Carbon-based calcium peroxide material with slow-release oxygen function and preparation method and application thereof

Abstract

The present application belongs to the technical field of biochar oxygen-releasing materials, and particularly relates to a carbon-based calcium peroxide material with oxygen-releasing function, a preparation method and application thereof. Silicon-rich agricultural waste is converted into biochar through controllable pyrolysis, the pore structure of the biochar is regulated, mesoporous biochar is prepared, the mesoporous biochar is modified by phosphates to prepare phosphorus-rich biochar, and finally, the phosphorus-rich biochar is combined with calcium peroxide to obtain the carbon-based calcium peroxide material with oxygen-releasing function. The material has excellent oxygen-releasing performance and can continuously and stably release oxygen into the soil. Meanwhile, the phosphorus-rich biochar can also provide phosphorus nutrients to promote the growth of rice. The material can be widely applied to the improvement of gleyed paddy fields, effectively solves the problem of soil oxygen deficiency, improves soil fertility and rice yield, and has the characteristics of environmental protection, economy and high efficiency.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of biochar oxygen-releasing materials, and particularly relates to a carbon-based calcium peroxide material with oxygen-releasing function and a preparation method and application thereof. BACKGROUND

[0002] Paddy soils with gleying are widely distributed in southern China, accounting for about one-third of the total area of paddy fields, especially in Hunan, Hubei and Guangdong provinces. Although these soils are rich in organic matter and nutrients, the oxygen content in the soil is reduced due to long-term waterlogging, resulting in a decrease in oxidation-reduction potential and accumulation of a large amount of harmful reducing substances. These substances not only destroy the biological activity of the soil and reduce the availability of nutrients, but also inhibit the growth of rice and severely limit the yield of rice. Traditional improvement measures, such as water conservancy construction and land use adjustment, can solve the problem, but often have high costs and short-term effects. Emerging improvement methods, such as the application of calcium peroxide-based slow-release oxygen materials to increase the dissolved oxygen content in gleyed paddy fields, can accurately control the oxygen supply in the soil, but the preparation process is complex, the cost is high, and it may have adverse effects on the soil environment. Therefore, it is necessary to find an economical and environmentally friendly improvement method to improve the soil quality and rice yield of gleyed paddy fields.

[0003] A large amount of agricultural waste is generated in China every year, which can be converted into biochar with environmental benefits and economic value through pyrolysis technology. Due to its large specific surface area, low density, high stability, strong adsorption capacity, excellent chemical stability, and resistance to microbial degradation, biochar has been widely used in agriculture and environmental protection. Recent studies have found that biochar can be used as a carrier for calcium peroxide, and its good chemical stability and large specific surface area can help to solve the problem of calcium peroxide agglomeration, thereby increasing its oxygen release capacity. At the same time, the hydrophobicity and porosity of biochar can also reduce the mass transfer efficiency of water and prolong the oxygen release time of calcium peroxide. Although mixing biochar with calcium peroxide or using biochar as a coating material can improve the oxygen release performance, this method may result in a large oxygen release capacity of calcium peroxide, but its effective utilization rate is not high. In particular, calcium hydroxide generated by the reaction of calcium peroxide with water can form a covering layer on the surface of calcium peroxide, hindering further reaction inside the calcium peroxide, thereby reducing its utilization efficiency. Therefore, it is an important topic to study how to effectively combine biochar with calcium peroxide to enhance the oxygen release performance of calcium peroxide and improve its utilization efficiency.

[0004] In the prior art, patent CN2016102291547 discloses a slow-release oxidant with calcium peroxide as a matrix and polyethylene as a coating and a preparation method, which can effectively solve the problem of oxygen release time of calcium peroxide in a gleization paddy field and improve the growth environment of rice in the gleization paddy field. However, in the production process of the slow-release oxidant, the granulation and coating steps will cause a loss of 8.3% of calcium peroxide, mainly due to its decomposition in water and high-temperature treatment. Large-scale industrial production may further increase the loss. In addition, the dimethylbenzene solvent used in production is toxic and carcinogenic, and the non-degradability of polyethylene may cause soil pollution and ecological problems. A paper entitled "Controlled synthesis of innovative carbon-based CaO2 materials with boosted oxygen release performance in the aqueous environment" discloses a new type of carbon-based calcium peroxide material as an oxygen release agent in the process of groundwater bioremediation. Although the modification of biochar significantly improves the mass fraction of calcium peroxide in the carbon-based calcium peroxide material, the oxygen release rate of the carbon-based calcium peroxide material prepared by the modified biochar is too fast compared with the oxygen release materials prepared by pure calcium peroxide and original biochar, which limits its slow-release oxygen capacity. SUMMARY

[0005] In view of the above problems, the purpose of the present application is to provide a carbon-based calcium peroxide material with slow-release oxygen function and its preparation method and application.

