A nanotube-based adsorption material and its application in resource utilization of waste incineration fly ash

Abstract

The invention discloses a nanotube-based adsorption material and its application in the resource utilization of waste incineration fly ash. The preparation steps of the adsorption material are as follows: carbon nanotubes and an acid solution are mixed in proportion, and ultrasonicated; refluxed at 60-70°C for 5-6 hours, cooled and diluted, filtered with a filter membrane, washed with distilled water until neutral, dried and ground to obtain acid-modified carbon nanotubes; then, the acid-modified carbon nanotubes, zinc oxide, water, stearic acid and a dispersant are mixed and stirred according to the example, ultrasonicated, natural rubber latex is added and stirred evenly, and ultrasonicated again to obtain a mixed solution; the mixed solution is dried and then roasted and carbonized; the carbonized adsorbent is ground in a mortar and sieved to obtain a final adsorption material, the adsorption material is added to the washed fly ash to stabilize heavy metals, and the detoxified fly ash can be used for resource utilization to prepare building materials, and the heavy metal leaching of the obtained building materials meets the GB9878 standard.

Description

Technical Field

[0001] The present invention belongs to the technical field of heavy metal adsorption materials, and particularly relates to an adsorption material based on nanotubes and its application in resource utilization of waste incineration fly ash. Background Art

[0002] With the development of waste incineration technology in my country, the production and stockpiling of fly ash are large. At present, the problem of resource utilization of fly ash is being solved. The main heavy metals studied in fly ash include As, Ba, Be, Cd, Cr, Cu, Hg, Ni, Pb, Se, Zn and other heavy metals, among which Pb and Zn have relatively high content. The main ones that are easy to exceed the standard in fly ash are Cd, Cr, Cu, Ni, Pb, and Zn, which are also the focus of research on heavy metals in fly ash. When fly ash comes into contact with water in the external environment, especially acid rain or corrosive liquids, the heavy metals in the fly ash will leach into the liquid, and then enter the ecological environment system, polluting groundwater, rivers, lakes, seas and soil, and finally entering the human body. When the heavy metals in the human body are enriched to a certain concentration, it will cause serious harm to the human body and even lead to disease and death.

[0003] Currently, heavy metals are primarily stabilized through cement curing and chemical stabilization. Landfilling after cement curing is currently the most convenient method for fly ash disposal. Fly ash is simply mixed with cement or other gel materials, added with water, and then demolded and cured. The resulting cement blocks can be directly landfilled. Due to its ease of use, cement curing has become widely used worldwide. During the curing process, cement and water undergo a hydration reaction to produce calcium silicate hydrate gel (CSH) and ettringite (AFt), which encapsulate heavy metals in the fly ash and inhibit their leaching. However, the weight and volume of the cement product increase significantly, leading to increased disposal costs. Furthermore, over the long term, heavy metals such as Cd and Zn in the fly ash are at risk of leaching, making long-term stability unattainable.

[0004] Chemical stabilization involves converting heavy metals in fly ash into more stable forms, such as inorganic mineral salts or polymer complexes, through chemical reactions. Chemical agents are primarily categorized as inorganic and organic. Because chemical agents are selective for heavy metals, multiple chemical agents or a combination of chemical agents and cement are often used for disposal, but this can be costly. Summary of the Invention

[0005] In order to solve at least one of the above problems, the present invention provides a nanotube-based adsorption material and its application in resource utilization of waste incineration fly ash.

[0006] In order to achieve the above object, the present invention adopts the following technical means:

[0007] A first aspect of the present invention provides a method for preparing a nanotube-based adsorption material, comprising the following steps:

[0008] S1. CNTs and acid solution were mixed in a ratio of 1 g of CNTs: 250 mL of concentrated sulfuric acid: 50-80 mL of concentrated nitric acid, and ultrasonicated. The mixture was refluxed at 60-70°C for 5-6 h. After cooling and dilution, the mixture was filtered through a filter membrane, washed with distilled water until neutral, dried in a vacuum drying oven, and ground to obtain acid-modified CNTs.

