Sulfur quantum dot modified zero-valent iron, and preparation method and application thereof

Abstract

The application belongs to the technical field of water treatment, and provides sulfur quantum dot modified zero-valent iron as well as a preparation method and application thereof.The sulfur quantum dot modified zero-valent iron is composed of zero-valent iron and sulfur quantum dots loaded on the surface of the zero-valent iron, and the sulfur quantum dots are uniformly and discretely distributed on the surface of the zero-valent iron.By adjusting the coordination environment and electronic structure of the metal center of the zero-valent iron, the reaction activity of the zero-valent iron is enhanced, the ability of the zero-valent iron to activate oxidants to degrade organic pollutants is improved, meanwhile, the pH applicable range of the zero-valent iron in treating wastewater is widened, and the degradation efficiency of the zero-valent iron on organic pollutants in wastewater is improved.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, and relates to a sulfur quantum dot modified zero-valent iron, its preparation method and application. Background Technology

[0002] Zero-valent iron (ZVI), as a non-toxic, abundant, inexpensive, easily produced and recycled metallic material that does not cause secondary pollution, has received widespread research and attention in the field of water treatment. ZVI can continuously generate Fe(II), thereby activating oxidants including oxygen, hydrogen peroxide, ozone, and persulfate to produce reactive oxygen species to degrade organic pollutants, or it can directly reduce and degrade organic pollutants as an electron donor. However, during production and use, ZVI easily forms a dense passivation film of iron oxides and hydroxides. This passivation film hinders the transfer of electrons to pollutants or oxidants, resulting in a slow Fe(II) release rate, which in turn reduces the activity and utilization efficiency of ZVI and limits its applicable pH range. Simultaneously, the redox kinetics between the single iron metal center of ZVI and oxidants are slow; for example, the consumption of Fe(II) is much faster than its regeneration, leading to low utilization of oxidants by ZVI. These factors limit the further application of ZVI in water treatment. Therefore, developing highly active modified ZVI materials is an important research direction in the current water treatment field.

[0003] Currently reported methods for modifying zero-valent iron mainly include compound coupling and heteroatom doping. Zero-valent iron modified materials prepared through compound coupling mainly include Fe@Fe2O3, nZVI@Ti3C2-based MXene, carbon dots@ZVI, and oxalic acid-ball-milled ZVI, etc. Heteroatom doping includes doping zero-valent iron materials through carbonization, sulfidation, phosphating, and silicideation. However, these methods are mostly constrained by problems such as secondary pollution, complex operation, and high preparation costs, making them difficult to promote and apply in practical engineering. Furthermore, the activity of the modified zero-valent iron materials prepared by the above methods needs further improvement. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a sulfur quantum dot modified zero-valent iron, its preparation method and application. By adjusting the coordination environment and electronic structure of the zero-valent iron metal center, the reactivity of zero-valent iron is enhanced, the ability of zero-valent iron to activate oxidants to degrade organic pollutants is improved, the pH range of zero-valent iron in wastewater treatment is broadened, and the degradation efficiency of organic pollutants in wastewater is improved.

[0005] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

[0006] A sulfur quantum dot modified zero-valent iron, the modified zero-valent iron being composed of zero-valent iron and sulfur quantum dots loaded on the surface of zero-valent iron, wherein the sulfur quantum dots are uniformly and discretely distributed on the surface of zero-valent iron.

[0007] In the above-mentioned technical solution for sulfur quantum dot-modified zero-valent iron, the mass content of sulfur quantum dots in the modified zero-valent iron is 0.08% to 0.61%; further, the mass content of sulfur quantum dots in the modified zero-valent iron is preferably 0.2% to 0.61%.

[0008] In the above-mentioned technical solution for modifying zero-valent iron with sulfur quantum dots, the zero-valent iron is micron-sized zero-valent iron or nano-sized zero-valent iron. The specific size of the zero-valent iron can be selected according to the actual application requirements; typically, the particle size of the zero-valent iron is 500 nm to 40 μm.

[0009] This invention also provides a method for preparing the above-mentioned sulfur quantum dot modified zero-valent iron, comprising the following steps:

[0010] (1) The sulfur source, water, sodium hydroxide or potassium hydroxide and passivating agent are thoroughly mixed at 70-120℃ to obtain a sulfur point solution; the sulfur point solution is mixed with hydrogen peroxide solution and reacted thoroughly under stirring to obtain a sulfur quantum dot solution;

[0011] When preparing the sulfur point solution, the mass ratio of sulfur source, water, sodium hydroxide or potassium hydroxide, and passivating agent is controlled to be (28-224):(500-3000):(120-240):(0.81-2.43); the passivating agent is polyethylene glycol, propynyl alcohol, polyvinylpyrrolidone, or sodium poly4-styrene sulfonate; when preparing the sulfur quantum dot solution, the volume ratio of sulfur point solution to hydrogen peroxide solution is controlled to be 1:(1-2), and the mass fraction of hydrogen peroxide solution is 2%-20%.

[0012] (2) Adjust the pH of the sulfur quantum dot solution to 5-8. Mix the sulfur quantum dot solution with zero-valent iron according to the molar ratio of sulfur quantum dots to zero-valent iron of (0.025-0.2):1. React fully at 60-90℃. Wash the resulting reaction product with water. Collect the sulfur quantum dot-modified zero-valent iron in the reaction product with a magnet and dry it.

[0013] In step (2) of the above preparation method, it is preferable to react at 60-90°C for 5-8 hours.

[0014] In the above preparation method, in step (1), when preparing the sulfur quantum dot solution, the sulfur quantum dot solution is mixed with the hydrogen peroxide solution, and preferably reacted under stirring conditions for 15 to 60 minutes.

[0015] In the above preparation method, the sulfur source is sublimed sulfur, sodium sulfide, thiosulfate, or dithionite.

[0016] In the above preparation method, the passivating agent polyethylene glycol can be polyethylene glycol 6000, polyethylene glycol 400, etc.

