CN110548487B - A kind of hydrothermal carbon-based composite material, its preparation and application - Google Patents

Abstract

The invention belongs to the technical field of composite materials, and more particularly relates to a hydrothermal carbon-based composite material, its preparation and application. Mixing the biomass and the metal organic framework material precursor solution to obtain a raw material mixed solution; the raw material mixed solution is subjected to a hydrothermal reaction in a closed reactor, and the carbonization of the biomass and the metal organic framework material occur during the hydrothermal reaction process. After the hydrothermal reaction is completed, solid-liquid separation is performed, and the obtained solid material is washed and dried to obtain the hydrothermal carbon-based composite material. By adding metal-organic framework precursors in the preparation process of hydrothermal carbon, the hydrothermal carbon and metal-organic framework are organically combined to obtain a hydrothermal carbon-based composite material, and its adsorption capacity for heavy metals is improved, thereby solving the problem of hydrothermal energy in the prior art. The technical problems of carbon-based composite material adsorption of heavy metal raw materials are not easy to obtain, and the adsorption effect is not good.

Description

A kind of hydrothermal carbon-based composite material, its preparation and application

technical field

The invention belongs to the technical field of composite materials, and more particularly, relates to a hydrothermal carbon-based composite material, its preparation and application.

Background technique

Water pollution and its treatment have received extensive attention in recent years. Among them, heavy metals are listed as key control objects due to their high toxicity, easy accumulation and refractory degradation. The adsorption method is a convenient, effective and easy-to-operate method for the treatment of heavy metals in the liquid phase, and the key lies in the selection and improvement of the adsorbent. Hydrothermal carbon is prepared from biomass or other carbon-containing raw materials by hydrothermal method. Because of its abundant surface functional groups, low energy consumption in the preparation process, and greenness, it has the potential to be used as a green adsorbent for liquid-phase pollutants. In order to improve its adsorption performance, many studies are based on the modification treatment of hydrothermal carbon or the material composite.

Patent CN106904625 discloses a preparation method of hydrothermal carbon/montmorillonite composite material, wherein the raw material of hydrothermal carbon is cellulose, and cellulose is not easy to obtain, so limited by raw materials, the process is difficult to be applied in large scale. Patent CN201910110705 discloses a preparation method of surface functional group-functionalized hydrothermal carbon and has a good adsorption effect on Cr(VI), but for industrial wastewater, it is not only Cr(VI), but contains a variety of Heavy metal pollutants, so this process has limitations in application. Moreover, the improvement of the physicochemical properties of hydrothermal carbon in the existing reports is mostly limited to one of surface functionalization or pore structure, while the adsorption process is a physicochemical process involving two aspects, so it needs to be considered at the same time. CN106732374 discloses a method for simultaneously improving the surface functionalization and specific surface area of hydrothermal carbon, but the addition of β-FeOOH and KOH greatly reduces the greenness of the preparation process, and KOH is highly toxic, making it difficult to apply on a large scale.

Metal-organic frameworks are an emerging class of materials in recent years. They have the characteristics of large specific surface area, tunable pore structure, abundant surface functional groups, and open metal centers. They are widely used in various fields, especially in the field of adsorption. However, its water stability is not very good, and its sole use for the adsorption of liquid-phase pollutants will inevitably lead to the problem of poor cyclic adsorption stability, thus limiting its application in the adsorption of liquid-phase pollutants.

SUMMARY OF THE INVENTION

Aiming at the above defects or improvement needs of the prior art, the present invention provides a hydrothermal carbon-based composite material, its preparation and application. By adding a metal-organic framework precursor during the preparation of the hydrothermal carbon, the hydrothermal carbon and the The metal-organic framework is organically combined to obtain a hydrothermal carbon-based composite material, which improves its adsorption capacity for heavy metals, thereby solving the technical problems that the hydrothermal carbon-based composite material in the prior art is difficult to obtain heavy metal raw materials and has poor adsorption effect.

