JP3716850B2 - Environmental purification function base material by diatomaceous earth - Google Patents

Description

The present invention relates to an environmental purification functional base material using diatomaceous earth used for decomposing and detoxifying harmful substances in a living environment, for example .

A photocatalyst is a catalyst that absorbs light and enters a high energy state and gives that energy to a reactant to cause a chemical reaction. Utilizing this property, it adsorbs harmful organic compounds and absorbs carbon dioxide, water, etc. Used for environmental purification that decomposes into harmless substances. Semiconductors used as the photocatalyst include gallium phosphide (GaP), gallium arsenide (GaAs), cadmium sulfide (CdS), strontium titanate (SrTiO ₃ ), titanium oxide (TiO ₂ ), and zinc oxide (ZnO). ), Iron oxide ( Fe ₂ O ₃ ), tungsten oxide (WO ₃ ), and the like. At present, titanium oxide is mostly used as a photocatalyst.

  A photocatalyst is usually used with an increased surface area by making it ultrafine particles in order to increase the efficiency by increasing the contact area with the reactant and the area exposed to light. In this case, since the photocatalyst powder is difficult to handle, it is used by dissolving it with a binder or a solvent and applying it to a substrate such as a plywood or a plastic plate. Further, a proposal has also been made to use a molded plate-like body comprising a porous granular material having an ability of adsorbing harmful substances as a constituent component for these substrates themselves (Japanese Patent Laid-Open No. 2001-90214).

  As described above, a porous material that adsorbs harmful substances is used as a base material on which the photocatalyst is applied. However, natural materials such as zeolite, diatomaceous earth, and sepiolite are powdered and kneaded with cement or water. The product is manufactured by solidifying and molding, and then air-drying or calcining the product, and applying or impregnating it with a photocatalyst. There existed a problem that many man-hours would be required for manufacture of a base material, such as requiring a process and a curing process. In addition, it was still not fully satisfactory in terms of adsorption of harmful substances.

  In other words, the environmental purification function base material by the conventional photocatalyst using the porous material needs to make the mineral into an ultrafine particle, even if the porous base material can adsorb harmful substances, It is very troublesome to knead and mold it with a binder and then mold it, dry it, and fire it, and it is negative in terms of its ability to absorb harmful substances.

In view of the above situation, the present invention can be used as a porous base material having a toxic substance adsorption area that is much better than conventional products just by firing the cut natural mineral as it is, and its excellent An object of the present invention is to provide a substrate for environmental purification function using diatomaceous earth, in which the function of the photocatalyst is more easily exhibited by the adsorption ability.

In order to achieve the above-mentioned object, the present invention provides a block obtained by cutting a porous diatomaceous earth existing as a sedimentary layer in Noto, Ishikawa Prefecture, as it is, and firing it as it is. An environmental purification functional substrate made of diatomaceous earth characterized by being coated with titanium oxide as a photocatalyst .

  Since the substrate for environmental purification function of diatomaceous earth is configured as described above, harmful substances are adsorbed by the porous void surface of diatomaceous earth, and the adsorbed harmful substances are decomposed into harmless substances by the photocatalyst. This void is already present in a larger amount than that of the conventional product at the time of natural products, and the large amount of void is already fixed at the time of cutting and imparts activity to the diatomaceous earth material. The adsorption capacity of the water is greatly increased and stabilized.

In particular, it has been found that the environmental purification functional base material using diatomaceous earth according to the present invention is extremely effective as a deodorizing material ( deodorizing material ).

  As described above, the present invention is used as a porous base material having an adsorption area of harmful substances that is nearly three times that of conventional products by simply firing the diatomaceous earth as a cut natural mineral as it is, The environmental purification function base material by diatomaceous earth can be provided at low cost, and the excellent adsorptivity of the cut-out unglazed diatomaceous earth material makes the photocatalyst function more effective, and the synergistic effects remover, deodorant, Exhibits extremely excellent effects as odorants, sanitizers, and sterilizers.

  The present invention is based on the finding that cut-out unglazed diatomite obtained by cutting out diatomite existing as sedimentary rocks and firing it as it is is extremely excellent in the ability to adsorb harmful substances in its porous structure. High resolution of harmful substances can be obtained by the synergistic effect.

  Diatomaceous earth is a white or off-white chalky silicic acid deposit formed by depositing dead bodies of diatoms in lakes and ponds. In the present invention, diatomaceous earth from Noto, Ishikawa Prefecture is preferred. Among Noto products, for example, the chemical composition (%) of Iizuka Formation diatomite in Suzu City is as shown in [Table 1].

Noto diatomaceous earth is called diatomaceous mudstone, and because of its origin, it contains many kinds of substances such as clay materials, volcanic ash, fine sand, iron compounds, organic matter, soluble salts, and fossilized fossil diatoms. As shown in [Table 1], the content of SiO ₂ is low, and the content of Al ₂ O ₃ , Fe ₂ O _3, etc. is large. In addition, the loss on ignition is considerably higher than that of other products (5 to 9.4%).

