A bio-manganese oxide-based passivator for thallium pollution remediation, a preparation method thereof, and a remediation method

Abstract

The present invention discloses a biological manganese oxide-based passivator for thallium pollution remediation, its preparation method and application. The passivator is obtained by preparing a mixed solution from soluble manganese salts, soluble carbonates and soluble iron salts, adding a complexing agent for gel precipitation and aging, and then oxidizing the aged product with manganese-oxidizing bacteria. It has been experimentally confirmed that the passivator has excellent remediation effects on thallium pollution in wastewater and soil. The synthesis raw materials of the passivator of the present invention are simple and the preparation cost is low. By using biological bacteria to oxidize manganese in situ, the adsorption performance of the passivator material for thallium can be improved, the efficient removal of thallium in water can be realized, and the concentration of thallium in wastewater can be significantly reduced; the passivator of the present invention can effectively repair thallium in soil, reduce the desorption rate of thallium in soil, significantly reduce the release of thallium, and realize the detoxification and long-term solidification and stabilization of thallium in soil.

Description

Technical Field

[0001] The present invention relates to the technical field of soil heavy metal pollution remediation, and particularly relates to a biological manganese oxide-based passivator for thallium pollution remediation, a preparation method thereof, and a remediation method thereof. Background Art

[0002] Thallium (Tl) is a highly toxic trace metal, and its toxicity to mammals exceeds that of common heavy metals such as mercury, lead, and cadmium. The discharge of wastewater or solid waste caused by mining, metal smelting, and other human activities has led to widespread Tl pollution. The drinking water standard for Tl set by the US Environmental Protection Agency (EPA) is 2 μg / L, and the drinking water standard for Tl set by the Chinese national drinking water standard is 0.1 μg / L. Even at very low concentrations, Tl poses a significant threat to human health due to acute or chronic poisoning. Every year, a large amount of Tl is discharged into the environment by industrial processes worldwide. Tl may enter river water areas and endanger drinking water quality, aquatic habitats, and human health through the food chain.

[0003] In groundwater, Tl mainly exists in two forms, namely Tl(I) and Tl(III). Tl(I) mainly exists in the form of free cations, and its chemical properties are similar to those of alkali metals. Tl(III) can be formed under oxidizing conditions and is easily hydrolyzed to Tl2O3. Therefore, it is more difficult to remove Tl(I) from groundwater than to remove Tl(III). Tl that enters sediments or soil can be recycled and released, posing a threat to the ecological environment system again. On the other hand, Tl in sediments may migrate to agricultural soil through floods and accumulate in plants. Long-term low-dose exposure to Tl will cause a series of environmental and ecological problems. The global soil background value of thallium content does not exceed 0.58 mg / kg, and most of it exists in a stable phase combined with silicate, with low release activity, long environmental cycling and toxicity enrichment time (20 - 30a), and has not attracted enough attention for a long time. In recent years, with the large-scale development of mineral resources, a large amount of thallium has been released into the environment, resulting in frequent occurrences of thallium chronic poisoning incidents, and the main route of poisoning is the food chain. The adsorption-desorption of heavy metals in soil is the main process controlling their bioavailability, directly affecting the morphological transformation, migration, and fate of heavy metals in soil and the ecological environment, and ultimately affecting the quality of agricultural products.

[0004] Currently, there are more reports on the removal of thallium pollution in water, while the adsorption-desorption behavior in thallium-contaminated soil has not been reported. Due to the increasing number of environmental thallium pollution and thallium poisoning incidents discovered in recent years, it has become important to carry out research on thallium-contaminated soil remediation.

[0005] Chinese Patent Application CN 107381926 A discloses a purification method for thallium-containing wastewater, in which magnet powder is added to the thallium-containing wastewater for adsorption reaction. CN 109437465 A provides a method for using manganese ferrite to remove high-concentration industrial thallium-containing wastewater. However, the adsorption effects of these two technologies are limited by the influence of iron oxide magnetic materials, etc., and the removal effect and separation effect are not ideal. At the same time, their recycling and regeneration capabilities are weak. CN 107008739 B provides a method for treating thallium pollution in soil, classifying thallium-polluted soil, and adopting a method of classified control and classified remediation for precise treatment. However, the metal thallium inhibitor requires more than a dozen kinds of materials, and its ecological negative effects have not been evaluated in the actual application process. The existing technologies have achieved certain effects in the removal of thallium pollutants and the treatment of thallium-polluted soil, but each method has its applicable scope and limitations, and there is also a lack of long-term stability evaluation for the remediation of thallium-polluted soil.

[0006] How to repair thallium-polluted soil, reduce the release of thallium in the polluted soil, and at the same time achieve the detoxification and long-term solidification and stabilization of thallium in the soil is crucial for soil environmental protection. Summary of the Invention

[0007] In view of the above problems, one of the objectives of the present invention is to provide a biological manganese oxide-based passivator for thallium pollution remediation. The passivator is prepared by using soluble manganese salt, soluble carbonate, and soluble iron salt as raw materials to prepare a mixed solution, adding a complexing agent for gel precipitation and aging, and then oxidizing the aged product with manganese-oxidizing bacteria.

