Method for intensively removing parachloronitrobenzene in water after removing phosphorus pollution in water by using nanoscale zero-valent iron

Abstract

The invention belongs to the field of water treatment, and relates to a method for intensively removing parachloronitrobenzene in water after removing phosphorus pollution in water by using nano zero-valent iron. The method comprises the following steps: adding nano zero-valent iron into phosphorus-containing to-be-treated water, carrying out a stirring reaction to remove phosphorus in the water, then adding parachloronitrobenzene-containing to-be-treated water, and continuously carrying out a stirring reaction to remove parachloronitrobenzene in the water. The invention provides a novel and efficient method for removing parachloronitrobenzene in water, nanoscale zero-valent iron is used for removing phosphorus and organic pollutants, parachloronitrobenzene can be rapidly and efficiently removed, and the method can adapt to a wide pH value range. The phosphorylated nano zero-valent iron generated in situ after phosphorus removal of the nano zero-valent iron has good reduction performance, and parachloronitrobenzene in water can be efficiently removed. Meanwhile, the nZVI in the method can remove phosphorus and parachloronitrobenzene pollution in water at the same time, the effect of treating waste with waste can be achieved, operation is easy, and the method has wide application prospects.

Description

Technical Field

[0001] This invention belongs to the field of water treatment, specifically relating to a method for enhancing the removal of p-chloronitrobenzene after removing phosphorus pollution from water using nano-zero valent iron. Background Technology

[0002] As an essential element for the growth of plants and animals, excessive phosphorus intake into surface water bodies can lead to eutrophication. Therefore, limiting the total amount of phosphorus in water bodies is crucial to ensuring good water quality and aquatic ecosystem health.

[0003] p-Chlorotibene (p-CNB), a typical chloronitrobenzene, readily enters the human body through inhalation, ingestion, and skin contact. It damages the liver, kidneys, lungs, and spleen, impairs the immune and nervous systems, induces blood diseases, and in severe cases, can lead to death. It is a typical organic pollutant with carcinogenic, mutagenic, and genotoxic effects. p-Chlorotibene has a high octanol-water partition coefficient, readily accumulating in organisms, aquatic sediments, and soil organic matter. It also strongly inhibits the growth of aquatic organisms. Its release into the environment is extremely toxic, and it is listed as a priority controlled organic pollutant.

[0004] Currently, the main methods for removing p-CNB from water bodies include adsorption, advanced oxidation, and biological methods. Adsorption is characterized by its directness, simplicity, and effectiveness. The most commonly used adsorbent is resin, but the adsorbent remains hazardous solid waste after use, with high regeneration costs and risks of secondary pollution such as leaching. Advanced oxidation technologies, including photocatalytic oxidation and ozone oxidation, are highly efficient at degrading p-CNB, but they are energy-intensive, have low safety, and are difficult to apply to in-situ remediation. Biodegradation technologies offer advantages in terms of low cost and ease of operation, but their application is limited by their large footprint, long cycle time, and the ease with which microorganisms can be deactivated. Therefore, developing a green, simple, and efficient method for degrading low concentrations of p-CNB in ​​surface water remains a pressing issue in this field.

[0005] Nano-zero valent iron (nZVI) has been widely used in water treatment due to its excellent reducing ability. However, nZVI particles are prone to agglomeration due to their high surface energy and interparticle magnetic attraction, thus reducing their flowability. In addition to agglomeration, nZVI can rapidly react with surrounding water or oxygen to form an oxide layer covering the particle surface, leading to passivation and reduced activity. Surface-modified nZVI exhibits enhanced stability and flowability, as well as reduced agglomeration and environmental toxicity. Phosphorylated nano-zero valent iron (P-nZVI) is obtained by mixing KH₂PO₄ and ferric chloride, followed by reduction with sodium borohydride. Phosphate modification enhances the adsorption capacity of nano-zero valent iron (nZVI) by altering the binding configuration of heavy metal ions and inducing the Kirkendall effect, resulting in numerous radial nanocracks in nZVI. These cracks promote the diffusion of heavy metal ions, electrons, and ferrous ions, causing electron exchange at the surface and interface, thus forming significant cavitation. However, the aforementioned studies primarily focus on the removal of target pollutants, and the preparation of the aforementioned zero-valent iron phosphate requires mixing, which is energy-intensive, and the reuse of materials is not considered. Furthermore, existing patent CN110606536A, a method for simultaneous phosphorus removal and preparation of zero-valent iron phosphate and its application, prepares iron phosphate by adding micron-sized zero-valent iron to phosphorus-containing wastewater under heating and acidic conditions. However, this method requires heating and acidic conditions, further increasing energy consumption and limiting its application. Additionally, it requires filtration and drying before application, making the process cumbersome.

