TWI238148B - Method for treating fluoride containing waste water - Google Patents

Abstract

A method for treating fluoride containing waste water which comprises supplying fluoride containing waste water to a reactor and adding a mixing solution of calcium compound whereas the pH of waste water is 2 to 5. Because the calcium ions react with the fluoride ion to form calcium fluoride precipitate and the calcium ions can't react with the other acid ions to form precipitate in acid environment; the fluoride ion can be precipitated effectively. The waste water is supplied to a coagulation precipitation trough. A coagulator and an neutralizer is added to the coagulation precipitation trough whereas the pH of waste water is 7 to 8. The fluoride in the waste water to form a calcium fluoride precipitate and all fluoride is removed from the waste water.

Description

1238148 _Case No. 91125107_ Year Month Amendment ___ V. Description of the Invention (1) Field of the Invention The present invention relates to a method for treating wastewater, and more particularly to a method for treating fluorine-containing wastewater. BACKGROUND OF THE INVENTION In industrial activities, such as glass manufacturing, electricity and mining operations, aluminum and steel refining, and semiconductor component manufacturing, a large number of fluorides are used in the manufacturing process, so a large amount of fluoride ions are also contained in their discharged wastewater. . In order to avoid the pollution of fluoride ion by the environment, the waste water from the above process must be properly treated to remove the fluoride ion from the waste water. The conventional method for removing fluoride ions from fluorine-containing wastewater is the coagulation precipitation method of calcium compounds. This method uses calcium compounds (including calcium hydroxide (C a (Ο Η) 2, calcium chloride (CaCl2), etc.)) to remove fluoride ions into precipitates of insoluble calcium fluoride (CaF2) and removes them. Currently, The calcium compound coagulation precipitation method commonly used in the industry includes calcium chloride coagulation precipitation mode (called pure calcium chloride mode) and calcium hydroxide coagulation Shendian mode (called lime mode). For example, first introduce the fluorine-containing wastewater into the neutralization tank, and neutralize the fluorine-containing wastewater with sodium hydroxide so that the acid test value is p Η value of 7 to 8, and then ρ Η value of 7 to 8 fluorine Wastewater is introduced into the reaction tank, and then calcium chloride solution is added to the reaction tank, so that fluoride ions in the fluorine-containing wastewater react with calcium chloride to form calcium fluoride crystals. Then, the fluorine-containing wastewater is introduced into the mixed precipitation tank, and Using coagulant (PAC) and polymer sedimentation agent in order to agglomerate and settle the calcium fluoride crystals, and discharge clarified wastewater from the upper part of the mixed sedimentation tank. The calcium fluoride precipitates left under the mixed sedimentation tank The sludge cake machine is used to dehydrate to form calcium fluoride sludge to achieve The purpose of fluoride ion removal from wastewater.

9953 t.wf 1. ptd Page 5 1238148 _ Case No. 91125107_ Year Month_ V. Description of the invention (2) In the case of calcium hydroxide coagulation precipitation mode, calcium hydroxide is used instead of calcium chloride. The advantage of replacing calcium chloride with calcium hydroxide is that calcium hydroxide itself can provide # 5 ion (Ca2 +) and two equivalent hydroxide ion (OH —), so it can reduce the use of sodium hydroxide in medicine, and There is no need to set a neutralization tank. However, calcium hydroxide medicines are more expensive than calcium chloride medicines, and the addition of calcium hydroxide is not easy to control. Therefore, the industry is currently less used. However, for the above-mentioned method for removing fluorine ions in fluorine-containing wastewater, due to the manufacturing process, in general fluorine-containing wastewater in semiconductor factories, in addition to fluoride ions, it usually contains considerable other acid solutions (such as sulfuric acid, nitric acid, etc.). And phosphoric acid), so when calcium hydroxide or calcium chloride is added to the waste water system, in addition to generating calcium fluoride crystals, calcium ions will also react with other acid ions to form calcium sulfate, calcium nitrate, and calcium phosphate. And so on. If the treatment is not controlled properly, it is possible to add calcium hydroxide or calcium chloride to the waste water system. The calcium ion first reacts with sulfate ion, nitrate ion, and phosphate ion to form compounds such as calcium sulfate, calcium nitrate, calcium phosphate, and then calcium. Only the ions form fluoride with the fluoride ions, thus wasting calcium hydroxide or calcium chloride. In addition, as for the method for removing fluorine ions in the fluorine-containing wastewater, the precipitation of compounds such as calcium sulfate, calcium nitrate, and calcium phosphate will also cause an increase in the amount of sludge in the entire fluorine-containing wastewater treatment process and improve the treatment of sewage. The cost of mud. Therefore, how to achieve sludge reduction is very important. SUMMARY OF THE INVENTION In view of this, an object of the present invention is to provide a method for treating fluorine-containing wastewater, which can reduce the amount of calcium chloride used, reduce the amount of sludge, and the concentration of fluorine ions in the discharged wastewater is lower than the regulatory standard. The invention provides a method for treating fluorine-containing wastewater, which is an advanced method.

