Method for sterilization and decontamination of post-consumer absorbent hygiene products contaminated with organic compounds originating from human metabolism

Abstract

A method for sanitizing and decontaminating a post-consumer absorbent hygiene product contaminated with organic compounds originating from human metabolism and comprising drug residues, said post-consumer absorbent hygiene product comprising plastic, superabsorbent polymer (SAP) and optionally cellulose parts, said method comprising at least the following steps: i) sanitizing (SR) said post-consumer absorbent hygiene product by heating to a temperature equal to or lower than 140°C and at a pressure comprised between 1 bar and 3.6 bars to obtain a sanitized post-consumer absorbent hygiene product; and ii) removing the organic compounds contamination (DC) of said sanitized post-consumer absorbent hygiene product by an oxidative treatment. Said oxidative treatment is preferably carried out by contacting said sanitized post-consumer absorbent hygiene product with an ozone-containing gas at a temperature equal to or higher than 60°C, more preferably between 60°C and 80°C. The sanitized post-consumer absorbent hygiene product subjected to said decontamination step has a humidity of less than 80%, preferably comprised between 60% and 75%.

Description

Technical Field

[0001] This disclosure relates to the recycling of post-consumer absorbent hygiene products. Specifically, this disclosure relates to methods for sterilizing and removing organic compound contamination from human metabolism in post-consumer absorbent hygiene products. Background Technology

[0002] Absorbent hygiene products for human use are typically made from a variety of materials, including, for example, membranes made of plastic materials, cellulose fibers, superabsorbent polymers (SAP), and breathable sheets made of synthetic fibers. Therefore, these hygiene products contain high-quality materials, making recycling them for repeated use in the market a highly desirable goal.

[0003] Key aspects related to the handling of post-consumer absorbent hygiene products involve not only the presence of organic excrement and bacterial contamination, but also the presence of compounds derived from drugs that have post-metabolism properties used by users for specific treatments.

[0004] Therefore, post-consumer absorbent hygiene products must not only be sterilized, but also chemically decontaminated for subsequent recycling and sale as recycled raw materials (rather than as waste).

[0005] However, exposing post-consumer absorbent hygiene products to sterilization temperatures may not be sufficient to remove organic residues with post-metabolism properties (such as those derived from pharmaceuticals).

[0006] On the other hand, methods that envision subjecting post-consumer absorbent hygiene products to heating steps at very high temperatures and pressures may have significant drawbacks. Methods currently known, for example, described in document EP 3 162 455B1, envision treating post-consumer absorbent hygiene products at temperatures of at least 200°C and pressures above 20 bar. However, while such temperature and pressure schemes may be effective from the perspective of removing contamination from chemical residues with post-metabolism properties, they can prove to be significantly corrosive to the treated blends. Specifically, cellulose-based components (carbohydrates composed of glucose units) brown above 140°C, caramelize above 160°C, and depolymerize above 200°C, thus reducing softness and absorbency, while plastics begin to soften above 160°C until they melt and encapsulate other materials, thereby losing their inherent mechanical properties. Therefore, the yield and quality of recycled materials may be compromised.

[0007] As an alternative, absorbent hygiene products can be treated with chemical oxidants such as hydrogen peroxide, persulfate, permonosulfate, and ozone.

[0008] As described, for example, in documents WO 2019 / 084203 A1, RO 129 948 B1 and US 2011 / 076192 A1, the oxidation of such compounds has been used in methods for treating surgical instruments, medical devices, electronic devices, and surfaces (e.g., workspaces, wards, and organic materials).

[0009] However, when processing post-consumer absorbent hygiene products for the purpose of facilitating recycling, the oxidation of the aforementioned compounds (which must not be limited to chemical cleaning alone, but also must not be limited to sterilization, bleaching and deodorization) may require the structural disruption of SAP and the depolymerization of cellulose fibers.

[0010] Furthermore, even if oxidants such as hydrogen peroxide and ozone do not release specific pollutants when they decompose into water and oxygen, respectively, they may still lead to the formation of peroxides under given operating conditions. These peroxides are particularly reactive substances that can form in situ and trigger the combustion of existing solid organic materials.

[0011] For example, document KR 101 044 439 B1 describes a method for treating a used diaper by exposing it to washing and sterilization steps, wherein ozone is introduced into a sterilization reactor while the post-consumer absorbent hygiene product is exposed to a water stream.

