KR100960363B1 - Method for treating wastewater containing fluorine - Google Patents

Abstract

PURPOSE: A processing method of wastewater containing fluorine is provided to improve process efficiency of the wastewater by separating steps for processing the wastewater, and to reduce the fluorine concentration of final processed water to 10mg/L or less. CONSTITUTION: A processing method of wastewater containing fluorine comprises the following steps: producing calcium fluoride by reacting wastewater containing high concentration fluorine with fluorine concentration 50,000 ~ 500,000 mg / L and slaked lime; dehydrating the calcium fluoride with a coagulant including acrylamide - acrylic acid copolymer; gaining the wastewater containing low concentration fluorine of 10,000 ~ 30,000 mg / L; producing the calcium fluoride; hydrolyzing fluoboric acid(HBF4) within the processing water; putting a coagulant aid including a hydrolyzed effluent, a lime slurry, acid and acrylamide - acrylic acid copolymer, forming flock and separating solid from liquid.

Description

Method for Treating Wastewater containing Fluorine

The present invention relates to a fluorine-containing wastewater treatment method, and more specifically, even when the wastewater contains a high concentration of fluorine and hardly decomposable fluorine compounds, the fluorine concentration of the final treated water can be reduced to 10 mg / L or less, and the high concentration of fluorine The wastewater treatment step and the low concentration fluorine-containing wastewater treatment step are separated and treated simultaneously according to the fluorine content of the incoming wastewater, thereby increasing the treatment efficiency, and reducing the fluorine concentration in the final treated water to 10 mg / L or less. It relates to a wastewater treatment method.

While fluorine is a useful substance used in large quantities in various industrial fields, fluorine contained in various industrial effluents is strictly regulated because it is harmful to humans and the environment.

In general, the major sources of fluorine-containing wastewater are hydrofluoric acid, octane fuel (catalyst), aluminum, semiconductor, steel, metal processing, electroplating, glass, ceramic, stainless, and fertilizer. In the industrial production process, a large amount of wastewater containing fluorine is generated, and various fluorine treatment methods for treating the same are being developed.

The most widely used method is a method using calcium salts, aluminum salts, etc., as shown in FIG. That is, the method shown in FIG. 1 includes a primary treatment step of sequentially adding calcium salt, acid, ferrous chloride, and polymer flocculant to form a primary floc; A second treatment step of sequentially adding aluminum salt, sodium hydroxide, and a polymer flocculant to form a secondary floc; And adding aluminum salt, sodium hydroxide, and a polymer coagulant to discharge or aftertreat the solid-liquid separated liquid after forming the final floc.

The conventional method has a defect that the hardly decomposable fluorine compound is not treated even after repeated tertiary treatment steps, and the floc formation method using calcium salt and aluminum salt has a low fluorine treatment efficiency of 10 mg / In order to reduce the fluorine concentration of the treated water below L there is a problem that a large amount of calcium salt and aluminum salt should be added. In particular, the fluorine-containing wastewater from the semiconductor etching process has a high fluorine concentration and contains a hardly decomposable fluorine compound such as hydrofluoric acid (HBF ₄ ), which is an urgent need for efficient treatment thereof.

In order to solve the problems of the prior art as described above, the inventors of the present invention can make the fluorine concentration less than 10mg / L during the final treatment, even when containing a high concentration of fluorine and hardly decomposable fluorine compound, and using a flocculant in excess The present invention was completed during the research on a method for treating fluorine-containing wastewater having high fluorine treatment efficiency, which can lower the fluorine concentration to 10 mg / L or less.

It is an object of the present invention to provide a method for treating fluorine concentrations of 10 mg / L or less in the final treatment through a stepwise fluorine wastewater treatment method, even when containing high concentrations of fluorine and hardly decomposable fluorine compounds.

The fluorine-containing wastewater treatment method of the present invention specifically includes treating 50,000 to 500,000 mg / L of high concentration fluorine-containing wastewater; And treating 10,000 to 30,000 mg / L of low concentration fluorine-containing wastewater.

Fluorine-containing wastewater treatment method according to an embodiment of the present invention

Treating a high concentration fluorine-containing wastewater having a fluorine concentration of 50,000 to 500,000 mg / L to obtain a low concentration fluorine-containing wastewater having a fluorine concentration of 10,000 to 30,000 mg / L, and treating the low concentration fluorine-containing wastewater. As a wastewater treatment method,

In the high concentration fluorine-containing wastewater treatment step, a high concentration of fluorine-containing wastewater having a fluorine concentration of 50,000 to 500,000 mg / L and calcined lime powder is added to a closed reactor to generate calcium fluoride, and a coagulation aid comprising an acrylamide-acrylic acid copolymer. Obtaining a low concentration fluorine-containing wastewater having a fluorine concentration of 10,000 to 30,000 mg / L in a dehydration liquid, which includes a step of forming a floc after inputting the floc;

The low concentration fluorine-containing wastewater treatment step

(a) The low concentration of fluorine-containing wastewater of 10,000 to 30,000mg / L is continuously introduced into the first reactor together with the hydrated lime powder to produce calcium fluoride, and the selenite and iron chloride are sequentially added to the wastewater transferred from the first reactor. A composition comprising a salt, an acid, and a coagulant aid containing an acrylamide-acrylic acid copolymer are added to form flocs, and then transferred to a first precipitation tank for solid-liquid separation.

(b) hydrolyzing the hardly decomposable fluorine compound in the solid-liquid separated treated water in a hydrolysis reaction tank,

(c) the hydrolyzed wastewater is sequentially poured into a flocculent aid comprising liquid lime, acid, and acrylamide-acrylic acid copolymer to form floc, and then transferred to a second precipitation tank for solid-liquid separation. And a fluorine-containing wastewater treatment step having a fluorine concentration of 10 mg / L or less.

