A solidified material applied to a non-flame combustion process of copper-containing sludge and a preparation method thereof

Abstract

The application belongs to the technical field of auxiliary agent preparation, and provides a solidified material applied to copper-containing sludge flameless combustion process and a preparation method; firstly, iron nitrate nonahydrate, ferrous sulfate heptahydrate, manganese nitrate solution and citric acid are mixed to prepare ferrite precursor; further, rare earth phosphate nanodispersion is synthesized by a hydrothermal method, lanthanum nitrate hexahydrate and cerium nitrate hexahydrate are used as rare earth sources, ammonium dihydrogen phosphate and ammonium fluoride are introduced to provide phosphate and fluoride ions; meanwhile, multi-component co-doped amorphous powder is prepared by a sol-gel method, tetraethyl orthosilicate is used as a silicon source, zirconium oxychloride octahydrate, titanium acid tetrabutyl ester and niobium pentachloride are used as auxiliary materials, and a thermally stable amorphous oxide matrix is formed under high-temperature heat treatment to provide high-temperature mechanical properties; finally, kaolin or bentonite mineral powder is mixed with the above-synthesized ferrite precursor, rare earth phosphate nanodispersion, multi-component amorphous powder and other auxiliary agents, a slurry is formed, and the slurry is dried and formed into a solidified material.

Description

Technical Field

[0001] This invention belongs to the field of additive preparation technology, and relates to a solidification material and its preparation method for use in the flameless combustion process of copper-containing sludge. Background Technology

[0002] With rapid industrialization, copper-containing sludge, a byproduct of industries such as metallurgy, electroplating, printing and dyeing, and battery manufacturing, is increasingly produced. Copper-containing sludge is typically rich in heavy metal ions, possessing not only potential resource recovery value but also posing a serious threat to the environment and human health. Improper treatment of copper-containing sludge can lead to the pollution of soil and water bodies through dissolution and migration, ultimately entering the food chain and posing a significant threat to the ecological environment and biosecurity. Currently, the main treatment methods for copper-containing sludge include physical treatment, chemical treatment, and thermal treatment. Physical treatment methods (such as sludge drying and dewatering) can only reduce sludge volume and cannot fundamentally solve the problem of heavy metal pollution. Chemical treatment methods (such as chemical precipitation and oxidation-reduction methods) can fix some heavy metals in sludge, but their treatment efficiency is limited by the type and amount of chemical agents and they are prone to secondary pollution. Thermal treatment methods (such as incineration and melt solidification) are a more thorough treatment method that can significantly reduce sludge volume and fix some heavy metals, but high-temperature treatment is often accompanied by the release of harmful gases, and existing thermal treatment methods have high requirements for equipment and energy consumption, which limits their widespread application.

[0003] Flameless combustion, as an emerging thermal treatment technology, offers new possibilities for the treatment of copper-containing sludge. Flameless combustion refers to the process of achieving efficient pyrolysis and oxidation reactions of materials without open flame by controlling combustion conditions. Compared with traditional combustion technologies, flameless combustion has advantages such as lower combustion temperature, higher thermal efficiency, and lower pollutant emissions, making it particularly suitable for the treatment of highly polluting and toxic wastes. However, two major problems still exist with copper-containing sludge under flameless combustion conditions: First, the volatilization or migration of copper ions under high-temperature conditions cannot be avoided. In particular, copper ions easily react with oxygen or sulfides at high temperatures to form volatile cuprous oxide, copper oxide, or copper sulfide compounds, which can enter the flue gas, increasing the risk of secondary pollution. Therefore, to fully utilize the advantages of flameless combustion technology in sludge treatment, developing a highly efficient solidification material capable of fixing copper ions under high-temperature conditions is particularly important. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention aims to provide a solidified material and its preparation method for flameless combustion of copper-containing sludge. The preparation process involves a multi-step design and synthesis of ferrate precursors, rare earth phosphate nano-dispersions, and multi-component co-doped amorphous powders, combined with mineral powders and additives, to achieve excellent structural stability and functional properties. Specifically, the ferrate precursor is prepared via a sol-gel method, utilizing the synergistic effect of iron, manganese, and other metal ions to impart excellent redox properties. The rare earth phosphate nano-dispersion is prepared via a hydrothermal reaction, where the combination of rare earth ions with phosphate and fluoride ions provides dispersion stability. The multi-component co-doped amorphous powder is formed via a sol-gel method, with the synergistic effect of metals such as silicon, zirconium, titanium, and niobium enhancing the material's skeletal structure and thermal stability. Finally, through multi-component composite processing, a solidified material with high-temperature stability and excellent chemical properties is prepared, thus meeting the needs of practical production.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a solidified material applicable to the flameless combustion process of copper-containing sludge, the preparation method comprising:

[0007] S1, ferric nitrate nonahydrate and ferrous sulfate heptahydrate are dispersed in deionized water, then manganese nitrate solution is added, then citric acid is added, the temperature is raised to the first temperature, the pH is maintained at 4.5, and the mixture is stirred until it becomes a viscous semi-colloid. The mixture is then transferred to an oven to dry at the second temperature, and after drying, it is transferred to a muffle furnace to heat to the third temperature and held at that temperature. Finally, it is transferred to a nitrogen atmosphere and heated to 800°C and held at that temperature to obtain the ferrate precursor.

[0008] S2, Lanthanum nitrate hexahydrate and cerium nitrate hexahydrate are dispersed in deionized water to obtain a rare earth solution. Ammonium dihydrogen phosphate, ammonium fluoride and PVP are dispersed in deionized water to obtain a fluorophosphate solution. The fluorophosphate solution is added to the rare earth solution, and the pH of the solution is maintained at 4.5. The mixture is transferred to a hydrothermal reactor lined with polytetrafluoroethylene and hydrothermally reacted at the fourth temperature. After the reaction is completed, the large agglomerates are removed by centrifugation, and the supernatant is the rare earth phosphate nanodispersion.

