JP6467651B2 - Method for producing aluminum compound solution - Google Patents

Description

  The present invention relates to a method for producing an aluminum compound solution as an agent used for decomposing a flocculant and various reactive agents, particularly borofluoride, from an alkaline wastewater containing aluminum.

  Conventionally, in the field of aluminum processing, a large amount of alkaline chemicals is used for surface treatment of products and cleaning of molds and jigs, and used alkaline chemicals are discharged as aluminum-containing alkaline waste water.

  Among these alkaline wastewaters, wastewater having a high alkali concentration and low aluminum content is widely used as a neutralizing agent and the like. However, for wastewater with a high aluminum content, when used as a neutralizing agent, etc., the viscosity of the reaction solution increases, and not only the intended reaction cannot be performed, but the reaction solution is gelled and sufficient liquid stirring cannot be performed. Safety was also hindered, such as not being able to remove heat smoothly. Moreover, since a large amount of sludge is generated after the reaction, a large cost has occurred for the disposal. For this reason, alkaline waste liquids containing a large amount of aluminum cannot be effectively used, and most of them are disposed as landfills after stabilization treatment as industrial waste.

  In recent years, from the viewpoint of resource recycling, proposals have been made to extract beneficial aluminum from aluminum-containing alkaline wastewater. For example, as described in Patent Document 1, an alkali waste solution containing aluminum is continuously extracted in an etching process, and aluminum hydroxide crystals are added thereto to hydrolyze aluminate ions, thereby solid-liquid separation. Thus, a method has been proposed in which aluminum hydroxide is recovered and the liquid is returned to the etching step.

According to this method, since the neutralization step of the aluminum-containing alkaline waste liquid is not performed, the gelation of the liquid can be suppressed, but the hydrolysis reaction takes time and there is a problem in productivity. Furthermore, since the crystal grains of the produced aluminum hydroxide are large, there is a problem that the reactivity when used as a raw material for other aluminum compounds becomes poor.

  Patent Document 2 discloses a method in which a neutralizing agent is added to a waste solution containing aluminum hydroxide for neutralization and then agglomerated, and a seed crystal of aluminum hydroxide is further added to continuously obtain aluminum hydroxide crystals. Has been proposed.

  According to this method, it is possible to continuously obtain aluminum hydroxide crystals, but in order to suppress gelation, it is necessary to reduce the aluminum concentration in the solution to perform a neutralization reaction. Since the crystallization of aluminum hydroxide is promoted based on the seed crystal of aluminum hydroxide, there is a problem that the reactivity when used as a raw material for other aluminum compounds becomes poor.

  On the other hand, the aluminum compound is used as a decomposition agent for borofluoride contained in waste water. Borofluoride is an ion generated by etching with hydrofluoric acid such as borosilicate glass and has extremely high ionic stability. Therefore, in order to treat wastewater containing borofluoride, borofluoride is decomposed and fluorine And boron need to be treated separately. As the decomposition agent, an aluminum compound such as aluminum sulfate / aluminum chloride or polyaluminum chloride is used. Moreover, these compounds are widely used as inorganic flocculants in water treatment, and inexpensive production methods are required.

  Such aluminum sulfate or aluminum chloride is generally produced by reacting an acid with crystalline aluminum hydroxide produced by the Bayer method. For example, Patent Document 3 proposes a method for producing an aluminum compound solution by using aluminum hydroxide obtained by the Bayer method as a raw material and heating and dissolving it in sulfuric acid or hydrochloric acid.

  According to this method, since an aluminum compound solution is produced using high-purity aluminum hydroxide as a raw material, an aluminum compound solution having a low impurity concentration can be obtained. However, since aluminum hydroxide produced by the Bayer method has high crystallinity, there is a problem in productivity, such as increasing the reaction temperature or increasing the reaction time in order to dissolve it in sulfuric acid or hydrochloric acid. there were.

