Method for recovering materials from used absorbent hygiene products

Abstract

A method for sterilizing and decontaminating a used absorbent sanitary product contaminated with organic compounds derived from internal metabolism, including drug residues, wherein the absorbent sanitary product comprises a plastic fraction and at least one of a superabsorbent polymer (SAP) and cellulose, and the method comprises the following steps: - A step of crushing the absorbent sanitary product at least once, preferably to a uniform size of 30 cm or less, - A process of sterilizing absorbent sanitary products by heating them at a temperature of 140°C or lower and a relative pressure between 1 bar and 3 bar, - A process of oxidizing sanitary products using a hypochlorite aqueous solution at a temperature of less than 80°C. Methods that include...

Description

Technical Field

[0001] The present invention relates to a method for the recovery of materials from absorbent hygiene products, and more particularly to a method for the recovery of materials from post-use absorbent hygiene products contaminated with organic compounds derived from the metabolism of humans and animals, such as pets like cats.

Background Art

[0002] Absorbent hygiene products for human and animal use are generally composed of various materials including plastics, cellulose, and superabsorbent polymers (SAP). Since these materials have economic value even after the use of the health products, recovery and reuse are important.

[0003] However, in order to recover these materials from used absorbent hygiene products and be able to resell them, a series of serious problems caused by the presence of organic contaminants derived from metabolism must be overcome.

[0004] The first serious problem is represented by the achievement of suitable chemical-physical properties, which are obtained by a decontamination process, whereby the objects derived from used absorbent hygiene products are no longer considered waste but can become recycled materials (or secondary raw materials) for creating other absorbent products, for example. Achieving the decontamination level necessary to ensure that these objects are no longer considered waste is a well-known process called oxidation. The use of chemical oxidants such as hydrogen peroxide, persulfate, and ozone is also known, and these chemical oxidants have a standard potential E° expressed in volts greater than 1.8.

[0005] Although a number of decontamination treatments are known in the art, they seem expensive considering the type of oxidants used. In fact, due to their strong action, these oxidants guarantee no risk in the reuse of decontaminated materials, but at the same time have an adverse effect on the yield and quality of recycled materials.

[0006] Document WO2022137008A1 describes, for example, a sterilization-oxidation process of used absorbent hygiene products using a gas (i.e., ozone) as an oxidizing agent at a temperature of 60 °C or higher.

[0007] Document US Patent Application Publication No. 2019169795A1 describes a method for recovering cellulose fibers from absorbent articles. In particular, this process involves oxidatively depolymerizing the resulting superabsorbent polymer (in the form of LPA) by immersing these articles in a sodium hypochlorite solution, resulting in solubilization, thereby separating the SAP from the cellulose.

[0008] WO2021130575A1 describes a process for recycling absorbent hygiene products, which is similar to the aforementioned process, but the depolymerization-solubilization of SAP in the form of LPA is carried out using a stronger oxidizing agent (e.g., persulfate).

[0009] Document WO2014203922A1 describes a process for sterilizing-whitening hygiene products by using sodium hypochlorite in a pH range between neutral and weakly acidic.

[0010] In addition, document JP2002292304 describes a process for disinfecting diapers using sodium hypochlorite, but the process conditions are not specified, and the hypochlorite is only used as a disinfectant.

[0011] In the processes described in the known art, efficient recovery is impossible with respect to the quality and quantity of the materials used in the realization of absorbent hygiene products.

Prior Art Documents

Patent Documents

[0012]

Patent Document 1

Patent Document 2

[0013] [Non-Patent Document 1] CNR IRSA Method 2 Notebook 64, Volume 2, 1984 [Overview of the Initiative] [Problems that the invention aims to solve]

[0014] The main objective of the present invention is to provide a method for recycling used absorbent sanitary products that overcomes significant problems and limitations arising from known technologies, and enables efficient recovery without affecting or degrading the quality of the processed material.

[0015] Another object of the present invention is to provide a method for using an oxidizing agent that is readily available and less aggressive than other oxidizing agents used in known techniques, prevents degradation of recycled materials, and does not affect the quality of recovered products.

[0016] A further objective is to neutralize oxidizing agents by using readily available and easy-to-use deactivators, typically reducing agents, sometimes in combination with acidifying agents.

[0017] A further object of the present invention is to provide a method for decontaminating, sanitizing, and sterilizing these used absorbent sanitary products, comprising oxidation, neutralization, and sterilization steps for these used absorbent sanitary products.

[0018] A further objective is to make usable intermediate and final recycled products obtained from the decontamination, sanitization, and sterilization of used absorbent sanitary products. [Means for solving the problem]

[0019] These and further objectives can be achieved by methods for sterilizing and decontaminating used absorbent sanitary products contaminated with organic compounds derived from bodily metabolism, including drug residues. These absorbent sanitary products comprise a plastic fraction and at least one of superabsorbent polymers (SAP) and cellulose.

[0020] The method of the present invention involves at least the following steps: - A step of crushing used absorbent sanitary products to a uniform average size of preferably 40 cm or less, - A process of oxidizing a sanitary product using hypochlorite in an aqueous solution at a temperature of less than 80°C, - A process of sterilizing absorbent sanitary products by heating them at a temperature of 140°C or lower and a relative pressure between 1 bar and 3 bar, Includes.

[0021] In this way, components such as plastics, superabsorbent polymers (SAPs), and possibly cellulose contained in used absorbent sanitary products are thoroughly decontaminated from both organic compounds derived from bodily metabolism and unwanted chemical residues from drugs administered to both humans and animals, especially pets.

[0022] These absorbent products may include plastic and at least one of a superabsorbent polymer and a cellulose polymer.

[0023] According to a preferred embodiment, the grinding process results in an average uniform size of 40 cm or less, preferably 30 cm or less, and preferably 10 cm or less.

[0024] Preferably, the method further includes a step of inactivating these chemical residues that remain on the used absorbent sanitary product at the end of the oxidation step using an antioxidant, in particular an antioxidant selected from the group including carboxylic acid organic acids or hydrogen peroxide, if the previously used oxidizing agent was stabilized by hydroxides and / or carbonates.

[0025] Other advantages of the present invention are discussed in the specification and referred to in the dependent claims.

[0026] The present invention is further described based on embodiments that are not limited to relative scope and are illustrated by the following drawings, which refer to the following, respectively. [Brief explanation of the drawing]

[0027] [Figure 1] This diagram illustrates oxidation within a reactor. The oxidation and oxidizing agent deactivation processes are carried out sequentially within the reactor. The arrows indicate how the treated material is handled from one component to another within the system. [Figure 2] This diagram shows oxidation in an autoclave. The oxidation process is performed in the autoclave immediately before sterilization. The oxidizing agent deactivation process is always performed in the autoclave simultaneously with the cooling process. [Figure 3] This diagram shows oxidation in an autoclave after sterilization. Oxidation takes place in the autoclave after the cooling process. The deactivation process always takes place in the autoclave after the oxidation process. The arrows indicate how the treated material is handled from one component to another in the system. [Figure 4] This figure shows an autoclave-dried mixed fraction composed of cellulose, SAP, and polyolefin. Unbleached. [Figure 5] This figure shows an autoclave-dried mixed fraction composed of cellulose, SAP, and polyolefin. Evidence of post-treatment bleaching using sodium hypochlorite according to the present invention. [Figure 6]This figure shows the fraction of treated cellulose only, separated from the mixture removed from the autoclave. This is evidence of post-treatment bleaching using sodium hypochlorite according to the present invention. [Figure 7] This figure shows the ATR spectrum (attenuated total reflection spectrum) of commercially available pure SAP. The 3000 cm⁻¹ band is due to water and is not characteristic of the product being tested. [Figure 8] This figure shows the ATR spectrum (attenuated total reflection spectrum) of the used SAP obtained, as shown in Example 4. The 3000 cm⁻¹ band is due to water and is not characteristic of the product under test. [Figure 9] This figure shows the ATR (Attenuation Total Reflectance) spectrum of a mixed polyolefin used fraction separated from cellulose and SAP. The main bands coincide with the known bands shown for polypropylene (Figure 10). [Figure 10] This figure shows the ATR spectrum (attenuation total reflection spectrum) of pure polypropylene. (Data is available from the SpectraBase® database of John Wiley & Sons, Inc., https: / / spectrabase.com / ). [Figure 11] The upper part of the diagram shows the ATR spectrum (attenuation total reflectance spectrum) of the cellulose fraction recovered after thermo-oxidative post-treatment, and the lower part shows a well-known spectrum of pure cellulose available in the SpectraBase® database of John Wiley & Sons, Inc. (https: / / spectrabase.com / ). [Figure 12] This figure shows the ATR spectrum (attenuation total reflection spectrum) of a commercially available pure linear polyacrylate LPA at 40% concentration in water. The 3000 cm⁻¹ band is due to water and is not characteristic of the product being tested. [Figure 13]This figure shows the ATR spectrum (attenuation total reflectance spectrum) of a water-extractable soluble compound obtained by oxidizing SAP under known technical conditions (U.S. Patent Application Publication No. 2022 / 0257823). This spectrum is consistent with the spectrum of pure LPA (Figure 12), except for the 1000-1100 cm⁻¹ band associated with sulfates derived from Caroat®, the CO₂ band around 2350 cm⁻¹, and the 3000 cm⁻¹ band, which is derived from water and not characteristic of the product under test. [Figure 14] This figure shows the 13C-NMR spectrum of a water-soluble, linear polyacrylate LPA. This was obtained in a release test performed downstream of oxidative de-networking of the SAP superabsorbent polymer (Example 5). The signal of approximately 84 ppm of methylene group-CH2-, characteristic of the crosslinking agent in the SAP crosslinked polymer (Figure 16), has disappeared. [Figure 15] This figure shows the 13C-NMR spectrum of a water-soluble pure linear polyacrylate LPA, as shown in Reference 1. The signal of the methylene group -CH2-, approximately 84 ppm, which is characteristic of the crosslinking agent in SAP crosslinked polymers (Figure 16), has disappeared. [Figure 16] This figure shows the 13C-NMR spectrum of pure, water-insoluble SAP, as reported in Reference 1. A signal of approximately 84 ppm of methylene group -CH2-, characteristic of the crosslinking agent in SAP crosslinked polymers, is present. [Modes for carrying out the invention]

