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Translation - English Translation from Japanese
(19) Japanese Patent Office (JP)
(12) Official Gazette for Unexamined Patent Applications (A)
(11) Japanese Unexamined Application [Kokai] Patent No.: Hei 6(1994)-315614
(43) Kokai Publication Date: November 15, 1994
(51) Int. Cl.5 Identification Nos. Intra-Bureau Nos.
B 01 D 53/36 102 F 9042-4D
D 9042-4D
ZAB 9042-4D
B 01 J 21/06 ZAB A 8017-4G
21/18 ZAB A 8017-4G
Request for Examination: Not Filed Number of Claims: 5 (8 pages total) (cont. on last page)
____________________________________________________________________
(21) Application No.: Hei 6(1994)-40488
(22) Filing Date: February 15, 1994
(31) Priority No.: Hei 5(1993)-77746
(32) Priority Date: March 11, 1993
(33) Priority Country: Japan (JP)
(71) Applicant: Director-General of the Agency of Industrial Science & Technology (000001144)
1-3-1 Kasumigaseki, Chiyoda-ku, Tokyo-to
(74) 1 sub-agent: Yoshihide Komada (patent attorney) (and 1 other)
(72) Inventor: Akitsuku Ibusuki c/o National Institute for Resources and
Environment, Agency of Industrial Science &
Technology
16-3 Onogawa, Tsukuba-shi, Ibaraki-ken
___________________________________________________________________
(54) [Title of the Invention] Method for Removing Contaminants and Cleaning Material
(57) [Abstract]
[Purpose] To remove nitrogen oxides and the like of concentration in environmental atmosphere.
[Constitution] A cleaning material 13 in the form of a sheet or a panel is constituted by fixing a photocatalyst composed mainly of titanium dioxide or a mixture of titanium dioxide and activated carbon using a fluororesin or the like, and it is installed outdoors by using two external walls of a building 2, etc. The photocatalyst irradiated with the near UV rays in sunlight in a 300 to 400 nm wavelength range is activated to turn the nitrogen oxides or the like in the air into nitric acid and the like which is captured on the surface thereof. On the other hand, a photocatalyst lowered in activity by the accumulation of products is washed by precipitation to restore its function. And volatile contaminants transferred to gas from out of water by using the cleaning material 13, or contaminants in water are decomposed by titanium dioxide.
[Claim(s)]
[Claim 1] A method for removing contaminants in atmosphere characterized by fixing a photocatalyst composed mainly of titanium dioxide or a mixture of titanium dioxide and activated carbon and leaving it outdoors so that it is cleaned by irradiation of sunlight and precipitation.
[Claim 2] A cleaning material characterized by being constituted by molding a photocatalyst powder composed mainly of titanium dioxide or a mixture of titanium dioxide and activated carbon in the form of a sheet or panel using a synthetic resin.
[Claim 3] A cleaning material characterized by being constituted by adhering a photocatalyst powder composed mainly of titanium dioxide or a mixture of titanium dioxide and activated carbon to the surface of a sheet or panel material using an adhesive.
[Claim 4] A method for removing contaminants characterized by transferring the volatile contaminants in water to a gas, and contacting this gas with the cleaning material of claim 2 or 3 while irradiating it with light having a 400 nm or shorter wavelength to decompose the aforesaid volatile contaminants.
[Claim 5] A method for removing contaminants characterized by contacting water containing contaminants with the cleaning material of claim 2 or 3 while irradiating it with light having a 400 nm or shorter wavelength to decompose the aforesaid contaminants.
[Detailed Description of the Invention]
[0001]
[Field of Industrial Application] This invention relates to a method for removing low concentration of contaminants in the environmental atmosphere (nitrogen oxides, etc.) and contaminants in water (volatile organochlorine compounds, etc.), and a cleaning material used in this method.
[0002]
[Prior Art] In order to prevent air pollution caused by nitrogen oxides and the like, emission regulations for contaminants from mobile and stationary sources have been performed so far. However, in spite of these measures against their sources, contaminant concentrations exceeding individual environmental standards are still observed in metropolitan regions, along roads, etc. Hereafter, in addition to detailed countermeasures corresponding to various pollution circumstances, i.e., measures against conventional sources, and environmental measures are demanded by sides being contaminated. However, the removal of environmental contaminants (cleaning the environment) has been partially attempted in the field of water purification of lakes, marshes, and the like but there have been no examples related to the atmospheric environment.
