A natural pyrite rich in sulfur vacancies and a preparation method and application thereof

Abstract

This invention discloses a sulfur-vacancy-rich natural pyrite, its preparation method, and its applications, belonging to the field of environmentally friendly new materials technology. This sulfur-vacancy-rich natural pyrite is prepared by ball milling a mixture of trivalent iron salt and natural pyrite, wherein the trivalent iron salt contains Fe... 3+ The molar ratio of the modified natural pyrite (calculated as FeS2) to natural pyrite is 3-5:100. The modified natural pyrite rich in sulfur vacancies obtained in this invention is used to treat ClO2-containing materials. ‑ In wastewater treatment, ClO2 can be achieved over a relatively wide pH range. ‑ Efficient conversion to Cl ‑ Furthermore, no other chloride species are produced; at the same time, the obtained modified natural pyrite has high stability, can be recycled multiple times, and has a simple preparation process and low cost, making it a promising candidate for application.

Description

Technical Field

[0001] This invention belongs to the field of environmentally friendly new materials technology, and specifically relates to a natural pyrite rich in sulfur vacancies, its preparation method and application. Background Technology

[0002] Natural pyrite (FexSy) has attracted widespread attention in the field of geochemistry due to its abundant reserves, low cost, and environmental friendliness, and it is also highly regarded for its application in the remediation of groundwater, industrial wastewater, domestic sewage, and contaminated soil. Importantly, FexSy exhibits excellent pH adaptability by spontaneously generating acid effects in redox reactions. Furthermore, its surface Fe(II) and polysulfides demonstrate significant reducing activity, enabling it to act as a reducing agent for environmental pollutants. However, the presence of a passivation layer, small specific surface area, and complex composition of natural pyrite presents challenges in practical applications, including slow dissolution rates, insufficient surface reactivity, limited solid-liquid interface reaction rates, and low electron transport efficiency. Therefore, modifying natural pyrite to enhance its reactivity has become a key research focus.

[0003] Surface vacancies, as a key structural defect in catalytic materials, significantly affect the electron distribution on the material surface. They create an electron-nonequilibrium surface on the catalyst, greatly promoting electron transfer between internal metal sites and electron-rich contaminants, thus significantly influencing reaction selectivity. Furthermore, the abundant local electrons surrounding the vacancies can activate hydrogen peroxide, persulfate, etc., generating active free radicals and achieving rapid redox and degradation of contaminants. Various methods exist for constructing catalyst surface vacancies, including solvothermal synthesis, high-temperature calcination, and vapor deposition. However, these techniques typically rely on large amounts of chemical solvents / reagents and are relatively complex. In contrast, mechanical ball milling, due to its simplicity, wide applicability, and ability to reduce particle size and destroy the oxide layer, has become an ideal choice for inducing surface defect formation and significantly improving catalyst reactivity. Modified pyrite prepared by this method exhibits excellent reactivity in a short time. However, with prolonged oxidation time, the increase in the number of secondary iron species (such as ferric hydroxide and ferric oxide) on the pyrite surface negatively impacts reactivity. Therefore, in order to ensure the good reactivity of pyrite, the key lies in regulating its surface structure and increasing the number of active sites to promote the generation of reducing species on its surface.

[0004] Chemical additives can be used to improve the surface structure and physicochemical properties of iron-based materials and natural minerals modified by mechanical ball milling. For example, oxalic acid-modified zero-valent iron prepared by mechanical ball milling exhibits highly efficient ability to activate persulfate (PDS) to degrade 2,4-dinitrotoluene, while phosphoric acid-modified kaolin can enhance its ability to degrade K+. + The adsorption performance of kaolin was improved. Furthermore, sulfuric acid-modified kaolin significantly enhanced its efficiency in removing As(V) and humic acid by generating a highly active aluminum-based coagulant. Although exogenous small molecules can increase the active sites on the catalyst surface through chemical corrosion, additional chemical reactions may adversely affect the activity of the modified catalyst. For example, the solubility of oxalic acid molecules may lead to their complexation with ferrous ions in solution, thereby reducing their efficiency in activating persulfate. Similarly, incompletely ball-milled phosphoric acid may release H₂ in aqueous solution. + Excessive phosphoric acid addition affects the surface charge of kaolin, thus interfering with its exchange and adsorption process. Furthermore, excessive phosphoric acid addition can lead to phosphorus pollution. Conversely, excessive sulfuric acid modification can cause kaolin to clump and may generate acidic waste liquid or acid mist. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a natural pyrite rich in sulfur vacancies, its preparation method, and its applications. This method features a simple and low-cost preparation process, yields natural pyrite rich in sulfur vacancies with high stability and significantly improved redox properties, making it effective for treating residual ClO2 in domestic sewage disinfection processes. - The removal of.

