Nano zero-valent iron modified hemicellulose biochar composite material, preparation method and application thereof
Nano-zero-valent iron modified hemicellulose biochar was prepared by ball milling and microwave pyrolysis, forming a core-shell structure. This solved the problem of unstable performance of biochar zero-valent iron complex in the prior art, achieved efficient removal of chlorinated hydrocarbons, and reduced cost and energy consumption.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI CONSTR ENG ENVIRONMENTAL TECH CO LTD
- Filing Date
- 2026-04-24
- Publication Date
- 2026-07-07
AI Technical Summary
Existing biochar zero-valent iron complexes suffer from significant performance variations, numerous impurities, and high energy consumption during the treatment of chlorinated hydrocarbon pollution, and current technologies have failed to effectively address these issues.
Using xylan and iron oxide as raw materials, nano-zero-valent iron modified hemicellulose biochar was prepared by a combination of ball milling and microwave pyrolysis to form a core-shell topology, achieving molecular-level dispersion of zero-valent iron in the biochar matrix. The particles were stabilized by covalent bonding and physical confinement effect, thereby improving the adsorption and reduction capabilities of the material.
It significantly improved the removal efficiency of chlorinated hydrocarbons to 78.3%, reduced the preparation cost, simplified the preparation process, and avoided the agglomeration and oxidative deactivation of zero-valent iron.
Smart Images
Figure CN122343045A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of chlorinated hydrocarbon pollution remediation technology, and in particular to nano-zero-valent iron modified hemicellulose biochar, its preparation method, and its application. Background Technology
[0002] Soil and groundwater pollution caused by chlorinated hydrocarbons is a common type of contaminated site. As an important organic solvent and product intermediate, chlorinated hydrocarbons are widely used in automotive parts, electronic components, industrial cleaning and printing industries. Due to their higher density than water, lower viscosity and low water solubility, they migrate downwards under the action of gravity, penetrate the soil surface, enter the shallow groundwater system, and spread to the surrounding areas or accumulate to form pollution plumes, causing pollution to the soil and groundwater environment.
[0003] Over the past decade, carbon-supported modified materials have gradually gained attention in the remediation of soil and groundwater pollution. Common carbon materials include biochar, activated carbon, and graphene. Among these, biochar is widely available and, compared to activated carbon and graphene, is much cheaper, reducing preparation costs by 60%-80%. However, in the actual preparation process, biochar from different sources and using different processes exhibits significant performance differences, and the preparation process often involves issues such as high levels of ash and other impurities.
[0004] Currently, modifying biochar with nano-zero-valent iron (ZCE) reduces the aggregation of ZCE due to surface energy and magnetism, creating multiple active sites and effectively enhancing the adsorption and degradation efficiency of pollutants. In existing environmental remediation work, biochar is used as a loading material for ZCE to maintain its stable activity, reduce aggregation, and mitigate oxidation rates, as described in Chinese Patent CN114984911, "A Method for Preparing a High-Adsorption Performance Biochar-Nano-ZCE Composite." However, existing biochar-ZCE composite technologies only address the activity of ZCE and the reducing capacity of chlorinated hydrocarbon pollutants, but do not solve the problem of performance differences in various iron-carbon materials due to impurities and ash content. Furthermore, the preparation process involves two pyrolysis stages, resulting in high energy consumption. Summary of the Invention
[0005] To address the shortcomings of existing technologies, this application provides a hemicellulose biochar-supported zero-valent iron composite material, its preparation method, and its application.
[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: A method for preparing a nano-zero-valent iron modified hemicellulose biochar composite material includes the following steps: Step 1: Mix xylan raw material and iron oxide raw material in a certain proportion, and then place them in a ball mill for ball milling. Step 2: After ball milling, the mixture is pyrolyzed and carbonized in a microwave pyrolysis apparatus under constant temperature conditions with an inert gas as a protective atmosphere. After cooling, nano-zero-valent iron modified hemicellulose biochar material is obtained.
