Oil-containing diatomite in-situ growth carbon nanotube adsorbent and preparation method thereof
By growing carbon nanotubes in situ on the surface of oily diatomaceous earth, the problems of waste diatomaceous earth treatment and the easy aggregation of carbon nanotubes were solved, realizing efficient and low-cost adsorbent preparation and organic dye wastewater treatment.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NEW MATERIAL INST OF SHANDONG ACADEMY OF SCI
- Filing Date
- 2023-12-19
- Publication Date
- 2026-06-09
Smart Images
Figure CN117718007B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of solid waste resource utilization and adsorption material technology, specifically to an in-situ grown carbon nanotube adsorbent from oil-containing diatomaceous earth and its preparation method. Background Technology
[0002] With the rapid development of science and technology and industry, industrial wastewater discharges contain a variety of highly toxic and persistent harmful substances exceeding normal ranges, causing significant damage to the environment and organisms, and easily accumulating through the food chain to directly threaten human health. Organic dyes, as one of the main pollutants in industrial wastewater, have become a key focus of environmental protection due to their effective treatment. Currently, methods for treating organic dyes mainly include photocatalytic degradation, chemical oxidation, biological methods, and adsorption methods. Among these, adsorption methods offer advantages such as simple operation, high efficiency, and low cost, making them particularly suitable for the advanced treatment of low-concentration organic dye wastewater. Ideal adsorbents for treating organic dye wastewater should be materials with a large specific surface area, numerous active sites, and strong adsorption capacity, while also being easy to produce and inexpensive.
[0003] Diatomaceous earth is an amorphous natural siliceous mineral, mainly composed of SiO2. It is abundant and has a porous, disc-shaped structure. It possesses advantages such as large specific surface area, low specific gravity, high porosity, low heavy metal content, strong adsorption capacity, and stable chemical properties. It is used as a filtration medium for various industrial, food, and pharmaceutical liquids, as well as packaging, filler, or carrier in the feed, chemical, and building materials industries. However, directly using diatomaceous earth as an adsorbent, due to its large pore size and hydrophilic nature, results in water molecules occupying the adsorption sites when adsorbing methylene blue, leading to a lower adsorption capacity for the organic dye and reduced adsorption efficiency.
[0004] In the aluminum processing industry, friction occurs between the rolls and the rolled material during the operation of aluminum sheet, strip, and foil rolling mills. This friction leaves a large amount of aluminum shavings, aluminum powder, dust, and other fine particles in the rolling oil. Therefore, the rolling oil needs to be filtered and purified using a plate filter, with diatomaceous earth commonly used as the filter medium. Once the diatomaceous earth filter becomes saturated, it needs to be replaced, resulting in a large amount of waste oily diatomaceous earth. Producing one ton of aluminum foil requires approximately 100 kg or more of diatomaceous earth, and the amount of oily diatomaceous earth to be disposed of is conservatively estimated to be over 700,000 tons. According to the "National Hazardous Waste List," "waste mineral oil generated from metal rolling using rolling oil, coolant, and acid" is classified as "toxic." Waste oily diatomaceous earth is not permitted to be directly landfilled; its transportation, storage, utilization, or disposal must be managed and implemented in accordance with hazardous waste regulations. The amount of oily diatomaceous earth that needs to be replaced is substantial, and improper handling can cause pollution and safety hazards to the enterprise's environment and the social environment. Enterprises generally incur significant costs to dispose of the oily diatomaceous earth.
[0005] Currently, methods for treating waste oily diatomaceous earth include distillation, acid washing, oil-water azeotropic distillation, and steam flushing. These methods primarily remove or extract the oil. However, existing methods still yield diatomaceous earth with a high proportion of residual oil, meaning the treated diatomaceous earth remains hazardous waste. Furthermore, distillation is complex and carries fire and explosion risks; acid washing uses hazardous chemicals such as sulfuric acid, posing significant operational risks; and oil-water azeotropic distillation and steam flushing consume large amounts of water, resulting in high energy consumption. Therefore, a safe and effective disposal method is urgently needed to achieve high-value resource utilization of waste oily diatomaceous earth.
[0006] Carbon nanotubes possess a large specific surface area and a strong adsorption capacity for organic matter. The adsorption forces of carbon nanotubes for organic matter mainly include van der Waals interactions (such as hydrophobic interactions and electrostatic interactions), hydrogen bonding interactions, and π-π interactions. However, using carbon nanotubes alone as an adsorbent is costly. Furthermore, the strong van der Waals forces between carbon nanotubes, coupled with their high aspect ratio and large specific surface area, make them prone to aggregation during use, limiting their full performance potential.
