Hydrogen sustained-release particles based on charcoal-magnesium hydride and preparation method thereof

Abstract

The invention discloses hydrogen slow-release particles based on biochar-magnesium hydride and a preparation method of the hydrogen slow-release particles. The hydrogen slow-release particles are formed by mixing magnesium hydride with the purity larger than 99%, biochar and an adhesive. The high-purity magnesium hydride finished product is adopted, the environment heavy metal pollution repairing function of the biochar is utilized, the hydrogen release time in magnesium hydride is prolonged, crop growth and environment pollution repairing are promoted through controllable slow-release hydrogen, and crop growth is promoted.

Description

Technical Field

[0001] The present invention relates to a technology in the field of environmental engineering, specifically a biochar-magnesium hydride-based hydrogen slow-release particle and a preparation method thereof. Background Art

[0002] Magnesium hydride (MgH2) has the potential for agricultural applications due to its high hydrogen storage capacity (7.6%), low cost, and ease of operation. However, its hydrogen release cycle is short (up to 35 hours) and is susceptible to the formation of an insoluble layer of Mg(OH)2 or acidic environments, limiting its slow-release capacity. Therefore, the development of slow-release materials is urgently needed to extend the hydrogen supply cycle and meet the needs of field crops. Summary of the Invention

[0003] In response to the above-mentioned deficiencies in the prior art, the present invention proposes a biochar-magnesium hydride-based hydrogen slow-release particle and a preparation method thereof. High-purity magnesium hydride products are directly used, and the environmental heavy metal pollution remediation function of biochar is utilized to extend the release time of hydrogen in magnesium hydride. The controlled slow release of hydrogen promotes crop growth and environmental pollution remediation, thereby promoting crop growth.

[0004] The present invention is achieved through the following technical solutions:

[0005] The invention relates to a biochar-magnesium hydride-based hydrogen slow-release particle, which is composed of a mixture of magnesium hydride with a purity greater than 99%, biochar and a binder.

[0006] The biochar is crushed and carbonized crop straw, agricultural waste, livestock and poultry manure and / or kitchen waste, which includes but is not limited to corn straw, wheat straw, wood powder, peanut shells, cotton shells, rice husks, etc., and its usage is 16.7-100 times the mass of magnesium hydride.

[0007] The adhesive is prepared by mixing ethyl cellulose and anhydrous ethanol or methanol in a ratio of 1:6.7-1:80 g / mL, heating and stirring in a 60° C. water bath for 1.5 hours, and the amount used satisfies the mass ratio of the adhesive to the biochar-magnesium hydride mixture of 1:1.

[0008] The sustained-release particles are spherical particles with a diameter of 2-3 mm.

[0009] The sustained-release particles have a specific surface area of ​​23.9045-30.9409 m² / g, a total pore volume of 0.020536-0.033713 cm³ / g, and an average adsorption pore diameter of 3.4364-4.3584 nm.

[0010] The present invention relates to a method for preparing the above-mentioned hydrogen slow-release particles, comprising:

[0011] Step 1) The crop straw is cleaned and air-dried, processed by a pulverizer, placed in a carbonization furnace, carbonized in an oxygen-deficient environment at 500° C. for 2-3 hours, and cooled to 25° C. to obtain biochar;

[0012] The bulk density of the biochar is in the range of 500-550 kg / m³.

[0013] Step 2) Mixing the magnesium hydride with the biochar obtained in step 1, and stirring using a rotary mixer for 1 hour to obtain a biochar-magnesium hydride mixture;

[0014] The particle size of the magnesium hydride is 50nm-100µm.

[0015] The weight ratio of the magnesium hydride to the biochar is preferably 1:20.

[0016] Step 3) Ethyl cellulose is mixed with anhydrous ethanol or methanol, and heated and stirred in a 60° C. water bath for 1.5 hours to prepare an adhesive;

[0017] Step 4) mixing the biochar-magnesium hydride mixture with the binder and stirring evenly to form a biochar-magnesium hydride adhesive;

[0018] Step 5) granulating the bonded product by an extrusion granulator to obtain granules with a diameter of 2-3 mm;

[0019] Step 6) The particles were placed in a 60° C. environment and dried for 2 hours to evaporate the solvent, thereby obtaining uniform hydrogen slow-release particles.

