CN113753895A - Method for preparing activated carbon by using areca and sludge as materials - Google Patents
Method for preparing activated carbon by using areca and sludge as materials Download PDFInfo
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- C—CHEMISTRY; METALLURGY
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- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
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- C01B32/342—Preparation characterised by non-gaseous activating agents
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Abstract
The invention provides a method for preparing activated carbon by taking betel nuts and sludge as materials, which comprises the following steps: s1, preparation of raw materials: mixing Arecae semen and sludge, oven drying, pulverizing, and sieving to obtain Arecae semen and sludge mixed granule; s2, high-temperature carbonization: placing the mixed raw materials in a tubular furnace, and carrying out carbonization primary treatment in a nitrogen atmosphere; s3, soaking by an activating agent: mixing carbonized areca and sludge mixed particles with an activator aqueous solution, wherein the activator aqueous solution is prepared from phosphoric acid, zinc chloride and water, and soaking after uniformly stirring to obtain a mixed product; s4, high-temperature activation: putting the mixed product into a tubular furnace, activating in a nitrogen atmosphere, and cooling to obtain a crude product; s5, finished product: and (4) carrying out acid washing, water washing and drying on the crude product to obtain a target activated carbon product. The areca sludge activated carbon prepared by the method has the advantages of rich pore structure, large specific surface area, strong iodine adsorption capacity, high yield and the like. And has the characteristics of low energy consumption and simple operation.
Description
Technical Field
The invention relates to the field of activated carbon, and particularly relates to a method for preparing activated carbon by taking betel nuts and sludge as materials.
Background
With the rapid development of municipal sewage plants, a large amount of sludge is produced. The sewage sludge is a byproduct of sewage treatment, about 50 percent of the sewage sludge is organic matters, most of the organic matters are hemicellulose, cellulose, lignin, lipids and proteins, and resource utilization can be realized.
Lignocellulose materials (such as coconut shells, corn straws, sawdust, plant straws, areca nuts and the like) are used as carbon-rich active carbon preparation materials containing a large amount of organic matters, and active carbon with large specific surface area, stable physicochemical properties and excellent adsorption capacity can be prepared simply through a pyrolysis process. In addition, the materials rich in cellulose have the advantages of abundant sources, reproducibility, low production raw material cost, simple preparation method and the like, and have excellent performance compared with the traditional materials (such as coal, petroleum and the like). But the carbon content of the sludge is low, so that the wide application of the sludge is limited. Thus, these lignocellulosic materials are added to sludge precursors to enhance the performance of activated carbon, particularly lignocellulosic materials (e.g., coconut shells, etc.), because of their high carbon content and are readily available from widely used carburant sources.
At present, the main methods for synthesizing activated carbon include chemical activation, physical activation and a combination thereof. In physical activation, an activating gas, such as carbon dioxide, air or water vapor, is used during pyrolysis to corrode the surface of the carbon matrix at high temperatures, i.e., to cause significant changes in the morphology and pore structure of the carbon matrix. Oxidative dehydrogenation reactions occur during pyrolysis, leading to structural disorder and pore formation. The active carbon prepared by the physical activation method is mainly microporous active carbon, but the operation conditions (high temperature and high energy consumption) of the physical activation limit the industrial application of the active carbon, and meanwhile, the surface of the active carbon is seriously burnt and damaged, so that the carbon yield is reduced. The chemical activation process is well established and involves the use of alkali metals, acids and salts, e.g. KOH, NaOH, H3PO4、H2SO4、ZnCl2And CaCl2. Chemical activation causes swelling, dehydration and aromatic condensation of activated carbon and carbon, forming a large amount of uniform mesoporous structure and high specific surface area. Compared with the physical activation method, the chemical method has lower energy consumption and time consumption and higher efficiency. Lin et al observed that co-pyrolysis of oil palm solid waste and paper sludge at low temperatures increased thermochemical reactivity. They are attributed to hydrogenation and thermocatalytic effects. The mixed activated carbon is used as a porous carbon-containing adsorption material, has low preparation cost, is beneficial to the treatment of environmental pollution, can meet the requirements of reduction, harmlessness, reclamation and stabilization of a large amount of municipal sludge, can change waste into valuables and treat waste with waste, brings environmental benefits, promotes economic benefits, and is a significant research direction. However, the existing sludge for preparing synthetic activated carbon has poor performance, insufficient adsorption capacity and low yield. Therefore, the areca and the sludge need to be mixed to prepare the active carbon, so that the adsorption performance and the yield can be improved, and the waste can be utilized to reduce the environmental pollution.