[0009] S3, tetraethyl orthosilicate, ethanol and glacial acetic acid are mixed and stirred at 60°C to obtain a silanol solution. Zirconium oxychloride octahydrate is then dispersed in HCl solution and added to the silanol solution. Tetrabutyl titanate and niobium pentachloride are added and stirring is continued. The pH is adjusted to 2.5 to obtain a sol. The sol is dried under vacuum at 80°C, heated to 450°C and held at 500°C under a nitrogen atmosphere to obtain multi-component co-doped amorphous powder.

[0010] S4 involves mixing mineral powder, ferrate precursor, rare earth phosphate nano-dispersion, multi-component co-doped amorphous powder, PVA, and polystyrene microspheres to form a slurry, which is then dried at 80°C to obtain a solidified material applicable to the flameless combustion process of copper-containing sludge.

[0011] In the experimental scheme of this invention, the addition of ferric nitrate nonahydrate and ferrous sulfate heptahydrate provides the system with two oxidation states of iron ions: ferrous (Fe2+) and ferric (Fe3+). These two oxidation states of iron ions are fundamental to the formation of spinel-type ferrates, as the spinel lattice is typically occupied by both ferrous and ferric ions occupying their respective lattice positions. Simultaneously, the addition of manganese nitrate provides ferrous (Mn+) ions, which will be doped into the ferrate lattice during subsequent heat treatment, partially replacing the positions of ferrous or ferric ions to form a Mn-doped spinel structure. The doping of ferrous ions not only improves the thermal stability of the ferrate material but also increases the number of sites for metal ion substitution in the lattice, providing additional chemical space for the entry of copper ions. The addition of citric acid to the metal ion solution improves the chemical stability of the system. Citric acid is a multidentate ligand; its carboxyl and hydroxyl groups can form stable chelate complexes with metal ions, effectively suppressing the hydrolysis tendency of ferric ions and preventing the formation of ferric hydroxide precipitate. Through complexation, citric acid ensures a uniform distribution of metal ions while reducing the possibility of uneven reactions in the solution. Furthermore, the complexing effect of citric acid imparts a certain pH buffering capacity to the solution, allowing subsequent reactions to proceed in a relatively stable pH environment. Heating the solution causes partial dissociation of the metal-citric acid complex in the system. As the temperature rises, metal ions are gradually released from the complex and exist in free form within the system. At this point, the metal ions may connect with each other through hydroxyl bridges, gradually forming a preliminary polymer network. Due to their higher charge density and strong coordination ability, ferric ions tend to form polymer precursors through hydroxyl bridges, while ferrous and manganese ions are embedded in this network in a more dispersed form. The semi-colloidal system is transferred to an oven for further evaporation of moisture and the decomposition of some citric acid molecules. During this process, the thermal decomposition of citric acid releases small molecules (such as carbon dioxide and water), while the remaining organic groups may act as dispersants, preventing excessive aggregation of metal oxide particles. After drying, during heat treatment, citric acid molecules begin to decompose, releasing the metal ions coordinated with them. These metal ions gradually approach each other in the solid environment and undergo solid-phase reactions to form the prototype of a spinel structure. At the same time, divalent manganese ions are doped into the crystal lattice, which further improves the complexity and stability of the structure.

[0012] High-temperature heat treatment is carried out in a nitrogen atmosphere to suppress the excessive oxidation of ferrous ions to ferric ions. Under high-temperature conditions, metal ions are further uniformly distributed through diffusion, and the initially formed amorphous oxide gradually crystallizes, eventually transforming into a ferrite material with a spinel structure. Since the ionic radius of ferrous ions is close to that of divalent copper ions, they can partially enter the crystal lattice through anisovalent substitution mechanism, replacing the positions of ferrous or ferric ions. Furthermore, oxygen vacancies in the spinel lattice may also coordinate with ferrous ions, further enhancing their fixation ability. Secondly, the surface adsorption effect of spinel materials also plays an important role in the fixation of copper ions. After high-temperature treatment, ferrite materials typically have a large specific surface area and highly active surfaces. These surface sites can bind copper ions through electrostatic attraction or chemical bonding, achieving surface fixation. Simultaneously, the redox properties of the spinel structure enable it to undergo electron exchange reactions with copper ions at high temperatures. Divalent copper ions can be reduced to cuprous ions through electron transfer reactions with ferrous ions, further stabilizing them in the crystal lattice. This redox reaction not only enhances the bonding strength of copper, but also improves the overall chemical stability of the material.

[0013] By dissolving lanthanum nitrate and cerium nitrate in deionized water, rare earth ions completely dissociate and are uniformly distributed in the solution. Rare earth ions have large ionic radii and high charge densities, enabling them to form strong hydration reactions with solvent molecules, generating stable hydrated rare earth ions. This invention disperses ammonium dihydrogen phosphate, ammonium fluoride, and polyvinylpyrrolidone in deionized water, forming a multifunctional reaction system. Ammonium dihydrogen phosphate dissociates in solution to generate dihydrogen phosphate ions, and ammonium fluoride dissociates to generate fluoride ions. Fluoride ions can form stable coordinate bonds with rare earth ions. Polyvinylpyrrolidone, as a polymeric dispersant, has carbonyl groups that can weakly coordinate with the particle surface, forming a physical adsorption layer, effectively preventing the aggregation of rare earth phosphate particles during the reaction. By gradually adding the fluorophosphate solution to the rare earth ion solution, the rare earth ions react with phosphate and fluoride ions to generate precursor particles of rare earth phosphate. Rare earth ions, due to their high charge density and strong nucleophilicity, can rapidly adsorb and bind phosphate and fluoride ions, forming initial amorphous particles. The mixed solution was then transferred to a polytetrafluoroethylene-lined hydrothermal reactor for hydrothermal reaction under specific temperature conditions. The rare earth ions in the reaction system, along with phosphate and fluoride ions, promote the nucleation of amorphous rare earth phosphate particles. After the hydrothermal reaction, any large agglomerates present in the reaction system were removed by centrifugation, retaining only the supernatant as a rare earth phosphate nanodispersion. The rare earth phosphate nanoparticles in the dispersion are coated with a polymer adsorption layer due to the action of polyvinylpyrrolidone. This adsorption layer effectively prevents particle aggregation and further improves the dispersibility and stability of the particles in solution. The final rare earth phosphate nanodispersion exhibits high dispersibility, high specific surface area, and good chemical stability, providing unique chemical properties for subsequent copper ion fixation and material performance optimization. Rare earth phosphate nanodispersions have multiple functions in the final cured material: First, the ion exchange capacity of rare earth phosphate crystals enables them to capture copper ions through mechanisms such as chemical adsorption, ion exchange, or lattice embedding. The interaction between rare earth phosphate and copper ions forms a stable compound, thereby significantly reducing the risk of copper ion migration. Second, the high thermal stability of rare earth phosphate ensures that it can maintain its structural integrity during high-temperature flameless combustion, which is of great significance for preventing the volatilization of copper ions.

