JP2001026418A - Recovering method of industrially useful inorganic material and industrially useful inorganic material recovered by the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method to recover an industrially useful inorganic material, which enables recovering an industrially usable high purity alkali metal salt containing no needless components such as heavy metals, and the industrially useful inorganic material recovered by the recovering method. SOLUTION: The method includes a process for making waste water harmless by removing the heavy metals contained in waste water, an electrodialyzing process for separating and recovering concentrated water containing a univalent ion from the treated water by an electrodialyser possessing a univalent ion selective ion exchange membrane and a process for separating and recovering the inorganic material as the alkali metallic salt such as sodium chloride (NaOH), potassium chloride (KCl) by the crystallization of the recovered water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering an industrially useful inorganic material and an industrially useful inorganic material recovered by the recovery method.

[0002]

2. Description of the Related Art Conventionally, wastewater such as domestic wastewater and industrial wastewater is
Separate and remove only conventionally harmful substances such as heavy metals, discard the collected heavy metals again, and discharge the treated water to the river, etc. after satisfying the allowable standards for drainage, etc. They had to carry them into the treatment plant or to separate solids by concentration and evaporation. Of these, when released to rivers or brought into sewage treatment plants, calcium, sodium, potassium, chlorine, sulfate, etc., contained in large amounts in the wastewater, are discharged in a mixed state without being collected. Was supposed to be. In the case of using a method such as concentration and evaporation, calcium and the like are recovered as solids, but such solids are in a mixed state of various components, and are in a state where they can be recycled in some form. Not. For this reason, it was treated as waste having no usefulness.

[0003] Standards for chlorine and the like in wastewater are not strictly defined at present. However, the conventional methods described above are not always desirable from the viewpoint of resource saving and environmental conservation. In particular, alkali metal salts such as potassium chloride and sodium chloride have high industrial utility, so that high purity and economical separation and recovery have been demanded.
Further, with respect to such alkali metal salts, there has been a further demand for a method of separating and recovering sodium chloride and potassium chloride individually with high purity and economically.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is intended to recover an alkali metal salt having high purity and containing no unnecessary components such as heavy metals and having high purity. In addition, it is possible to separately recover potassium chloride and sodium chloride among the alkali metal salts, and to generate, precipitate, and recover industrially sufficiently usable substances generated in the intermediate process. Accordingly, it is an object of the present invention to provide a method for recovering an industrially useful inorganic material in which unnecessary substances that cannot be reused are not generated at all, and an industrially useful inorganic material recovered by the recovery method.

[0005]

In order to achieve the above object, an industrially useful method for recovering an inorganic material according to the present invention comprises a detoxification treatment step for removing heavy metals in wastewater, and a method for treating the treated water. An electrodialysis process in which an electrodialysis device equipped with a monovalent ion-selective ion exchange membrane separates and collects concentrated water containing monovalent ions, and sodium chloride (NaCl) or potassium chloride (KCl )) And a step of separating and recovering the inorganic material as an alkali metal salt. In the present invention, as the "drainage", wastewater containing chlorine and alkali components generated when incinerated ash generated when municipal waste or industrial waste or the like is incinerated or melted or dust generated in a cement manufacturing process is washed with water. And leachate generated from refuse incineration ash burial plants, smoke washing wastewater from incinerators, sewage and wastewater generated in human waste treatment processes. The detoxification step is a step of precipitating, adsorbing, and removing heavy metals by a treatment using a heavy metal insolubilizing agent, a pH adjustment, and a chelate resin adsorption treatment in advance. This detoxification process,
As will be described later in the embodiment, an operation may be included in which a mixture of the removed material and calcium carbonate generated and recovered at the same time is used as a part of an industrial raw material such as a cement raw material.

In the method for recovering an industrially useful inorganic material according to the present invention, the residual liquid after recovering the industrially useful inorganic material is circulated to the previous step by the composition of the solute, and the solute is recovered. Waste can be prevented from leaving the system. Such residual liquid may be circulated to wastewater before detoxification. Therefore, when the term “drainage” is referred to in the present specification, a concept in which such a residual liquid is mixed with drainage is also included. In addition, the method for recovering an industrially useful inorganic material according to the present invention includes the steps of separating and recovering the inorganic material, a crystallization step of recovering sodium chloride by a crystallization operation, and cooling the remaining liquid. A cooling crystallization step of recovering potassium chloride separately.

