[0001] This invention relates to a process for treating a liquid comprising organic compounds and/or microbes. The invention also relates to a device configured to allow the liquid to pass through whilst exposing the liquid to a catalyst in the presence of an organic compound.

BACKGROUND

[0002] Industrial wastewater produced by various industries such as chemical, food and beverage and agriculture is typically contaminated with organic compounds. Producers of the waste must pay a surcharge to the municipal treatment supplier, which is often defined by the level of contamination for instance as determined per chemical oxygen demand (COD) level. Alternatively, waste producers must employ cost-intensive, on-site advanced oxidation processes. The overall treatment costs are estimated to be around US$100 billion globally (at 2015 values). Therefore, efficient pre-treatment options are highly desirable. Filtration and removal of solids can reduce COD levels by 10-30%, and is a multi-billion-dollar market. However, to date, for dissolved COD, there are biological treatments, which may have many drawbacks (such as being time-consuming, difficult to control and not suitable for toxic waste streams), chemical treatments, which are harsh and costly, Fenton treatment, ozone treatment, wet air oxidation or electrochemical oxidation. The present invention seeks to provide an alternative approach.

[0003] Dissolved COD is decreased by oxidation of the organic matter. The dissolved COD are oxidised to carbon dioxide as well as other oxidised species and released from the waste water stream. However, the electrochemical oxidation of organic species on metal catalysts such as platinum has shown to lead to the formation of adsorbed carbon monoxide on the metal surface which can lead to the poisoning of the catalyst (J.

Hydrogen Energy 36, 15731-15738 (2011)). This has led to the introduction of metals such as lead or ruthenium which, when alloyed with platinum, enhance the formation of adsorbed species, such as hydroxyl groups, which help oxidize the adsorbed CO from the metal surface (J. Phys. Chem. 97, 12020-12029 (1993)). Besides the formation of CO adsorbates, the oxidation of organic species in industrial wastewater is particularly challenging when using metal and metal alloy catalysts. This is due to presence of cations and anions which have the ability to strongly attach to the catalyst surface further decreasing the number of sites available for the oxidation of the organic contaminants.

[0004] This drawback prevented the utilisation of electrochemical devices with precious metal anodes at moderate to low potentials. Industrially, only electrochemical devices utilising metal oxide catalysts, doped-diamond or other compositions are available. These require energy input and operate at relatively high oxidation potentials.

[0005] The prior art contemplates a catalytic material which will oxidise the organics in the wastewater using oxygen from the air placed in close vicinity, and in electrical contact, with a catalyst with the ability to oxidise organic species which are normally present in industrial wastewater and materials with ability to enhance formation of either water or H2O2 upon reaction with molecular oxygen. This enabled removal of contamination within industrial wastewater and enhanced material durability. As H2O2 is a potent oxidant which is occasionally used to decompose organic matter in wastewater, the enhanced production of H2O2 during the oxygen reduction process might not only support the cleaning of the catalyst surface of the oxidation catalyst but also aid an increase in the cleaning efficacy of the overall catalytic system.

[0006] The present invention seeks to utilise a simplified method of liquid treatment utilising a simplified catalytic system and a sacrificial organic material. This has the benefit of avoiding the need for a direct oxidation catalyst. The present invention utilises an indirect oxidising catalyst in the presence of an aldehyde to form a species which carries out the oxidation of organic contaminants in the liquid. In some embodiments, the species may be a peracid. In an embodiment, the species may be an organic peroxide. In some embodiments, the in situ generated peracid reacts with a further aldehyde to form an organic peroxide e.g. benzoyl peroxide. In some embodiments, the species i) increases the ORP (oxidation reduction potential) of the solution, ii) responds to a peracid colour strip test or iii) oxidises iodide-catalyzed selectivily 2,2 -azino-bis(3- ethylbenzothiazoline)-6-sulfonate diammonium salt (ABTS) to a green radical cation as described in Effkemann etal., Anal. Chem., 1998, vol. 70, No. 18, pp3857-3862.

[0007] In an embodiment, the liquid is water e.g. deionised (Dl) water. In an embodiment, the liquid is a waste stream e.g. a waste water stream.

[0008] Additional benefits of using this type of catalytic material with in-situ promotion of peracid and/or organic peroxide formation include:

[0009] The in-situ generated peracid and/or organic peroxide is a disinfectant which kills viruses, yeast, fungi and bacteria present in the liquid. This minimises possible deactivation of the catalyst due to formation of bacterial bio-films.

[0010] The in-situ generated peracid and/or organic peroxide is a strong oxidant which can directly attack organic species dissolved in the liquid. This contributes to enhancing the water cleaning capabilities of the material. [0011] The activity of sites involved in the direct oxidation of organic species is preserved.

BRIEF SUMMARY OF THE DISCLOSURE

[0012] In accordance with the present invention there is provided a method of removing organic compounds from a liquid. Removing organic compounds from a liquid in this way may be referred to as treating the liquid. The method of removing organic compounds from a liquid comprises: a) supplying:

(1) a catalytic material, wherein the catalytic material is a transition metal-N/C catalyst,

(2) an aldehyde,

(3) a liquid comprising 1) at least one organic compound that is different from the aldehyde and/or 2) at least one microbe, and

(4) oxygen; b) contacting the catalytic material with the liquid, the aldehyde and oxygen; and c) oxidising the at least one organic compound and/or killing or inhibiting growth of the microbe.

[0013] Oxidising the organic compound results in the organic compound being converted into an organic species with a higher oxidation state, for example the organic compound may be converted into carbon monoxide or carbon dioxide.

[0014] The aldehyde present in the liquid may be a contaminant already present in the liquid. Alternatively, the aldehyde may be added to a liquid, optionally wherein the liquid is free of an aldehyde. Accordingly, the aldehyde may form part of the liquid or it may be an additive to the liquid. In an embodiment the liquid comprises one or more aldehydes. In an embodiment the liquid comprises one or more aldehydes and a further aldehyde is added to the liquid.

[0015] In supplying the oxygen to the method of the invention it is preferred that the oxygen is added to the liquid prior to contacting the catalyst. However, the oxygen may be supplied to the catalyst at the same time as the liquid without prior contact between the oxygen and the liquid. The oxygen may be added to the liquid by dissolving or bubbling gaseous oxygen through the liquid. Accordingly, in embodiments the oxygen is dissolved or dispersed in the liquid. In embodiments the oxygen is supplied to the liquid, wherein the liquid comprises the at least one organic compound. In embodiments the oxygen is supplied to the liquid, wherein the liquid comprises the at least one organic compound and the aldehyde.

[0016] Alternatively, in embodiments the oxygen and the aldehyde are pre-mixed to form an oxygenated aldehyde premix. The oxygenated aldehyde premix may be added to the liquid. The oxygenated aldehyde premix may alternatively be supplied to the catalyst at the same time as the liquid without prior contact between the oxygen and the liquid.

[0017] Accordingly, in embodiments of the invention there is provided a method of removing organic compounds from a liquid comprising: a) supplying:

(1) a catalytic material, wherein the catalytic material is a transition metal-N/C catalyst,

(2) an aldehyde,

(3) a liquid comprising at least one organic compound that is different from the aldehyde, and

(4) oxygen; b) mixing the aldehyde and the oxygen to form an oxygenated aldehyde premix; c) contacting the catalytic material with the liquid and the oxygenated aldehyde premix; and d) oxidising the at least one organic compound.

[0018] The oxygenated aldehyde premix may further comprise a carrier. The aldehyde may be dissolved in the carrier. The oxygen may be dissolved in the carrier or dispersed in the carrier by dissolving or bubbling gaseous oxygen through the carrier. Accordingly, in an embodiment the method of the invention comprises supplying the oxygenated aldehyde premix comprising an aldehyde, oxygen and a carrier.

