KR102735710B1 - Treatment method of BOE waste liquid - Google Patents

Abstract

The present invention relates to a method for treating BOE waste liquid, and more specifically, to a method for treating BOE waste liquid which can not only recover high-purity fluorite from BOE waste liquid but also effectively treat fluoride ions (F ^- ) and/or ammonium ions (NH ₄ ⁺ ) contained in BOE waste liquid.

Description

{Treatment method of BOE waste liquid}

The present invention relates to a method for treating BOE waste liquid, and more specifically, to a method for treating BOE waste liquid which can not only recover high-purity fluorite from BOE waste liquid but also effectively treat fluoride ions (F ^- ) and/or ammonium ions (NH ₄ ⁺ ) contained in BOE waste liquid.

In general, hydrofluoric acid has been used for etching silicon dioxide (SiO ₂ ) films or glass in semiconductor and/or display manufacturing processes, but currently, for fine and precise etching and cleaning, ammonium fluoride (NH ₄ F) solutions mixed in various ratios according to the process purpose of each manufacturer are widely used as ammonium fluoride compound-containing solutions. That is, diluted hydrofluoric acid solutions and BOE (Buffered Oxide Etchant) solutions are widely used for wet etching or cleaning of silicon dioxide films or glass in semiconductor and/or display manufacturing processes at present, and BOE solution is a representative etching/cleaning solution containing ammonium fluoride compounds made by mixing ammonium fluoride solution in HF solution at an appropriate ratio. The main purpose of using a buffer solution like this is to control the pH and obtain a stable etching speed by continuously replenishing the fluoride ions that become deficient as the process progresses with ammonium fluoride. Additionally, there is also the advantage of eliminating or suppressing hydrofluoric acid volatilization.

Meanwhile, since BOE solution has a very high concentration of hydrofluoric acid, research is actively being conducted on a method to safely and economically treat BOE waste solution remaining after being used in etching or cleaning processes in the manufacturing process of semiconductors and/or displays. However, the treatment methods for BOE waste solution reported to date have the following problems, which limits their practical use.

First, BOE waste liquid remaining after being used in the conventional semiconductor and/or display manufacturing process has a high concentration of pollutants (fluorine, nitrogen, etc.) and is highly corrosive, making it difficult to process using general methods. Therefore, most semiconductor and/or display manufacturers entrust the hydrofluoric acid waste liquid to separate specialized treatment companies for processing or landfilling. As a result, the cost of entrusting the treatment of BOE waste liquid is excessive, which significantly worsens the economic feasibility of manufacturers using it.

Second, in order to solve the above-mentioned problem, there have been attempts to recycle hydrofluoric acid, etc. in BOE waste liquid, but the recycling process is not efficient, so there is a limit to improving economic feasibility. That is, in order to recycle the fluorine contained in BOE waste liquid into calcium fluoride in a cement plant, lime, etc. is directly added to the BOE waste liquid to precipitate calcium fluoride and obtain it. However, in order for these to react completely, a very complex reaction environment such as temperature control, reaction time, and reaction pressure must be created, so not only is it not practical for industrial mass production, but also, when sludge and filtrate are generated through a filter press after the reaction, this sludge and filtrate are landfilled or treated as wastewater at high cost. Therefore, there is another problem that a recycling technology is required to reduce the amount of landfill or wastewater.

Third, BOE waste liquid contains ammonium ions in addition to hydrofluoric acid, but most BOE waste liquid recycling technologies focus on hydrofluoric acid recycling, and there is a problem that research on recycling ammonium ions is minimal. In other words, ammonium can also be recycled in fields that require it, such as the fertilizer industry, rather than simply being processed through a neutralization/landfill process, but research on recycling such ammonium ions from high-concentration BOE waste liquid has rarely been introduced, and even if it has been introduced, it is difficult to obtain high-concentration ammonium ions, making it difficult to commercialize in practice.

Therefore, research on BOE waste liquid treatment that can efficiently treat BOE waste liquid, significantly reduce social/economic costs incurred during the treatment process, and prevent environmental pollution is urgently needed.

Korean Patent Registration No. 2023-0169655 (Publication Date: 2023.12.18)

The present invention has been made in consideration of the above points, and aims to provide a method for treating BOE waste liquid, which can not only recover high-purity fluorite from BOE waste liquid, but also effectively treat fluoride ions (F ^- ) and/or ammonium ions (NH ₄ ⁺ ) contained in BOE waste liquid.

In order to solve the above-described problem, the method for treating BOE waste liquid of the present invention may include a first step of preparing BOE waste liquid containing fluoride ions (F ^- ) and ammonium ions (NH ₄ ⁺ ), a second step of introducing BOE waste liquid and a first calcium salt into a first dissolution tank to prepare a first mixture and mixing and reacting the first mixture to prepare a first reaction liquid, a third step of filtering the first reaction liquid to recover a first solid and a first filtrate, respectively, a fourth step of introducing the first filtrate, a second calcium salt, and caustic soda (NaOH) into a second dissolution tank to prepare a second mixture and mixing and reacting the second mixture to prepare a second reaction liquid, and a fifth step of filtering the second reaction liquid to recover a second solid and a second filtrate, respectively.

In a preferred embodiment of the present invention, the purity of fluorite included in the first solid may be 80% or more.

In a preferred embodiment of the present invention, the fluoride ion (F ^- ) and calcium ion (Ca ²⁺ ) included in the first mixture prepared in the second step may have a molar ratio of 1:0.3 to 0.5.

In a preferred embodiment of the present invention, the second step reaction can be performed while injecting air into the first dissolution tank at a rate of 2 to 6 L/min·kg.

In a preferred embodiment of the present invention, the fourth step reaction can be performed by maintaining the pH of the second mixture at 11 or higher.

In a preferred embodiment of the present invention, the reaction of the fourth step can satisfy the following condition (1).

(1) 80% ≤

In the above condition (1), A represents the total reaction time of the second mixture performing the reaction, and B represents the time during which the pH of the second mixture is maintained at 12.5 or higher during the total reaction time of the second mixture performing the reaction.

