KR20140023827A - Method for preparing hydrophobic surface aerogel by using silica gel recovered from slag and aerogel prepared therefrom - Google Patents

Abstract

The present invention relates to the manufacturing method of hydrophobic aerogel using silica collected from slag and to granular aerogel. The manufacturing method of hydrophobic aerogel using silica collected from slag consists of a first aging step through which 1-10 parts by weight of water per 1 parts by weight of slag is added; a second aging step through which the reactant is aged at 20-90 °C so that silica wet gel and metal salt are obtained; a step for obtaining high purity silica wet gel by washing and filtering the metal salt; a step through which putting the silica wet gel into a mixed solution which includes a silylating agent and one or more kinds of hydrophobic alcohol solvents selected from propanol, n-butanol, n-pentanol, n-hexanol, and n-octanol and simultaneously conducting a sylation process and a solvent substation process; and a drying step. By the present invention, slag can be sufficiently recycled by using silica gel collected from slag, and the hydrophobic aerogel obtained by the present invention has excellent insulating performance, soundproof performance, light weight, and low dielectric performance so that it can be usefully applied to related fields. [Reference numerals] (AA) Slag; (BB) Water; (CC) Aging I; (DD) Inorganic acid; (EE) Forming silica wet gel; (FF) Aging II; (GG) Washing; (HH) Filtering; (II) Silica wet gel + Silylating agent; (JJ) n-butanol and n-pentanol; (KK) Vacuum distillation; (LL) Collecting a solvent; (MM) Water removal; (NN) Drying; (OO) Aerogel

Description

[0001] The present invention relates to a method for producing a hydrophobic aerogel using silica gel recovered from slag and an airgel produced therefrom,

The present invention relates to a method for producing a hydrophobic aerogel using silica gel recovered from slag and an airgel produced therefrom. More particularly, the present invention relates to a method for producing an aerogel using silica gel obtained by treating slag with inorganic acid, The present invention relates to a hydrophobic aerogel produced.

Of the wastes generated in the steelworks, slag contains a large amount of silica (SiO ₂ ) and calcium oxide, and also contains a small amount of metal components such as Al, Fe, Mg and Mn. These slag have generated an enormous amount of 10 million tons per year, and the recycling of such slag is of interest in terms of the recycling of oil resources.

Currently, slag is used as a raw material for roadbed, civil engineering aggregate, or cement, or as a land improvement agent using Ca component or silica component in slag.

However, in order to use the slag as a roadbed material, it is necessary to stand for a certain period of time or to pretreat it with steam or the like in order to prevent the expansion due to free CaO, and therefore there are many restrictions on recycling. In addition, in order to use slag as a raw material for cement, it is very difficult to utilize slag because it is expensive to atomize slag and the burden of logistics cost is insufficient.

On the other hand, silica is used not only in various fields such as dentifrices, paints, coatings, paper, construction materials, catalysts or catalyst carriers, abrasives and adsorbents, but silica gel is also used as a raw material for producing aerogels which are high-tech materials. Therefore, there is a need for a method for recycling slag that can be applied by recovering silica, especially silica gel, contained in the slag.

Accordingly, one aspect of the present invention provides a method for producing a hydrophobic aerogel using silica gel recovered from slag under specific conditions.

Another aspect of the present invention is to provide a hydrophobic aerogel produced using this method.

According to one aspect of the present invention, there is provided a method for producing a slag, comprising: a first aging step in which 1 to 10 parts by weight of water is added per 1 part by weight of slag; Reacting the aged slag with 0.5 to 3 parts by weight of inorganic acid per 1 part by weight of slag; A second aging step of aging the reaction product at a temperature of from 20 캜 to 90 캜 to obtain a silica wet gel and a metal salt; Washing and filtering the metal salt to recover a high purity silica wet gel; The silica wet gel is put into a mixed solution containing at least one hydrophobic alcohol solvent and silylating agent selected from the group consisting of propanol, n-butanol, n-pentanol, n-hexanol and n-octanol, Performing a solvent replacement step at the same time; And a step of drying, wherein the hydrophobic aerogels are recovered from the slag.

It is preferable that the slag is at least one selected from the group consisting of blast furnace slag, steel making slag, electric furnace slag, refining slag, water glass slag, and sponge slag.

The inorganic acid is preferably at least one selected from the group consisting of nitric acid and hydrochloric acid.

The inorganic acid preferably has a concentration of 3N to 12N.

The second aging step is preferably performed for 3 to 48 hours.

The filtration is preferably carried out using any one of the following methods: pressurization at a pressure of 1.5 to 5 atm, reduction at 30 to 200 mmHg, and centrifugation at 1,000 to 10,000 RPM.

It is preferable that the metal salt is washed 1 to 8 times by using water or an alkali aqueous solution of 1N or less so that the pH is 5 to 8 after washing.

Preferably, the silica wet gel is a porous silica wet gel having a moisture content of 70% or greater.

The metal salt preferably includes at least one selected from the group consisting of calcium nitrate, aluminum nitrate, iron nitrate, magnesium nitrate, manganese nitrate, calcium chloride, aluminum chloride, iron chloride, magnesium chloride and manganese chloride.

