Method for sterilizing and decontaminating used absorbent sanitary products contaminated with organic compounds derived from human metabolism - Patents.com

Abstract

A method for sterilizing and decontaminating used absorbent products contaminated with organic compounds originating from human metabolism, including drug residues, the used absorbent sanitary products comprising plastic, superabsorbent polymers (SAP) and optionally cellulose fractions, the method comprising a temperature equal to or lower than 140°C and a pressure of 4 bar (4 x 10 3 1. A method comprising at least the steps of: sterilizing (SR) a used absorbent sanitary product by heating to a pressure of less than 1000 kJ / hour (hectopascals); and decontaminating (DC) the used absorbent sanitary product of organic compounds by treating with an oxidizing composition having at least one compound selected from the group consisting of hydrogen peroxide, sodium percarbonate, potassium percarbonate, sodium perborate, potassium perborate, potassium monopersulfate, ammonium persulfate, sodium persulfate, potassium persulfate, and ozone, wherein the at least one compound is included in the oxidizing composition in an amount equal to or greater than 2% by weight, based on the dry weight of the used absorbent sanitary product.

Description

[Technical Field]

[0001] This description relates to recycling used absorbent sanitary products. In particular, this description relates to a method for sterilizing and decontaminating used human absorbent sanitary products (AHPs) contaminated with organic compounds derived from human metabolism. [Background technology]

[0002] Absorbent hygiene products for humans are generally composed of different materials, including, for example, plastic films, cellulose fluff, superabsorbent polymers (SAPs), and breathable sheets made of synthetic fiber materials. These hygiene products therefore involve expensive materials, the recovery of which for commercial reuse is clearly a worthwhile goal.

[0003] A significant challenge in treating used absorbent sanitary products relates to the presence of organic waste and bacterial contamination, as well as the presence of metabolic compounds derived from the drugs used by the user for certain treatments.

[0004] Therefore, in order to be subsequently recycled and sold as recovered raw materials (rather than waste), used absorbent hygiene products must not only be sterilized but also decontaminated from a chemical point of view.

[0005] However, exposing used absorbent sanitary products to sterilization temperatures may be insufficient to obtain decontamination of, for example, post-metabolic organic residues from pharmaceuticals.

[0006] On the other hand, methods that require the used absorbent sanitary product to be subjected to a heating step at very high temperatures and pressures can present significant problems.

[0007] Up to now, a method is known, for example as described in EP 316245, which requires a temperature of at least 200° C. and a pressure of 20 bar (20×10 3It is envisaged that used absorbent hygiene products will be treated at pressures exceeding 1000 kJ / h (hectopascals). However, these temperature and pressure regimes, while potentially effective in terms of decontaminating post-metabolism chemical residues, can also be significantly aggressive to the materials mixed during the treatment. In particular, cellulose-based components (carbohydrates composed of glucose units) undergo browning above 140°C, caramelization above 160°C, and depolymerization above 200°C, resulting in a loss of flexibility and absorbent capacity, while plastics, above 160°C, begin to soften until they melt, incorporating other materials and thus losing their essential mechanical properties. As a result, the absorbency and quality of the recycled materials may be reduced. Summary of the Invention

[0008] The present description aims to provide a method for treating used absorbent sanitary products that makes it possible to obtain sterilization and decontamination of organic compounds originating from human metabolism, e.g., residual pharmaceuticals, while at the same time preserving the quality of the products recovered from the used materials for convenient reuse or recycling on the market.

[0009] Used absorbent sanitary products that are amenable to the methods described herein can include, for example, baby diapers, adult incontinence pads, sanitary napkins, bed liners, etc. These absorbent products can comprise only plastic, superabsorbent polymer, cellulose, or, more appropriately, plastic and superabsorbent polymer.

[0010] According to the present description, this object is achieved thanks to a method having the characteristics forming the subject matter of the appended claims, which, in relation to the described method, form an integral part of the disclosure provided herein.

[0011] The described embodiments provide a method for sterilizing and decontaminating used absorbent sanitary products contaminated with organic compounds, the used absorbent sanitary products comprising plastic, superabsorbent polymer (SAP) and optionally a cellulose fraction, the method comprising: up to a temperature equal to or less than 140°C, at 4 bar (4 x 10 3 sterilizing the used absorbent sanitary product by heating at a pressure of less than 1000 kJ / hour; decontaminating the used absorbent hygiene product of organic compounds by treatment with an oxidizing composition having at least one compound selected from the group consisting of hydrogen peroxide, sodium percarbonate, potassium percarbonate, sodium perborate, potassium perborate, potassium monopersulfate, ammonium persulfate, sodium persulfate, potassium persulfate, and ozone; At least the following is provided.

[0012] In one or more embodiments, treating with the oxidizing composition comprises contacting a used absorbent sanitary product with the composition.

[0013] In one or more embodiments, the oxidizing composition is an aqueous solution having at least one compound selected from the group consisting of hydrogen peroxide, sodium percarbonate, potassium percarbonate, sodium perborate, potassium perborate, potassium monopersulfate, ammonium persulfate, sodium persulfate, potassium persulfate, and ozone.

[0014] The method also includes the steps of shredding used absorbent sanitary products, obtaining shredded used absorbent sanitary products, drying the shredded used absorbent sanitary products, obtaining shredded and dried used absorbent sanitary products having plastic, superabsorbent polymer (SAP) and optionally cellulose, and separating the plastic, superabsorbent polymer (SAP) and optionally cellulose from the shredded and dried used absorbent sanitary products. It may comprise at least one of:

[0015] The decontamination step may be carried out simultaneously with the sterilization step by treating the used absorbent sanitary product with an oxidizing composition.

[0016] In one or more embodiments, the decontamination step may be carried out by treating the sterilized product with an oxidizing composition simultaneously with the shredding step and / or by treating the sterilized and shredded product with an oxidizing composition simultaneously with the drying step.

[0017] In one or more embodiments, the decontamination step is carried out by treating the plastic and / or cellulose with an oxidizing composition.