In a preferred embodiment of the present invention, the fourth step reaction can be performed for 16 to 24 hours.

In a preferred embodiment of the present invention, the fourth step reaction can be performed while injecting air into the second dissolution tank at a rate of 2 to 6 L/min·kg.

In a preferred embodiment of the present invention, the second filtrate of the fifth step may have a pH of 10 or higher.

In a preferred embodiment of the present invention, the method for treating BOE waste liquid of the present invention may have an ammonium ion treatment efficiency of 90% or more as measured by the following equation 1.

[Equation 1]

In the above equation 1, C represents the concentration of ammonium ions contained in the BOE waste liquid prepared in the first step, and D represents the concentration of ammonium ions contained in the second filtrate recovered in the fifth step.

In a preferred embodiment of the present invention, the BOE waste liquid treatment method of the present invention may have a fluoride ion treatment efficiency of 95% or more as measured by the following equation 2.

[Equation 2]

In the above equation 2, E represents the concentration of fluoride ions contained in the BOE waste liquid prepared in the first step, and F represents the concentration of fluoride ions contained in the second filtrate recovered in the fifth step.

In a preferred embodiment of the present invention, the BOE waste liquid prepared in the first step may contain 60,000 to 100,000 mg/L of fluoride ion (F ^- ) and 10,000 to 30,000 mg/L of ammonium ion (NH ₄ ⁺ ).

In a preferred embodiment of the present invention, the BOE waste liquid prepared in the first step may have a pH of 3 to 7.

In a preferred embodiment of the present invention, the first calcium salt and the second calcium salt may each include at least one selected from slaked lime (Ca(OH) ₂ ) and quicklime (CaO).

In a preferred embodiment of the present invention, the fluoride ion (F ^- ) and calcium ion (Ca ²⁺ ) included in the second mixture prepared in the fourth step may have a molar ratio of 1:0.65 to 0.85.

In a preferred embodiment of the present invention, ammonium ion (NH ₄₊ ) and caustic soda (NaOH) included in the second mixture prepared in the fourth step may have a molar ratio of ¹ :1.0 to 1.4.

The method for treating BOE waste liquid of the present invention can not only recover high-purity fluorite from BOE waste liquid, but also effectively treat fluoride ions (F ^- ) and/or ammonium ions (NH ₄ ⁺ ) contained in BOE waste liquid.

Hereinafter, with reference to the attached drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily practice the present invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein. In the drawings, parts that are not related to the description are omitted in order to clearly describe the present invention, and the same reference numerals are added to the same or similar components throughout the specification.

The method for treating BOE waste liquid of the present invention comprises steps 1 to 5.

First, in the first step of the BOE waste liquid treatment method of the present invention, BOE waste liquid containing fluorine ions (F ^- ) and ammonium ions (NH ₄ ⁺ ) can be prepared.

Specifically, BOE waste liquid may contain, in addition to fluoride ions (F ^- ) and ammonium ions (NH ₄ ⁺ ), silicon salts (Si ⁴⁺ ), magnesium salts (Mg ²⁺ ), etc.

Meanwhile, the BOE waste liquid prepared in the first stage may contain, but is not limited to, 60,000 to 100,000 mg/L of fluoride ion (F ^- ), preferably 70,000 to 90,000 mg/L of fluoride ion and 10,000 to 30,000 mg/L of ammonium ion (NH ₄ ⁺ ), preferably 15,000 to 25,000 mg/L of ammonium ion.

Additionally, the BOE waste liquid prepared in the first step may have a pH of 3 to 7, preferably 4 to 6, and more preferably 4.5 to 5.5.

Next, in the second step of the BOE waste liquid treatment method of the present invention, the BOE waste liquid and the first calcium salt prepared in the first step are introduced into the first dissolution tank to prepare a first mixture, and the first reaction liquid can be prepared by mixing and reacting the prepared first mixture.

At this time, the second stage reaction can be performed for 16 to 24 hours, preferably 18 to 22 hours, and more preferably 19 to 21 hours. If the reaction time is less than 16 hours, fluoride ions and ammonium ions may not be sufficiently removed, and if it exceeds 24 hours, there may be a problem of reduced process efficiency.

In addition, the second stage reaction can be performed while injecting air into the first dissolution tank at 2 to 6 L/min·kg, preferably 3 to 5 L/min·kg. If air is not injected, there may be problems of precipitation of the first calcium salt due to the specific gravity difference, a decrease in the production of fluorite, and/or a decrease in the fluoride ion removal rate. In addition, if the amount of air injected is less than 2 L/min, there may be a problem of the BOE waste liquid and the first calcium salt not being sufficiently mixed, and if it exceeds 6 L/min, there may be problems of excessive energy use and/or increased operating costs.

In addition, the fluoride ion (F ^- ) and calcium ion (Ca ²⁺ ) included in the first mixture manufactured in the second step may have a molar ratio of 1:0.3 to 0.5, preferably 1:0.35 to 0.45. If the molar ratio is less than 1:0.3, there may be a problem of a decrease in the production amount and/or purity of fluorspar, and if it exceeds 1:0.5, there may be a problem of a decrease in the purity of fluorspar due to the residual first calcium salt.

In addition, the first calcium salt may include at least one selected from slaked lime (Ca(OH) ₂ ) and quicklime (CaO), and preferably may include slaked lime (Ca(OH) ₂ ).

Next, in the third step of the BOE waste liquid treatment method of the present invention, the first reaction liquid prepared in the second step can be filtered to recover the first solid and the first filtrate, respectively.

At this time, the purity of fluorite contained in the first solid may be 80% or more, preferably 83% or more, and more preferably 85 to 95%.

Next, in the fourth step of the BOE waste liquid treatment method of the present invention, the first filtrate recovered in the third step, the second calcium salt, and caustic soda (NaOH) are added to the second dissolution tank to prepare a second mixture, and the second reaction solution can be prepared by mixing and reacting the prepared second mixture.

