WO2022219356A1

WO2022219356A1 - Air purification

Info

Publication number: WO2022219356A1
Application number: PCT/GB2022/050958
Authority: WO
Inventors: David Crofts
Original assignee: Filter8 Limited
Priority date: 2021-04-15
Filing date: 2022-04-14
Publication date: 2022-10-20
Also published as: GB2593603A; GB202105410D0; GB2593603B

Abstract

A filter (1) for air purification, the filter (1) comprises a filter element (10), the filter element (10) comprising one or more layers (11a, b, c), wherein at least one layer (11a, b, c) is formed from a first porous body comprising titanium dioxide, the filter element (10) further 5 comprising copper (13) and silver (14).

Description

Air Purification

This invention relates generally to air purification. More specifically, although not exclusively, this invention relates to a filter for air purification and an air purification appliance comprising the same.

Indoor air pollution has become an important environmental factor affecting human health. Indoor air may contain particulates and trace amounts of contaminants, such as pollen, dust, mould, spores, bacteria, viruses, animal dander, skin cells, volatile organic compounds (VOC’s), formaldehyde, cleansers, pesticides, fungicides, combustion by products, odours and toxic gases. At present, most air purifiers use high efficiency particulate air (HEPA) filters and/or activated carbon adsorption technology. As contaminated air flows through the filter, the filter blocks the path of the contaminant and allows air free of contaminants to flow from the filter. However, these systems do not destroy the contaminant, are inefficient in blocking small contaminants such as carbon monoxide and need to be regularly replaced.

Titanium dioxide has been widely investigated for its optical, dielectric and photocatalytic characteristics. There is increasing interest in the photocatalytic properties of titanium dioxide for disinfection of surfaces, air and water. Titanium dioxide has been employed as a photocatalyst in air purifiers to destroy contaminants. When titanium dioxide is irradiated with ultraviolet (UV) light, a photocatalytic reaction occurs. Water or oxygen in the air is catalysed into a reactive oxygen species, such as hydroxyl radicals. When contaminants in the air contact or are absorbed onto the titanium dioxide surface, the free radicals, having strong oxidative decomposition capabilities, attack the contaminants, decomposing unstable chemical bonds to carbon dioxide and water. Further, the free radicals can chemically react with all types of molecules present in cells. For example, hydroxyl radicals can kill red blood cells, degrade DNA, cell membranes and polysaccharide compounds, thereby destroying bacterial cell membranes and coagulating virus protein carriers. The Titanium Dioxide Manufacturing Association (TDMA) maintain that controlled/minimal exposure of titanium dioxide is safe, if the recommended exposure limits are adhered to. However, the necessity to use UV irradiation and the low quantum yield of titanium dioxide limits its application in air purification.

The use of noble metal doping is known to improve the catalytic efficiency of titanium dioxide. For example, gold nanoparticles can interact with visible light to produce a surface plasmon resonance effect, so that titanium dioxide loaded with precious metals can use visible light to initiate chemical reactions. However, precious metals are often expensive, rare and may be prone to chemical and/oro photochemical corrosion.

It is therefore a first non-exclusive object of the invention to provide a filter, for example an air purification filter, that overcomes, or at least partially mitigates, one or more of the aforementioned issues of the prior art.

Accordingly, a first aspect of the invention provides a filter element, the filter element having one or more layers, wherein said at least one layer is formed from a porous metal body comprising titanium dioxide, the filter element further comprising copper and silver.

The filter element may be an air purification filter element. The filter element may be part of a filter, e.g. an air purification filter.

Accordingly, a further aspect of the invention provides a filter for air purification, the filter comprising a filter element, the filter element comprising one or more layers, wherein said at least one layer is formed from a porous metal body comprising titanium dioxide, the filter element further comprising copper and silver.

Advantageously, provision of titanium dioxide, copper and silver in a filter element results in an increased destruction rate of pollutants passing through the filter/filter element compared to filters/filter elements of the prior art. The filter/filter element may result in 75, 76, 77, 78, 79, 80, 81 , 82, 83, 84, 85, 86, 87, 88, 89, 90, 91 , 92, 93, 94, 95, 96, 97, 98, 99 or 100% destruction of pollutants passing through the filter/filter element.

One or more layers, e.g. plural layers, of the filter element may be formed from a metal body, e.g. a porous metal body. One or more layers, e.g. plural layers, of the filter element may comprise titanium dioxide. For example, the filter element may comprise plural layers formed from a metal body, e.g. a porous metal body, comprising titanium dioxide.

The, some or each layer of the filter element and/or the some or each metal body, e.g. porous metal body, may be formed from aluminium. For example, titanium dioxide coated aluminium. The titanium dioxide coating may be formed from titanium dioxide nanoparticles (diameter £100 nm). The provision of micron thick coatings (i.e. less than 100 microns, preferably less than 90, 80, 70, 60, 50, 40, 30, 20, 10, 9, 8, 7, 6, 5 microns) formed from nanoparticles has been found to be particularly effective in removing pollutants. The, some or each layer of the filter element and/or the some or each metal body, e.g. porous metal body, may be formed from silver. The, some or each layer of the filter element and/or the some or each metal body, e.g. porous metal body, may be formed from copper.

