A method for microbial regeneration of a biochar that adsorbs trichloroethylene

Abstract

The application discloses a method for regenerating biochar adsorbing trichloroethylene, which comprises the following steps: 1) mixing a Micrococcus halophilus bacterial solution and biochar adsorbing trichloroethylene in a culture medium solution, adding nutrients required for growth of the microorganism to the mixed solution, and degrading and removing trichloroethylene adsorbed on the biochar under anaerobic conditions; and 2) performing solid-liquid separation on the biochar after degradation and removal of trichloroethylene and the Micrococcus halophilus bacterial solution, so as to realize regeneration of the biochar. The application adopts the Micrococcus halophilus to degrade and regenerate the biochar adsorbing trichloroethylene, can degrade trichloroethylene pollutants adsorbed on the biochar, can regenerate the biochar, can make high adsorption performance of the biochar on organic pollutants be kept for a long time, can be applied to remediation of groundwater halogenated hydrocarbon pollutants for a long time, can reduce consumption of material resources, can reduce biochar use and groundwater remediation cost, can reduce secondary pollution, and has good economic and environmental benefits.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for regenerating biochar adsorbing trichloroethylene, and belongs to the technical field of adsorption material regeneration. BACKGROUND

[0002] Trichloroethylene (TCE) is a common halogenated hydrocarbon organic pollutant in groundwater, which has significant environmental health risks. Long-term exposure of human body to trichloroethylene pollution will significantly increase the probability of suffering from diseases such as cancer. Biochar is a stable, high specific surface area and environmentally friendly carbon adsorption material obtained by high-temperature pyrolysis of biomass such as wood chips and crop straw under anaerobic or anoxic conditions. The adsorption type permeable reactive barrier (PRB) using biochar as adsorbent can quickly and effectively fix trichloroethylene in groundwater and has been applied to groundwater pollution remediation. However, in practical application, the adsorption capacity of biochar for trichloroethylene is often limited. After adsorption saturation, the adsorption performance of biochar will be significantly reduced, which cannot continuously adsorb trichloroethylene and is invalid, resulting in frequent replacement of biochar materials and significantly increasing the cost of groundwater remediation. Therefore, it is urgent to develop a regeneration technology for biochar adsorbing trichloroethylene to maintain the good adsorption performance of biochar for trichloroethylene and prolong the service life of biochar, thereby reducing the remediation cost.

[0003] Removing the adsorbed trichloroethylene on biochar is the key to biochar regeneration. The adsorbed trichloroethylene on biochar can be removed by physical techniques such as solvent extraction and heating desorption, and can also be removed by chemical degradation, but few microbial degradation methods are used. There are reports that aerobic bacteria are used to remove adsorbed trichloroethylene on biochar, but they are not suitable for groundwater pollution remediation. In addition, due to the use of non-trichloroethylene degradation specific bacteria, the regeneration effect is not ideal. Generally speaking, the degradation principle of adsorbed pollutants is desorption degradation, in which desorption is the rate-limiting step. The microbial degradation technology based on this principle has the shortcomings of low utilization rate of pollutants and difficulty in realizing biochar regeneration.

[0004] Therefore, there is currently no microbial regeneration technology for biochar adsorbing trichloroethylene under anaerobic conditions. SUMMARY

[0005] The present application provides a microbial regeneration method for biochar adsorbing trichloroethylene to overcome the shortcomings of the prior art. The technical scheme of the present application is as follows:

[0006] The present application first provides a microbial regeneration method for biochar adsorbing trichloroethylene, which comprises the following steps:

[0007] 1) mixing the dehalococcoides mccartyi 195 and the biochar adsorbed with trichloroethylene in the culture medium solution, adding nutrients required for microbial growth to the mixed solution, and degrading and removing the trichloroethylene adsorbed on the biochar under anaerobic conditions;

[0008] 2) solid-liquid separation of the biochar after degrading and removing the trichloroethylene and the dehalococcoides mccartyi 195, to realize regeneration of the biochar.

[0009] Preferably, the biochar is a biochar prepared by pyrolysis of biomass under anoxic conditions, and the addition concentration of the biochar in the mixed solution is 0.6-2.0 g / L.