At this time, the low concentration fluorine-containing wastewater treatment step is introduced with a low concentration of fluorine-containing wastewater of 10,000 to 30,000mg / L generated in the factory that does not go through the high concentration fluorine-containing wastewater treatment step, the low concentration fluorine through the high concentration fluorine-containing wastewater treatment step It can be treated simultaneously with wastewater containing.

Meanwhile, the step of adding the slaked lime powder of the closed reactor in the high concentration of fluorine-containing wastewater treatment step and the step of adding the slaked lime powder of the first reactor of the low concentration of fluorine-containing wastewater treatment step are shown in the following formula (1). As is, for solid-liquid separation in the form of calcium fluoride.

Ca ^{2 +} + 2F ^- ⇔ CaF ₂ (s) ↓ ------------------------------ Equation (1)

At this time, the hydrated lime (Ca (OH) ₂ ) is added to the closed reactor and the first reaction tank in the form of a powder, the powdered hydrated lime is easy to maintain, low chemical cost, per unit cost or There is an advantage in that the final wastewater throughput per unit weight is large. On the other hand, In the case of using liquid slaked lime, liquid slaked lime having a concentration of 20 to 30% by weight is usually used. The liquid slaked lime has water added in addition to slaked lime which is a main component, and when used, it increases the amount of wastewater to be treated. This has the disadvantage of falling.

On the other hand, in the high concentration fluorine-containing wastewater treatment step, the closed reactor is not limited in shape, but preferably a first hermetic reactor connected to the inlet of the slaked lime powder, a second hermetic reactor equipped with a pH meter, a third hermetic reactor It is preferred to be designed as a reactor that is sequentially connected and the wastewater is transported in an overflow. 2 is a first hermetically sealed reactor connected with an inlet of slaked lime powder during treatment of high concentration fluorine-containing wastewater according to the embodiment, a second hermetically sealed reactor equipped with a pH meter, and a third hermetically sealed reactor sequentially connected and overflowed. It shows a brief illustration of a sealed reactor in which wastewater is transferred.

At this time, hydrated lime powder with high concentration of hydrofluoric acid wastewater may be added to the first sealed reactor, and the reaction temperature of the reactor may rise to 100 ° C according to the generation of calcium fluoride, wherein the mixed acids contained in the fluorine-containing wastewater The reaction temperature may vary depending on the type.

Meanwhile, the inflow rate of the high concentration fluorine-containing wastewater and the slaked lime powder flowing into the first hermetic reactor can be controlled through a pH meter installed in the second hermetic reactor. At this time, it is preferable to control the rate of high concentration of fluorine-containing wastewater and slaked lime powder in the first hermetic reaction tank so that the pH value of the pH meter installed in the second hermetic reactor is in the range of 6 to 9. By adjusting the feed rate of wastewater and slaked lime powder flowing into the first hermetic reactor so that the pH range of the second hermetic reactor is 6 to 9, the first hermetic reactor becomes a favorable condition for the generation of calcium fluoride precipitates. Dehydration of calcium fluoride also has the advantage of easy.

The most important reactor in the treatment of high concentration fluorine-containing wastewater is the first hermetically sealed reactor, in which the high concentration of fluorine-containing wastewater and slaked lime powder react to produce calcium fluoride, thereby generating heat of neutralization. In order to control the rapid generation of the heat of neutralization, it is possible to appropriately limit the amount of high concentration hydrofluoric acid wastewater and slaked lime powder. The slaked lime powder may be added in an amount of 1 to 2 equivalents of slaked lime relative to one equivalent of fluorine contained in the wastewater. Even if the slaked lime powder is added at the above ratio, it is preferable to slowly inject the slaked lime powder in order to suppress the rapid generation of neutralization heat. When the input amount of the slaked lime powder is less than one equivalent of the fluorine in the wastewater, the rapid generation of heat of neutralization can be controlled, but the fluorine concentration in the wastewater cannot be lowered within the desired range. In addition, when the amount of slaked lime powder is added in excess of 2 equivalents of slaked lime to 1 equivalent of fluorine in the wastewater, the temperature of the reaction tank is rapidly increased due to the rapid generation of heat of neutralization, and the amount of fumed hydrofluoric acid is also increased, thereby treating a large amount of fume. A separate system is required, and the viscosity of the wastewater in the reactor is sharply increased so that the wastewater cannot be treated smoothly. In addition, in order to control various problems caused by the rapid generation of neutralization heat as described above, there is a disadvantage that a special reaction tank must be designed.

On the other hand, the second hermetic reactor equipped with a pH meter is a reaction vessel for completing the production of calcium fluoride, the calcium fluoride generation rate of the second hermetic reactor is the amount of calcined lime powder injected according to the fluorine equivalent in the wastewater flowing into the first hermetic reactor It is determined by the equivalence ratio.

Meanwhile, the wastewater in which the reaction is completed in the second hermetic reactor can be transferred to the third hermetic reactor by natural overflow method, and the third hermetic reactor is sent to the sludge tank as the reaction vessel which completes the reaction with the low concentration fluorine-containing wastewater. It is a reactor for temporarily storing waste water. The level of the third sealed reactor in which the reaction is completed with low concentration hydrofluoric acid wastewater is attached with a level gauge for adjusting the highest level and operating level of the reactor, and the treated wastewater can be transferred to a pump in conjunction with the level gauge. At this time, the flocculation aid containing the acrylamide-acrylic acid copolymer may be introduced into the wastewater transferred from the third hermetic reaction tank to the sludge tank, and the flocculation aid in the sludge tank is further accelerated by the flocculation aid.

In this case, in addition to the acrylamide-acrylic acid copolymer described above, the aggregation aid may further include an additive such as a solvent for dissolving the copolymer, and a surfactant. In this case, as a solvent that may be added to the coagulant aid containing the acrylamide-acrylic acid copolymer, one or more solvents selected from the group consisting of water, distillates of petroleum, and alcohols may be used. . In this case, the water can be selected without limitation, such as industrial water or tap water (tap water), in the case of alcohol can also dissolve the acrylamide-acrylic acid copolymer such as primary alcohol, secondary alcohol, tertiary alcohol If so, it can be selected regardless of its configuration.