[0028] definition - In this document, the expression "liquid / solid ratio" means volume / mass ratio, where the volume, expressed in liters [L], is the volume of the liquid used, typically water or an aqueous solution (e.g., an aqueous solution of an oxidizing agent), and the mass, expressed in kilograms [kg], is the mass of the sanitary product to be processed. - In this document, the term "heated autoclave" refers to an autoclave equipped with a shell through which a high-temperature fluid flows. This fluid heats the autoclave body, thereby indirectly heating the material contained inside. - In this document, the term "thermal sterilization cycle" means exposing the material to be sterilized to different temperatures and pressures at regular time intervals in order to sterilize the material. - In this document, "used absorbent sanitary products" means, but is not limited to, infant diapers, adult diapers, adult incontinence absorbents, sanitary absorbents, bed traverses, sheets, covers, animal traverses and sanitary bags, cat litter absorbent materials, toilet paper, sanitary wet wipes for the delicate area, sanitary napkins, etc. - In this document, the term "animal traverse" refers to a pre-assembled element that includes a layer of absorbent material or superabsorbent material between two pieces of plastic film, which can be placed, for example, inside a toilet. - In this document, the term "animal hygiene bag" refers to a package containing flake-shaped superabsorbent material that is placed in the litter box in the same way as animal litter. - In this document, used absorbent sanitary products may optionally be cellulose-free. Cellulose-free products can be subjected to the same process conditions as in the present invention. An example of a substantially cellulose-free sanitary product is the Pampers Progressi® series. - In this document, the term "m / v" indicates a mass / volume ratio, where mass is expressed in kilograms [kg] and volume in liters [L]. - In this document, the terms "antioxidant" and "reducing agent" are synonymous. - In this document, when referring to measurable values ​​such as quantity or duration, the words “approximately” or “near” as used herein include variations of ±20%, ±10%, ±5%, ±1%, or ±0.1% from a given value, and these variations are appropriate for carrying out the described method. - In this document, “release test” means a simulation test of pollutant release performed by contacting a known amount of solid with a known volume of extractant (bleaching agent) for a specified time (contact time), and then separating the two processes according to the method of UNI EN12457-2:2004 to obtain a liquid eluate in the most suitable solvent.

[0029] Detailed description of the invention In this invention, the inventors have identified a procedure for decontamination and sterilization of used absorbent sanitary materials, including not only biological waste from the body metabolism of humans and animals, but also trace amounts of metabolized drugs.

[0030] This method offers the use of an economical and readily available oxidizing agent that allows for the recovery of a certain amount of superabsorbent polymer (SAP). This advantage is achievable because the oxidizing action carried out in the decontamination process is not very strong, thereby avoiding damage to recyclable materials such as cellulose, plastics, and superabsorbent polymer (SAP).

[0031] Non-limiting examples of drugs or compounds contained in drugs that are absorbed into used absorbent sanitary materials according to the present invention are as follows:

[0032] [Table 1]

[0033] Powerful decontamination means the use of chemical oxidizing agents that have a standard potential E° exceeding 1.8V and can therefore induce a strong thermodynamic reaction, thereby reducing contaminants present in used absorbent sanitary products.

[0034] Furthermore, it should be noted that the reactivity of chemical agents depends not only on the inherent characteristics of the species being tested, but also on other parameters such as temperature, time, and chemical environment, which can also lead to secondary reactions caused by undesirable parasites.

[0035] Based on these considerations, the inventors have identified hypochlorites, preferably sodium hypochlorite, calcium hypochlorite, and lithium hypochlorite, as effective alternatives to well-known oxidizing agents, because these hypochlorites respect the materials being treated and do not cause harmful secondary reactions under the specific oxidation conditions commonly employed in the process of used absorbent products.

[0036] Sodium hypochlorite, calcium hypochlorite, or lithium hypochlorite (similarly for magnesium or other metals), when mixed with water, dissociates into anions and their respective metal cations (taking sodium hypochlorite as an example) and dissolves while dissociating according to reaction (1). - anions and their respective metal cations (e.g., Na + ) while dissociating and dissolving.

[0037] NaClO → ClO - + Na + (1)

[0038] The hypochlorite anion ClO - solvated by water molecules has a reduction potential corresponding to +0.90 V related to the following half-reaction (2).

[0039] ClO - + H2O + 2e - ⇔ Cl - + 2OH - (2)

[0040] At the same time, the hypochlorite anion ClO - dissolved in water is partially hydrolyzed to produce hypochlorous acid HOCl according to the following acid-base equilibrium reaction (3).

[0041] ClO - + H2O ⇔ HClO + OH - (3)

[0042] Hypochlorous acid HClO has a standard reduction potential of +1.63 V according to the following half-reaction (4), and its respective conjugate base ClO -Unlike that, it has been found to be a much stronger oxidizing agent.

[0043] 2HClO + 2H + +2e - ⇔Cl2(gas)+2H2O (4)

[0044] Due to its pronounced oxidizing properties, HClO acts as a biocide against many pathogens (e.g., Escherichia coli) and as a decontaminant against organic residues that may be oxidized and decomposed primarily through metabolism. Sodium hypochlorite is known to be used as a whitening agent or for water purification.

[0045] However, it is necessary to consider that hypochlorous acid is also involved in another undesirable redox equilibrium (5) described below.

[0046] 2HClO ⇔ Cl₂ (gas) + 1 / 2O₂ + H₂O (5)

[0047] As can be seen from reaction (5), hypochlorous acid itself undergoes a disproportionation reaction and decomposes into chlorine gas, oxygen, and water. The greater the amount of HClO in the aqueous solution, the more pronounced the chemical equilibrium becomes.

[0048] However, this reaction is strictly pH-dependent. For example, an acidic environment in which the alkaline acid reaction (3) is likely to occur is accompanied by an increase in HClO concentration, a shift in the equilibrium reaction (5) to the product, and consequently an undesirable increase in the decomposition of hypochlorous acid.

[0049] For precisely this reason, commercially available hypochlorite solutions are generally formulated and sold under alkaline conditions.

[0050] The addition of a strong base, sodium hydroxide (NaOH), inhibits reaction (3), maintaining a low (but sufficient for oxidation) concentration of HClO, and consequently limiting the decomposition of HClO in reaction (5). Therefore, the presence of a strong base stabilizes NaClO solutions at concentrations not exceeding 15% m / v. Sodium hydroxide is also used to slow down the decomposition of sodium hypochlorite in sodium chloride and sodium chlorate in the disproportionation reaction (6), or the decomposition to chlorides based on reaction (7), which proceeds depending on temperature and / or pH conditions and / or the presence of a metal as a catalyst.

[0051] 3NaOCl (aqueous solution) → 2NaCl (aqueous solution) + NaClO3 (aqueous solution) (6)

[0052] 2NaOCl (aqueous solution) → 2NaCl (aqueous solution) + O2 (gas) (7)

[0053] For example, using hypochlorite as a relatively mild oxidizing agent with a standard potential of 1.7V or less in aqueous solution offers the significant advantage of solubilizing SAP without depolymerization, thus not affecting the yield and quality of recycled material. When a stronger oxidizing agent is used in aqueous solution, it has an excessive effect on SAP, resulting in chemical decontamination of the SAP, but under conditions where efficient and quantitative recovery is impossible.

[0054] Grinding process Absorbent sanitary products are generally crumpled up and discarded after use by consumers due to space constraints, hygiene concerns, and potential odors. However, the compact shape of discarded sanitary items makes it difficult to utilize the internal biological materials for decontamination and sterilization.

[0055] Unlike WO2021130575A1, the present invention proposes crushing used absorbent sanitary products before any chemical or heat treatment, with the aim of increasing the surface area of ​​the material exposed to decontamination and sterilization agents.

[0056] Therefore, the collection bag containing the used absorbent sanitary product is opened and crushed until the average size is less than 40 cm, preferably less than 30 cm, and more preferably between 10 cm and 30 cm.

[0057] In a preferred embodiment, the average size obtained is 10 cm or less.

[0058] According to a further embodiment, at least two grinding steps can be provided to gradually reduce the average size obtained.

[0059] In addition, preferably, the grinding can be completed entirely before oxidation, thereby preventing the grinder from being exposed to the chemical invasiveness of oxidation.

[0060] From the perspective of economic convenience of the process, it is always possible to use a general industrial grinder for grinding, such as a grinder equipped with knife-rotor technology that can guarantee the desired average size.

[0061] During the grinding process prior to decontamination, odorous emissions may be generated due to the very nature of the product. Therefore, to avoid the diffusion of these emissions into the manufacturing environment and into the outdoors, the grinding process can be carried out using a suction system to reduce airborne pollutants, such as a scrubber, or a filter that uses a water flow in the opposite direction to the flow of contaminated air, thereby cleaning the contaminated air before it is released into the atmosphere.

[0062] oxidation process As described above, the oxidation process makes it possible to decontaminate used absorbent sanitary products.

[0063] According to a preferred embodiment, the oxidation step can be carried out in a commercially available autoclave.

[0064] Before adding the oxidizing agent, and preferably always in a preferred embodiment, an initial reduced pressure between -0.9 bar and -0.7 bar may be applied, thereby promoting the subsequent absorption of the oxidizing solution by the used absorbent sanitary material. This pressure reduction also allows the pulverized sanitary product in the autoclave to dry completely, which can create favorable conditions for subsequent oxidative activity. In fact, by removing any residual moisture (even partially) absorbed and remaining in the pulverized fragments of the used absorbent sanitary product, dilution of the oxidizing agent solution can be avoided or controlled, thus ensuring better control of the concentration of the added chemical agent.

