Serine grafted sulfidized nano zero-valent iron material, and preparation method and application thereof

Abstract

The application provides a serine grafted sulfidized nano zero-valent iron material and a preparation method and application thereof, the preparation method of the material is as follows: potassium borohydride solution in which a sulfidizing agent is dissolved is added dropwise into a ferrous sulfate solution, stirring and mixing are performed to carry out a sulfidization reaction and a liquid phase reduction reaction, and sulfidized nano zero-valent iron is obtained; the sulfidized nano zero-valent iron is washed with pure water and ethanol, a serine solution is added to carry out a grafting reaction, and the serine grafted sulfidized nano zero-valent iron material is obtained. The catalyst material is prepared by sulfidization modification and serine grafting, has low thermal conductivity and high specific heat capacity, can inhibit local overheating, particle agglomeration and Fe 0 rapid oxidation. The material is applied to heterogeneous Fenton-like catalytic degradation of organic solvents, and the method has the advantages of simple process, mild conditions, high volume reduction rate, no interference of radionuclides, and suitability for safe disposal of waste organic solvents in nuclear fuel reprocessing, and has a good engineering application prospect.

Description

Technical Field

[0001] This invention belongs to the field of functional composite materials technology, specifically relating to a serine-grafted sulfurized nanomaterial of zero valent iron, its preparation method, and its application. Background Technology

[0002] Nuclear energy is a high-potential energy source that can replace dwindling fossil fuels. Nuclear power plants are characterized by stable and reliable operation, long refueling cycles, and are well-suited for base load management and necessary peak shaving in my country's large power grids. With the rapid development of nuclear power, the safe handling and disposal of spent nuclear fuel has attracted widespread attention. Tributyl phosphate (TBP) is the most commonly used solvent in liquid-liquid extraction for nuclear fuel reprocessing due to its excellent extraction properties for uranium (U) and plutonium (Pu). In the PUREX process, spent nuclear fuel is dissolved in nitric acid to form uranium nitrate and plutonium nitrate, which are then mixed with an organic extraction solution containing TBP and a hydrocarbon diluent. Currently, the most common diluent is n-dodecane, with a volume of 70%. During mixing, TBP molecules selectively form complexes with actinides, separating these actinides from other metals present. With increasing usage time, TBP undergoes various chemical and radiation-induced transformations during solvent extraction, primarily due to hydrolysis and radiation reactions. Over time, these transformations lead to the degradation of the solvent phase, thereby reducing extraction efficiency. After several cycles, the solvent phase undergoes significant degradation and is no longer suitable for further processing of uranium and plutonium recovered from the dissolution solution. Subsequently, the degraded solvent phase is stored as organic waste. Because TBP is a stable compound that can persist in soil and water for extended periods, it must be properly treated before safe disposal.

[0003] The Fenton oxidation process has advantages such as low reaction temperature, high efficiency, low cost, and no harmful gas emissions, and is widely used in the treatment of various recalcitrant organic compounds. Traditional homogeneous Fenton oxidation relies on H₂O₂ and Fe₂O₃. 2+ The catalyst generates hydroxyl radicals (•OH). However, this process can only be carried out at low pH, requires a large amount of reagent solution, and results in the formation of a large amount of iron sludge. In contrast, the heterogeneous Fenton method can alleviate some of the limitations of the homogeneous Fenton process. Nano-zero valent iron (nZVI) has a high specific surface area, excellent catalytic activity, and significant adsorption properties, making it an excellent catalyst for the heterogeneous Fenton reaction.

[0004] Existing technologies have developed amino acid-modified nano-zero-valent iron materials (such as CN202110597633.5), which utilize the amino and carboxyl functional groups of amino acids to enhance the dispersibility and interfacial interaction of nano-zero-valent iron particles in the reaction solution, achieving electrostatic interaction between amino acids and zero-valent iron. However, this type of modified material still has core defects: the surface of the nano-zero-valent iron is not modified, the grafting efficiency of directly grafting amino acids is low, and the thermal properties of the nano-zero-valent iron itself (high thermal conductivity, low specific heat capacity) are not improved. In Fenton-like reactions, local overheating, particle agglomeration, and surface oxidation problems are prone to occur. Especially in the nitric acid oxygen-rich system of nuclear fuel reprocessing, an iron (hydrogen) oxide passivation layer easily forms on the surface of the nano-zero-valent iron, hindering electron transfer and Fe. 2+ The continuous release of TBP results in limited catalytic degradation efficiency of organic solvents such as TBP.

