WO2009119684A1

WO2009119684A1 - Process and equipment for recovering phosphoric acid from phosphoric acid-containing water

Info

Publication number: WO2009119684A1
Application number: PCT/JP2009/055996
Authority: WO
Inventors: 信博織田
Original assignee: 栗田工業株式会社
Priority date: 2008-03-26
Filing date: 2009-03-25
Publication date: 2009-10-01
Also published as: JPWO2009119684A1; CN101977849B; KR20100127241A; KR101621835B1; JP5413192B2; TWI424964B; CN101977849A; TW201002627A

Abstract

A process and equipment for recovering high-purity phosphoric acid useful as a recycled material in the form of a high -concentration transportable liquid from phosphoric acid -containing water at a low cost and high efficiency by simple constitution and operation without using a special chemical or the like while inhibiting the development of microorganisms such as mould or yeast. The process comprises adjusting phosphoric acid-containing water to a pH of 2 or below, a concentration of 600 mg/L or above, and an electric conductivity of 200 mS/m or above, subjecting the resulting phosphoric acid-containing water to reverse osmosis treatment in a first RO unit (4) to conduct the permeation of acids other than phosphoric acid and water to a permeate chamber (4b) side and the concentration of phosphoric acid on a concentrate chamber (4c) side, subjecting the permeate to post treatment to recover pure water (7a), feeding the concentrate into a second RO unit (5), circulating part of the concentrate formed in the second RO unit (5) as a phosphoric acid solution (9a) for adjustment, and feeding the remainder of the concentrate into an evaporative concentration unit (8) to remove volatile components and water and thus recover a concentrated phosphoric acid solution (10a).

Description

Method and apparatus for recovering phosphoric acid from phosphoric acid-containing water

The present invention relates to a method and an apparatus for recovering phosphoric acid from phosphoric acid-containing water using a reverse osmosis device, and in particular, from washing wastewater containing phosphoric acid after etching a liquid crystal substrate, a wafer or other electronic devices, mold, yeast, etc. The present invention relates to a method and an apparatus for recovering phosphoric acid that can suppress generation of microorganisms and recover valuable materials such as phosphoric acid and pure water as treated water.

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 costs 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 agent added in a large amount in the coagulation sedimentation treatment increases the power cost due to the increase in the operating pressure of the reverse osmosis membrane process, the deterioration 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 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.

If you try to concentrate using a reverse osmosis (RO) membrane instead of such an ion exchange resin, harmful microorganisms such as mold and yeast will grow on the membrane surface, increasing the transmembrane pressure difference and reducing the amount of permeated water. To do. For the control of harmful microorganisms such as mold and yeast, physical control (growth inhibition, sterilization, blocking, sterilization), physicochemical control (growth inhibition), chemical control (growth inhibition, drug sterilization), biological control There is. Among these, there are temperature control and chemical substances (growth inhibitors) for growth inhibition, pasteurization for pasteurization, high temperature sterilization, electromagnetic wave sterilization (γ rays, ultraviolet rays, microwaves, etc.), high pressure sterilization (pressure) ), Electric sterilization (high pressure pulse), gas sterilizer (EO, formaldehyde, ozone, hydrogen peroxide, etc.), liquid / solution sterilizer (alcohol, hydrogen peroxide, organic sterilizer, etc.), solid There are bactericides (silver-based bactericides, photocatalytic bactericides, etc.), immobilized bactericides (silicon-based quaternary ammonium, etc.) and the like.

However, these methods have high energy consumption, high equipment costs, adverse effects on reverse osmosis membranes (clogging due to oxidation, chemical adsorption and alteration), and reverse osmosis membrane performance degradation. was there. In addition, as for chemicals used for chemical control such as gas germicide (EO, formaldehyde, etc.), organic germicide, etc., toxicity and environmental measures are problems. When harmful microorganisms such as mold and yeast propagate on the membrane surface, clogging of the resin and reverse osmosis membrane makes stable operation impossible, but it is difficult to remove the generated mold such as mold and yeast, In particular, there is no corresponding method because an oxidant cannot be used for ion exchange resins and reverse osmosis membranes.
JP 2006-75820 A

The object of the present invention is to suppress the generation of microorganisms such as mold and yeast from phosphoric acid-containing water by using a simple configuration and operation without using a special drug or the like, and high-purity phosphoric acid useful as a recovered product. Is to propose a method and an apparatus for recovering phosphoric acid that can be recovered at a low cost and efficiently in a liquid with a high concentration that can be transported.

