Liquid fluorine removal agent and application thereof

Abstract

The pH value of the liquid fluorine removal agent is 2-4, and the liquid fluorine removal agent comprises a basic fluorine removal component used for achieving the fluorine removal effect and a synergistic adjustment component used for promoting fluorine removal and accelerating pH up-regulation after reaction so as to reduce the dosage of liquid caustic soda and compact sludge floc. The basic defluorination component and the synergistic regulation component are mixed in a ratio of (3-4): 1; the basic defluorination component takes monobasic acid salt as a main component and dibasic acid salt as an auxiliary component; the synergistic adjusting component takes neutral salt and / or strong alkali and weak acid salt as a main component and is matched with an auxiliary agent. The method can be used for treating fluorine-containing wastewater with various initial concentrations of F <->, the F <-> concentration of effluent can be smaller than or equal to 0.5 mg / L, and the method is wide in wastewater pH application range, fast in pH up-regulation, small in liquid caustic soda consumption, small in sludge amount and compact.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, in particular to a liquid defluoridating agent and application thereof. Background Art

[0002] With the continuous development of modern industry, the number of fluoride producers and users is increasing. The environmental pollution caused by fluoride-containing wastewater is drawing increasing attention from the government and related companies. Fluoride-containing wastewater primarily originates from industries such as coal chemical industry, fluorine chemical industry, phosphate fertilizer industry, and integrated circuit board production. If discharged directly without treatment, it can increase fluoride concentrations in water bodies, further harming the environment and human health. Therefore, strictly enforcing discharge standards for fluoride-containing wastewater and implementing effective treatment measures are of great significance for protecting water resources and maintaining ecological balance.

[0003] In the field of industrial wastewater treatment, the widely used fluoride removal technologies are mainly calcium salt precipitation method and aluminum salt coagulation method, which are collectively referred to as pharmaceutical methods. Among them, the calcium salt precipitation method mainly uses the reaction of calcium salt and fluoride to generate calcium fluoride precipitate to remove pollutants. However, due to the limitation of solubility product, this method can usually only treat the fluoride concentration to about 10 mg / L, and it is difficult to meet lower treatment requirements in one step. - The most difficult part of fluorine removal is to reduce the concentration to below 1.5 mg / L. Although it is technically feasible, it mainly faces the problem of engineering application cost.

[0004] Currently, most liquid defluoridants are strongly acidic, with a pH value of only between 1 and 2, which is determined by the raw materials and production process. The extremely low pH value makes the pH of the wastewater after defluoridation also low, generally around 3, so a large amount of liquid alkali is needed to adjust it back to neutral. However, the price of liquid alkali is relatively high. In the cost of treating a ton of water, the cost of liquid alkali per ton of water can reach 1 to 2 yuan or even more. This leads to an embarrassing situation: even if the cost of the defluoridant itself per ton of water is not high, the cost of liquid alkali per ton of water is too high, even exceeding the cost of the defluoridant itself, which greatly increases the overall cost per ton of water. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a liquid defluoridating agent and its application, which can be used for various initial concentrations of F - The treatment of fluorine-containing wastewater can make the fluorine content of the effluent - The concentration is ≤0.5 mg / L, and it has a wide adaptability to wastewater pH, quickly adjusts pH, requires less liquid alkali, and produces small and dense sludge.

[0006] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows.

[0007] A liquid defluoridant with a pH of 2-4 comprises a basic defluoridation component for achieving defluoridation and a synergistic regulating component for promoting defluoridation and accelerating the upward adjustment of pH after the reaction to reduce the amount of liquid alkali used and compact sludge flocs; the basic defluoridation component and the synergistic regulating component are mixed in a ratio of 3-4:1; the basic defluoridation component is mainly composed of a monobasic acid salt and supplemented with a dibasic acid salt; the synergistic regulating component is mainly composed of a neutral salt and / or a strong base and weak acid salt and is combined with an auxiliary agent.

[0008] Preferably, the content ratio of the monobasic acid salt to the dibasic acid salt in the basic defluorination component is ≥4:1.

[0009] Preferably, the monobasic acid salt is one or more of: polyaluminum chloride, polyaluminum ferric chloride, rare earth chloride, aluminum chloride, ferric chloride, and magnesium chloride.

[0010] Preferably, the dibasic acid salt is one or more of aluminum sulfate, ferrous sulfate, polyaluminum sulfate, and polyaluminum ferric sulfate.

[0011] Preferably, the basic defluorination component contains 2 to 3.5 parts of monobasic acid salt and 0.3 to 0.5 parts of dibasic acid salt.