At this time, the fourth step reaction can be performed by maintaining the pH of the second mixture at 11 or higher, and if the pH falls below 11 during the fourth step reaction time, there may be a problem of a decrease in the ammonium ion degassing rate.

Specifically, the reaction of the fourth stage can satisfy the following condition (1).

(1) 80% ≤ , preferably ≤ 90% ≤ 99.9%, more preferably ≤ 94% ≤ 99.5%

In the above condition (1), A represents the total reaction time of the second mixture performing the reaction, and B represents the time during which the pH of the second mixture is maintained at 12.5 or higher during the total reaction time of the second mixture performing the reaction.

If condition (1) is not satisfied, there may be a problem of reduced degassing rate of ammonium ions.

In addition, the reaction of the fourth step can be performed for 16 to 24 hours, preferably 18 to 22 hours, and more preferably 19 to 21 hours. If the reaction time is less than 16 hours, there may be a problem of a decrease in the removal rate of residual fluoride ions and/or a decrease in the degassing rate of ammonium ions. If it exceeds 24 hours, there may be a problem of an increase in operating costs due to excessive energy use.

Additionally, the reaction of the fourth step can be performed while injecting air into the second dissolution tank at 2 to 6 L/min·kg, preferably 3 to 5 L/min. If air is not injected, there may be a problem that ammonium ions are not degassed. In addition, if the amount of air injected is less than 2 L/min·kg, the first filtrate and the second calcium salt are not sufficiently mixed, and there may be a problem of a decrease in the ammonium ion degassing rate, and if it exceeds 6 L/min·kg, there may be a problem of excessive energy use and/or increased operating costs.

Meanwhile, the second calcium salt may include at least one selected from slaked lime (Ca(OH) ₂ ) and quicklime (CaO), and preferably may include slaked lime (Ca(OH) ₂ ).

In addition, the fluoride ion (F ^- ) and calcium ion (Ca ²⁺ ) included in the second mixture prepared in the fourth step may have a molar ratio of 1:0.65 to 0.85, preferably 1:0.7 to 0.8. If the molar ratio is less than 1:0.65, there may be a problem of reduced removal rate of residual fluoride ions, and if it exceeds 1:0.85, there may be a problem of excessive use of chemicals.

In addition, the ammonium ion ( _NH4 ⁺ ) and caustic soda (NaOH) included in the second mixture manufactured in the fourth step may have a molar ratio of 1:1.0 to 1.4, preferably a molar ratio of 1:1.1 to 1.3, and more preferably a molar ratio of 1:1.15 to 1.25. If the molar ratio is less than 1:1.0, the pH may decrease during the reaction, which may cause a problem of a decrease in the ammonium ion stripping rate. If it exceeds 1:1.4, there may be a problem of increased operating costs due to excessive use of chemicals and/or increased use of chemicals in the subsequent process.

Finally, in the fifth step of the BOE waste liquid treatment method of the present invention, the second reaction liquid prepared in the fourth step can be filtered to recover the second solid and the second filtrate, respectively.

Specifically, the second filtrate recovered in step 5 may have a pH of 10 or higher, preferably 11.5 or higher, and more preferably 12.0 to 14.0. If the pH of the filtrate is less than 10, there may be a problem in that the degassing rate of ammonium ions decreases due to a decrease in pH during the reaction.

In addition, the BOE waste liquid treatment method of the present invention can have an ammonium ion treatment efficiency of 90% or more, preferably 95% or more, and more preferably 98 to 99.99%, as measured by the following equation 1, and thus, the BOE waste liquid treatment method of the present invention can have an excellent ammonium ion treatment efficiency.

[Equation 1]

In the above equation 1, C represents the concentration of ammonium ions contained in the BOE waste liquid prepared in the first step, and D represents the concentration of ammonium ions contained in the second filtrate recovered in the fifth step.

In addition, the BOE waste liquid treatment method of the present invention can have a fluoride ion treatment efficiency of 95% or more, preferably 98% or more, and more preferably 99 to 99.99%, as measured by the following equation 2, and thus, the BOE waste liquid treatment method of the present invention can have excellent fluoride ion treatment efficiency.

[Equation 2]

In the above equation 2, E represents the concentration of fluoride ions contained in the BOE waste liquid prepared in the first step, and F represents the concentration of fluoride ions contained in the second filtrate recovered in the fifth step.

Although the present invention has been described above with reference to embodiments, these are merely examples and do not limit the embodiments of the present invention. Those skilled in the art to which the embodiments of the present invention pertain will appreciate that various modifications and applications not exemplified above are possible without departing from the essential characteristics of the present invention. For example, each component specifically shown in the embodiments of the present invention can be modified and implemented. In addition, the differences related to such modifications and applications should be interpreted as being included in the scope of the present invention defined in the appended claims.

Example 1: Method for treating BOE (Buffered Oxide Etchant) waste liquid

(1) 500 g of BOE waste solution with a pH of 5.0 containing 80,000 mg/L of fluoride ion (F- ⁾ and 20,000 mg/L of ammonium ion ( _NH4 ⁺ ) was prepared.

(2) The prepared BOE waste liquid and the first calcium salt were put into the first dissolution tank to prepare a first mixture, and while injecting air (Air) at 4 L/min·kg into the first dissolution tank, the first reaction liquid was prepared by mixing and reacting for 20 hours. At this time, the first calcium salt was put with 63 g of slaked lime (Ca(OH) ₂ ) as the first calcium salt so that the molar ratio of the fluoride ion ( ^F- ) contained in the BOE waste liquid and the calcium ion (Ca2 ⁺ ) contained in the first calcium salt was 1:0.4.

(3) The manufactured first reaction solution was filtered to recover the first solid and the first filtrate, respectively, and the purity of fluorspar included in the recovered first solid was analyzed and shown in Table 11 below. At this time, the purity of fluorspar included in the recovered first solid was analyzed by the ion chromatography (IC) method.

