Preparation and application of iron-magnesium co-doped biochar material for degrading benzopyrene

Abstract

The invention relates to preparation and application of an iron-magnesium co-doped biochar material for degrading benzopyrene pollution. Wherein the iron-magnesium co-doped biochar material is prepared by the following steps: carrying out water bath co-precipitation mixing on pennisetum sinese straw powder and turbid liquid of ferric chloride hexahydrate and magnesium chloride hexahydrate according to a solid-to-liquid ratio of (19-20) g: 100mL for 2 hours at 60 DEG C, drying, and pyrolyzing at 700 DEG C for 2 hours to obtain the iron-magnesium co-doped biochar material. The molar ratio of ferric chloride hexahydrate to magnesium chloride hexahydrate is 2: 1. The iron-magnesium co-doped biochar can efficiently adsorb and degrade benzopyrene in a water body within a short time, and the optimal removal rate of benzopyrene within 90 minutes can reach 90%; the removal rate of benzopyrene under the condition that the pH value is 3-9 can also be kept at 90% or above, and meanwhile, the material has high stability in adsorption and degradation of benzopyrene under the influence of different interfering ions. The iron and magnesium co-doped biochar is obtained through water bath co-precipitation and one-time pyrolysis of raw materials, operation is easy, and the removal effect on benzopyrene is remarkable.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental pollution treatment, and specifically relates to the preparation and application of an iron-magnesium co-doped biochar material for degrading benzopyrene. Background Art

[0002] Benzopyrene (BaP) is a highly carcinogenic polycyclic aromatic hydrocarbon, classified as a Class 1 carcinogen by the International Agency for Research on Cancer. It can induce lung cancer, skin cancer and other cancers by forming DNA adducts, and has health risks such as genotoxicity, reproductive harm and immunosuppression. Currently, benzopyrene pollution is widely present in the atmosphere, soil and water bodies, mainly from fossil fuel combustion, industrial emissions and motor vehicle exhaust. Benzopyrene can easily accumulate in organisms through the food chain, further exacerbating health risks. Therefore, it is crucial to repair benzopyrene pollution.

[0003] At present, the removal technologies for organic pollutants include adsorption, biodegradation, ozone oxidation, membrane separation and advanced oxidation. Although biodegradation can achieve efficient degradation, there is a risk of new pollution. The oxidation utilization rate of ozone oxidation is not high and the power consumption is high. The membrane separation method is prone to deformation and blockage of membrane pores and is costly. The adsorption method has a simple process and high cost-effectiveness, and is one of the most promising technologies in the field of environmental pollution control. Advanced oxidation methods are mainly divided into Fenton method, photocatalytic oxidation method and persulfate oxidation method.

[0004] Biochar prepared from agricultural waste such as straw has the advantages of developed pore structure, stable fatty chain structure, and wide sources, and has been widely used as an economical adsorbent. Compared with unmodified biochar, iron-based and magnesium-based modified biochar have better adsorption and degradation capabilities for benzopyrene. The Chinese invention patent document "A method for degrading benzopyrene and its application" (application number: CN202411466009.1) uses Bacillus to degrade benzopyrene. Although the degradation effect of this method is as high as 83.92%, it takes 9 days and takes a long time. The Chinese invention patent document "A method for degrading food-borne benzopyrene using Bacillus cereus and its application" (application number: CN202410853606.3) discloses a method for degrading food-borne benzopyrene using Bacillus cereus. Although this method has good effects, it is not adaptable, and the long processing time does not reflect its anti-interference ability. Summary of the invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide an iron-magnesium co-doped carbon material for degrading benzopyrene and its application. The method enriches the active sites of biochar and realizes that the iron-based and magnesium-based functional groups are simultaneously loaded on the biochar material. At the same time, after repeated experimental studies, the present invention has a strong anti-interference ability for various pH values ​​and various ions, can maintain a high efficiency of organic adsorption and oxidation, and has a high efficiency of adsorption and degradation of benzopyrene.

[0006] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: dissolve the giant fungus grass powder in ultrapure water, and shake at 200 rpm for 30 minutes to make the material dispersed evenly. Add FeCl 3 6H 2 O and MgCl 2 6H 2 O was prepared by coprecipitation in a water bath at 60°C and ultrapure water was used to wash away the sodium chloride generated in the system. The modified giant grass powder was dried to constant weight. 2 The iron-magnesium modified biochar was prepared by calcining at 700 °C in atmosphere for two hours.

[0007] The present invention also provides the application of the iron-magnesium co-doped biochar material in benzopyrene-contaminated water. Further, the modified biochar is added to benzopyrene-contaminated wastewater at 0.1-1 g / L for oscillation reaction, degradation treatment is performed, and the solution before and after the reaction is taken to measure the concentration of benzopyrene. At the same time, the application of the material in benzopyrene-contaminated wastewater at different pH values ​​is to apply the material to benzopyrene wastewater with a pH value of 3-11, preferably 3-9. The material is applied to different anions (Cl - 、SO 4 2- , HCO 3 - 、NO 3 - ) interferes with the degradation of benzopyrene.

