A method for removing bisphenol A by microbial extracellular secretion and inorganic ligand in cooperation with beta-MnO2

Abstract

The present invention discloses a method for removing bisphenol A by using microbial extracellular secretions and inorganic ligands in collaboration with β-MnO2, comprising the following steps: S1, purifying and culturing microorganisms in the anaerobic end of activated sludge in a municipal sewage treatment plant, and then inoculating them into an inorganic salt culture medium containing β-MnO2 to perform concentration gradient acclimation and culture on the microorganisms; S2, extracting the extracellular secretions of the acclimated microorganisms in step S1; S3, adding the extracellular secretions and the inorganic ligand sodium pyrophosphate to a liquid containing β-MnO2 and bisphenol A, aerating the liquid with nitrogen to remove oxygen, sealing and maintaining anaerobic conditions, and reacting to remove bisphenol A. The method of the present invention utilizes microbial extracellular secretions and inorganic ligands in collaboration with β-MnO2 to achieve efficient degradation of bisphenol A. In the present invention, the microbial extracellular secretions and manganese minerals are both very common and readily available substances in the environment, are simple to obtain and have low cost, and the degradation process does not generate new pollution.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of water treatment and environmental protection, and particularly relates to a method for removing bisphenol A by cooperation of microbial extracellular secretion and inorganic ligand and beta-MnO2. BACKGROUND

[0002] Bisphenol A (BPA) is a raw material for producing polycarbonate plastic products and epoxy resin. Due to the wide use of BPA and the difficulty in completely removing BPA in conventional water treatment, BPA is detected in a large amount in surface water. Factory emissions and wastewater from wastewater treatment plants are the main sources of BPA in the environment. BPA is a typical environmental endocrine disruptor, which can cause irreversible damage to the body's reproductive development, immune system, nervous system and other aspects, and is related to breast cancer, cardiovascular disease, infertility and other diseases.

[0003] The existing methods for removing BPA mainly include physical adsorption, chemical degradation and microbial degradation. Among them, physical adsorption can remove more than 90% of BPA, but adsorption is a dynamic balance process and is not the final removal, and the process is reversible, and the adsorbed BPA may return to the environment under certain conditions. Chemical method for degrading BPA is an important research direction at present. Many scholars have confirmed that BPA can be efficiently degraded by photocatalytic method, electrochemical method and advanced oxidation method, but this may produce toxic by-products, causing secondary pollution, greatly reducing the significance of degradation.

[0004] Therefore, it is necessary to develop a method for removing bisphenol A by cooperation of microbial extracellular secretion and inorganic ligand and beta-MnO2, which has high degradation efficiency and no secondary pollution. SUMMARY

[0005] The purpose of the present application is to provide a method for removing bisphenol A by cooperation of microbial extracellular secretion and inorganic ligand and beta-MnO2, which utilizes the reduction characteristics of microbial extracellular secretion to beta-MnO2 to provide more active Mn(III), and then complexes unstable Mn(III) with inorganic ligand sodium pyrophosphate (PP) to efficiently degrade BPA.

[0006] The purpose of the present application is achieved by including the following steps:

[0007] S1, after purifying and culturing the microorganisms in the anaerobic end of the activated sludge of the municipal sewage treatment plant, inoculating the microorganisms into an inorganic salt culture medium containing beta-MnO2 to domesticate and culture the microorganisms at a concentration gradient;

[0008] S2, extracting the extracellular secretion of the domesticated microorganisms in step S1;

[0009] S3, adding extracellular secretion and inorganic ligand sodium pyrophosphate into the liquid containing β-MnO2 and bisphenol A, removing oxygen in the liquid by nitrogen gas, sealing and keeping anaerobic condition, and removing bisphenol A by reaction.

[0010] The basic structural unit of manganese dioxide is MnO6 octahedron, which can be assembled into tunnel or layer structure by sharing edges or corners, and a large number of cations and water molecules exist in the interlayer region, resulting in good adsorption, catalysis and oxidation performance; among them, β-MnO2 with tunnel structure is widely distributed in natural water bodies and has high stability.