[0005] The thermal conductivity and specific heat capacity of nano-zero ferric iron have significant defects, which severely restrict its catalytic performance. On the one hand, the high thermal conductivity of nano-zero ferric iron leads to rapid accumulation of local exothermic heat during the Fenton reaction. This not only exacerbates the thermal aggregation between nanoparticles, significantly reducing the specific surface area and the number of active sites, but also accelerates the oxidation process on the particle surface, resulting in a significant decrease in reactivity. On the other hand, the low specific heat capacity of nano-zero ferric iron cannot effectively buffer the temperature fluctuations of the reaction system, making it difficult to maintain the stable thermal environment required for the efficient generation of •OH. Especially when dealing with systems with complex heat transfer characteristics, such as organic solvents, insufficient temperature stability will further reduce catalytic efficiency and reaction controllability. In addition, although existing technologies include sulfidation-based zero-valent iron modification technology (such as CN202411597016.5), which mainly solves the problems of zero-valent iron oxidation passivation and low electron transfer efficiency through sulfidation modification, there is no technical solution that combines sulfidation modification with serine grafting. Nor has there been a solution that addresses the degradation requirements of TBP-type organic solvents in nuclear fuel reprocessing by utilizing sulfidation modification to regulate the thermal properties of nano-zero-valent iron, improve serine grafting efficiency, and achieve synergistic improvement of catalytic and adsorption performance.

[0006] Therefore, it is urgent to carry out composite modification of nano-zero valent iron by sulfidation and serine grafting to solve the problems of low grafting efficiency, poor thermal properties, and easy passivation in nitric acid system of existing amino acid-modified nano-zero valent iron. At the same time, it is necessary to overcome the defects of insufficient adsorption and catalytic synergy of pure sulfidated zero valent iron for organic solvents and improve its degradation performance of TBP-type organic solvents in nuclear fuel reprocessing. Summary of the Invention

[0007] The purpose of this invention is to overcome the defects of the prior art and address the problems of low grafting efficiency, poor thermal properties, easy passivation in nitric acid system, and insufficient synergistic effect of simple sulfided zero-valent iron on organic solvent adsorption and catalysis of existing amino acid modified nano-zero-valent iron materials (CN202110597633.5). This invention provides a serine-grafted sulfided nano-zero-valent iron material, its preparation method, and its application.

[0008] This invention provides the following technical solution:

[0009] This invention provides a method for preparing serine-grafted sulfidated nano-zero valent iron material, comprising the following steps: adding a potassium borohydride solution containing a sulfidating agent dropwise to a ferrous sulfate solution, stirring and mixing to carry out a sulfidation reaction and a liquid-phase reduction reaction, thereby obtaining sulfidated nano-zero valent iron;

[0010] Sulfide nano-zero valent iron was washed with pure water and ethanol, and then a serine solution was added to carry out a grafting reaction to obtain serine-grafted sulfide nano-zero valent iron material.

[0011] The serine-grafted sulfidated nanomaterials of zero-valent iron prepared by this invention are produced through a two-step process of sulfidation modification and serine grafting. They exhibit low thermal conductivity and high specific heat capacity, and can inhibit localized overheating and particle agglomeration, thus delaying the degradation of Fe. 0 Oxidative passivation, and accelerated Fe through the FeS active phase 3+ / Fe 2+ The cycle enhances the efficiency of hydroxyl radical generation, enabling efficient degradation of organic solvents (including radioactive elements).

