System and method of generating singlet oxygen for water purification

Abstract

A system for generating singlet oxygen comprises a photosensitizer device comprising a substrate on the surface of which a photosensitizer material is coated, at least one light source configured to illuminate light at a wavelength to the photosensitizer device, a water stream containing dissolved oxygen by injecting oxygen gas into the water, a water inlet configured to feed the water stream to a flow chamber that contains the photosensitizer device, wherein the singlet oxygen is generated by contact of the water stream with the photosensitizer material under light illumination, simultaneously, the generated singlet oxygen purifies the water stream by oxidizing impurities and inactivates biological contaminants in the water stream, and a water outlet, configured to discharge a purified water.

Description

SYSTEM AND METHOD OF GENERATING SINGLET OXYGEN FOR WATER PURIFICATIONCross Reference to Related Applications

[0001] The present application claims the benefit of U.S. Provisional Patent Application No. 63 / 553,489 filed February 14, 2024, being incorporated herein by reference in its entirety for all purposes.Field of the Invention

[0002] The present invention relates to systems and methods of generating singlet oxygen (1C>2) for water purification, in particular, related to generation of singlet oxygen through photosensitization of triplet oxygen into singlet oxygen by a photosensitizer deposited or coated on the surface of a substrate selected from a stack of layers of planar meshes, a stack of layers of planar porous membranes, a stack of alternating layers of planar meshes and planar porous membranes, a spiral wound of planar meshes, a spiral wound of planar porous membrane, a plurality of transparent and rigid plastic rods, a plurality of hollow fiber porous membranes, or a bunch of meshes, saddles, or rings made from plastic materials wrapped with a planar porous membrane, etc.Background

[0003] Singlet oxygen is a strong oxidation and disinfection agent that reacts in water quickly leaving no residual other than breathable oxygen. The most widely used method for singlet oxygen production is via a photochemical activation of ground, triplet state of oxygen into singlet oxygen in which a photosensitizer is used to transfer the energy of photons to the triplet oxygen molecule exiting it to the first-excited singlet state. The problem is that the conventional systems for singlet oxygen generation involve dispersing a photosensitizer (PS) in liquid medium that is exposed to the light source at the wavelength specific to the type of the photosensitizer. The photosensitizer in these types of applications generally degrades quickly during the reaction and is discarded after each use. Degraded sensitizer would need to be separated from the mixture as well. Therefore, methods for the generation and use of singlet oxygen other than the ones that involve dispersing the photosensitizer in the media to be reacted with were not successful. In addition, due to the very short lifetime of singlet oxygen in the water and gas phase, it has to be generated in- situ at the point of use. Thus, new methods of generation singlet oxygen are demanded.

[0004] US9150431 discloses a method of purifying or sanitizing contaminated water to be potable, by exposing the water in the presence of light, to an electrically neutral metal complex of a perfluoroalkylated fluorinated phthalocyanine photosensitizer, having only external R groups with C-F bonds, preferably F64PcZn, providing a sufficient quantity of singlet oxygen by the chemical reaction of the light and the photosensitizer to destroy the pollutants or pathogens present in the contaminated water.

[0005] US20140106127 discloses polymer having optically transparent superhydrophobic surface. The disclosure relates to an optically transparent superhydrophobic surface and methods of fabrication including laminating an optically transparent polymer sheet with hydrophobic nanoparticles such that the nanoparticles are partially embedded and partially exposed. The resulting device remains optically transparent.

[0006] US9040145 discloses polymer having a superhydrophobic surface and methods of fabrication including laminating a polymer sheet having a surface to a template having a textured surface or a layer of a nanomaterial (e.g., nanoparticles or nanofibers) to convert the surface of the polymer sheet to a hydrophobic surface having a water contact angle of at least about 150°.

[0007] US9556554 discloses a flexible fabric having superhydrophobic surface and methods of fabrication including laminating an optically transparent polymer sheet with hydrophobic nanoparticles such that the nanoparticles are partially embedded and partially exposed. The resulting device remains optically transparent. Additional methods include the lamination of nanoparticles to flexible fabrics and the production of molded articles using nanoparticle-treated molds.

[0008] US10835629 discloses a singlet oxygen generation system for selective destruction of pathogens, in which the system has elongated posts extending from a surface, the lateral sides of which have particles with a sensitizer that converts triplet oxygen to singlet oxygen upon exposure to light. An optical fiber conveys light to the sensitizer and a gas supply tube conveys oxygen to the sensitizer. The system is configured to keep the sensitizer from contacting external fluids, such as saliva.

[0009] US10568961 B2 discloses a photosensitizing composition comprising a mixture of at least one oxygen carrier, at least one oxidizing agent and at least one surfactant, and its uses. The ratio of the at least one oxygen carrier to the at least one oxidizing agent to the at least one surfactant may be in the range of 50:40:10 to 80:19.8:0.2. The photosensitizing composition may be used for treating and / or preventing conditions caused by microorganisms.

[0010] CN106139145B discloses an exciton-plasmon coupling system that is of a coreshell structure formed by adsorbing photosensitizer exciton and plasmon nano-particles, and the LSPR (localized surface plasmon resonance) absorption peak of the plasmon nano-particles covers the exciton absorption peak of photosensitizer in a visible region. The method includes the step of selecting the peak position and the concentration of the plasmon nano-particles, the type and the concentration of electrified substances and the peak position and the concentration of the photosensitizer to form the stable coupling system.

[0011] US7368570 discloses a series of organometallic complexes and the singlet oxygen sensitization properties of these complexes, in which the complexes with acetylacetonate ligands give singlet oxygen quantum yields near unity, whether exciting the ligand-based state or the lowest energy excited state (MLCT+3LC).

[0012] CN108929339 discloses a photosensitizer capable of generation singlet oxygen, and a preparation and application of the photosensitizer. The photosensitizer may be synthesized in a simple and efficient method, and the yield is high.

[0013] US20210221717 discloses a reactive oxygen species formulation by preparing a peracid mixture in an activated pH range including mixing alkaline hydrogen peroxide solution with acyl donor in molar proportions with an excess of the acyl donor to hydrogen peroxide. The hydrogen peroxide and acyl donor are reacted to produce a peracid mixture comprising no more than a small quantity of hydrogen peroxide, and pH is adjusted as needed to initially prepare the formulation in the activated pH range. Water treatment with the reactive oxygen species formulation facilitates formation and separation of solids removable during clarification, and which may be followed by a second treatment with the reactive oxygen species formulation for antimicrobial treatment of clarified water.

[0014] US11629052 discloses a single-atom catalyst for activation of persulfate to generate pure singlet oxygen in which the single-atom catalyst of the present disclosure includes supports and single iron atoms loaded on the support; the supports are graphitic carbon nitride nanosheets; the single iron atoms are bound to the supports in the form of a Fe-N4coordination structure.

[0015] US20190111168 discloses a photosensitizer dispersion in which the dispersion comprises: (a) at least one photosensitizer, (b) at least one liquid polar phase, and (c) at least one surfactant. The dispersion comprises and is preferably constituted by a microemulsion, a gel or a mixture thereof, at a temperature in the range 2°C to 50°C and a pressure in the range 800 to 1200 mbar.Summary

[0016] There is disclosed a system for generating singlet oxygen for purifying water, the system comprising a photosensitizer device comprising a substrate on the surface of which a photosensitizer material is coated; at least one light source, configured to illuminate light at a wavelength to the photosensitizer device; at least one transparent window, each transparent window mounted in between one light source and the photosensitizer device forming a flow chamber with enclosure walls of the system for placing the photosensitizer device therein, the at least one transparent window configured to have the light pass through and to ensure the flow chamber is water tight; a water stream, containing dissolved oxygen by injecting oxygen gas into the water; a water inlet, configured to feed the water stream to the flow chamber that contains the photosensitizer device, wherein the singlet oxygen is generated by contact of the water stream with the photosensitizer material under light illumination, simultaneously, the generated singlet oxygen purifies the water stream by oxidizing impurities and inactivates biological contaminants in the water stream; and a water outlet, configured to discharge a purified water.

[0017] In some embodiments, the substrate is a material with a surface roughness less than a ! wavelength of the light illuminated onto the photosensitizer device that increases a total water-photosensitizer contact area thereby increasing a yield of singlet oxygen generated thereon.

[0018] In some embodiments, the substrate and the photosensitizer material are hydrophobic and do not dissolved in water, respectively.

[0019] In some embodiments, the substrate is hydrophobic and does not dissolved in water.

[0020] In some embodiments, the photosensitizer material is hydrophobic and does not dissolved in water.

[0021] In some embodiments, the substrate is hydrophobic.

[0022] In some embodiments, the substrate does not dissolved in water.

[0023] In some embodiments, the material is hydrophobic.

[0024] In some embodiments, the material does not dissolved in water.

[0025] In some embodiments, the photosensitizer material is hydrophobic.

[0026] In some embodiments, the photosensitizer material does not dissolved in water.