[0014] Using tetraethyl orthosilicate as the silicon source, a small amount of glacial acetic acid was added to an ethanol solution to form a homogeneous system with an acidic environment. Under acidic conditions, tetraethyl orthosilicate undergoes hydrolysis to generate silanol groups. In the reaction, water molecules gradually replace the ethoxy groups in the tetraethyl orthosilicate molecules to generate silanol groups. Subsequently, the silanol molecules further crosslink through condensation reactions to form silicon-oxygen bonds, thereby forming silicon oxide sol particles with nanoscale dimensions. Subsequently, zirconium oxychloride, as a zirconium source, was dissolved in dilute hydrochloric acid to form a homogeneous metal salt solution. The introduction of zirconium ions can enhance the thermal stability and structural integrity of the material. When the zirconium oxychloride solution is added to the silanol solution, it interacts with the silicon oxide sol particles, further embedding into the silicon oxide network structure through coordination or bridging oxygen bonds, thus forming a preliminary multimetallic sol system. In the multimetallic sol system, tetrabutyl titanate and niobium pentachloride are then gradually added as titanium and niobium sources, respectively. Tetrabutyl titanate undergoes hydrolysis under acidic conditions to generate titanium oxide precursors, which simultaneously form Ti-O-Si bonds with silicon oxides and zirconium oxides. These chemical bonds not only enhance the overall chemical stability of the material but also provide more active sites by regulating the material's structure. Similarly, niobium pentachloride undergoes hydrolysis in solution to generate niobium oxide precursors, which are then embedded into the silicon oxide network in a similar manner. The sol particles gradually form a three-dimensional network structure through further condensation and cross-linking reactions, resulting in a gel-like material. During this process, metal oxide precursors in the solution (such as oxides of zirconium, titanium, and niobium) further enhance the uniformity of the gel and the distribution of multiple metals through chemical bonding with the silicon oxide network. After drying, the material is transferred to a high-temperature furnace for preliminary heat treatment, where further heating decomposes the organic components in the material, releasing carbon dioxide, water, and other volatile organic byproducts. Simultaneously, the metal oxide precursors form a stable amorphous oxide network through further condensation reactions. In this stage, the chemical bonding between silicon oxides and various metal oxides is further strengthened, significantly improving the structural stability of the material.

[0015] Following initial heat treatment, the material was transferred to a nitrogen atmosphere for high-temperature heat treatment to further improve its chemical homogeneity and structural stability, while avoiding excessive oxidation reactions that might occur under an oxidizing atmosphere. High-temperature treatment provided the necessary thermodynamic conditions for the uniform distribution of metal oxides and the rearrangement of chemical bonds within the material, making the synergistic effect between the silicon oxide network and the metal oxides more significant. Under the high-temperature conditions of a nitrogen atmosphere, the material remained amorphous. This amorphous characteristic endowed the material with a higher specific surface area and more active sites, which are crucial for the capture and fixation of copper ions and the optimization of the overall material performance. The multi-doped amorphous structure provided numerous chemically active sites for the adsorption and fixation of copper ions. These sites can form stable bonds with copper ions through mechanisms such as surface adsorption, coordination bonding, or ion exchange. Furthermore, the doped zirconium, titanium, and niobium elements, through synergistic effects, significantly improved the thermal and chemical stability of the material, enabling it to maintain structural integrity under high-temperature flameless combustion conditions. The amorphous structure of this powder material also possesses a high specific surface area, providing more reaction sites for the capture of copper ions, while simultaneously enhancing the material's mechanical properties and thermal shock resistance.

