JP2010132480A - Method for recovering phosphoric acid from which nitric acid and dissolved metal have been removed from phosphoric acid mixed acid waste liquid - Google Patents

Abstract

The present invention provides a method for recovering phosphoric acid by which nitric acid and metals can be removed from a phosphoric acid mixed acid waste liquid and phosphoric acid having a high purity can be separated and recovered.
The method for recovering phosphoric acid according to the present invention comprises mixing a mixed acid waste solution containing nitric acid, phosphoric acid and a metal with a first extractant solution containing a trialkyl phosphate, thereby mixing the first extractant. A nitric acid extraction step in which the nitric acid is selectively dissolved and extracted in the chemical solution, a phosphoric acid-containing extraction residual liquid of the aqueous phase from the nitric acid extraction step, and a second extraction containing an acidic phosphate ester A metal extraction step in which a metal is dissolved in the second extractant solution and extracted by mixing the agent solution, and the phosphoric acid is extracted from the phosphoric acid-containing extraction residual liquid of the aqueous phase that has come out of the metal extraction step. And a recovering step.
[Selection] Figure 1

Description

  The present invention relates to a method for recovering phosphoric acid from which nitric acid and dissolved metal have been removed from a nitric acid-containing phosphoric acid mixed acid waste liquid discharged from, for example, a liquid crystal manufacturing process or a semiconductor manufacturing process.

  The acetic acid and nitric acid-containing phosphoric acid etching waste liquid discharged from liquid crystal devices and semiconductor LSI manufacturing factories is generally reused as fertilizer while containing acetic acid, nitric acid, and metals (aluminum, molybdenum, etc.) Alternatively, acetic acid and nitric acid are removed and reused as crude phosphoric acid while containing the metal.

  The latter technique for recovering crude phosphoric acid, that is, a method for recovering crude phosphoric acid by removing acetic acid and nitric acid from acetic acid and nitric acid-containing phosphoric acid mixed acid waste liquid, was described in Patent Documents 1 and 2 below. A method for separating and recovering phosphoric acid is known.

  In Patent Document 1, as a method for separating and recovering phosphoric acid from an acetic acid-nitric acid-phosphoric acid mixed acid waste liquid, a waste liquid containing acetic acid, nitric acid and phosphoric acid and an extract liquid containing trialkyl phosphate are mixed. Acetic acid and nitric acid extraction step for selectively dissolving and extracting the acetic acid and nitric acid in the extract solution, and the step of recovering the phosphoric acid from the extraction residual liquid produced in the extraction step, A step of recovering acetic acid and nitric acid by bringing the acetic acid and nitric acid-containing extractant obtained in the acetic acid and nitric acid extraction step into contact with the stripping water to dissolve and transfer the acetic acid and nitric acid into the stripping water. A method for separating and recovering phosphoric acid, comprising circulating the extractant solution by supplying the extractant solution of the oil phase produced in the acetic acid / nitric acid recovery step (peeling step) to the acetic acid / nitric acid extraction step Is described.

In addition, in Patent Document 2, in the method for separating and recovering phosphoric acid described in Patent Document 1, by using water containing a salt such as a metal chloride salt as the water for peeling, an actual machine scaled up as well as a small scale is used. It is also described that the separation of the phosphoric acid can be performed by improving the separability of the oil phase and the aqueous phase in the state of standing in the peeling process at the level, sufficiently enabling the circulating use of the extractant. Yes.
JP 2004-160292 A JP 2006-160534 A

  However, when the latter crude phosphoric acid is reused as a raw material for an etchant used in, for example, a liquid crystal manufacturing process or a semiconductor manufacturing process, the crude phosphoric acid removes dissolved metals such as aluminum and molybdenum. As a result, the etching rate is slow. For this reason, the crude phosphoric acid could not be reused as a raw material for such an etchant.

  The present invention has been made in view of such a technical background, and removes nitric acid and metal from a phosphoric acid mixed acid waste liquid containing nitric acid and metal to separate and recover high purity phosphoric acid. Another object of the present invention is to provide a method for recovering phosphoric acid from which nitric acid and dissolved metal have been removed from a phosphoric acid mixed acid waste liquid.

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

[1] A mixed acid waste liquid containing nitric acid, phosphoric acid and metal and a first extract liquid containing trialkyl phosphate are mixed to selectively dissolve the nitric acid in the first extract liquid. Nitric acid extraction step to extract,
By mixing the aqueous phosphoric acid-containing extraction residue obtained from the nitric acid extraction step and the second extract liquid containing an acidic phosphate, the metal is dissolved in the second extract liquid. A metal extraction step of extracting and
Recovering the phosphoric acid from the phosphoric acid-containing extraction residual liquid of the aqueous phase from the metal extraction step, and removing phosphoric acid from which nitric acid and dissolved metals have been removed from the phosphoric acid mixed acid waste solution How to recover.

[2] By mixing a mixed acid waste liquid containing nitric acid, phosphoric acid and metal and a first extract liquid containing trialkyl phosphate, the nitric acid is selectively dissolved in the first extract liquid. Nitric acid extraction step to extract,
A dilution step of adding water to the phosphoric acid-containing extraction residual liquid of the aqueous phase from the nitric acid extraction step to obtain a diluted solution having a phosphoric acid concentration of 10 to 30% by mass;
A metal extraction step of dissolving and extracting a metal in the second extract liquid by mixing the diluent and a second extract liquid containing an acidic phosphate;
Recovering the phosphoric acid from the phosphoric acid-containing extraction residual liquid of the aqueous phase from the metal extraction step, and removing phosphoric acid from which nitric acid and dissolved metals have been removed from the phosphoric acid mixed acid waste solution How to recover.

[3] By mixing a mixed acid waste solution containing nitric acid, phosphoric acid and metal and a first extract liquid containing trialkyl phosphate, the nitric acid is selectively dissolved in the first extract liquid. Nitric acid extraction step to extract,
By mixing the aqueous phosphoric acid-containing extraction residue obtained from the nitric acid extraction step and the second extract liquid containing an acidic phosphate, the metal is dissolved in the second extract liquid. A metal extraction step of extracting and
Recovering the phosphoric acid from the phosphoric acid-containing extraction residue of the aqueous phase from the metal extraction step;
The oil-phase metal-containing second extractant liquid extracted from the metal extraction step is mixed with one or more stripping acids selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, and phosphoric acid. A metal stripping step for dissolving and moving the metal in the stripping acid,
A cleaning step of dissolving and transferring the residual stripping acid in the cleaning liquid by mixing the second extractant liquid of the oil phase that has come out of the metal stripping process and the cleaning liquid,
Removal of nitric acid and dissolved metal from a phosphoric acid mixed acid waste liquid, wherein the second extractant liquid is circulated and used by supplying the second extractant liquid in the oil phase from the washing step to the metal extraction step To recover the phosphoric acid used.

