Extraction solution and method for recovering iodine from discarded polarizing plate

Abstract

The invention provides an iodine recovery method of a waste polarizing plate. The iodine recovery method comprises the following steps. A discarded polarizing plate including iodine is pulverized to form discarded polarizing plate fragments. Mixing the waste polarizer fragments with an extraction solution to obtain an extraction mixture; the extraction solution comprises 0.5 wt%-5 wt% of polyphenol compounds, 0.1 wt%-10 wt% of alkalis and the balance of water. And separating the extraction mixture to obtain an iodine-containing extraction solution and the waste polarizer fragments without iodine.

Description

Technical Field

[0001] The present disclosure relates to an extraction solution and a method for recovering iodine from waste polarizing plates. Background Art

[0002] A polarizer is one of the main raw materials of a liquid crystal display (LCD). Its structure may include a polarizer and protective layers on opposite sides of the polarizer. The dyeing material of the above polarizer is usually iodine; however, iodine will sublime at a temperature slightly higher than room temperature, causing purple smoke generated by iodine sublimation to appear during the incineration treatment of waste polarizing plates, thereby causing serious environmental problems. Therefore, how to effectively treat iodine in waste polarizing plates has become one of the current research focuses.

[0003] The prior art uses an extraction solution including an organic solvent to extract iodine from waste polarizing plates; however, it has the following problems: (1) The organic solvent is volatile, resulting in poor recovery rate of the extraction solution; (2) The gel in the waste polarizing plate is easily dissolved in the extraction solution, resulting in the need for additional processes to separate the gel from the extraction solution; (3) A large amount of organic solvent is required to extract iodine from waste polarizing plates, resulting in a relatively high process cost for the prior art of removing iodine from waste polarizing plates. Summary of the Invention

[0004] The present disclosure provides an extraction solution that can increase the iodine recovery rate.

[0005] The extraction solution provided by an embodiment of the present disclosure includes 0.5 wt% - 5 wt% of polyphenolic compounds, 0.1 wt% - 10 wt% of alkalis, and the balance of water.

[0006] The method for recovering iodine from waste polarizing plates provided by an embodiment of the present disclosure includes the following steps. First, crush the waste polarizing plate including iodine to form waste polarizing plate fragments. Then, mix the waste polarizing plate fragments with the extraction solution to obtain an extraction mixture. The extraction solution includes 0.5 wt% - 5 wt% of polyphenolic compounds, 0.1 wt% - 10 wt% of alkalis, and the balance of water. After that, separate the extraction mixture to obtain an iodine-containing extraction liquid and iodine-removed waste polarizing plate fragments. Description of the Drawings

[0007] Figure 1 It is a flowchart of the method for recovering iodine from waste polarizing plates according to an embodiment of the present disclosure. Detailed Description

[0008] The present disclosure can be understood by referring to the following detailed description and in conjunction with the accompanying drawings. It should be noted that, for the convenience of the reader's understanding and the simplicity of the drawings, only a part of the electronic device is shown in the multiple drawings of the present disclosure, and the specific components in the drawings are not drawn to actual scale. In addition, the number and size of each component in the drawings are only for illustration and are not used to limit the scope of the present disclosure.

[0009] The directional terms mentioned in the present disclosure, such as "upper", "lower", "front", "rear", "left", "right", etc., are only with reference to the directions in the accompanying drawings. Therefore, the directional terms used are for illustration and not for limiting the present disclosure. In the accompanying drawings, each drawing shows the general characteristics of the methods, structures, and / or materials used in specific embodiments. However, these drawings should not be construed as defining or limiting the scope or nature covered by these embodiments. For example, for clarity, the relative dimensions, thicknesses, and positions of each film layer, region, and / or structure may be reduced or enlarged.

[0010] The terms "about", "equal to", "equivalent to" or "the same as", "substantially" or "approximately" are generally interpreted as within 20% of the given value or range, or within 10%, 5%, 3%, 2%, 1%, or 0.5% of the given value or range.

[0011] It should be noted that, without departing from the spirit of the present disclosure, the features in several different embodiments can be replaced, reorganized, and mixed to complete other embodiments in the following examples. As long as the features between the embodiments do not violate the inventive spirit or conflict with each other, they can be arbitrarily mixed and used.