The present invention is a method and apparatus for recovering phosphoric acid from the following phosphate ion-containing water.
(1) A method of recovering phosphoric acid by subjecting phosphoric acid-containing water to membrane separation treatment with a reverse osmosis device,
A method for recovering phosphoric acid, comprising subjecting adjusted phosphoric acid-containing water adjusted to a pH of 2 or less, a phosphoric acid concentration of 600 mg / L or more, and an electric conductivity of 200 mS / m or more to membrane separation in a reverse osmosis apparatus.
(2) A method of recovering phosphoric acid by membrane separation treatment of phosphoric acid-containing water with a reverse osmosis device,
Phosphoric acid, characterized in that adjusted phosphoric acid-containing water adjusted to a pH of 2 or less, a phosphoric acid concentration of 600 mg / L or more, and an electric conductivity of 200 mS / m or more is intermittently supplied to a reverse osmosis apparatus for membrane separation treatment Recovery method.
(3) The reverse osmosis device has two or more stages,
Membrane separation treatment of the adjusted phosphoric acid-containing water in the first stage reverse osmosis device,
The method according to (1) or (2) above, wherein the phosphoric acid concentrate of the first-stage reverse osmosis device is subjected to membrane separation treatment in the second and subsequent stages in the second and subsequent reverse osmosis apparatuses.
(4) The adjusted phosphoric acid-containing water supplied to the reverse osmosis device is adjusted to a predetermined value by adding phosphoric acid to the treated phosphoric acid-containing water, according to any one of (1) to (3) above Method.
(5) The adjusted phosphoric acid-containing water supplied to the reverse osmosis device was adjusted to a predetermined value by adding the phosphoric acid concentrate of the reverse osmosis device and / or the phosphoric acid solution of the evaporation concentration device to the treated phosphoric acid-containing water. The method according to any one of (1) to (4) above.
(6) An apparatus for recovering phosphoric acid from phosphoric acid-containing water,
A phosphoric acid-containing water adjusting unit for adjusting the phosphoric acid-containing water to be treated to adjusted phosphoric acid-containing water having a pH of 2 or less, a phosphoric acid concentration of 600 mg / L or more, and an electric conductivity of 200 mS / m or more;
Adjusted phosphoric acid-containing water adjusted to pH 2 or lower, phosphoric acid concentration 600 mg / L or higher and electric conductivity 200 mS / m or higher is subjected to membrane separation treatment, and acid other than phosphoric acid is permeated to the permeate chamber side together with water. A reverse osmosis device for concentrating phosphoric acid to the concentrate chamber side;
A phosphoric acid-containing water supply unit for supplying adjusted phosphoric acid-containing water to the concentrated liquid chamber side of the reverse osmosis device;
A permeate extractor for extracting permeate from the permeate chamber side of the reverse osmosis device;
A circulation path for circulating a part of the concentrated phosphoric acid solution from the concentrated liquid chamber side of the reverse osmosis device to the phosphoric acid-containing water adjusting unit;
A phosphoric acid recovery apparatus, comprising: a concentrated phosphoric acid solution extraction unit that extracts a remaining part from the concentrated liquid chamber side of the reverse osmosis device.
(7) The reverse osmosis device has a two-stage configuration,
A first-stage phosphoric acid concentrate supply unit for supplying the first-stage phosphoric acid concentrate of the first-stage reverse osmosis device to the second-stage reverse osmosis device;
The circulation path is configured to circulate a part of the second-stage phosphoric acid concentrate from the concentrate chamber side of the second-stage reverse osmosis device to the phosphoric acid-containing water adjustment unit,
The apparatus according to (6) above, wherein the concentrated phosphoric acid liquid extraction unit is configured to extract the remaining portion of the second-stage phosphoric acid concentrated liquid from the concentrated liquid chamber side of the second-stage reverse osmosis device.
(8) The apparatus according to (7) above, further comprising an evaporative concentration apparatus for evaporating and concentrating the remainder of the second stage phosphoric acid concentrate taken out from the concentrate chamber side of the second stage reverse osmosis apparatus.

In the present invention, the phosphoric acid-containing water to be treated can be any water as long as it contains phosphoric acid, but phosphate ions are 50 mg / L or more and less than 600 mg / L (adjusted phosphoric acid). When the contained water is 1500 mg / L or more, it contains 50 mg / L or more and less than 1500 mg / L), and the pH is more than 2 and 3 or less (if the adjusted phosphoric acid-containing water is pH 1.5 or less, 1.5 is contained) And 3 or less) and an electrical conductivity of less than 200 mS / m (if the adjusted phosphoric acid-containing water is 1800 mS / m or more, it is less than 1800 mS / m).

In any case, acidic water is preferable as a treatment target, and in addition to phosphate ions, acid components such as nitrate ions and acetate ions, other anions, cations such as metal ions, and other impurities may be contained. However, the cations are preferably removed prior to treatment. 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.