[0012] However, dissolved ozone in water exhibits lower reactivity than gaseous ozone. Furthermore, the high humidity of materials exposed to water flow necessitates i) squeezing the material after the sterilization step and ii) opening the material to expose it to subsequent drying steps. Additionally, exposing the material to washing steps and water flow requires consideration of wastewater treatment and disposal.

[0013] Purpose and content of the invention

[0014] The object of the present invention is to overcome the above-mentioned disadvantages and to provide a method for recycling post-consumer absorbent hygiene products, which will be able to sterilize and decontaminate organic compounds derived from human metabolism (e.g., drug residues) while maintaining the quality of products recovered from post-consumer materials (plastics, superabsorbent polymers (SAP), and optionally cellulose) for reuse or recycling in the market.

[0015] Post-consumer absorbent hygiene products subjected to the methods of this disclosure may include, for example, baby diapers, adult incontinence pads, feminine hygiene products, and bed linens. These absorbent hygiene products may contain plastics, superabsorbent polymers, cellulose, or even only plastics and superabsorbent polymers.

[0016] According to this specification, the above-mentioned objective is achieved by means of a method having the features that form the subject matter of the appended claims. The claims form an integral part of the teachings provided herein regarding the method.

[0017] One embodiment of the present invention provides a method for sterilizing and decontaminating a post-consumer absorbent hygiene product contaminated with organic compounds derived from human metabolism and containing pharmaceutical residues, the post-consumer absorbent hygiene product comprising a plastic, a superabsorbent polymer (SAP), and optionally a cellulose portion, the method comprising the following steps:

[0018] - The post-consumer absorbent hygiene product is sterilized by heating to a temperature equal to or below 140°C and under a pressure between 1 bar and 3.6 bar to obtain a sterilized post-consumer absorbent hygiene product; and

[0019] -Removal of the organic compound contaminants DC from the sterilized post-consumer absorbent hygiene products by oxidation treatment.

[0020] The oxidation process is carried out at a temperature equal to or higher than 60°C, more preferably between 60°C and 80°C, by arranging the sterilized post-consumer absorbent hygiene product to contact ozone-containing gas.

[0021] Post-consumer absorbent hygiene products sterilized by ozone treatment have a humidity of less than 80%, preferably between 60% and 75%.

[0022] The humidity of a sample is the percentage of water it contains, and is calculated by subtracting from 100 the amount of dry matter obtained by drying a known amount of sample to constant weight (IIRSA-CNR Procedures 1-10-manuale_3_2011_compost-2:Umiditàe sostanza secca).

[0023] Treating post-consumer absorbent hygiene products with gaseous ozone, keeping their humidity below 80% (thus avoiding exposure to washing and immersion in water), presents a number of advantages over the oxidative treatment previously thought to use water. First, gaseous ozone has proven to be more reactive than ozone dissolved in water, and the equipment used for the oxidative treatment is simpler, thus more economical. The treated material then does not need to undergo a pressing step and is directly conveyed to a dryer. Furthermore, this method does not generate wastewater or sewage that must be treated and then disposed of.

[0024] The method of forming the subject matter of this disclosure may also include the following steps: shredding sterilized and decontaminated post-consumer absorbent hygiene products to obtain shredded post-consumer absorbent hygiene products with a particle size of less than 10 cm, preferably less than 3 cm, and even more preferably less than 1 cm.

[0025] The method may also include the following steps: drying the shredded post-consumer absorbent hygiene product to obtain a shredded and dried post-consumer absorbent hygiene product containing plastic, SAP and optionally cellulose.

[0026] In addition, the method may include the following steps: separating plastics, cellulose and SAP from the shredded and dried post-consumer absorbent hygiene product.

[0027] In one or more embodiments, the decontamination step DC may be performed after the sterilization step SR and before the chopping step SH.

[0028] The methods that form the subject matter of this disclosure facilitate the preparation of separate sterilization components for cellulose, plastics, and SAP, which remove contamination from organic compounds, such as residues with post-metabolic properties derived from pharmaceuticals. These components are bleached and odorless. These characteristics make them suitable for convenient reuse.

