Electrode, a process of fabricating an electrode, a reactor and decontamination process

Abstract

Here an electrode for electrochemical decontamination of a fluid or fluid-containing mixture is described. The electrode comprises a coating that is configured to promote electrochemical decomposition of a contaminant. In addition an electrochemical reactor configured for electrochemical decontamination of a fluid or fluid-containing mixture is provided. The reactor comprises a first electrode that can be operated as an anode and that is configured to promote electrochemical decomposition of a contaminant. The reactor and the electrode are configured such that the fluid or fluid-containing mixture flows by the electrode, contacting at least a portion of the surface of the first electrode.

Description

[0001] Description

[0002] Electrode , a process of fabricating an electrode , a reactor and decontamination process

[0003] The present application relates to an electrode , a process of fabricating an electrode , a reactor, and a decontamination process .

[0004] Fluids or mixtures comprising fluids , and in particular water, are often contaminated by contaminants that are resilient to conventional treatment methods or that pose signi ficant risks to the environment or human health . Such contaminants may originate from industrial processes or pharmaceutical processes or may have another origin . Decontaminating such contaminated fluids or mixtures comprising fluids has not been satis factory so far . In particular per- and polyfluoro ( alkyl ) substances

[0005] ( abbreviated PEAS ) , such as PEOA or PEGS , are often di f ficult to decompose . Ef fectiveness and / or energy consumption of previous approaches were often unsatis factory .

[0006] Accordingly, it is an aim of the embodiments discussed in the following to overcome or improve one or more of the above discussed problems or to provide alternative approaches .

[0007] The embodiments claimed in the independent claims overcome or at least improve or provide alternative approaches for one or more of the above discussed problems or the problems discussed below . Preferred embodiments having additional features or advantages are provided in the dependent claims . According to a first embodiment , an electrode is described . The electrode can be applicable for or configured for electrochemical decontamination of a fluid or fluidcontaining mixture . The electrode comprises a coating that is configured to promote electrochemical decomposition of a contaminant in said fluid or fluid-containing mixture .

[0008] Here "a contaminant" can mean that one or more substance is present in the fluid or fluid-containing mixture that is considered in the field as contaminating said fluid or fluidcontaining mixture . When the electrode is used to decontaminate the mixture , this can mean that the concentration of at least one contaminant is reduced by this process .

[0009] The term " fluid" can be understood in accordance with the general understanding in the field . It at least includes homogeneous liquids and emulsions that can be considered fluid under the conditions of electrochemical treatment . A " fluid-containing mixture" is understood in this application as any mixture of di f ferent fluids or fluids and solids that comprise di f ferent phases and which would not be considered as an emulsion under the conditions of electrochemical treatment . Preferably the fluid is an aqueous fluid, i . e . it may comprise water . It can be an aqueous solution or aqueous suspension . Likewise , it is preferred that at least part of the fluid in the fluid-containing mixture is water . In such a case , for example , the fluid-containing mixture can be a slurry comprising water and solid components such as earth from a contaminated landfill or colloidal carbon slurry .

[0010] According to an embodiment , the electrode is configured to promote electrochemical decomposition when applied as an anode . For example , the conditions under which the electrode promotes electrochemical decomposition are those of the process described below .

[0011] The contaminant is not limited, and the above applies . In particular according to an embodiment , the contaminant can be a per- and polyfluoroalkyl substance , abbreviated to PFAS .

[0012] For example , the PFAS may be or may comprise a perfluoroalkyl acid PFAA. An example of PFAA is perfluorooctanesul fonic acid, abbreviated to PFOS . Many PFASs are known for their resilience against conventional treatment methods and they may pose signi ficant risks to both environmental and human health . The electrochemical decontamination approach described herein, for example using the electrode described herein, can help to destroy the persistent PFAS . In particular it is possible to decompose PFAS with comparatively simple setups , as this approach is capable of cleaving at least some of the thermodynamically and kinetically stable carbon- f luorine bonds .

[0013] Starting from the destruction of PFAS , the inventors surprisingly found that the inventive approach can be trans ferred to the destruction or decontamination of other compounds , providing similar advantages . Thus , besides the above listed, according to embodiments the contaminant can be one or more of mixed per- / poly- f luoro- / halo-substances , pharmaceuticals , antibiotics , pesticides , flame-retardants , poly-chloro-dibenzodioxines or dibenzodi furans , poly-cyclic- aromatic compounds , trans former oils , any or other forever chemicals , or any or other chemical falling under the Stockholm Convention substances . The mixed per- / poly- f luoro- / halo-substances can for example be CFC ( Chlorofluorocarbon) , HCFC (Hydrochlorofluorocarbon) or similar substances . The pesticides may for example be a per-chloro-based substances . The flame-retardants may be for example a per-bromo-biphenyl . The poly-chloro-dibenzodioxines and dibenzodi furans can be abbreviated to PCDD and PCDF, respectively . These may include , for example , Seveso type chemicals . The poly-cyclic- aromatic compounds can, for example , be a benzpyren . The trans former oils can include , for example , poly-chloro- biphenyls , abbreviated to PCB .

[0014] So far, decontamination processes have had several drawbacks . One of the most common methods and technologies for PFAS destruction so far was high temperature incineration, for example of adsorbent materials enriched with the contaminants . This has the disadvantage that the adsorbent material is destroyed . In the literature other approaches are also suggested for PFAS destruction, e . g . other AOP - Advanced Oxidation Processes , such as photocatalysis , ozonation, etc . , or plasma treatment . However, their ef ficacy and energy consumption are unsatis factory or are too high for industrial-scale PFAS destruction applications . A further approach discussed in literature is super critical water oxidation ( abbreviated to SCWO) , which uses high temperature and high pressure to oxidi ze PFAS , but which requires speciali zed equipment and high energy input . In principle other persistent chemicals are conventionally destroyed in a similar manner .

[0015] According to an embodiment , the coating can be applied to at least a portion of the surface of an electrically conducting substrate . In other words , the coating can be arranged on at least a portion of a main surface of said substrate . It can also be applied to two or more main surfaces . The substrate can distribute the voltage and current applied to the electrode . Thus , it is not necessary for the material of the coating to provide this current conduction functionality . Furthermore , using a substrate and having a coating of a material promoting the electrochemical reaction helps to reduce the amount of that material compared to bulk electrodes .

[0016] Generally, the substrate is not limited . According to said embodiment it is electrically conductive . According to an embodiment , it can be a metal or comprise a metal , for example .

[0017] According to another embodiment , the substrate may also be non-conductive . In this case the electrical conductivity is provided by the coating . This still provides the advantage of reducing the material consumption . For example , the material may be a non-conducting polymer foil or polymer plate .

[0018] According to an embodiment , the substrate may comprise or consist of titanium, stainless steel or a carbon-containing material . In particular, the inventors found that substrates comprising or consisting of titanium or stainless steel are particularly preferred, as these substrates are simple to manufacture and can be easily processed and coated with the material of the coating, which is also described below for speci fic examples .

[0019] According to an embodiment the electrode can be configured to be used in a flow-by configuration . In a flow-by configuration the fluid or fluid-containing mixture is not required to penetrate or completely soak the entire electrode but is merely required to be in contact with its surface . Therefore , according to a related embodiment , the electrode cannot be penetrated fully by the fluid or fluid-containing mixture . In contrast to previous conventional approaches that used membrane electrodes or porous electrodes that can be fully penetrated or soaked by a fluid, the electrode described herein can be an electrode that has no pores or similar structures that fully run through the electrode . For example , the substrate may be dense and continuous , such that the fluid or fluid-containing mixture cannot penetrate the substrate . Alternatively or in addition, the coating can also be so dense that the fluid or fluid-containing mixture cannot penetrate the full thickness of the coating . For example , the outer surface of the coating may be rough, but it may be free of pores that penetrate to the substrate .

[0020] At least according an embodiment , the electrode may in particular be impenetrable in that sense that the fluid or fluid-containing mixture cannot penetrate through holes or slits . This may, according to an embodiment , include the absence of macroscopic holes or slits . In particular, a main portion of the electrode may be impenetrable in that sense . Said main portion can be the portion that is in contact with the fluid or fluid-containing mixture in a reactor or a decontamination process . In particular this main portion can be microscopically and macroscopically impenetrable .

[0021] According to an embodiment , the coating can comprise or consist of a substoichiometric titanium oxide . A " substoichiometric titanium oxide" is understood to be any titanium oxide that has an oxygen deficiency compared to titanium dioxide . The inventors have found that titanium oxides that are oxygen-deficient may ef fectively promote electrochemical decomposition of many contaminants . According to a preferred embodiment , the substoichiometric titanium oxide is a Magneli phase titanium oxide . Such Magneli phase titanium oxides can surprisingly promote electrochemical decomposition of a contaminant also as a coating, even i f the coating is a thin film . In contrast , previously Magneli phase titanium oxides were used as bulk electrodes and in particular as membrane electrodes .

[0022] According to an embodiment , the coating can comprise TigO? or TigOg as the Magneli phase titanium oxide . These materials have shown good performance in electrochemical decomposition of contaminants , in particular of perf luoroheptanoic acid ( abbreviated PFHpA) , perf luorooctanoic acid ( abbreviated PFOA) , perf luorononanoic acid ( abbreviated PFNA) , perfluorodecanoic acid ( abbreviated PFDA) , and perfluorooctanesul fonic acid ( abbreviated PFOS ) and are thus considered to provide good performances for PFAS in general .