[0018] In one or more embodiments, the sterilization stage of the used absorbent sanitary products is carried out at a temperature between 120°C and 140°C and at a pressure of 1 bar (1 x 10 3 hectopascals) and 3.6 bar (3.6 x 10 3 It is carried out at pressures between 1000 and 1000 kJ / s.

[0019] The method described in this description is advantageous for obtaining cellulose, plastic and superabsorbent polymer (SAP) components recovered from sterilized and decontaminated used absorbent sanitary products contaminated with organic compounds, the components having properties that make them suitable for recycling or reuse.

[0020] In one or more embodiments, the present description relates to plastics, superabsorbent polymers (SAPs) and cellulose derived from used absorbent hygiene products contaminated with organic compounds, such as metabolic residues from pharmaceuticals, obtained by the methods described.

[0021] The at least one oxidizing compound may be used in an amount equal to or greater than 2% by weight, based on the dry weight of the used absorbent sanitary product.

[0022] The oxidizing composition may have hydrogen peroxide in an amount greater than 5% by weight, preferably greater than 10% by weight, more preferably between 10% and 90% by weight, based on the dry weight of the used absorbent sanitary product.

[0023] The dry weight of used absorbent sanitary products is determined in accordance with formal UNI 936 UNICHIM10506 / 1996.

[0024] In one or more embodiments, the oxidizing composition preferably has a weight ratio of hydrogen peroxide and potassium monopersulfate between 3:1 and 20:1, preferably between 5:1 and 18:1. [Brief explanation of the drawings]

[0025] The method will now be described in detail with reference to the accompanying drawings, given for non-limiting illustrative purposes only. [Figure 1] 1 shows a schematic diagram of a method for sterilizing and separating plastic, superabsorbent polymer (SAP) and cellulose from used absorbent hygiene products. [Figure 2] FIG. 2 is a plan view of an apparatus that can be used in the method organized in FIG. 1. [Figure 3] 1 shows a schematic diagram of a method according to an embodiment of the present description, in which a compound decontamination step is carried out simultaneously with a sterilization step. [Figure 4] 1 shows a schematic representation of a method according to an embodiment of the present description, in which a step of decontaminating compounds is carried out simultaneously with the step of shredding. [Figure 5] 1 shows a schematic representation of a method according to an embodiment of the present description, in which a step of decontaminating the compound is carried out simultaneously with the drying step. [Figure 6] 1 shows a schematic representation of a method according to another embodiment of the present description, in which a compound decontamination step is carried out downstream of a drying step. [Figure 7] 1 depicts a graph showing the percentage decomposition of 43 compounds as a function of the oxidation potential of the 43 compounds when the 43 compounds are subjected to an oxidation reaction at a potential of 2.0 V. [Figure 8] 1 presents a graph showing the rate of decomposition of 43 compounds as a function of temperature due to the combined oxidation-temperature effect. DETAILED DESCRIPTION OF THE INVENTION

[0026] In the following description, numerous specific details are provided to enable a thorough understanding of the embodiments. The embodiments may be realized without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the embodiments.

[0027] References throughout this disclosure to "one embodiment" or "an embodiment" indicate that a particular aspect, structure, or characteristic described with reference to this embodiment is included in at least one embodiment. Thus, at various points throughout this description, the appearances of the phrases "in one embodiment" or "in an embodiment" are not necessarily all referring to the same embodiment. Furthermore, particular aspects, structures, or characteristics may be combined in any convenient manner in one or more embodiments. The headings provided in this description are for convenience only and do not interpret the scope or intent of the present embodiments.

[0028] As anticipated in the previous section, the sterilization methods for used absorbent hygiene products may not guarantee decontamination of the treated material of organic residues of a post-metabolic nature, e.g., derived from pharmaceuticals.

[0029] The present inventors have discovered that operating conditions (e.g., temperatures above 200°C and pressures above 20 bar (20×10°C)) can affect the quality of the separated components recovered from these used absorbent products, such as cellulose, plastics, and superabsorbent polymers (SAPs). 3 The present invention has identified specific operating conditions for a method that can facilitate sterilization and, at the same time, decontamination of organic compounds from used absorbent hygiene products without the need for the use of heating at pressures above hectopascals.

[0030] In particular, the described method is for sterilizing and decontaminating used absorbent sanitary products contaminated with organic compounds derived from human metabolism, including drug residues, the used absorbent sanitary products comprising plastic, superabsorbent polymers (SAP) and optionally cellulose fractions, the method comprising: Heating to a temperature equal to or less than 140°C and heating at 4 bar (4 x 10 3 sterilizing the used absorbent sanitary product by treating it at a pressure of less than 1000 kJ / hour; decontaminating the used absorbent hygiene product of organic compounds derived from human metabolism, including drug residues, by treating it with an oxidizing composition having at least one compound selected from the group consisting of hydrogen peroxide, sodium percarbonate, potassium percarbonate, sodium perborate, potassium perborate, potassium monopersulfate, ammonium persulfate, sodium persulfate, potassium persulfate, and ozone; At least the following is provided.

[0031] In one or more embodiments, the oxidizing composition is an aqueous solution having at least one compound selected from the group consisting of hydrogen peroxide, sodium percarbonate, potassium percarbonate, sodium perborate, potassium perborate, potassium monopersulfate, ammonium persulfate, sodium persulfate, potassium persulfate, and ozone.

[0032] The expression "absorbent hygiene product" generally refers to disposable absorbent products such as, for example, baby diapers, adult incontinence pads, sanitary napkins, bed liners, etc. These absorbent products may comprise only plastic, superabsorbent polymer, cellulose, or, more appropriately, plastic and superabsorbent polymer.

[0033] In one or more embodiments, the treatment in the decontamination step comprises contacting the used absorbent sanitary product with an oxidizing composition.

[0034] In one or more embodiments, the sterilization step comprises heating the used absorbent sanitary product to a temperature between 120°C and 140°C and applying a pressure of 1 bar (1 x 10 3 hectopascals) and 3.6 bar (3.6 x 10 3 This is done by processing the pressure between hectopascals.

