A method for removing refractory organic matter in water by using a ferrous-based composite catalyst

Abstract

This invention discloses a method for removing recalcitrant organic pollutants from water using a ferrous-based composite catalyst. The method involves activating persulfate with the ferrous-based composite catalyst to degrade the recalcitrant organic pollutants in the water. The ferrous-based composite catalyst includes a nitrogen-doped carbon layer with ferrous sulfide nanoparticles loaded on it. The ferrous-based composite catalyst used in this invention possesses advantages such as excellent catalytic activity and strong stability, effectively activating persulfate. The constructed system can rapidly generate a large number of active species. Therefore, this method for removing recalcitrant organic pollutants from water using a ferrous-based composite catalyst can quickly and thoroughly remove recalcitrant organic pollutants from wastewater. It has advantages such as low cost, high treatment rate, good removal effect, and low metal leaching rate. It is a widely applicable method for removing recalcitrant organic pollutants from water, with high practical value and promising application prospects.

Description

Technical Field

[0001] This invention belongs to the fields of heterogeneous catalysis and advanced oxidation technology, and relates to a method for removing recalcitrant organic matter from water, specifically a method for removing recalcitrant organic matter from water using an ferrous-based composite catalyst. Background Technology

[0002] During industrial production and applications, large amounts of recalcitrant organic matter (RCDs) are generated that easily enter water bodies through various environmental activities. These RCDs are difficult to degrade in water, posing a threat to the environment and human health. For example, antibiotics, as low-cost broad-spectrum antibacterial drugs, are widely used in medicine and aquaculture. Similarly, bisphenol A (BPA) is a chemical widely used in plastics manufacturing, especially in the production of polycarbonate plastics (such as water cups, food packaging, and medical devices) and epoxy resins (such as coatings and adhesives). Furthermore, because these substances are difficult for the body to absorb or effectively remove using conventional methods, they easily enter water bodies. In particular, they are frequently detected in surface water, aquaculture wastewater, and sewage treatment plants, with concentrations reaching hundreds of nanograms per liter to tens of micrograms per liter, causing significant harm to the entire ecosystem. Therefore, effectively removing RCDs from water bodies is extremely urgent.

[0003] Currently, the most common method for removing recalcitrant organic matter from water bodies is the advanced oxidation process based on hydrogen peroxide and persulfate. This method is favored because persulfate is easy to store and transport safely, and because it generates reactive species (such as sulfate radicals SO42-). ·- Persulfate-based advanced oxidation processes (PMS-AOPs) are not easily consumed by impurities in water and exhibit superior degradation effects. Therefore, PMS-AOPs, as a more efficient and stable environmental remediation technology, can be widely used to remove recalcitrant organic matter from water. However, when using PMS-AOPs to remove recalcitrant organic matter from water, the catalysts used are not only complex and expensive to prepare, but also have poor activation effects on persulfate, making it difficult to efficiently and rapidly generate active species. This results in insufficient and incomplete degradation of recalcitrant organic matter in the water, hindering effective water purification. Therefore, obtaining a catalyst that can effectively activate persulfate is crucial for promoting the widespread application of PMS-AOPs in purifying recalcitrant organic wastewater.

[0004] Iron, as a green transition metal, possesses unique electronic properties that result in multiple valence states that can be transformed into each other, offering the possibility of efficient activation of persulfate. Among numerous iron-based metal catalysts, iron nanoparticle / supported composite catalysts are widely used due to their simple synthesis methods and low metal leaching rates. However, when existing iron nanoparticle / supported composite catalysts are used to activate oxidants such as permonosulfate (PMS), the low conversion rates between metals of different valence states and the high activation energy barrier of the oxidant (especially the short peroxy bond in PMS) present challenges. The relatively high activation energy barrier of iron nanoparticles (and their supporting structures) makes it difficult for existing catalysts to effectively activate oxidants, resulting in low production amounts and rates of various highly oxidizing active species. Furthermore, existing iron nanoparticle / supported composite catalysts suffer from poor structural stability, leading to the easy detachment of active components from the support into the degradation system during use, potentially causing secondary pollution. These shortcomings limit the widespread application of existing iron nanoparticle / supported composite catalysts in advanced oxidation technologies, thus hindering the widespread use of these technologies for treating recalcitrant organic pollutant wastewater. Therefore, obtaining a highly active and stable ferrous-based composite catalyst is crucial for improving the activation effect of persulfates (such as PMS) and promoting the widespread application of advanced oxidation technologies in water treatment. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for removing recalcitrant organic matter in water using a ferrous-based composite catalyst that is low in cost, has a high processing rate, good removal effect, and low metal leaching rate.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0007] A method for removing recalcitrant organic matter from water using a ferri-based composite catalyst, wherein the method involves activating persulfate with the ferri-based composite catalyst to degrade the recalcitrant organic matter in the water; the ferri-based composite catalyst comprises a nitrogen-doped carbon layer on which ferri sulfide nanoparticles are loaded.

