Treatment process of alkaline fluoride-containing wastewater

Abstract

The present invention discloses a treatment process for alkaline fluorine-containing wastewater, and relates to the technical field of wastewater treatment. The process comprises the following steps: adjusting the pH value of fluorine-containing wastewater to 3-6 to obtain pre-treated wastewater; adding a multi-level adsorbent to the pre-treated wastewater, wherein the dosage of the multi-level adsorbent is 3.5-6g / L, and after shearing treatment for 60-150min at a shear rate of 5400-5600r / min, precipitation and water outlet are obtained to obtain a first-level water outlet; the multi-level adsorbent includes the following components in parts by weight: 90-120 parts of goethite, 30-60 parts of A-type zeolite molecular sieves containing sodium ions, and 5-10 parts of nano-hydroxyapatite; adding activated diatomaceous earth and / or fly ash to the first-level water outlet, stirring evenly, mixing with polyacrylamide, precipitation, water outlet, and obtaining a second-level water outlet; after the second-level water outlet is adsorbed by an ion exchange resin, water outlet is obtained to complete the treatment. The treatment efficiency of fluorine-containing wastewater with a high fluoride content is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, in particular to a treatment process for alkaline fluorine-containing wastewater. Background Art

[0002] Industrial wastewater containing fluoride is discharged from various production processes, including the manufacture of fluorine-containing products, coke production, electronic component production, electroplating, glass and silicate production, steel and aluminum manufacturing, metal processing, wood preservation, and pesticide and fertilizer production. Fluoride-containing wastewater poses significant risks to both the environment and humans. Fluoride concentrations exceeding certain limits can have numerous adverse effects on humans, animals, and plants.

[0003] Treatment methods for fluoride-containing wastewater can be categorized into two main types: precipitation and adsorption. Precipitation is suitable for treating industrial wastewater with high fluoride content, but incomplete treatment often requires secondary treatment, which requires chemicals such as lime, alum, and dolomite. Therefore, precipitation has a relatively low treatment efficiency. Adsorption is suitable for treating process wastewater with low fluoride content, or wastewater whose fluoride concentration still fails to meet relevant regulations after precipitation treatment. Common adsorption methods include ion exchange, activated alumina adsorption, and activated carbon adsorption. Therefore, the adsorption method has a narrow scope of application and is difficult to treat for industrial wastewater with high fluoride content.

[0004] Therefore, how to efficiently treat fluoride-containing wastewater with high fluoride content is a problem that needs to be solved at present. Summary of the Invention

[0005] In order to improve the treatment efficiency of fluoride-containing wastewater with a high fluoride content, the present application provides a treatment process for alkaline fluoride-containing wastewater.

[0006] The present application provides a treatment process for alkaline fluoride-containing wastewater, which adopts the following technical solution:

[0007] A process for treating alkaline fluoride-containing wastewater comprises the following steps:

[0008] Pretreatment: Adjust the pH value of fluorine-containing wastewater to 3-6 to obtain pretreated wastewater;

[0009] Primary adsorption: adding a multi-level adsorbent to the pretreated wastewater at a dosage of 3.5-6 g / L, subjecting the wastewater to shear treatment at a shear rate of 5400-5600 r / min for 60-150 min, followed by precipitation and effluent to obtain primary effluent; the multi-level adsorbent comprises the following components in parts by weight: 90-120 parts of goethite, 30-60 parts of sodium ion-containing A-type zeolite molecular sieve, and 5-10 parts of nano-hydroxyapatite;

[0010] Secondary adsorption: add activated diatomaceous earth and / or fly ash to the first-stage effluent, stir evenly, mix with polyacrylamide, precipitate, and effluent to obtain the second-stage effluent;

[0011] Post-treatment: The secondary effluent is adsorbed by ion exchange resin and then discharged to complete the treatment.