9953t.wfl.ptd Page 6 1238148 _Case No. 91125107_ Year Month Amendment __ V. Description of the invention (3) Perform a reaction treatment step, and add hydroxide # 5 and The mixed solution of chlorinated dance and adjusted the acid-base value (pH value) of the fluorine-containing wastewater in the first reaction tank to about 2 to 5, so that calcium ions and fluorine ions in the fluorine-containing wastewater generate calcium fluoride. Next, a coagulation sedimentation treatment step is performed, and the fluorine-containing wastewater is introduced into the coagulation sedimentation tank, and sodium hydroxide solution and a coagulant are added to the coagulation sedimentation tank to adjust the pH value of the fluorine-containing wastewater in the coagulation sedimentation tank. (P Η value) is about 7 to 8, and fluorinated # 5 is coagulated and precipitated. Then, a wastewater discharge step is performed to discharge clarified wastewater from the upper part of the mixed sedimentation tank, and a sludge treatment step is performed to dehydrate the calcium fluoride precipitate remaining in the mixed sedimentation tank to form calcium fluoride sludge. The above reaction treatment step further includes introducing the fluorine-containing wastewater into the second reaction tank, and then adding a mixed solution of calcium hydroxide and calcium chloride to the second reaction tank, and adjusting the acid-base value of the fluorine-containing wastewater in the second reaction tank. (Ρ Η value) is about 2 to 5 so that calcium ion and fluoride ion in the fluorine-containing wastewater generate fluoride! Bow. Moreover, the above coagulation and precipitation step further includes adding a polymer sedimentation agent to the fluorine-containing wastewater to coagulate and precipitate calcium fluoride. In the present invention, in an acid environment (at an acid-base value (ρ Η value) of about 2 to 5), calcium ions will react with fluoride ions to form calcium fluoride and precipitate out, but the calcium ions will not react with other acid ions. Such as the sulfate ion, nitrate ion, phosphate ion and other reactions to form calcium sulfate, calcium nitrate and calcium phosphate, etc. and the principle of precipitation. In the reaction treatment step, the acid-base value (ρ Η value) of the fluorine-containing wastewater is adjusted to about 2 to 5, so that the fluoride ions are first precipitated from the wastewater, so the content of fluorine ions in the wastewater can be effectively reduced. Moreover, because most of the calcium ions have reacted with the fluoride ions to precipitate

9953t.wfl.ptd Page 7 1238148 _Case No. 9125107_year month_iti_ V. Description of the invention (4), and the remaining calcium ions will be combined with sulfate ions and nitrate in the subsequent coagulation precipitation process Ions, phosphate ions, etc. form precipitates such as calcium sulfate, calcium nitrate and calcium phosphate. Therefore, the method of the present invention can not only effectively remove fluoride ions, but also reduce the amount of calcium compounds and the amount of sludge in the fluorine-containing wastewater treatment process, and can save costs. In order to make the above and other objects, features, and advantages of the present invention more comprehensible, a preferred embodiment is given below in conjunction with the accompanying drawings to make a detailed description as follows: Symbols of the drawings: 1 ◦ 0 : Wastewater 1 0 2, 1 ◦ 6: Reaction tank 1 0 4: Compound mixing solution 1 0 8: Coagulation sedimentation tank 1 1 0: Quick mixing tank 1 1 4: Settling tank 1 1 6: Concentration tank 1 1 8 : Coagulant 1 2 0: Neutralizer 1 2 2: Description of a preferred embodiment of a polymer precipitant The treatment method of the fluorine-containing wastewater of the present invention is in a reaction treatment step by adjusting the acid test of the fluorine-containing wastewater The value (pH value) is about 2 to 5, so that # 5 ion will only form calcium fluoride with fluoride ion, but will not form compound precipitation with other acid ion, so it can effectively reduce the fluoride ion content in wastewater, and Reduce the amount of calcium compounds and the sludge in the process of fluorine-containing wastewater treatment

