WO2013185560A1 - 一种利用稻壳制备表面改性纳米二氧化硅的方法 - Google Patents

一种利用稻壳制备表面改性纳米二氧化硅的方法 Download PDF

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WO2013185560A1
WO2013185560A1 PCT/CN2013/076864 CN2013076864W WO2013185560A1 WO 2013185560 A1 WO2013185560 A1 WO 2013185560A1 CN 2013076864 W CN2013076864 W CN 2013076864W WO 2013185560 A1 WO2013185560 A1 WO 2013185560A1
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gas
rice husk
reaction tank
water
acid
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PCT/CN2013/076864
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English (en)
French (fr)
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陶磊明
陈义龙
张岩丰
薛永杰
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武汉凯迪工程技术研究总院有限公司
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Priority to DK13803750.2T priority Critical patent/DK2862841T3/en
Priority to EP13803750.2A priority patent/EP2862841B1/en
Publication of WO2013185560A1 publication Critical patent/WO2013185560A1/zh
Priority to US14/569,771 priority patent/US9127022B2/en

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
    • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
    • C07F7/02—Silicon compounds
    • C07F7/025—Silicon compounds without C-silicon linkages
    • C—CHEMISTRY; METALLURGY
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures

Definitions

  • the invention belongs to the field of preparation of surface-modified nano silica materials, and particularly relates to a method for preparing surface-modified nano silica by using rice husk.
  • Nanomaterials have been widely concerned by many countries in the world in recent decades. The fundamental reason is that nanomaterials have found basic properties such as small size effect, surface interface effect, quantum size effect and quantum tunneling effect and great potential application value.
  • Silica nano-powders are widely used in many fields, such as reinforcing agents for synthetic rubber, thickeners, synthetic oils, blending agents for insulating varnishes, matting agents for paints, and encapsulating materials for electronic components.
  • the industrial interface with the polymer compound is considered to achieve a better use effect, and the nano-silica is required to be hydrophobic, and it is necessary to modify the surface of the silica with an organic modifying agent.
  • the methods for producing nano-silica at home and abroad mainly include precipitation method and gas phase method.
  • the main raw material is quartz, and non-metallic minerals such as wollastonite are used to replace quartz ore, but all are non-renewable resources, and most of the production processes can It is expensive, and there are problems such as serious pollution and many post-processing procedures.
  • the nano silica thus prepared is generally hydrophilic and cannot meet the current industrial requirements, and thus it is required to be surface-modified.
  • the modification method mainly uses a suitable chemical substance to react with the hydroxyl group on the surface of the nano silica by a certain process, and eliminates or reduces the amount of the surface silanol group to change the product from hydrophilic to hydrophobic.
  • Rice husk contains about 20% lignin, about 40% cellulose, about 20% five-carbon sugar polymer (mainly hemicellulose), and about 20% ash and a small amount of crude protein, crude fat, etc. Organic compound.
  • the mass fraction of silica in rice husk can reach about 18%, and it has the advantages of amorphous, less impurities and regenerability.
  • the nano-scale pores ( ⁇ 50nm) formed by the non-compact adhesion of SiO 2 gel particles in rice hulls are distributed in a network and act as a skeleton. Lignin, cellulose and the like are filled in the network, and lignin and cellulose are filled. A large amount of hydroxyl groups exist in the substance.
  • the metal is ion-adsorbed in the rice husk and can be separated from the rice husk under acidic conditions.
  • rice husks to prepare nano-silica has obvious advantages such as abundant raw materials, low cost, renewableness and environmental protection. China is the world's largest rice producer. In 2008, rice planting area reached about 430 million mu, with a total output of about 189 million tons, which can produce nearly 40 million tons of rice husks, and the total annual rice husk reached more than 6,800. Ten thousand tons.
  • the technical problem to be solved by the present invention is to provide a method for preparing surface-modified nano silica by using rice husks inexpensively.
  • the surface-modified nano silica prepared by the method is hydrophobic amorphous nano-silica and has a particle diameter of 60 nm to 200 nm.
  • the technical solution adopted by the present invention is:
  • a method for preparing surface-modified nano silica by using rice husk inexpensively characterized in that it comprises the following steps:
  • the soaking temperature is not higher than 10 °C, suction filtration, removing the filtrate ,dry;
  • the process gas containing CO 2 in the step (1) is preferably industrial flue gas.
  • the method for pretreating the treatment gas containing CO 2 according to the step (1) is to provide a gas dispersing device for discharging industrial flue gas at the bottom of the water storage reaction tank, and to bag and throw the rice husk.
  • the bagged rice husk is pressed into the water surface, and then the industrial flue gas is sprayed into the pool by the gas dispersing device, and the water pressure in the water storage reaction tank is utilized to make the carbon dioxide in the industrial flue gas soluble in water.
  • the metal ions in the rice husk react to form a precipitate.
  • the rice husk is washed and washed with deionized water to remove the metal ions adsorbed on the rice husk.
  • the carbon dioxide solubility which can be achieved in the water storage reaction tank system by the above-mentioned method using the CO 2 -containing treatment gas is 100 g of water-soluble 1 g of carbon dioxide.
  • the treatment time in the above method of pretreating with the treatment gas containing CO 2 is 1-6 days.
  • the depth of the water storage reaction tank is 6-10 m.
  • the water storage reaction tank needs to have a suitable depth to satisfy the carbon dioxide dissolved in the industrial flue gas discharged from the bottom of the pool to form a proper concentration of carbonic acid solution.
  • the gas dispersing device is provided with a gas injection hole for vortexing the water body, and the industrial flue gas is ejected from the gas injection hole.
  • the degree of dispersion of carbon dioxide gas in water can be further increased to increase the concentration of carbonic acid formation.
  • the gas dispersing device comprises a longitudinal gas pipe and at least one annular gas pipe disposed horizontally and communicating with the upper end of the longitudinal gas pipe, and the annular gas pipe is provided with a plurality of inclined downwards in the circumferential direction.
  • the jet holes allow the spurt to vortex the water.
  • the axial line of the gas injection hole is at an angle of 5 to 35 degrees from the horizontal plane, more preferably 20 degrees.
  • the height of the annular gas pipe is more than 1.5 meters from the bottom of the water storage reaction tank. Since carbonic acid and rice hulls precipitate during the reaction, in order to prevent the sediment from clogging the gas injection holes, the annular gas delivery pipe is placed at a position 1.5 m or more from the bottom of the water storage reaction tank.
  • the longitudinal wall of the longitudinal gas pipe is provided with a plurality of obliquely upward jet ports.
  • the axial line of the air vent is at an angle of 10 to 45 degrees from the vertical direction, more preferably 20 degrees.
  • the longitudinal gas pipe is located at the center of the annular gas pipe, and communicates with the annular gas pipe through a transverse gas pipe.
  • the annular gas pipe comprises an upper annular gas pipe, a middle annular gas pipe and a lower annular gas pipe, and the annular diameters of the upper annular gas pipe, the middle annular gas pipe and the lower annular gas pipe are sequentially increased in size, and The top-down sequence is arranged to form a tower structure on the longitudinal gas pipe.
  • the tower-shaped annular gas pipe can eliminate the dead angle of industrial smoke dispersing into the water, forming a swirling agitation of the water body, and preventing the dust in the water body from blocking the gas jet hole.