[4] By mixing a mixed acid waste solution containing nitric acid, phosphoric acid and metal and a first extract liquid containing trialkyl phosphate, the nitric acid is selectively dissolved in the first extract liquid. Nitric acid extraction step to extract,
A dilution step of adding water to the phosphoric acid-containing extraction residual liquid of the aqueous phase from the nitric acid extraction step to obtain a diluted solution having a phosphoric acid concentration of 10 to 30% by mass;
A metal extraction step of dissolving and extracting a metal in the second extract liquid by mixing the diluent and a second extract liquid containing an acidic phosphate;
Recovering the phosphoric acid from the phosphoric acid-containing extraction residue of the aqueous phase from the metal extraction step;
The oil-phase metal-containing second extractant liquid extracted from the metal extraction step is mixed with one or more stripping acids selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, and phosphoric acid. A metal stripping step for dissolving and moving the metal in the stripping acid,
A cleaning step of dissolving and transferring the residual stripping acid in the cleaning liquid by mixing the second extractant liquid of the oil phase that has come out of the metal stripping process and the cleaning liquid,
Removal of nitric acid and dissolved metal from a phosphoric acid mixed acid waste liquid, wherein the second extractant liquid is circulated and used by supplying the second extractant liquid in the oil phase from the washing step to the metal extraction step To recover the phosphoric acid used.

  [5] The method for recovering phosphoric acid from which nitric acid and dissolved metals have been removed from the phosphoric acid mixed acid waste liquid according to the above item 3 or 4, wherein an acid having a pH of 1.5 or less is used as the cleaning liquid.

  [6] In the metal stripping step, the second extractant liquid is obtained by mixing the metal-containing second extractant in the oil phase from the metal extraction step and stripping phosphoric acid having a concentration of 60% by mass or more. 6. The nitric acid and dissolved metal are removed from the phosphoric acid mixed acid waste liquid according to any one of 3 to 5 above, characterized by comprising at least an aluminum peeling step for dissolving and moving aluminum in the peeling phosphoric acid. A method for recovering phosphoric acid.

  [7] In the metal stripping step, the oil-phase metal-containing second extractant liquid extracted from the metal extraction step and stripping sulfuric acid having a concentration of 70% by mass or more or stripping hydrochloric acid having a concentration of 22% by mass or more are mixed. From the phosphoric acid mixed acid waste liquid according to any one of the preceding items 3 to 5, further comprising a molybdenum stripping step of dissolving and transferring molybdenum in the second extractant solution to the stripping acid. A method for recovering phosphoric acid from which nitric acid and dissolved metals have been removed.

[8] The metal peeling step includes
The aluminum in the second extractant solution is dissolved in the exfoliating phosphoric acid by mixing the second extractant solution of the oil phase extracted from the metal extraction step with the exfoliating phosphoric acid having a concentration of 50% by mass or more. An aluminum stripping step to move,
By mixing the second extractant liquid in the oil phase from the metal extraction step with the stripping sulfuric acid having a concentration of 70% by mass or more or the stripping hydrochloric acid having a concentration of 22% by mass or more, A molybdenum stripping step in which molybdenum is dissolved and transferred into the stripping acid, and phosphoric acid from which nitric acid and dissolved metals have been removed from the phosphoric acid mixed acid waste liquid according to any one of items 3 to 5 above How to recover.

  [9] In the recovery step, the concentrated phosphoric acid having a concentration of 70 to 90% by mass is recovered by concentrating the aqueous phase phosphoric acid-containing extraction residue from the metal extraction step. 9. A method for recovering phosphoric acid from which nitric acid and dissolved metals have been removed from the phosphoric acid mixed acid waste liquid according to any one of 8 above.

  [10] By bringing the aqueous phase phosphoric acid-containing extraction residual liquid from the metal extraction step into contact with an adsorbent, the residual extractant in the extraction residual liquid is removed and the phosphoric acid is recovered. 10. A method for recovering phosphoric acid from which nitric acid and dissolved metal have been removed from the phosphoric acid mixed acid waste liquid according to any one of 1 to 9 above.

  [11] The method for recovering phosphoric acid from which nitric acid and dissolved metals have been removed from the phosphoric acid mixed acid waste liquid according to item 10 using activated carbon as the adsorbent.

  [12] The mixed acid waste liquid is a mixed acid waste liquid containing acetic acid, nitric acid, phosphoric acid and a metal, and phosphoric acid from which nitric acid and dissolved metal have been removed from the phosphoric acid mixed acid waste liquid according to any one of 1 to 11 above How to recover.

  [13] Phosphoric acid recovered by the recovery method according to any one of items 1 to 12.

  In the inventions [1] and [2], since the trialkyl phosphate is used as the first extractant liquid, nitric acid can be extracted from the mixed acid waste liquid with high selectivity, whereby a nitric acid-containing extract (oil phase) can be extracted. And phosphoric acid-containing extraction residual liquid (aqueous phase). That is, phosphoric acid and nitric acid can be separated. Further, in the metal extraction step, the aqueous phase phosphoric acid-containing extraction residual liquid from the nitric acid extraction step is mixed with the second extractant solution containing an acidic phosphate ester. The metal can be sufficiently extracted by dissolving in the liquid, and the metal component can be removed from the phosphoric acid-containing extraction residual liquid. Thus, phosphoric acid from which nitric acid and dissolved metal have been removed can be recovered from the extraction residue with high efficiency.

  In addition, in the invention of [2], there is provided a dilution step in which water is added to the phosphoric acid-containing extraction residual liquid in the aqueous phase from the nitric acid extraction step to obtain a diluted solution having a phosphoric acid concentration of 10 to 30% by mass. Therefore, the metal extraction efficiency in the metal extraction step can be sufficiently improved.

  [3] In the invention of [4], since trialkyl phosphate is used as the first extractant liquid, nitric acid can be extracted from the mixed acid waste liquid with high selectivity, and thereby a nitric acid-containing extract (oil phase) And phosphoric acid-containing extraction residual liquid (aqueous phase). That is, phosphoric acid and nitric acid can be separated. Further, in the metal extraction step, the aqueous phase phosphoric acid-containing extraction residual liquid from the nitric acid extraction step is mixed with the second extractant solution containing an acidic phosphate ester. The metal can be sufficiently extracted by dissolving in the liquid, and the metal component can be removed from the phosphoric acid-containing extraction residual liquid. Thus, phosphoric acid from which nitric acid and dissolved metal have been removed can be recovered from the extraction residue with high efficiency.

  Furthermore, the oil-phase metal-containing second extractant solution extracted from the metal extraction step is mixed with one or more stripping acids selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid and phosphoric acid. By mixing the metal stripping step for dissolving and moving the metal into the stripping acid, the second extractant liquid of the oil phase that has come out of the metal stripping step, and the cleaning liquid, And a cleaning step for dissolving and transferring the stripping acid. The second extract liquid obtained through the cleaning step is not only nitric acid but also a high-purity extractant solution that does not contain metal. Therefore, the second extractant solution can be returned to the metal extraction step and recycled. Since the second extractant can be repeatedly used in this way, phosphoric acid can be separated and recovered at a low cost.

  In addition, in the invention of [4], there is provided a dilution step in which water is added to the phosphoric acid-containing extraction residue of the aqueous phase from the nitric acid extraction step to obtain a diluted solution having a phosphoric acid concentration of 10 to 30% by mass. Therefore, the metal extraction efficiency in the metal extraction step can be sufficiently improved.

