JP5277559B2 - Method and apparatus for recovering phosphoric acid from phosphoric acid-containing water - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a method and apparatus for recovering phosphoric acid from phosphoric acid-containing water using a reverse osmosis device, and in particular, from waste water containing phosphoric acid after etching a liquid crystal substrate, a wafer, or other electronic equipment, such as phosphoric acid. The present invention relates to a method and an apparatus for recovering phosphoric acid suitable for recovery of waste water and treated water.

  An etching solution containing phosphoric acid is used for etching liquid crystal substrates, wafers, and other electronic devices. The high-concentration waste etchant generated in the etching process is recovered and recycled, but the electronic equipment after etching is washed with pure water, and a large amount of low-concentration washing wastewater is generated. Such washing wastewater contains phosphoric acid, nitric acid, acetic acid, other acid components, etc., which are components of the etching solution, as well as metal ions and other impurities that are eluted by etching, but most are pure water. .

Such etching cleaning wastewater is conventionally treated by mixing with other wastewater. As a general treatment technique for wastewater containing phosphoric acid or hydrofluoric acid, coagulation sedimentation treatment can be mentioned. However, when coagulating and precipitating with phosphoric acid or hydrofluoric acid , there are problems such as an increase in processing cost due to the use of a large amount of chemicals and the generation of a large amount of sludge, and an increase in environmental burden. In addition, increase of the water-soluble ions by a large amount of drug added in the coagulation-sedimentation process, upon water recovery, increase of the dynamic power costs due to the operation pressure rise of the reverse osmosis membrane process, deterioration of the treated water, the scale of the occurrence, also The ion exchange method has led to an increase in the amount of regenerant used.

In Patent Document 1 (Japanese Patent Laid-Open No. 2006-75820), ions such as phosphoric acid and nitric acid are removed with an ion exchange resin, and pure water and phosphate are recovered. However, in this method, it is recovered as a phosphate (sodium dihydrogen phosphate, etc.). However, since there is almost no sales channel for phosphate, and the sodium salt of phosphoric acid has low solubility, the content of phosphoric acid in liquid form The caustic potash is expensive to make potassium salt. In addition, a method of passing through an H-type cation resin to make sodium dihydrogen phosphate is shown, but acid such as hydrochloric acid is consumed by regeneration of the cation resin, and sodium hydroxide used for regeneration of the anion resin is also used. There were drawbacks such as wasted waste.
JP 2006-75820 A

  It is an object of the present invention to provide a high-concentration liquid phosphoric acid that can be transported in a high-concentration liquid state with a simple structure and operation, and that can be efficiently recovered from phosphoric acid-containing water at a low cost. It is to propose a method and apparatus for recovering acid.

The present invention is a method and apparatus for recovering phosphoric acid from the following phosphate ion-containing water.
(1) A method for recovering phosphoric acid from phosphoric acid-containing water from which cations have been removed ,
Phosphoric acid-containing water from which cations have been removed is supplied to a reverse osmosis device under conditions of pH 3 or lower and a phosphoric acid concentration of 1 to 15% by weight, and membrane separation treatment is performed. A method of recovering phosphoric acid, characterized in that the phosphoric acid is concentrated on the side of the concentrate chamber, and the phosphoric acid concentrate is recovered.
(2) The above-mentioned (1), which has a process of taking out the concentrate in the concentrate chamber and circulating it to the concentrate chamber, and adding the treated phosphoric acid-containing water from which cations have been removed to the circulating concentrate. The method described.
(3) The method according to (1) or (2) above, wherein the method comprises the step of taking out the concentrate from the concentrate chamber and circulating it to the concentrate chamber, and performing membrane separation treatment by adding dilution water to the circulating concentrate.
(4) before being supplied to the reverse osmosis device phosphoric acid-containing water to remove cations, according to any one of (1) to effect removal of impurities including cationic and A anions (3) as a pre-treatment the method of.
(5) The method according to any one of (1) to (4) above, wherein pure water is recovered by removing impurities including acid from the permeated water of the reverse osmosis device.
(6) The method according to (5) above, wherein the impurities are removed by an electric regenerative ion exchange apparatus.
(7) The method according to any one of (1) to (6) above, wherein the phosphoric acid concentrate is concentrated by evaporation to remove volatile components together with water.
(8) The method according to (3) above, wherein the dilution water is pure water obtained by removing impurities from the permeated water.
(9) An apparatus for recovering phosphoric acid from phosphoric acid-containing water from which cations have been removed ,
Phosphoric acid-containing water from which cations have been removed is subjected to a membrane separation treatment under conditions of pH 3 or lower and a phosphoric acid concentration of 1 to 15% by weight, and an acid other than phosphoric acid is allowed to permeate to the permeate chamber side together with water. A reverse osmosis device for concentrating to the concentrate chamber side;
A phosphoric acid-containing water supply unit that supplies phosphoric acid-containing water from which cations have been removed to the concentrated liquid chamber side of the reverse osmosis device under conditions of pH 3 or lower and a phosphoric acid concentration of 1 to 15% by weight;
A permeate extractor for extracting permeate from the permeate chamber side of the reverse osmosis device;
A concentrated phosphoric acid solution extraction section for extracting the concentrated phosphoric acid solution from the concentrated liquid chamber side of the reverse osmosis device ;
And a circulation path for circulating the concentrated phosphoric acid solution extracted from the concentrated phosphoric acid solution extraction unit to the concentrated liquid chamber side.
(10) The apparatus according to (9), further including a dilution water supply unit that adds dilution water to the concentrate circulating in the circulation path.
(11) (9) having a processor before the removal of impurities, including cations and A anions in the raw water supply unit or (10) apparatus as claimed.
(12) The device according to any one of (9) to (11), further including an impurity removing device that removes impurities including acid from the permeated water of the reverse osmosis device.
(13) The apparatus according to (12), wherein the impurity removing device is an electric regenerative ion exchange device.
(14) The apparatus according to any one of the above (9) to (13), further comprising an evaporation concentrator that evaporates and concentrates the phosphoric acid concentrate and removes volatile components together with water to concentrate.

