阅读说明：本技术 一种利用吸附-解析后的废弃吸附剂制备单原子催化剂的方法 (Method for preparing monatomic catalyst by using adsorbed-resolved waste adsorbent ) 是由 高宝玉 潘静文 高悦 岳钦艳 于 2020-12-31 设计创作，主要内容包括：本发明提供一种利用吸附-解析后的废弃吸附剂制备单原子催化剂的方法,本发明将吸附重金属离子的催化剂与氮源混合,在氮气保护的气氛中分阶段热解后得到了单原子催化剂。本发明以廉价的危险废弃物为原料,利用被吸附的重金属离子在吸附剂中的分散形态,实现了单原子催化剂的制备,且金属单原子分布均匀,分散性良好,避免了吸附重金属后的废弃吸附剂的二次污染,缓解了固废处置压力,保护了环境；操作简单、成本较低,制备得到的产品金属单原子负载量高、分散性好,为大规模生产单原子催化剂提供了一条新思路。(The invention provides a method for preparing a monatomic catalyst by using an adsorbed-resolved waste adsorbent. According to the invention, cheap hazardous waste is used as a raw material, the preparation of the monatomic catalyst is realized by utilizing the dispersion form of the adsorbed heavy metal ions in the adsorbent, the metal monatomic is uniformly distributed and has good dispersion, the secondary pollution of the waste adsorbent after heavy metal adsorption is avoided, the solid waste disposal pressure is relieved, and the environment is protected; the preparation method is simple to operate and low in cost, and the prepared product has high metal monatomic load and good dispersibility, so that a new idea is provided for large-scale production of the monatomic catalyst.)

1. A method for preparing a monatomic catalyst by using a waste adsorbent after adsorption-desorption comprises the following steps:

(1) mixing the waste adsorbent subjected to heavy metal ion adsorption and desorption for multiple times with a nitrogen source to obtain a mixture, wherein the waste adsorbent subjected to heavy metal ion adsorption and desorption is an adsorbent adsorbed with zinc ions and other one or more heavy metal ions;

(2) the mixture is loaded in a porcelain boat and placed in a tube furnace, is pyrolyzed and carbonized at low temperature and high temperature in sequence under the nitrogen atmosphere, and then is cleaned and dried to obtain the monatomic catalyst.

2. The method according to claim 1, wherein in the step (1), the waste adsorbent subjected to heavy metal ion adsorption and desorption for a plurality of times is a waste adsorbent obtained by adsorbing heavy metal ions in heavy metal wastewater by using a biomass adsorbent, then desorbing the heavy metal ions in the heavy metal wastewater by using the desorbed adsorbent, and then desorbing and drying the heavy metal ions.

3. The method of claim 2, wherein the number of times of repeated adsorption and desorption is 4-8, the biomass adsorbent is biogas residue, crop straw, bagasse, vinasse or a material obtained by modifying the biogas residue, the crop straw, the bagasse, and the vinasse, and the particle size of the biomass adsorbent is 2-4 mm.

4. The method of claim 1, wherein the other heavy metal ions are iron ions, cobalt ions, copper ions, nickel ions, or manganese ions.

5. The method according to claim 1, wherein in step (1), the nitrogen source is one or a mixture of two or more of urea, dicyandiamide and melamine.

6. The method according to claim 1, wherein in the step (1), the mass mixing ratio of the waste adsorbent after the multiple heavy metal ion adsorption-desorption and the nitrogen source is 1 (5-10).

7. The method according to claim 1, wherein the mass mixing ratio of the waste adsorbent after multiple adsorption and heavy metal ion desorption to the nitrogen source is 1: 6-8.

8. The method as claimed in claim 1, wherein in the step (2), the low-temperature pyrolysis carbonization temperature is 400-600 ℃, and the carbonization time is 0.5-2 h.

9. The method as claimed in claim 1, wherein in the step (2), the pyrolysis carbonization temperature is 800-1000 ℃ and the carbonization time is 1-4 h.

