A phosphating-modified zero-valent iron material, its preparation method and application

Abstract

The present invention provides a method for preparing a phosphating-modified zero-valent iron material, comprising the following steps: (1) adding zero-valent iron with surface dirt and passivation layer removed into a surface conditioning solution and soaking it sufficiently to obtain surface-treated zero-valent iron; (2) adding the surface-treated zero-valent iron into a phosphating solution, and performing surface phosphating at 20-100°C under stirring conditions, and cleaning the surface-phosphated zero-valent iron to obtain a phosphating-modified zero-valent iron material. The phosphating-modified zero-valent iron material prepared by this method is composed of zero-valent iron and a phosphide coating. The structure of the phosphide coating is dense, and the phosphide coating uniformly and completely coats the surface of the zero-valent iron to form a core-shell structure. The present invention also provides the application of the above phosphating-modified zero-valent iron material in environmental pollution treatment and environmental remediation. The present invention can effectively improve the activity and cyclic use performance of zero-valent iron, and enhance its ability to repair and treat environmental pollution.

Description

Technical Field

[0001] The present invention belongs to the field of environmental remediation and treatment, and relates to a phosphating modified zero-valent iron material, a preparation method thereof and an application thereof. Background Art

[0002] Zero-valent iron is an inexpensive and easily available environmental functional material. Zero-valent iron can remove pollutants such as heavy metals, inorganic nutrients, and organic substances in polluted environments through direct reduction or catalytic oxidation, and has been widely used in the fields of wastewater treatment, water environment governance, soil remediation, and reservoir silt treatment. However, there are still major problems in the direct application of zero-valent iron at present. Commonly used zero-valent iron includes nano zero-valent iron, micro zero-valent iron, and millimeter zero-valent iron. Nano zero-valent iron has high reaction and catalytic activities, but due to its too small particle size, there are problems such as easy passivation and inactivation, difficult storage, difficult recovery, and too high production costs. Although the prices of micro zero-valent iron and millimeter zero-valent iron are relatively cheap, there are problems such as low pollutant degradation efficiency, easy caking and passivation, narrow pH application range, and large amount of iron sludge generation. Therefore, how to effectively enhance the catalytic activity and service performance of zero-valent iron remains one of the key problems to be solved in the field of environmental remediation and treatment.

[0003] Surface modification of zero-valent iron is one of the effective means to improve the activity of zero-valent iron, delay passivation, and extend the service life. For example, there are reports of forming a core-shell structure zero-valent iron by loading a sulfur-containing coating on the surface of zero-valent iron through ball milling, surface treatment, etc. Although loading a sulfur-containing coating on the surface of zero-valent iron can effectively promote electron transfer, accelerate the electron release process of zero-valent iron inside zero-valent iron, thereby improving the pollutant treatment efficiency, preventing caking and passivation, and broadening the pH application range, the sulfur-containing coating of the currently prepared sulfurized zero-valent iron is not dense enough, and the coating thickness and density are difficult to accurately control, and the efficiency of using sulfurized zero-valent iron for pollutant degradation also needs to be further improved.

[0004] Surface phosphating of zero-valent iron is a method to improve the reactivity of zero-valent iron. Chinese patent application No. 201811066530.0 discloses a method for promoting the reduction and removal of heavy metal ions by nano-zero-valent iron by phosphating, wherein a sodium borohydride solution is added dropwise to a ferric chloride solution, and phosphate is immediately added, followed by aging, filtration, and drying to obtain phosphated nano-zero-valent iron. Adding the phosphated nano-zero-valent iron to an aqueous solution containing heavy metal ions can achieve the reduction and removal of heavy metals. Chinese patent application No. 202210035565.8 discloses a method for efficiently removing complexed lead from high-salinity wastewater by using phosphorus-modified nano-zero-valent iron. Phosphorus-modified nano-zero-valent iron is prepared by reacting phosphate with nano-zero-valent iron in a liquid phase, and an appropriate P / Fe molar ratio is controlled to generate iron-phosphorus compounds on the surface of nano-zero-valent iron, which are then used to remove complexed lead from high-salinity wastewater. However, the above methods all form discrete and loose phosphating layers on the surface of zero-valent iron, which can be seen in Removal of lead complexes by ferrous phosphate and iron phosphate: Unexpected favorable role of ferrous ions. The degree of improvement on the activity of zero-valent iron is relatively limited. Therefore, how to form a more dense, uniform and complete phosphating layer on the surface of zero-valent iron, promote electron transfer through a complete core-shell structure, further improve the reaction activity of zero-valent iron, protect the internal zero-valent iron, slow down the passivation of zero-valent iron, and extend its service life is a problem that needs to be solved urgently. Summary of the invention