[0019] The liquid may be a waste stream e.g. a wastewater stream. The waste stream may be any liquid effluent produced in an industrial process, for example the waste stream may be a liquid effluent produced in the chemical, food, beverage or agricultural industry. In embodiments the waste stream comprises at least one organic compound and a carrier liquid. The carrier liquid may be the same as or different to the carrier referred to above in relation to the oxygenated aldehyde premix. [0020] In embodiments, the method of removing organic compounds from a waste stream comprises: a) supplying:

(1) a catalytic material, wherein the catalytic material is a transition metal-N/C catalyst,

(2) an aldehyde,

(3) a waste stream comprising at least one organic compound that is different from the aldehyde and a carrier liquid, wherein the waste stream is a liquid, and

(4) oxygen; b) contacting the catalytic material with the waste stream, the aldehyde and oxygen; and c) oxidising the at least one organic compound.

[0021] The at least one organic compound may be dissolved or dispersed in the carrier liquid.

[0022] In embodiments, the liquid comprises a carrier liquid. In embodiments, the carrier liquid is water. In embodiments, the waste stream comprises water. In embodiments, the waste stream is a water stream comprising at least one organic compound.

[0023] In embodiments, the method of removing organic compounds from a waste stream comprises: a) contacting a waste stream comprising at least one organic compound that is different from the aldehyde with a catalytic material; b) supplying an aldehyde and oxygen to the components of step a): and c) oxidising the at least one organic compound. [0024] The organic compound can generally be understood as any contaminant within a liquid that it is desirable to be removed from the liquid and that can be removed by an oxidative process. In embodiments the organic compound is selected from: a carboxylic acid, a carboxylic acid salt, an alkene, an alkane, a ketone, a sugar, an alcohol, a polymerised sugar (for example starch), sugar alcohols, glycols, amino-compounds (such as ammonia), amino acids, nitrogen containing heterocyclic molecules and sulphur containing heterocyclic molecules or any combination thereof. For the avoidance of doubt it should be noted that the organic compound encompasses ammonia. In embodiments it is possible that one of the at least one organic compounds is an aldehyde. Where an aldehyde is present within the liquid it is possible that no additional aldehyde is added to the liquid.

[0025] Thus, the method of the present invention may comprise: contacting a liquid comprising an aldehyde and at least one organic compound that is different from the aldehyde with a catalytic material; supplying oxygen; and oxidising the at least one organic compound.

[0026] The at least one organic compound may be present in the liquid in any form. The organic compound may be a gas, liquid or a solid. The organic compound may be dissolved or dispersed in the liquid. Accordingly, the organic compound may be dissolved or dispersed in the liquid carrier.

[0027] In embodiments, the liquid and/or the carrier liquid is selected from the group consisting of short-chain carboxylic acids e.g. Ci to Cs carboxylic acids e.g. acetic acid, ethanoic acid, propanoic acid, butanoic acid, pentanoic acid and hexanoic acid etc., alcohols and glycols e.g. methanol, ethanol, propanol, isopropanol, butanol, isobutanol, diethylene glycol, ethylene glycol, glycerol, diglyme etc., organic liquids e.g. DMF, DME. DMSO, THF, Toluene, ethyl acetate; ketones e.g. acetone; acetonitrile, pentane, hexane, Heptane, trichloromethane, carbon tetrachloride and chloroethanes

[0028] In embodiments the aldehyde is selected from: formaldehyde, ethanal (acetaldehyde), propanal, butanal (butyraldehyde), isobutanal, pentanal, metaldehyde, citral, cinnamaldehyde, octanal, and acetaldehyde or a combination thereof. In embodiments, the aldehyde is formaldehyde, ethanal (acetaldehyde), propanal, butanal (butyraldehyde), isobutanal, pentanal, metaldehyde or a combination thereof. In embodiments, the aldehyde is citral, cinnamaldehyde, octanal, and ethanal (acetaldehyde) or a combination thereof.

[0029] In embodiments the aldehyde is formaldehyde, ethanal, propanal, butanal (butyraldehyde) or pentanal. Preferably, the aldehyde is formaldehyde or butyraldehyde (butanal).

[0030] In embodiments the aldehyde is present in the liquid or added to the liquid in an amount of greater than 10ppm. Preferably, the aldehyde is present in the liquid or added to the liquid in an amount of greater than 50ppm. In embodiments the aldehyde is present in the liquid or added to the liquid in an amount of greater than 75ppm, greater than 100ppm, greater than 200ppm, greater than 250ppm, greater than 300ppm. [0031] As will be appreciated by the skilled person, if the aldehyde is to be added to the liquid it is preferable that there is an upper limit to the amount of aldehyde added. The upper limit may be lOOOppm, 750ppm or 500ppm. A range of aldehyde added to the liquid may be selected from 100ppm to lOOOppm, from 100ppm to 750 ppm, 100ppm to 500ppm, 200ppm to lOOOppm, from 200ppm to 750 ppm, 200ppm to 500ppm, 250ppm to lOOOppm, from 250ppm to 750 ppm, or 250ppm to 500ppm.

[0032] Where the aldehyde is present within the liquid (and it is not added to the liquid) there will not necessarily be an upper limit to the amount of aldehyde, as this will be dependent on the effluent forming the liquid. A range of aldehyde present in the liquid may be selected from: 100ppm to 500,000ppm, 100ppm to 450,000ppm, 100ppm to 400,000ppm, 100ppm to 350,000ppm, 100ppm to 300,000ppm, 100ppm to 250,000ppm, 100ppm to 200,000ppm, 100ppm to 150,000ppm, 100ppm to 100,000ppm, 100ppm to 90,000ppm, 100ppm to 85,000ppm, 100ppm to 80,000ppm, 100ppm to 75,000ppm, 100ppm to 70,000ppm, 100ppm to 65,000ppm, 100ppm to 60,000ppm, 100ppm to 55,000ppm, 100ppm to 50,000ppm, 100ppm to 45,000ppm, 100ppm to 40,000ppm, 100ppm to 35,000ppm, 100ppm to 30,000ppm, 100ppm to 25,000ppm, 100ppm to 20,000ppm, 100ppm to 15,000ppm, 100ppm to 10,000ppm, 100ppm to 5,000ppm,

100ppm to 4,000ppm, 100ppm to 3,000ppm, 100ppm to 2,000ppm, or 100ppm to 1,000ppm. However, there is still the possibility that the aldehyde may have an upper limit of lOOOppm, 750ppm or 500ppm. A range of aldehyde present in the liquid may be selected from: 100ppm to lOOOppm, from 100ppm to 750 ppm, 100ppm to 500ppm, 200ppm to lOOOppm, from 200ppm to 750 ppm, 200ppm to 500ppm, 250ppm to lOOOppm, from 250ppm to 750 ppm, or 250ppm to 500ppm.

[0033] The method of the present invention may be carried out at a temperature between 0 °C and 100 °C. The temperature range may apply to the entire method. Alternatively, the temperature range may apply to one or more of the steps of the method. For example, the step of contacting the catalytic material with the liquid, the aldehyde and oxygen (step b)) may be carried out at the recited temperatures or the step of oxidising the at least one organic compound (step c)) may be carried out at the recited temperatures. Accordingly, the method of the present invention further comprises heating to a temperature of between 0 °C and 100 °C.

[0034] In embodiments the method of removing organic compounds from a liquid comprises: a) supplying: (1) a catalytic material, wherein the catalytic material is a transition metal-N/C catalyst,

(2) an aldehyde,

(3) a liquid comprising at least one organic compound that is different from the aldehyde, and

(4) oxygen; b) contacting the catalytic material with the liquid, the aldehyde and oxygen at a temperature of between 0 °C and 100 °C; and c) oxidising the at least one organic compound.