[0006] The technical content of the present application is as follows:

[0007] The present application provides a preparation method of a carbon-based calcium peroxide material with slow-release oxygen function, comprising the following steps:

[0008] 1) Preparation of mesoporous biochar

[0009] The silicon-rich biochar is mixed with Na2CO3 and K2CO3, and then calcined. After natural cooling to room temperature, it is taken out;

[0010] The amount of the silicon-rich biochar and Na2CO3 and K2CO3 is mixed according to the SiO2 content calculated from the Si content in the silicon-rich biochar, and according to the equimolar ratio of SiO2 content and Na2CO3 and K2CO3;

[0011] The calcination temperature is 800-1000℃, the heating rate is 20-30℃ / min, and the time is 150-200min;

[0012] The carbonized product is subjected to suction filtration and washing until the conductivity of the suction filtrate remains constant, then the solid obtained by suction filtration is soaked in a hydrochloric acid solution, the solid is collected by suction filtration and washed until the conductivity of the suction filtrate remains constant, and finally the solid is dried and sieved to obtain the mesoporous biochar;

[0013] The concentration of the hydrochloric acid solution is 3 mol / L;

[0014] The preparation of the silicon-rich biochar is as follows: selecting silicon-rich agricultural and forestry waste for calcination to obtain;

[0015] The silicon-rich agricultural and forestry waste includes one or more of rice husk, rice leaves, rice straw, reed, switchgrass, miscanthus, bamboo, and sugarcane residue;

[0016] The calcination temperature is 300-700°C, and the heating rate is 10-30°C / min;

[0017] 2) Preparation of phosphorus-rich biochar

[0018] The silicon-rich biochar and the mesoporous biochar are respectively placed in deionized water and stirred at room temperature, and then dried;

[0019] The phosphate particles include one of KH2PO4 and K2HPO4;

[0020] The mass ratio of the silicon-rich biochar, the mesoporous biochar, and the phosphate particles is 1:0.2;

[0021] The dried solid is calcined, naturally cooled to room temperature, and then the solid is collected by suction filtration, washed until the conductivity of the suction filtrate remains constant, and finally dried and sieved to obtain two kinds of phosphorus-rich biochar, denoted as PBC and PBC M ;

[0022] The calcination temperature is 200-300°C, the heating rate is 20-30°C / min, and the time is 100-150 min;

[0023] 3) Preparation of carbon-based calcium peroxide material

[0024] Nano calcium peroxide CaO2 and anhydrous ethanol are added to the phosphorus-rich biochar, mixed uniformly, oscillated, then dried to constant weight, and calcined;

[0025] The calcined product is cooled to room temperature, suctioned with cold deionized water (4°C) until the conductivity of the suction filtrate remains constant, then suctioned with anhydrous ethanol, the final solid is collected, dried to constant weight, and sieved to obtain carbon-based calcium peroxide materials CaO2@PBC and CaO2@PBC M ;

[0026] The mass ratio of the activated biochar to CaO2 is 2:1;

[0027] The temperature of the calcination is 200-300 DEG C, the temperature rising speed is 15-25 DEG C / min, and the time is 100-150 min;

[0028] The conductivity of the filtrate keeps constant until the relative deviation of the last two measured values is less than 1 %;

[0029] The preparation of the nano calcium peroxide CaO2 comprises the following steps:

[0030] The calcium salt, the ammonium salt and the dispersing agent are mixed, and the hydrogen peroxide is dropped in while stirring until the suspension changes from white to light yellow, and the pH value is adjusted;

[0031] The product is centrifuged and precipitated until the conductivity of the supernatant is basically unchanged, and then washed, so that the nano calcium peroxide is obtained;

[0032] The calcium salt comprises calcium chloride;

[0033] The ammonium salt comprises ammonium chloride and ammonia;

[0034] The dispersing agent comprises polyethylene glycol.

[0035] The application further provides the carbon-based calcium peroxide material prepared by the preparation method, and the application of the carbon-based calcium peroxide material in improving gley soil.

[0036] The beneficial effects of the application are as follows:

[0037] The application provides a preparation method of carbon-based calcium peroxide material with slow-release oxygen function, which is prepared from silicon-rich agricultural waste by controllable pyrolysis into biochar, avoids raw materials such as dimethylbenzene and polyethylene that may cause soil pollution and ecological problems, realizes the resource utilization of agricultural waste, then the pore structure of the biochar is regulated to prepare mesoporous biochar, the phosphorus-rich biochar is prepared by modifying the biochar with phosphates, and finally the carbon-based calcium peroxide material with slow-release oxygen function is obtained by compounding the calcium peroxide. The method optimizes the pyrolysis temperature-activator to construct mesoporous biochar with high specific surface area. The phosphorus-rich biochar can not only be used as slow-release phosphorus fertilizer, but also be used as a carrier of calcium peroxide, which can significantly improve the mass fraction and dispersity of calcium peroxide and avoid the agglomeration problem of calcium peroxide. The modification of the biochar with phosphates endows the biochar with rich phosphorus-containing functional groups to form a phosphorus-rich biochar carrier, which has the functions of slow-release of phosphorus fertilizer and stable fixation of CaO2. The finally prepared carbon-based calcium peroxide material has excellent slow-release oxygen performance and can continuously and stably release oxygen into the soil, and the phosphorus-rich biochar can also provide phosphorus nutrients to promote the growth of rice. The material can be widely applied to the improvement of gleization paddy fields, effectively solves the problem of soil oxygen deficiency, improves soil fertility and rice yield, and has the characteristics of environmental protection, economy and high efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 The mass fraction of CaO2 in the biochar-based oxygen release material;

