A weathered coal-loaded zero-valent iron composite material and its preparation method and application

Abstract

The present invention discloses a weathered coal-loaded zero-valent iron composite material and its preparation method and application. The weathered coal is ground and impurities removed, then sealed in a brown storage bottle for storage; then added to an aqueous potassium ferrate solution, stirred and mixed at room temperature, dried and ground, and then calcined at high temperature under an inert atmosphere; the calcined product is cooled to room temperature and washed with pure water until neutral, and finally vacuum-dried to obtain CM@ZVI, which is sealed for storage to prevent oxidation. The present invention synthesizes CM@ZVI using a simple carbothermal reduction method. The surface of the material is loaded with zero-valent iron particles of different sizes, which increases the specific surface area of ​​the composite material and exposes the active sites of the material. These properties provide more adsorption sites and effectively prevent the agglomeration of zero-valent iron during the synthesis process. At the same time, it can effectively shorten the contact distance between the pollutant and the activator / oxidant, accelerating the reaction process.

Description

Technical Field

[0001] The present invention belongs to the field of water / soil treatment, and in particular relates to a weathered coal-loaded zero-valent iron composite material and a preparation method and application thereof. Background Art

[0002] Due to the impact of human activities such as accelerated industrialization, increased waste emissions, and fuel combustion, polycyclic aromatic hydrocarbons (PAHs) have become widespread and disseminated in environmental media. To date, over a hundred PAH compounds are known. The vast majority of PAHs exhibit carcinogenic, teratogenic, and mutagenic effects. As typical persistent organic pollutants, they continuously circulate in the atmosphere, water, soil, and biosphere, making them difficult to completely mineralize. The hydrophobic and lipophilic properties of PAHs make them easily adsorbed on the surfaces of aquatic sediments or soil colloids. Furthermore, PAHs in water and soil can enter ecosystems through the food chain, ultimately threatening human health. Therefore, there is an urgent need to develop cost-effective new technologies or materials to achieve the complete mineralization and removal of PAHs, thereby mitigating their negative impacts on the environment and health.

[0003] Currently, common methods for treating PAHs include physical, biological, and chemical methods. While all of these methods can be applied to PAH pollution, they each have their own advantages and disadvantages. Physical remediation methods only involve phase transfer, not complete removal of the pollutants. Furthermore, removal efficiency is limited by the pollutant's solubility and the properties of the adsorbent. Bioremediation is an environmentally friendly, low-cost, and relatively low-tech remediation technique. However, its degradation efficiency is affected by environmental factors such as the microbial community and the chemical properties of the PAHs, and its degradation rate is slow. Furthermore, high PAH concentrations can significantly impact degradation due to limited biological activity. Chemical remediation methods offer rapid results, short remediation cycles, and strong environmental adaptability, making them particularly effective for site-contaminated soils or environmental media heavily contaminated by PAHs. Among these chemical remediation methods, persulfate-based advanced oxidation processes have attracted widespread attention and application due to their ease of operation, strong environmental adaptability, efficient oxidative degradation, particularly for high-concentration PAHs, and virtually no secondary pollution. Among the numerous persulfate activators, zero-valent iron (ZVI) has attracted widespread attention due to its nontoxicity, environmental friendliness, and relative affordability compared to other transition metal ions. However, ZVI readily aggregates in water, resulting in a reduction in surface area, insufficient exposure of active sites, and a consequent decline in its adsorption catalytic performance. Preventing ZVI aggregation requires the selection of efficient, inexpensive, and readily available supports. While carbon-based materials, metal compounds, or biomaterials have been reported as ZVI-supporting supports, these materials still suffer from relatively poor stability, suboptimal dispersibility and regeneration, and high support material costs. Therefore, the development of a green, efficient, and low-cost persulfate activator for the removal or reduction of PAHs in water and soil is of great significance. Summary of the Invention

[0004] Purpose of the invention: The technical problem to be solved by the present invention is to address the deficiencies of the existing technology and provide a method for preparing a persulfate activator that is simple, easy to prepare, green, efficient, and low-cost. This material is used to activate persulfate to remove PAHs in water / soil, which is of great significance in the treatment of PAHs-contaminated water / soil.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a weathered coal-loaded zero-valent iron composite material comprises the following steps:

[0007] (1) Grind the weathered coal, remove impurities, and store it in a brown storage bottle and seal it;

[0008] (2) adding the weathered coal obtained in step (1) to a potassium ferrate (K2FeO4) aqueous solution, stirring and mixing at room temperature, drying and grinding, and then calcining at high temperature under an inert atmosphere to perform a carbothermal reduction reaction. During the high-temperature carbonization and decomposition process of organic matter such as humus in the weathered coal, some reducing gases are generated, and the potassium ferrate is reduced by the reducing gases to generate zero-valent iron in situ;

[0009] (3) The calcined product in step (2) is cooled to room temperature and washed with pure water until neutral, and finally dried under vacuum to obtain CM@ZVI, which is sealed and stored to prevent oxidation, thereby preparing a weathered coal-loaded zero-valent iron activated permonosulfate adsorption degradation material.

