Separation method

Abstract

The separation method includes a supply step (S2) for supplying bubbles including at least one of nanobubbles or microbubbles to a mixture including a water-absorbent polymer and a pulp. The separation method includes a recovery step (S5) for recovering a water-absorbent polymer that is separated in a mixed solution including a water-absorbent polymer and a pulp because the water-absorbent polymer to which bubbles are attached floats upward, while the pulp settles in the mixed solution. The separation method separates the water-absorbent polymer and the pulp from each other.

Description

Technical Field

[0001] This disclosure relates to a separation method. Background Technology

[0002] In recent years, efforts have been made to recycle hygiene products, such as used diapers. Recycling hygiene products instead of burning them allows for efficient resource utilization and reduces the amount of carbon dioxide produced during combustion. Ordinary diapers consist of absorbent polymers and pulp, and separating and recycling these components is desired to improve recycling efficiency.

[0003] As a technology for recycling hygiene products, Patent Document 1 describes a method for generating recycled fibers by removing absorbent polymers from fibers containing absorbent polymers. The method includes supplying a mixture containing water and fibers containing absorbent polymers to a processing tank containing a processing solution capable of dissolving the absorbent polymers, while simultaneously discharging the processing solution containing the fibers from which the absorbent polymers have been dissolved and removed to the outside of the processing tank.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: WO 2019 / 003657 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] In Patent Document 1, recycled fibers can be effectively generated by dissolving and removing the absorbent polymer from the fiber. However, from a recycling point of view, it is preferable to separate and recover not only the fiber but also the absorbent polymer.

[0009] The purpose of this disclosure is to provide a separation method that enables the recovery of absorbent polymers from mixtures comprising absorbent polymers and pulp.

[0010] Solution for solving the problem

[0011] The separation method according to this disclosure includes a feeding step for supplying bubbles, including at least one of nanobubbles or microbubbles, to a mixture comprising a superabsorbent polymer and pulp. The separation method includes a recovery step for recovering the superabsorbent polymer, which is separated in the mixture comprising the superabsorbent polymer and pulp by the superabsorbent polymer with attached bubbles floating upwards and the pulp settling in the mixture. In the separation method, the superabsorbent polymer and the pulp are separated.

[0012] The water-absorbing polymer can float upwards in the mixture while remaining in a solid state. The water-absorbing polymer can include polyacrylate-based water-absorbing polymers. The bubbles can have an average bubble diameter of 1 nm to 100 μm. The bubbles can include at least one gas selected from the group consisting of hydrogen, nitrogen, oxygen, carbon dioxide, air, and inert gases. The separation method can also include a settling step between the feeding step and the recovery step to allow the pulp in the mixture to settle. The separation method can also include a stirring step between the feeding step and the settling step to agitate the mixture.

[0013] The separation method according to this disclosure includes a feeding step for supplying charged bubbles to a mixture comprising a superabsorbent polymer and pulp. The separation method includes a recovery step for recovering the superabsorbent polymer, which is separated in the mixture comprising the superabsorbent polymer and pulp by the superabsorbent polymer with attached bubbles floating upwards and the pulp settling in the mixture. In the separation method, the superabsorbent polymer and the pulp are separated.

[0014] The effects of the invention

[0015] This disclosure enables the provision of a separation method that allows the separation of a water-absorbing polymer from a mixture comprising a water-absorbing polymer and pulp. Attached Figure Description

[0016] [ Figure 1 ] Figure 1 This is a flowchart illustrating the separation method according to this implementation scheme. Detailed Implementation

[0017] Exemplary embodiments are described below with reference to the accompanying drawings. Note that for ease of explanation, the dimensions in the drawings are exaggerated and may differ from the actual ratios.

[0018] The separation method according to this embodiment is a method for separating absorbent polymers and pulp. The separation method is, for example, a method for separating absorbent polymers and pulp from an absorbent article comprising absorbent polymers and pulp. Examples of such absorbent articles include disposable diapers, diaper pads, sanitary napkins, bed sheets, and pet pads. The absorbent article includes, for example, a permeable topsheet, a waterproof bottomsheet, and absorbent material disposed between the topsheet and the bottomsheet. The absorbent material comprises absorbent polymers and pulp and is capable of absorbing water that permeates through the topsheet.

[0019] like Figure 1 As shown, the separation method includes a feeding step S2 and a recovery step S5. The separation method may also include a pretreatment step S1, a stirring step S3, and a settling step S4.