[0023] According to an embodiment , the coating can comprise a material that is derived from a precursor or made of a composition comprising 70 to 99 wt% of TigO? and 1 to 30 wt% of TigOg . Depending on the application technique , this composition may change slightly in the formed coating . However, it can be preferred that the composition of the coating also comprises 70 to 99 wt% of H4O7 and 1 to 30 wt% of TigOg . The coating described here has shown good performance in electrochemical decomposition of contaminants , in particular of PFAS in general and in particular of PFHpA, PFOA, PFNA, PFDA and PFOS . In both cases of the precursor or of the material of the coating it can be preferred that the portion of H4O7 is between 75 wt% and 97 wt% , such as between 85 wt% and 95 wt% . In this case the portion of TigOg can be 3 wt% to 25 wt% and 5 wt% to 15 wt% , respectively . However, the coating is not limited to the above titanium oxide based materials . The inventors have also found that a coating comprising a silicon carbide , a manganese oxide , a cobalt oxide , a cobalt hydroxide oxide , an Fe-N4-graphene , a tungsten carbide , a nickel-containing tungsten carbide , a lead oxide , a boron-doped diamond ( abbreviated to BDD) material , or a ferrite-based material also work well for electrochemical decontamination . Here , silicon carbide can be abbreviated to "SiC" . The manganese oxide generally can be any oxide of manganese , but preferably it is or comprises MnCt as this has been shown to ef fectively promote electrochemical decontamination . Similarly, cobalt oxide is not limited to any speci fic oxide or mixture of oxides , but preferably the cobalt oxide is or comprises spinel cobalt oxide . Spinel cobalt oxide can be represented by the formula C03O4 . Regarding the cobalt hydroxide oxide , the stoichiometry is not limited, but preferably the cobalt hydroxide oxide can be represented by CoOOH . Tungsten carbide can be abbreviated as "WC" . The nickel-containing tungsten carbide is not limited to any stoichiometry, but is preferably WCNi . Also the lead oxide is not limited to any particular mixture of lead oxides , but it is preferably PbCt . The boron-doped diamond material can surprisingly be used as a coating . The ferrite-based material is not limited and can be understood according to the general understanding . At least the following examples are covered by the term " ferrite-based material" : Fe2Oa, FeaCH , MnZn, NiZn, MnFe2C>4 , NiFe .

[0024] According to an embodiment , the coating can also comprise or consist of two or more di f ferent materials . For example it can comprise or consist of two or more of the above mentioned materials .

[0025] Generally, the process of applying a coating is not limited and the properties explained below for the process can apply . However, according to a preferred embodiment the coating can be a plasma sprayed coating . In other words , the coating may be applied or deposited by plasma spray deposition . In particular the inventors found that thin continuous coating films of mainly homogenous thickness can be formed by plasma spray deposition . The plasma spray approach can be seen in the morphology of the film . Besides other features , this method can lead to the deposition of splat-like structures which, as a consequence , in this case can make up the plasma sprayed coating . Plasma spray deposition can be best applied to flat surfaces or to convex surfaces . However, i f accessible from one direction that is mainly perpendicular to the surface that is to be coated, plasma spray can also be applied to concave surfaces .

[0026] According to an embodiment , the thickness of the coating can be 1 pm to 500 pm . Depending on the deposition method di f ferent film thicknesses for the coating can be preferred . The inventors found that thin films down to 1 pm can promote the electrochemical decomposition of contaminants . More preferably the coating has a thickness of at least 2 pm . This helps to ensure a continuous coating . More preferably the coating is at least 10 pm thick . In particular when using the speci fic techniques for deposition described in this application, the inventors found that applying a thickness of at least 10 pm is easier to reali ze than thinner coatings . A lower limit for the thickness can also be 70 pm or thicker, such as 100 pm or thicker . These thicknesses are easily accessible by plasma spraying or other processes . An upper limit for the thickness can be 400 pm, 300 pm or preferably 200 pm . Having a less thick film can save material and helps ensure that the electrode does not become unnecessarily thick . In particular for a thickness of 300 pm and below, or better of 200 pm and below, the inventors found that these thicknesses can be easily reali zed by the methods described herein, and in particular by plasma spray deposition . The values discussed above can preferably be average thicknesses of the coating . The thickness values discussed above have shown to be preferable for titanium suboxide coatings .

[0027] In the case of plasma spray deposition, but also achievable by the other techniques described here or by other techniques not described here , according to an embodiment the standard deviation in thickness can be below 70 pm and more preferably below 50 pm and even more preferably below 30 pm or below 25 pm .

[0028] According to an embodiment , the electrode can have an overall thickness of between 0 . 1 mm and 5 mm, such as between 0 . 7 and 3 mm . This thickness preferably is the thickness of the as prepared coated electrode . The inventors found that this thickness range allows for easy construction of electrochemical reactors . Furthermore , the inventors found that a thicker substrate of above 0 . 7 mm thickness may handle the temperatures of plasma spray coating better than a thinner substrate . This has been observed for example for a metal containing substrate .

[0029] According to an embodiment , the electrode can have a flat shape . For example , the active portion of the electrode , i . e . the portion that is configured to be in contact with the fluid or fluid-containing mixture, can be flat. This can mean that the thickness of at least the active portion is considerably thinner than its dimensions perpendicular to the thickness direction. For example, the above-described thicknesses can apply. The shape of the active portion is not limited, but may be circular, rectangular or square-shaped. The electrode may have an active portion having a size of between 2,5 xlO3mm2and 1 xlO6mm2, such as preferably between 6 x 103mm2and 2,5 xlO5mm2. For example, in the case that the active area is square-shaped, it can have sizes of between 20 mm x 20 mm and 500 mm x 500 mm. Besides the active portion, the electrode may have a mounting portion and / or a lead portion.

[0030] According to two further or other embodiments, the electrode can have a rod-like shape or a tube-like shape. These shapes are particularly preferred if a counter-electrode has a complementary shape. This will be described in detail below. For example the rod-like electrode or the tube-like electrode can have the coating on its outside. The shape of the rod or the tube is not limited. The cross section can have any shape, such as rectangular, square, any other polygon, or preferably oval or circular. The average diameter of these can be between 5 mm and 100 mm, such as between 8 mm to 50 mm, such as preferably 10 to 30 mm. These values are particularly preferred in the case of a circular cross section for a rod-like or tube-like electrode. In the case of the tube-like electrode, the tube wall can have a thickness of between 0.1 mm and 5 mm, such as between 0.7 and 3 mm, or 0.7 and 1.5 mm. The length of this electrode is not limited by, for example between 200 mm and 2500 mm, such as between 500 mm and 1500 mm. Furthermore , in the following a process of producing an electrode is described . The properties of the electrode may also apply to the process as far as applicable . In particular, features concerning the manufacturing of an electrode discussed above may of course apply . Also features discussed for the manufacturing may also relate to corresponding embodiments of an electrode even when not explicitly labeled as such .

[0031] According to an embodiment , a process of producing an electrode is described . In the process an electrically conductive substrate is provided . The substrate may have the above-described properties . A coating is applied to a main surface of the substrate , wherein the coating is configured to promote electrochemical decomposition of a contaminant .

[0032] According to an embodiment , the coating is made with or comprises substoichiometric titanium oxide , a silicon carbide , a manganese oxide , a cobalt oxide , a cobalt hydroxide oxide , an Fe-N4-graphene , a tungsten carbide , a nickel-containing tungsten carbide , a lead oxide , a boron- doped diamond material , or a ferrite-based material . The above-described may apply .

[0033] According to an embodiment , the coating may be applied by plasma spray coating . Any of the above-described materials can be deposited by plasma spray coating, i . e . all of these materials can be fed into the plasma stream as raw materials . However, this method is particularly preferred for fabricating a coating comprising or consisting of substoichiometric titanium oxide , such as Magneli phase titanium oxide . According to an embodiment of the plasma spray coating, a raw material may contain substoichiometric titanium oxide. For example, it may contain a Magneli phase titanium oxide such as TigO? or TigOg. For example it may contain the abovedescribed ratio of TigO? and TigOg.

[0034] According to an embodiment, the raw material for the plasma spray coating may be granular. The morphology of the grains is not particularly limited as long as the material can be deposited by plasma spraying. For example, an average particle size may lie between 1 pm and 100 pm and preferably between 5 pm and 50 pm, such as even more preferably between 10 pm and 30 pm.

[0035] According to another embodiment, the particles may be porous. The pores may be 5 to 500 times smaller than the particles. An average pore size can be between 0.2 pm and 5 pm or 0.5 and 5 pm, for example.

[0036] The inventors have found that particles in this size range and with such porosity can be effectively deposited by plasma spray deposition.

[0037] According to an embodiment, the plasma spray process can be carried out using an argon and hydrogen containing gas stream. The partial pressures of hydrogen and argon can be between 2 bar and 10 bar. The flow rate of argon can be between 10 to 70 1 / min. The flow rate of hydrogen can be between 5 to 15 1 / min.

[0038] According to an embodiment, the coating can retain some features of the raw material, while the porosity is often reduced and continuous films can be formed. According to an embodiment , as described above two or more materials can be applied to the surface . This may be done via plasma spraying . For example , two or more materials may be fed into the plasma spray apparatus subsequently or simultaneously . For example , Magneli phase titanium suboxide and a ferrite-based material can be deposited by this . Thus a mixed coating comprising a Magneli phase titanium suboxide and a ferrite-based material can be formed . This can be applied to any combination of the above-described materials . The relative ratios of these materials can be adj usted to each other and thus optimi zed . Such mixed coatings can be used to speci fically adapt an activity, speci ficity or other properties to the contaminant to be destroyed or the composition of the fluid to be treated . The selection of mixed coatings is not limited to those mentioned . All combinations of advantageous materials that are suitable for improving the success of the treatment , improving the stability of the coating, etc . can be selected .