The silylating agent may be selected from the group consisting of hexamethyldisilane, trimethoxysilane, trimethoxymethylsilane, ethyltriethoxysilane, triethylethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, methoxytrimethylsilane, trimethyl It is preferably at least one selected from the group consisting of chlorosilane, hexamethyldisiloxane (HMDSO) and triethylchlorosilane.

According to another aspect of the present invention, there is provided a particulate hydrophobic aerogel having an average diameter of 2 to 200 mu m of particles produced by the above method.

The particulate hydrophobic aerogels preferably have a specific surface area of 400 to 1300 m ² / g.

The average pore diameter of the particulate hydrophobic aerogels is preferably 7 to 200 nm.

According to the present invention, slag can be usefully recycled by producing aerogels using the silica wet gel recovered from the slag, and the hydrophobic aerogels obtained by the method of the present invention are excellent in heat insulation, soundproofness, light weight, It can be usefully applied to related fields.

1 shows a schematic diagram of an exemplary manufacturing process according to the present invention.
Fig. 2 is a graph showing the distribution of pore diameters of aerogels formed by Embodiment 2 of the present invention. Fig.
3 shows the purity of the silica wet gel formed according to the present invention by measuring the number of times of washing.
Fig. 4 is a graph showing the distribution of particle diameters of aerogels formed by Embodiment 2 of the present invention. Fig.

Hereinafter, preferred embodiments of the present invention will be described. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below.

The present invention relates to a method for producing an aerogel by obtaining silica wet gel contained in slag by aging slag with water and reacting with inorganic acid.

More specifically, according to the present invention, there is provided a method for producing a slag, comprising: a first aging step in which 1 to 10 parts by weight of water is added per 1 part by weight of slag; Reacting the aged slag with 0.5 to 3 parts by weight of inorganic acid per 1 part by weight of slag; A second aging step of aging the reaction product at a temperature of from 20 캜 to 90 캜 to obtain a silica wet gel and a metal salt; Washing and filtering the metal salt to recover a high purity silica wet gel; The silica wet gel is put into a mixed solution containing at least one hydrophobic alcohol solvent and silylating agent selected from the group consisting of propanol, n-butanol, n-pentanol, n-hexanol and n-octanol, Performing a solvent replacement step at the same time; And a step of drying, wherein the hydrophobic aerogels are recovered from the slag. Figure 1 illustrates an exemplary method in accordance with the present invention.

Generally, the slag contains a large amount of silica and calcium oxide, and contains a small amount of other aluminum oxide, iron, manganese, magnesium, molybdenum, phosphorus and the like.

The slag may be any slag known in the art and may be selected from the group consisting of, but not limited to, for example, blast furnace slag, steel slag, electric furnace slag, refining slag, At least one slag may be used. The slag may be used singly or in combination of two or more.

The slag is preferably pulverized in a size of 10 mesh to 500 mesh, preferably 30 mesh to 200 mesh, considering reactivity with inorganic acid and yield.

In the method of the present invention, the silica is converted from a silica sol having an ionic state to a silica wetgel (hydrogel) having a network structure by reacting slag with water and inorganic acid, thereby forming a network structure. In order to obtain the desired silica wet gel, it is important to add water to the slag, aging and stabilizing it, and subsequently reacting the inorganic acid. In order to obtain a silica gel wet gel having particularly desirable characteristics, The step should be performed under specific conditions.

The reaction between the slag and the inorganic acid not only explosively reacts but also the reaction temperature rapidly rises to 150 ° C or higher within a few minutes. Due to the increase of the reaction temperature, poisonous acid vapor is emitted, and a chemically unstable metal salt . For example, nitric acid is converted to nitrite at a temperature of 130 ° C or higher, which is not only unstable but also forms a metal salt of a different nature.

Therefore, in order to prevent the explosion reaction between the slag and the inorganic acid and the problem caused by the increase in the reaction temperature, water is added in an amount of 1 to 10 parts by weight per 1 part by weight of the slag before the reaction of the slag and the inorganic acid in the first aging step, It is preferable to control the reaction temperature and the network structure of the slag and the inorganic acid by aging and stabilize them so that they can be sufficiently contacted. More preferably, the water is added in an amount of 3 to 8 parts by weight per 1 part by weight of the slag.

When water is added in an amount of less than 1 part by weight per 1 part by weight of slag, the reaction occurs explosively and the reaction temperature rapidly increases. When water is added in an amount exceeding 10 parts by weight per 1 part by weight of slag, The aggressiveness is lowered and the silica component of the slag can not be sufficiently eluted. The introduction of water in an amount within the above range is preferable in view of the rapid reactivity of the inorganic acid and the control of the reaction temperature.

On the other hand, the first aging step in which water is added and aged is preferably performed for 1 to 9 hours, more preferably for 2 to 5 hours. If the first aging step is carried out for less than 1 hour, the water is not sufficiently absorbed in the slag and is unstable in reaction with inorganic acid. If the step is carried out for more than 9 hours, There is a problem that this becomes longer.

The reaction between the slag and the inorganic acid proceeds explosively as a spontaneous exothermic reaction, and the reaction proceeds by the contact between the slag and the inorganic acid.

The contacting can be carried out by any means known in the art which allows the slag to contact the inorganic acid and includes, but is not limited to, for example, mixing, mixing, stirring, dropping, .

