Iron-based modified biochar and its preparation method and application

Abstract

The present application discloses an iron-based modified biochar and a preparation method and application thereof. The present application adopts raw biochar and Thiobacillus ferrooxidans to be co-cultured in an iron-based culture medium, and then pyrolyzes them at a temperature of 800-1100°C for 10min-40min under a protective gas atmosphere to obtain iron-based modified biochar to prepare iron-based modified biochar; the obtained iron-based modified biochar not only has an excellent specific surface area, but also optimizes the pore distribution on the biochar through the loading process, and the iron-based modified biochar has an excellent removal effect on Cr(VI) in water and soil due to the adsorption functional groups on the load, and the adsorption effect of the iron-based modified biochar on Cr(VI) is 5 times that of the unmodified biochar.

Description

Technical Field

[0001] The present application relates to the field of environmental protection technology, and in particular to an iron-based modified biochar and a preparation method and application thereof. Background Art

[0002] Chromium pollution control has become an urgent problem to be solved in my country's water environment and soil. Cr (VI) pollution is easy to migrate in water and soil environments due to its high biological toxicity and solubility, and it will accumulate through the food chain with human activities and cause harm to the human body.

[0003] The Cr(VI) pollution problem in my country's current water environment and soil, as well as the remediation technology for Cr(VI) pollution in both water and soil phases, were studied. Among the many Cr(VI) remediation technologies, biochar has become a common adsorbent for removing Cr(VI) pollution due to its wide source, low cost, and can be used in both water and soil phases. However, the adsorption capacity of unmodified biochar for Cr(VI) is limited, and a large amount of biochar added is difficult to meet practical applications.

[0004] Therefore, there is an urgent need to modify biochar to improve its removal performance for Cr(VI). Summary of the invention

[0005] The embodiment of the present application provides an iron-based modified biochar and a preparation method and application thereof. The iron-based modified biochar is prepared by a bioleaching-pyrolysis method, so that the iron-based modified biochar not only has an excellent specific surface area, but also optimizes the pore distribution on the biochar through the loading process. The adsorption functional groups on the load make the iron-based modified biochar have an excellent removal effect on Cr(VI) in water and soil. The adsorption effect of the iron-based modified biochar on Cr(VI) is nearly 5 times that of the unmodified biochar.

[0006] The present invention provides a method for preparing iron-based modified biochar, comprising the following steps:

[0007] Step 1: Take biochar and Thiobacillus ferrooxidans and culture them together in an iron-based medium for 24-84 hours, filter, wash and dry to obtain the initial material; the iron-based medium contains Fe 2+ or iron sulfide;

[0008] Step 2: Pyrolyze the initial material in step 1 at 800-1100° C. for 10-40 min under a protective gas atmosphere to obtain iron-based modified biochar.

[0009] Optionally, in the step 1, the inoculation amount of the Thiobacillus ferrooxidans corresponding to the iron-based culture medium is 8-12%, the addition amount of the biochar corresponding to the iron-based culture medium is 8-12 g / L, the culture temperature is 20-40° C., and the oscillation speed is 100-140 rpm.

[0010] Optionally, the iron-based culture medium includes a modified 9K culture medium, the modified 9K culture medium includes liquid A and liquid B, the liquid A includes: FeSO4·7H2O and sterile water; the liquid B includes:

[0011] K2HPO4·3H2O, MgSO4·7H2O, (NH4)2SO4, KCl and deionized water, pH value is 2.0-2.5.

[0012] Optionally, in the solution A, the ratio of FeSO4·7H2O to the sterile water is: 22.1 g: 150 ml;

[0013] In the B solution, the ratio of K2HPO4·3H2O:MgSO4·7H2O:(NH4)2SO4:KCl and deionized water is 0.66g:0.5g:1g:0.1g:700ml, and its pH is 2.0.

[0014] Optionally, in the step 1, the inoculation amount of the bacterial liquid corresponding to the iron-based culture medium is 10 mg / L, the addition amount of the biochar corresponding to the iron-based culture medium is 10 g / L, and the culture temperature is 37°C.