10. The method as claimed in claim 1, wherein in the step (2), the temperature rising rate is 3-6 ℃/min, the high-temperature pyrolysis carbonization is performed, the cooling is performed to the room temperature, and then the cleaning is performed by using a mixed solution of absolute ethyl alcohol and deionized water.

Technical Field

The invention relates to a method for preparing a monatomic catalyst by using an adsorbed-resolved waste adsorbent, and belongs to the technical field of waste resource utilization and nano materials.

Background

In recent years, with the continuous development and progress of nano-catalytic technology, researchers find that atoms with surface unsaturated coordination are potential active sites for catalysis, and therefore, the researchers are dedicated to further improving the catalytic performance of materials by regulating the distribution and the structure of atoms on the surface of a catalyst by regulating the size, the morphology, the crystal face and the like of nano-materials. Research shows that when the size of the nano material is reduced to a cluster or a single atom level, the energy level structure and the electronic structure of the nano material are fundamentally changed, and the single atom catalyst shows better activity, selectivity and stability than the traditional nano catalyst due to the unique structural characteristics. The monatomic material not only provides a new model for understanding the mechanism of catalytic reaction from the microscopic level, but also is expected to become a novel high-efficiency catalyst with industrial catalytic application potential.

At present, methods for preparing monatomic catalysts reported in relevant documents mainly include electron/ion irradiation atomic layer deposition, wet chemical synthesis, physical and chemical vapor deposition, electrochemical deposition, ball milling and the like. However, these methods have many disadvantages, such as difficulty in scaling up, need of special equipment, complexity of process, easy aggregation of metal atoms, and the like.

For example, chinese patent document CN110270348A discloses a noble metal monatomic catalyst, the active component is a noble metal loaded on a carrier in the form of monatomic, and the carrier is a metal composite oxide derived from hydrotalcite by heating; the content of active components in the catalyst is 0.1-0.3 wt%; the noble metal is any one of Au, Pt, Pd and Ru; the hydrotalcite is one or two of NiAl, CoAl, ZnAl, MgAl and NiFe hydrotalcite. The preparation process comprises the following steps: adding a certain amount of aqueous solution of noble metal salt into a suspension containing hydrotalcite, performing ultrasonic dispersion, adding a proper amount of alkali liquor, performing ultrasonic treatment, centrifuging to obtain a precipitate, and performing heat treatment in an inert atmosphere to obtain the noble metal monatomic catalyst. The noble metal monatomic catalyst has the problems of high cost, complex process and easy aggregation of metal atoms. Therefore, there is a need for a simple method for synthesizing a high content, low agglomeration metal monatomic catalyst.

For a long time, the problem of heavy metal pollution of water in China is very prominent, and the method has important threats to the environment and the human health. The enrichment of heavy metal ions by adopting a solid adsorbent is one of important components and effective means for removing the heavy metal ions in water. The adsorbent has the characteristics of high efficiency, low cost, simple and convenient operation, environmental friendliness and the like, is widely used and is continuously and widely concerned by researchers. However, the regeneration and reuse of the adsorbent saturated with heavy metal ions is also called as a problem, the adsorbent adsorbing heavy metals will eventually become solid waste and is called secondary pollution, and no better treatment method is available at present.

Based on the problems facing today: the adsorbent saturated by adsorbing heavy metal ions cannot be effectively treated, and the environment is seriously polluted; the preparation of the monatomic catalyst is difficult to realize in large scale, high in cost, complex in process and easy to gather metal atoms; there is a need to develop a novel method for preparing a monatomic catalyst.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a method for preparing a monatomic catalyst by using a waste adsorbent after adsorption-desorption.

