Preparation method and application of graphene / LDH hybrid composite material

Abstract

The application discloses a preparation method of a graphene / LDH hybrid composite material, and comprises the following steps: adding waste incineration fly ash and aluminum ash into fermentation waste liquid respectively, mixing and leaching sufficiently, filtering, and taking the filtrate; mixing the obtained fly ash filtrate and aluminum ash filtrate according to a molar ratio of Ca 2+ and Al 3+ greater than 1.5:1, adjusting the pH to 10-12, fully stirring to obtain a mixed suspension; transferring the mixed suspension into a ball mill tank, adding graphene oxide, steel slag, fly ash and deionized water, performing mechanical ball milling, centrifuging, suction filtering, and performing washing and drying to obtain the graphene / LDH hybrid composite material. Through the synergistic disposal of the waste incineration fly ash, the aluminum ash, the steel slag and the fermentation waste liquid, the GLDH with the graphene oxide and the montmorillonite as the base is directly synthesized by using the mechanical chemical method, the GLDH has a large adsorption capacity for heavy metals Cd and Cu, and can be widely applied to the adsorption of heavy metals in wastewater and the improvement of soil.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of environmental protection, and particularly relates to a preparation method and application of a graphene / LDH hybrid composite material. BACKGROUND

[0002] A large amount of waste such as waste incineration fly ash, aluminum ash, slag, slag, fly ash, electroplating wastewater and the like generated in the process of life and urban development mostly contains toxic substances, and if not disposed of, will pollute the environment, for example, waste incineration fly ash contains highly toxic organic compounds and heavy metals, which can cause serious harm to the human body; small particles of aluminum ash dust are easy to enter the air pollution atmosphere, and water-soluble salt ions, heavy metals and the like may cause land salinization, therefore, harmless resourceful disposal of solid waste will also become one of the important environmental protection problems. On the other hand, a large amount of valuable elements such as Ca, Si and Al are contained in these wastes, and the preparation of layered double hydroxides (LDHs) and the application thereof can effectively promote the resource utilization of waste and reduce the production cost of LDHs.

[0003] LDHs is an anion type clay material composed of a main layer plate, interlayer anions and water molecules, and the most typical synthesis method is coprecipitation combined with hydrothermal method, and at present, corresponding researches are mainly in the application directions of catalysts, adsorbents and flame retardants, corrosion inhibitors and the like. The LDHs prepared from waste has similar performance to the LDHs synthesized from pure chemical reagents, but since the composition of waste is often complex, the composition of the obtained LDHs is also more complex, for example, the main layer plate may contain multiple metal elements, and the interlayer may also contain multiple different anions, which may affect the properties and performance thereof and increase the difficulty of exploring the application mechanism. However, the complex composition may enhance the performance, and compared with ordinary LDHs, the LDHs prepared from waste has higher economic and environmental value.

[0004] Therefore, it is very necessary to explore an efficient and low-cost method for preparing GLDH from waste incineration fly ash and aluminum ash slag, and to realize the collaborative treatment of hazardous waste and industrial solid waste. SUMMARY

[0005] In order to solve at least one of the above problems, the application provides a preparation method and application of a graphene / LDH hybrid composite material.

[0006] In order to achieve the above purpose, the application adopts the following technical means:

[0007] The first aspect of the application provides a preparation method of a graphene / LDH hybrid composite material, comprising the following steps:

[0008] S1. Add the fly ash from waste incineration and aluminum ash to the fermentation waste liquid, mix and extract thoroughly, filter and take the filtrate, and collect the fly ash residue for later use.

[0009] S2: Combine the obtained fly ash filtrate and aluminum ash filtrate according to the divalent metal cation Ca... 2+ and trivalent metal cation Al 3 + The molar ratio of the components is greater than 1.5:1. The mixture is then adjusted to pH 10-12 and stirred thoroughly to obtain a mixed suspension.