[0039] Figure 2 The oxygen release kinetics curve of CaO2 and the biochar-based oxygen release material;

[0040] Figure 3 The first-order kinetics curve of the change of dissolved oxygen concentration with time, and the solid line represents the fitting value of the data. DETAILED DESCRIPTION

[0041] The application will be further described in detail through specific implementation examples and the description of the drawings, and it should be understood that these examples are only used to illustrate the application and are not used to limit the protection scope of the application, and various equivalent modifications of the application made by those skilled in the art after reading the application all fall within the scope defined by the claims attached to the application.

[0042] Unless otherwise specified, all raw materials and reagents of the application are conventional market raw materials and reagents.

[0043] Example 1

[0044] A preparation method of carbon-based calcium peroxide material with slow-release oxygen function

[0045] 1) Preparation of nano calcium peroxide

[0046] Take 20 g CaCl2dissolved in 200 mL deionized water, add 75 mL of 1 mol / L concentration of NH3·H2O and 75 mL of polyethylene glycol 200, magnetic stirring for 10 min (500 rpm). With peristaltic pump at a speed of 1 mL / min dropwise add 65 mL of 30% concentration of H2O2, stirring, until the suspension from white to light yellow. Add 1 mol / L of NH3·H2O, adjust the pH to 10.

[0047] 4000 rpm centrifugation for 5 min, carefully pour the supernatant, add 40 mL of deionized water at about 4 ℃ to the precipitate, stir evenly, centrifuge as above, continue to operate 3-5 times, until the conductivity of the supernatant is basically unchanged (relative deviation of two measured values is less than 1%). Continue to add 40 mL of anhydrous ethanol, stir and centrifuge as above, repeat the operation 3 times to remove residual H2O. Collect the residue, dry at 60 ℃ overnight to obtain CaO2.

[0048] 2) Preparation of silicon-rich biochar

[0049] The washed, dried and crushed rice husk is passed through a 50-mesh sieve for use. The rice husk is loaded into a 300-mL ceramic crucible and transferred to a muffle furnace, heated to 500 ℃ at a rate of 20 ℃ / min, and kept for 120 min. After natural cooling to room temperature, it is taken out and passed through a 60-mesh sieve to obtain silicon-rich biochar, denoted as BC.

[0050] 3) Preparation of mesoporous biochar

[0051] The silicon-rich biochar, Na2CO3 and K2CO3 are mixed uniformly in a mass ratio of 1:0.56:0.74 and then placed in a nickel crucible, covered with a lid and transferred to a muffle furnace, heated to 900 ℃ at a rate of 20 ℃ / min and kept for 180 min. After natural cooling to room temperature, it is taken out.

[0052] The carbonized product is washed with deionized water by filtration until the conductivity of the filtrate remains constant. Then the solid obtained by filtration is soaked in a 3 mol / L hydrochloric acid solution, and the solid is collected and washed by filtration with deionized water until the conductivity of the filtrate remains constant. Finally, the solid is dried at 60 ℃ and passed through a 60-mesh sieve to obtain mesoporous biochar, denoted as BC. M ;

[0053] 4) Preparation of phosphorus-rich biochar

[0054] 10 g of BC and BC M are respectively placed in 250 mL of deionized water, and stirred magnetically at room temperature for 24 h, and dried in an oven at 60 ℃.

[0055] The BC and BC ME1 : 0.2 by mass to phosphate particles;

[0056] The dried solid was loaded into a ceramic crucible and transferred to a muffle furnace, and heated at 20°C / min to 250°C for 120 min. After natural cooling to room temperature, the solid was collected by suction filtration, washed until the conductivity of the filtrate remained constant, and finally dried at 60°C. The phosphorus-rich biochar was obtained by sieving through a 60-mesh screen, and was denoted as PBC and PBC M .