[0007] The inventors discovered that although application number 201810973054.4 discloses a method for preparing diatomaceous earth-supported carbon nanotube adsorbents, using diatomaceous earth ore as the main raw material and employing chemical vapor deposition to load carbon nanotubes onto the diatomaceous earth surface, and controlling the mass fraction of carbon nanotubes by adding and adjusting carbon source gases such as acetylene, methane, or carbon monoxide, thus solving the problem of uniform dispersion of carbon nanotubes, it has the advantages of large specific surface area and good thermal stability, and is used for the adsorption treatment of phenol-containing wastewater. However, the diatomaceous earth ore requires high-temperature calcination and hydrochloric acid cleaning pretreatment, and the chemical vapor deposition process requires switching gases, making the operation steps relatively complex. Summary of the Invention
[0008] To overcome the aforementioned shortcomings and deficiencies of existing technologies, the present invention aims to provide an in-situ grown carbon nanotube adsorbent from oil-containing diatomaceous earth and its preparation method. The method uses oil-containing diatomaceous earth (a hazardous waste material) as the main raw material, utilizes the pyrolysis of rolling oil in the oil-containing diatomaceous earth as the carbon source, and uniformly deposits carbon nanotubes on the surface of the diatomaceous earth using a chemical deposition method. This in-situ growth of carbon nanotubes alters the surface functional groups of the diatomaceous earth, making it oleophilic. This allows it to be used as an adsorbent for methylene blue in organic dye wastewater, increasing the adsorption efficiency. The prepared in-situ grown carbon nanotube adsorbent from oil-containing diatomaceous earth has a specific surface area of 20–60 m². 2 / g, carbon nanotubes account for 5-13% of the total mass, have a large specific surface area and good chemical stability, and their adsorption performance is 1.8 times higher than that of pure diatomaceous earth.
[0009] To achieve the above objectives, the technical solution of the present invention is as follows:
[0010] In a first aspect, the present invention provides a method for preparing an in-situ grown carbon nanotube adsorbent from oil-containing diatomaceous earth, comprising the following steps:
[0011] (1) Dry the oil-containing diatomaceous earth;
[0012] (2) Take the oily diatomaceous earth dried in step (1) and add it to the catalyst solution, and add sodium carboxymethyl cellulose as a protective agent and stir evenly.
[0013] (3) The sample that was stirred evenly in step (2) was filtered and then vacuum dried to obtain solid powder;
[0014] (4) The solid powder obtained in step (3) is heated to 700-900°C in a hydrogen-argon mixed atmosphere, kept at the temperature for 2-4 hours, and then cooled to room temperature to obtain black solid powder.
[0015] (5) The black solid powder obtained in step (4) is annealed and cooled to room temperature. It is then added to an acid solution for acid activation treatment. After washing, drying, grinding and sieving, the oil-containing diatomaceous earth in-situ grown carbon nanotube adsorbent is obtained.
[0016] Furthermore, in step (1), the oil-containing diatomaceous earth contains 37% rolling oil by mass, and the drying treatment is performed at 100-120℃ for 2-6 hours.
[0017] Furthermore, in step (2), the catalyst is one or more of Ni(CH3COO)2, Ni(NO3)2, and Co(NO3)2; the concentration of the catalyst is 0.1 mol / L to 1 mol / L.
[0018] Furthermore, in step (2), the mass ratio of diatomaceous earth to catalyst solution is 1:5 to 1:15; the mass ratio of sodium carboxymethyl cellulose to catalyst solution is 1:50 to 1:100; and the stirring is carried out at 30-60°C for 0.5-2 hours.
[0019] Furthermore, in step (3), vacuum drying is performed at 60-100℃ for 6-10 hours.
[0020] Furthermore, in step (4), the volume of hydrogen in the hydrogen-argon mixture is 5% to 15%, the flow rate of the hydrogen-argon mixture is 200 to 600 mL / min, and the heating rate is 5 to 10 °C / min.
[0021] Furthermore, in step (5), the annealing temperature is 300-400℃, the acid solution is hydrochloric acid or nitric acid solution, the mass fraction of the acid solution is 20-30%, and the acid activation treatment temperature is 80-100℃.
[0022] Research has found that carboxymethyl cellulose, used in this invention, has suspending and emulsifying properties, enabling oil droplets or other immiscible liquids in oil-containing diatomaceous earth to form stable emulsions or suspensions, thereby improving the stability and uniformity of the oil-containing diatomaceous earth. The catalyst affects nucleation sites and nucleus growth, thus influencing the growth and yield of carbon nanotubes. Simultaneously, the main components of the rolling oil adsorbed in the oil-containing diatomaceous earth are kerosene, emulsifiable oil, and some lubricating additives. Under a hydrogen-argon mixed atmosphere, these components can be decomposed and volatilized at 700–900℃, directly serving as a carbon source gas for deposition and growth on the surface of the diatomaceous earth.
