JP2001017859A - Adsorbent comprising carbonized wood - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an adsorbent comprising carbonized wood usable as a deodorant and an adsorbent of an environmental pollutant by optimally controlling a carboning condition of a woody material. SOLUTION: A woody material is baked in a carbonizing furnace into which inert gas is introduced to form carbonized material and a specific chemical component is exposed to the surface of the carbonized material to hold adsorbing power by the specific component. Concretely, the woody material is baked at high temp. in the carbonizing furnace into which inert gas introduced to obtain carbonized wood having an alkali component eluted to the surface thereof or baked at medium-high temp. therein to obtain carbide having acidic oxide exposed to the surface thereof. As the woody material, lumber from thinning of SUGI (Japanese cedar) or HINOKI (Japanese cypress) being a needle- leaf tree is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material for improving the alkali expression of carbides and the chemical properties of carbide surfaces by optimally controlling the carbonization conditions of wood-based materials, and adsorbing and removing various environmental pollutants. The present invention relates to an adsorbent composed of a woody carbide which can be used as an adsorbent.

[0002]

2. Description of the Related Art In general, charcoal is a wood charcoal produced by carbonizing wood-based materials by self-combustion in a kiln with a low oxygen concentration. A method of using the deodorizing property is known.
Even in the case of mass production industrially by heating and carbonizing with a gas burner or the like in a rotary kiln, the self-combustion method is similarly used.
In the case of this self-combustion method, the carbonization temperature varies depending on the kiln and the carbonization conditions at that time, but is generally in the range of 500 to 800 ° C., and is produced in a large temperature distribution range.

On the other hand, thinning materials such as cedar and cypress, which are discharged in large quantities in domestic planted forests, have been left in forested land due to the increase in transportation costs and the aging of forestry workers. Most of these are social issues in terms of cultivating forests and maintaining ecosystems. Effective utilization of such thinned lumber and wood industry residues that have been discarded in large quantities has become one of today's issues.

[0004] Further, in the current industrial society, various types of environmental pollutants are being released, and in order to maintain the global environment well, these environmental pollutants must be effectively removed. Preventing release to the environment is an important issue. As conventional adsorbents for environmental pollutants, activated carbon, mineral adsorbents such as alumina, zeolite and silica, and ion exchange resins are known.

[0005] Particularly in the field of environmental purification, activated carbon is widely used as an adsorbent, and many activated carbon manufacturers produce more than 120,000 tons of activated carbon per year, and import more than 70,000 tons per year from overseas. Approximately half of activated carbon is used for water treatment and the other half is used for deodorization and gas adsorption as a measure against environmental pollution.

[0006]

As described above, wood-based carbides such as charcoal can be used for fuels, absorbents such as moisture absorbents, harmful gases and the like, but conventional wood-based carbides can be produced. At the present time, there is no means for controlling carbonization conditions such as carbonization temperature and atmosphere according to the substance to be removed. Therefore, the quality of the obtained adsorbent varies greatly, and there is a drawback that reproducibility is poor particularly when the adsorption characteristics of harmful substances are measured. Activated carbon, which is widely used as an adsorbent in the field of environmental purification,
An activation step under the supply of oxygen gas is required after carbonization of ordinary charcoal, which causes a problem that the number of manufacturing steps increases and the product price rises.

[0007] In general, charcoal made from conifers such as cedar and hinoki has a larger surface area than charcoal made from hardwood such as oak and oak, and has a higher adsorptive power. Therefore, it is promising for application development as an adsorbent. Material. In particular, it is important to effectively use unused thinned wood such as cedar and cypress left in forest land as wood resources.

[0008] In addition, the deodorizing action and the adsorbing action of charcoal have been empirically recognized as one of the functions of charcoal. However, woody materials have a fine structure such as pores and a surface of carbide in the carbonization process. Since physical and chemical changes such as the properties of the oxides are involved, it is considered that excellent adsorbability can be exhibited by controlling the carbonization conditions according to the target substance. In particular, the adsorption performance of charcoal is greatly affected by the carbonization temperature in addition to the factors due to the difference in tree species, and due to the difference in the carbonization temperature, the physical properties such as the surface area and pore distribution of carbides and the types of functional groups on the carbide surface are large. Differently, there is a difference between the amount of harmful gas adsorbed per unit weight and the type of substance that can be adsorbed.

The reproducibility of the carbonization conditions is high in a small-scale firing furnace on an experimental scale, but the temperature distribution in the furnace is large in a large-scale firing furnace. In addition, variations in the quality of carbides increase.

Therefore, the present invention solves such problems of the conventional woody carbides and optimally controls the carbonization conditions of the woody material, thereby deodorizing and adsorbing environmental pollutants. It is an object of the present invention to obtain an adsorbent composed of a wood-based carbide that can be effectively used as an adsorbent.