[0009] S2. The obtained acid-modified carbon nanotubes are mixed and stirred in a weight ratio of acid-modified carbon nanotubes: zinc oxide: water: stearic acid: dispersant = 1: (0.5-1): (130-150): (1-1.2): (1-1.5), and ultrasonicated. 50-70 g of natural rubber latex is added and stirred uniformly, and ultrasonicated again to obtain a mixed solution;

[0010] S3. The mixed solution is dried in a vacuum drying oven and then calcined and carbonized; the carbonized adsorbent is ground in a mortar and passed through 200-250 mesh to obtain the final adsorption material.

[0011] In some embodiments of the present invention, the dispersant is one or both of gum arabic and sodium dodecylbenzene sulfonate. In some specific embodiments of the present invention, when two dispersants are mixed, the mass ratio of gum arabic to sodium dodecylbenzene sulfonate is 1:1.

[0012] In some embodiments of the present invention, in steps S1 and S2, the ultrasonication time is 30-60 min.

[0013] In some embodiments of the present invention, in step S1, the drying temperature is 90-100° C., and the drying time is 4-8 hours.

[0014] In some embodiments of the present invention, in step S1, the filter membrane is a 0.22 μm polytetrafluoroethylene filter membrane.

[0015] In some embodiments of the present invention, in step S3, the calcination temperature is 800-850° C., and the carbonization time is 4-6 hours.

[0016] In some embodiments of the present invention, the carbon nanotubes have a length of 2-10 nm.

[0017] The second aspect of the present invention provides a nanotube-based adsorption material, which is prepared by the method described in the first aspect.

[0018] The third aspect of the present invention provides the use of the adsorption material described in the second aspect in the resource utilization of waste incineration fly ash, comprising the following steps:

[0019] S1. After washing the waste incineration fly ash with water at a liquid-to-solid ratio of (8-10):1, the washed fly ash is obtained by plate and frame filter pressing;

[0020] S2: The washed fly ash obtained in S1 and water are added to a ball mill at a liquid-to-solid ratio of (2-3):1. At the same time, a nanotube-based adsorption material accounting for more than 3% of the weight of the washed fly ash is added. The nanotube-based adsorption material is divided into three parts and added three times. After ball milling for a period of time, a mixed solution is obtained.

[0021] S3. After the mixed liquid is filtered through plate and frame, the solid is the waste incineration fly ash that can be recycled.

[0022] The heavy metal leaching in the waste incineration fly ash after the above treatment meets the GB9878 standard. In the subsequent resource utilization, the relevant heavy metal indicators of related products can also meet the environmental protection requirements.

[0023] In some embodiments of the present invention, the amount of adsorbent material added is 3%-6% of the mass of the washed fly ash, and is added in three times, with each addition ratio being 1%-2%.

[0024] In some embodiments of the present invention, the ball mill has a ball milling speed of 500-600 rpm, a ball-to-material ratio of (8-10):1, and a ball milling time of 1-3 hours. In some specific embodiments, the ball mill is a planetary ball mill.

[0025] In some embodiments of the present invention, the detoxified fly ash after ball milling is used in the preparation of building materials, such as building blocks, building filling materials, building cement raw materials, unburned bricks, etc.

[0026] Beneficial effects of the present invention

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention first changes the dispersion characteristics of carbon nanotubes through acid modification, then uses ultrasound to further increase the dispersion of carbon nanotubes, and then obtains a heavy metal adsorption material with strong adsorption capacity through a latex method; the prepared heavy metal adsorption material achieves heavy metal stabilization in fly ash through a coupled mechanochemical method, and the leaching of heavy metals in fly ash meets the requirements of GB9878 standard. In its resource utilization, the quality of fly ash resource products such as building blocks, building filling materials, building cement raw materials, unburned bricks and the like is further improved, thereby avoiding heavy metal pollution caused by the leaching of heavy metals during use.