[0015] Optionally, the biochar is obtained by pyrolysis of wood at 800-1100°C.

[0016] Optionally, in step 2, the protective atmosphere includes any one or more combinations of N2, CO2 or H2O vapor.

[0017] Optionally, the protective atmosphere includes H2O vapor.

[0018] The present application also provides an iron-based modified biochar, using biochar as a carrier, the biochar is loaded with at least Fe3O4, and the iron content of the iron-based modified biochar is 245.475 mg / g-528.67 mg / g;

[0019] The loading of Fe3O4 on the biochar is achieved by co-culturing Thiobacillus ferrooxidans and the biochar material in an iron-based culture medium for 24-84 hours and then pyrolyzing them at 800-1100°C in a protective atmosphere for 10 min-40 min.

[0020] The present application also provides an application of iron-based modified biochar, wherein the iron-based modified biochar described in the above embodiment or the iron-based modified biochar obtained by the preparation method of iron-based modified biochar is used to remove Cr(VI) in chromium-contaminated water and soil.

[0021] The beneficial effects of the present invention include at least:

[0022] The present invention successfully prepared iron-based modified biochar by using the bioleaching-pyrolysis method. It pioneered the use of the bioleaching-pyrolysis method and selected suitable preparation conditions such as raw materials, culture time, and pyrolysis temperature. The obtained iron-based modified biochar not only has excellent specific surface area, but also optimizes the pore distribution on the biochar through the loading process. At the same time, the active groups introduced into the iron-based modified biochar make the iron-based modified biochar have excellent removal effects on Cr(VI) in water and soil. The adsorption effect of iron-based modified biochar on Cr(VI) is 5 times that of unmodified biochar. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 It is the scanning electron microscope image and EDS point scanning result of the iron-based modified biochar of Example 1 of the present application;

[0025] Figure 2 It is the scanning electron microscope image and EDS point scanning result of the iron-based modified biochar of Example 2 of the present application;

[0026] Figure 3 is a scanning electron microscope image of BC of Comparative Example 1 of the present application;

[0027] Figure 4 is a scanning electron microscope image of the MBC of Comparative Example 2 of the present application;

[0028] Figure 5 It is the XRD characterization result of comparative example 2 of the present application;

[0029] Figure 6 It is the FTIR spectra of Comparative Example 1, Comparative Example 2 and Example 1 of the present application;

[0030] Figure 7 These are the Cr(VI) adsorption test results of Comparative Example 1, Comparative Example 2 and Example 1 of the present application;

[0031] Figure 8These are the Cr(VI) adsorption test results of Examples 1, 6, and 7 of the present application. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0033] The embodiments of the present application provide an iron-based modified biochar and a preparation method and application thereof. The following are described in detail. It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments. In addition, in the description of the present application, the term "including" means "including but not limited to". The terms first, second, third, etc. are used only as labels, and no numerical requirements or order are imposed. Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and simplicity, and should not be understood as a rigid limitation on the scope of the present invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single values ​​within the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the numbered ranges, such as 1, 2, 3, 4, 5 and 6, which are applicable regardless of the range. In addition, whenever a numerical range is indicated in this article, it is meant to include any quoted numbers (fractions or integers) within the indicated range.

[0034] The present invention is described below by specific examples to make the technical solution of the present invention easier to understand and grasp, but the present invention is not limited thereto. The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are all commercially available unless otherwise specified; and different sources have no significant effect on product performance.

[0035] The drugs used in the examples are ferrous sulfate heptahydrate (FeSO4·7H2O), potassium dihydrogen phosphate (K2HPO4·3H2O), magnesium sulfate (MgSO4·7H2O), potassium chloride (KCl), sulfuric acid (H2SO4), nitric acid (HNO3), perchloric acid (HClO4), potassium dichromate (K2CrO4), diphenylcarbazide (C 13 H 14 N4O), sodium hydroxide (NaOH), sodium chloride (NaCl), sodium nitrate (NaNO3), and sodium sulfate (NaSO4) were purchased from Shanghai Sinopharm Reagent Group.

