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    • 专利摘要:
    The present disclosure is related to the field of biochar materials, and in particular to a graphene-ferric oxide modified biochar and a method for making the same as well as the use thereof. The modified biochar comprises graphene, ferric oxide, and biochar, with a 5 mass ratio of graphene:ferric oxidezbiochar being in a range of (O.5-1.5):(O.25-1.5):100. The modified biochar, after being applied to arsenic-contaminated soil, enables activity and bio-availability of the arsenic to be reduced and thus the effects thereof on plants and accumulation thereof in plants to be reduced.
    公开号:NL2027898A
    申请号:NL2027898
    申请日:2021-04-01
    公开日:2021-07-13
    发明作者:Wang Fangli；Zong Haiying
    申请人:Univ Qingdao Agricultural；
    IPC主号:
    专利说明:

    GRAPHENE-FERRIC OXIDE MODIFIED BIOCHAR AND METHOD
    FOR MAKING SAME AS WELL AS USE THEREOF Technical Field The present disclosure is related to the field of biochar materials, and in particular to a graphene-ferric oxide modified biochar and a method for making the same as well as the use thereof. Background Numerous biochemical studies have shown that trivalent and pentavalent arsenic compounds are highly toxic substances and can cause damage to respiratory, digestive, and nervous systems, human skin, etc. In severe cases, they may induce multiple organs to become cancerous. Moreover, the elemental arsenic (As) may cause hindrance to water transport in plants, adversely affecting mineral nutrition and water absorption capabilities thereof. Further, the elemental As may also cause some damage to chlorophyll and thus inhibition of plant growth and development. Therefore, it is a problem urgently to be solved to decrease the toxicity of As on plants.
    Currently, the toxicity of As on plants is decreased mainly by remediation of arsenic- contaminated soil. Known soil remediation methods mainly include solidification/stabilization and phytoremediation techniques. However, in practice, the solidification/stabilization technique is rarely used for treating arsenic-contaminated soil, because it may cause some damage to soil ecosystem. And the plants adapted to the phytoremediation technique cannot be widely used in northern China. So, this technique is also not in widespread use now.
    Biochar is considered to be promising for the remediation of arsenic-contaminated soil due to its high porosity, huge specific surface area, and high adsorption capability. However, the existing prior art biochar has a low capability of adsorbing arsenic in the soil and thus a low capability of remediating the arsenic-contaminated soil.
    Summary In view of the above problems, an objective of the present disclosure is to provide a graphene-ferric oxide modified biochar and a method for making the same as well as the use thereof, the modified biochar, after being applied to arsenic-contaminated soil,
    enabling activity and bio-availability of the arsenic to be reduced and thus the effects thereof on plants and accumulation thereof in plants to be reduced. One objective of the disclosure is realized by a graphene-ferric oxide modified biochar, comprising graphene, ferric oxide, and biochar, with a mass ratio of graphene: ferric oxide:biochar being in a range of (0.5-1.5):(0.25-1.5):100. The graphene preferably has a diameter of 0.2 to 50 um and a thickness of 0.7 to 4 nm. Moreover, the graphene preferably has a carbon content equal to or more than 97.9 wt %. The ferric oxide preferably has a specific surface area of 20 to 60 cm /g. Moreover, the ferric oxide is preferably nanometer ferric oxide having an average particle size of 28 to 32 nm. The biochar component preferably has a density of 0.3 to 1.4 g/m’, a pH value of 7.3 to
    9.6, and a carbon content of 64.2 to 88.1 wt %. Another objective of the disclosure is realized by a method for making the graphene- ferric oxide modified biochar as described above, comprising steps of: mixing a biomass material with graphene and ferric oxide to form a mixture, with a mass ratio of biomass material: graphene: ferric oxide being in a range of 100:(0.25-1.1):(0.15-
    1.1); and subjecting the mixture to a carbonization process so as to obtain a graphene-ferric oxide modified biochar. The carbonization process preferably comprises a preheating process and then a high- temperature carbonization process. Preferably, the preheating process is carried out at a temperature of 100 to 135 °C for
    1.5 to 2 hours. Preferably, the high-temperature carbonization process is carried out at a temperature of 450 to 550 °C for 3.5 to 5.5 hours. The biomass material preferably has a particle size of 80 to 100 mesh. Yet another objective of the disclosure is realized by the use of the modified biochar as described above or of a modified biochar made according to the method as described above for improvement of arsenic-contaminated soil. The use is preferably performed by applying the modified biochar to the soil to be treated, with an amount of 1 to 5 wt % with respect to a total amount of the modified biochar and the soil.