[0003]
[Problems to be Solved by the Invention] This is because removing contaminants with good efficiency is difficult since the concentration of contaminants is extremely low and their diffusibility in air is high. For example, if a conventional ammonia catalytic reducing method or the like was applied to the air in general, a high concentrating ratio was indispensable, which was impractical in terms of energy consumption. It is an object of this invention to provide a method for not only removing low concentration of contaminants from environmental air with good efficiency but also contaminants in air, with the high possibility of being economically reduced to practice with inexpensive materials and substantially no operating costs, and a cleaning material used in this method.
[0004] Meanwhile, although large amounts of volatile organochlorine compounds, such as trichloroethene and tetrachloroethane, are used as degreasers and cleaning liquids in various industries, these volatile organochlorine compounds are carcinogenic, and thus, environmental pollution of drinking water or the like is a social problem. Therefore, it is another object of this invention to provide a method for removing contaminants rendered harmless by readily decomposing volatile organochlorine compounds and the like contained in water, and a cleaning material used in this method.
[0005]
[Means for Solving the Problems] The inventors of the present invention invented a photocatalyst comprising a mixture of titanium dioxide (TiO2) and activated carbon and able to remove nitrogen oxides and the like in air with good efficiency and at room temperature at the ppm level without a pretreatment by irradiation of 300 nm or longer light (Japanese Patent No. 1,613,301) and they developed techniques for applying this photocatalyst to tunnel exhaust treatments (Unexamined Patent Publication No. 3-233100 and 3 other cases). They discovered that the photocatalyst activity could further increase by adding a third constituent, such as iron oxide (III), thereto. The conditions required for this photocatalyst to function include merely cleaning it with irradiation using light and with water. Therefore, the inventors of the present invention considered that these were conditions able to be accomplished relatively easily in a natural outdoor environment, such as irradiation with sunlight and cleaning with precipitation, which led them to achieving the present invention.
[0006] That is, this invention attempts to remove contaminants in environmental air by fixing and leaving outdoors a photocatalyst composed mainly of titanium dioxide or a mixture of titanium dioxide and activated carbon so that they are cleaned by irradiation with sunlight and washing by precipitation. The above photocatalyst should be fixed by composing a cleaning material by premolding a powder of the photocatalyst into the form of a sheet or panel using a synthetic resin and adhering it to the surface of a sheet or panel material using an adhesive.
[0007] Moreover, the inventors of the present invention developed a technique for rendering volatile organochlorine compounds harmless by decomposing them by irradiating waste gas containing volatile organochlorine compounds in the presence of titanium dioxide (Unexamined Patent Publication No. 2-107314). But the above cleaning material is ideal for rendering contaminants in water harmless by applying this technique. That is, this invention attempts to decompose the aforesaid volatile contaminants by transferring the volatile contaminants in water to a gas, then contacting this gas with the above cleaning material while irradiating it with 400 nm wavelength light or less. This invention, moreover, attempts to decompose the aforesaid contaminants by contacting water containing the contaminants with the above-mentioned cleaning material while irradiating it with 400 nm or shorter light.
[0008]
[Effects] UV rays in the long wavelength region of 300 to 400 nm required for activating the photocatalyst is contained abundantly in sunlight. Consequently, by setting this photocatalyst outdoors where it is exposed to sunlight, the low concentration of nitrogen oxides and the like in air are oxidized and can be trapped on the photocatalyst. As the active part of the photocatalyst surface is primarily covered with a product, such as nitric acid, its contaminant-removing capacity decreases gradually over time. But its activity is restored by washing away the product with precipitation. The photocatalyst functions over and over again, and operation and maintenance labor and costs are especially unnecessary.