[0035] Preferably the temperature is selected from: between 10 °C and 100 °C, between 15 °C and 100 °C, between 15 °C and 80 °C, between 15 °C and 60 °C, between 25 °C and 80 °C, between 35 °C and 80 °C, between 40 °C and 80 °C, or between 50 °C and 70 °C. In embodiments the method or one or more steps of the method is carried out at a temperature between 10 °C and 100 °C, between 15 °C and 100 °C, between 15 °C and 80 °C, between 15 °C and 60 °C, between 25 °C and 80 °C, between 35 °C and 80 °C, between 40 °C and 80 °C, or between 50 °C and 70 °C.

[0036] In embodiments the catalytic material is the sole catalytic material comprised within the process. This is an advantage of the present invention. The absence of a further expensive catalyst represents a significant improvement over the prior art.

[0037] Alternative methods of synthesising peracids involve reacting a carboxylic acid with hydrogen peroxide in 1% acid e.g. H2SO4 at between 30 °C and 90 °C in the absence of a metal catalyst.

[0038] The catalytic material of the present invention is generally referred to in the art as a transition metal-N/C catalyst. This is a term that is recognised in the art for example see “Heterogenous iron containing carbon catalyst” (Fe-N/C) for epoxidation with molecular oxygen (Journal of Catalysis, 370 (2019) 357-363), “Convenient and mild epoxidation of alkenes sing heterogenous cobalt oxide catalysts” (Angew. Chem. Int. Ed. 53 (2014) 4359-4363), “Heterogenized cobalt oxide catalysts for nitroarene reduction by pyrolysis of molecularly defined complexes (Nat Chem. 5 (2013) 537-543), and “Selective catalytic hydrogenation of heteroarenes with N-graphene-modified cobalt nanoparticles (Co304- Co/NGr@a-AI203)” (J. Am Chem. Soc. 137 (2015) 11718-11724). [0039] As such, in an embodiment the catalytic material is a transition metal-N/C catalyst. In embodiments the transition metal-N/C catalyst is prepared by a process as discussed below in relation to the catalytic material. The transition metal may be a group 8 or group 9 transition metal, such as Fe, Ru, Os, Co, Rh, or Ir. Preferably, the transition metal is Fe or Co. Thus, the catalytic material may be a catalyst selected from Fe-N/C, Ru-N/C, Os-N/C, Co-N/C, Rh-N/C, or Ir-N/C. Preferably, the catalytic material is a Fe-N/C catalyst or a Co-N/C catalyst.

[0040] In certain embodiments the catalytic material comprises a transition metal present in an amount of greater than 0.5 wt %. In certain embodiments the catalyst comprises a transition metal present in an amount greater than 1.0 wt%. In certain embodiments the catalyst comprises a transition metal present in an amount from 0.5 wt% to 5 wt%. In certain embodiments the catalyst comprises a transition metal present in a range selected from: from 0.5 wt% to 4 wt%, from 1 wt% to 4 wt%, from 0.5 wt% to 3 wt%, from 1 wt% to 3 wt%, and from 1 wt% to 2 wt%. The wt% discussed within this paragraph is the percentage weight of the transition metal compared to the overall weight of the catalyst. The disclosure here relating to the transition metal generally is equally applicable to a specific transition metal such as Fe, Ru, Os, Co, Rh, or I, preferably iron or cobalt.

[0041] In embodiments the catalytic material comprises an active site comprising a transition metal. The transition metal may be present as an atomic species or as a transition metal compound further comprising nitrogen. The transition metal may be a group 8 or group 9 transition metal, such as Fe, Ru, Os, Co, Rh, or Ir. Preferably, the transition metal is Fe or Co. In particular the catalytic material may comprise an active site comprising FeN2, C0N2, FeN4 or C0N4. The composition of the active site may be determined by high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). Determination of the active site may be completed after subjecting the catalyst to treatment in H2SO4, optionally 0.5M H2SO4.

[0042] In embodiments the catalytic material comprises a transition metal, a multiplicity of N-donors and a carbonaceous material. The carbonaceous material may be as described below. In embodiments the multiplicity of N-donors forms part of the carbonaceous material. Accordingly, in embodiments the catalytic material comprises a transition metal and a carbonaceous material comprising a multiplicity of N-donors.

[0043] Use of the term N-donor relates to a nitrogen atom within the catalytic material where the nitrogen atom can coordinate with a metal centre, for example via a lone pair on the nitrogen atom or via a covalent bond. As would be appreciated by the skilled person, within a catalytic material there will be a large number of nitrogen atoms. The amount of nitrogen atoms will ultimately be dependent on the amount of catalytic material. As such, it is appropriate to refer to a multiplicity of N-donors being present within the catalytic material. Providing a specific amount of N donors would not be appropriate given the dependence of this value on the number of moles of catalytic material. The metal centre may be the transition metal discussed elsewhere herein.

[0044] In embodiments, the catalytic material comprises a transition metal and a carbonaceous material comprising nitrogen atoms, wherein the nitrogen atoms are coordinated to the transition metal and the catalytic material is the sole catalytic material of the process.

[0045] In embodiments the catalytic material is a transition metal-N/C catalyst obtainable by a process comprising the steps of: oxidatively polymerising a precursor in the presence of a compound comprising a transition metal, wherein the precursor is a compound comprising an aromatic group and an amine group or a compound comprising a heteroaromatic group comprising at least one nitrogen atom; and subjecting the product of the oxidative polymerisation to pyrolysis to obtain the catalytic material. As would be understood by the skilled person, the transition metal utilised within the process will be the same transition metal as the transition metal of the transition metal-N/C catalyst.

[0046] In embodiments the compound comprising a transition metal is a inorganic salt of a transition metal. For example, the transition metal salt may be a salt of Fe, Ru, Os, Co, Rh, or Ir.

[0047] The transition metal salt may comprise a counter ion selected from chloride or oxalate acetate, nitrate, sulphate, phosphate, or porphyrin salt. The compound comprising a transition metal may be FeCh, C0CI2, or FeC ₂ 0 ₄ .

[0048] The compound comprising a transition metal may be a hydrate or a solvate. For example, the compound comprising a transition metal may be FeCl _2* 4H ₂ 0 or FeC ₂ 0 ₄ -2H ₂ 0.

[0049] In embodiments the catalytic material is a catalyst comprising a transition metal, a multiplicity of N-donors and a carbonaceous material, wherein the catalytic material is obtainable by a process comprising the steps of: oxidatively polymerising a precursor in the presence of a compound comprising the transition metal, wherein the precursor is a compound comprising an aromatic group and an amine group or a compound comprising a heteroaromatic group comprising at least one nitrogen atom; and subjecting the product of the oxidative polymerisation to pyrolysis to obtain the catalytic material. [0050] The precursor may be a nitrogen containing hydrocarbon. The nitrogen containing hydrocarbon may be a compound comprising an aromatic group and an amine group or a compound comprising a heteroaromatic group comprising at least one nitrogen atom. In embodiments the nitrogen containing hydrocarbon is selected from substituted or unsubstituted: pyridine, 2,2-bipyridine, phenanthroline, terpyridine, pyrrole, indole, isoindole, pyrazine, pyrimidine, pyridazine, quinazoline, quinoline, isoquinoline, or triazine. When the nitrogen containing hydrocarbon is substituted it may be substituted with Ci-e alkyl, Ci-e alkenyl, Ci-e alkynyl, Ci-e haloalkyl, Ci-e alkoxy

[0051] The step of oxidative polymerisation refers to a process of oxidising the precursor with an oxidising agent, for example ammonium persulfate. The resulting oxidised precursor undergoes polymerisation. This polymerisation is preferably spontaneous but could be prompted by a further chemical reagent or a further modification of the conditions.

[0052] The step of subjecting the product of the oxidative polymerisation to pyrolysis may involve heating the product at a temperature of greater than 600 °C. In embodiments heating the product may be conducted at a temperature greater than 700 °C, greater than 750 °C, greater than 800 °C, greater than 850 °C, or greater than 900 °C.