[0012] Preferably, the synergistic regulating component comprises 2 to 4 parts of neutral salt and / or acid salt of strong base and weak acid, and 0.3 to 0.5 parts of auxiliary agent.

[0013] Preferably, the neutral salt and / or strong base and weak acid salt in the synergistic regulating component is one or more of sodium chloride, sodium sulfate, potassium chloride, potassium sulfate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, and sodium acetate.

[0014] Preferably, the auxiliary agent in the synergistic regulating component is at least two or more of magnesium oxide, chitosan, starch, sodium benzenesulfonate, sodium alginate, and lignin.

[0015] An application of a liquid defluoridant, the application method is: according to the initial F - Add a certain amount of liquid defluoridant according to the concentration and target value. If the pH is lower than 4 after 15-30 minutes of reaction, adjust the pH to 6-7, add anionic PAM, react for 10-30 minutes, and precipitate for 10-30 minutes.

[0016] Preferably, the pH is adjusted to 6.2-6.5, anionic PAM is added and reacted for 10-30 min, and precipitation is carried out for 10-30 min. Due to the adoption of the above technical solution, the technical progress achieved by the present invention is as follows.

[0017] Due to the characteristics of the neutral salt and / or strong base and weak acid salt in the synergistic regulating component, the pH of the present invention is rapidly increased during the pH adjustment process after the reaction. Compared with other acidic defluoridants, under the same pH conditions, the amount of liquid alkali used can be reduced by 30% to 50%.

[0018] The basic defluorination component and the synergistic regulating component complement each other and are mixed in a ratio of 3 to 4:1, which can neutralize the pH of part of the basic defluorination component raw material. The pH of the final liquid defluorination agent is between 2 and 4. Under this condition, the hydrolysis of the strong acid and weak base salt in the synergistic regulating component can be promoted.

[0019] The low proportion of the dibasic acid salt in the present invention helps to prevent the pH of the liquid defluoridating agent from reaching extreme values and helps to adjust the pH after the reaction. If the raw water is alkaline, the pH will most likely fall between 6 and 7 after addition, and there is no need to add liquid caustic soda. In addition, the low content of the dibasic acid salt helps to expand the selection of synergistic regulating components.

[0020] The addition of the auxiliary agent in the present invention is not only more conducive to flocculation nucleation and makes the sludge more compact, but also strengthens the net capture and bridging effect of suspended matter and anionic PAM in the flocculation process of the water body, and promotes F - Removal from water.

[0021] The present invention proposes that the optimal flocculation pH is 6.2-6.5, at which the flocculation effect is good, the flocculated sludge is dense, and the sedimentation is fast. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below with reference to specific embodiments.

[0023] A liquid defluoridant comprises two components: a basic defluoridation component and a synergistic adjustment component. The basic defluoridation component primarily provides defluoridation, while the synergistic adjustment component promotes defluoridation and accelerates post-reaction pH adjustment, reducing the amount of liquid caustic soda required and compacting sludge flocs. The basic defluoridation component is primarily composed of monobasic acid salts, supplemented with a small amount of dibasic acid salts; the synergistic adjustment component is primarily composed of neutral salts and / or strong base and weak acid salts, and is supplemented with auxiliary agents.

[0024] Specifically, the basic defluorination component and the synergistic regulating component are mixed in a ratio of 3 to 4:1. The pH of the liquid defluorination agent is 2 to 4, which can promote the hydrolysis of the synergistic regulating component.

[0025] The ratio of the quasi-monobasic acid salt to the quasi-dibasic acid salt in the basic defluorination component is ≥ 4:1. Specifically, the quasi-monobasic acid salt can be one or more of polyaluminum chloride, polyaluminum ferric chloride, rare earth chloride, aluminum chloride, ferric chloride, and magnesium chloride. The quasi-dibasic acid salt can be one or more of aluminum sulfate, ferrous sulfate, polyaluminum sulfate, and polyaluminum ferric sulfate. The basic defluorination component contains 2-3.5 parts of the quasi-monobasic acid salt and 0.3-0.5 parts of the quasi-dibasic acid salt.

[0026] The neutral salt and / or strong base and weak acid salt in the synergistic regulating component accounts for about 2-4 parts, and the auxiliary agent accounts for 0.3-0.5 parts. Specifically, the neutral salt and / or strong base and weak acid salt in the synergistic regulating component is one or more of sodium chloride, sodium sulfate, potassium chloride, potassium sulfate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, and sodium acetate; the auxiliary agent in the synergistic regulating component is at least two or more of magnesium oxide, chitosan, starch, sodium benzenesulfonate, sodium alginate, and lignin.