[0006] Based on this, the present invention proposes to use zero-valent iron to remove phosphorus from water, which is also a process of interaction with phosphate, which helps to generate "in-situ phosphorylated zero-valent iron". This makes the zero-valent iron after phosphorus removal have the potential to enhance the removal of typical pollutant p-CNB in ​​water, while achieving the purpose of treating waste with waste. Summary of the Invention

[0007] The purpose of this invention is to provide a method for removing phosphorus pollution from water using nano-zero valent iron and then enhancing the removal of parachloronitrobenzene from the water, thereby achieving efficient removal of both phosphorus and parachloronitrobenzene and realizing waste treatment.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows: A method for removing phosphorus pollution from water using nano-zero-valent iron followed by enhanced removal of p-chloronitrobenzene from water. The method involves adding nano-zero-valent iron to water containing phosphate, stirring the reaction to remove phosphorus from the water, and simultaneously generating in-situ phosphorylated nano-zero-valent iron. Then, water containing p-chloronitrobenzene is added to the water to be treated, and the reaction is continued with stirring to remove p-chloronitrobenzene from the water.

[0009] Preferably, the average size of the nano-zero valent iron is 500~1200nm, more preferably 809.7nm, and the average size of the in-situ phosphorylated nano-zero valent iron is 500~900nm, more preferably 688.5nm.

[0010] Preferably, the preparation method of the nano-zero valent iron includes: adding 0.3~0.5 mol / L sodium borohydride solution dropwise to 0.01~0.05 mol / L FeCl3·6H2O solution, wherein the volume ratio of sodium borohydride solution to FeCl3·6H2O solution is 2:5, the whole process is completed within 5~10 minutes, and then standing for 2 hours, followed by filtration, freeze drying, and grinding.

[0011] Preferably, the phosphate-containing water to be treated includes eutrophic water bodies that are naturally contaminated with phosphorus.

[0012] Preferably, the phosphate-containing water to be treated is water containing phosphorus-containing acid radicals, and / or the pH of the water containing phosphorus-containing acid radicals is adjusted to 3-13, wherein the phosphorus-containing acid radicals include at least one of phosphate, monohydrogen phosphate, dihydrogen phosphate, etc.

[0013] Preferably, the dosage of the nano-zero valent iron, calculated as a phosphorus-iron molar ratio, is 0.185~3.69:1000; And / or, the TP concentration in the phosphate-containing water to be treated is 1~20 mg / L; more preferably 5~20 mg / L.

[0014] Preferably, the in-situ phosphorylated nano-zero-valent iron is generated in situ at room temperature, i.e., the stirring reaction is carried out at room temperature. The room temperature is preferably 10-30℃, more preferably 20-25℃.

[0015] Preferably, the pH of the reaction after adding nano-zero valent iron is 3-13, the stirring speed is 150-200 rpm, and the stirring time is 4-6 h.

[0016] Preferably, the in-situ phosphorylated nano-zero-valent iron surface includes FeOOH (hydroxylated iron oxide) and phosphate minerals such as FePO4·2H2O (iron phosphate) and Fe3(PO4)2.

[0017] Preferably, the initial concentration of p-CNB in ​​the solution system after adding p-chloronitrobenzene to the water to be treated is 200-500 μg / L.

[0018] Preferably, after adding water containing p-chloronitrobenzene to be treated, the mass ratio of phosphorylated nano-zero-valent iron to p-chloronitrobenzene in the solution system is in the range of 10000~20000.

