JP2009233607A - Method and apparatus for recovering phosphoric acid from phosphoric acid-containing water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phosphoric acid recovering method capable of efficiently recovering phosphoric acid of high purity, which can be transported in a liquid state of high concentration by a simple constitution and simple operation and is useful as a recovered substance, from phosphoric acid-containing water at a low cost, and a phosphoric acid recovering apparatus. <P>SOLUTION: The phosphoric acid-containing water with a pH of 3 or below and a phosphoric acid concentration of 1-15 wt.% is supplied to a reverse osmosis device 4 equipped with a reverse osmosis membrane 4a with a desalting ratio of 50-90% to be subjected to reverse osmosis treatment and an acid other than phosphoric acid is permeated toward a permeated liquid chamber 4c while phosphoric acid is concentrated on the side of a concentrated liquid chamber 4b. The permeated liquid is desalted to recover pure water 7a and a volatile component is removed from the concentrated liquid along with water to recover a concentrated phosphoric acid liquid 9a. <P>COPYRIGHT: (C)2010,JPO&INPIT

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, the increase in water-soluble ions due to the chemicals added in a large amount in the coagulation sedimentation treatment increases the dynamic cost due to the increase in the operating pressure of the reverse osmosis membrane process, the quality of the treated water, the generation of scale, The ion exchange method has led to an increase in the amount of regenerant used.

In Patent Document 1 (Japanese Patent Publication 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.
Japanese Patent Publication No. 2006-75820

  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,
A reverse osmosis device equipped with a reverse osmosis membrane with a salt desalination rate of 50 to 90% is supplied with phosphoric acid-containing water under conditions of pH 3 or lower to perform membrane separation treatment, and permeates acids other than phosphoric acid together with water. A method for recovering phosphoric acid, characterized by allowing phosphoric acid to permeate to the liquid chamber side, concentrating phosphoric acid to the concentrate chamber side, and recovering the phosphoric acid concentrate.
(2) A method for recovering phosphoric acid from phosphoric acid-containing water,
Membrane separation treatment is performed by supplying phosphoric acid-containing water to a reverse osmosis device having a salt desalination rate of 50 to 90% under conditions of pH 3 or lower and a phosphoric acid concentration of 1 to 15% by weight. A method for recovering phosphoric acid, wherein an acid other than phosphoric acid is allowed to permeate to the permeate chamber side together with water and the phosphoric acid is concentrated to the concentrate chamber side to recover the phosphoric acid concentrate.
(3) The above-described (1) or (2), which has a process of taking out the concentrate from the concentrate chamber and circulating it to the concentrate chamber, and performing reverse osmosis treatment by adding the phosphoric acid-containing water to be treated to the circulating concentrate The method described.
(4) The method according to any one of (1) to (3) above, wherein impurities containing acid are removed from the permeated water of the reverse osmosis device to recover pure water.
(5) An apparatus for recovering phosphoric acid from phosphoric acid-containing water,
A reverse osmosis membrane with a salt desalting rate of 50 to 90% is provided, and phosphoric acid-containing water is subjected to membrane separation treatment under the condition of pH 3 or lower, 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 the acid toward the concentrate chamber;
A raw water supply unit for supplying phosphoric acid-containing water to the concentrated liquid chamber side of the reverse osmosis membrane device under a pH of 3 or less;
A permeate extractor for extracting permeate from the permeate chamber side of the reverse osmosis device;
A phosphoric acid recovery apparatus, comprising: a concentrated phosphoric acid solution extraction unit that extracts a concentrated phosphoric acid solution from the concentrated liquid chamber side of the reverse osmosis device.
(6) An apparatus for recovering phosphoric acid from phosphoric acid-containing water,
A reverse osmosis membrane having a salt desalination rate of 50 to 90% is provided, and phosphoric acid-containing water is subjected to membrane separation treatment under conditions of pH 3 or less and phosphoric acid concentration of 1 to 15% by weight to remove acids other than phosphoric acid. And a reverse osmosis device that permeates the permeate chamber side and concentrates phosphoric acid to the concentrate chamber side,
A phosphoric acid-containing water supply unit for supplying phosphoric acid-containing water 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 take-out section for taking out the concentrated phosphoric acid solution from the concentrated solution chamber side of the reverse osmosis device, and a circulation path for circulating the concentrated phosphoric acid solution taken out from the concentrated phosphoric acid solution take-out portion to the concentrate solution chamber side. Characteristic phosphoric acid recovery device.
(7) The apparatus according to (5) or (6), further including a dilution water supply unit that adds dilution water to the concentrate circulating in the circulation path.
(8) The device according to any one of (5) to (7), further including an impurity removing device that removes impurities including acid from the permeated water of the reverse osmosis device.

