CN109970073B - Method for preparing boric acid and potassium chloride by recycling polarizing plate waste liquid - Google Patents
Method for preparing boric acid and potassium chloride by recycling polarizing plate waste liquid Download PDFInfo
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- C01B35/00—Boron; Compounds thereof
- C01B35/08—Compounds containing boron and nitrogen, phosphorus, oxygen, sulfur, selenium or tellurium
- C01B35/10—Compounds containing boron and oxygen
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- C01B35/1054—Orthoboric acid
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- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D3/00—Halides of sodium, potassium or alkali metals in general
- C01D3/04—Chlorides
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- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F11/00—Compounds of calcium, strontium, or barium
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Abstract
The invention discloses a method for preparing boric acid and potassium chloride by recycling polarizing plate waste liquid, which comprises the following steps: (1) pulping; (2) acidifying 1; (3) calcification; (4) acidifying 2; (5) and (5) concentrating. The method does not generate secondary waste in the process, has moderate separation effect requirement, does not use organic agents, has no accurate requirement on proportion control during evaporation concentration, can obtain high-purity boric acid and potassium chloride, and realizes the recycling of waste liquid.
Description
Technical Field
The invention relates to the technical field of wastewater treatment, in particular to a method for preparing boric acid and potassium chloride by recycling polarizing plate waste liquid.
Background
With the rapid development of the electronic industry, the use of liquid crystal screens is more and more common, and in the case of liquid crystal television, the number of outlets of liquid crystal televisions in the last half of 2017 reaches 4027 thousands. The polarizer is a core component of the liquid crystal panel, and is mainly used for transmitting and blocking light emitted from the backlight module. Data show that the market of the domestic polarizing plate in 2018 reaches more than 30 hundred million dollars. The polarizing plate is classified into three categories, i.e., metal, iodine, and dye, according to different materials, and the iodine-based polarizing plate having iodine molecules and polyvinyl alcohol combined therein has the highest market share due to its low cost. In the preparation process of the iodine-based polarizing plate, the polyvinyl alcohol film needs to be dyed in an iodine-containing solution, the main components of the iodine-containing solution are iodine and potassium iodide, and boric acid is usually added to improve the hardness of the polyvinyl alcohol film. With the consumption of the dyeing process, the used iodine-containing solution can not be used any more and needs to be handed to qualified disposal units for treatment.
The common disposal method of the waste iodine-containing solution is to finally obtain iodine-containing crude boric acid solid by utilizing the difference of solubility through certain pretreatment, distillation and separation modes, and the iodine-containing crude boric acid has low boric acid purity and generally has no economic and recycling value. Therefore, how to recover and purify the iodine-containing crude boric acid determines the treatment process and economic feasibility of the waste iodine-containing solution.
Acidification is the most common method for purifying boric acid, and since boric acid is a weak acid, strong organic acids such as sulfuric acid, nitric acid, etc. are often used to react with the crude boric acid solution to convert the borate in the crude boric acid to boric acid. The acidification method is simple to operate, but the salt-containing filtrate generated after acidification has the characteristics of large production amount and high treatment difficulty. The salt-containing filtrate mainly comprises boric acid and inorganic salt, and is an acidic waste liquid with high salt content. The most common method for disposing the waste liquid is to obtain a mixed solid of boric acid and inorganic salt by distillation, and the mixed solid is generally disposed in a landfill directly or extracted and separated by utilizing the difference of the solubility of the boric acid and the inorganic salt in an organic solvent. The extraction process requires relatively strict equipment and reagents, and the organic solvent used is harmful to the body of the operator.
The method for treating the waste liquid from the production of the polarizing plate proposed in CN 107416866 a mainly utilizes the difference in solubility between boric acid and potassium iodide, and separates boric acid and potassium iodide by a distillation concentration method. Although this method can dispose of the polarizing plate waste liquid and obtain two products, it has a high demand for separation effect. The preparation process for recovering boric acid and magnesium sulfate by evaporating and concentrating boric acid mother liquor in the saltern described in CN 1673079A mainly utilizes a flotation method to separate a mixture of boric acid and magnesium sulfate, the separation effect of the method has certain requirements on the particle size of solid, and an organic medicament is also used in the flotation process. CN 101659418A describes a method for preparing boric acid in a boron-containing sodium chloride and potassium chloride saturated bittern solution, which utilizes the solubility difference between borate and sodium chloride and potassium chloride, and separates by evaporation concentration, but in the process of finally obtaining a boric acid product, a large amount of acid and alkali are consumed, and the requirement for accurately controlling the concentration ratio is high.