[0035] The time interval for carrying out the sterilization step may be comprised between 20 minutes and 2 hours.

[0036] In one or more embodiments, the at least one oxidizing compound may be present in the oxidizing composition in an amount equal to or greater than 2% by dry weight of the used absorbent sanitary product.

[0037] The dry weight of used absorbent sanitary products is determined in accordance with formal UNI 936 UNICHIM10506 / 1996.

[0038] In one or more embodiments, the oxidizing composition may comprise at least one compound selected from hydrogen peroxide and potassium monopersulfate.

[0039] In one or more embodiments, the composition may have an amount of hydrogen peroxide greater than 5% by weight, preferably greater than 10% by weight, more preferably between 20% and 90% by weight, based on the dry weight of the used absorbent sanitary product to be treated.

[0040] In one or more embodiments, the composition may preferably have hydrogen peroxide as the only oxidizing compound in an amount greater than 5% by weight, preferably greater than 10% by weight, more preferably between 10% and 90% by weight, based on the dry weight of the used absorbent sanitary product to be treated.

[0041] In one or more embodiments, the composition preferably has an amount of potassium monopersulfate greater than 2% by weight, preferably greater than 10% by weight, based on the dry weight of the used absorbent sanitary product to be treated.

[0042] In one or more embodiments, the composition may comprise hydrogen peroxide and potassium monopersulfate. The composition may comprise greater than 5% by weight of hydrogen peroxide and greater than 2% by weight of potassium monopersulfate, based on the dry weight of the used absorbent sanitary product being treated.

[0043] In one or more embodiments, the oxidizing composition has a weight ratio of hydrogen peroxide and potassium monopersulfate between 3:1 and 20:1, preferably between 5:1 and 18:1.

[0044] In one or more embodiments, the oxidizing composition consists of hydrogen peroxide and potassium monopersulfate in a weight ratio between 3:1 and 20:1, preferably between 5:1 and 18:1.

[0045] In one or more embodiments, oxidizing compounds preferably excluded from the composition are sodium hypochlorite, potassium dichromate, chlorine, fluorine, and potassium permanganate.

[0046] In particular, beneficial results have been observed when used absorbent sanitary products are treated with the oxidizing composition at temperatures above 50°C.

[0047] The subject of the method described herein allows recovered products, namely cellulose, plastics and superabsorbent polymers (SAP), to be obtained from used materials, the quality of which is preserved for convenient reuse in the market. As shown schematically, for example in Figure 1, the method may comprise a step SH of shredding used absorbent sanitary products, a step DR of drying the shredded products, a step SEP I of separating the dried shredded products into plastics and cellulose, and a step SEP II of separating the cellulose into superabsorbent polymers (SAP) and cellulose fluff, as described, for example, in WO 2018 / 060827 of the same applicant.

[0048] In particular, the method may comprise a step ST of collecting used absorbent sanitary products coming from the recycling collection in a storage container. Figure 2 shows the device 10, in which the storage container is designated by the reference number 12. A refuse collection vehicle unloads the used absorbent sanitary products into an unloading area 14, and a conveyor 16 loads the used absorbent sanitary products into the storage container 12.

[0049] The collected used absorbent hygiene products are 150-300 kg / m 3 It may have a density of the order of 1000 and a humidity of the order of 65-80%.

[0050] The total moisture content of a material is understood as the percentage of water contained in it and is calculated from the dry weight of the sample (according to methods IRSA-CNR 1984-notebook 64 and UNI 936 UNICHIM 10506 / 1996).

[0051] The collecting step ST is followed by a sterilization step SR, which is carried out, for example, by loading the product into a rotary autoclave 18 .

[0052] In the example shown in Figure 2, the device 10 comprises two autoclaves 18, into which used absorbent sanitary products coming from the storage containers 12 are alternately loaded. A conveyor 28 takes the products from the storage containers 12 and transports them to the autoclaves 18. Two loaders 30 load the products into each autoclave 18. During product loading, the autoclave door 20 opens and the cylindrical body rotates to gradually shift the products towards the rear. Once loading is complete, the door 20 closes and the autoclave 18 is heated to a temperature of approximately 135°C and a pressure of approximately 3.1 bar (3.1 x 10 3 It is heated and pressurized by direct or indirect supply of steam until it reaches an internal pressure of 1000 kJ / hour (3000 kcal).

[0053] During the sterilization process, the autoclave may alternatively be moved clockwise and counterclockwise about its axis to allow movement of the product contained therein.

[0054] The sterilization stage SR has the objective of bringing the temperature of the product to a temperature at which it is possible to obtain complete sterilization of the bacterial load, rather than bringing the temperature of the product above 121° C. The sterilization stage can be carried out for a time interval ranging from 20 minutes to 2 hours.

[0055] At the end of the sterilization process, the vapors contained in the autoclave 18 are extracted and purified in a scrubber 34. The door 20 is then opened and the body rotates to unload the product. In the example of Figure 2, two autoclaves 18 are provided which operate in an alternating manner: the first autoclave 18 carries out the sterilization process, while the other autoclave 18 unloads the sterilized material and loads a new batch. In this way, an essentially continuous stream of sterilized material can be obtained downstream of the autoclave 18.

[0056] At the end of the sterilization process, the sterilized material leaving the autoclave is collected in a storage container 32. The sterilized material leaving the autoclave may have a density of approximately 300-400 kg / m3, a temperature of 80-100°C and a total humidity of the order of 70-85%.

[0057] From the storage container 32, the sterilized material is conveyed by a conveyor belt 38 to a shredder 36. The shredder may, for example, have two rotors driven by a motor. The rotor is provided with teeth that perform the shredding of the material. Shredding makes it possible to obtain shredded material with a particle size smaller than 10 cm, preferably smaller than 3 cm, and more preferably smaller than 1 cm. After the shredding stage SH, the material may be present at a density of the order of 400-500 kg / m3, at a temperature of approximately 75-95°C and at a total humidity of the order of 70-85%.