[0010] Dehalococcoides mccartyi 195 is an anaerobic dechlorination bacterium that can completely dechlorinate trichloroethylene, tetrachloroethylene and other chlorinated ethylenes into non-toxic and harmless ethylene. 10.1126 / science.276.5318.1568; 10.1128 / aem.71.7.3866-3871.2005; 10.1021 / acs.est.9b06527, etc. have reported and studied it, and its accession number is ATCC BAA-2266 and KCTC 15142. However, the current research and application of dehalococcoides mccartyi 195 are only for the treatment of free pollutants.

[0011] The volume ratio of the dehalococcoides mccartyi 195 to the culture medium solution is 1-10:50.

[0012] Preferably, the nutrients include hydrogen and a mixed vitamin solution, and the volume addition ratio of the mixed vitamin solution in the mixed solution is 0.2%-1%.

[0013] Preferably, the solvent of the mixed vitamin solution is water, and the composition is: biotin 0.04 g / L, folic acid 0.04 g / L, pyridoxine hydrochloride 0.2 g / L, riboflavin 0.1 g / L, thiamine 0.1 g / L, nicotinic acid 0.1 g / L, pantothenic acid 0.1 g / L, p-aminobenzoic acid 0.1 g / L, lipoic acid 0.1 g / L, and vitamin B12 0.002 g / L.

[0014] Preferably, the culture medium solution is an anaerobic liquid medium, the pH is 6.5-7.2, and the temperature for degrading and removing the trichloroethylene adsorbed on the biochar under anaerobic conditions is 28-32℃.

[0015] Preferably, the 1L medium solution comprises 1ml trace element stock solution, 10ml salt stock solution and 1ml Se / W stock solution, and the rest is water;

[0016] The trace element stock solution comprises FeCl2.4H2O 1.5g / L, CoCl2.6H2O 0.19g / L, MnCl2.4H2O 0.1g / L, ZnCl2 0.07g / L, H3BO3 0.006g / L, Na2MoO4.2H2O 0.036g / L, NiCl2.6H2O 0.024g / L, CuCl2.2H2O 0.002g / L;

[0017] The salt stock solution comprises NaCl 100.0g / L, MgCl2.6H2O 50.0g / L, KH2PO4 20.0g / L, NH4Cl 30.0g / L, KCl 30.0g / L, CaCl2.2H2O 1.5g / L;

[0018] The Se / W stock solution comprises Na2SeO3.5H2O 0.006g / L, NaWO4.2H2O 0.008g / L, NaOH 0.5g / L.

[0019] Preferably, the time for degrading and removing the trichloroethylene adsorbed on the biochar under anaerobic conditions in step 1) is 28-32 days.

[0020] The application also provides the application of the biochar regenerated by the above method in the cyclic adsorption of trichloroethylene in water bodies.

[0021] The application adopts Dehalococcoides mccartyi 195 to degrade and regenerate the biochar adsorbed with trichloroethylene, which can degrade the trichloroethylene pollutants adsorbed on the biochar and regenerate the biochar, so that the high adsorption performance of the biochar on organic pollutants can be maintained for a long time, the biochar can be cyclically applied to the remediation of groundwater halogenated hydrocarbon pollutants for a long time, the consumption of material resources can be reduced, the cost of biochar use and groundwater remediation can be reduced, and secondary pollution can be reduced.

[0022] Compared with the prior art, the application has the following beneficial effects:

[0023] 1. The application utilizes Dehalococcoides mccartyi 195 to realize the regeneration of biochar, realizes the in-situ degradation of the adsorbed trichloroethylene on the biochar through electron transfer instead of desorption, and has the advantages of microbial degradation, such as low energy consumption, low cost, environmental friendliness and the advantage of realizing in-situ regeneration, and has a good application prospect.