Disclosure of Invention
In order to solve the problems in the prior art, the applicant of the present invention provides a method for recycling a polarizing plate waste liquid to prepare boric acid and potassium chloride. The method does not generate secondary waste in the process, has moderate separation effect requirement, does not use organic agents, has no accurate requirement on proportion control during evaporation concentration, can obtain high-purity boric acid and potassium chloride, and realizes the recycling of waste liquid.
The technical scheme of the invention is as follows:
a method for preparing boric acid and potassium chloride by recycling polarizing plate waste liquid comprises the following steps:
(1) pulping: distilling and concentrating the polarizing plate waste liquid to obtain iodine-containing crude boric acid and iodine products, pulping and washing the iodine-containing crude boric acid by using a potassium sulfite aqueous solution, centrifugally separating a solid phase and a liquid phase after washing, pulping and washing twice to obtain pulped boric acid, and returning the generated iodine-containing filtrate to the polarizing plate waste liquid for recycling;
(2) acidification 1: stirring and dissolving the pulped boric acid obtained in the step (1) in water, adjusting the pH value to be 3, cooling and crystallizing, and centrifugally separating a solid phase and a liquid phase from an obtained crystallized solution to obtain a finished product boric acid and a salt-containing boric acid solution;
(3) calcification: heating the saliferous boric acid solution prepared in the step (2), adding calcium hydroxide powder, stirring and reacting for 1-5 h, and filtering and separating a solid phase and a liquid phase while the solution is hot after the reaction is finished to obtain calcium mud and saliferous filtrate;
through the step, 98% of boric acid in the solution can be separated from potassium chloride, so that the purity of a subsequent potassium chloride product can be improved by 40%.
(4) And (3) acidification 2: adding a hydrochloric acid solution into the calcium mud obtained in the step (3) while stirring for acidification until the pH value is 3, and filtering and separating a solid phase and a liquid phase after the acidification is finished to obtain a finished product boric acid and a calcium chloride solution;
(5) concentration: and (4) distilling the salt-containing filtrate obtained in the step (3) to obtain a crude potassium chloride product, dissolving the crude potassium chloride product in water, filtering to remove impurities, and distilling the obtained filtrate to obtain a potassium chloride product with the purity of more than 98%.
The polarizing plate waste liquid is a solution produced in the polarizing plate manufacturing industry, and includes, but is not limited to, a mixed aqueous solution composed of boric acid, potassium tetraborate, potassium iodide and iodine.
The mass ratio of the potassium sulfite aqueous solution to the iodine-containing crude boric acid in the step (1) is 1: 1.5-5; the concentration of potassium sulfite in the potassium sulfite aqueous solution is 50g/L, and the molar ratio of the iodine simple substance containing the iodine crude boric acid to the required potassium sulfite is 1:1.
The mass ratio of the boric acid to the water after pulping in the step (2) is 1: 3-6, and the temperature of the water is 80-90 ℃.
The temperature after cooling in the step (2) is 10-25 ℃.
The heating temperature in the step (3) is 70-95 ℃; the mass ratio of the calcium hydroxide to the saliferous boric acid filtrate is 1: 25.
The distillation temperature in the steps (1) and (5) is 100 ℃; the distillation pressure is-0.02 to-0.08 MPa.
In the step (5), the mass ratio of the water to the crude potassium chloride product is 2-4: 1.
The beneficial technical effects of the invention are as follows:
98 percent of boric acid in the salt-containing boric acid solution can be separated from potassium chloride; compared with an extraction method for separating boric acid and potassium chloride, the method is more environment-friendly without using an organic solvent; compared with a direct evaporation concentration mode, the purity of the subsequent potassium salt can be improved by 40%.
Compared with the method for directly evaporating and concentrating the treated salt-containing boric acid solution, the method does not generate any secondary waste.
