JP5189255B2 - Iodine recovery from polarizing film manufacturing wastewater - Google Patents

Description

  The present invention relates to a method for recovering iodine from a polarizing film manufacturing waste liquid that recovers iodine from the waste liquid generated when manufacturing a polarizing film, and more particularly, to a method for recovering iodine from a polarizing film manufacturing waste liquid capable of recovering boron after iodine recovery. .

  In the manufacturing process of a polarizing film used for a liquid crystal display or the like, a waste liquid containing iodine ions, boric acid, potassium ions, water-soluble organic substances, and the like is generated. Such a polarizing film production waste liquid is generally discharged as industrial wastewater after the specific component contained therein is reduced to a value determined by the wastewater standard or less by a coagulation method and a filtration method, or After volume reduction by concentrating, it is treated as industrial waste.

  However, in recent years, the standard value of boron and boron compounds in wastewater standards has become strict as 10 mg / liter, and in conventional treatment methods such as the agglomeration method and filtration method, it is not possible to make the boron concentration in wastewater below the standard value. Have difficulty. In addition, regarding industrial waste, it is desired to reduce the emission amount from the viewpoints of processing costs and environmental problems. Therefore, conventionally, electrodialysis was performed to separate the organic components contained in the polarizing film manufacturing waste liquid from inorganic components such as iodine and boron, and the subsequent concentration treatment was facilitated to reduce the amount of waste. A processing method has been proposed (see Patent Document 1). FIG. 6 is a diagram schematically showing a method for processing a polarizing film production waste liquid described in Patent Document 1. As shown in FIG. 6, in the treatment method described in Patent Document 1, the polarizing film manufacturing waste liquid 102 stored in the waste liquid tank 101 is sent to a desalting liquid tank 104 by a pump 103, and from here, an electrodialyzer is pumped by a pump 109. Sent to 105. At the same time, pure water stored in the concentrate tank 106 is sent to the electrodialyzer 105 by the pump 110, and electrodialysis is started. The desalted liquid 107 containing organic components and the concentrated liquid 108 containing inorganic components separated in the electrodialyzer 105 are returned to the desalted liquid tank 104 and the concentrated liquid tank 106, respectively, and then again electrodialyzed. Sent to the device 105. By repeating this, electrodialysis is performed in a circulation processing system.

  Further, in Patent Document 1, the concentrated liquid 108 is further separated into a liquid containing iodine and a liquid containing boron by an ion chromatography method or a boron-selective ion exchange resin treatment method. It is disclosed that it can be reused as a manufacturing solution. However, the technique described in Patent Document 1 is only for the purpose of reducing the amount of waste by volume reduction, and for separating the organic component and the inorganic component in order to facilitate the concentration treatment of the polarizing film production waste liquid. Technology. For this reason, there is a description that the inorganic component after separation can be further separated into a liquid containing iodine and a liquid containing boron by a known method, but specific processes and conditions have not been studied. Absent. In general, polarizing film production waste liquid is often mixed with multiple types of waste liquids with different components and concentrations, and the concentration of each component is not constant, so the iodine and boron concentrations used in the iodine dyeing process and boron crosslinking process From the viewpoint of maintaining the quality of the polarizing film product, it is not practical to reuse these as a polarizing plate production solution.

  Furthermore, when separating and recovering boron from an aqueous solution containing an inorganic component, a boron-selective ion exchange resin is generally used. Conventionally, boron that has been adsorbed and removed from waste water using a boron-selective ion exchange resin. A method for regenerating a boron-selective ion exchange resin that can be recovered as boric acid has been proposed (see Patent Document 2). In addition, the cation in the waste water is adsorbed and removed by the weakly acidic cation exchange resin, and the anion other than boron in the waste water is removed by the weakly basic anion exchange resin. A method of adsorbing and removing boron in waste water by using an anion exchange resin or a mixture of this anion exchange resin and a strongly acidic cation exchange resin adjusted to H type has also been proposed (Patent Documents 3 and 4). reference.).

  On the other hand, with respect to iodine, methods for recovering iodine from various waste liquids have been developed (see, for example, Patent Documents 5 and 6). For example, Patent Document 5 discloses a method for recovering iodine from water containing hydroiodic acid using an ion exchange resin. In addition, in the patent document 6, the present inventor oxidizes or reduces a waste liquid containing iodine and / or an inorganic iodine compound, and a free base produced thereby absorbs iodine ions under acidic conditions. After adsorbing to the basic anion exchange resin and separating it from inorganic salts and organic substances contained in the waste liquid, the iodine solution adsorbed on the strongly basic anion exchange resin is eluted as a hydroiodic acid solution, so that the waste liquid Proposes a method for recovering iodine from sewage.

