Method for treating a fluid and corresponding reactor

Abstract

The present invention relates to a method for treating a fluid, comprising passing said fluid through an alkali-activated inorganic polymer material obtainable by a process of treating a slag comprising AI2O3, SiO2, and at least one iron oxide and / or iron oxy-hydroxide and / or iron hydroxide, for example red mud.

Description

METHOD FOR TREATING A FLUID AND CORRESPONDING REACTORDescription

[0001] Field of the invention

[0002] The present invention relates to a method for treating a fluid and a corresponding reactor. In particular, the present invention relates to a method for treating a fluid containing organic compounds and / or ionic compounds and / or a microbiological load. More particularly, the present invention relates to a method for degrading and / or removing from a fluid organic compounds and / or ionic compounds and / or a microbiological load contained in the fluid itself.

[0003] Prior art

[0004] Wastewater purification treatments are defined as the processes for removing pollutants from wastewater generally of urban or industrial origin. These usually consist of a sequence of several steps through which the wastewater is decontaminated from undesirable substances, resulting in a final effluent of such quality that it can be discharged into soil, lakes, rivers, or the sea without causing harm thereto.

[0005] The purification cycle of wastewater usually consists of a combination of several processes that may be chemical, physical, and biological.

[0006] There currently exist numerous technologies for the chemical-physical removal of pollutants from wastewater. However, these are associated with high costs, significant environmental impact, as well as a specificity in the removal of pollutants that necessarily leads to the design of complex plants that integrate multiple technologies to achieve purification compliant with discharge requirements.

[0007] One of these technologies is activated carbon. However, it is not particularly effective in the removal of heavy metals, and its use is almost exclusively limited tothe sole removal of organic pollutants. Furthermore, activated carbon is an expensive solution with high environmental impact due to its ex situ regeneration which takes place at high temperature and in an inert atmosphere.

[0008] Another known technology is ion exchange resins. However, they are very expensive, only allow the removal of ionic pollutants, and require inlet water that is not excessively contaminated. For these reasons, one of their main applications is desalination.

[0009] Membranes of various types, appropriately functionalised, are also known for the removal of organic molecules and heavy metals by reverse osmosis or nanofiltration. However, these require very high pressures to remove the aforementioned pollutants. They also require extensive pretreatment of the waste, thus serving only as a final refinement solution. Therefore, they find main application in desalination and potabilization.

[0010] Therefore, the problem underlying the present invention is to provide a method for treating a fluid, for example wastewater, which allows the removal of a wide range of compounds. This would make superfluous the implementation of various complementary technologies to eliminate pollutants of different nature. The present invention also aims to provide a method which is economical and has low environmental impact.

[0011] Summary of the invention

[0012] The problem set out above is solved by a method for treating a fluid and by a corresponding reactor, as well as by the use of an alkali-activated inorganic polymer material as an iron-based catalyst in a chemical process, as defined in the appended claims, the definitions of which form an integral part of the present description.

[0013] A first object of the present invention is a method for treating a fluid, comprisingpassing said fluid through an alkali-activated inorganic polymer material obtainable by a process of treating a slag comprising AI2O3, SiC>2 and at least one iron oxide and / or iron oxy-hydroxide and / or iron hydroxide, said process comprising the following steps: a) possibly removing water from the slag; b) reducing the slag, possibly resulting from step a), into grains; c) mixing the grains resulting from step b) with carbon, preferably in an amount up to 50% by weight with respect to the weight of said grains; d) thermally treating the mixture resulting from step c) at a temperature between 1000 and 1600°C, preferably between 1300 and 1400°C, optionally in CO / CO2 or CO2 atmosphere, obtaining an at least partially melted mixture; e) quenching the at least partially melted mixture at a temperature between 0 and 100°C, preferably at room temperature, preferably in water or with compressed air, obtaining an at least partially vitrified mixture; f) grinding the at least partially vitrified mixture, obtaining respective grains; g) optionally, screening the grains at 150 pm, preferably 75 pm; h) alkaline activation by mixing the grains with an alkaline activator; i) polymerising the mixture resulting from step h) by means of heat treatment at a temperature between 50 and 100°C, preferably of about 80°C, obtaining an alkali- activated inorganic polymer material in the form of granules, preferably having a particle size between 0.001 and 10 mm, preferably between 0.15 and 3 mm, for example between 0.3 and 0.6 mm; j) optionally, neutralising the pH of the material resulting from step h).

[0014] A second object of the present invention is a reactor for treating a fluid, comprising:a reactor body inside which an alkali-activated inorganic polymer material is contained; an inlet for said fluid, said fluid being adapted to pass through the polymer material, preferably said fluid being air or water, preferably containing organic compounds and / or inorganic or ionic compounds and / or a microbiological load; a drain for said fluid once it has passed through the polymer material, wherein said alkali-activated inorganic polymer material is a material obtainable by the process of treating a slag comprising AI2O3, SiC>2 and at least one iron oxide and / or iron oxy-hydroxide and / or iron hydroxide as described above in connection with the method object of the present invention.

[0015] A third object of the present invention is the use of an alkali-activated inorganic polymer material as an iron-based catalyst in a chemical process, wherein said alkali- activated inorganic polymer material is a material obtainable by the process of treating a slag comprising AI2O3, SiC>2 and at least one iron oxide and / or iron oxy-hydroxide and / or iron hydroxide as described above in connection with the method object of the present invention.

[0016] Advantageously, the method for treating a fluid according to the present invention allows the removal from the fluid of both organic compounds (for example, dyes, surfactants, pharmaceuticals, PFAS) and inorganic or ionic compounds (for example, heavy metals, phosphates, ammoniacal nitrogen), as well as the abatement of the microbiological load of the fluid itself. The removal of contaminants of different types in the known art was possible by employing a plurality of complementary technologies, for example activated carbon for organic pollutants and ion exchange resins for inorganic pollutants. With the method of the present invention, on the other hand, it is possible to simultaneously remove organic and inorganic compounds, aswell as reduce the microbiological load, using a single material, which allows for the combination of multiple treatments and thus avoids the need to combine several technologies.

[0017] Compared to activated carbon, the polymer material used in the method of the present invention can be regenerated on site at low cost and with low environmental impact, making the method easily scalable and applicable to various fluids, for example wastes of different origins, including those with a high load of organic pollutants of urban origin.

[0018] Furthermore, the method object of the present invention is capable of ensuring a continuous treatment at low pressure, thus allowing the treatment of large volumes of fluid with low energy consumption.

[0019] Furthermore, the method object of the present invention uses a polymer material obtainable through a process of treating a slag, typically a metallurgical slag. Metallurgical slags are hazardous, abundant and unused slags, the disposal of which constitutes a significant environmental problem for the mining industry.

[0020] The method object of the present invention allows for the valorisation and reuse of a slag otherwise disposed of as waste. Therefore, the method of the present invention allows for a significant reduction in the annual disposal volumes and costs of metallurgical slags, which, as mentioned above, constitutes a major environmental problem, up to their complete elimination in a perspective of total circular economy.