[0010] S3: Transfer the mixed suspension to a ball mill jar, add graphene oxide, steel slag, and fly ash filter residue obtained in step S1, and perform mechanochemical ball milling treatment;

[0011] S4: Centrifuge, filter, wash, and dry the mixture in S3 to obtain the graphene / LDH hybrid composite material.

[0012] In a specific embodiment of the present invention, after the fly ash filtrate and aluminum ash filtrate are mixed, the pH is adjusted to 11.

[0013] In some embodiments of the present invention, the fermentation waste liquid is an acidic waste liquid with a pH of 1 to 5 generated from a biochemical process.

[0014] In some embodiments of the present invention, the fermentation waste liquid can also be replaced by an inorganic acid solution, wherein the inorganic acid is acetic acid or hydrochloric acid.

[0015] In some specific implementation schemes, fly ash from waste incineration is added to a 0.4-0.5M acetic acid solution at a rotation speed of 600-700 rpm and acid-washed and stirred for 20-24 hours; aluminum ash is added to a 0.2-0.3M hydrochloric acid solution at a rotation speed of 400-500 rpm and acid-washed and stirred for 10-12 hours; the resulting mixture is then filtered through a 0.45μm filter membrane to collect the filtrate.

[0016] In some embodiments of the present invention, in step S1, the liquid-to-solid ratio is (5~10):1, and the extraction time is 12~24 hours.

[0017] In some embodiments of the present invention, the mass ratio of the graphene oxide, steel slag, and fly ash filter residue obtained in step S1 is (0.01-0.1):1:1; the graphene oxide and the divalent metal cation Ca in the mixed suspension are... 2+ The molar ratio is (0.01-0.1):1.

[0018] In some embodiments of the present invention, the mechanochemical ball milling treatment conditions in step S3 are: ball-to-material ratio (8-10):1.

[0019] In some embodiments of the present application, the mechanical chemical method ball milling treatment is performed for 2-6 hours at a rotation speed of 300-600 rpm.

[0020] In some embodiments of the present application, the washing step in step S4 is twice deionized water washing and once ethanol washing.

[0021] In some embodiments of the present application, the drying condition in step S4 is 50-110℃.

[0022] The present application also provides a graphene / LDH hybrid composite material prepared by the method of the first aspect.

[0023] The present application also provides a graphene / LDH hybrid composite material prepared by the method of the first aspect for use in adsorption of heavy metals in wastewater.

[0024] In some embodiments of the present application, the graphene / LDH hybrid composite material is used in adsorption of heavy metal Cd in wastewater.

[0025] In some embodiments of the present application, the graphene / LDH hybrid composite material is used in adsorption of heavy metal Cu in wastewater.

[0026] The present application also provides a graphene / LDH hybrid composite material prepared by the method of the first aspect for use in improving soil contaminated by heavy metal Cd and / or Cu.

[0027] In the application of soil improvement, the graphene / LDH hybrid composite material is mixed with the contaminated soil.

[0028] Advantages of the present application

[0029] Compared with the prior art, the present application has the following advantages:

[0030] (1) The present application uses biological or chemical process fermentation waste liquid to leach the effective components in fly ash and aluminum ash, replacing the use of industrial hydrochloric acid, sulfuric acid, acetic acid, etc. In addition to reducing the purchase cost and disposal cost caused by the use of industrial inorganic acid, the present application also cooperatively processes the biological or chemical process fermentation waste liquid, thereby reducing the additional disposal cost of the fermentation waste liquid. The present application uses garbage incineration fly ash, aluminum ash, graphene, and steel slag to synthesize GLDH. Through the cooperative disposal and high-value utilization of multiple hazardous wastes, the present application replaces waste landfill treatment, fully applies the effective components, reduces environmental pollution, and improves economic value.