As the surfactant, one or more selected from the group consisting of fatty acid alkanol amides, alkyl phenols, fatty acids, fatty alcohols, esters of fatty acids and polyhydric alcohols, and polyoxypropylene block copolymers may be used. It is not limited to the example. Specifically, among the above-mentioned surfactants, polyoxyethylene lauryl ether, nonylphenol ethoxylates, pentaethylene glycol, and sorbitan monooleate which are readily available Etc. can be used. At this time, preferably the acrylamide-acrylic acid copolymer in the coagulant aid is preferably included at least 35% by weight, in the case of a solvent may be contained 35 to 50% by weight, surfactant 1 to 5% by weight. When the coagulant aid contains less than 35% by weight of acrylamide-acrylic acid copolymer, the coagulation aid effect of administration of the strong anionic coagulant aid is insignificant, and when the solvent is less than 35% by weight of the acrylamide-acrylic acid copolymer If the solubility is insignificant, and if it exceeds 50% by weight, the solvent content in the waste water increases, there is a problem to increase the amount of waste water to be treated. In addition, in the case of the surfactant may be included 1 to 5% by weight, when included in less than 1% by weight, the effect of emulsification of strong anionic polymers such as acrylamide-acrylic acid copolymer is insignificant, exceeding 5% by weight If you do, it is uneconomical.

The coagulant aid including the acrylamide-acrylic acid copolymer as described above may be added without limitation to the amount of the coagulation aid, which may promote aggregation of precipitated calcium fluoride, but the concentration of fluorine in the wastewater to be initially introduced is 50,000 to 500,000. Given that it is mg / L, it may be administered at 1 to 250 ppm.

On the other hand, using a pump from the sludge tank, sludge, etc., including the wastewater transferred to the dehydrator can be separated into the calcium fluoride precipitate and the dehydration filtrate through the solid-liquid separation, the dehydration liquor to go through the low concentration fluorine-containing wastewater treatment step, Can be moved to low concentration sump. The concentration of fluorine in the wastewater in the dehydration liquor is 10,000 to 30,000 mg / L of low concentration fluorine-containing wastewater, and the low concentration fluorine wastewater generated in the plant is moved to a low concentration sump tank which is temporarily stored, and then undergoes a low concentration fluorine-containing wastewater treatment step. .

Meanwhile, in the fluorine-containing wastewater treatment method according to the embodiment, a fume suction pipe and a wet scrubber connected to the pipe are additionally installed on each of the closed reactor, and in the closed reactor. After treating the generated hydrofluoric acid fume (fume) and the hydrated lime powder sucked into the fume suction pipe of the hydrated lime powder introduced into the first closed-type reaction tank by treating the hydrofluoric acid fume through the calcium fluoride generation reaction according to the reaction formula (1) The treated water can be subjected to a low concentration fluorine-containing wastewater treatment step. To this end, the treated water can be transferred to a low concentration sump. At this time, the wet scrubber may be installed in each of the upper portion of the hermetic reactor, preferably three hermetic reactors connected in sequence. Specifically, after installing the hydrofluoric acid fume suction pipes in each of the upper portion of the sealed reactor, the wet cleaning may be performed using a blower.

At this time, the treated water treated by the wet scrubber may be temporarily stored in the lower portion of the scrubber, and then moved to a low concentration sump tank to undergo a low concentration fluorine-containing wastewater treatment step. When the wet scrubber is additionally installed in the hermetic reactor as described above, the hydrofluoric acid fume generated from the hermetic reactor and the fly ash of the slaked lime powder flowing into the hermetic reactor react in the scrubber to produce calcium fluoride, and then wet. Through the washing step, the hydrofluoric acid fume generated in the treatment of high concentration fluorine-containing wastewater can be removed without additional alkaline chemical injection.

In addition, in the fluorine-containing wastewater treatment method according to the embodiment, a cooling water jacket is additionally mounted on the outer wall of the hermetic reaction tank to control the heat of reaction during the calcium fluoride generation reaction in the hermetic reaction vessel during the high concentration fluorine-containing wastewater treatment step, The coolant may further comprise the step of recycling. In a closed reactor, the reaction tank temperature may be raised to 100 ° C due to the heat of reaction (neutralization) of calcium fluoride. A cooling water jacket may be mounted on the outer wall of the reactor to control the temperature of the reactor to reduce the heat of neutralization generated in the sealed reactor. In addition, the heat generated cooling water can be reused for living water and floor control equipment, etc., which has advantages in terms of energy reuse. 3 is a view briefly showing a reaction tank in which a coolant jacket is additionally installed on an outer wall of the sealed reactor according to one embodiment of the present invention.

On the other hand, the flocculent aid used in the high concentration fluorine wastewater treatment step and low concentration fluorine wastewater treatment step is preferably a coagulation aid comprising an acrylamide-acrylic acid copolymer. The use of a coagulant aid comprising an acrylamide-acrylic acid copolymer facilitates agglomeration of precipitated calcium fluoride, thereby reducing the volume of floc and the like to be finally formed and facilitating solid-liquid separation. . Possible embodiments of the flocculent aid comprising the acrylamide-acrylic acid copolymer are as described above.

Hereinafter, the treatment step of the low concentration fluorine-containing wastewater will be described in more detail.

The fluorine concentration of the dehydration filtrate after the above-described high concentration fluorine-containing wastewater treatment step is solid-liquid separated from the dehydrator at 10,000 to 30,000 mg / L and then stored in a low concentration sump. In this case, in addition to the dehydration liquid that has undergone the high concentration fluorine-containing wastewater treatment step, the low concentration water collection tank may further include a fluorine-containing wastewater having the fluorine concentration range as a by-product, such as an etching process. As described above, in the fluorine-containing treatment method according to an embodiment of the present invention, the low-concentration fluorine-containing wastewater treatment step is specifically stored in a low concentration sump after solid-liquid separation in the dehydrator.

