CN110577219A - Magnetic sludge straw-based activated carbon and preparation method thereof - Google Patents
Magnetic sludge straw-based activated carbon and preparation method thereof Download PDFInfo
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- C01B32/00—Carbon; Compounds thereof
- C01B32/30—Active carbon
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- C01B32/324—Preparation characterised by the starting materials from waste materials, e.g. tyres or spent sulfite pulp liquor
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- C01B32/342—Preparation characterised by non-gaseous activating agents
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- C01P2006/42—Magnetic properties
Abstract
A magnetic sludge straw-based activated carbon and a preparation method thereof are disclosed, wherein the activated carbon is mainly prepared from the following raw materials: the method comprises the following steps of drying sludge, drying straws, a foaming agent, carbonate and ferric salt. The method comprises the following steps: (1) crushing, drying, crushing and sieving the dried sludge and the dried straws; (2) adding foaming agent, mixing, adding carbonate water solution, oscillating and activating, and drying; (3) heating and carbonizing under inert atmosphere, cooling, ultrasonically cleaning, washing with water, filtering, and drying; (4) adding aqueous solution of ferric salt, oscillating for adsorption, and drying; (5) and (3) heating and carbonizing in an inert atmosphere, cooling, ultrasonically cleaning, washing with water, filtering, and drying to obtain the product. The magnetic sludge straw-based activated carbon has the advantages of wide raw material source, low price, easy obtainment, rich pore structure, stable magnetism, high compressive strength, good wear resistance and water resistance, and can be repeatedly used; the method is simple, low in cost and suitable for industrial production.
Description
Technical Field
The invention relates to activated carbon and a preparation method thereof, in particular to magnetic sludge straw-based activated carbon and a preparation method thereof.
Background
at present, most of commercial activated carbon in the market is prepared from coal, wood, fruit shells and the like as materials, but the raw materials have limited resources and higher cost. With the development of the industrialization process, the environmental protection requirement is improved, the demand of the activated carbon is gradually increased, and the search for a preparation technology of the activated carbon with high performance and low cost is increasingly urgent.
Municipal sludge is a main byproduct of a domestic sewage treatment plant, and the municipal sludge amount tends to increase year by year along with the improvement of the urbanization rate. At present, the annual total yield of municipal sludge in China exceeds 4000 million tons/year (the water content is 80 percent), and the annual total yield is increased year by year at a rate of 15-18 percent, but more than 80 percent of municipal sludge in China is not properly treated. 30-50% of COD and 40-70% of organic matters in the sewage are accumulated in the municipal sludge, and the municipal sludge is a carbon resource with high carbon content and can be used as a raw material for preparing activated carbon. The preparation of the sludge-based activated carbon can be used as a substitute for activated carbon prepared by precious materials such as coal, wood and the like in the prior art, simultaneously solves the difficult problems of municipal sludge treatment and disposal, realizes the utilization of carbon resources of the municipal sludge, and achieves the purposes of recycling waste and treating waste with waste.
The sludge-based activated carbon is granular and has the advantages of low price, high adsorption speed and the like, but the application in the field of environmental protection is greatly limited due to the defects of high sand content in municipal sludge, low quality of activated carbon, difficult recovery in practical application and the like. In addition, the active carbon has the problems of blockage of a filtering and separating method or loss of the active carbon in the traditional use process.
CN103521179A discloses a one-step method for preparing sludge-based formed activated carbon, which is prepared by mixing sludge and nanoscale Fe3O4Mixing, adding a binder and a foaming agent, and molding to obtain the sludge-based molded magnetic activated carbon. However, the sludge contains high sand content, which has adverse effect on the specific surface area and pore structure of the prepared sludge-based activated carbon, and the nano-scale Fe3O4And is also relatively high in cost.
CN103521180A discloses a preparation method of sludge-based formed magnetic activated carbon, which takes sludge as raw material and KOH or ZnCl2As activator, nanoscale Fe3O4is a magnetic source, and the organic-inorganic complexing agent is a foaming agent and a binding agent. However, the defects that the specific surface area and the pore structure of the magnetic sludge-based activated carbon are not developed enough are not solved; in addition, the activating agent in the process of the method has high corrosivity or toxicity and is easy to manufacturesecondary pollution and relatively high cost.