[0058] The material subjected to the sterilization and shredding steps is sent by conveyor 44 to dryer 42, where the drying step DR is carried out. Dryer 42 comprises a housing housing horizontally perforated conveyors, driven alternately in opposite directions and stacked vertically. Conveyor 44 deposits the material onto the upper conveyor. At the outlet of each horizontal conveyor, the material falls onto the lower conveyor. While the material is transported horizontally, passing continuously from one conveyor to the next, a heated air stream passes through the housing from bottom to top. The air stream passes through the perforated conveyors and the material placed on them. The air stream is generated by a fan 50 connected to a filter. The air stream is heated in a battery of heat exchangers 54, which are supplied with steam. The air stream leaving heat exchanger 42 is sucked in by a second fan and sent to a scrubber through a compressed discharge device 58. At the outlet of the dryer, the material is deposited onto a conveyor belt. The dryer 42 may have a microwave generator facing the upper conveyor, which accelerates heating of the material and increases the effectiveness of the dryer. The material at the dryer inlet has a temperature of approximately 70-90°C. The drying temperature of the air in the dryer 42 is approximately 140°C. The product at the discharge of the dryer 42 has a temperature of approximately 50-70°C, a density of approximately 35-50 kg / m3, and a total humidity of approximately 5-20%.

[0059] Downstream of the drying stage DR, the sterilized, shredded and dried material is sent to a separation assembly 64 where a plastic and cellulose separation stage (SEP I) is carried out. The separation assembly 64 may comprise at least one first centrifuge having a base and having an air inlet for the material to be separated. In the example shown in Figure 2, two centrifuges 66, 67 are provided in cascade.

[0060] The centrifuge 66 may have a separation chamber 72 that houses a cylindrical perforated filter, a rotor mounted thereon, and is rotatable about a horizontal axis. The inlet material protrudes radially outward relative to the perforated filter. Cellulose, having smaller dimensions than plastic, passes through the filter and is collected at a first outlet, while plastic remains inside the filter and is collected at a second outlet. Preferably, the plastics exiting the first centrifuge 66 are sent to a second centrifuge 67, which has a filter with smaller perforations. At the outlet of the first centrifuge, cellulose is obtained with a purity on the order of 85-95%, and plastics with a purity on the order of 60-80%. At the outlet of the second centrifuge, cellulose is obtained with a purity on the order of 85-95%, and plastics with a purity on the order of 85-97%.

[0061] 2, at the outlet of the centrifuge 66, the cellulose flow 80 may be sent to a cellulose shredder and cellulose pelletizer 82. Alternatively, the cellulose flow may be sent to an additional separator for another separation stage SEP II to separate the cellulose and superabsorbent polymer (SAP) and obtain highly pure cellulose.

[0062] The plastics exiting the separator 66 may be sent to a plastic shredder 84 and then to an extruder or densifier 86 .

[0063] Treatment with the oxidizing compositions described herein to remove compounds, e.g., from pharmaceuticals, can be performed at different stages of the described methods, as shown schematically in Figures 3 to 6, for recovery of different components such as sterilized and decontaminated plastics, cellulose, and superabsorbents.

[0064] In one or more embodiments, the organic compound decontamination step DC can be carried out simultaneously with the sterilization step (SR+DC), for example, as shown in Figure 3. In this case, the oxidizing composition defined herein is preferably added to a rotary autoclave (e.g., as described in the previous section) to allow movement and mixing of the products through rotation. The oxidizing composition can be sprayed onto the materials placed in the autoclave, for example, by suction.

[0065] The absorbent hygiene product is heated at temperatures between 120°C and 140°C and 1 bar (1 x 10 3 hectopascals) and 3.6 bar (3.6 x 10 3 It is heated to an internal pressure of between 100 and 1000 kJ / cm².

[0066] The temperature of the used absorbent sanitary products that have been sterilized and treated with the oxidizing composition may vary from 30°C to 130°C during the sterilization step.

[0067] The time interval for carrying out the sterilization and decontamination steps may be between 20 minutes and 2 hours.

[0068] Used absorbent sanitary products that have been sterilized and simultaneously treated with an oxidizing composition may have a moisture value between 70% and 85%.

[0069] An oxidizing composition that can be used may, for example, have potassium monopersulfate dissolved in an aqueous solution in an amount equal to or greater than 5% by weight (for example, 10% or 15%), based on the dry weight of the used absorbent sanitary product.

[0070] In one or more embodiments, the composition is a solution of potassium monopersulfate used in an amount equal to or greater than 5% by weight (e.g., 10% or 15% by weight) based on the dry weight of the used absorbent sanitary product.

[0071] 4 shows an embodiment in which the decontamination step DC, instead of being performed simultaneously with the sterilization step SR, is performed downstream of the sterilization step, and rather simultaneously with the shredding step SH (SH+DC). In this case, the oxidizing compound of interest in the present description can be added, for example by spraying, directly to the shredder where the sterilized material is present. 3 Spraying may be carried out using a nozzle which is in turn fed using a piston pump delivering 5 L / min of the oxidizing composition at 1000 kJ / h (hectopascals).

[0072] The product is shredded to produce a final particle size of less than 10 cm, preferably less than 3 cm, and even more preferably less than 1 cm. The shredded product is mixed in a screw conveyor. The hygiene product subjected to the shredding and treating steps with the oxidizing composition may have an average temperature of between 75-95°C and a total humidity of between 70-85%.

[0073] The steps of shredding and treating with the oxidizing composition may be carried out for a time interval between 30 and 120 minutes.

[0074] The oxidizing composition may, for example, have hydrogen peroxide in combination with potassium monopersulfate in a weight ratio comprised between 5: 1 and 18: 1. For example, the composition may have amounts of hydrogen peroxide and potassium monopersulfate of 89% and 5%, respectively, based on the dry weight of the used absorbent sanitary product.

[0075] 5 shows an example of an embodiment in which a decontamination step DC is performed in conjunction with a drying step DR (DC+DR). In this case, for example, an oxidizing compound of interest herein may comprise hydrogen peroxide and potassium monopersulfate in a weight ratio of 5:1 to 18:1 (e.g., in amounts of 26% and 5% by weight, respectively, based on the weight of the dry material). To produce such a composition, 33% v / v hydrogen peroxide may be used in water in which potassium monopersulfate is dissolved.