[0012] By adopting the above technical solution, the wastewater is now adjusted to the above pH range, which is conducive to subsequent adsorption. Goethite has the characteristics of fine particles, large specific surface area, many surface coordinated hydroxyl groups and high surface charge zero point. It can adsorb fluoride ions in wastewater through mechanisms such as internal lattice doping co-precipitation, ion exchange, electrostatic attraction, and surface complexation; the sodium ion-containing A-type zeolite molecular sieve is a mineral with a framework structure. It has abundant pores and a large internal surface area. During the adsorption process, it can adsorb fluoride ions not only through the external surface but also through the internal surface. The miniaturization of nanohydroxyapatite particle size causes a sharp increase in specific surface area and has more excellent physical and chemical properties. The atomic group forces on the surface of nanohydroxyapatite are unbalanced and have a high surface energy. Therefore, nanohydroxyapatite can adsorb fluoride ions and combine with fluoride ions through chemical bonding forces. Therefore, goethite, sodium-ion-containing A-type zeolite molecular sieve, and nano-hydroxyapatite are all able to more fully contact the fluoride ions in the wastewater. They can also simultaneously adsorb fluoride ions in the wastewater through different mechanisms such as physical adsorption, chemical adsorption, and ion exchange adsorption, thereby accelerating the adsorption rate and helping to reach adsorption equilibrium in a short period of time. Moreover, because goethite, sodium-ion-containing A-type zeolite molecular sieve, and nano-hydroxyapatite have different structural morphologies and particle sizes, they can form a multi-level, multi-directional adsorption system for fluorides with different particle sizes and different physical and chemical properties in the wastewater, resulting in more thorough treatment of fluoride.

[0013] In the secondary adsorption step, both diatomaceous earth and fly ash selectively adsorb fluoride ions and fluorine-containing particles. Diatomaceous earth also has flocculation and clarification properties, further removing fine particles from the wastewater. Fly ash is readily available and inexpensive, contributing to cost savings. The ion exchange resin in the post-treatment step adsorbs extremely small particles, further improving effluent quality.

[0014] In summary, the process of the present application can accelerate the adsorption rate, and adsorb fluoride ions and fluorides of different particle size ranges and different properties in a multi-level and multi-directional manner, thereby improving the treatment efficiency of fluoride-containing wastewater with a high fluoride content.

[0015] In a specific embodiment, the goethite has a particle size of 300-500 mesh.

[0016] By adopting the above technical solution, the present applicant has experimentally found that adjusting the particle size of goethite to within the above range helps to further improve the treatment efficiency of the present process. This may be because goethite within the above particle size range has better dispersibility and can be dispersed more evenly in the wastewater, thereby better adsorbing fluoride in the wastewater.

[0017] In a specific embodiment, the specific surface area of ​​the goethite is 202-209m 2 / g.

[0018] By adopting the above technical solution, the larger the specific surface area of ​​goethite, the larger the contact area with the wastewater, and therefore can be adsorbed with more fluoride and fluoride ions, thereby removing more fluoride and fluoride ions. However, goethite with too large a particle size is not only expensive and difficult to obtain, but also has too small a particle size and is prone to agglomeration. The present application has found through experiments that the use of goethite within the above-mentioned specific surface area range not only has excellent adsorption effect, but also has high adsorption rate, wide source, moderate price, and can be recycled and reused, which helps to improve the processing efficiency and economy of this process at the same time.

[0019] In a specific embodiment, the particle size of the sodium ion-containing A-type zeolite molecular sieve is 600-650 mesh.

[0020] By adopting the above technical solution, the sodium ion-containing type A zeolite molecular sieve within the above particle size range not only has good dispersibility, but can also form a complex with the goethite within the above particle size range and be dispersed between the goethites, thereby further improving the adsorption effect.

[0021] In a specific embodiment, the specific surface area of ​​the sodium ion-containing A-type zeolite molecular sieve is 4-4.2 m 2 / g, pore volume is 0.025-0.035cm 3 / g.

[0022] By adopting the above technical solution, the present applicant has experimentally found that molecular sieves within the above-mentioned specific surface area and pore volume ranges can further improve the processing efficiency of this process. This may be because molecular sieves within the above-mentioned index ranges not only have good adsorption effects on the outer surface, but also have internal pore surfaces that can more quickly adsorb fluoride ions and fluorides, and in large amounts.

[0023] In a specific embodiment, the particle sizes of the activated diatomaceous earth and fly ash are both 40-60 nm.

[0024] By adopting the above technical solution, since the particle sizes of fluoride and other particulate matter in the primary effluent are relatively small after one adsorption, the particle sizes of the activated diatomaceous earth and fly ash are controlled within the above range in this application, which helps to adsorb fluoride and other particulate matter in the primary effluent.

[0025] In a specific possible implementation scheme, the secondary adsorption is as follows: a mixture of activated diatomaceous earth and fly ash is added to the primary effluent, the addition amount of the mixture of activated diatomaceous earth and fly ash is 2 g / L, and the weight ratio of activated diatomaceous earth to fly ash in the mixture of activated diatomaceous earth and fly ash is 1: (0.8-1.2). After stirring for reaction, it is mixed with polyacrylamide, precipitated, and discharged to obtain secondary effluent.

[0026] By adopting the above technical solution, using the above ratio and dosage, not only can an excellent adsorption effect be achieved, but also activated diatomaceous earth and fly ash can be saved, thereby improving the economy of the process.

