CN113336581B - Method for preparing thermal decomposition liquid containing humic acid by rape hydrothermal method and application - Google Patents

Abstract

The invention provides a method for treating waste vegetables and preparing a humic acid-containing pyrolysis liquid based on a hydrothermal conversion technology and application, wherein fresh or stacked waste vegetables in a vegetable production park are taken as raw materials, a KOH solution is added into the raw materials and uniformly mixed, and then polytetrafluoroethylene is utilized for hydrothermal reaction to carry out hydrothermal treatment to obtain a solid-liquid hydrothermal product; centrifuging and filtering the hydrothermal product to obtain filtrate, namely feeding the pyrolysis liquid containing humic acid into the kettle; the pyrolysis liquid has obvious inhibition effect on pathogenic bacteria of Botrytis cinerea (Botrytis cinerea) and Phytophthora capsici (Phytophthora capsicii); meanwhile, the method has a certain promotion effect on the yield and the quality of the green vegetables, is simple to operate, has cheap and easily-obtained raw materials and strong sustainability, and has the potential of large-scale production.

Description

Method for preparing thermal decomposition liquid containing humic acid by rape hydrothermal method and application

Technical Field

The invention relates to the field of disease prevention and disease resistance of soil fertilizers and crops, in particular to a method for preparing a thermal decomposition liquid containing humic acid by a tailed vegetable hydrothermal method.

Background

China, as the first big world, has a great demand for vegetables. Vegetables are the second largest crops in the planting industry of China, which is second to grains, and China is the largest world in China at present. Vegetable planting is also an important industry for increasing the income of farmers. According to the data of the State administration of statistics, the seeding area of vegetables in China in 2019 is about 3.13 hundred million acres, the total yield reaches 7.21 hundred million tons, the development is rapid, and the scale is increased continuously. The tail vegetables refer to the residual leaves of fresh vegetables removed during harvesting, processing, transporting and selling. The ratio of vegetable yield to real intake is 1: 0.7, i.e. about 30% of the vegetables are discarded as tail vegetables. The tailed vegetable has large water content, high carbohydrate, hemicellulose, soluble sugar and volatile solid content, and is easy to decay and acidify.

At present, the common modes for treating the tailstocks include mixed anaerobic fermentation, feed conversion, aerobic composting and the like, but the conventional treatment modes generally have the problems of high pretreatment cost, poor product quality, difficulty in thoroughly removing pollutants such as pathogenic microorganisms and the like, and influence on the quality and the safety of products.

The hydrothermal conversion is a chemical reaction which takes water (usually in a subcritical state) as a reaction medium and the materials are carried out in a closed high-pressure reaction kettle at a certain temperature (usually below 300 ℃) and pressure. The initial application of the hydrothermal conversion technology is the production of biofuel, and after the 30 s in the 20 th century, the technology is applied to various fields such as energy, materials, environment and the like.

