CN110484275A - A kind of anaerobic sulfate reducer collaboration iron-based material repairs the method and reagent of mercury and chromium deep layer contaminated soil - Google Patents

Abstract

The invention discloses a method and a reagent for repairing mercury and chromium deep-contaminated soil by anaerobic sulfate-reducing bacteria in cooperation with iron-based materials. The mercury-chromium contaminated soil repair reagent includes iron-based materials and anaerobic sulfate-reducing bacteria liquid; The iron-based material is obtained by reacting iron-containing silicate minerals with oxalic acid in an aqueous medium. Mercury-chromium-contaminated soil remediation reagents are applied to mercury (II) and chromium (VI) deep-contaminated soil to stabilize mercury (II) and Cr (VI) at the same time, which can effectively improve the overall remediation efficiency and scope, and the cost is low. The operation is simple and will not cause secondary pollution to the soil, so it has wide application prospects.

Description

An anaerobic sulfate-reducing bacteria synergistically remediates mercury and chromium deep-contaminated soil with iron-based materials Soil Methods and Reagents

technical field

The invention relates to a remediation reagent for chromium-mercury polluted soil, in particular to a remediation reagent for mercury-chromium-contaminated soil by anaerobic sulfate-reducing bacteria in cooperation with iron-based materials, and also relates to the source of mercury (II) and chromium (VI) deep-contaminated soil The invention discloses a site restoration method, which belongs to the technical field of heavy metal pollution restoration.

Background technique

Mercury(II) and Cr(VI), as typical heavy metal pollutants, are commonly found in industrially polluted sites after decommissioning, mining and smelting plants, tailings and slag dumps, polluted rivers or lake sediments in various parts of my country. among.

Mercury(II) and Cr(VI) in soil can be divided into dissolved state and exchangeable state, adsorption state, iron and manganese oxidation state, organic binding state and residue state, and the residue state is a non-bioavailable state, so it reduces soil The bioavailability of mercury and chromium is the main way of remediation of heavy metals in soil. However, due to the physical and chemical characteristics of mercury and chromium, how to achieve effective treatment of mercury-contaminated soil at a lower cost and avoid secondary pollution during the treatment process is one of the technical difficulties faced by my country's contaminated site remediation industry.

The remediation technologies of mercury(Ⅱ) and Cr(Ⅵ) contaminated soil mainly include stable immobilization technology, soil leaching technology, electrodynamic remediation technology and microbial remediation technology. Among them, the in-situ chemical passivation restoration technology is to reduce the biologically available content of heavy metals by adding restoration agents, adjusting and changing the physical and chemical properties of heavy metals in the soil, and producing a series of reactions such as precipitation, adsorption, ion exchange, and redox. With the advantages of simplicity, speed, and high efficiency, it is a good choice for remediating large areas of heavy metal-contaminated soil, but this method often requires multiple remediation agents due to changes in the soil environment, resulting in increased costs and increased the risk of secondary pollution. On the other hand, due to the long history of various industrial pollution sites in my country, soil pollution by mercury(II) and Cr(VI) is no longer a single surface pollution, but often involves deep and multi-scale pollution. Using a single chemical remediation agent, due to related factors such as changes in soil properties and environmental conditions, such as soil compaction and pH changes during the remediation process, it is easy to cause the remediation agent to fail to penetrate deep contaminated soil, resulting in a reduction in its remediation efficiency for deep contaminated soil .

For the remediation of deep heavy metal-contaminated soil, microbial remediation is a better choice, which refers to the method of reducing the bioavailability of heavy metals based on the interaction between microorganisms and their metabolites and heavy metal ions. This method has the characteristics of good permeability, low cost, sustainability and environmental friendliness, but it requires a long repair time and is not stable.

From the above, for mercury (II) and chromium (VI) contaminated soil, especially deep contaminated soil, it is difficult to effectively and continuously remediate it through one method, and often requires a combination of multiple remediation methods or processes.