[0020] (Preprocessing step S1)

[0021] Pretreatment step S1 is performed before supply step S2. In pretreatment step S1, the absorbent article is treated in a manner that allows the absorbent polymer and pulp to be easily separated in subsequent steps. In pretreatment step S1, the absorbent material and other materials besides the absorbent material are separated by at least one of mechanical or chemical treatment, and the separated absorbent material is recovered. Examples of mechanical treatment include crushing and pressurization. Examples of chemical treatment include, for example, chemical reagent treatment to dissolve the adhesive. Residues that are materials other than the absorbent material and cannot be separated may adhere to the absorbent material, which includes the absorbent polymer and pulp, obtained in pretreatment step S1.

[0022] (Supply step S2)

[0023] In the supply step S2, bubbles are supplied to the mixture comprising the absorbent polymer and pulp. The method of supplying the bubbles is not limited; for example, a bubble liquid in which bubbles are dispersed in a liquid can be prepared, and the bubble liquid can be added to a container containing the mixture comprising the absorbent polymer and pulp. The bubbles can also be generated in a mixture comprising the absorbent polymer, pulp, and liquid.

[0024] A water-absorbing polymer is, for example, a hydrogel having a three-dimensional network structure formed by cross-linking and capable of absorbing water from a mixture. The water-absorbing polymer can be at least one polymer selected from the group consisting of polyacrylate polymers, polysulfonate polymers, maleic anhydride polymers, polyaspartate polymers, polyglutamate polymers, and polyalgate polymers.

[0025] The preferred water-absorbing polymers include polyacrylate water-absorbing polymers. This is because polyacrylate water-absorbing polymers are common and widely used, and can be widely applied in recycling technologies. Polyacrylate water-absorbing polymers are water-absorbing polymers comprising at least one polyacrylate structure selected from the group consisting of sodium polyacrylate, potassium polyacrylate, calcium polyacrylate, and magnesium polyacrylate. The shape and size of the water-absorbing polymer are not limited; water-absorbing polymers with desired shapes and sizes can be used.

[0026] For example, pulp is an aggregate of cellulose fibers. Pulp includes at least one selected from wood pulp made from wood, non-wood pulp made from plants other than wood, and recycled pulp made from waste paper. Pulp can be produced by mechanical processing, chemical processing, or a combination thereof. The shape and size of pulp are not limited; pulp with the desired shape and size can be used.

[0027] The bubbles include at least one of nanobubbles or microbubbles. These bubbles readily attach to the absorbent polymer and can cause the polymer to float upwards. The smaller the diameter of these bubbles, the less buoyancy they have, the easier they are to remain in the water, and the less likely they are to disappear once they float to the surface. However, in this embodiment, the bubbles are not limited to those including at least one of microbubbles or nanobubbles, and charged bubbles may also be used.

[0028] For example, the average bubble diameter ranges from 1 nm to 100 μm. By setting the average bubble diameter within this range, bubbles can adhere to the hydrophobic polymer, and the hydrophobic polymer can easily float upwards. The average bubble diameter can be smaller than the diameter of the swollen hydrophobic polymer piece. The average bubble diameter is, for example, the average diameter of approximately 100 bubbles measured through image analysis.

[0029] The gas contained in the bubbles is not limited, as long as it allows the hygroscopic polymer to float upwards in the mixture. Inert gases that do not decompose the hygroscopic polymer can be used, examples of which include hydrogen, nitrogen, oxygen, carbon monoxide, carbon dioxide, air, inert gases, hydrocarbons such as methane, and nitrogen oxides such as nitric oxide. Preferably, the bubbles include at least one gas selected from the group consisting of hydrogen, nitrogen, oxygen, carbon dioxide, air, and inert gases. Examples of inert gases include helium and argon. Gases of the above types are readily available and suitable for the recycling of hygroscopic polymers because they are less reactive and less likely to damage the polymers.

[0030] The method for generating bubbles is unrestricted and can utilize known methods such as rotating fluid flow, static mixer, ejector, cavitation, Venturi method, pressure melting, pore method, cyclone method, ultrasonic method, vapor condensation method, and electrolysis. Bubbles can be generated directly in a mixture comprising absorbent polymers and pulp, or after generating a bubble-containing liquid by generating bubbles in a liquid excluding absorbent polymers and pulp, the bubble-containing liquid can be added to a mixture comprising absorbent polymers and pulp.