[0010] Specifically, in step (1), the weathered coal is a natural organic-inorganic complex, the organic component of which is mainly humic acid with a mass fraction greater than 30%, and the inorganic components in the weathered coal contain aluminosilicates; the inorganic components in the weathered coal also contain a small amount of metal compounds, and the metal compounds are metal compounds such as iron, magnesium or calcium.

[0011] Specifically, in step (1), the weathered coal is first dried at 60-80°C (preferably 80°C) for 6-12 hours (preferably 8 hours), ground through a 100-200 mesh (preferably 200 mesh) sieve, washed with water and filtered to remove water-soluble impurities, and then dried and ground again to obtain weathered coal fine powder with an average particle size of not more than 30 microns.

[0012] Specifically, in step (2), the mass concentration of potassium ferrate in the potassium ferrate aqueous solution is 0.1-1 g / 50 ml, preferably 0.5 g / 50 ml; the mass ratio of the weathered coal to potassium ferrate is (10:1)-(1:1), preferably 2:1.

[0013] Specifically, in step (2), the stirring and mixing is performed by magnetic stirring to achieve uniform mixing, the stirring speed is 500-600 r / min, preferably 550 r / min, and the stirring time is 10-12 h, preferably 12 h; the drying is performed at 60-80 ° C for 12-24 h, and the grinding is performed using an agate mortar to grind into fine particles.

[0014] Specifically, in step (2), the high-temperature calcination is carried out under the following conditions: heating to 600-900°C at a heating rate of 5-10°C / min, and then calcining for 1-3 hours, preferably calcining at 800°C for 2 hours, and the inert atmosphere is N2 atmosphere.

[0015] Specifically, in step (3), the neutral pH is 7-7.5, and the vacuum drying is carried out under the conditions of drying at 60°C-80°C for 12h-24h, and then sealed and stored to isolate from air.

[0016] Furthermore, the weathered coal-loaded zero-valent iron composite material prepared by the above-mentioned preparation method is also within the protection scope of the present invention.

[0017] Furthermore, the present invention also claims to protect the use of the above-mentioned weathered coal-loaded zero-valent iron composite material in activating permonosulfate to adsorb and degrade polycyclic aromatic hydrocarbons in water or soil.

[0018] Specifically, the polycyclic aromatic hydrocarbons are at least one of naphthalene (NAP), phenanthrene (PHE) and pyrene (PYR).

[0019] The specific method is to add a certain amount of CM@ZVI and permonosulfate (PMS) to water / soil containing a certain concentration of PAHs, and remove PAHs through adsorption and degradation reaction.

[0020] The weathered coal-loaded zero-valent iron-activated permonosulfate adsorption and degradation material of the present invention achieved a removal rate of up to 97.3% for NAP in artificially contaminated water. The material also achieved removal rates of 86.2% for NAP (41.83 mg / kg), 87.3% for PHE (10.08 mg / kg), and 92.2% for PYR (11.17 mg / kg), respectively, in artificially contaminated soil. The material also demonstrated a moderate remediation effect on polycyclic aromatic hydrocarbons (PAHs) in actual contaminated soil, with removal rates of 53.9% for pyrene (PYR), 73.2% for phenanthrene (PHE), 55.3% for anthracene (ANT), and 58.7% for fluoranthene (FLT), respectively.

[0021] Weathered coal is a natural metamorphic product of coal, primarily composed of organic matter such as humus and inorganic minerals. Organic matter includes humic acid and residual coal (humin); inorganic matter (ash) primarily comprises aluminosilicates, carbonates (kaolinite, quartz), and small amounts of iron, magnesium, zinc, and manganese compounds. Humic acid, due to its inherent abundance of oxygen-containing functional groups such as carboxyl, hydroxyl, and quinone groups, possesses high adsorption and reactivity. Mineral-derived humic acid is extracted and isolated from weathered coal, and thus humic substances in weathered coal possess similar functions such as adsorption, complexation, exchange, and electron transfer to promote oxidative degradation. Previous studies have demonstrated that ZVI effectively removes a variety of pollutants through mechanisms such as adsorption, precipitation, oxidation, reduction, and surface complexation. However, when used alone, ZVI has significant drawbacks, including its small size, strong magnetic properties, high surface energy, and high oxidizability. It readily aggregates into chain-like structures in aqueous or soil solutions, resulting in reduced surface area and insufficient exposure of active sites. Weathered coal, a naturally occurring organic-inorganic complex, exhibits high reactivity and versatility due to its stable structure and rich surface functional groups. When used as a carrier, it not only enables uniform loading of nano-zero-valent iron but also enhances its adsorption and activation degradation performance through synergistic effects. Furthermore, humus and metal elements such as potassium, calcium, and magnesium contained in weathered coal are essential nutrients for plant growth. The inventors' research results show that when K2FeO4, a precursor to ZVI, is added and annealed at high temperature, the reducing gases generated during the carbonization of humus and other organic matter in the weathered coal can reduce K2FeO4 to ZVI, which is then uniformly loaded in situ onto the modified weathered coal. Simultaneously, KOH and other substances generated by the decomposition of K2FeO4 chemically activate the weathered coal, significantly increasing the specific surface area of ​​the composite material. In summary, using weathered coal as a carrier, activated by annealing, and loaded with zero-valent iron in situ, can be used to activate persulfate to remove PAHs from water and soil, achieving low-cost and efficient adsorption and degradation of PAHs in water and soil.

