High-load stability fly ash ceramsite composite water purification material and preparation method thereof

Abstract

The application belongs to the technical field of mine wastewater treatment and solid waste resource utilization, and discloses a high-load stable fly ash ceramsite composite water purification material and a preparation method thereof.The composite water purification material comprises a sinter-free silico-aluminate cementing inner core and an outer heavy metal fixing layer fixed on the outer side of the inner core by steam curing, the inner core is made of fly ash, slag powder, calcium-magnesium regulating components, slow-release alkali activating components and pore-forming regulating agents, and the outer layer is made of fly ash fine powder, slag powder, iron-manganese precursors, phytic acid-iron-manganese-silicate pre-complex composite modifier, silicate cementing auxiliary components and slurry stabilizers.During preparation, the pre-complex composite modifier is prepared first, and then the inner core granulation, outer layer rolling, steam curing and acid pre-stabilization treatment are sequentially performed.The material obtained by the application has high active component load stability, anti-scouring property and heavy metal removal stability, and is suitable for mine acid heavy metal sulfate-containing wastewater treatment.

Description

Technical Field

[0001] This invention belongs to the technical field of mine wastewater treatment and solid waste resource utilization, specifically relating to a high-load-stability fly ash ceramsite composite water purification material and its preparation method. Background Technology

[0002] Acidic wastewater containing heavy metals is easily generated during mining, mineral processing, and tailings storage. This type of wastewater typically features low pH, high sulfate content, complex metal ion composition, and significant water quality fluctuations, and may also contain heavy metal ions. Existing technologies for treating heavy metal wastewater from mines include chemical precipitation, adsorption filtration, ion exchange, membrane separation, and constructed wetlands. Among these, adsorption filtration materials are relatively simple to operate and suitable for use in fixed-bed or percolation systems. In adsorption filtration material research, solid wastes or mineral materials such as fly ash, slag, red mud, clay, and zeolite are often used to prepare porous granular water purification materials. Fly ash and slag contain components such as silicon, aluminum, and calcium. After sintering, alkali activation, or non-fired gelling and solidification, they can form ceramsite materials with certain mechanical strength and porous structure, which is beneficial for the resource utilization of industrial solid waste and also helps reduce the preparation cost of water purification materials. To further improve the heavy metal removal capacity, iron oxides, manganese oxides, or iron-manganese composite oxides can be loaded into the ceramsite material to enhance the material's adsorption, complexation, oxidation, and co-precipitation fixation of heavy metal ions.

[0003] As applications expand from general wastewater treatment to the treatment of acidic mine sulfate wastewater, some limitations of existing fly ash ceramsite materials are becoming increasingly apparent. While high-temperature sintered ceramsite boasts high strength, it also consumes significant energy. Ordinary non-sintered cementitious ceramsite is prepared at lower temperatures, but its structural stability, alkalinity release stability, and ability to retain functional components under long-term acidic water erosion still have room for improvement. For iron and manganese functional components, post-impregnation or surface coating methods easily lead to surface agglomeration and weak bonding, while one-time mixing and granulation may embed the active components, affecting their effective utilization rate. Summary of the Invention

[0004] To address the shortcomings mentioned in the background art, the present invention aims to provide a high-load-stability fly ash ceramsite composite water purification material and its preparation method. The material comprises a non-fired aluminosilicate gel core and an outer heavy metal fixing layer solidified on its outer side by steam curing. Through phytic acid-iron-manganese-silicate pre-complexation, core granulation, outer layer rolling, stepped steam curing, and acid pre-stabilization treatment, the iron and manganese functional components are stably loaded in the outer structure, thereby improving the purification stability of ceramsite in acidic mine wastewater containing heavy metal sulfates.

[0005] The objective of this invention can be achieved through the following technical solutions: A high-load-stability fly ash ceramsite composite water purification material, comprising a non-fired aluminosilicate gel core and an outer heavy metal fixing layer solidified on the outside of the non-fired aluminosilicate gel core by steam curing, wherein the average thickness of the outer heavy metal fixing layer is 5% to 25% of the average particle size of the composite water purification material; The raw materials for preparing the non-fired aluminosilicate cementitious core include, by weight, 60-100 parts of fly ash, 10-35 parts of slag powder, 5-20 parts of calcium and magnesium regulating components, 2-10 parts of slow-release alkali activating components by solids, and 1-8 parts of pore-forming regulator. The raw materials for preparing the outer heavy metal fixing layer include, by weight, 20-50 parts of fly ash fine powder, 8-25 parts of slag powder, 3-15 parts of iron-manganese precursor, 3-15 parts of phytic acid-iron-manganese-silicate pre-complexing composite modifier, 2-10 parts of silicate cementing auxiliary components by solids, and 0.1-1.5 parts of slurry stabilizer. The phytic acid-iron-manganese-silicate pre-complexed composite modifier is prepared by pre-complexing phytic acid, trivalent iron salt, divalent manganese salt and silicate components.