[0021] Further features and advantages of the invention will become more apparent from the description of some illustrative embodiments, given hereinafter by way of non-limiting example.

[0022] Brief description of the figures

[0023] Figure 1 schematically illustrates an example of a reactor for treating a fluid inaccordance with an embodiment of the invention.

[0024] Detailed description of the invention

[0025] The object of the present invention is a method for treating a fluid, comprising passing said fluid through an alkali-activated inorganic polymer material obtainable by a process of treating a slag comprising alumina, silica and at least one inorganic iron-based compound selected from: iron oxides, iron oxy-hydroxides, iron hydroxides. Said alkali-activated inorganic polymer material is advantageously formed by a predominantly amorphous three-dimensional polymer matrix comprising an aluminosilicate network comprising at least Fe2+ions.

[0026] Preferably, said fluid is water or air. Within the scope of the present invention, "water" means an aqueous solution or suspension comprising substances to be removed, for example contaminants, as will clearly emerge from the description that follows; in the following description, it will also be referred to as "aqueous fluid". Similarly, within the scope of the present invention, "air" means air comprising substances to be removed, such as contaminants.

[0027] Preferably, said fluid comprises one or more organic compounds and / or one or more inorganic or ionic compounds and / or a microbiological load.

[0028] Preferably, the treatment method object of the present invention is a chemicalphysical treatment method.

[0029] Preferably, the treatment method object of the present invention comprises the degradation and / or removal from the fluid of organic compounds and / or inorganic or ionic compounds and / or microbiological load contained in said fluid.

[0030] According to an embodiment, said organic compounds and / or said inorganic or ionic compounds and / or said microbiological load are contaminants. According tothis embodiment, the treatment method object of the present invention is advantageously a method for the degradation and / or removal of contaminants from said fluid, preferably contaminated water or contaminated air. According to this embodiment, the treatment method object of the present invention is preferably a method for the purification of a fluid, preferably contaminated water or contaminated air.

[0031] According to an embodiment, said fluid is wastewater, for example, industrial, process or urban wastewater. Preferably, said wastewater does not contain suspended or precipitated solid material. According to an embodiment, said wastewater is filtered to remove any solid material contained therein before being subjected to the treatment method of the invention.

[0032] By way of example, said inorganic or ionic compounds include one or more of: heavy metals, phosphates, nitrites, nitrates, ammonium salts.

[0033] By way of example, said organic compounds include one or more of:- polycyclic aromatic hydrocarbons (PAHs);- chlorinated hydrocarbons, for example chlorobenzene, chloroform, carbon tetrachloride, 1 ,1 ,1 -trichloroethane, dichlorobenzene, trichloroethane, polychlorinated biphenyls (PCBs) and chlorinated pesticides;- fluorinated hydrocarbons, for example PFAS;- volatile organic compounds (VOCs), for example trichloroethylene (TCE) and tetrachloroethylene (PCE);- phenols and phenolic derivatives, for example phenol, cresol, bisphenol A, nonylphenol;- aliphatic, aromatic and heteroaromatic hydrocarbons, for example alkanes, alkenes, benzene, toluene, ethylbenzene, xylenes (BTEX), naphthalene, anthracene,phenanthrene, dioxins, pyridine, thiophene, furan;- alcohols and glycols, for example methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol;- ethers and esters, for example diethyl ether, MTBE (methyl tert-butyl ether), ethyl acetate, butyl acetate, phthalates;- carboxylic acids, for example formic acid, acetic acid, propionic acid, benzoic acid, phthalic acid;- amines and amides, for example aniline, methylamine, ethylamine, acetamide, benzamide;- aldehydes and ketones, for example formaldehyde, acetone, methyl ethyl ketone (MEK), cyclopentanone;- dyes and colorants, for example azo dyes, anthraquinone dyes, triphenylmethane dyes;- pesticides and herbicides, for example atrazine, diuron, malathion;- pharmaceutical compounds, for example antibiotics, analgesics, synthetic estrogens;- surfactants;- plastic additives.

[0034] According to an embodiment, the slag from which the alkali-activated inorganic polymer material is obtained comprises 5-75% by weight of at least one iron oxide and / or at least one iron oxy-hydroxide and / or at least one iron hydroxide, 2-40% by weight of AI2O3, 0.5-50% by weight of SiC>2. For example, said slag comprises said at least one iron oxide and / or at least one iron oxy-hydroxide and / or at least one iron hydroxide in an amount between 15 and 60% by weight, or in an amount between 20 and 50% by weight, or in an amount between 30 and 45% byweight. For example, said slag comprises AI2O3 in an amount between 10 and 40% by weight, or in an amount between 15 and 35% by weight, or in an amount between 20 and 30% by weight. For example, said slag comprises SiC>2 in an amount between 1 and 50% by weight, or in an amount between 5 and 30% by weight, or in an amount between 10 and 20% by weight.

[0035] Optionally, said slag further comprises CaO, preferably 0.5-45% by weight of CaO, for example 1-20% by weight of CaO; and / or TiO2, preferably 1-25% by weight of TiO2; and / or Na2O, preferably 0.1-20% by weight of Na2O.

[0036] Optionally, said slag further comprises one or more trace metal oxides, preferably in a total amount of less than 5% by weight, for example of less than 1% by weight; for example, said metal oxides that may be present in traces include MgO, MnO, V2O5, C^Os.

[0037] Preferably, said at least one iron oxide is selected from Fe2Os and FeO; preferably, said at least one iron oxy-hydroxide is FeO(OH); preferably, said at least one iron hydroxide is selected from Fe(OH)2 and Fe(OH)3. Optionally, said at least one iron oxide is a hydrated iron oxide selected from Fe2O3*nH2O and FeO*nH2O.

[0038] According to an embodiment, said slag comprises AI2O3, SiO2 and Fe2Os. Preferably, said slag comprises AI2O3, SiO2 and Fe2Os in the percentages by weight mentioned above.

[0039] According to various embodiments, said slag is selected from the group consisting of:- red mud;- ore smelting slags;- blast furnace slags;- steelmaking slags;- coal-fired power plant slags;- a mixture of one or more of the above slags.

[0040] Preferably, said slag is red mud. Red mud is a by-product of the Bayer process for refining bauxite in order to obtain alumina. Depending on the composition of the bauxite and the technology used for its processing, the resulting red mud comprises different amounts of Fe2Os, AI2O3, SiC>2, TiC>2, CaO and Na2O, preferably 5-75% by weight of Fe2Os, 2-40% by weight of AI2O3, 0.5-50% by weight of SiC>2, 0.5-45% by weight of CaO, 1-25% by weight of TiO2, 0.1-20% by weight of Na2O. Red mud may also contain trace metal oxides, for example MnO, V2O5, C^Os, for example in an amount less than 1 % by weight.

[0041] The above process of treating the slag, for example red mud, preferably comprises a first step a) of removal of water (dehydration step) from the slag, obtaining a slag in solid phase. The resulting slag may contain residual water in an amount not exceeding 10% by weight, for example not exceeding 5% by weight, or not exceeding 1% by weight.