[0011]

According to the present invention, in order to solve the above-mentioned problems, a wood-based material is fired in a carbonization furnace into which an inert gas has been introduced to form a carbide, and a specific chemical substance is formed on the surface of the carbide. A specific chemical component on the surface of the carbide by controlling the carbonization conditions of the wood-based carbide by controlling the carbonization conditions of the wood-based carbides. By controlling the carbonization conditions of the wood-based carbide, to express a specific chemical component on the carbide surface, and by controlling the surface area of the carbide, the specific component and the controlled surface area The basic means is to maintain the adsorptive power and to make the specific components alkaline, basic oxides and acidic oxides.

As a specific means, a wood-based material obtained by firing at high temperature in a carbonization furnace into which an inert gas has been introduced is immersed in a liquid layer to elute an alkali component on the surface, and is adsorbed by the alkali component. Increase volume. By setting the firing temperature in the carbonization furnace to about 1100 ° C., an alkali component is exposed on the carbide surface. The substances adsorbed by the alkali component in the liquid phase are cadmium and lead, and the main component of the alkali component appearing on the carbide surface is potassium.

Further, the wood-based material is fired at a high temperature in a carbonization furnace into which an inert gas has been introduced to expose a basic oxide on the surface and to be adsorbed by the basic oxide. The content of the basic oxide on the carbide surface is increased by setting the firing temperature in the carbonization furnace at 600 to 800 ° C. The substance adsorbed in the gas phase by the basic oxide is an acidic gas such as hydrogen sulfide and methyl mercaptan, and a volatile organic compound such as formaldehyde. The substance adsorbed in the liquid phase by the basic oxide is mercury.

Further, the wood-based material is calcined at a low temperature in a carbonization furnace into which an inert gas has been introduced, so that an acidic oxide is exposed on the surface and is adsorbed by the acidic oxide. By setting the firing temperature in the carbonization furnace at 300 to 500 ° C., the acidic oxide on the carbide surface is exposed. The substance adsorbed in the gas phase by the acidic oxide is a basic gas such as ammonia, amine or amide. In addition, conifers such as cedar and cypress are used as the wood-based material.

According to such an adsorbent made of a woody carbide, an alkali component is exposed on the surface of the carbide by baking at a high temperature in a carbonization furnace. It acts as an adsorbent for cadmium and lead in the phase. In addition, a basic oxide is exposed on the surface by medium-high-temperature baking in a carbonization furnace, and the basic oxide is used as an adsorbent for volatile organic compounds such as formaldehyde in the gas phase and in the gas phase. It acts as an adsorbent for acidic gases such as hydrogen sulfide and methyl mercaptan, and acts as an adsorbent for mercury in the liquid phase. Further, by the low-temperature firing in the carbonization furnace, an acidic oxide is exposed on the surface, and the acidic oxide acts as an adsorbent for a basic gas such as ammonia, amine, or amide in a gas phase.

That is, while the surface of the woody carbide carbonized in the low temperature range shows an acidity, the woody carbide carbonized in the middle temperature range shows a basic property due to a decrease in acidic groups, and further shows a high temperature range. The alkali component is exposed on the surface of the wood-based carbide fired in the above. Therefore, wood-based carbides that are carbonized in the low temperature range are used as selective adsorbents for basic gases such as ammonia, amines, and amides, and wood-based carbides that are carbonized in the middle temperature range are acid gases such as hydrogen sulfide and methyl mercaptan. It can be used as a selective adsorbent for malodorous substances such as mercury and mercury, and a wood-based carbide carbonized in a high temperature range can be effectively used as a selective adsorbent for cadmium and lead. It can also contribute to the purification of water and soil contaminated with heavy metals, recovery as valuable metals, and measures to release formaldehyde from building materials. By doing so, it is possible to effectively utilize forest thinning, which is a valuable wood resource, to help revitalize forestry.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of an adsorbent comprising a woody carbide according to the present invention will be described below. Since the present invention involves physical and chemical changes such as microstructures such as pores and the properties of oxides on the carbide surface during the carbonization process, the carbonization conditions are controlled by controlling the carbonization conditions according to the target substance to be removed. By expressing a specific chemical component on the surface of the carbide and controlling the surface area of the carbide, the specific component and the controlled surface area allow the excellent adsorption function and deodorization function to be exhibited. It is characterized in that the components are alkaline components, basic oxides and acidic oxides.

As described above, in order to reduce the variation in the quality of carbides and to ensure uniformity, a carbonization furnace capable of controlling the temperature into which an inert gas is introduced is required. Therefore, in the present invention, the temperature distribution at the set temperature at the time of firing is controlled to about ± 5 ° C. by using a nitrogen introduction type electric carbonization furnace. The performance of the obtained carbide as an environmental purification material for pollutants such as heavy metals in the liquid phase and volatile organic compounds in the gas phase was examined.

