A microbial remediation agent for water vanadium pollution control and its preparation method and application

Abstract

The present invention discloses a microbial remediation agent for water vanadium pollution control and a preparation method thereof, comprising microorganisms and a carrier, wherein the microorganisms include denitrifying Thiobacillus and sulfur-reducing Geobacter, the carrier includes activated carbon, sulfur powder and sodium acetate, and the microbial remediation agent is obtained by loading the microorganisms onto the carrier. The present invention targets V(V) in groundwater, and uses a microbial agent to reduce V(V) in groundwater into V(IV) precipitation, so as to reduce the toxicity and mobility of vanadium in groundwater, and significantly reduce the content of highly toxic V(V). The microbial preparation has high activity, fast reproduction, environmental protection and no pollution, low cost, and reasonable compatibility between denitrifying Thiobacillus and Geobacter, symbiotic coordination, and neither the problem of eutrophication caused by the introduction of a large amount of organic nutrients nor the generation of a large amount of sulfate acidification of groundwater.

Description

Technical Field

[0001] The invention relates to the technical field of heavy metal pollution remediation, and in particular to a microbial remediation agent for water vanadium pollution treatment, and a preparation method and application thereof. Background Art

[0002] Vanadium (V) is a redox-sensitive metal that is widely found in the earth's crust and is used in metallurgy, manufacturing and refining industries. It is an effective catalyst for the selective catalytic reduction of nitrogen oxides in exhaust gases. The dissolution of vanadium-rich rocks and human activities lead to the presence of vanadium in groundwater. For example, mining and smelting processes emit vanadium into the soil, after which vanadium can enter aquifers through infiltration. Vanadium contamination in groundwater is receiving increasing attention due to growing public health concerns. Ingestion of large amounts of V by humans can lead to acute or chronic poisoning of the blood, respiratory system, nervous system, skin and kidneys, leading to corresponding diseases.

[0003] Vanadium exists in different oxidation states, and its toxicity increases with the increase of vanadium compound state. Pentavalent vanadium, vanadium (V), is considered to be the most toxic and mobile form. Physical and chemical treatment methods, such as adsorption, precipitation, and immobilization, have been used to remove vanadium (V), however, the generation of large amounts of sludge and high operating costs limit these applications. Compared with vanadium (V), vanadium (IV) is less toxic and insoluble at natural pH. So far, various methods have been proposed to remove vanadium (V) from contaminated water. For example, vanadium (V) can be removed by adsorption, ion exchange, and chemical reduction reactions. However, these physical and chemical methods are not economically feasible due to high operating costs, thus limiting their application in groundwater remediation.

[0004] In contrast, microbial reduction of vanadium (V) is a promising biological removal method because of its low cost and high potential for in-situ remediation of groundwater. However, there are still few reports on the remediation of vanadium pollution in the environment. Chinese patent application CN114317369A discloses Bacillus and its use in reducing pentavalent vanadium and hexavalent chromium. It discloses that Bacillus amyloliquefaciens SM01 can reduce vanadium and chromium at the same time, has a high tolerance to vanadium and chromium in the environment, can adapt to the living environment of high background pollution areas, has a high reduction rate for hexavalent chromium and pentavalent vanadium, and needs to add citric acid as an electron donor when used. However, this remediation technology requires the introduction of a large amount of reducing bacteria and citric acid into the environment, which will affect the microecological balance of the environment. Summary of the invention

[0005] One of the purposes of the present invention is to provide an environmentally friendly, pollution-free and low-cost microbial remediation agent for the treatment of vanadium pollution in water in response to the above-mentioned problems.

[0006] In order to achieve its purpose, the present invention adopts the following technical solution:

[0007] A microbial remediation agent for treating vanadium pollution in water, comprising microorganisms and a carrier, wherein the microorganisms include denitrifying Thiobacillus and sulfur-reducing Geobacter, and the carrier includes activated carbon, sulfur powder and sodium acetate, and the microbial remediation agent is obtained by loading the microorganisms onto the carrier;

[0008] Preferably, the mass ratio of activated carbon, sulfur powder and sodium acetate in the carrier is 10:0.8-1.7:0.8-1.7 or 10:0.9-1.6:0.9-1.6.

