Modified biochar loaded nano zero-valent iron material, and preparation method and application thereof

Abstract

The application provides a modified biochar loaded nano zero-valent iron material and a preparation method and application thereof. The material effectively disperses nano zero-valent iron particles on the basis of the stable structure and loose porous characteristics of the wooden biochar, improves the pollutant removal capacity of the nano zero-valent iron, and simultaneously, the adsorption performance of the biochar on organic pollutants is favorable for improving the degradation efficiency.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of water remediation, in particular to a modified biochar loaded nano zero-valent iron material and a preparation method and application thereof. BACKGROUND

[0002] Chlorinated hydrocarbons (CHCs) are widely used as important organic solvents and chemical raw materials in various fields such as industry, agriculture and life. However, due to improper operation during production, use, storage and treatment, chlorinated hydrocarbons may leak into soil and groundwater, becoming a common environmental pollution source in many contaminated sites. Especially 1,2-DCA, as a typical "three-teratogenic" compound, its high solubility, difficulty in adsorption and stability make it easy to accumulate in the groundwater environment, posing a potential threat to human health and the ecological environment.

[0003] Nano zero-valent iron has a large specific surface area and surface energy, and exhibits strong reaction desorption effect on many water pollutants, and is widely used in the remediation of contaminated water. However, the preparation process of nano zero-valent iron is complicated, the cost is high, and it is easy to be deactivated by oxidation, agglomeration and other phenomena, which may have biological toxicity to the human body after use, thereby limiting its practical application.

[0004] Biochar has attracted the attention of experts and scholars in recent years as a new means of agricultural waste resource utilization. Its raw materials are easy to obtain, and it has high surface porosity and adsorption functional groups, making it have a wide application prospect in soil remediation and pollutant adsorption. However, most pure biochar has unsatisfactory adsorption effect on various pollutants, and the preparation process of high-efficiency activated carbon is complex and expensive, which poses a challenge to the popularization and application of biochar.

[0005] To improve the application effect of biochar, an effective way is to modify the biomass raw material or biochar, or load other exogenous substances to form a hybrid composite material. By studying the modification of biomass raw materials, the modification method of biochar at different stages, and the types and loading methods of loaded substances, the adsorption and removal effect of biochar on specific substances in specific environments can be effectively improved, the application field of biochar can be expanded, and new ideas and methods can be provided for solving related problems. The preparation method of biochar dispersed nano zero-valent iron provides a new possibility for the removal of various pollutants in water, and overcomes the problem of easy agglomeration and difficult separation of traditional nano zero-valent iron. SUMMARY

[0006] In view of this, the present application aims to provide a modified biochar loaded nano zero-valent iron material and its preparation method and application. The material effectively disperses nano zero-valent iron particles relying on the stable structure and porous characteristics of wood biochar, thereby improving the pollutant removal capacity of nano zero-valent iron. At the same time, the adsorption performance of biochar on organic pollutants is beneficial to improve the degradation efficiency.

[0007] To achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0008] A preparation method of a modified biochar loaded nano zero-valent iron material, comprising the following steps:

[0009] (1) The biomass is crushed, washed, dried, and then placed in a succinic acid solution. After soaking for a period of time, the biomass is washed and dried, and then pyrolyzed under a nitrogen atmosphere. After cooling to room temperature, a modified biochar is obtained.

[0010] (2) FeCl3·6H2O is dissolved in a mixture of ethanol and deionized water. Nitrogen is blown in and stirred uniformly to obtain solution 1.

[0011] (3) Under the protection of nitrogen, the modified biochar is added to solution 1, and continuous stirring is performed to obtain solution 2.

[0012] (4) KBH4 solution is added dropwise to solution 2. After the addition of KBH4 solution is completed, succinic acid solution is added. Continuous stirring is performed under the condition of nitrogen being blown in. The composite is separated by suction filtration.

[0013] (5) The composite is washed with anhydrous ethanol and anaerobic water, and vacuum freeze-dried to obtain a modified biochar loaded nano zero-valent iron material.

[0014] Further, the biomass in step (1) is corn cob.

[0015] Further, the molar concentration of the succinic acid solution in step (1) is 1-3 mol / L. The solid-liquid ratio of the succinic acid solution to the corn cob is 1:8 (g / ml). The soaking time is 2-4 h, and the soaking temperature is 45-70℃.

[0016] Further, the pyrolysis in step (1) is carried out in a tube furnace. Specifically, the soaked biomass is placed in the tube furnace and pyrolyzed at a heating rate of 5℃ / min to 500-700℃.