[0031] Overall, the LDHs are prepared by using ball milling method with waste incineration fly ash, aluminum ash and acidic fermentation waste liquid generated by biological chemical process, on the one hand, the waste incineration fly ash, aluminum ash, acidic waste liquid generated by biological chemical process and steel slag are resourceized, the related costs of fly ash solidification landfill, fly ash aluminum ash steel slag treatment and acidic waste liquid treatment are reduced, on the other hand, the prepared graphene / LDH hybrid composite material is used for heavy metal adsorption, the consumption of pure reagent is reduced, and great economic benefits are generated. The method of the application can not only realize the stable treatment of fly ash, but also has simple process, easy preparation, low equipment requirement and universality, and can be widely used.

[0032] (2) In the preparation process of the graphene / LDH hybrid composite material (GLDH), the mechanical chemical method is used to directly complete the synthesis of the composite GLDH with graphene oxide (GO) and montmorillonite as the base, so that the step-by-step preparation process of the GLDH is omitted, the overall reaction process is more efficient, and the economic cost is reduced.

[0033] (3) In the application, through ball milling treatment, the steel slag and fly ash generate montmorillonite in the process, and under the action of graphene oxide, the prepared GLDH has a large specific surface area and can expose more active sites, so that the GLDH can be widely applied to the adsorption of heavy metals in wastewater and the improvement of soil. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The XRD graph of the graphene / LDH hybrid composite material obtained in Example 3 of the application is shown;

[0035] Figure 2 The heavy metal adsorption performance comparison of the composite materials prepared under different pH conditions in Examples 1 to 6 is shown;

[0036] Figure 3 The heavy metal adsorption performance comparison of the composite materials prepared under different pH conditions in Examples 1 to 3 is shown;

[0037] Figure 4 The heavy metal adsorption performance comparison of the composite materials prepared under different Ca 2+ , Al 3+ ratio conditions in Example 1, Examples 7-10 is shown;

[0038] Figure 5 The heavy metal adsorption performance comparison of the composite materials prepared under different graphene addition amount conditions in Example 1, Examples 15-20 is shown. DETAILED DESCRIPTION

[0039] The following examples are put forth so as to demonstrate preferred embodiments of the application. Those in the art will recognize that the examples set forth herein demonstrate techniques that can be used in carrying out the application, and that the present application is capable of making numerous other variations upon the preferred embodiments as set forth herein without departing from the spirit or scope of the present application.

[0040] Unless otherwise defined, 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 application belongs, and the materials described herein will be referred to by the citation of the reference that first introduced such term into the art. In case of conflict between the citation in the specification and that of a document incorporated herein by reference, the document incorporated by reference will control. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the application described herein. Such equivalents are intended to be encompassed by the following claims.

[0041] The technical solutions of the present application are further described in detail below in conjunction with the specific embodiments.

[0042] A preparation method of a graphene / LDH hybrid composite material, comprising the following steps:

[0043] S1, the waste incineration fly ash and aluminum ash are respectively added into the acidic fermentation waste liquid with pH 1-5 generated in the biological chemical process, the liquid-solid ratio (5-10):1, and the leaching is carried out for 12-24 hours after sufficient mixing, the filtrate is taken after filtration, and the fly ash filter residue is collected for standby;

[0044] S2: the fly ash filtrate and the aluminum ash filtrate obtained are mixed according to the molar ratio of the divalent metal cation Ca 2+ and the trivalent metal cation Al 3 + and the pH is adjusted to 10-12, and the mixed suspension is obtained after sufficient stirring;

[0045] S3: the mixed suspension is transferred into a ball mill tank, graphene oxide, steel slag and the fly ash filter residue obtained in step S1 are added, and mechanical chemical ball milling treatment is carried out, wherein the mass ratio of the graphene oxide, the steel slag and the fly ash filter residue obtained in step S1 is (0.01-0.1):1:1; the molar ratio of the graphene oxide to the divalent metal cation Ca 2+ in the mixed suspension is (0.01-0.1):1; in the ball milling treatment, the ball-to-material ratio (8-10):1, the ball milling time is 2-6h, and the ball milling rotation speed is 300-600rpm,

[0046] S4: the mixed liquid in S3 is centrifuged, suction filtered and washed, the washing step is two times of deionized water washing and one time of ethanol washing; and the graphene / LDH hybrid composite material is obtained after drying at 50-110 DEG C after washing.

