CN112387247B - Modified fly ash adsorbent and preparation method thereof, and trimethylamine adsorption method - Google Patents
Modified fly ash adsorbent and preparation method thereof, and trimethylamine adsorption method Download PDFInfo
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Abstract
The invention discloses a modified fly ash adsorbent, a preparation method thereof and a trimethylamine adsorption method. The adsorbent is prepared by modifying fly ash serving as a raw material by the following method: adding a hydrogen peroxide solution into the coal ash after pretreatment and molding, carrying out ultrasonic modification at normal temperature under ultrasonic waves, taking out and drying; adding the obtained product into a metal salt and fluorine salt solution, carrying out ultrasonic modification at normal temperature under ultrasonic waves, taking out, drying and then carrying out gradient calcination. The adsorbent is low in price, green and environment-friendly, resource utilization of solid waste is realized, and meanwhile, the adsorbent prepared by the method has the advantages of large specific surface area, high strength, large adsorption capacity, high adsorption efficiency, hydrophobicity and high stability.
Description
Technical Field
The invention belongs to the field of industrial waste gas purification and environment-friendly adsorption materials, and particularly relates to a trimethylamine adsorbent suitable for adsorption, a preparation method thereof and a trimethylamine adsorption method.
Background
China is a country mainly using coal as a disposable energy source, along with the development of the power industry, the emission amount of fly ash of a coal-fired power plant is increased every year, fly ash emission can generate dust to pollute the atmosphere, heavy metal elements can be diffused if the fly ash is emitted into a water body, the heavy metal elements seriously harm the survival and health of human beings, and huge negative effects are caused to national economic construction and ecological environment of China. The fly ash has large surface area and porosity and good adsorption activity, and how to realize the resource and high-value utilization of the fly ash is a big problem which needs to be solved urgently at present.
In recent years, malodorous gas not only seriously affects the ecological environment, but also has great harm to human health, and malodorous gas pollution has been widely paid attention to and paid attention to. Trimethylamine is colorless organic amine gas, is toxic, can generate unpleasant pungent fish fishy smell, has wide application, can be used for preparing an alarm agent, an analytical reagent and an organic synthetic raw material of a disinfectant and natural gas, and is also one of eight malodorous gases specified in the national emission standard of malodorous pollutants (GB 14554-1993). In actual production, due to the characteristics of extremely high volatilization and extremely low odor threshold of trimethylamine, the leakage of the trimethylamine gas can be caused by the interfaces of the storage tank, the reaction kettle, such as flanges, manholes, a liquid level meter and the like, so that a factory area has unpleasant fishy smell, a respiratory system of people is stimulated, the environment of the factory area is damaged, and the health of a human body is influenced.
At present, the treatment method for trimethylamine gas mainly comprises a physical method, a biological method, a photocatalytic method and the like. The biological method and the photocatalytic method are mainly used for treating high-concentration trimethylamine waste gas, and the low-concentration trimethylamine odor is mainly absorbed and treated by a physical method, so that the physical absorption method has the problems that the on-site trimethylamine odor is large when a saturated absorbent is detached and replaced, and the capacity of absorbing the trimethylamine is low. The adsorbent for treating the peculiar smell of trimethylamine is newly reported in the prior patents, and the trimethylamine adsorbent with high adsorption capacity and stable performance needs to be developed.
Disclosure of Invention
The invention aims to provide a modified fly ash adsorbent which is suitable for trimethylamine adsorption treatment, has higher adsorption capacity, adsorption efficiency and stability, and is green and environment-friendly.
Another object of the present invention is to provide a method for preparing the adsorbent.
The invention also aims to provide a method for adsorbing trimethylamine by using the adsorbent, which is simple and easy to implement, has high treatment efficiency, can effectively treat the trimethylamine and does not produce secondary pollution.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a preparation method of the modified fly ash adsorbent comprises the following steps:
(1) after the fly ash is pretreated and molded, adding hydrogen peroxide solution, carrying out ultrasonic modification at normal temperature under ultrasonic waves, taking out and drying;
(2) and (2) adding the product obtained in the step (1) into a metal salt and fluorine salt solution, carrying out ultrasonic modification at normal temperature under ultrasonic waves, taking out, drying and calcining.
The fly ash is the fly ash collected from the flue gas generated after coal combustion. The fly ash is mainly from a power plant, has large specific surface area and loose porous structure, and is Al 2 O 3 And SiO 2 High content and good adsorption performance, thus being capable of being used as an adsorbent.
