KR101130823B1 - Method for recovering high purity phosphoric acid from mixed waste acid occupied in preparing process of liquid crystal display - Google Patents

Abstract

The present invention relates to a method for recovering high-purity phosphoric acid from the mixed waste acid generated in the liquid crystal display device manufacturing process, wherein the recovery method comprises solvent extraction of the mixed waste acid generated in the liquid crystal display device and an aqueous phase containing phosphoric acid and a metal component, and nitric acid. And separating into an organic phase containing acetic acid, and the aqueous phase is subjected to diffusion dialysis to first remove the metal component contained in the aqueous phase, and the dialysis solution obtained after the diffusion dialysis treatment is subjected to ion exchange resin treatment to remove the metal component remaining in the dialysis solution. Removing the residue and vacuum evaporating the filtrate remaining after the ion exchange resin treatment.

By the method of recovering high purity phosphoric acid according to the present invention, it is possible to recover high purity phosphoric acid in which the impurity content is reduced to several ppm level from the mixed waste acid generated in the liquid crystal display manufacturing process. Accordingly, the recovered phosphoric acid may be recycled into an etching solution, high purity phosphoric acid, various pickling solutions, and the like in manufacturing a liquid crystal display.

Liquid crystal display, mixed waste acid, acid recovery, solvent extraction, diffusion dialysis, ion exchange resin

Description

METHOD FOR RECOVERING HIGH PURITY PHOSPHORIC ACID FROM MIXED WASTE ACID OCCUPIED IN PREPARING PROCESS OF LIQUID CRYSTAL DISPLAY}

1 is a process diagram schematically showing a method for recovering phosphoric acid from mixed waste acid according to an embodiment of the present invention,

2 is a process diagram schematically showing a solvent extraction step in the phosphoric acid recovery method according to an embodiment of the present invention.

[Technical Field]

The present invention relates to a method for recovering high-purity phosphoric acid from mixed waste acid generated in a liquid crystal display (LCD) manufacturing process, and more particularly, to high concentration of high-purity phosphoric acid in which impurities are reduced to several ppm. The present invention relates to a method for recovering high-purity phosphoric acid that can be recycled to an etching solution, high-purity phosphoric acid, various pickling solutions, and the like in the manufacture of a liquid crystal display device.

[Private Technology]

Recently, as the production amount of liquid crystal display (LCD) is rapidly increased, the amount of mixed waste acid generated during manufacturing of the LCD is also rapidly increasing. However, recycling techniques for these mixed waste acids are not yet established.

The mixed waste acid is usually mixed with other etching waste liquids in LCD and semiconductor manufacturing processes, and is incinerated, thus, an excessive energy cost is required for the mixed waste acid treatment. In addition, the neutralization precipitation method is also used as a treatment method of the mixed waste acid. In the neutralization precipitation method, since the mixed waste acid is a high concentration of acid, an alkaline neutralizing agent is excessively consumed during neutralization, and a large amount of sludge is generated after the treatment. In addition, since the sludge generated at this time contains heavy metals, general landfilling is not possible, and there is a problem of incineration separately. The treatment method of mixed waste acid as described above has a problem in that resources cannot be recycled because the treatment cost is high and expensive organic metals and acids are discarded.

On the other hand, as a technique for recycling mixed waste acid, Korean Patent No. 461849 describes a method for purifying a high concentration of phosphoric acid from an etching process waste liquid through a vacuum concentration and extraction process, and also in Korean Patent Application No. 2004-0008608 A method for regenerating phosphate containing waste etchant through distillation, cation exchange resins and electrochemical activation processes is described. However, in the above method, since nitric acid and acetic acid which are first removed by distillation under reduced pressure are mixed, nitric acid and acetic acid cannot be separated and recycled separately, and the concentration of metal components in the residual liquid remaining after distillation under reduced pressure is high. Or when nitric acid and acetic acid remain or when the concentration of phosphoric acid is high, it is difficult to use the ion exchange resin method. Because the acid concentration is high, even the strong acid resin having a high degree of crosslinking is very difficult to adsorb the resin of the metal component. In addition, when the metal concentration is high, the amount of resin used increases the processing cost. In many cases, the metal component in the waste liquid forms a complex, and the complex is often present in the solution as an anion. Therefore, the cation exchange resin alone cannot completely separate and remove metal components.