[0024] The regenerated biochar obtained by the biochar regeneration method developed by the application can maintain good adsorption performance on trichloroethylene, and the adsorption capacity of the biochar can be maintained at more than 80% after 5 cycles of adsorption and regeneration;

[0025] 2. The biochar regeneration method developed by the application is simple in process, and can regenerate biochar in situ in groundwater remediation, and is a high-efficiency, green and low-cost regeneration method. DETAILED DESCRIPTION

[0026] Dehalococcoides mccartyi 195 was cultured in a culture medium solution (the composition of the culture medium solution is shown in Table 1), and hydrogen and nutrients (the composition of the mixed vitamin solution is shown in Table 2) were added during the culture process, and an anaerobic and dark environment was maintained, the temperature was 30°C, and the culture was static, to obtain a dehalococcoides bacterial solution.

[0027] Tenax assisted desorption is proved to be a technology that can characterize the bioavailability of adsorbed pollutants. The Tenax assisted desorption experiment on the biochar adsorbed trichloroethylene shows that the desorption rate of the adsorbed trichloroethylene on the biochar is less than 7% for 5 consecutive times, which indicates that the biochar is tightly combined with trichloroethylene, and the adsorbed trichloroethylene on the biochar is difficult to be converted into free trichloroethylene through desorption, and at the same time, it is also difficult to regenerate the biochar adsorbed trichloroethylene through desorption degradation.

[0028] Further, the dehalococcoides bacterial solution was centrifuged at high speed, and then the supernatant was centrifuged to obtain the dehalococcoides extracellular supernatant, and the supernatant was used to degrade the adsorbed trichloroethylene on the biochar, and the experimental results showed that there was no degradation, which also ruled out the possibility of degradation by dehalococcoides secretions.

[0029] The above experiments show that the degradation of the adsorbed trichloroethylene on the biochar is very difficult. Through a large amount of research on dehalococcoides, combined with the characteristics of dehalococcoides itself, it is found that dehalococcoides can degrade the adsorbed trichloroethylene through electron transfer. The application uses biochar as a medium, and through the electrochemical structure of the biochar, the degradation of the adsorbed trichloroethylene by dehalococcoides is mediated, and very good degradation effect is obtained; and the regenerated biochar can maintain good adsorption performance on trichloroethylene, and the adsorption capacity of the biochar after multiple cycles of adsorption and regeneration can be maintained at a high level.

[0030] The application will be further described below in combination with examples.

[0031] Example 1

[0032] The 1 mL of the dehalogenating Pseudomonas sp. bacterial solution obtained by culturing for 3 weeks was mixed with 30 mg of the wood biochar adsorbing 97.3 mg / g of trichloroethylene in 50 mL of the culture medium solution (Table 1) (pH = 7.2), 5 ml of hydrogen and 0.1 ml of the mixed vitamin solution (Table 2) were added, and the trichloroethylene adsorbed on the wood biochar was degraded and removed for 30 days under anaerobic conditions; the biochar after the trichloroethylene was degraded and removed was subjected to solid-liquid separation with the dehalogenating Pseudomonas sp. bacterial solution to realize regeneration of the biochar. The degradation rate of the trichloroethylene adsorbed on the biochar by the dehalogenating Pseudomonas sp. was 87.5%, and the adsorption capacity of the biochar could be maintained at 81.2% of the original after 5 cycles of adsorption and regeneration.

[0033] The culture medium solution (1 L) contains 1 ml of trace element stock solution, 10 ml of salt stock solution, and 1 ml of Se / W stock solution, and the specific components are shown in Table 1:

[0034] Table 1 Composition of the culture medium solution

[0035]

[0036] The specific components of the mixed vitamin solution are shown in Table 2:

[0037] Table 2 Composition of the mixed vitamin solution

[0038]

[0039]

[0040] Example 2

[0041] The 1 mL of the dehalogenating Pseudomonas sp. bacterial solution obtained by culturing for 3 weeks was mixed with 30 mg of the wood biochar adsorbing 97.3 mg / g of trichloroethylene in 50 mL of the culture medium solution (Table 1) (pH = 7.2), 5 ml of hydrogen and 0.1 ml of the mixed vitamin solution (Table 2) were added, and the trichloroethylene adsorbed on the wood biochar was degraded and removed for 30 days under anaerobic conditions; the biochar after the trichloroethylene was degraded and removed was subjected to solid-liquid separation with the dehalogenating Pseudomonas sp. bacterial solution to realize regeneration of the biochar. The degradation rate of the trichloroethylene adsorbed on the biochar by the dehalogenating Pseudomonas sp. was 87.5%, and the adsorption capacity of the biochar could be maintained at 81.2% of the original after 5 cycles of adsorption and regeneration.