[0039] According to an embodiment , the coating may be reali zed by a chemical modi fication of the main surface of the substrate . Such a chemical modi fication is not limited . However, it may be understood here that a chemical modi fication can include a chemical reaction in which the material of the substrate or the substrate surface is chemically altered or modi fied . For example , the chemical modi fication may be oxidation or reduction of the material of the substrate . In particular in the case of titanium suboxides , a titanium-containing substrate may be oxidi zed to the oxidation state is that of a desired suboxide or several suboxides . Likewise the surface of a substrate may already include a titanium oxide such as titanium dioxide . This may be reduced to a suboxide stoichiometry. In the case of iron-, nickel- and / or manganese metal-based electrodes a similar approach may be used to create ferrite layers as active materials.

[0040] According to an embodiment the coating may be applied by a ceramic-like process. The process may include a sintering step. For example, a slurry comprising the material of the coating or a precursor can be applied to the main surface of the substrate. The deposited slurry can be sintered to the substrate. Sintering temperatures can range between 800°C to 1600°C. For example for the titanium suboxides sintering can be performed at temperatures of 800 °C to 1400 °C, such as 900 to 1350 °C. For other materials sintering may also be carried out at higher temperatures of 1200 °C to 1600 °C. Prior to sintering, debinding, i.e. removing binder materials, can be performed at temperatures of 300 °C to 600 °C. A calcination step, which can remove residual organic and decomposable materials, can be also performed. Calcination can be carried out at temperatures of 700 °C to 900 °C . Controlled cooling can help to prevent thermal shock and improve adhesion between the substrate and the coating and microstructure development. According to an embodiment a preferred cooling profile can be as follows: After sintering the electrode can be cooled from the sintering temperature to a first cooling temperature at a controlled cooling rate of 1 °C to 3 °C per minute. The first cooling temperature can be between 600 °C and 800 °C. From the first cooling temperature to a second cooling temperature a cooling rate of 2 °C to 5 °C per minute can be applied. The second cooling temperature can be between 500 °C and 300 °C, such as 400 °C. Below the second cooling temperature, natural cooling to room temperature can be applied. This may take a few hours to complete . Also according to an embodiment two or more processes for forming the coating may be combined . For example , subsequent coatings can be applied . This can lead to an improved production of a coating . For example a coating comprising a Magneli phase titanium suboxide material and a ferrite-based material can be formed . Other material combinations can also be achieved thus . Also the coating can be formed by applying the same material via two or more di f ferent techniques . This may have the advantage to have more than one morphology in the coating .

[0041] According to a modi fication of the previous embodiment , individual coating processes can be applied in an alternating fashion , i . e . two or more layers can be applied by applying a first coating technique and a second coating technique in an alternating manner . This may help to improve the internal structure of the coatings .

[0042] In the case of a coating with only one coating material , for example , a superficial layer comprising a Magnelli phase titanium suboxide material can be produced on a titanium substrate by targeted oxidation . A layer of Magnelli material can then be deposited on this layer, for example using plasma spraying . A coating produced in this way can have improved properties , for example the mechanical adhesion of the coating to the electrode can be improved or the electrical contact between the active surfaces of the coating and the electrode can be improved .

[0043] In the case of a coating with two or more coating materials , for example , a mixed layer of ferrite and Magnelli phase titanium suboxide can be formed on the substrate . For this purpose , a Magnelli phase titanium suboxide layer can be deposited on the substrate , for example by plasma spraying . Subsequently, a ferrite material layer can be deposited on this Magnelli material layer, for example by a ceramic-like process . In this way, for example , also a coating comprising a Magnelli phase titanium suboxide as a main component having a small amount of ferrite-based material on its reactive surface .

[0044] Such mixed coatings may be used to adapt the activity, speci ficity or other properties speci fically to the substances to be destroyed or the composition of the fluid to be treated . The choice of coating processes to be combined is not limited to those mentioned . All combinations of advantageous processes can be selected which are suitable for producing the coatings , which are suitable for improving the success of the treatment , improving the stability of the coating, etc .

[0045] Furthermore , embodiments of a reactor are described in the following . These embodiments may have the above-described electrode as a first electrode and / or as a second electrode , but this is not required . The reactor may have any electrode fitting its mode of operation . The above-described electrode is a particularly preferred electrode fitting the mode of operation of the embodiment of an electrochemical reactor . The first electrode and the second electrode may be operated as anode or cathode . Depending on the construction, the polarity of the electrodes can be switched, as described in the embodiments described below in detail .

[0046] According to an embodiment , an electrochemical reactor is described that can be configured for electrochemical decontamination of a fluid or fluid-containing mixture . The above-said concerning the fluid or fluid-containing mixture also applies here . The reactor can comprise a first electrode . This first electrode can be configured such that it can be operated as an anode . Furthermore , it can be configured to promote electrochemical decomposition of a contaminant . The above-said concerning the contaminant can apply here . The reactor according to the present embodiment can be a flow-by reactor . This can mean that at least a maj ority of the decontamination takes place via the fluid or fluid-containing mixture flowing by the electrode , contacting at least a portion of the surface of the first electrode .

[0047] This may, for example , mean that the maj ority of the reaction occurs by the contaminant contacting the electrode during flow-by and becoming decomposed . It may mean, for example , that only a minority of the contaminant is decomposed in penetrating or membrane-like decomposition mode . According to a preferred embodiment , no penetrating or membrane-like decomposition takes place .

[0048] In particular, according to an embodiment and in contrast to common electrodes , the electrode may be configured such that it cannot be fully penetrated by the fluid or the fluidcontaining mixture . The above said may apply, for example .

[0049] According to an embodiment , the electrochemical reactor also can comprise a second electrode . This second electrode may be configured to be operated as a cathode . This second electrode can be arranged such in the reactor that at least a portion of its surface is in contact with the fluid or fluidcontaining mixture under operation conditions . According to an embodiment the first electrode and the second electrode can be arranged such that the fluid or fluidcontaining mixture can pass in a gap between anode and cathode . The inventors found that it is advantageous in particular for a flow-by configuration that the fluid or fluid-containing mixture can pass in the gap between the first and the second electrode .

[0050] According to an embodiment , the width of said gap can be adj usted to accommodate for di f ferent rheological properties . For example , the gap can be adj usted to the properties of a certain fluid or fluid-containing mixture , such that it can pass the gap without clogging . In other words , the width of the gap can be chosen such that no clogging takes place for a fluid or fluid-containing mixture of certain viscosity or thickness or other rheological property, for example .

[0051] According to a modi fication of the previous embodiment , the reactor may be configured such that the si ze of the gap can be adj usted manually, for example by removing the first and second electrode from the reactor, adapting the gap and remounting the first and second electrode . According to another embodiment the reactor can have means for adj usting the gap within the assembled reactor . Also according to another embodiment , the electrodes can be mounted by a rapid exchange mechanism that allows for the simple switch of a first pair of electrodes to a second pair of electrodes having a di f ferent gap . This can also be reali zed for the array, that is described below .

[0052] According to an embodiment , the width of said gap can be between 0 . 5 mm and 10 mm . The inventors found that in this range many fluids and fluid-containing mixtures can flow by the electrode . This applies in particular for aqueous fluids or aqueous fluid-containing mixtures . For many fluids , and in particular for contaminated water with low to no suspended solid content , a gap si ze of for example 1 mm to 6 mm or 1 . 5 mm to 4 mm can be preferred .

[0053] As described above , the first electrode can be operated as an anode and the second electrode can be operated as a cathode . According to an embodiment , it may be preferred that the polari zation of the electrodes can be switched . Accordingly it may be preferred that the reactor and the first electrode are configured such that the first electrode can be operated as a cathode . Likewise it may be preferred that the reactor and the second electrode are configured such that the second electrode can be operated as an anode . This switch of polari zation can be used, for example , to clean or regenerate the first electrode that may in this case be the usual or main anode under operation . It may be preferred that the second electrode also cannot be fully penetrated by the fluid or fluid-containing mixture . The first electrode and the second electrode can be di f ferent but are preferably identical for reasons of simpler manufacturing .

[0054] According to an embodiment that is a modi fication of the prior embodiment , the second electrode may also be configured to promote electrochemical decomposition of the contaminant i f operated as an anode . Both electrodes can be used as anodes in this configuration . This allows for the use of various voltage profiles in which one or both electrodes decompose the contaminant . Whilst one electrode is operated as an anode , the other electrode can regenerate in the role of the cathode , for example . According to an embodiment , the first electrode and the second electrode can have a plate-like shape and can be arranged with main surfaces facing each other . Such platelike electrodes , as described above , are simple to manufacture . Furthermore , replacing a pair or a block of such electrodes can be simple . The si ze of the electrode can be the si ze discussed above , but it is not limited here to an electrode having a substrate and a coating . The electrode here may also be a bulk electrode in the form of a plate . For example , it may be a ceramic sinter body of that shape .

[0055] According to an embodiment , the reactor may have more than one pair of electrodes . It may have , for example , an array of alternately stacked first electrodes and second electrodes , wherein all of the first electrodes are electrically connected and all of the second electrodes are electrically connected . For example , such an array may comprise two or more electrode pairs . Such an array can easily be scaled up to 5 or more , 10 or more or 20 or more pairs . In principle , the si ze of the reactor is not limited . However, the inventors think that the number of electrodes should be below 1000 pairs or below 500 pairs for many practical applications . A small-scale or medium-scale reactor may have between 10 and 100 pairs , such as between 15 and 50 pairs . The array may alternatively be addressed as electrode stack .

[0056] According to embodiments , as discussed above an array can be fixedly mounted into the reactor or can be mounted in a rapid exchange or simple exchange configuration . For example , a modular electrode assembly in a cartridge-like configuration can be used . This may allow for switching the complete electrode array in the reactor with a new array . Further it may allow for shipping a constructed electrode array separately . Also it may allow for easier maintenance of individual electrodes within the electrode stack .

