A method for treating sediments containing heavy metal pollutants

Abstract

This disclosure relates to a method for treating sediments containing heavy metal pollutants. The method includes: (1) adding sulfate to sediment I and allowing it to stand to obtain sediment II; (2) taking sediment II samples from different depths for testing to determine the content of heavy metals at different depths in sediment II; and (3) removing sediment II with a heavy metal content of more than 70% by dredging. In step (1), sediment I is selected from sediments in a lake and contains heavy metal pollutants. This disclosure utilizes a stratified treatment method to treat heavy metal-polluted sediments, which can effectively fix the available heavy metals in the sediments and remove sediments with a heavy metal content of more than 70% by dredging. The process is simple, efficient, and stable, providing a new approach for the control and treatment of heavy metal pollution in sediments, and has high engineering application value and good economic and environmental benefits.

Description

Technical Field

[0001] This disclosure relates to the field of environmental protection treatment technology for heavy metal contaminated sediments, and in particular to a method for treating sediments containing heavy metal pollutants, as well as a method for preventing heavy metal pollutants from existing in the ionic state in sediments. Background Technology

[0002] Human activities and daily life have resulted in the discharge of large amounts of heavy metal pollutants into the aquatic environment. Because heavy metal pollutants exhibit high toxicity even at low doses, are non-degradable, and can continuously accumulate in the food chain (web), heavy metal pollution in aquatic environments has seriously threatened human health. After entering water bodies, heavy metal pollutants can rapidly bind to suspended particles and, during sedimentation, enter the sediment along with the suspended particles, ultimately resulting in over 90% of heavy metal pollutants in surface water being transferred to the sediment. However, some heavy metal ions bound to the sediment are attached to the solid surface through relatively weak electrostatic interactions. Under changing environmental conditions (such as pH, ORP, etc.), these heavy metal ions may desorb and be released back into the overlying water.

[0003] Currently, there are methods to stabilize heavy metals in sediments by enhancing the activity of indigenous microorganisms. For example, patent CN112429827A discloses a green preparation method and application of a nearshore polluted sediment remediation material. It uses seaweed extract as a reaction material and stabilizer to prepare a composite material containing seaweed organic matter and magnetic iron oxide for remediation of nearshore polluted sediments. However, the process of synthesizing materials by these methods is complex and requires high investment, and the efficiency of relying on microorganisms to stabilize heavy metals is low.

[0004] Therefore, finding a simple, easy-to-implement, and stable method for treating heavy metal pollutants in sediments is an urgent problem to be solved. Summary of the Invention

[0005] To address the aforementioned technical problems, this disclosure provides a method for treating sediments containing heavy metal pollutants. The aim is to provide a practical, economically feasible, and reasonable method for stabilizing available heavy metals in sediments. This method combines dredging with stratified treatment to reduce the environmental risks of heavy metal pollutants, providing a new approach to controlling the ecological risks of heavy metals in the aquatic environment.

[0006] In a first aspect, this disclosure provides a method for treating sediments containing heavy metal pollutants, the method comprising:

[0007] (1) Add sulfate to sediment I and let it stand to obtain sediment II;

[0008] (2) Take sediment II samples from different depths for testing to determine the content of heavy metals at different depths in sediment II;

[0009] (3) Remove sediments with a heavy metal content of more than 70% by dredging;

[0010] In step (1), sediment I is selected from sediments in the lake, and sediment I contains heavy metal pollutants. Sediment II is sediment containing heavy metal pollutants after the addition of sulfate.