JP-A-47-042436 JP-A-2005-272210 JP 2006-045053 A

  The present invention has been made in view of the above circumstances, and is an agent that decomposes borofluoride contained in wastewater by extracting aluminum contained in the wastewater by treating alkaline wastewater having a high aluminum content. And a method for producing an aluminum compound solution which is a flocculant such as factory waste water.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors added an alkaline wastewater having a high aluminum content to the acid to separate the aluminum compound, and reacted the aluminum compound with hydrochloric acid and / or sulfuric acid. The present inventors have found that the above problems can be solved and have completed the present invention.

That is, the present invention is an alkaline wastewater containing aluminum,
(1) Add the waste water to a tank holding an acid solution in the range of 1.0 to 3.0 mol / L over 30 minutes, and neutralize to pH 4-8 In this step, aluminum hydroxide and / or aluminum sulfate is synthesized by mixing the solid separated in the first step (2) (1) with hydrochloric acid and / or sulfuric acid after the aluminum hydroxide is precipitated. A method for producing an aluminum compound solution comprising two steps.

  According to this structure, the precipitation reaction of aluminum hydroxide can be performed in the acidic region in the first step, and the amount of aluminate ions dissolved in the reaction solution is increased by adjusting the addition time. Therefore, aluminum hydroxide can be obtained without causing gelation. In addition, by setting the end point pH of the first step to the acid side, even when other metal ions are contained in the acid or alkali drainage used, the precipitation of these metal salts and metal hydroxides is suppressed. Therefore, the purity of the finally obtained aluminum compound solution can be improved.

  The solid obtained in the first step can be dissolved by mixing with hydrochloric acid and / or sulfuric acid in the second step to obtain an aluminum compound solution. In particular, since the solid obtained in the first step has a low crystallinity, unlike the case where it is produced by the Bayer method, the solid is rich in reactivity and rapidly proceeds at room temperature.

  The acid used in the first step is desirably at least one acid selected from mineral acids such as hydrochloric acid, sulfuric acid and nitric acid, and organic acids such as acetic acid / oxalic acid and paratoluenesulfonic acid. These acids may be by-products, reused materials, or waste materials. When impurities are contained in these acids, the impurity concentration in the precipitated aluminum hydroxide can be lowered by adjusting the end point pH of the first step. Among these acids, it is desirable to use hydrochloric acid / sulfuric acid or a highly biodegradable organic acid in consideration of treatment and disposal of the reaction solution.

  By using these acids, the reaction with the aluminate ions is carried out quickly, the amount of aluminum dissolved in the reaction solution can be suppressed, gelation can be suppressed, and it is contained in alkaline drainage. Most of the aluminum can be recovered as aluminum hydroxide.

  Further, in the present invention, in the second step, it is preferable to mix hydrochloric acid and / or sulfuric acid using a part of the produced aluminum compound solution as a dispersion medium of aluminum hydroxide.

  A part of the aluminum compound solution produced in the second step is returned and used as a dispersion medium of aluminum hydroxide to dilute the reaction components, and heat generated during the reaction of aluminum hydroxide with hydrochloric acid and / or sulfuric acid. Can be controlled, and the reaction can be performed safely. Furthermore, since aluminum hydroxide is dispersed in advance, the contact with hydrochloric acid and / or sulfuric acid is smoothly performed, so that the reactivity is improved.

  Moreover, it is preferable that the aluminum content in the alkaline waste water in this invention is 2 wt% or more, More preferably, it is 4 wt% or more.

  When the aluminum content in the alkaline wastewater is less than 2 wt%, not only the amount of aluminum hydroxide obtained per reaction is decreased, but the alkaline wastewater with a low aluminum content generally has a higher alkali concentration. Therefore, a large amount of acid necessary for neutralization is required, which increases the cost. In order to manufacture more efficiently, it is desirable to contain 4 wt% or more of aluminum.

  In the present invention, an aluminum compound solution is used for decomposition of borofluoride.

