NL2030639B1

NL2030639B1 - Biochar-loaded nanoscale zero-valent iron composite material as well as preparation method and application thereof

Info

Publication number: NL2030639B1
Application number: NL2030639A
Authority: NL
Inventors: Liu Shuting; Dong Yangyang; Wang Xinyu; Shi Zeming; Zhu Jing
Original assignee: Univ Chengdu Technology
Priority date: 2022-01-21
Filing date: 2022-01-21
Publication date: 2023-08-01

Abstract

The disclosure provides a biochar-loaded nanoscale zero-valent iron composite material as well as a preparation method and application thereof, and belongs to the field 5 of adsorption materials. The method comprises steps of, calcining rice husks to obtain rice hull biochar, mixing FeSO4~7HzO, an ethanol aqueous solution and rice husk biochar to obtain a mixture; and mixing the mixture with a KBH4 solution to perform a redox reaction to obtain the biochar-loaded nanoscale zero-valent iron composite material. Based on the superiority of biochar and nanoscale zero-valent iron in removing lO heavy metals, nanoscale zero-valent iron is loaded on the biochar through a liquid-phase reduction method, so that the nanoscale zero-valent iron composite material taking biochar as a carrier is prepared, the advantages of the nanoscale zero-valent iron composite material and the biochar are fully exerted, and a better effect is achieved in the aspect of uranium pollution water body remediation. 15

Description

BIOCHAR-LOADED NANOSCALE ZERO-VALENT IRON COMPOSITE

MATERIAL AS WELL AS PREPARATION METHOD AND APPLICATION

THEREOF

TECHNICAL FIELD

[01] The disclosure relates to the technical field of adsorption materials, in particular to a biochar-loaded nanoscale zero-valent iron composite material as well as a preparation method and application thereof.

BACKGROUND ART

[02] Nano material is a new kind of material which has attracted widespread attention in recent years. It can absorb many metal ions and has strong adsorption capacity.

Nanoscale zero-valent iron not only has the nature of the zero-valent iron, but also has a larger specific surface area, higher reaction activity and better adsorption performance compared with ordinary zero-valent iron, and can remove the various heavy metal ions in the solution. Its removal mechanism includes adsorption, sedimentation, reduction and coprecipitation, of which reduction is the main one.

[03] As a new generation of environmental remediation materials, nanoscale zero- valent iron has been widely used in the remediation of organic pollutants and heavy metals in the environment. However, nanoscale zero-valent iron is prone to agglomeration, oxidation and deactivation, and has problems of poor dispersion and stability.

SUMMARY

[04] In view of this, an object of the present disclosure is to provide a biochar-loaded nanoscale zero-valent iron composite material as well as a preparation method and application thereof. The prepared biochar-loaded nanoscale zero-valent iron composite material realizes uniform dispersion of nanoscale zero-valent iron and improves stability.

[05] In order to achieve the above objective of the disclosure, the disclosure provides the following technical solution:

[06] The disclosure provides a preparation method of a biochar-loaded nanoscale zero-valent iron composite material, specifically comprising the following steps:

[07] Calcining rice husks to obtain rice hull biochar;

[08] Mixing FeSO4 7H20, an ethanol aqueous solution and the rice husk biochar to obtain a mixture; and

[09] Mixing the mixture with a KBH4 solution to perform a redox reaction to obtain the biochar-loaded nanoscale zero-valent iron composite material.

[10] Preferably, the calcination temperature is 700 DEG C and the time is 2.0 h.

[11] Preferably, a volume ratio of ethanol to water in the ethanol aqueous solution is 3.7.

[12] Preferably, a redox reaction ends up with no hydrogen generation in a reaction system.

[13] The disclosure also provides the biochar-loaded nanoscale zero-valent iron composite material prepared by the preparation method. The biochar-loaded nanoscale zero-valent iron composite material comprises rice husk biochar and nanoscale zero- valent iron, the nanoscale zero-valent iron is loaded on the surface of the rice husk biochar.

[14] Preferably, the mass ratio of the rice husk biochar to the nanoscale zero-valent ironis 2: 1.

[15] The disclosure also provides application of the biochar-loaded nanoscale zero- valent iron composite material in adsorbing uranium elements in water.