[0076] The oxidizing composition can be applied to shredded, dried, used absorbent sanitary products by spraying to penetrate the material from the shredder. 3 Spraying may be carried out by nozzles which are in turn fed by a piston pump delivering 4 L / min of oxidizing composition at a pressure of 1000 kJ / hour (hectopascals).

[0077] The total moisture content of the material subjected to the drying and treatment with the oxidizing composition steps can vary between an average value of 70% and 85% when the material enters the dryer, and can vary between an average value of 5% and 20% when the material exits the dryer at the end of the drying step.

[0078] The hygiene products subjected to the steps of drying and simultaneous treatment with the oxidizing composition may have an average temperature of 50-90°C.

[0079] The drying step and the treating step with the oxidizing composition may be carried out for a time interval of about 2 hours.

[0080] 6 shows an example of an additional embodiment in which decontamination DC is performed downstream of a drying stage DR, e.g., downstream of a cellulose and plastic separation stage SEP I. In this case, an oxidizing composition may be used to treat the individual separated components. In one or more embodiments, the oxidizing composition is placed in direct contact with the cellulose and / or plastics from the separation stage.

[0081] In one or more embodiments, the oxidizing composition has at least one compound in an amount equal to or greater than 2% by weight, based on the dry weight of the plastic and / or cellulose separated from the shredded and dried used absorbent sanitary product.

[0082] In one or more embodiments, the oxidizing composition has hydrogen peroxide in an amount greater than 5% by weight, preferably greater than 10% by weight, more preferably between 10% and 90% by weight, based on the dry weight of plastic and / or cellulose separated from the shredded and dried used absorbent sanitary product.

[0083] In one or more embodiments, the composition may comprise hydrogen peroxide and potassium monopersulfate. The composition may comprise greater than 5% by weight of hydrogen peroxide and greater than 2% by weight of potassium monopersulfate, based on the dry weight of the plastic and / or cellulose separated from the shredded and dried used absorbent sanitary product.

[0084] In one or more embodiments, the oxidizing composition has a weight ratio of hydrogen peroxide and potassium monopersulfate between 3:1 and 20:1, preferably between 5:1 and 18:1.

[0085] The oxidizing composition can be applied through a nozzle to the plastic and / or cellulose contained in an oxidizing treatment unit, e.g., a chemical reactor. Distribution of the composition can be achieved by mixing with a blade or screw, or by rotation of the reaction chamber.

[0086] The material (plastic and / or cellulose) subjected to the step of treatment with the oxidizing composition is heated to a temperature of 30°C to 120°C, preferably between 50°C and 110°C, and subjected to a pressure of -1 bar (-1 x 10 3 hectopascals) to 2 bar (2 x 10 3 hectopascals), preferably 1 bar (1 x 10 hectopascals) and 2 bar (2 x 10 3 It is processed at a pressure between 1000 and 1000 kJ / hour.

[0087] The time the material (plastic and / or cellulose) remains in the reactor is between 2 and 3 hours. The total moisture content of the material can be between 5 and 25%.

[0088] In this case, the oxidizing composition may, for example, comprise hydrogen peroxide in an amount greater than 5% by weight, for example equal to 26% by weight, based on the dry weight of the plastic and / or cellulose. The oxidizing composition may be obtained by diluting hydrogen peroxide from a water concentration of 30% (w / w) to a water concentration of 50% (w / w). The composition may further comprise ozone in an amount comprised between 1% (w / w) and 10% (w / w), based on the dry weight of the plastic and / or cellulose.

[0089] The method described in this description is advantageous for sterilizing used absorbent hygiene products and also for reducing the possible amount of organic residues of a metabolic nature resulting from the use of drugs, as well as for decontaminating more than 99% of organic compounds.

[0090] The methods described herein therefore enable the recycling and trading of hygiene products that are treated as recovered raw materials (rather than waste). example

[0091] The following explanation: i) verify the degree of contamination with compounds from sterilized used absorbent hygiene products; ii) Test the effectiveness of specific oxidizing compositions in obtaining decontamination of residual compounds in treated used absorbent hygiene products. The present invention relates to experimental tests carried out by the inventors of the present application in order to: The results below demonstrate that the decontamination step carried out by treating used absorbent hygiene products with a specific composition of oxidizing agents allows a significant reduction of the remaining organic compounds, even to a level of more than 99%. Chemical contamination of sterile used hygiene products

[0092] The inventors of the present application have obtained the following material samples: i) Used absorbent hygiene products that have been collected but not treated with pre-contamination; ii) 580 μg / kg of "contaminating" compound per kg of dry material ss, used absorbent hygiene products spiked at microgram concentrations (spiked samples rather than fortified), iii) "contaminating" compound is 1000 μg / kg / kg of dry material ss , spent cellulose recovered during the separation step (overspiked sample), added at a concentration of micrograms. A series of experimental tests were carried out in which the

[0093] The contaminating compounds were 580 and 1000 μg / kg of dry material. ss , was added to the hygiene product to obtain two distinct amounts of micrograms. The dry weight of the material was determined according to the official method 936 UNICHIM10506 / 1994: 580 μg / kg ss The amount equivalent to 580 μg / kg is the amount potentially found in a used (non-fortified) absorbent hygiene product in which all users take all the drugs selected as indicators at the maximum dose. ss The amount is derived from estimates derived from studies that consider drug administration and pharmacokinetics as the only parameters to be considered. ss The amount is an overestimate that serves to better test the efficiency of the decontamination process.

[0094] The contaminating compounds used to obtain the fortified samples are listed in Table 1 below. [Table 1] [Table 1]

[0095] The contaminating compounds listed in Table 1 are also compounds selected as indicators of the efficiency of the process among all the chemicals relevant to the type of user of absorbent hygiene products, and by using the databases of AIFA (Italian Medicines Agency) or ASL (Local Health Offices).

