Photocatalysis device and methods thereof

Abstract

The present disclosure relates to a photocatalysis device (200) including: a mixing area (202) configured to receive a medium (206) and solid photocatalytic elements (210), and to output the solid photocatalytic elements (210) immersed in the medium (206); a reaction chamber (220) configured to receive the solid photocatalytic elements (210) immersed in the medium (206), wherein the reaction chamber (220) is configured such that the solid photocatalytic elements (210) are freely movable in the reaction chamber (220), wherein the reaction chamber (220) is configured to enable introducing light in the reaction chamber (220), wherein the reaction chamber (220) is configured to enable a mass-based position probability change of the solid photocatalytic elements (210) in the medium (206); and a recirculation system (226) configured to receive solid photocatalytic elements (210b) separated from the medium (206b), and to recirculate the separated solid photocatalytic elements (210b) to the mixing area (202).

Description

PHOTOCATALYSIS DEVICE AND METHODS THEREOFTechnical Field

[0001] The present disclosure relates generally to a photocatalysis device, and methods thereof (e.g., a method of purifying a medium using the photocatalysis device, a method of splitting a medium into a plurality of components using the photocatalysis device).Background

[0002] In general, photocatalysis refers to a photoreaction accelerated by the presence of a so-called photocatalyst. A common configuration makes use of solid elements as photocatalysts (e.g., nanoparticles, nanorods) irradiated with light in the ultraviolet (UV), visible, or infrared (IR) wavelength range. A well-established application of photocatalysis is the purification of a medium such as air or water. In this scenario, upon irradiation with light of sufficient energy electron-hole pairs are generated in the (solid) photocatalyst, thus leading to the formation of radicals that cause the decomposition of microorganisms present in the medium, such as viruses, bacteria, and the like. Another well-established application of photocatalysis is the so- called water splitting, in which photocatalysis contributes to separate water into hydrogen and oxygen, thus mimicking a photosynthesis process. To obtain a high efficiency for the photocatalytic reaction it is important to maximize the exposure of the surface of the solid photocatalysts to the medium and to the light. Thus, improvements in photocatalytic reactions, in particular in relation to how the solid photocatalytic elements are provided in the medium, may be of particular relevance for the further advancements of several applications.Brief Description of the Drawings

[0003] In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various aspects of the invention are described with reference to the following drawings, in which:FIG.1A shows a schematic representation of photocatalysis for purifying a medium, according to various aspects;FIG. IB shows a schematic representation of photocatalysis for water splitting, according to various aspects;FIG 2 shows a photocatalysis device in a schematic representation according to various aspects;FIG.3A to FIG.3F show exemplary configurations of a reaction chamber of the photocatalysis device in a schematic representation according to various aspects;FIG.4 shows an exemplary configuration of a recirculation system of the photocatalysis device in a schematic representation according to various aspects;FIG.5 A and FIG.5B show exemplary configurations of solid photocatalytic elements for use in the photocatalysis device in a schematic representation according to various aspects;FIG.6A and FIG.6B show exemplary configurations of the photocatalysis device in a schematic representation according to various aspects;FIG.7A shows a schematic flow diagram of a method of processing a medium using the photocatalysis device according to various aspects;FIG 7B shows an illustrative representation of the use of the photocatalysis device for purifying a medium, according to various aspects; andFIG.7C shows an illustrative representation of the use of the photocatalysis device for splitting a medium into a plurality of components, according to various aspects.Description

[0004] The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and aspects in which the invention may be practiced. These aspects are described in sufficient detail to enable those skilled in the art to practice the invention. Other aspects may be utilized and structural, logical, and electrical changes may be made without departing from the scope of the invention. The various aspects are not necessarily mutually exclusive, as some aspects may be combined with one or more other aspects to form new aspects. Various aspects are described in connection with methods and various aspects are described in connection with devices (e.g., a photocatalysis device, a cyclone filter). However, it is understood that aspects described in connection with methods may similarly apply to the devices, and vice versa.

[0005] In general, the purification of gases (e.g., air) and liquids (e.g., water) from compounds that are harmful to the human body is an increasingly important task. The most critical compounds are pathogens such as bacteria and viruses, and substances harmful to the human body such as volatile organic compounds (VOCs) as well as ammonia, Nitrogen(II) oxide and Nitrogen(V) oxide (both referred to as NOx), and sulfur oxide (SOx). Bacteria and viruses are typically rendered harmless by means of ultraviolet radiation, in particular UV-C for itsgermicidal effects. In this framework, photocatalysis provides an effective approach to enhance the purification of gases and liquids, by exploiting a photocatalyst activated via irradiation with light (e.g., natural light or artificial light) to accelerate a chemical reaction. The basic concepts and principles of photocatalysis are well-known in the art. A brief description is provided herein to introduce aspects relevant for the present disclosure.

[0006] Photocatalysis may be understood as a chemical reaction accelerated by the light absorption of a solid photocatalytic element (also referred to herein as photocatalyst). As a first exemplary application, as shown in FIG.1A, photocatalysis is effective in removing harmful compounds from a medium by causing their decomposition into harmless substances, such as oxygen, carbon dioxide, etc. In this scenario, a solid photocatalytic element 102 (e.g., a nanoparticle) is irradiated with light 104. For example, the solid photocatalytic element 102 may include titanium dioxide, TiCh, or any other suitable material, usually a semiconductor material. The light 104 may have any suitable wavelength, e.g. in the visible range, infrared range, or ultraviolet range, although UV light is usually preferred as mentioned above.

[0007] Considering a semiconductor material such as TiCh, assuming that the photons with which the solid photocatalytic element 102 is irradiated have same or greater energy than its band gap (EG), electrons 112 are excited from the valence band to the conduction band, while leaving holes 114 in the valence band, as shown in the inset 120 in FIG.1 A (see also FIG. IB). The electrons 112 and holes 114 generated via the light irradiation migrate to the surface of the solid photocatalytic element 102, where a reduction-oxidation reaction occur. The photocatalytic redox reaction causes the formation of radicals at the surface of the solid photocatalytic element 102, and the radicals react with the dangerous compounds 106 leading to the generation of harmless components, e.g. oxidized species 108. The holes 114 in particular have a high oxidizing effect. Illustratively, the pairs of electrons 112 and holes 114 undergo a redox reaction with substances that come into contact with the solid photocatalytic element 102 and convert them into suitable resulting products. For example, considering air purification from a commonly present pollutant NOx, the radicals formed via the photocatalytic redox reaction reacting with NOx produce oxidation species that are harmless (e.g., NO3-). As another example, considering organic substances the end products may be carbon dioxide, CO2, and water. Photocatalysis may thus enable the decomposition of environmental pollutants, and is effective in removing pathogens from a medium such as air or water.

[0008] Another exemplary application of photocatalysis is the so-called water splitting, as shown in FIG.1B. In this application, the photocatalysis induces a dissociation of water (H2O) into hydrogen (H2) and oxygen (O). The dissociation of the water is caused by reactions at thesurface of the solid photocatalytic element 102, towards which free electrons 112 and holes 114 generated by the light irradiation have migrated. For this application the solid photocatalytic element 102 may further include a cocatalyst 116 (e.g., platinum) to enhance the performance of the reaction.

[0009] As mentioned, the relevant reactions to decompose the harmful compounds (or to split water) occur at the surface of the solid photocatalytic element, so that it is of great importance to maximize the surface area available for the compounds to come into contact with the photocatalysts. This may however be challenging. For example, for many applications the photocatalysts are disposed (e.g., bonded) on a surface, e.g. a so-called “self-cleaning” surface, or at binding sites in a membrane to form a filter. This configuration may however limit the “free” surface area of the photocatalysts, leaving the portion at which the photocatalysts are bonded inaccessible for the substances to be decomposed. On the other hand, maintaining the solid photocatalytic elements freely movable in the medium may require further adaptations to then separate the purified medium from the photocatalysts after the reaction has been carried out.

[0010] The present disclosure is based on the realization that the principles of inertia and mass-based separation may be exploited in the context of a photocatalytic reaction to obtain both a maximization of the surface available for the substances to be decomposed for coming into contact with the photocatalysts, and also an efficient illumination of the photocatalysts in the medium and then a separation of the photocatalysts from the medium. Illustratively, the present disclosure is based on the realization that mass-based separation allows having the photocatalysts fully immersed and freely movable in the medium, thus maximizing the exposed surface area, and further allows removing the photocatalysts from the purified medium in a rapid and reliable manner.

[0011] The configuration proposed herein may thus be understood as a separator device capable of sorting substances (e.g., particles) according to their mass, further adapted to enable carrying out photocatalytic reactions. The proposed configuration provides thus a photocatalysis device with enhanced efficiency, and capable to implement a process for efficiently cleaning (e.g., purifying) a medium, and a process for efficiently separating a certain component from a medium (e.g., for water splitting). The principle of inertia allows maintaining the solid photocatalytic elements immersed in the medium by keeping the solid photocatalytic elements confined in a localized volume, and further allows an efficient separation of the photocatalysts from the medium.

[0012] By way of illustration, the approach described herein provides a further mechanism of action integrated at filter element level (photocatalytic reaction) in order to be able to decompose VOCs and pathogens directly and also to strengthen disinfecting properties. Furthermore, the proposed configuration avoids the problem of limited reaction cross-sections, which otherwise occurs in concepts that include the fixed placement of photocatalytic particles on component surfaces and filter element surfaces. Considering water splitting (also referred to as hydrolysis), the photocatalysis device described herein ensures immersion of the solid photocatalytic elements in water, thus increasing the effective cross-section, and enhancing the reaction efficiency by maintaining the solid photocatalytic elements localized in a defined volume for irradiation with light (e g., UV light).

[0013] According to various aspects, a photocatalysis device includes a mixing area configured to receive a first stream including a medium and a second stream including solid photocatalytic elements, and to output a third stream including the solid photocatalytic elements immersed in the medium; a reaction chamber coupled with the mixing area and configured to receive the third stream of solid photocatalytic elements immersed in the medium, wherein the reaction chamber is configured such that the solid photocatalytic elements are freely movable in an inner volume of the reaction chamber, wherein the reaction chamber is configured to enable introducing light energy in the inner volume of the reaction chamber to cause a photocatalytic reaction, wherein the reaction chamber is configured to enable a mass-based position probability change of the solid photocatalytic elements in the medium; and a recirculation system coupled with the reaction chamber and configured to receive (e.g., collect) solid photocatalytic elements separated from the medium, and to recirculate the separated solid photocatalytic elements as second stream to the mixing area for mixing with the first stream including the medium. In some aspects, the reaction chamber may be configured to enable a mass-based separation of the solid photocatalytic elements from the medium.

[0014] According to various aspects, a photocatalysis device includes a mixing area configured to receive a first stream including a medium and a second stream including solid photocatalytic elements, and to output a third stream including the solid photocatalytic elements immersed in the medium; a reaction chamber coupled with the mixing area and configured to receive the third stream of solid photocatalytic elements immersed in the medium, wherein the reaction chamber is configured such that the solid photocatalytic elements are freely movable in an inner volume of the reaction chamber, wherein the reaction chamber is configured to enable introducing light energy in the inner volume of the reaction chamber to cause a photocatalytic reaction, wherein the reaction chamber is configured to enable a mass-based separation of thesolid photocatalytic elements from the medium; and a recirculation system coupled with the reaction chamber and configured to receive (e.g., collect) the solid photocatalytic elements separated from the medium, and to recirculate the separated solid photocatalytic elements as second stream to the mixing area for mixing with the first stream including the medium.