In the step of reacting the slag with the inorganic acid, 0.5 to 3 parts by weight of inorganic acid is preferably used per 1 part by weight of the slag, and more preferably 1 to 2 parts by weight of inorganic acid is used per 1 part by weight of the slag.

When the inorganic acid is used in an amount of less than 0.5 part by weight per 1 part by weight of the slag, the silica component in the slag is not sufficiently eluted and unreacted slag impurities are mixed. Inorganic acids are used in an amount exceeding 3 parts by weight per 1 part by weight of slag There is a problem that the silica sol in the ionic state of silica does not transfer to the network structure and remains or precipitates as simple silica particles. In view of the reactivity of the slag with the inorganic acid, the sufficient elution of the silica gel component in the slag, and the formation of the silica wet-gel of the stable-type network structure, it is preferable that the inorganic acid is used in the content within the scope of the present invention.

The step of reacting the slag with the inorganic acid may subsequently be followed by a second aging step in which the reactants are aged at a temperature of from 20 캜 to 90 캜 to obtain the silica wet gel and the metal salt. More preferably, the second aging step is carried out at a temperature in the range of 30 캜 to 80 캜. If the temperature is lower than 20 ° C, there is a problem that the gelling time of the network structure becomes very long. When the temperature exceeds 90 ° C, there is a problem that the vaporization of inorganic acid occurs.

On the other hand, the silica wet gel obtained above and the metal salt in the metal salt may be washed and filtered to recover a high purity silica wet gel.

The inorganic acid may be at least one selected from the group consisting of nitric acid and hydrochloric acid, that is, the inorganic acid may be used singly or in combination of two or more.

The slag containing silica gel and the inorganic acid can be reacted, for example, according to the following reaction formulas (1) and / or (2). In the following reaction formula, n is a value that depends on the charge of the metal.

Slag (including Si, Ca, Al, Fe, and Mg) + HNO ₃ → SiO ₂ ↓ + M (NO ₃ ) n, M =

Slag (including Si, Ca, Al, Fe and Mg) + HCl → SiO ₂ ↓ + M (Cl) n, M = Ca, Al,

The inorganic acid used in the present invention may have a concentration of 3N to 12N, more preferably 5N to 10N.

When the inorganic acid having a concentration of less than 3N is used, a larger amount of acid should be used, and when an inorganic acid having a concentration exceeding 12N is used, the inorganic acid is contacted with the slag due to excessive inorganic acid concentration and the reaction occurs explosively There is a problem in that it is difficult to control the reaction so that a silica wet gel of a non-uniform network structure may be formed or a precipitate may be partially formed with silica particles. Use of the inorganic acid at the concentration according to the present invention is preferable in terms of elution of the silica gel component contained in the slag and control of the reaction between the inorganic acid and the slag.

Meanwhile, the second aging step is preferably performed for 3 to 48 hours, more preferably for 10 to 24 hours. If the step is carried out for less than 3 hours, there is a problem that the network structure of the silica gel is not sufficiently formed. If the step is performed for more than 48 hours, due to excessive processing time, There is a problem that the internal structure of the silica wet gel may be shrunk, and furthermore, it is not preferable from the economical point of view.

The addition of the slag and water and the step of reacting the inorganic acid can be carried out in both the stirred reactor and the tubular reactor, but it is preferable to use the stirred reactor in consideration of the reactivity of the network structure. The stirring reactor is equipped with a stirring impeller device inside a cylindrical reactor. The slag is conveyed from the upper end of the cylindrical reactor by a screw conveying device, and passes through a hole or a nozzle provided in the upper part of the cylindrical reactor, Water and inorganic acid are added to form a silica wet gel from the slag. Preferably, the reaction with the inorganic acid is started, and at the same time, the agitation is stopped and the aging process can be proceeded. The silica wet gel having a very stable network structure Can be obtained.

In the reaction product obtained through the reaction between the slag and the inorganic acid and the second aging step, the silica wet gel exists in a solid phase and the salt of the other metal component contained in the slag is present in a dissolved state. Thus, the metal salt may be washed and filtered to recover a high purity silica wet gel.

The metal salt may be at least one selected from the group consisting of calcium nitrate, aluminum nitrate, iron nitrate, manganese nitrate, calcium chloride, aluminum chloride, iron chloride, magnesium chloride and manganese chloride, ≪ / RTI > in solution.

The kind of the metal salt may vary depending on the type of the metal component contained in the inorganic acid and the slag used. The metal salt is dissolved in an ion-binding material, and may be a mixture of various metal salts.

The filtration is preferably carried out using any one of the following methods: pressurization at a pressure of 1.5 to 5 atm, reduction at 30 to 200 mmHg, and centrifugation at 1,000 to 10,000 RPM. When the filtration is performed by centrifugal separation, a centrifugal dehydration apparatus can be used.

In the case of the first filtration method, when the filtration is performed at a pressure lower than 1.5 atm, filtration time becomes longer and excessive processing time is required. When the filtration is performed at a pressure exceeding 5 atm, There is a problem that the structure may be deformed. It is preferable to pressurize and pressurize to a pressure within the range of the present invention to efficiently separate solid silica gel in terms of viscosity, filtration time and energy consumption of the first reaction product.