[0009] To increase the catalytic area between the photocatalyst and air, the photocatalyst should be used as a powder. However, when putting this invention to practical use, if the photocatalyst is contacted the air as a powder, it is difficult to handle it because the photocatalyst scatters and so forth during installation, use, reclamation, recovery, substitution, etc., so it is necessary to fix it to some media. Adhering the photocatalyst to the surface of a structure or the like by using an adhesive or the like is considered as a method for fixing the photocatalyst powder. However, in such a case, if the powdered photocatalyst adheres directly to the surface of the structure, various difficulties in building are anticipated, and construction costs also rise. As a consequence, the photocatalyst powder is composed as a cleaning material formed in advance into the shape of a sheet or panel in a factory, and it is practical to stick it to a structure or the like at the actual site.
[0010] Incidentally, after molding the powdered catalyst with a binder, it is generally worked into any given shape by baking it at a high temperature. However, it is impossible to bake this photocatalyst containing activated carbon at a high temperature of 300°C or higher, and also, a photocatalyst reclaimed using water cannot be applied as this photocatalyst because it is now water-resistant. That is, not increasing the temperature in the manufacturing process too much (preferably keeping it to 200°C or less) and sufficient water resistance and durability are demanded as the conditions for stably fixing this photocatalyst.
[0011] Meanwhile, a fluororesin outstanding in chemical and environmental resistance (polytetrafluoroethylene, etc,) can be molded into any given shape from a powder by exerting pressure on it. Therefore, a cleaning material in the form of a sheet or panel is composed in advance by rolling the fluororesin powder mixed with the photocatalyst powder. Since a fluororesin is hydrophobic, it is expected that the water resistance of the resulting cleaning material will be high and the influence by temperature low. Moreover, since the affinity of the fluororesin with the constituents constituting the photocatalyst is low, each of the constituents simply aggregate mechanically, so it is anticipated that the activity on the photocatalyst surface is not hindered that much due to the presence of the fluororesin. Moreover, it is possible constitute the cleaning material by adhering the photocatalyst to a sheet or panel material comprising metal, resin, inorganic matter, or the like using various adhesives. However, since the types and characteristics of adhesives are diversified, it is necessary to select the most suitable adhesive experimentally.
[0012] When the technique pertaining to Unexamined Patent Publication No. 2-107314 above is put to practical use, various construction difficulties occur, as previously mentioned, in relation to removing contaminants in air if titanium dioxide particles are adhered directly to the wall of a device even if volatile contaminants in water are transferred to a gas and contacted with titanium dioxide. Therefore, in such a case, construction or transport is extremely simple by using the titanium dioxide particles by carrying them on the cleaning material in the form of a sheet or panel.
[0013] The contaminants in water are decomposable even by contacting them with titanium dioxide as is, but in such case, various problems occur if titanium dioxide is used as granules as is. A configuration example of a device for contacting water containing contaminants directly with titanium dioxide particles is shown in Fig. 13. In the drawing, water in which titanium dioxide particles 42 were suspended is accommodated in a reactor 41 having a light source 40 for irradiating light having a 400 nm or shorter wavelength, and stirred with a rotary blade 43. Water containing volatile organochlorine compounds is fed into the reactor 41 through the bottom by a pump 44, and the contained volatile organochlorine compounds contact the titanium dioxide particles 42 and decompose. The water to be treated is transferred to a precipitation tank 46 through an overflow pipe 45, where the titanium dioxide particles 42 are separated, and they are evacuated through an evacuation pipe 47. The titanium dioxide particles 42 settled in the precipitation tank 46 are returned to the reactor 41 by a pump 48.
[0014] However, in such a method using granular titanium dioxide as is, a precipitation tank for separating titanium dioxide particles from water after the treatment is illustrated, pump piping for returning the separated titanium dioxide particles to the reactor, and the like are necessary, the device is complicated, as already described, and managing its operation also is inevitably difficult. By carrying the titanium dioxide particles on the above-mentioned cleaning material, the titanium dioxide particles are fixed, so the aforementioned problems do not arise and the device is simplified.