[0029] Furthermore, the subject of this invention is the plastics, superabsorbent polymers (SAPs), and cellulose obtained by the method described above, which have been isolated from post-consumer absorbent hygiene products, removing contamination from organic compounds derived from human metabolism and containing drug residues. Attached Figure Description

[0030] The method will now be described in detail with reference to the accompanying drawings, which are provided by way of non-limiting example only, and in which:

[0031] - Figure 1 A schematic diagram of a method known in the art for sterilizing and separating plastics, superabsorbent polymers (SAPs), and cellulose from post-consumer absorbent hygiene products is shown.

[0032] - Figure 2 It can be used Figure 1 A top plan view of the device schematically illustrating the method;

[0033] - Figure 3 A schematic diagram of a method according to one embodiment of this specification is shown, wherein a step for removing compound contaminants is performed downstream of the sterilization step and before the chopping step; and

[0034] - Figure 4 A diagram is shown illustrating one embodiment of the present specification regarding the generation of gaseous ozone and its introduction into a reactor. Detailed Implementation

[0035] The following description provides numerous specific details to enable a thorough understanding of the implementation scheme. The implementation scheme may be implemented without one or more specific details or by utilizing other methods, components, materials, etc. In other cases, well-known structures, materials, or operations are not detailed or described in order to leave aspects of the implementation scheme unambiguous.

[0036] In all the accompanying drawings, unless otherwise stated in the context, similar parts or elements are indicated by the same reference numerals and numbers, and for the sake of brevity, the corresponding descriptions will not be repeated.

[0037] Throughout this specification, references to "an embodiment" or "an embodiment" mean that a particular aspect, structure, or feature described in connection with that embodiment is included in at least one embodiment. Therefore, phrases such as "in one embodiment" or "in an embodiment" that may appear at various points in this specification do not necessarily refer to the same embodiment. Furthermore, in one or more embodiments, a particular aspect, structure, or feature may be combined in any suitable manner. The section headings used herein are provided for convenience only and do not explain the scope or purpose of this embodiment.

[0038] As anticipated in the preceding sections, methods for sterilizing post-consumer absorbent hygiene products may not guarantee the removal of organic residues with post-metabolism properties (such as drug-derived residues).

[0039] The inventors have identified specific operating conditions for a method that facilitates sterilization and simultaneously removes organic compound contamination from post-consumer absorbent hygiene products without relying on operating conditions (e.g., heating to temperatures above 200°C and pressures above 20 bar) that could impair the quality of components (such as cellulose, plastics, and superabsorbent polymers (SAP)) separated and recovered from such post-consumer absorbent hygiene products.

[0040] Specifically, the method forming the subject of this disclosure is a method for sterilizing and decontaminating post-consumer absorbent hygiene products contaminated with organic compounds derived from human metabolism and containing drug residues, said post-consumer absorbent hygiene products comprising plastics, superabsorbent polymers (SAP), and optionally a cellulose portion, the method comprising the following steps:

[0041] - The post-consumer absorbent hygiene product is sterilized by heating to a temperature equal to or below 140°C and under a pressure between 1 bar and 3.6 bar to obtain a sterilized post-consumer absorbent hygiene product; and

[0042] -Removal of contaminating DCs from the organic compounds in sterilized post-consumer absorbable hygiene products by oxidation treatment;

[0043] The oxidation treatment is carried out by contacting the sterilized post-consumer absorbent hygiene product with ozone-containing gas; and

[0044] The oxidation process is carried out at a temperature equal to or higher than 60°C, and preferably between 60°C and 80°C.

[0045] The sterilized post-consumer absorbent hygiene products that have undergone this decontamination step have a moisture content of less than 80%, preferably between 60% and 75%.

[0046] The moisture content of a sample indicates the amount of water it contains (expressed as a percentage) and is calculated by subtracting the content of dried matter obtained by drying a known amount of sample to constant weight from 100. The drying of a sample previously weighed as P° is typically carried out in an oven at a temperature between 103°C and 105°C for at least 4 hours, usually at constant weight. At the end of oven drying, the sample is weighed again as P, and the content of dried matter DS is obtained by applying the following formula: DS = P / P° × 100, where P is the weight of the dehydrated sample (in grams) and P° is the weight of the sample before dehydration (in grams). The humidity of the sample was calculated by subtracting the dry matter content (DS) from 100 (IRSA-CNR Procedures 1-10-manuale_3_2011_compost-2:Umiditàe sostanza secca:proceduresIRSA-CNR 1984and UNICHIM 10780 / 1998).

[0047] Advantageously, the post-consumer absorbent hygiene products undergoing the various steps of this method neither come into contact with nor are immersed in the aqueous solution. The method does not envision a washing step in water, which subsequently forms sludge awaiting treatment and disposal.