[0057] According to an embodiment , the pair of electrodes or the array can be arranged in a holder in the reactor . In case of the array this holder can be addressed as array holder . The holder or array holder is configured to accommodate the pair of electrodes or the array . It may have the shape or properties of a frame . The holder or array holder can be designed to provide rills or grooves for accommodating the electrodes . For example , the rills or grooves can be designed such that the electrodes or the pair of electrodes can be slid into and out of the holder or array holder without otherwise performing substantial changes on the reactor casing .

[0058] According to an embodiment , the array may be also configured such that single electrodes can be easily exchanged individually .

[0059] The replaceable electrode cartridge system can be modular . . Each electrode can be housed within a cartridge that can be easily inserted and removed from the main assembly . This modular approach ensures that each component can be replaced independently without the need for speciali zed tools or extensive technical expertise . The system can support both single electrode replacement and full electrode assembly change . The inventors found that single electrode replacement can thus be performed in about 15 min . The assembly may be changed in about 5 min . This capability satis fies di f ferent maintenance needs and operational scales . The previous embodiments may help to reduce downtimes and help to ensure that the system remains functional and in operation .

[0060] According to embodiments , the electrode arrangement can be oriented in parallel or angled or perpendicular to a flow of the fluid or fluid-containing mixture . This can be chosen depending on the fluid or fluid-containing mixture that is to be treated .

[0061] According to an embodiment , the first electrodes and the second electrodes may each be electrically connected via a busbar . The busbars may be in contact with the two poles of power supply .

[0062] According to an embodiment , the array may also have electrodes that are not stacked in one geometrical line with the other electrodes but are in flow direction arranged behind a number of electrodes stacked in line . In a similar manner, two or more arrays can also be arranged after each other in flow direction .

[0063] According to a further embodiment , the electrochemical reactor can be configured such that the contaminated fluid or fluid-containing mixture enters into a first volume , subsequently flows into an electrode volume in which the first electrode is arranged, and flows into a second volume . The first volume , the electrode volume and the second volume may be compartments or part of compartments of the reactor . The electrode volume is defined where at least the first electrode or preferably all electrodes are arranged . For example the fluid or fluid-containing mixture may enter into the first volume via an inlet , which may be an inlet tube . From this first volume it passes by the electrodes and reaches the second volume . It may exit the reactor via an outlet , such as an outlet tubing .

[0064] According to an embodiment , at least the electrode volume may be separated from the second volume such that after passing the electrode volume the fluid or fluid-containing mixture can overflow into the second volume . This arrangement allows for simple separation of treated fluid or fluid-containing mixture from the inflow or from the fluid or fluid-containing mixture j ust passing the electrodes . In case of an overflowchamber system this may also allow for the extraction of liquid from the bottom of the overflow chamber, without minding any foam that is generated due to the treatment .

[0065] According to an embodiment of the previous embodiment the overflow-approach can be , for example , reali zed in the following construction but is not limited thereto . In operation the fluid or fluid-containing mixture may enter into the first volume . The electrode volume is arranged above the first volume . The fluid or fluid-containing mixture enters under suf ficient pressure to flow against gravity past the electrode , i . e . through the electrode volume . The electrode volume is separated from the second volume by a wall or separation that allows for the fluid or fluidcontaining mixture to overflow and fall with gravity into the second volume after having passed the electrodes .

[0066] According to an embodiment , the first volume may have a drainage such as a drainage tube , via which the first volume and possibly the electrode volume can be drained of the fluid or fluid-coating mixture , for example maintenance purposes . According to an embodiment , the second electrode can have a shape complementary to an outer circumference of the first electrode . Both may be arranged such with respect to each other that the fluid or fluid-containing mixture can pass a gap between first and second electrode . This can mean that the second electrode follows part of the outer profile of the first electrode . The above-said concerning the gap may apply . Here the shape of the first electrode is not limited . The above-said regarding the electrode comprising the substrate and the coating may apply . However, here the electrode is not limited to an electrode having a substrate and a coating . The electrode here may be a bulk electrode , for example . The first electrode may be rod-shaped or tube-shaped, with the outer shape of the rod-like shape or tube like-shape not being particularly limited . The second electrode can have a tube-like shape or semi-tube-like shape that complementarily follows the outer circumference of the first electrode . For example , the first electrode may have a circular or oval circumference and the second electrode has a complementary tube-like or semi-tube-like shape .

[0067] According to an embodiment , the complementarily shaped electrodes of the second embodiment can also be provided in an array . In principle all of the properties discussed for the previous array may apply here . However, in the present case a two- or three-dimensional array of the electrodes can be more preferred than the linear stack, that is the preferred example for the plate-like electrode . For example a tube-like or rod-like first electrode may be surrounded by a tube-like second electrode , forming an electrode pair . In this case it may be preferred that several pairs are arranged in a hexagonal arrangement , when viewed in cross section . Alternatively, a square or rectangular arrangement may be used . These types of arrangements may be preferred for any elongated electron pair . For example , in such an array 5 to 500 electrode pairs , such as 50 to 500 electrode pairs or 100 to 250 electrode pairs may be arranged

[0068] According to a further embodiment , the reactor can be configured such that gas can be added to the fluid or fluidcontaining mixture . The gas may help to facilitate mass trans fer and create turbulence . Additionally, the mechanical action of the bubbles may help to clean the electrode surface and reduce fouling . For example the gas can be inj ected or bubbled into the stream of the fluid or fluid-containing mixture . A flow rate of the gas relative to the flow rate of the fluid or fluid-containing mixture may be 0 . 2 % to 100% . It may, for example , be between 1 1 / h and 50 1 / h . The gas can, for example , be air, which is easily available , or nitrogen as an inert gas . Alternatively or additionally the gas may be or may contain ozone . Ozone , as a strong oxidant , can directly react with and degrade various organic pollutants . This may be complementary to the electrochemical decomposition .

[0069] As discussed above , the si ze and properties of the reactor are not limited and the reactor is easily scalable . However, according to an embodiment the inventors found it to be preferred that the electrochemical reactor may be configured for a flow rate lying between 1 1 / h and 500 1 / h . In this context , according to a further or alternative embodiment , the outer housing of the reactor may have a volume of 8 x 106mm3to 4 x 1010mm3.

[0070] According to an embodiment , the reactor may be box-shaped .

[0071] This can be particularly advantageous for the linearly stacked array of electrodes . This reactor may have a volume of 8 x 106mm3to 3 , 5 x 109mm3.

[0072] According to another embodiment the reactor may have a cylindrical portion . This can be particularly advantageous for a hexagonal array of electrodes . The cylindrical portion may have a diameter of 200 mm to 2500 mm, such as 300 mm to 1000 mm .

[0073] According to embodiments , the reactor wall may comprise or consist of a polymer or a metal . The polymer may be polypropylene ( abbreviation : PP ) , high density polyethylene ( abbreviation : HDPE ) or similar polymer materials , for example . The metal may be stainless steel or similar materials , for example .

[0074] According to an embodiment the thickness of the outer walls or inner walls of the reactor may be between 2 mm and 30 mm, such as between 10 mm and 20 mm .

[0075] According to a further embodiment the reactor can be configured for the decontamination process discussed below and the features discussed there may apply to the reactor . For example , according to embodiments the reactor can be configured for an operation voltage of -30 V to +30 V . It may be configured for current densities of 0 . 5 mA / cm2to 500 mA / cm2. For example , reaction time in batch operation mode may be 15 min to 18 h, such as nominal 6 ± 1 h .

[0076] According to an embodiment the reactor design may not only simpli fy the replacement process but may also extend the li fespan of the equipment . The need for frequent comprehensive maintenance checks may be reduced by allowing targeted replacements . This targeted approach may also minimi ze wear and tear on the system as a whole , which may help to reduce long-term maintenance costs and may help to enhance reliability .

[0077] According to an embodiment , the reactor design may have built-in safety features , such as automatic shut-of f mechanisms during electrode replacement and safeguards against incorrect installation . These features may help to ensure the safety of maintenance personnel and prevent potential system mal functions .

[0078] According to an embodiment , the reactor can be integrated into existing treatment trains . This can be aided particularly by the modularity, which may support quick installation and / or integration into existing treatment trains . Each module can be designed to facilitate so-called plug-and-run or plug-and-treat , requiring only basic electrical and fluid connections to be established to start operation . For example , this design may allow for installation of a reactor module into a treatment train within about 1 hour .

[0079] According to an embodiment , the reactor can be incorporated into a treatment train including one or several of pretreatment or post-treatment technologies , such as UV treatment , ozonation, filtration such as nanofiltration, reverse osmosis , granular activated carbon filtration or ion exchange resins filtration .

[0080] According to embodiments , the reactor may comprise means for accessing or detecting the technical state of health or predicting the need for maintenance . For example , the reactor may comprise means for assessing the state of health of the electrodes . This can be electrochemical impedance spectroscopy ( abbreviation : EIS ) , cyclic voltammetry ( abbreviation : CV) , linear sweep voltammetry ( LSV) and / or other methods .

[0081] The electrochemical impedance spectroscopy may be applied during operation, for example via a modulated voltage and frequency sweep that is integrated into the voltage profile of the decontamination protocol . Alternatively, the electrochemical impedance spectroscopy can be performed after decontamination or in pauses during decontamination . The electrochemical impedance spectroscopy may be operated with the two electrodes or may also make use of a reference electrode that can be built into the reactor . The impedance spectra can be analyzed directly via an equivalent circuit diagram or simply compared to a reference recording of a healthy electrode . In addition or alternatively, advanced algorithms and software may be used to analyze the impedance spectra, extracting key parameters that indicate the condition of the electrodes . Other methods can also be used or implemented accordingly . This analysis can detect early signs of wear, corrosion, or fouling, allowing for timely maintenance actions . Thus , an implemented or real-time monitoring can be enabled which helps a proactive maintenance of the electrodes , enhancing the reliability and ef ficiency of PFAS destruction processes .