[0015]
[Practical Examples] First of all, Fig. 6 shows a configuration of the test device used for the indoor test described later. 1 is a high pressure vessel with a standard gas (about 50 ppm concentration) of the contaminants (nitric oxide in this case); 2 is a high pressure vessel with highly purified air for diluting this standard gas; 3 is a decompression valve; 4 is an accurate flow rate regular; 5 is a four-way valve; 6 is a glass Petri dish-type reaction vessel; 7 is a cleaning material sample placed in the reaction vessel 6; 8 is a photochemical fluorescent light (10W × 3 ea.); 9 is a chemiluminescent-type nitrogen oxide meter; 10 is an air pump; and 11 and 12 are exhaust ports. The reaction vessel 6 is provided as two vessels in series and the cleaning material sample 7 is divided and placed in them.
[0016] In the illustrated device, by mixing the standard gas in the high pressure vessel 1 with the air in the high pressure vessel 2 at the proper flow rate ratio determined by the accurate flow rate regular 4, a low concentration of any given simulated polluted air can be generated. And by switching the four-way valve 5, as illustrated, a low concentration of this simulated polluted air is guided to the reaction vessel 6 at a prescribed flow rate, contacted with the sample 7, and this sample 7 is simultaneously irradiated with the near-UV light in the long wavelength region of 300 to 400 nm from the fluorescent light 8. The polluted air (treatment air) is guided to the nitrogen oxide meter 9 by the air pump 10 after contact with the sample 7, the change in the nitrogen oxide concentration is recorded, after which it is exhausted through the exhaust port 11. Then the results of the test for confirming the effect of the cleaning material sample pertaining to this invention on removing contaminants using the device above and a test in which the same cleaning material sample is actually placed in air will be discussed.
[0017] Test Example 1
The photocatalyst and fluororesin particles were mixed sufficiently and subsequently rolled into the shape of a sheet about 1 mm thick. The composition ratio thereof is 6:3:1 (polytetrafluoroethylene resin/titanium dioxide/activated carbon). 2% by weight of iron oxide (III) may be added to the catalyst constituent. Moreover, the catalyst constituent may be titanium dioxide alone, in which case the performance decreases slightly. A sample of this sheet is obtained by cutting it to a size of 10 cm × 10 cm, of which one piece each was supplied to the two reaction vessels 6 (effective area: 200 cm2). The concentration of the nitric oxide (NO) supplied to the reaction vessels 6 is 1.0 ppm and the flow rate of the air is 0.5 L/min. Furthermore, the UV ray intensity at a wavelength of 365 nm was 0.45 mW/cm2 maximum. This corresponds to about one-fourth that on a clear summer day and about half the UV ray intensity on a clear winter day.
[0018] The change in the NO concentration in the treated air at the outlet of the reaction vessel 6 is shown in Fig. 1. The Y axis in the drawing is the NO concentration at the outlet of the reaction vessel 6 and the X axis is the elapsed time after the treatment starts. In the drawing, if the simulated polluted air passes through the reaction vessel 6 by switching the four-way valve 5 without initially performing irradiation of light, the NO concentration at the outlet decreases, adsorbed with a simple removal mechanism even though the photocatalyst in it contains activated carbon; hence, this effect is not long-lasting (but its function can be utilized at night without exposure to sunlight). Therefore, if irradiation of light started as is after about nine hours, the NO concentration at the outlet decreased markedly again. This removal effect was long-lasting; hence, it was considered to be a photocatalytic action, not a simple adsorption phenomenon.
[0019] In this case, the removal rate is shown in Fig. 2 as the initial NO concentration changes. The Y axis in the drawing is the average removal rate to 12 hours after starting the treatment and the X axis is the initial NO concentration in the supplied simulated air. As evident from this drawing, a removal rate greater than 90% is obtained over the investigative initial concentration range (0.05 to 5 ppm) at a flow rate of 0.5 L/min. This removal rate was hardly dependent on the initial NO concentration. If the sample was washed with purified water after testing, nitric oxide equivalent to 60% of the removed NO was recovered. If it was further washed with a weak alkaline solution (1 mM sodium hydroxide) after testing, the recovery rate increased to 80%. However, in relation to removing the nitrogen oxide by merely washing with water, it was seen that the activity was recovered to that before use, enabling use over and over again.
