Method for remediation of low permeable fluorine contaminated sediment

Abstract

The application discloses a kind of low permeability fluorine pollution sediment repair methods, comprising: S1, citric acid, diethylene triamine pentaacetic acid and coconut amide propyl betaine three solutions are mixed in proportion, to obtain leaching agent;S2, fluorine pollution sediment is repaired: to fluorine pollution sediment, leaching agent obtained in S1 is added, continuously stirring 1~2h in leaching stirring tank;In the process of leaching, gas is pumped from the porous disc at the bottom of leaching stirring tank using pressurized air pump, and the fluorine pollution sediment saturated with leaching is repaired using micro-bubble-leaching combined enhancement repair formed by micro-bubble;S3, the sediment after S2 repair is separated, and the leaching is completed.The application has the advantages of simple process, convenient operation, fast reaction speed, good leaching effect, easy to obtain leaching agent and micro-bubble device, and has combined enhancement effect on fluorine pollution sediment repair, and is suitable for fluorine pollution repair of low permeability sediment such as clay, silty clay and silt.

Description

Technical Field

[0001] This invention belongs to the field of fluoride-contaminated sediment remediation technology, and in particular relates to a method for remediating low-permeability fluoride-contaminated sediment. Background Technology

[0002] Industrial activities such as aluminum electrolysis, coal combustion, steel processing, and phosphate fertilizer production generate large amounts of fluoride-containing waste. This waste can enter the environment through various pathways, impacting ecosystem safety and human health. Furthermore, the high background fluoride content in soil, coupled with increasing fluoride use and emissions, leads to excessively high fluoride levels in soils in some areas. Under the scouring action of rainfall, these fluorides flow into rivers and lakes with sediment, gradually accumulating in sediments and posing a serious threat to water quality. Therefore, environmental management of water source areas urgently needs to address this issue. Dredging, as an important measure to eliminate endogenous pollution and improve water quality, faces the challenge of fluoride contamination in sediment. Without effective remediation, directly landfilling contaminated sediment as hazardous waste is not only costly but also presents a significant challenge in finding suitable landfill sites, further complicating environmental management.

[0003] Leaching remediation technology involves injecting a specific leaching agent into the soil medium. Gravity and hydraulic pressure propel the leaching solution through the soil, dissolving and separating contaminants to achieve remediation. This technology primarily removes contaminants in two ways: first, through chemical reactions that bind contaminants to the leaching solution, removing them through desorption, chelation, dissolution, or fixation; second, through physical flushing that directly removes contaminants from the medium. Water, chemical solvents, or gases can all be used as leaching agents, considered as fluids capable of extracting contaminants from the medium. Compared to other soil remediation technologies, leaching remediation offers superior removal efficiency and effectiveness, significantly reducing heavy metal pollution and effectively clearing contaminated sites. Therefore, it eliminates the need for long-term monitoring of the remediation area, making it a convenient and efficient treatment method. However, currently, leaching technology is mainly applied to the remediation of coarse-grained contaminated soils with high sand content and strong permeability. For poorly permeable clayey soils or sediments in rivers, lakes, and reservoirs, leaching remediation efficiency is lower, and research on fluoride pollution is relatively limited. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a method for enhancing the remediation of low-permeability fluoride-contaminated sediment using microbubbles combined with leaching agents. This method can treat poorly permeable fluoride-contaminated sediment in situ, achieving leaching remediation of fluoride in the sediment. This method has high remediation efficiency and minimal environmental impact.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for remediating fluoride-contaminated sediment with low permeability, characterized by the following steps:

[0007] S1, Preparation of rinsing agent: Mix solutions of citric acid, diethylenetriaminepentaacetic acid, and cocamidopropyl betaine, such that the concentrations of citric acid, diethylenetriaminepentaacetic acid, and cocamidopropyl betaine in the solution are 0.1–0.5 mol / L, 0.01–0.1 mol / L, and 0.01–0.1 mol / L, respectively;

[0008] S2, Remediation of Fluorocontaminated Sediment: Add the leaching agent prepared in S1 to the fluorocontaminated sediment and stir continuously in the leaching mixing tank for 1-2 hours. The mass ratio of fluorocontaminated sediment to leaching agent is 1:(10-30). During the leaching process, use a pressurized air pump to pump air from the porous disc at the bottom of the leaching mixing tank to form microbubbles for combined microbubble-leaching enhancement remediation of the saturated fluorocontaminated sediment.