[0008] Among them,

[0009] The soluble manganese salt is selected from one or more of manganese chloride, manganese nitrate, and manganese sulfate;

[0010] The soluble carbonate is sodium carbonate or / and potassium carbonate;

[0011] The soluble iron salt is selected from one or more of iron chloride, iron nitrate, and iron sulfate;

[0012] The complexing agent is selected from one or more of citric acid, malic acid, EDTA, and sodium dodecyl sulfate;

[0013] Preferably, the manganese-oxidizing bacteria are Pseudomonas putida, preferably P. putida MnB1.

[0014] Another objective of the present invention is to provide a preparation method for the above-mentioned passivator, including the following steps:

[0015] (1) Preparation of the aged product by the gel precipitation method: Dissolve soluble manganese salt and soluble carbonate in water, add a soluble iron salt solution, mix evenly, add a complexing agent solution, and mix well. The concentration of soluble manganese salt in the mixed solution is 0.02 - 0.1 mol / L, the concentration of soluble carbonate is 0.02 - 0.08 mol / L, the concentration of soluble iron salt is 0.02 - 0.06 mol / L, and the concentration of complexing agent is 0.02 - 0.04 mol / L. Age the mixed solution, and after aging, filter and separate to obtain the aged product;

[0016] (2) Oxidation of the aged product using manganese-oxidizing bacteria: Add the aged product and manganese-oxidizing bacteria to an oxidation medium, and culture them at 25 - 30 °C with shaking for 18 - 144 h under dark conditions. The oxidation medium is used to provide energy for the growth of manganese-oxidizing bacteria so that they can oxidize divalent manganese in the aged product to form higher-valent manganese oxides (Mn(III) / Mn(IV));

[0017] (3) Obtaining the passivator: After the oxidation culture is completed, collect the cultured precipitate, dry it, and grind it into granular form to obtain the passivator.

[0018] In step (1), the concentration of soluble manganese salt in the mixed solution is 0.02 - 0.08 mol / L; the molar ratio of manganese salt, carbonate, iron salt, and complexing agent is 1 - 5:1 - 4:1 - 3:1 - 2, preferably 4 - 5:1 - 4:2 - 3:1 - 2 or 5:4:3:2 or 1:1:1:1 or 4:1:3:2;

[0019] Both the soluble iron salt solution and the complexing agent solution are added in a dropwise manner;

[0020] Preferably, the dropping rate of the soluble iron salt is 0.1 - 1 mL / min, and the dropping rate of the complexing agent is 0.5 - 2 mL / min.

[0021] Preferably, age the mixed solution at 20 - 60 °C for 12 - 24 h.

[0022] In step (2), the manganese-oxidizing bacteria used is the cell suspension of manganese-oxidizing bacteria grown to the stationary phase, and the inoculation amount is 1 - 3%, preferably 1 - 2%;

[0023] The activation method of the manganese-oxidizing bacteria is: Take the strain and culture it in a nutrient agar medium at 25 - 30 °C for 20 - 28 hours, then transfer and inoculate it into a culture flask containing a liquid nutrient medium and culture it at 25 - 30 °C until the stationary phase for oxidizing the aged product; preferably, culture it in a nutrient agar medium at 25 - 28 °C for 20 - 28 hours, then transfer and inoculate it into a culture flask containing a liquid nutrient medium and culture it at 25 - 28 °C;

[0024] The nutrient agar medium contains the following components: 2.0 - 4.0 g / L beef extract, 2.0 - 6.0 g / L peptone, 5.0 - 10.0 g / L sodium chloride, 10 - 30 g / L agar, pH 6.5 - 7.5; preferably, the nutrient agar medium contains: 3.0 g / L beef extract, 5.0 g / L peptone, 5.0 g / L sodium chloride, 20 g / L agar, pH ~ 7; preferably, it is cultured at 28 °C for 24 hours;

[0025] The liquid nutrient medium contains the following components: 2.0 - 3.0 g / L beef extract, 2.0 - 6.0 g / L peptone, 5.0 - 10.0 g / L sodium chloride, pH 6.5 - 7.5; preferably, the liquid nutrient medium contains: 3.0 g / L beef extract, 5.0 g / L peptone, 5.0 g / L sodium chloride, pH ~ 7; preferably, it is cultured at 28 °C.

[0026] In step (2), the oxidation medium contains the following components: 0.4 - 0.6 g / L yeast extract, 0.4 - 0.6 g / L casein amino acids, 0.8 - 1.2 g / L glucose, 0.18 - 0.26 g / L CaCl2, 0.6 - 1.0 g / L MgSO4·7H2O, 0.0008 - 0.0012 g / L FeCl3·6H2O, 2.0 - 2.6 mL / L HEPES solution, 0.8 - 1.2 mL / L trace element solution, where the trace elements include 6.4 mg / L CuSO4, 44 mg / L ZnSO4·7H2O, 20 mg / L CoCl2·6H2O, 13 mg / L Na2MoO4·2H2O;

[0027] Preferably, the oxidation medium contains the following components: 0.5 g / L yeast extract, 0.5 g / L casein amino acids, 1 g / L glucose, 0.222 g / L CaCl2, 0.8118 g / L MgSO4·7H2O, 0.001 g / L FeCl3·6H2O, 2.38 mL / L HEPES solution, 1.0 mL / L trace element solution;

[0028] Preferably, it is cultured with shaking at 100 - 200 rmp or 100 - 180 rmp or 110 - 160 rmp at 25 - 28 °C in the dark for 18 - 100 h or 20 - 50 h or 20 - 40 h or 20 - 30 h or 20 - 28 h or 22 - 26 h;

[0029] The addition amount of the aging product is such that the mass - volume ratio of the aging product to the oxidation medium is 1 g﹕70 - 130 mL, preferably 1 g﹕80 - 120 mL or 1 g﹕90 - 110 mL or 1 g﹕100 mL.