[0048] The term "absorbent hygiene product" typically refers to disposable absorbent hygiene products, such as baby diapers, adult incontinence pads, feminine hygiene products, and bed linens. Absorbent hygiene products may contain plastic, SAP, cellulose, or even just plastic and SAP.

[0049] In one or more embodiments, the sterilization step can be performed by heating the post-consumer absorbent hygiene product to a temperature between 120°C and 140°C. The time interval between sterilization steps can range from 20 minutes to 2 hours.

[0050] The sterilization step, such as the decontamination step, can be carried out in a closed reactor, preferably an autoclave, and more preferably a rotary autoclave, that allows the post-consumer hygiene product to remain mobile.

[0051] In one or more embodiments, the method includes the step of moving a post-consumer absorbent hygiene product that has undergone sterilization and decontamination steps.

[0052] The oxidative treatment in the decontamination step is preferably designed to contact the sterilized post-consumer absorbent hygiene product with ozone-containing gas. This treatment does not include immersing the post-consumer absorbent hygiene product in water or an aqueous solution. The decontamination step by oxidation does not involve the use of oxidants other than ozone.

[0053] Maintaining the humidity of absorbent hygiene products below 80% (thus preventing them from being exposed to washing and immersion in water) promotes greater ozone reactivity, avoids the need for product squeezing steps, and eliminates the generation of wastewater and sludge that must be treated and then disposed of.

[0054] The oxidation treatment using ozone gas is carried out at a temperature equal to or higher than 60°C, preferably between 60°C and 80°C.

[0055] The concentration of ozone in the gas can range from 0.06 kg / m³. 3 and 0.14kg / m 3 Between; preferably it is equal to 0.08 kg / m 3 Oxidation treatment using gaseous ozone can be carried out at a pressure between about 0.3 bar and 1 bar, preferably equal to 0.5 bar.

[0056] Preferably, the oxidation treatment can be carried out for a period of time between 30 minutes and 90 minutes, preferably 60 minutes.

[0057] Due to specific operating conditions, the method that forms the subject matter of this disclosure enables the production of products (cellulose, plastics, SAP) recovered from post-consumer materials, wherein the quality is maintained so that they can be readily sold for reuse.

[0058] For example in Figure 1 and Figure 3 As illustrated schematically, the method may further include the following steps: shredding (SH) the post-consumer absorbent hygiene product, drying (DR) the shredded product, separating the shredded and dried product (SEP I) into plastic and cellulose, and separating the cellulose (SEP II) into SAP and cellulose fibers, as described, for example, in document WO 2018 / 060827 filed in the name of the applicant.

[0059] Specifically, the method of forming the subject matter of this disclosure may include the following steps: collecting (ST) post-consumer absorbable hygiene products from a differentiated collection into an accumulation container. Figure 2The apparatus 10 is shown, with the accumulation container indicated by reference numeral 12. A waste collection vehicle unloads post-consumer absorbent hygiene products in the dumping area 14, and a conveyor 16 loads the post-consumer absorbent hygiene products into the accumulation container 12. The collected post-consumer absorbent hygiene products can have a density of 150 kg / m³. 3 -300kg / m 3 Density within the range and humidity within the range of 65%-80%.

[0060] The moisture content of the material is calculated from the dry weight of the sample and should be understood as the percentage of water contained therein (IRSA-CNR Procedures 1-10-manuale_3_2011_compost-2:Umiditàe sostanza secca:proceduresIRSA-CNR 1984and UNICHIM 10780 / 1998).

[0061] The collection step (ST) is followed by a sterilization step (SR), which is performed, for example, by loading the product into a rotary autoclave 18. Figure 2 In the example shown, apparatus 10 includes two autoclaves 18, which are alternately loaded with post-consumer absorbent hygiene products from accumulation containers 12. A conveyor 28 picks up products from accumulation containers 12 and delivers them to the autoclaves 18. Two loaders 30 load products into the respective autoclaves 18. During product loading, the autoclave hatches 20 are opened, and the cylindrical bodies are rotated to gradually move the products to the rear. Once loading is complete, the hatches 20 are closed, and the autoclaves 18 are heated and pressurized by direct and indirect steam supply until a temperature of approximately 135°C and an internal pressure of approximately 3.1 bar are reached. During sterilization, the autoclaves can be alternately rotated clockwise and counterclockwise around their own axis to allow movement of the products contained within. The purpose of the sterilization step (SR) is to bring the product temperature to above 121°C, a temperature at which complete sterilization of the bacterial load is possible. The sterilization step can be performed at intervals between 20 minutes and 2 hours.