The method for pre-processing and forming comprises the following steps: grinding the fly ash into fine powder, sieving the fine powder by a sieve of 80-200 meshes, washing and drying the sieved fine powder, adding bentonite and distilled water, uniformly mixing, wherein the mass ratio of the bentonite to the fly ash is (0.6-0.8) to 1, the mass of the distilled water is 60-80% of the total mass of the fly ash and the bentonite, carrying out extrusion forming, and then roasting at the temperature of 500-600 ℃ for 3-5h to obtain the pretreatment adsorbent.
The concentration of the hydrogen peroxide solution is 5 to 25 weight percent, preferably 10 to 15 weight percent; the dosage of the hydrogen peroxide solution is 2-3mL/g of fly ash.
The ultrasonic frequency of the invention is 80-120Hz, and the ultrasonic time is 2-3 h.
The drying temperature is 100-120 ℃, and the drying time is 2-3 h.
The coal ash is modified by hydrogen peroxide, so that the amount of acidic oxygen-containing functional groups on the surface of the coal ash can be effectively increased, the adsorption capacity of the coal ash on polar substances such as trimethylamine can be enhanced, the hydrogen peroxide can be dispersed along with ultrasonic treatment, meanwhile, the void structure of the coal ash can be effectively expanded by ultrasonic treatment, impurities on the surface of the coal ash can be effectively removed, the specific surface area of the coal ash is improved, the adsorption effect is enhanced, and the adsorption effect on the trimethylamine is improved.
The metal salt is one or more of copper salt, iron salt, cobalt salt and nickel salt, and the copper salt, the iron salt, the cobalt salt and the nickel salt are nitrate or sulfate, preferably nitrate.
The fluoride salt is one or more of sodium fluoride and ammonium fluoride, preferably ammonium fluoride.
In the metal salt and fluoride salt solution of the present invention, the concentration of copper element is 2wt% to 5wt%, preferably 3wt% to 4.5wt%, the concentration of iron element is 1wt% to 4wt%, preferably 2wt% to 3wt%, the concentration of cobalt element is 0.5wt% to 3.5wt%, preferably 1.5wt% to 2.5wt%, and the concentration of nickel element is 1wt% to 6wt%, preferably 2wt% to 4 wt%.
In the metal salt and fluorine salt solutions of the present invention, the concentration of elemental fluorine is 1wt% to 5wt%, preferably 2wt% to 3 wt%.
The dosage of the metal salt and the fluorine salt solution is 2-3mL/g of the product obtained in the step (1).
The metal salt can effectively increase the metal content on the surface of the activated carbon, the trimethylamine gas can generate a complex reaction with the metal, the binding force between the adsorbent and the adsorbate is enhanced, and the adsorption performance of the activated carbon on the adsorbate is increased, so that the removal rate of the trimethylamine gas can be improved. The fluoride salt is used as a modifier, the coal ash is modified, the integrity of the original structure and property of the carrier is kept, and a-F group is introduced, so that the loading rate and the loading uniformity of metal on the coal ash carrier can be obviously improved; the water content in the industrial waste gas has larger difference along with the change of the environment, and the fluorine modified fly ash can improve the hydrophobicity of the adsorbent, reduce the adsorption competition of the water content and improve the adsorption capacity of the adsorbent to trimethylamine.
The calcination is gradient calcination, preferably three-stage calcination, the three-stage temperatures are respectively 180- 2 Atmosphere, calcining atmosphere at the third stage temperature, selective oxidizing atmosphere, preferably CO 2 。
A large amount of impurities (such as ammonium salt and the like) on the surface of the fly ash can be removed by adopting the calcining treatment in the reducing atmosphere, the pore passage becomes more unobstructed, the specific surface area is increased, the fly ash is further calcined and activated at high temperature by adopting the oxidizing atmosphere, so that holes can be effectively opened, expanded and new holes can be created, a developed pore structure is formed, the adsorption capacity is enhanced, and meanwhile, the mechanical strength of the adsorbent can be enhanced by adopting the three-stage calcining.
A trimethylamine adsorption method comprises the following steps: passing a gas containing trimethylamine through the adsorbent of the present invention; the adsorption temperature is 0-40 ℃, preferably 10-30 ℃; the space velocity of the gas containing trimethylamine is 200-2000h -1 Preferably 600- & lt800 h- -1 (ii) a The concentration of trimethylamine in the trimethylamine-containing gas is less than 20mg/m 3 Preferably ≤ 10mg/m 3 And greater than 0.