[0015] The configuration of the photocatalysis device is thus based on using the operating principle of mass force separators to maintain solid photocatalytic elements (e.g., photocatalytically active particles) in a confined volume. The solid photocatalytic elements are thus immersed in the medium to be processed (e.g., a gas, or a liquid) and may become highly effective. In some aspects, compared to other configurations that make use of membranes, the area in which the solid photocatalytic elements are maintained may be defined by the principle of inertia, which keeps the solid photocatalytic elements in a geometrically defined area. Furthermore, in contrast to conventional separators, the solid photocatalytic elements are not completely removed but rather recirculated to undergo further reactions in further medium to be processed. The free mobility of the solid photocatalytic elements and the complete immersion in the medium increase the cross-sectional area immensely.

[0016] In a preferred configuration, the photocatalysis device may be configured as a cyclone filter, in which the cyclone chamber is adapted to allow introducing electromagnetic radiation (e.g., light in the visible range, infrared range, or ultraviolet range). The cyclone filter provides a simple, yet efficient mass-based separation of the solid photocatalytic elements from the medium, and the proposed adaptation allows carrying out medium purification or photocatalytic-assisted photolysis in the cyclone chamber. Furthermore, the cyclone filter is adapted to provide a recirculation of the separated solid photocatalytic elements for further photocatalysis and further separation, thus enabling a resource-efficient process.

[0017] FIG.2 shows a photocatalysis device 200 in a schematic representation, according to various aspects. The photocatalysis device 200 is adapted according to the approach described herein, and may thus be a device for carrying out a photocatalytic reaction (also referred to herein simply as photocatalysis), adapted to enable mass-based position probability change (e.g., mass-based separation) of the solid photocatalysts used in the reaction. The photocatalysis device 200 may also be referred to herein as photocatalytic device, photoactive device, photocatalytic reactor, device for photocatalysis, or simply as device. For example, the photocatalysis device 200 may be a filter element for cleaning a medium or a photolysis cell for splitting a component of the medium.

[0018] The photocatalysis device 200 may include a mixing area 202 in which a medium 206 to be processed gets mixed with solid photocatalytic elements 210. The mixing area 202 maythus be configured to receive a first stream 204 including the medium 206, and a second stream 208 including the solid photocatalytic elements 210. For example, the mixing area 202 may include a first inlet 212 at which the mixing area 202 receives the stream 204 of medium 206, and a second inlet 214 at which the mixing area 202 receives the stream 208 of solid photocatalytic elements 210.

[0019] The first inlet 212 may be a single inlet, or may include a plurality of (first) inlets. A configuration with a plurality of (first) inlets may facilitate having a laminar flow of the medium 206 into the mixing area 202, and ensure more reproducible processing conditions. In a corresponding manner, the second inlet 214 may be a single inlet, or may include a plurality of (second) inlets.

[0020] In this regard the term “stream” may describe a flow or a current of a certain entity, e.g. a steady flow of medium and / or solid photocatalytic elements. A “stream” may be a continuous flow of the corresponding entity, e g. continuous flow of fluid medium, a continuous flow of solid photocatalytic elements. For example, the solid photocatalytic elements may be transported in a buffer medium (e.g., a gas or liquid, such as air or water for example) as “stream” for mixing with the stream of medium.

[0021] In some aspects, the photocatalysis device 200 may be coupled with an external device from which the photocatalysis device 200 receives the medium 206 to be processed. In some aspects, the photocatalysis device 200 may deliver the processed medium to the external device, illustratively after photocatalysis and separation. Illustratively, the first inlet 212 may be configured to be coupled with the external device, e g. via a conduit (e.g., a pipe, a tube), from which the medium 206 is injected into the mixing area 202. For example, the external device may include a pumping system to pump the medium 206 into the mixing area 202. In an exemplary configuration, a system may include the photocatalysis device 200 and the external device coupled with the first inlet 212. In some aspects, an outlet of the photocatalysis device 200 (e.g., an outlet 224 of the reaction chamber 220) may be configured to be coupled with the external device or may be coupled with the external device.

[0022] The medium 206 to be processed may be any suitable substance for processing via a photocatalytic reaction. In general, the medium 206 may be a fluid, e.g. a liquid or a gas. For example, considering the scenario in which the photocatalytic reaction is carried out to purify the medium 206, the medium 206 may be or include air (e.g., contaminated air) or another suitable gas (or a suitable liquid). As another example, considering the scenario in which the photocatalytic reaction is carried out to split the components of the medium 206, the medium 206 may be or include water (or another suitable substance). It is however understood that themedium 206 may be or include any other suitable gas or liquid, such as ammonia or an industrial gas, as other examples.

[0023] In some aspects, the medium 206 may include harmful compounds. The term “harmful compounds” may be used herein to describe any type of components that may be considered potentially dangerous for the human body, and that may be present in a medium that may be processed via photocatalysis. The term “harmful compounds” may describe impurities, for example in the form of particles, germs, pollutants and / or microplastics. For example, a medium to be processed (e.g., the medium 206) may include as harmful compounds organic pollutants, e.g. volatile organic compounds. For example, the medium to be processed may include as harmful compounds pathogens, such as viruses, bacteria, fungi, worms, and the like. As another example, the medium to be processed may include as harmful compounds Nitrogen(II) oxide, Nitrogen(V) oxide, and / or sulfur oxide (SOx). Examples of harmful compounds that may be present in the medium to be processed include bacteria such as Escherichia coli, salmonella, listeria, staphylococcus, and the like, and compounds such as alkanes, alkenes, halo-alkanes, halo-alkenes, aldehydes, ketones, aromatics, and / or dioxins.

[0024] In other aspects, the medium 206 may be free of impurities, e g. the medium 206 may be a substantially uncontaminated liquid or gas, e.g. substantially uncontaminated water or air (for example in case the photocatalysis is used for splitting the components of the medium 206). In this regard, the term “substantially uncontaminated” may describe that a concentration of harmful compounds in the medium 206 may be less than 5% by volume, for example less than 2% by volume, for example less than 1% by volume.

[0025] The solid photocatalytic elements 210 may have any suitable configuration for accelerating the photocatalytic reaction for processing the medium 206. In general, the solid photocatalytic elements 210 may be configured to accelerate a chemical reaction triggered by electromagnetic radiation (e.g., by light). Illustratively, the solid photocatalytic elements 210 may be configured to act as catalysts for a light-induced chemical reaction. In a preferred configuration the solid photocatalytic elements 210 may be photocatalytic particles (e.g., spherical particles), which is a shape that ensures a high surface-to-volume ratio. As other examples, the solid photocatalytic elements 210 may be photocatalytic rods or tubes, or may have any suitable polygon shape (e g., a cube, a cuboid, a tetrahedron, a pyramid, and the like). Various exemplary configurations will be described in further detail in relation to FIG.5A and FIG.5B.

[0026] In a corresponding manner, the solid photocatalytic elements 210 may include or may be made of any suitable material for accelerating the photocatalytic reaction. For example, thematerial of the solid photocatalytic elements 210 may be adapted depending on a target type or family of impurities of the medium 206, or depending on a target wavelength to be used for triggering the photocatalytic reaction. In general, the solid photocatalytic elements 210 may include or may be made of a photocatalytically active material. In particular, the solid photocatalytic elements 210 may include or may be made of a semiconductor material, which provides a suitable band gap for obtaining the redox reaction at the surface of the solid photocatalytic elements 210. For example, the semiconductor material may have a band gap (also referred to as bandgap, or energy gap) in the range from 1.5 eV (electronvolt) to 3.5 eV, e.g. a band gap in the range from 2 eV to 3 eV.

[0027] In a preferred configuration, the solid photocatalytic elements 210 may include or may be made of a metal oxide, which is a type of semiconductor particularly suitable for photocatalytic reactions. For example, the solid photocatalytic elements 210 may include or may be made of titanium oxide, e g. in anatase form, which provides a crystal structure that provides high photocatalytic activity. Other examples may include chromium oxide, zinc oxide, or cerium oxide. Further examples of suitable semiconductor materials may include semiconductors based on dO-transition metal cations and / or organometallic frameworks.

[0028] It is however understood that in principle the solid photocatalytic elements 210 may include or may be made of other types of suitable materials, such as carbon or carbon-based materials, a ceramic material, a metal material (e g , gold, platinum, silver, cobalt), or a polymer material. Further examples may include n-type semiconductors, such as cadmium sulfide, strontium titanate, graphitic carbon nitride, zirconium oxide, bismuth vanadate, tungsten trioxide, and / or iron(III) oxide. Further examples may include p-type semiconductors, such as copper(I) oxide, chalcocite, antimony selenide, and / or CuInS2.

[0029] In some aspects, the solid photocatalytic elements 210 may include a base material (e.g., a metal oxide, such as titanium dioxide), doped with one or more dopants. For example, the solid photocatalytic elements 210 may include a base material doped with a metal, such as silver, platinum, iron, chromium, cobalt, molybdenum, vanadium and the like, or with a non- metal, such as boron, carbon, nitrogen, sulfur, or fluorine. Doping may allow tailoring the excitation spectrum of the solid photocatalytic elements 210.

[0030] In a preferred configuration, the solid photocatalytic elements 210 used in the photocatalysis device 200 for carrying out a photocatalytic reaction may all have the same configuration, e.g. the same shape, the same material, the same size, etc. For example, for different photocatalytic reactions (e g., for different types of medium), different types of solid photocatalytic elements may be introduced in the photocatalysis device 200. It is howeverunderstood that, in principle, the solid photocatalytic elements 210 may also include solid photocatalytic elements having different properties, e.g. different shape, different material, different size, etc., for example to target different components of a same medium.

[0031] In general, the mixing area 202 may be configured to allow the stream 208 of solid photocatalytic elements 210 to mix with the stream 204 of medium 206 to obtain a (third) stream 216 of a resulting medium 218 that includes the solid photocatalytic elements 210 immersed in the medium 206. Illustratively, the mixing area 202 may be adapted such that the solid photocatalytic elements 210 from the second stream 208 combine with the medium 206 from the first stream 204 to result in the resulting medium 218. For example, the mixing area 202 may provide a sufficient length to allow the second stream 208 to mix with the first stream 204. In some aspects, the mixing area 202 may be configured to define flow conditions that allow the mixing of the stream 208 of solid photocatalytic elements 210 with the stream 204 of medium 206.

[0032] In some aspects, the mixing area 202 may be a dedicated chamber of the photocatalysis device 200, e.g. the mixing area 202 may be a mixing chamber. In other aspects, the mixing area 202 may be a portion of the reaction chamber 220 of the photocatalysis device 200 (described in further detail below). In this configuration, an inlet portion of the reaction chamber 220 may act as mixing area 202 where the solid photocatalytic elements 210 get mixed with the medium 206 to be processed. Illustratively, the mixing area 202 may be understood as a portion of the photocatalysis device 200 adapted such that the incorporation of the solid photocatalytic elements 210 in the medium 206 may occur.