In order to achieve the above object, according to one aspect of the present invention, a preparation method of a hydrothermal carbon-based composite material is provided, comprising the following steps:

(1) mixing the biomass with the metal organic framework material precursor solution to obtain a raw material mixed solution;

(2) hydrothermal reaction is carried out with the raw material mixture in the closed reactor, and the carbonization of biomass and the crystallization reaction of the metal-organic framework material occur in the hydrothermal reaction process; After the obtained solid material is washed and dried, the hydrothermal carbon-based composite material is obtained.

Preferably, the biomass is granular biomass with a particle size of 1 mm to 10 mm.

Preferably, the biomass is one or more of straw, wood chips and bamboo chips.

Preferably, the metal-organic framework material precursor solution includes a metal salt solution obtained by dissolving a metal salt in a solvent and an organic framework ligand solution obtained by dissolving an organic framework ligand in a solvent; the metal salt is copper nitrate trihydrate , cobalt nitrate hexahydrate, ferric chloride hexahydrate or aluminum nitrate nonahydrate; the organic framework ligand is trimesic acid, terephthalic acid or 2-aminoterephthalic acid.

Preferably, the solvent is water and/or ethanol.

Preferably, the mass ratio of the metal salt to the organic framework ligand is 1:5 to 5:1, and the mass ratio of the solvent to the metal salt is 1:1 to 10:1.

Preferably, the mass ratio of the biomass to the metal organic framework material precursor solution is 1:1-1:10.

Preferably, in the hydrothermal reaction, the reaction temperature is 150°C to 300°C, and the reaction time is 8h to 48h.

According to another aspect of the present invention, a hydrothermal carbon-based composite material prepared by the preparation method is provided.

According to another aspect of the present invention, an application of the hydrothermal carbon-based composite material as a heavy metal adsorbent is provided.

In general, compared with the prior art, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

(1) In the present invention, biomass and metal organic framework material precursor solution are mixed, and the hydrothermal carbon-based composite material is prepared by one-pot hydrothermal method. The present invention fully combines the greenness, low energy consumption, abundant oxygen-containing functional groups, high specific surface area and adjustable pore size of metal-organic framework materials of hydrothermal carbon, and organically combines the two in a one-pot method. The compound method is simple and easy to implement.

(2) Compared with the hydrothermal carbon, the hydrothermal carbon-based composite material prepared by the present invention has significantly improved specific surface area, improved pore size controllability, and optimized pore structure greatly improved its physical adsorption capacity, thereby effectively improving Its adsorption capacity for heavy metals can meet the requirements of sewage treatment.

(3) The present invention uses the hydrothermal carbon as the composite substrate. On the one hand, the water stability of the metal organic framework can be effectively improved, so that it can be suitable for adsorbing pollutants in the liquid phase, thereby broadening the application range of the composite material. On the other hand, the one-pot preparation method can also increase the dispersion degree of the metal-organic framework, avoid the reduction of the effect of adsorption sites due to overlapping with each other, thereby effectively improving its adsorption effect on heavy metals, and has broad application prospects.

Description of drawings

Figure 1 is the X-ray diffraction pattern of the hydrothermal carbon-based composite material in Example 1 and its immersion in water for 24 hours.

FIG. 2 is a Fourier transform infrared spectrum of the hydrothermal carbon-based composite material in Example 1 and its immersion in water for 24 hours.

FIG. 3 is a scanning electron microscope image of the hydrothermal carbon-based composite material in Example 1. FIG.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

A preparation method of a hydrothermal carbon-based composite material provided by the invention comprises the following steps:

(1) mixing the biomass with the metal organic framework material precursor solution to obtain a raw material mixed solution;

(2) hydrothermal reaction is carried out with the raw material mixture in the closed reactor, and the carbonization of biomass and the crystallization reaction of the metal-organic framework material occur in the hydrothermal reaction process; After the obtained solid material is washed and dried, the hydrothermal carbon-based composite material is obtained.