When such treated phosphoric acid-containing water has a higher pH and lower concentration than the above-mentioned adjusted phosphoric acid-containing water, harmful microorganisms such as mold and yeast propagate on the membrane surface of the reverse osmosis membrane and cause clogging. Therefore, in the present invention, in order to recover phosphoric acid from phosphoric acid-containing water, phosphoric acid-containing water, particularly phosphoric acid-containing water from which cations have been removed, has a pH of 2 or less, preferably 1.5 or less, and a phosphoric acid concentration of 600 mg / The adjusted phosphoric acid-containing water adjusted to L or higher, preferably 1500 mg / L or higher and electrical conductivity of 200 mS / m or higher, preferably 1800 mS / m or higher, is subjected to membrane separation treatment in a reverse osmosis apparatus. Since the adjusted phosphoric acid-containing water only needs to have the above-mentioned pH, phosphoric acid concentration, and electrical conductivity at the stage of membrane separation treatment, when it is concentrated in the concentration chamber of the reverse osmosis device during membrane separation treatment, What is necessary is just to become said pH, phosphoric acid concentration, and electrical conductivity in the concentrated state.

The adjustment of the phosphoric acid-containing water to be treated is performed when the pH and the concentration are lower than those of the adjusted phosphoric acid-containing water at the stage of supplying to the reverse osmosis apparatus. In the case where the reverse osmosis apparatus has one stage and two or more stages, the treated phosphoric acid-containing water supplied to the first stage reverse osmosis apparatus has a higher pH and lower concentration than the adjusted phosphoric acid-containing water. is there. When the reverse osmosis apparatus has two or more stages, the phosphate concentrate of the first stage reverse osmosis apparatus has a low pH and a high concentration. There is no need to adjust the density.

In order to adjust high pH and low concentration treated phosphoric acid-containing water to low pH and high concentration, it is preferable to inject acid into the treated phosphoric acid-containing water as pH and concentration adjustment. In addition, it is preferable to adjust to a predetermined value of adjusted phosphoric acid-containing water. As phosphoric acid added to the phosphoric acid-containing water to be treated, a phosphoric acid concentrated solution of a reverse osmosis device and / or a phosphoric acid solution of an evaporation concentrating device can be used. The phosphoric acid concentrate of the reverse osmosis apparatus is preferably used in a circulating manner because impurities such as nitric acid and acetic acid are removed and the phosphoric acid concentration is high. The phosphoric acid solution of the evaporating and concentrating device is a concentrated phosphoric acid solution when evaporating and concentrating the concentrated solution of the reverse osmosis device, particularly the concentrated solution of the second stage, and this can be recycled.

If the adjusted phosphoric acid-containing water adjusted to such a low pH and high concentration is subjected to a membrane separation treatment in a reverse osmosis device, the growth of harmful microorganisms such as mold and yeast on the membrane surface of the reverse osmosis membrane is inhibited. For this reason, clogging of reverse osmosis membranes due to the growth of microorganisms does not occur without the use of special agents such as oxidizing agents or sterilizing means such as ultraviolet rays, increasing the transmembrane pressure difference and decreasing the amount of permeated water. And a stable reverse osmosis device can be operated. Since the harmful microorganism inhibiting effect lasts to some extent, it is possible to intermittently supply the adjusted phosphoric acid-containing water, but it is preferable to continue the supply of the adjusted phosphoric acid-containing water.

That is, it is preferable that the adjusted phosphoric acid-containing water adjusted to a low pH and high concentration is always supplied to the reverse osmosis device to perform the membrane separation treatment, but intermittently supplied to the reverse osmosis device to perform the membrane separation treatment. You can also. In the latter case, usually, the phosphoric acid-containing water having a higher pH and lower concentration than the adjusted phosphoric acid-containing water is supplied to the reverse osmosis apparatus as it is to perform membrane separation treatment, and intermittently, for example, for 1-2 days. The membrane separation treatment can be performed once by supplying adjusted phosphoric acid-containing water adjusted to a low pH and high concentration for about 1-2 hours, for example. In this case, the phosphoric acid-containing water to be treated can be supplied as it is to the reverse osmosis apparatus to perform membrane separation treatment, and phosphoric acid can be injected intermittently to adjust the pH and concentration of the phosphoric acid-containing water.

In the present invention, before supplying the phosphoric acid-containing water to the reverse osmosis device, impurities including cations and / or anions can be removed as a pretreatment. In particular, phosphoric acid-containing water from which cations have been removed is treated. By adjusting to the phosphoric acid concentration, the separation effect of phosphoric acid and other acids by membrane separation treatment can be enhanced. In this case, it is possible to remove solids by precipitation separation, filtration, etc. as pretreatment, and removal of cations such as metal ions by cation exchange resin as pretreatment, and further, perchloric acid, organic acid complex by anion exchange resin Etc. can be removed. 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.

