A coal gasification slag-based defect-rich carbon-iron composite material and its preparation method and application

Abstract

The present invention belongs to the technical field of coal-based solid waste resource treatment and carbon-containing catalytic materials. In order to solve the problem of how to utilize the residual carbon and valuable metal iron elements in coal gasification slag and make a defect-rich carbon-iron composite material, a coal gasification slag-based defect-rich carbon-iron composite material and its preparation method and application are provided. Under mild conditions, the coal gasification slag is impregnated with weak acid to remove calcium from the coal gasification slag, activate silicon-oxygen and aluminum-oxygen bonds, and retain iron; modified with potassium hydroxide and sodium hydroxide, silicon in the coal gasification slag is removed, carbon-iron structure is enriched, and modified gasification slag is obtained; high-temperature roasting in an inert atmosphere obtains a coal gasification slag-based defect-rich carbon-iron composite material. The high-value application of carbon and iron, the components of coal gasification slag itself, is realized without the need to add additional metal elements. By regulating the weak acid impregnation process, the calcium and aluminum elements are removed while reducing the leaching of iron. During the high-temperature roasting process, the iron catalytic carbon is used to further form defect sites, and the material exhibits good bisphenol A degradation performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of coal-based solid waste resource treatment and carbon-containing catalytic materials, and specifically relates to a coal gasification slag-based defect-rich carbon-iron composite material and a preparation method and application thereof, specifically an application in catalytic activation of persulfate to degrade phenolic organic pollutants. Background Art

[0002] Coal gasification slag is a solid waste generated during the coal gasification process. At present, the comprehensive utilization rate of coal gasification slag is low, and it has not yet been used on a large scale. Stockpiling and landfilling are still the main disposal methods for coal gasification slag, which not only occupies a large amount of land, but also causes soil and water pollution. Traditional ways of resource utilization of coal gasification slag, such as construction materials, carbon selection and blending, have problems such as high residual carbon content and high water content in actual application. Developing high-value utilization of coal gasification slag can effectively alleviate the dual problems of resource waste and environmental pollution.

[0003] Coal gasification slag is rich in aluminum, silicon, carbon, iron, and calcium. The residual carbon and inorganic particles are intermixed and difficult to be effectively separated. The iron and calcium elements are evenly intermixed and distributed, mostly wrapped in inert amorphous aluminosilicates. Weak acid activation is expected to reduce the Si-O and Al-O bond energies of aluminosilicates in coal gasification slag. At the same time, calcium, aluminum, and iron elements can be partially or completely removed according to the activation process, thereby directional regulation of the dissolution of various components in coal gasification slag. On this basis, its surface structure and physical and chemical properties are further regulated to achieve the comprehensive utilization of silicon, aluminum, carbon and other valuable elements, showing good application prospects. In addition, the graphitization degree of the carbon structure in coal gasification slag is relatively high. When graphitized carbon coexists with iron oxide and copper oxide in the form of chemical bonds, the effect of aromatization of large π bonds will produce electronic polarization distribution. This feature is conducive to the electron transfer of electron-rich organic pollutants on its surface, thereby promoting the oxidative degradation of organic pollutants. Therefore, degrading organic matter, especially electron-rich organic matter, may be a better way out for the high-value application of coal gasification slag.

[0004] Acid activation can greatly improve the properties of coal gasification slag. The controlled variable method is used to select the optimal acid hydrogen ion concentration, reaction time, reaction temperature and liquid-solid ratio, which can remove calcium from coal gasification slag as much as possible, activate silicon-oxygen and aluminum-oxygen bonds, and retain iron. Most of the inorganic components in coal gasification slag are wrapped in amorphous aluminosilicates. Through acid leaching activation, this amorphous wrapping structure is destroyed, the particle pore structure is opened, and a large number of reactive sites are exposed due to the removal of aluminum and other impurity elements, thereby improving the reactivity of coal gasification slag. After acid leaching activation, most of the silicon and oxygen in the coal gasification slag are converted into a more active structure, and silicon is more easily removed by sodium hydroxide. The acid-activated coal gasification slag reacts with sodium hydroxide to remove most of the silicon and aluminum in the coal gasification slag, thereby enriching the carbon-iron structure.