The present invention is to solve the above problems, the present invention is to provide a phosphoric acid recovery method that can recover high-purity phosphoric acid by reducing the content of impurities to several ppm level from the mixed waste acid generated in the manufacturing process of the liquid crystal display device For the purpose of

In order to achieve the above object, the present invention is solvent extraction of the mixed waste acid generated in the liquid crystal display device to separate the aqueous phase comprising phosphoric acid and metal components, and the organic phase containing nitric acid and acetic acid, the aqueous phase by diffusion dialysis treatment Firstly removing the metal component contained in the membrane, and treating the dialysate obtained after the diffusion dialysis treatment with ion exchange resin to remove second metal component remaining in the dialysate and vacuum evaporating the remaining filtrate after the ion exchange resin treatment. It provides a method for recovering high-purity phosphoric acid from the mixed waste acid generated in the liquid crystal display device manufacturing process comprising a.

Hereinafter, the present invention will be described in more detail.

The recycling of mixed waste acids from the manufacturing process of LCDs depends on the degree of purification of the waste acids, and the added value that results. For example, ferric acid can be used if the content of acetic acid, nitric acid, and metals in phosphoric acid is less than about 3%, but in the case of phosphoric acid solutions used in LCD manufacturing processes, the total amount of impurity components in the phosphoric acid solution can be used. The content should be 1 ppm or less.

Therefore, in order to increase the added value in recycling the mixed waste acid, a recycling technology capable of purifying impurities such as nitric acid, acetic acid, aluminum, molybdenum, etc. to 1 ppm or less is required. Accordingly, various techniques such as vacuum evaporation, solvent extraction, diffusion or electrodialysis, and ion exchange resins have been used as techniques for recycling mixed waste acid.

In the case of vacuum evaporation, however, organic components such as nitric acid and acetic acid contained in the waste acid can be separated and removed by using a boiling point difference, but metal components, such as aluminum and molybdenum, cannot be removed. In addition, in the case of solvent extraction, organic materials capable of extracting some metal components have been developed but cannot be completely removed. In the case of diffusion dialysis and electrodialysis, removal rates vary depending on the metal component and the type of acid solution, but are usually not removed to several ppm levels. In addition, in the case of the ion exchange resin method, if the metal ion concentration is too high, the exchange cycle and the cleaning cycle are too short, which is not economical. In addition, even if the acid concentration is too high or the pH is too low, it is difficult to apply, and the adsorption rate tends to drop rapidly, and thus cannot be used.

In the present invention, by treating the mixed waste acid in the order of solvent extraction, diffusion dialysis and ion exchange resin, it is possible to recover high purity phosphoric acid having a high content of impurities reduced in the level of several ppm from the mixed waste acid. The phosphoric acid thus obtained may be recycled into an etching solution, high purity phosphoric acid, various pickling solutions, and the like in the manufacture of a liquid crystal display device.

1 is a process diagram schematically showing a method for recovering high purity phosphoric acid from mixed waste acid according to an embodiment of the present invention. Hereinafter, a method of recovering high purity phosphoric acid from the mixed waste acid of the present invention will be described with reference to the process diagram of FIG. 1. The method of recovering high purity phosphoric acid according to an embodiment of the present invention is performed by using the mixed waste acid 1 generated in the liquid crystal display device. Solvent extraction (10) to separate the aqueous phase (12) comprising phosphoric acid and metal components and the organic phase (14) comprising nitric acid and acetic acid, and the aqueous phase (12) by diffusion dialysis treatment (20) to the aqueous phase (12). Firstly removing the metal component contained therein as the waste liquid 22, and secondly removing the metal component present in the dialysate by ion exchange resin treatment 30 on the dialysis solution 24 obtained after the diffusion dialysis treatment, And performing vacuum evaporation 40 on the high purity phosphoric acid 32 obtained after the ion exchange resin treatment to concentrate the high purity phosphoric acid at a high concentration to obtain a high purity and high concentration phosphoric acid 42.