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

[0007] A method for preparing natural pyrite rich in sulfur vacancies is provided, comprising the following steps:

[0008] By ball milling a mixture of ferric salts and natural pyrite, a natural pyrite rich in sulfur vacancies is obtained; wherein:

[0009] Fe in trivalent iron salt 3+ The molar ratio with natural pyrite (calculated as FeS2) is 3-5:100.

[0010] According to the above scheme, the trivalent iron salt is either a nitrate or a sulfate.

[0011] According to the above scheme, the ball milling time is 2-6 hours.

[0012] According to the above scheme, the ball mill speed is 500-600 r / min.

[0013] A natural pyrite rich in sulfur vacancies prepared by the above preparation method is provided.

[0014] This provides a method for processing natural pyrite rich in sulfur vacancies containing ClO2. - Applications in wastewater.

[0015] According to the above scheme, the application is as follows: adding natural pyrite rich in sulfur vacancies to a ClO2-containing... - In the wastewater, the reaction proceeds for 50-60 minutes, separating the natural pyrite rich in sulfur vacancies from the wastewater solution, thus completing the ClO2 reaction. - Removal. Preferably, a magnet is used to separate natural pyrite rich in sulfur vacancies from the wastewater solution.

[0016] According to the above scheme, containing ClO2 - The wastewater is domestic sewage.

[0017] According to the above scheme, the ClO2-containing - The pH value of the wastewater is 2.7-8.7; preferably 2.7-6.8.

[0018] According to the above scheme, the ClO2-containing - ClO2 in wastewater - The concentration should not exceed 0.15 mmol / L; preferably 0.04-0.10 mmol / L.

[0019] According to the above scheme, the natural ferrous sulfate rich in sulfur vacancies in ClO2 - The concentration in the wastewater is 1.0-3.0 g / L; preferably 2.0-3.0 g / L.

[0020] This invention provides a method for preparing natural pyrite rich in sulfur vacancies, employing a synergistic ball milling process between ferric salts and pyrite. During the ball milling process, the acidic effect of the continuous acidic microenvironment provided by the ferric salts erodes the passivation layer on the surface of the pyrite, thereby promoting the activity of the FeS phase. x The formation of FeS (Equation 1-7) x It can promote electron transfer. In the formation of FeS x During the process, the original crystal lattice S2 2- When damaged, defects are generated on the surface of pyrite, leading to the creation of sulfur vacancies. This helps to improve electron transport efficiency, thereby enhancing the adsorption and redox properties of natural pyrite for specific molecules.

[0021]

[0022] The beneficial effects of this invention are as follows:

[0023] 1. This invention provides a method for preparing natural pyrite rich in sulfur vacancies, employing a trivalent iron salt with a specific acidity to assist in ball milling. The acidic iron salt continuously provides an acidic microenvironment during ball milling, facilitating more complex chemical reactions with the matrix material or other components, enhancing interparticle interactions, more effectively regulating the surface structure of the catalyst, enhancing the surface reconstruction of the natural mineral during ball milling, generating more active species, and improving its redox performance. The resulting modified natural pyrite rich in sulfur vacancies is used to treat ClO2-containing materials. - In wastewater treatment, ClO2 can be achieved over a relatively wide pH range. - Efficient conversion to Cl - Furthermore, no other chloride species are produced; at the same time, the modified natural pyrite has high stability and can be recycled multiple times, showing significant application prospects.