[0006] More preferably, the fly ash is at least one of Grade II fly ash, low-calcium fly ash, and high-calcium fly ash; the slag powder is at least one of S95 grade granulated blast furnace slag powder and S105 grade granulated blast furnace slag powder; the calcium-magnesium regulating component is at least one of quicklime, light-burned magnesium oxide, dolomite powder, and calcium carbonate, and contains at least one of quicklime and light-burned magnesium oxide; the slow-release alkali activating component is at least one of water glass, sodium metasilicate, and solid sodium silicate.

[0007] More preferably, the pore-forming regulator includes at least one of sodium bicarbonate, starch, and pulp fiber; the silicate gelling auxiliary component is at least one of silica sol, water glass with a modulus of 1.0 to 2.2, and sodium metasilicate; and the slurry stabilizer is at least one of sodium carboxymethyl cellulose, polyvinyl alcohol, and hydroxypropyl methyl cellulose.

[0008] More preferably, the iron-manganese precursor includes a trivalent iron salt and a divalent manganese salt; the trivalent iron salt is at least one of ferric sulfate, ferric nitrate nonahydrate, and ferric chloride hexahydrate; the divalent manganese salt is at least one of manganese sulfate monohydrate, manganese nitrate, and manganese chloride tetrahydrate; the raw materials for preparing the outer heavy metal fixing layer also include 0.05 to 1.0 parts by weight of an oxidation regulator, which is at least one of potassium permanganate and sodium persulfate.

[0009] More preferably, the raw materials for preparing the phytic acid-iron-manganese-silicate pre-complexed composite modifier include, by weight, 10-40 parts of a 50% phytic acid aqueous solution, 1-8 parts of ferric salt (calculated as Fe), 0.5-5 parts of divalent manganese salt (calculated as Mn), 1-8 parts of silicate component (calculated as SiO2), and 30-100 parts of deionized water; the silicate component is at least one of silica sol, water glass with a modulus of 1.0-2.2, and sodium metasilicate; the pH of the phytic acid-iron-manganese-silicate pre-complexed composite modifier is adjusted to 3.0-5.5 using a pH adjuster, which is at least one of sodium hydroxide, ammonia, citric acid, and dilute sulfuric acid.

[0010] More preferably, the average particle size of the non-fired aluminosilicate gel core is 3-7 mm, the average particle size of the composite water purification material is 4-10 mm, and the dry basis mass of the outer heavy metal fixing layer is 15%-60% of the dry basis mass of the non-fired aluminosilicate gel core.

[0011] A method for preparing a high-load-stability fly ash ceramsite composite water purification material includes the following steps: S1. Phytic acid, ferric salt, divalent manganese salt and silicate components are subjected to a pre-complexation reaction in an aqueous phase to obtain a phytic acid-ferric manganese-silicate pre-complexed composite modifier. S2. Mix fly ash, slag powder, calcium and magnesium regulating components, slow-release alkali activating components, pore-forming regulator and process water and granulate to obtain core wet particles; S3. Fly ash fine powder, slag powder, iron-manganese precursor, phytic acid-iron-manganese-silicate pre-complexing composite modifier, silicate gelling auxiliary component, slurry stabilizer, optional oxidation regulator and process water are mixed to prepare an outer active slurry, and the outer active slurry is rolled onto the surface of the core wet particles to obtain composite wet ceramsite. S4. The composite wet ceramsite is subjected to pre-curing, stepped steam curing and wet heat stabilization treatment in sequence to obtain ceramsite with a non-fired aluminosilicate cement core and an outer heavy metal fixing layer. S5. The cured ceramsite is subjected to acid pre-stabilization treatment, drying and sieving to obtain a high load-stability fly ash ceramsite composite water purification material.

[0012] More preferably, in step S1, phytic acid is added to water to form a phytic acid solution, and ferric salt and divalent manganese salt are added sequentially to the phytic acid solution to carry out a complexation reaction. Then, silicate components are added in batches and the pH of the system is adjusted to 3.0-5.5 to obtain a phytic acid-iron-manganese-silicate pre-complexed composite modifier.

[0013] More preferably, in step S4, the stepped steam curing includes a first stage of steam curing and a second stage of steam curing, wherein the temperature of the first stage of steam curing is 50-65°C and the temperature of the second stage of steam curing is 70-95°C; in step S5, the acidic pre-stabilization treatment uses an acidic sulfate solution with a pH of 3.0-5.5 to circulate the cured ceramsite.

[0014] Application of high load-stability fly ash ceramsite composite water purification material in the treatment of acidic mine wastewater containing heavy metal sulfates, wherein the acidic mine wastewater containing heavy metal sulfates contains one or more of Pb2+, Cd2+, Cu2+, Zn2+, Ni2+, and Mn2+.

