DEVICE FOR CLEANING A MEDIUM

Abstract

A device (10) for cleaning a medium (105) comprises a porous body (100) containing a photocatalytic material (102) and a waveguide (110) configured to guide electromagnetic radiation into the interior of the porous body (100).

Description

In general, there is a search for concepts with which media, for example gases (air) or liquids (water), can be purified. In particular, concepts are sought with which more efficient cleaning of media is possible.The object of the present invention is to provide an improved device for purifying a medium.According to embodiments, the object is achieved by the subject matter of the independent claims. Further developments are defined in the dependent claims.An apparatus for cleaning a medium includes a porous body containing a photocatalytic material, and a waveguide configured to guide electromagnetic radiation into the interior of the porous body.According to embodiments, a radial transmissivity of the waveguide for electromagnetic radiation increases with increasing distance from a coupling-in position of the electromagnetic radiation.For example, the waveguide is cylindrical and coated with a reflective material.According to embodiments, a layer thickness of the reflective material may decrease with increasing distance from the coupling position of the electromagnetic radiation.According to further embodiments, the reflective material may be applied with a variable occupancy density. Furthermore, the occupancy density may decrease with increasing distance from the coupling position of the electromagnetic radiation.According to further embodiments, the waveguide may taper as the distance from the coupling-in position of electromagnetic radiation increases.For example, the waveguide may be coated with a reflective material. A layer thickness of the reflective material may decrease with increasing distance from the coupling position of the electromagnetic radiation.According to embodiments, a surface of the waveguide may protrude from and be curved with respect to the porous body at a coupling-in position of the electromagnetic radiation.For example, the porous body can be designed as an aerogel.According to embodiments, the photocatalytic material is TiO 2 contained. For example, titanium dioxide in the anatase form can be used. According to further embodiments, titanium dioxide in the rutile crystal structure can be used. Alternatively or additionally, the photocatalytic material may comprise or consist of the following materials as photocatalyst: semiconductor materials based on d0 transition metal cations, such as Ta5+or Nb5+, nitrides or oxides of Ga 3+, In 3+ or Bi 3+, metal organic frameworks (MOFs), such as MOF-5, UiO-66 or UiO-66(NH2).The device can furthermore have a light source for emitting the electromagnetic radiation.According to embodiments, the device comprises a first boundary surface and a second boundary surface opposite the first boundary surface, as well as a plurality of waveguides. The porous body is disposed between the first and second boundary surfaces. A portion of the waveguides extend from the first boundary surface and another portion of the waveguides extend from the second boundary surface into the interior of the device.The accompanying drawings serve to understand embodiments of the invention. The drawings illustrate exemplary embodiments and together with the description serve to explain the same. Further exemplary embodiments and numerous of the intended advantages will become apparent directly from the following detailed description. The elements and structures shown in the drawings are not necessarily shown to scale with respect to one another. Like reference numerals refer to like or corresponding elements and structures. FIG. 1A shows a schematic cross-sectional view of an apparatus for cleaning a medium. FIG. 1B shows a schematic cross-sectional view through a porous body. FIG. 1C shows a schematic structure of a waveguide. FIG. 1D shows a schematic cross-sectional view through a part of the apparatus according to embodiments. FIG. 2A shows a schematic cross-sectional view of a waveguide according to further examples. FIG. 2B illustrates a transmissivity of layers. FIG. 3A shows a cross-sectional view of a waveguide according to further examples. FIG. 3B shows a radial cross-sectional view through a reflective material. FIG. 4 shows a cross-sectional view through the device according to further embodiments.In the following detailed description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments. In this context, directional terminology such as "top", "bottom", "front", "back", "over", "on", "in front", "behind", "in front", "behind", etc. is referred to the orientation of the figures just described. Since the components of the embodiments may be positioned in different orientations, the direction terminology is for the purpose of illustration only and is in no way limiting.The description of the embodiments is not limiting, as other embodiments also exist and structural or logical changes may be made without departing from the scope defined by the claims. In particular, elements of exemplary embodiments described below can be combined with elements of other of the described exemplary embodiments, unless the context indicates otherwise.FIG. 1A shows a cross-sectional view of an apparatus 10 for cleaning a medium 105, according to embodiments. The device 10 comprises a porous body 100. The porous body 100 includes a photocatalytic material 102 (not shown in FIG. 1A ). For example, the porous body 100 may be constructed of photocatalytic material 102. According to further embodiments, the porous body 100 may also be constructed from a suitable material and coated with the photocatalytic material 102. The device 10 further comprises a waveguide 110 configured to conduct electromagnetic radiation 15 into the interior of the porous body 100.As shown in FIG. 1A, for example, a medium to be purified 105, for example a liquid (e.g. water) or a gas to be purified (e.g. air), can flow into the porous body 100 from the left side and leave the same as purified medium 107. A