[16] The disclosure provides a preparation method of a biochar-loaded nanoscale zero-valent iron composite material, specifically comprising the following steps of, calcining rice husks to obtain rice hull biochar; mixing FeSO4-7H>0, an ethanol aqueous solution and the rice husk biochar to obtain a mixture; and mixing the mixture with a

KBHy solution to perform a redox reaction to obtain the biochar-loaded nanoscale zero- valent iron composite material. Based on the superiority of biochar and nanoscale zero- valent iron in removing heavy metals, nanoscale zero-valent iron is loaded on the biochar through a liquid-phase reduction method, so that the nanoscale zero-valent iron composite material taking biochar as a carrier is prepared, the advantages of the nanoscale zero-valent iron composite material and the biochar are fully exerted, and a better effect is achieved in the aspect of uranium pollution water body remediation. The data of the embodiments show that:

[17] (1) Biochar is prepared by using agricultural waste raw material rice husks, and a liquid-phase reduction method is used to synthesize nano zero-valent iron and a biochar-loaded nanoscale zero-valent iron composite material, three materials (biochar, nanoscale zero-valent iron and biochar-loaded nanoscale zero-valent iron composite material) are characterized by X-ray diffraction (XRD) and an electron microscope (SEM), and the result indicates that the nanoscale zero-valent iron is successfully loaded on the biochar, and the loaded nanoscale zero-valent iron has not been found to be agglomerated.

[18] (2) By analyzing through a kinetic experiment and an isothermal adsorption model, 1t is found that the adsorption process of the biochar on uranium better conforms to a Freestlich model and a quasi-secondary dynamics model; the adsorption process of the nanoscale zero-valent iron on uranium better conforms to a Langmuir model and the quasi-secondary dynamics model; and the adsorption process of the biochar-loaded nanoscale zero-valent iron composite material on uranium better conforms to the

Langmuir model and the quasi-secondary dynamics model. The adsorption process of the biochar on uranium is described as non-uniform adsorption of the surface, and adsorption of the biochar-loaded nanoscale zero-valent iron composite material on uranium is mainly single-layer adsorption.

[19] (3) Upon comparison of adsorption experiment, it 1s found that among the three materials, the experimental conditions required for adsorbing uranium by the biochar- loaded nanoscale zero-valent iron composite material are more easily met under the optimal adsorption condition, the adsorption capacity is maximum, uranium in the polluted water body can be better removed, and a certain feasibility is provided for the uranium-polluted water body remediation.

BRIEF DESCRIPTION OF THE DRAWINGS

[20] FIG. 1 is an X-ray diffraction diagram of biochar;

[21] FIG. 2 is an X-ray diffraction diagram of nanoscale zero-valent iron;

[22] FIG. 3 is an X-ray diffraction diagram of a biochar-loaded nano zero-valent iron composite material;

[23] FIG. 4 is an electron microscope diagram of biochar at different magnification times;

[24] FIG. 5 1s an electron microscope diagram of nanoscale zero-valent iron at different magnification times;

[25] FIG. 6 is an electron microscope diagram of a biochar-loaded nanoscale zero-

valent iron composite material at different magnification times.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[26] The disclosure provides a preparation method of a biochar-loaded nanoscale zero-valent iron composite material, specifically comprising the following steps:

[27] Calcining rice husks to obtain rice hull biochar;

[28] Mixing FeSO4 7H20, an ethanol aqueous solution and the rice husk biochar to obtain a mixture; and

[29] Mixing the mixture with a KBH: solution to perform a redox reaction to obtain the biochar-loaded nanoscale zero-valent iron composite material.

[30] The rice husks are calcined to obtain the rice husk biochar.

[31] The calcination temperature is preferably 700°C, and the time is preferably 2.0 h.

[32] Preferably, the rice husks are cleaned and then placed in a stainless steel reaction vessel, and the vessel is placed in a muffle furnace for calcination.

[33] After calcination is completed, a obtained calcined product is preferably naturally cooled to room temperature under the protection of N: to obtain the rice husk biochar.

[34] In the present disclosure, FeSO4- 7H20, an ethanol aqueous solution and the rice husk biochar are mixed to obtain a mixture.

[35] In the present disclosure, the volume ratio of ethanol to water in the ethanol aqueous solution is preferably 3: 7. The use amount of the ethanol aqueous solution is not specifically limited, and can ensure that FeSO4-7H:0 is completely dissolved.

[36] The use amount of FeSO4-7H20 and the rice husk biochar 1s not specifically limited, preferably, the mass ratio of the rice husk biochar to the nanoscale zero-valent iron in the obtained biochar-loaded nanoscale zero-valent iron composite material is 2:1.

