Preparation method and application of biogenic iron-manganese oxide catalyst

Abstract

The present invention relates to an oxidation treatment technology for organic pollutants in water bodies, and discloses a preparation method and application of a biogenic iron-manganese oxide catalyst. The biogenic iron-manganese oxide catalyst has a unique core-shell structure, and the core-shell structure includes a core containing iron-manganese oxide and a biochar shell coated on part or all of the surface of the core, wherein the weight ratio of the core to the biochar shell is 5-9:1. The preparation method of the catalyst includes: calcining the cells of iron-manganese oxidizing bacteria and their metabolites under nitrogen conditions to form a material with a core-shell structure, and the core-shell structure includes a core containing iron-manganese oxide and a biochar shell coated on part or all of the surface of the core. The catalyst material can efficiently catalyze the oxidation and degradation of organic pollutants such as phenol in wastewater by persulfate, and has low cost, environmental friendliness, simple preparation process, and wide application potential.

Description

Technical Field

[0001] The present invention relates to an advanced oxidation treatment technology for environmental pollutants, and in particular to a preparation method of a biogenic iron-manganese oxide catalyst and application thereof. Background Art

[0002] As an important industrial raw material, phenol is widely used in petrochemical, papermaking, printing and dyeing, medicine and other industries. However, phenolic chemicals are highly toxic and bioaccumulative, and even at low concentrations they still pose a serious threat to the ecological environment and human health. In recent years, with the rapid development of industry, the discharge of phenolic wastewater has increased, and the potential risks brought about are also increasing. According to national requirements and the trend of social development, efficient measures must be taken to strictly control the discharge of phenolic wastewater and reduce the concentration of phenol in the environment. Therefore, finding an efficient and fast treatment method is an urgent problem to be solved for phenolic wastewater.

[0003] Persulfate has strong oxidizing properties and can produce highly active free radicals to accelerate the bond breaking and degradation of phenolic compounds. However, unactivated persulfate has low reactivity with common pollutants and must be added with corresponding catalysts to work efficiently. However, traditional chemical catalysts mostly use metal materials, and their synthesis conditions are relatively harsh, the synthesis steps are relatively complicated, and the cost is high, making them difficult to use on a large scale.

[0004] Compared with chemical synthesis, biosynthesis utilizes the metabolic activities of microorganisms themselves to convert powerful metal ions in the environment into metal oxides with catalytic properties. It has the characteristics of low cost, simple operation, environmental protection and no pollution. It is a potential alternative method for the preparation of advanced oxidation catalysts with great application potential. Summary of the invention

[0005] The purpose of the present invention is to overcome the problems existing in the prior art and provide a preparation method and application of a biogenic iron-manganese oxide catalyst. The catalyst material can efficiently catalyze the oxidation and degradation of organic pollutants such as phenol in wastewater by persulfate, and has low cost, environmental friendliness, simple preparation process, and wide application potential.

[0006] In order to achieve the above-mentioned objectives, the first aspect of the present invention provides a biogenic iron-manganese oxide catalyst, which has a core-shell structure, comprising an inner core containing iron-manganese oxide and a biochar shell coating part or all of the surface of the inner core, wherein the weight ratio of the inner core to the biochar shell is 5-9:1.

[0007] Preferably, the iron-manganese oxide in the inner core contains zero-valent iron, FeMnO2 and manganese oxide;

[0008] The biochar shell is an organic biochar shell.

[0009] The second aspect of the present invention provides a method for preparing a biogenic iron-manganese oxide catalyst, which comprises: calcining the cells of iron-manganese oxidizing bacteria and their metabolites under nitrogen conditions to form a material with a core-shell structure, wherein the core-shell structure comprises an inner core containing iron-manganese oxide and a biochar outer shell coating part or all of the surface of the inner core.

[0010] Preferably, the preparation process of the iron-manganese oxidizing bacteria and its metabolites comprises the following steps:

[0011] (1) Iron and manganese oxidizing bacteria are obtained by enriching, culturing, separating and purifying the mine wastewater. Sphingobium sp .QBS-P4;

[0012] (2) the iron and manganese oxidizing bacteria Sphingobium sp .QBS-P4 is subjected to seed culture to obtain seed liquid, the seed liquid is inoculated into a fermentation medium for fermentation culture to obtain a fermentation liquid, the fermentation liquid is subjected to solid-liquid separation to obtain a bacterial precipitate, and the bacterial precipitate is dried I.

[0013] Preferably, the inoculation process in step (2) comprises: inoculating the seed liquid into the fermentation medium at an inoculation rate of 5-15% (v / v).

[0014] Preferably, the fermentation medium in step (2) contains: peptone 0.2-0.8 g / L, glucose 0.1-0.5 g / L, yeast extract powder 0.1-0.3 g / L, MnSO4·H2O 0.1-0.3 g / L, K2HPO4 0.05-0.2 g / L, MgSO4·7H2O 0.1-0.3 g / L, NaNO3 0.1-0.3 g / L, CaCl2 0.05-0.2 g / L, (NH4)2CO3 0.05-0.2 g / L, and ammonium ferric citrate 0.5-1.2 g / L.

[0015] Preferably, the fermentation culture in step (2) generally adopts shaking culture.

[0016] Preferably, the fermentation culture conditions at least include: a temperature of 28-30°C, a rotation speed of 100-150 rpm, and a time of 8-12 days.

[0017] Preferably, the conditions for solid-liquid separation in step (2) at least include: a centrifugal speed of 8000-10000 rpm and a time of 5-8 min.

[0018] Preferably, the conditions of the drying I at least include: a temperature of -55 to -40°C and a time of 40-48 hours.

[0019] Preferably, step (2) further comprises: taking out the bacterial cell precipitate after drying I, transferring it to a mortar and grinding it for 20-30 minutes, and passing it through a 50-100 mesh sieve to obtain bacterial cell powder.

[0020] Preferably, the calcination conditions at least include: a heating rate of 3-8°C / min, a temperature of 750-850°C, and a time of 0.5-2h.

[0021] Preferably, the method further comprises: rinsing and drying the solid obtained by calcination II.

[0022] Preferably, the cleaning agent for rinsing is an acid solution, more preferably an HCl solution with a concentration of 0.05-0.15 mol / L.