[0017] Further, the molar concentration of FeCl3·6H2O in step (2) is 0.011 mol / L-0.054 mol / L. The volume of the solution is 80-100 ml, and the volume ratio of ethanol to deionized water is 1:1. The nitrogen blowing time is 30-50 min.

[0018] Further, the mass ratio of FeCl3·6H2O to modified biochar in step (3) is 1:1-5, and the stirring time is 20-45 min.

[0019] Further, the molar concentration of the KBH4 solution in step (4) is 0.033mol / L-0.162mol / L; the addition amount of the KBH4 solution is 80-100 mL; the dropping speed of the KBH4 solution is 5ml / min, the molar concentration of the succinic acid solution is 0.1-0.3mol / L, the addition amount of the succinic acid solution is 30-50ml, and the nitrogen gas is continuously stirred for 20-45 min.

[0020] Further, the vacuum freezing temperature in step (5) is minus 50-70℃, and the drying time is 8-16h.

[0021] The application further provides a modified biochar loaded nano zero-valent iron material prepared by the preparation method.

[0022] The application further provides an application of the modified biochar loaded nano zero-valent iron material in 1,2-DCA (1,2-dichloroethane) contaminated water.

[0023] Compared with the prior art, the modified biochar loaded nano zero-valent iron material, the preparation method and the application thereof have the following advantages:

[0024] (1) The raw material of the biochar is corn cob, which is a waste produced in the rural planting and production process, is low in price and widely available, and solves the problem of easy agglomeration of pure nano zero-valent iron by loading the nano zero-valent iron on the biochar.

[0025] (2) The biochar modified by succinic acid increases the oxygen-containing functional groups on the biochar, expands the specific surface area of the biochar, and increases the adsorption capacity; on the other hand, after the nano zero-valent iron is modified by acid, when the pH value of the solution becomes acidic, the organic acid promotes the dissolution of Fe(II) ions in the iron-carbon material, and increases the utilization rate of the nano zero-valent iron.

[0026] (3) The preparation method of the modified biochar loaded nano zero-valent iron material is low in cost, simple in operation, easy to control, pollution-free, and has good comprehensive benefits. DETAILED DESCRIPTION

[0027] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the present application, and the illustrative embodiments of the present application and their descriptions are used to explain the present application, and do not constitute improper limitations on the present application. In the drawings:

[0028] Figure 1A nitrogen adsorption-desorption curve comparison chart of the biochar, the succinic acid modified biochar and the modified biochar loaded nano zero-valent iron material prepared in Example 1;

[0029] Figure 2 A scanning electron microscope comparison chart of the succinic acid modified biochar and the modified biochar loaded nano zero-valent iron material prepared in Example 1;

[0030] Figure 3 An infrared comparison chart of the biochar, the succinic acid modified biochar and the modified biochar loaded nano zero-valent iron material prepared in Example 1;

[0031] Figure 4 An XRD comparison chart of the succinic acid modified biochar, the modified biochar loaded nano zero-valent iron material and nano zero-valent iron prepared in Example 1;

[0032] Figure 5 A chart of adsorption effects of different acid modified biochars prepared in Example 1 and Comparative Examples 1-2 on 1,2-DCA;

[0033] Figure 6 A chart of degradation effects of different iron-carbon ratios and whether adding succinic acid of the modified biochar loaded nano zero-valent iron materials prepared in Examples 1-4 and Comparative Examples 3-6 on 1,2-DCA;

[0034] Figure 7 A chart of degradation effects of different dosages of the modified biochar loaded nano zero-valent iron material prepared in Example 1 on 1,2-DCA. DETAILED DESCRIPTION

[0035] It should be noted that the examples in the present application and the features in the examples can be combined with each other without conflict.

[0036] The technical solutions in the examples of the present application will be described clearly and completely below with reference to the drawings in the examples of the present application. Obviously, the described examples are only part of the examples of the present application, not all the examples. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0037] Example 1

[0038] A preparation method of a modified biochar loaded nano zero-valent iron material, the preparation method of the method is as follows:

[0039] (1) Corn cob biomass was crushed, washed and dried, then put into 1 mol / L succinic acid solution, the solid-liquid ratio of the solution and biomass was 1:8 (g / ml), the soaking time was 2 h, the soaking temperature was 65℃, the modified biomass after soaking was washed and dried, then put into a tube furnace, pyrolysis was carried out at a heating rate of 5℃ / min to 500℃, and then cooled to room temperature to obtain modified biochar.

[0040] (2) FeCl3·6H2O was dissolved in 100 ml of a mixture of ethanol and deionized water with a volume ratio of 1:1 to obtain solution 1, so that the molar concentration of FeCl3·6H2O reached 0.018 mol / L, and nitrogen was blown for 30 min and stirred uniformly.

