Method for removing fluorine, phosphorus and boron in wastewater

Abstract

The invention discloses a method for removing fluorine, phosphorus and boron in wastewater, which comprises the following steps: mixing the wastewater containing fluorine, phosphorus and boron with a calcium-containing compound, and adding a coagulant for primary impurity removal to obtain primary impurity removal liquid; mixing the primary impurity removal liquid with a boron removal agent, adjusting the pH value to be alkaline, and carrying out secondary impurity removal to obtain secondary impurity removal liquid; and mixing the secondary impurity removal liquid with a lanthanum-containing compound, adjusting the pH value to be alkaline, and carrying out third impurity removal to obtain an impurity removal liquid. According to the method, firstly, phosphorus and fluorine in the wastewater are preliminarily removed by using the calcium-containing compound, then boron is removed by using the boron removal agent, and finally, residual boron and fluorine in the wastewater are finely removed by using the lanthanum-containing compound, so that fluorine, phosphorus and boron in the wastewater are effectively removed, and the removal rate is up to 99% or above.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a method for removing fluorine, phosphorus and boron from wastewater. Background Art

[0002] Fluoride, phosphorus and boron in wastewater are significantly harmful to the environment and human health. Excessive fluoride can cause dental fluorosis and skeletal fluorosis, affect the development of bones and teeth, and may also cause memory loss, lack of concentration, sleep problems, and damage organs such as the heart, liver, and kidneys. Phosphates can cause eutrophication of water bodies and destroy the ecological balance. Borides are harmful to the human body and affect the reproductive system. Long-term exposure may lead to metabolic syndromes such as diabetes and hyperlipidemia. Therefore, it is crucial to remove fluoride, phosphorus and boron from wastewater to reduce the impact of these substances on the environment and human health. Existing sewage treatment technologies can be divided into physical methods, chemical methods, physical and chemical methods, and biological methods according to their principles. These methods have more or less disadvantages such as unstable removal effects, easy secondary pollution, and high treatment costs. Summary of the invention

[0003] In order to overcome the above-mentioned defects of the prior art, the purpose of the present invention is to provide a method for removing fluorine, phosphorus and boron from wastewater, so as to solve the technical problem that it is difficult to remove fluorine, phosphorus and boron from wastewater in the existing process.

[0004] To achieve the above object, the present invention is implemented through the following technical solutions: A method for removing fluorine, phosphorus and boron in wastewater comprises the following steps: (1) Mixing the wastewater containing fluorine, phosphorus and boron with the calcium compound, and adding a coagulant to perform primary impurity removal to obtain a primary impurity removal liquid; (2) mixing the primary impurity removal liquid with the boron removal agent, and adjusting the pH to alkaline for secondary impurity removal to obtain a secondary impurity removal liquid; (3) The secondary impurity removal liquid is mixed with the lanthanum-containing compound, and the pH is adjusted to alkaline for a third impurity removal to obtain an impurity removal liquid.

[0005] Preferably, in step (1), the calcium-containing compound is one or more of calcium oxide, calcium carbonate and calcium hydroxide.

[0006] Preferably, in step (1), the pH of the primary impurity removal is ≥ 8, preferably 8-9.

[0007] Preferably, in step (1), the coagulant is one or more of polyacrylamide, ferric chloride, and polyferric sulfate.

[0008] Preferably, in step (2), the boron removal agent is one or more of iron salts and magnesium salts.

[0009] Preferably, in step (2), the molar ratio of the boron removal agent to the boron element in the primary impurity removal liquid is (2-3):1.

[0010] Preferably, in step (2), the pH of the reaction is adjusted to 8-9.

[0011] Preferably, in step (3), the lanthanum-containing compound is one or more of lanthanum chloride, lanthanum nitrate and lanthanum carbonate.

[0012] Preferably, in step (3), the total mass ratio of the lanthanum-containing compound to the fluorine element and the boron element in the secondary impurity removal liquid is (15-20):1.

[0013] Preferably, in step (3), the pH of the reaction is adjusted to 8-9.

