Preparation method and application of biochar-loaded Fe2C composite material

Abstract

The present invention belongs to the field of water remediation material preparation, and specifically provides a preparation method and application of a biochar-loaded Fe2C composite material. The preparation method of the present invention uses crop straw as a raw material to prepare biochar-loaded Fe2C, thereby realizing the reuse of the straw. The preparation method is simple to operate, and the material is easy to recycle and reuse. At the same time, the prepared biochar-loaded Fe2C composite material enhances the removal ability of straw biochar for Pb, Cu, Co, Ni and Zn by introducing Fe, and the material has good selective adsorption of copper.

Description

Technical Field

[0001] The present invention relates to the field of water remediation material preparation, and in particular to a preparation method and application of a biochar-loaded Fe2C composite material. Background Art

[0002] Heavy metals in aquatic environments (such as Pb, Cu, Ni, Co, and Zn) are persistent and non-degradable, and can persist in nature for long periods of time. Heavy metals can accumulate in the food chain, affecting the growth and development of organisms and posing a serious threat to human health. With increasing concern for public health and environmental quality, scientists have developed methods such as chemical precipitation, ion exchange, electrolysis, membrane separation, coagulation-flocculation, and adsorption to remove heavy metal ions from aquatic environments. Adsorption is widely used due to its effectiveness in removing low-concentration metal ions and its affordability.

[0003] Crop straw has been shown to be a promising raw material for biochar production. Straw biochar offers advantages such as a readily replaceable surface, porous structure, and controllable chemical properties, making it environmentally friendly and a green adsorbent. However, its small particle size and limited metal ion adsorption capacity limit its large-scale application. Given these challenges, there is an urgent need to modify straw biochar to enhance its metal ion adsorption capacity.

[0004] Many studies have found that biochar can be loaded with Fe through pyrolysis and impregnation. 0 and Fe3C, etc., to improve the adsorption and removal capacity of biochar for heavy metals. However, few studies have found that biochar can be loaded with Fe2C. At the same time, under laboratory conditions, the output of a single preparation of iron-based biochar materials is very limited. Therefore, the development of a material and technology that can efficiently prepare biochar loaded with Fe2C under laboratory conditions is a key issue that needs to be addressed urgently.

[0005] Patent number CN202311682343 states: “Rice husks are washed, chopped, and dried, and then placed in an anaerobic tube furnace for pyrolysis at a high temperature of 450°C for 4 hours. After cooling, they are ground through a 100-mesh sieve to obtain biochar having a 100-mesh sieve; 20g of granular NaOH, 20g of Na2S2O4, and 5g of biochar having a 100-mesh sieve are weighed in a glove box and mixed uniformly to obtain a solid mixture; S2. In a glove box, 20g of ferrous chloride (FeCl2) is stirred on a stirring bar. The mixture was added to the solid mixture under the following conditions, stirred evenly, and reacted for 2 minutes. The mixture was then placed in an ice bath at 0-10°C, and 25 mL of deionized water was sprayed into the solid mixture using a spray bottle at a flow rate of 10 mL / min. The mixture was stirred while spraying, allowing the reactants to react in the rheological phase. Finally, a nano-zero-valent iron-ferroferric oxide composite biochar material was prepared. At a dosage of 0.1%, the adsorption rate for a 30 mg / L lead solution reached 70%. However, the single-shot preparation yield of this technology is low, and the adsorption effect needs to be improved. Summary of the Invention

[0006] The main purpose of the present invention is to provide a preparation method and application of a biochar-loaded Fe2C composite material, to prepare a biochar-loaded Fe2C composite material with better adsorption performance for heavy metals and good selectivity for Cu.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is: a method for preparing a biochar-loaded Fe2C composite material, which specifically includes the following steps:

[0008] Step S1: air-dry and crush the crop straw, place it in an iron can, seal it, and place it in a muffle furnace. Heat it to a predetermined temperature at a certain heating rate and hold it for a period of time for pyrolysis.

[0009] Step S2: Grinding and sieving the pyrolysis product to obtain biochar;

[0010] Step S3, mixing the biochar and the iron salt solution in a certain mass ratio, stirring them thoroughly, and soaking them for a period of time;

[0011] Step S4, drying and sieving the product obtained in step S3;

[0012] Step S5: placing the product obtained in step S4 into a tube furnace and heating the temperature to a predetermined temperature at a certain heating rate, and maintaining the temperature for a period of time;

[0013] Step S6: Grind and sieve the product obtained in step S5 to obtain the biochar-loaded Fe2C composite material.