[0012] This invention achieves several technical advantages through a composite modification of nano-zero-valent iron by first sulfidation and then serine grafting: 1) Sulfidation modification forms a FeS modified layer on the surface of nano-zero-valent iron, regulating the distribution of surface charge and functional groups, significantly improving the grafting efficiency of serine, and solving the problem of low efficiency in direct grafting in existing technologies; 2) The FeS modified layer can effectively reduce the thermal conductivity of the material, increase the specific heat capacity, avoid side reactions caused by local overheating during the reaction process, improve the thermal buffering capacity of the material, and simultaneously slow down the Fe... 0 Rapid oxidation inhibits the formation of the iron (hydrogen) oxide passivation layer in the nitric acid oxygen-rich system, thus prolonging the Fe... 0 As Fe 2+ 3) The added S element can also enhance the continuous release capability of the ion source; 3+ To Fe 2+ 4) Serine grafting and sulfur modification synergistically enhance the adsorption performance of materials for organic solvents, making it easier for organic solvents to accumulate on the surface of materials and increasing the probability of reaction between hydroxyl radicals and organic solvents.

[0013] Furthermore, by improving the overall process design and preparation conditions of the preparation method, this invention yields serine-grafted sulfurized nano-zero-valent iron materials with low thermal conductivity and high specific heat capacity. This material successfully prevents the aggregation of nanoparticles, resulting in a large specific surface area and porosity. It also enhances the material's catalytic degradation ability through modification and improves its adsorption performance on organic solvents.

[0014] Furthermore, the sulfur-iron molar ratio of the sulfur in the vulcanizing agent to the iron in the ferrous sulfate solution is 0.1-0.3.

[0015] Furthermore, the sulfiding agent is selected from one or more of sodium dithionite, sodium sulfide, potassium sulfide, and sodium thiosulfate; the concentration of the ferrous sulfate solution is 0.2-0.6 mol / L, the concentration of the potassium borohydride solution is 1-3 mol / L, and the concentration of the serine solution is 5-10 g / L.

[0016] The present invention also provides a serine-grafted sulfurized nano-zero-valent iron material prepared by the above preparation method.

[0017] The serine-grafted sulfurized nano-zero-valent iron material prepared in this invention has a thermal conductivity that is ≥30% lower and a specific heat capacity that is ≥2.0 times higher than that of unmodified nano-zero-valent iron. It also has a thermal buffering capacity in catalytic reactions, reducing iron dissolution and activity decay.

[0018] The present invention relates to the application of the serine-grafted sulfurized nano-zero-valent iron material prepared above in the heterogeneous Fenton-like catalytic degradation of organic solvents.

[0019] Further, the application includes the following steps: adding serine-grafted sulfurized nano-zero-valent iron material to an organic solvent, then adding hydrogen peroxide solution and an acidifying agent dropwise, and controlling the reaction temperature using a constant-temperature water bath to achieve the catalytic degradation of the organic solvent.

[0020] Furthermore, the organic solvent is a mixture of tributyl phosphate and n-dodecane in a ratio of 3:7. The organic solvent may contain uranium nuclides, and the catalytic degradation process is not affected by the uranium nuclides.

[0021] Furthermore, the mass ratio of serine-grafted sulfurized nano-zero-valent iron material to organic solvent is (0.2–1.0):10.

[0022] Furthermore, the volume fraction of H2O2 in the hydrogen peroxide solution is 30%, and the volume ratio of hydrogen peroxide solution to organic solvent is (100-250):10.

[0023] Further, the acidifying agent is a nitric acid or sulfuric acid solution with a concentration of 0.1-10 mol / L and a volume ratio of (15-50):10 with the organic solvent.

[0024] Furthermore, the reaction temperature is 80℃-98℃.

[0025] The present invention has the following beneficial effects:

[0026] 1. The serine-grafted sulfurized nanomaterial of zero-valent iron prepared in this invention exhibits low thermal conductivity and high specific heat capacity. During the Fenton-like reaction, it avoids side reactions caused by localized overheating, enhances the material's thermal buffering capacity, and strengthens its inherent stability. The low thermal conductivity reduces the temperature gradient on the material surface, minimizing high-temperature exposure of surface active sites, thereby mitigating the effects of Fe... 0 To Fe 2+ Fe 3+ Excessive oxidation reduces the dissolution of Fe in the reaction solution and prolongs the catalyst's lifespan.