  The aluminum compound solution of the present invention is considered difficult to take a network structure from the manufacturing process. For this reason, when the aluminum compound solution according to the present invention is added to borofluoride-containing wastewater, it is diffused at a higher rate than polyaluminum chloride and aluminum sulfate, which are generally used as chemicals for water treatment, and therefore borofluoride. It becomes possible to improve the decomposition rate of the.

  The waste water after decomposing borofluoride with the aluminum compound solution of the present invention can be treated by a conventionally known method. However, in the process of reacting with a calcium compound, the amount of precipitate produced can be suppressed. Therefore, it is preferable to use hydrochloric acid as the second step.

  According to the method of the present invention, the aluminum concentration, which has been difficult to reuse in the past, is high even when aluminum-containing alkaline drainage containing impurities such as silicon, or waste acid containing metal ions such as iron is used. It can be regenerated as a compound solution. The obtained aluminum compound solution can be used not only as a decomposition agent for borofluoride ions, which are hardly decomposable compounds, but also as a flocculant in wastewater treatment.

It is a processing flowchart which shows one Embodiment of the manufacturing method of the aluminum compound solution from the alkaline waste liquid containing aluminum based on this invention. It is a processing flow figure showing one embodiment of the 1st process concerning the manufacturing method of the present invention. It is a processing flow figure showing one embodiment of the 2nd process concerning the manufacturing method of the present invention. It is a processing flow figure showing another embodiment of the 2nd process concerning the manufacturing method of the present invention. It is a diagram showing the decomposition rate of HBF ₄ by the aluminum compound solutions according to the invention

  Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, in the present invention, aluminum hydroxide is contained in an aluminum-containing alkaline waste liquid by introducing the waste water into a tank holding an acid having a specific acid concentration as a first step over a certain period of time. After precipitation, solid-liquid separation is performed. Next, as a second step, an aluminum compound solution is obtained by adding hydrochloric acid or sulfuric acid to the solid obtained in the first step and dissolving it.

(First step)
As shown in FIG. 2, in the first step, aluminum hydroxide is precipitated by supplying an aluminum-containing alkaline wastewater to a reaction tank 1 holding a solution having a specific acid concentration to perform a neutralization reaction. The reaction liquid is separated into a solid and a liquid by a solid-liquid separation device, and the liquid is checked for components and amounts contained and reused or appropriately processed as a waste liquid. The solid content is transferred to the second step after washing. The solid-liquid separation device is not particularly limited as long as it is generally used, but may be appropriately selected according to the properties of the reaction solution, such as a filter press, a centrifuge, a screw decanter or a thickener. it can.

(Second step)
As shown in FIG. 3, in the second step, the solid material made of aluminum hydroxide obtained in the first step is supplied to the reaction tank 2 and hydrochloric acid or sulfuric acid is added. The order of charging into the reaction tank 2 is not limited, but it is also possible to use an aluminum compound solution produced in advance as a dispersion medium for the aluminum hydroxide obtained in the first step as shown in FIG. In this case, the reaction can be carried out by adding the aluminum compound solution to the reaction tank 2 together with the aluminum hydroxide obtained in the first step and stirring, and then adding hydrochloric acid or sulfuric acid. The addition ratio of the aluminum compound solution can be appropriately selected in view of the dispersion state and productivity of aluminum hydroxide, but can be set to 1/4 to 1/2 of the final reaction solution amount as a guide. If the amount of the aluminum compound solution is less than 1/4 of the final reaction solution volume, it is difficult to disperse the aluminum hydroxide, and the addition effect is lacking. Since the amount of the aluminum compound solution that can be produced by the method is reduced, there is a possibility that the productivity may be affected.

  The aluminum compound solution obtained by these two steps can be used as a borofluoride decomposing agent or a coagulant as it is or after being diluted.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited by description of a following example.

