A fluorine removing agent, a production method and a fluorine removing method

Abstract

The present application provides a defluorination agent, a preparation method and a defluorination method. The defluorination agent comprises a trivalent metal source, a magnesium source and active methyl silicone oil. The trivalent metal source is polyaluminum ferric chloride, and the magnesium source is active magnesium oxide. The effective aluminum and iron content of the polyaluminum ferric chloride is greater than or equal to 13%. The pH of the defluorination agent is 8.5-9.5. The defluorination method using the defluorination agent comprises the following steps: detecting the pH of fluorine-containing wastewater, if the pH of the fluorine-containing wastewater is less than 5.5, adjusting the pH to 6.5-7.5, if the pH of the fluorine-containing wastewater is greater than or equal to 5.5, no pH adjustment is needed. The defluorination agent is added to the fluorine-containing wastewater and stirred, the volume ratio of the defluorination agent to the fluorine-containing wastewater is greater than or equal to 1 mL / m 3 The trivalent metal source of the defluorination agent of the present application is complexed with fluoride ions to form flocculation body precipitates, and the methyl silicone oil in the defluorination agent can increase the density of the flocculation body and reduce the settling time, which is conducive to flocculation and sedimentation, and no additional coagulant needs to be added.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, specifically to a defluoridating agent, its preparation method, and a defluoridation method. Background Technology

[0002] Fluoride pollution is receiving increasing attention, and how to treat fluoride in wastewater has always been a crucial issue in the environmental protection field both domestically and internationally. In recent years, significant work has been done both domestically and internationally in the treatment of fluoride-containing wastewater, with substantial progress made in the theory, methods, and technologies for fluoride removal. Currently, the composition of fluoride-containing industrial wastewater is complex and diverse, and numerous treatment methods are employed, including precipitation and adsorption methods, as well as ion exchange resin methods, reverse osmosis methods, electrocoagulation methods, and electrodialysis methods.

[0003] Deep defluoridation refers to the continuous treatment of fluoride-containing wastewater on the basis of conventional purification treatment, with the aim of improving the quality of effluent and its utilization level.

[0004] Commonly used methods for deep defluorination include precipitation, coagulation, and adsorption.

[0005] Typical precipitation methods include lime precipitation, phosphate precipitation, and cryolite precipitation. For high-concentration fluoride-containing wastewater, lime is added to cause fluoride ions to react with calcium ions to form calcium fluoride precipitate, which is then removed.

[0006] This process is simple and inexpensive, but the newly generated calcium fluoride has a certain solubility in water (16.3 mg / L at room temperature). In addition, certain components in the wastewater, such as SO4... 2- Anions adsorb onto the surface of newly formed calcium fluoride microcrystals, slowing down the further growth of calcium fluoride crystals and making it difficult for calcium fluoride precipitate to precipitate from the water. Therefore, the treated wastewater often contains 20–30 mg / L of fluoride, still exceeding the national discharge standard (10 mg / L), making it difficult to meet the requirements. In addition, it also suffers from drawbacks such as slow sludge settling and difficulty in dewatering.

[0007] Coagulation primarily uses two main types of coagulants: iron salts and aluminum salts, to remove fluoride from industrial wastewater. The principle is that the metal ions contained in the coagulant form tiny colloidal nuclei or flocs in the water. These positively charged particles adsorb fluoride from the water. - This causes the fluoride particles to aggregate into larger flocculent precipitates, thus achieving the purpose of defluorination.

[0008] Coagulation and sedimentation has the advantages of low reagent dosage, large treatment capacity, and the ability to meet national discharge standards after a single treatment. Coagulants work by creating flocculent flocculation in fluoride-containing water, adsorbing and reducing fluoride levels. However, coagulation and sedimentation is only suitable for treating low-fluoride wastewater, and its fluoride removal effect is unstable, easily affected by operational factors, resulting in inconsistent effluent quality.

[0009] Other defluorination methods, such as ion exchange, are limited by the regeneration and treatment of the resin, while electrodialysis is complex to operate and has high operating costs.