[0027] A preparation method of a liquid defluoridant comprises the following steps: firstly preparing all the above-mentioned raw materials into a liquid with a mass fraction of 10%; then mixing a basic defluoridation component according to the above-mentioned proportions; then mixing a synergistic adjustment component according to the above-mentioned proportions; and finally slowly adding the synergistic adjustment component to the basic defluoridation component while stirring. The entire process can be carried out at room temperature and pressure.

[0028] An application of a liquid defluoridating agent, specifically, an application method is: according to the initial F - Add a certain amount of liquid defluoridant according to the concentration and target value. After 15 to 30 minutes of reaction, the pH is generally lower than 4. Adjust the pH to 6 to 7, with 6.2 to 6.5 being the best (the flocculation effect of anionic PAM is the best at this time). Add anionic PAM and react for 10 to 30 minutes, and precipitate for 10 to 30 minutes.

[0029] In the above process, in addition to the basic defluorination component itself to F - In addition to the adsorption, ion exchange and chemical precipitation effects, the addition of additives strengthens the netting and bridging effect on suspended matter and anionic PAM flocculation in water, promoting the - The removal from water is equivalent to a two-step reaction.

[0030] The present invention will be further described below with reference to the embodiments. Example 1

[0031] Prepare a basic defluoridation component and its specific composition: 1 part polyaluminum ferric chloride, 1 part lanthanum chloride, and 0.5 part aluminum sulfate. Also prepare a synergistic adjustment component and its specific composition: 1 part sodium chloride, 1.5 parts sodium bicarbonate, 0.1 part magnesium oxide, 0.1 part lignin, and 0.1 part chitosan. Mix these two components in a ratio of 3:1 to obtain a final liquid defluoridation agent with a pH of 2.6.

[0032] The pH of a raw water is 7.5, F -The concentration is 40 mg / L, and it is to be treated to below 3 mg / L. A certain proportion of the present invention is added by volume, and compared with two defluoridants A (pH is 2.2) and B (pH is 1.4) on the market. As shown in Table 1 below, the three defluoridants all meet the standard requirements, but the amount of liquid alkali used in the present invention is less, and the comprehensive cost advantage is more obvious. The unit prices of the three defluoridants are similar, but the amount of liquid alkali used in A is about 2 times that of the present invention, and in B it is about 3 times, which means that the cost of liquid alkali per ton of water is significantly higher than that of the present invention. The current price of liquid alkali (32%) is around 1,200 yuan / t, which means that the comprehensive cost per ton of water of A and B will be 0.84 yuan and 2.04 yuan higher than that of the present invention.

[0033] Table 1 Comparison of the present invention and other defluoridation agents in Example 1 Example 2

[0034] Prepare a basic defluoridation component and its specific composition: 1 part polyaluminum ferric chloride, 1 part cerium chloride, and 0.4 part aluminum sulfate. Also prepare a synergistic adjustment component and its specific composition: 1 part potassium chloride, 1.5 parts sodium carbonate, 0.1 part magnesium oxide, 0.1 part lignin, and 0.1 part chitosan. Mix these two components in a ratio of 3:1 to obtain a final liquid defluoridation agent with a pH of 3.

[0035] The pH of a raw water is 11.5, F - The concentration was 50 mg / L, and the treatment was to reduce it to below 2 mg / L. The present invention was added in a certain volumetric ratio and compared with two commercially available defluoridants, A (pH 2.2) and B (pH 1.4). As shown in Table 2 below, at the same dosage, only the present invention and A met the required standards. The post-reaction pH was 6.3, eliminating the need for pH adjustment.

[0036] Table 2 Comparison of the present invention and other defluoridation agents in Example 2 Example 3

[0037] Prepare a basic defluoridation component and its specific composition: 2 parts polyaluminum ferric chloride, 0.8 parts lanthanum chloride, 0.4 parts cerium chloride, and 0.5 parts ferrous sulfate. Also prepare a synergistic adjustment component and its specific composition: 0.5 parts sodium acetate, 2.5 parts sodium carbonate, 0.05 parts magnesium oxide, 0.2 parts sodium alginate, and 0.1 parts starch. Mix these two components in a 3:1 ratio to obtain a final liquid defluoridation agent with a pH of 3.5.