[0005] KOH activation can enrich the defect structure of coal gasification slag. KOH reacts with carbon at high temperature to generate K vapor and CO. During the entire activation process, KOH first reacts with non-carbon atoms and some highly active disordered carbon in the ash to form a preliminary microporous structure. As the activation proceeds, in addition to generating new micropores, KOH can also play a role in expanding the pores by etching the carbon atoms on the walls of the already formed micropores. Therefore, the pore size distribution of coal gasification slag gradually widens and the pore volume increases. Summary of the invention

[0006] The first purpose of the present invention is to provide a coal gasification slag-based defect-rich carbon-iron composite material and a preparation method thereof, aiming to utilize the carbon and iron components of the coal gasification slag itself to prepare a defect-rich carbon-iron composite catalyst with excellent catalytic degradation performance of organic pollutants.

[0007] The second purpose of the present invention is to use the coal gasification slag-based defect-rich carbon-iron composite material prepared by the method in catalytic activation of persulfate to degrade phenolic organic pollutants.

[0008] To achieve the above-mentioned purpose, the present invention is implemented by the following technical scheme: a method for preparing a gasification slag-based defect-rich carbon-iron composite material, wherein under mild conditions, the gasification slag is impregnated with weak acid to remove calcium in the gasification slag, activate silicon-oxygen and aluminum-oxygen bonds therein, and retain the iron therein; on this basis, potassium hydroxide and sodium hydroxide are used for modification to remove silicon in the gasification slag, enrich the iron-carbon structure therein, obtain modified gasification slag, and then high-temperature calcination in an inert atmosphere obtains the gasification slag-based defect-rich carbon-iron composite material.

[0009] Furthermore, the coal gasification slag has a carbon content of >10% and an iron content of >5%.

[0010] Further, the specific steps include:

[0011] (1) Activation by weak acid leaching: Mix acetic acid and coal gasification slag at a liquid-solid ratio of 2:1-8:1 ml / g, heat in a water bath to 60-100°C, activate for 30-180 minutes, then cool to room temperature, filter, and dry to obtain activated gasification slag;

[0012] (2) Modification of gasified slag: Potassium hydroxide and sodium hydroxide are mixed in a mass ratio of 1:1-3:1, added to the activated gasified slag obtained in step (1), and deionized water is added and stirred to form a mixed solution. The mixed solution is heated to 100-200°C in an oil bath, reacted for 2-8 hours, cooled to room temperature, filtered, and dried to obtain modified gasified slag;

[0013] (3) Preparation of coal gasification slag-based defect-rich carbon-iron composite materials: The modified gasification slag obtained in step (2) is heated to 700-850°C at a rate of 10°C / min under a nitrogen atmosphere and kept at this temperature for 2 h. After the sample is naturally cooled, it is washed with deionized water until it is neutral, filtered, and dried to obtain a coal gasification slag-based defect-rich carbon-iron composite material.

[0014] The hydrogen ion concentration in the acetic acid in step (1) is 2 mol / L.

[0015] The concentration of hydroxide ions in the mixed solution of step (2) is 4-8 mol / L; the liquid-solid ratio of the mixed solution to the activated gasified slag is 1-8:1 ml / g. The concentration of hydroxide ions in the mixed solution of step (2) is 6 mol / L; the liquid-solid ratio of the mixed solution to the activated gasified slag is 5:1 ml / g.

[0016] The present invention also provides a coal gasification slag-based defect-rich carbon-iron composite material prepared by the preparation method.

[0017] The present invention also provides the use of the coal gasification slag-based defect-rich carbon-iron composite material as a catalyst in catalytic activation of persulfate to degrade phenolic organic pollutants, which specifically comprises the following steps:

[0018] (1) Concentration of 100mL is 20-50 mg·L -1 In a bisphenol A (BPA) solution, 1-10 mmol / L potassium peroxymonosulfate is added to the solution, and then 20-30 mg of the above-mentioned slag-based defect-rich carbon-iron composite material is added, and the degradation reaction starts timing;

[0019] (2) Samples were taken using a disposable syringe according to the time gradient. 1 mL of the sample was taken each time. The sample was filtered through a 0.22 μm polyethersulfone (PES) filter and added to a 2 mL brown chromatographic bottle. 0.5 mL of methanol was added to the chromatographic bottle in advance to terminate the free radical reaction still in progress in the sample. The concentration of bisphenol A in the solution was determined by liquid chromatography.

[0020] The method of the present invention can achieve the removal of calcium and aluminum while reducing iron leaching by regulating the amount of acetic acid used during acid impregnation. In addition, iron can be used to catalyze carbon to further form defect sites during high-temperature roasting, and the defect-rich carbon-iron composite material exhibits good bisphenol A degradation performance.