[0019] More preferably, the dosage of the nano-zero valent iron is 3 g / L, the volume of the water to be treated containing phosphate is 150 mL, and the TP concentration of the phosphate solution is 1~20 mg / L; the water to be treated containing p-chloronitrobenzene is added using p-CNB mother liquor, the volume of p-CNB mother liquor is 0.3 mL, the concentration is 100 mg / L, and the initial concentration of p-CNB in ​​the solution system after addition is 200~500 μg / L.

[0020] Preferably, the removal reaction of p-chloronitrobenzene is carried out at room temperature, i.e., the stirring reaction is carried out at room temperature. The room temperature is preferably 10-30℃, more preferably 20-25℃.

[0021] Preferably, the pH of the reaction for removing chloronitrobenzene is 3 to 13, more preferably 6.5.

[0022] Preferably, the stirring speed for the removal reaction of p-chloronitrobenzene is 150-200 rpm and the stirring time is 10-12 h.

[0023] Preferably, all reactions described in this invention can be carried out in an aerobic environment.

[0024] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention provides a method for enhanced removal of p-chloronitrobenzene (p-CNB) from water after removing phosphorus pollution with nano-zero-valent iron (nZVI). This invention can remove phosphorus pollution from water under aerobic conditions at room temperature, while simultaneously generating phosphoric acid nano-zero-valent iron in situ. Subsequently, the phosphoric acid nano-zero-valent iron (P-nZVI) generated in situ after phosphorus removal is directly used for the removal of organic pollutants, achieving rapid and efficient removal of p-CNB, and is adaptable to a wide pH range. P-nZVI has good reducing properties and can efficiently remove p-CNB from water. Furthermore, in this method, nZVI removes total phosphorus from water and then continues to remove p-chloronitrobenzene pollution, achieving the effect of treating waste with waste. The operation is simple and has broad application prospects. Attached Figure Description

[0025] Figure 1 This is a SEM image of in-situ phosphorylated nano-zero-valent iron in Example 1.

[0026] Figure 2 These are the nitrogen adsorption-desorption curves and pore size distribution diagrams of in-situ phosphorylated nano-zero-valent iron in Example 1.

[0027] Figure 3 This is a particle size distribution diagram of (a) nano-zero valent iron and (b) in-situ phosphorylated nano-zero valent iron in Example 1.

[0028] Figure 4 This is the FTIR spectrum of in-situ phosphorylated zero-valent iron in Example 1.

[0029] Figure 5 This is a comparison chart of the effect of nZVI in removing TP at different initial concentrations in Example 1, where [nZVI]0 = 3 g / L, pH = 6.5, and rotation speed = 200 rpm.

[0030] Figure 6 This is a comparison chart of the effects of nZVI on the removal of p-CNB after removing TP at different initial concentrations in Example 1. [nZVI]0=3g / L, [p-CNB]0=200 μg / L, pH=6.5, rotation speed=200 rpm.

[0031] Figure 7 This is the effect of different initial pH values ​​on the removal of p-CNB by in-situ phosphorylated nano-zero valent iron in Example 2, [P-nZVI]0=3 g / L, [p-CNB]0=200 μg / L, rotation speed=200 rpm, initial TP=5 mg / L.

[0032] Figure 8 This is a diagram showing the reuse effect of in-situ phosphorylated nano-zero-valent iron for removing p-CNB in ​​Example 3, with [P-nZVI]0=3 g / L, [p-CNB]0=200 μg / L, initial TP=5 mg / L, pH=6.5, and rotation speed=200 rpm.

[0033] Figure 9 This is an actual water body effect diagram of in-situ phosphorylated nano-zero valent iron removal of p-CNB in ​​Example 4, [P-nZVI]0=3 g / L, [p-CNB]0=200 μg / L, initial TP=5 mg / L, pH=6.5, rotation speed=200 rpm.

[0034] Figure 10 This is a comparison chart of the effect of mZVI on removing TP at different initial concentrations in Comparative Example 1, where [mZVI]0 = 3 g / L, pH = 6.5, and rotation speed = 200 rpm.

