Preparation method of pyrite / carbon nitride composite material and application thereof

Abstract

The application discloses a preparation method of a pyrite carbon nitride composite material and application thereof. The natural pyrite after crushing and sieving is fully mixed with pyrolytic carbon nitride and is subjected to ball milling treatment to obtain the pyrite carbon nitride composite material. The ball-milled pyrite carbon nitride composite material is characterized by XRD and XPS, and it is proved that the natural pyrite is successfully compounded with the carbon nitride material. New bonds such as Fe-N and C-S-C are generated in the ball milling process, the electronic distribution and electronic path of the catalyst are changed, the interface electron transmission is enhanced, the composite material is uniformly distributed in the ball milling process, the specific surface area is increased, and more active sites can be exposed, so that a good catalytic degradation effect is achieved, 10 mg / L of sulfamethoxazole can be completely catalytically degraded within 5 min, the catalyst and the persulfate are used in small amounts, the preparation process of the catalyst is simple, and the catalyst has the characteristics of low cost and high efficiency.

Description

Technical Field

[0001] This invention relates to the fields of environmental remediation material preparation and water pollution control, specifically to a method for preparing a pyrite-carbon nitride composite material and its application. Background Technology

[0002] Iron, the fourth most abundant element in the Earth's crust, is a transition metal widely used in advanced oxidation processes (AOPs) for persulfate degradation due to its high abundance and low toxicity. Pyrite (primarily composed of FeS2), an abundant and inexpensive natural mineral, demonstrates promising application potential in AOPs for degrading organic pollutants due to its unique chemical composition. The Fe(II) in pyrite can directly activate persulfates to produce active species. More importantly, its S2 component... 2- It is the main electron donor and has strong reducing properties, which can reduce the generated high-valence Fe(III) to low-valence Fe(II), thereby promoting the Fe(II) / Fe(III) cycle process of the system and maintaining the continuous progress of the reaction.

[0003] However, the use of pyrite alone as a catalyst in existing technologies has significant limitations: its surface active sites are limited, and the particles are prone to agglomeration during the reaction, resulting in organic matter degradation efficiency that fails to meet practical application requirements. More importantly, iron-based catalysts in advanced persulfate oxidation technologies all face a crucial rate-limiting step: the Fe(II) / Fe(III) cycle. Improving this rate hinges on the catalyst's electron transfer capability. Iron-based catalysts in advanced persulfate oxidation technologies generally face a core bottleneck—the Fe(II) / Fe(III) cycle rate is a significant rate-limiting step. Therefore, enhancing the catalyst's electron transfer capability is key to overcoming this bottleneck and improving catalytic activity.

[0004] Carbon nitride (g-C3N4), as a nitrogen-rich semiconductor material, has attracted attention due to its excellent electron transfer capabilities. The electron-rich pyridine N sites in its structure possess Lewis basicity, readily complexing with transition metal ions such as iron, which possess Lewis acidity, to form metal-N groups. x Coordination structure. This structure not only optimizes the geometry but also induces uneven electron distribution, significantly enhancing interfacial electron transfer efficiency, thus potentially improving catalytic performance.

[0005] Based on the above analysis, natural pyrite (which provides abundant Fe source, Fe(II) activation sites, and endogenous reducing agent S2) 2-Combining pyrite with carbon nitride (which provides excellent electron transfer capabilities and potential coordination sites) to prepare composite materials can theoretically synergistically solve the aforementioned problems: the Fe sites in pyrite may coordinate with the pyridine N of g-C3N4 to form Fe-N bonds, further optimizing the electronic structure, enhancing electron transfer, thereby accelerating the Fe(II) / Fe(III) cycle and improving the overall catalytic degradation ability. However, traditional methods for preparing such composite materials usually rely on chemical processes (such as impregnation with iron salts in specific proportions, treatment with excess chemical reagents, etc.). These chemical methods are not only relatively cumbersome, but also inevitably lead to reagent waste and increased costs. Summary of the Invention

[0006] To address the technical problems of existing pyrite-carbon nitride composite materials, such as inherent defects in pyrite, limited iron cycling rates, and drawbacks of chemical synthesis methods, this invention provides a method for preparing and applying ball-milled pyrite-carbon nitride composite materials. A simple ball-milling method is used to prepare a pyrite-carbon nitride composite material, which features a simple preparation process, low raw material cost, uniform dispersion, high reactivity, excellent catalytic degradation efficiency, and strong electron transfer capability. The resulting pyrite-carbon nitride composite material, when used as a catalyst for advanced persulfate oxidation, exhibits excellent catalytic performance, overcoming the problems of low catalytic degradation efficiency, difficult Fe(II) / Fe(III) cycling during the reaction, and complex and expensive synthesis processes of current iron-based catalysts.

[0007] The technical solution adopted by the present invention to achieve the above-mentioned objectives is as follows:

[0008] A method for preparing a pyrite-carbon nitride composite material involves first pyrolyzing urea, a precursor of carbon nitride, into carbon nitride via pyrolysis, and then uniformly combining pyrite and carbon nitride through ball milling. The specific steps include:

[0009] S1. After preliminary grinding of pyrite particles, pass them through a 200-mesh sieve to obtain screened pyrite;

[0010] S2. Carbon nitride precursor urea is converted into carbon nitride by pyrolysis;

[0011] S3. The carbon nitride prepared in step S2 is ultrasonically dispersed in methanol and then dried;

[0012] S4. Mix the pyrite obtained in step S1 with the carbon nitride obtained in step S3, add ethanol, and then ball mill the mixture to ensure that the pyrite and carbon nitride are uniformly combined.

[0013] S5. Dry the ball-milled mixture obtained in step S4 to obtain a pyrite carbon nitride composite material.