[0008] In a further improvement to the above method, the mass ratio of nitrogen-doped carbon layer to ferrous sulfide nanoparticles in the ferrous-based composite catalyst is 5 to 50:1.

[0009] In a further improvement to the above method, the mass fraction of nitrogen in the nitrogen-doped carbon layer is 22.85%.

[0010] A further improvement to the above method is the preparation method of the ferri-based composite catalyst, which includes the following steps:

[0011] S1. Mix ferric chloride with ethanol, add thiourea and o-phenanthroline, stir to obtain a precursor dispersion;

[0012] S2. Mix the precursor dispersion with melamine, stir, and dry to obtain precursor powder;

[0013] S3. The precursor powder is calcined and acid-washed to obtain the ferrous-based composite catalyst.

[0014] In a further improvement to the above method, in step S1, the mass ratio of ferric chloride to ethanol is 1:80-100; the mass ratio of thiourea to ethanol is 1:100-120; and the mass ratio of o-phenanthroline to ethanol is 1:30-50.

[0015] In a further improvement to the above method, in step S2, the mass-to-volume ratio of melamine to precursor liquid is 50g to 150g: 1L.

[0016] In a further improvement to the above method, in step S1, the stirring time is 5 min to 15 min;

[0017] In a further improvement to the above method, in step S2, the stirring temperature is 20℃~40℃; the stirring time is 2h~4h; the drying is carried out under vacuum conditions; the drying temperature is 60℃~100℃; and the drying time is 10h~15h.

[0018] In a further improvement to the above method, in step S3, the calcination is carried out under a protective atmosphere; the protective atmosphere is an argon atmosphere; the calcination involves first heating the precursor powder to 600℃ and holding it at that temperature for 1 to 3 hours, then heating it to 800℃ and holding it at that temperature for 1 to 3 hours; the heating rate during the calcination process is 2 to 10℃ / min; the acid solution used in the acid washing process is a sulfuric acid solution; the concentration of the acid solution is 80 to 100 g / L; the acid washing time is 10 to 18 hours; after the acid washing is completed, the following step is also included: drying the acid-washed product under vacuum conditions; the drying temperature is 60℃ to 100℃; the drying time is 10 to 15 hours.

[0019] The above method is further improved by using a ferrous-based composite catalyst to activate persulfate to degrade recalcitrant organic matter in water. The method includes the following steps: mixing the ferrous-based composite catalyst with the water containing recalcitrant organic matter, adding persulfate to carry out a catalytic oxidation reaction, and completing the removal of recalcitrant organic matter from the water.

[0020] In a further improvement to the above method, the amount of the ferrous-based composite catalyst is 0.01g to 0.2g per liter of water containing recalcitrant organic matter; the amount of persulfate is 0.05g to 0.2g per liter of water containing recalcitrant organic matter; and the persulfate is permonosulfate.

[0021] In a further improvement to the above method, the recalcitrant organic matter in the water body includes at least one of antibiotics and bisphenol A; the antibiotics include at least one of sulfamethoxazole, tetracycline, and amoxicillin; the initial concentration of the recalcitrant organic matter in the water body is 0.5 mg / L to 50 mg / L; and the initial pH value of the water body is 4 to 10.

[0022] In a further improvement to the above method, the mixing is carried out under stirring conditions until adsorption-desorption equilibrium is reached; the stirring time is 20 min to 40 min; the catalytic oxidation reaction is carried out at a temperature of 15 to 40 °C; and the catalytic oxidation reaction time is 5 min to 40 min.