[0042] According to an embodiment, said step a) is carried out by heat treatment at a temperature above 100°C, preferably above 110°C. For example, said step a) comprises drying the slag, for example red mud, in an oven at 110°C, obtaining tiles suitable for crushing.

[0043] According to another embodiment, said step a) is carried out in a microwave, for example at a temperature of about 50°C.

[0044] Said process of treating the slag comprises a step b) of reducing the slag into grains. If the above step a) of water removal is present, the step b) of reduction into grains is carried out on the slag in solid phase resulting from step a). Preferably, during said step b), the slag is crushed and subsequently ground, for example with ablade mill, a ball mill, or a cross beater mill.

[0045] The grains thus obtained are subjected to a step c) in which they are mixed with carbon, preferably with an amount of carbon up to 50%, or up to 40%, or up to 30%, or up to 20%, or up to 10% by weight. According to an embodiment, said grains are mixed with an amount of carbon between 1% and 10% by weight, for example between 1 % and 5% by weight, or between 1 % and 4% by weight, or between 1 % and 3% by weight, or between 1% and 2% by weight. Said percentage amounts are percentages by weight with respect to the weight of said grains. For example, the carbon is in the form of graphite, or may derive from a selected slag, for example, among those mentioned above.

[0046] According to an embodiment, during said step c), the grains may also be mixed with an amount of silica up to 50% and / or with an amount of alumina up to 50%, said percentage amounts being percentages by weight with respect to the weight of said grains. For example, said amount of silica is up to 40%, or up to 30%, or up to 20%, or up to 10%, or up to 5% by weight with respect to the weight of said grains. For example, said amount of alumina is up to 40%, or up to 30%, or up to 20%, or up to 10%, or up to 5% by weight with respect to the weight of said grains. For example, the silica is in the form of quartz, or may derive from a selected slag, for example, among those mentioned above. For example, the alumina may derive from a slag selected from those mentioned above.

[0047] Optionally, the grains resulting from the above step b) are subjected to screening at 150 pm before being subjected to the above step c) of mixing with carbon. Said screening step is conducted using sieves with mesh sizes not exceeding 150 pm, in order to exclude grains having dimensions greater than 150 pm.

[0048] The mixture resulting from the above step c) is subjected to a step d) of heattreatment at a temperature between 1000 and 1600°C, preferably between 1300 and 1400°C, obtaining a mixture that is at least partially melted. Preferably, during said step d), at least 50% of the mixture melts, more preferably at least 60%, or at least 70%, or at least 80%, or at least 90% of the mixture. Advantageously, during said step d), the mixture reaches the eutectic point.

[0049] During said step d), the Fe(lll) present is at least partially reduced to Fe(ll) by means of a carbothermal reduction reaction. Optionally, step d) is carried out in an inert atmosphere, for example nitrogen. Optionally, step d) is carried out in a CO / CO2 or CO2 atmosphere to prevent Fe(ll) from being reduced to elemental Fe. Advantageously, once melting is reached during step d), the temperature is kept constant for a variable time, for example up to one hour. For example, said step d) is carried out in an electric, gas, or induction furnace, for example inside a crucible made of alumina or zirconia or cast iron.

[0050] The mixture resulting from step d) is subjected to a step e) of quenching at a temperature between 0 and 100°C, preferably at room temperature, obtaining a mixture that is at least partially vitrified. Preferably, said step e) is carried out in water or with compressed air. During said step e), the at least partially melted mixture is cooled rapidly, preferably in few seconds.

[0051] During said step e), there is an increase in the amorphous phase of the slag.

[0052] The percentage amount of the amorphous phase in the at least partially vitrified mixture resulting from step e) is at least 10%, preferably greater than 10%, for example at least 20%, or at least 30%, or at least 40%.

[0053] Preferably, the amorphous phase prevails over the crystalline phase, the latter comprising for example crystalline residues of unreacted slag. Preferably, the at least partially vitrified mixture resulting from step e) has an amorphous phase percentageof at least 50%, or at least 55%, or at least 60%, or at least 65%, or at least 70%, or at least 75%, or at least 80%, or at least 85%, or at least 90%, or at least 95%, or at least 96%, or at least 97%, or at least 98%, or at least 99%. The % amount of the amorphous phase is obtainable, for example, by performing a quantitative XRD analysis through full spectrum Rietveld refinement, using rutile as an internal standard for quantification; the % value of the amorphous phase is obtained indirectly using the known % of internal standard and the % provided by the analysis.

[0054] The at least partially vitrified mixture is then subjected to a step f) of grinding, obtaining respective grains. The at least partially vitrified mixture is ground for a period of time sufficient to reach the desired specific surface area, which can be measured, by way of example, through the Blaine setup.

[0055] Preferably, said step f) of grinding is carried out until a specific surface area not exceeding 20,000 cm2 / g of said grains is obtained, more preferably up to 10,000 cm2 / g, for example between 4,000 and 5,000 cm2 / g.

[0056] According to a specific embodiment, said step f) of grinding is carried out for 24-48 hours, for example in a ball mill, until a specific surface area between 4,000 and 5,000 cm2 / g of said grains is obtained, measured through the Blaine setup.

[0057] If step e) of quenching is conducted in water, the at least partially vitrified mixture is advantageously dried in order to remove residual water, after which it is subjected to the subsequent step f) of grinding.

[0058] According to an embodiment, the grains resulting from step f) are subjected to a step g) of screening at 150 pm, preferably 75 pm. This step is conducted using sieves with mesh sizes not exceeding 150 pm, preferably of 75 pm, in order to exclude any fragments of elemental iron and any fragment / grain having a size greater than 150 pm, preferably greater than 75 pm.

[0059] The grains resulting from step f) of grinding of the at least partially vitrified mixture or resulting from step g) of screening, if the latter is present, are subjected to a step h) of alkaline activation by mixing the grains with an alkaline activator.

[0060] According to an embodiment, the molar ratio between the alkaline activator and the grains is between 10 and 0.1 , preferably between 1 and 0.1 , or between 0.9 and 0.1 , or between 0.8 and 0.1 , or between 0.7 and 0.1 , or between 0.6 and 0.1 , or between 0.5 and 0.1 , or between 0.4 and 0.1 , or between 0.3 and 0.1 , or between 0.2 and 0.1. For example, said molar ratio is 0.45.

[0061] According to an embodiment, said alkaline activator is a sodium silicate solution having a molar ratio SiO2 / Na2O between 0.1 and 10 and a molar ratio H2O / Na2O between 1 and 50. Preferably, the molar ratio SiO2 / Na2O is between 0.1 and 9, or between 0.1 and 8, or between 0.1 and 7, or between 0.1 and 6, or between 0.1 and 5, or between 0.1 and 4, or between 0.1 and 3, or between 0.1 and 2, or between 0.1 and 1. Preferably, the molar ratio H2O / Na2O is between 1 and 40, or between 1 and 30, or between 1 and 20, or between 1 and 10.

