阅读说明：本技术 一种金属单原子催化剂及其制备方法和环境修复中的应用 (Metal monatomic catalyst, preparation method thereof and application thereof in environmental remediation ) 是由 白杨 聂工哲 苏娜 王现博 李道雄 李思洁 于 2021-09-27 设计创作，主要内容包括：一种金属单原子催化剂及其制备方法和环境修复中的应用。该方法包括：首先采用其他金属酞菁与酞菁锌,聚合物氮化碳以一定比例混合均匀,然后加入适量的乙醇后,进行碾磨,直到乙醇完全挥发。得到的样品,在惰性气体的氛围中进行分段式高温热解,使金属原子分散为单原子状态。本发明可以高效活化过一硫酸盐(PMS)降解有机污染物,在环境修复领域得以运用。(A metal monatomic catalyst, a preparation method thereof and application in environmental remediation. The method comprises the following steps: firstly, other metal phthalocyanine, zinc phthalocyanine and polymer carbon nitride are uniformly mixed according to a certain proportion, then a proper amount of ethanol is added, and grinding is carried out until the ethanol is completely volatilized. The obtained sample is subjected to segmented high-temperature pyrolysis in an inert gas atmosphere, so that metal atoms are dispersed into a monoatomic state. The invention can efficiently activate the Peroxymonosulfate (PMS) to degrade organic pollutants and is applied to the field of environmental remediation.)

1. A metal monatomic catalyst, a preparation method thereof and an application in environmental remediation are characterized by comprising the following steps: firstly, metal phthalocyanine is uniformly dispersed in a mixture of zinc phthalocyanine and polymer carbon nitride, wherein ethanol is used as a solvent to help the three substances to be uniformly mixed, and then an obtained sample is transferred to an inert gas atmosphere for pyrolysis, so that metal is formed and doped into carbon containing nitrogen sites in a monoatomic state.

2. The method for preparing the monatomic catalyst according to claim 1, wherein the method comprises the steps of:

s1, uniformly mixing metal phthalocyanine, zinc phthalocyanine and polymer carbon nitride to obtain a mixture A;

s2, adding absolute ethyl alcohol into the mixture A until the mixture A is submerged to obtain a suspension B;

s3, stirring and grinding the suspension B by using a mortar rod until the ethanol is completely volatilized to obtain a sample C;

s4 sample C was heated to 650 deg.C for two hours under an inert gas atmosphere, followed by heating to 910 deg.C for two hours. Cooling to obtain the metal monatomic catalyst D.

3. The method for preparing the monatomic catalyst according to claim 2, wherein: the metal phthalocyanine in the step 1) is: copper phthalocyanine, iron phthalocyanine, magnesium phthalocyanine, cobalt phthalocyanine, vanadyl phthalocyanine.

4. The method for preparing a monatomic catalyst according to claim 2 or 3, wherein: in the step S1, the mass ratio of the metal phthalocyanine to the zinc phthalocyanine to the polymer carbon nitride is 0.05: 10: 20-0.2: 10: 20.

5. the method for preparing the monatomic catalyst according to claim 2, wherein: in step S2, the mass fraction of absolute ethanol is 99.7%.

6. The method for preparing the monatomic catalyst according to claim 2, wherein: in the step S4, the temperature increase rate when the sample C is pyrolyzed in the nitrogen atmosphere is 10 ℃/min.

7. The process for preparing the monatomic catalyst according to claim 2, characterized in that: in step S4, the inert gas is nitrogen or argon.

8. The process for preparing the monatomic catalyst according to claim 2, characterized in that: in the step S4, the cooling process also needs to maintain an inert gas atmosphere.

9. The process for preparing the monatomic catalyst according to claim 2, characterized in that: in step S1, the purity of the metal phthalocyanine is greater than 95%.

10. A metal monatomic catalyst, characterized in that: is a monoatomic catalyst produced by the production method according to any one of claims 1 to 6.

Technical Field

The invention belongs to the field of monatomic catalysts, and particularly relates to a preparation method of a metal monatomic catalyst and application of the metal monatomic catalyst in the field of environmental remediation for removing organic pollutants.

Background

With the rapid development of global economy, environmental pollution is becoming more serious. How to efficiently treat organic wastewater is an important problem to be solved urgently. The persulfate advanced oxidation technology for treating organic pollutants is receiving more and more attention since 1894 environmental governance. The reason is that compared with the traditional advanced oxidation technology of hydrogen peroxide, the technology has the characteristics of wide application range, good selectivity for target pollutants and the like.