Disclosure of Invention
In view of the above, the invention provides a method for preparing activated carbon by using areca and sludge as materials, which overcomes the defects of the prior art.
The technical scheme of the invention is realized as follows:
a method for preparing activated carbon by taking areca and sludge as materials comprises the following steps:
s1, preparation of raw materials: mixing Arecae semen and sludge, oven drying, pulverizing, and sieving to obtain Arecae semen and sludge mixed granule;
s2, high-temperature carbonization: placing the mixed particles of the betel nuts and the sludge obtained in the step S1 into a tubular furnace, and carrying out primary carbonization treatment in a nitrogen atmosphere, wherein the carbonization temperature is 600-700 ℃, and the carbonization time is 30-90min, so as to obtain carbonized mixed particles of the betel nuts and the sludge;
s3, soaking by an activating agent: mixing the areca and sludge mixed particles carbonized in the step S2 with an activator aqueous solution, wherein the activator aqueous solution is prepared from phosphoric acid, zinc chloride and water, the concentration of the zinc chloride in the activator aqueous solution is 2.0-3.5mol/L, and the concentration of the phosphoric acid is 2.5-3.5 mol/L; the mass volume ratio kg/L of the areca-nut and sludge mixed particles to the activator aqueous solution is 1:2.0 to 3.0, evenly stirring and then soaking for 12 to 48 hours to obtain a mixed product;
s4, high-temperature activation: putting the activated mixed product obtained in the step S3 into a tube furnace, activating in a nitrogen atmosphere, wherein the activation temperature is 700-800 ℃, the activation time is 0.5-2h, and cooling to obtain a crude product;
s5, finished product: and (5) carrying out acid washing and water washing on the crude product obtained in the step S4, and drying to obtain a target activated carbon product.
Further, in step S1, the betel nut and the sludge are mixed and dried until the moisture content is 10% to 20%.
Further, in step S1, the mesh number of the sieve is 100-200 meshes.
Further, in step S2, the temperature is raised to 600-700 ℃ at a temperature-raising rate of 10-20 ℃/min for carbonization.
Further, in step S3, the soaking temperature is 20 to 33 ℃.
Further, in step S4, the temperature is raised to 700-800 ℃ at a temperature-raising rate of 10-20 ℃/min for activation.
Further, the step S5 specifically includes: the crude product was repeatedly washed with hydrochloric acid and distilled water to remove inorganic substances, and then dried to constant weight at 105 ℃.
Further, in step S3, the concentration of zinc chloride and the concentration of phosphoric acid in the activator aqueous solution are respectively 3.0mol/L and 3.0 mol/L; the mass volume ratio kg/L of the areca-nut and sludge mixed particles to the activator aqueous solution is 1: 2.0.
further, in step S3, the soaking time is 20 h.
Further, in step S4, the activation temperature is 800 ℃, and the activation time is 1 h.
Compared with the prior art, the invention has the beneficial effects that:
(1) the method adopts the steps of blending betel nuts and sludge, carrying out primary carbonization at a specific carbonization temperature condition, soaking by using a certain amount of phosphoric acid, zinc chloride and water to compound an activator aqueous solution, activating at a specific activation temperature condition, and finally washing and drying to prepare the betel nut sludge activated carbon. The preparation method has the characteristics of low energy consumption and simple operation, so the preparation method is suitable for wide application, can be better used as an adsorbent for wastewater treatment, gas purification technology and energy storage, and realizes the treatment of wastes with processes of wastes against one another and resource utilization.
(2) In the carbonization process, under the specific temperature (700-. In this process, volatile substances and extractable organic compounds can be removed. Therefore, the aromaticity and the condensed carbon of the material can be improved in the carbonization process. The activated carbon prepared by the carbonization process optimizes the microstructure of the carbon matrix at this temperature, laying the foundation for the porous structure of the activated carbon in the step of chemical activation.
