Method for removing combined pollution of heavy metal ions and organic matters in soil by activating sulfite with manganese dioxide assisted by complexing agent

Abstract

The invention relates to a method for removing combined pollution of heavy metal ions and organic matters in soil by activating sulfite with manganese dioxide assisted by a complexing agent. The method specifically comprises the following steps: providing a mixture of a complexing agent, sulfite and MnO2; and the mixture and the polluted soil are fully infiltrated and mixed for reaction, and finally the heavy metal ions and the organic matter in the soil are removed. According to the method, humic acid is used as a complexing agent to assist manganese dioxide in activating sodium sulfite, heavy metal ions in soil are adsorbed, and organic matter is removed synchronously. The used complexing agent humic acid can enhance the fertility of the soil, improve the soil structure, improve the water-retaining property and drought resistance of the soil and promote the growth and development of plants.

Description

Technical Field

[0001] The invention relates to the technical field of soil remediation, and in particular to a method for removing the combined pollution of heavy metal ions and organic matter in soil by activating sulfite with the aid of a complexing agent using manganese dioxide. Background Art

[0002] The environmental quality and safety of soil and groundwater are crucial to the sustainable development of agriculture, society and economy, as well as human health. With the rapid advancement of urbanization and industrialization, the problem of soil heavy metal and organic pollution caused by human activities is becoming increasingly serious. Heavy metals are not only highly mobile, but also extremely toxic, and once they enter the environment, they are difficult to degrade. In addition to heavy metal pollution, organic pollutants are also an important manifestation of soil pollution. Although the concentration of organic matter in water is relatively low, they are easily accumulated in organisms, their toxic side effects are significant, and they have the potential risk of causing cancer and teratogenesis.

[0003] At present, the main methods for removing heavy metals from soil include cleaning and remediation, phytoremediation and microbial remediation. Although cleaning and remediation are effective, the cost of remediation is usually high, and it may cause significant disturbances to the basic properties of the soil, affecting its normal functions. Phytoremediation has problems such as long time, low removal efficiency and unstable heavy metal enrichment capacity. Only a very small number of specific plants have strong heavy metal enrichment capacity, and plants in different regions also have obvious differences in physiological characteristics. In terms of microbial remediation, changes in species composition due to environmental factors may affect the remediation effect. At the same time, it has high requirements for environmental conditions and requires pretreatment of difficult-to-degrade or toxic compounds. Soil remediation technologies for organic contaminated sites can be divided into physical remediation, chemical remediation and biological remediation according to the operating principle. Physical remediation requires higher soil property requirements, has a limited scope of application and a long remediation cycle; common oxidation technologies in chemical remediation, such as ozone oxidation, not only have high energy consumption and low ozone utilization, but may also produce by-products such as bromate. The Fenton oxidation method is limited by a narrow pH range and ferrous ions are easily precipitated. Bioremediation technology also faces the disadvantages of high environmental requirements, suitability for low-concentration pollution, and long remediation cycles.

[0004] In order to achieve the remediation of soil contaminated by heavy metals and organic matter, the present invention proposes a method for simultaneously removing manganese and organic pollutants in manganese-containing soil by using a chelating agent and sulfite. Summary of the invention

[0005] In order to solve the technical problem of excessive manganese and organic pollutants in soil in the prior art, the present invention proposes a method for removing the combined pollution of heavy metal ions and organic matter in soil by using a complexing agent to assist manganese dioxide to activate sulfite. The present invention uses humic acid as a complexing agent to assist manganese dioxide to activate sodium sulfite, thereby reducing the biologically effective state of Mn in the soil and simultaneously removing the combined pollutants of heavy metal ions and organic matter.

[0006] The object of the present invention is to provide a method for removing the combined pollution of heavy metal ions and organic matter in soil by activating sulfite with the aid of a complexing agent using manganese dioxide, comprising the following steps:

[0007] Providing a mixture of a complexing agent, a sulfite and MnO2;

[0008] The mixture is fully infiltrated and mixed with the contaminated soil to react, thereby ultimately achieving the removal of heavy metal ions and organic matter.