CN107175078A discloses a preparation method of sludge buckwheat-based magnetic activated carbon, which is to mix sludge and buckwheat straws and utilize ZnCl2And FeCl3And (3) soaking the mixed solution and then carbonizing. However, this method utilizes ZnCl which is toxic2Is an activating agent and is easy to cause secondary pollution.
CN104028221A discloses a preparation method of magnetic activated carbon, which is prepared by microwave heating cow dung, sludge, crop straws and coal powder as raw materials, KOH solution as an activating agent and an iron powder core or an iron-silicon-aluminum powder core as a magnetic source. However, the preparation process of the method is complex, the requirements on raw materials and magnetic source materials are high, and the selected activating agent has strong corrosivity.
In conclusion, at present, a lot of documents and reports are provided about preparation of sludge-based activated carbon and magnetic loading of the sludge-based activated carbon, but the documents are limited by raw materials, are not beneficial to development of specific surface area and pore structure of magnetic sludge-based activated carbon, and are easy to corrode equipment and generate secondary pollution.
Disclosure of Invention
the invention aims to solve the technical problem of overcoming the defects in the prior art and providing the magnetic sludge straw-based activated carbon which has the advantages of wide raw material source, low price, easy obtainment, large specific surface area, small average pore diameter, large total pore volume, rich pore structure, stable magnetism, high compressive strength, good wear resistance and water resistance and can be repeatedly used.
The invention further aims to solve the technical problem of overcoming the defects in the prior art and provide a preparation method of the magnetic sludge straw-based activated carbon, which is simple in process, low in cost and suitable for industrial production.
the technical scheme adopted by the invention for solving the technical problems is as follows: a magnetic sludge straw-based activated carbon is mainly prepared from the following raw materials: the method comprises the following steps of drying sludge, drying straws, a foaming agent, carbonate and ferric salt. The carbon content in the raw materials can be improved by adding the straws into the sludge, so that the internal pore structure of the sludge-based activated carbon is increased, and the adsorption performance of the activated carbon is improved; meanwhile, the straw is agricultural waste and is used as an auxiliary raw material to prepare the activated carbon, so that the aims of recycling the waste and treating the waste by the waste are fulfilled. The foaming agent and the carbonate can regulate and control the pore structure of the sludge-based activated carbon. The foaming agent is added into the mixed material of the sludge and the straw, so that the generation of a pore structure can be promoted in the activation stage, the strength and flexibility of the mixed material can be enhanced, and the material hardness of the sludge-based activated carbon can be improved; in the activation stage, the carbonate not only can adjust the pore structure of the sludge-based activated carbon, but also can promote the formation of the mesoporous structure of the sludge-based activated carbon. Through loading the variable-valence metal material, the chemical adsorption process of the sludge-based activated carbon can be improved, the adsorption performance of the sludge-based activated carbon is further improved, and the sludge-based activated carbon can be recovered through magnetic separation in the use process, so that the technical defects of filter separation blockage or activated carbon loss and the like are overcome. The dried sludge and the dried straws are preferably obtained by natural air drying.
Preferably, the magnetic sludge straw-based activated carbon comprises the following raw materials in parts by weight: 20-40 parts of dried sludge, 60-80 parts of dried straw, 5-10 parts of foaming agent, 5-15 parts of carbonate and 5-10 parts of iron salt. Too much sludge can cause higher sand content in raw materials, which is not beneficial to improving the pore structure and the specific surface area of the sludge straw-based activated carbon, and if the content of the straw is too high, the yield and the compressive strength of the product can be reduced.
Preferably, the water content of the dried sludge is 50-60%, the carbon content is 15-30%, and the fixed carbon content is 5-10%.
Preferably, the sludge is one or more of municipal sludge, paper-making sludge or waste water sludge of a farm and the like.