[0015] The beneficial effects of this invention are: This invention addresses the problems of easy loss of active components, easy degradation of ceramsite structure, and insufficient stability of heavy metal fixation in acidic sulfate wastewater containing heavy metals from mines. It constructs a technical system that integrates pre-complexation regulation, layered molding, simultaneous steam solidification, and acidic pre-stabilization. Phytic acid-iron-manganese-silicate pre-complexing composite modifiers complex and disperse iron-manganese components before outer layer molding, preventing iron-manganese precursors from directly entering the cementation system as simple salts or free precipitates, thus reducing their rapid hydrolysis, agglomeration, and disordered deposition in alkaline environments. Layered roll molding ensures that the iron-manganese functional components are mainly enriched in the outer heavy metal fixation layer, avoiding the embedding of active components in the core during single-stage mixing and granulation, thereby improving effective utilization. During stepped steam curing, the core fly ash, slag powder, and silicate components gradually form a non-fired aluminosilicate cementitious skeleton, while the iron-manganese components in the outer active slurry are simultaneously transformed and fixed in the outer cementitious structure, creating a more stable interfacial bond between the functional layer and the core, rather than relying on post-impregnation or ordinary coating to achieve surface loading. Furthermore, by undergoing acidic pre-stabilization treatment, the ceramsite is subjected to an environmental adjustment similar to that of acidic sulfate wastewater from a mine, reducing the risk of initial alkalinity release and the erosion and loss of iron and manganese components. Attached Figure Description

[0016] The invention will now be further described with reference to the accompanying drawings.

[0017] Figure 1 This is a process flow diagram for preparing the high-load-stability fly ash ceramsite composite water purification material of the present invention. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Unless otherwise stated, all raw materials used in the following examples are commercially available products. The silica sol used in the examples has a SiO2 mass fraction of 30%; the water glass used is commercially available water glass with a solid content of 40%; the amounts of silica sol and water glass are recorded according to actual weighing. When calculating the dry basis mass, solid content mass, or the dry basis proportion of each component, the silica sol is converted according to its SiO2 mass fraction, and the water glass is converted according to its solid content. The phytic acid aqueous solution used has a mass concentration of 50%; the ferric sulfate used is anhydrous ferric sulfate, the ferric nitrate used is ferric nitrate nonahydrate, and the manganese salt used is manganese sulfate monohydrate; the sodium hydroxide solution used has a mass concentration of 10%. The fly ash fine powder is fly ash fine particles after grinding or sieving. In the examples, fly ash fine powder with a D50 particle size of 5-45 μm is used. The high-calcium fly ash is preferably high-calcium fly ash that has passed the stability test. The acidic sulfate solution is prepared from one or more of sodium sulfate, calcium sulfate, ferrous sulfate, and manganese sulfate, and the pH is adjusted with dilute sulfuric acid. The process water is mainly used as a mixing, granulation, and pulping medium, and is not a limiting factor in the dry composition of the final composite water purification material.

[0020] Example 1: This example provides a high-load-stability fly ash ceramsite composite water purification material, the preparation method of which includes the following steps: S1. Take 10g of 50% phytic acid aqueous solution, add it to 30g of deionized water, stir at room temperature for 10min to obtain phytic acid solution; add 3.58g of anhydrous ferric sulfate while stirring, react for 30min, then add 1.54g of manganese sulfate monohydrate, and continue to react for 30min; then add 3.33g of 30% SiO2 silica sol in batches, and adjust the pH to 3.5 with 10% sodium hydroxide solution, and continue stirring for 60min to obtain phytic acid-iron-manganese-silicate pre-complexed composite modifier.

[0021] S2. Mix 60g of Grade II fly ash, 10g of S95 grade granulated blast furnace slag powder, 3g of quicklime, 2g of lightly calcined magnesium oxide, 5g of water glass with a solid content of 40% and a modulus of 1.5, 0.6g of sodium bicarbonate, 0.4g of starch and 18g of process water, and granulate to obtain core wet particles with an average particle size of about 3.5mm.

[0022] S3. Mix 20g of fly ash fine powder, 8g of S95 grade granulated blast furnace slag powder, 2g of anhydrous ferric sulfate, 1g of manganese sulfate monohydrate, 3g of phytic acid-iron-manganese-silicate pre-complexed composite modifier obtained in step S1, 6.67g of silica sol with a SiO2 mass fraction of 30%, 0.1g of sodium carboxymethyl cellulose, and 22g of process water to prepare an outer active slurry. Roll the outer active slurry onto the surface of the core wet particles, and control the dry basis mass of the outer heavy metal fixing layer to be 18% of the dry basis mass of the non-fired aluminosilicate cemented core to obtain composite wet ceramsite.

[0023] S4. Pre-cur the composite wet ceramsite at 30℃ for 8 hours; then perform stepped steam curing. The first stage of steam curing is at 55℃ for 3 hours, and the second stage of steam curing is at 75℃ for 8 hours. After steam curing, perform humid heat stabilization at 50℃ for 8 hours to obtain cured ceramsite.

[0024] S5. The ceramsite was circulated for 4 hours using an acidic sulfate solution with a pH of 4.0, at a liquid-to-solid ratio of 10 mL / g. The acidic sulfate solution was prepared using sodium sulfate and calcium sulfate, with a total sulfate concentration of 1000 mg / L, and the pH was adjusted using dilute sulfuric acid. After treatment, the ceramsite was dried at 60℃ to constant weight and sieved to obtain a high-load-stability fly ash ceramsite composite water purification material. The average particle size of the obtained material was approximately 4.0 mm, the average thickness of the outer heavy metal fixing layer was approximately 6% of the average particle size of the composite water purification material, and the dry basis mass of the outer heavy metal fixing layer was approximately 18% of the dry basis mass of the non-fired aluminosilicate gel core.

