WO2009026568A1

WO2009026568A1 - Superoxide liquid decontamination system

Info

Publication number: WO2009026568A1
Application number: PCT/US2008/074110
Authority: WO
Inventors: Adams B.J
Original assignee: New Tech, Llc
Priority date: 2007-08-22
Filing date: 2008-08-22
Publication date: 2009-02-26

Abstract

A novel fluid decontamination system comprising contacting the fluid with a colloidal metal oxide from an electrolysis process and exposing the fluid to a light source. An alternating electric current of a particular wave shape is passed through the irradiated fluid creating super oxide molecules and other radicals, enhancing the killing of biological particles. This electric current also forces compounds that would foul the system to stay in solution within the reaction chamber and are carried away with the water flow. The system can be used in water systems such as ponds, swimming pools, and spa tubs, but it is not limited to these closed systems.

Description

SUPEROXIDE LIQUID DECONTAMINATION SYSTEM

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 60/957,368, filed August 22, 2007, and whose entire contents are hereby incorporated by reference.

TECHNICAL FIELD

[0002] Embodiments of the present invention relate to treatment of contaminants in a fluid stream, and more specifically, to the photocatalytic treatment of water for removal of contaminants therein by an oxidation-reduction reaction.

BACKGROUND

[0003] Since the discovery of photo-induced water cleavage on titanium dioxide (UO2) electrodes by Fujishima and Honda in the early 1970s {Nature, 1972, 238: 37), TiO2 photocatalysts have attracted great attention as alternative materials to aid in the purification of water and air. In 1985, Matsunaga and coworkers reported for the first time the microbiocidal effect of Tiθ2 photocatalytic reactions (FEMS Microbiol. Lett., 1985, 29: 211 ). Since then, research work on TiO2 photocatalytic killing has been intensively conducted on a wide spectrum of organic materials including viruses, bacteria, fungi, algae, and cancer cells.

[0004] While the art recognizes generally the utility of photocatalytic destruction of organic materials in fluid streams, specifically employing TiO2 as the photocatalyst and 185 nm and 254 nm ultraviolet (UV) light as the radiation, the art has not provided a suitably efficient, readily-manufacturable, cost-effective system for destruction of organics in fluid streams.

[0005] There are several reasons why the prior processes have not been commercially successful. For example, although not bound by any theory, it is believed that destruction of organic contaminants takes place on the surface of the photocatalyst. Therefore, an increase in surface area can attribute to high rates of reaction. To achieve this, slurries of TiO2 powders (e.g., generally about 20 microns to about 80 microns) have been used in processes in the prior art. However, commercial TiO2 powders tend to settle out from aqueous suspension, greatly reducing the efficiency of the photocatalytic reaction. The TiO2 powders can also have an opaque white color, which is not aesthetically pleasing for water use. The method to replenish TiO2 powders in the fluid stream can also be costly for high volume applications.

[0006] There is therefore a need for a system for photocatalytic destruction of organic materials in a fluid stream, in which the photocatalyst is efficiently exposed to both radiation that can activate the photocatalyst and the fluid stream.

SUMMARY

[0007] Embodiments of the present invention provide a novel system for use in the photocatalzed conversion of fluid decontamination to other less harmful or more easily extracted compound that satisfies these needs. The fluid that can be treated by the system includes water at high contaminant levels, such as waste water containing sludge and soil, human excreta, sewage water containing excreta of domestic animals, household waste water, clinical waste water, papermaking waste water, and industrial liquid waste, and water at low contaminant levels, such as water in rivers, lakes or ponds, water used in spas and bathhouses, swimming pools, and the like.

[0008] One embodiment of the invention is a decontamination system that comprises a colloidal generator for providing colloidal titanium dioxide (Tiθ2) as a photocatalyst in a fluid stream, and a reaction chamber comprising a light source for activating the photocatalyst in the fluid stream. [0009] In one embodiment, the colloidal TiO₂ is produced by electrolysis, in which an electric current is passed through an anode comprising TiO₂ to release the colloidal TiO₂ in the fluid stream.

[0010] In another embodiment, the light source of the reaction chamber comprises one or more lamps for activating the photocatalyst in the fluid stream.

