KR101256613B1 - Recovery of high purity phosphoric acid from mixed waste acid - Google Patents

Abstract

Diffusion dialysis method is used to remove the mixed aluminum and phosphoric acid mixed in the liquid crystal display (LCD) manufacturing process and to separate and remove the mixed waste acid containing phosphoric acid, nitric acid, acetic acid and aluminum in the mixed solution of nitric acid and acetic acid by vacuum evaporation. First, the aluminum is separated and removed by using a second diffusion dialysis process, the aluminum is more completely separated and removed, concentrated by vacuum evaporation method, and purified, recovered and recycled into a high-purity phosphate aqueous solution. It is related with the recycling method of mixed waste acid.

LCD, mixed waste acid, acid recovery, vacuum evaporation, diffusion dialysis

Description

Recovery of high purity phosphoric acid from mixed waste acid {RECOVERY OF HIGH PURITY PHOSPHORIC ACID FROM MIXED WASTE ACID}

The present invention is a method for recovering and recycling high-purity phosphoric acid from a mixed waste liquid containing aluminum in a mixed acid solution containing phosphoric acid, nitric acid and acetic acid, which is used in a liquid crystal display (LCD) manufacturing process. After recovering nitric acid and acetic acid as a mixed solution by vacuum evaporation method, aluminum is first separated and removed from the phosphate-aluminum mixture remaining in the vacuum evaporation process by diffusion dialysis method, and then again by the second diffusion dialysis process. By separating and removing the high purity of phosphoric acid to reduce the impurity content to several ppm level to a high concentration to recover high-purity phosphoric acid that can be recycled to etching solutions, high-purity phosphoric acid, various pickling solutions, etc. in the manufacture of liquid crystal display It is about a method.

Recently, the production of liquid crystal display devices is rapidly increasing, and thus, the amount of mixed waste acid generated is rapidly increasing. However, recycling technology for such mixed waste acid has not been established. The prior art for such waste acid is mixed with other etching waste liquids in the LCD and semiconductor manufacturing process and incinerated, resulting in excessive energy costs. In addition, when the waste liquid is treated by the neutralization precipitation method, since it is a high concentration of acid, alkaline neutralizer is excessively consumed, a large amount of sludge is generated after treatment, and it is impossible to bury it in general because of heavy metals. Therefore, these methods have a problem in that resources cannot be recycled because of high processing cost and disposal of expensive valuable metals and acids.

In the related art, a method of recovering high purity phosphoric acid by separating nitric acid and acetic acid by vacuum evaporation method and removing metal components by ion exchange resin method (Patent No. 10-2004-0023986, Pub. 10-2004-0008608) In this method, however, the nitric acid and acetic acid which have been first removed are mixed, and thus, nitric acid and acetic acid cannot be separated and recycled separately. It is difficult to use the ion exchange resin method at any concentration of nitric acid and acetic acid or high concentration of phosphoric acid. Because if 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 alone, which is the method of the above patent, 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

The use of LCD mixed liquor can be recycled depending on the level of refinement of the waste liquor and the added value varies greatly. For example, in the case of ferric acid for fertilizer, acetic acid, nitric acid, and metals are distributed as commodities when the content is less than about 3%, but in the case of phosphoric acid solution used in the LCD manufacturing process, the content of all impurity components is 1 ppm or less. It is strictly regulated. Therefore, in order to increase the added value in recycling the LCD mixed waste liquid of the present invention, a recycling technology capable of purifying impurities such as nitric acid, acetic acid, aluminum, and molybdenum to 1 ppm or less is required.

In order to achieve the above object, the present invention provides a first vacuum evaporation process of the mixed waste acid generated in the liquid crystal display device to remove nitric acid and acetic acid in the mixed waste acid, and the first residual dialysis treatment of the remaining liquid after the first vacuum evaporation. And primary removal of the metal component, secondary dialysis treatment of the dialysis solution obtained after the diffusion dialysis to remove the remaining metal components to be less than 1 pm aluminum, and the second dialysis solution to the second vacuum evaporation treatment. Provided are a liquid crystal display device and a method for recovering high purity phosphoric acid from mixed waste acid generated in a semiconductor manufacturing process.