As raw wood, coniferous cedar and cypress wood flour were used. Each of them was wood flour discharged during wood processing, and about 100 liters were used for each. The size of the wood flour was 2 mm or less in diameter and was appropriate as the size of the sample used for the adsorption test. Therefore, the obtained wood flour was used as it was for carbonization. It should be noted that other conifers or broadleaf trees other than cedar and cypress can be used, but cedar and cypress are suitable as those having high adsorption ability.

The carbonization apparatus includes a vertical electric annular furnace (ADVAN).
TEC company: OKT-S type) was used. Stainless steel core tube inside furnace body (Length 1000mm x Inner diameter 135mm)
Was filled with 6 liters of raw wood flour dried at 110 ° C. for 24 hours, and both ends thereof were fixed with ceramics wool and carbonized. The carbonization temperature was 9 levels at intervals of 100 ° C. in the range of 300 ° C. to 1100 ° C., and the carbonization time was 1 level of 5 hours. Further, the inside of the furnace was previously purged with nitrogen gas for one hour, and during the carbonization process, nitrogen gas was fed into the furnace at a flow rate of 4 liter / min from the temperature raising process to the temperature lowering process to form an inert atmosphere.

The change in weight of the sample with respect to the carbonization temperature was determined by measuring the weight of the sample before and after carbonization (filled sample: 6 liters). In addition, the measurement of ash content of the raw wood is carried out by measuring the residue on ignition of the activated carbon test method (JIS K14).
74). That is, about 0.5 g of raw wood flour
Was put in a crucible and heated at 850 ° C. for 5 hours to incinerate.
For heating, use an electric muffle furnace (ADVANTEC: K
M-280) was used.

The infrared absorption spectrum of the carbide is measured by a Fourier transform infrared spectrophotometer (manufactured by Shimadzu Corporation: FT).
IR-8600) using the KBr tablet method.

According to the present invention, a wood-based carbide having controlled carbonization conditions such as a carbonization temperature and a carbonization atmosphere can be used not only as a deodorant and a gas adsorbent in a gas phase but also in a liquid phase. Show characteristics. For example, cadmium (C
Even for heavy metals such as d), lead (Pb) and mercury (Hg), charcoal obtained in a specific carbonization temperature range is superior to activated carbon in terms of adsorption amount and adsorption speed. Therefore, since the carbide according to the present invention can be used as an adsorbent for heavy metals contained in wastewater or soil, it can be widely used in the field of environmental pollution countermeasures in combination with a gas phase purifier.

When focusing on gas adsorption, a carbonization temperature of 50
At 0 ° C., it has good adsorption to basic gases such as ammonia, and at 800 ° C., it has good adsorption to acidic gases such as hydrogen sulfide. When the carbonization temperature is 600 ° C., VOC (Vol
Atile Organic Compound (a volatile organic compound) exhibits excellent adsorptivity to formaldehyde. Conifers are superior to hardwoods in terms of such gas adsorbability. Among them, cedar is carbonized at an optimum carbonization temperature, so that it exhibits an adsorbability equivalent to activated carbon or several times higher than activated carbon.

Hereinafter, six examples of specific adsorption characteristic measurement will be described. (1) Measurement of Cd adsorption characteristics in liquid phase Carbide: Sugi, Hinoki Comparative sample: Commercial activated carbon Optimum carbonization temperature Sugi 1100 ° C

(2) Measurement of Pb adsorption characteristics in liquid phase Carbide: Sugi, Hinoki Comparative sample: Commercial activated carbon Optimum carbonization temperature Sugi 1100 ° C.

(3) Measurement of Hg adsorption characteristics in liquid phase Carbide: Japanese cedar, hinoki Comparative sample: Commercial activated carbon Optimum carbonization temperature Japanese cedar 800 ° C.

(4) Measurement of formaldehyde adsorption characteristics in gas phase Carbide: Japanese cedar, hinoki, Japanese red pine, Japanese oak Comparative sample: Commercial activated carbon, commercial mineral adsorbent Optimum carbonization temperature Japanese cedar 600 ° C

(5) Measurement of Adsorption Characteristics of Ammonia Gas in Gas Phase Carbide: Japanese cedar, hinoki Comparative sample: Commercial activated carbon Optimum carbonization temperature Japanese cedar 500 ° C.

(6) Measurement of hydrogen sulfide gas adsorption characteristics in the gas phase Carbide: Sugi, Hinoki Comparative sample: Commercial activated carbon Optimum carbonization temperature Sugi 800 ° C.