[0021] The present invention prepares a coal gasification slag-based carbon-iron composite material with a rich defect structure, and successfully prepares a carbon-based catalyst with high activation ability for PMS. The raw material of the carbon-based catalyst prepared by the present invention is the waste generated by coal gasification - coal gasification fine slag, which expands a new coal gasification slag treatment path and realizes the environmental protection demand for waste recycling. The coal gasification slag-based defect-rich carbon-iron composite material prepared by the present invention has a rich iron-carbon structure. 3+ -π, the prepared carbon material has high stability and good structural compactness. The present invention uses coal gasification slag with a low carbon content as a raw material to prepare a defect-rich carbon-iron composite material with a high carbon content, a high specific surface area, and rich carbonyl oxygen-containing functional groups, which is another method for high-value utilization of coal gasification slag. The method of the present invention can realize the high-value application of carbon and iron, the components of coal gasification slag itself, without the need to add additional metal elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The SEM comparison diagram of the coal gasification fine slag used in Example 1 and the coal gasification slag-based defect-rich carbon-iron composite material finally prepared; in the diagram: A is the coal gasification slag FS; B is the defect-rich carbon-iron composite material FSD;

[0023] Figure 2 The infrared spectra (FT-IR) of the raw material FS, FSH after acid leaching activation, FSOH after alkali leaching desiliconization, and the finally prepared defect-rich carbon-iron composite material FSD;

[0024] Figure 3 The Raman spectra (Raman) of the raw material FS, FSH after acid leaching activation, FSOH after alkali leaching desiliconization, and the finally prepared defect-rich carbon-iron composite material FSD;

[0025] Figure 4 The N2 adsorption-desorption isotherms and pore size distribution curves of the raw material FS, FSH after acid leaching activation, FSOH after alkali leaching desiliconization, and the finally prepared defect-rich carbon-iron composite material FSD; in the figure: (a) is FS; (b) is FSH; (c) is FSOH; (d) is FSD;

[0026] Figure 5 The X-ray photoelectron diffraction XPS analysis spectra of C1s of the raw material FS, FSH after acid leaching activation, FSOH after alkali leaching desiliconization, and the finally prepared defect-rich carbon-iron composite material FSD; in the figure: (a) is FS; (b) is FSH; (c) is FSOH; (d) is FSD;

[0027] Figure 6The XPS spectra of O1s of the raw material FS, FSH after acid leaching activation, FSOH after alkali leaching desiliconization, and the finally prepared defect-rich carbon-iron composite material FSD; in the figure: (a) is FS; (b) is FSH; (c) is FSOH; (d) is FSD;

[0028] Figure 7 The Fe2p XPS analysis spectra of the raw material FS, FSH after acid leaching activation, FSOH after alkali leaching desiliconization, and the finally prepared defect-rich carbon-iron composite material FSD; in the figure: (a) is FS; (b) is FSH; (c) is FSOH; (d) is FSD. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0030] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, and the disclosure and materials cited therein are hereby incorporated by reference.

[0031] Technical equivalents to the specific embodiments described that are apparent to those skilled in the art using no more than routine experimentation are intended to be encompassed by this application.

[0032] The experimental methods in the following examples are all conventional methods unless otherwise specified. The instruments and equipment used in the following examples are all conventional laboratory instruments and equipment unless otherwise specified; the experimental materials used in the following examples are all purchased from conventional biochemical reagent stores unless otherwise specified.

[0033] Example 1: A method for preparing a gasification slag-based defect-rich carbon-iron material. Under mild conditions, the gasification slag is impregnated with a certain proportion of acetic acid to efficiently remove calcium and aluminum in the gasification slag within a certain period of time, activate the silicon-oxygen and aluminum-oxygen bonds therein, and retain the iron therein. On this basis, the silicon in the gasification slag is further removed by using a mixed strong alkali, and the carbon-iron structure therein is enriched, and then placed in a tubular furnace and calcined at high temperature in an inert atmosphere to obtain a gasification slag-based defect-rich carbon-iron composite material.

[0034] The specific steps include:

[0035] 1) Dry the coal gasification slag (FS) and pass it through an 80-mesh sieve for later use. The chemical analysis and industrial analysis of the coal gasification fine slag used are shown in Tables 1 and 2. As can be seen from the table, the carbon content (26.22%) and iron content (28.15%) of the coal gasification slag described in this study are both high, providing conditions for the preparation of defect-rich carbon-iron composite materials.