[0014] The beneficial effects of the present invention are: 1. The present invention firstly utilizes calcium-containing compounds to react with phosphate and fluoride ions in wastewater to generate calcium phosphate and calcium fluoride precipitates, thereby preliminarily removing phosphorus and fluorine in the wastewater, and then utilizes a boron removal agent to remove boron, and finally utilizes a lanthanum-containing compound to finely remove the remaining boron and fluorine in the wastewater, thereby achieving effective removal of fluorine, phosphorus and boron in the wastewater, with a removal rate of more than 99%.

[0015] 2. The method for removing fluorine, phosphorus and boron of the present invention has a simple process flow, low operating cost, reduces the types of added reagents, has good filtering performance, and has a low moisture content of the filter residue.

[0016] 3. The present invention can achieve a good impurity removal effect at a pH of about 8-9, greatly reducing the consumption of reagents and reducing processing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the drawings of the embodiment are briefly introduced below.

[0018] Figure 1 The present invention is a schematic flow chart of a method for removing fluorine, phosphorus and boron from wastewater. DETAILED DESCRIPTION

[0019] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] See also Figure 1 The embodiment of the present invention provides a method for removing fluorine, phosphorus and boron from wastewater, comprising the following steps: (1) Mix the wastewater containing fluorine, phosphorus and boron with calcium compounds, adjust the pH to ≥ 8 and react for 0.5 to 2 hours, add a coagulant to flocculate and precipitate for 0.5 to 2 hours, and after solid-liquid separation, obtain a primary impurity removal liquid and a primary filter residue; the calcium-containing compound is preferably an alkaline calcium-containing compound, including but not limited to one or more of calcium oxide, calcium carbonate, and calcium hydroxide. The alkaline calcium-containing compound can make phosphate and fluoride ions react to generate calcium phosphate and calcium fluoride precipitation to remove phosphorus and fluoride, while reducing the addition of alkali, reducing the type and amount of reagents, and saving costs. The primary filter residue can be reused to adjust the pH. The coagulant is one or more of polyacrylamide, ferric chloride, and polyferric sulfate.

[0021] (2) The primary impurity removal liquid is mixed with a boron removal agent for reaction for 0.5 to 2 hours, the molar ratio of the boron removal agent to the boron element in the primary impurity removal liquid is (2 to 3): 1, and the pH is adjusted to 8-9. After solid-liquid separation, a secondary impurity removal liquid and a secondary filter residue are obtained. The boron removal agent is one or more of an iron salt and a magnesium salt, such as ferrous sulfate, magnesium oxide, etc., and the boron is adsorbed and removed by the adsorption effect of the boron removal agent. Preferably, the pH is adjusted using one or more of calcium oxide, calcium carbonate, and calcium hydroxide, and the secondary filter residue can be reused to adjust and maintain the pH and remove impurities.

[0022] (3) The secondary impurity removal liquid is mixed with a lanthanum-containing compound for reaction for 0.5 to 2 hours, the total mass ratio of the lanthanum-containing compound to the fluorine element and the boron element in the secondary impurity removal liquid is (15 to 20): 1, and the pH is adjusted to 8-9. After solid-liquid separation, an impurity removal liquid and a tertiary filter residue are obtained. The lanthanum-containing compound is one or more of lanthanum chloride, lanthanum nitrate, and lanthanum carbonate. The lanthanum-containing compound reacts with borate and fluoride ions to generate lanthanum borate and lanthanum fluoride precipitates, and boron and fluorine are further removed. Preferably, the pH is adjusted using one or more of calcium oxide, calcium carbonate, and calcium hydroxide, and the tertiary filter residue can be reused to adjust and maintain the pH and remove impurities.

[0023] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be described in further detail below.

