Method for recovering hypophosphite from wastewater by simultaneous oxidation

Abstract

The application provides a method for synchronously oxidizing and recovering hypophosphite in wastewater. The method for synchronously oxidizing and recovering hypophosphite in wastewater of the application adds Fe-Fe2O3 core-shell material and peroxymonosulfate (PMS) into wastewater, utilizes the Fe-Fe2O3 core-shell material and peroxymonosulfate (PMS) to realize oxidation of hypophosphite and recovery of generated orthophosphorus in the form of iron phosphate precipitation, and does not need to first perform oxidation and then add a precipitating agent for precipitation; the method of the application is simple, only needs to add Fe-Fe2O3 core-shell material and peroxymonosulfate (PMS), and the reaction time is within 30 min, and is convenient for large-scale use.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a method for simultaneous oxidation and recovery of phosphorus hypochlorite from wastewater. Background Technology

[0002] Sodium hypophosphite (NaH2PO2) is mainly used in the food industry as a preservative and antioxidant, or as a reducing agent in electroless plating and electroplating. Currently, the industrial production of sodium hypophosphite primarily uses yellow phosphorus and alkali metal or alkaline earth metal hydroxides as raw materials, generating large amounts of sodium hypophosphite waste liquid and calcium hypophosphite waste residue during the process. Simultaneously, in the electroplating industry, sodium hypophosphite is the most commonly used reducing agent. As the surface treatment time continues to extend, metal ions and hypophosphites in the plating solution are gradually consumed, resulting in wastewater containing large amounts of phosphite ions and electroplated metals.

[0003] However, due to their high solubility, hypophosphite and phosphite can be directly added using traditional chemical precipitation methods with Ca. 2+ Fe 3+ Ions are difficult to precipitate, making it impossible to achieve the required standards for effluent.

[0004] Given the shortcomings of current chemical precipitation methods for removing hypophosphite and phosphite, it is necessary to improve them. Summary of the Invention

[0005] In view of this, the present invention provides a method for simultaneous oxidation and recovery of phosphorus hypochlorite from wastewater to overcome the deficiencies in the prior art.

[0006] This invention provides a method for simultaneous oxidation and recovery of phosphorus hypochlorite from wastewater, comprising the following steps:

[0007] Fe-Fe2O3 core-shell material was added to wastewater containing hypophosphite, along with persulfate. The mixture was stirred and reacted. After the reaction was completed, the hypophosphite was oxidized and precipitated as iron phosphate with recycling value.

[0008] Preferably, the pH of the wastewater containing phosphorus hypophosphite is 3 to 7.

[0009] Preferably, the mass ratio of the Fe-Fe2O3 core-shell material to the phosphorus nitride in the wastewater is greater than or equal to 5:1.

[0010] Preferably, the mass ratio of the persulfate to the hypophosphite in the wastewater is greater than or equal to 15:1.

[0011] Preferably, Fe-Fe2O3 core-shell material is added to the wastewater containing phosphorus sulfite, and persulfate is added to the wastewater at the same time. In the step of stirring the reaction, the reaction time is 10 to 30 minutes.

[0012] Preferably, the concentration of the phosphorus-containing wastewater is 15-25 mg P / L.

[0013] Preferably, Fe-Fe2O3 core-shell material is added to the wastewater containing phosphorus hyposulfite to a concentration of 0.01–0.2 g / L.

[0014] Preferably, Fe-Fe2O3 core-shell material is added to the wastewater containing phosphorus sulfide, and persulfate is added to the wastewater at a concentration of 0.1-2 mM.

[0015] Preferably, the preparation method of the Fe-Fe2O3 core-shell material includes the following steps:

[0016] Adding ferric salts to water yields a ferric solution;

[0017] A reducing agent is added to water to obtain a reducing agent solution;

[0018] The reducing agent solution is added to the ferric iron solution, and after reaction, filtration and drying, the Fe-Fe2O3 core-shell material is obtained.

[0019] Ferric salts include at least one of FeCl3, ferric sulfate, and ferric nitrate;

[0020] The reducing agent includes at least one of NaBH4, Al(BH4)3, KBH4, and hydrazine hydrate;

[0021] The reducing agent solution is added to the ferric iron solution at a flow rate of 0.1–0.3 mL / s;

[0022] In the step of adding ferric salt to water, the mass ratio of ferric salt to water is (1-5):(800-1200);

[0023] In the step of adding the reducing agent to the water, the mass ratio of the reducing agent to the water is (3-9):(300-500).

[0024] Preferably, the persulfate is potassium persulfate.

[0025] The present invention has the following advantages over the prior art:

[0026] The present invention discloses a method for the simultaneous oxidation and recovery of phosphorus hyposulfite from wastewater. This method involves adding Fe-Fe2O3 core-shell material and persulfate (PMS) to the wastewater. The Fe-Fe2O3 core-shell material works synergistically with PMS to oxidize phosphorus hyposulfite and recover the generated orthophosphate as ferric phosphate precipitate. This eliminates the need for prior oxidation followed by the addition of a precipitant. The method is simple, requiring only the addition of Fe-Fe2O3 core-shell material and PMS, and the reaction time is less than 30 minutes, making it suitable for large-scale application. Attached Figure Description

[0027] 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.