The oxide, e.g. the titanium dioxide coating, may be present in higher amounts (w/w) than the copper and/or silver.

The filter element may comprise a mesh. The, some or each layer of the filter element and/or the, some or each metal body, e.g. porous metal body, may be or form a mesh. The pores of the mesh may be diamond shaped. For example, the or each pore may be formed of two triangles forming a diamond, e.g. two equilateral triangles. The pore size, e.g. hole diameter (maximum transverse dimension), of the mesh may vary from 1.0 to 4.0 mm, e.g. 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1 , 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9 or 4.0 mm.

The filter element may comprise a honeycomb structure. The, some or each layer of the filter element and/or the, some or each metal body may be or form a honeycomb structure. The cells of the honeycomb structure may have a pore size, e.g. hole transverse dimension/width in the range 1.0 to 5.0 mm, e.g. 1.0, 1.1 , 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8,

1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8,

3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9 or 5.0 mm. The cells of the honeycomb structure may have a height, e.g. the sides of the cells may have a length, in the range 1.5 to 2.5 mm, e.g. 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4 or 2.5 mm. The pore size and/or cell height may be chosen depending on the intended application of the filter element. A honeycomb structure may be suited to larger applications, due to its composition and/or depth, i.e. filter elements may have a pore size of 5.0 mm, which may be the maximum size for air-conditioning applications.

The filter element may comprise 1 to 10 layers, e.g. 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 layers. Where plural layers are provided, the, some or each layer, e.g. the some or each metal body, e.g. porous metal body, may be of uniform size. Optionally, the, some or each layer may be different sizes. The filter may comprise a filter element having 1 to 10 layers, e.g. 1 , 2, 3, 4, 5, 6, 7, 8, 9 or 10 layers, formed from aluminium or titanium dioxide-coated aluminium. The filter may comprise a filter element having 1 to 5 layers, e.g. 1 , 2, 3, 4 or 5 layers, formed from a first metal and 1 to 5 layers, e.g. 1 , 2, 3, 4 or 5 layers, formed from a second, different metal. Optionally, the filter may comprise 1 to 5 layers, e.g. 1 , 2, 3, 4 or 5 layers, formed from a third metal. The first, second and or third metals may be aluminium, copper and/or silver. The metals, e.g. aluminium, copper and/or silver, may be at least partially coated with titanium dioxide.

For example, the filter element may have 3 layers. The 3 layers may be formed from titanium dioxide coated aluminium. Alternatively, 2 layers may be formed from titanium dioxide coated aluminium and the third layer may be formed from copper or silver. The 3 layers may be overlapped. The first layer, i.e. the upstream layer through which incoming air flows, may be the or a layer formed from copper or silver. Alternatively, the second layer, i.e. the layer sandwiched between the first and third layers, may be the layer formed from copper or silver. Alternatively, the third layer, i.e. the layer through which outgoing air flows, may be the layer formed from copper or silver.

It will be appreciated that the larger the pores in the, some or each layer and/or the, some or each metal body, the larger the air flow. To increase photocatalytic oxidation (PCO) effectiveness, air flow must be slowed down to ensure an efficient disinfection rate with minimal effect to the drop in pressure. Alternatively, plural passes of the air flow might be considered to allow for efficient PCO whilst maintaining a low pressure drop.

Where plural layers are present, the, some or each layer and/or the, some or each metal body, e.g. porous metal body, may overlap and/or be offset. The pores of the, some or each layer and/or the, some or each metal body, e.g. porous metal body, may be misaligned. By offsetting one or more layers or metal body’s, the flow path may be tortuous, resulting in reduced airflow but increased PCO effectiveness. Accordingly, in embodiments the air flow path from the upstream to the downstream faces of the filter or filter element may be tortuous. The pressure drop may be calculated across the filter using an Anemometer. Further, the resultant irregular hole distribution and or tortuous air path through the layers may provide an increased surface area which is advantageous for trapping bacteria/viruses and/or for photocatalytic oxidation (PCO). Where the filter element comprises plural layers, e.g. plural layers of mesh, the plural layers, e.g. plural layer of mesh, may be overlapped and offset and/or the pores are misaligned, the pores of the layers, e.g. mesh, may be effectively reduced in size, e.g. in comparison to a single layer, e.g. a single layer of mesh. For example, the pore size (effective transverse dimension) may be less than 4.0 mm, e.g. less than 3.5, 3.0, 2.5, 2.0, 1.5, 1.25, 1.0, 0.75, 0.5, 0.25 mm. For example, the pore size may be effectively reduced to 0.1 mm, 0.125 mm, 0.15 mm, 0.175 mm, 0.2 mm 0.25 mm, 0.5 mm, 0.75mm, 1.0 mm, 1.25 mm or 1.5 mm.

Metal, e.g. copper and/or silver may be distributed throughout the filter element. Metal, e.g. copper and/or silver may be interwoven in one or more layers of the filter element and/or one or more layers of the metal body, e.g. porous metal body, for example to provide a warp and/or weft. The metal, e.g. copper and/or silver, may be interwoven in lines, e.g. a straight, rectilinear, line and/or curve. The metal, e.g. copper and/or silver, may be interwoven in a pattern, e.g. as one or more squares, rectangles or the like. The larger the filter, the more metal, e.g. copper and/or silver, may be interwoven in the one or more layers of the filter element and/or the one or more layers of the metal body, e.g. porous metal body. For example, as the size of a filter is increased, additional lines, e.g. squares and/or infill, may be interwoven in the one or more layers of the filter element and/or the one or more layers of the metal body, e.g. porous metal body.