[0057] 5) Preparation of carbon-based calcium peroxide material

[0058] 2 g of BC (PBC or PBC M ) was placed in a 100-mL beaker, and 1 g of CaO2 was added. An appropriate amount of anhydrous ethanol was added to the mixture to form a homogenate. After shaking on a shaker for 30 min (200 rpm), the mixture was dried at 60°C to constant weight. The mixture was loaded into a 25-mL ceramic crucible and transferred to a muffle furnace, and heated at 20°C / min to 250°C for calcination. After cooling to room temperature, the mixture was removed. Filtration was performed with cold (about 4°C) deionized water (100 mL each time) until the conductivity of the filtrate remained essentially unchanged (the relative deviation of two measured values was less than 1%). Then, 50 mL of anhydrous ethanol was used for filtration three times as above to remove residual H2O. The solid was collected and dried at 60°C to constant weight. The powder was sieved through a 60-mesh screen and denoted as CaO2@BC (CaO2@PBC or CaO2@PBC M ).

[0059] Example 2

[0060] A method for preparing a carbon-based calcium peroxide material with slow-release oxygen function

[0061] 1) Preparation of nano calcium peroxide

[0062] 25 g of CaCl2 was dissolved in 200 mL of deionized water, and 85 mL of 1 mol / L NH3·H2O and 80 mL of polyethylene glycol 200 were added. The mixture was stirred magnetically for 10 min (500 rpm). 70 mL of 30% H2O2 was added dropwise at a rate of 1 mL / min using a peristaltic pump, and the mixture was stirred until the suspension changed from white to light yellow. Then, 1 mol / L NH3·H2O was added to adjust the pH to 10.

[0063] 4000rpm under centrifugal force for 5 min, carefully pour off the supernatant, add 40 mL of deionized water at about 4 ℃ to the precipitate, stir evenly, centrifuge as above, continue to operate 3-5 times until the conductivity of the supernatant is basically unchanged (the relative deviation of two measured values is less than 1%). Continue to add 50 mL of anhydrous ethanol, stir as above and centrifuge, repeat the operation 3 times to remove the residual H2O. Collect the residue, dry at 60 ℃ overnight to obtain CaO2.

[0064] 2) Preparation of silicon-rich biochar

[0065] The washed, dried and crushed bamboo canes are sieved through a 50-mesh sieve for use. The bamboo canes are loaded into a 300-mL ceramic crucible and transferred to a muffle furnace, heated to 700 ℃ at a rate of 15 ℃ / min, and kept for 100 min. After natural cooling to room temperature, it is taken out and sieved through a 60-mesh sieve to obtain silicon-rich biochar, denoted as BC.

[0066] 3) Preparation of mesoporous biochar

[0067] The silicon-rich biochar, Na2CO3 and K2CO3 are mixed uniformly according to a mass ratio of 1:0.46:0.61 and then placed in a nickel crucible, covered with a lid and transferred to a muffle furnace, heated to 800 ℃ at a rate of 25 ℃ / min and kept for 200 min. After natural cooling to room temperature, it is taken out.

[0068] The carbonized product is washed by deionized water filtration until the conductivity of the filtrate remains constant. Then the solid obtained by filtration is soaked in a 3 mol / L hydrochloric acid solution, and the solid is collected by deionized water filtration and washed until the conductivity of the filtrate remains constant. Finally, the solid is dried at 60 ℃ and sieved through a 60-mesh sieve to obtain mesoporous biochar, denoted as BC. M ;

[0069] 4) Preparation of phosphorus-rich biochar

[0070] 10 g of BC and BC M are respectively placed in 250 mL of deionized water, and magnetically stirred at room temperature for 24 h, and dried in an oven at 60 ℃.

[0071] The mass ratio of the BC and BC ME to the phosphate particles is both 1:0.2.

[0072] The dried solid is loaded into a ceramic crucible and transferred to a muffle furnace, heated to 280 ℃ at a rate of 20 ℃ / min and kept for 100 min. After natural cooling to room temperature, the solid is collected by filtration and washed until the conductivity of the filtrate remains constant. Finally, the solid is dried at 60 ℃ and sieved through a 60-mesh sieve to obtain phosphorus-rich biochar, denoted as PBC and PBC M , respectively.

[0073] 5) Preparation of carbon-based calcium peroxide material

[0074] 2g BC (PBC or PBC M ) was added into 100 mL beaker, 1g CaO2 was added. Appropriate amount of anhydrous ethanol was added to make it into homogenate. After shaking for 30 min (200 rpm), it was dried at 60 ℃ until constant weight. The mixture was loaded into 25 mL ceramic crucible and transferred into muffle furnace, heated to 300 ℃ at 15 ℃ / min, and calcined for 100 min. After cooling to room temperature, it was taken out. Filtration was performed with cold (about 4 ℃) deionized water (100 mL / time) until the conductivity of filtrate was basically unchanged (relative deviation of two measured values was less than 1%). Then, 50 mL of anhydrous ethanol was used for filtration for 3 times to remove residual H2O. The solid was collected and dried at 60 ℃ until constant weight. It was crushed through 60 mesh sieve and recorded as CaO2@BC (CaO2@PBC or CaO2@PBC M ).