The pulping step is carried out before the acidification step, so that the safety risk caused by iodine simple substance under the acidic condition is reduced, the purity of the boric acid product can be improved by about 5 percent, and meanwhile, the iodine element enters the material circulation to avoid generating secondary waste; a large amount of boron-calcium-containing mud is generated in the calcification step, 98% of boron element is recovered in a mode of purity of more than 98% of boric acid through the step, and the residual calcium chloride solution can be directly sold as a product, so that secondary waste is avoided.
Drawings
FIG. 1 is a schematic view of the process of the present invention.
Detailed Description
The present invention will be described in detail with reference to the accompanying drawings and examples.
Example 1
Distilling and concentrating 2L of polarizing plate waste liquid at 100 ℃ and under the pressure of-0.02 MPa to obtain iodine-containing crude boric acid, wherein the mass fraction of the iodine-containing crude boric acid is 70% of boric acid, 27% of potassium tetraborate, 2.3% of potassium iodide and 0.01% of iodine.
Taking 200g of iodine-containing crude boric acid, adding 140mL of water and 1mL of 50g/L K in total2SO3The mixed solution is repeatedly pulped twice, after pulping is finished, filtration and separation are carried out, and the crude boric acid does not contain KI after pulping is detected. Slowly adding beaten boric acid into 600mL of water at 80 deg.C, stirring to dissolve, slowly adding 45mL of 30% HCl, adjusting to dissolveAnd (3) stirring and cooling the solution at the temperature of 10 ℃, filtering and separating, collecting and drying crystals, and detecting the purity of the obtained boric acid product to be 99.1%.
560mL of the saliferous boric acid filtrate obtained after acidification was taken, and 25g of Ca (OH) was added2Stirring, heating the solution to 70 ℃, reacting for 5h, filtering while hot after the reaction is finished, and separating to obtain the hydrous calcium mud and the salt-containing filtrate.
And (2) adding 30mL of water into 95g of hydrous calcium mud, uniformly stirring, slowly adding 70mL of 30% HCl while stirring, adjusting the pH to be 3, cooling, filtering and separating the solution, drying the obtained crystals, and detecting the purity of the obtained boric acid product to be 99.3%. The filtrate obtained is CaCl2The concentration was 260 g/L.
500mL of salt-containing filtrate is taken, distillation and concentration are carried out under the conditions of 100 ℃ and-0.02 MPa to obtain about 40g of crude KCl, the crude KCl is dissolved in 80mL of water, filtration and separation are carried out to obtain 4g of insoluble substances and a plurality of filtrates, the filtrate is subjected to distillation and concentration under the conditions of 100 ℃ and-0.02 MPa to obtain dried crystals, the weight of the crystals is 35g, and the content of KCl is 98.7%.
Example 2
2L of polarizing plate waste liquid is taken, and distilled and concentrated under the conditions of 100 ℃ and-0.06 MPa to obtain iodine-containing crude boric acid, wherein the mass fraction of the iodine-containing crude boric acid is as follows, and the boric acid comprises 75 percent of boric acid, 23 percent of potassium tetraborate, 1 percent of potassium iodide and 0.01 percent of iodine.
200g of crude boric acid containing iodine are taken, 100mL of water and 1mL of 50g/L K are added in total2SO3The mixed solution is repeatedly pulped twice, after pulping is finished, filtration and separation are carried out, and the crude boric acid does not contain KI after pulping is detected. Slowly adding the beaten boric acid into 900mL of water with the temperature of 85 ℃, stirring for dissolving, slowly adding 40mL of 30% HCl, adjusting the pH value of the solution to be 4, stirring for cooling the solution at the temperature of 10 ℃, filtering for separation, collecting crystals, drying, and detecting the purity of the obtained boric acid product to be 99.4%.
560mL of the saliferous boric acid filtrate obtained after acidification was taken, and 24g of Ca (OH) was added2Stirring, heating the solution to 85 ℃, reacting for 3h, filtering while hot after the reaction is finished, and separating to obtain the hydrous calcium mud and the salt-containing filtrate.
Mixing 95g of hydrous calcium mud with 30mL of water, stirring, and slowly adding 70mL of 30 percent while stirringAdjusting the pH value to 3 by HCl, cooling the solution, filtering and separating, drying the obtained crystals, and detecting the purity of the obtained boric acid to be 99.2%. The filtrate obtained is CaCl2The concentration is 258 g/L.