[0023] Preferably, the drying conditions II at least include: a temperature of 45-55° C. and a time of 20-30 h.

[0024] The third aspect of the present invention provides the use of the aforementioned biogenic iron-manganese oxide catalyst and / or the biogenic iron-manganese oxide catalyst prepared by the aforementioned preparation method in catalyzing the degradation of organic pollutants by persulfate; the organic pollutant is preferably phenol.

[0025] Through the above technical solution, the beneficial effects of the present invention are:

[0026] Compared with chemically synthesized iron-manganese oxides, the biogenic iron-manganese oxide catalyst provided by the present invention is obtained by calcining iron-manganese oxidizing bacteria and their metabolites, and its preparation process is simple, low-cost and environmentally friendly. In addition, the biogenic iron-manganese oxide catalyst has a typical core-shell structure, characterized by: a core containing iron-manganese oxide and a biochar shell covering part or all of the surface of the core; this core-shell structure can effectively prevent the problem of metal dissolution occurring during the catalytic reaction, greatly extending the cycle life of the catalytic material.

[0027] Compared with chemical iron-manganese oxides, the efficiency of the biogenic iron-manganese oxide catalyst obtained by high-temperature calcination in the present invention in catalyzing the degradation of phenol by persulfate is also greatly improved, showing higher catalytic performance.

[0028] In addition, the biogenic iron-manganese oxide catalyst exhibits strong magnetism after nitrogen calcination. Its magnetic characteristics make the repeated recycling of the catalyst material extremely convenient and also improve the ability of the catalyst material to treat complex water bodies.

[0029] In summary, compared with chemical iron-manganese oxides, biogenic iron-manganese oxide catalysts not only have simple preparation processes, low costs, and are environmentally friendly, but also have high catalytic efficiency, strong adaptability to complex water bodies, and are easy to recycle, and have wider application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a scanning electron microscope image of the biogenic iron-manganese oxide catalyst in Example 1;

[0031] Figure 2 is a transmission electron micrograph of the biogenic iron-manganese oxide catalyst in Example 1, wherein (A) is scaled at 100 nm, and (B) is scaled at 10 nm;

[0032] Figure 3 is the XRD pattern of the biogenic iron-manganese oxide catalyst in Example 1;

[0033] Figure 4 is the hysteresis loop diagram of the biogenic iron-manganese oxide catalyst in Example 1;

[0034] Figure 5 The effect of different dosages of biogenic iron-manganese oxide catalysts on phenol degradation in Example 2;

[0035] Figure 6 The effect of different persulfate dosages on phenol degradation in Example 3;

[0036] Figure 7 is the effect of different pH on phenol degradation in Example 4;

[0037] Figure 8 This is one of the diagrams showing the effect of coexisting cations on phenol degradation in Example 5;

[0038] Fig. 9 This is the second diagram of the effect of coexisting anions on phenol degradation in Example 5;

[0039] Fig.10 is a cycle experiment diagram of phenol degradation by biogenic iron-manganese oxide catalyst in Example 5;

[0040] Fig.11 This is a comparison chart of the effects of different iron-manganese oxide catalysts in activating PMS to degrade phenol in water in Test Example 1;

[0041] Fig.12 This is a comparison chart of the effects of different iron-manganese oxide catalysts activating PMS in Test Example 2 to degrade different types of phenol-containing wastewater. DETAILED DESCRIPTION

[0042] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0043] The first aspect of the present invention provides a biogenic iron-manganese oxide catalyst having a unique core-shell structure, wherein the core-shell structure comprises an inner core containing iron-manganese oxide and a biochar shell coating part or all of the surface of the inner core, wherein the weight ratio of the inner core to the biochar shell is 5-9:1.

[0044] The inventors of the present invention discovered during the research process of iron-manganese oxidizing bacteria that a biomass material with a core-shell structure can be formed by calcining the iron-manganese oxidizing bacteria and their metabolites with nitrogen, and that the material can efficiently catalyze the oxidation and degradation of organic pollutants such as phenol in wastewater by persulfate, greatly improving the rate of oxidation and degradation of organic pollutants, reducing the reaction time, and improving the removal efficiency of organic pollutants in wastewater; and in the process of catalyzing the oxidation and degradation of organic pollutants in wastewater by persulfate, the unique biochar shell can effectively avoid the secondary pollution problem caused by the precipitation of metal materials during the catalytic reaction.

[0045] The core-shell structure of the biogenic iron-manganese oxide catalyst provided by the present invention can be obtained by scanning electron microscopy and transmission electron microscopy. The metal elements are relatively agglomerated, indicating that the iron-manganese oxide forms an inner core, and the biochar is distributed on the surface of the inner core to form an outer shell, and the surface of the material has a large number of holes distributed thereon. By measuring the hysteresis loop of the material, it is found that the material as a whole exhibits strong magnetism, which is conducive to subsequent recycling.

[0046] In the present invention, X-ray diffraction (XRD) detection can be used to obtain information such as the composition of the biogenic iron-manganese oxide catalyst, the structure or morphology of the internal atoms or molecules. Preferably, the iron-manganese oxide in the inner core contains zero-valent iron, FeMnO2 and manganese oxide, and the biochar shell is an organic biochar shell.

[0047] The second aspect of the present invention provides a method for preparing a biogenic iron-manganese oxide catalyst, which comprises: calcining the cells of iron-manganese oxidizing bacteria and their metabolites under nitrogen conditions to form a material with a core-shell structure, wherein the core-shell structure comprises an inner core containing iron-manganese oxide and a biochar outer shell coating part or all of the surface of the inner core.

[0048] The biogenic iron-manganese oxide catalyst provided by the invention has simple preparation process, low cost, environmental friendliness and wide application potential.

[0049] According to the present invention, the iron-manganese oxidizing bacteria and its metabolites can be obtained by culturing commercially available iron-manganese oxidizing bacteria, or by isolating and screening the iron-manganese oxidizing bacteria and then culturing them. Preferably, the iron-manganese oxidizing bacteria and its preparation process include the following steps:

[0050] (1) Iron and manganese oxidizing bacteria are obtained by enriching, culturing, separating and purifying the mine wastewater. Sphingobium sp .QBS-P4 (its genome sequence has been uploaded to the National Center for Biotechnology Information, NCBI GenBank ID: SUB12506216);

[0051] (2) the iron and manganese oxidizing bacteria Sphingobium sp .QBS-P4 is subjected to seed culture to obtain seed liquid, the seed liquid is inoculated into a fermentation medium for fermentation culture to obtain a fermentation liquid, the fermentation liquid is subjected to solid-liquid separation to obtain a bacterial precipitate, and the bacterial precipitate is dried I.