  • a plurality of microporous aeration heads are disposed in the gas injection holes or the gas injection ports in the gas dispersing device, and industrial flue gas is ejected from the microporous aeration head.
  • the pore size of the gas injection hole is 0.005 to 0.012 mm, and the pore size of the gas injection port is 4 to 6 mm.
  • the additional pressure of the spherical liquid surface is proportional to the surface tension coefficient and inversely proportional to the spherical radius.
  • the surface tension coefficient is constant, the smaller the radius, the greater the additional pressure. .
  • the method for pretreating the treatment gas containing CO 2 according to the step (1) may further include a gas distributor with a microporous aeration head disposed at a lower portion of the reaction tank, and a reaction under the gas distributor.
  • a tank outlet is provided with a circulating liquid outlet, a gas outlet is arranged at the top of the reaction tank, a sediment outlet is arranged at the bottom, and a movable grid-shaped pressure bag plate is arranged at the upper part of the reaction tank; when the reaction tank is used First, fill the rice husk and water in the reaction tank, press the rice husk into the liquid surface with a grid-shaped pressure bag plate, then fix the grid-shaped pressure bag plate, and keep the gas outlet closed, industrial smoke from The microporous aeration head on the gas distributor is sprayed out, and the solubility of the carbon dioxide in the industrial flue gas in the water is increased by the pressure of the industrial flue gas in the reaction tank, and the formed carbonic acid solution and the metal in the rice husk are generated. The ions react to form a precipitate. After the reaction is completed, the rice husk is washed and washed with no brine to remove the metal ions adsorbed on the rice husk.
  • a demister is further disposed above the grid-shaped pressure bag plate.
  • the carbon dioxide solubility which can be achieved in the water storage reaction tank system is 100 g of water-soluble 4 g of carbon dioxide.
  • the soaking temperature of the step (2) is preferably -5 ° C ⁇ At 5 ° C, the volume ratio of the rice husk and the dilute solution for soaking is 1:5 to 20 g/mL.
  • the step (2) further comprises performing a washing and grinding step before drying.
  • the heating rate in the step (3) is 8-20 ° C / min; the anaerobic roasting time is 1 ⁇ 3h.
  • the principle of the method for removing metal ions in rice husk by using industrial flue gas in the above scheme is: using carbon dioxide in industrial flue gas to dissolve in water to form carbonic acid, acidifying rice husk, and metal such as aluminum, calcium, magnesium, iron and manganese therein.
  • the ionic reaction forms a poorly soluble salt, and the reaction precipitate is mainly a metal carbonate or an oxide, thereby efficiently removing metal ions in the rice husk.
  • Carbon dioxide (CO 2 ) is a non-polar molecule, but it can be dissolved in a solvent with a relatively high polarity.
  • the solubility is related to temperature, pressure and solvent properties.
  • the volume of carbon dioxide dissolved in a saturated aqueous solution at normal temperature and pressure is water.
  • the volume ratio is about 1:1, most of the carbon dioxide is present in the form of weakly bound hydrate molecules, only a small portion of which forms carbonic acid, and this concentration of carbonic acid cannot handle large quantities of rice hulls.
  • the solubility is proportional to the pressure.
  • the pressure exceeds 0.5 MPa, the increase in the solubility of carbon dioxide will increase as the pressure increases, so the concentration of carbonic acid in the water is increased.
  • it is critical to increase the gas pressure of carbon dioxide.
  • the method for setting a water storage reaction tank provided by the present invention is to use a water pressure and a gas dispersing device to increase the solubility of carbon dioxide in water, and the method for setting the reaction tank is to use a closed container to make the carbon dioxide in the liquid level in the container high.
  • the pressure causes the carbon dioxide gas to dissolve and achieve better metal ion removal.
  • Rice husk is an organic-inorganic composite material.
  • Amorphous silica and lignin are closely linked by hydroxyl covalent bond and mainly distributed in the lignin layer of rice husk.
  • Lignin contains a large amount of phenolic substances, which are composed of phenol or polyphenols and are not easily decomposed under weak acid conditions.
  • the hydroxyl groups contained in cellulose and hemicellulose are linear hydroxyl groups. The structure is different, and the degree of decomposition is not the same.
  • cellulose By controlling the acid concentration, soaking temperature and soaking time, cellulose can be decomposed into short-chain xylose, and The polyphenols in the lignin are not decomposed, thereby preventing the decomposition of lignin, but also the purpose of decomposing hemicellulose and cellulose into small molecule xylose. Then by controlling the firing conditions, after 300 ° C ⁇ Anaerobic calcination at 450 ° C, because amorphous silica easily combines with hydroxyl groups, the decomposed hydroxy organics will bind to the surface of amorphous silica, and an organic layer, ie hydrophilic hydroxyl group, is coated on the outside of amorphous silica.
  • the group is surrounded by a large hydrophobic benzene ring to form a hydrophobic silica, which is modified like a silica surface with a modifier to achieve surface modification of the silica.
  • too low calcination temperature (below 300 °C) makes it difficult for silica to break bonds to form particles with small particle size
  • too high calcination temperature (temperature exceeds 450 ° C)
  • silica is easy to recrystallize and aggregate Granules, and polyphenols will decompose significantly.
  • Anaerobic can also prevent organic matter on the surface of the silica from burning at high temperatures.
  • the invention utilizes a treatment gas containing CO 2 , preferably industrial flue gas, to pretreat the rice husk of agricultural by-products, remove metal ions and impurity dust therein, and then further digest the cellulose and hemicellulose by acid leaching with a dilute acid solution. Then, anaerobic roasting at 350 ° C ⁇ 450 ° C, the silica is broken, and a layer of organic matter is wrapped on the outside, that is, the hydrophilic hydroxyl group is surrounded by a large hydrophobic benzene ring to form a hydrophobic dioxide. Silicon, similar to silica surface modification with modifier, to achieve surface modification of silica, to prepare surface-modified amorphous silica.
  • a treatment gas containing CO 2 preferably industrial flue gas
  • the invention utilizes the structural characteristics of the rice husk, can directly prepare the surface-modified nano silica without adding any modifier, has simple and controllable process, low carbon environmental protection and high comprehensive benefit.
  • the surface-modified nano silica thus prepared is amorphous nano-silica having a particle diameter of 60 nm to 200 nm, an oil absorption value of 1.00 to 2.50 mL/g, a surface contact angle to water of >128°, and a BET specific surface area of 60. ⁇ 120 m 2 /g.
  • the use of carbon dioxide, preferably industrial fumes containing a large amount of carbon dioxide (including power plant flue gas or industrial exhaust gas, etc.) to remove metal ions in the rice husk not only saves costs, but also makes rational use of industrial flue gas to avoid industrial waste gas pollution.
  • the solution of the rice husk containing the nutrients of the nutrients required by plants such as sodium, potassium, nitrogen, phosphorus, sulfur, etc. can be directly used as a nutrient solution of the plant, and the reaction precipitate can be used for construction or as a material additive. Use, no water pollution.
  • Example 1 is a transmission electron micrograph of surface-modified nano silica prepared in Example 1 of the present invention.
  • Example 2 is an XRD pattern of the surface-modified nano silica prepared in Example 1 of the present invention
  • Example 3 is an energy spectrum diagram of surface-modified nano silica prepared in Example 1 of the present invention.
  • Example 4 is an infrared diagram of surface-modified nano silica prepared in Example 1 of the present invention.