[0023] Compared with the prior art, the advantages of the present invention are as follows:

[0024] (1) This invention provides a method for removing recalcitrant organic matter from water using a ferrous-based composite catalyst. The ferrous-based composite catalyst activates persulfate to degrade the recalcitrant organic matter in the water. The ferrous-based composite catalyst includes a nitrogen-doped carbon layer loaded with ferrous sulfide nanoparticles. It possesses advantages such as strong catalytic activity, strong anti-interference ability, and good stability. It can efficiently activate persulfate (especially PMS) and rapidly generate a large amount of highly oxidizing reactive oxygen species. Therefore, when the advanced oxidation system constructed by the ferrous-based composite catalyst and persulfate catalyzes the oxidation of recalcitrant organic matter, it can rapidly and efficiently degrade recalcitrant organic matter (such as sulfamethoxazole) in water. It has advantages such as simple process, convenient operation, low cost, and high mineralization efficiency, showing good economic benefits and application prospects. More importantly, the advanced oxidation system constructed by the ferrous-based composite catalyst and persulfate in this invention operates within a wide pH range (4-10) and at 200 mM common anions (SO42-SO42-). 2- NO3 - H2PO4 - and Cl -Even under the presence of certain conditions, it maintains high efficiency in removing recalcitrant organic pollutants (such as sulfamethoxazole) from water. Furthermore, the ferrous-based composite catalyst used maintains excellent catalytic efficiency in natural water bodies. Moreover, compared to conventional iron-based composite catalysts, the ferrous-based composite catalyst used in this invention has a more stable structure and a lower metal leaching rate. Therefore, the method for removing recalcitrant organic pollutants from water using a ferrous-based composite catalyst has advantages such as low cost, high treatment rate, good removal effect, and low metal leaching rate. It can quickly and thoroughly remove recalcitrant organic pollutants (such as antibiotics) from wastewater and is a widely applicable method for removing recalcitrant organic pollutants from water, with high practical value and promising application prospects.

[0025] (2) The ferrous-based composite catalyst used in this invention has ferrous sulfide nanoparticles loaded on a nitrogen-doped carbon layer. On the one hand, the nitrogen-doped carbon layer has a two-dimensional layered structure, which can not only effectively disperse and encapsulate the ferrous sulfide nanoparticles, reducing metal aggregation and leaching, but also provide sufficient surface area for the adsorption of pollutants and persulfates (such as PMS). On the other hand, the surface of the ferrous sulfide crystals exposes a large number of unsaturated metal sites, which can be used to activate persulfates. Based on this, the electron-rich S atoms in the ferrous sulfide nanoparticles can provide electrons during the activation process of persulfates, thereby changing the valence state of Fe and enhancing the binding ability of Fe sites with persulfates, thus producing excellent catalytic activity. It can be seen that the introduction of S atoms realizes the charge regulation of the metal active center, which can effectively enhance the interaction between the metal and persulfates (especially PMS), and ultimately improve the catalytic activity. The ferrous-based composite catalyst of this invention has the advantages of excellent catalytic activity and strong stability. It is a new type of efficient Fenton-like catalyst that can effectively activate persulfate. The constructed system can rapidly generate a large number of active species, which is beneficial for the rapid and thorough degradation of recalcitrant organic pollutants (such as antibiotics) in wastewater.

[0026] (3) In the ferrous composite catalyst used in this invention, the mass ratio of nitrogen-doped carbon layer to ferrous sulfide nanoparticles is 5 to 50:1. By optimizing the mass ratio of the two, ferrous sulfide nanoparticles can be moderately dispersed on nitrogen-doped carbon layer, maximizing the use of the carrier dispersion effect of nitrogen-doped carbon layer, which is more conducive to improving the catalytic activity of ferrous sulfide composite catalyst.

