charged, which enhances the electrostatic adsorption of anionic pollutants (such as Cr(VI), As(V)). Due to the interlayer anchoring of layered silicate minerals, metal ions can be converted into oxide (such as MgO, ZnO) nanoparticles, whose size is limited by the spatial limitations of the layered structure (usually <10nm), and can exhibit higher catalytic activity; and chelating agents (such as ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, diethyltriacetic acid, nitrilotriacetic acid) chelate metal ions (MgO, ZnO) through carboxylic acid groups. 2+ 、Zn 2+ , Ca 2+ etc.), inhibiting their premature precipitation, ensuring that the metal ions are evenly dispersed in the silicate skeleton, avoiding pore blockage caused by local agglomeration, and thus avoiding pore reduction. The coordination of metal compounds and complexes is conducive to regulating the size of the pores, especially producing a mesoporous structure of appropriate size, thereby improving the reasonable pore distribution and enhancing the adsorption performance.

[0038] Prepare layered silicate minerals from coal gangue, directly mix with soluble silicate and / or soluble silicic acid, metal compound, organic complexing agent and water, and then carry out heating and pressurization reaction to obtain a solid organic modified porous functional material, which is beneficial to form a multi-level pore structure and increase the generation of carbon pores. Without the addition of acid and alkali treatment, problems such as impurity dissolution and large consumption of acid and alkali in acid and alkali treatment are avoided, the process is simplified, and the mineral components and metals in coal gangue are in-situ synthesized into an organic modified porous functional material by a one-pot method, making it have characteristics such as high specific surface area and porous structure.

[0039] Among them, in step (1), the coal gangue is crushed and sieved. During the low-temperature calcination of the powder, 1-3 wt% of potassium permanganate aqueous solution (that is, the mass of potassium permanganate accounts for 1-3 wt%) is sprayed through a nozzle, and the spraying mass accounts for 0.1-0.2 wt% of the mass of the coal gangue, and the spraying time is 0.5-1 h; the potassium permanganate aqueous solution is used for water treatment and has the functions of removing organic pollutants and heavy metal ions; potassium permanganate can release oxygen, MnO2, etc. above 120 °C, especially above 150 °C. Due to its unique redox activity, high specific surface area, porous structure and rich surface hydroxyl functional groups, MnO2 shows significant advantages in removing pollutants such as organic dyes, heavy metals, antibiotics and phosphorus. The hydroxyl groups (-OH) and oxygen vacancies on the surface of MnO2 can adsorb heavy metal ions (such as Pb 2+ 、Cd 2+), MnO2 can reduce Cr(VI) to less toxic and easily precipitable Cr(III), oxidize more toxic As(III) to As(V), which is more easily adsorbed or co-precipitated. The carboxylic acid group of antibiotic molecules (such as ofloxacin) forms hydrogen bonds or coordination bonds with the hydroxyl groups on the surface of MnO2. However, in the prior art, when coal gangue is soaked in potassium permanganate solution, the decomposed MnO2 is likely to block the pores of coal gangue, affecting the improvement of adsorption performance. MnO2 is easily desorbed during acid-base treatment and other processes, making it difficult to be effectively utilized. During the low-temperature calcination of coal gangue, the reaction between oxygen and carbon is slow, which also affects the formation of carbonaceous micropores. By spraying a 1-3 wt% aqueous solution of potassium permanganate during the low-temperature calcination of coal gangue powder, the water reacts with the carbon in the coal gangue through the water-gas reaction to generate hydrogen, CO, and accompanying water vapor, which can effectively improve the gas flow within the layered structure of coal gangue, facilitate the formation of mesopores with moderate pores, and enhance the generation of carbonaceous pores. At the same time, the low content of potassium permanganate is sprayed onto the surface of coal gangue for a long time and decomposed into MnO2 during heating, which is accompanied by the formation of pores, realizing the loading of MnO2 on the surface and inside of coal gangue, thereby improving its loading dispersion uniformity and loading rate. The generated oxygen reacts with carbon, and the water reacts with the carbon in the coal gangue through the water-gas reaction, which is more conducive to the partial consumption of carbon in the coal gangue, generating gas to promote the formation of pores and facilitating the improvement of adsorption performance. The concentration and usage amount of the potassium permanganate aqueous solution should not be too large, as it will lead to excessive reaction of carbon, even complete reaction, unable to form carbonaceous micropores, and too large pores, as well as the risk of explosion due to excessive generation of oxygen. The concentration and usage amount of the potassium permanganate aqueous solution should not be too low, as it cannot fully load enough MnO2 and cannot effectively create pores quickly to increase the porosity and specific surface area.