[0005] In response to the current problems in the application of zero-valent iron in environmental remediation and treatment, the present invention provides a phosphating-modified zero-valent iron material and its preparation method and application, so as to effectively improve the activity and recycling performance of zero-valent iron and enhance its environmental pollution remediation and treatment capabilities.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a phosphating modified zero-valent iron material comprises the following steps:

[0008] (1) adding zero-valent iron after removing surface dirt and passivation layer into a surface conditioning solution and fully soaking it to obtain zero-valent iron after surface treatment;

[0009] The surface conditioning liquid is obtained by dissolving at least one of pyrophosphate and sodium phosphate and titanium sulfate in water, wherein the concentration of pyrophosphate in the surface conditioning liquid does not exceed 1 g / L, the concentration of sodium phosphate does not exceed 1 g / L, and the concentration of titanium sulfate is 0.1 to 1 g / L;

[0010] (2) Add the surface-treated zero-valent iron into the phosphating solution, and perform surface phosphating at 20-100°C under stirring conditions. Wash the surface-phosphated zero-valent iron to obtain the phosphating-modified zero-valent iron material; the phosphating solution includes dihydrogen phosphate, phosphoric acid, and an oxidant. The concentration of dihydrogen phosphate in the phosphating solution is 30-100 g / L, the concentration of phosphoric acid is 0.1-10 g / L, and the concentration of the oxidant is 5-100 g / L.

[0011] In the technical solution of the preparation method of the above phosphating-modified zero-valent iron material, after step (1) uses the surface conditioning solution to soak the zero-valent iron, an activation center layer can be formed on the surface of the zero-valent iron, which is beneficial to the deposition of phosphorus on the surface of the zero-valent iron. At the same time, it ensures that the surface acidity of the zero-valent iron is appropriate, which is beneficial to the formation of a uniform and dense phosphide coating during the subsequent phosphating reaction process.

[0012] In the technical solution of the preparation method of the above phosphating-modified zero-valent iron material, the dihydrogen phosphate includes at least one of zinc dihydrogen phosphate, manganese dihydrogen phosphate, iron dihydrogen phosphate, manganese-iron dihydrogen phosphate salt, and calcium dihydrogen phosphate.

[0013] In the technical solution of the preparation method of the above phosphating-modified zero-valent iron material, the oxidant includes at least one of nitrates, chlorides, and hydrogen peroxide. The nitrates include potassium nitrate, sodium nitrate, zinc nitrate, manganese nitrate, etc., and the chlorides include potassium chloride, sodium chloride, etc.

[0014] Furthermore, in order to achieve a better phosphating effect, in step (2) of the technical solution of the preparation method of the above phosphating-modified zero-valent iron material, the phosphating solution also contains one or more of a reducing substance, a metal salt with a positive potential, and an organic matter. The main function of the reducing substance is to remove hydrogen and Fe 2+ , accelerate the reaction rate, and improve the efficiency and quality of phosphating; the main function of the metal salt with a positive potential is to refine and densify the crystallization of the phosphating film and improve the quality of the phosphide coating; the main function of the organic matter is to complex metals to increase the effective nucleation points and reduce the deposition of phosphating slag. Preferably, the concentration of the reducing substance, the metal salt with a positive potential, or the organic matter in the phosphating solution is 0.1-100 g / L.

