JP3663682B2 - Production method of granulated activated carbon - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to granulated activated carbon and a method for producing the same.
The granulated activated carbon produced by the present invention is extremely excellent in terms of immobilization of titanium dioxide to activated carbon particles, and titanium dioxide is present on the surface without filling the pores of the activated carbon. Further, the activated carbon produced according to the present invention has greatly improved the ability to remove harmful substances in water or in the gas phase under irradiation of ultraviolet rays or sunlight. Such activated carbon is used for water treatment, sewage treatment, waste liquid. It is suitably used for treatment, waste gas treatment, malodor removal, and the like.
[0002]
Since activated carbon has a high specific surface area, it has excellent adsorption ability and is used to adsorb and remove harmful substances in water or gas phase.
In recent years, water pollution, marine pollution, air pollution, and the like due to domestic and industrial wastewater have spread globally. Eutrophication of lakes and rivers with domestic wastewater containing synthetic detergents, contamination of groundwater and water sources with organic solvents used in high-tech industries and laundry stores, pollution of water quality due to runoff of agricultural chemicals used in golf courses, etc. Is a representative example.
[0003]
Currently, most of the wastewater treatment methods that are widely used are activated sludge methods. However, since microorganisms are used, conditions such as temperature, pH, gas atmosphere, toxicity are severe, and the above-mentioned agricultural chemicals and organic solvents (halogen compounds) are used. In other words, the surfactants are difficult to decompose and remove, and are ineffective against them. Examples of such biologically difficult-to-decompose organic matter treatment methods include chlorination treatment methods, ozone treatment methods, incineration treatment methods, and activated carbon adsorption methods. The chlorination method has problems such as generation of organic halogen compounds typified by trihalomethane having carcinogenicity by reacting with residual chlorine due to excessive injection or with organic substances contained in the water to be treated. Recently, ozone treatment has been highlighted as an advanced water purification method in water purification plants and the like, but there is a problem that both the equipment cost and the operation cost are expensive. Incineration methods are not practical for dilute solutions. Although the activated carbon adsorption method is a very effective method, the adsorption removal ability of organic halogen compounds is slightly inferior, and it is not effective for all harmful substances in water.
[0004]
The removal of activated carbon by adsorption is also effective in removing harmful substances in the gas phase such as air pollution and malodorous substances. In general, an adsorption technique for polluting components in the gas phase must be effective against low-concentration gases in the presence of water vapor or carbon dioxide. Activated carbon is used for many types of organic and inorganic compounds under such conditions. The activated carbon for gas phase has a particularly large specific surface area and a pore structure with a small pore diameter, and has a large adsorption affinity for low concentration gas. Further, since the surface is hydrophobic, the adsorption affinity for water vapor is small, and harmful gases and odorous substances, particularly organic compounds, mixed in the gas phase can be efficiently removed. However, there are some gases with weak adsorption affinity, and the adsorption removal ability of activated carbon was not universal.
[0005]
On the other hand, since it was discovered in 1969 that light energy can be directly used for water decomposition using a semiconductor photoelectrode having a titanium dioxide crystal as a photoelectrode (Honda-Fujishima effect), Representative photocatalysts can be an effective means for converting light energy into chemical energy, and research and development are actively being promoted in various fields worldwide. Such a reaction is called a photocatalytic reaction, and is a catalytic reaction that proceeds with the aid of light. The catalyst coexists in the reaction system, and the reaction does not proceed by itself, but the reaction is accelerated by light irradiation. Is defined. This photocatalytic reaction is closely related to ordinary catalytic reactions and photochemical reactions, but has a marked difference from those reactions. The driving force of a normal catalyst is heat, and the rate at which the reaction system shifts to the production system varies depending on the presence of the catalyst. Therefore, the role of the catalyst is to control the speed of reaching the equilibrium state defined by the temperature, pressure, etc. of the system, and the reaction achieved is limited to a reaction that can proceed thermodynamically. In contrast, a photochemical reaction changes into a production system when light is absorbed by the reaction system and changes occur in the electronic state and chemical bonding of the substance, and a thermal reaction like a normal catalytic reaction. Then, you can realize a reaction that can't happen.