Further, in the method for recovering an industrially useful inorganic material according to the present invention, sodium hydroxide (NaOH) is added to wastewater from which heavy metals have been precipitated and removed in the detoxification step before the electrodialysis step. At the same time, a gas containing carbon dioxide (CO ₂ ) is introduced, and the calcium component in the wastewater etc. is precipitated and separated and recovered as calcium carbonate (CaCO ₃ ). can do. Then, after such a precipitation separation / recovery step of calcium carbonate, a decarbonation step of adding a small amount of hydrochloric acid or the like to perform decarboxylation may be further included. In this case, the sodium chloride recovered in the crystallization step is electrolyzed, and the sodium hydroxide generated by the electrolysis is circulated as sodium hydroxide to be added before the electrodialysis step, so that the sodium hydroxide can be closed. .
Similarly, the hydrochloric acid generated by such electrolysis can be circulated as hydrochloric acid added in the above-mentioned decarboxylation step to achieve a closed state.

Still further, the method for recovering industrially useful inorganic materials according to the present invention provides a method for recovering industrially useful inorganic materials, wherein wastewater from which heavy metals are precipitated and removed in a detoxification step is added to sodium sulfate (Na ₂ SO ₄ .10H) before the electrodialysis step.
₂ O) was added and the calcium content in the waste water can be carried out as further comprising embodiments the step of precipitating separate and recover gypsum (CaSO ₄ · 2H ₂ O) which can be a raw material for cement.

Further, the method of recovering an industrially useful inorganic material according to the present invention is characterized in that soda ash (Na ₂ CO ₃ ) is added to wastewater from which heavy metals have been precipitated and removed in a detoxification step before an electrodialysis step.
Is added, and the process further includes a step of separating and collecting the calcium component as calcium carbonate by precipitation. In this case, the sodium chloride recovered in the crystallization step is used as a starting material to produce soda ash by the ammonia-soda method, and the soda ash is circulated as soda ash added before the electrodialysis step, and closed. It can be designed.

According to another aspect of the present invention, there is provided an industrially useful inorganic material, which is recovered by the above-described method for recovering an industrially useful inorganic material.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for recovering industrially useful inorganic materials according to the present invention will be described below with reference to embodiments shown in the accompanying drawings. First Embodiment A first embodiment will be described with reference to FIGS. 1 to 4 with respect to a method for recovering an industrially useful inorganic material according to the present invention.
FIG. 1 is a flowchart illustrating a processing procedure according to the first embodiment. Here, before describing the flow of each step, the composition of the wastewater treated by the industrially useful inorganic material recovery method according to the present invention, including the first embodiment, will be described below. An example is shown in Table 1.

[0012]

[Table 1]

As can be understood from Table 1, these wastewaters contain not only various heavy metals but also Ca ²⁺ (calcium), Na
⁺ (Sodium), K ⁺ (potassium), Cl ^- (chlorine), SO ₄
^2- Contains a large amount of ions such as (sulfuric acid). In the present embodiment, first, heavy metals are separated and recovered from wastewater, and the detoxification and recycling are performed (step 101). Such heavy metals have been regarded as harmful in the past.

[0014] Regarding the detoxification treatment of heavy metals, there is a general treatment method conventionally used in the field of water treatment and the like. Furthermore, the heavy metals separated and recovered can also be purified for each component by a conventionally known method. However, recovery of heavy metals is desired to be improved from the viewpoint of economy. FIG. 2 shows an embodiment of the detoxification process in which such an improvement is made.