[0047] In the above scheme, the fermentation waste liquid can also be replaced by an inorganic acid solution, wherein the inorganic acid is acetic acid or hydrochloric acid.

[0048] In some specific implementation schemes, fly ash from waste incineration is added to a 0.4-0.5M acetic acid solution at a rotation speed of 600-700 rpm and acid-washed and stirred for 20-24 hours; aluminum ash is added to a 0.2-0.3M hydrochloric acid solution at a rotation speed of 400-500 rpm and acid-washed and stirred for 10-12 hours; the resulting mixture is then filtered through a 0.45μm filter membrane to collect the filtrate.

[0049] This invention also relates to a graphene / LDH hybrid composite material prepared by the above method and its application in the adsorption of heavy metals in wastewater and soil improvement.

[0050] Example 1

[0051] A method for preparing a graphene / LDH hybrid composite material includes the following steps:

[0052] S1. Add the fly ash from waste incineration and aluminum ash to the acidic fermentation waste liquid with pH 4 produced in the biochemical process, with a liquid-to-solid ratio of 8:1. Mix and extract for 22 hours, filter and take the filtrate. Collect the fly ash residue for later use.

[0053] S2: Combine the obtained fly ash filtrate and aluminum ash filtrate according to the divalent metal cation Ca... 2+ and trivalent metal cation Al 3 + The mixture was prepared by mixing the components at a molar ratio of 2:1 and adjusting the pH to 11. After thorough stirring, a mixed suspension was obtained.

[0054] S3: Transfer the mixed suspension to a ball mill jar, add graphene oxide, steel slag, and fly ash filter residue obtained in step S1 at a mass ratio of 0.02:1:1, and perform mechanochemical ball milling treatment, wherein the graphene oxide reacts with the divalent metal cation Ca in the mixed suspension. 2+ The molar ratio was 0.02:1; during ball milling, the ball-to-material ratio was 10:1, the milling time was 6 hours, and the milling speed was 600 rpm.

[0055] S4: The mixture in S3 was centrifuged and filtered at 5500 rpm, and washed twice with deionized water and once with ethanol. After washing, it was dried at 80°C to obtain the graphene / LDH hybrid composite material.

[0056] Example 2

[0057] The other operating steps are the same as in Example 1, except that in step S2, 2M NaOH solution is added to adjust the pH to 10.

[0058] Example 3

[0059] The other operating steps are the same as in Example 1, except that in step S2 a 2M NaOH solution is added to adjust the pH to 12.

[0060] Example 4

[0061] The other operating steps are the same as in Example 1, except that in step S2 a 2M NaOH solution is added to adjust the pH to 12.5.

[0062] Example 5

[0063] The other operating steps are the same as in Example 1, except that in step S2 a 2M NaOH solution is added to adjust the pH to 13.

[0064] Example 6

[0065] The other operating steps are the same as in Example 1, except that in step S2 a 2M NaOH solution is added to adjust the pH to 13.5.

[0066] Example 7

[0067] The other operating steps are the same as in Example 1, except that in step S2 the molar ratio of the divalent metal cation Ca 2+ and the trivalent metal cation Al 3+ is 3:1.

[0068] Example 8

[0069] The other operating steps are the same as in Example 1, except that in step S2 the molar ratio of the divalent metal cation Ca 2+ and the trivalent metal cation Al 3+ is 4:1.

[0070] Example 9

[0071] The other operating steps are the same as in Example 1, except that in step S2 the molar ratio of the divalent metal cation Ca 2+ and the trivalent metal cation Al 3+ is 5:1.

