JPS6257398B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a method for treating water containing borofluoric acid and borofluorinated heavy metal compounds. Compounds with the borofluoride ion BF ₄ ^- , such as borofluoric acid and borofluoride heavy metal compounds (e.g., lead borofluoride, zinc borofluoride, etc.), are stable compounds that do not easily react with calcium salts. It is difficult to treat water containing . Various processing methods have been proposed for this purpose. The conventionally proposed treatment method is
As seen in Publication No. 92561, one or more of aluminum sulfate, aluminum bromide, aluminum chloride, or ferric salt is added to water containing a borofluoride compound, and then a water-soluble aluminum compound is added. A treatment method in which a water-soluble aluminum compound is added after adding a calcium salt has been reported. JP-A-52-26759 discloses that at least one selected from metallic aluminum, aluminum hydroxide, sodium aluminate, aluminum nitrate, aluminum acetate, or alum [KAl(SO ₄ ) ₂ ] is added to the borofluorine compound-containing water. A treatment method of adding the above, then separating and removing the formed precipitate with or without addition of a calcium salt to the solution, and adding water-soluble aluminum to the supernatant liquid. Furthermore, JP-A-52-68754 discloses that borofluoride compound-containing wastewater contains metallic aluminum or aluminum hydroxides, chlorides, bromides, nitrates,
A method of mixing with one or more selected from sulfates, acetates, aluminates, alum [KAl(SO ₄ ) ₂ ], and ferric salts, and treating with or without addition of calcium salts, and a method in advance A method for pre-treating wastewater by adding calcium salts is described. According to the above-mentioned known treatment method, it is possible to treat the fluorine content to a much lower concentration than the fluorine concentration (15 mg/or less) regulated by the Water Pollution Control Law. However, in the conventional method, when carried out industrially, it is necessary to shorten the decomposition time of borofluoric acid and borofluorinated heavy metal compounds (hereinafter collectively referred to simply as borofluorides) and reduce the amount of decomposition agent used. The reality is that there is a strong demand for this. In order to meet the above-mentioned needs, the present invention was developed with the intention of improving the conventionally known method for treating borofluorides. It is characterized by adding one or more of aqueous ammonia, ammonium sulfate, ammonium chloride, and urea as a decomposition aid to the main decomposition agent to decompose the borofusate, and then adding calcium hydroxide to separate and remove the formed precipitate. do. The decomposition mechanism by the decomposition main agent of borofuside is presumed to be based on the following formula. 2 [BF ₄ ] ^- +Al ₂ (SO ₄ ) ₃ +6H ₂ O→ _{2H 3} BO ₄ +3H ₂ SO ₄ +2AlF ₃ +2HF In this decomposition reaction, the higher the concentration of borofluoride, the more the amount of main decomposition agent added. Although it increases logarithmically, when the above-mentioned decomposition aid is added, the amount of the decomposition main agent added decreases, as shown in the test examples described later. The reason for the action of the decomposition aid is not clear, but the ammonia ion of the decomposition aid generates NH ₄ BF ₄ ,
Furthermore, heavy metals and [Cu
It is thought that the decomposition reaction proceeds smoothly by producing salts such as (NH ₃ ) ₄ ]SO ₄ and [Zn(NH ₃ ) ₄ ]SO ₄ . In addition, substances such as urea that decompose to generate carbon dioxide gas (NH ₂ ) ₂ CO + 2H ₂ O→2NH ₄ ⁺ +CO ₂ +H ₂ O are particularly susceptible to the formation of grain boundaries of borofusated heavy metal compounds due to this CO ₂ gas. It also contributes to making the membrane gas-destructive. Although the above decomposition reaction is accelerated even at room temperature, heating is effective in accelerating the decomposition rate. However, the temperature should be kept at a level that does not encourage ammonia dispersion. Adjusting the pH value during the decomposition reaction to 5 or less promotes the decomposition reaction. The amounts of the main decomposition agent and the auxiliary agent are regulated by the decomposition temperature, decomposition time, and desired fluorine concentration after treatment, and should be determined in advance through experiments. Calcium hydroxide is added to the treatment solution resulting from the decomposition reaction to fix the fluorine component produced by the decomposition as an insoluble fluoride, and a portion of it is adsorbed to the undecomposed base decomposition agent. The fixation reaction of the above-mentioned fluorine components is promoted under pH values in the neutral range or higher. After the calcium reaction, the resulting precipitate is separated into solid and liquid according to a conventional method. At this time, if the pH is high, it is naturally necessary to make it neutral due to regulations. During the above-mentioned solid-liquid separation, most of the boron becomes an insoluble fluoride and is removed, and at the same time, most of the heavy metals are also removed. In an embodiment of the present invention, as described in conventional treatment methods, a calcium salt is added to the borofluoride-containing water before the decomposition reaction to remove some of the decomposition inhibitors and free fluorine in the borofluoride. Removal may also be adopted. By pre-treating with calcium salts in this way, the amounts of both drugs used can be reduced. Furthermore, as another method, when the fluorine concentration of the wastewater after treatment is required to be particularly low, aluminum hydroxide gel or a water-soluble aluminum compound may be added to the supernatant liquid of solid-liquid separation according to the treatment method of the present invention. A treatment method may also be adopted in which the PH value is adjusted to produce an aluminum hydroxide gel, the fluorine content is adsorbed to the gel, and then solid-liquid separation is performed. According to the treatment method of the present invention, the amount of the main decomposition agent used is reduced due to the synergistic effect of the decomposition aid, and as a result, the amount of calcium salt added is also reduced, so the amount of sludge is reduced and the overall sludge treatment cost is reduced. It becomes cheaper. Further, since the decomposition time can be shortened, the processing amount can be increased and the processing apparatus can be made smaller, which can bring about benefits. Next, test examples of the present invention will be shown to clarify the effects. In each test example shown below, the analysis value of fluorine is
After distilling according to the method shown in JIS K0102,
This is a value measured using a fluorine ion electrode (manufactured by Orion Co., Ltd.). In addition, in the test examples, the amount of the main decomposition agent was reduced in order to see the effect of the decomposition aid, so in some cases the residual fluorine concentration after treatment appeared higher than the specified value (15 mg/or less). Test example 1 Dilute 42% HBF ₄ (reagent) to determine fluorine concentration
11,250mg/dose, take out 200ml of this liquid,
Add 1.8 equivalents of aluminum sulfate (Al ₂ O ₃ 8%) and ammonium water (28% product) to fluorine in a specified amount,
Tests were conducted under the conditions shown in Table 1. The results are summarized in Table 1. In the table, filter paper was used.