[0075] Example 3

[0076] Preparation method of carbon-based calcium peroxide material with slow-release oxygen function

[0077] 1) Preparation of nano calcium peroxide

[0078] 30g CaCl2 was dissolved in 250 mL deionized water, 90 mL of 1 mol / L NH3·H2O and 85 mL of polyethylene glycol 200 were added, and magnetic stirring was performed for 10 min (500 rpm). 80 mL of 30% H2O2 was added dropwise at a speed of 1 mL / min, and stirring was performed until the suspension changed from white to light yellow. 1 mol / L NH3·H2O was added to adjust the pH to 10.

[0079] Centrifugation was performed at 4000 rpm for 5 min, and the supernatant was carefully poured off. 40 mL of 4 ℃ deionized water was added to the precipitate, and after stirring, centrifugation was performed as above, and the operation was continued for 3-5 times until the conductivity of the supernatant was basically unchanged (relative deviation of two measured values was less than 1%). 55 mL of anhydrous ethanol was continuously added, and after stirring and centrifugation, the operation was repeated for 3 times to remove H2O in the residue. The residue was collected and dried at 60 ℃ overnight to obtain CaO2.

[0080] 2) Preparation of silicon-rich biochar

[0081] The washed, dried and crushed switchgrass was passed through a 50-mesh sieve for use. The switchgrass was loaded into a 300-mL porcelain crucible and transferred to a muffle furnace, and was heated to 400°C at a rate of 25°C / min, and was kept for 150 min. After natural cooling to room temperature, the product was taken out and passed through a 60-mesh sieve to obtain silicon-rich biochar, denoted as BC;

[0082] 3) Preparation of mesoporous biochar

[0083] The silicon-rich biochar, Na2CO3 and K2CO3 were mixed uniformly at a mass ratio of 1:0.32:0.42, and were placed in a nickel crucible, and were transferred to a muffle furnace, and were heated to 1000°C at a rate of 30°C / min, and were kept for 150 min. After natural cooling to room temperature, the product was taken out.

[0084] The carbonized product was washed by deionized water filtration until the conductivity of the filtrate remained constant. Then the solid obtained by filtration was soaked in a 3 mol / L hydrochloric acid solution, and was collected by deionized water filtration and washed until the conductivity of the filtrate remained constant. Finally, the solid was dried at 60°C and passed through a 60-mesh sieve to obtain mesoporous biochar, denoted as BC M .

[0085] 4) Preparation of phosphorus-rich biochar

[0086] 10 g of BC and BC M were respectively placed in 250 mL of deionized water, and were magnetically stirred at room temperature for 24 h, and were dried in an oven at 60°C.

[0087] The mass ratio of the BC and BC ME to the phosphate particles was 1:0.2.

[0088] The dried solid was loaded into a porcelain crucible and transferred to a muffle furnace, and was heated to 200°C at a rate of 30°C / min, and was kept for 150 min. After natural cooling to room temperature, the solid was collected by filtration and washed until the conductivity of the filtrate remained constant. Finally, the solid was dried at 60°C and passed through a 60-mesh sieve to obtain phosphorus-rich biochar, denoted as PBC and PBC M .

[0089] 5) Preparation of carbon-based calcium peroxide material

[0090] 2 g of BC (PBC or PBC M) In a 100 mL beaker, 1 g of CaO2 was added. An appropriate amount of absolute ethanol was added to the mixture to form a slurry. After shaking for 30 min (200 rpm) on a shaker, it was dried at 60°C to constant weight. The mixture was loaded into a 25 mL ceramic crucible and transferred to a muffle furnace, which was heated to 200°C at a rate of 25°C / min and held for 150 min for calcination. After cooling to room temperature, it was removed. Filtration was performed with cold (about 4°C) deionized water (100 mL / time) until the conductivity of the filtrate was essentially unchanged (relative deviation of two measured values was less than 1%). Then, 50 mL of absolute ethanol was used to perform the same filtration three times to remove residual H2O. The solid was collected and dried at 60°C to constant weight. It was ground through a 60-mesh sieve and recorded as CaO2@BC (CaO2@PBC or CaO2@PBC M ).