The invention has the positive effects that:
(1) the invention utilizes the fly ash modification to prepare the adsorbent, improves the added value of the fly ash, and has obvious economic benefit;
(2) according to the invention, hydrogen peroxide and ultrasonic modified fly ash are adopted, so that the number of oxygen-containing functional groups and acidic groups on the surface of the fly ash is increased, the adsorption performance on trimethylamine is enhanced, the stability of the adsorbent and the acting force with the trimethylamine are enhanced by modifying the fly ash through metal salt, the adsorption capacity of the adsorbent is improved, the load rate and the load uniformity of metal on a fly ash carrier are obviously improved by introducing-F group, the adsorption efficiency on the trimethylamine is improved, and the hydrophobicity of the adsorbent can be effectively improved by modifying fluorine.
Detailed Description
The technical solution and the effects of the present invention are further described by the following specific examples. The following embodiments are merely illustrative of the present invention and are not intended to limit the scope of the present invention. Any combination of the different embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as the idea of the present invention is not violated.
Fly ash from huanengtai octagon thermoelectric co;
the specific surface area is measured by a V-Sorb 2800S type specific surface area measuring instrument manufactured by Beijing gold Ept technology company;
the contact angle was measured by a contact angle tester model SL200B manufactured by shanghai mullen corporation;
the concentration of trimethylamine waste gas is absorbed and concentrated by active carbon, and analyzed by a gas chromatography external standard method after methanol analysis, wherein the gas chromatography is Agilent 7890B produced by Agilent.
Example 1
(1) Grinding the collected fly ash into fine powder, sieving the fine powder with a 80-mesh sieve, washing and drying the fine powder passing through the sieve, adding 120g of bentonite and 224g of distilled water into 200g of the fine powder, uniformly mixing, carrying out extrusion forming, and roasting at the temperature of 500 ℃ for 3 hours to obtain a pretreatment adsorbent;
(2) adding 400mL of 10wt% hydrogen peroxide solution into 200g of pretreatment adsorbent, performing ultrasonic treatment for 2h under the ultrasonic condition of 120Hz, taking out, and drying at 100 ℃ for 4h to obtain hydrogen peroxide modified adsorbent;
(3) preparing a mixed solution containing ferric nitrate, copper nitrate, cobalt nitrate, nickel nitrate and ammonium fluoride, wherein the mass fractions of Fe, Cu, Co and Ni are respectively 2wt%, 1.5wt%, 3wt% and 2wt%, and the mass fraction of F is 2wt%, adding 600mL of the mixed solution into 200g of the adsorbent modified by hydrogen peroxide, carrying out ultrasonic treatment for 3h under the ultrasonic condition of 80Hz, and then taking out and drying at 120 ℃ for 4h to obtain the adsorbent modified by hydrogen peroxide, metal and F;
(4) performing three-stage calcination by using hydrogen peroxide, metal and F modified adsorbent, wherein the three-stage calcination is performed at 180 ℃, 420 ℃ and 480 ℃, the calcination time is 1H, 2H and 2H, the heating rate is 4 ℃/min, and the calcination atmosphere at the temperature below 420 ℃ is selected from H 2 Atmosphere, the temperature is higher than 420 ℃ and the calcining atmosphere is CO 2 Atmosphere to obtain the final modified adsorbent, which is marked as adsorbent # 1.
Example 2
(1) Grinding the collected fly ash into fine powder, sieving the fine powder with a 160-mesh sieve, remaining the fine powder passing through the sieve, washing and drying the fine powder, taking 200g of the fine powder, adding 160g of bentonite and 216g of distilled water, uniformly mixing, carrying out extrusion forming, and then roasting at 550 ℃ for 4 hours to obtain a pretreatment adsorbent;
(2) adding 200g of pretreatment adsorbent into 500mL of 12 wt% hydrogen peroxide solution, performing ultrasonic treatment for 2.5h under the ultrasonic condition of 100Hz, taking out, and drying at 105 ℃ for 4.5h to obtain hydrogen peroxide modified adsorbent;
(3) preparing a mixed solution containing ferric nitrate, copper nitrate, cobalt nitrate, nickel nitrate and ammonium fluoride, wherein the mass fractions of Fe, Cu, Co and Ni are respectively 2.5wt%, 4wt% and 3wt%, and the mass fraction of F is 2.5wt%, adding 500mL of the mixed solution into 200g of the hydrogen peroxide modified adsorbent, carrying out ultrasonic treatment for 2.5h under the ultrasonic condition of 90Hz, and then taking out and drying at 115 ℃ for 4.5h to obtain the hydrogen peroxide, metal and F modified adsorbent;
(4) performing three-stage calcination by using hydrogen peroxide, metal and F modified adsorbent, wherein the three-stage calcination is performed at 190 ℃, 410 ℃ and 490 ℃, the calcination time is 1.5H, the heating rate is 5 ℃/min, and the calcination atmosphere at the temperature below 410 ℃ is selected from H 2 Atmosphere, the temperature is higher than 410 ℃ and the calcining atmosphere is CO 2 Atmosphere to obtain the final modified adsorbent, which is marked as adsorbent 2 #.