[0009] The microbial remediation agent is obtained by mixing a bacterial solution containing microorganisms with a solid carrier, placing the mixture in a static load for 10-24 hours, and drying at 3-10° C., preferably placing the mixture in a static load for 10-16 hours, and drying at 3-6° C.;

[0010] The concentrations of Thiobacillus denitrificans and Geobacter sulfurreducens in the bacterial solution were both 1.4×10 8 ~1.6×10 8 CFU / mL; the mass ratio of activated carbon, sulfur powder and sodium acetate in the carrier is 10:1-1.5:1-1.5; the mass ratio of bacterial solution to carrier is 1:0.3-0.5; preferably, the concentrations of denitrifying Thiobacillus and sulfur-reducing Geobacter in the bacterial solution are both 1.5×10 8 CFU / mL.

[0011] The bacterial solution is an aqueous solution containing denitrifying Thiobacillus and sulfur-reducing Geobacter, wherein the aqueous solution contains 0.1-0.5 g / L calcium chloride, 0.8-1.5 g / L magnesium chloride hexahydrate, 0.2-0.6 g / L sodium chloride, 0.5-2.0 g / L sodium bicarbonate and 0.01-0.2 g / L potassium dihydrogen phosphate, with a pH of 6.0-8.0; preferably, the aqueous solution contains 0.2-0.3 g / L calcium chloride, 0.9-1.1 g / L magnesium chloride hexahydrate, 0.4-0.5 g / L sodium chloride, 0.7-0.9 g / L sodium bicarbonate, 0.02-0.04 g / L potassium dihydrogen phosphate, 0.1-0.2 g / L ammonium chloride and 0.02-0.035 g / L potassium chloride;

[0012] Preferably, the aqueous solution is synthetic groundwater, which contains: 0.1557 g / L ammonium chloride, 0.2464 g / L calcium chloride, 1.0572 g / L magnesium chloride hexahydrate, 0.4459 g / L sodium chloride, 0.0283 g / L potassium chloride, 0.8082 g / L sodium bicarbonate and 0.0299 g / L potassium dihydrogen phosphate.

[0013] The bacterial solution is obtained by culturing denitrifying Thiobacillus and sulfur-reducing Geobacter to an OD600 of 0.8 to 1.0, inoculating them into synthetic groundwater respectively, culturing them at 25 to 35° C. for 12 to 24 hours, and then mixing the two bacterial-containing synthetic groundwaters; preferably, denitrifying Thiobacillus and sulfur-reducing Geobacter are expanded and cultured in a culture medium respectively, and then inoculated into synthetic groundwater respectively.

[0014] Another object of the present invention is to provide a method for preparing the microbial remediation agent described in any one of the above, comprising the following steps:

[0015] 1) preparing a mixed bacterial solution containing Thiobacillus denitrificans and Geobacter sulfurreducens;

[0016] 2) Mix the mixed bacterial solution with the carrier so that the microorganisms are loaded onto the carrier.

[0017] The step 1) is to inoculate denitrifying Thiobacillus and sulfur-reducing Geobacter into aqueous solution for cultivation, and then mix the two bacterial aqueous solutions to obtain a mixed bacterial solution; the concentrations of denitrifying Thiobacillus and sulfur-reducing Geobacter are both 1.4×10 8 ~1.6×10 8 CFU / mL; the aqueous solution contains 0.1-0.5 g / L calcium chloride, 0.8-1.5 g / L magnesium chloride hexahydrate, 0.2-0.6 g / L sodium chloride, 0.5-2.0 g / L sodium bicarbonate and 0.01-0.2 g / L potassium dihydrogen phosphate, with a pH of 6.0-8.0.

[0018] The step 1) is to expand the culture medium of Thiobacillus denitrificans and Geobacter sulfurreducens respectively, and then inoculate them into an aqueous solution and culture them at 25-35° C. for 12-24 hours; preferably, culture them at 30° C. in the aqueous solution for 12 hours.

[0019] In step 2), the mass ratio of the mixed bacterial solution to the carrier is 1:0.3-0.5, and the mass ratio of activated carbon, sulfur powder and sodium acetate in the carrier is 10:1-1.5:1-1.5; after mixing the mixed bacterial solution and the carrier, the mixed bacterial solution is allowed to stand for 10-24 hours and dried at 3-10°C to obtain the product.

[0020] The last object of the present invention is to provide the use of any of the above-mentioned microbial remediation agents in removing pentavalent vanadium from vanadium-contaminated wastewater.

[0021] Preferably, 0.5 to 1.4 grams of the microbial remediation agent is added per cubic meter of sewage, once every 2 to 4 days, until the V(V) concentration in the sewage reaches below the target concentration;

[0022] It is further preferred that 1 gram of the microbial remediation agent is added per cubic meter of sewage, once every 3 days.