・ Process 1
In a 1000 mL beaker, 400 g of diluted sulfuric acid diluted to a sulfuric acid concentration of 6.9 wt% (acid concentration = 1.5 mol / L) is placed, and a desktop stirrer / pH meter is inserted. From the dropping funnel, 106 g of aluminum-containing alkaline waste water having an Al concentration of 7.8 wt% and an NaOH concentration of 5.7 wt% was quantitatively added to the dilute sulfuric acid over 60 minutes. When the pH of the reaction solution reached 6, the addition was stopped and the reaction solution was subjected to solid-liquid separation by filtration under reduced pressure to obtain aluminum hydroxide (1) (water content 73.6 wt%, Al = 31.6 wt% (dry base)) 122 g Got.
・ Process 2
110 g of aluminum hydroxide (1) obtained in the above step 1 is prepared in a 500 mL beaker, and a table stirrer is inserted. To this beaker, 110 g of 35% hydrochloric acid was added and stirred for 180 minutes to obtain 220 g of an aluminum compound solution (1) (Al = 4.7 wt%). The maximum temperature at this time was 70 ° C., and the temperature change from the initial temperature was 44 ° C.

・ Process 1
In a 1000 mL beaker, 400 g of diluted sulfuric acid diluted to a sulfuric acid concentration of 6.9 wt% (acid concentration = 1.5 mol / L) is placed, and a desktop stirrer / pH meter is inserted. From the dropping funnel, 106 g of aluminum-containing alkaline waste water having an Al concentration of 7.8 wt% and an NaOH concentration of 5.7 wt% was quantitatively added to the dilute sulfuric acid over 60 minutes. When the pH of the reaction solution reaches 6, the addition is stopped, and the reaction solution is solid-liquid separated by filtration under reduced pressure to obtain 125 g of aluminum hydroxide (2) (water content 74.2 wt%, Al = 31.8 wt% (dry base)). Got.
・ Process 2
In a 500 mL beaker, 100 g of the aluminum hydroxide (2) obtained in the above step 1 and 200 g of the aluminum compound solution (1) (Al = 4.7 wt%) obtained in Example 1 were prepared, and a table stirrer was inserted. Stir for about 30 minutes until the compound is dispersed. To this beaker, 100 g of 35% hydrochloric acid was added and stirred for 120 minutes to obtain 400 g of an aluminum compound solution (2) (Al = 4.8 wt%). The maximum temperature at this time was 45.0 ° C., and the temperature change from the initial temperature was 17.1 ° C.

・ Process 1
In a 500 mL beaker, 200 g of diluted sulfuric acid diluted to a sulfuric acid concentration of 12.0 wt% (acid concentration = 2.6 mol / L) is placed, and a desktop stirrer / pH meter is inserted. From the dropping funnel, 93 g of aluminum-containing alkaline waste water having an Al concentration of 7.8 wt% and an NaOH concentration of 5.7 wt% was quantitatively added to the dilute sulfuric acid over 60 minutes. When the pH of the reaction solution reached 6, the addition was stopped, and the reaction solution was subjected to solid-liquid separation by filtration under reduced pressure to obtain aluminum hydroxide (3) (water content 75.5 wt%, Al = 31.6 wt% (dry basis)) 112 g Got.
・ Process 2
In a 500 mL beaker, 100 g of the aluminum hydroxide (3) obtained in the above step 1 and 200 g of the aluminum compound solution (2) (Al = 4.8 wt%) obtained in Example 2 were prepared, and a table stirrer was inserted. Stir for about 30 minutes until the compound is dispersed. 100 g of 35% hydrochloric acid was added to this beaker and stirred for 120 minutes to obtain 400 g of an aluminum compound solution (3) (Al = 4.7 wt%). The maximum temperature at this time was 44.3 ° C., and the temperature change from the initial temperature was 16.4 ° C.