[0052] In the present invention, the mine wastewater can be mine water collected from a mine, for example, collected from the Qibaoshan mining area in Liuyang City, Hunan Province; the iron and manganese oxidizing bacteria can be obtained from the mine wastewater by conventional enrichment culture, separation and purification methods in the art. Sphingobium sp .QBS-P4.

[0053] For example, iron and manganese oxidizing bacteria Sphingobium sp .QBS-P4 is obtained as follows:

[0054] a. Enrichment culture: inoculating the mine wastewater into an enrichment culture medium at a ratio of 1-5% for culture I to obtain an enrichment culture solution;

[0055] Preferably, the enrichment medium contains: peptone 0.2-0.8 g / L, glucose 0.1-0.5 g / L, yeast extract powder 0.1-0.3 g / L, MnSO4·H2O 0.1-0.3 g / L, K2HPO4 0.05-0.2 g / L, MgSO4·7H2O 0.1-0.3 g / L, NaNO3 0.1-0.3 g / L, CaCl2 0.05-0.2 g / L, (NH4)2CO3 0.05-0.2 g / L, and ammonium ferric citrate 0.5-1.2 g / L;

[0056] Preferably, the conditions of the culture I at least include: an inoculation amount of 5-15% (v / v), a temperature of 28-30° C., a rotation speed of 100-150 rpm, and a time of 8-12 days.

[0057] b. Isolation and purification: Take 1 mL of the supernatant of the enrichment medium and spread it evenly on a solid plate of the separation medium. Set up 3 replicates for each group and place it in a 30°C constant temperature incubator for 7 days. Pick a single colony in the medium and transfer it to a new separation medium plate. Perform streaking transfer at least 3 times for purification until a single colony with a single morphology is isolated. Finally, streak the single colony on a slant medium and store it at 4°C for later use.

[0058] Preferably, the separation medium contains: peptone 0.2-0.8 g / L, glucose 0.1-0.5 g / L, yeast extract powder 0.1-0.3 g / L, MnSO4·H2O 0.1-0.3 g / L, K2HPO4 0.05-0.2 g / L, MgSO4·7H2O 0.1-0.3 g / L, NaNO3 0.1-0.3 g / L, CaCl2 0.05-0.2 g / L, (NH4)2CO3 0.05-0.2 g / L, ammonium ferric citrate 0.5-1.2 g / L, and agar powder 20-25 g / L.

[0059] According to the present invention, the seed culture of the iron and manganese oxidizing bacteria can be carried out by activating the iron and manganese oxidizing bacteria strains and then inoculating them into a seed culture medium for seed culture. The seed culture medium can adopt a conventional liquid culture medium to provide the nutrients required for the growth and reproduction of the iron and manganese oxidizing bacteria. Furthermore, the parameters such as the temperature, rotation speed, and time of the seed culture can also be designed according to the growth requirements of the iron and manganese oxidizing bacteria to promote the growth and reproduction of the bacteria.

[0060] According to the present invention, preferably, the inoculation process in step (2) comprises: inoculating the seed liquid into the fermentation medium at an inoculation rate of 5-15% (v / v).

[0061] According to the present invention, preferably, the fermentation medium in step (2) contains: peptone 0.2-0.8 g / L, glucose 0.1-0.5 g / L, yeast extract powder 0.1-0.3 g / L, MnSO4·H2O 0.1-0.3 g / L, K2HPO4 0.05-0.2 g / L, MgSO4·7H2O 0.1-0.3 g / L, NaNO3 0.1-0.3 g / L, CaCl2 0.05-0.2 g / L, (NH4)2CO3 0.05-0.2 g / L, and ammonium ferric citrate 0.5-1.2 g / L.

[0062] According to the present invention, preferably, the fermentation culture in step (2) generally adopts shaking culture.

[0063] According to the present invention, preferably, the fermentation culture conditions at least include: a temperature of 28-30° C., a rotation speed of 100-150 rpm, and a time of 8-12 days.

[0064] In the present invention, the fermentation culture liquid obtained by fermentation culture is subjected to solid-liquid separation to remove the supernatant to obtain a precipitate, the precipitate is repeatedly washed with deionized water, and then freeze-dried and ground to obtain the bacterial body of the iron and manganese oxidizing bacteria, which is stored in a dry place for future use.

[0065] According to the present invention, the solid-liquid separation can be carried out by conventional separation methods in the art, such as centrifugation, filtration, etc. Preferably, the solid-liquid separation is carried out by centrifugation, and the conditions thereof include at least: the centrifugal speed is 8000-10000rpm, and the time is 5-8min. Exemplarily, the solid-liquid separation process is: the fermentation broth is added to a 10-25mL centrifuge tube in batches, centrifuged at a speed of 8000-10000rpm for 5-8min, then the supernatant in the centrifuge tube is poured out, and the fermentation broth is continued to be added and repeated for 3-5 times to obtain a sufficient amount of bacterial precipitation (0.2-0.4g).

[0066] According to the present invention, preferably, the conditions of drying I in step (2) at least include: a temperature of -55 to -40°C and a time of 40-48 hours. Exemplarily, the method of drying I is: placing the bacterial precipitate in a vacuum freeze dryer and continuously freeze-drying it at a temperature of -55 to -40°C for 40-48 hours.

[0067] According to the present invention, preferably, step (2) further comprises: taking out the bacterial cell precipitate after drying I, transferring it to a mortar and grinding it for 20-30 minutes, passing it through a 50-100 mesh sieve to obtain bacterial cell powder as a raw material for high-temperature calcination to prepare a biogenic iron-manganese oxide catalyst.

[0068] According to the present invention, preferably, the calcination conditions at least include: a heating rate of 3-8°C / min, a temperature of 750-850°C, and a time of 0.5-2h (the time refers to the time after the temperature reaches the calcination temperature). Under the preferred conditions, impurities in the bacteria can be more effectively removed, so that the surface of the inner core containing iron and manganese oxides is coated with organic biochar, and more active sites are exposed.