  In the invention of [5], since an acid having a pH of 1.5 or less is used as the cleaning liquid, the residual stripping acid can be sufficiently separated and removed from the second extractant solution, thereby achieving high purity with respect to the metal extraction step. It becomes possible to circulate and supply the second extractant.

  In the invention of [6], since phosphoric acid having a concentration of 60% by mass or more is used as a peeling acid in the metal peeling step, aluminum or the like can be sufficiently peeled (separated) from the second extractant solution.

  In the invention of [7], sulfuric acid having a concentration of 70% by mass or more or hydrochloric acid having a concentration of 22% by mass or more is used as a stripping acid in the metal stripping step, so that molybdenum or the like can be sufficiently stripped (separated) from the second extractant solution. .

  In the invention of [8], a metal stripping process using phosphoric acid having a concentration of 50% by mass or more as a stripping acid, and a metal using sulfuric acid having a concentration of 70% by strip or more or hydrochloric acid having a concentration of 22% by weight or more as a stripping acid. And a peeling step, aluminum and molybdenum can be sufficiently peeled (separated) from the second extractant solution.

  In the invention of [9], highly purified concentrated phosphoric acid from which nitric acid and metals have been sufficiently removed can be efficiently recovered.

  In the invention of [10], the aqueous phase phosphoric acid-containing extraction residual liquid from the metal extraction step is brought into contact with the adsorbent, so that the residual extractant in the extraction residual liquid can be sufficiently removed, Higher purity phosphoric acid can be recovered.

  In the invention [11], activated carbon is used as the adsorbent, so that even higher purity phosphoric acid can be recovered.

  In the invention of [12], highly pure phosphoric acid from which acetic acid, nitric acid and metal have been sufficiently removed can be separated and recovered.

  The recovered phosphoric acid according to the invention of [13] is highly purified phosphoric acid from which nitric acid and metals have been sufficiently removed, and is therefore suitably used as a raw material for an etching solution used in, for example, a liquid crystal manufacturing process or a semiconductor manufacturing process. It is done.

  An embodiment of a method for recovering phosphoric acid from which dissolved metal has been removed from a 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, acetic acid, nitric acid, and metal (Al, Mo, etc.) are removed from mixed acid wastewater containing acetic acid, nitric acid, phosphoric acid, and metal (Al, Mo, etc.), and high purity phosphoric acid is separated and recovered. Is. In the present embodiment, the phosphoric acid concentration in the mixed acid wastewater is 35% by mass or more (in particular, 60 to 80% by mass), but the target mixed acid wastewater has such a phosphoric acid concentration. It is not limited to things.

  First, in the nitric acid extraction step, the first extractant solution (trialkyl phosphate / organic solvent mixture) is supplied into the mixer tank, and also mixed acid wastewater containing acetic acid, nitric acid, phosphoric acid and metal is supplied. After stirring and mixing them, they are 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 first extractant composed of a mixed solution of trialkyl phosphate / organic solvent is excellent in extraction selectivity for nitric acid, but hardly extracts phosphoric acid, so that nitric acid is extracted from the mixed acid waste water. It selectively melt | dissolves in a chemical | medical solution and is extracted to the extraction liquid phase which is an oil phase.

  In the next nitric acid stripping step, the extract obtained in the nitric acid extraction step (first extractant solution containing extracted nitric acid) is fed into the mixer tank, and stripping water is also fed and stirred. After mixing these, transfer to a settler tank and let stand. Since nitric acid is transferred to the aqueous phase by mixing, it is separated into two layers of an oil phase and an aqueous phase composed of an aqueous nitric acid solution.

  As the first extraction liquid, an extraction liquid containing trialkyl phosphate is used. For example, the first extractant solution may be composed of only a trialkyl phosphate, or may be a mixed system of a trialkyl phosphate and an organic solvent. Among them, it is preferable to use an extractant having a composition of trialkyl phosphate / organic solvent = 10/90 to 90/10 (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, extraction selectivity to 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, there is an advantage that the extraction selectivity for nitric acid can be further improved. is there.

  Examples of the organic solvent include aliphatic organic solvents and aromatic organic solvents. Among these, as the organic solvent, it is preferable to use an aliphatic straight-chain saturated hydrocarbon having 6 to 13 carbon atoms. When an aliphatic straight chain saturated hydrocarbon having 6 to 13 carbon atoms is used as a dialkyl phosphate dilution solvent, the peelability of the extractant and the water for stripping in the nitric acid stripping process is improved, and the scale up Even at the level, the emulsification of the oil phase and the aqueous phase can be suppressed in the stationary state in the settler tank, which can significantly improve the separability of the oil phase and the aqueous phase. The oil phase extract liquid obtained through the process is a high-purity extract liquid that does not contain acetic acid and nitric acid. Accordingly, the first extract liquid is supplied to the nitric acid extraction process (returned back). ) It is fully possible to use in circulation. That is, if this first extractant solution is used in the nitric acid extraction step, nitric acid can be sufficiently extracted. As described above, when the aliphatic straight-chain saturated hydrocarbon having 6 to 13 carbon atoms is used as the organic solvent, the first extractant can be repeatedly used in this manner even in a large scale of actual equipment. Therefore, phosphoric acid can be separated and recovered at a low cost. Further, when an aliphatic straight chain saturated hydrocarbon having 6 to 13 carbon atoms is used as a dialkyl phosphate dilution solvent, the aliphatic straight chain saturated hydrocarbon having 6 to 13 carbon atoms can be used in the presence of nitric acid. Therefore, the oil phase and the aqueous phase in the nitric acid extraction step and the nitric acid stripping step can be maintained with good separation properties over a long period of time. There is an advantage that the liquid can be circulated and used for a long period of time and a stable and good operating state can be maintained for a long period of time.

  Among them, it is preferable to use an extractant having a composition of trialkyl phosphate / aliphatic linear saturated hydrocarbon having 6 to 13 carbon atoms = 10/90 to 90/10 (volume ratio). A more preferable ratio range is trialkyl phosphate / aliphatic linear saturated hydrocarbon having 6 to 13 carbon atoms = 15/85 to 50/50 (volume ratio), and a particularly preferable range is trialkyl phosphate / carbon number. 6-13 aliphatic linear saturated hydrocarbons = 20 / 80-40 / 60 (volume ratio).

  Examples of the aliphatic straight chain saturated hydrocarbon (solvent) having 6 to 13 carbon atoms include n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n- Examples include tridecane, and one of these may be used alone, or two or more thereof may be used. In addition, aliphatic straight-chain saturated hydrocarbons having 5 or less carbon atoms are not preferred as solvents because of their low boiling points, and aliphatic straight-chain saturated hydrocarbons having 14 or more carbon atoms are also solids at room temperature, so they are also suitable as solvents. Is not preferred.

  Among these, the aliphatic linear saturated hydrocarbon is one or more fats selected from the group consisting of n-hexane, n-octane, n-decane, n-undecane, n-dodecane and n-tridecane. It is preferable to use a straight chain saturated hydrocarbon, and in this case, good separability between the oil phase and the aqueous phase in the nitric acid stripping step can be maintained for a longer period of time.

  In addition, if it is a range which does not inhibit the effect of this invention, you may mix another well-known extractant (for example, neutral extractant) in the said 1st extract liquid (a trialkyl phosphate and an organic solvent). .