[0035] Figure 11 This is a diagram showing the actual water quality effect of in-situ phosphorylation of micron-sized zero-valent iron in Comparative Example 1 for removing p-CNB. [P-mZVI]0 = 3 g / L, [p-CNB]0 = 200 μg / L, pH = 6.5, rotation speed = 200 rpm.

[0036] Figure 12 This is a comparison chart of the effect of nZVI on the removal of atrazine after removing different initial concentrations of TP in Comparative Example 2. [nZVI]0=3 g / L, [Atrazine]0=100 μg / L, pH=6.5, rotation speed=200 rpm. Detailed Implementation

[0037] To better clarify and understand the objectives, process solutions, and advantages of this invention, the technical solutions and implementation methods of this invention will be further described clearly, completely, and in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the embodiments described in this invention are implemented under the premise of the technical solutions of this invention, providing detailed implementation methods and specific operating procedures, but are only some embodiments of this invention, not all embodiments. The specific implementation methods described are limited to illustrating and explaining this invention and do not limit this invention. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0038] Unless otherwise specified, the experimental methods and conditions used in the embodiments of this invention are conventional methods and conditions. The materials, reagents, instruments, and equipment used in the embodiments, unless otherwise specified, are all conventional substances or equipment known to those skilled in the art and can be obtained commercially or prepared by conventional methods. The reaction conditions described in the invention's content can all achieve the stated reactions and obtain the desired products. Due to space limitations, some embodiments are listed below to further illustrate the advantages of the technical solution of this invention.

[0039] Example 1

[0040] (1) In-situ P-nZVI material obtained from phosphorus removal experiment: Nano-zero valent iron (nZVI): In this study, nano-zero valent iron was prepared by reducing trivalent iron with sodium borohydride. The specific method is as follows: A solution A of 0.01 mol / L FeCl3·6H2O was prepared, and a solution B of 0.4 mol / L NaBH4 was prepared, with a volume ratio of A:B = 5:2. Solution B was added dropwise to solution A over 10 min, and the mixture was allowed to stand for 2 h. After standing, the obtained nZVI was vacuum filtered, repeatedly washed with deionized water and anhydrous ethanol, and then freeze-dried at -40℃ and below 10 kPa for 2 h to obtain nano-zero valent iron (nZVI). The nano-zero valent iron was then ground and stored for later use.

[0041] The in-situ P-nZVI material formation process was as follows: 0.45 g of nano-zero-valent iron and 150 mL of initial TP=5 mg / L solution (prepared with KH2PO4, pH=5.6) were added to a 150 mL Erlenmeyer flask. The flask was tightly sealed and placed on a shaker at 200 rpm for 4 h. The reaction temperature was 25℃. The in-situ P-nZVI material was then collected in the Erlenmeyer flask. After vacuum filtration, repeated washing with deionized water and anhydrous ethanol, and lyophilization for 2 h, the resulting solid sample was used for characterization. Figure 1These are SEM images of in-situ phosphorylated zero-valent iron (a: nZVI 500x, b: P-nZVI 500x; c: nZVI 5000x, d: P-nZVI 5000x; e: nZVI 20000x, f: P-nZVI 20000x, where nZVI is nano-zero-valent iron and P-nZVI is in-situ phosphorylated zero-valent iron). It can be seen that the particle distribution of P-nZVI is more dispersed than that of nZVI. Figure 2 It shows the nitrogen adsorption-desorption curve and pore size distribution of in-situ phosphorylated zero-valent iron. Figure 3 The particle size distribution diagrams of (a) nano-zero valent iron and (b) in-situ phosphorylated nano-zero valent iron in Example 1 show that the average particle size of P-nZVI is significantly smaller than that of nZVI. Figure 4 The FTIR spectrum of P-nZVI shows the presence of Fe-OP, OH, PO, and POH functional groups on its surface. Based on this, it can be inferred that the surface of P-nZVI contains FeOOH (hydroxylated iron oxide), FePO4·2H2O (iron phosphate), Fe3(PO4)2, and other phosphate minerals. Table 1 summarizes the specific surface area, pore volume, and average pore size of nZVI and P-nZVI. It can be seen that the specific surface area and pore volume of P-nZVI are significantly greater than those of nZVI.