[Table] As seen in the table above, when the amount of ammonium chloride added is less than 3% (volume %), the residual fluorine concentration is higher than when it is not added, so-called decomposition inhibition is observed. ), even if the same amount of aluminum sulfate is added, decomposition will proceed and it will act as an auxiliary agent. Test example 2 Dilute 45% Pb (BF ₄ ) ₂ (reagent) to determine the fluorine concentration
13250mg/dose, take out 200ml of this liquid,
A test was conducted under the conditions shown in Table 2 by adding 1.8 equivalents of aluminum sulfate (Al ₂ O ₃ 8%) and ammonium water in an amount relative to fluorine. The results are shown in Table 2.

【table】

[Table] Addition of ammonium water to Pb(BF ₄ ) ₂ showed the same tendency as HBF ₄ . Next, the following test was conducted to investigate the effect of the auxiliary agent on the decomposition reaction rate. Test example 3 Handametsuki factory waste liquid (fluorine 10000mg/, PH
1.8) was used as a sample, and using sample 1, 200 ml was extracted at each elapsed time of decomposition, subjected to calcium reaction, and subjected to solid-liquid separation. Aluminum sulfate (8
%Al ₂ O ₃ ) was used in an amount of 2 equivalents relative to fluorine. Using 29% ammonium water as the auxiliary agent, a comparative test was conducted with and without the addition of ammonium water, and the results are shown in Table 3. In addition, the table also includes an example in which aluminum sulfate was added again to the supernatant liquid of solid-liquid separation after the calcium reaction to perform reprocessing.