In the method shown in FIG. 2, first, the wastewater 201 is neutralized with carbon dioxide (step 202). In order to carry out this method, preferably, a treatment facility for carrying out the detoxification treatment is installed near a facility that generates and discharges combustion exhaust gas 203 such as a furnace exhaust gas containing carbon dioxide gas, such as a cement manufacturing plant.
And the exhaust gas discharged from such a facility is drained 2
01 to be introduced. In particular, in the case of a cement manufacturing plant, in the exhaust gas discharged from the cement firing furnace, in addition to carbon dioxide generated by fuel combustion, all of limestone (CaCO ₃ ), the main raw material of cement, is decarbonated during the firing process. It changes to calcium oxide (CaO), and contains a large amount of carbon dioxide released at that time. As a result, the concentration of carbon dioxide in the exhaust gas has reached about 20%. By adjusting the pH of the wastewater by neutralizing carbon dioxide, lead, zinc, which is a central component of the heavy metal contained therein, can be precipitated, separated, and recovered as a hydroxide (step 204). This method is extremely effective in terms of both reducing the cost of chemicals as compared with the methods conventionally used in the field of water treatment and reducing the emission of carbon dioxide. However, in some cases, not all heavy metals can be recovered by the neutralization step 202 alone. Therefore, for heavy metals that still remain in the wastewater, a conventional method such as addition or adsorption of a liquid chelate such as ACREE M (trade name) or other chemicals is applied to separate heavy metals (sedimentation separation,
Step 205), sand filtration (Step 206), and mercury removal (Step 207) can be performed to satisfy the sewage drainage standard.

When utilizing a cement facility, the sediment containing heavy metals is collectively collected in this way and used as a part of the cement raw material without purifying each component. That is, the neutralization step 202 and the heavy metal separation step 20
5 and the precipitate generated in the mercury removing step 207 are filtered and separated using a filter press or the like.
And recovered as part of the cement raw material. A general cement plant in Japan consumes more than 10,000 tons of raw material (limestone is about 80%) a day. Compared to this, heavy metals recovered by the detoxification process according to the present invention are Considering the amount and content of wastewater, it is extremely small. For this reason, all of the heavy metals are taken into the cement clinker and fixed in the cement firing step. As a result, it has been confirmed by experiments that heavy metals from the cement thus produced do not elute into the environment at all.

Returning to FIG. 1, the wastewater (processed water) that has passed through the detoxification process 101 is subjected to precipitation and separation of calcium carbonate.
In the recovery step 102, sodium hydroxide (NaOH) equivalent to the calcium ions therein is added and softened. Furthermore, by guiding the combustion exhaust gas containing carbon dioxide, most of the calcium in the treated water is precipitated as calcium carbonate. The chemical reaction formula at that time is as follows. ^{Ca 2+ + K + + Cl -} + ...... + 2NaOH + CO 2 → Na + + K + +
Cl ⁻ +... + CaCO ₃ (precipitation) As the combustion exhaust gas containing carbon dioxide, it is preferable to use the combustion exhaust gas from a cement firing furnace or the like as in the detoxification treatment step 101 described above. This is effective both economically and in terms of reducing carbon dioxide emissions (environmental protection). In particular, the exhaust gas discharged from the cement firing furnace has a carbon dioxide gas concentration of about 20% as described above, which is extremely effective in view of the object of the present invention. The calcium carbonate 103 precipitated in this way is recovered by filtration and separation using a filter press or the like. The calcium carbonate separated by filtration can be washed as necessary and used as an industrial material such as a cement material.

On the other hand, since the liquid side (remaining waste water) contains a small amount of carbonate ions, hydrochloric acid or the like is added to carry out decarboxylation (step 104), and then the mixture is led to an electrodialysis apparatus to perform electrodialysis. (Step 105) is performed. 3 and 4,
The electrodialysis apparatus used in the electrodialysis step 105 will be described. First, FIG. 3 shows the principle of an electrodialysis apparatus employing a monovalent ion selectively permeable ion exchange membrane. As shown in the figure, this apparatus comprises a monovalent anion selectively permeable ion exchange membrane 3, 4, 5 and a monovalent cation selective permeable ion exchange membrane 6 between an anode plate 1 and a cathode plate 2. , 7, and 8 are provided alternately. Thereby, the dilute solution chambers 9 and 12 and the concentrate solution chamber 1
0, 11, and 13 are formed, and an anode chamber 14 and a cathode chamber 15 are further formed.