[0011] In another embodiment, the reaction chamber comprises a helical plate that defines a helical path for the fluid stream. The helical path and the light source are arranged to enhance light interception by the photocatalyst in the fluid stream.

[0012] In another embodiment, the helical plate comprises a photocatalyst (e.g., TiO₂), so that the fluid stream contacts the photocatalyst when traveling through the helical path. As the fluid stream contacts the photocatalyst, light emanating from the light source can activate the photocatalyst on the surface of the helical plate to promote fluid decontamination. In yet another embodiment, the reaction chamber comprises an inner surface comprising a photocatalyst (e.g., TiO₂) to further promote the extent of photocatalytic decontamination of the fluid stream.

[0013] In another embodiment, the reaction chamber comprises electrodes for providing electric current flows in the fluid stream. The electric current can provide free radicals for fluid decontamination. The electric current can also help keep the contaminants from sticking to the reaction chamber and decreasing the efficiency of the system through physical vibration caused by electrostriction.

[0014] A further embodiment of the current invention comprises one or more components for enhancing fluid decontamination. Such an embodiment can comprise one or more of ultraviolet (UV) light source, infrared (IR) light source, or both for disabling photoprotection mechanisms of organic materials (e.g., bacteria) in the fluid stream prior to entering the reaction chamber. If can be preferable for ozone to be provided for decomposing organic materials in the fluid stream. Further, filters can be provided to capture and remove debris in the fluid stream. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Embodiments of the invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements, wherein:

[0016] FIG. 1 is a diagram depicting a decontamination system in accordance with an embodiment of the present invention;

[0017] FIG. 2 is a disassembled view of a reaction chamber in accordance with an embodiment of the present invention;

[0018] FIG. 3 is a partially assembled view of a reaction chamber similar to in FIG. 2;

[0019] FIG. 4 depicts a configuration of reaction chambers in accordance with an embodiment of the present invention;

[0020] FIG. 5a is a reaction chamber in accordance with an embodiment of the present invention, and FIG. 5b is a partial view of a reaction chamber similar to FIG. 5a; and

[0021] FIG. 6 is a colloidal generator in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0022] In the following description, for the purposes of explanation, specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent that the invention may be practiced without these specific details. In other instances, well-known structures and devices are depicted in block diagram form in order to avoid unnecessary obscuring of the invention. Section titles and references appearing within the following paragraphs are intended for the convenience of the reader and should not be interpreted to restrict the scope of the information presented at any given location. DEFINITION OF TERMS

[0023] To aid in understanding the following detailed description of the embodiments of the present invention, the terms and phrased used herein shall have the following, non-limiting, definitions:

[0024] As used herein, the term "photocatalyst" means any compound in which irradiation or activation of such compound with visible light will result in the generation of conduction band electrons and valence band holes that can then undergo oxidation reactions at the photocatalyst surface with species such as water or inorganic and organic compounds. Photocatalyst includes photoactive transition metal oxides selected from the group consisting of Tiθ2, ZnO, WO3, SnO2, CaTiOs, Fe2θ3, MOO3, NbO₅, TixZr₍i_-X)θ2, and SiC. In a preferred embodiment in accordance to the present invention, the photocatalyst is TiO2. Photocatalytic activation requires illumination with light of energy higher than the band gap of the photocatalyst, typically within a wavelength range of from about 250 nm to about 630 nm (e.g., <360 nm for anatase TiO₂).

[0025] As used herein, the term "colloidal" means particles generally having a largest dimension averaging about less than one micron.

I. SYSTEM AND METHOD

[0026] Referring to FIG. 1 , the decontamination system 100 in accordance with a preferred embodiment of the present invention and its method of operation will now be described. A fluid 10, typically contaminated water, enters through a colloidal generator 20 that generates colloidal titanium dioxide (TiO₂) in contact with the fluid flowing through the system. The system 100 can comprise a control mechanism 15 (e.g., pump, valve, etc.) for directing fluid 10 flow (e.g., to or away from the colloidal generator 20) in the system. In one embodiment, the control mechanism 15 comprises a sensor (not shown) that can detect and measure contaminants in the fluid 10 (e.g., based on conductivity or spectrophotometeric data of the fluid) and provide such information to a computer (not shown) that can control power delivery (e.g., from a power supply 50) to components of the system 100 (e.g., the colloidal generator 20) based on such information. The computer, for example, can reduce the amount of power provided to the colloidal generator 20 in response to a decreased contaminant level in the fluid, thereby reducing the amount of power or photocatalyst used by the system 100.