The reverse osmosis device in the membrane separation step in the present invention is also called an RO device, and is divided into a permeate chamber and a concentrate chamber by a reverse osmosis (RO) membrane, and contains phosphoric acid-containing water at a pH of 2 or less and a phosphoric acid concentration of 600 mg / L and a reverse osmosis membrane treatment by supplying to the concentrated liquid chamber side under conditions of electric conductivity of 200 mS / m or higher, allowing acid other than phosphoric acid to permeate to the permeate liquid chamber side together with water, It is configured to concentrate on the concentrate chamber side. 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 is formed between the concentrated phosphoric acid solution extraction unit and the phosphoric acid-containing water supply unit to circulate the concentrated phosphoric acid solution extracted from the concentrated phosphoric acid solution extraction unit to the concentrated liquid chamber side as adjusting phosphoric acid. be able to.

When the reverse osmosis device has a two-stage configuration, it has a first-stage phosphoric acid concentrate supply unit that supplies the first-stage phosphoric acid concentrate of the first-stage reverse osmosis device to the second-stage reverse osmosis device, and circulates. The route is constructed so that a part of the second-stage phosphoric acid concentrate is circulated from the second-stage reverse osmosis device side of the second-stage reverse osmosis device to the first-stage reverse osmosis device of the first-stage reverse osmosis device. The part can be configured to take out the remainder of the second-stage phosphoric acid concentrate from the concentrate chamber side of the second-stage reverse osmosis device. As a result, the phosphoric acid concentrate of the first-stage reverse osmosis device is supplied to the second-stage reverse osmosis device to perform the membrane separation treatment, and a part of the phosphoric acid concentrate of the second-stage reverse osmosis device is used as the adjustment phosphorus The acid can be circulated to the concentrate chamber side of the first-stage reverse osmosis device, and the remainder can be recovered.

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 provided with such a reverse osmosis membrane, but preferably a device provided with 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.

When phosphoric acid-containing water, especially phosphoric acid-containing water from which cations have been removed, is subjected to membrane separation treatment in a reverse osmosis device under a pH of 2 or less, acids other than phosphoric acid such as nitric acid and acetic acid permeate through the reverse osmosis membrane together with water. Then, 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 a condition where the phosphoric acid concentration is 600 mg / L or more, the blocking rate of acids other than phosphoric acid is low, and the transmittance is low. Since it becomes high, a highly purified phosphoric acid concentrate can be recovered. The pressure of the phosphoric acid-containing water supplied to the reverse osmosis device can be 0.3 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, when the reverse osmosis membrane treatment is carried out under pH 2 or less where phosphoric acid is difficult to dissociate, the rejection rate of phosphoric acid is overwhelmingly higher than that of nitric acid and acetic acid. Can be collected separately.

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, 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, a biological treatment device, or the like can be employed as the impurity removal device.

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 has two or more stages, the adjusted phosphoric acid-containing water is supplied to the first stage reverse osmosis apparatus to perform the membrane separation treatment, and the phosphoric acid concentrate of the first stage reverse osmosis apparatus is supplied to the first stage reverse osmosis apparatus. It supplies to the reverse osmosis apparatus of the 2nd stage and after, and the membrane separation process after the 2nd stage is performed. In this case, the reverse osmosis device has a first-stage phosphoric acid concentrate supply unit that supplies the first-stage phosphoric acid concentrate of the first-stage reverse osmosis device to the second-stage reverse osmosis device, and the circulation path is the second. A part of the second-stage phosphoric acid concentrate is circulated from the concentrate chamber side of the stage reverse osmosis apparatus to the phosphoric acid-containing water adjustment unit, and the concentrated phosphoric acid liquid take-out part is the concentration of the second-stage reverse osmosis apparatus. The remaining portion of the second-stage phosphoric acid concentrate is taken out from the liquid chamber side. The taken-out second stage phosphoric acid concentrate can be further concentrated by evaporation using an evaporation concentrator and recovered as a phosphoric acid concentrate. The concentrated phosphoric acid solution after evaporation is circulated to the phosphoric acid-containing water adjusting unit and can be used for adjustment.

That is, if acetic acid remains in the phosphoric acid solution permeated through the second-stage reverse osmosis device, acetic acid cannot be completely removed even with anion exchange resin. Therefore, the recovered phosphoric acid solution is obtained by removing volatile components such as acetic acid. In order to increase the purity and concentration of the solution, the phosphoric acid solution is concentrated by evaporating with an evaporation concentrator, removing the volatile component together with water, and concentrating it to obtain a high concentration that hardly contains volatile components such as acetic acid. Phosphoric acid can be recovered. 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, and can be recovered as highly purified concentrated phosphoric acid. In the present invention, reverse osmosis treatment is carried out under the condition of pH 2 or lower, but the treated phosphoric acid-containing water is usually obtained in an acidic state of pH 3 or lower, so it is easy to inject the recovered phosphoric acid as a pH adjuster. Can be adjusted. The method and apparatus for recovery can be adjusted to pH 2 or lower, 600 mg / L or higher, and electric conductivity 200 mS / m or higher with a simple configuration and operation.