JP 2001-314864 A Japanese Patent Publication No. 3-10378 Japanese Patent No. 3727212 JP-A-2005-296953 JP-A-6-63547 JP-A-6-157008

  As described above, in the conventional method, it is difficult to reuse the polarizing film manufacturing waste liquid as it is as the polarizing film manufacturing solution for reasons of concentration, quality maintenance, economy, and the like. For this reason, when reusing the waste liquid for producing a polarizing film, it is desirable to separate and recover reusable components such as iodine and boron, and use them after purification. However, in order to separate and collect iodine and boron from the polarizing film production waste liquid, there are the following problems.

  That is, as described in Patent Documents 1 and 2, when boron is separated and recovered from waste water or the like, a boron-selective chelate resin is generally used. Since components other than boron are also adsorbed, the amount of boron that can be adsorbed decreases, and if the treatment liquid contains a component such as iodine that degrades the resin, there is a problem that the life of the resin is shortened. On the other hand, as in the treatment methods described in Patent Documents 3 and 4, by previously removing components that degrade the resin such as organic matter and iodine from the polarizing film production waste liquid, the life of the resin and the recovery efficiency of boron are improved. However, this method has a problem that the number of facilities and the process is increased. In addition, the treatment methods described in Patent Documents 3 and 4 are methods for treating a large amount of industrial wastewater with a small amount of components to be removed such as boron and iodine, and a polarizing film having a high concentration of boron and iodine. It is not suitable for the treatment of manufacturing waste liquid. That is, when the polarizing film production waste liquid is processed by these methods, a large amount of resin is required, and the processing cost is increased, and the resin must be frequently replaced, which is troublesome.

  On the other hand, the conventional methods described in Patent Documents 5 and 6 both require that the pH be on the acidic side, preferably pH 3 or lower, so that an acid for pH adjustment and an oxidizing agent for oxidizing iodine ions are added. It is necessary to add. For this reason, the deterioration of the boron-selective chelate resin is accelerated and it takes time to adsorb iodine, and all the iodine in the waste liquid cannot be adsorbed to the resin. About 2 g / liter remains. Thereby, there exists a problem that it becomes difficult to collect | recover boron further from the waste liquid after iodine collection | recovery.

  The present invention has been devised in view of the above-mentioned problems, and provides a method for recovering iodine from a polarizing film manufacturing waste liquid that can easily and efficiently recover iodine and boron from the polarizing film manufacturing waste liquid. The purpose is to do.

  The iodine recovery method from the polarizing film production waste liquid according to the first invention of the present application contains iodine: 2 to 35 g / liter in total iodine amount, boron: 0.2 to 8 g / liter, and potassium: 0.6 to 11 g / liter. A method for recovering iodine from a polarizing film manufacturing waste liquid, wherein the waste liquid is adjusted to a pH of less than 7, and then electrodialyzed to convert iodine and potassium contained in the waste liquid into potassium iodide. Separating the waste solution after electrodialysis through a strongly basic anion exchange resin to adsorb iodine remaining in the waste solution to the strongly basic anion exchange resin; and the potassium iodide and Recovering iodine from the strongly basic anion exchange resin.

  The method for recovering iodine from the polarizing film manufacturing waste liquid according to the second invention of the present application recovers iodine from the polarizing film manufacturing waste liquid containing iodine: 2 to 35 g / liter in total iodine amount and boron: 0.2 to 8 g / liter. A method comprising adjusting the waste liquid so that the pH is 2 or less, and then adsorbing iodine contained in the waste liquid to a strongly basic anion exchange resin adsorbed with iodine ions, A step of passing the waste liquid after the adsorption treatment with the strong basic anion exchange resin through another strong basic ion exchange resin to adsorb the iodine remaining in the waste liquid to the other strong basic ion exchange resin. And a step of recovering iodine from the strong basic anion exchange resin and the other strong basic ion exchange resin.

  The iodine recovery method from the polarizing film manufacturing waste liquid according to the third invention of the present application recovers iodine from the polarizing film manufacturing waste liquid containing iodine: 2 to 35 g / liter in total iodine amount and boron: 0.2 to 8 g / liter. In this method, the waste liquid is adjusted so that the pH is less than 7, and then passed through a strongly basic anion exchange resin to adsorb iodine in the waste liquid to the strongly basic anion exchange resin. It has the process.

  In the iodine recovery method of the first to third inventions of the present application described above, the waste liquid after iodine separation is further adjusted to have a pH of 7 or more, and then passed through a boron-selective chelate resin, the waste liquid A step of adsorbing boron in the boron-selective chelate resin and a step of recovering boron from the boron-selective chelate resin may be included.