  In the present invention, the phosphoric acid-containing water to be treated can be used without limitation as long as it contains phosphoric acid. However, phosphate ions are contained in an amount of 50 to 10,000 mg / L, particularly 50 to 2000 mg / L. However, acidic water having a pH of 3 or less, particularly 2.8 or less, and in each case 1 or more, particularly 1.8 or more is preferable as a treatment target. In addition to phosphate ions, nitrate ions, acetate ions And other impurities, and other anions, cations such as metal ions, and other impurities may be contained. 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 this invention, the reverse osmosis membrane used for the reverse osmosis apparatus for performing a membrane separation process is a reverse osmosis membrane with a salt desalination rate of 50 to 90%. Reverse osmosis membranes allow water to permeate by osmotic pressure, or conversely, supply salt-containing water at a pressure higher than the osmotic pressure to perform membrane separation, permeate water as a solvent to the permeate side, salinity, organic matter It is a membrane that does not allow other solutes to permeate and remains on the concentrate side for desalting. The reverse osmosis membrane used for normal water treatment and seawater desalination is generally a reverse osmosis membrane having a high salt rejection rate of 99% or more. Examples of low desalting rate membranes with a salt desalting rate of less than 99% include nanofiltration membranes with a salt desalting rate of 70% or less. These membranes are mainly used to separate relatively high molecular organic substances. Although not used for separation of salt, those having a salt desalting rate of 50 to 90% can be used as the reverse osmosis membrane of the present invention. The salt desalting rate is a value measured by supplying 0.05% by weight saline to a reverse osmosis membrane at an operating pressure of 0.75 MPa and separating the membrane at a water temperature of 25 ° C. and a recovery rate of 15%.

  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.

  The reverse osmosis membrane used in the present invention is a membrane marketed as a reverse osmosis membrane having a salt desalting rate of 50 to 90%, such as the nanofiltration membrane (for example, NF-90-400 manufactured by Dow Water Solution). A membrane having a salt desalting rate falling within the above range can be used as it is. However, when a reverse osmosis membrane having a desalting rate other than that is used, a known reverse osmosis membrane having a high desalting rate (for example, Japanese Patent Application Laid-Open No. 102624 [0018] to [0030] can be obtained by reducing the desalination rate by the desalination rate adjusting step. As a method of adjusting the desalting rate, there is a method of adjusting to a low desalting rate by hydrolysis, oxidant treatment or the like. Examples of the hydrolysis treatment include a method of immersing in an alkali or acid such as a 1 to 4% by weight sodium hydroxide aqueous solution for 5 to 40 hours. Examples of the oxidizing agent treatment include a method of immersing in 1 to 4% by weight of hydrogen peroxide solution for 5 to 40 hours.

  In the present invention, in order to recover phosphoric acid from phosphoric acid-containing water, phosphoric acid-containing water is supplied to a reverse osmosis device having a reverse osmosis membrane having a salt desalting rate of 50 to 90% under a pH of 3 or less. Then, a membrane separation process is performed. In this case, it is preferable to carry out the membrane separation treatment by supplying them under conditions of pH 3 or less and a phosphoric acid concentration of 1 to 15% by weight. In the present invention, it is preferable to remove impurities including cations and / or anions as pretreatment before supplying phosphoric acid-containing water to the reverse osmosis membrane device. In this case, solid separation by precipitation separation, filtration, etc., removal of cations such as metal ions by cation exchange resin, and removal of anions such as perchloric acid, molybdic acid and organic acid complexes by anion exchange resin are performed. be able to. 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 may cause clogging of the reverse osmosis (RO) membrane in the membrane separation process, and perchloric acid and molybdic acid may cause membrane damage when the concentration is high. Therefore, it is preferable to remove these cations and anions because clogging and 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 such as perchloric acid.

  In the present invention, the reverse osmosis device (hereinafter sometimes referred to as RO device) in the membrane separation step is divided into a permeate chamber and a concentrate chamber by a reverse osmosis (RO) membrane having a salt desalination rate of 50 to 90%. Compartmented, the phosphoric acid-containing water is supplied to the concentrated liquid chamber side under the condition of pH 3 or less, and preferably under the condition of the phosphoric acid concentration of 1 to 15% by weight, and the reverse osmosis membrane treatment is performed. It is configured to allow acid to permeate to the permeate chamber side along with water and to concentrate phosphoric acid to the concentrate chamber side. On the concentrated solution chamber side of the reverse osmosis membrane 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 side of the permeate chamber of the reverse osmosis membrane 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 extraction unit to the concentrated liquid chamber side is formed between the concentrated phosphoric acid solution extraction unit and the phosphoric acid-containing water supply unit.