(4) The first filtrate, the second calcium salt, and caustic soda (NaOH) were added to the second dissolution tank to prepare a second mixture, and while injecting air (Air) at 4 L/min·kg into the second dissolution tank, the mixture was mixed and reacted for 20 hours to prepare a second reaction solution. At this time, 24 g of slaked lime (Ca(OH)2) was added as the second calcium salt so that the molar ratio of the fluoride ion (F ^- ) included in the first filtrate and the calcium ion (Ca2 ⁺ ) included in the second calcium salt was 1:0.75, and ₂₀ g of caustic soda was added so that it had a molar ratio of 1:1.2 with the ammonium ion ( _NH4 ⁺ ) included in the first filtrate. Meanwhile, the pH of the second mixture in which the reaction occurred was measured at 30-minute intervals while the reaction was in progress, and the results are shown in Table 1 below. Based on the pH values listed in Table 1 below, the pH maintenance rate of the second mixture above 12.5 during the reaction time calculated using Equation 1 below was 95%.

[Relationship 1]

The rate at which the pH of the second mixture remains above 12.5 during the reaction time (%) =

In the above relational expression 1, A represents the total reaction time of the second mixture performing the reaction, and B represents the time during which the pH of the mixture is maintained at 12.5 or higher during the total reaction time of the second mixture performing the reaction.

(5) The manufactured second reaction solution was filtered to recover the second solid and the second filtrate, respectively, and the concentration of fluoride ion (F ^- ), the concentration of ammonium ion (NH ₄ ⁺ ) and pH contained in the recovered second filtrate were measured and shown in Table 11 below.

Example 2: Method for treating BOE (Buffered Oxide Etchant) waste liquid

(1) 500 g of BOE waste solution with a pH of 5.0 containing 80,000 mg/L of fluoride ion (F- ⁾ and 20,000 mg/L of ammonium ion ( _NH4 ⁺ ) was prepared.

(2) The prepared BOE waste liquid and the first calcium salt were put into the first dissolution tank to prepare a first mixture, and while injecting air (Air) at 4 L/min·kg into the first dissolution tank, the first reaction liquid was prepared by mixing and reacting for 20 hours. At this time, the first calcium salt was put with 63 g of slaked lime (Ca(OH) ₂ ) as the first calcium salt so that the molar ratio of the fluoride ion ( ^F- ) contained in the BOE waste liquid and the calcium ion (Ca2 ⁺ ) contained in the first calcium salt was 1:0.4.

(3) The manufactured first reaction solution was filtered to recover the first solid and the first filtrate, respectively, and the purity of fluorspar included in the recovered first solid was analyzed and shown in Table 11 below. At this time, the purity of fluorspar included in the recovered first solid was analyzed by the ion chromatography (IC) method.

(4) The first filtrate, the second calcium salt, and caustic soda (NaOH) were added to the second dissolution tank to prepare a second mixture, and while injecting air (Air) at 4 L/min·kg into the second dissolution tank, the mixture was mixed and reacted for 20 hours to prepare a second reaction solution. At this time, 24 g of slaked lime (Ca(OH)2) was added as the second calcium salt so that the molar ratio of the fluoride ion (F ^- ) included in the first filtrate and the calcium ion (Ca2 ⁺ ) included in the second calcium salt was 1:0.75, and ₁₃ g of caustic soda was added so that it had a molar ratio of 1:0.8 with the ammonium ion ( _NH4 ⁺ ) included in the first filtrate. Meanwhile, the pH of the second mixture in which the reaction occurred was measured at 30-minute intervals while the reaction was in progress, and the results are shown in Table 2 below. Based on the pH values described in Table 2 below, the pH maintenance rate of the second mixture above 12.5 during the reaction time calculated using the above equation 1 was 20%.

(5) The manufactured second reaction solution was filtered to recover the second solid and the second filtrate, respectively, and the concentration of fluoride ion (F ^- ), the concentration of ammonium ion (NH ₄ ⁺ ) and pH contained in the recovered second filtrate were measured and shown in Table 11 below.

Example 3: Method for treating BOE (Buffered Oxide Etchant) waste liquid

(1) 500 g of BOE waste solution with a pH of 5.0 containing 80,000 mg/L of fluoride ion (F- ⁾ and 20,000 mg/L of ammonium ion ( _NH4 ⁺ ) was prepared.

(2) The prepared BOE waste liquid and the first calcium salt were put into the first dissolution tank to prepare a first mixture, and while injecting air (Air) at 4 L/min·kg into the first dissolution tank, the first reaction liquid was prepared by mixing and reacting for 20 hours. At this time, the first calcium salt was put with 63 g of slaked lime (Ca(OH) ₂ ) as the first calcium salt so that the molar ratio of the fluoride ion ( ^F- ) contained in the BOE waste liquid and the calcium ion (Ca2 ⁺ ) contained in the first calcium salt was 1:0.4.

(3) The manufactured first reaction solution was filtered to recover the first solid and the first filtrate, respectively, and the purity of fluorspar included in the recovered first solid was analyzed and shown in Table 11 below. At this time, the purity of fluorspar included in the recovered first solid was analyzed by the ion chromatography (IC) method.

(4) The first filtrate, the second calcium salt, and caustic soda (NaOH) were added to the second dissolution tank to prepare a second mixture, and while injecting air (Air) at 4 L/min·kg into the second dissolution tank, the mixture was mixed and reacted for 20 hours to prepare a second reaction solution. At this time, 24 g of slaked lime (Ca(OH)2) was added as the second calcium salt so that the molar ratio of the fluoride ion (F ^- ) included in the first filtrate and the calcium ion (Ca2 ⁺ ) included in the second calcium salt was 1:0.75, and ₂₇ g of caustic soda was added so that it had a molar ratio of 1:1.6 with the ammonium ion ( _NH4 ⁺ ) included in the first filtrate. Meanwhile, the pH of the second mixture in which the reaction occurred was measured at 30-minute intervals while the reaction was in progress, and the results are shown in Table 3 below. Based on the pH values described in Table 3 below, the pH maintenance rate of the second mixture above 12.5 during the reaction time calculated using the above equation 1 was 100%.

