JP7165344B2 - Method and apparatus for treating polarizing plate manufacturing waste liquid - Google Patents

Description

The present invention relates to a polarizing plate manufacturing waste liquid treatment method and apparatus, and more particularly to a polarizing plate manufacturing waste liquid treatment method and apparatus for recovering potassium iodide from a polarizing plate manufacturing waste liquid.

Waste liquid generated in the manufacturing process of polarizing plates used in liquid crystal displays and the like contains inorganic substances such as iodine, boron, and potassium, and organic substances such as polyvinyl alcohol (PVA). methods have been considered in the past.

For example, Patent Document 1 discloses a concentration step of evaporatively concentrating a polarizing plate manufacturing waste liquid to form a precipitate containing boric acid and polyvinyl alcohol, and a cooling crystallization step of cooling and crystallization of the polarizing plate manufacturing waste liquid after evaporation and concentration. and a solid-liquid separation step of recovering a filtrate obtained by solid-liquid separation of precipitates.

JP 2017-209607 A

According to the method for treating the polarizing plate manufacturing waste liquid, most of the impurities such as boron and PVA contained in the polarizing plate manufacturing waste liquid can be removed, but the recovered potassium iodide solution contains impurities. Due to the low residue, there was room for further improvement in improving the quality of the potassium iodide solution.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method and apparatus for treating polarizing plate manufacturing waste liquid, which can efficiently recover a high-quality potassium iodide solution from the polarizing plate manufacturing waste liquid.

The object of the present invention is a method for treating a polarizing plate manufacturing waste liquid for recovering potassium iodide from the polarizing plate manufacturing waste liquid, wherein the precipitate produced by concentrating the polarizing plate manufacturing waste liquid and then performing crystallization is solidified. a first treatment step of liquid separation to produce a potassium iodide solution with reduced impurities including boron and polyvinyl alcohol; a first impurity adsorption step of adsorbing onto an adsorbent; and a second impurity adsorption step of causing a boron selective adsorption resin to adsorb boron remaining in the potassium iodide solution from which polyvinyl alcohol has been removed by adsorption in the first impurity adsorption step. This is achieved by a method for treating polarizing plate manufacturing waste liquid.

In this method for treating polarizing plate manufacturing waste liquid, a second treatment for further reducing the impurities in the potassium iodide solution obtained in the first treatment step is performed between the first treatment step and the first impurity adsorption step. It is preferable to include steps.

Alternatively, the object of the present invention is a method for treating a polarizing plate manufacturing waste liquid for recovering potassium iodide from the polarizing plate manufacturing waste liquid, wherein the precipitate is formed by concentrating the polarizing plate manufacturing waste liquid and then crystallization. A first treatment step of solid-liquid separation to produce a potassium iodide solution in which impurities including boron and polyvinyl alcohol are reduced, and the polyvinyl alcohol remaining in the resulting potassium iodide solution is adsorbed on a polyvinyl alcohol adsorbent. and a second impurity adsorption step of causing a boron selective adsorption resin to adsorb boron remaining in the potassium iodide solution that has undergone the first impurity adsorption step, wherein the first treatment step and the first impurity adsorption step are provided. Between the impurity adsorption step, a second treatment step for further reducing the impurities in the potassium iodide solution obtained in the first treatment step, wherein the second treatment step is obtained in the first treatment step. a step of further concentrating the potassium iodide solution to precipitate potassium iodide crystals; a step of solid-liquid separation of the precipitated potassium iodide crystals; and a step of washing the solid-liquid separated potassium iodide crystals to remove impurities. This is achieved by a polarizing plate manufacturing waste liquid treatment method comprising the steps of recovering the removed potassium iodide crystals and dissolving the recovered potassium iodide crystals in a solvent to produce a potassium iodide solution. In this case, it is preferable to further include a step of filtering impurities precipitated due to a decrease in saturation solubility due to an endothermic reaction due to dissolution of potassium iodide crystals.

Alternatively, the second treatment step may comprise removing calcium borate precipitates formed by reacting boron contained in the potassium iodide solution with calcium ions. In this case, the second treatment step preferably further includes a step of removing calcium carbonate precipitates produced by reacting calcium ions remaining in the potassium iodide solution with carbonate ions.