(a) continuously injecting the low concentration fluorine-containing wastewater of 10,000 to 30,000 mg / L together with the hydrated lime powder to produce calcium fluoride,

After forming a floc by sequentially inputting a composition comprising selenite and iron chloride, an acid, and an agglomeration aid comprising an acrylamide-acrylic acid copolymer to wastewater transferred from the first reactor. Transferred to the settling tank and separated into solid and liquid,

(b) hydrolyzing the hardly decomposable fluorine compound in the solid-liquid separated treated water in a hydrolysis reaction tank,

(c) the hydrolyzed wastewater is sequentially poured into a flocculent aid comprising liquid lime, acid, and acrylamide-acrylic acid copolymer to form floc, and then transferred to a second precipitation tank for solid-liquid separation. And a fluorine-containing wastewater treatment step having a fluorine concentration of 10 mg / L or less.

Specifically, in the first reactor, hydrated lime powder with low concentration of fluorine-containing wastewater is added. As described above, the hydrated lime powder is used for the production of calcium fluoride. It is advantageous in terms of reducing wastewater generation.

At this time, the low concentration fluorine-containing wastewater flowing into the first reaction tank can be continuously supplied by a pump, it is preferable that the lime powder is also continuously supplied. The flow rate of the slaked lime powder and the wastewater introduced into the first reactor can be controlled by a pH meter installed in the second reactor (the reactor into which the composition containing the selenite and ferric chloride is added), and the pH of the second reactor is 9 to It is preferable to set it to 11 on favorable conditions for the calcium fluoride formation reaction of the first reactor. In this case, the production rate of calcium fluoride in the first reactor is preferably 80% or more based on the fluorine ion concentration in the low concentration fluorine-containing wastewater flowing into the first reactor.

The wastewater transferred from the first reactor is sequentially passed through three reactors, respectively, and a composition, an acid, and a coagulant aid containing selenite and iron chloride may be sequentially added to each reactor.

First, a composition containing selenite and iron chloride may be injected into the second reactor to remove unreacted fluorine in the first reactor.

At this time, the composition containing the injected selenite and iron chloride promotes the precipitation reaction by chemical bonding of fluoride ions and alkali ions in the wastewater, and also the aggregation between calcium fluoride precipitates produced by the precipitation reaction of fluoride ions and alkali ions. To promote this.

The present inventors found that when a composition containing only iron chloride without iron selenate was administered to a low concentration wastewater treatment step, the fluorine treatment efficiency in wastewater was 20% higher than that when the composition containing selenite and iron chloride was administered. It was found that the decrease. In this case, the content of the selenite salt in the composition containing the selenite salt and iron chloride may be included in an amount of 0.002 to 0.1 parts by weight based on 100 parts by weight of iron chloride. If the selenite salt is contained in an amount less than 0.002 parts by weight based on 100 parts by weight of iron chloride, the effect of improving the fluorine treatment efficiency in the wastewater due to the addition of the selenite salt is insignificant. It is not desirable to have a separate treatment process to lower the concentration below the legal threshold. More preferably, it may include 0.02 to 0.1 parts by weight of the selenic acid salt relative to 100 parts by weight of iron chloride.

On the other hand, when the calcium fluoride is continuously produced by adding hydrated lime powder to the fluorine-containing wastewater, and then further administering a composition containing selenite and iron chloride, the fluorine in the wastewater reacts with the limestone powder to form calcium fluoride. It was found that iron hydroxide and calcium fluoride, which were solidified and produced by ferric chloride, had a coprecipitation effect to increase the fluorine treatment removal efficiency in wastewater. Thus, it was observed that by the selenite salt contained in the composition, the coprecipitation effect by the iron chloride as described above is further promoted to increase the fluorine removal efficiency.

At this time, the composition containing the selenite salt and ferric chloride may be further included in water, it may be administered in a solution phase. The amount of water added is not limited in configuration, but may be included in an amount of 130 to 170 parts by weight based on 100 parts by weight of iron chloride in consideration of the volume of the wastewater to be treated and the solubility of selenite and iron chloride.

The iron chloride may be ferrous chloride, ferric chloride, or a mixture thereof, although the composition thereof is not limited thereto. Ferrous chloride or ferric chloride as described above are iron chloride salts that can be easily obtained, and are easy to handle. In addition, the selenite salt is not limited in composition, but preferably anhydrous sodium selenite salt (Na ₂ SeO ₃ ), sodium selenite pentahydrate (Na ₂ SeO _{3 ·} 5H ₂ O), and hydrogen selenite Sodium (NaHSeO ₃ ) It may be one or more selected from the group consisting of. Such selenite can be easily obtained by being compatible. When the composition containing the selenite and ferric chloride as described above is added to the second reactor, the unreacted fluorine ions can be effectively removed, thereby reducing the concentration of fluorine ions in the treated water to 10 mg / L or less. There is an advantage. At this time, the amount of the composition containing the introduced selenite and iron chloride is not limited, but in consideration of the concentration of fluorine in the treated water, it is preferable to administer so that the composition is included in the waste water at a concentration of 300 to 1500ppm.

The wastewater passed through the second reactor is sent to the third reactor where acid is injected for flocculation by overflow. In the third reactor, acid may be added to adjust the pH of the slurry including the wastewater in order to aggregate the calcium fluoride product and the precipitate added in the second reactor. At this time, the acid used for pH adjustment may use any one or more selected from hydrochloric acid, nitric acid and sulfuric acid.

