Biochar-loaded zero-valent iron composite material and preparation method thereof

[0029] The present invention provides a preparation method of biochar loaded zero-valent iron composite material, which includes the following steps:

[0030] (1) Mixing the biomass material and the aqueous solution of the iron source, and dispersing by ultrasonic to obtain a raw material mixture; the iron source is at least one of iron salt and ferrous salt;

[0031] (2) subjecting the raw material mixture to a hydrothermal reaction to obtain an iron-carbon precursor;

[0032] (3) calcining the iron-carbon precursor in an inert gas atmosphere to obtain a biochar-supported zero-valent iron composite material.

[0033] The invention mixes the biomass material and the aqueous solution of the iron source, and disperses by ultrasonic to obtain a raw material mixture.

[0034] In the present invention, the biomass material is preferably at least one of orange peel, orange peel, pomelo peel, lemon peel, orange peel, moso bamboo powder and cellulose; the pomelo peel is preferably grapefruit peel.

[0035] In the present invention, the orange peel, orange peel, pomelo peel, lemon peel and orange peel are preferably particles with a particle size of not more than 150 μm; the particle size of the moso bamboo powder is preferably not more than 150 μm; the median value of the cellulose The particle size is preferably 170 to 190 μm. In the present invention, when the particle size of the moso bamboo powder is greater than 150 μm, the moso bamboo powder is preferably crushed and sieved to obtain the moso bamboo powder that meets the requirements. In the present invention, the biomass material with small particle size can better contact the iron salt and participate in the subsequent hydrothermal pyrolysis reaction.

[0036] In the present invention, the orange peel, orange peel, pomelo peel, lemon peel and orange peel are preferably pretreated to obtain particles that meet the requirements, and then used.

[0037] In the present invention, the pretreatment preferably includes washing, drying, crushing and sieving in sequence.

[0038] The present invention does not specifically limit the cleaning method, as long as the dust on the biomass raw material can be removed.

[0039] In the present invention, the drying method is not particularly limited, as long as a product of constant weight can be obtained.

[0040] The present invention does not specifically limit the pulverization method, as long as the product with the required particle size can be obtained.

[0041] In the present invention, ultrasonic dispersion is conducive to the full adsorption of iron ions in the biomass material, especially when the biological material is orange peel, orange peel, pomelo peel, lemon peel or orange peel, ultrasonic dispersion can enhance the content of biomass molecules The carboxyl groups and hydroxyl groups of the compound are combined with iron or ferrous ions, and at the same time, iron or ferrous ions can act as a bridge to make biomass molecules close to each other, interlace, and aggregate to form a network structure, thereby obtaining a solid appearance with water in the middle The gelatinous raw material mixture can better fix the iron in the carbon skeleton.

[0042] In the present invention, the mass ratio of the iron element in the biomass material and the iron source is preferably 100:1-20, more preferably 100:3-7; the solid-liquid of the aqueous solution of the biomass material and the iron source The ratio is preferably 0.1 to 0.2 g: 1 mL.

[0043] In the present invention, the iron source is preferably at least one of ferric chloride, ferric nitrate, ferric sulfate, ferrous sulfate, and ferrous chloride.

[0044] In the present invention, the power of the ultrasonic dispersion is preferably 40-100 W, and the time of the ultrasonic dispersion is preferably 1 to 2 hours, more preferably 1.5 to 1.6 hours.

[0045] After the raw material mixture is obtained, the present invention subjects the raw material mixture to a hydrothermal reaction to obtain an iron-carbon precursor. In the present invention, during the hydrothermal reaction process, the biomass material is hydrolyzed to generate aromatic compounds and oligosaccharides. The oligosaccharides undergo intermolecular dehydration, cross-link each other, are isotropic, and finally form partial carbonized nuclei and hydrophilic properties. Surface, and iron ions are hydrolyzed to form Fe(OH) x (x=2 or 3).

[0046] In the present invention, the hydrothermal reaction is preferably carried out under closed conditions; the temperature of the hydrothermal reaction is preferably 180-200°C; the time of the hydrothermal reaction is preferably 1 to 4 hours, more preferably 2 to 3 hours ; The time of the hydrothermal reaction starts when the system temperature reaches the required temperature.

[0047] In the present invention, the heating rate to the temperature required for the hydrothermal reaction is preferably 1 to 5°C/min. In the present invention, the slow temperature rise can make the temperature of the system rise uniformly, avoid local overheating and cause uneven reaction.