[0072] Example 10

[0073] The other operating steps are the same as in Example 1, except that in step S2 the molar ratio of the divalent metal cation Ca 2+ and the trivalent metal cation Al 3+ is 6:1.

[0074] Example 11

[0075] Other operation steps are the same as example 1, the difference is that the ball milling speed in step S3 is set to 300 rpm.

[0076] Example 12

[0077] Other operation steps are the same as example 1, the difference is that the ball milling speed in step S3 is set to 400 rpm.

[0078] Example 13

[0079] Other operation steps are the same as example 1, the difference is that the ball milling time in step S3 is set to 2 h.

[0080] Example 14

[0081] Other operation steps are the same as example 1, the difference is that the ball milling time in step S3 is set to 4 h.

[0082] Example 15

[0083] Other operation steps are the same as example 1, the difference is that the mass ratio of steel slag and fly ash filter residue obtained in step S1 is 1:1 in step S3.

[0084] Example 16

[0085] Other operation steps are the same as example 1, the difference is that the mass ratio of graphene oxide, steel slag and fly ash filter residue obtained in step S1 is 0.01:1:1 in step S3.

[0086] Example 17

[0087] Other operation steps are the same as example 1, the difference is that the mass ratio of graphene oxide, steel slag and fly ash filter residue obtained in step S1 is 0.015:1:1 in step S3.

[0088] Example 18

[0089] Other operation steps are the same as example 1, the difference is that the mass ratio of graphene oxide, steel slag and fly ash filter residue obtained in step S1 is 0.3:1:1 in step S3.

[0090] Example 19

[0091] Other operation steps are the same as example 1, the difference is that the mass ratio of graphene oxide, steel slag and fly ash filter residue obtained in step S1 is 0.5:1:1 in step S3.

[0092] Example 20

[0093] Other operation steps are same as example 1, the difference is that in step S3, the mass ratio of graphene oxide, steel slag and fly ash filter residue obtained in step S1 is 1:1:1.

[0094] (1) The composite material prepared in example 1 is tested by X-ray diffraction (XRD) to test the main crystal phase composition. The XRD result is shown in Figure 1 .

[0095] It can be seen from the figure that there are relatively sharp peaks at 10.5°, 11.3°, 22.6°, 23.4°, 31.0°, 38.8°, etc. These are typical characteristic peaks of LDHs.

[0096] (2) The adsorption test is carried out on the adsorption material prepared in the above examples 1 to 20:

[0097] 0.05 g of the above prepared GLDH material and 100 ml of simulated solution are mixed, the initial concentration of cadmium nitrate and copper nitrate in the simulated solution is 500 mg / L, 200 rpm stirring for 6 h, 7000 rpm centrifugation for 5 min to obtain supernatant and separation slurry, the supernatant is filtered through a 0.22 μm filter to obtain a filtrate, and the concentration of heavy metal ions in the liquid phase before and after adsorption is determined by ICP-OES. The test results are shown in Table 1, Figures 2 to 5 .

[0098] Table 1 Adsorption performance of the adsorption material obtained in examples 1 to 20

[0099]

[0100] The results show that as shown in Figure 2 and 3 , examples 1 to 6 show that the pH of the fly ash filtrate mixed with the aluminum ash filtrate has an important influence on the adsorption performance of the final product, and the optimal pH is 11, and when the pH value is more than 12, the adsorption performance of the product decreases obviously.

[0101] As shown in Figure 4 , examples 1, 7 to 10 show that with the increase of the ratio of Ca 2+ and Al 3+ in the fly ash filtrate and the aluminum ash filtrate, the synthesis efficiency of the prepared GLDH is further improved, and the adsorption capacity is gradually improved. This method can improve the efficiency of the synergistic treatment of fly ash and aluminum ash, and the product also has good application prospect.