[0091] The following tests were performed using Example 1 as a representative case:

[0092] 1. Elemental analysis

[0093] Elemental analysis was performed on the prepared biochar materials, and the results are shown in Table 1:

[0094] Table 1 Elemental content of biochar materials

[0095]

[0096]

[0097] As can be seen from Table 1, the phosphorus content of PBC material modified by phosphate only increased slightly from 0.09% to 0.11%, indicating that the conventional impregnation method has limited efficiency for phosphorus loading. However, the PBC M material after activation treatment exhibits significant elemental restructuring characteristics: the oxygen content is significantly increased compared to BC and PBC, which is due to the deep oxidation and restructuring of rice husk carbon during the activation of carbonates. Hydrocarbons and surface oxygen-containing functional groups (carboxyl, hydroxyl, etc.) undergo oxidative cleavage under the catalysis of K2CO3 / Na2CO3, forming a more abundant oxidized carbon skeleton. At the same time, the activation process leads to a significant decrease in the silicon content from 14.95% to 0.02%. The selective removal of siliceous minerals effectively reduces the physical barrier effect of non-carbon components on the pore structure of the material. It is worth noting that the phosphorus content of PBC M (4.72%) is significantly higher than that of BC (0.09%) and PBC (0.11%), confirming that the activation process achieves stable enrichment of phosphorus elements through the synergistic effect of carbon matrix oxidation and phosphate anchoring.

[0098] 2. Structure analysis

[0099] Specific surface area and pore tests were performed on the prepared biochar materials, and the results are shown in Table 2:

[0100] Table 2. Specific surface area and porosity properties of biochar materials

[0101]

[0102] As shown in Table 2, the pore parameters of BC, PBC and PBCM show significant differences. Compared with the original biochar (BC), the PBC material shows significant improvement in key pore parameters such as specific surface area (increased from 7.92 m 2 / g to 79.6712 m 2 / g), total pore volume (increased from 0.01322 cm 3 / g to 0.049377 cm 3 / g), and mesopore volume (increased from 0.008123 cm 3 / g to 0.019294 cm 3 / g). This phenomenon can be attributed to the elution of surface soluble substances and weakly bound functional groups during the loading of phosphates, effectively exposing the internal pores of the biochar.

[0103] PBC activated by carbonates M , with a specific surface area further jumping to 786.85 m 2 / g and a mesopore volume of 0.259 cm 3 / g (accounting for 48.8%). The pore evolution mechanism involves a multi-step reaction: at high temperatures, SiO2 reacts with carbonates to form soluble silicates (K2SiO3, Na2SiO3) and release CO2 gas, followed by the reaction of CO2 with the carbon matrix to generate CO gas, thus forming a rich mesoporous network inside the material. This multi-step activation process not only regulates the pore size distribution, but also significantly improves the specific surface area and adsorption performance of the material by selectively removing non-carbon components.

[0104] 3. The ability of biochar to load CaO2 was evaluated using the potassium permanganate titration method. 0.10 g of CaO2@biochar was placed in a 100 mL triangular flask, 20 mL of deionized water was added, and it was stirred thoroughly to disperse it. 10 mL of 2 mol / L sulfuric acid and 1 mL of 0.05 mol / L manganese sulfate solution were added, and it was stirred at 100 rpm for 5 min. It was filtered with a 0.45 um filter membrane. The filtrate was titrated with 0.02 mol / L potassium permanganate standard solution, and the volume of potassium permanganate solution consumed was recorded.

[0105] The formula for calculating the mass fraction of CaO2 is as follows:

[0106]

[0107] Wherein, is the mass fraction of CaO2 (%); and Molar concentration (mol / L) and volume (L) of KMnO4, respectively; Molar mass of CaO2(72.08 g / mol); m is the mass of CaO2@PBC (g).

[0108] By Figure 1 It can be seen that the mass fraction of CaO2 loading of CaO2@BC, CaO2@PBC and CaO2@PBCM presents a significant gradient difference, and the value increases with the deepening of the modification degree of biochar. The gradient improvement of this loading capacity is closely related to the synergistic evolution of the element composition and structural characteristics of the carrier material. Mechanism analysis shows that, on the one hand, the content of oxygen-containing and phosphorus-containing functional groups in biochar gradually increases after step-by-step modification. Studies have shown that these functional groups can form stable chelate structures with Ca 2+ through Ca-O and Ca-P coordination bonds, thereby enhancing the chemical adsorption capacity. On the other hand, the multi-level pore structure of modified biochar provides anchoring sites for CaO2 loading, and its microporous-mesoporous hierarchical structure realizes the efficient physical adsorption of CaO2 nanoparticles through van der Waals forces and capillary effects. Under the synergistic action of the two, the loading capacity of CaO2@PBC M is 5.3 times higher than that of CaO2@PBCM, showing a significant structure-performance coupling effect.

[0109] 4. To determine the oxygen release kinetics of the oxygen release material in the glei acidified paddy soil, a simulation test method

[0110] 0.33 g of CaCl2 was weighed into a flask, 300 mL of deionized water was added for dissolution, and 1% acetic acid was used to adjust the pH to 4.5. N2 was introduced (0.75 L / min, 20 min) to reduce the dissolved oxygen concentration to 0.5 mg / L. 10 mg of pure CaO2 or biochar-based oxygen release material with the same CaO2 content was quickly added to the medium. The bottle opening was sealed to avoid the headspace, and the oxygen release kinetics test was carried out in a 25°C dark incubator. Within 12 h after the start of the test, the dissolved oxygen concentration was measured every 4 h. From 12 to 36 h, the dissolved oxygen concentration was measured every 8 h. When the relative deviation of two consecutive measurements was less than 1%, the oxygen release process was considered to be completed. If the test exceeds 36 h, the measurement is changed to every 12 h.