After adjusting the pH of the third reactor in the range of 6 to 7, the flocculation aid comprising acrylamide-acrylic acid copolymer may be added to the wastewater and sludge transported by natural oil into the fourth reactor. The coagulant aid may be the same as the coagulant aid administered in the above-described high concentration fluorine-containing wastewater treatment step. Agglomeration aids including acrylamide-acrylic acid copolymers facilitate the aggregation of precipitates such as calcium fluoride, and can be preferably used as the liquid-liquid separation is easy in the future. Waste water, sludge, etc., which have passed through the fourth reaction tank, are transferred to the first precipitation tank, and solid-liquid separation occurs.

In addition, the solid precipitated in the first settling tank may be transferred to the sludge tank, and then a flocculent aid including an acrylamide-acrylic acid copolymer may be added to form a floc. After the floc is formed in the first settling tank, the floc may be transferred to a dehydrator, and then the dehydrated cake may be taken out. At this time, the supernatant except for the floc in the first settling tank and the dehydration liquid in the dehydrator may be transferred to a high temperature high pressure reactor for hydrolysis for the treatment of the hardly decomposable fluorine compound.

Most of the hardly decomposable fluorine compounds contained in the wastewater transferred to the high temperature and high pressure reactor for hydrolysis were formed in the form of hydrofluoric acid (HBF ₄ ) by melting the glass component generated during the etching process by hydrogen fluoride (HF). to be. On the other hand, BF ₄ is a stable compound and is well known as a hardly decomposable compound which is difficult to remove by a general treatment. Therefore, in order to remove the fluorine component in the wastewater containing the hardly decomposable compound, the chemical bond of BF must be separated through hydrolysis. Through the hydrolysis reaction as described below, the hardly decomposable fluorine compound can be generated and removed with hydrogen fluoride.

HBF ₄ + H ₂ O ⇒ HBF ₃ (OH) + HF ------- (2)

HBF ₃ (OH) + H ₂ O ⇒ HBF ₂ (OH) ₂ + HF ------- (3)

HBF ₂ (OH) ₂ + H ₂ O ⇒ HBF (OH) ₃ + HF ------- (4)

HBF (OH) ₃ + H ₂ O ⇒ HB ₃ O ₃ + HF ------- (5)

The hydrolysis step of the hardly decomposable fluorine compound may be performed in a high temperature and high pressure reactor having a pressure of pH 3 to 4, 1.5 kg / cm ² to 3 kg / cm ² , and an optimum condition of 80 to 130 ° C., Preferably, a composition containing selenite and ferric chloride may be added thereto. At this time, the composition of the composition containing the selenite and iron chloride is the same as that administered to the second reaction tank described above. However, in the hydrolysis step of the hardly decomposable fluorine compound, in consideration of the concentration of fluorine in the wastewater to be treated and the like, the amount of the composition containing the selenite and the iron chloride is preferably 10 to 300 ppm.

Through the hydrolysis step, the hardly decomposable fluorine compound may be hydrolyzed in a high temperature and high pressure reactor to be separated into a fluorine compound which is easy to treat, thereby maximizing fluorine treatment efficiency. For reference, if the BF ₄ component is present in the waste water 30ppm, a large amount of dilution water to be used in the conventional manner or requires a separate treatment method.

In addition, by using a composition containing selenite and iron chloride, there is an advantage that can be treated by calcium fluoride treatment using only a small amount of the treatment agent.

Meanwhile, the wastewater undergoing the hydrolysis step is subjected to a step of separating liquid-liquid in a second settling tank after forming flocs by sequentially adding liquid calcined lime, an acid and a coagulant.

In this case, in the fifth reaction tank in which the liquid lime is added, it is preferable to adjust the pH in the fifth reactor to 9 to 11 in order to create a favorable condition for the production of calcium fluoride. I can adjust it.

On the other hand, in order to agglomerate wastewater transferred from the fifth reactor to the sixth reactor by natural oil, it is preferable to adjust the pH of the sixth reactor to 6 to 8, and to adjust the pH, a group consisting of hydrochloric acid, nitric acid and sulfuric acid. You can use one or more selected from.

In the seventh reaction tank transferred from the sixth reaction tank, a coagulation aid containing an acrylamide-acrylic acid copolymer may be added as the coagulation aid. At this time, the composition of the additive that may be additionally included in the coagulant aid and the content range thereof, and the like are the same as the coagulant aid comprising an acrylamide-acrylic acid copolymer administered in the above-described high concentration fluorine-containing wastewater treatment step. The dosage of the coagulant is not limited, but may be administered in the range of 1 to 250 ppm in consideration of the concentration of fluorine in the treated wastewater. On the other hand, floc is formed in the seventh reaction tank into which the coagulant aid containing the acrylamide-acrylic acid copolymer is added.

The wastewater that passed through the seventh reaction tank is separated into solid solution in the second settling tank, and finally transferred to the sludge tank, and the dehydrated cake is treated, and the fluorine concentration of the dewatered filtrate is 10 mg / L or less, preferably 8 mg / L or less. Can be The final treated water can be subjected to a post treatment step if discharged or after treatment is required.

On the other hand, in the treatment step of the low concentration fluorine-containing wastewater according to the embodiment, the step of adding together the sediment of the first sedimentation tank when the composition containing selenite and iron chloride in the wastewater transferred from the first reactor It may further comprise. This is for reuse in the production of calcium fluoride by reuse of the unreacted slaked lime component in the precipitate of the first settling tank. In the same principle, the precipitate of the second precipitation tank may further include the step of adding together the liquid calcined lime into the fifth reactor.

The fluorine-containing wastewater treatment method of the present invention can lower the fluorine concentration in the treated water to 10 mg / L or less at the time of final treatment, even in the case of containing high concentrations of fluorine and hardly decomposable fluorine compounds, such as semiconductor etching processes and various industrial fields. It can be widely applied to the treatment of fluorine-containing wastewater generated in

Hereinafter, the configuration and effect of the present invention through the specific embodiments of the present invention will be described in more detail. However, the following examples are only intended to more clearly understand the invention, the scope of the invention is not limited to the following examples.