Alternatively, the filtration may be performed at a reduced pressure of 30 to 200 mmHg. If the reduced pressure is less than 30 mmHg, there is a limitation in the process facility, which may lead to excessive equipment cost and energy cost , And when it is carried out in excess of 200 mmHg, the filtration speed is not high, resulting in an excessive process time.

Alternatively, filtration can be performed by centrifugation at 1,000 to 10,000 RPM with another alternative filtration method. If centrifugation is performed at less than 1,000 RPM, there is a problem that excessive filtration time occurs because the filtration speed is not fast. When the centrifugation is performed at more than 10,000 RPM, there is a limit in the process facility, so that excessive equipment cost and energy cost There is an accompanying problem.

The washing of the metal salt is preferably performed using water or an alkali aqueous solution of 1N or less so that the pH is 5 to 8 after washing. The pH after washing is important because the stability of the reaction can be obtained in the subsequent silylation of the wetting gel and the solvent substitution process, and if the pH after washing is less than 5, the silylation of the wetting gel And the inorganic acid ions remaining in the solvent substitution step interfere with the reaction to cause the hydrophobic treatment to become unstable or uneven. When the pH exceeds 8, there is a problem that the alkaline ions react in the silylation and solvent replacement step of the wet gel. There is a problem that aggregation between the particles occurs or the hydrophobic treatment becomes unstable.

The silica wet gel obtained by filtration above can be obtained in the form of a porous silica wet gel having a water content of 70% or more and exhibits a high purity with a silica content of 95% by weight or more. More specifically, the porous silica gel is obtained in the form of a wet gel, that is, a gel containing 70% or more of water in the porous pores.

As shown in FIG. 2, as the number of washing and filtration increases, the purity of the silica increases. However, when the washing and filtering are performed about 8 times or more, the purity is nearly 100% It is economically unnecessary to carry out further washing and filtration.

Particularly, the silica wet gel is composed of silica particles forming a skeleton and a large amount of water. Here, effectively removing water without shrinking the silica particles forming the skeleton is a very important control condition for recovering the airgel.

In this connection, in the present invention, the hydrophilization of the silica gel, that is, the silylation and the solvent substitution process is performed simultaneously.

That is, the porous silica gel in a wet gel state is a mixed solution containing at least one hydrophobic alcohol solvent selected from the group consisting of propanol, n-butanol, n-pentanol, n-hexanol and n- And refluxing, the surface of the silica gel is hydrophobically modified by silylation and water in the silica gel can be removed by solvent substitution. The airgel can be recovered through the step of performing the silylation and the solvent replacement step simultaneously and the drying step.

The hydrophobicization and solvent replacement process is preferably carried out at about the boiling point of the silylation solution at normal pressure for about 2 hours to 24 hours, and when the refluxing time is less than 2 hours, the silylation is not sufficiently effected depending on the type of silylation agent And an undesired side reaction may occur if it exceeds 24 hours.

In addition, the hydrophobing and solvent replacement step can also be performed by a reduced pressure process. The hydrophilization process and the solvent substitution process by the depressurization process are carried out by adjusting the pressure in the reactor containing the mixed solution and the silica gel to 30 to 200 mmHg and refluxing at 45 to 100 DEG C to carry out silylation and solvent substitution .

The depressurization process can shorten the reaction time as compared with the atmospheric pressure process, and more specifically, complete the reaction within 60 minutes. When the pressure in the reactor exceeds 200 mmHg, the reaction time becomes longer. The lower the pressure, the faster the reaction speed. However, the application of pressure less than 30 mmHg is practically caused by the pressure loss of the connection line connected to the reactor or the vacuum pump itself it's difficult.

On the other hand, it is preferable that the temperature in the reactor is maintained at 45 to 100 ° C because the internal temperature is lowered by the rapid evaporation heat of the solvent, so that it is preferable to supply heat from outside in order to shorten the reaction time to be.

The simultaneous step of silylation and solvent replacement can be carried out, for example, by introducing a mixed solution of the silica gel, a hydrophobic alcohol solvent and a silylating agent into a reactor, controlling the pressure in the reactor to 200 to 30 mmHg, Deg.] C, and then the water is removed and the solvent is refluxed again. This process is repeated until moisture in the silica gel is completely removed to remove moisture in the silica gel and hydrogenate the wet gel. The solvent discharged in the simultaneous silylation and solvent substitution process can be reused by separating into a cooling tube or a centrifuge.

The mixed solution containing the hydrophilic alcohol solvent and the silylating agent used in the silylation and solvent substitution process preferably contains 1-10% by weight of a silylating agent and 90-99% by weight of a hydrophobic alcohol solvent. If the content of the silylating agent is less than 1% by weight, an airgel without surface modification may remain, and if the content of the silylating agent exceeds 10% by weight, a silylating agent not participating in the reaction is produced, .

By the silylation treatment as in the present invention, it is possible to realize a thermal conductivity value higher than that of a conventional airgel powder while using a low concentration of a silylating agent, and the silylation reaction condition is improved to strongly acidic, The surface of the silica gel can be permanently silylated as shown in Formula 1 below.