The method comprises the steps of mixing a waste adsorbent subjected to heavy metal ion adsorption and desorption for multiple times with a nitrogen source, taking the waste adsorbent subjected to adsorption and desorption as a precursor, and carbonizing the precursor through a one-step pyrolysis method under an anaerobic condition to obtain the monatomic catalyst. The waste adsorbent after heavy metal ion adsorption and desorption adsorbs zinc ions and other one or more heavy metal ions, and because the heavy metal ions are adsorbed by the adsorbent based on the chelation between chemical functional groups and the metal ions, the monatomic catalyst is finally obtained after low-temperature and high-temperature pyrolysis carbonization due to the dispersion and occupation sites of the zinc ions, so that the problem that the adsorbent saturated by heavy metal ions cannot be effectively treated is solved, a new way is provided for large-scale production of the monatomic catalyst, and the operation is simple and the cost is low.

The invention is realized by the following technical scheme:

a method for preparing a monatomic catalyst by using a waste adsorbent after adsorption-desorption comprises the following steps:

(1) mixing the waste adsorbent subjected to heavy metal ion adsorption and desorption for multiple times with a nitrogen source to obtain a mixture, wherein the waste adsorbent subjected to heavy metal ion adsorption and desorption is an adsorbent adsorbed with zinc ions and other one or more heavy metal ions;

(2) the mixture is loaded in a porcelain boat and placed in a tube furnace, is pyrolyzed and carbonized at low temperature and high temperature in sequence under the nitrogen atmosphere, and then is cleaned and dried to obtain the monatomic catalyst.

According to the invention, in the step (1), the waste adsorbent subjected to heavy metal ion adsorption and desorption for a plurality of times is preferably a waste adsorbent obtained by adsorbing heavy metal ions in heavy metal wastewater by using a biomass adsorbent, then desorbing the heavy metal ions in the heavy metal wastewater by using the desorbed adsorbent, and then desorbing and drying the heavy metal ions.

More preferably, the number of times of adsorption and analysis is 4 to 8.

Preferably, the biomass adsorbent is biogas residue, crop straws, bagasse, vinasse or a material obtained by modifying the biogas residue, the crop straws, the bagasse and the vinasse, and the particle size of the biomass adsorbent is 2-4 mm.

Modifying the raw materials of biogas residue, crop straws, bagasse and vinasse according to the prior art, wherein carboxyl, hydroxyl or sulfydryl is grafted on the raw materials.

Further preferably, the other heavy metal ions are iron ions, cobalt ions, copper ions, nickel ions or manganese ions.

According to the invention, preferably, in the performance of the prepared monatomic catalyst, the biomass adsorbent obtained after the biomass adsorbent adsorbs heavy metal ions in wastewater for one time has almost the same effect as the biomass adsorbent obtained 4-8 times after multiple adsorption and analysis.

The method of resolution is carried out according to conventional techniques in the art, and the present invention preferably employs 0.1M hydrochloric acid for resolution.

According to the invention, in step (1), the nitrogen source is one or a mixture of more than two of urea, dicyandiamide and melamine.

According to the invention, in the step (1), the mass mixing ratio of the waste adsorbent subjected to heavy metal ion adsorption and desorption for multiple times to the nitrogen source is preferably 1 (5-10).

More preferably, the mass mixing ratio of the waste adsorbent subjected to heavy metal ion adsorption and desorption for multiple times to the nitrogen source is 1: 6-8.

Preferably, in the step (2), the low-temperature pyrolysis carbonization temperature is 400-600 ℃, and the carbonization time is 0.5-2 h.

According to the invention, in the step (2), the high-temperature pyrolysis carbonization temperature is 800-1000 ℃, and the carbonization time is 1-4 h.

According to the invention, in the step (2), the heating rate is 3-6 ℃/min, and after high-temperature pyrolysis carbonization, the product is cooled to room temperature and then cleaned.

According to the invention, in the step (2), the cleaning is preferably performed by using a mixed solution of absolute ethyl alcohol and deionized water.

Preferably, according to the present invention, the adsorbed zinc ions are evaporated during pyrolysis at high temperature, and the obtained metal monatomic catalyst is other metal monatomic catalyst or catalysts adsorbed in the adsorbent.