[0027] In some embodiments, the substrate is composed of a stack of layers of planar meshes, a stack of layers of planar membranes, a stack of alternating layers of planar meshes and planar membranes, a spiral wound of planar meshes, a spiral wound of planar membrane, a plurality of transparent and rigid plastic rods, a plurality of hollow fiber membranes, or a bunch of meshes, saddles, or rings made from plastic materials wrapped with a planar membrane.

[0028] In some embodiments, the substrate is a stack of layers of planar meshes.

[0029] In some embodiments, the substrate is a stack of layers of planar membranes.

[0030] In some embodiments, the substrate is a stack of alternating layers of planar meshes and planar membranes.

[0031] In some embodiments, the substrate is a spiral wound of planar meshes.

[0032] In some embodiments, the substrate is a spiral wound of planar membrane.

[0033] In some embodiments, the substrate is a plurality of transparent and rigid plastic rods.

[0034] In some embodiments, the substrate is a plurality of hollow fiber membranes.

[0035] In some embodiments, the substrate is a bunch of meshes, saddles, or rings made from plastic materials wrapped with a planar membrane.

[0036] In some embodiments, the planar meshes are composed of woven or nonwoven filaments.

[0037] In some embodiments, the planar meshes are composed of woven or nonwoven filaments with a mesh opening size of < 1 mm.

[0038] In some embodiments, the planar mesh is a polymer composed of woven or non-woven filaments selected from a group consisting of polytetrafluoroethylene, fluorinated ethylene propylene, polyolefin, polyethylene, polypropylene, polyethylene terephthalate, crystalline polymer and nylon.

[0039] In some embodiments, the planar mesh is woven or non-woven filaments of polytetrafluoroethylene.

[0040] In some embodiments, the planar mesh is woven or non-woven filaments of fluorinated ethylene propylene.

[0041] In some embodiments, the planar mesh is woven or non-woven filaments of polyolefin.

[0042] In some embodiments, the planar mesh is woven or non-woven filaments of polyethylene.

[0043] In some embodiments, the planar mesh is woven or non-woven filaments of polypropylene.

[0044] In some embodiments, the planar mesh is woven or non-woven filaments of polyethylene terephthalate.

[0045] In some embodiments, the planar mesh is woven or non-woven filaments of crystalline polymer.

[0046] In some embodiments, the planar mesh is woven or non-woven filaments of nylon.

[0047] In some embodiments, the planar membrane is a polymer selected from a group consisting of polytetrafluoroethylene, fluorinated ethylene propylene, polyolefin, polyethylene, polypropylene, polyethylene terephthalate, crystalline polymer and nylon.

[0048] In some embodiments, the planar membrane is a polymer of polytetrafluoroethylene.

[0049] In some embodiments, the planar membrane is a polymer of fluorinated ethylene propylene.

[0050] In some embodiments, the planar membrane is a polymer of polyolefin.

[0051] In some embodiments, the planar membrane is a polymer of polyethylene.

[0052] In some embodiments, the planar membrane is a polymer of polypropylene.

[0053] In some embodiments, the planar membrane is a polymer of polyethylene terephthalate.

[0054] In some embodiments, the planar membrane is a polymer of crystalline polymer.

[0055] In some embodiments, the planar membrane is a polymer of nylon.

[0056] In some embodiments, a distance between adjacent layers of the stack of the layers of the planar meshes or planar membranes and the stack of the alternating layers of the planar meshes and planar membranes is less than 0.1 mm.

[0057] In some embodiments, the planar membranes and the hollow fiber membranes are porous.

[0058] In some embodiments, the planar membranes and the hollow fiber membranes are non-porous membranes.

[0059] In some embodiments, the planar membranes is porous.

[0060] In some embodiments, the planar membranes is non-porous membranes.

[0061] In some embodiments, the hollow fiber membranes is porous.

[0062] In some embodiments, the hollow fiber membranes is non-porous membranes.

[0063] In some embodiments, the planar porous membrane and the hollow fiber porous membrane have a pore dimension less than 1 micron.

[0064] In some embodiments, the planar porous membrane has a pore dimension less than 1 micron.

[0065] In some embodiments, the hollow fiber porous membrane has a pore dimension less than 1 micron.

[0066] In some embodiments, the amount of the photosensitizer material coated on the substrate of the photosensitizer device is optimized so that at least 50% of the light reaches the center of the photosensitizer device.

[0067] In some embodiments, a light intensity is chosen so that the maximum light penetration into the photosensitizer device is achieved without overheating and degrading the photosensitizer device on the substrate closest to the at least one light sources.

[0068] In some embodiments, the photosensitizer material is phthalocyanine.

[0069] In some embodiments, the phthalocyanine is a metal-containing phthalocyaninie.

[0070] In some embodiments, the phthalocyanine is Zn-phthalocyanine.

[0071] In some embodiments, the photosensitizer material is porphyrine.

[0072] In some embodiments, the porphyrine is a metal free porphyrin.

[0073] In some embodiments, the porphyrine is tetraphenyl porphyrin, fullerene or fullerene derivatives.

[0074] In some embodiments, the photosensitizer material produces singlet oxygen for 1000 hours at less than 10% reduction in singlet oxygen yield over the 1000 hours of operation.

[0075] In some embodiments, the photosensitizer material is Zinc phthalocyanine (ZnPC), or its fluoro-substituents selected from Zinc1 ,2, 3, 4, 8, 9, 10, 11 , 15, 16, 17, 18,22,23,24,25-hexadecafluoro-29H,31 H-phthalocyanine (Fi6ZnPC).

[0076] In some embodiments, the photosensitizer material is a substituted phthalocyanine where a metal or non-metal atom, such as Is, Cu, Cd, Si, Ge, etc., is substituted for Zinc, porphyrin, phenyl porphyrin.

[0077] In some embodiments, the photosensitizer material is tetrakis(p- phenyl)porphyrin (TPP) or its fluoro-substituents.

[0078] In some embodiments, the photosensitizer material is 5,10,15,20- tetrakis(pentafluorophenyl)-21 H, 23H-porphyrin (TFPP).

[0079] In some embodiments, the photosensitizer material is fluorine-containing phthalocyanine.

[0080] In some embodiments, the photosensitizer material is a fluorine-containing porphyrin.

[0081] In some embodiments, the photosensitizer material is fullerenes and substitutedfullerenes and similar graphite-based particles.

[0082] In some embodiments, the photosensitizer material is coated on the substrate by dip-coating, spray-coating, printing, or brush-coating method.

[0083] In some embodiments, the photosensitizer material is deposited on the substrate by dip-coating, spray-coating, printing, or brush-coating method.

[0084] In some embodiments, the amount of the photosensitizer material coated on the substrate of the photosensitizer is determined so that at least 50% of the light reaches the center of the photosensitizer.

[0085] In some embodiments, a concentration of the photosensitizer material coated on the substrate of the photosensitizer is determined so that at least 50% of the light reaches the center of the photosensitizer.

[0086] In some embodiments, the wavelength ranges from 250 to 1000 nm.

[0087] In some embodiments, the wavelength ranges from 400 to 750 nm.

[0088] In some embodiments, oxygen gas is a gas composed of at least 90% of oxygen.

[0089] In some embodiments, oxygen gas is liquid oxygen from liquid oxygen containers with industry grade.

[0090] In some embodiments, oxygen gas is oxygen gas from air.

[0091] In some embodiments, the water is a liquid or a fluid typically composed primarily of water, selected from fresh water, tap water, process water, effluent water, municipal and industrial wastewater, wastewater already treated by the secondary treatment process.

[0092] There is disclosed a method of generating singlet oxygen for purifying water, the method comprising the steps of injecting oxygen gas into the water forming a water stream containing dissolved oxygen; flowing the water stream into a photosensitizer device that comprises a substrate on the surface of which a photosensitizer material is coated; illuminating the photosensitizer device with a light source at a wavelength to generate the singlet oxygen therein; and simultaneously, oxidizing impurities and inactivating biological contaminants in the water stream with the generated singlet oxygen.

[0093] In some embodiments, the substrate is composed of a stack of layers of planar meshes, a stack of layers of planar porous membranes, a stack of alternating layers of planar meshes and planar porous membranes, a spiral wound of planar meshes, a spiralwound of planar porous membrane, a plurality of transparent and rigid plastic rods, a plurality of hollow fiber porous membranes, or a bunch of meshes, saddles, or rings made from plastic materials wrapped with a planar porous membrane.

[0094] In some embodiments, the substrate is a material with a surface roughness less than a ! wavelength of the light illuminated onto the photosensitizer device that increases a total water-photosensitizer contact area thereby increasing a yield of singlet oxygen generated thereon.

[0095] In some embodiments, the substrate and the photosensitizer material are hydrophobic and do not dissolved in water.

[0096] In some embodiments, the planar membranes and the hollow fiber membranes are porous or non-porous membranes.

[0097] In some embodiments, the wavelength ranges from 250 to 1000 nm.

[0098] In some embodiments, the wavelength ranges from 400 to 750 nm.

[0099] In some embodiments, a distance between adjacent layers of the stack of the layers of the planar meshes or planar membranes and the stack of the alternating layers of the planar meshes and planar membranes is less than 0.1 mm.

