Preparation method and application of iron-doped γ-MnOOH

Abstract

The present invention relates to a preparation method and application of iron-doped γ-MnOOH. The method comprises the following steps: (1) adding hydrogen peroxide, ammonia, an iron source and a manganese source into water and stirring to obtain a mixed solution, wherein the molar ratio of hydrogen peroxide, iron, manganese and ammonia is 3.3:y:(1.0-y):1(0.05≤y≤0.20); (2) heating the mixed solution to 90-100°C in a water bath, and continuously stirring for 6-8h; (3) after the reaction is completed, the obtained product is centrifuged, washed and dried to obtain the iron-doped γ-MnOOH. The object of the present invention is to provide a preparation method, iron-doped γ-MnOOH and its application, which solves the problem of large Mn ion dissolution and high secondary pollution risk in the process of manganese oxide catalyzing persulfate degradation of organic pollutants. At the same time, the reaction conditions of the present invention are mild, the synthesis temperature is relatively low, the time is short, it is easy to control, the production cost is low, and it is easy to industrially scale up.

Description

Technical Field

[0001] The invention relates to the field of new environmental materials, and in particular to a preparation method of iron-doped γ-MnOOH and application thereof. Background Art

[0002] In recent years, the problem of organic pollution in the environment has become increasingly serious during the rapid development of industrialization. A large number of organic pollutants are highly toxic, long-term and persistent, posing a serious threat to the ecological environment and human health. At present, traditional physical and biological technologies for the treatment of organic pollution still have many shortcomings and there is a large room for improvement. It is urgent to develop more green, efficient and economical organic pollution control technologies.

[0003] Advanced oxidation technology based on sulfate radicals has broad application potential in the field of organic pollution control due to its rapidity, high efficiency and wide application range. Persulfate (PS) can produce strong oxidizing sulfate radicals (SO4 · ˉ), which can treat a variety of difficult-to-degrade organic pollutants. Among them, manganese-based catalysts have the advantages of variable crystal structure and properties, large specific surface area, low toxicity, high natural abundance, environmental friendliness, low cost and large-scale preparation. As a catalytic material for advanced oxidation technology based on sulfate free radicals, it can be used to catalyze the degradation of organic pollutants in environmental media by persulfate. However, due to the diversity of oxidation states and structures of Mn (Ⅱ, Ⅲ, Ⅳ and Ⅶ) oxides, there are also large differences in the catalytic efficiency of persulfate. γ-MnOOH is a strongly hydrophilic compound mainly composed of trivalent manganese, with an efficient electron transfer rate, abundant surface active sites and surface hydroxyl sites. Its characteristics lead to the excellent catalytic performance of γ-MnOOH, which can efficiently catalyze the degradation of organic pollutants by persulfate. However, since manganese-based catalysts often have a large amount of Mn ion dissolution during use, it is easy to cause secondary pollution, which limits the practical application of related materials in organic pollution control.

[0004] Therefore, in order to solve the above problems, it is urgent to develop a method for modifying manganese-based catalysts, obtain suitable modified manganese-based catalysts and explore their application conditions. Summary of the invention

[0005] In view of the current shortcomings, the purpose of the present invention is to provide a preparation method of iron-doped γ-MnOOH, iron-doped γ-MnOOH and its application, which solves the problem of large amount of Mn ion dissolution and high risk of secondary pollution in the process of γ-MnOOH catalyzing persulfate degradation of organic pollutants. In addition, the preparation method has mild reaction conditions, relatively low synthesis temperature, short time, easy control, low production cost, and easy industrial scale-up.

[0006] To achieve the purpose of the present invention, the following technical solutions are used:

[0007] A method for preparing iron-doped γ-MnOOH comprises the following steps:

[0008] (1) adding an iron source and a manganese source into ultrapure water according to a certain proportion and stirring evenly, adding hydrogen peroxide and ammonia water in sequence, and stirring vigorously to obtain a mixed solution;

[0009] (2) heating the mixed solution at 95° C. with stirring, cooling and filtering to obtain a precipitate;

[0010] (3) The precipitate was washed with ultrapure water until neutral, vacuum dried, and finally crushed with an agate mortar and sieved through a sieve to obtain an iron-doped γ-MnOOH.

[0011] Preferably, in step (1), the iron source is selected from one or two of ferric salts; wherein the ferric salt is any one or more of ferric chloride, ferric nitrate, ferric sulfate, and ferric acetate. The present invention has found through experiments that ferric chloride can achieve the best effect, so the iron source is more preferably ferric chloride.

[0012] Preferably, in step (1), the manganese source is selected from any one or more of manganese nitrate, manganese sulfate and manganese chloride. The present invention has found through experiments that manganese sulfate monohydrate can achieve the best effect, so the manganese source is more preferably manganese sulfate.

[0013] Preferably, the iron source is ferric chloride, the manganese source is manganese sulfate, and the molar ratio of iron to manganese is y:(1-y), wherein y=0.05, 0.10, 0.15 and 0.20, preferably y=0.05. The present invention has found through optimization experiments that this is the best raw material combination and ratio.