Contents of the invention

Aiming at the defects existing in the remediation technology of mercury (II) and chromium (VI) polluted soil in the prior art, the first object of the present invention is to provide a kind of anaerobic sulfate-reducing bacteria synergistic iron-based material which can realize the remediation of mercury (II) and chromium (VI) Ⅱ) and chromium (Ⅵ) deep-contaminated soil with high-efficiency, sustained and stable remediation reagents, the reagent has low cost of raw materials, wide range of sources, easy to obtain, and the mercury (Ⅱ) and chromium (Ⅵ) contaminated soil of mercury (Ⅱ) and chromium (Ⅵ) (Ⅵ) realizes simultaneous stabilization and fixation, and is especially suitable for the stable restoration of deep mercury (II) and chromium (VI) deep contaminated soil.

The second object of the present invention is to provide a method for in-situ remediation of mercury (II) and chromium (VI) deep-seated contaminated soil, which uses anaerobic sulfate-reducing bacteria to couple iron-based materials to mercury and chromium-contaminated soil Remediation reagents, which simultaneously achieve efficient stabilization of mercury (II) and chromium (VI) in mercury (II) and chromium (VI) deep-contaminated soils Stability fixes.

In order to achieve the above-mentioned technical purpose, the present invention provides a reagent for remediation of mercury-chromium-contaminated soil by anaerobic sulfate-reducing bacteria in cooperation with iron-based materials, which includes iron-based materials and anaerobic sulfate-reducing bacteria bacterial liquid; the iron-based material It is obtained by reacting iron-containing silicate minerals with oxalic acid in water medium at a temperature of 60-120°C.

In a preferred scheme, the iron-containing silicate minerals include biotite, iron-aluminum garnet, phillipsite, fayalite, fushanite, orthopyroxene, neonite, ferropyroxene, magnephite, sodium At least one of amphibole. Iron-containing silicate minerals are preferred, and a composite material in which highly active nanometer ferrous oxalate is loaded on silicate minerals can be produced by reacting with oxalic acid. Silicate minerals as a carrier can improve the dispersion of nano-ferrous oxalate and ensure high activity of nano-ferrous oxalate.

In a preferred solution, the liquid-solid ratio of iron-containing silicate minerals to oxalic acid and water is 2-6mL:1g, and the mass ratio of iron-containing silicate minerals to oxalic acid is 1:2-3:1.

In a preferred scheme, the reaction time is 1 to 48 hours.

In a preferred solution, the ratio of the iron-based material to the anaerobic sulfate-reducing bacteria solution is 50-500 g/L.

In a preferred solution, the bacterial density in the anaerobic sulfate-reducing bacteria liquid is 10 ⁸ -10 ¹⁰ cells/mL.

The anaerobic sulfate-reducing bacteria bacterial liquid of the present invention is obtained by expanding the purchased anaerobic Desulfovibrio sp. ATCC 7757. The medium formula is KH ₂ PO ₄ 0.5g/L, NH ₄ Cl 1g/L, CaCl ₂ 0.1g/L, MgSO ₄ ·7H ₂ O 2.5g/L, sodium lactate 3.5g/L, and the pH value is 6.5. Inoculate the anaerobic Desulfovibrio strains into the sterilized transgenic medium, culture them at 30°C for a period of time, and wait until they reach the logarithmic phase.

The present invention also provides a method for anaerobic sulfate-reducing bacteria to cooperate with iron-based materials to restore mercury and chromium deep-contaminated soil. The method is to add the reagent to mercury (II) and Cr (VI) contaminated soil, repair.

In a preferred scheme, the added mass of the iron-based material in the reagent is 1/50-1/5 relative to mercury(II) and Cr(VI)-contaminated soil.

In a preferred solution, the reagent is applied to mercury(II) and Cr(VI) deep-seated contaminated soil by perfusion.

