Biochar electroactive bacterium complex for enhancing degradation of hydrophobic organic pollutants and preparation method of biochar electroactive bacterium complex

Abstract

The invention discloses a biochar electroactive bacterium complex for enhancing degradation of hydrophobic organic pollutants and a preparation method of the biochar electroactive bacterium complex. The method comprises the following steps: (1) pyrolyzing lignocellulose-based biomass under a high-temperature anaerobic condition to obtain original biochar; (2) under an ice bath condition, mixing the original charcoal, NaNO3, concentrated sulfuric acid and KMnO4, carrying out a first oxidation reaction, and keeping continuous stirring; (3) adding a sulfuric acid solution for a second oxidation reaction of the biochar, and after the temperature is reduced by 60 DEG C, adding an H2O2 solution to terminate the reaction; and (4) cleaning the modified biochar material with a mixed solution of sulfuric acid and H2O2, an HCl solution and deionized water until the pH value is neutral, and finally obtaining the modified biochar material. According to the method, the dual advantages of physical adsorption and biodegradation are combined, and an efficient, green and sustainable solution is provided for removal of hydrophobic organic pollutants in a water body.

Description

Technical Field

[0001] The present invention belongs to the field of environmental pollution control and remediation, and specifically relates to a type of carbon-based material derived from biomass that captures hydrophobic organic pollutants in the environment and self-assembles with electroactive bacteria to form a biochar / electroactive bacteria complex, which further degrades the captured hydrophobic organic pollutants. Background Art

[0002] Hydrophobic organic matter is a class of compounds with low water solubility and high molecular weight. Hydrophobic organic matter has a wide range of uses and has the characteristics of being difficult to degrade, having strong environmental persistence and stable chemical properties. Once entering the environment, it will be stored in soil, riverbed mud and sewage control system sludge for a long time. At the same time, hydrophobic organic pollutants are easy to remain in the body, posing a potential threat to human health and the ecosystem. Therefore, the pollution control of hydrophobic organic pollutants is a major problem in ecological environmental protection.

[0003] Biochar is a carbon-based material derived from biomass. It has a well-developed pore structure and strong hydrophobicity, so it can be used as an efficient adsorbent to capture hydrophobic pollutants. However, the capture effect of biochar on hydrophobic organic matter is far from sufficient to meet actual environmental needs. When environmental disturbances occur, the captured hydrophobic organic matter is likely to be desorbed again and released back into the environment, causing secondary pollution. Therefore, it is necessary to take appropriate measures to further degrade the hydrophobic organic matter after biochar capture, so as to alleviate potential environmental hazards.

[0004] Microbial degradation is an important way to reduce hydrophobic organic pollutants in the environment, and it is also one of the most economical and green treatment methods. However, microbial technology has a strong specificity for pollutant degradation, and the degradation rate is easily affected by factors such as carbon sources or native microorganisms. Therefore, it is necessary to use other physical and chemical means to enhance the efficiency of microbial degradation from the perspective of maintaining biomass.

[0005] The microbial-biochar composite treatment strategy is an emerging cutting-edge technology. The different components in the complex can play their respective strengths and interact synergistically to achieve the capture and degradation of organic pollutants in water bodies. Compared with traditional microbial degradation technology, the microbial-biochar composite treatment strategy is more efficient and thorough in removing pollutants. It is suitable for resolving environmental emergencies, strengthening pollution control systems or repairing the surrounding environment of industrial parks. Compared with adsorption technology, the microbial-biochar composite treatment strategy cleverly circumvents the problem of adsorbent regeneration and extends the effective repair time of the adsorbent. The preparation of a microbial-biochar complex that can efficiently remove organic pollutants will have great practical significance and application potential for the remediation of hydrophobic organic pollutants. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a biochar / electroactive bacteria complex for enhancing the degradation of hydrophobic organic pollutants in the environment.

[0007] In order to achieve the above-mentioned invention object, the present invention provides a method for synthesizing a modified biochar material. The material is the main executor of capturing hydrophobic organic pollutants, and is also the base material for the self-assembly of electroactive bacteria in the complex. The raw materials of the material are easily available, low in price, highly hydrophilic, large in specific surface area, and have good electroactive properties.