Example 3
(1) Grinding the collected fly ash into fine powder, sieving the fine powder with a 200-mesh sieve, remaining the fine powder passing through the sieve, washing and drying the fine powder, taking 200g of the fine powder, adding 140g of bentonite and 272g of distilled water, uniformly mixing, carrying out extrusion forming, and then roasting at the temperature of 600 ℃ for 5 hours to obtain a pretreatment adsorbent;
(2) adding 200g of pretreatment adsorbent into 600mL of 12.5 wt% hydrogen peroxide solution, performing ultrasonic treatment for 3h under the ultrasonic condition of 80Hz, and then taking out and drying at 110 ℃ for 5h to obtain a hydrogen peroxide modified adsorbent;
(3) preparing a mixed solution containing ferric nitrate, copper nitrate, cobalt nitrate, nickel nitrate and ammonium fluoride, wherein the mass fractions of Fe, Cu, Co and Ni are 3wt%, 2wt%, 4.5wt% and 4wt% respectively, and the mass fraction of F is 3wt%, adding 400mL of the mixed solution into 200g of the adsorbent modified by hydrogen peroxide, carrying out ultrasonic treatment for 2h under the ultrasonic condition of 100Hz, and then taking out and drying at 110 ℃ for 5h to obtain the adsorbent modified by hydrogen peroxide, metal and F;
(4) performing three-stage calcination by using hydrogen peroxide, metal and F modified adsorbent, wherein the three-stage calcination is performed at 200 ℃, 400 ℃ and 500 ℃, the calcination time is performed for 2H, 1H and 1H, the heating rate is 5 ℃/min, and the calcination atmosphere at the temperature below 400 ℃ is selected from H 2 Atmosphere, temperatureSelecting CO in the calcining atmosphere at the temperature higher than 400 DEG C 2 And (5) obtaining an adsorbent which is modified by hydrogen peroxide, heavy metal and gradient calcination and is marked as adsorbent # 3.
Example 4
(1) Grinding the collected fly ash into fine powder, sieving the fine powder by a 140-mesh sieve, remaining the fine powder passing through the sieve, washing and drying the fine powder, taking 200g of the fine powder, adding 160g of bentonite and 252g of distilled water, uniformly mixing, carrying out extrusion forming, and then roasting at the temperature of 500 ℃ for 4 hours to obtain a pretreatment adsorbent;
(2) adding 500mL of 14 wt% hydrogen peroxide solution into 200g of pretreatment adsorbent, carrying out ultrasonic treatment for 2.5h under the ultrasonic condition of 90Hz, and then taking out and drying at 115 ℃ for 4.5h to obtain hydrogen peroxide modified adsorbent;
(3) preparing a mixed solution containing ferric nitrate, copper nitrate, cobalt nitrate, nickel nitrate and ammonium fluoride, wherein the mass fractions of Fe, Cu, Co and Ni are respectively 2.5wt%, 2wt%, 3wt% and 2.5wt%, and the mass fraction of F is 2.5wt%, adding 500mL of the mixed solution into 200g of the hydrogen peroxide modified adsorbent, carrying out ultrasonic treatment for 2.5h under the ultrasonic condition of 110Hz, taking out, and drying at 105 ℃ for 4.5h to obtain the hydrogen peroxide, metal and F modified adsorbent;
(4) performing three-stage calcination by using hydrogen peroxide, metal and F modified adsorbent, wherein the three-stage calcination is performed at 210 ℃, 390 ℃ and 510 ℃, the calcination time is 1.5H, the heating rate is 5 ℃/min, and the calcination atmosphere is selected from H under 390 DEG C 2 Atmosphere, the temperature is higher than 390 ℃ and the calcining atmosphere is CO 2 Atmosphere to obtain the final modified adsorbent, which is marked as adsorbent 4 #.