[0025] Example 2: This example provides a high-load-stability fly ash ceramsite composite water purification material, the preparation method of which includes the following steps: S1. Add 40g of 50% phytic acid aqueous solution and 100g of deionized water to the reaction vessel and stir at room temperature until the system is homogeneous. Then add 57.90g of ferric nitrate nonahydrate and stir for 50min. Then add 15.39g of manganese sulfate monohydrate and continue stirring for 50min. After that, add 26.67g of 30% SiO2 silica sol in batches while stirring. The pH of the system is slowly adjusted to 5.2 using 10% sodium hydroxide solution and stirred for 90min to obtain the phytic acid-ferric manganese-silicate pre-complexed composite modifier.

[0026] S2. Add 100g of high-calcium fly ash, 35g of S105 grade granulated blast furnace slag powder, 8g of quicklime, 6g of lightly calcined magnesium oxide, 3g of dolomite powder, 3g of calcium carbonate, 15g of water glass with a solid content of 40% and a modulus of 1.8, 4g of sodium metasilicate, 3g of sodium bicarbonate, 3g of starch, 2g of pulp fiber, and 35g of process water to a mixing device, mix evenly, and then granulate to obtain wet core particles with an average particle size of about 7.0mm.

[0027] S3. Take 50g of fly ash fine powder, 25g of S105 grade granulated blast furnace slag powder, 10g of anhydrous ferric sulfate, 5g of manganese sulfate monohydrate, 15g of phytic acid-iron-manganese-silicate pre-complexed composite modifier obtained in step S1, 20g of silica sol with a SiO2 mass fraction of 30%, 10g of water glass with a solid content of 40% and a modulus of 1.8, 1.0g of polyvinyl alcohol, 0.5g of hydroxypropyl methylcellulose, 0.8g of sodium persulfate, and 45g of process water, and stir to prepare an outer active slurry. Gradually roll the outer active slurry onto the surface of the core wet particles, and control the rolling amount of the outer active slurry according to the target dry basis mass of the outer layer, so that the dry basis mass of the outer heavy metal fixing layer is about 55% of the dry basis mass of the non-fired aluminosilicate cementitious core, to obtain composite wet ceramsite.

[0028] S4. The composite wet ceramsite is first pre-cured at 35℃ for 16 hours, and then subjected to two-stage steam curing. The first stage of steam curing is at 65℃ for 5 hours, and the second stage of steam curing is at 90℃ for 16 hours. After steam curing, the ceramsite is placed at 55℃ for humid heat stabilization for 18 hours to obtain cured ceramsite.

[0029] S5. The ceramsite was circulated for 10 hours using an acidic sulfate solution with a pH of 5.2, at a liquid-to-solid ratio of 10 mL / g. The acidic sulfate solution was prepared with sodium sulfate, ferrous sulfate, and manganese sulfate, with a total sulfate concentration of 2000 mg / L. The pH was adjusted with dilute sulfuric acid. After circulation, the ceramsite was dried at 70°C to constant weight and then sieved to obtain a high-load-stability fly ash ceramsite composite water purification material. The average particle size of the obtained composite water purification material was approximately 9.5 mm, the average thickness of the outer heavy metal fixing layer was approximately 13% of the average particle size of the composite water purification material, and the dry basis mass of the outer heavy metal fixing layer was approximately 55% of the dry basis mass of the non-fired aluminosilicate gel core.

[0030] Example 3: This example provides a high-load-stability fly ash ceramsite composite water purification material, the preparation method of which includes the following steps: S1. Take 25g of 50% phytic acid aqueous solution and add it to 65g of deionized water. Stir and mix evenly to obtain phytic acid solution. Add 14.32g of anhydrous ferric sulfate under continuous stirring. After reacting for 40min, add 7.69g of manganese sulfate monohydrate and continue to react for 40min. Then add 13.33g of silica sol with a SiO2 mass fraction of 30% in batches. Adjust the pH of the system to 4.5 with a 10% sodium hydroxide solution and continue stirring for 80min to obtain phytic acid-iron-manganese-silicate pre-complexed composite modifier.

[0031] S2. Add 80g of low-calcium fly ash, 22g of S95 grade granulated blast furnace slag powder, 6g of quicklime, 4g of lightly calcined magnesium oxide, 2g of calcium carbonate, 10g of water glass with a solid content of 40% and a modulus of 1.6, 2g of sodium metasilicate, 2g of sodium bicarbonate, 1g of starch, 1g of pulp fiber, and 26g of process water to a mixing device, mix evenly, and then granulate to obtain wet core particles with an average particle size of about 5.0mm.