[0024] 2. The raw material, metallic iron salt, is abundant and inexpensive, and has good biocompatibility. It can be used to improve and modify the performance of natural pyrite by ball milling. The preparation process is simple and low-cost, which is conducive to industrial application. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0026] Figure 1 The images show the XRD characterization of natural pyrite modified with ferric nitrate nonahydrate in Example 1 and Comparative Examples 1-2 of this invention.

[0027] Figure 2 The above are EPR characterization diagrams of natural pyrite modified with ferric nitrate nonahydrate in Example 1 and Comparative Examples 1-2 of the present invention.

[0028] Figure 3 This invention relates to the removal of ClO2 from natural pyrite modified with ferric nitrate nonahydrate in Examples 4-5 and Comparative Examples 6-7. - The rendered image.

[0029] Figure 4 This refers to the conversion of natural pyrite into ClO2 using ferric nitrate nonahydrate modified with ferric nitrate in Example 6 of the present invention. - For Cl - The efficiency graph.

[0030] Figure 5 To remove ClO2 from natural pyrite modified with ferrous sulfate heptahydrate in Comparative Example 8 of this invention. - The rendered image.

[0031] Figure 6 To remove ClO2 from hydrated ferric sulfate-modified natural pyrite in Examples 7 and 9 of this invention.- The rendered image.

[0032] Figure 7 This invention relates to the treatment of ClO2 at different initial pH levels using nonahydrate ferric nitrate modified natural pyrite in Examples 4 and 8 of this invention. - The rendered image.

[0033] Figure 8 To remove ClO2 from natural pyrite modified with ferric nitrate nonahydrate in Examples 4 and 9 of this invention. - The rendered image.

[0034] Figure 9 The images show the effect of ferric nitrate nonahydrate modified pyrite in Examples 4 and 10 of the present invention on the removal of different concentrations of chlorite.

[0035] Figure 10 This invention relates to the method of removing ClO2 by modifying natural ferric sulfate nonahydrate with ferric nitrate in Example 11. - The loop effect diagram. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0037] Example 1

[0038] A method for preparing natural pyrite rich in sulfur vacancies is provided, comprising the following steps:

[0039] 2.0 g of natural pyrite and 0.2082 g of ferric nitrate nonhydrate (the molar ratio of pyrite (calculated as FeS2) / ferric nitrate nonhydrate was 1:0.03) were added to a ball mill jar. The ball mill speed was set to 500 r / min, and the mill was operated alternately in both forward and reverse directions for 1 hour each time. This process was repeated once, for a total duration of 4 hours. After ball milling, the product was washed and dried to obtain the modified natural pyrite rich in sulfur vacancies, which was named FF3.

[0040] Example 2

[0041] The specific operation is the same as in Implementation Case 1, except that the molar ratio of pyrite and ferric nitrate nonahydrate is 1:0.04 and 1:0.05, respectively, and the resulting modified natural pyrite is denoted as FF4 and FF5.

[0042] Comparative Example 1

[0043] The specific operation is the same as in Implementation Case 1, except that ferric nitrate nonahydrate is not added (i.e., the molar ratio of pyrite and ferric nitrate nonahydrate is 1:0), and the resulting modified natural pyrite is denoted as FF0.

[0044] Comparative Example 2

[0045] The specific operation is the same as in Example 1, except that the molar ratio of pyrite and ferric nitrate nonahydrate is 1:0.02 and 1:0.01, respectively, and the resulting modified natural pyrite is denoted as FF2 and FF1.

[0046] Comparative Example 3

[0047] The specific operation is the same as in Example 1, except that the molar ratio of pyrite and ferric nitrate nonahydrate is 1:0.025, and the resulting modified natural pyrite is denoted as FF2.5.

[0048] The crystal structure and surface vacancies of the FF3, FF0, FF2, and FF1 samples prepared in Example 1, Comparative Example 1, and Comparative Example 2 were characterized by X-ray powder diffraction and electron paramagnetic resonance spectroscopy, respectively. See details in [link to documentation]. Figure 1 and Figure 2 . Figure 1 The results show that the main components of the above samples are FeS2 and Fe3O4, and they also contain SiO2 and S. Figure 2 The results show that the signal peak at g = 2.0029 is the signal peak of sulfur vacancies. Fe(III)-assisted mechanical ball milling generates sulfur vacancies on the surface of natural pyrite. As the amount of Fe(III) added increases, the signal peak intensity of sulfur vacancies also increases.