[0042]

[0043] (2) Experimental method: 1. Add 0.45g of nano-zero valent iron prepared in (1) and 150mL of TP solution with different initial concentrations (1 mg / L, 5 mg / L, 10 mg / L, 20 mg / L) (referring to the mass concentration of P, prepared with KH2PO4) to a 150mL conical flask, seal the flask tightly, and place it on a shaker at 200rpm for 4h. The experimental reaction temperature is 25℃. Sampling time points are 30, 60, 120, 180, and 240min. The solution after reaction is drawn with a 1mL syringe and filtered through a 0.45μm mixed cellulose membrane. The TP concentration of the liquid sample is determined using a UV spectrophotometer.

[0044] Test results are available Figure 5 As shown, Figure 5 The graph shows a comparison of the effects of nZVI on removing TP at different initial concentrations. It can be seen that the initial dosage of nZVI was 3 g / L. After 4 hours of reaction, the removal rate of nZVI for initial TP of 1 mg / L and 5 mg / L was over 99%, and the remaining TP met the national Class III water standard. The removal rate for initial TP of 10 mg / L and 20 mg / L was also over 75%.

[0045] 2. Based on Experiment 1, add 0.3 mL of 100 mg / L p-CNB stock solution to bring the initial p-CNB concentration in the conical flask to 200 μg / L. Simultaneously, set up an example of the removal effect of unphosphorylated nano-zero-valent iron (nZVI) on p-CNB. Specifically, repeat the steps of Experiment 1, but add only pure water with TP = 0 mg / L. After reacting for 4 hours, add 0.3 mL of 100 mg / L p-CNB stock solution to bring the initial p-CNB concentration in the conical flask to 200 μg / L. After tightening the stopper, place the conical flask on a shaker at 200 rpm at room temperature. The initial pH of the solution is 6.5. During the reaction, take 1 mL samples periodically, filter through a 0.45 μm mixed cellulose membrane, inject into a liquid chromatography vial, and finally analyze by high-performance liquid chromatography (HPLC).

[0046] Test results are available Figure 6 As shown, Figure 6 The graph compares the effects of nZVI on p-CNB removal after removing TP with different initial concentrations. It shows that with an nZVI dosage of 3 g / L and an initial p-CNB concentration of 200 μg / L, after 10 hours of reaction, the removal rate of p-CNB by nZVI was 60.2%. Furthermore, the in-situ generated p-nZVI, after removing TP with an initial concentration above 5 mg / L, achieved a p-CNB removal rate of over 97.2% after 10 hours. This indicates that compared to nZVI, the in-situ generated p-nZVI significantly improves the removal efficiency of p-CNB.

[0047] Example 2

[0048] The method described in Example 1 was used. First, 0.45 g of nZVI material was weighed and added to a 150 mL Erlenmeyer flask, followed by 150 mL of a TP = 5 mg / L solution, and then diluted with a 1 mol / L solution. Adjust the pH of the solution to 3, 5, 6.5, 9, or 13 using HCl or NaOH, tighten the stopper, and place the flask on a shaker at 200 rpm for 4 hours. The reaction temperature is 25℃. After phosphorus removal, add 0.3 mL of 100 mg / L p-CNB solution to bring the initial concentration to 200 μg / L. Tighten the stopper and place the conical flask on a shaker at 200 rpm at room temperature. Take 1 mL samples periodically during the reaction, filter them through a 0.45 μm mixed cellulose membrane, and inject them into a liquid chromatography vial. Finally, analyze the results by high-performance liquid chromatography (HPLC).

[0049] Test results are available Figure 7 As shown, Figure 7The effect of initial solution pH on the removal of p-CNB by P-nZVI was investigated. It can be seen that within the pH range of 3–13, the removal rate of p-CNB by the material within 10 hours can reach over 95%. With increasing pH, the removal rate of p-CNB by the material increases; within the pH range of 6.5–13, the removal rate of p-CNB can be maintained above 97% after 10 hours of reaction, and within the pH range of 9–13, the removal rate can be maintained above 99% after 10 hours of reaction.

