Method for recovering hypophosphite in wastewater through synchronous oxidation

Abstract

The invention provides a method for recovering hypophosphite in wastewater through synchronous oxidation. According to the method for synchronously oxidizing and recycling the hypophosphite in the wastewater, the Fe-Fe2O3 core-shell material and the peroxymonosulfate (PMS) are added into the wastewater, the Fe-Fe2O3 core-shell material is used for cooperating with the peroxymonosulfate (PMS), oxidation of the hypophosphite is achieved, generated orthophosphorus is recycled in the form of ferric phosphate precipitate, and a precipitator does not need to be added for precipitation after oxidation; the method is simple in process, only the Fe-Fe2O3 core-shell material and peroxymonosulfate (PMS) need to be added, the reaction time is within 30 min, and large-scale application is facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to a method for recovering hypophosphorous acid in wastewater by synchronous oxidation. Background Art

[0002] Sodium hypophosphite (NaH2PO2) is mainly used as a preservative, antioxidant, or a reducing agent for chemical plating and electroplating in the food industry. Currently, yellow phosphorus and alkali metal or alkaline earth metal hydroxides are mainly used as raw materials in the industrial production of sodium hypophosphite. A large amount of sodium hypophosphite waste liquid and calcium phosphite waste residue will be generated during the preparation process. At the same time, in the electroplating industry, sodium hypophosphite is the most commonly used reducing agent. As the surface treatment time continues to increase, the metal ions and hypophosphites in the plating solution are gradually consumed, thereby generating wastewater containing a large amount of phosphite ions and electroplated metals.

[0003] However, due to the high solubility of hypophosphite and phosphite, the conventional chemical precipitation method is used to directly add Ca 2+ , Fe 3+ The ions are difficult to precipitate and the effluent cannot meet the standards.

[0004] Based on the defects of the current chemical precipitation method for removing hypophosphite and phosphite, it is necessary to improve it. Summary of the invention

[0005] In view of this, the present invention provides a method for recovering hypophosphorous acid in wastewater by synchronous oxidation to solve the defects existing in the prior art.

[0006] The present invention provides a method for recovering hypophosphorous acid in wastewater by synchronous oxidation, comprising the following steps:

[0007] Fe-Fe2O3 core-shell material is added to wastewater containing hypophosphorous, and peroxymonosulfate is added to the wastewater at the same time, and the reaction is stirred. After the reaction is completed, the hypophosphorous is oxidized and iron phosphate precipitate with recovery value is generated.

[0008] Preferably, the pH of the wastewater containing hypophosphorous acid is 3-7.

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

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

[0011] Preferably, Fe-Fe2O3 core-shell material is added to the wastewater containing hypophosphorous acid, and peroxymonosulfate is added to the wastewater at the same time, and in the step of stirring the reaction, the reaction time is 10 to 30 minutes.

[0012] Preferably, the concentration of hypophosphorous acid in the wastewater is 15-25 mg P / L.

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

[0014] Preferably, Fe-Fe2O3 core-shell material is added to the wastewater containing hypophosphorous acid, and peroxymonosulfate is added to the wastewater at the same time to make its concentration 0.1-2 mM.

[0015] Preferably, the method for preparing the Fe-Fe2O3 core-shell material comprises the following steps:

[0016] Adding a ferric iron salt to water to obtain a ferric iron solution;

[0017] adding a reducing agent into 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] The ferric salt includes 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] Add the reducing agent solution to the ferric iron solution at a flow rate of 0.1 to 0.3 mL / s;

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

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

[0024] Preferably, the peroxymonosulfate is potassium peroxymonosulfate.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The method for recovering hypophosphorous in wastewater by synchronous oxidation of the present invention adds Fe-Fe2O3 core-shell material and permonosulfate (PMS) to the wastewater, utilizes the Fe-Fe2O3 core-shell material to cooperate with permonosulfate (PMS), realizes the oxidation of hypophosphorous and recovers the generated orthophosphorus in the form of ferric phosphate precipitation, without the need to first oxidize and then add a precipitant for precipitation; the method of the present invention has a simple process, only needs to add Fe-Fe2O3 core-shell material and permonosulfate (PMS), and the reaction time is within 30 minutes, which is convenient for large-scale application. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 The oxidation efficiency of five materials, namely zero-valent iron, Fe2O3, Fe3O4, Fe / Fe2O3 (i.e., the Fe-Fe2O3 core-shell material of the present invention) and Fe / Fe3O4, in cooperation with permonosulfate (PMS) on hypophosphite; Figure 2 The removal effects of zero-valent iron, Fe2O3, Fe3O4, Fe / Fe2O3, Fe / Fe3O4 and PMS on hypophosphite.