[0011] Mn(Ⅳ) will be reduced to Mn(Ⅲ) and Mn(Ⅱ) in the reaction process with phenolic compounds, resulting in changes in the overall reactivity of the oxide; Mn(Ⅲ) plays a key role in the process of manganese dioxide oxidizing organic pollutants; compared with Mn(Ⅳ), Mn(Ⅲ) has faster ligand exchange rate, longer Mn-O bond and higher redox activity, so Mn(Ⅲ) can act as a strong oxidizing agent for organic compounds in the reaction process; however, dissolved Mn(Ⅲ) is very unstable and can be easily oxidized or reduced, quickly disproportionating into Mn(Ⅱ) and Mn(Ⅳ); but it can be stabilized by inorganic ligands such as sodium pyrophosphate (PP), forming more stable active Mn(Ⅲ)-PP complexes, significantly extending the occurrence time of Mn(Ⅲ) and enhancing the oxidation of phenolic compounds.

[0012] Microbial degradation is different from physical adsorption and chemical degradation, microorganisms have the characteristics of fast growth and reproduction, strong genetic variability and wide distribution in the environment, and can improve the ability to degrade organic pollutants by domestication to improve specific performance. Metabolites or enzymes secreted by microorganisms play an important role in the biodegradation of organic pollutants.

[0013] Preferably, the preparation method of β-MnO2 is as follows: 0.8 mol / L KMnO4 and 1.2 mol / L MnCl2 are dissolved in 60 mL ultrapure water, mixed and stirred for 30 min, then the suspension is poured into a 100 mL Teflon autoclave and sealed; the reaction is carried out in an oven at 180℃ for 24 h, then the solid material is obtained by centrifugal washing with ultrapure water after cooling, and then dried at 120℃ for 24 h; after natural cooling and grinding, it is ready.

[0014] Preferably, the microbial purification culture in S1 is as follows: active sludge is taken from the anaerobic end of a municipal sewage plant, the sludge is mixed and oxygen is removed by nitrogen gas, then the sludge is purified in a constant temperature water bath shaker, and after purification, the active sludge is allowed to stand and stratify; the supernatant is taken and added to a pre-sterilized and nitrogen-exposed expanded culture medium, then the microorganisms and glycerol are mixed after expansion culture, and the mixture is stored at low temperature.

[0015] Preferably, the S1 step of domestication is to domesticate the microorganism after purification culture in a gradient concentration domestication mode, specifically: adding the microorganism after purification culture to the expanded culture medium at a concentration of 1%, expanding culture for three times, and expanding for 1 day each time; setting five concentration gradients of β-MnO2, i.e., 50 mg / L, 100 mg / L, 200 mg / L, 300 mg / L and 500 mg / L, domesticating once at each concentration for 4 days, circulating for 3 times, and totally for 12 days, and the whole domestication process is totally for 60 days.

[0016] Preferably, in the expanded culture medium, the peptone is 10.00 g / L, the yeast powder is 5.00 g / L, and the sodium chloride is 10.00 g / L; in the inorganic salt culture medium used for domestication, the sodium chloride is 1.00 g / L, the ammonium chloride is 0.80 g / L, the potassium dihydrogen phosphate is 0.50 g / L, the dipotassium hydrogen phosphate is 0.60 g / L, the magnesium chloride hexahydrate is 0.20 g / L, and the calcium chloride dihydrate is 0.05 g / L; the expanded culture medium and the inorganic salt culture medium are sterilized before use.

[0017] Preferably, the S2 step of extracting extracellular secretion is specifically: adding the expanded anaerobic microorganism to the inorganic salt culture medium containing 1 g / L sodium acetate and taking sodium acetate as the only carbon source at a concentration of 1% (the culture medium is sterilized and exposed to nitrogen for 30 min before use), culturing for 5 days, centrifuging at 8000 rpm and 4 DEG C for 5 min, and then filtering the supernatant with a glass fiber of 0.45 µm to obtain EPS (extracellular secretion).

[0018] Preferably, in the S3 step, the concentration of the extracellular secretion is 1 mgC / L-20 mgC / L, the concentration of the inorganic ligand sodium pyrophosphate is 5 mM, and the concentration of β-MnO2 is 150 mg / L.

[0019] Preferably, the S3 step is reacted for 120 h.

[0020] The degradation mechanism of the method is as follows: the EPS has the reduction ability to manganese minerals, can reduce the manganese minerals in the pollutant degradation system, so that Mn(IV) in the manganese minerals can be induced to convert into Mn(III) with higher reaction activity, Mn(III) is unstable and needs to be complexed with inorganic ligand PP to form Mn(III)-PP, thereby prolonging the retention time of the Mn(III)-PP in the water environment and enhancing the degradation of BPA.

