Preparation method of biochar-loaded bimetallic MnFeO2 heterogeneous Fenton-like catalyst

Abstract

The invention discloses a preparation method and application of a biochar-loaded bimetal MnFeO2 heterogeneous Fenton-like catalyst, the biochar-loaded bimetal MnFeO2 heterogeneous Fenton-like catalyst comprises a substrate biochar particle and a MnFeO2 catalyst loaded on the substrate, MnFeO2 in the biochar-particle-loaded MnFeO2 catalyst is a catalyst, the catalyst can effectively inhibit metal leaching toxicity through a bimetal synergistic effect, and the biochar-loaded bimetal MnFeO2 heterogeneous Fenton-like catalyst can effectively inhibit metal leaching toxicity. The electron transfer capacity of the catalyst is improved through combination of bimetal and biochar, so that the metal valence cycle speed is increased, and the material is good in stability, reusable, low in price and preparation cost, wide in applicable pH range and wide in application prospect in the field of water treatment.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to a method for preparing a biochar-loaded bimetallic MnFeO2 heterogeneous Fenton-like catalyst. Background Art

[0002] Advanced catalytic oxidation (Fenton oxidation and Fenton-like oxidation) reacts at room temperature and pressure, is easy to operate, has strong oxidation ability, and has broad prospects for application in organic wastewater treatment. However, in the current Fenton oxidation technology, Fenton catalysts cannot be used in neutral systems, and their performance deteriorates severely after multiple cycles, and a large amount of iron-containing sludge and wastewater will be produced. Therefore, in the development of efficient heterogeneous catalysts, the preparation of Fenton-like catalyst materials that are cheap, easy to obtain, have large specific surface area and high activity has important application value in the field of water treatment.

[0003] Some transition metals, due to having two or more valence states, can react with oxidants such as H2O2, persulfate, etc., and attack the corresponding chemical bonds of organic pollutants to degrade them. At present, iron, copper, manganese, as well as tungsten, gold, silver, palladium, etc. are often used as heterogeneous Fenton-like catalysts to treat many refractory substances. However, single metal or metal oxide catalysts are easy to agglomerate, and the inherent low mechanical strength of some metals themselves limits their further application.

[0004] my country is a large agricultural country. Every year, a large amount of crop straw is discarded by farmers because it is difficult to store, easy to mold and has low utilization rate. This not only wastes resources, but also causes serious pollution to the environment. Crop straw contains a large amount of carbon-containing organic matter such as rich cellulose, which can be used as a raw material for preparing biochar. Biochar is an ideal catalyst carrier. Combining it with heterogeneous Fenton materials can reduce the agglomeration of catalysts, increase the specific surface area, expose more catalytic active sites, enhance the adsorption capacity of H2O2 and pollutants, and reduce the cost of catalysts. This can not only realize the resource utilization of crop straw, but also use heterogeneous Fenton technology to achieve the degradation of pollutants in the water environment. Summary of the invention

[0005] In view of the above situation, in order to overcome the defects of the prior art, the purpose of the present invention is to provide a preparation method and application of a biochar-supported bimetallic MnFeO2 heterogeneous Fenton-like catalyst to solve the problems raised in the above background technology. The technical solution solved by the present invention is:

[0006] A method for preparing a biochar-supported bimetallic MnFeO2 heterogeneous Fenton-like catalyst comprises the following steps:

[0007] S1, Fe 3+ Salt and Mn 2+The salt was added to 20 ml of deionized water and stirred vigorously in a thermostatic oscillator for 15 min;

[0008] S2, dissolving the biomass powder in 5 ml of deionized water and quickly mixing the two solutions;

[0009] S3, subjecting the solution to deep-freezing treatment to obtain a sample;

[0010] S4, freeze-drying the frozen sample;

[0011] S5, placing the treated powder into a tube furnace and calcining it at 600-700 degrees Celsius under a nitrogen atmosphere for 6 hours to obtain MnFeO2 / biochar catalyst powder;

[0012] S6. After cooling to room temperature, wash with deionized water and anhydrous ethanol alternately;

[0013] S7. The washed sample was placed in a vacuum drying oven for drying. After being completely dried, it was ground with an agate mortar to obtain a MnFeO2 / biochar heterogeneous Fenton-like catalyst.