The LCD mixed waste acid used in the present invention is a waste etching solution generated in the process of forming the metal circuit of the multilayer circuit board during the LCD manufacturing process. The waste etching solution contains phosphoric acid, nitric acid, acetic acid, aluminum, molybdenum and the like.

Each of these components is separated and solvent mixed extraction of the mixed waste acid is the first step to recover high purity phosphoric acid. At this time, in order to remove the insoluble solid impurities contained in the mixed waste acid prior to the solvent extraction process, it may optionally further perform a filtration process using a micro filter or the like.

The solvent extraction process is performed with respect to the mixed waste acid or the filtrate obtained by the said filtration process.

2 is a process diagram schematically showing a solvent extraction step in the phosphoric acid recovery method according to an embodiment of the present invention. As shown in FIG. 2, the nitric acid and acetic acid contained in the mixed waste acid 1 are separated into the organic phase 14 using an extractant, and the metal component and phosphoric acid contained in the mixed waste acid are extracted toward the aqueous phase 12. Can be separated. Thereafter, the nitric acid and acetic acid may be separated from the separated organic phase 14 by vacuum evaporation, and the organic phase 14 may be stripped 15 using a stripping agent prior to the vacuum evaporation process to remove the stripping solution ( 16) may be carried out.

At this time, the extractant may be selected from the group consisting of alkyl phosphate, haloalkyl phosphate, aryl phosphate and mixtures thereof, more preferably the extractant is trioctyl phosphate, trichloroethyl phosphate, n-butyldi ( m-crezyl) phosphate, n-butyldi (3,5-dimethylphenyl) phosphate, 2-ethylbutyldi (m-crezyl) phosphate and mixtures thereof may be used.

In addition, the extractant is dissolved in an organic solvent to form an organic phase, wherein the extractant may be included in 20 to 70% by weight, more preferably 40 to 60% by weight relative to the total weight of the organic phase. If the content of the extractant is less than 20% by weight, the separation rate of the extract is very slow. If the content of the extractant exceeds 70% by weight, the concentration of the extractant must be continuously maintained in the multi-step extraction, washing, and stripping process. It is not preferable because it is difficult to control.

As the organic solvent, petroleum hydrocarbon compounds such as kerosene may be used.

Water was used as the aqueous phase when the solvent was extracted for the mixed waste acid.

The water phase (A) and the organic phase (O) is preferably used in a mixed ratio (A / O) of 1/1 to 1/5, more preferably in a mixed ratio of 1/2 to 1/4 It is preferred to be used. If the ratio is less than 1/1, the separation and extraction rate of acetic acid and nitric acid is low, which is not preferable. If the ratio is more than 1/4, the extraction ratio of nitric acid and acetic acid is almost constant.

The mixed waste acid by the solvent extraction is an organic phase comprising nitric acid and draft; And an aqueous phase containing phosphoric acid and a metal component. Thereafter, the separated organic phase may be removed to separate nitric acid and acetic acid contained in the mixed waste acid.

At this time, nitric acid and acetic acid contained in the organic phase may be separated by performing stripping treatment and vacuum evaporation treatment on the separated organic phase.

The stripping treatment may be carried out by separating a mixture of nitric acid and acetic acid contained in the organic phase into an aqueous phase using a stripping agent such as distilled water. The stripping agent used in the stripping treatment may be one or more selected from the group consisting of distilled water, hydrochloric acid and sulfuric acid aqueous solution. The stripping agent itself becomes an aqueous phase.

The aqueous phase (A) including the stripping agent is preferably added so that the phase ratio (A / O) is 1/2 to 1/7 with respect to the organic phase (O) separated in the solvent extraction step, more preferably 1 It is good to add so that it is / 4 to 1/6. If the ratio of the aqueous phase and the organic phase is less than 1/2, the amount of wastewater generated is excessive and undesirable.

The stripping solution comprising the mixture of separated nitric acid and acetic acid can then be separated into individual materials by vacuum evaporation under appropriate vacuum and temperature ranges.

Subsequently, diffusion dialysis treatment is performed on the separated aqueous phase after the solvent extraction treatment to first remove metal components contained in the aqueous phase.