When an electric field is applied to the bipolar plates 1 and 2, ions are electrophoresed as shown. Monovalent cations such as Na ⁺ , K ^{+ and the} like in the wastewater are converted to monovalent cation selectively permeable ion exchange membrane 6,
7 and 8 are selectively permeated, and Cl ⁻ is selectively permeated through the monovalent anion selectively permeable ion exchange membranes 3, 4, and 5. Since SO ₄ ²⁻ is prevented from moving, it remains in the dilute liquid chambers 9 and 12. According to such a principle, the remaining wastewater 16 contains Na ⁺ , K ⁺ , C
l ^- ions and the water containing (monovalent ions concentrated water 17),
It is separated into water (desalinated water 18) which does not contain monovalent ions and contains a trace amount of divalent or more ions such as Ca ²⁺ and SO ₄ ^2- . The concentrated water 17 circulates as shown. The anode chamber 14 and the concentrated solution chamber 10 in the vicinity of the anode plate 1 are blocked by a normal cation exchange membrane, and a 3% H ₂ SO ₄ solution is passed as the anolyte 19. On the other hand, the cathode chamber 15 near the cathode plate 2 and the concentrated liquid chamber 1
3 is cut off with a normal ion exchange membrane, and a 3% NaCl solution is passed as the catholyte 20.

FIG. 4 shows a configuration example of a processing facility including an electrodialysis apparatus based on such a principle. In this processing equipment, the above-described monovalent anion selective permeable ion exchange membrane 42 and the monovalent cation selective permeable ion exchange membrane 43 are alternately arranged in the electrodialysis apparatus 41 and the concentrated liquid chamber 46 is concentrated. A liquid chamber 47 is provided, and a cathode chamber 44 and an anode chamber 45 having electrodes disposed at both ends are provided. The wastewater 49 is temporarily stored in a desalinated water tank 48 and supplied to the diluted liquid chamber 46 by a pump, and the concentrated water is supplied from the concentrated water tank 42 to the concentrated liquid chamber 47 and returned to the respective tanks. Then, electrodialysis is performed by applying a current to both electrodes. The desalinated water 50 returns to the desalinated water tank 48 and eventually overflows. The concentrated water 52 returns to the concentrated water tank 51 and circulates or overflows. From the anolyte tank 53, sodium chloride solution, hydrochloric acid and the like are constantly replenished to compensate for the consumption due to the electrode reaction and the fluctuation of hydrogen ions.

By adopting the electrodialysis step 105 using such an electrodialysis apparatus 41, the ratio of concentrated water to demineralized water in this step can be reduced to about 1: 4 even on an industrial scale. is there. ^{That, Na +, K +, Cl} - ions separated recovered concentrated water is volume reduction to approximately 20% of the wastewater supplied to the electrodialysis step 105. This step 1
The effect of using an electrodialyzer equipped with a monovalent ion selective ion exchange membrane at 05 is as follows. (1) Almost no unnecessary components such as Ca ²⁺ and SO ₄ ^2-
Only Na ⁺ , K ⁺ , and Cl ⁻ ions that are to be recovered as industrial raw materials can be separated with high purity and high yield. (2) In order to recover sodium chloride and potassium chloride as solids in the subsequent step, it is necessary to concentrate the solids to an appropriate concentration, thereby significantly reducing the heat energy required for boiling down, etc. The concentration and crystallization equipment can be downsized to 1/5, and both running cost and investment can be reduced. (3) The use of a softener can be reduced by using a monovalent ion selectively permeable ion exchange membrane.

In particular, the effect (1) is important in using the recovered sodium chloride or potassium chloride as an industrial raw material. The reason is that if many impurities such as Ca ²⁺ and SO ₄ ^2- are mixed, it cannot be used as an industrial raw material in many cases. As another method for performing such concentration separation, there is a reverse osmosis method. However, this method has disadvantages in the following points. ^{(1) Na +, K +} , Cl - in addition, is recovered also all Ca ²⁺ and SO ₄ ^2-like unnecessary components in the concentration-side, the purity of the finally to be collected sodium chloride or potassium chloride solids It is so low that it cannot be used as an industrial material. (2) The concentration rate is low, and the volume reduction of about 50% is the limit. For this reason, the method using electrodialysis is effective in all aspects of the quality, equipment, and energy of the collected material.