[0008] The specific synthesis steps are as follows:

[0009] (1) Pyrolysis of lignocellulosic biomass under high temperature anaerobic conditions to obtain raw biochar;

[0010] (2) In an ice bath, the raw biochar, NaNO3, concentrated sulfuric acid and KMnO4 were mixed for the first oxidation reaction with continuous stirring;

[0011] (3) Sulfuric acid solution is then added for the second oxidation reaction of biochar. After the temperature drops by 60°C, H2O2 solution is added to terminate the reaction;

[0012] (4) The modified biochar material is washed with a mixed solution of sulfuric acid and H2O2, an HCl solution, and deionized water, respectively, until the pH is neutral, and finally the modified biochar material is obtained.

[0013] Preferably, the step (1) is as follows: grinding the dried straw into powder, and pyrolyzing the powder at 900° C. in a nitrogen atmosphere to obtain raw biochar.

[0014] Preferably, the step (2) is to carry out the first oxidation reaction under ice bath conditions by mixing the original biochar: NaNO3: concentrated sulfuric acid: KMnO4 in a mass ratio of 1:0.75:138:3, stirring at 5°C for 2h and stirring at room temperature for 48h.

[0015] Preferably, the step (3) is to add 5wt% H2SO4, stir while heating, keep the temperature at 80°C for the first hour, then stir at 98°C for 2 hours to complete the second oxidation reaction, and when the temperature drops to 60°C, 30wt% H2O2 is added to the mixture, and the oxidation reaction is terminated.

[0016] Preferably, the step (4) is to use 3wt% H2SO 4,0.5wt% H2O2 mixed solution is added to the mixture, the precipitate is washed, and the solid matter is obtained by suction filtration; then it is washed with 5wt% HCl, and the solid matter is obtained by suction filtration, and then the solid matter is washed with deionized water until the pH reaches neutral, and then it is filtered and dried to obtain the modified biochar material.

[0017] The present invention also provides the use of the modified biochar material in capturing hydrophobic organic pollutants.

[0018] Preferably, the modified biochar material is added to a nutrient medium containing hydrophobic organic matter at 30° C. and a rotation speed of 170 rpm and maintained under anaerobic sterile conditions.

[0019] Preferably, the dosage of the modified biochar material is 1 g / L, the final concentration of the hydrophobic organic matter is 200 mg / L, the nutrient medium formula is 1.50 g / L NH4Cl, 0.10 g / L KCl, 11.35 g / L Na2HPO4, 2.40 g / L NaH2PO4, and the solvent is deionized water.

[0020] The present invention also provides a method for self-assembly of a biochar electroactive bacteria complex for enhancing the degradation of hydrophobic organic pollutants, the steps of which are as follows: after the adsorption reaction of the modified biochar material on the hydrophobic organic matter reaches equilibrium, electroactive bacteria are added to the mixed system of the modified biochar material capturing the hydrophobic organic matter, and an electron donor is added to self-assemble the biochar electroactive bacteria complex.

[0021] Preferably, the adsorption equilibrium time is 7 h, and the final OD of the electroactive bacteria after being added to the mixed reaction system is 600 is 0.1, and the electron donor content and type is 20 mM sodium lactate.

[0022] The present invention also provides the use of the above-mentioned biochar electroactive bacteria complex in enhancing the degradation of hydrophobic organic pollutants.

[0023] Preferably, the temperature condition for enhanced degradation is 30°C.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0025] (1) The present invention designs a "bacteria-charcoal" complex with synergistic effects of modified biochar and electroactive bacteria. The matrix material of the complex can effectively capture hydrophobic organic pollutants while also achieving stable degradation of pollutants through self-assembly with electroactive bacteria. This combination strategy reduces the risk of pollutants desorbing due to environmental disturbances after adsorption, thereby reducing the possibility of secondary pollution.

[0026] (2) The present invention does not require additional chemical reagents and is green and environmentally friendly throughout the process. The present invention significantly improves the stability of electroactive bacteria with the help of the synergistic effect of modified biochar. As a carrier of bacteria, modified biochar not only improves the attachment of microorganisms, but also promotes the electron transfer efficiency of microorganisms through its high specific surface area and excellent electroactive properties, thereby accelerating the degradation rate of pollutants.