[0065] A further advantage of the drying process is that it maximizes the absorption of the oxidizing agent aqueous solution by the sanitary product, thereby actually improving the efficiency of the oxidation treatment.

[0066] The oxidizing agent aqueous solution can be administered by a sprayer (a pump system with a nozzle) in an autoclave, according to a liquid / solid ratio between 0.2 and 3, preferably between 0.8 and 2, and preferably in the range of about 1, allowing for uniform impregnation of the used absorbent sanitary product.

[0067] The amount of oxidizing agent aqueous solution is administered so that the crushed used absorbent sanitary product incorporates / absorbs / contains this solution, thereby avoiding the formation of a suspension, i.e., the liquid / solid separation process, and effectively producing a moist solid impregnated with the oxidizing agent.

[0068] Therefore, unlike known methods, the present invention treats the crushed used sanitary product not by immersing it in an oxidizing agent bath, but only with an administered aqueous solution of an oxidizing agent containing only a small amount of water necessary to dissolve the oxidizing agent and promote its oxidizing action.

[0069] Preferably, the oxidizing agent solution is administered at room temperature.

[0070] Preferably, the oxidizing agent aqueous solution is an aqueous solution of sodium hypochlorite.

[0071] The sodium hypochlorite aqueous solution introduced may have a mass concentration in the range of 6% m / v to 15% m / v.

[0072] Preferably, the mass concentration in the sodium hypochlorite aqueous solution is between 13% m / v and 15% m / v.

[0073] A sodium hypochlorite aqueous solution contains 0.01 to 0.5 moles of hypochlorite (ClO) per kilogram of used absorbent sanitary materials. - (In the sense of anions only) Preferably, 0.02 to 0.3 moles of hypochlorite (ClO) per kilogram of used absorbent sanitary article. - ) in ratio, Preferably, 0.03 to 0.17 moles of hypochlorite (ClO) per kilogram of used absorbent sanitary article. - It can be administered in the ratio of ).

[0074] The treatment of the crushed used absorbent sanitary product with an oxidizing agent solution lasts for 3 hours, preferably 2 hours, preferably 1 hour, and preferably less than 1 hour.

[0075] Treatment of crushed used absorbent sanitary products with an oxidizing agent solution can be carried out by continuously moving the material during treatment.

[0076] The treatment of the crushed used sanitary products with an oxidizing agent solution is preferably carried out at a temperature of less than 80°C, preferably less than 70°C, preferably less than 60°C, preferably less than 50°C, preferably less than 40°C, preferably less than 30°C, and preferably at room temperature.

[0077] In further, less restrictive embodiments, the oxidizing agent used is one of lithium hypochlorite, calcium hypochlorite, potassium hypochlorite, or magnesium hypochlorite.

[0078] The hypochlorite aqueous solution used, preferably sodium hypochlorite, is strongly alkaline with a pH of 13 or higher.

[0079] Since the pH of used absorbent hygiene products themselves is around 7, it is clear that when this oxidizing agent solution is added to the reaction medium, the pH will change rapidly to a value between 7.1 and 10, for example, between 7.1 and 7.5, between 7.5 and 10, between 8 and 10, and between 8.5 and 10.

[0080] Therefore, according to the present invention, the oxidation of used absorbent sanitary products is carried out under alkaline conditions.

[0081] The alkaline conditions achieved are such that they ensure appropriate oxidative activity by hypochlorite without accompanying reactions such as decomposition.

[0082] Sodium hypochlorite solution has sufficient oxidizing power to decontaminate secondary metabolites excreted from the body, while simultaneously being mild enough to prevent deterioration, damage, or decomposition of materials in used absorbent hygiene products. In particular, hypochlorite solutions, preferably sodium hypochlorite, make it possible to avoid undesirable depolymerization of superabsorbent polymers (SAPs).

[0083] In non-limiting embodiments, alkaline hypochlorites (such as NaClO, KClO, and LiClO) can be obtained in situ from calcium hypochlorite (Ca(ClO)2) by treatment with a phosphate salt.

[0084] Preferably, the phosphorus salt is orthophosphate ion (PO4 3- ) or its conjugate acid, for example, hydrogen phosphate (HPO4) 2- ) or dihydrogen phosphate (H2PO4) - ) may be based on this.

[0085] Preferably, the phosphorus salt may be a sodium salt or a potassium salt.

[0086] According to a non-limiting form of the embodiment, the oxidation process can be carried out while sucking in a special sealed tank located between a crusher arranged upstream and an autoclave arranged downstream and used in subsequent sterilization and drying processes.

[0087] Inactivation process However, at the end of the aforementioned process, the used absorbent hygiene product oxidized here may contain unreacted locally concentrated residues. The latter may cause the cellulose fibers to be partially oxidized to oxidized cellulose. In addition, due to the presence of hydroxides and carbonates with respect to bases used as stabilizers of some oxidants, such as sodium hypochlorite and calcium hypochlorite, there may be an excessive accumulation of alkaline substances, and then the waste of the process for obtaining secondary raw materials will not comply with Legislative Decree 62 / 2019 and will therefore not be acceptable from the perspective of End of Waste. In fact, the secondary raw materials subjected to the release test need to return an eluate having 5.5 < pH < 9.5 (Table 4 of Legislative Decree 62 / 2019).

[0088] To overcome this problem, it is possible to provide one or more inactivation processes downstream of the oxidation process, whereby, as required by Legislative Decree 62 / 2019, the oxidation of cellulose to oxidized cellulose can be avoided and the pH of the secondary raw material can be readjusted.

[0089] The first inactivation process relates to the inactivation of any oxidant residues still present at the end of the previous oxidation process, preferably hypochlorite. Residues of hypochlorite, if locally concentrated, may affect the quality and quantity of recycled materials because the cellulose fibers are partially oxidized to oxidized cellulose, accompanied by a decrease in the mechanical resistance of the fibers themselves.

[0090] The mechanical resistance of recycled cellulose fibers is one of the key qualities sought by cellulose buyers. Reducing or eliminating the presence of oxidized cellulose can significantly increase the value of recycled materials. This improvement concretely contributes to the economic sustainability of the process and promotes a virtuous cycle model of the circular economy where materials are continuously reused in high-value applications.

[0091] Furthermore, this inactivation prevents the accumulation of potentially hazardous unreacted oxidizing agents in the subsequent drying process of the treated used absorbent sanitary products.

[0092] The inactivation is carried out by introducing a solution containing an antioxidant or reducing agent through a sprayer located inside an autoclave, or, according to another embodiment, by drawing it into a special sealed tank in which the oxidation process is carried out.

[0093] The antioxidant solution may have a concentration of 5% by mass relative to the mass in kilograms of the used sanitary product to be processed.

[0094] Preferably, the concentration of the antioxidant corresponds to 1% by mass relative to the mass in kilograms of the used sanitary product to be processed.

[0095] As explained regarding the oxidation process, the amount of antioxidant solution added is administered in a manner that allows it to be absorbed by the crushed used sanitary products, thus avoiding the formation of a suspension.

[0096] The antioxidant (or reducing agent) can be selected from, in non-limiting examples, carboxylic acid-based organic acids or hydrogen peroxide.

[0097] Antioxidants selected from among carboxylic acid-based organic acids may include, but are not limited to, citric acid, malic acid, tartaric acid, ascorbic acid, oxalic acid, or combinations thereof.

[0098] According to another embodiment, mineral acids can be used in combination with non-acidic antioxidants. Examples of mineral acids that can be used include, but are not limited to, phosphoric acid, hydrochloric acid, sulfuric acid, or appropriately administered mixtures thereof, within the limits set by the End of Waste standard for the release of chlorides and / or sulfates (Delegated Legislative Decree 62 / 2019) (1200 and 1000 mg / l, respectively).

[0099] The aforementioned deactivation process using antioxidants lowers the pH of the medium, but always maintains an alkaline pH, i.e., above 7.

[0100] In a preferred embodiment, the antioxidant selected from among organic acids is oxalic acid.

[0101] In a particularly preferred embodiment, the antioxidant is hydrogen peroxide (H2O2), which performs its antioxidant / reducing action in the presence of an alkaline pH.

[0102] When the oxidizing agent used in the oxidation process is stabilized with hydroxides and / or carbonates, hydrogen peroxide is particularly preferred as an antioxidant.

[0103] The first deactivation step of the oxidizing agent is followed by a second deactivation step of any alkaline residues that may result, for example, when hydroxides and / or carbonates are used as stabilizers for sodium hypochlorite. A neutralizing agent for alkaline pH can be added into the autoclave in which the oxidation step is carried out (or, according to another embodiment, by suction into a special sealed tank) through a sprayer that introduces an acidic solution at a concentration of 5% by mass relative to the mass per kilogram of the used sanitary product to be processed.

[0104] Preferably, the acid concentration corresponds to 1% by mass relative to the mass in kilograms of the used sanitary product to be treated.

[0105] According to a preferred embodiment, the inactivation of alkaline residues and oxidizing agent residues can preferably be carried out simultaneously using an acidic antioxidant at a concentration of 5% by mass per kg of the used sanitary product to be treated, the acidic antioxidant may be any of citric acid, malic acid, tartaric acid, ascorbic acid, oxalic acid, or hydrogen peroxide.

[0106] Preferably, the mass concentration of the acidic antioxidant relative to the mass in kilograms of the used sanitary product to be processed is 1% by mass.

[0107] Preferably, the acidic antioxidant is oxalic acid or a percarbonate, such as sodium percarbonate.

[0108] More preferably, the acidic antioxidant is hydrogen peroxide.

[0109] Different deactivation processes depend on the type of hypochlorite used in the oxidation process. For example, sodium hypochlorite is highly reactive and is sold as a concentrated solution not exceeding 15% m / v, and is also stabilized with bases such as sodium hydroxide and / or sodium carbonate. When sodium hypochlorite is used as an oxidizing agent, a deactivation process is necessary not only to remove any oxidizing agent residue but also to remove hydroxides and / or carbonates that could affect the quality of the raw materials to be recycled.

