Organic fertilizer for soil remediation and preparation method thereof

Abstract

The invention belongs to the technical field of fertilizers, and particularly relates to an organic fertilizer for soil remediation and a preparation method thereof. The organic fertilizer for soil remediation comprises the following raw materials in parts by weight: 65-75 parts of an organic fertilizer, 5-10 parts of straw powder, 10-17 parts of a fermentation inoculant, 8-12 parts of a composite adsorbent, 5-10 parts of urea and 1-5 parts of schizophyllum commune polysaccharide. According to the organic fertilizer for soil remediation, the content of heavy metal elements in soil can be effectively reduced, the microbial activity of the soil can be effectively improved, the soil state can be improved, and the soil fertility can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of fertilizers, and particularly relates to an organic fertilizer for soil remediation and a preparation method thereof. Background Art

[0002] Soil is an important basic resource for agricultural production and ecological systems, and its quality is directly related to food security, ecological balance, and the healthy development of human beings. However, with the acceleration of industrialization and urbanization, although the yield of crops has been greatly improved, the accompanying problem of soil pollution has become increasingly prominent, which severely restricts the sustainable development of agriculture and ecological security. Among them, heavy metal pollution is one of the common types of soil pollution. Due to its characteristics of being difficult to degrade, having strong bioaccumulation, being easily transmitted through the food chain, and being irreversible, it has become a global environmental challenge. Common heavy metal pollutants include arsenic (As), lead (Pb), chromium (Cr), etc., which mainly enter the soil through various channels such as industrial wastewater discharge, excessive use of pesticides and fertilizers, mining, and smelting, resulting in excessive heavy metals in the soil, serious pollution, and a decline in soil fertility. Therefore, it is necessary to repair and improve the current soil conditions to meet the requirements of various agricultural plantings.

[0003] Organic fertilizers, as a type of fertilizer made from plant and animal residues or excreta through biological fermentation or composting processes, contain rich organic matter, nitrogen, phosphorus, potassium and other nutrient elements, as well as various microorganisms and bioactive substances. It can not only supplement soil nutrients, but also improve soil structure, enhance the soil's water and fertilizer retention capacity, and promote crop growth. However, traditional organic fertilizers often have limited heavy metal adsorption ability and are difficult to meet the repair requirements of severely polluted soils. Moreover, conventional soil remediation agents are costly and have poor effects when applied to large-scale farmland soil remediation.

[0004] Therefore, in view of the current serious situation of soil heavy metal pollution, combining the soil improvement advantages of organic fertilizers and the heavy metal removal ability of new adsorption materials, developing a functional organic fertilizer that can not only effectively adsorb heavy metals but also improve soil fertility is of great significance for promoting the innovation and application of soil remediation technologies. Summary of the Invention

[0005] In order to overcome the limitations of the prior art, the primary object of the present invention is to provide an organic fertilizer for soil remediation.

[0006] Another object of the present invention is to provide a preparation method of an organic fertilizer for soil remediation.

[0007] The object of the present invention is achieved by the following technical solutions:

[0008] An organic fertilizer for soil remediation, comprising the following raw materials in parts by weight: 65-75 parts of organic fertilizer, 5-10 parts of straw powder, 10-17 parts of fermentation bacterium agent, 8-12 parts of composite adsorbent, 5-10 parts of urea, and 1-5 parts of schizophyllan polysaccharide.

[0009] Further, the preparation process of the composite adsorbent is as follows:

[0010] (1) Take diatomite, treat it with acid and then calcine it to obtain pretreated diatomite;

[0011] (2) Take the pretreated diatomite obtained in step (1) and add it to water containing sodium mercaptoethanesulfonate, heat and stir, and collect the product;

[0012] (3) Add β-cyclodextrin to an aqueous sodium hydroxide solution, and then add glycidyltrimethylammonium chloride, heat and react to obtain cationic cyclodextrin;

[0013] (4) Add the cationic cyclodextrin obtained in step (3) to water, and then add the product obtained in step (2), and react at room temperature to obtain a composite adsorbent.

