CN114229855B - Method for extracting mesoporous silica from fly ash by utilizing boron oxide circulating phase separation - Google Patents
Method for extracting mesoporous silica from fly ash by utilizing boron oxide circulating phase separation Download PDFInfo
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- 239000010881 fly ash Substances 0.000 title claims abstract description 61
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims abstract description 60
- 229910052810 boron oxide Inorganic materials 0.000 title claims abstract description 34
- 238000000034 method Methods 0.000 title claims abstract description 31
- 239000000377 silicon dioxide Substances 0.000 title claims abstract description 28
- JKWMSGQKBLHBQQ-UHFFFAOYSA-N diboron trioxide Chemical compound O=BOB=O JKWMSGQKBLHBQQ-UHFFFAOYSA-N 0.000 title claims abstract description 21
- 238000005191 phase separation Methods 0.000 title claims description 16
- 239000002253 acid Substances 0.000 claims abstract description 37
- 238000002386 leaching Methods 0.000 claims abstract description 34
- 239000000843 powder Substances 0.000 claims abstract description 20
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims abstract description 17
- 229910017604 nitric acid Inorganic materials 0.000 claims abstract description 17
- 238000010438 heat treatment Methods 0.000 claims abstract description 15
- 239000007788 liquid Substances 0.000 claims abstract description 12
- 239000007787 solid Substances 0.000 claims abstract description 12
- 239000000203 mixture Substances 0.000 claims abstract description 10
- 238000002156 mixing Methods 0.000 claims abstract description 9
- 238000001035 drying Methods 0.000 claims abstract description 8
- 239000012298 atmosphere Substances 0.000 claims abstract description 7
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 claims abstract description 7
- 239000004327 boric acid Substances 0.000 claims abstract description 7
- 238000000926 separation method Methods 0.000 claims abstract description 7
- 238000005406 washing Methods 0.000 claims abstract description 6
- 238000001914 filtration Methods 0.000 claims abstract description 5
- 238000000498 ball milling Methods 0.000 claims abstract description 3
- 238000002425 crystallisation Methods 0.000 claims abstract description 3
- 230000008025 crystallization Effects 0.000 claims abstract description 3
- 238000005516 engineering process Methods 0.000 claims abstract description 3
- 230000001590 oxidative effect Effects 0.000 claims abstract description 3
- 239000012265 solid product Substances 0.000 claims abstract description 3
- 235000021110 pickles Nutrition 0.000 claims description 3
- 239000002245 particle Substances 0.000 claims description 2
- 238000004064 recycling Methods 0.000 claims description 2
- 229910044991 metal oxide Inorganic materials 0.000 abstract description 12
- 150000004706 metal oxides Chemical class 0.000 abstract description 12
- 239000002699 waste material Substances 0.000 abstract description 2
- 238000005119 centrifugation Methods 0.000 abstract 1
- 239000000047 product Substances 0.000 description 11
- 239000000243 solution Substances 0.000 description 11
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 7
- 235000012239 silicon dioxide Nutrition 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 238000002441 X-ray diffraction Methods 0.000 description 4
- 239000011521 glass Substances 0.000 description 4
- 239000011148 porous material Substances 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 229910004298 SiO 2 Inorganic materials 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000013335 mesoporous material Substances 0.000 description 3
- 238000002791 soaking Methods 0.000 description 3
- 239000002910 solid waste Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 229910021486 amorphous silicon dioxide Inorganic materials 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 229910021645 metal ion Inorganic materials 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 239000002689 soil Substances 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- 241000196324 Embryophyta Species 0.000 description 1
- 241000282414 Homo sapiens Species 0.000 description 1
- 241001465754 Metazoa Species 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 238000003723 Smelting Methods 0.000 description 1
- 229910021536 Zeolite Inorganic materials 0.000 description 1
- 239000003463 adsorbent Substances 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000009388 chemical precipitation Methods 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000000502 dialysis Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 229910003439 heavy metal oxide Inorganic materials 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 238000005342 ion exchange Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 239000005373 porous glass Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 239000005368 silicate glass Substances 0.000 description 1
- 239000003238 silicate melt Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000002893 slag Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000002336 sorption--desorption measurement Methods 0.000 description 1
- 239000010457 zeolite Substances 0.000 description 1
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- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/113—Silicon oxides; Hydrates thereof
- C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
- C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