[0032] S3. Take 35g of fly ash fine powder, 16g of S95 grade granulated blast furnace slag powder, 5g of anhydrous ferric sulfate, 3g of manganese sulfate monohydrate, 8g of phytic acid-iron-manganese-silicate pre-complexed composite modifier obtained in step S1, 13.33g of silica sol with a SiO2 mass fraction of 30%, 5g of water glass with a solid content of 40% and a modulus of 1.6, 0.5g of sodium carboxymethyl cellulose, 0.3g of polyvinyl alcohol, 0.3g of sodium persulfate, and 32g of process water, and stir to prepare an outer active slurry. Take an appropriate amount of the outer active slurry and roll it onto the surface of the core wet particles in batches, and control the rolling amount according to the target dry basis mass of the outer layer, so that the dry basis mass of the outer heavy metal fixing layer is about 35% of the dry basis mass of the non-fired aluminosilicate cemented core, to obtain composite wet ceramsite.

[0033] S4. Pre-cur the composite wet ceramsite at 30℃ for 12 hours, and then perform stepped steam curing. The first stage of steam curing is at 60℃ for 4 hours, and the second stage of steam curing is at 85℃ for 12 hours. After steam curing, the ceramsite is humidified at 50℃ for 12 hours to obtain cured ceramsite.

[0034] S5. The ceramsite was circulated for 6 hours using an acidic sulfate solution with a pH of 4.5, at a liquid-to-solid ratio of 10 mL / g. The acidic sulfate solution was prepared with sodium sulfate, calcium sulfate, and ferrous sulfate, with a total sulfate concentration of 1500 mg / L. The pH was adjusted with dilute sulfuric acid. After the circulation treatment, the ceramsite was dried at 65°C to constant weight and sieved to obtain a high-load-stability fly ash ceramsite composite water purification material. The average particle size of the obtained composite water purification material was approximately 6.5 mm, the average thickness of the outer heavy metal fixing layer was approximately 12% of the average particle size of the composite water purification material, and the dry basis mass of the outer heavy metal fixing layer was approximately 35% of the dry basis mass of the non-fired aluminosilicate gel core.

[0035] Comparative Example 1: This comparative example does not perform S1 of Example 3, and does not add phytic acid-iron-manganese-silicate pre-complexing composite modifier when preparing the outer active slurry, and replaces it with an equal amount of process water.

[0036] Specifically, the core wet particles were prepared according to S2 of Example 3; subsequently, when preparing the outer active slurry, 35g of fly ash fine powder, 16g of S95 grade granulated blast furnace slag powder, 5g of anhydrous ferric sulfate, 3g of manganese sulfate monohydrate, 13.33g of silica sol with a SiO2 mass fraction of 30%, 5g of water glass with a solid content of 40% and a modulus of 1.6, 0.5g of sodium carboxymethyl cellulose, 0.3g of polyvinyl alcohol, 0.3g of sodium persulfate, and 40g of process water were taken and stirred to prepare the outer active slurry; the outer active slurry was rolled onto the surface of the core wet particles in the manner of Example 3, and the dry basis mass of the outer heavy metal fixing layer was controlled to be about 35% of the dry basis mass of the non-fired aluminosilicate cemented core to obtain composite wet ceramsite.

[0037] The curing, consolidation, acid pre-stabilization treatment, drying and sieving steps of the obtained composite wet ceramsite were the same as those in Example 3, resulting in the fly ash ceramsite water purification material of Comparative Example 1.

[0038] Comparative Example 2: This comparative example provides a fly ash ceramsite water purification material, the preparation method of which is basically the same as that of Example 3, except that: the S1 pre-complexation treatment of Example 3 is not performed, but when preparing the outer active slurry, the phytic acid aqueous solution, anhydrous ferric sulfate, manganese sulfate monohydrate and silica sol obtained according to the proportion of the main raw materials of the pre-complexation system in Example 3 are directly added to the outer active slurry.

[0039] Specifically, core wet particles were prepared according to S2 of Example 3; subsequently, when preparing the outer active slurry, 35g of fly ash fine powder, 16g of S95 grade granulated blast furnace slag powder, 5.91g of anhydrous ferric sulfate, 3.49g of manganese sulfate monohydrate, 1.60g of phytic acid aqueous solution with a mass concentration of 50%, 14.18g of silica sol with a SiO2 mass fraction of 30%, 5g of water glass with a solid content of 40% and a modulus of 1.6, 0.5g of sodium carboxymethyl cellulose, 0.3g of polyvinyl alcohol, 0.3g of sodium persulfate, and 36.15g of process water were stirred to prepare the outer active slurry; an appropriate amount of the outer active slurry was rolled onto the surface of the core wet particles in batches, and the rolling amount was controlled according to the target dry basis mass of the outer layer, so that the dry basis mass of the outer heavy metal fixing layer was about 35% of the dry basis mass of the non-fired aluminosilicate cemented core, thus obtaining composite wet ceramsite.

[0040] The curing, consolidation, acid pre-stabilization treatment, drying and sieving steps of the obtained composite wet ceramsite were the same as those in Example 3, resulting in the fly ash ceramsite water purification material of Comparative Example 2.

[0041] Comparative Example 3: This comparative example provides a fly ash ceramsite water purification material, the preparation method of which is basically the same as that of Example 3, except that: the core wet particles and the outer active slurry are not prepared separately, and the outer layer is not rolled, but the core raw materials and the outer layer raw materials are mixed at one time and then granulated.