[0027] The colloidal generator 20 generates colloidal TiO2 by electrolysis, which is a process in which electric current passed through a substance causes a chemical change, usually the gaining or losing of electrons (reduction or oxidation, respectively). It has been observed that upon electrolysis, the phase of Tiθ2 is mostly anatase. The colloidal generator 20 comprises an anode 21 and a cathode 22. In one embodiment, anode 21 comprises TiO2. In another embodiment, anode 21 comprises zinc and TiO2 mounted onto a copper carrier electrode. In yet another embodiment, the TiO₂ is doped with a dopant comprising a transition metal (e.g., gallium, indium, or mixtures thereof), which can enhance its ability to absorb visible light (<380 nm) as well its colloidal dispersion and suspension. Cathode 22 preferably comprises a material that cannot be plated in the fluid 10 during electrolysis. In one embodiment, cathode 22 comprises titanium.

[0028] During electrolysis, an electric current is applied through anode 21 and cathode 22, and oxidation occurs at the anode 21 , where colloidal TiO₂ forms and releases to the fluid 10. In embodiments where anode 21 comprises zinc and TiO₂, colloidal TiO₂ and zinc form and release to the fluid 10 during the electrolysis process. Zinc is a well known fungicide that can provide added benefits of killing or inhibiting fungi in the fluid 10. Zinc is also a flocculating/coagulating agent that can promote flocculation/coagulation by causing suspended organic and inorganic contaminants in the fluid 10 to aggregate, forming a floc/coagulant, thereby improving the sedimentation or filterability of small particles.

[0029] The electrolysis process preferably generates and releases colloidal TiO₂ in the fluid 10 in the concentration range of from about 100 ppm to about 1 ,000 ppm. However, zinc level in drinking water is limited to no more than 5 milligrams per liter by the U.S. government (http://www.atsdr.cdc.gov/tfacts60.html). Therefore, in embodiments where anode 21 comprises zinc and TiO₂, the release of zinc during the electrolysis process preferably does not exceed 5 milligrams per liter. For example, for an average pool (about 90,849 L), the zinc delivery rate is set at about 3.5 mg or 53.5 micromoles of zinc per second to stay below the government limit, which typically requires no more than 10.32 A of electric current for the electrolysis process.

[0030] As shown in FIG. 1 , the decontamination system 100 comprises a reaction chamber 30 for activating photocatalyst in the fluid 10. The reaction chamber 30 comprises a fluid inlet 31 , a fluid outlet 32, and a light source 33. As fluid 10 passes along from the fluid inlet 31 to the fluid outlet 32, the light source 33 activates the colloidal TiO2 therein, thereby converting the contaminants in the fluid to other less harmful or more easily extracted compound. The inner wall 39 of the reaction chamber 30 can comprise a reflective material (e.g., aluminum or aluminum magnesium alloy) (not shown) to multiply the light source 33 available for activating the photocatalyst in the reaction chamber 30.

[0031] In one embodiment, the light source 33 provides energy higher than the band gap of the colloidal TiO₂ (e.g., 3.2 eV for anatase type), which is within the visible wavelength range of from about 380 nm to about 750 nm. When illuminated with the lamps, the colloidal TiO₂ can generate strong oxidizing power. With holes (h⁺) and hydroxyl radicals (OH^') generated in the valence band, and electrons and superoxide ions (O₂ ^") generated in the conduction band, the activated colloidal TiO₂ can decompose and mineralize organic contaminants (e.g., bacteria, viruses, fungi, organic compounds) by participating in a series of oxidation reactions.

