阅读说明：本技术 一种用于活化过一硫酸盐的碳掺杂二氧化锰催化剂及其制备方法与应用 (Carbon-doped manganese dioxide catalyst for activating peroxymonosulfate and preparation method and application thereof ) 是由 黄理辉 韩宇飞 谢美玲 孙昀潇 马西祥 李万峰 高延军 于 2020-05-11 设计创作，主要内容包括：本发明公开了一种碳掺杂二氧化锰催化剂及其制备方法与应用,制备方法,包括如下步骤：采用浓硫酸将高锰酸钾与羧基化碳纳米管的混合溶液酸化后,加热反应,制得碳掺杂二氧化锰。通过引入羧基化碳纳米管,有效提高了二氧化锰催化剂的界面极化电阻,增大了表面羟基的数量,因此,其表面含有大量可与过一硫酸盐络合的表面羟基位点,大大增强了催化剂的催化能力,同时提高了催化剂内部的电子转移速率,使得有机污染物可更快速的被降解。在低pH值条件下其效果提升尤其强烈,提高了过一硫酸盐的利用率,大大节约了成本。(The invention discloses a carbon-doped manganese dioxide catalyst and a preparation method and application thereof, wherein the preparation method comprises the following steps: and acidifying the mixed solution of potassium permanganate and carboxylated carbon nanotubes by adopting concentrated sulfuric acid, and heating for reaction to prepare the carbon-doped manganese dioxide. By introducing the carboxylated carbon nanotube, the interfacial polarization resistance of the manganese dioxide catalyst is effectively improved, and the number of surface hydroxyl groups is increased, so that the surface of the manganese dioxide catalyst contains a large number of surface hydroxyl sites capable of being complexed with peroxymonosulfate, the catalytic capability of the catalyst is greatly enhanced, the electron transfer rate in the catalyst is improved, and organic pollutants can be degraded more quickly. The effect is improved particularly strongly under the condition of low pH value, the utilization rate of the peroxymonosulfate is improved, and the cost is greatly saved.)

1. A preparation method of a carbon-doped manganese dioxide catalyst is characterized by comprising the following steps: the method comprises the following steps:

and acidifying the mixed solution of potassium permanganate and carboxylated carbon nanotubes by adopting concentrated sulfuric acid, and heating for reaction to prepare the carbon-doped manganese dioxide.

2. The method of preparing a carbon-doped manganese dioxide catalyst according to claim 1, characterized in that: the mass ratio of the potassium permanganate to the carboxylated carbon nanotube is 8:1-12: 1;

furthermore, the mass ratio of the potassium permanganate to the carboxylated carbon nanotube is 10: 1.

3. The method of preparing a carbon-doped manganese dioxide catalyst according to claim 1, characterized in that: deionized water is used as a solvent;

furthermore, 80-120ml of deionized water is added into each gram of carboxylated carbon nano-tubes.

4. The method of preparing a carbon-doped manganese dioxide catalyst according to claim 3, characterized in that: the volume ratio of the concentrated sulfuric acid to the deionized water is 1: 180-220.

5. The method of preparing a carbon-doped manganese dioxide catalyst according to claim 4, characterized in that: adding concentrated sulfuric acid, stirring for 2-4 hours, and acidifying the system;

further, after adding concentrated sulfuric acid, stirring for 2 hours, and carrying out system acidification.

6. The method of preparing a carbon-doped manganese dioxide catalyst according to claim 5, characterized in that: after the system is acidified, heating the reaction system to 60-80 ℃, and continuously stirring for reaction to obtain a solid product, namely a target product;

further, the reaction time is 0.8-1.2h under continuous stirring.

7. The method of preparing a carbon-doped manganese dioxide catalyst according to claim 1, characterized in that: the method also comprises the steps of washing and drying the prepared solid product.

8. The method of preparing a carbon-doped manganese dioxide catalyst according to claim 7, characterized in that: the washing is repeated washing by adopting deionized water.

9. A carbon-doped manganese dioxide catalyst, characterized by: prepared by the preparation method of any one of claims 1 to 8.

10. Use of a carbon doped manganese dioxide catalyst according to claim 9 for wastewater treatment by activation of peroxymonosulfate.

Technical Field

The invention belongs to the technical field of heterogeneous catalyst preparation, and particularly relates to a carbon-doped manganese dioxide catalyst for activating peroxymonosulfate, and a preparation method and application thereof.