[0100] There is disclosed a method for generation of singlet oxygen for purifying water, the method comprising the steps of flowing the water into a photosensitizer device; injecting oxygen gas into the water either before or after flowing into the photosensitizer device; illuminating the photosensitizer device with a light source at a wavelength to generate the singlet oxygen therein; and simultaneously, oxidizing impurities and inactivating biological contaminants from the water with the generated singlet oxygen, wherein the photosensitizer device comprises a substrate on the surface of which a photosensitizer material is coated.Brief Description of the Drawings

[0101] For a further understanding of the nature and objects of the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein:FIG. 1 shows a cross-sectional block diagram of an embodiment of an exemplary singlet oxygen generation system equipped with a photosensitizer device composed of asupport that has a stack of layers of planar meshes or planar membranes in accordance with an exemplary embodiment of the present invention;FIG. 2 shows an oblique view of an exemplary photosensitizer device in FIG. 1, wherein the support is the stacked layers of planar meshes or planar membranes on the surface of which a photosensitizer material is coated;FIG. 3 shows a cross-sectional block diagram of an alternative embodiment of an exemplary singlet oxygen generation system equipped with a photosensitizer device composed of a support that has a packing material covered with hydrophobic porous membranes in accordance with an exemplary embodiment of the present invention;FIG. 4 shows a cross-sectional block diagram of an alternative embodiment of an exemplary singlet oxygen generation system equipped with a photosensitizer device composed of a support that has a packing material covered with hydrophobic porous membranes and at least two stacks of layers of planar meshes or planar membranes each covers the hydrophobic porous membranes in accordance with an exemplary embodiment of the present invention;FIG. 5 shows a cross-sectional block diagram of an embodiment of a cylindrical shaped singlet oxygen generation system equipped with a photosensitizer device composed of a support that has a spiral wounded planar mesh or planar membrane in accordance with an exemplary embodiment of the present invention;FIG. 6 shows a top view of the spiral wound planar mesh or planar membrane in the singlet oxygen generation system shown in FIG. 5;FIG. 7 shows a cross-sectional block diagram of an embodiment of a cylindrical shaped singlet oxygen generation system packed with a photosensitizer device composed of a support that has a plurality of transparent and rigid plastic rods in accordance with an exemplary embodiment of the present invention;FIG. 8 shows a top view of the plurality of transparent and rigid plastic rods in the singlet oxygen generation system shown in FIG. 7;FIG. 9 shows a cross-sectional block diagram of an embodiment of a cylindrical shaped singlet oxygen generation system packed with a photosensitizer device composed of a support that has a plurality of hydrophobic hollow fiber porous membranes in accordance with an exemplary embodiment of the present invention;FIG. 10 shows a water treatment flowchart with oxygenation prior to the singlet oxygen generation system in accordance with an exemplary embodiment of the present invention;FIG. 11 shows a water treatment flowchart with oxygen injection into the singletoxygen generation system in accordance with an exemplary embodiment of the present invention;FIG. 12 shows the specific energy consumption for the singlet oxygen generation system shown in FIG. 1 and uric acid oxidation at different irradiation light intensities;FIG. 13 shows the oxidation of select pharmaceutical compounds by the singlet oxygen generation system shown in FIG. 7, where PM MA rods were used as a support for the Fi6ZnPC photosensitizers; andFIG. 14 shows the oxidation of select pharmaceutical compounds by the singlet oxygen generation system shown in FIG. 7, where PM MA rods were used as a support for the TFPP photosensitizers.Description of Preferred Embodiments

[0102] Disclosed is a system and method of generation of singlet oxygen for water purification. More specifically, the disclosed is the system and method of generating singlet oxygen through photosensitization of triplet oxygen and method of using the same for purifying water. The disclosed comprises design criteria of the disclosed singlet oxygen generation system to optimize singlet oxygen production. The singlet oxygen generation system may be a flow cell or a reactor with various configurations, such as, cylindrical shapes or rectangular cuboids, equipped with various photosensitizer coated / embedded materials on a support or a substrate. The disclosed is a novel method of producing singlet oxygen in which the singlet oxygen is generated through photosensitization of triplet oxygen into the singlet oxygen by a photosensitizer under light illumination. One novelty is the presentation of a photosensitizer device, on which the photosensitizer or photosensitizer material is deposited or coated on the surface of a support or a substrate. The support or the substrate may be a stack of layers of planar meshes, a stack of layers of planar porous membranes, a stack of alternating layers of planar meshes and planar porous membranes, a spiral wound of planar meshes, a spiral wound of planar porous membrane, a plurality of transparent and rigid plastic rods, a plurality of hollow fiber porous membranes, or a bunch of meshes, saddles, or rings made from plastic materials wrapped with a planar porous membrane, etc., which serve as a support layer, a support material, a substrate or a carrier for the photosensitizer (PS). Herein, the planar mesh may be a plastic mesh composed of woven or non-woven filaments; the planar membrane may be a porous membrane or hydrophobic porous membrane; the transparent and rigid transparent plastic rods may be polymethyl methacrylate (PMMA) rods. In this way, the photosensitizer material is not lost after each use and has significantly longer service life than if it wasdispersed in a media without a carrier.

[0103] Here, the term “photosensitizer” or “photosensitizer material” refers to a substance that absorbs light energy and transfers it to other molecules, causing them to become reactive. It is understandable that a photosensitizer may correspond to, or be related to a photosensitizer material, and that the photosensitizer material may refer to the photosensitizer. One of the applications is that the photosensitizer or photosensitizer material absorbs energy directly from a light source, which it may then transfer to molecular oxygen to create an activated form of oxygen called singlet oxygen

[0104] Here term “photosensitizer device” refers to a device that equips with a support layer, support material, substrate or carrier for the photosensitizer or photosensitizer material on the surface of which the photosensitizer or photosensitizer material is coated. That is, the photosensitizer device includes a support and a photosensitizer that is coated on the support. The support layer, support material, substrate or carrier may be a stack of layers of planar meshes, a stack of layers of planar porous membranes, a stack of alternating layers of planar meshes and planar porous membranes, a spiral wound of planar meshes, a spiral wound of planar porous membrane, a plurality of transparent and rigid plastic rods, a plurality of hollow fiber porous membranes, or a bunch of meshes, saddles, or rings made from plastic materials wrapped with a planar porous membrane, etc.

[0105] Note that herein, the terms “support” and “support layer” and “support material” and “substrate” and “carrier” and “carrier material” may be used interchangeably to refer to a material for supporting the photosensitizer in a photosensitizer device. It is understood that a support may correspond to, or be related to a support material or a substrate, and that the support material or substrate may refer to the support. It is understandable that a support may correspond to, or be related to a carrier or a carrier material, and that the carrier and the carrier material may refer to the support.

[0106] Specifically, the photosensitizer is deposited or coated onto the surface of a support and is exposed to light (electromagnetic radiation) in a range of wavelengths specific to the photosensitizer. In one embodiment, the support may be several layers of planar meshes or planar membranes that may be stacked together to increase contact surface area between the photosensitizer and water. When water containing dissolved oxygen gas or water saturated with dissolved oxygen gas passes through layers of such support material that is exposed to a light source, triplet oxygen dissolved in the water is converted to singlet oxygen that purifies water by oxidizing impurities and inactivating biological contaminants immediately. Alternatively, when oxygen gas and watersimultaneously passes through the layers of such support material that is exposed to light, triplet oxygen is converted to singlet oxygen in the gas phase and then the generated singlet oxygen is dissolved in the water whereby oxidizing impurities and inactivating biological contaminants in water.

[0107] The range of wavelengths specific to a photosensitizer may be from 250 to 1000 nm, preferably from 400 to 750 nm depending on the photosensitizer material deposited or coated on a support.

[0108] Here water or water to be treated may be a liquid or a fluid typically composed primarily of water, such as fresh water, tap water, fish-tank water, process water, effluent water, municipal and industrial wastewater, and wastewater already treated by a secondary treatment process. The water and the water to be treated may be pre-treated through water filtration system before feeding to the disclosed singlet oxygen generation system.

[0109] Oxygen gas used herein may be liquid oxygen from liquid oxygen containers with industry grade, oxygen gas from air or a gas composed of at least 90% of oxygen.