[0023] Secondly, the present invention provides an oil-containing diatomite in-situ grown carbon nanotube adsorbent prepared by the above method, wherein the oil-containing diatomite in-situ grown carbon nanotube adsorbent has a porous structure in which carbon nanotubes encapsulate diatomite particles.
[0024] Furthermore, the specific surface area of the carbon nanotube adsorbent grown in situ on oil-containing diatomaceous earth is 20–60 m². 2 / g, carbon nanotubes account for 5-13% of the total mass.
[0025] Thirdly, the present invention provides an application of an in-situ grown carbon nanotube adsorbent from oil-containing diatomaceous earth in the adsorption of methylene blue organic dye.
[0026] The beneficial effects of the above embodiments of the present invention are as follows:
[0027] (1) The oil-containing diatomaceous earth in-situ grown carbon nanotube adsorbent of the present invention uses oil-containing diatomaceous earth from hazardous waste as the main raw material, and utilizes chemical vapor deposition technology to grow carbon nanotubes in-situ on its surface, thus solving the problem of uniform dispersion of carbon nanotubes. The carbon nanotubes account for 5-13% of the total mass, and the specific surface area of the adsorbent is 20-60 m². 2 / g, with a large specific surface area and good chemical stability, which is 1.8 times higher than that of pure diatomaceous earth.
[0028] (2) The oil-containing diatomite in the raw materials of this invention is hazardous waste, with high disposal costs and serious environmental risks and resource waste due to stockpiling. The preparation method of this invention is simple and low-cost, and can realize large-scale resource utilization of oil-containing diatomite, with significant economic and environmental benefits.
[0029] (3) The oil-containing diatomaceous earth in-situ grown carbon nanotube adsorbent prepared by the present invention is green and pollution-free, with short adsorption time and strong adsorption capacity. Compared with pure diatomaceous earth material, the adsorption performance is improved by nearly 1.8 times. This is because the surface groups of diatomaceous earth change after in-situ growth of carbon nanotubes, making the hydrophilic groups of pure diatomaceous earth become lipophilic, which is conducive to the adsorption of methylene blue in organic dye wastewater and increases the adsorption efficiency. Attached Figure Description
[0030] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.
[0031] Figure 1 This is a scanning electron microscope image of the adsorbent prepared in Example 1 of the present invention;
[0032] Figure 2 Thermogravimetric diagrams of the adsorbents prepared in Examples 1-4 of this invention;
[0033] Figure 3 This is a scanning electron microscope image of the adsorbent prepared in Example 2 of the present invention;
[0034] Figure 4 This is a scanning electron microscope image of the adsorbent prepared in Example 3 of the present invention;
[0035] Figure 5 This is a scanning electron microscope image of the adsorbent prepared in Example 4 of the present invention;
[0036] Figure 6 This is a scanning electron microscope image of the adsorbent prepared in Comparative Example 1 of the present invention;
[0037] Figure 7 This is a comparison chart showing the adsorption capacity of the adsorbents prepared in Examples 1-4 and Comparative Example 1 for methylene blue. Detailed Implementation
[0038] I. The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited thereto.
[0039] Example 1
[0040] In a typical embodiment of the present invention, a method for preparing an in-situ grown carbon nanotube adsorbent from oil-containing diatomaceous earth is provided:
[0041] (1) Dry an appropriate amount of oil-containing diatomaceous earth with a rolling oil mass fraction of 37% at 100℃ for 4 hours to remove the moisture from the oil-containing diatomaceous earth.
[0042] (2) Take the dried oily diatomaceous earth from step (1) and add it to a Ni(CH3COO)2 solution with a concentration of 0.5 mol / L. Then add sodium carboxymethyl cellulose and stir at 60°C for 1 hour. The mass ratio of oily diatomaceous earth to Ni(CH3COO)2 solution is 1:10 and the mass ratio of sodium carboxymethyl cellulose to Ni(CH3COO)2 solution is 1:100.
[0043] (3) The sample that was stirred evenly in step (2) was filtered and then placed in a vacuum drying oven and dried at 100°C for 8 hours to remove the residual solution and obtain solid powder.