  • Figure 5 is a cross-sectional structural view showing a water storage reaction tank in Embodiment 1 of the present invention.
  • Figure 6 is a top plan view of Figure 5;
  • Figure 7 is a schematic enlarged view of the annular gas pipe and the longitudinal gas pipe of Figure 5;
  • Figure 8 is a top plan view of Figure 7;
  • Figure 9 is a cross-sectional structural view showing a reaction can in Embodiment 2 of the present invention.
  • water storage reaction tank 1 water storage reaction tank 1, longitudinal gas pipeline 2, annular gas pipeline 3 , upper annular gas pipe 3.1, middle annular gas pipe 3.2, lower annular gas pipe 3.3, gas main pipe 4, rice husk 5, transverse gas pipe 6, pressure bag strip 7, circulating liquid outlet 8, gas distributor 9
  • the sediment outlet 10 the tapered portion 11, the gas outlet 12, the mesh-shaped pressure bag plate 13, the demister 14, and the reaction tank 15.
  • a water storage reaction tank 1 having a depth of 7 m and a length and a width of 100 m is provided, and 25 gas dispersing devices for discharging industrial flue gas are provided at the bottom of the water storage reaction tank 1,
  • the gas dispersion device comprises a longitudinal gas delivery tube 2 and at least one annular gas delivery tube 3 disposed horizontally and in communication with the upper end of the longitudinal gas delivery tube.
  • the annular gas delivery pipe 3 is provided with a plurality of downwardly directed gas injection holes (not shown) in the circumferential direction, so that the sprayed smoke can cause vortex agitation to the water body.
  • the axial line of the gas jet hole is at an angle of 20° to the horizontal plane.
  • the projection of the axial line of the gas injection hole in the horizontal plane is tangent to the annular side of the annular gas pipe 3, and the plurality of gas injection holes are distributed on the annular gas delivery pipe 3 in a clockwise or counterclockwise direction.
  • a plurality of obliquely upward air injection ports are disposed on the pipe wall of the longitudinal air pipe 2, and the axial line of the air injection port is at an angle of 20° to the vertical direction.
  • a plurality of microporous aeration heads are disposed in the gas injection holes or the gas injection ports in the gas dispersion device, and industrial flue gas is ejected from the microporous aeration heads.
  • the height of the annular gas pipe 3 is 1.5 meters from the bottom of the pool.
  • the annular gas delivery pipe 3 comprises an upper annular gas pipe 3.1, a middle annular gas pipe 3.2 and a lower annular gas pipe 3.3, an upper annular gas pipe 3.1, a middle annular gas pipe 3.2 and a lower annular gas pipe 3.3.
  • the annular diameters are sequentially increased in size, and are arranged in a top-down order on the longitudinal gas pipe 2 to constitute a tower structure.
  • the longitudinal gas delivery pipe 2 is located at the center of the annular gas delivery pipe 3, and is in communication with the annular gas delivery pipe 3 through the transverse gas delivery pipe 6.
  • the pore size of the gas jet hole is 0.01 mm, and the pore size of the gas jet port is 4 to 6 mm.
  • soluble matter and reaction precipitation are produced.
  • the soluble matter is rich in nitrogen, phosphorus, potassium, sodium, small molecule organic matter, etc.
  • the reaction precipitates are mainly aluminum, calcium, magnesium, iron, manganese, etc.
  • the metal carbonate or oxide, the reaction insoluble matter and the dust in the flue gas precipitate to form a precipitate layer at the bottom of the tank.
  • the reaction tank is treated for 6 days in the rice husk. After two washings, the squeezing is carried out with deionized water to remove 60% ⁇ 75% of the metal ions in the rice husk, and the rice husk volume can be treated 2500 ton at a time.
  • the rice husk pretreated in the previous step is dried and ground, weighed to 1 kg, placed in 5 L of a boric acid solution with a molar concentration of 0.1 M, and immersed in an ice bath at 0 ° C for 8 hours, using a suction filter device. The excess solution and the boric acid solution are filtered, leaving a composite of organic matter and silicon, and dried at 110 ° C;
  • the silica powder is round particles in the silica powder, and the dispersion is uniform, and the particle diameter is 120 nm;
  • the silica powder is an amorphous silica structure
  • the silica powder contains silicon dioxide and organic matter
  • the silica silica is coated with an organic group on the outside;
  • Oil absorption test slowly add dibutyl phthalate to 100g silica, stir while adding, until the silica is loosely granulated into a large group, calculate the consumption of dibutyl phthalate. The number of volumes. The oleophilic value of silica obtained in Test Example 1 was 1.5. mL/g;
  • a reaction tank 15 is provided, the reaction tank is 15 m high, and the internal volume is 1000 m 3 .
  • a gas distributor 9 with a microporous aeration head is disposed at the lower portion of the reaction tank, and the tank wall of the reaction tank below the gas distributor is placed.
  • a circulating liquid outlet 8 is provided, and a gas outlet 12 is disposed at the top of the reaction tank, the bottom of the reaction tank is a cone portion 11 for collecting sediment, and a sediment outlet 10 is disposed at the bottom of the reaction tank, and an upper portion of the reaction tank is disposed at the upper portion of the reaction tank.
  • the demister 14 and the grid-shaped pressure bag plate 13 are provided on the mesh-shaped pressure bag plate.
  • the rice husk 5 and water are first filled in the reaction tank, and the rice husk floats on the water surface, and the bagged rice husk is pressed into the water surface with a grid-shaped pressure bag plate, and the grid-shaped pressure bag plate is fixed. And keeping the gas outlet closed, the industrial flue gas is ejected from the microporous aeration head on the gas distributor, and the pressure of the industrial flue gas in the reaction tank increases sharply due to the closed tank and microporous aeration conditions.
  • the amount of carbon dioxide and water dissolved in industrial flue gas is 20 times that of normal temperature and normal pressure, and the solubility is 100 g of water-soluble 4 g of carbon dioxide.
  • the resulting carbonic acid solution reacts with the rice husk floating on it to form a precipitate.
  • the rice husk is cleaned and washed with no brine to remove the metal ions adsorbed on the rice husk. In this way, 80% of the metal ions in the rice husk can be removed, and the rice husk volume can be treated 100 tons at a time.
  • the pressure in the reaction tank during the treatment can be adjusted by adjusting the gas outlet opening provided at the top of the reaction tank (or venting the reaction tank after the treatment is completed).
  • the residual carbonic acid solution after the completion of the treatment can be discharged through the circulation liquid outlet for reuse, such as a nutrient solution directly used for plants.
  • the rice husk treated by the above industrial flue gas is weighed to a weight of 1 kg and placed in a molar concentration of The 0.05 M hydrochloric acid solution was immersed in an ice bath at 10 ° C for 6 hours, and the excess solution and the hydrochloric acid solution were suction filtered to remove the filtrate, leaving a complex of organic matter and silicon, and dried;
  • a water storage reaction tank 1 having a depth of 7 m and a length and a width of 100 m is provided, and 25 gas dispersing devices for discharging industrial flue gas are provided at the bottom of the water storage reaction tank 1,
  • the gas dispersion device comprises a longitudinal gas delivery tube 2 and at least one annular gas delivery tube 3 disposed horizontally and in communication with the upper end of the longitudinal gas delivery tube.