[Table] As shown in Table 3, even with the same amount of main decomposition agent, there is a large difference in decomposition time when ammonium water is added as an auxiliary agent compared to when no additive is added. Comparing the residual fluorine concentration of about 20 mg/distance, it would take 240 minutes to decompose without the addition of ammonium water, but this was significantly shortened to 120 minutes with the addition of ammonium water. Furthermore, it can be seen that the amount of calcium used is also reduced. Test Example 4 Aluminum sulfate (8%
Al ₂ O ₃ ) is set to a constant amount of 1.8 equivalents to fluorine,
A test was conducted with a sample amount of 250 ml according to Test Example 3, with the amount of ammonium water added as an auxiliary agent changed. The results are shown in Table 4.

[Table] As shown in the table above, ammonia is a substance that prevents the action of the main decomposition agent, and ammonia is used to form acetic acid. When the required amount of ammonium water is added as an auxiliary agent, the decomposition reaction is sufficiently promoted. It turns out that it will be done. This suggests that the amount of auxiliary added should be varied depending on the water quality. Test Example 5 Contrary to Test Example 4, Test Example 3 is a case where the amount of the auxiliary agent is kept constant and the amount of the main decomposition agent added is changed.
Table 5 lists the results of testing a 250 ml sample using the same sample as above.

[Table] As shown in the table above, the main decomposition agent and the auxiliary agent need to be blended in a well-balanced amount. In addition, the fluorine concentration after the decomposition reaction was 6700 mg/in the case where only ammonium water was added as an auxiliary agent, and the residual fluorine concentration after treatment was 4200 mg/in because free fluorine was removed by the calcium reaction. It seems likely that Test Examples 6 to 11 Using wastewater with a fluorine concentration of 10,000 mg/PH 1.8, various decomposition aids shown in the table below and aluminum sulfate were added to this wastewater, and after stirring, The samples were left at room temperature and treated under the conditions listed in the same table, and the results are summarized in Table 6. In addition,
A 250 ml sample was used.

[Table] As shown in the table above, the same equivalent (for fluorine)
The addition of each auxiliary agent to aluminum sulfate promoted the decomposition reaction, and it was possible to reduce the amount of the main decomposition agent and calcium agent used. In addition, in the example shown in the comparative example, JP-A-52-6875
In the decomposition reaction by mixing aluminum sulfate and ferric salt described in the above publication, the ferric salt is understood to play the role of an auxiliary agent. Test Examples 12 to 16 Tests were conducted using 100 ml of sample wastewater from a borofusated heavy metal compound manufacturing factory (fluorine concentration: 75,000 mg/, PH: 0.89). The results are summarized in Table 7.

【table】

[Table] As shown in the above table, even though the properties of the auxiliary compound were changed, those with additives as in Test Example 16 showed a significant difference compared to those without additives. Further, in this example, the residual fluorine concentration is further reduced by reprocessing. Next, an example of an experiment conducted on the amount of sludge produced by a method mainly based on the treatment method of the present invention and a conventional method will be shown below.

[Table] That is, the amount of the method of the present invention decreased per 99.0-74.0=25Kg/ ^m3 .

[Table] The method of the present invention was 1502 kg/m ³ less than the conventional method.

Claims (1)

[Claims] 1 Add aluminum sulfate as a main decomposition agent to the water containing borofusic acid and/or a borofusated heavy metal compound, and add aqueous ammonia, ammonium sulfate,
After adding one or more of ammonium chloride and urea as a decomposition aid to decompose the borofusic acid and borofutated heavy metal compound, calcium hydroxide is added to the decomposition solution to decompose and remove the formed precipitate. Features: A method for treating water containing borofusic acid and borofutated heavy metal compounds.