[0022] Weathered coal (CM) used in this invention is a naturally occurring composite material primarily composed of natural organic polymers such as humus and inorganic minerals. The organic portion is rich in oxygen-containing functional groups. In environmental remediation applications, weathered coal removes PHAs from the environment through mineralization and degradation via adsorption, complexation, or redox reactions. Iron is the fourth most abundant element in the Earth's crust. Zero-valent iron (ZVI) is non-toxic, abundant, inexpensive, and easy to prepare. It is widely used as a catalyst for the degradation of organic pollutants by AOPs through adsorption, precipitation, redox, and surface complexation mechanisms and is considered a promising material. As a natural organic-inorganic complex, weathered coal, due to its stable structure and rich surface functional groups, can be annealed at high temperature with K2FeO4 to not only generate ZVI in situ and achieve uniform loading, but also further enhance its adsorption and activation degradation performance through synergistic effects. Furthermore, ZVI is magnetically separable, offering significant economic and environmental benefits.

[0023] The weathered coal-loaded zero-valent iron material CM@ZVI was in situ synthesized by a simple carbothermal reduction method, which can solve the problem of easy agglomeration of zero-valent iron, increase the specific surface area of ​​the material, improve the adsorption and degradation properties, and accelerate the reaction process and efficiency. Beneficial effects

[0024] (1) The present invention uses a simple carbothermal reduction method to synthesize CM@ZVI. The surface of the material is loaded with zero-valent iron particles of different sizes, which increases the specific surface area of ​​the composite material and exposes the active sites of the material. These properties provide more adsorption sites and effectively prevent the agglomeration of zero-valent iron during the synthesis process. At the same time, it can effectively shorten the contact distance between the pollutant and the activator / oxidant, thereby accelerating the reaction process.

[0025] (2) The removal rates of naphthalene in water and naphthalene, phenanthrene, and pyrene in soil prepared by the present invention can reach 97.3%, 86.2%, 87.3%, and 92.2%, respectively. This indicates that CM@ZVI can effectively activate PMS to remove PAHs in water and soil. CM@ZVI can be recycled after use in water or restored through annealing. When CM@ZVI is used in soil contaminated with naphthalene, it also has a certain beneficial effect on soil improvement. This indicates that CM@ZVI has certain application prospects for the remediation of PAHs in soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more apparent.

[0027] Figure 1This is the performance diagram of CM@ZVI removing NAP from water at different temperature ratios in Example 1.

[0028] Figure 2 This is a graph showing the removal performance of NAP in water by different iron precursors in Example 2.

[0029] Figure 3 The SEM and TEM images of CM and CM@ZVI materials in Example 3 are shown; Figure 3 a is weathered coal raw material, Figure 3 b is CM@ZVI, Figure 3 c is the Mapping diagram of CM@ZVI, Figure 3 df is the TEM image of CM@ZVI.

[0030] Figure 4 This is the nitrogen adsorption-desorption isotherm of CM@ZVI.

[0031] Figure 5 This is the XRD pattern of CM@ZVI.

[0032] Figure 6 FTIR spectrum of CM@ZVI.

[0033] Figure 7 This is the XPS pattern of CM@ZVI.

[0034] Figure 8 Figure 2 is a graph of CM@ZVI and its removal performance for NAP in water.

[0035] Figure 9 This is the cycle performance diagram of CM@ZVI.

[0036] Figure 10 This is the removal performance diagram of CM@ZVI on NAP, PHE, and BYR in soil.

[0037] Figure 11 This is the removal performance diagram of CM@ZVI for several typical polycyclic aromatic hydrocarbons in actual contaminated soil. DETAILED DESCRIPTION

[0038] The present invention can be better understood with reference to the following examples.

[0039] The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials are commercially available unless otherwise specified.

[0040] The weathered coal used in the embodiment of the present invention comes from Jiaokou County, Lüliang City, Shanxi Province, with a pH of 6.2. After drying, the mass fraction of the organic component humic acid is about 45%, aluminum oxide is about 9.3%, silicon dioxide is 33.0%, and calcium oxide / potassium and iron are about 12%.