[0010] In actual defluorination processes at factories, the treatment methods and processes for fluoride-containing wastewater are determined by comprehensively considering defluorination efficiency and economics, taking into account different environments and defluorination requirements. This approach achieves both good defluorination results and good economic efficiency, thus realizing the goal of treating fluoride-containing wastewater and utilizing its resources. Therefore, a more optimized and efficient defluorination technology is still needed for advanced defluorination. Summary of the Invention

[0011] To address the above problems, this invention provides a defluorinating agent, its preparation method, and a defluorination method. By adding methyl silicone oil to divalent and trivalent metal sources, the combined effect of these three substances increases floc density and reduces settling time; simultaneously, it lowers the water content of the flocculated sludge, facilitating subsequent dewatering and resulting in excellent overall performance. This invention is suitable for low-concentration fluoride-containing wastewater (F... - Treatment of ≤20mg / L, effluent F - Concentration ≤ 1 mg / L.

[0012] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0013] One aspect of this invention is to provide a defluorinating agent comprising a trivalent metal source, a magnesium source, and an active methyl silicone oil.

[0014] Preferably, the trivalent metal source is polyaluminum ferric chloride, and the magnesium source is active magnesium oxide.

[0015] Preferably, the effective aluminum and iron content of the polyaluminum ferric chloride is ≥13%.

[0016] Preferably, the pH of the defluorinating agent is 8.5 to 9.5.

[0017] Preferably, the defluorinating agent comprises, by weight parts:

[0018]

[0019] Preferably, the defluorinating agent comprises, by weight parts:

[0020]

[0021] Another aspect of this invention is a method for defluorination using the aforementioned defluorinating agent, comprising the following steps: detecting the pH value of the fluoride-containing wastewater; if the pH value of the fluoride-containing wastewater is <5.5, adjusting the pH to 6.5–7.5; if the pH value of the fluoride-containing wastewater is ≥5.5, no pH adjustment is required; adding the aforementioned defluorinating agent to the fluoride-containing wastewater and stirring, wherein the volume ratio of the defluorinating agent added to the volume of the fluoride-containing wastewater is ≥1 mL / m³. 3 .

[0022] Preferably, the fluoride ion concentration of the fluoride-containing wastewater is ≤20 mg / L.

[0023] Preferably, the defluorinating agent is added and stirred for 3 to 5 minutes.

[0024] Another inventive point of this invention is to provide a method for preparing the above-mentioned defluorinating agent, comprising: (1) adding 60-80 parts of a trivalent metal source in small amounts and multiple times to water and stirring to dissolve, wherein each time no more than 5 parts of the trivalent metal source are added; (2) after the trivalent metal source has completely dissolved, adding 5-15 parts of a magnesium source and stirring thoroughly to obtain a suspension containing metal ion coprecipitates; (3) adding 2-10 parts of active methyl silicone oil and stirring thoroughly to allow the metal ion coprecipitates to fully chelate with the active methyl silicone oil to obtain the defluorinating agent.

[0025] Compared with the prior art, the main beneficial effects of the present invention are:

[0026] First, the trivalent metal source used in the defluorinating agent of this invention undergoes a complexation reaction with fluoride ions to form flocs. The methyl silicone oil in the defluorinating agent can increase the density of the flocs and reduce the settling time, which is beneficial to flocculation and settling, and no additional coagulant is required.

[0027] Secondly, the defluorinating agent of this invention results in a lower moisture content in the flocculated sludge after defluorination, making subsequent dewatering relatively easier.

[0028] Third, this invention is applicable to low-concentration fluoride-containing wastewater (F - Treatment of ≤20mg / L, effluent F - A concentration ≤1mg / L provides good fluoride removal.

[0029] Fourth, the defluorination method provided by this invention does not require pH adjustment if the pH value of the fluoride-containing wastewater is ≥5.5. It can treat fluoride-containing wastewater in a targeted manner, optimize the defluorination process, and reduce the amount of liquid alkali used. Detailed Implementation

[0030] The present invention will be further explained below with reference to the embodiments. The following embodiments do not limit the present invention in any way. All technical solutions obtained by equivalent substitution or equivalent transformation are within the protection scope of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply.