[0014] Further, the calcination temperature in step (1) is 300-400 °C, and the time is 1.5-2 h; the acid is nitric acid, and the concentration is 2-3 mol / L.

[0015] Further, the mass ratio of the pretreated diatomite to sodium mercaptoethanesulfonate in step (2) is 1:1.5-2; the heating and stirring temperature is 40-45 °C, and the time is 1-2 h.

[0016] Further, the mass ratio of β-cyclodextrin to glycidyltrimethylammonium chloride in step (3) is 1:0.1-0.3, the heating reaction temperature is 55-65 °C, and the time is 2-3 h.

[0017] Further, the mass ratio of the cationic cyclodextrin to the product obtained in step (2) in step (4) is 1:0.03-0.05, the concentration of the cationic cyclodextrin in water is 1-3 wt%; the reaction time is 3-4 h.

[0018] Further, the molecular weight of the schizophyllan polysaccharide is 2-5 kDa.

[0019] Further, the effective viable count of Bacillus subtilis and Bacillus licheniformis in the fermentation bacterium agent is 10 8 per g.

[0020] A preparation method of organic fertilizer for soil remediation, comprising the following steps: mixing organic fertilizer, straw powder, fermentation bacteria agent, composite adsorbent, urea, and schizophyllan polysaccharide evenly according to the said weight parts, and fermenting under anaerobic conditions, and obtaining the product after fermentation is completed.

[0021] Further, the temperature of the fermentation is 37 - 39 °C, and the period is 24 - 27 d.

[0022] The present invention has the following effects compared with the prior art:

[0023] 1. The present invention provides an organic fertilizer for soil remediation. Composite adsorbent and schizophyllan polysaccharide are added to the organic fertilizer. The test results show that the organic fertilizer can effectively reduce the content of heavy metal elements in the soil, improve the soil microbial activity, improve the soil state, and increase the soil fertility. Among them, the composite adsorbent is obtained by combining mercapto-modified diatomite and cationic cyclodextrin through electrostatic and porous adsorption. It is easy to be evenly distributed in the soil without agglomeration and plays the role of adsorbing heavy metals. Specifically, after pretreatment, the diatomite forms a developed pore structure. After surface modification with sodium 2-mercaptoethanesulfonate, mercapto groups (-SH) can be introduced. Mercapto groups have the function of adsorbing heavy metals. For example, arsenic in the soil can be adsorbed and fixed by mercapto groups to form a stable complex. At the same time, sulfur elements also have good affinity for heavy metals such as chromium and lead metal cations. And some chromium elements in the soil exist in the form of anions such as Cr 2 O 7 2- , HCrO 4- etc., and can be adsorbed by binding with cationic cyclodextrin with positive charges through electrostatic attraction. In addition, the addition of schizophyllan polysaccharide in the present invention can improve the microbial activity, and cooperate with components such as urea to improve the soil state and increase the soil fertility.

[0024] 2. The present invention provides a preparation method of an organic fertilizer for soil remediation. The method is simple and feasible to operate and can realize large-scale industrial production. Specific Embodiments

[0025] The embodiments of the present invention will be described in detail below. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded within the range.

[0026] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the description of the present invention, which are obvious to those skilled in the art. Other embodiments obtained from the description of the present invention are obvious to those skilled in the art. The description and examples of this application are merely exemplary.

[0027] The experimental methods in the following examples are all conventional methods unless otherwise specified; the reagents or instruments used are all conventional products obtained through commercial channels unless otherwise specified.

[0028] The preservation numbers of Bacillus subtilis described in the present invention: CICC 10732; the preservation number of Bacillus licheniformis: CICC10103.