[0028] Figure 1 The five materials, namely zero-valent iron, Fe2O3, Fe3O4, Fe / Fe2O3 (i.e., the Fe-Fe2O3 core-shell material of this invention), and Fe / Fe3O4, work together to enhance the oxidation efficiency of permonosulfate (PMS) on hypophosphite. Figure 2 The removal effects of five materials (zero-valent iron, Fe2O3, Fe3O4, Fe / Fe2O3, Fe / Fe3O4, and PMS alone) on hypophosphite were compared.

[0029] Figure 3 SEM images of the Fe-Fe2O3 core-shell material of the present invention before and after the reaction;

[0030] Figure 4 The images show the XRD patterns of the Fe-Fe2O3 core-shell material of this invention before and after the reaction.

[0031] Figure 5 XPS images of the Fe-Fe2O3 core-shell material of the present invention before and after the reaction;

[0032] Figure 6 The effect of Fe-Fe2O3 core-shell material on the removal efficiency of hypophosphite under different dosages;

[0033] Figure 7 The effect of different dosages of persulfate (PMS) on the removal efficiency of hypophosphite;

[0034] Figure 8 The graph shows the concentration change of persulfate (PMS) during the reaction when the initial dosage is 1 mM.

[0035] Figure 9The effect of wastewater pH on the removal efficiency of hypophosphite;

[0036] Figure 10 The graph shows the change in pH value of the wastewater during the reaction process, with the initial pH value of the wastewater being 3.

[0037] Figure 11 The effect of hypophosphite concentration in wastewater on hypophosphite removal efficiency;

[0038] Figure 12 Cl- anion - NO 3- CO3 2- The effect on the removal efficiency of hypophosphite;

[0039] Figure 13 The effect of the number of times Fe-Fe2O3 core-shell materials are reused on the removal efficiency of hypophosphite;

[0040] Figure 14 This is a graph showing the change in iron ion concentration during the reaction process;

[0041] Figure 15 This is a diagram illustrating the effect of a homogeneous iron ion system.

[0042] Figure 16 EPR spectrum for measuring reactive free radicals during the reaction process using EPR technology;

[0043] Figure 17 This is a diagram showing the effect of the quenching experiment.

[0044] Figure 18 Image showing the results of the high-priced iron identification;

[0045] Figure 19 This is a diagram showing the changes in phosphorus speciation during the reaction process. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0047] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single digits within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0048] This application provides a method for simultaneous oxidation and recovery of phosphorus hypochlorite from wastewater, including the following steps:

[0049] Fe-Fe2O3 core-shell material was added to wastewater containing hypophosphite, along with persulfate. The mixture was stirred and reacted. After the reaction was completed, the hypophosphite was oxidized and precipitated as iron phosphate with recycling value.

[0050] The present invention provides a method for the simultaneous oxidation and recovery of hypophosphite from wastewater. This method involves adding Fe-Fe2O3 core-shell material and persulfate (PMS) to the wastewater. The Fe-Fe2O3 core-shell material works synergistically with PMS to oxidize hypophosphite and recover the generated orthophosphate as ferric phosphate precipitate. The present invention can achieve simultaneous oxidation and recovery of hypophosphite without the need for prior oxidation followed by the addition of a precipitant.

[0051] In some embodiments, wastewater containing hypophosphite refers to wastewater containing hypophosphite ions (H2PO2). - ) and phosphate ions (HPO3) 2- ) wastewater.

[0052] In some embodiments, persulfate (PMS) is a class of compounds containing persulfate ions, which have strong oxidizing properties and instability. Common persulfates include potassium persulfate, sodium persulfate, and ammonium persulfate.

[0053] Preferably, in some embodiments, persulfate (PMS) is potassium peroxymonosulfate with the molecular formula: KHSO5·0.5KHSO4·0.5K2SO4.

[0054] In some embodiments, the pH of the wastewater containing phosphorus hyposulfite is 3-7. Specifically, the pH of the wastewater containing phosphorus hyposulfite is adjusted to 3-7, and then Fe-Fe2O3 core-shell material is added to the wastewater, along with persulfate, and the reaction is stirred. Specifically, the pH of the wastewater is adjusted to 3-7 using conventional acids such as HCl or H2SO4.

[0055] In some embodiments, the mass ratio of Fe-Fe2O3 core-shell material to phosphorus hypochlorite in wastewater is greater than or equal to 5:1.

[0056] In some embodiments, the mass ratio of persulfate to phosphorus hypochlorite in the wastewater is greater than or equal to 15:1.

[0057] In some embodiments, Fe-Fe2O3 core-shell material is added to wastewater containing phosphorus sulfite, and persulfate is added to the wastewater at the same time. In the step of stirring the reaction, the reaction time is 10 to 30 minutes.

[0058] In some embodiments, the concentration of phosphorus-containing wastewater is 15–25 mg P / L, specifically, it means that each liter of wastewater contains 15–25 mg of phosphorus.

[0059] In some embodiments, Fe-Fe2O3 core-shell material is added to wastewater containing phosphorus hyposulfite at a concentration of 0.01–0.2 g / L, for example, concentrations of 0.01 g / L, 0.02 g / L, 0.05 g / L, 0.1 g / L, 0.15 g / L, and 0.2 g / L.

[0060] In some embodiments, Fe-Fe2O3 core-shell material is added to wastewater containing phosphorus sulfite, and persulfate is added to the wastewater at a concentration of 0.1 to 2 mM, for example, concentrations of 0.1 mM, 0.3 mM, 0.5 mM, 1 mM, or 2 mM.