  • the annular gas delivery pipe 3 is provided with a plurality of downwardly directed gas injection holes (not shown) in the circumferential direction, so that the sprayed smoke can cause vortex agitation to the water body.
  • the axial line of the gas jet hole is at an angle of 20° to the horizontal plane.
  • the projection of the axial line of the gas injection hole in the horizontal plane is tangent to the annular side of the annular gas pipe 3, and the plurality of gas injection holes are distributed on the annular gas delivery pipe 3 in a clockwise or counterclockwise direction.
  • a plurality of obliquely upward air injection ports are disposed on the pipe wall of the longitudinal air pipe 2, and the axial line of the air injection port is at an angle of 20° to the vertical direction.
  • a plurality of microporous aeration heads are disposed in the gas injection holes or the gas injection ports in the gas dispersion device, and industrial flue gas is ejected from the microporous aeration heads.
  • the height of the annular gas pipe 3 is 2.0 meters from the bottom of the pool.
  • the annular gas delivery pipe 3 comprises an upper annular gas pipe 3.1, a middle annular gas pipe 3.2 and a lower annular gas pipe 3.3, an upper annular gas pipe 3.1, a middle annular gas pipe 3.2 and a lower annular gas pipe 3.3.
  • the annular diameters are sequentially increased in size, and are arranged in a top-down order on the longitudinal gas pipe 2 to constitute a tower structure.
  • the longitudinal gas delivery pipe 2 is located at the center of the annular gas delivery pipe 3, and is in communication with the annular gas delivery pipe 3 through the transverse gas delivery pipe 6.
  • the pore size of the gas jet hole is 0.01 mm, and the pore size of the gas jet port is 4 to 6 mm.
  • the carbon dioxide-containing industrial flue gas discharged from the biomass power plant is dedusted by the dedusting equipment, and then enters the gas main pipe 4, and then sprayed into the 5 m deep water storage reaction tank by the gas dispersing device. Under such pressure, the industrial flue gas
  • the carbon dioxide solubility is 100 g water-soluble 0.5 g carbon dioxide
  • the resulting carbonic acid solution acidifies the rice husk 5 and reacts with the metal ions in the rice husk 5 to form a precipitate.
  • the rice husk 5 is cleaned and washed with no brine. , the metal ions adsorbed on the rice husk 5 are removed.
  • soluble matter and reaction precipitation are produced.
  • the soluble matter is rich in nitrogen, phosphorus, potassium, sodium, small molecule organic matter, etc.
  • the reaction precipitates are mainly aluminum, calcium, magnesium, iron, manganese, etc.
  • the metal carbonate or oxide, the reaction insoluble matter and the dust in the flue gas precipitate to form a precipitate layer at the bottom of the tank.
  • the reaction tank is treated for 2 days in the rice husk. After two washings, the squeezing is carried out with deionized water to remove 60% ⁇ 75% of the metal ions in the rice husk, and the rice husk volume can be treated 2500 ton at a time.
  • the rice husk treated in the industrial flue gas of Example 1 was weighed to a weight of 1 kg, and placed in a 20 L molar solution of 0.5 M acetic acid solution in an ice bath at 5 ° C for 8 hours to remove excess solution and acetic acid.
  • the solution was suction filtered, the filtrate was removed, and the complex of organic matter and silicon was left, washed three times with deionized water, and the rice husk was dried, ground, and dried at 110 ° C;
  • the rice husk after the industrial flue gas treatment in Example 1 was weighed to a weight of 1 kg, placed in a 5 L phosphoric acid solution having a molar concentration of 0.05 M, and reacted in an ice bath at 5 ° C for 5 hours to pump the excess solution and the phosphoric acid solution. Filtration, removing the filtrate, leaving a complex of organic matter and silicon, rinsing three times with deionized water, drying the rice husk, grinding, and drying at 110 ° C;
  • the sample was heated to a temperature of 10 ° C / min in a nitrogen furnace to slowly raise the temperature to 350 ° C, and kept for 2 h, to obtain a sample of SiO 2 powder, which was tested to have a particle size of 60 nm and a BET specific surface area of 120 m 2 /g;
  • the oil absorption value is 2.0, and the contact angle to the water surface is 138°.
  • the rice husk after the industrial flue gas treatment in Example 1 was weighed to a weight of 1 kg, placed in a 5 L phosphoric acid solution having a molar concentration of 0.05 M, and reacted in an ice bath at 5 ° C for 5 hours to pump the excess solution and the phosphoric acid solution. Filtration, removing the filtrate, leaving a complex of organic matter and silicon, rinsing three times with deionized water, drying the rice husk, grinding, and drying at 110 ° C;
  • the temperature was gradually increased to 500 ° C in a nitrogen-protected tube furnace at a heating rate of 10 ° C / min, and kept for 2 h to obtain a sample of SiO 2 powder, which was tested to have a particle diameter of 250 nm or more and a BET specific surface area of 60 m 2 /g;
  • the oil absorption value was 1.0, and the contact angle to the water surface was 10°, indicating that the SiO 2 powder had poor hydrophobic properties.
  • test method of the oil absorption value in the above Example 2-5 was the same as that in the first embodiment.
  • the above two methods of pretreatment using industrial flue gas water storage reaction tank and reaction tank method
  • water storage reaction cell method water storage reaction cell method
  • the crude treatment is carried out once, and then the reaction tank method is used for the secondary finishing treatment, and then the subsequent steps are successively carried out.