[0082] Continuous or periodic monitoring of the electrode state of health can allow for the detection of performance trends and potential failure modes before they impact system ef ficiency . Real-time monitoring of the electrode state of health can help to ensure continuous operation at optimal performance levels . The system may dynamically adj ust operational parameters based on the real-time data to maintain ef ficiency . The ability to monitor and respond to electrode health in real-time can reduce the risk of sudden failures and maintains the integrity of the contaminant destruction process .

[0083] Based on the diagnostic data, the system may generate a maintenance schedule that can be optimi zed to prevent unexpected failures . This proactive approach can help to ensure that electrodes are maintained or replaced only when necessary, which may help to maximi ze their li fespan and reduce operational downtime .

[0084] Using a predictive maintenance algorithm may allow to generate alerts and reports , which can be integrated with the maintenance management system for seamless workflow integration .

[0085] The state of health and predictive maintenance system can be integrated with existing control and monitoring infrastructures , which may allow for seamless implementation without signi ficant modi fications to an already existing setup .

[0086] According to a further embodiment , the reactor may feature an automated monitoring and control system, incorporating one or several integrated sensors designed to continuously monitor operational parameters . This system can help to ensure the maintenance of good conditions for contaminant destruction while minimi zing the necessity for manual adj ustments . The integration of real-time diagnostics and alert mechanisms may further enhance operational ef ficiency and reliability . According to an embodiment , the operational parameters monitored may include the pH value . To this end the reactor may have one or more pH Sensors . Real-time monitoring of the pH level of the output flow after contaminant destruction pH may help to control and adj ust good conditions for contaminant destruction processes .

[0087] According to an embodiment , the operational parameters monitored may include voltage and the current . To this end the reactor may have means for monitoring the voltage and / or the current . Most preferably the reactor has means for continuous measurement of applied voltage and current density across the electrodes . These parameters help to maintain the electrochemical conditions required for ef fective contaminant degradation .

[0088] According to an embodiment , the operational parameters monitored may include the temperature . To this end the reactor may have one or more temperature sensors . Monitoring of the temperature of the system may help to maintain good thermal conditions . Temperature control can help ef ficient contaminant decomposition and help to reduce or prevent thermal degradation of system components .

[0089] According to an embodiment , the operational parameters monitored may include the electric conductivity . To this end the reactor may have one or more conductivity sensors . Monitoring of the electric conductivity of the system may help to monitor energy ef ficiency . Thus it can be easier to keep the energy ef ficiency at an optimum level . According to an embodiment , the operational parameters monitored may include the fluoride content . To this end the reactor may have an in-line fluoride selective electrode analysis setup . This may allow detection and quanti fication of fluoride ions released during contaminant breakdown, in particular during PFAS decomposition or decomposition of other fluorine containing compounds . This sensor may provide direct feedback on the progress and ef ficiency of the contaminant destruction process .

[0090] According to a further embodiment , the reactor can have means for real-time monitoring and data acquisition . For example , this may include continuous data collection . The integrated sensors or other above-described means can continuously collect data on the operational parameters . These may then be transmitted to a central data acquisition system . This realtime data collection can help to promptly detect deviations from optimal operating conditions . Furthermore in addition or alternatively, the real-time monitoring and data acquisition may include data processing and analysis . Here advanced data processing algorithms may be used to analyze collected data in order to identi fy trends , anomalies , or potential issues . These algorithms may utili ze historical data and predictive models to forecast system behavior or preemptively address any emerging issues .

[0091] According to a further embodiment , the reactor can have means for automated control and adj ustment . This may in particular include dynamic parameter adj ustment . Based on the real-time data and analysis , the system may automatically adj ust operational parameters such as voltage and current density or additional adding of speci fic electrolytes or salt-additives , such as sodium sul fite or sodium chloride , or other chemicals . This dynamic adj ustment capability helps to support continuous operation and maintain preferable conditions .

[0092] According to a further embodiment , the reactor can have means for real-time diagnostics and alerts . This may, in particular, include diagnostics and fault detection . By analyzing sensor data, the system can detect signs of wear, degradation, or mal function in real-time . The system may generate real-time alerts and noti fications to inform operators of issues or required interventions . These alerts can be delivered via multiple channels , including on-screen messages , emails , or text messages , ensuring that operators are promptly informed . Such means may be included into a reactor system .

[0093] According to a further embodiment , the reactor can have means for providing a predictive maintenance scheduling . By using real-time diagnostics and historical data, the system may be able to predict when maintenance activities will be needed . This predictive maintenance capability may help in planning and scheduling maintenance tasks before critical failures occur, reducing downtime and maintenance costs . Real-time diagnostics and fault detection may enhance the overall reliability of the system, preventing unexpected failures and ensuring continuous operation . To this end the reactor can have means for advanced sensor data acquisition combined with machine learning algorithms to analyze operational data dynamically . The system may be configured to adapt and optimi ze process parameters in real-time based on the characteristics of the incoming stream, signi ficantly enhancing the ef ficiency and ef fectiveness of PFAS destruction . According to an embodiment, means for comprehensive data collection can be realized. In this case the system may be equipped with an array of different sensors that continuously monitor various parameters of the incoming stream. These sensors can be the ones discussed above. The sensor data may be collected in real-time and transmitted to a central processing unit for immediate analysis. This continuous monitoring helps to provide up-to-date information on the characteristics of the incoming fluid stream or stream of the fluid-containing mixture.

[0094] According to an embodiment, machine learning algorithms may be implemented. This may allow for data analysis and pattern recognition. Machine learning algorithms may be employed to analyze collected sensor data. These algorithms may be trained on historical operational data and may recognize patterns and trends that indicate changes in the incoming stream. The machine learning models may identify correlations between different parameters and predict how changes in the incoming stream will affect the contaminant destruction process. Based on the analysis, the machine learning algorithms may dynamically adjust process parameters such as temperature, chemical dosages, and electrode voltage settings or current settings. These adjustments may help to optimize the destruction efficiency for the specific characteristics of the incoming stream. The system may be configured to continuously learn and update its models, improving its predictive accuracy and responsiveness over time.

[0095] According to an embodiment, real-time operational optimization may be implemented. This may include, in particular, immediate response to changes. The integration of sensor data and machine learning may allow for immediate response to variations in the incoming stream . Such real-time adaptability may help to keep the contaminant destruction process ef ficient under varying conditions . The system may also handle sudden fluctuations in contaminant levels or stream properties without manual intervention, maintaining optimal performance continuously . The adaptive control system may enhance overall process stability and control . By constantly fine-tuning operational parameters , the system may minimi ze the risk of inef ficiencies or failures caused by unexpected changes in the incoming stream and may thereby help to maintain compliance with contaminant-level regulations in di f ferent discharge streams . The process may also help to reduce the consumption of resources such as energy and chemicals , contributing to more sustainable and cost-ef fective operations .

[0096] Also according to an embodiment , the real-time operational optimi zation or the machine learning discussed above may enable seamless integration . The sensor and machine learning system may be designed to integrate seamlessly with existing contaminant destruction technologies . It can be retrofitted to current setups or included in new installations without signi ficant modi fications .

[0097] In the following, embodiments of a decontamination process are described . The processes may be carried out using a reactor described above or an electrode described above , but is not limited to that . In particular the features of the above-described embodiments of the electrode or of the reactor may each apply to the process . Also features disclosed for the process may apply to the reactor or the electrode . According to an embodiment a decontamination process is described . In this process a fluid or fluid-containing mixture passes by a pair of electrodes that has a first electrode and a second electrode . The first electrode is configured to promote electrochemical decomposition of a contaminant , when operated as an anode . In particular the first electrode may be operated as an anode . However, the first electrode is not necessarily continuously operated as an anode . The above-described may apply .

[0098] The contaminant targeted by the process is not limited . However according to an embodiment it can be one of the above-described substances . According to another embodiment , the contaminant may be present in the fluid or fluidcontaining mixture . The fluid or fluid-containing mixture can be aqueous . For example , it can be a regenerate stream of a filter comprising granular activated carbon or exchange resin, or it can be a slurry . The fluid or fluid-containing mixture can also be a concentrate .

[0099] According to an embodiment , the second electrode is also configured to promote electrochemical decomposition of a contaminant , when operated as an anode . This enables switching of voltage or polari zation between first and second electrode . The above-described may apply .

[0100] According to an embodiment , a voltage profile may be applied between both electrodes . The of fset of the voltage profile is not limited in general . The of fset may be 0 V or any other voltage . According to an embodiment, the voltage profile may be a pulse-width-modulated voltage profile. For example, such a profile may have off-times and on-times. The off-times and on-times may have a continuous repeating pattern. During the off-times the voltage is that of the offset voltage, which may be 0 V here, but may also be another base voltage. In the on-times the voltage is changed. The on-times may be longer than the off-times, or alternatively the other way round. For example, both the off-time and the on-time may individually lie in a range of 1 ms and 6 h.

[0101] According to an embodiment, the voltage profile may be triangular, rectangular, saw-tooth shaped, sinusoidal, or staircase-shaped. For all of these profiles the above said may apply mutatis mutandis, as far as applicable. All of these shapes are repeating patterns.

[0102] According to an embodiment, the voltage signal amplitude can be any value range lying between -30 V and +30 V. This applies to all voltage profiles and to the pulse-width- modulated voltage profile in particular.