[0062] At the end of the sterilization process, the steam contained in the autoclave 18 is extracted and purified in the scrubber 34. Then, the hatch 20 opens, and the main body is rotated to unload the product. Figure 2 In the example, two autoclaves 18 are provided that operate alternately. While the first autoclave 18 is sterilizing, the other autoclave 18 is unloading sterilized material and loading a new batch. In this way, a substantially continuous stream of sterilized material is obtained downstream of the autoclaves 18. The sterilized material may have a density of approximately 300 kg / m³. 3 -400kg / m3 The density, temperature of 80℃-100℃ and humidity of about 70%-85%.

[0063] like Figure 3 The method, schematically illustrated, that forms the subject matter of this disclosure envisions the following steps: removing compound contamination (DC) from sterilized post-consumer absorbent hygiene products originating, for example, from drugs downstream of a sterilization step (SR). Specifically, the load of the sterilized post-consumer absorbent hygiene product, contained in an autoclave, is subjected to an oxidation treatment using ozone-containing gas.

[0064] The inventors have noted that the effectiveness of decontamination increases when a vacuum condition is created in the reactor before the introduction of ozone-containing gas. For example, a vacuum condition is obtained using a vacuum pump connected to the reactor, such as... Figure 4 The diagram illustrates the process. The vacuum pump VP generates a relative pressure within the reactor that can range between -0.6 bar and -0.8 bar. Creating a vacuum in the reactor before introducing ozone-containing gas allows for a reduction in air content and optimization of the gaseous ozone concentration.

[0065] After a vacuum is created, gas containing gaseous ozone is introduced into the autoclave AC to contact the sterilized product. During this stage, the humidity of the sterilized product is less than 80%, preferably between 60% and 75%.

[0066] The autoclave is treated with ozone-containing gas to maintain a temperature equal to or higher than 60°C, preferably between 60°C and 80°C.

[0067] Ozone-containing gases can be generated, for example, using an ozone generator. Figure 4 The illustration shows that, to produce gaseous ozone, liquid oxygen (O2) can be used, contained in a tank at a pressure of 200 bar, supplied, for example, by a specialized company transporting it by tanker. After the pressure is reduced to 1.5 bar via a pressure reducer PR, gaseous oxygen is obtained.

[0068] Ozone generators, or ionizers (OGs), consist of a high-voltage generator that ionizes some oxygen molecules to convert them into ozone (O3). The gas produced by an ozone generator has a concentration between 0.06 kg / m³. 3 and 0.14kg / m 3 Between, preferably 0.08 kg / m 3 Gaseous ozone.

[0069] In one or more embodiments, ozone-containing gas is directly introduced into a reactor containing sterilizing materials, preferably into an autoclave. The ozone-containing gas, under pressure (maximum pressure 1.5 bar), can be gradually injected into the autoclave AC through a steam inlet pipe via the pressure difference between the ozone generator (OG) and the autoclave AC.

[0070] The interior of the autoclave AC is initially under negative pressure, and the pressure is gradually increased by introducing ozone gas, thereby reaching a value between 0.3 bar and 1.5 bar, preferably equal to 0.5 bar.

[0071] The treatment of sterilized post-consumer absorbent hygiene products with gaseous ozone can be carried out for a period of 30 to 90 minutes, preferably equal to 60 minutes. At the end of said time period, unreacted excess ozone-containing gas is removed from the autoclave AC, for example by a vacuum pump VP. Figure 4 It is shown schematically in the diagram.

[0072] At the end of the oxidation process, the material discharged from the autoclave can be collected in storage container 32, for example... Figure 2 As shown in the diagram. After the ozone treatment step, the product may undergo shredding, drying, and separation steps, as described below.

[0073] Sterilized and decontaminated material is fed from storage container 32 to shredder 36 via conveyor belt 38. The shredder may include, for example, two rotors driven by a motor. The rotors are provided with teeth to perform material shredding. Shredding enables the production of shredded material with a particle size of less than 10 cm, preferably less than 3 cm, and more preferably less than 1 cm. After shredding, the material may exhibit a particle size of 400 kg / m³. 3 -500kg / m 3 Density within the range, temperature of approximately 75°C-95°C, and humidity within the range of 70%-85%.