[0111] The results, as shown in Figure 2 , show that the carrier structure has a significant influence on the oxygen release behavior and its rate characteristics. CaO2 and biochar-based oxygen release materials both exhibit similar kinetic trends. Specifically, the oxygen release period of CaO2@PBC M is the longest, followed by CaO2 and CaO2@PBC, and CaO2@BC is the shortest.

[0112] According to Figure 2The trend of the change of the concentration of the dissolved oxygen with time can be seen from the curve, which shows an exponential growth characteristic. Therefore, an exponential growth model is selected to fit the data (equation 1). By derivation, equation 1 is converted into equation 2, which is consistent with the form of the kinetics of the first-order reaction, where A0 is the initial concentration, A is the concentration of the dissolved oxygen at a specific time t, and k is the rate constant. According to Figure 2 and equation 3 is drawn Figure 3 , and a linear fitting is performed. Where A1 is the initial concentration, y-y0 is the concentration of the dissolved oxygen at a specific time x, and 1 / b1 is the negative value of the rate constant.

[0113]

[0114] In(A / A0)=-kt; 2;

[0115]

[0116] Figure 3 The fitting curve of the oxygen release kinetics parameter (k value) shows that the oxygen release rate constant of CaO2@BC and CaO2@PBC is significantly higher than that of CaO2 and CaO2@PBCM (p<0.05), and there is no statistical difference between the latter two. This difference is due to the coupling effect between the structure of the biochar carrier and the active component: BC realizes the uniform dispersion of CaO2 particles by virtue of the homogeneous pore structure, promotes the full exposure of CaO2 to the liquid phase environment, and thus accelerates the hydrolysis reaction, making the k value of CaO2@BC 4.8 times higher than that of pure CaO2. In comparison, PBC has a higher specific surface area, but its rich oxygen-containing and phosphorus-containing functional groups form stable chelate structures through Ca-O and Ca-P coordination, significantly delaying the CaO2 hydrolysis kinetics, resulting in a 63.9% reduction in the k value of CaO2@PBC compared to CaO2@BC.

[0117] For the oxygen release inhibition phenomenon of CaO2@PBCM, its mechanism has a dual regulation feature: first, the ultra-high specific surface area (786.85 m 2 / g) produced by the activation of carbonates is accompanied by a surge in the number of oxygen-containing and phosphorus-containing functional groups, which restricts the exposure of CaO2 active sites through chemical bonding; second, its optimized mesoporous structure (mesopore volume 0.259 cm 3 / g; mesopore ratio 48.81%) forms a precise match with the particle size of CaO2 nanoparticles, which not only avoids the enrichment and rapid release of particles on the surface caused by small pore size, but also prevents particle shedding and instability caused by large pore size. This multi-scale synergistic regulation makes CaO2@PBC M achieve the slow-release characteristics of oxygen in the simulated gleyed acid soil environment, and exhibit a significant structural adaptability advantage.

[0118] Table 3 is the pH of the medium after the end of oxygen release and the efficiency of CaO2 conversion to dissolved oxygen:

[0119]

[0120] wherein η is the efficiency of CaO2 conversion to dissolved oxygen (%); DO1 is the dissolved oxygen concentration of the medium after oxygen release (mg / L); DO0 is the original dissolved oxygen concentration of the medium (mg / L); V is the volume of the medium (L); and DO is the amount of O2 theoretically generated from the complete reaction of CaO2 with water (mg).

[0121] Table 3 pH of the medium after oxygen release and efficiency of CaO2 conversion to dissolved oxygen

[0122]

[0123] As can be seen from Table 3, after oxygen release, the pH of each treatment medium has no significant difference. The experimental data in Table 3 show that after the oxygen release reaction is completed, the pH values of each treatment system do not show significant differences, but the oxygen conversion rate of the CaO2@biocarbon composite material is significantly improved compared with the pure CaO2 system (the improvement range is 6.31%-126.35%). The mechanism of this performance transition is that the biocarbon carrier dynamically regulates the hydrolysis reaction of CaO2: the Ca(OH)2precipitate generated by pure CaO2 in the reaction process will form a dense passivation layer, which hinders the exposure of active sites through physical shielding effect, resulting in low efficiency of CaO2 conversion to dissolved oxygen. On the contrary, the biocarbon carrier realizes the uniform dispersion of CaO2 due to its high specific surface area, effectively maintaining the permeability of the reaction interface, thereby significantly improving the oxygen conversion efficiency.