[0021] Compared with the prior art, the present application has the following technical effects:

[0022] 1. The extracellular secretion of the microorganism and the manganese minerals in the present application are very common and easy to obtain in the environment, the acquisition operation is simple and the cost is low, the degradation efficiency of the method is high, and no new pollution is generated in the degradation process of bisphenol A;

[0023] 2、The microbial extracellular secretion (EPS) in the application has a reduction and dissolution effect on manganese minerals, increases the concentration of total dissolved manganese in the reaction solution, produces unstable Mn(III), and the inorganic ligand PP complexes the active Mn(III) to form Mn(III)-PP, which has the effect of efficiently degrading endocrine disruptors, provides new cognition for the degradation of pollutants by active substances in the natural environment, and provides further direction and evidence for understanding the migration and transformation of endocrine disruptors in water bodies; the system of PP and EPS and the combination of the two and β-MnO2 synergistically effectively promotes the degradation process of BPA. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The XRD analysis diagram of β-MnO2 in Example 2;

[0025] Figure 2 The effect diagram of EPS, PP and the combination of the two for promoting the degradation of BPA by β-MnO2 in Example 7 Experiment 1;

[0026] Figure 3 The effect diagram of EPS and PP of different concentrations on the degradation of BPA by β-MnO2 in Example 7 Experiment 2;

[0027] Figure 4 The reduction and dissolution effect diagram of PP and EPS on β-MnO2 in the reaction process in Example 7 Experiment 3;

[0028] Figure 5 The effect diagram of the oxidation of EPS in Example 7 Experiment 3. DETAILED DESCRIPTION

[0029] The application will be further described below in conjunction with the embodiments and the drawings, but the application is not limited in any way by the embodiments, and any transformation or replacement based on the teaching of the application belongs to the protection scope of the application.

[0030] Example 1

[0031] The method for removing bisphenol A by the microbial extracellular secretion and the inorganic ligand in cooperation with β-MnO2 in this embodiment comprises the following steps:

[0032] S1, after the purification and culture of the microorganisms in the anaerobic end of the activated sludge of the municipal sewage treatment plant, the microorganisms are inoculated into an inorganic salt culture medium containing β-MnO2 for concentration gradient acclimation culture;

[0033] S2, extract the extracellular secretion of the microorganisms acclimated in step S1;

[0034] S3, extracellular secretion, inorganic ligand sodium pyrophosphate is added to the liquid containing β-MnO2 and bisphenol A, the liquid is exposed to nitrogen gas for 30 min to remove oxygen, and is sealed to maintain anaerobic conditions, and reaction removes bisphenol A.

[0035] Example 2

[0036] The method for removing bisphenol A by extracellular secretion of microorganisms and inorganic ligand in cooperation with β-MnO2 of the present embodiment is based on Example 1, wherein the preparation method of β-MnO2 is as follows: 0.8 mol / L KMnO4 and 1.2 mol / L MnCl2 are dissolved in 60 mL ultrapure water, mixed and stirred for 30 min, and then the suspension is poured into a 100 mL Teflon autoclave and sealed; the reaction is carried out in an oven at 180°C for 24 h, and after cooling, the solid material is washed by centrifugation with ultrapure water, and then dried at 120°C for 24 h; after natural cooling and grinding, the β-MnO2 is obtained.

[0037] The β-MnO2 prepared in Example 2 is subjected to XRD analysis, and a D / MAX-2500 type x-ray diffractometer is used under the condition of Cu Kα radiation in the range of 5°-90° of 2θ, the scanning speed is 5° / min, and the results are as follows: Figure 1 It can be seen that there are diffraction peaks at 28.64, 37.32, 42.8, 46.06, 56.6, 59.35, and 72.33° of 2θ, all of which are consistent with the reflection peaks of β-MnO2 (pyrolusite), corresponding to the standard card JCPDS No. 24-0735, and the purity meets the experimental requirements.

[0038] Example 3

[0039] The method for removing bisphenol A by extracellular secretion of microorganisms and inorganic ligand in cooperation with β-MnO2 of the present embodiment is based on Example 2, wherein the specific purification of the microorganisms in step S1 is as follows: the activated sludge is taken from the anaerobic end of the municipal sewage plant, the sludge is mixed and exposed to nitrogen gas to remove oxygen, and then is sealed and placed in a constant temperature water bath shaker for purification, and after purification, the activated sludge is allowed to stand and stratify; the supernatant is taken and added to the pre-sterilized and nitrogen-exposed expanded culture medium, and after expansion, the microorganisms and glycerol are mixed and stored at low temperature.