[0014] Furthermore, in step S1, the pyrite is natural pyrite (its main component is FeS2, which is also the main component of activated persulfate). Natural pyrite inherently contains S2... 2- Iron ions are a powerful natural reducing agent that can efficiently reduce Fe(III) generated during activation to Fe(II), thereby intrinsically and continuously promoting the Fe(II) / Fe(III) cycle. This is a natural advantage in overcoming the limitation of iron cycling rate. This endogenous reduction mechanism is the key difference between it and simply adding iron salts or synthesizing iron-based materials.

[0015] Fe(II) in natural pyrite can directly activate persulfate to generate reactive oxygen species in the advanced persulfate oxidation system. However, iron-based catalysts used in the advanced persulfate oxidation process suffer from a serious drawback: the difficulty in the Fe(II) / Fe(III) cycle, which is also the most challenging rate-limiting step. 2- As a natural reducing agent, it can reduce Fe(III) generated during activation to Fe(II) to promote the Fe(II) / Fe(III) cycle. Graphite carbon nitride (g-C3N4) is an excellent nitrogen-rich semiconductor material with excellent electron transport capabilities. The electron-rich pyridine N sites in g-C3N4, which are Lewis basic, tend to complex with transition metal elements that are Lewis acidic. Fe in natural pyrite is a very typical transition metal with Lewis acidity, and it easily bonds with the N sites in carbon nitride. XPS analysis comparing Example 1 and Comparative Example 1 shows that this invention successfully combined natural pyrite and carbon nitride to prepare a composite material through ball milling. The ball milling process causes Fe in pyrite to combine with the N sites in carbon nitride, generating new Fe-N bonds. The Fe-N bond is a stable chemical bond that plays an important role in catalytic reactions. Fe-N is difficult to break, ensuring the recycling of the catalyst and also serving as a catalytically active site to promote the reaction process. The Fe-N generated during ball milling... x It can optimize the intermolecular geometry of catalysts, promote the uneven distribution of electrons, and enhance the electron transfer at the interface, thereby accelerating the Fe(II) / Fe(III) cycling process and greatly improving the catalytic degradation efficiency.

[0016] XPS analysis also confirmed the formation of new CSC bonds during ball milling, bonds absent in natural pyrite, indicating that sulfur (S) in natural pyrite successfully intercalated into the carbon (C) skeleton of carbon nitride. This bonding altered the electronic pathway, leading to electron reconstruction and enhanced electron transfer capabilities, thus accelerating persulfate activation and the Fe(II) / Fe(III) cycle. The ball milling process not only facilitates the successful combination of natural pyrite and carbon nitride to form new bonds but also ensures a uniform distribution of the pyrite-carbon nitride composite material, increasing its specific surface area and exposing more active sites. Therefore, the ball-milled pyrite-carbon nitride composite material of this invention, prepared through ball milling, possesses excellent catalytic degradation capabilities.

[0017] Furthermore, in step S2, pyrolysis is carried out in a muffle furnace.

[0018] Furthermore, the pyrolysis adopts an ascending heating method, specifically: heating to 500-600 ℃ (preferably 550 ℃) at a heating rate of 2-5 ℃ / min, and maintaining at 500-600 ℃ for 1-5 h (preferably 2-3 h).

[0019] Furthermore, step S3 also includes centrifugation after sonication, wherein the sonication time is preferably 30 to 100 min (more preferably 30 to 50 min), the centrifugation rate is 4000 to 6000 r / min (preferably 5000 r / min), the centrifugation time is 3 to 8 min (preferably 4 to 6 min), the drying temperature is 50 to 80 ℃ (preferably 60 to 70 ℃), and the drying time is 2 to 6 h (preferably 3 to 4 h).

[0020] Further, in step S4, the mass ratio of pyrite to carbon nitride is 2~6:1, preferably 3~4:1; the amount of ethanol added is 20~40% of the total mass of the pyrite and carbon nitride mixture, preferably 30~40%; the grinding media used for ball milling is preferably zirconia balls, and the mass ratio of zirconia balls to the mixture is 10~20:1, preferably 14~16:1.

[0021] Furthermore, the ball mill rotates at a speed of 300-500 r / min (preferably 350-400 r / min), and the milling time is 2-6 h (preferably 3-4 h), with the mill turning once every 1.5-2 h.

[0022] Furthermore, in step S5, the drying is carried out in a vacuum oven at a temperature of 40~70 ℃ (preferably 50~60 ℃) for a time of 2~8 h (preferably 5~6 h).

[0023] The aforementioned pyrite-carbon nitride composite material is used as a catalyst for advanced persulfate oxidation. It has a good degradation effect on sulfonamide antibiotics or chlorophenol organic pollutants (preferably sulfamethoxazole) in water bodies with a concentration of 8-15 mg / L and pH=3-9 (preferably 3-5).

[0024] Furthermore, the dosage of the pyrite carbon nitride composite material is 0.1~0.5 g / L water (preferably 0.2~0.3 g / L water), and the concentration of persulfate (preferably permonosulfate) in the water is 0.2~0.6 mM (preferably 0.3~0.4 mM).

[0025] Taking the degradation of sulfamethoxazole in water as an example, the activation principle of the pyrite-carbon nitride composite material obtained in this invention is as follows:

[0026] (1) Compared with pure natural pyrite, the pyrite carbon nitride composite material obtained in this invention exposes more Fe(II) and S2 content. 2- The active site, Fe(II), reacts directly with persulfate to produce an active substance that attacks sulfamethoxazole, S2 2- The reduction of Fe(III) promotes the Fe(II) / Fe(III) cycle, and the activation principle is shown in equations (1)-(6):

[0027] (1)

[0028] (2)

[0029] (3)

[0030] (4)

[0031] (5)

[0032] (6)

[0033] In equations (1)-(6), "•" represents the lone pair of electrons in sulfate radicals, hydroxyl radicals, and superoxide radicals; 1 "O2" represents singlet oxygen, a type of excited oxygen. The "1" indicates that the oxygen molecule's electrons are in a singlet state, meaning the spins of the two outermost electrons in the molecule are antiparallel. - "Indicates a chemical valence state of -1;" + " " indicates a chemical valence state of +1.