[0020] The present invention relates to an application based on the above-mentioned hydrogen slow-release particles, which are used for soil improvement and environmental remediation. Specifically, the slow-release particles are evenly spread or buried in strips in the cultivated layer (0-20 cm) of soil at a mass ratio of 1-5‰, and are fully mixed into the soil through shallow plowing.

[0021] The particles slowly release hydrogen when they meet water in the soil, effectively regulating the soil microenvironment and promoting the growth of crops. At the same time, the high specific surface area and porous structure of biochar can remove heavy metal ions (such as Cd 2+ 、Cu 2+ ) through physical adsorption and chemical complexation, reducing their activity and bioavailability, thereby achieving in situ remediation of contaminated soil. This method is suitable for ecological remediation of lightly and moderately contaminated cultivated land, such as farmland, mining areas, and sewage irrigation areas. It is simple to operate, environmentally friendly, and has good prospects for widespread application.

[0022] Technical Effects

[0023] The present invention disperses and embeds the hydrogen storage material magnesium hydride through biochar, effectively preventing the magnesium hydroxide generated during the reaction of magnesium hydride with water from forming a passivation layer on its surface, hindering subsequent reactions, while introducing a hydrophobic adhesive to construct a porous structure on the basis of structural molding, effectively delaying the direct contact between magnesium hydride and water, thereby achieving a hydrogen slow-release function at room temperature and forming a stable and controllable slow-release system. Compared with the prior art, the preparation process of the present invention is simple, the material source is wide, the cost is low, and the raw materials used are all environmentally friendly and have good ecological adaptability; secondly, the hydrogen release cycle is significantly extended, and the slow-release time can reach more than 15 days, which can meet the continuous hydrogen supply demand during the crop growth cycle for a long time, and help promote crop growth and improve stress resistance; in addition, the biochar used not only constructs a pore structure that is conducive to slow release, but also has good heavy metal adsorption capacity, which can effectively reduce Cd in the soil. 2+ 、Cu 2+ The concentration of pollutants can be reduced to further alleviate environmental stress, and it has the dual functions of increasing agricultural production and remediating pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the effect of Example 1;

[0025] Figure 2 This is a schematic diagram of the effect of Example 2;

[0026] Figure 3 This is a schematic diagram of the effect of Example 3;

[0027] Figure 4 This is the XRD characteristic analysis diagram of the sustained-release particles in the embodiment;

[0028] Figure 5 This is the SEM characteristic analysis diagram of the particles in the embodiment;

[0029] Figure 6 is the hydrogen release curve of the example particles in aqueous solution;

[0030] Figure 7 For example, the particles are Cd 2+ Adsorption curve of

[0031] Figure 8 For example, the particles are Cu 2+ The adsorption curve. DETAILED DESCRIPTION

[0032] Example 1

[0033] This embodiment relates to a method for preparing hydrogen slow-release particles based on biochar-magnesium hydride, comprising:

[0034] Step 1) The air-dried corn stalks are crushed and fed into a carbonization furnace for carbonization at 500°C in an oxygen-deficient environment for 2–3 hours. After carbonization, the corn stalks are naturally cooled to 25°C and crushed again to a bulk density of approximately 514 kg / m³ to obtain biochar raw material.

[0035] Step 2) Magnesium hydride and biochar were placed in a rotary mixer and mixed for 1 hour at a mass ratio of 1:100, 1:50, and 1:16.7 to prepare three biochar-magnesium hydride mixtures with different ratios.

[0036] Step 3) Ethyl cellulose (g) and anhydrous ethanol or methanol (mL) were added in a ratio of 1:40 in a 60°C water bath and stirred and heated for 1.5 hours to prepare an ethyl cellulose adhesive.

[0037] Step 4) The adhesive and the biochar-magnesium hydride mixture are evenly mixed in a mass ratio of 1:1 and stirred to form a stable adhesive system.

[0038] Step 5) The bonded material is fed into an extrusion granulator to produce biochar-magnesium hydride particles with a diameter of 2–3 mm.

[0039] Step 6) The granules obtained by granulation are placed in a dryer and dried at 60° C. for 12 hours to finally obtain finished hydrogen slow-release granules with different bonding properties.