[0031] (Recycling step S5)

[0032] In the recycling step S5, in a mixture comprising a superabsorbent polymer and pulp, the superabsorbent polymer with attached bubbles floats upwards, while the pulp settles, and the superabsorbent polymer separated in the mixture is recovered. Note that an example in which the mixture comprises superabsorbent polymer, pulp, and water will be described, but this embodiment is not limited to this form. Since ordinary superabsorbent polymers and ordinary pulp have a greater relative density than water, and both settle in water even after absorbing water and swelling, it is not easy to separate superabsorbent polymers and pulp using the difference in specific gravity. However, bubbles, including at least one of microbubbles or nanobubbles, more selectively attach to superabsorbent polymers rather than to pulp. The superabsorbent polymer floats upwards in the mixture because its apparent relative density becomes less than that of water due to the attachment of the bubbles. Conversely, the pulp, with a relative density greater than that of water, settles in the mixture because the bubbles are less likely to attach to it compared to the superabsorbent polymer. As described above, the absorbent polymer floats upward in the mixture, while the pulp settles, thus separating the absorbent polymer and the pulp.

[0033] As mentioned above, the relative density of polyacrylate hygroscopic polymers is greater than the relative density of the liquid in the mixture; an example of the relative density of sodium polyacrylate is approximately 1.2 g / cm³. 3 As mentioned above, the relative density of pulp is also greater than the relative density of the liquid in the mixture; an example of the relative density of cellulose is approximately 1.5 g / cm³. 3 In this embodiment, since the liquid in the mixture is water, its density is approximately 1 g / cm³. 3 However, the liquid in the mixture can be any liquid other than water. Examples of liquids other than water are not limited, as long as the absorbent polymer floats upwards due to the adhesion of air bubbles and the pulp settles, but it can be a liquid that includes organic substances such as alcohols.

[0034] The superabsorbent polymer floats upwards in the mixture while remaining in its solid state. This facilitates the recovery of the superabsorbent polymer from the container containing the mixture. The recovered superabsorbent polymer can be recycled through processes such as washing. Note that "solid" here also includes gels. "Floating upwards in the mixture while remaining in its solid state" means that the superabsorbent polymer floats upwards in the mixture without dissolving by using an oxidizing agent such as ozone to reduce its molecular weight. Therefore, it is preferable that the bubbles include gases with a lower ability to decompose the superabsorbent polymer than ozone.

[0035] The pH of the mixture is not limited, as long as the absorbent polymer and pulp can be separated. From the viewpoint of improving the recovery rate of the absorbent polymer, the pH of the mixture is preferably set between 2.5 and 11. The pH of the mixture can be above 6. The pH of the mixture can be below 8. The pH of the mixture can be adjusted by adding citric acid, sodium hydroxide, etc. to the above liquid.

[0036] As described above, in this embodiment, when the absorbent polymer floats upwards in the mixture, it is easily recovered from the container containing the mixture. The method for recovering the absorbent polymer is not limited; for example, it can be recovered by tilting the container containing the mixture and removing the absorbent polymer floating on the surface of the mixture. Alternatively, the absorbent polymer can be recovered from the container by scooping it out from the surface of the mixture.

[0037] In recycling step S5, not only can the absorbent polymers be recycled, but also the settled pulp. The method of pulp recycling is not limited; for example, the pulp can be recycled by sucking it from the bottom of a container containing the mixture. The pulp and liquid above the settled pulp can be removed from the container, and the remaining pulp at the bottom of the container can be recycled. Oxidants such as ozone can be added to the recycled pulp to decompose and remove trace amounts of absorbent polymers adhering to the pulp.

[0038] (Settlement step S4)

[0039] The pulp in the mixture is allowed to settle in settling step S4, between the feeding step S2 and the recycling step S5. The relative density of the pulp is greater than that of water, making it less likely that air bubbles that would cause the pulp to float upwards will adhere to the pulp surface. Therefore, the pulp tends to settle in the mixture. The method for settling the pulp is not limited, and known methods can be used to achieve this. As described above, since the relative density of the pulp is greater than that of water, the pulp can settle, for example, by stopping the generation of air bubbles to create a static state.

[0040] (Stirring step S3)

[0041] The mixture is stirred in stirring step S3, between the feeding step S2 and the settling step S4. By stirring the mixture in the presence of air bubbles, the bubbles adhere to the absorbent polymer, while the entanglement between the absorbent polymer and the pulp is broken. Pulp located in the floating path of the absorbent polymer can also be moved, inhibiting the upward floating of the absorbent polymer. This makes it easier for the absorbent polymer to float upward and for the pulp to settle, thus promoting the separation of the absorbent polymer and the pulp. The method of stirring the mixture is not limited and can be performed by known methods. For example, a stirrer, a glass rod, etc., can be used to stir the mixture. For example, the mixture can also be stirred by shaking the container containing the mixture.