[0040] Optionally, before the coal gangue is crushed, sieved, and the powder is subjected to low-temperature calcination in step (1), it is subjected to high-temperature calcination for 5-10 min at a calcination temperature of 850-945 °C with microwave-assisted heating. Through short-time high-temperature calcination, it is beneficial to remove components such as colloidal volatile components (such as hydrocarbon and tar organic components) in the coal gangue, avoiding the retention of colloids and volatile components during low-temperature calcination, which makes it difficult to create pores. The short-time high-temperature treatment can quickly complete the volatilization of the above components, avoid excessive carbon combustion, and the rapid escape of volatile components, which is conducive to the formation of micropores and mesopore channels inside the coal gangue, increasing the specific surface area. Microwave is beneficial to the loosening and premature activation of the mineral phase, generating microcracks inside the mineral, expanding the layer spacing, and improving the effect of low-temperature calcination. That is, through short-time high-temperature calcination and assisted by microwave-assisted heating, pre-pore formation is carried out to prevent pore formation failure, loosen the mineral phase, increase the layer spacing, and then cooperate with low-temperature calcination (calcination temperature is 195-296 °C), which is more conducive to optimizing the pore formation process to form a suitable multi-stage pore structure of coal gangue.

[0041] The understandable calcination can be carried out in a flash calciner, by stirring and heating, or by heat ball milling, etc., to make the calcination process uniform and the spraying of potassium permanganate solution uniform.

[0042] Optionally, the content of kaolinite in the layered silicate mineral obtained after calcining the coal gangue is not less than 40%. By controlling the content of kaolinite in the layered silicate mineral obtained after calcining the coal gangue at a high level, overcalcination is avoided, which can prevent the destruction of the layered structure of the coal gangue and affect the formation of an open and loose active silicoaluminate network. After calcination, dehydroxylation occurs and it is transformed into metakaolinite, and its unique layered structure has significant advantages for pore formation, specific surface area improvement and material property optimization.

[0043] Optionally, the particle size of the powder after crushing the coal gangue is 48 - 200 μm (which can be 48 μm, 53 μm, 57 μm, 64 μm, 69 μm, 78 μm, 82 μm, 91 μm, 101 μm, 113 μm, 124 μm, 135 μm, 142 μm, 156 μm, 167 μm, 178 μm, 182 μm, 195 μm, 200 μm, etc.). Preferably: 48 - 85 μm. The internal mass transfer distance of the fine particles is shortened, and the residual organic volatiles (such as tar and hydrocarbons) during calcination are more likely to escape quickly. The dehydroxylation of layered silicates such as kaolinite in the fine particles is more complete, and it is transformed into the active structure of metakaolinite, which is beneficial to the formation of uniformly distributed micropores and mesopores.

[0044] Optionally, the soluble silicate is one or any combination of lithium silicate, sodium silicate, ammonium silicate, and potassium silicate, and the soluble silicic acid is orthosilicic acid. The addition amount is such that the mass ratio of the coal gangue to the soluble silicate and / or soluble silicic acid is 1:(4.5 - 5.5) (which can be 1:4.5, 1:4.6, 1:4.7, 1:4.8, 1:4.9, 1:5, 1:5.1, 1:5.2, 1:5.3, 1:5.4, 1:5.5, etc.). Controlling the addition amount of the soluble silicate is beneficial to forming pores of appropriate size through polycondensation reactions. If the amount is too much, intercalation of the layered silicate occurs and coating is formed simultaneously, which affects the formation of the hierarchical pore system. If the amount is too low, the amount of voids filled is small, which is not conducive to the formation of a three-dimensional interpenetrating network and enhancing the mechanical strength of the material. At the same time, the pores become larger. Both too high and too low amounts are not conducive to improving the adsorption performance.

[0045] Optionally: The soluble silicate is lithium silicate, sodium silicate, and potassium silicate. Based on the total mass of the soluble silicate, the ratio of lithium silicate:sodium silicate:potassium silicate is 1:(12 - 13):(13 - 14); Sodium silicate hydrolyzes to form silicate ions, and its gelation process has strong controllability and is easy to control the formation of mesoporous structures; Potassium ions have a relatively large ionic radius, which is conducive to delaying the polycondensation rate and expanding the pore size distribution (coexistence of mesopores and macropores). The strong polarization effect of lithium ions promotes the densification of the silicate gel structure, which is thus conducive to improving the pore strength and maintaining pore stability; The ternary cation system of sodium, potassium, and lithium can balance the gelation rate, structural stability, and pore-forming radius, thereby improving the adsorption performance.