[0061] In some embodiments, the preparation method of Fe-Fe2O3 core-shell material includes the following steps:

[0062] Adding ferric salts to water yields a ferric solution;

[0063] A reducing agent is added to water to obtain a reducing agent solution;

[0064] The reducing agent solution is added to the ferric iron solution, and after reaction, filtration and drying, the Fe-Fe2O3 core-shell material is obtained.

[0065] Ferric salts include at least one of FeCl3, ferric sulfate, and ferric nitrate;

[0066] The reducing agent includes at least one of NaBH4, Al(BH4)3, KBH4, and hydrazine hydrate;

[0067] The reducing agent solution is added to the ferric iron solution at a flow rate of 0.1–0.3 mL / s;

[0068] In the step of adding ferric salt to water, the mass ratio of ferric salt to water is (1-5):(800-1200);

[0069] In the step of adding the reducing agent to the water, the mass ratio of the reducing agent to the water is (3-9):(300-500).

[0070] The present invention provides a method for the simultaneous oxidation and recovery of phosphorus hyposulfite from wastewater. This method utilizes Fe-Fe2O3 core-shell material in conjunction with persulfate (PMS) to oxidize phosphorus hyposulfite and recover the generated orthophosphate as ferric phosphate precipitate, eliminating the need for prior oxidation followed by the addition of a precipitant. The method of the present invention is simple, requiring only the addition of Fe-Fe2O3 core-shell material and persulfate (PMS), and the reaction time is within 30 minutes, making it suitable for large-scale application.

[0071] The following specific embodiments further illustrate the method for simultaneous oxidation and recovery of phosphorus hypochlorite from wastewater according to this application. This section further illustrates the content of the present invention in conjunction with specific embodiments, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.

[0072] The preparation method of the Fe-Fe2O3 core-shell material used in the following examples includes the following steps:

[0073] S1. Add 3g FeCl3·6H2O to 1000mL of deionized water to obtain a ferric solution;

[0074] S2. Add 6g of NaBH4 to 400mL of deionized water to obtain a NaBH4 solution;

[0075] S3. Add NaBH4 solution dropwise to ferric solution at a flow rate of 0.2 mL / s (using a peristaltic pump). After all NaBH4 solution has been added, collect the black precipitate, wash it with deionized water, and finally dry it under a nitrogen flow or vacuum environment to obtain Fe-Fe2O3 core-shell material.

[0076] In the following examples and comparative examples, persulfate (PMS) is potassium peroxymonosulfate with the molecular formula: KHSO5·0.5KHSO4·0.5K2SO4 and CAS number: 70693-62-8.

[0077] In the following examples, zero-valent iron (Fe) in Comparative Example 1 0 The synthesis method of ) is referenced in the existing literature: Gao Shumei, Wang Xiaodong, Qin Liang, et al. Improved liquid phase reduction method for the preparation of nano zero-valent iron particles [J]. Journal of Nanjing University (Natural Science Edition), 2007, (04): 358-364.

[0078] For the synthesis method of Fe2O3, refer to the existing literature: Ma J, Lian J, Duan X, Liu X, Zheng W. α-Fe2O3: Hydrothermal Synthesis, Magnetic and Electrochemical Properties. The Journal of Physical Chemistry C. 2010, 114(24): 10671-10676;

[0079] For the synthesis method of Fe3O4, please refer to the existing literature: Zhang Xiao. Synthesis, characterization and application of Fe3O4 and TiO2 nanoparticles [D]. Huazhong University of Science and Technology, 2007;

[0080] For the synthesis method of Fe / Fe3O4, refer to existing literature: Shizong Wang, Jun Hu, Jianlong Wang, Enhanced uranium removal from aqueous solution by core-shell Fe 0 @Fe3O4:Insightintothesynergistic effectofFe 0 andFe3O4,Chemosphere,2024,354,141730.

[0081] Example 1

[0082] This embodiment provides a method for simultaneous oxidation and recovery of phosphorus hypochlorite from wastewater, including the following steps:

[0083] Wastewater containing hypophosphite (phosphorus in the wastewater is in the form of hypophosphite ions (H2PO2)) - The pH of the wastewater containing hypophosphite was adjusted to 3, and Fe-Fe2O3 core-shell material was added to make its concentration 0.1 g / L. At the same time, persulfate (PMS) was added to the wastewater to make its concentration 1 mM. The mixture was stirred and reacted for 20 min. After the reaction was completed, hypophosphite was oxidized and ferric phosphate precipitate was formed. The concentration of hypophosphite in each L of wastewater was 20 mg P / L, that is, each L of wastewater contained 20 mg of phosphorus.

[0084] Following the method described in Example 1 above, the Fe-Fe2O3 core-shell material was respectively treated with zero-valent iron (Fe2O3). 0 The five materials—zero-valent iron, Fe2O3, Fe3O4, Fe / Fe2O3 (i.e., the Fe-Fe2O3 core-shell material of this invention), and Fe / Fe3O4—were replaced with Fe2O3, Fe3O4, and Fe / Fe3O4, while keeping other process conditions unchanged. The oxidation efficiency of the activated PMS system on hypophosphite and its effect on phosphorus in wastewater were investigated. The results are as follows: Figure 1 As shown.

[0085] Figure 1 The vertical axis C0 represents the initial phosphorus concentration in the wastewater. t C represents the phosphorus concentration in the wastewater at reaction time t. t / C0 represents the phosphorus removal rate.