[0103] According to another embodiment of reactor and process, means can be implemented to precipitate decomposition product. For example, in the case of PFAS or other f luorine-containing contaminants, the Ca2+-ions may be added with which practically insoluble CaF2 precipitates. Thus contaminating chemicals, such as fluoride ions in the case of the example, can be bound. The fluorine ion ins are an example of regulation-affected stream components that may be generated from PFAS decomposition. Calcium-containing electrolytes, such as CaOH, may be used as electrolyte for the electrochemical treatment. Such a calcium-containing electrolyte can be capable of precipitating as CaF2 after the electrochemical decomposition . Thus in a generali zed manner the electrolyte can be configured to precipitate a decomposition product .

[0104] According to a further embodiment , the process can be performed as a closed loop, where the contaminated liquid or liquid-containing mixture is pumped through the reactor from a recirculation tank, which can be particularly convenient for streams which are di f ficult to treat and require longer reaction times .

[0105] Further advantageous embodiments may become apparent from the following exemplary embodiments described in connection with the figures . However, the invention is not limited to said exemplary embodiments . Further, said exemplary embodiments are at least partially depicted in figures showing schematic drawings . These schematic drawings are not true to scale , and absolute and relative dimensions can be depicted in a distorted manner . Rather, individual elements may be shown exaggeratedly large for better representability or better understanding . Accordingly, no absolute or relative dimensions can be taken from the schematic depictions unless otherwise indicated . Elements that are identical , similar or have the same ef fect are denoted by the same reference signs in the figures .

[0106] Figure 1 shows a schematic exterior view of a first exemplary embodiment of an electrochemical reactor .

[0107] Figure 2 shows a first schematic cross section view of the first exemplary embodiment of an electrochemical reactor . Figure 3 shows a second schematic cross section view of the first exemplary embodiment of an electrochemical reactor .

[0108] Figure 4 shows a third schematic cross section view of the first exemplary embodiment of an electrochemical reactor .

[0109] Figure 5 shows a first schematic cross section view of a second exemplary embodiment of an electrochemical reactor .

[0110] Figure 6 shows a second schematic cross section view of the second exemplary embodiment of an electrochemical reactor .

[0111] Figure 7 shows a third schematic cross section view of the second exemplary embodiment of an electrochemical reactor .

[0112] Figure 8 shows a schematic cross section view of a first exemplary embodiment of an electrode .

[0113] Figure 9 shows a cross section microscope image of a second exemplary embodiment of an electrode .

[0114] Figure 10 shows a cross section microscope image of a third exemplary embodiment of an electrode .

[0115] Figure 11 shows a photographic image of a fourth exemplary embodiment of an electrode .

[0116] Figure 12 shows a first scanning electron microscopy image of an exemplary embodiment of a titanium suboxide precursor .

[0117] Figure 13 shows a second scanning electron microscopy image of the exemplary embodiment of a titanium suboxide precursor . Figure 14 shows a third scanning electron microscopy image of the exemplary embodiment of a titanium suboxide precursor .

[0118] Figure 15 shows a particle si ze distribution of the exemplary embodiment of a titanium suboxide precursor .

[0119] Figure 16 shows an X-ray powder di f fraction pattern of the exemplary embodiment of a titanium suboxide precursor .

[0120] Figure 17 shows a composition distribution graph of the exemplary embodiment of a titanium suboxide precursor .

[0121] Figures 18 to 24 show voltage profiles .

[0122] Figure 25 shows the results of a first PFOA decomposition experiment .

[0123] Figure 26 shows the results of a second PFOA decomposition experiment .

[0124] In Figures 1 to 4 a first exemplary embodiment of an electrochemical reactor 1 for PFAS decomposition or decontamination is shown . The design may be also used for other contaminants . Please note that in Figures 2 to 4 the reactor 1 is shown in di f ferent schematic cross sections .

[0125] Some of these show window-like surfaces . These are not part of the reactor but indicate a cross section surface .

[0126] The reactor 1 has a housing 2 of which a bottom and four side walls are depicted . In addition the housing 2 can have a cover, which is not depicted in the Figures . The housing 2 of the reactor can be polypropylene ( PP ) , high density polyethylene (HDPE ) , stainless steel or similar materials . The dimensions of the housing (x- , y- , and z- direction) can be adapted and may be between 200 mm and 1500 mm . A wall thickness here is 15 mm .

[0127] The reactor can stand on feet 10 , which can be adaptable in their height so that a level standing of the reactor 1 can also be ensured on ground that is not fully even .

[0128] The inside 3 of the reactor 1 has three main volumes , the first volume 22 , the electrode volume 4 and the second volume 19 . Contaminated water or a slurry can enter the reactor via the inlet 9 . The inlet 9 leads the water or slurry into the first volume 22 via an inlet tube 13 which has opening holes 23 . The water or slurry may be pumped into the first volume . Alternatively, a container having the contaminated water may be arranged at an elevated position so that the water or slurry flows with into the reactor gravity-induced pressure .

[0129] As visible from the figures , the inlet 9 can also be shaped as a tube which can be connected to a tank containing the contaminated water or the slurry .

[0130] A drainage hole 12 is arranged at the bottom of the first volume 22 . The drainage hole 12 allows for drainage of the first volume 22 and the electrode volume 4 via the drainage tube 6 . The drainage tube 6 has a valve (not explicitly labeled but visible in the Figures ) . It remains closed under operation . It can be opened to drain the first volume 22 and the electrode volume 4 . The above-described pressure can push the water or slurry into the electrode volume 4 . An array of electrodes is arranged in the electrode volume 4 . The array comprises first electrodes 14 ( in the color picture depicted in blue ) and second electrodes 15 ( in the color picture depicted in red) . All first electrodes 14 are electrically connected by a first bus bar 20 ( in the color picture depicted in blue ) . All second electrodes 15 are electrically connected by a second bus bar 21 ( in the color picture depicted in red) . The first bus bar 20 can be contacted by a power supply via the first external contact 16 . The second bus bar 21 can be contacted by the power supply via the second external contact 17 .

[0131] As discussed, all electrodes 14 and 15 are arranged in an array in alternating fashion, i . e . a repeating unit of the array comprises an electrode couple consisting of a first electrode 14 and a second electrode 15 . The shape and construction of the electrodes 14 and 15 is discussed below with respect to Figures 8 to 11 . The electrodes are flat , with a square-shaped main portion and the electrochemical reaction takes place on the surface of the square-shaped main portion . A gap is established between each first electrode 14 and each neighboring second electrode 15 . The gap has a si ze of 3 mm, but can be adapted between 0 . 5 mm to 10 mm depending on the rheological properties of the water or slurry that is to be treated . The electrode array is placed in an array holder 24 , which has rills or grooves accommodating the electrodes .

[0132] The water or slurry flows through the gaps between the first electrodes and the second electrodes . During the flow-by the PFAS contaminant comes into contact with the electrode surface and becomes decomposed . The described method of the water or slurry flowing in from the bottom into the first volume 22 and into the electrode volume 4 can help to evenly distribute it through the reactor .

[0133] After having passed the electrode array, the water or slurry reaches the level of a separating wall 18 . As the water or slurry is continuously flowing into the first volume 22 and through the electrode volume 4 , the at least partially decontaminated water or slurry overflows into the second volume 19 . At the bottom of the second volume 19 an outlet hole 11 is arranged via which the water or slurry can flow into the outlet 5 . The outlet 5 is a tube that can be connected to a tank or similar to collect the at least partially decontaminated water or slurry .

[0134] In addition to the features discussed above , the present exemplary embodiment of the reactor 1 has a first additional inlet 7 and a second additional inlet 8 . These can be used to vent the inside 3 of the reactor 1 . Alternatively they can be used for removing excess gases that might form during the operation . Also water or another rinsing fluid may be added for cleaning the reactor 1 . Alternatively additives may also be introduced into the reactor via the first additional inlet 7 or the second additional inlet 8 .

[0135] The reactor can be operated by being fed a contaminated aqueous solution or slurry from a tank . Most preferably a concentrate of the PFAS is used . The concentration of the total PFAS can, for example , range from 0 . 1 pg / 1 to 100 mg / 1 , such as 10 pg / 1 to 20 mg / 1 . After the treatment the at least partially decontaminated water or slurry can be collected in a second tank . Alternatively the reactor can be implemented into existing treatment lines , and the treated concentrate with reduced PFAS concentration can be reintroduced into the treatment line before the concentration step, for reconcentration of remaining PFAS . The reactor can also be operated in a closed loop, where the PFAS solution is pumped through the reactor 1 from a recirculation tank, which can be particularly convenient for streams that are di f ficult to treat and thus provide longer reaction times .

[0136] The reactor is designed such that it can process both clear liquids as well as suspensions or slurries , which can be pumped through the reactor without risk of clogging . Thus , the reactor can be suitable for the treatment of streams that are more di f ficult to treat , such as landfill leachate , without the need for extensive pretreatment such as filtration of solids , or for the treatment of previously untreatable streams , such as thin sludge , which until now has always been dewatered into dry sludge and then incinerated . For example porous membrane-based approaches for electrochemical oxidation processes have di f ficulties or cannot treat such di f ficult streams .

[0137] Regarding the operation of the electrochemical reaction, when operated as an anode both the first electrodes 14 and the second electrodes 15 are configured for promoting the electrochemical decomposition of PFAS due to a coating with Magneli phase titanium oxide that is explained below . Thus , both electrodes can be operated as anodes . The other electrodes that are not operated as anodes act as counter electrodes , i . e cathodes . This has the advantages described in the introduction . Furthermore , di f ferent voltage profiles can be used as explained below . Additionally, air, ozone or other gases can be inj ected into the reactor with a flow rate between 1 1 / h and 50 1 / h to increase mass trans fer rates and create turbulence . Ozone , as a strong oxidant , can directly react with and degrade various organic pollutants and / or PFAS precursors . Additionally, the mechanical action of the bubbles helps to clean the electrode surface and to prevent fouling .