[0102] Examples 1, 11 to 12 show that with the increase of the ball milling time, the synthesis efficiency of the prepared GLDH is further improved, and the adsorption capacity is gradually improved.

[0103] Examples 1, 13 and 14 show that as the ball milling speed increases, the synthesis efficiency of GLDH is further improved and the adsorption capacity is gradually increased.

[0104] like Figure 5 As shown in Examples 1, 15 to 20, the adsorption capacity of the prepared GLDH gradually increases with the increase of the amount of graphene oxide added. However, when the amount added exceeds 0.5 g / L, the growth rate of the adsorption capacity gradually decreases. When the amount of graphene oxide added is greater than 0.01 g / L, the adsorption capacity of the prepared material for Cd reaches more than 734 mg / g, and the adsorption capacity for Cu also reaches more than 428 mg / g. Considering the cost of adding graphene oxide, the amount of graphene oxide added should not be too high. The optimal amount of graphene oxide added is 0.01-0.02 g / L.

[0105] LDHs are prepared by ball milling from acidic fermentation wastewater generated during the co-processing of waste incineration fly ash, aluminum ash, and biochemical processes. This method achieves resource utilization of these materials, reducing costs associated with fly ash solidification and landfill, aluminum ash treatment, steel slag treatment, and acidic wastewater treatment. Furthermore, the resulting graphene / LDH hybrid composite material is used for heavy metal adsorption, reducing the consumption of pure reagents and generating significant economic benefits. The method described in this invention not only achieves stabilization of fly ash but also features a simple process, ease of preparation, low equipment requirements, and broad applicability, making it suitable for widespread use.

[0106] All documents mentioned in this invention are incorporated herein by reference as if each document were individually incorporated by reference. Furthermore, it should be understood that after reading the foregoing teachings of this invention, those skilled in the art can make various alterations or modifications to this invention, and these equivalent forms also fall within the scope defined by this application.

Claims

1. A method for preparing a graphene / LDH hybrid composite material, characterized in that, Includes the following steps: S1. Add the fly ash from waste incineration and aluminum ash to the fermentation waste liquid, mix and extract thoroughly, filter and take the filtrate, and collect the fly ash residue for later use. S2: Combine the obtained fly ash filtrate and aluminum ash filtrate according to the divalent metal cation Ca... 2+ and trivalent metal cation Al 3+ The molar ratio of the components is greater than 1.5:

1. The mixture is then adjusted to pH 11 and stirred thoroughly to obtain a mixed suspension. S3: Transfer the mixed suspension to a ball mill jar, add graphene oxide, steel slag, and fly ash filter residue obtained in step S1, and perform mechanochemical ball milling treatment; S4: Centrifuge, filter, wash, and dry the mixture in S3 to obtain the graphene / LDH hybrid composite material. The fermentation waste liquid is an acidic waste liquid with a pH of 1-5 generated from a biochemical process; The mass ratio of the graphene oxide, steel slag, and fly ash filter residue obtained in step S1 is (0.01-0.1):1:1; the graphene oxide and the divalent metal cation Ca in the mixed suspension are... 2+ The molar ratio is (0.01-0.1):1; The mechanochemical ball milling conditions in step S3 are: ball-to-material ratio (8-10):1; The ball milling time for the mechanochemical ball milling treatment is 2-6 hours, and the ball milling speed is 300-600 rpm.

2. The method according to claim 1, characterized in that: The fermentation waste liquid can also be replaced by an inorganic acid solution, wherein the inorganic acid is acetic acid or hydrochloric acid.

3. The method according to claim 1, characterized in that: In step S1, the liquid-to-solid ratio is (5~10):1, and the extraction time is 12~24 hours.

4. The method according to claim 1, characterized in that: In step S4, the washing steps consist of two deionized water washes and one ethanol wash.

5. The method according to claim 1, characterized in that: In step S4, the drying conditions are 50-110℃.

6. A graphene / LDHs hybrid composite material prepared by the method according to claims 1-5.

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