[0027] In a specific embodiment, the fluoride ion concentration of the fluoride-containing wastewater is 100-180 mg / L.

[0028] By adopting the above technical solution, the process of the present application has a better treatment effect on fluorine-containing wastewater with the above fluoride ion concentration, which helps to improve the fluoride ion adsorption rate.

[0029] In summary, this application includes at least one of the following beneficial technical effects:

[0030] 1. The process of the present application can accelerate the adsorption rate and adsorb fluoride ions and fluorides of different particle size ranges and different properties in a multi-level and multi-directional manner, thereby improving the treatment efficiency of fluoride-containing wastewater with high fluoride content;

[0031] 2. The process of this application helps to improve both the processing efficiency and economy of this process by optimizing raw materials with high performance indicators;

[0032] 3. The process of this application helps to further improve the processing efficiency of this process by improving the steps. DETAILED DESCRIPTION

[0033] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application were all commercially available.

[0034] The present application is further described in detail below with reference to the following examples and comparative examples.

[0035] Example

[0036] Example 1

[0037] This embodiment provides a multi-level adsorbent, which uses the following components: 105 kg of goethite, 45 kg of 5A zeolite molecular sieve, and 7 kg of nano-hydroxyapatite. The particle size of the goethite is 300-500 mesh and the specific surface area is 206 m 2 / g; the particle size of 5A zeolite molecular sieve is 600-650 mesh and the specific surface area is 4.1m 2 / g, pore volume of 0.03cm 3 The goethite, 5A zeolite molecular sieve and nano-hydroxyapatite are mixed evenly to obtain a multi-level adsorbent.

[0038] This embodiment provides a treatment process for alkaline fluorine-containing wastewater, which comprises the following steps:

[0039] The pH value of the fluoride-containing wastewater with a fluoride ion concentration of 140 mg / L is adjusted to 4.5 to obtain pretreated wastewater.

[0040] Multi-layer adsorbent was added to the pretreated wastewater at a dosage of 5 g / L. After stirring for 3 minutes, a high-speed shearing machine was used for shearing treatment at a shear rate of 5500 r / min. After shearing treatment for 110 minutes, the wastewater was input into the sedimentation tank for sedimentation and then discharged to obtain primary effluent.

[0041] The activated diatomaceous earth is crushed and sieved to obtain activated diatomaceous earth with a particle size of 40-60 nm. The activated diatomaceous earth with a particle size of 40-60 nm is added to the first-level effluent at a dosage of 2 g / L. After stirring evenly, polyacrylamide is added at a dosage of 1 g / L. After continuing to stir for 5 minutes, the mixture is input into a sedimentation tank for precipitation, and then discharged to obtain the second-level effluent.

[0042] The secondary effluent is passed through the ion exchange resin, and after being adsorbed by the ion exchange resin, the water is discharged and the treatment is completed.

[0043] Example 2

[0044] This embodiment provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this embodiment and Example 1 is that the multi-level adsorbent uses the following components: 90 kg of goethite, 30 kg of 5A zeolite molecular sieve, and 5 kg of nano-hydroxyapatite.

[0045] Example 3

[0046] This embodiment provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this embodiment and Example 1 is that the multi-level adsorbent uses the following components: 120 kg of goethite, 60 kg of 5A zeolite molecular sieve, and 10 kg of nano-hydroxyapatite.

[0047] Example 4

[0048] This embodiment provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this embodiment and Example 1 is that the dosage of the multi-level adsorbent is 3 g / L.

[0049] Example 5

[0050] This embodiment provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this embodiment and Example 1 is that the dosage of the multi-level adsorbent is 6 g / L.

[0051] Example 6

[0052] This embodiment provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this embodiment and Example 1 is that a high-speed shearing machine is used for shearing treatment at a shear rate of 5400 r / min. After shearing treatment for 150 minutes, the wastewater is input into a sedimentation tank for precipitation.

[0053] Example 7

[0054] This embodiment provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this embodiment and Example 1 is that a high-speed shearing machine is used for shearing treatment at a shear rate of 5600 r / min. After shearing treatment for 60 minutes, the wastewater is input into a sedimentation tank for precipitation.

[0055] Example 8

[0056] This embodiment provides a treatment process for alkaline fluoride-containing wastewater. The only difference between this embodiment and Example 1 is that an equal amount of primary fly ash with a particle size of 40-60 nm is used to replace the activated diatomaceous earth.