[0029] The preparation method of the present invention is simple and can be applied to the control of heavy metals in fly ash in various scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The SEM images of carbon nanotubes before and after acid modification are shown, wherein A is the original carbon nanotubes and B is the acid-modified carbon nanotubes;

[0031] Figure 2 The XRD patterns of carbon nanotubes before and after acid modification are shown. DETAILED DESCRIPTION

[0032] The following examples are provided to illustrate preferred embodiments of the present invention. Those skilled in the art will appreciate that the techniques disclosed in the following examples represent techniques discovered by the inventors that can be used to practice the present invention and, therefore, can be considered preferred embodiments of the present invention. However, those skilled in the art will appreciate from this disclosure that many modifications may be made to the specific embodiments disclosed herein while still achieving the same or similar results without departing from the spirit or scope of the present invention.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one skilled in the art to which this invention belongs, and the disclosures herein and the materials they cite are hereby incorporated by reference. Those skilled in the art will recognize or be able to ascertain, through routine experimentation, many technical equivalents to the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the claims.

[0034] The technical solution of the present application will be further described in detail below in conjunction with specific implementation methods.

[0035] Example 1

[0036] 1. The preparation of adsorption material includes the following steps:

[0037] (1) The average length of carbon nanotubes was 5 nm. A mixture of 1 g carbon nanotubes, 250 mL concentrated sulfuric acid, and 80 mL concentrated nitric acid was mixed and ultrasonicated for 30 min. The mixture was then refluxed at 70°C for 5 h. After cooling and dilution, the mixture was filtered through a 0.22 μm polytetrafluoroethylene filter membrane and washed with distilled water until neutral. The mixture was finally dried in a vacuum oven at 100°C for 4 h and ground to obtain acid-modified carbon nanotubes.

[0038] (2) The obtained acid-modified carbon nanotubes were mixed and stirred in a weight ratio of acid-modified carbon nanotubes: zinc oxide: water: stearic acid: gum arabic = 1:1:140:1:1.5, and ultrasonicated for 30 min. Then, 50 g of natural rubber latex was added and stirred for 30 min, and ultrasonicated for 30 min to obtain a mixed solution.

[0039] (3) The obtained mixed solution was dried in a vacuum drying oven at 100°C for 6 h; then, it was calcined and carbonized in a muffle furnace at 800°C for 6 h; the carbonized adsorbent was ground in a mortar and passed through 200 mesh to obtain the final adsorption material.

[0040] 2. The application of adsorption materials in waste incineration fly ash includes the following steps:

[0041] (1) The fly ash from garbage incineration was washed with water at a liquid-to-solid ratio of 10:1 for 1 h. The washed fly ash was obtained by plate and frame filter pressing.

[0042] (2) The washed fly ash and water were added to a planetary ball mill at a liquid-to-solid ratio of 2:1 for ball milling. The ball milling speed was 500 rpm and the ball-to-material ratio was 10:1. At the same time, the heavy metal adsorption material obtained above was added. The adsorption material was 3% of the mass of the washed fly ash. The adsorption material was added in three times, with each addition ratio of 1%. After ball milling for a period of time, a mixed liquid was obtained.

[0043] (3) The mixed liquid obtained in the previous step is filtered through a plate and frame filter to obtain ball-milled fly ash, which can be used in subsequent building materials and other products.

[0044] Example 2

[0045] The method and steps are consistent with those in Example 1, except that: in the preparation step (1) of the adsorption material, the average length of the carbon nanotubes is 5 nm, and the mixture is mixed in a ratio of carbon nanotubes: water = 1 g: 300 mL, and ultrasonication is performed for 30 minutes.

[0046] Example 3

[0047] The method steps are consistent with those of Example 1, except that in the preparation step (1) of the adsorption material, the average length of the carbon nanotubes is 15 nm.

[0048] Example 4

[0049] The method and steps are consistent with those in Example 1, except that: in the preparation step (1) of the adsorption material, the average length of the carbon nanotubes is 5 nm, and the mixture is mixed in a ratio of carbon nanotubes: concentrated sulfuric acid: concentrated nitric acid = 1 g: 250 mL: 80 mL, refluxed at 70°C for 5 h, cooled and diluted, filtered with a 0.22 μm polytetrafluoroethylene filter membrane, and washed with distilled water until the sample is neutral; finally, dried in a vacuum drying oven at 100°C for 4 h, and ground to obtain acid-modified carbon nanotubes.