The interwoven lines of metal, e.g. copper and/or silver, may be spaced apart by a defined distance. For example, the interwoven lines of metal, e.g. copper and/or silver, may be separated by a distance of at least 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1 , 1.2, 1.3, 1.4 or 1.5 cm, i.e. the distance between each row of horizontal and vertical lines of metal, e.g. silver and/or copper, may be at least 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1 , 1.2, 1.3, 1.4 or 1.5 cm. The interwoven lines of metal, e.g. copper and/or silver, may be spaced apart by 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1 , 1.2, 1.3, 1.4 or 1.5 cm. The interwoven lines of metal, e.g. copper and/or silver, may be spaced apart to allow for an optimum rate of metal, e.g. copper and/or silver, calculated according to the surface area of titanium dioxide, for example in an area presented to air flow. The distance between the rows of horizontal and vertical wires may be scaled up/down according to the surface area of the titanium dioxide, in order to maximise PCO with titanium dioxide. The total optimum balance between metal, e.g. copper and/or silver, and titanium dioxide (/..e. the ratio of surface area presented to an air flow) may be in the range 1.0 to 3.0% or 2.0 to 3.0%, e.g. 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1 , 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 or 3.0%. The optimum balance per element between metal, e.g. copper and/or silver, and titanium dioxide may be in the range 1.0 to 1.5% per element, e.g. the optimum balance may be 1.0, 1.1, 1.2, 1.3, 1.4 or 1.5% (Ag/CU:PO2), e.g. in an area presented to air flow.

The metal e.g. copper and/or silver, may be woven as a plurality of squares e.g. 1 cm ^c 1 cm squares (H ^c W) in a 4 ^c 4 grid.

The metal e.g. copper and/or silver, may be woven as a plurality of squares or other shapes, e.g. 1 , 2... n^th squares. The squares may increase in size. For example, a first square may be smaller than a second square and/or an n^th square. The first square may be located inside the second square and the n^th square. The second square may be smaller than the n^th square. The second square may be located inside the n^th square. The distance between each horizontal and vertical line forming the square, e.g. the first, second and/or n^th square, may be at least 1 cm. The squares or other shapes may be arranged concentrically or non- concentrically

The copper interwoven in the one or more layers of the filter element and/or one or more layers of the metal body, e.g. porous metal body, may be 0.2 to 1 mm diameter copper wire.

The silver interwoven in the one or more layers of the filter element and/or more or more layers of the metal body, e.g. porous metal body, may be a soft silver wire, e.g. 0.2 to 1 mm diameter wire of, say, 925 Sterling silver.

The metal, e.g. copper and/or silver, woven into the one or more layers of the filter element and/or more or more layers of the metal body, e.g. porous metal body, may be visible from a first, e.g. front, side of the filter, i.e. the side of the filter through which incoming air flows. Only minimal amounts of metal, e.g. copper and silver, may be exposed on a second, e.g. rear, side of the filter, i.e. the side of the filter through which outgoing air flows. The metal, e.g. copper and/or silver, may only be exposed on the second, rear side of the filter where they are secured to the filter.

The distance between each metal, e.g. copper and/or silver, line interwoven in the one or more layers of the filter element and/or more or more layers of the metal body, e.g. porous metal body, may be, e.g. at 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4 or 1.5 cm. The filter and/or filter element may further comprise a HEPA filter, a carbon filter and/or a VOC filter. For example, one or more layers of the filter element may be a HEPA filter, a carbon filter and/or a VOC filter.

The filter and/or filter element may have a height, a depth and a width. The height may be the same as the width. Alternatively, the height may be different to the width. The depth may be smaller than the height and/or the width. The depth may be larger than the height and/or the width. It is to be understood that the size of the filter and/or filter element, i.e. the height, the width and/or the depth, may be altered according to its intended application. For example, the width may be expanded in larger applications, e.g. to provide increased rigidity. As the filter and/or filter element is scaled up more metal, e.g. copper and/or silver, may be interwoven in the one or more layers of the filter element and/or more or more layers of the metal body, e.g. porous metal body, e.g. by adding additional lines, squares or infill.

The filter may further comprise a frame. The frame may be an adonised or pure aluminium frame or a titanium dioxide coated frame, e.g. aluminium frame coated with titanium dioxide. The frame may be rectangular, square or any suitable shape for encasing and/or enclosing the components of the filter, e.g. the filter element. The size of the frame may be selected to match the size of the filter element and/or chosen according to its intended application. The frame may be absent a corner. For example, the frame may be absent a 45-degree angle from a corner. The removal of one or more portions, e.g. corners, of the frame may provide an aperture through which wiring can be passed.

Advantageously, the filter and/or filter element may be effective against bacteria, viruses and/or VOCs.

The filter may be self -cleaning and/or scented to provide a pleasant aroma.