[0029] The preparation method of the fermentation inoculant described in the present invention is as follows:

[0030] The purchased Bacillus subtilis and Bacillus licheniformis are respectively subjected to enlarged culture to obtain fermentation broth, and then the fermentation broth is spray-dried to obtain bacterial powder, and the two are mixed in equal mass to obtain a compound microbial inoculant; the effective viable counts of Bacillus subtilis and Bacillus licheniformis in the fermentation inoculant are both 10 8 CFU / g.

[0031] The straw powder described in the present invention is wheat straw powder; the organic fertilizer is black soldier fly manure.

[0032] Example 1

[0033] An organic fertilizer for soil remediation, comprising the following raw materials in parts by weight: 70 parts of organic fertilizer, 8 parts of straw powder, 15 parts of fermentation inoculant, 10 parts of composite adsorbent, 7.5 parts of urea, 3 parts of schizophyllan polysaccharide (molecular weight 3KD);

[0034] The preparation process of the composite adsorbent is as follows:

[0035] (1) Take diatomite and soak it in a nitric acid solution (2mol / L) at 50°C for 8h. After discharging, wash it with deionized water until neutral, and then calcine it at 350°C for 2h in a nitrogen atmosphere, crush and grind it, and pass through a 300-mesh sieve to obtain pretreated diatomite for standby;

[0036] (2) Add the pretreated diatomite obtained in step (1) to water containing sodium mercaptoethanesulfonate, and the mass ratio of the pretreated diatomite to sodium mercaptoethanesulfonate is 1:1.75; then stir at 42°C for 1.5h, let it stand, collect the solid material, wash it, and dry it in vacuum to obtain the product;

[0037] (3) Add β-cyclodextrin to an aqueous sodium hydroxide solution with a concentration of 0.1 mol / L, and then add glycidyltrimethylammonium chloride. The mass ratio of β-cyclodextrin to glycidyltrimethylammonium chloride is 1:0.2, and the concentration of β-cyclodextrin in sodium hydroxide is 2.5 g / mL. React at 60 °C for 2.5 h. After discharging, wash with deionized water until neutral, and then dry in vacuum to obtain cationic cyclodextrin.

[0038] (4) Add the cationic cyclodextrin obtained in step (3) to water, and then add the product of step (2). The mass ratio of the cationic cyclodextrin to the product of step (2) is 1:0.04, and the concentration of the cationic cyclodextrin in water is 2 wt%. After reacting at room temperature for 3.5 h, filter and collect the solid material to obtain the composite adsorbent.

[0039] This Example 1 also provides a preparation method of the above organic fertilizer for soil remediation, including the following steps: Mix the organic fertilizer, straw powder, fermentation inoculant, composite adsorbent, urea, and schizophyllan polysaccharide evenly according to the above weight parts, and ferment at 38 °C for 25 d. After fermentation, it is obtained.

[0040] Example 2

[0041] An organic fertilizer for soil remediation, including the following raw materials in weight parts: 65 parts of organic fertilizer, 5 parts of straw powder, 10 parts of fermentation inoculant, 8 parts of composite adsorbent, 5 parts of urea, and 1 part of schizophyllan polysaccharide (molecular weight 5 KD); The preparation process of the composite adsorbent is as follows:

[0042] (1) Take diatomite and soak it in a nitric acid solution (2 mol / L) at 45 °C for 8 h. After discharging, wash with deionized water until neutral, then calcine at 300 °C for 2 h in a nitrogen atmosphere, crush, grind, and pass through a 300-mesh sieve to obtain pretreated diatomite for standby.

[0043] (2) Add the pretreated diatomite obtained in step (1) to water containing sodium 2-mercaptoethanesulfonate. The mass ratio of the pretreated diatomite to sodium 2-mercaptoethanesulfonate is 1:1.5; Then stir at 40 °C for 2 h, let it stand, collect the solid material, wash, and dry in vacuum to obtain the product.