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

The use of recycled mixed acid generated in the manufacturing process of LCD depends on the level of purification of the waste acid, and the added value thus obtained also varies. 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 contained 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 contrast, the present invention treats the mixed waste acid in the order of first vacuum evaporation, first and second diffusion dialysis, and second vacuum evaporation, whereby high concentration of high purity phosphoric acid which reduces the content of impurities from the mixed waste acid to several ppm level is high. Can be recovered. 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, the high purity phosphoric acid recovery method of the present invention will be described with reference to the process diagram of FIG. 1. In the method of recovering high purity phosphoric acid from the mixed waste acid according to an embodiment of the present invention, a first vacuum evaporation process of the mixed waste acid generated in the liquid crystal display device is performed. Removing nitric acid and acetic acid in the mixed waste acid as an evaporation liquid, and firstly removing the remaining liquid after the vacuum evaporation by treating the residual metal component as a waste liquid, and removing the dialysate obtained after the diffusion dialysis. Performing secondary diffusion dialysis treatment to remove the metal component as a waste solution secondly, and performing a second vacuum evaporation process on the aqueous phosphoric acid solution obtained after the diffusion dialysis to obtain high purity and high concentration of phosphoric acid.

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. This waste acid contains phosphoric acid, nitric acid, acetic acid, aluminum, molybdenum and the like.

Each of these components is separated and subjected to a first vacuum evaporation treatment as the first step to recover high purity phosphoric acid. At this time, prior to the first vacuum evaporation process, a filtration process using a microfilter or the like may be selectively performed to remove insoluble solid impurities contained in the mixed waste acid.

The first vacuum evaporation step uses a difference in boiling points of acids present in the mixed waste acid, and nitric acid and acetic acid contained in the mixed waste acid are evaporated and removed by the method, and only phosphoric acid and metal components remain.

The first vacuum evaporation treatment step may be carried out using a conventional vacuum evaporation treatment apparatus. In order to increase the removal efficiency of acetic acid and nitric acid from the mixed waste acid, the first vacuum evaporation treatment is preferably performed at -650 to -760 mmHg vacuum degree, and more preferably at -680 to -730 mmHg vacuum degree. . If the vacuum degree is less than -650 mmHg, since the evaporation temperature must be increased to 140 ° C. or more, the energy cost and the investment cost of the manufacturing equipment are excessively increased, which is not preferable. In addition, when the degree of vacuum exceeds -760 mmHg, it is not preferable because a large-capacity vacuum pump cannot be continuously operated above -760 mmHg in a commercialization facility.

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 process, nitric acid and acetic acid contained in the mixed waste acid can be completely removed. In the vacuum evaporation process, nitric acid and acetic acid are mixed with each other and evaporated. Accordingly, nitric acid and acetic acid may be separated by further performing a vacuum evaporation treatment on the evaporating liquid containing nitric acid and acetic acid.

Subsequently, a diffusion dialysis treatment is performed on the residual liquid remaining after the vacuum evaporation treatment of the mixed waste liquid to first remove the metal component contained in the residual liquid.

A large amount of metal can be efficiently removed by the diffusion dialysis method. In the present invention, a high-purity phosphoric acid aqueous solution can be obtained by removing the metal components contained in the residual liquid by using the selective permeability of the anion exchange membrane that passes only the acid solution but does not pass the metal salt.