[0041] Potassium ferrate was purchased from Aladdin Biochemical Technology Co., Ltd.

[0042] In the embodiment of the present invention, the removal of PAHs by the material was determined by high performance liquid chromatography to determine the concentration of PAHs. The removal rate of NAP in water was calculated according to Formula 1, the removal rate of NAP in soil was calculated according to Formula 2, and the removal rates of PHE and PYR in soil were calculated according to Formula 3.

[0043] (Formula 1);

[0044] (Formula 2);

[0045] In formula 1:

[0046] is the removal rate (%);

[0047] C0, C i represent the initial concentration and the concentration of NAP in the solution at the time of sampling (mg·L -1 ).

[0048] In formula 2:

[0049] is the removal rate (%);

[0050] C0 is the concentration of NAP in blank soil (mg / kg);

[0051] C is the concentration of residual NAP in the soil measured after the reaction (mg / kg);

[0052] m is the mass of soil used in the experiment (kg);

[0053] C w is the concentration of NAP dissolved in the supernatant (mg / kg);

[0054] V w is the volume of the supernatant (L).

[0055] (Formula 3);

[0056] is the removal rate (%);

[0057] C0, C z represent the initial and final concentrations of PHE and PYR in soil (mg / kg), respectively. Example 1

[0058] Screening of permonosulfate adsorption and degradation materials activated by weathered coal loaded with zero-valent iron.

[0059] Preparation of weathered coal-loaded zero-valent iron material: Weathered coal (CM) was dried, ground, sieved through 200 mesh, washed, filtered, and dried for later use. 1 g of weathered coal was weighed and added to 50 ml of a solution containing 0.01 g, 0.5 g, and 1 g of K2FeO4, respectively. The mixture was magnetically stirred at room temperature for 12 h, dried at 80 °C, ground, and calcined at 600 °C, 700 °C, 800 °C, and 900 °C (heating rate of 5 °C / min) for 2 h (N 2 atmosphere), cooled to room temperature, washed with pure water until neutral, and then placed in a vacuum oven at 60 °C for 12 h to obtain materials with different temperatures and proportions, which were abbreviated as 600-CZ10, 600-CZ2, 600-CZ1, 700-CZ10, 700-CZ2, 700-CZ1, 800-CZ10, 800-CZ2, 800-CZ1, 900-CZ10, 900-CZ2, and 900-CZ1, respectively.

[0060] Removal of NAP from water using materials at different temperatures and ratios: First, prepare a 1 g / L naphthalene stock solution. This solution is then diluted to a 10 mg / L simulated NAP contamination solution (using 20% ​​acetonitrile for solubilization and shaking thoroughly before use). Weigh 20 mg of the materials and 20 mg of PMS at different temperature ratios into an Erlenmeyer flask. Then, add 100 mL of the NAP solution to each flask and shake thoroughly. The mixture is shaken at 180 rpm for 120 minutes at room temperature (25°C). A 1 mL sample is then transferred to a 5 mL syringe and filtered through a 0.22 μm organic needle filter. 0.5 mL of the filtered solution is then added to a liquid chromatography vial containing 0.5 mL of methanol. The residual concentration is determined by high-performance liquid chromatography.

[0061] Depend on Figure 1 It can be seen that the 800-CZ2 material has the highest NAP removal rate of 91.9%. Therefore, the preferred calcination temperature is 800°C, and the preferred ratio is weathered coal: potassium ferrate = 2:1. The materials used subsequently are all calcined at this temperature and ratio and are recorded as CM@ZVI. Example 2

[0062] Screening of different iron precursor materials.

[0063] Preparation of different iron precursor materials: Weigh 1g of weathered coal and add it to 50ml solutions of FeCl3•6H2O, FeSO4•7H2O, and K2FeO4 containing the same iron content. After magnetic stirring at room temperature for 12h, dry and grind at 80℃, calcine at 800℃ (heating rate of 5℃ / min) for 2h (under N2 atmosphere), cool to room temperature, wash with pure water until neutral, and then place in vacuum and bake at 60℃ for 12h to obtain different iron precursor materials.

[0064] Removal of NAP from water using different iron precursors: A 10 mg / L simulated NAP-contaminated solution was prepared, along with 40 mg of different iron precursors and 30 mg of PMS in a conical flask. 100 mL of each NAP solution was then added to the flask and shaken evenly. The mixture was shaken at 180 rpm for 120 minutes at room temperature (25°C). At 5, 10, 30, 60, 90, and 120 minutes, 1 mL of the solution was sampled into a 5 mL syringe and filtered through a 0.22 μm organic needle filter. 0.5 mL of the filtered solution was added to a liquid chromatography vial containing 0.5 mL of methanol, and the residual concentration was determined by high-performance liquid chromatography.

