Waste polarizing plate recycling system and method

Abstract

The present invention provides a waste polarizer recycling system and method. The recycling system includes a first and a second extraction unit, a first and a second separation unit, and a purification and concentration system. The first extraction unit is used to extract iodine-containing waste polarizer fragments, and the iodine-containing extract and waste polarizer plastic fragments are separated by the first separation unit. The second extraction unit is used to re-extract the waste polarizer plastic fragments, and the re-extracted liquid and waste polarizer plastic fragments are separated by the second separation unit. The purification and concentration system includes a filter unit, a membrane separation unit, and a distillation and concentration unit connected in series. The filter unit is used to receive the iodine-containing extract and filter out the gel to obtain the iodine-containing filtrate. The membrane separation unit includes at least one reverse osmosis membrane to receive the iodine-containing filtrate and separate the iodine reverse osmosis liquid and the permeate solvent by reverse osmosis. The distillation and concentration unit is used to receive the iodine reverse osmosis liquid and distill it to obtain the iodine concentrated liquid and the distillation liquid. The re-extraction solvent in the second extraction unit includes the permeate solvent and the distillation liquid.

Description

Technical Field

[0001] This invention relates to a waste recycling system, and more particularly to a waste polarizing plate recycling system and method. Background Technology

[0002] Polarizers are one of the main raw materials for liquid crystal displays (LCDs). Their structure typically includes a polarizing layer, upper and lower adhesive layers, upper and lower protective / release layers, and a reflective film. The polarizing layer is primarily made of dyed and stretched PVA (polyvinyl alcohol) film. This layer is the main component of the polarizer, determining its polarization performance and light transmittance, and also significantly affecting its color tone and optical durability. The upper and lower protective / release layers and the reflective film can be recycled after cleaning. The dyeing material for the polarizing layer is usually iodine. However, iodine sublimates under slight heating, causing purple smoke during the incineration of waste polarizers, raising environmental concerns and leading to a ban on this method of waste polarizer disposal. Therefore, how to dispose of waste polarizers has become a key research focus. Furthermore, the complex composition of polarizers makes sorting difficult, and their bulky and space-consuming nature further complicates recycling. Summary of the Invention

[0003] This invention relates to a waste polarizing plate recycling system that not only removes iodine from the polarizing plate but also recycles iodine and plastics for reuse.

[0004] The present invention also relates to a method for recycling waste polarizing plates, which can purify and concentrate the extracted iodine ion solution and recycle the solvent for reuse, thereby reducing recycling costs.

[0005] According to an embodiment of the present invention, a waste polarizing plate recycling system includes a first extraction unit, a first separation unit, a second extraction unit, a second separation unit, and a purification and concentration system. The first extraction unit receives iodine-containing waste polarizing plate fragments and extracts them using an extraction solvent to obtain an extraction mixture. The first separation unit receives the extraction mixture from the first extraction unit and separates it to obtain an iodine-containing extract and waste polarizing plate plastic fragments. The second extraction unit receives the waste polarizing plate plastic fragments from the first separation unit and performs re-extraction to obtain a re-extraction mixture. The second separation unit receives the re-extraction mixture from the second extraction unit and separates it to obtain a re-extraction liquid and waste polarizing plate plastic fragments. The purification and concentration system includes multiple filtration units, a membrane separation unit, and a distillation and concentration unit connected in series. The filtration unit receives the iodine-containing extract and filters out the gel-like substance to obtain an iodine-containing filtrate. The membrane separation unit includes at least one reverse osmosis membrane to receive the iodine-containing filtrate and separates the iodine reverse osmosis liquid and the permeate solvent via reverse osmosis. The distillation and concentration unit is used to receive the iodine reverse osmosis solution and distill it to obtain iodine concentrate and distillate. The re-extraction solvent in the second extraction unit includes the osmosis solvent and the distillate.

[0006] According to another embodiment of the present invention, a method for recycling waste polarizing plates includes mixing and stirring iodine-containing waste polarizing plate plastic fragments with an extraction solvent to obtain an extraction mixture, and then separating the extraction mixture to separate the iodine-containing extract and the waste polarizing plate plastic fragments. The iodine-containing extract is then filtered to remove the gel-like substance, and an iodine-containing filtrate is obtained. The iodine-containing filtrate is then treated using a membrane separation unit containing at least one reverse osmosis membrane to separate the iodine reverse osmosis solution and the permeate solvent. The iodine reverse osmosis solution from the membrane separation unit is then distilled to obtain an iodine concentrate and a distillate. The permeate solvent and the distillate are recovered and formulated into a re-extraction solvent or the extraction solvent, and then the waste polarizing plate plastic fragments are extracted again. The re-extraction mixture is then separated to separate the re-extraction solution and the waste polarizing plate plastic fragments, wherein the obtained re-extraction solution is recycled for formulating the extraction solvent.