In the diffusion dialysis treatment, a conventional diffusion dialysis apparatus may be used. In the present invention, a large amount of ion exchange membranes are alternately mounted with a gasket in order to allow waste acid solution and water to flow in the diffusion dialysis apparatus. The waste acid solution flowing upwards and the water flowing upwards and downwards are brought into contact with each other by countercurrent, and the recovered acid solution is ousted to the bottom of the dialyzer and concentrated. On the other hand, metal salts and dilute acid solutions in the spent acid solution that do not pass through the membrane come out upwards. The gasket, which supplies waste acid solution and water in the dialysis machine, is made of plastic meshes that are woven together in a net to minimize the contamination of membranes by inducing turbulent flow.

The dialysis membrane used in the diffusion dialysis treatment is an anion selective exchange membrane having selective permeability that passes through an anion but does not allow a cation to pass through.

In theory during diffusion dialysis, the dialysis membrane passes only the anion and the cations cannot pass through the membrane, so that if the metal ions are independently present in the solution, they will be present as cations and cannot pass through the dialysis membrane. However, complexation of metal ions, i.e., anions can be electrically coupled in solution and complexes can be anionized. High concentrations of metal ions in the waste acid may increase the probability of metal ions forming complexes and anionization. Therefore, in the first diffusion dialysis, since a relatively high concentration of metal ions is contained, it is likely to pass through the membrane, and the metal ion concentration is reduced to about 30 to 10 ppm at several hundred ppm. After the first diffusion dialysis, the metal ion concentration was lowered and slightly lowered to an acidic concentration. Therefore, the metal ion was assumed to exist as a single cation rather than a complex, and therefore, the concentration of the metal ion was less than 1 ppm in the secondary diffusion dialysis. It can be removed. That is, in order to remove the metal ion concentration at the concentration of 1 ppm or less during the first diffusion dialysis process, the metal ion concentration of the primary diffusion dialysis solution should be reduced to about 10 ppm, and the metal ion concentration is about several hundred ppm before the first diffusion dialysis. One diffusion dialysis cannot reduce the metal ion concentration to about 1 ppm.

In the diffusion dialysis apparatus, the residual liquid is supplied upwards from the bottom of the diffusion dialysis apparatus, and water is supplied downwards from the top. The residual liquid fed into the diffusion dialysis apparatus is separated from metal ions and phosphoric acid by 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 primary diffusion dialysis treatment, a treatment liquid containing 10 ppm or less of aluminum concentration contained in the residual liquid obtained after the evaporation treatment can be obtained. In addition, a treatment liquid containing aluminum concentration of 1 ppm or less can be obtained by secondary diffusion dialysis treatment of the treatment liquid.

Since the aqueous phosphoric acid solution obtained by the primary and secondary diffusion dialysis treatment is high purity, but the concentration of phosphoric acid is low, a high concentration of phosphoric acid can be obtained by performing a secondary vacuum evaporation treatment. The second vacuum evaporation treatment step for obtaining the high concentration phosphoric acid may be performed in the same manner as in the first vacuum evaporation treatment for the mixed waste acid. By the second vacuum evaporation treatment, high purity phosphoric acid can be obtained at a high concentration of 85% or more.

By the high-purity recovery method as described above, it is possible to recover high-purity phosphoric acid in which the impurity content is reduced to several ppm levels 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.

As described above, by recovering nitric acid, phosphoric acid and acetic acid using the LCD mixed acid waste liquid, the LCD etching solution, high purity phosphoric acid, and various pickling solutions can be recycled.

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.

1 shows a process in which a method of recovering nitric acid, acetic acid and phosphoric acid according to an exemplary embodiment of the present invention is performed.

1-1: Preparation of Mixed Waste Acid

LCD mixed waste liquid used in the present invention is a waste etching solution generated in the process of forming a metal circuit of a multilayer circuit board during the LCD manufacturing process. This waste liquid contains phosphoric acid, nitric acid, acetic acid and aluminum. The present invention is the waste liquid as a main object and the results of the component analysis of the waste liquid are shown in Table 1.