The particle size of biomass raw materials affects the physical properties of the formed hydrothermal carbon, thereby affecting its composite with the metal-organic framework. Controlling the particle size within the above range can effectively make the growth process of the metal-organic framework and the hydrothermal carbon. The char formation process is closely combined and has better dispersion, so that the composite material has more adsorption sites to adsorb heavy metals in the liquid phase. In some embodiments, the biomass is granular biomass with a particle size ranging from 1 mm to 10 mm.

In some embodiments, the biomass agricultural and forestry waste, such as one or more of straw, wood chips and bamboo chips.

In some embodiments, the metal-organic framework material precursor solution includes a metal salt solution obtained by dissolving a metal salt in a solvent and an organic framework ligand solution obtained by dissolving an organic framework ligand in a solvent; the metal salt is trihydrate copper nitrate, cobalt nitrate hexahydrate, ferric chloride hexahydrate or aluminum nitrate nonahydrate; the organic framework ligand is trimesic acid, terephthalic acid or 2-aminoterephthalic acid.

In some embodiments, the solvent is water and/or ethanol.

In some embodiments, the mass ratio of the metal salt to the organic framework ligand is 1:5 to 5:1, and the mass ratio of the solvent to the metal salt is 1:1 to 10:1.

In some embodiments, the mass ratio of the biomass to the metal organic framework material precursor solution is 1:1-1:10.

Among the reaction parameters, the reaction temperature and reaction time greatly affect the char formation of the hydrothermal carbon, the crystallization effect and particle size of the metal-organic framework, and the reaction time and stirring rate affect the dispersion of the metal-organic framework when combined with the hydrothermal carbon. The degree and degree of bonding, and the relevant parameters are controlled within the above range, so that the final composite material has an excellent pore structure and sufficient adsorption sites, so that its adsorption performance for heavy metals is better.

In some embodiments, in the hydrothermal reaction, the heating rate is 5°C/min-20°C/min, the reaction temperature is 150°C-300°C, the reaction time is 8h-24h, and the stirring rate is not higher than 1000rpm. Too high agitation rate will make the crystals less prone to nucleation.

In some embodiments, in step (2), solvent water and/or ethanol are used to clean the solid substance obtained by solid-liquid separation, and drying is performed by vacuum drying, and the vacuum drying temperature is 50°C to 120°C.

The present invention also provides a hydrothermal carbon-based composite material prepared according to the preparation method. The composite material includes a hydrothermal carbon substrate and an organic metal framework material, and the organic metal framework is organically combined with the hydrothermal carbon.

The invention also provides the application of the hydrothermal carbon-based composite material, which is used as a heavy metal adsorbent to adsorb heavy metal ions in polluted water.

The invention utilizes the characteristics of large specific surface area and abundant functional groups of organic metal framework materials, as well as the characteristics of regenerable and strong water stability of hydrothermal carbon, and adopts a one-pot method to prepare a new type of hydrothermal carbon-based composite material to improve the adsorption of heavy metals. Effect.

Specifically, the present invention utilizes the characteristics that the preparation conditions of hydrothermal carbon and metal organic framework are similar, and adopts a one-pot method, that is, in the process of preparing hydrothermal carbon, the precursor of metal organic framework is added at the same time, so that metal organic framework and hydrothermal carbon can be organically combined. Firstly, the specific surface area of hydrothermal carbon can be increased, especially the number of micropores, and the advantages of physical adsorption can be fully utilized to improve its adsorption performance for heavy metals in the liquid phase. Secondly, due to the one-pot preparation, the two are grown in situ, so it is not a simple mixture of the two, but is closely connected, which can effectively retain the adsorption sites enhanced by the abundant oxygen-containing functional groups on the surface of the hydrothermal carbon. In addition, the metal-organic framework can be better dispersed on the hydrothermal carbon, which avoids the reduction of the effect of the adsorption sites due to overlapping with each other. In addition, considering the excellent water stability of the hydrothermal carbon, the hydrothermal carbon-based composite can also greatly improve the water stability of the metal-organic framework, thereby overcoming the cycle stability of using the metal-organic framework alone to adsorb liquid-phase pollutants. Disadvantages of poor sex.