[0034] (2) Ball milling produces new Fe-N composite materials. xWith CSC bond, Fe-N x The optimized intermolecular geometry of the catalyst promotes uneven electron distribution and enhances interfacial electron transfer, thereby accelerating the Fe(II) / Fe(III) cycle. Furthermore, Fe-N can serve as a catalytically active site to further promote the reaction. The CSC bond alters the electronic pathway, leading to electron reconstruction and enhanced electron transfer capabilities, thus accelerating the activation of persulfate and the Fe(II) / Fe(III) cycle.

[0035] Compared with the prior art, the technical advantages of the present invention are as follows:

[0036] (1) The pyrite carbon nitride composite material obtained by the present invention has a simple preparation process, low price, environmental friendliness, high activation efficiency and can rapidly degrade pollutants.

[0037] (2) In this invention, pyrite and carbon nitride are combined by ball milling. On the one hand, ball milling can increase the specific surface area of ​​pyrite, thereby exposing more active sites. On the other hand, the combination of pyrite and carbon nitride can enhance electron transfer capacity, and the degradation rate of sulfamethoxazole can reach 100%. Moreover, the removal rate can reach 100% under different pH conditions. Compared with the component without catalyst and only persulfate, the removal rate is increased by 81.4%. Furthermore, the effect of the presence of anions in different environments on the removal rate was tested, indicating that the pyrite-carbon nitride composite material obtained in this invention is a very efficient and low-cost catalyst for advanced oxidation of persulfate. Attached Figure Description

[0038] Figure 1 The image shows the X-ray diffraction (XRD) analysis of the ball-milled pyrite carbon nitride composite material obtained in Example 1.

[0039] Figure 2 This is a scanning electron microscope (SEM) image of natural pyrite.

[0040] Figure 3 This is a scanning electron microscope (SEM) image of carbon nitride.

[0041] Figure 4 The image shown is a scanning electron microscope (SEM) image of the ball-milled pyrite carbon nitride composite material obtained in Example 1.

[0042] Figure 5 This is a transmission electron microscope (TEM) image of the ball-milled pyrite carbon nitride composite material obtained in Example 1.

[0043] Figure 6 The full spectrum of X-ray photoelectron spectroscopy (XPS) analysis of the ball-milled pyrite carbon nitride composite material obtained in Example 1 is shown in (a) as the material before the catalytic degradation reaction and (b) as the material after the catalytic degradation reaction.

[0044] Figure 7 The fine Fe 2p spectra of the ball-milled pyrite carbon nitride composite material obtained in Example 1 are shown in (a) before the catalytic degradation reaction and (b) after the catalytic degradation reaction.

[0045] Figure 8 The S2p fine spectrum of the ball-milled pyrite carbon nitride composite material obtained in Example 1 is shown in (a) before the catalytic degradation reaction and (b) after the catalytic degradation reaction.

[0046] Figure 9 The N1s fine spectrum of the ball-milled pyrite carbon nitride composite material obtained in Example 1 is shown in (a) before the catalytic degradation reaction and (b) after the catalytic degradation reaction.

[0047] Figure 10 The fine Fe 2p spectrum of the pyrite-carbon nitride composite material prepared without ball milling process in Comparative Example 1 is obtained from X-ray photoelectron spectroscopy (XPS).

[0048] Figure 11 The fine S 2p spectrum of the pyrite-carbon nitride composite material prepared without ball milling process in Comparative Example 1 is obtained from X-ray photoelectron spectroscopy (XPS).

[0049] Figure 12 The fine N 1s spectrum of the pyrite carbon nitride composite material prepared without ball milling process in Comparative Example 1 is shown in the X-ray photoelectron spectroscopy (XPS) analysis.

[0050] Figure 13 The X-ray photoelectron spectroscopy (XPS) spectra of composite material A obtained in Comparative Example 2 are shown in (a) for the Fe 2p fine spectrum, (b) for the N 1s fine spectrum, and (c) for the S 2p fine spectrum.

[0051] Figure 14 The X-ray photoelectron spectroscopy (XPS) spectra of composite material B obtained in Comparative Example 3 are shown in (a) for the Fe 2p fine spectrum, (b) for the N 1s fine spectrum, and (c) for the S 2p fine spectrum.

[0052] Figure 15 The figure shows the effect of pH on the activation performance of the ball-milled pyrite carbon nitride composite material obtained in Example 1. The vertical axis C / C0 represents the ratio of the residual sulfamethoxazole concentration to the initial sulfamethoxazole concentration in the sample at each sampling time point.

[0053] Figure 16The figure shows the effect of environmental factors on the activation performance of the ball-milled pyrite carbon nitride composite material obtained in Example 1. The vertical axis C / C0 represents the ratio of the residual sulfamethoxazole concentration to the initial sulfamethoxazole concentration in the sample at each sampling time point. Detailed Implementation

[0054] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited thereto. The described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The specific embodiments described below further illustrate the present invention.