[0012] The following are examples of exemplary embodiments of the present disclosure. The same reference numerals are used in the drawings and the description to represent the same or similar parts.

[0013] Figure 1 It is a flowchart of an iodine recovery method for a waste polarizing plate according to an embodiment of the present disclosure.

[0014] Please refer to Figure 1, in step S10, the waste polarizing plate including iodine is crushed to form waste polarizing plate fragments. In some embodiments, the waste polarizing plate including iodine may include the following structures, but the present disclosure is not limited thereto. For example, the waste polarizing plate including iodine may have a laminated structure composed of a polarizer and a protective layer. The polarizer may be, for example, a thin film having properties such as light transmission and light deflection, and the material of the polarizer may be, for example, polyvinyl alcohol (PVA), but the present disclosure is not limited thereto. The protective layer may be, for example, used to support and protect the polarizer to increase the mechanical strength of the polarizing plate, and the material of the protective layer may be, for example, tri-acetyl cellulose (TAC), poly(methyl methacrylate) (PMMA), or polyethylene terephthalate (PET), but the present disclosure is not limited thereto.

[0015] In step S10, the waste polarizing plate including iodine can be crushed by an external force. In some embodiments, crushing the waste polarizing plate including iodine may include performing the following steps, but the present disclosure is not limited thereto. First, the waste polarizing plate including iodine to be crushed is placed on a conveying device. Then, the waste polarizing plate including iodine placed on the conveying device is subjected to a crushing process by a crushing device to obtain the crushed waste polarizing plate. In some embodiments, the crushed waste polarizing plate can be sieved to reduce the influence on the subsequent iodine removal efficiency of the extraction solution due to the oversized size of some of the waste polarizing plates, but the present disclosure is not limited thereto.

[0016] In step S20, the waste polarizing plate fragments are mixed with an extraction solution to obtain an extraction mixture. In some embodiments, the waste polarizing plate fragments and the extraction solution can be fed into an extraction unit (not shown) to mix the waste polarizing plate fragments and the extraction solution, and the extraction solution can be first prepared by a solution preparation unit (not shown) and then fed into the extraction unit, but the present disclosure is not limited thereto. In some embodiments, the extraction unit may include a stirring unit and a heating unit, but the present disclosure is not limited thereto.

[0017] In this embodiment, the extraction solution includes polyphenolic compounds, alkalis, and a solvent.

[0018] Polyphenolic compounds are, for example, organic compounds having multiple hydroxyl groups on an aromatic ring. In some embodiments, the polyphenolic compounds may include tannic acid and condensed tannic, but the present disclosure is not limited thereto.

[0019] In some embodiments, the polyphenolic compound may be selected from at least one of the following structural formulas:

[0020] Structural formula (I)

[0021]

[0022] wherein R is hydrogen or a hydroxyl group;

[0023] Structural formula (II)

[0024]

[0025] Structural formula (III)

[0026]

[0027] In some embodiments, when the extraction solution includes a polyphenolic compound, the iodine recovery rate of the extraction solution can be increased.

[0028] The bases may include, for example, potassium hydroxide, sodium hydroxide, alkaloids, or other suitable bases. The bases in the extraction solution can react with the iodine in the waste polarizing plate to remove the iodine in the waste polarizing plate. For example, the base in this embodiment is potassium hydroxide. After mixing the waste polarizing plate fragments with the extraction solution, the potassium hydroxide in the extraction solution can chemically react with iodine to obtain potassium iodide (KI).

[0029] In this embodiment, the solvent in the extraction solution is water and does not contain other organic solvents with high volatility. Based on this, the extraction solution in this embodiment is an aqueous extraction solution, which has a low evaporation rate during the iodine extraction process and can increase the recovery rate of the extraction solution. Furthermore, since the extraction solution in this embodiment does not include organic solvents, it can reduce the possibility that the components of the waste polarizing plate fragments dissolve in the extraction solution to form a gel (such as gels like polyvinyl alcohol, water glue, or UV glue), and the procedure of removing the gel from the extraction mixture can be omitted.

[0030] In this embodiment, the extraction solution includes 0.5 wt% - 5 wt% of polyphenolic compound, 0.1 wt% - 10 wt% of base, and the balance of solvent.