  In the present invention, in the membrane separation step, the phosphoric acid-containing water is reversed under a pH of 3 or less, preferably under a condition where the phosphoric acid concentration is 1 to 15% by weight, and more preferably under a condition where the concentration is 2 to 10% by weight. The osmosis membrane device is supplied, and membrane separation (reverse osmosis) treatment is performed with a reverse osmosis membrane having a salt desalination rate of 50 to 90%. When the phosphoric acid-containing water is obtained in a pH of 3 or less, it can be supplied to the reverse osmosis membrane device 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. May be. 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 at a pH of 3 or less, it can be supplied to a reverse osmosis membrane device without adjusting pH, and the amount of pH adjuster added even when adjusting pH Will be less.

  When phosphoric acid-containing water is obtained at a phosphoric acid concentration of 1 to 15% by weight, the membrane separation treatment can be carried out as it is to perform separation by reverse osmosis, but when the phosphoric acid concentration is less than 1% by weight, the circulation path By carrying out a membrane separation process while circulating the concentrate through, the phosphoric acid concentration can be concentrated to 1% by weight or more. Alternatively, the concentration process may be performed in advance by a concentration apparatus such as a separately provided RO apparatus, or the recovered high concentration phosphoric acid solution may be added.

  When the phosphoric acid concentration is concentrated to 1% by weight or more by performing membrane separation treatment while circulating the concentrate through the circulation path, the phosphoric acid concentration is 1% by weight by concentrating while circulating the low-concentration phosphoric acid-containing water. A batch-type process may be performed in which the circulating solution is replaced at the time when it is concentrated as described above. However, while circulating the concentrated solution concentrated to a phosphoric acid concentration of 1 to 15% by weight, It is preferable to add treated phosphoric acid-containing water and take out the concentrated solution partly as a phosphoric acid concentrated solution because an apparently transient treatment 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 membrane separation treatment is performed by supplying phosphoric acid-containing water to a reverse osmosis device under a pH of 3 or less, acids other than phosphoric acid such as nitric acid and acetic acid permeate the reverse osmosis membrane together with water and pass through the permeate chamber. 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. In this case, even if the membrane separation treatment is performed with a reverse osmosis membrane having a salt desalting rate of 50 to 90%, the removal rate of phosphoric acid does not decrease so much, but the permeability of acetic acid and nitric acid increases and the separability improves. That is, if the salt desalting rate is 50% or more, the transmittance of phosphoric acid is within 10%, and phosphoric acid is efficiently concentrated. The permeability of acetic acid and nitric acid increases as the salt desalting rate decreases. For this reason, phosphoric acid is efficiently purified and concentrated, and purified and concentrated concentrated phosphoric acid can be recovered with high purity.

  The concentrated liquid on the concentrated liquid chamber side may be passed through temporarily or may be circulated to increase the concentration rate. A small amount of acid other than phosphoric acid remains in the concentrate, but when the membrane separation treatment is performed under the condition of phosphoric acid concentration of 1 to 15% by weight, the blocking rate of acids other than phosphoric acid is lowered and the transmittance is reduced. Since it becomes high, a highly purified phosphoric acid concentrate can be recovered. When the membrane separation treatment is performed by supplying phosphoric acid-containing water to the reverse osmosis device under conditions of pH 3 or lower and phosphoric acid concentration of 1 to 15% by weight, the pressure of the phosphoric acid-containing water supplied to the reverse osmosis device is 0. The pressure can be 3 to 5 MPa, preferably 0.5 to 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. The reason why phosphoric acid is strongly blocked by the reverse osmosis membrane at low pH is that phosphoric acid is trivalent and has a large molecular weight, and at low pH, phosphoric acid becomes a form of heavy phosphoric acid, resulting in a large molecular weight. This is probably because the rejection rate has increased. In addition, the reason why phosphoric acid is strongly blocked by reverse osmosis membranes at low pH and high concentration is considered to be because phosphoric acid is polymerized into larger molecules when the phosphoric acid concentration is increased. .

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). The same applies to the salt desalting rate.
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 an example using a stainless steel flat membrane test apparatus described later, the concentration rate is calculated as C ₁ = C ₂ because the concentrated liquid chamber is stirred.

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 performing membrane treatment while circulating the concentrate, the greater the number of times the concentrate is circulated, the greater the opportunity for acids other than phosphoric acid to contact the reverse osmosis membrane and permeate the membrane. The acid concentration can be further reduced. At this time, if the phosphoric acid concentration exceeds 15% by weight, the osmotic pressure (operating pressure) becomes too high, and membrane treatment cannot be performed, so dilute water is added to the concentrate, diluted and circulated, and reverse osmosis treatment is performed. Furthermore, the concentration of acids other than phosphoric acid can be lowered, 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 membrane device taken out from the permeate chamber side contains permeated acids such as phosphoric acid, nitric acid, and acetic acid. Therefore, these acids and other impurities are impurities from the permeated water of the reverse osmosis membrane device. Pure water can be recovered by removing the water with a removing device. 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, in the regeneration of an ion exchange resin, an acid is used for the regeneration of the cation exchange resin and an alkali is used as the regeneration agent for the regeneration of the anion exchange resin. However, 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 apparatus is an apparatus 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 concentrated liquid taken out from the concentrated liquid chamber side has most of acids other than phosphoric acid such as nitric acid and acetic acid removed, but further removing them to increase the purity and concentration of the recovered phosphoric acid liquid. Purification by post-treatment can be performed to enhance. 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. To remove volatile components such as acetic acid and increase the purity and concentration of the recovered phosphoric acid solution 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 performed under the condition of pH 3 or less, but since phosphoric acid-containing water as raw water is usually obtained in an acidic state of pH 3 or less, it is easily adjusted by injecting a pH adjuster such as hydrochloric acid. be able to.