[0027] (4) In the preparation method of the ferrous-based composite catalyst used in this invention, ferric chloride is used as the iron source, thiourea as the sulfur source and complexing agent, o-phenanthroline as the auxiliary complexing agent, and melamine as the carbon source and nitrogen source. The iron source and sulfur source are first mixed with the complexing agent, and then calcined in one step to prepare the ferrous-based composite catalyst with excellent catalytic activity and strong stability. Compared with other sulfur sources, in this invention, thiourea is both a sulfur source and a complexing agent. By undergoing a complexation reaction with iron ions, it facilitates the doping of sulfur during the formation of iron particles, thus forming ferrous sulfide nanoparticles instead of zero-valent iron particles. At the same time, under the promoting effect of o-phenanthroline, the iron ions can be dispersed by utilizing the complexation between o-phenanthroline and iron ions. Thus, nano-sized ferrous sulfide anchored on the nitrogen-doped carbon layer can be obtained by a simple one-step pyrolysis and acid washing. It not only has good dispersibility but is also firmly anchored on the nitrogen-doped carbon layer. In addition, the method for preparing the ferrous-based composite catalyst in this invention has the advantages of simple process, convenient operation, and low cost. It also has low equipment requirements, strong repeatability, and can realize large-scale production, which is conducive to industrial application. Attached Figure Description

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0029] Figure 1 This is a comparison chart showing the removal efficiency of ferrous-based composite catalysts (Fe@N / CS-1.00, Fe@N / CS-1.25, Fe@N / CS-1.50, Fe@N / CS-1.75, Fe@N / CS-2.00) on sulfamethoxazole in water in Example 1 of this invention.

[0030] Figure 2 This is a comparison chart showing the removal effects of the ferrous-based composite catalyst (Fe@N / CS-1.75) on sulfamethoxazole, tetracycline, amoxicillin, and bisphenol A in water in Example 2 of this invention.

[0031] Figure 3 The graph shows the removal effect of the ferrous-based composite catalyst (Fe@N / CS-1.75) on sulfamethoxazole in water under different oxidant dosage conditions in Example 3 of this invention.

[0032] Figure 4 The image shows the removal effect of different doses of ferrous-based composite catalyst (Fe@N / CS-1.75) on sulfamethoxazole in water in Example 4 of this invention.

[0033] Figure 5This is a comparison chart showing the removal effect of the ferrous-based composite catalyst (Fe@N / CS-1.75) on sulfamethoxazole in water under different pH and representative interfering ions conditions in Example 5 of this invention. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0035] In this embodiment of the invention, all raw materials and instruments used are commercially available. Unless otherwise specified, the process used is a conventional process, the equipment used is conventional equipment, and the data obtained are all average values ​​from three or more repeated experiments.

[0036] Example 1:

[0037] A method for removing recalcitrant organic matter from water using a ferrous-based composite catalyst, specifically involving the activation of persulfate by the ferrous-based composite catalyst to degrade sulfamethoxazole in the water, includes the following steps:

[0038] Accurately weigh 5 mg of each of the ferrous-based composite catalysts (Fe@N / CS-1.00, Fe@N / CS-1.25, Fe@N / CS-1.50, Fe@N / CS-1.75, Fe@N / CS-2.00) and add them to 100 mL of 10 ppm sulfamethoxazole aqueous solution. Adjust the initial pH of the solution to 7.4 with borate buffer (2.0 mM). Stir magnetically (800 r / min) at 25 °C for 30 min to reach adsorption-desorption equilibrium. Then add 250 μL of persulfate solution (0.2 M) and carry out catalytic oxidation reaction at 25 °C and 800 r / min for 15 min to complete the removal of sulfamethoxazole from the water.

[0039] In this embodiment, the ferrous-based composite catalyst (Fe@N / CS-1.75) includes a nitrogen-doped carbon layer, on which ferrous sulfide nanoparticles are loaded. The mass ratio of ferrous sulfide nanoparticles to the nitrogen-doped carbon layer is 3.89%, and the nitrogen content in the nitrogen-doped carbon layer is 22.85 wt%.

[0040] In this embodiment, the preparation method of the ferrous-based composite catalyst (Fe@N / CS-1.75) includes the following steps:

[0041] (1) Add 0.183g of ferric chloride to 20mL of anhydrous ethanol (15.824g) and stir for 5min to obtain a ferric chloride dispersion.

[0042] (2) Add 0.133g (1.75mmol) thiourea and 0.396g o-phenanthroline to the ferric chloride dispersion obtained in step (1) and stir for 5min to obtain a complexing agent (thiourea, o-phenanthroline) / ferric ion dispersion, which is the precursor dispersion.

[0043] (3) Weigh 2.0g of melamine and add it to the complexing agent (thiourea, o-phenanthroline) / iron ion dispersion obtained in step (2). Stir at room temperature (20-40℃, for example 25℃) for 3h, and then vacuum dry at 80℃ for 12h to obtain the precursor powder.