[0048] In the present invention, the volume of the raw material mixture preferably accounts for 1/3 to 2/3 of the volume of the hydrothermal reaction equipment.

[0049] The present invention has no special requirements for the hydrothermal reaction equipment, and a high-temperature and high-pressure reactor commonly used in the field can be used. In the embodiment of the present invention, a high-pressure reactor with a polytetrafluoroethylene lining is preferably used.

[0050] After the hydrothermal reaction is completed, the present invention preferably cools the product obtained from the hydrothermal reaction to room temperature naturally, and then undergoes post-treatment to obtain an iron-carbon precursor.

[0051] In the present invention, the post-treatment preferably includes solid-liquid separation, washing, and drying sequentially performed.

[0052] The present invention does not specifically limit the solid-liquid separation method, as long as the solid product can be separated.

[0053] In the present invention, the washing is preferably washing the solid product obtained after solid-liquid separation. The present invention does not specifically limit the washing method, as long as the conventional washing method is adopted. In the embodiment of the present invention, the detergent used for washing is preferably deionized water; the washing method is preferably soaking; and the number of washings is preferably 3 to 5 times.

[0054] In the present invention, the drying method of the washed solid product is preferably freeze drying. The present invention does not specifically limit the temperature and time of the freeze-drying, as long as a solid product of constant weight can be obtained.

[0055] After the iron-carbon precursor is obtained, the present invention calcines the iron-carbon precursor in an inert gas atmosphere to obtain a biochar-loaded zero-valent iron composite material. In the present invention, in the calcination process, Fe(OH) x Dehydration produces iron oxides, and partially carbonized biomass materials release some reducing gases such as CO and H 2 And C realizes the self-reduction process of iron.

[0056] In the present invention, the calcination temperature is preferably 400 to 800°C, more preferably 600 to 700°C; the calcination time is preferably 0.5 to 2h, more preferably 1 to 1.5h; the calcination time is from It starts when the temperature reaches the temperature required for calcination.

[0057] In the present invention, the temperature rise rate to the temperature required for calcination is preferably 5-10°C/min. In the present invention, the slow heating rate can make the iron-carbon precursor uniformly rise in temperature, and the calcination reaction can proceed uniformly.

[0058] The invention also provides a biochar-loaded zero-valent iron composite material obtained by the preparation method described in the above technical scheme.

[0059] In the present invention, the biomass material is preferably pomelo peel. In the present invention, when the biomass material is pomelo peel, the resulting biochar-loaded zero-valent iron composite material has a spherical shape, and the particle size is preferably 3-10 μm.

[0061] Example 1

[0062] The pomelo peel is washed, dried and crushed in sequence, and then passed through a 100-mesh sieve to obtain the biomass material.

[0063] The biomass material and the ferric chloride aqueous solution were mixed in a solid-to-liquid ratio of 0.1g:1mL, and the biomass material and the ferric chloride aqueous solution had a mass ratio of iron of 100:10; after mixing, the resulting mixture Ultrasonic dispersion for 120 minutes to obtain a raw material mixture; the power of ultrasonic dispersion is 100W;

[0064] Put the raw material mixture in a polytetrafluoroethylene-lined autoclave for hydrothermal reaction, raise the temperature to 200°C at a heating rate of 1°C/min, and react at 200°C for 2h; after the reaction is completed, it is filtered and washed sequentially And freeze-drying to obtain iron-carbon precursor;

[0065] The iron-carbon precursor is transferred to a tube furnace, heated to 600° C. at a heating rate of 5° C./min under an inert gas atmosphere, and calcined at 600° C. for 0.5 h to obtain a biochar-loaded zero-valent iron composite material.

[0066] ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometer) was used to detect the iron loading of the biochar-loaded zero-valent iron composite material obtained in this example, and the result was 0.23% (the proportion of iron in the bio-char loaded zero-valent iron composite material).

[0067] The biochar-loaded zero-valent iron composite material obtained in this example was characterized by scanning electron microscopy, and the results are as follows figure 1 Shown. by figure 1 It can be seen that the biochar-loaded zero-valent iron composite material prepared by the hydrothermal-pyrolysis method is 3-10 μm iron-loaded carbon microspheres.