[0057] Example 9

[0058] This embodiment provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this embodiment and Example 1 is that the activated diatomaceous earth is replaced by an equal amount of a mixture of primary fly ash and activated diatomaceous earth. The mixture of primary fly ash and activated diatomaceous earth includes primary fly ash and activated diatomaceous earth in a weight ratio of 1:1.

[0059] Example 10

[0060] This embodiment provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this embodiment and Example 10 is that the mixture of primary fly ash and activated diatomaceous earth includes primary fly ash and activated diatomaceous earth in a weight ratio of 1:0.8.

[0061] Example 11

[0062] This embodiment provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this embodiment and Example 10 is that the mixture of primary fly ash and activated diatomaceous earth includes primary fly ash and activated diatomaceous earth in a weight ratio of 1:1.2.

[0063] Example 12

[0064] This embodiment provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this embodiment and Example 10 is that the mixture of primary fly ash and activated diatomaceous earth includes primary fly ash and activated diatomaceous earth in a weight ratio of 1:1.3.

[0065] Example 13

[0066] This embodiment provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this embodiment and Example 10 is that the mixture of primary fly ash and activated diatomaceous earth includes primary fly ash and activated diatomaceous earth in a weight ratio of 1:0.7.

[0067] Example 14

[0068] This embodiment provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this embodiment and Example 1 is that the fluoride ion concentration of the fluorine-containing wastewater is 100 mg / L.

[0069] Example 15

[0070] This embodiment provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this embodiment and Example 1 is that the fluoride ion concentration of the fluorine-containing wastewater is 180 mg / L.

[0071] Example 16

[0072] This embodiment provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this embodiment and Example 1 is that the fluoride ion concentration of the fluorine-containing wastewater is 90 mg / L.

[0073] Example 17

[0074] This embodiment provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this embodiment and Example 1 is that the fluoride ion concentration of the fluorine-containing wastewater is 190 mg / L.

[0075] Example 18

[0076] This embodiment provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this embodiment and Example 1 is that the particle size of the goethite is 200-300 mesh.

[0077] Example 19

[0078] This embodiment provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this embodiment and Example 1 is that the particle size of the goethite is 500-600 mesh.

[0079] Example 20

[0080] This embodiment provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this embodiment and embodiment 1 is that the specific surface area of ​​goethite is 202m 2 / g.

[0081] Example 21

[0082] This embodiment provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this embodiment and embodiment 1 is that the specific surface area of ​​goethite is 209m 2 / g.

[0083] Example 22

[0084] This embodiment provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this embodiment and Example 1 is that the particle size of the 5A zeolite molecular sieve is 550-600 mesh.

[0085] Example 23

[0086] This embodiment provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this embodiment and Example 1 is that the particle size of the 5A zeolite molecular sieve is 650-700 mesh.

[0087] Example 24

[0088] This embodiment provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this embodiment and embodiment 1 is that the specific surface area of ​​5A zeolite molecular sieve is 4m 2 / g, pore volume is 0.025cm 3 / g.

[0089] Example 25

[0090] This embodiment provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this embodiment and embodiment 1 is that the specific surface area of ​​5A zeolite molecular sieve is 4.2m 2 / g, pore volume is 0.035cm 3 / g.

[0091] Example 26

[0092] This embodiment provides a treatment process for alkaline fluoride-containing wastewater. The only difference between this embodiment and Example 1 is that the particle size of the activated diatomaceous earth is 30-40 nm.

[0093] Example 27

[0094] This embodiment provides a treatment process for alkaline fluoride-containing wastewater. The only difference between this embodiment and Example 1 is that the particle size of the activated diatomaceous earth is 60-70 nm.

[0095] Comparative Example

[0096] Comparative Example 1

[0097] This comparative example provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this comparative example and Example 1 is that the multi-level adsorbent uses the following components: 85 kg of goethite, 25 kg of 5A zeolite molecular sieve, and 4 kg of nano-hydroxyapatite.

[0098] Comparative Example 2

[0099] This comparative example provides a treatment process for alkaline fluoride-containing wastewater. The only difference between this comparative example and Example 1 is that the multi-level adsorbent uses the following components: 125 kg of goethite, 65 kg of 5A zeolite molecular sieve, and 11 kg of nano-hydroxyapatite.

[0100] Comparative Example 3

[0101] This comparative example provides a treatment process for alkaline fluoride-containing wastewater. The only difference between this comparative example and Example 1 is that the multi-level adsorbent does not include nano-hydroxyapatite.

[0102] Comparative Example 4

[0103] This comparative example provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this comparative example and Example 1 is that the multi-level adsorbent does not include 5A zeolite molecular sieve.