FIG. 1 shows C and C of cedar carbide and activated carbon in the liquid phase.
FIG. 2 is a graph showing the Cd adsorption characteristics of hinoki carbide and activated carbon in the liquid phase, both of which are 0.2 g of a sample and a Cd aqueous solution of 5.0 / d.
1-50 ml, shaking 200 rpm, pH of the liquid phase on the cedar carbide side is 3.5, pH of the liquid phase on the hinoki carbide side is 3.5.
3. The carbonization temperature is 400 ° C, 600 ° C, 800 ° C, 100
0 ° C. and 1100 ° C. Fig. 3 shows Cd against the Cd equilibrium concentration (mg / l) of cedar carbide, hinoki carbide and activated carbon.
It is a graph of Cd adsorption isotherm showing d adsorption amount (mg / g).

Compared with the graphs of FIGS. 1 and 2, the cedar has a higher adsorption speed than the hinoki, and the charcoal of 1100 ° C. of the cedar has the largest adsorption power than the saturated adsorption amount shown by the adsorption isotherm in FIG. It showed better adsorption performance than activated carbon.

Woody materials are accompanied by changes in microstructure such as pores and physical and chemical changes due to thermal decomposition of constituents such as cellulose and lignin during the carbonization process. Figure 4 shows the carbonization conditions (temperature and time) and BE for the carbides of cedar and hinoki.
4 is a graph showing a relationship between T specific surface area (m ² / g), and each sample size was 250 μm or less. According to FIG. 4, the BET specific surface area shows a maximum under the conditions of a carbonization temperature of 600 ° C. for 5 hours, and the BET specific surface area is increased by raising the temperature to 600 ° C. or more.
The ET specific surface area has decreased.

FIG. 5 is an infrared absorption spectrum of the cedar carbide, and FIG. 6 is an infrared absorption spectrum of the hinoki carbide. The carbonization condition is 5 hours at a predetermined temperature, and the nitrogen gas flow rate is 4 hours.
The measurement method was based on the KBr tablet method.

According to FIGS. 5 and 6, in the time carbonization process, up to 600 ° C., the specific surface area increases due to the increase in pores accompanying the decomposition of organic substances, but at 600 ° C. or higher, the carbonization occurs due to the progress of carbonization. The specific surface area has decreased. Since the Cd adsorption amount increases as the temperature rises and reaches a maximum value at 1100 ° C., no particular correlation is seen between the specific surface area of the carbide and the adsorption power.

FIG. 7 is a graph showing the relationship between the carbonization temperature and the pH of the carbide. As the carbonization temperature rises, the pH rises to show alkalinity. FIG. 8 is a graph showing the relationship between the carbonization temperature and the alkali elution amount (mg / l). FIG. 8A shows the magnesium elution amount, and FIG.
Is the amount of calcium eluted, and FIG.
FIG. 3D shows the potassium elution amount. The alkali elution amount of each component increases with the rise in the carbonization temperature, and particularly, since the potassium elution amount is remarkably observed,
It is considered that the pH change is mainly caused by the elution of potassium.

Since there is a correlation between the change in pH, the amount of potassium eluted, and the amount of Cd adsorbed on carbides, the amount of potassium eluted and the amount of Cd adsorbed are closely related. That is, when Cd comes into contact with the carbide in the liquid phase, a mechanism is conceivable in which a high concentration of alkali on the surface of the carbide precipitates as hydroxide on the surface or in the pores. Accordingly, the decomposition of the organic substance proceeds with the rise of the carbonization temperature, and the alkali component is easily released, so that the higher the temperature of the carbide, the higher the adsorption power.

FIG. 9 is a graph showing a comparison of the alkali elution amount of the carbides of cedar and hinoki. The alkali elution amount of cedar is larger, and particularly the potassium elution amount indicated by K in the figure is remarkable. The high adsorbability of cedar also results from the alkali elution amount. K initially eluted from carbide
Although an ion exchange reaction between Cd and an alkali component such as was considered, the stoichiometry was not found when comparing the amount of alkali elution and the equivalent of the amount adsorbed, and the above-described deposition mechanism by alkali more closely matches the phenomenon. I do.

FIG. 10 is a graph showing the Cd recovery rate (%) with respect to the pH in comparison with the cedar carbide and the activated carbon. The adsorbed Cd hardly re-elutes by washing with water near neutrality and is well retained in the carbide. Have been. Cleaning solution pH
When the Cd is changed, the adsorbed Cd comes to be eluted with an acidic solution.
It was possible to recover. Therefore, when the cedar carbide is applied as an adsorbent, Cd in the waste liquid can be reused as a valuable resource.