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

[0030] Figure 4 The XRD diagram of the Fe-Fe2O3 core-shell material of the present invention before and after the reaction;

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

[0032] Figure 6 The effect of different dosages of Fe-Fe2O3 core-shell materials on the removal of phosphorus;

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

[0034] Figure 8 This is the concentration change diagram of permonosulfate (PMS) during the reaction when the initial dosage is 1 mM;

[0035] Fig. 9The effect of wastewater pH value on the removal of hypophosphorus;

[0036] Fig.10 This is the pH value change diagram of the wastewater during the reaction when the initial pH value of the wastewater is 3;

[0037] Fig.11 The effect of the concentration of secondary phosphorus in wastewater on the removal of secondary phosphorus;

[0038] Fig.12 The anion Cl - 、NO 3- 、CO3 2- Impact on the removal of hypophosphorus;

[0039] Fig.13 The effect of the number of times the Fe-Fe2O3 core-shell material is reused on the removal of secondary phosphorus;

[0040] Fig.14 This is the graph showing the change in iron ion concentration during the reaction;

[0041] Fig.15 This is the effect diagram of the homogeneous system of iron ions;

[0042] Fig.16 The EPR spectrum used to measure the active free radicals in the reaction process by EPR technology;

[0043] Fig.17 This is the effect diagram of quenching experiment;

[0044] Fig.18 This is the result of high-valent iron identification;

[0045] Fig.19 This is a diagram showing the changes in phosphorus form distribution during the reaction. DETAILED DESCRIPTION

[0046] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work 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 the embodiments. In addition, in the description of the present application, the term "including" means "including but not limited to". Various embodiments of the present invention may be in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single values ​​within the 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., as well as single numbers within the numbered ranges, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated in this article, it is meant to include any quoted numbers (fractions or integers) within the indicated range.

[0048] The present application provides a method for recovering hypophosphorous acid in wastewater by synchronous oxidation, comprising the following steps:

[0049] Fe-Fe2O3 core-shell material is added to wastewater containing hypophosphorous, and peroxymonosulfate is added to the wastewater at the same time, and the reaction is stirred. After the reaction is completed, the hypophosphorous is oxidized and iron phosphate precipitate with recovery value is generated.

[0050] The method for recovering hypophosphorous in wastewater by synchronous oxidation of the present invention comprises adding Fe-Fe2O3 core-shell material and permonosulfate (PMS) into the wastewater, wherein the Fe-Fe2O3 core-shell material cooperates with the permonosulfate (PMS) to achieve oxidation of hypophosphorous and recover the generated orthophosphorus in the form of ferric phosphate precipitation. The method can achieve synchronous oxidation and recovery of hypophosphorous without the need for first oxidizing and then adding a precipitant for precipitation.

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

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

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

[0054] In some embodiments, the pH of the wastewater containing hypophosphorous is 3 to 7. Specifically, the pH of the wastewater containing hypophosphorous is adjusted to 3 to 7, and then the Fe-Fe2O3 core-shell material is added to the wastewater containing hypophosphorous, and peroxymonosulfate is added to the wastewater, and stirred for reaction. Specifically, the pH of the wastewater is adjusted to 3 to 7, and conventional acids such as HCl, H2SO4, etc. can be used.

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

[0056] In some embodiments, the mass ratio of permonosulfate to hypophosphorous 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 hypophosphorous acid, and peroxymonosulfate 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 hypophosphorous in wastewater is 15-25 mg P / L, specifically, it means that each L of wastewater contains 15-25 mg of phosphorus.

[0059] In some embodiments, Fe-Fe2O3 core-shell material is added to wastewater containing hypophosphorous acid to a concentration of 0.01 to 0.2 g / L, for example, 0.01 g / L, 0.02 g / L, 0.05 g / L, 0.1 g / L, 0.15 g / L, or 0.2 g / L.

[0060] In some embodiments, Fe-Fe2O3 core-shell material is added to wastewater containing hypophosphorous acid, and peroxymonosulfate is added to the wastewater to a concentration of 0.1-2 mM, for example, 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 comprises the following steps:

[0062] Adding a ferric iron salt to water to obtain a ferric iron solution;

[0063] adding a reducing agent into 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] The ferric salt includes 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] Add the reducing agent solution to the ferric iron solution at a flow rate of 0.1 to 0.3 mL / s;

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

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

[0070] The method for recovering hypophosphorous in wastewater by synchronous oxidation of the present invention utilizes Fe-Fe2O3 core-shell materials in coordination with permonosulfate (PMS) to achieve oxidation of hypophosphorous and recover the generated orthophosphorus in the form of ferric phosphate precipitation, without the need for first oxidizing and then adding a precipitant for precipitation. The method of the present invention has a simple process, requiring only the addition of Fe-Fe2O3 core-shell materials and permonosulfate (PMS), and the reaction time is within 30 minutes, which is convenient for large-scale application.