[0033] In the resulting medium 218, the solid photocatalytic elements 210 are immersed in the medium 206, so that the solid photocatalytic elements 210 are surrounded by the medium 206. Illustratively, at the output from the mixing area 202, the outer surface of the solid photocatalytic elements 210 may be fully exposed to the medium 206. As an exemplary configuration, the mixing area 202 may include an outlet from which the third stream 216 is output. As another exemplary configuration, considering the scenario in which the mixing area 202 is part of the reaction chamber 220 (e.g., of the inlet portion), the output of the mixing area 202 may correspond to a portion of the reaction chamber 220 at which the mixing of the solid photocatalytic elements 210 into the medium 206 has occurred.

[0034] The photocatalysis device 200 may further include a reaction chamber 220 coupled with the mixing area 202 (e g., including the mixing area 202 in case the mixing area 202 corresponds to an inlet portion of the reaction chamber 220). The reaction chamber 220 may thus be configured to receive the third stream 216 of solid photocatalytic elements 210 immersed in themedium 206. The reaction chamber 220 may be configured or adapted to enable carrying out a photocatalytic reaction to process the medium 206 using the solid photocatalytic elements 210. The reaction chamber 220 may also be referred to herein as processing chamber, photocatalytic chamber, or photocatalysis and separation chamber.

[0035] In an exemplary configuration, a system may include the photocatalysis device 200 and the solid photocatalytic elements 210 disposed in the photocatalysis device 200. For example, the solid photocatalytic elements 210 may be disposed in the reaction chamber 220. In this scenario, the solid photocatalytic elements 210 may mix with the medium 206 upon the medium 206 flowing into the reaction chamber 220 (e.g., at the inlet portion). As another example, the solid photocatalytic elements 210 may be disposed in a collection chamber of the recirculation system 226 (described in further detail in relation to FIG.4). In this scenario, the solid photocatalytic elements 210 may mix with the medium 206 upon being recirculated towards the mixing area 202.

[0036] In general, the reaction chamber 220 may define a (inner) volume in which the solid photocatalytic elements 210 are free to move immersed in the medium 206. The reaction chamber 220 may thus include one or more sidewalls that define the spatial volume in which the photocatalytic elements 210 may circulate. The reaction chamber 220 (e.g., its geometry, for example its shape and dimensions) may be adapted to allow the solid photocatalytic elements 210 to freely move within the spatial volume, thus facilitating the contacting with the medium 206. The one or more sidewalls of the reaction chamber 220 may be impermeable to the medium 206 and to the solid photocatalytic elements 210, so that the resulting medium 218 remains confined in the reaction chamber 220 during the photocatalytic reaction.

[0037] The reaction chamber 220 may thus be configured such that the solid photocatalytic elements 210 are freely movable (freely mobile) in the inner volume of the reaction chamber 220. The reaction chamber 220 may be free of binding sites for the solid photocatalytic elements 210, e.g. the reaction chamber 220 may be free of anchor points at which the solid photocatalytic elements 210 may be fixed or get fixed. Stated in a different fashion, the reaction chamber 220 may be configured such that solid photocatalytic elements 210 may change their position relative to the spatial volume, and are exposed in the spatial volume so that their surface area is accessible to the medium 206. This allows maximizing the interaction between the solid photocatalytic elements 210 and the components of the medium 206.

[0038] The reaction chamber 220 may be further configured to enable introducing light energy in the inner volume of the reaction chamber 220 to cause a photocatalytic reaction. Illustratively, the reaction chamber 220 may be configured to allow electromagnetic radiation222, e.g. light, to illuminate the inner volume of the reaction chamber 220 to trigger a photocatalytic reaction to process the medium 206 under the assistance of the solid photocatalytic elements 210. Stated in a different fashion, the reaction chamber 220 may be configured or adapted such that the inner volume in which the solid photocatalytic elements 210 and the medium 206 are present or introduced may be illuminated via electromagnetic radiation 222. The reaction chamber 220 may thus be adapted to allow providing (e.g., transferring) light energy to the solid photocatalytic elements 210 and the medium 206 to induce a photocatalytic reaction. Various configurations may be provided in this regard, as will be discussed in further detail in relation to FIG.3A to FIG.3F.

[0039] According to the approach proposed herein, the reaction chamber 220 may be further configured to enable a mass-based position probability change of the solid photocatalytic elements 210 in the medium 206 within the reaction chamber 220. In this regard, the term “position probability” may describe the probability of an entity to have a certain position, e g within the reaction chamber 220. Illustratively, the “position probability” of an entity (e.g., of a solid photocatalytic element 210, of a constituent of the medium 206) may describe a distribution of probabilities each associated with a corresponding spatial coordinate within the reaction chamber 220. Accordingly, a “mass-based position probability change” may include a variation of the probability distribution for the position of the solid photocatalytic elements 210 in view of their different (greater) mass compared to the constituents of the medium 206.

[0040] In a preferred configuration, the reaction chamber 220 may be configured such that the solid photocatalytic element 210 have a greater position probability in correspondence of locations within the reaction chamber closer to a light source used to illuminate the reaction chamber 220 (see also FIG.3A to FIG.3F). By way of illustration, the reaction chamber 220 may be configured to foster a higher density of solid photocatalytic element 210 closer to the light source(s). For example, the reaction chamber 220 may be configured such that the solid photocatalytic element 210 have a greater position probability in correspondence of a sidewall of the reaction chamber 220.

[0041] The reaction chamber 220 may thus be configured that upon the solid photocatalytic element 210 and the medium 206 entering the reaction chamber 220, the position probability of the solid photocatalytic element 210 is different from the position probability of the components of the medium 206 (due to the greater mass of the elements 210). Such configuration of the reaction chamber 220 facilitates the triggering of the photocatalysis by bringing the solid photocatalytic element 210 closer to the light source(s), while maintaining the solid photocatalytic element 210 immersed in the medium 206 to enhance the reactionefficiency. Illustratively, the reaction chamber 220 may be configured (e.g., may have geometrical properties) such that a flow forms within the reaction chamber 220 upon the solid photocatalytic element 210 and medium 206 entering therein, and the flow pushes the solid photocatalytic element 210 closer to the light source(s), e.g. closer to the sidewall of the reaction chamber 220 compared to where the flow pushes the medium 206.

[0042] In some aspects, the reaction chamber 220 may be configured to enable a mass-based separation of the solid photocatalytic elements 210 from the medium 206. The photocatalysis device 200 may be configured to carry out a mass-based separation of the solid photocatalytic elements 210 present in the reaction chamber 220 from the medium 206 present in the reaction chamber 220 (e.g., after having carried out the photocatalytic reaction). For example, geometrical properties of the reaction chamber 220, e.g. of the inner volume, may be adapted to allow the solid photocatalytic elements 210 to be separated from the medium 206 by virtue of the greater mass of the solid photocatalytic elements 210 compared to the constituents of the medium 206.

[0043] In general, the solid photocatalytic elements 210 having greater mass may have greater inertia compared to the components of the medium 206. In some aspects, the reaction chamber 220 may thus be configured such that a flow (e.g., a vortex) forms within the inner volume that transports the components of the medium 206 in a first direction (e g., upwards), while the solid photocatalytic elements 210 are not transported by the flow and move in a second direction different from the first direction, e.g. a direction opposite to the first direction (e.g., downwards).

[0044] In general, the solid photocatalytic elements 210 may have a greater mass compared to the components of the medium 206 (see also FIG.5A and FIG.5B), and the reaction chamber 220 may be adapted to allow the difference in mass to be exploited for transporting the solid photocatalytic elements in a desired direction (e.g., closer to the sidewall), and for removing the solid photocatalytic elements 210 from the medium 206. Thus, after having carried out the photocatalytic reaction, the medium 206 may be output from the reaction chamber 220, e.g. from a corresponding outlet 224 (or plurality of outlets), as output medium 206b. The output medium 206b may be for example a purified version of the medium 206, or may include the components of the medium 206 separated from one another. As an example, considering medium purification, the output medium 206b may be free of impurities, e.g. free of pathogens. As another example, considering water splitting, the output medium 206b may include hydrogen and oxygen separated from one another.

[0045] In some aspects, the outlet 224 may include a filter element (e.g., a membrane) configured to allow the output medium 206b to pass through, and to prevent the solid photocatalytic elements 210 from passing through. For example, the filter element may have pores having a size (e.g., a diameter) greater than a size of the components of the medium 206b, and smaller than a size of the solid photocatalytic elements 210. This may prevent an undesired presence of photocatalysts in the output medium 206b.

[0046] The output medium 206b may be provided for any suitable application. In this regard, the reaction chamber 220 (e.g., the outlet 224) may be coupled or couplable with any suitable external device or system for delivering the output medium 206b, as mentioned above. Illustratively, the external device may provide contaminated medium 206 as input, and receive the purified medium as output medium 206b. For example, considering air purification, the reaction chamber 220 may be coupled with an air circulation system, that provides contaminated air as input medium 206 and receives the purified air as output medium 206b for further recirculation (e.g., in a room or in a building). Similarly, considering water purification, the reaction chamber 220 may be coupled with a water circulation system, that provides contaminated water as input medium 206 and receives the purified water as output medium 206b for further recirculation (e.g., in a pool, in a bathtub, and the like).

[0047] The solid photocatalytic elements 210 may thus be separated from the medium 206, and output from the reaction chamber 220 as separated solid photocatalytic elements 210b, as shown in FIG.2. For example, the reaction chamber 220 may include a further (second) outlet from which the separated solid photocatalytic elements 210b are output.

[0048] In general, there may be various options and configurations to enable the mass-based position probability change and to enable separating the solid photocatalytic elements 210 from the medium 206 according to their (greater) mass. In a preferred configuration (see also FIG.6A and FIG.6B), the reaction chamber 220 itself may be shaped to cause a centrifugal force in the inner volume to separate the solid photocatalytic elements 210 from the medium 206. Illustratively, the centrifugal force may transport the solid photocatalytic elements 210 towards one side the reaction chamber 220 (e.g., the bottom), while the medium 206 may travel towards the opposite side of the reaction chamber 220 (e.g., the top).

[0049] In some aspects, the geometrical properties of the reaction chamber 220 may thus be adapted to enable such mass-based position probability change (and separation) due to the action of a centrifugal force, in view of the different inertia of the solid photocatalytic elements 210 compared to the components of the medium 206. In a preferred configuration, the photocatalysis device 200 may be configured as a cyclone filter (see also FIG.6A and FIG.6B),which provides a reliable and efficient mass-based separation of particles from a medium as in general well-known in the art. In some aspects, the photocatalysis device 200 may thus be configured as a cyclone filter further adapted to enable introducing light energy for causing a photocatalytic reaction. In this scenario, the reaction chamber 220 may include the cyclone body and a conical section, and may be configured to cause within the reaction chamber 220 a first flow that transports the medium 206 towards the top of the reaction chamber 220 and a second flow that transports the (heavier) solid photocatalytic elements 210 towards the bottom of the reaction chamber 220. The operating principles of cyclone filters and cyclonic separation are well known in the art, so that a detailed description is dispensed with. The overall shape and geometry of the reaction chamber 220 for cyclonic separation may be adapted according to the properties of the solid photocatalytic elements 210 and medium 206, e.g. according to the respective mass or density, the mass difference, and the like.