[0009] S3 involves separating the mud and water in the bottom mud after S2 repair, completing the rinsing process.

[0010] Preferably, the concentrations of citric acid, diethylenetriaminepentaacetic acid, and cocamidopropyl betaine in S1 are 0.3 mol / L, 0.05 mol / L, and 0.1 mol / L, respectively.

[0011] Preferably, the volume ratio of the gas pumped in S2 to the mud-liquid mixture in the rinsing mixing tank is 1:(3-10). More preferably, the volume ratio of the gas pumped in to the mud-liquid mixture in the rinsing mixing tank is 1:3.

[0012] Preferably, the porous disk has a pore size of 0.5 μm, and the generated microbubble diameter ranges from 0.300 to 100 μm.

[0013] In S2, the mass ratio of fluoride-contaminated sediment to leaching agent is 1:20.

[0014] The fluoride-contaminated sediment is sediment that has been cleaned, mechanically ground, and sieved through a 5-10 mm sieve. The fluoride-contaminated sediment is low-permeability clay, silty clay, or silt.

[0015] Preferably, the stirring speed of the rinsing mixing tank is 100-200 r / min, and the temperature is 20-40℃. Alternatively, the stirring speed of the rinsing mixing tank is 200 r / min, the temperature is 25℃, and the stirring time is 2 hours.

[0016] Compared with existing methods, the present invention has the following advantages and beneficial effects:

[0017] 1. This invention uses citric acid, diethylenetriaminepentaacetic acid and cocamidopropyl betaine as rinsing solutions, combined with microbubble technology for enhanced repair. Citric acid increases the solubility of fluorides in sediment by lowering the sediment's pH, while simultaneously promoting the conversion from a solid to a soluble state through ion exchange. Diethylenetriaminepentaacetic acid (DTA) chelates and complexes with water-soluble and exchangeable fluorides, further reducing the bioavailability of fluorides in the sediment. It also promotes the conversion of iron-manganese-bound and organically bound fluorides to water-soluble and exchangeable fluorides, effectively preventing the re-adsorption of fluoride ions to the sediment surface and further improving leaching efficiency. The combined use of cocamidopropyl betaine and microbubbles synergistically reduces the surface tension of sediment particles, mutually reinforcing each other with the bubbles, improving sediment viscosity, and enhancing the permeability of the leaching agent. This allows the agent to more effectively contact and remove fluorides from the sediment, promoting a shift in the equilibrium reaction of the leaching system towards the release of fluoride ions, thus enhancing the leaching and remediation process.

[0018] 2. The addition of microbubbles in this invention can promote the shift of the equilibrium reaction of the rinsing system towards the release of fluoride ions, thereby improving the effectiveness of the rinsing agent in sediment remediation, reducing the amount of rinsing agent used, and lowering costs.

[0019] 3. In this invention, the microbubbles also react with cocamidopropyl betaine to form surfactant microbubbles or colloidal gas foams with small volume and large specific surface area. This effectively reduces the surface tension between pollutants and the liquid phase, promotes the adsorption of pollutants on the surface of microbubbles or colloidal gas foams and their transfer to the gas phase, and ultimately enhances the rinsing efficiency of fluoride-contaminated sediment.

[0020] 3. The process of this invention is simple, easy to operate, fast in reaction, and has good leaching effect. It can effectively overcome the problem of difficult leaching of low-permeability sediments and is applicable to the remediation of fluoride pollution in sediments of various texture types such as clay, silty clay, and silt. It can also be widely applied to the leaching remediation of fluoride-containing soils.

[0021] 3. When the sediment remediated by the method of this invention is backfilled after being washed with clean water, it will not cause secondary pollution. Citric acid, diethylenetriaminepentaacetic acid, and cocamidopropyl betaine are all biodegradable, environmentally friendly, and will not cause secondary pollution.