By adjusting the pH, phosphoric acid concentration, and electrical conductivity as described above, and supplying a regulated phosphoric acid concentrate and reverse osmosis treatment, the generation of microorganisms such as mold and yeast is suppressed, and high purity phosphoric acid is recovered. Is possible. As a result, 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 useful as recovered materials can be recovered. The recovered phosphoric acid can be used not only for adjusting phosphoric acid-containing water, but also for immersing a reverse osmosis module taken out from the reverse osmosis apparatus and for suppressing generation of microorganisms such as mold and yeast.

As described above, according to the present invention, phosphoric acid-containing water, particularly phosphoric acid-containing water from which cations have been removed, is adjusted to have a pH of 2 or less, a phosphoric acid concentration of 600 mg / L or more, and an electric conductivity of 200 mS / m or more. Since water is configured to be membrane-separated in a reverse osmosis device, the generation of microorganisms such as mold and yeast can be suppressed from phosphoric acid-containing water with a simple configuration and operation without using special chemicals. High-purity phosphoric acid useful as a recovered product can be recovered in a low-concentration and efficient manner in a liquid with a high concentration that can be transported.

It is a flowchart of the phosphoric acid collection | recovery method and apparatus in embodiment. It is a graph which shows the result of an Example.

Explanation of symbols

1: raw water tank, 1a: raw water, 2: pretreatment device, 3: adjustment liquid tank, 3a: adjustment liquid, 4: first RO device, 4a, 5a: RO membrane, 4b, 5b: permeate chamber, 4c, 5c : Concentration chamber, 5: Second RO device, 6: Post-treatment device, 7: Recovery water tank, 7a: Recovery water, 8: Evaporation concentration device, 9: Adjustment phosphoric acid tank, 9a: Adjustment phosphoric acid solution, 10 : Recovered phosphoric acid tank, 10a: Recovered phosphoric acid solution.

Hereinafter, 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 that stores raw water (treated phosphoric acid-containing water) 1a. Reference numeral 2 denotes a pretreatment device, which includes a cation exchange device, an anion exchange device, and other impurity removal devices, but is preferably provided with at least a cation exchange device so as to remove cations. 3 is an adjustment liquid tank, which stores the adjustment liquid (adjusted phosphoric acid-containing water) 3a. Reference numeral 4 denotes a first RO (reverse osmosis) device, and reference numeral 5 denotes a second RO device, which are divided into

permeate chambers

4b and 5b and concentrate

chambers

4c and 5c by

RO membranes

4a and 5a, respectively. Reference numeral 6 denotes a post-processing device, which includes an ion exchange device, a biological processing device, and other impurity removal devices. 7 is a recovery water tank, 8 is an evaporative concentration apparatus, 9 is a phosphoric acid tank for adjustment, and 10 is a recovery phosphoric acid tank.

1, P1 is a pressurizing pump, and constitutes a raw water supply unit that supplies the adjustment liquid (adjusted phosphoric acid-containing water) 3 a to the concentrated liquid chamber 4 c side of the first RO device 4. The adjustment phosphoric acid tank 9 constitutes a concentrated phosphoric acid liquid extraction part, and the pump P2, the adjustment liquid tank 3 and the pH meter pH provided in the circulation path L4 constitute the phosphoric acid-containing water adjustment part.

In the above phosphoric acid recovery apparatus, raw water 1a (phosphate ion-containing water), from which impurities have been removed by precipitation separation, filtration, and the like as a preliminary treatment step, is introduced into the raw water tank 1 from the line L1. The raw water 1a of the raw water tank 1 is introduced into the pretreatment device 2 from the line L2 to remove cations such as indium and other metal ions contained in the raw water, but further, anions such as perchloric acid and organic acid complexes It is preferable to remove impurities. Pretreatment water is introduced into the adjustment liquid tank 3 from the line L3.

Phosphoric acid-containing water as raw water is usually obtained in an acidic state of pH 3 or lower, but for reverse osmosis treatment under conditions of pH 2 or lower, the adjustment liquid tank 9 is adjusted to the adjusting liquid tank 3 through the circulation path L4. Circulate the phosphoric acid solution 9a. At this time, the pH of the adjustment liquid 3a in the adjustment liquid tank 3 is measured with a pH meter pH, and the pump P2 provided in the circulation path L4 is controlled to adjust the pH of the adjustment liquid 3a to 2 or less. In this case, when the concentrated phosphoric acid solution is circulated and adjusted to pH 2 or less, the adjusting solution 3a is adjusted to a phosphoric acid concentration of 600 mg / L or more and an electric conductivity of 200 mS / m or more. In FIG. 1, the pH of the adjustment liquid 3a is adjusted by a pH meter, but the phosphoric acid concentration and the electric conductivity can also be adjusted by a hydrometer or an electric conductivity meter.

