Modified spartina alterniflora biochar for improving saline-alkali soil as well as preparation method and application of modified spartina alterniflora biochar

Abstract

The invention discloses modified spartina alterniflora biochar for improving saline-alkali soil and a preparation method and application thereof, and relates to the technical field of biochar, the preparation method comprises the following steps: soaking spartina alterniflora straw in a calcium chloride solution and stirring, and then sequentially filtering, washing and drying; performing anaerobic pyrolysis on the straws, and collecting a carbon material; the carbon material is soaked in wood vinegar for ultrasonic treatment, and the modified spartina alterniflora biochar for improving the saline-alkali soil is obtained through filtration and freeze drying. The invention discloses the modified spartina alterniflora biochar for improving the saline-alkali soil prepared by the method and application of the modified spartina alterniflora biochar in improving the saline-alkali soil. Calcium doping and acidification modification operations are performed on the spartina alterniflora biochar, the prepared modified biochar can effectively improve the salinity and pH of saline alkali soil, biomass accumulation and raising value improvement of raised plant pennisetum sinese are facilitated, meanwhile, flooding of invasive species spartina alterniflora can be restrained, and important production and application value is achieved.

Description

Technical Field

[0001] This invention relates to the field of biochar technology, specifically to a modified Spartina alterniflora biochar for improving saline-alkali land, its preparation method, and its application. Background Technology

[0002] Soil salinization can lead to the accumulation of high concentrations of soluble salts or the formation of high proportions of exchangeable sodium salts in the topsoil and root zone, which can negatively impact various soil properties and inhibit plant growth.

[0003] Biochar contains nutrients such as nitrogen, phosphorus, and potassium, and can improve soil aggregates and porosity, making it commonly used for saline-alkali land improvement. Spartina alterniflora is a rampant invasive species. With its high annual biomass and C4 vascular bundle structure, Spartina alterniflora is an effective raw material for biochar production. However, research and application of technologies for utilizing the invasive species Spartina alterniflora as a raw material to produce biochar for saline-alkali land improvement are extremely limited.

[0004] One of the core aspects of saline-alkali land improvement is lowering its pH value, as saline-alkali soils typically have a pH greater than 8.5, which is detrimental to plant growth. The pyrolysis temperature has a significant impact on the physicochemical properties of biochar. Biochar is usually alkaline due to the loss of acidic groups and the increase of alkaline minerals during pyrolysis, making it unsuitable for lowering the pH when used for saline-alkali land improvement. However, current research has paid very little attention to the optimal biochar pyrolysis temperature for saline-alkali land improvement.

[0005] Another key aspect of saline-alkali land improvement is reducing salinity. Biochar itself contains a small amount of calcium... 2+ Mg 2+ K + Plasma can react with high Na content in saline-alkali soil + Exchange occurs, reducing the percentage of exchangeable sodium in the soil and increasing Na during irrigation. + Leaching reduces the sodium content in the topsoil, thereby reducing ion stress on plants. However, biochar itself has a limited ion content, and current technological development does not address the need to prepare high-ion (e.g., Ca) biochar to improve ion exchange and lower pH in saline-alkali soils. 2+ The content of modified biochar and acidification. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide a modified Spartina alterniflora biochar for improving saline-alkali land, its preparation method, and its application. This invention, through calcium doping and acidification modification of Spartina alterniflora biochar, produces modified biochar that effectively improves the salinity and pH of saline-alkali soils, promotes biomass accumulation and nutritional quality improvement of forage plants, and simultaneously curbs the proliferation of the invasive species Spartina alterniflora, thus possessing significant production and application value.

[0007] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for preparing modified Spartina alterniflora biochar for improving saline-alkali land is provided, comprising the following steps:

[0008] (1) Soak Spartina alterniflora straw in calcium chloride solution and stir, then filter, wash and dry in sequence. The resulting straw is pyrolyzed under anaerobic conditions, cooled to room temperature and the carbon material is collected.

