Heavy metal contaminated soil remediation method based on magnetic separation

Abstract

The invention relates to the field of contaminated soil remediation, and provides a heavy metal contaminated soil remediation method based on magnetic separation, which comprises the following steps: acquiring contaminated soil, and air-drying, crushing and screening the contaminated soil to obtain to-be-treated soil; determining a magnetic field magnetic value, and performing magnetic separation on the to-be-treated soil according to the magnetic field magnetic value to obtain magnetic separation soil; obtaining first leaching acid and second leaching acid, and preparing the first leaching acid and the second leaching acid to obtain a compound leaching agent; and adding the compound eluting agent into the magnetic separation soil, determining a water-soil ratio, adding purified water into the magnetic separation soil according to the water-soil ratio, uniformly mixing, carrying out oscillation reaction at normal temperature, and separating the compound eluting solution, thereby finishing the remediation of the heavy metal contaminated soil.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of contaminated soil remediation, and particularly relates to a heavy metal contaminated soil remediation method based on magnetic separation. BACKGROUND

[0002] With the rapid development of industrialization and urbanization, soil pollution and degradation problems are increasingly prominent. Soil is an important sink of heavy metals, and activities such as mining, smelting, electroplating, and coal burning can exacerbate soil heavy metal pollution problems. Due to the biological toxicity, non-degradability, and bioaccumulation of heavy metals, remediation of heavy metal contaminated soil is imminent. Remediation technologies for heavy metal contaminated soil generally include solidification and stabilization remediation technology, electrokinetic remediation technology, phytoremediation technology, and soil washing remediation technology. Considering factors such as remediation cost, remediation period, and remediation effect, soil washing remediation technology is most widely used in actual remediation cases. Soil washing technology is to add a washing agent to the soil to contact the soil sufficiently, transfer heavy metals from the soil to the washing liquid, and finally treat the washing liquid to meet the discharge standard. However, for the case of high content of difficult-to-wash heavy metals in soil, low-concentration washing agents often cannot achieve good washing effect, and high-concentration washing agent addition will lead to increased remediation cost and secondary pollution. SUMMARY

[0003] The present application aims to at least solve one of the problems in the related art. To this end, the present application provides a heavy metal contaminated soil remediation method based on magnetic separation, which realizes efficient remediation of heavy metal contaminated soil.

[0004] The present application provides a heavy metal contaminated soil remediation method based on magnetic separation, comprising: S1: obtaining contaminated soil, drying, crushing, and screening the contaminated soil to obtain treated soil; S2: determining a magnetic field magnetic force value, and performing magnetic separation on the treated soil according to the magnetic field magnetic force value to obtain magnetic separation soil; S3: obtaining a first washing acid and a second washing acid, and configuring the first washing acid and the second washing acid to obtain a compounded washing agent; S4: adding the compounded washing agent to the magnetic separation soil, determining a water-soil ratio, adding pure water to the magnetic separation soil according to the water-soil ratio, mixing, and then oscillating and reacting at room temperature to separate the compounded washing liquid, thereby completing remediation of the heavy metal contaminated soil.

[0005] According to the heavy metal contaminated soil remediation method based on magnetic separation provided by the present application, in step S1, the water content of the treated soil is less than 20%.

[0006] According to the heavy metal contaminated soil remediation method based on magnetic separation provided by the application, in step S1, the diameter of the soil to be treated is less than 2mm.

[0007] According to the heavy metal contaminated soil remediation method based on magnetic separation provided by the application, in step S2, the magnetic field magnetic force value ranges from 6000Gs to 10000Gs.

[0008] According to the heavy metal contaminated soil remediation method based on magnetic separation provided by the application, in step S2, the soil to be treated is subjected to magnetic separation by a dry-type magnetic separation device, and the soil to be treated is in full contact with the dry-type magnetic separation device.

[0009] According to the heavy metal contaminated soil remediation method based on magnetic separation provided by the application, in step S3, the first leaching acid is citric acid, the second leaching acid is oxalic acid, and the molar ratio of the first leaching acid to the second leaching acid ranges from 1:1 to 3:1.

[0010] According to the heavy metal contaminated soil remediation method based on magnetic separation provided by the application, in step S3, the mass of the first leaching acid and the second leaching acid in the compound leaching agent accounts for 1% to 3% of the soil subjected to magnetic separation.

[0011] According to the heavy metal contaminated soil remediation method based on magnetic separation provided by the application, in step S4, the water-soil ratio ranges from 1:1 to 3:1.

[0012] According to the heavy metal contaminated soil remediation method based on magnetic separation provided by the application, in step S4, the duration of the oscillation reaction ranges from 30 minutes to 4 hours.

