JP2006160534A - Method of separating and recovering phosphoric acid from mixed acid waste liquid containing acetic, nitric and phosphoric acids - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of highly efficiently, selectively separating and recovering phosphoric acid from a mixed acid waste liquid containing acetic, nitric and phosphoric acids even in a practical large scale production by suppressing the emulsification of an oil phase with a water phase in a settling state in a separation process to enable the circulating use of an extractant solution sufficiently. <P>SOLUTION: The separating/recovering method comprises an extraction process for selectively dissolving acetic and nitric acids in the extractant solution to extract by mixing the waste liquid containing those acids with the extractant solution containing trialkyl phosphate, a recovery process for recovering phosphoric acid from a residual liquid left by the above process, and a separation process for bringing the obtained acetic/nitric acids-containing extractant solution into contact with a salt-containing water for separation to dissolve and transfer their acids into the above water for separation. The extractant solution can circularly be used by feeding back the oil-phase solution obtained from the separation process to the extraction process. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for separating and recovering phosphoric acid with high efficiency and selectivity, for example, from an acetic acid-nitric acid-phosphoric acid mixed acid waste liquid discharged from, for example, a liquid crystal manufacturing process or a semiconductor manufacturing process. The present invention relates to a method of supplying a phase extractant solution to an extraction process and circulatingly using the extractant solution.

  In the liquid crystal manufacturing industry and the semiconductor manufacturing industry that have grown dramatically in recent years, various types of wastewater are produced in the manufacturing process, but they are discharged after being subjected to appropriate treatment according to the type and nature of each type of wastewater. For example, a mixed acid waste liquid in which acetic acid, nitric acid, and phosphoric acid are mixed comes out from the liquid crystal manufacturing process and the semiconductor manufacturing process. Of these, for example, if phosphoric acid can be separated and recovered, it can be expected to be effectively used as a fertilizer. Since it is technically difficult to separate and recover phosphoric acid from such a mixed acid waste liquid, it has been common practice to neutralize the mixed acid waste liquid and drain it.

  When the mixed acid waste liquid mixed with acetic acid, nitric acid, and phosphoric acid is subjected to neutralization treatment and drained as described above, salt such as acetate and nitrate is generated in the wastewater due to this neutralization treatment. It is inevitable that it causes environmental pollution, and this neutralization treatment is by no means a desirable means from the viewpoint of environmental conservation. The importance of recycling has been sought in recent years due to demands for global environmental conservation. However, the conventional neutralization treatment discharge method is a method of discarding waste acid without recycling at all. It was impossible to meet the social demands at all.

Therefore, the present inventors have been able to achieve effective utilization of resources and fully meet the demand for environmental protection, and as a method for separating and recovering phosphoric acid from acetic acid-nitric acid-phosphoric acid mixed acid waste liquid, acetic acid, Acetic acid / nitric acid extraction in which the acetic acid and nitric acid are selectively dissolved in the extraction liquid by mixing the waste liquid containing nitric acid and phosphoric acid and the extraction liquid containing trialkyl phosphate. By bringing the step of recovering the phosphoric acid from the extraction residue obtained in the extraction step, the acetic acid / nitric acid-containing extractant obtained in the acetic acid / nitric acid extraction step, and the peeling water, A step of recovering acetic acid and nitric acid by dissolving and transferring the acetic acid and nitric acid in the stripping water, and extracting the extract liquid of the oil phase from the acetic acid / nitric acid recovery step (peeling step) into the acetic acid / nitric acid extraction step By supplying to Developed a phosphate separation recovery method, characterized by recycling the agent solution applied for a patent (see Patent Document 1).
JP 2004-160292 A (Claims 1, 6 and FIG. 1)

  The separation and recovery method described above is, for example, a small test apparatus using 20 tanks of a research mixer mixer with a tank volume of about 2 L. There is no separation failure in the peeling process, and the extractant liquid can be circulated and used in a good state. It was.

  However, in order to carry out with the minimum level of circulation required for commercial operation and the amount of waste mixed acid supply using 22 tanks of the demonstration mixer settler with a tank volume of about 200L (about 100 times that of a small machine) The shear rate at the tip of the mixer must be increased to about 100 m / min with respect to about 37-38 m / min for small machines, but in a state corresponding to such an actual machine level (to the actual machine level) When the operation is performed (with a corresponding circulation amount and waste mixed acid supply amount), that is, when the shearing speed at the tip of the mixer is increased, a separation failure occurs in the separation step, and phosphoric acid cannot be separated and recovered.