    As described above, the present disclosure provides a graphene-ferric oxide moditied biochar, which comprises graphene, ferric oxide, and biochar, with a mass ratio of graphene:ferric oxide:biochar being in a range of (0.5-1.5):(0.25-1.5):100. It has been found that, the modified biochar of the disclosure, after being applied to arsenic- contaminated soil, enables activity and bio-availability of the arsenic to be reduced, thereby facilitating growth of plants and reducing accumulation of the arsenic in the plants. As described above, the present disclosure further provides a method for making the modified biochar as described above, comprising mixing a biomass material with graphene and ferric oxide to form a mixture, with a mass ratio of biomass material graphene ferric oxide being in a range of 100:(0.25-1.1):(0.15-1.1); and subjecting the mixture to a carbonization process so as to obtain a graphene-ferric oxide modified biochar. The method 1s easy to implement and is suitable for mass production. Detailed Description A first aspect of the disclosure provides a graphene-ferric oxide modified biochar, which comprises graphene, ferric oxide, and biochar with a mass ratio of graphene:ferric oxide:biochar being in a range of (0.5-1.5):(0.25-1.5):100. In this description, unless otherwise specifically indicated, all raw materials used are conventional, commercially available ones.
    The modified biochar according to the first aspect of the present disclosure comprises graphene. The graphene preferably has a diameter of 0.2 to 50 un, more preferably 0.5 to 30 um, and further preferably 14 to 20 um. Moreover, the graphene preferably has a thickness of 0.7 to 4 nm, more preferably 0.8 to 3.6 nm, and further preferably 2 to 3 nm. Further, the graphene preferably has a carbon content equal to or greater than 97.9 wt %, more preferably of 98 to 99.9 wt %. In this description, the graphene used was purchased from SHANDONG JINCHENG GRAPHENE TECHNOLOGY Co. Ltd. The modified biochar according to the first aspect of the present disclosure further comprises ferric oxide. The ferric oxide is preferably nanometer ferric oxide, which preferably has an average particle size of 28 to 32 nm, more preferably 29 to 30 nm.
    Moreover, the ferric oxide preferably has a specific surface area of 20 to 60 cm /g, more preferably 30 to 58 cm /g, and further preferably 37 to 44 cm /g. In this description, the ferric oxide was purchased from BEIJING GAOKE NEW MATERIAL TECHNOLOGY Co. Ltd. It has been found that, when the particle size and specific surface area of the nanometer ferric oxide are within the above ranges, improved magnetic properties and adsorption capacity of the modified biochar of the disclosure are enabled. The modified biochar according to the first aspect of the present disclosure further comprises biochar. The biochar component preferably has a density of 0.3 to 1.4 g/m’, more preferably 0.4 to 1.3 g/m’. Moreover, the biochar component preferably has a pH value of 7.3 to 9.6, more preferably 7.4 to 9.3. Further, the biochar component preferably has a carbon content of 64.2 to 88.1 wt %, more preferably 66 to 84 wt %. In this description, the biochar used was produced from a biomass material. The biomass IO material is preferably crop waste, which preferably includes rice straw, corn straw, corncob, peanut shell, and wheat straw. More preferably, the crop waste is rice straw. A mass ratio of graphene:ferric oxide:biochar in the modified biochar according to the first aspect of the present disclosure is (0.5-1.5):(0.25-1.5):100, preferably (0.8-1):(0.3-
    0.8):100.