  According to the present invention, adsorption treatment with electrodialysis and anion exchange resin, two-step adsorption treatment with strong basic anion exchange resin adsorbed with iodine and another ion exchange resin, or strong basic anion exchange Since the adsorption treatment with the resin alone is performed and the pH of the waste liquid in each step is optimized, iodine can be easily and efficiently recovered from the polarizing film production waste liquid. Further, since iodine is not contained in the waste liquid after iodine separation, boron can be recovered easily and efficiently without deteriorating the boron-selective chelate resin.

  Hereinafter, a method for recovering iodine from a polarizing film production waste liquid according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. First, the iodine recovery method according to the first embodiment of the present invention will be described. The polarizing film production waste liquid to be treated in this embodiment has a pH of 3 to 10, iodine is 2 to 35 g / liter in terms of total iodine, boron is 0.2 to 8 g / liter, and potassium is 0.6 to 11 g. The aqueous solution may contain 1.5 g / liter or less of zinc and / or 1 g / liter or less of a water-soluble organic compound in terms of TOC (Total organic carbon). Moreover, the ORP (Oxidation Reduction Potential) of such a polarizing film manufacturing waste liquid is, for example, 100 to 350 mv.

FIG. 1 is a diagram schematically showing the iodine recovery method of this embodiment. FIG. 2 is a graph showing the relationship between the pH of the solution and the presence form of boron, with pH on the horizontal axis and the concentration of non-dissociated boric acid (H ₃ BO ₃ ) on the vertical axis. As shown in FIG. 1, in the iodine recovery method of this embodiment, first, a polarizing film manufacturing waste liquid to be processed is introduced into the electrodialysis apparatus 1. In the electrodialysis apparatus 1 used in this embodiment, for example, a cation exchange membrane 4k and an anion exchange membrane 4a are alternately arranged between an anode (+) 2 and a cathode (−) 3, and these cations The exchange membrane 4k and the anion exchange membrane 4a constitute a plurality of cells. When a waste liquid is introduced into the central cell 5a in a state where a direct current is applied between the anode 2 and the cathode 3 of the electrodialyzer 1, iodine ions (I ⁻ ) and potassium ions (K ⁺ ) in the waste liquid are generated. They move to the anode side and the cathode side, respectively, and potassium iodide (KI) is generated in the cells 5b and 5c on both sides of the central cell 5a. Then, an aqueous solution containing about 50 to 150 g / liter of KI is discharged from the electrodialysis apparatus 1.

  Here, as shown in FIG. 2, when the pH of the solution is less than 7, most of boric acid is present as boric acid molecules without dissociating. For this reason, in the iodine collection | recovery method of this embodiment, pH of the waste liquid thrown into the electrodialysis apparatus 1 shall be less than 7. Thus, dissociation of boric acid can be suppressed, so that boric acid does not move even when electrodialysis is performed, and is discharged as it is, and the amount of iodine is reduced to 0 without changing the amount of boron in the waste liquid. It can be reduced to 0.5 g / liter or less. On the other hand, when the pH of the waste liquid is 7 or more, boric acid is dissociated and the amount of borate ions increases, so that borate ions are mixed into the iodine concentrate during electrodialysis and are discharged from the electrodialyzer 1. The amount of boron in the waste liquid will decrease. When the waste liquid is acidic, free iodine may be generated, the ion exchange membrane may be deteriorated, and the efficiency of electrodialysis may be reduced. Therefore, the pH of the waste liquid is preferably 3 or more. Thereby, the production | generation of the free iodine by the air oxidation of an iodine ion can also be suppressed.

  Next, the waste liquid discharged from the electrodialyzer 1 is passed through the strong basic ion exchange resin 6, and iodine ions are adsorbed on the strong basic anion exchange resin 6, thereby reducing the amount of iodine in the waste liquid to 1 mg / liter. Reduce to: At this time, if the waste liquid is alkaline, boric acid is dissociated to become borate ions and adsorbed on the strongly basic anion exchange resin 6. Therefore, the pH of the waste liquid when passing through the strongly basic anion exchange resin 6 is less than 7 as in the electrodialysis described above, and when the pH of the waste liquid is out of this range, it is appropriately determined by a known method. Adjust. In addition, the preferable range of pH of a waste liquid is 3 or more and less than 7.

  Next, the waste liquid that has passed through the strongly basic anion exchange resin 6 is adjusted to have a pH of 7 or more by a known method such as addition of sodium hydroxide, and then the boron selective chelate resin 7 Pass through. Thereby, boron in the waste liquid can be recovered. At this time, if the pH of the waste liquid is less than 7, the amount of borate ions in the waste liquid decreases, and the boron recovery efficiency decreases. Therefore, the pH of the waste liquid that passes through the boron-selective chelate resin 7 is 7 or more.