[0030] In step (3), the precipitate after cultivation is collected by vacuum filtration and dried at 60-90° C. for 6-24 hours. After drying, the precipitate is ground into granules to obtain a passivating agent; preferably, the precipitate is ground into 150-250 mesh.

[0031] Another object of the present invention is to provide the use of the above-mentioned passivating agent in removing thallium from thallium-containing wastewater or repairing thallium-contaminated soil.

[0032] Another object of the present invention is to provide a method for treating thallium-containing wastewater, which is treated with a passivating agent prepared by any of the preparation methods described above, comprising the following steps: adding the passivating agent to the thallium-containing wastewater, stirring evenly, and then standing to allow it to react fully, filtering out the precipitate after the reaction is completed, and significantly reducing the thallium content in the supernatant;

[0033] Preferably, the mixture is stirred for 20 to 50 minutes after the passivating agent is added, preferably for 20 to 40 minutes;

[0034] After stirring, the mixture is preferably allowed to stand for 30 to 80 minutes to allow for sufficient reaction, and preferably allowed to stand for 50 to 70 minutes.

[0035] Preferably, in the technical solution of the above treatment method, the thallium-containing wastewater is steel smelting wastewater, the thallium content in the wastewater is ≤800 μg / L, and the amount of passivating agent added is 100-500 mg / L, preferably 300-500 mg / L;

[0036] Another object of the present invention is to provide a method for ex situ remediation of thallium-contaminated soil, which comprises the following steps:

[0037] For slightly contaminated soil with a thallium content of less than 1 mg / kg, take the soil to be repaired and add it to a reaction tank. Add the passivator to the soil at an addition amount of 0.1-2.5% (w / w), mix well, then add water to make the soil moisture content 50-90%, stir well until the mixture is evenly mixed, and let it stand for 1-4 weeks;

[0038] For moderately contaminated soil with a thallium content of 1 to 5 mg / kg or heavily contaminated soil with a thallium content of more than 5 mg / kg, take the soil to be repaired and add it to a reaction tank, then spray calcium nitrate powder on the soil surface, the mass ratio of calcium nitrate to soil is 1:3000 to 5000, add water so that the water surface is higher than the soil, stir thoroughly until the mixture is uniform, let it stand for full reaction and then discharge the supernatant, then apply a passivator, add the passivator to the soil at a dosage of 0.1 to 2.5% (w / w), mix well, then add water to keep the soil at 50 to 90% of the field water holding capacity, stir thoroughly until the mixture is uniform, and let it stand for 1 to 4 weeks for equilibrium.

[0039] In the technical solution of the above-mentioned off-site remediation method for thallium-contaminated soil, preferably,

[0040] For slightly contaminated soil, the passivator is added to the soil at an addition amount of 0.5-2% or 0.5-1.5%, mixed evenly, and then water is added to make the soil moisture content 60-80%, stirred for 20-50 min, and left to stand and balance for 1-3 weeks;

[0041] For moderately or severely contaminated soil, the soil to be remediated is taken and added to a reaction tank, and then calcium nitrate powder is sprayed on the soil surface. The mass ratio of calcium nitrate to the soil is 1:3000-5000. Water is added to make the water surface 2-5 cm higher than the soil, stirred for 20-50 min, and the supernatant is discharged after standing for 0.5-2 d. Then the passivator is applied. The passivator is added to the soil at a dose of 0.5-2% or 0.5-1.5%, mixed evenly, and then water is added to make the soil maintain 60-80% of the field water holding capacity, stirred for 20-50 min, and left to stand and balance for 1-3 weeks.

[0042] The final object of the present invention is to provide an in-situ soil remediation method for thallium contamination, which is remediated with the passivator prepared by the preparation method described in any one of the above, and includes the following steps:

[0043] (1) Pretreat the soil: Mechanically plow the soil to be remediated to loosen the soil so that the passivator can fully contact the soil;

[0044] (2) Apply the passivator: Apply the passivator to the soil at an application amount of 100-300 kg / mu, mix evenly, and maintain the field water holding capacity of the area to be remediated at 50-90%, and balance for 1-4 weeks.

[0045] In the technical solution of the above-mentioned in-situ soil remediation method for thallium contamination, the land with different thallium contamination levels is classified and treated:

[0046] For slightly contaminated soil with thallium content less than 1 mg / kg in the soil, the passivator is applied to the pretreated soil at an application dose of 100-200 kg / mu, and the soil is mechanically plowed to fully mix the passivator, and water is added to make the soil maintain 60-80% of the field water holding capacity, and naturally balance for 1-3 weeks;

[0047] For moderately polluted soil with thallium content in the soil of 1 - 5 mg / kg or severely polluted soil with thallium content in the soil > 5 mg / kg, after soil pretreatment, calcium nitrate powder is evenly sprayed on the soil surface at a spraying amount of 20 - 60 kg / mu. The soil is mechanically plowed to mix the calcium nitrate evenly with the topsoil, and then left standing to allow sufficient reaction. Then, a passivator is applied to the soil. The application amount of the passivator for moderately polluted soil is 150 - 250 kg / mu, and the application amount of the passivator for severely polluted soil is 200 - 300 kg / mu. After mixing evenly by mechanical plowing, water is applied to keep the soil at 60 - 80% of the field water holding capacity, and natural balance is maintained for 1 - 3 weeks.