- B01J20/10—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising silica or silicate
- B01J20/103—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising silica or silicate comprising silica
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- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
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- B01J20/28078—Pore diameter
- B01J20/28083—Pore diameter being in the range 2-50 nm, i.e. mesopores
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- B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
- B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
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Abstract
A method for extracting mesoporous silica from fly ash by utilizing boron oxide cyclic phase splitting belongs to the technical field of waste resource utilization. Mixing the fly ash and the boron oxide according to a proportion, and performing ball milling to uniformly mix the fly ash and the boron oxide; placing the mixed fly ash powder in a muffle furnace, and carrying out heating treatment under the condition of air or oxidizing atmosphere; crushing the obtained glassy solid product into powder; performing acid leaching treatment on the powder by using a nitric acid solution to obtain an acid leaching mixture; carrying out solid-liquid separation on the acid leaching mixture liquid by a centrifugation or filtration method to respectively obtain acid leaching liquid and solid residues, and washing and drying the obtained solid residues to obtain mesoporous silica with the purity of more than 90%; and recovering boric acid from the acid leaching solution by a crystallization technology, wherein the acid leaching solution is a high-concentration nitric acid solution, can be recycled, and is subjected to acid leaching for multiple times. Meanwhile, the method can rapidly and efficiently remove most of metal oxides in the fly ash, and the removal rate reaches over 90 percent.
Description
Technical Field
The invention belongs to the technical field of waste resource utilization, and particularly relates to a method for extracting mesoporous silica from fly ash by utilizing boron oxide cyclic phase separation.
Background
The fly ash is a main solid waste generated after coal combustion, the yield of the fly ash in China in 2019 is up to 6.55 hundred million tons, and the fly ash is single industrial solid waste with the largest yield. The main chemical composition of the fly ash is SiO 2 、Al 2 O 3 、Fe 2 O 3 CaO, etc., and also contains a small amount of heavy metal oxides such as lead, mercury, chromium, etc. The fly ash is not treated properly, and harmful elements in the fly ash can pollute soil, water and atmosphere and cause harm to human beings, animals and plants. The fly ash is mainly applied to building engineering, road engineering, ceramic industry, soil improvement and the like at present, the preparation of materials such as zeolite, adsorbent, microcrystalline glass and the like by utilizing the high added value of the fly ash still belongs to the research level at presentAnd (4) section.
At present, valuable substances in the fly ash are not fully and highly utilized in the main utilization mode of the fly ash, and the main utilization mode is a utilization mode with lower economy, while related researches on applying the fly ash to manufacture materials do not fully remove metal oxides in the fly ash, and silicon dioxide in the fly ash is not efficiently purified. The application of the phase separation method to the treatment of the fly ash mainly aims at preparing microcrystalline glass or porous glass, but metal oxides in the fly ash are not effectively removed but fixed in a glass material, and meanwhile, the experimental operation is relatively complex, the economic benefit is general, and large-scale industrial production is not realized. In addition, no application of boron oxide to promotion of phase splitting of the fly ash and realization of full removal of metal oxides in the fly ash and purification of silicon dioxide is found at present, so the method is a new way for resource utilization of the fly ash, the method is simple to operate, low in energy consumption, low in cost of the boron oxide additive, excellent in effect of removing the metal oxides, and capable of achieving removal rate of most of the metal oxides by more than 90%, and meanwhile, the final product is a mesoporous material with good performance, and high value-added utilization of the fly ash can be realized. The method of the invention applies glass phase splitting to the treatment of the fly ash, wherein the phase splitting is a phenomenon that certain components in silicate melt and glass are deflected to form different phases of chemical compositions in some areas, boron oxide is added and melted at high temperature, so that silicon dioxide and boron oxide in the fly ash can be deflected, the boron oxide can melt metal oxide, in the heat treatment process, the metal realizes the migration from a silicon-rich phase to a boron-rich phase, the boron oxide is easily dissolved in acid and can be completely dissolved in nitric acid solution, and therefore, the purposes of complete removal of the metal oxide in the fly ash and purification of the silicon dioxide are realized. The invention provides a new mode for the treatment and high-quality application of the fly ash, and realizes the resource utilization of the fly ash.