(5) The manufactured second reaction solution was filtered to recover the second solid and the second filtrate, respectively, and the concentration of fluoride ion (F ^- ), the concentration of ammonium ion (NH ₄ ⁺ ) and pH contained in the recovered second filtrate were measured and shown in Table 11 below.

Example 4: Method for treating BOE (Buffered Oxide Etchant) waste liquid

(1) 500 g of BOE waste solution with a pH of 5.0 containing 80,000 mg/L of fluoride ion (F- ⁾ and 20,000 mg/L of ammonium ion ( _NH4 ⁺ ) was prepared.

(2) The prepared BOE waste liquid and the first calcium salt were put into the first dissolution tank to prepare a first mixture, and while injecting air (Air) at 4 L/min·kg into the first dissolution tank, the first reaction liquid was prepared by mixing and reacting for 20 hours. At this time, the first calcium salt was put with 32 g of slaked lime (Ca(OH) ₂ ) as the first calcium salt so that the molar ratio of the fluoride ion ( ^F- ) contained in the BOE waste liquid and the calcium ion (Ca2 ⁺ ) contained in the first calcium salt was 1:0.2.

(3) The manufactured first reaction solution was filtered to recover the first solid and the first filtrate, respectively, and the purity of fluorspar included in the recovered first solid was analyzed and shown in Table 11 below. At this time, the purity of fluorspar included in the recovered first solid was analyzed by the ion chromatography (IC) method.

(4) The first filtrate, the second calcium salt, and caustic soda (NaOH) were added to the second dissolution tank to prepare a second mixture, and while injecting air (Air) at 4 L/min·kg into the second dissolution tank, the mixture was mixed and reacted for 20 hours to prepare a second reaction solution. At this time, 19 g of slaked lime (Ca(OH)2) was added as the second calcium salt so that the molar ratio of the fluoride ion (F ^- ) included in the first filtrate and the calcium ion (Ca2 ⁺ ) included in the second calcium salt was 1:0.6, and ₂₀ g of caustic soda was added so that it had a molar ratio of 1:1.2 with the ammonium ion ( _NH4 ⁺ ) included in the first filtrate. Meanwhile, the pH of the second mixture in which the reaction occurred was measured at 30-minute intervals while the reaction was in progress, and the results are shown in Table 4 below. Based on the pH values described in Table 4 below, the pH maintenance rate of the second mixture above 12.5 during the reaction time calculated using the above equation 1 was 90%.

(5) The manufactured second reaction solution was filtered to recover the second solid and the second filtrate, respectively, and the concentration of fluoride ion (F ^- ), the concentration of ammonium ion (NH ₄ ⁺ ) and pH contained in the recovered second filtrate were measured and shown in Table 11 below.

Example 5: Method for treating BOE (Buffered Oxide Etchant) waste liquid

(1) 500 g of BOE waste solution with a pH of 5.0 containing 80,000 mg/L of fluoride ion (F- ⁾ and 20,000 mg/L of ammonium ion ( _NH4 ⁺ ) was prepared.

(2) The prepared BOE waste liquid and the first calcium salt were put into the first dissolution tank to prepare a first mixture, and while injecting air (Air) at 4 L/min·kg into the first dissolution tank, the first reaction liquid was prepared by mixing and reacting for 20 hours. At this time, the first calcium salt was put with 95 g of slaked lime (Ca(OH) ₂ ) as the first calcium salt so that the molar ratio of the fluoride ion ( ^F- ) contained in the BOE waste liquid and the calcium ion (Ca2 ⁺ ) contained in the first calcium salt was 1:0.6.

(3) The manufactured first reaction solution was filtered to recover the first solid and the first filtrate, respectively, and the purity of fluorspar included in the recovered first solid was analyzed and shown in Table 11 below. At this time, the purity of fluorspar included in the recovered first solid was analyzed by the ion chromatography (IC) method.

(4) The first filtrate, the second calcium salt, and caustic soda (NaOH) were added to the second dissolution tank to prepare a second mixture, and while injecting air (Air) at 4 L/min·kg into the second dissolution tank, the mixture was mixed and reacted for 20 hours to prepare a second reaction solution. At this time, 29 g of slaked lime (Ca(OH)2) was added as the second calcium salt so that the molar ratio of the fluoride ion (F ^- ) included in the first filtrate and the calcium ion (Ca2 ⁺ ) included in the second calcium salt was 1:0.9, and ₂₀ g of caustic soda was added so that it had a molar ratio of 1:1.2 with the ammonium ion ( _NH4 ⁺ ) included in the first filtrate. Meanwhile, the pH of the second mixture in which the reaction occurred was measured at 30-minute intervals while the reaction was in progress, and the results are shown in Table 5 below. Based on the pH values described in Table 5 below, the pH maintenance rate of the second mixture above 12.5 during the reaction time calculated using the above equation 1 was 97.5%.

(5) The manufactured second reaction solution was filtered to recover the second solid and the second filtrate, respectively, and the concentration of fluoride ion (F ^- ), the concentration of ammonium ion (NH ₄ ⁺ ) and pH contained in the recovered second filtrate were measured and shown in Table 11 below.

Example 6: Method for treating BOE (Buffered Oxide Etchant) waste liquid

(1) 500 g of BOE waste solution with a pH of 5.0 containing 80,000 mg/L of fluoride ion (F- ⁾ and 20,000 mg/L of ammonium ion ( _NH4 ⁺ ) was prepared.

(2) The prepared BOE waste liquid and the first calcium salt were put into the first dissolution tank to prepare a first mixture, and while injecting air (Air) at 4 L/min·kg into the first dissolution tank, the first reaction liquid was prepared by mixing and reacting for 25 hours. At this time, the first calcium salt was put with 63 g of slaked lime (Ca(OH) ₂ ) as the first calcium salt so that the molar ratio of the fluoride ion ( ^F- ) contained in the BOE waste liquid and the calcium ion (Ca2 ⁺ ) contained in the first calcium salt was 1:0.4.

(3) The manufactured first reaction solution was filtered to recover the first solid and the first filtrate, respectively, and the purity of fluorspar included in the recovered first solid was analyzed and shown in Table 11 below. At this time, the purity of fluorspar included in the recovered first solid was analyzed by the ion chromatography (IC) method.