[ Example  1] Treatment of high concentration fluorine-containing wastewater

Wastewater treatment was performed using a high concentration of fluorine-containing wastewater having a fluorine concentration of 200,000 mg / L from the etching process after the semiconductor process. In order to treat the high concentration of fluorine-containing wastewater according to Example 1, the treated water temporarily stored in the third sealed reactor is transferred to the sludge tank, and then the high concentration of hydrofluoric acid wastewater and slaked lime are first injected into the first sealed reactor. It was.

Calculate calcium fluoride by injecting 1.0㎥ of high concentration fluorine-containing wastewater into the first hermetic reactor (capacity: 2㎥) using a pump into a high concentration water tank (capacity: 70㎥), and then injecting 0.85㎥ of hydrated lime powder. The reaction proceeded. At this time, the amount of calcined lime powder in the first hermetic reactor was adjusted so that the pH of the second hermetic reactor was 7.

After the reaction of the first hermetic reactor was completed, high concentration of fluorine-containing wastewater and slaked lime were injected in the above-described manner, and the treated water was transferred to the second hermetic reactor by natural flow. After completion of the calcium fluoride formation reaction in the second hermetic reactor, the wastewater was transferred to the third hermetic reactor by natural flow. After the conveyed waste water was stirred in the third hermetic reactor for about 3 minutes, it was temporarily stored and then transferred to a sludge tank, after solid-liquid separation, and the solids were removed by dehydration. At this time, the concentration of fluorine in the wastewater solid-separated from the dewatering and sludge tanks was 10,500 mg / L.

The solid-liquid separated wastewater and dehydration liquid were temporarily stored in a low concentration water collection tank (capacity: 200m 3), and then transferred to the first reactor. Calcium fluoride was produced by adding hydrated lime powder to the wastewater transferred to the first reactor. The input amount of the slaked lime powder was adjusted by a pH meter installed at the inlet side of the second reactor, and at this time, the input amount of the slaked lime powder of the first reactor was adjusted so that the pH value of the pH meter installed at the second reactor inlet side was 10.

The treated wastewater was transferred from the first reactor to the second reactor through natural flow, and 300 ppm of a composition (DCF-B, manufacturer; Save Technology Co., Ltd.) containing selenite and iron chloride was added to the second reactor. To promote the production of calcium fluoride. The DCF-B is a composition containing 0.006 parts by weight of SODIUM SELENITE PENTAHYDRATE (Na ₂ SeO _{3 ·} 5H ₂ O) and 160 parts by weight of water based on 100 parts by weight of ferrous chloride.

On the other hand, the unreacted calcined lime of the first settling tank was conveyed to the first reactor for reuse.

After the wastewater was transferred from the second reactor to the third reactor (volume: 2㎥) through natural flow, hydrochloric acid (HCl) was added to the third reactor to adjust the pH of the third reactor to 6.5. After transferring the wastewater of the pH-controlled third reactor to the fourth reactor (volume: 2m 3), flocculant was formed by introducing a flocculent aid containing acrylamide-acrylic acid copolymer at a concentration of 15 ppm. Specific constituents of the flocculent aid comprising the acrylamide-acrylic acid copolymer used in Example 1 are as shown in Table 1 below. Immediately after the floc was formed, the wastewater containing the floc was transferred to a first settling tank (surface load rate: 25 m 3 / m 2 .day).

After the solid-liquid separation from the first settling tank, the supernatant is a high temperature and high pressure reactor for hydrolysis having a temperature of 85 ° C. and an internal pressure of 1.5 kg / cm ² for the treatment of hardly decomposable fluorine compounds (capacity: 20 m ³ , hydrolysis). Reactor). At this time, the composition containing the selenite and ferric chloride salt (DCF-P, manufacturer; Save Technology Co., Ltd.) to 200ppm to the high-temperature high-pressure reactor for hydrolysis, and chemical bonding of BF of HBF ₄ component in the waste water After the destruction, the mixture was transferred to a fifth reaction tank (capacity: 5 m 3) through a heat exchanger.

The DCF-P is a composition containing 0.05 parts by weight of SODIUM SELENITE PENTAHYDRATE (Na ₂ SeO _{3 ·} 5H ₂ O) and 150 parts by weight of water based on 100 parts by weight of ferric chloride.

Liquid calcined lime was added to the fifth reactor to produce fluorine remaining in the waste water in the form of calcium fluoride. At this time, the precipitate of the second precipitation tank was internally transported to the fifth reaction tank and added together when the liquid slaked lime was added, thereby reducing the amount of liquid slaked lime.

In addition, a pH meter was installed in the fifth reaction tank to control the input amount of the liquid slaked lime introduced into the fifth reaction tank and the input amount of the precipitate returned from the second settling tank. The input amount of the liquid slaked lime and the input amount of the precipitate conveyed from the second settling tank were adjusted so that the pH of the fifth reaction tank was 9.

After the wastewater was transferred from the fifth reactor to the sixth reactor (volume: 5 m 3) by natural discharge, hydrochloric acid (HCl) was added to the sixth reactor to adjust the pH to 7. After transferring the pH-controlled wastewater from the sixth reactor to the seventh reactor (volume: 5 m 3), the coagulation aid (according to Table 1) containing the acrylamide-acrylic acid copolymer in the seventh reactor was 15 ppm. Concentration was carried out to form flocs. The wastewater containing the formed floc was transferred to a second settling tank (surface load rate: 25 m 3 / m 2 .day), and then solid-liquid separated and transferred to a post-treatment process.

4 is a schematic view showing a wastewater treatment process according to the first embodiment.

In order to confirm the treatment efficiency of the fluorine-containing wastewater treatment method according to Example 1, high concentration fluorine-containing wastewater, the third hermetic reaction tank, and the overflow water in the second sedimentation tank were collected and analyzed by the process test method. Indicated.

