WO2005066080A1

WO2005066080A1 - Method of cleaning wastewater and cleaning method

Info

Publication number: WO2005066080A1
Application number: PCT/JP2004/007315
Authority: WO
Inventors: Hodaka Ikeda; Kenichi Ito; Naoko Akita; Koji Kanagawa; Tsutomu Sato
Original assignee: Sophia Co., Ltd.
Priority date: 2004-01-08
Filing date: 2004-05-21
Publication date: 2005-07-21
Also published as: JP2005193167A

Abstract

A method of wastewater cleaning which comprises: a step in which a calcium compound is added to a fluorine-containing wastewater to generate calcium fluoride; a step in which the liquid resulting from the reaction for generating calcium fluoride is subjected to solid-liquid separation through, e.g., flocculation, to remove the calcium fluoride; a step in which the pH of the treated water after the calcium fluoride removal is regulated and a hydrotalcite is added thereto to adsorb the residual fluorine onto the hydrotalcite; a step in which the treated water after the adsorption is subjected to solid-liquid separation through, e.g., flocculation, to remove the hydrotalcite on which fluorine has been adsorbed; a step in which the hydrotalcite having fluorine adsorbed thereon is subjected to a fluorine desorption treatment; a step in which the hydrotalcite which has undergone the fluorine desorption treatment is added again in the fluorine adsorption step; and a step in which the fluorine-containing water yielded in the fluorine desorption treatment is added to a fluorine-containing wastewater to be subjected to calcium fluoride generation. The method enables the fluorine contained in a fluorine-containing wastewater to be efficiently removed. Thus, treated water having an exceedingly low fluorine concentration is obtained.

Description

Description Wastewater purification method and purification method

The present invention relates to a wastewater purification method and a purification method for removing fluorine from fluorine-containing wastewater discharged from, for example, a semiconductor factory or a power plant. Background art

For example, as a technology for removing fluorine from fluorine-containing wastewater discharged from semiconductor factories and power plants, a method of reacting calcium hydroxide and calcium chloride with fluorine to produce calcium fluoride and coagulating and precipitating is used. Is being done. In the removal process, for example, a pH adjuster is added to an acidic wastewater containing fluorine to adjust the pH, and the pH-adjusted wastewater is sent to a reaction tank, where calcium hydroxide or calcium chloride is added. To produce calcium fluoride. Thereafter, the reaction solution containing calcium fluoride is sent to a coagulation tank, a coagulant is added to coagulate calcium fluoride, and sludge containing calcium fluoride coagulated in the settling tank is settled and removed. Things.

Patent Document 1 is a known document relating to a technology for removing fluorine from fluorine-containing wastewater. Patent Document 1 (Japanese Patent Application Laid-Open No. 7-214702) describes a treatment method for removing fluorine in wastewater using calcium chloride, and a method for adding a chloride solution to a wastewater before adding the solution to the wastewater. In addition, the total or partial pH of the calcium chloride solution is adjusted to 11.5 or more in advance, and the solution is allowed to react with wastewater.This reduces the amount of calcium chloride used or uses a large amount of flocculant. that you can avoid is disclosed. Disclosure of the invention At this time, when calcium fluoride is generated by the above-mentioned reaction of calcium chloride etc. with fluorine, and sludge containing calcium fluoride is removed, the fluorine is removed so that the treated water has a high level or lower than the standard value. to require large amounts of calcium such as calcium and hydroxide of calcium chloride compound, in addition, in the case of recovery by coagulation sedimentation requires large amount of aggregating agent, also the amount of sludge to be discharged There is practically difficult and very large amount of such order, Turkey to fluorine remove fluorine cormorants by a reference value or less of the treated water of high level. For this reason, we do not have a cormorant problem either, technology that fluorine can be that you remove the high level has been desired from the waste water.