[0049] Comparative Example 4

[0050] The specific operation is the same as in Example 1, except that the molar ratio of pyrite and ferrous sulfate heptahydrate is 1:0.03, 1:0.02 and 1:0.01, respectively, and the resulting modified natural pyrite is denoted as FF-3%, FF-2% and FF-1%.

[0051] Example 3

[0052] The specific operation is the same as in Implementation Case 1, except that the ball milling aid, ferric nitrate nonahydrate, is replaced with ferric sulfate hydrate. The Fe content in natural pyrite and ferric sulfate hydrate is... 3+ The molar ratio is 1:0.03, denoted as FF-3.

[0053] Comparative Example 5

[0054] The specific operation is the same as in Example 3, the difference being that the Fe in natural pyrite and hydrated ferric sulfate... 3+ The molar ratios are 1:0.02 and 1:0.01, respectively, denoted as FF-2 and FF-1.

[0055] Example 4

[0056] An application of the aforementioned sulfur-vacancy-rich natural pyrite in the treatment of chlorite-containing wastewater is provided, comprising the following steps:

[0057] Weigh 0.20 g of the sulfur-vacancy-rich natural pyrite (FF3) obtained in Example 1 and add it to an Erlenmeyer flask containing 100 mL of 0.1 mmol / L NaClO2 solution with an initial pH of 6.7 ± 0.1. Then, place the Erlenmeyer flask in a shaker and conduct the experiment at room temperature for 50 min. After the experiment, use a magnet to separate the modified natural pyrite powder from the wastewater solution, thus completing the ClO2 reaction. - The removal of.

[0058] Example 5

[0059] The specific operation is the same as in Example 4, except that the natural pyrite rich in sulfur vacancies used is FF4 and FF5 obtained in Example 2.

[0060] Comparative Example 6

[0061] The specific operation is the same as in Example 4, except that the natural pyrite rich in sulfur vacancies used is FF0, FF1 and FF2 obtained from Comparative Examples 1-2, and is compared with Example 4.

[0062] Comparative Example 7

[0063] The specific operation is the same as in Example 4, except that the natural pyrite rich in sulfur vacancies used is FF2.5 obtained from Comparative Example 3, and is compared with Example 4.

[0064] In Examples 4, 5, 6, and 7, the chlorite removal efficiency of sulfur-vacancy-rich natural pyrite (FF0, FF1, FF2, FF2.5, FF3, FF4, and FF5) is described in [reference needed]. Figure 3 The percentages were 41.3%, 45.8%, 56.4%, 66.5%, 100.0%, 100.0%, and 100.0%, respectively. This indicates that as the Fe(III) loading increases, the defects on the surface of natural pyrite increase, which is conducive to ClO2 formation. - Remove.

[0065] Example 6

[0066] ClO2 in Example 4 and Comparative Example 6 was analyzed by ion chromatography. - The conversion products were analyzed:

[0067] The specific operation is the same as in Example 4. Every 10 minutes, 2.5 mL of sample is drawn from the conical flask using a syringe. After passing through a 0.22 µm Teflon filter, the sample is injected into a 5 mL centrifuge tube. 0.2 g of ion exchange resin is added and thoroughly mixed with the 2.5 mL sample. After the ion exchange resin has settled, it is filtered again using a 0.22 µm Teflon filter. After filtration, 2.0 mL of sample is accurately transferred to a 6 mL ion chromatography tube. 4 mL of ultrapure water is transferred to the ion chromatography tube, and air bubbles are removed. After removing the air bubbles, the prepared test sample tube is placed in the ion chromatography autosampler for analysis. ClO2 is analyzed using an ion chromatograph. - The conversion products were analyzed under the following conditions: the eluent was 4.5 mmol / L Na2CO3 and 0.8 mmol / L NaHCO3, the eluent flow rate was 1 mL / min, the column oven temperature was 30℃, and the injection volume was 25 μL.