[0138] The reactor can be operated with a working voltage of -30 V to +30 V and a current density of 0 . 5 mA / cm2to 500 mA / cm2. A reaction time in batch operation mode can be : 15 min to 18 h, such as nominal 6 h . Flow rates in continuous operation mode can be 1 1 / h to 500 1 / h, such as nominal 100 1 / h .

[0139] Also , various means may be implemented for monitoring, diagnostics and other features , as discussed in the introduction .

[0140] In Figures 5 to 7 a second exemplary embodiment of an electrochemical reactor 1 for the decomposition of PFAS is shown in di f ferent schematic cross sections . Please note that the window-like surface indicated in Figure 7 is not part of the reactor but only indicates a cross-section surface . Also , the second exemplary embodiment is a flow-by reactor .

[0141] The housing 3 of the reactor 1 consists of a first dome portion 27 that is connected via a screw-held flange 30 to a cylindrical portion 28 . On the other side of the cylindrical portion 28 , again via a flange 30 , a second dome portion 29 is attached . The reactor 1 shown here is symmetrical . The material of the housing can be the same as discussed for the first exemplary embodiment . The wall thickness of the housing is 15 mm in the speci fic example shown here .

[0142] Similarly to the first exemplary embodiment , the reactor can be operated with di f ferent contaminated solutions or slurries . In the current design it is preferably used for aqueous solutions . However the design and in particular the gap between electrodes , as discussed below, can be adapted for di f ferent rheological properties .

[0143] As the reactor 1 is symmetrical it can be operated mainly equally from both directions . In the following a mode is explained in which the first dome portion 27 is showing upwards and the water can flow downwards from the first dome portion 27 through the cylindrical portion 28 into the second dome portion 29 with gravity . Other orientations are possible and may employ a pump or other source of pressure to let the water flow through the reactor .

[0144] In the embodiment of operation, the contaminated water enters via the inlet 9 through the opening hole 23 into the first volume 22 formed between a first separation plate 25 and the first dome portion 27 .

[0145] The electrode volume is established in the cylindrical portion 28 . Cylindrical first electrodes 14 ( depicted blue in the colored figures ) are arranged in the electrode volume . Each first electrode is surrounded by an also cylindrical second electrode 15 ( depicted red in the colored figures ) .

[0146] Both electrodes 14 and 15 are cylinders with a wall thickness of 1 mm . The inner diameter of the first electrode 14 is 20 mm . The inner diameter of the second electrode 15 is 23 mm . As both are concentric, the gap between the first electrode 14 and the second electrode 15 is 0 . 5 mm . Alternatively, the said dimensions can be the same , except that the inner diameter of the second electrode 15 is 24 mm, resulting in a gap of 1 mm . The electrodes can also be chosen such that a gap is 2 mm or 3 mm or any other value between 0 . 5 mm and 10 mm .

[0147] The outside of the first electrode 15 that is facing the inside of the second electrode 15 is coated by a Magneli phase titanium oxide , as described for the plate electrodes of the first exemplary embodiment of the reactor . Furthermore , the inside of the second electrode 15 is also coated by a Magneli phase titanium oxide . Accordingly, both sides of the gap are covered by the Magneli phase titanium oxide .

[0148] In the reactor 1 the array of electrodes that is always partially shown belongs to a hexagonal arrangement of electrode pairs ( one first electrode 14 surrounded by one second electrode 15 ) . The total number of electrode pairs in the shown arrangement was 127 .

[0149] The electrodes are held between the first separation plate 25 and a second separation plate 26 . Each of the separation plates 25 and 26 can be constructed such that they not only hold the electrodes in place , but each may comprise means for electrically contacting one type of the electrodes 14 and 15 and isolating the other . For example , the first separation plate 25 may comprise means for contacting the second electrodes 15 . For example , it can comprise a conducting layer that is in contact with all second electrodes 15 . The first electrodes 14 are electrically insulated from the contacting means of the first separation plate 25 . In a similar manner, the second separation plate 26 may comprise means for contacting the first electrodes 14 . For example it can comprise a conducting layer that is in contact with all first electrodes 14 . The second electrodes 15 are electrically insulated from the contacting means of the second separation plate 26 .

[0150] In addition, the first separation plate 25 seals the first volume 22 from the electrode volume 4 . Likewise the second separation plate 26 seals the electrode volume 4 from the second volume 19 . The only way for the contaminated water to flow is through the gaps between the first electrodes 14 and the second electrodes 15 . As explained for the first exemplary embodiment of a reactor, decontamination takes place at the surface of said electrodes that can both be operated as an anode .

[0151] The at least partially decontaminated water flows from the electrodes into the second volume 19 and leaves through the outlet hole 11 and the outlet 5 .

[0152] Besides the di f ference in construction, the properties of the first exemplary embodiment of the reactor may also apply to the second exemplary embodiment .

[0153] In Figures 8 to 11 di f ferent depictions of similar exemplary embodiments of an electrode are shown .

[0154] Figure 8 shows a schematic cross section view of a first exemplary embodiment of an electrode . The electrode has a substrate 31 . A first coating 34 is arranged on a first main surface 32 of the substate 31 . In a similar manner, a second coating 34 is arranged on a second main surface that is opposite to the first main surface . The first coating 34 and the second coating 35 consist of a Magneli phase titanium oxide material , the composition and manufacturing of which is explained below . The substrate is a titanium plate substrate . Alternatively, the substrate could be stainless steel .

[0155] In Figures 9 and 10 cross section microscopic images of a second and a third exemplary embodiment of an electrode are shown . The electrodes shown have the same structure as the electrode in Figure 8 . The overall thickness of the electrode is about 2 mm in both cases . The first coating 34 has a thickness of about 0 . 14 mm and the second coating 35 has a thickness of about 0 . 12 mm in both cases . As can be seen in both pictures , towards the end of the electrode the coatings 34 and 35 have been partly peeled of f to measure their thickness .

[0156] Figure 11 shows a photographic image of a fourth exemplary embodiment of an electrode . The shown electrode can have the structure of the electrodes shown in Figures 8 to 10 . The electrode has a main portion 36 which is coated as described for Figures 8 to 10 . Furthermore it has a contacting and mounting portion 37 . The electrode shown here can be the one used in the first exemplary embodiment of an electrochemical reactor shown in Figures 1 to 4 , both as first electrode and as second electrode . It can be linked to a bus bar via the contacting and mounting portion 37 , which is not fully shown in the image here .

[0157] The electrodes discussed for Figures 1 to 4 , Figures 5 to 7 and in particular Figures 8 to 11 can be fabricated by plasma spray deposition . A material discussed with respect to Figures 12 to 17 was used as a raw material for plasma spray deposition.

[0158] Figures 12 to 14 show scanning electron microscopy images of an exemplary embodiment of a titanium suboxide precursor that can be used as a raw material. As can be seen in the images, a Magneli phase titanium oxide powder was used. The particles of the powder were porous, with pore sizes in the order of 0.5 pm to 5 pm as estimated from the images.

[0159] Figure 15 shows a particle size distribution of the titanium suboxide precursor. As becomes clear from the image, a homogeneous distribution of particles was used. The average particle diameter d(0.5) was measured to be 18.641 pm, so about 18.6 ± 0.1 pm. The value d(0.1) was measured to be 10.972 pm, so about 11.0 ± 0.1 pm. The value d(0.9) was measured to be 30.938 pm, so about 30.9 ± 0.1 pm. Thus the particles used were mostly larger than 5 pm and smaller than 50 pm.

[0160] The X-ray powder diffraction pattern of Figure 16 shows that the precursor consists nearly exclusively of TigO? and TigOg. Quantitative evaluation shown in Figure 17 produced as measurement results in a portion of TigO? to be 88.8 wt%, thus about 89 wt% and a portion of TigOg was measured to be 11.2 wt%, so rounded 11 wt%.

[0161] The plasma spray coating was conducted in the following way. An argon pressure of 7.2 bar and a flow rate of 35 1 / min and a hydrogen pressure of 6.6 bar and a flow rate of 10.0 1 / min was used. The plasma spray machine was water-cooled. It was operated at about 620 A and about 72 V with a power of about 45 kW. From the argon-hydrogen gas stream a plasma is created by electrodes, which exits a nozzle as a plasma jet. The particles are fed into said stream. The stream is pointed onto the titanium substrate as a target. In the plasma stream the particles are at least partially melted and are deposited on the surface of the substrate as splats. The abovedescribed thickness of about 120 to 140 pm was achieved with three depositions. Each deposition took about 30 seconds.

[0162] The plasma spray approach works well for coating the described plate electrodes. Also the outside of the cylindrical electrodes can be coated well that way. To coat the inside of a cylinder, the cylinder can be coated as halfcylinders with semi-circular profile and subsequently assembled. Alternatively, the electrodes and in particular more complex-shaped electrodes can be coated by the methods described in the introduction.

[0163] In Figures 18 to 24 show different voltage profiles which can be applied to electrodes in the above-described reactors or similar reactors.

[0164] In Figure 18 a pulse-width-modulated voltage profile is shown. As can be seen, the profile has off-times and on- times. The off-times and on-times have a continuous repeating pattern. During the off-times the voltage is that of an offset voltage, which may be 0 V here, but may also be another base voltage. The voltage is changed in the on-times. The off-times shown here are longer than the on-times, creating the pulse pattern.

[0165] In Figures 19, 20 and 24 two saw-tooth profiles are shown. In

[0166] Figures 21 a sinusoidal voltage profile is shown. In Figure 22 a rectangular voltage profile is shown. Also here the voltage form can be pulse-width-modulated.