9953 t.wf 1. pt.d page 8 1238148 _ case number 91125107 _ year month day _ amendment ____ 5. Description of the invention (5) Quantity. The method for treating fluorine-containing wastewater of the present invention includes at least a reaction treatment step, a coagulation sedimentation treatment step, a wastewater discharge step, and a sludge treatment step. The following is a detailed description of the method for treating fluorine-containing wastewater of the present invention. Please refer to FIG. 1 for a schematic diagram of a fluorine-containing wastewater treatment mode according to a preferred embodiment of the present invention. First, a reaction treatment step is performed, and waste water 1000 is introduced into the reaction tank 102. The wastewater 100 includes, in addition to fluoride (such as hydrofluoric acid), other waste acid liquids such as sulfuric acid, nitric acid, and phosphoric acid. After the wastewater 100 is introduced into the reaction tank 102, a calcium compound mixed solution 104 is added to the reaction tank 100 and the amount of the bow compound mixed solution 104 is controlled to make the reaction tank 10 The acid-base value (ρ η value) of the wastewater 100 is maintained at about 2 to 5, for example. The calcium compound mixed solution 104 is, for example, a solution prepared from calcium hydroxide and calcium chloride. Since the acid-base value (pH value) of the wastewater 100 in the reaction tank 100 is, for example, about 2 to 5, the # 5 ion will easily combine with the fluoride ions in the wastewater 100 to form calcium fluoride. And it is not easy to form calcium sulfate, calcium nitrate and calcium phosphate with other acid ions such as sulfate ion, nitrate ion, phosphate ion and the like in the wastewater to precipitate out. Then, the waste water 100 is introduced into another reaction tank 1q6. The purpose of setting this reaction tank 106 is to prevent the incomplete reaction of fluoride ions in the reaction tank 102, and it is additionally provided. Similarly, after the wastewater is introduced into the reaction tank, the calcium compound mixed solution is added to the reaction tank 106, and the reaction tank 106 is made of hydrochloric acid (HC1) and sodium hydroxide (NaOH). The acid-base value (ρ Η value) of the wastewater is, for example, controlled at about 2 to 5, so that fluoride ions in the wastewater can further form calcium fluoride with calcium ions. In addition, since the pH value of the wastewater in the reaction tank 丨 〇6 is still maintained at about 2 to 5, the calcium ion