[0016] Rare earth phosphate nanodispersions form a stable crystal structure through the coordination of rare earth ions with phosphate groups. This structure provides numerous active sites, enabling the capture of copper ions through mechanisms such as ion exchange, adsorption, and lattice embedding. Under high-temperature flameless combustion conditions, the crystal structure of rare earth phosphates remains stable, effectively preventing the volatilization and migration of copper ions. The introduction of multi-component co-doped amorphous powder further enhances the copper ion immobilization effect. Its amorphous network structure and the synergistic effect of multiple metal elements provide additional chemical binding sites. These metal elements can further improve the copper ion immobilization efficiency by forming stable chemical bonds with copper ions (such as oxygen bridges or coordination bonds). Furthermore, the multi-component co-doped amorphous powder exhibits strong ion exchange capacity at high temperatures, complementing the ion capture mechanism of rare earth phosphates, thus achieving multiple chemical immobilization of copper ions. The iron oxide phase generated by the ferrate precursor at high temperatures provides additional chemical support for copper ion capture. The iron oxide lattice can embed copper ions, and the combination of the ferrate precursor, rare earth phosphate, and amorphous powder forms a chemically stable three-dimensional network. Meanwhile, the three core components in this invention exhibit significant synergistic thermal stability at high temperatures, thus ensuring the long-term fixation of copper ions and the structural integrity of the material. Due to the high thermal stability of rare earth elements, the rare earth phosphate nanodispersion maintains the integrity of its crystal structure at high temperatures. This thermal stability prevents copper ions from being released from the crystal due to high temperatures. Simultaneously, the high melting point and antioxidant properties of rare earth phosphates allow them to continue to provide chemical protection at high temperatures, offering a stable environment for other components. The metal elements in the multi-component co-doped amorphous powder possess high-temperature thermal stability and synergistic enhancement effects. The amorphous structure exhibits strong resistance to thermal shock, preventing changes in material structure or performance degradation caused by temperature fluctuations. The iron oxide phase generated from the ferrate precursor at high temperatures also exhibits good thermal stability. Iron oxides can form thermodynamically stable interfacial structures with rare earth phosphates and amorphous powders, further improving the material's stability and resistance to decomposition at high temperatures.

[0017] As a preferred embodiment of the present invention, in S1, the mass ratio of the ferric nitrate nonahydrate, ferrous sulfate heptahydrate, manganese nitrate solution, and citric acid is (20-25):(20-25):(50-55):(30-35), for example, it can be (20.0, 20.5, 21.0, 21.5, 22.0, 22.5, 23.0, 23.5, 24.0, 24.5, or 25.0):(20.0, 20.5, 21.0, 21.5, 22.0, 22. 5, 23.0, 23.5, 24.0, 24.5 or 25.0: (50.0, 50.5, 51.0, 51.5, 52.0, 52.5, 53.0, 53.5, 54.0, 54.5 or 55.0): (30.0, 30.5, 31.0, 31.5, 32.0, 32.5, 33.0, 33.5, 34.0, 34.5 or 35.0), but not limited to the listed values, other unlisted values ​​within this range also apply.

[0018] In some optional examples, the manganese nitrate solution has a mass fraction of 10 wt.%.

[0019] In some alternative embodiments, the first temperature is 80-90°C, for example, it can be 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C or 90°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0020] In some alternative embodiments, the second temperature is 110-120°C, for example, it can be 110°C, 111°C, 112°C, 113°C, 114°C, 115°C, 116°C, 117°C, 118°C, 119°C or 120°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0021] In some optional embodiments, the drying time at the second temperature is 4-5 hours, for example, 4 hours, 4.1 hours, 4.2 hours, 4.3 hours, 4.4 hours, 4.5 hours, 4.6 hours, 4.7 hours, 4.8 hours, 4.9 hours, or 5 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0022] In some alternative embodiments, the third temperature is 300-310°C, for example, it can be 300°C, 301°C, 302°C, 303°C, 304°C, 305°C, 306°C, 307°C, 308°C, 309°C or 310°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0023] In some optional embodiments, the time for maintaining the third temperature is 2-3 hours, for example, 2 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours or 3 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] In some optional embodiments, the heat preservation time at 800°C is 2-3 hours, for example, it can be 2 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours or 3 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] As a preferred embodiment of the present invention, in S2, the mass ratio of lanthanum nitrate hexahydrate, cerium nitrate hexahydrate, ammonium dihydrogen phosphate, ammonium fluoride, and PVP is (8-10):(6-8):(5-6):(3-4):(5-7), for example, it can be (8.0, 8.2, 8.4, 8.6, 8.8, 9.0, 9.2, 9.4, 9.6, 9.8 or 10.0):(6.0, 6.2, 6.4, 6.6, 6.8, 7.0, 7.2, 7.4, 7.6, 7. 8 or 8.0): (5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9 or 6.0): (3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9 or 4.0): (5.0, 5.2, 5.4, 5.6, 5.8, 6.0, 6.2, 6.4, 6.6, 6.8 or 7.0), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0026] In some optional instances, the PVP is PVP-K30.

[0027] In some alternative embodiments, the fourth temperature is 130-140°C, for example, it can be 130°C, 131°C, 132°C, 133°C, 134°C, 135°C, 136°C, 137°C, 138°C, 139°C or 140°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0028] In some alternative embodiments, the hydrothermal reaction time is 8-9 hours, for example, 8 hours, 8.1 hours, 8.2 hours, 8.3 hours, 8.4 hours, 8.5 hours, 8.6 hours, 8.7 hours, 8.8 hours, 8.9 hours, or 9 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0029] In a preferred embodiment of the present invention, in S3, the mass-to-volume ratio of tetraethyl orthosilicate, ethanol and glacial acetic acid is 30g:30mL:5mL.

[0030] In some optional embodiments, the stirring time at 60°C is 2-3 hours, for example, 2 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours, or 3 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] In some optional examples, the mass-to-volume ratio of the zirconium oxychloride octahydrate to the HCl solution is 20 g: 50 mL.

[0032] In some optional instances, the concentration of the HCl solution is 1M.

[0033] In some optional examples, the mass ratio of tetrabutyl titanate to niobium pentachloride is 5:2.