[0044] (3) Add β-cyclodextrin to an aqueous sodium hydroxide solution with a concentration of 0.1 mol / L, and then add glycidyltrimethylammonium chloride. The mass ratio of β-cyclodextrin to glycidyltrimethylammonium chloride is 1:0.1, and the concentration of β-cyclodextrin in sodium hydroxide is 2.5 g / mL. React at 55 °C for 3 h. After discharging, wash with deionized water until neutral, and then dry in vacuum to obtain cationic cyclodextrin.

[0045] (4) Add the cationic cyclodextrin obtained in step (3) to water, and then add the product obtained in step (2). The mass ratio of the cationic cyclodextrin to the product obtained in step (2) is 1:0.03, and the concentration of the cationic cyclodextrin in water is 1 wt%. After reacting at room temperature for 3 h, filter to collect the solid material to obtain the composite adsorbent.

[0046] Example 2 of the present invention also provides a method for preparing the above organic fertilizer for soil remediation, which includes the following steps: Mix the organic fertilizer, straw powder, fermentation inoculant, composite adsorbent, urea, and schizophyllan polysaccharide evenly according to the above weight parts, and ferment at 37 °C for 27 d. After fermentation is completed, it is obtained.

[0047] Example 3

[0048] An organic fertilizer for soil remediation includes the following raw materials in parts by weight: 75 parts of organic fertilizer, 10 parts of straw powder, 17 parts of fermentation inoculant, 12 parts of composite adsorbent, 10 parts of urea, and 5 parts of schizophyllan polysaccharide (molecular weight 2 KD); the preparation process of the composite adsorbent is as follows:

[0049] (1) Take diatomite and soak it in a nitric acid solution (2 mol / L) at 55 °C for 7 h. After discharging, wash it with deionized water until neutral, then calcine it at 400 °C for 1.5 h in a nitrogen atmosphere, crush and grind it, and pass through a 300-mesh sieve to obtain pretreated diatomite for standby.

[0050] (2) Add the pretreated diatomite obtained in step (1) to water containing sodium mercaptoethanesulfonate, where the mass ratio of the pretreated diatomite to sodium mercaptoethanesulfonate is 1:2; then stir at 45 °C for 1 h, let it stand, collect the solid material, wash it, and dry it in vacuum to obtain the product.

[0051] (3) Add β-cyclodextrin to an aqueous sodium hydroxide solution with a concentration of 0.1 mol / L, and then add glycidyltrimethylammonium chloride. The mass ratio of β-cyclodextrin to glycidyltrimethylammonium chloride is 1:0.3, and the concentration of β-cyclodextrin in sodium hydroxide is 2.5 g / mL; react at 65 °C for 2 h. After discharging, wash it with deionized water until neutral, and dry it in vacuum to obtain cationic cyclodextrin.

[0052] (4) Add the cationic cyclodextrin obtained in step (3) to water, and then add the product obtained in step (2). The mass ratio of the cationic cyclodextrin to the product obtained in step (2) is 1:0.05, and the concentration of the cationic cyclodextrin in water is 3 wt%. After reacting at room temperature for 4 d, filter to collect the solid material to obtain the composite adsorbent.

[0053] Example 3 also provides a method for preparing the organic fertilizer for soil remediation, which includes the following steps: Mix the organic fertilizer, straw powder, fermentation inoculant, composite adsorbent, urea, and schizophyllan polysaccharide evenly according to the said parts by weight, and ferment at 39 °C for 24 days. After fermentation, it is obtained.

[0054] Comparative Example 1

[0055] This Comparative Example 1 is basically the same as Example 1, except that the composite adsorbent is replaced with pretreated diatomite, and the others are the same as Example 1.

[0056] Comparative Example 2

[0057] This Comparative Example 2 is basically the same as Example 1, except that steps (3) and (4) are omitted in the preparation process of the composite adsorbent, and the others are the same as Example 1.

[0058] Comparative Example 3

[0059] This Comparative Example 3 is basically the same as Example 1, except that the composite adsorbent is replaced with cationic cyclodextrin, and the others are the same as Example 1.