[0068] The biochar-loaded zero-valent iron composite material obtained in this example was subjected to X-ray diffraction characterization, and the results were as follows figure 2 Shown. 2θ=44~45° is the broadened X-ray diffraction peak of the nano-zero-valent iron (100) crystal plane. It can be seen that the zero-valent iron synthesized in the present invention exists in an amorphous form; Any diffraction peaks of iron oxides and iron carbides are observed, indicating that the composite material prepared by hydrothermal-pyrolysis has almost no iron oxides and iron carbides, and its purity is high; the diffraction angle in the spectrum is 22°. The peak is caused by aromatization and graphitization of organic matter in biomass at high pyrolysis temperature; the diffraction angle in the figure The baseline shift at <30° is caused by the amorphous carbon structure of the composite material and the presence of micropores.

[0069] The biochar-loaded zero-valent iron composite material obtained in this example was characterized by nitrogen adsorption and desorption, and the results are as follows image 3 Shown. From the calculation of the figure, it can be seen that the specific surface area of ​​the biochar loaded zerovalent iron composite material obtained in this example is 396m 2 /g; and according to the classification of IUPAC, the composite material prepared by hydrothermal-pyrolysis shows a type IV nitrogen adsorption and desorption curve: the H4 hysteresis loop at the relative pressure P/P°=0.2~0.95 is the nitrogen molecule in the material The accumulation of condensation in the pores indicates the existence of slit pores; the upward trend at P/P°=0.95-1 under relative pressure can be roughly attributed to the existence of macropores or carbon particle accumulation pores; under relative pressure P/P° The steep absorption at the y-axis at =0.05 indicates that the material has a strong force with the nitrogen molecules and also indicates the existence of a large number of micropores.

[0070] The pore size distribution of the biochar-loaded zero-valent iron composite material obtained in this example was tested, and the results were as follows Figure 4 As shown, using the NLDFT method to calculate the micropore distribution of the material, by Figure 4 It can be seen that the pore size of the biochar loaded zero-valent iron composite material obtained in this example is mostly distributed in In the micropores of <2nm, the curve starts to rise from 0.5nm, reaches the peak at 0.6nm, the curve drops, reaches the inflection point at 0.67nm, then rises, reaches the peak at 0.77nm, and the curve drops, at 0.9nm Reach the inflection point, rise again, and finally reach the peak at about 1nm. After more than 1.2nm, there is almost no change, and all tend to zero.

[0071] Infrared characterization was performed on the biochar-loaded zero-valent iron composite material obtained in this example, and the results are as follows Figure 5 Shown. by Figure 5 It can be seen that the biomass material is rich in many inorganic and organic functional groups after hydrothermal reaction, 3620cm -1 Free hydroxyl group, 3500~3200cm -1 Bonded hydroxyl group at position, 1745cm -1 Carbonyl group, 1598cm -1 Aroma at C=C, 1030cm -1 C-O-C at the place, 885cm -1 Compared with biomass materials, the hydrothermal process and the presence of iron can cause the partial shift of the carbonyl group, indicating that there is an interaction between the iron and the carbonyl group. After the high temperature pyrolysis reaction, most of the oxygen-containing functional groups disappear or The intensity is weakened.

[0072] Example 2

[0073] The pomelo peel is washed, dried and crushed in sequence, and then passed through a 100-mesh screen to obtain a biomass material;

[0074] The biomass material and the ferric chloride aqueous solution were mixed in a solid-to-liquid ratio of 0.1g: 1mL, and the biomass material and the ferric chloride aqueous solution had a mass ratio of 100:5; after mixing, the resulting mixture Ultrasonic dispersion for 120 minutes to obtain a raw material mixture; the power of ultrasonic dispersion is 100W;

[0075] Put the raw material mixture in a polytetrafluoroethylene-lined autoclave for hydrothermal reaction, raise the temperature to 200°C at a heating rate of 1°C/min, and react at 200°C for 2h; after the reaction is completed, it is filtered and washed sequentially And freeze-drying to obtain iron-carbon precursor;

[0076] The iron-carbon precursor is transferred to a tube furnace, heated to 600° C. at a heating rate of 5° C./min under an inert gas atmosphere, and calcined at 600° C. for 0.5 h to obtain a biochar-loaded zero-valent iron composite material.

[0077] The biochar-loaded zero-valent iron composite material obtained in this example was characterized by scanning electron microscopy, and the result was similar to Example 1.

[0078] The biochar-supported zero-valent iron composite material obtained in this example was subjected to X-ray diffraction characterization, and the result was similar to Example 1.