[0034] In some optional embodiments, the vacuum drying time is 10-12 hours, for example, 10 hours, 10.2 hours, 10.4 hours, 10.6 hours, 10.8 hours, 11 hours, 11.2 hours, 11.4 hours, 11.6 hours, 11.8 hours or 12 hours, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0035] In some optional embodiments, the 450°C holding time is 3-4 hours, for example, it can be 3 hours, 3.1 hours, 3.2 hours, 3.3 hours, 3.4 hours, 3.5 hours, 3.6 hours, 3.7 hours, 3.8 hours, 3.9 hours or 4 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0036] In some optional embodiments, the heat preservation time at 500°C is 2-3 hours, for example, it can be 2 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours or 3 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0037] As a preferred embodiment of the present invention, in S4, the mass-to-volume ratio of the mineral powder, ferrate precursor, rare earth phosphate nanodispersion, multi-component co-doped amorphous powder, PVA, and polystyrene microspheres is (30-40) g:(15-20) g:(20-25) mL:(10-13) g:(2-3) g:(5-7) g, for example, it can be (30, 31, 32, 33, 34, 35, 36, 37, 38, 39, or 40) g:(15.0, 15.5, 16.0, 16.5, 17.0, 17.5, 18.0, 18.5, 19.0, 19.5, or 20.0) g:(20.0, 20.5, ... 21.0, 21.5, 22.0, 22.5, 23.0, 23.5, 24.0, 24.5 or 25.0) mL; (10.0, 10.3, 10.6, 10.9, 11.2, 11.5, 11.8, 12.1, 12.4, 12.7 or 13.0) g; (2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 or 3.0) g; (5.0, 5.2, 5.4, 5.6, 5.8, 6.0, 6.2, 6.4, 6.6, 6.8 or 7.0) g, but not limited to the listed values, other unlisted values ​​within this range also apply.

[0038] In some optional instances, the PVA has a Mw of 47000.

[0039] In some optional examples, the polystyrene microspheres have a particle size of 5 μm.

[0040] In some optional instances, the mineral powder is kaolin / bentonite in a mass ratio of 1:1.

[0041] In some optional instances, the drying time is 10-11 hours, for example, 10 hours, 10.1 hours, 10.2 hours, 10.3 hours, 10.4 hours, 10.5 hours, 10.6 hours, 10.7 hours, 10.8 hours, 10.9 hours, or 11 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0042] Secondly, the present invention provides a solidified material prepared by the preparation method described in the first aspect, which is applied to the flameless combustion process of copper-containing sludge.

[0043] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) By introducing rare earth phosphate nanodispersants, multi-component co-doped amorphous powders and ferrate precursors, a multifunctional synergistic curing system is constructed. Rare earth phosphates have excellent chemical stability and ion capture ability, and can efficiently fix copper ions through ion exchange, adsorption and lattice embedding mechanisms. The amorphous structure and multi-metal synergistic effect of multi-component co-doped amorphous powders provide more chemical active sites and thermal stability, which greatly improves the stability of the curing material, enhances the material's capture efficiency for copper ions, and maintains chemical and physical stability in a high-temperature flameless combustion environment. (1) The invention solves the problem of easy migration or volatilization of copper ions in traditional technology; (2) The ferrate precursor prepared by the present invention has excellent thermal stability and chemical activity, which can further capture copper ions and embed them into the iron oxide lattice, thereby achieving deep fixation of copper ions. The formation of the iron oxide lattice not only enhances the metal ion capture ability of the material, but also provides a highly stable chemical structure in the high temperature environment, preventing the re-release of copper ions. The synergistic effect of the ferrate precursor and rare earth phosphate nanodispersion significantly improves the overall performance of the material. In the high temperature flameless combustion process, it can effectively reduce the volatilization problem of copper ions. Attached Figure Description

[0044] Figure 1 The flowchart shows a method for preparing a solidified material for flameless combustion of copper-containing sludge, as provided in Embodiments 1-4 of the present invention. Detailed Implementation

[0045] The technical solutions of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings. The embodiments described herein are specific implementations of the present invention, used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary, and should not be construed as limiting the implementation methods or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0046] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone any further purification treatment.

[0047] Example 1

[0048] This embodiment provides a solidification material and its preparation method for use in the flameless combustion process of copper-containing sludge. The preparation method specifically includes the following steps:

[0049] S1, 20g of ferric nitrate nonahydrate and 20g of ferrous sulfate heptahydrate were dispersed in 100mL of deionized water, then 50g of manganese nitrate solution with a mass fraction of 10wt.% was added, followed by 30g of citric acid. The mixture was heated to 88℃, and the pH was maintained at 4.5. The mixture was stirred until it became a viscous semi-colloid. It was then transferred to an oven and dried at 112℃ for 4.2h. After drying, it was transferred to a muffle furnace and heated to 304℃ for 2.3h. Finally, it was transferred to a nitrogen atmosphere and heated to 800℃ for 2.4h to obtain the ferrate precursor.

[0050] S2, 8.0g of lanthanum nitrate hexahydrate and 6.0g of cerium nitrate hexahydrate were dispersed in 100mL of deionized water to obtain a rare earth solution. 5.2g of ammonium dihydrogen phosphate, 3.3g of ammonium fluoride and 5.5g of PVP-K30 were dispersed in 50mL of deionized water to obtain a fluorophosphate solution. The fluorophosphate solution was added to the rare earth solution to maintain the pH of the solution at 4.5. The mixture was transferred to a hydrothermal reactor lined with polytetrafluoroethylene and hydrothermally reacted at 133℃ for 8.8h. After the reaction, large agglomerates were removed by centrifugation, and the supernatant was the rare earth phosphate nanodispersion.

[0051] S3, 30g of tetraethyl orthosilicate, 30mL of ethanol and 5mL of glacial acetic acid were mixed and stirred at 60℃ for 2.4h to obtain a silanol solution. Then, 20g of zirconium oxychloride octahydrate was dispersed in 50mL of 1M HCl solution and added to the silanol solution. 5g of tetrabutyl titanate and 2g of niobium pentachloride were added and stirring was continued. The pH was adjusted to 2.5 to obtain a sol. The sol was vacuum dried at 80℃ for 10.5h, heated to 450℃ and held for 3.4h, and then held at 500℃ for 2.5h under a nitrogen atmosphere to obtain a multi-component co-doped amorphous powder.