[0011] This disclosure employs a stratified treatment approach for sediments, utilizing sulfides generated from sulfate reduction to fix available heavy metals in the sediments. This is combined with dredging to remove sediments containing over 70% heavy metals, thus effectively removing heavy metals from the sediments. The process is simple, efficient, and stable, and sulfates are inexpensive, readily available, and easy to transport, making it highly valuable for practical engineering applications. Specifically:

[0012] When the sulfate disclosed herein enters the water body, it undergoes a sulfate reduction process under the action of sulfate-reducing bacteria to generate sulfides, which then react with Fe(II) in the sediment to form pyrite (FeS). The available heavy metal ions from the heavy metal pollutants can replace the Fe in FeS. 2+ This process forms insoluble metal sulfides, i.e., F3-state heavy metals, thereby fixing the available heavy metals in the sediment, reducing the bioavailability of heavy metals, and preventing secondary heavy metal pollution. Simultaneously, by detecting the heavy metal content at different depths in the sediment, sediments with a heavy metal content exceeding 70% can be removed through dredging, resulting in a more thorough treatment of heavy metals in the sediment.

[0013] Among them, the F1 state heavy metal is a weak acid soluble state; the F2 state heavy metal is a reducible state (iron-manganese oxide combined state); the F3 state heavy metal is an oxidizable state (mainly forming metal sulfides with sulfides, and some heavy metals combined with organic matter); and the F4 state heavy metal is a residue state.

[0014] The present invention has found that more than 70% of the heavy metals in the heavy metal-contaminated sediments are concentrated in a layer of sediment less than 2 cm deep. Therefore, the present invention uses dredging to remove sediments with a heavy metal content of more than 70%, which makes the removal of heavy metals from the sediments more thorough.

[0015] As a preferred technical solution of this disclosure, the method of adding sulfate in step (1) is to add sulfate to the overlying water of the sediment I.

[0016] As a preferred embodiment of this disclosure, the concentration of sulfate in the overlying water is 150-250 mg / L, such as 160 mg / L, 180 mg / L, 200 mg / L, 220 mg / L, 240 mg / L, etc.

[0017] This disclosure limits the concentration of sulfate in the overlying water to within the range specified herein, effectively fixing available heavy metal ions in the sediments and preventing heavy metals from re-entering the water body, without causing sulfate pollution. Alternatively, the method of adding sulfate described in this disclosure can also involve adding sulfate to the pore water of the sediments.

[0018] As a preferred technical solution of this disclosure, the sulfate contains SO4 2- The molar ratio of the heavy metal to the pollutant is (1-2):1, for example, 1.2:1, 1.4:1, 1.6:1, 1.8:1, etc.

[0019] When sulfate contains SO4 2- When the molar ratio of heavy metals in the aforementioned heavy metal pollutants is within the range of this disclosure, it can effectively reduce the content of available heavy metals in sediments and prevent the re-release of heavy metals into water bodies, thus preventing secondary pollution.

[0020] This disclosure does not impose excessive limitations on the heavy metal content in sediments, and the treatment methods provided in this disclosure can be used for sediments contaminated with heavy metals. The heavy metal content is only illustrative in this disclosure; for example, the concentration of the heavy metal in the overlying water is 0-125 mg / L, such as 0.005 mg / L, 0.01 mg / L, 0.05 mg / L, 0.1 mg / L, 0.5 mg / L, 1 mg / L, 5 mg / L, 10 mg / L, 50 mg / L, 100 mg / L, 120 mg / L, etc.

[0021] As a preferred embodiment of this disclosure, the concentration of the heavy metal in the overlying water is 50-125 mg / L, preferably 95-125 mg / L.

[0022] The concentration of heavy metals in the overlying water mentioned in this disclosure refers to the concentration of heavy metals before they are deposited into sediments after polluting the water body. It can also be understood as the ratio of the total amount of heavy metals in the heavy metal pollutants to the total volume of the overlying water.

[0023] Since heavy metal pollution may be a continuous process in real life, the sulfates described in this disclosure can be added as needed to ensure that available heavy metal ions in the sediment can be effectively fixed.

[0024] As a preferred embodiment of this disclosure, the sulfate is selected from sodium sulfate.

[0025] As a preferred technical solution of this disclosure, the detection method in step (2) is to use ICP-MS and / or ICP-OES for detection.

[0026] ICP-MS, or inductively coupled plasma mass spectrometry, is suitable for trace and ultra-trace element analysis. When the heavy metal content in the sediments of this disclosure is in the ppt range, ICP-MS is used for detection. ICP-OES, or inductively coupled plasma optical emission spectrometry, has a detection limit of medium ppb to medium ppm. When the heavy metal content in the sediments of this disclosure is high, ICP-OES is used for detection.