  Thereafter, iodine is recovered from the aqueous KI solution discharged from the electrodialyzer 1 and the anion exchange resin 6 and boron is recovered from the boron selective chelate resin 7 by a known method. On the other hand, the waste liquid that has passed through the boron-selective chelate resin 7 removes heavy metals such as Zn by a coagulation sedimentation method, etc., and removes water-soluble organic substances by an activated sludge method, etc. Less than the value. And after adjusting pH to 5.8-8.6, it discharges.

  As described above, in the iodine recovery method of the present embodiment, the iodine in the polarizing film production waste liquid is separated by electrodialysis and a strongly basic anion exchange resin, so that the iodine amount in the waste liquid is 0.01 g / liter or less. After the reduction, boron is separated by the boron-selective chelate resin 7, and the pH of the waste liquid in each process is optimized, so that iodine and boron can be efficiently recovered from the polarizing film manufacturing waste liquid in a short time. Can do. Moreover, in the iodine collection | recovery method of this embodiment, since the amount of iodine in a waste liquid is reduced to 0.5 g / liter or less with the electrodialysis apparatus 1, the quantity of the strongly basic ion exchange resin 6 used after that. The (filling amount) can be reduced as compared with the conventional case. Furthermore, in the iodine recovery method of this embodiment, since iodine and boron are separated from the waste liquid by electrodialysis or adsorption to a resin, there is no mixing of other components and can be easily reused. .

  Next, an iodine recovery method according to the second embodiment of the present invention will be described. The polarizing film production waste liquid to be treated in the present embodiment is an aqueous solution containing 2-35 g / liter of iodine in terms of total iodine and 0.2-8 g / liter of boron, and further, 0.6-11 g / liter of potassium. In some cases, 1.5 g / liter or less of zinc and / or zinc and / or 1 g / liter or less of a water-soluble organic compound in terms of TOC may be contained. The polarizing film production waste liquid has a pH of, for example, 3 to 10, and an ORP of, for example, 100 to 350 mv.

FIG. 3 is a diagram schematically showing the iodine recovery method of the present embodiment. As shown in FIG. 3, in the iodine recovery method of the present embodiment, first, the polarizing film production waste liquid is put into a tank 11 filled with a strongly basic anion exchange resin 12 saturated with iodine ions, While stirring these with a stirrer 15, an acid such as sulfuric acid or hydrochloric acid is added to adjust the pH to 2 or less. Subsequently, while stirring, chlorine gas, and adding an oxidizing agent such as sodium hypochlorite (NaClO) or hydrogen peroxide, iodine ions in the effluent as molecular iodine (I _2), further, the I ₂ Is adsorbed on the strongly basic ion exchange resin 12 saturated with iodine ions as polyiodine molecules (I ₃ ⁻ , I ₅ ⁻ ). Thereafter, the strongly basic anion exchange resin 12 and the waste liquid are separated.

Next, the waste liquid separated from the strong basic anion exchange resin 12 is passed through a normal strong basic ion exchange resin 13 not saturated with iodine ions, and the strong basic ion exchange resin 13 contains the waste liquid in the waste liquid. Unadsorbed I ₂ , an acid for adjusting the pH, and anions such as sulfate ions derived from the oxidizing agent are adsorbed to reduce the total iodine amount in the waste liquid to 0.01 g / liter or less.

  Next, the waste liquid that has passed through the strongly basic anion exchange resin 13 is adjusted to a pH of 7 or more by a known method such as addition of sodium hydroxide, and then the boron selective chelate resin 14 is added. Through which the boron in the waste liquid is adsorbed. At this time, the reason why the pH of the waste liquid introduced into the boron selective chelate resin 14 is 7 or more is the same as in the first embodiment.

Thereafter, iodine (I ₂ , I ₃ ⁻ , I ₅ ⁻ ) adsorbed on the strong basic anion exchange resin 12 and the strong basic ion exchange resin 13 and boron adsorbed on the boron selective chelate resin 14 are recovered. And reuse. Specifically, iodine adsorbed on the strongly basic anion exchange resin 12 is recovered as iodine ions by passing an aqueous solution of a reducing agent such as Na ₂ SO ₃ or NaHSO ₃ through the strongly basic anion exchange resin 12. To do. Further, by passing an aqueous NaOH solution through the strong basic ion exchange resin 13, iodine adsorbed on the strong basic anion exchange resin 13 is recovered as iodine ions. Furthermore, boron adsorbed on the boron-selective chelate resin 14 is recovered by passing an aqueous H ₂ SO ₄ solution through the boron-selective chelate resin 14. On the other hand, the waste liquid that has passed through the boron-selective chelate resin 14 is subjected to treatments such as a coagulation sedimentation method and an activated sludge method, so that the values of heavy metals such as Zn and water-soluble organic substances are reduced below the effluent standard value, and further pH Is adjusted to within a predetermined range and then discharged.