[0014] Further, in step S1, the Fe 3+ The salt is any one of ferric chloride, ferric sulfate, and ferric nitrate, Mn 2+ The salt is any one of manganese chloride, manganese acetate, manganese nitrate and manganese carbonate.

[0015] Furthermore, in step S1, the molar ratio of the iron salt to the manganese salt is 1:1, and the concentration range of the solution is 5 mmol / L to 20 mmol / L.

[0016] Furthermore, in step S2, the biomass powder is any one of corn straw powder, wheat straw powder and alfalfa powder.

[0017] Further, in step S4, the freezing time is 10 hours and the freezing temperature is -40±5 degrees Celsius.

[0018] Furthermore, in step S5, the heating rate is 5°C / min.

[0019] Furthermore, in step S5, the temperature of the tube furnace is 600-700 degrees Celsius.

[0020] Furthermore, in step S7, the drying time is 6 hours and the drying temperature is 60±5 degrees Celsius.

[0021] An application of a biochar-loaded bimetallic MnFeO2 heterogeneous Fenton-like catalyst, characterized in that the bimetallic MnFeO2 heterogeneous Fenton-like catalyst is used to mineralize emerging pollutants such as antibiotics under pH 4-6 conditions.

[0022] Compared with the traditional technology, the advantages of the present invention are:

[0023] 1. The present invention realizes high-speed activation of hydrogen peroxide by loading bimetallic MnFeO2 heterogeneous Fenton-like catalyst on biochar particles, and can achieve efficient removal of pollutants under a wide pH value.

[0024] 2. The present invention utilizes the Mn element to play a catalytic role, and can utilize the Mn cycle to drive the Fe cycle, thereby reducing the ≡Fe(III) produced by the Fenton-like reaction to ≡Fe(II), thereby realizing the rapid occurrence of the cycle of the heterogeneous Fenton-like reaction, avoiding the formation of iron sludge and subsequent catalyst recovery, and simply realizing the degradation of organic pollutants.

[0025] 3. The present invention provides a method for preparing a bimetallic MnFeO2 heterogeneous Fenton-like catalyst loaded on biochar particles, using biochar as a carrier. The carrier itself has good stability. The MnFeO2 heterogeneous Fenton-like catalyst is directly loaded on the biochar, has a stable structure, and a simple preparation process.

[0026] 4. The present invention eliminates potential risks to the environment by using biochar, which is widely available, cheap and easy to obtain, and the raw materials are non-toxic and harmless. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The XRD patterns of the MnFeO2 heterogeneous Fenton-like catalysts in Examples 2 and 4 of the present invention are shown;

[0028] Figure 2 A comparison of the effects of the MnFeO2 heterogeneous Fenton-like catalyst in Examples 2 and 4 of the present invention on the degradation of the antibiotic tetracycline hydrochloride under pH 4-6 conditions is shown;

[0029] Figure 3 The embodiment of the present invention is shown Figure 3 The PL steady-state photoluminescence spectra of MnFeO2 / biochar and MnFeO2 materials in Examples 3 and 4 are used to evaluate the separation and recombination of photogenerated carriers. As shown in the figure, the fluorescence intensity of MnFeO2 / biochar is weaker than that of MnFeO2, indicating that the recombination rate of photogenerated carriers in MnFeO2 / biochar is low.

[0030] Figure 4 The VSM hysteresis loop diagram of MnFeO2 / biochar and MnFeO2 materials in Examples 3 and 4. As shown in the figure, the magnetism of MnFeO2 / biochar is weaker than that of MnFeO2, indicating that the addition of biochar has little effect on the magnetism of MnFeO2.