(3) The invention immerges the carbonized areca and sludge mixed particles into a certain amount of activator aqueous solution (ZnC 1) at normal temperature2，H3P04And water), the pore structure and the specific surface area of the carbonized carbon particles can be well enhanced, the ash content can be reduced, and the energy consumption can be reduced; but also is beneficial to the formation of multiple pores and the generation of volatile tar. Mainly by H3P04Development of mesoporous structure, and ZnCl2Developing a microporous structure; wherein ZnC12，H3P04Has the dewatering function, can promote the pyrolysis reaction, reduce the discharge of oil fume gas and generate a graphite crystal structure with a large number of micropores.
(4) The invention further controls the micropore and mesopore structure of the active carbon by adopting specific activation temperature and activation time.
(5) The method can effectively reduce the preparation cost of the active carbon adsorbent, reduce the preparation flow in the conventional process, improve the adsorption performance, reduce the reaction time, and reduce the cost and equipment loss.
Drawings
Scanning electron microscope images of (a) (500 ×) and (b) (5000 ×) of the activated carbon of fig. 1;
FIG. 2N of activated carbon2An adsorption-desorption isotherm (a) and a pore size distribution (b);
FIG. 3 is a graph showing the influence of the activation temperature factor on the yield and adsorption iodine value of activated carbon;
FIG. 4 is a graph showing the effect of activation time factors on the yield and adsorption iodine value of activated carbon;
FIG. 5 the effect of activator concentration factors on activated carbon yield and adsorbed iodine value;
FIG. 6 influence of solid-to-liquid ratio factors on the yield and iodine value of activated carbon.
Detailed Description
In order to better understand the technical content of the invention, specific examples are provided below to further illustrate the invention.
The experimental methods used in the examples of the present invention are all conventional methods unless otherwise specified.
The materials, reagents and the like used in the examples of the present invention can be obtained commercially without specific description.
EXAMPLE 1 preparation of sludge activated carbon from Areca catechu L
1.1 Experimental Equipment and Chemicals
ZnCl2、H3PO4Reagents such as sodium thiosulfate, iodine, potassium iodide, hydrochloric acid and the like are all chemically pure; activated sludge, areca (local direct sampling).
An electric heating blast drying box, a tube furnace, a crucible, an electronic precision balance, a nitrogen cylinder, a glass instrument and the like.
1.2 preparation of activated carbon
S1, preparation of raw materials: washing the selected whole areca nuts with water to remove surface dirt, mixing and drying the areca nuts and sludge according to the mass ratio of 1:1 until the water content is 10% -20%, and drying at 105 +/-5 ℃; crushing the dried product, and sieving the crushed product with a 100-plus-200-mesh sieve to obtain mixed particles of areca and sludge;
s2, high-temperature carbonization: placing the mixed particles of the betel nuts and the sludge obtained in the step S1 into a tubular furnace, carbonizing in nitrogen atmosphere, heating the mixed particles to 700 ℃ from the room temperature of 20-33 ℃ at the heating rate of 10-20 ℃/min by using the tubular furnace, preserving heat, carbonizing for 60min, and finally cooling to the room temperature to obtain carbonized mixed particles of the betel nuts and the sludge;
s3, soaking by an activating agent: taking the carbonized areca-sludge mixed particles obtained in the step S2 and an activator aqueous solution according to the mass-volume ratio kg/L of 1:2.0, mixing, wherein an activator aqueous solution is prepared from phosphoric acid, zinc chloride and water, the concentration of the zinc chloride in the activator aqueous solution is 3.0mol/L, the concentration of the phosphoric acid is 3.0mol/L, uniformly mixing and stirring, and soaking for 20 hours at the temperature of 20-33 ℃ to obtain a mixed product;
s4, high-temperature activation: putting the activated mixed product obtained in the step S3 into a tubular furnace, activating in a nitrogen atmosphere, heating to 800 ℃ from the room temperature of 20-33 ℃ at the heating rate of 10-20 ℃/min, and preserving heat for activation for 1 h; finally, cooling the hearth to be below 100 ℃, uninterruptedly introducing nitrogen into the tubular furnace, naturally cooling to room temperature of 20-33 ℃ in the nitrogen atmosphere, and taking out a product to obtain a crude product;
s5, finished product: taking the crude product obtained in the step S4, carrying out acid washing, water washing and drying to obtain a target activated carbon product; the method comprises the following specific operations: the crude product obtained is repeatedly washed with 1M hydrochloric acid and distilled water to remove ZnCl2And other inorganic matters, and then drying the mixture to constant weight at 105 ℃, thus obtaining the betel nut sludge activated carbon product.