[0065] Depend on Figure 2 The results show that the material with K2FeO4 as a precursor has the best NAP removal efficiency, reaching a maximum of 99.2%. The common FeCl3•6H2O and FeSO4•7H2O precursors cannot match the effect of K2FeO4, with values ​​of 74% and 48.8%, respectively. This indicates that the superior effect of K2FeO4 as a precursor is due to the synergistic effect between K2FeO4 and weathered coal that the other two precursors cannot achieve. Example 3

[0066] Preparation of weathered coal loaded zero-valent iron activated permonosulfate adsorption degradation material.

[0067] Preparation of weathered coal-loaded zero-valent iron material: Weathered coal (CM) was dried, ground, sieved through 200 mesh, washed with water, filtered, and dried for later use. 1g of weathered coal was weighed and added to 50ml of a solution containing 0.5g of K2FeO4. After magnetic stirring at room temperature for 12h, it was dried and ground at 80℃. It was calcined at 800℃ (heating rate of 5℃ / min) for 2h (under N2 atmosphere). After cooling to room temperature, it was washed with pure water until neutral and then placed in a vacuum and dried at 60℃ for 12h to obtain CM@ZVI.

[0068] Table 1 shows the elemental analysis results of weathered coal (CM) and CM@ZVI.

[0069] Table 1

[0070] ;

[0071] Figure 3 The SEM images of CM and CM@ZVI and the TEM images of CM@ZVI are shown in Figure 2. Figure 3 (a) Weathered coal is available in irregular blocks with a relatively smooth surface and few pores; Figure 3 (b) shows that there are obvious small particles on the surface of weathered coal, and the distribution is relatively dispersed. Figure 3(c) The element distribution of CM@ZVI mapping confirms that this particle is zero-valent iron and has some pores on its surface. Figure 3 (di) is the TEM image of CM@ZVI. It can be seen from the figure that zero-valent iron particles of different sizes and shapes are distributed on the surface and inside the material, which is consistent with the SEM. There are lattice fringes with a spacing of 0.2016nm, corresponding to Fe 0 This indicates that zero-valent iron particles are formed on the surface and inside of the weathered coal during the reaction.

[0072] Figure 4 The nitrogen adsorption-desorption isotherm of CM@ZVI shows a clear hysteresis loop at medium-high relative pressures of 0.4-1.0 p / p0, which is a type IV isotherm, corresponding to mesoporous materials. The specific surface area, total pore volume, pore size distribution, and other information of the sample are shown in Table 2. As can be seen from the table, the specific surface area of ​​CM@ZVI is much larger than that of CM (7.1633 m 2 / g, which is 324.79m 2 / g, the main reason is that KOH introduced by K2FeO4 plays a role in partial pore formation, and Fe 0 , the total pore volume ranges from 0.0345cm 3 / g increased to 0.0621cm 3 / g, the average pore size decreased from 16.28nm to 2.7495nm, which is consistent with the SEM results of Fe 0 The structural phenomenon is consistent.

[0073] Table 2 Comparison of BET parameters of materials

[0074] ;

[0075] Figure 5 The XRD pattern of CM@ZVI shows that the sharp diffraction peaks of CM@ZVI at 2θ = 44.6 nm, 65.0 nm and 82.3 nm are respectively related to the Fe 0 The (100), (200) and (211) planes of the α-Fe ions are well matched (JCPDS06-0696), indicating that α-Fe ions are successfully formed on the weathered coal. 0Among weathered coal, SiO2 has the best crystallinity. Simply calcining at 800°C does not change the crystal form of weathered coal, which is basically consistent with the crystal form of CM. The main component is SiO2, which mainly corresponds to the (100), (101), and (112) crystal planes of SiO2, corresponding to the standard card JCPDS46-1045. After the weathered coal reacts with K2FeO4, the intensity of the characteristic peak of SiO2 decreases. This is mainly attributed to the introduction of new substances, which will cause a series of reactions and phase transformations caused by the heat treatment process, transforming the crystalline SiO2 into an amorphous state.

[0076] Figure 6 This is the Fourier infrared spectrum of CM@ZVI. CM has a wavelength of 3406 cm -1 and CM@ZVI's 3423cm -1 There is a broad peak related to the -OH group nearby, which corresponds to the stretching vibration of water molecules, indicating the presence of hydroxyl groups on the surface of the material. 1800~1500cm -1 represents C=O (carboxyl, ester, ketone, etc.), which exists at 1578 cm in the spectra of CM and CM@ZVI, respectively. -1 and 1634 cm -1 , are stretching vibrations of aromatic rings. CM at 1387cm -1 There is a characteristic peak at 1113~896 cm, which is attributed to the CO absorption peak. -1 is the asymmetric stretching vibration of Si-OT (T represents Al or Si), and this characteristic peak exists in the spectra of CM and CM@ZVI within this range. In addition, the 457 cm -1 A new broad peak appears at , which may correspond to the characteristic peak of Fe-O stretching vibration, indicating that the reaction of K2FeO4 with CM forms new functional groups on its surface. At the same time, many characteristic peaks of CM are weakened, which indicates that the structure of CM is destroyed during the reaction with K2FeO4.