[0167] The voltage profiles can be used either to switch the reaction on and off, i.e. to switch from 0 V to an operation voltage or they may be used to switch the polarization of the electrodes, i.e. inverse anode and cathode.

[0168] In Figures 25 and 26 the results of two PFOA decomposition experiments are shown. Both experiments were carried out in a test setup using two electrodes as described with respect to Figure 11 as anode and cathode. In both cases a concentration of PFOA (perf luorooctanoic acid) was 20 pg / 1. In the experiment of Figure 25 NaCl was used as electrolyte. The concentration of NaCl was 20 mmol / 1. In the second experiment shown in Figure 26 the electrolyte was 10 mmol / 1 of Na2SO4. As can be seen from both Figures effective PFOA degradation was reached with the inventive electrodes.

[0169] Reference sign list

[0170] 1 reactor

[0171] 2 housing

[0172] 3 inside of the reactor

[0173] 4 electrode volume

[0174] 5 outlet

[0175] 6 drainage tube

[0176] 7 first additional inlet

[0177] 8 second additional inlet

[0178] 9 inlet

[0179] 10 foot

[0180] 11 outlet hole

[0181] 12 drainage hole

[0182] 13 inlet tube

[0183] 14 first electrode

[0184] 15 second electrode

[0185] 16 first external contact

[0186] 17 second external contact

[0187] 18 separating wall

[0188] 19 second volume

[0189] 20 first bus bar

[0190] 21 second bus bar

[0191] 22 first volume

[0192] 23 opening hole

[0193] 24 array holder

[0194] 25 first separation plate

[0195] 26 second separation plate

[0196] 27 first dome portion

[0197] 28 cylindrical portion

[0198] 29 second dome portion

[0199] 30 flange

[0200] 31 substrate 32 first main substrate surface

[0201] 33 second main substrate surface

[0202] 34 first coating

[0203] 35 second coating 36 main portion of the electrode

[0204] 37 contacting and mounting portion

Claims

Claims1. Electrode for electrochemical decontamination of a fluid or fluid-containing mixture comprising a coating that is configured to promote electrochemical decomposition of a contaminant .

2. Electrode according to claim 1, wherein the coating comprises or consists of a substoichiometric titanium oxide, a silicon carbide, a manganese oxide, a cobalt oxide, a cobalt hydroxide oxide, an Fe-N4-graphene, a tungsten carbide, a nickel-containing tungsten carbide, a lead oxide, a boron-doped diamond material, or a ferrite-based material.

3. Electrode according to claim 1 or 2, wherein the coating comprises or consists of a Magneli phase titanium oxide.

4. Electrode according to any of claims 1 to 3, wherein the coating is derived from a precursor comprising 70 to 99 wt% of T14O7 and 1 to 30 wt% of TigOg.

5. Electrode according to any of claims 1 to 4, wherein the coating is a plasma sprayed coating.

6. Electrode according to any of claims 1 to 5 that is configured for the treatment of fluids or mixtures comprising fluids that contain persistent organic pollutants, such as for example per- and polyfluoro ( alkyl ) substances or mixed per- / poly- fluoro- / halo- subst ances , pharmaceuticals , antibiotics, pesticides, such as for example per-chloro-based substances, flame-retardants, such as for example per-bromo- biphenyls, poly-chloro-dibenzodioxines or dibenzodifurans, such as for example Seveso type chemicals, Poly-cyclic-aromatic compounds, such as for example benzpyren, transformer oils, such as for example poyl-chloro-biphenyls , forever chemicals, or chemicals falling under the Stockholm Convention substances.

7. Electrode according to any of claims 1 to 6, wherein the thickness of the coating is 1 pm to 500 pm, such as preferably 10 pm to 200 pm.

8. Electrode according to any of claims 1 to 7, wherein the coating is arranged on at least a portion of the surface of an electrically conducting substrate.

9. Electrode according to claim 8, wherein the substrate comprises titanium, stainless steel or a carbon-containing material .

10. Electrode according to any of claims 1 to 9, which has a thickness of 0.1 mm to 5 mm.

11. Electrode according to any of claims 1 to 10, which has a flat shape, a rod-like shape or a tube-like shape.

12. Electrode according to any of claims 1 to 11, that is configured for treating a contaminated water-containing fluid or water-containing mixture.

13. Electrochemical reactor comprising the electrode according to claims 1 to 12 as an anode or as an anode and a cathode .

14. Electrochemical reactor configured for electrochemical decontamination of a fluid or fluid-containing mixturecomprising a first electrode that can be operated as an anode and that is configured to promote electrochemical decomposition of a contaminant , wherein the reactor and the electrode are configured for the fluid or fluid-containing mixture to flow by the electrode , contacting at least a portion of the surface of the first electrode .15 . Electrochemical reactor according to claim 14 , wherein a second electrode that can be operated as a cathode is arranged such that it is configured for at least a portion of its surface to contact the fluid or fluid-containing mixture .16 . Electrochemical reactor according to claim 15 , wherein the first electrode and the second electrode are arranged such that the fluid or fluid-containing mixture can pass in a gap between anode and cathode .17 . Electrochemical reactor according to claim 16 , wherein the gap has a width of 0 . 5 mm to 10 mm, such as for example 1 mm to 6 mm .18 . Electrochemical reactor according to claim 16 or 17 , wherein the width of the gap can be adj usted to accommodate for di f ferent rheological properties .19 . Electrochemical reactor according to any of claims 15 to 18 , wherein the first electrode is configured to be operated as a cathode and wherein the second electrode is configured to be operated as an anode and is configured to promote electrochemical decomposition of the contaminant .20 . Electrochemical reactor according to any of claims 15 to19 , wherein the first electrode and the second electrode havea plate-like shape and are arranged with main surfaces facing each other .21 . Electrochemical reactor according to claim 20 , having an array of alternately stacked first electrodes and second electrodes , wherein all of the first electrodes are electrically connected and all of the second electrodes are electrically connected .22 . Electrochemical reactor according to any of claims 15 to 21 , which is configured such that a contaminated fluid or fluid-containing mixture enters into a first volume , subsequently flows into the electrode volume in which the first electrode is arranged, and flows into a second volume .23 . Electrochemical reactor according to claim 22 , wherein at least the electrode volume is separated from the second volume such that , after passing the electrode volume , the fluid or fluid-containing mixture can overflow into the second volume .24 . Electrochemical reactor according to any of claims 16 to 23 , wherein the second electrode has a shape complementary to an outer circumference of the first electrode and both are arranged with respect to each other such that the fluid or fluid-containing mixture can pass a gap between first and second electrode .25 . Electrochemical reactor according to claim 24 , wherein the first electrode has a circular or oval circumference and the second electrode has a complementary tube-like or semitube-like shape .26 . Electrochemical reactor according to claim 24 or 25 , wherein the first electrode and the second electrode are arranged in an array of several first and second electrodes .27 . Electrochemical reactor according to any of claims 14 to26 , wherein the first electrode cannot be fully penetrated by the fluid or fluid-containing mixture .28 . Electrochemical reactor according to any of claims 14 to27 , wherein the first electrode and / or the second electrode is an electrode according to at least one of claims 1 to 13 .29 . Electrochemical reactor according to any of claims 13 to28 , which is configured for a flow rate lying between 1 1 / h and 500 1 / h .30 . Electrochemical reactor according to any of claims 13 to 28 , comprising means for adding a gas to the fluid or fluidcontaining mixture .31 . Decontamination process , wherein a fluid or fluid-containing mixture passes by a pair of electrodes that has a first electrode and a second electrode , the first electrode is configured to promote electrochemical decomposition of a contaminant when operated as an anode .32 . Decontamination process according to claim 31 , wherein the second electrode is also configured to promote electrochemical decomposition of a contaminant , when operated as an anode .33 . Decontamination process according to claim 31 or 32 , whereinan applied voltage profile is pulse-width-modulated, triangular, rectangular, saw-tooth shaped, sinusoidal , or st air case- shaped .34 . Decontamination process according to any of claims 31 to33 , wherein the voltage signal amplitude is between -30 V and + 30 V .35 . Decontamination process according to any of claims 31 to34 , wherein the contaminant is one or more from the following list including organic pollutants , such as for example per- and polyfluoro ( alkyl ) substances or mixed per- / poly- f luoro- / halo-substances , pharmaceuticals , antibiotics , pesti zides , such as for example per-chloro-based substances , flameretardants , such as for example per-bromo-biphenyls , poly- chloro-dibenzodioxines or dibenzodi furans , such as for example Seveso type chemicals , Poly-cyclic-aromatic compounds , such as for example benzpyren, trans former oils , such as for example poyl-chloro-biphenyls , forever chemicals , or chemicals falling under the Stockholm Convention substances .36 . Decontamination process according to any of claims 31 to35 , wherein the fluid or fluid-containing mixture is a water containing regenerate stream of a filter comprising granular activated carbon or exchange resin, or a slurry .37 . Process of producing an electrode , wherein an electrically conductive substrate is provided, and a coating is applied to a main surface of the substrate , wherein the coating is configured to promote electrochemical decomposition of a contaminant .

38. Process according to claim 37, wherein the coating is made with or comprises substoichiometric titanium oxide, a silicon carbide, a manganese oxide, a cobalt oxide, a cobalt hydroxide oxide, an Fe-N4-graphene, a tungsten carbide, a nickel-containing tungsten carbide, a lead oxide, a boron- doped diamond material, or a ferrite-based material.

39. Process according to claim 37 or 38 wherein the substrate comprises or consists of titanium, stainless steel or a carbon-containing material.

40. Process according to any of claims 37 to 39, wherein the coating is applied by plasma spray coating, a chemical modification of the main surface of the substrate, or via sintering of a slurry or powder.

Images