[0036] The strain of Bacillus ferrooxidans (ATCC 23270) was purchased from Beijing Baozang Biotechnology Co., Ltd.

[0037] Biochar (BC) is a byproduct of rapid pyrolysis of pulverized wood in a cyclone furnace at 1000-1100°C in the Tongshan County Biomass Energy Plant in Hubei Province. The pulverized wood is taken from a mixture of local agricultural and forestry waste wood.

[0038] The instruments used in the examples and the instruments used for characterization are all conventional experimental characterization instruments unless otherwise specified.

[0039] The abbreviations of some materials in the following embodiments and drawings of the specification are as follows:

[0040] Biochar-BC; Initial material-MBC; Iron-based modified biochar-PMFeBC;

[0041] Iron-based impregnated modified biochar - FeBC;

[0042] Example 1

[0043] A method for preparing iron-based modified biochar comprises the following steps:

[0044] Step 1: Take biochar and Thiobacillus ferrooxidans and culture them together in an iron-based medium for 72 hours; filter, wash and dry at room temperature to obtain the initial material;

[0045] The culture temperature was 37°C, the dosage of biochar corresponding to the iron-based culture medium was 10 g / L, and the inoculation amount of Thiobacillus ferrooxidans was 10% (mass fraction); the iron-based culture medium was a modified 9K culture medium; the culture was carried out in a full-temperature culture shaker, and the culture speed was 120 rpm;

[0046] The improved 9K culture medium includes liquid A and liquid B;

[0047] Solution A: FeSO4·7H2O 44.2g; sterile water 300ml; pH value is natural; sterilization method is microporous membrane filtration sterilization (φ=0.22um);

[0048] Solution B: K2HPO4·3H2O 0.66g; MgSO4·7H2O 0.5g; (NH4)2SO4 1g; KCl 0.1g; deionized water 700ml; pH value 2.0; sterilization method is conventional high-pressure steam sterilization;

[0049] Step 2: The initial material (MBC) is pyrolyzed in a tubular furnace at 1000° C. for 30 min under a H2O steam atmosphere using N2 as a driving gas to obtain iron-based modified biochar (PMFeBC).

[0050] The iron content of the sample tested in Example 1 was 294.86 mg / g;

[0051] The PMFeBC sample of Example 1 was obtained by XRD scanning electron microscopy and EDS point scanning. Figure 1 .

[0052] Example 2

[0053] A method for preparing iron-based modified biochar, which is different from Example 1 in that:

[0054] In step 2, pyrolysis is performed at a temperature of 800°C.

[0055] Take the sample of Example 2, use the same test conditions as Example 1, and the iron content is 274.02 mg / g;

[0056] The PMFeBC sample of Example 2 was obtained by XRD scanning electron microscopy and EDS point scanning. Figure 2 ;

[0057] Example 3

[0058] A method for preparing iron-based modified biochar, which is different from Example 1 in that:

[0059] In step 2, pyrolysis is performed at a temperature of 1100°C.

[0060] Example 4

[0061] A method for preparing iron-based modified biochar, which is different from Example 1 in that:

[0062] In step 2, the pyrolysis time is 10 min.

[0063] Take the sample of Example 4 and use the same test conditions as Example 1 to test the iron content to be 245.475 mg / g;

[0064] Example 5

[0065] A method for preparing iron-based modified biochar, which is different from Example 1 in that:

[0066] In step 2, the pyrolysis time is 40 min.

[0067] Example 6

[0068] A method for preparing iron-based modified biochar, which is different from Example 1 in that:

[0069] In step 2, the protective atmosphere is N2.

[0070] Example 7

[0071] A method for preparing iron-based modified biochar, which is different from Example 1 in that:

[0072] In step 2, the protective atmosphere is CO2.

[0073] Example 8

[0074] A method for preparing iron-based modified biochar, which is different from Example 1 in that:

[0075] In step 1, biochar and Thiobacillus ferrooxidans were co-cultured in an iron-based medium for 24 hours.