[0069] According to the present invention, preferably, the method further comprises: rinsing and drying the calcined solid to remove impurities on its surface, thereby improving the catalytic efficiency of the obtained biogenic iron-manganese oxide catalyst in degrading organic pollutants with persulfate.

[0070] According to the present invention, preferably, the rinsing cleaning agent is an acid solution, more preferably a 0.05-0.15 mol / L HCl solution, so as to remove metal particles that may be exposed on the surface of the material and prevent the metal particles from precipitating during the catalytic persulfate oxidation reaction.

[0071] According to the present invention, preferably, the drying conditions II at least include: a temperature of 45-55° C. and a time of 20-30 h.

[0072] The third aspect of the present invention provides the use of the aforementioned biogenic iron-manganese oxide catalyst and / or the biogenic iron-manganese oxide catalyst prepared by the aforementioned preparation method in catalyzing the degradation of organic pollutants by persulfate; the organic pollutant is preferably phenol.

[0073] The biogenic iron-manganese oxide catalyst provided by the present invention can not only efficiently catalyze the oxidation degradation of organic pollutants such as phenol in wastewater by persulfate, increase the rate of oxidation degradation of organic pollutants, reduce reaction time, and improve the removal efficiency of organic pollutants in wastewater, but also has a simple preparation process, low cost, and environmental friendliness, and has wide application potential; the catalyst material also has the characteristics of large specific surface area, strong adsorption performance, and strong magnetism, so that it can cope with more complex water environments, and subsequent recycling is extremely convenient.

[0074] The present invention will be described in detail below through examples.

[0075] In the following examples, the morphology of the biogenic iron-manganese oxide catalyst was analyzed by scanning electron microscopy (SEM, NovaNanoSEM450, USA, with an acceleration voltage and beam current range of 200 V to 30 kV and 0.6 pA to 200 nA, respectively) and transmission electron microscopy (TEM, Tecnai F20, Japan, with a resolution of 0.1 to 0.2 nm and an acceleration voltage of 200 kV); the morphology of the biogenic iron-manganese oxide catalyst was analyzed by X-ray photoelectron spectroscopy (XPS, VGEscalab250, Japan). Qualitative and semi-quantitative analysis of the chemical information on the surface and interface of the catalyst; hysteresis loop (MPMS, SQUIDVSM, QuantumDesign) was used to analyze the magnetic properties of the biogenic iron-manganese oxide catalyst; the concentration of phenol was detected by high performance liquid chromatography; the metal ion concentration was measured by inductively coupled plasma (ICP) using ICP-OES (8300) according to the national standard HJ776-2015 "Determination of 32 elements in water quality by inductively coupled plasma emission spectrometry"; iron-manganese oxidizing bacteria Sphingobium sp QBS-P4 was separated from mine water from Qibaoshan mining area in Liuyang City, Hunan Province. Other raw materials and reagents were commercially available.

[0076] In the following examples, the components of the enrichment medium, seed medium and fermentation medium are: peptone 0.5 g / L, glucose 0.3 g / L, yeast extract powder 0.2 g / L, K2HPO4 0.1 g / L, MgSO4·7H2O 0.2 g / L, NaNO3 0.2 g / L, CaCl2 0.1 g / L, (NH4)2CO3 0.1 g / L, after the preparation is completed, it is filtered through a 0.22 μm organic filter membrane, and then MnSO4·H2O 0.2 g / L and ammonium ferric citrate 1 g / L are added separately;

[0077] The components of the separation medium are: peptone 0.5g / L, glucose 0.3g / L, yeast extract powder 0.2g / L, K2HPO4 0.1g / L, MgSO4·7H2O 0.2g / L, NaNO3 0.2g / L, CaCl2 0.1g / L, (NH4)2CO3 0.1g / L. After preparation, it is filtered through a 0.22μm organic filter membrane, and then MnSO4·H2O 0.2g / L, ammonium ferric citrate 1g / L and agar powder 25g / L are added separately.

[0078] The preparation process of phenol standard stock solution is as follows: use an electronic analytical balance to accurately weigh 0.4705g of phenol and dissolve it in deionized water. After it is completely dissolved by magnetic stirring for 12 hours, it is fixed to volume in a 1000mL volumetric flask with a concentration of 5mM, and the prepared phenol standard stock solution is stored in a refrigerator; use this 5mM phenol standard stock solution as the mother liquor to prepare a 0.1mM phenol solution as phenol simulated wastewater.

[0079] Example 1

[0080] (1) The mine water was inoculated into the enrichment medium at a ratio of 10% (v / v), and cultured at a temperature of 29°C and a rotation speed of 120 rpm for 10 days to obtain an enrichment culture solution. 1 mL of the supernatant of the enrichment culture medium was evenly coated on a solid plate of the separation medium. Each group was repeated 3 times and cultured in a 30°C constant temperature box for 7 days. A single colony in the culture medium was picked and transferred to a new separation medium plate. The streaking transfer was performed at least 3 times for purification until a single colony with a single morphology was isolated. The single colony was identified by 16s rDNA strain identification, which was found to be an iron-manganese oxidizing bacterium. Sphingobium sp.QBS-P4, whose genome sequence has been uploaded to the National Center for Biotechnology Information, NCBI GenBank ID is SUB12506216. The single colony was streaked on a slant medium and stored at 4°C for later use.

[0081] (2) Iron and manganese oxidizing bacteria Sphingobium sp .QBS-P4 was inoculated into the activation culture medium, and cultured in a constant temperature air bath incubator at 30°C and 120 rpm for 12 days to obtain an activation culture solution, and then the activation culture solution was inoculated into the fermentation medium at an inoculum amount of 10% (v / v), and cultured continuously in a constant temperature air bath incubator at 30°C and 120 rpm for 12 days to obtain a fermentation culture solution;

[0082] (3) 100 mL of fermentation culture medium was centrifuged at 8000 rpm for 6 min. After centrifugation, the supernatant was filtered out to obtain bacterial precipitate. The bacterial precipitate was repeatedly washed with deionized water three times and then placed in a vacuum freeze dryer for freeze drying at -50 °C for 48 h. The freeze-dried bacterial precipitate was taken out, transferred to a mortar and ground for 20-30 min, passed through a 60-mesh sieve, and ground evenly to obtain bacterial powder, which was stored in a dry place for later use;

[0083] (4) Weigh 0.9 g of bacterial powder (initial biogenic iron-manganese oxide) and add it to a magnetic boat. Place the boat in a tube furnace and heat the temperature to 800 °C at a rate of 5 °C / min and calcine for 1 h (nitrogen was introduced for 0.4 h before calcination, and nitrogen was continuously introduced at a rate of 70 mL / min during the calcination process). Rinse the calcined solid with 0.5 mol / L HCl solution, then repeatedly wash with deionized water until the material is neutral, and then place the solid in an oven and dry it at 50 °C for 24 h to obtain a biogenic iron-manganese oxide catalyst (hereinafter referred to as BFMO-N800).