  In addition, the method and apparatus for recovery is a reverse osmosis membrane having a salt desalting rate of 50 to 90% under a pH of 3 or less, and in some cases a phosphate concentration of 1 to 15% by weight, with a simple configuration and operation. By performing a membrane separation treatment (reverse osmosis treatment), it is possible to recover the phosphoric acid concentrate. 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, a reverse osmosis apparatus including a reverse osmosis membrane having a salt desalination rate of 50 to 90% is supplied with phosphoric acid-containing water under a pH of 3 or less to perform a membrane separation treatment. By passing acid other than phosphoric acid together with water to the permeate chamber side, concentrating phosphoric acid to the concentrate chamber side and recovering the phosphoric acid concentrate, it is possible to obtain a highly concentrated liquid with a simple configuration and operation. High-purity phosphoric acid that can be transported and is useful as a recovered product can be efficiently recovered from phosphoric acid-containing water at low cost.

  Further, according to the present invention, phosphoric acid-containing water is supplied to a reverse osmosis device having a reverse osmosis membrane having a salt desalting rate of 50 to 90% under conditions of pH 3 or less and a phosphoric acid concentration of 1 to 15% by weight. The membrane separation process is performed, and an acid other than phosphoric acid is allowed to permeate to the permeate chamber side together with water, the phosphoric acid is concentrated to the concentrate chamber side, and the phosphoric acid concentrate is recovered. By operation, high-purity phosphoric acid that can be transported in a high-concentration liquid state and useful as a recovered product can be efficiently recovered from phosphoric acid-containing water at a lower cost.

  An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a flow diagram of a phosphoric acid recovery apparatus in one 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. 3 is a concentrate tank, and stores the concentrate 3a. A reverse osmosis device 4 is divided into a permeate chamber 4b and a concentrate chamber 4c by a reverse osmosis membrane 4a having a salt desalting rate of 50 to 90%. Reference numeral 5 denotes an anion exchange tower having an anion exchange resin layer 5a. Reference numeral 7 denotes a recovered water tank that stores recovered water 7a. Reference numeral 5b denotes a second anion exchange tower having an anion exchange resin layer 5c. 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.

  In FIG. 1, P is a pressurization pump and comprises a raw | natural water supply part with the raw | natural water tank 1, the cation exchange tower 2, and the concentrate tank 3, and among these, the cation exchange tower 2 comprises a pre-processing apparatus. The anion exchange tower 5 and the recovered water tank 7 constitute a permeate take-out section, and among these, the anion exchange tower 5 constitutes an impurity removing device. The second anion exchange column 5b, 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 second anion exchange column 5b and the evaporating and concentrating device 8 constitute a purification device.

  In the phosphoric acid recovery apparatus, the raw water 1a (phosphate ion-containing water) having a pH of 3 or less and a phosphoric acid concentration of 1 to 15% by weight from which impurities have been removed by precipitation separation, filtration or the like as a pretreatment step is supplied from the line L1. Introduce 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 cations such as aluminum, indium and other metal ions contained in the raw water. Adsorb and 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 concentrate tank 3 from the line L5 and stored. Phosphoric acid-containing water as raw water is usually obtained in an acidic state of pH 3 or lower, and even when the pH is high, acid is generated by cation exchange as a pretreatment to a pH of 3 or lower. What is necessary is just to supply to the reverse osmosis apparatus 4 as it is in reverse osmosis processing. 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 L5 or the concentrated liquid tank 3. it can.

  The decationized water (concentrate 3a) in the concentrate tank 3 is pressurized by the pressure pump P and introduced into the concentrate chamber 4c of the reverse osmosis device 4 from the line L6, and reverse osmosis with a salt desalination rate of 50 to 90%. Membrane separation processing (reverse osmosis processing) is performed by the membrane 4a, and acids other than phosphoric acid such as nitric acid and acetic acid are permeated to the permeate chamber 4b side together with water, and phosphoric acid is concentrated to the concentrate chamber 4c 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 4a and are concentrated. It is concentrated on the liquid chamber 4c side. On the other hand, when the reverse osmosis treatment is performed by introducing the phosphoric acid-containing water into the reverse osmosis device 4 under the condition of pH 3 or less, the phosphoric acid is prevented from permeating by the reverse osmosis membrane 4a and concentrated. Although concentrated to the liquid chamber 4c side, acids other than phosphoric acid such as nitric acid and acetic acid permeate to the permeate liquid chamber 4b side together with water and are separated. In this case, even if the membrane separation treatment is performed with the reverse osmosis membrane 4a having a salt desalting rate of 50 to 90%, the removal rate of phosphoric acid is not lowered so much, the permeability of acetic acid and nitric acid is increased, and the separability is improved. . Since the phosphoric acid-containing water introduced into the reverse osmosis device 4 is decationized, the reverse osmosis membrane 4a is not clogged, and the efficiency of the reverse osmosis treatment is maintained high.