In the present invention, the phosphoric acid-containing water from which the cations to be treated are removed can be used without limitation as long as it contains phosphoric acid, but phosphate ions are 50 to 10,000 mg / L, particularly 50 to Acidic water containing 2000 mg / L and having a pH of 3 or less, particularly 2.8 or less, and in any case 1 or more, particularly 1.8 or more is preferable as the treatment target. ions, acid components such as acetic acid ion, and other anionic, but may contain other impurities arrangement Niso, to be processed phosphoric acid containing water to remove cations such as metal ions. In the present invention, it is particularly suitable for recovering highly pure phosphoric acid by removing other acid components such as nitrate ion and acetate ion from phosphoric acid-containing water containing other acid components such as nitrate ion and acetate ion. ing.

  Particularly preferable phosphoric acid-containing water as a treatment target is low-concentration cleaning wastewater generated when pure water cleaning is performed after etching with a phosphoric acid-containing etching solution for liquid crystal substrates, wafers, and other electronic devices. Examples of such cleaning waste water after etching include phosphate ions 50 to 2000 mg / L, nitrate ions 10 to 500 mg / L, acetate ions 5 to 300 mg / L, and an acidity of pH 1.8 to 2.8. There is water.

In the present invention, in order to recover phosphoric acid from phosphoric acid-containing water from which cations have been removed, phosphoric acid-containing water from which cations have been removed is supplied to a reverse osmosis device under conditions of pH 3 or lower and a phosphoric acid concentration of 1 to 15% by weight. Although for supplying to membrane separation processes, before supplying phosphate-containing water to remove cations reverse osmosis apparatus, to carry out the removal of impurities, including cations and a anion as a pretreatment preferable. In this case, precipitation separation, removal of solids by filtration, etc., removal of cations such as metal ions by cation exchange resin, and removal of anions such as perchloric acid and organic acid complexes by anion exchange resin can be performed. . As a pretreatment apparatus used for such a pretreatment step, a general apparatus employed for the above purpose is used.

  Metal ions such as indium, iron, and aluminum contained in the cleaning waste water after etching cause clogging of the reverse osmosis (RO) membrane in the membrane separation process, and perchloric acid and the like cause membrane damage at high concentrations. Therefore, it is preferable to remove these cations and anions because clogging or damage of the membrane can be prevented. As the cation exchange resin, a strong acid or weak acid cation exchange resin can be used. However, when these cations are exchanged and removed using an H-form strong acid cation exchange resin, the treatment liquid has an increased acid component, resulting in a pH of 3 Since adjustment to the following becomes easy, it is preferable. The cation exchange resin may be a chelate resin. As the anion exchange resin, a strongly basic or weakly basic anion exchange resin can be used. The anion exchange resin is used in an acid form such as a phosphoric acid form, and passes through phosphoric acid, nitric acid, acetic acid and the like to remove other impurity anions.

  In the present invention, the reverse osmosis device in the membrane separation step is also called an RO device, and is divided into a permeate chamber and a concentrate chamber by a reverse osmosis (RO) membrane, and the phosphoric acid-containing water has a pH of 3 or less and a phosphoric acid concentration of 1 Reverse osmosis treatment is performed by supplying to the concentrate chamber side under a condition of ˜15% by weight so that an acid other than phosphoric acid is permeated to the permeate chamber side together with water, and phosphoric acid is concentrated to the concentrate chamber side. Configured. On the concentrated liquid chamber side of the reverse osmosis device, a phosphoric acid-containing water supply unit that supplies phosphoric acid-containing water and a concentrated phosphoric acid solution extraction unit that extracts the concentrated phosphoric acid solution are formed. On the permeate chamber side of the reverse osmosis device, a permeate extractor for taking out the permeate is formed. A circulation path for circulating the concentrated phosphoric acid solution extracted from the concentrated phosphoric acid solution extracting unit to the concentrated solution chamber side is formed between the concentrated phosphoric acid solution extracting unit and the phosphoric acid-containing water supply unit. Reverse osmosis membranes allow water to permeate by osmotic pressure, or conversely, pressurize to a pressure higher than osmotic pressure and supply the liquid to be treated to allow water to permeate by reverse osmosis, while not allowing salt and other solutes to permeate. A semi-permeable membrane to block.

  The material of the reverse osmosis membrane is not particularly limited as long as it has the above characteristics, and examples thereof include a polyamide-based permeable membrane, a polyimide-based permeable membrane, and a cellulose-based permeable membrane. A composite reverse osmosis membrane in which an active skin layer having substantially selective separability is formed on a support is preferred. The reverse osmosis device may be any device that includes such a reverse osmosis membrane, but preferably includes a membrane module in which a reverse osmosis membrane, a support mechanism, a water collection mechanism, and the like are integrated. There is no restriction | limiting in particular as a membrane module, For example, a tubular membrane module, a plane membrane module, a spiral membrane module, a hollow fiber membrane module etc. can be mentioned. As the reverse osmosis apparatus provided with these, a known apparatus can be used, and a highly permeable apparatus operated at a low pressure is preferable.