In the chemical composition, a substance rich in SiO ₂ means containing a lot of fossil diatoms or quartz, and a substance rich in Al ₂ O ₃ means containing a lot of clay material. A thing with much ignition loss means that there are many organic substances, carbonates, sulfides, and substances containing compound water. This means that the mold itself is moldable and the porosity is further increased by combustion.

As described above, diatomaceous earth from Noto, Ishikawa Prefecture is characterized by a large amount of clay, a large adsorptivity, a large and small particle size, and a large porosity of the diatom shell. In the present invention, this diatomaceous earth produced by Noto was cut out to be an unglazed diatomaceous earth .

  On the other hand, until now, for example, when manufacturing insulating bricks and tiles, naturally occurring porous minerals such as diatomaceous earth are powdered, kneaded together with binders and molded, and then air-dried or fired. It was manufactured.

The cut out unglazed diatomaceous earth described above , and diatomaceous earth as a main material, filled with plant fiber materials such as "sawdust" to increase the porosity, kneaded together with clay and fired A description will be given in comparison with “diatomaceous earth brick (Class B 1 type)”.

(Manufacturing method of uncut diatomaceous earth)
Materials used: Natural diatomaceous earth cut into blocks from a tunnel in Suzu City, Ishikawa Prefecture; Firing method; Firing in heavy oil kiln at 650 ° C to 800 ° C for 48 hours Processing method: Cutting the calcined diatomaceous earth into a predetermined size with a grinding stone processing

(Weight per unit volume)
Uncut diatomaceous earth 0.61 g / cm ³
Diatomaceous earth brick (Class B, 1 type) 0.58 g / cm ³
Measurement method: The weight after drying at 100 ° C. for 7 hours was divided by the volume.

(Surface area per unit weight)
Uncut ceramic diatomaceous earth 22m ² / g
Diatomaceous earth brick (Class B 1 type) 8m ² / g
Measuring method: Requested by Toyama Prefectural Industrial Technology Center (single point method for gas distribution)

(Water absorption per unit volume)
Cut out unglazed diatomaceous earth 0.67 g / cm ³
Diatomaceous earth brick (Class 1 B) 0.63 g / cm ³
Measurement method: The increased weight of the test piece immersed in water overnight was divided by the volume.

  From the above description, when compared with diatomaceous earth brick (Class B 1 type) (hereinafter abbreviated as (Class B 1 type)), the weight per unit volume is light (Unit B 1 type). In terms of surface area per weight, uncut diatomaceous earth has a surface area that is slightly less than three times. From this point, it is considered that the cut-out unglazed diatomaceous earth has more advantageous conditions for adsorption than (B type 1).

Examples of the photocatalyst used include titanium oxide (TiO ₂ ) , which is dissolved in a binder and / or a solvent in an ultrafine particle powder and applied to the surface of uncut diatomaceous earth. For application, use a brush, spray gun or soak. And if necessary, it is baked and finished after coating.

In the production of the environmental purification functional substrates C and D according to the present invention, diatomaceous earth in a tunnel in Suzu City, Ishikawa Prefecture is used, cut into blocks, and then placed in a kiln and baked at about 700 ° C for two days and nights. did. Then, this was processed into a tile of a predetermined size with a cutting grindstone, and a photocatalyst of titanium dioxide was applied to the surface (hereinafter referred to as “the product of the present invention”) . The photocatalyst, using Ltd. photocatalytic Research Laboratory of (PSA-015), after coating with a spray at a rate of 164 ml / ^{m 2,} dried for 10 minutes at 80 ° C, 1 hour at 500 ° C Baked.

  Next, an adsorption / decomposition test example in which the indoor environment of the tile base materials C and D according to the present invention is compared with the indoor environment using the other environmental purification functional base materials A, B, E, and F will be described.

[Experiment 1 (Transition of acetaldehyde concentration) (See FIGS. 1 and 2)]
(experimental method)
Assuming a living environment, a box having a volume of 1,247 liters (0.77 × 1.8 × 0.9 m) and an inner surface area of 7.4 m ² is prepared, and the above-mentioned substrates are bonded to the inner surface. Also, two UV lamps 40W (FL40S / BLB Toshiba Lighting & Technology) and a blower are placed inside and sealed. Acetaldehyde 0.5g (reagent grade 90%) (weighing A & D HL-200 minimum scale 0.1g) is put into the box from a silicon injection tube, and the air is stirred with a blower. Thereafter, the concentration is measured by sucking from the suction tube with a detection tube (Gastech GV-100 92M) every time.