[0074] Material undergoing sterilization (SR), decontamination (DC), and shredding (SH) steps is conveyed via conveyor 44 to dryer 42, where the drying step (DR) takes place. Dryer 42 includes a housing housing perforated horizontal conveyors that drive alternately in opposite directions and overlap each other vertically. Conveyor 44 unloads material onto a top conveyor. At the output of each horizontal conveyor, material falls onto a lower conveyor. As material is conveyed horizontally and sequentially from one conveyor to the next, a stream of hot air flows upward through the housing. The airflow passes through the perforated conveyors and the material located thereon. The airflow is generated by a fan 50 connected to a filter. The airflow is heated in a set of heat exchangers 54 supplied with steam. The airflow output from the heat exchangers 42 is drawn in by a second fan and sent to a condensate drain and a washer. At the output of dryer 42, material is unloaded onto conveyor belt 62. Dryer 42 may be equipped with a microwave generator facing the top conveyor to accelerate the heating of the material and thus improve the drying effect. The material at the dryer inlet has a temperature of approximately 70°C-90°C. The temperature of the drying air inside dryer 42 is approximately 140°C. The product exiting dryer 42 has a temperature of approximately 50°C-70°C and a density of approximately 35 kg / m³. 3 -50kg / m 3 The density and humidity are between 5% and 20%.

[0075] Downstream of the drying step DR, the sterilized, decontaminated, shredded, and dried material is fed to the separation assembly 64, where a separation step (SEP I) of plastics and cellulose is performed. The separation assembly 64 may include at least one first centrifuge, which includes a base and has an inlet for the material to be separated. Figure 2 In the example shown, two centrifuges 66 and 67 are provided in a cascaded arrangement. Centrifuge 66 may include a separation chamber housing a perforated cylindrical filter in which a rotor is rotatably mounted about a horizontal axis. Material at the inlet protrudes radially from the inside to the outside against the perforated filter. Cellulose, having a smaller particle size than plastic, passes through the filter and is collected in a first outlet, while plastic remains inside the filter and is collected in a second outlet. Preferably, the plastic at the output of the first centrifuge 66 is fed to a second centrifuge 67, which has a filter with smaller perforations. At the output of the first centrifuge, cellulose with a purity in the range of 85%-95% and plastic with a purity in the range of 60%-80% are obtained. At the output of the second centrifuge, cellulose with a purity in the range of 85%-95% and plastic with a purity in the range of 85%-97% are obtained.

[0076] The plastic output from separator 66 can be sent to plastic shredder 84, and then to extruder or compactor 86.

[0077] See Figure 2 At the output of centrifuge 66, the cellulose stream 80 can be sent to a cellulose chopper and a cellulose granulator 82. Alternatively, for another separation step SEP II, the cellulose stream can be sent to another separation device to separate cellulose and SAP, thereby obtaining cellulose and SAP with higher purity. Specifically, the separation of SAP and cellulose in step SEP II may include two steps.

[0078] The first separation step, SEP II, can be envisioned using a mechanical separator equipped with a perforated fixed shroud and a central rotor. Larger cellulose fibers remain trapped by the screen, while the portion containing SAP passes through holes between 2 mm and 5 mm in size and is conveyed through a second mechanical separator to undergo the second separation step. At the output of the second mechanical separator, the SAP portion may contain smaller cellulose fibers that were not trapped by the shroud of the mechanical separator.

[0079] The second separation step, SEP II, can utilize an additional separator, such as an air classifier, which has a cyclone system equipped with a metal wheel capable of rotating at approximately 4500 rpm. The material to be separated is inserted into the top of this classifier and subjected to a flow rate between 10 m / s². 3 / min and 30m 3 The airflow impacts at a rate of / min. The separator includes two outlets, one for high-purity SAP and the other for cellulose fibers.

[0080] In one or more embodiments, the decontamination step by ozone oxidation is performed downstream of the sterilization step and before the step of shredding and sterilizing the absorbent hygiene product. Figure 3 ).

[0081] The method of forming the subject matter of this disclosure facilitates the sterilization of post-consumer absorbable hygiene products and also effectively removes organic compound contamination by reducing the amount of organic residues that may also originate from pharmaceutical use and have post-metabolic properties.