[0110] FIG. 1 is a cross-sectional block diagram of an exemplary singlet oxygen generation system with a photosensitizer device. In this embodiment, a support of the photosensitizer device is a stack of layers of planar meshes or planar membranes on which a photosensitizer material is coated. The planar mesh may be a plastic mesh composed of woven or non-woven filaments. The planar membrane may be a sheet of porous membrane or hydrophobic porous membrane. The exemplary singlet oxygen generation system may be a reactor or a flow cell in which various parts are installed. As shown, reactor 100 comprises light sources 101 at a particular wavelength suitable for a photosensitizer to be used, transparent windows 102, and photosensitizer device 105, Reactor 100 may be a rectangular cuboid shaped reactor or flow cell in which light sources 101, transparent windows 102 and photosensitizer device 105 are mounted inside of the cuboid along the length of the cuboid and enclosed in reactor enclosure 110; water inlet 103 and oxygen gas inlets 108 are mounted on the left wall of the cuboid; and water outlet 104 is mounted on the right wall of the cuboid. Here two light sources 101 may be used in the upper and lower sides of photosensitizer device 105 for maximum illumination. Photosensitizer device 105 is illuminated by light source 101 through transparent window 102. Transparent window 102 is located between light source 101 and photosensitizer device 105 to ensure light from light source 101 pass through it to illuminate photosensitizer device 105. Two transparent windows 102 are installed with this embodiment and each separates light source 101 from photosensitizer device 105 and ensure no water leaks to photosensitizer device 105. Three separate chambers are formed in reactor 100 by two transparentwindows 102. The upper and the lower chambers each contains light source 101. The middle chamber is a flowing chamber that is water tight and contains photosensitizer device 105 that connects to water inlet 103, oxygen inlets 108 and water outlet 104, so that water and water to be treated is able to flow through photosensitizer device 105. Two oxygen inlets 108 may be installed and close to water inlet 103 for maximum oxygen dissolution or saturation in water if used. In some embodiments, oxygen gas is injected into water before the water feeding into water inlet 103, and forms the water containing dissolved oxygen or saturated with dissolved oxygen outside reactor 100. Then the water containing dissolved oxygen or saturated with dissolved oxygen is fed to water inlet 103. In some embodiments, oxygen gas and water may be fed to reactor 100 through oxygen inlets 108 and water inlet 103 separately. The water may be a liquid or a fluid typically composed primarily of water, such as fresh water, tap water, fish-tank water, process water, effluent water, municipal and industrial wastewater, wastewater already treated by the secondary treatment process, or a pre-treated through water filtration system before feeding to the disclosed singlet oxygen generation system. Photosensitizer device 105 includes a substrate or a support on the surface of which a photosensitizer material is coated or deposited. The photosensitizer material used for coating onto the support material or the substrate may be any photosensitizer that is hydrophobic and does not dissolve in water. The substrate or support is a stack of layers of planar meshes or planar membranes for increasing contact areas between oxygen gas and the photosensitizer. The planar meshes may be plastic meshes composed of woven or non-woven filaments with a meshes opening size of less than 1 mm. The planar membrane may be a porous or non-porous membrane. The planar membrane may be a hydrophobic membrane. The photosensitizer material is coated or deposited on the substrate by dip-coating, spray-coating, printing, brush-coating method or the like. The amount of the photosensitizer material coated on the substrate of photosensitizer device 105 may be optimized so that at least 50% of the light from light sources 101 reaches the center of photosensitizer device 105. Alternatively, a concentration of the photosensitizer material coated on the substrate of the photosensitizer device may be optimized so that at least 50% of the light from light sources 101 reaches the center of photosensitizer device 105.

[0111] The particular wavelength of light sources 101 may range from 250 to 1000 nm, preferably from 400 to 750 nm depending on the photosensitizer material deposited or coated on the support.

[0112] When reactor 100 is under operation, oxygen gas is injected to a body of water to be treated forming a water stream containing dissolved oxygen gas or saturated withdissolved oxygen gas first. Then the water stream containing dissolved oxygen or saturated with dissolved oxygen is fed to reactor 100 from water inlet 103, passes through photosensitizer device 105, and gets out of reactor 100 through water outlet 104. Water inlet 103 and water outlet 104 enable water flows through reactor 100. Thus, when photosensitizer device 105 and the water stream containing dissolved oxygen gas or saturated with dissolved oxygen gas are exposed to light source 101 , triplet oxygen in water is converted to singlet oxygen 106 (herein in FIG. 1 a circle shape is used to demonstrate generated singlet oxygen 106) in liquid phase. The generated singlet oxygen immediately purifies the water by oxidizing impurities and inactivating biological contaminants in the water. Thus, the water stream, i.e. , the body of waterto be treated, enters reactor 100 from water inlet 103 and a purified water comes out of reactor 100 through water outlet 104. Here, singlet oxygen 106 is generated by contact of photosensitizer device 105 with the water stream containing dissolved oxygen or saturated with dissolved oxygen under light illumination. Here, singlet oxygen 106 may be measured using various chemical probes, such uric acid, furfuryl alcohol or the like.

[0113] Alternatively, when reactor lOO is under operation, oxygen gas and water maybe mixed in the flowing chamber of reactor 100, rather than prior to entering reactor 100. In this embodiment, water to be treated is fed to reactor 100 from water inlet 103, passes through photosensitizer device 105, and gets out of reactor 100 through water outlet 104. Oxygen gas is injected into the flowing chamber through oxygen inlets 108 and dissolved in the water flowing there through. Thus, when photosensitizer device 105 and the water containing dissolved oxygen gas are exposed to light source 101, triplet oxygen in water is converted to singlet oxygen 106 (herein in FIG. 1 a circle shape is used to demonstrate generated singlet oxygen 106) in liquid phase. The generated singlet oxygen immediately purifies the water by oxidizing impurities and inactivating biological contaminants in the water. Thus, the water to be treated, enters reactor 100 from water inlet 103 and a purified water comes out of reactor 100 through water outlet 104. Here, singlet oxygen 106 is generated by contact of photosensitizer device 105 with the water containing dissolved oxygen under light illumination.

[0114] Alternatively, for the part of oxygen gas in the flowing chamber that does not dissolved in water, when oxygen gas passes through photosensitizer device 105 that is exposed to light source 101, triplet oxygen is converted to singlet oxygen 106 in gas phase. The generated singlet oxygen in gas phase is injected into water and some of it is dissolved in water. Then immediately the dissolved singlet oxygen oxidizes impurities and inactivating biological contaminants in the water. Here, the singlet oxygen is generated inthe gas phase by oxygen gas passing through a stack of layers of planar meshes or planar membranes coated with a photosensitizer material and illuminated with light at a particular wavelength. Some of oxygen gas is converted to the singlet oxygen. Then oxygen gas containing singlet oxygen is injected into the flowing water in the flowing chamber that contains the stack of layers of planar meshes or planar membranes to increase contact area between the photosensitizer and water.

[0115] In some embodiments, the support of photosensitizer device 105 is composed of a stack of layers of planar meshes, such as a stack of layers of plastic meshes, or a stack of layers of planar membranes. The planar meshes may be plastic meshes and composed of woven or non-woven filaments with a meshes opening size of less than 1 mm. The planar membrane may be a porous or non-porous membrane or a hydrophobic membrane such as planar porous membranes or planar hydrophobic porous membranes.

[0116] FIG. 2 is a block diagram of an exemplary support of the photosensitizer device 105 shown in FIG. 1. The support is a stack of layers of planar meshes or planar membranes, such as plastic meshes composed of woven or ono-woven filaments, porous membranes, non-porous membranes, hydrophobic porous membranes, hydrophobic non- porous membranes, etc., on the surface of which a photosensitizer material is coated. The spaces between the layers of the planar meshes or planar membranes form fluid or water flow channels therein when water flow through photosensitizer device 105. A height of the water flow channel is shown in FIG. 2. Preferably, when the stack of layers of the planar meshes or planar membranes is used in photosensitizer device 105 as a support, oxygen gas may be injected into the water to be treated before the water to be treated feeds to reactor 100. Alternatively, oxygen gas and the water to be treated may be fed to reactor 100 simultaneously thro ugh water inlet 103 and oxygen inlets 108 and oxygen gas and the water are mixed in the flowing chamber of reactor 100 as described above.