[0053] In embodiments the method of the present invention does not comprise a further catalyst. In embodiments the method does not comprise an oxidative catalyst. In embodiments the catalytic material does not comprise an oxidative catalyst.

[0054] In embodiments the catalytic material is selected from:

(a) a carbonaceous material comprising;

(i) 80 to 95 wt% carbon;

(ii) 0 to 20 wt% of at least one transition metal;

(iii) 0 to 20 wt% nitrogen;

(iv) 0 to 20 wt% sulphur; and

(v) 0 to 20 wt% phosphorus.

(b) nitrogen doped carbon compounds which comprise from 50 - 98wt% carbon and 10- 50wt% nitrogen;

(c) transition metal carbides;

(d) transition metal nitrides and carbonitrides; (e) metal chalcogenides; and

(f) transition metal oxides.

[0055] In embodiments the catalytic material is a carbonaceous material comprising:

(i) 80 to 95 wt% carbon; (ii) 0 to 20 wt% of at least one transition metal;

(iii) 0 to 20 wt% nitrogen;

(iv) 0 to 20 wt% sulphur; and

(v) 0 to 20 wt% phosphorus.

[0056] Preferably, the catalytic material has a high surface area of about 200m ² g ¹ or higher as determined by nitrogen adsorption analysis. Optionally, the carbonaceous material has a high surface area of about 200m ² g ¹ or higher as determined by nitrogen adsorption analysis

[0057] The carbonaceous material may be a carbon based material derived from the pyrolysis of a nitrogen containing hydrocarbon. The nitrogen containing hydrocarbon may be a compound comprising an aromatic group and an amine group or a compound comprising a heteroaromatic group comprising at least one nitrogen atom. In embodiments the nitrogen containing hydrocarbon is selected from pyridine, 2,2- bipyridine, phenanthroline, terpyridine, pyrrole, indole, isoindole, pyrazine, pyrimidine, pyridazine, quinazoline, quinoline, isoquinoline, or triazine. [0058] Advantageously, the carbonaceous material is obtainable by oxidative polymerisation of diaminonaphthalene. Preferably, the diaminonaphthalene is 1,5- diaminonaphthalene or 1,8-diaminonaphthalene, more preferably 1,5- diaminonaphthalene.

[0059] Optionally, the carbonaceous material is obtainable by oxidative polymerisation of a diaminonaphthalene in the presence of a metal salt.

[0060] Suitably, the metal salt is a ferrous or cobalt salt, preferably as a halide, more preferably as the chloride.

[0061] The catalytic material can be defined by its electrochemical activity to electrochemically reduce oxygen as measured by the rotating disk electrode method, as described in “In situ electrochemical quantification of active sites in Fe-N/C non-precious metal catalysts” (Nat. Commun. 7, 13285, doi: 10.1038/ncomms13285 (2016)). Accordingly, in embodiments the catalytic material has an electrochemical activity measured through a reductive current of between 0.1 and 6.5 mA cm ^-2 at 0.7V versus the reversible hydrogen electrode at a rotation of 1600 rpm. The electrochemical activity may be measured at a loading of 0.325 mg cm ^-2 and at steady state conditions in 0.5M H2SO4 as electrolyte at room temperature and after at least 30 min of operation in this electrolyte. Preferably the current is between 1 and 5.2 mA cm ^-2 , more preferably between 2.5 and 5.2 mA cm ^-2 .

[0062] The catalytic material of the invention will lose electrochemical activity in the presence of nitrite. However, the loss of activity is reversible. Therefore, put another way, the catalytic material of the present invention will revert to close to the original electrochemical activity after a loss of activity following exposure to nitrite and subsequent reactivation. Reactivation is defined as applying a reductive potential of -0.3V versus the reversible hydrogen electrode and subjecting the catalytic material to a fresh electrolyte solution. The reversible nature of the present catalytic material is not a feature of prior art electrochemical reduction catalysts.

[0063] Accordingly, in embodiments the catalytic material is a material having a first activity to electrochemically reduce oxygen and a second activity to electrochemically reduce oxygen, wherein the first activity is measured on the catalytic material and the second activity is measured after the same catalytic material has been exposed to nitrite and subsequently reactivated wherein the second activity is within 20% of the first activity.

[0064] The activity to electrochemically reduce oxygen maybe measured by the rotating disk electrode method. The exposure to nitrite may be subjecting the catalytic material to a 0.125M solution of pH 7 NaNC>2 solution.

[0065] In embodiments of the present invention the catalytic material is a material that loses more than 10% (optionally more than 20%, more than 30%, more than 50%, more than 60%, more than 70%, or more than 80%) of its electrochemical activity to electrochemically reduce oxygen as measured by the rotating disk electrode method after being subjected to a 0.125M solution of pH 7 NaNC>2 solution. The catalyst then regains more that 80% of its previously lost activity after being subjected to reactivation by applying a reductive potential of -0.3V versus the reversible hydrogen electrode and subjected to a fresh electrolyte solution.

[0066] Advantageously the catalytic material is applied to a substrate. Preferably, the substrate is a porous substrate. In embodiments, the substrate is a conductive substrate. [0067] The catalytic material may be extruded, formed or moulded. In some embodiments, the catalytic material is formed as pellets or granules. In alternative embodiments, the catalytic material is formed as a porous plate.

[0068] Suitably, the catalytic material is: i) in form of pellets made from the catalytic material finely dispersed and supported on a lignosulfonate salt, carbon, silica, alumina or any other support commonly known in the art; or ii) formed by depositing the catalytic material directly on carbon pellets.

[0069] The catalytic material may be coated onto a surface such as a waste pipe, catalyst support pellets (which can be selected from those well known in the art) or a reactor wall. A catalytic support is used when the catalytic material is supplied in form of a coating. It merely serves as “support” to keep the coating in place. In the examples described below there is provided an alternative method to making the catalyst. Instead of making the pellets out of the catalytic material itself, and therefore creating a self- supporting structure, an existing support structure such as S1O ₂ pellets, AI ₂ O ₃ pellets, carbon pellets or any other commonly used supports may be used.

[0070] Preferably, the catalytic material further comprises at least one binder.

[0071] Suitably, the at least one binder is one or more binders selected from microcrystalline cellulose, carboxymethylcellulose, phenolic resin, ion exchange resins (Nafion, Aquivion, Tokoyama Cation exchange resin), sugars, humic acid-derived sodium salt (HAS), polyvinylalcohol, proprietary binder from Waterlink Sutcliffe Carbons (WSC), PTFE (Teflon etc), adhesive cellulose-based binder (ADH) (Saint Honore), wax, linseed oil, gum arabic, gum tragacanth, methyl cellulose, gums, protein, polyvinylpyrrolidone, polyisobutylene or styrene-butadiene rubber and other common binder polymers.

[0072] The catalytic material once mixed with the binder may be heat treated to remove or convert the binder to form a monolithic structure.

[0073] In an embodiment, the invention provides a method of treating a liquid comprising: a) supplying:

(1) a catalytic material, wherein the catalytic material is a transition metal-N/C catalyst,

(2) an aldehyde,

(3) a liquid comprising at least one microbe, and (4) oxygen; b) contacting the catalytic material with the liquid, the aldehyde and oxygen; and inhibiting growth of the microbe.

[0074] In some embodiments, the microbe is selected from a bacterium e.g. Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, Salmonella, Enterococcus faecalis or a thermotolerant coliform; a virus e.g. polio virus, murine norovirus, adenovirus, coronavirus; a yeast e.g. Saccharomyces cerevisiae NCYC 762, Saccharomyces cerevisiae NCYC 1026, Zygosaccharomyces bailli NCYC 580; and a bacterial spore e.g. Bacillus subtilis ATCC 1544 or combinations thereof.