[0023] The beneficial effects of the present invention are:

[0024] Mixed nutritional microbial reduction of V(V) is carried out using sodium acetate and elemental sulfur. The heterotrophic microorganism Geobacillus sulfur-reducing uses the electrons and energy provided by the organic electron donor sodium acetate oxidation to reduce the highly toxic and highly mobile V(V) to the less toxic and less mobile V(IV). The autotrophic microorganism Thiobacillus denitrifying uses the electrons and energy generated during the oxidation of elemental sulfur to sulfate to reduce V(V). The sulfate generated can be used by Geobacillus sulfur-reducing, which not only saves the amount of sodium acetate, but also avoids the accumulation of large amounts of sulfate. There are a large number of tiny pores in the activated carbon, which has a large surface area, giving it a strong adsorption capacity. While providing the space required for microbial growth and reproduction, it can also adsorb sodium acetate and sulfur to provide nutrition for the microorganisms.

[0025] The present invention targets V(V) in groundwater and uses microbial agents to reduce V(V) in groundwater into V(IV) precipitation, so as to reduce the toxicity and mobility of vanadium in groundwater and significantly reduce the content of highly toxic V(V). The microbial agent has high activity, fast reproduction, environmental protection and no pollution, low cost, and reasonable compatibility between denitrifying Thiobacillus and Geobacter, symbiotic coordination, and neither the problem of eutrophication caused by the introduction of a large amount of organic nutrients nor the generation of a large amount of sulfate acidifying groundwater. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is an analysis of the effect of different dosing times on V(V) reduction.

[0027] Figure 2 XPS analysis confirmed the generation of V(IV). DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with embodiments, but the present invention is not limited thereto.

[0029] The experimental methods in the following examples are all conventional methods unless otherwise specified; the biological and chemical reagents used are all conventional reagents in the art unless otherwise specified.

[0030] Example 1. Strain isolation and expansion culture

[0031] 1. Strain Isolation

[0032] Soil from a mining area in Yiyang City, Hunan Province was domesticated in a domestication solution containing 100 mg / LV(V) for 8 weeks. Three microorganisms were isolated using the plate streak method and identified as Geobacter sulfurreducens, Enterococcus faecalis and Thiobacillus denitrificans.

[0033] 2. Expansion of bacterial strains

[0034] The isolated strains were cultured.

[0035] The formula of the expansion medium of Thiobacillus denitrificans is as follows: 10 g / L sodium thiosulfate pentahydrate, 4 g / L potassium nitrate, 2 g / L potassium dihydrogen phosphate, 1 g / L sodium bicarbonate, 0.5 g / L magnesium chloride hexahydrate, and 0.05 g / L sulfur powder. The culture was carried out at 180 r / min on a shaking table and 30 to 35° C. for 24 to 36 hours, and the OD600 was 0.8 to 1.0. In this embodiment, the culture was carried out at 30° C. for 24 hours.

[0036] The formula of the culture medium for expanding Geobacter is: 20 g / L sodium chloride, 10 g / L yeast extract, 20 g / L peptone. The culture was carried out at 30-35° C. for 24-36 hours with a shaking table at 180 r / min, and the OD600 was 0.8-1.0. In this embodiment, the culture was carried out at 30° C. for 24 hours.

[0037] Formula of Enterococcus faecalis expansion medium: 20g / L sodium chloride, 10g / L yeast extract, 20g / L peptone. Shake at 180r / min, culture at 30-35°C for 24-36 hours, OD600 is 0.8-1.0. In this embodiment, culture is carried out at 30°C for 24 hours.

[0038] After the culture is completed, the culture solution is centrifuged separately, the culture solution of the strain is centrifuged at 6000rpm for 20min, the supernatant is poured out, and the lower sediment is rinsed three times with sterile deionized water to finally obtain the microorganisms in the lower layer. All the obtained microorganisms are inoculated into synthetic groundwater for culture, and 1L of synthetic groundwater is inoculated for every 100ml of the culture solution. Different strains are cultured separately, and the pH of the synthetic groundwater is 6.0-8.0, which contains: 0.1557g / L ammonium chloride, 0.2464g / L calcium chloride, 1.0572g / L magnesium chloride hexahydrate, 0.4459g / L sodium chloride, 0.0283g / L potassium chloride, 0.8082g / L sodium bicarbonate and 0.0299g / L potassium dihydrogen phosphate, and cultured at about 30℃ for 12h.

[0039] 3. Preparation of mixed bacterial solution

[0040] The synthetic groundwater containing different bacterial species after culture is mixed to obtain a mixed bacterial solution.