  The permeate that has permeated into the permeate chamber 4b of the reverse osmosis device 4 is introduced into the anion exchange column 5 from the line L7, and is passed through the anion exchange resin layer 5a to exchange anions. Thereby, anions other than phosphate ions such as nitric acid and acetic acid contained in the permeate are removed by exchange adsorption for purification, and the treated water is taken out from the line L8 to the recovered water tank 7 and stored as recovered water 7a. The anion exchange column 5 uses an anion exchange resin layer 5a filled with an OH type strongly basic anion exchange resin, but adopts a double layer or mixed bed type with an H type cation exchange resin to remove impurities other than anions. May be. When the anion exchange resin layer 5a is saturated with anions other than phosphate ions, a regenerant containing an alkali such as a 2 to 10% by weight aqueous alkali solution such as sodium hydroxide or potassium hydroxide is passed through the line L9. And the eluted salt is discharged from line L10. When a cation exchange resin is used, it is regenerated by passing a regenerant containing acid.

The concentrated liquid concentrated in the concentrated liquid chamber 4c of the reverse osmosis device 4 is introduced into the second anion exchange column 5b through the line L11 and passed therethrough, and anion exchange is performed in the anion exchange resin layer 5c. Then, anions other than phosphate ions such as acetic acid are exchanged and removed to perform purification. In this case, the anion exchange resin layer 5c uses a strongly basic anion exchange resin of OH type or PO _{4 type} . Since the selectivity of anions other than phosphate ions such as nitric acid with respect to anion exchange resins is higher than phosphate ions in a low pH range, separation from phosphate ions is easy. When the anion exchange resin layer 5c is saturated with anions other than phosphate ions, the regeneration agent containing alkali is passed through the line L12 for regeneration, and the eluted salt is discharged from the line L13.

  When the phosphoric acid solution from which anions other than phosphate ions have been removed in the second anion exchange column 5b still contains a volatile component such as acetic acid, it is introduced into the evaporation concentrator 8 from the line L14 and distilled, and is volatile with water. The components are evaporated and separated and discharged from line L15. The concentrated phosphoric acid solution obtained by removing the volatile components by the evaporation concentrating device 8 is introduced into the recovered phosphoric acid tank 9 from the line L16 and stored as the recovered phosphoric acid solution 9a. As the evaporative concentration apparatus 8, a known evaporative concentration apparatus such as a rotary evaporator can be used. The concentrate in the concentrate chamber 4c of the reverse osmosis device 4 is circulated from the line L17 or L18 to the concentrate tank 3 to increase the concentration rate, and can be stored as the concentrate 3a.

  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, reverse osmosis treatment is performed under the condition of pH 3 or less, but phosphoric acid-containing water as raw water is usually obtained in an acidic state of pH 3 or less, and even when the pH is high, pH 3 or less is obtained by cation exchange as pretreatment. Therefore, in order to perform the treatment under the condition of pH 3 or lower, it may be supplied as it is, and it is not necessary to adjust the pH. 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 5 and the second anion exchange column 5b, and are not necessary for recovering phosphoric acid. The method and apparatus for recovery can be recovered as a phosphoric acid concentrate by reverse osmosis treatment under conditions of pH 3 or less with a simple configuration and operation. 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, phosphoric acid-containing water is supplied to the reverse osmosis device 4 under a pH of 3 or less, and reverse osmosis treatment is performed by the reverse osmosis membrane 4a having a salt desalting rate of 50 to 90%. Is allowed to permeate to the permeate chamber 4b side together with water, phosphoric acid is concentrated to the concentrate chamber 4c side, and pure water and phosphoric acid concentrate are recovered, so that a high concentration liquid can be obtained with a simple configuration and operation. High-purity phosphoric acid and pure water that are transportable and useful as a recovered material can be efficiently recovered from phosphoric acid-containing water at low cost.