Where plural layers are present, the layers may be compressed together and/or joined at the edges, e.g. using silicone sealant. Metal, e.g. copper and/or silver, may then be interwoven in the one or more layers of the filter element and/or more or more layers of the metal body, e.g. porous metal body. The filter element may then be enclosed in a frame. The filter element may be joined to the frame using silicone. The filter may be used in conjunction with appliances, e.g. air purifiers and/or air- conditioning units, where there is movement of natural air passing through the filter element in a single direction.

The filter may be recycled. The filter may be modified to replace an existing filter. For example, the filter may be retrofitted to an existing appliance, e.g. air purifier or air- conditioning unit. For example, the filter may replace an existing filter in an appliance, e.g. air purifier or air-conditioning unit. Alternatively, the filter may be integrated into an appliance, e.g. air purifier or air-conditioning unit. For example, the filter may be provided in combination with an appliance, e.g. air purifier or air-conditioning unit.

Advantageously, the costs of manufacturing, running and servicing the filter and filter element of the invention are low.

In use, air, e.g. contaminated air, flows from a first side, e.g. front, of the filter to a second side, e.g. rear, of the filter through the filter element.

The first side, e.g. front, of the filter may be exposed to UV light, e.g. UV germicidal light of a frequency of 254 to 270 nm, for example 254 nm (UVC). As air passes through the filter the filter element may be activated by the UV light, e.g. UVC light. Activation of the filter may result in a PCO reaction occurring, which may release hydroxyl radicals in the form of ions.

The filter, e.g. the some or each layer of the filter element, may be perpendicular to the air flow and/or irradiating UV, e.g. UVC, light, for example in order to maximise photocatalytic oxidation (PCO).

The filter may use multiple nanoparticle technologies to eradicate airborne bacteria/viruses, reducing their cells to water and carbon dioxide. For example, the one or more layers of the filter element, silver, copper and/or frame may work independently of one another against bacteria/viruses. The elements are inert to each other but once activated may together attack the cell construction of bacteria/virus, to prevent cell reproduction and mutation.

The photocatalytic activity of titanium dioxide results in the filter element and/or frame exhibiting self-cleaning and disinfecting properties under exposure to UV radiation. The negatively charged ions from the titanium dioxide radicals, activated by PCO, may interact with water in the air, breaking the negatively charge ions down into hydroxyl radicals. The hydroxyl radicals are highly active, short lived, uncharged forms of hydroxide ions (OH ). The hydroxide ions may attack carbon-based pollutant molecules, breaking them down into carbon dioxide and water.

Copper, which may form one or more layers of the filter element and/or more or more layers of the metal body, e.g. porous metal body, or may be interwoven in the one or more layers of the filter element and/or more or more layers of the metal body, e.g. porous metal body, may be activated by PCO to cause cell damage to bacteria/viruses, i.e. contact with copper or with products generated as a result of PCO result in destruction of DNA and/or RNA so that they cannot mutate or become resistant to copper or pass on genes for antibiotic resistance to other microbes.

Silver, which may form one or more layers of the filter element and/or more or more layers of the metal body, e.g. porous metal body, or may be interwoven in the one or more layers of the filter element and/or more or more layers of the metal body, e.g. porous metal body, may be activated by PCO, i.e. acting as a catalyst by absorbing oxygen. Contact or proximity with silver may kill bacteria, for example by interfering with their respiration.

Copper and/or silver may also be effective against bacteria/viruses in the absence of photocatalytic activation, i.e. only in the presence of constant air flow, but to a lesser degree. Water may oxidise the copper and/or silver to create ions that degrade bacteria/virus cells.

The filter may be most effective in humid conditions. The filter may most efficient between -1 °C and + 36°C. For example, at -1 °C, 0, +1 , +2, +3, +4, +5, +6, +7, +8, +9, +10, +11 , + 12, +13, +14, +15, +16, +17, +18, +19, +20, +21 , +22, +23, +24, +25, +26, +27, +28, +29, +30, +31, +32, +33, +34, +35 or + 36°C. The filter may be used at ambient conditions.

A further aspect of the invention provides an appliance, e.g. an air purifier or air-conditioning unit, comprising a filter as set out above.

The appliance may comprise a UV light, e.g. an ultraviolet germicidal light having a frequency of 254 nm to 270 nm, e.g. 254 nm (UVC). The appliance may comprise a plurality of baffles or deflectors, a fan, an electronics module a humidifier and/or a passive component, e.g. an ioniser, a heater or one or more further filters or filter elements.

The appliance may comprise a housing. The components may be located within the housing.

Advantageously, provision of one or more baffles and/or a filter may reduce the air pressure within the appliance, and the deflection of the UVC to maximise the PCO activation of the filter.

Air, e.g. contaminated air, may be drawn by a fan into the appliance through an inlet of the appliance. One or more baffles may direct the flow of air towards the filter. The filter may operate as set-out above, i.e. the filter may eradicate airborne bacteria/viruses. One or more baffles may direct the flow of air from the filter, e.g. the rear of the filter, towards the outlet. The UV light may be downstream or upstream of the filter, or both. UV light may irradiate the upstream or downstream surfaces of the filter element.

One or more of the baffles may be formed from metal, e.g. aluminium or copper, e.g. pure copper. Advantageously, the or each baffle formed from copper, e.g. pure copper, may enable contaminated air to be treated beyond the UV light and/or should the UV light fail or if it is turned off. The appliance may comprise a first baffle or baffles and a second baffle or baffles, wherein the first baffle or baffles may be located upstream of the filter and the second baffle or baffles may be located downstream of the filter.