[0044] (4) Grind the precursor powder obtained in step (3) evenly, and calcine it at 600℃ for 2h at a heating rate of 5℃ / min in an argon atmosphere. Then, calcine it at 800℃ for 2h at the same heating rate to obtain a black powder. The calcined product is acid washed with 1M H2SO4 for 15h, and then washed, filtered, and vacuum dried at 80℃ for 12h to obtain the ferrous-based composite catalyst, namely Fe@N / CS-1.75.

[0045] In this embodiment, the ferrous-based composite catalyst (Fe@N / CS-1.00) used is basically the same as that of Fe@N / CS-1.75, except that the mass ratio of ferrous sulfide nanoparticles to nitrogen-doped carbon layer in Fe@N / CS-1.00 is 2.19%.

[0046] In this embodiment, the ferrous-based composite catalyst (Fe@N / CS-1.25) used is basically the same as that of Fe@N / CS-1.75, except that in Fe@N / CS-1.25, the mass ratio of ferrous sulfide nanoparticles to nitrogen-doped carbon layer is 2.75%.

[0047] In this embodiment, the ferrous-based composite catalyst (Fe@N / CS-1.50) used is basically the same as that of Fe@N / CS-1.75, except that the mass ratio of ferrous sulfide nanoparticles to nitrogen-doped carbon layer in Fe@N / CS-1.50 is 3.32%.

[0048] In this embodiment, the ferrous-based composite catalyst (Fe@N / CS-2.00) used is basically the same as that of Fe@N / CS-1.75, except that in Fe@N / CS-2.00, the mass ratio of ferrous sulfide nanoparticles to nitrogen-doped carbon layer is 4.47%.

[0049] In this embodiment, at different time intervals of oxidation reactions, 1 ml of sample was taken, filtered through a 0.22 μm polytetrafluoroethylene filter membrane, and residual persulfate in the sample was quenched with sodium thiosulfate solution (15 μL, 1.0 M). The content of sulfamethoxazole in the sample was then determined using high-performance liquid chromatography (HPLC), and its removal rate was calculated. The results are as follows: Figure 1 As shown.

[0050] Figure 1 This is a comparative graph showing the removal efficiency of ferrous-based composite catalysts (Fe@N / CS-1.00, Fe@N / CS-1.25, Fe@N / CS-1.50, Fe@N / CS-1.75, Fe@N / CS-2.00) from sulfamethoxazole in water in Example 1 of this invention. Figure 1 It was found that all ferrous-based composite catalysts could efficiently activate PMS to remove sulfamethoxazole from water, with Fe@N / CS-1.75 exhibiting the highest reaction rate, achieving complete removal of sulfamethoxazole from water within 15 minutes. These results demonstrate that the ferrous-based composite catalyst prepared in this invention possesses excellent PMS activation performance, rapidly generating a large number of active species, thereby enabling the rapid and thorough degradation of sulfamethoxazole in water.

[0051] Example 2

[0052] A method for removing recalcitrant organic matter from water using a ferrous-based composite catalyst is described. Specifically, a ferrous-based composite catalyst (Fe@N / CS-1.75) is used to activate persulfate to degrade sulfamethoxazole, tetracycline, amoxicillin, and bisphenol A in water. Other conditions are the same as in Example 1.

[0053] In this embodiment, samples were taken from the reaction system at 30 s, 1 min, 2 min, 3 min, 5 min, 10 min, and 15 min, respectively, to determine the content of each recalcitrant organic compound in the product solution obtained at the reaction time. The corresponding removal rate was then calculated, and the results are as follows: Figure 2 As shown.

[0054] Figure 2 This is a comparison chart showing the removal efficiency of the ferrous-based composite catalyst (Fe@N / CS-1.75) in Example 2 of this invention for sulfamethoxazole, tetracycline, amoxicillin, and bisphenol A in water. Figure 2 It is evident that the ferrous-based composite catalyst (Fe@N / CS-1.75) of this invention can rapidly and efficiently remove various recalcitrant organic compounds from water. The removal rate of four recalcitrant organic compounds reached 100% within a 15-minute reaction time. The apparent reaction rate constant (k) for the oxidative removal of tetracycline by the ferrous-based composite catalyst (Fe@N / CS-1.75) is [not specified in the original text].obs It even reached as high as 1.589 minutes. -1 .