Background

The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.

In recent years, in order to cope with environmental crisis caused by industrial pollution, the search for a cheap and efficient environmental pollution treatment technology becomes the focus of attention of scientific workers, and peroxymonosulfate is widely studied as a strong oxidant in the wastewater treatment technology. Permonosulfates have a high redox potential (E)₀1.82V) but due to its slower reaction rate with organic contaminants. Therefore, it must be activated by a certain means to decompose it to generate hydroxyl radicals and sulfate radicals with strong oxidizing ability for the purpose of degrading organic pollutants. In various catalytic methods, the peroxymonosulfate is activated by using a heterogeneous catalyst, and the method has the characteristics of environmental friendliness, low cost, excellent performance and the like. Researchers have found that manganese dioxide can effectively activate peroxymonosulfate, thereby generating sulfate radicals and hydroxyl radicals to achieve the purpose of degrading pollutants. The method can treat various pollutants, has wide application range, and particularly has good oxidative decomposition effect on organic matters which are difficult to degrade. However, the activation effect of manganese dioxide is still difficult to meet the treatment requirements.

Disclosure of Invention

In order to solve the technical problems in the prior art, the invention aims to provide a carbon-doped manganese dioxide catalyst for activating peroxymonosulfate and a preparation method and application thereof.

In order to achieve the above object, one or more embodiments of the present invention disclose the following technical solutions:

in a first aspect, the present invention provides a process for the preparation of a carbon doped manganese dioxide catalyst for the activation of peroxymonosulfate, comprising the steps of:

and acidifying the mixed solution of potassium permanganate and carboxylated carbon nanotubes by adopting concentrated sulfuric acid, and heating for reaction to prepare the carbon-doped manganese dioxide.

In a second aspect, the present invention provides a carbon-doped manganese dioxide catalyst for activating peroxymonosulfate, prepared by the above preparation method.

In a third aspect, the present invention provides the use of a carbon doped manganese dioxide catalyst as described above for the activation of peroxymonosulfate in the treatment of wastewater by activation of peroxymonosulfate.

Compared with the prior art, the above one or more embodiments of the present invention achieve the following beneficial effects:

(1) compared with the traditional hydrothermal method, coprecipitation method and sol-gel method, the improved preparation method of carbon-doped manganese dioxide for activating peroxymonosulfate provided in one or more embodiments of the invention uses carboxylated carbon nanotubes as a reducing agent and a template agent, and can also dope carbon into manganese dioxide during the reaction process, and the manganese dioxide can uniformly grow on the tube wall of the carbon nanotube, thereby avoiding agglomeration.

(2) By introducing the carboxylated carbon nanotube, the interfacial polarization resistance of the manganese dioxide catalyst is effectively improved, and the number of surface hydroxyl groups is increased, so that the surface of the manganese dioxide catalyst contains a large number of surface hydroxyl sites capable of being complexed with peroxymonosulfate, the catalytic capability of the catalyst is greatly enhanced, the electron transfer rate in the catalyst is improved, and organic pollutants can be degraded more quickly. The effect is improved particularly strongly under the condition of low pH value, the utilization rate of the peroxymonosulfate is improved, and the cost is greatly saved.

(3) The preparation method of the carbon-doped manganese dioxide catalyst for activating the peroxymonosulfate, which is provided by one or more embodiments of the invention, has the advantages of convenience in operation, simple conditions and easiness in control, and is more suitable for industrial production compared with methods such as a hydrothermal method.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

FIG. 1 is an EIS plot of manganese dioxide and carbon doped manganese dioxide heterogeneous catalysts prepared in example 1 and comparative example 1 of the present invention;

FIG. 2 is an XPS spectrum of manganese dioxide and carbon doped manganese dioxide heterogeneous catalysts prepared in example 1 of the present invention and comparative example 1;

FIG. 3 is an XRD spectrum of manganese dioxide and carbon doped manganese dioxide heterogeneous catalysts prepared in example 1 and comparative example 1 of the present invention;

FIG. 4 is an FTIR spectrum of a carbon doped manganese dioxide heterogeneous catalyst prepared in example 1 of the present invention;

FIG. 5 is an SEM image of a carbon doped manganese dioxide heterogeneous catalyst prepared according to example 1 of the present invention;

fig. 6 is a TEM image of the carbon doped manganese dioxide heterogeneous catalyst prepared in example 1 of the present invention.