[0007] Based on the above, this invention, in addition to the first extraction unit and the first separation unit to extract the iodine-containing extract, also includes a purification and concentration system for the recycling of waste polarizing plates. This system performs filtration and membrane separation on the extracted iodine-containing extract, gradually increasing the iodine concentration and thereby improving recycling efficiency and reducing recycling costs. Furthermore, the second extraction unit and the second separation unit can re-extract the waste polarizing plate plastic fragments separated by the first separation unit, allowing even trace amounts of iodine to be recovered. Since the waste polarizing plate plastic fragments contain almost no iodine, facilitating subsequent recycling, and the re-extraction liquid, containing only trace amounts of iodine, can be directly recycled as raw material for the next extraction solvent, and the permeate solvent and distillate from the aforementioned membrane separation and distillation stages can be recycled and reused, saving material costs, avoiding secondary pollution, and achieving the goals of energy conservation and carbon reduction. Attached Figure Description

[0008] Figure 1 This is a block diagram of a waste polarizing plate recycling system according to the first embodiment of the present invention;

[0009] Figure 2 This is a flowchart illustrating the waste polarizing plate recycling process according to the second embodiment of the present invention;

[0010] Figure 3 It is a graph of KI concentration versus conductivity, prepared using a calibration solution;

[0011] Figure 4 This is the absorption spectrum of the plastic solution before and after iodine removal, obtained by UV absorption measurement.

[0012] Explanation of reference numerals in the attached figures

[0013] 100: Waste Polarizing Plate Recycling System

[0014] 110: First Extraction Unit

[0015] 112: First Separation Unit

[0016] 114: Second Extraction Unit

[0017] 116: Second Separation Unit

[0018] 118: Temporary Storage Slot

[0019] 120: Purification and Concentration System

[0020] 122: Filter unit

[0021] 124: Membrane detachment unit

[0022] 126: Distillation and Concentration Unit

[0023] 200, 202, 204, 206, 208, 210: Steps

[0024] WP: Waste polarizing plate fragments containing iodine Detailed Implementation

[0025] The present invention will now be described in detail with reference to exemplary embodiments thereof, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numerals are used in the drawings and description to denote the same or similar parts. The terms “comprising,” “including,” “having,” etc., as used herein are open-ended terms; that is, they include, but are not limited to, these terms.

[0026] Figure 1 This is a block diagram of a waste polarizing plate recycling system according to the first embodiment of the present invention.

[0027] Please refer to Figure 1The waste polarizing plate recycling system 100 of this embodiment basically includes a first extraction unit 110, a first separation unit 112, a second extraction unit 114, a second separation unit 116, and a purification and concentration system 120. The first extraction unit 110 receives iodine-containing waste polarizing plate fragments WP and extraction solvent. The extraction solvent may include alkalis and solvents, and the extraction solvent may be prepared first by a solvent preparation unit (not shown) before being sent to the first extraction unit 110; or, extraction solvent raw materials prepared in proportion may be added separately to the first extraction unit 110 for preparation. In the first extraction unit 110, the above-mentioned extraction solvent and iodine-containing waste polarizing plate fragments WP are extracted to obtain an extraction mixture. The first extraction unit 110 may include a stirring element and a heating element. The alkali in the extraction solvent may be selected from sodium hydroxide, potassium hydroxide, or alkaloids, and the solvent in the extraction solvent may include alcohols; in one embodiment, the solvent is, for example, an ethanol solution. However, the present invention is not limited thereto, and the above-mentioned extraction solvent may also be a known extraction solvent. In one embodiment, if the extraction solvent contains potassium hydroxide, a potassium iodide (KI) solution will be obtained through a chemical reaction. The first separation unit 112 is disposed between the first extraction unit 110 and the purification and concentration system 120, for receiving and separating the extraction mixture from the first extraction unit 110 to obtain an iodine-containing extract and waste polarizing plate plastic fragments. The iodine-containing extract is conveyed to the purification and concentration system 120, while the waste polarizing plate plastic fragments are conveyed to the second extraction unit 114. The first separation unit 112 may include a filter or a centrifuge. However, the invention is not limited to this; other solid-liquid separation devices may also be used for the first separation unit 112. The second extraction unit 114 is disposed after the first separation unit 112 to re-extract the waste polarizing plate plastic fragments, obtaining a re-extracted mixture. In one embodiment, the re-extraction solvent used in the second extraction unit 114 may be an ethanol solution of approximately the same concentration as the extraction solvent. In another embodiment, the re-extraction solvent may include an alkali and a solvent, wherein the alkali is sodium hydroxide, potassium hydroxide, or an alkaloid, and the solvent may include ethanol.