[0050] Example 3

[0051] The method described in Example 1 was followed. First, 0.45 g of nZVI material was weighed and added to a 150 mL Erlenmeyer flask, followed by 150 mL of TP = 5 mg / L solution. The flask was then tightly sealed and placed on a shaker at 200 rpm for 4 hours at a reaction temperature of 25°C. After phosphorus removal, 0.3 mL of 100 mg / L p-CNB solution was added to bring the initial concentration to 200 μg / L. The stopper was tightened, and the Erlenmeyer flask was placed on a shaker at 200 rpm at room temperature with an initial pH of 6.5. After 10 hours of reaction, a certain volume of 100 mg / L p-CNB solution was added again to bring the initial concentration to 200 μg / L. The above steps were repeated five times. Samples were taken periodically during the reaction, 1 mL each time. The sample was filtered through a 0.45 μm mixed cellulose membrane and injected into a liquid chromatography vial. Finally, the samples were analyzed by high-performance liquid chromatography (HPLC).

[0052] Test results are available Figure 8 As shown, Figure 8 The image shows the effect of reusing P-nZVI to remove p-CNB. It can be seen that in the first three reuses, the removal rate of p-CNB can be maintained above 90% within 10 hours. As the number of reuses increases, the removal rate of p-CNB by the material gradually decreases. When the number of reuses is 4-5, the removal rate of p-CNB by the material is still above 75%.

[0053] Example 4

[0054] The method described in Example 1 was followed. First, 0.45 g of nZVI material was weighed and added to a 150 mL Erlenmeyer flask. Then, 150 mL of different water sources (pure water, tap water, river water, or lake water) with a TP concentration of 5 mg / L were added. The flask was tightly sealed and placed on a shaker at 200 rpm for 4 hours at a reaction temperature of 25°C. After phosphorus removal, an appropriate volume of p-CNB solution was added to achieve an initial concentration of 200 μg / L. The stopper was tightened, and the Erlenmeyer flask was placed on a shaker at 200 rpm at room temperature with an initial pH of 6.5. Samples were taken periodically during the reaction, 1 mL each time. After filtration through a 0.45 μm mixed cellulose membrane, the sample was injected into a liquid chromatography vial and finally analyzed by high-performance liquid chromatography (HPLC). The purified water was purchased from Wahaha Purified Water, the tap water was taken from the laboratory's tap water network, the lake water was taken from Xianghu Lake in Xiaoshan District, Hangzhou, and the river water was taken from the lower reaches of the Qiantang River in Hangzhou. Both samples were taken on May 14, 2025.

[0055] Test results are available Figure 9 As shown, Figure 9 The image shows the actual water body effect of P-nZVI removing p-CNB. It can be seen that the degradation rate of the group using Qiantang River water is slightly lower than that of other groups, but all types of actual water bodies can guarantee a p-CNB removal rate of over 95% within 10 hours.

[0056] Comparative Example 1

[0057] Based on Example 1, the preparation method of micron-sized zero-valent iron ZVI is the same as the experimental method in (2) above, except that nZVI is replaced with commercially available micron-sized zero-valent iron (mZVI). The test results are shown in […]. Figure 10 As shown, the initial dosage of mZVI was 3 g / L. After 4 hours of reaction, the removal rate of mZVI for the initial TP of 1~20 mg / L was less than 50%.

[0058] Figure 11 A comparison of the effects of mZVI on the removal of p-CNB after different initial TP concentrations is shown. It can be seen that the mZVI dosage was 3 g / L, and the initial p-CNB concentration was 200 μg / L. After 10 h of reaction, the maximum removal rate of p-CNB by mZVI was 63.8%, indicating that compared with nZVI, the in-situ generated p-mZVI had a worse removal effect on p-CNB. Micron-sized zero-valent iron is not suitable for the modification method of this invention.

[0059] Comparative Example 2

[0060] Based on Example 1, 0.3 mL of 100 mg / L p-CNB stock solution was replaced with 0.15 mL of 100 mg / L atrazine stock solution, so that the initial concentration of atrazine in the conical flask was 100 μg / L. Other operating procedures were the same as in Example 1. Test results are shown below. Figure 12 As shown, after 6 hours of reaction, the removal rate of atrazine by P-nZVI was at most 9.8%, which was lower than the removal rate of atrazine by nZVI. This indicates that, compared with nZVI, the in-situ generated P-nZVI had a worse removal effect on atrazine. Atrazine is not suitable for the modification method of this invention.