[Chemical Formula 1]

Specific examples of the silylating agent include, but are not limited to, hexamethyldisilane, trimethoxysilane, trimethoxymethylsilane, ethyltriethoxysilane, triethylethoxysilane, methyltrimethoxysilane, ethyltriethoxysilane, There may be mentioned at least one selected from the group consisting of methoxysilane, methoxytrimethylsilane, trimethylchlorosilane, hexamethyldisiloxane (HMDSO) and triethylchlorosilane, which may be used singly or as a mixture of two or more kinds thereof have.

As in the present invention, a continuous process is possible by simultaneously performing silylation and solvent substitution, and the hydrophobic alcohol solvent used can be sent to a distillation process and reused for solvent replacement of the silica wet gel.

Generally, the solvents which can be used for the solvent substitution of the wet gel in the production of aerogels are 1) to effectively remove the water in the wet gel pores, 2) to satisfy all of the solvent conditions capable of evaporating while giving a capillary pressure as low as possible in the gel structure do.

In order to satisfy these two conflicting conditions, the polarity such as methanol, ethanol, THF, and acetone should not be high, and it should not be non-polar such as heptane, pentane and the like.

In the case of polarity as in the case of electrons, a very large capillary pressure can be imparted to the gel structure at the gas-liquid interface generated at the time of drying. In the latter case, the non-polarity is not compatible with water, This is because it is difficult to remove effectively. Therefore, in the present invention, propanol, n-butanol, n-pentanol, n-hexanol, n-octanol and the like are used as solvents satisfying these conditions.

The hydrophobized silica gel obtained by hydrophobicization and solvent substitution can be dried to obtain a granular airgel. The drying can be carried out under normal pressure or reduced pressure.

When drying is carried out at normal pressure, drying is carried out at about 100 to 250 DEG C, preferably 120 to 150 DEG C, and if the temperature is less than 100 DEG C, the drying rate is too slow and the drying is carried out at a temperature exceeding 250 DEG C , The hydrophilized silylated group may be lost due to pyrolysis.

The time suitable for the drying is affected by the structure of the produced aerogels, the particle size, the type of solvent used, the residual content in the gel structure, and the like. Therefore, the optimal drying time can be determined by measuring the time during which the residual solvent of the dried particles is not detected using a thermogravimetric analyzer (TGA).

On the other hand, in the case of drying under reduced pressure, when the water is completely removed in the hydrophobing and solvent replacement step, the reflux line is closed and the conditions in the reactor are changed to 30-200 mmHg at a pressure of 30-200 mmHg, Deg.] C, drying can be completed within 20 minutes, and a granular aerogel can be obtained.

During drying under reduced pressure, the solvent is selectively evaporated in the vacuum distillation apparatus to a weight ratio of 1: 3 to 1: 5, and then sent to a dewatering device to dewater the solvent as much as possible, It can be dried in a lathe (atmospheric or reduced pressure) oven drier.

When the content of the solvent is less than the above range, it is undesirable because it becomes too powdery, and when the content of the solvent exceeds the above range, unnecessary energy is consumed. This method has the disadvantage of increasing the step to two steps as compared with the process of closing and drying the reflux line, but the energy required to completely evaporate the solvent in the fine pores in the silica can be reduced through the physical dehydration process device.

As in the present invention, the structure of the hydrophobic surface-modified aerogel is permanently maintained and the drying speed is also increased by performing the solvent substitution process together with the silylation followed by the drying process.

Preferably, the permanently hydrophobized aerogels produced by the method of the present invention have a mean particle diameter of 2 to 200 μm, more preferably a mean particle diameter of 4 to 60 μm.

On the other hand, the permanently hydrophobized aerogels produced by the method of the present invention preferably have a specific surface area of 400 m 2 / g to 1300 m 2 / g, more preferably 500 m 2 / g to 800 m 2 / g.

Further, the permanently hydrophobized aerogels produced by the method of the present invention preferably have an average pore diameter of 7 to 200 nm, more preferably 10 to 50 nm.

In addition, the permanently hydrophobized airgel produced by the method of the present invention preferably has an average porosity of 80% or more, more preferably 90% or more. In the present invention, the porosity indicates the percentage of the area occupied by the pore portion on the surface of the entire airgel. When the average porosity of the airgel is less than 80%, the thermal conductivity becomes high.

Hereinafter, the present invention will be described more specifically by way of specific examples. The following examples are provided to aid understanding of the present invention, and the scope of the present invention is not limited thereto.

Example

< Example >

One. From slag  Hydrophobicity using recovered silica gel Aerogel  Produce

Example  One

500 g of wastewater slag (about 50 to 100 mesh) was charged into the stirring type reactor. Then, 500 g of water was injected through a nozzle provided at the upper end and aged for 5 hours. Then, 1,500 g of 6N nitric acid was added through the inner nozzle while agitating the reactor. After the addition of nitric acid was terminated, agitation was stopped at a temperature of 30 to 80 ° C for 24 hours to form a silica wet gel having a network structure, Respectively.

The reaction product contained solid silica wet gel and other metal salts, and the metal salts were metal nitrate salts such as calcium nitrate, aluminum nitrate, iron nitrate, magnesium nitrate, and manganese nitrate, and they were dissolved (eluted) in solution . The reaction product was pressurized at 2 atmospheres, filtered, and washed five times with 0.5 N aqueous ammonia solution to recover a solid porous silica wet gel having a pH in the range of 6 to 6.5, wherein the porous silica wet gel (SiO ₂ ) The water content was 75% by weight.