Composition of Mixed Waste Solution Emitted from LCD Manufacturing Process Analysis item
solution density(%) Metal ion (mg / kg) Analysis item
solution Acetic acid nitric acid Phosphoric Acid  Al LCD Mixed Waste 5 to 10 5 to 10 60 to 70 200 to 250

As shown in Table 1, the LCD mixed liquor is a mixed waste liquid containing acetic acid, nitric acid, phosphoric acid, and aluminum, and the LCD mixed waste liquid is used as a first step to separate and recycle each of these components. Therefore, a process of separating phosphoric acid and aluminum and separating acetic acid and nitric acid by vacuum evaporation may be considered first. As a second step, aluminum and phosphoric acid were separated by diffusion dialysis to recover high-purity phosphoric acid by separating and removing aluminum from the aluminum and phosphoric acid solution remaining in the vacuum evaporation process. As a third step, a second diffusion dialysis process may be considered in order to purify the dozens of ppm metal components remaining in the HR solution purified in the first diffusion dialysis process to 1 ppm or less. Finally, the concentration of phosphate in the diffusion dialysis process tends to be low, so it is necessary to concentrate it by the vacuum evaporation method and adjust it to the use of recycled products.

1-2: 1st vacuum evaporation of mixed waste acid

In order to separate acetic acid and nitric acid present in the mixed waste acid, the first vacuum evaporation process was performed using a vacuum evaporation apparatus in the following manner.

In order to remove the insoluble solid impurities of the mixed waste liquid of Table 1, the result of performing the first vacuum evaporation of the waste liquid filtered through a microfilter is shown in Table 2.

Constituent composition of the solution by evaporating and condensing LCD mixed waste liquid in the first vacuum evaporation step Analysis item
solution density(%) Metal ion (mg / kg) Analysis item
solution Acetic acid nitric acid Phosphoric Acid Al LCD Mixed Waste 6.2 6.4 63.1 214 Evaporate 17.7 19.2 - - Residue - - 85.8 290

Vacuum evaporation of the LCD mixed waste liquid causes phosphoric acid and metals to remain, and nitric acid and acetic acid evaporate. As shown in Table 2, the concentrations of nitric acid and acetic acid in the evaporated solution were concentrated to about three times that of the original waste liquid, and no mixing of phosphoric acid and aluminum was found. After completion of the first vacuum evaporation step, the nitrate-acetic acid evaporate is sent to a recycling tank, and the phosphate-aluminum solution remaining inside the evaporator is sent to the first diffusion dialysis step via a storage tank to remove aluminum.

Vacuum evaporator is composed of reactor, vacuum pump, cooling tube, acid recovery tank, and heating mantle. The Pyrex reactor is an improved round bottom flask with a capacity of 2 liters. The cooling tube uses a normal reflux condenser and is connected to tap water to serve as a cooler. The ash tank was used with a 300 ml Erlenmeyer flask. The heating mantle used to raise the temperature inside the reactor used a digital heating magnetic stirrer (MSH-10, WiseStir) capable of temperature control up to 400 ℃ ± 2 ℃. LCD mixed acid waste containing 6.2wt% nitric acid, 6.4wt% acetic acid, 63.1t% phosphoric acid and the rest of the water was added to a Pyrex reactor and maintained at 120 ° C using a digital heated magnetic stirrer (MSH-10, WiseStir). The pressure inside the reactor was kept constant at -730 mmHg using a vacuum pump.

At this time, the inside of the reactor was decompressed to a condition lower than atmospheric pressure so that the low boiling point nitric acid and acetic acid mixtures were first evaporated, and the evaporated nitric acid and acetic acid mixtures were liquefied and separated and removed through a condenser in which cooling water was circulated. At this time, the concentration of phosphoric acid in the distillation filtrate (high concentration phosphoric acid) from which acetic acid and nitric acid were separated and removed is vacuum concentrated. The acid concentration was recovered 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 result of vacuum evaporation of LCD mixed waste liquid in the first vacuum evaporation step Exam conditions density(%) Vacuum degree (mmHg) Temperature (℃) Acetic acid nitric acid Phosphoric Acid 650 120 1.28 1.45 87.6 650 140 0 0 88.5 650 160 0 0 85.5 700 100 1.33 1.58 78.8 700 110 0.71 0 81.4 700 125 0 0 81.7 730 100 0.92 0 79.6 730 110 0 0 82.8 730 150 0 0 84.9