[0077] Figure 7 This is the XPS graph of CM@ZVI. The C and O contents are relatively high on the surface of the material, while the Fe content is relatively low. It is possible that some Fe has entered the interior of the material. Figure 7 (b) is C1s. The C at 284.8 eV, 285.68 eV, and 289.32 eV come from the C atoms in CC, CO, and C=O, respectively. Due to the complex components of weathered coal, the metal carbonates contained therein have certain residues during the preparation process of the entire material. The C at 293.72 eV may come from the C atoms in the metal carbonates. Figure 7(c) is the O1s fine spectrum, with 530.65eV, 531.34eV, and 532.48eV corresponding to Fe-O, C=O, and CO, respectively. During the preparation and storage of the material, it is inevitable that the zero-valent iron on the surface of the material will be oxidized and combined with O to form Fe-O. Figure 7 (d) is the fine spectrum of Fe2p, where the peaks at 707.18eV, 711.09eV, 714.77eV, and 724.69eV correspond to Fe 0 、Fe 2+ 、Fe 3+ 、Fe 2+ . Example 4

[0078] Removal of naphthalene (NAP) from water.

[0079] (1) Removal of NAP from water by CM@ZVI: 40 mg of CM@ZVI composite material and 40 mg of PMS were weighed into a conical flask. 100 mL of NAP solution was then added to the conical flask and shaken evenly. The mixture was shaken at 180 r / min for 120 min at room temperature (25 °C). 1 mL of sample was taken at 2, 5, 10, 30, 60, 90, and 120 min, respectively, and placed in a 5 mL syringe. The sample was then filtered through a 0.22 μm organic pinhole filter. 0.5 mL of the filtered solution was added to a liquid chromatography vial containing 0.5 mL of methanol, and the residual concentration was determined by high-performance liquid chromatography.

[0080] Depend on Figure 8 The CM@ZVI+PMS system has the best removal effect on NAP, which can reach up to 97.3%. CM@ZVI also has a good removal effect on NAP. This is because the zero-valent iron on the surface of the CM@ZVI material is oxidized to Fe 2+ , transfers two electrons to O2 to produce H2O2, while Fe 2+ It can react with the generated hydroxyl radicals and react with dissolved oxygen in the environment to generate superoxide radicals, which have a certain oxidizing effect on NAP. Superoxide radicals can react with H + The reaction further generates 1 O2, after adding PMS, the removal effect and rate of NAP were significantly improved, which shows that CM@ZVI as an activated persulfate material has a good removal effect on NAP in water.

[0081] (2) Cyclic performance of CM@ZVI: The specific degradation experimental steps were the same as above, with a PMS concentration of 300 mg / L and a catalyst concentration of 400 mg / L. After each degradation experiment, the material was recovered with a magnet, washed with pure water several times until neutral, and then vacuum-dried at 60°C for 12 h for the next use. After repeating the above steps twice, the material after the second cycle was dried and placed in a tubular furnace at 800°C for 2 h for annealing and regeneration, and then subjected to another degradation experiment.

[0082] like Figure 9 As shown in the figure, when the material was used for the first time, the removal rate of NAP reached up to 97.9%. However, when the material was collected, washed with water, and dried for reuse, the removal rate of NAP was only 63.47%. The effect of the material was greatly reduced when it was used for the second time. However, after the material was recycled and annealed at 800℃, the removal rate of NAP was restored and even better, reaching 100%. The effect of the material was reduced by 34.43% when it was used for the second time, and the stability performance was poor. The reason is (1) Fe 0 It is easy to oxidize. The activation effect of PMS of the oxidized material will be weakened, and after the reaction of Fe 0 (2) The products or pollutants generated after the reaction will be adsorbed onto the surface or pores of the material, blocking the active sites and making it difficult for them to function. However, this shortcoming can be solved by re-annealing. The effect after re-annealing is as good as or even better than the first preparation, which shows that the material still has certain application advantages. Example 5

[0083] Removal of naphthalene (NAP), phenanthrene (PHE) and pyrene (PYR) in soil.

[0084] (1) CM@ZVI removes NAP, PHE, and PYR from soil: First, the soil is air-dried, and after impurities are removed, the air-dried soil is ground and passed through an 80-mesh sieve. A certain amount of ground and sieved soil is poured into a 1000 ml beaker, and a certain amount of naphthalene / phenanthrene / pyrene is weighed and dissolved in acetone (naphthalene is contaminated alone, and phenanthrene and pyrene are contaminated together). The prepared contaminated solution is poured into the beaker and stirred thoroughly with a glass rod to mix evenly. Then, the solution is placed in a fume hood for 7 days to allow the acetone to evaporate, matured for 1-2 weeks, and the prepared contaminated soil is refrigerated in a 4°C refrigerator for later use. CM@ZVI is used in soil. 2 g of soil is placed in a 50 ml brown bottle, and a certain amount of PMS solution and CM@ZVI are added in sequence. The solution is placed in a shaker at 25°C and 180 r / min in the dark for 24 h. After extraction, the content of the remaining PAHs is determined by HPLC, and the blank value of each time is used as the initial concentration of PAHs in the soil.