Disclosure of Invention
In view of the above problems and technical analyses, the present invention provides a method for extracting mesoporous silica from fly ash by using boron oxide cyclic phase separation, the method comprising: smelting oxidationThe method has the advantages of simple operation, obvious effect and better economy, and the prepared SiO has high purity of more than 90 percent 2 Has larger specific surface area and pore volume, concentrated pore size distribution and is a mesoporous material.
The invention adopts the following technical scheme:
a method for extracting mesoporous silica from fly ash by utilizing boron oxide cyclic phase separation comprises the following steps:
(1) Mixing fly ash and boron oxide according to a mass ratio of 1:0.17-0.54, and ball milling to mix evenly;
(2) Placing the mixed fly ash powder obtained in the step (1) in a muffle furnace, and performing heating treatment under the condition of air or oxidizing atmosphere, wherein the final temperature of the heating treatment is 800-1500 ℃, the temperature is kept for 0-4h at the current temperature after the temperature is raised, and the temperature is reduced at a slow speed after the heat treatment stage is finished;
(3) Crushing the glassy solid product obtained in the step (2) into powder;
(4) Performing acid leaching treatment on the powder in the step (3) by using a nitric acid solution to obtain an acid leaching mixture;
(5) Carrying out solid-liquid separation on the acid leaching mixture liquid obtained in the step (4) by a centrifugal or filtering method to respectively obtain acid leaching liquid and solid residues, and washing and drying the obtained solid residues to obtain mesoporous silica with the purity of more than 90%;
(6) And (5) recovering boric acid from the pickle liquor obtained in the step (5) by a crystallization technology, and drying the boric acid to obtain boron oxide for recycling. The acid leaching solution is a high-concentration nitric acid solution, acid and metal ions can be separated through a diffusion dialysis method, nitric acid is recycled, and acid leaching is carried out for multiple times. The metal ions are recovered by chemical precipitation, ion exchange techniques, and the like.
In the step (1), the boron oxide can be produced by chemical industry, or the boron oxide obtained by separation and extraction from solid waste boron slag can be adopted.
In the step (2), the heating rate is 5-10 ℃/min.
In the step (3), the particle size of the crushed powder is less than 0.15mm.
In the step (4), the concentration of the nitric acid solution is 0.5-8mol/L.
In the step (4), the temperature of acid leaching treatment is 20-90 ℃; the time of acid leaching treatment is 1.5-6h.
In the step (4), the volume ratio of the powder obtained in the step (3) to the nitric acid solution is 1:5-50.
The invention has the beneficial effects that: the method can rapidly and efficiently remove most of metal oxides in the fly ash, and the removal rate reaches over 90 percent. The purity of the silicon dioxide in the purified fly ash is up to more than 97%, and the obtained silicon dioxide powder is mesoporous silicon dioxide, has larger specific surface area and concentrated pore diameter, and can be applied to the application fields of mesoporous materials such as pollutant adsorption or catalyst carriers. The method has the advantages of simple process, short treatment time, low energy consumption, low additive cost and high product economic value, can be applied to large-scale industrial treatment, and provides a new way for high value-added utilization of the fly ash.
Drawings
FIG. 1 is a nitrogen adsorption-desorption curve and a pore size distribution diagram of the silica powder obtained by the present invention.