[0076] Example 9

[0077] A method for preparing iron-based modified biochar, which is different from Example 1 in that:

[0078] In step 1, biochar and Thiobacillus ferrooxidans were co-cultured in an iron-based medium for 84 hours.

[0079] It should be noted that when the culture time of step 1 is the first 24 hours, the iron content increases less, and then the growth of Thiobacillus ferrooxidans enters the logarithmic phase until the iron content in the initial material increases to a stable level at 84 hours. After 84 hours of culture, the iron content of MBC after step 1 in Example 9 was measured to be 202.24 mg / g.

[0080] Example 10

[0081] A method for preparing iron-based modified biochar, which is different from Example 1 in that:

[0082] In step 1, the inoculation amount of the Thiobacillus ferrooxidans corresponding to the iron-based culture medium is 8%, the addition amount of the biochar corresponding to the iron-based culture medium is 8 g / L, the culture temperature is 20° C., and the rotation speed is 100 rpm.

[0083] Embodiment 11

[0084] A method for preparing iron-based modified biochar, which is different from Example 1 in that:

[0085] In step 1, the inoculation amount of the Thiobacillus ferrooxidans corresponding to the iron-based culture medium is 12%, the addition amount of the biochar corresponding to the iron-based culture medium is 12 g / L, the culture temperature is 40° C., and the rotation speed is 140 rpm.

[0086] Comparative Example 1

[0087] The same biochar (BC) as in Example 1 was used as the material and pyrolyzed at 1000°C for 30 min.

[0088] Comparative Example 2

[0089] The preparation method of Comparative Example 2 is the same as that of Example 1, except that step 2 is not performed to obtain the initial material (MBC).

[0090] The iron content of the sample of Comparative Example 2 was tested to be 190.04 mg / g.

[0091] Comparative Example 3

[0092] The preparation method of Comparative Example 3 is the same as that of Example 1, except that Thiobacillus ferrooxidans is not added in step 1, that is, the iron-based impregnated modified biochar (FeBC) is prepared by impregnation pyrolysis method.

[0093] The iron content of the sample of Comparative Example 3 was tested to be 197.43 mg / g.

[0094] Test results and testing

[0095] Relevant characterizations were performed on Example 1, Comparative Example 1 and Comparative Example 2;

[0096]

[0097]

[0098] like Figure 1 , Figure 3 , Figure 4 As shown, Figure 1 Includes scanning electron microscope images of Example 1 (PMFeBC); Figure 3 This is the scanning electron microscope image of Comparative Example 1 (BC), Figure 4 is a scanning electron microscope image of comparative example 2 (MBC);

[0099] The SEM results show that Figure 3 The medium BC has a porous micron-scale structure with holes of varying sizes on the surface, which can provide certain iron loading sites for bioleaching. Figure 4 It can be seen that after step 1, relatively regular pyramidal particles are attached to the surface of MBC and the pores of biochar, with particle sizes ranging from 1 μm to 0.3 μm; Figure 1 It can be seen that PMFeBC is completely surrounded by iron oxide crystals. The formed iron oxide particles have a particle size of about 500 nm and a relatively regular tetrahedral crystal structure with a good crystal structure and a relatively complete shape.

[0100] Figure 5 This is the XRD characterization result of Comparative Example 2; it shows that the main component of the particles on the surface of MBC is jarosite (KFe3(SO4)2(OH)6) produced in step one.

[0101] Figure 6The FTIR spectra of Example 1, Comparative Example 1, and Comparative Example 2 are shown in Figure 1. It can be seen that the iron-containing functional groups can be effectively introduced into BC after step 1. The accumulation of secondary minerals produced by Thiobacillus ferrooxidans - jarosite on the solid surface will reduce the hydrometallurgical leaching efficiency, but can effectively load iron onto biochar. After pyrolysis, some oxygen-containing functional groups on MBC are destroyed by high temperature, and only 1083 cm -1 、1624cm -1 and 3446cm -1 The peaks at are retained, and the intensity of these peaks is relatively low, playing a limited role in the removal of Cr(VI). Therefore, the removal efficiency of PMFeBC for Cr(VI) is mainly due to the Fe3O4 loaded on it.