[0075] In an embodiment, the microbe is selected from the group consisting of E. coli, Salmonella spp., listeria monocytogenes and thermotolerant coliform. In an embodiment, the microbe is E. coli. In some embodiments, the microbe is a pathogen.

[0076] In an embodiment, the growth of the microbe is inhibited up to 100% i.e. growth is completely inhibited. In an embodiment, the growth of the pathogen is inhibited by up to 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or 100%. In an embodiment, the microbe is killed. In an embodiment, growth of the microbe is prevented entirely.

BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which:

Figure 1 is a graph showing the HPLC chromatogram for formate concentration.

Figure 2 is a graph comparing the formate concentration reduction during treatment, with and without formaldehyde in the wastewater.

Figure 3 is a graph showing the formate reduction compared between samples with and without butyraldehyde.

Figure 4 shows the HPLC chromatogram for ammonia concentration.

Figure 5 shows a graph of the ammonia amount after treatment evaluated for two different pH values.

Figure 6 shows a graph of oxidation-reduction potential (ORP) readings measured at various time intervals for deionised water and samples of peracids generated in situ from corresponding aldehydes using the ODAN catalyst. The horizontal line represents the ORP reading for the ODAN catalyst in deionised water. DETAILED DESCRIPTION

[0078] The term “liquid” encompasses any liquid. For example, the term “liquid” encompasses water e.g. deionised water, a waste stream having a liquid component, short-chain carboxylic acids e.g. Ci to Cs carboxylic acids e.g. acetic acid, ethanoic acid, propanoic acid, butanoic acid, pentanoic acid and hexanoic acid etc., alcohols and glycols e.g. methanol, ethanol, propanol, isopropanol, butanol, isobutanol, diethylene glycol, ethylene glycol, glycerol, diglyme etc., organic liquids e.g. DMF, DME. DMSO, THF, Toluene, ethyl acetate; ketones e.g. acetone; acetonitrile, pentane hexane Heptane, trichloromethane, carbon tetrachloride, chloroethanes, etc. The liquid for use with the catalyst and methods of the present invention typically comprise one or more organic compounds. The organic compound may be a liquid (e.g. it may be liquid at the temperature at which the reaction is operated) or it may be dissolved in the waste stream, in other words the waste stream may comprise a solvent and an organic solute (e.g. the organic compound which is dissolved). It will be appreciated that if an organic compound is solid at room temperature (i.e. about 20°C), and has partial solubility in the solvent, the part which is dissolved in the solvent is referred to as the "solute".

[0079] The term “waste stream” encompasses any discharge of liquid waste comprising at least one organic compound. The at least one organic compound may be liquid (e.g. an alcohol such as methanol, ethanol, or glycerol) or the organic compound may be dissolved in a solvent. Thus, the term waste stream encompasses waste water (also written as wastewater), e.g. where the solvent is water. It will be appreciated that the waste stream may comprise one type of organic compound, or a mixture of organic compounds. A waste stream encompasses the effluent from domestic, industrial, commercial or agricultural activities. Thus, the waste stream may be effluent from a petroleum refinery, chemical or petrochemical plant, paper of pulp production, food or beverage production processes (including those from breweries, wineries, distilleries, abattoirs, creameries, sugar manufacturers and refineries, confectionery (such as chocolate and candy) production, and pharmaceutical and pesticide manufacturing processes). The materials and process of the present invention are particularly useful and suitable for waste streams from food or beverage production processes.

[0080] The waste stream may additionally comprise solids which are suspended or dispersed in the stream. It may also comprise further compounds which are dissolved in the liquid of the stream, such as nitrogen-containing compounds (e.g. ammonia, nitrogen heterocycles, amino acids, urea, etc), sulphur-containing compounds (e.g. thiocyanates, sulphides, sulphur-containing heterocycles, sulfoxides, and thiosulphates), and salts which may comprise a metal cation (such as an alkali metal cation or alkaline earth metal cation) or a halide anion (e.g. chloride, bromide or iodide).

[0081] Catalytic Material

[0082] The term “catalytic material” refers to a catalyst that can catalyse the formation of a peroxy acid from an aldehyde in the presence of oxygen. A peroxy acid is a term recognised in the art (also referred to as a peracid). It is understood to be a hydrocarbon containing a -C(=0)OOH group.

[0083] The catalytic material is generally a transition metal-N/C catalyst. More specifically, the catalytic material may be selected from:

(a) carbonaceous materials which have a high surface area of >200m ² g ¹ as determined by nitrogen adsorption analysis;

(b) nitrogen doped carbon compounds which comprise from 50 - 98wt% carbon and 10- 50wt% nitrogen;

(c) transition metal carbides;

(d) transition metal nitrides and carbonitrides;

(e) metal chalcogenides; and

(f) transition metal oxides.

[0084] Advantageously, the carbonaceous material comprises: (i) 80 to 95 wt% carbon;

(ii) 0 to 20 wt% of at least one transition metal; (iii) 0 to 20 wt% nitrogen; (iv) 0 to 20 wt% sulphur; and (v) 0 to 20 wt% phosphorus.

[0085] The elemental composition characterisation of the catalysts may be determined as is standard in the art and as set out, for example, in Malko, D., Kucernak, A. & Lopes, T., Nature Communications 7, 13285 (2016) and Malko, D., Lopes, T., Symianakis, E. & Kucernak, A. R., J. Mater. Chem. A 4, 142-152 (2015), the entire contents of which are incorporated herein by reference and to which further reference should be made. For example, the elemental composition may be determined by X-ray photoelectron spectroscopy and/or total reflection X-ray fluorescence.

[0086] Total reflection x-ray fluorescence may be carried out, for example, using a Bruker S2 Picofox. For example, samples may be prepared from a suspension of 10 mg of the poison resistant cathode catalyst in 1 ml H2O (MiliQ 18.2 MW-cm), which may contain 1 wt% Triton X-100 (Sigma Aldrich) as surfactant, 0.2 wt% polyvinylalcohol (Mowiol® 4-88, Sigma-Aldrich) as binder and 100pg Ga, as internal standard (from 1 g/l Standard Solution, TraceCert®, Sigma-Aldrich). 10 mg may be deposited onto a quartz glass sample carrier and dried at room temperature in a laminar flow hood to give a homogenous thin film.

[0087] X-ray Photoelectron Spectroscopy (XPS) analyses may be performed, for example, using a Kratos Analytical AXIS UltraDLD spectrometer. For example, a monochromatic aluminium source (Al Ka = 1486.6 eV) may be used for excitation. The analyser may be operated in constant pass energy of 40 eV using an analysis area of approximately 700mhi x 300mhi. Charge compensation may be applied to minimise charging effects occurring during the analysis. The adventitious C1s (285.0 eV) binding energy (BE) may be used as internal reference. The pressure may be about 10KPa during the experiments. Quantification and simulation of the experimental photopeaks may be carried out using CasaXPS and XPSPEAK41 software. Quantification may be performed using non-linear Shirley background subtraction. As used herein, wt% means, unless the context indicates otherwise, dry weight percentage of said elemental component of the total of weight of the catalyst.

[0088] The catalytic material is preferably comprises a transition metal and a carbonaceous material comprising nitrogen atoms, wherein the nitrogen atoms are coordinated to the transition metal and the catalytic material is the sole catalytic material of the process.

[0089] The catalytic material may also be a carbonaceous material which has a high surface area of >200m ² g ¹ as determined by nitrogen adsorption analysis. In preferred embodiments, the carbonaceous material comprises:

(i) 80 to 95 wt% carbon;

(ii) 0 to 20 wt% of at least one transition metal;

(iii) 0 to 20 wt% nitrogen;

(iv) 0 to 20 wt% sulphur; and

(v) 0 to 20 wt% phosphorus.