[0084] Comparative Example 1

[0085] Dissolve 5.05g of Fe(NO3)3·9H2O and 3.14g of Mn(NO3)3·4H2O in 50mL of ethanol, add 2.123g of citric acid monohydrate after stirring evenly, continue stirring for 2h, then put into an oven and dry at 80℃ for 24h, collect the powder and grind it evenly to obtain a chemical iron manganese oxide precursor;

[0086] 0.9 g of chemical iron manganese oxide precursor was weighed and added to a magnetic boat, which was placed in a tube furnace and heated to 800 °C at a heating rate of 5 °C / min and calcined for 1 h (nitrogen was introduced for 0.4 h before calcination, and nitrogen was continuously introduced at a rate of 70 mL / min during the calcination process). The calcined solid was rinsed with 0.5 mol / L HCl solution, and then repeatedly washed with deionized water until the material was neutral, and then placed in an oven and dried at 50 °C for 24 h to obtain chemical iron manganese oxide (CFMO).

[0087] The BFMO-N800 obtained in Example 1 was tested by scanning electron microscopy and transmission electron microscopy. Figure 1 and Figure 2 From the scanning electron microscopy image, we can see that the surface of the biogenic iron-manganese oxide catalyst has many holes. This porous structure is conducive to the adsorption of catalyst materials and pollutants, which can accelerate the catalytic reaction to a certain extent. At the same time, the transmission electron microscopy ( Figure 2 ) more clearly shows that the calcined biogenic iron-manganese oxide catalyst is a typical core-shell structure, which is an inner core composed of iron-manganese oxide and a biochar outer shell coated on the surface of the iron-manganese oxide (inner core). This unique core-shell structure can reduce the metal dissolution in the catalyst material and increase the recyclability of the catalyst material, while providing more active sites and improving the reaction efficiency.

[0088] The BFMO-N800 obtained in Example 1 was subjected to XRD detection, and the results are shown in Figure 3 As shown, there are obvious characteristic peaks, and their specific components are zero-valent iron, FeMnO2 and manganese oxide.

[0089] The BFMO-N800 obtained in Example 1 was subjected to hysteresis loop detection, and the results were as follows: Figure 4 As shown, BFMO-N800 exhibits strong magnetism.

[0090] The BFMO-N800 obtained in Example 1 and the CFMO obtained in Comparative Example 1 were subjected to a cyclic degradation experiment, and the specific process was as follows: 50 mL of 0.1 mM phenol simulated wastewater was added to a 100 mL conical flask, and 0.025 g of BFMO-N800 prepared in Example 1 or CFMO prepared in Comparative Example 1 was added respectively, the solution was oscillated at 150 rpm for 30 min, 0.0154 g of potassium persulfate was added and continued to oscillate for 30 min; the solution after the reaction was filtered, washed three times with deionized water, and then dried in an oven at 50 ° C for 24 h, and the potassium persulfate degradation experiment of phenol was repeated. The cyclic experiment was repeated five times, and three groups were set in parallel.

[0091] The metal dissolution after each potassium persulfate degradation reaction of phenol was tested by ICP. The results are shown in Table 1. BFMO-N800 dissolves less metal than CFMO.

[0092] Table 1

[0093]

[0094] Example 2

[0095] The BFMO-N800 prepared in Example 1 was used as a catalyst to activate persulfate to degrade phenol, and the dosage of the BFMO-N800 material was changed to compare the degradation rate to obtain the optimal catalytic reaction conditions. The specific steps are as follows:

[0096] A certain volume of phenol simulated wastewater was added to a conical flask, and the BFMO-N800 prepared in Example 1 was added. The mixture was shaken for 30 minutes to allow the BFMO-N800 material to reach adsorption saturation. Persulfate was added and the shaking was continued for 30 minutes. The specific experimental conditions were as follows:

[0097] a. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask, add 0.005 g of BFMO-N800 prepared in Example 1, oscillate the solution at 150 rpm for 30 min, add 0.0154 g of potassium persulfate and continue oscillating for 30 min;

[0098] b. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask, add 0.01 g of BFMO-N800 prepared in Example 1, oscillate the solution at 150 rpm for 30 min, add 0.0154 g of potassium persulfate and continue oscillating for 30 min;

[0099] c. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask, add 0.015 g of BFMO-N800 prepared in Example 1, oscillate the solution at 150 rpm for 30 min, add 0.0154 g of potassium persulfate and continue oscillating for 30 min;

[0100] d. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask, add 0.02 g of BFMO-N800 prepared in Example 1, oscillate the solution at 150 rpm for 30 min, add 0.0154 g of potassium persulfate and continue oscillating for 30 min;

[0101] e. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask, add 0.025 g of BFMO-N800 prepared in Example 1, oscillate the solution at 150 rpm for 30 min, add 0.0154 g of potassium persulfate and continue oscillating for 30 min;

[0102] f. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask, add 0.03 g of BFMO-N800 prepared in Example 1, oscillate the solution at 150 rpm for 30 min, add 0.0154 g of potassium persulfate and continue oscillating for 30 min;

[0103] Three parallel groups were set up for each material dosage experiment;

[0104] Then, samples were taken at -30, 0, 5, 10, 15, 20, and 30 minutes after potassium persulfate was added. The samples were filtered through a 0.22 µm microporous filter membrane (organic system) and the filtrate was taken to determine the concentration C of the remaining phenol in the filtrate. The phenol concentration at -30 minutes was taken as C0, and the relative proportion C / C0 of the remaining phenol at each time point was calculated. The reaction results are shown in FIG. Figure 5 As shown, with the increase of BFMO-N800 dosage, the rate of phenol degradation by potassium persulfate accelerated. When comparing groups e and f, it was found that the reaction rate had basically not changed. Considering the cost issue, 0.5 g / L was selected as the optimal dosage of BFMO-N800.