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  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
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Abstract

一种利用稻壳制备表面改性纳米二氧化硅的方法，包括以下步骤：将稻壳用含有CO2的处理气预处理，去除金属离子及杂质灰尘，干燥，研磨；于浓度为0.05-0.5mol/L的磷酸、硼酸、盐酸、甲酸、醋酸、丙酸、丁酸或强酸弱碱盐的稀溶液中浸泡4-8小时，浸泡温度不高于10°C，抽滤，除去滤液，干燥；300-450°C厌氧焙烧，得到表面改性纳米二氧化硅。产品粒径60-200nm，吸油值1.00-2.50mL/g，对水的表面接触角〉128°，BET比表面积60-120m2/g。

Description

[根据细则37.2由ISA制定的发明名称]　一种利用稻壳制备表面改性纳米二氧化硅的方法 技术领域
本发明属于表面改性纳米二氧化硅材料制备领域，具体涉及利用稻壳制备表面改性纳米二氧化硅的方法。
 背景技术
纳米材料在近几十年来受到世界各国多方面的广泛关注，根本原因是人们发现纳米材料存在小尺寸效应、表面界面效应、量子尺寸效应及量子隧道效应等基本性能和极大的潜在应用价值。
二氧化硅纳米粉体在许多领域中有广泛的用途，如用作合成橡胶的补强剂，稠化剂，合成油类、绝缘漆的调和剂，油漆的消光剂，电子元件包封材料的触变剂，荧光屏涂覆时荧光粉的沉淀剂，彩印胶版填充剂，铸造的脱模剂等。其加入树脂内，可提高防潮和绝缘性能，填充在塑料制品内，可增加抗滑性和防油性，填充在硅树脂中，可制成耐温200℃以上的塑料。在造纸业中用作填充剂和纸的表面配料。还有用作杀虫剂及农药的载体或分散剂，防结块剂以及液体吸附剂和润滑剂等。
除此，工业上考虑其同聚合物胶料的界面结合力以达到更好的使用效果，要求纳米二氧化硅具有疏水性，需要对二氧化硅表面加有机修饰试剂改性。
目前国内外生产纳米二氧化硅的方法主要有沉淀法和气相法，其主要原料是石英，也有以硅灰石等非金属矿替代石英矿，但皆为非可再生资源，且大多生产工艺能耗大，存在污染严重、后处理程序多等问题。除此，由此制备得到的纳米二氧化硅一般为亲水性，不能满足目前的工业要求，因而多需要对其进行表面改性。目前改性方法主要是利用合适的化学物质通过一定的工艺方法使之与纳米二氧化硅表面的羟基发生反应，消除或减少表面硅醇基的量使产品由亲水性变为疏水性，以达到改性的目的。如使用有机硅烷、醇等物质与纳米二氧化硅的表面活性基团发生化学反应，以消耗表面大量自由的活性羟基，改变粉体的表面性能。
稻壳约含20%的木质素，40%左右的纤维素、20%左右的五碳糖聚合物(主要为半纤维素)，另外，约含20%的灰分及少量粗蛋白、粗脂肪等有机化物。稻壳中二氧化硅的质量分数可达到18%左右，具有无定形、杂质少、可再生等优点。稻壳中SiO2凝胶粒子非紧密粘聚而形成的纳米尺度孔隙(<50nm)，以网络状分布，起着骨架作用，木质素、纤维素等填充在网络中，并且木质素、纤维素等物质存在大量羟基。金属以离子吸附方式存在稻壳里，在酸性条件下可以从稻壳里分离出来。
利用稻壳制备纳米二氧化硅，具有原料丰富、成本低廉、可再生性和绿色环保等明显优势。我国是世界上稻谷生产第一大国，2008年，水稻种植面积大约达到4.3亿亩，总产量约1.89亿吨，能产生近4000万吨的稻壳，而全球每年的稻壳总量达到6800多万吨。
 技术问题
本发明所要解决的技术问题是提供一种利用稻壳廉价制备表面改性纳米二氧化硅的方法。该方法制备得到的表面改性纳米二氧化硅为疏水性无定形纳米二氧化硅，粒径为60nm~200nm。
 技术解决方案
为解决上述技术问题，本发明采用的技术方案为：
一种利用稻壳廉价制备表面改性纳米二氧化硅的方法，其特征在于：它包括以下步骤：
（1）将稻壳用含有CO2的处理气预处理，去除金属离子及杂质灰尘，干燥，研磨；
（2）于浓度为0.05 mol/L ~ 0.5 mol/L的磷酸、硼酸、盐酸、甲酸、醋酸、丙酸、丁酸或强酸弱碱盐的稀溶液中浸泡4 ~ 8小时，所述的浸泡温度不高于10℃，抽滤，除去滤液，干燥；
（3）300℃ ~ 450℃厌氧焙烧，得到表面改性纳米二氧化硅。
按上述方案，所述步骤（1）中含有CO2的处理气优选为工业烟气。
按上述方案，步骤（1）所述的利用含有CO2的处理气进行预处理的方法，是在蓄水反应池底部设有用于排放工业烟气的气体分散装置，将稻壳装袋并抛入所述蓄水反应池内，将袋装稻壳压入水面下，然后由气体分散装置将工业烟气喷入池内，利用蓄水反应池内的水压，使工业烟气中的二氧化碳在水中溶解度增大，生成的碳酸溶液和稻壳中的金属离子发生反应生成沉淀物，反应完毕后，清洗稻壳并用去离子水清洗挤压，脱去稻壳上吸附的金属离子。
按上述方案，上述利用含有CO2的处理气进行预处理的方法中蓄水反应池体系中所能达到的二氧化碳溶解度为100克水溶1克二氧化碳。
按上述方案，上述利用含有CO2的处理气进行预处理的方法中所述处理时间为1-6天。
按上述方案，所述蓄水反应池的深度为6~10m。蓄水反应池需具有适宜的深度，满足从池底喷出的工业烟气中的二氧化碳在水中溶解形成浓度适当的碳酸溶液。
按上述方案，所述气体分散装置上开设有使水体涡旋搅动的喷气孔，且工业烟气从所述喷气孔中喷出。水体涡旋搅动时，可进一步增加二氧化碳气体在水中的分散程度，以增加碳酸的形成浓度。
按上述方案，所述的气体分散装置包括纵向输气管和至少一个水平设置、并与纵向输气管的上端相连通的环形输气管，所述环形输气管上沿周向开设有多个倾斜向下的喷气孔，从而可使喷出烟气对水体产生涡旋搅动。
按上述方案，所述喷气孔的轴心线与水平面呈5~35°夹角，更优选为20°。
按上述方案，所述环形输气管的高度与蓄水反应池池底相距1.5米以上。由于碳酸和稻壳在反应过程中会产生沉淀，为了避免沉淀堵塞喷气孔，将环形输气管设置在距离蓄水反应池池底1.5m以上的位置。
按上述方案，所述纵向输气管的管壁上设置有多个倾斜向上的喷气口。利用纵向输气管上的喷气口的排布，使得喷气口喷出的气体可以使得水体达到涡旋搅动，使得上下层的水体可以循环流动，以使得气体溶解后分布均匀，进一步增加气体在水中的溶解度。
按上述方案，所述喷气口的轴心线与竖直方向呈10~45°夹角，更优选为20°。
按上述方案，所述纵向输气管位于环形输气管的中心，且通过横向输气管与所述环形输气管相连通。
按上述方案，所述环形输气管包括上层环形输气管、中层环形输气管和下层环形输气管，所述上层环形输气管、中层环形输气管和下层环形输气管的环形直径大小顺序递增，且由上至下顺序设置在纵向输气管上构成塔式结构。塔式结构的环形输气管可以消除工业烟气分散到水中的死角，对水体形成涡旋形搅动，避免水体里尘埃阻塞喷气孔。