Preferably, the water content of the dried straw is 50-60%, the carbon content is 30-50%, and the fixed carbon content is 5-10%. The sum of the water content and the carbon content is less than 100 percent.
Preferably, the straw is one or more of corn straw, rice straw or sorghum straw and the like.
Preferably, the foaming agent is one or more of azodicarbonamide, azodicarbonamide or p-toluenesulfonyl hydrazide and the like. The foaming agents are all organic foaming agents which are non-toxic and can be decomposed at the temperature of more than 200 ℃ to generate a large amount of nitrogen, so that the pore-forming behavior of the internal pore structure of the sludge straw-based activated carbon is facilitated.
Preferably, the carbonate is one or more of potassium carbonate, calcium carbonate or sodium carbonate. The carbonate is neutral salt, has small corrosivity, and can be decomposed at high temperature to generate CO2The gas is beneficial to the further pore-forming action of the internal pore structure of the sludge straw-based activated carbon, and the internal pore structure of the sludge straw-based activated carbon can be adjusted.
Preferably, the iron salt is one or more of ferric nitrate, ferric chloride or ferric sulfate, and hydrates thereof.
The technical scheme adopted for further solving the technical problems is as follows: a preparation method of magnetic sludge straw-based activated carbon comprises the following steps:
(1) Crushing the dried sludge and the dried straws, drying to constant weight, crushing and sieving to obtain mixed powder of the sludge and the straws;
(2) Adding a foaming agent into the sludge and straw mixed powder obtained in the step (1), uniformly mixing, adding a carbonate aqueous solution, oscillating and activating, and drying to obtain a sludge and straw based active carbon precursor;
(3) Heating and carbonizing the sludge straw-based activated carbon precursor obtained in the step (2) in an inert atmosphere, cooling to room temperature along with the furnace, ultrasonically cleaning, washing, filtering, and drying to constant weight to obtain sludge straw-based activated carbon;
(4) Adding a ferric salt water solution into the sludge straw-based activated carbon obtained in the step (3), oscillating, dipping and drying to obtain a magnetic sludge straw-based activated carbon precursor;
(5) And (4) heating and carbonizing the precursor of the magnetic sludge straw-based activated carbon obtained in the step (4) in an inert atmosphere, cooling to room temperature along with the furnace, ultrasonically cleaning, washing with water, performing suction filtration, and drying to constant weight to obtain the magnetic sludge straw-based activated carbon.
Preferably, in the step (1), the drying temperature is 90-110 ℃.
Preferably, in the step (1), the mesh number of the sieve is 40-80 meshes. The sludge and the straws can be uniformly mixed under the mesh number.
Preferably, in the step (2), the mass fraction of the aqueous solution of carbonate is 5-15%. The aqueous solution of carbonate is preferably prepared with carbon dioxide-free deionized water.
Preferably, in the step (2), the speed of the oscillation activation is 80-120 r/min, and the time is 4-8 h. The oscillation activation can promote the carbonate solution to fully impregnate the sludge and straw mixture, and the sludge and straw mixture is uniformly mixed.
Preferably, in the step (2), the drying temperature is 100-110 ℃ and the drying time is 10-14 h.
Preferably, in the step (3), the inert atmosphere is one or more of nitrogen, argon or helium.
Preferably, in the step (3), the temperature rise rate is 2-8 ℃/min, and the temperature rises to 750-900 ℃. Organic matters in the sludge and the straws are heated and decomposed in the temperature rising process to form steam and micromolecular hydrocarbon to escape, so that a porous structure with a developed pore structure is formed. Wherein, the straw is beneficial to the increase of the micropore content, and the sludge is beneficial to the formation of the carbon skeleton and the increase of the hardness of the active carbon. If the temperature rising rate is too slow, the carbon making efficiency is affected, and if the temperature rising rate is too fast, the formation of a microporous structure is affected.