The present invention has been proposed in view of the above problems, and does not require a large amount of a calcium compound such as calcium chloride or calcium hydroxide or a coagulant, and does not discharge a large amount of sludge. Another object of the present invention is to provide a wastewater purification method capable of removing fluorine from a fluorine-containing wastewater to a high level, thereby obtaining treated water having a very low fluorine concentration. Another object of the present invention is to provide a wastewater purification method and a purification method capable of regenerating and efficiently using hydrotalcites and performing advanced fluorine purification at a low cost.

The method for purifying wastewater of the present invention comprises the steps of adjusting the pH as necessary to the fluorine-containing wastewater, adding a calcium compound to generate calcium fluoride, and solidifying the reaction solution after the generation of the fluorinated water. A step of liquid separation to remove calcium fluoride, a step of adjusting the pH of the treated water after the removal of calcium fluoride, and a step of adding hydrotalcites to adsorb remaining fluorine on the hydrotalcites. And a step of solid-liquid separation of the treated water after the adsorption to remove hydrosites after the fluorine adsorption.

In the present invention, solid-liquid separation in the case of removing calcium fluoride or talcites at the mouth after adsorption of fluorine by solid-liquid separation is performed by, for example, adding a flocculant to coagulate and precipitate the solid phase. or to recover the solid phase in flotation by Bapuri ring of air, or Ri appropriately der like to recover the solid phase membrane filtration using a filter Chief, also forces Rushiumu compound Karushiumu chloride Wakashi Ku hydroxide It is suitable to the Karushiumu However, any material capable of producing calcium fluoride by reacting with fluorine may be used. For example, calcium carbonate may be used. Further, the pH of the treated water or the like in the case where fluorine is adsorbed to the hydrotalcites is preferably pH 4 to 10 and more preferably pH 5 to 7.

Further, the method for purifying waste water of the present invention includes a step of performing a fluorine desorption treatment on the removed hydrosites after the adsorption of fluorine, and a step of dehydrating the hydrotalcites after the fluorine desorption treatment with fluorine. In addition to the step of adding again in the adsorption step, the method further comprises the step of combining the fluorine-containing water generated by the fluorine desorption treatment with the fluorine-containing wastewater before the generation of the calcium fluoride.

Furthermore, in the wastewater purification method of the present invention, in the fluorine desorption treatment step, the fluorine-adsorbed hydrotalcites may be stirred in a solution having a pH of 9 and ρΗ <11 to obtain a fluorine solution. It is characterized in that it is subjected to a desorption treatment, and preferably, the pH of the solution to be subjected to the fluorine desorption treatment is set to approximately 10.

Further, the method for purifying wastewater of the present invention comprises the steps of adjusting the pH as necessary to the fluorine-containing wastewater, adding a calcium compound to generate calcium fluoride, and after the formation of the calcium fluoride, A step of adding hydrosites to the reaction solution to adsorb remaining fluorine on the hydrosites, and a step of solid-liquid separation of the adsorbed reaction solution to adsorb calcium fluoride and adsorbed fluorine. And a step of removing the hydrosites.

Furthermore, waste water purification process of the present invention, the high Dorotarusai Bok compound is characterized that it is a Hydro barrel site. From high Dorotarusai preparative acids (layered double hydroxide minerals, LDH) and this exhibits good anion adsorption characteristics, the fluorine or high Dorotarusai preparative acids to adsorb full Tsu containing Ion of the present invention have the general formula: [MS + i— xM ³ " ¹ " _x (OH) 2] [Α ^η - _{χ / η} · ζ Η ₂₀ ] (M ^{2 +} is divalent metal, M ^{3 +} is trivalent metal, ^An is n-valent It is possible to use any of the hydrotalcites represented by (anion), for example, hydrotalcite: Mg ₆ A12 (OH)! ₆ CO 3 · 4H ₂₀ is preferable. Furthermore, purification methods of the present invention, in the purification method of adsorbing fluorine by adding Hyde port Tarusai preparative acids to be purified which contains fluorine, Hyde port Tarusai preparative such after fluorine adsorption of 9 rather ρ Eta <stirred at 1 1 in solution subjected to fluorine desorption process, characterized that you adsorbing off Tsu containing added again Hydro Tarusai preparative such after the fluorine desorption process for the purification target Preferably, the pH of the solution to be subjected to the fluorine desorption treatment is approximately 10. It should be noted that the object of purification containing fluorine can be soil or the like in addition to wastewater.