  Next, phosphoric acid remains in the aqueous phase extraction residue obtained in the nitric acid extraction step, and the phosphoric acid-containing extraction residue is diluted by adding water (dilution step). In this dilution step, it is preferable to obtain a diluted solution having a phosphoric acid concentration of 10 to 30% by mass by adding water to the phosphoric acid-containing extraction residue. By using such a diluted solution in the phosphoric acid concentration range, the metal extraction operation in the next metal extraction step proceeds efficiently. That is, when the phosphoric acid concentration in the diluted solution exceeds 30% by mass, the metal extraction efficiency is lowered in the next metal extraction step, which is not preferable. In addition, if the phosphoric acid concentration is less than 10% by mass, a large time and energy are required in the subsequent phosphoric acid concentration operation, which is not preferable. Among them, it is particularly preferable to add water to the phosphoric acid-containing extraction residue to obtain a diluted solution having a phosphoric acid concentration of 15 to 25% by mass.

  In the next metal extraction step, the diluent is supplied into the mixer tank and the second extractant solution (a mixed solution of acidic phosphate ester / organic solvent) is also supplied and stirred to mix them. Then, it is separated into two layers of an extraction liquid phase that is an oil phase and an extraction residual liquid phase that is an aqueous phase by moving to a settler tank and allowing to stand. At this time, the second extractant solution (containing acidic phosphate ester) is excellent in extraction selectivity for metals such as aluminum and molybdenum, but hardly extracts phosphoric acid. 2 It selectively melt | dissolves in extractant liquid, and it extracts to the extraction liquid phase which is an oil phase. On the other hand, phosphoric acid remains in the extraction residual liquid phase which is an aqueous phase. Thus, in this metal extraction step, phosphoric acid and dissolved metal are separated.

  As the second extract liquid, an extract liquid containing an acidic phosphate is used. For example, as the second extractant solution, a configuration composed only of an acidic phosphate ester may be adopted, or a mixed system of an acidic phosphate ester and an organic solvent may be used. Among them, it is preferable to use an extractant having a composition of acidic phosphate ester / organic solvent = 10/90 to 90/10 (volume ratio).

  Examples of the acidic phosphate ester include, but are not limited to, 2-ethylhexyl phosphate, di- (2-ethylhexyl) phosphate, methyl acid phosphate, butyl acid phosphate, dibutyl phosphate, monobutyl phosphate, 2- Examples include ethyl hexyl acid phosphate. Among these, as the acidic phosphate ester, it is preferable to use 2-ethylhexyl acid phosphate having the best overall balance in terms of viscosity, solubility in water, cost and the like.

  Examples of the organic solvent include aliphatic organic solvents and aromatic organic solvents. As the aliphatic organic solvent, an aliphatic organic solvent having 6 to 13 carbon atoms is preferably used. In addition, as the aromatic organic solvent, it is preferable to use an aromatic organic solvent having 6 to 13 carbon atoms.

  In addition, if it is a range which does not inhibit the effect of this invention, another well-known extractant (for example, neutral extractant, acidic extractant) is added in said 2nd extract liquid (acidic phosphate ester and organic solvent). It may be mixed.

  In the next residual extract removal step, the residual extract in the extraction residual solution is removed by bringing the extraction residual solution (aqueous phase) from the metal extraction step into contact with the adsorbent. The adsorbent is not particularly limited, but it is preferable to use activated carbon. When activated carbon is used, the residual extractant in the extraction residual liquid can be sufficiently removed.

  Thereafter, in the next concentration step, the extraction residual liquid from the residual extract removing step is concentrated using a concentration facility, so that the concentration is preferably 70 to 90% by mass, more preferably 82 to 85% by mass. The concentrated phosphoric acid is recovered. Although it does not specifically limit as said concentration equipment, For example, a 2 to 3 double effect can etc. are mentioned.

  Table 1 shows an example of the content of each component after the above steps are performed. As apparent from Table 1, the recovered concentrated phosphoric acid is one in which nitric acid, acetic acid, Al, and Mo are sufficiently removed.

  On the other hand, the oil phase extraction liquid (second extractant liquid) from the metal extraction step contains metal, so that it can be supplied to (returned to) the metal extraction step and circulated for use. Can not. Therefore, in the present embodiment, the following process is performed on the oil-phase extract extracted from the metal extraction process in order to enable the second extractant to be circulated.

  That is, as shown in FIG. 1, in the first metal stripping step, the second extractant liquid from the metal extraction step is supplied into the mixer tank, and phosphoric acid as a stripping acid is also supplied. After stirring, these are mixed and then transferred to a settler tank and allowed to stand. At this time, the aluminum in the second extractant solution is selectively dissolved in the phosphoric acid (peeling acid) and transferred to the aqueous phase. Therefore, the oil phase (second extractant solution) and the aluminum-containing phosphorus are used. It separates into two layers of an aqueous phase consisting of an acid aqueous solution. That is, in this first metal stripping step, dissolved aluminum is separated and removed from the second extractant solution.

  In the next second metal stripping step, the second extractant liquid from the first metal stripping step is supplied into the mixer tank, and hydrochloric acid as a stripping acid is also supplied and stirred. After mixing these, it moves to a settler tank and leaves still. At this time, since the molybdenum in the second extractant solution is selectively dissolved in the hydrochloric acid (peeling acid) and transferred to the aqueous phase, the oil phase (second extractant solution) and the molybdenum-containing hydrochloric acid aqueous solution Separate into two layers of an aqueous phase consisting of That is, in this second metal peeling step, the dissolved molybdenum is separated and removed from the second extractant solution.

  In the above embodiment, phosphoric acid is used as the stripping acid in the first metal stripping step, and hydrochloric acid is used as the stripping acid in the second metal stripping step. However, the stripping acid is not particularly limited to these. Absent. That is, as the stripping acid used in the metal stripping step, for example, one or two or more acids selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid and phosphoric acid are used.

  Therefore, when phosphoric acid is used as the peeling acid, it is preferable to use phosphoric acid having a concentration of 50% by mass or more. In this case, dissolved aluminum can be sufficiently separated and removed (peeled) from the second extractant solution. . When sulfuric acid is used as the stripping acid, it is preferable to use sulfuric acid having a concentration of 70% by mass or more. In this case, dissolved molybdenum can be sufficiently separated and removed (stripped) from the second extractant solution. When hydrochloric acid is used as the stripping acid, it is preferable to use hydrochloric acid having a concentration of 22% by mass or more. In this case, dissolved molybdenum can be sufficiently separated and removed (stripped) from the second extractant solution. When nitric acid is used as the stripping acid, it is preferable to use nitric acid having a concentration of 10% by mass or more. In this case, the dissolved molybdenum can be sufficiently separated and removed (stripped) from the second extractant solution. When hydrofluoric acid is used as the stripping acid, it is preferable to use hydrofluoric acid having a concentration of 10% by mass or more. In this case, dissolved molybdenum can be sufficiently separated and removed (peeled) from the second extractant solution.