[0110] When calcium hypochlorite is used as an oxidizing agent, its reactivity is lower than that of the aforementioned oxidizing agents, so the deactivation process mainly aims to remove oxidizing agent residue. This is because a hypochlorite solution prepared from solid calcium hypochlorite sold as 65-70% Ca(ClO)2 does not contain the same amount of alkaline compounds as a hypochlorite solution of the same concentration prepared using sodium hypochlorite sold as 14-15% NaClO. On average, the same number of moles of ClO -When using this method, the initial alkali concentration (intended as total OH) will be up to one-third of the second concentration. Therefore, pH correction may not be necessary.

[0111] According to one embodiment, when sodium hypochlorite is used as an oxidizing agent, subsequent deactivation can be carried out at different timings, first using an antioxidant and then using an acid.

[0112] According to a preferred embodiment, the deactivation step for simultaneously neutralizing pH and alkaline residue can be carried out using oxalic acid or hydrogen peroxide.

[0113] When using calcium hypochlorite, the subsequent inactivation process only requires neutralization of the oxidizing agent residue; acid-based inactivation is unnecessary.

[0114] In the case of calcium hypochlorite, the concentration in aqueous solution can be between 15 and 30% m / v.

[0115] In a particularly preferred embodiment, the deactivating chemical agent for simultaneously neutralizing the alkaline pH and oxidizing agent residue is hydrogen peroxide.

[0116] The agent for this simultaneous inactivation possesses both reducing activity, i.e., inactivation of oxidizing agent residues, and acidic activity, i.e., a reduction in the pH of the material. The acidic nature of the hydrogen peroxide solution is retained only until it is mixed with the reaction medium. In fact, the acid-base reaction that occurs between hydrogen peroxide and alkaline residues (e.g., hydroxides) in the medium solution reduces the pH from near or above 10 to a preferred value of around 8-9, thereby reducing the alkalinity of the medium, although the solution remains alkaline. Therefore, the added hydrogen peroxide is no longer dissolved in an acidic medium, but rather clearly in an alkaline medium. Under these alkaline conditions, hydrogen peroxide cannot act as an oxidizing agent and instead exhibits reducing activity, neutralizing residual oxidizing agents, for example, preferably hypochlorites, preferably sodium hypochlorite.

[0117] The deactivation reaction of unreacted hypochlorite with hydrogen peroxide produces chlorides with harmless chemical properties and elemental oxygen, which can be easily removed from the medium.

[0118] The inactivator is added, preferably in the form of an aqueous solution, preferably hydrogen peroxide, by spraying it through a sprayer in an autoclave, or, according to another embodiment, by drawing it into a special sealed tank that has been pre-oxidized.

[0119] Preferably, the number of moles of hydrogen peroxide and the number of moles of hypochlorite (ClO - The ratio (intended only for) is between 0.05 and 2.00, preferably between 0.1 and 1.3, and preferably between 0.4 and 0.8.

[0120] Preferably, the inactivation solution is added at room temperature.

[0121] Preferably, the deactivation reaction of residual alkali and unreacted oxidizing agents is carried out at room temperature.

[0122] Preferably, the deactivation reaction of residual alkali and unreacted oxidizing agents is carried out while the mixture is moving.

[0123] Preferably, the deactivation reaction of residual alkali and unreacted oxidizing agents is carried out at ambient pressure.

[0124] Preferably, the deactivation reaction of residual alkalinity and unreacted oxidizing agents leads to a pH value between 8 and 9.

[0125] Preferably, the added solution is left to react for 1 hour, preferably 45 minutes, preferably 30 minutes, preferably 20 minutes, preferably 15 minutes, preferably 10 minutes, preferably 5 minutes, preferably 1 minute.

[0126] In one embodiment, the inactivator is sodium percarbonate.

[0127] Sterilization process In a preferred embodiment, the crushed and decontaminated used absorbent sanitary products are sanitized / sterilized to remove pathogens.

[0128] In procedures described by known technologies, used absorbent sanitary products are generally sterilized in a crumpled and sealed form. For products that have not been pre-crushed, the waterproof plastic film present on the outer surface of these sanitary products acts as both a sealant and an insulator, significantly complicating the sterilization process. Indeed, if not properly broken, this film acts as an insulator and resists heat, requiring more thermal sterilization cycles (at least three). Furthermore, if the outer plastic film is intact, its presence necessitates the use of high temperatures and prolonged sterilization to ensure that thermal energy can penetrate deep into the crumpled used absorbent sanitary product. This, therefore, leads to increased energy consumption.

[0129] Alternatively, according to the present invention, sterilization of used absorbent sanitary products can be performed by reducing temperature and sterilization time by carrying out the grinding process upstream.

[0130] Sterilization is performed in a heated autoclave, and the sterilization is carried out at a temperature of less than 134°C, preferably less than 125°C, preferably 120°C, at a pressure of less than 3 bar, preferably less than 2 bar, preferably 1 bar, for a time of at least 5 minutes, preferably at least 7 minutes, preferably at least 10 minutes, preferably at least 12 minutes, preferably at least 15 minutes, preferably more than 15 minutes.

[0131] This sterilization is preferably carried out by distributing saturated steam to come into direct contact with the crushed used absorbent sanitary products, which have already been treated with an oxidizing agent and a neutralizing agent.

[0132] Preferably, this sterilization is performed while the items are in motion.

[0133] Preferably, one thermal cycle is sufficient for sterilizing the sanitary product.

[0134] Preferably, before placing the used absorbent sanitary product into the autoclave, the autoclave is depressurized to remove the air.

[0135] According to a non-limiting embodiment, sterilization is performed before the oxidation and neutralization steps, but always after the crushing of the used absorbent sanitary product.

[0136] According to this embodiment, at the end of the sterilization process, the temperature reached by the crushed and sterilized used absorbent sanitary products will cause decomposition of the oxidizing agent in the subsequent oxidation process, resulting in the oxidation of the cellulose fibers contained in these absorbent sanitary products. This phenomenon can occur at temperatures exceeding 90°C.

[0137] To avoid oxidation of cellulose fibers, which would affect the quality of the recycled material, it is possible to include a step of cooling the material to a temperature of at least 80°C before subjecting it to chemical oxidation.

[0138] According to a preferred embodiment, the cooling step includes raising the temperature of the sterilized material to 70°C.

[0139] In a more preferred embodiment, the cooling step includes raising the temperature of the sterilized material to 60°C.

[0140] The order in which the oxidation, deactivation, and sterilization steps are performed is not binding.

[0141] In a preferred embodiment of the present invention, oxidation, inactivation, and sterilization are carried out sequentially within the same autoclave.

[0142] In another embodiment, sterilization may be performed before oxidation and inactivation.

[0143] In further embodiments, sterilization can be performed between oxidation and inactivation.

[0144] In further embodiments, sterilization can be carried out simultaneously with oxidation or inactivation.

[0145] In non-limiting embodiments, the autoclave may be equipped with a non-stick coating, such as silicone, Teflon®, or other non-stick materials, which can provide protection for the autoclave against corrosion and prevent cellulose and superabsorbent materials from remaining on the inner surface of the autoclave during the subsequent drying process.

[0146] Drying process Once sterilization is complete, a partial drying process is implemented for used absorbent sanitary products to return any remaining moisture to the original level of the decontaminated product before sterilization itself.

[0147] Preferably, the residual moisture level is less than 80% m / m (intended as the percentage ratio of the mass of water in grams [g] contained in 100 grams of the treated material), preferably less than 70%, preferably less than 65%, and preferably less than 60%.

[0148] The partial drying can be carried out in an autoclave for a time of less than 60 minutes, preferably less than 45 minutes, preferably less than 30 minutes, preferably less than 20 minutes, preferably less than 15 minutes, preferably less than 15 minutes, preferably less than 12 minutes, via the application of a heated shell and void.

[0149] Next, the used absorbent sanitary product is subjected to an actual drying process, which can be carried out by introducing hot air in a dryer for at least 2 minutes, preferably at least 5 minutes, preferably at least 10 minutes, preferably at least 15 minutes, thereby reducing the residual moisture content to less than 50% by mass, preferably less than 40%, preferably less than 30%, preferably less than 20%, preferably less than 10%, preferably less than 7%, and preferably less than 5%.

[0150] Separation process After drying, the used absorbent sanitary material is sent to at least one separator, for example, a centrifuge for separating plastics from composite materials containing or composed of cellulose and / or SAP. The centrifuge utilizes materials of different densities to separate the plastic components from the non-plastic components, typically from SAP+cellulose aggregates.

[0151] SAP+cellulose aggregates are, in reality, cellulose products in which the percentage of SAP can vary, and the percentage of SAP depends on the initial amount of SAP contained in the used absorbent sanitary material and the separation performed downstream in the process. This composite product is • Cellulose with high SAP content • Cellulose with low SAP content It can be recovered in its original form.

[0152] SAP content 1 cellulose High-SAP cellulose obtained by separating plastic materials may contain superabsorbent polymer (SAP) in a percentage of the order of 30-40%, for example, 40% or less, preferably less than 35%, and preferably around 34%.

[0153] Preferably, the high-SAP cellulose may contain residual moisture at a percentage of less than 20% m / m.

[0154] Preferably, the high-SAP cellulose may contain foreign matter (other than SAP and cellulose) at a percentage of 5% m / m or less (evaluated using dry material, i.e., water-free material).

[0155] Preferably, the water absorption capacity of the high-SAP cellulose is more than 10 times its mass.

[0156] The aforementioned high-SAP cellulose can be used as a recycled material for the preparation of new absorbent sanitary products or other similar products.

[0157] Cellulose with low SAP content SAP+cellulose aggregates with a high SAP content can be subjected to further separation processes (e.g., by a rotary mechanical separator with a perforated fixed filter section) to partially or completely remove the superabsorbent polymer content, thereby producing cellulose with a low SAP content.