[0022] 4. The total fluoride content of fluoride-contaminated sediment treated by this method can be reduced by more than 67.5%. Attached Figure Description

[0023] Figure 1 The fluoride removal rate of the remediated contaminated sediment under different citric acid addition conditions;

[0024] Figure 2 The fluoride removal rate of contaminated sediment remediated under different diethylenetriaminepentaacetic acid (DITA) addition conditions;

[0025] Figure 3 The fluoride removal rate of the remediated contaminated sediment under different cocamidopropyl betaine addition conditions;

[0026] Figure 4 It represents the fluoride removal rate of the fluoride-contaminated sediment being remediated under different gas-liquid ratios.

[0027] Figure 5 It combines microbubbles with rinsing agents to enhance the fluoride removal rate of polluted sediments of different textures. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the present invention clearer, the method of the present invention will be described in detail below with reference to the embodiments and accompanying drawings.

[0029] Example 1

[0030] Sediment samples were collected from a reservoir in Hebei Province. The sediment had a water content of 13.9%, a pH of 7.9, a texture of silt, and a total fluoride content of 562 mg / kg.

[0031] The specific steps for remediating the above-mentioned fluoride-contaminated sediment under different citric acid addition conditions are as follows:

[0032] S1. Remove impurities from the fluoride-contaminated sediment, mechanically grind it, and then pass it through a 10mm sieve. Then divide it into 5 groups of equal quality.

[0033] S2. Prepare 5 sets of rinsing solutions, wherein the concentrations of citric acid in the 5 sets of solutions are 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.5 mol / L and 1.0 mol / L respectively, the concentration of diethylenetriaminepentaacetic acid in the 5 sets of solutions is 0.05 mol / L, and the concentration of cocamidopropyl betaine in the 5 sets of solutions is 0.1 mol / L.

[0034] S3. Add the five sets of leaching agent solutions prepared in S2 to the five sets of fluoride-contaminated sediments obtained in S1, with a solid-liquid ratio of 1:20. Stir continuously for 2 hours at 25℃ and 200 r / min. During the leaching process, microbubbles (0.300~100μm) are pumped into the porous disc at the bottom of the mixing tank using a pressurized air pump, with a gas-liquid ratio of 1:3, to perform microbubble-leaching combined enhanced remediation on the fluoride-contaminated sediments that have been saturated with leaching.

[0035] S4. Five groups of sediments after microbubble-rinsing combined enhancement and remediation were subjected to mud-water separation to obtain five groups of remediated fluoride-contaminated sediments.

[0036] Five groups of remediated fluoride-contaminated sediments were dried and their total fluoride content was determined according to the method specified in "Determination of Fluorine in Solid Waste - Alkali Fusion-Ion Selective Electrode Method" (HJ 999-2018). The results are as follows: Figure 1 and Figure 5 As shown in (silt).

[0037] As shown in the figure, the amount of citric acid added has a significant impact on the leaching effect of fluoride-contaminated sediment. Considering both the fluoride removal rate and the cost of the leaching agent, the optimal fluoride removal rate was achieved when the citric acid addition was 0.3 mol / L. The total fluoride content of the contaminated sediment decreased from 562 mg / kg to 69.7 mg / kg, with a removal rate as high as 87.6%.

[0038] Example 2

[0039] A sediment sample was collected from the bottom of a river in Tianjin. The sediment had a water content of 13.8%, a pH of 8.1, a texture of clay, and a total fluoride content of 775 mg / kg.

[0040] The remediation of the above-mentioned fluoride-contaminated sediment under different amounts of diethylenetriaminepentaacetic acid (DITA) was carried out using the following specific steps:

[0041] S1. After removing impurities from the fluoride-contaminated sediment and mechanically grinding it, pass it through a 10mm sieve and divide it into 5 groups of equal quality.

[0042] S2. Prepare 5 sets of rinsing solutions, wherein the concentration of citric acid in each of the 5 solutions is 0.3 mol / L, the concentration of diethylenetriaminepentaacetic acid in each of the 5 solutions is 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.2 mol / L and 0.3 mol / L respectively, and the concentration of cocamidopropyl betaine in each of the 5 solutions is 0.1 mol / L.

[0043] S3. Add the five leaching solutions prepared in S2 to the five groups of fluoride-contaminated sediments obtained in S1, with a solid-liquid ratio of 1:20. Stir continuously for 2 hours at 25℃ and 200r / min. During the leaching process, use a pressurized air pump to pump microbubbles from the porous disc at the bottom of the mixing tank, with a gas-liquid ratio of 1:3, to perform microbubble-leaching combined enhanced remediation on the saturated fluoride-contaminated sediments.