[0036] Table 1: Chemical composition of coal gasification slag

[0037]

[0038] Table 2: Industrial analysis of coal gasification slag

[0039]

[0040] 2) Mix 10 mL of dilute acetic acid with a hydrogen ion concentration of 2 mol / L with 2.5 g of coal gasification slag in a beaker, heat to 80°C in a water bath, cool to room temperature after 60 minutes, filter, and dry the residue in a forced air drying oven at 100°C for 6 hours, and mark it as FSH.

[0041] 3) Mix 200 mg of potassium hydroxide and 3200 mg of sodium hydroxide, add deionized water to 10 mL, and stir evenly in a beaker. Add 2 g of the dried filter residue in step (2), stir evenly, and place in an oil bath at 180°C for 8 h. After cooling to room temperature, filter with suction, and dry the filter residue in a forced air drying oven at 100°C for 6 h. Mark it as FSOH.

[0042] 4) The filter residue after drying in step (3) is placed in a stainless steel tube and moved to a tube furnace. In a nitrogen atmosphere, the temperature is increased to 700°C at a rate of 10°C / min and kept at this temperature for 2 hours. After the tube furnace is naturally cooled, the sample is taken out, washed with deionized water until neutral, filtered, and the filter residue is dried to obtain a coal gasification slag-based defect-rich carbon-iron material, which is marked as FSD.

[0043] The above-prepared coal gasification slag-based defect-rich carbon-iron composite material is used as a catalyst to activate PMS to degrade phenolic organic pollutants, which specifically includes the following steps:

[0044] (1) Add 100 mL of the prepared 20 mg·L -1 654 mg of PMS was added to the bisphenol A solution, and the PMS concentration was 10 mmol·L -1 , and then 30 mg of the above-mentioned coal gasification slag-based defect-rich carbon-iron composite material was added, and the degradation reaction timing began.

[0045] (2) 1 mL of sample was taken using a disposable syringe at time intervals of 2, 5, 10, 20, 30, 60, and 90 min, respectively. The sample was filtered through a 0.22 μm PES filter and added to a 2 mL brown chromatographic vial. 0.5 mL of methanol was added to the chromatographic vial in advance to terminate the ongoing free radical reaction in the sample. The concentration of bisphenol A in the solution was determined by liquid chromatography.

[0046] (3) After the degradation experiment is completed, the solution is filtered to obtain the catalyst after the reaction, which is dispersed in 100 mL of ethanol. After ultrasonic treatment for 45 min, the effect of adsorption on the degradation removal rate of bisphenol A is eliminated, and the concentration of bisphenol A in the solution is measured by liquid chromatography to obtain the concentration of bisphenol A adsorbed by the catalyst. Thus, the concentration of bisphenol A degraded by the catalyst can be known.

[0047] The present invention discloses a method for using a coal gasification slag-based defect-rich carbon-iron composite material to activate PMS to degrade phenolic organic pollutants. The carbon-based composite material prepared by the method has a highly developed pore structure ( Figure 1 ), rich oxygen-containing functional groups ( Figure 2 ), more amorphous carbon ( Figure 3 ), larger specific surface area (Table 3) and pore structure ( Figure 4 ).

[0048] The surface functional groups of the raw material FS, FSH after acid leaching activation, FSOH after alkali leaching desiliconization, and the finally prepared defect-rich carbon-iron composite material FSD were determined. The infrared spectra are shown in the figure below. Figure 2 3430 cm -1 The absorption peak near 2937 cm represents the characteristic peak of -OH, and its change may be affected by water molecules on the catalyst surface. -1 The small absorption peak near 1630 cm represents the asymmetric stretching vibration of the -CH group. -1 The peak at 1410 cm represents the characteristic peak of C=O. The reduction of C=O components in FSD may be due to the formation of CO-Fe by unstable double bonds at high temperatures. -1 The small absorption peak at 1050 cm -1 The absorption peaks near 700 cm represent the characteristic peaks of COC. It can be observed from the figure that the characteristic peaks representing -OH gradually increase with modification, which may be due to the exposure of -OH in the carbon-based structure by the leaching of aluminosilicate. -1 and 475 cm -1Two new peaks appeared at , which are attributed to the characteristic peak vibration of Fe-O, and they were further increased after high-temperature pyrolysis. The appearance of Al-O and Fe-O characteristic peaks is due to the decomposition of dense aluminosilicate to form metal oxides, which also led to the displacement of CO-Fe characteristic peak.