Monatomic catalysts (SAC) are receiving increasing attention for their advantages of maximizing atomic utilization, dispersing active sites, and various catalytic mechanisms in different catalytic systems. The individual metal-support interactions facilitate arc volume transfer, thereby coordinating catalyst structure or direct out-gold reactant activation. Although many of the unique advantages of SAC have been explored to accelerate various catalytic processes, the research on SAC for PMS activation is still in its infancy. At the same time, making a low cost, scalable and easy to design SAC for practical applications remains a great challenge.

For example, Jungwen Pan et al (J.Mater.chem.A., 2021,9,11604-²⁺And Zn²⁺And mixing dicyandiamide with the weight ten times that of adsorbed metal ions for pyrolysis to successfully prepare the monatomic copper catalyst with the function of catalyzing and activating PMS, and has good effect on degrading various organic matters such as bisphenol A, tetrachlorophenol, 4-nitrophenol, phenol and the like. Hongchao Li et al (Li H, Qian J, Pan B. N-coordinated Co-coordinated pore carbon as a catalyst with improved dispersion and stability to active peroxide for degradation of organic polutants [ J]Chemical Engineering Journal,2021,403:126395) is mixed with cobalt phthalocyanine and melamine and then pyrolyzed, the obtained sample is subjected to acid washing to finally obtain a carbon-based single-atom cobalt catalyst, the catalyst has excellent performance in the application of catalyzing and activating PMS to degrade phenol serving as an organic pollutant, and the phenol with the concentration of 50uM can be completely degraded in 15 minutes when the concentration of the catalyst is 20mg/L and the concentration of PMS is 2.0 mM. Peixin Cui et al (Cui P, Yang Q, Liu C, et al. an N, S-adsorbed Single-Atom Catalyst removed from social fashion for Environmental Redition [ J)].ACS ES&T Engineering,2021.) use of inexpensive coffee grounds and hexahydrateCobalt chloride (CoCl)₂·6H₂O) as metal source, mixing the two in water solution and stirring thoroughly to make Co²⁺Fully adsorbed by coffee grounds, and pyrolyzing the dried sample to obtain the monoatomic cobalt catalyst with coordination of cobalt ions and nitrogen (N) and sulfur (S). The catalyst has excellent performance and good stability in catalyzing and activating PMS to degrade organic pollutant bisphenol A.

Although many excellent scientists have prepared monatomic catalysts by various methods and have good performance in degrading organic pollutants in catalytic activation of PMS, compared with the methods, the scientists only show the preparation method of the monatomic catalyst of a certain metal element and do not explain the universality of the method.

Therefore, a general method for preparing metal monoatomic compounds is urgently needed, and prepared samples have good capability of catalytically activating PMS. To solve the problem that the growing organic substances destroy the environment.

Disclosure of Invention

In view of the above problems, the present invention provides a simple and general method for preparing a metal monatomic catalyst, comprising only two simple steps: grinding and pyrolyzing. The preparation method is simple and easy to implement, the obtained monoatomic catalysts of copper, cobalt, iron and nickel have good activity of catalyzing and activating PMS, the generated free radicals and non-free radicals have strong destructive capacity on micromolecular organic matters, and the catalysts have good stability. The application of organic waste water in the treatment environment has great potential.

The technical scheme of the invention is as follows:

s1, placing 0.05-0.2 part by weight of metal phthalocyanine (Cu, Fe, Co, Mg, Ni, OV), 2 parts by weight of polymer carbon nitride and 1 part by weight of zinc phthalocyanine in a mortar, adding an auxiliary mixing agent absolute ethyl alcohol, and grinding to uniformly mix until the ethyl alcohol is completely volatilized to obtain a precursor of the monatomic catalyst.

S2, placing the precursor in a quartz boat, heating to 650 ℃ at a heating rate of 10 ℃/min for two hours under the protection of nitrogen, and then continuing heating to 910 ℃ at a heating rate of 10 ℃/min for two hours.

And S3, cooling to room temperature to obtain the metal monatomic catalyst.

Several metal monatomic catalysts were prepared using the preparation method described above.

The application of a plurality of metal monatomic catalysts in environmental remediation, wherein the plurality of metal monatomic catalysts are used for catalytically activating PMS.