[0158] In fact, by utilizing the density difference between cellulose (cotton-like appearance and texture) and SAP (granular, sandy texture), it is possible to induce dissociation between the two components.

[0159] Low-content cellulose obtained by partially separating SAP from cellulose may contain superabsorbent polymer (SAP) in a percentage of 5% or less, preferably 3%, and preferably 1%.

[0160] Preferably, the cellulose with a low SAP content may contain residual moisture at a percentage of less than 20% m / m.

[0161] Preferably, the cellulose with a low SAP content may contain foreign matter (other than SAP and cellulose) at a percentage of 5% m / m or less (evaluated using dry material, i.e., water-free material).

[0162] Preferably, the water absorption capacity of the cellulose with a low SAP content is more than five times its mass.

[0163] The cellulose with low SAP content can be used as a recycled material, either directly in the manufacture of new absorbent sanitary products or other substantially similar products, or as a biochemical building block.

[0164] According to further embodiments, the further separation process makes it possible to obtain substantially pure cellulose, i.e., substantially SAP-free cellulose, and the recovered SAP can be recovered almost quantitatively from the absorbent sanitary article before use.

[0165] Recovered SAP This further separation process makes it possible to obtain pure superabsorbent polymer (SAP) in parallel, and the recovery rate of SAP depends on the number of separation cycles performed in the SAP+cellulose composite material.

[0166] Advantageously, the superabsorbent polymer is recovered purely mechanically at the end of a thermochemical process in which its structural properties are fully respected, without any change or modification of its technical properties. The recovered SAP can be considered the original material, as it retains substantially unchanged chemical and physical properties. In fact, contrary to what is reported in the well-known art, the superabsorbent polymer is never exposed to an excessive oxidizing environment that would induce depolymerization to oligomeric fragments soluble in aqueous environments (e.g., linear polyacrylates).

[0167] Subsequently, in the process of the present invention, no solubilization or undesirable depolymerization of SAP occurs, and the superabsorbent material can be completely recovered in a variable percentage, either in its pure form or in a form aggregated with cellulose in the SAP+cellulose composite material.

[0168] To verify the integrity and quality of the SAP recovered after the oxidative sterilization process, the FTIR spectrum of the ATR (attenuated total internal reflection) spectrum was recorded (Figure 8) and compared with the reference spectrum of pure SAP (Figure 7).

[0169] The two spectra match and can be superimposed (3000 cm²). -1 The broad bandwidth exceeding this is, as will be apparent to those skilled in the art, caused by the extension of water molecules absorbed by moisture, which further demonstrates that the chemical and physical properties of the material being treated are respected throughout the thermochemical process according to the present invention.

[0170] The cellulose, SAP, and plastic components constituting the absorbent product are recovered quantitatively, while preserving their structural integrity and key chemical-physical properties.

[0171] Recovered pure cellulose In the recovered cellulose fibers, the apparent density (defined in the "Determination of Apparent Density of Cellulose Fibers" paragraph in the "Analytical Methods" section) decreases, while the specific surface area increases. Pure cellulose fibers used in packaging for absorbent hygiene products have a specific surface area of ​​46 m². 2 The density is 720 mg / g, which is consistent with the specific surface area of ​​typical cotton fibers [1], and the apparent density is 720 mg / ml. On the other hand, the pure cellulose fibers (SAP% and plastic% < 1 mass%) recovered after treatment with hypochlorite according to the present invention have an apparent density not exceeding, for example, approximately 518 mg / ml (the apparent density will decrease in the case of contamination of 1 mass% or more of SAP), and a specific surface area of, for example, approximately 107 m². 2 It is / g.

[0172] The type of cellulosic material obtained after processing, having the chemical-physical properties described above, is suitable for certain purposes as building materials, such as thermal insulation and soundproofing materials, as specified in Article 4, Paragraph 3 of the delegated legislative 62 / 2019. Similar to cotton textile waste (CTW), the cellulose recovered according to the present invention can be used as a substrate for obtaining other composite materials based on low-density cellulose and a higher specific surface area, and these composite materials are low-cost in addition to being completely biodegradable.

[0173] An advantageous aspect is that the main raw materials used in realizing the sanitary product can be obtained again in a quantitatively and substantially separated or separable state.

[0174] Therefore, the method of the present invention makes it possible to obtain plastic and at least one of SAP and cellulose in a state that is separated from each other or separable from each other, and the plastic and at least one of SAP and cellulose have substantially the same properties as the starting product before being subjected to the treatment of the present invention.

[0175] It has been experimentally confirmed that after the treatment of the present invention, the cellulose is not decomposed and maintains its apparent density, and its apparent density is preferably less than 50%, preferably less than 45%, preferably less than 40%, preferably less than 35%, preferably less than 30%, preferably less than 25%, and preferably less than 20% of the apparent density of cellulose present in the sanitary product before treatment according to the present invention.

[0176] Furthermore, it was experimentally confirmed that after the treatment according to the present invention, the cellulose was not decomposed and appeared to have a higher specific surface area than the cellulose present in the sanitary product before treatment according to the present invention.

[0177] Compared to the specific surface area of ​​cellulose present in the sanitary product before treatment according to the present invention, the increase in specific surface area corresponds to at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 100%, 110%, 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190%, 200%, or more than 200%.

[0178] Similarly advantageously, SAP was found to remain unchanged after processing and to be almost 100% recoverable by mechanical separation from cellulose.

[0179] Non-limiting embodiments of the present invention will be described below with reference to the attached drawings.

[0180] Method 1 Based on the above process, it is possible to create a preferred method for recovering materials constituting contaminated absorbent sanitary products, according to the exemplary scheme shown in Figure 1.

[0181] In the first step of this method, the obtained used absorbent sanitary product is crushed in a pulverizer until it reaches a desired average size, thereby shortening the time of the subsequent stage and reducing energy consumption, thus facilitating the subsequent stage.

[0182] This is followed by an oxidation process (OX) intended to decontaminate the crushed absorbent sanitary product by introducing an oxidizing agent as an aqueous solution into the reactor using a sprayer.

[0183] According to another form of a non-limiting embodiment, the oxidation process can be carried out while suctioning in a special sealed tank located between a grinder positioned upstream and an autoclave positioned downstream for subsequent sterilization and drying processes.

[0184] Next, a deactivation step is performed to remove any localized accumulation of unreacted oxidizing agent and neutralize any alkaline residue. Depending on whether the reducing agent is acidic or not, these two operations can be performed simultaneously or separately.

[0185] The next step is to sterilize the crushed and chemically treated used absorbent sanitary products and reduce any present pathogenic microorganisms.

[0186] The cooling process (RF) aims to lower the temperature of used absorbent sanitary products after the sterilization process (ST) and return them to ambient temperature.

[0187] Next, as reported in Figure 1, a step ES is provided in which the thermochemically treated product is dried in a dryer at a temperature between 110°C and 130°C for approximately 2 hours, thereby ensuring that the color of the material remains unchanged, for example, white, as it was at the time of entry into the method.

[0188] Finally, as the final step, a process called SE is performed to separate the plastic components from the SAP+cellulose composite product using a fixed screen with holes, along with a separator such as a rotary centrifuge.

[0189] In the described method, the hypochlorite does not depolymerize the SAP and dissolve it in water as would occur by the action of other oxidizing agents such as hydrogen peroxide (used as an oxidizing agent under acidic conditions) and / or potassium peroxymonosulfate and / or potassium persulfate and / or sodium persulfate, thus making it possible to recover the superabsorbent polymer (SAP) substantially 100%, i.e., in its pure form or in combination with cellulose.

[0190] Method 2 Figure 2 shows an illustrative scheme of a further embodiment for recovering materials constituting a contaminated absorbent sanitary product.

[0191] In the first step TR of this method, the used absorbent sanitary product is placed in a pulverizer and pulverized until it reaches a desired average size, thereby shortening the time of the subsequent stage and consequently reducing energy consumption, thus facilitating the subsequent stage.

[0192] Next, the oxidizing (OX) and sterilizing (ST) processes are carried out consecutively in an autoclave to decontaminate the crushed absorbent sanitary product by oxidation and reduce pathogenic microorganisms (OX+ST).

[0193] This combined process is preferentially carried out at temperatures below 90°C to avoid the degradation of recycled material quality due to oxidation of cellulose fibers contained in absorbent hygiene products.

[0194] Subsequently, in this process method, a deactivation step IN to neutralize the base and oxidizing agent residue is performed simultaneously with a cooling step RF (IN + RF). With regard to implementation by Method 1, the neutralization operation can be provided by simultaneous acidification and reduction by selected chemical agents, or by individual treatments performed by adding each agent sequentially or simultaneously.

[0195] Next, as reported in Figure 2, a drying process ES is scheduled for the product, which has been thermochemically treated in a dryer for approximately 2 hours at a temperature between 110°C and 130°C. As a result, the color of the material does not change, as it did at the time of entry into this method, and remains, for example, white.

[0196] Finally, as the final step, a separation process (SE) is performed in which plastic components are separated from the SAP+cellulose composite product using a fixed perforated screen and a separator such as a rotary centrifuge.

[0197] Method 3 Further embodiments of the present invention follow the process scheme shown in Figure 3.

[0198] In the first step of this method, used absorbent sanitary products are placed in a pulverizer and pulverized in a pulverization process TR until a desired average size is reached. This shortens the time required for subsequent stages and, consequently, reduces energy consumption, thereby facilitating subsequent stages.

[0199] Next, a sterilization step ST is performed to remove any present pathogenic microorganisms from the crushed used absorbent sanitary products.

[0200] According to a preferred embodiment, the sterilization step also includes introducing steam into the sterilized and pulverized absorbent sanitary product.

[0201] The subsequent cooling step RF aims to lower the temperature of the used absorbent sanitary product after the sterilization step ST to a temperature at which the oxidizing agent cannot decompose when introduced into the autoclave. If the reaction occurs at a temperature exceeding 90°C, the oxidation of the cellulose fibers contained in the absorbent sanitary product will impair the quality of the recyclable material.