[0031] In step S30, the extraction mixture is separated to obtain an iodine-containing extraction liquid and iodine-removed waste polarizing plate fragments. In some embodiments, the extraction mixture can be separated by performing a filtration process, but the present disclosure is not limited thereto. For example, the extraction mixture can be separated by using a filtration unit such as a filter mesh to obtain an iodine-containing extraction liquid and iodine-removed waste polarizing plate fragments.

[0032] After performing step S30, the deiodinated waste polarizer fragments hardly contain iodine, so they can be incinerated, separated, or processed by other suitable processes before being reused, and the present disclosure is not limited thereto. In addition, iodine can be separated from the iodine-containing extract by performing a suitable separation process. For example, the iodine-containing extract can be concentrated to separate iodine, obtaining an iodine concentrate, and this iodine concentrate can be reused after being purified, but the present disclosure is not limited thereto. In addition, the recovered extract obtained after separating iodine from the iodine-containing extract can be returned to step S20 for use as an extraction solution to achieve the recycling of the extraction solution in this embodiment.

[0033] Experimental Example

[0034] The present disclosure will be described below with reference to experimental examples, but these experimental examples are only for illustrative purposes and do not limit the scope of the present disclosure.

[0035] In this experimental example, a spectrophotometer can be used to measure the iodine content. For example, ultraviolet light can be used to analyze and measure waste polarizer fragments containing iodine to obtain their original iodine content. Furthermore, ultraviolet light can be used to analyze and measure the solution of deiodinated waste polarizer fragments to obtain the iodine content of the waste polarizer fragments in the following examples and comparative examples.

[0036] [Example 1]

[0037] First, waste polarizers containing iodine are crushed using a crusher to obtain waste polarizer fragments, and the weight of the waste polarizer fragments is weighed. Then, the waste polarizer fragments are placed in a reaction vessel containing a known weight of extraction solution, stirred, and heated to 50 °C, and a chemical reaction is carried out for 1 hour to obtain an extraction mixture (it can be observed that the color of the extraction solution changes from black to colorless). The composition of the extraction solution is 0.5 wt% of the polyphenol compound represented by structural formula (I), 0.3 wt% of potassium hydroxide, and 99.2 wt% of water. After that, the extraction mixture is filtered using a filter to obtain an iodine-containing extract and deiodinated waste polarizer fragments, and iodine is separated from the iodine-containing extract to obtain a recyclable extraction solution, and the weight of the recovered extraction solution is weighed. Then, the weight of the deiodinated waste polarizer fragments is weighed. The deiodinated waste polarizer fragments are weighed once before being washed and dried, and weighed again after being washed and dried. Based on the results of the above weighings and the data of the iodine content measured by the spectrophotometer, the percentages of (A) the extraction solution absorbed by the waste polarizer, (B) the recovery percentage of the waste polarizer, (C) the recovery percentage of the extraction solution, and (D) the deiodination rate percentage of the waste polarizer can be calculated. The calculation formulas are listed as follows:

[0038] (A) Percentage of the extraction solution absorbed by the waste polarizing plate (%) = ((Weight of the iodine-removed waste polarizing plate fragments before drying - Weight of the iodine-removed waste polarizing plate fragments after drying) / Weight of the extraction solution in the reaction vessel) * 100%;

[0039] (B) Percentage of the recovery rate of the waste polarizing plate (%) = (Weight of the iodine-removed waste polarizing plate fragments after drying / Weight of the waste polarizing plate including iodine) * 100%;

[0040] (C) Percentage of the recovery rate of the extraction solution (%) = (Weight of the extraction solution after recovery / Weight of the extraction solution before the reaction) * 100%;

[0041] (D) Percentage of the iodine removal rate of the waste polarizing plate (%) = ((Iodine content of the waste polarizing plate originally including iodine - Iodine content of the iodine-removed waste polarizing plate fragments) / Iodine content of the waste polarizing plate originally including iodine) * 100%.

[0042] Among them, the calculation method of the iodine content is as follows:

[0043] React a standard product for determining the iodine content with an aqueous potassium hydroxide solution, dilute the reaction solution to prepare a detection solution, measure its ultraviolet-visible absorption spectrum, mark the absorption wavelength of 225 nm, and make a relationship curve between the signal intensity and the iodine content. The iodine content of the examples and comparative examples is measured by the above method for its absorption spectrum, and the iodine content therein is calculated using the relationship curve.