[0060] Comparative Example 4

[0061] This Comparative Example 4 is basically the same as Example 1, except that schizophyllan polysaccharide is omitted, and the others are the same as Example 1.

[0062] Comparative Example 5

[0063] This Comparative Example 5 is basically the same as Example 1, except that schizophyllan polysaccharide is replaced with schizophyllan polysaccharide with a molecular weight of 20 KD, and the others are the same as Example 1.

[0064] Test Example

[0065] Taking the soil of Nantaihu Village, Lijingpu Sub-district, Ningxiang City as the test site, the basic physical and chemical properties of the soil in the above test area are as follows: The pH value is 6.8, and the contents of chromium, lead, and arsenic in the soil are 353.56 mg / kg, 159.25 mg / kg, and 54.38 mg / kg respectively. The contents of total nitrogen, available phosphorus, and available potassium are 0.95 g / kg, 3.8 g / kg, and 8.5 g / kg respectively, and the organic matter content is 12.1 g / kg.

[0066] The organic fertilizers for soil remediation prepared in Examples 1-3 and Comparative Examples 1-5 were evenly spread on the surface of the contaminated soil at a dosage of 30 kg / mu respectively. In addition, a blank group (only applying an equal amount of conventional fertilizer) was set up. The above were divided into 9 groups in total. The area of each plot is 300 m 2, Each treatment was set with 3 replicates, and then the soil was plowed to mix it thoroughly with the contaminated soil. After 45 days, rice was planted, and the field management was the same as normal agricultural production. After the crops matured, soil samples were collected to measure the contents of heavy metals chromium and lead in the soil, and the results are shown in Table 1. Then, the growth conditions and yields of the rice were detected, and the results are shown in Table 2;

[0067] Table 1

[0068]

[0069] From the test results in Table 1, it can be seen that compared with the blank group, the contents of heavy metal elements Cr and Pb in Examples 1-3 of the present invention are significantly reduced, and are far lower than those in Comparative Examples 1-3. This shows that the organic fertilizer for soil remediation prepared by the present invention can effectively reduce the heavy metal elements Cr and Pb in the soil, improve the basic properties of the soil, and thus increase the soil fertility.

[0070] Compared with Example 1, in Comparative Examples 1-3, the composite adsorbent was replaced with pretreated diatomite, steps (3) and (4) were omitted during the preparation of the composite adsorbent, and the composite adsorbent was replaced with cationic cyclodextrin, and the contents of heavy metal elements Cr and Pb in the soil were relatively high. The reason for the above results is that the functionalized mercapto group (-SH) introduced into the composite adsorbent has an adsorption effect on heavy metal cations, so that heavy metal cations such as chromium and lead can be adsorbed and fixed by the mercapto group to form stable complexes, while Cr 2 O7 2- 、HCrO 4- and other anions combine with the positively charged cationic cyclodextrin through electrostatic attraction, thus realizing the effective adsorption of Cr and Pb.

[0071] Statistical results of the growth conditions and yields of rice in Table 2

[0072] Experimental field Ear weight (g) Ear length (cm) 1000-grain weight (g) Yield (kg / mu) Control group 4.56 15.89 26.42 562.28 Example 1 5.32 17.43 31.25 640.67 Example 2 5.13 17.18 30.82 631.53 Example 3 5.21 17.32 31.09 638.42 Comparative example 1 5.06 17.03 30.15 594.33 Comparative example 2 5.11 17.16 30.34 612.43 Comparative example 3 5.09 17.11 30.22 605.74 Comparative example 4 5.07 17.06 30.18 603.17 Comparative example 5 5.12 17.17 30.47 627.51