The invention has the technical characteristics and advantages that:

1. according to the invention, the adsorbent (adsorbent after heavy metal ions are adsorbed and analyzed for multiple times) adsorbing zinc ions and other one or more heavy metal ions is used as a precursor for the first time, and the metal monatomic catalyst is prepared through nitrogen doping and pyrolysis processes, so that the high-efficiency and high-value utilization of the waste adsorbent is realized, a new thought is provided for the reutilization of the biomass adsorbent after heavy metal ions are adsorbed, the secondary pollution of the waste adsorbent after heavy metal ions are adsorbed is avoided, a resource road is found for the waste adsorbent, the solid waste treatment pressure is relieved, and the environment is protected. The invention not only enables the waste adsorbent to be better recycled, but also saves resources. And the catalyst prepared from the waste adsorbent has high activation capacity, changes waste into valuable and can be recycled.

2. The invention provides a simple and convenient preparation method of a metal monatomic catalyst, which comprises the steps of mixing a catalyst for adsorbing heavy metal ions with a nitrogen source, and carrying out staged (low temperature → high temperature) pyrolysis in an atmosphere protected by nitrogen to obtain the monatomic catalyst. Compared with the prior art, the preparation method takes cheap dangerous waste as a raw material, realizes the preparation of the monatomic catalyst by utilizing the dispersion form of the adsorbed heavy metal ions in the adsorbent, has uniform distribution of metal monatomics and good dispersibility, and can control the loading capacity of the metal monatomics by the amount of adsorbed heavy metals; meanwhile, the preparation method is simple to operate, reaction conditions are controllable, and the cost is low. Finally, in the preparation method of the invention, the preparation of different metal monatomic catalysts can be realized by changing the types of the adsorbed heavy metal ions, the success rate is high, and the large-scale preparation of the monatomic catalysts can be realized.

Drawings

FIG. 1 is a schematic diagram of the synthesis of a metal monatomic catalyst according to the present invention;

FIG. 2 is a structural representation diagram of the prepared copper monatomic catalyst. (a) Correcting the transmission electron microscope image for spherical aberration; (b) the image is a high-resolution high-angle annular dark field image of the sample, and the bright point is a copper monoatomic atom; (c) is the element energy spectrum analysis result of the sample;

FIG. 3 is a structural representation diagram of the prepared iron monatomic catalyst. (a) Correcting the transmission electron microscope image for spherical aberration; (b) the image is a high-resolution high-angle annular dark field image of the sample, and the bright point is an iron monoatomic atom; (c) is the element energy spectrum analysis result of the sample;

FIG. 4 is a structural representation diagram of the prepared iron monatomic catalyst. (a) Correcting the transmission electron microscope image for spherical aberration; (b) the image is a high-resolution high-angle annular dark field image of the sample, and the bright point is a cobalt monoatomic atom; (c) is the element energy spectrum analysis result of the sample;

figure 5 is an X-ray diffraction (XRD) pattern of copper monatomic catalysts prepared to give different copper atom loadings.

Detailed Description

The present invention is further illustrated by the following examples, but is not limited thereto.

The biomass adsorbent used in the embodiment is a cationic adsorbent prepared by taking wheat straws as a raw material and introducing carboxyl functional groups after modification.

Example 1:

a method for preparing copper monatomic catalyst by using the waste adsorbent after adsorption-desorption is disclosed, and the process is shown in figure 1.

