A modified biochar and its preparation method

Abstract

This invention discloses a modified biochar and its preparation method, relating to the field of biochar materials technology. The invention modifies pine nut shells and, based on this modification, obtains a soda-saline-alkali soil conditioner. This conditioner is prepared by mixing modified biochar, biochar-based fermentation products, phosphogypsum, oxalic acid, and wood ash as raw materials. The soil conditioner of this invention can significantly improve the soil conditions of soda-saline-alkali paddy fields, enhance soil fertility, and ensure increased rice yield, thus having significant positive implications for promoting agricultural development in soda-saline-alkali areas.

Description

Technical Field

[0001] This invention relates to the field of biochar materials technology, and in particular to a modified biochar and its preparation method. Background Technology

[0002] Soda saline-alkali land is one of the most difficult types of saline-alkali land to manage. This type of soil has high sodium ion content, low infiltration coefficient, poor soil aeration, low organic matter content, and extremely poor nutrient status. The pH value of severely soda saline-alkali land can even be higher than 10. Soda saline-alkali land mainly inhibits crop growth through osmotic stress and ion toxicity.

[0003] Salt stress affects plant root growth and restricts the absorption of nutrients and water, thus impacting plant growth and development. Rice cultivation is an important way to utilize soda-saline-alkali land, primarily because flooding not only ensures the rice's growth needs but also allows for salt leaching, reducing the adverse effects of salt and alkali on crops. However, with the increasing severity of soil salinization and infertility in soda-saline-alkali areas, coupled with significant water shortages, rice growth in soda-saline-alkali paddy fields has been seriously threatened, hindering agricultural development in these regions. Therefore, improving rice yield in soda-saline-alkali areas has become an urgent problem to be solved.

[0004] Biochar is a carbon-rich solid material produced by high-temperature pyrolysis of biomass materials under limited or anaerobic conditions. It has abundant raw material sources, a rich porous structure, and special physicochemical properties, and has a wide range of applications in many fields. However, with the rapid development of science, technology, and economy, the inherent characteristics of biochar are no longer sufficient to meet the performance requirements of various fields.

[0005] Modifying biochar materials can regulate and improve their properties, thereby expanding their application areas, and has become a current research hotspot. Different modification methods can yield modified biochar materials for various applications, significantly broadening the scope of biomass material applications.

[0006] Currently, the improvement effect of directly applying biochar materials to soda saline-alkali soil is limited. At the same time, research on the application of modified biochar materials in soda saline-alkali paddy fields is insufficient. If soil improvement can be achieved based on appropriate biochar modification treatment, thereby increasing rice yield in soda saline-alkali areas, it will have important practical significance for promoting agricultural development in soda saline-alkali areas. Summary of the Invention

[0007] The purpose of this invention is to provide a modified biochar and its preparation method to solve the problems existing in the prior art and achieve soil improvement in soda saline-alkali areas.

[0008] To achieve the above objectives, the present invention provides the following solution:

[0009] One of the technical solutions of this invention is to provide a modified biochar, the preparation method of which includes the following steps:

[0010] The pine nut shells, after being heat-treated at 120-150℃, were first soaked in a sodium hydroxide solution, then pyrolyzed at 450-500℃ under a protective atmosphere. After cooling, they were placed in a mixed aqueous solution of citric acid and jujube seed extract for a second soaking, and then dried to obtain the modified biochar.

[0011] The protective atmosphere described in this invention is more preferably an argon atmosphere.

[0012] As a further preferred embodiment of the present invention, the heat treatment time is 0.5-1h; the pyrolysis treatment time is 1.5-2h.

[0013] As a further preferred embodiment of the present invention, the concentration of the sodium hydroxide solution is 1-2 mol / L; in the mixed aqueous solution of citric acid and jujube seed extract, the concentration of citric acid is 2-3 wt%, and the concentration of jujube seed extract is 1-2 wt%.

[0014] As a further preferred embodiment of the present invention, the first soaking time is 15-20 minutes, and the second soaking time is 15-20 minutes.

[0015] In this invention, the aqueous extract of jujube seed is prepared by the following steps: jujube seed powder is boiled with water, the resulting decoction is concentrated and freeze-dried to obtain the aqueous extract of jujube seed.

[0016] The second technical solution of this invention is to provide the application of the above-mentioned modified biochar in the preparation of soda saline-alkali soil conditioner.

[0017] The third technical solution of this invention provides a soda-based saline-alkali soil conditioner, comprising the following raw material components in parts by weight:

[0018] 25-35 parts modified biochar, 45-55 parts biochar-based fermentation product, 6-8 parts phosphogypsum, 15-20 parts oxalic acid, and 10-12 parts wood ash; the modified biochar is the modified biochar prepared by the above method.

[0019] As a further preferred embodiment of the present invention, the method for preparing the biochar-based fermentation product includes the following steps:

[0020] Biochar, bacterial residue, and beet leaves were mixed in a mass ratio of 3-5:4-5:5-8, and Bacillus polymyxa was added and fermented at 37±2℃ to obtain the biochar-based ferment.