[0031] Example 1

[0032] A defluorinating agent, comprising, by weight parts:

[0033]

[0034]

[0035] The above-mentioned defluorinating agent, by mass parts, is preferably:

[0036]

[0037] Among them, the trivalent metal source includes polyaluminum ferric chloride, polyaluminum ferric sulfate, etc., preferably polyaluminum ferric chloride, with an effective aluminum and iron content of ≥13%, which can be 13%, 30%, 40%, etc., and the magnesium source is active magnesium oxide.

[0038] The defluorinating agent has a pH of 8.5 to 9.5, for example, it can be 8.5, 9, or 9.5.

[0039] The preparation steps of the defluorinating agent are as follows: (1) Add 60-80 parts of trivalent metal source in small amounts and multiple times to 5-200 parts of ultrapure water and stir to dissolve at room temperature. In order to enhance its solubility, it is advisable not to add more than 5 parts of trivalent metal source each time. (2) After the trivalent metal source is completely dissolved, slowly add 5-15 parts of magnesium source at one time and stir thoroughly to obtain a suspension containing metal ion coprecipitate. (3) Quickly add 2-10 parts of active methyl silicone oil at one time and stir thoroughly to fully chelate the metal ion coprecipitate with the active methyl silicone oil to finally obtain a mixed solution.

[0040] The defluorination method using the above-mentioned defluorinating agent includes the following steps: taking fluoride-containing wastewater (F... - ≤20mg / L), test the pH value of the fluoride-containing wastewater. If the pH value is <5.5, adjust the pH to 6.5-7.5. If the pH value is ≥5.5, no pH adjustment is needed. Add the aforementioned defluorinating agent to the fluoride-containing wastewater and stir for 3-5 minutes. The defluorinating agent and F - It forms dense flocs that can settle directly. The dosage of the defluorinating agent is ≥1 mL / m³ of the fluoride-containing wastewater. 3 .

[0041] During the defluorination process, the defluorinating agent of this invention reacts with fluoride ions in fluoride-containing wastewater to form fluoride flocs that precipitate with a high density, reaching 1.3 g / cm³. 3 The reduced settling time is beneficial for flocculation and sedimentation, eliminating the need for additional coagulant aids.

[0042] In this embodiment, the defluorination process includes metal complexation and adsorption precipitation. Conventional defluorinating agents react with fluoride ions in fluoride-containing wastewater to form fluorides, which precipitate out as flocculents, thus removing fluoride ions from the wastewater. The defluorinating agent of this invention not only produces aluminum-iron fluoride precipitates through the interaction of aluminum and iron ions with fluoride ions, and magnesium fluoride precipitates through the interaction of magnesium and fluoride ions, but also utilizes a trivalent metal source, a magnesium source, and active methyl silicone oil in a specific ratio to facilitate the aggregation of these substances into larger flocs. Furthermore, the addition of a certain amount of methyl silicone oil further enhances the interaction of the flocculants, resulting in denser flocs with a high density, reaching 1.3 g / cm³. 3 No coagulant aid is needed, and the settling time is reduced. However, when the amount of methyl silicone oil added is lower than that in this application, the resulting flocs are relatively loose, and the settling effect is poor; if the amount is higher than that in this application, although the density will still be relatively high, it is not economical, and the overall effect is not as good as that in this application.

[0043] The defluorinating agent of this invention includes methyl silicone oil, which can also reduce the moisture content of the flocculent sludge. The flocculent sludge produced by conventional defluorinating agents has a moisture content of over 99%, while the flocculent sludge produced by this invention has a lower moisture content of about 96%, making subsequent dehydration relatively easier.