[0102] Sample specific surface area and pore size analysis, some sample test results are shown in Table 1;

[0103] Table 1

[0104]

[0105]

[0106] It can be seen from Table 1 that the specific surface area of ​​PMFeBC in Example 1 can reach 305.9230 m 2 / g; it is significantly increased compared with Comparative Example 1 and Comparative Example 2; the higher the pyrolysis temperature, the more volatile substances will be produced in the pyrolysis process of biochar, resulting in an increase in the specific surface area of ​​​​the iron-based modified biochar (PMFeBC); Step 1 will produce jarosite, and jarosite loaded on the biochar will block the pores of the biochar to a certain extent, resulting in a decrease in the specific surface area of ​​the initial material (MBC); It should be noted that continuing to increase the temperature will lead to carbonization of biochar, reduce the amount of active functional groups on the biochar, and affect the adsorption of metal ions.

[0107] Cr(VI) adsorption experiment

[0108] Experimental conditions: Take a 100 mg / L Cr(VI) solution, add the sample with a sample number of 1 g / L, pH of the Cr(VI) solution = 2, ambient temperature 27°C, shaker speed 140 rpm;

[0109] Sample groups: Comparative Example 1 (BC), Comparative Example 2 (MBC), Comparative Example 3 (FeBC), Example 1 (PMFeBC), Example 6, Example 7;

[0110] The samples were taken at the adsorption time of 5min, 15min, 30min, 60min and 90min to detect the concentration of Cr(VI);

[0111] Characterization methods: The concentration of Cr(VI) before and after adsorption was detected by UV spectrophotometer;

[0112] A coordinate graph was drawn according to the adsorption time and the concentration ratio of Cr(VI) before and after adsorption, such as Figure 7 , Figure 8 As shown;

[0113] It can be seen that although comparative example 1 has a higher specific surface area, the removal rate of Cr(VI) is only 16.59%; after step 1, a large amount of jarosite is attached to the MBC, the porous structure of the biochar is blocked, and the specific surface area is reduced to 175.2237 m 2 / g, the adsorption sites decreased, and the Cr(VI) removal rate decreased to 7.54%. However, the iron-based modified biochar (PMFeBC) had better Cr(VI) removal performance. After 5 minutes of reaction, the Cr(VI) removal rate could reach 81.99%. At 90 minutes, the Cr(VI) removal rate in the solution reached 98.63%, which was nearly 5 times that of Comparative Example 1.

[0114] like Figure 8 As shown, the removal rate of Cr(VI) by PMFeBC prepared under water vapor atmosphere can reach 99.42%, which is 5 times that of comparative example 1. After the material is modified under N2 and CO2 atmospheres, the removal rate of Cr(VI) is also good at about 75%. The possible reason is that water vapor can provide a reducing atmosphere for the decomposition of potassium ferroaluminate into Fe3O4, and provide conditions for the decomposition of biochar materials at high temperature.

[0115] The mechanism of Cr(VI) removal by PMFeBC obtained in the present application may be as follows: Cr(VI) in the solution is adsorbed onto the surface of PMFeBC through porous adsorption and electrostatic attraction of positively charged functional groups on the surface of the material; Cr(VI) attached to the surface of PMFeBC is reduced to Cr(III) by a small amount of oxygen-containing functional groups as electron donors, while most of the Cr(VI) is reduced to Cr(III) by Fe(II); the reduced Cr(III) ions are precipitated in the form of Cr(III) / Fe(III) hydroxides or co-precipitated in the form of Cr2O3, thereby achieving the effect of removing Cr(VI) from water.

