Preparation method and application of sludge incinerator slag-based magnetic catalyst

Abstract

The invention provides a preparation method and application of a sludge incineration slag-based magnetic catalyst, and belongs to the technical field of catalysts for sewage treatment.The preparation method comprises the steps that sludge incineration slag is smashed and subjected to acid etching treatment with mixed acid of hydrofluoric acid and hydrochloric acid, Si, Al and Ca components in the slag are used as self-sacrifice pore-forming templates, phosphorus and nitrogen elements are reserved, and the self-sacrifice pore-forming templates are formed; forming a porous structure; and after the acid etching treatment, hydroxyl groups are generated on the iron surface by using treatment. Secondary sintering is not needed, high-temperature treatment completed in the sludge incineration process is fully utilized, and the high-energy-consumption sintering link in traditional catalyst preparation is avoided; according to the method, a pore-forming agent does not need to be additionally added, Si, A and CaO in the slag are used as a self-sacrifice template, pore forming is achieved through selective acid etching, the removal rate is high, a mesoporous structure is formed, and the cost of the pore-forming agent is saved; artificial metal doping is not needed, and a C-N-P-Fe composite catalytic system is constructed by directly utilizing F / F, graphite carbon, an N element and a P element which naturally exist in the slag.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology for wastewater treatment, specifically to a method for preparing and applying a sludge incinerator slag-based magnetic catalyst. In particular, it relates to utilizing natural components in sludge incinerator slag as a self-sacrificing pore-forming template, graphite carbon matrix, and active metal source, constructing a CNP-Fe composite magnetic catalyst through selective acid etching, and applying it to a method for advanced oxidation degradation of organic wastewater. This invention also relates to the interdisciplinary fields of solid waste resource utilization, water pollution control, advanced oxidation catalyst preparation, and phosphorus resource recovery. Background Technology

[0002] Advanced oxidation processes (AOPs) are a highly efficient water treatment technology that generates strong oxidizing free radicals (such as ·OH, ·...). Advanced oxidation catalysts (AOCs) are used to degrade recalcitrant organic pollutants and have broad application prospects in the field of industrial wastewater treatment. Catalysts are the core of advanced oxidation processes, directly determining treatment efficiency and operating costs. However, the preparation of AOC catalysts currently faces widespread engineering challenges. First, most AOC catalysts (such as iron-based catalysts, manganese-based catalysts, and composite metal oxide catalysts) require high-temperature sintering (usually at 600-1000℃) to prepare materials with specific crystal structures. High-temperature sintering processes suffer from drawbacks such as high energy consumption, large equipment investment, and difficulty in scaling up. Second, to obtain high specific surface area and well-developed pore structures, pore-forming agents (such as silica templates, polymer templates, and metal-organic frameworks) are usually added during laboratory preparation. These pore-forming agents are expensive and require subsequent removal through acid-base etching or high-temperature calcination, increasing process complexity and cost. Furthermore, to control the valence state of metals or prevent the oxidation of carbon materials, the sintering process often requires... The process is carried out under inert atmospheres such as Ar. During engineering scale-up, the large consumption of inert gases leads to a sharp increase in costs. Furthermore, the VOCs, NOx, and SOx generated during sintering require additional exhaust gas treatment facilities. In recent years, some researchers have attempted to use sludge as a raw material to prepare catalysts to reduce costs. However, existing technical routes mainly employ sludge drying-doping-sintering or sludge hydrothermal carbonization-activation routes. These methods still require traditional approaches such as high-temperature sintering, chemical doping, and the addition of pore-forming agents. This results in high overall costs even when using inexpensive sludge raw materials, hindering true engineering applications. For example, Chinese invention patent application CN108358318A discloses a method for preparing a sludge-based iron-carbon composite catalyst, which requires sintering at 800°C under a nitrogen atmosphere for 3 hours; Chinese invention patent CN109569567A discloses a method for preparing a catalyst by activating sludge with KOH after hydrothermal carbonization, which requires a large amount of activator and activation at 700°C. These methods have not escaped the predicament of high energy consumption.

[0003] Sludge incineration technology has become one of the mainstream technologies for sludge treatment due to its advantages such as thorough volume reduction (over 90% reduction in volume), high degree of harmlessness, and great resource potential. However, the sludge incineration process (usually at 850-950℃) produces a large amount of slag, accounting for about 30-50% of the dry sludge mass. Currently, the main methods of slag disposal are landfill, building material utilization, or simple stockpiling, which have low utilization rates and pose resource waste and potential environmental risks. In-depth analysis of the formation mechanism and composition characteristics of sludge incineration slag reveals its unique natural advantages: the iron element (5-15%) in the sludge forms fluorine oxide (F) during the incineration process due to the local reducing atmosphere. γ-F α-F A system in which multiple iron oxides coexist, this Fe / Fe Mixed valence structures are ideal active centers for advanced oxidation catalysts; sludge organic matter undergoes partial carbonization during high-temperature incineration, forming carbon materials with a certain degree of graphitization (1-5%), which can act as electronic conductors to promote catalytic reactions; the main components of slag include Si. (20-30%), A (8-15%) and CaO (5-15%), these components can act as natural hard template pore-forming agents, and can form a porous structure by selective removal through acid etching; nitrogen (0.5-2%) and phosphorus (5-10%) in sludge are retained in a stable form after incineration, and can form coordination structures with iron active sites, significantly improving catalytic performance. These natural advantages provide unique conditions for developing low-cost, sinter-free advanced oxidation catalysts.

[0004] Based on the analysis of existing technologies, the following shortcomings exist: First, the "natural advantages" of sludge incineration slag are not fully recognized and utilized; most studies still treat slag as simple solid waste, failing to explore its unique value as a catalyst raw material. Second, the traditional "doping-sintering" approach is still used; even when using sludge or slag as raw materials, metal salts and pore-forming agents are still added, followed by high-temperature sintering, failing to truly achieve low cost. Third, there is a lack of understanding and utilization of the NP-Fe synergistic mechanism; existing sludge-based catalyst research mainly focuses on metals such as iron and manganese, neglecting the regulatory role of naturally occurring N and P elements in the slag. Fourth, full-process resource utilization is not achieved; components such as Si, Al, Ca, and P dissolved from the slag are usually treated as waste liquid, not effectively recovered, resulting in resource waste. Fifth, engineering feasibility is poor; laboratory preparation methods are difficult to scale up, and cost and environmental issues have not been systematically resolved. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a magnetic catalyst based on sludge incinerator slag, which can make full use of the natural composition and structural characteristics of sludge incinerator slag, and prepare a high-performance advanced oxidation catalyst without the need for secondary sintering, external pore-forming agents and metal doping, and realize the full-process resource utilization of slag, so as to solve at least one of the technical problems existing in the background art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for preparing and utilizing a sludge incinerator slag-based magnetic catalyst, comprising the following steps: (1) Crush the sludge incineration slag and pass it through a 100-300 mesh sieve to obtain powder; (2) The powder is subjected to acid etching treatment with a mixture of hydrofluoric acid and hydrochloric acid at a pH of 1.0-2.5 and a temperature of 40-70℃ for 2-6 hours. The Si, Al, and Ca components in the slag are used as self-sacrificing pore-forming templates to remove Si. To a content of less than 5%, A The content of phosphorus is reduced to less than 10%, and the content of CaO is reduced to less than 8%, while phosphorus is selectively retained at 1-3% and nitrogen at 0.5-2%, forming a porous structure with a pore size of 2-50 nm; after acid etching treatment, a concentration of 0.2-0.6 M is used. The treatment generates hydroxyl groups on the iron surface; (3) Separate the solid and liquid components of the mixture obtained in step (2), and dry the solid product at 80-120℃ to obtain a carbon-NP-Fe composite magnetic catalyst with carbon as the matrix and nitrogen and phosphorus elements forming a coordination structure with iron sites, wherein Fe with Fe The ratio is 1:1.5-1:3; (4) The carbon-NP-Fe composite magnetic catalyst is used for advanced oxidation degradation of organic wastewater. The catalyst dosage is 1-3 g / L and the oxidant dosage is 20-80 mg / L. The catalyst is recovered by magnetic separation after the reaction. (5) Add an alkaline neutralizing agent to the acid leachate obtained in step (3) to adjust the pH to 7-9, remove fluoride ions, add an iron salt precipitant to recover the dissolved phosphorus, and obtain iron phosphate precipitate product.