[0028] The purification and concentration system 120 can be directly connected to the first separation unit 112, allowing the extracted iodine-containing extract to directly enter the purification and concentration system 120. However, the invention is not limited thereto; in another embodiment, a temporary storage tank (not shown) can be provided between the first separation unit 112 and the purification and concentration system 120 to temporarily store the iodine-containing extract. The purification and concentration system 120 includes a filtration unit 122, a membrane separation unit 124, and a distillation and concentration unit 126 connected in series. Figure 1Although only one filtration unit 122, one membrane separation unit 124, and one distillation concentration unit 126 are shown, it should be understood that the number of the aforementioned units can be increased according to needs. For example, coarse filtration can be performed before filtration unit 122, and different filter membranes can be used in filtration unit 122, such as ultrafiltration (UF) membranes, nanofiltration (NF) membranes, or UF membranes and NF membranes in series. Taking ultrafiltration (UF) membranes as an example, filter membranes with pore sizes below 0.02 μm can be used. The filtration unit 122 is used to receive the above-mentioned iodine-containing extract and filter out the colloidal matter to obtain an iodine-containing filtrate. The filtered filtrate is transported to the membrane separation unit 124, and the colloidal matter, which may include PVA and glue (such as aqueous glue or UV glue), is discharged together, and the PVA and solid waste can be recycled.

[0029] Please continue to refer to Figure 1 The membrane separation unit 124 includes at least one reverse osmosis membrane for receiving the iodine-containing filtrate and separating the iodine reverse osmosis solution and the permeate solvent via reverse osmosis. The number of reverse osmosis membranes in the membrane separation unit 124 can be increased as needed, for example, using two types of reverse osmosis membranes to concentrate the filtrate. In one embodiment, the total dissolved solids (TDS) removal rate of the reverse osmosis membrane can be greater than 90%. In other words, most of the solvent contained in the iodine-containing filtrate can be permeated and separated by the membrane separation unit 124, and can be piped to the first extraction unit 110 or the second extraction unit 114 to be prepared as an extraction solvent or a re-extraction solvent. The distillation concentration unit 126 receives the iodine reverse osmosis solution from the membrane separation unit 124 and performs distillation to obtain an iodine concentrate and a distillate, wherein the distillation concentration unit 126 is, for example, an ambient temperature distillation concentration unit or a vacuum distillation concentration unit. Since most of the permeate solvent in the iodine-containing filtrate has been removed by the membrane separation unit 124 before distillation in the distillation concentration unit 126, the energy required in the distillation concentration process can be greatly reduced, thus significantly reducing the recovery cost and making it suitable for industrial processing with large recovery volumes.

[0030] The distillate collected by the distillation and concentration unit 126 can be piped to a recovery tank (not shown) for use in preparing extraction or re-extraction solvents, thus saving material costs, avoiding secondary pollution, and achieving the goals of energy conservation and carbon reduction. According to the above system design, the solvent recovery rate can reach over 90%. Specifically, a recovery tank (not shown) can be added to the transport path from the permeate solvent discharged from the membrane separation unit 124 and the distillate discharged from the distillation and concentration unit 126 back to the second extraction unit 114. The concentration of the recovery tank can be adjusted according to the required re-extraction solvent concentration for the second extraction unit 114 before being sent from the recovery tank to the second extraction unit 114. The second extraction unit 114 is mainly used for re-extracting the waste polarizing plate plastic fragments separated by the first separation unit 112. These waste polarizing plate plastic fragments may contain trace amounts of unextracted iodine. Therefore, the re-extraction mixture from the second extraction unit 114 can enter the second separation unit 116 to separate waste polarizing plate plastic fragments and a re-extraction liquid containing solvent and trace amounts of iodine. The re-extraction liquid containing solvent and trace amounts of iodine can be recycled to prepare extraction solvents and re-enter the first extraction unit 110. The aforementioned waste polarizing plate plastic fragments may contain plastics such as TAC (cellulose triacetate), PMMA (polymethyl methacrylate), COP (cyclic olefin polymer), and PET (ethylene terephthalate), which are commonly found in polarizing plates, and have an iodine content of <0.1% w / w. Therefore, they can be directly incinerated or separated and reused. The second separation unit 116 may include a filter or a centrifugal separator. Since the alkali concentration of the extraction solvent in the first extraction unit 110 is related to the iodine equivalent, in order to ensure that the alkali concentration is maintained within a preset range, a temporary storage tank 118 can be added in the transport path of the re-extraction liquid discharged from the second separation unit 116 into the first extraction unit 110 to replenish water or adjust the pH value in a timely manner.