[0014] Preferably, in step S1, the heating rate is 8-12°C / min, the predetermined temperature is 250-400°C, and the holding time is 1-3 hours.

[0015] Preferably, in step S3, the mass ratio is 1:3 to 1:6;

[0016] Preferably, in step S5, the heating rate is 8-12°C / min, the predetermined temperature is 500-800°C, and is maintained for 1-3 hours.

[0017] The present invention also provides an application of a biochar-loaded Fe2C composite material in adsorbing heavy metals.

[0018] Preferably, the heavy metal includes one or more of Pb, Cu, Co, Ni and Zn.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The carbon raw material of the composite material of the present invention adopts crop straw, which realizes the reuse of straw and is more environmentally friendly. The biochar-loaded Fe2C composite material of the present invention can enhance the electrostatic interaction, π-π interaction, coprecipitation and ion exchange capacity of the straw biochar by introducing Fe(II), Fe(III), Fe(0) or iron-containing minerals in an exogenous form, and increase the specific surface area and adsorption sites of the biochar, which can significantly improve the performance of the straw biochar in removing heavy metals in the water environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 , X-ray diffraction patterns of biochar-loaded Fe2C composites;

[0022] Figure 2 , SEM images of biochar-loaded Fe2C composite materials;

[0023] Figure 3 , N2 adsorption and desorption isotherms on biochar-loaded Fe2C composites

[0024] Figure 4 , adsorption kinetics of heavy metals by biochar-loaded Fe2C composites;

[0025] Figure 5 , adsorption isotherms of heavy metals on biochar-loaded Fe2C composites;

[0026] Figure 6 , adsorption effect diagram of biochar-loaded Fe2C composite materials under single and composite metal systems;

[0027] Figure 7, Comparison of the adsorption effects of biochar-loaded Fe2C composite materials and reference materials under the same experimental conditions. DETAILED DESCRIPTION

[0028] The following description is intended to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are merely examples, and those skilled in the art may conceive of other obvious variations.

[0029] A method for preparing a biochar-loaded Fe2C composite material comprises the following steps:

[0030] Step S1, air-drying and crushing the crop straw, placing it in an iron can, sealing it, and placing it in a muffle furnace. Heating the temperature to 250-400° C. at a heating rate of 8-12° C. / min and maintaining it for 1-3 hours for pyrolysis;

[0031] Step S2: Grinding and sieving the pyrolysis product to obtain biochar;

[0032] Step S3, mixing the biochar with ferrous sulfate or ferric chloride solution at a mass ratio of 1:3 to 1:6, stirring thoroughly, and soaking for 8 to 24 hours;

[0033] Step S4, drying and sieving the product obtained in step S3;

[0034] Step S5, placing the product obtained in step S4 into a tube furnace and heating it to 500-800° C. at a heating rate of 8-12° C. / min, and maintaining it for 1-3 hours;

[0035] Step S6: Grind and sieve the product obtained in step S5 to obtain the biochar-loaded Fe2C composite material.

[0036] The biochar-loaded Fe2C composite material can be used as an adsorbent to adsorb heavy metals in water, wherein the heavy metals are one or more of Pb, Cu, Co, Ni and Zn, and the addition amount of the adsorbent is 0.5 g / L.

[0037] Example 1

[0038] Step S1, air-drying and crushing the corn stalks, placing them in an iron can, sealing them, and placing them in a muffle furnace, heating them to 300° C. at a heating rate of 10° C. / min and maintaining them for 1 h for pyrolysis;

[0039] Step S2: Grind the product obtained in step S1 and pass it through a 40-mesh sieve to obtain raw biochar (BC);

[0040] Step S3: Dissolve 210 g of ferrous sulfate in pure water and dilute to 500 mL. Mix 45 g of BC with the ferrous sulfate solution, stir at a constant speed on a magnetic stirrer, and soak for 12 h.

[0041] Step S4: placing the product obtained in step S3 in an oven at 105° C. for 48 hours until dry, and grinding it to pass through a 100-mesh sieve;

[0042] Step S5: placing the product obtained in step S4 into a quartz boat, placing it into a tube furnace, and heating it to 700° C. at a heating rate of 10° C. / min and holding it for 1 hour;

[0043] Step S6: Grind and sieve the product obtained in step S5 to obtain a biochar-loaded Fe2C composite material, recorded as (LCF), and place the obtained material in a vacuum drying oven for later use.