In the method described in Japanese Patent Application Laid-Open No. 9-1105, after heavy metals are removed, concentration and separation are carried out by crystallization without electrodialysis or reverse osmosis, that is, without prior concentration. Even with this method, Na ⁺ , K
^Since it contains many impurities such as Ca ²⁺ and SO ₄ ^{2- in} addition to ⁺ and Cl ⁻ and is recovered as a mixture thereof, industrial use and economic efficiency are extremely inferior. Further, in such a process, a large amount of heat energy is required for concentration, and even if concentrated, since multiple ions are present in the concentrated water, they interact with each other, and the crystallization described later is performed. It is difficult to separate high purity sodium chloride and potassium chloride by operation.

By The electrodialysis step 105, the demineralised water separated in the manner described above (recovered ^{water), Na +, K +,} Cl -
Almost all the monovalent ions to be recovered as solids, such as, have been removed, and contain trace amounts of divalent or more ions such as Ca ²⁺ and SO ₄ ^2- that remained when supplied to the electrodialysis device. In. The demineralized water has been detoxified as described above. Therefore, there is no problem even if it is used as discharge water or factory cooling water. Further, when there is a step of washing incineration ash and dust before the detoxification processing step 101, the incineration ash and dust can be circulated and used as the washing water. In this case, there is no outflow of demineralized water (recovered water) out of the system. Further, as mentioned in other portions of the present specification, the present invention can be used for washing calcium carbonate, gypsum, and the like precipitated and separated in the process of separating and recovering sodium chloride and potassium chloride.

On the other hand, in the concentrated water subjected to electrodialysis,
Na ^+, K ^+, Cl ^- almost all are concentrated.
By adding calcium hydroxide (Ca (OH) ₂₎ as required to, to recover the SO ₄ ^2-that may be mixed in a very small amount as gypsum (CaSO ₄ · 2H ₂ O) Step 106 can be performed. Then, as a component adjustment for facilitating crystallization in the next steps 107 and 108, step 107,
A small portion of the sodium chloride or potassium chloride recovered in 108 is added as needed.

Next, in the present embodiment, the concentration crystallization step 1
07 and a cooling crystallization step 108. Although the solubility of sodium chloride and potassium chloride are almost the same when used alone, they can be separated by controlling the concentration and temperature in a mixed state, as shown in the experimental results in Table 2 below.

[0027]

[Table 2]

For separation, the concentrated water is introduced into an evaporator and concentrated by evaporation to first crystallize high-purity sodium chloride, which is separated by filtration and, if necessary, washed with pure water. And concentrated (concentration crystallization step 107). The temperature at which this crystallization operation is performed is generally from 60 ° C to 95 ° C, preferably from 70 ° C to 85 ° C. The sodium chloride recovered here has a purity that can be used as an industrial salt of a raw material for soda industry such as sodium hydroxide and soda ash.

On the other hand, the filtrate (residual liquid) side in the concentration crystallization step 107 is cooled to about 10 ° C. to 40 ° C., preferably 20 ° C. to 30 ° C. to perform crystallization (cooling crystallization step 108). As a result, high-purity potassium chloride is recovered as a solid. This potassium chloride is also high in purity and can be used as an industrial raw material such as a raw material for potassium fertilizer.

In some cases, components of wastewater (particularly Na
Depending on the use of the recovered product, both components may be crystallized and separated at the same time without separating sodium chloride and potassium chloride and recovered as a mixture thereof. In each case, since it has gone through the detoxification process,
There is no problem of heavy metal content.

In both cases of separation and recovery of sodium chloride and potassium chloride, and mixed recovery, the residual liquid after concentration, crystallization and separation contains a small amount of Na ⁺ and K ^{+ which} could not be recovered.
, Cl ^- addition, there is a possibility that a mix of very trace amounts of impurities. For this reason, depending on the degree, the residual liquid is removed before the detoxification treatment step 101 or the concentration crystallization step 107.
And before the cooling crystallization step 108 or before the calcium carbonate precipitation separation / collection step 102 or the electrodialysis step 105. As a result, the method according to the present embodiment can implement a so-called closed system in which no waste flows out.