[0017] In step (2) of the above preparation method, it is preferable to adjust the pH value of the sulfur quantum dot solution to 5-7, and then mix the pH-adjusted sulfur quantum dot solution with zero-valent iron.

[0018] This invention also provides the application of the above-mentioned sulfur quantum dot modified zero-valent iron in the degradation of organic pollutants by activated oxidants.

[0019] In the above-mentioned application, the oxidant includes at least one of hydrogen peroxide, ozone, and persulfate, wherein the persulfate is at least one of permonosulfate and perdisulfate.

[0020] When the above-mentioned sulfur quantum dot modified zero-valent iron is used in the degradation of organic pollutants by activated oxidants, the sulfur quantum dot modified zero-valent iron and oxidants are added to wastewater containing organic pollutants, and the pH value of the wastewater is controlled at 3 to 7 for wastewater treatment.

[0021] When the above-mentioned sulfur quantum dot-modified zero-valent iron is used in the degradation of organic pollutants by activated oxidants, the sulfur quantum dot-modified zero-valent iron activated oxidant generates active oxygen species to degrade the organic pollutants in the wastewater during the wastewater treatment process.

[0022] Furthermore, when applying the above-mentioned sulfur quantum dot-modified zero-valent iron in the degradation of organic pollutants by activated oxidants, the dosage of sulfur quantum dot-modified zero-valent iron and oxidant is determined based on the actual water quality of the wastewater containing organic pollutants (e.g., the type and concentration of organic pollutants). Once the water quality is determined, suitable dosages of sulfur quantum dot-modified zero-valent iron and oxidant can be experimentally screened to ensure high degradation efficiency for organic pollutants in the wastewater. Typically, the dosages of sulfur quantum dot-modified zero-valent iron and oxidant are controlled such that the concentration of sulfur quantum dot-modified zero-valent iron in the wastewater is 0.3–10 g / L, and the concentration of oxidant in the wastewater is 1–20 mmol / L. Preferably, the dosages of sulfur quantum dot-modified zero-valent iron and oxidant are controlled such that the concentration of sulfur quantum dot-modified zero-valent iron in the wastewater is 0.3–0.8 g / L, and the concentration of oxidant in the wastewater is 1–10 mmol / L.

[0023] When the above-mentioned sulfur quantum dot modified zero-valent iron is used in the degradation of organic pollutants by activated oxidants, it is preferable to control the pH value of the wastewater to be 3-5.

[0024] When the above-mentioned sulfur quantum dot-modified zero-valent iron is used in the degradation of organic pollutants by activated oxidants, the organic pollutants include at least one of antibiotics, endocrine disruptors, nonsteroidal anti-inflammatory drugs, dyes, and other benzene ring organic pollutants. For example, common organic pollutants include sodium diclofenac, naproxen, sulfamethoxazole, nitrobenzene, phenol, bisphenol A, ofloxacin, and norfloxacin.

[0025] When the above-mentioned sulfur quantum dot-modified zero-valent iron is used in the degradation of organic pollutants by activated oxidants, the wastewater treatment time is determined according to the water quality of the wastewater containing organic pollutants. For example, the wastewater treatment time can usually be determined based on the type and concentration of organic pollutants in the wastewater. Generally, treatment is sufficient until the removal rate of organic pollutants in the wastewater reaches equilibrium. Typically, the wastewater treatment time does not exceed 120 minutes; for example, the wastewater treatment time can be controlled between 10 and 120 minutes.

[0026] This invention demonstrates through experiments that when using the sulfur quantum dot-modified zero-valent iron described in this invention to activate hydrogen peroxide for the degradation of bisphenol A, rapid and complete degradation of bisphenol A can be achieved within 15 minutes. Furthermore, when the sulfur quantum dot-modified zero-valent iron described in this invention is used to activate hydrogen peroxide for the degradation of nitrophenol industrial wastewater, it exhibits excellent removal effects on both COD and TOC in the wastewater. This indicates that the sulfur quantum dot-modified zero-valent iron possesses superior performance.

[0027] Compared with the prior art, the technical solution provided by the present invention has the following beneficial technical effects:

[0028] 1. This invention provides a sulfur quantum dot-modified zero-valent iron (ZVFe), comprising ZVFe and sulfur quantum dots loaded on the surface of ZVFe, wherein the sulfur quantum dots are uniformly and discretely distributed on the surface of ZVFe. This invention proposes the use of sulfur quantum dot-modified ZVFe to prepare highly active ZVFe-based water treatment materials. Electrochemical impedance spectroscopy and Tafel curve tests show that the sulfur quantum dot-modified ZVFe provided by this invention has a stronger electron transfer capacity than ZVFe. Experiments have demonstrated that when the sulfur quantum dot-modified ZVFe of this invention is used to activate oxidants for the degradation of organic pollutants, it exhibits better pollutant degradation effects compared to using unmodified ZVFe to activate oxidants for the degradation of organic pollutants.

[0029] 2. Experiments have demonstrated that when the sulfur quantum dot-modified zero-valent iron described in this invention is used to activate hydrogen peroxide for the degradation of bisphenol A, it can achieve rapid and complete degradation of bisphenol A within 15 minutes. Furthermore, when the sulfur quantum dot-modified zero-valent iron described in this invention is used to activate hydrogen peroxide for the degradation of nitrophenol industrial wastewater, it exhibits excellent removal effects on both COD and TOC in the wastewater. This indicates that the sulfur quantum dot-modified zero-valent iron possesses superior performance and significant potential for practical applications.

[0030] 3. Experiments have demonstrated that when the sulfur quantum dot-modified zero-valent iron described in this invention is used to activate hydrogen peroxide for the degradation of bisphenol A, the removal performance of the sulfur quantum dot-modified zero-valent iron / hydrogen peroxide system for bisphenol A is higher than that of the zero-valent iron / hydrogen peroxide system under the corresponding pH conditions when the wastewater pH is 3-7. The removal rate of bisphenol A in wastewater with pH 3-7 by the sulfur quantum dot-modified zero-valent iron / hydrogen peroxide system reaches over 90%, the removal rate in wastewater with pH 3-6 reaches over 95%, and the removal rate in wastewater with pH 3-5 reaches 100%. This indicates that when using the sulfur quantum dot-modified zero-valent iron of this invention to activate hydrogen peroxide for the degradation of pollutants in wastewater, it has excellent degradation effects on pollutants in wastewater with pH values ​​of 3-7, overcoming the limitation of the narrow pH applicable range of existing zero-valent iron / hydrogen peroxide systems.