[0027] 2. This invention modifies the material to form a FeS layer on the surface. The generated FeS also participates in a Fenton-like reaction cycle, accelerating the Fe... 3+ To Fe 2+ The transformation accelerates the Fenton-like reaction cycle, leading to an increase in the quantity and efficiency of •OH generated, resulting in more •OH and ultimately improving the degradation effect of organic solvents.

[0028] 3. This invention improves the material's adsorption capacity for organic solvents through modification. During the reaction, the organic solvent is located above the aqueous phase, while the catalyst material is deposited at the bottom of the aqueous phase. The catalyst material adsorbs more organic solvents onto the material surface, making it easier for the hydroxyl radicals generated by the Fenton reaction to react with the organic solvents on the material surface rather than with the organic solvents above the aqueous phase, thereby improving the degradation efficiency of organic solvents.

[0029] 4. Compared with nano-zero valent iron, the serine-grafted sulfur nano-zero valent iron material prepared by this invention has lower thermal conductivity and larger specific heat capacity. While having good adsorption performance, its ability to oxidize and degrade organic solvents is also particularly outstanding. When using the material of this invention to treat organic solvents, it can achieve a 90% organic matter volume reduction rate while having a good COD removal effect. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1This is the EDS spectrum of Ser-SnZVI prepared in Example 1 of this invention;

[0032] Figure 2 The Ser-SnZVI and nZVI prepared in Example 1 of this invention are Fe, which are similar to Fenton's process of degrading organic solvents. 2+ concentration;

[0033] Figure 3 These are the ESR spectra of the Ser-SnZVI / H2O2 system and the nZVI / H2O2 system prepared in Example 1 of this invention;

[0034] Figure 4 These are XPS spectra of the Ser-SnZVI prepared in Example 1 of this invention before and after adsorption of organic solvent. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, 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.

[0036] This invention provides a serine-grafted sulfidated nano-zero-valent iron material, its preparation method, and its applications. By sulfidating the nano-zero-valent iron, its thermal conductivity and specific heat capacity are optimized—by constructing a sulfidation modification layer, the material's heat transfer efficiency is controlled, reducing the risk of local overheating and inhibiting agglomeration and oxidation; simultaneously, the material's specific heat capacity is increased, enhancing its heat buffering capacity to stabilize the reaction temperature. Furthermore, the addition of nitric acid during spent fuel processing can easily passivate the surface of the nano-zero-valent iron, hindering Fe... 0 The key issue in further participating in Fenton-like reactions is that the sulfur element introduced by sulfidation modification can preferentially react with nitric acid, fundamentally preventing the formation of a passivation layer on the material surface and ensuring the protection of Fe. 0 The reactivity of the material was improved. Based on this, the surface properties of the material were further enhanced to improve the grafting performance of serine. Finally, characterization demonstrated that the modified material exhibited improved adsorption capacity for organic solvents, ensuring the efficient and stable conduct of the heterogeneous Fenton catalytic reaction.

[0037] The sulfur-modified nano-zero-valent iron material with low thermal conductivity and high specific heat capacity prepared in this invention catalyzes the degradation of organic solvents. The principle is as follows: the Fenton-like reaction mainly generates •OH through the chain process described in formulas (1) and (2). Since the reaction constant of formula (4) is relatively small, it indicates that this reaction is the key reaction controlling the •OH generation efficiency. 3+ To Fe 2+The slow conversion of Fe limits the efficiency of •OH formation. However, the presence of FeS can accelerate Fe... 3+ To Fe 2+ The conversion (see equations (3)-(5)) improves the overall efficiency of •OH generation. In summary, FeS generated in the modified material participates in the Fenton-like reaction cycle, resulting in the generation of more •OH during the degradation process and an increased •OH generation rate, thereby enhancing the degradation effect.