[0071] The following further illustrates the method for recovering hypophosphorous acid in wastewater by synchronous oxidation of the present application with specific examples. This section further illustrates the content of the present invention in conjunction with specific examples, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means adopted in the examples 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 comprises the following steps:

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

[0074] S2, adding 6 g NaBH4 into 400 mL deionized water to obtain a NaBH4 solution;

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

[0076] In the following examples and comparative examples, permonosulfate (PMS) is potassium peroxymonosulfate, molecular formula: KHSO5·0.5KHSO4·0.5K2SO4, CAS No.: 70693-62-8.

[0077] In the following examples, the zero-valent iron (Fe 0 ) is synthesized by referring to the existing literature: Gao Shumei, Wang Xiaodong, Qin Liang, et al. Preparation of Nano Zero-Valent Iron Particles by Improved Liquid Phase Reduction Method [J]. Journal of Nanjing University (Natural Science Edition), 2007, (04): 358-364.);

[0078] 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] The synthesis method of Fe3O4, 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] The synthesis method of Fe / Fe3O4, refer to the 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 recovering hypophosphorous acid in wastewater by synchronous oxidation, comprising the following steps:

[0083] Wastewater containing hypophosphite (phosphorus in wastewater in the form of hypophosphite ions (H2PO2 - ) in the form of hypophosphorous) is adjusted to 3, Fe-Fe2O3 core-shell material is added to the wastewater containing hypophosphorous to make its concentration 0.1g / L, and permonosulfate (PMS) is added to the wastewater to make its concentration 1mM, and the reaction is stirred for 20min. After the reaction, the hypophosphorous is oxidized and iron phosphate precipitate is generated; wherein the concentration of each L of wastewater containing hypophosphorous is 20mgP / L, that is, each L of wastewater contains 20mg of phosphorus element.

[0084] According to the method in Example 1 above, the Fe-Fe2O3 core-shell materials are respectively made of zero-valent iron (Fe 0 ), Fe2O3, Fe3O4 and Fe / Fe3O4 were replaced, and the other process conditions remained unchanged. Five materials, zero-valent iron, Fe2O3, Fe3O4, Fe / Fe2O3 (i.e., the Fe-Fe2O3 core-shell material of the present invention) and Fe / Fe3O4 were studied to investigate the oxidation efficiency of the activated PMS system on hypophosphite and its effect on phosphorus in wastewater. The results are as follows Figure 1 shown.

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

[0086] Figure 1 Fe 0 +PMS means that according to the above method, zero-valent iron and PMS are added to the wastewater at the same time, and the removal rate of phosphorus is calculated over time; Fe2O3+PMS means that according to the above method, Fe2O3 and PMS are added to the wastewater at the same time, and the removal rate of phosphorus is calculated over time; Fe3O4+PMS means that according to the above method, Fe3O4 and PMS are added to the wastewater at the same time, and the removal rate of phosphorus is calculated over time; Fe / Fe2O3+PMS means that according to the above method, Fe-Fe2O3 core-shell material and PMS are added to the wastewater at the same time, and the removal rate of phosphorus is calculated over time; Fe / Fe3O4+PMS means that according to the above method, Fe / Fe3O4 and PMS are added to the wastewater at the same time, and the removal rate of phosphorus is calculated over time.

[0087] from Figure 1 It can be seen that under the same conditions of initial conditions of pH = 3, hypophosphite = 20 mg-P / L, PMS = 1 mM, and iron material dosage = 0.1 g / L, it is found that the Fe-Fe2O3 core-shell material activated PMS system of the present invention has the best removal effect on hypophosphite, and the removal rate can reach 95%.

[0088] Comparative Example 1

[0089] This comparative example provides a method for removing hypophosphorous acid in wastewater, comprising the following steps:

[0090] Wastewater containing hypophosphite (phosphorus in wastewater in the form of hypophosphite ions (H2PO2 - ) in the form of a PH value of 3, and Fe-Fe2O3 core-shell material (i.e. Figure 2Fe / Fe2O3) is added to make its concentration 0.1g / L, and the reaction is stirred for 30 minutes; wherein, the concentration of each L of wastewater containing hypophosphorous is 20mgP / L, that is, each L of wastewater contains 20mg of phosphorus element.