[0086] Figure 1 Fe 0 +PMS indicates that, following the above method, the removal rate of phosphorus from wastewater by PMS with the simultaneous addition of zero-valent iron varies with time; Fe2O3+PMS indicates that, following the above method, the removal rate of phosphorus from wastewater by PMS with the simultaneous addition of Fe2O3 varies with time; Fe3O4+PMS indicates that, following the above method, the removal rate of phosphorus from wastewater by PMS with the simultaneous addition of Fe3O4 varies with time; Fe / Fe2O3+PMS indicates that, following the above method, the removal rate of phosphorus from wastewater by PMS with the simultaneous addition of Fe-Fe2O3 core-shell material varies with time; Fe / Fe3O4+PMS indicates that, following the above method, the removal rate of phosphorus from wastewater by PMS with the simultaneous addition of Fe / Fe3O4 varies with time.

[0087] from Figure 1 As can be seen, under the same initial conditions of pH=3, hypophosphite=20mg-P / L, PMS=1mM, and iron dosage=0.1g / L, the Fe-Fe2O3 core-shell material activated PMS system of the present invention showed the best removal effect on hypophosphite, with a removal rate of up to 95%.

[0088] Comparative Example 1

[0089] This comparative example provides a method for removing phosphorus hypochlorite from wastewater, including the following steps:

[0090] Wastewater containing hypophosphite (phosphorus in the wastewater is in the form of hypophosphite ions (H2PO2)) - The pH was adjusted to 3, and Fe-Fe2O3 core-shell material (i.e., present in the form of phosphorus hypophosphite) was added to the wastewater containing phosphorus hypophosphite. Figure 2The concentration of Fe / Fe2O3 was set to 0.1 g / L, and the mixture was stirred for 30 min. The concentration of phosphorus in each L of wastewater containing phosphorus was 20 mg P / L, which means that each L of wastewater contained 20 mg of phosphorus.

[0091] In Comparative Example 1 above, the Fe-Fe2O3 core-shell material was replaced with zero-valent iron (Fe2O3). 0 Four materials, Fe2O3, Fe3O4, and Fe / Fe3O4, were used in the reaction while keeping all other process conditions unchanged.

[0092] Meanwhile, the Fe-Fe2O3 core-shell material in Comparative Example 1 was replaced with persulfate (PMS) at a concentration of 1 mM, while all other process conditions remained unchanged, and the reaction was carried out.

[0093] To differentiate the contributions of oxidation and adsorption, the removal effects of different iron materials at 0.1 g / L and 0.1 mM PMS on hypophosphite (hypophosphate ion) were compared using the method described above. The results are as follows: Figure 2 As shown. Figure 2 In the diagram, the vertical axis C0 represents the initial phosphorus concentration in the wastewater, C t C represents the phosphorus concentration in the wastewater at reaction time t. t / C0 represents the phosphorus removal rate; Figure 2 In the middle, Fe 0 Fe2O3, Fe3O4, Fe / Fe2O3, and Fe / Fe3O4 represent the addition of zero-valent iron (Fe2O3, Fe3O4, Fe / Fe2O3, Fe / Fe ... 0 Five materials are listed: Fe2O3, Fe3O4, Fe-Fe2O3 core-shell material, and Fe / Fe3O4. PMS indicates the addition of persulfate (PMS).

[0094] from Figure 2 It can be seen that the oxidation effect of PMS oxidant alone on hypophosphite is low, and the Fe-Fe2O3 core-shell material has almost no adsorption effect on hypophosphite. Therefore, the individual effects of the material and oxidant on hypophosphite can be ignored. In the Fe-Fe2O3 core-shell material / PMS system, the oxidation of hypophosphite is mainly caused by the active substances generated by the activation of PMS by the iron-based material.

[0095] Example 2

[0096] The Fe-Fe2O3 core-shell materials before and after the reaction were characterized according to the method in Example 1. SEM, XRD, and XPS results are shown below. Figure 3 , 4 As shown in Figure 5. Figure 3In the image, (a) and (b) represent SEM images of the Fe-Fe2O3 core-shell material before the reaction, and (c) and (d) represent SEM images of the Fe-Fe2O3 core-shell material after the reaction for 20 min according to the method in Example 1.

[0097] Figure 4 In the figure, (a) shows the XRD pattern of the Fe-Fe2O3 core-shell material before the reaction (i.e., Fresh), and (b) shows the XRD pattern of the Fe-Fe2O3 core-shell material after the reaction for 20 min according to the method in Example 1 (i.e., Used).

[0098] Figure 5 In the image, (a) shows the X-ray photoelectron spectrum of the Fe-Fe2O3 core-shell material before the reaction; (b) shows the X-ray photoelectron spectrum of the Fe-Fe2O3 core-shell material after 20 min of reaction according to the method in Example 1; (c) shows the fine X-ray photoelectron spectrum of Fe 2p of the Fe-Fe2O3 core-shell material before the reaction; (d) shows the fine X-ray photoelectron spectrum of Fe 2p of the Fe-Fe2O3 core-shell material after 20 min of reaction according to the method in Example 1; (e) shows the fine X-ray photoelectron spectrum of O1s of the Fe-Fe2O3 core-shell material before the reaction; and (f) shows the fine X-ray photoelectron spectrum of O1s of the Fe-Fe2O3 core-shell material after 20 min of reaction according to the method in Example 1.