[0049] Raman spectroscopy was used to characterize the carbon-based structures in FS, FSH, FSOH, and FSD to determine the degree of graphitization of the carbon structures during different preparation processes. Figure 3 The Raman spectrum of carbonaceous materials is in the range of 800-1600 cm -1 There are two obvious peaks in the range, called D peak and G peak. -1 The D band at 1590 cm -1 The G band at is related to the graphite carbon structure. D / I G The ratio reflects the degree of defects in carbon-based materials. D / I G The ratio of FSD increases with the modification. D / I G The value reaches 2.02, indicating that the degree of material defects is getting worse.

[0050] Figure 4 The nitrogen adsorption-desorption isotherms and pore size distribution curves of FS, FSH, FSOH, and FSD. According to IUPAC rules, the four catalysts all belong to type II adsorption curves and H4 hysteresis curves. When P / P0 is close to 0, the nitrogen adsorption of the catalyst increases sharply. This is due to the monolayer adsorption of nitrogen molecules under low pressure, which quickly fills the micropores. As the pressure gradually increases, multilayer adsorption gradually forms, and the nitrogen adsorption-desorption isotherm shows a hysteresis phenomenon, which is a manifestation of adsorption to mesopores after the micropores are filled. The pore size distribution curves of FS, FSH, FSOH, and FSD show that the pore sizes of the four catalysts are all concentrated below 30 nm, indicating that their pore size structure is mainly mesopores.

[0051] Table 3 shows the detailed pore structure of FS, FSH, FSOH, and FSD. Comparing FS and its FSA after acid leaching, it is found that the specific surface area of ​​FSH does not change significantly. After alkali leaching, the specific surface area and micropore specific surface area of ​​FSOH increase sharply, and the average pore size decreases to 2.88 accordingly. This is because in the alkaline solution, the Si-O-Al in FSH breaks and some tiny particles are leached, resulting in a large number of micropores, which also leads to an increase in specific surface area. After high-temperature pyrolysis, the specific surface area and micropore specific surface area of ​​FSD decrease, but its pore volume and average pore size increase sharply. This is because the alkali metal carbonate formed during alkali leaching forms a large amount of gas overflow at high temperature, and in this process, the pore size of a large number of micropores is further increased.

[0052] Table 3 BET specific surface area, BET micropore specific surface area, total pore volume and average pore diameter of FS, FSH, FSOH and FSD

[0053]

[0054] C1s XPS characterization of FS, FSH, FSOH, and FSD can be found in Figure 5 As can be seen from the figure, the contents of C=C and C=O in the coal gasification slag obtained under different preparation processes are constantly decreasing, while the content of CO is constantly increasing. The changes in FSH and FSOH may be due to the reaction between the acid and alkali solution and the C component, resulting in the increase of structures such as COH. FSD is due to the fact that the unstable C=O of alkali metals is pyrolyzed into CO at a high temperature of 800℃.

[0055] Figure 6 The O1s XPS analysis of FS, FSH, FSOH, and FSD is shown, and the oxygen species in the catalysts are fitted as lattice oxygen (O a 2- ), adsorbed oxygen (O ) associated with oxygen vacancies (OVs), b - :O2 2- , O - ) and other weakly bound oxygen (O c , such as surface adsorption of H2O, etc. As can be seen from the figure, O a 2- The content of O b - The content of O c The change trend of is not obvious. This may be because the leaching of aluminosilicates leads to a decrease in the content of lattice oxygen combined with metals, while the enrichment of carbon components increases the content of adsorbed oxygen related to oxygen-containing functional groups.

[0056] Figure 7The Fe2p XPS analysis spectra of FS, FSH, FSOH, and FSD. 1 / 2 and FeⅡ2p 3 / 2 The total content is 41.77%, FeⅢ2p 1 / 2 and FeⅢ2p 3 / 2 The total content of FeⅡ2p in FSM is 44.74%; 1 / 2 and FeⅡ2p 3 / 2 The total content is 44.55%, FeⅢ2p 1 / 2 and FeⅢ2p 3 / 2 The total content of FeⅡ2p in FSD is 38.90%; 1 / 2 and FeⅡ2p 3 / 2 The total content is 44.97%, FeⅢ2p 1 / 2 and FeⅢ2p 3 / 2 The total content of Fe2p was 40.82%. In addition, no obvious Fe2p XPS spectrum was observed by FSH, which may be due to the reduction of Fe content by acid leaching. Subsequently, other components were removed by alkaline leaching and pyrolysis processes, thereby re-exposing Fe sites.