[0032] A variety of lamps can be utilized and intensity of the light source 33 is preferably at least about 600,000 μW per square inch of exposure area to achieve complete decomposition within a reasonable exposure period. Light source 33 is commercially available (e.g., a mercury vapor fluorescent lamp source, white light LED source) or sunlight may be used. The distance that the light source 33 is located from a fluid to be irradiated in reaction chamber 33 is important since much of the light energy can be absorbed by the fluid. Therefore, depending upon the size and geometry of the reaction chamber 30, as well as the intensity of the light source 33, it can be appropriate to use a plurality of light source 33 (e.g., a plurality of lamps), dispersed around the perimeter of the reaction chamber 30, within the reaction chamber 30, or combinations thereof. Light source 33 is preferably of sufficient intensity or energy to initiate photocatalytic decomposition of substantially all of the contaminants within the reaction chamber 30. The decomposition rate will also depend on the type and concentration of the photocatalyst in the reaction chamber 30.

[0033] The light source 33 needs not be constant - the reaction chamber 30 can comprise a modulated or pulsed light to achieve substantially similar efficiency as a constant light source for the treatment of contaminants. For example, the light can be generated in a modulated or pulsed manner, which includes subsequent time-on and time-off intervals. In one embodiment the light time is less than 500 μs. In another embodiment, the light time is less than 100 μs. Suitable light sources include one or more LED lamp assemblies, such as those described in co-pending U.S. Pat. Application entitled "SOLID STATE LAMP LIGHT SYSTEM," Ser. No. 12/127,184, filed May 28, 2008, the disclosure of which is incorporated by reference herein in its entirety.

[0034] FIG. 2 is a disassembled view of components of a reaction chamber 30a in accordance with an embodiment of the current invention. FIG. 3 is a partially assembled view of the reaction chamber 30a. As shown in FIG. 2, the reaction chamber 30a comprises an outer cylinder 36, an inner cylinder 37, and end caps 31 a and 32a. The outer cylinder 36 surrounds the inner cylinder 37 and the end caps 31a and 32a cover the ends of the outer cylinder 36. In one embodiment, the outer cylinder 36 is made of a material that can provide structural support and electrical insulation to the reaction chamber 30a, such as polyvinyl chloride (PVC).

[0035] The reaction chamber 30a also comprises a helical plate 34 disposed along the longitudinal axis of the reaction chamber 30a that defines a helical path extending from a fluid inlet 31a to a fluid outlet 32a of the chamber. The pitch of the helical plate 34 can be equal to or greater than the diameter of the helical plate 34, but preferably is smaller than the diameter of the helical plate 34. In one specific embodiment, the helical plate 34 comprises lamps 33a, 33b, and 33c spaced about 120 degrees apart around the longitudinal axis of the helical plate 34. The lamps can be held in place at either or both ends of the helical plate 34 with a supporting structure 35. The lamps 33a, 33b, and 33c preferably extend over the entire length of the reaction chamber 30a. [0036] The helical plate 34 increases the distance and the amount of time fluid travels within the reaction chamber 30a, which can increase the amount of light intercepted by photocatalyst in the fluid stream. The helical plate 34 can be made of a variety of materials (e.g., polymers, plastic, glass). In one embodiment, the material is transparent to light. In another embodiment, the helical plate 34 comprises TiO₂. In yet another embodiment, the helical plate 34 is etched to enhance exposure of the TiO₂ therein to the fluid stream. As a fluid (not shown) travels through the helical path, it is constantly agitated causing the contaminants in the fluid to contact the TiO₂ on the surface of the helical plate 34. During that time, light emanating from one or more lamps 33a, 33b and 33c illuminates and activates the TiO₂ photocatalyst, thereby converting the contaminants in the fluid to other less harmful or more easily extracted compound.

[0037] In another embodiment, the extent of photocatalytic reaction is further promoted by providing a photocatalyst along the inner wall 39a of the inner cylinder 37. In one specific embodiment, the inner wall 39a comprises a mesh screen 38 comprising TiO₂, which can be activated by light emanating from one or more lamps 33a, 33b and 33c. In another embodiment, mesh screen 38 comprises opening spaces that expose the reflective surface of inner wall 39a to multiply the light sources available for activating photocatalyst in the reaction chamber 30a.

[0038] The reaction chamber 30a further comprises electrode 45 for introducing an electric current (e.g., alternating electric current at 120 V or 240 V, 50 Hz or 60 Hz) in the fluid in the reaction chamber 30a. The electric current can create free radicals that can enhance fluid decontamination. The electric current flow also motivates migration of the contaminants in the fluid and helps keep the contaminants from sticking to and decreasing the efficiency of the system through physical vibration caused by electrostriction.