[0038] <![CDATA[Fe 2+ + H2O2 → Fe 3+ + •OH + HO - ]]> <![CDATA[k= 50-80 mol -1 Ls -1 ]]> (1) <![CDATA[Fe 3+ + H2O2 → Fe 3+ + HO2• + H + ]]> <![CDATA[k= 0.002-0.01 mol -1 Ls -1 ]]> (2) <![CDATA[FeS → Fe 2+ + S 2- ]]> (3) <![CDATA[2Fe 3+ + S 2- → 2Fe 2+ + S 0 ]]> (4) <![CDATA[8Fe 3+ + S 2- + 4H2O → 8Fe 2+ + SO4 2- + 8H + ]]> (5)

[0039] The present invention will be further illustrated below through specific embodiments:

[0040] All raw materials used in the preparation method in the examples were commercially available.

[0041] Example 1:

[0042] The preparation steps of serine-grafted sulfurized nano-zero-valent iron (Ser-SnZVI) in this embodiment are as follows: First, 100 mL of 0.4 mol / L FeSO4·7H2O solution was added to a reaction vessel and stirred vigorously. Then, maintaining a flow rate of 2 mL / min, 100 mL of 2 mol / L KBH4 and 0.04 mol / L Na2S2O4 solution was added dropwise to a four-necked flask. After the addition was complete, stirring was continued for 1 h to ensure complete reaction. Subsequently, 50 mL of 5 g / L serine solution was added to the solution, and stirring was continued for 12 h to graft serine onto the material surface. Finally, the material was washed multiple times with deoxygenated water and anhydrous ethanol, pre-frozen, and then freeze-dried in a vacuum freeze-drying oven to obtain Ser-SnZVI.

[0043] Figure 1 This is the X-ray energy dispersive spectroscopy (EDS) spectrum of Ser-SnZVI. The graph shows that S and N elements constitute a large proportion of the serine-grafted sulfurized nano-zero-valent iron, indicating successful sulfurization and successful serine grafting.

[0044] Table 1 shows the thermal conductivity and specific heat capacity of Ser-SnZVI and nZVI, as well as the concentration of Fe in the solution after the degradation of organic solvents by the Fenton-like reaction. As can be seen from the table, compared with nano-zero-valent iron, the thermal conductivity of serine-grafted sulfurized nano-zero-valent iron material decreased by 36%, while the specific heat capacity increased by 2.5 times. When using Ser-SnZVI as a catalyst, the final concentration of Fe dissolved in the solution was lower than when using nZVI as a catalyst, indicating that reducing thermal conductivity and increasing specific heat capacity can indeed slow down the degradation of Fe. 0 To Fe 2 + Fe 3+Excessive oxidation reduces the dissolution of Fe in the reaction solution, thereby extending the catalyst's lifespan.

[0045] Table 1 Thermal conductivity, specific heat capacity, and Fe precipitation concentration after degradation reaction of Ser-SnZVI and nZVI

[0046]

[0047] Figure 2 It is a process similar to Fenton's degradation of organic solvents, where Fe in the solution... 2+ As shown in the figure, when Ser-SnZVI is used as a catalyst, the Fe concentration in the solution is... 2+ Higher concentrations lead to the production of more •OH in the Fenton-like reaction, and the rate of •OH production also increases, resulting in enhanced degradation.

[0048] Figure 3 These are the ESR spectra of the Ser-SnZVI / H2O2 system and the nZVI / H2O2 system, from... Figure 3 It can be seen that, compared to nano-zero-valent iron, the reaction of Ser-SnZVI with H2O2 can generate more hydroxyl radicals, which is consistent with... Figure 2 Fe in 2+ Increased concentration is associated with more hydroxyl radicals, which enhance the degradation performance of organic solvents.

[0049] Figure 4 This is the XPS spectrum of Ser-SnZVI after adsorbing organic solvent in Example 1 of this invention. As shown in the figure, the XPS spectrum of the serine-grafted sulfurized nano-zero-valent iron material after adsorption shows PO peaks or P=O peaks, indicating that the organic solvent can be adsorbed on the surface of the material, which is conducive to the direct reaction of hydroxyl radicals with the organic solvent adsorbed on the surface, thereby improving the degradation effect of the organic solvent.