[0082] The advantages of directly treating sterilized products with ozone gas are:

[0083] - At the end of the sterilization step SR, the product output from the autoclave has a humidity in the range of 60%-75% and a temperature equal to or higher than 60°C; this makes it possible to eliminate the steps of heating and humidifying the materials to be subjected to oxidation treatment with gaseous ozone;

[0084] - Treatment with gaseous ozone can be carried out in the same reactor, preferably in an autoclave, where the product has already undergone the sterilization SR step;

[0085] - The sterilization step SR is applied to post-consumer hygiene products derived from differentiated collections, enabling them to come into more effective contact with ozone-containing gases.

[0086] Furthermore, the inventors noted that the SAP recovered using the method described above maintained a significant absorbance capacity (AC). Specifically, the absorbance capacity was reduced by less than 4% compared to that of the original SAP. This absorbance capacity was measured by adding a pre-weighed sample Mi to an excess of deionized water (liquid-to-solid ratio of 100 g / ml). After complete swelling, the mixture was centrifuged at 1350 rpm for 3 minutes. The swollen material with a mass M2 was weighed. The absorbance capacity was calculated using the following formula: AC = (M2M1) / M1 (g / g), where M1 and M2 are the weights (in grams) of the anhydrous material and the swollen material, respectively.

[0087] Therefore, the method described herein enables the recycling and sale of hygiene products as recycled raw materials (rather than as waste).

[0088] Example

[0089] The following description relates to experimental tests conducted to test the effectiveness of the methods forming the subject matter of this disclosure in removing residual compounds from treated post-consumer absorbent hygiene products. The following results demonstrate that a decontamination step involving treatment of sterilized post-consumer hygiene products with gaseous ozone resulted in a significant reduction in residual organic compounds, even at levels exceeding 95%.

[0090] Chemical contamination of sterilized post-consumer hygiene products

[0091] According to the 62nd document dated May 15, 2019 1 The effectiveness of ozone oxidation decomposition in reducing substances listed in Table 3b of the Legislative Decree was assessed. Cellulose samples derived from post-consumer absorbent hygiene products, sterilized in an autoclave at 135°C and an internal pressure of 3.1 bar for 20 minutes, were fortified with the aforementioned substances, specifically using concentrations 100 times higher than the limits specified in the Legislative Decree itself. Samples were treated with gaseous ozone (humidity between 60% and 75%) under varying pressure conditions and treatment times.

[0092] Analysis of aqueous extracts from materials that are first fortified and then treated indicates that, depending on operating conditions, substances used as contamination indicators may persist in amounts exceeding the limits set forth in the aforementioned legislation.

[0093] Preliminary results show that using a concentration of 0.08 kg / m³... 3 The ozone gas at a pressure of 1.5 bar was used for treatment for a total period of 60 minutes, which resulted in a greater effect in reducing the amount of indicator material used to enhance the sample upstream.

[0094] When the oxidation treatment was carried out at a pressure of 1.5 bar for 60 minutes, the reduction was equal to 93% of the total initial contamination. The percentage reduction decreased as the pressure decreased; specifically, it decreased to 89%, shifting to the isobaric value for exposure to the gas, but for an exposure time of less than 20 minutes; and decreased to 87%, shifting to the isochronic exposure value, but for a pressure reduction of one-third compared to the most extreme conditions. Increasing the pressure to 1.5 bar, while leading to increased effectiveness from a decontamination perspective, may result in decrosslinking and depolymerization reactions, respectively, under SAP and cellulose loadings. Regarding bleaching effect, this appears to be related to the duration of exposure to gaseous ozone rather than pressure. In fact, the best bleaching effect was obtained by exposing the material to ozone-containing gas at a pressure of 0.5 bar for a total duration of 60 minutes.

[0095] Further experimental tests were repeated on the fortified cellulose samples (as in the preliminary tests), using the substances already used in the tests mentioned above and indicated in Table 1 below, at concentrations... The concentration was 100 times higher than the limit set in the aforementioned legislative decree (Table 3b of Legislative Decree No. 62 of May 15, 2019). The samples were treated with gaseous ozone for 60 minutes at a pressure of 0.5 bar and a temperature of 70°C, while maintaining motion. The results are provided in Table 1 below, showing a total reduction percentage greater than 95%.