In order to better explain the present invention, specific examples are given below, wherein the agricultural and forestry wastes used in the present invention are collected locally, and the chemicals are purchased from Sinopharm Group or Aladdin Company.

The following are examples:

A preparation method of a hydrothermal carbon-based composite material, comprising the following steps:

(1) The bamboo chips are air-dried and ground into fine particles;

(2) copper nitrate trihydrate and trimesic acid are respectively dissolved in the reaction solvent in a certain proportion, fully mixed, the solvent is ethanol and deionized water (mass ratio is 1:1), copper nitrate trihydrate, trimesic acid The mass ratio of formic acid to solvent is 2:1:40;

(3) the bamboo chips particles of step 1 are added in the mixed solution that step 2 makes, fully mix, and the mass ratio of bamboo chips and mixed solution is 1:5;

(4) put the mixed solution obtained in step 3 into a closed reaction kettle with a stirrer to carry out carbonization and crystallization reaction, the heating rate is 10°C/min, the reaction temperature is 180°C, the reaction time is 18h, and the stirring rate is is 800rpm.

(5) After cooling, the solid obtained in step 4 was collected by centrifugation, and washed three times with ethanol and deionized water.

(6) After vacuum drying the solid obtained in step 5, a hydrothermal carbon-based composite material can be obtained, and the vacuum drying temperature is 80°C.

It can be seen from Table 1 that the pore structure of the hydrothermal carbon itself is not good, but the pore structure of the hydrothermal carbon after being compounded with MOFs is significantly improved, especially the introduction of a large number of microporous structures, which will also greatly improve the pore structure. Improve its physical adsorption properties.

The heavy metal adsorption conditions in Table 2 are as follows, adsorption temperature: normal temperature; initial concentration: 10 mg/L; adsorbent input amount: 20 mg/L; reaction time: 24 hours. It can be found from the figure that compared with the hydrothermal carbon, the hydrothermal carbon-based composite material has a significantly improved adsorption effect on heavy metals, so it is suitable for application as a heavy metal adsorption material.

Figure 1 is the X-ray diffraction pattern of the hydrothermal carbon-based composite material and its immersion in water for 24 hours. It can be seen from the figure that the intensity and position of the crystal diffraction peak of the hydrothermal carbon-based composite material after immersion in water for 24 hours are not The change shows that the crystal structure is still stable, and it also proves that the composite material has high water stability; Figure 2 is the Fourier infrared image of the hydrothermal carbon-based composite material and its immersion in water for 24 hours. The composites are rich in surface functional groups and have excellent water stability, so they are suitable for adsorption applications of liquid-phase pollutants. Figure 3 is the scanning electron microscope image of the hydrothermal carbon-based composite material. It can be seen from the figure that the regular octahedral structure of Cu-BTC is closely combined with the structure of the hydrothermal carbon, which proves the feasibility of this method.

The specific surface area and pore structure of the hydrothermal carbon and the hydrothermal carbon-based composite material in Example 1 are as follows:

Table 1

In Example 1, the adsorption efficiency of hydrothermal carbon and hydrothermal carbon-based composite materials to a variety of heavy metals in liquid phase is as follows:

Table 2

Example 2

A preparation method of a hydrothermal carbon-based composite material, comprising the following steps:

(1) Air-dry the straw and pulverize it into fine particles;

(2) dissolving aluminum nitrate nonahydrate and trimesic acid in the reaction solvent in a certain proportion respectively, mixing fully, the solvent is deionized water, and the mass ratio of aluminum nitrate nonahydrate and trimesic acid to solvent is 5:1 :8;

(3) adding the straw particles of step 1 into the mixed solution prepared in step 2, and mixing them fully; the mass ratio of straw to the mixed solution is 1:1;

(4) put the mixed solution obtained in step 3 into a closed reaction kettle with a stirrer to carry out carbonization and crystallization reaction, the heating rate is 5°C/min, the reaction temperature is 250°C, the reaction time is 48h, and the stirring rate is is 300rpm.