[0015] Even further, in the technical solution of the preparation method of the above phosphating-modified zero-valent iron material, the reducing substance includes at least one of sodium nitrite and sodium sulfite; the metal salt with a positive potential includes at least one of nickel salt, copper salt, cobalt salt, and manganese salt; the organic matter includes at least one of tartaric acid and tannic acid.

[0016] In the technical solution of the preparation method of the above phosphating-modified zero-valent iron material, the time for surface phosphating in step (2) is 5-1200 min.

[0017] In the technical solution of the above preparation method of the phosphating modified zero-valent iron material, step (2) can be carried out under the conditions of static state, stirring or ultrasonic treatment for surface phosphating.

[0018] In the technical solution of the above preparation method of the phosphating modified zero-valent iron material, the zero-valent iron for removing surface dirt and passivation layer is obtained by cleaning zero-valent iron by combining one or more of pickling, alkali washing and alcohol washing. The zero-valent iron is nano-scale, micro-scale or millimeter-scale zero-valent iron.

[0019] The present invention also provides a phosphating modified zero-valent iron material prepared by the above preparation method of the phosphating modified zero-valent iron material, which is composed of zero-valent iron and a phosphide coating. The structure of the phosphide coating is dense, and the phosphide coating uniformly and completely coats the surface of zero-valent iron to form a core-shell structure.

[0020] The present invention also provides an application of the above phosphating modified zero-valent iron material in environmental pollution treatment and environmental remediation. The application is to add the phosphating modified zero-valent iron material, or the phosphating modified zero-valent iron material and an oxidizing material together into the environmental medium to be treated for pollutant removal.

[0021] Further, in the above application, the oxidizing material is at least one of hydrogen peroxide, persulfate, peracetic acid, ozone, oxygen, ferrate, permanganate, periodate, calcium peroxide. The environmental medium to be treated includes polluted water bodies and soils, such as sewage, polluted soil, reservoir and river sludge, etc.

[0022] In the above application, the application includes the removal of heavy metals, organic substances, nutrients and inorganic anions.

[0023] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0024] 1. The present invention provides a zero-valent iron modification technology. By surface phosphating, a complete, uniform and dense phosphide coating is formed on the surface of zero-valent iron, and a phosphating modified zero-valent iron material with a core-shell structure is obtained. Compared with the existing zero-valent iron surface modification technology, the method of the present invention coats a complete phosphide coating on the surface of zero-valent iron, and the density of the phosphide coating is better. On the one hand, this can effectively promote the electron transfer of iron and improve the oxidation efficiency. On the other hand, the complete, uniform and dense phosphide coating can effectively prevent the direct contact between the internal zero-valent iron and the environmental medium, and thus can effectively alleviate the problem of caking and passivation during long-term use, improve the recycling performance of zero-valent iron, and extend the service life.

[0025] 2. By adjusting the process parameters of the surface treatment and surface phosphating process, the method of the present invention can control the thickness, crystal structure and porosity of the phosphide coating, and then specifically develop highly active phosphating modified zero-valent iron materials for different pollutants and environmental media to be treated.

[0026] 3. The method of the present invention is easy to operate, low in cost, with few limiting conditions. The phosphating solution can be recycled, has low cost and is suitable for industrial production, having potential economic benefit advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a scanning electron microscope image of the phosphating modified zero-valent iron material prepared in Example 1.

[0028] Figure 2 is a scanning electron microscope image of unmodified zero-valent iron.

[0029] Figure 3 is a scanning electron microscope image of the phosphating modified zero-valent iron material prepared in Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0030] The following further illustrates the phosphating modified zero-valent iron material, its preparation method and application according to the present invention by way of examples. It is necessary to point out that the following examples are only for further illustrating the present invention and should not be construed as limiting the protection scope of the present invention. Those skilled in the art make some non-essential improvements and adjustments to the present invention based on the above-mentioned invention content and carry out specific implementation, which still fall within the protection scope of the invention.