[0055] Example 1

[0056] (1) Select natural pyrite ore (main component is FeS2) as raw material, grind it and pass it through a 200-mesh sieve to obtain pyrite powder;

[0057] (2) In a muffle furnace, urea, the precursor of carbon nitride, is pyrolyzed at 550°C for 3 h to obtain carbon nitride;

[0058] (3) According to the mass ratio of pyrite to carbon nitride of 4:1, the amount of pyrite added is 3.24 g and the amount of carbon nitride added is 0.78 g. According to the mass ratio of zirconium oxide balls to (pyrite + carbon nitride) of 15:1, the amount of zirconium oxide balls added is 59.4 g, and then 2 ml of ethanol is added. After mixing, the mixture is ball-milled at a speed of 350 r / min for 4 h, and the rotation is changed every 2 h.

[0059] (4) After vacuum drying in a vacuum oven at 50°C, a pyrite carbon nitride composite material prepared by ball milling is obtained. For ease of explanation below, it is referred to as ball-milled pyrite carbon nitride composite material.

[0060] Comparative Example 1

[0061] The rest is the same as in Example 1, except that: in step (3), ball milling is not used, but the mixture is mixed evenly by manual grinding, and the resulting product is a pyrite carbon nitride composite material prepared without ball milling.

[0062] Comparative Example 2

[0063] The rest is the same as in Example 1, except that step (2) is omitted, and urea, the precursor of carbon nitride, is directly ball-milled with pyrite, and the amount of urea added is 15.6 g. Since the yield of carbon nitride from urea pyrolysis in step (2) is 20:1, that is, 20 g of urea can produce 1 g of carbon nitride through pyrolysis, in order to maintain the same mass ratio of ball-milled materials as in Example 1, the 0.78 g of carbon nitride in Example 1 is adjusted to 15.6 g of urea, and the resulting composite material is denoted as composite material A.

[0064] Comparative Example 3

[0065] The rest is the same as in Example 1, except that instead of natural pyrite, purified pyrite with a purity of 99.5% is used, and the resulting composite material is denoted as Composite Material B.

[0066] The X-ray diffraction (XRD) analysis of the ball-milled pyrite-carbon nitride composite material obtained in Example 1 is shown in the figure below. Figure 1 As shown, by Figure 1 It can be seen that, compared with the standard card of natural pyrite, the ball-milled pyrite carbon nitride composite material has an additional (002) characteristic peak of carbon nitride, indicating that pyrite and carbon nitride were successfully composited.

[0067] Scanning electron microscope (SEM) images of natural pyrite, carbon nitride, and the ball-milled pyrite-carbon nitride composite material obtained in Example 1 are shown below. Figures 2 to 4 As shown. Figure 2 The natural pyrite shown has a smooth, non-porous surface. Figure 3 The carbon nitride shown exhibits a typical two-dimensional sheet-like structure, while the carbon nitride produced by the carbon nitride is composed of a carbon nitride. Figure 4 It can be seen that the surface of the pyrite-carbon nitride composite material is broken and rough after the ball milling process, and the particle size is smaller. The pyrite and carbon nitride are very uniformly combined, which is conducive to the exposure of more active sites.

[0068] Transmission electron microscopy (TEM) image of the ball-milled pyrite-carbon nitride composite material obtained in Example 1 is shown below. Figure 5 As shown, by Figure 5 It can be seen that the lattice stripes with a lattice spacing of 0.242 nm represent the (210) crystal plane of pyrite, while the part without lattice stripes represents carbon nitride, indicating that pyrite and carbon nitride are well bonded.

[0069] The full X-ray photoelectron spectroscopy (XPS) spectrum of the ball-milled pyrite-carbon nitride composite material obtained in Example 1 is shown below. Figure 6 As shown, (a) is the material before the catalytic degradation reaction, and (b) is the material after the catalytic degradation reaction. It can be seen that the ball-milled pyrite carbon nitride composite material mainly contains four elements: Fe, N, C, and S.

[0070] The fine Fe 2p spectrum of the ball-milled pyrite-carbon nitride composite material obtained in Example 1 is shown in the following figure. Figure 7 As shown, (a) is the material before the catalytic degradation reaction, and (b) is the material after the catalytic degradation reaction. Figure 10 The fine Fe 2p spectrum of the pyrite-carbon nitride composite material prepared by the ball-mill-free process in Comparative Example 1 is shown in the X-ray photoelectron spectroscopy (XPS) analysis. This is compared with... Figure 7 and Figure 10 It can be seen that in the Fe 2p XPS spectrum of the pyrite-carbon nitride composite material prepared without ball milling, the peaks at 711.77 eV and 715.36 eV belong to Fe(III), and the peak at 707.3 eV belongs to Fe(II), i.e., FeS2. This indicates that Fe in the pyrite-carbon nitride composite material prepared without ball milling mainly exists in the forms of Fe(III) and Fe(II). However, in the Fe 2p XPS spectrum of the ball-milled pyrite-carbon nitride composite material, in addition to the peaks at 711.28 eV (belonging to Fe(III)) and 706.80 eV (belonging to Fe(II)), there is also an additional peak at 709.30 eV, which belongs to Fe-N. x The electron-rich pyridine N site of g-C3N4 exhibits Lewis basicity and tends to complex with transition metals such as iron, which are Lewis acids. The ball milling process promotes the complexation of the N site with the Fe site, forming Fe-N bonds. x Bond, newly formed Fe-N x The Fe-N bond can optimize the geometric configuration, promote the uneven distribution of electrons, and enhance interfacial electron transfer, thereby effectively improving catalytic activity. The Fe-N bond is a very stable chemical bond and plays an important role in various catalytic reactions. On the one hand, the Fe-N bond is difficult to break, ensuring the recycling of the catalyst; on the other hand, the Fe-N bond can also serve as an active site for catalysis to promote the reaction process. (Comparison) Figure 7 (a) and Figure 7 (b) It can be seen that after the reaction, Fe-N x The decrease in content indicates that Fe-N x It did indeed participate in the reaction. The Fe(II) content decreased and the Fe(III) content increased in the ball-milled pyrite-carbon nitride composite material after the reaction, indicating that Fe(II) in the material participated in the activation reaction to generate Fe(III). The reaction process is shown in the following equation:

[0071] .