FIG. 11 is a graph comparing the Pb adsorption characteristics of cedar carbide and activated carbon in the liquid phase, FIG. 12 is a graph illustrating the Pb adsorption characteristics of hinoki carbide and activated carbon in the liquid phase, and FIG. Pb of charcoal and activated carbon of cedar and hinoki
Pb adsorption amount (mg / g) against equilibrium concentration (mg / l)
6 is a graph of a Pb adsorption isotherm showing FIG. 11, FIG.
In comparison, the cedar had a higher Pb adsorption rate, and the carbide at 1100 ° C. of cedar had the largest adsorption power than the saturated adsorption amount indicated by the adsorption isotherm in FIG. 13, indicating an adsorption performance exceeding that of activated carbon.

As described above, the Pb adsorption in the liquid phase of the carbides of cedar and hinoki is also similar to that of Cd adsorption.
It was found that 0 ° C. carbide was the most excellent in the adsorption characteristics and exhibited an adsorption power higher than that of activated carbon. The adsorption mechanism can be considered to be based on alkali elution as in the case of Cd. It was possible to recover 100% of the adsorbed Pb by washing with a solution of pH 1 as in the case of Cd.

FIG. 14 is a graph showing the Hg adsorption characteristics of cedar carbide and activated carbon in the liquid phase in comparison, and FIG. 15 is a graph showing the Hg adsorption characteristics of hinoki carbide and activated carbon in the liquid phase. 16 and FIG. 17 show Hg equilibrium concentrations (mg /
1 is a graph of an Hg adsorption isotherm showing an Hg adsorption amount (mg / g) with respect to 1). When comparing the graphs of FIG. 14 and FIG. 15, the cedar has a higher Hg adsorption speed, and FIG. 16 and FIG.
800 ° C of cedar from the saturated adsorption amount shown by the adsorption isotherm of
Carbide had the largest adsorption power and exhibited an adsorption performance much higher than that of activated carbon.

For example, the Hg concentration on the horizontal axis of FIG.
When the amount of carbide adsorbed in the Hg solution at 1 l was measured, it was found that the carbonization temperature of cedar was 800 ° C. and the amount of adsorption was the largest. According to the adsorption isotherm, the adsorption power is saturated when the Hg concentration is sequentially increased, so that the adsorption performance can be compared based on the saturated adsorption amount. In FIG. 16, since the saturated adsorption amount was not reached, FIG. 17 shows that the Hg concentration was increased and saturated using cedar carbide at 800 ° C., which has the best adsorption amount among the carbides. In FIG. 17, activated carbon is almost saturated at 20 mg / l, whereas in the case of cedar, it is saturated at around 95 mg / l, and there is a large difference between the respective saturated adsorption amounts.

As to the adsorption of Hg in the liquid phase of the carbides of cedar and hinoki, it was found that the carbides of cedar at 800 ° C. had the best adsorption characteristics and exhibited an adsorption power higher than that of activated carbon. No clear correlation was observed between the adsorption characteristics and the elution amount of alkali such as Cd and Pb. Therefore, the mechanism of adsorption of Hg is considered to be different from the mechanism of adsorption of Cd and Pb. Further, there is no clear correlation between the BET specific surface area showing the maximum value at 600 ° C.

FIG. 18 shows the carbonization temperature and the NaOH adsorption amount (me
q / g), which was used as an index for evaluating the surface acidic oxide content. The acidic oxide content on the carbide surface, which is indicated by the amount of NaOH adsorbed, almost disappears at 600 ° C. or higher. In the infrared absorption spectra of FIGS. 5 and 6, almost all organic matter spectra are observed at around 800 ° C. Is gone. Therefore, it is considered that the adsorption of Hg is closely related to the change in the content of the acidic oxide accompanying the decomposition of the organic substance.

FIG. 19 shows the carbonization temperature and the amount of HCl adsorption (meq
/ G), which was used as an index for evaluating the content of surface basic oxide. a is a control sample and b is a demineralized sample. 400-500 ° C carbonization temperature
In this case, the basic oxide content on the carbide surface, which is indicated by the amount of HCl adsorbed, is extremely low at about 0.2 to 0.3 meq / g, and the acidic oxide is dominant. When the carbonization temperature is from 600 to 800 ° C, the basic oxide content on the carbide surface is as high as 0.3 to 0.6 meq / g, and the basic oxide content around 800 ° C of the control sample is particularly high. ing. Therefore, the basic oxide is dominant. When the carbonization temperature is 900 to 1100 ° C., the basic oxide content on the carbide surface is as low as 0.2 to 0.5 meq / g, and the surface oxide itself disappears to be in a physical adsorption state.