[0041] (3) Under the protection of nitrogen, 0.3 g of modified biochar was added to solution 1, and stirring was continued for 30 min to obtain solution 2.

[0042] (4) 100 ml of KBH4 solution with a concentration of 0.054 mol / L was added to solution 2 at a speed of 5 ml / min, 50 ml of succinic acid solution with a concentration of 0.2 mol / L was added after the addition of KBH4 solution was completed, and stirring was continued for 40 min under the condition of nitrogen blowing, and the composite was separated by suction filtration.

[0043] (5) The composite was washed with anhydrous ethanol and anaerobic water, vacuum freeze-dried at -60℃ for 12 h to obtain the succinic acid biochar supported modified nano zero-valent iron material with a mass ratio of iron to carbon of 1:3.

[0044] From Figure 1 it can be seen that the specific surface area of the composite material has greatly improved after loading modified nano zero-valent iron, which may be due to the fact that nano zero-valent iron itself has a large specific surface area, so the overall specific surface area is increased; from Figure 2 the modified biochar supported nano zero-valent iron material can be seen that there are some chain-like distributed particles with uniform particle size on the surface of the biochar, which is inferred to be nano zero-valent iron, indicating that the biochar supported nano zero-valent iron composite material can be successfully prepared by liquid phase reduction method; from Figure 3 it can be seen that the surface of the material contains rich functional groups, and the absorption peak at 690 cm -1 is the Fe-O bond, indicating that the biochar supported nano zero-valent iron material is successfully prepared; from Figure 4 it can be seen that the 2θ diffraction peak at 44.68° is the characteristic peak of iron (Fe 0 ), indicating that the biochar successfully supports nano zero-valent iron.

[0045] Example 2

[0046] A method for preparing a modified biochar supported nano zero-valent iron material, the preparation method of which is as follows:

[0047] (1) The corn cob biomass is crushed, washed and dried, and then put into a 1 mol / L succinic acid solution. The solid-liquid ratio of the solution to the biomass is 1:8 (g / ml), the impregnation time is 2 h, and the impregnation temperature is 65°C. The impregnated modified biomass is washed and dried, and then put into a tube furnace for pyrolysis at a heating rate of 5°C / min to 500°C. After cooling to room temperature, the modified biochar is obtained.

[0048] (2) Dissolve FeCl3·6H2O in a mixture of 100 ml of ethanol and deionized water with a volume ratio of 1:1 to obtain solution 1, so that the molar concentration of FeCl3·6H2O reaches 0.054 mol / L. Blow in nitrogen for 30 min and stir uniformly.

[0049] (3) Under the protection of nitrogen, 0.3 g of modified biochar is added to solution 1, and stirring is continued for 30 min to obtain solution 2.

[0050] (4) Add 100 ml of KBH4 solution with a concentration of 0.162 mol / L to solution 2 at a rate of 5 ml / min. After the KBH4 solution is added, add 50 ml of succinic acid solution with a concentration of 0.2 mol / L. Continue stirring for 40 min under the condition of nitrogen flow, and then separate the composite by suction filtration.

[0051] (5) Wash the composite with anhydrous ethanol and anaerobic water, and vacuum freeze-dry at -60°C for 12 h to obtain the succinic acid biochar-supported modified nano zero-valent iron material with an iron-to-carbon mass ratio of 1:1.

[0052] Example 3

[0053] A method for preparing a modified biochar-supported nano zero-valent iron material, the preparation method of which is as follows:

[0054] (1) The corn cob biomass is crushed, washed and dried, and then put into a 1 mol / L succinic acid solution. The solid-liquid ratio of the solution to the biomass is 1:8 (g / ml), the impregnation time is 2 h, and the impregnation temperature is 65°C. The impregnated modified biomass is washed and dried, and then put into a tube furnace for pyrolysis at a heating rate of 5°C / min to 500°C. After cooling to room temperature, the modified biochar is obtained.

[0055] (2) Dissolve FeCl3·6H2O in a mixture of 100 ml of ethanol and deionized water with a volume ratio of 1:1 to obtain solution 1, so that the molar concentration of FeCl3·6H2O reaches 0.026 mol / L. Blow in nitrogen for 30 min and stir uniformly.

[0056] (3) Under the protection of nitrogen, 0.3 g of modified biochar was added to solution 1, and stirring was continued for 30 min to obtain solution 2.