[0040] like Figure 1 Figure 2 shows the hydrogen release behavior of biochar-magnesium hydride slow-release particles with three different magnesium hydride addition ratios (0.01, 0.02, and 0.06, respectively). Under the same preparation viscosity conditions, the hydrogen release period of all three particles was 168 hours. The experimental results show that the higher the magnesium hydride addition concentration, the greater the amount of hydrogen released, showing a significant positive correlation. The total hydrogen release within 168 hours for the three ratio particles was approximately 14.2 mL / g (0.01), 28.6 mL / g (0.02), and 66.5 mL / g (0.06), respectively. Furthermore, within the first 48 hours of release, all three groups of samples exhibited a relatively fast hydrogen release rate, which then slowed down and entered a plateau phase between 48 and 168 hours, demonstrating a typical "fast-slow" dual-stage slow-release characteristic.

[0041] Example 2

[0042] This embodiment relates to a method for preparing hydrogen slow-release particles based on biochar-magnesium hydride, comprising:

[0043] Step 1) crush the air-dried corn stalks and send them into the carbonization furnace for carbonization at 500℃ in a low-oxygen environment for 2-3 hours. After carbonization, cool to 25℃ and crush to a bulk density of 514kg / m 3 , and obtain biochar raw materials.

[0044] Step 2) Magnesium hydride and biochar were mixed in a rotary mixer at a ratio of 1:20 for 1 hour to prepare a uniform biochar-magnesium hydride mixture.

[0045] Step 3) Ethyl cellulose (g) was mixed with anhydrous ethanol or methanol (mL) in ratios of 1:80, 1:40, 1:20, 1:10, and 1:6.7, and heated in a 60°C water bath with stirring for 1.5 hours to obtain adhesives with different degrees of adhesion.

[0046] Step 4) The adhesive prepared in step 3) is mixed with the mixture prepared in step 2) in a ratio of 1:1, and stirred evenly to form a biochar-magnesium hydride adhesive.

[0047] Step 5) The binder obtained in step 4) is placed in an extrusion granulator for granulation to obtain biochar-magnesium hydride particles with a diameter of 2-3 mm.

[0048] Step 6) The granules obtained in step 5) are placed in a dryer and dried at 60° C. for 12 hours to obtain the final sustained-release granules with different viscosities.

[0049] like Figure 2 As shown, the biochar-magnesium hydride slow-release particles prepared in this embodiment were placed in a pH 7 aqueous solution for hydrogen release testing. The results showed that the overall release period was between 168 and 360.6 hours. All groups of particles showed a typical "fast release-slow release" dual-stage release pattern, that is, the hydrogen release rate was faster in the early stage (0-100 hours), and then entered a plateau phase with a slow release rate. Among them, the low viscosity groups (0.625 and 1.25) had a lower amount of binder added, a loose particle structure, high permeability, a faster hydrogen release rate, and a shorter release period. Both completed the release within 168 hours, and there was no obvious dose effect between the two. In the higher viscosity groups, as the binder ratio increased, the release period showed a significant dose dependence: 264.5 hours for the 2.5 group, 300.5 hours for the 5 group, and 360.6 hours for the 7.5 group, showing excellent slow-release performance.

[0050] Comprehensive analysis shows that a higher binder dosage results in a denser particle structure, which in turn reduces the specific surface area, pore volume, and average pore diameter. This restricts hydrogen diffusion channels, thereby extending the release cycle and improving release controllability. Therefore, this type of sustained-release material offers advantages such as smooth release, adjustable cycles, and strong adaptability, providing important material support for achieving the continuous supply and precise control of hydrogen in agricultural applications.

[0051] Example 3

[0052] In order to evaluate the slow-release hydrogen supply regulation effect of magnesium hydride slow-release particles on plant growth under cadmium-copper combined pollution conditions, a hydroponic simulation system was constructed for comparative experiments. The experiment set up three treatment groups: ① blank control group (CK), without adding any materials, only using Cd-containing 2+ 0.5mg / L and Cu 2+ 2.5 mg / L contaminated Hoagland nutrient solution; ② A magnesium hydroxide control group, using the same process as for magnesium hydride granules, replaced the magnesium hydride raw material with magnesium hydroxide to produce granules; ③ A magnesium hydride slow-release granule group, supplemented with magnesium hydride slow-release granules with a viscosity grade of 5. Test plants were 14-day-old Shanghai Qing seedlings. Each treatment was placed in a 2L volume of 0.5x the concentration of Hoagland nutrient solution and cultured hydroponically in an artificial climate chamber under conditions of 16 hours of light per day, 25°C, and 60% relative humidity. The treatment period was 14 days.