As described above, in the iodine recovery method of the present embodiment, after the iodine ions in the polarizing film production waste liquid are separated as polyiodine molecules by the strongly basic anion exchange resin 12 saturated with iodine ions, further iodine ions Since the unadsorbed I ₂ in the waste liquid is separated by the normal strong basic ion exchange resin 13 which is not saturated with the iodine, only the iodine ions are removed by the strong basic anion exchange resin 12 saturated with the iodine ions. Compared to the case of adsorption, the amount of ion exchange resin to be used can be reduced to 1/5 to 1/3, and the iodine recovery efficiency can be improved. In the iodine recovery method of the present embodiment, after passing the strong basic anion exchange resin 12 and the strong basic ion exchange resin 13 to reduce the amount of iodine in the waste liquid to 0.01 g / liter or less, Since boron is separated by the boron-selective chelate resin 14, boron can be efficiently recovered without deteriorating the boron-selective chelate resin 14. Furthermore, in the iodine recovery method of this embodiment, since iodine and boron are separated from the waste liquid by adsorption to the resin, there is no mixing of other components, and the recovered product can be easily reused.

  Next, an iodine recovery method according to the third embodiment of the present invention will be described. The polarizing film production waste liquid to be treated in this embodiment is an aqueous solution containing 2 to 35 g / liter of iodine in total iodine amount and 0.2 to 8 g / liter of boron in the same manner as in the second embodiment. Furthermore, it may contain 0.6 to 11 g / liter of potassium, 1.5 g / liter or less of zinc and / or 1 g / liter or less of water-soluble organic compound in terms of TOC. The polarizing film production waste liquid has a pH of, for example, 3 to 10, and an ORP of, for example, 100 to 350 mv.

  FIG. 4 is a diagram schematically showing the iodine recovery method of the present embodiment. As shown in FIG. 4, in the iodine recovery method of the present embodiment, first, a polarizing film production waste liquid having a pH adjusted to less than 7 by a known method is passed through a strongly basic anion exchange resin 21, and this strong base is used. Iodine ions are adsorbed on the functional anion exchange resin 21. At this time, since the pH of the waste liquid is less than 7, dissociation of boric acid in the waste liquid is suppressed, and a decrease in the amount of boron before and after passing through the strongly basic anion exchange resin 21 can be prevented.

  Next, the waste liquid that has passed through the strongly basic anion exchange resin 21 is adjusted to have a pH of 7 or more by a known method such as addition of sodium hydroxide, and then the boron selective chelate resin 22 is added. Pass through. Thereby, boron in the waste liquid can be recovered. Here, the reason why the pH of the waste liquid introduced into the boron selective chelate resin 22 is 7 or more is the same as in the first and second embodiments described above.

  The iodine adsorbed on the strongly basic anion exchange resin 21 and the boron adsorbed on the boron selective chelate resin 22 are recovered and reused. On the other hand, the waste liquid that has passed through the boron-selective chelate resin 7 is subjected to a treatment such as a coagulation sedimentation method and an activated sludge method. Then, after adjusting the pH within a predetermined range, it is discharged.

  As described above, in the iodine recovery method of the present embodiment, the polarizing film production waste liquid is passed through the strongly basic anion exchange resin 21 and only the iodine ions contained therein are adsorbed to the resin. Iodine in the waste liquid can be separated. Further, in the iodine recovery method of the present embodiment, iodine and boron are separated from the waste liquid by adsorbing to the resin, so the recovered iodine and boron are not mixed with other components and can be easily reused. can do. Furthermore, in the iodine recovery method of the present embodiment, conventionally used chemicals such as acid and oxidizing agent for pH adjustment are not required, and therefore, anions such as sulfate ions derived from these chemicals are treated. Can be omitted.

  Next, an iodine recovery method according to the fourth embodiment of the present invention will be described. The polarizing film production waste liquid to be treated in this embodiment is an aqueous solution containing 2 to 35 g / liter of iodine in total iodine amount and 0.2 to 8 g / liter of boron in the same manner as in the second embodiment. Furthermore, it may contain 0.6 to 11 g / liter of potassium, 1.5 g / liter or less of zinc and / or 1 g / liter or less of water-soluble organic compound in terms of TOC. The polarizing film production waste liquid has a pH of, for example, 3 to 10, and an ORP of, for example, 100 to 350 mv.