[0073] From the test data in Table 2, it can be seen that the panicle weight, panicle length, 1000-grain weight and yield of rice in Examples 1-3 are all higher than those in Comparative Examples 1-3 and are all higher than those in the control group, indicating that the organic fertilizer for soil remediation obtained by the present invention can effectively increase the soil fertility and promote the growth of rice. Among them, in Comparative Example 4, schizophyllan polysaccharide was omitted, and the panicle weight, panicle length, 1000-grain weight and yield of rice decreased significantly, which indicates that the addition of schizophyllan polysaccharide in the organic fertilizer can improve the microbial activity, cooperate with components such as urea to improve the soil state, and increase the soil fertility. In Comparative Example 5, schizophyllan polysaccharide was replaced with schizophyllan polysaccharide with a molecular weight of 20KD, and the soil fertility decreased compared with Example 1, indicating that the molecular weight of schizophyllan polysaccharide also affects the microbial activity to a certain extent, and thus affects the soil fertility.

[0074] In summary, the organic fertilizer for soil remediation according to the present invention can effectively reduce the content of heavy metal elements in the soil, and can effectively improve the activity of soil microorganisms, improve the soil condition, and increase the soil fertility.

[0075] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. An organic fertilizer for soil remediation, characterized in that: The invention comprises the following raw materials in parts by weight: 65-75 parts of organic fertilizer, 5-10 parts of straw powder, 10-17 parts of fermentation bacteria agent, 8-12 parts of composite adsorbent, 5-10 parts of urea and 1-5 parts of schizophyllum polysaccharide.

2. The organic fertilizer for soil remediation according to claim 1, characterized in that: The preparation process of the composite adsorbent is as follows: (1) treating diatomaceous earth with acid and then calcining it to obtain pretreated diatomaceous earth; (2) adding the diatomaceous earth pretreated in step (1) into water containing sodium mercaptoethanesulfonate, heating and stirring, and collecting the product; (3) adding β-cyclodextrin to a sodium hydroxide aqueous solution, then adding glycidyltrimethylammonium chloride, and heating for reaction to obtain cationic cyclodextrin; (4) Add the cationic cyclodextrin of step (3) into water, then add the product of step (2), and react at room temperature to obtain a composite adsorbent.

3. The organic fertilizer for soil remediation according to claim 2, characterized in that, The calcination temperature in step (1) is 300-400° C. and the calcination time is 1.5-2 h; the acid is nitric acid and the concentration is 2-3 mol / L.

4. The organic fertilizer for soil remediation according to claim 2, characterized in that, The mass ratio of the pretreated diatomaceous earth to sodium mercaptoethanesulfonate in step (2) is 1:1.5-2; the heating and stirring temperature is 40-45°C and the time is 1-2h.

5. The organic fertilizer for soil remediation according to claim 2, characterized in that, In step (3), the mass ratio of β-cyclodextrin to glycidyltrimethylammonium chloride is 1:0.1-0.3, the temperature of the heating reaction is 55-65° C., and the time is 2-3 h.

6. The organic fertilizer for soil remediation according to claim 2, characterized in that, The mass ratio of the cationic cyclodextrin in step (4) to the product of step (2) is 1:0.03-0.05, and the concentration of the cationic cyclodextrin in water is 1-3wt%; the reaction time is 3-4h.

7. The organic fertilizer for soil remediation according to claim 2, characterized in that: The molecular weight of the Schizophyllan is 2-5 kDa.

8. The organic fertilizer for soil remediation according to claim 1, characterized in that: The effective viable counts of Bacillus subtilis and Bacillus licheniformis in the fermentation agent are both 10 8 Pieces / g.

9. A method for preparing organic fertilizer for soil remediation, characterized in that: The method comprises the following steps: uniformly mixing organic fertilizer, straw powder, fermentation agent, composite adsorbent, urea and Schizophyllum polysaccharide according to the weight proportions, fermenting under anaerobic conditions, and obtaining the product after the fermentation is completed.

10. The method for preparing organic fertilizer for soil remediation according to claim 9, characterized in that: The fermentation temperature is 37-39° C. and the fermentation period is 24-27 days.

Images