Preferably, in the step (3), the temperature-rising carbonization time is 0.5-2.0 h. When the carbonization time is less than 0.5h, organic matters in the raw materials are not completely decomposed, aromatization is not sufficient enough, and the formation of an internal pore structure of the activated carbon is not facilitated; when the carbonization time is more than 2 hours, on one hand, energy is wasted, and on the other hand, the curing reaction, the shrinkage cavity effect or the collapse effect of the internal pore structure of the carbonized product can be initiated, so that the specific surface area and the pore volume of the activated carbon are reduced.
Preferably, in the step (3), the ultrasonic cleaning temperature is 60-100 ℃, the ultrasonic frequency is 20-40 kHz, and the time is 15-25 min. The purpose of ultrasonic cleaning is to remove ash from the carbonized material, thereby increasing the specific surface area and pore structure of the activated carbon. Warming and ultrasonic treatment are beneficial to improving the removal rate of ash in the carbide.
Preferably, in the step (3), the water washing and the suction filtration are repeated for more than or equal to 1 time until the pH value of the water washing liquid is neutral.
Preferably, in the step (4), the concentration of the aqueous solution of the iron salt is 0.5-1.5 mol/L.
Preferably, in the step (4), the speed of the shaking and dipping is 100-140 r/min, and the time is 4-8 h. The purpose of the vibration impregnation is to uniformly mix the sludge straw-based activated carbon substrate with the ferric salt solution, so that the ferric salt can be fully and uniformly loaded on the surface of the sludge straw-based activated carbon.
Preferably, in the step (4), the drying temperature is 70-90 ℃ and the drying time is 10-20 h.
Preferably, in the step (5), the inert atmosphere is one or more of nitrogen, argon or helium.
Preferably, in the step (5), the temperature rise rate is 2-8 ℃/min, and the temperature rise rate is 150-300 ℃. In the temperature rising process, the ferrite solution is subjected to thermal decomposition reaction, and a magnetic ferromagnetic material is formed inside the activated carbon, so that the sludge straw-based activated carbon has stable magnetism.
preferably, in the step (5), the temperature-rising carbonization time is 0.5-2.0 h.
preferably, in the step (5), the ultrasonic cleaning temperature is 60-100 ℃, the ultrasonic frequency is 20-40 kHz, and the time is 15-25 min.
Preferably, in the step (5), the water washing and the suction filtration are repeated for more than or equal to 1 time until the pH value of the water washing liquid is neutral.
The inert atmosphere used in the invention is high-purity atmosphere with the purity of more than or equal to 99.9 percent.
the room temperature of the invention is 20-30 ℃.
The invention has the following beneficial effects:
(1) The magnetic sludge straw-based activated carbon has wide raw material source, is cheap and easy to obtain, and realizes the recycling of solid wastesWith a specific surface area of up to 596.78m2Per g, average pore diameter as small as 2.467nm, total pore volume as high as 0.389cm3The proportion of the volume of the micropores in the total pore volume is up to 75.96 percent, the pore structure is rich, the magnetism is stable, the specific saturation magnetization intensity is up to 8.5139emu/g, the compressive strength is high, the wear resistance is good, the water resistance is good, and the composite material can be repeatedly used;
(2) the method has simple process and low cost, and is suitable for industrial production;
(3) The magnetic sludge straw-based activated carbon has a good application prospect in the field of environmental management such as sewage purification treatment, soil heavy metal pollution prevention and control and the like, and has good environmental effect and economic benefit.
Drawings
FIG. 1 is a nitrogen adsorption/desorption isotherm diagram of magnetic sludge straw-based activated carbon obtained in example 1 of the present invention;
FIG. 2 is a pore size distribution diagram of the magnetic sludge straw-based activated carbon obtained in example 1 of the present invention.
Detailed Description
The invention is further illustrated by the following examples and figures.