Ions may be released from an outlet of the appliance into the exterior space, where they may continue to be active. These ions are not harmful to public health and may eliminate pathogens according to the volume produced.

When the appliance is turned off the released ions may continue to work, being charged by sun or artificial light for at least 24 hours, destroying harmful molecules and/or oxidising them to harmless levels of carbon dioxide, water and/or oxygen. Advantageously, if there is a component failure within the appliance, contaminated air passing through the appliance may still be treated. Accordingly, the filter described herein may provide safety from pollutants/pathogens, in homes, schools, hospitals, workplaces and the like.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. For the avoidance of doubt, the terms “may”, “and/or”, “e.g.”, “for example” and any similar term as used herein should be interpreted as non-limiting such that any feature so-described need not be present. Indeed, any combination of optional features is expressly envisaged without departing from the scope of the invention, whether or not these are expressly claimed. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:

Figures 1 A and 1 B are schematic views of a filter according to an example;

Figures 1C to 1 E are perspective views of the filter of Figure 1A;

Figures 2A and 2B are schematic views of a filter according to a further example; Figure 2B is a perspective view of the filter of Figure 2A;

Figures 3A and 3B are perspective views of filters according to different examples; and

Figure 4 is an appliance comprising a filter according to an embodiment of the invention.

Referring now to Figures 1A and 1 B there are shown schematic views of a filter 1 from a front view (Figure 1A) and a partial side sectional view (Figure 1B).

The filter 1 comprises a filter element 10 and a frame 12. The filter element 10 comprises layers of mesh 11 (here 3 layers 11a, 11b, 11c are shown although there can be more layers or fewer). The filter element 10 further comprises copper 13 and silver 14 interwoven in at least one or more layers of the mesh 11.

The filter 1 has a height H, a depth D and a width W. The height H is the same as the width W. The depth D is smaller than the height H and the width W. In this example, the height H and width W are 12 cm and the depth D is 7 mm. The size of the example filter 1 was established by measuring the area of intensity of the UV on the filter 1 , taking into consideration the distance from the UV bulbs to maximise PCO, and to maximise air flow.

It is to be understood that the size of the filter, i.e. the height H, the width W and the depth D, may be altered according to the application. The width W and/or depth may be increased in larger applications to provide increased rigidity.

The frame 12 may be an anodised or pure aluminium frame. The size of the frame 12 will be selected to match the size of the filter element 10 and/or mesh 11 and/or according to the intended application. The frame 12 of this example has a 45 degree angle removed from one corner 12a. The removal of one or more portions, e.g. corners, of the frame 12 may provide an aperture through which wiring can be passed. Alternatively, the frame may be absent the removed corner 12a.

The or each layer of mesh 11 may be formed from aluminium. The aluminium may be coated with titanium dioxide. Referring to Figure 1 , the filter 1 comprises three layers of titanium dioxide coated aluminium mesh 11a, 11b and 11c. Each layer of mesh 11 is a diamond mesh, i.e. the layers of mesh have diamond shaped flow passages 15. The three layers of mesh 11 are all of a uniform size. The layers of mesh 11 are overlapped and offset, for example as shown in Figure 1C. By offsetting the adjacent layers of mesh 11, the size of the flow passages 15 in the mesh layers 11, and hence through the filter element 10, are effectively narrowed. This resulted in a 12.03 m³/h drop in pressure, as measured using an Anemometer based on a fan producing 85 m³/h. Further, the irregular hole distribution provides an increased surface area for contacting and/or inactivating bacteria/viruses and for PCO.

As seen in Figure 1A, copper wire 13 may be woven into one or more layers of mesh 11 (e.g. in the first layer 11a, second layer 11b, or third layer 11 c or two or more of the layers 11a, 11b, 11c) in lines, forming a first square 13a and a second square 13b, the second square 13b being smaller than, and located within, the first square 13a. The copper may be a 1 mm diameter copper wire.

In an embodiment the first square of copper 13a is 8 cm ^c 8 cm (H ^c W) and the second square 13b is 6 cm ^c 6 cm (H ^c W). As the filter 1 is scaled up (increased in size) more copper 13 may be woven into one or more of the layers of mesh 11 by adding additional squares or infill.

As shown in Figure 1 E, silver 14 may be woven into one or more layers of mesh 11 (e.g. in the first layer 11a, second layer 11b, or third layer 11c or two or more of the layers 11a, 11b, 11c), in this case a 0.5 mm diameter 925 Sterling silver wire.

In an embodiment the silver wire 14 is woven into the layers of mesh 11 in lines which form 16 1 cm x 1 cm squares (H ^c W) in a 4 ^c 4 grid (see Figure 1A). As the filter is scaled up more silver 14 may be woven into the mesh 11 by adding additional squares.

The three layers of mesh 11a, 11b, 11c, 11c are compressed together and may be joined at the edges using silicone to form the filter element 10. The layers of mesh 11 are enclosed by the frame 12. The layers of mesh 11 may be joined to the frame 12 using silicone.