[0068] like Figure 4 As shown, modified natural pyrite removes ClO2. - During the process, ClO2 - Almost completely converted to stable Cl - No other chlorinated species are produced. The specific conversion rates are as follows: FF0, FF1, FF2, and FF3 convert to ClO2. - For Cl - The efficiencies were 100.0%, 92.9%, 96.4%, and 99.1%, respectively.

[0069] Comparative Example 8

[0070] The specific operation is the same as in Example 4, except that the modified natural pyrite used is the modified natural pyrite (FF-3%, FF-2% and FF-1%) obtained in Comparative Example 4 and the pyrite (FF0) obtained in Comparative Example 1.

[0071] 0.20 g of modified pyrite powder FF-3%, FF-2%, FF-1%, and FF0 were weighed separately and added to conical flasks containing 100 mL of NaClO2 solution with a concentration of 0.1 mmol / L and an initial pH of 6.7 ± 0.1. The conical flasks were then placed in a shaker and reacted at room temperature for 50 min.

[0072] like Figure 5 As shown, the efficiencies of modified natural pyrite (FF0, FF-1%, FF-2%, FF-3%) in removing chlorite were 41.3%, 49.8%, 55.5%, and 65.7%, respectively. This indicates that ferrous salt-modified pyrite is less effective at removing chlorite than ferric salt-modified pyrite.

[0073] Example 7

[0074] The specific operation is the same as in Example 4, except that the natural pyrite rich in sulfur vacancies used is FF-3 obtained in Example 3.

[0075] Comparative Example 9

[0076] The specific operation is the same as in Example 7, except that the natural pyrite rich in sulfur vacancies used are FF0 of Comparative Example 1 and FF-2 and FF-1 obtained from Comparative Example 5, respectively, and are compared with Example 7.

[0077] like Figure 6 As shown in Example 7 and Comparative Example 9, the efficiencies of modified natural pyrite (FF0, FF-1, FF-2, and FF-3) obtained in Example 3, Comparative Example 1, and Comparative Example 4 in removing chlorite were 41.3%, 59.9%, 91.8%, and 100.0%, respectively. This indicates that different iron salts can be used to modify natural pyrite, which contains ClO2, and can effectively treat chlorite-containing materials. - Wastewater.

[0078] Example 8

[0079] The natural pyrite rich in sulfur vacancies obtained in Example 1 was used to treat ClO2 in chlorite-containing wastewater. - The specific operation is the same as in Example 4, except that ClO2 - The solutions had pH values ​​of 2.7, 4.7, and 8.7, respectively.

[0080] ClO2 in Examples 4 and 8 - The results of the solution removal rate comparison are as follows: Figure 7 As shown, natural pyrite (FF3) rich in sulfur vacancies reacts with ClO2 at initial pH values ​​of 2.7, 4.7, 6.7, and 8.7 for 50 min. - The solution removal rates were 100.0%, 100.0%, 100.0%, and 63.1%, respectively. This indicates that natural pyrite rich in sulfur vacancies has a wide applicable pH range for chlorite removal, maintaining a removal rate above 50.0% even under neutral and alkaline conditions. Therefore, the modified natural pyrite prepared by this method can effectively treat ClO2 over a wide pH range. - Wastewater.

[0081] Example 9

[0082] The natural pyrite rich in sulfur vacancies obtained in Example 1 was used to treat ClO2 in chlorite-containing wastewater. -The specific operation is the same as in Example 4, except that 0.30 g, 0.25 g, 0.15 g and 0.10 g of the natural pyrite rich in sulfur vacancies obtained in Example 1 are weighed respectively.

[0083] ClO2 in Examples 4 and 9 - The results of the solution removal rate comparison are as follows: Figure 8 As shown, different doses (3.0 g / L, 2.5 g / L, 2.0 g / L, 1.5 g / L and 1.0 g / L) of sulfur-vacancy-rich natural pyrite affect ClO2. - The removal efficiencies were 100.0%, 100.0%, 100.0%, 89.4%, and 75.5%, respectively. This result indicates that natural pyrite rich in sulfur vacancies is effective in removing ClO2. - The efficiency in this regard is significantly dependent on the dosage, and ClO2 can be achieved when the dosage is in the range of 1.5-3.0 g / L. - Highly efficient removal.