  Next, another embodiment of the present invention will be described with reference to FIG. FIG. 2 is a flowchart of a phosphoric acid recovery method and apparatus according to another 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. 3 is a concentrate tank, and stores the concentrate 3a. A reverse osmosis device 4 is divided into a permeate chamber 4b and a concentrate chamber 4c by a reverse osmosis membrane 4a having a salt desalting rate of 50 to 90%. Reference numeral 5 denotes an anion exchange tower having an anion exchange resin layer 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. An anode chamber 6g is partitioned on the outside by a cation exchange membrane 6f, mixed-bed ion exchange layers 6h and 6i are provided in the desalting chamber 6a and the concentration chamber 6b, a cathode (-) in the cathode chamber 6e, and an anode in the anode chamber 6g. (+) 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. 2, P is a pressure pump, and constitutes a raw water supply unit together with the raw water tank 1, the cation exchange tower 2, the anion exchange tower 5 and the concentrated liquid tank 4, and among these, the cation exchange tower 2 and the anion exchange tower 5 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 into the raw water tank 1 from a line L21. The raw water 1a in the raw water tank 1 is introduced into the cation exchange tower 2 from the line L22 and passed therethrough, and is exchanged with the cation exchange resin layer 2a to exchange cations such as aluminum, indium and other metal ions contained in the raw water. Adsorb and 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 L23, and the eluted cations are recovered from the line L24.

  Decationized water, which is the treated water of the cation exchange tower 2, is introduced into the anion exchange tower 5 from the line L25 and passed therethrough, and anion exchange is performed in the anion exchange resin layer 5a, so that perchloric acid, molybdic acid, Anions such as organic acid complexes are removed by exchange adsorption. It is preferable to use a phosphoric acid strong basic anion exchange resin for the anion exchange resin layer 5a. When the anion exchange resin layer 5a is saturated, it is regenerated by passing a regenerant containing an alkali such as sodium hydroxide through the line L26, and the eluted anion is recovered from the line L27. Thereafter, an acid such as phosphoric acid is passed through the line L26 to make the anion exchange resin into phosphoric acid form.

  The treated water of the anion exchange column 5 is introduced into the concentrate tank 3 from the line L28. Phosphoric acid-containing water as raw water is usually obtained in an acidic state having a pH of 3 or less, and can be supplied to the reverse osmosis device 4 as it is in order to perform reverse osmosis treatment under a pH of 3 or less. 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 L28 or the concentrated liquid tank 3. it can.

  The phosphoric acid-containing water in the concentrate tank 3 is pressurized by the pressure pump P and introduced into the concentrate chamber 4c of the reverse osmosis device 4 from the line L31, and the membrane is separated by the reverse osmosis membrane 4a having a salt desalination rate of 50 to 90%. Separation (reverse osmosis treatment) is performed, and acids other than phosphoric acid such as nitric acid and acetic acid are permeated to the permeate chamber 4b side together with water to concentrate phosphoric acid to the concentrate chamber 4c side. When the phosphate-containing water is neutralized and subjected to reverse osmosis treatment in a neutral state, neither the salt of acid other than phosphoric acid, such as nitric acid or acetic acid, nor phosphate passes through the reverse osmosis membrane 4a, and the concentrated solution It is concentrated on the side of the chamber 4c. On the other hand, when the reverse osmosis treatment is performed by introducing the phosphoric acid-containing water into the reverse osmosis device 4 under the condition of pH 3 or less, the phosphoric acid is prevented from permeating by the reverse osmosis membrane 4a and concentrated. Although concentrated to the liquid chamber 4c side, acids other than phosphoric acid such as nitric acid and acetic acid permeate to the permeate liquid chamber 4b side together with water and are separated. In this case, even if the membrane separation treatment is performed with the reverse osmosis membrane 4a having a salt desalting rate of 50 to 90%, the removal rate of phosphoric acid is not lowered so much, the permeability of acetic acid and nitric acid is increased, and the separability is improved. . Since the phosphoric acid-containing water introduced into the reverse osmosis device 4 is decationized, the reverse osmosis membrane 4a 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 L28 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. When the concentration is less than%, the concentrated solution taken out from the concentrated solution chamber 4c through the line L32 is subjected to membrane separation treatment while circulating from the line L33, which is a circulation path, to the concentrated solution tank 3, so that the phosphoric acid concentration is 1% by weight or more. 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 concentrate concentrated to 15% by weight, adding low-concentration treated phosphoric acid-containing water to the circulating concentrate and removing the concentrate partly from the line L34 as a phosphoric acid concentrate, it appears that This is preferable because a one-time process can be performed.

  The permeate that has permeated through the permeate chamber 4b of the reverse osmosis device 4 is introduced from the line L35 into the desalting chamber 6a of the electric regenerative ion exchanger 6 and a voltage is applied between the anode (+) and the cathode (−). Desalting by ion exchange while regenerating electricity. Thus, 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 L36 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 L38 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 L39 to the cathode chamber 6e and is discharged from the line L40.