Second Embodiment Referring to FIG. 5, a second embodiment of the method for recovering industrially useful inorganic materials according to the present invention will be described. This second embodiment is different from the first embodiment in that carbon dioxide gas and sodium hydroxide are not supplied and sodium sulfate (Na ₂ SO ₄ .10H) is used.
₂ O) was added, as well as soften the wastewater, a method of recovering calcium ions as gypsum. In the present embodiment, to the detoxified wastewater (step 501), sodium sulfate equivalent to the calcium ion in the wastewater is added to soften, and calcium is recovered as gypsum (step 5).
02). The chemical reaction formula at that time is as follows. ^{Ca 2+ + K + + Cl -} + ...... + Na 2 SO 4 → 2Na + + K + + Cl -
+ …… + CaSO ₄ .2H ₂ O (precipitation) This gypsum is washed as necessary and can be used as an industrial raw material such as a cement raw material. On the other hand, the treatment on the liquid side (remaining waste water) is the same as in the first embodiment. That is, the electrodialysis step 503, the gypsum precipitation / separation step 504, the concentration crystallization step 505, the cooling crystallization step 506, and the like can be performed in the same manner as in the first embodiment.

Third Embodiment Referring to FIG. 6, a third embodiment of the method for recovering an industrially useful inorganic material according to the present invention will be described. In this embodiment, soda ash (Na ₂ C) equivalent to the calcium ion therein is added to the wastewater after the detoxification process 601.
O ₃ ) is added to soften, and calcium ions are separated and recovered as calcium carbonate (step 60).
2). The chemical reaction formula at that time is as follows. ^{Ca 2+ + K + + Cl -} + ...... + Na 2 CO 3 → 2Na + + K + + Cl -
+ CaCO ₃ (precipitation) In this case, the calcium carbonate is washed as necessary, as in the first embodiment, and can be used as an industrial material such as a cement material. On the other hand, the liquid side (remaining waste water) is decarbonated with hydrochloric acid (HCl) or the like as necessary (step 60).
3). Then, the electrodialysis step 604, the gypsum precipitation / separation step 605, the concentration crystallization step 606, the cooling crystallization step 607, and the like can be performed in the same manner as in the first embodiment.

In the methods according to the first to third embodiments, since most of Ca ²⁺ and SO ₄ ²⁻ are removed as calcium carbonate and gypsum at the beginning of the process, It has the feature that the possibility of causing process troubles due to the generation of calcium carbonate or gypsum scale therein is extremely low, and is highly practical. Note that among these embodiments, the first embodiment is the most excellent in consideration of running costs and environmental protection against carbon dioxide emission.

Here, the method according to any of the first to third embodiments requires a chemical agent such as sodium hydroxide, sodium sulfate, soda ash, and possibly a small amount of hydrochloric acid. However, for example, in the first embodiment, the generated and recovered sodium chloride can be electrolyzed to obtain sodium hydroxide (caustic soda) and hydrochloric acid.
Sodium hydroxide can be circulated to the preceding step of adding sodium hydroxide, and hydrochloric acid can be circulated to the step of adding hydrochloric acid. Such circulation can be performed in either one or both. This makes it possible to achieve closedness. Further, in the third embodiment, soda ash is produced by the ammonia / soda method (solvay method) or the like using the produced / recovered sodium chloride as a starting material, and the soda ash is circulated to the soda ash addition in the previous step to close the soda ash. Can also be planned. As a result, the whole or most of the drug to be added can be recovered and purified in a post-process, so that the running cost can be reduced and the product can be used most effectively.

[0036]

Example 1 The method according to the first embodiment described with reference to FIG. 1 was used to treat the incineration ash washing wastewater. The composition of the treated wastewater was as shown in Table 3 below. Table 3 also shows the processing results.

[0037]

[Table 3]

Example 2 The method according to the second embodiment described with reference to FIG. 5 was used to treat the incineration ash washing wastewater. The composition of the treated wastewater was as shown in Table 4 below. Table 4 also shows the processing results.