The 4 cm x 4 cm grid of silver 14 is woven into the layers of mesh 11 in the centre of the mesh 11 , as shown in Figure 1A. The copper wire 13 is woven in lines around the silver wire 14 through the layers of mesh 11. The distance between each row of horizontal and vertical copper and silver wires 13, 14 (as indicated by the arrows in Figure 1A) may be around 1 cm. Advantageously, a distance of 1 cm between each row of horizontal and vertical copper and silver wires 13, 14 allows for an optimum rate of 1.5% copper and 1.5% silver (calculated according to the surface area of titanium dioxide), maximising PCO with titanium dioxide. The distance between the rows of horizontal and vertical wires may be scaled up/down according to the surface area of the titanium dioxide.

In an embodiment the copper 13 and silver 14 only need to be are woven into the first layer 11a of mesh 11 so as to be visible from a first, leading side of the filter 1a, /.e. the side of the filter 1 through which incoming air flows (indicated by arrow F in Figure 1B). Only minimal amounts of copper and silver wire 13, 14 are exposed on the trailing (rear) side of the filter 1. Referring now to Figures 2A and 2B there is shown a schematic view of a filter 2 from a front view (Figure 2A) and a side view (Figure 2B). The filter 2 is similar to the filter 1 of Figures 1A to 1E. Like references depict like features with the prefix ‘2’ in place of and will not be described further.

The filter 2 comprises a filter element comprising layers of mesh 21. The filter 2 of this example is absent a frame. Although, it is to be understood that the filter 2, e.g. the filter element, may be enclosed within a frame in use.

The filter 2 has a height H of 16 cm, a width W of 15.5 cm and a depth D of 5 cm. The filter 2 has a surface area of 248 cm².

The filter 2, e.g. the filter element, is absent the copper wire squares 13 of filter 1. The filter 2, e.g. the filter element, comprises silver wires 24a to 24d woven into the layers of mesh

21.

The layers of mesh 21 are formed of three layers 21a, 21b, 21c. The first layer of mesh 21a, i.e. the layer forming the front of the filter 2a, through which incoming air flows, is formed from coarse 16 LPI (holes per linear inch) ^c 0.36 mm diameter, copper woven wire mesh. The copper mesh layer 21a is pure copper, e.g. 99%, and has 1.23 mm² pores /flow passages 25. The second and third layers of mesh 21b, 21c are formed from 3 mm ^c 2.5 cm titanium dioxide coated aluminium 21b, 21c (see Figure 2B). The third layer of mesh 21c forms the downstream portion of the filter 2b, through which outgoing air passes. The layers of mesh 21 are overlapped and offset with respect to one another with the second layer of mesh 21b being sandwiched between the first layer of mesh 21a and the third later of mesh 21c.

Alternatively, each layer of mesh 21a, 21b, 21c may be formed from titanium dioxide coated aluminium.

Each of the flow passages 25 in the layers of mesh 21 are diamond shaped flow passages. The flow passages 25 may be formed from two equilateral triangles, forming a diamond shape. The height of each equilateral triangle may be 0.1732 mm and the surface area of each triangle may be 1.732 mm². In this example, there are 24 triangles per cm², resulting in an open area, i.e. flow passages 25, of 0.42 cm² and a closed area of 0.58 cm².

The total surface area per layer of mesh 21 is 289.8 cm². The total surface area of three layers of mesh 21a, 21b, 21c, i.e. the total surface area per filter 2, is 869.4 cm².

The optimum total amount of metal, e.g. copper and/or silver, is 3%. The optimum amount of metal, e.g. copper and/or silver, for a filter 2 comprising three layers of titanium dioxide coated aluminium mesh 21, i.e. wherein the layers 21a, 21b and 21c are formed of titanium dioxide coated aluminium, is 26.082 cm². The amount of metal, e.g. copper and or silver, may then be calculated based on the optimum surface area to be covered.

The silver wire 24, shown in Figure 2C, is a 0.5 mm diameter 1 m long wire of Sterling silver. The soft silver wire 24 is threaded through the layers of copper and titanium dioxide coated aluminium meshes 21a, 21b, 21c in lines to form squares 24a to 24d (see Figure 2C) of increasing size (1 cm « 1 cm, 3 cm ^c 3 cm, 5 cm ^c 5 cm and 8 cm ^c 8 cm). The distance between each row of horizontal and vertical silver wires 24 (indicated by the arrows A in Figure 2A) is 1 cm. The silver wire 24 is woven into the layers of mesh 21 so as to be visible form a first, upstream, leading side of the filter 2a, i.e. the side of the filter 2 through which incoming air flows (indicated by arrow F in Figure 2B). Only minimal amounts of silver wire 24 are exposed on the downstream, trailing side of the filter 2. The silver wires 24 are only exposed on the rear side of the filter 2 where they are secured to the filter 2.