[0052] S4, 33g of mineral powder, 15g of ferrate precursor, 21mL of rare earth phosphate nano-dispersion, 11g of multi-component co-doped amorphous powder, 2.4g of PVA and 5.7g of polystyrene microspheres are mixed and stirred to form a slurry. The mineral powder is kaolin / bentonite in a mass ratio of 1:1. The Mw of the PVA is 47000 and the particle size of the polystyrene microspheres is 5μm. The mixture is dried at 80℃ for 10.5h to obtain a solidified material for flameless combustion of copper-containing sludge.

[0053] Example 2

[0054] This embodiment provides a solidification material and its preparation method for use in the flameless combustion process of copper-containing sludge. The preparation method specifically includes the following steps:

[0055] S1, 25g of ferric nitrate nonahydrate and 23g of ferrous sulfate heptahydrate were dispersed in 100mL of deionized water, then 55g of manganese nitrate solution with a mass fraction of 10wt.% was added, followed by 33g of citric acid. The mixture was heated to 80℃, and the pH was maintained at 4.5. The mixture was stirred until it became a viscous semi-colloid. It was then transferred to an oven and dried at 110℃ for 4.0h. After drying, it was transferred to a muffle furnace and heated to 300℃ for 2.0h. Finally, it was transferred to a nitrogen atmosphere and heated to 800℃ for 2.0h to obtain the ferrate precursor.

[0056] S2, 9.2g of lanthanum nitrate hexahydrate and 7.1g of cerium nitrate hexahydrate were dispersed in 100mL of deionized water to obtain a rare earth solution. 5.0g of ammonium dihydrogen phosphate, 3.7g of ammonium fluoride and 6.3g of PVP-K30 were dispersed in 50mL of deionized water to obtain a fluorophosphate solution. The fluorophosphate solution was added to the rare earth solution, and the pH of the solution was maintained at 4.5. The mixture was transferred to a hydrothermal reactor lined with polytetrafluoroethylene and hydrothermally reacted at 138℃ for 8.4h. After the reaction, large agglomerates were removed by centrifugation, and the supernatant was the rare earth phosphate nanodispersion.

[0057] S3, 30g of tetraethyl orthosilicate, 30mL of ethanol and 5mL of glacial acetic acid were mixed and stirred at 60℃ for 2.0h to obtain a silanol solution. Then, 20g of zirconium oxychloride octahydrate was dispersed in 50mL of 1M HCl solution and added to the silanol solution. 5g of tetrabutyl titanate and 2g of niobium pentachloride were added and stirred. The pH was adjusted to 2.5 to obtain a sol. The sol was vacuum dried at 80℃ for 10.0h, heated to 450℃ and held for 3.8h, and then held at 500℃ for 2.0h under a nitrogen atmosphere to obtain a multi-component co-doped amorphous powder.

[0058] S4, 36g of mineral powder, 17g of ferrate precursor, 24mL of rare earth phosphate nano-dispersion, 10g of multi-component co-doped amorphous powder, 2.0g of PVA and 6.8g of polystyrene microspheres are mixed and stirred to form a slurry. The mineral powder is kaolin / bentonite in a mass ratio of 1:1. The Mw of the PVA is 47000 and the particle size of the polystyrene microspheres is 5μm. The mixture is dried at 80℃ for 10.0h to obtain a solidified material for flameless combustion of copper-containing sludge.

[0059] Example 3

[0060] This embodiment provides a solidification material and its preparation method for use in the flameless combustion process of copper-containing sludge. The preparation method specifically includes the following steps:

[0061] S1, 22g of ferric nitrate nonahydrate and 21g of ferrous sulfate heptahydrate were dispersed in 100mL of deionized water, then 52g of manganese nitrate solution with a mass fraction of 10wt.% was added, followed by 35g of citric acid. The mixture was heated to 84℃, and the pH was maintained at 4.5. The mixture was stirred until it became a viscous semicolloid. It was then transferred to an oven and dried at 120℃ for 4.7h. After drying, it was transferred to a muffle furnace and heated to 310℃ for 3.0h. Finally, it was transferred to a nitrogen atmosphere and heated to 800℃ for 2.6h to obtain the ferrate precursor.

[0062] S2, 10.0g of lanthanum nitrate hexahydrate and 7.5g of cerium nitrate hexahydrate were dispersed in 100mL of deionized water to obtain a rare earth solution. 6.0g of ammonium dihydrogen phosphate, 3.0g of ammonium fluoride and 7.0g of PVP-K30 were dispersed in 50mL of deionized water to obtain a fluorophosphate solution. The fluorophosphate solution was added to the rare earth solution, and the pH of the solution was maintained at 4.5. The mixture was transferred to a hydrothermal reactor lined with polytetrafluoroethylene and hydrothermally reacted at 130℃ for 8.0h. After the reaction, large agglomerates were removed by centrifugation, and the supernatant was the rare earth phosphate nanodispersion.

[0063] S3, 30g of tetraethyl orthosilicate, 30mL of ethanol and 5mL of glacial acetic acid were mixed and stirred at 60℃ for 2.6h to obtain a silanol solution. Then, 20g of zirconium oxychloride octahydrate was dispersed in 50mL of 1M HCl solution and added to the silanol solution. 5g of tetrabutyl titanate and 2g of niobium pentachloride were added and stirred. The pH was adjusted to 2.5 to obtain a sol. The sol was vacuum dried at 80℃ for 11.4h, heated to 450℃ and held for 3.0h, and then held at 500℃ for 2.7h under a nitrogen atmosphere to obtain a multi-component co-doped amorphous powder.

[0064] S4, 30g of mineral powder, 16g of ferrate precursor, 20mL of rare earth phosphate nano-dispersion, 13g of multi-component co-doped amorphous powder, 3.0g of PVA and 7.0g of polystyrene microspheres are mixed and stirred to form a slurry. The mineral powder is kaolin / bentonite in a mass ratio of 1:1. The Mw of the PVA is ~47000 and the particle size of the polystyrene microspheres is 5μm. The mixture is dried at 80℃ for 11.0h to obtain a solidified material for flameless combustion of copper-containing sludge.