[0099] SEM images show that the basic unit of the Fe-Fe2O3 core-shell material is a small sphere with a diameter of approximately 250–400 nm. The spheres have relatively smooth surfaces and are interconnected, forming a nano-necklace-like structure. Several linear structures further interweave to form a network structure. After the reaction, the increased and varying sizes of voids in the network structure indicate that some of the cross-linked materials were corroded during the reaction, causing the linear structures to break and increasing the voids between them. XRD patterns show that the main component of the Fe-Fe2O3 core-shell material is zero-valent iron, with a weak Fe2O3 characteristic peak. After the reaction, a weak Fe3O4 characteristic peak appears, indicating a change in the valence state of the material. XPS data shows that before the reaction, Fe... 2+ Fe 3+ So and Fe 0 The proportions were 33.25%, 33.22%, and 33.53% respectively, which changed to 52.36%, 42.48%, and 5.16% after the reaction. (Fe) 0 The proportion decreases, Fe 2+ and Fe 3+ The increased proportion is mainly due to the corrosion and dissolution of Fe, where the zero-valent iron in the core undergoes electron transfer and gradually transforms into Fe. 2+ .

[0100] Example 3

[0101] This embodiment provides a method for simultaneous oxidation and recovery of phosphorus hypochlorite from wastewater, including the following steps:

[0102] Wastewater containing hypophosphite (phosphorus in the wastewater is in the form of hypophosphite ions (H2PO2)) - The pH of the solution (in its phosphonium-containing form) was adjusted to 3. Fe-Fe2O3 core-shell material (i.e., Fe / Fe2O3 in the figure) was added to the wastewater containing phosphonium hyposulfite, and persulfate (PMS) was added to the wastewater to a concentration of 1 mM. The mixture was stirred and reacted for 20 min. After the reaction, phosphonium hyposulfite was oxidized and ferric phosphate precipitate was formed. The concentration of phosphonium hyposulfite in each L of wastewater was 20 mg P / L, which means that each L of wastewater contained 20 mg of phosphorus.

[0103] The Fe-Fe2O3 core-shell material was added to achieve concentrations of 0.01 g / L, 0.02 g / L, 0.05 g / L, 0.1 g / L, 0.15 g / L, and 0.2 g / L, respectively.

[0104] Following the above method, the removal efficiency of hypophosphite was studied under the following conditions: Fe-Fe2O3 core-shell material (Fe / Fe2O3) dosages of 0.01 g / L, 0.02 g / L, 0.05 g / L, 0.1 g / L, 0.15 g / L, and 0.2 g / L, with pH=3, hypophosphite=20 mg-P / L, and PMS=1 mM. Figure 6 As shown. Figure 6 The vertical axis C0 represents the initial phosphorus concentration in the wastewater. t C represents the phosphorus concentration in the wastewater at reaction time t. t / C0 represents the phosphorus removal rate.

[0105] from Figure 6 It can be seen that the removal effect of hypophosphite is best when the dosage of Fe-Fe2O3 core-shell material (Fe / Fe2O3) is 0.1 g / L.

[0106] Example 4

[0107] This embodiment provides a method for simultaneous oxidation and recovery of phosphorus hypochlorite from wastewater, including the following steps:

[0108] Wastewater containing hypophosphite (phosphorus in the wastewater is in the form of hypophosphite ions (H2PO2)) -The pH of the solution (in its phosphonium sulfide form) was adjusted to 3. Fe-Fe2O3 core-shell material was added to the wastewater containing phosphonium sulfide to a concentration of 0.1 g / L. Simultaneously, persulfate (PMS) was added to the wastewater. The mixture was stirred and reacted for 20 min. After the reaction, phosphonium sulfide was oxidized and ferric phosphate precipitate was formed. The concentration of phosphonium sulfide in each L of wastewater was 20 mg P / L, which means that each L of wastewater contained 20 mg of phosphorus.

[0109] The concentrations of persulfate (PMS) added were 0.1 mM, 0.3 mM, 0.5 mM, 1 mM, and 2 mM, respectively.

[0110] Following the above method, the removal efficiency of hypophosphite was studied under the following conditions: persulfate (PMS) dosage of 0.1 mM, 0.3 mM, 0.5 mM, 1 mM, and 2 mM; pH = 3; hypophosphite concentration of 20 mg-P / L; and Fe-Fe₂O₃ core-shell material dosage of 0.1 g / L. Figure 7 As shown. Figure 7 The vertical axis C0 represents the initial phosphorus concentration in the wastewater. t C represents the phosphorus concentration in the wastewater at reaction time t. t / C0 represents the phosphorus removal rate.

[0111] from Figure 7 It can be seen that the removal effect of persulfate (PMS) is best when the dosage is 0.1 mM.

[0112] Furthermore, following the above method, the dosage of persulfate (PMS) was controlled at 1 mM, and its concentration change during the reaction was tested. Figure 8 As shown.

[0113] from Figure 8 As can be seen, the concentration of permonosulfate (PMS) gradually decreases as the reaction proceeds, eventually remaining at 0.2 mM. This indicates that during the oxidation of hypophosphite, the removal of hypophosphite is negatively correlated with the concentration of permonosulfate (PMS), and under these conditions, permonosulfate (PMS) is in excess.