[0105] Example 3

[0106] The BFMO-N800 prepared in Example 1 was used as a catalyst to activate persulfate to degrade phenol, and the phenol degradation rate was compared by changing the dosage of persulfate to determine the optimal dosage of persulfate. The specific steps are as follows:

[0107] The experiment was carried out in a 100 mL conical flask. The experimental operation steps were the same as those in Example 2, and the specific groups were as follows:

[0108] a. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask, add 0.025 g of BFMO-N800 prepared in Example 1, oscillate the solution at 150 rpm for 30 min, add 0.2 mM potassium persulfate (0.0031 g) and continue oscillating for 30 min;

[0109] b. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask, add 0.025 g of BFMO-N800 prepared in Example 1, oscillate the solution at 150 rpm for 30 min, add 0.4 mM potassium persulfate (0.0062 g) and continue oscillating for 30 min;

[0110] c. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask, add 0.025 g of BFMO-N800 prepared in Example 1, oscillate the solution at 150 rpm for 30 min, add 0.6 mM potassium persulfate (0.0092 g) and continue oscillating for 30 min;

[0111] d. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask, add 0.025 g of BFMO-N800 prepared in Example 1, shake the solution at 150 rpm for 30 min, add 0.8 mM potassium persulfate (0.0123 g) and continue shaking for 30 min;

[0112] e. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask, add 0.025 g of BFMO-N800 prepared in Example 1, shake the solution at 150 rpm for 30 min, add 1.0 mM potassium persulfate (0.0154 g) and continue shaking for 30 min;

[0113] Each persulfate dosage experiment was set up with three parallel groups;

[0114] Then, samples were taken at -30, 0, 5, 10, 15, 20, and 30 minutes after potassium persulfate was added. The samples were filtered through a 0.22 µm microporous filter membrane (organic system) and the filtrate was taken to determine the concentration C of the remaining phenol in the filtrate. The phenol concentration at -30 minutes was taken as C0, and the relative proportion C / C0 of the remaining phenol at each time point was calculated. The reaction results are shown in FIG. Figure 6 As shown, with the increase of the dosage of potassium persulfate, the rate of phenol degradation by potassium persulfate catalyzed by BFMO-N800 material is accelerated. When comparing groups d and e, it is found that the reaction rate has basically not changed. Considering the cost issue, 0.8mM is taken as the optimal dosage of persulfate.

[0115] Example 4

[0116] The BFMO-N800 prepared in Example 1 was used as a catalyst to activate persulfate to degrade phenol, and the initial pH of the reaction was changed to compare the phenol degradation rate in order to determine the effect of the initial pH on the degradation of phenol by the material. The specific steps are as follows:

[0117] The reaction was carried out in a 100 mL conical flask. The dosage of BFMO-N800 material was set to 0.5 g / L, the dosage of potassium persulfate was set to 0.8 mM, and the initial pH of the reaction was adjusted to 3, 5, 7, 9 and 11, respectively. The specific groups are as follows:

[0118] a. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask, add HCl solution to adjust the pH to 3, add 0.025 g of BFMO-N800 prepared in Example 1, shake the solution at 150 rpm for 30 min, add 0.8 mM potassium persulfate and continue shaking for 10 min;

[0119] b. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask, add HCl solution to adjust the pH to 5, add 0.025 g of BFMO-N800 prepared in Example 1, oscillate the solution at 150 rpm for 30 min, add 0.8 mM potassium persulfate and continue oscillating for 10 min;

[0120] c. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask, add NaOH solution to adjust the pH to 7, add 0.025 g of BFMO-N800 prepared in Example 1, shake the solution at 150 rpm for 30 min, add 0.8 mM potassium persulfate and continue shaking for 10 min;

[0121] d. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask, add NaOH solution to adjust the pH to 9, add 0.025 g of BFMO-N800 prepared in Example 1, oscillate the solution at 150 rpm for 30 min, add 0.8 mM potassium persulfate and continue oscillating for 10 min;

[0122] e. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask, add NaOH solution to adjust the pH to 11, add 0.025 g of BFMO-N800 prepared in Example 1, shake the solution at 150 rpm for 30 min, add 0.8 mM potassium persulfate and continue shaking for 10 min;

[0123] Each persulfate dosage experiment was set up with three parallel groups;

[0124] Then, samples were taken at -30, 0, 1, 2, 4, 6, 8, and 10 minutes after potassium persulfate was added. The samples were filtered through a 0.22µm microporous filter membrane (organic system) and the filtrate was taken to determine the concentration C of the remaining phenol in the filtrate. The phenol concentration at -30 minutes was taken as C0, and the relative proportion C / C0 of the remaining phenol at each time point was calculated. The reaction results are shown in Figure 7 As shown in the figure, with the increase of pH, the rate of phenol degradation by potassium persulfate catalyzed by BFMO-N800 material decreased slightly, but phenol could still be completely degraded within a reaction time of 10 minutes, indicating that BFMO-N800 can adapt to most pH ranges and function stably.

[0125] Example 5

[0126] The BFMO-N800 prepared in Example 1 was used as a catalyst to activate persulfate to degrade phenol, and different anions and cations were added to simulate the components in actual wastewater to test the anti-interference ability of BFMO-N800 for the reaction environment. The specific steps are as follows:

[0127] The experiment was carried out in a 100mL conical flask. The dosage of BFMO-N800 material was set to 0.5g / L, the dosage of potassium persulfate was set to 0.8mM, and different types of anions and cations were added so that the concentration of each anion and cation was 5 times the concentration of potassium persulfate (4.0mM). The specific groups are as follows:

[0128] a. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask and add KCl solution to adjust K + The concentration was raised to 4.0 mM, 0.025 g of BFMO-N800 prepared in Example 1 was added, the solution was shaken at 150 rpm for 30 min, 0.8 mM potassium persulfate was added and the shaking was continued for 30 min;