[0117] FIG. 3 is a cross-sectional block diagram of an alternative exemplary singlet oxygen generation system with a photosensitizer device. In this embodiment, a support of the photosensitizer device is composed of a packing material covered or wrapped with a hydrophobic porous membrane and a photosensitizer material is coated on the surface of the hydrophobic porous membrane. This exemplary singlet oxygen generation system may also be a reactor or a flow cell in which various parts are installed. As shown, reactor 200 comprises light sources 201 at a particular wavelength suitable for a photosensitizer to be used, transparent windows 202, packing material 205, hydrophobic porous membrane 207, water inlet 203, water outlet 204 and oxygen gas inlets 208. Two hydrophobic porous membranes 207 each covers packing material 205 from the top and the bottom of packingmaterial 205 respectively. Two hydrophobic porous membranes 207 may be planar hydrophobic porous membranes. Reactor 200 may be a rectangular cuboid shaped reactor or flow cell in which light sources 201 , transparent windows 202, packing material 205 and hydrophobic porous membranes 207 are mounted inside of the cuboid along the length of the cuboid and enclosed in reactor enclosure 210; water inlet 203 and oxygen gas inlets 208 are mounted on the left wall of reactor enclosure 210; and water outlet 204 is mounted on the right wall of reactor enclosure 210. Here two light sources 201 may be used in the upper and lower sides of hydrophobic porous membranes 207 for maximum illumination respectively. Packing material 205 and hydrophobic porous membranes 207 are illuminated by light source 201 through transparent windows 202. Transparent windows 202 is located between light source 201 and hydrophobic porous membrane 207 to ensure light from light source 201 pass through transparent windows 202 to illuminate hydrophobic porous membranes 207 and packing material 205. Two transparent windows 202 are installed. Five separate chambers may be formed in reactor 200 by two transparent windows 202 and two hydrophobic porous membranes 207. The upper and the lower chambers each contains one light source 201, which are water free. The middle chamber is a flowing chamber containing packing material 205 and connecting to water inlet 203 and water outlet 204, so that water is able to flow through packing material 205. The rest two chambers or gas spaces 212 are gas chambers, each is formed with one transparent window 202 and one hydrophobic porous membranes 207 and connected to oxygen inlet 208, in which oxygen gas is injected. Since the hydrophobic property of hydrophobic porous membranes 207, gas spaces 212 are water free, which results in the flowing chamber containing packing material 205 maintains water free too. In this way, the five separate chambers each are water tight. Packing material 205 may be a bunch of meshes, saddles, or rings made from plastic materials that cause water turbulence so that to increase water flowing time in the flowing chamber and to increase contact area and interaction between water and the photosensitizer. Hydrophobic porous membranes 207 each covering packing material 205 forms gas spaces 212 between transparent window 202 and one hydrophobic porous membrane 207 where one oxygen inlet 208 is connected therein. A photosensitizer material is coated or deposited on hydrophobic porous membranes 207 and optionally coated on packing material 205. The photosensitizer material used herein may be any photosensitizer that is hydrophobic and does not dissolve in water. The photosensitizer material is coated or deposited on the substrate by dip-coating, spray-coating, printing, brush-coating method or the like. The amount of the photosensitizer material coated on the substrate of the photosensitizer device, composed of packing material 205 andhydrophobic porous membranes 207 in this embodiment, may be optimized so that at least 50% of the light from light sources 201 reaches the center of packing material 205. Alternatively, a concentration of the photosensitizer material coated on the substrate of the photosensitizer device, composed of packing material 205 and hydrophobic porous membranes 207 in this embodiment, may be optimized so that at least 50% of the light from light sources 201 reaches the center of packing material 205.

[0118] The particular wavelength of light sources 201 may range from 250 to 1000 nm, preferably from 400 to 750 nm depending on the photosensitizer material deposited or coated on the support.

[0119] When reactor 200 is under operation, water and oxygen gas are fed to reactor 200 through water inlet 203 and oxygen inlets 208 simultaneously. Water passes through packing material 205 and hydrophobic porous membrane 207 in the flowing chamber and gets out of reactor 200 through water outlet 204. Water inlet 203 and water outlet 204 enable water flows through reactor 200. Oxygen gas is injected into reactor 200 through oxygen inlets 108 and gets contact with hydrophobic porous membranes 207 in gas spaces 212. When oxygen gas is blown into reactor 200 through oxygen inlets 208 while water is flowing through reactor 200 from water inlet 203 under illumination from light source 201, triplet oxygen is converted to singlet oxygen 206 (herein in FIG. 3 a circle shape is used to demonstrate generated singlet oxygen 206) in gas phase in gas spaces 212. Since hydrophobic porous membrane 207 repels water, water may not pass through hydrophobic porous membranes 207 into gas spaces 212, but the generated singlet oxygen 206 is able to pass through hydrophobic porous membrane 207 and enters packing material 205 where the singlet oxygen purifies the water by oxidizing impurities and inactivating biological contaminants in the water immediately. Thus, contaminated water enters reactor 200 from water inlet 203 and a purified water comes out of reactor 200 through water outlet 204. Here two oxygen inlets 208 may be installed for enhancing singlet oxygen generation.

[0120] FIG. 4 is a cross-sectional block diagram of an alternative exemplary singlet oxygen generation system with a photosensitizer device. The difference between FIG. 4 and FIG. 3 is gas spaces 212 in FIG. 3 is filled with material 309 in FIG. 4. Material 309 is a stack of planar meshes or planar membranes or a stack of alternating layers of meshes and planar membranes. In this embodiment, the photosensitizer device includes a support that is composed of material 309, hydrophobic porous membranes 307 and packing material 305. A photosensitizer material is coated on the surface of material 309 and hydrophobic porous membranes 307, and optionally on packing material 305. The photosensitizer material coated on the stack of planar meshes or planar membranes or thestack of alternating layers of meshes and planar membranes may be the same as the photosensitizer material coated on hydrophobic porous membranes 307. The singlet oxygen is generated in material 309 and around hydrophobic porous membranes 307 in gas phase, then penetrates to packing material 305 and is dissolved in water. In this case, the support of the photosensitizer device increases surface area for contact of the photosensitizer and oxygen gas or contact of the photosensitizer and the water containing dissolved oxygen or started with dissolved oxygen.

[0121] FIG. 5 is a block diagram of an alternative exemplary singlet oxygen generation system with a photosensitizer device. The exemplary singlet oxygen generation system may be a cylindrical reactor or a cylindrical flow cell packed with a spiral wound of planar mesh or planar membrane on the surface of which a photosensitizer material is coated. As shown, reactor 400 comprises light source 401 at a particular wavelength, transparent window 402, photosensitizer device 405, composed of a spiral wound of planar mesh or planar membrane, enclosed in transparent enclosure 407, and water inlet 403, water outlet 404, and oxygen gas inlet 408 mounted on transparent enclosure 407. Transparent enclosure 407 forms a flow chamber in which water flows from water inlet 403 to water outlet 404 and is enclosed in external light housing device 410. Photosensitizer device 405 is enclosed in the flow chamber that is water tight. Water inlet 403 and water outlet 404 are mounted on the top and bottom of transparent enclosure 407 respectively. Oxygen inlet 408 is installed on the top of transparent enclosure 407 and close to water inlet 403. In reactor 400, light source 401 is mounted along the center axis of the cylinder; transparent window 402 and photosensitizer device 405 are mounted symmetrically surrounding light source 401 in which transparent window 402 separates light source 410 from photosensitizer device 405 and allows light illuminating photosensitizer device 405; oxygen gas inlet 408 is mounted on top of the cylinder, and water inlet 403, water outlet 404 are mounted on the sidewall of the cylinder, respectively, in which water inlet 403 is installed higher than water outlet 404. Transparent window 402 is a transparent inner light source enclosure symmetrically surrounded light source 401. Here one light source 401 may be used along the axis of the cylinder, and one transparent window 402 surrounded light source 401 is used to separates light source 401 from photosensitizer device 405 and ensure no water leaks to light source 401. Photosensitizer device 405 is the spiral wound meshes or membrane coated with the photosensitizer material. Photosensitizer device 405 is enclosed in transparent enclosure 407 that is no water leaks. Outside transparent enclosure 407 is external light housing 410 that absorbs light. Photosensitizer device 405 is illuminated by light source 401 through transparent window 402. Oxygen gas is blowninto photosensitizer device 405 through oxygen inlet 408. Water inlet 403 and water outlet 404 enable water flows through reactor 400. The particular wavelength of light source 401 may range from 250 to 1000 nm, preferably from 400 to 750 nm depending on the material of the photosensitizer coated on the spiral wound mesh or membrane.

[0122] When reactor 400 is under operation, water enters reactor 400 from water inlet 403, passes through photosensitizer device 405, and comes out of reactor 400 through water outlet 404. When oxygen gas is blown into reactor 400 through oxygen inlet 408 while water is flowing through reactor 400 from water inlet 403, oxygen gas is dissolved in water resulting in a water stream containing dissolved oxygen or a water stream saturated with dissolved oxygen, Thus, when photosensitizer device 405 and the water stream containing dissolved oxygen or water saturated with dissolved oxygen are exposed to light source 401, triplet oxygen in water is converted to singlet oxygen 406 (herein in FIG. 5 a circle shape is used to demonstrate generated singlet oxygen 406) in liquid phase. The generated singlet oxygen then simultaneously purifies the water by oxidizing impurities and inactivating biological contaminants in water. Singlet oxygen 406 is generated by contact of a flowing water stream containing dissolved oxygen or saturated with dissolved oxygen with photosensitizer device 405 under light illumination.

[0123] FIG. 6 is a top view of reactor 400 shown in FIG. 5 with a spiral wound of planar mesh or planar membrane. Wth the spiral wound shape, water channels or flow channels are formed within photosensitizer device 405, which increase contact surface area between the photosensitizer and flowing water.

[0124] FIG. 7 shows a block diagram of an alternative exemplary singlet oxygen generation system with a photosensitizer device. The difference between FIG. 7 and FIG. 5 is photosensitizer device 405 composed of a spiral wound of planar mesh or planar membrane in FIG. 5 is replaced with photosensitizer device 505 in FIG. 7 that is composed of a plurality of plastic rods, preferably a plurality of transparent and rigid plastic rods. In addition, an external light housing outside transparent enclosure 410 in FIG. 5 is optional in FIG. 7 (not shown).