  That is, an emulsion state that is difficult to break when stirring in the mixer tank of the peeling process is formed by scale-up, and this does not eliminate the emulsion of the oil phase and the aqueous phase even in a stationary state in the settler tank of the peeling process. In this way, the separation between the oil phase and the aqueous phase is reduced, so that the separation is not performed sufficiently. As a result, the extract liquid of the oil phase produced in this separation step has a content of acetic acid / nitric acid as impurities. For this reason, even if the extractant liquid extracted in this stripping process is supplied to the next acetic acid / nitric acid extraction process and circulated, it is not possible to sufficiently extract acetic acid / nitric acid in this process. As a result, the extraction residual liquid (phase from which phosphoric acid is separated) also contains a considerable amount of acetic acid and nitric acid, which makes it difficult to recover high-purity phosphoric acid. Although it was not so much of a problem at the small scale of the experimental level, when it was scaled up to a commercial operation level such as an actual machine, the separability of the oil phase and the water phase due to the emulsion of the oil phase and the water phase. The decrease of was remarkable. That is, when the method of circulating and using the extractant described in Patent Document 1 (Claim 6) was scaled up to a commercial operation level, a high-purity phosphoric acid aqueous solution could not be recovered. is there.

  The present invention has been made in view of such technical background, and sufficiently suppresses emulsification of an oil phase and an aqueous phase not only in a small scale but also in a scaled-up actual machine level in a stationary state in a peeling process. The separation of the oil phase and the water phase can be improved, and the extractant solution can be recycled and used to efficiently remove phosphoric acid from the acetic acid-nitric acid-phosphoric acid mixed acid waste liquid. An object is to provide a method for separating and recovering phosphoric acid from an acetic acid-nitric acid-phosphoric acid mixed acid waste liquid, which can be separated and recovered well and can sufficiently meet the demand for environmental protection by effectively utilizing resources. And

  In order to achieve the above object, the present invention provides the following means.

[1] Extracting by selectively dissolving acetic acid and nitric acid in the extract liquid by mixing waste liquid containing acetic acid, nitric acid and phosphoric acid, and extract liquid containing trialkyl phosphate Acetic acid / nitric acid extraction process,
A step of recovering the phosphoric acid from the extraction residue obtained in the extraction step;
An acetic acid / nitric acid stripping step in which the acetic acid / nitric acid-containing extractant obtained in the acetic acid / nitric acid extraction step and the stripping water containing salt are brought into contact with each other to dissolve and move the acetic acid and nitric acid in the stripping water; With
From the acetic acid-nitric acid-phosphate mixed acid waste liquid, the extractant liquid is circulated and used by supplying the extractant liquid of the oil phase produced in the acetic acid / nitric acid stripping process to the acetic acid / nitric acid extraction process. A method for separating and recovering phosphoric acid.

  [2] The method for separating and recovering phosphoric acid from the acetic acid-nitric acid-phosphoric acid mixed acid waste liquid according to item 1, wherein the salt is a metal salt.

  [3] The method for separating and recovering phosphoric acid from the acetic acid-nitric acid-phosphoric acid mixed acid waste solution according to the above item 2, wherein a metal chloride salt is used as the metal salt.

[4] The acetic acid-nitric acid-phosphate system according to item ₂ above, wherein one or more metal chlorides selected from the group consisting of NaCl, KCl, CaCl ₂ , BaCl ₂ and AlCl ₃ are used as the metal salt. Method for separating and recovering phosphoric acid from mixed acid waste liquid.

[5] The acetic acid-nitric acid-phosphoric acid mixed acid waste solution according to item ₂ above, wherein one or more metal chlorides selected from the group consisting of CaCl ₂ , BaCl ₂ and AlCl ₃ are used as the metal salt. A method for separating and recovering phosphoric acid.

  [6] The method for separating and recovering phosphoric acid from the acetic acid-nitric acid-phosphoric acid mixed acid waste liquid according to any one of 1 to 5 above, wherein the salt concentration in the stripping water is 1 to 5000 ppm.

  [7] Any one of [1] to [6], wherein an extractant having a composition of trialkyl phosphate / aromatic organic solvent = 10/90 to 90/10 (volume ratio) is used as the extractant. Of and recovering phosphoric acid from acetic acid-nitric acid-phosphoric acid mixed acid waste liquid.