[0024] Example 1 A method for removing fluorine, phosphorus and boron in wastewater comprises the following steps: (1) The wastewater contains 234.4 mg / L phosphorus, 550.9 mg / L fluorine, 488 mg / L boron, and a pH of 7.5. Take the wastewater containing fluorine, phosphorus and boron and add calcium oxide to adjust its pH to 8-9 for 2 hours for preliminary impurity removal. Then add polyacrylamide (PAM) for flocculation and precipitation for 1 hour, and then filter press to obtain a primary impurity removal liquid and a primary filter residue; at this time, the primary impurity removal liquid obtained after preliminary impurity removal contains 1.5 mg / L phosphorus, 59.8 mg / L fluorine, 486 mg / L boron, and a pH of 8.95.

[0025] (2) Add 5g of magnesium oxide per liter to the primary impurity removal liquid, react for 2 hours, add calcium hydroxide during the reaction to maintain the pH at 8-9, and then filter to obtain the secondary impurity removal liquid and secondary filter residue. At this time, the secondary impurity removal liquid after impurity removal contains 1.2mg / L phosphorus, 31.48mg / L fluorine, 45.5mg / L boron, and pH 9.01.

[0026] (3) Add 1.5g of lanthanum chloride per liter to the secondary impurity removal liquid, react for 2 hours to remove residual fluoride ions and boron ions, and add calcium hydroxide to maintain the pH at 8-9 during the reaction. Then, filter press to obtain the impurity-removed wastewater and the tertiary filter residue. At this time, the impurity-removed wastewater contains 0.1mg / L phosphorus, 0.8mg / L fluorine, 3.9mg / L boron, 0.3mg / L lanthanum, and pH 9.03.

[0027] Example 2 A method for removing fluorine, phosphorus and boron in wastewater comprises the following steps: (1) The wastewater contains 273.1 mg / L phosphorus, 960 mg / L fluorine, 478 mg / L boron, and a pH of 7.4. Calcium hydroxide was added to the wastewater containing fluorine, phosphorus and boron to adjust its pH to 8-9 and react for 2 hours for preliminary impurity removal. Then, polyferric sulfate (PFS) was added for flocculation and precipitation for 1 hour, and then filtered to obtain a primary impurity removal liquid and a primary filter residue. At this time, the primary impurity removal liquid obtained after preliminary impurity removal contained 2.4 mg / L phosphorus, 67.1 mg / L fluorine, 477 mg / L boron, 0.1 mg / L iron, and a pH of 9.01.

[0028] (2) Add 5g of magnesium oxide per liter to the primary impurity removal liquid, react for 2 hours, add calcium hydroxide during the reaction to maintain the pH at 8-9, and then filter to obtain the secondary impurity removal liquid and secondary filter residue. At this time, the secondary impurity removal liquid after impurity removal contains 1.3mg / L phosphorus, 28.8mg / L fluorine, 46.7mg / L boron, 0.1mg / L iron, and pH 9.02.

[0029] (3) Add 1.5g of lanthanum chloride per liter to the secondary impurity removal liquid, react for 2 hours to remove residual fluoride ions and boron ions, and add calcium hydroxide to maintain the pH at 8-9 during the reaction. Then, filter press to obtain the impurity-removed wastewater and the tertiary filter residue. At this time, the impurity-removed wastewater contains 0.2mg / L phosphorus, 0.5mg / L fluorine, 3.1mg / L boron, 0.1mg / L iron, 2.5mg / L lanthanum, and pH 9.05.

[0030] Example 3 A method for removing fluorine, phosphorus and boron in wastewater comprises the following steps: (1) The wastewater contained 214.4 mg / L phosphorus, 315 mg / L fluorine, 286 mg / L boron, and a pH of 7.1. Calcium oxide was added to the wastewater containing fluorine, phosphorus, and boron to adjust its pH to 8-9 and react for 1.5 hours for preliminary impurity removal. Polyacrylamide (PAM) was then added for flocculation and precipitation for 2 hours. The first impurity removal liquid and the first filter residue were obtained by filter pressing. At this time, the first impurity removal liquid obtained after preliminary impurity removal contained 1.9 mg / L phosphorus, 43 mg / L fluorine, 287 mg / L boron, and a pH of 8.9.