Detailed Description

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

In a first aspect, the present invention provides a process for the preparation of a carbon doped manganese dioxide catalyst for the activation of peroxymonosulfate, comprising the steps of:

and acidifying the mixed solution of potassium permanganate and carboxylated carbon nanotubes by adopting concentrated sulfuric acid, and heating for reaction to prepare the carbon-doped manganese dioxide.

In some embodiments, the mass ratio of potassium permanganate to carboxylated carbon nanotubes is from 8:1 to 12: 1.

Furthermore, the mass ratio of the potassium permanganate to the carboxylated carbon nanotube is 10: 1.

Further, deionized water is used as a solvent.

Furthermore, 80-120ml of deionized water is added into each gram of carboxylated carbon nano-tubes.

Further, the volume ratio of the concentrated sulfuric acid to the deionized water is 1: 180-220.

Furthermore, after adding concentrated sulfuric acid, stirring for 2-4 hours, and carrying out system acidification.

And further, adding concentrated sulfuric acid, stirring for 2 hours, and acidifying the system.

Further, after the system is acidified, the reaction system is heated to 60-80 ℃, and is continuously stirred for reaction, and a solid product is the target product.

Further, the reaction time is 0.8-1.2h under continuous stirring.

In some embodiments, the method further comprises the step of washing and drying the prepared solid product.

Further, the washing is repeated washing by using deionized water.

In a second aspect, the present invention provides a carbon-doped manganese dioxide catalyst for activating peroxymonosulfate, prepared by the above preparation method.

In a third aspect, the present invention provides the use of a carbon doped manganese dioxide catalyst as described above for the treatment of wastewater by activating peroxymonosulfate.

Example 1

A preparation method of carbon-doped manganese dioxide nano powder for activating peroxymonosulfate mainly comprises the following steps:

(1) carboxylated carbon nanotubes in mass ratio: adding a certain amount of potassium permanganate and carboxylated carbon nanotubes in a corresponding proportion into deionized water, wherein each gram of carboxylated carbon nanotubes corresponds to 100ml of deionized water, so as to obtain a mixed solution;

(2) fully stirring the mixed solution, and after the carboxylated carbon nanotubes in the solution are uniformly dispersed, adding deionized water: adding 98% concentrated sulfuric acid into the mixed solution while stirring at a ratio of 98% concentrated sulfuric acid to 200:1, and continuously stirring for 2 hours to obtain an acidified mixed solution;

(3) the acidified mixed solution was kept for 1 hour under stirring in a water bath at 80 ℃ to allow complete reaction. After the reaction is finished, separating the brownish black solid in the solution and washing the solution for 3 times by using deionized water;

(4) and drying the washed brownish black solid at the temperature of 80 ℃ for 12 hours, and grinding the product after the drying is finished to obtain the carbon-doped manganese dioxide nano powder.

FIG. 4 is an FTIR spectrum of a carbon doped manganese dioxide heterogeneous catalyst prepared in example 1 of the present invention;

FIG. 5 is an SEM image of a carbon doped manganese dioxide heterogeneous catalyst prepared according to example 1 of the present invention;

fig. 6 is a TEM image of the carbon doped manganese dioxide heterogeneous catalyst prepared in example 1 of the present invention.

The carbon-doped manganese dioxide heterogeneous catalyst obtained in example 1 was observed under a scanning electron microscope and a transmission electron microscope. As shown in fig. 5 and 6, the prepared carbon-doped manganese dioxide heterogeneous catalyst has a uniform fibrous structure, the surface of the carbon nanotube is completely covered by the manganese dioxide nanosheets, and the dispersibility of the composite is good. Fourier transform infrared spectroscopy analysis was performed on the carbon nanotube and carbon-doped manganese dioxide heterogeneous catalyst, respectively, and the results are shown in fig. 4. As can be seen, the two materials are 3800cm^-1-2400cm^-1Obvious wide absorption peak appears in the interval, which is the absorption peak of the surface hydroxyl stretching vibration, in comparison, the carbon-doped manganese dioxide heterogeneous catalyst has the surface hydroxylThe absorption peak of the base stretching vibration is stronger, which shows that the synthesis of the carbon-doped manganese dioxide heterogeneous catalyst increases the number of surface hydroxyl groups.