[0053] like Figure 3 As shown, in Cd 2+ (0.5ppm)-Cu 2+ Under the combined stress conditions of (2.5ppm), 14-day-old Shanghai Qing seedlings were treated with different treatments and their growth performance was observed. The results showed that there were significant differences among the three groups. The seedlings in the CK group (no added materials) showed typical stress symptoms such as growth inhibition, yellowing of leaves, and short and sparse root system, with a fresh weight of only 22.68g; the growth of plants in the magnesium hydroxide control group improved, with slightly stretched leaves and more developed root system than CK, and the fresh weight increased to 28.08g, indicating that it has a buffering effect on the toxicity of some heavy metals; and the seedlings in the magnesium hydride slow-release granule group had the best overall performance, with dark green leaves, high leaf expansion, thick root system, abundant lateral roots, and a fresh weight of 36.65g. While alleviating the combined heavy metal stress, this treatment significantly promoted the coordinated growth of the aboveground part and the root system, verifying the dual regulatory effect of slow-release hydrogen supply on plant growth promotion and stress resistance, and providing an effective solution for coping with heavy metal stress in facility agriculture.

[0054] like Figure 4 As shown, the sustained-release particles prepared in this embodiment were subjected to XRD characteristic analysis. Different sustained-release particles showed obvious diffraction peaks. After comparison with the element standard cards in the Jade software, it was identified that the substance corresponding to these diffraction peaks was magnesium hydride, that is, magnesium hydride was successfully loaded on the sustained-release particles.

[0055] like Figure 5As shown in Table 1, the slow-release particles prepared in this embodiment were subjected to SEM characterization analysis and BET pore size analysis. SEM observation showed that there were many pores of different sizes on the surface of the slow-release particles, which ensured excellent controlled-release performance and the ability to slowly release hydrogen. The BET analysis results showed that the characteristic indicators of particles with different viscosities were significantly different. The BET surface area of ​​the particles in group L was 30.9409 m² / g, the total pore volume of single-point adsorption was 0.033713 cm³ / g, and the average adsorption pore diameter was 4.3584 nm. As the viscosity increased, the BET surface area of ​​the particles in group M decreased to 28.6025 m² / g, the total pore volume was 0.028144 cm³ / g, and the average adsorption pore diameter was 3.9359 nm; while the BET surface area of ​​the particles in group H further decreased to 23.9045 m² / g, the total pore volume was 0.020536 cm³ / g, and the average adsorption pore diameter was 3.4364 nm. These results indicate that the surface area, pore volume, and adsorption pore size of the particles gradually decrease with increasing viscosity, ensuring excellent controlled-release properties and slow release of hydrogen.

[0056] Table 1

[0057] like Figure 6 As shown, the hydrogen slow-release particles prepared in this embodiment were placed in an aqueous solution with a pH of 7 to observe their hydrogen release cycle, and the release cycle ranged from 264.5 to 360.6 hours. Among them, the release cycle of group L was 264.5 hours, that of group M was 300.5 hours, and that of group H was 360.6 hours. The results show that the level of binder addition significantly affects the hydrogen release cycle; the higher the amount of binder added, the smaller the specific surface area, pore volume and adsorption pore size of the particles, which leads to an extension of the hydrogen release cycle. At the same time, the hydrogen slow-release particles of the present invention can slowly and steadily release hydrogen, effectively controlling its release rate.

[0058] like Figure 7 As shown, the hydrogen slow-release particles prepared in this example were placed in 250 mg / L Cd 2+ Investigate the Cd 2 + Dynamic adsorption curve, Cd 2+ The adsorption capacity of the three particles is 47.24-82.58 mg / g. 2+ The adsorption capacities of the binders were 82.58 mg / g(L), 72.88 mg / g(M), and 47.24 mg / g(H), respectively. 2+ Adsorption capacity, the lower the amount of binder added, the larger the specific surface area, pore volume and adsorption pore size of the particles, and the Cd 2+ This shows that the hydrogen slow-release particles of the present invention can adsorb a large amount of Cd 2+, reducing its ecotoxicity, and is suitable for application in agricultural practices of soil improvement and pollution remediation.