In the present invention, in the membrane separation step, phosphoric acid-containing water from which cations have been removed is supplied to a reverse osmosis apparatus under conditions of pH 3 or lower and phosphoric acid concentration of 1 to 15% by weight, preferably 2 to 10% by weight. Reverse osmosis) treatment. When the phosphoric acid-containing water is obtained in a state of pH 3 or lower, it can be supplied to the reverse osmosis apparatus without adjusting the pH as it is, but if necessary, the pH can be adjusted by adding a pH adjusting agent such as hydrochloric acid or nitric acid. Also good. The same applies when the pH is adjusted to 3 or less by removing cations such as metal ions with a cation exchange resin in the pretreatment. Since cleaning wastewater after etching of liquid crystal substrates and wafers is usually obtained in a state of pH 3 or lower, it can be supplied to a reverse osmosis device without adjusting pH, and even when adjusting pH, the amount of pH adjuster added is Less.

When the phosphoric acid-containing water from which cations have been removed is obtained at a phosphoric acid concentration of 1 to 15% by weight, it can be separated by reverse osmosis as it is, but when the phosphoric acid concentration is less than 1% by weight. Can be concentrated to a phosphoric acid concentration of 1% by weight or more by performing membrane separation treatment while circulating the concentrate through the circulation path. In this case, concentration may be performed while circulating low-concentration phosphoric acid-containing water, and when the phosphoric acid concentration is concentrated to 1% by weight or more, a batch process may be performed in which the circulating fluid is replaced. While circulating the concentrated solution concentrated to 15% by weight, adding low-concentration treated phosphoric acid-containing water to the circulating concentrated solution and taking out the concentrated solution partly as a phosphoric acid concentrated solution, apparently transient This is preferable because the above process can be performed. In the process of taking out the concentrate in the concentrate chamber and circulating it to the concentrate chamber, the removal rate of acids other than phosphoric acid can be increased by adding dilution water to the circulating concentrate and performing reverse osmosis treatment. As the dilution water, recovered water obtained by removing impurities from the permeated water can be used.

When water containing phosphonic acid containing cations is supplied to a reverse osmosis device under a pH of 3 or less and membrane separation treatment is performed, acids other than phosphoric acid such as nitric acid and acetic acid permeate through the reverse osmosis membrane together with water. It moves to the permeate chamber side and is taken out from the permeate chamber side. Since phosphoric acid is prevented from permeating through the reverse osmosis membrane and remains on the concentrate chamber side to be concentrated, it can be recovered from the concentrate chamber side as a phosphoric acid concentrate. At this time, a small amount of acid other than phosphoric acid remains in the concentrated solution. However, when membrane separation treatment is performed under conditions of phosphoric acid concentration of 1 to 15% by weight, the blocking rate of acids other than phosphoric acid is lowered, and the transmittance Therefore, a high-purity phosphoric acid concentrate can be recovered. The pressure of the phosphoric acid containing water supplied to a reverse osmosis apparatus can be 0.3-5 Mpa, Preferably it can be 0.5-3 Mpa.

Comparing the permeation of ionic and nonionic substances in the permeation of reverse osmosis membranes, even if the reverse osmosis membrane blocking rate is the same molecular weight, ionic substances are overwhelming compared to nonionic substances. It is said that it is easy to be blocked. However, as a result of repeated research by the present inventors, unlike such common sense, when a reverse osmosis membrane treatment is performed under a pH of 3 or less where phosphoric acid is difficult to dissociate, the rejection rate of phosphoric acid is overwhelmingly higher than that of nitric acid or acetic acid. Thus, it was found that acids other than phosphoric acid, such as nitric acid and acetic acid, and phosphoric acid can be separated and recovered. Reason phosphoric acid at low pH is strongly blocked by the reverse osmosis membrane, phosphate molecular weight increases becomes the form of Polymerization phosphate, rejection is presumed to be because the up.

  The blocking rate of acids other than phosphoric acid such as nitric acid and acetic acid under pH 3 or lower is low, and the blocking rate when a normal phosphoric acid-containing etching solution is processed is 1% or less. The higher the acid blocking rate, the lower the blocking rate of acids other than phosphoric acid. When the phosphoric acid concentration is 1% by weight or more, the blocking rate of acids other than phosphoric acid becomes negative. Here, the blocking rate is a rate at which the reverse osmosis membrane blocks the permeation of the solute, and is represented by the following formula (1).

Blocking rate (%) = [1-C ₃ / (C ₁ · C ₂ ) ^1/2 ] × 100 (1)
(In formula (1), C ₁ is the solute concentration at the inlet of the supply liquid, C ₂ is the solute concentration at the outlet of the concentrate, and C ₃ is the solute concentration of the permeate.)
In formula (1), ((C ₁ · C ₂ ) ^1/2 ) represents the geometric mean, and (C ₃ / (C ₁ · C ₂ ) ^1/2 ) is the (synergistic) average concentration of the solute in the concentrate. Shows the ratio of the solute concentration of the permeate to. For this reason, it has shown that a solute permeate | transmits to the permeate side, so that the rejection rate is low. Although it is easy to recognize that the rejection rate is not negative in the normal concept, the rejection rate may be negative due to the structure of the equation (1). In this case, the permeated liquid is higher than the solute concentration of the concentrate. This indicates that the solute concentration is high and the solute permeates at high transmittance.