FIG. 2 is a scanning electron micrograph of the silica powder obtained according to the present invention.
Figure 3 is an XRD pattern of the acid leach product obtained in accordance with the present invention.
Detailed Description
The present invention will be described in detail below with reference to examples to enable those skilled in the art to better understand the present invention, but the present invention is not limited to the following examples.
Example 1:
uniformly mixing 75g of fly ash and 25g of boron oxide, uniformly mixing the fly ash and the boron oxide by using a ball mill, treating the mixture to 200 meshes, putting 10g of mixed fly ash powder into a muffle furnace, heating at a rate of 10 ℃/min, and carrying out high-temperature heat treatment at 1100 ℃ in an air atmosphere for 60min; naturally cooling to room temperature, and crushing the heat-treated blocky product to 200 meshes; adding the crushed product into a nitric acid solution of 7.4mol/L, wherein the volume ratio is 1:10, soaking for 5 hours at 90 ℃. And (3) centrifuging the acid leaching product, performing solid-liquid separation, washing the solid residue with water for 3 times, and drying at 105 ℃ for 10 hours to obtain high-purity silicon dioxide powder. . Condensing the acid leaching solution to separate out boric acid crystal, filtering and recovering.
XRF and XRD analysis shows that the solid residue after acid leaching is water washed and dried to obtain SiO as main component 2 (98.11％)、Al 2 O 3 (0.659%) and CaO (0.309%), diffraction peaks corresponding to SiO 2 Characteristic peak. The specific surface area of the silica powder was 364.2m 2 In the range of 3-6nm in micropore size. Na removing rate of metal oxide in fly ash 2 100% of O, 99.456% of MgO and Al 2 O 3 97.686%, caO 96.99%, and the removal rate of CuO, znO and SrO is 100%.
Example 2:
mixing fly ash and boron oxide according to a mass ratio of 1:0.18, uniformly mixing by using a ball mill, treating to 200 meshes, putting 20g of mixed fly ash powder into a muffle furnace, heating at a rate of 10 ℃/min, and carrying out high-temperature heat treatment at 1000 ℃ in an air atmosphere for 60min; naturally cooling to room temperature, and crushing the heat-treated blocky product to 200 meshes; adding the crushed product into a 5mol/L nitric acid solution, wherein the volume ratio is 1:10, soaking for 4 hours at 90 ℃. And (3) centrifuging the acid leaching product, performing solid-liquid separation, washing the solid residue with water for 3 times, and drying at 105 ℃ for 10 hours to obtain high-purity silicon dioxide powder. Condensing the acid leaching solution to separate out boric acid crystal, filtering and recovering.
XRF and XRD analysis shows that the solid residue after acid leaching is water washed and dried to obtain SiO as main component 2 (91.68％)、Al 2 O 3 (3.06％)、Fe 2 O 3 (1.63%) and CaO (1.06%), the diffraction peak is a bulge-shaped broad peak corresponding to amorphous SiO 2 . Removal rate Na of metal oxide in fly ash 2 97.76% of O, 90.49% of MgO and Al 2 O 3 The content was 88.9%.
Example 3:
mixing fly ash and boron oxide according to a mass ratio of 1:0.33, uniformly mixing by using a ball mill, treating to 200 meshes, putting 20g of mixed fly ash powder into a muffle furnace, heating at a rate of 10 ℃/min, and carrying out high-temperature heat treatment at 1100 ℃ in an air atmosphere for 120min; naturally cooling to room temperature, and crushing the heat-treated blocky product to 200 meshes; adding the crushed product into a 5mol/L nitric acid solution, wherein the volume ratio is 1:10, soaking for 4 hours at 90 ℃. And (3) centrifuging the acid leaching product, performing solid-liquid separation, washing solid residues for 3 times, and drying at 105 ℃ for 10 hours to obtain high-purity silicon dioxide powder.