[0085] like Figure 10Comparison of the removal rates of different pollutants using CM@ZVI / PMS reveals that the addition of 2.5 wt% PMS and 2.5 wt% CM@ZVI resulted in 83.6% removal of NAP (41.83 mg / kg). The addition of 1 wt% PMS and 4 wt% CM@ZVI resulted in 87.3% removal of PHE (10.08 mg / kg). The addition of 1 wt% PMS and 4 wt% CM@ZVI resulted in 92.2% removal of PYR (11.17 mg / kg). This demonstrates that CM@ZVI has considerable potential for removing PAHs from soil.

[0086] (2) Determination of physical and chemical properties of NAP-contaminated soil before and after remediation: ① Soil pH: Referring to GB7859-87, weigh 10g of the soil to be tested into a conical flask, add 25ml of deionized water (maintaining a water-to-soil ratio of 2.5:1), shake and let it stand for half an hour, and measure using a pH meter. At least three replicates per group. ② Soil available potassium: Referring to NYT889-2004, weigh 5g of soil, measure 50ml of 1mol / L neutral ammonium acetate extract, and measure using a flame atomic spectrophotometer. ③ Soil available phosphorus: Referring to HJ704-2014, weigh 2.5g of soil, extract with 50ml of 0.5mol / L sodium bicarbonate solution, add a colorimetric reagent for color development, and measure the absorbance using a spectrophotometer. ④ Soil CEC: Weigh 3.5g of soil and extract with 50ml of 1.66cmol / L hexaamminecobalt trichloride. Measure the absorbance using a spectrophotometer. ⑤ Soil electrical conductivity: Measure using the Soil Electrical Conductivity Electrode Method (HJ802-2016). Air-dried soil samples were added to water at a ratio of 1:5, extracted with shaking at 20°C, and the electrical conductivity of the extract was measured at 25°C. ⑥ Soil organic carbon: Weigh 3g of air-dried soil samples and add 10ml of 10% dilute hydrochloric acid. Shake for 1h, centrifuge, discard the supernatant, dry at 55°C for 24h, pass through a 0.15mm sieve, weigh approximately 12mg, wrap the sample in tinfoil, and measure using an EA3000 elemental analyzer.

[0087] Table 3 Physical and chemical properties of soil before and after remediation

[0088] ;

[0089] As shown in Table 3, the physical and chemical properties of the soil changed significantly before and after remediation. The pH of the soil was buffered after remediation, which may be due to the consumption of some OH in the reaction process. - The generated iron ions can react with OH -Combined to form iron polymers; soil cation exchange capacity (CEC) refers to the total amount of various cations that soil colloids can adsorb. This indicator is an important parameter for measuring the soil's ability to retain fertilizer. Generally speaking, the higher the soil's CEC value, the stronger its fertilizer retention capacity. The normal range of CEC is 10-20 cmol + / kg, with certain differences in different regions. The CEC before and after restoration was slightly higher than the normal range. Soil organic carbon is an important indicator of changes in soil fertility and the basis for high and stable crop yields and sustainable agricultural development. The soil organic carbon increased significantly before and after restoration. This is because some of the carbon substances in the materials entered the soil. Soil electrical conductivity can timely and effectively grasp various properties of the soil, such as salt concentration and moisture conditions. The normal soil electrical conductivity range is between 1-4mS / cm. Within this range, plants can usually grow normally. Too low electrical conductivity may prevent plants from obtaining sufficient nutrients, while too high electrical conductivity may damage the plant root system, affecting its ability to absorb water and nutrients. The conductivity before remediation was too low, but after remediation, it was able to increase to normal levels. Available potassium refers to the potassium in the soil that is easily absorbed and utilized by crops, reflecting the soil's immediate potassium supply to plants. The available potassium content in the soil generally ranges from 30 to 160 mg / kg. High levels of available potassium were observed before and after remediation, indicating that no additional potassium fertilizer application was necessary. The increased available potassium content after remediation was due to residual potassium entering the soil during material preparation. PMS also contains potassium, which may have entered the soil. Soil available phosphorus is the phosphorus component in the soil that can be absorbed by plants. The normal range for available phosphorus in the soil is typically 10 to 20 mg / kg. Within this range, the soil provides sufficient phosphorus for plant absorption without causing excessive phosphorus accumulation. After remediation, the available phosphorus content increased slightly, reaching a normal range.