[0090] An example of carbonaceous material can be produced by oxidatively polymerising 1,5-diaminonaphthalene in an ethanolic solution, optionally whilst adding 1wt% iron ions in the form of a salt such as FeCl _2* 4H ₂ 0, and pyrolyzing the dry precursor at 900°C under inert atmosphere in a tube furnace for 2h. The result is a catalyst that can electrochemically reduce oxygen. [0091] The catalytic material may also be selected from: nitrogen-doped carbon compounds which comprise from 50-98wt% carbon and 10-50wt% nitrogen; transition metal carbides such as; FeC and WC; transition metal nitrides and carbonitrides, such as TiN and TaC _x N _y ; metal chalcogenides such as transition metal compounds with S, Se or Te, for example, RU2M04SE8M0S; and transition metal oxides, for example, ZrC>2-x, C03O4-X and TaO.

[0092] The catalytic material can electrochemically oxidise aldehydes to a peroxy acid. The peroxy acid acting as an oxidising agent to oxidise organic compounds in the liquid or waste stream.

[0093] Oxidation of organic compounds occurs in combination with oxygen, a peroxy acid along with the catalytic material. Typical organic compounds for oxidation in a wastewater stream are outlined in WO2017/0493754A1, which is incorporated herein by reference and to which further reference should be made.

[0094] Structure

[0095] Both the catalytic material may be deposited on carbon pellets or particles as a support or substrate.

[0096] Pellets or particles may also be made from the catalytic material. Additionally, the catalytic material may be manufactured as microparticles or nanoparticles deposited onto a support.

[0097] The catalytic mixture may be deposited onto catalyst beads which may then be filled into a reaction vessel.

[0098] The catalytic material may be extruded, formed or moulded and is preferably in the form of a pellet or a porous plate. The catalytic material may be deposited onto a plate or electrode substrate such as a gas diffusion layer. The porous plate can be either a porous metal mesh, carbon electrode that is typically used in fuel cells or a porous polymer sheet (i.e. polyethylene, polypropylene etc).

[0099] The catalytic material may be coated onto a surface such as a waste pipe, catalyst support pellets (which can be selected from those well known in the art) or a reactor wall. A catalytic support is used when the catalyst is supplied in form of a coating. It merely serves as “support” to keep the coating in place. In the examples described below there is provided an alternative method to making the catalyst. Instead of making the pellets out of the catalytic material itself, and therefore creating a self-supporting structure, an existing support structure such as S1O2 pellets, AI2O3 pellets, carbon pellets or any other commonly used supports may be used.

[00100] Waste streams

[00101] The waste stream for use with the catalyst and methods of the present invention typically comprise one or more organic compounds. The organic compound may be a liquid (e.g. it may be liquid at the temperature at which the reaction is operated) or it may be dissolved in the waste stream, in other words the waste stream may comprise a solvent and an organic solute (e.g. the organic compound which is dissolved). It will be appreciated that if an organic compound is solid at room temperature (i.e. about 20°C), and has partial solubility in the solvent, the part which is dissolved in the solvent is referred to as the "solute".

[00102] Examples of organic compounds which are liquid at room temperature include ethanol, methanol and glycerol. Thus, the waste stream may comprise one or more liquid organic compounds. If the organic compound is dissolved in the waste stream, the solvent may be water, acetonitrile, an ether, ethyl acetate, a halogenated hydrocarbon (e.g. dichloromethane or dichloroethane), or N-methylpyrrolidone, or it may be a further organic compound, which is liquid (e.g. methanol, ethanol, glycerol, etc.), or a mixture thereof (e.g. glycerol and water, ethanol and water, methanol and waster etc.). Preferably the solvent comprises water, or in other words, the waste stream is preferably a wastewater stream.

[00103] It will be appreciated that the term "dissolved" in the context of the invention means that the organic compound is capable of dissolving, at least in part, in a solvent. The organic compound may be selected from a carbohydrate, an alcohol, an aldehyde, an ester, a ketone, a hydrocarbon, an acid, and amino acid, a protein and combinations thereof.

[00104] When the organic compound is a carbohydrate, it may be a monosaccharide (such as glucose, galactose, fructose, mannose and ribose), a disaccharide (such as sucrose, lactose, maltose, isomaltose, isomaltulose, trehalose and trehalulose), an oligosaccharide (such as FOS, MOS or GOS), a polysaccharide (such as inulin), or mixtures thereof.

[00105] When the organic compound is an alcohol, it may be selected from an alcohol, such as methanol, ethanol, glycerol, isomalt, lactitol, maltitol, mannitol, sorbitol, xylitol, and erythritol. [00106] When the organic compound is an acid, it may be a carboxylic acid or dicarboxylic acid, for example the acid may be selected from citric acid, tartaric acid, malic acid, lactic acid, acetic acid, or propionic acid. When the organic compound is an amino acid or protein, it may be a selected from bovine serum albumin (BSA), cysteine, lysine, alanine, arginine, asparagine, aspartic acid, glutamine, glutamic acid, glycine, histidine, isoleucine, leucine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine and valine.

[00107] When the organic compound is an ester, it may be selected from ethyl acetate, n- butyl acetate, n-propyl acetate, isopropyl acetate, ethyl formate, and methyl formate.

[00108] When the organic compound is an aldehyde, it may be selected from formaldehyde (methanal), acetaldehyde (ethanal), propionaldehyde (propanal), butyraldehyde (butanal), pentanal, benzaldehyde, cinnamaldehyde, vanillin, tolualdehyde, furfural, retinaldehyde, glyoxal, malondialdehyde, succindialdehyde, glutaraldehyde, and phthalaldehyde.

[00109] When the organic compound is a ketone, it may be selected from acetone, propanone, butanone, 3-pentanone, cyclohexanone, dimethyl ketone, methyl ethyl ketone, methyl isobutyl ketone, and isophorone.

[00110] When the organic compound is a hydrocarbon, it may be a branched or unbranched, saturated, partially saturated or unsaturated, cyclic or acyclic compound consisting of hydrogen and carbon atoms. The hydrocarbon preferably contains from about 1 to about 20 carbon atoms. The hydrocarbon may be an aromatic hydrocarbon which comprises one or more five or six membered rings. If more than one ring is present, the rings may be linked by a single bond, or may be fused to give larger polycyclic compounds. Exemplary hydrocarbons include methane, ethane, propane, butane (n or iso), pentane (n, iso or cyclo), hexane (n, iso or cyclo), benzene, naphthalene, anthracene, phenanthracene, pyrene, chrysene etc.

[00111] The nature of the organic compound in the waste stream will depend on the source of the waste stream. For example, if the waste stream is from a winery or a brewery, the waste stream may comprise water, and the organic compound may include carbohydrates, alcohols, organic acids, esters and combinations thereof. Organic compounds of a winery or brewery waste stream typically include ethanol, glycerol, phenolic compounds (e.g. tannins), acids (e.g. citric acid, tartaric acid, malic acid, lactic acid and acetic acid), monosaccharides and disaccharides (e.g. glucose and sucrose), and starches. [00112] It will be appreciated that exposing the liquid or waste stream to the catalytic material referred to herein will reduce the concentration of the organic compound(s) in the liquid or waste stream. For example the concentration of the organic compound(s) in the liquid or waste stream which have contacted and reacted with the catalytic material may be at least about 5% less, preferably at least about 10% less, more preferably at least about 20% less, even more preferably at least about 30% less, even more preferably at least about 50% less, even more preferably about 70% less, even more preferably at least about 90% less, even more preferably at least about 95% less than the concentration of the organic compound(s) in the liquid or waste stream prior to contacting the catalytic material.

[00113] It will be appreciated that if the liquid or waste stream comprises more than one type of organic compound, then each of these organic compounds may be oxidised.