[0050] A configuration of the photocatalysis device 200 as cyclone filter adapted to enable photocatalysis provides a simple, yet efficient configuration that requires minimal adaptations to existing cyclone filter designs. It is however understood that in principle also other approaches for mass-based separation may be provided.

[0051] As another example, the reaction chamber 220 may be rotatable around an axis, and the rotation of the reaction chamber 220 may cause a centrifugal force that separates the solid photocatalytic elements 210 from the medium 206. In this configuration, the photocatalysis device 200 may include a rotating motor to drive the rotation of the reaction chamber 220. In this configuration, the reaction chamber 220 may have a different shape other than the conical shape of a cyclone filter, for example the reaction chamber 220 may have a cylinder shape in this exemplary scenario.

[0052] In some aspects, the reaction chamber 220 may further include a plurality of electrodes to define an electric field within the inner volume of the reaction chamber 220, e g. in correspondence of a confined portion of the inner volume. The electric field may further enhance the efficiency of the mass-based separation of the solid photocatalytic elements 210 from the medium 206.

[0053] The configuration proposed herein thus enables having the solid photocatalytic elements 210 immersed in the medium 206 to maximize the available surface area for the photocatalysis, and further enables removing the solid photocatalytic elements 210b from the medium 206b, without having to maintain the solid photocatalytic elements 210 fixed at certain locations (e.g., on a surface, or in a membrane).

[0054] The photocatalysis device 200 may further include a recirculation system 226 coupled with the reaction chamber 220. The recirculation system 226 will be described in further detail in relation to FIG.4. In general, the recirculation system 226 may be configured to receive the solid photocatalytic elements 210b separated from the medium 206b, and to recirculate the separated solid photocatalytic elements 210b in the photocatalysis device 200. Illustratively, the recirculation system 226 may be configured to bring the separated solid photocatalytic elements 210b again to the mixing area 202 (as second stream 208) for mixing with the first stream 204 of medium 206.

[0055] The recirculation system 226 may be coupled with the (second) outlet of the reaction chamber 220 towards which the solid photocatalytic elements 210b travel upon being separated from the medium 206b (e.g., due to the action of the centrifugal force), and may thus collect the separated solid photocatalytic elements 210b. The recirculation system 226 may further transport the separated solid photocatalytic elements 210b to the mixing area, e g. by mixing the solid photocatalytic elements 210b with a buffer medium (e g., air, water) and providing a stream of solid photocatalytic elements 210b. Considering a “passive” mass-based separation (without an actively driven rotation of the reaction chamber 220), the recirculation system 226 may be configured to transport the solid photocatalytic elements 210b with a flow rate that enables the action of the centrifugal force within the inner volume of the reaction chamber 220.

[0056] The presence of the recirculation system 226 further enhances the capabilities of the photocatalysis device 200, by continuously replenishing the stream 208 of solid photocatalytic elements 210 and reduce the overall time needed to complete the processing of large amounts of medium 206.

[0057] FIG.3A to FIG.3F illustrate exemplary configurations 300a-300f of a reaction chamber 300 for use in a photocatalysis device adapted as proposed herein, e g. the reaction chamber 300 may be an exemplary realization of the reaction chamber 220 of the photocatalysis device 200.

[0058] As mentioned, the reaction chamber 300 may be configured to allow light energy to be introduced in the inner volume of the reaction chamber 300 to illuminate the solid photocatalytic elements immersed in the medium to be processed, thus triggering a photocatalytic reaction. In this regard, the photocatalysis device described herein (e.g., the photocatalysis device 200) may include or may be coupled with a source of electromagnetic radiation, e.g. a light source 302, configured to emit light towards the inner volume of the reaction chamber 300.

[0059] The light source 302 may be configured to emit light 322 having suitable properties for triggering a photocatalytic reaction. The properties of the light source 302 may thus be adapted depending on the type of solid photocatalytic elements used, and / or on the type of medium to be processed. In general, the light source 302 may be configured to emit light 322 having a wavelength that provides energy equal to or greater than the band gap of the solid photocatalytic elements, to allow electrons from the valence band to jump to the conduction band.

[0060] In a preferred configuration, the light source 302 may be configured to emit light 322 having wavelength in the ultraviolet range (e.g., in the range from 100 nm to 400 nm), in particular in the UV-C range (e.g., from 100 nm to 280 nm). Such wavelength range may be particularly suitable for deactivating harmful compounds in a medium. In other configurations, the light source 302 may be configured to emit light 322 having wavelength in the UV-A range (e.g., from 315 nm to 400 nm), UV-B (e.g., from 280 nm to 315 nm) range, visible range (e.g., from 400 nm to 700 nm), or infrared range (e g., from 700 nm to 5000 nm).

[0061] In some aspects, the photocatalysis device may include a plurality of light sources 302 (see also FIG.3C). As an exemplary configuration, the plurality of light sources 302 may include, at least, a first light source configured to emit light in a first wavelength range (e g , at a first wavelength), and a second light source configured to emit light in a second wavelength range (e.g., at a second wavelength). The plurality of light sources 302 may further include a third light source configured to emit light in a third wavelength range (e g., at a third wavelength), etc.

[0062] For example, the light sources 302 may be configured to emit light 322 in the same wavelength range to enhance the illumination of the volume of the reaction chamber 300. As an exemplary configuration, the first wavelength range may be equal to the second wavelength range (and to the third wavelength range, etc.), e.g. the first wavelength may be equal to the second wavelength (and to the third wavelength etc ). For example, the light sources 302 may be disposed at different locations to illuminate the volume of the reaction chamber 300 from different directions.

[0063] As another example, the light sources 302 may be configured to emit light 322 in different wavelength ranges to increase the flexibility of the arrangement, e.g. by activating different light sources depending on the type of reaction to be carried out, on the type of photocatalysts used, and the like. As an exemplary configuration, the first wavelength range may be different from the second wavelength range (and from the third wavelength range, etc.), e.g. the first wavelength may be different from the second wavelength (and from the third wavelength etc.). For example, the first wavelength range may be the UV range, and the secondwavelength range may be the visible range (and the third wavelength range may be the infrared range). As another example, the first wavelength range may be the UV-C range, and the second wavelength range may be the UV-B range (and the third wavelength range may be the UV-A range).

[0064] In some aspects, some of the light sources 302 may be configured to emit light 322 in the same wavelength range, and other light sources 302 may be configured to emit light 322 in different wavelength ranges. For example, the first wavelength range may be equal to the second wavelength range, and may be different from the third wavelength range, etc.

[0065] In general, the light source(s) 302 may be configured to emit light 322 having an irradiance level capable of triggering the photocatalytic reaction in the reaction chamber 300. As a numerical example, which has been found to ensure effective photocatalysis, the light source(s) 302 may be configured to deliver an irradiance level equal to or greater than 0.2 mW / cm2in the reaction chamber 300, e g. an irradiance level equal to or greater than 0.5 mW / cm2. The properties and the number of light source(s) 302 may be adapted to provide the desired irradiance level based on the overall surface area of the reaction chamber 300. For example, considering a reaction chamber 300 with surface area of 7000 cm2, the light source(s) 302 may be adapted to provide 1400 mW of optical power. For example a suitable number of light source(s) 302 may be provided to deliver, in combination, the desired optical power. As a numerical example, the photocatalysis device may include a number of light sources 302 in the range from 1 to 15, for example in the range from 2 to 10, for example in the range from 4 to 8.

[0066] The light source(s) 302 may be realized in any suitable manner. As an example, a light source 302 may include one or more light emitting diodes, LEDs, e.g. an array of light-emitting diodes for example arranged in a one-dimensional fashion or a two-dimensional fashion. For example a light source 302 may include one or more Micro-LEDs, to provide a more compact arrangement. As another example, the light source 302 may be or include a laser source, e.g. a Vertical Cavity Surface Emitting Laser (VCSEL) or a VCSEL-array. As another example, a light source 302 may be or include a gas discharge lamp. A light source 302 may be configured to emit light in any suitable manner depending on the desired operation. As an example, the light source 302 may emit continuous light. As another example, the light source 302 may emit light in a pulsed manner, e.g. the light source 302 may emit a sequence of light pulses.

[0067] Various arrangements are possible for providing a light source 302 (or a plurality of light sources 302) in the photocatalysis device proposed herein.

[0068] As a first exemplary configuration 300a, the photocatalysis device may include a light source 302 disposed internally to the reaction chamber 300. In this configuration, the lightsource 302 may thus be an internal light source disposed within the inner volume of the reaction chamber 300. For example, the internal light source may be attached to a sidewall of the reaction chamber 300 and emit light towards the interior of the reaction chamber 300. In some aspects, the photocatalysis device may include a plurality of light sources 302 disposed internally to the reaction chamber 300. Providing the light source(s) 302 internally to the reaction chamber 300 may enhance the illumination efficiency of the solid photocatalytic elements immersed in the medium. The light source(s) 302 may be disposed completely internally to the reaction chamber 300.

[0069] As a second exemplary configuration 300b, the photocatalysis device may include a light source 302 disposed externally to the reaction chamber 300. In this configuration, the light source 302 may thus be an external light source disposed outside of the inner volume of the reaction chamber 300. For example, the internal light source may be attached to an external sidewall of the reaction chamber 300, or may be at a distance from the external sidewall of the reaction chamber 300. In some aspects, the photocatalysis device may include a plurality of light sources 302 disposed externally to the reaction chamber 300. The light source(s) 302 may be disposed completely externally to the reaction chamber 300.

[0070] In this exemplary configuration 300b, the reaction chamber 300 may further include an optical element 304 configured to allow the light 322 emitted by the external light source(s) 302 to enter the inner volume of the reaction chamber 300. In other words, the electromagnetic radiation from the external light source is coupled into the volume of the reaction chamber 300 via the optical element 304. The optical element 304 may be further configured to prevent the medium and solid photocatalytic elements to escape from the reaction chamber 300. Illustratively, the optical element 304 may be impermeable to the medium and solid photocatalytic elements. The optical element 304 may thus receive the light 322 emitted by the external light source(s) 302 and allow the light to enter the reaction chamber 300.

[0071] As an example, the optical element 304 may be a window configured to be transparent for the light 322 emitted by the external light source 302. The window may be formed in a sidewall of the reaction chamber 300. For example, the window may include or may be made of glass (e.g., fused silica), or a transparent polymer. In the preferred configuration, the window may be transparent for light in the UV wavelength range, or in any other suitable wavelength range depending on the type of light source used. In case of a plurality of external light sources 302, the reaction chamber 300 may include a plurality of windows, e.g. one for each external light source 302. For example, the plurality of windows may be disposed in correspondence ofdifferent sidewalls of the reaction chamber 300. As a numerical example, the window(s) may transmit at least 80% of the incident light, e.g. at least 90%, e.g. at least 95% or 99%.

[0072] As another example, the optical element 304 may include an optical waveguide, or a plurality of optical waveguides, configured to receive (at one end) the light 322 emitted by the external light source(s) 302 and to direct the light to the inner volume of the reaction chamber. In case of a plurality of external light sources 302, the reaction chamber 300 may include a plurality of optical waveguides, e.g. one for each external light source 302.