[0046] Optionally, the metal compound is one or any combination of magnesium chloride, magnesium oxide, basic magnesium carbonate, zinc chloride, zinc sulfate, zinc nitrate, zinc dihydrogen phosphate, calcium oxide, calcium chloride, magnesium sulfate, magnesium nitrate, magnesium acetate, calcium halide, calcium carbonate, calcium nitrate, calcium chlorate, calcium perchlorate, and the addition amount is such that the mass ratio of coal gangue to the metal compound is 1:2.5 - 3.5 (optionally 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3, 1:3.1, 1:3.2, 1:3.3, 1:3.4, 1:3.5, etc.). The appropriate addition amount of the metal compound is conducive to the stable formation of small pore structures and has high catalytic ability. Too high or too low amounts are not conducive to the formation of pore structures, especially micro-pores.

[0047] Preferably, the metal compounds are magnesium oxide, zinc chloride, and calcium oxide. Based on the total mass of the metal compounds, the ratio of magnesium oxide:zinc chloride:calcium oxide is 1:(0.2 - 0.3):(1.3 - 1.5); The surface sites of MgO (O 2- ) and the sites of MnO2 (Mn - OH) are complementary and synergistically adsorb anionic pollutants (such as Cr(VI)); Zinc chloride can improve the decomposition of tetracycline, etc. under visible light; After the combination of CaO and MnO2, it can fix SO4 2- , PO4 3- in wastewater, reduce the competitive adsorption of the active sites of MnO2, and simultaneously improve the removal rate of heavy metals (such as Cd 2+ ). Through the selection of the appropriate ratio of the above metal compounds, it is conducive to improving the removal of heavy metal ions and the decomposition efficiency of tetracycline, etc.

[0048] Optionally, the amount of deionized water added is such that the mass ratio of coal gangue to deionized water is 1:35 - 45 (optionally 1:35, 1:36, 1:37, 1:38, 1:39, 1:40, 1:41, 1:42, 1:43, 1:44, 1:45, etc.).

[0049] Optionally, the complexing agent is one or any combination of nitrilotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, and diethylenetriacetic acid, with a mass concentration of 0.1 - 30% (optionally 0.1%, 0.6%, 1.8%, 3.3%, 5.4%, 6.8%, 9.1%, 11%, 15%, 17%, 19%, 21%, 23%, 25%, 27%, 28%, 29%, 30%, etc.). Preferably 1.1 - 5.3%.

[0050] Preferably: the complexing agent is ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid. Based on the total mass of the complexing agent, the ratio of ethylenediaminetetraacetic acid to diethylenetriaminepentaacetic acid is 1:(0.3 - 0.4); ethylenediaminetetraacetic acid has four carboxylic acid groups and two amino groups, with strong chelating ability, which is conducive to forming stable coordination complexes with metal ions. The strong chelating effect can inhibit the premature precipitation of metal ions, ensure the uniform dispersion of metal ions in the precursor solution, thereby forming a uniform pore structure during the subsequent heating process, delaying the polycondensation rate of silicate or metal oxide, and promoting the formation of hierarchical pores (micropores - mesopores); diethylenetriaminepentaacetic acid has eight coordinating atoms (three amino groups and five carboxylic acid groups), and its chelating ability for transition metal Mn ions is greater than that of ethylenediaminetetraacetic acid. It can stabilize the active sites on the surface of MnO2 and promote its catalytic effect. The long-chain structure of diethylenetriaminepentaacetic acid can shield the competitive adsorption of anions (such as Cl - and SO4 2- ) in water on the active sites of MnO2, and still maintain high removal ability in complex water quality. By controlling the appropriate ratio, the catalytic effect of manganese dioxide can be promoted, and at the same time, the formation of hierarchical pores can be promoted, which is beneficial to improving the adsorption effect.

[0051] Optionally, the pH value of the suspension A is 5 - 12 (optionally 5, 6, 7, 8, 9, 10, 11, 12, etc.). To adjust the pH, an alkaline metal compound can be added.