Example 5
(1) Grinding the collected fly ash into fine powder, sieving the fine powder by a 100-mesh sieve, remaining the fine powder passing through the sieve, washing and drying the fine powder, taking 200g of the fine powder, adding 120g of bentonite and 192g of distilled water, uniformly mixing, carrying out extrusion forming, and roasting at 550 ℃ for 3 hours to obtain a pretreatment adsorbent;
(2) adding a 15 wt% hydrogen peroxide solution into 200g of the pretreatment adsorbent to 400mL in total, carrying out ultrasonic treatment for 3h under the ultrasonic condition of 110Hz, taking out, and drying at 120 ℃ for 4h to obtain a hydrogen peroxide modified adsorbent;
(3) preparing a mixed solution containing ferric nitrate, copper nitrate, cobalt nitrate, nickel nitrate and ammonium fluoride, wherein the mass fractions of Fe, Cu, Co and Ni are 3wt%, 1.5wt%, 3wt% and 2wt% respectively, and the mass fraction of F is 3wt%, adding 600mL of the mixed solution into 200g of the adsorbent modified by hydrogen peroxide, carrying out ultrasonic treatment for 3h under the ultrasonic condition of 120Hz, and then taking out and drying at 100 ℃ for 4h to obtain the adsorbent modified by hydrogen peroxide, metal and F;
(4) performing three-stage calcination by using hydrogen peroxide, metal and F modified adsorbent, wherein the three-stage calcination is performed at 220 ℃, 380 ℃ and 520 ℃, the calcination time is 1H, 2H and 2H, the heating rate is 4 ℃/min, and the calcination atmosphere at the temperature below 380 ℃ is selected from H 2 Atmosphere, the temperature is higher than 380 ℃ and the calcining atmosphere is CO 2 Atmosphere to obtain the final modified adsorbent, which is marked as adsorbent No. 5.
Comparative example 1
(1) Grinding the collected fly ash into fine powder, sieving the fine powder with a 160-mesh sieve, remaining the fine powder passing through the sieve, washing and drying the fine powder, taking 200g of the fine powder, adding 160g of bentonite and 216g of distilled water, uniformly mixing, carrying out extrusion forming, and then roasting at 550 ℃ for 4 hours to obtain a pretreatment adsorbent;
(2) adding 200g of pretreatment adsorbent into 500mL of 12 wt% hydrogen peroxide solution, performing ultrasonic treatment for 2.5h under the ultrasonic condition of 100Hz, taking out, and drying at 105 ℃ for 4.5h to obtain hydrogen peroxide modified adsorbent;
(3) preparing an ammonium fluoride solution, wherein the mass fraction of F is 2.5wt%, adding 500mL of the ammonium fluoride solution into 200g of the adsorbent modified by hydrogen peroxide, carrying out ultrasonic treatment for 2.5h under the ultrasonic condition of 90Hz, taking out, and drying at 115 ℃ for 4.5h to obtain the adsorbent modified by hydrogen peroxide and F;
(4) performing three-stage calcination by hydrogen peroxide and F modified adsorbent at 190 deg.C, 410 deg.C, 490 deg.C, calcining for 1.5H, heating rate of 5 deg.C/min, and calcining atmosphere below 410 deg.C by selecting H 2 Atmosphere, the temperature is higher than 410 ℃ and the calcining atmosphere is CO 2 Atmosphere to obtain the final modified adsorbent, which is marked as adsorbent D1 #.
Comparative example 2
(1) Grinding the collected fly ash into fine powder, sieving the fine powder with a 160-mesh sieve, remaining the fine powder passing through the sieve, washing and drying the fine powder, taking 200g of the fine powder, adding 160g of bentonite and 216g of distilled water, uniformly mixing, carrying out extrusion forming, and then roasting at 550 ℃ for 4 hours to obtain a pretreatment adsorbent;
(2) adding 200g of pretreatment adsorbent into 500mL of 12 wt% hydrogen peroxide solution, performing ultrasonic treatment for 2.5h under the ultrasonic condition of 100Hz, taking out, and drying at 105 ℃ for 4.5h to obtain hydrogen peroxide modified adsorbent;
(3) preparing a mixed solution containing ferric nitrate, copper nitrate, cobalt nitrate and nickel nitrate, wherein the mass fractions of Fe, Cu, Co and Ni are respectively 2.5wt%, 4wt% and 3wt%, adding 500mL of the mixed solution into 200g of the adsorbent modified by hydrogen peroxide, carrying out ultrasonic treatment for 2.5h under the ultrasonic condition of 90Hz, taking out, and drying at 115 ℃ for 4.5h to obtain the adsorbent modified by hydrogen peroxide and metal;
(4) performing three-stage calcination by hydrogen peroxide and metal modified adsorbent at 190 deg.C, 410 deg.C, 490 deg.C, calcining for 1.5H, heating rate of 5 deg.C/min, and calcining atmosphere below 410 deg.C by selecting H 2 Atmosphere, the temperature is higher than 410 ℃ and the calcining atmosphere is CO 2 Atmosphere to obtain the final modified adsorbent, which is marked as adsorbent D2 #.