[0072] X-ray photoelectron spectroscopy analysis of the ball-milled pyrite-carbon nitride composite material obtained in Example 1: S 2p fine spectrum as shown below. Figure 8As shown, (a) is the material before the catalytic degradation reaction, and (b) is the material after the catalytic degradation reaction. The fine S 2p spectrum of the pyrite-carbon nitride composite material prepared by the ball mill-free process in Comparative Example 1 is shown in the figure. Figure 11 As shown. Comparison Figure 8 , Figure 11 It can be seen that, Figure 11 The peak at 168.72 eV is attributed to SO4. 2- The peak at 162.50 eV belongs to S2. 2- This indicates that in the pyrite-carbon nitride composite material prepared without ball milling, S mainly exists as SO4. 2- With S2 2- It exists in the form of, and Figure 8 A new peak at a binding energy of 165.18 eV appeared, attributed to the CSC bond, proving that the ball milling process successfully incorporated S atoms into the C framework. The resulting new bond can alter the electron pathway, further demonstrating that the composite of carbon nitride and pyrite can accelerate electron transfer. Figure 8 It can be seen that the sulfur content in the material does not change significantly before and after the reaction, and it is mainly composed of S2. 2- The presence of this form indicates that the composite material has good stability.

[0073] Figure 9 The N 1s fine spectrum of the ball-milled pyrite carbon nitride composite material prepared in Example 1 is shown in (a) before the catalytic degradation reaction and (b) after the catalytic degradation reaction. Figure 12 The fine N 1s spectrum of the pyrite-carbon nitride composite material prepared by the non-ball milling process in Comparative Example 1 is shown in the X-ray photoelectron spectroscopy (XPS) analysis. Figure 9 and Figure 12 It can be seen that, Figure 12 The peak at 398.64 eV belongs to the CN=C bond, and the peak at 400.57 eV belongs to the -NH bond. x The peak at 404.09 eV belongs to The excited state of N, and Figure 9 An additional peak with a binding energy of 399.40 eV appears, which is attributed to Fe-N. x This further proves the view that Fe-N bonds are generated during the ball milling process.

[0074] Figure 13 The X-ray photoelectron spectroscopy (XPS) spectra of composite material A prepared in Comparative Example 2 are shown. (a) is the fine spectrum of Fe 2p, (b) is the fine spectrum of N 1s, and (c) is the fine spectrum of S 2p. Composite material A is a composite material prepared by directly ball milling urea, the precursor of carbon nitride, with pyrite without undergoing a calcination process. Figure 13In (a), the peak at 706.28 eV is attributed to Fe(II), which originates from natural pyrite, and the peak at 710.79 eV is attributed to Fe(III); Figure 13 (b) The peak at 398.95 eV is attributed to the CN bond and originates from urea; Figure 13 The peak at 161.62 eV in (c) belongs to S2. 2- Originating from natural pyrite, the peak at 167.72 is attributed to SO4. 2- .Depend on Figure 13 It is evident that composite material A lacks Fe-N and CSC bonds and has a low Fe(II) content. In contrast, the ball-milled pyrite-carbon nitride composite material prepared in Example 1 contains Fe-N and CSC bonds and has a higher Fe(II) content. This demonstrates that the composite material prepared using urea, a precursor of carbon nitride, and natural pyrite has no practical application value. Theoretically, carbon nitride contains numerous CN=C bonds, which are easily broken. This is crucial for the formation of new Fe-N and CSC bonds during ball milling. Urea, on the other hand, only contains CN single bonds, making it difficult to form new bonds. This further proves that Fe-N and CSC bonds can enhance the catalytic degradation performance of the material.

[0075] Figure 14 The X-ray photoelectron spectroscopy (XPS) spectra of composite material B prepared in Comparative Example 3 are shown. (a) is the fine spectrum of Fe 2p, (b) is the fine spectrum of N 1s, and (c) is the fine spectrum of S 2p. Composite material B is a composite material prepared by ball milling high-purity pyrite (99.5%) with carbon nitride. Figure 14 In (a), in addition to Fe(II) and Fe(III), Fe-N bonds also appear at 708.97 eV, thus composite material B also has good catalytic degradation efficiency. However, compared to natural pyrite, high-purity pyrite has a very high FeS2 content, resulting in a smaller proportion of carbon nitride in the composite material. This leads to insufficient N sites to combine with the Fe sites of high-purity pyrite to form Fe-N bonds. Therefore, Fe-N accounts for only 16.5% of the iron element, which is significantly less than the ball-milled pyrite carbon nitride composite material prepared in Example 1. This may be one of the reasons why the catalytic degradation efficiency of composite material B is lower than that of the ball-milled pyrite carbon nitride composite material. In addition, the Fe(II) content in composite material B is significantly higher than that in the ball-milled pyrite carbon nitride composite material. Excessive Fe(II) will quench free radicals and other reactive oxygen species during the catalytic degradation process, inhibiting the degradation process. This is also a reason why the catalytic degradation efficiency of composite material B is lower than that of the ball-milled pyrite carbon nitride composite material. Figure 14 (b) may not show obvious Fe-N characteristic peaks due to the low Fe-N content. Figure 14The presence of a CSC characteristic peak (at 164.79 eV) in (c) indicates the presence of CSC bonds in composite material B. These CSC bonds accelerate electron transfer within the composite material, which is one reason for its strong catalytic degradation performance. Although composite material B also exhibits high catalytic degradation performance, the ball-milled pyrite-carbon nitride composite material is significantly superior to composite material B in terms of both performance and cost, and thus has better application prospects.