  A part of the concentrated liquid concentrated in the concentrated liquid chamber 4c of the reverse osmosis apparatus 4 and taken out from the line L34 is introduced into the evaporative concentration apparatus 8 and distilled, and separated by evaporating volatile components such as acetic acid together with water. , Discharged from the line L41. The phosphoric acid concentrate obtained by removing the volatile components by the evaporation concentrator 8 and concentrating is introduced into the recovered phosphoric acid tank 9 from the line L42 and stored as the recovered phosphoric acid solution 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 apparatus 4 is performed 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 at a high transmittance. The concentration of acids other than phosphoric acid in the concentrate can be further reduced by performing membrane separation treatment with the reverse osmosis membrane 4a having a salt desalting rate of 50 to 90%. Thus, high purity phosphoric acid can be recovered. In addition, by circulating the concentrate to increase membrane separation opportunities, it is possible to increase the permeation rate by increasing the opportunity for these acids to permeate. Will be. For this reason, the removal rate of acids other than phosphoric acid can be raised and high-purity phosphoric acid can be collect | recovered by adding dilution water to the concentrate which circulates, and performing a reverse osmosis process. As the dilution water, recovered water obtained by removing impurities from the permeated water can be used.

  For this reason, in FIG. 2, the recovered water 7a is supplied as dilution water from the recovered water tank 7 to the concentrated liquid tank 3 through the line L43 by the pump P2, and the circulating concentrated liquid 3a is diluted to perform reverse osmosis treatment. The concentration of acids other than phosphoric 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 3 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 recovered 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 lower, but the phosphoric acid-containing water as the raw water is usually obtained in an acidic state of pH 3 or lower, so it may be supplied as it is, and it is not necessary to adjust the pH. 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. 2, phosphoric acid-containing water is supplied to the reverse osmosis device 4 under conditions of pH 3 or lower and a phosphoric acid concentration of 1 to 15% by weight, and the salt desalination rate is 50 to 90%. The reverse osmosis treatment is performed by the reverse osmosis membrane 4a, and an acid other than phosphoric acid is permeated to the permeate chamber 4b side together with water, and phosphoric acid is concentrated to the concentrate chamber 4c side. By collecting it, it can be transported in a high-concentration liquid state with a simple configuration and operation, and high-purity phosphoric acid and pure water, which are useful as recovered materials, can be efficiently recovered from phosphoric acid-containing water at low cost. can do.

  The embodiment of the present invention is not limited to FIGS. 1 and 2. For example, in order to further increase the purity of the recovered phosphoric acid solution in FIG. 2, the second anion exchange column is evaporated and concentrated in line L34. It can also be provided in front of the device 8. In the present embodiment, the electric regeneration type ion exchange device 6 for purifying the permeate from the reverse osmosis device 4 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 percentage other than the blocking rate, and weight% unless otherwise indicated.

[Examples 1-3, Comparative Examples 1-2]:
A reverse osmosis membrane (flat membrane) with a different salt desalting rate is punched into a circle with a diameter of 32 mm, and a flat membrane test device simulating the reverse osmosis device of FIGS. 1 and 2 is a small diameter flat made of stainless steel (SUS304) with an inner diameter of 32 mmφ. The membrane cell was mounted with an effective membrane diameter of 29 mmφ supported by a sintered porous plate, phosphoric acid-containing water was supplied to the concentrate chamber, and membrane separation was performed while stirring and circulating the concentrate in the concentrate chamber. NF-270-400 made by Dow Water Solution as a reverse osmosis membrane with a salt desalination rate of 45%, NF-90-400 made by Dow Water Solution as a reverse osmosis membrane with a salt desalination rate of 90%, salt desalination rate A reverse osmosis membrane ES-20 manufactured by Nitto Denko Corporation was used as a 99.5% reverse osmosis membrane. As a reverse osmosis membrane with other salt desalination rate, reverse osmosis membrane ES-20 (salt desalination rate 99.5%) manufactured by Nitto Denko Co., Ltd. What adjusted the time and adjusted so that it might become a salt desalting rate, and adjusted the salt desalting rate was used.

  As phosphoric acid-containing water, raw water having a conductivity of 830 mS / m and pH 0.5 containing phosphoric acid 2500 mg / L, nitric acid 250 mg / L, and acetic acid 250 mg / L is supplied to the concentrated liquid chamber of the flat membrane test apparatus at a water temperature of 25 ° C. Supply at an operating pressure of 1.8 MPa and a flow rate of 1 mL / min, concentrate and concentrate the concentrated solution by performing membrane separation at a recovery rate of 80% while stirring and circulating, and use a back pressure valve to concentrate the concentrated solution to 5 times. The discharge was controlled and the permeate was removed at 0.8 mL / min. As test results using each reverse osmosis membrane, Table 1 shows the water quality of the concentrated solution and the permeated solution, and the phosphoric acid purity and the phosphoric acid recovery rate of the recovered phosphoric acid solution obtained by concentrating the concentrated solution 5 times.