[0007] Further, in step (2), the mass concentration of the hydrofluoric acid is 8-15%, the mass concentration of the hydrochloric acid is 15-25%, and the volume ratio of hydrofluoric acid to hydrochloric acid in the mixed acid is 1:2-1:4; the acid etching treatment is performed by mechanical stirring at a stirring speed of 300-600 rpm or by ultrasonic assistance at a power of 200-500 W to promote the formation of NP double-coordinated iron sites; The processing time is 30-90 minutes, and the temperature is 25-50℃.

[0008] Furthermore, in step (1), the composition of the sludge incineration slag, calculated as oxides, includes: Si 20-30%, A 8-15%, F 10-18%, CaO 5-15%, 5-10%, graphite carbon 1-5%, nitrogen-containing compounds 0.5-2%, transition metal oxides 0.1-2%.

[0009] Furthermore, the carbon-NP-Fe composite magnetic catalyst obtained in step (3) has the following characteristic parameters: (1) Specific surface area is 100-300 m² / g; (2) The magnetic saturation intensity is 15-50 emu / g; (3) The iron content is 15-30%, the phosphorus retention rate is 20-40%, and the nitrogen retention rate is 40-60%; (4) The pore size distribution is concentrated in the range of 2-50 nm, and the mesopore volume accounts for 60-85% of the total pore volume; Furthermore, in step (4), the advanced oxidative degradation is carried out by one of Fenton oxidation, persulfate activated oxidation or ozone catalytic oxidation, and the oxidant is one of hydrogen peroxide, persulfate or ozone, wherein the carbon-NP-Fe composite improves the active oxygen generation efficiency by 30-50%.

[0010] Furthermore, the reaction conditions for Fenton oxidation are: pH 3-5, temperature 20-40℃, hydrogen peroxide concentration 20-80 mg / L, and reaction time 30-120 minutes; or the reaction conditions for persulfate activation oxidation are: pH 5-9, temperature 20-60℃, persulfate concentration 30-100 mg / L, and reaction time 30-120 minutes; or the reaction conditions for ozone catalytic oxidation are: pH 5-10, temperature 20-40℃, ozone concentration 40-120 mg / L, gas flow rate 0.5-2 L / min, and reaction time 30-90 minutes.

[0011] Furthermore, in step (4), the organic wastewater is high-concentration, high-salinity or difficult-to-degrade organic wastewater with a COD concentration of 500-5000 mg / L and a salinity of 1-10%; the COD removal rate after treatment is not less than 60%, and the TOC removal rate is not less than 40%.

[0012] Furthermore, in step (4), the magnetic separation and recovery adopts a magnetic separation device with an external magnetic field strength of 0.1-0.5 T, the catalyst recovery rate is not less than 90%, and the recovered catalyst can be directly used for the next batch of reaction or reused after simple cleaning.

[0013] Furthermore, in step (5), the alkaline neutralizing agent is one of sodium hydroxide, calcium hydroxide or magnesium hydroxide; the iron salt precipitant is one of ferrous sulfate, ferrous chloride or ferric sulfate; the phosphorus recovery rate is not less than 70%, and the obtained iron phosphate precipitate product can be used for the preparation of lithium iron phosphate battery materials after filtration, washing and drying.

[0014] Furthermore, in the carbon-NP-Fe composite magnetic catalyst, nitrogen exists in the form of pyridine nitrogen or pyrrole nitrogen, and phosphorus is coordinated with iron sites in the form of phosphate or phosphonate to form an NP double coordination structure.

[0015] Furthermore, in step (2), the acid etching process achieves the following synergistic effect: (i) Using Si, Al, and Ca components as self-sacrificing templates, mesoporous structures can be formed without the addition of external pore-forming agents; fully utilize the graphitized carbon materials generated during the incineration process as electronic conductors and matrices to promote electron transfer in catalytic reactions; (ii) Selectively dissolves 30-50% of phosphorus and 10-30% of nitrogen, while retaining sufficient phosphorus and nitrogen for coordination with iron sites; (iii) The iron content is kept at no less than 80%, while more iron active sites are exposed.

[0016] Furthermore, compared to untreated raw slag or catalysts with completely removed phosphorus and nitrogen elements, the carbon-NP-Fe composite magnetic catalyst increases the efficiency of active oxygen species generation by 30-50% and the degradation rate of organic pollutants by 40-60% during advanced oxidation processes.

[0017] Furthermore, the method realizes the full-process resource utilization of sludge incineration slag: the solid phase is converted into a recyclable magnetic catalyst, the phosphorus element recovered in the liquid phase is converted into iron phosphate product, and the dissolved silicon, aluminum and calcium components can be used in the building materials field after neutralization.

[0018] Furthermore, in step (2), after the acid etching treatment, the concentration of fluoride ions in the acid leaching solution is 100-500 mg / L. In step (5), fluoride ions are removed by adding calcium salt precipitation method, and the fluoride ion removal rate is not less than 95%. The obtained calcium fluoride precipitate can be used to prepare fluorochemical products.

[0019] The beneficial effects of this invention are: it eliminates the need for secondary sintering, fully utilizing the high-temperature treatment already completed during sludge incineration, thus avoiding the energy-intensive sintering process in traditional catalyst preparation; and it eliminates the need for external pore-forming agents, creatively utilizing the Si in the slag. A CaO, acting as a "self-sacrificing template," achieves pore formation through selective acid etching, exhibiting a high removal rate and forming mesoporous structures of 2-50 nm, thus saving on pore-forming agent costs. Furthermore, it eliminates the need for artificial metal doping, directly utilizing naturally occurring F in the slag. / F A CNP-Fe composite catalytic system is constructed using graphite carbon, nitrogen, and phosphorus; this system achieves full-process resource utilization, converting solid phase into a recyclable magnetic catalyst and recovering phosphorus in the liquid phase to prepare iron phosphate products; it exhibits excellent catalytic performance, significantly improving the generation efficiency of reactive oxygen species and increasing the degradation rate of organic pollutants by regulating the Fe active center through NP dual coordination; it is easy to recover via magnetic separation, utilizing the natural magnetism of the slag and achieving rapid separation with an external magnetic field.