500mL of salt-containing filtrate is taken, distilled and concentrated under the conditions of 100 ℃ and-0.06 MPa to obtain about 20g of crude KCl, the crude KCl is dissolved in 60mL of water, 2g of insoluble substances and a plurality of filtrates are obtained by filtration and separation, the filtrate is distilled and concentrated under the conditions of 100 ℃ and-0.06 MPa, the obtained crystals are dried, 17g of crystals are weighed, and the content of KCl is 98.5%.
Example 3
2L of polarizing plate waste liquid is taken, and distilled and concentrated under the conditions of 100 ℃ and-0.08 MPa to obtain iodine-containing crude boric acid, wherein the mass fraction of the iodine-containing crude boric acid is 65 percent of boric acid, 32 percent of potassium tetraborate, 2.2 percent of potassium iodide and 0.02 percent of iodine. .
200g of crude boric acid containing iodine are taken, 40mL of water and 2mL of 50g/L K are added in total2SO3The mixed solution is repeatedly pulped twice, after pulping is finished, filtration and separation are carried out, and the crude boric acid does not contain KI after pulping is detected. Slowly adding the beaten boric acid into 1200mL of water with the temperature of 90 ℃, stirring for dissolving, slowly adding 50mL of 30% HCl, adjusting the pH value of the solution to 3, stirring for cooling the solution at the temperature of 10 ℃, filtering for separation, collecting crystals, drying, and detecting the purity of the obtained boric acid product to be 99.6%.
560mL of the saliferous boric acid filtrate obtained after acidification was taken, and 23g of Ca (OH) was added2Stirring, heating the solution to 95 ℃, reacting for 1h, filtering while hot after the reaction is finished, and separating to obtain the hydrous calcium mud and the salt-containing filtrate.
And (2) adding 30mL of water into 95g of hydrous calcium mud, uniformly stirring, slowly adding 70mL of 30% HCl while stirring, adjusting the pH to 3, cooling, filtering and separating the solution, drying the obtained crystals, and obtaining a product boric acid with the detection purity of 99.8%. The filtrate obtained is CaCl2The concentration was about 255 g/L.
500mL of salt-containing filtrate is taken, distillation and concentration are carried out under the conditions of 100 ℃ and-0.08 MPa to obtain about 18g of crude KCl, the crude KCl is dissolved in 70mL of water, filtration and separation are carried out to obtain 1g of insoluble substances and a plurality of filtrates, the filtrate is subjected to distillation and concentration under the conditions of 100 ℃ and-0.08 MPa to obtain dried crystals, the weight of the crystals is 16g, and the content of KCl is 98.9%.
Claims (8)
1. A method for preparing boric acid and potassium chloride by recycling polarizing plate waste liquid is characterized by comprising the following steps:
(1) distilling and concentrating the polarizing plate waste liquid to obtain iodine-containing crude boric acid and iodine products, pulping and washing the iodine-containing crude boric acid twice by using a potassium sulfite aqueous solution, centrifugally separating a solid phase and a liquid phase after washing to obtain pulped boric acid, and returning the generated iodine-containing filtrate to the polarizing plate waste liquid for recycling;
(2) acidification 1: stirring and dissolving the pulped boric acid obtained in the step (1) in water, adjusting the pH value to be 3, cooling and crystallizing, and centrifugally separating a solid phase and a liquid phase from an obtained crystallized solution to obtain a finished product boric acid and a salt-containing boric acid solution;
(3) calcification: heating the saliferous boric acid solution prepared in the step (2), adding calcium hydroxide powder, stirring and reacting for 1-5 h, and filtering and separating a solid phase and a liquid phase while the solution is hot after the reaction is finished to obtain calcium mud and saliferous filtrate;
through the step, 98% of boric acid in the solution can be separated from potassium chloride, so that the purity of a subsequent potassium chloride product can be improved by 40%;
(4) and (3) acidification 2: adding a hydrochloric acid solution into the calcium mud obtained in the step (3) while stirring for acidification until the pH value is 3, and filtering and separating a solid phase and a liquid phase after the acidification is finished to obtain a finished product boric acid and a calcium chloride solution;
(5) concentration: and (4) distilling the salt-containing filtrate obtained in the step (3) to obtain a crude potassium chloride product, dissolving the crude potassium chloride product in water, filtering to remove impurities, and distilling the obtained filtrate to obtain a potassium chloride product with the purity of more than 98%.