The wastewater purification method of the present invention does not use a large amount of calcium compounds such as calcium chloride or calcium hydroxide, a large amount of coagulant, does not discharge a large amount of sludge, and eliminates a fluorine-containing wastewater. Very high levels of fluorine can be removed. For example, it is possible to convert fluorine-containing wastewater to treated water with a very low fluorine concentration, for example, by setting the emission standard for public water bodies to 8 ppm or less. Furthermore, since a large amount of calcium chloride or the like or a flocculant need not be used, and a large amount of sludge is not discharged, chemical and sludge treatment costs are reduced, and a high level of fluorine removal is achieved. Is possible at low cost and efficiently.

Further, the wastewater purification method or purification method of the present invention desorbs fluorine from the hydrosites after the adsorption of fluorine, and causes the hydrosites after the desorption treatment to adsorb fluorine again. In addition, it is possible to regenerate and effectively use the hydrotalcites, and it is possible to perform advanced fluorine purification at a very low cost. In particular, the dehydration treatment is performed by stirring the hydrotalcites after the adsorption of fluorine in a solution having a pH of 9 and more preferably in a solution having a pH of about 10. Therefore, extremely high regeneration efficiency can be realized. Brief Description of Drawings

1 is an explanatory diagram showing a flow of waste water purification process of the first embodiment, FIG. 2 is an explanatory diagram showing a flow of waste water purification process of the second embodiment shaped condition, Fig 3 is fluorine ions from the stirring time and the high Dorotarusai DOO Graph showing the relationship with the amount of desorption, Figure 4 shows pH 9, 10 and 11 4 is a graph showing the amount of fluorine adsorbed by re-adsorption of each hydrotalcite from which fluorine was desorbed in FIG. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be specifically described based on wastewater purification treatments and examples of the first and second embodiments, but the present invention is not limited to such embodiments and examples.

First, a wastewater purification treatment of the first embodiment for circulating and reusing a hydrotalcite to remove and purify fluorine from a fluorine-containing wastewater will be described. In the wastewater purification treatment of the first embodiment, as shown in Fig. 1, wastewater containing fluorine is introduced into the primary reaction coagulation / sedimentation tank 1, and a PH adjuster is added to the primary reaction coagulation / sedimentation tank 1. Then, the fluorine-containing wastewater is adjusted to a predetermined pH, for example, a pH of about 8 to 10. As the pH adjusting agent to be added, an appropriate one of an acid and an alkali can be used. For example, when the fluorine-containing wastewater is an acidic wastewater, sodium hydroxide (Na) OH) is added as a pH adjuster.

Then, by adding chloride force Rushiumu (C a C l ₂₎ in the fluorine-containing waste water was adjusted to p H of the primary reaction coagulating sedimentation tank 1, the fluorine ions (F-) and calcium chloride in the fluorine-containing waste water It reacted to generate the full Tsu of calcium (C a F ₂₎ by the reaction of ^{C a 2 + + 2 F- →} C a F 2. Furthermore, a flocculant such as a band of sulfuric acid or PAC is added to the primary reaction flocculation and sedimentation tank 1 to flocculate calcium fluoride and precipitate sludge containing calcium fluoride. The settled sludge is led out of the primary reaction coagulation sedimentation tank 1 to the dewatering machine 4, where the sludge is dewatered by the dewatering machine 4 and discharged as a dewatered cake. Further, the primary treated water obtained by removing the sludge in the first reaction coagulating sedimentation tank 1 is introduced into the second reaction flocculation tank 2, the secondary reaction flocculation tank 2 by the addition of p H adjusting agent , to adjust the primary treated water a predetermined PH, for example, before and after p H 6 adsorption performance of Hyde port Tarusai Bok is Mizunoto揮 the best to be described later. The p H adjusting agent, wherein the addition are possible and Mochiiruko those suitable Yichun, for example in the primary treated water, hydrochloric acid (HC 1), etc. Is added as pH adjuster.