[0044] (4) Place the solid powder obtained in step (3) into a crucible, place the crucible into a tube furnace, heat it to 900°C in an atmosphere of hydrogen-argon mixture (hydrogen gas fraction 5%), the gas flow rate is 400 mL / min, the heating rate is 7°C / min, hold for 2 hours, and cool to room temperature to obtain a black solid.
[0045] (5) The black solid obtained in step (4) was annealed in a muffle furnace at 350°C. After cooling, the solid was added to a 30% hydrochloric acid solution and acid activated at 100°C. The solid was washed, dried, lightly ground and sieved to obtain a uniformly sized in-situ grown carbon nanotube adsorbent from oil-containing diatomaceous earth.
[0046] The adsorbent prepared in Example 1 was subjected to scanning electron microscopy, specific surface area measurement, and thermogravimetric analysis. The scanning electron microscopy results are as follows: Figure 1 As shown in the figure, carbon nanotubes are uniformly grown on the surface of diatomaceous earth. These carbon nanotubes uniformly coat the surface of the oil-containing diatomaceous earth, forming a more porous structure and increasing its specific surface area. The surface area of the adsorbent, as measured by the specific surface area measurement, is 28.35 m². 2 / g. Figure 2 The thermogravimetric diagrams of the adsorbents prepared in Examples 1-4 show that carbon nanotubes account for 13.16% of the total mass.
[0047] Example 2
[0048] Unlike Example 1, the concentration of Ni(CH3COO)2 solution in step (2) is 0.1 mol / L; the other steps are the same as in Example 1 and will not be repeated here.
[0049] The adsorbent prepared in Example 2 was subjected to scanning electron microscopy, specific surface area measurement, and thermogravimetric analysis. The scanning electron microscopy results are as follows: Figure 3 As shown in the figure, some carbon nanotubes still grow on the surface of the diatomaceous earth, but compared with Example 1, the carbon nanotubes are sparsely distributed and have a smaller diameter. The carbon nanotubes are uniformly distributed on the surface of the oil-containing diatomaceous earth and do not cover the pores of the oil-containing diatomaceous earth. The surface area of the adsorbent measured by specific surface area is 20.18 m². 2 / g. From Figure 2 As can be seen, carbon nanotubes account for 5.30% of the total mass.
[0050] Example 3
[0051] Unlike Example 1, the concentration of Ni(CH3COO)2 solution in step (2) is 1 mol / L; the other steps are the same as in Example 1 and will not be repeated here.
[0052] The adsorbent prepared in Example 3 was subjected to scanning electron microscopy, specific surface area measurement, and thermogravimetric analysis. The scanning electron microscopy results are as follows: Figure 4 As shown in the figure, with the increase of Ni(CH3COO)2 concentration, the diameter of carbon nanotubes increases, indicating particle aggregation and a decrease in carbon nanotube yield. This is because excessive Ni(CH3COO)2 catalyst concentration leads to the aggregation of in-situ formed Ni nanoparticles and reduces catalytic activity, thus hindering carbon nanotube formation. The surface area of the adsorbent, measured by specific surface area measurement, is 21.33 m². 2 / g. Carbon nanotubes account for 8.57% of the total mass.
[0053] Example 4
[0054] Unlike Example 1, the temperature is raised to 700°C in step (4); the other steps are the same as in Example 1 and will not be repeated here.
[0055] The adsorbent prepared in Example 4 was subjected to scanning electron microscopy, specific surface area measurement, and thermogravimetric analysis. The scanning electron microscopy results are as follows: Figure 5 As shown in the figure, the adsorbent maintains the disk-shaped structure of diatomaceous earth, with a very small amount of carbon nanotubes distributed on the surface of the oil-containing diatomaceous earth. This is due to insufficient preparation temperature leading to a low yield of carbon nanotubes. The surface area of the adsorbent, measured by specific surface area measurement, is 14.82 m². 2 / g. Carbon nanotubes account for 0.35% of the total mass.
[0056] Comparative Example 1
[0057] An appropriate amount of oil-containing diatomaceous earth with a rolling oil mass fraction of 37% was placed directly into a crucible. The crucible was then placed in a tube furnace and heated to 900℃ in an air atmosphere. The gas flow rate was 400mL / min, the heating rate was 5℃ / min, and the temperature was maintained for 2 hours. After cooling to room temperature, the oil-removed diatomaceous earth was obtained.
[0058] The diatomaceous earth prepared in Comparative Example 1 was subjected to scanning electron microscopy and specific surface area testing, and the scanning electron microscopy results are as follows: Figure 6 As shown in the figure, the adsorbent retains part of the porous structure of the diatomaceous earth crude oil. The surface area of the adsorbent, as measured by specific surface area measurement, is 14.65 m². 2 / g.