[0073] Providing external light source(s) 302 may enhance the flexibility of the arrangement, e.g. by allowing to substitute the external light source(s) 302 with other light sources to emit light in different wavelength ranges, or at higher power, in a simpler manner compared to the case in which the light source(s) 302 is / are arranged internally to the reaction chamber 300.

[0074] In some aspects, as shown in the configuration 300c in FIG.3C, the photocatalysis device may include one or more internal light sources 302a, and one or more eternal light sources 302b (and corresponding optical element(s) 304), to combine the advantages of the two approaches. For example, the photocatalysis device may include a first light source 302a internal to the reaction chamber 300, and a second light source 302b external to the reaction chamber 300. The first light source 302a may emit first light 322a, and the second light source 302b may emit second light 322b, e.g. in the same or different wavelength range, as discussed above.

[0075] According to various aspects, as shown in FIG.3D to FIG.3F, the reaction chamber 300 may further include a reflective coating 306, e.g. disposed on at least one sidewall of the reaction chamber 300 (e.g., disposed on each sidewall of the reaction chamber 300). The reflective coating 306 may be configured to be reflective for light in a predefined wavelength range, e.g. for light 322 emitted by the light source 302, e.g. the reflective coating 306 may be configured to be reflective for the corresponding wavelength range such as the UV range. Stated in a different fashion, in some aspects the inner walls of the reaction chamber 300 may be configured to be reflective for light 322 emitted by the light source(s) 302, thus allowing the emitted light 322 to travel multiple times within the inner volume of the reaction chamber 300. The reflective coating 306 may also be referred to herein as reflective layer.

[0076] In a preferred configuration, the reflective coating 306 may completely cover the sidewalls of the reaction chamber 300 facing towards the inner volume of the reaction chamber 300. It is however understood that in principle the reflective coating 306 may be disposed only on part of the sidewalls of the reaction chamber 300, e.g. considering the disposition of the light source(s) 302 and the direction from which the light 322 comes into the reaction chamber 300.The presence of the reflective coating 306 may enhance the illumination of the inner volume of the reaction chamber, and thus the activation of the photocatalytic reaction in presence of the solid photocatalytic elements in the medium. The reflective coating 306 may leave the inlet(s) and outlet(s) of the reaction chamber 300 free to allow the flow of medium and solid photocatalytic elements.

[0077] The reflective coating 306 may include or may be made of any suitable reflective material, such as a metal, a reflective polymer, and the like. As exemplary materials particularly suitable for reflecting UV light, the reflective coating 306 may include or may be made of aluminum or a fluoropolymer such as polytetrafluoroethylene (PTFE). In a corresponding manner, the reflective coating 306 may have any suitable geometrical properties, e.g. any suitable thickness. As an example, the reflective coating 306 may have a thickness in the range from 100 nm (nanometers) to 200 pm (micrometers), e.g. a thickness in the range from 500 nm to 50 pm, e g. a thickness in the range from 1 pm to 10 pm.

[0078] As shown in FIG.3D to FIG.3F, the reflective coating 306 may be provided in combination with an internal light source 302 (configuration 300d), with an external light source 302 (configuration 300e), or with both internal light source 302 and an external light source 302 (configuration 3001). In some aspects, the reflective coating 306 may be provided in combination with a plurality of internal light sources 302 and / or a plurality of external light sources 302 In case of external light sources 302 the optical element 304 (e g., the window, or the end of the optical waveguide) may be free of the reflective coating 306.

[0079] In some aspects (not shown), the photocatalysis device proposed herein may further include a control circuit configured to control the light emission by the light source(s) 302. For example, the control circuit may be configured to provide a control signal to each light source 302 (e.g., to a driver of the light source 302) to cause a corresponding light emission 302. The control circuit may thus control the timing of the light emission, e.g. to synchronize the light emission with the presence of solid photocatalytic elements and medium in the reaction chamber 300.

[0080] FIG.4 shows an exemplary configuration of a recirculation system 400 for use in a photocatalysis device adapted as proposed herein, e g. the recirculation system 400 may be an exemplary realization of the recirculation system 226 of the photocatalysis device 200.

[0081] As mentioned, the recirculation system 400 may be configured to receive the solid photocatalytic elements 210b separated from the medium in the reaction chamber, and to recirculate the separated solid photocatalytic elements 210b towards the mixing area of the photocatalysis device. The recirculation system 400 may have any suitable configuration toimplement such functionality. In this regard, FIG.4 provides an exemplary implementation that has been found to allow an efficient realization of the strategy proposed herein, but it is understood that the recirculation system 400 may include alternative or additional components with respect to the configuration of FIG.4.

[0082] According to various aspects, the recirculation system 400 may include a collection chamber 402 configured to be coupled with the reaction chamber. For example, the collection chamber 402 may include an inlet 404 (also referred to herein as collection inlet) couplable with the reaction chamber, e.g. with the outlet (or outlets) of the reaction chamber towards which the solid photocatalytic elements 210b are transported upon being separated from the medium. In a preferred configuration, the collection chamber 402 may be disposed at the bottom of the reaction chamber to collect the solid photocatalytic elements 210b. The collection chamber 402 may thus receive from the reaction chamber the solid photocatalytic elements separated from the medium.

[0083] The recirculation system 400 may further include a pumping system 408 configured to pump the solid photocatalytic elements 210b from the collection chamber 402 towards the mixing area of the photocatalysis device. For example, the collection chamber 402 may include an outlet 406 (also referred to herein as collection outlet) coupled with the pumping system 408, and the pumping system 408 may be further configured to be coupled with the mixing area of the photocatalysis device.

[0084] The pumping system 408 may include any suitable type of pump or pumping device to cause a movement of the solid photocatalytic elements 210b from the collection chamber 402 towards the mixing area. For example, the pumping system 408 may include a rotary pump, a screw pump, an air-operated pump, a gear pump, a peristaltic pump, and the like. In some aspects, the pumping system 408 may include a buffer medium into which the solid photocatalytic elements 210b are transported, e.g. a fluid such as a liquid (e g., water) or a gas (e.g., air).

[0085] The recirculation system 400 may further include conduits (e.g., pipes, or tubes) to interconnect the components of the recirculation system 400 (e g., the collection chamber with the pumping system 408) and to connect the recirculation system 400 with the other components of the photocatalysis device (e.g., with the mixing area). For example, the recirculation system 400 may further include a conduit coupled with the mixing area and through which the pumping system 408 pumps the solid photocatalytic elements 210b to bring them back for mixing with the medium.

[0086] Considering a “passive” mass-based approach, the pumping system 408 may be configured to provide a flow rate for the stream of solid photocatalytic elements 210b sufficient to cause mass-based position probability change of the solid photocatalytic elements 210b in the medium in the reaction chamber, and to cause mass-based separation of the solid photocatalytic elements 210b from the medium in the reaction chamber. The flow rate may be adjusted depending on various system parameters, such as the geometry of the reaction chamber, the mass of the solid photocatalytic elements 210b, the mass difference with the constituents of the medium, etc.

[0087] According to various aspects, the photocatalysis device may include a control circuit configured to control the pumping system 408. The control circuit may be dedicated to the pumping control and may be separate from the (first) control circuit controlling the light emission, or may be a dedicated portion of the same control circuit that controls the light emission In general, the control circuit may define the pumping parameters, such as activation time, deactivation time, pumping speed, and the like. In an exemplary configuration, the control circuit may control the pumping system 408 in accordance (e.g., in synchronization) with the control of the light emission, to ensure that the recirculation occurs after having triggered the photocatalytic reaction in the reaction chamber.

[0088] According to various aspects, the recirculation system 400 may be configured to allow retrieving the separated solid photocatalytic elements 210b. For example, the collection chamber 402 may be detachably coupled with the reaction chamber, e g. via detachable fastening means such as screws or mechanical latches. As another example, the collection chamber 402 may include a door that may be opened to allow access to the interior of the collection chamber 402. This configuration allows replacing the solid photocatalytic elements 210b, e.g. to provide photocatalysts with different properties to process a different medium, to add further photocatalysts for processing more medium, and the like.

[0089] As discussed in relation to FIG.2, the solid photocatalytic elements may have any suitable properties for use in the photocatalysis device. In this regard, FIG.5A and FIG.5B illustrate possible configurations 500a-500h, 550a-550h of solid photocatalytic elements, e.g. exemplary realizations of the solid photocatalytic elements 210. Although the solid photocatalytic elements 500a-500h, 550a-550h are shown as spherical particles, it is understood that the aspects discussed in relation to FIG.5 A and FIG.5B may apply in a corresponding manner to other shapes of the solid photocatalytic elements.

[0090] In general, the solid photocatalytic elements 500a-500h, 550a-550h may have any suitable dimension that enables the mass-based separation. As a numerical example, a solidphotocatalytic element 500a-500h, 550a-550h may have a lateral dimension (e.g., a diameter) in the range from 1 gm to 5 mm (millimeters), e.g. in the range from 10 gm to 1 mm, e.g. in the range from 100 gm to 500 gm.

[0091] According to various aspects, as shown in FIG.5A, a solid photocatalytic element 500a-500f may include a base body 502a-f and a photoactive material 504a-504f disposed on the outer surface of the base body 502a-f. Illustratively, in some aspects a solid photocatalytic element 500a-500f may include a carrier body 502a-502f (e.g., a carrier particle) coated with a photoactive material 504a-504f. The photoactive material 504a-504f may be disposed on the outer surface of the carrier body 502a-502f, e.g. in form of a layer or in form of particles. The layer of photoactive material 504b, 504e may be a continuous layer, e.g. the outer surface of the carrier body 502b, 502e may be completely covered by the layer of photoactive material 504b, 504e.

[0092] The carrier body 502a-502f may include or may be made of a material that is transparent in the wavelength range used for the photocatalytic reaction, e.g. a material that is transparent in the UV range (or any other suitable wavelength range), illustratively a material that is transparent in the wavelength range of light emitted by the light source(s) of the photocatalysis device. As exemplary materials, the carrier body 502a-502f may include or may be made of glass, silica, fused silica, and the like. The photoactive material 504a-504f may be or include any of the materials discussed in relation to the solid photocatalytic elements 210 in FIG.2, e g a semiconductor material (e g., titanium oxide).

[0093] According to various aspects, as shown for the solid photocatalytic elements 500a, 500b, the carrier body 502a, 502b may be a full body, illustratively without any cavities. In other aspects, as shown for the solid photocatalytic elements 500d, 500e, the carrier body 502d, 502e may be a hollow body, illustratively the carrier body 502d, 502e may include an inner empty volume. For example, the carrier body 502d, 502e may be a hollow sphere. In general, the type of carrier body may be adapted depending on the desired resulting mass for the solid photocatalytic elements, e.g. to tailor the mass difference with the constituents of a certain medium to be processed.