[0042] Specifically, phytic acid-iron-manganese-silicate pre-complexed composite modifier was prepared according to S1 of Example 3; then 80g of low-calcium fly ash, 35g of fine fly ash powder, 38g of S95 grade granulated blast furnace slag powder, 6g of quicklime, 4g of lightly calcined magnesium oxide, 2g of calcium carbonate, 15g of water glass with a solid content of 40% and a modulus of 1.6, 2g of sodium metasilicate, 2g of sodium bicarbonate, 1g of starch, 1g of pulp fiber, 5g of anhydrous ferric sulfate, 3g of manganese sulfate monohydrate, 8g of the phytic acid-iron-manganese-silicate pre-complexed composite modifier prepared in step S1, 13.33g of silica sol with a SiO2 mass fraction of 30%, 0.5g of sodium carboxymethyl cellulose, 0.3g of polyvinyl alcohol, 0.3g of sodium persulfate and 58g of process water were mixed evenly and directly granulated to obtain composite wet ceramsite.

[0043] The pre-curing, stepped steam curing, wet heat stabilization, acid pre-stabilization treatment, drying and sieving steps of the obtained composite wet ceramsite are the same as those in Example 3, resulting in the fly ash ceramsite water purification material of Comparative Example 3.

[0044] Comparative Example 4: This comparative example provides a fly ash ceramsite water purification material, the preparation method of which is basically the same as that of Example 3, except that: instead of using the method of rolling an outer layer of active slurry and simultaneously steam-solidifying the iron and manganese functional components, ordinary fly ash ceramsite is prepared first, and then the iron and manganese components are loaded by post-impregnation.

[0045] Specifically, core wet particles were prepared according to S2 of Example 3; then 35g of fly ash fine powder, 16g of S95 grade granulated blast furnace slag powder, 13.33g of silica sol with a SiO2 mass fraction of 30%, 5g of water glass with a solid content of 40% and a modulus of 1.6, 0.5g of sodium carboxymethyl cellulose, 0.3g of polyvinyl alcohol and 32g of process water were taken and stirred to prepare an outer layer slurry without iron and manganese components; the outer layer slurry was rolled onto the surface of the core wet particles in batches, and the rolling amount was controlled according to the outer layer dry basis quality of Example 3 to obtain composite wet ceramsite.

[0046] The obtained composite wet ceramsite was subjected to pre-curing, stepped steam curing and wet heat stabilization treatment according to S4 of Example 3 to obtain ordinary cured ceramsite.

[0047] Ordinary curing ceramsite was immersed in an iron-manganese salt solution for post-impregnation treatment. The iron-manganese salt solution was prepared by 5g of anhydrous ferric sulfate, 3g of manganese sulfate monohydrate and deionized water. The amount of deionized water was determined according to a liquid-to-solid ratio of 10mL / g. The pH of the impregnation solution was 3.0-3.5, and the impregnation time was 6h. After impregnation, the ceramsite was taken out, drained and dried at 65℃. Then, acidic pre-stabilization treatment, drying and sieving were carried out according to S5 of Example 3 to obtain the fly ash ceramsite water purification material of Comparative Example 4.

[0048] Performance testing To verify the technical effects of the present invention, performance tests were conducted on the water purification materials obtained in Examples 1-3 and Comparative Examples 1-4. Before the tests, each group of water purification materials was sieved to the corresponding particle size range, rinsed with deionized water until the washing liquid was basically clear, and dried at 60-70°C to constant weight for later use. Three parallel samples were set up for each test, and the average value of the results was taken.

[0049] (1) Comprehensive removal rate test of heavy metals: A simulated acidic mine wastewater containing heavy metal sulfates was prepared with a pH of 4.0±0.1 and a sulfate concentration of 1500 mg / L (SO42-). The initial mass concentrations of Pb2+, Cd2+, Cu2+, Zn2+, Ni2+, and Mn2+ were 10 mg / L, 2 mg / L, 10 mg / L, 20 mg / L, 10 mg / L, and 20 mg / L, respectively. 10 g of each group of water purification materials was weighed and added to 250 mL of simulated wastewater. The mixture was shaken and reacted at 25℃ and 150 r / min for 24 h. After the reaction, the water sample was filtered through a 0.45 μm filter membrane, and the concentrations of Pb, Cd, Cu, Zn, Ni, and Mn in the water sample before and after treatment were determined according to HJ 700-2014 or HJ 776-2015. The removal rate of a single metal ion is calculated as η = (C0 - Ct) / C0 × 100%, and the comprehensive removal rate of heavy metals is the average of the removal rates of six heavy metal ions.