[0009] In some embodiments of the present invention, the complexing agent is selected from humic acid. The humic acid is derived from peat, lignite, weathered coal, etc. The present invention utilizes humic acid to react with manganese dioxide to form a complex, thereby promoting the autocatalytic oxidation of sulfite.

[0010] In some embodiments of the present invention, the sulfite is selected from one or more of sodium sulfite, potassium sulfite, sodium bisulfite, and potassium bisulfite.

[0011] In some embodiments of the present invention, the concentration of MnO2 is 50 μM to 2 mM, and the molar ratio of MnO2 to the complexing agent is (1:2)-(1:10).

[0012] In some embodiments of the present invention, the concentration of MnO2 is 50 μM to 2 mM, and the molar ratio of MnO2 to sulfite is (1:2)-(1:20).

[0013] In some embodiments of the present invention, the concentration of MnO2 is 50 μM to 2 mM, and the molar ratio of MnO2, complexing agent and sulfite is 1:(2-5):(2-20).

[0014] In some embodiments of the present invention, the pH of the contaminated soil is 5-7.

[0015] In some embodiments of the present invention, the content of organic matter in the contaminated soil is 100 μg / kg to 200 μg / kg.

[0016] In some embodiments of the present invention, the content of heavy metal ions in the contaminated soil is 0.1 mg / kg to 1 mg / kg.

[0017] In some embodiments of the present invention, the organic matter includes polycyclic aromatic hydrocarbons and organochlorine pesticides, including one or more of chlorophenols, naphthalene, acenaphthylene, acenaphthene, phenanthrene, anthracene, fluoranthene, benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, pyrene, benzopyrene, dibenzanthracene, indenopyrene, benzoperylene, organochlorine pesticides DDT, organochlorine pesticides 666, etc.

[0018] In some embodiments of the present invention, the reaction time is 15 to 30 minutes;

[0019] The heavy metals include one or more of Ti(I), Pb(II), Cd(II), As(III), and Sb(III).

[0020] The principle of the present invention is as follows: Humic acid is a macromolecular organic substance widely present in nature and an important component of soil. Using humic acid as a complexing agent has environmental advantages. The humic acid complexing agent is mixed with sulfite and manganese dioxide in a specific proportion and injected into the contaminated soil to be treated. The complexing agent reacts with manganese dioxide to form a complex, thereby promoting the autocatalytic oxidation of sulfite. In this process, HSO3- is oxidized to SO3 ·- , followed by SO3 ·- Further converted into SO5 ·- , and finally converted into HSO5 - At the same time, the Mn(IV)-complexing agent is reduced to form a Mn(III)-complex. HSO5 - It can oxidize Mn(III)-complexing agent to Mn(V)-complexing agent. Mn(V) can quickly oxidize and decompose organic matter, and itself is converted into MnO2. As the reaction proceeds, MnO2 gradually aggregates into particles to form residual MnO2 solid. The MnO2 generated by the reaction has a stronger ability to adsorb heavy metal ions and can adsorb heavy metal ions in the soil, thereby achieving the simultaneous removal of heavy metal ions and organic pollutants in the soil.

[0021] The above technical solution of the present invention has the following advantages compared with the prior art:

[0022] The present invention can oxidize and decompose organic matter in the soil by injecting a complexing agent, MnO2 and a sulfite mixture into the soil, and simultaneously generate MnO2 with a stronger heavy metal ion adsorption capacity. The generated MnO2 is a commonly used adsorption material in soil remediation, and can adsorb and remove heavy metal ions such as Ti(I), Pb(II), Cd(II), As(III), Sb(III), etc.

[0023] The invention is suitable for soil conditions with a pH of 5 to 7, and the method is simple, the use of agents is green and environmentally friendly, and the complexing agent humic acid used can enhance soil fertility, improve soil structure, increase soil water retention and drought resistance, and promote plant growth and development. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0025] Embodiment 1:

[0026] This embodiment provides a method for removing soil contaminated by Cd(II) and organic matter by activating sulfite with manganese dioxide assisted by a complexing agent, as follows:

[0027] Step 1: Provide a soil sample, wherein the Cd(II) content in the soil is 0.5 mg / kg and the pentachlorophenol content is 150 μg / kg; the MnO2 concentration in the mixed solution is 200 μM, and the molar ratio of MnO2: humic acid (derived from peat): sodium sulfite is 1:5:10; determine the dosage of humic acid and sulfite, adjust the soil to a pH of 6, and the reaction time after addition is 20 minutes.