[0076] Example 2

[0077] This embodiment is a catalytic activity test: Sulfamethoxazole (SMX), a representative of recalcitrant organic pollutants at a concentration of 10 mg / L, was selected as the target pollutant, and potassium persulfate (KHSO5) was selected as the oxidant. The degradation performance of SMX by the pyrite carbon nitride catalyst obtained in Example 1 above (a typical representative of the pyrite carbon nitride catalyst of this invention) was evaluated.

[0078] In this embodiment, the initial concentration of SMX was 10 mg / L, the concentration of persulfate was 0.4 mM, and the catalyst dosage was 0.3 g / L. Before the reaction, the catalyst was mixed with 50 ml of SMX solution under magnetic stirring for 30 min, and then 50 ml of persulfate solution was added to start the reaction. At predetermined time intervals, 1 mL of the reaction solution was taken, filtered through a 0.22 μm filter membrane, and the reaction was quenched using a 1:1 saturated sodium thiosulfate solution. The samples were detected by high-performance liquid chromatography (HPLC).

[0079] The catalytic degradation efficiency of SMX by the ball-milled pyrite-carbon nitride composite catalyst obtained in Example 1 is shown in Table 1 below.

[0080] As shown in Table 1, the ball-milled pyrite carbon nitride composite material obtained in Example 1 can degrade more than 90% of SMX in 1 min and completely degrade SMX in 5 min. This indicates that the catalyst effectively activates the persulfate, significantly improving the reaction rate. Moreover, the catalyst dosage is only 0.3 g / L and the persulfate concentration is only 0.4 mM, resulting in very low usage cost.

[0081] The above demonstrates that the ball-milled pyrite carbon nitride composite material obtained in Example 1 is highly efficient, requires only a small amount, is low in cost, and is simple to prepare as a catalyst for the efficient oxidation of persulfate, exhibiting significant effects on the catalytic degradation of pollutants.

[0082] Table 1. Catalytic degradation efficiency of SMX by ball-milled pyrite-carbon nitride composite material

[0083]

[0084] Example 3

[0085] Compared with Example 2, this example does not add a catalyst, but only uses potassium monosulfate (KHSO5) as an oxidant at a concentration of 0.4 mM.

[0086] The specific operation was as follows: The initial concentration of SMX in the catalytic degradation reaction was 10 mg / L, and the concentration of persulfate used in the reaction was 0.4 mM. No catalyst was added. 50 mL of persulfate solution was added to 50 mL of SMX solution to initiate the reaction. At predetermined time intervals, 1 mL of the reaction solution was taken, filtered through a 0.22 μm filter membrane, and the reaction was quenched using saturated sodium thiosulfate at a 1:1 ratio. The samples were analyzed using high-performance liquid chromatography (HPLC). The SMX degradation efficiency is shown in Table 2.

[0087] As shown in Table 2, without the addition of a catalyst, persulfate alone has a very limited ability to degrade SMX, with a removal rate of only 18.6% within 30 min. However, after adding the pyrite-carbon nitride composite catalyst, the removal rate of SMX is 100%, which is an increase of 81.4%. Therefore, it can be determined that the ball-milled pyrite-carbon nitride composite material obtained in Example 1 plays an important role in the activation of persulfate.

[0088] Table 2. SMX degradation efficiency by persulfate without catalyst

[0089]

[0090] Example 4

[0091] This embodiment is used to investigate the catalytic degradation performance of the pyrite carbon nitride composite material prepared without ball milling in Comparative Example 1, and to compare it with the catalytic degradation performance of the pyrite carbon nitride composite material obtained in Example 2, so as to explore the role of ball milling in the material preparation process.

[0092] The initial concentration of SMX was 10 mg / L, the concentration of sulfate used was 0.4 mM, and the catalyst dosage was 0.3 g / L. Before the reaction, the catalyst was magnetically stirred with 50 mL of SMX solution for 30 min, and then 50 mL of persulfate solution was added to initiate the reaction. At predetermined time intervals, 1 mL of the reaction solution was taken, filtered through a 0.22 μm filter membrane, and the reaction was quenched using a 1:1 saturated sodium thiosulfate solution. The samples were analyzed by high-performance liquid chromatography (HPLC).

[0093] The catalytic degradation efficiency of SMX by the ball-milled pyrite-carbon nitride composite catalyst (prepared in Comparative Example 1) is shown in Table 3 below.

[0094] Table 3 shows that the unmilled pyrite-carbon nitride composite system could only catalyze the degradation of 14.5% of SMX within 5 minutes, a decrease of 85.5% compared to the ball-milled pyrite-carbon nitride composite system. The degradation rate of the unmilled pyrite-carbon nitride composite system was only 24.5% within 30 minutes, an increase of only 5.9% compared to the system without catalyst (Example 3). This indicates that the unmilled pyrite-carbon nitride composite material has a very weak effect on improving the degradation of SMX by activated persulfate. These findings demonstrate that the ball milling process is a key step in improving the catalytic degradation performance of the composite material.

[0095] Table 3. Catalytic degradation efficiency of SMX by ball-milled pyrite-carbon nitride composite material

[0096]

[0097] Example 5

[0098] This embodiment tests the catalytic degradation efficiency of composite material A prepared in Comparative Example 2 and compares it with the catalytic degradation efficiency of pyrite carbon nitride composite material prepared in Example 1 (prepared in Example 1) on sulfamethoxazole (SMX) to explore the role of the calcination process in step (2) of Example 1.