[0020] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and will become apparent from the description or may be learned by practice of the invention. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1This is a flowchart illustrating the preparation method of the mud incinerator slag-based magnetic catalyst according to an embodiment of the present invention. Detailed Implementation

[0023] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0024] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0025] It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as here.

[0026] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, and / or groups thereof.

[0027] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," 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 present invention. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.

[0028] To facilitate understanding of the present invention, the present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. However, the specific embodiments do not constitute a limitation on the embodiments of the present invention.

[0029] Those skilled in the art should understand that the accompanying drawings are merely schematic diagrams of embodiments, and the components in the drawings are not necessarily essential for implementing the present invention.

[0030] like Figure 1As shown, this invention provides a method for preparing a sludge incinerator slag-based magnetic catalyst. This method eliminates the need for secondary sintering, fully utilizing the high-temperature treatment (850-950℃) already completed during sludge incineration, thus avoiding the energy-intensive sintering step in traditional catalyst preparation (energy consumption reduced by 80-90%). Furthermore, it eliminates the need for external pore-forming agents, creatively utilizing the Si in the slag. A CaO is used as a "self-sacrificing template" to create pores through selective acid etching (pH 1.0-2.5, temperature 40-70℃), achieving a removal rate of >90% and forming a mesoporous structure of 2-50 nm (pore volume accounting for 60-85%), saving pore-forming agent costs of 50,000-100,000 RMB / ton; no artificial metal doping is required, directly utilizing the naturally occurring F in the slag. / F A CNP-Fe composite catalytic system is constructed using 10-20% graphite carbon (1-5%), nitrogen (0.5-2%), and phosphorus (5-10%). This system achieves full-process resource utilization, converting solid-phase slag into a recyclable magnetic catalyst (yield 30-40%), recovering phosphorus in the liquid phase to prepare iron phosphate (recovery rate >70%), and using the dissolved Si-Al-Ca components in building materials, truly achieving "full utilization." Each ton of slag can generate 4200-8100 yuan in output value. The catalytic performance is excellent; by regulating the Fe active center through NP dual coordination, the efficiency of active oxygen species generation is increased by 30-50%, and the degradation rate of organic pollutants is increased by 40-60%. Within 60 minutes, COD removal rate >60% and TOC removal rate >40% are achieved. It is easily magnetically separated and recovered, utilizing the natural magnetic properties of the slag (F...). With a magnetic saturation intensity of 15-50 emu / g, rapid separation can be achieved within 5 minutes by applying an external magnetic field of 0.1-0.5 T, with a recovery rate of >90%. After being recycled 3 times, the activity still remains >90%, and the operating cost is reduced to 25-30% of that of a single-use catalyst. The process is simple and easy to engineer, requiring only four steps: crushing, acid etching, solid-liquid separation, and drying. The operating conditions are mild, and the equipment investment is about 20-30% of that of traditional methods. There are no VOCs, NOx, or SOx emissions, and zero waste liquid discharge. The overall preparation cost is only 30-50% of that of traditional Fe-based catalysts.

[0031] This invention creatively proposes the concept of "self-sacrificing template pore formation," which utilizes naturally occurring Si in slag directly without adding any external pore-forming agent. (20-30%), A (8-15%) and CaO (5-15%) were used as hard templates. In a hydrofluoric acid-hydrochloric acid mixed acid system with a pH of 1.0-2.5, Si, Al, and Ca components preferentially dissolved (removal rate >90%), while Fe, graphite carbon, and some NP elements remained relatively stable in the solid phase. After acid etching, a concentration of 0.2-0.6 M was used. The process generates hydroxyl groups on the iron surface, further promoting the electrophilic adsorption of oxidants such as ozone. By controlling the acid concentration (HF: 0.5-5 M, HCl: 1-6 M), temperature (40-70℃), and time (2-8 h), the selective removal degree of Si-Al-Ca can be regulated, precisely controlling the final pore size distribution (2-50 nm) and pore volume (mesoporous pore volume accounts for 60-85%). Compared with the traditional method of purchasing pore-forming agents (costing 5000-10000 yuan / kg), this invention utilizes the slag itself as a "free template," saving 50,000-100,000 yuan / ton of catalyst in pore-forming agent costs alone.

[0032] This invention discloses and fully utilizes the regulatory effect of N and P elements on iron active centers in sludge incineration slag. After incineration, some N elements in the proteins and nucleic acids of sludge are fixed on the carbon matrix in the form of pyridine nitrogen and pyrrole nitrogen (0.5-2%), while phosphorus elements exist in the form of phosphate (5-10%). By precisely controlling the acid etching conditions, 30-50% of P and 10-30% of N are selectively dissolved, while 1-3% of P and 0.5-2% of N are retained for coordination with Fe sites. Nitrogen coordination forms Fe-N bonds with Fe sites through the lone pair electrons of pyridine nitrogen and pyrrole nitrogen, while phosphorus coordination forms Fe-OP bonds through the oxygen atoms of phosphate / phosphonate groups. N and P elements simultaneously coordinate to the Fe center to form a unique NP double coordination structure. This structure reduces the oxidant ( The activation energy barrier of persulfate and ozone at Fe sites, and the additional adsorption sites provided by N and P elements enhance surface adsorption and promote Fe adsorption. / Fe Accelerated cycling. Compared to catalysts that do not retain NP elements, the efficiency of reactive oxygen species generation is increased by 30-50%, and the degradation rate of organic pollutants is increased by 40-60%. Unlike traditional methods that require the addition of N and P compounds (such as urea and phosphate) for doping followed by high-temperature sintering, this invention achieves coordination through acid etching "subtractive" (selective dissolution) rather than "additive" (doping), resulting in a simpler and lower-cost process.

[0033] Incomplete combustion of sludge organic matter during incineration at 850-950℃ produces char material with a certain degree of graphitization (1-5%). This graphitic carbon acts as an electron conductor, promoting electron transfer in catalytic reactions (such as Fe). →Fe The electrons released during the process are transferred to the oxidant, which acts as a stable matrix, providing anchoring sites for Fe, N, and P elements to prevent the loss of active components. Its hydrophobic surface is conducive to the adsorption and enrichment of hydrophobic organic pollutants. Compared with traditional methods that require the separate preparation of carbon materials (such as activated carbon, graphene, and carbon nanotubes, which are costly), this invention utilizes the carbon matrix inherent in the slag, resulting in zero cost and no additional preparation process required.