[0009] (2) The carbon material obtained in step (1) is soaked in wood vinegar and subjected to ultrasonic treatment. After filtration and freeze drying, modified Spartina alterniflora biochar for improving saline-alkali land is obtained.

[0010] Furthermore, in step (1), pyrolysis is performed at 250 °C for 3-5 h.

[0011] Furthermore, in step (1), the mass-to-volume ratio of Spartina alterniflora straw to calcium chloride solution is 1 g: 8-12 mL; the concentration of calcium chloride solution is 90-110 g / L.

[0012] Furthermore, in step (1), the mixture is stirred at 300-500 rpm for 10-15 h.

[0013] Furthermore, in step (1), the product is dried at 70-90℃ for 6-12 hours.

[0014] Furthermore, in step (2), the mass-to-volume ratio of charcoal material to wood vinegar is 1 g: 3-5 mL.

[0015] Furthermore, in step (2), soaking is performed for 1-2 hours.

[0016] The present invention also provides a modified Spartina alterniflora biochar prepared by the above-mentioned method for improving saline-alkali land, which is a modified Spartina alterniflora biochar prepared by improving saline-alkali land.

[0017] This invention also provides the application of the modified Spartina alterniflora biochar for improving saline-alkali land.

[0018] Furthermore, modified Spartina alterniflora biochar, used to improve saline-alkali soil, is applied to the soil at a weight percentage of 0.5%-2%.

[0019] The present invention has the following beneficial effects:

[0020] This invention utilizes the abundant Spartina alterniflora, a pest that has plagued coastal areas in eastern China, to prepare biochar. The optimal pyrolysis temperature for biochar preparation suitable for saline-alkali land improvement was determined. Furthermore, the biochar was modified to meet the core requirements of saline-alkali land improvement, resulting in calcium-doped acidic biochar. The modified biochar was used to improve the "saline-alkali land-Pennisetum giganteum" system in coastal areas of eastern China. Results showed that the pH, percentage of exchangeable sodium, and sodium adsorption ratio of the saline-alkali land were significantly reduced, while the soil fertility accumulation index was significantly increased. The biomass and relative foraging value of Pennisetum giganteum also significantly increased. Attached Figure Description

[0021] Figure 1 Scanning electron microscopy images of Spartina alterniflora biochar prepared at different pyrolysis temperatures, where AE represents BC250, BC350, BC450, BC550 and BC650, respectively.

[0022] Figure 2 pH values ​​of Spartina alterniflora biochar prepared at different pyrolysis temperatures;

[0023] Figure 3 Infrared spectra of Spartina alterniflora biochar prepared at different pyrolysis temperatures;

[0024] Figure 4 Statistical results of acidic groups in Spartina alterniflora biochar prepared at different pyrolysis temperatures;

[0025] Figure 5 Atomic ratio statistics of Spartina alterniflora biochar prepared at different pyrolysis temperatures;

[0026] Figure 6 Scanning electron microscope and elemental distribution map of modified Spartina alterniflora biochar prepared in Example 1 for improving saline-alkali land;

[0027] Figure 7 The elemental energy spectrum of the modified Spartina alterniflora biochar prepared in Example 1 for improving saline-alkali land is shown.

[0028] Figure 8 A graph showing the soil quality index (SQI) results after Spartina alterniflora biochar improved saline-alkali soil;

[0029] Figure 9 Statistical results of pH in saline-alkali soils under different treatment groups.

[0030] Figure 10 The figure shows the statistical results of sodium adsorption ratio and exchangeable sodium in saline-alkali soils of different treatment groups;

[0031] Figure 11 A graph showing the statistical results of the cumulative soil fertility index of saline-alkali soils in different treatment groups;

[0032] Figure 12 A comparison of changes in giant reed biomass after modifying the "saline-alkali soil-giant reed" system with unmodified Spartina alterniflora biochar;

[0033] Figure 13 A comparison of changes in giant reed biomass after modifying the "saline-alkali soil-giant reed" system with modified or unmodified Spartina alterniflora biochar.