[0028] Step 2: After the reaction is terminated, 1 gram of the prepared composite contaminated soil sample is weighed into a 100 mL conical flask, and 100 ml of 10 g / L Tween 80 eluent solution is added for elution. After the elution is completed, the mixed solution is centrifuged to obtain the supernatant, and the residual amount of Cd(II) and pentachlorophenol in the supernatant is determined.

[0029] The residual content of Cd(II) was quantitatively determined by ICP-OES, and the content of pentachlorophenol after filtration was quantitatively detected by high performance liquid chromatography. The removal rates of Cd(II) and pentachlorophenol were determined by comparing the results with those of the original soil.

[0030] The experimental results are shown in Table 1.

[0031] Embodiment 2:

[0032] The difference from Example 1 is that the soil pH is adjusted to pH = 5. The removal rates of Cd(II) and pentachlorophenol after treatment are shown in Table 1 below.

[0033] Embodiment 3:

[0034] The difference from Example 1 is that the soil pH is adjusted to pH = 7. The removal rates of Cd(II) and pentachlorophenol after treatment are shown in Table 1 below.

[0035] Embodiment 4:

[0036] The difference from Example 1 is that the reaction time after adding the drug in this example is 15 minutes. The removal rates of Cd(II) and pentachlorophenol after treatment are shown in Table 1 below.

[0037] Embodiment 5:

[0038] The difference from Example 1 is that the reaction time after adding the drug in this example is 30 minutes. The removal rates of Cd(II) and pentachlorophenol after treatment are shown in Table 1 below.

[0039] Embodiment 6:

[0040] Different from Example 1, the humic acid complexing agent in this example is derived from lignite. The removal rates of Cd(II) and pentachlorophenol after treatment are shown in Table 1 below.

[0041] Embodiment 7:

[0042] Different from Example 1, the humic acid complexing agent in this example is derived from weathered coal, and the removal rates of Cd(II) and pentachlorophenol after treatment are shown in Table 1 below.

[0043] Embodiment 8:

[0044] Different from Example 1, the molar ratio of MnO2: complexing agent: sulfite is 1:1:2:10. The removal rates of Cd(II) and pentachlorophenol after treatment are shown in Table 1 below.

[0045] Embodiment 9:

[0046] Different from Example 1, the molar ratio of MnO2: complexing agent: sulfite is 1:1:10:10. The removal rates of Cd(II) and pentachlorophenol after treatment are shown in Table 1 below.

[0047] Embodiment 10:

[0048] Different from Example 1, the molar ratio of MnO2: complexing agent: sulfite is 1:1:5:2. The removal rates of Cd(II) and pentachlorophenol after treatment are shown in Table 1 below.

[0049] Embodiment 11:

[0050] Different from Example 1, the molar ratio of MnO2: complexing agent: sulfite is 1:1:5:5. The removal rates of Cd(II) and pentachlorophenol after treatment are shown in Table 1 below.

[0051] Embodiment 12:

[0052] Different from Example 1, the molar ratio of MnO2: complexing agent: sulfite is 1:1:5:20. The removal rates of Cd(II) and pentachlorophenol after treatment are shown in Table 1 below.

[0053] Comparative Example 1:

[0054] Different from Example 1, no complexing agent was added in this comparative example. The removal rates of Cd(II) and pentachlorophenol after treatment are shown in Table 1 below.

[0055] Comparative Example 2:

[0056] Different from Example 1, no sulfite was added in this comparative example. The removal rates of Cd(II) and pentachlorophenol after treatment are shown in Table 1 below.