[0021] As a further preferred embodiment of the present invention, the moisture content of the mixture is adjusted to 50-60% before adding Bacillus polymyxa; the amount of Bacillus polymyxa added is 0.5%-1% of the mass of the mixture.

[0022] As a further preferred embodiment of the present invention, the biochar is obtained by pyrolysis of jujube kernels; the pyrolysis temperature is 450-500℃; and the preferred pyrolysis time is 2-3 hours.

[0023] As a further preferred embodiment of the present invention, the fermentation time is 3-4 days.

[0024] The fourth technical solution of this invention provides the application of the above-mentioned soda saline-alkali soil conditioner in the improvement of soda saline-alkali paddy field soil: after spring transplanting, apply 90-100 kg / hm² of the conditioner. 2 The dosage is applied in paddy fields. It is more preferable to apply it by broadcasting 2-4 days after transplanting rice seedlings in spring.

[0025] This invention modifies pine nut shells and uses the resulting modified biomass components as raw materials for soil conditioning, which can enhance the nutrients in soda saline-alkali soil, improve the soil environment, and promote rice growth. The biochar-based fermented product in this invention is rich in nutrients, which can ensure the improvement of soil fertility in saline-alkali land.

[0026] The addition of phosphogypsum in this invention ensures the release of calcium ions; oxalic acid and wood ash ensure the soil alkalinity regulation effect.

[0027] The present invention discloses the following technical effects:

[0028] This invention provides a soil conditioner for the soil characteristics of soda saline-alkali areas. This soil conditioner can significantly improve the soil conditions of soda saline-alkali paddy fields, enhance soil fertility, and ensure increased rice yield. It has important positive significance for promoting agricultural development in soda saline-alkali areas. Detailed Implementation

[0029] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0030] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0031] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0032] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0033] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0034] In the following embodiments and comparative examples of the present invention, *Bacillus polymyxa* was purchased from the China General Microbiological Culture Collection Center (CGMCC), with accession number CGMCC No. 7250; and *Bacillus amyloliquefaciens* was purchased from the China General Microbiological Culture Collection Center (CGMCC), with accession number CGMCC No. 1784.

[0035] Example 1

[0036] Modification treatment of biochar materials:

[0037] (1) Heat-treat pine nut shells at 150℃ for 1 hour, cool to room temperature, and grind them into powder;

[0038] (2) Soak the pine nut shells treated in step (1) in a 1 mol / L sodium hydroxide solution for 15 min. After soaking, filter and dry at room temperature.

[0039] (3) Under an argon atmosphere, the biochar material treated in step (2) was pyrolyzed at 500°C for 1.5 h;

[0040] (4) After cooling the biochar obtained from the pyrolysis in step (3) to room temperature, soak it in a mixed aqueous solution of citric acid and jujube seed extract (the concentration of citric acid is 2.5 wt% and the concentration of jujube seed extract is 1.5 wt%) for 20 min, and then dry it at room temperature to obtain modified biochar.

[0041] The preparation steps of the jujube seed water extract are as follows:

[0042] Add jujube seed powder to water at a ratio of 1:10 (W / V) and boil for 1.5 hours. Filter and discard the residue. Repeat the above steps 3 times, combine the decoctions, concentrate, and freeze-dry to obtain jujube seed water extract.

[0043] Preparation of soda-based soil conditioner for saline-alkali land:

[0044] a. Mix biochar, enoki mushroom residue, and beet leaves in a mass ratio of 3:5:7, adjust the moisture content to 55%, add 0.5% of the mixture by mass of Bacillus polymyxa, and ferment at 37±2℃ for 3 days to obtain biochar-based fermented product;

[0045] Biochar was obtained by pyrolyzing jujube seeds at 450℃ for 3 hours.

[0046] b. Mix modified biochar, biochar-based fermentation product, phosphogypsum, oxalic acid, and wood ash in a mass ratio of 25:40:7:16:11 to obtain a soda saline-alkali soil conditioner.

[0047] Example 2

[0048] Modification treatment of biochar materials:

[0049] (1) Heat-treat pine nut shells at 140℃ for 0.5h, cool to room temperature, and grind them into powder;

[0050] (2) Soak the pine nut shells treated in step (1) in a 2 mol / L sodium hydroxide solution for 20 min. After soaking, filter and dry at room temperature.

[0051] (3) Under an argon atmosphere, the biochar material treated in step (2) was pyrolyzed at 450°C for 1.5 h;

[0052] (4) After cooling the biochar obtained from the pyrolysis in step (3) to room temperature, soak it in a mixed aqueous solution of citric acid and jujube seed extract (the concentration of citric acid is 2wt% and the concentration of jujube seed extract is 1.5wt%) for 20 minutes, and then dry it at room temperature to obtain modified biochar.

[0053] Add jujube seed powder to water at a ratio of 1:15 (W / V) and boil for 2 hours. Filter and discard the residue. Repeat the above steps 3 times, combine the decoctions, concentrate, and freeze-dry to obtain jujube seed water extract.