[0042] Example 3

[0043] The 1 mL of the dehalogenating Pseudomonas sp. bacteria solution obtained by culturing for 3 weeks was mixed with 50 mg of the wood biochar adsorbing 58.4 mg / g of trichloroethylene in 50 mL of the culture medium solution (Table 1) (pH = 7.2), 5 ml of hydrogen and 0.1 ml of the mixed vitamin solution (Table 2) were added, and the trichloroethylene adsorbed on the wood biochar was degraded and removed for 30 days under anaerobic conditions; the wood biochar after the trichloroethylene was degraded and removed was subjected to solid-liquid separation with the dehalogenating Pseudomonas sp. bacteria solution, so as to realize the regeneration of the biochar. The degradation rate of the dehalogenating Pseudomonas sp. bacteria to the trichloroethylene adsorbed on the biochar was 86.5%, and the adsorption capacity of the biochar could be maintained at 94.7% of the original after 5 cycles of adsorption and regeneration.

[0044] Example 4

[0045] The 1 mL of the dehalogenating Pseudomonas sp. bacteria solution obtained by culturing for 3 weeks was mixed with 50 mg of the wood biochar adsorbing 58.4 mg / g of trichloroethylene in 50 mL of the culture medium solution (Table 1) (pH = 7.2), 5 ml of hydrogen and 0.1 ml of the mixed vitamin solution (Table 2) were added, and the trichloroethylene adsorbed on the wood biochar was degraded and removed for 30 days under anaerobic conditions; the wood biochar after the trichloroethylene was degraded and removed was subjected to solid-liquid separation with the dehalogenating Pseudomonas sp. bacteria solution, so as to realize the regeneration of the biochar. The degradation rate of the dehalogenating Pseudomonas sp. bacteria to the trichloroethylene adsorbed on the biochar was 86.5%, and the adsorption capacity of the biochar could be maintained at 94.7% of the original after 5 cycles of adsorption and regeneration.

[0046] Example 5

[0047] The 1 mL of the dehalogenating Pseudomonas sp. bacteria solution obtained by culturing for 3 weeks was mixed with 50 mg of the wood biochar adsorbing 58.4 mg / g of trichloroethylene in 50 mL of the culture medium solution (Table 1) (pH = 7.2), 5 ml of hydrogen and 0.1 ml of the mixed vitamin solution (Table 2) were added, and the trichloroethylene adsorbed on the wood biochar was degraded and removed for 30 days under anaerobic conditions; the wood biochar after the trichloroethylene was degraded and removed was subjected to solid-liquid separation with the dehalogenating Pseudomonas sp. bacteria solution, so as to realize the regeneration of the biochar. The degradation rate of the dehalogenating Pseudomonas sp. bacteria to the trichloroethylene adsorbed on the biochar was 86.5%, and the adsorption capacity of the biochar could be maintained at 94.7% of the original after 5 cycles of adsorption and regeneration.

[0048] Example 6

[0049] The 10 mL of the dehalogenating Pseudomonas sp. bacteria solution obtained by culturing for 3 weeks was mixed with 50 mg of the wood biochar adsorbing 58.4 mg / g of trichloroethylene in 50 mL of the culture medium solution (Table 1) (pH = 7.2), 5 ml of hydrogen and 0.1 ml of the mixed vitamin solution (Table 2) were added, and the trichloroethylene adsorbed on the wood biochar was degraded and removed for 30 days under anaerobic conditions; the biochar after the trichloroethylene was degraded and removed was subjected to solid-liquid separation with the dehalogenating Pseudomonas sp. bacteria solution to realize regeneration of the biochar. The degradation rate of the trichloroethylene adsorbed on the biochar by the dehalogenating Pseudomonas sp. bacteria was 83.4%, and the adsorption capacity of the biochar could be maintained at 87.8% of the original after 5 cycles of adsorption and regeneration.