  FIG. 5 is a diagram schematically showing the iodine recovery method of the present embodiment. As shown in FIG. 5, in the iodine recovery method of the present embodiment, first, the polarizing film production waste liquid 32 is put into a tank 31, and an acid such as sulfuric acid or hydrochloric acid is added while stirring with a stirrer 35, and the pH is set to 2. Adjust to: Subsequently, a sodium hypochlorite aqueous solution having a predetermined concentration is added to the polarizing film manufacturing waste liquid 32 while stirring is continued. Thereby, iodine in the polarizing film production waste liquid 32 crystallizes and precipitates, and settles on the bottom of the tank 31. Then, it isolate | separates into the iodine crystal 33 and a supernatant liquid with the filter 34. FIG. The iodine crystals 33 are washed with water, further dissolved in an aqueous reducing agent solution such as sodium sulfite, and then purified and reused by a known method. On the other hand, the supernatant liquid and the cleaning liquid for iodine crystals 33 are passed through the strongly basic anion exchange resin 36 to adsorb the remaining iodine ions, and the total iodine amount in the waste liquid (supernatant liquid and cleaning liquid) is reduced to 0. 0.01 g / liter or less.

  Next, the waste liquid (supernatant liquid and washing liquid) that has passed through the strongly basic anion exchange resin 36 is adjusted to have a pH of 7 or higher by a known method such as addition of sodium hydroxide, and then boron is added. Pass through selective chelating resin 37. Thereby, boron in the waste liquid (supernatant liquid and cleaning liquid) can be recovered. Here, the reason why the pH of the waste liquid introduced into the boron selective chelate resin 37 is 7 or more is the same as in the first to third embodiments described above.

  The iodine adsorbed on the strongly basic anion exchange resin 36 and the boron adsorbed on the boron selective chelate resin 37 are recovered and reused. On the other hand, the waste liquid that has passed through the boron-selective chelate resin 37 is subjected to a treatment such as a coagulation sedimentation method and an activated sludge method. Then, after adjusting the pH within a predetermined range, it is discharged.

  As described above, in the iodine recovery method of the present embodiment, iodine in the polarizing film production waste liquid is precipitated and recovered, and the supernatant liquid and the cleaning liquid are passed through a strongly basic anion exchange resin and remain in these. Since the iodine being absorbed is adsorbed to the resin, the amount of ion-exchange resin to be used with a strong basicity can be greatly reduced, and the recovery efficiency of iodine can be improved. Further, in the iodine recovery method of the present embodiment, since the iodine amount in the waste liquid is reduced to 0.01 g / liter or less and then passed through the boron selective chelating resin 37, the boron selective chelating resin 37 is used. Boron can be efficiently recovered without degrading the material.

Hereinafter, the effects of the present invention will be specifically described with reference to Examples and Comparative Examples. In addition, the form of this invention is not limited to these. First, Example 1 of the present invention will be described. In this example, first, 5 liters of a polarizing film production waste solution having a total iodine amount of 16 g / liter, a boron amount of 5.4 g / liter, a potassium amount of 4.9 g / liter, and a pH of 5.2 is obtained. Dialysis was performed for 1.5 hours at a constant voltage of 10 V using 1 liter of water as a dialysate using a dialysis machine (Aspirizer S3, manufactured by Astom Co., Ltd.). In addition, the membrane area in this electrodialysis apparatus is 0.055 m ² . A-192 was used for the anion exchange screen and K501-SB was used for the cation exchange screen. As a result, the waste liquid after electrodialysis had an iodine amount of 0.4 g / liter and a boron amount of 5.2 g / liter. Further, the aqueous KI solution discharged from the electrodialyzer had an iodine amount of 74 g / liter and a boron amount of 0.7 g / liter.

  Next, 20 ml of strongly basic anion exchange resin was packed in a chromatographic tube having a column inner diameter of 20 mm and a length of 300 mm, and the waste solution after electrodialysis was passed through at a flow rate of 0.15 liter / min. At that time, Diaion NSA100 manufactured by Mitsubishi Chemical Corporation was used as a strongly basic anion exchange resin (a quaternary ammonium salt bonded to a styrene / divinylbenzene copolymer). As a result, the liquid passage was completed in 33 minutes, and the iodine ion concentration after the liquid passage was 0.01 g / liter or less. Next, the pH of the waste liquid after passing through the strongly basic anion exchange resin was adjusted to 8 with a 0.1 mol / liter sodium hydroxide aqueous solution and then passed through the boron selective chelate resin. The iodine recovery rate by the above treatment was 99.5%, and the boron recovery rate was 99.8%.