  [8] The method for separating and recovering phosphoric acid from the acetic acid-nitric acid-phosphoric acid mixed acid waste liquid according to item 7, wherein kerosene is used as the aromatic organic solvent.

  [9] The acetic acid according to any one of items 1 to 6, wherein an extractant having a composition of trialkyl phosphate / trialkylamine = 99/1 to 70/30 (volume ratio) is used as the extractant. -Method for separating and recovering phosphoric acid from nitric acid-phosphoric acid mixed acid waste liquid.

  [10] Phosphoric acid recovered by the separation and recovery method according to any one of items 1 to 9.

  [11] The phosphoric acid as described in 10 above, which is used as a fertilizer.

  In the invention of [1], since a trialkyl phosphate is used as an extractant, acetic acid and nitric acid can be simultaneously extracted from the mixed acid waste liquid with high selectivity, thereby recovering phosphoric acid from the extraction residual liquid with high efficiency. It becomes possible to do. In addition, since acetic acid and nitric acid can be extracted simultaneously, the number of steps for the extraction / separation operation can be reduced, and the productivity is very good. Further, since the peeling water used in the peeling step contains salt, the surface tension of the peeling water can be increased, and as a result, the interface between the oil phase (extractant phase) and the water phase (peeling water). Since the tension can be increased, even in the scaled-up actual machine level (large scale), it is possible to sufficiently suppress the emulsification of the oil phase and the water phase in a stationary state. Separation can be improved remarkably, and the oil phase extract liquid obtained through this peeling step is a high-purity extract liquid that does not contain acetic acid or nitric acid. Can be sufficiently supplied to the acetic acid / nitric acid extraction step and recycled. That is, in the acetic acid / nitric acid extraction step, acetic acid / nitric acid can be sufficiently extracted by the circulating extract solution. According to this method, the extractant solution can be circulated and reused many times in this way, a stable and good operating state can be maintained, and phosphoric acid can be continuously separated. Phosphoric acid can be separated and recovered.

  In the invention of [2], since a metal salt is used as the salt, emulsification of the oil phase and the aqueous phase can be sufficiently suppressed in the stationary state in the peeling step.

  In the invention of [3], since a metal chloride salt is used as the metal salt, emulsification of the oil phase and the water phase can be more sufficiently suppressed in the stationary state in the peeling step, whereby the oil phase and water Phase separation can be further improved.

In the invention of [4], as the metal salt, one or more metal chlorides selected from the group consisting of NaCl, KCl, CaCl ₂ , BaCl ₂ and AlCl ₃ are used. In the above, emulsification of the oil phase and the aqueous phase can be further sufficiently suppressed, whereby the separability of the oil phase and the aqueous phase can be further improved.

In the invention of [5], one or more metal chlorides selected from the group consisting of CaCl ₂ , BaCl ₂ and AlCl ₃ are used as the metal salt. And water phase emulsification can be further sufficiently suppressed.

  In the invention of [6], since the salt concentration in the peeling water is 1 to 5000 ppm, the separability between the oil phase and the aqueous phase in the stationary state in the peeling step can be sufficiently improved.

  In the invention of [7], an extractant having a composition of trialkyl phosphate / aromatic organic solvent = 10/90 to 90/10 (volume ratio) is used as the extractant. There is an advantage that the extraction selectivity to nitric acid is improved as well.

  In the invention of [8], kerosene is used as the aromatic organic solvent. Since this kerosene does not substantially extract phosphoric acid, it can be separated and recovered with higher efficiency.

  In the invention of [9], since the extractant having a composition of trialkyl phosphate / trialkylamine = 99/1 to 70/30 (volume ratio) is used as the extractant, the extraction selectivity for acetic acid is improved. In addition, there is an advantage that the extraction selectivity to nitric acid is improved.

  The phosphoric acid according to the invention of [10] is recovered by any one of the separation and recovery methods described above, and since this phosphoric acid contains a very small amount of nitric acid, that is, a very small amount of N (nitrogen). Therefore, it is suitably used as a fertilizer.

  An embodiment of a method for separating and recovering phosphoric acid from an acetic acid-nitric acid-phosphoric acid mixed acid waste liquid according to the present invention will be described with reference to the flowchart of FIG. In the present embodiment, phosphoric acid is recovered from an extraction residue by simultaneously extracting acetic acid and nitric acid from mixed acid wastewater containing acetic acid, nitric acid and phosphoric acid.