A large amount of metal can be efficiently removed by the diffusion dialysis method. In the present invention, the phosphoric acid can be separated with high purity by removing the metal component contained in the aqueous phase as an extract using the selective permeability of the anion exchange membrane which passes only the phosphoric acid solution but does not pass the metal salt. As the diffusion dialysis membrane, a commercially available anion exchange membrane for acid recovery may be used.

In the diffusion dialysis treatment, a conventional diffusion dialysis apparatus may be used, and in the present invention, a diffusion dialysis apparatus in which a large number of ion exchange membranes are alternately interposed with a gasket in order to flow water and water sequentially is used. Accordingly, the gasket for supplying the water and the water in the diffusion dialysis apparatus is preferable because the plastic nets are woven like a net so that the solution can be uniformly mixed and the turbulence can be minimized to minimize membrane contamination.

In the diffusion dialysis apparatus, the water phase is supplied upward from the bottom of the diffusion dialysis apparatus, and water is supplied from the upper side downwards. The water phase fed into the diffusion dialysis apparatus is separated into metal ions and phosphoric acid by the selective permeability of the dialysis membrane. The separated phosphoric acid is then diluted in contact with the countercurrent water, and the dialysate containing the diluted phosphoric acid is discharged to the bottom of the diffusion dialysis apparatus. On the other hand, the metal component and some of the phosphoric acid that failed to pass through the dialysis membrane come out upwards.

By such diffusion dialysis treatment, 98% or more of metal components of aluminum and molybdenum contained in the water phase obtained after the solvent extraction treatment can be removed.

Next, the dialysis solution obtained after the diffusion dialysis treatment is subjected to ion exchange resin treatment to remove secondary metal components in the dialysis solution to obtain high purity phosphoric acid.

The ion exchange resin treatment can be used both cation exchange resin and anion exchange resin together. In the case of aluminum, it exists as a cation in the dialysate, but in the case of molybdenum, it exists in the form of an anion complex, so the molybdenum contained in the dialysate cannot be removed only by cation exchange resin treatment. Therefore, it is preferable to pass through two types of resin towers, a cation exchange resin and an anion exchange resin.

In addition, a styrene-based strong acid cation exchange resin may be used as the cation exchange resin when the cation exchange resin is treated. Preferably, since the concentration of phosphoric acid contained in the dialysate obtained after the diffusion dialysis treatment is high, a highly acidic cation having a high crosslinking degree It is better to use an exchange resin. Accordingly, the styrene-based strongly acidic cation exchange resin may more preferably have a crosslinking degree of 10% or more, and even more preferably 10-16%. If the crosslinking degree of styrene type strong acid cation exchange resin is higher than 10%, the water content in resin, ion exchange capacity is increased, and oxidation resistance is increased. On the other hand, it is difficult to regenerate after adsorption and easily contaminated by organic matter. . However, in the present invention, since a high concentration of acid solution is treated, when the crosslinking degree is lower than 10%, the resin is oxidized to reduce durability, and the ion exchange capacity is low, which is difficult to treat, which is not preferable. In addition, the strong acid resin in this invention means resin which has strong resistance to an acid and has more ion exchange ability in a strong acid solution.

Moreover, it is preferable to use the styrene type strong acidic anion exchange resin which is excellent in chemical stability and organic pollution resistance as said anion exchange resin. The anion exchange resin is also preferably a styrene-based strongly acidic anion exchange resin having a crosslinking degree of 10% or more.

The flow velocity S.V. (space velocity) of the dialysate during the ion exchange resin treatment means a value obtained by dividing the waste liquid through-hour by the resin volume and depends on the type of resin. In this invention, it is preferable to use the thing whose S.V. is 2-6. Within the above range, aluminum and molybdenum may be treated at 1 ppm or less, but if it is less than 2 outside the above range, the processing speed may be too slow, resulting in excessive investment of equipment required for a certain amount of waste liquid treatment. And molybdenum are not preferable because they cannot be treated at 1 ppm or less.

The dialysis solution obtained after the diffusion dialysis treatment in the above manner was first treated with a cation exchange resin to remove aluminum in the dialysate, and then treated with an anion exchange resin to remove molybdenum, thereby reducing the concentration of the metal component to 1 ppm or less. Aqueous phosphoric acid solution can be obtained. At this time, the order of treatment of the anion exchange resin and the cation exchange resin is not particularly limited.

