Application of a dual-effect remediation agent based on electrolytic manganese slag in the remediation of heavy metal contaminated soil

Abstract

The present invention relates to the technical field of environmental heavy metal soil remediation, and specifically to the application of a dual-effect remediation agent based on electrolytic manganese slag in the remediation of heavy metal contaminated soil. The present invention uses electrolytic manganese slag as a base material, mixes it with a calcium-containing material and performs ball milling modification, and utilizes the silicate components and iron and manganese elements therein to passivate the heavy metal ions in the soil, which can not only promote the passivation of heavy metals in the soil, but also increase the content of calcium, sulfur, magnesium, iron, manganese and other medium elements in the soil, and enhance the fertilizer effect of the soil. It only needs to mix the electrolytic manganese slag-based dual-effect remediation agent into the heavy metal contaminated soil without other operations, which has important environmental benefits and social value, and provides certain technical guidance for the resource utilization and harmlessness of electrolytic manganese slag.

Description

Technical Field

[0001] The invention relates to the technical field of environmental heavy metal soil remediation, and in particular to application of a dual-effect remediation agent using electrolytic manganese slag as a base material in the remediation of heavy metal contaminated soil. Background Art

[0002] With the increasing development of industrial and mining activities, a large amount of waste slag will be generated and piled up in mines or around factories. Through air deposition, rainwater melting, dust diffusion, etc., it will pollute the soil around mines or factories, causing heavy metal pollution in their surroundings, thus affecting human life and production activities.

[0003] Electrolytic manganese slag is the acid leaching residue produced by leaching ore powder with sulfuric acid in the process of producing electrolytic manganese. It has a very low content of heavy metals. The electrolytic manganese industry is a highly polluting industry. In the process of producing electrolytic manganese, a large amount of solid waste slag is produced, causing environmental pollution. The experimental results of Yu Qi et al. show that the leaching concentrations of metal elements such as Pb, As, and Zn in the solid waste slag are all lower than the leaching toxicity standard.

[0004] At present, for the treatment of heavy metal contaminated land, existing research at home and abroad mainly uses pure substances such as ferrous sulfate to compound into passivating agents to repair and stabilize heavy metals in the soil. However, since most compounds composed of pure chemical agents are chemically toxic in themselves, they are easy to cause soil pollution if used improperly. In addition, most passivating agents are aimed at soils contaminated by a single heavy metal or soils contaminated by similar heavy metals, and there are few studies on the simultaneous repair of soils contaminated by multiple heavy metals. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is firstly to provide a dual-effect repair agent based on electrolytic manganese slag that can be used in the remediation of heavy metal contaminated soil.

[0006] The substances in the electrolytic manganese slag can be activated to become substances containing muscovite and other similar silicates, providing silicon in the activated electrolytic manganese slag, and providing calcium, sulfur, magnesium, iron, manganese and other medium elements. Therefore, the use of electrolytic manganese slag to remove heavy metal ions in the passivated soil has broad prospects. The use of electrolytic manganese slag as a base material to prepare remediation materials that can be used for the remediation of heavy metal contaminated soil can effectively alleviate the heavy metal pollution in the soil and provide calcium, sulfur, magnesium, iron, manganese and other medium elements to the soil.

[0007] In order to achieve the above object, the present invention proposes the following technical solutions:

[0008] The present invention provides an application of a dual-effect repair agent with electrolytic manganese slag as a base material and the functions of passivating heavy metals and providing medium-element fertilizers in the repair of heavy metal-contaminated soil. The repair agent is a mixture of electrolytic manganese slag and a calcium-containing material, and the calcium-containing material is quicklime, slaked lime and / or limestone.

[0009] Furthermore, the heavy metals in the heavy metal contaminated soil include at least one of cadmium, lead and arsenic.

[0010] Furthermore, the specific operation of the application is: mixing the repair agent into the heavy metal contaminated soil according to a mass ratio of 0.2% to 5%.

[0011] When the above-mentioned repair agent based on electrolytic manganese slag is applied to heavy metal contaminated soil, it can not only promote the passivation of heavy metals in the soil, but also increase the content of effective silicon and other elements in the soil, and provide calcium, sulfur, magnesium, iron, manganese and other medium elements to enhance the fertilizer effect of the soil. At the same time, the application process of the repair agent is easy to implement, without strict objective conditions, can be applied to a variety of heavy metal contaminated soil environments, and the implementation cost is low.