[0020] A test was performed next by placing the above-mentioned sample outdoors in a city (considered to be a nonpolluted area). During the test performed several times, the typical value of the nitrogen oxide washed with water and recovered as nitric acid was 7 μmol/day. Upon considering the usual recovery rate by washing with water (60%), it is reckoned that 11.7 μmol/day (0.5 μmol/hour) of nitrogen oxide was removed. If this value is applied to the results of the indoor testing, 1.0 ppm NO is equivalent to the amount removed by flushing it for 3 days at 2.0 L/min. Assuming the average NO concentration within Tsukuba City is 0.025 ppm, it is reckoned that about 10 L/min. of air in which the sample was placed outdoors could be treated in twenty-four hours. That is, it was clear that the contaminants could be conveyed effectively outdoors to the surface of the sheet by wind, and also, this photocatalyst functioned with good efficiency in an open system. Moreover, 1 mol NO equals 30 g and 1 mol NO2 (nitrogen dioxide) equal 46 g. Therefore, 1 mol nitrogen oxide equals 38 g on average and 1 μmol equals 38 μg.
[0021] Test Example 2
Various adhesive resins (high-viscosity epoxy, low-viscosity epoxy, UV acrylic, high-viscosity-low-speed curing epoxy and spray urethane) were coated on a polyvinyl chloride sheet, subsequently sprinkled with a photocatalyst powder and cured, then washed with water and dried to obtain a sample. The effective surface area of each is 100 cm2. The initial nitric oxide concentration is 1.0 ppm, as in Test Example 1, and the air flow rate is 0.5 L/min. The change in the NO concentration over time at the outlet of the reaction vessel 6 in this case is shown in Fig. 3. As suggestion, in this drawing, the results of a sample having the photocatalyst fixed to a synthetic resin film as a powder by using a double-sided pressure-sensitive tape (effective surface area: 200 cm2) and a sample having the same amount of photocatalyst formed into the shape of a sheet using a synthetic resin (effective surface area: 200 cm2) were shown simultaneously.
[0022] The results upon fixing with an adhesive resin are worse than either the sample adhered as powder or the sheet-like sample. But it is thought that some epoxy resin and urethane resin can be used as the fixing material. The sample having the photocatalyst fixed as a powder has the highest removal effect according to the drawing (∆). Since the area of the sheet having the same amount of catalyst (○) is smaller than in Test Example 1, (consequently, there is an effect for being able to increase the amount of photocatalyst per unit area), there is no epoch-making removal effect, as shown in Fig. 1. Instead, the polluted air diffuses better into the sheet than by using the adhesive resin. It is clear that this is because there is no difference in the case of a powder twelve hours after the start of the treatment. Although it takes time for the polluted air to diffuse into the fluororesin sheet, it is suggested that the photocatalyst not just on the surface of the sheet but inside it also functions.
[0023] Test Example 3
Although its NO removal effects were shown in the above test examples, this photocatalyst is able to equally remove nitrogen dioxide (NiO2) and sulfur dioxide (SO2) as well. Figs. 4 and 5 show the change in the removal rate (12-hour average) of NO2 and SO2 by initial concentration when the sheet-like sample in Test Example 1 is used (test conditions are the same: effective surface area of sample is 200 cm2 and flow rate of simulated polluted air is 0.5 L/min.), respectively. As shown in the figures, a removal rate of 80% or more was obtained for 0.05 to 0.7 ppm of NO2 and a removal rate of 90% or more was obtained for 0.05 to 1.0 ppm of SO2.
[0024] According to the test results above, it is evident that cleaning of the environmental air can be anticipated by attaching the cleaning material of this invention to structures, etc., but a mode will now be described when this is actually carried out. To fix the photocatalyst using a synthetic resin, an air cleaning material in the form of a sheet or panel is constructed according to the following steps. First, a solvent and a surfactant are added to a photocatalyst (titanium dioxide or a mixture of titanium dioxide and activated carbon, or a mixture in which an iron-based metal oxide, such as iron oxide, is further added to this) powder and stirred. The solvent in this case is used for improving the dispersion of the photocatalyst constituent powders, but the surfactant further accelerates the function of this solvent.