[0034] Figure 14 Comparison of the nutritional quality and relative feeding value of giant Napier grass after improving the "saline-alkali soil-giant Napier grass" system with modified or unmodified Spartina alterniflora biochar. Detailed Implementation

[0035] The principles and features of this invention are described below. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0036] Example 1

[0037] A modified Spartina alterniflora biochar for improving saline-alkali land, the preparation method of which includes the following steps:

[0038] (1) Soak Spartina alterniflora straw in 100 g / L calcium chloride solution at a mass-volume ratio of 1 g: 10 mL, stir at 400 rpm for 12 h, then filter, wash with deionized water, dry at 80℃ for 8 h, place the dried straw in a tube furnace, pyrolyze at 250℃ for 4 h, cool to room temperature, and collect the obtained carbon material;

[0039] (2) The carbon material obtained in step (1) was soaked in wood vinegar and ultrasonically treated for 1 h at a mass-volume ratio of 1 g: 3 mL. After filtration and freeze drying, modified Spartina alterniflora biochar (CBC) for improving saline-alkali land was obtained.

[0040] Example 2

[0041] A modified Spartina alterniflora biochar for improving saline-alkali land, the preparation method of which includes the following steps:

[0042] (1) Soak Spartina alterniflora in 90 g / L calcium chloride solution at a mass-volume ratio of 1 g: 8 mL, stir at 300 rpm for 10 h, then filter, wash with deionized water, dry at 70℃ for 12 h, place the dried straw in a tube furnace, pyrolyze at 250℃ for 3 h, cool to room temperature, and collect the obtained carbon material.

[0043] (2) The carbon material obtained in step (1) was soaked in wood vinegar and ultrasonically treated for 0.5 h at a mass-volume ratio of 1 g: 2 mL. After filtration and freeze drying, modified Spartina alterniflora biochar for improving saline-alkali land was obtained.

[0044] Example 3

[0045] A modified Spartina alterniflora biochar for improving saline-alkali land, the preparation method of which includes the following steps:

[0046] (1) Soak Spartina alterniflora in 110 g / L calcium chloride solution at a mass-volume ratio of 1 g: 12 mL, stir at 500 rpm for 15 h, then filter, wash with deionized water, dry at 90℃ for 6 h, place the dried straw in a tube furnace, pyrolyze at 250℃ for 5 h, cool to room temperature, and collect the obtained carbon material.

[0047] (2) The carbon material obtained in step (1) was soaked in wood vinegar and ultrasonically treated for 1.5 h at a mass-volume ratio of 1 g: 4 mL. After filtration and freeze drying, modified Spartina alterniflora biochar for improving saline-alkali land was obtained.

[0048] Comparative Example 1

[0049] A method for preparing Spartina alterniflora biochar includes the following steps:

[0050] Spartina alterniflora straw was placed in a tube furnace and pyrolyzed at 250°C for 4 hours in an anaerobic environment. After cooling to room temperature, Spartina alterniflora biochar (BC) was obtained.

[0051] Experimental Example 1

[0052] In anaerobic pyrolysis, Spartina alterniflora straw was pyrolyzed at 250℃, 350℃, 450℃, 550℃ and 650℃ for 4 h to prepare Spartina alterniflora biochar, which were denoted as BC250, BC350, BC450, BC550 and BC650, respectively.

[0053] Scanning electron microscopy (SEM) images, pH values, infrared spectroscopy results, statistical results of acidic groups, and statistical results of atomic ratios of Spartina alterniflora biochar prepared at different pyrolysis temperatures are shown below. Figure 1-5 As shown.

[0054] The results showed that BC250 had the lowest pH (7.34), making it more suitable for improving saline-alkali soils compared to other biochars. The acidic groups (carboxyl, lactone, phenolic hydroxyl, etc.) in biochars BC250-BC650 decreased from a maximum of 2.202 mmol / g. Infrared spectroscopy results indicated that C=O, CH, OH, and other groups were almost completely absent in other biochars besides BC250, and the H / C atomic ratio also showed that BC250 had the highest H content. These data collectively indicate that biochar BC250 has the lowest acidity and the highest organic group content, which aligns with the improvement needs of saline-alkali soils by lowering pH and increasing soil fertility.