The principle of mercury (II) and Cr (VI) contaminated soil repaired by the mercury-chromium-contaminated soil remediation reagent of the present invention is as follows: the iron-based material in the mercury-chromium-contaminated soil remediation reagent is obtained by reacting iron-containing silicate minerals with oxalic acid, and iron-containing silicon Iron in salt minerals is activated by oxalic acid into ferrous oxalate, which can reduce mercury(II) and Cr(VI), and anaerobic sulfate-reducing bacteria can also immobilize mercury by reducing sulfate to produce hydrogen sulfide ( Ⅱ) and Cr(Ⅵ). In addition, excess hydrogen sulfide can react with active iron to form iron sulfide to further reduce or solidify mercury(Ⅱ) and Cr(Ⅵ). At the same time, the oxalate released in iron-based materials can not only complex Heavy metal ions, and can be further utilized by sulfate-reducing bacteria as electron donors, so that the microorganisms can play a longer and stable role in reducing and solidifying mercury and chromium.

Compared with the prior art, the advantages and innovations of the technical solution of the present invention are reflected in:

The anaerobic sulfate-reducing bacteria of the present invention cooperates with the iron-based material mercury and chromium contaminated soil remediation reagent to construct a coupling system of biochemical joint remediation of mercury (II) and Cr (VI), which promotes deep mercury (II) and Cr (VI) pollution The effective remediation of soil significantly reduces the bioavailability of Hg(II) and Cr(VI), and optimizes the resource allocation of the remediation system.

The anaerobic sulfate-reducing bacteria of the present invention cooperates with the iron-based material mercury-chromium-contaminated soil remediation reagent with low cost, the iron-based material can be simply synthesized from natural minerals, and the anaerobic sulfate-reducing bacteria can be directly commercially purchased.

The method for remediating mercury (II) and Cr (VI) deep-contaminated soil of the present invention has simple overall operation, low cost, no pollution to the environment, and long-term stability, which can effectively prevent the re-release of stabilized heavy metals and prevent damage to the soil. Secondary pollution, long-lasting treatment and green environmental protection, can be promoted and applied in a large area, and has certain economic value.

Detailed ways

The following examples are intended to further illustrate the content of the present invention, rather than limit the protection scope of the claims of the present invention.

Example 1

The Cr(Ⅵ)-contaminated soil samples with a depth of 20-80 cm were taken from Changsha Chromium Salt Factory. After air-drying and sieving (60 mesh), the Cr(Ⅵ) content in the soil was analyzed, as shown in Table 1.

Preparation of iron-based materials: Mix oxalic acid and phillips (100g) at a ratio of 2:1, add 600mL of deionized water, heat up to 80°C, and continue stirring for 36 hours. After the reaction is completed, filter, wash and dry to obtain Iron-based materials.

Cultivation of anaerobic sulfate-reducing bacteria: inoculate the bacteria in deoxygenated liquid medium (KH ₂ PO ₄ 0.5g/L, NH ₄ Cl 1g/L, CaCl ₂ 0.1g/L, MgSO ₄ 7H ₂ O 2.5g/L, sodium lactate 3.5g/L, pH value is 6.5), growth temperature is 30 ℃, grow to the logarithmic phase and wait for use. Simulated remediation of deep Cr(Ⅵ) contaminated soil: the remediation experiment was divided into four groups A, B, C and D, group A did not add remediation agents (no bacteria or iron-based materials), group B added remediation agents It is an iron-based material, the restoration agent of group C is culture solution of sulfate-reducing bacteria, and the restoration agent of group D is a mixture of iron-based material and sulfate-reducing bacteria liquid.

Take 10kg samples and put them into four reactors (60cm×20cm×40cm), add 2.5L deionized water to group A, add 150g iron-based materials to group B, mix and spread repeatedly, then add 2.5L deionized water Water, add 2.5L of bacterial solution to group C, add 150g of iron-based material to group D, mix well, and then add 2.5L of bacterial solution. After 40 days of remediation, the Cr(VI) content in the soil was analyzed. The obtained experimental results are shown in Table 1.

Table 1 Analysis of Cr(Ⅵ) contaminated deep soil and soil samples before and after remediation

Example 2

The Cr(Ⅵ) contaminated soil sample is consistent with the sample in Example 1.