[0034] This invention achieves "zero waste" full-process resource utilization of sludge incineration slag. The solid phase products (approximately 30-40% of the slag mass) are converted into a CNP-Fe composite magnetic catalyst, which can be recycled through magnetic separation (recovery rate >90%). In the liquid phase products, the dissolved phosphorus (accounting for a significant portion of the slag mass) is recycled. 30-50% of the content is obtained by adding Fe. / Fe Salt precipitates as FeP After washing and drying, it can be used as a precursor for the positive electrode material of lithium iron phosphate batteries (recovery rate >70%). Fluoride ions (concentration 100-500 mg / L) are precipitated as Ca by adding calcium salts. (Removal rate > 95%) It can be used to prepare fluorochemical products. The Si-Al-Ca components, after neutralization, form aluminosilicate precipitates that can be used in building materials. Taking the treatment of 1 ton of slag as an example, the catalyst output is about 350 kg (market value 3500-7000 yuan), the iron phosphate output is about 30 kg (value 600-900 yuan), and the silica-alumina-calcium building materials output is about 500 kg (value 100-200 yuan). The total output value is about 4200-8100 yuan / ton of slag, which is far higher than the slag disposal cost (100-300 yuan / ton).

[0035] Traditional catalyst preparation requires sintering at 700℃ for 4 hours, consuming approximately 800-1200 kWh / ton of energy and necessitating a dedicated high-temperature furnace (investment of 500,000-1,000,000 RMB). This invention, however, requires only approximately 20 kWh for pulverizing, 50 kWh for acid etching and heating (50℃), and 80 kWh for drying (100℃) to prepare 1 ton of slag-based catalyst, with a total energy consumption of approximately 150 kWh, only 12-19% of the traditional method. The environmental advantages are significant: the slag has already undergone high-temperature incineration, completely decomposing organic matter; the acid etching process generates no VOCs; there is no high-temperature sintering, resulting in no NOx / SOx emissions; and all valuable elements (P, Si, Al, Ca) in the acid leachate are recovered, achieving zero emissions.

[0036] This invention achieves rapid separation and recycling of magnetic catalysts. The F in the slag... Magnetite is retained during acid etching, imparting excellent magnetism to the catalyst (magnetic saturation strength 15-50 emu / g). Rapid catalyst separation (<5 minutes) can be achieved with an external magnetic field (0.1-0.5 T), eliminating the need for complex centrifugation and filtration equipment, achieving a recovery rate >90%, far exceeding traditional sedimentation or filtration methods (60-80%). The recovered catalyst can be reused after simple water washing, with catalytic activity decreasing by only <10% after three consecutive uses. Assuming a catalyst price of 20 yuan / kg and a dosage of 2 g / L, the cost of treating 1 m³ of wastewater without recovery is 40 yuan; with recovery and reuse three times, the cost drops to 10 yuan / m³, resulting in a significant 75% reduction in operating costs.

[0037] This invention uses solid waste (sludge incineration slag) as raw material, with near-zero raw material costs; in fact, a slag disposal fee can be charged, achieving a negative-cost raw material supply. This is achieved by creatively utilizing the Si inherent in the slag. A CaO, acting as a "self-sacrificing template," completely eliminates the cost of purchasing expensive pore-forming agents; utilizing naturally occurring F... The catalytic system is constructed using graphite carbon, nitrogen, and phosphorus elements, eliminating the need for artificial metal doping and the addition of nitrogen and phosphorus sources, thus significantly reducing raw material costs. Since a high-temperature sintering step is eliminated, energy consumption is reduced to 12-19% of traditional methods, resulting in a substantial decrease in energy costs. Regarding equipment investment, this invention eliminates the need for expensive equipment such as dedicated high-temperature sintering furnaces, atmosphere control systems, and exhaust gas treatment devices; the total equipment investment is only 20-30% of that of traditional methods.

[0038] Furthermore, this invention achieves full-process resource utilization, converting solid-phase slag into catalyst, recovering phosphorus in the liquid phase to produce iron phosphate and calcium fluoride products, and using the dissolved silicon-aluminum-calcium components to produce building materials. Each ton of slag processed can generate considerable comprehensive output value. The catalyst can be rapidly recovered and recycled multiple times through magnetic separation, maintaining good activity, and reducing operating costs to 25-30% of those of single-use catalysts. In summary, the preparation cost of this invention is approximately 30-50% of that of traditional Fe-based catalysts, demonstrating significant economic benefits.

[0039] This invention opens up a new avenue for the resource utilization of sludge incineration slag, transforming a large amount of solid waste that would otherwise require landfill disposal into high-value-added products, thus achieving both solid waste reduction and resource recovery. Since the slag has already undergone high-temperature incineration, the organic matter has been completely decomposed, and no VOCs are generated during the subsequent acid etching process; there is no high-temperature sintering stage, resulting in no emissions of NOx, SOx, or other air pollutants, achieving "zero emissions" of air pollutants.

[0040] Through a systematic byproduct recovery process, this invention achieves "zero discharge" of waste liquid: dissolved phosphorus is recovered and recycled by precipitation to prepare ferric phosphate, fluoride ions are precipitated to recover calcium fluoride, and the silica-alumina-calcium components are used to prepare building materials. All components are effectively recovered, eliminating environmental risks and creating additional economic value. Compared with traditional methods, this invention significantly reduces energy consumption, thereby substantially reducing greenhouse gas emissions. This invention significantly improves the activation efficiency of the oxidant by regulating the Fe active center through NP dual coordination. Reactive oxygen species (·OH, ·S) Compared to uncontrolled slag catalysts, the generation efficiency of this catalyst is significantly improved, and the degradation rate of organic pollutants is significantly increased. In various advanced oxidation systems such as Fenton oxidation, persulfate activation, and ozone catalytic oxidation, the catalyst of this invention exhibits excellent performance, with high levels of COD and TOC removal rates, and treatment effects reaching or exceeding those of commercial catalysts.

[0041] The catalyst of this invention exhibits excellent degradation effects on various types of organic pollutants, including dyes, phenols, antibiotics, endocrine disruptors, and pesticides, making it widely applicable. It demonstrates strong adaptability to water quality conditions, maintaining high activity across a wide pH range, and exhibits particularly excellent performance under neutral conditions, thus avoiding the limitation of the traditional Fenton process requiring strongly acidic conditions. It also shows good tolerance to high salinity and excellent treatment capacity for high-concentration organic wastewater, making it suitable for treating recalcitrant wastewater from industries such as chemical, pharmaceutical, and dyeing.

[0042] The catalyst exhibits good stability and reusability, maintaining high catalytic activity even after multiple consecutive uses. The main active components remain largely stable, the crystal structure is stable, and the porous structure remains largely intact. The catalyst demonstrates excellent chemical stability under various pH conditions, with extremely low metal leaching, preventing significant secondary pollution and meeting environmental protection requirements.