[0099] The initial concentration of SMX was 10 mg / L, the concentration of persulfate was 0.4 mM, and the catalyst dosage was 0.3 g / L. Before the reaction, the catalyst was magnetically stirred with 50 mL of SMX solution for 30 min, and then 50 mL of persulfate solution was added to initiate the reaction. At predetermined time intervals, 1 mL of the reaction solution was taken, filtered through a 0.22 μm filter membrane, and the reaction was quenched using a 1:1 saturated sodium thiosulfate solution. The samples were then analyzed by high-performance liquid chromatography (HPLC).

[0100] The catalytic degradation efficiency of SMX by composite material A prepared in Comparative Example 2 is shown in Table 4 below.

[0101] As shown in Table 4, the catalytic degradation efficiency of composite material A is very low. The system can only degrade 12.8% of SMX within 30 min. The catalytic degradation efficiency is far lower than that of the ball-milled pyrite carbon nitride composite material (prepared in Example 1), and even lower than that of the system without catalyst.

[0102] The above indicates that: First, the proportion of pyrite in composite material A is small, and the proportion of Fe(II), the effective component for activating persulfate, is also small, resulting in a very limited number of active sites. Second, carbon nitride contains abundant C=N bonds, which are easily broken and form new Fe-N bonds with Fe elements in pyrite, providing active sites and accelerating electron transfer. Urea, the precursor of carbon nitride, only contains CN bonds and not C=N bonds, making it difficult to form new bonds with Fe. Third, urea is easily soluble in water. When urea in composite material A dissolves in water, it easily quenches the active oxygen in the system, which may result in a lower removal rate than the system without a catalyst.

[0103] Table 4. Catalytic degradation efficiency of SMX by composite material A

[0104]

[0105] Example 6

[0106] This embodiment tests the catalytic degradation efficiency of sulfamethoxazole (SMX) by composite material B prepared in Comparative Example 3 and compares it with the pyrite carbon nitride composite material prepared in Example 1 to explore the difference in the catalytic degradation performance of SMX by using natural pyrite and pyrite carbon nitride composite material prepared using high-purity pyrite.

[0107] The initial concentration of SMX was 10 mg / L, the concentration of persulfate was 0.4 mM, and the catalyst dosage was 0.3 g / L. Before the reaction, the catalyst was magnetically stirred with 50 mL of SMX solution for 30 min, and then 50 mL of persulfate solution was added to initiate the reaction. At predetermined time intervals, 1 mL of the reaction solution was taken, filtered through a 0.22 μm filter membrane, and the reaction was quenched using a 1:1 saturated sodium thiosulfate solution. The samples were then analyzed by high-performance liquid chromatography (HPLC).

[0108] The efficiency of composite material B prepared in Comparative Example 3 in catalytic degradation of SMX is shown in Table 5 below.

[0109] As shown in Table 5, compared with the pyrite carbon nitride composite material prepared in Example 1, composite material B has a relatively low degradation efficiency for SMX. The degradation rate of SMX within 5 min is 76.1%, which is 23.9% lower than that of Example 2. After 30 min of reaction, the degradation efficiency of SMX by composite material B is 86.7%. This may be because the Fe(II) content in the pyrite carbon nitride composite material prepared using high-purity pyrite is too high, which may quench the active oxygen generated in the system during the reaction, resulting in a decrease in the degradation efficiency of SMX.

[0110] Table 5. Catalytic degradation efficiency of SMX by composite material B

[0111]

[0112] Example 7

[0113] This embodiment is used to investigate the catalytic degradation effect of the ball-milled pyrite carbon nitride composite material obtained in Example 1 on sulfamethoxazole (SMX) in water samples with different pH values.

[0114] The initial concentration of SMX was 10 mg / L, the concentration of persulfate was 0.4 mM, and the catalyst dosage was 0.3 g / L. The initial pH of the water samples was adjusted to 3, 5, 7, and 9 using NaOH and H2SO4, respectively (the initial pH of the water samples in Examples 2 to 6 was 4). Before the reaction, the catalyst was magnetically stirred with 50 mL of SMX solution for 30 min. At predetermined time intervals, 1 mL of the reaction solution was taken, filtered through a 0.22 μm filter membrane, and the reaction was quenched using a 1:1 saturated sodium thiosulfate solution. The samples were analyzed by high-performance liquid chromatography (HPLC). The catalytic degradation effects are shown in Tables 6 to 9.

[0115] Table 6 Degradation rate of SMX at initial pH 3

[0116]

[0117] Table 7 Degradation rate of SMX at initial pH 5

[0118]

[0119] Table 8 Degradation rate of SMX at initial pH 7

[0120]

[0121] Table 9 Degradation rate of SMX at an initial pH of 9

[0122]

[0123] Tables 6 to 9 show the catalytic degradation of SMX by the ball-milled pyrite carbon nitride composite material obtained in Example 1 at initial pH values ​​of 3, 4 (Table 1), 5, 7, and 9. Figure 15 This is a comparison of the catalytic degradation efficiency of SMX by the ball-milled pyrite carbon nitride composite material obtained in Example 1 under different initial pH conditions.

[0124] From Tables 6 to 9 and Figure 15 It can be seen that within the initial pH range of 3 to 5, the ball-milled pyrite carbon nitride composite material obtained in Example 1 has a very high degradation rate for SMX, which can be completely degraded in just 5 minutes. Under higher pH conditions (pH=7, 9), SMX can also be completely degraded in just 30 minutes, showing very high catalytic activity.

[0125] Example 8

[0126] This embodiment is used to investigate the effect of the ball-milled pyrite carbon nitride composite material obtained in Example 1 on the catalytic degradation of sulfamethoxazole (SMX) in the presence of common environmental anions or humic acids.