  First, in the acetic acid / nitric acid extraction step, an extractant solution (a mixed solution of trialkyl phosphate / aromatic organic solvent) is supplied into the mixer tank, and mixed acid wastewater containing acetic acid, nitric acid and phosphoric acid is also supplied. After stirring and mixing these, the mixture is transferred to a settler tank and allowed to stand to separate into two layers of an extraction liquid phase that is an oil phase and an extraction residual liquid phase that is an aqueous phase. At this time, the extract solution composed of a mixed solution of trialkyl phosphate / aromatic organic solvent is excellent in extraction selectivity to acetic acid and nitric acid, but hardly extracts phosphoric acid. Therefore, acetic acid and nitric acid are mixed acid wastewater. To the extract liquid and then extracted into an extract liquid phase that is an oil phase.

  On the other hand, since phosphoric acid remains in the aqueous phase extraction residue obtained in the acetic acid / nitric acid extraction step, this extraction residue can be recovered and used as a phosphoric acid aqueous solution as it is, It may be concentrated to a concentration and recovered in the form of a concentrated phosphoric acid aqueous solution, or may be further concentrated to recover phosphoric acid in a solid state. Moreover, you may make it use, after performing the refinement | purification operation for raising the purity of phosphoric acid further.

  In the next acetic acid / nitric acid stripping step, the extraction liquid (extracted solution containing extracted acetic acid / nitric acid) obtained in the extraction step is supplied into the mixer tank, and the stripping solution containing salt (en) is used. Water is also supplied and mixed by stirring, then transferred to a settler tank and allowed to stand. Since the acetic acid and nitric acid are transferred to the aqueous phase by mixing, the mixture is separated into two layers of an oil phase and an aqueous phase composed of an acetic acid / nitric acid aqueous solution. At this time, since the stripping water contains salt, the oil phase and the water phase are sufficiently emulsified in the still state in the settler tank, not only on the small scale at the experimental level, but also on the scaled up actual machine level. Since the separation property between the oil phase and the aqueous phase can be remarkably improved, the oil phase extractant obtained through this peeling step has a purity that does not contain acetic acid and nitric acid. Therefore, it becomes possible to supply this extractant solution to the acetic acid / nitric acid extraction step and to circulate it. That is, if this extractant solution is used in the acetic acid / nitric acid extraction step, acetic acid / nitric acid can be sufficiently extracted. In this method, the extractant solution can be circulated and used many times in this way even on a large scale at the actual machine level, so that phosphoric acid can be separated and recovered at low cost.

  In this embodiment, the countercurrent multistage extraction method is employed in both the acetic acid / nitric acid extraction step and the acetic acid / nitric acid stripping step. This counter-current multistage extraction method will be described by taking the acetic acid / nitric acid extraction step as an example. As shown in FIG. 2, a plurality of extraction tanks (A) are used to mix mixed acid wastewater and extractant (trialkyl phosphate). / Mixture of aromatic organic solvent) in each extraction tank while counterflowing, and the same method is employed in the acetic acid / nitric acid stripping step. By adopting such a countercurrent multi-stage extraction method, acetic acid and nitric acid can be sufficiently extracted, so that phosphoric acid with higher purity can be recovered.

  The extractant used in the present invention will be described. As the extractant, an extractant containing a trialkyl phosphate is used. For example, the extraction liquid may be composed only of a trialkyl phosphate, or may be a mixed system of a trialkyl phosphate and an organic solvent. By using a trialkyl phosphate, acetic acid and nitric acid can be simultaneously extracted with good selectivity from an acetic acid-nitric acid-phosphoric acid mixed acid waste liquid. Among them, it is preferable to use an extractant having a composition of trialkyl phosphate / aromatic organic solvent = 10/90 to 90/10 (volume ratio). In this case, extraction selectivity for acetic acid and extraction selection for nitric acid are preferred. There is an advantage that both sexes can be improved. A more preferable ratio range is trialkyl phosphate / aromatic organic solvent = 20/80 to 80/20 (volume ratio), and a particularly preferable range is trialkyl phosphate / aromatic organic solvent = 30/70 to 70/30 (volume ratio).

  Examples of the trialkyl phosphate include trioctyl phosphate and tributyl phosphate. Among these, it is preferable to use trioctyl phosphate. In this case, the extraction selectivity for acetic acid and nitric acid can be further improved. The trioctyl phosphate is not particularly limited, but it is preferable to use tris (2-ethylhexyl) phosphate. In this case, the extraction selectivity for acetic acid / nitric acid can be further improved. There are advantages.