[0031] Figure 5The SEM images of MnFeO2 / biochar and MnFeO2 materials in Examples 3 and 4 are as shown in the figure. MnFeO2 is dispersed on the surface of biochar, which prevents the aggregation of MnFeO2 particles to a certain extent and exposes more active sites compared with the two single materials. DETAILED DESCRIPTION

[0032] Here, exemplary embodiments will be described in detail, and unless otherwise indicated, the embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are only examples consistent with some aspects of the present disclosure as detailed in the appended claims.

[0033] The specific implementation of the present invention is as follows:

[0034] Embodiment 1:

[0035] A biochar-supported bimetallic MnFeO2 heterogeneous Fenton-like catalyst is prepared according to the following steps:

[0036] At room temperature (25°C, the same below), 1 to 20 mmol of MnC4H6O4·4H2O and Fe(NO3)3·9H2O were weighed and dissolved in 20 mL of deionized water in turn according to the Mn:Fe atomic ratio of 1:1, and stirred vigorously in a constant temperature oscillator for 15 minutes. Then, the biomass powder (10, 30, 50, 80 mg) was dissolved in 5 mL of deionized water and the two solutions were quickly mixed. After low temperature (-20°C, the same below), the sample was freeze-dried. Next, the sample was transferred to an ark and heat-treated at 700 degrees Celsius for 6 hours in a nitrogen atmosphere. After cooling to room temperature, the sample was washed alternately with deionized water and anhydrous ethanol three times, dried at 60 degrees Celsius, and ground with an agate mortar after complete drying to obtain a MnFeO2 / biochar heterogeneous Fenton catalyst. The MnFeO2 / biochar heterogeneous Fenton catalyst prepared according to the above preparation method can efficiently degrade the antibiotic tetracycline hydrochloride in water.

[0037] See also Figure 1 : The MnFeO2 / biochar catalyst of Example 1 was characterized by XRD. Figure 1 It can be clearly seen that the XRD pattern is consistent with the standard pattern, indicating that the MnFeO2 / biochar heterogeneous Fenton-like catalyst was successfully synthesized;

[0038] See also Figure 2 :The MnFeO2 / BC of Example 1 efficiently removes tetracycline hydrochloride. The comparison chart of the effect of bimetallic Fenton catalyst on the degradation of antibiotic tetracycline hydrochloride under pH 4-6 conditions, from Figure 2It can be clearly seen that the MnFeO2 / biochar bimetallic catalyst can efficiently remove tetracycline hydrochloride under pH 4-6 conditions.

[0039] Embodiment 2:

[0040] At room temperature, 10 mmol of MnC4H6O4·4H2O and Fe(NO3)3·9H2O were weighed and dissolved in 20 ml of deionized water in a Mn:Fe atomic ratio of 1:1, and stirred vigorously in a constant temperature oscillator for 15 min. Then, biomass powder (10, 30, 50, 80 mg) was dissolved in 5 ml of deionized water and the two solutions were quickly mixed. After low temperature treatment, the samples were freeze-dried. Next, the samples were transferred to an ark and heat-treated at 700 degrees Celsius for 6 hours in a nitrogen atmosphere. After cooling to room temperature, the samples were washed alternately with deionized water and anhydrous ethanol three times, dried at 60 degrees Celsius, and ground with an agate mortar after complete drying to obtain a MnFeO2 / biochar heterogeneous Fenton-like catalyst.