[0042] As described above, the separation method according to this embodiment includes a supply step S2, wherein bubbles, including at least one of nanobubbles or microbubbles, are supplied to a mixture comprising a water-absorbing polymer and pulp. The separation method includes a recovery step S5, wherein in the mixture comprising the water-absorbing polymer and pulp, the water-absorbing polymer with attached bubbles floats upwards while the pulp settles, thus recovering the water-absorbing polymer separated from the mixture. In this separation method, the water-absorbing polymer and pulp are separated.

[0043] The separation method according to this embodiment includes a feeding step S2, wherein charged bubbles are supplied to a mixture comprising a water-absorbing polymer and pulp. The separation method includes a recovery step S5, wherein, in the mixture comprising the water-absorbing polymer and pulp, the water-absorbing polymer with attached bubbles floats upwards while the pulp settles, thus recovering the water-absorbing polymer separated from the mixture. In this separation method, the water-absorbing polymer is separated from the pulp.

[0044] Therefore, in the separation method according to this embodiment, the absorbent polymer can be recovered from a mixture including the absorbent polymer and pulp.

[0045] Example

[0046] The present embodiment will now be described in more detail with reference to the embodiments and examples, but the present embodiment is not limited to these embodiments.

[0047] [Example 1]

[0048] (Preparation of sparkling water)

[0049] First, prepare the sparkling water. Specifically, first, place 1 L of ion-exchanged water into a pressure vessel (Unicontrols, TA90N). Next, pump nitrogen gas from a gas cylinder into the pressure vessel at 0.2 MPa and manually shake the vessel. Close the nitrogen inlet tube and pour the sparkling water, including at least one of nanobubbles or microbubbles, from the pressure vessel into an empty beaker.

[0050] (Separation test)

[0051] Next, a separation experiment was conducted. Specifically, first, 10 mL of deionized water was added to 30 mg (0.3% by mass) of a water-absorbing polymer made from sodium polyacrylate and 70 mg (0.7% by mass) of cellulose pulp, and the mixture was stirred for 1 minute to allow the water-absorbing polymer and pulp to swell. Next, 200 mL of the bubble water obtained as described above was added to the swollen water-absorbing polymer and pulp.

[0052] The mixture containing the superabsorbent polymer, pulp, and sparkling water was stirred 10 times with a spatula and allowed to stand for approximately 3 minutes. Then, after gently shaking the beaker manually, the upper and lower layers were collected by tilting the beaker. The collected liquids from each layer were filtered, air-dried, and weighed. The recovery rate of each layer was calculated by dividing the mass of the dried upper layer by the mass of the first added superabsorbent polymer (30 mg) and the mass of the dried lower layer by the mass of the first added pulp (70 mg). The results are shown in Table 1.

[0053] [Example 2]

[0054] In the separation experiment, after the absorbent polymer and pulp swelled with deionized water, 100 mg of citric acid was added at a concentration of approximately 1% by mass, and the mixture was stirred for 30 seconds. Otherwise, the recovery rate of each layer was calculated as in Example 1.

[0055] [Example 3]

[0056] (Preparation of sparkling water)

[0057] First, prepare the sparkling water. Specifically, first, place 300 mL of a NaOH aqueous solution with pH 13.5 into a pressure vessel (Unicontrols, TA90N). Next, pump nitrogen gas from a gas cylinder into the pressure vessel at 0.2 MPa while manually shaking the vessel. Close the nitrogen inlet tube and pour the sparkling water, including at least one of nanobubbles or microbubbles, from the pressure vessel into an empty beaker.

[0058] (Separation test)

[0059] Next, a separation experiment was conducted. Specifically, first, 10 mL of ion-exchanged water was added to 30 mg (0.3% by mass) of the absorbent polymer and 70 mg (0.7% by mass) of the pulp, and the mixture was stirred for 1 minute to allow the absorbent polymer and pulp to swell. Next, 300 mL of the aerated water obtained as described above was added to the mixture. In addition, the recovery rate of each layer was calculated as in Example 1.