The potassium iodide solution in which the first impurity adsorption step is performed preferably has a boron concentration of 100 to 1000 mg/L, and a polyvinyl alcohol concentration of 100 to 500 mg/L in terms of TOC. .

Further, the above object of the present invention is a polarizing plate manufacturing waste liquid treatment apparatus for recovering potassium iodide from a polarizing plate manufacturing waste liquid, wherein the precipitate is formed by concentrating the polarizing plate manufacturing waste liquid and then performing crystallization. by solid-liquid separation to produce a potassium iodide solution with reduced impurities including boron and polyvinyl alcohol; A first impurity adsorption device for adsorbing onto a polyvinyl alcohol adsorbent, and a second impurity adsorption device for adsorbing boron remaining in the potassium iodide solution from which polyvinyl alcohol has been removed by adsorption by the first impurity adsorption device, onto a boron selective adsorption resin. is achieved by a polarizing plate manufacturing waste liquid treatment apparatus comprising: It is preferable that this polarizing plate manufacturing waste liquid treatment apparatus includes a second treatment apparatus for further reducing the impurities in the potassium iodide solution obtained in the first treatment apparatus.

ADVANTAGE OF THE INVENTION According to this invention, the processing method and processing apparatus of the polarizing plate manufacturing waste liquid which can collect|recover efficiently a high-quality potassium iodide solution from a polarizing plate manufacturing waste liquid can be provided.

1 is a block diagram of a processing apparatus for polarizing plate manufacturing waste liquid according to an embodiment of the present invention; FIG. FIG. 4 is a block diagram of a processing apparatus for polarizing plate manufacturing waste liquid according to another embodiment of the present invention. FIG. 10 is a block diagram of a processing apparatus for polarizing plate manufacturing waste liquid according to still another embodiment of the present invention.

An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram of a polarizing plate manufacturing waste liquid processing apparatus according to an embodiment of the present invention. As shown in FIG. 1, the polarizing plate manufacturing waste liquid treatment apparatus 1 includes a first treatment apparatus 10, a first impurity adsorption apparatus 30 and a second impurity adsorption apparatus 40, and further includes a first filter apparatus 50 and a second impurity adsorption apparatus 40. A second filter device 52 and a third filter device 54 are provided. This polarizing plate manufacturing waste liquid treatment apparatus 1 treats polarizing plate manufacturing waste liquid generated in the manufacturing process of polarizing plates used in liquid crystal displays and the like. In the manufacturing process of a polarizing plate, generally, a film made of polyvinyl alcohol (PVA) is immersed in a potassium iodide (KI) solution, stretched in an aqueous boric acid (H ₃ BO ₃ ) solution, washed with water and dried. After that, a polarizing plate is manufactured. Therefore, the polarizing plate manufacturing waste liquid contains PVA, and furthermore, KI, boric acid, etc. are mainly contained in an ion state.

The first processing apparatus 10 includes an evaporative concentration apparatus 11, a cooling crystallizer 12, and a first solid-liquid separation apparatus 13. By removing most of the boron, PVA, etc. contained in the polarizing plate manufacturing waste liquid, A KI solution with reduced impurities including boron and PVA is produced.

The evaporative concentration device 11 evaporatively concentrates the polarizing plate manufacturing waste liquid. As a result, most of the boric acid and PVA contained in the polarizing plate manufacturing waste liquid become sludge under supersaturated conditions, and precipitates containing these are produced in the polarizing plate manufacturing waste liquid. The precipitate may contain impurities other than boric acid and PVA. The configuration of the evaporative concentration device 11 is not particularly limited as long as it can concentrate the polarizing plate manufacturing waste liquid. These can be configured by using one kind or two or more kinds. For example, the evaporative concentration device 11 is configured by arranging a heat pump type concentrating device in the front stage and arranging a flash type concentrating device in the subsequent stage for further evaporating and concentrating the concentrated liquid of the polarizing plate manufacturing waste liquid generated by this device. be able to.