1.3 results
1) Calculating the yield, wherein the mass yield of the activated carbon is calculated according to the following formula:
wherein m is the actual weight of the product active carbonMSAnd mBNIs the actual weight of the initial precursor. The results show that the yield of the betel nut sludge activated carbon product of example 1 is 45.30%.
2) The iodine value is an index for representing the adsorption capacity of the activated carbon, and the higher the iodine value is, the stronger the adsorption capacity of the prepared activated carbon is. And testing the iodine value of the product according to the national standard GB/T12496.8-2015 for obtaining the microscopic surface information of the activated carbon. The results show that the iodine value of the areca sludge activated carbon product of example 1 is 723.19 mg/g.
3) In order to understand the morphological characteristics of activated carbon, the morphology of the pyrolyzed activated carbon at various magnifications, the surface morphology of the samples was studied using a scanning electron microscope (thermo scientific verios G4 UC, usa).
As shown in fig. 1, it can be observed that the areca sludge activated carbon has a developed irregular surface and is rich in loose texture. Meanwhile, there are many abundant pore structures on the surface of the activated carbon, and many slit structures are formed. These slits help the contaminants to migrate to the interior of the activated carbon, thereby increasing adsorption capacity. This is caused by the fact that during carbonization, the activated carbon is caused to form a preliminary network structure, which accelerates further erosion of pores and deeper pore structure during activation. The result shows that the areca nut sludge activated carbon prepared in the embodiment 1 of the invention effectively increases the surface area of the activated carbon. Therefore, pyrolysis at 800 ℃ causes more pores to widen into macropores, and promotes the conversion of organic molecules into a developed porous structure.
4) Structural characteristics of the solid sample were obtained using a specific surface area analyzer (us ASAP 2460). Detection of N at Low temperature (77K)2Adsorption/desorption curves and pore characteristics, surface area and pore volume were calculated using brunauer-emmet-teller equation.
The adsorption and desorption isotherms and pore size distribution of the betel nut sludge activated carbon prepared in example 1 of the present invention are shown in fig. 2. The adsorption of nitrogen in the low-pressure area may be related to the monolayer adsorption of micropores, and the adsorption capacity of nitrogen can reach 175cm3(ii) in terms of/g. A clear hysteresis loop (0.4) is observed in the region of the relative pressure<P/P0<1.0), which is considered to be characteristic of mesoporous materials. According to IUPAC classification, isotherms show H4 hysteresis loops, revealing the presence of parallel slit holes formed by the accumulation of carbon flakes. The pore size distribution may directly reveal the pore nature of the activated carbon. The classification defined by IUPAC also includes micropores (diameters)<2nm), mesopores (2-50nm) and macropores (diameter)>50nm) according to the pore size distribution of the activated carbon, a broad peak appears in the range of 5-50 nm, so to speakMicropores and macropores exist in the bright activated carbon. These results indicate that activated carbon with microporous and mesoporous structure is chemically activated with a mixture of phosphoric acid and zinc chloride. The texture parameters of the activated carbon are shown in table 1. Wherein, the S of the betel nut sludge active carbon prepared by the inventiontotAnd VtotAre respectively 777.32m2G and 0.79cm3The product prepared has higher specific surface area and can well absorb pollutants. In addition, the micropore volume of the betel nut sludge activated carbon prepared by the method and the part of the betel nut sludge activated carbon occupying the total pore volume are large. This means that, precisely due to the co-pyrolysis at 800 ℃, there is a great improvement in the pore structure and surface area of the activated carbon.
TABLE 1 porous Structure parameters of activated carbon
The results show that the areca-nut sludge activated carbon prepared by the invention has irregular pore structure and total surface area of 777.32m2Per g, pore volume 0.79cm3/g。
Example 2 activation temperature study
The activation process mainly comprises the contact of an activating agent and a carbonized product and the change process of the pore structure after carbonization. The activation temperature is a key factor for preparing high-performance activated carbon. On the basis of example 1, the activation temperatures were adjusted to 400 ℃, 500 ℃, 600 ℃, 700 ℃, 800 ℃, 900 ℃, and the iodine values and yields at different activation temperatures are shown in FIG. 3.