On the other hand, the silica wet gel was filtered and charged into a distillation type reflux reactor, and 200 ml of trimethoxymethylsilane (TMMS) was added to 1,000 ml of propanol and 2000 ml of n-butanol as a solvent. When the pressure in the reactor is maintained at 100 mmHg and the temperature inside the reactor is 80 ° C, distillation of the solvent causes distillation of the solvent and water simultaneously, resulting in oil-water separation. At this time, the water was separated into the lower part and the solvent was separated into the upper part. Only the solvent layer on the upper side was refluxed and the water was separated. After the water was completely removed, the reflux line was closed and the solvent was evaporated by continued vacuum distillation.

As a result, about 150 g of dried aerogel powder was obtained by evaporating all of the solvent, and 94% of the used solvent was recovered. The thus prepared airgel powder was obtained as a high purity silica airgel whose surface was permanently hydrophobic, had a thermal conductivity of 19 mW / mk, a porosity of 91% and a purity of 94% by weight, and had a specific surface area of about 530 m 2 / Had an average diameter of about 20 탆 to 50 탆 and an average pore diameter of about 216 Å.

Example  2

1,000 g of wastewater slag (about 50 to 100 mesh) was added to the stirring type reactor. Then, 2,500 g of water was injected through the nozzle provided at the top and aged for 5 hours. Then, 2,000 g of 12N hydrochloric acid was added through the inner nozzle while agitating the reactor. After the addition of hydrochloric acid was completed, agitation was stopped at a temperature of 30 to 80 ° C for 12 hours to form a silica wet gel having a network structure, Respectively.

The reaction product contained solid silica wet gel and other metal salts, and the metal salt was a metal hydrochloride such as calcium chloride, aluminum chloride, iron chloride, magnesium chloride, and manganese chloride, and they existed as dissolved (eluted) in solution . The reaction product was filtered under reduced pressure of 50 mmHg atmospheric pressure, and washed with 0.1 N aqueous potassium hydroxide solution six times to recover a solid porous silica wet gel having a pH ranging from 6 to 6.5. The porous silica wet gel (SiO ₂ ) Had a water content of 79% by weight.

On the other hand, the silica wet gel was filtered and charged into a distillation type reflux reactor, and 200 ml of trimethoxymethylsilane (TMMS) was added to 1,000 ml of propanol and 2000 ml of n-butanol as a solvent. When the pressure in the reactor is maintained at 100 mmHg and the temperature inside the reactor is 80 ° C, distillation of the solvent causes simultaneous distillation of the solvent and water, resulting in oil-water separation. At this time, the water was separated into the lower part and the solvent was separated into the upper part. Only the solvent layer on the upper side was refluxed and the water was separated. After the water was completely removed, the reflux line was closed and the solvent was evaporated by continued vacuum distillation.

As a result, all of the solvent was evaporated to obtain about 300 g of dried airgel powder, and 95% of the used solvent was recovered. The thus prepared airgel powder was obtained as a high purity silica airgel whose surface had permanent hydrophobicity, thermal conductivity of 18 mW / mk, 91% porosity and purity of 95% by weight, and had a specific surface area of about 550 m 2 / As shown in Fig. 3, and an average pore diameter of about 234 Å, as shown in Fig.

Example  3

1,000 g of wastewater slag (100 mesh or less) was added to the stirring type reactor. Then, 1,500 g of water was injected through a nozzle provided at the top and aged for 3 hours. Thereafter, 1,000 g of 5N hydrochloric acid and 1,000 g of 5N nitric acid were added to the reactor through the inner nozzle, and the mixture was aged at a temperature of 30 to 80 ° C for 24 hours while the addition of the inorganic acid was stopped. A silica wet gel was formed to recover the reaction product.

The reaction product includes solid silica wet gel and other metal salts and the metal salt may be a metal such as calcium chloride, aluminum chloride, iron chloride, magnesium chloride, manganese chloride, calcium nitrate, aluminum nitrate, iron nitrate, magnesium nitrate, They were present in the solution (eluted) in solution. The reaction product was filtered using a centrifugal separator at 5,000 rpm and washed six times with 0.1 N aqueous potassium hydroxide solution to recover a solid porous silica wet gel having a pH in the range of 6.5 to 7.5, (SiO ₂ ) had a water content of 82% by weight.

On the other hand, the silica wet gel was filtered and charged into a distillation type reflux reactor, and 400 ml of hexamethyldisiloxane (HMDSO) was added to 3000 ml of n-hexanol as a solvent. When the pressure in the reactor is maintained at 50 mmHg and the temperature of the reactor is maintained at 75 ° C, distillation of the solvent causes distillation of the solvent and water at the same time, resulting in oil-water separation. At this time, the water was separated into the lower part and the solvent was separated into the upper part. Only the solvent layer on the upper side was refluxed and the water was separated. After the water was completely removed, the reflux line was closed and the solvent was evaporated by continued vacuum distillation.

As a result, all of the solvent was evaporated to obtain about 310 g of dried airgel powder, and 95% of the used solvent was recovered. The airgel powder thus obtained was obtained as a high purity silica airgel having a permanent hydrophobic surface, a thermal conductivity of 17 mW / mk, a 92% porosity and a purity of 96 wt%, and had a specific surface area of about 610 m 2 / The average diameter was about 25 μm and the average pore diameter was about 342 Å.