[0008] Compared with the prior art, the present invention has the following beneficial effects:

[0009] Compared with the existing technology, the present invention has the following advantages: the present invention mixes giant grass straw powder with ferric chloride hexahydrate and magnesium chloride hexahydrate by coprecipitation method, and obtains iron-magnesium co-doped modified biochar after one calcination. The operation is simple and the cost is low, which is conducive to large-scale use and practical application. The iron-magnesium co-doped biochar prepared by the present invention can efficiently remove benzopyrene in water, and has a relatively stable degradation effect under different pH values ​​and different interfering ions. Experiments have shown that the adsorption and degradation effect of the material on benzopyrene within 100 minutes is as high as 90%, which is much higher than that of single iron doping, single magnesium doping and original biochar; and when the dosage is 1g / L, the iron-magnesium biochar has the best degradation effect; when the pH is 3-9, it shows good degradation ability for benzopyrene. At the same time, the anions in the water have little effect on the removal of benzopyrene by iron-magnesium biochar, and the iron-magnesium biochar has good stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a comparison of different biochars and iron-magnesium co-doped biochars in Example 1;

[0011] Figure 2 The removal effect of the material on benzopyrene at different dosages in Example 2;

[0012] Figure 3 The effect of different initial pH values ​​on the removal of benzopyrene in Example 3;

[0013] Figure 4 The effect of different ion interferences on the removal of benzopyrene by the material in Example 4; DETAILED DESCRIPTION

[0014] The content of the present invention is further described below in conjunction with specific examples, but it is not to be construed as limiting the present invention. Unless otherwise specified, the technical means used in the examples are conventional means known to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0015] Example 1

[0016] Preparation of Fe-Mg co-doped biochar: 5 g of giant fungus grass powder was dissolved in 100 mL of ultrapure water and shaken at 200 rpm for 30 min to make the material dispersed evenly. 0.4 M (10.812 g) FeCl 3 6H 2 O and 0.2 M MgCl 2 6H 2O (4.066 g), and the pH of the system was adjusted to 10 with 5 M NaOH, then incubated in a water bath at 60 °C for 2 h, the mixed solution was centrifuged and rinsed with ultrapure water. The modified giant grass powder was dried in an oven at 100 °C to constant weight. Then, it was heated to 40 °C in N 2 The pyrolysis was carried out at a constant temperature of 700°C for two hours at a heating rate of 5°C / min under atmosphere, and finally iron-magnesium modified biochar was obtained.

[0017] Single iron-doped biochar: only FeCl was added 3 6H 2 O and giant grass biochar powder were co-precipitated in a water bath. 2 The pyrolysis was carried out at 700°C for 2 hours at a heating rate of 5°C / min.

[0018] Single magnesium doped biochar: only MgCl was added 2 6H 2 O and giant grass biochar powder were co-precipitated in a water bath. 2 The pyrolysis was carried out at 700°C for 2 hours at a heating rate of 5°C / min.

[0019] Raw biochar: Giant fungus grass powder was washed and dried, and then heated in N 2 The raw biochar was obtained by pyrolysis at 700 °C for two hours at a heating rate of 5 °C / min under atmosphere.

[0020] Application of iron-magnesium co-doped biochar:

[0021] Take 10 mg of pure BaP and dilute it to 100 mL with acetone to obtain 100 mg / L BaP stock solution, and dilute the stock solution 10 times to obtain BaP working solution. Take 25 mL of BaP working solution, 0.025 g (1 g / L) of original biochar, single iron-doped biochar, single magnesium-doped biochar and iron-magnesium-doped biochar in a 100 mL brown conical flask and place it in a constant temperature water bath oscillator (25°C, 200 rpm) for shaking. The results show that after 90 minutes of reaction, the BaP removal efficiency of iron-magnesium co-doped biochar is as high as 90%, while the BaP removal rate of the other three materials failed to reach 90% within the reaction time (300 minutes). Figure 1 Comparison of different biochars and iron-magnesium co-doped biochars. Figure 1 It can be seen that iron-magnesium co-doped biochar exhibits the best adsorption and degradation effect.

[0022] Example 2

[0023] Preparation of iron-magnesium co-doped biochar: refer to Example 1.