[0027] As a preferred technical solution of this disclosure, the settling time in step (1) is 30-40 days, such as 32 days, 34 days, 36 days, 38 days, etc.

[0028] In this disclosure, after adding sulfate to the water overlying the sediment, it needs to be left to stand for a period of time to allow the sulfate sufficient time to enter the sediment and react with sulfate-reducing bacteria.

[0029] As a preferred embodiment of this disclosure, the heavy metal is selected from Cd, Pd, Zn, Ni, or Cu.

[0030] Secondly, this disclosure provides a method for preventing heavy metal pollutants from existing in ionic form in sediments, the method comprising:

[0031] (1) Add sulfate to sediment III and let it stand to obtain sediment IV;

[0032] (2) After the sediment IV is contaminated with heavy metals, sediment V is cultured and samples of sediment V from different depths are taken for testing to determine the content of heavy metals at different depths in sediment V.

[0033] (3) Remove sediments V with a heavy metal content of more than 70% by dredging.

[0034] The sediment III mentioned in step (1) is selected from sediments at the river mouth after rainstorm runoff and / or sediments in the lake shoal area caused by seasonal flooding. This is because the river mouth after rainstorm runoff may be polluted by heavy metals due to runoff input, while the lake shoal area caused by seasonal flooding may be polluted by secondary heavy metals due to sediment resuspension and oxidation processes.

[0035] The heavy metal pollutant content in sediment III was lower than the background values ​​for heavy metals in the "Background Values ​​of Chinese Soils", with Cd content below 0.056 mg / kg, Pb content below 20.5 mg / kg, Zn content below 71.9 mg / kg, Ni content below 28.7 mg / kg, and Cu content below 21.0 mg / kg.

[0036] Sediment IV is sediment from the river mouth after storm runoff with added sulfate and / or sediment from the lake shoal area caused by seasonal flooding. Sediment V is sediment from the river mouth after storm runoff with added sulfate and / or sediment from the lake shoal area caused by seasonal flooding.

[0037] This disclosure involves adding sulfate to sediments before they become contaminated with heavy metals. The application scenarios are limited to areas such as river mouths after heavy rain runoff or shallow lake areas caused by seasonal flooding, as these areas are very susceptible to heavy metal contamination. By pre-adding sulfate, this disclosure can more effectively fix the available heavy metal ions in the sediments after they become contaminated with heavy metals, preventing heavy metal pollutants from existing in the sediments in ionic form and thus avoiding the desorption of heavy metal ions.

[0038] The sediments described in this disclosure contain indigenous sulfate-reducing bacteria and Fe(II), which can undergo a series of reactions with sulfate to generate FeS. When heavy metal pollutants enter the sediments, FeS reacts with available heavy metal ions to generate insoluble heavy metal sulfides, thereby fixing the available heavy metals in the sediments and preventing heavy metal ions from re-entering the overlying water.

[0039] As a preferred technical solution of this disclosure, the method of adding sulfate is to add sulfate to the overlying water of the sediment III.

[0040] As a preferred embodiment of this disclosure, the concentration of sulfate in the overlying water is 150-250 mg / L, such as 160 mg / L, 180 mg / L, 200 mg / L, 220 mg / L, 240 mg / L, etc.

[0041] This disclosure limits the concentration of sulfate in the overlying water to within the range specified herein. After the sediment is contaminated with heavy metals, it can effectively fix the available heavy metals in the sediment, reduce the concentration of free heavy metal ions in the sediment, avoid secondary pollution of the water body, and prevent sulfate pollution of the water body. Alternatively, the method of adding sulfate described in this disclosure can also involve adding sulfate to the pore water of the sediment.

[0042] As a preferred technical solution of this disclosure, the sulfate contains SO42- The molar ratio of the heavy metal to the pollutant is (1-2):1, for example, 1.2:1, 1.4:1, 1.6:1, 1.8:1, etc.