[0129] b. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask and add NaCl solution to adjust the Na + The concentration was raised to 4.0 mM, 0.025 g of BFMO-N800 prepared in Example 1 was added, the solution was shaken at 150 rpm for 30 min, 0.8 mM potassium persulfate was added and the shaking was continued for 30 min;

[0130] c. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask and add CaCl2 solution to adjust the Ca 2+ The concentration was raised to 4.0 mM, 0.025 g of BFMO-N800 prepared in Example 1 was added, the solution was shaken at 150 rpm for 30 min, 0.8 mM potassium persulfate was added and the shaking was continued for 30 min;

[0131] d. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask and add MgCl2 solution to adjust the Mg 2+ The concentration was raised to 4.0 mM, 0.025 g of BFMO-N800 prepared in Example 1 was added, the solution was shaken at 150 rpm for 30 min, 0.8 mM potassium persulfate was added and the shaking was continued for 30 min;

[0132] e. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask and add NaF solution to adjust the F - The concentration was raised to 4.0 mM, 0.025 g of BFMO-N800 prepared in Example 1 was added, the solution was shaken at 150 rpm for 30 min, 0.8 mM potassium persulfate was added and the shaking was continued for 30 min;

[0133] f. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask and add NaCl solution to adjust the Cl - The concentration was raised to 4.0 mM, 0.025 g of BFMO-N800 prepared in Example 1 was added, the solution was shaken at 150 rpm for 30 min, 0.8 mM potassium persulfate was added and the shaking was continued for 30 min;

[0134] g. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask and add NaNO3 solution to adjust NO3 -The concentration was raised to 4.0 mM, 0.025 g of BFMO-N800 prepared in Example 1 was added, the solution was shaken at 150 rpm for 30 min, 0.8 mM potassium persulfate was added and the shaking was continued for 30 min;

[0135] h. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask and add K2HPO4 solution to adjust PO3 3- The concentration was raised to 4.0 mM, 0.025 g of BFMO-N800 prepared in Example 1 was added, the solution was shaken at 150 rpm for 30 min, 0.8 mM potassium persulfate was added and the shaking was continued for 30 min;

[0136] i. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask and add Na2CO3 solution to adjust CO3 2- The concentration was raised to 4.0 mM, 0.025 g of BFMO-N800 prepared in Example 1 was added, the solution was shaken at 150 rpm for 30 min, 0.8 mM potassium persulfate was added and the shaking was continued for 30 min;

[0137] j. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask and add NaHCO3 solution to adjust HCO3 - The concentration was raised to 4.0 mM, 0.025 g of BFMO-N800 prepared in Example 1 was added, the solution was shaken at 150 rpm for 30 min, 0.8 mM potassium persulfate was added and the shaking was continued for 30 min;

[0138] k. Add 50 mL of 0.1 mM phenol simulated wastewater to a 100 mL conical flask, add 0.025 g of BFMO-N800 prepared in Example 1, oscillate the solution at 150 rpm for 30 min, add 0.8 mM potassium persulfate and continue oscillating for 30 min;

[0139] Each anion-cation coexistence experiment was set up in three parallel groups;

[0140] Then, samples were taken after the reaction was completed. After the samples were filtered through a 0.22µm microporous filter membrane (organic system), the filtrate was taken and the residual phenol concentration C in the filtrate was determined. The phenol concentration at -30min was taken as C0, and the phenol removal rate was calculated. The reaction results are shown in Figure 8 and Fig. 9 As shown, different types of anions and cations have little effect on the reaction rate, indicating that BFMO-N800 has strong environmental resistance and can function stably in actual water bodies.

[0141] Example 6

[0142] The BFMO-N800 prepared in Example 1 was used as a catalyst to activate persulfate to degrade phenol, and the BFMO-N800 material after the reaction was collected for repeated experiments to test the stability of the BFMO-N800 material. The specific steps are as follows:

[0143] In a 100 mL conical flask, 50 mL of 0.1 mM phenol simulated wastewater was added, 0.025 g of BFMO-N800 prepared in Example 1 was added, the solution was oscillated at 150 rpm for 30 min, 0.8 mM potassium persulfate was added and continued to oscillate for 30 min; the solution after the reaction was filtered, washed three times with deionized water, and then dried in an oven at 50 ° C for 24 h, and the experiment of potassium persulfate degradation of phenol was repeated. The cycle experiment was repeated five times, and three groups were set in parallel.

[0144] The reaction results are as follows Fig.10 As shown in the figure, with the increase of the number of cycles, the reaction rate of BFMO-N800 decreases slightly, but it can still react completely within 30 minutes, which fully proves that the material has a certain stability and can be recycled for repeated use.

[0145] Test Example 1

[0146] The biogenic iron-manganese oxide catalyst BFMO-N800 in Example 1 and the chemical iron-manganese oxide CFMO in Comparative Example 1 were used to perform a degradation experiment of phenol in simulated wastewater, and the specific operation was as follows:

[0147] In a 100 mL conical flask, 50 mL of 0.1 mM phenol simulated wastewater was added, and 0.025 g of BFMO-N800 prepared in Example 1 or CFMO in Comparative Example 1 was added, the solution was shaken at 150 rpm for 30 min, and 0.8 mM potassium persulfate (0.0123 g) was added and continued to shake for 30 min;

[0148] Three parallel groups were set up for each material dosage experiment;

[0149] Then, samples were taken at -30, 0, 1, 2, 4, 6, 8, and 10 minutes after potassium persulfate was added. The samples were filtered through a 0.22µm microporous filter membrane (organic system) and the filtrate was taken to determine the concentration C of the remaining phenol in the filtrate. The phenol concentration at -30 minutes was taken as C0, and the relative proportion C / C0 of the remaining phenol at each time point was calculated. The reaction results are shown in Fig.11 As shown in the figure: within a reaction time of 10 minutes, BFMO-N800 achieved 100% degradation of phenol, but CFMO only achieved 39.6% degradation, indicating that the catalytic performance of BFMO-N800 is better than that of CFMO.