[0048] In the above technical solution of the in-situ soil remediation method for thallium pollution, the mechanical plowing is carried out by rotary tillage with a rotary tillage depth of 10 - 30 cm, and preferably the rotary tillage is carried out twice each time for mechanical plowing;

[0049] After mechanically plowing the soil to mix the calcium nitrate evenly with the topsoil, it is left standing for 1 - 4 days, preferably 1 - 3 days.

[0050] In the above technical solution of the in-situ soil remediation method for thallium pollution, the method for grading the degree of land thallium pollution is as follows: Soil samples are taken from the land to be remediated, the soil samples are crushed, impurities are removed, ground, and digested until a clear solution is formed. Using a 1×10 -9 In solution as the internal standard solution, the total thallium in the digested sample is measured, and it is classified as slightly polluted soil, moderately polluted soil, or severely polluted soil according to the detection value.

[0051] The bio-manganese oxide-based passivator of the present invention is prepared by the method of "gel precipitation method + biological bacteria oxidation".

[0052] The gel precipitation method in step (1) mainly forms an iron-manganese compound by combining soluble manganese salts and iron salts, and further converts it into an organic-inorganic composite precipitate by combining carbonate and complex compounds. This is mainly because carbonate forms a flocculent precipitate with substances such as iron and manganese, and the flocculent precipitate is further converted into a precipitate by combining complex compounds through complexation reactions. The reaction becomes more complete through aging, and the obtained gel precipitate substance is more stable.

[0053] In step (2), manganese-oxidizing bacteria are used to oxidize the manganese in the gel precipitate substance obtained by aging, forming some manganese oxides with higher valence states (+3, +4, +5, and +6). At the same time, iron will also be oxidized to form some iron oxides with oxidation properties, obtaining a passivator with oxidation properties.

[0054] After applying the passivator of the present invention to thallium-contaminated soil, the passivator can oxidize free monovalent thallium ions into trivalent thallium. During this process, free thallium can also be adsorbed on the passivator-soil interface. Trivalent thallium is prone to precipitation and can be effectively stabilized in soil particles. On the other hand, the application of the passivator can significantly increase the content of iron and manganese in the soil, promote the increase of the content of thallium in the form of iron and manganese oxides in the soil, further promote the stabilization of thallium in the soil, effectively reduce the leaching content of thallium in the soil, and reduce its environmental risk.

[0055] The beneficial effects of the present invention are as follows: The synthesis raw materials of the passivator are simple and the preparation cost is low. By using biological bacteria to oxidize manganese in situ, the adsorption performance of the passivator material for thallium can be improved, the efficient removal of thallium in water can be achieved, and the concentration of thallium in wastewater can be significantly reduced; the passivator of the present invention can effectively repair thallium in soil, reduce the desorption rate of soil thallium, significantly reduce the release of thallium, and achieve the detoxification and long-term solidification and stabilization of thallium in soil. Brief Description of the Drawings

[0056] Figure 1 It is the culture situation when the aging product is oxidized and cultured with manganese-oxidizing bacteria.

[0057] Figure 2 It is the detection result of the TCLP-Tl leaching content after the remediation of thallium-contaminated soil.

[0058] Figure 3 It is the detection result of the timeliness of the passivator in remediating thallium contamination. Detailed Embodiments

[0059] The present invention will be further described below in conjunction with embodiments, but the present invention is not limited thereto.

[0060] The experimental methods in the following embodiments are all conventional methods unless otherwise specified; the biological and chemical reagents used are all conventional reagents in the art unless otherwise specified.

[0061] The manganese-oxidizing bacterium - Pseudomonas putida strain MnB1 (ATCC 23483) was purchased from the American Type Culture Collection (ATCC).

[0062] All culture media in the embodiments were autoclaved at 121 °C and 0.11 MPa for 15 min before use.

[0063] Example 1

[0064] I. Preparation of the biological manganese oxide-based passivator of the present invention

[0065] The raw materials of the passivator of the present invention include soluble manganese salt, soluble carbonate, soluble iron salt, complexing agent, and manganese-oxidizing bacterium P.putida MnB1 (ATCC23483).

[0066] Preparation method of the passivator:

[0067] (1) Preparation of the aged product by gel precipitation method: Take soluble manganese salt and soluble carbonate and add them into a 250 ml volumetric flask, dissolve them with 50 mL of deionized water, and make up the volume to 100 ml to obtain a mixed solution; add soluble iron salt solution dropwise to the mixed solution at a dropping rate of 0.1 - 1 mL / min, stir evenly, and ultrasonicate for 10 min to make it mix evenly; then add complexing agent solution (prepared with deionized water) dropwise at a dropping rate of 0.5 - 2 mL / min, and mix slowly after dropping. The concentration of soluble manganese salt in the mixed solution is 0.02 - 0.1 mol / L, the concentration of soluble carbonate is 0.02 - 0.08 mol / L, the concentration of soluble iron salt is 0.02 - 0.06 mol / L, and the concentration of complexing agent is 0.02 - 0.04 mol / L; age the mixed solution at 20 - 60 °C for 12 - 24 h, and filter and separate after aging to obtain the aged product.

