Co-pyrolysis biochar capable of reducing enrichment of methyl mercury in rice and preparation method and application of co-pyrolysis biochar
Through the preparation and application of copyrolytic biochar, the problem of methylmercury enrichment in rice is solved, which significantly reduces the accumulation of methylmercury in rice, and improves food safety and human health protection.
Patent Information
- Application Number
- CN202411788912.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-06
- Publication Date
- 2025-03-28
AI Technical Summary
The prior art is difficult to effectively reduce the enrichment of methylmercury in rice, affecting food safety and human health.
Using co-pyrolytic biochar, a biochar that can significantly reduce methylmercury enrichment was prepared by mixing the Uroth powder with rice straw powder and pyrolytic carbonization, and added to the rice field soil.
Copyrolytic biochar can significantly reduce the accumulation of methylmercury in rice, and a small amount of use can significantly reduce the concentration of methylmercury. The raw materials are widely sourced and low-cost, and have good application prospects.
Smart Images
Figure CN119709231A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of contaminated soil remediation, and mainly relates to a co-pyrolysis biochar for reducing methylmercury enrichment in rice, and a preparation method and application thereof. Background Art
[0002] Mercury is a highly toxic heavy metal pollutant with the characteristics of persistence, long-distance migration, and bioaccumulation. Mercury has many chemical forms, among which methylmercury is the most toxic. After entering the human body, methylmercury can cross the blood-brain barrier and the placenta, causing permanent damage to the central nervous system and posing a great threat to human health. Rice is one of the most important food crops in the world, and nearly 50% of the world's population relies on rice as their staple food. Studies have shown that eating rice is one of the important sources of human exposure to methylmercury. The methylmercury in rice mainly comes from paddy field soil. Therefore, passivating and stabilizing methylmercury in the soil and reducing the transfer of methylmercury from soil to rice are important means to reduce the accumulation of methylmercury in rice and ensure food safety and human health.
[0003] At present, the treatment methods of mercury-contaminated soil mainly include physical methods, biological methods and chemical methods. Common physical methods include soil leaching and thermal desorption. Such methods are quick to take effect, but they are costly, require a large amount of work, and may affect the physical and chemical properties of the soil. Biological remediation methods such as phytoremediation and microbial remediation have little impact on the environment, low cost, and can be used for large-scale remediation, but this method has a long remediation cycle, strict environmental requirements, and is not suitable for the remediation of heavily contaminated soil. Chemical remediation methods such as electric remediation, leaching, solidification and stabilization methods, etc. Electric remediation refers to a method of placing suitable anodes and cathodes vertically underground and applying a low-power DC electric field to remediate contaminated soil on site. The factors affecting electric remediation in the actual environment are complex, which restricts its large-scale application. The leaching method has a wide range of applications and is simple to operate, but it has problems such as high cost and damage to the original properties of the soil. The solidification and stabilization method mainly reduces the mobility and bioavailability of mercury in the soil by adding chemical passivators, soil conditioners (such as biochar, fertilizers) and other substances.
[0004] The solidification and stabilization method is currently a widely used and mature remediation method. In practical applications, the selection of passivators or passivation materials is particularly important for different pollution scenarios. For example, when repairing farmland soils such as rice fields, the selected passivator should not only have strong repair capabilities, but also should not have a negative impact on crop growth. Commonly used solidification and stabilization remediation materials mainly include: biochar, phosphates, metals and their oxides, silicon-containing materials, clay minerals, and organic fertilizers. Among them, biochar has a strong repair ability, and can also significantly improve soil nutrients, moisture, air permeability, acidity and alkalinity and other properties, which is very suitable for the repair and improvement of farmland soil. Summary of the invention
[0005] Purpose of the invention: The technical problem to be solved by the present invention is to provide a co-pyrolysis biochar that reduces methylmercury enrichment and a preparation method thereof in view of the deficiencies in the prior art.