The dry sludge used in the embodiment of the invention is obtained by natural air drying from a dehydration workshop of a certain municipal sewage treatment plant, the water content of the dry sludge is 55%, the carbon content is 23%, and the fixed carbon content is 8%; the dry straws used in the embodiment of the invention are all from a certain farm and are obtained by natural air drying, the moisture content of the dry corn straws is 52%, the carbon content is 45%, wherein the fixed carbon content is 10%, the moisture content of the dry sorghum straws is 57%, and the carbon content is 32%, wherein the fixed carbon content is 6%; the carbonate aqueous solution used in the embodiment of the invention is prepared by carbon dioxide-free deionized water; the nitrogen and argon used in the embodiment of the invention are high-purity gases with the purity of more than or equal to 99.9 percent; the starting materials or chemicals used in the examples of the present invention are, unless otherwise specified, commercially available in a conventional manner.
Examples 1 to 3 of magnetic sludge-straw-based activated carbon
The raw materials and the parts by weight of the magnetic sludge straw-based activated carbon in examples 1 to 3 are shown in table 1.
TABLE 1 raw materials and parts by weight of magnetic sludge straw-based activated carbon in examples 1 to 3
Note: in the table, "-" indicates no addition.
Example 1 preparation method of magnetic sludge straw-based activated carbon
(1) Crushing dry sludge and dry straws according to the weight parts of the raw materials in the example 1 in the table 1, drying the crushed dry sludge and dry straws to constant weight at 105 ℃, crushing the crushed dry sludge and dry straws by using a high-speed universal crusher, and sieving the crushed dry sludge and dry straws by using a 60-mesh sieve to obtain mixed powder of the sludge and the straws;
(2) According to the weight parts of the raw materials in the example 1 in the table 1, adding a foaming agent into the sludge and straw mixed powder obtained in the step (1), uniformly mixing, adding a carbonate aqueous solution with the mass fraction of 10% (prepared by 10 parts by weight of potassium carbonate and 90 parts by weight of carbon dioxide-free deionized water), vibrating and activating at the speed of 100r/min for 6 hours, and drying at the temperature of 105 ℃ for 12 hours to obtain a sludge straw-based activated carbon precursor;
(3) Placing the sludge straw-based activated carbon precursor obtained in the step (2) in a box-type atmosphere electric furnace hearth, heating to 800 ℃ at a speed of 5 ℃/min under high-purity nitrogen, carbonizing for 1h, cooling to 25 ℃ along with the furnace, ultrasonically cleaning for 20min at 80 ℃ and 30kHz, repeatedly washing and filtering for 3 times until the pH value of a washing solution is neutral, and drying to constant weight to obtain sludge straw-based activated carbon;
(4) According to the weight parts of the raw materials in the example 1 in the table 1, 1mol/L of aqueous solution of ferric salt (prepared by 7 weight parts of ferric nitrate and deionized water) is added into the sludge straw-based activated carbon obtained in the step (3), the activated carbon is subjected to oscillation impregnation for 6 hours at the speed of 120r/min, and then the activated carbon is dried for 15 hours at the temperature of 80 ℃ to obtain a precursor of the magnetic sludge straw-based activated carbon;
(5) and (3) placing the magnetic sludge straw-based activated carbon precursor obtained in the step (4) into a ceramic crucible in a box-type atmosphere furnace, heating to 250 ℃ at a speed of 5 ℃/min under high-purity nitrogen, carbonizing for 1.0h, cooling to 25 ℃ along with the furnace, ultrasonically cleaning for 20min at 80 ℃ and 30kHz, repeatedly washing and filtering for 3 times until the pH value of a washing solution is neutral, and drying to constant weight to obtain the magnetic sludge straw-based activated carbon.
Through observation, the obtained magnetic sludge straw-based activated carbon is granular, and has the advantages of good wear resistance, uniform size, high compressive strength and good water resistance.
As shown in fig. 1 and 2, BET characterization is performed on the magnetic sludge straw-based activated carbon obtained in the present example, and an isothermal adsorption/desorption curve of the magnetic sludge straw-based activated carbon belongs to a combination of type I and type IV isotherms, and an obvious hysteresis loop of type H4 is provided, which indicates that the magnetic sludge straw-based activated carbon obtained in the present example mainly has a mesoporous and microporous structure; the specific surface area of the magnetic sludge straw-based activated carbon obtained in the embodiment is 596.78m2per g, average pore diameter of 2.467nm and total pore volume of 0.389cm3The micropore volume represents 75.96% of the total pore volume.