[0041] Mixed bacterial solution 1: Mix synthetic groundwater containing Thiobacillus denitrificans and Geobacter sulfur-reducing in a mass ratio of 1:1.5;

[0042] Mixed bacterial solution 2: Mix synthetic groundwater containing Thiobacillus denitrificans and Geobacter sulfur-reducing at a mass ratio of 1.2:1.5;

[0043] Mixed bacterial solution 3: Mix synthetic groundwater containing Thiobacillus denitrificans and Geobacter sulfur-reducing in a mass ratio of 1:2;

[0044] Mixed bacterial solution 4: Mix synthetic groundwater containing Thiobacillus denitrificans and Enterococcus faecalis at a mass ratio of 1:1.5;

[0045] Mixed bacterial solution 5: Mix synthetic groundwater containing Thiobacillus denitrificans and Enterococcus faecalis at a mass ratio of 1.2:1.5;

[0046] Mixed bacterial solution 6: Mix synthetic groundwater containing Thiobacillus denitrificans and Enterococcus faecalis at a mass ratio of 1:1.8;

[0047] Single bacterial solution 1: Thiobacillus denitrificans bacterial solution;

[0048] Single bacterial solution 2: Geobacter sulfur-reducing bacterial solution;

[0049] Single bacterial liquid 3: Enterococcus faecalis bacterial liquid.

[0050] Example 2. Preparation of microbial remediation agent and remediation of vanadium pollution in water

[0051] 1. Preparation of different microbial remediation agents

[0052] The raw materials of microbial carrier are as follows:

[0053] Spherical activated carbon is used, and the diameter of the spherical shell is 0.4-0.6mm; the purity of sulfur powder (S) is 99.9%, and the purity of sodium acetate, sodium citrate, sodium lactate and ethanol is 99%.

[0054] The bacterial solution prepared in Example 1 was mixed with a carrier, stirred evenly, left to stand at room temperature for 12 hours, and then dried at low temperature at 4°C to obtain a microbial remediation agent. In this example, different carrier raw materials were used for comparison, and a total of 12 different microbial remediation agents were prepared, and their components and proportions are shown in Table 1.

[0055] Table 1

[0056]

[0057] 2. Experiment on the number of dosing times and interval time

[0058] Prepare wastewater containing 400 mg / L of pentavalent vanadium (V(V)), take repair agent 1 for experiment, set up three experimental groups: treatment 1: add repair agent 1 at the beginning of the reaction; treatment 2: add repair agent 1 at the beginning of the reaction and on the 6th day; treatment 3: add repair agent 1 at the beginning of the reaction and every 3 days; the dosage is calculated based on 1 gram of repair agent per cubic meter of wastewater. The method in "GBT19226-2003-Determination of Vanadium in Coal" was used to detect the V(V) content in the wastewater every day for 15 days. The test results are as follows: Figure 1 As shown in the figure, the V(V) removal rate of treatment 3 is the highest. Subsequent experiments determined that the best way to add the repair agent is to add it every 3 days.

[0059] XPS analysis of V in the aqueous solution of treatment 3 at 15 days was performed, as shown in Figure 2 As shown, V(IV) was detected and after treatment with the repair agent, V(V) was reduced to the less toxic V(IV).

[0060] 3. Vanadium pollution remediation treatment with different remediation agents

[0061] The prepared wastewater containing 400 mg / L of pentavalent vanadium (V(V)) was used for remediation treatment using the previously prepared microbial remediation agent: 1 gram of the remediation agent was added per cubic meter of wastewater, and the microbial remediation agent was added once every 3 days.

[0062] The method in GBT19226-2003-Determination of Vanadium in Coal was used to detect the V (V) content before and after sewage treatment. The test results are shown in Table 2.

[0063] Table 2

[0064]

[0065] Among the 12 prepared remediators, the V(V) reduction rate of remediators 1, 2, and 3 can reach about 90% within 15 days, and the V(V) reduction rate of remediators 4, 5, and 6 is about 70%, indicating that the combination of Geobacter sulfurreducens and Thiobacillus denitrificans is better than the combination of Enterococcus faecalis and Thiobacillus denitrificans. The V(V) reduction rate of remediators 7, 8, and 9 within 15 days is about 55%, indicating that the V(V) reduction performance of the remediator prepared by the mixed bacterial solution is significantly better than that of the remediator prepared by the single bacterial solution. The V(V) reduction rate of remediators 10, 11, and 12 is lower than that of remediators 1, 2, and 3, indicating that sodium acetate is better than sodium citrate, sodium lactate, and ethanol as an electron donor for microbial V(V) reduction, and the V(V) reduction rate of the remediator using sodium acetate as an organic electron donor in the carrier is significantly improved.