[0068] (2) Activation of manganese-oxidizing bacterium: The culture conditions of P.putida MnB1 (ATCC23483) are as follows: Take the strain and culture it in a nutrient agar medium (containing 3.0 g / L beef extract, 5.0 g / L peptone, 5.0 g / L sodium chloride, 20 g / L agar, pH - 7) at 28 °C for 24 h, and then transfer and inoculate it into a 100 ml Erlenmeyer flask of liquid nutrient medium (containing 3.0 g / L beef extract, 5.0 g / L peptone, 5.0 g / L sodium chloride, pH - 7) and culture at 28 °C until the stationary phase for oxidizing the aged product.

[0069] (3) Oxidation of the aged product with manganese-oxidizing bacterium: Prepare an oxidation medium (the composition is shown in Table 1) and sterilize it for standby. Add 10 g of the aged product into 1 L of the oxidation medium, transfer 1 - 2% (w / w) of the manganese-oxidizing bacterium cell suspension cultured to the stationary phase into the culture flask containing the aforementioned oxidation medium, and culture at 28 °C and 120 - 150 rpm under dark conditions for 24 h ( Figure 1 is the diagram of the culture process situation).

[0070] (4) Obtaining the passivator: After the oxidation culture is completed, collect the cultured precipitate by vacuum filtration, and dry it at 60 - 90 °C for 6 - 24 h. After sufficient grinding, sieve it through a 200-mesh nylon sieve to obtain the passivator material of the present invention.

[0071] Table 1. Composition of the culture flask in the oxidation medium

[0072]

[0073] Note: In Table 1, the trace element solution contains: 6.4 mg / L of CuSO4, 44 mg / L of ZnSO4·7H2O, 20 mg / L of CoCl2·6H2O, and 13 mg / L of Na2MoO4·2H2O.

[0074] Fifteen passivator samples were prepared according to the above method. The specific raw materials, ratios, and aging parameters in step (1) are shown in Table 2, and the working parameters for oxidizing the aged product in step (3) are shown in Table 3. In Table 2, for the passivator with a molar ratio of manganese salt: carbonate: iron salt: complexing agent of 5:4:3:2, the concentration of the complexing agent in the mixed solution is 0.02 mol / L; for the passivators with molar ratios of manganese salt: carbonate: iron salt: complexing agent of 4:1:3:2 and 1:1:1:1, the concentration of the complexing agent in the mixed solution is 0.04 mol / L.

[0075] Table 2

[0076]

[0077] Table 3

[0078]

[0079]

[0080] II. Detection of the thallium removal performance of the passivator

[0081] Wastewater sample 1: Desulfurization wastewater from the iron and steel industry with a thallium ion content of 702.0 μg / L and a pH of 6 - 7.

[0082] (1) Experiment for determining the dosage of the passivator

[0083] 10 mg, 20 mg, 30 mg, 40 mg, and 50 mg of Passivator No. 1 were respectively added to beakers containing 100 ml of desulfurization wastewater from the iron and steel industry, stirred well for 30 min, and after standing for 60 min, the thallium content in the supernatant of the five beakers was detected using an inductively coupled plasma mass spectrometer (ICP-MS). The detection results are shown in Table 4: The thallium content in the supernatant obtained after adding 30 mg, 40 mg, and 50 mg of the passivator was similar, all reaching below 2 μg / L, and the pH was 7.5 - 8.5. It can be determined that adding 300 - 500 mg of the passivator material per liter of desulfurization wastewater from the iron and steel industry is more appropriate. Considering cost savings, the dosage can be 300 mg.

[0084] Table 4

[0085] Dosage (mg / L) 100 200 300 400 500 Thallium concentration after treatment (μg / L) 29.4 5.34 1.9 1.65 0.98

[0086] (2) Detection of the effect of passivators on removing thallium from wastewater

[0087] Take 300 mg / L of each of the 15 previously prepared passivators to detect their effect on removing thallium from wastewater. Add 30 mg of the passivator to a beaker containing 100 ml of desulfurized wastewater from the iron and steel industry. After standing for 60 min, use an inductively coupled plasma mass spectrometer (ICP-MS) to detect the thallium content in the supernatant of the beaker. The detection results are shown in Table 5 as follows:

[0088] Table 5

[0089]

[0090] As can be seen from the results in Table 5, all 15 passivator samples have excellent effects on removing thallium from wastewater. Since manganese-oxidizing bacteria were not inoculated during the preparation of the No. 8 passivator, its effect on removing thallium from wastewater is lower than that of other similar treatments. The thallium content in the water treated with it is still higher than the regulation of 0.002 mg / L in the Local Environmental Standard of Guangdong Province, "Discharge Standard of Thallium Pollutants in Industrial Wastewater" (DB 44 / 1989 - 2017). This is mainly because Tl(I) in the wastewater cannot be oxidized to Tl(III) to achieve effective removal of Tl ions. In addition, some of the 15 prepared passivator samples cannot achieve the standard discharge of Tl in wastewater, which is mainly due to the differences in the preparation raw materials. To achieve the standard discharge of Tl, the dose of the passivator can be increased during the actual wastewater treatment process.

[0091] Example 2 Treatment of thallium-contaminated soil with passivators

[0092] Rating of soil pollution degree: Collect soil samples from 3 areas (A, B, and C) around a smelting yard in Shaoguan, Guangdong. Crush, remove impurities from the soil samples, grind them with an agate mortar to pass through a 100-mesh sieve, accurately weigh 0.1 g, digest them until a clear solution is formed, and make the volume up to 100 ml with an In solution of 1×10 -9 as the internal standard solution, and determine the thallium in the digested samples. The detection values are as shown in Table 6 below, and the pollution degree levels of the soil are divided.