(1) The waste adsorbent is dried after Zn ions and Cu ions in the wastewater containing Zn ions and Cu ions are adsorbed-resolved for 6 times to obtain a dried waste adsorbent with a Zn/Cu adsorption capacity ratio of about 4: 3; taking 10g of dry waste adsorbent, according to the following steps: dicyandiamide ═ 1: mixing at a mass ratio of 10, and putting into a porcelain boat for compaction;

(2) placing the copper monoatomic adsorbent into a tubular furnace, heating to 550 ℃ at the speed of 5 ℃/min under the nitrogen atmosphere, then preserving heat for 1h, subsequently heating to 900 ℃ at the same speed, preserving heat for 2h, cooling to room temperature, taking out, cleaning with deionized water and ethanol, and finally drying at 60 ℃ to obtain the copper monoatomic adsorbent, wherein the structural representation diagram of the copper monoatomic adsorbent is shown in figure 2. The results show that the copper atoms are present in the catalyst in monoatomic form. Inductively coupled plasma emission spectroscopy showed that the doping amount of copper single atoms was about 3.4%.

Example 2:

a method for preparing an iron monatomic catalyst by using a waste adsorbent after adsorption-desorption comprises the following steps:

(1) the waste adsorbent is dried after Zn ions and Fe ions in the wastewater containing Zn ions and Fe ions are adsorbed-resolved for 6 times to obtain a dried waste adsorbent with a Zn/Fe adsorption capacity ratio of about 4: 3; taking 10g of dry waste adsorbent, according to the following steps: dicyandiamide ═ 1: mixing at a mass ratio of 10, and putting into a porcelain boat for compaction;

(2) putting the iron monoatomic adsorbent into a tubular furnace, heating to 550 ℃ at the speed of 5 ℃/min under the nitrogen atmosphere, then preserving heat for 1h, subsequently heating to 900 ℃ at the same speed, preserving heat for 2h, cooling to room temperature, taking out, cleaning with deionized water and ethanol, and finally drying at 60 ℃ to obtain the iron monoatomic adsorbent, wherein the structural representation diagram is shown in figures 3 and 5. The results show that the iron atom is present in the catalyst in monoatomic form. Inductively coupled plasma emission spectroscopy showed that the iron monatomic doping was about 3.1%.

Example 3:

a method for preparing a cobalt monatomic catalyst by using a waste adsorbent after adsorption-desorption comprises the following steps:

(1) the waste adsorbent is dried after Zn ions and Co ions in the wastewater containing Zn ions and Co ions are adsorbed-resolved for 6 times to obtain the dried waste adsorbent with the Zn/Co adsorption capacity ratio of about 4: 3. Taking 10g of dry waste adsorbent, according to the following steps: dicyandiamide ═ 1: mixing the materials according to the mass ratio of 10, putting the mixture into a porcelain boat for compaction,

(2) putting the cobalt monoatomic adsorbent into a tubular furnace, heating to 550 ℃ at the speed of 5 ℃/min under the nitrogen atmosphere, then preserving heat for 1h, subsequently heating to 900 ℃ at the same speed, preserving heat for 2h, cooling to room temperature, taking out, cleaning with deionized water and ethanol, and finally drying at 60 ℃ to obtain the cobalt monoatomic adsorbent, wherein the structural representation diagram is shown in fig. 4. The results show that the iron atom is present in the catalyst in monoatomic form. Inductively coupled plasma emission spectroscopy showed that the iron monatomic doping was about 2.7%.

Example 4:

the same as example 1, except that: the Zn/Cu adsorption in the spent adsorbent was about 4: 1. The XRD pattern of the obtained product is shown in figure 4, and the result shows that no crystal form of copper exists, and the existence form of copper is in a single atom form. Inductively coupled plasma emission spectroscopy showed that the iron monatomic doping was about 1.3%.

Example 5:

the same as example 1, except that:

the Zn/Cu adsorption in the spent adsorbent was about 4: 2. The XRD pattern of the obtained product is shown in figure 4, and the result shows that no crystal form of copper exists, and the existence form of copper is in a single atom form. Inductively coupled plasma emission spectroscopy showed that the iron monatomic doping was about 2.2%.

The present invention is not limited to the above-described embodiments, which are merely exemplary and intended to illustrate the present invention, but are not to be construed as limiting the present invention.