The cooling crystallizer 12 crystallizes boric acid contained in the polarizing plate manufacturing waste liquid to further produce a precipitate from the polarizing plate manufacturing waste liquid. The structure of the cooling crystallizer 12 can be, for example, a known structure such as a jacket type or a vacuum type. (As a specific example, cooling to 30° C. or lower) is more preferable. As a method for crystallizing the polarizing plate manufacturing waste liquid, cooling crystallization by the cooling crystallizer 12 as in the present embodiment is preferable in order to obtain a good effect of reducing impurities such as boric acid. may be

The first solid-liquid separator 13 solid-liquid separates precipitates in the polarizing plate manufacturing waste liquid. The configuration of the first solid-liquid separation device 13 includes, for example, various filtration devices such as pressure filtration (filter press), vacuum filtration, and centrifugal filtration, and known configurations such as a decanter-type centrifugal separation device. .

The first impurity adsorption device 30 has a polyvinyl alcohol adsorbent (PVA adsorbent), and the KI solution supplied from the first treatment device 10 is passed through the PVA adsorbent, so that a small amount of KI solution remains in the KI solution. PVA is removed by adsorption. The PVA adsorbent is not particularly limited as long as it is solid so long as it is capable of adsorbing PVA on its surface. Granular or fibrous activated carbon filters can be preferably exemplified, but titanium oxide or the like can also be used. .

The second impurity adsorption device 40 is equipped with an adsorption tower filled with a boron selective adsorption resin, and the KI solution that has passed through the first impurity adsorption device 30 is passed through the adsorption tower to convert boric acid into the KI solution. A small amount of remaining boron is removed by adsorption. The boron selective adsorption resin is not particularly limited as long as it can selectively adsorb boron, and may be a known anion exchange resin (e.g., cerium hydroxide/ethylene vinyl alcohol copolymer, microporous styrene-based - methylglucamine functional groups, etc.) can be used.

Each of the first filter device 50, the second filter device 52 and the third filter device 54 includes a filter such as a ceramic membrane filter or a cartridge filter. , between the first impurity adsorption device 30 and the second impurity adsorption device 40, and after the second impurity adsorption device 40, respectively. The first filter device 50 removes impurities by filtering the KI solution supplied from the first processing device 10 . The second filter device 52 filters the KI solution that has passed through the first impurity adsorption device 30 to remove SS components (for example, activated carbon scraps, etc.) that may be mixed into the KI solution. The third filter device 54 filters the KI solution that has passed through the second impurity adsorption device 40 to remove SS components (for example, scraps of boron selective adsorption resin, etc.) that may be mixed into the KI solution.

Next, a method for treating a polarizing plate manufacturing waste liquid using the polarizing plate manufacturing waste liquid processing apparatus 1 will be described.

First, the polarizing plate manufacturing waste liquid is supplied to the first processing apparatus 10 . The pH of the polarizing plate manufacturing waste liquid is in the range of 3.5 to 8.0, and since it contains a boric acid solution, it is usually acidic, but the polarizing plate manufacturing waste liquid may be neutral. Alternatively, by adding a pH adjuster such as sodium hydroxide or potassium hydroxide to the polarizing plate manufacturing waste liquid, the pH of the polarizing plate manufacturing waste liquid is adjusted to alkaline (for example, 8.5 to 11, preferably 8.5 to 8.5). 9.5) may be adjusted.

In the first processing apparatus 10, after the polarizing plate manufacturing waste liquid is concentrated by the evaporative concentration apparatus 11, it is cooled by the cooling crystallizer 12 to perform cooling crystallization. When the pH of the polarizing plate manufacturing waste liquid to be concentrated by the evaporative concentration device 11 is adjusted to be alkaline, it is preferable to perform cooling crystallization while maintaining the pH of the concentrated waste liquid to be alkaline. After that, the precipitate is removed by the first solid-liquid separation device 13 . Thus, the first processing step is performed by the first processing device 10 to produce a KI solution with reduced impurities including boron and PVA.

The precipitates separated by the first treatment step are crystals mainly composed of boric acid and contain PVA. The boric acid-based crystals can be reused, for example, in the manufacturing process of semiconductors, LEDs, and the like by washing them with condensed water generated in the evaporative concentration device 11 and recovering them. Since the precipitate contains some KI crystals in addition to boric acid and PVA, the washing waste liquid after washing is introduced into the evaporative crystallizer 21 (see FIG. 2) in another embodiment described later. You may The crystallization in the first treatment step may be repeated until KI crystals are precipitated, and precipitates consisting of impurities can be removed by solid-liquid separation.