[37] After the rice husk biochar and the mixture are obtained, the mixture is mixed with a KBH4 solution to perform a redox reaction to obtain the biochar-loaded nanoscale zero-valent iron composite material.

[38] In the present disclosure, the oxidation reduction reaction preferably ends up with no hydrogen generation in the reaction system, and the temperature is preferably room temperature.

[39] Inthe present disclosure, the redox reaction 1s preferably performed in a nitrogen atmosphere.

[40] In the present disclosure, black floccules appear in the mixing process.

[41] After the redox reaction is completed, the obtained redox reaction product is preferably loaded into a centrifuge tube and placed in a centrifuge, supernate is poured out after centrifugation, and a remaining solid is dried in a vacuum drying oven to obtain the biochar-loaded nanoscale zero-valent iron composite material.

[42] The disclosure also provides a biochar-loaded nanoscale zero-valent iron composite material. The material comprises rice husk biochar and nanoscale zero-valent iron, and the nanoscale zero-valent iron is loaded on the surface of the rice husk biochar.

[43] Inthe present disclosure, the mass ratio of the rice husk biochar to the nanoscale zero-valent iron is preferably 2:1.

[44] The disclosure further provides application of the biochar-loaded nanoscale zero-valent iron composite material in adsorbing uranium elements in water.

[45] In order to further illustrate the present disclosure, the biochar-loaded nanoscale zero-valent iron composite material and the preparation method and application thereof are described in detail below with reference to examples, but should not be construed as limiting the protection scope of the present disclosure.

Embodiment

[46] Preparation of biochar

[47] The biocharis prepared by using a high temperature pyrolysis process. Weighing rice husks in a laboratory, washing clean, placing in a stainless steel reaction vessel and then in a muffle furnace, adjusting the temperature to 700 DEG C, maintaining the temperature for 2.0 hours, and obtaining the rice husk biochar after cooling to room temperature under the protection of Nz.

[48] Preparation of nanoscale zero-valent iron

[49] Preparing nanoscale zero-valent iron by dropwise adding a KBHj solution into the FeSO4 7H:O0 solution, continuously introducing nitrogen after the start of reaction until no significant hydrogen generation in a reactor. Carrying out centrifugation after the solid-liquid separation is completed, pouring out supernate carefully, repeating three times, and drying the remaining solid in a vacuum drying oven. Transferring the cooled nanoscale zero-valent iron into a glove box filled with Na, grinding into powder, and bagging the powder in a sealed manner.

[50] Preparation of biochar loaded nanoscale zero-valent iron

[51] Weighing FeSO4-7H20 into an ethanol aqueous solution [V (ethanol): V (water) = 3.7 | to fully dissolve, transferring the solution to a three-necked flask equipped with an electric stirnng device, and adding weighed biochar, so that the mass ratio of the biochar to the nanoscale zero-valent iron in the composite material is 2:1, then slowly adding a KBH: solution into the three-necked flask, immediately seeing black floccules, and them completing the redox reaction. Continuously introducing nitrogen and stirring continuously until no significant hydrogen generation in the three-necked flask. Putting the mixed solution into a centrifuge tube, putting the centrifuge tube into a centrifuge, centrifuging, pouring out supernate, and drying remaining solid in a vacuum drying oven to obtain the biochar-loaded nanoscale zero-valent iron composite material.

[52] The phase composition and the structure form of the biochar are analyzed by X- ray diffraction. As shown in FIG. 1, the biochar has strong diffraction peaks at 26 of 12 degrees and 20 degrees -30 degrees, respectively, which are a diffraction peak of a crystal plane of cellulose 101 and a diffraction peak of an organic crystalline compound, respectively. After the biochar is carbonized, hemicellulose is cleaved, the diffraction peaks are weakened, the structure does not change greatly, microcrystalline carbon fibers are present, and the organic crystalline compound becomes microcrystal carbon having a finer grain graphitization structure.

[53] The phase composition and the structure form of the nanoscale zero-valent iron are analyzed by X-ray diffraction. As shown in FIG. 2, it can be seen that in the scanning range of 10 degrees - 70 degrees, diffraction peaks appear at 2 theta = 44.8 degrees, 2 theta = 65.0 degrees, respectively, and the diffraction peaks of the crystal planes of Fe (110) and Fe (200) are exactly matched, and the characteristic peaks of other iron oxides are not found, so that the sample is pure.