[0040] Example 4

[0041] The method for removing bisphenol A by using microbial extracellular secretions and inorganic ligands in conjunction with β-MnO2 in this embodiment is based on Example 3, wherein the acclimation in step S1 is to acclimate the purified and cultured microorganisms in a gradient concentration acclimation mode, specifically: adding the purified and cultured microorganisms to the expansion medium at a concentration of 1%, and expanding the culture three times, each time for 1 day; setting 5 concentration gradients of β-MnO2 of 50 mg / L, 100 mg / L, 200 mg / L, 300 mg / L, and 500 mg / L, and acclimating once at each concentration for 4 days, and repeating 3 times for a total of 12 days. The entire acclimation process is a total of 60 days.

[0042] Example 5

[0043] The method for removing bisphenol A by using microbial extracellular secretions and inorganic ligands in conjunction with β-MnO2 in this embodiment is based on Example 4, wherein the expansion medium contains 10.00 g / L of peptone, 5.00 g / L of yeast powder, and 10.00 g / L of sodium chloride; the inorganic salt medium used for acclimation contains 1.00 g / L of sodium chloride, 0.80 g / L of ammonium chloride, 0.50 g / L of potassium dihydrogen phosphate, 0.60 g / L of potassium hydrogen phosphate, 0.20 g / L of magnesium chloride hexahydrate, and 0.05 g / L of calcium chloride dihydrate; the expansion medium and the inorganic salt medium are sterilized before use.

[0044] Example 6

[0045] The method for removing bisphenol A by using microbial extracellular secretions and inorganic ligands in conjunction with β-MnO2 in this embodiment is based on Example 5, wherein the extraction of extracellular secretions in step S2 is specifically as follows: the expanded anaerobic microorganisms are added at a concentration of 1% to an inorganic salt culture medium containing 1 g / L sodium acetate and sodium acetate as the sole carbon source (the culture medium is sterilized and aerated with nitrogen for 30 minutes before use). After culturing for 5 days, the culture medium is centrifuged at 8000 rpm and 4°C for 5 minutes, and the supernatant is filtered using a 0.45 µm glass fiber to obtain the EPS used.

[0046] Example 7: Degradation Experiment

[0047] In the following experiments, the PP concentration involved in the degradation process was 5 mM, the BPA concentration was 5 mg / L, and the β-MnO2 concentration was 150 mg / L;

[0048] Experiment 1: The degradation experiment was carried out by the method of Example 6, and four experimental groups were set, one of which was carried out according to the combination of β-MnO2+PP+EPS of the application, and the other three were β-MnO2, β-MnO2+PP, and β-MnO2+EPS respectively; the concentration of EPS was 10 mgC / L; the degradation experiment lasted for 120 h, and samples were taken at 12 h, 24 h, 36 h, 48 h, 72 h, 96 h, and 120 h respectively by using a 10 mL syringe, and the concentration of BPA was determined, and the results are shown in Figure 2 ;

[0049] Under the synergistic action of β-MnO2+PP+EPS, the degradation efficiency is higher than that of other groups, and is about four times the degradation efficiency of PP and EPS alone, so PP and EPS and the combination of the two with β-MnO2 synergistic system can effectively promote the degradation process of BPA.

[0050] Experiment 2: The degradation experiment was carried out by the method of Example 6, and the extracted microbial extracellular secretion was quantified by a total organic carbon analyzer, and the concentration was 1 mgC / L, 5 mgC / L, 10 mgC / L, and 20 mgC / L, respectively, under the conditions of not containing inorganic ligand PP and containing inorganic ligand PP, and the degradation of BPA by β-MnO2 was carried out, and the whole process was carried out under anaerobic conditions, and the results are shown in Figure 3 ;

[0051] Experiment 3: The degradation experiment was carried out by the method of Example 6, and the content change of total dissolved manganese in the reaction process was determined by atomic absorption method to illustrate the reduction and dissolution of EPS and PP to β-MnO2, and the concentration of EPS in this experiment was 10 mgC / L; the content change of Mn(III)-PP at 258 nm was determined by ultraviolet spectrophotometry to further illustrate that β-MnO2 was reduced and dissolved and generated active Mn(III), and the results are shown in Figure 4 ; The change of EPS in the reaction process was monitored by three-dimensional fluorescence spectroscopy, which illustrated that the protein substances in EPS were oxidized in the reduction and dissolution process of manganese minerals, and the results are shown in Figure 5 ;

[0052] The application carries out related experiments of EPS and PP synergizing with β-MnO2 to degrade BPA, which proves that EPS and PP have strong reduction capacity for manganese minerals, thereby significantly enhancing the oxidation and degradation efficiency of manganese minerals for BPA.