(4) The first filtrate, the second calcium salt, and caustic soda (NaOH) were added to the second dissolution tank to prepare a second mixture, and while injecting air (Air) at 4 L/min·kg into the second dissolution tank, the mixture was mixed and reacted for 25 hours to prepare a second reaction solution. At this time, 24 g of slaked lime (Ca(OH)2) was added as the second calcium salt so that the molar ratio of the fluoride ion (F ^- ) included in the first filtrate and the calcium ion (Ca2 ⁺ ) included in the second calcium salt was 1:0.75, and ₂₀ g of caustic soda was added so that it had a molar ratio of 1:1.2 with the ammonium ion ( _NH4 ⁺ ) included in the first filtrate. Meanwhile, the pH of the second mixture in which the reaction occurred was measured at 30-minute intervals while the reaction was in progress, and the results are shown in Table 6 below. Based on the pH values described in Table 6 below, the pH maintenance rate of the second mixture above 12.5 during the reaction time calculated using the above equation 1 was 76%.

(5) The manufactured second reaction solution was filtered to recover the second solid and the second filtrate, respectively, and the concentration of fluoride ion (F ^- ), the concentration of ammonium ion (NH ₄ ⁺ ) and pH contained in the recovered second filtrate were measured and shown in Table 11 below.

Example 7: Method for treating BOE (Buffered Oxide Etchant) waste liquid

(1) 500 g of BOE waste solution with a pH of 5.0 containing 80,000 mg/L of fluoride ion (F- ⁾ and 20,000 mg/L of ammonium ion ( _NH4 ⁺ ) was prepared.

(2) The prepared BOE waste liquid and the first calcium salt were put into the first dissolution tank to prepare a first mixture, and while injecting air (Air) at 4 L/min·kg into the first dissolution tank, the first reaction liquid was prepared by mixing and reacting for 15 hours. At this time, the first calcium salt was put with 63 g of slaked lime (Ca(OH) ₂ ) as the first calcium salt so that the molar ratio of the fluoride ion ( ^F- ) contained in the BOE waste liquid and the calcium ion (Ca2 ⁺ ) contained in the first calcium salt was 1:0.4.

(3) The manufactured first reaction solution was filtered to recover the first solid and the first filtrate, respectively, and the purity of fluorspar included in the recovered first solid was analyzed and shown in Table 11 below. At this time, the purity of fluorspar included in the recovered first solid was analyzed by the ion chromatography (IC) method.

(4) The first filtrate, the second calcium salt, and caustic soda (NaOH) were added to the second dissolution tank to prepare a second mixture, and while injecting air (Air) into the second dissolution tank at 4 L/min·kg, the mixture was mixed and reacted for 15 hours to prepare a second reaction solution. At this time, 24 g of slaked lime (Ca(OH)2) was added as the second calcium salt so that the molar ratio of the fluoride ion (F ^- ) included in the first filtrate and the calcium ion (Ca2 ⁺ ) included in the second calcium salt was 1:0.75, and ₂₀ g of caustic soda was added so that it had a molar ratio of 1:1.2 with the ammonium ion ( _NH4 ⁺ ) included in the first filtrate. Meanwhile, the pH of the second mixture in which the reaction occurred was measured at 30-minute intervals while the reaction was in progress, and the results are shown in Table 7 below. Based on the pH values described in Table 7 below, the pH maintenance rate of the second mixture above 12.5 during the reaction time calculated using the above equation 1 was 100%.

(5) The manufactured second reaction solution was filtered to recover the second solid and the second filtrate, respectively, and the concentration of fluoride ion (F ^- ), the concentration of ammonium ion (NH ₄ ⁺ ) and pH contained in the recovered second filtrate were measured and shown in Table 11 below.

Example 8: Method for treating BOE (Buffered Oxide Etchant) waste liquid

(1) 500 g of BOE waste solution with a pH of 5.0 containing 80,000 mg/L of fluoride ion (F- ⁾ and 20,000 mg/L of ammonium ion ( _NH4 ⁺ ) was prepared.

(2) The prepared BOE waste liquid and the first calcium salt were put into the first dissolution tank to prepare a first mixture, and while injecting air (Air) at 1 L/min·kg into the first dissolution tank, the first reaction liquid was prepared by mixing and reacting for 20 hours. At this time, the first calcium salt was put with 63 g of slaked lime (Ca(OH) ₂ ) as the first calcium salt so that the molar ratio of the fluoride ion ( ^F- ) contained in the BOE waste liquid and the calcium ion (Ca2 ⁺ ) contained in the first calcium salt was 1:0.4.

(3) The manufactured first reaction solution was filtered to recover the first solid and the first filtrate, respectively, and the purity of fluorspar included in the recovered first solid was analyzed and shown in Table 11 below. At this time, the purity of fluorspar included in the recovered first solid was analyzed by the ion chromatography (IC) method.

(4) The first filtrate, the second calcium salt, and caustic soda (NaOH) were added to the second dissolution tank to prepare a second mixture, and while injecting air (Air) into the second dissolution tank at a rate of 1 L/min·kg, the mixture was mixed and reacted for 20 hours to prepare a second reaction solution. At this time, 24 g of slaked lime (Ca(OH)2) was added as the second calcium salt so that the molar ratio of the fluoride ion (F ^- ) included in the first filtrate and the calcium ion (Ca2 ⁺ ) included in the second calcium salt was 1:0.75, and ₂₀ g of caustic soda was added so that it had a molar ratio of 1:1.2 with the ammonium ion ( _NH4 ⁺ ) included in the first filtrate. Meanwhile, the pH of the second mixture in which the reaction occurred was measured at 30-minute intervals while the reaction was in progress, and the results are shown in Table 8 below. Based on the pH values described in Table 8 below, the pH maintenance rate of the second mixture above 12.5 during the reaction time calculated using the above equation 1 was 100%.