[0096] The material samples introduced in points i), ii) and iii) were subjected to a temperature of 135°C and a pressure of 3.1 bar (3.1 x 10 3 The containers were autoclaved at an internal pressure of 1000 kJ / h (hectopascals) for a period of 20 minutes.

[0097] The analytical evaluation of the degree of decontamination of the treated samples was carried out by a migration test (leaching) that allows obtaining an analyzable solution from the solid matrix. For this purpose, in the absence of relevant legislation, the guidelines suggested by the general method EN 12457 (parts 1-2-3-4) and EPA 3500C were followed to identify the most appropriate conditions for the specific absorbency of the material. The following basic conditions were used: 1. Extraction step: water / methanol, 1:1 v / v, 2. Liquid / solid ratio: L / S, equal to 10L / Kg; 3.Liquid-solid contact time: 24 hours immersion, 4. The number of extractions is at least equal to three.

[0098] The resulting solution was analyzed by liquid chromatography coupled with a mass spectrometry detector.

[0099] Chemical analysis feedback for the tested samples was performed in an autoclave at a temperature of 135°C and 3.1 bar (3.1 x 10 3 It has been shown that sterilization methods carried out at internal pressures of 1000 kJ / h (hectopascals) result in partial decontamination effectiveness from the compounds and therefore do not meet the requirements, as explained below.

[0100] In particular, samples of non-reinforced used absorbent sanitary products further contain residues of primary and / or secondary metabolites related to the use of drugs taken by the user of the sanitary product in question to treat certain pathologies downstream of the autoclave process.

[0101] In fortified samples, or rather used absorbent hygiene products to which "contaminants" had been added, the chemical decontamination effectiveness of the sterilization method alone was not greater than 18%.

[0102] Having examined the extent of contamination with compounds in sterilized used absorbent sanitary products, the inventors tested the effectiveness of certain oxidizing compositions in obtaining decontamination of the remaining compounds in the used absorbent sanitary products. Criteria for selecting a specific oxidizing composition to obtain chemical decontamination

[0103] Table 2 lists some of the compounds known as "strong chemical oxidants" and are considered suitable for oxidative decontamination of the compounds reported in Table 1. Table 2 also reports the value of the standard potential E°, expressed in volts V, for the oxidizing compounds listed. [Table 2] [Table 2]

[0104] Having identified the targets to be oxidized (i.e., the compounds listed in Table 1), the inventors evaluated each compound's inherent tendency to be oxidized and its resistance to the oxidation reaction. From a thermodynamic point of view, the ease with which an oxidation reaction proceeds between two species with different potential standards E° is exponentially determined by the difference between the potentials of the two species involved. The greater the difference, the more favorable the reaction. Therefore, in order to select the most appropriate oxidant (or mixture of oxidants), the inventors first evaluated the oxidation potentials of the compounds of interest in order to estimate their resistance to electrochemical oxidation.

[0105] Table 3 below shows the compounds listed in Table 1, and for each compound the associated oxidation potential is expressed in volts V, conventionally relative to the reference NHE (normal hydrogen electrode). [Table 3] [Table 3] [Table 4]

[0106] It is clear that many of the compounds tested have potential values ​​E°,V greater than 1. This indicates that only relatively strong chemical oxidants, such as the compounds listed in Table 2, can significantly degrade them.

[0107] However, some of the compounds listed in Table 2 were excluded from the selection process by the present inventors. These include, for example, sodium hypochlorite, potassium dichromate, chlorine, fluorine, and potassium permanganate for the following reasons: The use of sodium hypochlorite was excluded because this compound has a standard potential equivalent to only one-third of the compounds listed in Table 3. However, while potassium dichromate has a standard potential equivalent to most of the substances listed in Table 3, its use requires the addition of concentrated acid, and all of the above, and is a source of the persistently toxic element chromium. Chlorine also has a standard potential equivalent to many of the substances listed in Table 3, but its use is highly toxic and dangerous. Potassium permanganate has a standard potential equivalent to many of the substances listed in Table 3, but its use requires the addition of concentrated acid. It also triggers secondary reactions that lead to the formation of brown manganese dioxide and the cleavage of carbon-carbon bonds in adjacent diols, which are consequently aggressive to cellulose. However, although fluorine has the highest standard potential value, it is highly toxic and corrosive.

[0108] Thus, the oxidizing compounds, especially those net of compounds preferably excluded from those listed in Table 2, are selected from ozone, monopersulfates, hydrogen peroxide and percarbonates, sulfuric acid, potassium or ammonium perborate. These compounds have standard potentials greater than 1.8 V and are therefore considered potentially suitable for oxidizing the compounds listed in Table 3, most of which have lower values. Furthermore, these oxidizing compounds have the advantage that, after or even during their use, they do not leave or release toxic and / or irritating residues, such as those excluded.

[0109] Therefore, the inventors of the present application were interested in identifying the operational limiting conditions (e.g., oxidation potential, concentration, temperature, and time) that would allow obtaining the highest rate of decomposition of the selected compound. Regarding oxidation potential, taking into account the data reported in Table 3, it is reasonable to assume that high decomposition by chemical oxidation of the same substance selected as the indicator is desirable only at oxidation potential values ​​of at least 1.9 V. This assumption was verified.

[0110] 1 Direct chemical oxidation was carried out in a homogeneous phase, i.e., in aqueous solutions of MPS and KPS at 100 °C, with oxidizing agents having a potential greater than 1.9 V. However, the action of these oxidizing agents in a homogeneous phase is far less practical than their practical action on a surface instead.

[0111] 2 By electrochemical oxidation carried out in a heterogeneous phase at the surface by a three-electrode potentiostatic circuit of the cell operating at a controlled potential of 2.0 V, close to the value of the most powerful chemical oxidizers.