[0150] Test Example 2

[0151] The degradation experiment of phenol in the wastewater to be treated was carried out using the biogenic iron-manganese oxide catalyst in Example 1 and the chemical iron-manganese oxide CFMO in Comparative Example 1. The specific operation adopted the method in Test Example 1, except that the phenol simulated wastewater to be treated was replaced with printing and dyeing wastewater, pesticide wastewater and coking wastewater. The phenol content in these three types of wastewater was 0.1mM-0.15mM. The specific operation was as follows:

[0152] 50 mL of phenol-containing wastewater (printing and dyeing wastewater, pesticide wastewater and coking wastewater) was added to a 100 mL conical flask, and 0.025 g of BFMO-N800 prepared in Example 1 or CFMO prepared in Comparative Example 1 was added respectively, the solution was shaken at 150 rpm for 30 min, 0.8 mM potassium persulfate (0.0123 g) was added and continued to shake for 30 min;

[0153] Three parallel groups were set up for each material dosage experiment;

[0154] Then, samples were taken at -30, 0, 5, 10, 15, 20, and 30 minutes after potassium persulfate was added. The samples were filtered through a 0.22 µm microporous filter membrane (organic system) and the filtrate was taken to determine the concentration C of the remaining phenol in the filtrate. The phenol concentration at -30 minutes was taken as C0, and the relative proportion C / C0 of the remaining phenol at each time point was calculated. The reaction results are shown in FIG. Fig.12 As shown in the figure: within 30 minutes of reaction time, BFMO-N800 achieved 100% degradation of phenol in three actual wastewaters, but the degradation rates of CFMO for phenol in printing and dyeing wastewater, pesticide wastewater and coking wastewater were only 16%, 24% and 34%, respectively. This shows that BFMO-N800 has stronger environmental resistance than CFMO, can play a stable role in actual water bodies, and has certain industrial application prospects.

[0155] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A biogenic iron-manganese oxide catalyst, characterized in that: The biogenic iron-manganese oxide catalyst has a core-shell structure, which includes an inner core containing iron-manganese oxide and a biochar outer shell covering part or all of the surface of the inner core, wherein the weight ratio of the inner core to the biochar outer shell is 5-9:1; The preparation method of the biogenic iron-manganese oxide catalyst comprises: calcining the iron-manganese oxidizing bacteria and its metabolites under nitrogen conditions to form a material with a core-shell structure; The preparation process of the iron-manganese oxidizing bacteria and its metabolites comprises the following steps: (1) Iron and manganese oxidizing bacteria are obtained by enriching, culturing, separating and purifying the mine wastewater. Sphingobium sp .QBS-P4; (2) the iron and manganese oxidizing bacteria Sphingobium sp .QBS-P4 is subjected to seed culture to obtain seed liquid, the seed liquid is inoculated into fermentation medium for fermentation culture to obtain fermentation liquid, the fermentation liquid is subjected to solid-liquid separation to obtain bacterial precipitate, the bacterial precipitate is dried I, the bacterial precipitate after drying I is taken out, transferred to a mortar and ground for 20-30 minutes, and passed through a 50-100 mesh sieve.

2. The biogenic iron-manganese oxide catalyst according to claim 1, characterized in that: The iron-manganese oxide in the core contains zero-valent iron, FeMnO2 and manganese oxide; The biochar shell is an organic biochar shell.

3. A method for preparing a biogenic iron-manganese oxide catalyst, characterized in that: The method comprises: calcining the cells of iron-manganese oxidizing bacteria and their metabolites under nitrogen conditions to form a material with a core-shell structure, wherein the core-shell structure comprises an inner core containing iron-manganese oxides and a biochar outer shell covering a part or all of the surface of the inner core; The preparation process of the iron-manganese oxidizing bacteria and its metabolites comprises the following steps: (1) Iron and manganese oxidizing bacteria are obtained by enriching, culturing, separating and purifying the mine wastewater. Sphingobium sp .QBS-P4; (2) the iron and manganese oxidizing bacteria Sphingobium sp .QBS-P4 is subjected to seed culture to obtain seed liquid, the seed liquid is inoculated into fermentation medium for fermentation culture to obtain fermentation liquid, the fermentation liquid is subjected to solid-liquid separation to obtain bacterial precipitate, the bacterial precipitate is dried I, the bacterial precipitate after drying I is taken out, transferred to a mortar and ground for 20-30 minutes, and passed through a 50-100 mesh sieve.

4. The preparation method according to claim 3, characterized in that: The inoculation process in step (2) includes: inoculating the seed liquid into the fermentation medium at an inoculation rate of 5-15% (v / v).

5. The preparation method according to claim 3, characterized in that: The fermentation medium in step (2) contains: peptone 0.2-0.8 g / L, glucose 0.1-0.5 g / L, yeast extract powder 0.1-0.3 g / L, MnSO4·H2O 0.1-0.3 g / L, K2HPO4 0.05-0.2 g / L, MgSO4·7H2O 0.1-0.3 g / L, NaNO3 0.1-0.3 g / L, CaCl2 0.05-0.2 g / L, (NH4)2CO3 0.05-0.2 g / L, and ammonium ferric citrate 0.5-1.2 g / L.

6. The preparation method according to claim 5, characterized in that: The fermentation culture conditions at least include: a temperature of 28-30° C., a rotation speed of 100-150 rpm, and a time of 8-12 days.

7. The preparation method according to claim 3, characterized in that: The conditions for solid-liquid separation in step (2) include at least: a centrifugal speed of 8000-10000 rpm and a time of 5-8 min; The drying conditions of the drying I at least include: a temperature of -55 to -40°C and a time of 40 to 48 hours.

8. The preparation method according to any one of claims 3 to 7, characterized in that: The calcination conditions at least include: a heating rate of 3-8°C / min, a temperature of 750-850°C, and a time of 0.5-2h.

9. The preparation method according to any one of claims 3 to 7, characterized in that: The method further comprises: rinsing and drying the solid obtained by calcination II.

10. The preparation method according to claim 9, characterized in that: The cleaning agent for rinsing is acid solution; The drying conditions of II at least include: a temperature of 45-55° C. and a time of 20-30 hours.

11. The preparation method according to claim 10, characterized in that: The cleaning agent for rinsing is a HCl solution with a concentration of 0.05-0.15 mol / L.

12. Use of the biogenic iron-manganese oxide catalyst according to claim 1 or 2 or the biogenic iron-manganese oxide catalyst prepared according to the preparation method according to any one of claims 3 to 11 in catalyzing the degradation of phenol by persulfate.

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