[0038] The pH of a raw water is 8.3, F -The concentration is 36 mg / L, and the treatment is intended to reduce it to below 2 mg / L. The present invention was added in certain volumetric proportions and compared with two commercially available defluoridants, A (pH 2.2) and B (pH 1.4). As shown in Table 3 below, at the same dosage, only the present invention and A met the required standards. Furthermore, it can be seen that the pH drop was minimal, which helps to reduce the amount of liquid caustic soda used subsequently. The amounts of liquid caustic soda used for A and B were 10 and 15 times that of the present invention, respectively.

[0039] Table 3 Comparison of the present invention and other defluoridation agents in Example 3 Example 4

[0040] Prepare a certain amount of the basic defluoridation component and its specific composition: 0.5 part polyaluminium ferric chloride, 1 part lanthanum chloride, 1 part cerium chloride, 0.5 part magnesium chloride, 0.3 part ferrous sulfate, and 0.1 part polyaluminium sulfate. Also prepare a certain amount of the synergistic adjustment component and its specific composition: 0.5 part sodium acetate, 2.5 parts sodium carbonate, 0.05 part magnesium oxide, 0.2 part sodium alginate, and 0.1 part starch. Mix these two components in a ratio of 3:1 to obtain the final liquid defluoridation agent with a pH of 4.

[0041] The pH of a raw water is 7.1, F - The concentration is 36 mg / L, and the goal is to reduce it to below 10 mg / L. The present invention was added in certain volumetric proportions and compared with two commercially available defluoridants, A (pH 2.2) and B (pH 1.4). As shown in Table 4 below, at the same dosage, all three met the required standards. However, it was found that the pH of the present invention after the reaction was 6.2, eliminating the need for pH adjustment.

[0042] Table 4 Comparison of the present invention and other defluoridation agents in Example 4 .

Claims

1. A liquid defluoridating agent, characterized in that: The pH value of the liquid defluoridating agent is 2-4, and the liquid defluoridating agent includes a basic defluoridating component for achieving defluoridation and a synergistic regulating component for promoting defluoridation and accelerating the increase of pH value after the reaction to reduce the amount of liquid alkali used and compact the sludge flocs; the basic defluoridating component and the synergistic regulating component are mixed in a ratio of 3-4:1; the basic defluoridating component is mainly composed of a monobasic acid salt and supplemented with a dibasic acid salt; the synergistic regulating component is mainly composed of a neutral salt and / or a strong base and weak acid salt and is combined with an auxiliary agent.

2. A liquid defluoridating agent according to claim 1, characterized in that: The content ratio of the monobasic acid salt to the dibasic acid salt in the basic fluorine removal component is ≥4:

1.

3. A liquid defluoridating agent according to claim 1, characterized in that: The monobasic acid salt is one or more of polyaluminium chloride, polyaluminium ferric chloride, rare earth chloride, aluminium chloride, ferric chloride and magnesium chloride.

4. A liquid defluoridating agent according to claim 1, characterized in that: The dibasic acid salt is one or more of aluminum sulfate, ferrous sulfate, polyaluminum sulfate, and polyaluminum ferric sulfate.

5. A liquid defluoridating agent according to claim 1, characterized in that: The basic defluorination component contains 2 to 3.5 parts of monobasic acid salt and 0.3 to 0.5 parts of dibasic acid salt.

6. A liquid defluoridating agent according to claim 1, characterized in that: The synergistic regulating component comprises 2 to 4 parts of neutral salt and / or acid salt of strong base and weak acid, and 0.3 to 0.5 parts of auxiliary agent.

7. A liquid defluoridating agent according to claim 1, characterized in that: The neutral salt and / or strong base and weak acid salt in the synergistic regulating component is one or more of sodium chloride, sodium sulfate, potassium chloride, potassium sulfate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, and sodium acetate.

8. A liquid defluoridating agent according to claim 1, characterized in that: The auxiliary agents in the synergistic regulating component are at least two or more of magnesium oxide, chitosan, starch, sodium benzenesulfonate, sodium alginate and lignin.

9. Use of a liquid defluoridating agent according to any one of claims 1 to 8, characterized in that: The application method is: according to the initial F - Add a certain amount of liquid defluoridant according to the concentration and target value. If the pH is lower than 4 after 15-30 minutes of reaction, adjust the pH to 6-7, add anionic PAM, react for 10-30 minutes, and precipitate for 10-30 minutes.

10. The use of a liquid defluoridating agent according to claim 9, characterized in that: The pH is adjusted to 6.2-6.5, anionic PAM is added, reacted for 10-30 minutes, and precipitated for 10-30 minutes.

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