[0007] In one embodiment, the mass ratio of xylan to iron oxide in step 1 is 1:1 to 3:1.
[0008] In one embodiment, the iron oxide is one or more of FeO, Fe3O4, and Fe2O3.
[0009] In one embodiment, the ball mill in step 1 is a stainless steel ball mill, the ball milling time is 4-8 hours, and the ball milling speed is 3000-600 r / min.
[0010] In one embodiment, in step 2, the inert gas is nitrogen, the heating rate of pyrolysis carbonization is 8-10℃ / min, the pyrolysis carbonization temperature is 400-800℃, and the pyrolysis carbonization retention time is 1.5-2h.
[0011] This application also provides a nano-zero-valent iron modified hemicellulose biochar composite material, which is prepared by the above-described preparation method.
[0012] This application also provides an application of the above-mentioned nano-zero-valent iron modified hemicellulose biochar composite material for the purification treatment of polluted wastewater containing chlorinated hydrocarbons, wherein the pH value of the polluted wastewater is 3 to 11.
[0013] In one embodiment, the chlorinated hydrocarbon is one or more of tetrachloroethylene, trichloroethylene, carbon tetrachloride, and chloroform; the concentration of the hemicellulose biochar-supported zero-valent iron composite material added to the polluted wastewater is 0.05–0.25 g / L; the concentration of the chlorinated hydrocarbon in the polluted wastewater is 20–500 ppm; and the purification treatment temperature is 25°C–55°C.
[0014] Compared with the prior art, this application has at least the following beneficial effects: This application uses xylan, a widely available and inexpensive raw material, as the raw material, which significantly reduces the production cost of nano-zero-valent iron modified biochar composite material. It does not require complex instruments and equipment and the preparation method is simple. This application utilizes a combination of mechanical grinding and microwave heating to prepare nano-zero-valent iron modified hemicellulose biochar composites for the efficient removal of chlorinated hydrocarbons from groundwater. During carbothermic reduction, the nano-zero-valent iron modified hemicellulose biochar composites form a unique "core-shell" topology. Quasi-spherical zero-valent iron particles are uniformly anchored on the surface of a three-dimensional porous carbon matrix, exhibiting a narrow particle size distribution. These particles are stabilized through two modes: embedding within the mesoporous walls of a honeycomb network structure, creating a physical confinement effect; and forming Fe-OC covalent bonds with epoxy and lactone groups at the carbon layer edges. This method achieves molecular-level dispersion of zero-valent iron within a hemicellulose biochar matrix, forming stable structural pores that provide efficient channels for mass transfer during the reaction and prevent the agglomeration of zero-valent iron during the reaction process. The oxygen-containing functional groups on the surface of the hemicellulose biochar material can greatly improve the performance of the composite material. The active groups can firmly fix the zero-valent iron particles onto the carbon substrate in the form of stable coordination bonds, preventing their oxidative deactivation. Furthermore, due to the presence of polar functional groups, they can also combine with hydroxyl, amino, and other groups in chlorinated hydrocarbon molecules through intermolecular forces, greatly improving the adsorption and reduction capacity of chlorinated hydrocarbon pollutants and increasing the removal efficiency of chlorinated hydrocarbons in groundwater to 78.3%. Attached Figure Description
[0015] Figure 1 This is a schematic diagram of the process for preparing and applying nano-zero-valent iron modified hemicellulose biochar composite materials; Figure 2 These are XRD patterns of hemicellulose biochar prepared at different temperatures; Figure 3 These are XRD patterns of nano-zero-valent iron modified hemicellulose biochar composites prepared at different mass ratios. Figure 4 This is a SEM image of a composite material prepared by mixing xylan and iron oxide in a mass ratio of 3:1. Figure 5 The graph shows the effect of different dosage ratios of nano-zero-valent iron modified hemicellulose biochar composite material on the removal of trichloroethylene. Figure 6 The graph shows the effect of different reaction temperatures on the removal of trichloroethylene from nano-zero-valent iron modified hemicellulose biochar composite material. Figure 7 The graph shows the effect of different reaction pH values on the removal of trichloroethylene from nano-zero-valent iron modified hemicellulose biochar composite material. Detailed Implementation
[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below through specific embodiments. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.