[0043] When SO4 in sulfate 2- When the molar ratio of heavy metals in the aforementioned heavy metal pollutants is within the range of this disclosure, it can effectively reduce the content of available heavy metals in sediments and prevent free heavy metal ions from re-entering the water body.

[0044] This disclosure does not impose excessive limitations on the heavy metal content in sediments that may be contaminated with heavy metals. The treatment methods provided in this disclosure can be used for any sediments that may be contaminated with heavy metals. The heavy metal content in this disclosure is only illustrative. For example, the concentration of the heavy metal in the overlying water is 0-125 mg / L, such as 0.005 mg / L, 0.01 mg / L, 0.05 mg / L, 0.1 mg / L, 0.5 mg / L, 1 mg / L, 5 mg / L, 10 mg / L, 50 mg / L, 100 mg / L, 120 mg / L, etc.

[0045] As a preferred embodiment of this disclosure, the concentration of the heavy metal in the overlying water is 50-125 mg / L, preferably 95-125 mg / L.

[0046] The concentration of heavy metals in the overlying water mentioned in this disclosure refers to the concentration of heavy metals before they are deposited into sediments after polluting the water body. It can also be understood as the ratio of the total amount of heavy metals in the heavy metal pollutants to the total volume of the overlying water.

[0047] As a preferred embodiment of this disclosure, the sulfate is selected from sodium sulfate.

[0048] As a preferred technical solution of this disclosure, the detection method in step (2) is to use ICP-MS and / or ICP-OES for detection. When the heavy metal content in the sediment of this disclosure is in the ppt range, ICP-MS is used for detection; when the heavy metal content in the sediment of this disclosure is high, ICP-OES is used for detection.

[0049] As a preferred technical solution of this disclosure, the settling time in step (1) is 30-40 days, such as 32 days, 34 days, 36 days, 38 days, etc.

[0050] In this disclosure, after adding sulfate to the water covering the sediment, it needs to be left to stand for a period of time to allow the sulfate to have enough time to enter the sediment and react with sulfate-reducing bacteria.

[0051] As a preferred technical solution of this disclosure, the cultivation in step (2) is static placement, and the cultivation time is 12-15 days, such as 13 days, 14 days, etc.

[0052] In this disclosure, after the sediment is contaminated with heavy metals, it is cultured for a period of time to allow the heavy metal contaminants to fully deposit in the sediment.

[0053] As a preferred embodiment of this disclosure, the heavy metal is selected from Cd, Pd, Zn, Ni, or Cu.

[0054] As one specific embodiment of this disclosure, the treatment method further includes sediment pretreatment: placing the sediment in a culture column, injecting overlying water, and culturing it stably under anaerobic conditions.

[0055] The present disclosure pre-treats the sediments to ensure that the state of the sediments during the experiment is close to their state in nature, thereby ensuring the accuracy of the experimental results.

[0056] As a preferred technical solution of this disclosure, the overlying water is deionized water, which ensures that the substances in the overlying water all come from the sediment, prevents interference from foreign substances, and replenishes the water lost due to evaporation during the standing, culturing or stable culturing period to maintain a constant liquid level in the overlying water.

[0057] As a preferred technical solution of this disclosure, the depth ratio of sediment to overlying water is 2:(3-4), such as 2:3.2, 2:3.4, 2:3.6, 2:3.8, etc.

[0058] As a preferred technical solution of this disclosure, the stable culture time is 14-21 days, such as 16 days, 18 days, 20 days, etc.

[0059] The culture column described in this disclosure is wrapped with tin foil to simulate the real environment of the sediment, so as to prevent the microorganisms in the sediment from undergoing other microbial activities after being exposed to light. Preferably, the height of the wrapping is 0-15cm, such as 2cm, 4cm, 6cm, 8cm, 10cm, 12cm, 14cm, etc., so as to keep the sediment in a light-proof environment.

[0060] As a specific embodiment of this disclosure, the sediment pretreatment includes the following steps: placing the sediment in a culture column, injecting overlying water, culturing stably under anaerobic conditions for 14-21 days, the depth ratio of sediment to overlying water being 2:(3-4), and wrapping the outer wall of the culture column with tin foil at a height of 0-15cm.