[0031] Figure 2 This is a flowchart illustrating a waste polarizer plate recycling process according to a second embodiment of the present invention, and the recycling system of the first embodiment can be used; therefore, it will be used hereinafter. Figure 1 The same element is represented by a symbol.

[0032] In step 200, the iodine-containing waste polarizing plate fragments WP are mixed and stirred with the extraction solvent to obtain an extraction mixture. The extraction solvent may include an alkali and a solvent. The alkali may be, for example, sodium hydroxide, potassium hydroxide or alkaloids, and the solvent may be an alcohol. From an environmentally friendly point of view, an ethanol solution may be used as the solvent.

[0033] In step 202, the above-mentioned extraction mixture is separated to separate the iodine-containing extract and the waste polarizing plate plastic fragments, wherein the mixture is separated by means such as filtration or centrifugation.

[0034] In step 204, the aforementioned waste polarizing plate plastic fragments are re-extracted, and the re-extraction solvent used can be an aqueous alcohol solution of similar concentration to the extraction solvent. Furthermore, the re-extraction mixture obtained in step 204 can be further separated into a re-extraction liquid, as shown by the dotted line, and recycled for use in preparing the extraction solvent in step 200. For example, the aforementioned re-extraction mixture can be separated by filtration or centrifugation to separate the waste polarizing plate plastic fragments from the re-extraction liquid containing solvent and trace amounts of iodine. The re-extraction liquid containing solvent and trace amounts of iodine can be used as a raw material for the extraction solvent in step 200. The aforementioned waste polarizing plate plastic fragments may contain plastics such as TAC, PMMA, COP, and PET, which are commonly found in polarizing plates.

[0035] In step 206, the iodine-containing extract is filtered to remove the gel-like substance and obtain an iodine-containing filtrate. The filtration method for the iodine-containing extract includes, for example, using an ultrafiltration (UF) membrane, a nanofiltration (NF) membrane, or a UF membrane and an NF membrane in series. If the iodine-containing waste polarizing plate fragments WP contain gels or molecules with large molecular weights, a UF membrane can be used for filtration; if the iodine-containing waste polarizing plate fragments WP contain gels or molecules with small molecular weights, a UF membrane and an NF membrane in series can be used; or, an NF membrane can be used for filtration.

[0036] In step 208, the iodine-containing filtrate is treated using membrane separation unit 124 to separate the iodine reverse osmosis solution and the permeate solvent. Membrane separation unit 124 includes one or more reverse osmosis membranes, and the TDS removal rate of the reverse osmosis membranes is, for example, greater than 90%. The permeate solvent separated during the treatment of the filtrate using membrane separation unit 124, as shown by the dashed line, can be recovered and formulated into the re-extraction solvent for re-extracting the waste polarizing plate plastic fragments in step 204. In another embodiment, the permeate solvent can also be recovered and formulated into the extraction solvent used in step 200.

[0037] In step 210, the iodine reverse osmosis solution from membrane separation unit 124 is distilled to obtain iodine concentrate and distillate. The iodine concentrate recovered from the aforementioned steps, with a solid content of approximately 3 to 10% w / w, can be incorporated into the existing iodine recovery system of the polarizing plate factory, or purified into industrial-grade high-purity potassium iodide solid for reuse as raw material for polarizing plates. In this embodiment, the distillate from step 210, as shown by the dotted line, can also be recovered and formulated as the re-extraction solvent for re-extracting waste polarizing plate plastic fragments in step 204. In another embodiment, the distillate can also be recovered and formulated as the extraction solvent used in step 200.

[0038] The following experiments are listed to verify the efficacy of the present invention, but the present invention is not limited to the following content.