[0012] The present invention also provides a method for preparing the above-mentioned repairing agent using electrolytic manganese slag as a base material, which comprises the following steps in sequence:

[0013] S1 Hybrid

[0014] The electrolytic manganese slag and the calcium-containing material are mixed in a certain proportion to obtain a mixture;

[0015] S2 ball mill

[0016] The mixture obtained in step S1 is put into a ball mill for ball milling, and then the solid after ball milling is taken out, ground and sieved to obtain a repairing agent.

[0017] Furthermore, the calcium-containing material is quicklime.

[0018] Furthermore, the mass ratio of the electrolytic manganese slag to the calcium-containing material in S1 is (0.5-3):1; the preferred mass ratio is 1:1.

[0019] The mechanism of adsorption of soil heavy metals by the remediation agent based on electrolytic manganese slag is:

[0020] When the electrolytic manganese slag is mixed with the calcium-containing material, the electrolytic manganese slag contains a high content of silicon dioxide and manganese dioxide, which is mixed with the hydroxyl substances of the calcium-containing material. The electrolytic manganese slag is activated by ball milling to become a silicate substance. Then, after contacting with the heavy metal-contaminated soil, the active groups in the activated electrolytic manganese slag will first react with the positive divalent ions such as lead, cadmium, and copper in the heavy metal-contaminated soil to generate precipitates such as lead sulfate, and then the calcium ions and iron ions activated by ball milling are slowly released and combined with arsenic in the soil, so that the arsenic in the soil is fixed by the iron and manganese elements in the electrolytic manganese slag and the Ca in the calcium-containing material to generate precipitates such as calcium arsenate, thereby reducing the mobility of arsenic, controlling the biological effectiveness of arsenic, fixing and stabilizing it, and reducing its leaching toxicity. On the other hand, it will provide calcium, sulfur, magnesium, iron, manganese and other medium elements to enhance its fertility.

[0021] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0022] The repair agent based on electrolytic manganese slag disclosed in the present invention has the characteristics of easy operation, simple preparation method, good passivation effect, low cost, provides a new idea for the resource utilization of electrolytic manganese slag, and has important environmental benefits, social value and good application prospects.

[0023] The present invention uses electrolytic manganese slag as a base material, mixes it with quicklime, slaked lime and / or limestone and performs ball milling modification, and utilizes silicate components and iron and manganese elements therein to passivate heavy metal ions in the soil, which can not only promote the passivation of heavy metals in the soil, but also increase the content of effective silicon and the like in the soil, provide medium elements such as calcium, sulfur, magnesium, iron, and manganese, and enhance the fertilizer effect of the soil. The present invention only needs to mix the electrolytic manganese slag-based repair agent into the heavy metal-contaminated soil without other operations, has important environmental benefits and social value, and provides certain technical guidance for the resource utilization and harmlessness of electrolytic manganese slag. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a comparison chart of TCLP leaching toxicity in contaminated soil before and after heavy metal remediation in Example 1;

[0025] Figure 2 : is the XRD pattern of the electrolytic manganese slag (EMR) used in the embodiment, and the numbers in the figure are: 1-calcium carbonate, 2-dolomite, 3-hydrogen calcite, 4-quartz, 5-gypsum, 6-white calcite, 7-rhodonite;

[0026] Figure 3This is the XRD pattern of the repair agent F-EMR1 obtained in Example 1, and the numbers in the figure are: 1-Ca(OH)2, 2-anhydrite, 3-quartz, 4-CaSO4·0.5H2O, 5-FeOOH, 6-Ca2SiO4, 7-Ca2SiO3.

[0027] As can be seen from the figure, the crystal phases of the electrolytic manganese slag are mainly quartz, gypsum, hydrosilverite, whitesilverite and ferromagnetite; then after adding calcium oxide and ball milling, its crystal form becomes an amorphous phase. Calcium oxide hydroxylates the material and increases the pH of the material, which helps to repair the acidified soil. The iron element in the electrolytic manganese slag is also converted into ferrihydrite (FeOOH), which helps to passivate and repair the arsenic element in the soil.