[0061] The technical solution provided in this disclosure has the following advantages compared with the prior art:

[0062] 1. This disclosure utilizes a layered treatment method to treat heavy metal-contaminated sediments, which can effectively fix the available heavy metals in the sediments and remove sediments with a heavy metal content of more than 70% by dredging. The process is simple, efficient and stable, providing a new approach for the control and treatment of heavy metal pollution in sediments, and has high engineering application value as well as good economic and environmental benefits.

[0063] 2. For areas with a high probability of heavy metal pollution, such as river inlets after rainstorm runoff or lake shallows caused by seasonal flooding, this disclosure can more effectively fix the available heavy metal ions in the sediments that will be subsequently polluted by heavy metals by pre-adding sulfate, preventing heavy metal pollutants from existing in the sediments in ionic form, thereby avoiding the desorption of heavy metal ions. Attached Figure Description

[0064] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0065] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0066] Figure 1 To investigate the distribution of sulfate in sediments in experiments 1-3;

[0067] Figure 2 The Cd content at different depths in the sediments of Examples 1-3;

[0068] Each layer is 2 cm deep, and each layer contains, from top to bottom, the Cd content in the sediments of Examples 1, 2, and 3. Detailed Implementation

[0069] To better understand the above-mentioned objectives, features, and advantages of this disclosure, the solutions disclosed herein will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0070] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this disclosure may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some, and not all, of the embodiments of this disclosure.

[0071] This disclosure describes the detection methods involved in the embodiments:

[0072] This disclosure utilizes ion chromatography to detect the concentration of sulfate at different depths in sediments. The detection method is as follows: pore water samples at different depths are collected using a Peeper filter, the pore water is filtered through a 0.45 μm cellulose acetate membrane, and the sulfate concentration is detected using ion chromatography.

[0073] Cd content detection: For the detection of Cd concentration in overlying water, this disclosure uses ICP-MS or ICP-OES to detect Cd concentration. First, the water sample is filtered through a 0.45μm cellulose acetate membrane and then acidified with nitric acid to pH≤2. Then, the total concentration is determined using ICP-MS or ICP-OES. For the extraction of different Cd forms from sediments, the BCR three-step extraction method is used for stepwise extraction. Then, the concentration of different Cd forms is determined using ICP-MS or ICP-OES. The Cd concentration is high in sediments with a depth of less than 6cm and is detected using ICP-OES, while the Cd concentration is low in sediments with a depth of more than 6cm and is detected using ICP-MS.

[0074] Sediment pretreatment:

[0075] In this embodiment, the sediments were collected from shallow sediments in Baiyangdian Lake. To simulate the state of sediments in a natural environment, the sediments underwent pretreatment, including the following steps:

[0076] 3.1L of shallow sediments from Baiyangdian Lake were collected, mixed under anaerobic conditions (using nitrogen stripping to maintain dissolved oxygen concentration below 2mg / L), and placed in a culture column. Deionized water (overhead water) was injected, and the column was stably cultured under anaerobic conditions for 14 days. The depths of the sediments and overhead water were 15cm and 25cm, respectively, and the bottom 15cm of the outer wall of the culture column was wrapped with tin foil.

[0077] Inquiry Experiments 1-3

[0078] To investigate the distribution of sulfate in sediments, this experiment involved adding different concentrations of sulfate to pretreated sediments.

[0079] Experiment 1 included the following steps: Dissolve Na2SO4 in 1L of overlying water and re-inject it into the culture column. Let it stand for 30 days. The concentration of Na2SO4 in the overlying water was 199.5 mg / L.

[0080] The difference between Experiment 2 and Experiment 1 is that the concentration of Na2SO4 in the overlying water is 247.6 mg / L.

[0081] The difference between Experiment 3 and Experiment 1 is that the concentration of Na2SO4 in the overlying water is 158.7 mg / L.

[0082] The concentration of sulfate at different depths in the sediment was detected using ion chromatography, and the results are as follows: Figure 1 As shown.