As shown in fig. 3, the iodine value rapidly increases with the activation temperature from 400 to 800 ℃, but when the temperature exceeds 800 ℃, the iodine value decreases. This may be due to the increase in diffusion of the activated molecules into the carbonized product at higher temperatures; thus, more carbon undergoes activation reactions with phosphoric acid and hydrogen chloride, resulting in a rich pore size structure. Too high an activation temperature also destroys the network structure of the carbon, which should be avoided when synthesizing porous materials. Furthermore, the yield decreases with increasing activation temperature. This is because the organic matter is continuously decomposed in the form of gas as the carbon is consumed. As described above, it is preferable that the activation temperature is 700 ℃ and 800 ℃ and that the activation temperature is 800 ℃ is the optimum condition for synthesizing activated carbon, the iodine value is 723.19mg/g and the yield is 45.3%.
Example 3 activation time study
On the basis of example 1, the activation times were adjusted to 30 to 120 minutes, respectively.
As shown in FIG. 4, the iodine value of AC increased sharply from 545.69mg/g to 634.72mg/g and then decreased from 634.72mg/g to 493.99mg/g before 60 minutes. With the carbonized precursor obtained at 600 ℃ for 60 minutes, a better iodine value of 634.72mg/g was exhibited, with a yield of 51%. The reasons may be that the shorter the activation time, the less complete the activation and the lower the adsorption capacity; highly developed pore structures require sufficient time to stimulate micropore corrosion to meet adsorption requirements; and the extended activation time has a negative effect on pore formation, even causing adjacent micropores to expand to form pores. With activation times from 30 to 120 minutes, a continuous decrease in yield can be observed, possibly due to further decomposition of organic and inorganic salts in the material. Finally, it is preferred that the activation time is 50 to 70 minutes, and most preferably the activation time is selected to be 60 minutes.
Example 4 activator concentration Studies
In addition to reacting with the carbon precursor to form pores, the activator also plays an important role in oxidation and dehydration during the manufacturing process. Some activator may remain in the micropores and mesopores to prevent pore collapse. The present inventors investigated the effect of mixing activator (phosphoric acid and zinc chloride) solutions at different concentrations on iodine number and yield. In example 1, the concentrations of zinc chloride and phosphoric acid in the aqueous solution of the activator were adjusted to 1.0mol/L, 1.5mol/L, 2.0mol/L, 2.5mol/L, 3.0mol/L, 3.5mol/L, 4.0mol/L and 4.5mol/L, respectively.
As shown in FIG. 5, the experimental data show that 3.0mol/L of mixed activator can provide better conditions for the preparation of high iodine value (607.88mg/g) activated carbon with yield 59.44% as the concentration of activator increases. This is probably because the mixed activator reacts with the oxygen-containing functional group on the surface of the previously carbonized product to form a large amount of pores, unlike the basic activator. The concentration of the mixed activator exceeding 3.0mol/L apparently results in a decrease in the iodine value of the blended activated carbon. This can be explained by the fact that too high a concentration of mixed activator has a negative effect on the iodine value, and the micropores are widened into macropores due to excessive activation; in addition, the pores may be clogged with crystals generated at high temperature. Variations in activator concentration do not have a significant effect on yield. From the viewpoint of cost and iodine value, the preferable concentration of zinc chloride in the aqueous activator solution is 2.0 to 3.5mol/L, the preferable concentration of phosphoric acid is 2.5 to 3.5mol/L, and 3.0mol/L is used as the optimum concentration.
Example 5 solid to liquid ratio study
The solid-liquid ratio is crucial to the development of the pores of the adsorption material. On the basis of the embodiment 1, the solid-to-liquid ratio kg/L of the carbonized areca-nut and sludge mixed particles to the activator aqueous solution is respectively adjusted to be 1: 1.0, 1: 1.5, 1:2.0, 1: 2.5, 1: 3.0, 1: 3.5.
as shown in fig. 6, the iodine value of activated carbon was different depending on the solid-to-liquid ratio. When the solid-to-liquid ratio is less than 1:2.0, little activator participates in the formation of the carbon skeleton and the development of pores, and thus the iodine value is relatively low. As long as the solid-liquid ratio exceeded 1:2.0, the iodine value decreased and reached the maximum value (624.9mg/g) when the solid-liquid ratio was 1:2.0, and the yield was 57.6%. However, a further increase in the ratio widens the generated micropores into macropores, which is likely to be closely related to the contact reaction of the carbon substrate with the activator. In view of the difference in yield, a solid-to-liquid ratio of 1:2.0 to 3.0 is preferred, and a solid-to-liquid ratio of 1:2.0 is most preferred.