[0025] Next, a powder of a resin, such as a fluororesin, is added to this as a binder, then mixed and stirred again. It is subsequently fed to a centrifugal separator to remove the solvent, then it is placed in a mold after kneading it well and compression molded to form a sheet about 0.5 to 1 mm thick. This sheet is finished into a flexible sheet-like cleaning material or a rigid panel-shaped cleaning material by lining it with a resin film and sticking it on a sheet material of stainless steel, resin, gypsum, etc. The size is optional—from a postcard to a tatami mat size. The sheet-like cleaning material also can be made into a roll material. To fix the photocatalyst powder with adhesive, moreover, the adhesive is coated on a resin film or a plate material of a metal, resin, or the like, sprinkled with the catalyst powder, then dried and fixed to obtain a sheet- or panel-shaped cleaning material. The shape and size are the same as in the case of the compression molding.
[0026] The cleaning material above is installed at streets, roads exclusively for cars, and the like which severely pollute the air in consideration of cleaning with sunlight and precipitation. Fig. 7 is an example in which a cleaning material 13 is attached to the outer wall of a building 14 and Fig. 8 is an example in which it is attached to sound insulation plates on both sides of an expressway 15. This is efficient if an existing building or structure is utilized, but as shown in Fig. 9, the cleaning material 13 also can be supported, of course, by exclusively providing the proper frame 16. Meanwhile, the motorway tunnel 17 shown in Fig. 10 ((A) is a plan view; (B) is a longitudinal section), an indoor underground tunnel, or the like, is exposed to the cleaning material 13 from an artificial light source 18, such as a fluorescent lamp for photochemical use. An air-cleaning chamber 19 is partitioned into an upper area in the motorway tunnel 17 in Fig. 10, and the soot in the polluted air in the roadway area introduced by a ventilator 20, as shown by the arrow, is removed first with an electric dust collector 21, then the nitrogen oxide and the like is removed with the cleaning material 13 and returned to the roadway area.
[0027] Working examples of this invention in which volatile organochlorine compounds are decomposed using the aforementioned cleaning material are shown in Figs. 11 and 12. First, Fig. 11 is a block diagram of a device for decomposing volatile organochlorine compounds contained in water by contacting them with the cleaning material after transferring them to a gas. The illustrated device comprises a stripping tank 22, wherein the volatile organochlorine compounds contained in water are transferred to a gas, and a reactor 23 in which this air is decomposed by contacting it with the cleaning material 13. The reactor 23 is composed of the cleaning material 13 using a photocatalyst comprising titanium dioxide (activated carbon is unnecessary in this case), manufactured in the method, already mentioned, and stuck to the inside wall surfaces of a sheath 24 having a square cross section, and the artificial light source 18 for irradiating light having a wavelength of 400 nm or less arranged about the sheath 24.
[0028] In the illustrated device, as the water containing volatile organochlorine compounds, such as trichloroethene and tetrachloroethane, is sent into the bottom of the stripping tank 22 using a pump 25, compressed air is blown into the water from a compressor 26, and the volatile organochlorine compounds are transferred into the air easily. This air is sent to the reactor 23 through an air pipe 27 next, contacted with the cleaning material 13, the volatile organochlorine compounds in the air are decomposed by the titanium dioxide excited by the light from the artificial light source 18, and subsequently released from the reactor 23. Moreover, the treated water is discharged through a drainpipe 28. If exhaust gas having volatile organochlorine compounds that evaporate is treated directly, the stripping tank 22 is unnecessary. In this working example, the cleaning material 13 carrying the titanium dioxide particles can be maintained with sufficient strength; hence, there is no risk of damage, and its construction and transport also are easy. Moreover, the contaminants eligible for this method are not limited to the volatile organochlorine compounds, but they should be volatile and decomposable by titanium dioxide.