[0202] The subsequent oxidation step OX is intended to decontaminate the crushed and sterilized absorbent sanitary products by introducing an oxidizing agent as an aqueous solution into the autoclave using a sprayer.

[0203] In the subsequent deactivation step IN, one or more deactivation steps are performed to remove oxidizing agent residue and adjust the pH.

[0204] After a drying process of approximately two hours in a dryer at a temperature between 110°C and 130°C, the color of the material remains unchanged, just as it was at the time of entry into this method; for example, it remains white. [Examples]

[0205] Analysis method All used materials were obtained from the Contarina SpA-Treviso waste recycling plant. For the separation of granular SAP, vibrating sieves were used to their fullest extent, and all pure material was recovered by mechanical separation of commercially available disposable diapers, adult diapers, and / or incontinence traverses of the Pampers®, Chicco®, Huggies®, or Tena® brands.

[0206] Determining the amount of water. The samples were dried in a stove at 105±2°C until a constant weight was reached, according to either UNI EN15414-3:2011 - Determination of the humidity content by means of drying in a stove, or UNI 10667-16-2015A - A gravimetric method for determining the residual humidity in post-use materials. The percentage value of the humidity content P° of any mass of material is obtained from the ratio (P°-P) / P°, %(mass / mass), where the P value is the mass of the material dried to a constant weight. In principle, pre-weighed samples in containers with a known tare weight are held in a stove at 105°C for 2 hours. After 2 hours, the P1 mass value is determined. The sample is placed in the stove for another 2 hours, and after 2 hours, the P2 mass value is determined at room temperature. If the difference between P1 and P2 is greater than the sensitivity of the balance used, the sample is placed in the stove again. n-1 and P n The mass of the sample after being placed on a stove n times until the mass difference between the two values ​​equals the sensitivity of the balance at room temperature. In the example discussed here, the sensitivity is ±0.01g.

[0207] Determining the SAP percentage. As reported in WO2021 / 130575A1 - A method for separating and recovering super-absorbent polymers (SAP) from post-use absorbent sanitary products, a dry sample containing a known mass of SAP is treated in a 10% (m / v) hydrogen peroxide solution at a liquid / solid ratio of 25 ml / g at 85-95°C for 20-30 minutes until the SAP dissolves. The percentage value of SAP content P° for any mass of material is obtained from the ratio (P°-P) / P°, %(mass / mass), where the mass P value is the value of the treated material after recovery with hydrogen peroxide, filtration, washing with hot water, and drying to a constant weight.

[0208] Determination of the polyolefin percentage. As reported in UNII ISO 6427:2013, Plastics: Determination of Matter Extractable by Organic Solvents, a known mass of dried sample containing polyolefin "foil" is treated in a Soxhlet extractor under reflux in xylene at a liquid / solid ratio of at least 10 ml / g for 24 hours. The percentage value of the polyolefin content P° of any given mass of material is obtained from the ratio (P°-P) / P°, %(mass / mass), where the mass value P is the value of the treated material recovered with xylene and dried to a constant weight.

[0209] Determination of water absorption capacity. A known mass of dry sample containing SAP is suspended in excess water at a liquid / solid ratio of at least 1000 ml per gram of material with high SAP content. A clear separation step is required. After 10 minutes, the entire sample is filtered through a pre-weighed basket as shown in NF V19-002:1993-02-01 and allowed to stand for 15 minutes.

[0210] Determination of water absorption capacity and moisture retention capacity. To evaluate the amount of water absorbed by the absorbent material by comparing it to the initial mass P°, the ratio (PP°) / P° and %(mass / mass) are calculated by subtracting the mass of the basket from the mass value P of the recovered material after filtration.

[0211] Determination of the apparent density of cellulose. The apparent density can be calculated using the volume method. Place a known mass W of cellulose (in a dry state or with a predetermined moisture percentage) into a graduated container with volume V markings and place it on a balance. Calibrate the balance to zero and add water up to the volume V marking. Record the mass and temperature of the added water.

[0212] The density value D is, D=W / V A , g / ml Calculate as follows. In the formula, W is the mass of cellulose expressed in grams, and V A This represents the apparent volume of cellulose in milliliters, and is expressed by the following relationship: V A =VW w / D w , ml It is evaluated by [this method]. In the formula, W W D is the mass of water added until it matches the mark on the container's volume V. W This is the density of water at room temperature (1.00 g / ml at 25°C).

[0213] For example, it is emphasized that a 500 ml container was required for 10 g of the material to evaluate the apparent volume of cellulose fibers.

[0214] Determination of the specific surface area of ​​cellulose fibers. Specific surface area is defined as the usable surface area of ​​a solid per unit mass. In the case of cellulose fibers, the specific surface area can be determined using the colorimetric method with methylene blue, a dye that has a maximum molecular absorption spectrum centered at 664 nm.

[0215] To determine this parameter, a known amount of cellulose fiber is placed in equilibrium for 24 hours with five dye solutions of different concentrations (C1, C2, C3, C4, and C5). After 24 hours, the solid is separated from the solutions by filtration, and the volume and concentration C of the unabsorbed residual dye are determined. The concentration known as the molar extinction coefficient ε of methylene blue is measured in the visible range using a spectrophotometer, and the absorbance A at 664 nm is measured, i.e., A 664 It is obtained by measuring. C is given by relation A 664 It is obtained from =ε × b × c (b=1cm). The value of ε can be obtained by preparing solutions of known dye concentrations in the range of 1 to 30 mM, using the same relation.

[0216] To calculate the specific surface area S of cellulose, use the Langmuir linearization: C / N i =C / N m +1 / (KN m ) (8) In the formula, C represents different concentrations of C i (i is the dye concentration at equilibrium achieved in the dye solutions of 1 to 7), and N i This represents the number of moles of methylene blue absorbed per gram of cellulose fiber, and for each concentration C i Regarding N i =(V(C i -C)) / W (where i is 1 to 7) (9) (In the formula, C i (where C is the initial analytical concentration, and C is the concentration of the corresponding solution after immersing a fiber of known mass W for 24 hours.) It is calculated as follows.

[0217] In the Langmuir linearization equation (8), the intercept is 1 / KN m and slope 1 / N m We can obtain the following equation, where K is a constant and N m is the number of moles of methylene blue absorbed per gram of cellulose fiber required to form a single layer. The value of S is given by Gregg's formula

[10] : Sm 2 / g=N m ×N A×α×10 -20 (10) In the formula, N A This is Avogadro's number, which is 6.022 × 10⁻⁶. 23 mol -1 This corresponds to α, where α is the occupied surface area of ​​methylene blue, which is 197.2 Å. 2 This corresponds to N m This is the number of moles of methylene blue absorbed per gram of cellulose fiber, as mentioned above. From m 2 It is given in units of / g.

[0218] The embodiments described below should be considered merely illustrative and not intended to limit the scope of the present invention.

[0219] Tests on spent cellulose combinations (CE PCs) were conducted in combination with spent superabsorbent polymers (SAP PCs) and spent polyolefins (PO PCs), in which case the combinations simulate the materials present in contaminated absorbent products intended for recycling in order to evaluate the efficiency of chemical and recycling processes.

[0220] (Example 1) The experimental sample was prepared as follows: 100g (22g CE PC + 7g SAP PC + 1g PO PC + 70g water). The materials were already sterilized in an autoclave.

[0221] Next, the sample was treated with 90 ml of ACE® (Procter & Gamble) containing 3% activated chlorine, without adding one or more acids for neutralization. As a result, the sodium hypochlorite / solid ratio was 9.0%, equivalent to w / w, and the liquid / solid ratio was 3 (ml / g), where the liquid was an aqueous solution of hypochlorite.

[0222] In tests conducted using ACE® at pH=13, the expected decontamination and bleaching effect was achieved with an activated chlorine concentration of 10% compared to the dry state (with a liquid / solid ratio of 3 ml / g) and a contact time of 10-15 minutes.

[0223] Subsequently, to inactivate residual sodium hypochlorite, the cellulose pulp was neutralized with 10% by mass hydrogen peroxide. As a result, the material remained white and odorless (however, the L / S ratio increased to 3.5), and the contact time was at least 15 minutes.

[0224] Subsequently, treatment with a 110°C forced-convection stove returns the material to its original white state. The recovered pulp and waste adhere to pH and chloride and sulfate standards (less than 1200 mg / l and less than 1000 mg / l, respectively).

[0225] Even after drying on a stove at 110°C for 15 hours, the color remains unchanged. There is almost no browning.

[0226] The decontamination effects described above were evaluated using dried and bleached samples. A certain amount of dried sample was subjected to release tests using appropriate solvents in accordance with official methods, and the extracts were analyzed to verify the concentrations of indicators (chemical substances designated by the legislator, method, or body as indicators of system contamination) as referred to in Tables 3B and 4 of delegated legislative decree 62 / 2019. All chemical criteria referred to in Tables 3b and 4 were met.

[0227] Whitening is evaluated visually. The contaminants consist of a mixture of various shades of gray, as can be seen from the different shades of gray in Figure 4. After treatment, the cellulose-based material is white, except for some dark fragments due to residual plastic components (Figures 5 and 6).

[0228] (Example 2) The experimental sample was prepared as follows: 100g (22g CE PC + 7g SAP PC + 1g PO PC + 70g water), and the material was already sterilized in an autoclave. Next, the sample was treated with 90ml of ACE® containing 3% activated chlorine, without adding one or more acids for neutralization. This resulted in a sodium hypochlorite / solid solution ratio of 9.0%, equivalent to w / w, and a liquid / solid ratio of 3. In tests performed with ACE® at pH=13, the expected decontamination and whitening effect was obtained with an activated chlorine concentration of 10% (with a liquid / solid ratio equivalent to 3) and a contact time of 10-15 minutes, compared to the mass in kg of the solid, i.e., the used sanitary product to be treated. Subsequently, to inactivate residual sodium hypochlorite, the cellulose pulp was neutralized with 2.5% by mass oxalic acid to maintain the pH of the medium alkaline. The material remains white and odorless (although the L / S ratio increases to 3.5 with the addition of an acid solution), and the contact time is at least 15 minutes. After drying, it returns to the same white material as it was upon entry in the stove. The recovered pulp and waste adhere to the respective standards for pH and chloride and sulfate (i.e., less than 1200 mg / l and less than 1000 mg / l). With forced convection stove drying, the color remains unchanged even after drying at 110°C for 15 hours. Browning is even milder on the outer surface of the cellulose fragments. The "center" of the flakes remains white and retains its flexibility.