HC of control sample a and decalcified sample b
The difference in the l adsorption amount (meq / g) is due to the alkali elution amount. In the control sample a, HCl is neutralized by the alkali elution, and the apparent HCl adsorption amount increases. On the other hand, the decalcified sample b is a sample in which the alkaline component is washed off in advance so that the apparent amount of HCl adsorption does not increase. Therefore, a more accurate measurement value is obtained for the decalcified sample b. According to FIG. 19, the carbonization temperature is 400 to 5
In the case of a low temperature of 00 ° C., the acidic oxide on the surface becomes dominant and the adsorption amount (mg / g) of ammonia or a basic gas such as amine or amide increases, while the carbonization temperature becomes 600 ° C.
In the case of a medium to high temperature of 800 ° C., a basic oxide becomes dominant instead of the acidic oxide on the surface, and the amount of Hg adsorbed (mg
/ G), acid gas such as hydrogen sulfide and methyl mercaptan, or the adsorption amount of formaldehyde and the like increases.

FIG. 20 is a graph showing the amount of formaldehyde adsorbed on the carbonized fired product in the gas phase with respect to the carbonization temperature using cedar as a sample. FIG. 21 shows hinoki, FIG.
FIG. 23 is a graph in which the amount of formaldehyde adsorbed on the carbonized fired material was similarly examined using hardwood samples. Each sample had a column packing amount of 1.0 g and a flow rate of 1.0 liter / m.
in, temperature 20 ° C, formaldehyde concentration 2000
2500 ppm, and the carbonization time was 1 hour, 2 hours, 3 hours, 4 hours, and 5 hours, respectively.

In the formaldehyde adsorption, a comparison was made between the charcoal made from softwood such as cedar, hinoki and Japanese red pine, and the charcoal made from hardwood oak as a raw material. Among the conifers, cedar showed the largest amount of adsorption, and as shown in FIG. 20, at a carbonization temperature of 600 ° C., the amount of adsorption was about twice that of activated carbon. In addition, these carbides exhibited a larger adsorption amount than the mineral adsorbent aldinite.

The tendency of the cedar to adsorb formaldehyde is correlated with the result of the BET specific surface area shown in FIG. Further, since it is superior to the adsorptive power of activated carbon having a BET specific surface area of about 1000 m ² / g, the influence other than the specific surface area is large, and the basic oxide content shown in FIG. 19 contributes. It is thought that it is. Therefore, it has been found that the formaldehyde adsorption is suitable for those having a large surface area of the carbide and a high basic oxide content.

The adsorption of ammonia gas in the gas phase is 8
Carbides at 400-500 ° C. exhibited better adsorption properties than high-temperature carbides at 00 ° C. or higher. This is due to the content of the acidic oxide shown in FIG. That is, it is considered that since the basic ammonia gas is adsorbed by the acidic oxide on the carbide surface, the content of the acidic oxide is large, and the adsorption amount is increased at 500 ° C. having a relatively large surface area. Accordingly, carbide at a relatively low temperature of about 400 to 500 ° C. can be applied as a selective adsorbent for basic gases such as ammonia, amines and amides.

For adsorption of hydrogen sulfide gas in the gas phase, carbides at 600 to 800 ° C. exhibited better adsorption characteristics than low-temperature carbides at 500 ° C. or lower. This phenomenon is the reverse of that of ammonia, and is also caused by the content of the basic oxide. That is, the acidic oxide decreases and the basic oxide increases with the rise of the carbonization temperature, so that the acidic hydrogen sulfide gas is adsorbed on the basic oxide and the relatively high temperature of 600 ° C.
It is considered that the adsorption amount increased at ~ 800 ° C.
Accordingly, carbides at a relatively high temperature of 600 to 800 ° C. can be applied as selective adsorbents for acidic gases such as hydrogen sulfide and methyl mercaptan.

Therefore, the content of the acidic oxide on the surface is reduced and the presence of the basic oxide is increased by the high carbonization temperature. At a higher temperature, the graphitization proceeds and the oxide itself as a residue of the organic substance is formed. Disappear. As shown in FIG. 18, at 600 ° C. or higher, acidic oxides such as phenol group and carboxyl group almost disappeared, and it is considered that basic oxides such as carbonyl group increased at this point.
At a high temperature of around 1100 ° C., the basic oxide disappears and the organic matter is decomposed as seen in the infrared absorption spectrum.

Therefore, according to the present invention, a large amount of acidic groups such as carboxyl groups are present on the surface of the woody carbide carbonized in the low temperature range, and the surface shows acidity. The acidic groups are reduced and become more basic. By utilizing such characteristics, charcoal carbonized in the low temperature range is used as a selective adsorbent for basic gases such as ammonia, amines, amides, etc. It can be used as a selective adsorbent for acidic gases such as methyl mercaptan, and can be used effectively as a selective adsorbent for cadmium and lead. it can.