[0017] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.
[0018] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various information, such information should not be limited to these terms and should not be construed as indicating or implying relative importance. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."
[0019] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical connection or internal connection between two components. They can be direct connection or indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.
[0020] To better understand the technical solution of the present invention, the present invention will be described in detail below with reference to specific embodiments and comparative examples.
[0021] This application provides a method for preparing a hemicellulose biochar-supported zero-valent iron composite material, comprising the following steps: Step 1: Mix xylan raw material and iron oxide raw material in a certain proportion, and ball mill the mixture using a stainless steel ball mill. The mass ratio of xylan raw material to iron oxide raw material is 1:1 to 3:1. The iron oxide is one or more of FeO, Fe3O4, and Fe2O3. The ball milling time is 4-8 hours and the ball milling speed is 300-600 r / min. Step 2: Place the mixture in a microwave pyrolysis apparatus and use nitrogen as a protective atmosphere to pyrolyze and carbonize the mixture to obtain a hemicellulose biochar-supported zero-valent iron composite material. The heating rate of the pyrolysis carbonization is 8-10℃ / min, the pyrolysis carbonization temperature is 400-800℃, and the pyrolysis carbonization retention time is 1.5-2h. Example 1
[0022] Example 1: Hemicellulose biochar material was prepared according to the above steps. Step 1 specifically included: placing 5g of xylan raw material (90% purity) in a high-energy ball mill for mechanical activation treatment. The process parameters were set to a milling speed of 500 rpm and a continuous milling cycle of 6 hours, obtaining a homogeneous mixture through mechanochemical modification. Step 2 specifically included: placing the mixture obtained in Step 1 in a microwave pyrolysis apparatus, introducing nitrogen gas into the microwave pyrolysis apparatus until it was filled with nitrogen to create an anaerobic pyrolysis environment, setting the instrument's heating rate to 10℃ / min, and performing pyrolysis treatments at 400℃, 500℃, 600℃, 700℃, and 800℃ respectively, holding at the target pyrolysis temperature for 2 hours; after the microwave pyrolysis apparatus naturally cooled to room temperature, the black pyrolysis product in the crucible was removed, thus obtaining hemicellulose biochar materials prepared at different temperatures.
[0023] XRD characterization was performed on hemicellulose biochar samples prepared at different temperatures, and the results are as follows: Figure 2 As shown, the broad peak between 15° and 30° is related to amorphous carbon, which is characteristic of biochar. For materials prepared at temperatures below 600°C, the crystallinity is low due to insufficient pyrolysis temperature, and this characteristic peak does not appear. However, as the pyrolysis power increases, the intensity of the material's diffraction peaks gradually increases. Pyrolysis power can effectively improve the material's crystallinity, and a pyrolysis carbonization temperature of 800°C is preferred. Example 2
[0024] Example 2: Nano-zero-valent iron modified hemicellulose biochar composites were prepared according to the above preparation method. Step 1 specifically included: selecting xylan and Fe2O3 as basic raw materials, and constructing a composite system with xylan and Fe2O3 in gradient mass ratios (3:1, 2:1, 1:1, 1:2, 1:3). The mixed raw materials were placed in a high-energy ball mill for mechanical activation treatment. The process parameters were set to a rotation speed of 500 rpm and a ball milling cycle of 6 hours, obtaining a homogeneous mixture through mechanochemical modification. Step 2 specifically included: the mixture obtained in Step 1 was subjected to a carbothermal reduction process in a microwave pyrolysis device under a nitrogen protective atmosphere and a constant temperature of 800℃, ultimately obtaining nano-zero-valent iron modified hemicellulose biochar composites with different mass ratios.