Then, the primary treated water was adjusted p H of the secondary reaction flocculation tank 2, was added Hydro Tarusai DOO, fluorine ions (F-) remaining in the primary treated water in Hyde port Tarusai DOO It is adsorbed. High Dorotarusai I composition formula the additive: the layered double hydroxide mineral der of _{M g 6 A 1 a (OH} ) 1 6 C 0 3 '4 H 2 0 is, have Anion exchange, various Anion It can be inserted between the layers. Hydrotal site: Mg ₆ Al ₂ (OH)! 6 CO 3 - 4 most of the H ₂ 0, the fluorine-I O emissions (F-) adsorbed crowded Captures the layers and high Dorota Rusai preparative adsorbed fluorine _{_{ions: M g 6 A l 2 (}} OH ) _{1 6} (F- ¹ ) ₂ · 4 Η ₂₀ is generated.

Furthermore, secondary reaction flocculation precipitation tank 2 by adding a coagulant such as sulfuric pan de and PAC, fluorine ions Hyde port Tarusai preparative _{_{adsorbed: M g 6 A l 2 (}} OH) 1 6 (F one ¹ ) _₂ · 4 H ₂ O, and Hydro Tarusai preparative fluoride ions could not be _{_{adsorbed: M g 6 a l 2 (}} OH) 1 6 C 0 3 - to 4 by agglomerating of H ₂ O precipitation. Ri by the flocculation, high Dorotarusai preparative process water is more fluorine concentration in the fluorine ion adsorption was reduced is obtained by, the treated water is discharged outside the system also includes a hard I mud Tarusai bets with adsorbed fluorine The hydrotalcite or sediment is sent to the fluorine desorption tank 3.

Is In the fluorine DatsuHanareso 3 or fluorine DatsuHanareso 3 reaches the delivery channels, Hyde port Tarusai preparative adsorbed the fluorine _{_{ion: M g 6 A l 2 (}} OH) 1 6 (F - 1) 2 • 4 H high Dorotarusai bets or the precipitate was suspended in a solution containing ₂ 0, was added p H adjusting agent such as hydroxide Na Application Benefits um (N a OH) to the solution, given the p H of the solution The pH is adjusted to, for example, pH 911, preferably around 10, and carbon dioxide (co ₂ ) is added to facilitate the desorption of fluorine.

Then, in the fluorine desorption tank 3, the solution was stirred, and a fluoride-adsorbed hydrated talcite: Mg ₆ Al ₂ (OH) ₁₆ (F- ¹ ) ₂ · 4 Η ₂₀ carafe Tsu-containing ion (F-) the desorbed Hyde port Tarusai Application: a _{_{M g 6 a l 2 (OH}} ) 1 6 CO a · 4 H 2 0, most of the high Dorotarusai with fluorine desorbed Doo: M g ₆ A 1 ₂ (OH) i ₆ CO ₃ · 4 H ₂ O, and the fluoride-free talcite that could not completely desorb fluorine: Mg ₆ Al ₂ (OH) ₁₆ (F- ¹ ) ₂ · 4固 Solid-liquid separation of the solid phase composed of ₂₀ and the liquid phase containing fluorine ions (F).

The separated solid phase is sent from fluorine DatsuHanareso 3 is introduced into the secondary reaction flocculation tank 2, it is circulated using a new high Dorotarusai into double-order flocculation tank 2 as required : introducing _{_{M g 6 a l 2 (OH}} ) 1 6 C 0 3 '4 H 2 0. Moreover, the separation and the liquid phase or a solution containing fluorine ions (F-) was sends back to the primary reaction flocculation precipitation buttocks tank 1, both the process and new fluorine-containing waste water to be introduced in the first reaction coagulating sedimentation tank 1 to.