9953t.wfl.ptd Page 9 1238148 _Case No. 9125107_Year Month Amendment_ ^ V. Description of the invention (6) It is not easy to form with other acid ion such as sulfate ion, nitrate ion, phosphate ion, etc. in wastewater Calcium sulfate, calcium nitrate and calcium phosphate. Next, a coagulation and sedimentation treatment step is performed, and the wastewater 100 is introduced into the coagulation and sedimentation tank 108. The coagulation sedimentation tank 1 0 8 includes at least a fast mixing tank 1 10, a slow mixing tank 1 1 2, a sedimentation tank 1 1 4 and a concentration tank 1 16. When wastewater 100 is introduced into the fast mixing tank 1 110, a coagulant 1 1 8 is added to the fast mixing tank 1 10 (the coagulant includes an aluminum salt (P AC), which is, for example, aluminum chloride, etc.), A neutralizer 1 2 0 (the neutralizer 1 2 0 is, for example, sodium hydroxide) is added to the fast mixing tank 1 10 to adjust the pH (p Η value) of the wastewater 1 0 to, for example, 7 to 8 Left and right to carry out the coagulation adsorption precipitation reaction, and generate a white precipitate of co-precipitation of white hydroxide and fluorinated # 5. Moreover, when the acid-base value (ρ Η value) of the wastewater 100 rises to about 7 to 8, the remaining calcium ions in the wastewater 100 and other acid ions such as sulfate ions, Nitrate ions, phosphate ions, etc. form calcium sulfate, calcium nitrate, calcium phosphate, etc. and precipitate out. These precipitates such as calcium sulfate, calcium nitrate and calcium phosphate also form co-precipitates with aluminum hydroxide. Then, the waste water 100 is re-introduced into the slow mixing tank 1 12 and a polymer sedimentation agent 1 2 2 is added to the slow mixing tank 1 12 to make calcium fluoride, calcium sulfate, nitric acid in the waste water 100 Calcium is further aggregated with precipitates such as calcium phosphate. Next, the wastewater 100 is sequentially introduced into the sedimentation tank 1 1 4 and the concentration tank 1 16 to cause the sludge to aggregate and settle. After that, a wastewater discharge step and a sludge treatment step are performed. When the sludge in the wastewater 100 is coagulated and settled in the mixed sedimentation tank 108, the clarified wastewater is discharged from the upper part of the mixed sedimentation tank 108. The calcium fluoride precipitate remaining in the mixed precipitation tank 108 is dehydrated by a sludge cake machine to form calcium fluoride sludge, so as to achieve the purpose of removing fluoride ions from the wastewater. Among them, after this

9953t.wfl.ptd Page 10 1238148 _Case No. 9125107_year month__ V. Description of the invention (7) The content of fluorine ion in wastewater 100 treated by the invention method can be reduced to 15 ppm or less, and Below regulatory standards. Moreover, the amount of sludge can be reduced by more than 20% ~ 30% compared with the conventional method. According to the embodiment of the present invention, in the present invention, it is easier to precipitate calcium fluoride by reacting with fluoride ions to form calcium fluoride in an acid environment (at an acid-base value (pH value) of about 2 to 5), but it is not easy to precipitate out. The principle of reaction with other acid ions such as sulfate ions, nitrate ions, phosphate ions and the like reduces the amount of calcium chloride used and reduces the amount of sludge. In the reaction treatment step, the acid-base value (pH value) of the fluorine-containing wastewater is adjusted to about 2 to 5, so that fluoride ions are first precipitated from the waste water, so the content of fluorine ions in the wastewater can be effectively reduced. In addition, most calcium ions have reacted with fluoride ions to precipitate out, and the remaining calcium ions will form calcium sulfate with sulfate ions, nitrate ions, phosphate ions, etc. in the subsequent coagulation and precipitation process. Precipitation of calcium nitrate and calcium phosphate. Therefore, the method of the present invention can not only effectively remove fluoride ions, but also reduce the amount of calcium compounds and the amount of sludge in the fluorine-containing wastewater treatment process, and can save costs. Moreover, in the above embodiment, two reaction tanks are taken as an example for explanation, and the second reaction tank is used as an auxiliary to precipitate fluorine ions that do not form calcium fluoride in the first reaction tank. of course. According to the present invention, only one reaction tank or two or more reaction tanks may be provided according to actual needs. Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make various modifications and retouches without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection shall be determined by the scope of the attached patent application.

9953twfl.ptd Page 11 1238148 Case No. 91125107_Year Month Amendment Brief Description of the Drawings Brief Description of the Drawings: Figure 1 is a schematic diagram showing the treatment of fluorine-containing wastewater in a preferred embodiment of the present invention.