Phosphoric acid-containing water in the adjustment liquid tank 3 is pressurized by the pressure pump P1, introduced into the concentrated liquid chamber 4c of the first RO device 4 from the line L5, membrane-separated (reverse osmosis treatment) by the RO membrane 4a, nitric acid, Acids other than phosphoric acid such as acetic acid are allowed to permeate to the permeate chamber 4b side together with water, and phosphoric acid is concentrated 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 the salt of phosphoric acid penetrates the RO membrane 4a, and the concentrated solution It is concentrated on the side of the chamber 4c. On the other hand, when the RO treatment is performed by introducing the phosphoric acid-containing water into the first RO device 4 under the condition of pH 2 or lower, the phosphoric acid is prevented from permeating by the RO membrane 4a and the concentrated liquid chamber. Although concentrated on the 4c side, acids other than phosphoric acid such as nitric acid and acetic acid permeate to the permeate chamber 4b side with water and are separated.

The adjusted phosphoric acid-containing water supplied to the first RO device 4 has a pH of 2 or less, preferably a pH of 1.5 or less, a phosphoric acid concentration of 600 mg / L or more, preferably 1500 mg / L or more, and an electric conductivity of 200 mS / m or more, preferably Since the adjusted phosphoric acid-containing water is supplied to the first RO device 4 and subjected to membrane separation treatment, since the adjusted phosphoric acid-containing water is adjusted to 1800 mS / m or more, harmful microorganisms such as mold and yeast on the membrane surface of the reverse osmosis membrane Breeding is inhibited. For this reason, clogging of the reverse osmosis membrane due to the propagation of microorganisms does not occur even without using special chemicals, etc., and there is no increase in transmembrane pressure difference or decrease in the amount of permeated water, and stable operation of the reverse osmosis device. it can. Since the harmful microorganism inhibiting effect lasts to some extent, the adjusted phosphoric acid-containing water can be supplied intermittently, but it is preferable to continuously supply the adjusted phosphoric acid-containing water.

The permeate permeated to the permeate chamber 4b side of the first RO device 4 is introduced into the post-treatment device 6 from the line L6, and nitric acid that has permeated the RO membrane 4a by the ion exchange device, biological treatment device, and other impurity removal devices, Anions such as acetic acid and other impurities are removed and discharged from the line L7. The pure water from which these impurities have been removed is recovered from the line L8 to the recovered water tank 7, stored as recovered water 7a, and taken out from the line L9.

When membrane treatment is performed with a single-stage RO device, the concentrated liquid concentrated in the concentrate chamber 4c of the first RO device can be post-treated to obtain recovered phosphoric acid. In the case of processing, the concentrated liquid concentrated in the concentrated liquid chamber 4c of the first RO device is introduced into the concentrated liquid chamber 5c of the second RO device 5 from the line L11, and membrane separation (reverse osmosis treatment) is performed by the RO membrane 5a. Then, an acid other than phosphoric acid such as 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. As a result, a part of the concentrated liquid whose purity and concentration are increased is introduced from the concentrated liquid chamber 5c of the second RO device 5 into the adjusting phosphoric acid tank 9 through the line L12 and stored as the adjusting phosphoric acid liquid 9a. To do.

The remaining portion of the concentrated liquid of the second RO device 5 is introduced into the evaporation concentration device 8 from the line L10 to perform evaporation concentration. Condensed water containing acetic acid generated in the evaporating and concentrating device 8 is introduced into the post-processing device 6 from the line L14 to remove impurities, and pure water is recovered. The phosphoric acid concentrated water from which the acetic acid has been removed by evaporating and concentrating with the evaporating and concentrating device 8 is collected in the recovered phosphoric acid tank 10 from the line L15. In the process, nitric acid and other impurities may be removed. A part of the recovered phosphoric acid solution 10a in the recovered phosphoric acid tank 10 can be circulated to the adjustment liquid tank 3 through the circulation path L4, and the remaining part can be taken out from the line L16 as recovered phosphoric acid. The permeate that has permeated the RO membrane 5a of the second RO device 5 toward the permeate chamber 5b is introduced from the line L13 into the post-treatment device 6 to remove impurities, and pure water is recovered.