[0039] <analyze>

[0040] 1. Concentration of potassium iodide (KI) in the solution

[0041] Test instrument: Conductivity meter, model HTC-202U.

[0042] Test environment: room temperature.

[0043] Correction solution: KI concentration from 0.01% w / w to 8% w / w, pH≈9.5.

[0044] Figure 3 This is a graph of KI concentration versus conductivity, created using a calibration solution. Therefore, the KI concentration in the solution can be detected online using a conductivity meter, eliminating the need for offline extraction and separate testing, making it suitable for industrial production.

[0045] 2. Quantitative Measurement Method for Iodine Depletion Rate

[0046] Using a UV-Vis spectrometer, the UV absorbance of iodine-free plastic solutions (iodine removal rate set to 99%) and non-iodine-removed plastic solutions (iodine removal rate set to 0%) was measured. The iodine content was determined using the absorbance value at 225 nm. The results are as follows: Figure 4 As shown, the UV absorbance corresponding to a deiodization rate of 0% is 2.5, and the UV absorbance corresponding to a deiodization rate of 99% is 0.6.

[0047] Therefore, according to Figure 4 The result can be used to derive the following linear regression formula:

[0048] Iodine removal rate = -0.5211x + 1.3026

[0049] In the above formula, x represents UV absorbance.

[0050] <Example 1>

[0051] Prepare a Figure 1 The waste polarizing plate recycling system includes a first extraction unit 110, a 100-liter double-jacketed stirred tank, to which 53.52 kg of a 2% w / w potassium hydroxide (KOH) aqueous solution has been added and heated to 50°C. Then, 6.66 kg of iodine-containing waste polarizing plate is crushed into 2-5 mm fragments and fed into the first extraction unit 110 for extraction until the pH value reaches 9-10 and remains stable, which is the reaction endpoint. The extracted mixture is then separated into waste polarizing plate plastic fragments and iodine-containing extract using a centrifuge (as the first separation unit 112).

[0052] The iodine-containing extract is then pre-filtered in filter unit 122 (1 μm, PALL, pressure 1 kg / cm²), and then filtered using the UF membrane listed in Table 1 to remove the colloidal matter, yielding an iodine-containing filtrate. The iodine-containing filtrate then enters membrane separation unit 124, where KI is concentrated using two RO stages (RO1 and RO2) listed in Table 1. The first RO1 stage increases the KI concentration to 0.5% w / w–0.7% w / w, and the second RO2 stage increases the KI concentration to 2.0% w / w–3.0% w / w. The KI concentration here can be obtained using the analytical methods described above. The KI solution, after reverse osmosis, then enters the distillation and concentration unit 126 (30-liter rotary concentrator, 40℃~50℃, vacuum degree 10mmHg) for distillation to a KI aqueous solution with a solid content of about 6% w / w. About 50 kg of the ethanol solution removed by the membrane separation unit 124 and the distillation and concentration unit 126 will be stored in a recovery tank. After adjusting the solvent ratio, it can be used as a re-extraction solvent and recycled to the second extraction unit 114.

[0053] The waste polarizing plate plastic fragments separated by the centrifuge will enter the second extraction unit 114 (100-liter stirred tank), where 50 kg of re-extraction solvent will be added and stirred at room temperature for 1 hour. The re-extraction solution will then be separated in the second separation unit 116 to obtain the washed plastic (KI < 0.1% w / w) and a liquid containing solvent and trace amounts of iodine. The deiodination rate of the washed plastic can be estimated using the aforementioned quantitative measurement method for deiodination rate, where the UV absorbance is 0.70 and the deiodination rate is approximately 93.8%.

[0054] <Example 2>

[0055] The same recycling system as in Example 1 was used, but the recycled waste polarizing plates were replaced with simple polarizers (without adhesive layer, protective layer, etc.), and the UF film was also different, as detailed in Table 1 below.

[0056] Using the same recycling method as in Example 1, the washed plastic was subjected to UV irradiation, and the UV absorption was 0.73. The calculated deiodine removal rate was approximately 92.1%.

[0057] Table 1

[0058]

[0059] As can be seen from Table 1, the waste polarizer recycling system according to the present invention can efficiently remove iodine contained in waste polarizers.