  Examples of the organic solvent include aliphatic organic solvents and aromatic organic solvents. Examples of the aliphatic organic solvent include isoparaffin and cycloparaffin.

  The aromatic organic solvent is not particularly limited, and examples thereof include kerosene, toluene, xylene and the like. Of these, kerosene is preferably used. Since kerosene is inexpensive, the cost of separation and recovery can be suppressed, and kerosene has the advantage that phosphoric acid can be separated and recovered with higher efficiency since it does not substantially extract phosphoric acid.

  In addition, if it is a range which does not inhibit the effect of this invention, in the said extract liquid (extract liquid containing a trialkyl phosphate), other well-known extractants (neutral extractant, acidic extractant, basicity) An extractant) may be mixed. In a mixed system with such other known extractants, it is preferable to use an extractant having a composition of trialkyl phosphate / trialkylamine = 99/1 to 70/30 (volume ratio). In some cases, both extraction selectivity to acetic acid and extraction selectivity to nitric acid can be improved. As the trialkylamine, trioctylamine is preferably used.

  The phosphoric acid recovered by the separation and recovery method as described above contains a very small amount of nitric acid, and also serves as a supply source of N (nitrogen), and therefore is preferably used as a fertilizer.

In the present invention, the salt contained in the stripping water used in the acetic acid / nitric acid stripping step is not particularly limited. For example, NaCl, KCl, CaCl ₂ , BaCl ₂ , AlCl ₃ , Na ₂ SO _4, etc. And metal salts thereof. The metal constituting the metal salt is not particularly limited. For example, alkali metal (Li, Na, K, Rb, Cs, Fr), alkaline earth metal (Be, Mg, Ca, Sr, Ba) Ra) and the like. The metal salt is preferably a metal chloride salt, and more preferably one or more metal chloride salts selected from the group consisting of NaCl, KCl, CaCl ₂ , BaCl ₂ and AlCl _3. .

  Moreover, it is preferable that the content density | concentration of the salt in the said water for peeling is set to the range of 1-5000 ppm. If it is less than 1 ppm, it is difficult to sufficiently suppress the emulsification of the oil phase and the aqueous phase, and the separability between the oil phase and the aqueous phase in a stationary state cannot be sufficiently improved, which is not preferable. On the other hand, if it exceeds 5000 ppm, there is a possibility that peeling of acetic acid and nitric acid may not proceed sufficiently, such being undesirable. Among these, the salt concentration in the stripping water is more preferably set in a range of 1000 to 3000 ppm, and a particularly preferable range is 1500 to 2500 ppm.

  Next, specific examples of the present invention will be described.

<Example 1>
Phosphoric acid was separated and recovered from the mixed acid wastewater containing acetic acid, nitric acid and phosphoric acid according to the separation and recovery method of the embodiment exemplified in the previous section (see FIG. 1). The mixed acid wastewater used in this example was a mixed acid wastewater from a liquid crystal manufacturing factory, and had a composition as shown in Table 1 (of course, all of the mixed acid wastewater from a liquid crystal manufacturing factory had such a composition ratio. However, it is different in each factory.) Detailed conditions such as the flow rate at each location, the number of stages in each step, and the phase ratio are shown in FIG. In addition, as the extractant, an extractant having a composition of tris (2-ethylhexyl) phosphate (TOP) / kerosene = 50/50 (volume ratio) was used. As the kerosene, “Solvesso 150” (trade name) manufactured by Showa Shell Sekiyu was used. Further, as the peeling water, water containing 2000 ppm of CaCl ₂ was used. The phase ratio is the ratio of the water phase flow rate to the oil phase flow rate (water phase flow rate / oil phase flow rate).

  In Example 1, the capacity of the mixer tank in the extraction process is 50 L, the capacity of the settler tank in the extraction process is 150 L, and 10 mixers (10 stages) of such mixer settlers (200 L) are connected to the extraction process unit. On the other hand, the capacity of the mixer tank in the peeling process is 50 L, the capacity of the settler tank in the peeling process is 150 L, and such a mixer settler (200 L) is connected to 12 tanks (12 stages) to connect the peeling process section. Configured. Moreover, the rotation speed of the stirring blade (paddle blade) of the mixer tank was set to 320 rpm.