Example 2

A preparation method of carbon-doped manganese dioxide nano powder for activating peroxymonosulfate mainly comprises the following steps:

(1) carboxylated carbon nanotubes in mass ratio: adding a certain amount of potassium permanganate and carboxylated carbon nanotubes in a corresponding proportion into deionized water, wherein each gram of carboxylated carbon nanotubes corresponds to 100ml of deionized water, so as to obtain a mixed solution;

(2) fully stirring the mixed solution, and after the carboxylated carbon nanotubes in the solution are uniformly dispersed, adding deionized water: adding 98% concentrated sulfuric acid into the mixed solution while stirring at a ratio of 220:1, and continuously stirring for 2 hours to obtain an acidified mixed solution;

(3) the acidified mixed solution was kept for 1 hour under stirring in a water bath at 80 ℃ to allow complete reaction. After the reaction is finished, separating the brownish black solid in the solution and washing the solution for 3 times by using deionized water;

(4) and drying the washed brownish black solid at the temperature of 80 ℃ for 12 hours, and grinding the product after the drying is finished to obtain the carbon-doped manganese dioxide nano powder.

Example 3

A carbon-doped manganese dioxide nano powder for activating peroxymonosulfate mainly comprises the following steps:

(1) carboxylated carbon nanotubes in mass ratio: adding a certain amount of potassium permanganate and carboxylated carbon nanotubes in a corresponding proportion into deionized water, wherein each gram of carboxylated carbon nanotubes corresponds to 100ml of deionized water, so as to obtain a mixed solution;

(2) fully stirring the mixed solution, and after the carboxylated carbon nanotubes in the solution are uniformly dispersed, adding deionized water: adding 98% concentrated sulfuric acid into the mixed solution while stirring at a ratio of 180:1, and continuously stirring for 4 hours to obtain an acidified mixed solution;

(3) the acidified mixed solution was kept for 1 hour under stirring in a water bath at 70 ℃ to allow complete reaction. After the reaction is finished, separating the brownish black solid in the solution and washing the solution for 3 times by using deionized water;

(4) and drying the washed brownish black solid at the temperature of 80 ℃ for 12 hours, and grinding the product after the drying is finished to obtain the carbon-doped manganese dioxide nano powder.

Comparative example 1

A preparation method of manganese dioxide nano powder mainly comprises the following steps:

(1) molar ratio KMnO of massage₄：MnSO₄·H₂O is 2:3, KMnO₄With MnSO₄·H₂Dissolving O in equivalent deionized water respectively;

(2) mixing KMnO₄The solution is slowly dripped into MnSO which is continuously stirred₄·H₂Obtaining a brown yellow solid liquid mixture in the O solution, and continuously stirring the mixture for 3 hours after the dropwise addition is finished;

(3) separating the stirred mixture to obtain brown solid, and washing the brown solid for 3 times by using deionized water;

(4) and drying the washed brown solid at 80 ℃ for 12 hours, and grinding the product after the drying is finished to obtain the manganese dioxide nano powder.

FIG. 1 is an EIS plot of manganese dioxide and carbon doped manganese dioxide heterogeneous catalysts prepared in example 1 and comparative example 1 of the present invention;

FIG. 2 is an XPS spectrum of manganese dioxide and carbon doped manganese dioxide heterogeneous catalysts prepared in example 1 of the present invention and comparative example 1;

fig. 3 is an XRD spectrum of manganese dioxide and carbon doped manganese dioxide heterogeneous catalysts prepared in example 1 of the present invention and comparative example 1.

As can be seen from fig. 1, by introducing the carboxylated carbon nanotubes, the interfacial polarization resistance of the manganese dioxide catalyst is effectively increased, and the electron transfer rate inside the catalyst is increased, so that the organic pollutants can be degraded more rapidly.

Application of X-ray photoelectron spectroscopy (XPS) to catalyst componentsThe chemical state of the element was analyzed and the results are shown in FIG. 2. FIG. 2(a) is an XPS spectrum of Mn 2p in manganese dioxide and carbon doped manganese dioxide heterogeneous catalysts, with peaks with bond energies of 642eV and 653.6eV corresponding to Mn 2p_3/2And Mn 2p_1/2Confirming that the oxide phase of manganese in the hybrid material is alpha-MnO₂. Further, the high-resolution XPS spectrum of the O element is shown in fig. 2 (b). The XPS spectrum of the O element in the manganese dioxide is characterized in that absorption peaks at three positions of 529.9eV, 531.3eV and 533.0eV respectively correspond to O atoms in three chemical environments of anhydrous manganese oxide (Mn-O-Mn), hydrated manganese oxide (Mn-O-H) and structural water, and the relative contents of the O atoms are 77.5%, 15.5% and 6.9%. An XPS spectrum of an O element in the carbon-doped manganese dioxide heterogeneous catalyst can be divided into three peaks located at 529.9eV, 531.3eV and 533.3eV, and the three peaks respectively correspond to an Mn-O-Mn bond, an Mn-O-H bond and a C-O/C-O bond, so that the manganese dioxide is successfully loaded on the surface of the carbon nanotube.