  When the phosphoric acid concentration is 1% by weight or more, the rejection rate of acids other than phosphoric acid is negative. When the phosphoric acid concentration is 1% by weight or more, particularly 2% by weight or more, the concentration of acids other than phosphoric acid remaining in the concentrated liquid Means that a highly concentrated phosphoric acid concentrate is obtained. If the concentration of phosphoric acid in the concentrate is too high, membrane treatment cannot be performed due to osmotic pressure, so the upper limit of the concentration of phosphoric acid in the concentrate is 15% by weight, preferably 10% by weight. While circulating the concentrated solution of such phosphoric acid concentration, adding the water to be treated containing phosphoric acid to the circulating concentrated solution, taking out the concentrated solution partly as a phosphoric acid concentrated solution, and performing a transient treatment, It is possible to efficiently perform the treatment while maintaining the phosphoric acid concentration.

  When membrane treatment is performed while circulating the concentrate, the more times the concentrate is circulated, the more chances of acids other than phosphoric acid passing through the membrane in contact with the reverse osmosis membrane. The acid concentration can be further reduced. At this time, if the phosphoric acid concentration exceeds 15% by weight, membrane treatment cannot be performed. Therefore, diluting water is added to the concentrated solution for dilution and circulation, and reverse osmosis treatment is performed to further reduce the concentration of acids other than phosphoric acid. And a high-purity phosphoric acid concentrate can be recovered. As the dilution water, recovered water from which impurities have been removed from the permeated water can be circulated and used.

  The permeated water of the reverse osmosis device taken out from the permeate chamber side contains permeated acids such as phosphoric acid, nitric acid, and acetic acid, so that these acids and other impurities are removed from the permeated water of the reverse osmosis device. It is possible to recover pure water by removing by the above. In this case, an ion exchange device using an ion exchange resin can be employed as the impurity removal device. By passing permeate through the anion exchange resin layer, these acids and other anions are removed, and by passing through the cation exchange resin layer and the anion exchange resin layer, or a mixed bed thereof, acetic acid and nitric acid. Pure water can be recovered by removing acids other than phosphoric acid such as phosphoric acid, other anions, and remaining cations. The anion exchange resin used here is preferably an OH-type strongly basic or weakly basic anion exchange resin, and the cation exchange resin is preferably an H-type strongly acidic cation exchange resin.

  In a general ion exchange apparatus, regeneration of an ion exchange resin uses an acid as a regeneration agent for regeneration of a cation exchange resin, and alkali as a regeneration agent for regeneration of an anion exchange resin, but such a regeneration method requires a regeneration agent. In addition, it is preferable to employ an electric regeneration type ion exchange apparatus because of disadvantages such as generation of a regenerated waste liquid. An electroregenerative ion exchange device is a device in which an ion exchange resin layer is partitioned by a cation exchange resin membrane and an anion exchange resin membrane, and a cathode and an anode are arranged at both ends. Ion exchange is performed by passing liquid while regenerating by energization. In this case, a special operation and a regenerant for regeneration are not required, and acid and other impurities can be continuously taken out and pure water can be recovered. The ion exchange resin used in the electric regenerative ion exchange apparatus can be filled only with an anion exchange resin when the purpose is only to remove acids and other anions, but it is also intended to remove other remaining cations. In some cases, a mixed bed of cation exchange resin and anion exchange resin can be filled. Since the acid concentrate discharged by regeneration is a concentrate such as phosphoric acid, nitric acid, and acetic acid, it can be treated by a biological denitrification method.

On the other hand, the phosphoric acid concentrate taken out from the concentrate chamber side has most of the acid other than phosphoric acid such as nitric acid and acetic acid removed, but these are further removed to obtain the purity and concentration of the recovered phosphoric acid solution. In order to increase the efficiency, purification by post-treatment can be performed. As purification by post-treatment, it can be purified by removing acids other than phosphoric acid from the phosphoric acid concentrate by anion exchange. In this case, an anion exchange device is provided as a purification device, the concentrated solution is passed through the anion exchange resin layer, strong acid ions such as nitric acid are removed from the concentrated solution, and high concentration phosphorous containing almost no strong acid ions such as nitric acid is removed. The acid can be recovered. When the reverse osmosis apparatus circulates the concentrate to perform concentration, the purification apparatus can be provided in the concentrate circulatory line of the reverse osmosis apparatus, but is preferably provided in a line for extracting the concentrate from the circulation line. The anion exchange resin is preferably a strongly basic anion exchange resin of OH type or PO _{4 type} .

  If acetic acid remains in the phosphoric acid concentrate, acetic acid cannot be completely removed even with an anion exchange resin. In order to increase the purity and concentration of the recovered phosphoric acid solution by removing volatile components such as acetic acid. The concentrated phosphoric acid solution is evaporated and concentrated with an evaporating and concentrating apparatus, and volatile components are removed together with water and concentrated to recover high-concentration phosphoric acid containing almost no volatile components such as acetic acid. A known device such as a rotary evaporator can be used as the evaporative concentration device.