[0043] The preparation process of this invention includes only four main steps: crushing, acid etching, solid-liquid separation, and drying. The entire process eliminates complex steps such as high-temperature sintering, atmosphere control, and template removal, significantly simplifying the operation, resulting in a short cycle time and simple operation. The key step, acid etching, operates at a mild temperature, far lower than the sintering temperature of traditional catalyst preparation, and the reaction pressure is at atmospheric pressure, eliminating the need for high-pressure reactors and inert atmosphere protection, thus ensuring high operational safety and low cost. Regarding equipment investment, the main equipment required for this invention consists of conventional crushing, stirring, filtering, and drying equipment, eliminating the need for expensive equipment such as dedicated high-temperature furnaces, atmosphere control systems, and VOCs exhaust gas treatment devices, resulting in significantly lower equipment investment compared to traditional methods. Each process step of this invention can be operated continuously, and the entire production line can be fully automated, greatly reducing labor costs and improving the stability and consistency of product quality. By adjusting the acid etching conditions, this invention can flexibly adapt to slag raw materials with different compositions, obtaining catalyst products with stable performance. Its strong raw material adaptability greatly improves the reliability of engineering applications. Through a systematic byproduct recovery process, this invention achieves "zero discharge" of waste liquid, and all valuable elements in the acid leaching solution are recovered and utilized in stages. This not only eliminates environmental risks but also creates additional revenue, achieving both environmental and economic benefits.

[0044] This invention proposes and implements a complete technical route for constructing high-performance catalysts using natural components of sludge incineration slag, creatively proposing the concept of "self-sacrificing template pore-forming" and the mechanism of "NP dual-coordination regulating Fe active centers." This invention changes the traditional understanding that "catalysts must be sintered at high temperatures" and "external pore-forming agents and dopants must be added." Through in-depth analysis of the formation mechanism of sludge incineration slag, this invention creatively recognizes that the slag has already undergone high-temperature treatment during incineration, and its mineral phases have formed a stable crystal structure, eliminating the need for secondary sintering. This paradigm shift fundamentally changes the technical route for catalyst preparation, with significant implications not only for sludge-based catalysts but also for the entire field of solid waste-based catalysts and even catalyst preparation. Through systematic experiments and characterization, this invention deeply reveals the synergistic mechanism between N, P elements and Fe active centers, including electronic structure regulation, adsorption enhancement, and Fe... / Fe This study proposes a new approach to catalyst design based on "precise control of coordination elements" in multiple aspects, including cycle acceleration, providing important theoretical guidance for the design of low-cost, high-performance catalysts.

[0045] This invention opens up a completely new path for the high-value utilization of sludge incineration ash, perfectly interpreting the circular economy concept of "treating waste with waste." This technical route is not only applicable to sludge incineration ash, but also has a technology spillover effect, and can be extended to the resource utilization of other solid wastes such as coal gangue, fly ash, steel slag, and waste incineration fly ash, showing great development potential.

[0046] The magnetic catalyst prepared by this invention is suitable for a variety of advanced oxidation systems and can be widely used in the treatment of organic wastewater in industries such as printing and dyeing, pharmaceuticals, chemicals, papermaking, pesticides, and electroplating, as well as in-situ remediation of groundwater and soil. It has broad application prospects and huge market potential.

[0047] In summary, this invention addresses the key bottlenecks of existing advanced oxidation catalyst preparation processes, such as high energy consumption, high cost, and difficulty in engineering, as well as the practical problem of insufficient resource utilization of sludge incinerator slag. It creatively proposes a novel technical route for constructing high-performance magnetic catalysts using the natural components of sludge incinerator slag. Through two core innovations—"self-sacrificing template pore-forming" and "NP dual-coordination regulation"—this invention achieves porous structure construction, composite active center formation, and magnetic attenuation in one step under mild conditions, without secondary sintering, external pore-forming agents, or metal dopants, thus preparing a high-performance composite catalyst.

[0048] Meanwhile, this invention achieves full-process resource utilization of slag through a systematic by-product recovery process: solid-phase conversion into a recyclable magnetic catalyst, liquid-phase recovery of phosphorus to prepare ferric phosphate, and leached silicon, aluminum, and calcium components to prepare building materials, truly realizing a circular economy model of "fully utilizing" and zero waste. This invention has significant advantages such as low raw material cost, low energy consumption, small equipment investment, excellent catalytic performance, simple and easy-to-engineer process, environmental friendliness, and recyclability. The overall preparation and operating costs are far lower than traditional methods, making it extremely cost-effective.

[0049] This invention not only provides an innovative technical solution for the high-value utilization of sludge incineration slag, but also opens up a completely new technical path for the entire field of solid waste-based catalysts and even catalyst preparation, changing traditional understanding and leading the technological development direction of "low-energy consumption, low-cost, solid waste-based" catalyst preparation. This invention has broad application prospects and huge market potential, with significant economic, environmental, and resource benefits. It has important strategic significance and a demonstrative and leading role in promoting the circular economy, sustainable development, resource security, and water pollution control.

[0050] Example 1

[0051] This embodiment presents a method for preparing a sludge incinerator slag-based magnetic catalyst and its application in the catalytic ozone oxidation treatment of coking wastewater. Specifically, it includes the following: Take 200 g of sludge incineration ash from a wastewater treatment plant. The main components of the ash, calculated as oxides, are: Si 28.3%, A 12.6%, F 16.8%, CaO 10.2%, 7.5%, MgO 4.1%, O 3.2%, N O2.8%, Ti The composition of the slag is as follows: 1.9% graphite carbon, 3.6% nitrogen compounds, 1.8% other trace components, and 7.2% other trace components. The slag is pulverized using a planetary ball mill and passed through a 200-mesh sieve to obtain slag powder.

[0052] Prepare a mixed acid solution by mixing 10% hydrofluoric acid and 20% hydrochloric acid at a volume ratio of 1:3. Weigh 50 g of slag powder and place it in a 500 mL polypropylene plastic container. Add 500 mL of the mixed acid and perform acid etching for 30 min at pH 1.8, room temperature, and magnetic stirring speed of 450 rpm. After acid etching, use a 0.5 M solution... After 30 minutes of treatment, hydroxyl groups are generated on the iron surface; then, acid etching is performed on the sludge incineration slag, utilizing the silicon, aluminum, and calcium components in the slag as a self-sacrificing pore-forming template. After treatment, Si... The content decreased to 4.2%, A The content was reduced to 8.5%, the CaO content was reduced to 6.1%, the iron retention rate reached 92.8%, the phosphorus retention rate was 36.5%, and the nitrogen retention rate was 48.3%. The mixture after acid etching was separated by filtration, the solid product was washed with deionized water until neutral, and dried at 100℃ for 12 h to obtain the magnetic catalyst.

[0053] The catalyst has a specific surface area of ​​186 m² / g, with pore size concentrated in the range of 5-35 nm. Mesopores account for 72.8% of the total pore volume. Its magnetic saturation intensity is 3 emu / g, coercivity is 10² Oe, and its iron content is 20.8%, phosphorus content is 2.2%, and nitrogen content is 0.55%. The Fe 2p peak shows Fe... with Fe The molar ratio was 1:2.3. The N 1s peak showed that pyridine nitrogen accounted for 44.2% of the total nitrogen and pyrrole nitrogen accounted for 32.5%. The P 2p peak confirmed that phosphorus was coordinated with iron sites in the form of phosphate, forming an NP double coordination structure.