[0039]

[Table 4]

Example 3 The method according to the third embodiment described with reference to FIG. 6 was used to treat the incineration ash washing wastewater. The composition of the treated wastewater was as shown in Table 5 below. Table 5 also shows the processing results.

[0041]

[Table 5]

As will be understood from the results of Examples 1 to 3, potassium chloride and sodium chloride which are high in purity and do not contain unnecessary components such as heavy metals and which can be used industrially are individually recovered. In addition, the effect of recycling the residual liquid after the treatment could be confirmed.

[0043]

As is apparent from the above description, according to the present invention, it is possible to recover an industrially usable alkali metal salt which does not contain unnecessary components such as heavy metals and has high purity. In addition, among the alkali metal salts, while enabling potassium chloride and sodium chloride to be individually recovered, by producing, precipitating, and recovering industrially sufficiently usable substances generated in the intermediate process,
Provided are a method for recovering an industrially useful inorganic material that does not generate any unrecyclable unnecessary materials, and an industrially useful inorganic material recovered by the recovery method.

That is, according to the present invention, all products can be recovered or recycled by an inexpensive method. All recovered materials can be used as industrial raw materials, and sodium chloride and potassium chloride, which occupy most of them, are extremely high in purity and have even higher industrial utility value. Accordingly, the present invention provides a method for washing and discharging waste incineration ash and dust generated in a cement manufacturing process, leachate generated from a burial site such as incineration ash, smoke cleaning drainage from an incinerator, drainage from a sewage treatment plant, and the like. Thus, no waste is leaked out of the system, which can be said to be harmless in terms of environmental preservation, and at the same time, a substance having high utility value as an industrial raw material can be produced. That is, the present invention is highly economical and excellent as a zero emission closed system.

[Brief description of the drawings]

FIG. 1 is a flow chart illustrating a first embodiment of a method for recovering an industrially useful inorganic material according to the present invention.

FIG. 2 is a flowchart illustrating an embodiment of a detoxification process that can be employed in the present invention.

FIG. 3 is a conceptual diagram illustrating the principle of electrodialysis.

FIG. 4 is a conceptual diagram illustrating an embodiment of an electrodialysis apparatus that can be employed in the present invention.

FIG. 5 is a flowchart illustrating a second embodiment of the method for recovering an industrially useful inorganic material according to the present invention.

FIG. 6 is a flowchart illustrating a third embodiment of the method for recovering an industrially useful inorganic material according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Anode plate 2 Cathode plate 3, 4, 5, 42 Monovalent anion selective permeable ion exchange membrane 6, 7, 8, 43 Monovalent cation selective permeable ion exchange membrane 9, 12, 46 Dilute liquid chamber 10, 11, 13, 47 Concentrated liquid compartment 14, 45 Anode compartment 15, 44 Cathode compartment 16 Residual drainage 17, 52 Monovalent ion concentrate 18, 50 Demineralized water 19 Anolyte 20 Catholyte 41 Electrodialyzer 48 Demineralized water tank 49 Drainage 51 Concentrated water tank 101, 501, 601 Detoxification process 102, 602 Calcium carbonate precipitation / separation process 104, 603 Decarboxylation process 105, 503, 604 Electrodialysis process 106, 504, 605 Gypsum precipitation / separation process 107, 505, 606 Concentration crystallization step 108, 506, 607 Cooling crystallization step 201 Wastewater 202 Neutralization step 203 Combustion exhaust gas 205 Heavy metal Genus separation step 206 sand filtration step 207 mercury removal step 208 filtration separation step 502 gypsum recovery step