Comparative example 3
(1) Grinding the collected fly ash into fine powder, sieving the fine powder with a 160-mesh sieve, remaining the fine powder passing through the sieve, washing and drying the fine powder, taking 200g of the fine powder, adding 160g of bentonite and 216g of distilled water, uniformly mixing, carrying out extrusion forming, and then roasting at 550 ℃ for 4 hours to obtain a pretreatment adsorbent;
(2) adding 200g of pretreatment adsorbent into 500mL of 12 wt% hydrogen peroxide solution, performing ultrasonic treatment for 2.5h under the ultrasonic condition of 100Hz, taking out, and drying at 105 ℃ for 4.5h to obtain hydrogen peroxide modified adsorbent;
(3) preparing a mixed solution containing ferric nitrate, copper nitrate, cobalt nitrate, nickel nitrate and ammonium fluoride, wherein the mass fractions of Fe, Cu, Co and Ni are respectively 2.5wt%, 4wt% and 3wt%, and the mass fraction of F is 2.5wt%, adding 500mL of the mixed solution into 200g of hydrogen peroxide modified adsorbent, carrying out ultrasonic treatment for 2.5h under the ultrasonic condition of 90Hz, taking out, drying for 4.5h at 115 ℃, roasting for 3h at 500 ℃, and obtaining the final modified adsorbent which is marked as D3 #.
Comparative example 4
(1) Grinding the collected fly ash into fine powder, sieving the fine powder with a 160-mesh sieve, remaining the fine powder passing through the sieve, washing and drying the fine powder, taking 200g of the fine powder, adding 160g of bentonite and 216g of distilled water, uniformly mixing, carrying out extrusion forming, and then roasting at 550 ℃ for 4 hours to obtain a pretreatment adsorbent;
(2) adding a total 500mL of 12 wt% hydrogen peroxide solution into 200g of the pretreatment adsorbent, carrying out ultrasonic treatment for 2.5h under the ultrasonic condition of 100Hz, taking out, and drying at 105 ℃ for 4.5h to obtain a hydrogen peroxide modified adsorbent;
(3) preparing a mixed solution containing ferric nitrate, copper nitrate, cobalt nitrate, nickel nitrate and ammonium fluoride, wherein the mass fractions of Fe, Cu, Co and Ni are respectively 2.5wt%, 4wt% and 3wt%, and the mass fraction of F is 2.5wt%, adding 500mL of the mixed solution into 200g of the hydrogen peroxide modified adsorbent, carrying out ultrasonic treatment for 2.5h under the ultrasonic condition of 90Hz, and then taking out and drying at 115 ℃ for 4.5h to obtain the hydrogen peroxide, metal and F modified adsorbent;
(4) performing secondary calcination by using hydrogen peroxide, metal and F modified adsorbent, wherein the secondary calcination temperature is 410 ℃ and 490 ℃, the calcination time is 1.5H, the heating rate is 5 ℃/min, and the calcination atmosphere at the temperature below 410 ℃ is selected from H 2 Atmosphere, the temperature is higher than 410 ℃ and the calcining atmosphere is CO 2 Atmosphere to obtain the final modified adsorbent, which is marked as adsorbent D4 #.
Comparative example 5
(1) Grinding the collected fly ash into fine powder, sieving the fine powder with a 160-mesh sieve, remaining the fine powder passing through the sieve, washing and drying the fine powder, taking 200g of the fine powder, adding 160g of bentonite and 216g of distilled water, uniformly mixing, carrying out extrusion forming, and then roasting at 550 ℃ for 4 hours to obtain a pretreatment adsorbent;
(2) adding 200g of pretreatment adsorbent into 500mL of 12 wt% hydrogen peroxide solution, performing ultrasonic treatment for 2.5h under the ultrasonic condition of 100Hz, taking out, and drying at 105 ℃ for 4.5h to obtain hydrogen peroxide modified adsorbent;
(3) preparing a mixed solution containing ferric nitrate, copper nitrate, cobalt nitrate, nickel nitrate and ammonium fluoride, wherein the mass fractions of Fe, Cu, Co and Ni are respectively 2.5wt%, 4wt% and 3wt%, and the mass fraction of F is 2.5wt%, adding 500mL of the mixed solution into 200g of the hydrogen peroxide modified adsorbent, carrying out ultrasonic treatment for 2.5h under the ultrasonic condition of 90Hz, and then taking out and drying at 115 ℃ for 4.5h to obtain the hydrogen peroxide, metal and F modified adsorbent;
(4) performing three-stage calcination by using hydrogen peroxide, metal and F modified adsorbent, wherein the three-stage calcination is performed at 190 ℃, 410 ℃ and 490 ℃, the calcination time is 1.5h, the heating rate is 5 ℃/min, and CO is selected as the calcination atmosphere 2 Atmosphere to obtain the final modified adsorbent, which is marked as adsorbent D5 #.