[0057] (4) 100 ml of KBH4 solution with a concentration of 0.078 mol / L was added to solution 2 at a speed of 5 ml / min, and after the addition of the KBH4 solution was completed, 50 ml of succinic acid solution with a concentration of 0.2 mol / L was added, and stirring was continued for 40 min under the condition of nitrogen being introduced, and the composite was separated by suction filtration.

[0058] (5) The composite was washed with anhydrous ethanol and anaerobic water for multiple times, vacuum freeze-dried at -60℃ for 12 h to obtain the succinic acid biochar loaded modified nano zero-valent iron material with an iron-to-carbon mass ratio of 1:2.

[0059] Example 4

[0060] A preparation method of a modified biochar loaded nano zero-valent iron material, and the preparation method is as follows:

[0061] (1) The corn cob biomass was crushed, washed and dried, and then put into a 1 mol / L succinic acid solution, the solid-liquid ratio of the solution and the biomass was 1:8 (g / ml), the immersion time was 2 h, and the immersion temperature was 65℃. The modified biomass after immersion was washed and dried, and then put into a tube furnace, and heated to 500℃ at a heating rate of 5℃ / min, and then cooled to room temperature to obtain modified biochar.

[0062] (2) FeCl3·6H2O was dissolved in 100 ml of a mixture of ethanol and deionized water with a volume ratio of 1:1 to obtain solution 1, so that the molar concentration of FeCl3·6H2O reached 0.011 mol / L, and nitrogen was blown for 30 min and stirred uniformly.

[0063] (3) Under the protection of nitrogen, 0.3 g of modified biochar was added to solution 1, and stirring was continued for 30 min to obtain solution 2.

[0064] (4) 100 ml of KBH4 solution with a concentration of 0.033 mol / L was added to solution 2 at a speed of 5 ml / min, and after the addition of the KBH4 solution was completed, 50 ml of succinic acid solution with a concentration of 0.2 mol / L was added, and stirring was continued for 40 min under the condition of nitrogen being introduced, and the composite was separated by suction filtration.

[0065] (5) The composite was washed with anhydrous ethanol and anaerobic water for multiple times, vacuum freeze-dried at -60℃ for 12 h to obtain the succinic acid biochar loaded modified nano zero-valent iron material with an iron-to-carbon mass ratio of 1:5.

[0066] Comparative Example 1

[0067] The difference from the above-mentioned embodiment 1 is that succinic acid is replaced by boric acid.

[0068] Comparative example 2

[0069] The difference from the above-mentioned embodiment 1 is that succinic acid is replaced by citric acid.

[0070] Comparative example 3

[0071] The difference from the above-mentioned embodiment 1 is that succinic acid is not added in step (4).

[0072] Comparative example 4

[0073] The difference from the above-mentioned embodiment 2 is that succinic acid is not added in step (4).

[0074] Comparative example 5

[0075] The difference from the above-mentioned embodiment 3 is that succinic acid is not added in step (4).

[0076] Comparative example 6

[0077] The difference from the above-mentioned embodiment 4 is that succinic acid is not added in step (4).

[0078] Experimental comparison

[0079] 1. Comparison of removal effects of 1,2-DCA by different acid-modified biochar materials

[0080] A 100ml 1,2-DCA solution with a concentration of 20mg / L was prepared in a 250ml salt water bottle, 0.02g of modified biochar loaded with nano zero-valent iron material prepared in embodiment 1 and comparative examples 1-2 was added to the pollutant solution respectively, and the salt water bottle was placed in a shaking bed with a speed of 180rpm, a temperature of 25℃ and a reaction time of 36h.

[0081] According to the test results of Figure 5 It can be seen that the removal rate of 1,2-DCA by the original corn cob without acid modification is only 6.96%, and after acid modification, it has been improved to different degrees, among which the modification of corn cob by succinic acid has the greatest effect, and the removal rate of 1,2-DCA reaches 47.7%, which shows that the organic acid succinic acid is the best acid for modifying biochar.

[0082] 2. Degradation of 1,2-DCA by modified biochar loaded with nano zero-valent iron material with different iron-carbon ratios and whether adding succinic acid

[0083] In a 250ml salt water bottle, 100ml 1,2-DCA solution with a concentration of 20mg / L was prepared, and 0.02g of modified biochar loaded nano zero-valent iron material with different iron-carbon ratios prepared by examples 1-4 and comparative examples 3-6 was added into the pollutant solution respectively, and the salt water bottle was placed in a shaking bed with a speed of 180rpm and a temperature of 25℃ for 36h.