Preparation of iron-based materials: Mix oxalic acid and biotite (50g) at a ratio of 3:2, add 200mL of deionized water, heat up to 90°C, and continue stirring for 6 hours. After the reaction is completed, filter, wash and dry to obtain Iron-based materials.

Cultivation of anaerobic sulfate-reducing bacteria: inoculate the bacteria in deoxygenated liquid medium (KH ₂ PO ₄ 0.5g/L, NH ₄ Cl 1g/L, CaCl ₂ 0.1g/L, MgSO ₄ 7H ₂ O 2.5g/L, sodium lactate 3.5g/L, pH value 6.5), the growth temperature is 30°C, grow to the logarithmic phase before use, and the bacterial density in the bacterial liquid is ⁷ *108/mL. Simulated remediation of deep Cr(Ⅵ) contaminated soil: the remediation experiment was divided into four groups A, B, C and D, group A did not add remediation agents (no bacteria or iron-based materials), group B added remediation agents It is an iron-based material, the restoration agent of group C is culture solution of sulfate-reducing bacteria, and the restoration agent of group D is a mixture of iron-based material and sulfate-reducing bacteria liquid.

Take 10kg of samples and put them into four reactors (60cm×20cm×40cm), add 2L of deionized water to group A, add 100g of iron-based materials to group B, mix and spread repeatedly, add 2L of deionized water, Add 2L of bacterial solution to group C, and add 50g of iron-based materials to group D, mix and spread evenly, and then add 2L of bacterial solution. After 45 days of remediation, the Cr(VI) content in the soil was analyzed. The obtained experimental results are shown in Table 2.

Table 2 Analysis of Cr(Ⅵ) contaminated deep soil and soil samples before and after remediation

Example 3

The Hg-contaminated soil samples with a depth of 20-100 cm were taken from Tongren, air-dried and sieved (40 mesh), and the content and form of Hg in the soil are shown in Table 3 and Table 4.

Preparation of iron-based materials: Mix oxalic acid and iron-aluminum garnet (100g) at a ratio of 2:1, add 600mL of deionized water, heat up to 80°C for 36 hours, and after the reaction is completed, filter, wash and dry to obtain iron base material.

Cultivation of anaerobic sulfate-reducing bacteria: inoculate the bacteria in deoxygenated liquid medium (KH ₂ PO ₄ 0.5g/L, NH ₄ Cl 1g/L, CaCl ₂ 0.1g/L, MgSO ₄ 7H ₂ O 2.5g/L, sodium lactate 3.5g/L, pH value is 6.5) to cultivate, the growth temperature is 30 ℃, after growing to the logarithmic phase, it is used for the remediation of contaminated soil.

Simulated remediation of deep Hg-contaminated soil: the remediation experiments were divided into four groups: A, B, C and D. Group A had no remediation agents (no bacteria or iron-based materials), and group B applied remediation agents with iron-based materials. , Group C is the culture solution of sulfate-reducing bacteria, and the repair agent of group D is a mixture of iron-based materials and sulfate-reducing bacteria solution.

Take 10kg samples and put them into four reactors (60cm×20cm×40cm), add 2.5L deionized water to group A, add 200g iron-based materials to group B, mix and spread repeatedly, then add 2.5L deionized water Water, add 2.5L of bacterial solution to group C, add 200g of iron-based material to group D, mix well, and then add 2.5L of bacterial solution. After 60 days of restoration, the mercury content and form in the soil were analyzed. The obtained experimental results are shown in Table 3.

Table 3 Mercury-contaminated deep soil samples

Table 4 Analysis of mercury speciation in mercury-contaminated soil before and after remediation

Example 4

The sample is the deep mercury pollution sample in Example 3.

Preparation of iron-based materials: Mix oxalic acid and calcium ferropyroxene (100g) at a ratio of 2:1, add 400mL of deionized water, heat up to 95°C and react for 36 hours. After the reaction is completed, filter, wash and dry to obtain iron base material.