[0044] [Example 2]

[0045] In Example 2, the steps of the iodine recovery method for the waste polarizing plate are substantially the same as those in Example 1. The main difference is that the composition of the extraction solution is 1.5 wt% of the polyphenolic compound represented by the structural formula (I), 0.3 wt% of potassium hydroxide, and 98.2 wt% of water.

[0046] [Example 3]

[0047] In Example 3, the steps of the iodine recovery method for the waste polarizing plate are substantially the same as those in Example 1. The main difference is that the composition of the extraction solution is 2.5 wt% of condensed tannins, 0.3 wt% of potassium hydroxide, and 97.2 wt% of water.

[0048] [Example 4]

[0049] In Example 4, the steps of the iodine recovery method for the waste polarizing plate are substantially the same as those in Example 1. The main difference is that the composition of the extraction solution is 3.5 wt% of the polyphenolic compound represented by the structural formula (I), 0.3 wt% of potassium hydroxide, and 96.2 wt% of water.

[0050] [Example 5]

[0051] In Example 5, it is substantially the same as the steps of the iodine recovery method for the waste polarizing plate in Example 1. The main difference is that the composition of the extraction solution is 2.5 wt% of the polyphenol compound represented by the structural formula (III), 0.3 wt% of potassium hydroxide, and 97.2 wt% of water.

[0052] [Comparative Example 1]

[0053] In Comparative Example 1, it is substantially the same as the steps of the iodine recovery method for the waste polarizing plate in Example 1. The main difference is that the composition of the extraction solution is 0.3 wt% of potassium hydroxide and 99.7 wt% of water. That is, the extraction solution used in Comparative Example 1 does not include polyphenol compounds.

[0054] [Comparative Example 2]

[0055] In Comparative Example 2, the main difference from Example 1 is that the composition of the extraction solution is 2.5 wt% of an ethanol solution, 0.3 wt% of potassium hydroxide, and 97.2 wt% of water. That is, in Comparative Example 2, ethanol is used to replace the polyphenol compound in the extraction solution.

[0056] [Comparative Example 3]

[0057] In Comparative Example 3, the main difference from Comparative Example 2 is that the composition of the extraction solution is 24.9 wt% of an ethanol solution, 0.3 wt% of potassium hydroxide, and 74.8 wt% of water. That is, the solvent of the extraction solution in Comparative Example 3 contains ethanol and water.

[0058] [Comparative Example 4]

[0059] In Comparative Example 4, the main difference from Comparative Example 2 is that the composition of the extraction solution is 49.85 wt% of an ethanol solution, 0.3 wt% of potassium hydroxide, and 49.85 wt% of water. That is, the solvent of the extraction solution in Comparative Example 4 contains ethanol and water.

[0060] The experimental data of Examples 1 to 5 are summarized in Table 1 below, and the experimental data of Comparative Examples 1 to 4 are summarized in Table 2 below.

[0061] [Table 1]

[0062]

[0063] [Table 2]

[0064]

[0065] In Table 1 and Table 2, (A) is the percentage of the extraction solution absorbed by the waste polarizing plate, (B) is the percentage of the recovery rate of the waste polarizing plate, (C) is the percentage of the recovery rate of the extraction solution, and (D) is the percentage of the iodine removal rate of the waste polarizing plate

[0066] Please refer to Table 1 and Table 2 simultaneously. First, compared with the iodine recovery method of the waste polarizing plate in Comparative Example 1, Examples 1 to 5 have a relatively low (A) percentage of the extraction solution absorbed by the waste polarizing plate, a relatively high (C) percentage of the recovery rate of the extraction solution, and a relatively high (D) percentage of the iodine removal rate of the waste polarizing plate. It can be seen therefrom that using an aqueous extraction solution added with polyphenolic compounds in this disclosure can increase the iodine extraction rate in the waste polarizing plate and the recovery rate of the extraction solution