[0055] Experimental Example 2

[0056] The scanning electron microscope (SEM) elemental spectrum and elemental spectrum of the modified Spartina alterniflora biochar prepared in Example 1 for improving saline-alkali land are shown below. Figure 6 and Figure 7 As shown.

[0057] The results showed that calcium ions were uniformly incorporated into the biochar, with an atomic relative weight of 8.51%.

[0058] The addition of calcium ions to biochar can enhance the exchange between calcium ions and sodium ions on soil colloids when biochar is used to improve saline-alkali soil, thereby increasing the leaching of sodium ions in saline-alkali soil and reducing the percentage of exchangeable sodium.

[0059] Experimental Example 3

[0060] Saline-alkali soil samples were collected in Yancheng City, Jiangsu Province (120.8355°E, 33.0119°N). Biochar (BC250-BC650) was added to 500 g of saline-alkali soil and mixed evenly at a ratio of 2 wt%. The soil-char mixture was placed at room temperature (approximately 25°C), and deionized water was sprayed every 3 days to maintain soil moisture at 20%. After 60 days, the improvement of saline-alkali soil was comprehensively evaluated based on the Soil Quality Index (SQI) to determine the optimal pyrolysis temperature of Spartina alterniflora biochar for saline-alkali soil improvement. Eight indicators were used for SQI calculation, including soil porosity, pH, available nitrogen (AN), available phosphorus (AP), available potassium (AK), dissolved organic carbon (DOC), electrical conductivity (EC), and percentage of exchangeable sodium (ESP). Each indicator was standardized to a score (Li) in the range of 0-1 using either Formula 1 (higher is better, such as DOC) or Formula 2 (lower is better, such as pH, EC), where X, X... m ᵢ n and X max These represent the measured value, minimum value, and maximum value of each indicator:

[0061]

[0062]

[0063]

[0064] A radar chart was plotted based on the Li scores of eight indicators (Table 1). The area of ​​the radar chart was calculated using Formula 3 (n=8), which represents the Soil Quality Index (SQI). The results are as follows: Figure 8 As shown.

[0065] Table 1. Li values ​​of various soil indicators after different Spartina alterniflora biochars improved saline-alkali soil.

[0066]

[0067] Note: Results are expressed as "mean ± standard deviation", with different letters indicating significant differences (p < 0.05, n = 3).

[0068] The results showed that when the biochar addition amount was 2 wt%, the SQI values ​​of CK, BC250, BC350, BC450, BC550, and BC650 were 1.57, 2.08, 1.82, 1.64, 1.67, and 2.00, respectively. Among them, the SQI of BC250 was the highest, at 2.08, which was 32.55% higher than that of the control group. This indicates that the optimal pyrolysis temperature of Spartina alterniflora biochar is 250℃.

[0069] Experimental Example 4: Improvement of Saline-Alkali Soil-Giant Napier Grass System

[0070] Saline-alkali soil samples were collected in Yancheng City, Jiangsu Province (120.8355°E, 33.0119°N), and giant reed seedlings were sourced from a demonstration base in Dafeng District, Yancheng City, Jiangsu Province (120.6878°E, 33.0382°N). Before transplanting, the giant reed seed nodes were soaked in water to encourage germination until the seedlings reached a height of 10 cm. The addition amounts of Spartina alterniflora biochar (BC250) or modified Spartina alterniflora biochar (CBC) were 0.5 wt%, 1.0 wt%, and 2.0 wt%, respectively, as detailed in Table 2.

[0071] Table 2 Pot Experiment Design Table

[0072]

[0073] The experiment was conducted in an open-top air chamber, with soil moisture maintained at 60% of maximum water holding capacity, temperature (25-35℃), and relative humidity (45-65%). Soil-plant physicochemical indicators were measured after 150 days, and the improvement in soil quality was assessed using the fertility accumulation index (FAI).