[0050] Example 2:

[0051] The organic solvent degradation experiment in this embodiment was conducted in a 500 mL four-necked flask placed in a water bath. The water bath temperature was set to 95℃, and 3 mL of tributyl phosphate and 7 mL of n-dodecane were added to the flask. To investigate the degradation effect of radioactive waste organic solvents using different types of catalysts, 0.5 g of nano-zero-valent iron powder and serine-grafted sulfurized nano-zero-valent iron were weighed and added to the flask, and 150 mL of H2O2 (30%) and 15 mL of 1 mol / L nitric acid solution were added dropwise to the flask at a rate of 2 mL / min, respectively. The reaction was started with stirring, and the condensate generated during the reaction was collected using a condenser. The tail gas was absorbed using concentrated sulfuric acid. The chemical oxygen demand (COD) of the aqueous phase was measured at intervals during the reaction. After the reaction was completed for 2 hours, the volume of the remaining organic phase in the four-necked flask and the volume of the condensed organic phase collected by the condenser were measured. The comparison results after the reaction are shown in Table 2.

[0052] Table 2. Effects of different catalyst types on the degradation of radioactive waste organic solvents.

[0053]

[0054] Wherein, the reduction rate (%) = (V 初始有机相 -V 剩余有机相 ) / V 初始有机相 ×100%, oxidation efficiency (%) = (V 初始有机相 -V 剩余有机相 -V 冷凝有机相 ) / V 初始有机相 ×100%.

[0055] As shown in Table 2, the Ser-SnZVI described in this invention, when used as a catalyst for Fenton-like degradation of organic solvents, exhibits superior catalytic degradation performance compared to nano-zero-valent iron. When using Ser-SnZVI, the volume reduction rate of organic matter (oil phase) can reach over 90%, the oxidation efficiency can reach over 50%, the residual chemical oxygen demand (COD) is low, the reaction conditions are mild, and no secondary pollution is generated.

[0056] Example 3:

[0057] The organic solvent degradation experiment in this embodiment was conducted in a 500 mL four-necked flask placed in a water bath. The water bath temperature was set to 95 °C. 3 mL of tributyl phosphate and 7 mL of n-dodecane were added to the flask. 0.5 g of serine-grafted sulfide nano-zero-valent iron was also weighed and added to the flask. To investigate the effect of different types and dosages of acidifying agents, 150 mL of H₂O₂ (30%) and 15 mL of 1 mol / L nitric acid solution or 50 mL of 2 mol / L sulfuric acid solution were added dropwise to the flask at a rate of 2 mL / min. The reaction was started with stirring. The condensate generated during the reaction was collected using a condenser, and the tail gas was absorbed using concentrated sulfuric acid. The chemical oxygen demand (COD) of the aqueous phase was measured at regular intervals during the reaction. After 2 hours of reaction, the volume of the remaining organic phase in the four-necked flask and the volume of the condensed organic phase collected by the condenser were measured. The results are shown in Table 3.

[0058] Table 3. Effects of different acidifiers on the degradation effect of modified nano-zero valent iron materials on organic solvents.

[0059]

[0060] As can be seen from Table 3, when the Ser-SnZVI described in this invention is used as a catalyst for Fenton-like degradation of organic solvents, different types of acids of varying concentrations can be used as acidifying agents in the reaction. At the same time, the volume reduction rate of organic matter (oil phase) can reach more than 90%, the oxidation efficiency can reach more than 50%, the residual chemical oxygen demand (COD) is low, and the reaction conditions are diverse, which is beneficial to the use of the material in practical engineering applications.