  Thereafter, in the cleaning process, the second extractant liquid from the second metal stripping process is supplied into the mixer tank, the cleaning liquid is also supplied, and the mixture is stirred to mix them. Move to stand. At this time, since the acid such as the stripping acid remaining in the second extract liquid moves to the cleaning liquid that is the aqueous phase, the aqueous phase is composed of the oil phase (second extract liquid) and the residual acid-containing cleaning liquid. The two layers are separated. That is, in this cleaning step, an acid such as a residual stripping acid is separated and removed from the second extractant solution.

  The second extractant liquid in the oil phase obtained through the washing step is a high-purity extractant liquid not containing acetic acid and nitric acid as well as metals such as aluminum and molybdenum. It becomes possible to supply (return) 2 extractant solution to the metal extraction step and use it in a circulating manner. That is, if the second extractant obtained through the washing step is used in the metal extraction step (if used in circulation), the metal can be sufficiently extracted. In this method, since the second extract liquid can be circulated and used many times in this way, phosphoric acid can be separated and recovered at low cost.

  The washing liquid used in the washing step is not particularly limited, but it is preferable to use an acid having a pH of 1.5 or lower. In this case, the separability can be further improved. Examples of the acid having a pH of 1.5 or less include a nitric acid aqueous solution having a pH of 1.5 or less, a phosphoric acid aqueous solution having a pH of 1.5 or less, and an acetic acid aqueous solution having a pH of 1.5 or less. Among these, it is particularly preferable to use an acid having a pH of 1.0 or less as the cleaning liquid. In addition, it is not preferable to use water as the cleaning liquid because the second extractant liquid is mixed with water to form a cloudy emulsion.

  In this embodiment, the countercurrent multistage extraction method is employed in any of the nitric acid extraction step, the nitric acid stripping step, the metal extraction step, the first metal stripping step, the second metal stripping step, and the cleaning step. This counter-current multistage extraction method will be described by taking the nitric acid extraction step as an example. As shown in FIG. 3, a plurality of extraction tanks (A) are used to counter-flow the mixed acid waste water and the first extractant solution. However, the extraction is performed in each extraction tank, and the same method is adopted in the nitric acid stripping step, the metal extraction step, the first metal stripping step, the second metal stripping step, and the cleaning step.

  Next, specific examples of the present invention will be described, but the present invention is not particularly limited to these examples.

<Example 1>
In accordance with the separation and recovery method of the embodiment exemplified in the previous section (see FIG. 1), a nitric acid extraction step, a dilution step, and a metal extraction step were performed on mixed acid wastewater containing acetic acid, nitric acid, phosphoric acid, and dissolved metal. The mixed acid wastewater used in Example 1 is a mixed acid wastewater from a liquid crystal manufacturing factory, and the composition thereof is acetic acid: 2.5 mass%, nitric acid: 2.5 mass%, and phosphoric acid: 78 mass%. (Of course, not all of the mixed acid wastewater from the liquid crystal manufacturing factory has such a composition ratio, and the factories differ in various ways).

  First, in the nitric acid extraction step, extraction of nitric acid is performed using an extractant having a composition of tris (2-ethylhexyl) phosphate (TOP) / n-dodecane = 30/70 (volume ratio) as the first extractant. went. The number of stages in this nitric acid extraction step was set to 12 and the phase ratio (O / A) was set to 1.0. The phase ratio (O / A) is the ratio of the oil phase flow rate to the water phase flow rate (oil phase flow rate / water phase flow rate).

  In the next dilution step, water was added to the extraction residue (aqueous phase; containing phosphoric acid) from the nitric acid extraction step to obtain a diluted solution having a phosphoric acid concentration of 20% by mass.

  Thereafter, 100 mL of the diluted solution is placed in a 300 mL separatory funnel shaker, and further a second extract solution having a composition of di- (2-ethylhexyl) phosphate / n-dodecane = 30/70 (volume ratio). 100 mL, and after shaking the separating funnel for 1 minute under the condition of a phase ratio (O / A) of 1.0, the mixture is left to stand to extract the extraction liquid phase that is the oil phase and the extraction residue that is the water phase. Separated into two layers with liquid phase (metal extraction step). The aqueous phase phosphoric acid-containing extraction residue was recovered from the separatory funnel.

<Example 2>
In the same manner as in Example 1, except that an extractant having a composition of methyl acid phosphate / n-dodecane = 30/70 (volume ratio) was used as the second extractant liquid, The phosphoric acid-containing extraction residue was recovered.

<Example 3>
In the same manner as in Example 1 except that an extractant having a composition of butyl acid phosphate / n-dodecane = 30/70 (volume ratio) was used as the second extractant liquid, The phosphoric acid-containing extraction residue was recovered.

<Example 4>
In the same manner as in Example 1, except that an extractant having a composition of dibutyl phosphate / n-dodecane = 30/70 (volume ratio) was used as the second extractant liquid, phosphorus in the aqueous phase was separated from the separatory funnel. The acid-containing extraction residue was recovered.

<Example 5>
As in the case of Example 1, except that an extractant having a composition of monobutyl phosphate / n-dodecane = 30/70 (volume ratio) was used as the second extractant liquid, The phosphoric acid-containing extraction residue was recovered.

<Example 6>
In the same manner as in Example 1, except that an extractant having a composition of 2-ethylhexyl acid phosphate / n-dodecane = 30/70 (volume ratio) was used as the second extractant liquid, water was separated from the separating funnel. The phosphoric acid-containing extraction residue of the phase was collected.

<Example 7>
In the same manner as in Example 1, except that an extractant having a composition of di- (2-ethylhexyl) phosphate / kerosene = 30/70 (volume ratio) was used as the second extractant liquid, The aqueous phase phosphoric acid-containing extraction residue was recovered.

<Example 8>
In the same manner as in Example 1, except that an extractant having a composition of methyl acid phosphate / kerosene = 30/70 (volume ratio) was used as the second extractant, phosphoric acid from the separating funnel to the aqueous phase The contained extraction residual liquid was recovered.

<Example 9>
In the same manner as in Example 1, except that an extractant having a composition of butyl acid phosphate / kerosene = 30/70 (volume ratio) was used as the second extractant, phosphoric acid from the separating funnel to the aqueous phase The contained extraction residual liquid was recovered.

<Example 10>
In the same manner as in Example 1, except that an extractant having a composition of dibutyl phosphate / kerosene = 30/70 (volume ratio) was used as the second extractant, phosphoric acid contained in the aqueous phase from the separatory funnel The extraction residual liquid was collected.

<Example 11>
In the same manner as in Example 1, except that an extractant having a composition of monobutyl phosphate / kerosene = 30/70 (volume ratio) was used as the second extractant, phosphoric acid from the separating funnel to the aqueous phase The contained extraction residual liquid was recovered.

<Example 12>
In the same manner as in Example 1, except that an extractant composed of 2-ethylhexyl acid phosphate / kerosene = 30/70 (volume ratio) was used as the second extractant liquid, The phosphoric acid-containing extraction residue was recovered.

<Example 13>
In the dilution step, the aqueous phase phosphoric acid-containing extraction residue was recovered from the separatory funnel in the same manner as in Example 1 except that a diluted solution having a phosphoric acid concentration of 30% by mass was obtained.

<Example 14>
In the dilution step, the aqueous phase phosphoric acid-containing extraction residue was recovered from the separatory funnel in the same manner as in Example 2 except that a diluted solution having a phosphoric acid concentration of 30% by mass was obtained.