Has the advantages that: the invention takes a plurality of metal phthalocyanines as metal sources, the polymer carbon nitride provides protective gas for preventing metal agglomeration in the high-temperature pyrolysis process, and the zinc phthalocyanine further plays a role in preventing metal agglomeration in the pyrolysis process. The process is extremely simple, and the used substances are few in variety; the obtained metal monatomic catalyst can show excellent capability of catalyzing and activating PMS to degrade small-molecular organic pollutants, has good stability, is low in metal ion leaching, and cannot cause secondary pollution to the environment.

Drawings

FIG. 1 is a TEM image of SAC-Cu-NC prepared in example 1 of the present invention: wherein, (a) is a low-magnification TEM image of SAC-Cu-NC, and (b) is a high-magnification TEM image of SAC-Cu-NC.

FIG. 2 is an X-ray diffraction pattern (XRD) of SAC-Cu-NC obtained in example 1 of the present invention

FIG. 3 is a view showing a spherical aberration correcting electron microscope (ac-STEM-HAADF) obtained by preparing SAC-Cu-NC in example 1 of the present invention

FIG. 4 is an X-ray diffraction pattern (XRD) of SAC-Co-NC obtained in example 2 of the present invention.

FIG. 5 is an X-ray diffraction pattern (XRD) of SAC-V-NC obtained in example 3 of the present invention.

FIG. 6 is an X-ray diffraction pattern (XRD) of SAC-Fe-NC obtained in example 4 of the present invention.

FIG. 7 is a performance diagram of a SAC-Cu-NC degradation dye rhodamine B prepared in example 5 of the present invention: wherein, (a) is a degradation curve chart, and (b) is a corresponding ultraviolet spectral absorption spectrogram.

FIG. 8 is a performance diagram of the SAC-Co-NC degradation dye rhodamine B prepared in the embodiment 5 of the invention: wherein, (a) is a degradation curve chart, and (b) is a corresponding ultraviolet spectral absorption spectrogram

FIG. 9 is a performance diagram of SAC-Fe-NC degradation dye rhodamine B prepared in example 5 of the present invention: wherein, (a) is a degradation curve chart, and (b) is a corresponding ultraviolet spectral absorption spectrogram

FIG. 10 is a performance diagram of the degradation dye rhodamine B prepared in the embodiment 5 of the invention: wherein, (a) is a degradation curve chart, and (b) is a corresponding ultraviolet spectral absorption spectrogram

FIG. 11 is a free radical and non-free radical detection graph of SAC-Cu-NC prepared in example 5 of the present invention: wherein, (a) is an ESR diagram for detecting hydroxyl radicals and sulfuric acid radicals, and (b) is a diagram for detecting non-radical singlet oxygen.

Detailed Description

The invention provides a method for preparing a metal monatomic catalyst and application thereof. In order to make the objects, technical solutions and effects of the present invention clearer and clearer, the present invention is described in further detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The embodiment of the invention provides a preparation method of a metal monatomic catalyst, which comprises the following steps:

s1, taking certain metal phthalocyanine, zinc phthalocyanine and polymer carbon nitride, wherein the mass ratio of the metal phthalocyanine to the polymer carbon nitride is 0.5: 10: 20-2: 10: 20. mixing the three materials in a mortar.

S2 adding absolute ethyl alcohol to submerge the mixture of the three, fully grinding the mixture by a grinding rod until the ethyl alcohol is completely volatilized, and recording the obtained sample as a sample A

And S3, loading the sample A into a quartz boat, transferring the quartz boat into a tube-type heating furnace, and introducing inert gas to carry out high-temperature sectional pyrolysis. Firstly heating to 650 ℃ at a heating rate of 5-15 ℃/min and keeping for 1-3 hours, and then heating to 910 ℃ at the same heating rate as before on the basis of 650 ℃ and keeping for 1-3 hours.

And S4, when the temperature is reduced to room temperature, the preparation of the metal monatomic catalyst is finished.

In this embodiment, the metal phthalocyanine may be five kinds, which are copper phthalocyanine, cobalt phthalocyanine, magnesium phthalocyanine, iron phthalocyanine, nickel phthalocyanine, and vanadyl phthalocyanine, but is not limited thereto. The method has the following advantages: the process has only two steps, is simple and controllable, and does not need to additionally adopt other carrier materials. The metal phthalocyanine has a structure with a single atom form, which is helpful for preventing the generation of metal agglomeration, and the protective gas generated by the polymer carbon nitride at high temperature further prevents the generation of metal clusters. The obtained metal catalyst has high catalytic activity and good stability, and has no secondary pollution to the environment when used in environmental treatment.