Constituents of Cohesion Adjuvants Containing Acrylamide-Acrylic Acid Copolymer Chemical name CAS number Content (% by weight) Acrylamide-acrylic acid copolymer
(ACRYLAMIDE-ACRYLIC ACID COPOLYMER) 9003-06-9 45 water 20 POLYOXYETHYLENE (9) LAURYL ETHER 9002-92-0 3 Distillate of Petroleumm, Hydrotreated light 64742-47-8 30 SORBITAN MONOOLEATE 1338-43-8 2

division Fluorine concentration (mg / L) Fluoride removal rate in wastewater (%) High concentration fluorine-containing wastewater treatment process Before treatment High concentration fluorine-containing wastewater 200,000 94.8 After treatment Third sealed reactor 10,500 Low concentration fluorine-containing wastewater treatment process Before treatment Third sealed reactor 10,500 99.9 After treatment Second settling tank overflow water 8

As can be seen from Table 2, when treating fluorine-containing wastewater according to Example 1 of the present invention, even if the high concentration of fluorine-containing wastewater with a fluorine concentration of 200,000 mg / L, the removal efficiency is 99.9%, the final treated water The concentration of fluorine in 8 mg / L effectively confirmed that the fluorine was removed in the wastewater. In addition, it was confirmed that the hardly decomposable fluorine compound after the semiconductor etching process was also removed, and thus it is expected to be useful for treating fluorine-containing wastewater generated in various industrial fields including the semiconductor process.

[ Example  2] hermetic In the reactor  Installed wet Scrubber  Foshan Fume  remove

In order to process the hydrofluoric acid fume (Fume) generated while proceeding to Example 1, after installing a fume suction pipe (wet scrubber) on the top of the first hermetic reactor, the second hermetic reactor, the third hermetic reactor Wet cleaning was performed using a 5CMM blower. The wet cleaning solution was temporarily stored in the lower portion of the scrubber and discharged into a low concentration sump, and the results of measuring the fluorine concentration through the gastec analyzer at the scrubber outlet are shown in Table 3 below.

division Before installing scrubber After installing scrubber Fluorine Concentration (mg / L) 10 to 250 N.D.

When the wet scrubber was used according to Example 2, it was confirmed that the hydrofluoric acid fume could be efficiently removed. In particular, it can be seen that the wet scrubber can be usefully used to treat the hydrofluoric acid fume generated during the treatment of high concentration fluorine-containing wastewater.

[ Example  3] hermetic In the reactor  Installed coolant Jacket  Reaction heat control using

When the high concentration hydrofluoric acid wastewater treatment as shown in Figure 3 to supply the cooling water to the first closed reactor, the second sealed reactor, the third sealed reactor to cool the neutralization heat according to the calcium fluoride to produce a reaction tank including a water cooling jacket (cooling water jacket) Produced. The general configuration of the reactor including the coolant jacket is as shown in FIG. 3. At the outlet side of the reactor, the cooling water heated by cooling is used as living water, and part of the reaction tank is stored in the municipal water storage tank through a heat exchanger. Temperature was measured using a digital thermometer, the results are shown in Table 4 below.

First hermetic reactor Second hermetic reactor Third hermetic reactor Before attaching the coolant jacket
Reactor external temperature (℃) 75-80 65-70 50-65 After attaching the coolant jacket
Reactor external temperature (℃) 35 to 39 26 to 32 24 to 28 Other temperature conditions (℃) Heat exchanger inlet temperature: 35 to 39
Heat exchanger outlet temperature: 19 ~ 23
-Shisu temperature: 14-20

[ Experimental Example  4] during the low concentration fluorine-containing wastewater treatment, DCF Comparison of Fluorine Treatment Efficiency in Wastewater with or without B-B Input

In order to determine the efficiency of wastewater treatment according to the presence or absence of DCF-B (composition comprising sodium selenite and ferrous chloride) introduced into the second reactor according to Example 1 during the low concentration fluorine-containing wastewater treatment step , Fluorine-containing wastewater having a concentration of fluorine in wastewater of 20,000 mg / L and fluorine-containing wastewater having 30,000 mg / L, respectively, were prepared.

Each of the fluorine-containing wastewater as described above was temporarily stored in a low concentration water collection tank (capacity: 200 m 3), and then transferred to the first reaction tank. Calcium fluoride was produced by adding hydrated lime powder to the wastewater transferred to the first reactor. The input amount of the slaked lime powder was adjusted by a pH meter installed at the inlet side of the second reactor, and at this time, the input of the slaked lime powder of the first reactor was adjusted so that the pH value of the pH meter installed at the second reactor inlet side was 10.

The treated wastewater was transferred from the first reactor to the second reactor through natural flow, and the composition containing the selenite and iron chloride used in Example 1 in the second reactor, namely DCF-B (manufacturer; save technology ( Note) was added to 300ppm each. Thereafter, the precipitate was solid-liquid separated, and the fluorine content in the supernatant was measured and shown in Table 5 below.

On the other hand, as a comparative example, fluorine-containing wastewater having a concentration of fluorine in wastewater of 20,000 mg / L and fluorine-containing wastewater having 30,000 mg / L, respectively, were treated in the same manner as described above. However, in contrast to the above-described method, instead of DCF-B, the ferric chloride solution excluding the composition of the selenite salt in the structure of DCF-B (specifically, water is 150 parts by weight based on 100 parts by weight of ferrous chloride). Ferrous chloride solution included) was added in the same amount (300ppm). Thereafter, the precipitate was solid-liquid separated, and the fluorine content in the supernatant was measured and shown in Table 5 below.

Wastewater HF Concentration (mg / L) Treated water concentration (mg / L) after administration of DCF-B After administration of iron salt solution except sodium selenite pentahydrate in the composition of DCF-B, treated water concentration (mg / L) 20,000 2,000 or less More than 5,000 30,000 3,000 or less More than 8,000

As shown in Table 5, when the composition containing a small amount of selenite in the iron salt solution to the fluorine-containing wastewater, it was found that the concentration of fluorine ions in the treated water drops sharply.