<Example 15>
In the dilution step, the aqueous phase phosphoric acid-containing extraction residue was recovered from the separatory funnel in the same manner as in Example 3 except that a diluted solution having a phosphoric acid concentration of 30% by mass was obtained.

<Example 16>
In the dilution step, the aqueous phase phosphoric acid-containing extraction residue was recovered from the separatory funnel in the same manner as in Example 4 except that a diluted solution having a phosphoric acid concentration of 30% by mass was obtained.

<Example 17>
In the dilution step, the aqueous phase phosphoric acid-containing extraction residue was recovered from the separatory funnel in the same manner as in Example 5 except that a diluted solution having a phosphoric acid concentration of 30% by mass was obtained.

<Example 18>
In the dilution step, the aqueous phase phosphoric acid-containing extraction residue was recovered from the separatory funnel in the same manner as in Example 6 except that a diluted solution having a phosphoric acid concentration of 30% by mass was obtained.

<Example 19>
In the dilution step, the aqueous phase phosphoric acid-containing extraction residue was recovered from the separatory funnel in the same manner as in Example 7 except that a diluted solution having a phosphoric acid concentration of 30% by mass was obtained.

<Example 20>
In the dilution step, the aqueous phase phosphoric acid-containing extraction residue was recovered from the separatory funnel in the same manner as in Example 8 except that a diluted solution having a phosphoric acid concentration of 30% by mass was obtained.

<Example 21>
In the dilution step, the aqueous phase phosphoric acid-containing extraction residue was recovered from the separatory funnel in the same manner as in Example 9, except that a diluted solution having a phosphoric acid concentration of 30% by mass was obtained.

<Example 22>
In the dilution step, the aqueous phase phosphoric acid-containing extraction residue was recovered from the separatory funnel in the same manner as in Example 10 except that a diluted solution having a phosphoric acid concentration of 30% by mass was obtained.

<Example 23>
In the dilution step, the aqueous phase phosphoric acid-containing extraction residue was recovered from the separatory funnel in the same manner as in Example 11 except that a diluted solution having a phosphoric acid concentration of 30% by mass was obtained.

<Example 24>
In the dilution step, the aqueous phase phosphoric acid-containing extraction residue was recovered from the separatory funnel in the same manner as in Example 12 except that a diluted solution having a phosphoric acid concentration of 30% by mass was obtained.

  In Examples 1 to 24, the following were used as the extractant and the organic solvent.

(Extractant)
Di- (2-ethylhexyl) phosphate: “PC-88A” (trade name) manufactured by Daihachi Chemical Co., Ltd.
Methyl acid phosphate: “AP-1” (trade name) manufactured by Daihachi Chemical Co., Ltd.
Butyl acid phosphate: “AP-4” (trade name) manufactured by Daihachi Chemical Co., Ltd.
Dibutyl phosphate: “DP-4” (trade name) manufactured by Daihachi Chemical Co., Ltd.
Monobutyl phosphate: “MP-4” (trade name) manufactured by Daihachi Chemical Co., Ltd.
2-ethylhexyl acid phosphate: “AP-8” (trade name) manufactured by Daihachi Chemical Co., Ltd.

(Organic solvent)
n-Dodecane: “N12D” (trade name) manufactured by Japan Energy Co., Ltd.
Kerosene: “Solvesso 150” (trade name) manufactured by Showa Shell Sekiyu.

<Evaluation method of metal removal performance (Examples 1 to 24)>
While measuring the phosphoric acid concentration of the said extraction residual liquid phase which came out of the said metal extraction process by the ion chromatograph, the metal component (Al, Mo) content of the said extraction residual liquid phase was measured by ICP-AES analysis.

Extraction equilibrium ratio of Al = Al concentration in the extract / Al concentration in the extraction residual liquid Mo extraction equilibrium ratio = Mo concentration in the extract / Mo concentration in the extraction residual liquid

  The extraction equilibrium ratio of Al and the extraction equilibrium ratio of Mo were determined by the above formula. These results are shown in Tables 2 and 3. From Tables 2 and 3, in Examples 1 to 24, since the acidic phosphate ester / organic solvent mixed solution is used as the second extractant solution, it is possible to extract and remove dissolved metals such as aluminum and molybdenum in the metal extraction step. I understand that. Moreover, the dissolved metal extraction removal of Examples 1-12 in which the phosphoric acid concentration of the dilution liquid was set to 20 mass% rather than Examples 13-24 in which the phosphoric acid concentration of the dilution liquid was set to 30 mass%. It turns out that it is excellent in performance. Therefore, it is particularly preferable to set the phosphoric acid concentration of the diluted solution to 25 to 35% by mass.

<Example 25>
In Example 6 (system using an extractant having a composition of 2-ethylhexyl acid phosphate / n-dodecane = 30/70 (volume ratio) as the second extractant), the phosphoric acid concentration of the diluted solution was Except for changing to 30% by mass, 40% by mass, 60% by mass, and 80% by mass, in the same manner as in Example 6, the aqueous phase phosphoric acid-containing extraction residual liquid was recovered from the separatory funnel. The removal performance was evaluated, and a summary of these evaluation data is shown in FIG.

  As is clear from FIG. 4, when the phosphoric acid concentration of the diluted solution was 80% by mass and 60% by mass, sufficient metal removal could not be performed, but 40% by mass, 30% by mass, and 20% by mass were phosphorous. It turns out that the metal removal performance in a metal extraction process improves rapidly as acid concentration becomes low.

<Example 26>
In accordance with the separation and recovery method of the embodiment exemplified in the previous section (see FIG. 1), a nitric acid extraction step, a dilution step, and a metal extraction step were performed on mixed acid wastewater containing acetic acid, nitric acid, phosphoric acid, and dissolved metal. The mixed acid wastewater used in Example 26 was mixed acid wastewater from a liquid crystal manufacturing factory, and the composition thereof was acetic acid: 2.5% by mass, nitric acid: 2.5% by mass, and phosphoric acid: 78% by mass. It was.

  First, in the nitric acid extraction step, extraction of nitric acid is performed using an extractant having a composition of tris (2-ethylhexyl) phosphate (TOP) / n-dodecane = 30/70 (volume ratio) as the first extractant. went. The number of stages in this nitric acid extraction step was set to 12 and the phase ratio (O / A) was set to 1.0. The phase ratio (O / A) is the ratio of the oil phase flow rate to the water phase flow rate (oil phase flow rate / water phase flow rate).

  In the next dilution step, water was added to the extraction residue (aqueous phase; containing phosphoric acid) from the nitric acid extraction step to obtain a diluted solution having a phosphoric acid concentration of 20% by mass.

  Thereafter, 100 mL of the diluted solution is put into a 300 mL separatory funnel shaker, and further 100 mL of a second extractant having a composition of 2-ethylhexyl acid phosphate / n-dodecane = 30/70 (volume ratio) is added. By shaking the separatory funnel for 1 minute under the condition of a phase ratio (O / A) of 1.0, the mixture is allowed to stand to extract the extraction liquid phase as an oil phase and the extraction residual liquid phase as an aqueous phase. Were separated into two layers (metal extraction step). From the separatory funnel, the phosphoric acid-containing extraction residue that was one of the separated products was recovered.