[0091] According to the above comparative example 1, the Fe-Fe2O3 core-shell materials were replaced by zero-valent iron (Fe 0 ), Fe2O3, Fe3O4 and Fe / Fe3O4, and the other process conditions remain unchanged to react;

[0092] At the same time, the Fe-Fe2O3 core-shell material in Comparative Example 1 was replaced with permonosulfate (PMS) to a concentration of 1 mM, and the other process conditions remained unchanged to carry out the reaction.

[0093] In order to distinguish the contribution of oxidation and adsorption, the removal effect of hypophosphite (hypophosphite ion) by adding 0.1g / L of different iron materials and 0.1mM PMS was compared according to the above method. The results are as follows: Figure 2 shown. Figure 2 In the figure, the ordinate C0 represents the initial phosphorus concentration in the wastewater, C t represents the phosphorus concentration in wastewater at reaction time t; C t / C0 represents the removal rate of phosphorus; Figure 2 In Fe 0 , Fe2O3, Fe3O4, Fe / Fe2O3, Fe / Fe3O4 respectively represent the addition of zero-valent iron (Fe 0 ), Fe2O3, Fe3O4, Fe-Fe2O3 core-shell material and Fe / Fe3O4, and PMS represents the addition of permonosulfate (PMS).

[0094] from Figure 2 It can be seen that the oxidation effect of PMS oxidant added alone on hypophosphite is low, and 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 produced by the activation of PMS by iron-based materials.

[0095] Example 2

[0096] According to the method in Example 1, the Fe-Fe2O3 core-shell material before and after the reaction was characterized, and SEM, XRD and XPS were as follows: Figure 3 , 4 , as shown in Figure 5. Figure 3(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 minutes according to the method in Example 1.

[0097] Figure 4 (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 minutes (i.e., Used) according to the method in Example 1.

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

[0099] From the SEM image, it can be seen that the basic unit of the Fe-Fe2O3 core-shell material is a small ball with a diameter of about 250 to 400 nm. The surface of the small ball is relatively smooth and connected to each other in the shape of a nano necklace. Several linear structures are further interwoven into a mesh-like material. After the reaction, the voids in the mesh structure increase and vary in size, indicating that part of the cross-linked material is corroded during the reaction, causing the linear structure to break and the voids to increase. From the XRD graph, it can be seen that the main component of the Fe-Fe2O3 core-shell material is zero-valent iron, and there is a weak Fe2O3 characteristic peak. After the reaction, a weak Fe3O4 characteristic peak appears, indicating that the material has changed in valence. From XPS, it can be seen that before the reaction, Fe 2+ , Fe 3+ So and Fe 0 The proportions were 33.25%, 33.22%, and 33.53%, respectively. After the reaction, they became 52.36%, 42.48%, and 5.16%. 0 The ratio decreases, Fe 2+ and Fe 3+ The increase in the ratio is mainly due to the corrosion and dissolution of Fe, and 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 recovering hypophosphorous acid in wastewater by synchronous oxidation, comprising the following steps:

[0102] Wastewater containing hypophosphite (phosphorus in wastewater in the form of hypophosphite ions (H2PO2 - ) in the form of phosphate) is adjusted to pH 3, Fe-Fe2O3 core-shell material (i.e., Fe / Fe2O3 in the figure) is added to the wastewater containing hypophosphorous, and peroxymonosulfate (PMS) is added to the wastewater to make its concentration 1mM, and the reaction is stirred for 20 minutes. After the reaction is completed, the hypophosphorous is oxidized and iron phosphate precipitates are generated; wherein, the concentration of each liter of wastewater containing hypophosphorous is 20mgP / L, that is, each liter of wastewater contains 20mg of phosphorus element;

[0103] Among them, after adding Fe-Fe2O3 core-shell material, the concentrations of Fe-Fe2O3 core-shell material are 0.01g / L, 0.02g / L, 0.05g / L, 0.1g / L, 0.15g / L and 0.2g / L respectively.

[0104] According to the above method, under the conditions of Fe-Fe2O3 core-shell material (Fe / Fe2O3) dosage of 0.01g / L, 0.02g / L, 0.05g / L, 0.1g / L, 0.15g / L, 0.2g / L, pH = 3, hypophosphorus = 20mg-P / L, PMS = 1mM, the removal effect of hypophosphorus is as follows: Figure 6 shown. Figure 6 The vertical axis C0 represents the initial phosphorus concentration in the wastewater, C t represents the phosphorus concentration in wastewater at reaction time t; C t / C0 represents the removal rate of phosphorus.