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Claims (1)

1238148 _Case No. 91125107_ Amendment Date ___ 6. Application for Patent Scope 1 · A method for treating fluorine-containing wastewater, the method includes the following steps: A reaction treatment step is performed, and one of the fluorine-containing wastewater has been introduced first. A calcium compound is added to the reaction tank, and the acid-base value (p Η value) in the first reaction tank is adjusted to about 2 to 5, so that the # 5 compound and fluorine ions in the fluorine-containing wastewater generate fluorinated # 5. And a coagulation precipitation treatment step, introducing the fluorinated wastewater into a coagulation sedimentation tank, adding a coagulant to precipitate fluorinated # 5, and adding a medicament to make the fluorinated wastewater pH (ρ Threshold value) is about 7 to 8 to make other acids react with calcium ions. 2. The method for treating fluorine-containing wastewater as described in item 1 of the patent application scope, wherein the reaction treatment step further includes introducing the fluorine-containing wastewater into a second reaction tank, and then adding the calcium compound to the second reaction tank And adjust the acid-base value (ρ Η value) in the second reaction tank to be about 2 to 5 so that the calcium compound and the fluoride ion remaining in the fluorine-containing wastewater generate calcium fluoride. 3. The method for treating fluorine-containing wastewater as described in item 1 of the scope of patent application, wherein the calcium compound includes calcium hydroxide and calcium chloride. 4. The method for treating fluorine-containing wastewater as described in item 1 of the scope of patent application, wherein the agent includes sodium hydroxide. 5. The method for treating fluorine-containing wastewater as described in item 1 of the scope of patent application, wherein the step of coagulating Shendian includes a step of adding a coagulant to the fluorine-containing wastewater. 6. The method for treating fluorine-containing wastewater as described in item 5 of the scope of the patent application, wherein the coagulant aid includes an aluminum salt. 7. The treatment party of fluorine-containing wastewater as described in item 1 of the scope of patent application 9953twfl, ptd page 13 1238148 _ case number 91125107_ year month date _ 6, the scope of patent application method, wherein the coagulation precipitation step includes the step of adding a polymer sedimentation agent to the fluorine-containing wastewater. 8 θ The method for treating fluorine-containing wastewater as described in item 1 of the scope of the patent application, further comprising performing a wastewater discharge step to discharge clarified wastewater from the upper part of the mixed sedimentation tank. 9 · The method for treating fluorine-containing wastewater as described in item 1 of the scope of the patent application, which further includes performing a sludge treatment step to dehydrate the calcium fluoride precipitate remaining in the mixed precipitation tank to form calcium fluoride sewage mud. 1 ◦ A method for treating fluorine-containing wastewater, the method includes the following steps: performing a reaction treatment step, adding a mixed solution of calcium hydroxide and calcium chloride to a first reaction tank that has been introduced into a fluorine-containing wastewater, and Adjusting the acid-base value (ρ Η value) of the fluorine-containing wastewater in the first reaction tank to be about 2 to 5 so that calcium ions and fluoride ions in the fluorine-containing wastewater generate calcium fluoride; In the treatment step, the fluorine-containing wastewater is introduced into a coagulation sedimentation tank, and a coagulant is added to the coagulation sedimentation tank to precipitate calcium fluoride, and the pH value of the fluorine-containing wastewater in the coagulation sedimentation tank is adjusted. (Ρ Η value) is about 7 to 8 to make other acids react with calcium ions; perform a waste water discharge step to discharge clarified waste water from the upper part of the mixed sedimentation tank; and perform a sludge treatment step, which will remain in the The fluorinated precipitate in the mixed precipitation tank is dehydrated to form fluorinated # 5 sludge. 11. The method for treating fluorine-containing wastewater as described in item 10 of the scope of patent application, wherein the reaction treatment step further includes introducing the fluorine-containing wastewater into a second 9953twfl.ptd Page 14 1238148 _Case No. 9125107_Year_Month__ Sixth, apply for a patent range reaction tank, and then add a mixed solution of calcium hydroxide and calcium chloride to the second reaction tank, and adjust the second The pH value (P Η value) in the reaction tank is about 2 to 5 so as to generate calcium fluoride from calcium ions and fluorine ions remaining in the fluorine-containing wastewater. 1 2 β The method for treating fluorine-containing wastewater as described in item 10 of the scope of the patent application, wherein the coagulant includes I Lu salt. 13. The method for treating fluorine-containing wastewater as described in item 10 of the scope of the patent application, wherein the coagulation and precipitation step further includes a step of adding a polymer sedimentation agent to the fluorine-containing wastewater. 9953t.wf 1. ptd p. 15