[0050] (2) Continuous operation removal retention rate and Fe / Mn loss test: A fixed bed column was used for continuous operation test. Each group of water purification materials was filled into a column with an inner diameter of 30 mm and a filling height of 300 mm. Acidic mine wastewater containing heavy metal sulfates was used as the influent. The empty bed contact time was controlled at 30 min, and 30 bed volumes were continuously operated. The effluent from the first bed volume and the 30th bed volume were collected respectively. After filtration through a 0.45 μm filter membrane, the concentrations of Pb, Cd, Cu, Zn, Ni, and Mn were measured and the comprehensive removal rate was calculated. The continuous operation removal retention rate was calculated as the ratio of the comprehensive removal rate of the 30th bed volume to the comprehensive removal rate of the first bed volume. At the same time, the concentrations of Fe and Mn in the effluent of continuous operation were measured, and the cumulative Fe / Mn loss per unit mass of water purification material was calculated in mg / g. The concentrations of relevant elements were determined according to HJ 700-2014 or HJ 776-2015.

[0051] (3) Acid leaching stability test: The acid leaching stability test was conducted in accordance with HJ / T 299-2007. 20g of each group of dried water purification materials were weighed and added to a sulfuric acid-nitric acid mixed extraction solution with a pH of 3.2±0.1, at a liquid-to-solid ratio of 10mL / g. The solution was shaken at 25℃ and 110r / min for 18h. After leaching, samples were taken by filtration through a 0.45μm filter membrane. The concentrations of Fe and Mn in the leachate were measured, and the release rate of the acid-leached functional components was calculated as a percentage of the cumulative release of Fe and Mn in the leachate relative to the theoretical load of Fe and Mn in the water purification material. The theoretical load of Fe and Mn was calculated based on the theoretical amount of Fe and Mn added during the preparation process.

[0052] (4) Breakage and abrasion rate test: Refer to the test methods for breakage and abrasion rate of filter media in CJ / T 299-2008 "Artificial ceramsite filter media for water treatment" or CJ / T43-2005 "Filter media for water treatment". Take each group of dried water purification materials for testing, and test each group 3 times. Take the average value of the results.

[0053] The results are shown in Table 1 below.

[0054] Table 1. Comprehensive performance test results of the water purification materials obtained in the examples and comparative examples.

[0055] As shown in Table 1, the water purification materials obtained in Examples 1-3 all exhibit high comprehensive heavy metal removal rates and continuous operation removal retention rates. Simultaneously, the cumulative Fe / Mn loss, acid leaching functional component release rate, and the sum of breakage and wear rates are all low. This indicates that the continuous technology design of this invention, involving "phytic acid-iron-manganese-silicate pre-complexation—outer layer rolling enrichment—steam synchronous solidification—acidic pre-stabilization," effectively improves the dispersibility, fixation stability, and acidic water flow adaptability of the iron-manganese functional components in the outer layer of fly ash ceramsite. Specifically, Example 3 achieved a comprehensive heavy metal removal rate of 96.5%, a continuous operation removal retention rate of 93.4%, a cumulative Fe / Mn loss of only 0.28 mg / g, and an acid leaching functional component release rate of 2.4%. This demonstrates that a moderate iron-manganese loading and outer layer thickness are beneficial for balancing active site exposure, pore mass transfer, and gelation stability. Comparative Example 1, without the addition of a pre-complexing composite modifier, lacked the complexing dispersion and silicate synergistic fixation effect of the iron and manganese components, resulting in a significant decrease in removal and retention rates. Comparative Example 2 directly added the relevant raw materials without pre-complexing, indicating that simple mixing is insufficient to form a stable functional component system. Comparative Example 3, with its single-stage mixing and granulation, resulted in the embedding of some iron and manganese components, leading to a reduction in effective utilization. Comparative Example 4, employing post-impregnation loading, while exhibiting some initial removal capacity, showed the highest Fe / Mn loss and acid leaching release rate, along with significant breakage and wear, indicating insufficient post-loading bonding stability. The above results demonstrate that the material obtained in this invention possesses both high-efficiency heavy metal removal, low functional component loss, and good operational stability.

[0056] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0057] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A high-load-stability fly ash ceramsite composite water purification material, characterized in that, The composite water purification material comprises a non-fired aluminosilicate gel core and an outer heavy metal fixing layer solidified on the outside of the non-fired aluminosilicate gel core by steam curing. The average thickness of the outer heavy metal fixing layer is 5% to 25% of the average particle size of the composite water purification material. The raw materials for preparing the non-fired aluminosilicate cementitious core include, by weight, 60-100 parts of fly ash, 10-35 parts of slag powder, 5-20 parts of calcium and magnesium regulating components, 2-10 parts of slow-release alkali activating components by solids, and 1-8 parts of pore-forming regulator. The raw materials for preparing the outer heavy metal fixing layer include, by weight, 20-50 parts of fly ash fine powder, 8-25 parts of slag powder, 3-15 parts of iron-manganese precursor, 3-15 parts of phytic acid-iron-manganese-silicate pre-complexing composite modifier, 2-10 parts of silicate cementing auxiliary components by solids, and 0.1-1.5 parts of slurry stabilizer. The phytic acid-iron-manganese-silicate pre-complexed composite modifier is prepared by pre-complexing phytic acid, trivalent iron salt, divalent manganese salt and silicate components.