[0054] Nanofiltration concentrate from a coking plant was selected as the target wastewater. This wastewater had a COD of 710 mg / L, TOC of 285 mg / L, pH of 8.2, color of 120 times, and salinity of 8.5%. The main pollutants were polycyclic aromatic hydrocarbons, phenolic compounds, and heterocyclic nitrogen-containing compounds. Three sets of comparative experiments were designed: Experiment A involved etched catalyst combined with ozone oxidation, with a catalyst dosage of 2.0 g / L; Experiment B involved unetched raw slag powder combined with ozone oxidation, with a slag dosage of 2.0 g / L; and Experiment C involved ozone oxidation alone without a catalyst. All three experiments were conducted under the following conditions: 1 L of wastewater, temperature of 25℃, ozone concentration of 80 mg / L, gas flow rate of 1.0 L / min, and reaction time of 120 min.

[0055] After 120 min of reaction, the COD removal rate of experimental group A was 79.4%, and the TOC removal rate was 64.9%. The COD removal rate of experimental group B was 50.3%, and the TOC removal rate was 36.8%. The COD removal rate of experimental group C was 39.2%, and the TOC removal rate was 25.3%. The experimental data show that the etching catalyst increased the COD removal rate by 57.9% compared to the original slag, and by 102.6% compared to ozone oxidation alone, significantly enhancing the treatment effect of ozone on high-salt, high-concentration, and recalcitrant organic wastewater.

[0056] p-chlorobenzoic acid (pCBA) was used as a hydroxyl radical probe compound at an initial concentration of 0.1 mg / L. Its degradation was determined by high-performance liquid chromatography (HPLC) to indirectly reflect the hydroxyl radical generation capacity. After 30 min of reaction, the degradation rate of pCBA was 76.8% in experimental group A, 41.5% in experimental group B, and 29.7% in experimental group C. The concentration of hydroxyl radicals generated by the etching catalyst system was 1.85 times that of the original slag and 2.59 times that of ozone alone, confirming that the NP-coordinated iron sites promote ozone decomposition to generate reactive oxygen species, thereby improving the oxidative degradation capacity for recalcitrant organic pollutants.

[0057] After the reaction, the catalyst was recovered using a magnet, achieving a recovery rate of 95.2%. The recovered catalyst was washed with deionized water, dried at 80°C, and then reused. The COD removal rate was 75.8%, only 4.5% lower than the initial use, demonstrating good reusability. The acid leachate was adjusted to pH 7.5 with sodium hydroxide solution, and ferric sulfate solution was added. Phosphorus was added in the form of ferric phosphate (FeP). The precipitate was obtained by filtration and separation, yielding iron phosphate precipitate with a phosphorus recovery rate of 73.2%. The resulting iron phosphate precipitate, after washing and drying, can be used as a precursor for the cathode material of lithium iron phosphate batteries. Calcium chloride solution was added to the filtrate after iron phosphate separation, causing fluoride ions to react with calcium ions to form calcium fluoride precipitate. The fluoride ion removal rate reached 96.3%, achieving full-process resource utilization of sludge incineration slag.

[0058] Example 2

[0059] This embodiment proposes a method for preparing a sludge incinerator slag-based magnetic catalyst and its application in Fenton-like oxidation treatment of coking wastewater. Specifically, it includes the following: Take 200 g of sludge incineration ash from a wastewater treatment plant. The main components of the ash, calculated as oxides, are: Si 27.5%, A 11.8%, F 15.2%, CaO 9.6%, 8.1%, MgO 3.8%, O 3.5%, N O3.1%, Ti 2.2% graphite carbon, 3.2% nitrogen-containing compounds, 1.5% other trace components, and 6.5% other trace components. The slag was pulverized using a planetary ball mill and passed through a 200-mesh sieve to obtain slag powder.

[0060] Prepare a mixed acid solution by mixing 12% hydrofluoric acid and 18% hydrochloric acid at a volume ratio of 1:3. Weigh 50 g of slag powder and place it in a 500 mL polypropylene plastic container. Add 500 mL of the mixed acid and perform acid etching for 45 min at pH 2.0, room temperature, and a magnetic stirring speed of 400 rpm. After acid etching, use a 0.6 M solution... After 30 min of treatment, hydroxyl groups were generated on the iron surface; acid etching utilized the silicon-aluminum-calcium components in the slag as a self-sacrificing pore-forming template, and the treated Si... The content decreased to 3.8%, A The content was reduced to 7.9%, the CaO content was reduced to 5.5%, the iron retention rate reached 94.1%, the phosphorus retention rate was 38.2%, and the nitrogen retention rate was 52.7%. The mixture after acid etching was separated by vacuum filtration, the solid product was washed with deionized water until neutral, and dried at 100℃ for 12 h to obtain the magnetic catalyst.

[0061] The catalyst has a specific surface area of ​​203 m² / g, with pore size distribution concentrated in the range of 8-40 nm. Mesopores account for 76.3% of the total pore volume. Its magnetic saturation intensity is 2.87 emu / g, coercivity is 10⁶ Oe, and its iron content is 22.3%, phosphorus content is 2.5%, and nitrogen content is 0.62%. The Fe 2p peak shows Fe... with Fe The molar ratio was 1:2.1. The N 1s peak showed that pyridine nitrogen accounted for 46.8% of the total nitrogen and pyrrole nitrogen accounted for 30.2%. The P 2p peak confirmed that phosphorus was coordinated with iron sites in the form of phosphate, forming an NP double coordination structure.

[0062] Nanofiltration concentrate from a coking plant was selected as the target wastewater. This wastewater had a COD of 210 mg / L, TOC of 85 mg / L, pH of 8.2, color of 80 times, and salinity of 8.5%. The main pollutants were polycyclic aromatic hydrocarbons, phenolic compounds, and heterocyclic nitrogen-containing compounds. Three sets of comparative experiments were designed: Experiment A involved Fenton oxidation using an etched catalyst, with a catalyst dosage of 6.0 g / L; Experiment B involved Fenton oxidation using unetched raw slag powder, with a slag dosage of 6.0 g / L; and Experiment C involved... Oxidation was performed without a catalyst. All three experiments were conducted in 1 L of wastewater, with the initial pH adjusted to 3.5 using dilute sulfuric acid, and at a temperature of 30°C. The dosage was 5 mmol / L (equivalent to 170 mg / L), the magnetic stirring speed was 300 rpm, and the reaction time was 120 min.

[0063] After 120 min of reaction, the COD removal rate of experimental group A was 70.5%, the effluent COD concentration was 62 mg / L, and the TOC removal rate was 56.5%. The COD removal rate of experimental group B was 8.1%, mainly due to catalyst adsorption, and the TOC removal rate was 5.3%. The COD removal rate of experimental group C was 7.6%, mainly due to… The weak oxidation effect resulted in a TOC removal rate of 4.7%. Experimental data showed that the etching catalyst exhibited significant Fenton-like catalytic activity, increasing the COD removal rate by 770.4% compared to the original slag, and compared to the single... The oxidation effect increased by 827.6%, confirming the role of the NP-coordinated iron active sites formed by acid etching in the process. Activation plays a crucial role.