[0060] [Example 4]

[0061] (Preparation of sparkling water)

[0062] First, 1.5 L of ion-exchanged water was placed in a beaker. Next, using a microbubble generator (AURA TEC: OM4-MDG-045), bubbled water was prepared by bubbling with air until the water in the beaker turned white and bubbles appeared on the surface, comprising at least one of nanobubbles or microbubbles. Note that, measured by laser diffraction and scattering, the average bubble diameter was approximately 1 μm when the cumulative value of the particle size distribution based on quantity was 50%.

[0063] (Separation test)

[0064] Next, a separation experiment was conducted. Specifically, first, 20 mL of deionized water was added to 60 mg (0.3% by mass) of the absorbent polymer and 140 mg (0.7% by mass) of the pulp, and the mixture was stirred for 1 minute to allow the absorbent polymer and pulp to swell. Next, 150 mL of the bubble water obtained as described above was added to the swollen absorbent polymer and pulp. In addition, the recovery rate of each layer was calculated as in Example 1.

[0065] [Example 5]

[0066] In the separation experiment, after the absorbent polymer and pulp swelled with deionized water, 200 mg of citric acid was added at a concentration of approximately 1% by mass, and the mixture was stirred for 30 seconds. Otherwise, the recovery rate of each layer was calculated as in Example 4.

[0067] [Example 6]

[0068] First, 1 L of ion-exchanged water was placed in a beaker. Next, using a microbubble generator (AURA TEC: OM4-MDG-045), bubbled water was prepared by bubbling until the water in the beaker turned white and bubbles appeared on the surface, comprising at least one of nanobubbles or microbubbles. Note that, measured by laser diffraction and scattering, the average bubble diameter was approximately 1 μm when the cumulative value of the particle size distribution based on quantity was 50%. Next, 200 mL of the above-mentioned bubbled water was added to a beaker containing 100 mL of a 1.78 g / L NaOH aqueous solution to prepare bubbled water with a pH of 12.3 NaOH aqueous solution.

[0069] Next, a separation experiment was conducted. Specifically, first, 20 mL of deionized water was added to 60 mg (0.3% by mass) of the superabsorbent polymer and 140 mg (0.7% by mass) of pulp, and stirred for 1 minute to allow the superabsorbent polymer and pulp to swell. Next, 300 mL of aerated water at pH 12.3, obtained as described above, was added to the swollen superabsorbent polymer and pulp. In addition, the recovery rate of each layer was calculated as in Example 4.

[0070] [Example 7]

[0071] (Preparation of sparkling water)

[0072] First, place 1 L of ion-exchanged water into a beaker. Next, using a microbubble generator (Fresh by Design, PY101CF-E), bubble water is prepared by bubbling with nitrogen gas from a gas cylinder, including at least one of nanobubbles or microbubbles.

[0073] Next, a separation experiment was conducted. Specifically, first, 20 mL of deionized water was added to 60 mg (0.3% by mass) of the absorbent polymer and 140 mg (0.7% by mass) of the pulp, and the mixture was stirred for 1 minute to allow the absorbent polymer and pulp to swell. Next, 150 mL of the bubble water obtained as described above was added to the swollen absorbent polymer and pulp. In addition, the recovery rate of each layer was calculated as in Example 1.

[0074] [Example 8]

[0075] In the separation experiment, after the absorbent polymer and pulp swelled with deionized water, 200 mg of citric acid was added at a concentration of approximately 1% by mass, and the mixture was stirred for 30 seconds. Otherwise, the recovery rate of each layer was calculated as in Example 7.

[0076] [Comparative Example 1]

[0077] First, 20 mL of deionized water was added to 60 mg (0.3% by mass) of the superabsorbent polymer and 140 mg (0.7% by mass) of the pulp, and stirred for 1 minute to allow the superabsorbent polymer and pulp to swell. Next, another 200 mL of deionized water was added to the swollen superabsorbent polymer and pulp, and bubbles with an average bubble diameter greater than 1 mm were generated in the mixture by bubbling. Then, the recovery rate of each layer was calculated as in Example 1.

[0078] [Comparative Example 2]

[0079] In the separation test, after the absorbent polymer and pulp swelled with deionized water, 200 mg of citric acid was added at a concentration of approximately 1% by mass, and the mixture was stirred for 30 seconds. Otherwise, the recovery rate of each layer was calculated as in Comparative Example 1.

[0080] [Comparative Example 3]

[0081] In the separation test, after the absorbent polymer and pulp were swollen with ion-exchanged water, 200 mL of bubble-filled water with pH 12.3 obtained in Example 6 was further added to the swollen absorbent polymer and pulp. Bubbling was then performed to generate bubbles with an average bubble diameter greater than 1 mm in the mixture. Otherwise, the recovery rate of each layer was calculated as in Comparative Example 1.