[0094] According to various aspects, as shown for the solid photocatalytic elements 500c, 500f, an adhesive layer 506c, 506f may be disposed between the carrier body 502c, 502f and the photoactive material 504c, 504f. The adhesive layer 506c, 506f may be disposed on the outer surface of the carrier body 502c, 502f, e.g. to cover the entire outer surface, and may be configured to increase the adhesion of the photoactive material 504c, 504f to the carrier body502c, 502f. As an example, the adhesive layer 506c, 506f may include or may be made of an adhesive polymer.

[0095] According to various aspects, as shown for the solid photocatalytic elements 500g, 500h, the carrier body may be dispensed with, and the solid photocatalytic element 500g, 500h may include only the photoactive material 504g, 504h. In this configuration, the solid photocatalytic element 500g, 500h may include a body made of photoactive material 504g, 504h, for example a full body (500g) or a hollow body (500h). For example, the solid photocatalytic element 500g, 500h may be a full solid sphere of photoactive material 504g or a hollow sphere of photoactive material 504h.

[0096] According to various aspects (not shown) a solid photocatalytic element 500a-500h may include surface modification, e.g. a coating, configured to provide hydrophobicity of the solid photocatalytic element 500a-500h. The surface modification may increase the hydrophobicity of the solid photocatalytic element 500a-500h compared to a configuration without the surface modification, thus enhancing reducing the formation of aggregates of solid photocatalytic element 500a-500h that could reduce the surface area exposed to the medium. As an example, the surface modification may include a fluorine compound.

[0097] According to various aspects, as shown in FIG.5B, a solid photocatalytic element 550a-550h may further include a cocatalyst 562, 564 in addition to the photoactive material 554a-554h. The cocatalyst 562, 564 may be configured to enhance the efficiency of the photocatalytic reaction compared to a “bare” solid photocatalytic element 550a-550h. In particular, a cocatalyst 562, 564 may be provided in case the solid photocatalytic element 550a-550h are used for splitting the components of a medium, e.g. for water splitting. For example, the cocatalyst 562, 564 may be provided in form of particles, as shown in FIG.5B. The amount of cocatalyst 562, 564 present in a solid photocatalytic element 550a-550h may be freely adapted depending on various considerations, such as the type of reaction to be carried out, the medium to be processed, and the like.

[0098] A solid photocatalytic element 550a-550h may include a single cocatalyst 562, or a plurality of different cocatalysts 562, 564, e.g. two different cocatalysts or even more than two different cocatalysts. Any suitable cocatalyst 562, 564 may be used. As an example, a cocatalyst 562, 564 may be a metal, such as platinum (Pt), nickel (Ni), rhodium (Rh), or ruthenium (Ru). As another example, a cocatalyst 562, 564 may be a metal oxide, e.g. NiO, or a doped metal oxide, e.g. chromium-doped RhOx. As a further example, a cocatalyst 562, 564 may be cobalt-based, e.g. including CoxP, CoSx, Co-selenides, Co-N-C composites, and / or M-Co alloys. As a further example, a cocatalyst 562, 564 may be nickel-based, e.g. including NiSx,NiSe2, Ni-phosphides, and / or Ni layer double hydroxides (LDHs). As a further example, a cocatalyst 562, 564 may include a transition metal dichalcogenide, such as M0S2, MoSe2, and / or M02C. As a further example, a cocatalyst 562, 564 may be iron-based, e.g. including FeOx, FeOOH, and / or Fe phosphides.

[0099] According to various aspects, as shown for the solid photocatalytic elements 550a-550d, the cocatalyst 562, 564 may be disposed on the outer surface of a carrier body 552a-552d, e.g. a full solid body 552a, 552c, or a hollow body 552b, 552d. The carrier body 552a-552d may in general be configured as the carrier body 502a-502f described in relation to FIG.5 A. In this configuration, the cocatalyst 562, 564 may be disposed in direct physical contact with the outer surface of the carrier body 552a-552d. Additionally or alternatively, the cocatalyst 562, 564 may be disposed in direct physical contact with the photoactive material 554a-554d (e.g., particles as shown, or a layer). Although not shown, in some aspects an adhesive layer may be disposed on the surface of the carrier body 552a-552d to enhance the adhesion of the photoactive material 554a-554d and cocatalyst 562-564.

[0100] According to various aspects, as shown for the solid photocatalytic elements 550e-550f, the carrier body may be dispensed with, and the cocatalyst(s) 562, 564 may be disposed on the outer surface of a body of the solid photocatalytic element 550e-550f made of photoactive material 552e, 552f, e.g. a solid body as shown or a hollow body.

[0101] According to various aspects, as shown for the solid photocatalytic elements 550g-550h, the photoactive material 552e, 552f and the cocatalyst(s) 562, 564 may be provided in form of individual particles that are aggregated together to form a cluster. Also in this configuration the carrier body may be dispensed with, while providing sufficient mass to enable the mass-based separation discussed herein.

[0102] FIG.6A and FIG.6B show a photocatalysis device 600a, 600b in a schematic representation, according to various aspects. The photocatalysis device 600a, 600b may be an exemplary realization of the photocatalysis device 200 described in FIG.2. As mentioned, according to a preferred configuration the photocatalysis device 600a, 600b may be configured as a cyclone filter (also referred to as cyclone separator, cyclonic separator, or simply as cyclone), thus allowing to implement the mass-based separation in a simple, yet efficient manner. In general, the photocatalysis device 600a, 600b may include a mixing area 602, a reaction chamber 620, and a recirculation system 626, as exemplary realizations of the mixing area 202, reaction chamber 220, and recirculation system 226 described in relation to FIG.2.

[0103] By way of illustration, the configuration of FIG.6A and FIG.6B may be understood as a cyclone filter adapted such that light energy may be introduced in the reaction chamber 620,e.g. in the conical section (and / or cyclone body), and such that the solid photocatalytic elements 610b separated from the medium 606b by virtue of centrifugal force may be reintroduced in the reaction chamber 620 after mixing again with the medium 606.

[0104] As discussed in relation to FIG 2, the mixing area 602 may be configured to receive a first stream 604 of a medium 606 to be processed, e.g. at a first inlet 612, and a second stream 608 of solid photocatalytic elements 610, e.g. at a second inlet 614. The mixing area 602 may be further configured to deliver, as output, a third stream 616 of a resulting medium 618 in which the solid photocatalytic elements 610 are immersed in the medium 606. The reaction chamber 620 may receive the resulting medium 618, and may be configured to enable introducing light energy in the inner volume of the reaction chamber 62O.In some aspects, the reaction chamber 620 may further be configured to enable a mass-based position probability change of the solid photocatalytic elements 610 in the medium 606. In some aspects, the reaction chamber 620 may be configured to enable a mass-based separation of the solid photocatalytic elements 610 from the medium 606. Accordingly, the medium 606b processed and separated from the solid photocatalytic elements 610b may be provided at an outlet 624 of the reaction chamber 620, whereas the solid photocatalytic elements 610b separated from the medium 606b may be received and recirculated by the recirculation system 626.

[0105] Considering a configuration as “cyclone filter”, the mixing area 602 may be at an inlet portion of the reaction chamber 620, e g. the mixing area 602 is not a dedicated chamber of the device 600a, 600b, but rather an entrance portion of the reaction chamber 620 where the mixing of the solid photocatalytic elements 610 with the medium 606 occurs.

[0106] In this configuration, as generally known in the art, the reaction chamber 620 may include a cyclone body 628 and a conical section 630 coupled with one another. The reaction chamber 620 may also be referred to herein as cyclone chamber in this configuration. The cyclone body 628 may have rotational symmetry around an axis passing through the center of the cyclone body 628 (and of the conical section 630), e.g. the cyclone body 628 may have a cylinder shape.

[0107] The cyclone body 628 and conical section 630 may be configured such that a spiral vortex forms inside the cyclone body 628 and conical section 630, thus causing the components of the medium 606 (which are lighter and have less inertia) to travel towards the top part of the reaction chamber 620. In a corresponding manner the solid photocatalytic elements 610 (having greater mass than the components of the medium) have more inertia and are not (or anyway less) influenced by the vortex and travel towards the bottom part of the reaction chamber 620. The vortex may further push the solid photocatalytic elements 610 towards the sidewall of thecyclone body 628 and conical section 630. Illustratively, the larger (and heavier) solid photocatalytic elements 610 do not follow the spiral vortex and drop down towards the recirculation system 626. The cyclone body 628 and conical section 630 may thus define an upside-down cone to facilitate the collection of the separated solid photocatalytic elements 610b, while the processed medium flows out from the top of the chamber 620 (e.g., from a corresponding outlet 624). For example, the first inlet 612 may be disposed tangentially to the cyclone body 628.

[0108] As generally known in the art, the separation principle is based on the fact that the heavier solid photocatalytic elements 610 cannot follow the flow movement towards the top of the reaction chamber 620. Such type of separation is well suited for objects (e.g., solid photocatalytic elements 610) of various sizes, depending on the entry velocity of the stream into the reaction chamber, as known in the art.

[0109] As discussed in relation to FIG.2, the specific dimensions of the cyclone filter, e g. the diameter of the cyclone body 628 and / or conical section 630, the inner volume of the reaction chamber 620, the flow rate of the medium 606 and / or solid photocatalytic elements 610 may be freely adapted depending on various considerations including the type of medium 606, the type of solid photocatalytic elements 610, the volume of medium 606 and solid photocatalytic elements 610, etc.

[0110] In some aspects, not shown, the photocatalysis device 600a, 600b may further include an additional inlet of the reaction chamber 620, and means to provide a secondary air flow into the reaction chamber 620. The secondary air flow may be provided at the top of the reaction chamber 620 and may travel downwards, and may be provided to enhance the separation efficiency of the cyclone filter.

[0111] The recirculation system 626 may include a collection chamber 632 coupled with the reaction chamber 620. As shown, the collection chamber 632 may be coupled with the conical section 630 of the reaction chamber 620, and may be disposed at the bottom of the conical section 630 to collect the solid photocatalytic elements 610b that travel in that direction due to the greater mass compared to the components of the medium 606. Although not shown, the recirculation system 626 may further include a pumping system to transport the solid photocatalytic elements 610b back towards the mixing area 602 (e.g., through a conduit, e.g. a pipe or tube, coupled with the collection chamber 632 at one end and with the second inlet 614 of the mixing area 602 at the other end).

[0112] FIG.6B shows an adaptation of the reaction chamber 620 to enable introducing light energy in its inner volume. The features shown and discussed in relation to FIG.6B may beprovided in combination with one another, or independently from one another, as generally discussed in relation to FIG.3A to FIG.3F.

[0113] In general, the photocatalysis device 600b may further include a light source 634a, 634b or a plurality of light sources 634a, 634b configured to emit light towards the inner volume of the cyclone chamber, e.g. configured as the light source(s) 302, 302a, 302b in FIG.3A to FIG.3F.