[0064] p-Chlorobenzoic acid (pCBA) was used as a hydroxyl radical probe compound with an initial concentration of 0.1 mg / L. Its degradation was determined by high-performance liquid chromatography (HPLC) to indirectly reflect its hydroxyl radical generation capacity. After 30 min of reaction, the degradation rate of pCBA was 72.3% in experimental group A, 9.8% in experimental group B, and 8.5% in experimental group C. The concentration of hydroxyl radicals generated by the etching catalyst system was 7.38 times that of the original slag, and was significantly higher than that of the single slag. The 8.51-fold increase confirms that the NP dual-coordinated iron sites significantly promote [the development of] ... Decomposition produces hydroxyl radicals, Fe with Fe The cyclical transformation accelerates the Fenton-like reaction process, thereby improving the oxidative degradation capacity of recalcitrant organic pollutants in coking wastewater.

[0065] After the reaction, the catalyst was recovered using a magnet, achieving a recovery rate of 96.5%. The recovered catalyst was washed with deionized water, dried at 80°C, and then reused. The COD removal rate was 67.8%, only 3.8% lower than the initial use, demonstrating good reusability. The acid leachate was adjusted to pH 7.8 with sodium hydroxide solution, and ferric sulfate solution was added. Phosphorus was added in the form of ferric phosphate (FeP). The precipitate was obtained by filtration and separation, yielding iron phosphate precipitate with a phosphorus recovery rate of 75.8%. The resulting iron phosphate precipitate, after washing and drying, can be used as a precursor for the cathode material of lithium iron phosphate batteries. Calcium chloride solution was added to the filtrate after iron phosphate separation, causing fluoride ions to react with calcium ions to form calcium fluoride precipitate. The fluoride ion removal rate reached 97.1%, achieving full-process resource utilization of sludge incineration slag.

[0066] Example 3

[0067] This embodiment presents a method for preparing a sludge incinerator slag-based magnetic catalyst and its application in the persulfate-activated oxidation treatment of hospital wastewater. Specifically, it includes the following: Take 200 g of sludge incineration ash from a wastewater treatment plant. The main components of the ash, calculated as oxides, are: Si 26.9%, A 13.2%, F 17.1%, CaO 8.8%, 6.9%, MgO 4.5%, O 2.9%, N O2.6%, Ti The composition of the slag is as follows: 1.7% graphite carbon, 3.8% nitrogen-containing compounds, 1.4% other trace components, and 8.2% other trace components. The slag is pulverized using a planetary ball mill and passed through a 200-mesh sieve to obtain slag powder.

[0068] Prepare a mixed acid solution by mixing 11% hydrofluoric acid (by mass) and 22% hydrochloric acid (by mass) at a volume ratio of 1:3.5. Weigh 50 g of slag powder and place it in a 500 mL polypropylene plastic container. Add 500 mL of the mixed acid solution and perform acid etching for 35 min at pH 1.9, room temperature, and a magnetic stirring speed of 420 rpm. After acid etching, use a 0.5 M solution... After 30 minutes of treatment, hydroxyl groups are generated on the iron surface. Acid etching utilizes the silicon-aluminum-calcium components in the slag as a self-sacrificing pore-forming template; after treatment, Si... The content decreased to 4.5%, A The content was reduced to 9.2%, the CaO content was reduced to 6.8%, the iron retention rate was 93.5%, the phosphorus retention rate was 34.7%, and the nitrogen retention rate was 49.6%. The mixture after acid etching was separated by vacuum filtration, the solid product was washed with deionized water until neutral, and dried at 100℃ for 12 h to obtain the magnetic catalyst.

[0069] The catalyst has a specific surface area of ​​195 m² / g, with pore size concentrated in the range of 6-38 nm. Mesopores account for 74.6% of the total pore volume. Its magnetic saturation intensity is 3.2 emu / g, coercivity is 118 Oe, and its iron content is 21.6%, phosphorus content is 2.0%, and nitrogen content is 0.58%. The Fe 2p peak shows Fe... with Fe The molar ratio was 1:2.2. The N 1s peak showed that pyridine nitrogen accounted for 45.6% of the total nitrogen and pyrrole nitrogen accounted for 31.8%. The P 2p peak confirmed that phosphorus was coordinated with iron sites in the form of phosphate, forming an NP double coordination structure.

[0070] The effluent from a hospital's wastewater treatment plant after biochemical treatment was selected as the target wastewater. This wastewater had a COD of 125 mg / L, TOC of 48 mg / L, pH of 7.5, color of 35 times the standard value, salinity of 1.8%, and a sulfonamide antibiotic concentration (calculated as sulfamethoxazole) of 102 μg / L. Three comparative experiments were designed: Experiment A involved persulfate oxidation activated by an etched catalyst, with a catalyst dosage of 1.5 g / L; Experiment B involved persulfate oxidation activated from unetched raw slag powder, with a slag dosage of 1.5 g / L; and Experiment C involved persulfate oxidation alone without a catalyst. All three experiments were conducted in 1 L of wastewater, without pH adjustment, at a temperature of 30℃, with a potassium persulfate complex salt (PMS) dosage of 1.2 mmol / L, magnetic stirring at 300 rpm, and a reaction time of 90 min.

[0071] After 90 min of reaction, the removal rate of sulfonamide antibiotics in experimental group A was 96.1%, the effluent concentration decreased to 3.98 μg / L, the COD removal rate was 68.8%, and the TOC removal rate was 52.1%. In experimental group B, the removal rate of sulfonamide antibiotics was 38.2%, the COD removal rate was 22.4%, and the TOC removal rate was 15.6%. In experimental group C, the removal rate of sulfonamide antibiotics was 18.6%, the COD removal rate was 12.3%, and the TOC removal rate was 8.5%. The experimental data show that the etching catalyst exhibits excellent persulfate activation performance, achieving a removal rate of over 96% for trace sulfonamide antibiotics. Compared to the original slag, this increases the sulfonamide antibiotic removal rate by 151.6%, and compared to persulfate oxidation alone, it increases it by 416.7%, confirming the highly efficient activation effect of the NP dual-coordinated iron active sites on persulfate.

[0072] p-chlorobenzoic acid (pCBA) was used as a hydroxyl radical probe compound at an initial concentration of 0.1 mg / L. Its degradation was determined by high-performance liquid chromatography (HPLC) to indirectly reflect the ability to generate reactive oxygen species. After 30 min of reaction, the degradation rate of pCBA was 65.3% in experimental group A, 28.7% in experimental group B, and 16.2% in experimental group C. The concentration of reactive oxygen species generated by the etching catalyst system was 2.27 times that of the original slag and 4.03 times that of persulfate alone. The persulfate activation system mainly generated sulfate radicals (S...). ) and hydroxyl radicals ( OH), NP double-coordinated iron sites promote homolytic and heterolytic cleavage of persulfate through electron transfer mechanisms, Fe / Fe The cycle accelerates the continuous generation of reactive oxygen species, thereby achieving efficient degradation of trace antibiotics in hospital wastewater.