    A second aspect of the disclosure provides a method for making the modified biochar according to the first aspect of the disclosure, comprising: mixing a biomass material with graphene and ferric oxide to form a mixture, with a mass ratio of biomass material: graphene: ferric oxide being in a range of 100:(0.25-1.1):(0.15-
    1.1); and subjecting the mixture to a carbonization process so as to obtain a graphene-ferric oxide modified biochar. According to the method of the second aspect of the disclosure, a biomass material, graphene, and ferric oxide are mixed together at a mass ratio of 100:(0.25-1.1):(0.15-
    1.1) to form a mixture. The biomass material preferably has a particle size of 80 to 100 mesh, more preferably 90 to 95 mesh. In a preferred embodiment, the method further comprises, before the mixing, subjecting the biomass material to impurity removal, pulverization, and then sieving. The impurity removal is preferably accomplished by water washing. The volume of water used by the water washing is not particularly limited, as long as the biomass material can be completely submerged. In a preferred embodiment, the water washing is preformed 3 to 4 times. In a preferred embodiment, the method further comprises, after the water washing, drying the biomass material. The drying is preferably accomplished by oven drying at a temperature of 75 to 90 °C, more preferably 80 to 85 °C, for a period of 10 to 36 hours, more preferably 24 to 30 hours.
    The pulverization process is not particularly limited herein, and may be performed in any manner well known to those skilled in the art.
    The sieving process is preferably performed by using a 80 to 100, more preferably 90 to 95, mesh screen.
    According to the method of the second aspect of the disclosure, the biomass material, 5 graphene, and ferric oxide are mixed at a mass ratio of 100:(0.25-1.1):(0.15-1.1), preferably 100:(0.3-1):(0.2-0.8). The mixing process is not particularly limited as long as a uniform mixing of the biomass material, graphene, and ferric oxide is ensured.
    According to the method of the second aspect of the disclosure, the mixture of the biomass material, graphene, and ferric oxide is then subjected to a carbonization process IO so as to obtain a graphene-ferric oxide modified biochar.
    The carbonization process preferably comprises a preheating process and a high-temperature carbonization process.
    The preheating process is preferably performed at 100 to 135 °C, more preferably 120 to 130 °C, for 1.5 to 2 hours, more preferably 1.7 to 1.8 hours.
    The high-temperature carbonization process is preferably performed at 450 to 550 °C, more preferably 500 to 520°C, for3.5to 5.5 hours, more preferably 4 to 5 hours.
    The high temperature, at which the mixture is carbonized, is preferably reached by raising the preheating temperature.
    The temperature rising rate is not particularly limited herein.
    The method preferably further comprises subjecting a product from the carbonization process to a water washing process to obtain the modified biochar.
    In particular, the product from the carbonization process is washed with water until the wash water is neutral.
    The water washing process is not particularly limited as long as a desired pH is obtained.
    During the carbonization process of the mixture, the biomass material, after decomposition and carbonization, forms a modified biochar having a porous structure and a large specific surface area together with graphene and ferric oxide.
    The modified biochar preferably has a density of 0.2 to 1.2 g/m’, more preferably 0.6 to 1 g/m’, and a specific surface area of 3.7 to 8 m /g, more preferably 4 to 7 m /g.
    A third aspect of the present disclosure provides the use of the graphene-ferric oxide modified biochar according to the first aspect of the disclosure or of a graphene-ferric oxide modified biochar made by the method according to the second aspect of the disclosure for improvement of arsenic-contaminated soil.
    The use is preferably performed by applying the modified biochar to the soil to be treated, with an amount of
    1 to 5 wt %, more preferably 2 to 3 wt %, with respect to a total amount of the modified biochar and the soil.
    The above mass percentage of the modified biochar applied to the soil to be treated is preferably obtained in accordance with the following equation I: Voprochas = M poche Moenen TM it (Equation I), where, Aoi (mass of the soil to be treated) represents the mass of surface soil, which preferably has a depth of O to 20 cm, more preferably 10 to 15 cm. Further, after application of the modified biochar it is preferably mixed with the surface soil. This mixing process is not particularly limited, and any manner well known to those skilled in the art may be used.