(5) The manufactured second reaction solution was filtered to recover the second solid and the second filtrate, respectively, and the concentration of fluoride ion (F ^- ), the concentration of ammonium ion (NH ₄ ⁺ ) and pH contained in the recovered second filtrate were measured and shown in Table 11 below.

Example 9: Method for treating BOE (Buffered Oxide Etchant) waste liquid

(1) 500 g of BOE waste solution with a pH of 5.0 containing 80,000 mg/L of fluoride ion (F- ⁾ and 20,000 mg/L of ammonium ion ( _NH4 ⁺ ) was prepared.

(2) The prepared BOE waste liquid and the first calcium salt were put into the first dissolution tank to prepare a first mixture, and while injecting air (Air) at 7 L/min·kg into the first dissolution tank, the first reaction liquid was prepared by mixing and reacting for 20 hours. At this time, the first calcium salt was put with 63 g of slaked lime (Ca(OH) ₂ ) as the first calcium salt so that the molar ratio of the fluoride ion ( ^F- ) contained in the BOE waste liquid and the calcium ion (Ca2 ⁺ ) contained in the first calcium salt was 1:0.4.

(3) The manufactured first reaction solution was filtered to recover the first solid and the first filtrate, respectively, and the purity of fluorite included in the recovered first solid was analyzed and shown in Table 3 below. At this time, the purity of fluorite included in the recovered first solid was analyzed by ion chromatography (IC) method.

(4) The first filtrate, the second calcium salt, and caustic soda (NaOH) were added to the second dissolution tank to prepare a second mixture, and while injecting air (Air) into the second dissolution tank at 7 L/min·kg, the mixture was mixed and reacted for 20 hours to prepare a second reaction solution. At this time, 24 g of slaked lime (Ca(OH)2) was added as the second calcium salt so that the molar ratio of the fluoride ion (F ^- ) included in the first filtrate and the calcium ion (Ca2 ⁺ ) included in the second calcium salt was 1:0.75, and ₂₀ g of caustic soda was added so that it had a molar ratio of 1:1.2 with the ammonium ion ( _NH4 ⁺ ) included in the first filtrate. Meanwhile, the pH of the second mixture in which the reaction occurred was measured at 30-minute intervals while the reaction was in progress, and the results are shown in Table 9 below. Based on the pH values described in Table 9 below, the pH maintenance rate of the second mixture above 12.5 during the reaction time calculated using the above equation 1 was 77.5%.

(5) The manufactured second reaction solution was filtered to recover the second solid and the second filtrate, respectively, and the concentration of fluoride ion (F ^- ), the concentration of ammonium ion (NH ₄ ⁺ ) and pH contained in the recovered second filtrate were measured and shown in Table 11 below.

Comparative Example 1: Method for treating BOE waste liquid

(1) 500 g of BOE waste solution with a pH of 5.0 containing 80,000 mg/L of fluoride ion (F- ⁾ and 20,000 mg/L of ammonium ion ( _NH4 ⁺ ) was prepared.

(2) The prepared BOE waste liquid and the first calcium salt were put into the first dissolution tank to prepare a first mixture, and while injecting air (Air) at 4 L/min·kg into the first dissolution tank, the first reaction liquid was prepared by mixing and reacting for 20 hours. At this time, the first calcium salt was put with 63 g of slaked lime (Ca(OH) ₂ ) as the first calcium salt so that the molar ratio of the fluoride ion ( ^F- ) contained in the BOE waste liquid and the calcium ion (Ca2 ⁺ ) contained in the first calcium salt was 1:0.4.

(3) The manufactured first reaction solution was filtered to recover the first solid and the first filtrate, respectively, and the purity of fluorspar included in the recovered first solid was analyzed and shown in Table 11 below. At this time, the purity of fluorspar included in the recovered first solid was analyzed by the ion chromatography (IC) method.

(4) The first filtrate and the second calcium salt were added to the second dissolution tank to prepare a second mixture, and while injecting air (Air) at 4 L/min·kg into the second dissolution tank, the mixture was mixed and reacted for 20 hours to prepare a second reaction solution. At this time, 24 g of slaked lime (Ca( ^OH) 2) was added as the second calcium salt so that the molar ratio of the fluoride ion (F ^- ) included in the first filtrate and the calcium ion (Ca2+ ₎ included in the second calcium salt was 1:0.75. Meanwhile, the pH of the second mixture in which the reaction occurred was measured at 30-minute intervals during the reaction, and the results are shown in Table 10 below. Based on the pH values described in Table 10 below, the pH maintenance rate of the second mixture above 12.5 during the reaction time calculated through the above equation 1 was 2.5%.

(5) The manufactured second reaction solution was filtered to recover the second solid and the second filtrate, respectively, and the concentration of fluoride ion (F ^- ), the concentration of ammonium ion (NH ₄ ⁺ ) and pH contained in the recovered second filtrate were measured and shown in Table 11 below.

As can be seen in Table 11, the method for treating BOE waste liquid of Example 1 not only recovered high-purity fluorite, but also effectively treated fluoride ions (F ^- ) and ammonium ions (NH ₄ ⁺ ) contained in BOE waste liquid.

However, compared to the BOE waste liquid treatment method of Example 1, it was confirmed that the BOE waste liquid treatment method of Comparative Example 1 had a significantly lower ammonium ion (NH ₄₊ ) ^treatment efficiency.

In addition, it was confirmed that the BOE waste liquid treatment method of Example 2 had a lower ammonium ion (NH ₄ ⁺ ) treatment efficiency compared to the BOE waste liquid treatment method of Example 1.

In addition, it was confirmed that the BOE waste liquid treatment method of Example 3 did not increase the efficiency of treating fluoride ions (F ^- ) and ammonium ions (NH ₄ ⁺ ) compared to the BOE waste liquid treatment method of Example 1, so that not only was the economic feasibility reduced due to excessive use of caustic soda compared to Example 1, but there was also a problem of increased costs for treating caustic soda remaining in the recovered filtrate.

In addition, compared to the BOE waste liquid treatment method of Example 1, it was confirmed that the BOE waste liquid treatment method of Example 4 not only lowered the purity of fluorite, but also lowered the fluoride ion (F ^- ) treatment efficiency.