[0059] like Figure 8 As shown, the amount of binder added significantly affects the Cu 2+ As the amount of binder decreases, the specific surface area, pore volume and adsorption pore size of the particles increase, thereby improving the adsorption capacity of Cu 2+ As shown in the figure, the hydrogen slow-release particles of the present invention have strong Cu 2+ Adsorption capacity, can effectively reduce Cu 2+ It has low ecotoxicity and has the potential for wide application in agricultural practices such as soil improvement and pollution remediation.

[0060] Compared with the prior art, the present invention has achieved significant improvement in the performance indicators of the slow-release hydrogen function, which is specifically reflected in the following aspects: by composite-encapsulating biochar and magnesium hydride for the first time and introducing a hydrophobic adhesive to construct a porous particle structure, it not only effectively avoids the inhibition of the Mg(OH)2 passivation layer on the hydrogenation reaction, but also significantly delays the direct contact between water and magnesium hydride, thereby achieving the unexpected technical effect of significantly extending the hydrogen release period from several hours of traditional materials to more than 15 days at room temperature and pressure. There is no report in the existing public literature that hydrogen storage particles with such structural design and material combination have such long-lasting controlled release performance, especially in the context of not relying on high temperature, catalyst or pressurized conditions. In addition, the porous biochar matrix designed by the present invention not only enhances the slow-release performance, but also synergistically achieves the control of Cd in the environment. 2+ 、Cu 2+ The efficient adsorption of heavy metals such as chlorinated polyols (Citric Acid) and chlorinated polyols (Citric Acid) endows the material with new capabilities in environmental remediation. This series of unexpected combined effects cannot be achieved by simply splicing known materials, demonstrating the substantial technological advancement and significant creativity of the present invention in terms of structural design and functional integration.

[0061] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principles and purpose of the present invention. The scope of protection of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. All implementation schemes within its scope shall be subject to the constraints of the present invention.

Claims

1. A hydrogen slow-release particle based on biochar-magnesium hydride, characterized in that: It is composed of a mixture of magnesium hydride with a purity greater than 99%, biochar and a binder.

2. The hydrogen slow-release particles based on biochar-magnesium hydride according to claim 1, characterized in that: The biochar is pulverized and carbonized crop straw, agricultural waste, livestock and poultry excrement and / or kitchen waste, and its usage is 16.7-100 times the mass of magnesium hydride.

3. The hydrogen slow-release particles based on biochar-magnesium hydride according to claim 1, characterized in that: The adhesive is prepared by mixing ethyl cellulose and anhydrous ethanol or methanol in a ratio of 1:6.7-1:80 g / mL, and heating and stirring in a 60° C. water bath for 1.5 hours.

4. The hydrogen slow-release particles based on biochar-magnesium hydride according to any one of claims 1 to 3, characterized in that: The amount of the adhesive is such that the mass ratio of the adhesive to the biochar-magnesium hydride mixture is 1:

1.

5. A method for preparing the hydrogen slow-release particles based on biochar-magnesium hydride according to any one of claims 1 to 4, characterized in that: Air-dried crop straw is crushed, carbonized, and crushed again to obtain a biochar raw material, which is then mixed with magnesium hydride to obtain a biochar-magnesium hydride mixture. The mixture is further mixed and stirred with a binder prepared by ethyl cellulose and anhydrous ethanol or methanol to form a stable bonding system. The mixture is then extruded, granulated, and dried to obtain hydrogen slow-release particles with a specific surface area of ​​23.9045-30.9409 m² / g, a total pore volume of 0.020536-0.033713 cm³ / g, and an average adsorption pore diameter of 3.4364-4.3584 nm.

6. The method according to claim 5, wherein: The extrusion granulation produces spherical particles with a diameter of 2-3 mm.

7. An application of the hydrogen slow-release particles according to any one of claims 1 to 4 or the hydrogen slow-release particles prepared by the method according to claim 5 or 6, characterized in that: It is used for soil improvement and environmental remediation. Specifically, the slow-release particles are evenly spread or buried in strips in the cultivated layer of soil at a mass ratio of 1-5‰, and are fully mixed into the soil through shallow plowing.

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