(A) Full-surface vinyl cloth pasting; area 7.40m ²
(B) Diatomaceous earth brick (Type 1 B) is pasted on the entire surface of the vinyl cloth; Area 3.04 m ² t = 20 mm (Area ratio 41% of Diatomaceous earth brick (Type 1 B)) Volume 0.06 m ³ (Diatomaceous earth) Brick (Volume B type 1) volume ratio 5%)
(C) Uncut diatomaceous earth plate cut out on the entire surface with a vinyl cloth ; Area 3.04 m ² t = 20 mm (Area ratio 41% of diatomaceous earth) Volume 0.06 m ³ (Volume ratio 5% of diatomaceous earth)
(D) Product of the present invention (cut out unglazed diatomaceous earth plate (C) coated with photocatalyst);
Photocatalyst: PSA-015 manufactured by Photocatalyst Laboratories Co., Ltd. was applied at a rate of 164 ml / m ² by spraying, dried at 80 ° C. for 10 minutes, and then fired at 500 ° C. for 1 hour. (E) A photocatalyst was applied to a plastic plate. Things; Area 3.04m ² (Plastic board area ratio 41%)
(F) Case saw coat (a plastering material using unglazed diatomaceous earth powder as a main raw material); area 3.04 m ² t = 3 mm (area ratio of painted wall 41%)

(Experimental result)
FIG. 1 shows the change in acetaldehyde concentration over the course of 96 hours (4 days), and FIG. 2 shows the change over the first 4.5 hours.

In A, the concentration decreased to 55 ppm after 96 hours. Therefore, 85 ppm disappeared in 96 hours.
In B, after 30 minutes, the concentration decreased to 85 ppm and then gradually decreased. Therefore, it is considered that 60 ppm was reliably adsorbed due to the difference from A.
In C, after 4.5 hours, the concentration decreased to 20 ppm, and then maintained a substantially constant concentration. Therefore, it is considered that about 90% of the acetaldehyde in the present experimental conditions was adsorbed rapidly in a short time.
In the present invention product of D , the concentration decreased to 15 ppm after 4.5 hours, and showed 10 ppm after 24 hours and 0 ppm after 96 hours. Therefore, it seems that it was gradually decomposed by the photocatalyst while rapidly adsorbing acetaldehyde in a short time.
In E, after 24 hours, the concentration decreased to 60 ppm. Therefore, it seems that 40 ppm was decomposed in 24 hours due to the difference from A.
In F, after 30 minutes, the concentration decreased to 120 ppm and then gradually decreased. Therefore, it is considered that 20 ppm was reliably adsorbed due to the difference from A.

[Experiment 2 (Transition of ammonia concentration) (See Fig. 3)]
(experimental method)
In the same box as above, 1.0 g (9.5 to 10.5 W / V%) of ammonia is introduced from a silicon injection tube, and the air is stirred with a blower. Thereafter, the sample is sucked from the suction tube with a detection tube (Gastech GV-100 3L) every time, and the concentration is measured in the same manner as described above.

(Experimental result)
-A showed a substantially constant value.
B decreased to 16 ppm after 5 minutes and to 1.5 ppm after 30 minutes. Thereby, the height of the deodorizing effect can be confirmed.
C adsorbed rapidly, decreased to 1 ppm after 10 minutes, and ammonia was not detected in 25 minutes. Thereby, the outstanding deodorizing effect was confirmed and it turned out that it can utilize effectively as a deodorizing material.
-The product of the present invention of D showed almost the same value as C. At a concentration of about 50 ppm, adsorption occurred in a short time, and the difference in decomposition by the photocatalyst could not be confirmed. If the measurement is not started at a concentration higher than the saturation state, the photocatalytic effect cannot be judged. Naturally, it turns out that it is effective as a deodorizing material.
・ E appears to have decomposed by about 2 ppm by photocatalyst in 30 minutes due to the difference from A. (By the way, it decreased to 4 ppm after 24 hours.)
F decreased to 18 ppm after 5 minutes and to 7 ppm after 30 minutes. Thereby, the height of the deodorizing effect can be confirmed.

  As a result of the above experiments, the excellent adsorption properties of the cut-out unglazed diatomaceous earth material adsorb and contain harmful substances in a short time, so that the impact on the human body due to scattering can be minimized, and in combination with the photocatalyst, It turns out that it is a very effective combination that decomposes while being included by ultraviolet rays from light and lighting, etc., and it is various such as harmful chemical substance removal material / deodorizing material / deodorizing material / sanitizing material / sterilizing material Possible use.

It is a test graph figure which shows adsorption | suction and resolution | decomposability of acetaldehyde about the environmental purification function base material which concerns on one Example of this invention in comparison with some other environmental purification function base materials. It is a figure which extracts and shows only the initial stage in the same graph. It is a test graph figure which shows adsorption | suction and resolution | decomposability of ammonia about the environmental purification function base material which concerns on the Example in comparison with some other environmental purification function base materials.

Explanation of symbols

A Vinyl cloth only B Diatomaceous brick (Type B)
C cut-out unglazed diatomaceous earth D product of the present invention (diatomaceous earth coated with photocatalyst)
E Plastic sheet coated with photocatalyst F Case saw coat plasterer

Claims (1)

A block obtained by cutting porous diatomaceous earth that exists as a sedimentary layer in Noto, Ishikawa Prefecture, is fired as it is, and the surface of the diatomaceous earth plate cut from the cut unglazed diatomaceous earth is coated with titanium oxide as a photocatalyst. Environmental purification function base material with diatomaceous earth.

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