[0031] Example 1

[0032] In this example, the preparation of the phosphating modified zero-valent iron material is as follows:

[0033] (1) Cleaning

[0034] Select zero-valent iron with a particle size of 120 μm, place the zero-valent iron in a 1 wt% hydrochloric acid solution, and mechanically stir for 30 min to remove the dirt and passivation layer on the surface of the zero-valent iron.

[0035] (2) Surface treatment

[0036] Add the zero-valent iron from which the surface dirt and passivation layer have been removed to the surface conditioning solution, soak it at 25 °C for 30 min to obtain the surface-treated zero-valent iron; the surface conditioning solution is obtained by dissolving titanyl sulfate and pyrophosphate in water. In the surface conditioning solution, the concentration of titanyl sulfate is 0.2 g / L and the concentration of pyrophosphate is 0.2 g / L.

[0037] (3) Surface phosphating

[0038] Add the surface-treated zero-valent iron to the phosphating solution, and treat it at 60 °C for 30 min under stirring conditions to phosphatize the surface of the zero-valent iron. Wash the surface-phosphatized zero-valent iron with deionized water to obtain the phosphatization-modified zero-valent iron material.

[0039] The phosphating solution is obtained by dissolving ferromanganese dihydrogen phosphate and zinc nitrate in deionized water, and then adjusting the free acidity to 5 with phosphoric acid. In this phosphating solution, the concentration of ferromanganese dihydrogen phosphate is 30 g / L, and the concentration of zinc nitrate is 80 g / L.

[0040] The scanning electron microscope image of the phosphatization-modified zero-valent iron material prepared in this example is as Figure 1 shown, and its surface element content is shown in Table 1. The morphology of the unmodified zero-valent iron, that is, the zero-valent iron raw material used in step (1), is as Figure 2 shown. By comparison Figures 1 - 2 it can be seen that the unmodified zero-valent iron presents a sponge-like shape. After the phosphatization process, a protective film can be formed on the surface of the zero-valent iron, and phosphorus elements can be detected on the surface (carbon elements mainly come from the instrument background matrix, not from the zero-valent iron).

[0041] Table 1 Surface element distribution table of phosphated zero-valent iron

[0042] element wt% At% C 37.87 63.18 O 14.59 18.26 Fe 42.16 15.08 P 5.38 3.48 total amount 100.00 100.00

[0043] The following is the wastewater treatment using the phosphatization-modified zero-valent iron material prepared in this example:

[0044] 1. Single use

[0045] Add the phosphatization-modified zero-valent iron material and persulfate to a 10 μmol / L carbamazepine solution to degrade carbamazepine. The addition amount of the phosphatization-modified zero-valent iron material is 200 mg / L, and the addition amount of persulfate is 0.2 mmol / L. During the degradation of carbamazepine, samples are taken at regular intervals to test the concentration of carbamazepine, and the removal rate of carbamazepine is calculated. The results show that after 30 min of degradation treatment, the removal rate of carbamazepine is 81%.

[0046] 2. Recycling

[0047] Step 1: Add the phosphatization-modified zero-valent iron material and persulfate to a 10 μmol / L carbamazepine solution to degrade carbamazepine. The addition amount of the phosphatization-modified zero-valent iron material is 200 mg / L, and the addition amount of persulfate is 0.2 mmol / L. After 30 min of degradation, filter and separate the phosphatization-modified zero-valent iron material from the carbamazepine solution.

[0048] Step 2: Add the phosphating-modified zero-valent iron material separated by filtration in Step 1 to a carbamazepine solution (concentration: 10 μmol / L) equal in amount to that in Step 1. Add persulfate. The addition amount of the phosphating-modified zero-valent iron material is 200 mg / L, and the addition amount of persulfate is 0.2 mmol / L. After 30 minutes of degradation, filter and separate the phosphating-modified zero-valent iron material from the carbamazepine solution.

[0049] Step 3: Repeat the operation in Step 2 until the recycling times of the phosphating-modified zero-valent iron material reach 5 times.