<Example 2>
Phosphoric acid was separated and recovered from the mixed acid wastewater containing acetic acid, nitric acid and phosphoric acid in the same manner as in Example 1 except that water containing 2000 ppm of NaCl was used as the peeling water. Detailed conditions such as the flow rate at each location, the number of stages in each step, and the phase ratio are the same as in Example 1 (see FIG. 1).

<Example 3>
Phosphoric acid was separated and recovered from the mixed acid wastewater containing acetic acid, nitric acid and phosphoric acid in the same manner as in Example 1 except that water containing 2000 ppm of KCl was used as the peeling water. Detailed conditions such as the flow rate at each location, the number of stages in each step, and the phase ratio are the same as in Example 1 (see FIG. 1).

<Example 4>
Phosphoric acid was separated and recovered from the mixed acid wastewater containing acetic acid, nitric acid and phosphoric acid in the same manner as in Example 1 except that water containing 2000 ppm of BaCl ₂ was used as the peeling water. Detailed conditions such as the flow rate at each location, the number of stages in each step, and the phase ratio are the same as in Example 1 (see FIG. 1).

<Example 5>
Phosphoric acid was separated and recovered from the mixed acid wastewater containing acetic acid, nitric acid and phosphoric acid in the same manner as in Example 1 except that water containing 2000 ppm of AlCl ₃ was used as the peeling water. Detailed conditions such as the flow rate at each location, the number of stages in each step, and the phase ratio are the same as in Example 1 (see FIG. 1).

<Example 6>
Phosphoric acid was separated and recovered from the mixed acid wastewater containing acetic acid, nitric acid and phosphoric acid in the same manner as in Example 1 except that water containing 2400 ppm of CaCl ₂ was used as the peeling water. Detailed conditions such as the flow rate at each location, the number of stages in each step, and the phase ratio are the same as in Example 1 (see FIG. 1).

<Example 7>
Phosphoric acid was separated and recovered from the mixed acid wastewater containing acetic acid, nitric acid and phosphoric acid in the same manner as in Example 1 except that water containing 1670 ppm of CaCl ₂ was used as the peeling water. Detailed conditions such as the flow rate at each location, the number of stages in each step, and the phase ratio are the same as in Example 1 (see FIG. 1).

<Comparative Example 1>
The separation and recovery of phosphoric acid was tried from the mixed acid wastewater containing acetic acid, nitric acid and phosphoric acid in the same manner as in Example 1 except that water containing no salt was used as the peeling water.

<Example 8>
Tris (2-ethylhexyl) phosphate (TOP) / tri-n-octylamine (TOA) = 95/5 (volume ratio) was used as the extractant, and water containing 3000 ppm CaCl ₂ was used as the stripping water. Except for the above, phosphoric acid was separated and recovered from the mixed acid wastewater containing acetic acid, nitric acid and phosphoric acid in the same manner as in Example 1. Detailed conditions such as the flow rate at each location, the number of stages in each step, and the phase ratio are the same as in Example 1 (see FIG. 1).

<Example 9>
Phosphoric acid was separated and recovered from the mixed acid wastewater containing acetic acid, nitric acid and phosphoric acid in the same manner as in Example 8 except that water containing 3000 ppm of NaCl was used as the peeling water. Detailed conditions such as the flow rate at each location, the number of stages in each step, and the phase ratio are the same as in Example 1 (see FIG. 1).

<Example 10>
Phosphoric acid was separated and recovered from the mixed acid wastewater containing acetic acid, nitric acid and phosphoric acid in the same manner as in Example 8, except that water containing 3000 ppm of KCl was used as the peeling water. Detailed conditions such as the flow rate at each location, the number of stages in each step, and the phase ratio are the same as in Example 1 (see FIG. 1).

<Example 11>
Phosphoric acid was separated and recovered from the mixed acid wastewater containing acetic acid, nitric acid and phosphoric acid in the same manner as in Example 8, except that water containing 3000 ppm of BaCl ₂ was used as the peeling water. Detailed conditions such as the flow rate at each location, the number of stages in each step, and the phase ratio are the same as in Example 1 (see FIG. 1).

<Example 12>
Phosphoric acid was separated and recovered from the mixed acid wastewater containing acetic acid, nitric acid and phosphoric acid in the same manner as in Example 8, except that water containing 3000 ppm of AlCl ₃ was used as the peeling water. Detailed conditions such as the flow rate at each location, the number of stages in each step, and the phase ratio are the same as in Example 1 (see FIG. 1).