[0059] II. Determination of Methylene Blue Adsorption Performance
[0060] 1. Preparation of methylene blue standard solution
[0061] Weigh out a certain amount of methylene blue and dissolve it in water, then dilute to a volumetric flask to a concentration of 400 mg / L.
[0062] 2. Methylene blue adsorption performance test
[0063] Six 100mg portions of the adsorbent prepared in Examples 1-4 and Comparative Example 1 were weighed and added to 25ml of methylene blue solution. The solutions were placed in a constant temperature stirrer and stirred at 120 rpm. Every 10 minutes, the prepared adsorbent sample solution was taken and filtered. The mass concentration of methylene blue in the clear solution was measured by a UV-Vis spectrophotometer. The adsorption amount at each time point was calculated based on the change in mass concentration at each time point.
[0064] Test results are as follows Figure 7 As shown, the adsorption capacities of Examples 1-4 and Comparative Example 1 were 75.26 mg / g, 55.14 mg / g, 58.19 mg / g, 44.67 mg / g, and 42.80 mg / g, respectively, which is consistent with the results of scanning electron microscopy and carbon nanotube content testing. The maximum adsorption capacity was nearly 1.8 times higher than that of pure diatomaceous earth. This is because, when diatomaceous earth is used alone as an adsorbent, its large pore size and hydrophilic nature mean that its adsorption sites are occupied by water molecules when adsorbing methylene blue, resulting in a low adsorption capacity for the organic dye and reduced effectiveness. However, after in-situ growth of carbon nanotubes, the surface groups change, becoming lipophilic, thus increasing the adsorption efficiency.
[0065] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for preparing an in-situ grown carbon nanotube adsorbent from oil-containing diatomaceous earth, characterized in that, Includes the following steps: (1) Dry the oil-containing diatomaceous earth; (2) Take the oily diatomaceous earth dried in step (1) and add it to the catalyst solution, and add sodium carboxymethyl cellulose and stir evenly; (3) The sample that was stirred evenly in step (2) was filtered and dried to obtain a solid powder; (4) The solid powder obtained in step (3) is heated to 700-900°C in a hydrogen-argon mixed atmosphere, kept at the temperature for 2-4 hours, and then cooled to obtain black solid powder; (5) The black solid powder obtained in step (4) is annealed, cooled to room temperature, added to an acid solution for acid activation, washed, dried, ground and sieved to obtain an oil-containing diatomaceous earth in-situ grown carbon nanotube adsorbent. The oil-bearing diatomaceous earth contains 37% rolling oil by mass. The concentration of the catalyst is 0.1 mol / L to 0.5 mol / L; After in-situ growth of carbon nanotubes, the surface groups of diatomaceous earth become oleophilic. Carbon nanotubes account for 5-13% of the total mass; In step (1), the drying process is performed at 100-120℃ for 2-6 hours; In step (2), the mass ratio of diatomaceous earth to catalyst solution is 1:5 to 1:15; the mass ratio of sodium carboxymethyl cellulose to catalyst solution is 1:50 to 1:100; and the stirring is carried out at 30-60℃ for 0.5-2 hours. In step (2), the catalyst is one or more of Ni(CH3COO)2, Ni(NO3)2, and Co(NO3)2.
2. The preparation method according to claim 1, characterized in that... In step (3), vacuum drying is carried out at 60-100℃ for 6-10 hours.
3. The preparation method according to claim 1, characterized in that, In step (4), the volume of hydrogen in the hydrogen-argon mixture is 5% to 15%, the flow rate of the hydrogen-argon mixture is 200 to 600 mL / min, and the heating rate is 5 to 10 °C / min.
4. The preparation method according to claim 1, characterized in that, In step (5), the annealing temperature is 300-400℃, the acid solution is hydrochloric acid or nitric acid solution, the mass fraction of the acid solution is 20-30%, and the acid activation treatment temperature is 80-100℃.
5. An oil-containing diatomaceous earth in-situ grown carbon nanotube adsorbent prepared by the preparation method according to any one of claims 1-4, characterized in that, The in-situ grown carbon nanotube adsorbent in oil-containing diatomite has a porous structure in which carbon nanotubes encapsulate diatomite particles.
6. The in-situ grown carbon nanotube adsorbent from oil-containing diatomaceous earth as described in claim 5, characterized in that, Specific surface area is 20-60 m² 2 / g.
7. The application of the in-situ grown carbon nanotube adsorbent in oil-containing diatomaceous earth as described in claim 6 in the adsorption of methylene blue organic dye.