按上述方案，所述气体分散装置中的喷气孔或喷气口内设置有多个微孔曝气头，且工业烟气从所述微孔曝气头中喷出。
按上述方案，所述喷气孔的孔径大小为0.005~0.012mm，所述喷气口的孔径大小为4~6mm。气体从喷气孔喷出时，符合拉普拉斯公式，既球形液面附加压强与表面张力系数成正比，与球面半径成反比；当表面张力系数一定时，半径越小，附加压强越大。喷头孔径越小，喷出的气泡越小，当小的二氧化碳气泡从喷气嘴喷出后，气泡增大，而表面张力迅速减小，气泡破裂，从而增大二氧化碳与水接触面积，提高水中碳酸形成速度。通过改变喷气孔放置水体中的深度和喷气孔的孔径大小，可调整二氧化碳水中溶解量，进而调整碳酸浓度。
按上述方案，步骤（1）所述的利用含有CO2的处理气进行预处理的方法，还可以是在反应罐下部设置有带微孔曝气头的气体分布器，气体分布器下方的反应罐的罐壁上设有循环液出口，在反应罐顶部设置有气体出口、底部设置有沉淀物出口，在反应罐的上部设置有可活动的网格状压袋板；使用所述反应罐时，先在反应罐内装填稻壳和水，用网格状压袋板将稻壳压入液面下，然后将网格状压袋板固定，并保持气体出口为关闭状态，工业烟气从气体分布器上的微孔曝气头中喷出，利用反应罐内的工业烟气本身的压力，使工业烟气中的二氧化碳在水中的溶解度增大，生成的碳酸溶液和稻壳中的金属离子发生反应生成沉淀物，反应完毕后，清洗稻壳并用无盐水清洗挤压，脱去稻壳上吸附的金属离子。
按上述方案，所述网格状压袋板的上方还设有除沫器。
按上述方案，上述利用含有CO2的处理气进行预处理的方法中所述蓄水反应池体系中所能达到的二氧化碳溶解度为100克水溶4克二氧化碳。
按上述方案，所述步骤（2）的浸泡温度优选为-5℃~ 5℃，所述稻壳的质量和浸泡用稀溶液的体积比为1:5 ~ 20g/mL。
按上述方案，所述步骤（2）还包括在干燥前进行洗涤、研磨步骤。
按上述方案，所述步骤（3）中的升温速率为8 ~ 20℃/min；所述的厌氧焙烧时间为1~ 3h。
上述方案中利用工业烟气去除稻壳中金属离子的方法的原理为：利用工业烟气中的二氧化碳溶解在水中生成碳酸，酸化稻壳，与其中的铝、钙、镁、铁、锰等金属离子反应生成难溶盐，反应沉淀物主要为金属碳酸盐或者氧化物，从而能高效地去除稻壳中的金属离子。二氧化碳（CO2）是非极性分子，但可以溶于极性较强的溶剂中，其溶解度大小与温度、压力和溶剂的性质有关，常温常压下饱和水溶液中所溶解的二氧化碳的体积与水的体积比约为1∶1，大部分二氧化碳是以结合较弱的水合物分子形式存在的，只有一小部分形成碳酸，而该浓度的碳酸无法处理大批量的稻壳。当二氧化碳气体压力低于0.5MPa时，其溶解度与压力成正比，超过0.5MPa时，由于碳酸的形成，压力升高时，二氧化碳溶解度增加的幅度将会增大，所以要增加水中碳酸的浓度，以满足去除稻壳中金属离子的要求，提高二氧化碳的气体压力是关键。
为了增加二氧化碳在液面上的平衡压力，可采用三种方式：一种是利用水压，第二种是选取一些气体分散装置，第三种是选用封闭容器增加容器内液面上的气压。本发明所提供的设置蓄水反应池的方法即是利用水压和气体分散装置来提高水中二氧化碳的溶解度，而设置反应罐的方法是利用封闭容器来使容器内的液面上的二氧化碳达到高压力，促使二氧化碳气体溶解，达到较好的金属离子去除效果。
稻壳是一种有机-无机复合材料，无定型二氧化硅与木质素以羟基共价键紧密结合而主要分布在稻壳的木质素层。木质素含有大量酚类物质，由酚或多酚构成，在弱酸条件不易分解。纤维素和半纤维素含有的羟基为直链羟基，结构不同其分解难易程度不一样，通过控制酸的浓度、浸泡温度和浸泡时间，可使纤维素分解成短链的木糖，而又不使木质素中的多酚分解，由此达到防止木质素分解，但也保证了半纤维素、纤维素分解成小分子木糖的目的。然后通过控制焙烧条件，经300℃ ~ 450℃厌氧焙烧，因无定形二氧化硅易与羟基结合，分解后的羟基有机物会结合在无定形二氧化硅表面，并在无定形二氧化硅外面包裹一层有机物，即亲水的羟基基团被大的疏水苯环包在里面而形成疏水二氧化硅，类似二氧化硅表面加修饰剂改性，实现二氧化硅的表面改性。其中：过低的焙烧温度（300℃以下）使二氧化硅较难发生断键形成小粒径的颗粒；过高的焙烧温度（温度超过450℃），二氧化硅又易重结晶聚集成大颗粒，且多酚类物质会明显分解。厌氧也可防止二氧化硅表面的有机物在温度高时燃烧。
本发明利用含有CO2的处理气优选工业烟气对农副产品稻壳进行预处理，除去其中的金属离子及杂质灰尘，然后再用稀酸溶液进行酸浸将纤维素和半纤维素进行进一步降解后，再于350℃~ 450℃厌氧焙烧，使二氧化硅断键，并在其外面包裹一层有机物，即亲水的羟基基团被大的疏水苯环包在里面而形成疏水二氧化硅，类似二氧化硅表面加修饰剂改性，实现二氧化硅的表面改性，制备得到表面改性无定形二氧化硅。
 有益效果
本发明的有益效果：
本发明利用稻壳的成分结构特点，不需要加任何修饰剂，可直接制备得到表面改性纳米二氧化硅，工艺简单可控，低碳环保、综合效益高。由此制备得到的表面改性纳米二氧化硅为无定形纳米二氧化硅，粒径为60nm~200nm，吸油值1.00 ~ 2.50 mL/g，对水的表面接触角>128°，BET比表面积60 ~ 120 m2/g。
其次采用二氧化碳优选采用含有大量二氧化碳的工业烟气（包括电站烟气或工业尾气等）进行稻壳中金属离子的去除反应，既节约成本，又合理利用了工业烟气，避免工业废气污染环境。另经此处理稻壳后的溶液中含有钠、钾、氮、磷、硫等植物需要的营养元素的可溶物，可直接作为植物的营养液，反应沉淀物可用于建筑或作为材料添加剂等用途，不造成水体污染。
 附图说明
图1是本发明实施例1制备的表面改性纳米二氧化硅的透射电镜照片；
图2是本发明实施例1制备的表面改性纳米二氧化硅的XRD图；
图3是本发明实施例1制备的表面改性纳米二氧化硅的能谱图；
图4 是本发明实施例1制备的表面改性纳米二氧化硅的红外图；
图5为本发明实施例1中的蓄水反应池的剖视结构示意图；
图6为图5的俯视结构示意图；
图7为图5中环形输气管和纵向输气管的放大结构示意图；
图8为图7的俯视结构示意图；
图9为本发明实施例2中的反应罐的剖视结构示意图。
图中：蓄水反应池1 ，纵向输气管2 ，环形输气管3 ，上层环形输气管3.1，中层环形输气管3.2，下层环形输气管3.3 ，气体总管4 ，稻壳5 ，横向输气管6，压袋条7 ，循环液出口8 ，气体分布器9 ，沉淀物出口10 ，锥形部11 ，气体出口12 ，网格状压袋板13 ，除沫器14 ，反应罐15。