[0029] Vis-à-vis, Fig. 12 is a block diagram of a device for decomposing contaminants by contacting water containing them with the cleaning material directly. In the figure, the same cleaning material 13 as in the case of Fig.11 is laminated inside a reactor 29 having a square cross section in intervals surrounding the artificial light source 18 in the center. The water containing the contaminants is sent into the reactor 29 through the bottom by a pump 30, contacted with the cleaning material 13 to decompose the volatile organochlorine compounds, and subsequently discharged through a drainpipe 31. Since the titanium dioxide particles are in a state fixed as a sheet or panel material in this working example, a precipitation tank for separating the titanium dioxide particles from the treated water, pump piping or the like for returning the separated titanium dioxide to the reactor, and so forth are unnecessary. In this case, the contaminants in water are not limited to the volatile organochlorine compounds. They should be decomposed by titanium dioxide bit are not necessarily volatile.
[0030]
[Advantages of the Invention] According to this invention, a low concentration of harmful substances in environmental air can be removed effectively by fixing and setting aside a photocatalyst composed mainly of titanium dioxide or a mixture of titanium dioxide and activated carbon outdoors where it is cleaned by irradiation with sunlight and precipitation. Moreover, even if a product accumulates on the photocatalyst surface, thus decreasing its activity, its function is restored by washing away the product by precipitation. Since outside energy is not required, which differs from the various conventional countermeasures, cleaning of environmental air can be realized at very low cost and operating expenses in conjunction with the titanium dioxide, activated carbon, iron oxide and the like being inexpensive, so the possibility of its reduction to practice is high. In that case, by constructing the cleaning material by molding the photocatalyst powder into a sheet or panel form and adhering it to a sheet by using a synthetic resin or adhering it to the surface of a sheet or panel material by using an adhesive, its construction and transport become extremely simple.
[0031] In crowded regions, such as large metropolitan areas, there is hardly any space for installing new structures. In that case, the cleaning material is attached by utilizing the existing structures, such as the outer walls of buildings, sound insulation plates along expressways, etc. According to estimates based on test results, it is thought that the concentration of nitrogen oxide can be cut by at least 20%, as mentioned next, by applying this cleaning material to both sides of streets in urban areas having a large amount of traffic. That is, considering a 1 km section of a road with two car lanes on one side (a total of four lanes), if the amount of traffic on this road per hour is assumed to be 10,000 cars, then 2,500 g of nitrogen oxide is discharged (average output of nitrogen oxide from automobiles is 0.25 g/km).
[0032] Meanwhile, assuming buildings 12-stories high on average (40 m) stand on each side of the above-mentioned road, when this cleaning material is stuck to the outside walls of buildings, with the walls, except for windows, making up 70%, of the area, assuming that only the walls on one side of the road are exposed to sunlight and function, the effective cleaning material surface area is 28,000 m2. 500 g of nitrogen oxide are adsorbed and decomposed in this area per hour. This is equivalent to 20% of the above-mentioned output, and the same advantages as decreasing traffic by 20%, increasing waste gas regulations by 20%, or introducing 20% more exhaust-free cars, such as electric automobiles, are achieved.
[0033] In underground parking lots, malls, passageways, and the like, not directly exposed to sunlight, the cleaning material is installed in vents or artificial light sources (photochemical fluorescent lamps, etc.) are jointly used. Moreover, the concentration of nitric acid or the like discharged from the cleaning material during precipitation is usually about the concentration contained in natural precipitation, such as several μg to several tens of μg per milliliter. The effects on structures and sewers has not been considered. Moreover, even if contaminants diffuse into the environment by some chance, they not only exist naturally per se, but there is no risk that new environmental problems will arise.
[0034] Moreover, when volatile organochlorine compounds in water are transferred to a gas and they are contacted with titanium dioxide and decomposed, by carrying the titanium dioxide particles on a cleaning material constituted in the form of a sheet or panel, the same benefits as in the case of removing contaminants in air are renewed. Furthermore, by using the above cleaning material when contaminants in water are decomposed by contacting them with titanium dioxide directly, recovery or the like of the titanium dioxide particles from the treated water is unnecessary, the device is simple, and managing operations also becomes easy.
[Brief Description of the Drawings]
[Fig.1] is a graph showing the nitric oxide removing effects of the cleaning material sample with a photocatalyst powder formed into the shape of a sheet using a synthetic resin.
[Fig. 2] is a graph showing the relationship between the initial nitric oxide concentration
and removal rate of the sheet-like cleaning agent sample.