EXAMPLE 6 preparation of sludge activated carbon from Areca catechu L
S1, using the starting material prepared in example 1;
s2, high-temperature carbonization: placing the mixed particles of the betel nut and the sludge obtained in the example 1 into a tubular furnace, carbonizing the mixed particles in a nitrogen atmosphere, heating the mixed particles to 600 ℃ from the room temperature of 20-33 ℃ at the heating rate of 10-20 ℃/min by using the tubular furnace, preserving the heat and carbonizing the mixed particles for 90min, and finally cooling the carbonized mixed particles to the room temperature to obtain the carbonized mixed particles of the betel nut and the sludge;
s3, soaking by an activating agent: taking the carbonized areca-sludge mixed particles obtained in the step S2 and an activator aqueous solution according to the mass-volume ratio kg/L of 1: 3.0, mixing, wherein an activator aqueous solution is prepared from phosphoric acid, zinc chloride and water, the concentration of the zinc chloride in the activator aqueous solution is 2.0mol/L, the concentration of the phosphoric acid is 2.5mol/L, uniformly mixing and stirring, and soaking at 20-33 ℃ for 12h to obtain a mixed product;
s4, high-temperature activation: putting the activated mixed product obtained in the step S3 into a tubular furnace, activating in a nitrogen atmosphere, heating to 700 ℃ from the room temperature of 20-33 ℃ at a heating rate of 10-20 ℃/min, and preserving heat for activation for 2 h; finally, cooling the hearth to be below 100 ℃, uninterruptedly introducing nitrogen into the tubular furnace, naturally cooling to room temperature of 20-33 ℃ in the nitrogen atmosphere, and taking out a product to obtain a crude product;
s5, finished product: taking the crude product obtained in the step S4, carrying out acid washing, water washing and drying to obtain a target activated carbon product; the method comprises the following specific operations: repeatedly washing the obtained crude product with hydrochloric acid and distilled water to remove ZnCl2And other inorganic matters, and then drying the mixture to constant weight at 105 ℃, thus obtaining the areca sludge activated carbon product, wherein the yield is 48.00 percent, and the iodine value is 661.15 mg/g.
EXAMPLE 7 preparation of sludge activated carbon from Areca catechu L
S1, preparation of raw materials: washing the selected betel nuts with water to remove surface dirt, mixing and drying the betel nuts and sludge until the water content is 10% -20%, and the drying temperature is 105 +/-5 ℃; crushing the dried product, and sieving the crushed product with a 100-plus-200-mesh sieve to obtain mixed particles of areca and sludge;
s2, high-temperature carbonization: placing the mixed particles of the betel nuts and the sludge obtained in the step S1 into a tubular furnace, carbonizing in nitrogen atmosphere, heating the mixed particles to 700 ℃ from the room temperature of 20-33 ℃ at the heating rate of 10-20 ℃/min by using the tubular furnace, preserving heat, carbonizing for 30min, and finally cooling to the room temperature to obtain carbonized mixed particles of the betel nuts and the sludge;
s3, soaking by an activating agent: taking the carbonized areca-sludge mixed particles obtained in the step S2 and an activator aqueous solution according to the mass-volume ratio kg/L of 1:2.0, mixing, wherein an activator aqueous solution is prepared from phosphoric acid, zinc chloride and water, the concentration of the zinc chloride in the activator aqueous solution is 3.5mol/L, the concentration of the phosphoric acid is 2.5mol/L, uniformly mixing and stirring, and soaking for 48 hours at the temperature of 20-33 ℃ to obtain a mixed product;
s4, high-temperature activation: putting the activated mixed product obtained in the step S3 into a tubular furnace, activating in a nitrogen atmosphere, heating to 800 ℃ from the room temperature of 20-33 ℃ at the heating rate of 10-20 ℃/min, and preserving heat for activation for 0.5 h; finally, cooling the hearth to be below 100 ℃, uninterruptedly introducing nitrogen into the tubular furnace, naturally cooling to room temperature of 20-33 ℃ in the nitrogen atmosphere, and taking out a product to obtain a crude product;
s5, finished product: taking the crude product obtained in the step S4, carrying out acid washing, water washing and drying to obtain a target activated carbon product; the method comprises the following specific operations: repeatedly washing the obtained crude product with hydrochloric acid and distilled water to remove ZnCl2And other inorganic matters, and then drying the mixture to constant weight at 105 ℃, thus obtaining the areca sludge activated carbon product, wherein the yield is 57.62 percent, and the iodine value is 675.94 mg/g.