[0006] Another technical problem to be solved by the present invention is to provide the application of the above-mentioned co-solution biochar.
[0007] In order to solve the first technical problem mentioned above, the present invention discloses a method for preparing co-pyrolysis biochar for reducing methylmercury enrichment, which is obtained by mixing Enteromorpha powder and rice straw powder and then pyrolyzing and carbonizing them.
[0008] In some embodiments, the enteromorpha is sourced from a enteromorpha processing factory in Fuzhou City, Fujian Province. Other enteromorpha in the prior art can also be used in the present technical solution and have the same effect.
[0009] In some embodiments, the Enteromorpha powder and the rice straw powder are powders after passing through a 45-80 mesh sieve, in some embodiments, they are powders after passing through a 50-70 mesh sieve, and in some embodiments, they are powders after passing through a 60 mesh sieve.
[0010] In some embodiments, the mass ratio of the enteromorpha powder to the rice straw powder is 1:3 to 3:1, in some embodiments, 0.5 to 1.5:1, and in some embodiments, 1:1.
[0011] In some embodiments, the pyrolysis temperature is 450-750°C, in some embodiments, 550-650°C, and in some embodiments, 600°C.
[0012] In some embodiments, the heating rate of the pyrolysis is 8-12°C / min, and in some embodiments, 10°C / min.
[0013] In some embodiments, Enteromorpha powder and rice straw powder are mixed, pyrolyzed, and then passed through a 45-80 mesh sieve to obtain; in some embodiments, the mixture is passed through a 50-70 mesh sieve, and in some embodiments, the mixture is passed through a 60 mesh sieve.
[0014] The co-pyrolysis biochar prepared by the above method is also within the protection scope of the present invention.
[0015] In order to solve the above second technical problem, the present invention discloses the application of the above co-pyrolysis biochar in reducing methylmercury enrichment.
[0016] In some embodiments, the application is the application of the co-pyrolysis biochar in reducing methylmercury enrichment in rice.
[0017] In some embodiments, the co-pyrolysis biochar is added at 0.1% to 1% of the soil mass, in some embodiments 0.1% to 0.5%, and in some embodiments 0.3%.
[0018] In some embodiments, the co-pyrolyzed biochar is mixed with soil containing methylmercury, fertilizer and water are applied, and then rice seeds are sown.
[0019] Beneficial effects: Compared with the prior art, the present invention has the following advantages:
[0020] (1) The present invention applies co-pyrolysis biochar to paddy field soil remediation in a relatively small amount, which can significantly reduce the absorption and accumulation of methylmercury in the soil by rice. Compared with single-material pyrolysis biochar, a usage amount of 0.3% can reduce the methylmercury concentration in rice by 83%, which can significantly reduce the accumulation of methylmercury in rice.
[0021] (2) The raw materials used in the co-pyrolysis biochar provided by the present invention are widely available and low in cost. The biochar production process is simple and has strong remediation performance. A small amount of addition can significantly reduce the methylmercury concentration in rice.
[0022] (3) The co-pyrolysis biochar provided by the present invention has good application prospects in paddy field soil restoration and improvement, waste biomass resource utilization, etc.
[0023] (4) The raw materials used for the co-pyrolysis biochar described in the present invention are all common organic wastes, which realizes the resource utilization of wastes such as Enteromorpha and rice straw, and at the same time passivates and stabilizes methylmercury in the soil, which has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more clear.
[0025] Figure 1 This is the simulated methylmercury concentration in the soil after 14 days of cultivation (different letters ac indicate significant differences among different treatment groups, one-way ANOVA, p<0.05).
[0026] Figure 2 The concentration of methylmercury extractable by ammonium thiosulfate in soil after 14 days of simulated incubation (different letters (ad) above the bar graph indicate significant differences among different treatment groups; one-way ANOVA, p<0.05).
[0027] Figure 3Graph showing rice yield in a pot experiment (different letters (ac) above the bar graph indicate significant differences among different treatment groups; one-way ANOVA, p<0.05).