Cultivation of anaerobic sulfate-reducing bacteria: inoculate the bacteria in deoxygenated liquid medium (KH ₂ PO ₄ 0.5g/L, NH ₄ Cl 1g/L, CaCl ₂ 0.1g/L, MgSO ₄ 7H ₂ O 2.5g/L, sodium lactate 3.5g/L, pH value is 6.5) for cultivation, the growth temperature is 30°C, when the growth reaches the logarithmic phase, the bacterial density is 7.5* ¹⁰⁸ /mL, used for pollution Soil remediation.

Simulated remediation of deep Hg-contaminated soil: the remediation experiments were divided into four groups: A, B, C and D. Group A had no remediation agents (no bacteria or iron-based materials), and group B applied remediation agents with iron-based materials. , Group C is the culture solution of sulfate-reducing bacteria, and the repair agent of group D is a mixture of iron-based materials and sulfate-reducing bacteria solution.

Take 10kg samples and put them into four reactors (60cm×20cm×40cm), add 1.5L deionized water to group A, add 150g iron-based materials to group B, mix and spread repeatedly, then add 1.5L deionized water Water, add 1.5L of bacterial solution to group C, add 150g of iron-based material to group D, mix well, and then add 1.5L of bacterial solution. After 40 days of restoration, the mercury content and form in the soil were analyzed. The obtained experimental results are shown in Table 5.

Table 5 Analysis of mercury speciation in mercury-contaminated soil before and after remediation

Claims (8)

1. A reagent for anaerobic sulfate-reducing bacteria synergistically remediating mercury and chromium deep-layer contaminated soil with iron-based materials, characterized in that: it includes iron-based materials and anaerobic sulfate-reducing bacteria bacterial liquid; It is obtained by reacting silicate minerals and oxalic acid at a temperature of 60-120°C in an aqueous medium. 2. A reagent for anaerobic sulfate-reducing bacteria in cooperation with iron-based materials to repair mercury and chromium deep-contaminated soil according to claim 1, characterized in that: the iron-containing silicate minerals include biotite, iron-aluminum pomegranate At least one of sonite, phillipsite, fayalite, fushanite, orthopyroxene, neonite, anandropyroxene, magnephite, and sodium amphibole. 3. the reagent of a kind of anaerobic sulfate-reducing bacteria cooperative iron-based material repairing mercury and chromium deep-layer polluted soil according to claim 1, is characterized in that: the liquid-solid ratio of iron-containing silicate mineral and oxalic acid and water is 2~6mL:1g, the mass ratio of iron-containing silicate minerals to oxalic acid is 1:2~3:1. 4. A reagent for remediating mercury and chromium deep-contaminated soil with anaerobic sulfate-reducing bacteria in cooperation with iron-based materials according to any one of claims 1 to 3, characterized in that: the reaction time is 1 to 48 hours. 5. A reagent for anaerobic sulfate-reducing bacteria in cooperation with iron-based materials to repair mercury and chromium deep-contaminated soil according to any one of claims 1 to 3, characterized in that: iron-based materials and anaerobic sulfate-reducing bacteria The ratio of the bacteria liquid is 50-500 g/L, and the cell density of the sulfate-reducing bacteria in the anaerobic sulfate-reducing bacteria liquid is 10 ⁸ -10 ¹⁰ cells/mL. 6. A method for anaerobic sulfate-reducing bacteria to cooperate with iron-based materials to repair mercury and chromium deep-contaminated soil, characterized in that: adding the reagent described in any one of claims 1 to 5 to mercury (II) and chromium (VI) ) Contaminated soil for remediation. 7. the method for a kind of anaerobic sulfate-reducing bacteria cooperative iron-based material repair mercury and chromium deep-contaminated soil according to claim 6, it is characterized in that: iron-based material in the reagent is relatively mercury (II) and chromium (VI) ) The added mass of contaminated soil is 1/50~1/5. 8. The in-situ remediation method for mercury-chromium-contaminated soil according to claim 6, characterized in that: the reagent is added to mercury (II) and chromium (VI) deep-layer contaminated soil by pouring.