[00114] The term “Ci-e alkyl” refers to a linear or branched hydrocarbon chain containing 1, 2, 3, 4, 5 or 6 carbon atoms, for example methyl, ethyl, n-propyl, /so-propyl, n-butyl, sec-butyl, tert- butyl, n-pentyl and n-hexyl. Alkylene groups may likewise be linear or branched and may have two places of attachment to the remainder of the molecule. Furthermore, an alkylene group may, for example, correspond to one of those alkyl groups listed in this paragraph. The alkyl and alkylene groups may be unsubstituted or substituted by one or more substituents. Possible substituents are described below. Substituents for the alkyl group may be halogen, e.g. fluorine, chlorine, bromine and iodine, OH, Ci-e alkoxy.

[00115] The term “Ci-e alkoxy” refers to an alkyl group which is attached to a molecule via oxygen. This includes moieties where the alkyl part may be linear or branched and may contain 1, 2, 3, 4, 5 or 6 carbon atoms, for example methyl, ethyl, n-propyl, /so-propyl, n- butyl, sec-butyl, tert- butyl, n-pentyl and n-hexyl. Therefore, the alkoxy group may be methoxy, ethoxy, n-propoxy, iso- propoxy, n-butoxy, sec-butoxy, tert- butoxy, n-pentoxy and n-hexoxy. The alkyl part of the alkoxy group may be unsubstituted or substituted by one or more substituents. Possible substituents are described below. Substituents for the alkyl group may be halogen, e.g. fluorine, chlorine, bromine and iodine, OH, Ci-e alkoxy.

[00116] The term “Ci-e haloalkyl” refers to a hydrocarbon chain substituted with at least one halogen atom independently chosen at each occurrence, for example fluorine, chlorine, bromine and iodine. The halogen atom may be present at any position on the hydrocarbon chain. For example, Ci-e haloalkyl may refer to chloromethyl, flouromethyl, trifluoromethyl, chloroethyl e.g. 1 -chloromethyl and 2-chloroethyl, trichloroethyl e.g. 1,2,2- trichloroethyl, 2,2,2-trichloroethyl, fluoroethyl e.g. 1-fluoromethyl and 2-fluoroethyl, trifluoroethyl e.g. 1,2,2-trifluoroethyl and 2,2,2-trifluoroethyl, chloropropyl, trichloropropyl, fluoropropyl, trifluoropropyl.

[00117] The term “C2-6 alkenyl” refers to a branched or linear hydrocarbon chain containing at least one double bond and having 2, 3, 4, 5 or 6 carbon atoms. The double bond(s) may be present as the E or Z isomer. The double bond may be at any possible position of the hydrocarbon chain. For example, the “C2-6 alkenyl” may be ethenyl, propenyl, butenyl, butadienyl, pentenyl, pentadienyl, hexenyl and hexadienyl.

[00118] The term “C2-6 alkynyl” refers to a branched or linear hydrocarbon chain containing at least one triple bond and having 2, 3, 4, 5 or 6 carbon atoms. The triple bond may be at any possible position of the hydrocarbon chain. For example, the “C2-6 alkynyl” may be ethynyl, propynyl, butynyl, pentynyl and hexynyl.

[00119] The term “microbe” refers to a bacterium e.g. Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, Salmonella, Enterococcus faecalis or a thermotolerant coliform; a virus e.g. polio virus, murine norovirus, adenovirus, coronavirus; a yeast e.g. Saccharomyces cerevisiae NCYC 762, Saccharomyces cerevisiae NCYC 1026, Zygosaccharomyces bailli NCYC 580; and a bacterial spore e.g. Bacillus subtilis ATCC 1544 and combinations thereof.

EXAMPLES

Preparation of the Catalyst

Example 1

An example of the catalyst was synthesized by dissolving 1.0 g (6.4 mmol) of 1,5- diaminonaphthalene (97%, Alfa Aesar), 1.0 g (4.4 mmol) of (NH ₄ ) ₂ S ₂ 0s (98%, Sigma- Aldrich) and 35.6 mg of FeCl _2* 4H ₂ 0 (99%, Sigma-Aldrich) in 250 ml of ethanol (absolute, VWR). The solution was stirred for 24 h at room temperature. The solvent was then removed with a rotary evaporator. When dry, the resulting residue was transferred to an alumina boat and heat treated at 950 °C for 2 h, after reaching the end temperature, in a tube (quartz) furnace (Carbolite) at a heating rate of 20 °Cmin ¹ . This heat treatment was performed in an inert atmosphere, under a continuous flow of nitrogen (50 com). After cooling down under nitrogen, the resulting material was removed from the quartz boat and refluxed in 0.5M H ₂ SO ₄ for 8 h, to remove any soluble metal phases. The material was then filtered and dried. The dried powder was then subjected to an optional second heat treatment at 900C for 2 h after reaching the target temperature at a heating rate of 20 Cmin ¹ under nitrogen and allowed to cool as above. The resulting powder was then ready to use.

Example 2

A second example of the catalyst was synthesized by dissolving 1.0 g (6.4 mmol) of 1,8- diaminonaphthalene (97%, Alfa Aesar), 1.0 g (4.4 mmol) of (NH^SaOs (98%, Sigma- Aldrich) and 35.6 mg of FeC HaO (99%, Sigma-Aldrich) in 250 ml of ethanol (absolute, VWR). The solution was stirred for 24 h at room temperature. The solvent was then removed with a rotary evaporator. When dry, the resulting residue was transferred to an alumina boat and heat treated at 950 C for 2 h, after reaching the end temperature, in a tube (quartz) furnace (Carbolite) at a heating rate of 20Cmin ¹ . This heat treatment was performed in an inert atmosphere, under a continuous flow of nitrogen (50 com). After cooling down under nitrogen, the resulting material was removed from the quartz boat and refluxed in 0.5M H ₂ SO ₄ for 8 h, to remove any soluble metal phases. The material was then filtered and dried.

The dried powder was then subjected to an optional second heat treatment at 900 °C for 2 h after reaching the target temperature at a heating rate of 20 °Cmin ¹ under nitrogen and allowed to cool under nitrogen. The resulting powder was then ready to use.

Example 3

Catalyst pelletization: The catalyst pellets were synthesized using untreated novolac phenolic resin binder and then carbonizing said binder at high temperatures. The ODAN catalyst, carbon black (VULCAN XC-72R, “Cabot”) and Pt-Pd/C catalyst (“Premetek”), at a ratio of 40:55:5 respectively, were mechanically mixed to obtain a uniform mixture of powders. The untreated phenolic resin was produced by dissolving phenol (99%, “VWR chemicals”) in 37% formaldehyde solution (“Sigma-Aldrich”). The molar ratio of phenol to formaldehyde was 0,5. Then NaOH (“VWR chemicals”) was added in the solution as crosslinking agent. The molar ratio of NaOH to phenol was 0,1. The untreated binder solution was stirred and then added dropwise into the powder mixture at a weight ratio of 1:1. Simultaneously, the powders and the liquid binder were mixed to produce a granule paste. This paste was transferred into a clay gun, to be extruded using an extrusion die with 2mm diameter hole. The extruded paste formed pellets of cylindrical shape, which were transferred in a sealed glass vial. Then the vial was inserted in an oven at 80°C, for 12 hours, in order to crosslink the resin. Subsequently, the pellets were placed in a quartz boat and inside a tube furnace (“Carbolite”) to carbonize the phenolic resin. The pyrolysis was carried out at 1000°C, rate of 1°C/min, with a dwell time of 2 hours, under N2 flow (0,2L/min). Then the produced pellets were rinsed with Dl water to remove any ash from the process, dried at 40°C and they were ready for use.

Example 4

Simulated wastewater formate removal: The simulated wastewater streams under investigation were a combination of formate-formaldehyde and formate-butyraldehyde.

The initial concetration of formate was 300 ppm in deionised water. The chemicals used: Sodium formate (CHNa02), 37% Formaldehyde solution (CH2O) and Butyraldehyde 99% (CH3CH2CH2CHO); were provided from ‘Sigma-Aldrich Merck’. The pH of each solution was stabilized using H2SO4.