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01D 9/02 606 B01D 9/02 606 615 615A 618 618A C01D 3/04 C01D 3/04 Z C01F 11/18 C01F 11/18 B 11/46 11/46 Z C02F 1/20 C02F 1/20 A 1/469 1/52 ZABK 1/52 ZAB 9/00 502B 9/00 502 502K 502P 502Z 503G 503 504B 504 504E 1 / 46 103 (72) Inventor Kazumasa Saka 3-8-1, Nishikanda, Chiyoda-ku, Tokyo Taiheiyo Cement Co., Ltd. (72) Inventor Hiroshi Kobayashi 2-1-2 Marunouchi, Chiyoda-ku, Tokyo Asahi Glass Co., Ltd. In-company (72) Inventor Hidenori Shibata Asahi Glass Co., Ltd. 2-1-2 Marunouchi, Chiyoda-ku, Tokyo F-term (reference) 4D037 AA11 AB07 AB08 BA23 BB09 CA01 CA04 CA06 CA15 4D061 DA08 DB18 EA09 EB01 EB13 EB17 EB19 FA02 FA03 FA14 FA20 4D062 BA21 BB02 CA17 CA20 DA39 EA23 EA32 FA12 FA16 FA30 BA03 A03 BC BE11 CA02

Claims (11)

[Claims] 1. A detoxification process for removing heavy metals in wastewater, and electricity for separating and recovering the treated water as concentrated water containing monovalent ions by an electrodialysis device equipped with a monovalent ion-selective ion exchange membrane. An industrially useful method for recovering an inorganic material, comprising: a dialysis step; and a step of separating and recovering the inorganic material as an alkali metal salt such as sodium chloride or potassium chloride from the recovered water by a crystallization operation. 2. The method according to claim 1, wherein the residual liquid obtained after recovering the industrially useful inorganic material is circulated to the previous step by the composition of the solute, and the solute is recovered so that no waste is generated outside the system. The method for recovering an industrially useful inorganic material according to claim 1. 3. The step of separating and recovering the inorganic material includes a crystallization step of recovering sodium chloride by a crystallization operation;
3. A method for recovering an industrially useful inorganic material according to claim 1, further comprising a cooling crystallization step of individually recovering potassium chloride by cooling the remaining liquid. 4. Addition of sodium hydroxide to the waste water from which heavy metals have been precipitated and removed in the detoxification step before the electrodialysis step and introduction of a gas containing carbon dioxide to reduce the calcium content in the waste water and the like. The method for recovering an industrially useful inorganic material according to any one of claims 1 to 3, further comprising a step of separating and recovering calcium carbonate by precipitation and recovery of calcium carbonate as calcium carbonate. 5. The industrially useful method according to claim 4, further comprising a decarboxylation step of adding a small amount of hydrochloric acid or the like to perform decarboxylation after the calcium carbonate precipitation separation / recovery step. For recovering inorganic materials. 6. The method for recovering an industrially useful inorganic material according to claim 4 or 5, wherein the sodium chloride recovered in the crystallization step is electrolyzed, and the sodium hydroxide generated thereby is subjected to the electrodialysis step. A method for recovering an industrially useful inorganic material, characterized in that it is circulated as sodium hydroxide to be added before the step (b) to make the material closed. 7. The method for recovering an industrially useful inorganic material according to claim 5, wherein the sodium chloride recovered in the crystallization step is electrolyzed, and the hydrochloric acid generated thereby is added in the decarbonation step. A method for recovering industrially useful inorganic materials, characterized in that it is circulated and closed. 8. To the wastewater from which heavy metals have been precipitated and removed in the detoxification step, sodium sulfate is added before the above-mentioned electrodialysis step, and the calcium content in the wastewater and the like is separated and collected as gypsum that can be used as a cement raw material or the like. The method for recovering an industrially useful inorganic material according to any one of claims 1 to 3, further comprising a step. 9. The method according to claim 1, further comprising the step of adding soda ash to the wastewater from which heavy metals have been precipitated and removed in the detoxification step before the electrodialysis step, and separating and recovering the calcium content as calcium carbonate. Item 5. The method for recovering an industrially useful inorganic material according to any one of Items 1 to 3. 10. The method for recovering an industrially useful inorganic material according to claim 9, wherein the soda ash is produced by an ammonia-soda method using sodium chloride recovered in the crystallization step as a starting material. Is recycled as soda ash added before the above-mentioned electrodialysis step so as to be closed, thereby recovering an industrially useful inorganic material. 11. An industrially useful inorganic material recovered by the industrially useful inorganic material recovery method according to any one of claims 1 to 10.