Furthermore, recently, in a house with high airtightness and high heat insulation,
VOCs emitted from building materials and wall coverings, particularly formaldehyde, are the causative substances of sick house syndrome, but the charcoal according to the present invention also provides excellent adsorption to VOCs. In addition, since wood-based carbides have a high biocompatibility and provide a living environment for microorganisms, supporting deodorized microorganisms on wood-based carbides not only contributes to the adsorption of harmful gases, but also the organic matter generated by microorganisms. It is also possible to use it as an active purification type high-performance material having a decomposition action.

FIG. 24 shows the relationship between the carbonization conditions of these woody carbides, the specific chemical components appearing on the carbide surface, and the substances adsorbed by the specific components.

By using the excellent adsorption characteristics of woody carbides as described above, purification of water and soil contaminated with heavy metals, recovery as valuable metals, and measures against sick house syndrome by releasing formaldehyde from building materials, or It is possible to contribute to environmental purification as an inexpensive material, such as countermeasures against bad odors caused by acidic and basic gases such as ammonia and hydrogen sulfide, and conifers such as cedar are promising materials for wood-based carbides. It is possible to effectively use the thinning material, which is a woody resource, and it is expected to help revitalize the stagnant forestry.

[0058]

As described above in detail, according to the adsorbent made of woody carbide according to the present invention, when the woody raw material is carbonized to produce a carbide, the adsorbent depends on the substance to be removed. By controlling the carbonization conditions such as the carbonization temperature and atmosphere, it can be used for an expanded use as an adsorbent and a deodorant for environmental pollutants such as harmful gases in addition to use as a fuel or as a moisture absorbent. Further, an activation step under the supply of oxygen gas after carbonization of ordinary charcoal, such as activated carbon, is not necessary, and the effect of reducing the number of manufacturing steps and reducing the product price can be obtained.

According to the present invention, an alkali component is exposed on the surface of a carbide by firing at a high temperature in a carbonizing furnace, so that it is used as an adsorbent for cadmium and lead in a liquid phase, while a base is applied to the surface by firing at a high temperature. By expressing the volatile oxides, it can be used as an adsorbent for volatile organic compounds such as formaldehyde in the gaseous phase, as an adsorbent for acidic gases such as hydrogen sulfide and methyl mercaptan in the gaseous phase, and in the liquid phase. It can be used as a mercury adsorption material. Further, the content of the acidic oxide on the surface can be increased by low-temperature firing in a carbonizing furnace, so that it can be effectively used as an adsorbent for a basic gas such as ammonia, amine or amide in a gas phase.

Further, it can be effectively used for purifying water and soil contaminated with heavy metals, and can easily cope with emission of formaldehyde from building materials.
In addition, thinning materials such as conifers such as cedar and cypress can be used as wood-based materials.Thus, thinning materials, which are valuable wood resources, can be used effectively, and the effect of promoting the activation of forestry can be achieved. Demonstrate.

[Brief description of the drawings]

FIG. 1 is a graph showing a comparison of Cd adsorption characteristics between cedar carbide and activated carbon in a liquid phase.

FIG. 2 is a graph showing Cd adsorption characteristics of hinoki carbide and activated carbon in a liquid phase.

FIG. 3 is a graph of a Cd adsorption isotherm showing a Cd adsorption amount with respect to a Cd equilibrium concentration of cedar carbide, hinoki carbide and activated carbon.

FIG. 4 is a graph showing the relationship between the carbonization conditions of carbides of cedar and hinoki and the BET specific surface area.

FIG. 5 is an infrared absorption spectrum of a cedar carbide.

FIG. 6 is an infrared absorption spectrum of a hinoki carbide.

FIG. 7 is a graph showing a relationship between a carbonization temperature and a pH of a carbide.

FIG. 8 is a graph showing the relationship between the carbonization temperature of carbides and the alkali elution amount.

FIG. 9 is a graph comparing the amounts of alkali elution of cedar and hinoki carbide.

FIG. 10 is a graph showing the Cd recovery rate with respect to pH in comparison with cedar carbide and activated carbon.

FIG. 11 is a graph showing a comparison of Pb adsorption characteristics between cedar carbide and activated carbon in a liquid phase.

FIG. 12 is a graph showing Pb adsorption characteristics of hinoki carbide and activated carbon in a liquid phase.

FIG. 13 is a graph of a Pb adsorption isotherm showing a Pb adsorption amount with respect to a Pb equilibrium concentration of carbides of cedar and hinoki and activated carbon.

FIG. 14 is a graph comparing the Hg adsorption characteristics of cedar carbide and activated carbon in the liquid phase.

FIG. 15 is a graph showing Hg adsorption characteristics of hinoki carbide and activated carbon in a liquid phase.

FIG. 16 shows Hg adsorption amount relative to Hg equilibrium concentration.
Graph of adsorption isotherm.