[0027] In summary, the present invention combines the dual advantages of physical adsorption and biodegradation, and provides an efficient, green and sustainable solution for the removal of hydrophobic organic pollutants in water. Its application in the field of environmental pollution control not only has important practical significance, but also helps to promote the further development of environmental protection technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 These are scanning electron microscope images of biochar, where A is the original biochar BC9 and B is the modified biochar MBC9.

[0029] Figure 2 This is the infrared spectrum of biochar.

[0030] Figure 3 The contact angle test results of biochar.

[0031] Figure 4 This is the N2 adsorption-desorption curve of biochar.

[0032] Figure 5 The electroactive properties of biochar, where Figure A is the redox property and Figure B is the electrical conductivity.

[0033] Figure 6 This is the capture effect of biochar on 2,5-dichloronitrobenzene.

[0034] Figure 7 These are scanning electron microscope images of self-assembled "bacteria-charcoal" polymers, where Figure A is the "bacteria-charcoal" complex of the original biochar BC9, and Figure B is the "bacteria-charcoal" complex of the modified biochar MBC9.

[0035] Figure 8 Figure 3 is the degradation effect of 2,5-dichloronitrobenzene after capture. Figure A is the concentration change of 2,5-dichloronitrobenzene after capture, Figure B is the degradation kinetic constant, and Figures C and D are both degradation product analyses. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and beneficial technical effects of the present invention clearer, the present invention is further described in detail below in conjunction with embodiments.

[0037] Example 1

[0038] (1) Preparation method of raw biochar

[0039] After drying the straw at room temperature for 24 hours, it was ground through a 100-mesh sieve. 4 g of straw powder was weighed and placed in a 35 mL corundum boat. In a nitrogen atmosphere of 100 mL / min, the temperature was raised to 900 °C at a rate of 7.73 °C / min for pyrolysis and held for 1 hour. The original biochar BC9 was obtained.

[0040] (2) Preparation method of modified biochar

[0041] 5 g of raw biochar BC9 was mixed with 3.75 g of NaNO3 in an ice bath. 375 ml of concentrated sulfuric acid was added to the mixture with continuous stirring and ice bath. 15 g of KMnO4 was gradually added to the mixture within 1 h and stirred for 2 h at 5 °C using a magnetic stirrer. Finally, the mixture was stirred at room temperature for 48 h to complete the first oxidation.

[0042] 700 mL of 5 wt% H2SO4 was slowly added to the mixture within 1 h, while heating and stirring, and the temperature was maintained at 80° C. in the first 1 h. Then, the mixture was stirred at 98° C. for 2 h to complete the second oxidation.

[0043] When the temperature dropped to 60°C, 15 ml of 30 wt% H2O2 was added to the mixture, and the oxidation reaction was terminated. After the mixture was stirred at room temperature for 2 h, the mixture was allowed to stand for 12 h.

[0044] 1L 3wt% H2SO 4, 0.5 wt% H2O2 was mixed and dissolved and added into the mixture, the precipitate was washed three times, and the solid matter was obtained by vacuum filtration using a 0.45 μm filter membrane.

[0045] The solid matter was washed with 5wt% HCl three times and vacuum filtered with a 0.45μm filter membrane to obtain a solid substance. The solid matter was washed with deionized water until the pH was neutral. The biochar was vacuum filtered with a 0.45μm filter membrane and dried in an oven at 80°C overnight to obtain modified biochar MBC9.