2. The high-load-stability fly ash ceramsite composite water purification material according to claim 1, characterized in that, The fly ash is at least one of Grade II fly ash, low-calcium fly ash, and high-calcium fly ash; the slag powder is at least one of S95 grade granulated blast furnace slag powder and S105 grade granulated blast furnace slag powder; the calcium and magnesium regulating component is at least one of quicklime, light-burned magnesium oxide, dolomite powder, and calcium carbonate, and contains at least one of quicklime and light-burned magnesium oxide; the slow-release alkali activating component is at least one of water glass, sodium metasilicate, and solid sodium silicate.

3. The high-load-stability fly ash ceramsite composite water purification material according to claim 1, characterized in that, The pore-forming regulator includes at least one of sodium bicarbonate, starch, and pulp fiber; the silicate gelling auxiliary component includes at least one of silica sol, water glass with a modulus of 1.0 to 2.2, and sodium metasilicate; the slurry stabilizer includes at least one of sodium carboxymethyl cellulose, polyvinyl alcohol, and hydroxypropyl methyl cellulose.

4. The high-load-stability fly ash ceramsite composite water purification material according to claim 1, characterized in that, The iron-manganese precursor includes trivalent iron salt and divalent manganese salt; the trivalent iron salt is at least one of ferric sulfate, ferric nitrate nonahydrate, and ferric chloride hexahydrate; the divalent manganese salt is at least one of manganese sulfate monohydrate, manganese nitrate, and manganese chloride tetrahydrate; the raw materials for preparing the outer heavy metal fixing layer also include 0.05 to 1.0 parts by weight of an oxidation regulator, which is at least one of potassium permanganate and sodium persulfate.

5. The high-load-stability fly ash ceramsite composite water purification material according to claim 1, characterized in that, The raw materials for preparing the phytic acid-iron-manganese-silicate pre-complexed composite modifier include, by weight, 10-40 parts of a 50% phytic acid aqueous solution, 1-8 parts of ferric salt (calculated as Fe), 0.5-5 parts of divalent manganese salt (calculated as Mn), 1-8 parts of silicate component (calculated as SiO2), and 30-100 parts of deionized water; the silicate component is at least one of silica sol, water glass with a modulus of 1.0-2.2, and sodium metasilicate; the pH of the phytic acid-iron-manganese-silicate pre-complexed composite modifier is adjusted to 3.0-5.5 using a pH adjuster, which is at least one of sodium hydroxide, ammonia, citric acid, and dilute sulfuric acid.

6. The high-load-stability fly ash ceramsite composite water purification material according to claim 1, characterized in that, The average particle size of the non-fired aluminosilicate gel core is 3-7 mm, the average particle size of the composite water purification material is 4-10 mm, and the dry basis mass of the outer heavy metal fixing layer is 15%-60% of the dry basis mass of the non-fired aluminosilicate gel core.

7. A method for preparing a high-load-stability fly ash ceramsite composite water purification material according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Phytic acid, ferric salt, divalent manganese salt and silicate components are subjected to a pre-complexation reaction in an aqueous phase to obtain a phytic acid-ferric manganese-silicate pre-complexed composite modifier. S2. Mix fly ash, slag powder, calcium and magnesium regulating components, slow-release alkali activating components, pore-forming regulator and process water and granulate to obtain core wet particles; S3. Fly ash fine powder, slag powder, iron-manganese precursor, phytic acid-iron-manganese-silicate pre-complexing composite modifier, silicate gelling auxiliary component, slurry stabilizer, optional oxidation regulator and process water are mixed to prepare an outer active slurry, and the outer active slurry is rolled onto the surface of the core wet particles to obtain composite wet ceramsite. S4. The composite wet ceramsite is subjected to pre-curing, stepped steam curing and wet heat stabilization treatment in sequence to obtain ceramsite with a non-fired aluminosilicate cement core and an outer heavy metal fixing layer. S5. The cured ceramsite is subjected to acid pre-stabilization treatment, drying and sieving to obtain a high load-stability fly ash ceramsite composite water purification material.

8. The preparation method according to claim 7, characterized in that, In step S1, phytic acid is added to water to form a phytic acid solution. Ferric salt and manganese salt are added to the phytic acid solution in sequence to carry out a complexation reaction. Then, silicate components are added in batches and the pH of the system is adjusted to 3.0-5.5 to obtain a phytic acid-ferric-manganese-silicate pre-complexed composite modifier.

9. The preparation method according to claim 7, characterized in that, In step S4, the stepped steam curing includes a first stage of steam curing and a second stage of steam curing. The temperature of the first stage of steam curing is 50-65℃, and the temperature of the second stage of steam curing is 70-95℃. In step S5, the acidic pre-stabilization treatment uses an acidic sulfate solution with a pH of 3.0-5.5 to circulate the cured ceramsite.

10. The application of the high-load-stability fly ash ceramsite composite water purification material according to any one of claims 1 to 6 in the treatment of acidic mine wastewater containing heavy metal sulfates, characterized in that, The acidic heavy metal sulfate wastewater from the mine contains one or more of the following: Pb2+, Cd2+, Cu2+, Zn2+, Ni2+, and Mn2+.

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