The filter 2 is dimensioned for a 100 mm device. The filter 2 can be scaled up for larger units. As the filter is scaled up more silver 24 can be woven into the layers of mesh 21 by adding additional squares or infill by cm². Alternatively, a filter can comprise a first layer of aluminium mesh coated with titanium dioxide, a second copper mesh layer and a third mesh layer comprising silver (e.g. a silver mesh). In use, air, e.g. contaminated air, flows from the front 1a, 2a to the rear 1b, 2b of the filter 1, 2 through the filter element, e.g. the layers of mesh 11, 21 and copper 13 and silver wires 14, 24, as indicated by arrow F in Figures 1B and 2B. The front of the filter 1a, 2a may be exposed to UV germicidal light of a frequency of 254 to 270 nm e.g. 254 nm (UVC). As air passes through the filter 1, 2 the filter element, e.g. the layers of mesh 11, 21 may be activated by the UVC light. Activation of the filter 1, 2 may result in a PCO reaction occurring, which releases hydroxyl radicals in the form of ions. The filter 1 , 2 uses multiple nanoparticle technologies to eradicate airborne bacteria/viruses, reducing their cells to water and carbon dioxide. Where present, layers of titanium dioxide coated aluminium mesh 11, 21b, 21c, the titanium dioxide coated aluminium frame 12, copper wire 13, copper mesh 21a and/or silver wire 14, 24 work independently of one another against bacteria/viruses. The elements are inert to each other but once activated together attack the cell construction of the bacteria/virus, to prevent cell reproduction and mutation.

The photocatalytic activity of titanium dioxide results in the coating of the aluminium (e.g. the layers of the mesh 11, 21b, 21c and/or frame 12) exhibiting self-cleaning and disinfecting properties under exposure to UV radiation.

The negatively charged ions from the titanium dioxide radicals, activated by PCO, interact with water in the air, breaking them down into hydroxyl radicals. The hydroxyl radicals are highly active, short lived, uncharged forms of hydroxide ions (OH ). The hydroxide ions attack carbon-based pollutant molecules, breaking them down into carbon dioxide and water.

The copper ions, present in the filter element as layers of copper mesh 21a or copper wires 13 interwoven in the layers of mesh of the filter element, are either dissolved by air or are activated by PCO from the copper to cause cell damage to bacteria/viruses. DNA and RNA are destroyed so they cannot mutate or become resistant to copper or pass on genes for antibiotic resistance to other microbes. Silver ions, present in the filter element as silver wires 14, 24 interwoven in the layers of mesh, are either dissolved by air or are activated by PCO, acting as a catalyst by absorbing oxygen and killing bacteria by interfering with their respiration.

Copper and silver are also effective against bacteria/viruses in the absence of photocatalytic activation, i.e. only in the presence of constant air flow, but to a lesser degree. Water oxidises the copper and silver surfaces to create ions that degrade bacteria/virus cells.

Figure 3A shows a filter element comprising an aluminium mesh 31a enclosed in a rectangular frame 32.

Optionally, the filter element may comprise a honeycomb structure 31b in place of one or more mesh layers 11 (see Figure 3A, 3B). For example, all of the mesh layers 11 may be replaced with a honeycomb structure 31b. This increases the rigidity of the filter element whilst allowing silver and /or copper to be interwoven therethrough. The honeycomb structure 31b may be formed from aluminium, e.g. titanium dioxide coated aluminium. The honeycomb structure 31b may have an increased surface area in comparison to the mesh 11 of Figure 1 and may suited to larger applications due to its composition and depth. The apertures 35 through each layer of the honeycomb structure 31b of Figure 3B may be 1 to 4 mm in diameter.

The filter 1 , 2 is most effective in humid conditions. The filter 1 , 2 is most efficient between -1 °C and + 36°C.

The filter 1 , 2 may be used in conjunction with appliances, e.g. air purifiers and air- conditioning units, where there is movement of natural air passing through the filter element in a single direction. The filter 1, 2 may be integrated within an appliance, e.g. air purifier or air conditioning system. Alternatively, the filter 1 , 2 may be retrofitted to an existing appliance, e.g. air purifier or air conditioning system.

Referring now to Figure 4 there is shown an appliance 4, e.g. an air purification system, comprising a filter 1 according to Figures 1A to 1 E. Alternatively, the filter may be a filter according to any example or embodiment of the application, e.g. the filter may be the filter 2 of Figures 2A to 2C. The appliance 4 comprises a housing 40, a plurality of baffles 43, a fan 44, an electronics module 45 and a UV Light 46 (e.g. a UVC light) or, alternatively an additional heater. The housing 40 is a rectangular cuboid. The housing 40 is formed of metal, e.g. aluminium. The housing 40 has an air inlet 41 and an air outlet 42. The opening of the air inlet and/or the air outlet may be covered by a filter, e.g. a gauze insect prefilter, a carbon filter, HEPA filter, VOC filter or similar. The air outlet 42 has a hood 42a for directing the flow of air therethrough.

The filter 1 is located in the centre of the housing 40. The filter 1 is secured to the housing 40 via attachment means. The front side 1a of the filter 1 faces a first portion of the housing 40a. The rear side 1B of the filter 1 faces a second side of the housing 40b. Where present, the or each filter may be removeable, e.g. the or each filter may be removed and/or replaced and/or washed or sterilised, e.g. to remove dust.

The UV light 46 is located in the second side of the housing 40b. The UV light 46 is positioned to direct light onto the filter 1 , specifically the downstream face of the filter 1.