[0065] Example 4

[0066] This embodiment provides a solidification material and its preparation method for use in the flameless combustion process of copper-containing sludge. The preparation method specifically includes the following steps:

[0067] S1, 24g of ferric nitrate nonahydrate and 25g of ferrous sulfate heptahydrate were dispersed in 100mL of deionized water, then 53g of manganese nitrate solution with a mass fraction of 10wt.% was added, followed by 32g of citric acid. The mixture was heated to 90℃, and the pH was maintained at 4.5. The mixture was stirred until it became a viscous semicolloid. It was then transferred to an oven and dried at 117℃ for 5.0h. After drying, it was transferred to a muffle furnace and heated to 307℃ for 2.8h. Finally, it was transferred to a nitrogen atmosphere and heated to 800℃ for 3.0h to obtain the ferrate precursor.

[0068] S2, 8.6g of lanthanum nitrate hexahydrate and 8.0g of cerium nitrate hexahydrate were dispersed in 100mL of deionized water to obtain a rare earth solution. 5.7g of ammonium dihydrogen phosphate, 4.0g of ammonium fluoride and 5.0g of PVP-K30 were dispersed in 50mL of deionized water to obtain a fluorophosphate solution. The fluorophosphate solution was added to the rare earth solution, and the pH of the solution was maintained at 4.5. The mixture was transferred to a hydrothermal reactor lined with polytetrafluoroethylene and hydrothermally reacted at 140℃ for 9.0h. After the reaction, large agglomerates were removed by centrifugation, and the supernatant was the rare earth phosphate nanodispersion.

[0069] S3, 30g of tetraethyl orthosilicate, 30mL of ethanol and 5mL of glacial acetic acid were mixed and stirred at 60℃ for 3.0h to obtain a silanol solution. Then, 20g of zirconium oxychloride octahydrate was dispersed in 50mL of 1M HCl solution and added to the silanol solution. 5g of tetrabutyl titanate and 2g of niobium pentachloride were added and stirred. The pH was adjusted to 2.5 to obtain a sol. The sol was vacuum dried at 80℃ for 12.0h, heated to 450℃ and held for 4.0h, and then held at 500℃ for 3.0h under a nitrogen atmosphere to obtain a multi-component co-doped amorphous powder.

[0070] S4, 40g of mineral powder, 20g of ferrate precursor, 25mL of rare earth phosphate nano-dispersion, 12g of multi-component co-doped amorphous powder, 2.7g of PVA and 5.4g of polystyrene microspheres are mixed and stirred to form a slurry. The mineral powder is kaolin / bentonite in a mass ratio of 1:1. The Mw of the PVA is 47000 and the particle size of the polystyrene microspheres is 5μm. The mixture is dried at 80℃ for 10.7h to obtain a solidified material for flameless combustion of copper-containing sludge.

[0071] Comparative Example 1

[0072] This comparative example provides a solidification material and preparation method for use in the flameless combustion process of copper-containing sludge. The difference between this example and Example 1 is that the volume of rare earth phosphate nanodispersion in S4 is 41 mL, which is 20 mL more than in Example 1. Other process parameters and operating conditions are exactly the same as in Example 1.

[0073] Comparative Example 2

[0074] This comparative example provides a solidified material and its preparation method for use in the flameless combustion process of copper-containing sludge. The difference between this example and Example 1 is that the volume of the rare earth phosphate nanodispersion in S4 is 1 mL, which is 20 mL less than that in Example 1. Other process parameters and operating conditions are exactly the same as those in Example 1.

[0075] Comparative Example 3

[0076] This comparative example provides a solidification material and its preparation method for use in the flameless combustion process of copper-containing sludge. The difference between this example and Example 1 is that the mass of the multi-component co-doped amorphous powder in S4 is 21g, which is 10g more than in Example 1. Other process parameters and operating conditions are exactly the same as in Example 1.

[0077] Comparative Example 4

[0078] This comparative example provides a solidification material and preparation method for use in the flameless combustion process of copper-containing sludge. The difference between this example and Example 1 is that the mass of the multi-component co-doped amorphous powder in S4 is 1g, which is 10g less than that in Example 1. Other process parameters and operating conditions are exactly the same as those in Example 1.

[0079] Flameless combustion method for copper-containing sludge: Mix 100 parts of dried and pulverized copper-containing sludge, 10 parts of solidification material and 5 parts of borax. Initial heating stage: First stage: heat up to 200℃ at a heating rate of 5℃ / min and hold for 2 hours; Second stage: heat up to 600℃ at a heating rate of 8℃ / min and hold for 2 hours; Third stage: heat up to 900℃ at a heating rate of 5℃ / min and hold for 2 hours. Remove the calcined product when the furnace temperature drops below 200℃. Crush the calcined product and acid leaching to obtain leachate.

[0080] Plot the standard curve: Transfer 0.00 ml, 1.00 ml, 2.00 ml, 3.00 ml, 4.00 ml, and 5.00 ml of 200 μg / ml copper standard solution, and measure their absorbance sequentially using an atomic absorption spectrophotometer to plot the standard curve.

[0081] Determination of copper content in sludge: 1.000 g of dried sludge was screened and placed in a polytetrafluoroethylene (PTFE) crucible. The crucible was placed on a hot plate, and 80 wt.% nitric acid was added. Heating was continued until nearly dry, then 40 wt.% HF and 70 wt.% perchloric acid were added. Heating was continued until nearly dry. The crucible was removed, and 10 wt.% nitric acid was added to bring the volume to a final volume to obtain the sample to be tested. The absorbance of the sample was measured, and the results were used to determine the copper content in the sludge, which was found to be 8.6 wt.%.