[0114] Example 5

[0115] This embodiment provides a method for simultaneous oxidation and recovery of phosphorus hypochlorite from wastewater, including the following steps:

[0116] Wastewater containing hypophosphite (phosphorus in the wastewater is in the form of hypophosphite ions (H2PO2)) -The pH of the solution (in its phosphonium-containing form) was adjusted to 3-8. Fe-Fe2O3 core-shell material was added to the wastewater containing phosphonium hyposulfite to a concentration of 0.1 g / L, and persulfate (PMS) was added to the wastewater to a concentration of 1 mM. The mixture was stirred and reacted for 20 min. After the reaction, phosphonium hyposulfite was oxidized and ferric phosphate precipitate was formed. The concentration of phosphonium hyposulfite in each L of wastewater was 20 mg P / L, which means that each L of wastewater contained 20 mg of phosphorus.

[0117] The pH of the wastewater was adjusted to 3, 4, 5, 6, 7, and 8 respectively using the method described above. Under these conditions (pH 3, 4, 5, 6, 7, and 8), the removal efficiency of hypophosphite was assessed using a concentration of 20 mg-P / L, PMS of 1 mM, and Fe-Fe₂O₃ core-shell material of 0.1 g / L. Figure 9 As shown. Figure 9 The vertical axis C0 represents the initial phosphorus concentration in the wastewater. t C represents the phosphorus concentration in the wastewater at reaction time t. t / C0 represents the phosphorus removal rate.

[0118] from Figure 9 It can be seen that the removal effect of hypophosphite is best when the pH value of the wastewater is adjusted to 3.

[0119] Furthermore, following the above method, the pH of the wastewater was adjusted to 3, and the change in pH during the reaction process was tested. The results are as follows. Figure 10 As shown.

[0120] from Figure 10 As can be seen, the pH of the solution does not change much during the reaction process, fluctuating within a range of 0.2, which can keep the pH of the solution in a stable state.

[0121] Example 6

[0122] This embodiment provides a method for simultaneous oxidation and recovery of phosphorus hypochlorite from wastewater, including the following steps:

[0123] Wastewater containing hypophosphite (phosphorus in the wastewater is in the form of hypophosphite ions (H2PO2)) - The pH of the wastewater containing hypophosphite was adjusted to 3, and Fe-Fe2O3 core-shell material was added to make its concentration 0.1 g / L. At the same time, persulfate (PMS) was added to the wastewater to make its concentration 1 mM. The mixture was stirred and reacted for 20 min. After the reaction was completed, hypophosphite was oxidized and ferric phosphate precipitate was formed. The concentration of hypophosphite in each L of wastewater was 10-50 mg P / L, that is, each L of wastewater contained 10-50 mg of phosphorus.

[0124] The removal efficiency of hypophosphite was assessed under the following conditions: phosphorus concentration (based on elemental phosphorus) in wastewater was 10, 20, 30, 40, and 50 mg-P / L; pH = 3; PMS = 1 mM; and Fe-Fe₂O₃ core-shell material dosage = 0.1 g / L. Figure 11 As shown. Figure 11 The vertical axis C0 represents the initial phosphorus concentration in the wastewater. t C represents the phosphorus concentration in the wastewater at reaction time t. t / C0 represents the phosphorus removal rate.

[0125] from Figure 11 As can be seen, the removal efficiency of this method for paraphosphine gradually decreases with the increase of paraphosphine concentration in wastewater.

[0126] Example 7

[0127] This embodiment provides a method for simultaneous oxidation and recovery of phosphorus hypochlorite from wastewater, including the following steps:

[0128] Wastewater containing hypophosphite (phosphorus in the wastewater is in the form of hypophosphite ions (H2PO2)) - The pH of the solution (in its phosphonium-containing form) was adjusted to 3. Fe-Fe2O3 core-shell material was added to the wastewater containing phosphonium hyposulfite to a concentration of 0.1 g / L. Simultaneously, persulfate (PMS) was added to the wastewater to a concentration of 1 mM. The mixture was stirred and reacted for 20 min. After the reaction, phosphonium hyposulfite was oxidized and ferric phosphate precipitate was formed. The concentration of phosphonium hyposulfite in each L of wastewater was 20 mg P / L, which means that each L of wastewater contained 20 mg of phosphorus.

[0129] Based on the above method, Cl is simultaneously added to the wastewater. - (Added in the form of NaCl), NO 3- (Added in the form of NaNO3), CO3 2- (Added in the form of Na2CO3), and to make the Cl in the wastewater... - NO3 - CO3 2- The concentration is 5 mM.

[0130] At 5mMCl - 5mMNO3 - 5mMCO3 2- Under the conditions of 20 mg P / L hypophosphite, pH 3, PMS 1 mM, and Fe-Fe2O3 core-shell material 0.1 g / L, the removal efficiency of hypophosphite was as follows: Figure 12 As shown; Figure 12 The 0.1g / LFe / Fe2O3 indicates the addition of 0.1g / LFe-Fe2O3 core-shell material, without the addition of other ions. Figure 12 The vertical axis C0 represents the initial phosphorus concentration in the wastewater. t C represents the phosphorus concentration in the wastewater at reaction time t. t / C0 represents the phosphorus removal rate.

[0131] from Figure 12 It can be seen from this that in the presence of Cl - NO 3- CO3 2- The effect of this method on the removal of hypophosphite is minimal, indicating that this method is highly adaptable.

[0132] Example 8: Following the method in Example 1, with hypophosphite concentration of 20 mg-P / L, pH of 3, PMS of 1 mM, and Fe-Fe2O3 core-shell material dosage of 0.1 g / L, the used Fe-Fe2O3 core-shell material was recycled and reused. The Fe-Fe2O3 core-shell material was reused three times to examine its effect on hypophosphite removal. Figure 13 As shown. Figure 12 The vertical axis C0 represents the initial phosphorus concentration in the wastewater. t C represents the phosphorus concentration in the wastewater at reaction time t. t / C0 represents the phosphorus removal rate.