In the wastewater purification treatment of the first embodiment, the primary reaction coagulation / sedimentation tank 1 and the secondary reaction coagulation / sedimentation tank 2, the fluorine desorption tank 3, and the dehydrator 4 are used to remove fluorine from the fluorine-containing wastewater. Since the hydrosite separated in the desorption tank 3 is reused, it is only necessary to add the hydrosite for the loss if necessary, and the hydrosite can be used effectively. Further, it is possible to reduce the consumption of the hydro-site and reduce the cost. Furthermore, by adsorbing the fluoride ions remaining after the formation of calcium fluoride on the hydrotalcite, it is possible to efficiently treat the treated water with a very low fluorine concentration and to use calcium chloride or the like. The need to use a large amount of coagulant is eliminated. Furthermore, it is possible to circulate the fluorine and finally recover the fluorine adsorbed on the hydrosite as calcium fluoride.

Incidentally, in the waste water purification process of the first embodiment, the same first reaction coagulating sedimentation tank 1, p H adjusting process, generating process, the aggregation treatment of calcium fluoride by reaction with calcium chloride, configured to perform precipitation process and it was, but a modification, for example, p H adjusting tank, a reaction tank for generating calcium fluoride, coagulating tank, configured to perform the processes in the sedimentation tank, the same tank combinations of certain There are suitable for these processes It is possible to adopt a configuration that is performed by using. Similarly, in the same secondary reaction coagulation and sedimentation tank 2, pH adjustment treatment, fluorine ion adsorption treatment using a hydrotalcite, coagulation treatment, and precipitation treatment are performed. The configuration is, for example, a pH adjustment tank, a reaction tank that performs fluorine ion adsorption treatment, a condensing tank, a sedimentation tank, or a combination of these appropriate treatments in the same tank. it is possible to.

Next, a wastewater purification process according to a second embodiment for removing and purifying fluorine from fluorine-containing wastewater by using a hydrotalcite in a single-tank type facility will be described. Wastewater purification process of the second embodiment, Remind as in FIG. 2, the wastewater containing fluorine is introduced into the reaction flocculation tank 5, addition of _P H modifiers alkaline or acid to the reaction flocculation tank 5 Then, the fluorine-containing wastewater is adjusted to a predetermined pH, for example, about pH 6. The p H of the reaction coagulating sedimentation tank 5 by adding calcium chloride adjusted fluorine-containing waste water (C a C 1 _2), fluorine ions in the full Tsu-containing wastewater (F-) is reacted with chloride Karushiu arm, ^{C a 2 + + 2 F- →} C a by Ri Futsui spoon calcium to the reaction of F ₂ (C a F ₂₎ to generate.

Furthermore, the hydrotalcite: Mg ₆ Al ₂ (OH)! It was added _{_{6 C 0 3 '4 H 2}} 0, is adsorbed fluorine ions (F-) remaining in the waste water after the formation of calcium fluoride (C a F ₂₎ to Hyde port Tarusai bets. Wherein the added high Dorotarusai Bok: Most of _{M g 6 A 1 2 (OH} ) i 6 CO 3 · 4 H 2 O is adsorbed crowded Captures the fluorine ion (F-) between the eyebrows, a fluorine ion adsorbed Hyde port Tarusai _{_{DOO: M g 6 A l 2 (}} OH) 1 6 (F - 1) 2 · 4 Η 2 0 is generated.

Thereafter, the reaction flocculation tank 5 by adding a coagulant such as sulfuric pan de and PAC, full Tsu of calcium (C a F _2), and fluorine adsorbed high Dorotarusai _{DOO: M g 6 A 1 2 (} OH _{^{) 1 6 (F - 1)}} 2 · 4 Η 2 0, and Hyde port Tarusai preparative fluorine could not be _{_{adsorbed: M g 6 a l 2 (}} OH) 1 6 (F - 1) 2 · 4 Η 2 0 Coagulate and sediment sludge containing these. The precipitated sludge is derived in the dehydrator 6 from the reaction coagulating sedimentation tank 5, and dehydrated sludge dehydrator 6, together with discharged as a dehydrated cake, the treated water obtained by removing the sludge is discharged out of the system that.