The phosphoric acid recovered by the above is useful as a recovered material, can be transported in a high concentration liquid state, and can be recovered as concentrated phosphoric acid with high purity. In this case, reverse osmosis treatment is carried out under the condition of pH 3 or lower, but since the phosphoric acid-containing water from which cations as raw water are removed is usually obtained in an acidic state of pH 3 or lower, by injecting a pH adjuster such as hydrochloric acid. It can be adjusted easily. The method and apparatus for recovery can be recovered as a phosphate concentrate by reverse osmosis treatment with a simple configuration and operation under conditions of pH 3 or lower and a phosphoric acid concentration of 1 to 15% by weight. It is. As a result, the amount of regenerant used and the amount of waste generated can be reduced, the processing cost can be reduced, and high-purity concentrated phosphoric acid and pure water can be recovered.

As described above, according to the present invention, phosphoric acid-containing water from which cations have been removed is supplied to a reverse osmosis device under conditions of pH 3 or lower and a phosphoric acid concentration of 1 to 15% by weight. The acid is permeated to the permeate chamber side with water, and the phosphoric acid is concentrated to the concentrate chamber side, and the phosphoric acid concentrate is recovered, so it is transported as a highly concentrated liquid with a simple configuration and operation. High-purity phosphoric acid that is possible and useful as a recovered product can be efficiently recovered from phosphoric acid-containing water at low cost.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart of a phosphoric acid recovery method and apparatus according to an embodiment. Reference numeral 1 denotes a raw water tank which stores raw water 1a. Reference numeral 2 denotes a cation exchange tower having a cation exchange resin layer 2a. Reference numeral 3 denotes an anion exchange tower having an anion exchange resin layer 3a. 4 is a concentrated liquid tank and stores the concentrated liquid 4a. A reverse osmosis device 5 is divided into a permeate chamber 5b and a concentrate chamber 5c by a reverse osmosis membrane 5a. 6 is an electric regenerative ion exchange device, in which a desalting chamber 6a and a concentration chamber 6b are partitioned by an anion exchange membrane 6c, and a cathode chamber 6e is partitioned by a cation exchange membrane 6d outside the desalting chamber 6a. The anode chamber 6g is partitioned on the outside by a cation exchange membrane 6f, the desalting chamber 6a and the concentration chamber 6b are filled with mixed-bed ion exchange layers 6h and 6i, the cathode chamber 6e has a cathode (-), and the anode chamber 6g has an anode. (+) Is provided. Reference numeral 7 denotes a recovered water tank that stores recovered water 7a. 8 is an evaporative concentration apparatus, which evaporates and separates volatile components together with water, and concentrates the phosphoric acid solution. Reference numeral 9 denotes a recovered phosphoric acid tank, which stores the recovered phosphoric acid solution 9a. Reference numeral 10 denotes a biological denitrification apparatus.

  In FIG. 1, P is a pressure pump, and constitutes a raw water supply unit together with a raw water tank 1, a cation exchange tower 2, an anion exchange tower 3 and a concentrated liquid tank 4, and among them, the cation exchange tower 2 and the anion exchange tower 3 A pre-processing device is configured. The electric regenerative ion exchange device 6 and the recovery water tank 7 constitute a permeate extraction unit, and among these, the electric regenerative ion exchange device 6 constitutes an impurity removal device. The evaporating and concentrating device 8 and the recovered phosphoric acid tank 9 constitute a concentrated phosphoric acid liquid take-out section, and among these, the evaporating and concentrating device 8 constitutes a purification device.

  In the phosphoric acid recovery apparatus, raw water 1a (phosphate ion-containing water) that has been subjected to removal of impurities by precipitation separation, filtration or the like as a pretreatment step is introduced from the line L1 into the raw water tank 1. The raw water 1a in the raw water tank 1 is introduced into the cation exchange tower 2 from the line L2 and passed therethrough, and cation exchange is performed in the cation exchange resin layer 2a to exchange and adsorb cations such as indium and other metal ions contained in the raw water. To remove. It is preferable to use an H-type strongly acidic cation exchange resin for the cation exchange resin layer 2a. When the cation exchange resin layer 2a is saturated, it is regenerated by passing a regenerant containing an acid such as hydrochloric acid from the line L3, and the eluted cations are recovered from the line L4.

  Decationized water, which is treated water of the cation exchange tower 2, is introduced into the anion exchange tower 3 from the line L5 and passed therethrough, and anion exchange is performed in the anion exchange resin layer 3a, so that perchloric acid and organic acid complex contained in the raw water are obtained. Anion such as is removed by exchange adsorption. For the anion exchange resin layer 3a, it is preferable to use a strongly basic anion exchange resin in the acid form. When the anion exchange resin layer 3a is saturated, it is regenerated by passing a regenerant containing an alkali such as sodium hydroxide from the line L6, and the eluted anion is recovered from the line L7. Thereafter, an acid such as phosphoric acid is passed through the line L6 to convert the anion exchange resin into an acid form.

The treated water of the anion exchange tower 3 is introduced into the concentrate tank 4 from the line L8. Obtained by cationic phosphate-containing water to remove the normal pH3 following acidic conditions as the raw water Runode, the reverse osmosis treatment in pH3 following conditions may be supplied to the reverse osmosis device 4 as it is. When adjusting the pH of raw water having a high pH, the phosphoric acid-containing water is obtained in a state close to pH 3, so that it can be easily adjusted by injecting a pH adjusting agent such as hydrochloric acid into the line L8 or the concentrate tank 4. it can.