After XRF and XRD analysis, the solid residue after acid leaching is washed and dried, and the main component is SiO 2 (97.3％)、Al 2 O 3 (0.611％)、Fe 2 O 3 (0.626%) and CaO (0.287%), the diffraction peak is a bulge-like broad peak corresponding to amorphous SiO 2 . Na removing rate of metal oxide in fly ash 2 100% of O, 99.6% of MgO and Al 2 O 3 97.8% by weight, K 2 99% of O and 97.2% of CaO.
Claims (10)
1. A method for extracting mesoporous silica from fly ash by utilizing boron oxide cyclic phase separation is characterized by comprising the following steps:
(1) Mixing fly ash and boron oxide according to a mass ratio of 1:0.17-0.54, and ball milling to mix evenly;
(2) Placing the mixed fly ash powder obtained in the step (1) in a muffle furnace, and performing heating treatment under the condition of air or oxidizing atmosphere, wherein the final temperature of the heating treatment is 800-1500 ℃, the temperature is kept for 0-4h at the current temperature after the temperature is raised, and the temperature is reduced at a slow speed after the heat treatment stage is finished;
(3) Crushing the glassy solid product obtained in the step (2) into powder;
(4) Performing acid leaching treatment on the powder in the step (3) by using a nitric acid solution to obtain an acid leaching mixture;
(5) Carrying out solid-liquid separation on the acid leaching mixture liquid obtained in the step (4) by a centrifugal or filtering method to respectively obtain acid leaching liquid and solid residues, and washing and drying the obtained solid residues to obtain mesoporous silica with the purity of more than 90%;
(6) Recovering boric acid from the pickle liquor obtained in the step (5) by a crystallization technology, and drying the boric acid to obtain boron oxide for recycling; the pickle liquor is a high-concentration nitric acid solution, can be recycled and is used for multiple acid leaching.
2. The method for extracting mesoporous silica from fly ash by using boron oxide cyclic phase separation as claimed in claim 1, wherein in the step (3), the particle size of the crushed powder is less than 0.15mm.
3. The method for extracting mesoporous silica from fly ash by using boron oxide cyclic phase separation as claimed in claim 1 or 2, wherein in the step (2), the temperature rise rate is 5-10 ℃/min.
4. The method for extracting mesoporous silica from fly ash by using boron oxide cyclic phase separation as claimed in claim 1 or 2, wherein in the step (4), the concentration of the nitric acid solution is 0.5-8mol/L.
5. The method for extracting mesoporous silica from fly ash by using boron oxide cyclic phase separation as claimed in claim 3, wherein in the step (4), the concentration of the nitric acid solution is 0.5-8mol/L.
6. The method for extracting mesoporous silica from fly ash by using boron oxide cyclic phase separation as claimed in claim 1, 2 or 5, wherein in the step (4), the temperature of acid leaching treatment is 20-90 ℃; the time of acid leaching treatment is 1.5-6h.
7. The method for extracting mesoporous silica from fly ash by using boron oxide circulating phase separation as claimed in claim 3, wherein in the step (4), the temperature of acid leaching treatment is 20-90 ℃; the time of acid leaching treatment is 1.5-6h.
8. The method for extracting mesoporous silica from fly ash by using boron oxide cyclic phase separation as claimed in claim 4, wherein in the step (4), the temperature of acid leaching treatment is 20-90 ℃; the time of acid leaching treatment is 1.5-6h.
9. The method for extracting mesoporous silica from fly ash by using boron oxide cyclic phase separation as claimed in claim 1, 2, 5, 7 or 8, wherein in the step (4), the volume ratio of the powder obtained in the step (3) to the nitric acid solution is 1:5-50.
10. The method for extracting mesoporous silica from fly ash by using boron oxide cyclic phase separation as claimed in claim 6, wherein in the step (4), the volume ratio of the powder obtained in the step (3) to the nitric acid solution is 1:5-50.
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