[0074]

[0075] FAI is calculated using Formula 4, where Xᵢ and X CK Calculations are based on soil fertility indices, including available nitrogen (AN), available phosphorus (AP), available potassium (AK), soil organic carbon (SOC), and cation exchange rate (CEC).

[0076] The statistical results of soil pH, sodium adsorption ratio, and percentage of exchangeable sodium, soil fertility index, giant reed biomass, and nutritional quality and relative feeding value of giant reed grass in different treatment groups are as follows: Figure 9-14 As shown.

[0077] The results showed that, compared with the blank control group (CK), modified Spartina alterniflora biochar (CBC) reduced the pH of saline-alkali soil by 0.43, 0.59, and 0.93 units, respectively; the sodium adsorption ratio of CBC-treated soil decreased by 28.32%, 58.91%, and 65.36%, respectively, and the percentage of exchangeable sodium decreased by 18.42%, 35.79%, and 46.05%, respectively; the soil fertility accumulation index of CBC-treated soil increased by 0.81, 1.38, and 1.88, respectively, with corresponding increases of 16.20%, 27.60%, and 37.6%. The experimental results indicate that, at the same addition ratio, the improvement effect of modified Spartina alterniflora biochar (CBC) is superior to or significantly superior to that of unmodified Spartina alterniflora biochar (BC250).

[0078] Furthermore, compared to the blank control group (CK), when the addition amount was 1%, the unmodified Spartina alterniflora biochar BC250 (T2) and the modified Spartina alterniflora biochar CBC (C2) significantly promoted the growth of Spartina giantiflora, increasing its total biomass from 40.88 g to 51.01 g and 63.5 g, respectively, representing increases of 24.78% and 55.42%. The total biomass of CBC was significantly higher than that of the BC250 addition group (51.01 g). CBC significantly increased the relative feed value of Spartina giantiflora by 18.37%, and the increase was higher than that of the 16.60% increase in the BC250 addition group (1%).

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing modified Spartina alterniflora biochar for improving saline-alkali land, characterized in that, Includes the following steps: (1) Soak Spartina alterniflora straw in calcium chloride solution and stir, then filter, wash and dry in sequence. The resulting straw is pyrolyzed under anaerobic conditions, cooled to room temperature and the carbon material is collected. (2) The carbon material obtained in step (1) is soaked in wood vinegar and subjected to ultrasonic treatment. After filtration and freeze drying, modified Spartina alterniflora biochar for improving saline-alkali land is obtained.

2. The method for preparing modified Spartina alterniflora biochar for improving saline-alkali land as described in claim 1, characterized in that, In step (1), pyrolysis is performed at 250℃ for 3-5 h.

3. The method for preparing modified Spartina alterniflora biochar for improving saline-alkali land as described in claim 1, characterized in that, In step (1), the mass-to-volume ratio of the Spartina alterniflora straw to the calcium chloride solution is 1 g: 8-12 mL; the concentration of the calcium chloride solution is 90-110 g / L.

4. The method for preparing modified Spartina alterniflora biochar for improving saline-alkali land as described in claim 1, characterized in that, In step (1), stir at 300-500 rpm for 10-15 h.

5. The method for preparing modified Spartina alterniflora biochar for improving saline-alkali land as described in claim 1, characterized in that, In step (1), dry at 70-90℃ for 6-12 h.

6. The method for preparing modified Spartina alterniflora biochar for improving saline-alkali land as described in claim 1, characterized in that, In step (2), the mass-to-volume ratio of the charcoal material to the wood vinegar is 1 g: 3-5 mL.

7. The method for preparing modified Spartina alterniflora biochar for improving saline-alkali land as described in claim 1, characterized in that, In step (2), soak for 1-2 hours.

8. Modified Spartina alterniflora biochar for improving saline-alkali land prepared by the method of any one of claims 1-7.

9. The application of the modified Spartina alterniflora biochar for improving saline-alkali land as described in claim 8 in the improvement of saline-alkali land.

10. The application as described in claim 9, characterized in that, The modified Spartina alterniflora biochar used to improve saline-alkali land was applied to the saline-alkali soil at a mass percentage of 0.5%-2%.

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