[0055] Example 3

[0056] A method for removing recalcitrant organic matter from water using a ferrous-based composite catalyst is described. Specifically, the method involves using a ferrous-based composite catalyst (Fe@N / CS-1.75) to activate persulfate to degrade sulfamethoxazole in water. This method is essentially the same as that in Example 1, except that the catalytic oxidation reaction in Example 3 used different doses of persulfate (PMS), namely 0.3 mM, 0.5 mM, 0.7 mM, and 1.0 mM.

[0057] Figure 3 This image shows the removal effect of the ferrous-based composite catalyst (Fe@N / CS-1.75) on sulfamethoxazole in water under different oxidant dosages in Example 3 of this invention. Figure 3 It was found that when the dosage of PMS reached 0.5 mM, the ferrous composite catalyst (Fe@N / CS-1.75) could completely remove sulfamethoxazole from the water within 15 min. Furthermore, with increasing PMS dosage, the catalytic oxidation removal efficiency of the ferrous composite catalyst (Fe@N / CS-1.75) for sulfamethoxazole in the water also continuously improved. The results indicate that the ferrous composite catalyst (Fe@N / CS-1.75) can efficiently and thoroughly remove recalcitrant organic matter from water in the presence of a relatively small amount of oxidant, demonstrating high economic practicality.

[0058] Example 4

[0059] A method for removing recalcitrant organic matter from water using a ferrous-based composite catalyst is described. Specifically, the ferrous-based composite catalyst (Fe@N / CS-1.75) is used to activate persulfate to degrade sulfamethoxazole in the water. This method is basically the same as that in Example 1, except that the catalytic oxidation reaction in Example 4 used different dosages of the ferrous-based composite catalyst (Fe@N / CS-1.75), namely 0.025 g / L, 0.05 g / L, 0.1 g / L, and 0.2 g / L.

[0060] Figure 4 This image shows the removal effect of different dosages of the ferrous-based composite catalyst (Fe@N / CS-1.75) on sulfamethoxazole in water in Example 4 of this invention. Figure 4It was found that even with a catalyst dosage of 0.025 g / L, the ferrous-based composite catalyst (Fe@N / CS-1.75) could still remove more than 90% of sulfamethoxazole at a concentration of 10 ppm from wastewater within 15 minutes. The results indicate that even in the presence of a very small amount of the ferrous-based composite catalyst (Fe@N / CS-1.75), recalcitrant organic matter in water can be removed efficiently and thoroughly, demonstrating high economic practicality.

[0061] Example 5

[0062] A method for removing recalcitrant organic matter from water using a ferrous-based composite catalyst is described. Specifically, the method involves activating persulfate with a ferrous-based composite catalyst (Fe@N / CS-1.75) to degrade sulfamethoxazole in water. This method is essentially the same as in Example 1, except that in Example 5, 200 mM SO42- was added to the sulfamethoxazole aqueous solution. 2- NO3 - H2PO4 - and Cl - The initial pH of the sulfamethoxazole aqueous solution was pre-adjusted to 4, 5, 7, 9 and 10, respectively.

[0063] Figure 5 This is a comparison chart showing the removal efficiency of the ferrous-based composite catalyst (Fe@N / CS-1.75) from sulfamethoxazole in water under different pH conditions and in the presence of different representative interfering ions, as described in Example 5 of this invention. Figure 5 It can be seen that when 200 mM of SO4 is present in the water body... 2- NO3 - H2PO4 - and Cl - At different concentrations (10 ppm), the ferrous-based composite catalyst (Fe@N / CS-1.75) achieved removal rates of 89.24%, 94.19%, 87.90%, and 100% for sulfamethoxazole in water, respectively. Furthermore, when the initial pH of the water was 4, 5, 7, 9, and 10, the ferrous-based composite catalyst (Fe@N / CS-1.75) maintained a removal rate of over 98% for sulfamethoxazole at 10 ppm. These results indicate that the ferrous-based composite catalyst (Fe@N / CS-1.75) possesses strong anti-interference capabilities and can efficiently remove recalcitrant pollutants from water under various interfering ion and pH conditions.