[0044] Example 2

[0045] Step S1, air-drying and crushing the corn stalks, placing them in an iron can, sealing them, and placing them in a muffle furnace, heating them to 300° C. at a heating rate of 10° C. / min and maintaining them for 1 h for pyrolysis;

[0046] Step S2: Grind the product obtained in step S1 and pass it through a 40-mesh sieve to obtain raw biochar (BC);

[0047] Step S3: Dissolve 230 g of ferrous sulfate in pure water and dilute to 500 mL. Mix 45 g of BC with the ferrous sulfate solution, stir at a constant speed on a magnetic stirrer, and soak for 12 h.

[0048] Step S4: placing the product obtained in step S3 in an oven at 105° C. for 48 hours until dry, and grinding it to pass through a 100-mesh sieve;

[0049] Step S5: placing the product obtained in step S4 into a quartz boat, placing it into a tube furnace, and heating it to 700° C. at a heating rate of 10° C. / min and holding it for 1 hour;

[0050] Step S6: Grind and sieve the product obtained in step S5 to obtain a biochar-loaded Fe2C composite material, which is recorded as (HCF), and place the obtained material in a vacuum drying oven for later use.

[0051] Test Example 1: X-ray Diffraction (XRD) Characterization

[0052] XRD was used to evaluate the crystal changes of biochar-loaded Fe2C composite materials. Figure 1 As shown in the figure, both LCF and HCF have the diffraction peak of Fe2C (PDF#036-1249), indicating that Fe2C is successfully loaded on the biochar. At the same time, the composite material also has CFe 15.1 Diffraction peaks of Fe7SiO 10 The diffraction peaks of (PDF#022-1118) and Fe 2.95 Si 0.05The diffraction peak of O4 (PDF#052-1140) is due to the fact that corn stalks are rich in Si, so Si-containing iron oxides are generated.

[0053] Test Example 2: SEM Characterization

[0054] Scanning electron microscopy (SEM) was used to evaluate the carbon and iron distribution of biochar-loaded Fe2C composites. Figure 2 As shown in the figure, in both LCF and HCF, iron is evenly distributed throughout the material, and as the iron content increases, the amount of iron distributed throughout the material increases accordingly. The increase in Fe content may alter the structure and size of the Fe2C particles, thereby changing the overall properties of the material.

[0055] Test Example 3: BET Characterization

[0056] The specific surface area (BET) of the materials was characterized to evaluate the effect of different iron contents on the specific surface area of ​​the materials. As shown in Table 1, the specific surface areas of LCF and HCF are 30.16 and 17.70 m 2 / g, the increase of iron content will reduce the specific surface area of ​​the material, which may be due to the iron filling the pores of biochar to a certain extent. Figure 3 As shown in Figure 3, the N2 adsorption-desorption curves of LCF and HCF are both type IV, and the hysteresis loops are both type H4, indicating that both materials are mesoporous materials.

[0057] Table 1. BET surface area and pore morphology of the materials

[0058]

[0059] Test Example 4: Adsorption Kinetics Experiment

[0060] Accurately weigh 100 mg of HCF and LCF and place them in a 250 mL blue-capped bottle. Add 200 mL of Pb, Ni, Co, Zn and Cu solutions with a molar concentration of 0.04 mM / L (PbCl2, NiCl2·6H2O, CoCl2·6H2O, ZnCl2 and CuCl2·2H2O, the pH of the solution is 5, adjusted with 0.1 M NaOH and HCl), place on a constant temperature shaker and shake at 25 ° C at a speed of 180 rpm. Sampling was done at 5, 30, 60, 120, 240, 480, 720, 960 and 1200 min, three times in parallel. After the shaking, the solution was filtered with a 0.22 μm filter head and tested on the machine. Figure 4 As shown in Table 2, the adsorption kinetics of the five metals were fitted. The results showed that the pseudo-second-order kinetic model was better than the pseudo-first-order kinetic model, and the fitting coefficient (R 2), therefore, chemical reactions may play a dominant role in the removal process. Compared with LCF, HCF has a higher adsorption rate for Pb, while the opposite is true for Cu. This may be because the relative ionic radius of Pb is closer to that of Fe, which may lead to ion exchange. However, there is no significant difference in the adsorption rate of Ni, Co, and Zn between HCF and LCF.