[0112] The percentage of decomposition for each species was determined by quantification of the analysis of the unchanged recovered residue downstream of the oxidation process carried out at +2.0 V. Oxidation was carried out at four different temperatures to estimate the percentage of decomposition at higher temperatures, more precisely, not accomplished on a laboratory scale, producing the cumulative graphs in Figures 7 and 8. The graph in Figure 7 shows the percentage of decomposition of the compounds reported in Table 1 according to their oxidation potential, and for 43 compounds, there is general validity in light of the broad correlation. Note that electrooxidation at +2.0 V (and T > 50 °C) is expected to produce more than 80% decomposition only for those species with potential values ​​lower than 1 V. This potential value is compatible with the potential values ​​of oxidized compounds such as MPS, KPS, and related compounds (Table 2). It is also clear that at 2 V, only those above 80 °C and only compounds with low oxidation potentials can be effectively decomposed. The same percent decomposition data obtained by oxidation at 2 V for 43 substances at four different temperatures can be reported according to temperature. Extrapolation of the test data at higher temperatures suggests that a chemical oxidizer operating at about 2 V can decompose at 135°C over 99% of species with oxidation potentials lower than 1.1 V operating at 1 atm (Figure 8). Figure 8 accurately depicts the percent decomposition of the compounds reported in Table 3 as a function of temperature due to the combined oxidation-temperature effect.

[0113] It should be noted that only from the i-th species with an oxidation potential lower than at least 1.1 V can limit decomposition be expected to be greater than 99% (at a temperature of 135° C.) with an oxidizing agent having a potential of at least +2.0 V; a potential of 2 V is compatible with compounds such as ozone, persulfates, monopersulfates, and peroxides such as hydrogen peroxide or the like. Efficacy test

[0114] The effectiveness of the decontamination of compounds carried out by oxidizing compounds selected on the basis of the criteria reported in the previous section was tested on post-metabolism residues present in untreated (raw) used absorbent hygiene products, on used absorbent hygiene products enriched with the compounds listed in Table 1, and on used cellulose recovered during separation and enriched with the compounds listed in Table 1. The latter material was the most suitable to test, as it is the most absorbent component of absorbent hygiene products. MPS (MPS or potassium peroxysulfate)

[0115] Potassium monopersulfate (provided by PeroxItalia or United Initiator) was placed in aqueous solution in the autoclave during the sterilization stage in an amount equal to or greater than 10% of the dry weight of the used absorbent hygiene product. The solid compound (a commercial triple salt with a solubility of 250 g / L at 20°C) was dissolved in a minimum amount of water to give a concentration of 580 μg / K. ss The MPS solution was applied to the material placed in the autoclave at a concentration equal to or greater than 10% of the dry weight of the fortified material sterilized at a concentration equal to 10% of the dry weight of the material. The dry weight of the material was determined according to official method 936 UNICHIM10506 / 1994. The material was sprayed with the MPS solution by suction from an external tank, performed during the vacuum phase. The material was then shredded to produce a final particle size of less than 10 cm and then dried. This decontamination step resulted in a decontamination of greater than 99%.

[0116] Similar results were obtained when potassium monopersulfate was added in solution to unfortified used absorbent sanitary products in an amount equal to or greater than 10% by dry weight of the material, with the total humidity of the material being greater than or equal to 70%. Potassium monopersulfate (MPS) in combination with ozone

[0117] MPS was placed in the autoclave in the form of a solution that was sprayed onto the reinforced material at a final humidity of 70%. Potassium monopersulfate was placed in the autoclave in an amount less than 10% (w / w) compared to the dry weight of the used absorbent hygiene product. The dry weight of the material was determined in accordance with official method 936 UNICHIM10506 / 1994. Two different amounts were tested: 5% and 8% by weight, based on the dry weight of the material. The method also assumes the introduction of an ozone flow (15 L / h) during the drying stage of the material.

[0118] Thus, the analyses performed on the treated material showed 72% and 92% of 580 μg / kg, respectively. ss At concentrations equal to 0.01, the material showed a decrease in the level of the compound added.

[0119] MPS was placed in the autoclave in the form of a solution sprayed onto the enriched recovered cellulose with a final humidity of 70% and a particle size smaller than 3 cm. Potassium monopersulfate was placed in the autoclave in an amount less than 10% by weight compared to the dry weight of the material. Three different amounts were tested: 2.4, 4.0, and 5.7% by weight relative to the dry weight of the recovered cellulose. The method also assumes the introduction of an ozone flow (15 L / h) during the drying stage of the material.

[0120] The analyses performed showed 80, 98 and >99% of the 580 μg / kg ss showed a reduction in the level of compounds added to recovered spent cellulose at concentrations equal to Sodium percarbonate (SPC) combined with ozone

[0121] Sodium percarbonate was tested in different amounts, namely 4%, 9% and 10% relative to the dry weight of the material placed in the autoclave determined according to the official 936 UNICHIM10506 / 1994 method.

[0122] It was added as a solution to the reinforced material with a total humidity greater than 45±5%. The material was then subjected to chopping to produce a final particle size of less than 10 cm.

[0123] The method also envisages the introduction of an ozone flow (15 L / h) during the drying stage of the material.

[0124] The analyses carried out on the material thus treated were equal to 78%, 95% and 97% (580 μg / kg ss It was shown that decontamination indicates the percentage reduction of contaminants (added at a concentration of 1000 ppm). hydrogen peroxide

[0125] The effect of hydrogen peroxide (H2O2) was tested on laboratory scale on spent cellulose, recovered in a separation stage and crushed to a size not exceeding 3 cm, at 1000 μg / kg. ss (overspike) and then treated under the total humidity, concentration, temperature and duration of operation as shown in Table 4 below. [Table 4] [Table 5]

[0126] The conditions for the oxidation treatment carried out on the recovered used cellulose are those treated on a laboratory scale (100.0 g of material). The % values ​​are intended to be the weight ratio between H2O2 alone and the treated dry cellulose. The total humidity also takes into account the water produced by the decomposition of H2O2. The reactor was heated to 1 bar (1 x 10 3 It is arranged in hectopascals.