  Next, a second embodiment of the present invention will be described. In this example, first, 10 liters of a polarizing film production waste solution having a total iodine amount of 16 g / liter, a boron amount of 5.4 g / liter, and a pH of 5.2 was placed in a beaker and then saturated with iodine ions. 250 ml of strongly basic anion exchange resin was added. Thereafter, sulfuric acid was added while stirring with a stirrer, and the pH was adjusted to 2. Thereafter, 330 ml of a 12% by mass aqueous sodium hypochlorite solution was added over 4 hours to convert the iodine ions into free iodine molecules, which were adsorbed on the ion exchange resin. At that time, Diaion NSA100 manufactured by Mitsubishi Chemical Corporation was used as the strongly basic anion exchange resin. As a result, the iodine amount of the waste liquid after the adsorption was 0.1 g / liter, the boron amount was 5.4 g / liter, and the iodine adsorption rate was 99.4%. Next, 40 ml of a strongly basic anion exchange resin (Diaion NSA100, manufactured by Mitsubishi Chemical Corporation) that is not saturated with iodine ions is packed in a chromatographic tube having an inner diameter of 20 mm and a length of 300 mm, and waste liquid after iodine adsorption. At a flow rate of 0.15 liter / min. As a result, the liquid passing was completed in 70 minutes, and the iodine ion concentration after the liquid passing was 0.01 g / liter or less.

Next, the resin adsorbed with iodine was separated from the waste liquid and transferred to a 2 L beaker, and 200 ml of 35 mass% NaHSO ₃ solution and 1600 ml of water were added and stirred for 3 hours. As a result, the amount of iodine in the solution after stirring for 3 hours was 88 g / liter, the amount of boron was 0.01 g / liter or less, and the desorption rate was 99.6%. On the other hand, the pH of the waste liquid after the adsorption treatment with the strongly basic anion exchange resin was adjusted to 8 with a 0.1 mol / liter sodium hydroxide aqueous solution and then passed through the boron selective chelate resin. The iodine recovery rate by the above treatment was 99.9%, and the boron recovery rate was 99.8%.

  Next, Embodiment 3 of the present invention will be described. In this example, first, 1 liter of strongly basic ion exchange resin is packed into a chromatographic tube having a column inner diameter of 50 mm and a height of 700 mm, the total iodine amount is 16 g / liter, and the boron amount is 5.4 g. A polarizing film production waste liquid having a pH of 5.2 / liter was passed at a flow rate of 0.15 liter / min. At that time, Diaion NSA100 manufactured by Mitsubishi Chemical Corporation was used as the strongly basic anion exchange resin. As a result, the amount of iodine in the liquid collected at the column outlet 60 minutes after the start of liquid flow was 0.01 g / liter or less, and the amount of boron was 5.4 g / liter. In addition, the iodine amount in the liquid collected at the column outlet 90 minutes after the start of liquid flow was 16 g / liter or less, and the boron amount was 5.4 g / liter.

  Next, a 1 mol / liter NaCl solution was passed through the ion exchange resin adsorbed with iodine ions at a flow rate of 1 ml / min to desorb iodine ions from the resin. As a result, the iodine ion desorption rate 24 hours after the start of liquid passage was 94%. On the other hand, the pH of the waste liquid after the adsorption treatment with the strongly basic anion exchange resin was adjusted to 8 with a 0.1 mol / liter sodium hydroxide aqueous solution and then passed through the boron selective chelate resin. The iodine recovery rate by the above treatment was 99.9%, and the boron recovery rate was 99.8%.

  Next, a fourth embodiment of the present invention will be described. In this example, first, 10 liters of a polarizing film production waste solution having a total iodine amount of 16 g / liter, a boron amount of 5.4 g / liter, and a pH of 5.2 was placed in a beaker, and then stirred with a stirrer. Sulfuric acid was added to adjust the pH to 2. Thereafter, 442 ml of a 12% by mass aqueous sodium hypochlorite solution was added to precipitate iodine in the waste liquid as iodine crystals. Thereafter, iodine crystals were allowed to settle and separated into iodine crystals and a supernatant by a filter. The separated iodine crystals are washed with 2 liters of city water, and the washing solution and the supernatant are put into a strongly basic anion exchange resin (manufactured by Mitsubishi Chemical Corporation) in a chromatographic tube having an inner diameter of 20 mm and a length of 300 mm. A solution filled with 20 ml of Diaion NSA100) was passed at a flow rate of 0.15 liter / min.