[0061] Table 2. Kinetic parameters of LCF and HCF for Pb, Ni, Co, Zn and Cu

[0062]

[0063]

[0064] Test Example 5: Adsorption Isotherm Experiment

[0065] Accurately weigh 100 mg of HCF and LCF respectively and place them in 250 mL blue-capped bottles. Add 200 mL of Pb, Ni, Co, Zn and Cu solutions of different concentrations (0.02 mM / L, 0.04 mM / L, 0.1 mM / L, 0.2 mM / L, 0.5 mM / L, 1 mM / L, 2 mM / L, 4 mM / L) respectively. The pH of the solution is 5 (adjusted with 0.1 M NaOH and HCl). Set up 3 parallels. Place on a thermostatic shaker at 25 ° C and 180 rpm for 20 hours. After the shaking, filter the solution with a 0.22 μm filter head and measure the sample on the machine. Figure 5 As shown in Table 3, adsorption isotherms were fitted for the five metals. The results show that the Langmuir isotherm model outperforms the Freundlich isotherm model, indicating that HCF and LCF exhibit uniform monolayer adsorption for Pb, Ni, Co, Zn, and Cu. HCF and LCF exhibited excellent adsorption properties for Pb and Cu, with maximum adsorption capacities of 51.035, 47.373, 41.937, and 42.246, respectively.

[0066] Table 3. Adsorption isotherms of LCF and HCF for Pb, Ni, Co, Zn, and Cu

[0067]

[0068] Test Example 6: Multivariate Adsorption Experiment

[0069] Accurately weigh 100 mg of HCF and LCF respectively and place them in a 250 mL blue cap bottle. Add 200 mL of a mixed solution of Pb, Ni, Co, Zn and Cu with a concentration of 0.06 mM / L. Set up three parallel tubes and place them on a thermostatic shaker at 25°C and 180 rpm for 20 hours. After the shaking, filter the solution with a 0.22 μm filter head and test the sample on the machine. Figure 6As shown in the figure, at a concentration of 0.06 mM / L, HCF and LCF exhibit excellent selective adsorption for Pb and Cu, and the adsorption rate for Ni and Co is almost 0. This may be because in the mixed system, the adsorption sites on the material surface are more replaced by Pb and Cu.

[0070] Comparative Example

[0071] The nano zero-valent iron-ferroferric oxide composite material disclosed in the invention patent publication number CN117654438A was used as a comparative material, as follows:

[0072] Accurately weigh 200mg of HCF and LCF respectively and place them in a 250mL blue-capped bottle. Add 200mL of 30mg / L Pb and Cu solutions respectively. Set up three parallels and place them on a constant temperature shaker at 25°C and 200rpm for 250min. After the shaking, filter the solution with a 0.22μm filter head and measure the sample on the machine. Add the nano zero-valent iron-ferroferric oxide composite material to 30mg / L Pb and Cu solutions at a dosage of 0.1%. The reaction time is 250min. The adsorption rate of the 30mg / L Pb-containing solution is 70%. Compared with the ones in this study, Figure 7 As shown in the figure, under the same experimental conditions, the adsorption rates of LCF and HCF for Pb were 99.4% and 98.5%, respectively, which were significantly better than those of the comparative example. It can be seen that the material prepared in this study has excellent adsorption performance for Pb and has good application prospects.

[0073] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions merely illustrate the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. Application of a biochar-loaded Fe2C composite material in the adsorption of heavy metals, wherein the preparation method of the biochar-loaded Fe2C composite material is as follows: Step S1: air-dry and crush the crop straw, place it in an iron can, seal it, and place it in a muffle furnace. Heat it to a predetermined temperature at a certain heating rate and hold it for a period of time for pyrolysis. Step S2: Grinding and sieving the pyrolysis product to obtain biochar; Step S3, mixing the biochar with an iron salt solution in a certain mass ratio, stirring the mixture thoroughly, and soaking the mixture for a period of time, wherein the iron salt solution is obtained by dissolving a certain amount of ferrous sulfate in pure water; Step S4, drying and sieving the product obtained in step S3; Step S5: placing the product obtained in step S4 into a tube furnace and heating the temperature to a predetermined temperature at a certain heating rate, and maintaining the temperature for a period of time; Step S6, grinding and sieving the product obtained in step S5 to obtain the biochar-loaded Fe2C composite material; In step S1, the heating rate is 8-12°C / min, the predetermined temperature is 250-400°C, and the holding time is 1-3 h; In step S3, the mass ratio is 1:3 to 1:6; The biochar-loaded Fe2C composite material contains Fe7SiO 10 .

2. The use according to claim 1, characterized in that In step S5, the heating rate is 8-12°C / min, the predetermined temperature is 500-800°C, and the temperature is maintained for 1-3 hours.

3. The use according to claim 1, characterized in that The heavy metals include one or more of Pb, Cu, Co, Ni and Zn.

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