    To illustrate the effects of the modified biochar of the present disclosure, arsenic- contaminated soil in Nanjing, Jiangsu Province (polluted water discharged from nearby smelting plants and atmospheric deposition have been recognized as its principal pollution sources) was collected as a soil sample. Preparation of the soil sample preferably comprises steps of: collecting surface soil with a depth of 0 to 20 cm; subjecting the collected surface soil to impurity removal and then air drying so as to obtain dried soil; and subjecting the dried soil to be pulverized and sieved to obtain a soil sample.
    The impurity removal step is preferably intended to remove large and hard particles present in the surface soil, such as rocks. The collected surface soil is air dried to constant weight and the time is not particularly limited herein. Further, the air drying step is preferably performed in a shadowy place. The pulverization preferably takes place via milling. The sieving step is preferably performed by using a 10 mesh screen. The milling process is not particularly limited as long as a desired particle size is obtained.
    After the preparation of the soil sample, its physicochemical properties were determined by methods for determination of common indexes for soil agrochemical analysis. Results are shown in Table 1.
    Table 1 Physicochemical properties of the soil sample
    Organi Total Total Cation ‚| Total Cc Total phosph | potassi Soil exchange | Clay arsenic p | matter | nitrogen | orus um sampl capacity content/(< content/ H | conten content/( | content/ | content/ e /(ecmol kg” | 2mm, %) (mg-kg t | mgkg)) | (mgke |(mgkg |, 1% ) h hy ) Nanji | 7.
    2.87 15.2 18.8 1.93 11.5 14.3 ng 04 The disclosure will now be described in further detail by way of the following examples, however, which should not be construed as limiting the scope of the disclosure. Example 1 Rice straw was washed 3 times with water, and was then dried at 80 °C for 28 h. The dried rice straw was pulverized and sieved through a 90 mesh screen, and the straw under the screen was collected and used as a biomass material. 100 g of the biomass material, 0.8 g of graphene having a diameter of 20 jun, a thickness of 1.2 nm, and a carbon content of 98 wt. %, and 1 g of ferric oxide having an average particle size of 30 nm and a specific surface area of 44 cm /g were mixed to form a mixture. The mixture was pre-heated at 120 °C for 1.5 h, and was then heated to 500 °C for carbonization. The mixture was kept at that temperature for 4 h. A product resulting from the carbonization was washed until neutral with water to give a graphene-ferric oxide modified biochar (G-Fe-BC), which had a density of 1 g/m and a specific surface area of 6 m%/g.
    Example 2 Rice straw was washed 3 times with water, and was then dried at 80 °C for 30 h. The dried rice straw was pulverized and sieved through a 90 mesh screen, and the straw under the screen was collected and used as a biomass material.
    100 g of the biomass material, 0.8 g of graphene having a diameter of 14 um, a thickness of 2 nm, and a carbon content of 99 wt. %, and 1 g of ferric oxide having an average particle size of 30 nm and a specific surface area of 37 cm /g were mixed to form a mixture.
    The mixture was pre-heated at 120 °C for 1.5 h, and was then heated to 500 °C for carbonization. The mixture was kept at that temperature for 4 h. A product resulting from the carbonization was washed until neutral with water to give a graphene-ferric oxide modified biochar (G-Fe-BC), which had a density of 0.9 g/m’ and a specific surface area of 6.7 m /g.
    Comparative Example | Rice straw was washed 3 times with water, and was then dried at 80 °C for 28 h. The dried rice straw was pulverized and sieved through a 90 mesh screen, and the straw under the screen was collected and used as a biomass material.
    The biomass material was pre-heated at 120 °C for 1.5 h, and was then heated to 500 °C tor carbonization. The biomass material was kept at that temperature for 4 h. A product resulting from the carbonization was washed until neutral with water to give a biochar (BC), which had a density of 0.3 g/m and a specific surface area of 1.2 mg. Comparative Example 2 Rice straw was washed 3 times with water, and was then dried at 80 °C for 29 h. The dried rice straw was pulverized and sieved through a 90 mesh screen, and the straw under the screen was collected and used as a biomass material.
