Compositions: ceramic – Ceramic compositions – Titanate – zirconate – stannate – niobate – or tantalate or...
Reexamination Certificate
1998-08-10
2001-01-30
Dunn, Tom (Department: 1754)
Compositions: ceramic
Ceramic compositions
Titanate, zirconate, stannate, niobate, or tantalate or...
C501S135000, C501S136000, C585S260000, C588S901000
Reexamination Certificate
active
06180548
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an environment purifying material and its manufacturing method wherein the material is used to remove offensive odors, to decompose and remove toxic substances or dust in the air, to provide wastewater treatment or water-purifying treatment, or to perform sterilization or algae elimination, or is added to organic fibers or plastics by means of mixing.
PRIOR ART
In recent years, offensive odors in residential or working spaces and contamination caused by toxic substances such as exhaust gas from vehicles have become an incresingly serious problem. Water contamination caused by gray water or industrial wastewater, particularly, the contamination of water sources by organic-chlorine solvents or agricultural chemicals in golf fields is difficult to treat using the current water treatment method under the Activated Sludge Process.
A common conventional method for preventing offensive odors or removing toxic substances in the air is to allow such odors or substances to be absorbed or adsorbed by an acid or alkali absorbent or adsorbent. This method, however, is disadvantageous in the disposal of wastewater or the used adsorbent, and may involve secondary pollution. An aromatic can also be used to conceal the offensive odor, but the odor of the aromatic may soak into and spoil foods (for further information, refer to “Encyclopedia”, Heibonsha, Vol. 1, p. 136, K. Nishida, 1984).
When titanium oxide is irradiated with light, electrons having a strong reduction effect and holes having a strong oxidation effect are generated to decompose molecular species that come into contact with them. This effect of titanium oxide, i.e., its photocatalyst effect, can be used to decompose and remove environmental-pollution materials such as organic solvents, agricultural chemicals, and surface-active agents that are dissolved in water as well as toxic substances or offensive odors in the air. This method can be repeated simply by using titanium oxide and light, and its reactive products are nontoxic carbon dioxide. Unlike biological treatments using microorganisms, it is not limited by reaction conditions such as temperature, pH, gas atmosphere, and toxicity, and is advantageous in its ability to decompose and remove organic halides or phosphides that cannot be treated easily using said biological treatments.
Conventional studies of the decomposition and removal of organisms using a titanium oxide photocatalyst used titanium oxide powder as a photocatalyst (for additional information, refer to the following: A. L. Pruden and D. F. Ollis, Journal of Catalysis, Vol. 82, 404 (1983), H. Hidaka, H. Jou, K. Nohara, and J. Zhao, Chemosphere, Vol. 25, 1589 (1992). and T. Hisanaga, K. Herada, and K. Tanaka, Industrial Water, Vol. 379, 12 (1990)).
Thus, this method is difficult to use for a variety of reasons, including the diffculty of collecting used catalysts. Attempts were therefore made to mix the titanium oxide photocatalyst into a medium such as fibers or plastics that are easy to handle. Due to its strong photocatalyst effect, however, the titanium oxide photocatalyst not only decompose toxic organisms or environmental-pollution materials but also decompose and significantly degrade the fibers or plastics, rendering mixture into the fibers or plastics extremely difficult. In addition, if the titanium oxide photocatalyst is used as an antibacterial or a antifungal material, bacteria do not adhere to the photocatalyst appropriately due to flowing water, thereby reducing the effects and efficiency of the treatment.
DISCLOSURE OF THE INVENTION
In view of the above problems, it is an object of this invention to provide an environment-purifying material and its manufacturing method wherein the material can be used to effectively and economically purify environments by removing offensive odors, decomposing and removing toxic substances or dust from the air, providing wastewater or water-purifying treatment, or enabling protection from bacteria or fungi. Even if this material is added to organic fibers or plastics by means of mixing, it does not degrade the medium but can maintain its durability.
As a result of their efforts in achieving this object, the inventors have found that by coating a calcium phosphate film around titanium oxide when the latter is added to a medium, the durability of the titanium oxide can be improved without negatively affecting its photocatalyst function due to the inactivity of the calcium phosphate film as a photocatalyst, its ability to adsorb various bacteria, and its porosity.
This invention provides an environment-purifying material composed of a porous calcium phosphate coated on a surface of a substrate, with the surface consisting of titanium oxide.
According to the environment-purifying material of this invention, the calcium phosphate film covering the surface is porous, so the titanium oxide is exposed from the bottoms of pores, where it is irradiated with light. The oxidation-reduction effect of electrons and holes generated during irradiation with light serves to decompose and remove offensive odors, or organic compounds contaminating environments, including toxic substances in the air and organic solvents or agricultural chemicals dissolved in water.
In addition, due to its inactivity as a photocatalyst, even if the environment-purifying material is added to a medium such as organic fibers or plastics by means of mixing, it is protected by the calcium phosphate film, preventing the fibers or plastics from being decomposed in order to ensure its effects last over a longer period of time.
Furthermore, due to the calcium phosphate film's ability to adsorb various bacteria, various adsorbed bacteria can be reliably and efficiently killed and decomposed by the powerful oxidation effect of the titanium oxide provided when irradiated with light.
In addition, to obtain this environment-purifying material, this invention provides a environment-purifying material manufacturing method characterized in that a substrate having a surface consisting of titanium oxide is immersed in a pseudo-body fluid containing an excessive amount of calcium phosphate compared with real human body fluid in order to coat a porous calcium phosphate film on the surface of the substrate. The concentration of calcium phosphate in the pseudo-body fluid is preferably about 1 to 20 times, or more preferably, 2 to 15 times greater than that in the human body fluid.
A carrier used for this invention includes activated carbon, activated alumina, silica gel, zeolite, clay sintered compacts, glass, foam ceramics, foam metal, and foam plastics, but silica gel or glass are the most preferable materials in terms of light transmissivity. In addition, the carrier preferably contains silicon or titanium.
The carrier used for this invention may have an arbitrary shape, and may be shaped like, for example, particles, a plate, a cylinder, a prism, a cone, a sphere, a gourd, or a rugby ball.
The titanium oxide film can be coated on the surface of the carrier using various methods, including evaporation, PVD, CVD, sputtering, coating of titanium oxide sol using the sol-gel process, and fixation of titanium oxide in very fine particles.
The titanium oxide particles and film used for this invention preferably have an anatase crystal form because it provides high performance as a photocatalyst. The rutile, brookite, or amorphous types are not very preferable due to their low level of photocatalyst activity. In addition, the titanium oxide particles may be of any size, but are preferably of submicron-scale size when mixed into organic fibers or plastics.
The environment-purifying material according to this invention is prepared by immersing in a pseudo body fluid a substrate the surface of which is coated with titanium oxide to generate porous calcium phosphate on the surface.
The pseudo body fluid used for this invention is prepared by dissolving in water NaCl, NaHCO
3
, KCl, K
2
HPO
4
.3H
2
O, MgCl
2
.6H
2
O, CaCl
2
, and Na
2
SO
4
or NaF. And pH is preferably adjusted t
Aramaki Fujio
Aramaki Shoshichi
Nonami Toru
Taoda Hiroshi
Agency of Industrial Science and Technology
Dunn Tom
Nguyen Cam N.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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