The aqueous solution of phosphoric acid obtained by the ion exchange resin treatment is high in purity, but the concentration of phosphoric acid is low, so that further concentration of phosphoric acid can be obtained by further vacuum evaporation treatment.

At this time, the vacuum evaporation treatment is preferably carried out at -650 to -760 mmHg vacuum degree, more preferably can be carried out at -680 to -730 mmHg vacuum degree. If the degree of vacuum is less than -650 mmHg, the evaporation temperature must be increased to 140 ° C or higher. Therefore, the energy cost and the investment cost of the manufacturing equipment are excessively increased. It is not preferable because it is difficult to continuously operate above 760 mmHg.

In addition, it is preferable to perform the said primary vacuum evaporation process in the temperature range of 100-160 degreeC, More preferably, it is good to carry out in the temperature range of 110-130 degreeC. It is not preferable because the evaporation itself does not occur below 100 ° C, and if it exceeds 160 ° C, the energy cost is excessive, and when the waste steam is used, it is difficult to use the waste steam because the waste steam usually does not exceed 140 ° C. Not desirable

Most preferably, the vacuum degree is -650 mmHg at a temperature of 140 ° C or higher, the vacuum degree is -700mmHg at a temperature of 120 ° C or higher, and in the case of a vacuum degree of -730mmHg, the temperature is set at 110 ° C or higher.

By the vacuum evaporation treatment as described above, high purity phosphoric acid can be obtained at a high concentration of 85% or more.

By the high-purity phosphoric acid recovery method as described above, it was possible to recover the high-purity phosphoric acid in which the impurity content was reduced to several ppm level from the mixed waste acid at a high concentration. The phosphoric acid thus obtained may be recycled into an etching solution, high purity phosphoric acid, various pickling solutions, and the like in the manufacture of a liquid crystal display device.

Hereinafter, preferred examples and comparative examples of the present invention are described. However, the following examples are only preferred embodiments of the present invention and the present invention is not limited to the following examples.

Example  1. Mix From waste acid  Recovery of high purity phosphoric acid.

1) LCD mix Waste acid  Ready

The mixed waste acid having the composition shown in Table 1 was used to recover high purity phosphoric acid from the mixed waste acid discharged from the LCD manufacturing process.

Analysis item density(%) Metal ion (mg / kg) Acetic acid nitric acid Phosphoric Acid Al Mo LCD mixed waste acid 6.8 6.7 62.2 211.5 206

2) LCD mix Waste acid  Solvent extraction treatment

In order to separate acetic acid and nitric acid which exist in mixed waste acid, the solvent extraction process was performed as follows.

The mixed waste acid having the composition shown in Table 1 above was mixed and added so that the phase ratio (A / O) of the aqueous phase (A) and the organic phase (O) became 1/4. By the solvent extraction treatment, nitric acid and acetic acid in the mixed waste acid diffuse and move into the organic phase, and phosphoric acid and metal components are extracted and remain in the aqueous phase. When the two phases were left to be completely separated and equilibrated, a separatory funnel was used to separate the aqueous phase and the organic phase. The amount of extraction was determined by measuring the acid concentration of the aqueous phase and the acid concentration of the organic phase.

In the stripping step, an aqueous phase containing a stripping agent was added to the organic phase so that the phase ratio (A / O) of the aqueous phase (A) and the organic phase (O) was 1, and acetic acid and nitric acid were recovered in two stages. At this time, distilled water was used as the stripping agent. By the stripping process, acetic acid and nitric acid were separated into an aqueous phase (a stripping solution). The theoretical extraction and stripping stages are optimal after constructing the McCabe-Thiele diagram, which is a combination of the extraction isothermal curve and the stripping isothermal curve with the operating line (A / O ratio). The theoretical number of stages required for extraction and removal of was determined.

In order to confirm complete separation of nitric acid and acetic acid from the mixed waste acid by the solvent extraction, the acid concentration in the solvent extract (aqueous phase) and stripping solution was measured using an ion chromatography (Ion Chromatography: ICS-2500, DIONEX) analyzer. Measured. In addition, metal components such as Al and Mo in the residual liquid were analyzed by using plasma spectrometry (ICP-AES). The measurement results are shown in Table 2 below.