flow direction 108 can run, for example, along an x-axis. The medium cleaning apparatus 10 may include a plurality of waveguides 110. The waveguide or waveguides 110 penetrate, for example, the porous body 100 in a vertical direction, for example in a direction perpendicular to the flow direction 108. Generally, the waveguides 110 may extend in any direction intersecting the flow direction 108. For example, an extension direction of the waveguide 110 may define a vertical direction. A radial or horizontal plane runs perpendicular to the vertical direction.For example, a portion of the waveguides 110 may extend from a first major surface 113 of the device 10. Another portion of the waveguides 110 may extend from a second major surface 114 of the device 10. The second main surface 114 may be opposite to the first main surface 113. According to further embodiments, further waveguides 110 may extend from further boundary surfaces of the device 10. According to further embodiments, the device 10 can also be formed cylindrically, and the waveguides are arranged along the cylindrical boundary surface of the device 10. In this way, more uniform illumination can be ensured.For example, the waveguides 110 can each be arranged such that waveguides 110 which extend from a specific boundary surface of the device 10 are illuminated with electromagnetic radiation 15 from this side. Further, waveguides 110 extending from the side of the first main surface 113 may alternate with waveguides extending from an opposing boundary surface. The individual waveguides 110 can be arranged at the same distance from one another or else at a different distance d from one another. For example, the distance d may be determined depending on a penetration depth of the electromagnetic radiation 15 into the porous body 100.According to further embodiments, the device 10 for cleaning a medium 105 can additionally have a light source 20 for emitting the electromagnetic radiation. According to further embodiments, however, the light source 20 can also be an external component. The light source 20 may be configured to emit electromagnetic radiation 15 having a wavelength by which the photocatalytic material 102 may be excited. More specific examples of suitable wavelengths are given below.The described configuration of the waveguide 110 makes it possible to prevent radiation 15 introduced from already being absorbed in the uppermost regions of the porous body 100. In particular, it can thus be achieved that a part of the introduced radiation 15 reaches regions in the interior of the porous body 100. As a result, more homogeneous cleaning can be achieved in the area of the device 10 or the porous body 100.FIG. 1B shows a schematic perspective view of the porous body 100 in the lower part. The porous body 100 can be constructed from individual structural elements 101 which can be formed, for example, in a spherical or rounded manner. Intermediate spaces can be provided between the individual structural elements. In this way, the medium to be purified can flow through the porous body 100. The single structural member 101 or the porous body 100 may be constructed of a photocatalytic material. According to a further embodiment, the individual structural elements 101 or the porous body 100 can also be constructed from a suitable carrier material and coated with a photocatalytic material 102. For example, nanoparticles made of the photocatalytic material 102 may be applied to the surface of the porous body 100 or the individual structural elements 101.In the context of the present description, the term "photocatalytic material" denotes a material which is suitable for inducing a catalytic reaction under irradiation of electromagnetic radiation of suitable wavelength. For example, the photocatalytic material can be excitable by the electromagnetic radiation. For example, the photocatalytic material may comprise a semiconductor material, for example TiO 2. Incident electromagnetic radiation may generate electron-hole pairs when the energy of the incident photons is greater than the band gap E g. The electrons or holes can diffuse to the surface in the semiconductor material and generate radicals there, which lead to the decomposition of organic substances. For example, the holes in particular can have a high oxidative effect. For example, OH radicals can be formed from water. Thereby, organic substances can be decomposed. Possible end products are, for example, CO 2 and water.The band gap of anatase, the most efficient form of TiO 2, for photocatalytic purposes, is 3.2 eV. This corresponds to a wavelength of electromagnetic radiation of approximately 390 nm. For example, for the photocatalytic process, ultraviolet light can be used, which can generate electron-hole pairs in the corresponding semiconductor material. For example, the light source 20 may be configured to emit UV radiation or electromagnetic radiation having a wavelength of 390 nm or less. As further illustrated in FIG. 1B, the photocatalytic material may be structured as an aerogel. More specifically, the photocatalytically active material may be formed into a highly porous form by, for example, a sol-gel process.FIG. 1C shows a cross-sectional view of the waveguide 110. The waveguide 110 may comprise, for example, a suitable waveguide material, for example SiO 2 or another suitable material. For example, the waveguide 110 can consist of or contain quartz glass. Further suitable materials can be, for example, sapphire (Al 2 O 3), aluminum nitride (AlN), magnesium fluoride (MgF 2) or calcium fluoride (CaF 2). Further, the waveguide 110 may be cylindrical. For example, a diameter of the cylinder along the z-direction may be constant. A reflective material 111 may be deposited on the surface of the cylinder or waveguide 110.According to embodiments, a radial transmissivity of the waveguide 110 may increase with increasing distance from an input position 109 of electromagnetic radiation.FIG. 1D shows an example of a cross-sectional view through the porous body 100 and the waveguides 110 along the direction I-I' as indicated in FIG. 1A. The cross-sectional view of FIG. 