[0062] According to another embodiment, said alkaline activator is a potassium silicate solution having a molar ratio SiO2 / K2O between 0.1 and 10 and a molar ratio H2O / K2O between 1 and 50. Preferably, the molar ratio SiO2 / K2O is between 0.1 and 9, or between 0.1 and 8, or between 0.1 and 7, or between 0.1 and 6, or between 0.1 and 5, or between 0.1 and 4, or between 0.1 and 3, or between 0.1 and 2, or between 0.1 and 1. Preferably, the molar ratio H2O / K2O is between 1 and 40, or between 1 and 30, or between 1 and 20, or between 1 and 10.

[0063] According to other embodiments, said alkaline activator is a NaOH solution or a KOH solution.

[0064] According to a particular embodiment, said alkaline activator is a sodium silicate solution having a molar ratio SiO2 / Na2O equal to 1.6 and a molar ratio H2O / Na2O equal to 20. According to this embodiment, the molar ratio between the alkaline activator and the grains is 0.45.

[0065] The mixture resulting from said step h) is subjected to a step i) of polymerisation by heat treatment at a temperature between 30 and 100°C, or between 50 and 100°C, preferably of about 80°C, obtaining an alkali-activated inorganic polymer material in the form of granules, preferably having a particle size between 0.001 and 10 mm, preferably between 0.15 and 3 mm, for example between 0.3 and 0.6 mm.

[0066] Preferably, the polymer material resulting from said step i) is subjected to a step j) of pH neutralisation, for example with hydrochloric acid.

[0067] The presence of said step d) and the subsequent step e) makes it possible to modify the chemical and structural composition of the starting slag, at least due to the fact that the iron present as Fe(lll) is at least partially reduced to Fe(ll) and there is an increase of the amorphous fraction which makes the slag more reactive, thus allowing it to react during the polymerisation step i) forming a polymeric network itself. Advantageously, the formation of a vitrified precursor during step e) makes it possible to immobilise any hazardous metals contained in the starting slag, which could otherwise lead to leaching.

[0068] According to an embodiment, said polymerisation step i) comprises polymerising the mixture resulting from step h) inside suitable moulds, for example in an oven at 80°C for about 24 hours; extracting the resulting polymer material from the moulds; grinding the extracted polymer material; preferably, sieving the groundpolymer material, obtaining the particle size described above. According to this embodiment, the granules of the polymer material are obtained by grinding and optionally sieving the polymer resulting from polymerisation.

[0069] According to an alternative embodiment, the polymerisation step i) comprises dispersing at said temperature the mixture resulting from step h) inside a viscous and apolar medium, for example a silicone or PEG bath, preferably under mechanical stirring, and subsequently completing the polymerisation at the same temperature in an oven, for example for about 24 hours. The resulting granules, after washing with an organic solvent to remove traces of the viscous and apolar medium and subsequent removal of said solvent, are preferably sieved to the particle size mentioned above.

[0070] According to an embodiment, the process of treating the slag comprises a step g2), before step h) of alkaline activation, in which the grains are mixed with an amount of silica, for example quartz, in a weight ratio between grains and silica of between 10:1 and 5:1 , preferably equal to 9:1. Advantageously, during this step g2), the grains are seeded with inert crystalline structures that can serve as nucleation sites for zeolites.

[0071] Alternatively or in addition to mixing the grains with silica during said step g2), the grains may be mixed with CaO, preferably up to 30% by weight of CaO, and / or AI2O3, preferably up to 30% by weight of AI2O3, to improve the performances, for example mechanical, of the material. Silica, alumina and calcium oxide may derive from a slag, for example selected from those indicated above.

[0072] According to an embodiment, the process of treating the slag comprises a step h2) referred to as foaming, before step i) of polymerisation, in which the mixture resulting from step h) is mixed with a surfactant, for example cetyltrimethylammoniumbromide (CTAB), and a foaming agent, for example hydrogen peroxide or aluminium. The foaming agent, together with the surfactant, advantageously acts as a templating agent, giving a certain porosity to the material. Alternatively, said step h2) may be a mechanical foaming step.

[0073] According to an embodiment, the process of treating the slag comprises a step k) of hydrothermal curing, before the optional step j) of pH neutralisation, in which the polymer material is subjected to a temperature between 50 and 500°C, preferably between 200 and 250°C, and to a pressure between 1 and 1000 bar, preferably between 10 and 100 bar, with formation of crystalline structures on the surface, for example zeolites.

[0074] According to an embodiment, the process of treating the slag comprises a step l) of functionalisation of the polymer material with functional groups having positive or negative charge. Said step I) may be carried out alternatively or in addition to said step k). An example of functionalisation is with carboxylic groups by carbonation process, during which the polymer material is exposed to an atmosphere with high content of CO2and moisture at temperatures ranging from 25 to 300°C.

[0075] According to an embodiment, the treatment method of the invention comprises a step of feeding the fluid to be treated through the polymer material and a subsequent step of draining the treated fluid from the polymer material.

[0076] According to an embodiment, the treatment method of the invention further comprises passing hydrogen peroxide through the polymer material. Preferably, the passage of hydrogen peroxide occurs simultaneously with the passage of the fluid to be treated through the polymer material.

[0077] According to an embodiment, the treatment method of the invention comprisesa step of feeding a hydrogen peroxide solution through the polymer material. Preferably, said step occurs simultaneously with the step of feeding the fluid to be treated through the polymer material. Even more preferably, said hydrogen peroxide solution is premixed with the fluid to be treated and the resulting solution is fed through the polymer material.

[0078] According to an embodiment, wherein the fluid to be treated is water (that is, an aqueous fluid, for example an aqueous solution or suspension, as described above), the treatment method of the invention also comprises a step of emitting ultrasounds into the fluid to be treated. Advantageously, the ultrasounds are emitted into the fluid to be treated simultaneously with its passage through the polymer material and / or before its passage through the polymer material. Advantageously, according to this embodiment, hydrogen peroxide is produced in situ.

[0079] According to an embodiment, wherein the fluid to be treated is water (that is, an aqueous fluid, for example an aqueous solution or suspension, as described above), the treatment method of the invention also comprises passing the fluid to be treated through appropriate electrodes and applying electric current therethrough, resulting in the in situ production of hydrogen peroxide. Advantageously, said electrodes are immersed in the polymer material and / or in the fluid to be treated before its passage through the polymer material. According to this embodiment, advantageously, the fluid to be treated comprises dissolved oxygen.

[0080] According to various embodiments, said electrodes include a cathode selected, for example, from graphite, activated carbon and GDE (“Gas Diffusion Electrode”), and an anode selected, for example, from graphite, platinum, Ti / lrO2,Ti / RuO2, BDD (boron-doped diamond electrode).

[0081] According to an embodiment, the treatment method of the invention also provides for irradiating the polymer material with LIV-VIS light.

[0082] According to an embodiment, the polymer material is kept suspended and / or in motion, for example by bubbling air or oxygen through the polymer material itself, forming a fluidised bed. Alternatively, the polymer material may form a static or packed bed. Advantageously, the bubbling of air or oxygen enriches the fluid to be treated with oxygen, promoting the in situ production of hydrogen peroxide in the presence of a source of electric current and appropriate electrodes.