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

[0106] Example 4

[0107] This embodiment provides a method for recovering hypophosphorous acid in wastewater by synchronous oxidation, comprising the following steps:

[0108] Wastewater containing hypophosphite (phosphorus in wastewater in the form of hypophosphite ions (H2PO2 -) in the form of 3, adding Fe-Fe2O3 core-shell material to the wastewater containing hypophosphorous to make its concentration 0.1g / L, adding peroxymonosulfate (PMS) to the wastewater, stirring and reacting for 20min, after the reaction, the hypophosphorous is oxidized to generate iron phosphate precipitation; wherein the concentration of each liter of wastewater containing hypophosphorous is 20mgP / L, that is, each liter of wastewater contains 20mg of phosphorus element;

[0109] Here, permonosulfate (PMS) was added to give concentrations of 0.1 mM, 0.3 mM, 0.5 mM, 1 mM, and 2 mM, respectively.

[0110] According to the above method, under the conditions of peroxymonosulfate (PMS) dosage of 0.1mM, 0.3mM, 0.5mM, 1mM, and 2mM, pH = 3, hypophosphorus = 20mg-P / L, and Fe-Fe2O3 core-shell material dosage of 0.1g / L, the removal effect of hypophosphorus is as follows: Figure 7 shown. Figure 7 The vertical axis C0 represents the initial phosphorus concentration in the wastewater, C t represents the phosphorus concentration in wastewater at reaction time t; C t / C0 represents the removal rate of phosphorus.

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

[0112] Further, according to the above method, the dosage of peroxymonosulfate (PMS) was controlled to be 1 mM, and the concentration change during the reaction was tested. Figure 8 shown.

[0113] from Figure 8 It can be seen that as the reaction proceeds, the concentration of permonosulfate (PMS) gradually decreases, and the final residual is 0.2 mM, indicating that during the oxidation of hypophosphite, the removal of hypophosphite is negatively correlated with the concentration of permonosulfate (PMS), and under this condition, permonosulfate (PMS) is excessive.

[0114] Example 5

[0115] This embodiment provides a method for recovering hypophosphorous acid in wastewater by synchronous oxidation, comprising the following steps:

[0116] Wastewater containing hypophosphite (phosphorus in wastewater in the form of hypophosphite ions (H2PO2 -) in the form of 3-8, adding Fe-Fe2O3 core-shell material to the wastewater containing hypophosphorous to make its concentration 0.1g / L, and adding peroxymonosulfate (PMS) to the wastewater to make its concentration 1mM, stirring and reacting for 20min, after the reaction, the hypophosphorous is oxidized and iron phosphate precipitate is generated; wherein the concentration of each liter of wastewater containing hypophosphorous is 20mgP / L, that is, each liter of wastewater contains 20mg of phosphorus element;

[0117] According to the above method, the pH value of the wastewater is adjusted to 3, 4, 5, 6, 7, and 8 respectively. Under the conditions of the pH value of the wastewater being 3, 4, 5, 6, 7, and 8, the removal effect of the hypophosphorus is as follows: Fig. 9 shown. Fig. 9 The vertical axis C0 represents the initial phosphorus concentration in the wastewater, C t represents the phosphorus concentration in wastewater at reaction time t; C t / C0 represents the removal rate of phosphorus.

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

[0119] Further, according to the above method, the pH value of the wastewater was adjusted to 3, and the change of the pH value of the wastewater during the reaction was tested. The results are as follows: Fig.10 shown.

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

[0121] Example 6

[0122] This embodiment provides a method for recovering hypophosphorous acid in wastewater by synchronous oxidation, comprising the following steps:

[0123] Wastewater containing hypophosphite (phosphorus in wastewater in the form of hypophosphite ions (H2PO2 - ) in the form of hypophosphorous) is adjusted to pH 3, Fe-Fe2O3 core-shell material is added to the wastewater containing hypophosphorous to make its concentration 0.1g / L, and peroxymonosulfate (PMS) is added to the wastewater to make its concentration 1mM, and the reaction is stirred for 20min. After the reaction, the hypophosphorous is oxidized and iron phosphate precipitate is generated; wherein the concentration of each L of wastewater containing hypophosphorous is 10-50mgP / L, that is, each L of wastewater contains 10-50mg of phosphorus element.

[0124] According to the above method, when the concentration of phosphorus in the wastewater (calculated as phosphorus element) is 10, 20, 30, 40, 50 mg-P / L, pH = 3, PMS = 1mM, and the dosage of Fe-Fe2O3 core-shell material = 0.1g / L, the removal effect of phosphorus is as follows: Fig.11 shown. Fig.11 The vertical axis C0 represents the initial phosphorus concentration in the wastewater, C t represents the phosphorus concentration in wastewater at reaction time t; C t / C0 represents the removal rate of phosphorus.