Fig. 3 shows XRD patterns of manganese dioxide nanopowder and carbon doped manganese dioxide. For manganese dioxide nanopowders, the two characteristic diffraction peaks at 2 theta diffraction angles of 37.4 ° and 65.5 °, corresponding to α -MnO respectively₂(JCPDS No.44-0141) showed that the manganese dioxide nanopowder prepared had high purity, single phase and no other impurity phase in the (211) and (002) diffraction planes. In XRD spectrogram of carbon-doped manganese dioxide heterogeneous catalyst, alpha-MnO₂The diffraction peak of (A) is relatively weak, which is mainly due to the addition of the carboxylated carbon nanotube, resulting in alpha-MnO₂Poor crystallinity.

The invention selects typical potassium peroxymonosulfate (2 KHSO)₅·KHSO₄·K₂SO₄) As an oxidant, tetracycline is used as a target substance, and the activation effect of the catalyst prepared by the method on the peroxymonosulfate under different reaction conditions is researched.

TABLE 1

TABLE 2

TABLE 3

The carbon-doped manganese dioxide nano powder prepared in example 1 was used as a catalyst, the amount of the catalyst added was controlled to be 0.4g/L, and the effect of the peroxymonosulfate concentration on the degradation amount of tetracycline was investigated by changing the concentration of peroxymonosulfate (potassium peroxymonosulfate), and the experimental results are shown in table 1. Experimental data show that the concentrations of the peroxymonosulfate are 1g/L, 2g/L and 3g/L, the concentration of the tetracycline solution is 12mg/L, and after degradation is carried out for 1 hour at the temperature of 25 ℃, the degradation amounts of the tetracycline are 9.636mg/L, 9.823mg/L and 9.811mg/L respectively. As can be seen, the highest degradation of tetracycline was achieved at a peroxomonosulfate concentration of 2 g/L. Therefore, the optimal adding amount of the peroxymonosulfate in the subsequent experiments is 2 g/L.

The influence of the addition amount of the catalyst on the degradation amount of tetracycline hydrochloride was investigated by controlling the addition amount of the catalyst (the carbon-doped manganese dioxide nanopowder prepared in example 1), and the experimental results are shown in table 2. Experimental data show that when the adding amount of the catalyst is 0.3g/L, 0.4g/L and 0.5g/L, the concentration of the tetracycline solution is 12mg/L, and after degradation is carried out for 1h at the temperature of 25 ℃, the degradation amounts of the tetracycline are 9.424mg/L, 9.820mg/L and 9.742mg/L respectively. As can be seen, the highest degradation of tetracycline was observed when the amount of catalyst added was 0.4 g/L. Therefore, the optimal catalyst adding amount is selected to be 0.4g/L in subsequent experiments.

The carbon-doped manganese dioxide heterogeneous catalysts prepared in example 1 and comparative example 1 of the present invention and manganese dioxide were used as catalysts, respectively, to study the catalytic effects of the two catalysts, two tetracycline solutions with the same volume and concentration were prepared, the concentration of the tetracycline solution was 10mg/L, and the concentration of the peroxymonosulfate in the tetracycline solution was 2mg/L, 0.4g/L of the carbon-doped manganese dioxide nanopowder prepared in example 1 was added to one of the tetracycline solutions, and 0.4g/L of the manganese dioxide nanopowder was added to the other tetracycline solution. After degradation is carried out for 1 hour at the temperature of 25 ℃, the degradation amount of tetracycline is shown in table 3, and when carbon-doped manganese dioxide nano-powder and manganese dioxide nano-powder are used as catalysts, the degradation amounts of tetracycline hydrochloride are 8.501mg/L and 6.590mg/L, respectively, which shows that the carbon-doped manganese dioxide heterogeneous catalyst prepared in example 1 of the present invention has a better catalytic effect.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.