[0052] Example 1 A method for in-situ synthesizing an organically modified porous functional material using coal gangue, comprising: (1) Crushing the coal gangue, with the average particle size of the powder being 84 μm. After sieving, before the powder is subjected to low-temperature calcination, it is subjected to high-temperature calcination for 6 min at a calcination temperature of 873 °C with microwave-assisted heating. Then, the powder is calcined at 211 °C for 6 h to obtain a layered silicate mineral; the content of kaolinite in the layered silicate mineral obtained after calcining the coal gangue is not less than 70%; among them, during the process of crushing, sieving, and low-temperature calcining the coal gangue in step (1), an aqueous solution of potassium permanganate with a concentration of 2 wt% is sprayed through a nozzle, and the spraying mass accounts for 0.2 wt% of the mass of the coal gangue, and the spraying time is 0.5 h.

[0053] (2) Mix 2.1 g of layered silicate minerals, 10.7 g of soluble silicate, 6.8 g of metal compound and 91 ml of deionized water, and after stirring, obtain suspension A through ultrasonic treatment with a cell crusher; the soluble silicate is lithium silicate, sodium silicate and potassium silicate. Based on the total mass of the soluble silicate, the ratio of lithium silicate:sodium silicate:potassium silicate is 1:12:14. The metal compound is magnesium oxide, zinc chloride and calcium oxide. Based on the total mass of the metal compound, the ratio of magnesium oxide:zinc chloride:calcium oxide is 1:0.2:1.4.

[0054] (3) Add 0.12 g of complexing agent to suspension A, and then obtain a homogeneous precursor solution after stirring; the mass concentration of the complexing agent is 3.1%. The complexing agent is ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid. Based on the total mass of the complexing agent, the ratio of ethylenediaminetetraacetic acid:diethylenetriaminepentaacetic acid is 1:0.3.

[0055] (4) Transfer the above-obtained precursor solution into a closed reactor, and react at a temperature of 84 °C and a pressure of 28 MPa for 5 h to obtain a mixed product containing solids and liquids.

[0056] (5) Perform solid-liquid separation on the above-obtained mixed product to obtain a solid organic-modified porous functional material. Combining Figures 1-5 with Table 1-2 shows that the organic-modified porous functional material prepared in Example 1 has small pore size, large specific surface area, high pore volume, and a nano-cluster structure, and has good adsorption performance for organic dyes, heavy metals, tetracycline hydrochloride and phosphorus. Among them Figure 4 is the pore size distribution curve of the organic-modified porous functional material in Example 1. The ordinate is dV / dlogD, indicating the change in pore volume (dV) within a unit logarithmic pore size interval (dlogD), with the unit of cm³ / g; the abscissa is the pore diameter, with the unit of nm.

[0057] Table 1 Pore structure parameters of the organic-modified porous functional material

[0058] Table 2 Adsorption performance of the organic-modified porous functional material for organic dyes, heavy metals, tetracycline hydrochloride and phosphorus

[0059] Example 2 It is basically the same as the method in Example 1, except that in step (1), the coal gangue is crushed, sieved, and the powder is calcined at a temperature of 793 °C. Compared with Example 1, the high calcination temperature is not conducive to improving the adsorption performance.

[0060] Example 3 Basically the same as the method of Example 1, except that: before the pulverized gangue is sieved and the powder is calcined at low temperature in step (1), it is not calcined at high temperature and assisted by microwave heating.

[0061] Example 4 Basically the same as the method of Example 1, except that: the average particle size of the powder after the gangue is pulverized is 195μm.

[0062] Example 5 Basically the same as the method of Example 1, except that: 2.1g of layered silicate minerals, 8.4g of soluble silicate, and 8g of metal compound.

[0063] Example 6 Basically the same as the method of Example 1, except that: the soluble silicate is lithium silicate.

[0064] Example 7 Basically the same as the method of Example 1, except that: the metal compound is zinc chloride.

[0065] Example 8 Basically the same as the method of Example 1, except that: the complexing agent is ethylenediaminetetraacetic acid.

[0066] Example 9 Basically the same as the method of Example 1, except that: it reacts under the conditions of a temperature of 312°C and a pressure of 30MPa to obtain a mixed product containing solids and liquids.

[0067] Comparative Example 1 Basically the same as the method of Example 1, except that: during the low-temperature calcination of the pulverized and sieved gangue powder in step (1), an aqueous solution of potassium permanganate is not sprayed through the nozzle.

[0068] Comparative Example 2 Basically the same as the method of Example 1, except that: the powder is calcined at 1,300°C for 2h.

[0069] Comparative Example 3 Basically the same as the method of Example 1, except that: the obtained precursor solution is transferred into a closed reactor and reacts under the conditions of a temperature of 500°C and a pressure of 5 - 30MPa.