  From Table 1, even when membrane separation treatment was performed with a reverse osmosis membrane having a salt desalting rate of 50 to 90%, the removal rate of phosphoric acid was not much lower than that of a reverse osmosis membrane having a salt desalting rate of 99.5%. The permeability of nitric acid is increased and the separability is improved. The permeability of phosphoric acid is within 10%, the phosphoric acid is concentrated efficiently, and the permeability of acetic acid and nitric acid decreases as the salt desalting rate decreases. You can see it grows.

[Reference Example 1]:
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. FIG. 3 shows the relationship between the change in the concentration of phosphoric acid in the concentrated solution and the rejection rate of nitric acid when the membrane separation treatment was performed and the number of circulation times of the concentrated solution was increased.

  As shown in FIG. 3, when the concentration of phosphoric acid in the concentrate is 1% by weight or more, 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%. When the concentration of phosphoric acid in the concentrate and the rejection rate of nitric acid are calculated from the results shown in Table 1, the same results as in FIG. 3 are obtained for the reverse osmosis membrane having a salt desalting rate of 50 to 90%. I understand that. .

  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.

FIG. 1 is a flowchart of a phosphoric acid recovery method and apparatus according to an embodiment. FIG. 2 is a flowchart of a phosphoric acid recovery method and apparatus according to another embodiment. FIG. 3 is a graph showing the results of Reference 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 Concentrated liquid tank 3a Concentrated liquid 4 Reverse osmosis apparatus 4a Reverse osmosis membrane 4b Permeate liquid room 4c Concentrated liquid room 5 Anion exchange tower 5a Anion exchange resin layer 6 Electric regeneration type Ion exchanger 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 Recovered water tank 7a Recovered water 8 Evaporating and concentrating device 9 Recovered phosphoric acid tank 9a Recovered phosphoric acid solution 10 Biological denitrification equipment

Claims (8)

A method for recovering phosphoric acid from phosphoric acid-containing water,
A reverse osmosis device equipped with a reverse osmosis membrane with a salt desalination rate of 50 to 90% is supplied with phosphoric acid-containing water under conditions of pH 3 or lower to perform membrane separation treatment, and permeates acids other than phosphoric acid together with water. A method for recovering phosphoric acid, characterized by allowing phosphoric acid to permeate to the liquid chamber side, concentrating phosphoric acid to the concentrate chamber side, and recovering the phosphoric acid concentrate. A method for recovering phosphoric acid from phosphoric acid-containing water,
Membrane separation treatment is performed by supplying phosphoric acid-containing water to a reverse osmosis device having a salt desalination rate of 50 to 90% under conditions of pH 3 or lower and a phosphoric acid concentration of 1 to 15% by weight. A method for recovering phosphoric acid, wherein an acid other than phosphoric acid is allowed to permeate to the permeate chamber side together with water and the phosphoric acid is concentrated to the concentrate chamber side to recover the phosphoric acid 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 reverse osmosis treatment by adding water to be treated containing phosphoric acid to the concentrate.   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. An apparatus for recovering phosphoric acid from phosphoric acid-containing water,
A reverse osmosis membrane with a salt desalting rate of 50 to 90% is provided, and phosphoric acid-containing water is subjected to membrane separation treatment under the condition of pH 3 or lower, 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 the acid toward the concentrate chamber;
A raw water supply unit for supplying phosphoric acid-containing water to the concentrated liquid chamber side of the reverse osmosis membrane device under a pH of 3 or less;
A permeate extractor for extracting permeate from the permeate chamber side of the reverse osmosis device;
A phosphoric acid recovery apparatus, comprising: a concentrated phosphoric acid solution extraction unit that extracts a concentrated phosphoric acid solution from the concentrated liquid chamber side of the reverse osmosis device. An apparatus for recovering phosphoric acid from phosphoric acid-containing water,
A reverse osmosis membrane having a salt desalination rate of 50 to 90% is provided, and phosphoric acid-containing water is subjected to membrane separation treatment under conditions of pH 3 or less and phosphoric acid concentration of 1 to 15% by weight to remove acids other than phosphoric acid. And a reverse osmosis device that permeates the permeate chamber side and concentrates phosphoric acid to the concentrate chamber side,
A phosphoric acid-containing water supply unit for supplying phosphoric acid-containing water 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 take-out section for taking out the concentrated phosphoric acid solution from the concentrated solution chamber side of the reverse osmosis device, and a circulation path for circulating the concentrated phosphoric acid solution taken out from the concentrated phosphoric acid solution take-out portion to the concentrate solution chamber side. Characteristic phosphoric acid recovery device.   The apparatus according to claim 5 or 6, further comprising a dilution water supply unit for adding dilution water to the concentrated liquid circulating in the circulation path.   The apparatus according to any one of claims 5 to 7, further comprising an impurity removing device for removing impurities including acid from the permeated water of the reverse osmosis device.

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