[0014] Preferably, in step (1), 20.4 mL of 30% hydrogen peroxide and 300 mL of 0.2 M ammonia water are added to every 1 L of the mixed solution of the iron source and manganese sulfate.

[0015] Preferably, in step (2), the heating method is water bath heating, the water bath temperature is 95° C., and the reaction time is 6 hours.

[0016] Preferably, the cooling method in step (2) is natural cooling to room temperature.

[0017] The present invention also provides an application based on the iron-doped γ-MnOOH as described above: adding persulfate and the iron-doped γ-MnOOH to organic polluted wastewater at room temperature for reaction; the persulfate concentration is 0.5-2 g / L, the material dosage is 0.2-2 g / L, and the oscillation reaction is carried out for 2 hours, thereby removing organic pollutants.

[0018] The advantages of the present invention over the prior art are: the present invention uses hydrogen peroxide, an iron source, a manganese source and ammonia water as reaction raw materials, and synthesizes iron-doped γ-MnOOH by a simple one-step precipitation method. Iron-doped γ-MnOOH can efficiently catalyze the degradation of organic pollutants in water by persulfate, while greatly reducing the amount of Mn ions dissolved during use. It can be seen that the present invention can solve the problem of large amount of manganese ions dissolved in the process of γ-MnOOH catalyzing the degradation of organic pollutants by persulfate, and further promote the practical application of γ-MnOOH in organic pollution treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The γ-MnOOH obtained in Comparative Example 1 of the present invention and the Fe y Mn 1-y X-ray diffraction pattern of OOH.

[0020] Figure 2 The γ-MnOOH obtained in Comparative Example 1 of the present invention and the Fe y Mn 1-y Scanning electron microscopy image of OOH.

[0021] Figure 3 The γ-MnOOH obtained in Comparative Example 1 of the present invention and the Fe y Mn 1-y Comparison of the effect of OOH-catalyzed persulfate on the degradation of aniline in water.

[0022] Figure 4 The γ-MnOOH obtained in Comparative Example 1 of the present invention and the Fe y Mn 1-y Comparison of manganese ion dissolution during the degradation of aniline in water by persulfate catalyzed by OOH. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described below in conjunction with a specific implementation method.

[0024] The following examples are only used to illustrate the present invention, but are not intended to limit the scope of the present invention. Unless otherwise specified, the reagents and technical means used in the examples are conventional means well known to those skilled in the art.

[0025] The experimental methods in the following embodiments and comparative examples are all conventional methods unless otherwise specified; the experimental materials used are all purchased from conventional biochemical reagent manufacturers unless otherwise specified.

[0026] Example 1: Preparation of Iron-doped γ-MnOOH

[0027] A method for preparing iron-doped γ-MnOOH, the specific steps of which are:

[0028] 60mmol MnSO4·H2O and 3.16mmol, 6.67mmol, 10.59mmol, and 15mmol FeCl3·6H2O were dissolved in 1L ultrapure water, and 20.4mL 30% H2O2 and 300mL 0.2M NH3·H2O were added in sequence. The mixture was stirred vigorously for 5min, heated in a water bath at 95℃ and stirred for 6h. After cooling to room temperature, the mixture was filtered and washed until the pH was neutral, vacuum dried, and finally crushed in an agate mortar and sieved through a 100-mesh sieve to obtain γ-MnOOH with different iron doping ratios, which were expressed as Fe y Mn 1- y OOH.

[0029] Comparative Example 1: Preparation of γ-MnOOH

[0030] The comparative example adopted in the present invention is γ-MnOOH, and the specific steps are as follows:

[0031] Dissolve 60mmol MnSO4·H2O in 1L ultrapure water, add 20.4mL 30% H2O2 and 300mL 0.2M NH3·H2O in sequence, stir vigorously for 5min, heat in a water bath at 95°C and stir for 6h; after cooling to room temperature, filter and wash until the pH is neutral, vacuum dry, and finally crush with an agate mortar and sieve through a 100-mesh sieve to obtain γ-MnOOH.

[0032] The Fe obtained in Comparative Example 1 of the present invention and Example 1 y Mn 1-y The X-ray diffraction analysis results of OOH are shown in Figure 1. As can be seen from the figure, iron-doped γ-MnOOH has diffraction peaks at 26.15°, 33.94°, 35.54°, 37.17°, 41.07° and 51.22°, which correspond to (11-1), (020), (111), (002), (01 2) and (022) of the monoclinic phase of γ-MnOOH, respectively. This shows that iron ion doping does not change the phase structure of γ-MnOOH. From the scanning electron microscopy characterization results ( Figure 2 ) showed that γ-MnOOH doped with iron in different proportions had similar morphological characteristics, which were nanorod-shaped with a diameter of about 200 nm, which was basically consistent with the morphological characteristics of γ-MnOOH. This showed that the morphological characteristics of γ-MnOOH did not change significantly after iron ion doping.

[0033] The Fe obtained in Comparative Example 1 of the present invention and Example 1 y Mn 1-yThe energy dispersive X-ray spectroscopy (EDS) analysis results of OOH are shown in Table 1. As can be seen from the table, with the increase of the iron doping ratio in γ-MnOOH, Fe y Mn 1-y The content of iron in OOH gradually increases, while the content of Mn gradually decreases, which indicates that the present invention successfully prepares γ-MnOOH with different iron doping ratios.