[0031] 4. Experiments have confirmed that the sulfur quantum dot modified zero-valent iron activating oxidant described in this invention has excellent degradation performance on a variety of organic pollutants, including sodium dichlorophenate, naproxen, sulfamethoxazole, nitrobenzene, phenol, bisphenol A, ofloxacin, and norfloxacin.

[0032] 5. The present invention also provides a method for preparing the above-mentioned sulfur quantum dot modified zero-valent iron. The raw materials used in this method are inexpensive and readily available, environmentally friendly, and the preparation process is simple. Attached Figure Description

[0033] Figure 1 These are the XPS S2p and Fe 2p spectra of the zero-valent iron used in Example 1 and the sulfur quantum dot-modified zero-valent iron prepared therefrom.

[0034] Figure 2 These are transmission electron microscopy (TEM) images and elemental distribution diagrams of the sulfur quantum dot-modified zero-valent iron prepared in Example 1.

[0035] Figure 3 This is a curve showing the change in BPA removal efficiency over treatment time when sulfur quantum dot-modified zero-valent iron activated hydrogen peroxide is used to degrade BPA with sulfur quantum dot solutions of different pH values.

[0036] Figure 4 This is the curve showing the change in BPA removal efficiency over treatment time when hydrogen peroxide is activated to degrade BPA using ZVI and sulfur quantum dots modified with different sulfur-iron molar ratios in Example 3.

[0037] Figure 5 The electrochemical impedance spectroscopy and Tafel curves are for ZVI and sulfur quantum dot-modified zero-valent iron with different sulfur-iron molar ratios in Example 4.

[0038] Figure 6This is the curve showing the change in BPA removal efficiency over treatment time when zero-valent iron modified with sulfur quantum dots and hydrogen peroxide activated with ZVI degrades BPA in simulated wastewater with different pH values ​​in Example 5.

[0039] Figure 7 This is the curve showing the change in BPA removal efficiency over treatment time when different amounts of ZVI and sulfur quantum dot-modified zero-valent iron were activated with different amounts of hydrogen peroxide to degrade BPA in Example 6.

[0040] Figure 8 This is the curve showing the change in removal efficiency of different types of pollutants over treatment time when using ZVI and sulfur quantum dots to modify zero-valent iron to activate hydrogen peroxide for the degradation of different types of pollutants in Example 7.

[0041] Figure 9 This is the curve showing the change in the treatment effect of sulfur quantum dot modified zero-valent iron activated hydrogen peroxide on nitrophenol industrial wastewater as of treatment time in Example 8.

[0042] Figure 10 The curves show the change in BPA removal efficiency over treatment time when sulfur quantum dot-modified zero-valent iron activated hydrogen peroxide is used to degrade BPA with different sulfur sources, passivating agents, sulfur point preparation raw material ratios, and sulfur point preparation temperatures in Examples 1 and 9.

[0043] Figure 11 The curves show the changes in the removal efficiency of sulfur quantum dot-modified zero-valent iron activated hydrogen peroxide for BPA degradation as of treatment time when different sulfur point solutions and hydrogen peroxide volumes were prepared in Examples 1 and 9, using different sulfur point solutions and hydrogen peroxide volume ratios, hydrogen peroxide mass fractions, and sulfur point solutions and hydrogen peroxide mixing times.

[0044] Figure 12 The curves show the change in BPA removal efficiency with treatment time when sulfur quantum dot-modified zero-valent iron activated hydrogen peroxide is used to degrade BPA with different reaction temperatures, reaction times, and zero-valent iron particle sizes of sulfur quantum dot solutions and zero-valent iron prepared in Examples 1 and 9.

[0045] Figure 13 The curves show the changes in the BPA removal efficiency of the sulfur quantum dot-modified zero-valent iron prepared in Example 1 with different oxidants during BPA degradation, as a function of treatment time. Detailed Implementation

[0046] The following examples further illustrate the sulfur quantum dot-modified zero-valent iron, its preparation method, and its applications provided by this invention. It should be noted that the following examples are only for further illustration of this invention and should not be construed as limiting the scope of protection of this invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the invention to implement it are still within the scope of protection of this invention.

[0047] Example 1

[0048] In this embodiment, the steps for preparing sulfur quantum dots modified zero-valent iron are as follows:

[0049] (1) Using sublimed sulfur as the sulfur source, the sulfur source, deionized water, sodium hydroxide and polyethylene glycol 6000 were mixed in a mass ratio of 224:3000:240:2.43. The mixture was then magnetically stirred in an oil bath at 70°C for 45 h to obtain a sulfur point solution. The obtained sulfur point solution was then mixed with hydrogen peroxide at a concentration of 7.5 wt% in a volume ratio of 1:1.33 and stirred vigorously for 20 min to obtain a sulfur quantum dot solution.

[0050] (2) Adjust the pH of the sulfur quantum dot solution to 6. Mix the sulfur quantum dots solution with zero-valent iron with an average particle size of 38 μm in a molar ratio of 0.2:1. The zero-valent iron is evenly dispersed in the sulfur quantum dot solution. Then, shake the solution at 200 rpm for 6 hours in a water bath at 70°C. Wash the resulting black suspension several times with deionized water to remove sulfur quantum dots that are not stably bound to zero-valent iron. Collect the reaction product after washing, which is the magnetic sulfur quantum dot modified zero-valent iron, with a magnet. Dry it in a vacuum oven at 70°C to obtain sulfur quantum dot modified zero-valent iron, denoted as S / Fe 0.2.