[0124] For carbon-based calcium peroxide materials, as the modification depth of the biocarbon carrier increases (such as carbonate activation-phosphate loading), the efficiency of CaO2 conversion to dissolved oxygen also increases. This may be because the increase in specific surface area provides more active sites for CaO2, thereby avoiding the reduction of conversion efficiency due to the coverage of insoluble Ca(OH)2. In addition, the confinement effect of the mesoporous structure increases the molecular diffusion resistance in the oxygen and water transport process, making it difficult for them to move within the pore channel, thereby reducing the transport efficiency.

[0125] In summary, CaO2@PBC M not only has the effect of slow oxygen release, but also can significantly improve the efficiency of CaO2 conversion to dissolved oxygen, so CaO2@PBC M can be used for the improvement of gley soil.

[0126] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled persons in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for preparing a carbon-based calcium peroxide material with slow-release oxygen function, characterized in that, Includes the following steps: 1) Preparation of mesoporous biochar Take silicon-rich biochar, mix it evenly with Na2CO3 and K2CO3, then calcine it, and take it out after naturally cooling to room temperature; The amount of silicon-rich biochar, Na2CO3, and K2CO3 used is calculated based on the Si content in the silicon-rich biochar to determine the SiO2 content, and then mixed in an equimolar ratio of SiO2 content to Na2CO3 and K2CO3. The carbonized product is filtered and washed until the conductivity of the filtrate remains constant. Then, the solid obtained by filtration is soaked in hydrochloric acid solution, and the solid is collected by filtration and washed until the conductivity of the filtrate remains constant. Finally, the solid is dried and sieved to obtain mesoporous biochar. The silicon-rich biochar is prepared by calcining silicon-rich agricultural and forestry waste. The silicon-rich agricultural and forestry waste includes one or more of the following: rice husks, rice leaves, rice straw, reeds, willow branches, miscanthus, bamboo poles, and sugarcane bagasse. The calcination temperature is 300~700℃, and the heating rate is 10~30℃ / min; 2) Preparation of phosphorus-rich biochar Silicon-rich biochar, mesoporous biochar and phosphate particles were placed in deionized water, stirred at room temperature and then dried. The dried solid was calcined, naturally cooled to room temperature, and then collected by vacuum filtration. The solid was washed until the conductivity of the filtrate remained constant. Finally, the solid was dried and sieved to obtain two types of phosphorus-rich biochar, denoted as PBC and PBC2. M ; 3) Preparation of carbon-based calcium peroxide materials Nano-calcium peroxide (CaO2) and anhydrous ethanol were added to phosphorus-rich biochar, mixed evenly, shaken, dried to constant weight, and then calcined. The calcined product was cooled to room temperature and extracted with cold deionized water until the conductivity of the filtrate remained constant. Then, it was filtered with anhydrous ethanol, and the final solid was collected, dried to constant weight, and sieved to obtain carbon-based calcium peroxide materials CaO2@PBC and CaO2@PBC. M ; The preparation of the nano-calcium peroxide (CaO2) includes the following steps: Mix calcium salt, ammonium salt and dispersant, add hydrogen peroxide dropwise while stirring until the suspension changes from white to pale yellow, and adjust the pH. The product is centrifuged and precipitated until the conductivity of the supernatant remains unchanged. After washing, nano-calcium peroxide is obtained. The calcium salt includes calcium chloride; The ammonium salt includes ammonium chloride and ammonia water; The dispersant includes polyethylene glycol.

2. The method for preparing the carbon-based calcium peroxide material with slow-release oxygen function according to claim 1, characterized in that, Step 2) The phosphate particles include one of KH2PO4 and K2HPO4.

3. The method for preparing the carbon-based calcium peroxide material with slow-release oxygen function according to claim 1, characterized in that, Step 2) The mass ratio of the silicon-rich biochar and mesoporous biochar to the phosphate particles is 1:0.

2.

4. The method for preparing the carbon-based calcium peroxide material with slow-release oxygen function according to claim 1, characterized in that, Step 2) The calcination temperature is 200~300℃, the heating rate is 20~30℃ / min, and the time is 100~150min.

5. The method for preparing the carbon-based calcium peroxide material with slow-release oxygen function according to claim 1, characterized in that, Step 3) The mass ratio of the phosphorus-rich biochar to nano-calcium peroxide (CaO2) is 2:

1.

6. The method for preparing the carbon-based calcium peroxide material with slow-release oxygen function according to claim 1, characterized in that, Step 3) The calcination temperature is 200~300℃, the heating rate is 20~30℃ / min, and the time is 100~150min.

7. The method for preparing the carbon-based calcium peroxide material with slow-release oxygen function according to claim 1, characterized in that, The conductivity of the filtrate is kept constant until the relative deviation between the two measurements is less than 1%.

8. A carbon-based calcium peroxide obtained by the preparation method according to any one of claims 1-7, characterized in that, Application of the carbon-based calcium peroxide material in improving gley soil.

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