Table 3 shows the results of vacuum evaporation of the LCD mixed waste liquid in the first vacuum evaporation step (I) in the process diagram of FIG. 1. Here, the test conditions were fixed at the vacuum degree of -730, -700, -650mmHg, respectively, and the temperature was raised to 160 ° C while sampling and analyzing the solution for each temperature section. From the results, the conditions and behavior of nitric acid and acetic acid separated from phosphoric acid were investigated. As can be seen here, when the degree of vacuum was -650 mmHg, it was completely separated at a temperature of 140 ° C or higher, and when the degree of vacuum was -700mmHg, it was completely separated at a temperature of 120 ° C or higher. In the case of a vacuum degree of -730 mmHg, complete separation was possible even at a temperature of 110 ° C. or higher.

2 is an IC analysis result showing that nitric acid and acetic acid are completely separated from phosphoric acid.

1-3: Primary and secondary diffusion dialysis treatment of the residual liquid obtained after the first vacuum evaporation

In order to separate and remove the metal component present in the residual liquid obtained after the first vacuum evaporation treatment of 1-2), diffusion dialysis treatment was performed as follows.

Acid composition was separated in the first vacuum evaporation step, purified by the first and second diffusion dialysis steps, and the composition of the treatment solutions concentrated in the second vacuum evaporation step. Analysis item
solution density(%) Metal ions (ppm) Remarks Analysis item
solution Acetic acid nitric acid Phosphoric Acid Al Remarks LCD Mixed Waste Liquid 6.2 6.4 63.1 214 1st vacuum evaporation - - 85.8 290 Nitric Acid, Acetic Acid Separation First Diffusion Dialysis - - 61.3 5.43 Aluminum removal 2nd Diffusion Dialysis - - 46.8 0.41 Aluminum removal 2nd vacuum evaporation - - 85.1 0.74 concentration

Table 4 shows the evaporation and removal of nitric acid and acetic acid in the vacuum evaporation step, and the removal of metal components up to 5.4 ppm by diffusion dialysis in order to commercialize the residual metal and phosphate solution. As a result, the result was completely removed to less than 1 ppm.

As shown in Table 4, it can be seen that in the diffusion dialysis process, the aluminum concentration was reduced to 290 ppm to 0.41 ppm. On the other hand, the concentration of phosphoric acid decreased from 85.8% to about 46.8%. It was again concentrated to 85.1% by vacuum evaporation.

Diffusion dialysis experiment of the test method in Table 4 was carried out in the following manner. Diffusion dialysis method is especially used to recover high concentration of acid from acid waste. The ion exchange membrane used in the diffusion dialysis is an anion exchange membrane that can separate high concentrations of acid in industrial wastewater from metal salts by using selective permeability, which allows only acid solution to pass through, but not metal salts. In the diffusion dialysis apparatus, a large number of ion exchange membranes are alternated with a gasket in order to flow waste acid solution and water in turn. The waste acid solution flowing from the bottom to the top and the water flowing from the top to the bottom are brought into contact with each other by backflow, and the recovered acid solution is ousted to the bottom of the dialyzer and concentrated. On the other hand, metal salts and dilute acid solutions in the spent acid solution that do not pass through the membrane come out upwards. The gasket, which supplies waste acid solution and water in the dialysis machine, is made of plastic meshes that are woven together in a net, so that the solution is mixed uniformly and causes turbulence to minimize membrane contamination.