(5) After cooling, the solid obtained in step 4 was collected by centrifugation, and washed three times with deionized water.

(6) After vacuum drying the solid obtained in step 5, a hydrothermal carbon-based composite material can be obtained, and the vacuum drying temperature is 100°C.

Example 3

A preparation method of a hydrothermal carbon-based composite material, comprising the following steps:

(1) The wood chips are air-dried and ground into fine particles;

(2) ferric chloride hexahydrate and terephthalic acid are respectively dissolved in the reaction solvent in a certain proportion, fully mixed, the solvent is deionized water, and the mass ratio of ferric chloride hexahydrate and terephthalic acid to the solvent is 3 :1:10;

(3) the wood chip particles of step 1 are added to the mixed solution obtained in step 2, and fully mixed; the mass ratio of wood chips and mixed solution is 2:1;

(4) put the mixed solution obtained in step 3 into a closed reaction kettle with a stirrer to carry out carbonization and crystallization reaction, the heating rate is 20°C/min, the reaction temperature is 150°C, the reaction time is 24h, and the stirring rate is is 0rpm.

(5) After cooling, the solid obtained in step 4 was collected by centrifugation, and washed three times with deionized water.

(6) After vacuum drying the solid obtained in step 5, a hydrothermal carbon-based composite material can be obtained, and the vacuum drying temperature is 60°C.

Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims (9)

1. a preparation method of hydrothermal carbon-based composite material, is characterized in that, comprises the steps: (1) mixing the biomass with the metal organic framework material precursor solution to obtain a raw material mixed solution; (2) hydrothermal reaction is carried out with the raw material mixture in the closed reactor, and the carbonization of biomass and the crystallization reaction of the metal-organic framework material occur in the hydrothermal reaction process; After the obtained solid material is washed and dried, the hydrothermal carbon-based composite material is obtained, and the biomass is granular biomass with a particle size of 1 mm to 10 mm. 2 . The preparation method according to claim 1 , wherein the biomass is one or more of straw, wood chips and bamboo chips. 3 . 3. The preparation method of claim 1, wherein the metal-organic framework material precursor solution comprises a metal salt solution obtained by dissolving a metal salt in a solvent and an organic framework obtained by dissolving an organic framework ligand in a solvent Ligand solution; the metal salt is copper nitrate trihydrate, cobalt nitrate hexahydrate, ferric chloride hexahydrate or aluminum nitrate nonahydrate; the organic framework ligand is trimesic acid, terephthalic acid or 2-amino terephthalic acid. 4. The preparation method of claim 3, wherein the solvent is water and/or ethanol. 5. preparation method as claimed in claim 3 is characterized in that, the mass ratio of described metal salt and organic framework ligand is 1:5～5:1, and the mass ratio of described solvent and metal salt is 1:1 ~10:1. 6 . The preparation method of claim 1 , wherein the mass ratio of the biomass to the metal-organic framework material precursor solution is 1:1 to 1:10. 7 . 7 . The preparation method according to claim 1 , wherein the reaction temperature in the hydrothermal reaction is 150° C.˜300° C., and the reaction time is 8 h˜48 h. 8 . 8. The hydrothermal carbon-based composite material prepared by the preparation method according to any one of claims 1 to 7. 9. The application of the hydrothermal carbon-based composite material according to claim 8, characterized in that, it is used as a heavy metal adsorbent.

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