[0093] Table 6

[0094] Region A B C Total amount of thallium in soil (mg / kg) 0.65 1.45 5.83 Pollution degree Light pollution Moderate pollution Heavy pollution

[0095] Basis for dividing the thallium pollution degree in Table 6: Severe pollution means the thallium content in the soil is higher than 5 mg / kg, moderate pollution means the thallium content in the soil is 1 - 5 mg / kg, and mild pollution means the thallium content in the soil is lower than 1 mg / kg. The soil pollution degree division standard refers to the division standard in Chinese Patent CN 107008739 B.

[0096] I. Ex-situ remediation of site soil

[0097] After soil collection, branches, large - sized stones, etc. in the soil are removed first, and after natural air - drying, it is ground through a 10 - mesh sieve for standby. The No. 1 passivator prepared in Example 1 is used for ex - situ remediation experiments on soils with different pollution degrees.

[0098] For slightly polluted soil in Area A, take 500 g of the soil to be remediated and add it to a 2 - L reaction tank. The passivator is added to the soil at an addition amount of 0 - 1.5 (w / w), mixed evenly, then water is added to make the soil water content 70%, stirred for 30 min, and left to stand and balance for 15 d. Soil samples are collected for analysis, and the TCLP toxicity leaching method of the US Environmental Protection Agency (EPA) is used to analyze the leaching of Tl in the soil.

[0099] For moderately polluted soil with thallium content of 1 - 5 mg / kg in the soil or severely polluted soil with thallium content > 5 mg / kg in the soil, take 500 g of the soil to be remediated and add it to a 2 - L reaction tank. Then, calcium nitrate powder is sprayed on the soil surface, and the mass ratio of calcium nitrate to soil is 1:4000. Water is added to keep the water surface 2 - 5 cm higher than the soil, stirred for 30 min, and after standing for 2 d, the supernatant is drained. Then, the passivator is applied, and the passivator is added to the soil at a dose of 0 - 1.5% (w / w), mixed evenly, then water is added to make the soil water content 70%, stirred for 30 min, and left to stand and balance for 15 d. Soil samples are collected for analysis, and the TCLP toxicity leaching method of the US EPA is used to analyze the leaching of Tl in the soil. The test results are shown in Table 7:

[0100] Table 7

[0101]

[0102] As can be seen from the results in Table 7, for slightly, moderately, and severely thallium - polluted soils, compared with the soil without passivation treatment, in Area A, as the dosage of the passivator increases, the leaching amounts of Tl in the soil decrease by 84.22%, 90.35%, and 93.59% respectively; in Area B, as the dosage of the passivator increases, the leaching amounts of Tl in the soil decrease by 80.20%, 93.54%, and 97.54% respectively; in Area C, as the dosage of the passivator increases, the leaching amounts of Tl in the soil decrease by 83.33%, 94.99%, and 96.09% respectively. Generally speaking, the application of the passivator has a significant inhibitory effect on the leaching of thallium in the soil.

[0103] II. In - situ remediation treatment of site soil

[0104] First, pre - treat the site soil: plow it once with a rotary tiller to a depth of 30 cm to loosen the soil. The No. 2 passivator prepared in Example 1 is used for in - situ remediation of the soil.

[0105] For the contaminated soil in Area A, a passivator was applied to the pre-treated soil at a rate of 100 kg / mu. The passivator was sprinkled on the soil surface and then the soil was turned over to mix the passivator evenly in the soil. Water was added to the soil so that the soil moisture maintained 70% of the field water holding capacity. The soil was rotary tilled twice with a rotary tiller, with each tilling depth of 20 cm. Then, after allowing it to naturally equilibrate for 15 days, soil samples were collected for analysis. The toxicity leaching of soil Tl was analyzed using the TCLP toxicity leaching method of the US EPA.

[0106] For the contaminated soil in Area B, after soil pre-treatment, calcium nitrate powder was evenly sprayed on the soil surface, with the usage amount of calcium nitrate being 25 kg / mu. Water was added to keep the soil moist. The soil was rotary tilled twice with a rotary tiller, with each tilling depth of 20 cm. After 2 days, a passivator was applied to the soil, and the passivator was added to the soil at a rate of 200 kg / mu. After mixing evenly by rotary tilling, water was added so that the soil moisture maintained 70% of the field water holding capacity. After equilibration for 15 days, soil samples were collected for analysis. Additionally, to evaluate the timeliness of the passivator for the remediation of thallium-contaminated soil, sampling was carried out at 1 day, 3 days, 5 days, 7 days, 14 days, 28 days, 54 days, 120 days, 180 days, and 1 year after remediation. The toxicity leaching of soil Tl was analyzed using the TCLP toxicity leaching method of the US EPA (EPA Test Method - 1311 - TCLP).

[0107] For the contaminated soil in Area C, after soil pre-treatment, calcium nitrate powder was evenly sprayed on the soil surface, with the usage amount of calcium nitrate being 50 kg / mu. Water was added to keep the soil moist. The soil was rotary tilled twice with a rotary tiller, with each tilling depth of 20 cm. After 2 days, a passivator was applied to the soil, and the passivator was added to the soil at a rate of 250 kg / mu. After mixing evenly by rotary tilling, the water content was maintained at 70% of the field water holding capacity. After allowing it to naturally equilibrate for 15 days, soil samples were collected for analysis. The toxicity leaching of soil Tl was analyzed using the TCLP toxicity leaching method of the US EPA.