[0061] Example 4:

[0062] The effect of different temperatures on the materials was investigated. The water bath temperatures were set at 80℃ and 98℃. 3 mL of tributyl phosphate and 7 mL of n-dodecane were added to the flasks. 0.5 g of serine-grafted sulfide nano-zero-valent iron was also weighed and added to the flasks. 150 mL of 30% H₂O₂ and 15 mL of 1 mol / L nitric acid solution were added dropwise at a rate of 2 mL / min to the flasks, respectively. The reaction was initiated with stirring. The condensate produced during the reaction was collected using a condenser, and the tail gas was absorbed using concentrated sulfuric acid. The chemical oxygen demand (COD) of the aqueous phase was measured periodically during the reaction. After 2 hours of reaction, the volume of the remaining organic phase in the four-necked flask and the volume of the condensed organic phase collected by the condenser were measured. The results are shown in Table 4.

[0063] Table 4. Effects of different temperatures on the degradation of organic solvents.

[0064]

[0065] As can be seen from Table 4, when the Ser-SnZVI described in this invention is used as a catalyst for Fenton-like degradation of organic solvents, the volume reduction rate of organic matter (oil phase) can reach 100% at 98°C. This indicates that increasing the temperature can improve the volume reduction rate of organic matter. However, excessively high temperatures may lead to the evaporation of a large amount of organic solvent, thereby reducing the oxidation efficiency. However, higher temperatures are beneficial for further oxidation and degradation of organic matter in the solution, so the final COD is reduced.

[0066] Example 5:

[0067] The water bath temperature was set to 95℃. 3 mL of tributyl phosphate and 7 mL of n-dodecane were added to the flask. To investigate the effect of different catalyst dosages on organic matter degradation, 0.2 g and 1.0 g of serine-grafted sulfide nano-zero-valent iron were weighed and added to the flask, respectively. 150 mL of 30% H₂O₂ and 15 mL of 1 mol / L nitric acid solution were added dropwise at a rate of 2 mL / min, respectively. The reaction was started with stirring. The condensate produced during the reaction was collected using a condenser, and the tail gas was absorbed using concentrated sulfuric acid. The chemical oxygen demand (COD) of the aqueous phase was measured periodically during the reaction. After 2 hours of reaction, the volume of the remaining organic phase in the four-necked flask and the volume of the condensed organic phase collected by the condenser were measured. The results are shown in Table 5.

[0068] Table 5. Effects of different catalyst dosages on the degradation of organic solvents.

[0069]

[0070] As can be seen from Table 5, when the Ser-SnZVI described in this invention is used as a catalyst for Fenton-like degradation of organic solvents, the organic solvent volume reduction rate increases when the catalyst dosage is increased. This is because with more catalyst, there are more reaction sites on the catalyst surface, and the reaction is more intense, resulting in a large amount of organic solvent not having time to degrade and evaporating directly, thus reducing the oxidation efficiency. However, the organic matter in the solution will be further degraded, leading to a final reduction in COD.

[0071] Example 6

[0072] The water bath temperature was set to 95℃. 3 mL of tributyl phosphate and 7 mL of n-dodecane were added to the flask. 0.5 g of serine-grafted sulfide nano-zero-valent iron was also weighed and added to the flask. To investigate the effect of H2O2 addition on organic solvent degradation, 100 mL or 250 mL of 30% H2O2 and 15 mL of 1 mol / L nitric acid solution were added dropwise at a rate of 2 mL / min to the flask. The reaction was started with stirring. The condensate generated during the reaction was collected using a condenser, and the tail gas was absorbed using concentrated sulfuric acid. The chemical oxygen demand (COD) of the aqueous phase was measured at regular intervals during the reaction. After 2 hours of reaction, the volume of the remaining organic phase in the four-necked flask and the volume of the condensed organic phase collected by the condenser were measured. The results are shown in Table 6.

[0073] Table 6. Effects of different H2O2 addition amounts on the degradation of organic solvents.

[0074]

[0075] As can be seen from Table 6, when the Ser-SnZVI catalyst of the present invention is used for Fenton-like degradation of organic solvents, the organic solvent volume reduction rate increases when the amount of H2O2 added is increased. This is because the increased amount of H2O2 makes the reaction more vigorous, resulting in more evaporated organic solvent. At the same time, the increased oxidant can generate more hydroxyl radicals, thereby increasing the oxidation efficiency. In addition, due to the dilution effect of the solvent, the final COD value will also decrease.