[0084] According to the test results of Figure 6 It can be seen from the test results that the removal rate of the modified biochar loaded nano zero-valent iron material without succinic acid modification for 1,2-DCA is lower than that of the modified biochar loaded nano zero-valent iron material with succinic acid. With the decrease of the iron-carbon ratio, the removal rate of the modified biochar loaded nano zero-valent iron material gradually increases, and when the iron-carbon ratio is 1:3, the removal rate reaches the highest, which is 50.27%. When the iron-carbon ratio decreases to 1:5, the removal rate begins to decrease to 39.96%, which indicates that the iron-carbon ratio of 1:3 is the best ratio of the modified biochar loaded nano zero-valent iron material.

[0085] 3, Comparison of removal effects of modified biochar loaded nano zero-valent iron material with different adding amounts on 1,2-DCA

[0086] In a 250ml salt water bottle, 100ml 1,2-DCA solution with a concentration of 20mg / L was prepared, and 0.02g, 0.06g and 0.12g of modified biochar loaded nano zero-valent iron material prepared by example 1 was added into the pollutant solution respectively, and the salt water bottle was placed in a shaking bed with a speed of 180rpm and a temperature of 25℃ for 36h.

[0087] According to the test results of Figure 7 It can be seen from the test results that with the increase of the adding amount, the removal rate of the succinic acid biochar loaded modified nano zero-valent iron increases from 47.51% to 86.09%. It indicates that the removal performance of the composite material is good, and with the increase of the adding amount of the composite material, the removal rate continuously increases, which indicates that increasing the adding proportion of the material can effectively remove 1,2-DCA in water.

[0088] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing modified biochar-supported nano-zero-valent iron materials, characterized in that: The method includes the following steps: (1) The biomass was crushed, washed and dried and then placed in succinic acid solution for soaking. After soaking, the biomass was washed and dried and then pyrolyzed under nitrogen atmosphere and cooled to room temperature to obtain modified biochar. (2) Dissolve FeCl3·6H2O in a mixture of ethanol and deionized water, blow in nitrogen gas and stir until homogeneous to obtain solution 1; (3) Under nitrogen protection, the modified biochar was added to solution 1 and stirred continuously to obtain solution 2; (4) Add KBH4 solution dropwise to solution 2. After the KBH4 solution is added, add succinic acid solution. Stir continuously under nitrogen gas and filter to separate the complex. (5) The composite was washed with anhydrous ethanol and oxygen-free water and then freeze-dried under vacuum to obtain modified biochar-supported nano-zero-valent iron material.

2. The method for preparing modified biochar-supported nano-zero-valent iron materials according to claim 1, characterized in that: The biomass in step (1) is corn cob.

3. The method for preparing modified biochar-supported nano-zero-valent iron materials according to claim 1, characterized in that: The molar concentration of the succinic acid solution in step (1) is 1-3 mol / L, the solid-liquid ratio of the succinic acid solution to the corn cob is 1:8, the soaking time is 2-4 h, and the soaking temperature is 45-70℃.

4. The method for preparing modified biochar-supported nano-zero-valent iron materials according to claim 1, characterized in that: In step (1), the pyrolysis is carried out in a tubular furnace. Specifically, the impregnated biomass is placed in a tubular furnace and pyrolyzed at a heating rate of 5℃ / min to 500-700℃.

5. The method for preparing modified biochar-supported nano-zero-valent iron materials according to claim 1, characterized in that: In step (2), the molar concentration of FeCl3·6H2O is 0.011mol / L-0.054mol / L; the solution volume is 80-100ml, in which the volume ratio of ethanol to deionized water is 1:1; and the time for blowing in nitrogen is 30-50min.

6. The method for preparing modified biochar-supported nano-zero-valent iron materials according to claim 1, characterized in that: In step (3), the mass ratio of FeCl3·6H2O to modified biochar is 1:1-5, and the stirring time is 20-45 min.

7. The method for preparing modified biochar-supported nano-zero-valent iron materials according to claim 1, characterized in that: In step (4), the molar concentration of KBH4 solution is 0.033mol / L-0.162mol / L; the amount of KBH4 solution added is 80-100mL; the dropping rate of KBH4 solution is 5ml / min; the molar concentration of succinic acid solution is 0.1-0.3mol / L; the amount of succinic acid solution added is 30-50ml; and the nitrogen gas is introduced and stirred continuously for 20-45min.

8. The method for preparing modified biochar-supported nano-zero-valent iron materials according to claim 1, characterized in that: In step (5), the vacuum freezing temperature is -50 to -70°C, and the drying time is 8 to 16 hours.

9. A modified biochar-supported nano-zero-valent iron material prepared by the preparation method according to any one of claims 1-8.

10. The application of the modified biochar-supported nano-zero-valent iron material as described in claim 9 in 1,2-DCA polluted water bodies.

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