In the first impurity adsorption device 30, a first impurity adsorption step is performed in which a small amount of PVA remaining in the KI solution obtained in the first treatment step is adsorbed and removed by a PVA adsorbent. Thereafter, in the second impurity adsorption apparatus 40, a second impurity adsorption step is performed in which a boron selective adsorption resin adsorbs and removes a small amount of boron remaining in the KI solution that has undergone the first impurity adsorption step. In this way, PVA and boron slightly contained in the KI solution are removed by the first impurity adsorption step and the second impurity adsorption step, respectively, so that a high-quality potassium iodide solution can be recovered from the polarizing plate manufacturing waste liquid. can be done.

According to the high-concentration KI solution test by the present inventors, when the concentration of the KI solution is at or near the saturation concentration (e.g., about 55%), the PVA contained in the KI solution is absorbed by the boron selective adsorption resin. It was clarified that the adsorption of boron is inhibited, and thus boron cannot be adsorbed sufficiently. Therefore, in the present embodiment, after the PVA in the KI solution is removed by the first impurity adsorption step, the boron in the KI solution is removed by the second impurity adsorption step, so that the high-concentration KI solution as described above is obtained. However, boron can be reliably removed.

Since the KI solution passing through the first impurity adsorption device 30 and the second impurity adsorption device 40 has sufficiently reduced boron and PVA by the first treatment device 10, the regeneration load of the boron selective adsorption resin and the PVA adsorbent is greatly reduced. to efficiently recover a high-quality potassium iodide solution.

As described above, one embodiment of the present invention has been described in detail. For reasons such as a large amount of impurities contained in the original polarizing plate manufacturing waste liquid, impurities including boron and PVA are sufficiently reduced by the first processing apparatus 10. If this is not possible, a second treatment step is provided after the first treatment device 10 to further reduce the impurities in the potassium iodide solution between the first treatment step and the first impurity adsorption step. may be performed. Although the configuration of the second processing device is not particularly limited, the configuration shown in FIGS. 2 and 3 can be preferably exemplified. In FIGS. 2 and 3, the same components as in FIG. 1 are given the same reference numerals.

FIG. 2 is a block diagram of a polarizing plate manufacturing waste liquid processing apparatus according to another embodiment of the present invention. The polarizing plate manufacturing waste liquid processing apparatus 1' shown in FIG. 2 is the polarizing plate manufacturing waste liquid processing apparatus 1 shown in FIG. The configuration other than the second processing device 20 is the same as that of the polarizing plate manufacturing waste liquid processing device 1 shown in FIG.

The second processing device 20 includes an evaporative crystallizer 21 , a second solid-liquid separator 22 and a dissolution tank 23 . Although the configurations of the evaporative crystallizer 21 and the second solid-liquid separation device 22 are not particularly limited, for example, they may have the same configuration as the evaporative concentration device 11 and the first solid-liquid separation device 13 of the first processing device 10, respectively. can. In this embodiment, a flash type evaporator is used as the evaporative crystallizer 21 .

The evaporative crystallizer 21 evaporates the KI solution concentrated by the first processor 10 to supersaturate KI, thereby producing a precipitate containing KI crystals. As the evaporative crystallization progresses, the pH may be adjusted by adding KOH to the KI solution. The second solid-liquid separation device 22 solid-liquid separates and recovers the precipitate generated in the evaporative crystallizer 21 .

Since the concentrations of boric acid and PVA contained in the KI solution are reduced by the first treatment step, the precipitates produced by the evaporative crystallizer 21 are crystals mainly composed of KI. However, if the concentration ratio is increased in order to increase the yield of KI, the amount of PVA that is likely to become a problem during recovery also increases. Therefore, by washing the KI crystals in the second solid-liquid separation device 22, the impurities adhering to the KI crystals are removed.