[0061] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications may be made without departing from the technical solutions described in the claims.

Claims

1. A method for enhancing the removal of p-chloronitrobenzene from water after removing phosphorus pollution with nano-zero valent iron, characterized in that, The method involves adding nano-zero-valent iron to water containing phosphate, stirring the reaction to remove phosphorus from the water, and simultaneously generating in-situ phosphorylated nano-zero-valent iron. Then, water containing p-chloronitrobenzene is added to the water to be treated, and the reaction is continued to remove p-chloronitrobenzene from the water.

2. The method for enhanced removal of p-chloronitrobenzene from water after removing phosphorus pollution with nano-zero valent iron according to claim 1, characterized in that, The phosphate-containing water to be treated is water containing phosphorus-containing acid radicals, and / or the pH of the water containing phosphorus-containing acid radicals is adjusted to 3-13.

3. The method for enhanced removal of p-chloronitrobenzene from water after removing phosphorus pollution with nano-zero valent iron according to claim 2, characterized in that, Phosphorus-containing acid radicals include at least one of phosphate, monohydrogen phosphate, and dihydrogen phosphate.

4. The method for enhanced removal of p-chloronitrobenzene from water after removing phosphorus pollution with nano-zero valent iron according to claim 1, characterized in that, The preparation method of the nano-zero valent iron includes: adding 0.3~0.5 mol / L sodium borohydride solution dropwise to 0.01~0.05 mol / L FeCl3·6H2O solution, with a volume ratio of sodium borohydride solution to FeCl3·6H2O solution of 2:

5. The whole process is completed within 5~10 minutes, and then standing for 2 hours, followed by filtration, freeze drying, and grinding.

5. The method for enhanced removal of p-chloronitrobenzene from water after removing phosphorus pollution with nano-zero valent iron according to claim 1, characterized in that, The dosage of the nano-zero valent iron, calculated as a phosphorus-iron molar ratio, is 0.185~3.69:1000; And / or, the TP concentration in the phosphate-containing water to be treated is 1~20 mg / L.

6. The method for enhanced removal of p-chloronitrobenzene from water after removing phosphorus pollution with nano-zero valent iron according to claim 1, characterized in that, After adding nano-zero valent iron, the pH of the reaction was 3-13, the stirring speed was 150-200 rpm, and the stirring time was 4-6 h. And / or, the stirring reaction is carried out at room temperature.

7. The method for enhanced removal of p-chloronitrobenzene from water after removing phosphorus pollution with nano-zero valent iron according to claim 1, characterized in that, The initial concentration of p-CNB in ​​the solution system after adding p-chloronitrobenzene was 200-500 μg / L.

8. The method for enhanced removal of p-chloronitrobenzene from water after removing phosphorus pollution with nano-zero valent iron according to claim 5 or 7, characterized in that, The dosage of the nano-zero-valent iron is 3 g / L, the volume of the water to be treated containing phosphate is 150 mL, and the TP concentration of the phosphate solution is 1~20 mg / L; the water to be treated containing p-chloronitrobenzene is added using p-CNB mother liquor, the volume of p-CNB mother liquor is 0.3 mL, the concentration is 100 mg / L, and the initial concentration of p-CNB in ​​the solution system after addition is 200~500 μg / L.

9. The method for enhanced removal of p-chloronitrobenzene from water after removing phosphorus pollution with nano-zero valent iron according to claim 1, characterized in that, The removal reaction of p-chloronitrobenzene was carried out at room temperature.

10. The method for enhanced removal of p-chloronitrobenzene from water after removing phosphorus pollution with nano-zero valent iron according to claim 1, characterized in that, The stirring speed for the removal reaction of chloronitrobenzene was 150-200 rpm, and the stirring time was 10-12 h. And / or, the pH for the removal reaction of chloronitrobenzene is 3 to 13.

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