FIG. 17 shows Hg indicating the amount of Hg adsorption relative to the Hg equilibrium concentration.
Graph of adsorption isotherm.

FIG. 18 is a graph showing the relationship between the carbonization temperature and the amount of adsorbed NaOH.

FIG. 19 is a graph showing the relationship between the carbonization temperature and the amount of HCl adsorption.

FIG. 20 is a graph showing the amount of formaldehyde adsorbed by the carbonized fired product in the gas phase with respect to the carbonization temperature of cedar.

FIG. 21 is a graph showing the amount of formaldehyde adsorbed on a carbonized fired product using hinoki as a sample.

FIG. 22 is a graph showing the amount of formaldehyde adsorbed on a carbonized fired product using red pine as a sample.

FIG. 23 is a graph showing the amount of formaldehyde adsorbed on a carbonized fired product using hardwood as a sample.

FIG. 24 is a graph showing the relationship between the carbonization conditions of woody carbides, specific chemical components appearing on the carbide surface, and substances adsorbed by the specific components. Reference number P2973

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) // C01B 31/08 F-term (Reference) 4D002 AA03 AA06 AA13 AA14 AA32 BA04 DA41 FA01 4D024 AA04 AB16 BA03 BB01 4G046 CA00 CC02 CC03 HA02 HB05 HB07 HC12 4G066 AA04B AA75A BA26 BA36 CA25 CA27 CA29 CA46 CA47 CA52 DA01 DA08 FA22 FA34

Claims (19)

[Claims] Claims 1. A wood-based material is fired in a carbonization furnace into which an inert gas has been introduced to form a carbide, and a specific chemical component is exposed on the surface of the carbide, and the adsorption power is increased by the specific component. An adsorbent comprising a wood-based carbide, characterized in that it is retained. 2. An adsorption method comprising a wood-based carbide, characterized in that carbonization conditions of the wood-based carbide are controlled to cause a specific chemical component to be expressed on the surface of the carbide, and that the specific component retains the adsorptive power. Agent. 3. The specific component and the controlled surface area by controlling a carbonization condition of the wood-based carbide to express a specific chemical component on the carbide surface and controlling a surface area of the carbide. An adsorbent comprising a wood-based carbide, wherein the adsorbent retains the adsorbing power. 4. The adsorbent according to claim 1, wherein the specific component is an alkaline component. 5. The adsorbent according to claim 1, wherein the specific component is a basic oxide. 6. The adsorbent according to claim 1, wherein the specific component is an acidic oxide. 7. A wood-based material fired at a high temperature in a carbonization furnace into which an inert gas has been introduced, is immersed in a liquid layer to elute an alkali component on the surface, and the amount of adsorption is increased by the alkali component. An adsorbent comprising a woody carbide. 8. The method according to claim 4, wherein the calcination temperature in the carbonization furnace is about 1100 ° C., and the alkali component is exposed on the carbide surface.
Or an adsorbent comprising the woody carbide according to 7. 9. The adsorbent according to claim 4, wherein the substance adsorbed in the liquid phase by the alkali component is cadmium or lead. 10. The adsorbent according to claim 4, wherein the main component of the alkali component appearing on the surface of the carbide is potassium. 11. A wood-based material is fired at a high temperature in a carbonization furnace into which an inert gas has been introduced to expose a basic oxide on the surface and to be adsorbed by the basic oxide. Adsorbent composed of woody carbide. 12. A sintering temperature in a carbonization furnace of 600 to 80.
The adsorbent comprising a woody carbide according to claim 5 or 11, wherein the content of the basic oxide on the carbide surface is increased at 0 ° C. 13. The adsorbent according to claim 5, wherein the substance adsorbed by the basic oxide in the gas phase is an acidic gas such as hydrogen sulfide or methyl mercaptan. 14. The adsorbent according to claim 5, wherein the substance adsorbed in the gas phase by the basic oxide is a volatile organic compound such as formaldehyde. 15. The adsorbent according to claim 5, wherein the substance adsorbed in the liquid phase by the basic oxide is mercury. 16. A wood-based material characterized in that the wood-based material is fired at a low temperature in a carbonization furnace into which an inert gas has been introduced, so that an acidic oxide is exposed on the surface and is adsorbed by the acidic oxide. Adsorbent made of carbide. 17. A sintering temperature in a carbonization furnace of 300 to 50.
17. The adsorbent comprising woody carbide according to claim 6 or 16, wherein acidic oxides on the surface of the carbide are exposed at 0 ° C. 18. The adsorbent according to claim 6, wherein the substance adsorbed in the gas phase by the acidic oxide is a basic gas such as ammonia, amine or amide. 19. The adsorbent according to claim 1, wherein a conifer such as cedar or hinoki is used as the wood-based material.