  On the other hand, a hydrochloric acid aqueous solution in which the concentration of hydrochloric acid is set to 7% by mass, 14% by mass, 21% by mass, 25% by mass, or 30% by mass in the metal-containing extract (oil phase) obtained from the metal extraction step. Were mixed and stirred, and then allowed to stand to separate into two layers of an extraction liquid phase as an oil phase and an extraction residual liquid phase as an aqueous phase (metal peeling step).

The metal component (Al, Mo) content in the extract (second extractant solution) and the metal component (Al, Mo) content in the extraction residual liquid phase were measured by ICP analysis.
Peeling equilibrium ratio of Al = Al concentration in the extract / Al concentration in the extraction residual liquid Mo peeling equilibrium ratio = Mo concentration in the extract / Mo concentration in the extraction residual liquid

  The Al peeling equilibrium ratio and the Mo peeling equilibrium ratio were determined by the above calculation formula. A summary of these data is shown in FIG.

  From FIG. 5, in order to fully peel both Al and Mo from the second extractant solution in the metal peeling step, the hydrochloric acid concentration is preferably 22% by mass or more, and particularly preferably 22-30% by mass. It is understood that the most preferable is 23 to 27% by mass.

<Example 27>
According to the separation and recovery method shown in FIG. 2, each step was performed on mixed acid wastewater containing acetic acid, nitric acid, phosphoric acid, and dissolved metal. The mixed acid wastewater used in Example 27 was a mixed acid wastewater from a liquid crystal manufacturing factory, and the composition thereof was acetic acid: 2.5% by mass, nitric acid: 2.5% by mass, and phosphoric acid: 78% by mass. It was.

  First, in the nitric acid extraction step, extraction of nitric acid is performed using an extractant having a composition of tris (2-ethylhexyl) phosphate (TOP) / n-dodecane = 30/70 (volume ratio) as the first extractant. went. The number of stages in this nitric acid extraction step was set to 12 and the phase ratio (O / A) was set to 1.0. The phase ratio (O / A) is the ratio of the oil phase flow rate to the water phase flow rate (oil phase flow rate / water phase flow rate).

  In the next dilution step, water was added to the extraction residue (aqueous phase; containing phosphoric acid) from the nitric acid extraction step to obtain a diluted solution having a phosphoric acid concentration of 20% by mass.

  In the next metal extraction step, a diluted solution having a phosphoric acid concentration of 20% by mass is supplied at 100 mL / min, and 2-ethylhexyl acid phosphate / n-dodecane = 30/70 (volume ratio) is used as the second extractant solution. Extraction liquid consisting of the composition was supplied at 29 mL / min, that is, metal extraction was performed under the condition of phase ratio (O / A) 1 / 3.45. The number of stages in this metal extraction step was 10.

  In the next metal stripping step, the extraction liquid (oil phase) from the metal extraction step is supplied at 29 L / min, and a hydrochloric acid aqueous solution having a concentration of 25% by mass as a stripping acid is supplied at 58 mL / min. The metal was peeled off at a phase ratio (O / A) of 1/2.

  In the next washing process, the oil phase (second extractant liquid) from the metal stripping process is supplied at 29 L / min, and city water (tap water) is supplied as the cleaning liquid at 29 L / min. Washing (removal of residual peeling acid) was performed under the condition of the ratio (O / A) 1/1. The second extractant after washing was circulated and supplied to the metal extraction step (see FIG. 2).

  In addition, the capacity | capacitance of the mixer tank in the nitric acid extraction process was 50L, and the capacity | capacitance of the settler tank was 150L, and 12 tanks (12 stages) of such mixer settlers (200L) were connected, and the nitric acid extraction process part was comprised. The capacity of the mixer tank in the nitric acid stripping process was 50 L, the capacity of the settler tank was 150 L, and 10 tanks (10 stages) were connected to form a nitric acid stripping process section. Moreover, the capacity | capacitance of the mixer tank in a metal extraction process was set to 50L, the capacity | capacitance of the settler tank was set to 150L, and 10 tanks (10 stages) of such mixer settlers (200L) were connected, and the metal extraction process part was comprised. Moreover, the capacity | capacitance of the mixer tank in a metal peeling process was 50L, and the capacity | capacitance of the settler tank was 150L, and 10 tanks (10 steps | paragraphs) of such mixer settlers (200L) were connected, and the metal peeling process part was comprised. Moreover, the capacity | capacitance of the mixer tank in the washing | cleaning process was set to 50L, the capacity | capacitance of the settler tank was set to 150L, and 4 tanks (4 steps | paragraphs) of such a mixer settler (200L) were connected, and the washing | cleaning process part was comprised.

  On the other hand, by adding activated carbon (“Taiko CW-12A” manufactured by Nimura Chemical Co., Ltd.) at a rate of 5 g with respect to 2000 mL of the phosphoric acid-containing extraction residual liquid (aqueous phase) obtained from the metal extraction step, the mixture is sufficiently stirred. Then, the residual extract was adsorbed and removed from the activated carbon (residual extract removal step). Subsequently, it filtered with the filter paper, and also microfiltered with the 0.2 micrometer membrane filter.

  In the next concentration step, the phosphoric acid-containing extraction residue after removal of the residual extractant is concentrated to 83% by mass with a glass rotary evaporator at a vacuum degree of 60 torr and a bath temperature of 85 ° C. It was collected.

  The measurement results (ICP analysis) of the content ratio (unit: ppm) of Al and Mo before and after each step are shown in FIG. Thus, it can be seen that both Al and Mo can be extracted at a high extraction rate of 95% by mass or more in the metal extraction step, and that both Al and Mo can be separated at a high separation rate of 95% by mass or more in the metal peeling step.

  The concentrated phosphoric acid solution recovered as described above was evaluated as an etching solution. For comparison, the etching performance was also evaluated for a new etching solution and a waste solution used for the etching treatment (mixed acid waste water to be treated in Example 27). Note that Mo / Al / Mo (50 nm / 200 nm / 50 nm) and Al (1000 nm) were used as the structure of the film layer on the surface of the substrate to be etched. These results are shown in Table 4.

  From Table 4, it can be seen that the etching solution prepared using the concentrated phosphoric acid solution (regenerated phosphoric acid) recovered by the recovery method of the present invention exhibits excellent etching performance equivalent to that of a new etching solution.

  The phosphoric acid recovered by the method of recovering phosphoric acid from which dissolved metal has been removed from the phosphoric acid mixed acid waste liquid according to the present invention is suitable as a raw material for an etching solution used in, for example, a liquid crystal manufacturing process or a semiconductor manufacturing process. However, it is not particularly limited to such applications.

It is a flowchart which shows each process of the phosphoric acid collection | recovery method concerning this invention. 10 is a flowchart showing each step of the phosphoric acid recovery method of Example 27. FIG. It is explanatory drawing of a countercurrent multistage extraction method. It is a graph which shows the relationship between phosphoric acid concentration and Al, Mo extraction equilibrium ratio. It is a graph which shows the relationship between Al and Mo peeling equilibrium ratio and the density | concentration of hydrochloric acid aqueous solution which is a peeling acid.