The recovered phosphoric acid solution 10a recovered by the above method is useful as a recovered material and is practically transportable because it is recovered in a high-concentration liquid state, and can be recovered as high-purity concentrated phosphoric acid. In this case, a special drug or the like can be obtained by supplying adjusted phosphoric acid-containing water adjusted to pH 2 or less, phosphoric acid concentration 600 mg / L or more, and electrical conductivity 200 mS / m or more to the RO device to perform membrane separation treatment. It is possible to carry out membrane separation treatment while suppressing the generation of microorganisms such as molds and yeasts. 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.

Hereinafter, examples of the present invention will be described. In each example,% indicates weight percentage other than the inhibition rate, and unless otherwise indicated.

[Examples 1 to 6, Comparative Examples 1 to 4]:
Use standard phosphoric acid-containing water with 11000 mg / L phosphoric acid, 1000 mg / L nitric acid, 1000 mg / L nitric acid, and electric conductivity 1150 mS / m, pH 1.3, and adjust the pH and others by diluting it with pure water. The raw water of Table 1 (adjusted phosphoric acid-containing water) was obtained. In Table 1, Comparative Example 1 was adjusted to raw water having the phosphoric acid concentration and pH shown in Table 1 by diluting standard phosphoric acid-containing water with pure water and then adjusting the pH with sodium hydroxide. Example 6 is an example in which raw water standard phosphoric acid-containing water was used as raw water as it was. Examples 1 and 2 are designed to have a concentrated state of pH 2 or lower, phosphoric acid 600 mg / L or higher, and electrical conductivity 200 mS / m or higher.

As a flat membrane test device simulating the reverse osmosis device of FIG. 1, a reverse osmosis membrane ES-20 manufactured by Nitto Denko Corporation cut into a circular shape with a diameter of 32 mmφ in a small diameter flat membrane cell made of stainless steel (SUS304) with an inner diameter of 32 mmφ. The flat membrane is supported by a sintered perforated plate with an effective membrane diameter of 29 mmφ, and the raw water is supplied to the concentrated liquid chamber of the cell by a pump and mixed with the concentrated liquid, and the concentrated liquid is discharged by the back pressure valve. A device for adjusting the operation pressure of the concentrate and stirring and circulating the concentrate in the concentrate chamber with a rotor was used.

While supplying the raw water (adjusted phosphoric acid-containing water) shown in Table 1 at a flow rate of 1 mL / min to the concentration chamber of the above flat membrane test apparatus, the liquid in the cell is mixed with the concentrated liquid that is retained by stirring with a rotor. The membrane separation was carried out by adjusting the back pressure valve so that the amount of permeated water and the amount of concentrated water were the same (0.5 mL / min). The pressure during this operation is shown in Table 2 as the operation pressure. Thereafter, the membrane separation was continued while maintaining this operating pressure. The change with time in the permeation flux at this time is shown in FIG. In addition, the concentration of each component of the concentrated water at the end of operation (comparative example 1 operation time 20 hours, comparative example 2 operation time 40 hours, others completed operation time 60 hours) Although the rejection rate is shown in Table 2, it became a numerical value equivalent to Table 2 in about 1 hour after the start of operation, and the value was maintained until the end of the operation. The rejection rate was calculated by the formula [(1-permeated water concentration / concentrated water concentration) × 100].

The concentrated water obtained in Examples 1 and 4 and Comparative Examples 1 to 3 was subjected to a culture test in a petri dish. The medium was an antibiotic-added PDA medium and cultured in a 30 ° C. constant temperature bath. As a result of the petri dish culture test, the yellow mold Penicillium chrysogenum formed many colonies in the neutral region. The fungal species generated at pH 3 or lower was fusarium spp. Table 3 shows the number of days until mold colonies are observed with the naked eye as a result of the petri dish culture test. In Table 3, “10 days or more” indicates that no colonies were observed in the 10-day culture test.

As a one-stage RO membrane water flow test device simulating the reverse osmosis device of Fig. 1, ultra-low pressure aromatic polyamide RO membrane "ES20-D2" manufactured by Nitto Denko Corporation (the vessel is an S2 vessel for seawater desalination) The raw water (adjusted phosphoric acid-containing water) of Examples 1 and 4 was washed with brine using a device in which a part of the concentrated liquid was circulated through the concentrated liquid chamber and the adjusted liquid tank of the 4-inch new membrane module. In the amount of water 5 L / min, supply from the adjustment liquid tank to the concentration chamber of the RO device to perform membrane separation, and circulate a part of the concentrate to the adjustment liquid tank so that the water quality shown in Table 2 is obtained. Part of the permeate and the permeate were circulated through the raw water tank for 1 month. Table 4 shows the processing results after processing for one month.