[0108] Figure 2 The detection results of the TCLP - Tl leaching content of the soil 15 days after the remediation of the contaminated soil at the site: The leaching content of Tl in the soil before and after remediation decreased significantly. Compared with before remediation, the leaching contents of TCLP - Tl in the soils of Areas A, B, and C after remediation decreased by 85%, 94%, and 95% respectively. This is mainly related to the binding of the passivator with the Tl free in the soil. In addition, part of the free Tl was transferred to a more stable Tl form in the soil.

[0109] Figure 3 The timeliness results of the passivator for the remediation of thallium-contaminated soil in Area B: In the 1-year timeliness evaluation, the leaching amount of thallium in the soil treated with the passivator remained in the range of 0.78 - 0.95 μg / L and maintained a long-term passivation effect, indicating that the prepared passivator can maintain the remediation characteristics for a long time.

Claims

1. A preparation method of a bio-manganese oxide-based passivator for thallium pollution remediation, characterized in that, The biological manganese oxide-based passivator is prepared by preparing a mixed solution with soluble manganese salt, soluble carbonate, and soluble iron salt as raw materials, adding a complexing agent for gel precipitation and aging, and then oxidizing the aged product with manganese-oxidizing bacteria; the soluble manganese salt is selected from one or two of manganese chloride and manganese sulfate; the soluble carbonate is sodium carbonate or / and potassium carbonate; the soluble iron salt is selected from one or more of ferric chloride, ferric nitrate, and ferric sulfate; the complexing agent is sodium dodecyl sulfate; the molar ratio of manganese salt, carbonate, iron salt, and complexing agent is 4-5:1-4:2-3:1-2; the manganese-oxidizing bacteria is Pseudomonas putida; It includes the following steps: (1) Preparing the aged product by gel precipitation method: Dissolve soluble manganese salt and soluble carbonate in water, add the soluble iron salt solution, mix evenly, add the complexing agent solution, and mix well. The concentration of soluble manganese salt in the mixed solution is 0.02-0.1 mol / L, the concentration of soluble carbonate is 0.02-0.08 mol / L, the concentration of soluble iron salt is 0.02-0.06 mol / L, and the concentration of complexing agent is 0.02-0.04 mol / L. Age the mixed solution, and after aging, filter and separate to obtain the aged product; (2) Oxidizing the aged product with manganese-oxidizing bacteria: Add the aged product and manganese-oxidizing bacteria to the oxidation medium, and culture at 25-30 °C with shaking for 18-144 h under dark conditions. The oxidation medium is used to provide energy for the growth of manganese-oxidizing bacteria so that it can oxidize divalent manganese in the aged product to form high-valent manganese oxide; (3) Obtaining the passivator: After the oxidation culture, collect the cultured precipitate, dry it, and grind it into granular form to obtain the passivator.

2. The preparation method according to claim 1, characterized in that: In step (1), the concentration of soluble manganese salt in the mixed solution is 0.02-0.08 mol / L; the molar ratio of manganese salt, carbonate, iron salt, and complexing agent is 4-5:1-4:3:2; both the soluble iron salt solution and the complexing agent solution are added dropwise; the dropping rate of the soluble iron salt is 0.1-1 mL / min, and the dropping rate of the complexing agent is 0.5-2 mL / min; Age the mixed solution at 20-60 °C for 12-24 h.

3. The preparation method according to claim 1, characterized in that: In step (2), the manganese-oxidizing bacteria uses the cell suspension of manganese-oxidizing bacteria grown to the stationary phase, and the inoculation amount is 1-3%; The activation method of the manganese-oxidizing bacteria is: Take the strain and culture it at 25-30 °C in a nutrient agar medium for 20-28 hours, and then transfer and inoculate it into a culture bottle containing a liquid nutrient medium and culture at 25-30 °C until the stationary phase for oxidizing the aged product; The nutrient agar medium contains the following components: 2.0-4.0 g / L beef extract, 2.0-6.0 g / L peptone, 5.0-10.0 g / L sodium chloride, 10-30 g / L agar, pH 6.5-7.5; The liquid nutrient medium contains the following components: 2.0 - 3.0 g / L beef extract, 2.0 - 6.0 g / L peptone, 5.0 - 10.0 g / L sodium chloride, and pH 6.5 - 7.

5.

4. The preparation method according to claim 1, characterized in that: In step (2), The oxidation medium contains the following components: 0.4 - 0.6 g / L yeast extract, 0.4 - 0.6 g / L casein amino acids, 0.8 - 1.2 g / L glucose, 0.18 - 0.26 g / L CaCl2, 0.6 - 1.0 g / L MgSO4·7H2O, 0.0008 - 0.0012 g / L FeCl3·6H2O, 2.0 - 2.6 mL / L HEPES solution, 0.8 - 1.2 mL / L trace element solution, where the trace elements include 6.4 mg / L CuSO4, 44 mg / L ZnSO4·7H2O, 20 mg / L CoCl2·6H2O, and 13 mg / L Na2MoO4·2H2O; The addition amount of the aging product is such that the mass - volume ratio of the aging product to the oxidation medium is 1 g﹕70 - 130 mL.

5. The preparation method according to claim 1, characterized in that: In step (3), the vacuum filtration method is used to collect the cultured precipitate, and it is dried at 60 - 90 °C for 6 - 24 h. After drying, it is ground into granular form to obtain the passivator.