[0050] Example 7

[0051] The 1 mL of the dehalogenating Pseudomonas sp. bacteria solution obtained by culturing for 3 weeks was mixed with 50 mg of the wood biochar adsorbing 58.4 mg / g of trichloroethylene in 50 mL of the culture medium solution (Table 1) (pH = 7.2), 5 ml of hydrogen and 0.3 ml of the mixed vitamin solution (Table 2) were added, and the trichloroethylene adsorbed on the wood biochar was degraded and removed for 30 days under anaerobic conditions; the biochar after the trichloroethylene was degraded and removed was subjected to solid-liquid separation with the dehalogenating Pseudomonas sp. bacteria solution to realize regeneration of the biochar. The degradation rate of the trichloroethylene adsorbed on the biochar by the dehalogenating Pseudomonas sp. bacteria was 84.2%, and the adsorption capacity of the biochar could be maintained at 87.3% of the original after 5 cycles of adsorption and regeneration.

[0052] Example 8

[0053] The 1 mL of the dehalogenating Pseudomonas sp. bacteria solution obtained by culturing for 3 weeks was mixed with 50 mg of the wood biochar adsorbing 58.4 mg / g of trichloroethylene in 50 mL of the culture medium solution (Table 1) (pH = 7.2), 5 ml of hydrogen and 0.5 ml of the mixed vitamin solution (Table 2) were added, and the trichloroethylene adsorbed on the wood biochar was degraded and removed for 30 days under anaerobic conditions; the biochar after the trichloroethylene was degraded and removed was subjected to solid-liquid separation with the dehalogenating Pseudomonas sp. bacteria solution to realize regeneration of the biochar. The degradation rate of the trichloroethylene adsorbed on the biochar by the dehalogenating Pseudomonas sp. bacteria was 82.3%, and the adsorption capacity of the biochar could be maintained at 85.1% of the original after 5 cycles of adsorption and regeneration.

[0054] Example 9

[0055] 1 mL of the dehalogenating Pseudomonas sp. bacterial solution obtained by culturing for 3 weeks was mixed with 50 mg of the corn biochar adsorbed with 58.4 mg / g of trichloroethylene in 50 mL of the culture medium solution (Table 1) (pH = 7.2), 5 ml of hydrogen and 0.5 ml of the mixed vitamin solution (Table 2) were added, and the trichloroethylene adsorbed on the corn biochar was degraded and removed under anaerobic conditions for 28 days; the biochar after the trichloroethylene was degraded and removed was subjected to solid-liquid separation with the dehalogenating Pseudomonas sp. bacterial solution, so as to realize regeneration of the biochar. The degradation rate of the dehalogenating Pseudomonas sp. to the trichloroethylene adsorbed on the biochar was 79.6%, and the adsorption capacity of the biochar could be maintained at 83.3% of the original after 5 cycles of adsorption and regeneration.

[0056] Example 10

[0057] 1 mL of the dehalogenating Pseudomonas sp. bacterial solution obtained by culturing for 3 weeks was mixed with 50 mg of the corn biochar adsorbed with 58.4 mg / g of trichloroethylene in 50 mL of the culture medium solution (Table 1) (pH = 7.2), 5 ml of hydrogen and 0.5 ml of the mixed vitamin solution (Table 2) were added, and the trichloroethylene adsorbed on the corn biochar was degraded and removed under anaerobic conditions for 28 days; the biochar after the trichloroethylene was degraded and removed was subjected to solid-liquid separation with the dehalogenating Pseudomonas sp. bacterial solution, so as to realize regeneration of the biochar. The degradation rate of the dehalogenating Pseudomonas sp. to the trichloroethylene adsorbed on the biochar was 79.6%, and the adsorption capacity of the biochar could be maintained at 83.3% of the original after 5 cycles of adsorption and regeneration.