[54] The phase composition and the structure form of the biochar-loaded nanoscale zero-valent iron material are analyzed by X-ray diffraction. The result is shown in FIG. 3. It can be seen that the characteristic peak of a carbon structure is 2 theta = 22.5 degrees, and the characteristic peak of a Fe structure is 2 theta = 44.8 degrees, indicating that both elements are present in the biochar-loaded nanoscale zero-valent iron composite material.

[55] In FIG. 4, a and b are microscopic structure features of the biochar under different magnification times analyzed by an electron microscope, and it can be clearly shown that the biochar has a tubular and hole-shaped structure, presents a barrel-shaped tissue, has developed holes, and a flat and smooth surface with lines, and has a loose and porous honeycomb void structure. [S6] InFIG. 5, aandb are microscopic structure features of the nanoscale zero-valent iron under different magnification times analyzed by an electron microscope, and it can be seen that the nanoscale zero-valent iron is a spherical particle, the particle size is uniform, the surface is smooth, and particles are randomly aggregated into a chain distribution. The particle size is about 30-100 nm, and the average particle size is 80 nm.

It can also be seen that the nanoscale zero-valent iron is easy to agglomerate, and the particles are closely linked, thus limiting its ability to treat pollutants in practical application. [S7] In FIG. 6, a and b are microscopic structure features of the biochar-loaded nanoscale zero-valent iron composite material under different magnification times analyzed by an electron microscope. The biochar has a porous and tubular structure and is darker in color, fine and bright spherical particles distributed on the biochar are nanoscale zero-valent particles, the particle size is more than 100 nm, and the nanoscale zero-valent particles are uniformly dispersed on the surface of the biochar, indicating that the nanoscale zero-valent iron particles exist in the surface and pores of the biochar.

The electron microscope diagram of the biochar-loaded nanoscale zero-valent iron composite material proves that the nanoscale zero-valent iron is uniformly dispersed on the surface of the biochar, so that the agglomeration of the iron is effectively reduced.

[58] The three materials are used for adsorption research of uranium in an aqueous solution, the use amount of the uranium solution is 20 mL, the initial concentration of the uranium solution is 20 ppm, and the following optimal adsorption conditions are obtained, specifically, the adsorption effect of the biochar is best under the condition that the adding amount is 0.018 g, pH is 5 and the time 1s 180 min, the adsorption capacity is 10.53 mg/L, and the adsorption rate is 47.38%; the adsorption effect of the nanoscale zero-valent iron is best under the condition that the adding amount is 0.025 g, pH is 3, the time is 60 min, the adsorption capacity is 15.96 mg/g, and the adsorption rate is 99.76%; and the adsorption rate reaches 96%, and the adsorption amount is 19.2 mg/L under the condition that the adding amount of the biochar-loaded zero-valent iron is 0.01 g, pH is 5, and the reaction time is 120 min. Experimental results show that the three materials are easier to react with uranium under acidic conditions, specifically, the three materials can better adsorb uranium under acidic conditions.

[59] The above is only a preferred embodiment of the present disclosure, and is not intended to limit the present disclosure in any form.

It should be noted that, for a person of ordinary skill in the art, several improvements and modifications may be made without departing from the principle of the present disclosure, and these improvements and modifications should also be regarded as the protection scope of the present disclosure.

Claims

Conclusions

A production method of a biocoal-loaded nanoscale zero-valent iron composite material, characterized in that it comprises the steps of: calcining rice husk to obtain rice husk biocoal; mixing FeSO3 7H:0, an aqueous ethanol solution and the rice husk biocoal to obtain a mixture, and mixing the mixture with a KBH4 solution to perform a redox reaction to obtain the biocoal-loaded nanoscale zero-valent iron composite material.

The preparation method according to claim 1, wherein the calcination temperature is 700 DEG C and the time is 2.0 hours.

The preparation method according to claim 1, wherein a volume ratio of ethanol to water in the aqueous ethanol solution is 3:7.

The preparation method according to claim 1, wherein the redox reaction ends without hydrogen generation in a reaction system.

The biocoal-loaded nanoscale zero-valent iron composite material prepared by the preparation method of any one of claims 1 to 4, wherein the composite material comprises rice husk biocoal and nanoscale zero-valent iron, and wherein the nanoscale zero-valent iron is loaded on the surface of the rice husk biocoal.

The preparation method according to claim 5, wherein a mass ratio of the rice husk biocoal to the nanoscale zero-valent iron is 2:1.

The use of the biocoal-loaded nanoscale zero-valent iron composite material in adsorbing uranium elements in water according to claim 5 or 6.