In one embodiment, in step S1, the purity requirement of the metal phthalocyanine is at least 95% or greater and the purity requirement of the zinc phthalocyanine is 95% or greater.

In one embodiment, in step S1, the mass ratio of the metal phthalocyanine, the zinc phthalocyanine and the polymeric carbon nitride is preferably 2: 10: 20, the obtained metal monatomic catalyst has the best catalytic activity.

In one embodiment, the purity of the absolute ethanol in step S2 should be more than 99.7%.

In one embodiment, the inert gas in step S3 is nitrogen, and nitrogen is introduced for at least 2 hours before pyrolysis is performed to ensure that no oxygen is present in the tube furnace.

In one embodiment, the heating temperature rise rate in step S3 is preferably 10 ℃/min, and the holding time is preferably 2 hours.

The embodiment of the invention also provides a metal monatomic catalyst, wherein the metal monatomic catalyst is prepared by adopting the preparation method.

The embodiment of the invention also provides an application of the metal monatomic catalyst in the water pollution treatment of the catalytic activated PMS in the environment.

The present invention will be described in detail below with reference to specific examples.

Example 1 monatomic copper catalyst: preparation of SAC-Cu-NC

S1, 0.2g of copper phthalocyanine with a purity of 99%, 1g of zinc phthalocyanine with a purity of more than 95% and 2g of polymeric carbon nitride are mixed in an agate mortar.

And S2, adding absolute ethyl alcohol with the purity of 99.5 percent into an agate mortar until the whole mixture is submerged, and grinding the formed suspension by using a grinding rod until the ethyl alcohol is completely volatilized to obtain the precursor copper.

S3, the precursor is put into a quartz boat with proper size and put into a tube-type heating furnace, after nitrogen is introduced for two hours, the quartz boat is heated to 650 ℃ at the heating rate of 10 ℃/min, the temperature is kept for 2 hours, and then the quartz boat is heated to 910 ℃ at the heating rate of 10 ℃/min on the basis of 650 ℃ and the temperature is kept for two hours.

And S4, after the temperature of the tubular heating furnace is reduced to room temperature, taking out a sample to obtain the monatomic copper catalyst, which is named as SAC-Cu-NC.

The SAC-Cu-NC prepared in example 1 was tested by a Transmission Electron Microscope (TEM), and the results are shown in FIG. 1(a, b), where a is a low-power TEM image and b is a high-power TEM image, and no obvious metal crystal nanoparticles were observed in the images

The SAC-Cu-NC obtained in example 1 was measured by X-Ray Diffractometer (XRD), and the results are shown in FIG. 2, where no diffraction peak of nano-metal crystal particles appeared in the image, corresponding to TEM image, demonstrating that the surface has no metal nano-crystal particles.

When the SAC-Cu-NC prepared in example 1 was measured by using an ac-STEM-HAADF (spherical aberration correction electron microscope), as shown in FIG. 3, it was found that different elements have different contrasts due to their different structures, and that heavy elements exhibit high brightness, as shown by circles in the drawing, and that heavy element Cu is uniformly dispersed in a carbon structure almost in a single site, confirming that the synthesized sample SAC-Cu-NC is a monoatomic copper catalyst.

Example 2 monoatomic cobalt catalyst: preparation of SAC-Co-NC

The preparation procedure is the same as in example 1, except that: cobalt phthalocyanine with the purity of 95 percent is adopted to replace copper phthalocyanine with the purity of 99 percent.

SAC-Co-NC obtained in example 2 was measured by X-Ray Diffractometer (XRD), and as a result, as shown in FIG. 4, no diffraction peak of nano-metal crystal particles was observed from the image.

Example 3 monoatomic vanadium catalyst: preparation of SAC-V-NC

The preparation procedure is the same as in example 1, except that: replacing the copper phthalocyanine with the purity of 99% with vanadyl phthalocyanine with the purity of 95%.

SAC-Co-NC obtained in example 3 was measured by X-Ray Diffractometer (XRD), and as a result, as shown in FIG. 5, no diffraction peak of nano-metal crystal particles was observed from the image.

Example 4 monatomic iron catalyst: preparation of SAC-Fe-NC

The preparation procedure is the same as in example 1, except that: replacing copper phthalocyanine with purity of 99% with iron phthalocyanine with purity of more than 97%

SAC-Fe-NC obtained in example 4 was measured by X-Ray Diffractometer (XRD), and as a result, as shown in FIG. 6, no diffraction peak of nano-metal crystal particles was found from the image.