Through saturation magnetic strength detection, the specific saturation magnetization of the magnetic sludge straw-based activated carbon obtained in the embodiment is 8.5139 emu/g.
Embodiment 2 of a method for preparing magnetic sludge straw-based activated carbon
(1) Crushing dry sludge and dry straws according to the weight parts of the raw materials in the example 2 in the table 1, drying the crushed dry sludge and dry straws to constant weight at the temperature of 110 ℃, crushing the crushed dry sludge and dry straws by using a high-speed universal crusher, and sieving the crushed dry sludge and dry straws by using a 40-mesh sieve to obtain mixed powder of the sludge and the straws;
(2) According to the weight parts of the raw materials in the example 2 in the table 1, adding a foaming agent into the sludge and straw mixed powder obtained in the step (1), uniformly mixing, adding a carbonate aqueous solution with the mass fraction of 5% (prepared by 5 parts by weight of potassium carbonate and 95 parts by weight of carbon dioxide-free deionized water), vibrating and activating at the speed of 120r/min for 4 hours, and drying at the temperature of 110 ℃ for 10 hours to obtain a sludge straw-based activated carbon precursor;
(3) placing the sludge straw-based activated carbon precursor obtained in the step (2) in a box-type atmosphere electric furnace hearth, heating to 750 ℃ at a speed of 4 ℃/min under high-purity nitrogen, carbonizing for 1h, cooling to 25 ℃ along with the furnace, ultrasonically cleaning for 15min at 70 ℃ and 40kHz, repeatedly washing and filtering for 2 times until the pH value of a washing solution is neutral, and drying to constant weight to obtain sludge straw-based activated carbon;
(4) According to the weight parts of the raw materials in the example 2 in the table 1, adding 1.2mol/L of aqueous solution of ferric salt (prepared by 5 parts by weight of ferric nitrate and deionized water) into the sludge straw-based activated carbon obtained in the step (3), vibrating and soaking for 8 hours at the speed of 100r/min, and drying for 10 hours at the temperature of 90 ℃ to obtain a precursor of the magnetic sludge straw-based activated carbon;
(5) And (3) placing the magnetic sludge straw-based activated carbon precursor obtained in the step (4) into a ceramic crucible in a box-type atmosphere furnace, heating to 200 ℃ at a speed of 4 ℃/min under high-purity nitrogen, carbonizing for 1.5h, cooling to 25 ℃ along with the furnace, ultrasonically cleaning for 15min at 70 ℃ and 40kHz, repeatedly washing and filtering for 3 times until the pH value of a washing solution is neutral, and drying to constant weight to obtain the magnetic sludge straw-based activated carbon.
Through observation, the obtained magnetic sludge straw-based activated carbon is granular, and has the advantages of good wear resistance, uniform size, high compressive strength and good water resistance.
Through detection, the magnetic sludge straw-based activated carbon obtained in the embodiment is subjected to BET representation, the isothermal adsorption/desorption curve of the magnetic sludge straw-based activated carbon belongs to a combination of I-type and IV-type isotherms, and an obvious H4-type hysteresis loop is formed, which indicates that the magnetic sludge straw-based activated carbon obtained in the embodiment contains a mesopore structure and a micropore structure, and the mesopore structure is taken as a main structure; the specific surface area of the magnetic sludge straw-based activated carbon obtained in the embodiment is 567.46m2per g, mean pore diameter 5.892 nm, total pore volume 0.354 cm3the micropore volume represents 41.56% of the total pore volume.
through saturation magnetic strength detection, the specific saturation magnetization of the magnetic sludge straw-based activated carbon obtained in the embodiment is 7.7328 emu/g.