    100 g of the biomass material and 0.8 g of graphene having a diameter of 0.2 to 50 pm, a thickness of 0.7 to 4 nm, and a carbon content of 99 wt. % were mixed to form a mixture. The mixture was pre-heated at 120 °C for 1.5 h, and was then heated to 500 °C for carbonization. The mixture was kept at that temperature for 4 h. A product resulting from the carbonization was washed until neutral with water to give a graphene-modified biochar (G-BC), which had a density of 0.1 g/m’ and a specific surface area of 2.7 m*/g.
    Comparative Example 3 No biochar was added to the soil sample as the blank control (C).
    Test Examples Arsenic-contaminated soil in Nanjing, Jiangsu Province was collected with a depth of 0 to 20 cm, and was then subjected to impurity removal (to remove large and hard particles, such as rocks), air drying (to constant weight) and milling. Thereafter, the soil was passed through a 10 mesh screen to obtain a soil sample having an arsenic content of 14.3 mg-kg!.
    10 kg of the soil sample having an arsenic content of 14.3 mg-kg™ and 1570 ml of a 100 mg LL"! arsenic standard solution were mixed and left to stand in the dark at room temperature for 2 months. Thereafter, the soil sample was air dried (to constant weight) and milled. The milled soil was then passed through a 10 mesh screen to obtain a soil sample having an arsenic content of 30 mg kg.
    kg of the soil sample having an arsenic content of 14.3 mg-kg™ and 3140 ml of a 100 mg Lt arsenic standard solution were mixed and left to stand in the dark at room temperature for 2 months. Thereafter, the soil sample was air dried (to constant weight) and milled. The milled soil was then passed through a 10 mesh screen to obtain a soil 10 sample having an arsenic content of 60 mg-kg™.
    The above soil samples obtained with different arsenic contents were each mixed with a base fertilizer (compound fertilizer with the ratio of N:P:K=16:16:16) and the modified biochar obtained in Example 1, the biochar obtained in Comparative Example 1, and the graphene-modified biochar obtained in Comparative Example 2, respectively, to obtain potting soils, where, the soil samples, the base fertilizer, and the respective biochar in Example 1, Comparative Example 1, and Comparative Example 2 were mixed at mass ratios of 100:15:1 and 100:15:5, respectively, to obtain potting soils with different mixing ratios.
    1.5 kg of each of the potting soils with the above two different mixing ratios were placed into flowerpots (200 mm*270 mm). Wheat seeds were evenly sown in the soils thereinside and cultured in a greenhouse located in Qindao Agricultural University.
    After the seeds had grown into seedlings, thinning was carried out to control the number of seedlings to 6 per pot. During the wheat growing period, the plants were watered periodically such that the water content of the soil was maintained at 60 % of the field water capacity.
    To ensure data accuracy, each kind of potting soil prepared above was used to culture three pots of wheat. Results were averaged.
    Determination of Wheat Biomass After 60 days, seedlings with a similar growth status were selected and removed from the flowerpots. Aerial and subterranean parts of the seedlings were separated from each other and dried in an oven to constant weight. Results are shown in Table 2.