Comparative example preparation of Nitrogen-doped carbon (NC)

The preparation procedure is the same as in example 1, except that: replacing copper phthalocyanine with purity of 99% with phthalocyanine with purity of more than 93%.

Example 5 testing and characterization of catalytic activation Performance of monatomic catalyst

S1, testing the performance of PMS activated by the catalyst for degrading small-molecular organic matters: weighing 5mg of catalyst, dispersing the catalyst in 50ml of 10mg/L dye rhodamine B (performance evaluation pollutant) solution, carrying out adsorption and desorption equilibrium for half an hour, adding 10mg of Peroxymonosulfate (PMS), and starting performance test

S2, taking 4 milliliters of solution every five minutes to carry out ultraviolet spectrophotometer test, taking four times, and leading rhodamine B to have an absorption peak at 554 nm.

S3 Performance tests were conducted on SAC-Cu-NC, SAC-Co-NC, SAC-Fe-NC and comparative example NC respectively obtained in examples 1 to 4 in accordance with the above-mentioned test procedures and conditions.

And S4, carrying out ultraviolet light splitting test on the solution, and accurately reacting the degradation degree of the dye rhodamine B through the absorbance of the solution. As shown in fig. 7, 8, 9, 10. As shown in FIG. 7a, SAC-Cu-NC single-atom catalyst can almost completely degrade 10mg/L dye rhodamine B within 20 minutes, and FIG. 7B is the ultraviolet spectroscopy of the corresponding dye rhodamine B. As shown in FIG. 8a, SAC-Co-NC single-atom catalyst can almost completely degrade 10mg/L dye rhodamine B within ten minutes, and FIG. 8B is the ultraviolet spectrum of the corresponding dye rhodamine B. As shown in FIG. 9a, the SAC-Fe-NC single-atom catalyst can almost completely degrade 10mg/L dye rhodamine B within fifteen minutes, such as 9B, which is the ultraviolet spectrum of the corresponding dye rhodamine B. As shown in FIG. 10a, the NC catalyst can only degrade 50% of the dye rhodamine B of 10mg/L within 20 minutes, for example, 10B is the ultraviolet spectrum of the corresponding dye rhodamine B. Therefore, copper, cobalt and iron are anchored on the nitrogen-doped carbon, and the performance of degrading organic micromolecular pollutants is greatly improved.

S5, taking SAC-Cu-NC as an example, the explanation of the mechanism of the catalyst in activating PMS to degrade small molecule pollutants is carried out by electron spin-resonance (ESR) test. As in fig. 11, when sulfate radical and hydroxyl radical scavenger DMPO were added, as in fig. 11a, the signal peaks appeared to be 1: 2: 1: 2: 1: 2: 1, unlike the conventional signal peak 1: 2: 2: 1, the signal peak represents non-free radical singlet oxygen through analysis; as shown in fig. 11b, when the non-radical singlet oxygen scavenger TEMP is added, signal peak 1, representing singlet oxygen, appears: 1: 1. the method explains that degrading dye rhodamine B in the PMS catalyzed and activated by SAC-Cu-NC plays a main role in non-free radical singlet oxygen.

In summary, the present invention provides a preparation method and application of a catalyst capable of preparing a plurality of metal monatomic catalysts. The invention takes metal phthalocyanine as a metal source, zinc phthalocyanine and polymer carbon nitride as protective agents (protecting metal atoms from agglomeration), absolute ethyl alcohol as a blending aid, and the metal phthalocyanine and the polymer carbon nitride are mixed and ground until the absolute ethyl alcohol is completely volatilized, and then the two-stage pyrolysis is carried out on the mixture. This approach has the following advantages: the process is simple and controllable, no additional carrier material is needed, the pyrolytic sublimation of the carbon nitride in the high-temperature calcination process can protect the metal atoms from agglomeration, the zinc atoms in the zinc phthalocyanine are physically isolated to prevent the metal atoms from being agglomerated, and finally the zinc atoms are evaporated and removed in the final pyrolysis. The obtained metal monoatomic catalyst has good catalytic activity and high stability.

It is to be understood that the invention is not limited in its application to the details of the foregoing description, and that modifications and variations may be effected by those skilled in the art in light of the above teachings, and that all such modifications and variations are within the scope of the invention as defined in the appended claims.