From Table 4, no significant difference was recognized in the treatment performance after the raw water of Examples 1 and 4 was treated for one month. However, when the adhesion state of the slime after the treatment for one month was examined, in the treatment of the raw water of Example 1, the filamentous slime was slightly caught on the electrode of the level gauge installed in the adjustment liquid tank. In the raw water treatment, no filamentous slime was observed even after one month.

From the above results, phosphate-containing water containing no cation has a pH of 2 or less, particularly 1.5 or less, a phosphoric acid concentration of 600 mg / L or more, particularly 1500 mg / L or more, and an electric conductivity of 200 mS / m or more, particularly 1800 mS / m. By performing membrane separation treatment in the reverse osmosis device with the adjusted phosphoric acid-containing water adjusted as described above, it is possible to remove microorganisms such as molds and yeasts from the phosphoric acid-containing water with a simple configuration and operation without using a special drug or the like. It turns out that generation | occurrence | production can be suppressed and useful high purity phosphoric acid can be collect | 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.

Claims

A method of recovering phosphoric acid by membrane separation treatment of phosphoric acid-containing water with a reverse osmosis device,
A method for recovering phosphoric acid, comprising subjecting adjusted phosphoric acid-containing water adjusted to a pH of 2 or less, a phosphoric acid concentration of 600 mg / L or more, and an electric conductivity of 200 mS / m or more to membrane separation in a reverse osmosis apparatus.
A method of recovering phosphoric acid by membrane separation treatment of phosphoric acid-containing water with a reverse osmosis device,
Phosphoric acid, characterized in that adjusted phosphoric acid-containing water adjusted to a pH of 2 or less, a phosphoric acid concentration of 600 mg / L or more, and an electric conductivity of 200 mS / m or more is intermittently supplied to a reverse osmosis apparatus for membrane separation treatment Recovery method.
The reverse osmosis device has two or more stages,
Membrane separation treatment of the adjusted phosphoric acid-containing water in the first stage reverse osmosis device,
The method according to claim 1 or 2, wherein the phosphoric acid concentrate of the first-stage reverse osmosis apparatus is subjected to a second-stage or later membrane separation treatment in a second-stage or later reverse osmosis apparatus.
4. The method according to any one of claims 1 to 3, wherein the adjusted phosphoric acid-containing water supplied to the reverse osmosis apparatus is adjusted to a predetermined value by adding phosphoric acid to the treated phosphoric acid-containing water.
The adjusted phosphoric acid-containing water supplied to the reverse osmosis device is adjusted to a predetermined value by adding the phosphoric acid concentrate of the reverse osmosis device and / or the phosphoric acid solution of the evaporation concentration device to the treated phosphoric acid-containing water. 5. A method according to any one of claims 1 to 4.
An apparatus for recovering phosphoric acid from phosphoric acid-containing water,
A phosphoric acid-containing water adjusting unit for adjusting the phosphoric acid-containing water to be treated to adjusted phosphoric acid-containing water having a pH of 2 or less, a phosphoric acid concentration of 600 mg / L or more, and an electric conductivity of 200 mS / m or more;
Adjusted phosphoric acid-containing water adjusted to pH 2 or lower, phosphoric acid concentration 600 mg / L or higher, and electric conductivity 200 mS / m or higher is subjected to membrane separation treatment, and acid other than phosphoric acid is permeated to the permeate chamber side together with water. A reverse osmosis device for concentrating phosphoric acid to the concentrate chamber side;
A phosphoric acid-containing water supply unit for supplying adjusted phosphoric acid-containing water to the concentrated liquid chamber side of the reverse osmosis device;
A permeate extractor for extracting permeate from the permeate chamber side of the reverse osmosis device;
A circulation path for circulating a part of the concentrated phosphoric acid solution from the concentrated liquid chamber side of the reverse osmosis device to the phosphoric acid-containing water adjusting unit;
A phosphoric acid recovery apparatus, comprising: a concentrated phosphoric acid solution extraction unit that extracts a remaining part from the concentrated liquid chamber side of the reverse osmosis device.
The reverse osmosis device has a two-stage configuration,
A first-stage phosphoric acid concentrate supply unit for supplying the first-stage phosphoric acid concentrate of the first-stage reverse osmosis device to the second-stage reverse osmosis device;
The circulation path is configured to circulate a part of the second-stage phosphoric acid concentrate from the concentrate chamber side of the second-stage reverse osmosis device to the phosphoric acid-containing water adjustment unit,
The apparatus according to claim 6, wherein the concentrated phosphoric acid solution take-out section is configured to take out the remaining portion of the second-stage phosphoric acid concentrate from the concentrate chamber side of the second-stage reverse osmosis device.
The apparatus according to claim 7, further comprising an evaporating and concentrating apparatus for evaporating and concentrating the remainder of the second stage phosphoric acid concentrate taken out from the concentrated liquid chamber side of the second stage reverse osmosis apparatus.