[0050] Example 5

[0051] The method and steps are the same as those in Example 1, except that: in the preparation step (2) of the adsorption material, the obtained acid-modified carbon nanotubes are mixed and stirred in a weight ratio of acid-modified carbon nanotubes: zinc oxide: water: stearic acid: dispersant = 1:1:140:1:1.5, and ultrasonicated for 30 minutes, and then 50g of natural rubber latex is added and stirred for 30 minutes, and ultrasonicated for 30 minutes to obtain a mixed solution. The dispersant is a mixture of gum arabic and sodium dodecylbenzene sulfonate in a ratio of 1:1.

[0052] Example 6

[0053] The method and steps are consistent with those of Example 1, except that: in the preparation step (2) of the adsorption material, the obtained acid-modified carbon nanotubes are mixed and stirred in a weight ratio of acid-modified carbon nanotubes: zinc oxide: water: stearic acid = 1:1:140:1, and ultrasonicated for 30 minutes, and then 50g of natural latex is added and stirred for 30 minutes, and ultrasonicated for 30 minutes to obtain a mixed solution.

[0054] Example 7

[0055] The method and steps are consistent with those in Example 1, except that: in the application step (2) of the adsorption material in waste incineration fly ash, the obtained washed fly ash and water are added to a planetary ball mill at a liquid-to-solid ratio of 2:1 for ball milling treatment, the ball milling speed is 500 rpm, and the ball-to-material ratio is 10:1. At the same time, the heavy metal adsorption material obtained above is added, and the adsorption material is 6% of the mass of the washed fly ash. The adsorption material is added in 3 times, and the addition ratio each time is 2%; after ball milling treatment for a period of time, a mixed solution is obtained.

[0056] Example 8

[0057] The method and steps are consistent with those in Example 1, except that: in the application step (2) of the adsorption material in waste incineration fly ash, the washed fly ash and water are added to a planetary ball mill at a liquid-to-solid ratio of 2:1 for ball milling. The ball milling speed is 500 rpm and the ball-to-material ratio is 10:1. At the same time, the heavy metal adsorption material obtained above is added. The adsorption material is 1.5% of the mass of the washed fly ash and is added in three times, with each addition ratio of 0.5%. After ball milling for a period of time, a mixed solution is obtained.

[0058] Example 9

[0059] The method steps are consistent with those of Example 1, except that: the obtained washed fly ash is stirred evenly at a liquid-to-solid ratio of 2:1, and the heavy metal adsorption material obtained above is added at the same time. The adsorption material is 3% of the mass of the washed fly ash and is added in 3 times, each addition ratio is 1%; after stirring for a period of time, a mixed solution is obtained.

[0060] Performance Comparison

[0061] (1) Comparative analysis of carbon nanotubes before and after acid modification, among which the SEM images are as follows Figure 1 As shown, the XRD pattern is Figure 2 As shown; wherein, A is the original carbon nanotube and B is the acid-modified carbon nanotube.

[0062] XRD results show that characteristic peaks at 25.7°, 42.6°, and 53.6° correspond to those of graphite. The peak at 25.7° exhibits an increase in area after modification, indicating that acid modification enhances the graphitization of carbon nanotubes. Furthermore, the peak at 45.6°, which can be attributed to the metals in the catalyst, decreases in intensity after acid modification, indicating that residual impurities in the carbon nanotubes have been further removed, improving their purity.

[0063] (2) The heavy metal content data in the fly ash prepared in Examples 1 to 9 were tested by leaching method. The test results are shown in Table 1.

[0064] Table 1 Heavy metal detection data in the fly ash prepared in Examples 1 to 9

[0065]

[0066] Note: ND means below the upper limit of detection and not detected by the device.

[0067] The test results show that the pass rate of the 10 heavy metals detected in the original fly ash is only 50%. Among them, the contents of heavy metals Cd, Cu, Ni, Pb, and Zn exceed the GB9878 standard, and Cd exceeds the standard by 224%, Cu exceeds the standard by 200.4%, Ni exceeds the standard by 51.1%, Pb exceeds the standard by 760.1%, and Zn exceeds the standard by 399.1%.