[0060] In summary, the waste polarizing plate recycling system of the present invention has a purification and concentration system, which includes a filtration unit and a membrane separation unit. This allows for the filtration and concentration of the extracted iodine-containing extract, thus reducing energy consumption in the concentration process and consequently lowering recycling costs. Furthermore, the integration of a recycling system for the permeate solvent, distillate, and re-extraction solution further reduces material costs, avoids secondary pollution, and achieves the goals of energy conservation and carbon reduction.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A waste polarizing plate recycling system, characterized in that, include: The first extraction unit is used to receive iodine-containing waste polarizing plate fragments, extract the iodine-containing waste polarizing plate fragments using an extraction solvent, and obtain an extraction mixture. The first separation unit is used to receive the extraction mixture from the first extraction unit and separate it to obtain iodine-containing extract and waste polarizing plate plastic fragments. The second extraction unit is used to receive the waste polarizing plate plastic fragments from the first separation unit and perform re-extraction to obtain a re-extracted mixture; The second separation unit is used to receive the re-extraction mixture from the second extraction unit and separate it; as well as The purification and concentration system includes multiple filtration units, membrane separation units, and distillation concentration units connected in series. The filtration unit is used to receive the iodine-containing extract and filter out the colloidal substance to obtain an iodine-containing filtrate. The membrane separation unit includes at least one reverse osmosis membrane for receiving the iodine-containing filtrate and for separating the iodine reverse osmosis solution and the permeate solvent by reverse osmosis. as well as The distillation and concentration unit is used to receive the iodine reverse osmosis solution and distill it to obtain iodine concentrate and distillate. The re-extraction solvent in the second extraction unit includes the permeation solvent and the distillate.

2. The waste polarizing plate recycling system according to claim 1, characterized in that, The first extraction unit includes a stirring element and a heating element.

3. The waste polarizing plate recycling system according to claim 1, characterized in that, The filtration unit includes an ultrafiltration membrane, a nanofiltration membrane, or the ultrafiltration membrane and the nanofiltration membrane connected in series.

4. The waste polarizing plate recycling system according to claim 1, characterized in that, The total dissolved solids removal rate of the at least one reverse osmosis membrane is greater than 90%.

5. The waste polarizing plate recycling system according to claim 1, characterized in that, The extraction solvent includes an alkali and a solvent, wherein the alkali is sodium hydroxide, potassium hydroxide or an alkaloid, and the solvent includes ethanol.

6. The waste polarizing plate recycling system according to claim 1, characterized in that, The re-extraction solvent includes an alkali and a solvent, wherein the alkali is sodium hydroxide, potassium hydroxide or an alkaloid, and the solvent includes ethanol.

7. The waste polarizing plate recycling system according to claim 1, characterized in that, The re-extraction liquid separated from the re-extraction mixture is recycled for the preparation of the extraction solvent.

8. The waste polarizing plate recycling system according to claim 1, characterized in that, It also includes a solvent preparation unit for preparing the extraction solvent.

9. A method for recycling waste polarizing plates, characterized in that, include: The waste polarizing plate fragments containing iodine are mixed and stirred with the extraction solvent to obtain an extraction mixture; The extraction mixture is separated to separate the iodine-containing extract and waste polarizing plate plastic fragments; The iodine-containing extract is filtered to remove the gel-like substance and obtain an iodine-containing filtrate. The iodine-containing filtrate is treated using a membrane separation unit containing at least one reverse osmosis membrane to separate the iodine reverse osmosis solution and the permeate solvent; The iodine reverse osmosis solution from the membrane separation unit is distilled to obtain iodine concentrate and distillate; The permeation solvent and the distillate are recovered and formulated into a re-extraction solvent or an extraction solvent; The waste polarizing plate plastic fragments are then extracted again to obtain a re-extraction mixture; and The re-extraction mixture is separated to separate the re-extraction liquid and waste polarizing plate plastic fragments, wherein the re-extraction liquid is recycled for the preparation of the extraction solvent. The extraction solvent and the re-extraction solvent each comprise an alkaline solvent and an alcohol solvent, respectively.

10. The method for recycling waste polarizing plates according to claim 9, characterized in that, The alkali is sodium hydroxide, potassium hydroxide, or an alkaloid, and the alcohol solvent includes ethanol.

11. The method for recycling waste polarizing plates according to claim 9, characterized in that, The method of filtering the iodine-containing extract includes using an ultrafiltration membrane, a nanofiltration membrane, or the ultrafiltration membrane and the nanofiltration membrane in series.

12. The method for recycling waste polarizing plates according to claim 9, characterized in that, The total dissolved solids removal rate of the at least one reverse osmosis membrane is greater than 90%.

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