[0083] Figure 1 To investigate the distribution of sulfate in the sediment in experiments 1-3, it was found that sulfate can be distributed in sediment at a depth of 0-14 cm, thus reacting with sulfate-reducing bacteria. Moreover, sulfate is mainly concentrated in sediment at a depth of 0-10 cm, and the dredging step does not affect the reaction between sulfate and sulfate-reducing bacteria.

[0084] Example 1

[0085] This embodiment provides a method for treating sediments containing heavy metal pollutants. First, the heavy metal pollutants are added to pretreated sediments to obtain sediments containing heavy metal pollutants. The method includes the following steps:

[0086] Dissolve Cd(NO3)2·4H2O in 1L of top dressing water and then reinject it into the culture column. At this time, Cd 2+ The concentration in the overlying water was 114.5 mg / L, and the culture was carried out for 14 days.

[0087] A method for treating sediments containing heavy metal pollutants includes the following steps:

[0088] (1) Sulfate input: Dissolve Na2SO4 in 1L of overlying water and then re-inject it into the culture column. At this time, the concentration of Na2SO4 in the overlying water is 199.5mg / L. Let it stand for 30 days.

[0089] (2) Cd content detection: ICP-MS and ICP-OES were used to detect the Cd content in sediments at depths of 0-16 cm to determine the Cd content at different depths. The results are shown in Table 1 and... Figure 2 As shown;

[0090] (3) Dredging: Remove sediments with a heavy metal content of more than 70%.

[0091] Example 2

[0092] This embodiment provides a method for treating sediments containing heavy metal pollutants. First, the heavy metal pollutants are added to pretreated sediments to obtain sediments containing heavy metal pollutants. The method includes the following steps:

[0093] Dissolve Cd(NO3)2·4H2O in 1L of top dressing water and then reinject it into the culture column. At this time, Cd 2+ The concentration in the overlying water was 96.5 mg / L, and the culture lasted for 14 days.

[0094] A method for treating sediments containing heavy metal pollutants includes the following steps:

[0095] (1) Sulfate input: Dissolve Na2SO4 in 1L of overlying water and then re-inject it into the culture column. At this time, the concentration of Na2SO4 in the overlying water is 247.6mg / L. Let it stand for 30 days.

[0096] (2) Cd content detection: ICP-MS and ICP-OES were used to detect the Cd content in sediments at depths of 0-16 cm to determine the Cd content at different depths. The results are shown in Table 1 and... Figure 2 As shown;

[0097] (3) Dredging: Remove sediments with a heavy metal content of more than 70%.

[0098] Example 3

[0099] This embodiment provides a method for preventing heavy metal pollutants from existing in ionic form in sediments, including the following steps:

[0100] (1) Sulfate input: Take 1L of overlying water from the pretreated sediment to dissolve Na2SO4 and then re-inject it into the culture column. At this time, the concentration of Na2SO4 in the overlying water is 158.7mg / L. Let it stand for 30 days.

[0101] (2) Cd input: Dissolve Cd(NO3)2·4H2O in 1L of topcoat water and then re-inject it into the culture column. At this time, Cd 2+ The concentration in the overlying water was 120.9 mg / L, and the culture lasted for 14 days.

[0102] (3) Cd content detection: ICP-MS and ICP-OES were used to detect the Cd content in sediments at depths of 0-16 cm to determine the Cd content at different depths. The results are shown in Table 1 and... Figure 2 As shown;

[0103] (4) Dredging: Remove sediments with a heavy metal content of more than 70%.

[0104] Comparative Example 1

[0105] This comparative example provides a method for treating sediments containing heavy metal pollutants. The difference from Example 1 is that step (1) sulfate input is omitted.

[0106] Comparative Example 2

[0107] This comparative example provides a method for treating sediments containing heavy metal pollutants. The difference from Example 1 is that step (3) dredging is omitted.

[0108] Comparative Example 3

[0109] This comparative example provides a method for treating sediments containing heavy metal pollutants. The difference from Example 2 is that step (1) sulfate input is omitted.