Analysis item Acid concentration (%) Metal ion (mg / kg) Acetic acid nitric acid Phosphoric Acid Al Mo Stripping liquid 2.7 3.9 - - - Extract (water phase) - - 61.7 212.0 206.5

As shown in Table 2 above, acetic acid and nitric acid were separated from the mixed waste acid by almost 99.9% or more into the organic phase. At this time, the extracted phosphoric acid and metal components were maintained at about the same level as the concentration in the initial mixed waste acid, but was different from the initial concentration because distilled water was used as a stripping agent for nitric acid and acetic acid.

3) Diffusion dialysis treatment of the aqueous phase obtained after solvent extraction

In order to separate the metal components present in the water phase obtained after the solvent extraction step of 2) was subjected to diffusion dialysis treatment as follows.

While adjusting the flow rates of the aqueous phase and water obtained in the solvent extraction step to 0.97L / Hr? M ² , the dialysis membrane (DSV, ASAHI GLASS Co.), which is an anion exchange membrane, was diffused in the opposite direction (T-Ob Selemion dialyzer). , ASAHI GLASS Co.). It carried out by the continuous process which continues to carry out until a recovery is reached to steady state. The pump used in the diffusion dialysis apparatus is a Masterflex pump (Cole Parmer) and a peristaltic pump having a maximum rotation speed of 600 rpm. In addition, the flow rate can be adjusted to 0.006 ~ 380mL / min depending on the tube size. Flow control was able to achieve the desired flow rate by controlling the rotational speed of the Masterflex pump and controlling the tube size. In addition, the area of the used dialysis membrane was 0.327 m ² / unit, and the flow rate was calculated by dividing the amount of the dialysate and the acid recovered in both measuring cylinders after passing through the dialyzer.

The dialysis solution recovered in the diffusion dialysis apparatus was measured using an ion chromatography (ICS-2500, DIONEX) analyzer to measure and analyze the acid concentration in the dialysis solution, and then a recovery rate was obtained. In addition, metal components such as Al and Mo in the dialysate were analyzed using plasma spectroscopy (ICP-AES). The measurement results are shown in Table 3 below.

Analysis item density(%) Metal ion (mg / kg) Acetic acid nitric acid Phosphoric Acid Al Mo Dialysate - - 51.6 5.06 6.50

As shown in Table 3, as a result of diffusion dialysis treatment for the aqueous phase obtained after the solvent extraction treatment, aluminum concentration 212.0mg / kg was lowered to 5.06mg / kg, molybdenum 206.5mg / kg to 6.5mg / kg. By such a diffusion dialysis treatment, a dialysis liquid obtained by removing about 98% of the metal component in the aqueous phase was obtained.

4) Spread After dialysis  Ion exchange resin treatment on the obtained dialysate

In order to remove the metal component remaining in the dialysate obtained after the diffusion dialysis step of 3), an ion exchange resin treatment was carried out as follows.

The filtrate obtained after the diffusion dialysis treatment was treated with a styrene strong acid cation exchange resin (SK1B, manufactured by Mitsubishi), and then passed through a column containing a strong acid anion exchange resin (A103, manufactured by PuroliteE) to treat an ion exchange resin. At this time, the flow rate of the aqueous solution of phosphoric acid so that S.V is 2.5.

About the filtrate obtained after the ion exchange resin treatment, the acid concentration in the filtrate was measured and analyzed using an ion chromatography (ICS-2500, DIONEX) analyzer, and then the recovery rate was determined. In addition, metal components such as Al and Mo in the filtrate were analyzed using plasma spectroscopy (ICP-AES). The measurement results are shown in Table 4 below.

Analysis item density(%) Metal ion (mg / kg) Acetic acid nitric acid Phosphoric Acid Al Mo Filtrate obtained after treatment with ion exchange resin - - 52.2 0.05 0.11

As shown in Table 4 above, as a result of performing ion exchange resin treatment on the dialysate with the metal component primarily by diffusion dialysis treatment, both aluminum and molybdenum were removed to 0.2 ppm or less. From this, it was confirmed that the metal component was completely removed to 1 ppm or less by the ion exchange resin treatment.