Claims

1. A microbial remediation agent for water vanadium pollution control, characterized in that: It is composed of microorganisms and carriers, wherein the microorganisms are denitrifying Thiobacillus and sulfur-reducing Geobacter, the carriers are activated carbon, sulfur powder and sodium acetate, and the microbial remediation agent is obtained by loading the microorganisms onto the carriers; The mass ratio of activated carbon, sulfur powder and sodium acetate in the carrier is 10:0.8-1.7:0.8-1.7; The microbial remediation agent is obtained by mixing a bacterial solution containing microorganisms with a solid carrier, placing the mixture in a static load for 10-24 hours, and drying at 3-10°C. The concentrations of Thiobacillus denitrificans and Geobacter sulfurreducens in the bacterial solution were both 1.4×10 8 ~1.6×10 8 CFU / mL; the mass ratio of bacterial solution to carrier is 1:0.3~0.

5.

2. The microbial remediation agent according to claim 1, characterized in that: The mass ratio of activated carbon, sulfur powder and sodium acetate in the carrier is 10:1-1.5:1-1.

5.

3. The microbial remediation agent according to claim 2, characterized in that: The bacterial liquid is an aqueous solution containing denitrifying Thiobacillus and sulfur-reducing Geobacter, wherein the aqueous solution contains 0.1-0.5 g / L calcium chloride, 0.8-1.5 g / L magnesium chloride hexahydrate, 0.2-0.6 g / L sodium chloride, 0.5-2.0 g / L sodium bicarbonate and 0.01-0.2 g / L potassium dihydrogen phosphate, with a pH of 6.0-8.

0.

4. The microbial remediation agent according to claim 3, characterized in that: The aqueous solution contains 0.2-0.3 g / L calcium chloride, 0.9-1.1 g / L magnesium chloride hexahydrate, 0.4-0.5 g / L sodium chloride, 0.7-0.9 g / L sodium bicarbonate, 0.02-0.04 g / L potassium dihydrogen phosphate, 0.1-0.2 g / L ammonium chloride and 0.02-0.035 g / L potassium chloride.

5. The microbial remediation agent according to claim 3, characterized in that: The bacterial solution is obtained by culturing Thiobacillus denitrificans and Geobacter sulfurreducens to OD600 of 0.8-1.0, inoculating them into synthetic groundwater respectively, culturing them at 25-35°C for 12-24h, and then mixing the two bacterial-containing synthetic groundwaters.

6. The method for preparing the microbial remediation agent according to any one of claims 1 to 5, characterized in that: The steps include: 1) preparing a mixed bacterial solution containing Thiobacillus denitrificans and Geobacter sulfurreducens; 2) Mix the mixed bacterial solution with the carrier so that the microorganisms are loaded onto the carrier.

7. The preparation method according to claim 6, characterized in that: The step 1) is to inoculate denitrifying Thiobacillus and sulfur-reducing Geobacter into aqueous solution for cultivation, and then mix the two bacterial aqueous solutions to obtain a mixed bacterial solution; the concentrations of denitrifying Thiobacillus and sulfur-reducing Geobacter are both 1.4×10 8 ~1.6×10 8 CFU / mL; the aqueous solution contains 0.1-0.5 g / L calcium chloride, 0.8-1.5 g / L magnesium chloride hexahydrate, 0.2-0.6 g / L sodium chloride, 0.5-2.0 g / L sodium bicarbonate and 0.01-0.2 g / L potassium dihydrogen phosphate, with a pH of 6.0-8.

0.

8. The preparation method according to claim 7, characterized in that: The step 1) is to expand the culture medium of Thiobacillus denitrificans and Geobacter sulfurreducens respectively, and then inoculate them into the aqueous solution and culture them at 25-35° C. for 12-24 hours.

9. The preparation method according to claim 7, characterized in that: In step 2), the mass ratio of the mixed bacterial solution to the carrier is 1:0.3-0.5, and the mass ratio of activated carbon, sulfur powder and sodium acetate in the carrier is 10:1-1.5:1-1.5; after mixing the mixed bacterial solution and the carrier, the mixed bacterial solution is allowed to stand for 10-24 hours and dried at 3-10°C to obtain the product.

10. Use of the microbial remediation agent according to any one of claims 1 to 5 in removing pentavalent vanadium from vanadium-contaminated wastewater.

11. The use according to claim 10, characterized in that: 0.5 to 1.4 grams of the microbial remediation agent is added to each cubic meter of sewage, once every 2 to 4 days, until the V(V) concentration in the sewage reaches below the target concentration.

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