Comparative example 6
(1) Grinding the collected fly ash into fine powder, sieving the fine powder with a 160-mesh sieve, remaining the fine powder passing through the sieve, washing and drying the fine powder, taking 200g of the fine powder, adding 160g of bentonite and 216g of distilled water, uniformly mixing, carrying out extrusion forming, and then roasting at 550 ℃ for 4 hours to obtain a pretreatment adsorbent;
(2) adding 200g of pretreatment adsorbent into 500mL of 12 wt% hydrogen peroxide solution, performing ultrasonic treatment for 2.5h under the ultrasonic condition of 100Hz, taking out, and drying at 105 ℃ for 4.5h to obtain hydrogen peroxide modified adsorbent;
(3) preparing a mixed solution containing ferric nitrate, copper nitrate, cobalt nitrate, nickel nitrate and ammonium fluoride, wherein the mass fractions of Fe, Cu, Co and Ni are respectively 2.5wt%, 4wt% and 3wt%, and the mass fraction of F is 2.5wt%, adding 500mL of the mixed solution into 200g of the hydrogen peroxide modified adsorbent, carrying out ultrasonic treatment for 2.5h under the ultrasonic condition of 90Hz, and then taking out and drying at 115 ℃ for 4.5h to obtain the hydrogen peroxide, metal and F modified adsorbent;
(4) performing three-stage calcination by using hydrogen peroxide, metal and F modified adsorbent, wherein the three-stage calcination is performed at 190 ℃, 410 ℃ and 490 ℃, the calcination time is 1.5H, the heating rate is 5 ℃/min, and the calcination atmosphere is selected from H 2 Atmosphere to obtain the final modified adsorbent, which is marked as adsorbent D6 #.
Application example 1
In this application example, the following experimental conditions were used to evaluate the adsorption performance of the adsorbents prepared in the above examples and comparative examples.
Before the experiment, the contact angle, specific surface area and strength of the 11 types of adsorbents were measured, and then the adsorbents were placed in a glass cylindrical adsorption tower (with a jacket, an inner diameter of 4cm and a height of 40cm), and trimethylamine waste gas (simulated by using a mixed gas of trimethylamine, water vapor and compressed air, the trimethylamine content was 10mg/m 3 The water content is 18g/m 3 Simulating the air state of 80% relative humidity at 25 ℃), introducing trimethylamine waste gas into an adsorption tower at the flow rate of 1.5L/min, and respectively controlling the space velocity to 1600h by adjusting the filling amount of an adsorbent in the adsorption tower -1 、800h -1 And 200h -1 The trimethylamine concentration was measured by gas chromatography at 25 ℃ and the treatment effect of the adsorbent is shown in table 1.
TABLE 1 treatment effect of adsorbent
Remarking: the lower limit of detection of trimethylamine concentration by gas chromatography is 0.0005mg/m 3 The undetected concentration represents a concentration below the lower detection limit of the apparatus.
The comparison of the adsorbents 2# and D1# shows that the initial adsorption effect of the adsorbent on trimethylamine can be greatly improved by metal modification, the comparison of the adsorbents 2# and D2# shows that the contact angle of the adsorbent and water is increased by F modification and exceeds 90 degrees, the hydrophobicity of the adsorbent is enhanced, meanwhile, the adsorption efficiency can be further improved by F modification, the comparison of the adsorbents 2# and D3# shows that the mechanical strength of the adsorbent can be greatly enhanced by three-stage calcination, the comparison of the adsorbents 2# and D5# shows that the specific surface area of the adsorbent can be enhanced by reduction atmosphere calcination, and the comparison of the adsorbents 2# and D6# shows that the adsorption efficiency of the adsorbent can be further improved by oxidizing atmosphere calcination.
Application example 2
Carrying out long-period adsorption experiment evaluation on the adsorbent 2#, wherein the adsorption period is selected for 100h, and the experiment conditions are as follows:
placing the prepared adsorbent No. 2 into an adsorption tower, and introducing trimethylamine waste gas (simulated by using mixed gas of trimethylamine, water vapor and compressed air, the trimethylamine content is 10mg/m 3 The water content is 18g/m 3 Simulating the air state of 80 percent relative humidity at 25 ℃) and introducing into the adsorption tower, wherein the flow rate is 1.5L/min and the space velocity is 800h -1 And at the temperature of 25 ℃, monitoring the concentration of the outlet trimethylamine by adopting gas chromatography, wherein the monitoring interval is 5 h/time, and the change of the concentration of the outlet trimethylamine along with time is shown in the following table 2:
the same conditions were used for the long-cycle adsorption experiment on adsorbent D2 #. The results are shown in Table 2.