[0054] Preparation of soda-based soil conditioner for saline-alkali land:

[0055] a. Mix biochar, enoki mushroom residue, and beet leaves in a mass ratio of 4:4:7, adjust the moisture content to 60%, add 0.8% of Bacillus polymyxa by mass of the mixture, and ferment at 37±2℃ for 4 days to obtain biochar-based fermented product;

[0056] Biochar was obtained by pyrolyzing jujube seeds at 500℃ for 2 hours.

[0057] b. Mix modified biochar, biochar-based fermentation product, phosphogypsum, oxalic acid, and wood ash in a mass ratio of 35:55:6:15:12 to obtain a soda saline-alkali soil conditioner.

[0058] Comparative Example 1

[0059] The only difference from Example 1 is that the jujube seed water extract in step (4) is replaced with an equal amount of citric acid.

[0060] Comparative Example 2

[0061] The only difference from Example 1 is that the jujube kernels in step a are replaced with an equal amount of peanut shells.

[0062] Comparative Example 3

[0063] The only difference from Example 1 is that Bacillus polymyxa in step a is replaced with Bacillus amyloliquefaciens.

[0064] Comparative Example 4

[0065] The only difference from Example 1 is that the biochar-based fermentation product is replaced with an equal amount of humic acid.

[0066] Example of effect verification:

[0067] The experimental soil type was severely soda-saline-alkali soil from the Songnen Plain: the pH of the 0-20cm soil layer was 10.61, and the soil volumetric mass was 1.63 g / cm³. 3 The electrical conductivity is 24.25 dS / m, the bicarbonate ion content is 1.67 g / kg, and the alkalinity is 41.21%. The rice variety planted is Dongdao No. 4.

[0068] The experimental site was divided into seven equal-sized plots, each 200m². 2 They were used as experimental groups 1-6 and the control group, respectively.

[0069] The day after spring rice transplanting, at 95 kg / hm 2 The application rate was as follows: experimental groups 1-2 were given the soil conditioner prepared in Examples 1-2, experimental groups 3-6 were given the soil conditioner prepared in Comparative Examples 1-4, and the control group was not given any soil conditioner.

[0070] The remaining management measures are the same for all groups.

[0071] Table 1 shows the decrease in bicarbonate ion (alkalizing ion) concentration in the aquifer of paddy fields in each experimental group relative to the control group.

[0072] Table 1

[0073] Decreased concentration of bicarbonate ions (mg / L) Experimental group 1 135 Experimental group 2 128 Experimental group 3 98 Experimental group 4 112 Experimental group 5 117 Experimental group 6 120 control group -

[0074] After the autumn harvest, the rice yield of each group was counted, and the results are shown in Table 2.

[0075] Table 2

[0076] <![CDATA[Yield (kg / hm 2 )]]> Experimental group 1 5041 Experimental group 2 4987 Experimental group 3 4015 Experimental group 4 4027 Experimental group 5 4556 Experimental group 6 3824 control group 487

[0077] As can be seen from experimental groups 4-5, there is a certain synergistic effect between the biochar obtained from the pyrolysis of jujube kernels and the fermentation bacteria in terms of increasing rice yield.

[0078] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A soda-based soil conditioner for saline-alkali soils, characterized in that, The raw material components include the following parts by weight: 25-35 parts modified biochar, 45-55 parts biochar-based fermentation product, 6-8 parts phosphogypsum, 15-20 parts oxalic acid, and 10-12 parts wood ash; The method for preparing the modified biochar includes the following steps: The pine nut shells, after being heat-treated at 120-150℃, were first soaked in a sodium hydroxide solution, then pyrolyzed at 450-500℃ under a protective atmosphere, cooled, and then soaked in a mixed aqueous solution of citric acid and jujube seed extract. After drying, the modified biochar was obtained. The method for preparing the biochar-based fermentation product includes the following steps: Biochar, bacterial residue, and beet leaves were mixed in a mass ratio of 3-5:4-5:5-8, and Bacillus polymyxa was added and fermented at 37±2℃ to obtain the biochar-based ferment.

2. The soda-based saline-alkali soil conditioner according to claim 1, characterized in that, The heat treatment time is 0.5-1h; the pyrolysis treatment time is 1.5-2h.

3. The soda-based saline-alkali soil conditioner according to claim 1, characterized in that, The concentration of the sodium hydroxide solution is 1-2 mol / L; in the mixed aqueous solution of citric acid and jujube seed extract, the concentration of citric acid is 2-3 wt% and the concentration of jujube seed extract is 1-2 wt%.

4. The soda-based saline-alkali soil conditioner according to claim 1, characterized in that, The first soaking time is 15-20 minutes, and the second soaking time is 15-20 minutes.

5. The soda-based saline-alkali soil conditioner according to claim 1, characterized in that, The biochar is obtained by pyrolysis of jujube kernels; the pyrolysis temperature is 450-500℃ and the time is 2-3h.

6. The soda-based saline-alkali soil conditioner according to claim 1, characterized in that, The fermentation time is 3-4 days.

7. The application of the soda saline-alkali soil conditioner as described in any one of claims 1-6 in the improvement of soda saline-alkali paddy field soil, characterized in that, After transplanting rice seedlings in spring, apply 90-100 kg / hm². 2 The application rate is applied in paddy fields.