[0039] In one embodiment, the reaction chamber 30a also comprises a sensor (not shown) that can detect and measure contaminants in the reaction chamber 30a (e.g., based on conductivity or spectrophotometeric data of the fluid in the chamber) and provide such information to a computer (not shown) that can control power delivery (e.g., power on, off, up or down) to the electrode 45 based on such information.

[0040] Components of the decontamination system can be configured in a variety of sizes or combinations to meet the particular fluid decontamination needs. For example, a decontamination system comprising a plurality of reaction chambers can be particularly well-suited for a large scale fluid treatment. In one embodiment as shown in FIG. 4, six reaction chambers 30a are connected with pipes, valves, etc. for directing fluid flow among the reaction chambers. In operation, a fluid enters the one or more reaction chambers 30a and the light sources therein (not shown) activate photocatalyst in contact with the fluid stream, thereby converting the contaminants in the fluid to other less harmful or more easily extracted compound.

[0041] In another embodiment, each of the reaction chambers 30a has an outer length about 40 inches and an outer diameter of about 4 inches. The combination of the reaction chambers is measured only about 92 inches in height, about 117 inches long and about 48 inches deep, but it can be used to treat potable water at the rate of 1 ,2000,000 gallons per day at a power consumption of less than 4.5 kW.

[0042] In yet another embodiment, smaller reaction chambers can be used for small scale fluid treatment, such as the reaction chamber 30b shown by FIG. 5a and FIG. 5b. Reaction chamber 30b has an outer length of about 24 inches and an outer diameter about 2 inches. In another embodiment, the reaction chamber 30b comprises a fluid inlet 31 b, a fluid outlet 32b, a helical plate 34b, lamps 33h, 33i, 33j, and 33k, and an electrode 45b. Each of the lamps 33h, 33i and 33j comprises a long wave light lamps having a wavelength range of from about 860 nm to 185 nm. In another embodiment, the lamp 33k comprises a short wave light lamp having a wavelength range from about 460 nm to about 185 nm. As shown in FIG. 5b, the lamps 33h, 33i and 33j extend over a partial length of the reaction chamber 30b (e.g., about the first two-third). The light provided by these lamps 33h, 33i and 33j can help block or deactivate the cellular repair mechanisms of certain types of organic materials (e.g., bacteria) after exposure to UV light. [0043] In this and other embodiments of the present invention, one or more additional components can be introduced in the decontamination system 100 that can further enhance treatment of the contaminants in the fluid. For example, an oxidizer, such as O2, O3 or H2O2, among many others, is added to the fluid coming out the reaction chamber 30. In another example, fluid coming out of the reaction chamber is passed through a bed of ozone impregnated zeolite. The ozone can be provided, e.g., by a corona discharge ozone generator with oxygen-enriched air pumped through a Peltier chiller to the fluid stream. The zeolite can be of a size that can capture the ozone molecules for treating the contaminants in the fluid while allowing photocatalyst to pass through the zeolite bed. In another example, the decontamination system 100 comprises a filter (e.g., micron filter) (not shown) for capturing debris and particles in the fluid stream.

[0044] It is anticipated that colloidal TiO₂ released from the decontamination system 100 will continue to decompose and mineralize organic contaminants (e.g., bacteria, viruses, fungi, organic compounds) in the treated fluid upon exposure to visible or sun light. Therefore, the system can also be used for wound healing and other medical applications where it is beneficial to eliminate bacterial, viruses, cancer cells, etc. in the body.

II. PRETREATMENT OF CONTAMINANTS

[0045] As shown in the embodiment depicted in FIG. 6 the colloidal generator 20a in accordance with an embodiment of the present invention comprises a UV source 110 and an IR sourcel 12 to enhance fluid decontamination. This treatment with UV and IR light sources is preferred for high volume applications (e.g., fluid flow rate above 50 gallons per minute in reaction chambers with an outer diameter of about 4 inches, or above 3 gallons per minute in reaction chambers with an outer diameter of about 2 inches) to help block or deactivate the cellular repair mechanisms of certain types of organic materials (e.g., bacteria) after exposure to UV light.