[0082] [Table 1]

[0083]

[0084] In Examples 1 through 8, bubbles comprising at least one of microbubbles or nanobubbles were generated using three types of microbubble generators. As a result, in all cases, the bubbles selectively adhered to the absorbent polymer, which floated upwards in the mixture, while the pulp settled to the bottom of the beaker due to its own weight, thus separating the upper layer, which mainly comprised the absorbent polymer, from the lower layer, which mainly comprised the pulp. Because the absorbent polymer separated from the pulp and floated upwards, it could be easily recovered. It is evident that the bubble density varied depending on the microbubble generator; the higher the bubble density, the higher the recovery rate of the absorbent polymer. Under acidic, neutral, and alkaline conditions, the mixture was separated into upper and lower layers, but the recovery rate of the absorbent polymer was higher under acidic and neutral conditions than under alkaline conditions.

[0085] On the other hand, in Comparative Examples 1 to 3, bubbles with an average bubble diameter greater than 1 mm were generated, but neither the superabsorbent polymer nor the pulp floated upwards in the mixture and both sank to the bottom of the beaker due to their own weight, so the superabsorbent polymer could not be recovered. In Comparative Examples 1 to 3, it was considered unlikely that bubbles with an average bubble diameter greater than 1 mm would adhere to either the superabsorbent polymer or the pulp.

[0086] The reason why more air bubbles adhere to absorbent polymers than to pulp is speculated as follows: Absorbent polymers such as polyacrylates have high ionization, and the electric double layer is believed to be formed by carboxylate ions (R-COO-) in the liquid. -The superabsorbent polymer (SAP) is formed by charged counterions. In contrast, pulp has a lower degree of ionization than the superabsorbent polymer. Bubbles, including at least one of microbubbles or nanobubbles, have a negative zeta potential, and are therefore believed to adhere to the superabsorbent polymer more readily than pulp, forming more counterions and causing the superabsorbent polymer to float upwards. In contrast, pulp is believed to settle due to its own weight, as it has fewer positive charges, making it less likely for bubbles to adhere to it. Note that this embodiment is not limited to the above mechanism, but is based on the above mechanism assuming that the same effect is achieved using charged bubbles, and is not limited to bubbles including at least one of microbubbles or nanobubbles.

[0087] The entire contents of Japanese Patent Application No. 2020-184207 (filed on November 4, 2020) are incorporated herein by reference.

[0088] Although embodiments have been described, they can be modified or altered based on the foregoing disclosure. All components of the foregoing embodiments and all features described in the claims can be extracted and combined individually, provided they do not contradict each other.

[0089] Explanation of reference numerals in the attached figures

[0090] S1 Pre-processing steps

[0091] S2 Supply Steps

[0092] S3 Stirring Step

[0093] S4 Settlement Steps

[0094] S5 Recycling Steps

Claims

1. A method for separating absorbent polymers and pulp, the method comprising: A supply step, wherein the supply step is used to supply bubbles, including at least one of nanobubbles or microbubbles, into a mixture comprising the absorbent polymer and the pulp; as well as The recycling step, used to recover the absorbent polymer, is separated in a mixture comprising the absorbent polymer and pulp by the absorbent polymer with attached air bubbles floating upwards and the pulp settling in the mixture. The average bubble diameter is between 1 nm and 100 μm.

2. The separation method according to claim 1, wherein the water-absorbing polymer floats upward in the mixture while maintaining a solid state.

3. The separation method according to claim 1 or 2, wherein the water-absorbing polymer includes polyacrylate water-absorbing polymers.

4. The separation method according to claim 1 or 2, wherein the bubbles comprise at least one gas selected from the group consisting of hydrogen, nitrogen, oxygen, carbon dioxide, air, and inert gases.

5. The separation method according to claim 1 or 2, further comprising: A settling step between the supply step and the recycling step, which causes the pulp in the mixture to settle.

6. The separation method according to claim 5 further includes: The stirring step of the mixture between the supply step and the settling step.

7. A method for separating absorbent polymers and pulp, the method comprising: A supply step, wherein the supply step is used to supply charged air bubbles into a mixture comprising the absorbent polymer and the pulp; as well as The recycling step, used to recover the absorbent polymer, is separated in a mixture comprising the absorbent polymer and the pulp by the absorbent polymer with attached air bubbles floating upwards and the pulp settling in the mixture. The average bubble diameter is between 1 nm and 100 μm.

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