[0006]
On the other hand, in the photocatalytic reaction, the reaction proceeds only on the surface of the catalyst by the action of the catalyst that has absorbed light and is in an electronically excited state acting on the reaction system. The electronically excited state of this catalyst corresponds to a non-equilibrium state in which only the temperature of the electron is extremely high, as with the excited species in the photochemical reaction, and as a result, the reaction is impossible thermodynamically. The reaction proceeds even under mild conditions. This means that the principle of “catalyst does not change the equilibrium of chemical reaction” known in ordinary catalytic reactions may not hold in photocatalytic reactions, which is an important feature of photocatalytic reactions. ing. This photocatalytic reaction consists of (1) a photoexcitation process in which a semiconductor absorbs light and excites it to generate electron-hole pairs, and (2) the generated electrons and holes are surfaced by potential gradient and diffusion in the semiconductor particles. (3) The surface reaction process in which the holes and electrons moved to the surface cause electron transfer with the substrate adsorbed on the catalyst, and each performs a redox reaction.
[0007]
[Problems to be solved by the invention]
Based on these findings, the present inventors have previously proposed activated carbon in which titanium dioxide having photocatalytic activity is appropriately present on the surface as Japanese Patent Application No. 7-037758.
Further, Japanese Patent Application No. 7-187954 proposes a method for producing coal-based activated carbon as a technique for immobilizing titanium dioxide on the activated carbon surface.
However, there is a problem that coking coal is limited to coal, control of the shape of activated carbon, etc., and furthermore, an activated carbon that has a wide industrial application range, can be selected according to the use, and is not limited to coking coal. Therefore, there has been a demand for a manufacturing method that can easily control the shape.
[0008]
Therefore, as a result of intensive studies to solve the above-mentioned problems, the present inventors have pulverized raw coal, kneaded with a binder, granulated, hardened carbonized, and activated granulated activated carbon. By adding titanium dioxide to the raw coal before granulation, surprisingly, for TiO2, it is placed in a very strong reducing atmosphere called carbonization, and further, steam activation (H2 is generated in the activation process, In addition, even if carbon is present in the surroundings, no by-products such as TinO2n-1 are produced, and it exists as anatase type or rutile type TiO2 having photocatalytic activity. It was found that any one of coke, charcoal, coal, etc. can be selected and the shape of the activated carbon can be freely controlled. Furthermore, according to such a method, titanium dioxide is present on the surface without filling the pores of the activated carbon, and the titanium dioxide is firmly fixed to the activated carbon particles, so that the titanium dioxide has a very small discrete structure. The present invention has been found out.
[0009]
That is, the present invention is a method of pulverizing raw coal, kneading with a binder, granulating, hardening carbonizing, activating and producing granulated activated carbon. In the manufacturing method of the granulated activated carbon characterized by adding.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
First, the raw coal used in the present invention includes, for example, coconut shell charcoal, coke, charcoal, coal and the like, and there is basically no restriction on the raw material. The raw coal is finely pulverized, and the particle size is preferably 100 μm or less, and more preferably 75 μm or less. A caking agent and titanium dioxide are added to the finely pulverized charcoal, heated and kneaded, and granulated by a granulator such as a pelletizer, a compactor or an injection press.
Although it does not specifically limit as a binder used by this invention, In a hardening carbonization process, what hardens | cures at 150-300 degreeC in the air is preferable, and what is carbonized at the temperature of 900 degrees C or less is preferable. Specifically, coal tar, pitch, sugar tightness, sap, starch, thermosetting resin and the like can be mentioned.
[0011]
The titanium dioxide used in the present invention may be rutile type or anatase type, and its crystal form is not limited. Further, the particle diameter is not particularly limited as long as it does not hinder granulation, but it is usually preferably 10 μm or less.
Since the final ratio of activated carbon and titanium dioxide varies depending on the degree of activation, it cannot be specified. The amount of titanium dioxide mixed into the raw coal is not particularly limited, but is preferably within a range that does not impair the granulating property, and is roughly 40% by weight or less, more preferably 30% by weight or less based on finely pulverized coal. . The blending ratio of the binder is preferably about 35 to 60% by weight based on the total weight of the finely pulverized charcoal and titanium dioxide.