1D may be taken in an x-y plane, i.e., a horizontal plane. For example, the individual waveguides 110 can be arranged in rows, wherein the electromagnetic radiation 15 is radiated into the rows of waveguides 110 from one direction. Electromagnetic radiation 15 is furthermore radiated into adjacent rows of respectively different sides. For example, the individual waveguides 110 may be arranged in a checkerboard pattern. According to further embodiments, however, other arrangement possibilities are also conceivable. Further, the cross-section of the waveguides 110 may be round or any other shape.FIG. 2A shows a cross-sectional view of a waveguide 110 along the vertical and z directions, respectively, according to embodiments. For example, a waveguide 110 may be coated with a reflective material 111 which has a sufficient penetration depth for the irradiated electromagnetic radiation 15. Accordingly, the proportion of the impinging radiation can be controlled by varying the thickness of the layer thickness of the reflective material 111. The layer thickness d, which is measured, for example, in the radial or horizontal direction perpendicular to the z-direction, varies. It is larger adjacent to a coupling-in position 109 where the electromagnetic radiation 15 is radiated and decreases towards the end of the waveguide. As a result, the proportion of the light coupled out in the radial direction is increased with increasing distance from the coupling-in position 109. As a result, the intensity in the porous body decreasing by absorption in the regions near the coupling position 109 can be compensated.In the right-hand part of FIG. 2A, the reflectivity is shown as a function of the distance from the coupling-in position of the electromagnetic radiation 15.For example, suitable fluorine-containing polymer films may be used as the material 111. A specific example includes CTFE / VDF (chlorotrifluoroethylene / vinylidene fluoride).Fig. 2B shows, as an example, the transmissivity of a CTFE / VDF polymer film having different film thicknesses depending on the wavelength. As can be seen, the smaller the layer thickness, the greater the transmissivity.FIG. 3A shows a cross-sectional view of a waveguide 110 along the z-direction according to further embodiments. For example, the waveguide 110 can be partially covered on its surface with a highly reflective material, so that individual material islands 112 result. Examples of a highly reflective material include, for example, aluminum. Furthermore, the occupancy density with the material islands 112 may decrease with increasing distance from a coupling position 109 into the waveguide. This is schematically illustrated in FIG. 3A. The right-hand part of FIG. 3A again shows the reflectivity as a function of the distance from an input surface of the electromagnetic radiation 15. For example, the highly reflective material can be applied here using a physical vapor deposition (PVD) method or a chemical vapor deposition (CVD) method.FIG. 3B shows cross-sectional views through the reflective material 111 at different distances from a coupling position 109 of the electromagnetic radiation. The lower part of FIG. 3B is accommodated between I and 1', i.e. close to a coupling-in position 109 for electromagnetic radiation 15. The upper part of FIG. 3B shows a cross-sectional view between II and II' with a greater distance from the coupling-in position 109. Here, the density of the material islands 112 is comparatively low.FIG. 4 shows a cross-sectional view through the device 10 according to further embodiments. As shown, in accordance with further embodiments, the waveguide 110 may be formed in a shape that is not cylindrical. For example, the waveguide 110 may taper with increasing distance from the coupling-in position 109 of electromagnetic radiation. As a result, a corresponding curvature along the z-axis of the waveguides 110 may occur. For example, the waveguide 110 can taper conically with increasing distance from the coupling-in position 109. This shape of the waveguide ("cone") serves as a converging lens for the light to be coupled in and increases the "coupling cross section" into the waveguide.The downward tapering of the waveguide 110 ensures that the surface normal is tending to be rotated in the direction of the scattered light and thus the coupling-out efficiency-already purely through the geometry of the waveguide-increases downward.As a result, the introduced radiation 15 can be prevented from being already absorbed in the uppermost regions of the porous body 100. More specifically, it can thus be achieved that a part of the introduced radiation 15 reaches regions in the interior of the porous body 100. As a result, more homogeneous cleaning can be achieved in the area of the device 10 or the porous body 100.In the structure shown in FIG. 4, for example, a surface 115 of the waveguide may be curved and thus act as a lens, thereby increasing the collecting effect.In addition, variable transmission in the radial direction may be provided by a suitable coating. For example, a gradual coating may be additionally provided on a surface of the region of the waveguide 110 extending through the porous body 100. For example, this may again comprise a reflective layer 111 which has a sufficient penetration depth for electromagnetic radiation.Although specific embodiments have been illustrated and described herein, it will be appreciated by those skilled in the art that a variety of alternative and / or equivalent configurations may be substituted for the specific embodiments shown and described without departing from the scope of the invention. The application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, the invention is limited only by the claims and their equivalents.LIST OF REFERENCE CHARACTERS10 Device for cleaning a medium 15 electromagnetic radiation 20 light source 100 porous body 101 structural element 102 photocatalytic material 105 medium 107 cleaned medium 108 flow direction 109 coupling position 110 waveguide 111 reflective material 112 material island 113 first main surface 114 second main surface 115 surface of the waveguide