为了更好地理解本发明，下面结合实施例进一步阐明本发明的内容，但本发明的内容不仅仅局限于下面的实施例；也不应视为对本发明的限制。
 本发明的实施方式
实施例1
1. 取稻壳10kg，用工业烟气预处理，去除金属离子及杂质灰尘，具体为：
（1）如如图5~6所示：设置深度为7m、长宽均为100m的蓄水反应池1，在蓄水反应池1底部设有用于排放工业烟气的25个气体分散装置，所述的气体分散装置包括纵向输气管2和至少一个水平设置、并与纵向输气管的上端相连通的环形输气管3。
具体地，所述环形输气管3上沿周向开设有多个倾斜向下的喷气孔（图未示），从而可使喷出烟气对水体产生涡旋搅动。该喷气孔的轴心线与水平面呈20°夹角。喷气孔的轴心线在水平面上的投影与环形输气管3的环形边相切，且多个喷气孔沿顺时针或逆时针方向分布于环形输气管3上。
具体地，纵向输气管2的管壁上设置有多个倾斜向上的喷气口（图未示），且喷气口的轴心线与竖直方向呈20°夹角。
具体地，所述气体分散装置中的喷气孔或喷气口内设置有多个微孔曝气头，且工业烟气从所述微孔曝气头中喷出。
具体地，环形输气管3的高度与池底相距1.5米。
再如图7、8所示，环形输气管3包括上层环形输气管3.1、中层环形输气管3.2和下层环形输气管3.3，上层环形输气管3.1、中层环形输气管3.2和下层环形输气管3.3的环形直径大小顺序递增，且由上至下顺序设置在纵向输气管2上构成塔式结构。
再如图8所示，纵向输气管2位于环形输气管3的中心，且通过横向输气管6与环形输气管3相连通。
喷气孔的孔径大小为0.01mm，喷气口的孔径大小为4~6mm。
（2） 将稻壳5装袋并抛入蓄水反应池1内，将袋装稻壳5利用压袋条7压入水面下。
（3）将生物质电厂排放的含二氧化碳的工业烟气经过除尘设备除尘后，进入气体总管4，然后由气体分散装置2喷入5.5m深的蓄水反应池内，在这样压力作用下，工业烟气中的二氧化碳与水体的溶解量提高为常温常压时的5倍，溶解度为100克水溶1克二氧化碳，生成的碳酸溶液酸化稻壳5，并与稻壳5中的金属离子发生反应生成沉淀物，反应完毕后，清洗稻壳5并用去离子水清洗挤压，脱去稻壳5上吸附的金属离子。
稻壳处理过程中，产生可溶物和反应沉淀两类，可溶物中富含氮、磷、钾、钠、小分子有机物等，反应沉淀物主要为铝、钙、镁、铁、锰等金属碳酸盐或者氧化物，反应不溶物和烟气中的尘埃沉淀到池子底部形成沉淀层。反应池处理稻壳周期6天，经过两次清洗后，再用去离子水清洗挤压，脱去稻壳中60%~75%的金属离子，一次能处理稻壳量2500吨。
2.将上步预处理后的稻壳凉干、研磨，称量重量为1kg，放进5L摩尔浓度为0.1M的硼酸溶液里，0℃冰浴中浸泡处理8小时，使用抽滤装置，将多余的溶液和硼酸溶液过滤，留下有机质和硅的复合物，110℃干燥；
3. 置于氮气保护的管式炉中以10℃/min的升温速率缓慢升温至400℃，保温1h，得到二氧化硅粉末，将其经透射电镜、XRD、能谱测试及红外测试，测试结果分别见图1-图4；
由图1可知：该二氧化硅粉末中二氧化硅为圆形颗粒，分散均匀，粒径在120nm；
由图2可知：该二氧化硅粉末为无定形二氧化硅结构；
由图3可知：该二氧化硅粉末中含有二氧化硅和有机物；
由图4可知：该二氧化硅二氧化硅外面包裹有有机基团；
另测得：其BET比表面积：100m2/g；
吸油值测试：100g二氧化硅中缓慢加入邻苯二甲酸二丁酯，边加边搅拌，至到二氧化硅以松散的小粒粘成一大团时，计算所耗的邻苯二甲酸二丁酯的体积数。经测试实例1得到二氧化硅的亲油值为1.5 mL/g ；
对水表面接触角：135°。
 本发明的实施方式
实施例2
1. 取稻壳10kg，用工业烟气预处理，去除金属离子及杂质灰尘，具体为：
如图7所示：设置反应罐15，反应罐高15m，内容积1000m3，在反应罐下部设置有带微孔曝气头的气体分布器9，气体分布器下方的反应罐的罐壁上设有循环液出口8，在反应罐顶部设置有气体出口12，反应罐罐底为用来收集沉淀物的锥形部11，反应罐底部设置有沉淀物出口10，在反应罐的上部设置有除沫器14和网格状压袋板13，除沫器设置在网格状压袋板之上。
使用反应罐时，先在反应罐内装填稻壳5和水，稻壳浮在水面上，用网格状压袋板将袋装稻壳压入水面下，将网格状压袋板固定，并保持气体出口为关闭状态，工业烟气从气体分布器上的微孔曝气头中喷出，由于封闭的罐体和微孔曝气条件，反应罐内的工业烟气的压力急剧增加，工业烟气中的二氧化碳与水体的溶解量达到常温常压时的20倍，溶解度为100克水溶4克二氧化碳，生成的碳酸溶液和漂浮其上的稻壳反应，生成沉淀物，反应完毕后，清洗稻壳并用无盐水清洗挤压，脱去稻壳上吸附的金属离子。如此可以脱去稻壳中80%的金属离子，一次可以处理稻壳量100吨。
在处理过程中（处理完毕后），可分别可通过该反应罐顶部设置的气体出口开度的调节，而调节处理过程中反应罐内的压力（或在处理完成后对反应罐进行放空）。处理完成后残留的碳酸溶液可通过循环液出口流出，进行重复利用如直接用于植物的营养液。
2.将上述工业烟气处理后的稻壳，称量重量为1kg，放进摩尔浓度为 0.05M的盐酸溶液中在10℃冰浴中浸泡处理6小时，将多余的溶液和盐酸溶液抽滤，除去滤液，留下有机质和硅的复合物，干燥；
3. 置于氮气保护气氛中、以20℃/min的升温速率升温至350℃，保温2h，得到细小的SiO2粉末样品，经测试，其为无定形结构，粒径为80nm，BET比表面积120 m2/g；吸油值为2.5mL/g，对水表面接触角130°。
 本发明的实施方式
实施例3
1. 取稻壳10kg，用工业烟气预处理，去除金属离子及杂质灰尘，具体为：
（1）如如图5~6所示：设置深度为7m、长宽均为100m的蓄水反应池1，在蓄水反应池1底部设有用于排放工业烟气的25个气体分散装置，所述的气体分散装置包括纵向输气管2和至少一个水平设置、并与纵向输气管的上端相连通的环形输气管3。
具体地，所述环形输气管3上沿周向开设有多个倾斜向下的喷气孔（图未示），从而可使喷出烟气对水体产生涡旋搅动。该喷气孔的轴心线与水平面呈20°夹角。喷气孔的轴心线在水平面上的投影与环形输气管3的环形边相切，且多个喷气孔沿顺时针或逆时针方向分布于环形输气管3上。
具体地，纵向输气管2的管壁上设置有多个倾斜向上的喷气口（图未示），且喷气口的轴心线与竖直方向呈20°夹角。
具体地，所述气体分散装置中的喷气孔或喷气口内设置有多个微孔曝气头，且工业烟气从所述微孔曝气头中喷出。
具体地，环形输气管3的高度与池底相距2.0米。
再如图7、8所示，环形输气管3包括上层环形输气管3.1、中层环形输气管3.2和下层环形输气管3.3，上层环形输气管3.1、中层环形输气管3.2和下层环形输气管3.3的环形直径大小顺序递增，且由上至下顺序设置在纵向输气管2上构成塔式结构。