5) Vacuum evaporation of remaining filtrate after ion exchange resin treatment

As a result of the ion exchange resin treatment, the metal component was completely removed, but the concentration of phosphoric acid in the filtrate was lowered from 61.7% to 52.2%. Accordingly, in order to obtain a high concentration of phosphoric acid, a vacuum evaporation process was performed in the following manner.

After passing through the ion exchange resin step, the filtrate containing 52.2% of purified phosphoric acid was placed in a 2L Pyrex reactor using a digital heating magnetic stirrer (MSH-10, WiseStir) capable of temperature control up to 400 ° C ± 2 ° C. The temperature was maintained at a temperature of 120 ° C., and the pressure inside the reactor was kept constant at −730 mm Hg using a vacuum pump. At this time, inside the reactor, the pressure is reduced to a condition lower than atmospheric pressure, and the vacuum concentration proceeds to a phosphoric acid concentration of 85%.

The acid concentration was measured using an ion chromatography (ICS-2500, DIONEX) analyzer, and the Al and Mo components in the acid solution were analyzed using plasma spectrometry (ICP-AES). The results are shown in Table 5 below.

Analysis item
solution density(%) Metal ion (mg / kg) Acetic acid nitric acid Phosphoric Acid Al Mo Phosphoric acid aqueous solution obtained after vacuum evaporation - - 85.8 0.07 0.15

As shown in Table 5, the high-purity phosphoric acid could be concentrated to a high concentration of 85.8% through the vacuum evaporation treatment.

By the method of recovering high purity phosphoric acid according to the present invention, it is possible to recover high purity phosphoric acid in which the impurity content is reduced to several ppm level from the mixed waste acid generated in the liquid crystal display manufacturing process. Accordingly, the recovered phosphoric acid may be recycled into an etching solution, high purity phosphoric acid, various pickling solutions, and the like in manufacturing a screen display device.

Claims (10)

Solvent extraction of the mixed waste acid generated in the liquid crystal display device to separate the aqueous phase including phosphoric acid and a metal component and the organic phase including nitric acid and acetic acid; Diffusing dialysis of the aqueous phase to first remove metal components contained in the aqueous phase; Treating the dialysate obtained after the diffusion dialysis treatment with ion exchange resin to remove second metal components remaining in the dialysate; And After the ion exchange resin treatment step comprising a vacuum evaporation step A method for recovering high purity phosphoric acid from mixed waste acid generated in a liquid crystal display manufacturing process. The method of claim 1, The solvent extraction treatment step is a water phase (A) in the mixed waste acid; And recovering high-purity phosphoric acid from the mixed waste acid, wherein the organic phase (O) comprising the extractant is added by mixing the mixture in a phase ratio (A / O) of 1/1 to 1/5. 3. The method of claim 2, Wherein said extractant is at least one selected from the group consisting of alkyl phosphates, haloalkyl phosphates, aryl phosphates and mixtures thereof. 3. The method of claim 2, Wherein said extractant is used in a concentration of 20 to 70% by weight relative to the total weight of the organic phase. The method of claim 1, Wherein said ion exchange resin treatment is performed by treating a cation exchange resin treatment and an anion exchange resin to recover high purity phosphoric acid from mixed waste acid. The method of claim 5, The cation exchange resin is a styrene-based strong acid cation exchange resin, the anion exchange resin is a styrene-based strong basic anion exchange resin is a method for recovering high purity phosphoric acid from mixed waste acid. The method of claim 6, Wherein said styrenic strongly acidic cation exchange resin has a crosslinking degree of at least 10% and less than 100%. The method of claim 6, Wherein said styrenic strongly acidic anion exchange resin has a crosslinking degree of at least 10% and less than 100%. The method of claim 1, Wherein said vacuum evaporation treatment is carried out at a vacuum degree of -650 to -760 mmHg. The method of claim 1, The vacuum evaporation process is a method for recovering high purity phosphoric acid from mixed waste acid which is carried out at 100 to 160 ℃.

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