6. Application of the passivator prepared by the preparation method of claim 1 in removing thallium from thallium-containing wastewater or remediating thallium-polluted soil.

7. A treatment method for thallium-containing wastewater, characterized in that, Treatment is carried out using the passivator prepared by the preparation method according to any one of claims 1 to 5, including the following steps: adding the passivator to the thallium - containing wastewater, stirring evenly, then standing still to allow sufficient reaction, and filtering out the precipitate after the reaction ends. The thallium content in the supernatant is significantly reduced.

8. The treatment method according to claim 7, characterized in that: The thallium - containing wastewater is steel - smelting wastewater, the thallium content in the wastewater is ≤800 μg / L, and the addition amount of the passivator is 100 - 500 mg / L.

9. An in-situ remediation method for thallium-polluted soil, characterized in that, Repair is carried out using the passivator prepared by the preparation method according to any one of claims 1 to 5, including the following steps: For slightly contaminated soil with a thallium content less than 1 mg / kg in the soil, take the soil to be repaired and add it to a reaction tank. The passivator is added to the soil at an addition amount of 0.1 - 2.5% (w / w), mixed evenly, then water is added to make the soil water content 50 - 90%, and it is fully stirred until evenly mixed, and then left to stand and balance for 1 - 4 weeks; For moderately contaminated soil with a thallium content of 1 - 5 mg / kg in the soil or severely contaminated soil with a thallium content > 5 mg / kg in the soil, take the soil to be repaired and add it to a reaction tank, then spray calcium nitrate powder on the soil surface. The mass ratio of calcium nitrate to the soil is 1:3000 - 5000. Water is added to make the water surface higher than the soil, and it is fully stirred until evenly mixed. After standing still to allow sufficient reaction, the supernatant is drained, and then the passivator is applied. The passivator is added to the soil at a dose of 0.1 - 2.5% (w / w), mixed evenly, then water is added to make the soil maintain 50 - 90% of the field water - holding capacity, and it is fully stirred until evenly mixed, and then left to stand and balance for 1 - 4 weeks.

10. The in-situ remediation method for thallium-polluted soil according to claim 9, characterized in that: For slightly contaminated soil, the passivator is added to the soil at an addition amount of 0.5 - 2%, mixed evenly, then water is added to make the soil water content 60 - 80%, stirred for 20 - 50 min, and left to stand and balance for 1 - 3 weeks; For moderately contaminated soil or severely contaminated soil, take the soil to be repaired and add it to the reaction tank. Then, spray calcium nitrate powder on the soil surface. The mass ratio of calcium nitrate to soil is 1:3000 - 5000. Add water to make the water surface 2 - 5 cm higher than the soil. Stir for 20 - 50 min, let it stand for 0.5 - 2 d, then drain the supernatant. Then, apply a passivator. The passivator is added to the soil at a dose of 0.5 - 2%. Mix well, and then add water to keep the soil at 60 - 80% of the field water holding capacity. Stir for 20 - 50 min and let it stand and balance for 1 - 3 weeks.

11. An in-situ soil remediation method for thallium pollution, characterized in that, Repair using the passivator prepared by the preparation method according to any one of claims 1 to 5, including the following steps: (1) Pretreat the soil: Mechanically plow the soil to be repaired to loosen the soil so that the passivator can fully contact the soil; (2) Apply the passivator: Apply the passivator to the soil at an application rate of 100 - 300 kg / mu, mix well, and keep the field water holding capacity of the land to be repaired at 50 - 90%. Balance for 1 - 4 weeks.

12. The remediation method according to claim 11, characterized in that: Carry out grading treatment on lands with different thallium pollution levels: For slightly contaminated soil with thallium content less than 1 mg / kg in the soil, apply the passivator to the pretreated soil at an application dose of 100 - 200 kg / mu. Mechanically plow the soil to fully mix the passivator, and water the soil to keep it at 60 - 80% of the field water holding capacity. Naturally balance for 1 - 3 weeks; For moderately contaminated soil with thallium content of 1 - 5 mg / kg in the soil or severely contaminated soil with thallium content > 5 mg / kg in the soil, evenly spray calcium nitrate powder on the soil surface after soil pretreatment. The spraying amount is 20 - 60 kg / mu. Mechanically plow the soil to mix calcium nitrate evenly with the topsoil, then let it stand for sufficient reaction. Then, apply the passivator to the soil. The application amount of the passivator for moderately contaminated soil is 150 - 250 kg / mu, and the application amount of the passivator for severely contaminated soil is 200 - 300 kg / mu. After mixing evenly by mechanical plowing, water the soil to keep it at 60 - 80% of the field water holding capacity. Naturally balance for 1 - 3 weeks.

13. The remediation method according to claim 12, characterized in that: The mechanical plowing is carried out by rotary tillage with a rotary tillage depth of 10 - 30 cm; After mechanically plowing the soil to mix calcium nitrate evenly with the topsoil, let it stand for 1 - 4 days.

14. The remediation method according to claim 12, characterized in that: The method for grading the thallium pollution degree of land is as follows: Take soil samples from the land to be repaired, crush, remove impurities, grind the soil samples, and digest them until a clear solution is formed. Use an In solution with a concentration of 1×10 -9 as the internal standard solution to measure the total thallium in the digested samples, and classify them into slightly polluted soil, moderately polluted soil or severely polluted soil according to the detection values.

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