[0125] FIG. 8 is a cross sectional view of reactor 500 shown in FIG. 7 with a photosensitizer device that contains a plurality of transparent and rigid plastic rods. With the rods placed closely, e.g., less than 0.1 mm, water channels or flow channels is formed within photosensitizer device 505, which increase contact surface area between the photosensitizer and flowing water. Photosensitizer device 505 comprises a substrate or a support of the plurality of plastic rods on which a photosensitizer material is coated or deposited. In some embodiments, the plurality of the plastic rods may be transparent andrigid plastic rods that are roughened and coated with a photosensitizer material.

[0126] FIG. 9 shows a cross sectional view of an alternative exemplary singlet oxygen generation system with a photosensitizer device. The difference between FIG. 9 and FIG. 7 is a support of photosensitizer device 605 of reactor 600 in FIG. 9 is composed of a plurality of hollow fiber porous membranes and oxygen gas chamber 612 is installed in FIG. 9 for delivering oxygen gas into the hollow fiber porous membranes. Each hollow fiber porous membrane is connected to gas chamber 612 and sealed therein. With the hollow fiber porous membranes placed closely, water channels or flow channels are formed within photosensitizer device 605, which increase contact surface area between the photosensitizer and flowing water. Since oxygen gas is injected into the hollow fiber porous membranes, oxygen gas chamber 612 is installed in the top portion of transparent enclosure 607. Photosensitizer device 605 comprises a substrate or a support of the plurality of hollow fiber porous membranes on which a photosensitizer material is coated or deposited. In some embodiments, the plurality of the hollow fiber porous membranes may be hydrophobic hollow fiber porous membranes on the surface of which a photosensitizer material is coated or deposited.

[0127] FIG. 10 shows a general water treatment process with oxygen injection into water prior to a singlet oxygen generation system. The water treatment process comprises water filtration step 1, water oxygenation step 2 and singlet oxygen generation step 3. Water treatment 1 pretreats the water by oxidizing biological materials and this step may be optional. At water oxygenation step 2, oxygen gas is injected into the water fed from water filtration step 1 and produces oxygen saturated water that is forwarded to step 3 of singlet oxygen generation that is performed in a disclosed singlet oxygen generation system as stated above. The singlet oxygen is generated by contact of flowing water saturated with dissolved oxygen with photosensitizers coated on the support layers of photosensitizer device in the singlet oxygen generation system as stated above, and simultaneously the generated singlet oxygen oxidizes impurities and inactivating biological contaminants in the water and a purified water is coming out of the singlet oxygen generation system.

[0128] FIG. 11 shows a general water treatment process with oxygen injection into water in a singlet oxygen generation system through a hydrophobic porous membrane coated with photosensitizer material. The water treatment process comprises water filtration step 10 and singlet oxygen generation step 30. Water treatment 10 pretreats the water by oxidizing biological materials and this step may be optional. The pretreated water from water filtration step 10 is fed to singlet oxygen generation step 30 that is performed ina disclosed singlet oxygen generation system as stated above. When oxygen gas is injected into the singlet oxygen generation system with water flowing in, singlet oxygen is generated in the singlet oxygen generation system and simultaneously the generated singlet oxygen oxidizes impurities and inactivating biological contaminants in the water and a purified water is coming out of the singlet oxygen generation system.

[0129] In some embodiments, water containing dissolved oxygen or water saturated with dissolved oxygen gas flows through a photosensitizer device that are illuminated with a light source with a specific wavelength range for the type of a photosensitizer material from 250 to 1000 nm, preferably from 400 to 750 nm.

[0130] In some embodiments, water entering the disclosed singlet oxygen generation system is saturated with dissolved oxygen gas in a concentration range 30-40 mg / L.

[0131] In some embodiments, oxygen is injected into water to be purified under 2 to 5 bar pressure to achieve high oxygen saturation concentrations such as 80 to 200 mg / L.

[0132] In some embodiments, a feed water may be saturated with dissolved oxygen using an ultrafine bubble generator such as microbubble or nanobubble generator. When oxygen in oxygen saturated water comes in contact with a substrate that is porous in nature, coated with a photosensitizer and exposed to an electromagnetic radiation (e.g., light) in a specific range of wavelengths, triplet oxygen in water is converted to singlet oxygen. The singlet oxygen generated in water both oxidizes impurities in water and disinfects water as well. The substrate may be a mesh preferably made from transparent nylon or polypropylene fibers and has a woven structure to improve water mixing and contact as it travels along the surface of the photosensitizer material.

[0133] In some embodiments, as shown in FIG. 2, planar meshes or planar membranes of the substrate coated with a photosensitizer material are stacked to increase a contact surface area between the photosensitizer and flowing water that is saturated with dissolved oxygen.

[0134] In some embodiments, as shown in FIG. 2, planar meshes or planar membranes of the substrate coated with photosensitizer material are stacked to increase the contact surface area between the photosensitizer and flowing water that contains dissolved oxygen.

[0135] In some embodiments, a spiral wound substrate is used for the same purpose of increasing the contact area as the planar mesh or planar membrane substrate does, as shown in FIG. 5 and FIG. 6.

[0136] Alternatively, as shown in FIG. 3 and FIG. 4, singlet oxygen is generated by passing oxygen gas through a hydrophobic porous membrane substrate coated with thephotosensitizer and exposed to electromagnetic radiation in the specific range of wavelengths. The gas containing singlet oxygen is then injected into a flowing body of water. The hydrophobic porous membrane substrate is preferably made from fluoropolymers such as polytetrafluoroethylene or polyvinylidene fluoride, or ultrahigh density polyethylene.

[0137] In some embodiments, layers of support material and a spiral wound of support material coated with photosensitizer are used to increase the oxygen gas and photosensitizer contact area.

[0138] In some embodiments, a packing material is used in the water flow reactor to optimize oxygen-water mixing and minimize the time for transfer of singlet oxygen into water.

[0139] In some embodiments, the substrate is transparent, rigid plastic rods that roughened and coated with a photosensitizer as shown in FIG. 7 and FIG. 8.

[0140] Alternatively, in some embodiments, a hollow fiber porous membrane that is hydrophobic may be used as a support material for photosensitizer coating as shown in FIG. 9. A photosensitizer material may be coated onto the inner (lumen) or outer (shell) surface of the hydrophobic hallow fiber porous membrane support. Preferably the photosensitizer material is coated on the inner surface of the support material. Upon exposure to the light, oxygen in the gas phase flowing though the lumen side of the membrane comes in contact with the photosensitizer material and is transferred into water flowing on the shell side of the membrane.

[0141] Throughout the embodiments stated above, a photosensitizer material may be any photosensitizer that is hydrophobic and does not dissolve in water may be used for coating onto a support material or a substrate. The photosensitizer material that produces singlet oxygen for 1000 hours at less than 10% reduction in singlet oxygen yield over the 1000 hours of operation is preferred. Examples of the photosensitizers include Zinc phthalocyanine (ZnPC), or its fluoro-substituents such as Zinc 1 ,2, 3, 4, 8, 9, 10, 11 , 15, 16, 17, 18,22,23,24,25-hexadecafluoro-29H,31 H-phthalocyanine (Fi6ZnPC) or an similarly substituted phthalocyanine where a metal or non-metal atom, such as Is, Cu, Cd, Si, Ge, etc., is substituted for Zinc, porphyrin, phenyl porphyrin, or tetrakis(p-phenyl)porphyrin (TPP) or its fluoro-substituents such as 5,10,15,20- tetrakis(pentafluorophenyl)-21 H, 23H-porphyrin (TFPP), or any other fluorine-containing phthalocyanine, or a fluorine-containing porphyrin. Fullerenes and substituted fullerenes and similar graphite-based particles could also be used.

[0142] Light emitting diodes (LEDs) may be used as light sources that generate light inthe inner enclosure or chamber and external light enclosure. Both inner and outer enclosures are made of transparent material such as polycarbonate, acrylic, or any other material having low refractive index.

[0143] Different methods for coating the photosensitizer on the support material may be used such as dip-coating, spray-coating, printing, brush-coating, etc.

[0144] One important factor is all of the water flowing through the disclosed singlet oxygen generation system needs to come within close proximity of the singlet oxygen generation surface (i.e., coated photosensitizer). If the height of the flow or water channel above the surface is too large, then the water traveling furthest from the surface may not be exposed to a sufficient quantity of singlet oxygen (1O2) before it decays back to triplet oxygen (3O2). This is especially true in laminar flow systems. Thus, some of the water could bypass the singlet oxygen generation surface and not be disinfected. Here disinfected not only means killing pathogens, but also means oxidizing any organic contaminant. Optimal channel height will depend on the viscosity of the fluid, the smoothness / flatness of the surface, and the required flow rate amongst other factors. Channel heights or distances, e.g., as shown in FIG. 2 and FIG. 8, are typically less than 1 mm, preferably less than 0.1 mm, more preferably less than 0.001 mm.

[0145] A second important factor is a need for sufficient light of a wavelength that may be effectively absorbed by the photosensitizer to penetrate and illuminate all the photosensitizer-coated support layers. The light penetration depth is a combination of several factors: light intensity; photosensitizer loading level; the geometry and chemistry of the support layer; and the illumination design, as described in more detail below.