[0012]
Depending on the infusibilization temperature of the binder, the granulated molded product is cured at 150 to 300 ° C. in the air, and then heat-dried to about 600 to 900 ° C. to decompose and carbonize the carbonaceous organic matter. Subsequently, activation is performed by heating in the presence of water vapor. The temperature at the time of activation may be higher than the temperature at the time of carbonization, and is preferably 900 to 1100 ° C.
[0013]
By such a production method of the present invention, titanium dioxide can be firmly fixed in the activated carbon grains, the shape can be easily controlled, and there is no restriction of raw coal, and titanium dioxide having photocatalytic activity can be easily and reliably obtained. It can be present on the surface of the activated carbon granules. The activated carbon of the present invention thus obtained can be used in the same manner as conventionally used activated carbon, regardless of the usage method such as fluidized bed and fixed bed. For this reason, the conventional apparatus can be used as it is, and it is not necessary to enlarge the apparatus.
[0014]
Furthermore, by using the activated carbon of the present invention under irradiation of ultraviolet rays or sunlight, the removal of harmful substances in water or in the gas phase is accompanied by decomposition and removal by photocatalytic reaction of titanium dioxide compared to adsorption removal by activated carbon alone. , Its removal ability will increase dramatically. In particular, activated carbon is suitably used for water to be treated or gas to be treated, which contains a large amount of organic halogen compounds, odorous substances, and the like that have been difficult to remove by adsorption. In addition, there are advantages such as that the activated carbon is less likely to grow algae and the time until regeneration of the activated carbon is longer, so that the maintenance and management of the apparatus becomes easier than ever.
[0015]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by the following Example, unless the summary is exceeded.
[0016]
(Example 1)
90 g of coconut shell charcoal is pulverized to about 45 μm or less with a vibratory pulverizer, mixed with 10 g of titanium dioxide (Anatase MC-50) manufactured by Ishihara Sangyo Co., Ltd., and further added with 45 g of pitch as a binder, and heated. The mixture was kneaded and granulated into a 1 mmφ × 3 mm column with a disk petter (manufactured by Fuji Paudal). The molded body after granulation was infusibilized at 200 ° C. in air and cured. Subsequently, carbonization was performed at 750 ° C. in an N 2 5 liter / min air stream, and activation was performed for 2 hours in a 1000 ° C. kiln into which nitrogen gas containing 50 vol% of water vapor was introduced at 1 liter / min. The specific surface area was 1130 m 2 / g as measured by the BET method with a nitrogen adsorption device manufactured by Carlo Elba (Sorptomatic 2100). When the X-ray diffraction measurement of the obtained sample was performed, only carbon and titanium dioxide (anatase and rutile) were found, and no by-product was detected. The solid content concentration of titanium dioxide was 7 wt% as determined by ICP emission spectroscopic analysis.
[0017]
0.2 g of the activated carbon thus obtained was placed in 130 ml of raw water of 25 ppm chloroform, and a chloroform removal test was performed under irradiation of a 140 W ultraviolet lamp while shaking with a constant temperature shaker at 25 ° C. in a quartz container. went. Two hours later, when the chloroform concentration was measured by the headspace method, it was reduced to 4.3 ppm.
[0018]
(Comparative Example 1)
A chloroform removal test was conducted in the same manner as in Example 1 except that the ultraviolet lamp was not irradiated. As a result, the chloroform concentration after 2 hours was 7.5 ppm.
From this, it can be clearly seen that the removal ability is excellent because the photocatalytic function of the activated carbon to which the photocatalytic ability is imparted is not lost.
[0019]
【The invention's effect】
The activated carbon of the present invention can greatly improve the ability to remove harmful substances in water or gas phase, and provides a great industrial advantage. Moreover, the manufacturing method of this invention can manufacture such activated carbon efficiently and easily.

Claims (1)

    In the method of finely pulverizing raw material coal, kneading with binder, granulating, hardening carbonization, activating and producing granulated activated carbon, it is characterized by adding titanium dioxide to raw material coal before granulation A method for producing granulated activated carbon.