The wastewater purification treatment of the second embodiment is performed by one reaction coagulation sedimentation tank 5 and one A fluorine-containing waste water carafe Tsu iodine was removed by machine 6, with a small capital-investment Ri by the low-cost, fluorine can and child removal and space-saving. Further, Ri by the and this to adsorb fluorine ion-remaining after generation of fluoride Karushiu beam at Hydro Tarusai Bok, with efficient fluorine concentration can very low treated water and child, calcium chloride It is not necessary to use a large amount of a coagulant or the like.

In the wastewater purification treatment of the second embodiment, in the same reaction coagulation sedimentation tank 5, a pH adjustment treatment, a treatment for generating calcium fluoride by reaction with calcium chloride, and a fluoride ion treatment using hydrotalcite It is configured to perform the adsorption treatment, the aggregation treatment, and the sedimentation treatment, but it is possible to use a modification example of the first embodiment and the like in the second embodiment as appropriate. , A reaction tank that performs fluorine ion adsorption treatment, a coagulation tank, a precipitation tank, or a combination of these appropriate treatments in the same tank, or calcium fluoride It is possible to add a tank for performing coagulation or sedimentation after the production process of water.

Next, a description will be given of a simulation test of the adsorption, desorption, and re-adsorption of fluorine on the hydrosite, which corresponds to the wastewater purification treatment process of the first embodiment, and the results thereof. First, the fluorine adsorption test of Hydro Tanoresai Bok, about 0. lmo 1 ZL of full Kkaka Li © beam solution 1 L (fluorine content measured values by ion chroma Togurafi one: 1 8 5 0. 0 mg / L ), And then add 10 g of a talcite at the mouth: Mg ₆ Al 2 (OH) i ₆ C 0 ₃ '4 H _{20, and} adjust the pH of the solution using HC 1. The mixture was stirred for 1 hour while adjusting to around 6. After the 攒拌, the suspension was filtered and the solid phase K 1 remaining dried 5 0 ¾ at a constant temperature dryer.

. The filtration through the filtrate was measured Ri by a fluorine content of R 1 to Ionkuroma preparative chromatography and rollers, 2 3 1 O mg / L der is, high Dorotarusai sheet 1 was added O g is 1 8 5 0.0 - 2 31.0 = 16 19.0 mg / L of fluoride ion was adsorbed, and the amount of fluorine adsorbed per 1 g of the added hydrotalcite was 161.9 mgg (see Table 2 below). ① reference). The remaining solid phase K 1 absorbs fluorine and Hide mouth talcite: Mg ₆ Al ₂ (OH)! 6 (F - ¹⁾ and _₂ · 4 _{Η 2} 0, normal high Dorotarusai _{_{door: M g 6 A l 2 (}} OH)! Consists of 6 CO a · 4 H ₂₀ .

Next, in the fluorine desorption test of the hydrofluoric acid-adsorbed hydrosite, first, NaOH solutions were adjusted to 9, 10, and 11 using NaOH, and 50 OmL of each NaOH solution was adjusted. In a beaker, add 50 mg of the solid phase K1 containing hydrofluoric acid adsorbed to each beaker so that the solid-liquid ratio becomes 1 g / L, and add N to each beaker. Stir while adjusting the pH to 9, 10, and 11 using aOH, and every 5 minutes, 10 minutes, 15 minutes, 30 minutes, and 60 minutes of stirring time , Respectively.