[0146] Light intensity. A more intense light source (i.e. a light source with higher irradiance) will be able to penetrate deeper into the system with enough optical fluence to generate a sufficient amount of singlet oxygen to kill pathogens and oxidize contaminants in water. There are limitations, however, to the level of brightness. At excessively high irradiance values, the photosensitizer-coated layers closest to the light source may absorb enough photons to cause the photosensitizer to increase in temperature. When exposed to elevated temperatures for long periods of time, the photosensitizer may degrade. The photosensitizer would cease to function when degraded and the resulting lower1O2yields would reduce the efficacy of the singlet oxygen generation system. Expense would be incurred to purchase and install replacement photosensitizer-coated support layers as well as a downtime that the user would incur.

[0147] Photosensitizer loading. The rate of heating to the singlet oxygen system may depend not only on the incident irradiance, but also on the photosensitizer loading. Thegreater the photosensitizer loading, the more light that will be absorbed and the higher the temperature increase that will occur. The photosensitizer molecules at the outer support surface will release singlet oxygen1C>2 into the flowing water readily, whereas the photosensitizer located closest to the support surface will not effectively release singlet oxygen1C>2 into the flowing water for two reasons: i)3C>2 needs to diffuse through the photosensitizer coating to reach the inner photosensitizer surfaces, thus, this diffusion rate will limit the reaction; ii) singlet oxygen1C>2 released from the inner photosensitizer surfaces would need to diffuse through the photosensitizer coating before it reaches the water. This longer path length would lower the lifetime during which1C>2 would be able to react with contaminants in the water. Thus, minimizing the photosensitizer loading level (or photosensitizer coating thickness) provides two benefits: i) light is able to penetrate more deeply into the photosensitizer and thus increase the number of photosensitizer-coated support surfaces; ii) overheating is avoided and the durability of the system is increased and iii) lower photosensitizer loading also causes less aggregation / reduced size of photosensitizer on polymer supports which further enhances the efficiency of1C>2 generation. Here, the terms “overheating” refers to raising the temperature of a substrate closest to a light source more than 5°C above an inlet water temperature that would decrease a singlet oxygen yield by more than 20%.

[0148] Support Laver. The geometry and chemistry of the support layers that support the photosensitizer are also critical to the efficient operation of the singlet oxygen generation system. a. Surface chemistry. The support layer surface chemistry may be stable to ensure durable adhesion with the photosensitizer coating. Typically, hydrophobic photosensitizers may be used to minimize and / or prevent their dissolution into the flowing water. Thus, the surface of the support layer may also be hydrophobic in order to maximize intermolecular London forces with the photosensitizer. The support layer also needs to be hydrolytically stable, as it is continuously immersed in flowing water. Polymer support materials that could be used include fluoropolymers such as PTFE and FEP, polyolefins such as polyethylene and polypropylene, and crystalline polymers such as nylons. b. Geometry and optical properties. The photosensitizer-coated support layer should allow light to penetrate into the photosensitizer. Thus, the support layer should be composed of a polymer that does not absorb the incident radiation. The polymers listed in the previous paragraph are transparent to visible light and are good candidates. However, because these polymers are crystalline, the boundariesbetween crystallites will scatter light. Some scattering may be beneficial, because it may lead to a uniform light distribution, but excessive light scattering may reduce light penetration. Several factors affect polymer scattering: i. One factor is the degree of crystallinity and the size of the crystalline grains, which impact light penetration even for polymers that do not absorb the incident light. Thus, polymer support materials that are fabricated with a lower degree of crystallinity and / or with grain sizes less than ! of the wavelength of the incident light would be preferred. ii. A second factor that affects scattering is the roughness of the surface. Polymer surfaces that exhibit roughness on the order of ! of the wavelength of incident light or larger will scatter light to a greater extent than smoother surfaces. Thus, smooth support layers would be preferred over roughened layers. iii. A third factor that affects light penetration is the percent openings (i.e. pores) of the support layer. In one approach, a smooth, continuous film or sheet of a transparent polymer support layer would minimize scattering and maximize light transmittance for a given photosensitizer coating thickness. The only reductions in transmittance that would occur result from the difference in refractive index between polymer sheets and water. In another approach, a meshes made from polymer filaments would maximize light transmittance. The openings between filaments in a meshes support would not block any light. Larger pores would allow more light to be transmitted through a layer. Such meshes supports are typically made from more highly crystalline polymers and the filaments may contribute to scattering. As mentioned previously, a small amount of scattering may be beneficial for achieving uniformity. Thus, smaller diameter filaments would minimize the total scattering areal fraction and allow for deeper overall penetration. Again, using less crystalline polymers with an index of refraction that more closely matches the environment would reduce scattering effects. For example, a meshes support layer with a large pore size (2-3 mm) but made with fine (20- 30 pm) filaments would allow the light to penetrate through many support layers, and provide sufficient scattering to ensure the uniform distribution of light amongst layers.Rough surface are preferred over smooth surfaces. However, if the scale of the surface roughness is greater than ! of the wavelength of incident light,the light scattering would be detrimental for singlet oxygen yield. The higher surface area of this fine-scale roughness would increase the total waterphotosensitizer contact area and increase the yield of singlet oxygen generated per layer.

[0149] Illumination. It is essential that all the photosensitizer-coated support layers are illuminated with sufficient light that the water passing through the system may be effectively treated, regardless of the location within the system. If the support layers are illuminated from one side only, the light intensity will decrease as successful layers are illuminated. Photosensitizer-coated support surfaces nearest to the light source will generate more singlet oxygen than surfaces furthest from the light source. At some point, insufficient light reaches a layer to effectively disinfect the fluid without organisms bypassing treatment. Thus, the number of support layers would need to be reduced so that only those layers that receive sufficient light are included in the system. Such a system is inherently inefficient as some light will be transmitted by the layer furthest from the light source and will be wasted. Placing a highly reflective surface on the opposite side of the reactor could mitigate this wasted light in part, but mirrors are <100% reflective. To reduce the variation in singlet oxygen yield as a function of distance from the light source, a second light source could be installed opposite the first light source. Thus, as the light intensity from one source decays the light intensity from the opposite light source would increase. Balancing the light intensity and the optical properties of the support layers would result in a relatively uniform distribution of singlet oxygen yields with no light wasted.

[0150] Channel walls. Minimizing the static boundary layer in the fluid at the photosensitizer-coated layer surface would help ensure that all of the water in a flow channel will be exposed to sufficiently high concentrations of singlet oxygen. Several approaches may be used to accomplish this. In one approach, flow disrupters may be used to impinge the flowing water onto photosensitizer-coated surfaces. This approach could be especially efficient when smooth support layers are used. In another approach, a meshes layer may be used as the photosensitizer support. The woven, or non-woven polymer meshes is composed of filaments that would induce waviness into the flow stream. As water flows above or below the individual filaments, a waviness would be introduced into the otherwise laminar flow, thereby thinning the boundary layer.

[0151] In summary, to maximize efficiency of the singlet oxygen system, the following parameters need to be optimized: a. Minimize photosensitizer coating thickness while achieving >100% coverage of all support layers;b. Maximize photosensitizer and fluid contact area by using high surface area support layers that are made from polymers that do not absorb the incident radiation and that have surface roughness that is less than ! of the wavelength of incident light; c. Match light penetration depth with the incident irradiance and the number of photosensitizer-coated support layers. For example, using two light sources mounted on opposite sides of the system provides more uniform singlet oxygen generation and thus disinfection, as shown in FIG. 1 for rectangular cuboid shaped flow cell assemblies; d. Minimize the distance between support layers to ensure that singlet oxygen may reach the center of every channel; e. Impart waviness into the channel walls to reduce the thickness of the boundary layer between photosensitizer surface and the fluid; and f. Design the support layers to minimize scattering either through the use of large pores or smooth surfaces.Examples

[0152] The following non-limiting examples are provided to further illustrate embodiments of the invention. However, the examples are not intended to be all inclusive and are not intended to limit the scope of the inventions described herein.Example 1:

[0153] FIG. 12 shows the specific energy consumption for singlet oxygen generation system and uric acid oxidation at different irradiation light intensities for singlet oxygen generation system shown in FIG. 1. The photosensitizer support was nylon meshes with meshes open area size of 0.2 mm. Oxygen gas is injected into water first, as shown in FIG. 9, such that oxygen gas is dissolved in water. The water contains oxygen and may be saturated with dissolved oxygen gas. Then the water containing oxygen or saturated with dissolved oxygen enters the singlet oxygen generation system and flows through layers of nylon meshes coated with Fi6ZnPC exposed to the light source in the range 660-670 nm.