[0057] In summary, after a series of modifications, FSD presents a loose and porous flocculent structure with a larger specific surface area and pore size structure. In addition, the removal of aluminosilicates during the modification process exposes a variety of active sites, such as carbon defects, -OH, oxygen vacancies, and FeⅡ. The presence of porous structures and active sites in FSD is conducive to the binding and activation of PMS, thereby producing a variety of active substances to degrade phenolic pollutants.

[0058] Example 2: Compared with Example 1, the only difference is that the liquid-to-solid ratio of acetic acid to coal gasification slag is 2:1 ml / g.

[0059] Example 3: Compared with Example 1, the only difference is that the acetic acid concentration is 7 mol / L.

[0060] Example 4: Compared with Example 1, the only difference is that the water bath temperature is 100° C. and the reaction time is 120 min.

[0061] Embodiment 5: Compared with embodiment 1, the only difference is that the weight ratio of potassium hydroxide to sodium hydroxide is 3:1.

[0062] Example 6: Compared with Example 1, the only difference is that the oil bath temperature is 120° C. and the reaction time is 2 h.

[0063] Example 7: Compared with Example 1, the only difference is that the calcination temperature is 800°C.

[0064] The test data on the degradation rate of bisphenol A in Examples 1 to 7 are shown in Table 3.

[0065] Table 4: Bisphenol A degradation rate test data in Examples 1-7

[0066]

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a coal gasification slag-based defect-rich carbon-iron composite material, characterized in that: Under mild conditions, the coal gasification slag is impregnated with weak acid to remove calcium from the coal gasification slag, activate silicon-oxygen and aluminum-oxygen bonds therein, and retain iron therein; on this basis, potassium hydroxide and sodium hydroxide are used for modification to remove silicon from the coal gasification slag, enrich the iron-carbon structure therein, and obtain modified gasification slag, which is then calcined at high temperature in an inert atmosphere to obtain a coal gasification slag-based defect-rich carbon-iron composite material; the coal gasification slag has a carbon content of >10% and an iron content of >5%; The specific steps include: (1) Activation by weak acid leaching: Mix acetic acid and coal gasification slag at a liquid-solid ratio of 2:1-8:1 ml / g, heat in a water bath to 60-100°C, activate for 30-180 minutes, then cool to room temperature, filter, and dry to obtain activated gasification slag; the hydrogen ion concentration in acetic acid is 2 mol / L; (2) Modification of gasified slag: Potassium hydroxide and sodium hydroxide are mixed in a mass ratio of 1:1-3:1, added to the activated gasified slag obtained in step (1), and deionized water is added and stirred to form a mixed solution. The mixed solution is heated to 100-200°C in an oil bath, reacted for 2-8 hours, cooled to room temperature, filtered, and dried to obtain modified gasified slag; (3) Preparation of coal gasification slag-based defect-rich carbon-iron composite materials: The modified gasification slag obtained in step (2) is heated to 700-850°C at a rate of 10°C / min under a nitrogen atmosphere and kept at this temperature for 2 h. After the sample is naturally cooled, it is washed with deionized water until it is neutral, filtered, and dried to obtain a coal gasification slag-based defect-rich carbon-iron composite material.

2. The preparation method according to claim 1, characterized in that: The hydroxide ion concentration in the mixed solution of step (2) is 4-8 mol / L; the liquid-to-solid ratio of the mixed solution to the activated gasified slag is 1-8:1 ml / g.

3. The preparation method according to claim 2, characterized in that: The hydroxide ion concentration in the mixed solution of step (2) is 6 mol / L; the liquid-to-solid ratio of the mixed solution to the activated gasified slag is 5:1 ml / g.

4. A coal gasification slag-based defect-rich carbon-iron composite material prepared by the preparation method described in any one of claims 1 to 3.

5. Use of the coal gasification slag-based defect-rich carbon-iron composite material as a catalyst in catalytic activation of persulfate to degrade phenolic organic pollutants according to claim 4, characterized in that: The specific steps include: (1) Concentration of 100mL is 20-50 mg·L -1 1-10 mmol / L potassium peroxymonosulfate is added to the bisphenol A solution, and then 20-30 mg of the above-mentioned slag-based defect-rich carbon-iron composite material is added, and the degradation reaction starts timing; (2) Samples were taken using a disposable syringe according to the time gradient. 1 mL of the sample was taken each time. The sample was filtered through a 0.22 μm polyethersulfone (PES) filter head and added to a 2 mL brown chromatographic bottle. 0.5 mL of methanol was added to the chromatographic bottle in advance to terminate the free radical reaction still in progress in the sample. The concentration of bisphenol A in the solution was determined by liquid chromatography.

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