FIG. 3 is a graph showing the relationship between the amount of desorbed fluorine and the stirring time obtained by measuring the fluorine content of the filtrate R2 by the filtration. The graph in Fig. 3 shows that the higher the pH and the longer the stirring time, the greater the desorption amount of fluorine for each of the beakers of pH 9, 10 and 11 For example, when pH 9 is stirred for 5 minutes, fluorine: 44.2 mg / g per solid phase K: lg, and when pH II is stirred for 60 minutes, solid phase K: lg Fluorine: 1 3 2. O mg was desorbed. The F desorption amounts at 60,000 minutes of stirring at pH 9, 10, and 11 are shown in Tables 2 and 2 below, and after desorption at 60 minutes of stirring time. This solid phase is referred to as solid phase K 2.

After that, in the fluorine re-adsorption test of the hydrotalcite, a test method basically similar to that of the above-mentioned hydrotalcite fluorine adsorption test was carried out.First, each of pH 9, 10 and 11 was applied. Prepare about 1 lL of potassium fluoride solution of about 0.1 mol (actual value of fluorine content by ion chromatography: 1850.0 mg / L), and use it as a sample for the desorption test. The solid phase K 2 of each of pH 9, 10 and 11 obtained by filtration with a stirring time of 60 minutes was added at a ratio of 10 gZL (see Tables 2 and 2 below), and HC 1 The solution was stirred for 1 hour while adjusting the pH of each solution to around 6 using. Thereafter, solid-liquid separation was performed using a membrane filter (0.2 / Im), and the mixture was filtered to obtain a filtrate R 3 in a liquid phase and a solid phase K 3, and analysis was performed. The results are shown in Table 1 and FIG. Table 1 shows that the fluorine content per 1 L of about 0.1 mo1 / L of the calcium fluoride solution before adding the solid phase K 2: , 10 and 11, the fluorine content of filtrate R 3 after re-adsorption of fluorine by solid phase K 2 (filtrate: F), the amount of fluorine absorbed by solid phase K 3 (solid phase: F), and solid phase K 3 shows the amount of fluorine adsorbed per lg, and FIG. 4 shows the amount of fluorine adsorbed per 1 g of solid phase K 3 at pH 9, 10, and 11 respectively. Solid K 3 is Hyde port Tarusai bets with adsorbed _{_{fluorine: M g 6 A l 2 (}} OH) i 6 (F - 1) 2 - 4 H 2 0, or fluorine adsorbed high Dorotarusai DOO: M g ₆ Al ₂ (OH) 16 (F- ¹ ) ₂ · 4 Η ₂₀ and normal high ドロ Dotal site: Mg ₆ Al ₂ (OH)! Consisting of _{6 CO a · 4 H 2 0} .

table 1

Table 2 shows the amount of fluorine adsorbed after the re-adsorption of fluorine at pH 9, 10 and 11 based on the above-mentioned simulation tests of adsorption, desorption and re-adsorption of fluorine. The amount of fluorine adsorbed after resorption in Table 2 is the value obtained by subtracting the amount of fluorine desorption from the fluorine desorption test in (2) from the amount of fluorine adsorption in the adsorption test (2) and adding the amount of fluorine adsorption from the resorption test in (3). is there.

Table 2

As shown in Table 2, as the pH at the time of fluorine desorption increases to 9, 10, and 11, Although the amount of desorbed fluorine increases, the amount of adsorbed fluorine decreases as the pH at the time of desorption increases to 9, 10, and 11 when re-adsorbing fluorine. is, and the also the degree of Al force Li at the time of leaving if example example enters between the layers of different and high mud Tarusai door is OH -, the Son and the like can be considered to be C 0 3 ² different. At pH 11, the amount of fluorine adsorbed at the time of re-adsorption is lower than that at the time of desorption, while at pH 9 and 10, the amount of adsorption at the time of fluorine re-adsorption is lower. The amount was larger than the amount desorbed at the time of desorption. This is probably because there was room for fluorine adsorption between the layers of the hydro- talcite after the adsorption test (1).

In addition, Table 3 shows the amount of fluorine desorbed when the desorption rate after desorption is assumed to be the same as the desorption rate in the desorption test in Table 2 and (2).