[0083] The above embodiments providing for the passage of hydrogen peroxide through the polymer material are particularly advantageous for the non-selective degradation of organic compounds from the fluid to be treated and / or for the reduction of microbiological load.

[0084] Without being bound by theory, it is believed that such compounds are adsorbed onto the surface of the polymer material and oxidised by hydroxyl radicals generated by the hydrogen peroxide during the oxidation of Fe(ll) present on the polymer material to Fe(lll). The polymer material is then, advantageously, regenerated by irradiation with LIV-VIS light and Fe(lll) is reduced to Fe(ll).

[0085] Without being bound by theory, it is believed that during the treatment method of the invention a Fenton-type reaction takes place, for example photo-Fenton, electro-Fenton, sono-Fenton, or a combination thereof.

[0086] According to an embodiment, the treatment method of the invention includes a step of feeding a saline solution (for example, NaCI) and / or an acidic solution (for example, HCI) and / or a basic solution (for example, NaOH) through the polymer material. Advantageously, said step is carried out after the passage of the fluid to be treated through the polymer material, that is, after the step of draining the treated fluidfrom the polymer material. According to this embodiment, the fluid to be treated preferably contains ionic compounds. Advantageously, during said step, the polymer material is regenerated from said ionic compounds, said ionic compounds being removed from the fluid by ion exchange with the polymer material.

[0087] Preferably, the treatment method of the invention comprises one or more steps of monitoring the pH and / or turbidity of the fluid to be treated, by means of suitable sensors.

[0088] Advantageously, the treatment method of the invention is carried out in a dedicated reactor within which said polymer material is contained.

[0089] A further object of the present invention is a reactor, in particular for carrying out the treatment method described above. An example of a reactor according to the present invention is shown in Figure 1 in schematic form, purely by way of example.

[0090] Said reactor, indicated as a whole by reference number 1 , comprises:- a reactor body 2 inside which the alkali-activated inorganic polymer material 3 is contained, said material being obtainable by the process of treating a slag comprising AI2O3, SiO2and at least one iron oxide and / or iron oxy-hydroxide and / or iron hydroxide as described above with reference to the method of the invention;- an inlet 4 for a fluid, said fluid being adapted to pass through said polymer material 3, preferably said fluid being air or water, preferably containing organic compounds and / or inorganic or ionic compounds and / or a microbiological load;- a drain 5 for said fluid once it has passed through the polymer material 3.

[0091] Therefore, the fluid to be treated is fed into the reactor 1 through the inlet 4, passes through the polymer material 3, and is discharged from the reactor 1 through the drain 5, from which the treated fluid exits.

[0092] According to the embodiment shown in the figure, the reactor body 2 is cylindrical.

[0093] According to an embodiment, the reactor 1 comprises an inlet 6 for a hydrogen peroxide solution adapted to pass through the polymer material 3.

[0094] According to an embodiment, the reactor 1 comprises at least one ultrasonic transducer (not illustrated). Advantageously, said at least one ultrasonic transducer is such as to come into contact with the fluid to be treated, preferably said at least one ultrasonic transducer is at least partially immersed in the fluid to be treated. According to an embodiment, said at least one ultrasonic transducer is at least partially immersed in the polymer material; alternatively, said at least one ultrasonic transducer is positioned outside the reactor, for example, inside a pipe feeding the fluid to be treated to the reactor.

[0095] According to an embodiment, the reactor 1 comprises an anode and a cathode (not illustrated), as well as a source of electric current (not illustrated) for supplying the current through the anode and the cathode. Advantageously, the anode and the cathode are such as to be passed through by the fluid to be treated, preferably the anode and the cathode are immersed in the fluid to be treated. According to an embodiment, said anode and said cathode are immersed in the polymer material; alternatively, they are positioned outside the reactor, for example, inside a pipe feeding the fluid to be treated to the reactor.

[0096] According to some embodiments, said electrodes include a cathode selected, for example, from graphite, activated carbon, and GDE (“Gas Diffusion Electrode”), and an anode selected, for example, from graphite, platinum, Ti / lrO2, Ti / RuO2, BDD(boron-doped diamond electrode).

[0097] According to an embodiment, the reactor 1 comprises at least one lamp 7 of LIV-VIS light. Preferably, said at least one lamp 7 of LIV-VIS light is at least partially immersed in the polymer material 3. According to the embodiment shown in the figure, the lamp 7 is housed inside a flanged blind tube 8, made for example of quartz. Preferably, the reactor 1 also comprises a controller 9 for monitoring the operating status of the LIV-VIS light lamp 7.

[0098] According to an embodiment, the reactor 1 comprises an air or oxygen bubbler 10 for bubbling air or oxygen into the polymer material 3. According to the embodiment shown in the figure, the reactor 1 also comprises an inlet 11 for air or oxygen, preferably at the bottom of the reactor 1 , and a respective outlet 12, preferably at the top of the reactor 1.

[0099] According to an embodiment, the reactor 1 comprises an inlet 13 for a saline solution and / or an acidic solution and / or a basic solution. Said solution is adapted to pass through the polymer material 3.

[0100] Preferably, the reactor 1 comprises one or more pH sensors and / or one or more turbidity sensors (not shown) adapted to monitor, respectively, the pH and turbidity of the fluid passing through the polymer material 3. In particular, said sensors are such that, in the event of acidic pH or turbidity above a certain threshold, the reactor 1 will shut down.

[0101] Another object of the present invention is the use of the alkali-activated inorganic polymer material obtainable by the treatment process described above to treat a fluid, said fluid advantageously having one or more of the characteristics described above. Said use comprises passing the fluid to be treated through the polymer material itself and, optionally, one or more of the further steps described above with reference to the treatment method. Preferably, said use comprisesdegrading and / or removing contaminants from the fluid, preferably from contaminated air or contaminated water, for example wastewater such as industrial, process or urban wastewater. Preferably, said contaminants are organic compounds and / or inorganic or ionic compounds and / or a microbiological load.

[0102] It has surprisingly been found that the alkali-activated inorganic polymer material obtainable by the process of treating a slag comprising AI2O3, SiO2and at least one iron oxide and / or iron oxy-hydroxide and / or iron hydroxide as described above with reference to the method of the invention acts as a catalyst in chemical processes catalysed by iron-based catalysts, particularly Fe(ll)-based catalysts.

[0103] Therefore, a further object of the present invention is the use of said alkali- activated inorganic polymer material as an iron-based catalyst, in particular Fe(ll)- based, in a chemical process.

[0104] Preferably, said chemical process is selected from the group consisting of: Fenton process, photo-Fenton process, electro-Fenton process, sono-Fenton process, or a combination thereof, Haber-Bosch process, Fischer-Tropsch process, Wacker reaction, ferrocene synthesis, reduction reactions of aromatic nitro compounds to aromatic amines, Friedel-Crafts alkylation reactions, catalytic oxidation reactions, for example oxidation of alkanes, alkenes and alcohols.