[0051] Figure 1 These are the XPS S2p and Fe 2p spectra of the zero-valent iron used in Example 1 and the sulfur quantum dot-modified zero-valent iron prepared therefrom. Figure 1 It can be determined that the sulfur quantum dot modified zero-valent iron prepared in this embodiment contains atomic sulfur, and the sulfur quantum dots are connected to the zero-valent iron through Fe-S bonds, which indicates that the sulfur quantum dots are successfully dispersed on the surface of the zero-valent iron.

[0052] Figure 2 These are transmission electron microscopy (TEM) images and elemental distribution diagrams of the sulfur quantum dot-modified zero-valent iron prepared in Example 1. Figure 2 It can be seen that in the sulfur quantum dot modified zero-valent iron prepared in this embodiment, the mass content of sulfur quantum dots is 0.61%, and they are uniformly distributed on the surface of zero-valent iron.

[0053] Example 2

[0054] In this embodiment, sulfur quantum dot-modified zero-valent iron was prepared using sulfur quantum dot solutions with different pH values.

[0055] The operation of this embodiment is basically the same as that of Example 1, except that in step (2), the pH value of the sulfur quantum dot solution is adjusted to 5.1, 5.6, 6.4, 6.9, 7.9 and 12.8 respectively, and then the sulfur quantum dot solution after pH adjustment is thoroughly mixed with zero-valent iron. A series of sulfur quantum dot modified zero-valent iron are prepared.

[0056] The following examines the performance of sulfur quantum dot-modified zero-valent iron prepared based on sulfur quantum dot solutions with different pH values ​​in the degradation of bisphenol A (BPA) by activated hydrogen peroxide in Examples 1 and 2.

[0057] BPA was dissolved in deionized water to prepare a BPA solution with a concentration of 10 μmol / L. The pH of the BPA solution was adjusted to 5.0 to obtain simulated wastewater.

[0058] Seven portions of simulated wastewater were taken, and sulfur quantum dot-modified zero-valent iron (BPA) prepared based on sulfur quantum dot solutions with pH values ​​of 5.1, 5.6, 6.0, 6.4, 6.9, and 12.8 in Examples 1 and 2 were added to each portion. Hydrogen peroxide was then added, and the wastewater was treated for 15 minutes under stirring. The amount of sulfur quantum dot-modified zero-valent iron added was controlled to ensure a concentration of 0.1 g / L in the simulated wastewater, and the amount of hydrogen peroxide added was controlled to ensure a concentration of 1 mmol / L. During the wastewater treatment, samples were taken at 0 min, 1 min, 3 min, 5 min, 7 min, 10 min, and 15 min, filtered through a 0.22 μm polyethersulfone membrane, and the concentration C of BPA was measured. The initial concentration of BPA was recorded as C0, and the change in C / C0 with wastewater treatment time was calculated. The results are shown below. Figure 3 As shown.

[0059] Depend on Figure 3 It can be seen that when sulfur quantum dot-modified zero-valent iron activated hydrogen peroxide is used to degrade BPA based on sulfur quantum dot solutions with pH values ​​of 5.1, 5.6, 6.0, 6.4, 6.9, and 12.8, the removal rate of BPA can reach over 85%. Among them, the sulfur quantum dot-modified zero-valent iron activated hydrogen peroxide prepared based on sulfur quantum dot solutions with pH values ​​of 5.1, 5.6, 6.0, 6.4, 6.9, and 7.9 has a better effect on BPA degradation, with a removal rate of over 90% for all solutions. When sulfur quantum dot-modified zero-valent iron activated hydrogen peroxide is used to degrade BPA based on sulfur quantum dot solutions with pH values ​​of 5.1, 5.6, 6.0, 6.4, and 6.9, BPA can be completely removed.

[0060] Example 3

[0061] In this embodiment, a series of sulfur quantum dot-modified zero-valent iron with different sulfur-iron molar ratios were prepared.

[0062] The operation of this embodiment is basically the same as that of embodiment 1. The only difference is that the molar ratio of sulfur quantum dots to zero-valent iron in step (2) is adjusted to 0.025:1, 0.05:1, and 0.1:1, respectively, to prepare a series of sulfur quantum dot modified zero-valent iron with different sulfur-iron molar ratios. The prepared sulfur quantum dot modified zero-valent iron is successively denoted as S / Fe 0.025, S / Fe 0.05, and S / Fe 0.1.

[0063] The following investigation examines the ability of zero-valent iron (ZVI) and sulfur quantum dots modified with different sulfur-iron molar ratios prepared in Examples 1 and 3 to activate hydrogen peroxide to degrade BPA.

[0064] BPA was dissolved in deionized water to prepare a BPA solution with a concentration of 10 μmol / L. The pH of the BPA solution was adjusted to 5.0 to obtain simulated wastewater.

[0065] Five portions of simulated wastewater were taken, and ZVI, S / Fe 0.025, S / Fe 0.05, S / Fe 0.1, and S / Fe 0.2 were added to each portion, followed by hydrogen peroxide. The wastewater was treated for 15 minutes under stirring. The amounts of ZVI, S / Fe 0.025, S / Fe 0.05, S / Fe 0.1, and S / Fe 0.2 added were controlled to ensure that the concentrations of ZVI, S / Fe 0.025, S / Fe 0.05, S / Fe 0.1, and S / Fe 0.2 in the simulated wastewater were all 0.1 g / L, and the concentration of hydrogen peroxide added was controlled to ensure that the concentration of hydrogen peroxide in the simulated wastewater was 1 mmol / L. During the wastewater treatment, samples were taken at 0 min, 1 min, 3 min, 5 min, 7 min, 10 min, and 15 min, filtered through a 0.22 μm polyethersulfone membrane, and the concentration C of BPA was measured. Let the initial concentration of BPA be C0. Calculate the change of C / C0 over the wastewater treatment time. The results are as follows: Figure 4 As shown.