[0133] from Figure 13 As can be seen from the above, the Fe-Fe2O3 core-shell material of the present invention still has a high removal effect on hypophosphite after being reused three times.

[0134] Example 9

[0135] Following the method in Example 1, at a phosphorus content of 20 mg-P / L, pH = 3, PMS = 1 mM, and Fe-Fe2O3 core-shell material dosage of 0.1 g / L, the different valence states of iron ions released during the reaction were measured, and the results are as follows: Figure 14 As shown.

[0136] from Figure 14 As can be seen, the total iron concentration continued to rise before 10 minutes, with a maximum value of 40 mg / L. The ferrous iron concentration remained at around 5 mg / L. After 10 minutes, the total iron concentration dropped sharply to 25 mg / L, and the ferrous iron concentration increased to 22 mg / L, becoming the main component of iron. This was because ferric iron and orthophosphate precipitated after 10 minutes.

[0137] To investigate the role of iron ions in a homogeneous system, the highest total iron concentration during the reaction and the final iron ion concentration at the end of the reaction were used as standards. 20 mg / L and 40 mg / L of Fe were added, respectively. 2+ (Added in the form of FeSO4), 40 mg / L of Fe3+ Homogeneous experiments were conducted (using Fe2(SO4)3 as an additive), such as... Figure 15 As shown. Specifically, the experimental method is as follows:

[0138] Wastewater containing hypophosphite (phosphorus in the wastewater is in the form of hypophosphite ions (H2PO2)) - The pH of the solution containing phosphorus hyposulfite was adjusted to 3. FeSO4 or Fe2(SO4)3 was added to the wastewater containing phosphorus hyposulfite, and persulfate (PMS) was added to the wastewater to a concentration of 1 mM. The mixture was stirred for 20 min. After the reaction, the phosphorus hyposulfite was oxidized and ferric phosphate precipitate was formed. The concentration of phosphorus hyposulfite in each L of wastewater was 20 mg P / L, meaning that each L of wastewater contained 20 mg of phosphorus. The addition of FeSO4 increased the phosphorus content of the solution. 2+ The concentrations were 20 mg / L and 40 mg / L, respectively. The addition of Fe2(SO4)3 resulted in Fe... 3+ The concentration is 40 mg / L;

[0139] Meanwhile, Fe-Fe2O3 core-shell material was added to replace FeSO4 or Fe2(SO4)3 as a comparison, with the dosage of Fe-Fe2O3 core-shell material = 0.1 g / L.

[0140] Figure 15 The vertical axis C0 represents the initial phosphorus concentration in the wastewater. t C represents the phosphorus concentration in the wastewater at reaction time t. t / C0 represents the phosphorus removal rate.

[0141] from Figure 15 As can be seen from the data, the reaction rate is extremely fast in the homogeneous system, and ferrous iron is more effective than ferric iron, but the addition of 40 mg / L of ferrous iron... 2+ The removal rate of hypophosphate was only about 50%, which is far lower than that of heterogeneous materials.

[0142] Example 10

[0143] Following the method in Example 1, at a phosphorus content of 20 mg-P / L, pH = 3, PMS = 1 mM, and Fe-Fe₂O₃ core-shell material dosage of 0.1 g / L, the reactive free radicals during the reaction process were measured using EPR technology. Figure 16 As shown.

[0144] from Figure 16 As can be seen, signals of DMPO-·OH and DMPO-SO4·- appeared (DMPO stands for 5,5-dimethyl-1-pyrrolline N-oxide, which is a commonly used free radical scavenger), indicating that hydroxyl radicals and sulfate radicals were generated in the reaction. As the reaction proceeded, the hydroxyl signal gradually weakened, and the main free radical gradually changed to sulfate radicals.

[0145] Further experiments were conducted using tert-butanol (TBA), ethanol (EtOH), and aniline (AN) as quenchers at a ratio of quencher:PMS = 500:1. The results are as follows: Figure 17 As shown. The specific experimental method is as follows: Wastewater containing hypophosphite (phosphorus in the wastewater is in the form of hypophosphite ions (H₂PO₂)) is treated. - The pH of the wastewater containing phosphorus was adjusted to 3. Fe-Fe₂O₃ core-shell material was added to the wastewater containing phosphorus hyposulfite to a concentration of 0.1 g / L. Simultaneously, persulfate (PMS) was added to the wastewater to a concentration of 1 mM. Then, quenchers tert-butanol (TBA), ethanol (EtOH), and aniline (AN) were added, and the mixture was stirred for 20 min. The concentration of phosphorus hyposulfite in each L of wastewater was 20 mg P / L, meaning each L of wastewater contained 20 mg of phosphorus. The molar ratios of quenchers tert-butanol (TBA) to PMS, ethanol (EtOH), and aniline (AN) to PMS were 500:1.

[0146] Meanwhile, a comparison was made using the same method described above, without the addition of any quenching agent.

[0147] Figure 17 (a) shows the removal effect of different quenchers on hypophosphite, and (b) shows the apparent reaction rate constant. Figure 17 The vertical axis C0 represents the initial phosphorus concentration in the wastewater. t C represents the phosphorus concentration in the wastewater at reaction time t. t / C0 represents the phosphorus removal rate; Figure 17 "Fe / Fe2O3" indicates that no quencher is added, and "None" indicates that no quencher is added.