[0041] Example 3: (Except that the dosage of biomass powder is kept at 50 mg, the remaining steps are exactly the same as those of Example 2)

[0042] At room temperature, 10 mmol of MnC4H6O4·4H2O and Fe(NO3)3·9H2O were weighed and dissolved in 20 ml of deionized water in a Mn:Fe atomic ratio of 1:1, and stirred vigorously in a constant temperature oscillator for 15 minutes. Then 50 mg of biomass powder was dissolved in 5 ml of deionized water and the two solutions were quickly mixed. After low temperature treatment, the sample was freeze-dried. Next, the sample was transferred to an ark and heat-treated at 700 degrees Celsius for 6 hours in a nitrogen atmosphere. After cooling to room temperature, the sample was washed alternately with deionized water and anhydrous ethanol three times, dried at 60 degrees Celsius, and ground with an agate mortar after complete drying to obtain a MnFeO2 / biochar heterogeneous Fenton-like catalyst.

[0043] Embodiment 4:

[0044] Preparation method of pure MnFeO2: At room temperature, 10 mmol of MnC4H6O4·4H2O and Fe(NO3)3·9H2O were weighed and dissolved in 20 ml of deionized water in turn according to the Mn:Fe atomic ratio of 1:1, and stirred vigorously in a constant temperature oscillator for about 15 minutes. After low temperature treatment, the sample was freeze-dried. Next, the sample was transferred to an ark and heat-treated at 700 degrees Celsius for 6 hours in a nitrogen atmosphere. After cooling to room temperature, the sample was washed alternately with deionized water and anhydrous ethanol three times, dried at 60 degrees Celsius, and ground with an agate mortar after complete drying to obtain a MnFeO2 heterogeneous Fenton-like catalyst.

[0045] The above is only one of the specific implementations of the present invention, but the technical features of the present invention are not limited thereto. Any modification, equivalent replacement or improvement made within the technical concept of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a biochar-supported bimetallic MnFeO2 heterogeneous Fenton-like catalyst, characterized in that: The steps include: S1, Fe 3+ Salt and Mn 2+ The salt was added to 20 ml of deionized water and stirred vigorously in a thermostatic oscillator for 15 min; S2, dissolving the biomass powder in 5 ml of deionized water and quickly mixing the two solutions; S3, subjecting the solution to deep-freezing treatment to obtain a sample; S4, freeze-drying the frozen sample; S5, placing the treated powder into a tube furnace and calcining it at 600-700 degrees Celsius under a nitrogen atmosphere for 6 hours to obtain MnFeO2 / biochar catalyst powder; S6. After cooling to room temperature, wash with deionized water and anhydrous ethanol alternately; S7. The washed sample was placed in a vacuum drying oven for drying. After being completely dried, it was ground with an agate mortar to obtain a MnFeO2 / biochar heterogeneous Fenton-like catalyst.

2. The method according to claim 1, characterized in that: In step S1, the Fe 3+ The salt is any one of ferric chloride, ferric sulfate, and ferric nitrate, Mn 2+ The salt is any one of manganese chloride, manganese acetate, manganese nitrate and manganese carbonate.

3. The method according to claim 1, characterized in that: In step S1, the molar ratio of the iron salt to the manganese salt is 1:1, and the concentration range of the solution is 5 mmol / L to 20 mmol / L.

4. The method according to claim 1, characterized in that: In step S2, the biomass powder is any one of corn straw powder, wheat straw powder and alfalfa powder.

5. The method according to claim 1, characterized in that: In step S4, the freezing time is 10 hours and the freezing temperature is -40±5 degrees Celsius.

6. The method according to claim 1, characterized in that: In step S5, the heating rate is 5°C / min.

7. The method according to claim 1, characterized in that: In step S5, the temperature of the tube furnace is 600-700 degrees Celsius.

8. The method according to claim 1, characterized in that: In step S7, the drying time is 6 hours and the drying temperature is 60±5 degrees Celsius.

9. Use of a biochar-supported bimetallic MnFeO2 heterogeneous Fenton-like catalyst according to any one of claims 1 to 8, characterized in that: The bimetallic MnFeO2 heterogeneous Fenton-like catalyst is used to mineralize emerging pollutants such as antibiotics under pH 4-6 conditions.

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