[0028] CaO+H2O→Ca 2+ +2OH - (1)

[0029]

[0030]

[0031] 4Fe 2+ +O2+8OH - →4FeOOH+2H2O (4)

[0032] MnSO4+Ca(OH)2→Mn(OH)2+CaSO4 (5)

[0033] AsO4 3- +FeOOH→FeAsO4+H2O (5)

[0034] 2AsO4 3- +3Ca 2+ →Ca3(AsO4)2 (6)

[0035] Figure 4 This is the XRD diagram of the repair agent F-EMR1 in Example 1 after adsorbing arsenic in the soil. The numbers in the figure are: 1-Ca3(AsO4)2, 2-FeAsO4, and the comparison is Figure 3 and Figure 4 It can be seen that arsenic has been adsorbed by the repair agent. The mechanisms of arsenic adsorption by the repair agent of the present invention include electrostatic adsorption and surface complexation. Electrostatic adsorption is mainly the adsorption of arsenic by manganese dioxide, and surface complexation is mainly precipitation. Calcium, iron, etc. are the precipitation of arsenic. Obviously, after the repair agent of the present invention is mixed with soil, it helps to passivate heavy metals. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below in conjunction with specific embodiments so that those skilled in the art can understand the present invention more clearly.

[0037] The following embodiments are only used to illustrate the present invention, but are not used to limit the scope of the present invention. Based on the specific embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work belong to the protection scope of the present invention.

[0038] In the following examples, the raw materials used: electrolytic manganese slag (EMR) comes from CITIC Dameng Mining Co., Ltd., and its particle size is 149 μm; the electrolytic manganese slag is tested by XRF (X-ray fluorescence spectrometer: Zetium, Netherlands, PANalytical B.V.), and the weight percentage content of the components is analyzed, as shown in Table 1 below:

[0039] Table 1

[0040]

[0041] Example 1 Preparation of electrolytic manganese slag-based repair material, the steps are as follows:

[0042] S1 Hybrid

[0043] 5 g of electrolytic manganese slag and 5 g of quicklime (Chinese medicine, CaO content greater than 97.0%) were mixed to obtain a mixture;

[0044] S2 ball mill

[0045] The mixture obtained in step S1 was placed in a ball mill with a ball-to-material ratio of 10:1, and ball-milled at 500 r / min for 1 h; the obtained solid was taken out and ground, and passed through a 100-mesh sieve to obtain a repair agent, which was recorded as F-EMR1 and set aside.

[0046] 0.02 g of F-EMR1 was placed into 20 mL of arsenic acid solution with an initial arsenic concentration of 52 mg / L and As2O3 solution with an initial arsenic concentration of 65 mg / L, respectively. After tumbling and shaking at room temperature for 1 hour, the mixture was filtered and the remaining arsenic content was determined by an atomic spectrophotometer. It was detected that the adsorption capacity of F-EMR1 for As(V) was 51.07 mg / g, and the adsorption capacity for As(III) was 64.74 mg / g.

[0047] The prepared F-EMR1 was applied to heavy metal contaminated soil to test the soil remediation performance. Specifically, soil (with a moisture content of 60%) with severe heavy metal contamination from a mining area was taken. The heavy metal content in the soil is shown in Table 2. 100g of the above soil was evenly mixed with 3g of the repair agent F-EMR1, and then cultured at room temperature for 10d-40d. The soil was stirred irregularly during the culture process, and water was added in time to maintain the moisture content in the soil at the same level as the original soil. The heavy metals were then extracted using the TCLP leaching method and analyzed and tested. The results are shown in Table 3.

[0048] Table 2 Heavy metal content in contaminated soil

[0049]

[0050] Table 3 Effects of remediation agents on the concentrations of heavy metals and other cations in contaminated soil (TCLP, μg / L)

[0051]

[0052] From the data in the above table, it can be seen that the repair agent prepared in this embodiment has a passivation effect on various heavy metals in the soil, and significantly reduces the leaching toxicity of Cr, As, Cd, Pb, Ni, Cu, etc. in the contaminated soil. At the same time, the results of monitoring the amount of manganese leaching in the soil show that with the increase of incubation time, the manganese content leached in the soil does not increase, indicating that the manganese has been fixed in the soil and will not cause harm to its groundwater.

[0053] Example 2 Preparation of electrolytic manganese slag-based repair material, the steps are as follows:

[0054] S1 Hybrid

[0055] 5 g of electrolytic manganese slag and 5 g of slaked lime (Chinese medicine, calcium hydroxide content ≥ 93.0%) were mixed to obtain a mixture;

[0056] S2 ball mill

[0057] The mixture obtained in step S1 was placed in a ball mill with a ball-to-material ratio of 10:1, and ball-milled at 500 r / min for 1 h; the obtained solid was taken out and ground, and passed through a 100-mesh sieve to obtain a repair agent, which was recorded as F-EMR2 and set aside.