Phosphoric acid-containing water from which cations in the concentrate tank 4 have been removed is pressurized with a pressure pump P and introduced into the concentrate chamber 5c of the reverse osmosis device 5 from the line L11, and membrane separation (reverse osmosis treatment) by the reverse osmosis membrane 5a. Then, an acid other than phosphoric acid such as nitric acid and acetic acid is allowed to permeate to the permeate chamber 5b side together with water to concentrate phosphoric acid to the concentrate chamber 5c side. When neutralizing phosphoric acid-containing water and performing reverse osmosis treatment, neither acid salts other than phosphoric acid such as nitric acid and acetic acid and phosphoric acid salts pass through the reverse osmosis membrane 5a and are concentrated. It is concentrated on the liquid chamber 5c side. On the other hand, when the reverse osmosis treatment is performed by introducing into the reverse osmosis device 5 under the condition of pH 3 or less without neutralizing the phosphoric acid-containing water from which cations have been removed , phosphoric acid permeates through the reverse osmosis membrane 5a. Although blocked and concentrated on the concentrated liquid chamber 5c side, acids other than phosphoric acid such as nitric acid and acetic acid permeate to the permeated liquid chamber 5b side together with water and are separated. Since the phosphoric acid-containing water introduced into the reverse osmosis device 5 is decationized, the reverse osmosis membrane 5a is not clogged, and the efficiency of the reverse osmosis treatment is maintained high.

  When the phosphoric acid-containing water as raw water obtained from the line L8 is obtained at a phosphoric acid concentration of 1 to 15% by weight, the membrane separation treatment can be performed as it is to perform separation by reverse osmosis, but the phosphoric acid concentration is 1% by weight. If the concentration is less than%, the membrane separation process is performed while circulating the concentrate taken out from the concentrate chamber 5c through the line L12 to the concentrate tank from the line L13, which is the circulation path, so that the phosphoric acid concentration becomes 1% by weight or more. It can be concentrated. In this case, concentration may be performed while circulating low-concentration phosphoric acid-containing water, and when the phosphoric acid concentration is concentrated to 1% by weight or more, a batch process may be performed in which the circulating fluid is replaced. While circulating the concentrated solution concentrated to 15% by weight, adding low-concentration treated phosphoric acid-containing water to the circulating concentrated solution, and removing the concentrated solution partly as a phosphoric acid concentrated solution from the line L14, apparently This is preferable because a one-time process can be performed.

  The permeate that has permeated into the permeate chamber 5b of the reverse osmosis device 5 is introduced from the line L15 into the desalting chamber 6a of the electric regenerative ion exchange device 6, and a voltage is applied between the anode (+) and the cathode (−). Desalting by ion exchange while regenerating electricity. As a result, the anion such as phosphoric acid, nitric acid, and acetic acid contained in the permeate and the remaining cations are removed by exchange adsorption for purification, and the treated water is taken out from the line L16 to the recovered water tank 7 and stored as recovered water 7a. . In the desalting chamber 6a, anions such as acids adsorbed on the mixed bed ion exchange layer 6h permeate to the concentration chamber 6b through the anion exchange membrane 6c and are adsorbed on the mixed bed ion exchange layer 6i. The anion adsorbed by the regeneration is eluted while flowing a part of the permeate to the concentration chamber 6b, and sent to the biological denitrification apparatus 10 from the line L18 to perform the biological denitrification treatment. Since the cations adsorbed on the mixed bed type ion exchange layer 6h permeate the cathode chamber 6e, the electrode solution flows from the anode chamber 6g through the line L19 to the cathode chamber 6e and is discharged from the line L20.

  A part of the concentrated liquid concentrated in the concentrated liquid chamber 5c of the reverse osmosis apparatus 5 and taken out from the line L14 is introduced into the evaporative concentration apparatus 8 and distilled, and separated by evaporating volatile components such as acetic acid together with water. And discharged from the line L21. The phosphoric acid concentrated liquid obtained by removing the volatile components by the evaporation concentrating apparatus 8 and concentrating is introduced into the recovered phosphoric acid tank 9 from the line L22 and stored as the recovered phosphoric acid liquid 9a. As the evaporative concentration apparatus 8, a known evaporative concentration apparatus such as a rotary evaporator can be used.

  Membrane separation (reverse osmosis treatment) in the reverse osmosis device 5 is carried out under conditions where the phosphoric acid-containing water has a pH of 3 or less and the phosphoric acid concentration is 1 to 15% by weight, so that acids other than phosphoric acid can be permeated with high permeability. However, in order to further reduce the concentration of acids other than phosphoric acid in the concentrate, these concentrates can be circulated to increase the opportunities for membrane separation. It is possible to increase the transmittance by increasing the opportunity for the acid to permeate. In this case, since the permeation of water also occurs, the circulating fluid is concentrated. For this reason, the removal rate of acids other than phosphoric acid can be raised by adding dilution water to the circulating concentrate and performing reverse osmosis treatment. As the dilution water, recovered water obtained by removing impurities from the permeated water can be used.