TABLE 2 trimethylamine concentration monitoring
Remarking: the lower limit of detection of trimethylamine concentration by gas chromatography is 0.0005mg/m 3 The undetected concentration represents a concentration below the lower detection limit of the instrument.
As can be seen from the results in table 2, the adsorbent D2# has a good adsorption effect on trimethylamine in the initial state, but the adsorption efficiency gradually deteriorates with the passage of time, and the competitive adsorption of water content in the exhaust gas except for trimethylamine results in the gradual decrease of the adsorption sites available for trimethylamine, and the F modification makes the adsorbent have hydrophobicity, greatly prolongs the adsorption period of the adsorbent, and improves the service life of the adsorbent, as is obtained by combining the contact angle data of application example 1.
As can be seen from the evaluation data of the 2 application examples, the adsorbent prepared by the preparation method disclosed by the invention is excellent in adsorption performance and long in service life.
Claims (12)
1. A preparation method of the modified fly ash adsorbent comprises the following steps:
(1) adding a hydrogen peroxide solution into the coal ash after pretreatment and molding, carrying out ultrasonic modification at normal temperature under ultrasonic waves, taking out and drying;
(2) adding the product obtained in the step (1) into a metal salt and fluorine salt solution, carrying out ultrasonic modification at normal temperature under ultrasonic waves, taking out, drying and calcining;
the calcination is three-stage calcination, the first, second and third-stage calcination temperatures are respectively 180-;
the first and second sections of calcining atmosphere are selected to be reducing atmosphere, and the calcining atmosphere at the third section of calcining temperature is selected to be oxidizing atmosphere;
the metal salts are copper salts, iron salts, cobalt salts and nickel salts.
2. The method of claim 1, wherein the method of preconditioning forming comprises the steps of: grinding the fly ash into fine powder, sieving the fine powder by a sieve of 80-200 meshes, washing and drying the sieved fine powder, adding bentonite and distilled water, uniformly mixing, wherein the mass ratio of the bentonite to the fly ash is (0.6-0.8) to 1, the mass of the distilled water is 60-80% of the total mass of the fly ash and the bentonite, carrying out extrusion forming, and then roasting at the temperature of 500-600 ℃ for 3-5h to obtain the pretreatment adsorbent.
3. The method of claim 1, wherein the aqueous hydrogen peroxide solution has a concentration of 5wt% to 25 wt%; the dosage of the hydrogen peroxide solution is 2-3mL/g of fly ash.
4. The method according to claim 3, wherein the concentration of the aqueous hydrogen peroxide solution is 10wt% to 15 wt%.
5. The method of claim 1, wherein the copper salt, iron salt, cobalt salt, nickel salt is nitrate or sulfate; the fluorine salt is one or more of sodium fluoride and ammonium fluoride.
6. The method of claim 1, wherein the metal salt and fluoride salt solution has a copper concentration of 2wt% to 5 wt%; the concentration of the iron element is 1 to 4 weight percent; the concentration of the cobalt element is 0.5-3.5 wt%; the concentration of the nickel element is 1wt% -6 wt%; the concentration of fluorine element is 1wt% -5 wt%.
7. The method of claim 6, wherein the metal salt and fluoride salt solution has a copper concentration of 3wt% to 4.5 wt%; the concentration of the iron element is 2 to 3 weight percent; the concentration of the cobalt element is 1.5-2.5 wt%; the concentration of the nickel element is 2-4 wt%; the concentration of fluorine element is 2wt% -3 wt%.
8. The method according to claim 1, wherein the metal salt and fluoride salt solution is used in an amount of 2 to 3mL/g of the product obtained in step (1).
9. The method of claim 1, wherein the first and second calcination atmospheres are H 2 The calcining atmosphere at the third stage calcining temperature is CO 2 An atmosphere.
10. A modified fly ash adsorbent prepared according to the method of any one of claims 1-9.
11. A trimethylamine adsorption method comprises the following steps: passing a trimethylamine-containing gas through the modified fly ash adsorbent of claim 10; the adsorption temperature is 0-40 ℃; the space velocity of the gas containing trimethylamine is 200-2000h -1 (ii) a The concentration of trimethylamine in the trimethylamine-containing gas is less than 20mg/m 3 And greater than 0.
12. The adsorption process according to claim 11, wherein the adsorption temperature is 10-30 ℃; the space velocity of the gas containing trimethylamine is 600-800h -1 (ii) a The concentration of trimethylamine in the trimethylamine-containing gas is less than or equal to 10mg/m 3 And is greater than 0.
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