[0057] Table 1

[0058] Cd(II) removal rate (%) Pentachlorophenol removal rate (%) Example 1 87.3 93.6 Example 2 80.6 88.3 Example 3 89.5 59.6 Example 4 76.9 89.2 Example 5 89.2 94.3 Example 6 87.5 92.1 Example 7 88.1 94.8 Example 8 81.6 86.1 Example 9 88.2 93.6 Example 10 63.2 70.5 Embodiment 11 80.6 82.1 Example 12 63.9 64.1 Comparative Example 1 8.1 5.7 Comparative Example 2 5.3 4.5

[0059] It can be seen from Examples 1-3 that pH affects the removal rate of Cd(II) and pentachlorophenol in the present invention. The present invention has a better removal effect on pentachlorophenol under the condition of pH=6. A lower pH will affect the conversion of MnO2 in the reaction system and inhibit the removal of Cd(II). A higher pH will affect the formation and stability of active species in the reaction system, thereby having a poor removal effect on pentachlorophenol. The treatment effect is best when pH=6.

[0060] It can be seen from Examples 1, 4, and 5 that the reaction time after adding the drug affects the removal effect. When the reaction time is 20 min, not only is there a better removal rate, but also time cost can be saved. If the reaction time is insufficient, the active species cannot effectively remove the organic pollutants, and the conversion rate of MnO2 is low, and the adsorption capacity for Cd(II) is also insufficient.

[0061] It can be seen from Examples 1, 6 and 7 that the removal effects of humic acid from different sources on pentachlorophenol and Cd(II) are similar, and each of the three has its own advantages.

[0062] It can be seen from Examples 1, 8-12 that the molar ratio of MnO2, complexing agent, and sulfite has a certain effect on the removal rate of Cd(II) and pentachlorophenol. Among them, the molar ratio of MnO2, complexing agent, and sulfite is 1:5:10, which has the best effect. Low concentration of complexing agent will lead to the conversion of active intermediates and reduced stability, thereby reducing the overall removal rate. When the concentration of sulfite is low, HSO5- is insufficiently generated, thereby affecting the occurrence of subsequent reactions. When the concentration of sulfite is high, sulfite will compete with HSO5- and active intermediates, resulting in poor removal effect.

[0063] It can be seen from Example 1 and Comparative Examples 1-2 that in the absence of a complexing agent, MnO2 cannot effectively activate sulfite to generate HSO 5-, thus failing to effectively oxidize and decompose organic matter, and failing to generate MnO2 with stronger metal ion adsorption capacity. In the absence of sulfite, HSO3 cannot be generated, and subsequent reactions cannot proceed, and simultaneous removal of Cd(II) and organic matter cannot be achieved.

[0064] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A method for removing the combined pollution of heavy metal ions and organic matter in soil by using a complexing agent to assist manganese dioxide in activating sulfite, characterized in that: The following steps are involved: Providing a mixture of a complexing agent, a sulfite and MnO2; The mixture is fully infiltrated and mixed with the contaminated soil to react, thereby ultimately achieving the removal of heavy metal ions and organic matter.

2. The method according to claim 1, characterized in that: The complexing agent is selected from humic acid.

3. The method according to claim 1, characterized in that: The sulfite is selected from one or more of sodium sulfite, potassium sulfite, sodium bisulfite and potassium bisulfite.

4. The method according to claim 1, characterized in that The molar ratio of MnO2 to the complexing agent is (1:2)-(1:10).

5. The method according to claim 1, characterized in that: The molar ratio of MnO2 to sulfite is (1:2)-(1:20).

6. The method according to claim 1, characterized in that The pH of the contaminated soil is 5-7.

7. The method according to claim 1, characterized in that The content of organic matter in the contaminated soil is 100 μg / kg to 200 μg / kg.

8. The method according to claim 1, characterized in that: The content of heavy metal ions in the contaminated soil is 0.1 mg / kg to 1 mg / kg.

9. The method according to claim 1, characterized in that: The organic substances include polycyclic aromatic hydrocarbons and organochlorine pesticides.

10. The method according to claim 1, characterized in that The reaction time is 15 to 30 minutes; The heavy metal ions include one or more of Ti(I), Pb(II), Cd(II), As(III), and Sb(III).