  For this reason, in FIG. 1, the recovered water 7a is supplied as dilution water from the recovered water tank 7 through the line L16 to the concentrated liquid tank 4 by the pump P2, and the circulating concentrated liquid is diluted to perform reverse osmosis treatment, thereby further increasing the phosphorus concentration. The concentration of an acid other than the acid can be lowered, and a high-purity phosphoric acid concentrate can be recovered. The amount of the recovered water 7a supplied to the concentrated liquid tank 4 is an amount that maintains the condition that the circulating concentrated liquid has a phosphoric acid concentration of 1 to 15% by weight. Thereby, it can prevent that the permeation | transmission efficiency of acids other than phosphoric acid by the highly concentrated circulating concentrate is reduced, and can raise the phosphoric acid purity of a concentrate.

The phosphoric acid solution 9a recovered by the above method is useful as a recovered product and can be transported practically because it is recovered as a high-concentration liquid, and can be recovered as highly purified concentrated phosphoric acid. In this case, the reverse osmosis treatment is performed under the condition of pH 3 or less, but the phosphoric acid-containing water from which the cation as raw water has been removed is usually obtained in an acidic state of pH 3 or less, so it may be supplied as it is, and it is particularly necessary to adjust the pH. Absent. The chemicals such as acid and alkali are limited to the cation regenerating agent in the cation exchange column 2 and the anion regenerating agent in the anion exchange column 3, and are not necessary for recovering phosphoric acid and purifying permeate. The method and apparatus for recovery can be recovered as a phosphate concentrate by reverse osmosis treatment with a simple configuration and operation under conditions of pH 3 or lower and a phosphoric acid concentration of 1 to 15% by weight. It is. Thereby, the amount of chemicals used and the amount of waste generated can be reduced, the processing cost can be reduced, and high-purity concentrated phosphoric acid and pure water can be recovered.

  In the phosphoric acid recovery method and apparatus of FIG. 1, phosphoric acid-containing water is supplied to the reverse osmosis device 5 under conditions of pH 3 or lower and phosphoric acid concentration of 1 to 15% by weight, and reverse osmosis treatment is performed by the reverse osmosis membrane 5a. By allowing permeation of acids other than phosphoric acid together with water to the permeate chamber 5b side, concentrating phosphoric acid to the concentrate chamber 5c side, and collecting pure water and phosphoric acid concentrate, the simple configuration and operation High-purity phosphoric acid and pure water that can be transported in a high-concentration liquid form and are useful as a recovered product can be efficiently recovered from phosphoric acid-containing water at low cost.

  The embodiment of the present invention is not limited to FIG. 1. For example, in order to further increase the purity of the recovered phosphoric acid solution, the second anion exchange column is placed upstream of the evaporation concentrator 8 in the line L14. It can also be provided. In this embodiment, the electric regeneration type ion exchange device 6 for purifying the permeate from the reverse osmosis device 5 is a simple electric regeneration in which the desalting chamber 6a and the concentration chamber 6b are partitioned by an anion exchange membrane 6c. Type ion exchange apparatus is used, and an anion exchange membrane and a cation exchange membrane are alternately arranged between a cathode chamber and an anode chamber to form a desalting chamber and a concentration chamber, and the desalting chamber It is also possible to use a normal electrodeionization apparatus in which the chamber is filled with an ion exchanger.

  Examples of the present invention will be described below. In each example, “%” indicates a percentage other than the blocking rate and “% by weight” unless otherwise indicated.

[Reference Examples 1 and 2]:
<Reverse osmosis treatment>:
The raw water having a conductivity of 122 mS / m and pH 2.4 containing 550 mg / L of phosphoric acid, 50 mg / L of nitric acid and 50 mg / L of acetic acid was passed through a reverse osmosis membrane ES-20 manufactured by Nitto Denko Corporation at 0.7 MPa. Then, reverse osmosis treatment was performed to obtain a 5-fold concentrated concentrate (brine) (Reference Example 1). On the other hand, a sodium hydroxide aqueous solution was poured into the raw water to adjust to pH 6, and the same test was performed (Reference Example 2). The results of the blocking rates of phosphoric acid, nitric acid and acetic acid are shown in Table 1. In Reference Example 1, phosphoric acid is blocked and nitric acid and acetic acid are permeated, whereas in Reference Example 2, all are blocked and permeated. I understand that I don't.

[Example 1]:
In Reference Example 1, FIG. 2 shows the relationship between the change in the concentration of phosphoric acid in the concentrated liquid and the inhibition rate of nitric acid when the circulation of the concentrated liquid is increased.

  As shown in FIG. 2, when the concentration of phosphoric acid in the concentrated solution is 1% by weight or less, the rejection of nitric acid is negative and decreases linearly. In particular, the concentration of phosphoric acid is 2% by weight or less, and the concentration of phosphoric acid is 4% by weight. It can be seen that the permeation of nitric acid is promoted at less than%. Similar results were obtained for acetic acid.

[Examples 2 and 3]:
In the apparatus of FIG. 1, a cation exchange column using the same reverse osmosis membrane as in Reference Example 1 and filled with the same phosphoric acid-containing water as in Reference Example 1 with an H-type strongly acidic cation exchange resin (DiaionSK1B, manufactured by Mitsubishi Chemical Corporation). And a phosphoric acid form weakly salted anion exchange resin (DiaionWA30, manufactured by Mitsubishi Chemical Corporation), and then supplied to the reverse osmosis unit and circulated without diluting the concentrated solution. And concentrated to 100 times (Example 2), and the recovered water obtained by desalting the permeate with an electric regenerative ion exchanger was supplied as dilution water to the concentrate tank (20% by volume of the amount of raw water supplied) and concentrated. Table 2 shows the solute concentration in the concentrated solution when the membrane was separated and concentrated 100 times (Example 3) while diluting and circulating the solution. Assuming that the concentrated solution obtained in Reference Example 1 was concentrated 100 times in total by distillation, the solute concentration obtained by calculation is also shown as Reference Example 1.