Comparative Example  One

500 g of wastewater slag (about 50 to 100 mesh) was charged into the stirring type reactor. Thereafter, 1,000 g of 12N nitric acid was injected through the inner nozzle while stirring the reactor without adding water. After the addition of nitric acid was completed, agitation was stopped at the temperature of 30 to 80 ° C for 24 hours while stirring was stopped, The product was recovered.

The reaction product contained silica wet gel, silica precipitate and other metal salts, and the metal salt was a metal nitrate such as calcium nitrate, aluminum nitrate, iron nitrate, magnesium nitrate, manganese nitrate, etc., and was dissolved (eluted) Respectively. The reaction product was filtered at 2 atmospheres, filtered and washed 6 times with 0.5 N ammonia solution to recover a solid silica wet gel having a pH in the range of 6 to 6.5, wherein the silica wet gel (SiO ₂ ) had a water content of 45 Weight%.

On the other hand, the silica wet gel was filtered and charged into a distillation type reflux reactor. To 1,000 ml of propanol and 2000 ml of N-butanol were added 200 ml of trimethoxymethylsilane (TMMS) as a solvent. When the pressure in the reactor is maintained at 100 mmHg and the temperature of the reactor is maintained at 80 ° C, distillation of the solvent causes simultaneous distillation of the solvent and water, resulting in oil-water separation. At this time, the water was separated into the lower part and the solvent was separated into the upper part. Only the solvent layer at the upper part was refluxed and the water was separated. After the water was completely removed, the reflux line was closed and the solvent was evaporated by continued vacuum distillation.

As a result, all of the solvent was evaporated to obtain about 150 g of dried silica powder, and 94% of the used solvent was recovered. The silica powder thus obtained was obtained as silica gel having a purity of 93% by weight in a dry state, but exhibited a thermal conductivity of 61 mW / mK and a porosity of 56%. The specific surface area was about 810 m 2 / g, About 15 탆 to about 550 탆 and an average pore diameter of about 32 Å.

As shown above, the purity, the average particle size and the specific surface area were good, but the product obtained in Comparative Example 1 had a higher thermal conductivity and a lower porosity than that of Example 1, There is distance.

Comparative Example  2

1,000 g of wastewater slag (about 50 to 100 mesh) was added to the stirring type reactor. Then, 2,500 g of water was injected through the nozzle provided at the top and aged for 5 hours. Then, 2,000 g of 2.5 N hydrochloric acid was added through the inner nozzle while agitating the reactor. After the addition of hydrochloric acid was completed, agitation was performed at 30 to 80 ° C for 12 hours to form a silica wet gel having a network structure, The product was recovered. In this case, the recovery of the silica wet gel of the network structure was unstable at about 50% level as compared with Example 2.

The reaction product contained solid silica wet gel and other metal salts, and the metal salt was a metal hydrochloride such as calcium chloride, aluminum chloride, iron chloride, magnesium chloride, and manganese chloride, and they existed as dissolved (eluted) in solution . The reaction product was filtered under reduced pressure of 50 mmHg atmospheric pressure, and washed with 0.1 N aqueous potassium hydroxide solution six times to recover a solid porous silica wet gel having a pH ranging from 6 to 6.5. The porous silica wet gel (SiO ₂ ) Had a water content of 41% by weight.

On the other hand, the silica wet gel was filtered and charged into a distillation type reflux reactor, and 200 ml of trimethoxymethylsilane (TMMS) was added to 1,000 ml of propanol and 2000 ml of n-butanol as a solvent. When the pressure in the reactor is maintained at 100 mmHg and the temperature inside the reactor is 80 ° C, distillation of the solvent causes simultaneous distillation of the solvent and water, resulting in oil-water separation. At this time, the water was separated into the lower part and the solvent was separated into the upper part. Only the solvent layer on the upper side was refluxed and the water was separated. After the water was completely removed, the reflux line was closed and the solvent was evaporated by continued vacuum distillation.

As a result, about 125 g of the dried airgel powder was obtained by evaporating all of the solvent, and 94% of the solvent used was recovered. The silica powder thus obtained was obtained as silica gel having a purity of 94% by weight in a dry state, but exhibited a thermal conductivity of 68 mW / mK and a porosity of 51%. The specific surface area was about 410 m 2 / g, About 12 탆 to 15 탆 and an average pore diameter of about 21 Å.

As shown above, the purity, the average particle size and the specific surface area were good, but the product obtained in Comparative Example 2 had a higher thermal conductivity and a lower porosity than that in Example 2, There is distance.

Comparative Example  3

1,000 g of wastewater slag (100 mesh or less) was added to the stirring type reactor. Then, 1,500 g of water was injected through a nozzle provided at the top and aged for 3 hours. Thereafter, 1,000 g of 5N hydrochloric acid and 1,000 g of 5N nitric acid were added to the reactor through the inner nozzle, and the mixture was aged at a temperature of 30 to 80 ° C for 24 hours while the addition of the inorganic acid was stopped. A silica wet gel was formed and the reaction product was recovered in the same manner as in Example 3.