[0114] As an exemplary configuration, the photocatalysis device 600b may include one or more light sources 634a disposed internally to the reaction chamber 620. For example, the photocatalysis device 600b may include one or more internal light sources 634a disposed on an inner sidewall of the reaction chamber 620, e.g. an inner sidewall of the conical section 630. Disposing the internal light source(s) 634a in correspondence of the conical section 630 may ensure sufficient time for the solid photocatalytic elements 610 to mix with the medium 606 before initiating the photocatalytic reaction. It is however understood that in principle one or more of the internal light sources 634a may be disposed on an inner sidewall of the cyclone body 628 (additionally or alternatively to the internal light sources 634a in correspondence of the conical section 630)

[0115] As a further exemplary configuration, in addition or in alternative to having internal light sources 634a, the photocatalysis device 600b may include one or more light sources 634b disposed externally to the reaction chamber 620. For example, the photocatalysis device 600b may include one or more external light sources 634b disposed outside of the inner volume of the reaction chamber 620. For example, the one or more external light sources 634b may be disposed in contact with an outer sidewall of the reaction chamber 620, or at a distance from such outer sidewall. In a corresponding manner as for the internal light source(s) 632a, the one or more external light sources 634b may be disposed in correspondence of the conical section 630 (e.g., to illuminate the inner volume of the reaction chamber 620 through the sidewall of the conical section 630), and / or in correspondence of the cyclone body 628.

[0116] In case the photocatalysis device 600b includes one or more external light sources 634b, the photocatalysis device 600b may further include an optical element 636 (or a plurality of optical elements 636) configured to allow the light emitted by the external light source(s) 634b to enter the reaction chamber 620. For example, the optical element 636 may be or include a window (or a plurality of windows) transparent for the wavelength range of the light emitted by the external light source(s) 634b. The window may be formed in the sidewall of the reaction chamber 620, e.g. in the sidewall of the conical section 630 and / or of the cyclone body 628. As another example, the optical element 636 may be or include a waveguide (or a plurality ofwaveguides) configured to collect the light from the external light sources 634b and bring the collected light into the inner volume of the reaction chamber 620.

[0117] According to various aspects, as shown in FIG.6B, the reaction chamber 620 may further include a reflective coating 638 formed on the inner sidewall(s) of the reaction chamber 620. The reflective coating 638 may be configured in general as the reflective coating 306 described in relation to FIG.3A to FIG.3F, and may include any suitable material being reflective for the light emitted by the light source(s) 634a, 634b. For example, the reflective coating 638 may be disposed on the sidewall of the conical section 630, e.g. to completely cover the inner surface of the conical section 630 (except where an optical element 636 and / or internal light source 634a is / are provided). As another example, additionally or alternatively, the reflective coating 638 may be disposed on the sidewall of the cyclone body 628, e.g. to completely cover the inner surface of the cyclone body 628.

[0118] In the following, two methods of processing a medium using photocatalysis and massbased separation will be described, e.g. two methods of processing a medium using the photocatalysis device proposed herein. A method of purifying a medium will be described in relation to FIG.7B, and a method of splitting a medium into a plurality of components will be described in relation to FIG.7C. Although in FIG.7B and FIG.7C a certain configuration of the photocatalysis device is illustrated (e.g., as cyclone filter with external light sources), it is understood that the aspects described in relation to FIG.7A to FIG 7C may apply in a corresponding manner to any of the configurations of the photocatalysis device described in relation to FIG.2 to FIG.6B. It is also understood that the aspects discussed in relation to the methods apply in a corresponding manner to the photocatalysis device, and vice versa.

[0119] In general, a method 700 to process a medium according to the approach proposed herein may include carrying out a photocatalytic reaction in a medium assisted by solid photocatalytic elements immersed in the medium, and carrying out a mass-based separation of the solid photocatalytic elements from the medium (after having triggered / carried out the photocatalytic reaction). For example, the method may include carrying out the photocatalytic reaction within a cyclone chamber of a cyclone filter. For example, the method may include causing a mass-based position probability change of the solid photocatalytic elements immersed in the medium.

[0120] FIG .7A shows a schematic flow diagram of a method 700 of processing a medium, according to various aspects. The method 700 may include, in 710, introducing a medium into a photocatalysis device adapted described herein (e.g., the photocatalysis device 200, 600a, 600b). For example, introducing the medium may include pumping or injecting a stream of themedium into an inlet of the photocatalysis device (e.g., into the inlet of the mixing area). In some aspects, introducing the medium may include introducing the stream of medium into a cyclone filter adapted to allow carrying out a photocatalytic reaction in the cyclone chamber. In this scenario, introducing the medium may include imposing a flow rate to the stream of medium to enable forming a vortex in the cyclone chamber. The flow of medium may be laminar or turbulent.

[0121] For example, the medium may be a medium to be purified (e.g., contaminated air or water), e.g. a medium including harmful compounds. As another example, the medium may be processed to separate one or more components of the medium from one another, e g. the medium may be water and the method may be a method of water splitting.

[0122] In some aspects, the method 700 may further include, in 720, causing a mixing of a stream of solid photocatalytic elements with the stream of medium. Illustratively, the method 700 may include providing a stream of a resulting medium in which the solid photocatalytic elements are immersed in the medium. For example, the method 700 may include introducing a stream of solid photocatalytic elements in the photocatalysis device (in correspondence of the mixing area). As another example, in case the solid photocatalytic elements are disposed within the photocatalysis device, the method 700 may include transporting the solid photocatalytic elements to the mixing area of the photocatalysis device for mixing with the stream of medium.

[0123] The method 700 may further include, in 730, illuminating the solid photocatalytic elements immersed in the medium using electromagnetic radiation, e.g. light (for example UV light). Illustratively, the method 700 may include providing light energy in the inner volume of a reaction chamber of the photocatalysis device to trigger a photocatalytic reaction in the reaction chamber. As discussed above, the illuminating may be carried out using internal light sources and / or external light sources that emit light towards the inner volume of the reaction chamber.

[0124] The method 700 may further include, in 740, causing a mass-based position probability change of the solid photocatalytic elements in the medium. For example, the method 700 may further include, in 740, separating the solid photocatalytic elements from the medium in the reaction chamber, and recirculating the separated solid photocatalytic elements for further mixing with the stream of medium to be purified. For example, the separating may include carrying out a mass-based separation of the solid photocatalytic elements from the medium in the reaction chamber. In a preferred configuration, the method 700 may include introducing the solid photocatalytic elements and the medium in the reaction chamber with a flow rate that causes the formation of a vortex in the reaction chamber. The vortex may push the solidphotocatalytic elements towards the light source(s), e.g. towards the sidewall of the reaction chamber. In some aspects, the vortex may separate the (heavier) solid photocatalytic elements from the medium.

[0125] Recirculating the separated solid photocatalytic elements may illustratively include transporting the separated solid photocatalytic elements towards the mixing area of the photocatalysis device for mixing with the stream of medium. For example, the recirculating may include using a buffer medium to transport (e g., to pump) the solid photocatalytic elements.

[0126] In an exemplary configuration, the method 700 may further include delivering the medium separated from the solid photocatalytic elements as output. For example, the purified medium may be delivered as output. As another example, the individual components of the medium, separated from one another, may be delivered as output.

[0127] The proposed method 700 enables thus an efficient photocatalytic reaction by having the solid photocatalytic elements immersed in the medium, thus increasing the available surface area for the reaction to occur, and further facilitates the reusing of the solid photocatalytic elements by efficiently separating them from the medium and recirculating them for further processing.

[0128] The method 700 is illustrated in FIG.7B for the purification of a medium 752 in case of a photocatalysis device 750 configured as cyclone filter and including external light sources 762 (with corresponding optical element 764, e g. windows) in correspondence of the conical section of the cyclone chamber. It is however understood that the method 700 may be carried out with any of the configurations of the adapted photocatalysis device described herein.

[0129] As shown, the photocatalysis device 750 may receive a medium to be purified 752 at an inlet 754. The medium 752 may include harmful compounds 756, illustratively, impurities that should be removed from the medium or deactivated into harmless substances (e.g., pollutants, bacteria, viruses, etc.). The medium 752 may be mixed with solid photocatalytic elements 758, e g. photocatalytic particles, and the resulting medium may be delivered to the cyclone chamber 760 of the cyclone filter.

[0130] The light sources 762 may illuminate the inner volume of the cyclone chamber with light, e.g. visible light, ultraviolet light, infrared light, or any suitable type of light, thus triggering the photocatalytic reaction that deactivates (e.g., oxidizes) the harmful compounds 756, transforming them into deactivated compounds 770. In view of the mass-based separation occurring in the cyclone chamber 760, the purified medium 768 (and the deactivated compounds 770) are transported at a first outlet 774 of the cyclone chamber 760. The heaviersolid photocatalytic elements 766 are instead transported at another (second) outlet 776 of the cyclone chamber 760. The separated solid photocatalytic elements 766 may be collected in a collection chamber 772 of a recirculation system of the photocatalysis device 750, and may be recirculated to mix again with the stream of medium 752 to be purified.

[0131] In some aspects, the light used to trigger the photocatalytic reaction may also be suitable to render harmful compounds harmless. This may be the case, for example, if ionizing light is used (e.g., UVC), which is capable of deactivating bacteria, viruses, and other types of pathogens. A direct decomposition of harmful compounds in the medium 752 via the electromagnetic radiation is shown in the inset 780. A decomposition mediated by the solid photocatalytic elements is shown in the inset 790. In some aspects, the photocatalytic reaction (e.g., mediated by the solid photocatalytic elements) may allow removing microplastic residues from the medium.

[0132] The method 700 is illustrated in FIG.7C for the splitting of the components of a medium 752c. The aspects and features of the photocatalysis device 750 described in relation to FIG.7B are not repeated. In general, it is understood that also in relation to splitting the components of a medium, the method 700 may be carried out with any of the configurations of the adapted photocatalysis device described herein. As described above, the concept proposed herein may be extended to photocatalytically moderated splitting of component, e.g. hydrolysis. The actual photocatalytic elements (and the cocatalysts) prevented from escaping into the output medium by the centrifugal forces. As a result, the photocatalytic elements only leave the reaction chamber temporarily and are returned therein. In this case, the photocatalysis device 750 may act as a photolysis cell.

[0133] As shown, the photocatalysis device 750 may receive a medium 752c having a plurality of components to be separated from one another. For example, the medium 752c may be water, or ammonia, to split the components into the individual atoms forming the medium 752c. The medium 752 may be mixed with solid photocatalytic elements 758c, e.g. photocatalytic particles, and the resulting medium may be delivered to the cyclone chamber 760 of the cyclone filter. In this configuration, the solid photocatalytic elements 758c may further include one or more cocatalysts, e.g. a first cocatalyst 778 and a second cocatalyst 782. For example, for water splitting a first cocatalyst 778 may be configured for hydrogen evolution reaction (HER) and the second cocatalyst 782 may be configured for oxygen evolution reaction (HER).

[0134] In this scenario, the light sources 762 may illuminate the inner volume of the cyclone chamber with light causing a splitting of the medium 752c into individual components 784, 786(e.g., hydrogen and oxygen in case of water splitting, or hydrogen and nitrogen in case of ammonia). The separated components 784, 786 are delivered to the outlet 774 of the photocatalysis device 750, as output medium 768c. For example, the photocatalysis device 750 may include a filter 788 at the outlet 774 configured to be permeable for the separated components 784, 786 and impermeable to the solid photocatalytic elements 758c (and cocatalysts 778, 782). For example, the filter 788 may be a membrane.

[0135] Also in this configuration, the heavier solid photocatalytic elements and cocatalysts 766c are instead transported at another (second) outlet 776 of the cyclone chamber 760. The separated solid photocatalytic elements and cocatalysts 766c may be collected in a collection chamber 772 of a recirculation system of the photocatalysis device 750, and may be recirculated to mix again with the stream of medium 752c.