  At this time, the supernatant liquid has a total iodine amount of 0.3 g / liter, a boron amount of 5.4 g / liter, a sulfate ion concentration of 7.8 g / liter, a chlorine ion concentration of 3.0 g / liter, and a sodium concentration of 1 0.9 g / liter. The cleaning solution has a total iodine amount of 0.3 g / liter, a boron amount of 0.09 g / liter, a sulfate ion concentration of 0.1 g / liter, a chlorine ion concentration of 0.05 g / liter, and a sodium concentration of 0.04 g. / Liter. The passing of the supernatant and the cleaning liquid was completed in 80 minutes, and the iodine ion concentration after the passing was 0.01 g / liter or less.

Next, the separated iodine crystals were dissolved in 1600 ml of ₃ % by weight NaHSO ₃ solution and purified by a known method to obtain 153 g of iodine. Further, the resin adsorbed with iodine was separated from the waste liquid and transferred to a 200 ml beaker, and ₃ ml of 35% by weight NaHSO ₃ solution and 40 ml of water were added and stirred for 3 hours. As a result, the amount of iodine in the solution after stirring for 3 hours was 90 g / liter, the amount of boron was 0.01 g / liter or less, and the desorption rate was 99.0%. Further, the pH of the waste liquid after the adsorption treatment with the strongly basic anion exchange resin was adjusted to 8 with a 0.1 mol / liter sodium hydroxide aqueous solution, and then passed through the boron selective chelate resin. The iodine recovery rate by the above treatment was 97.5%, and the boron recovery rate was 99.8%.

It is a figure which shows typically the iodine collection | recovery method of the 1st Embodiment of this invention. Taking the pH to the horizontal axis, the vertical axis represents the concentration of undissociated boric acid (H 3 _{BO 3),} is a graph showing the relationship between the existing forms of pH and solution of boron. It is a figure which shows typically the iodine collection | recovery method of the 2nd Embodiment of this invention. It is a figure which shows typically the iodine collection | recovery method of the 3rd Embodiment of this invention. It is a figure which shows typically the iodine collection | recovery method of the 4th Embodiment of this invention. It is a figure which shows typically the processing method of the polarizing film manufacture waste liquid of patent document 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,105 Electrodialyzer 2 Anode 3 Cathode 4k Cation exchange membrane 4a Anion exchange membrane 5a, 5b, 5c Cell 6, 21, 36 Strongly basic anion exchange resin 7, 14, 22, 37 Boron selective chelate resin 11, 31 Tank 12 Strongly basic anion exchange resin 13 Ion exchange resin 15, 35 Stirrer 32, 102 Polarized film production waste liquid 33 Iodine crystal 34 Filter 101 Waste liquid tank 103, 109, 110 Pump 104 Desalted liquid tank 106 Concentrated liquid tank 107 Desalted solution 108 Concentrated solution

Claims (4)

A method for recovering iodine from a polarizing film production waste solution containing iodine: 2 to 35 g / liter in total iodine, boron: 0.2 to 8 g / liter and potassium: 0.6 to 11 g / liter,
Adjusting the waste liquid so that the pH is less than 7, and then electrodialyzing to separate iodine and potassium contained in the waste liquid as potassium iodide;
Passing the waste liquid after electrodialysis through a strongly basic anion exchange resin to adsorb iodine remaining in the waste liquid to the strongly basic anion exchange resin;
Recovering iodine from the potassium iodide and the strongly basic anion exchange resin;
A method for recovering iodine from a waste liquid for producing a polarizing film, comprising: Iodine: A method for recovering iodine from a polarizing film production waste liquid containing 2-35 g / liter of total iodine and boron: 0.2-8 g / liter,
A step of adsorbing iodine contained in the waste liquid to a strongly basic anion exchange resin adsorbed with iodine ions after adjusting the waste liquid to have a pH of 2 or less;
The waste liquid after the adsorption treatment with the strong basic anion exchange resin is further passed through another strong basic ion exchange resin, and the iodine remaining in the waste liquid is adsorbed on the other strong basic ion exchange resin. Process,
Recovering iodine from the strongly basic anion exchange resin and the other strongly basic ion exchange resin;
A method for recovering iodine from a waste liquid for producing a polarizing film, comprising: Iodine: A method for recovering iodine from a polarizing film production waste liquid containing 2-35 g / liter of total iodine and boron: 0.2-8 g / liter,
Adjusting the waste liquid to have a pH of less than 7, and then passing the liquid through a strongly basic anion exchange resin to adsorb iodine in the waste liquid to the strongly basic anion exchange resin. A method for recovering iodine from a polarizing film production waste liquid. Adjusting the waste liquid after iodine separation so that the pH is 7 or more, and then passing the boron selective chelate resin to adsorb the boron in the waste liquid to the boron selective chelate resin;
Recovering boron from the boron selective chelating resin;
The method for recovering iodine from the polarizing film production waste liquid according to any one of claims 1 to 3, wherein:

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