Comparative example 1
The main difference between this comparative example 1 and example 1 is that no betel nut was added in step S1, i.e., sludge particles were obtained in step S1.
Comparative example 2
The main difference between this comparative example 1 and example 1 is that no sludge was added in step S1, i.e. betel nut particles were obtained in step S1.
Comparative example 3
The comparative example 1 is different from the example 1 mainly in that the carbonization temperature in the step S2 is 500 ℃ and the carbonization time is 120 min.
Comparative example 4
This comparative example 1 is different from example 1 mainly in that the aqueous activator solution in step S3 was prepared from zinc chloride and water and had a concentration of 3.0 mol/L.
Comparative example 5
This comparative example 1 is different from example 1 mainly in that the aqueous activator solution in step S3 was prepared from phosphoric acid and water and had a concentration of 3.0 mol/L.
Comparative example 6
The main difference between this comparative example 1 and example 1 is that the aqueous activator solution of step S3 is composed of zinc chloride and H2SO4Is prepared by mixing with waterZinc chloride, H2SO4The concentration is 3.0 mol/L.
Comparative example 7
This comparative example 1 is different from example 1 mainly in that the aqueous activator solution in step S3 was prepared from calcium chloride, phosphoric acid and water, and the concentrations of both calcium chloride and phosphoric acid were 3.0 mol/L.
The product yields and iodine value results for examples 6-7 and comparative examples 1-7 above are shown in table 2 below, in comparison to example 1:
| product yield (%) | Iodine value (mg/g) | |
| Example 1 | 45.30 | 723.19 |
| Example 6 | 48.00 | 661.15 |
| Example 7 | 57.62 | 675.94 |
| Comparative example 1 | 35.12 | 256.31 |
| Comparative example 2 | 55.71 | 765.42 |
| Comparative example 3 | 59.77 | 649.63 |
| Comparative example 4 | 50.11 | 680.88 |
| Comparative example 5 | 43.19 | 669.77 |
| Comparative example 6 | 40.45 | 617.52 |
| Comparative example 7 | 38.62 | 633.74 |
As can be seen from comparative example 1, the activated carbon prepared from the sludge has low yield, very low iodine value and low application value. As seen in comparative example 2, the active carbon prepared from betel nuts has high yield and high iodine value, but the preparation cost is high, and the popularization and the application are not facilitated. The areca seed sludge activated carbon product prepared by the embodiment of the invention has strong iodine value adsorption capacity, high application value and low manufacturing cost, keeps the product yield at about 50%, is beneficial to popularization and application, gives play to the use value of sludge to the maximum extent and is beneficial to the environment. Among them, the iodine value adsorption capacity of example 1 is high, and the comprehensive evaluation of example 1 is a preferable scheme.
In addition, compared with the example 1, the comparative example 3 has lower carbonization temperature, longer carbonization time and obviously reduced iodine value adsorption capacity of the prepared product.
Compared with example 1, the iodine value adsorption capacity of the prepared product is obviously reduced when the activator aqueous solution is prepared from only zinc chloride and water in comparative example 4, the activator aqueous solution is prepared from only phosphoric acid and water in comparative example 5, the phosphoric acid is replaced by sulfuric acid in comparative example 6, and the zinc chloride is replaced by calcium chloride in comparative example 7. The invention uses a certain amount of activator aqueous solution (ZnC 1)2，H3P04And water) to effectively improve the performance of the betel nut sludge activated carbon.
Comparative example 8
Literature[1]Coconut shells and sludge are blended to prepare the activated carbon. The betel nut sludge active carbon prepared by the invention and documents[1]And comparing the iodine values of the prepared coconut shell sludge activated carbon.