The diffusion dialysis apparatus used in this experiment was T-Ob Selemion dialyzer of ASAHI GLASS Co., and APS-4 manufactured by ASAHI GLASS Co. of Japan was used for the ion exchange membrane. The pump used in the unit is Cole Parmer's Masterflex pump, a peristaltic pump with a maximum rotational speed of 600 rpm and a flow rate of 0.006-380 mL / min depending on tube size. Flow control was able to achieve the desired flow rate by controlling the size of the tube while controlling the rotational speed of the Masterflex pump. The crude phosphate aqueous solution and water flow rate were controlled to 0.97 L / Hr.m ^2, and the dialysis membrane was continuously fed in the opposite direction, and the experiment was continued until the recovery rate reached a steady state. The area of the ion exchange membrane was 0.327 m ² / unit, and the flow rate calculation was calculated by dividing the amount of waste acid solution and the acid recovered in both measuring cylinders after passing through the dialysis machine. The recovered acid was analyzed by ion chromatography (ICS-2500, DIONEX) analyzer as an analysis method, and the acid concentration was analyzed and the recovery was determined. Metal components such as Al and Mo in the solution were analyzed using plasma spectroscopy (ICP-AES).

1-4: Second vacuum evaporation treatment for dialysate by diffusion dialysis treatment

As a result of the first and second diffusion dialysis treatment, the metal component was completely removed, but the concentration of phosphoric acid in the filtrate was lowered from 85.8% to about 46.8%. Accordingly, in order to obtain a high concentration of phosphoric acid, a secondary vacuum evaporation process was performed as follows.

After passing through the second diffusion dialysis step, the concentration of 46.8wt% purified phosphoric acid is placed in a 2L Pyrex reactor and 120 ℃ using a digital heated magnetic stirrer (MSH-10, WiseStir) capable of temperature control up to 400 ℃ ± 2 ℃. The temperature was maintained at a temperature of and the reactor internal pressure was kept constant at 730 mmHg using a vacuum pump. At this time, in the reactor, the pressure is reduced to a condition lower than atmospheric pressure, and the vacuum concentration proceeds to the phosphoric acid concentration of 85wt%. 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 4 above, and the concentration of phosphoric acid was concentrated to 85.1% by secondary vacuum evaporation.

1 is a schematic diagram of a process showing a method of recovering high purity phosphoric acid from a mixed acid waste liquid of the present invention,

2 is an IC analysis result showing that nitric acid and acetic acid are completely separated from phosphoric acid in the first vacuum evaporation step of the embodiment of the present invention.

Claims (4)

(a) treating nitric acid and acetic acid in the mixed waste acid by treating the mixed waste acid generated in the liquid crystal display and the semiconductor manufacturing process with a first vacuum evaporation method to obtain a residual liquid; (b) separating and removing the aluminum by the first diffusion dialysis process to obtain an aqueous phosphoric acid solution having an aluminum content of 10 to 30 ppm as a residual solution; (c) separating and removing the aluminum as a residual solution from the aqueous phosphoric acid solution in a secondary diffusion dialysis process to obtain an aqueous phosphoric acid solution having an aluminum content of 1 ppm or less as a dialysate; And (d) treating the phosphoric acid solution of step (c) by a secondary vacuum evaporation method to obtain a phosphoric acid solution having an aluminum content of 1 ppm or less and a phosphoric acid concentration of 85 wt% or more; Recovering high purity phosphoric acid from mixed waste acid. The method of claim 1, wherein the vacuum evaporation method recovers high purity phosphoric acid from mixed waste acid carried out at a vacuum degree of -650 to -760 mmHg. The method of claim 1, wherein the vacuum evaporation method recovers phosphoric acid from mixed waste acid carried out at a temperature range of 100 ~ 160 ℃. The method for recovering high purity phosphoric acid from mixed waste acid according to claim 1, wherein the dialysis membrane used in the primary diffusion dialysis process is an anion exchange membrane having selective permeability that allows only anions to pass but not to pass cations.

Images