[0068] After adding the adsorption material prepared in this application to treat fly ash, the qualified rate of the corresponding 10 heavy metals in the obtained fly ash reached 100%, meeting the GB9878 standard.

[0069] During the development of the proposed solution, we investigated the impact of different treatment methods on the final fly ash. We found that without acid modification, the heavy metal content in the final fly ash only met the standard at 50%. Without the use of a dispersant, the heavy metal content in the final fly ash only met the standard at 60%. Without ultrasonic treatment during adsorption material preparation or ball milling of the fly ash and adsorption material, the heavy metal content in the final fly ash only met the standard at 70%. The length of the carbon nanotubes had little impact on the final results, achieving a heavy metal content compliance rate of 90%.

[0070] In the process of exploring the amount of adsorption material added, it was found that the greater the amount added, the better the stability of heavy metals in fly ash. Adding 6% adsorption material to treat fly ash is different from adding 3% adsorption material, and the leaching of heavy metals in fly ash is less. However, from an economic point of view, the addition ratio should not be too high. Adding 3% can make the leaching of heavy metals in fly ash meet the standard requirements.

[0071] All documents mentioned in this application are incorporated herein by reference, just as if each document were incorporated herein by reference individually. It should also be understood that after reading the above teachings of the present invention, those skilled in the art may make various changes or modifications to the present invention, and that such equivalents also fall within the scope of the present application.

Claims

1. Application of nanotube-based adsorption materials in resource utilization of waste incineration fly ash, characterized in that: The steps include: (1) After the waste incineration fly ash and water are washed with water at a liquid-to-solid ratio of (8-10):1, the washed fly ash is obtained by plate and frame filter pressing; (2) The obtained washed fly ash and water are added into a ball mill at a liquid-solid ratio of (2-3):1, and a nanotube-based adsorption material accounting for 3%-6% of the mass of the washed fly ash is added at the same time. The adsorption material is divided into three parts and added three times, each adding a proportion of 1%-2%. After ball milling for a period of time, a mixed solution is obtained; (3) After the mixed liquid passes through the plate and frame filter press, the solid is the waste incineration fly ash that can be recycled; The preparation of the adsorption material comprises the following steps: S1. CNTs and acid solution were mixed in a ratio of 1 g of CNTs: 250 mL of concentrated sulfuric acid: 50-80 mL of concentrated nitric acid, and ultrasonicated. The mixture was refluxed at 60-70°C for 5-6 h. After cooling and dilution, the mixture was filtered through a filter membrane, washed with distilled water until neutral, dried in a vacuum drying oven, and ground to obtain acid-modified CNTs. S2. The obtained acid-modified carbon nanotubes are acid-modified according to the weight ratio: Zinc oxide: water: stearic acid: dispersant = 1: (0.5-1): (130-150): (1-1.2): (1-1.5) are mixed and stirred, ultrasonicated, 50-70 g of natural rubber latex is added and stirred evenly, and ultrasonicated again to obtain a mixed solution; S3. The mixed solution is dried in a vacuum drying oven and then calcined and carbonized; the carbonized adsorbent is ground in a mortar and passed through 200-250 mesh to obtain the final adsorption material.

2. The use according to claim 1, characterized in that: The ball-to-material ratio of the ball mill is (8-10):1, and the ball milling time is 1-3 hours.

3. The use according to claim 1, characterized in that: The dispersant is one or both of gum arabic and sodium dodecylbenzenesulfonate.

4. The use according to claim 1, characterized in that: In steps S1 and S2, the ultrasonication time is 30-60 min.

5. The use according to claim 1, characterized in that: In step S1, the drying temperature is 90-100° C. and the drying time is 4-8 hours.

6. The use according to claim 1, characterized in that: In step S1, the filter membrane is a 0.22 μm polytetrafluoroethylene filter membrane.

7. The use according to claim 1, characterized in that: In step S3, the calcination temperature is 800-850° C., and the carbonization time is 4-6 hours.

8. The use according to claim 1, characterized in that: The length of the carbon nanotubes is 2-10 nm.

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