[0084] Example 10

[0085] The natural pyrite rich in sulfur vacancies obtained in Example 1 was used to treat ClO2 in chlorite-containing wastewater. - The specific operation is the same as in Example 4, except that the concentrations of the NaClO2 solution are 0.15 mmol / L, 0.08 mmol / L, 0.06 mmol / L and 0.04 mmol / L, respectively.

[0086] ClO2 in Examples 4 and 10 - The results of the solution removal rate comparison are as follows: Figure 9 As shown, the removal rates of different concentrations of chlorite (0.15 mmol / L, 0.1 mmol / L, 0.08 mmol / L, 0.06 mmol / L, and 0.04 mmol / L) by adding 2.0 g / L of sulfur-vacancy-rich natural pyrite were 81.0%, 100.0%, 100.0%, 100.0%, and 100.0%, respectively. This result indicates that sulfur-vacancy-rich natural pyrite has a good removal effect on different concentrations of chlorite.

[0087] Example 11

[0088] A recycling method for efficiently removing chlorite from the aforementioned sulfur-vacancy-rich natural pyrite includes the following steps:

[0089] Weigh 0.2 g of the sulfur-vacancy-rich natural pyrite (FF3) obtained in Example 1 and add it to 100 mL of 0.1 mmol / L ClO2. -The solution was then placed in a shaker, and the experiment was conducted at room temperature. After the reaction had continued for 50 minutes, the ClO2 concentration in the reaction solution was measured. - The concentration of the sample was determined, and its removal rate was calculated.

[0090] Natural pyrite rich in sulfur vacancies was separated from the reaction solution using a magnet. The separated natural pyrite rich in sulfur vacancies was then added again to 100 mL of 0.1 mmol / L ClO2. - The solution was further evaluated for its removal of ClO2. - Efficiency. Each completion of the above steps is considered one cycle.

[0091] Experimental results are as follows Figure 10 As shown, after four consecutive cycles, natural pyrite rich in sulfur vacancies effectively removes ClO2. - The efficiency remains as high as 95.3%. This indicates that the natural pyrite rich in sulfur vacancies prepared by this method has a stable and efficient ability to remove ClO2. - active.

[0092] The above description represents only some embodiments of the present invention and does not constitute any limitation thereof. Furthermore, the application scope of the present invention is not limited to the treatment of wastewater containing chlorite, but is also applicable to the treatment of other types of oxidizing pollutants. Any equivalent changes, modifications, or improvements made to the above embodiments / comparative examples based on the core technical principles of the present invention are considered to fall within the protection scope of the present invention.

Claims

1. The use of natural pyrite enriched with sulphur vacancies for the treatment of wastewater containing CIO2 - characterized in that, The preparation method of the natural pyrite rich in sulfur vacancies comprises the following steps: mixing a ferric salt and natural pyrite and ball milling, so as to obtain the natural pyrite rich in sulfur vacancies. wherein: Fe in the ferric salt 3+ in a molar ratio of 3-5: 100 with the natural pyrite; the ferric salt is nitrate or sulfate.

2. Use according to claim 1, characterized in that, The application is: adding the natural pyrite rich in sulfur vacancy to the wastewater containing ClO2 - In the wastewater, the reaction is carried out for 50-60 min, and the natural pyrite rich in sulfur vacancy is separated from the wastewater solution, that is, the removal of ClO2 - is completed.

3. Use according to claim 1 or 2, characterized in that, The ClO2 - The pH of the wastewater is 2.7-8.

7.

4. Use according to claim 1 or 2, characterized in that, the ClO2 - ClO2 - not greater than 0.15 mmol / L.

5. Use according to claim 2, characterized in that, The natural pyrite enriched in sulfur vacancies at ClO2 - The concentration in the wastewater is 1.0-3.0 g / L.

6. Use according to claim 1, characterized in that, The ball milling time is 2-6 h.

7. Use according to claim 1, characterized in that, The ball milling rotating speed is 500-600 r / min. The ball milling rotating speed is 500-600 r / min.

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