[0127] The initial concentration of SMX was 10 mg / L, the concentration of persulfate was 0.4 mM, and the environmental anions included Cl. - CO3 2- H2PO4 - HCO3 - NO3 - The concentration of the catalyst was 10 mM, the concentration of humic acid was 10 mg / L, and the catalyst dosage was 0.3 g / L. Before the reaction, the catalyst and the added environmental anion or humic acid were mixed with 50 mL of SMX solution and magnetically stirred for 30 min. In this embodiment, after magnetic stirring for 30 min, 50 mL of persulfate solution was added to start the reaction. At predetermined time intervals, 1 mL of the reaction solution was taken out, filtered through a 0.22 μm filter membrane, and the reaction was quenched using a 1:1 saturated sodium thiosulfate solution. The sample was detected by high performance liquid chromatography.

[0128] Table 10 Degradation efficiency of SMX by pyrite-carbon nitride composite material in the presence of humic acid

[0129]

[0130] Table 11 Cl - The degradation efficiency of SMX by pyrite-carbon nitride composite material in the presence of

[0131]

[0132] Table 12 H2PO4 - The degradation efficiency of SMX by pyrite-carbon nitride composite material in the presence of

[0133]

[0134] Table 13 CO3 2- The degradation efficiency of SMX by pyrite-carbon nitride composite material in the presence of

[0135]

[0136] Table 14 NO3 - The degradation efficiency of SMX by pyrite-carbon nitride composite material in the presence of

[0137]

[0138] Table 15 HCO3 -The degradation efficiency of SMX by pyrite-carbon nitride composite material in the presence of

[0139]

[0140] The catalytic degradation effects of the ball-milled pyrite-carbon nitride composite material obtained in Example 1 on SMX under different environmental conditions with the presence of anions or humic acids are shown in Tables 10 to 15. Figure 16 Comparison of SMX concentration changes during degradation of the ball-milled pyrite carbon nitride composite material obtained in Example 1 under the presence of anions or humic acid.

[0141] From Tables 10 to 15 and Figure 16 It can be known that: Cl - NO3 - The presence of [a substance] has almost no effect on the degradation of SMX, indicating that the Cl produced in the reactions of formulas (7) to (10) may be [a substance]. • With NO3 • The effect on the reaction was minimal. In the presence of 10 mg / L humic acid, the degradation rate of SMX decreased slightly, possibly because humic acid quenched some of the free radicals generated during the reaction, thus affecting the degradation. However, SMX could still be completely degraded within 10 minutes, with minimal impact on the system. (H2PO4) - CO3 2- HCO3 - The presence of H2PO4 significantly inhibits the degradation of SMX. - It readily complexes with Fe(II) and Fe(III) in the system, thus preventing the persulfate from being effectively activated. As can be seen from equations (11) and (12), CO3... 2- It reacts with sulfate and hydroxyl radicals during the reaction to generate carbonate radicals with weak redox potential, which may be the main reason for the inhibition of degradation.

[0142] (7)

[0143] (8)

[0144] (9)

[0145] (10)

[0146] (11)

[0147] (12)

[0148] This indicates that the ball-milled pyrite carbon nitride composite material of the present invention performs well in water bodies with high organic content, but is affected by water bodies with high salinity, thereby reducing degradation efficiency.

[0149] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An application of a pyrite-carbon nitride composite material, characterized in that, The pyrite-carbon nitride composite material is used as a catalyst in the advanced oxidation reaction of persulfate. The preparation method of the pyrite-carbon nitride composite material includes the following steps: S1. After preliminary grinding of pyrite particles, the pyrite is sieved to obtain sieved pyrite; S2. Carbon nitride precursor urea is converted into carbon nitride by pyrolysis; S3. The carbon nitride prepared in step S2 is ultrasonically dispersed in methanol and then dried; S4. Mix the pyrite obtained in step S1 with the carbon nitride obtained in step S3, add ethanol and then ball mill to make the pyrite and carbon nitride evenly combined. S5. The ball-milled mixture obtained in step S4 is dried to obtain a pyrite carbon nitride composite material.

2. The application according to claim 1, characterized in that, In step S1, the pyrite is natural pyrite.

3. The application according to claim 1, characterized in that, In step S2, the pyrolysis is carried out in a muffle furnace.

4. The application according to claim 1, characterized in that, The pyrolysis adopts an ascending heating method, specifically: the temperature is increased to 500-600℃ at a heating rate of 2-5℃ / min, and then maintained at 500-600℃ for 1-5 hours.

5. The application according to claim 1, characterized in that, Step S3 also includes centrifugation after sonication, with sonication time of 30-100 min, centrifugation rate of 4000-6000 r / min, centrifugation time of 3-8 min, drying temperature of 50-80℃, and drying time of 2-6 h.

6. The application according to claim 1, characterized in that, In step S4, the mass ratio of pyrite to carbon nitride is 2~6:1; the amount of ethanol added is 20~40% of the total mass of the pyrite and carbon nitride mixture; the grinding media used in the ball mill is zirconia balls, and the mass ratio of zirconia balls to the mixture is 10~20:

1.

7. The application according to claim 1, characterized in that, The ball mill rotates at a speed of 300-500 r / min for 2-6 hours, and rotates once every 1.5-2 hours.

8. The application according to claim 1, characterized in that, In step S5, the drying is carried out in a vacuum oven at a temperature of 40-70°C for 4-8 hours.

9. The application according to claim 1, characterized in that, Using persulfate as an oxidant and pyrite-carbon nitride composite material as a catalyst, sulfonamide antibiotics or chlorophenol organic pollutants in water bodies are degraded. The concentration of sulfonamide antibiotics or chlorophenol organic pollutants in the water body is 8~15 mg / L, pH=3-9, the dosage of pyrite-carbon nitride composite material is 0.1~0.5 g / L of water body, and the concentration of persulfate in the water body is 0.2~0.6 mM.

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