[0070] Comparative Example 4 Basically the same as the method of Example 1, except that: no complexing agent is added.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for in-situ synthesizing an organically modified porous functional material using coal gangue, characterized in that, Including: (1) Crushing gangue, sieving it, and calcining the powder at 100 - 1000 °C for 2 - 24 h to obtain layered silicate minerals; (2) Mixing 1 - 10 g of layered silicate minerals, 5 - 50 g of soluble silicate and / or soluble silicic acid, 3 - 30 g of metal compounds, and 40 - 400 ml of deionized water, stirring, and then subjecting the reaction mixture to ultrasonic treatment using a cell crusher to obtain suspension A; (3) Adding 0.05 - 5 g of complexing agent to suspension A, and then stirring to obtain a homogeneous precursor solution; (4) Transferring the obtained precursor solution into a closed reactor, reacting at a temperature of 50 - 400 °C and a pressure of 5 - 30 MPa for 1 - 30 h to obtain a mixed product containing solids and liquids; (5) Separating the solid and liquid of the obtained mixed product to obtain a solid organically modified porous functional material; Among them, during the process of crushing, sieving, and performing low-temperature calcination on the gangue powder in step (1), an aqueous solution of potassium permanganate with a concentration of 1 - 3 wt% is sprayed through a nozzle, and the spraying mass accounts for 0.1 - 0.2 wt% of the mass of the gangue, and the spraying time is 0.5 - 1 h.

2. The method for in-situ synthesizing an organically modified porous functional material using coal gangue according to claim 1, wherein In step (1), the gangue is crushed, sieved, and the powder is calcined at a temperature of 195 - 296 °C.

3. The method for in-situ synthesizing an organically modified porous functional material using coal gangue according to claim 2, wherein, Before performing low-temperature calcination on the crushed and sieved gangue powder in step (1), high-temperature calcination is carried out for 5 - 10 min at a calcination temperature of 850 - 945 °C with microwave-assisted heating.

4. The method for in-situ synthesizing an organically modified porous functional material using coal gangue according to claim 1, characterized in that, The content of kaolinite in the layered silicate minerals obtained after calcining the gangue is not less than 40%; the particle size of the crushed gangue powder is 48 - 200 μm.

5. The method for in-situ synthesizing an organically modified porous functional material using coal gangue according to claim 1, characterized in that, The soluble silicate is one or any combination of lithium silicate, sodium silicate, ammonium silicate, and potassium silicate. The soluble silicic acid is orthosilicic acid, and the addition amount is such that the mass ratio of gangue to soluble silicate and / or soluble silicic acid is 1:(4.5 - 5.5); the metal compound is one or any combination of magnesium chloride, magnesium oxide, basic magnesium carbonate, zinc chloride, zinc sulfate, zinc nitrate, zinc dihydrogen phosphate, calcium oxide, calcium chloride, magnesium sulfate, magnesium nitrate, magnesium acetate, calcium halide, calcium carbonate, calcium nitrate, calcium chlorate, and calcium perchlorate, and the addition amount is such that the mass ratio of gangue to the metal compound is 1:2.5 - 3.5; the complexing agent is one or any combination of nitrilotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, and diethyltriacetic acid, and the mass concentration is 0.1 - 30%.

6. The method for in-situ synthesizing an organically modified porous functional material using coal gangue according to claim 5, characterized in that, The soluble silicate is lithium silicate, sodium silicate, and potassium silicate, and based on the total mass of the soluble silicate, the mass ratio of lithium silicate:sodium silicate:potassium silicate is 1:(12 - 13):(13 - 14).

7. The method for in-situ synthesizing an organically modified porous functional material using coal gangue according to claim 5, characterized in that, The metal compound is magnesium oxide, zinc chloride, and calcium oxide, and based on the total mass of the metal compound, the mass ratio of magnesium oxide:zinc chloride:calcium oxide is 1:(0.2 - 0.3):(1.3 - 1.5).

8. The method for in-situ synthesizing an organically modified porous functional material using coal gangue according to claim 5, wherein The complexing agent is ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid, and based on the total mass of the complexing agent, the mass ratio of ethylenediaminetetraacetic acid:diethylenetriaminepentaacetic acid is 1:(0.3 - 0.4).

9. The method for in-situ synthesizing an organically modified porous functional material using coal gangue according to claim 1, characterized in that, The amount of deionized water added is such that the mass ratio of gangue to deionized water is 1:35 - 45.

10. The method for in-situ synthesizing an organically modified porous functional material using coal gangue according to claim 1, wherein, The pH value of the suspension A is 5 - 12, and an alkaline metal compound can be added to adjust the pH.

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