[0090] The changes in the above physical and chemical properties indicate that using CM@ZVI materials to repair pollutants in the soil can not only remove pollutants in the soil but also improve the soil to a certain extent and enhance soil fertility. CM@ZVI provides a new idea for soil remediation. Example 6

[0091] Removal of polycyclic aromatic hydrocarbons from actual contaminated soil.

[0092] Compared with the simulated soil, the remediation effect of CM@ZVI on various PAHs in actual contaminated soil needs to be further investigated. To this end, soil samples were collected from a closed coking plant in Shaanxi Province, China, and CM@ZVI / PMS was used to remediate PAHs in the collected soil. Figure 11As shown in the results, at a 4% CM@ZVI dosage and a 3.5% PMS dosage, CM@ZVI demonstrated a moderate remediation effect on PAHs in actual contaminated soil. The removal efficiency of pyrene (PYR), the most contaminated compound (initial concentration of 116 mg / kg), was 53.9%. Removal efficiencies for phenanthrene (PHE) (initial concentration of 44.2 mg / kg), anthracene (ANT) (initial concentration of 11.9 mg / kg), and fluoranthene (FLT) (initial concentration of 98.6 mg / kg) were 73.2%, 55.3%, and 58.7%, respectively. These results demonstrate that CM@ZVI exhibits relatively good remediation efficacy for 3- and 4-ring PAHs and holds promise for treating actual contaminated soils. Further optimization of the conditions is expected to yield even higher removal efficiencies.

[0093] The present invention provides a weathered coal-loaded zero-valent iron composite material, its preparation method, and its application. Numerous methods and approaches exist for implementing this technical solution. The foregoing merely represents a preferred embodiment of the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are considered within the scope of the present invention. Components not specified in this embodiment may be implemented using existing technologies.

Claims

1. An application of a weathered coal-loaded zero-valent iron composite material in activating persulfate adsorption and degradation of polycyclic aromatic hydrocarbons in water or soil, characterized in that: The weathered coal-loaded zero-valent iron composite material is prepared by the following steps: (1) Grind the weathered coal, remove impurities, and store it in a brown storage bottle and seal it; (2) adding the weathered coal obtained in step (1) to a potassium ferrate aqueous solution, stirring and mixing at room temperature, drying and grinding, and then calcining at a high temperature under an inert atmosphere; (3) The calcined product in step (2) is cooled to room temperature and washed with pure water until neutral, and finally vacuum dried to obtain the product; In step (1), the weathered coal has an organic component humic acid mass fraction of more than 30%, and the inorganic component contains aluminosilicate; the inorganic component in the weathered coal also contains a small amount of metal compounds, and the metal in the metal compound is iron, magnesium or calcium.

2. The use of the weathered coal-loaded zero-valent iron composite material according to claim 1 in activating persulfate adsorption and degradation of polycyclic aromatic hydrocarbons in water or soil, characterized in that: In step (1), the weathered coal is first dried at 60-80°C for 6-12 hours, ground through a 100-200 mesh sieve, washed with water and filtered to remove water-soluble impurities, and then dried and ground again to obtain weathered coal fine powder with an average particle size of no more than 30 microns.

3. The use of the weathered coal-loaded zero-valent iron composite material according to claim 1 in activating persulfate adsorption and degradation of polycyclic aromatic hydrocarbons in water or soil, characterized in that: In step (2), the mass concentration of potassium ferrate in the potassium ferrate aqueous solution is 0.1-1 g / 50 ml; and the mass ratio of the weathered coal to potassium ferrate is (10:1)-(1:1).

4. The use of the weathered coal-loaded zero-valent iron composite material according to claim 1 in activating persulfate adsorption and degradation of polycyclic aromatic hydrocarbons in water or soil, characterized in that: In step (2), the stirring and mixing is magnetic stirring and mixing, the stirring speed is 500-600 r / min, and the stirring time is 10-12 h; the drying is carried out at 60-80° C. for 12-24 h; and the grinding is carried out using an agate mortar.

5. The use of the weathered coal-loaded zero-valent iron composite material according to claim 1 in activating persulfate adsorption and degradation of polycyclic aromatic hydrocarbons in water or soil, characterized in that: In step (2), the high-temperature calcination is carried out under the following conditions: heating to 600-900°C at a heating rate of 5-10°C / min, and then calcining for 1-3 hours.

6. Use of the weathered coal-loaded zero-valent iron composite material according to claim 1 in activating persulfate adsorption and degradation of polycyclic aromatic hydrocarbons in water or soil, characterized in that: In step (3), the neutral pH is 7-7.5; the vacuum drying is carried out at 60°C-80°C for 12h-24h, and then the mixture is sealed and stored in an airtight state.

7. Use of the weathered coal-loaded zero-valent iron composite material according to claim 1 in activating persulfate adsorption and degradation of polycyclic aromatic hydrocarbons in water or soil, characterized in that: The polycyclic aromatic hydrocarbons are at least one of naphthalene, phenanthrene and pyrene.

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