[0066] Depend on Figure 4 It can be seen that, compared with ZVI, the effect of activating hydrogen peroxide with S / Fe 0.025, S / Fe 0.05, S / Fe 0.1 and S / Fe 0.2 on BPA degradation is significantly better. The activation of hydrogen peroxide with S / Fe 0.025, S / Fe 0.05, S / Fe 0.1 and S / Fe 0.2 can completely remove BPA from the simulated wastewater after 15 minutes of treatment. Relatively speaking, the activation of hydrogen peroxide with S / Fe 0.05, S / Fe 0.1 and S / Fe 0.2 has a higher BPA removal efficiency, and can completely remove BPA from the simulated wastewater after 10 minutes of treatment.

[0067] Example 4

[0068] In this embodiment, the differences in electron transfer capabilities of zero-valent iron (ZVI) and sulfur quantum dot-modified ZVI with different sulfur-iron molar ratios were investigated by analyzing electrochemical impedance spectroscopy and Tafel curves.

[0069] Five aliquots of a mixture were prepared by thoroughly mixing 0.4 mL of methanol with 30 μL of Nafion. 10 mg of ZVI, S / Fe 0.025, S / Fe 0.05, S / Fe 0.1, and S / Fe 0.2 were added to each aliquot, respectively. The mixtures were then ultrasonically dispersed for 20 min. The resulting slurries were uniformly coated onto a glassy carbon electrode, which served as the working electrode. A platinum wire electrode and a silver / silver chloride electrode were used as the auxiliary and reference electrodes, respectively. Electrochemical impedance spectroscopy and Tafel curves were recorded on an electrochemical workstation at a scan rate of 0.05 V / s using a 0.5 mol / L sodium sulfate solution as the electrolyte.

[0070] Electrochemical impedance spectroscopy and Tafel curves of ZVI and sulfur quantum dot-modified zero-valent iron with different sulfur-iron molar ratios are shown below. Figure 5 Figures (a) and (b) show the results. Based on the electrochemical impedance spectroscopy and Tafel curves, it can be determined that with the increase of the sulfur-iron molar ratio, the semicircle diameter of the electrochemical impedance spectrum of sulfur quantum dot-modified zero-valent iron decreases and the self-corrosion voltage in the Tafel curve increases, indicating that the electron transfer ability of sulfur quantum dot-modified zero-valent iron is enhanced with the increase of the sulfur-iron molar ratio.

[0071] Example 5

[0072] In this embodiment, the removal capacity of zero-valent iron (ZVI) and sulfur quantum dot-modified zero-valent iron activated hydrogen peroxide for BPA removal in simulated wastewater with different pH values ​​was investigated.

[0073] BPA was dissolved in deionized water to prepare a BPA solution with a concentration of 10 μmol / L. The pH of the BPA solution was adjusted to 3.0, 5.0, 6.0, 7.0 and 9.0 respectively to obtain a series of simulated wastewater with different pH values.

[0074] Two portions of simulated wastewater were taken. ZVI and S / Fe0.2 prepared in Example 1 were added to the simulated wastewater at each pH value, followed by hydrogen peroxide. The wastewater was treated for 15 min under stirring. The amounts of ZVI and S / Fe0.2 added were controlled so that the concentrations of ZVI and S / Fe0.2 in the simulated wastewater were both 0.1 g / L, and the amount of hydrogen peroxide added was controlled so that the concentration of hydrogen peroxide in the simulated wastewater was 1 mmol / L. During the wastewater treatment, samples were taken at 0 min, 1 min, 3 min, 5 min, 7 min, 10 min, and 15 min, filtered through a 0.22 μm polyethersulfone membrane, and the concentration C of BPA was measured. The initial concentration of BPA was recorded as C0. The change of C / C0 with wastewater treatment time under each pH value was calculated, and the results are shown below. Figure 6 As shown.

[0075] Figure 6 Figures (a) and (b) show the changes in C / C ratio with wastewater treatment time when zero-valent iron is modified with sulfur quantum dots and hydrogen peroxide is activated with ZVI to degrade BPA in simulated wastewater at different pH values. Figure 6 It is evident that when the pH of the simulated wastewater is between 3.0 and 9.0, the removal capacity of the sulfur quantum dot-modified zero-valent iron / hydrogen peroxide system for BPA is higher than that of the zero-valent iron / hydrogen peroxide system under the corresponding pH conditions. The sulfur quantum dot-modified zero-valent iron / hydrogen peroxide system achieves a BPA removal rate of over 90% in simulated wastewater with pH between 3.0 and 7.0, over 95% in simulated wastewater with pH between 3.0 and 6.0, and 100% in simulated wastewater with pH between 3.0 and 5.0. This demonstrates that when using the sulfur quantum dot-modified zero-valent iron activated hydrogen peroxide of this invention to degrade pollutants in wastewater, it exhibits excellent degradation effects on pollutants in wastewater with pH values ​​between 3.0 and 9.0, overcoming the limitation of the narrow pH application range of existing zero-valent iron / hydrogen peroxide systems.

[0076] Example 6

[0077] In this embodiment, the effects of zero-valent iron (ZVI), sulfur quantum dot modified zero-valent iron, and hydrogen peroxide dosage on BPA removal efficiency were investigated.

[0078] BPA was dissolved in deionized water to prepare a BPA solution with a concentration of 10 μmol / L. The pH of the BPA solution was adjusted to 5.0 to obtain simulated wastewater.