2. The method of claim 1, wherein the polarizer waste solution is a solution generated from the polarizer manufacturing industry, including but not limited to a mixed aqueous solution of boric acid, potassium tetraborate, potassium iodide, and iodine.
3. The method according to claim 1, wherein the mass ratio of the potassium sulfite aqueous solution to the iodine-containing crude boric acid in the step (1) is 1: 1.5-5; the concentration of potassium sulfite in the potassium sulfite aqueous solution is 50g/L, and the molar ratio of the iodine simple substance containing the iodine crude boric acid to the required potassium sulfite is 1:1.
4. The method according to claim 1, wherein the mass ratio of the beaten boric acid to water in step (2) is 1: 3-6, and the temperature of water is 80-90 ℃.
5. The method according to claim 1, wherein the temperature after the cooling in the step (2) is 10 to 25 ℃.
6. The method according to claim 1, wherein the heating temperature in the step (3) is 70 to 95 ℃; the mass ratio of the calcium hydroxide to the saliferous boric acid solution is 1: 25.
7. The method according to claim 1, wherein the temperature of the distillation in steps (1), (5) is 100 ℃; the distillation pressure is-0.02 to-0.08 MPa.
8. The method according to claim 1, wherein the mass ratio of the water to the crude potassium chloride in the step (5) is 2-4: 1.
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| JP7048950B2 (en) * | 2020-03-27 | 2022-04-06 | 日東電工株式会社 | Method for treating polarizing plate manufacturing waste liquid |
| CN111498861B (en) * | 2020-04-23 | 2022-07-26 | 无锡中天固废处置有限公司 | Polarizing plate waste liquid treatment method |
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| US7820080B2 (en) * | 2003-09-29 | 2010-10-26 | Nitto Denko Corporation | Method for producing polarizing film, polarizing film, and image display using the polarizing film |
| JP5189255B2 (en) * | 2006-07-03 | 2013-04-24 | 合同資源産業株式会社 | Iodine recovery from polarizing film manufacturing wastewater |
| KR100781566B1 (en) * | 2006-11-08 | 2007-12-03 | (주)비룡 | Equipment for regenerating waste solution of potassium iodide and method thereof |
| JP4948305B2 (en) * | 2007-07-23 | 2012-06-06 | 合同資源産業株式会社 | Method and system for circulating use of polarizing film manufacturing chemicals |
| JP2009090256A (en) * | 2007-10-11 | 2009-04-30 | Shinryo Corp | Method for treating waste liquid containing borate and alkali metal iodide salt and apparatus therefor |
| KR101044463B1 (en) * | 2009-07-29 | 2011-06-27 | 양우석 | Equipment For Reusing Potassium Iodide Waste Solution Of Polarizing Film Manufacturing Process and Method Thereof |
| CN101659418B (en) * | 2009-09-02 | 2013-03-06 | 达州市恒成能源（集团）有限责任公司 | Method for preparing boric acid in boracic sodium chloride and potassium chloride saturated bittern solution containing boron |
| KR101407616B1 (en) * | 2012-05-23 | 2014-06-13 | 타운마이닝캄파니(주) | Method for recovering high purity potassium iodide and borides from aqueous waste from polarizing film manufacturing process |
| KR20150046905A (en) * | 2013-10-23 | 2015-05-04 | 동우 화인켐 주식회사 | Preparing method for a polarizer |
| KR101650446B1 (en) * | 2013-10-31 | 2016-08-23 | 주식회사 엘지화학 | Apparatus and method for recycling solution for manufacturing polarizing plate |
| CN203768156U (en) * | 2013-12-25 | 2014-08-13 | 明基材料有限公司 | Boron and iodine wastewater treatment system |
| CN104003552B (en) * | 2014-05-28 | 2016-02-10 | 佛山纬达光电材料有限公司 | The treatment process of a kind of dyestuff system polaroid waste water |
| JP6841481B2 (en) * | 2016-05-24 | 2021-03-10 | 株式会社ササクラ | Method for treating polarizing plate manufacturing waste liquid |
| KR101935818B1 (en) * | 2017-05-23 | 2019-01-07 | 세종화학 (주) | Method for recycling a potassium iodide solution in waste solution from polarizing film process |
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