    Table 2 Biomass of the aerial and subterranean parts of the wheat seedlings
    Total arsenic 1% 15% content in soil 1% 15 %|1% 5% C G-Fe- | G-Fe- sample BC |BC | G-BC | G-BC
    BC BC /(mg-kg™) Biomass of aerial part/g w spmpe sn a a The data shown in Table 2 shows that biomass of the aerial and subterranean parts of the wheat seedlings were decreased as the content of arsenic in the soil increased; while the biomass thereof was increased when the modified biochar of the present disclosure was added to the soil. This indicates that the modified biochar of the present disclosure is capable of effectively reducing the effects of arsenic to the plants. Determination of Arsenic Content in Wheat Seedlings After 60 days, seedlings with a similar growth status were selected and removed from the flowerpots to determine the arsenic content therein. The removed seedlings were first rinsed 4 times with a 0.1 mol/L aqueous CaCl: solution at 25 °C, and were then rinsed 4 times with deionized water. Thereafter, the seedlings were dried at 70 °C for 48 h, and were then mixed with 5 ml of ultra pure nitric acid (HNOs) and 3 ml of 30 wt % H;0:2. Microwave digestion was then performed on the mixture by using CEM Marsv (Matthews, NC, USA) to obtain a digestion solution. The digestion solution was analyzed by means of hydride generation atomic fluorescence spectrometry (HG-AFS) by using an AFS-610A type atomic fluorescence spectrometer (BRAIC, Beijing, China) and of inductively coupled plasma atomic emission spectrometry (ICP-AES) by using Optima 2000 DV (perkinelmer Co., Wellesley, MA, USA) to determine the arsenic content. Results are shown in Table
    3. Table3 Arsenic content in the aerial and subterranean parts of the wheat seedlings
    Total Arsenic arsenic 1% 5% content in content 1% 5 %|1% 5% seedlings | in soil ¢ BC |BC |GBC GBC | OTC OT /(mg-keg™) (mg kg Be Be ) © Sannes na [120 [oor | Subterranean The data shown in Table 3 shows that the arsenic content accumulated in the wheat seedlings was increased as the arsenic content in the soil increased; while the arsenic content accumulated in the wheat seedlings was decreased when the modified biochar of the present disclosure was added to the soil.
    This indicates that the addition of the modified biochar of the present disclosure to the soil allows absorption of arsenic by the plants to be substantially suppressed and thus the arsenic content accumulated in the wheat seedlings to be effectively reduced.. Determination of Available Arsenic in Soil Ultrapure water was added to the potting soils and mixed, such that the soil water level reached 60 % of the maximum water holding capacity of the soils.
    The soils were then sealed and left to stand for 48 h.
    Thereafter, ultrapure water was added to the soils and mixed again, such that the soil water level reached 80 to 110 % of the maximum water holding capacity of the soils and the soils were in a paste form and had a smooth surface.
    The soils were then sealed again and left to stand at 30 °C for 24 h for soil water balance.
    Available arsenic content in the soils was then determined by means of the diffusive gradients in thin films (DGT) technique.
    Results are shown in Table 4. Table 4 Available arsenic contents in the soils
    Total arsenic | | content 1% 5 % 1% 5% te > insol | BC BC |GBC |GBC |e OTe
    BC BC (mg'kg ) content in soils (60 | | days after 328.64 | 291.43 | 24493 177.02 173.02 | 173.78 | 141.63 planting) The data shown in Table 4 shows that the addition of the modified biochar of the present disclosure to the soils allows the available arsenic content in the soils to be effectively reduced and thus enables remediation of arsenic-contaminated soil. Analysis and Determination of Arsenic in Various Forms in the Soils Arsenic present in an exchangeable form: the soils, at 60 days after planting, were air dried and then mixed with a 1 mol/L potassium chloride aqueous solution for extraction. The extract was centrifuged, and the supernatant was analyzed by an atomic fluorescence spectrometer (AFS3 100). Results are shown in Table 5. Arsenic present in a calcium-bound form: the precipitate resulting from the centrifugation process was mixed with a 1 mol/L sodium acetate (CH;COONa) aqueous solution for extraction. The extract was centrifuged, and the supernatant was analyzed by an atomic fluorescence spectrometer (AFS3 100). Results are shown in Table 5. Arsenic present in an iron-bound form: the precipitate resulting from the preceding centrifugation process was mixed with 20 ml of a 0.04 mol/L hydroxylamine hydrochloride solution. Extraction was then performed by shaking in a water bath at 60 °C for 6 h. The extract was centrifuged, and the supernatant was analyzed by an atomic fluorescence spectrometer (AFS3 100). Results are shown in Table 5. Arsenic present in an organic bound form: the precipitate resulting from the preceding centrifugation process was mixed with 15 ml of 30 % hydrogen peroxide (H20:). Extraction was then performed by shaking in a water bath at 80 °C for 5.5 h. After the resulting mixture was cooled to room temperature, 5 ml of a 3.2 mol/L ammonium acetate solution (obtained by dissolving ammonium acetate in 20 wt % HNO:3) was added thereto.
    The solution resulting therefrom was shaken for 0.5 h and then centrifuged.