[0044] S4. Five groups of sediments after microbubble-rinsing combined enhancement and remediation were subjected to mud-water separation to obtain five groups of remediated fluoride-contaminated sediments.

[0045] Five groups of remediated fluoride-contaminated sediments were dried and their total fluoride content was determined according to the method specified in "Determination of Fluorine in Solid Waste - Alkali Fusion-Ion Selective Electrode Method" (HJ 999-2018). The results are as follows: Figure 2 and Figure 5 As shown in (clay).

[0046] As can be seen from the figure, the amount of diethylenetriaminepentaacetic acid (DICA) added has a significant impact on the leaching effect of fluoride-contaminated sediment. When the amount of DICA added is 0.05 mol / L, the fluoride removal rate of the remediated sediment reaches the optimal level, and the total fluoride content of the contaminated sediment decreases from the original 775 mg / kg to 251.9 mg / kg, with a removal rate as high as 67.5%.

[0047] Example 3

[0048] A sediment sample was collected from the bottom of a reservoir in Shanxi Province. The sediment had a water content of 20.1%, a pH of 7.8, a texture of silty clay, and a total fluoride content of 866 mg / kg.

[0049] The specific steps for remediating fluoride-contaminated sediment under different amounts of cocamidopropyl betaine are as follows:

[0050] S1. After removing impurities from the fluoride-contaminated sediment and mechanically grinding it, it is sieved through a 10mm sieve and divided into 5 groups of equal mass.

[0051] S2. Prepare 5 sets of rinsing solutions, wherein the concentration of citric acid in each of the 5 sets of solutions is 0.3 mol / L, the concentration of diethylenetriaminepentaacetic acid in each of the 5 sets of solutions is 0.05 mol / L, and the concentrations of cocamidopropyl betaine in the 5 sets of solutions are 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, and 0.3 mol / L, respectively.

[0052] S3. Add the leaching agent solution prepared in S2 to the 5 groups of fluoride-contaminated sediments obtained in S1, with a solid-liquid ratio of 1:20, and stir continuously at 25℃ and 200r / min for 2 hours. During the leaching process, use a pressurized air pump to pump microbubbles from the porous disc at the bottom of the mixing tank, with a gas-liquid ratio of 1:3, to perform microbubble-leaching combined enhanced remediation on the saturated fluoride-contaminated sediments.

[0053] S4. Five groups of sediments after microbubble-rinsing combined enhancement and remediation were subjected to mud-water separation to obtain five groups of remediated fluoride-contaminated sediments.

[0054] Five groups of remediated fluoride-contaminated sediments were dried and their total fluoride content was determined according to the method specified in "Determination of Fluorine in Solid Waste - Alkali Fusion-Ion Selective Electrode Method" (HJ 999-2018). The results are as follows. Figure 3 As shown.

[0055] Depend on Figure 3It was found that the amount of cocamidopropyl betaine added had a significant impact on the leaching effect of fluoride-contaminated sediment. The optimal fluoride removal rate was achieved when the added amount of cocamidopropyl betaine was 0.1 mol / L. The total fluoride content of the contaminated sediment decreased from 886 mg / kg to 185.3 mg / kg, with a removal rate as high as 78.6%.

[0056] Example 4

[0057] Taking the sediment sample from a reservoir in Shanxi Province in Example 3 as an example, the sediment had a water content of 20.1%, a pH of 7.8, a texture type of silty clay, and a total fluoride content of 866 mg / kg.

[0058] The specific steps for remediating fluoride-contaminated sediment under different gas-liquid ratios are as follows:

[0059] S1. Remove impurities from the fluoride-contaminated sediment, mechanically grind it, and then sieve it through a 10mm sieve. Divide it into 6 groups according to the uniformity of quality.

[0060] S2. Prepare 6 sets of rinsing solutions, wherein the concentration of citric acid in all 6 sets of solutions is 0.3 mol / L, the concentration of diethylenetriaminepentaacetic acid in all 6 sets of solutions is 0.05 mol / L, and the concentration of cocamidopropyl betaine in all 6 sets of solutions is 0.1 mol / L.