・ Process 1
In a 500 mL beaker, 200 g of diluted sulfuric acid diluted to a sulfuric acid concentration of 12.0 wt% (acid concentration = 2.6 mol / L) is placed, and a desktop stirrer / pH meter is inserted. From the dropping funnel, 84 g of aluminum-containing alkaline waste water having an Al concentration of 4.3 wt% and an NaOH concentration of 11.0 wt% was quantitatively added to the dilute sulfuric acid over 30 minutes. When the pH of the reaction solution reached 6, the addition was stopped and the reaction solution was solid-liquid separated by filtration under reduced pressure to obtain 116 g of aluminum hydroxide (4) (water content 76.5 wt%, Al = 31.0 wt% (dry base)). Got.
・ Process 2
In a 500 mL beaker, 100 g of the aluminum hydroxide (4) obtained in the above step 1 and 200 g of the aluminum compound solution (3) (Al = 4.7 wt%) obtained in Example 3 were prepared, and a table stirrer was inserted. Stir for about 30 minutes until the compound is dispersed. To this beaker, 100 g of 35% hydrochloric acid was added and stirred for 120 minutes to obtain 400 g of an aluminum compound solution (4) (Al = 4.6 wt%). The maximum temperature at this time was 50.6 ° C., and the temperature change from the initial temperature was 16.6 ° C.

・ Process 1
In a 1000 mL beaker, 400 g of diluted sulfuric acid diluted to a sulfuric acid concentration of 6.9 wt% (acid concentration = 1.5 mol / L) is placed, and a desktop stirrer / pH meter is inserted. From the dropping funnel, 104 g of aluminum-containing alkaline waste water having an Al concentration of 7.8 wt% and an NaOH concentration of 5.7 wt% was quantitatively added to the dilute sulfuric acid over 120 minutes. When the pH of the reaction solution reached 6, the addition was stopped, and the reaction solution was subjected to solid-liquid separation by filtration under reduced pressure to obtain 110 g of aluminum hydroxide (5) (water content 72.8 wt%, Al = 30.5 wt% (dry base)). Got.
・ Process 2
In a 500 mL beaker, 100 g of the aluminum hydroxide (5) obtained in the above step 1 and 200 g of the aluminum compound solution (4) (Al = 4.6 wt%) obtained in Example 4 were prepared, and a table stirrer was inserted. Stir for about 30 minutes until the compound is dispersed. 100 g of 35% hydrochloric acid was added to this beaker and stirred for 120 minutes to obtain 400 g of an aluminum compound solution (5) (Al = 4.7 wt%). The maximum temperature at this time was 48.0 ° C., and the temperature change from the initial temperature was 18.2 ° C.

・ Process 1
In a 500 mL beaker, put 200 g of an iron chloride aqueous solution with an HCl concentration of 8.2 wt% (acid concentration = 2.7 mol / L) and an Fe concentration of 6.0 wt%, and insert a desktop stirrer and pH meter. From the dropping funnel, 78 g of aluminum-containing alkaline waste water having an Al concentration of 10.9 wt% and an NaOH concentration of 8.0 wt% was quantitatively added to the acidic aqueous solution over 60 minutes. When the pH of the reaction solution reached 4, the addition was stopped and the reaction solution was subjected to solid-liquid separation by filtration under reduced pressure to obtain aluminum hydroxide (6) (water content 74.9 wt%, Al = 30.7 wt% (dry base), Fe = 9.7 wt% (dry base)) 106 g was obtained.
・ Process 2
In a 500 mL beaker, 100 g of the aluminum hydroxide (6) obtained in Step 1 above, 100 g of the aluminum compound solution (4) obtained in Example 4 (Al = 4.6 wt%) and the aluminum compound solution obtained in Example 5 ( 5) Prepare 100 g of (Al = 4.7 wt%), insert a desktop stirrer, and stir for about 30 minutes until the aluminum compound is dispersed. 100 g of 35% hydrochloric acid was added to this beaker and stirred for 120 minutes to obtain 400 g of an aluminum compound solution (6) (Al = 4.0 wt%, Fe = 0.5 wt%). The maximum temperature at this time was 49.0 ° C., and the temperature change from the initial temperature was 12.8 ° C.