[0125] from Fig.11 It can be seen that with the increase of the concentration of secondary phosphorus in the wastewater, the removal effect of this method on secondary phosphorus gradually decreases.

[0126] Example 7

[0127] This embodiment provides a method for recovering hypophosphorous acid in wastewater by synchronous oxidation, comprising the following steps:

[0128] Wastewater containing hypophosphite (phosphorus in wastewater in the form of hypophosphite ions (H2PO2 - ) in the form of 3, adding Fe-Fe2O3 core-shell material to the wastewater containing hypophosphorous to make its concentration 0.1g / L, and adding peroxymonosulfate (PMS) to the wastewater to make its concentration 1mM, stirring and reacting for 20min, after the reaction, the hypophosphorous is oxidized and ferric phosphate precipitate is generated; wherein, the concentration of each liter of wastewater containing hypophosphorous is 20mgP / L, that is, each liter of wastewater contains 20mg of phosphorus element;

[0129] Based on the above method, Cl was 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 make the Cl - 、NO3 - 、CO3 2- The concentration is 5mM.

[0130] In 5mMCl - 、5mMNO3 - 、5mMCO3 2- Under the conditions of 20mg-P / L, pH=3, PMS=1mM, Fe-Fe2O3 core-shell material=0.1g / L, the removal effect of hypophosphorus is shown in the figure. Fig.12 As shown; Fig.12 0.1g / LFe / Fe2O3 means adding 0.1g / LFe-Fe2O3 core-shell material without adding other ions. Fig.12 The vertical axis C0 represents the initial phosphorus concentration in the wastewater, C t represents the phosphorus concentration in wastewater at reaction time t; C t / C0 represents the removal rate of phosphorus.

[0131] from Fig.12 It can be seen that in the presence of Cl - 、NO 3- 、CO3 2- The effect on the removal of secondary phosphorus is basically small, which shows that this method has strong adaptability.

[0132] Example 8 According to the method in Example 1, when phosphorus = 20 mg-P / L, pH = 3, PMS = 1 mM, and Fe-Fe2O3 core-shell material dosage = 0.1 g / L, the used Fe-Fe2O3 core-shell material was recovered and reused, and the Fe-Fe2O3 core-shell material was reused 3 times to examine the removal effect of phosphorus. Fig.13 shown. Fig.12 The vertical axis C0 represents the initial phosphorus concentration in the wastewater, C t represents the phosphorus concentration in wastewater at reaction time t; C t / C0 represents the removal rate of phosphorus.

[0133] from Fig.13 It can be seen that after the Fe-Fe2O3 core-shell material of the present invention is reused three times, it still has a high removal effect on secondary phosphorus.

[0134] Example 9

[0135] According to the method in Example 1, when phosphorus = 20 mg-P / L, pH = 3, PMS = 1 mM, and Fe-Fe2O3 core-shell material dosage = 0.1 g / L, the iron ions of different valence states overflowing during the reaction were measured, and the results were as follows: Fig.14 shown.

[0136] from Fig.14 It can be seen that the total iron maintained an upward trend before 10 minutes, with the highest value being 40 mg / L, and the divalent iron remained at around 5 mg / L. After 10 minutes, the total iron concentration dropped sharply to 25 mg / L, and the divalent iron increased to 22 mg / L, which is the main component of the iron form. This is because the trivalent iron and orthophosphate precipitated after 10 minutes.

[0137] In order to explore the role of iron ions in the homogeneous system, the maximum total iron concentration during the reaction and the final iron ion concentration at the end of the reaction were used as the standard. 20 mg / L and 40 mg / L Fe 2+ (added in the form of FeSO4), 40 mg / L Fe3+ (Added in the form of Fe2(SO4)3) to carry out homogeneous experiments, such as Fig.15 Specifically, the experimental method is:

[0138] Wastewater containing hypophosphite (phosphorus in wastewater in the form of hypophosphite ions (H2PO2 - ) in the form of 3, add FeSO4 or Fe2(SO4)3 to the wastewater containing hypophosphorous, and add peroxymonosulfate (PMS) to the wastewater to make its concentration 1mM, stir and react for 20min, after the reaction, the hypophosphorous is oxidized and ferric phosphate precipitate is generated; wherein, the concentration of each liter of wastewater containing hypophosphorous is 20mg P / L, that is, each liter of wastewater contains 20mg of phosphorus; adding FeSO4 makes Fe 2+ The concentrations were 20mg / L and 40mg / L respectively, and Fe2(SO4)3 was added to make Fe 3+ The concentration is 40 mg / L;

[0139] At the same time, Fe-Fe2O3 core-shell material was added to replace FeSO4 or Fe2(SO4)3 for comparison, and the dosage of Fe-Fe2O3 core-shell material was 0.1 g / L.