[0058] Example 11

[0059] 1 mL of the dehalogenating Pseudomonas sp. bacterial solution obtained by culturing for 3 weeks was mixed with 50 mg of the corn biochar adsorbed with 58.4 mg / g of trichloroethylene in 50 mL of the culture medium solution (Table 1) (pH = 7.2), 5 ml of hydrogen and 0.5 ml of the mixed vitamin solution (Table 2) were added, and the trichloroethylene adsorbed on the corn biochar was degraded and removed under anaerobic conditions for 28 days; the biochar after the trichloroethylene was degraded and removed was subjected to solid-liquid separation with the dehalogenating Pseudomonas sp. bacterial solution, so as to realize regeneration of the biochar. The degradation rate of the dehalogenating Pseudomonas sp. to the trichloroethylene adsorbed on the biochar was 79.6%, and the adsorption capacity of the biochar could be maintained at 83.3% of the original after 5 cycles of adsorption and regeneration.

[0060] The biochar regeneration method has low operation and equipment requirements, almost no damage to the structure of the biochar, high efficiency, can effectively reduce the use cost of the biochar, and has good market prospect.

[0061] The above described embodiments are only illustrative and not restrictive, and although the present application is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the purpose and scope of the technical solutions, and all should be covered in the scope of the claims of the present application.

Claims

1. A method for microbial regeneration of biochar that adsorbs trichloroethylene, characterized in that, Includes the following steps: 1) A dehalogenated *Bacteroides halogenatus* bacterial culture solution is mixed with biochar adsorbed with trichloroethylene in a culture medium solution. Nutrients required for microbial growth are added to the mixture, and the trichloroethylene adsorbed on the biochar is degraded and removed under anaerobic conditions. The biochar is prepared by pyrolysis of biomass under anaerobic conditions, and the concentration of biochar added to the mixture is 0.6~2.0 g / L. The dehalogenated *Bacteroides halogenatus* is... Dehalococcoides mccartyi 195. The volume ratio of dehalogenated *Streptococcus* bacterial culture to culture medium solution is 1-10:50; the nutrients include hydrogen gas and a mixed vitamin solution, with the mixed vitamin solution added to the mixture at a volume ratio of 0.2%-1%; the culture medium solution is an anaerobic liquid culture medium with a pH of 6.5-7.2, and the temperature for degrading and removing trichloroethylene adsorbed on biochar under anaerobic conditions is 28-32℃; 2) The biochar after degrading and removing trichloroethylene is separated from the dehalogenated Streptococcus bacteria liquid to achieve biochar regeneration.

2. The method for microbial regeneration of biochar adsorbed with trichloroethylene according to claim 1, characterized in that, The solvent for the mixed vitamin solution is water, and its composition is: biotin 0.04 g / L, folic acid 0.04 g / L, pyridoxine hydrochloride 0.2 g / L, riboflavin 0.1 g / L, and thiamine. 0.1 g / L, niacin 0.1 g / L, pantothenic acid 0.1 g / L, para-aminobenzoic acid 0.1 g / L, lipoic acid 0.1 g / L, vitamin B12 0.002 g / L.

3. The method for microbial regeneration of biochar adsorbed with trichloroethylene according to claim 1, characterized in that, 1L of culture medium solution contains 1 ml of trace element stock solution, 10 ml of salt stock solution and 1 ml of Se / W stock solution, with the remainder being water; The composition of the trace element stock solution is as follows: FeCl2•4H2O 1.5 g / L, CoCl2•6H2O 0.19 g / L, MnCl2•4H2O 0.1 g / L, ZnCl2 0.07 g / L, H3BO3 0.006 g / L, Na2MoO4•2H2O 0.036 g / L, NiCl2•6H2O 0.024 g / L, CuCl2•2H2O 0.002 g / L; The salt stock solution has the following composition: NaCl 100.0 g / L, MgCl2•6H2O 50.0 g / L, KH2PO4 20.0 g / L, NH4Cl 30.0 g / L, KCl 30.0 g / L, CaCl2•2H2O 1.5 g / L; The Se / W stock solution has the following composition: Na2SeO3•5H2O 0.006 g / L, NaWO4•2H2O 0.008 g / L, and NaOH 0.5 g / L.

4. The microbial regeneration method for biochar adsorbing trichloroethylene according to claim 1, characterized in that, The time for degrading and removing trichloroethylene adsorbed on biochar under anaerobic conditions, as described in step 1), is 28-32 days.

5. The application of the biochar regenerated by the method of claim 4 in the cyclic adsorption of trichloroethylene in water.

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