[0105] In particular, the photo-Fenton process involves the use of a LIV-VIS light source for the regeneration of the catalyst; the electro-Fenton process involves the in situ generation of hydrogen peroxide by an electrochemical reaction; the sono-Fenton process involves the use of ultrasounds.

[0106] It has also been surprisingly found that the alkali-activated inorganic polymer material obtainable by the process of treating a slag comprising AI2O3, SiO2and atleast one iron oxide and / or iron oxy-hydroxide and / or iron hydroxide as described above with reference to the method of the invention also acts as an adsorbent for organic compounds and / or inorganic or ionic compounds and / or microbiological load.

[0107] An object of the present invention is also a chemical process catalysed by an iron-based catalyst, particularly Fe(ll)-based, wherein said catalyst is an alkali- activated inorganic polymer material obtainable by the process of treating a slag comprising AI2O3, SiO2and at least one iron oxide and / or iron oxy-hydroxide and / or iron hydroxide as described above with reference to the method of the invention.

[0108] Experimental part

[0109] Aqueous solutions containing methylene blue (as organic compound) and zinc chloride (as heavy metal), as well as industrial wastewater, were subjected to the treatment method of the present invention. Tests were also conducted to determine the catalytic capacity of the alkali-activated inorganic polymer material.

[0110] The alkali-activated inorganic polymer material was obtained by a treatment process of red mud coming from the Euroallumina aluminium extraction plant in Sardinia, as described below.

[0111] The red mud was dried in an oven at 110°C, obtaining solid red mud in the form of tiles. The red mud so obtained was then crushed and subsequently ground with a blade mill. The resulting grains were screened at 150 pm using square mesh sieves with a side of 150 pm.

[0112] The grains of red mud were mixed with an amount of quartz equal to 10% by weight and an amount of graphite equal to 1.44% by weight.

[0113] The resulting mixture was placed inside an alumina crucible in an electric (or gas) furnace, which was brought to 1300-1400°C, until melting of the red mud-basedmixture. The temperature was maintained constant for about one hour.

[0114] The mixture was then cooled rapidly in a water tank (or with compressed air) to room temperature, in order to vitrify the molten mixture and increase the amorphous fraction.

[0115] The vitrified mixture was recovered, dried and ground, first in a grinder and then in a ball mill. The grinding in the ball mill lasted about 48 hours, reaching a specific surface area of about 4500-5000 cm2 / g. The resulting grains were then screened at 75 pm using square mesh sieves with a side of 75 pm.

[0116] Said grains were then mixed with quartz in a weight ratio of 9:1.

[0117] To the resulting mixture was added an activating solution of sodium silicate in a liquid-to-solid mass ratio of 0.45, having the following molar ratios: SiO2 / Na2O = 1.6 and H2O / Na2O = 20.

[0118] Mixing was carried out obtaining a solution which was poured into moulds, specifically polypropylene (or silicone or metal) test tubes. Said moulds were placed in an oven at 80°C for 24 hours. After 24 hours, the samples were extracted from the moulds.

[0119] The resulting samples were ground and sieved to obtain the desired particle size range ( / .e. 0.15-3 mm), and finally the pH was neutralised with HCI, obtaining the desired alkali-activated inorganic polymer material.

[0120] Treatment of aqueous solutions containing methylene blue and aqueous solutions containing zinc chloride

[0121] The following procedure was used, on a laboratory scale, to determine the specific uptake of pollutants (methylene blue and Zn2+ion from zinc chloride) by the alkali-activated inorganic polymer material obtained with the procedure describedabove:1) A stock solution was prepared with a concentration of 1000 ppm of methylene blue and a stock solution was prepared with a concentration of 1000 ppm of Zn2+.2) Standards of known concentration were prepared by diluting the stock solutions to construct the calibration curve of the spectrophotometer.3) Solutions of different concentrations of methylene blue and Zn2+were prepared by diluting the respective stock solutions.4) The resulting solutions were poured into 50 mL test tubes, inside which a specific amount of the alkali-activated inorganic polymer material had been previously weighed. For methylene blue 0.1 g of polymer material were used, while for Zn2+ion 0.05 g of polymer material were used.5) The test tubes were kept under agitation with a rotary shaker at constant temperature for about 24 hours.6) The final concentration of the solutions contained in the test tubes was measured.

[0122] The specific uptake is the difference between the initial concentration and the final concentration, multiplied by the volume and normalised to the mass of polymer material used.

[0123] For the determination of the final concentration, two different procedures were employed for the solutions containing methylene blue and for the solutions containing Zn2+.

[0124] For the solutions containing methylene blue:1) 15 mL of solution were transferred into a 15 mL test tube, centrifuged and, if necessary, diluted.2) 3 or 4 mL of the supernatant were collected using a Pasteur pipette and pouredinto a disposable 10 mm square cuvette made of optical grade PMMA. Absorbance was measured at 664 nm and, using the calibration curve and the dilution factor, the concentration was determined.

[0125] Table 1 below reports the values of initial concentration (Ci), final concentration (Cf), specific uptake, and percentage of removal of methylene blue by the polymer material.Table 1

[0126] For the solutions containing Zn2+:1) 15 mL of solution were transferred into a 15 mL test tube, centrifuged and, if necessary, diluted.2) The initial and final concentrations of the Zn2+ion were determined with a LIV-VISspectrophotometer using a colorimetric method.3) 3 or 4 mL of the supernatant were collected using a Pasteur pipette and poured into a disposable 10 mm square cuvette made of optical grade PMMA. Absorbance was measured at 620 nm and, using the calibration curve and the dilution factor, the concentration was determined.

[0127] Table 2 below reports the values of initial concentration (Ci), final concentration (Cf), specific uptake, and percentage of removal of Zn2+ion by the polymer material.Table 2

[0128] Table 3 below reports the values of maximum specific uptake for methylene blue and Zn2+ion, which were determined according to the Langmuir model describing the monolayer adsorption on ideal adsorbent surfaces.Table 3

[0129] Treatment of industrial wastewater

[0130] The treatment according to the invention was carried out, separately, on: 1) a wastewater from an aluminium anodizing plant; 2) a wastewater from an alkaline zinc-nickel galvanic plant; 3) a wastewater from the treatment of wool mill effluents.

[0131] The procedure employed, on a laboratory scale, to test the treatment capacity of said industrial wastewaters by means of the alkali-activated inorganic polymer material obtained with the procedure described above is reported below.

[0132] A bench reactor was loaded with 10 grams of the alkali-activated inorganic polymer material. Subsequently, the wastewater was continuously loaded into the reactor with an Empty Bed Contact Time (EBCT) of 60 minutes for 24 hours using peristaltic pumps. The concentration of the pollutants contained in the wastewater was measured before and after the treatment, using the same method employed to determine the concentration of Zn2+ion in aqueous solutions containing zinc chloride and described in the preceding description ( / .e., with a quantitative colorimetric method using a LIV-VIS spectrophotometer and a calibration curve).