[0110] Comparative Example 4

[0111] This comparative example provides a method for preventing heavy metal pollutants from existing in ionic form in sediments. The difference from Example 3 is that step (1) sulfate input is omitted.

[0112] The cadmium distribution in the sediments of Examples 1-4 and Comparative Examples 1-3 is shown in Table 1 below:

[0113] Table 1

[0114]

[0115]

[0116] As shown in Examples 1-3, heavy metals are mainly concentrated in a layer of sediment less than 2 cm deep, with heavy metal content exceeding 70%. Therefore, this disclosure uses dredging to remove sediment with a heavy metal content exceeding 70%, resulting in more thorough removal of heavy metals. A comparison of Examples 1-3 and Comparative Examples 1-4 shows that this disclosure, through a layered treatment method combining sulfate addition and dredging, can effectively fix heavy metal ions in sediments and effectively remove over 70% of heavy metals, resulting in a more thorough treatment of heavy metals in sediments.

[0117] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0118] The above description is merely a specific embodiment of this disclosure, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for treating sediments containing heavy metal pollutants, comprising a stratified treatment approach, utilizing sulfides generated from sulfate reduction to fix available heavy metals in the sediments, and combining this with dredging to remove sediments containing more than 70% heavy metals, characterized in that, The processing method includes: (1) Sulfate was added to the pretreated sediment I and allowed to stand to obtain sediment II; (2) Take sediment II samples from different depths for testing to determine the content of heavy metals at different depths in sediment II; (3) Remove sediments with a heavy metal content of more than 70% by dredging; The sediment I mentioned in step (1) is selected from sediments in a lake, and the sediment I contains heavy metal pollutants; The treatment method further includes sediment pretreatment: placing the sediment in a culture column, injecting overlying water, and culturing it stably under anaerobic conditions to obtain pretreated sediment I, wherein the overlying water is deionized water; The method of adding sulfate is to add sulfate to the overlying water of the sediment I, wherein the concentration of sulfate in the overlying water is 150-250 mg / L; The settling time is 30-40 days to allow sufficient time for sulfates to enter the sediment and react with sulfate-reducing bacteria.

2. A method for preventing heavy metal pollutants from existing in ionic form in sediments, comprising treating the sediments using a stratified treatment approach, utilizing sulfides generated by sulfate reduction to fix the available heavy metals in the sediments, and combining this with dredging to remove sediments with a heavy metal content of 70% or more, characterized in that... The processing method includes: (1) Sulfate was added to the pretreated sediment III and allowed to stand to obtain sediment IV; (2) After the sediment IV is contaminated with heavy metals, sediment V is cultured and samples of sediment V from different depths are taken for testing to determine the content of heavy metals at different depths in sediment V; (3) Remove sediments V with a heavy metal content of more than 70% by dredging; Sediment III mentioned in step (1) is selected from sediments at the river mouth after storm runoff and / or sediments in the shallow lake area caused by seasonal flooding; The treatment method further includes sediment pretreatment: placing the sediment in a culture column, injecting overlying water, and culturing it stably under anaerobic conditions to obtain pretreated sediment III, wherein the overlying water is deionized water; The method of adding sulfate is to add sulfate to the overlying water of sediment III, wherein the concentration of sulfate in the overlying water is 150-250 mg / L; The settling time is 30-40 days to allow sufficient time for sulfates to enter the sediment and react with sulfate-reducing bacteria.

3. The processing method according to claim 1 or 2, characterized in that, SO4 in sulfate 2- The molar ratio of the heavy metal to the heavy metal pollutant is (1-2):

1.

4. The processing method according to claim 1 or 2, characterized in that, The sulfate is selected from sodium sulfate.

5. The processing method according to claim 1 or 2, characterized in that, The detection method is to use ICP-MS and / or ICP-OES for detection.

6. The processing method according to claim 2, characterized in that, The culture time is 12-15 days.

7. The processing method according to claim 1 or 2, characterized in that, The heavy metal is selected from Cd, Pd, Zn, Ni or Cu.

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