[0116] An application of iron-based modified biochar, the iron-based modified biochar obtained in the above embodiment is used to remove Cr(VI) in chromium-contaminated water and soil, the specific implementation method is as follows:

[0117] Example 10

[0118] The soil used in the soil culture experiment came from the rice fields in Jingmen City, Hubei Province. The soil was artificially aged for 6 months after removing debris, weeds and other debris in the soil. The aging method was to add 1000 ml of K2CrO4 solution of different concentrations per 1 kg of soil, and then grind it for use after natural air drying.

[0119] The soil index detection method can be tested in accordance with HJ 1082-2019, HJ 962-2018, and HJ 889-2017 standards.

[0120] 1‰ unmodified biochar BC, 1‰ PMFeBC, and 10‰ PMFeBC were applied to the soil aged at the same K2CrO4 solution concentration; PMFeBC was obtained according to the method of Example 1;

[0121] At the 60th day, the solidification rate of Cr(VI) in the aged soil with 1‰ (here and below are all weight fractions) of unmodified biochar BC applied was 90.85%; the solidification rate of Cr(VI) in the aged soil with 1‰ PMFeBC applied was 90.85%; the solidification rate of Cr(VI) in the aged soil with 10‰ PMFeBC applied was 99.65%.

[0122] The PMFeBC prepared in the embodiment of the present application has a high specific surface area and is loaded with a large amount of Fe3O4, which can undergo an electrostatic attraction-complexation reaction with Cr(VI) in the soil, thereby more effectively fixing Cr(VI) in the soil.

[0123] The above is a detailed introduction to the iron-based modified biochar and its preparation method and application provided in the embodiments of the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea; at the same time, for technical personnel in this field, according to the ideas of the present application, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A method for preparing iron-based modified biochar, characterized in that: The following steps are involved: Step 1: Take biochar and Thiobacillus ferrooxidans and culture them together in an iron-based medium for 24-84 hours, filter, wash and dry to obtain the initial material; the iron-based medium contains Fe 2+ ; Step 2: Pyrolyze the initial material in step 1 at 800-1100° C. for 10 min-40 min under a protective gas atmosphere to obtain iron-based modified biochar; The biochar is obtained by pyrolysis of wood at 800-1100°C; The protective atmosphere includes H2O vapor.

2. The method for preparing iron-based modified biochar according to claim 1, characterized in that: In the step 1, the inoculation amount of the Thiobacillus ferrooxidans corresponding to the iron-based culture medium is 8-12wt%, the addition amount of the biochar corresponding to the iron-based culture medium is 8-12g / L, the culture temperature is 20-40°C, and the oscillation speed is 100-140rpm.

3. The method for preparing the iron-based modified biochar according to claim 1, characterized in that: The iron-based culture medium includes a modified 9K culture medium, the modified 9K culture medium includes liquid A and liquid B, the liquid A includes: FeSO4·7H2O and sterile water; The B solution includes: K2HPO4·3H2O, MgSO4·7H2O, (NH4)2SO4, KCl and deionized water, and the pH value is 2.0-2.

5.

4. The method for preparing the iron-based modified biochar according to claim 2, characterized in that: In the step 1, the inoculation amount of the Thiobacillus ferrooxidans corresponding to the iron-based culture medium is 10 mg / L, the addition amount of the biochar corresponding to the iron-based culture medium is 10 g / L, and the culture temperature is 37°C.

5. An iron-based modified biochar, characterized in that: Using biochar as a carrier, the biochar is loaded with at least Fe3O4, and the iron content of the iron-based modified biochar is 245.475 mg / g -528.67 mg / g; The loading of Fe3O4 on the biochar is achieved by co-culturing Thiobacillus ferrooxidans and the biochar material in an iron-based medium for 24-84 hours, followed by pyrolysis at 800-1100°C in a protective atmosphere for 10 min-40 min; The protective atmosphere includes H2O vapor.

6. Use of the iron-based modified biochar prepared by the method for preparing the iron-based modified biochar as described in any one of claims 1 to 4 or the iron-based modified biochar as described in claim 5 in removing Cr(VI) from chromium-contaminated water and soil.

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