[0082] Leaching rate determination: Take the supernatant of the leachate, dilute to 50 mL, determine the concentration by atomic absorption spectrometry, convert it into the mass fraction in the copper-containing leachate, and compare it with the copper content in the sludge to obtain the leaching rate. The test results are shown in Table 1.

[0083] Table 1. Test results of a solidification material applied to the flameless combustion process of copper-containing sludge in Examples 1-4 and Comparative Examples 1-4.

[0084] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Leaching rate (%) 95.1 96.4 94.6 94.9 80.7 82.4 81.2 80.1

[0085] As shown in Table 1, the leaching rate of Comparative Example 1 decreased compared to Example 1, and the leaching rate of Comparative Example 2 also decreased. This is because in Comparative Example 1, the rare earth phosphate nanodispersion was excessive. Rare earth phosphate nanoparticles have small particle sizes and high specific surface areas; excessive rare earth phosphate may cause the particles to agglomerate during preparation, forming local aggregates and reducing the leaching rate of copper ions. In Comparative Example 2, the rare earth phosphate nanodispersion was insufficient. Rare earth ions and phosphate ions in the rare earth phosphate nanodispersion are key active sites for copper ion capture. The reduction in active sites available for binding with copper ions in the material resulted in incomplete fixation of copper ions, leading to a decrease in the leaching rate.

[0086] As shown in Table 1, the leaching rate of Comparative Example 3 decreased compared to Example 1, and the leaching rate of Comparative Example 4 also decreased. This is because Comparative Example 3 contained an excessive amount of multi-component co-doped amorphous powder. Excessive amorphous powder may cover the active sites of rare earth phosphates, weakening their ion-capturing ability and thus reducing the copper ion fixation efficiency. Comparative Example 4 contained insufficient multi-component co-doped amorphous powder. The metal oxides in the multi-component co-doped amorphous powder provide additional copper ion adsorption sites through their amorphous structure. If the amount added is insufficient, the material's adsorption and chemical fixation capacity for copper ions will significantly decrease.

[0087] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a solidified material for use in the flameless combustion process of copper-containing sludge, characterized in that, The preparation method includes: S1, ferric nitrate nonahydrate and ferrous sulfate heptahydrate are dispersed in deionized water, then manganese nitrate solution and citric acid are added, the pH is maintained at 4.5 and stirred, transferred and dried, and then transferred to a muffle furnace for heat preservation to obtain ferrate precursor; S2, Lanthanum nitrate hexahydrate and cerium nitrate hexahydrate are dispersed in deionized water to obtain a rare earth solution. Ammonium dihydrogen phosphate, ammonium fluoride and PVP are dispersed in deionized water to obtain a fluorophosphate solution. The fluorophosphate solution is added to the rare earth solution to maintain the pH of the solution at 4.

5. After the hydrothermal reaction is completed, large agglomerates are removed and the supernatant is the rare earth phosphate nanodispersion. S3, Tetrabutyl titanate, ethanol and glacial acetic acid are mixed to obtain a silanol solution, zirconium oxychloride octahydrate is dispersed in HCl solution and added to the silanol solution, tetrabutyl titanate and niobium pentachloride are added and stirred, the pH is adjusted to 2.5 to obtain a sol, dried and kept at a temperature to obtain multi-component co-doped amorphous powder; S4, mineral powder, ferrate precursor, rare earth phosphate nanodispersion, multi-component co-doped amorphous powder, PVA and polystyrene microspheres are mixed to obtain a solidified material for use in the flameless combustion process of copper-containing sludge.

2. The method for preparing a solidified material for flameless combustion of copper-containing sludge according to claim 1, characterized in that, In S1, The mass ratio of the solution of ferric nitrate nonahydrate, ferrous sulfate heptahydrate, and manganese nitrate to citric acid is (20-25):(20-25):(50-55):(30-35).

3. The method for preparing a solidified material for flameless combustion of copper-containing sludge according to claim 1, characterized in that, In S1, The manganese nitrate solution has a mass fraction of 10 wt.%.

4. The method for preparing a solidified material for flameless combustion of copper-containing sludge according to claim 1, characterized in that, In S2, The mass ratio of lanthanum nitrate hexahydrate, cerium nitrate hexahydrate, ammonium dihydrogen phosphate, ammonium fluoride and PVP is (8-10):(6-8):(5-6):(3-4):(5-7).

5. The method for preparing a solidified material for flameless combustion of copper-containing sludge according to claim 1, characterized in that, In S2, The PVP is PVP-K30.

6. The method for preparing a solidified material for flameless combustion of copper-containing sludge according to claim 1, characterized in that, In S3 The mass-to-volume ratio of the tetraethyl orthosilicate, ethanol and glacial acetic acid is 30g:30mL:5mL; The mass-to-volume ratio of zirconium oxychloride octahydrate to HCl solution is 20g:50mL.

7. The method for preparing a solidified material applied to the flameless combustion process of copper-containing sludge according to claim 1, characterized in that, In S3 The concentration of the HCl solution is 1M; The mass ratio of tetrabutyl titanate to niobium pentachloride is 5:

2.

8. The method for preparing a solidified material for flameless combustion of copper-containing sludge according to claim 1, characterized in that, In S4, The mass-volume ratio of the mineral powder, ferrate precursor, rare earth phosphate nanodispersant, multi-component co-doped amorphous powder, PVA and polystyrene microspheres is (30-40) g: (15-20) g: (20-25) mL: (10-13) g: (2-3) g: (5-7) g.

9. The method for preparing a solidified material for flameless combustion of copper-containing sludge according to claim 1, characterized in that, In S4, The mineral powder is kaolin / bentonite in a mass ratio of 1:1; The drying time is 10-11 hours.

10. A solidified material for use in the flameless combustion process of copper-containing sludge, obtained by the preparation method according to any one of claims 1-9.

Images