[0028] Figure 4 is the methylmercury concentration of rice in the pot experiment (different letters (ad) above the bar graph indicate significant differences among different treatment groups; one-way ANOVA, p<0.05).
[0029] Figure 5 is the total mercury concentration of rice in the pot experiment (different letters (ab) above the bar graph indicate significant differences among different treatment groups; one-way ANOVA, p<0.05).
[0030] Figure 6 Scanning electron microscope (SEM) images of biochar: 600℃ Enteromorpha biochar (a), 600℃ rice straw biochar (b), and 600℃ Enteromorpha and rice straw co-pyrolysis biochar in a ratio of 1:1 (c). DETAILED DESCRIPTION
[0031] The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified. Enteromorpha was collected from a certain enteromorpha processing factory in Fuzhou, Fujian Province, and rice straw was purchased from a certain straw processing factory in Lianyungang, Jiangsu Province.
[0032] In a basic implementation case in the following embodiments, a method for preparing co-pyrolysis biochar for reducing the accumulation of methylmercury in rice and an application case are provided. In the method, the co-pyrolysis biochar with the best remediation effect is optimized by adjusting the raw material ratio and pyrolysis temperature of the co-pyrolysis biochar;
[0033] In this implementation case, the methylmercury concentration in the soil extracted by ammonium thiosulfate was well correlated with the methylmercury concentration in rice grown in the soil environment. The soil ammonium thiosulfate extraction method can be used to predict the accumulation of methylmercury in the soil by rice under different soil environments.
[0034] In the following examples, the methylmercury, unless otherwise specified as extractable methylmercury, refers to the total concentration of methylmercury in soil or the total concentration of methylmercury in rice.
[0035] Example 1
[0036] Step S1, measuring the total mercury concentration and methylmercury concentration in a paddy field soil in Nantong City, Jiangsu Province. The test results are: the total mercury concentration of the tested soil is 550 μg / kg, the methylmercury concentration is 0.8 μg / kg, and the pH value is 6.5;
[0037] Step S2, pyrolyzing five groups of co-pyrolysis biochar raw materials with different proportions at different temperatures, and the specific raw material proportions and their names are shown in Table 1 below;
[0038] Table 1 Proportion and name of biochar raw materials
[0039]
[0040] The above five types of biochar raw materials were pyrolyzed at three temperatures of 450°C, 600°C, and 750°C, respectively, to obtain 15 different types of biochar. The specific steps are as follows:
[0041] (1) grinding dried Enteromorpha and rice straw respectively and passing through a 60-mesh sieve to obtain Enteromorpha powder and rice straw powder;
[0042] (2) mixing the two powders in different proportions and mixing them thoroughly to obtain mixed biomass powder;
[0043] (3) filling the entire crucible with the mixed biomass powder and compacting it, covering the crucible with a lid and wrapping the entire crucible with tin foil;
[0044] (4) placing the tin foil wrapped crucible in a tube furnace, heating the crucible to 450° C., 600° C. and 750° C. at a heating rate of 10° C. / min under oxygen-limited conditions, and then pyrolyzing the crucible at the corresponding temperature for 2 hours. After the pyrolysis time is over, the biochar is taken out after naturally cooling to room temperature;
[0045] (5) Grind the prepared biochar and pass it through a 60-mesh sieve to obtain the co-pyrolysis biochar.
[0046] The biochar was characterized using scanning electron microscopy (SEM). Figure 6 The specific surface area and surface pores of biochar were measured using the ASAP2420 fully automatic specific surface area and pore analyzer. The results are shown in Table 2. The specific surface area of Enteromorpha biochar is 18.4 m 2 / g, and the specific surface area of rice straw biochar is 46.0m 2 / g, but the specific surface area of the co-pyrolysis biochar was reduced to 6.98m 2 / g, and its surface area is much smaller than that of Enteromorpha biochar and rice straw biochar. At the same time, the pore volume of co-pyrolysis biochar is smaller than that of Enteromorpha and rice straw biochar, and the average pore size is significantly increased.