Example 3 of preparation method of magnetic sludge straw-based activated carbon
(1) crushing dry sludge and dry straws according to the weight parts of the raw materials in the example 3 in the table 1, drying the crushed dry sludge and dry straws to constant weight at the temperature of 100 ℃, crushing the crushed dry sludge and dry straws by using a high-speed universal crusher, and sieving the crushed dry sludge and dry straws by using a sieve of 80 meshes to obtain mixed powder of the sludge and the straws;
(2) According to the weight parts of the raw materials in the example 3 in the table 1, adding a foaming agent into the sludge and straw mixed powder obtained in the step (1), uniformly mixing, adding a 15% carbonate aqueous solution (prepared from 15 parts by weight of sodium carbonate and 85 parts of carbon dioxide-free deionized water), vibrating and activating at a speed of 80 r/min for 8 hours, and drying at 100 ℃ for 14 hours to obtain a sludge and straw based activated carbon precursor;
(3) Placing the sludge straw-based activated carbon precursor obtained in the step (2) in a box-type atmosphere electric furnace hearth, heating to 850 ℃ at the speed of 6 ℃/min under high-purity argon gas, carbonizing for 1.5h, cooling to 25 ℃ along with the furnace, ultrasonically cleaning for 25min at 90 ℃ and 20kHz, repeatedly washing and filtering for 3 times until the pH value of a washing solution is neutral, and drying to constant weight to obtain sludge straw-based activated carbon;
(4) According to the weight parts of the raw materials in the example 3 in the table 1, 0.8mol/L of aqueous solution of ferric salt (prepared by 10 parts by weight of ferric sulfate and deionized water) is added into the sludge straw-based activated carbon obtained in the step (3), and after oscillation and immersion are carried out for 4 hours at the speed of 140r/min, the precursor of the magnetic sludge straw-based activated carbon is dried for 20 hours at the temperature of 70 ℃ to obtain the precursor of the magnetic sludge straw-based activated carbon;
(5) And (3) placing the magnetic sludge straw-based activated carbon precursor obtained in the step (4) into a ceramic crucible in a box-type atmosphere furnace, heating to 300 ℃ at the speed of 6 ℃/min under high-purity argon gas, carbonizing for 0.5h, cooling to 25 ℃ along with the furnace, ultrasonically cleaning for 25min at the temperature of 90 ℃ and the frequency of 20kHz, repeatedly washing and filtering for 2 times until the pH value of a washing liquid is neutral, and drying to constant weight to obtain the magnetic sludge straw-based activated carbon.
through observation, the obtained magnetic sludge straw-based activated carbon is granular, and has the advantages of good wear resistance, uniform size, high compressive strength and good water resistance.
Through detection, the magnetic sludge straw-based activated carbon obtained in the embodiment is subjected to BET representation, the isothermal adsorption/desorption curve of the magnetic sludge straw-based activated carbon belongs to a combination of I-type and IV-type isotherms, and an obvious H4-type hysteresis loop is formed, which indicates that the magnetic sludge straw-based activated carbon obtained in the embodiment contains a mesopore structure and a micropore structure; the specific surface area of the magnetic sludge straw-based activated carbon obtained in the embodiment is 571.25m2g, mean pore diameter of 6.042nm, total pore volume of 0.365cm2The micropore volume represents 48.92% of the total pore volume.
Through saturation magnetic strength detection, the specific saturation magnetization of the magnetic sludge straw-based activated carbon obtained in the embodiment is 7.4327 emu/g.
Claims (9)
1. the magnetic sludge straw-based activated carbon is characterized by mainly being prepared from the following raw materials: the method comprises the following steps of drying sludge, drying straws, a foaming agent, carbonate and ferric salt.
2. the magnetic sludge straw-based activated carbon as claimed in claim 1, which is prepared from the following raw materials in parts by weight: 20-40 parts of dried sludge, 60-80 parts of dried straw, 5-10 parts of foaming agent, 5-15 parts of carbonate and 5-10 parts of iron salt.