[0064] In summary, the ferrous-based composite catalyst of this invention possesses advantages such as excellent catalytic activity and strong stability. It is a novel and highly efficient Fenton-like catalyst that can effectively activate persulfate. The constructed system can rapidly generate a large number of active species. Therefore, the method of removing recalcitrant organic matter from water using the ferrous-based composite catalyst of this invention can quickly and thoroughly remove recalcitrant organic pollutants (such as antibiotics) from wastewater. It has advantages such as low cost, high treatment rate, good removal effect, and low metal leaching rate. It is a method that can be widely used to remove recalcitrant organic matter from water, with high application value and good application prospects.

[0065] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for removing recalcitrant organic matter from water using a ferrous-based composite catalyst, characterized in that, The method employs a ferrous-based composite catalyst to activate persulfate for the degradation of recalcitrant organic matter in water. The ferrous-based composite catalyst comprises a nitrogen-doped carbon layer on which ferrous sulfide nanoparticles are loaded. The mass ratio of the nitrogen-doped carbon layer to the ferrous sulfide nanoparticles in the ferrous-based composite catalyst is 5–50:

1. The preparation method of the ferrous-based composite catalyst includes the following steps: S1. Mix ferric chloride with ethanol, add thiourea and o-phenanthroline, stir to obtain a precursor dispersion; S2. Mix the precursor dispersion with melamine, stir, and dry to obtain precursor powder; S3. The precursor powder is calcined and acid-washed to obtain the ferrous-based composite catalyst.

2. The method according to claim 1, characterized in that, The nitrogen content in the nitrogen-doped carbon layer is 22.85% by mass.

3. The method according to claim 2, characterized in that, In step S1, the mass ratio of ferric chloride to ethanol is 1:80-100; the mass ratio of thiourea to ethanol is 1:100-120; and the mass ratio of o-phenanthroline to ethanol is 1:30-50. In step S2, the mass-to-volume ratio of melamine to precursor liquid is 50g to 150g: 1L.

4. The method according to claim 3, characterized in that, In step S1, the stirring time is 5 min to 15 min; In step S2, the stirring temperature is 20℃~40℃; the stirring time is 2h~4h; the drying is carried out under vacuum conditions; the drying temperature is 60℃~100℃; and the drying time is 10h~15h. In step S3, the calcination is carried out under a protective atmosphere, namely argon. The calcination involves first heating the precursor powder to 600°C and holding it at that temperature for 1 to 3 hours, then heating it to 800°C and holding it at that temperature for 1 to 3 hours. The heating rate during the calcination process is 2 to 10°C / min. The acid solution used in the acid washing process is sulfuric acid solution. The concentration of the acid solution is 80 to 100 g / L. The acid washing time is 10 to 18 hours. After the acid washing is completed, the following step is also included: drying the acid-washed product under vacuum conditions. The drying temperature is 60°C to 100°C. The drying time is 10 to 15 hours.

5. The method according to any one of claims 1 to 4, characterized in that, The degradation of recalcitrant organic matter in water by activating persulfate with ferrous-based composite catalyst includes the following steps: mixing ferrous-based composite catalyst with water containing recalcitrant organic matter, adding persulfate to carry out catalytic oxidation reaction, and completing the removal of recalcitrant organic matter from water.

6. The method according to claim 5, characterized in that, The amount of the ferrous-based composite catalyst is 0.01 g to 0.2 g per liter of water containing recalcitrant organic matter; the amount of the persulfate is 0.05 g to 0.2 g per liter of water containing recalcitrant organic matter; and the persulfate is permonosulfate.

7. The method according to claim 6, characterized in that, The recalcitrant organic matter in the water body includes at least one of antibiotics and bisphenol A; the antibiotics include at least one of sulfamethoxazole, tetracycline, and amoxicillin; the initial concentration of the recalcitrant organic matter in the water body is 0.5 mg / L to 50 mg / L; and the initial pH value of the water body is 4 to 10.

8. The method according to claim 6, characterized in that, The mixing is carried out under stirring until adsorption-desorption equilibrium is reached; the stirring time is 20 min to 40 min; the catalytic oxidation reaction is carried out at a temperature of 15 to 40 °C; the catalytic oxidation reaction time is 5 min to 40 min.

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