[0058] 0.02g of F-EMR2 was placed into 20mL of arsenic acid solution with an initial arsenic concentration of 52mg / L and As2O3 solution with an initial arsenic concentration of 65mg / L, respectively. After tumbling and shaking at room temperature for 1h, the mixture was filtered and the remaining arsenic content was determined by an atomic spectrophotometer. It was detected that the adsorption capacity of F-EMR2 for As(V) was 50.75mg / g, and the adsorption capacity for As(III) was 64.72mg / g.

[0059] The prepared F-EMR2 was applied to soil contaminated by heavy metals to test its soil remediation performance. Specifically, soil seriously contaminated by heavy metals was taken, which was the same soil sampled together with Example 1.

[0060] After mixing 100 g of the above-mentioned soil with 3 g of the repair agent F-EMR2 evenly, the mixture was cultured at room temperature for 10 d to 30 d. During the culture process, the soil was stirred irregularly, and water was added in time to maintain the moisture content in the soil at the same level as the original soil. Then, the heavy metals were extracted by the TCLP leaching method (same as in Example 1) and analyzed and tested. The results are shown in Table 4.

[0061] Table 4 Effects of remediation agents on heavy metal concentrations in contaminated soil (TCLP, μg / L)

[0062] Cr As Cd Pb Ni Cu Before repair 370.65 62.81 131.65 612.28 192.47 729.29 10d 38.2 18.98 49.55 25.11 89.78 641.82 20d 21.33 17.48 54.53 15.49 82.51 545.69 30d 25.69 18.49 65.83 14.9 123.54 681.87

[0063] It can be seen from the data in the above table that the repair agent prepared in this embodiment has a passivation effect on various heavy metals in the soil, significantly reducing the leaching toxicity of Cr, As, Cd, Pb, Ni, Cu, etc. in the contaminated soil. At the same time, the results of monitoring the manganese leaching amount in the soil show that with the increase of incubation time, the manganese content leached in the soil does not increase.

[0064] Example 3 Preparation of electrolytic manganese slag-based repair material, the steps are as follows:

[0065] S1 Hybrid

[0066] 5 g of electrolytic manganese slag and 5 g of limestone (Youso Chemical Co., Ltd., composition and content are as follows: CaO (55.16%), MgO (1.73%), SiO2 (0.281%), CO2 (42.645%), Al2O3 (0.078%)) were mixed to obtain a mixture;

[0067] S2 ball mill

[0068] The mixture obtained in step S1 was placed in a ball mill with a ball-to-material ratio of 10:1, and ball-milled at 500 r / min for 1 h; the obtained solid was taken out and ground, and passed through an 80-mesh sieve to obtain a repair agent, which was recorded as F-EMR3 and set aside.

[0069] 0.02g F-EMR3 was placed in 20mL of arsenic acid solution with an initial arsenic concentration of 52mg / L and As2O3 solution with an initial arsenic concentration of 65mg / L, respectively. After tumbling and oscillating at room temperature for 1h, the mixture was filtered and the remaining arsenic content was determined by an atomic spectrophotometer. The results showed that the adsorption capacity of F-EMR3 for As(V) was 19.88mg / g, and the adsorption capacity for As(III) was 35mg / g. This may be because its carbonate ions reacted with silica after ball milling to form calcium silicate, which weakened the adsorption effect on arsenic.

[0070] The prepared F-EMR3 was applied to soil contaminated with heavy metals to test the soil remediation performance. Specifically, soil seriously contaminated with heavy metals was taken, and the same soil sampled together with Example 1 was taken. 10 g of the above soil was mixed with 0.3 g of the remediation agent F-EMR3, and then cultured at room temperature for 10 days. During the culture process, the soil was stirred irregularly, and water was added in time to maintain the moisture content in the soil at the same level as the original soil. Then, the heavy metals were extracted by the TCLP leaching method (same as Example 1) and analyzed and tested. The results are shown in Table 5.

[0071] Table 5 Effects of remediation agents on heavy metal concentrations in contaminated soil (TCLP, μg / L)

[0072] heavy metal TCLP (ug / L) Before repair As 62.81 Cd 131.65 Cu 729.29 Pb 612.28 Cr 370.65 Ni 192.47 After Repair As 50.62 Cd 104.52 Cu 282.23 Pb 156.43 Cr 89.52 Ni 190.22

[0073] It can be seen from the data in the above table that the repair agent prepared in this embodiment has a passivation effect on various heavy metals in the soil, significantly reducing the leaching toxicity of Cr, As, Cd, Pb, Ni, Cu, etc. in the contaminated soil. At the same time, the results of monitoring the manganese leaching amount in the soil show that with the increase of incubation time, the manganese content leached in the soil does not increase.