    The supernatant was collected and diluted with distilled water to 20 ml and was then analyzed by an atomic fluorescence spectrometer (AFS3100). Results are shown in Table 5. Arsenic present in a residual form: the precipitate resulting from the preceding centrifugation process was mixed with 5 ml of ultra pure HNO; and 3 ml of 30 % H:02. Microwave digestion was then performed on the mixture by using CEM Marsv IO (Matthews, NC, USA) to obtain a digestion solution.
    The digestion solution was analyzed by an atomic fluorescence spectrometer (AFS3100). Results are shown in Table 5. Table 5 Contents of arsenic in various forms in the soils for planting the wheat Total arsenic | Soil for content in soil planting Water | Excha Al- Fe- Ca- Resid /(mg-kg™h) wheat solubl | ngeabl bound | bound | bound | ual e e sa Jo ss [mi [on |= Jan) san [ossa (KE [en [GE [oo s
    Total arsenic | Soil for content in soil planting Water | Excha Al- Fe- Ca- Resid /(mg kg) wheat ow re bound | bound bound | ual The data shown in Table 5 shows that the addition of the modified biochar of the present disclosure to the soils allows the contents of arsenic in water soluble, exchangeable, and Al-bound forms therein to be reduced and the contents of arsenic in Fe-bound, Ca-bound and residual forms to be increased.
    This indicates that the modified biochar of the present disclosure can promote conversion of active arsenic to stable arsenic.
    So, the biochar of the present disclosure can significantly promote remediation of arsenic-contaminated soil.
    The present disclosure has been described with reference to specific embodiments.
    However, it is clear that the described embodiments are only a part, but not all, of the embodiments of the disclosure.
    Other embodiments can be conceived by those skilled in the art based on the described embodiments, and shall fall within the scope of the disclosure as defined by the appended claims.
    权利要求:
    Claims (10)
    [1]
    -15 - Conclusions l. Modified biocarbon that has been modified with graphene-iron oxide, wherein the modified biocarbon comprises graphene, iron oxide and biocarbon, having a mass ratio of graphene:iron oxide:biocarbon being in the range of (0.5 — 1.5):(0.25 — 1.5):100.
    [2]
    The modified biocoal according to claim 1, wherein the graphene has a diameter of 0.2 - 50 µm, a thickness of 0.7 - 4 nm and a carbon content equal to or greater than 97.9 % by weight.
    [3]
    The modified biochar of claim 1, wherein the iron oxide has a specific surface area of 20-60 cm 2 /g, and wherein the iron oxide is a nanometer iron oxide with an average particle size of 28-32 nm.
    [4]
    The modified biochar according to claim 1, wherein the constituent part of biocoal has a density of 0.3 - 1.4 g/m', a pH value of 7.3 - 9.6 and a carbon content of 64.2 - 88.1% by weight.
    [5]
    A method for making the graphene-iron oxide-modified biocarbon according to any one of claims 1 to 4, wherein the method comprises the steps of: mixing a biomass material with graphene and iron oxide to form a mixture, with a Mass ratio of biomass material:graphene:iron oxide which is in a range of 100:(0.25 — 1.1):(0.15 —1.1); and subjecting the mixture to a carbonization process to obtain the graphene-iron oxide-modified biocarbon.
    [6]
    The method of claim 5, wherein the carbonization process comprises a preheating process and then a high temperature carbonization process.
    [7]
    A method according to claim 6, wherein the preheating process is carried out at a temperature of 100-135°C for 1.5-2 hours; and where it
    - 16 - high temperature carbonization process is carried out at a temperature of 450 - 550°C for 3.5 - 5.5 hours.
    [8]
    The method of claim 5, wherein the biomass material has a particle size of 80-100 mesh.
    [9]
    Use of the modified bio-coal according to any one of claims 1 to 4 or of the modified bio-coal made by the method according to any one of claims 5 to 8 for improvement of arsenic-contaminated soil.
    [10]
    Use according to claim 9, which is carried out by applying the modified biocoal to the soil to be treated in an amount of 1 to 5% by weight with respect to a total amount of the modified biocoal and the soil.
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