[0050] Test the removal rate of carbamazepine during each degradation of carbamazepine. The results show that the removal rates of carbamazepine during the 1st and 5th recycling times are 81% and 69% respectively. After recycling 5 times, the degradation effect on carbamazepine only decreases slightly, indicating that the phosphating-modified zero-valent iron material prepared in this example has good recycling performance.

[0051] The following examines the recycling performance of the phosphating solution:

[0052] Under the same conditions as in Steps (1) - (3), without re-preparing the phosphating solution, reuse the phosphating solution used last time to prepare the phosphating-modified zero-valent iron material. Use the phosphating-modified zero-valent iron material prepared when the phosphating solution is recycled 3 times to degrade carbamazepine. Add the phosphating-modified zero-valent iron material and persulfate to a carbamazepine solution with a concentration of 10 μmol / L to degrade carbamazepine. The addition amount of the phosphating-modified zero-valent iron material is 200 mg / L, and the addition amount of persulfate is 0.2 mmol / L. After 30 minutes of degradation treatment, the removal rate of carbamazepine in the carbamazepine aqueous solution is 78%. This shows that the plating solution can also be recycled, and recycling the plating solution 3 times basically does not affect the activity of the prepared phosphating-modified zero-valent iron material in degrading carbamazepine.

[0053] Comparative Example 1

[0054] In this comparative example, the phosphating-modified zero-valent iron material is prepared by changing the concentration of the phosphating solution for comparison with Example 1. The steps are as follows:

[0055] (1) Cleaning, the operation is the same as in Example 1.

[0056] (2) Surface treatment, the operation is the same as in Example 1.

[0057] (3) Surface phosphating, the operation is basically the same as in Example 1, except that the concentration of the phosphating solution is different. The phosphating solution in this comparative example is obtained by dissolving manganese iron dihydrogen phosphate and zinc nitrate in deionized water and then adjusting the free acidity to 5 with phosphoric acid. In this phosphating solution, the concentration of manganese iron dihydrogen phosphate is 10 g / L and the concentration of zinc nitrate is 20 g / L.

[0058] The scanning electron microscope image of the phosphating-modified zero-valent iron material prepared in this comparative example is as Figure 3 shown. Compared with Figure 1 , the compactness of the phosphating layer on the surface of the phosphating-modified zero-valent iron prepared in this comparative example is relatively poorer. It shows that by changing the phosphating conditions, such as the composition of the phosphating solution and the concentration of each component, the morphology, compactness, thickness and other characteristics of the coating on the surface of zero-valent iron can be adjusted.

[0059] Example 2

[0060] In this example, a phosphating-modified zero-valent iron material was prepared, and the steps are as follows:

[0061] (1) Cleaning

[0062] Select nano zero-valent iron with a particle size of 500 - 800 nm. The zero-valent iron was successively placed in a 1 wt% hydrochloric acid solution, a 1 wt% sodium hydroxide solution, and ethanol, and mechanically stirred for 30 min each to remove the dirt and passivation layer on the surface of the zero-valent iron.

[0063] (2) Surface treatment

[0064] The zero-valent iron from which the dirt and passivation layer on the surface have been removed was added to the surface conditioning solution and soaked at 25 °C for 30 min to obtain surface-treated zero-valent iron; the surface conditioning solution was obtained by dissolving titanium oxysulfate and sodium phosphate in water. In the surface conditioning solution, the concentration of titanium oxysulfate was 1 g / L and the concentration of sodium phosphate was 1 g / L.

[0065] (3) Surface phosphating

[0066] The surface-treated zero-valent iron was added to the phosphating solution and treated at 90 °C for 10 min under stirring conditions to perform phosphating on the surface of the zero-valent iron. The phosphated zero-valent iron was successively washed with a 1 wt% hydrochloric acid solution, a 1 wt% sodium hydroxide solution, and ethanol to obtain the phosphating-modified zero-valent iron material.