<Comparative example 2>
The separation and recovery of phosphoric acid was tried from the mixed acid wastewater containing acetic acid, nitric acid and phosphoric acid in the same manner as in Example 8 except that water containing no salt was used as the peeling water.

  As is clear from the table, according to the separation and recovery methods of the present invention of Examples 1 to 12, phosphoric acid can be separated and recovered with high concentration and high purity from mixed acid wastewater containing acetic acid, nitric acid and phosphoric acid. did it. Moreover, since salt was contained in the peeling water, the emulsification of the oil phase and the aqueous phase could be sufficiently suppressed in the stationary state in the settling tank in the peeling step. That is, the oil phase extractant obtained through the stripping process is a high-purity extractant that does not contain acetic acid / nitric acid. It was possible to separate and recover phosphoric acid with high concentration and high purity while being repeatedly used. Thus, phosphoric acid could be continuously separated and recovered while maintaining a stable and good operating state.

  On the other hand, in Comparative Examples 1 and 2 in which no salt was contained in the stripping water, a separation failure occurred in almost all tanks in a short time after the start of operation, and phosphoric acid could not be separated and recovered.

It is a flow figure showing the separation recovery process of phosphoric acid from mixed acid wastewater. It is explanatory drawing of a countercurrent multistage extraction method.

Explanation of symbols

  A ... Extraction tank

Claims (11)

Acetic acid and nitric acid extracted by selectively dissolving the acetic acid and nitric acid in the extract liquid by mixing the waste liquid containing acetic acid, nitric acid and phosphoric acid, and the extract liquid containing trialkyl phosphate. Nitric acid extraction process;
A step of recovering the phosphoric acid from the extraction residue obtained in the extraction step;
An acetic acid / nitric acid stripping step in which the acetic acid / nitric acid-containing extractant obtained in the acetic acid / nitric acid extraction step and the stripping water containing salt are brought into contact with each other to dissolve and move the acetic acid and nitric acid in the stripping water; With
From the acetic acid-nitric acid-phosphate mixed acid waste liquid, the extractant liquid is circulated and used by supplying the extractant liquid of the oil phase produced in the acetic acid / nitric acid stripping process to the acetic acid / nitric acid extraction process. A method for separating and recovering phosphoric acid.   The method for separating and recovering phosphoric acid from an acetic acid-nitric acid-phosphoric acid mixed acid waste liquid according to claim 1, wherein the salt is a metal salt.   The method for separating and recovering phosphoric acid from an acetic acid-nitric acid-phosphoric acid mixed acid waste liquid according to claim 2, wherein a metal chloride salt is used as the metal salt. As the metal _{salt, NaCl, KCl, CaCl 2,} BaCl 2 and acetic acid according to claim 2 using one or more metal chloride salt selected from the group consisting of AlCl ₃ - nitric - phosphoric acid type mixed acid waste Method for separating and recovering phosphoric acid from The phosphoric acid from the acetic acid-nitric acid-phosphate mixed acid waste liquid according to claim 2, wherein one or more metal chlorides selected from the group consisting of CaCl ₂ , BaCl ₂ and AlCl ₃ are used as the metal salt. Separation and recovery method.   The method for separating and recovering phosphoric acid from an acetic acid-nitric acid-phosphoric acid mixed acid waste liquid according to any one of claims 1 to 5, wherein the salt concentration in the stripping water is 1 to 5000 ppm.   The acetic acid according to any one of claims 1 to 6, wherein an extractant solution having a composition of trialkyl phosphate / aromatic organic solvent = 10/90 to 90/10 (volume ratio) is used as the extractant solution. -Method for separating and recovering phosphoric acid from nitric acid-phosphoric acid mixed acid waste liquid.   The method for separating and recovering phosphoric acid from an acetic acid-nitric acid-phosphoric acid mixed acid waste liquid according to claim 7, wherein kerosene is used as the aromatic organic solvent.   The acetic acid-nitric acid according to any one of claims 1 to 6, wherein an extractant having a composition of trialkyl phosphate / trialkylamine = 99/1 to 70/30 (volume ratio) is used as the extractant. A method for separating and recovering phosphoric acid from a phosphoric acid mixed acid waste liquid.   The phosphoric acid collect | recovered by the separation-and-recovery method of any one of Claims 1-9.   The phosphoric acid according to claim 10, which is used as a fertilizer.

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