[0229] (Example 3) The experimental sample was prepared as follows: 100g (22g CE PC + 7g SAP PC + 1g PO PC + 70g water) was already sterilized. The sample was treated with 90ml of ACE® containing 3% activated chlorine, without adding one or more acids for neutralization. This resulted in a sodium hypochlorite / solid solution ratio of 9.0%, equivalent to w / w, and a liquid / solid ratio of 3. In tests performed with ACE® at pH=13, the expected decontamination and bleaching effect was obtained with an activated chlorine concentration of 10% compared to the dry state (with a liquid / solid ratio of 3) and a contact time of at least 10-15 minutes. Subsequently, to inactivate residual sodium hypochlorite, the cellulose pulp was neutralized with 10% by mass citric acid while maintaining the pH of the medium alkaline. The material remained white and odorless (however, the L / S ratio increased to 3.5 with the addition of the acid solution), and the contact time was at least 15 minutes. Subsequently, drying at 110°C returns the material to its almost white state, similar to the initial state. The recovered pulp and waste adhere to pH and chloride and sulfate (i.e., less than 1200 mg / l and less than 1000 mg / l) standards, respectively. The color remains unchanged even after drying at 110°C on a stove. The "center" of the flakes remains white and retains its flexibility. Similar results were obtained with tartaric acid.

[0230] In the example above, sodium hypochlorite, which is usually available in aqueous solution, is used. However, since cations do not participate in any oxidation reaction, the same results can be obtained with other hypochlorites.

[0231] In the foregoing example, hypochlorite is provided in an aqueous solution, the number of moles of hypochlorite in this solution is considered in relation to the kg of the product to be treated, and the volume of this solution is considered in relation to l / kg. When directly providing hypochlorite in an aqueous solution, the hypochlorite in the aqueous solution may indicate the amount and concentration in a solution suitable for meeting both the mol / kg and l / kg requirements for handling a predetermined mass of the used (spent) product. On the other hand, when the aqueous solution meets the mol / kg requirement but the concentration is too high, water is added to also comply with the l / kg requirement.

[0232] When using calcium hypochlorite powder for the treatment of a predetermined mass of used (spent) hygiene products, by appropriate conversion, the amount of the powder is weighed according to the mol / kg requirement, and a certain amount of water is added based on the l / kg requirement.

[0233] (Example 4) Verification of the stability of SAP against oxidation treatment under the conditions of the present invention. Research case: Oxidation treatment using NaClO at alkaline pH, followed by reduction treatment using hydrogen peroxide in an alkaline environment.

[0234] The comminuted experimental samples were prepared as follows: 20.2 g of pure cellulose + 9.1 g of pure SAP + 1.1 g of polyolefin + 70.0 g of water. Water was sprayed onto the sample composed of mixing the three components and mixed to approximate the actual material, and the average moisture was set to 65 - 70%. All the water was absorbed by the material. 69.7% of the wet material was first treated with NaClO in a reactor under alkaline pH conditions such that the hypochlorite / sample molar ratio corresponded to 0.16 mol / kg, and then treated with hydrogen peroxide always under alkaline pH conditions such that the molar ratio (of hydrogen peroxide to hypochlorite) corresponded to 0.4%. The two solutions were sprayed onto the material. Next, the material was placed in an autoclave and three cycles were carried out at 2.1 bar and 134 °C. The samples taken out from the autoclave (ICAN-Clave (registered trademark) model) were dried and subjected to mechanical separation using various wire mesh sieves covering the range from 2 mm to 150 μm. The stacked sieves were placed on a vibrating sieve machine (Retsch (registered trademark)), which made it possible to separate SAP particles with dimensions smaller than 1 millimeter from cellulose flakes and plastic threads larger than 1 millimeter. If there is a very small amount of small cellulose fibers mixed in the SAP, it is not excluded. If there is a very small amount of small SAP particles trapped in the cellulose flakes, it is not excluded. The three fractions are probably in the range of 20.3 g of cellulose with partially mixed SAP, 8.5 g of SAP, and 1.0 g of polyolefin, and the mass loss is 2%, which is consistent with the process loss estimated to be negligible.

[0235] The identity of the three isolated fractions was confirmed by analysis carried out by ATR spectroscopic photometry.

[0236] Figure 8 shows the spectrum for the recovered SAP fraction. This spectrum coincides with the spectrum of pure SAP in Figure 7 and can be superimposed.

[0237] Figure 9 shows the spectrum of the recovered polyolefin fraction. This spectrum matches the spectrum of pure polypropylene in Figure 10 (available from the SpectraBase® database of John Wiley & Sons, Inc., https: / / spectrabase.com / ).

[0238] Figure 11 shows a comparison of the spectrum of the recovered cellulose fraction (top) with the known spectrum of pure cellulose (bottom) (from the SpectraBase® database of John Wiley & Sons, Inc., https: / / spectrabase.com / ). Available from the Spectra-Database.

[0239] Therefore, Figures 7, 8, 9, 10, and 11 demonstrate how the method according to the present invention fully respects the chemical and physical properties of the material being processed and enables efficient and quantitative recovery.

[0240] The addition of cellulose with SAP was confirmed by the fact that its water absorption capacity increased: the water absorption capacity increased from 4.4 g of water per gram of cellulose before treatment to 15.6 g of water per gram of cellulose after treatment. The structural integrity of 8.3 g of SAP after treatment was confirmed by the determination of its water absorption capacity: the water absorption capacity increased from 168 g of water per gram of SAP before treatment to 172 g of water per gram of SAP after treatment. The values ​​are consistent.

[0241] Therefore, by subtracting process losses, it is possible to estimate the quantitative amount of intact SAP recovered.

[0242] (Example 5) Verification of the stability of SAP against oxidation treatment under the conditions of a known technique (US Patent Application Publication No. 2022 / 0257823). Study case: Caroat® (potassium peroxymonosulfate) at an acidic pH.

[0243] The experimental sample was prepared as follows: 22.1 g pure cellulose + 8.4 g pure SAP + 1.5 g polyolefin + 70.0 g water. The sample, composed of cellulose-based SAP particles and plastic dispersed, was mixed with water to approximate the actual material and achieve an average moisture content of 65-70%. All the water was absorbed by the material. Next, the material, in a 68.6% wet state, was treated with 8.5% by mass of Caroat® under acidic pH conditions in an open reactor, under known technique conditions (US Patent Application Publication No. 2022 / 0257823). For this purpose, the acidic oxidizing agent, i.e., a saturated solution of the 2KHSO5·KHSO4·K2SO4 triple salt, was sprayed onto the material. The material was then placed in an autoclave and subjected to 3 cycles at 2.1 bar and 134°C. Samples removed from the autoclave (ICAN-Clave® model) were mechanically ground, dried, and subjected to mechanical separation using various wire mesh sieves consistently covering a range of 2 mm to 150 μm. The stacked sieves were placed on a vibrating sieve machine (Retsch®), which allowed for the separation of SAP particles smaller than 1 mm from cellulose flakes and plastic threads larger than 1 mm. Small cellulose fibers present in small quantities within the SAP were not excluded. Small SAP particles remaining trapped in flakes within the cellulose were also not excluded. The three fractions, likely containing 21.8 g of cellulose, 4.1 g of SAP, and 1.5 g of polyolefin, were recovered by mechanical separation, with a mass loss of 14.4%, higher than the estimated process loss of 2%. However, the recovered SAP still appears significantly deficient, even after accounting for losses and any residual contaminants in the cellulose. This loss can be quantified as over 47% by mass.

[0244] The identity of the three isolated fractions is ATR and 13This was confirmed by analysis performed by 13C-NMR spectroscopy. The clear inclusion of cellulose from SAP was confirmed by the fact that its water absorption capacity increased: the water absorption capacity increased from 4.4 g of water per gram of cellulose before treatment to 9.7 g of water per gram of cellulose after treatment. While the presence of linear polyacrylate derived from the oxidative de-netting of SAP cannot be ruled out as contributing to the mass of the cellulose fraction, this polyacrylate is water-soluble, penetrates the cellulose fibers, and does not increase the water absorption capacity. In the release test performed on the cellulose, the mixture was released into water and the IR spectrum (Figure 13, 1000-1100 cm⁻¹) was measured by ATR (attenuated total internal reflection). -1 There is a band of sulfate derived from Caroat (registered trademark), while on the other hand, approximately 2350 cm -1 The CO2 absorption peak is shown in Figure 12, 3000 cm³. -1 The band is caused by water and is not characteristic of the product under test. As evidence of this, 13 Structural analysis performed by 13C-NMR carbon nuclear magnetic resonance spectrometry (Figure 14) revealed that the signal related to the methylene bridge (-CH2-) between heteroatoms, which is a typical crosslinking agent (-NCH2N-) of SAP, disappears at 84 ppm (Figure 16, pure SAP). 13 ¹¹C-NMR spectroscopy [4]) confirmed the depolymerization of SAP. Furthermore, the depolymerization was performed on SAP de-networked samples. 13 The 1C-NMR spectrum can be superimposed on the spectrum of pure LPA (Figure 15). [4]

[0245] The structural integrity of 4.1 g of SAP recovered after treatment was confirmed by both IR spectroscopy and determination of its water absorption capacity: the water absorption capacity increased from 168 g of water per gram of SAP before treatment to 156 g of water per gram of SAP after treatment. The value is within the error limits of the method used, namely the 1993 NFV standard 19-002 - Determination of Absorbent Power.