[0047] Table 2 Surface structure of biochar
[0048]
[0049] Step S3, cooling and sieving the 15 kinds of biochars, adding them to a paddy field soil collected in Nantong City, Jiangsu Province at 0.3% of the soil mass (5 g), adding 30 mL of deionized water and 5 mM sodium lactate (simulating rice root secretions), and culturing them for 14 days in a sealed and light-proof environment, and setting the soil without adding biochar as a blank control group;
[0050] Step S4: After the incubation time of the control group and the different biochar treatment test groups is completed, the methylmercury concentration in the soil is measured ( Figure 1 : Soil methylmercury concentration after 14 days of simulated incubation) and ammonium thiosulfate-extractable methylmercury concentration ( Figure 2 : Ammonium thiosulfate-extractable methylmercury concentration in soil after 14 days of simulated incubation);
[0051] Step S5, in all treatment groups, the concentration of methylmercury extractable by ammonium thiosulfate in the blank control group (experimental group without adding biochar) was 0.47 μg / kg. The concentration of methylmercury extractable by ammonium thiosulfate in the soil treated with biochar prepared at a ratio of Enteromorpha to rice straw of 1:1 and a pyrolysis temperature of 600°C was only 0.07 μg / kg, which was 83% lower than that of the blank control group, while the concentration of methylmercury extractable by ammonium thiosulfate in the single Enteromorpha biochar treatment group, the rice straw biochar treatment group, and the co-pyrolysis biochar treatment group with other temperatures or raw material ratios decreased by 42% to 70% compared with the blank control group. It was determined that when the mass ratio of Enteromorpha to rice straw was 1:1 and the pyrolysis temperature was 600°C, the co-pyrolysis biochar with the best remediation effect could be prepared.
[0052] Example 2
[0053] According to the optimization in Example 1 for a paddy field soil in Nantong City, Jiangsu Province, the optimal raw material ratio of the best co-pyrolysis biochar is a mass ratio of Enteromorpha to rice straw of 1:1, and the optimal pyrolysis temperature is 600°C. The co-pyrolysis biochar was added in a potted experiment at a mass ratio of 0.3% to verify.
[0054] The specific scheme of the pot experiment includes 4 treatment groups and a total of 12 pots (each treatment contains 3 repeated controls) (see Table 3 for details) to study the effects of co-pyrolysis and the addition of single pyrolysis biochar on the accumulation of methylmercury in rice. When conducting the pot experiment, the biochar and soil were mixed evenly and placed in a high-density polypropylene white bucket. At the same time, basic fertilizer (urea 0.275g / kg, calcium dihydrogen phosphate 0.325g / kg, potassium chloride 0.2g / kg) and deionized water were added to make the soil moisture content reach saturation. The seeds of Nipponbare rice, which had been germinated for 3 days, were directly sown in the container. The rice seedlings were not flooded, only the soil surface was kept moist, and the soil was flooded with deionized water (about 3 cm above the soil surface) after about 20 days. During the experiment, all treatment groups were placed in a greenhouse at ambient temperature.
[0055] Table 3 Potted plant experiment treatment groups
[0056]
[0057] The rice was harvested after it matured and the rice yield was analyzed. The results showed that the treatment of co-pyrolysis biochar significantly increased the rice yield by 61%. The results show that co-pyrolysis biochar can promote crop growth ( Figure 3 ).