[0133] Table 4 below reports the values of initial concentration (Ci) and finalconcentration (Cf) of Zn2+, Ni2+, Cu2+, and Fe3+contained in the wastewater coming from an aluminium anodizing plant, as well as their percentage of reduction by the polymer material.Table 4

[0134] Table 5 below reports the values of initial concentration (Ci) and final concentration (Cf) of Zn2+and Ni2+contained in the wastewater coming from an alkaline zinc-nickel galvanic plant, specifically from a dynamic first rinse tank, as well as their percentage of reduction by the polymer material.Table 5

[0135] The metals removed by the polymer material were advantageously recovered to reformulate the galvanic bath, thereby advantageously reducing the economic and environmental impact of the process.

[0136] Table 6 below reports the values of initial concentration (Ci) and final concentration (Cf) of the pollutants (total surfactants, ammonium ion, COD, Zn2+)contained in the wastewater coming from the treatment of wool mill effluents, as well as the percentage of reduction of said pollutants by the polymer material.Table 6

[0137] Advantageously, total surfactants and COD were degraded within discharge limits.

[0138] Test for determining the catalytic capacity of the alkali-activated inorganic polymer material obtained by the above described procedure

[0139] This test is intended to demonstrate, by way of example, the catalytic degradation of an organic dye, specifically methylene blue, in a continuous flow system.

[0140] 5 grams of alkali-activated inorganic polymer material obtained by the above described procedure were used as the stationary catalytic phase inside a column reactor. An aqueous solution having a concentration of 50 ppm of methylene blue was continuously fed by a peristaltic pump with a flow rate of 0.17 mL / min, after in-line mixing with 30% hydrogen peroxide (0.05 mL / min). The effluent was collected in an approximately 2-liter tank.

[0141] The effluent collected after the first 7 days of operation and the effluent collected during the subsequent 7 days of operation were analysed using LIV-VISspectrophotometry at 664 nm.

[0142] The results showed complete removal of methylene blue both during the first 7 days of operation and during the subsequent 7 days of operation, with an overall degradation of 132.4 mg of methylene blue over 14 days. This amount is significantly higher than the theoretical adsorption capacity of the polymer material (equal to 75 mg, calculated as 15 mg / g), thereby confirming the predominantly catalytic nature of this removal process.

[0143] The above test has therefore made it possible to demonstrate the effectiveness of the polymer material in the continuous treatment of water contaminated by organic dyes.

[0144] It is evident that what has been described is only a particular embodiment of the present invention. A person skilled in the art will be able to make any necessary modifications to adapt the invention to specific conditions, without departing from the scope of protection as defined in the appended claims.

Claims

CLAIMS1. A method for treating a fluid, comprising passing said fluid through an alkali- activated inorganic polymer material obtainable by a process of treating a slag comprising AI2O3, SiC>2 and at least one iron oxide and / or iron oxy-hydroxide and / or iron hydroxide, said process comprising the following steps: a) possibly removing water from the slag; b) reducing the slag, possibly resulting from step a), into grains; c) mixing the grains resulting from step b) with carbon, preferably in an amount up to 50% by weight with respect to the weight of said grains; d) thermally treating the mixture resulting from step c) at a temperature between 1000 and 1600°C, preferably between 1300 and 1400°C, optionally in CO / CO2 or CO2 atmosphere, obtaining an at least partially melted mixture; e) quenching the at least partially melted mixture at a temperature between 0 and 100°C, preferably at room temperature, preferably in water or with compressed air, obtaining an at least partially vitrified mixture; f) grinding the at least partially vitrified mixture, obtaining respective grains; g) optionally, screening the grains at 150 pm, preferably 75 pm; h) alkaline activation by mixing the grains with an alkaline activator; i) polymerizing the mixture resulting from step h) by means of heat treatment at a temperature between 50 and 100°C, preferably of about 80°C, obtaining an alkali- activated inorganic polymer material in the form of granules, preferably having a particle size between 0.001 and 10 mm, preferably between 0.15 and 3 mm, for example between 0.3 and 0.6 mm; j) optionally, neutralizing the pH of the material resulting from step h).

2. A method according to claim 1 , wherein said grinding step f) is carried out until a specific surface area not exceeding 20,000 cm2 / g of said grains is obtained, preferably up to 10,000 cm2 / g, for example between 4,000 and 5,000 cm2 / g.

3. A method according to claim 1 or 2, comprising a step g2), before the alkaline activation step h), wherein the grains are mixed with silica in a weight ratio of grains to silica between 10:1 and 5:1 , preferably equal to 9:1.

4. A method according to any one of the preceding claims, comprising a step h2), before the polymerization step i), wherein the mixture resulting from step h) is mixed with a surfactant, for example cetyltrimethylammonium bromide (CTAB), and a foaming agent, for example hydrogen peroxide.

5. A method according to any one of the preceding claims, wherein said step i) includes polymerizing the mixture resulting from step h) inside suitable molds, extracting the obtained polymer material from the molds, grinding the extracted polymer material, and preferably sieving the ground polymer material obtaining a particle size preferably between 0.15 and 3 mm, for example between 0.3 and 0.6 mm.

6. A method according to any one of the preceding claims, comprising a hydrothermal curing step k), wherein the polymer material resulting from step i) is subjected to a temperature between 50 and 500°C, preferably between 200 and250°C, and to a pressure between 1 and 1000 bar, preferably between 10 and 100 bar, with formation of crystalline structures on the surface, for example zeolites.

7. A method according to any one of the preceding claims, wherein said slag comprises 5-75% by weight of at least one iron oxide and / or iron oxy-hydroxide and / or iron hydroxide, 2-40% by weight of AI2O3, 0.5-50% by weight of SiC>2, optionally said slag further comprises 0.5-45% by weight of CaO and / or 1-25% by weight of TiC>2 and / or 0.1-20% by weight of Na2O.

8. A method according to any one of the preceding claims, wherein said at least one iron oxide is selected from Fe2Os and FeO; said at least one iron oxyhydroxide is FeO(OH); said at least one iron hydroxide is selected from Fe(OH)2 and Fe(OH)s, optionally said at least one iron oxide being a hydrated iron oxide selected from Fe2C>3*nH2O and FeO*nH2O.

9. A method according to any one of the preceding claims, wherein said slag comprises AI2O3, SiC>2 and Fe2Os, preferably said slag being red mud.

10. A method according to any one of the preceding claims, wherein said fluid is air or water, preferably containing one or more organic compounds and / or one or more inorganic or ionic compounds and / or a microbiological load.

11. A method according to claim 10, being a method of degrading and / or removing from the fluid organic compounds and / or inorganic or ionic compounds and / or the microbiological load contained in said fluid.