再如图8所示，纵向输气管2位于环形输气管3的中心，且通过横向输气管6与环形输气管3相连通。
喷气孔的孔径大小为0.01mm，喷气口的孔径大小为4~6mm。
（2） 将稻壳5装袋并抛入蓄水反应池1内，将袋装稻壳5利用压袋条7压入水面下。
（3）将生物质电厂排放的含二氧化碳的工业烟气经过除尘设备除尘后，进入气体总管4，然后由气体分散装置喷入5m深的蓄水反应池内，在这样压力作用下，工业烟气中的二氧化碳溶解度为100克水溶0.5克二氧化碳，生成的碳酸溶液酸化稻壳5，并与稻壳5中的金属离子发生反应生成沉淀物，反应完毕后，清洗稻壳5并用无盐水清洗挤压，脱去稻壳5上吸附的金属离子。
稻壳处理过程中，产生可溶物和反应沉淀两类，可溶物中富含氮、磷、钾、钠、小分子有机物等，反应沉淀物主要为铝、钙、镁、铁、锰等金属碳酸盐或者氧化物，反应不溶物和烟气中的尘埃沉淀到池子底部形成沉淀层。反应池处理稻壳周期2天，经过两次清洗后，再用去离子水清洗挤压，脱去稻壳中60%~75%的金属离子，一次能处理稻壳量2500吨。
2.将实施例1中工业烟气处理后的稻壳，称量重量为1kg，放进20L摩尔浓度为0.5M的醋酸溶液在5℃冰浴中浸泡处理8小时，将多余的溶液和醋酸溶液抽滤，除去滤液，留下有机质和硅的复合物，用去离子水冲洗三次，将稻壳凉干、研磨，110℃干燥；
3.置于氮气保护的管式炉中缓慢升温升温至450℃，保温1h，得到细小的SiO2粉末样品，经测试，其为无定形结构，粒径为100nm，BET比表面积80m2/g；吸油值为2.0mL/g，对水表面接触角128°。
 本发明的实施方式
实施例4
将实施例1中工业烟气处理后的稻壳，称量重量为1kg，放进5L摩尔浓度为0.05M的磷酸溶液中在5℃冰浴中反应5小时，将多余的溶液和磷酸溶液抽滤，除去滤液，留下有机质和硅的复合物，用去离子水冲洗三次，将稻壳凉干、研磨，110℃干燥；
置于氮气保护的管式炉中以10℃/min的升温速率缓慢升温至350℃，保温2h，得到SiO2粉末样品，经测试：其粒径在60nm，BET比表面积120 m2/g；吸油值为2.0，对水表面接触角138°。
 本发明的实施方式
实施例5
将实施例1中工业烟气处理后的稻壳，称量重量为1kg，放进5L摩尔浓度为0.05M的磷酸溶液中在5℃冰浴中反应5小时，将多余的溶液和磷酸溶液抽滤，除去滤液，留下有机质和硅的复合物，用去离子水冲洗三次，将稻壳凉干、研磨，110℃干燥；
置于氮气保护的管式炉中以10℃/min的升温速率缓慢升温至500℃，保温2h，得到SiO2粉末样品，经测试：其粒径在250nm以上，BET比表面积60m2/g；吸油值为1.0，对水表面接触角10°，表明该SiO2粉末疏水性能不好。
上述实施例2-5中吸油值的测试方法同实施例1相同。另外，为达到更佳的金属离子脱除效果，上述两种利用工业烟气进行预处理的方法（蓄水反应池和反应罐方法）中可联合使用，即可先用蓄水反应池方法作一次粗处理，再用反应罐方法作二次精处理，然后再相继进行后续步骤。

Claims (10)

1. 一种利用稻壳廉价制备表面改性纳米二氧化硅的方法，其特征在于：它包括以下步骤：
（1）将稻壳用含有CO2的处理气预处理，去除金属离子及杂质灰尘，干燥，研磨；
（2）于浓度为0.05 mol/L～0.5 mol/L的磷酸、硼酸、盐酸、甲酸、醋酸、丙酸、丁酸或强酸弱碱盐的稀溶液中浸泡4 ～ 8小时，所述的浸泡温度不高于10℃，抽滤，除去滤液，干燥；
（3）300℃～450℃厌氧焙烧，得到表面改性纳米二氧化硅。
2.根据权利要求1所述的利用稻壳廉价制备表面改性纳米二氧化硅的方法，其特征在于：所述步骤（1）中含有CO2的处理气为工业烟气。
3.根据权利要求1或2所述的利用稻壳廉价制备表面改性纳米二氧化硅的方法，其特征在于：步骤（1）所述的利用含有CO2的处理气进行预处理的方法，是在蓄水反应池底部设有用于排放工业烟气的气体分散装置，将稻壳装袋并抛入所述蓄水反应池内，将袋装稻壳压入水面下，然后由气体分散装置将工业烟气喷入池内，利用蓄水反应池内的水压，使工业烟气中的二氧化碳在水中溶解度增大，生成的碳酸溶液和稻壳中的金属离子发生反应生成沉淀物，反应完毕后，清洗稻壳并用去离子水清洗挤压，脱去稻壳上吸附的金属离子。
4.根据权利要求3所述的利用稻壳廉价制备表面改性纳米二氧化硅的方法，其特征在于：所述气体分散装置上开设有使水体涡旋搅动的喷气孔，且工业烟气从所述喷气孔中喷出。
5.根据权利要求3所述的利用稻壳廉价制备表面改性纳米二氧化硅的方法，其特征在于：所述的气体分散装置包括纵向输气管和至少一个水平设置、并与纵向输气管的上端相连通的环形输气管，所述环形输气管上沿周向开设有多个倾斜向下的喷气孔，从而可使喷出烟气对水体产生横向涡旋搅动。
6.根据权利要求5所述的利用稻壳廉价制备表面改性纳米二氧化硅的方法，其特征在于：所述纵向输气管的管壁上设置有多个倾斜向上的喷气口。
7.根据权利要求1或2所述的利用稻壳廉价制备表面改性纳米二氧化硅的方法，其特征在于：步骤（1）所述的利用含有CO2的处理气进行预处理的方法，还可以是在反应罐下部设置有带微孔曝气头的气体分布器，气体分布器下方的反应罐的罐壁上设有循环液出口，在反应罐顶部设置有气体出口、底部设置有沉淀物出口，在反应罐的上部设置有可活动的网格状压袋板；使用所述反应罐时，先在反应罐内装填稻壳和水，用网格状压袋板将稻壳压入液面下，然后将网格状压袋板固定，并保持气体出口为关闭状态，工业烟气从气体分布器上的微孔曝气头中喷出，利用反应罐内的工业烟气本身的压力，使工业烟气中的二氧化碳在水中的溶解度增大，生成的碳酸溶液和稻壳中的金属离子发生反应生成沉淀物，反应完毕后，清洗稻壳并用无盐水清洗挤压，脱去稻壳上吸附的金属离子。
8.根据权利要求1或2所述的利用稻壳廉价制备表面改性纳米二氧化硅的方法，其特征在于：所述步骤（2）的浸泡温度为-5℃～5℃，所述稻壳的质量和浸泡用稀溶液的体积比为1:5~20g/mL。
9.根据权利要求1或2所述的利用稻壳廉价制备表面改性纳米二氧化硅的方法，其特征在于：所述步骤（2）还包括在干燥前进行洗涤、研磨步骤。
10.根据权利要求1或2所述的利用稻壳廉价制备表面改性纳米二氧化硅的方法，其特征在于：所述步骤（3）中的升温速率为8～20℃/min；所述的厌氧焙烧时间为1～3h。
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CN102730703B (zh) 2014-05-28
DK2862841T3 (en) 2018-03-12
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