3. The magnetic sludge straw-based activated carbon as claimed in claim 1 or 2, which is characterized in that: the water content of the dried sludge is 50-60%, the carbon content is 15-30%, and the fixed carbon content is 5-10%; the sludge is one or more of municipal sludge, papermaking sludge or waste water sludge of a farm; the water content of the dried straw is 50-60%, the carbon content is 30-50%, and the fixed carbon content is 5-10%; the straws are one or more of corn straws, rice straws or sorghum straws; the foaming agent is one or more of azodicarbonamide, azoformamide or p-toluenesulfonyl hydrazide; the carbonate is one or more of potassium carbonate, calcium carbonate or sodium carbonate; the ferric salt is one or more of ferric nitrate, ferric chloride or ferric sulfate and hydrate thereof.
4. A preparation method of the magnetic sludge straw-based activated carbon as claimed in any one of claims 1 to 3, characterized by comprising the following steps:
(1) Crushing the dried sludge and the dried straws, drying to constant weight, crushing and sieving to obtain mixed powder of the sludge and the straws;
(2) adding a foaming agent into the sludge and straw mixed powder obtained in the step (1), uniformly mixing, adding a carbonate aqueous solution, oscillating and activating, and drying to obtain a sludge and straw based active carbon precursor;
(3) heating and carbonizing the sludge straw-based activated carbon precursor obtained in the step (2) in an inert atmosphere, cooling to room temperature along with the furnace, ultrasonically cleaning, washing, filtering, and drying to constant weight to obtain sludge straw-based activated carbon;
(4) Adding a ferric salt water solution into the sludge straw-based activated carbon obtained in the step (3), oscillating, dipping and drying to obtain a magnetic sludge straw-based activated carbon precursor;
(5) And (4) heating and carbonizing the precursor of the magnetic sludge straw-based activated carbon obtained in the step (4) in an inert atmosphere, cooling to room temperature along with the furnace, ultrasonically cleaning, washing with water, performing suction filtration, and drying to constant weight to obtain the magnetic sludge straw-based activated carbon.
5. the method for preparing magnetic sludge straw-based activated carbon as claimed in claim 4, wherein the method comprises the following steps: in the step (1), the drying temperature is 90-110 ℃; the number of the sieved meshes is 40-80 meshes.
6. The method for preparing magnetic sludge straw-based activated carbon as claimed in claim 4 or 5, wherein the method comprises the following steps: in the step (2), the mass fraction of the aqueous solution of the carbonate is 5-15%; the oscillation activation rate is 80-120 r/min, and the time is 4-8 h; the drying temperature is 100-110 ℃, and the drying time is 10-14 h.
7. The method for preparing magnetic sludge straw-based activated carbon according to any one of claims 4 to 6, wherein the method comprises the following steps: in the step (3), the inert atmosphere is one or more of nitrogen, argon or helium; the heating rate is 2-8 ℃/min, and the temperature is increased to 750-900 ℃; the time for heating and carbonizing is 0.5-2.0 h; the ultrasonic cleaning temperature is 60-100 ℃, the ultrasonic frequency is 20-40 kHz, and the time is 15-25 min; repeatedly washing with water, and vacuum filtering for more than 1 time until the pH value of the washing solution is neutral.
8. The preparation method of the magnetic sludge straw-based activated carbon as claimed in any one of claims 4 to 7, which is characterized in that: in the step (4), the concentration of the aqueous solution of the ferric salt is 0.5-1.5 mol/L; the speed of the oscillation dipping is 100-140 r/min, and the time is 4-8 h; the drying temperature is 70-90 ℃, and the drying time is 10-20 h.
9. The method for preparing magnetic sludge straw-based activated carbon according to any one of claims 4 to 8, wherein the method comprises the following steps: in the step (5), the inert atmosphere is one or more of nitrogen, argon or helium; the heating rate is 2-8 ℃/min, and the temperature is increased to 150-300 ℃; the time for heating and carbonizing is 0.5-2.0 h; the ultrasonic cleaning temperature is 60-100 ℃, the ultrasonic frequency is 20-40 kHz, and the time is 15-25 min; repeatedly washing with water, and vacuum filtering for more than 1 time until the pH value of the washing solution is neutral.
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