[0127] Initially, it has been chosen to evaluate only the COD value (Chemical Oxygen Demand), which already represents the amount of oxygen required for the complete chemical oxidation of organic and inorganic oxidizable compounds that may be present in the aqueous matrix extracted from the material subjected to decontamination. High values ​​of this parameter (>160 mg / L) are considered sufficient to indicate that the content of organic residues is also high in downstream chemical analyses aimed at the post-treatment identification of the compounds listed in Table 1 and their associated derivatives.

[0128] The oxidation treatments that caused a decrease in the values ​​of the compounds greater than 99% resulted in detected COD values ​​lower than 100 mg / L (tests 1 to 7 listed in Table 4) in the blank net, i.e., values ​​corresponding to those found in the same treatments, but carried out on uncontaminated cellulose.

[0129] The tests conducted demonstrate the effectiveness of hydrogen peroxide used both alone and in combination with potassium monopersulfate.

[0130] Particularly effective decontamination has been observed for compositions containing hydrogen peroxide as the only oxidizing compound in an amount greater than 50% by dry weight of the material to be decontaminated. Optimal application times include a period of at least 1.5 hours at a temperature not lower than 60°C with a total moisture content not lower than 53%.

[0131] Compositions containing hydrogen peroxide in combination with potassium monopersulfate caused significant decontamination of the compounds, even exceeding 99% (COD values ​​<100 mg / L).

[0132] For example, beneficial results are obtained with compositions containing hydrogen peroxide in an amount equal to or greater than 26% by dry weight of the material and potassium monopersulfate in an amount equal to at least 5% by dry weight of the material.

[0133] The decontamination of the compounds was particularly effective when the treated material had a total humidity greater than 50%.

[0134] The role of water is clearly important for reducing the migration of oxidizing and reducing species. It also protects the integrity of materials from exothermic phenomena such as the decomposition of hydrogen peroxide into water and oxygen. Therefore, excess water can improve chemical processes.

[0135] Decontamination of the compounds was particularly effective when the materials were treated at temperatures above 60°C.

[0136] In particular, the favorable conditions, characterized by a reduction of chemical residues even higher than 99% in the fortified samples, are compatible with the implementation of chemical decontamination steps at different stages of the method as shown in Figures 3 to 6.

[0137] Furthermore, treatment with hydrogen peroxide also allows a bleaching effect of the resulting treated material, which occurs after chemical conversion of contaminating residues into volatile decomposition products.

[0138] Of course, without violating the principles of the present invention, the details of construction and the present embodiment may be widely varied without thereby departing from the scope of the present invention as defined by the following claims.

Claims

1. 1. A method for sterilizing used absorbent sanitary products contaminated with metabolic organic compounds derived from pharmaceuticals and for removing said organic compounds from said used absorbent sanitary products, said used absorbent sanitary products comprising plastic, superabsorbent polymer (SAP) and optionally a cellulose fraction, said method comprising: Heating to a temperature between 120°C and 140°C and applying 1 bar (1 x 10 ３ hectopascals) and 3.6 bar (3.6 x 10 ３ (SR) treating said used absorbent sanitary product at a pressure comprised between 0.5 and 1.0 hectopascals; treating the used absorbent sanitary product with an oxidizing composition (DC) comprising at least one compound selected from the group consisting of hydrogen peroxide, sodium percarbonate, potassium percarbonate, sodium perborate, potassium perborate, potassium monopersulfate, ammonium persulfate, sodium persulfate, potassium persulfate, and ozone; At least the at least one compound is included in the oxidizing composition in an amount equal to or greater than 2% by weight, based on the dry weight of the used absorbent sanitary product; the oxidizing composition having hydrogen peroxide and potassium monopersulfate in a weight ratio of hydrogen peroxide:potassium monopersulfate between 3:1 and 20:1; method.

2. Shredding the used absorbent sanitary products (SH) and obtaining shredded used absorbent sanitary products having a particle size smaller than 10 cm. Also equipped, The step (SH) (i) After the steps (SR) and (DC) are performed simultaneously, (ii) after step (SR) has been performed and before step (DC) has been performed; or (iii) after step (SR) has been performed and simultaneously with step (DC), The method of claim 1 .

3. 3. The method of claim 2, wherein the method also comprises the steps of drying (DR) the shredded used absorbent sanitary products and obtaining shredded dried used absorbent sanitary products comprising plastic, superabsorbent polymer (SAP) and optionally cellulose.

4. 4. The method of claim 3, wherein the method also comprises separating plastic from the shredded and dried used absorbent sanitary products.

5. 5. The method of claim 3 or 4, wherein the method also comprises separating cellulose from the shredded and dried used absorbent sanitary products.

6. 6. The method of any one of claims 3 to 5, wherein the method also comprises separating the superabsorbent polymer (SAP) from the shredded and dried used absorbent sanitary products.

7. 7. The method according to claim 1, wherein said step (DC) is carried out simultaneously with said step (SR).

8. 7. The method according to claim 2, wherein said step (DC) is carried out simultaneously with said step (SH).

9. 7. The method according to claim 3, wherein said step (DC) is carried out simultaneously with said step (DR).

10. 10. The method according to any one of claims 1 to 9, wherein the used absorbent sanitary product is treated with the oxidizing composition at a temperature above 50°C.

11. 11. The method of any one of claims 1 to 10, wherein the oxidizing composition has an amount of hydrogen peroxide greater than 5% by weight, based on the dry weight of the used absorbent sanitary product.

12. 7. The method according to any one of claims 4 to 6, wherein step (DC) is carried out by treating the plastic and / or the cellulose separated from the shredded and dried used absorbent sanitary products with the oxidizing composition.

13. 13. The method of claim 12, wherein the at least one compound is included in the oxidizing composition in an amount equal to or greater than 2% by weight, based on the dry weight of the plastic and / or the cellulose separated from the shredded and dried used absorbent sanitary product.

14. 14. The method of claim 12 or 13, wherein the oxidizing composition has hydrogen peroxide in an amount greater than 5% by weight, relative to the dry weight of the plastic and / or cellulose separated from the shredded and dried used absorbent sanitary product.

15. 15. The method of any one of claims 1 to 14, wherein the oxidizing composition comprises potassium monopersulfate.

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