The present inventors found that even in the case of using a composition containing selenite and ferric chloride as well as a composition containing selenite and ferrous chloride as in the DCF-B composition described above, the present inventors found that the fluorine concentration in wastewater can be drastically reduced. Observed.

On the other hand, the present inventors through the above-described embodiments, even if the fluorine-containing wastewater treatment method according to Example 1 includes a high concentration of fluorine and hardly decomposable fluorine compound, the fluorine concentration at the final treatment to 10 mg / L or less It has been found that the present invention can be widely applied to the treatment of fluorine-containing wastewater generated in a semiconductor etching process and many other industrial fields.

1 is a simplified view of a process for treating fluorine-containing wastewater by a conventional method,

Figure 2 is a simplified illustration of the closed reactor used in the high concentration fluorine-containing wastewater treatment step according to an embodiment of the present invention,

3 is a view briefly illustrating a reactor in which a coolant jacket is additionally installed on an outer wall of a closed reactor used for a high concentration fluorine-containing wastewater treatment step according to one embodiment of the present invention.

4 is a simplified illustration of a process for treating fluorine-containing wastewater in accordance with one embodiment of the present invention.

<Brief Description of Drawings>

100: high concentration sump

101: first sealed reactor 102: second sealed reactor

103: third sealed reactor 106: coolant jacket inlet

108: heat exchanger 110: water tank

120: wet scrubber

Claims (11)

Treating a high concentration fluorine-containing wastewater having a fluorine concentration of 50,000 to 500,000 mg / L to obtain a low concentration of fluorine-containing wastewater having a fluorine concentration of 10,000 to 30,000 mg / L, and treating the low concentration of fluorine-containing wastewater. As wastewater treatment method, In the high concentration fluorine-containing wastewater treatment step, a high concentration of fluorine-containing wastewater having a fluorine concentration of 50,000 to 500,000 mg / L and calcined lime powder are added to a closed reactor to produce calcium fluoride, and a coagulation aid comprising an acrylamide-acrylic acid copolymer. After the floc to form a floc, to obtain a low concentration of fluorine-containing wastewater having a fluorine concentration of 10,000 to 30,000 mg / L of the dehydration liquid comprising the step of dehydration; The low concentration fluorine-containing wastewater treatment step (a) The low concentration of fluorine-containing wastewater of 10,000 to 30,000 mg / L with hydrated lime powder is continuously added to the first reactor to produce calcium fluoride, and selenite and iron chloride sequentially in the wastewater transferred from the first reactor. A flocculant was formed by adding a composition containing a salt, an acid, and an acrylamide-acrylic acid copolymer to form a floc, and then, transferred to a first precipitation tank to solid-liquid separation. (b) hydrofluoric acid hydrofluoric acid (HBF ₄ ), which is a hardly decomposed fluorine compound in the solid-liquid separated treated water, has a pressure of pH 3 to 4, 1.5 kg / cm ² to 3 kg / cm ² , and a high temperature of 80 to 130 ° C. In a high pressure reactor, a composition containing selenite and ferric chloride is charged to hydrolyze it, (c) sequentially separating the hydrolyzed wastewater by flocculation aids comprising liquid calcined lime, an acid, and an acrylamide-acrylic acid copolymer to form flocs, and then transferring the hydrolyzed wastewater to a second settling tank for solid-liquid separation. Comprising the steps, A fluorine-containing wastewater treatment method having a fluorine concentration of 10 mg / L or less in the treated water. The method of claim 1, The hermetically sealed reactor is a first hermetically sealed reactor connected with an inlet of slaked lime powder, a second hermetically sealed reactor equipped with a pH meter, and a third hermetically sealed reactor, in which wastewater is transferred in a natural flow method (overflow). Fluorine-containing wastewater treatment method for controlling the inflow rate of the slaked lime powder flowing into the first hermetic reactor so that the pH of the treated water of the second hermetic reactor to 6 to 9 using a pH meter. The method of claim 1, The hermetic reaction tank is a hermetic reaction tank in which a fume suction pipe and a wet scrubber connected to the pipe are additionally installed, and the fluorine fume generated in the hermetic reaction tank is sucked into the fume suction pipe, and the fume suction pipe is sucked. A method for treating fluorine-containing wastewater, which is treated in the wet scrubber after forming calcium hydroxide and calcined lime sucked into the ducting pipe. The method of claim 1, The closed reactor is further equipped with a coolant jacket on the outer wall to control the reaction heat of the calcium fluoride generation reaction in the closed reactor in the high concentration fluorine-containing wastewater treatment step, and the elevated temperature cooling water further comprises the step of recycling the fluorine-containing wastewater treatment Way. delete The method of claim 1, The composition containing the selenite salt and iron chloride is a fluorine-containing wastewater treatment method comprising 0.002 to 0.1 parts by weight of selenite relative to 100 parts by weight of iron chloride. The method of claim 1, The composition comprising the selenite salt and ferric chloride is prepared in a solution containing 130 to 170 parts by weight of water with respect to 100 parts by weight of iron chloride. The method of claim 1, The ferric chloride salt is ferrous chloride, ferric chloride, or a mixture thereof. The method of claim 1, The selenite is one selected from the group consisting of anhydrous sodium selenite (Na ₂ SeO ₃ ), sodium selenite pentahydrate (Na ₂ SeO _{3 ·} 5H ₂ O), and sodium selenite (NaHSeO ₃ ). The above fluorine-containing wastewater treatment method. The method of claim 1, The low concentration fluorine-containing wastewater treatment step, the composition containing the selenite and iron chloride added in the step (a) of the fluorine-containing wastewater treatment method is administered at a concentration of 300 to 1500ppm. The method of claim 1, The low concentration fluorine-containing wastewater treatment step, the composition containing the selenite and iron chloride added in step (b) of the step is administered in a concentration of 10 to 300ppm fluorine-containing wastewater treatment method.

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