[0046] Example 2

[0047] 1g modified biochar MBC9 powder (hereinafter referred to as biochar powder) was dried and subjected to surface morphology observation, surface functional group analysis, hydrophilicity determination, specific surface area analysis and electroactivity test. After the biochar powder was adhered to a conductive table and sprayed with gold, the morphology was observed using a field emission scanning electron microscope at an accelerating voltage of 3kV and a horizontal field width of 12.7μm. After the biochar powder was mixed with KBr and pressed into a tablet, a Fourier transform infrared spectrometer was used at 400-4000cm -1The scanning was performed within the wavenumber range. After the biochar powder was pressed into a tablet, the hydrophilicity was determined using a contact angle meter. The nitrogen adsorption isotherm was determined using a specific surface area analyzer at 77K. The redox properties of biochar were tested in a three-electrode system under anaerobic conditions. The three-electrode system used a glassy carbon crucible, a platinum sheet, and an Ag / AgCl electrode as the working electrode, counter electrode, and reference electrode, respectively. At working voltages of 0.61V and -0.69V, 0.1mL of 2,2′-nitro-bis(3-ethylbenzothiazole-6-sulfonic acid) diammonium salt or diquat solution was added as an electron transfer medium to determine its redox activity. The four-conductive probe method was used to determine the conductivity of biochar.

[0048] Figure 1 This is a scanning electron microscope image of the biochar of the present invention, and it can be seen that the porosity of the modified biochar MBC9 is improved. Figure 2 In the infrared spectrum, the hydroxyl peak, carbonyl peak and olefin functional group of MBC9 increased after modification. The contact angle results show that the hydrophilicity of biochar is enhanced after modification ( Figure 3 ). Figure 4 The N2 adsorption isotherms of the two biochars are shown. The N2 adsorption capacity of the modified biochar increased, indicating that the porosity of MBC9 is more developed. Figure 5 The electroactive properties of biochar were demonstrated, and the results showed that the redox properties of MBC9 were significantly improved after modification, but the conductivity was slightly decreased.

[0049] Example 3

[0050] A mineral salt culture medium was prepared with a formula of 1.50 g / L NH4Cl, 0.10 g / L KCl, 11.35 g / L Na2HPO4, and 2.40 g / LNaH2PO4, and the solvent was deionized water. 1 g / L of modified biochar MBC9 powder (with original biochar BC9 as a control) was added to 50 mL of mineral salt culture medium, aerated with N2 for 30 min and sealed with an aluminum cap, followed by high-pressure sterilization at 121 °C for 20 min. 100 g / L of 2,5-dichloronitrobenzene was added to the reaction system after filtration and sterilization, resulting in a final concentration of 200 mg / L. At 30 °C, the adsorption kinetics of 2,5-dichloronitrobenzene were tested in a shaker at 170 rpm. It can be seen that the capture effect of original biochar and modified biochar on 2,5-dichloronitrobenzene ( Figure 6 ). The equilibrium adsorption capacities of BC9 and MBC9 for 2,5-dichloronitrobenzene were 97.01 mg / L and 83.96 mg / L, respectively.

[0051] Example 4

[0052] Electroactive bacteria S. oneidensis MR-1 were inoculated from the glycerol tube into the lysing broth medium and activated after 12 hours. A certain amount of bacterial solution was taken and diluted to OD with 50 mmol / L PBS buffer. 600 0.1. After 7h, the adsorption of 2,5-dichloronitrobenzene by the biochar powder in Example 3 reached equilibrium, and the diluted S. oneidensis MR-1 bacterial solution was added to the mineral salt culture medium mixed system containing biochar powder and 2,5-dichloronitrobenzene in Example 3, and 20mM sodium lactate was added as an electron donor. The self-assembled biochar / electroactive bacteria complex was cultured and the enhanced degradation of 2,5-dichloronitrobenzene was carried out at 30°C. At a certain time interval, 2ml of sample was extracted from the reaction system and filtered through a 0.22μm nylon filter membrane to separate the solid phase and the liquid phase. The solid phase sample was ultrasonically treated with 3mL methanol for 60min to complete the extraction of 2,5-dichloronitrobenzene in the solid sample. The concentration of 2,5-dichloronitrobenzene was determined by high performance liquid chromatography C18 column. The mobile phase was a methanol / water solution with a volume ratio of 8:2, and the flow rate was 1.0mL min -1 The Langmuir equation was used to calculate the degradation kinetic constants of 2,5-dichloronitrobenzene after capture. A gas chromatograph-mass spectrometer was used to determine the degradation products of 2,5-dichloronitrobenzene. The injection port temperature and the detector temperature were set to 250°C and 300°C, respectively. The tuning mode was the electron impact ionization source.