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

[0141] from Fig.15 It can be seen that the reaction rate in the homogeneous system is extremely fast, and the effect of divalent iron is better than that of trivalent iron, but the addition of 40mg / LFe 2+ The removal rate of hypophosphite is only about 50%, which is much lower than the effect of heterogeneous materials.

[0142] Example 10

[0143] According to the method in Example 1, when phosphorus = 20 mg-P / L, pH = 3, PMS = 1 mM, and Fe-Fe2O3 core-shell material dosage = 0.1 g / L, the active free radicals in the reaction process were measured by EPR technology, as shown in FIG. Fig.16 shown.

[0144] from Fig.16 It can be seen that the signals of DMPO-·OH and DMPO-SO4·- appeared (the full name of DMPO is 5,5-dimethyl-1-pyrroline N-oxide, which is a commonly used free radical scavenger), indicating that hydroxyl radicals and sulfate radicals were produced in the reaction, and as the reaction proceeds, the hydroxyl signal gradually weakened, and the main active radical gradually turned into sulfate radical.

[0145] Further experiments were conducted using tert-butyl alcohol (TBA), ethanol (EtOH) and aniline (AN) as quenchers at a ratio of quencher:PMS = 500:1. Fig.17 The specific experimental method is: wastewater containing hypophosphorous (phosphorus in the wastewater is in the form of hypophosphite ions (H2PO2 - ) in the form of 3, adding Fe-Fe2O3 core-shell material to the wastewater containing hypophosphorous to make its concentration 0.1g / L, adding peroxymonosulfate (PMS) to the wastewater to make its concentration 1mM, and then adding quenchers tert-butyl alcohol (TBA), ethanol (EtOH) and aniline (AN) respectively, stirring and reacting for 20min; wherein, the concentration of each L of wastewater containing hypophosphorous is 20mg P / L, that is, each L of wastewater contains 20mg of phosphorus; wherein, the molar concentration ratio of quencher tert-butyl alcohol (TBA) to PMS is 500:1, the molar concentration ratio of ethanol (EtOH) to PMS is 500:1, and the molar concentration ratio of aniline (AN) to PMS is 500:1;

[0146] At the same time, a comparison was performed according to the above method without adding any quenching agent.

[0147] Fig.17 (a) shows the removal effect of hypophosphite after adding different quenchers, (b) the apparent reaction rate constant; Fig.17 The vertical axis C0 represents the initial phosphorus concentration in the wastewater, C t represents the phosphorus concentration in wastewater at reaction time t; C t / C0 represents the removal rate of phosphorus; Fig.17 Fe / Fe2O3 means no quenching agent is added, and None means no quenching agent is added.

[0148] from Fig.17It can be seen that the removal rate of hypophosphite is reduced to 75% when TBA is added, 10% when EtOH is added, and 5% when AN is added. The contribution of different free radicals can be calculated based on the removal rate when no quencher is added, among which ·OH contribution rate is 21%, SO4·- contribution rate is 68%, SO5·- contribution rate is 5%, and the remaining 6% is contributed by other active substances. The main free radicals in the reaction are SO4·-, followed by ·OH. When no quencher is added, the apparent reaction rate constant of hypophosphite in the system is kobs=0.25064min-1. After adding TBA, the apparent reaction rate constant is reduced to kobs=0.07912min-1, indicating that the reaction rate of ·OH with hypophosphite is strong. After inhibiting the ·OH free radical, the reaction rate drops sharply. After adding EtOH, the apparent reaction rate is reduced to kobs=0.01158min-1, indicating that the reaction rate of SO4·- with hypophosphite is low.

[0149] Embodiment 11

[0150] When pH = 3, PMS = 1mM, Fe-Fe2O3 core-shell material dosage = 0.1g / L, PMSO = 0.1mM, PMSO (methyl phenyl sulfoxide) and PMSO2 were tested. Fig.18 The specific experimental method is: wastewater containing hypophosphorous (phosphorus in the wastewater is in the form of hypophosphite ions (H2PO2 - ) in the form of 3, Fe-Fe2O3 core-shell material is added to the wastewater containing hypophosphorous acid to make its concentration 0.1g / L, and peroxymonosulfate (PMS) is added to the wastewater to make its concentration 1mM, and then PMSO is added to make its concentration 0.1mM, and the reaction is stirred for 20min; wherein, the concentration of each L of wastewater containing hypophosphorous acid is 20mg P / L, that is, each L of wastewater contains 20mg of phosphorus element.