[0067] The phosphating solution was prepared by adding calcium dihydrogen phosphate, manganese nitrate, sodium sulfite, and tannic acid to water, and then adding nitric acid until all components were completely dissolved. The free acidity was adjusted to 5 points and the total acidity was adjusted to 30 points by phosphoric acid and phosphate. In this phosphating solution, the concentration of calcium dihydrogen phosphate was 100 g / L, the concentration of manganese nitrate was 10 g / L, the concentration of nitric acid was 5 g / L, the concentration of sodium sulfite was 10 g / L, and the concentration of tannic acid was 10 g / L.

[0068] The following is the wastewater treatment using the phosphating-modified zero-valent iron material prepared in this example:

[0069] The phosphating-modified zero-valent iron material was added to a p-nitrophenol solution with a concentration of 10 μmol / L to degrade p-nitrophenol, and the addition amount of the phosphating-modified zero-valent iron material was 5 g / L. After 30 minutes of degradation treatment, the removal rate of p-nitrophenol was 85%.

[0070] Example 3

[0071] In this example, the phosphating-modified zero-valent iron material was prepared as follows:

[0072] (1) Cleaning

[0073] Millimeter zero-valent iron with a particle size range of 1 - 10 mm was selected, and the zero-valent iron was placed in a 1 wt% hydrochloric acid solution and mechanically stirred for 30 minutes to remove the dirt and passivation layer on the surface of the zero-valent iron.

[0074] (2) Surface treatment

[0075] The zero-valent iron with the dirt and passivation layer removed from its surface was added to the surface conditioning solution and soaked at 25°C for 30 minutes to obtain surface-treated zero-valent iron; the surface conditioning solution was prepared by dissolving titanium oxysulfate and pyrophosphate in water. In the surface conditioning solution, the concentration of titanium oxysulfate was 0.5 g / L and the concentration of pyrophosphate was 0.5 g / L.

[0076] (3) Surface phosphating

[0077] The surface-treated zero-valent iron was added to the phosphating solution and treated at 30°C for 30 minutes under stirring conditions to perform surface phosphating on the zero-valent iron. The surface-phosphated zero-valent iron was washed with deionized water to obtain the phosphating-modified zero-valent iron material.

[0078] The phosphating solution was prepared by dissolving zinc dihydrogen phosphate, sodium nitrite, copper nitrate, and sodium tartrate in water, and then adjusting the free acidity to 5 points with phosphoric acid. In this phosphating solution, the concentration of zinc dihydrogen phosphate was 100 g / L, the concentration of sodium nitrite was 5 g / L, the concentration of copper nitrate was 5 g / L, and the concentration of sodium tartrate was 5 g / L.

[0079] The following is the treatment of reservoir sediment using the phosphating-modified zero-valent iron material prepared in this example:

[0080] The phosphating-modified zero-valent iron material and peracetic acid were added to the contaminated reservoir sediment with a nickel concentration of 50 μg / L, a lead concentration of 50 μg / L, and an arsenic concentration of 20 μg / L, and the reservoir sediment was treated under the shaking condition of a shaker; the addition amount of the phosphating-modified zero-valent iron material was 100 mg / L, and the addition amount of peracetic acid was 1 mmol / L. After 120 minutes of treatment, the removal rate of the three heavy metals reached more than 80%, and the removal rate of arsenic exceeded 60%.

[0081] Example 4

[0082] In this example, the preparation of the phosphating-modified zero-valent iron material is carried out as follows:

[0083] (1) Cleaning

[0084] Select zero-valent iron with a particle size of 120 μm, place the zero-valent iron in a 1 wt% hydrochloric acid solution, and mechanically stir for 30 min to remove the dirt and passivation layer on the surface of the zero-valent iron.

[0085] (2) Surface treatment

[0086] Add the zero-valent iron with the dirt and passivation layer removed from its surface to the surface conditioning solution, soak it at 90 °C for 5 min to obtain the surface-treated zero-valent iron; the surface conditioning solution is obtained by dissolving titanyl sulfate and pyrophosphate in water. In the surface conditioning solution, the concentration of titanyl sulfate is 0.5 g / L and the concentration of pyrophosphate is 0.1 g / L.