・ Process 1
400 g of p-toluenesulfonic acid aqueous solution having a concentration of 37.0 wt% (acid concentration = 2.4 mol / L) is put into a 1000 mL beaker, and a desktop stirrer / pH meter is inserted. From the dropping funnel, 126 g of aluminum-containing alkaline waste water having an Al concentration of 8.6 wt% and an NaOH concentration of 6.0 wt% was quantitatively added to the acidic aqueous solution over 120 minutes. When the pH of the reaction solution reached 8, the addition was stopped, and the reaction solution was separated into solid and liquid by filtration under reduced pressure to obtain 138 g of aluminum hydroxide (7) (water content 68.8 wt%, Al = 32.2 wt% (dry base)). Got.
・ Process 2
In a 500 mL beaker, 100 g of the aluminum hydroxide (7) obtained in the above step 1 and 200 g of the aluminum compound solution (5) (Al = 4.7 wt%) obtained in Example 5 were prepared, and a table stirrer was inserted. Stir for about 30 minutes until the compound is dispersed. To this beaker, 100 g of 35% hydrochloric acid was added and stirred for 120 minutes to obtain 400 g of an aluminum compound solution (7) (Al = 5.0 wt%). The maximum temperature at this time was 47.5 ° C., and the temperature change from the initial temperature was 15.2 ° C.

・ Process 1
In a 500 mL beaker, 200 g of diluted sulfuric acid diluted to a sulfuric acid concentration of 5.0 wt% (acid concentration = 1.0 mol / L) is placed, and a desktop stirrer / pH meter is inserted. From the dropping funnel, 74 g of aluminum-containing alkaline waste water having an Al concentration of 8.3 wt% and an NaOH concentration of 5.8 wt% was quantitatively added to the dilute sulfuric acid over 120 minutes. When the pH of the reaction solution reached 6, the addition was stopped, and the reaction solution was subjected to solid-liquid separation by filtration under reduced pressure, and aluminum hydroxide (8) (water content 68.1 wt%, Al = 30.0 wt% (dry base)) 130 g Got.
・ Process 2
In a 500 mL beaker, 130 g of aluminum hydroxide (8) obtained in the above step 1 is prepared, and a desktop stirrer is inserted. 100 g of 35.0% sulfuric acid was added to this beaker and stirred for 300 minutes to obtain 400 g of an aluminum compound solution (8) (Al = 3.6 wt%). The maximum temperature at this time was 52.8 ° C., and the temperature change from the initial temperature was 15.8 ° C.

The HBF ₄ -containing hydrofluoric acid waste solution was neutralized with 10% calcium hydroxide solution to pH = 6, and then diluted so that the F concentration was 3000 mg / L (F = 3000 mg / L, HBF ₄ = 3466 mg / L) Prepare 1000 mL. In a 200 mL plastic beaker, 100 mL of this treated stock solution is collected, and the aluminum compound solution (1) is added at a ratio of Al: 0.5 mol to F: 1 mol of the test solution. Similarly, a solution to which aluminum compound solutions (2) to (8) are added and a solution in which PAC (polyaluminum chloride: Al = 5.4 wt%) is added after adjusting the pH to 3 with sulfuric acid are prepared. Each is stirred for 3 hours, then neutralized with 10 wt% calcium hydroxide solution to pH = 8.5, separated into solid and liquid, and the F concentration of the filtrate is analyzed. The results are shown in Table 1. It turns out that all have HBF ₄ decomposition | disassembly performance equivalent to or more than PAC.
Further, regarding the aluminum compound solution (2), when the HBF ₄ decomposition test was similarly performed under the condition that the addition amount was doubled, the F reduction rate was 98.7%.

Under the condition that the stirring time was 1 hour using the aluminum compound solution (2) and PAC, an HBF ₄ decomposition test was performed in the same manner as in Example 9, and the F decrease rate relative to the Al addition amount was measured. The result is shown in FIG. Compared to PAC, the system using the aluminum compound solution of the present invention had a larger F reduction rate, and the aluminum compound solution effectively acted on HBF ₄ decomposition even for a short time reaction.