[0104] Comparative Example 5

[0105] This comparative example provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this comparative example and Example 1 is that the multi-level adsorbent does not include goethite.

[0106] Comparative Example 6

[0107] This comparative example provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this comparative example and Example 1 is that the pH value of the fluorine-containing wastewater with a fluoride ion concentration of 60 mg / L is adjusted to 3 to obtain pretreated wastewater.

[0108] Comparative Example 7

[0109] This comparative example provides a treatment process for alkaline fluorine-containing wastewater. The only difference between this comparative example and Example 1 is that the pH value of the fluorine-containing wastewater with a fluoride ion concentration of 60 mg / L is adjusted to 7 to obtain pretreated wastewater.

[0110] Performance testing

[0111] The following performance tests were performed on the final effluent of Examples 1-28 and Comparative Examples 1-7:

[0112] F - Adsorption rate = (C0-C e ) / C0·100%, (unit: %).

[0113] F - The equilibrium adsorption capacity = V0·(C0-C t ) / m, (unit: mg / g).

[0114] Where C0 is the initial F - Concentration, (mg / L); Ct is the F in the solution at time t - Concentration, (mg / L); C e is the solution F after adsorption equilibrium - Concentration, (mg / L); V0 is the total volume of the mixed solution, (mL); m is the mass of the added multi-level adsorbent, (g).

[0115] Table 1

[0116]

[0117] Combining Example 1 and Comparative Examples 1-7 and Table 1, it can be seen that compared with Example 1, the absorption rate and equilibrium adsorption capacity of Comparative Examples 1-7 are smaller, which shows that under the process conditions of Example 1, it is helpful to improve the treatment efficiency of fluoride-containing wastewater with a high fluoride content and improve the effluent water quality.

[0118] It can be seen from Examples 1-27 and Table 1 that Examples 1-27 all have high absorption rates and equilibrium adsorption capacities. Therefore, within the process conditions of Examples 1-27, they all contribute to improving the treatment efficiency of fluoride-containing wastewater with a high fluoride content.

[0119] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A process for treating alkaline fluorine-containing wastewater, characterized in that: The steps include: Pretreatment: Adjust the pH value of fluorine-containing wastewater to 3-6 to obtain pretreated wastewater; Primary adsorption: adding a multi-level adsorbent to the pretreated wastewater at a dosage of 3.5-6 g / L, subjecting the wastewater to shear treatment at a shear rate of 5400-5600 r / min for 60-150 min, followed by precipitation and effluent to obtain primary effluent; the multi-level adsorbent comprises the following components in parts by weight: 90-120 parts of goethite, 30-60 parts of sodium ion-containing A-type zeolite molecular sieve, and 5-10 parts of nano-hydroxyapatite; Secondary adsorption: add activated diatomaceous earth and / or fly ash to the first-stage effluent, stir evenly, mix with polyacrylamide, precipitate, and effluent to obtain the second-stage effluent; Post-treatment: The secondary effluent is adsorbed by ion exchange resin and then discharged to complete the treatment.

2. The process for treating alkaline fluorine-containing wastewater according to claim 1, characterized in that: The particle size of the goethite is 300-500 meshes.

3. The process for treating alkaline fluorine-containing wastewater according to claim 1, characterized in that: The specific surface area of ​​the goethite is 202-209m 2 / g.

4. The process for treating alkaline fluorine-containing wastewater according to claim 1, characterized in that: The particle size of the sodium ion-containing A-type zeolite molecular sieve is 600-650 meshes.

5. The process for treating alkaline fluorine-containing wastewater according to claim 1, characterized in that: The specific surface area of ​​the sodium ion-containing A-type zeolite molecular sieve is 4-4.2 m 2 / g, pore volume is 0.025-0.035cm 3 / g.

6. The process for treating alkaline fluorine-containing wastewater according to claim 1, characterized in that: The particle sizes of the activated diatomaceous earth and fly ash are both 40-60 nm.

7. The process for treating alkaline fluorine-containing wastewater according to claim 1, characterized in that: The secondary adsorption is as follows: adding a mixture of activated diatomaceous earth and fly ash to the primary effluent, wherein the addition amount of the mixture of activated diatomaceous earth and fly ash is 2 g / L and the weight ratio of the activated diatomaceous earth to fly ash in the mixture is 1:(0.8-1.2), stirring for reaction, mixing with polyacrylamide, precipitating, and effluent to obtain secondary effluent.

8. The process for treating alkaline fluorine-containing wastewater according to claim 1, characterized in that: The fluoride ion concentration of the fluoride-containing wastewater is 100-180 mg / L.

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