[0096] Table 1

[0097]

[0098] *The control sample was not fortified with diazepam, torasemide, and clavulanic acid. These values ​​are expressed as weight ratios (the ratio of the mass of the substance to the mass of the sample dried to constant weight at 105°C). Release tests were conducted in water with a liquid-to-solid ratio of L / S = 100 ml / g (recovery of the eluent after soaking for 24 hours). The substance was extracted at an alkaline pH according to law (Legislative Decree No. 62 of May 15, 2019).

[0099] The specific operating conditions of the method steps that form the subject matter of this disclosure make it possible to effectively decontaminate, achieve bleaching and odor elimination effects, and simultaneously resist the degradation of the material to be recycled and sell it for reuse.

[0100] Of course, the details of the construction and implementation can vary widely without departing from the scope of the invention as defined by the appended claims, without departing from the principles of the invention.

Claims

1. A method for sterilizing and decontaminating a post-consumer absorbent hygiene product to be recycled, wherein the post-consumer absorbent hygiene product is contaminated with an organic compound derived from human metabolism and containing drug residues, the post-consumer absorbent hygiene product comprising a plastic, a superabsorbent polymer, and optionally a cellulose portion, the method comprising the following sterilization and decontamination steps: - The post-consumer absorbent hygiene product is sterilized by heating to a temperature equal to or below 140°C and under a pressure between 1 bar and 3.6 bar to obtain a sterilized post-consumer absorbent hygiene product; and - The organic compound contamination of the sterilized post-consumer absorbent hygiene products is removed by oxidation treatment. The oxidation treatment is carried out by contacting the sterilized post-consumer absorbent hygiene product with ozone-containing gas. The oxidation treatment is carried out at a temperature equal to or higher than 60°C, and The sterilized post-consumer absorbent hygiene product that has undergone the decontamination step via the oxidation treatment has a humidity of less than 80%.

2. The method of claim 1, wherein the post-consumer absorbent hygiene product to be recycled comprises plastic, cellulose, and superabsorbent polymer portions, and includes baby diapers, adult incontinence pads, sanitary napkins, and bed linens.

3. The method according to claim 1 or claim 2, wherein the concentration of ozone in the gas is between 0.6 kg / m³. 3 and 0.14kg / m 3 between.

4. The method according to claim 1 or claim 2, wherein the oxidation treatment in the decontamination step is carried out at a pressure between 0.3 bar and 1.5 bar.

5. The method according to claim 1 or claim 2, wherein the oxidation treatment in the decontamination step is carried out for a period of time between 30 minutes and 90 minutes.

6. The method according to claim 1 or claim 2, wherein the method does not include the step of immersing the post-consumer absorbent hygiene product in water or an aqueous solution.

7. The method according to claim 1 or claim 2, wherein the sterilization step and the decontamination step are carried out in a closed reactor.

8. The method of claim 7, wherein the oxidation treatment in the decontamination step is carried out by introducing the ozone-containing gas into the reactor.

9. The method of claim 7, wherein the decontamination step includes the step of creating vacuum conditions in the reactor, the vacuum-creating step preceding the introduction of the ozone-containing gas into the reactor.

10. The method according to claim 1 or claim 2, further comprising the following step: The sterilized and decontaminated post-consumer absorbent hygiene product is shredded to obtain shredded post-consumer absorbent hygiene product with a particle size of less than 10 cm.

11. The method according to claim 10, further comprising the step of: The shredded post-consumer absorbent hygiene product is dried to obtain a shredded and dried post-consumer absorbent hygiene product comprising plastic, superabsorbent polymer and optional cellulose.

12. The method of claim 11, wherein the method further comprises the following step: The plastic, optional cellulose, and superabsorbent polymer are separated from the shredded and dried post-consumer absorbent hygiene product.

13. Plastics separated from post-consumer absorbable hygiene products, which can be obtained by the method according to claim 12, wherein the plastics are free from organic compound contamination derived from human metabolism and containing drug residues.

14. Cellulose isolated from post-consumer absorbable hygiene products, which can be obtained by the method according to claim 12, wherein the cellulose is free from organic compound contamination derived from human metabolism and containing pharmaceutical residues.

15. A superabsorbent polymer derived from a post-consumer absorbent hygiene product, which can be obtained by the method of claim 12, wherein the superabsorbent polymer is free from organic compound contamination derived from human metabolism and containing drug residues, and wherein the absorption capacity is reduced by less than 4% compared to the absorption capacity of the original superabsorbent polymer.

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