[0136] Illustratively, in this configuration, the method 700 described herein is adapted to produce an elemental gas or a plurality of elemental gases from a component of the medium 752c. This gas or these gases may be separated as reaction products. As shown in the inset 795, the solid photocatalytic elements 758c and cocatalysts 778, 782 moderate the cleavage of the components.

[0137] The adapted photocatalysis device and method proposed herein ensure thus an efficient photocatalytic reaction that enhances the purification of a medium or the splitting of the components of a medium. The complete immersion of the photocatalytic particles in the medium (e.g., water, air, etc.), result in a highly efficient cross-section. Considering water, such medium has a high transmission in the visible and ultraviolet range, so that the activating radiation may be efficiently supplied to the solid photocatalytic elements. In contrast to previous approaches (e.g., based on the application of the particles to filters), the entire surface of the solid photocatalytic elements is available as an interaction surface with harmful compounds. The solid photocatalytic elements can move freely within the cyclone and are nevertheless limited to this spatial area. Very high concentrations of solid photocatalytic elements may be achieved, and high radiation density may be realized.

[0138] The terms “processor”, “processing circuit”, or “control circuit” as used herein may be understood as any kind of technological entity that allows handling of data. The data may be handled according to one or more specific functions that the processor / processing circuit / control circuit may execute. Further, a processor / processing circuit / control circuit as used herein may be understood as any kind of circuit, e g., any kind of analog or digital circuit. A processor / processing circuit / control circuit may thus be or include an analog circuit, digital circuit, mixed-signal circuit, logic circuit (e.g., a hard-wired logic circuit or a programmablelogic circuit), microprocessor, Central Processing Unit (CPU), Graphics Processing Unit (GPU), Digital Signal Processor (DSP), Field Programmable Gate Array (FPGA), integrated circuit, Application Specific Integrated Circuit (ASIC), etc., or any combination thereof. It is understood that any two (or more) of the processors / processing circuits / control circuits detailed herein may be realized as a single entity with equivalent functionality or the like, and conversely that any single processor / processing circuit / control circuit detailed herein may be realized as two (or more) separate entities with equivalent functionality or the like.

[0139] The word “exemplary” is used herein to mean “serving as an example, instance, or illustration”. Any embodiment or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or designs.

[0140] The phrase “at least one” and “one or more” may be understood to include a numerical quantity greater than or equal to one (e.g., one, two, three, four, [...], etc.). The phrase “at least one of’ with regard to a group of elements may be used herein to mean at least one element from the group consisting of the elements. For example, the phrase “at least one of’ with regard to a group of elements may be used herein to mean a selection of: one of the listed elements, a plurality of one of the listed elements, a plurality of individual listed elements, or a plurality of a multiple of individual listed elements.

[0141] While the above descriptions and connected figures may depict optical components as separate elements, skilled persons will appreciate the various possibilities to combine or integrate discrete optical functions into a single element. Such may include combining two or more components from a single component. Conversely, skilled persons will recognize the possibility to separate a single element into two or more discrete elements, such as splitting a single component into two or more separate component.

[0142] All acronyms defined in the above description additionally hold in all claims included herein.

[0143] While the invention has been particularly shown and described with reference to specific aspects, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The scope of the invention is thus indicated by the appended claims and all changes, which come within the meaning and range of equivalency of the claims, are therefore intended to be embraced.List of reference signs102 Solid photocatalytic element 404 Inlet104 Light 406 Outlet106 Dangerous compound 408 Pumping system108 Oxidized species 500a Solid photocatalytic element112 Electron 500b Solid photocatalytic element114 Hole 500c Solid photocatalytic element116 Co-catalyst 500d Solid photocatalytic element120 Inset 500e Solid photocatalytic element200 Photocatalysis device 500f Solid photocatalytic element202 Mixing area 500g Solid photocatalytic element204 First stream 500h Solid photocatalytic element206 Medium 502a Carrier body206b Output medium 502b Carrier body208 Second stream 502c Carrier body210 Solid photocatalytic elements 502d Carrier body210b Separated solid photocatalytic 502e Carrier body elements 502f Carrier body212 First inlet 504a Photoactive material214 Second inlet 504b Photoactive material216 Third stream 504c Photoactive material218 Resulting medium 504d Photoactive material220 Reaction chamber 504e Photoactive material222 Electromagnetic radiation 504f Photoactive material224 Outlet 504g Photoactive material226 Recirculation system 504h Photoactive material300 Reaction chamber 506c Adhesive layer300a Reaction chamber 506f Adhesive layer300b Reaction chamber 550a Solid photocatalytic element300c Reaction chamber 550b Solid photocatalytic element300d Reaction chamber 550c Solid photocatalytic element300e Reaction chamber 550d Solid photocatalytic element300f Reaction chamber 550e Solid photocatalytic element302 Light source 550f Solid photocatalytic element302a Internal light source 550g Solid photocatalytic element302b External light source 550h Solid photocatalytic element304 Optical element 552a Carrier body306 Reflective coating 552b Carrier body322 Emitted light 552c Carrier body322a First emitted light 552d Carrier body322b Second emitted light 554a Photoactive material400 Recirculation system 554b Photoactive material402 Collection chamber 554c Photoactive material554d Photoactive materiale Photoactive material 766 Separated solid photocatalyticf Photoactive material elements g Photoactive material 766c Separated solid photocatalytich Photoactive material elements First cocatalyst 768 Purified medium Second cocatalyst 768c Output medium a Photocatalysis device 770 Deactivated compoundsb Photocatalysis device 772 Collection chamber Mixing area 774 First outlet First stream 776 Second outlet Medium 780 Inset b Output medium 778 Cocatalyst Second stream 782 Cocatalyst Solid photocatalytic elements 784 Separated component b Separated solid photocatalytic 786 Separated component elements 788 Membrane First inlet 790 Inset Second inlet 795 Inset Third stream Resulting medium Reaction chamber Outlet Recirculation system Cyclone body Conical section Collection chamber a Internal light source b External light source Optical element Reflective coating Method Method step Method step Method step Method step Photocatalysis device Medium c Medium Inlet Harmful compounds Solid photocatalytic elements Cyclone chamber External light source Optical element

Claims

Claim1. A photocatalysis device (200) comprising: a mixing area (202) configured to receive a first stream (204) comprising a medium (206) and a second stream (208) comprising solid photocatalytic elements (210), and to output a third stream (216) comprising the solid photocatalytic elements (210) immersed in the medium (206); a reaction chamber (220) coupled with the mixing area (202) and configured to receive the third stream (216) of solid photocatalytic elements (210) immersed in the medium (206), wherein the reaction chamber (220) is configured such that the solid photocatalytic elements (210) are freely movable in an inner volume of the reaction chamber (220), wherein the reaction chamber (220) is configured to enable introducing light energy in the inner volume of the reaction chamber (220) to cause a photocatalytic reaction, wherein the reaction chamber (220) is configured to enable a mass-based position probability change of the solid photocatalytic elements (210) in the medium (206); and a recirculation system (226) coupled with the reaction chamber (220) and configured to receive solid photocatalytic elements (210b) separated from the medium (206b), and to recirculate the separated solid photocatalytic elements (210b) as second stream (208) to the mixing area (202) for mixing with the first stream (204) comprising the medium (206).

2. The photocatalysis device (200) according to claim 1, wherein the mass-based position probability change of the solid photocatalytic elements (210) in the medium (206) comprises a mass-based separation of the solid photocatalytic elements (210) from the medium (206).

3. The photocatalysis device (200) according to claim 1 or 2,wherein the reaction chamber (220) is configured such that a flow forms within the inner volume of the reaction chamber (220) upon the third stream (216) of solid photocatalytic elements (210) immersed in the medium (206) entering the reaction chamber (220), and wherein the reaction chamber (220) is configured such that the flow transports the medium (206b) in a first direction and the solid photocatalytic elements (210b) in a second direction different from the first direction.

4. The photocatalysis device (200) according to any one of claims 1 to 3, further comprising: a light source (302) configured to emit light (322) towards the inner volume of the reaction chamber (220, 300).

5. The photocatalysis device (200) according to claim 4, wherein the light source (302) is disposed externally to the reaction chamber (220, 300); and wherein the reaction chamber (220, 300) further comprises an optical element (304) configured to allow the light (322) emitted by the light source (302) to enter the inner volume of the reaction chamber (200, 300).

6. The photocatalysis device (200) according to claim 4, wherein the light source (302) is disposed internally to the reaction chamber (220, 300).

7. The photocatalysis device (200) according to any one of claims 1 to 6, further comprising: a reflective coating (306) disposed on at least one sidewall of the reaction chamber (220, 300),wherein the reflective coating (306) is configured to be reflective for light in a predefined wavelength range.

8. The photocatalysis device (200) according to any one of claims 1 to 7, wherein the recirculation system (226, 400) comprises: a collection chamber (402) coupled with the reaction chamber (220) to receive from the reaction chamber (220) the solid photocatalytic elements (210b) separated from the medium (206); and a pumping system (408) configured to cause a recirculation of the solid photocatalytic elements (210b) from the collection chamber (402) towards the mixing area (202).

9. The photocatalysis device (200) according to any one of claims 1 to 8, further comprising: the solid photocatalytic elements (210) disposed within the photocatalysis device (200).

10. A cyclone filter (600a) comprising: a cyclone chamber (620) configured to receive a stream of solid photocatalytic elements (610) immersed in a medium (606); wherein the cyclone chamber (620) is configured such that the solid photocatalytic elements (610) are separated from the medium (606) by action of a centrifugal force in the cyclone chamber (620); and wherein the cyclone chamber (620) is configured to allow introducing light energy in the cyclone chamber (620) to cause a photocatalytic reaction.

11. The cyclone filter (600a) according to claim 10, further comprising:a recirculation system (626) configured to receive from the cyclone chamber (620) the solid photocatalytic elements (610b) separated from the medium (606) and to cause a recirculation of the separated solid photocatalytic elements (610b) towards an inlet portion of the cyclone chamber (620).

12. The cyclone filter (600a, 600b) according to claim 10 or 11, further comprising: a light source (634a, 634b) configured to emit light towards an inner volume of the cyclone chamber (620).

13. The cyclone filter (600a, 600b) according to claim 11, wherein the light source (634a, 634b) is disposed externally to the cyclone chamber (620); and wherein the cyclone chamber (620) further comprises an optical element (634) configured to allow the light emitted by the light source (634a, 634b) to enter the inner volume of the cyclone chamber (620); or wherein the light source is disposed internally to the cyclone chamber (620).

14. The cyclone filter (600a, 600b) according to any one of claims 9 to 13, further comprising: a reflective coating (638) disposed on at least one sidewall of the cyclone chamber (620), wherein the reflective coating (638) is configured to be reflective for light in a predefined wavelength range.

15. A method of processing a medium, the method comprising: carrying out a photocatalytic reaction in the medium assisted by solid photocatalytic elements immersed in the medium; and carrying out a mass-based separation of the solid photocatalytic elements from the medium after having carried out the photocatalytic reaction.

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