[0079] The S / Fe 0.2 prepared in Example 1 was added to simulated wastewater, followed by hydrogen peroxide. The wastewater was treated for 15 min under stirring. During the wastewater treatment, samples were taken at 0 min, 1 min, 3 min, 5 min, 7 min, 10 min, and 15 min, filtered through a 0.22 μm polyethersulfone membrane, and the concentration C of BPA was measured. The initial concentration of BPA was recorded as C0, and the change of C / C0 with wastewater treatment time was calculated. Three sets of experiments were set up, as follows:

[0080] Group 1 experiment: The amount of S / Fe 0.2 added was controlled so that its concentration in the simulated wastewater was 0.05 g / L, and the amount of hydrogen peroxide added was controlled so that its concentration in the simulated wastewater was 0.5 mmol / L, 0.8 mmol / L, 1 mmol / L and 2 mmol / L, respectively;

[0081] Group 2 experiment: The amount of S / Fe 0.2 added was controlled so that its concentration in the simulated wastewater was 0.1 g / L, and the amount of hydrogen peroxide added was controlled so that its concentration in the simulated wastewater was 0.5 mmol / L, 0.8 mmol / L, 1 mmol / L and 2 mmol / L, respectively;

[0082] Group 3 experiment: The amount of S / Fe 0.2 added was controlled so that its concentration in the simulated wastewater was 0.2 g / L, and the amount of hydrogen peroxide added was controlled so that its concentration in the simulated wastewater was 0.5 mmol / L, 0.8 mmol / L, 1 mmol / L and 2 mmol / L.

[0083] The changes in C / C0 with wastewater treatment time in experiments 1 through 3 are as follows: Figure 7 As shown in Figures (a), (b), and (c), it can be seen that when the concentration of S / Fe 0.2 in the simulated wastewater is 0.05–0.2 g / L, the removal rate of BPA by the sulfur quantum dot modified zero-valent iron / hydrogen peroxide system increases with the increase of hydrogen peroxide dosage. When the dosage of hydrogen peroxide in the simulated wastewater is 1–2 mmol / L, BPA in the simulated wastewater can be completely removed. When the amount of hydrogen peroxide is the same, the removal rate of BPA is significantly enhanced with the increase of S / Fe 0.2 dosage.

[0084] Example 7

[0085] In this embodiment, the removal capabilities of zero-valent iron (ZVI) and sulfur quantum dot-modified zero-valent iron activated hydrogen peroxide for different types of pollutants were investigated.

[0086] The pollutants sodium diclofenac, naproxen, sulfamethoxazole, nitrobenzene, phenol, ofloxacin, and norfloxacin were dissolved in deionized water to prepare pollutant solutions with a concentration of 10 μmol / L. The pH of the pollutant solutions was then adjusted to 5.0 to obtain a series of simulated wastewaters.

[0087] ZVI and S / Fe 0.2 prepared in Example 1 were added to each simulated wastewater, followed by hydrogen peroxide. The wastewater was treated for 15 min under stirring. The amounts of ZVI and S / Fe 0.2 added were controlled so that their concentrations in the simulated wastewater were both 0.1 g / L, and the amount of hydrogen peroxide added was controlled so that its concentration was 1 mmol / L. During the wastewater treatment, samples were taken at 0 min, 1 min, 3 min, 5 min, 7 min, 10 min, and 15 min, filtered through a 0.22 μm polyethersulfone membrane, and the concentration C of the pollutants was measured. The initial concentration of the pollutants was recorded as C0, and the change of C / C0 with the wastewater treatment time was calculated. The results are shown below. Figure 8 As shown.

[0088] Figure 8 Figures (a) and (b) respectively represent the changes in C / C ratio of different pollutants with wastewater treatment time when using sulfur quantum dots modified with zero-valent iron and ZVI-activated hydrogen peroxide prepared in Example 1. Figure 8 It was found that when the pollutants in the simulated wastewater were sodium diclofenac, naproxen, sulfamethoxazole, nitrobenzene, phenol, ofloxacin, and norfloxacin, the sulfur quantum dot-modified zero-valent iron / hydrogen peroxide system showed significantly higher removal rates for these pollutants compared to the zero-valent iron / hydrogen peroxide system. After 15 minutes of treatment, the removal rates for these pollutants all reached over 85%. This indicates that the sulfur quantum dot-modified zero-valent iron activated hydrogen peroxide provided by this invention has excellent degradation effects on wastewater containing different types of pollutants.

[0089] Example 8

[0090] In this embodiment, the treatment effect of sulfur quantum dot modified zero-valent iron on nitrophenol industrial wastewater was investigated.

[0091] Nitrophenol industrial wastewater with pH adjusted to 5 was used as the treatment target.

[0092] S / Fe 0.2 prepared in Example 1 was added to nitrophenol industrial wastewater, followed by hydrogen peroxide. The wastewater was treated for 2 hours under stirring. The amount of S / Fe 0.2 added was controlled to achieve a concentration of 0.2 g / L in the simulated wastewater, and the amount of hydrogen peroxide added was controlled to achieve a concentration of 2 mmol / L in the simulated wastewater. During the wastewater treatment, samples were taken at 0 min, 30 min, 60 min, 90 min, and 120 min, filtered through a 0.45 μm polyethersulfone membrane, and the COD and TOC of the wastewater were measured. The COD and TOC removal rates were calculated based on the initial COD and TOC of the wastewater.

[0093] The removal rates of COD and TOC in sulfur quantum dot-modified zero-valent iron p-nitrophenol industrial wastewater are as follows: Figure 9 As shown. By Figure 9 It is evident that sulfur quantum dot-modified zero-valent iron exhibits excellent performance in treating nitrophenol industrial wastewater. After 120 minutes of reaction, the COD removal rate of the wastewater was 90.7%, and the TOC removal rate was 88.5%. This demonstrates that sulfur quantum dot-modified zero-valent iron also exhibits excellent performance when activating hydrogen peroxide using the sulfur quantum dot-modified zero-valent iron described in this invention to treat actual wastewater.

[0094] Example 9

[0095] In this embodiment, a series of zero-valent iron modified with different sulfur quantum dots were prepared.

[0096] The operation in this embodiment is basically the same as in embodiment 1, except that experimental groups numbered ① to ⑩ are set up. The only difference between each numbered experimental group and those in embodiment 1 is that:

[0097] ①The sulfur source in step (1) is sublimed sulfur and adjusted to sodium sulfide, thiosulfate or dithionite to prepare a series of sulfur quantum dot modified zero-valent iron with different sulfur sources.