12. A method according to claim 10 or 11 , wherein said organic compounds are selected from the group consisting of: polycyclic aromatic hydrocarbons (PAHs); chlorinated hydrocarbons, for example chlorobenzene, chloroform, carbon tetrachloride, 1 ,1 ,1 -trichloroethane, dichlorobenzene, trichloroethane, polychlorinated biphenyls (PCBs), and chlorinated pesticides; fluorinated hydrocarbons, for example PFAS; volatile organic compounds (VOCs), for example trichloroethylene (TCE) and tetrachloroethylene (PCE); phenols and phenolic derivatives, for example phenol, cresol, bisphenol A, nonylphenol; aliphatic, aromatic, and heteroaromatic hydrocarbons, for example alkanes, alkenes, benzene, toluene, ethylbenzene, xylenes (BTEX), naphthalene, anthracene, phenanthrene, dioxins, pyridine, thiophene, furan; alcohols and glycols, for example methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol; ethers and esters, for example diethyl ether, MTBE (methyl tert-butyl ether), ethyl acetate, butyl acetate, phthalates; carboxylic acids, for example formic acid, acetic acid, propionic acid, benzoic acid, phthalic acid;amines and amides, for example aniline, methylamine, ethylamine, acetamide, benzamide; aldehydes and ketones, for example formaldehyde, acetone, methyl ethyl ketone (MEK), cyclopentanone; dyes and colorants, for example azo dyes, anthraquinone dyes, triphenylmethane dyes; pesticides and herbicides, for example atrazine, diuron, malathion; pharmaceutical compounds, for example antibiotics, analgesics, synthetic estrogens; surfactants; plastic additives.

13. A method according to any one of the preceding claims, comprising passing hydrogen peroxide through the polymer material, preferably simultaneously with the passage of the fluid to be treated through the polymer material.

14. A method according to claim 13, comprising a step of feeding a hydrogen peroxide solution through the polymer material, preferably said hydrogen peroxide solution is premixed with the fluid to be treated and the resulting solution is fed through the polymer material.

15. A method according to claim 13 or 14, comprising a step of emitting ultrasounds into the fluid to be treated, the fluid to be treated being aqueous, preferably the ultrasounds being emitted into the fluid to be treated simultaneouslywith its passage through the polymer material and / or before its passage through the polymer material.

16. A method according to any one of claims 13 to 15, comprising passing the fluid to be treated through appropriate electrodes and applying electric current therethrough, resulting in the in situ production of hydrogen peroxide, the fluid to be treated being aqueous.

17. A method according to any one of claims 13 to 16, wherein said polymer material is irradiated with LIV-VIS light.

18. A method according to any one of the preceding claims, wherein said fluid contains ionic compounds and said method comprises passing a saline solution and / or an acidic solution and / or a basic solution through the polymer material, preferably following the passage of the fluid to be treated through the polymer material.

19. A reactor (1) for treating a fluid, comprising: a reactor body (2) inside which an alkali-activated inorganic polymer material (3) is contained; an inlet (4) for said fluid, said fluid being adapted to pass through the polymer material (3), preferably said fluid being air or water, preferably containing organic compounds and / or inorganic or ionic compounds and / or a microbiological load; a drain (5) for said fluid once it has passed through the polymer material (3),wherein said alkali-activated inorganic polymer material (3) is a material obtainable by a process of treating a slag comprising AI2O3, SiC>2 and at least one iron oxide and / or iron oxy-hydroxide and / or iron hydroxide, said process comprising the following steps: a) possibly removing water from the slag; b) reducing the slag, possibly resulting from step a), into grains; c) mixing the grains resulting from step b) with carbon, preferably in an amount up to 50% by weight with respect to the weight of said grains; d) thermally treating the mixture resulting from step c) at a temperature between 1000 and 1600°C, preferably between 1300 and 1400°C, optionally in CO / CO2 or CO2 atmosphere, obtaining an at least partially melted mixture; e) quenching the at least partially melted mixture at a temperature between 0 and 100°C, preferably at room temperature, preferably in water or with compressed air, obtaining an at least partially vitrified mixture; f) grinding the at least partially vitrified mixture, obtaining respective grains; g) optionally, screening the grains at 150 pm, preferably 75 pm; h) alkaline activation by mixing the grains with an alkaline activator; i) polymerizing the mixture resulting from step h) by means of heat treatment at a temperature between 50 and 100°C, preferably of about 80°C, obtaining an alkali- activated inorganic polymer material in the form of granules, preferably having a particle size between 0.001 and 10 mm, preferably between 0.15 and 3 mm, for example between 0.3 and 0.6 mm; j) optionally, neutralizing the pH of the material resulting from step h).

20. A reactor (1) according to claim 19, comprising an inlet (6) for a hydrogen peroxide solution, said solution being adapted to pass through the polymer material (3).

21. A reactor (1) according to claim 19 or 20, comprising an ultrasonic transducer, preferably at least partially immersed in the fluid to be treated, and / or comprising an anode, a cathode, and a source of electric current, the anode and the cathode being such as to be passed through by the fluid to be treated.

22. A reactor (1) according to any one of claims 19 to 21 , comprising at least one LIV-VIS light lamp (7), preferably said at least one lamp (7) being at least partially immersed in the polymer material (3).

23. A reactor (1) according to any one of claims 19 to 22, comprising an inlet (13) for a saline solution and / or an acidic solution and / or a basic solution, said solution being adapted to pass through the polymer material (3).

24. Use of an alkali-activated inorganic polymer material as an iron-based catalyst, in particular Fe(ll)-based, in a chemical process, said alkali-activated inorganic polymer material being obtainable by a process of treating a slag comprising AI2O3, SiC>2 and at least one iron oxide and / or iron oxy-hydroxide and / or iron hydroxide, said process comprising the following steps: a) possibly removing water from the slag; b) reducing the slag, possibly resulting from step a), into grains;c) mixing the grains resulting from step b) with carbon, preferably in an amount up to 50% by weight with respect to the weight of said grains; d) thermally treating the mixture resulting from step c) at a temperature between 1000 and 1600°C, preferably between 1300 and 1400°C, optionally in CO / CO2 or CO2 atmosphere, obtaining an at least partially melted mixture; e) quenching the at least partially melted mixture at a temperature between 0 and 100°C, preferably at room temperature, preferably in water or with compressed air, obtaining an at least partially vitrified mixture; f) grinding the at least partially vitrified mixture, obtaining respective grains; g) optionally, screening the grains at 150 pm, preferably 75 pm; h) alkaline activation by mixing the grains with an alkaline activator; i) polymerizing the mixture resulting from step h) by means of heat treatment at a temperature between 50 and 100°C, preferably of about 80°C, obtaining an alkali- activated inorganic polymer material in the form of granules, preferably having a particle size between 0.001 and 10 mm, preferably between 0.15 and 3 mm, for example between 0.3 and 0.6 mm; j) optionally, neutralizing the pH of the material resulting from step h).

25. Use according to claim 24, wherein said chemical process is selected from the group consisting of: Fenton process, photo-Fenton process, electro-Fenton process, sono-Fenton process, or a combination thereof, Haber-Bosch process, Fischer-Tropsch process, Wacker reaction, ferrocene synthesis, reduction reactions of aromatic nitro compounds to aromatic amines, Friedel-Crafts alkylation reactions, catalytic oxidation reactions, for example oxidation of alkanes, alkenes, and alcohols.

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