Condensed water generated in the evaporative concentration device 11, for example, can be used as the cleaning liquid used for cleaning the KI crystals, but the solubility of KI is high, and loss due to dissolution increases. Therefore, for the purpose of reducing depletion due to dissolution, it is preferable to generate a saturated solution of KI by using a part of already recovered KI, and wash the KI crystals using this saturated KI solution. . The concentration of the KI saturated solution does not necessarily have to be the saturated concentration, and may be a high concentration close to the saturated concentration. PVA can be efficiently removed by washing with a high-concentration KI solution, and KI crystals containing little PVA can be collected by solid-liquid separation using a filter or the like. The cleaning liquid can be stored in a tank or the like and recycled.

The collected KI crystals are dissolved in a solvent such as water in the dissolution tank 23 to produce a KI solution with reduced impurities. When water is used as the solvent, the dissolution of KI crystals in water is an endothermic reaction. -5°C. Since the collected KI crystals contain impurities such as boron and PVA, the saturated solubility of the impurities (mainly PVA) decreases as the temperature of the solvent in which the KI crystals are dissolved at a high concentration decreases. As a result, some or most of the impurities are precipitated. This precipitate is filtered by the first filter device 50 .

By washing the collected KI crystals in this way, it is possible to mainly reduce the impurities adhering to the surface of the KI crystals, and at the same time, by utilizing the endothermic reaction caused by the dissolution of the KI crystals, Since the PVA that is present in the metal can be precipitated and removed, a KI solution in which the PVA is sufficiently reduced can be produced. Therefore, the load on the PVA adsorbent included in the first impurity adsorption device 30 can be reduced.

FIG. 3 is a block diagram of a processing apparatus for polarizing plate manufacturing waste liquid according to still another embodiment of the present invention. The polarizing plate manufacturing waste liquid processing apparatus 1'' shown in FIG. 3 is the polarizing plate manufacturing waste liquid processing apparatus 1 shown in FIG. Except for the second processing device 120, the configuration is the same as that of the polarizing plate manufacturing waste liquid processing device 1 shown in FIG.

The second treatment device 120 shown in FIG. 3 includes a first reaction device 121 for removing precipitates formed by supplying calcium ions to the KI solution whose impurities have been reduced in the first treatment device 10, and a first reaction device. and a second reactor 122 for supplying carbonate ions to the KI solution that has passed through 121 and removing the precipitate formed.

In the first reaction device 121, the slightly remaining boron in the KI solution is reacted with calcium ions by adding calcium hydroxide to form a precipitate of calcium borate, which is removed by a filter or the like. , to further reduce the boron content in the KI solution. Since the KI solution supplied to the first reactor 121 has been concentrated by the first treatment step, the concentration of the KI solution can be adjusted to an appropriate concentration ( for example 15-30%).

The second reactor 122 supplies carbonate ions to the KI solution that has passed through the first reactor 121 . As a result, the calcium ions remaining in the KI solution react with the carbonate ions to form calcium carbonate precipitates. By removing the precipitates with a filter or the like, the calcium ions can be removed from the KI solution. Carbonate ions are preferably supplied by addition of potassium carbonate or carbon dioxide in order to suppress the increase of impurities in the KI solution. Thus, the second treatment step by the second treatment device 120 can be performed to further reduce impurities in the KI solution.

In the configuration of FIGS. 1 to 3, the concentrations of boron and PVA in the KI solution introduced into the first impurity adsorption device 30 are not particularly limited. The frequency of replacement or regeneration increases, making it difficult to use practically. Specifically, the boron concentration is preferably 100 to 1000 mg/L, and the polyvinyl alcohol concentration is preferably 100 to 500 mg/L in terms of TOC. The boron concentration and PVA concentration of the KI solution can be finally reduced to several mg/L by the subsequent first impurity adsorption step and second impurity adsorption step.