[0025] XRD characterization was performed on nano-zero-valent iron modified hemicellulose biochar composite samples prepared with different mass ratios, and the results are as follows: Figure 3 As shown, when the mass ratio of xylan to iron raw material is 3:1, the material exhibits the most ideal crystal structure characteristics. The sharp diffraction peak observed at 44.7° proves the presence of zero-valent iron, indicating that zero-valent iron is successfully loaded on hemicellulose biochar. Therefore, the preferred mass ratio of hemicellulose biochar to iron raw material is 3:1.
[0026] Figure 4 This image shows a SEM image of a nano-zero-valent iron-modified hemicellulose biochar composite sample with a xylan to Fe2O3 mass ratio of 3:1. SEM characterization revealed that the hemicellulose-based composite system formed a unique "core-shell" topology during carbothermic reduction. Quasi-spherical particles are uniformly anchored on the surface of the three-dimensional porous carbon matrix. The nanoparticles exhibit a narrow particle size distribution and are stabilized through two modes: embedding within the mesoporous walls of a honeycomb network structure, creating a physical confinement effect; and forming Fe-OC covalent bonds with epoxy and lactone groups at the carbon layer edges. This material achieves molecular-level dispersion of the Fe2O3 precursor within a biomass matrix, providing an efficient channel for reaction mass transfer. Example 3
[0027] This embodiment provides an application of a nano-zero-valent iron-modified hemicellulose biochar composite material, as shown in the attached figure. Figure 1 As shown, the method for degrading trichloroethylene in groundwater specifically includes the following steps: The nano-zero-valent iron modified hemicellulose biochar composite material prepared in Example 2 by xylan and Fe2O3 in a mass ratio of 3:1 was used to conduct a trichloroethylene degradation experiment in groundwater. The experimental conditions were controlled at room temperature (25±0.5 ℃) and neutral (pH = 7.0±0.2). 100 mL of a 60 mg / L trichloroethylene solution was prepared in a conical flask containing groundwater and placed in a 500 mL conical flask. 0.05 g, 0.1 g, 0.15 g, 0.2 g, and 0.25 g of the nano-zero-valent iron modified hemicellulose biochar composite material were added to the flask respectively, and the flask was placed in a constant temperature shaker for a shaking reaction.
[0028] Figure 5 The removal efficiency of trichloroethylene by nano-zero-valent iron-modified hemicellulose biochar composite material under different dosage conditions was investigated. As the dosage increased, the efficiency of the composite material decreased. Figure 5It can be seen that after 1 hour of reaction, the removal rate increased from the initial 48.4% to the final 78.18%. As the dosage of the material gradually increased from 0.05 g to 0.25 g, its adsorption effect on TCE significantly improved, which is attributed to the fact that more adsorbent provides more effective sites. In particular, when the dosage was in the range of 0.15–0.25 g, the removal rate of TCE by the material remained basically stable within 1 hour, indicating that adsorption had reached saturation at this point. Example 4
[0029] This embodiment provides an application of a nano-zero-valent iron-modified hemicellulose biochar composite material for the degradation of trichloroethylene in groundwater, specifically including the following steps: The nano-zero-valent iron modified hemicellulose biochar composite material prepared in Example 2 by xylan and Fe2O3 in a mass ratio of 3:1 was used to conduct a trichloroethylene degradation experiment in groundwater. The experimental conditions were neutral (pH = 7.0±0.2). The groundwater trichloroethylene was prepared by placing 200 mL of a 60 mg / L trichloroethylene solution in a 500 mL Erlenmeyer flask. The amount of nano-zero-valent iron modified hemicellulose biochar composite material added was 0.3 g. The mixture was placed in a shaker and oscillated at a speed of 200 r / min. The temperature of the shaker was adjusted to a constant temperature of 25℃~55℃.