[0154] FIG. 12 shows the specific energy consumption for singlet oxygen generation using uric acid as a singlet oxygen trapping agent and the reactor system is shown in FIG.1 with dimensions 30mm(D) x 30mm(W) x 150mm (L). To determine the maximum amount of singlet oxygen generated, the uric acid concentration in water was at 1000 mg / L. To dissolve this amount uric acid, the pH of the solution was raised to 11 ±0.2. The uric acidundergoes slow autodegradation in water under ambient conditions. To prevent uric acid autodegradation, the temperature of the uric acid solution was maintained at 13°C. The uric acid solution was saturated with dissolved oxygen flow before entering the reactor. The results show that the disclosed system for singlet oxygen generation is very energy efficient. The energy efficiency declines as light intensity increases, however, a singlet oxygen yield increases nearly linearly with increase in light intensity. The increase of light power from 8.6 W to 25.8 W, increased uric acid degradation from 798 mg / h to 1742 mg / h, corresponding to a singlet oxygen yield of 142 to 331 mg / h.Example 2:

[0155] FIG. 13 and FIG. 14 show the oxidation of select pharmaceutical compounds by the singlet oxygen generation system shown in FIG. 7, where PM MA rods with diameter of 2 mm were used as the support for the Fi6ZnPC and TFPP photosensitizers, respectively. When Fi6ZnPC was used as photosensitizer, the reactor was illuminated with LED light source emitting light in the range of 660-670 nm. When TFPP was used as a photosensitizer, the reactor was illuminated with LED light source emitting light in the range of 420-430 nm.

[0156] The results presented in FIG.13 and FIG. 14 were generated in semi-batch mode using the singlet oxygen generation system shown in FIG. 7. Oxygen gas was injected directly into the reactor containing water with 0.1 mM of individual compounds. The test was carried out at room temperature and pH of 7.4. The results show fast and effective degradation of the three compounds by singlet oxygen.

[0157] Reference herein to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the invention. The appearances of the phrase "in one embodiment" or “in some embodiments” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments necessarily mutually exclusive of other embodiments. The same applies to the term “implementation.”

[0158] As used in this application, the word “exemplary” is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects or designs. Rather, use of the word exemplary is intended to present concepts in a concrete fashion.

[0159] As used herein, the indefinite article “a” or “an” means one or more.

[0160] As used herein, “about” or “around” or “approximately” in the text or in a claim means ±10% of the value stated.

[0161] As used herein, “room temperature” in the text or in a claim means from approximately 20°C to approximately 25°C.

[0162] The standard abbreviations of the elements from the periodic table of elements are used herein. It should be understood that elements may be referred to by these abbreviation (e.g., Si refers to silicon, N refers to nitrogen, O refers to oxygen, C refers to carbon, H refers to hydrogen, F refers to fluorine, etc.).

[0163] Ranges may be expressed herein as from about one particular value, and / or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and / or to the other particular value, along with all combinations within said range. Any and all ranges recited herein are inclusive of their endpoints (i.e., x=1 to 4 or x ranges from 1 to 4 includes x=1 , x=4, and x=any number in between), irrespective of whether the term “inclusively” is used.

[0164] Additionally, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or”. That is, unless specified otherwise, or clear from context, “X employs A or B” is intended to mean any of the natural inclusive permutations. That is, if X employs A; X employs B; or X employs both A and B, then “X employs A or B” is satisfied under any of the foregoing instances. In addition, the articles “a” and “an” as used in this application and the appended claims should generally be construed to mean “one or more” unless specified otherwise or clear from context to be directed to a singular form.

[0165] "Comprising" in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing (i.e., anything else may be additionally included and remain within the scope of “comprising”). “Comprising” is defined herein as necessarily encompassing the more limited transitional terms "consisting essentially of" and “consisting of’; “comprising” may therefore be replaced by "consisting essentially of" or “consisting of” and remain within the expressly defined scope of “comprising.”

[0166] “Providing” in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actors in the absence of express language in the claim to the contrary.

[0167] It will be understood that many additional changes in the details, materials, steps, and arrangement of parts, which have been herein described and illustrated in orderto explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above and / or the attached drawings.

[0168] While embodiments of this invention have been shown and described, modifications thereof may be made by one skilled in the art without departing from the spirit or teaching of this invention. The embodiments described herein are exemplary only and not limiting. Many variations and modifications of the composition and method are possible and within the scope of the invention. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims which follow, the scope of which shall include all equivalents of the subject matter of the claims.

Claims

What is claimed is:1 . A system for generating singlet oxygen for purifying water, the system comprising: a photosensitizer device comprising a substrate on the surface of which a photosensitizer material is coated; at least one light source, configured to illuminate light at a wavelength to the photosensitizer device; at least one transparent window, each transparent window mounted in between one light source and the photosensitizer device forming a flow chamber with enclosure walls of the system for placing the photosensitizer device therein, the at least one transparent window configured to have the light pass through and to ensure the flow chamber is water tight; a water stream, containing dissolved oxygen by injecting oxygen gas into the water; a water inlet, configured to feed the water stream to the flow chamber that contains the photosensitizer device, wherein the singlet oxygen is generated by contact of the water stream with the photosensitizer material under light illumination, simultaneously, the generated singlet oxygen purifies the water stream by oxidizing impurities and inactivates biological contaminants in the water stream; and a water outlet, configured to discharge a purified water.

2. The system of claim 1 , wherein the substrate is a material with a surface roughness less than a ! wavelength of the light illuminated onto the photosensitizer device that increases a total water-photosensitizer contact area thereby increasing a yield of singlet oxygen generated thereon.

3. The system of claim 1 , wherein the substrate and the photosensitizer material are hydrophobic and do not dissolved in water, respectively.

4. The system of claim 1 , wherein the substrate is composed of a stack of layers of planar meshes, a stack of layers of planar membranes, a stack of alternating layers of planar meshes and planar membranes, a spiral wound of planar meshes, a spiral wound of planar membrane, a plurality of transparent and rigid plastic rods, a plurality of hollow fiber membranes, or a bunch of meshes, saddles, or rings made from plastic materials wrapped with a planar membrane.

5. The system of claim 4, wherein the planar meshes are composed of woven or non-woven filaments with a mesh opening size of < 1 mm.

6. The system in claim 4, wherein a distance between adjacent layers of the stack of the layers of the planar meshes or planar membranes and the stack of the alternating layers of the planar meshes and planar membranes is less than 0.1 mm.

7. The method of claim 4, wherein the planar membranes and the hollow fiber membranes are porous or non-porous membranes.

8. The system of claim 7, wherein the planar porous membrane and the hollow fiber porous membrane have a pore dimension less than 1 micron.

9. The system in claim 1 , wherein the amount of the photosensitizer material coated on the substrate of the photosensitizer device is optimized so that at least 50% of the light reaches the center of the photosensitizer device.

10. The system in claim 1 , wherein a light intensity is chosen so that the maximum light penetration into the photosensitizer device is achieved without overheating and degrading the photosensitizer device on the substrate closest to the at least one light sources.

11. The system in claim 1 , wherein the photosensitizer material is Zinc phthalocyanine (ZnPC), or its fluoro-substituents selected from Zinc1 ,2, 3, 4, 8, 9, 10, 11 , 15, 16, 17, 18,22,23,24,25-hexadecafluoro-29H,31 H-phthalocyanine (Fi6ZnPC).

12. The system of claim 1 , wherein the wavelength ranges from 250 to 1000 nm.

13. A method of generating singlet oxygen for purifying water, the method comprising the steps of: injecting oxygen gas into the water forming a water stream containing dissolved oxygen; flowing the water stream into a photosensitizer device that comprises a substrate on the surface of which a photosensitizer material is coated;illuminating the photosensitizer device with a light source at a wavelength to generate the singlet oxygen therein; and simultaneously, oxidizing impurities and inactivating biological contaminants in the water stream with the generated singlet oxygen.

14. The method of claim 13, wherein the substrate is composed of a stack of layers of planar meshes, a stack of layers of planar porous membranes, a stack of alternating layers of planar meshes and planar porous membranes, a spiral wound of planar meshes, a spiral wound of planar porous membrane, a plurality of transparent and rigid plastic rods, a plurality of hollow fiber porous membranes, or a bunch of meshes, saddles, or rings made from plastic materials wrapped with a planar porous membrane.

15. The method of claim 13, wherein the substrate is a material with a surface roughness less than a ! wavelength of the light illuminated onto the photosensitizer device that increases a total water-photosensitizer contact area thereby increasing a yield of singlet oxygen generated thereon.

16. The method of claim 13, wherein the substrate and the photosensitizer material are hydrophobic and do not dissolved in water.

17. The method of claim 13, wherein the planar membranes and the hollow fiber membranes are porous or non-porous membranes.

18. The method of claim 13, wherein the wavelength ranges from 250 to 1000 nm.

19. The method in claim 13, wherein a distance between adjacent layers of the stack of the layers of the planar meshes or planar membranes and the stack of the alternating layers of the planar meshes and planar membranes is less than 0.1 mm.

20. A method for generation of singlet oxygen for purifying water, the method comprising the steps of: flowing the water into a photosensitizer device; injecting oxygen gas into the water either before or after flowing into the photosensitizer device;illuminating the photosensitizer device with a light source at a wavelength to generate the singlet oxygen therein; and simultaneously, oxidizing impurities and inactivating biological contaminants from the water with the generated singlet oxygen, wherein the photosensitizer device comprises a substrate on the surface of which a photosensitizer material is coated.

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