[0061] S3. The leaching agent solution prepared in S2 was added to the 6 groups of fluoride-contaminated sediments obtained in S1, with a solid-liquid ratio of 1:20. The mixtures were stirred continuously for 2 hours at 25℃ and 200r / min. During the leaching process, microbubbles were pumped into the porous disc at the bottom of the mixing tank using a pressurized air pump. The gas-liquid ratios (the volume ratio of the pumped gas to the mud-liquid mixture in the leaching mixing tank) of the 6 leaching systems were 0:9, 1:9, 3:9, 5:9, 7:9, and 9:9, respectively. The microbubble-leaching combined enhanced remediation was carried out on the leached saturated fluoride-contaminated sediments.

[0062] S5. The sediment after microbubble-rinsing combined enhancement and repair was subjected to mud-water separation to obtain 6 groups of repaired fluoride-contaminated sediment.

[0063] After drying, the total fluoride content of the six groups of remediated fluoride-contaminated sediments was determined according to the method specified in "Determination of Fluorine in Solid Waste - Alkali Fusion-Ion Selective Electrode Method" (HJ 999-2018). The results are as follows: Figure 4 and Figure 5 As shown in (silty clay).

[0064] As can be seen from the figure, the gas-liquid ratio of the rinsing system has a significant impact on the rinsing effect of fluoride-contaminated sediment. When the gas-liquid ratio is 1:3 (i.e., 3:9 in the figure), the fluoride removal rate of the remediated sediment reaches the best, and the total fluoride content of the contaminated sediment is reduced from the original 886 mg / kg to 169.74 mg / kg, with a removal rate as high as 80.4%.

Claims

1. A method for remediating fluoride-contaminated sediment with low permeability, characterized in that... Includes the following steps: S1, Preparation of rinsing agent: Mix solutions of citric acid, diethylenetriaminepentaacetic acid, and cocamidopropyl betaine, such that the concentrations of citric acid, diethylenetriaminepentaacetic acid, and cocamidopropyl betaine in the solution are 0.1–0.5 mol / L, 0.01–0.1 mol / L, and 0.01–0.1 mol / L, respectively; S2, Remediation of Fluorocontaminated Sediment: Add the leaching agent prepared in S1 to the fluorocontaminated sediment and stir continuously in the leaching mixing tank for 1-2 hours. The mass ratio of fluorocontaminated sediment to leaching agent is 1:(10-30). During the leaching process, use a pressurized air pump to pump air from the porous disc at the bottom of the leaching mixing tank to form microbubbles for combined microbubble-leaching enhancement remediation of the saturated fluorocontaminated sediment. S3 involves separating the mud and water in the bottom mud after S2 repair, completing the rinsing process.

2. The repair method according to claim 1, characterized in that: In S1, the concentrations of citric acid, diethylenetriaminepentaacetic acid, and cocamidopropyl betaine are 0.3 mol / L, 0.05 mol / L, and 0.1 mol / L, respectively.

3. The repair method according to claim 1, characterized in that: In S2, the volume ratio of the pumped gas to the mud mixture in the scrubbing tank is 1:(3~10).

4. The repair method according to claim 3, characterized in that: The volume ratio of the pumped gas to the mud mixture in the scrubbing tank is 1:

3.

5. The repair method according to claim 1, characterized in that: The porous disk has a pore size of 0.5 μm, and the generated microbubbles have a diameter range of 0.300 to 100 μm.

6. The repair method according to claim 1, characterized in that: In S2, the mass ratio of fluoride-contaminated sediment to leaching agent is 1:

20.

7. The repair method according to claim 1, characterized in that: The fluoride-contaminated sediment is sediment that has been cleaned, mechanically ground, and passed through a 5-10 mm sieve.

8. The repair method according to claim 7, characterized in that, The fluoride-contaminated sediment is low-permeability clay, silty clay, or silt.

9. The repair method according to claim 1, characterized in that: The stirring speed of the rinsing mixing tank is 100-200 r / min, and the temperature is 20-40℃.

10. The repair method according to claim 9, characterized in that: The stirring speed of the rinsing mixing tank is 200 r / min, the temperature is 25℃, and the stirring time is 2h.

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