REFERENCE SIGNS LIST 1 polarizing plate manufacturing waste liquid processing device 10 first processing device 11 evaporative concentration device 12 cooling crystallizer 13 first solid-liquid separation device 20 second processing device 21 evaporative crystallizer 22 second solid-liquid separation device 23 dissolution tank 30 First impurity adsorption device 40 Second impurity adsorption device 50 First filter device 52 Second filter device 54 Third filter device 120 Second treatment device 121 First reaction device 122 Second reaction device

Claims (9)

A method for treating a polarizing plate manufacturing waste liquid for recovering potassium iodide from the polarizing plate manufacturing waste liquid,
a first treatment step of concentrating the polarizing plate manufacturing waste liquid and then performing solid-liquid separation of the precipitate produced by crystallization to produce a potassium iodide solution in which impurities including boron and polyvinyl alcohol are reduced;
a first impurity adsorption step of adsorbing the polyvinyl alcohol remaining in the potassium iodide solution obtained in the first treatment step to a polyvinyl alcohol adsorbent;
and a second impurity adsorption step of adsorbing boron remaining in the potassium iodide solution from which the polyvinyl alcohol has been adsorbed and removed in the first impurity adsorption step onto a boron selective adsorption resin. The polarized light according to claim 1, further comprising a second treatment step for further reducing the impurities in the potassium iodide solution obtained in the first treatment step, between the first treatment step and the first impurity adsorption step. A method for treating board manufacturing waste liquid. A method for treating a polarizing plate manufacturing waste liquid for recovering potassium iodide from the polarizing plate manufacturing waste liquid,
a first treatment step of concentrating the polarizing plate manufacturing waste liquid and then performing solid-liquid separation of the precipitate produced by crystallization to produce a potassium iodide solution in which impurities including boron and polyvinyl alcohol are reduced;
a first impurity adsorption step of adsorbing polyvinyl alcohol remaining in the resulting potassium iodide solution to a polyvinyl alcohol adsorbent;
a second impurity adsorption step of adsorbing boron remaining in the potassium iodide solution that has undergone the first impurity adsorption step, onto a boron selective adsorption resin;
Between the first treatment step and the first impurity adsorption step, a second treatment step for further reducing the impurities in the potassium iodide solution obtained in the first treatment step,
The second treatment step includes a step of further concentrating the potassium iodide solution obtained in the first treatment step to precipitate potassium iodide crystals;
a step of solid-liquid separation of the precipitated potassium iodide crystals;
a step of washing the solid-liquid separated potassium iodide crystals to recover the potassium iodide crystals from which impurities have been removed;
and dissolving the recovered potassium iodide crystals in a solvent to form a potassium iodide solution. 4. The method for treating a polarizing plate manufacturing waste liquid according to claim 3, further comprising a step of filtering impurities precipitated due to a decrease in saturation solubility due to an endothermic reaction due to dissolution of potassium iodide crystals. 3. The treatment of polarizing plate manufacturing waste liquid according to claim 2, wherein said second treatment step comprises a step of removing precipitates of calcium borate produced by reacting boron contained in a potassium iodide solution with calcium ions. Method. 6. The polarizing plate manufacturing waste liquid according to claim 5, wherein said second treatment step further comprises a step of removing calcium carbonate precipitates formed by reacting calcium ions remaining in the potassium iodide solution with carbonate ions. Processing method. The potassium iodide solution in which the first impurity adsorption step is performed has a boron concentration of 100 to 1000 mg/L, and a polyvinyl alcohol concentration of 100 to 500 mg/L in terms of TOC. The method for treating a polarizing plate manufacturing waste liquid according to any one of the above. A polarizing plate manufacturing waste liquid treatment apparatus for recovering potassium iodide from a polarizing plate manufacturing waste liquid,
a first processing device for solid-liquid separation of precipitates produced by concentrating the polarizing plate manufacturing waste liquid and then performing crystallization to produce a potassium iodide solution in which impurities including boron and polyvinyl alcohol are reduced;
a first impurity adsorption device for adsorbing polyvinyl alcohol remaining in the potassium iodide solution obtained in the first processing device on a polyvinyl alcohol adsorbent;
and a second impurity adsorption device for adsorbing boron remaining in the potassium iodide solution from which the polyvinyl alcohol has been adsorbed and removed by the first impurity adsorption device to a boron selective adsorption resin. 9. The polarizing plate manufacturing waste liquid treatment apparatus according to claim 8, further comprising a second treatment apparatus for further reducing the impurities in the potassium iodide solution obtained in the first treatment apparatus.

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