(Comparative Example 1)
A 100 mL beaker is charged with 100 g of an aluminum-containing alkaline wastewater having an Al concentration of 7.8 wt% and an NaOH concentration of 5.7 wt%, and a desktop stirrer and a pH meter are inserted. Dilute sulfuric acid diluted to a sulfuric acid concentration of 6.9 wt% (acid concentration = 1.5 mol / L) from the dropping funnel was quantitatively added to the alkaline waste liquid over 60 minutes. However, the reaction solution gelled at about pH = 10 and could not be stirred.

(Comparative Example 2)
In a 500 mL beaker, 200 g of diluted sulfuric acid diluted to a sulfuric acid concentration of 24.7 wt% (acid concentration = 5.0 mol / L) is placed, and a desktop stirrer / pH meter is inserted. From the dropping funnel, an aluminum-containing alkaline wastewater having an Al concentration of 4.3 wt% and an NaOH concentration of 10.1 wt% was quantitatively added to the dilute sulfuric acid over 60 minutes. However, the reaction solution gelled at about pH = 3.5 and could not be stirred.

(Comparative Example 3)
In a 1000 mL beaker, 400 g of diluted sulfuric acid diluted to a sulfuric acid concentration of 6.9 wt% (acid concentration = 1.5 mol / L) is placed, and a desktop stirrer / pH meter is inserted. From the dropping funnel, 106 g of aluminum-containing alkaline waste water having an Al concentration of 7.8 wt% and an NaOH concentration of 5.7 wt% was quantitatively added to the dilute sulfuric acid over 10 minutes. When about 1 minute had elapsed after completion of the addition, the reaction solution gelled and could not be stirred.

(Comparative Example 4)
・ Process 1
Aluminum hydroxide was synthesized in the same manner as in Step 6 of Example 6 except that the final pH was 10. Comparative aluminum hydroxide (2) (water content 70.76 wt%, Al = 25.6 wt%, Fe = 25.9 wt%).
・ Process 2
In a 500 mL beaker, 100 g of the comparative aluminum hydroxide (2) obtained in the above step 1, [Example 2] 100 g of the aluminum compound solution (2) (Al = 4.8 wt%) obtained in the step 2, and [Example 3]. 100 g of the aluminum compound solution (3) obtained in step 2 (Al = 4.7 wt%) is prepared, a table stirrer is inserted, and the mixture is stirred for about 30 minutes until the aluminum hydroxide is dispersed. To this beaker, 100 g of 35% hydrochloric acid was added and stirred for 120 minutes to obtain 400 g of a comparative aluminum compound solution (1) (Al = 4.0 wt%, Fe = 1.7 wt%). The maximum temperature at this time was 44.1 ° C., and the temperature change from the initial temperature was 12.0 ° C. When this comparative aluminum compound solution (1) was used as an HBF ₄ decomposition chemical in the same manner as in Example 9, a large amount of iron hydroxide sludge was generated by neutralization after the decomposition treatment because of high Fe concentration.

Claims (4)

In alkaline wastewater containing aluminum,
(1) Add the waste water to a tank holding an acid solution in the range of 1.0 to 3.0 mol / L over 30 minutes, and neutralize to pH 4-8 In this step, aluminum hydroxide and / or aluminum sulfate is synthesized by mixing the solid separated in the first step (2) and (1) with hydrochloric acid and / or sulfuric acid. The manufacturing method of the aluminum compound solution which consists of two processes. The method for producing an aluminum compound solution according to claim 1, wherein in the second step, hydrochloric acid and / or sulfuric acid are mixed using a part of the produced aluminum compound solution as a dispersion medium for aluminum hydroxide. The method for producing an aluminum compound solution according to claim 1 or 2, wherein the aluminum content in the alkaline waste water is 2 wt% or more. The method for producing an aluminum compound solution according to any one of claims 1 to 3, wherein the aluminum compound solution is used for decomposition of borofluoride.

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