[0031] (2) Add 5g magnesium oxide per liter to the primary impurity removal liquid, react for 1.5h, add calcium oxide during the reaction to maintain pH 8-9, and then filter to obtain secondary impurity removal liquid and secondary filter residue. At this time, the secondary impurity removal liquid after impurity removal contains 1.6mg / L phosphorus, 33mg / L fluorine, 39mg / L boron, and pH 9.1.

[0032] (3) Add 1.4g of lanthanum chloride per liter to the secondary impurity removal liquid, react for 1.5 hours to remove residual fluoride ions and boron ions, and add calcium oxide to maintain the pH at 8-9 during the reaction. Then, filter press to obtain the impurity-removed wastewater and the tertiary filter residue. At this time, the impurity-removed wastewater contains 0.2mg / L phosphorus, 1.0mg / L fluorine, 2.3mg / L boron, 0.3mg / L lanthanum, and pH 9.09.

[0033] The removal effects of fluorine, phosphorus and boron in the wastewater of Examples 1 to 3 are shown in Table 1.

[0034] Table 1

[0035] It can be seen from the above table that the method for removing fluorine, phosphorus and boron in wastewater proposed in the present invention first uses calcium-containing compounds to remove phosphorus and fluorine in the wastewater, then uses a boron removal agent to remove boron, and finally uses a lanthanum-containing compound to finely remove the remaining boron and fluorine in the wastewater, thereby achieving effective removal of fluorine, phosphorus and boron in the wastewater, with a removal rate of more than 99%.

[0036] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For matters that are not described in detail in some embodiments, reference may be made to the description in other embodiments.

[0037] The above-mentioned embodiments only express the implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for removing fluorine, phosphorus and boron from wastewater, characterized in that: The following steps are involved: (1) Mixing the wastewater containing fluorine, phosphorus and boron with the calcium compound, and adding a coagulant to perform primary impurity removal to obtain a primary impurity removal liquid; (2) mixing the primary impurity removal liquid with a boron removal agent, and adjusting the pH to alkaline for secondary impurity removal to obtain a secondary impurity removal liquid; (3) The secondary impurity removal liquid is mixed with a lanthanum-containing compound, and the pH is adjusted to alkaline for a third impurity removal to obtain an impurity removal liquid.

2. The method for removing fluorine, phosphorus and boron from wastewater according to claim 1, characterized in that: In step (1), the calcium-containing compound is one or more of calcium oxide, calcium carbonate and calcium hydroxide.

3. The method for removing fluorine, phosphorus and boron from wastewater according to claim 1, characterized in that: In step (1), the pH of the primary impurity removal is ≥8.

4. The method for removing fluorine, phosphorus and boron from wastewater according to claim 1, characterized in that: In step (1), the coagulant is one or more of polyacrylamide, ferric chloride, and polyferric sulfate.

5. The method for removing fluorine, phosphorus and boron from wastewater according to claim 1, characterized in that: In step (2), the boron removal agent is one or more of iron salt and magnesium salt.

6. The method for removing fluorine, phosphorus and boron from wastewater according to claim 1, characterized in that: In step (2), the molar ratio of the boron removal agent to the boron element in the primary impurity removal liquid is (2-3):

1.

7. The method for removing fluorine, phosphorus and boron from wastewater according to claim 1, characterized in that: In step (2), the pH is adjusted to 8-9.

8. The method for removing fluorine, phosphorus and boron from wastewater according to claim 1, characterized in that: In step (3), the lanthanum-containing compound is one or more of lanthanum chloride, lanthanum nitrate and lanthanum carbonate.

9. The method for removing fluorine, phosphorus and boron from wastewater according to claim 1, characterized in that: In step (3), the total mass ratio of the lanthanum-containing compound to the fluorine element and the boron element in the secondary impurity removal liquid is (15-20):

1.

10. The method for removing fluorine, phosphorus and boron from wastewater according to claim 1, characterized in that: In step (3), the pH is adjusted to 8-9.

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