[0098] ② The passivating agent polyethylene glycol 6000 in step (1) is adjusted to polyethylene glycol 400, propynyl alcohol, polyvinylpyrrolidone or sodium poly-4-styrene sulfonate to prepare a series of sulfur quantum dot modified zero-valent iron with different passivating agents.

[0099] ③ Adjust the mass ratio of sulfur source, deionized water, sodium hydroxide and polyethylene glycol 6000 in step (1) to 224:500:120:0.81 or 28:3000:240:2.43 to prepare a series of sulfur quantum dot modified zero-valent iron with different sulfur point preparation raw material ratios;

[0100] ④ Adjust the sulfur point preparation temperature in step (1) to 90℃ or 120℃ to prepare a series of sulfur quantum dot modified zero-valent iron with different sulfur point preparation temperatures.

[0101] ⑤ Adjust the volume ratio of the sulfur point solution in step (1) to hydrogen peroxide with a concentration of 7.5 wt% to 1:2 or 1:1 to prepare a series of sulfur quantum dot modified zero-valent iron with different volume ratios of sulfur point solution to hydrogen peroxide.

[0102] ⑥ Adjust the mass fraction of hydrogen peroxide in step (1) to 2% or 20% to prepare a series of sulfur quantum dot modified zero-valent iron with different mass fractions of hydrogen peroxide.

[0103] ⑦ The mixing and stirring time of the sulfur point solution in step (1) with hydrogen peroxide at a concentration of 7.5 wt% was adjusted to 15 min or 60 min to prepare a series of sulfur quantum dot modified zero-valent iron with different mixing and stirring times of sulfur point solution and hydrogen peroxide.

[0104] ⑧ Adjust the reaction temperature of the sulfur quantum dot solution with zero-valent iron in step (2) to 60℃ or 90℃ to prepare a series of sulfur quantum dot modified zero-valent iron with different reaction temperatures of sulfur quantum dot solution with zero-valent iron.

[0105] ⑨ The reaction time of the sulfur quantum dot solution with zero-valent iron in step (2) was adjusted to 5h or 8h to prepare a series of sulfur quantum dot modified zero-valent iron with different reaction times of sulfur quantum dot solution with zero-valent iron.

[0106] ⑩ The reaction time of micron-sized zero-valent iron in step (2) was adjusted to that of nano-sized zero-valent iron with a particle size of 500 nm to prepare sulfur quantum dot-modified zero-valent iron with different particle sizes.

[0107] The following investigation examines the ability of different sulfur quantum dots prepared in Examples 1 and 9 to degrade BPA using zero-valent iron activated hydrogen peroxide.

[0108] BPA was dissolved in deionized water to prepare a BPA solution with a concentration of 10 μmol / L. The pH of the BPA solution was adjusted to 5.0 to obtain simulated wastewater.

[0109] Simulated wastewater was collected, and sulfur quantum dot-modified zero-valent iron (FeO) prepared in experimental groups ① to ⑩ was added to each group, followed by hydrogen peroxide. The wastewater was treated for 15 minutes under stirring. The amount of different sulfur quantum dot-modified FeO was controlled to ensure that the concentration of different amounts of FeO in the simulated wastewater was 0.1 g / L, and the amount of hydrogen peroxide was controlled to ensure that the concentration of hydrogen peroxide in the simulated wastewater was 1 mmol / L. During the wastewater treatment, samples were taken at 0 min, 1 min, 3 min, 5 min, 7 min, 10 min, and 15 min, filtered through a 0.22 μm polyethersulfone membrane, and the concentration C of BPA was measured. The initial concentration of BPA was recorded as C0, and the change of C / C0 with the wastewater treatment time was calculated. The results are shown below. Figure 10 , 11 As shown in Figure 12.

[0110] Figure 10 Figures (a), (b), (c), and (d) respectively represent the changes in the C / C ratio of BPA with wastewater treatment time when sulfur quantum dot-modified zero-valent iron activated hydrogen peroxide was prepared using different sulfur sources, passivating agents, sulfur point preparation raw material ratios, and sulfur point preparation temperatures in Examples 1 and 9. Figure 10 It is known that when sulfur quantum dots modified with zero-valent iron activated hydrogen peroxide degrade BPA using different sulfur sources, passivating agents, sulfur point preparation raw material ratios, and sulfur point preparation temperatures, the BPA removal rate can reach over 90%. Among them, sulfur quantum dots modified with zero-valent iron activated hydrogen peroxide using different sulfur point preparation raw material ratios and sulfur point preparation temperatures can completely remove BPA. Sulfur quantum dots modified with zero-valent iron activated hydrogen peroxide using polyethylene glycol 400 and polyethylene glycol 6000, as well as sulfur quantum dots modified with sodium sulfide and sublimed sulfur as sulfur sources, can also completely remove BPA.

[0111] Figure 11 Figures (a), (b), and (c) respectively represent the changes in the C / C ratio of BPA with wastewater treatment time when sulfur quantum dot-modified zero-valent iron activated hydrogen peroxide was prepared using different volume ratios of sulfur point solution to hydrogen peroxide, hydrogen peroxide mass fractions, and mixing times of sulfur point solution and hydrogen peroxide as described in Examples 1 and 9. Figure 11 It can be seen that when sulfur quantum dot-modified zero-valent iron activated hydrogen peroxide is used to degrade BPA with different sulfur point to hydrogen peroxide volume ratios, hydrogen peroxide mass fractions, and sulfur point to hydrogen peroxide mixing times, the removal rate of BPA can reach over 95%. Among them, sulfur quantum dot-modified zero-valent iron activated hydrogen peroxide prepared with different sulfur point to hydrogen peroxide mixing times can completely remove BPA. Sulfur quantum dot-modified zero-valent iron activated hydrogen peroxide prepared with sulfur point to hydrogen peroxide volume ratios of 1:1.33 and 1:1, as well as with a hydrogen peroxide mass fraction of 7.5%, can also completely remove BPA.