[0044] Example 2

[0045] This embodiment provides a defluorinating agent comprising 70g polyaluminum ferric chloride, 10g activated magnesium oxide, 5g activated methyl silicone oil, and 15g ultrapure water. The effective aluminum and iron content of the polyaluminum ferric chloride is 13%, and the pH of the defluorinating agent is 8.5. The defluorinating agent can be prepared by the following method: (1) 70g of polyaluminum ferric chloride is added to 15g of ultrapure water in small amounts and stirred at room temperature to dissolve. 5g of polyaluminum ferric chloride is added each time, and the next addition is carried out after each dissolution. (2) After the polyaluminum ferric chloride is completely dissolved, 10g of activated magnesium oxide is slowly added at once and stirred thoroughly to obtain a suspension containing metal ion coprecipitates. (3) 5g of activated methyl silicone oil is quickly added at once and stirred thoroughly to allow the metal ion coprecipitates to fully chelate with the activated methyl silicone oil, ultimately obtaining the defluorinating agent.

[0046] Comparative Example

[0047] This comparative example is a defluorinating agent without active methyl silicone oil. The components include 70g of polyaluminum ferric chloride, 10g of active magnesium oxide, and 20g of water. The effective aluminum and iron content of the polyaluminum ferric chloride is 13%. The preparation method is as follows: (1) 70g of polyaluminum ferric chloride is added to 15g of ultrapure water in small amounts and stirred at room temperature to dissolve. Each time, 5g of polyaluminum ferric chloride is added. (2) After the polyaluminum ferric chloride is completely dissolved, 10g of active magnesium oxide is slowly added at once and stirred thoroughly to obtain a suspension containing metal ion coprecipitates, which is the final defluorinating agent.

[0048] Defluorination test 1:

[0049] 1m of fluoride-containing wastewater 3 pH is 6, F - The concentration is 20 mg / L, and it needs to be treated to reduce it to below 1 mg / L.

[0050] Equal amounts of fluoride-containing wastewater were taken and divided into two groups: Experiment 1, which used the defluorinating agent from Example 2 for wastewater treatment, and Experiment 2, which used the comparative defluorinating agent. The specific details are as follows:

[0051] Experimental Group 1: Since the pH of the fluoride-containing wastewater is 6, no pH adjustment is required. 1 mL of the defluoridating agent from Example 2 was added to the fluoride-containing wastewater, stirred for 5 min, and allowed to stand for 5 min. The fluoride content of the supernatant was then measured. - The concentration was 0.3 mg / L, and the time from the addition of the defluorinating agent to the completion of defluorination was recorded as 12 minutes. The generated flocs were extracted, and the floc density was measured to be 1.3 g / cm³. 3 .

[0052] Experimental Group 2: Since the pH of the fluoride-containing wastewater is 6, no pH adjustment is required. 1 mL of the comparative defluorinating agent was added to the fluoride-containing wastewater and stirred for 5 minutes. The density of the flocs formed at this time is generally less than 1 g / cm³. 3 It cannot settle on its own and requires the addition of 5% to 10% coagulant to aid settling. The supernatant F... - The concentration was 0.92 mg / L, which met the treatment requirements. The time from the addition of the defluorinating agent to the completion of defluorination was recorded as 18 minutes. The flocs formed after the addition of the coagulant aid were extracted, and the floc density was measured to be 1.44 g / cm³. 3 .

[0053] The results show that the present invention is applicable to low-concentration fluoride-containing wastewater (F... - Treatment of ≤20mg / L, effluent F - With a concentration ≤1mg / L, the defluorination effect is good. When the pH value of the fluoride-containing wastewater is ≥5.5, no pH adjustment is required. The flocs generated during the defluorination process of this invention have a high density and a reduced settling time, which is conducive to flocculation and sedimentation, and no additional coagulant aid is required.

[0054] Defluorination test 2:

[0055] 10m³ of fluoride-containing wastewater 3 pH is 4.5, F - The concentration is 15 mg / L, and it needs to be treated to reduce it to below 1 mg / L.