[0148] from Figure 17The results show that the hypophosphite removal rate decreased to 75% with the addition of TBA, to 10% with the addition of EtOH, and to 5% with the addition of AN. Using the removal rate without quencher as a benchmark, the contribution percentages of different free radicals can be calculated. ·OH contributed 21%, SO4·- 68%, SO5·- 5%, and the remaining 6% was contributed by other active substances. The main free radical involved in the reaction was SO4·-, followed by ·OH. Without quencher, the apparent reaction rate constant of hypophosphite in the system was kobs = 0.25064 min⁻¹. After adding TBA, the apparent reaction rate constant decreased to kobs = 0.07912 min⁻¹, indicating a strong reaction rate between ·OH and hypophosphite. Inhibiting ·OH free radicals significantly reduced the reaction rate. After adding EtOH, the apparent reaction rate decreased to kobs = 0.01158 min⁻¹, indicating a low reaction rate between SO4·- and hypophosphite.

[0149] Example 11

[0150] PMSO (methyl phenyl sulfoxide) and PMSO2 were detected at pH=3, PMS=1mM, Fe-Fe2O3 core-shell material dosage=0.1g / L, and PMSO=0.1mM. Figure 18 As shown. The specific experimental method is as follows: Wastewater containing hypophosphite (phosphorus in the wastewater is in the form of hypophosphite ions (H₂PO₂)) is treated. - The pH of the wastewater containing phosphorus hyposulfite was adjusted to 3. Fe-Fe2O3 core-shell material was added to the wastewater containing phosphorus hyposulfite to a concentration of 0.1 g / L. At the same time, persulfate (PMS) was added to the wastewater to a concentration of 1 mM. Then, PMSO was added to a concentration of 0.1 mM. The mixture was stirred and reacted for 20 min. The concentration of phosphorus hyposulfite in each L of wastewater was 20 mg P / L, which means that each L of wastewater contained 20 mg of phosphorus.

[0151] from Figure 18 As can be seen, no PMSO2 was produced, indicating that no high-valent iron was generated during the reaction.

[0152] Example 12: Following the method in Example 1, at pH = 3, PMS = 1 mM, and Fe-Fe2O3 core-shell material dosage = 0.1 g / L, the levels of orthophosphorus, hypophosphorus, phosphorus nitrite, and total phosphorus during the reaction were determined. The results are as follows: Figure 19 As shown.

[0153] Figure 19 Phosphate represents orthophosphorus, Total phosphorus represents total phosphorus, Hypophosphorus represents hypophosphorus, and Phosphite represents phosphorus nitrite.

[0154] from Figure 19 As can be seen, the concentrations of phosphorus nitrite and phosphorus orthophosphate gradually increased before 10 minutes, with phosphorus nitrite concentration higher than phosphorus orthophosphate, while total phosphorus decreased slowly. After 10 minutes, the concentrations of phosphorus orthophosphate, phosphorus nitrite, and total phosphorus decreased sharply. At 20 minutes, the total phosphorus removal rate was about 80%, with residual concentrations of 1.7 mg / L phosphorus orthophosphate, 1.2 mg / L phosphorus nitrite, and 0.9 mg / L hypophosphite, meaning that 87% of hypophosphite was converted to phosphorus orthophosphate. Overall, the reaction process can be divided into two stages: oxidation before 10 minutes and precipitation after 10 minutes, which is consistent with the changes in iron ion concentration.

[0155] 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 simultaneous oxidation and recovery of phosphorus hypochlorite from wastewater, characterized in that, Includes the following steps: Fe-Fe2O3 core-shell material was added to wastewater containing hypophosphite, and persulfate was added to the wastewater at the same time. The mixture was stirred and reacted. After the reaction was completed, hypophosphite was oxidized and generated iron phosphate precipitate with recycling value. The pH of the wastewater containing phosphorus hypophosphite is 3 to 4; Fe-Fe2O3 core-shell material was added to wastewater containing phosphorus hyposulfite to achieve a concentration of 0.1–0.2 g / L; Fe-Fe2O3 core-shell material was added to wastewater containing phosphorus sulfite, and persulfate was added to the wastewater to make its concentration 0.1-2 mM. The concentration of phosphorus-containing wastewater is 15–25 mg P / L; The preparation method of the Fe-Fe2O3 core-shell material includes the following steps: Adding ferric salts to water yields a ferric solution; A reducing agent is added to water to obtain a reducing agent solution; The reducing agent solution is added to the ferric iron solution, and after reaction, filtration and drying, the Fe-Fe2O3 core-shell material is obtained. Ferric salts include at least one of FeCl3, ferric sulfate, and ferric nitrate; The reducing agent includes at least one of NaBH4, Al(BH4)3, KBH4, and hydrazine hydrate; The reducing agent solution is added to the ferric iron solution at a flow rate of 0.1–0.3 mL / s; In the step of adding ferric salt to water, the mass ratio of ferric salt to water is (1-5):(800-1200); In the step of adding the reducing agent to the water, the mass ratio of the reducing agent to the water is (3-9):(300-500); The persulfate is potassium peroxymonosulfate.

2. The method for simultaneous oxidation and recovery of hypophosphite from wastewater as described in claim 1, characterized in that, Fe-Fe2O3 core-shell material was added to wastewater containing phosphorus sulfite, and persulfate was added to the wastewater at the same time. The reaction time was 10-30 minutes during the stirring reaction step.

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