[0058] Determination of methylmercury in rice grains of blank group and treatment group Figure 4 ) and total mercury ( Figure 5 ) concentration, the results showed that the total mercury and methylmercury concentrations of rice in the blank group were 148μg / kg and 124μg / kg, respectively; the total mercury and methylmercury concentrations of rice in the co-pyrolysis biochar treatment group were 27.4μg / kg and 21.6μg / kg, respectively. Compared with the blank control group, the total mercury concentration of rice in the co-pyrolysis biochar treatment group decreased by 81%, and the methylmercury concentration decreased by 83%; compared with the rice straw biochar treatment group, the total mercury and methylmercury concentrations of rice in the co-pyrolysis biochar treatment group decreased significantly by 81% and 83%.
[0059] Through the pot experiment, the methylmercury concentration in rice treated with co-pyrolysis biochar was significantly reduced by 83% compared with the blank group, and the total mercury concentration was significantly reduced by 81%. This shows that co-pyrolysis biochar inhibits the accumulation of methylmercury in the soil by rice, significantly reduces the methylmercury concentration of rice, and has a strong repair ability for mercury-contaminated farmland soil.
[0060] Analysis of the test results shows that the co-pyrolysis of biochar reduces the methylmercury concentration in rice for the following two reasons:
[0061] First, the co-pyrolysis biochar fixed methylmercury in the soil by direct adsorption, which reduced the concentration of methylmercury available to rice in the soil, thereby reducing the mobility of methylmercury and the proportion of methylmercury transported from the soil to the roots, and thus reducing the concentration of methylmercury in rice ( Figure 4 );
[0062] Second, pot experiments revealed that the addition of co-pyrolysis biochar can reduce the proportion of methylmercury transported from roots to aboveground parts, and reduce the proportion of methylmercury transported from straw to rice, thereby inhibiting the transport of methylmercury from rice to rice.
[0063] Third, the co-pyrolysis biochar contains rich nutrients such as nitrogen, phosphorus, potassium and sulfur. Compared with the blank group, the rice yield of the co-pyrolysis biochar treatment group increased significantly ( Figure 3 ), thereby reducing the concentration of methylmercury in rice through the "biodilution" effect.
[0064] In summary, the present invention provides a method for preparing and applying co-pyrolysis biochar for reducing the accumulation of methylmercury in rice. The optimal raw material ratio and pyrolysis temperature of the co-pyrolysis biochar are obtained through simulation experiments, and the co-pyrolysis biochar with the best remediation performance is prepared at this temperature and ratio, and the effect is verified through potted experiments.
[0065] The present invention has been introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method and core idea of the present invention. At the same time, for those skilled in the art, according to the idea of the present invention, there will be changes in the specific implementation methods and application scopes, and these changes also fall within the scope of protection of the claims of the present invention.
Claims
1. A method for preparing co-pyrolysis biochar with reduced methylmercury enrichment, characterized in that: The powder of Enteromorpha and the powder of rice straw are mixed and then pyrolyzed to obtain the powder.
2. The preparation method according to claim 1, characterized in that: The enteromorpha powder and the rice straw powder are powders that have passed through a 45-80 mesh sieve.
3. The preparation method according to claim 1, characterized in that: The mass ratio of the enteromorpha powder to the rice straw powder is 1:3 to 3:
1.
4. The preparation method according to claim 1, characterized in that: The pyrolysis temperature is 450-750°C.
5. The preparation method according to claim 1, characterized in that: The heating rate of the pyrolysis is 8-12°C / min.
6. The preparation method according to claim 1, characterized in that: The enteromorpha powder and the rice straw powder are mixed, pyrolyzed, and then passed through a 45-80 mesh sieve to obtain the product.
7. Use of the co-pyrolysis biochar prepared by the method according to any one of claims 1 to 6 in reducing methylmercury enrichment.
8. The use according to claim 7, characterized in that: The application is the use of the co-pyrolysis biochar in reducing methylmercury enrichment in rice.
9. The use according to claim 7, characterized in that: The co-pyrolysis biochar is added at 0.1% to 1% of the soil mass.
10. The use according to claim 8, characterized in that: The co-pyrolysis biochar was mixed with soil containing methylmercury, and then fertilizer and water were applied before sowing rice seeds.