[0112] Figure 12 Figures (a), (b), and (c) respectively represent the changes in the C / C ratio of BPA with wastewater treatment time when sulfur quantum dot-modified zero-valent iron activated hydrogen peroxide was prepared using different reaction temperatures, reaction times, and zero-valent iron particle sizes of sulfur quantum dot solutions and zero-valent iron, as described in Examples 1 and 9. Figure 12It can be seen that when sulfur quantum dot-modified zero-valent iron activated hydrogen peroxide is used to degrade BPA with different reaction temperatures, reaction times, and zero-valent iron particle sizes, the removal rate of BPA can reach over 95%. Among them, when sulfur quantum dot-modified zero-valent iron activated hydrogen peroxide is used to degrade BPA with different reaction times and zero-valent iron particle sizes, BPA can be completely removed. When sulfur quantum dot-modified zero-valent iron activated hydrogen peroxide is used to degrade BPA with different reaction temperatures of sulfur quantum dot solution and zero-valent iron (70℃ and 120℃), BPA can also be completely removed.

[0113] Example 10

[0114] In this embodiment, the removal capacity of sulfur quantum dot-modified zero-valent iron activated by different oxidants, including hydrogen peroxide, ozone, potassium persulfate, and potassium perdisulfate, for BPA removal from simulated wastewater was investigated.

[0115] BPA was dissolved in deionized water to prepare a BPA solution with a concentration of 10 μmol / L. The pH of the BPA solution was adjusted to 5.0 to obtain simulated wastewater.

[0116] Four portions of simulated wastewater were taken, and S / Fe 0.2 prepared in Example 1 was added to each portion, followed by hydrogen peroxide, ozone, potassium persulfate, and potassium persulfate. The wastewater was treated for 15 minutes under stirring. The amount of S / Fe 0.2 added was controlled so that its concentration in the simulated wastewater was 0.1 g / L. The amounts of hydrogen peroxide, potassium persulfate, and potassium persulfate added were controlled so that their concentrations in the simulated wastewater were 1 mmol / L. The amount of ozone added was controlled so that its concentration in the simulated wastewater was 50 mg / L. During the wastewater treatment, samples were taken at 0 min, 1 min, 3 min, 5 min, 7 min, 10 min, and 15 min, filtered through a 0.22 μm polyethersulfone membrane, and the concentration C of BPA was measured. The initial concentration of BPA was recorded as C0. The change of C / C0 with wastewater treatment time under different oxidants was calculated, and the results are shown below. Figure 13 As shown.

[0117] Figure 13 This section describes the change in C / C ratio over time when hydrogen peroxide, ozone, potassium persulfate, and potassium perdisulfate are activated using sulfur quantum dot-modified zero-valent iron to degrade BPA in simulated wastewater. Figure 12It can be seen that the sulfur quantum dot-modified zero-valent iron / oxidant system achieved a removal rate of over 90% for BPA in simulated wastewater, while the sulfur quantum dot-modified zero-valent iron / hydrogen peroxide system and the sulfur quantum dot-modified zero-valent iron / potassium persulfate system achieved a removal rate of 100% for BPA in simulated wastewater. This indicates that the sulfur quantum dot-modified zero-valent iron of this invention exhibits excellent degradation effects when activating different oxidants to degrade pollutants in wastewater.

Claims

1. A sulfur quantum dot-modified zero-valent iron, characterized in that, The modified zero-valent iron consists of zero-valent iron and sulfur quantum dots loaded on the surface of the zero-valent iron. The sulfur quantum dots are uniformly and discretely distributed on the surface of the zero-valent iron. The mass content of sulfur quantum dots in the modified zero-valent iron is 0.08%~0.61%. This modified zero-valent iron was prepared by the following method: (1) Mix the sulfur source, water, sodium hydroxide or potassium hydroxide, and passivating agent thoroughly at 70~120 °C to obtain a sulfur point solution; The sulfur point solution was mixed with the hydrogen peroxide solution and reacted under stirring for 15-60 min to obtain the sulfur quantum dot solution. When preparing the sulfur point solution, the mass ratio of sulfur source, water, sodium hydroxide or potassium hydroxide, and passivating agent is controlled to be (28~224):(500~3000):(120~240):(0.81~2.43); the passivating agent is polyethylene glycol 6000; when preparing the sulfur quantum dot solution, the volume ratio of sulfur point solution to hydrogen peroxide solution is controlled to be 1:(1~2), and the mass fraction of hydrogen peroxide solution is 2%~20%. (2) Adjust the pH of the sulfur quantum dot solution to 5~8. Mix the sulfur quantum dot solution with zero-valent iron according to the molar ratio of sulfur quantum dots to zero-valent iron of (0.025~0.2):

1. React fully at 60~90 °C. Wash the resulting reaction product with water. Collect the sulfur quantum dot-modified zero-valent iron in the reaction product with a magnet and dry it.

2. The sulfur quantum dot modified zero-valent iron according to claim 1, characterized in that, The zero-valent iron is micron-sized zero-valent iron with a particle size of micrometers or nano-sized zero-valent iron with a particle size of nanometers.

3. The sulfur quantum dot modified zero-valent iron according to claim 1, characterized in that, In step (2), the reaction is carried out at 60~90 ℃ for 5~8 h.

4. The sulfur quantum dot modified zero-valent iron according to claim 1, characterized in that, The sulfur source is sublimed sulfur, sodium sulfide, thiosulfate, or dithionite.

5. The application of sulfur quantum dot modified zero-valent iron as described in claim 1 or 2 in the degradation of organic pollutants by activated oxidants, wherein sulfur quantum dot modified zero-valent iron and oxidants are added to wastewater containing organic pollutants, the pH of the wastewater is controlled at 3-7 for wastewater treatment, and the dosage of sulfur quantum dot modified zero-valent iron and oxidants is controlled so that the concentration of sulfur quantum dot modified zero-valent iron in the wastewater is 0.3-0.8 g / L, and the concentration of oxidants in the wastewater is 1-10 mmol / L; wherein the oxidants include at least one of hydrogen peroxide, ozone, and persulfate.

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