[0087] (3) Surface phosphating

[0088] Add the surface-treated zero-valent iron to the phosphating solution, and treat it at 60 °C for 5 min under stirring conditions to carry out phosphating on the surface of the zero-valent iron. Wash the surface-phosphated zero-valent iron with a 1 wt% hydrochloric acid solution to obtain the phosphating-modified zero-valent iron material.

[0089] The phosphating solution is obtained by adding zinc dihydrogen phosphate, zinc nitrate, and manganese carbonate to water, and then adjusting the free acidity to 5 points and the total acidity to 60 with phosphoric acid to completely dissolve each component. In this phosphating solution, the concentration of zinc dihydrogen phosphate is 30 g / L, the concentration of zinc nitrate is 50 g / L, and the content of manganese carbonate is 10 g / L.

[0090] The following is the wastewater treatment using the phosphating-modified zero-valent iron material prepared in this example:

[0091] Add the phosphating-modified zero-valent iron material to the environmental water body contaminated by nitrate, and the addition amount of the phosphating-modified zero-valent iron material is 2000 mg / L. After 30 min of degradation treatment, the removal rate of total nitrogen in the environmental water body is 30%, and the removal rate of nitrate nitrogen is 86%.

[0092] Comparative Example 2

[0093] In this comparative example, an unmodified zero-valent iron is used to construct a system to treat pollutants.

[0094] 1. Single use

[0095] Zero-valent iron with a particle size of 120 μm and persulfate were added to a carbamazepine solution with a concentration of 10 μmol / L to degrade carbamazepine. The addition amount of zero-valent iron was 200 mg / L, and the addition amount of persulfate was 0.2 mmol / L. After 30 min of degradation treatment, the removal rate of carbamazepine was 37%.

[0096] Combined with Example 1, it can be seen that by surface phosphating modification of zero-valent iron by the method of the present invention, the activity of zero-valent iron can be effectively improved.

[0097] 2. Recycling

[0098] Step 1: Zero-valent iron with a particle size of 120 μm and persulfate were added to a carbamazepine solution with a concentration of 10 μmol / L to degrade carbamazepine. The addition amount of zero-valent iron was 200 mg / L, and the addition amount of persulfate was 0.2 mmol / L. After 30 min of degradation, the zero-valent iron was filtered and separated from the carbamazepine solution.

[0099] Step 2: The zero-valent iron filtered and separated in Step 1 was added to an equal amount of carbamazepine solution (concentration of 10 μmol / L) as in Step 1, and persulfate was added. The addition amount of zero-valent iron was 200 mg / L, and the addition amount of persulfate was 0.2 mmol / L. After 30 min of degradation, the zero-valent iron was filtered and separated from the carbamazepine solution.

[0100] Step 3: Repeat the operation in Step 2 until the recycling times of zero-valent iron reach 5 times.

[0101] The removal rate of carbamazepine during each degradation of carbamazepine was tested. The results showed that the removal rates of carbamazepine during the 1st and 5th recycling were 37% and 14% respectively. After recycling 5 times, the removal rate of carbamazepine was less than half of that of the first time, indicating that the activity and recycling performance of zero-valent iron were not good.

[0102] Combined with Example 1, it can be seen that by surface phosphating modification of zero-valent iron by the method of the present invention, not only can the activity of zero-valent iron be effectively improved, but also the recycling performance of zero-valent iron can be effectively improved.

[0103] Comparative Example 3

[0104] In this comparison, zero-valent iron sulfide was used to construct a system to treat pollutants.

[0105] (1) Cleaning

[0106] Zero-valent iron with a particle size of 120 μm was selected and placed in a 1 wt% hydrochloric acid solution, and mechanically stirred for 30 min to remove the dirt and passivation layer on the surface of zero-valent iron.

[0107] (2) Surface sulfidation

[0108] Zero-valent iron and elemental sulfur that have had the dirt and passivation layer removed from the surface of the zero-valent iron are added to a ball mill at a molar ratio of 10:1 and ball milled for 48 h to obtain iron sulfide zero-valent iron.