Example 5

Simulated wastewater ammonia removal: The wastewater initial composition was 100ppm of Ammonia, plus 50ppm of formaldehyde in Dl water. The pH was stabilized using diluted H2SO4.

Batch reactor testing for both Example 4 and 5

The batch reactor is composed of a glass single neck round bottom flask, that acts as the reaction chamber. The prepared simulated wastewaters are inserted in the reaction chamber along with 1.7 gramms of catalyst pellets and a magnetic stirring bar, that acts as agitator. A presicion seal septa (Sigma Aldrich Merck) was used to seal the flask, while the necessary gas for the reaction was provided from a balloon filled with oxygen gas. The balloon outlet was adjusted to a needle which was used to pierce the septa. The reactor was placed on a silicon oil bath at 60°C to provide energy for the reaction. A syringe with a screw needle was used to pierce the septa and take a sample after a certain time of treatment.

High Performance Liquid Chromatography (HPLC) for Example 4

The formate ion concentration in the wastewater samples, before and after treatment, was monitored using a ‘MetrOhm 850 Professional IC‘ HPLC ion exchange chromatographer. The anion exchange column used was the ‘Metrosepp A Supp 5’ in combination with a conductivity detector. The temperature of the column was set at 30°C and the flowrate at 0.8ml_/min. The eluent used was 3.2 mM Na2CC>3 and 1 mM NaHCC>3. The same experimental setup was used for ammonia concentration monitoring, with the difference of implementing cation detection, with a conductivity detector, a cation separation column ‘Metrosepp C 4’ at 30°C, with flowrate 2ml_/min. The eluent used was 1.7 mmol/L Nitric acid and 0.7 mmol/L dipicolinic acid.

HPLC chromatogram for formate ion concentration monitoring is shown in Figure 1. The y- axis is the conductivity measured by the detector, in pS/cm and the x- axis the retention time of the sample inside the column, in minutes. The formate is detected at 4.40 minutes of retention time. The area of the peak is proportional to the concentration of the detected substance in the sample. In this graph it is shown that the formate concentration of the original sample (the uppermost line at 4.40 min) is reduced after 63 hours of treatment in the batch reactor (lowermost line at 4.40 min), in the presence of butyraldehyde.

Figure 2 shows a graph comparing the formate ion concentration reduction during treatment, with and without formaldehyde in the wastewater. The y- axis is the formate concentration in ppm and the x- axis is the time of treatment in the reactor, in hours. It is shown that the formate reduction in the presence of formaldehyde is faster and more intense than without adding formaldehyde. The faster kinetics are evident from the slope of the curve (orange curve), in addition the concentration of the final sample is much lower when formaldehyde is added.

Figure 3 shows the formate ion reduction compared between samples with and without butyraldehyde. Initially the amount of 50ppm of butyraldehyde was not enough to see a clear variation, that is until 300ppm of butyraldehyde was added in the wastewater. The y- axis is the formate concentration in ppm and in x- axis the time of treatment in the reactor, in hours. It is shown that the reaction towards the formate concentration reduction is occurring with the presence of butyraldehyde inside the reactor (purple colour). It seems that without the aldehyde there is no significant formate reduction in the sample.

High Performance Liquid Chromatography (HPLC) for Example 5

Figure 4 shows the HPLC chromatogram for ammonia concentration monitoring. The y- axis is the conductivity measured by the detector, in pS/cm and the x- axis the retention time of the sample inside the column, in minutes. Ammonia is detected at 4.70 minutes of retention time. Figure 4 demonstrates that the process of the present invention significantly reduces the amount of ammonia in a sample after the process of the present invention (time at 15h). The evolution of another unknown peak is shown in the after treatment sample, which was not in the original sample.

Figure 5 shows a graph of the ammonia reduction after treatment evaluated for two different pH values. Test 1 represents the treatment conducted at pH 8.10. Test 2 represents the treatment conducted at pH 6.75. The y- axis is the ammonia concentration, in ppm and the x- axis the time the sample was treated in the reactor, in hours. It is evident that the reaction kinetics are enhanced when the pH is at 6.75.

Disinfectants

Five peracids were generated from their corresponding aldehydes in situ in the presence of the ODAN catalyst. The aldehydes tested were acetaldehyde, cinnamaldehyde, octanal and citral. The disinfection performance of each resulting peracid was investigated.

ODAN, 0 ₂ ,

Example 6

Peracid Concentration studies: Peracids are known to decompose to carboxylic acid and hydrogen peroxide. The decomposition is enhanced at higher pH. For instance, commercial 15% peracetic acid solutions contain residual levels of hydrogen peroxide (up to 25%) and acetic acid (up to 35%) as well as other acids such as H ₂ SO ₄ , 2,6- pyridinedicarboxylic (dipicolinic) acid, octanoic acid; peroxyoctanoic acid; sodium 1- octanesulfonate; or 1-hydroxyethylidene-1 ,1-diphosphonic acid as stabilisers. In contrast, the above peracids are produced in deionised water and achieved relatively high concentrations of peracid determined with different techniques (with values shown in Table 1).

Each aldehyde (500 pl_) was added to water, methanol, ethanol, acetic acid, or MeCN (10ml_), powdered ODAN catalyst (10 mg) was added and the solution shaken. A peroxide test strip was then use on the reaction mixture immediately. The solution was then mixed for 2 minutes further in air and the peroxide test was repeated. A balloon of O2 was then bubbled through the stirred reaction mixture and the peroxide test repeated.

The peroxide test was repeated once more after 20 minutes of O2 bubbling. The results of the peroxide concentration studies are provided in Table 1 below, showing the concentrations of each peracid in mg/L:

Table 1

Example 7

Indirect determination of disinfection capability was performed via oxidation-reduction potential (ORP) measurements. ORP (oxidation-reduction potential) studies attempt to relate the oxidation potential of solutions to their disinfection potential. Higher readouts from the ORP are, in general, positively correlated with disinfection potential. The ORP is the potential at which oxidation occurs at the anode and reduction at the cathode in an electrochemical cell. The ORP reading against survival time for various pathogens is provided in Oxidation-Reduction Potential (ORP) for Water Disinfection Monitoring, Control, and Documentation, Suslow, T. V., University of California Division of Agriculture and Natural Resources, Table 1.

The ORP readings for each reaction solution at various time intervals are provided in Table 2 below and in Figure 6. Each of the five aldehydes had a higher ORP reading (mV) at all time points than the ODAN catalyst in Dl water. Table 2

Example 8

Direct measurement of disinfection capability for each sample was investigated using E. coli cultures. Each aldehyde (500 mI_) was mixed with water (10ml_), powdered ODAN catalyst (100 mg) was added, and the reaction mixture was stirred for 10 minutes in air. The solution was filtered through a 0.2 mI_ sterile Fisher PES filter. Each resulting solution was then added to samples of E. coli strain BL21 DE3 with insert Kanamycin resistant, at v/v ratios of 1:9, 1:4, 1:2 and 1:1 made up to a total volume of 500 pl_ (Inoculation ratio 1:1020h. Incubation parameter 37°C 800 RPM. DLAB HCM 100 Probe). The optical density of each sample at each v/v ratio was measured at 600 nm with a 1 :1 ratio of sample to deionised water. The results of the optical measurements are provided in Table 3 below.

Table 3

In the cases where optical density is 0.00 or close to 0.00, growth of E. coli has been inhibited. Thus, cinnamaldehyde and acetaldehyde achieved inhibition of E. coli growth at all concentrations, while octanal achieved inhibition of E. coli at ratios of 1:2 and 1:1. Citral only achieved inhibition of E. coli at a ratio of 1:1.

[00120] Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[00121] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[00122] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.