  From Table 2, by performing reverse osmosis treatment under the condition that the concentration of phosphoric acid in the concentrated solution is 1% by weight or more, the concentration of acids other than phosphoric acid in the concentrated solution decreases, and the concentrated solution is further diluted and circulated. It can be seen that by performing reverse osmosis treatment, the concentration of acids other than phosphoric acid in the concentrated solution is further reduced, and a high-purity phosphoric acid concentrated solution can be recovered.

  The present invention is a method and apparatus for recovering phosphoric acid and pure water from phosphoric acid-containing water, particularly valuable materials such as phosphoric acid and treated water from cleaning wastewater after etching a liquid crystal substrate, a wafer and other electronic devices. The present invention is applicable to a method and an apparatus for recovering phosphoric acid suitable for recovering pure water.

It is a flowchart of the phosphoric acid collection | recovery method and apparatus in embodiment. 3 is a graph showing the results of Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Raw water tank 1a Raw water 2 Cation exchange tower 2a Cation exchange resin layer 3 Anion exchange tower 3a Anion exchange resin layer 4 Concentrated liquid tank 4a Concentrated liquid 5 Reverse osmosis device 5a Reverse osmosis membrane 5b Permeate chamber 5c Concentrated liquid chamber 5 Anion exchange tower 5a, 7a Anion exchange resin layer 6 Electric regeneration type ion exchange device 6a Desalination chamber 6b Concentration chamber 6c Anion exchange membrane 6d, 6f Cation exchange membrane 6e Cathode chamber 6g Anode chamber 6h, 6i Mixed bed type ion exchange layer 7 Recovery water tank 7a Recovered water 8 Evaporative concentration device 9 Recovered phosphoric acid tank 9a Recovered phosphoric acid solution 10 Biological denitrification device

Claims (14)

A method of recovering phosphoric acid from phosphoric acid-containing water from which cations have been removed ,
Phosphoric acid-containing water from which cations have been removed is supplied to a reverse osmosis device under conditions of pH 3 or lower and a phosphoric acid concentration of 1 to 15% by weight, and membrane separation treatment is performed. A method of recovering phosphoric acid, characterized in that the phosphoric acid is concentrated on the side of the concentrate chamber, and the phosphoric acid concentrate is recovered. The method according to claim 1, further comprising the step of taking out the concentrate in the concentrate chamber and circulating it to the concentrate chamber, and performing reverse osmosis treatment by adding water to be treated containing phosphoric acid from which cations have been removed to the circulating concentrate.   The method according to claim 1 or 2, further comprising a step of taking out the concentrate in the concentrate chamber and circulating it to the concentrate chamber, and performing membrane separation treatment by adding dilution water to the circulating concentrate. Before supplying phosphate-containing water to remove cations reverse osmosis apparatus, a method according to any one of claims 1 to 3 to remove the impurities containing a cationic and A anion as a pretreatment.   The method according to claim 1, wherein impurities containing acid are removed from the permeated water of the reverse osmosis device to recover pure water.   6. The method according to claim 5, wherein the impurities are removed by an electric regenerative ion exchange apparatus.   The method according to any one of claims 1 to 6, wherein the phosphoric acid concentrate is concentrated by evaporation to remove volatile components together with water.   The method according to claim 3, wherein the dilution water is pure water obtained by removing impurities from the permeated water. An apparatus for recovering phosphoric acid from phosphoric acid-containing water from which cations have been removed ,
Phosphoric acid-containing water from which cations have been removed is subjected to a membrane separation treatment under conditions of pH 3 or lower and a phosphoric acid concentration of 1 to 15% by weight, and an acid other than phosphoric acid is allowed to permeate to the permeate chamber side together with water. A reverse osmosis device for concentrating to the concentrate chamber side;
A phosphoric acid-containing water supply unit that supplies phosphoric acid-containing water from which cations have been removed to the concentrated liquid chamber side of the reverse osmosis device under conditions of pH 3 or lower and a phosphoric acid concentration of 1 to 15% by weight;
A permeate extractor for extracting permeate from the permeate chamber side of the reverse osmosis device;
A concentrated phosphoric acid solution extraction section for extracting the concentrated phosphoric acid solution from the concentrated liquid chamber side of the reverse osmosis device ;
And a circulation path for circulating the concentrated phosphoric acid solution extracted from the concentrated phosphoric acid solution extraction unit to the concentrated liquid chamber side. The apparatus of claim 9, further comprising a dilution water supply unit to add dilution water to the concentrated liquid circulating through the circulation path. The apparatus of claim 9 or 10, wherein a pre-processing device in the raw water supply unit for removing impurities including cationic and A anion.   The apparatus according to claim 9, further comprising an impurity removing device that removes impurities including acid from the permeated water of the reverse osmosis device.   The apparatus according to claim 12, wherein the impurity removing apparatus is an electric regenerative ion exchange apparatus.   The apparatus according to any one of claims 9 to 13, further comprising an evaporating and concentrating device for evaporating and concentrating the phosphoric acid concentrated solution to remove volatile components together with water and concentrating.

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