[0067] Next, compared with the iodine recovery method of the waste polarizing plate in Comparative Example 2, Examples 1 to 5 have a relatively low (A) percentage of the extraction solution absorbed by the waste polarizing plate, a relatively high (C) percentage of the recovery rate of the extraction solution, and a relatively high (D) percentage of the iodine removal rate of the waste polarizing plate. It can be seen therefrom that alcohols cannot replace polyphenolic compounds and be added to the aqueous extraction solution of this disclosure. Furthermore, it can be seen from the extraction solution of Comparative Example 2 that there are more colloids in the solution, and steps for treating the colloids need to be added in the subsequent process of recovering the extraction solution

[0068] Furthermore, compared with the iodine recovery methods of the waste polarizing plates in Comparative Example 3 and Comparative Example 4, the extraction solution in the iodine recovery method of the waste polarizing plates in Examples 1 to 5 includes a relatively small amount of polyphenolic compounds, which can improve the iodine removal effect. Furthermore, the iodine recovery methods of the waste polarizing plates in Examples 1 to 5 can also have a relatively high (C) percentage of the recovery rate of the extraction solution. Furthermore, it can be seen from the extraction solutions of Comparative Examples 3 and 4 that there are more colloids in the solution, and steps for treating the colloids need to be added in the subsequent process of recovering the extraction solution

[0069] In summary, the iodine recovery method for waste polarizing plates provided by an embodiment of this disclosure can at least have the following effects through the technical means described in the above embodiments

[0070] (1) The extraction solution for extracting iodine from waste polarizing plate fragments in an embodiment of this disclosure includes 0.5 wt% - 5 wt% of polyphenolic compounds, which improves the recovery rate of the extraction solution provided by an embodiment of this disclosure. Furthermore, as recorded in the above experimental examples, the extraction solution for extracting iodine from waste polarizing plate fragments only needs to include a small amount of polyphenolic compounds to obtain an ideal iodine removal result

[0071] (2) The extraction solution for extracting iodine from waste polarizer fragments provided by an embodiment of the present disclosure uses water as a solvent and does not contain other organic solvents with high volatility, which can reduce the evaporation rate of the solvent during the process of removing iodine from waste polarizer fragments and improve the recovery rate of the extraction solution.

[0072] (3) The aqueous extraction solution provided by an embodiment of the present disclosure can reduce the dissolution of waste polarizer fragment components in the extraction solution to form a gel (such as a gel like polyvinyl alcohol, aqueous glue or UV glue, etc.), and the procedure for removing the gel from the extraction mixture can be omitted.

[0073] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than to limit them; although the present disclosure has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present disclosure.

Claims

1. An extraction solution, characterized in that include: 0.5wt%-5wt% of polyphenolic compounds; 0.1wt%-10wt% of alkali; as well as The remaining amount of water.

2. The extraction solution according to claim 1, wherein the polyphenol compound is selected from at least one of the following structural formulas: Structural formula (I) in, R is hydrogen or hydroxyl; Structural formula (II) Structural formula (III) 3. The extraction solution of claim 1, wherein the base comprises potassium hydroxide, sodium hydroxide or sodium carbonate.

4. A method for recovering iodine from waste polarizing plates, characterized in that: include: crushing the waste polarizing plate including iodine to form waste polarizing plate fragments; The waste polarizing plate fragments are mixed with an extraction solution to obtain an extraction mixture, wherein the extraction solution comprises: 0.5wt%-5wt% of polyphenolic compounds; 0.1wt%-10wt% of alkali; and The balance of water; and The extraction mixture is separated to obtain an iodine-containing extract and the deiodinated waste polarizing plate fragments. 5 . The method for recovering iodine from waste polarizing plates according to claim 4 , wherein the extraction mixture does not include a colloid that dissolves the waste polarizing plate fragments. 6 . The method for recovering iodine from waste polarizing plates according to claim 4 , wherein a filtration process is performed to separate the extraction mixture.

7. The method for recovering iodine from waste polarizing plates according to claim 4, further comprising the step of separating iodine from the iodine-containing extract to obtain a recovered extract.

8. The method for recovering iodine from waste polarizing plates according to claim 4, wherein the polyphenol compound is selected from at least one of the following structural formulas: Structural formula (I) in, R is hydrogen or hydroxyl; Structural formula (II) Structural formula (III) 9 . The method for recovering iodine from waste polarizing plates according to claim 4 , wherein the alkali comprises potassium hydroxide, sodium hydroxide or sodium carbonate.

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