Claims

An apparatus (10) for cleaning a medium (105), comprising: a porous body (100) containing a photocatalytic material (102); and a waveguide (110) configured to guide electromagnetic radiation into the interior of the porous body (100).The device (10) according to claim 1, wherein a radial transmissivity of the waveguide (100) for electromagnetic radiation (15) increases with increasing distance from a coupling-in position (109) of the electromagnetic radiation (15).The device (10) of claim 1 or 2, wherein the waveguide (110) is cylindrical and coated with a reflective material (111).Device (10) according to Claim 3, wherein a layer thickness of the reflective material (111) decreases with increasing distance from the coupling-in position (109) of the electromagnetic radiation (15).The device (10) according to claim 3, wherein the reflective material (111) is applied with a variable occupancy density, and the occupancy density decreases with increasing distance from the coupling position (109) of the electromagnetic radiation (15).Device (10) according to claim 1 or 2, wherein the waveguide (110) narrows with increasing distance from the coupling-in position (109) of electromagnetic radiation (15).Device (10) according to claim 6, wherein the waveguide (110) is coated with a reflective material (111), the layer thickness of which decreases with increasing distance from the coupling-in position (109) of the electromagnetic radiation (15).The device (10) according to any one of the preceding claims, wherein a surface (115) of the waveguide (110) protrudes and is curved at a coupling position (109) of the electromagnetic radiation (15) opposite the porous body (100).Device (10) according to one of the preceding claims, wherein the porous body (100) is designed as an aerogel.The apparatus (10) of any preceding claim, wherein the photocatalytic material (102) includes TiO 2 is selected.Device (10) according to one of the preceding claims, further comprising a light source (20) for emitting the electromagnetic radiation (15).Device (10) according to one of the preceding claims, having a first boundary surface (113) and a second boundary surface (114) which is opposite the first boundary surface (113), and a plurality of waveguides (110), wherein the porous body (100) is arranged between the first and the second boundary surface (113, 114) and a part of the waveguides (110) extends from the first boundary surface (113) and another part of the waveguides (110) extends from the second boundary surface (114) into the interior of the device (10).

Images