[0046] In another embodiment, the UV source 100 comprises a plurality of UV light emitting diodes (e.g., 365 nm UV LEDs). In another embodiment, the IR source 112 comprises a plurality of IR LEDs (e.g., 858 nm IR LEDs). [0047] The invention is illustrated by the following non-limiting examples.

III. EXAMPLES

[0048] A cylindrical mold is used to cast an anode comprising TiO₂ and zinc. Zinc in power or pellet form and doped TiO₂ powder (8:1 w/w) are placed into the mold, which fill the mold about halfway, and the mold is caped off with a lid fitted with a copper rod in the center.

[0049] The mixture is heated to just above 787.15 degrees F to cause the zinc to become liquid and then the mold is placed into a vibration mixer for about 15 seconds. Once mixed, the mold is placed in a dry cooling chamber. The solidified mixture is then removed from the mold. The copper rod can be cut to a desired length for use.

[0050] Molds of various sizes are available for making the anode. In this example, the anode has a radius of about 0.5 inches and a height of about 8 inches. One pound of zinc can yield about 11 such anodes, which will be used for electrolysis over a three month period at maximum capacity.

PRESENT DISCLOSURE

[0051] Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about" or "approximately." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0052] The terms "a" and "an" and "the" and similar referents used in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. "such as") provided herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[0053] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member may be referred to and claimed individually or in any combination with other members of the group or other elements found herein. It is anticipated that one or more members of a group may be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.

[0054] Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Of course, variations on those preferred embodiments will become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventor expects skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.

[0055] Furthermore, numerous references have been made to patents and printed publications throughout this specification. Each of the above cited references and printed publications, if any, are herein individually incorporated by reference in their entirety.

[0056] In closing, it is to be understood that the embodiments of the invention disclosed herein are illustrative of the principles of the present invention. Other modifications that may be employed are within the scope of the invention. Thus, by way of example, but not of limitation, alternative configurations of the present invention may be utilized in accordance with the teachings herein. Accordingly, the present invention is not limited to that precisely as shown and described.

Claims

CLAIMSI claim:

1. A method for treating contaminants in a fluid comprising the steps of:

contacting the fluid with a photocatalyst comprising colloidal UO2; and

exposing the fluid to visible light.

2. The method according to claim 1 , wherein the colloidal UO2 is formed by an electrolysis process comprising electrolyzing an anode and a cathode in contact with the fluid, wherein the anode comprises UO2.

3. The method according to claim 2, wherein the anode comprises TiO2 and zinc.

4. The method according to claim 2, wherein the TiO2 is doped with a transition metal.

5. The method according to claim 2, wherein the cathode comprises titanium.

6. The method according to claim 2, wherein the colloidal TiO2 is prevalently in the form of anatase.

7. The method according to claim 4, wherein the fluid is exposed to light of wavelengths ranging from about 380 nm to about 750 nm.

8. The method according to claim 7, wherein the exposing the fluid to visible light is generated in a modulated or pulsed manner.

9. A system for treating contaminant in a fluid comprising:

a colloidal generator that generates and releases a photocatalyst into the fluid; and

a reaction chamber that provides a visible light source that activates the photocatalyst for treating the contaminant in the fluid;

wherein the photocatalyst comprises colloidal TiO₂.

10. The system according to claim 9, wherein the colloidal TiO₂ is formed by an electrolysis process comprising electrolyzing an anode and a cathode in contact with the fluid, and wherein the anode comprises TiO₂.

11. The system according to claim 10, wherein the anode comprises zinc and TiO₂.

12. The system according to claim 10, wherein the TiO₂ is doped with a transition metal.

13. The system according to claim 9, wherein the colloidal TiO₂ is prevalently in the form of anatase.

14. The system according to claim 12, wherein the visible light source comprises wavelengths ranging from about 380 nm to about 750 nm.

15. The system according to claim 9, wherein the reaction chamber comprises a structure for directing the fluid into optical proximity of the visible light source, wherein the structure comprises a helical plate.

16. The system according to claim 15, wherein the helical plate comprises a second photocatalyst capable of being activated by the visible light source for treating the contaminant in the fluid.

17. The system according to claim 16, wherein the second photocatalyst comprises TiO₂.

18. The system according to claim 9, wherein the reaction chamber comprises an electrode that provides an electric current to the fluid within the reaction chamber.