[Fig. 3] is a graph showing the nitric oxide removal effects of the cleaning agent sample in which photocatalyst particles were adhered to a synthetic resin sheet using a resin adhesive.
[Fig. 4] is a graph showing the nitrogen dioxide removing effects of the cleaning material sample in which photocatalyst particles were formed into the shape of a sheet using a synthetic resin.
[Fig. 5] is a graph showing the nitrogen dioxide removing effects of the cleaning material sample in which photocatalyst particles were formed into the shape of a sheet using a synthetic resin.
[Fig. 6] is a drawing showing the configuration of a test device for confirming the contaminant removing effects of this invention.
[Fig. 7] is a longitudinal section conceptually showing a state in which the cleaning material of this invention is used by sticking it to the walls of buildings.
[Fig. 8] is a longitudinal section conceptually showing a state in which the cleaning material of this invention is used by sticking it to sound insulation plates along an expressway.
[Fig. 9] is a perspective view conceptually showing a state in which the cleaning material of this invention is installed singly.
[Fig. 10] is a conceptual drawing showing a state in which the cleaning material of this invention is used in a motorway tunnel; (A) is a plan view and (B) is a longitudinal section.
[Fig. 11] is a block diagram of a device showing a working example in which volatile organochlorine compounds transferred from water into a gas are decomposed by the cleaning material of this invention.
[Fig. 12] is a block diagram of a device showing a working example in which contaminants in water are decomposed by the cleaning material of this invention.
[Fig. 13] is a block diagram of a device showing a conventional example in which contaminants in water are decomposed by a granular photocatalyst.
[Explanation of the Reference Symbols]
1: high pressure vessel for contaminants; 2: high pressure vessel for highly purified air; 3: decompression valve; 4: accurate flow rate regular; 5: four-way valve; 6: Petri dish-type reaction vessel; 7: cleaning material sample; 8: photochemical fluorescent lamp; 9: chemiluminescent nitrogen oxide meter; 10: air pump; 11: exhaust port; 12: exhaust port; 13: cleaning material; 14: building; 15: expressway; 16: frame; 17: motorway tunnel; 18: artificial light source; 19: air cleaning chamber; 20: ventilator; 21: electric dust collector; 22: stripping tank; 23: reactor; 25: pump; 26: compressor; 29: reactor; 30: pump
_________________________________________________________________
(cont. from front page)
(51) Int. Cl.5 Identification Nos. Intra-Bureau Nos.
B 01 J 35/02 ZAB J 8017-4G
C 02 F 1/32 ZAB
(72) Inventor: Hiroshi Takeuchi c/o National Institute for Resources and
Environment, Agency of Industrial Science &
Technology
16-3 Onogawa, Tsukuba-shi, Ibaraki-ken
(72) Inventor: Kazuteru Aragai c/o Fuji Electric Co., Ltd.
1-1 Tanabeshinden, Kawasaki-ku, Kawasaki-shi,
Kanagawa-ken
(72) Inventor: Satoshi Nishikata c/o Fuji Electric Co., Ltd.
1-1 Tanabeshinden, Kawasaki-ku, Kawasaki-shi,
Kanagawa-ken
(72) Inventor: Masahiro Miyamoto c/o Fuji Electric Co., Ltd.
1-1 Tanabeshinden, Kawasaki-ku, Kawasaki-shi,
Kanagawa-ken
(72) Inventor: Koyo Noguchi c/o Fuji Electric Co., Ltd.
1-1 Tanabeshinden, Kawasaki-ku, Kawasaki-shi,
Kanagawa-ken
(72) Inventor: Takeo Takahashi c/o Fuji Electric Co., Ltd.
1-1 Tanabeshinden, Kawasaki-ku, Kawasaki-shi,
Kanagawa-ken
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Experience
Years of experience: 36. Registered at ProZ.com: Oct 2001.
With over 20 years of experience in patent translation and technical articles, I'm busy in various fields, such as chemistry, biotechnical, composites, semiconductor, medical, mechanical, telecommunications, electronics, electrical, etc. Plus I thoroughly enjoy my chosen occupation. Cheers.