Explanation of symbols

A ... Extraction tank

Claims (13)

By mixing a mixed acid waste liquid containing nitric acid, phosphoric acid and metal and a first extract liquid containing trialkyl phosphate, the nitric acid is selectively dissolved in the first extract liquid and extracted. Nitric acid extraction step to
By mixing the aqueous phosphoric acid-containing extraction residue obtained from the nitric acid extraction step and the second extract liquid containing an acidic phosphate, the metal is dissolved in the second extract liquid. A metal extraction step of extracting and
Recovering the phosphoric acid from the phosphoric acid-containing extraction residual liquid of the aqueous phase from the metal extraction step, and removing phosphoric acid from which nitric acid and dissolved metals have been removed from the phosphoric acid mixed acid waste solution How to recover. By mixing a mixed acid waste liquid containing nitric acid, phosphoric acid and metal and a first extract liquid containing trialkyl phosphate, the nitric acid is selectively dissolved in the first extract liquid and extracted. Nitric acid extraction step to
A dilution step of adding water to the phosphoric acid-containing extraction residual liquid of the aqueous phase from the nitric acid extraction step to obtain a diluted solution having a phosphoric acid concentration of 10 to 30% by mass;
A metal extraction step of dissolving and extracting a metal in the second extract liquid by mixing the diluent and a second extract liquid containing an acidic phosphate;
Recovering the phosphoric acid from the phosphoric acid-containing extraction residual liquid of the aqueous phase from the metal extraction step, and removing phosphoric acid from which nitric acid and dissolved metals have been removed from the phosphoric acid mixed acid waste solution How to recover. By mixing a mixed acid waste liquid containing nitric acid, phosphoric acid and metal and a first extract liquid containing trialkyl phosphate, the nitric acid is selectively dissolved in the first extract liquid and extracted. Nitric acid extraction step to
By mixing the aqueous phosphoric acid-containing extraction residue obtained from the nitric acid extraction step and the second extract liquid containing an acidic phosphate, the metal is dissolved in the second extract liquid. A metal extraction step of extracting and
Recovering the phosphoric acid from the phosphoric acid-containing extraction residue of the aqueous phase from the metal extraction step;
The oil-phase metal-containing second extractant liquid extracted from the metal extraction step is mixed with one or more stripping acids selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, and phosphoric acid. A metal stripping step for dissolving and moving the metal in the stripping acid,
A cleaning step of dissolving and transferring the residual stripping acid in the cleaning liquid by mixing the second extractant liquid of the oil phase that has come out of the metal stripping process and the cleaning liquid,
Removal of nitric acid and dissolved metal from a phosphoric acid mixed acid waste liquid, wherein the second extractant liquid is circulated and used by supplying the second extractant liquid in the oil phase from the washing step to the metal extraction step To recover the phosphoric acid used. By mixing a mixed acid waste liquid containing nitric acid, phosphoric acid and metal and a first extract liquid containing trialkyl phosphate, the nitric acid is selectively dissolved in the first extract liquid and extracted. Nitric acid extraction step to
A dilution step of adding water to the phosphoric acid-containing extraction residual liquid of the aqueous phase from the nitric acid extraction step to obtain a diluted solution having a phosphoric acid concentration of 10 to 30% by mass;
A metal extraction step of dissolving and extracting a metal in the second extract liquid by mixing the diluent and a second extract liquid containing an acidic phosphate;
Recovering the phosphoric acid from the phosphoric acid-containing extraction residue of the aqueous phase from the metal extraction step;
The oil-phase metal-containing second extractant liquid extracted from the metal extraction step is mixed with one or more stripping acids selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, and phosphoric acid. A metal stripping step for dissolving and moving the metal in the stripping acid,
A cleaning step of dissolving and transferring the residual stripping acid in the cleaning liquid by mixing the second extractant liquid of the oil phase that has come out of the metal stripping process and the cleaning liquid,
Removal of nitric acid and dissolved metal from a phosphoric acid mixed acid waste liquid, wherein the second extractant liquid is circulated and used by supplying the second extractant liquid in the oil phase from the washing step to the metal extraction step To recover the phosphoric acid used.   The method for recovering phosphoric acid from which nitric acid and dissolved metals have been removed from a phosphoric acid mixed acid waste liquid according to claim 3 or 4, wherein an acid having a pH of 1.5 or less is used as the cleaning liquid.   The metal stripping step mixes the oil-phase metal-containing second extractant liquid extracted from the metal extraction step with stripping phosphoric acid having a concentration of 60% by mass or more, whereby aluminum in the second extractant solution is mixed. A phosphoric acid from which nitric acid and dissolved metal have been removed from the phosphoric acid mixed acid waste liquid according to any one of claims 3 to 5, further comprising an aluminum stripping step for dissolving and transferring the base material into the stripping phosphoric acid. How to recover.   The metal stripping step is performed by mixing the oil-phase metal-containing second extractant liquid extracted from the metal extraction step with stripping sulfuric acid having a concentration of 70% by mass or more or stripping hydrochloric acid having a concentration of 22% by mass or more. And at least a molybdenum stripping step for dissolving and transferring molybdenum in the second extractant solution to the stripping acid, from the phosphoric acid mixed acid waste solution according to any one of claims 3 to 5, A method for recovering phosphoric acid from which dissolved metal has been removed. The metal peeling step includes
The aluminum in the second extractant solution is dissolved in the exfoliating phosphoric acid by mixing the second extractant solution of the oil phase extracted from the metal extraction step with the exfoliating phosphoric acid having a concentration of 50% by mass or more. An aluminum stripping step to move,
By mixing the second extractant liquid in the oil phase from the metal extraction step with the stripping sulfuric acid having a concentration of 70% by mass or more or the stripping hydrochloric acid having a concentration of 22% by mass or more, Molybdenum stripping step for dissolving and transferring molybdenum into the stripping acid; and phosphorous from which nitric acid and dissolved metal have been removed from the phosphoric acid mixed acid waste solution according to any one of claims 3 to 5 A method for recovering acid.   The said collection | recovery process collect | recovers the concentrated phosphoric acid with a density | concentration of 70-90 mass% by concentrating the phosphoric acid containing extraction residual liquid of the water phase extracted from the said metal extraction process. A method for recovering phosphoric acid from which nitric acid and dissolved metals have been removed from the phosphoric acid mixed acid waste liquid according to any one of the above items.   The phosphoric acid is recovered by removing the residual extractant from the extraction residue by bringing the aqueous phase-containing phosphate-containing extraction residue from the metal extraction step into contact with an adsorbent. A method for recovering phosphoric acid from which nitric acid and dissolved metal have been removed from the phosphoric acid mixed acid waste liquid according to any one of claims 1 to 9.   The method for recovering phosphoric acid from which nitric acid and dissolved metals have been removed from the phosphoric acid mixed acid waste liquid according to claim 10, wherein activated carbon is used as the adsorbent.   The said mixed acid waste liquid is a mixed acid waste liquid containing acetic acid, nitric acid, phosphoric acid, and a metal, The collect | recovered phosphoric acid from which nitric acid and the dissolved metal were removed from the phosphoric acid type mixed acid waste liquid of any one of Claims 1-11 how to.   The phosphoric acid collect | recovered by the collection | recovery method of any one of Claims 1-12.

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