[0246] Therefore, after subtracting process losses, it is only possible to estimate a semi-quantitative amount of intact SAP recovered. The remainder is LPA, i.e., linear polyacrylate derived from the oxidative de-netting of SAP. This demonstrates how the undesirable depolymerization of LPA is promoted and the integrity of the superabsorbent polymer (SAP) is compromised, especially when using a particularly strong oxidizing agent (e.g., potassium peroxymonosulfate) under acidic reaction conditions.

[0247] (Example 6) Determination of the apparent density value of only the cellulose component in the recovered post-treatment fraction.

[0248] Ten 10.0 g samples consisting solely of cellulose fiber flakes were prepared from the cellulose sample obtained after oxidation treatment. The residual plastic fraction was evaluated and removed by selective extraction with xylene (UNIEN ISO6427:2013, Plastics: Determination of Matter Extractable by Organic Solvents), while the residual SAP fraction, which may negatively compete in apparent density, was removed by an aqueous step in the oxidation de-networking of superabsorbent polymers (WO2021 / 130575A1 - a Method for separating and recovery super-absorbent polymers (SAP) from post-consumer absorbent sanitary products). The cellulose samples processed in this manner were dried in a stove at (105±2)°C until a constant weight was reached (Moisture content in the material: residue at 105°C, CNR IRSA method 2 notebook 64, Vol. 2, 1984; UNI EN15414-3:2011 - Determination of the humidity content by drying method in stove). Next, the cellulose flake samples were individually transferred to 500 ml graduated containers on a balance with an accuracy of 0.01 g and pre-zeroed. The mass of the tested cellulose was recorded, the balance was cleared, deionized water was added up to the 500.0 ml mark, and the mass of the water added at room temperature was measured. By combining the two formulas reported in the paragraph "Determination of apparent density of cellulose" in the "Analytical Methods" section of this document, ten apparent density values ​​were obtained, and their average value (518±33) mg / ml was obtained with a relative uncertainty of 6% for the measurement. This uncertainty arises, in particular, from errors related to volume readings corresponding to the 500ml graduated container used.

[0249] (Example 7) Determination of the apparent density value of cellulose in the entry material to be processed.

[0250] Five 10.0 g samples of cellulose fiber flakes alone were prepared, derived from cellulose samples obtained from commercially available diapers, adult diapers, and mattress protector traverses. The plastic fraction of these intact products was readily removed. The SAP fraction, on the other hand, was removed by water extraction and de-netting of the superabsorbent polymer after oxidation (WO2021 / 130575A1 - a method for separating and recovering super-absorbent polymers (SAP) from post-use absorbent sanitary products). In this way, the samples were dried to a constant weight to obtain approximately 66 g of pure cellulose. Approximately 10 g of each of the five cellulose flake samples was then individually transferred to 500 ml graduated containers on a balance with an accuracy of 0.01 g and pre-zeroed. The mass of the cellulose tested with the aforementioned precision was recorded, the balance was cleared, deionized water was added up to the 500.0 ml mark, and the mass of the added water was measured. By combining the two formulas reported in the paragraph "Determination of Apparent Density of Cellulose" in the "Analytical Methods" section of this document, five apparent density values ​​were obtained, and their average value (720 ± 32) mg / ml was obtained with a relative uncertainty of 4% for the measurement. This uncertainty mainly arises from errors related to the reading of the volume corresponding to the 500 ml graduated container used. The obtained value is consistent with values ​​obtained from similar measurements performed on samples of commercially available common "hygienic hydrophilic absorbent pure cotton packing," which yielded an average value of (753 ± 30) mg / ml.

[0251] (Example 8) Determination of the specific surface area of ​​pure cellulose contained in absorbent sanitary products to be processed.

[0252] A 250.0 ml solution of methylene blue with a known concentration of 3.0 mM was prepared. From this, five solutions diluted to 1.0 - 30.0 μM were prepared to obtain the value of the molar absorption coefficient ε.

[0253] Seven lumps of 2.0 g of pure cellulose derived from commercially available diapers, adult diapers, and the filling of traverses for mattress protection were placed in seven containers, and 100.0 ml of a methylene blue solution with a concentration C of 2 - 300 μM was added and weighed for 24 hours. After 24 hours, the solution was separated from the cellulose, the volume V was determined, and the absorbance value at 664 nm was read. Knowing the value of ε, referring to equations 8, 9, and 10 reported in the paragraph "Determination of the Specific Surface Area of Cellulose Fibers" in the "Analysis Method" section of this document, the corresponding concentration C of the residual dye in the solution was calculated, and thus N i value was obtained. N m is obtained from equation (8), and the specific surface area value of 46 m 2 / g is obtained from equation (10).

[0254] (Example 9) Determination of the specific surface area of cellulose recovered after implementing the method according to the present invention.

[0255] Seven lumps of 2.0 g of used cellulose recovered and separated after thermal oxidation treatment with hypochlorite were placed in seven containers, and 100.0 ml of a methylene blue solution with a concentration C i of 2 - 300 μM was added and weighed for 24 hours. After 24 hours, the solution was separated from the cellulose, the volume V was determined, and the absorbance value at 664 nm was read. Knowing the value of ε, referring to equations 8, 9, and 10 reported in the paragraph "Determination of the Specific Surface Area of Cellulose Fibers" in the "Analysis Method" section of this document, the corresponding concentration C of the residual dye in the solution was calculated, and thereby N i value was obtained. N m value from equation (8) and the specific surface area value of 107 m 2 / g were obtained.

[0256] References [1]C.Kaewprasit,E.Hequet,N.Abidi,J.P.Gourlot,Application of Methylene Blue Adsorption to Cotton Fiber Specific Surface Area Measurement:Part I.Methodology,Journal of Cotton Science,Vol.2,p.164-173,1998. [2]L.Druel,T.Budtova,Aerogel-like(low density and high surface area)cellulose monoliths and beads obtained without supercritical-or freeze-drying,Cellulose,30,8339-8353,2023. [3]Gregg,S.J.,and K.S.W.Sing.The physical adsorption of gases by nonporous solids:The type II isotherm.Eq.2.1 p.41.1982.In Adsorption,surface area and porosity.Academic Press,London. [4]Liu,Z.S.,Rempel,G.L.,Preparation of SAP by crosslinking Acrylic Acid and Acrylamide Copolymers,Appl.Polym.Sci.64,1345,1997.

Claims

1. A method for sterilizing and decontaminating used absorbent sanitary products contaminated with organic compounds derived from internal metabolism, wherein the absorbent sanitary product comprises a plastic fraction and at least one of superabsorbent polymer (SAP) and cellulose, and the method comprises the following steps: - A step of crushing the absorbent sanitary product at least once, preferably to a uniform size of 40 cm or less, - A step of sterilizing the absorbent sanitary product by heating it at a temperature of 140°C or lower and a relative pressure between 1 bar and 3 bar, - A process of oxidizing a sanitary product using hypochlorite in an alkaline aqueous solution at a temperature of less than 80°C, - A step of inactivating using a reducing substance selected from carboxylic acid-based organic acids, hydrogen peroxide, and sodium percarbonate, Methods that include...

2. The method according to claim 1, further comprising a step of separating the obtained material.

3. The method according to claim 1 or 2, wherein the grinding step is performed during suction of the extractor hood and the extracted flow is processed through a scrubber.

4. During the oxidation process, preferably sodium hypochlorite or calcium hypochlorite-derived hypochlorite ions (ClO) are used. － The method according to any one of claims 1 to 3, wherein the concentration of is between 0.3 and 0.5 moles [mol / kg] per kilogram of the contaminated absorbent sanitary product to be treated, and the volume of the liquid is between 1 and 3 liters per kilogram of the contaminated absorbent sanitary product to be treated.

5. The method according to any one of claims 1 to 4, wherein the deactivation of the oxidized sanitary product is carried out at a pH higher than 7.

6. The method according to claim 5, wherein the deactivation step of the oxidized sanitary product is carried out using a reducing agent selected from a carboxylic acid-based organic acid, hydrogen peroxide, and sodium percarbonate, preferably hydrogen peroxide.

7. The method according to any one of claims 1 to 6, wherein the organic acid is selected from the group comprising citric acid, malic acid, tartaric acid, ascorbic acid, oxalic acid, or mixtures thereof.

8. The method according to any one of claims 1 to 7, wherein in the deactivation step, an aliquot of a pH-correcting compound is added, the pH-correcting compound is selected from an inorganic acid, preferably phosphoric acid, hydrochloric acid, sulfuric acid, or a mixture thereof, and the pH is maintained above 7.

9. The method according to any one of claims 1 to 8, wherein the sterilization step is carried out in an autoclave, the oxidation step is carried out in the same autoclave, and the autoclave comprises an oxidation-resistant, non-stick layer inside, preferably silicone or Teflon®.

10. The method according to any one of claims 1 to 9, wherein the contaminated absorbent sanitary product contains drug residue.

11. The method according to any one of claims 1 to 10, wherein the contaminated absorbent sanitary product is selected from infant diapers, adult diapers, adult incontinence absorbents, sanitary absorbents, bed traverses, sheets, covers, animal traverses and sanitary bags, cat bedding absorbent materials, toilet paper, sanitary wet wipes for the delicate area, and napkins.

12. A material comprising aliquots of a plastic and at least one of SAP and cellulose, which are separated or separable from each other, wherein the plastic and at least one of SAP and cellulose have substantially the same properties as the absorbent sanitary product before being subjected to the treatment method according to any one of claims 1 to 11, and the cellulose has a specific surface area higher than the specific surface area of ​​cellulose present in the absorbent sanitary product before treatment.

13. The material according to claim 12, wherein the cellulose has a specific surface area greater than twice the specific surface area of ​​the cellulose present in the absorbent sanitary product before treatment.

14. The material according to claim 12 or 13, wherein the cellulose has an apparent density lower than the apparent density of cellulose present in the absorbent sanitary product before treatment.

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