Table 3

As shown in Tables 2 and 3, the amount of fluorine adsorbed and the amount of desorbed fluorine show that in the case of pH 9, the amount of adsorption during re-adsorption is large, but the amount of desorption is small, so Regeneration efficiency decreases when hydrotalcite is repeatedly used to remove fluorine by adsorption.In the case of pH 11, the amount of desorption is large, but the amount of adsorption when re-adsorbing is small. Similarly, the regeneration efficiency of the hydro-site is reduced. On the other hand, in the case of pH l 0, both the amount of adsorption and the amount of desorption when re-adsorbing are large, so the regeneration when repeatedly using a hydrotalcite for fluorine removal by desorption and re-adsorption efficiency is highest. Further, p H l 0 optimum p H Der because the synthesis of the front and rear Hydro Tarusai Bok, have low solubility, the loss of high Dorotarusai Bok is not less when used in reproduction. From such a viewpoint, desorption around pH 10 contributes to improvement of the regeneration efficiency. In addition, when HC 1 was added for pH adjustment in the above re-adsorption test, the amount of HC 1 added in terms of solid phase K 2: lg was calculated as follows. In the case of re-adsorption of iL and pH10: 388.4 / iL, in the case of re-adsorption of pHll: 458.3 μL, indicating that the regeneration efficiency of the hydrosite is high. required HC 1 added in H l 0 The amount was the fewest. This is considered to be because the hydrotalcite or solid phase K2 desorbed at pH 10 has a large amount of weak acid CO 3 ² _ between layers, indicating the high regeneration efficiency of pH 10. there. Industrial applicability

By using the wastewater purification method or the purification method of the present invention, fluorine is removed from, for example, fluorine-containing wastewater discharged from a semiconductor plant, a power plant, or the like, and the fluorine-containing wastewater is efficiently reduced to a low fluorine concentration. Effluent, for example, effluent below the emission standard determined in view of environmental protection.

Claims

The scope of the claims

1. a step of adding a calcium compound to the fluorine-containing wastewater to produce calcium fluoride, a step of solid-liquid separation of the reaction solution after the production of calcium fluoride to remove calcium fluoride, Adjusting the pH of the treated water after removing calcium, adding hydrotalcites to adsorb fluorine remaining on the hydrosites, and solid-liquid separating the treated water after the adsorption. A method for removing hydrosites after fluorine adsorption by at least a method for purifying wastewater.

2. A step of performing a fluorine desorption treatment on the removed hydrosites after the adsorption of fluorine, and a step of re-adding the hydrosites after the desorption of fluorine in the fluorine adsorption step 2. The method according to claim 1, further comprising a step of combining the fluorine-containing wastewater generated by the fluorine desorption treatment with the fluorine-containing wastewater before the formation of calcium fluoride. .

3. The fluorine desorption process is characterized in that the hydrotalcites after the adsorption of fluorine are subjected to a fluorine desorption process by stirring in a solution having a pH of 9 and a pH of <11. 3. The method for purifying wastewater according to claim 2, wherein:

4. Step of adding calcium compound to fluorine-containing wastewater to generate calcium fluoride, and adding hydrotalcites to the reaction solution after the formation of calcium fluoride to adsorb fluorine remaining on hydrotalcites Wastewater characterized by comprising at least a step of removing the calcium fluoride and hydrotalcites after the adsorption of calcium fluoride and fluorine by solid-liquid separation of the reaction solution after the adsorption. Purification method.

5. The wastewater purification method according to claim 1, wherein the hydrotalcites are hydrotalcites.

6. In a purification method in which hydrotalcites are added to a fluorine-containing substance to be purified and the fluorine is adsorbed, the hydrotalcites after the adsorption of fluorine are reduced to 9 pH. Ku 1 stirring subjected to fluorine desorption process in the first solution, purification method, characterized that you adsorbing fluorine high mud Tarusai Bok such after the fluorine desorption process was again added to be purified.