[0030] Figure 6 The removal efficiency of trichloroethylene by nano-zero-valent iron-modified hemicellulose biochar composite material under different temperature conditions was investigated. Increasing temperature improved the initial adsorption rate, accelerated molecular diffusion, promoted the activation of active sites, and enhanced interfacial reactivity, resulting in a slight increase in the overall removal rate from 75.67% to 80.10%. The removal rate at 35℃ was 77.28%, close to that at 45℃ and 55℃. Considering both energy consumption and efficiency, 35℃ was selected as the optimal temperature condition. Example 5
[0031] This embodiment describes the application of a hemicellulose biochar-supported zero-valent iron composite material for the degradation of trichloroethylene in groundwater, specifically including the following steps: The nano-zero-valent iron modified hemicellulose biochar composite material prepared in Example 2 by a mass ratio of xylan to Fe2O3 of 3:1 was used to conduct a trichloroethylene degradation experiment in groundwater. The experimental conditions were controlled at room temperature (35±0.5 ℃). The groundwater trichloroethylene degradation experiment was conducted by placing 200 mL of a 60 mg / L trichloroethylene solution in a 500 mL Erlenmeyer flask. The amount of the nano-zero-valent iron modified hemicellulose biochar composite material added was 0.3 g, and the mixture was placed in a constant temperature shaker for the reaction. The initial pH range of the reaction was adjusted to 3–11.
[0032] Figure 7The removal efficiency of trichloroethylene by nano-zero-valent iron-modified hemicellulose biochar composite material under different pH conditions was investigated. The removal rate of trichloroethylene by the material was highest at pH = 5 (79.32%). This may be due to the higher redox potential of hydroxyl radicals (·OH) under acidic conditions, which allows zero-valent iron to react and generate Fe2+, thus improving the reactivity of the system. Furthermore, the formation of the pseudo-iron oxide film on the surface is slowed down under acidic conditions, thereby reducing the loss of active sites. Therefore, pH 5 is the preferred pH.
[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.
Claims
1. A method for preparing a nano-zero-valent iron modified hemicellulose biochar composite material, characterized in that, Includes the following steps: Step 1: Mix xylan raw material and iron oxide raw material in a certain proportion, and then place them in a ball mill for ball milling. Step 2: The ball-milled mixture is pyrolyzed and carbonized in a microwave pyrolysis apparatus under constant temperature conditions with an inert gas as a protective atmosphere. After cooling, nano-zero-valent iron modified hemicellulose biochar composite material is obtained.
2. The preparation method according to claim 1, characterized in that, In step 1, the mass ratio of xylan raw material to iron oxide is 1:1 to 3:
1.
3. The preparation method according to claim 1, characterized in that, The iron oxide is one or more of FeO, Fe3O4, and Fe2O3.
4. The preparation method according to claim 1, characterized in that, The ball mill mentioned in step 1 is a stainless steel ball mill, with a milling time of 4-8 hours and a milling speed of 3000-600 r / min.
5. The preparation method according to claim 1, characterized in that, In step 2, the inert gas is nitrogen, the heating rate of pyrolysis carbonization is 8-10℃ / min, the pyrolysis carbonization temperature is 400-800℃, and the pyrolysis carbonization retention time is 1.5-2h.
6. A nano-zero-valent iron-modified hemicellulose biochar, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 5.
7. An application of the nano-zero-valent iron modified hemicellulose biochar as described in claim 6, characterized in that, Used for the purification treatment of polluted wastewater containing chlorinated hydrocarbons, wherein the pH value of the polluted wastewater is 3 to 11.
8. As described in claim 7, characterized in that, The chlorinated hydrocarbon is one or more of tetrachloroethylene, trichloroethylene, carbon tetrachloride, and chloroform. The concentration of the nano-zero-valent iron modified hemicellulose biochar added to the polluted wastewater is 0.05-0.25 g / L, the concentration of chlorinated hydrocarbon in the polluted wastewater is 20-500 ppm, and the purification treatment temperature is 25℃-55℃.