In this example there are five baffles 43a to 43e. The baffles 43 may be attached to the housing 40 or the baffles 43 may be integral with the housing 40. Three of the baffles 43a to 43c are located on a first side of the housing 40A. The three baffles 43a to 43c are curved and direct the incoming air towards the front of the filter 1a. The fourth and fifth baffles 43d, 43e are flat, rectangular plates. The fourth and fifth baffles 43d, 43e are in parallel alignment with the filter 1. The fourth and fifth baffles 43d are located on the second side of the housing 40B and direct the outgoing air towards the outlet 42.

The fifth baffle 43e is or may be formed of or comprise copper, e.g. pure copper. Advantageously, this enables contaminated air to be treated beyond the UV light and/or if the UV light fails or is turned off.

The fan 44 is an electrically operated by the electronics module 45. In use, air, e.g. contaminated air, is drawn by the fan 44 into the appliance 4 through the inlet 41. The baffles 43a, 43b and 43c direct the flow of air towards the filter 1. Air passes from the front of the filter 1a to the rear of the filter 1b through the filter element. The or each baffle 43 and/or the filter 1 may reduce the air pressure within the appliance 4, maximising the effects of PCO.

The filter 1 use multiple nanoparticle technologies, as explained above, to eradicate airborne bacteria/viruses, reducing their cells to water and carbon dioxide.

The baffles 43d and 43e direct the air from the rear of the filter 1b towards the outlet 42. The hood 42a of the outlet 42 directs the air through the outlet 42 (and any filter that may be present). Ions may be released from the outlet 42 of the appliance 4 vertically into the exterior space, where they may continue to be active. These ions are not harmful to public health and eliminate pathogens according to the volume produced.

When the appliance 4 is turned off the released ions may continue to work, being charged by sun or artificial light for at least 24 hours, destroying harmful molecules and reducing them to harmless levels of carbon dioxide, water and oxygen. Advantageously, if there is a component failure within the appliance 4, contaminated air passing through the appliance 4 may still be treated. The same results may be achieved by adapting the technology to be installed in air conditioning, where they are vented into a room, or close to the exhaust of the appliance, as the ions will still travel through ducting and be activated by any form of light as they enter the room itself. It will be appreciated by those skilled in the art that any number of combinations of the aforementioned features and/or those shown in the appended drawings provide clear advantages over the prior art and are therefore within the scope of the invention described herein.

Claims

1. A filter for air purification, the filter comprising a filter element, the filter element comprising one or more layers, wherein at least one layer is formed from a first porous body comprising titanium dioxide, the filter element further comprising copper and silver.

2. A filter according to Claim 1, wherein a second layer of the filter element is formed from a second porous body.

3. A filter according to Claim 2, wherein the second porous body comprises titanium dioxide.

4. A filter according to any of Claims 1 to 3, wherein said at least one layer comprises silver and/or copper, for example wherein the silver and/or copper is interwoven in the first porous body.

5. A filter according to any preceding Claim, wherein said at least one layer comprises silver and/or copper wires or threads interwoven into the porous body.

6. A filter according to Claim 5, wherein at least some of the silver and/or copper wires or threads are parallel and said parallel wires or threads may be offset by at least 1cm.

7. A filter according to any preceding Claim, wherein the or a second layer or further layer comprises silver and/or copper, for example the silver and/or copper is interwoven in the or a second layer and/or further layer and/or is in the form of a mesh.

8. A filter according to any preceding Claim, comprising plural layers and wherein one of said plural layers comprises a copper mesh.

9. A filter according to Claim 8, wherein one or more silver wires are provided on the copper mesh.

10. A filter according to Claim 8 or 9, wherein one or more silver wires are interwoven into the copper mesh.

11. A filter according to any preceding Claim, comprising plural layers and wherein one of said plural layers comprises a silver mesh.

12. A filter according to Claim 11, wherein one or more copper wires are provided on the silver mesh.

13. A filter according to Claim 10 or 11 , wherein one or more copper wires are interwoven into the silver mesh.

14. A filter according to any of preceding Claim, wherein the first porous body and/or a or the second porous body comprises a mesh or honeycomb structure.

15. A filter according to any preceding Claim, further comprising as a layer of the filter element, a high efficiency particulate air filter, a carbon filter and/or a volatile organic compound filter.

16. A filter according to any preceding Claim, wherein the filter element comprises up to 10 layers, e.g. 2, 3, 4, 5, 6, 7, 8, 9 or 10 layers.

17. A filter according to Claim 16, wherein said plural layers each comprise a mesh or honeycomb structure and the mesh of honeycomb structure of a first layer is offset with respect to an adjacent layer.

18. A filter according to any preceding Claim, further comprising a frame.

19. An appliance, e.g. an air purifier or air-conditioning unit, comprising a filter of any of Claims 1 to 18.

20. An appliance according to Claim 19, further comprising a UV light.

21. An appliance according to Claim 20, wherein the UV light is located upstream or downstream of the filter to irradiate the upstream or downstream surface respectively.

22. An appliance according to any one of Claims 19, 20 or 21, further comprising a fan and/or a humidifier.

23. An appliance according to any one of Claims 19 to 22, further comprising a housing.

24. An appliance according to any of Claims 19 to 23, further comprising one or more baffles.

25. An appliance according to Claim 23, comprising a first baffle or baffles and second baffle or baffles, wherein the first baffle or baffles are located upstream of the filter and the second baffle or baffles are located downstream of the filter.