In addition, it was confirmed that the purity of fluorite was lowered in the BOE waste liquid treatment method of Example 5 compared to the BOE waste liquid treatment method of Example 1. In addition, it was confirmed that the treatment efficiency of fluoride ions (F ^- ) and ammonium ions (NH ₄ ⁺ ) was not increased, so that not only was the economic feasibility lowered due to the excessive use of slaked lime (Ca(OH) ₂ ) compared to Example 1, but there was also a problem that the cost for treating slaked lime (Ca(OH) ₂ ) remaining in the recovered filtrate increased.

In addition, it was confirmed that the purity of fluorite was lowered in the BOE waste liquid treatment method of Example 6 compared to the BOE waste liquid treatment method of Example 1. In addition, it was confirmed that the process efficiency was lowered compared to Example 1 because the treatment efficiency of fluorine ions (F ^- ) and ammonium ions (NH ₄ ⁺ ) did not increase.

In addition, compared to the BOE waste liquid treatment method of Example 1, it was confirmed that the BOE waste liquid treatment method of Example 7 not only lowered the purity of fluorite, but also lowered the efficiency of treating fluoride ions (F ^- ) and ammonium ions (NH ₄ ⁺ ).

In addition, compared to the BOE waste liquid treatment method of Example 1, it was confirmed that the BOE waste liquid treatment method of Example 8 not only lowered the purity of fluorite, but also lowered the efficiency of treating fluoride ions (F ^- ) and ammonium ions (NH ₄ ⁺ ).

In addition, it was confirmed that the purity of fluorite was lowered in the BOE waste liquid treatment method of Example 9 compared to the BOE waste liquid treatment method of Example 1. In addition, it was confirmed that the efficiency of treating fluoride ions (F ^- ) and ammonium ions (NH ₄ ⁺ ) did not increase, and thus the economic feasibility was lowered due to excessive energy use compared to Example 1.

Simple modifications or changes of the present invention can be easily implemented by those skilled in the art, and all such modifications or changes can be considered to be included in the scope of the present invention.

Claims (16)

Step 1: preparing BOE waste liquid containing fluoride ions (F ^- ) and ammonium ions (NH ₄ ⁺ );
A second step of preparing a first mixture by adding the BOE waste liquid and the first calcium salt to the first dissolution tank, and mixing and reacting the first mixture to prepare a first reaction solution;
A third step of filtering the first reaction solution to recover the first solid and the first filtrate, respectively;
Step 4 of preparing a second mixture by adding the first filtrate, the second calcium salt, and caustic soda (NaOH) to the second dissolution tank, and mixing and reacting the second mixture to prepare a second reaction solution; and
A fifth step of filtering the second reaction solution to recover the second solid and the second filtrate, respectively;
The fluoride ion (F ^- ) and calcium ion (Ca ²⁺ ) contained in the first mixture prepared in the second step above have a molar ratio of 1:0.3 to 0.5.
A method for treating BOE wastewater, characterized in that the ammonium ion ( _NH4 ⁺ ) and caustic soda (NaOH) included in the second mixture prepared in the fourth step have a molar ratio of 1:1.0 to 1.4.
In the first paragraph,
A method for treating BOE waste liquid, characterized in that the purity of fluorite contained in the first solid material is 80% or higher.
delete In the first paragraph,
A method for treating BOE wastewater, characterized in that the second step reaction is performed while injecting air into the first dissolution tank at a rate of 2 to 6 L/min·kg.
In the first paragraph,
A method for treating BOE wastewater, characterized in that the reaction of the fourth step is performed while maintaining the pH of the second mixture at 11 or higher.
In paragraph 5,
A method for treating BOE wastewater, characterized in that the reaction of the fourth step above satisfies the following condition (1).
(1) 80% ≤
In the above condition (1), A represents the total reaction time of the second mixture performing the reaction, and B represents the time during which the pH of the second mixture is maintained at 12.5 or higher during the total reaction time of the second mixture performing the reaction.
In Article 6,
A method for treating BOE wastewater, characterized in that the reaction in the fourth step is performed for 16 to 24 hours.
In Article 7,
A method for treating BOE wastewater, characterized in that the reaction of the fourth step is performed while injecting air into the second dissolution tank at a rate of 2 to 6 L/min·kg.
In the first paragraph,
A method for treating BOE wastewater, characterized in that the second filtrate of the fifth step has a pH of 10 or higher.
In the first paragraph,
A method for treating BOE wastewater, characterized in that the ammonium ion treatment efficiency measured by the following equation 1 is 90% or more.
[Equation 1]

In the above equation 1, C represents the concentration of ammonium ions contained in the BOE waste liquid prepared in the first step, and D represents the concentration of ammonium ions contained in the second filtrate recovered in the fifth step.
In the first paragraph,
A method for treating BOE wastewater, characterized in that the fluoride ion treatment efficiency measured by the following equation 2 is 95% or higher.
[Equation 2]

In the above equation 2, E represents the concentration of fluoride ions contained in the BOE waste liquid prepared in the first step, and F represents the concentration of fluoride ions contained in the second filtrate recovered in the fifth step.
In the first paragraph,
A method for treating BOE waste liquid, characterized in that the BOE waste liquid prepared in the above first step contains 60,000 to 100,000 mg/L of fluoride ion (F ^- ) and 10,000 to 30,000 mg/L of ammonium ion (NH ₄ ⁺ ).
In Article 12,
A method for treating BOE waste liquid, characterized in that the BOE waste liquid prepared in the above first step has a pH of 3 to 7.
In the first paragraph,
A method for treating BOE wastewater, characterized in that the first calcium salt and the second calcium salt each include at least one selected from slaked lime (Ca(OH) ₂ ) and quicklime (CaO).
In the first paragraph,
A method for treating BOE wastewater, characterized in that the fluoride ion (F ^- ) and calcium ion (Ca ²⁺ ) contained in the second mixture prepared in the fourth step have a molar ratio of 1:0.65 to 0.85.
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