[0053] Figure 7 The surface morphology of the self-assembled "bacteria-charcoal" aggregate is shown. A large number of bacteria adhere to the surface of MBC9 to form a densely structured "bacteria-charcoal" aggregate. Figure 8 The degradation efficiency of 2,5-dichloronitrobenzene after capture was investigated. In MBC9, the removal rate and degradation kinetic constant of 2,5-dichloronitrobenzene after capture were significantly higher than those in BC9. The analysis of degradation products showed that 2,5-dichloronitrobenzene was converted into 2,5-dichloroaniline, which has less toxicity.

Claims

1. A method for preparing a modified biochar material, characterized in that: Here are the steps: (1) Pyrolysis of lignocellulosic biomass under high temperature anaerobic conditions to obtain raw biochar; (2) In an ice bath, the raw biochar, NaNO3, concentrated sulfuric acid and KMnO4 were mixed for the first oxidation reaction with continuous stirring; (3) Sulfuric acid solution is then added for the second oxidation reaction of biochar. After the temperature drops by 60°C, H2O2 solution is added to terminate the reaction; (4) The modified biochar material is washed with a mixed solution of sulfuric acid and H2O2, an HCl solution, and deionized water, respectively, until the pH is neutral, and finally the modified biochar material is obtained.

2. The preparation method according to claim 1, characterized in that: The step (1) is as follows: grinding the dried straw into powder, and pyrolyzing it at 900° C. in a nitrogen atmosphere to obtain raw biochar.

3. The preparation method according to claim 1, characterized in that: The step (2) is to carry out the first oxidation reaction under ice bath conditions by mixing the original biochar: NaNO3: concentrated sulfuric acid: KMnO4 in a mass ratio of 1:0.75:138:3, stirring at 5°C for 2h and stirring at room temperature for 48h.

4. The preparation method according to claim 1, characterized in that: The step (3) is to add 5wt% H2SO4, stir while heating, keep the temperature at 80°C for the first hour, then stir at 98°C for 2 hours to complete the second oxidation reaction, wait until the temperature drops to 60°C, add 30wt% H2O2 to the mixture, and the oxidation reaction is terminated.

5. The preparation method according to claim 1, characterized in that: The step (4) is to use 3wt% H2SO 4, 0.5wt% H2O2 mixed solution is added to the mixture, the precipitate is washed, and the solid matter is obtained by suction filtration; then it is washed with 5wt% HCl, and the solid matter is obtained by suction filtration, and then the solid matter is washed with deionized water until the pH reaches neutral, and then it is filtered and dried to obtain the modified biochar material.

6. The modified biochar material prepared by any preparation method of claims 1-5.

7. The use of the modified biochar material described in claim 6 in capturing hydrophobic organic pollutants, preferably, is to add the modified biochar material to a nutrient medium containing hydrophobic organic matter at 30°C and a rotation speed of 170 rpm and maintain anaerobic sterile conditions. Preferably, the addition amount of the modified biochar material is 1 g / L, the final concentration of the hydrophobic organic matter is 200 mg / L, the nutrient medium formula is 1.50 g / L NH4Cl, 0.10 g / L KCl, 11.35 g / L Na2HPO4, 2.40 g / LNaH2PO4, and the solvent is deionized water.

8. A method for self-assembly of a biochar electroactive bacteria complex for enhancing the degradation of hydrophobic organic pollutants, characterized in that: The steps are as follows: after the modified biochar material described in claim 6 reaches equilibrium in the adsorption reaction of hydrophobic organic matter, electroactive bacteria are added to the mixed system of the modified biochar material capturing hydrophobic organic matter, and an electron donor is added to self-assemble the biochar electroactive bacteria complex.

9. The self-assembly method according to claim 9, characterized in that: The adsorption equilibrium time was 7 h, and the final OD of the electroactive bacteria after being added to the mixed reaction system was 600 is 0.1, and the electron donor content and type is 20 mM sodium lactate.

10. Use of the biochar electroactive bacteria complex obtained by the self-assembly method of claims 9-10 in enhanced degradation of hydrophobic organic pollutants, preferably, the temperature condition for enhanced degradation is 30°C.

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