[0151] from Fig.18 It can be seen that no PMSO2 is produced, indicating that no high-valent iron is generated during the reaction.

[0152] Example 12 According to the method in Example 1, at pH = 3, PMS = 1mM, Fe-Fe2O3 core-shell material dosage = 0.1g / L, the orthophosphorus, hypophosphorus, phosphorous and total phosphorus in the reaction process were measured. The results are as follows: Fig.19 shown.

[0153] Fig.19 Phosphate means orthophosphorus, Total phosphorus means total phosphorus, Hypophosphorus means hypophosphorus, and Phosphite means subphosphorus.

[0154] from Fig.19 It can be seen that the concentrations of hypophosphorus and orthophosphorus gradually increased before 10 minutes, the concentration of hypophosphorus was higher than that of orthophosphorus, and the total phosphorus slowly decreased. After 10 minutes, the concentrations of orthophosphorus, hypophosphorus and total phosphorus decreased sharply. At 20 minutes, the total phosphorus removal rate was about 80%, with 1.7 mg / L orthophosphorus, 1.2 mg / L hypophosphorus and 0.9 mg / L hypophosphorus remaining, that is, 87% of hypophosphorus was converted to orthophosphorus. In general, the reaction process can be divided into two stages, mainly oxidation before 10 minutes, and mainly precipitation after 10 minutes, which is consistent with the change of 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 in the protection scope of the present invention.

Claims

1. A method for recovering hypophosphorous acid from wastewater by simultaneous oxidation, characterized in that: The following steps are involved: Fe-Fe2O3 core-shell material is added to wastewater containing hypophosphorous, and peroxymonosulfate is added to the wastewater at the same time, and the reaction is stirred. After the reaction is completed, the hypophosphorous is oxidized and iron phosphate precipitate with recovery value is generated.

2. The method for recovering hypophosphorous acid from wastewater by synchronous oxidation according to claim 1, characterized in that: The pH of the wastewater containing hypophosphorous acid is 3-7.

3. The method for recovering hypophosphorous acid from wastewater by synchronous oxidation according to claim 1, characterized in that: The mass ratio of the Fe-Fe2O3 core-shell material to the hypophosphorous in the wastewater is greater than or equal to 5:

1.

4. The method for recovering hypophosphorous acid from wastewater by synchronous oxidation according to claim 1, characterized in that: The mass ratio of the peroxymonosulfate to the hypophosphorous in the wastewater is greater than or equal to 15:

1.

5. The method for recovering hypophosphorous acid from wastewater by synchronous oxidation according to claim 1, characterized in that: The Fe-Fe2O3 core-shell material is added to the wastewater containing hypophosphorous acid, and peroxymonosulfate is added to the wastewater at the same time. In the step of stirring the reaction, the reaction time is 10 to 30 minutes.

6. The method for recovering hypophosphorous acid from wastewater by synchronous oxidation according to claim 1, characterized in that: The concentration of hypophosphorous acid in the wastewater is 15-25 mg P / L.

7. The method for recovering hypophosphorous acid from wastewater by synchronous oxidation according to claim 6, characterized in that: Fe-Fe2O3 core-shell material is added to wastewater containing hypophosphorous acid to make its concentration 0.01-0.2 g / L.

8. The method for recovering hypophosphorous acid from wastewater by synchronous oxidation according to claim 6, characterized in that: Fe-Fe2O3 core-shell material is added to wastewater containing hypophosphorous acid, and peroxymonosulfate is added to the wastewater at the same time to make its concentration 0.1-2mM.

9. The method for recovering hypophosphorous acid from wastewater by synchronous oxidation according to claim 1, characterized in that: The preparation method of the Fe-Fe2O3 core-shell material comprises the following steps: Adding a ferric iron salt to water to obtain a ferric iron solution; adding a reducing agent into 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; The ferric salt includes 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; Add the reducing agent solution to the ferric iron solution at a flow rate of 0.1 to 0.3 mL / s; In the step of adding the ferric iron salt to the water, the mass ratio of the ferric iron salt to the water is (1-5):(800-1200); In the step of adding the reducing agent to water, the mass ratio of the reducing agent to water is (3-9):(300-500).

10. The method for recovering hypophosphorous acid from wastewater by synchronous oxidation according to claim 1, characterized in that: The peroxymonosulfate is potassium peroxymonosulfate.

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