[1]Bing Yang,Yucheng Liu,Qingling Liang,Mingyan Chen,Lili Ma.Evaluation of activated carbon synthesized by one-stage and two-stage co-pyrolysis from sludge and coconut shell[J].Ecotoxicology and Environmental Safety,2019,170:
The result shows that the iodine value of the betel nut sludge activated carbon prepared by the invention is obviously higher than that of coconut shell sludge activated carbon.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A method for preparing activated carbon by using areca and sludge as materials is characterized by comprising the following steps:
s1, preparation of raw materials: mixing Arecae semen and sludge, oven drying, pulverizing, and sieving to obtain Arecae semen and sludge mixed granule;
s2, high-temperature carbonization: placing the mixed particles of the betel nuts and the sludge obtained in the step S1 into a tubular furnace, and carrying out primary carbonization treatment in a nitrogen atmosphere, wherein the carbonization temperature is 600-700 ℃, and the carbonization time is 30-90min, so as to obtain carbonized mixed particles of the betel nuts and the sludge;
s3, soaking by an activating agent: mixing the areca and sludge mixed particles carbonized in the step S2 with an activator aqueous solution, wherein the activator aqueous solution is prepared from phosphoric acid, zinc chloride and water, the concentration of the zinc chloride in the activator aqueous solution is 2.0-3.5mol/L, and the concentration of the phosphoric acid is 2.5-3.5 mol/L; the mass volume ratio kg/L of the areca-nut and sludge mixed particles to the activator aqueous solution is 1:2.0 to 3.0, evenly stirring and then soaking for 12 to 48 hours to obtain a mixed product;
s4, high-temperature activation: putting the activated mixed product obtained in the step S3 into a tube furnace, activating in a nitrogen atmosphere, wherein the activation temperature is 700-800 ℃, the activation time is 0.5-2h, and cooling to obtain a crude product;
s5, finished product: and (5) carrying out acid washing and water washing on the crude product obtained in the step S4, and drying to obtain a target activated carbon product.
2. The method for preparing activated carbon from betel nut and sludge as claimed in claim 1, wherein in step S1, the betel nut and sludge are mixed and dried until the water content is 10% -20%.
3. The method for preparing activated carbon by using betel nuts and sludge as materials according to claim 1, wherein in step S1, the mesh number of the sieve is 100-200 meshes.
4. The method as claimed in claim 1, wherein the temperature is increased to 600-700 ℃ at a temperature rate of 10-20 ℃/min for carbonization in step S2.
5. The method for preparing activated carbon using betel nut and sludge as materials according to claim 1, wherein the soaking temperature is 20-33 ℃ in step S3.
6. The method for preparing activated carbon from betel nut and sludge as claimed in claim 1 or 4, wherein in step S4, the temperature is raised to 700-800 ℃ at a temperature raising rate of 10-20 ℃/min for activation.
7. The method for preparing activated carbon by using betel nuts and sludge as materials according to claim 1, wherein the step S5 is specifically performed by: the crude product was repeatedly washed with hydrochloric acid and distilled water to remove inorganic substances, and then dried to constant weight at 105 ℃.
8. The method for preparing activated carbon by using betel nuts and sludge as materials according to claim 1, wherein in step S3, the concentration of zinc chloride and the concentration of phosphoric acid in the aqueous solution of the activator are 3.0mol/L and 3.0mol/L respectively; the mass volume ratio kg/L of the areca-nut and sludge mixed particles to the activator aqueous solution is 1: 2.0.
9. the method for preparing activated carbon from betel nut and sludge as claimed in claim 8, wherein the soaking time is 20h in step S3.
10. The method for preparing activated carbon using betel nut and sludge as materials according to any one of claims 1 to 9, wherein the activation temperature is 800 ℃ and the activation time is 1h in step S4.
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| CN114307966A (en) * | 2022-01-26 | 2022-04-12 | 江苏地质矿产设计研究院(中国煤炭地质总局检测中心) | Method for preparing dry activated sludge adsorbent and sludge activated carbon adsorbent |
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| CN115140735A (en) * | 2022-05-27 | 2022-10-04 | 桂林理工大学 | Preparation method and application of passion fruit peel-based activated carbon |
| WO2023024365A1 (en) * | 2021-08-25 | 2023-03-02 | 海南大学 | Method for preparing activated carbon by using areca nut and sludge as materials |
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