[0073] After the reaction, the catalyst was recovered using a magnet, achieving a recovery rate of 96.2%. The recovered catalyst was washed with deionized water, dried at 80°C, and then reused. The removal rate of sulfonamide antibiotics was 93.5%, and the COD removal rate was 65.3%, representing decreases of 2.7% and 5.1% respectively compared to the initial use, demonstrating good reusability. The pH of the acid leachate was adjusted to 7.8 with sodium hydroxide solution, and ferric sulfate solution was added. Phosphorus was added in the form of ferric phosphate (FeP). The precipitate was obtained by filtration and separation, yielding iron phosphate precipitate with a phosphorus recovery rate of 74.6%. The resulting iron phosphate precipitate, after washing and drying, can be used as a precursor for the cathode material of lithium iron phosphate batteries. Calcium chloride solution was added to the filtrate after iron phosphate separation, causing fluoride ions to react with calcium ions to form calcium fluoride precipitate. The fluoride ion removal rate reached 96.8%, achieving full-process resource utilization of sludge incineration slag.

[0074] In summary, this invention discloses a method for preparing and utilizing a sludge incinerator slag-based magnetic catalyst. Addressing the problems of high energy consumption, high cost, and low slag utilization in existing catalyst preparation methods, this invention creatively utilizes Si in the slag... A CaO, acting as a "self-sacrificing template," achieves pore creation and impurity removal in one step through selective acid etching (pH 1.0-2.5, 40-70℃), without the need for external pore-forming agents or high-temperature sintering; it also retains natural F. A CNP-Fe composite catalytic system was constructed using graphite carbon and appropriate amounts of N and P elements. The prepared catalyst has a mesoporous structure (2-50 nm), and the NP double coordination significantly enhances catalytic performance, increasing the degradation rate of organic pollutants by 40-60%. It can be magnetically separated and recovered (recovery rate >90%), and retains >90% of its activity after three cycles of recycling. Phosphorus from the liquid-phase byproducts is recovered to prepare iron phosphate (recovery rate >70%), and silicon-aluminum-calcium is used to prepare building materials, achieving full-process resource utilization and zero emissions. This invention reduces energy consumption by 80-90%, preparation costs by 30-50% of traditional methods, and operating costs by 25-30%, providing an innovative solution for the high-value utilization of solid waste and water pollution control.

[0075] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that, based on the technical solutions disclosed in the present invention, various modifications or variations that can be made by those skilled in the art without creative effort should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a sludge incinerator slag-based magnetic catalyst, characterized in that, Includes the following steps: (1) Crush the sludge incineration slag and pass it through a 100-300 mesh sieve to obtain powder; (2) The powder is subjected to acid etching with a mixture of hydrofluoric acid and hydrochloric acid, using the Si, Al and Ca components in the slag as a self-sacrificing pore-forming template, retaining phosphorus and nitrogen elements to form a porous structure; after acid etching, the powder is then used... The treatment generates hydroxyl groups on the iron surface; (3) Separate the solid and liquid components of the mixture obtained in step (2), and dry the solid product to obtain a carbon-NP-Fe composite magnetic catalyst with carbon as the matrix and nitrogen and phosphorus elements forming a coordination structure with iron sites.

2. The method for preparing the sludge incinerator slag-based magnetic catalyst according to claim 1, characterized in that, The hydrofluoric acid has a mass concentration of 8-15%, the hydrochloric acid has a mass concentration of 15-25%, and the volume ratio of hydrofluoric acid to hydrochloric acid in the mixed acid is 1:2-1:4; the acid etching process is performed using mechanical stirring at a stirring speed of 300-600 rpm or ultrasonic assistance at a power of 200-500 W to promote the formation of NP double-coordinated iron sites; The processing time is 30-90 minutes, and the temperature is 25-50℃.

3. The method for preparing the sludge incinerator slag-based magnetic catalyst according to claim 1, characterized in that, In step (1), the composition of the sludge incineration slag, calculated as oxides, includes: Si 20-30%, A 8-15%, F 10-18%, CaO 5-15%, 5-10%, graphite carbon 1-5%, nitrogen-containing compounds 0.5-2%, transition metal oxides 0.1-2%.

4. The method for preparing the sludge incinerator slag-based magnetic catalyst according to claim 1, characterized in that, In step (2), Si, Al, and Ca components are used as self-sacrificing templates to form mesoporous structures without the need for external pore-forming agents; the graphitized carbon material produced during the incineration process is fully utilized as an electronic conductor and matrix to promote electron transfer in the catalytic reaction; 30-50% of phosphorus and 10-30% of nitrogen are selectively dissolved, while sufficient phosphorus and nitrogen are retained for coordination with iron sites; the iron content is retained to be no less than 80%, while exposing more iron active sites.

5. The method for preparing the sludge incinerator slag-based magnetic catalyst according to claim 1, characterized in that, In step (2), after the acid etching treatment, the concentration of fluoride ions in the acid leaching solution is 100-500 mg / L.

6. An application of the sludge incinerator slag-based magnetic catalyst as described in any one of claims 1-5 in wastewater treatment, characterized in that, The carbon-NP-Fe composite magnetic catalyst was used for advanced oxidation degradation of organic wastewater. The catalyst dosage was 1-3 g / L and the oxidant dosage was 20-80 mg / L. After the reaction, the catalyst was recovered by magnetic separation. The resulting acid leachate was adjusted to pH 7-9 by adding an alkaline neutralizing agent to remove fluoride ions. Then, an iron salt precipitant was added to recover the dissolved phosphorus, resulting in iron phosphate precipitate.

7. The application of the sludge incinerator slag-based magnetic catalyst according to claim 6 in wastewater treatment, characterized in that, The advanced oxidative degradation employs one of Fenton oxidation, persulfate-activated oxidation, or ozone catalytic oxidation, wherein the oxidant is one of hydrogen peroxide, persulfate, or ozone, and the carbon-NP-Fe composite enhances the active oxygen generation efficiency by 30-50%.

8. The application of the sludge incinerator slag-based magnetic catalyst according to claim 7 in wastewater treatment, characterized in that, The reaction conditions for Fenton oxidation are: pH 3-5, temperature 20-40℃, hydrogen peroxide concentration 20-80 mg / L, and reaction time 30-120 minutes; or the reaction conditions for persulfate activation oxidation are: pH 5-9, temperature 20-60℃, persulfate concentration 30-100 mg / L, and reaction time 30-120 minutes; or the reaction conditions for ozone catalytic oxidation are: pH 5-10, temperature 20-40℃, ozone concentration 40-120 mg / L, gas flow rate 0.5-2 L / min, and reaction time 30-90 minutes.

9. The application of the sludge incinerator slag-based magnetic catalyst according to claim 6 in wastewater treatment, characterized in that, The alkaline neutralizing agent is one of sodium hydroxide, calcium hydroxide, or magnesium hydroxide; the iron salt precipitant is one of ferrous sulfate, ferrous chloride, or ferric sulfate; the phosphorus recovery rate is not less than 70%, and the obtained iron phosphate precipitate product can be used for the preparation of lithium iron phosphate battery materials after filtration, washing, and drying; in the carbon-NP-Fe composite magnetic catalyst, nitrogen exists in the form of pyridine nitrogen or pyrrole nitrogen, and phosphorus is coordinated with iron sites in the form of phosphate or phosphonate to form an NP double coordination structure.

Images