The reaction product includes solid silica wet gel and other metal salts and the metal salt may be a metal such as calcium chloride, aluminum chloride, iron chloride, magnesium chloride, manganese chloride, calcium nitrate, aluminum nitrate, iron nitrate, magnesium nitrate, They were present in the solution (eluted) in solution. The reaction product was filtered using a centrifugal separator at 5,000 rpm and the solid silica gel wet gel (SiO ₂ ) was recovered, owing to the omission of the washing process, to obtain a solid porous silica wet gel having a pH ranging from 1.5 to 2.5. Had a water content of 77% by weight.

On the other hand, the silica wet gel was filtered and charged into a distillation type reflux reactor, and 400 ml of hexamethyldisiloxane (HMDSO) was added to 3000 ml of n-hexanol as a solvent. When the pressure in the reactor is maintained at 50 mmHg and the temperature of the reactor is maintained at 75 ° C, distillation of the solvent causes distillation of the solvent and water at the same time, resulting in oil-water separation. At this time, the water was separated into the lower part and the solvent was separated into the upper part. Only the solvent layer on the upper side was refluxed and the water was separated. After the water was completely removed, the reflux line was closed and the solvent was evaporated by continued vacuum distillation.

As a result, about 315 g of the dried airgel powder was obtained by evaporating the solvent, and 94% of the used solvent was recovered. The silica powder thus obtained was obtained as a low purity silica gel having a purity of 44% by weight in a dry state, and had a thermal conductivity of 58 mW / mK and a porosity of 58%. The specific surface area was about 330 m 2 / g, About 18 탆 to 25 탆 and an average pore diameter of about 215 Å.

As shown above, the average particle size and the average pore diameter were good, but the product obtained in Comparative Example 3 had a higher thermal conductivity and a lower porosity than that of Example 3, .

2. Change of purity according to number of washing and filtration

Hydrophobic aerogels were prepared using the silica gel recovered from the slag by the same procedure as in Example 1, except that the number of washing and filtration was varied from 1 to 10.

As shown in FIG. 2, the purity of the silica was increased with the number of washing and filtration, and the purity of the silica was increased with the number of washing and filtration. If the performance is more than about 100%, it is possible to obtain a purity close to 100%.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be obvious to those of ordinary skill in the art.

Claims (13)

A first aging step in which 1 to 10 parts by weight of water is added per 1 part by weight of the slag to aged;
Reacting the aged slag with 0.5 to 3 parts by weight of inorganic acid per 1 part by weight of slag;
A second aging step of aging at a temperature of from 20 캜 to 90 캜 to obtain a silica wet gel and a metal salt;
Washing and filtering the metal salt to recover a high purity silica wet gel;
The silica wet gel is put into a mixed solution containing at least one hydrophobic alcohol solvent and silylating agent selected from the group consisting of propanol, n-butanol, n-pentanol, n-hexanol and n-octanol, Performing a solvent replacement step at the same time; And
Drying step
&Lt; / RTI &gt; wherein the silica is recovered from the slag.
The method according to claim 1, wherein the slag is at least one selected from the group consisting of blast furnace slag, steel slag, electric furnace slag, refining slag, water slag, and loose slag, and a method for producing hydrophobic aerogels using silica recovered from slag .
The method of producing a hydrophobic aerogels according to claim 1, wherein the inorganic acid is at least one selected from the group consisting of nitric acid and hydrochloric acid.
4. The method of producing a hydrophobic aerogels according to claim 3, wherein the inorganic acid has a concentration of 3N to 12N, and recovered from the slag.
The method of claim 1, wherein the second aging step is performed for 3 to 48 hours.
The method according to claim 1, wherein the filtration is carried out by any one of a method of performing filtration at a pressure of 1.5 to 5 atm, a method of performing decompression at 30 to 200 mmHg, and a method of performing centrifugation at 1,000 to 10,000 RPM A process for preparing hydrophobic aerogels using silica recovered from slag.
The method of claim 1, wherein the washing of the metal salt is performed 1 to 8 times using water or an alkali aqueous solution of 1N or less so that the pH is 5 to 8 after washing.
The method of claim 1, wherein the silica wet gel is a porous silica wet gel having a water content of at least 70%.
The method according to claim 1, wherein the first metal salt includes at least one selected from the group consisting of calcium nitrate, aluminum nitrate, iron nitrate, magnesium nitrate, manganese nitrate, calcium chloride, aluminum chloride, iron chloride, magnesium chloride, Wherein the silica is recovered from the slag.
The method of claim 1, wherein the silylating agent is selected from the group consisting of hexamethyldisilane, trimethoxysilane, trimethoxymethylsilane, ethyltriethoxysilane, triethylethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, Wherein at least one selected from the group consisting of methoxytrimethylsilane, trimethylchlorosilane, hexamethyldisiloxane (HMDSO) and triethylchlorosilane is used.
A hydrophobic airgel prepared by the method of claim 1, wherein the average diameter of the particles is 2 to 200 μm.
The hydrophobic airgel of claim 11, wherein the hydrophobic airgel has a specific surface area of 400 to 1300 m ² / g.
The hydrophobic airgel of claim 11, wherein the hydrophobic airgel has an average pore diameter of 7 to 200 nm.

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