[0013] The one or more technical solutions in the embodiments of the application have at least one of the following technical effects: The heavy metal contaminated soil remediation method based on magnetic separation provided by the application can separate the heavy metal in the soil by magnetic separation before leaching, and the contaminated particles with high magnetic permeability can be separated by applying a magnetic field, so that the resource recycling of the magnetic residue soil is realized, the content ratio of the residual state and the iron-manganese oxide combined state heavy metal in the soil is reduced, the influence of the heavy metal particles on the leaching process is reduced, and the amount of the leaching agent can be greatly reduced. The separated residue soil can be disposed by sintering due to the high content of iron and other raw materials, and will not be affected by the leaching agent. In addition, a new compound leaching agent, oxalic acid / citric acid leaching agent, is developed, which can wash most of the exchangeable and unstable state heavy metals in the soil into the eluent. The remediation technology provided by the application has low cost and good effect, and has wide practical application prospect in the field of soil remediation.

[0014] Additional aspects and advantages of the present application will be made apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the present application or the prior art, the drawings needed to be used in the following embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort.

[0016] Figure 1 is a flowchart of a heavy metal contaminated soil remediation method based on magnetic separation provided by the present application. DETAILED DESCRIPTION

[0017] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort belong to the protection scope of the present application. The following embodiments are used to illustrate the present application, but cannot be used to limit the scope of the present application.

[0018] In the description of the embodiments of the present application, it should be noted that, in addition, the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0019] In the description of the embodiments of the present application, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected", "connected" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0020] In the embodiments of the present application, unless otherwise explicitly specified and limited, the first feature is "on" or "under" the second feature, which can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature "above", "over" and "on" the second feature can be that the first feature is directly above or obliquely above the second feature, or it only means that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "under" and "under" the second feature can be that the first feature is directly below or obliquely below the second feature, or it only means that the horizontal height of the first feature is less than that of the second feature.

[0021] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the embodiments of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Also, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples without contradiction.

[0022] The specific embodiments of the present application will be described below in conjunction with Figure 1 The specific embodiments of the present application will be described below in conjunction with Figure 1 A flowchart of a heavy metal contaminated soil remediation method based on magnetic separation.

[0023] Embodiment 1: First, the contaminated soil needs to be obtained, which is a heavy metal contaminated soil with a manganese concentration of 10500 mg / kg and a vanadium concentration of 985 mg / kg in the soil. Then, the contaminated soil is naturally air-dried to have a moisture content of less than 20%. After air-drying, it is broken and sieved through a 2mm sieve to make the diameter of the soil to be treated less than 2mm, so that the soil to be treated is obtained. Here, the moisture content of the contaminated soil is controlled, the contaminated soil is broken and sieved to facilitate subsequent magnetic separation, to avoid interference of the magnetic separation process caused by too large soil particles or too high moisture content, and to ensure that the soil and water can be mixed and reacted fully.

[0024] Then, the magnetic field magnetic force value is determined, and the value range of the magnetic field magnetic force value is 6000Gs~10000Gs. In this embodiment, the magnetic field magnetic force value is selected as 6000Gs, and then 1kg of the soil to be treated is sent into the dry magnetic separation equipment, so that the dry magnetic separation equipment can generate a magnetic field with a magnetic field strength of the magnetic field magnetic force value, and the soil to be treated needs to be in full contact with the dry magnetic separation equipment, and the non-magnetic substances are attracted and removed, so as to perform magnetic separation on the soil to be treated. The dry magnetic separation equipment can separate the heavy metal particles in the soil to be treated, and the processing capacity is large, so that a large amount of soil to be treated can be processed, so that the heavy metal particles in the soil to be treated are removed in advance to obtain the magnetic separation soil. In this way, not only can the heavy metal particles be recycled, but also the interference of the heavy metal particles and debris on the subsequent oscillation reaction or the interference of the wet heavy metal particles and debris on the magnetic separation process can be avoided, so that the compounded leaching agent can fully play its effect.

[0025] Then the first elution acid and the second elution acid are obtained, where the first elution acid is citric acid, the second elution acid is oxalic acid, and the molar ratio of the first elution acid to the second elution acid is 1:1-3:1. In this embodiment, the molar ratio of the first elution acid to the second elution acid is 3:1, the first elution acid and the second elution acid are mixed according to the molar ratio, and the sum of the mass of the first elution acid and the second elution acid is 1%-3% of the mass of the magnetic separation soil. Here, the sum of the mass of the first elution acid and the second elution acid is 3% of the mass of the magnetic separation soil, the first elution acid and the second elution acid are dissolved in water, and the compound eluant is obtained.