[0074] Comparative Example 1

[0075] The electrolytic manganese slag was ball-milled at 400 r / min for 2 h, and the obtained solid was taken out and ground, and passed through a 120-mesh sieve to obtain the electrolytic manganese slag after ball milling for standby use.

[0076] 0.02 g of the ball-milled electrolytic manganese slag was placed in 20 mL of arsenic acid solution with an initial arsenic concentration of 52 mg / L and As2O3 solution with an initial arsenic concentration of 65 mg / L, respectively. After tumbling and oscillating at room temperature for 1 hour, the mixture was filtered and the remaining arsenic content was determined by an atomic spectrophotometer. It was detected that the adsorption capacity of the electrolytic manganese slag for As(V) was 5 mg / g, and the adsorption capacity for As(III) was 6 mg / g.

[0077] The obtained electrolytic manganese slag after ball milling was applied to soil contaminated by heavy metals to test the soil remediation performance. Specifically, soil seriously contaminated by heavy metals in a mining area was taken, 100g of the above soil was mixed with 3g of electrolytic manganese slag after ball milling, and then cultured at room temperature for 10 days. During the culture process, the soil was stirred irregularly, and water was added in time to maintain the moisture content in the soil at the same level as the moisture content of the original soil. Then, the heavy metals were extracted by TCLP leaching method (same as Example 1) and analyzed and tested. The results are shown in Table 6.

[0078] Comparative Example 2

[0079] 0.02 g of electrolytic manganese slag was placed in 20 mL of arsenic acid solution with an initial arsenic concentration of 52 mg / L and As2O3 solution with an initial arsenic concentration of 65 mg / L, respectively. After tumbling and shaking at room temperature for 1 hour, the mixture was filtered and the remaining arsenic content was determined by an atomic spectrophotometer. It was detected that the adsorption capacity of the above electrolytic manganese slag for As(V) was 0.9 mg / g, and the adsorption capacity for As(III) was 4.29 mg / g.

[0080] Electrolytic manganese slag was applied to soil contaminated by heavy metals to test soil remediation performance. Specifically, soil severely contaminated by heavy metals was taken, and the same soil sampled together with Comparative Example 1 was taken. 100 g of the above soil was mixed evenly with 3 g of electrolytic manganese slag, and then cultured at room temperature for 10 days. During the culture process, the soil was stirred irregularly, and water was added in time to maintain the moisture content in the soil at the same level as the moisture content of the original soil. Then, the heavy metals were extracted by TCLP leaching method (same as Example 1) and analyzed and tested. The results are shown in Table 6.

[0081] Table 6 Effects of remediation agents on heavy metal concentrations in contaminated soil (TCLP, μg / L)

[0082]

[0083] Conclusion: The leaching toxicity of heavy metals in the soil treated with electrolytic manganese slag and ball-milled electrolytic manganese slag did not decrease significantly, indicating that the passivation effect of electrolytic manganese slag and ball-milled electrolytic manganese slag on heavy metals in the soil is not very obvious.

[0084] The present invention combines electrolytic manganese slag with quicklime, slaked lime and / or limestone, and prepares a soil remediation agent after mechanical ball milling. On the one hand, it can save costs, avoid secondary pollution of electrolytic manganese slag, and treat waste with waste, and can be used to repair soil heavy metal pollution. On the other hand, as time goes by, calcium, sulfur, magnesium, iron, manganese and other medium elements in the soil remediation agent are slowly released into the soil, which can provide a large amount of nutrients for the growth of plants in the soil, thereby further improving the environment of the soil contaminated by heavy metals.

Claims

1. An application of a dual-effect repair agent based on electrolytic manganese slag in the repair of heavy metal contaminated soil, wherein the dual-effect repair agent is a mixture of electrolytic manganese slag and a calcium-containing material, wherein the calcium-containing material is limestone; the heavy metal in the heavy metal contaminated soil contains at least one of cadmium, lead and arsenic; It is characterized in that The specific operation of the application is: mixing the repair agent into the heavy metal contaminated soil at a mass ratio of 0.2% to 5%; the dual-effect repair agent based on electrolytic manganese slag is prepared by the following method: S1 Hybrid The electrolytic manganese slag and the calcium-containing material are mixed in a certain ratio to obtain a mixture; the mass ratio of the electrolytic manganese slag and the calcium-containing material is (0.5-3):1; S2 ball mill The mixture obtained in step S1 is put into a ball mill for ball milling, and then the solid after ball milling is taken out, ground and sieved to obtain a dual-effect repair agent.

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