[0076] Example 7:

[0077] The water bath temperature was set to 95℃. To investigate the effect of the presence of nuclides on the degradation of organic solvents, 10 mL of the organic solvent after extraction of U was added to the flask. 0.5 g of serine-grafted sulfide nano-zero-valent iron was then weighed and added to the flask. 150 mL of 30% H₂O₂ and 15 mL of 1 mol / L nitric acid solution were added dropwise at a rate of 2 mL / min. The reaction was started with stirring. The condensate produced during the reaction was collected using a condenser, and the tail gas was absorbed using concentrated sulfuric acid. The chemical oxygen demand (COD) of the aqueous phase was measured periodically during the reaction. After 2 hours of reaction, the volume of the remaining organic phase in the four-necked flask and the volume of the condensed organic phase collected by the condenser were measured. The results are shown in Table 7.

[0078] Table 7. The effect of radionuclide presence on the degradation of organic solvents.

[0079]

[0080] As shown in Table 7, when the Ser-SnZVI catalyst described in this invention is used for Fenton-like degradation of organic solvents, the presence of radionuclides does not affect the degradation of the organic solvents and may even promote it. The concentration of radionuclides in the reaction system was measured, and the results showed that more than 97% of the U element was retained in the reaction system, indicating that the radionuclides do not volatilize or leak during the organic solvent degradation process, and the system has good safety. Therefore, this method has a good treatment effect on radioactive waste organic solvents.

[0081] 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, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing serine-grafted sulfurized nanomaterials of zero valent iron, characterized in that, Includes the following steps: A potassium borohydride solution containing a sulfiding agent was added dropwise to a ferrous sulfate solution, and the mixture was stirred to carry out a sulfidation reaction and a liquid-phase reduction reaction to obtain sulfidated nano-zero valent iron. Sulfide nano-zero valent iron was washed with pure water and ethanol, and then a serine solution was added to carry out a grafting reaction to obtain serine-grafted sulfide nano-zero valent iron material.

2. The preparation method according to claim 1, characterized in that: The sulfur-iron molar ratio of the sulfur in the sulfiding agent to the iron in the ferrous sulfate solution is 0.1-0.

3.

3. The preparation method according to claim 1, characterized in that: The sulfiding agent is selected from one or more of sodium dithionite, sodium sulfide, potassium sulfide, and sodium thiosulfate; the concentration of the ferrous sulfate solution is 0.2-0.6 mol / L, the concentration of the potassium borohydride solution is 1-3 mol / L, and the concentration of the serine solution is 5-10 g / L.

4. Serine-grafted sulfurized nano-zero-valent iron material is prepared by the preparation method described in any one of claims 1 to 3.

5. The application of the serine-grafted sulfide nano-zero-valent iron material according to claim 4 in the heterogeneous Fenton-like catalytic degradation of organic solvents.

6. The application as described in claim 5, characterized in that: The application includes the following steps: serine-grafted sulfurized nano-zero-valent iron material is added to an organic solvent, followed by the addition of hydrogen peroxide solution and an acidifying agent. The reaction temperature is controlled by a constant-temperature water bath to achieve the catalytic degradation of the organic solvent.

7. The application as described in claim 6, characterized in that, The organic solvent is a mixture of tributyl phosphate and n-dodecane in a ratio of 3:

7.

8. The application as described in claim 6, characterized in that, The mass ratio of serine-grafted sulfurized nano-zero-valent iron material to organic solvent is (0.2–1.0):

10.

9. The application as described in claim 6, characterized in that, The volume fraction of H2O2 in the hydrogen peroxide solution is 30%, and the volume ratio of hydrogen peroxide solution to organic solvent is (100-250):

10.

10. The application as described in claim 6, characterized in that, The acidifying agent is a nitric acid or sulfuric acid solution with a concentration of 0.1-10 mol / L and a volume ratio of (15-50):10 with the organic solvent; the reaction temperature is 80℃-98℃.

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