[0024] Application of different dosages to BaP adsorption and degradation: Different from Example 1, it is necessary to weigh 0.0025, 0.0075, 0.0125, 0.0250 g (± 0.0005) of iron-magnesium co-doped biochar in a 100 mL brown stoppered conical flask, so that the amount of iron-magnesium co-doped biochar added to the system is 0.1, 0.3, 0.5, 1 g / L. Place it in a 25°C constant temperature oscillator and oscillate at 200 rpm. Take 1 mL of the reaction solution at 10, 30, 60, 90, 120, and 300 minutes and mix it with an equal volume of ethanol, and pass it through the membrane for testing. The results show that when the dosage is increased from 0.1 to 1 g / L, the removal rate increases from 22.52% to 95.29%. Figure 2 The removal effect of the material on benzopyrene at different dosages in Example 2 is shown in FIG. Figure 2 It can be seen that 1g / L is the optimal carbon dosage for iron-magnesium co-doped biochar.

[0025] Example 3

[0026] Different from Example 1, five portions of BaP-contaminated wastewater were prepared during the application process, and 0.1M NaOH or HCl was used to adjust the initial pH of the working solution to 3, 5, 7, 9, and 11. 0.0250 g of iron-magnesium co-doped biochar was weighed, 25 mL of 5 mg / L BaP working solution with different initial pH values ​​was added, and samples were taken for testing at 10, 30, 60, 90, 120, and 300 min.

[0027] The results showed that BaP removal was significantly inhibited when the pH was 11. The material can maintain good adsorption and degradation performance at pH 3-9.

[0028] Figure 3 Effect of different initial pH values ​​on the removal of benzopyrene. Figure 3 It can be seen that within 120 minutes, the degradation effect of this material on BaP at a pH of 3-9 is as high as more than 90%, and after 150 minutes, the removal rate reaches 100%.

[0029] Example 4

[0030] Different from Example 1, 4 portions of wastewater were prepared during the application process, and 0.25 mL or 2.5 mL of NaCl, Na2SO4, NaHCO3, and NaNO3 ion stock solutions with a concentration of 10 mM were added to the use solution. The dosage of iron and magnesium co-doped biochar in each portion of wastewater was stabilized at 1 g / L, and the BaP concentration was stabilized at 5 mg / L. At 10, 30, 60, 90, 120, and 300 min, 1 mL of the reaction solution was taken and mixed with an equal volume of ethanol, and passed through a 0.22 um nylon 66 filter membrane and placed in a liquid phase vial for testing.

[0031] Figure 4The effect of different ions on the removal of benzopyrene by the material. Figure 4 It can be seen that, except for Cl-, other common anions in water all promote the removal, proving that when a small amount of anions exist in water, it has little effect on the removal of BaP by Fe-Mg co-doped biochar, and even promotes its removal. The results show that the material can be applied to environmental water bodies containing different ions.

[0032] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations and simplifications that do not deviate from the spirit and principle of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing an iron-magnesium co-doped biochar material for degrading benzopyrene pollution, characterized in that: The following steps are involved: 1) Co-precipitate the giant grass straw with ferric chloride hexahydrate and magnesium chloride hexahydrate in a water bath at 60°C for 2 hours, stirring thoroughly during the precipitation; 2) centrifuging the mixture and washing the surface with ultrapure water, and drying the solid in the mixture at 100°C; 3) In a nitrogen atmosphere, the biochar was pyrolyzed at 700°C for 2 h to obtain iron-magnesium co-doped biochar.

2. The preparation method according to claim 1, characterized in that Step 1) wherein the solid-to-liquid ratio is 17-22 g:100 mL, preferably 19-20 g:100 mL.

3. The preparation method according to claim 1, characterized in that Step 1) wherein the molar ratio of ferric chloride hexahydrate to magnesium chloride hexahydrate in the mixed solution is 1.8-2.2:1, preferably 2:

1.

4. The preparation method according to claim 1, characterized in that In step 2), the centrifugal speed is 3000-4000 rpm, and the drying temperature is 90-100°C, preferably 95-100°C.

5. The preparation method according to claim 1, characterized in that Step 3) wherein the pyrolysis rate is 5-10°C / min, preferably 5°C / min.

6. The preparation method according to claim 1, characterized in that Step 3) The calcination temperature under the N2 protective atmosphere is 600-800°C.

7. The iron-magnesium co-doped biochar material prepared by the method according to any one of claims 1 to 6.

8. Use of the iron-magnesium co-doped biochar material according to claim 7 in treating wastewater containing benzopyrene.

9. The use of the iron-magnesium co-doped biochar material in treating benzopyrene wastewater according to claim 8, characterized in that: The iron-magnesium co-doped biochar material is added to the benzopyrene-contaminated water body at 0.5-2 g / L, preferably 1 g / L.

10. The use of the iron-magnesium co-doped biochar material in treating benzopyrene wastewater according to claim 8, characterized in that: The initial pH value of the benzopyrene-contaminated water body is adjusted to 2-10, preferably 3-9; the wastewater also contains interfering ions, such as Cl - 、SO4 2- 、HCO3 - 、NO3 - , concentration is 8-12mmol / L.

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