Claims

1. A method for removing bisphenol A by using microbial extracellular secretions and inorganic ligands in conjunction with β-MnO2, characterized in that The following steps are involved: S1. Purify and culture the microorganisms from the anaerobic end of the activated sludge of the municipal sewage treatment plant, inoculate them into an inorganic salt culture medium containing β-MnO2, and perform concentration gradient acclimation culture on the microorganisms; S2, extracting the extracellular secretions of the microorganisms acclimated in step S1; S3. Add extracellular secretions and inorganic ligand sodium pyrophosphate to a liquid containing β-MnO2 and bisphenol A, aerate the liquid with nitrogen to remove oxygen, and seal it to maintain anaerobic conditions, so that bisphenol A can be removed by reaction.

2. The method for removing bisphenol A by using microbial extracellular secretions and inorganic ligands in collaboration with β-MnO2 according to claim 1, characterized in that The preparation method of β-MnO2 is as follows: 0.8 mol / L KMnO4 and 1.2 mol / L MnCl2 are dissolved in 60 mL ultrapure water, mixed and stirred for 30 minutes, and then the suspension is poured into a 100 mL Teflon autoclave and sealed; reacted in an oven at 180°C for 24 hours, cooled and centrifuged with ultrapure water to obtain a solid substance, and then dried at 120°C for 24 hours; after natural cooling and grinding, it is ready.

3. The method for removing bisphenol A by using microbial extracellular secretions and inorganic ligands in collaboration with β-MnO2 according to claim 1, characterized in that The specific steps of microbial purification and cultivation in step S1 are as follows: activated sludge is taken from the anaerobic end of the municipal sewage treatment plant, the sludge is mixed and then aerated with nitrogen to remove oxygen, and then sealed and placed in a constant temperature water bath shaker for purification. After purification, the activated sludge is allowed to stand and separate into layers; the supernatant is taken and added to the expansion culture medium that has been sterilized in advance and aerated with nitrogen, and after expansion culture, the microorganisms and glycerol are mixed and stored at low temperature.

4. The method for removing bisphenol A by using microbial extracellular secretions and inorganic ligands in collaboration with β-MnO2 according to claim 1, characterized in that The S1 step of acclimation is to acclimate the purified and cultured microorganisms using a gradient concentration acclimation mode. Specifically, the purified and cultured microorganisms are added to the expansion medium at a concentration of 1%, and the expansion culture is carried out three times, each time for 1 day; 5 concentration gradients of β-MnO2 are set, namely 50 mg / L, 100 mg / L, 200 mg / L, 300 mg / L, and 500 mg / L. The acclimation time for each concentration is 4 days, and the cycle is repeated 3 times for a total of 12 days. The entire acclimation process takes a total of 60 days.

5. The method for removing bisphenol A by using microbial extracellular secretions and inorganic ligands in cooperation with β-MnO2 according to claim 4, characterized in that The expansion medium contains 10.00 g / L of peptone, 5.00 g / L of yeast powder, and 10.00 g / L of sodium chloride. The inorganic salt medium used for acclimation contains 1.00 g / L of sodium chloride, 0.80 g / L of ammonium chloride, 0.50 g / L of potassium dihydrogen phosphate, 0.60 g / L of dipotassium hydrogen phosphate, 0.20 g / L of magnesium chloride hexahydrate, and 0.05 g / L of calcium chloride dihydrate. Both the expansion medium and the inorganic salt medium are sterilized before use.

6. The method for removing bisphenol A by using microbial extracellular secretions and inorganic ligands in conjunction with β-MnO2 according to claim 1, characterized in that The specific steps for extracting extracellular secretions in step S2 are as follows: the expanded anaerobic microorganisms are added to an inorganic salt culture medium containing 1 g / L sodium acetate and sodium acetate as the sole carbon source at a concentration of 1%. After culturing for 5 days, the culture medium is centrifuged at 8000 rpm and 4°C for 5 minutes, and the supernatant is filtered with a 0.45 µm glass fiber to obtain EPS.

7. The method for removing bisphenol A by using microbial extracellular secretions and inorganic ligands in conjunction with β-MnO2 according to claim 1, characterized in that In step S3, the concentration of extracellular secretion was 1 mgC / L-20 mgC / L, the concentration of inorganic ligand sodium pyrophosphate was 5 mM, and the concentration of β-MnO2 was 150 mg / L.

8. The method for removing bisphenol A by using microbial extracellular secretions and inorganic ligands in cooperation with β-MnO2 according to claim 1, characterized in that The reaction in step S3 was continued for 120 h.

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