[0056] Equal amounts of fluoride-containing wastewater were taken and tested in two groups: Group 3, which used the defluoridating agent from Example 2, and Group 4, which used the comparative defluoridating agent. The specific details are as follows:

[0057] Experimental Group 3: First, adjust the pH of the fluoride-containing wastewater to 7 with liquid alkali. Then, add 10 mL of the defluoridating agent from Example 2 to the fluoride-containing wastewater, stir for 3 minutes, let stand for 5 minutes, and test the fluoride content of the supernatant. - The concentration was 0.3 mg / L, and the time from the addition of the defluorinating agent to the completion of defluorination was recorded as 10 minutes. The generated flocs were extracted, and the floc density was measured to be 1.41 g / cm³. 3 .

[0058] Experimental Group 4: First, adjust the pH of the fluoride-containing wastewater to 7 using liquid alkali. Then, add 10 mL of the comparative defluorinating agent to the fluoride-containing wastewater and stir for 6 minutes. At this time, the density of the flocs formed is generally less than 1 g / cm³. 3 It cannot settle on its own and requires the addition of 5% to 10% coagulant to aid settling. The supernatant F... - The concentration was 0.88 mg / L, which met the treatment requirements. The time taken from the addition of the defluorinating agent to the completion of defluorination was recorded as 20 minutes. The flocs formed after the addition of the coagulant aid were extracted, and the floc density was measured to be 1.54 g / cm³. 3 .

[0059] The results show that the present invention is applicable to low-concentration fluoride-containing wastewater (F... - Treatment of ≤20mg / L, effluent F - With a concentration ≤1mg / L, it has a good defluorination effect and does not require coagulant aids.

[0060] It should also be noted that the methyl silicone oil (i.e., active methyl silicone oil), polyaluminum ferric chloride and active magnesium oxide mentioned in this embodiment are all commercially available products and can be easily purchased from the corresponding actual manufacturers.

[0061] Obviously, the above examples are merely some specific embodiments of the present invention and are not limited to these embodiments. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a defluorinating agent, characterized in that, The defluorinating agent includes a trivalent metal source, a magnesium source, and active methyl silicone oil; the preparation method of the defluorinating agent includes the following steps: (1) 60-80 parts of trivalent metal source are added in batches to 5-200 parts of water and stirred to dissolve, with no more than 5 parts of the trivalent metal source added each time; (2) after the trivalent metal source is completely dissolved, 5-15 parts of magnesium source are added and stirred thoroughly to obtain a suspension containing metal ion coprecipitates; (3) 2-10 parts of active methyl silicone oil are added and stirred thoroughly to fully chelate the metal ion coprecipitates with the active methyl silicone oil to obtain the defluorinating agent; wherein, the active methyl silicone oil works synergistically with the trivalent metal source and the magnesium source to form a floc density of up to 1.3 g / cm³; and the defluorinating agent does not contain coagulant aids.

2. The method for preparing a defluorinating agent according to claim 1, characterized in that, The trivalent metal source is polyaluminum ferric chloride, and the magnesium source is active magnesium oxide.

3. The method for preparing a defluorinating agent according to claim 2, characterized in that, The effective aluminum and iron content of the polyaluminum ferric chloride is ≥13%.

4. A method for preparing a defluorinating agent according to claim 1 or 2, characterized in that, The pH of the defluorinating agent is 8.5–9.

5.

5. The method for preparing a defluorinating agent according to claim 1, characterized in that, The defluorinating agent comprises, by weight, 70 parts trivalent metal source, 10 parts magnesium source, 5 parts active methyl silicone oil, and 15 parts water.

6. A defluorination method using a defluorinating agent prepared according to any one of claims 1 to 5, characterized in that, Includes the following steps: The pH value of the fluoride-containing wastewater is tested. If the pH value is < 5.5, the pH is adjusted to 6.5–7.

5. If the pH value is ≥ 5.5, no pH adjustment is needed. The defluorinating agent is added to the fluoride-containing wastewater and stirred. The volume ratio of the defluorinating agent to the fluoride-containing wastewater is ≥ 1 mL / m³. 3 .

7. The defluorination method according to claim 6, characterized in that, The fluoride ion concentration in the fluoride-containing wastewater is ≤20 mg / L.

8. The defluorination method according to claim 6, characterized in that, Add the defluorinating agent and stir for 3-5 minutes.

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