[0026] Subsequently, the compound eluant is added to the magnetic separation soil, and the water-soil ratio is determined. The water-soil ratio is in the range of 1:1-3:1, and in this embodiment, the water-soil ratio is selected as 3:1. Pure water is added to the magnetic separation soil to which the compound eluant is added, so that the ratio of water to magnetic separation soil reaches the water-soil ratio and is uniformly mixed, and the suspension to be treated is obtained. The suspension to be treated is subjected to oscillation reaction at room temperature, and the oscillation reaction time is 30 minutes-4 hours. In this embodiment, the oscillation reaction time is selected as 4 hours, and the elution is completed. Subsequently, the compound eluant, i.e., the compound eluant and the added pure water, is separated from the soil, so that the heavy metal pollution in the soil is removed. The compound eluant and the soil are separated, and the treated soil is obtained, and the heavy metal contaminated soil is repaired.

[0027] Embodiment 2 In embodiment 2, the other steps and parameters are the same as those in embodiment 1, except that the magnetic field magnetic force value in step S1 is changed to 8000Gs, and the repair effect is shown in Table 1.

[0028] Embodiment 3 In embodiment 3, the other steps and parameters are the same as those in embodiment 1, except that the magnetic field magnetic force value in step S1 is changed to 10000Gs, and the repair effect is shown in Table 1.

[0029] Embodiment 4 In embodiment 4, the other steps and parameters are the same as those in embodiment 1, except that the magnetic field magnetic force value in step S1 is changed to 10000Gs, and the sum of the mass of the first elution acid and the second elution acid in step S3 is selected as 2% of the mass of the magnetic separation soil, and the repair effect is shown in Table 1.

[0030] Embodiment 5 In embodiment 5, the other steps and parameters are the same as those in embodiment 1, except that the magnetic field magnetic force value in step S1 is changed to 10000Gs, and the sum of the mass of the first elution acid and the second elution acid in step S3 is selected as 1% of the mass of the magnetic separation soil, and the repair effect is shown in Table 1.

[0031] Example 6: In Example 6, other steps and parameters are the same as Example 1, except that the magnetic field magnetic force value in step S1 is changed to 10000Gs, and the molar ratio of the first leaching acid and the second leaching acid in step S3 is 1:1, and the repair effect is shown in Table 1.

[0032] Example 7: In Example 7, other steps and parameters are the same as Example 1, except that the magnetic field magnetic force value in step S1 is changed to 10000Gs, and the water-soil ratio selected in step S4 is 1:1, and the repair effect is shown in Table 1.

[0033] Example 8: In Example 8, other steps and parameters are the same as Example 1, except that the magnetic field magnetic force value in step S1 is changed to 10000Gs, and the water-soil ratio selected in step S4 is 2:1, and the repair effect is shown in Table 1.

[0034] Example 9: In Example 9, other steps and parameters are the same as Example 1, except that the magnetic field magnetic force value in step S1 is changed to 10000Gs, and the duration of the oscillation reaction in step S4 is 30 minutes, and the repair effect is shown in Table 1.

[0035] Example 10: In Example 10, other steps and parameters are the same as Example 1, except that the magnetic field magnetic force value in step S1 is changed to 10000Gs, and the duration of the oscillation reaction in step S4 is 1 hour, and the repair effect is shown in Table 1.

[0036] Example 11: In Example 11, other steps and parameters are the same as Example 1, except that the magnetic field magnetic force value in step S1 is changed to 10000Gs, and the duration of the oscillation reaction in step S4 is 2 hours, and the repair effect is shown in Table 1.

[0037] In addition to Examples 1-11, Comparative Example 1 is also provided: In Comparative Example 1, other steps and parameters are the same as Example 1, except that step S2 is deleted, and after obtaining the soil to be treated and configuring the compound leaching agent, the compound leaching agent is directly added to the soil to be treated, and the repair effect is shown in Table 1.

[0038] The source and data of the heavy metal contaminated soil used in each embodiment and comparative example are the same, and the exchangeable state, carbonate bound state, iron and manganese oxide bound state, organic bound state and residual state heavy metals in the remediated soil are extracted to obtain the removal rates of vanadium and manganese, and each embodiment and comparative example is repeated three times, and the average of the removal rates of vanadium and manganese obtained by the three times of execution is taken as the removal rate of vanadium and manganese in the comparative example or embodiment. Table 1 is a comparison table of heavy metal removal rates of heavy metal contaminated soil: Table 1 Comparison table of heavy metal removal rates of heavy metal contaminated soil