[0109] Iron sulfide zero-valent iron and persulfate are added to a 10 μmol / L carbamazepine solution to degrade carbamazepine. The addition amount of zero-valent iron is 200 mg / L, and the addition amount of persulfate is 0.2 mmol / L. After 30 min of degradation treatment, the removal rate of carbamazepine is 62%.

[0110] Combining Example 1 and Comparative Example 3 shows that although the activity of zero-valent iron can be improved by sulfurization modification, the surface phosphating modification of zero-valent iron by the method of the present invention can more effectively improve the activity of zero-valent iron.

Claims

1. A preparation method of a phosphating-modified zero-valent iron material, characterized in that, it comprises the following steps: (1) Adding zero-valent iron with surface dirt and passivation layer removed into the surface conditioning solution and soaking it sufficiently to obtain surface-treated zero-valent iron; The surface conditioning solution is obtained by dissolving at least one of pyrophosphate and sodium phosphate and titanium oxysulfate in water. The concentration of pyrophosphate in the surface conditioning solution does not exceed 1 g / L, the concentration of sodium phosphate does not exceed 1 g / L, and the concentration of titanium oxysulfate is 0.1 - 1 g / L; (2) Adding the surface-treated zero-valent iron into the phosphating solution, and performing surface phosphating at 20 - 100 °C under stirring conditions, and cleaning the surface-phosphated zero-valent iron to obtain a phosphating-modified zero-valent iron material; The phosphating solution includes dihydrogen phosphate, phosphoric acid and an oxidant. The concentration of dihydrogen phosphate in the phosphating solution is 30 - 100 g / L, the concentration of phosphoric acid is 0.1 - 10 g / L, and the concentration of the oxidant is 5 - 100 g / L; The oxidant includes at least one of nitrate, chloride, and hydrogen peroxide.

2. The preparation method of the phosphating-modified zero-valent iron material according to claim 1, characterized in that, the dihydrogen phosphate includes at least one of zinc dihydrogen phosphate, manganese dihydrogen phosphate, iron dihydrogen phosphate, manganese iron dihydrogen phosphate salt, and calcium dihydrogen phosphate.

3. The preparation method of the phosphating-modified zero-valent iron material according to claim 1, characterized in that, the phosphating solution further contains one or more of a reducing substance, a metal salt with a positive potential, and an organic matter. The concentration of the reducing substance, the metal salt with a positive potential or the organic matter in the phosphating solution is 0.1 - 100 g / L; The reducing substance includes at least one of sodium nitrite and sodium sulfite; The metal salt with a positive potential includes at least one of nickel salt, copper salt, cobalt salt, and manganese salt; The organic matter includes at least one of tartaric acid and tannic acid.

4. The preparation method of the phosphating-modified zero-valent iron material according to any one of claims 1 to 3, characterized in that, the time for surface phosphating in step (2) is 5 - 1200 min.

5. The preparation method of the phosphating-modified zero-valent iron material according to any one of claims 1 to 3, characterized in that, the zero-valent iron with surface dirt and passivation layer removed in step (1) is obtained by cleaning zero-valent iron by combining one or more of pickling, alkali washing, and alcohol washing.

6. The phosphating-modified zero-valent iron material prepared by the method according to any one of claims 1 to 5 is composed of zero-valent iron and a phosphide coating. The structure of the phosphide coating is dense, and the phosphide coating uniformly and completely coats the surface of zero-valent iron to form a core-shell structure.

7. The application of the phosphating-modified zero-valent iron material according to claim 6 in environmental pollution treatment and environmental remediation. The application is to add the phosphating-modified zero-valent iron material, or the phosphating-modified zero-valent iron material and an oxidizing material together into the environmental medium to be treated for pollutant removal; The oxidizing material is at least one of hydrogen peroxide, persulfate, peracetic acid, ozone, oxygen, ferrate, permanganate, periodate, and calcium peroxide.

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