[0034] Table 1

[0035]

[0036] Example 2: Comparison of the removal effect of aniline in water by persulfate catalyzed by iron-doped γ-MnOOH

[0037] Aniline was selected as a typical organic pollutant and the Fe y Mn 1-y The effect of OOH catalyzing persulfate to degrade organic pollutants in water. A 150 mg / L aniline solution was prepared, 10 mL of aniline solution was added to 130 mL of ultrapure water, and then 0.2 g of γ-MnOOH prepared in Comparative Example 1 or Fe prepared in Example 1 was added. y Mn 1-y OOH, and then add 10mL 15g / L sodium persulfate solution, shake for 2 hours, take samples, filter, and use HPLC to determine the content of aniline in the samples. Figure 4 shown.

[0038] As can be seen from the figure, the removal rate of aniline in the γ-MnOOH treatment group was 70.14%. y Mn 1-y The removal rate of aniline in the OOH treatment group decreased with the increase of Fe doping amount. 0.05 Mn 0.95 The aniline degradation rate of the OOH treatment group was 66.03%, which was slightly lower than that of the γ-MnOOH treatment group, indicating that the catalytic performance of γ-MnOOH towards persulfate did not change significantly after low proportion of iron doping.

[0039] Example 3: Comparison of manganese ion dissolution during persulfate degradation of aniline catalyzed by iron-doped γ-MnOOH

[0040] Aniline was selected as a typical organic pollutant, and the amount of manganese ions dissolved in γ-MnOOH and iron-doped γ-MnOOH during use was analyzed through a wastewater treatment simulation experiment. A 150 mg / L aniline solution was prepared, 10 mL of the aniline solution was taken into 130 mL of ultrapure water, and then 0.2 g of γ-MnOOH prepared in Comparative Example 1 or Fe prepared in Example 1 was added.y Mn 1-y OOH, and then add 10mL15g / L sodium persulfate solution, shake for 2 hours, take samples, filter and dilute, and use them for the analysis of Mn ion dissolution. Figure 4 shown.

[0041] As shown in the figure, compared with the γ-MnOOH treatment group, Fe y Mn 1-y The amount of manganese ion dissolution in the OOH-treated group was significantly reduced, by 63.04%-87.22%, and the amount of Mn ion dissolution decreased with the increase of iron doping amount, which indicates that iron doping treatment can reduce the amount of Mn ion dissolution in γ-MnOOH during use.

[0042] In summary, the present invention significantly reduces the amount of manganese ion dissolution and the risk of secondary pollution in the process of γ-MnOOH catalyzing persulfate degradation of organic pollutants by iron doping γ-MnOOH. 0.05 Mn 0.95 The catalytic performance of OOH on persulfate was slightly reduced, but the dissolution of manganese ions decreased sharply, and the risk of secondary pollution was significantly reduced. Therefore, the Fe 0.05 Mn 0.95 OOH is the best.

[0043] The applicant declares that the present invention illustrates the detailed features and detailed methods of the present invention through the above embodiments, but the present invention is not limited to the above detailed features and detailed methods, that is, it does not mean that the present invention must rely on the above detailed features and detailed methods to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. An application of iron-doped γ-MnOOH catalyzing persulfate to degrade organic pollutants in water, characterized in that: Persulfate and iron-doped γ-MnOOH are added to organic polluted wastewater at room temperature for reaction; the persulfate concentration is 0.5-2 g / L, the material dosage is 0.2-2 g / L, and the reaction is shaken for 2 hours; the preparation method of iron-doped γ-MnOOH comprises the following steps: (1) adding an iron source and a manganese source into ultrapure water and stirring evenly, then sequentially adding hydrogen peroxide and ammonia water, and stirring vigorously to obtain a mixed solution; (2) heating the mixed solution at 90-100° C. with stirring, cooling and filtering to obtain a precipitate; (3) washing the precipitate with ultrapure water until it is neutral, vacuum drying, and finally crushing it with an agate mortar and sieving it through a sieve to obtain an iron-doped γ-MnOOH; The heating time in step (2) is 6-8 hours; the iron source is ferric chloride, and the manganese source is manganese sulfate; the molar ratio of hydrogen peroxide, iron, manganese and ammonia is 3.3:y:(1.0-y):1, wherein y=0.05; the initial concentration of the manganese source is 0.06M, and the molar ratio of iron to manganese is y:1-y, wherein y=0.05; and 20.4mL of 30% hydrogen peroxide and 300mL of 0.2M ammonia are added to each 1L of the mixed solution of ferric chloride and manganese sulfate.

2. The method for preparing iron-doped γ-MnOOH according to claim 1, characterized in that: The heating method is water bath heating, the water bath temperature is 95° C., and the water bath heating reaction time is 6 hours.

3. The method for preparing iron-doped γ-MnOOH according to claim 1, characterized in that: The cooling method is natural cooling to room temperature.

Images