[0039] In addition, the distribution form of heavy metal pollution in the remediated soil is also particularly counted for example 3 and comparative example 1, and table 2 is a schematic table of the distribution form of heavy metal pollution in the remediated soil: Table 2 Schematic table of the distribution form of heavy metal pollution in the remediated soil From the above analysis, it can be seen that examples 1-3, under the condition that other steps and parameters are the same, set the magnetic field magnetic force value of 6000Gs, 8000Gs and 10000Gs respectively, and it can be found that the higher the magnetic field magnetic force value, the higher the heavy metal removal efficiency in the soil. Examples 3-5 show the influence of different amounts of compound leaching agent on the removal rate after magnetic separation treatment, it can be seen that the larger the amount of compound leaching agent, the higher the removal rate, but too large amount of compound leaching agent may affect other aspects of the characteristics of the remediated soil. Examples 3, 6 compare the heavy metal removal effect of the compound leaching agent prepared by different molar ratios of the first leaching acid and the second leaching acid, the results show that when the molar ratio of the first leaching acid to the second leaching acid is 3:1, the heavy metal removal effect in the soil is better. Examples 3, 7-8 compare the heavy metal removal effect in the soil under different water-soil ratios, the results show that the higher the water-soil ratio, the more fully the soil and the leaching agent are mixed, and the better the heavy metal removal effect in the soil, but too high water-soil ratio may lead to difficulty in separating the compound leaching agent from the soil. Examples 3, 10, 11 compare the heavy metal removal effect in the soil under different oscillation reaction times, the results show that the longer the oscillation reaction time, the better the removal effect. Comparative example 1 and example 3 show the contribution of magnetic separation in step S2 to heavy metals, it can be seen that early magnetic separation can more effectively remove the form of heavy metals that are difficult to leach, and the leaching in step S4 does not affect the effect of magnetic separation because it is performed later. It can be seen that the removal rate of vanadium in example 3 can reach 85.6%, and the removal rate of manganese can reach 78.6%. In comparative example 1 without magnetic separation treatment and directly leaching, the removal rate of vanadium is only 25.3%, and the removal rate of manganese is only 30.1%, which shows that magnetic separation before leaching can significantly improve the removal efficiency of heavy metals in the soil.

[0040] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the same; although the present application has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for remediation of heavy metal contaminated soil based on magnetic separation, characterized in that, The method comprises the following steps: S1: obtaining contaminated soil, air-drying, crushing and screening the contaminated soil to obtain treated soil; S2: determining the magnetic field magnetic force value, and performing magnetic separation on the treated soil according to the magnetic field magnetic force value to obtain magnetic separation soil; S3: obtaining a first leaching acid and a second leaching acid, and configuring the first leaching acid and the second leaching acid to obtain a compound leaching agent; S4: adding the compound leaching agent to the magnetic separation soil, determining the water-soil ratio, adding pure water to the magnetic separation soil according to the water-soil ratio, mixing, and then performing oscillation reaction at room temperature and separating the compound leaching liquid to complete the remediation of the heavy metal contaminated soil.

2. A method for remediation of heavy metal contaminated soil based on magnetic separation according to claim 1, characterized in that, In step S1, the moisture content of the treated soil is less than 20%.

3. The method for remediation of heavy metal contaminated soil based on magnetic separation according to claim 1, characterized in that, In step S1, the diameter of the treated soil is less than 2 mm.

4. The method for remediation of heavy metal contaminated soil based on magnetic separation according to claim 1, characterized in that, In step S2, the magnetic field magnetic force value ranges from 6000Gs to 10000Gs.

5. The method for remediation of heavy metal contaminated soil based on magnetic separation according to claim 1, characterized in that, In step S2, the treated soil is subjected to magnetic separation by a dry magnetic separation device, and the treated soil is in full contact with the dry magnetic separation device.

6. The method for remediation of heavy metal contaminated soil based on magnetic separation according to claim 1, characterized in that, In step S3, the first leaching acid is citric acid, the second leaching acid is oxalic acid, and the molar ratio of the first leaching acid to the second leaching acid is 1:1 to 3:

1.

7. The method for remediation of heavy metal contaminated soil based on magnetic separation according to claim 1, characterized in that, In step S3, the mass of the first leaching acid and the second leaching acid in the compound leaching agent is 1% to 3% of the magnetic separation soil.

8. The method for remediation of heavy metal contaminated soil based on magnetic separation according to claim 1, characterized in that, In step S4, the water-soil ratio is 1:1 to 3:

1.

9. The method for remediation of heavy metal contaminated soil based on magnetic separation according to claim 1, characterized in that, In step S4, the oscillation reaction lasts for 30 minutes to 4 hours.

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