Humic acid is a kind of organic substance accumulated by remains of animals and plants through decomposition and transformation of microorganisms and a series of chemical processes. It is a high molecular organic acid formed from aromatic and its several functional groups, and possesses good physiological activity and the functions of absorption, complexation and exchange, etc.. It can be classified into three categories, namely soil humic acid, water humic acid and coal humic acid. Presently, humic acid formation by treating coal by artificial oxidation (e.g., with air, ozone, or nitric acid) is the most common method of humic acid development. Secondly, the excellent directional strains screened by the bioengineering are utilized to extract organic acid substances such as biochemical humic acid and the like after inoculation and fermentation. At present, researches on preparation of liquid humic acid by using tail vegetables as raw materials are less. The literature, "hydrothermal conversion of cabbage leaves in alkali-catalyzed kitchen garbage" (Wangzhini et al, environmental engineering, 2017) discloses a study on hydrothermal reaction by using cabbage leaves, and finds that the cabbage leaves are in NH ₄ The optimal process conditions for preparing the humic acid-containing liquid in the OH-KOH hydrothermal system are as follows: the hydrothermal temperature is 195 deg.C, the KOH consumption is 25%, NH ₄ The OH dosage is 20 percent, and the retention time is 4 hours. Under the condition, the content of humic acid in the pyrolysis liquid is about 7.6g/L, and the pyrolysis liquid and a commercial humic acid-containing water-soluble fertilizer have similar functional group structures, namely, a large number of structures such as hydroxyl, carboxyl, aldehyde and aromatic groups are contained. In addition, the inhibitory action of humic acid obtained by hydrothermal conversion of red beet on pathogenic microorganisms has not been reported, but the inhibitory effect of various humic acids on different pathogenic microorganisms is greatly different (Shiping Wei, Meng Wu, Guilinng Li, Ming Liu, Chunyu Jiang, Zhongpei L)i.e. fungal activity of multiple humic acids in the reaction to the chemical structure, Agricultural and Food Chemistry,2018,66:7514-7521), the difference of the inhibitory effect of humic acid prepared by different methods on microorganisms also affects the utilization of the product and the development of the product. Therefore, the conversion efficiency of humic acid is improved, the product performance is improved, and the technical problem of urgent solution of the hot-water conversion technology popularization of the tailed vegetables is formed.

Disclosure of Invention

Aiming at the problems, the invention provides a method for preparing a thermal decomposition liquid containing humic acid by a rape hydrothermal method, so as to improve the application value of the rape thermal decomposition liquid in the fields of fertilizers and plant protection.

Specifically, the invention firstly provides a method for preparing a thermal decomposition liquid containing humic acid by a rape hydrothermal method, which comprises the following steps:

1) crushing fresh or stacked tailstocks to 1-2 cm in size to obtain tailstocks;

in the present application, the brassica rapa can be leaf vegetables (such as cabbage leaves), rhizome vegetables (such as roots of broccoli) or vine vegetables (such as sweet potato vines) all taken from vegetable production parks;

crushing the waste vegetables to 1-2 cm in size to obtain a waste vegetable raw material; the stacking time of the tail vegetables is not more than 24 h;

2) taking the waste vegetable raw material obtained in the step 1), adding 50% of KOH solution by mass, wherein the addition amount is 10% -30% (w: w) of the weight of the dry waste vegetable, fully and uniformly mixing, putting into a high-temperature high-pressure reaction kettle, and raising the temperature at 160-220 ℃ at the rate of 1-5 ℃ per minute ^-1 Carrying out hydrothermal reaction for 1-3 h under the condition of the autogenous pressure of 5-10 MPa; after the reaction is finished, cooling in a water bath or naturally cooling to room temperature (20-25 ℃), collecting and carrying out solid-liquid separation on the hot products of the rape, and obtaining filtrate which is the hot hydrolysate containing humic acid; and naturally drying or baking the obtained solid to obtain the hot carbon of the tailed vegetable.

In the application, the Chinese medicinal herbs belonging to the leaf vegetables, the root stems and the vine vines are all common terms in the field; see also the introduction in the literature "(Chenci, Zhao Jiang, Gong Jing, the technical route and suggestion of resource utilization of vegetable waste, North horticulture, 2021 (06): 156-.

In the application, the filling degree of a high-temperature high-pressure reaction kettle for hydrothermal reaction is 60-70%.

Secondly, the application provides the application of the humic acid-containing pyrolysis liquid obtained by the method in inhibiting botrytis cinerea and phytophthora capsici.

Thirdly, the application provides the application of the humic acid-containing pyrolysis liquid obtained by the method in improving the yield of the green vegetables.

In the application, the obtained liquid humic acid needs to be diluted by a certain multiple and then used.

Compared with the prior method for preparing liquid humic acid by a hydrothermal method, the method has the following beneficial effects,

1) the invention utilizes a proper amount of KOH solution to carry out catalysis in the pyrolysis process, and the humic acid content in the pyrolysis solution (Y-L7) of the Chinese cabbage tail is 7.72 g/L; the humic acid content in the thermal decomposition liquid (X-L2) of broccoli tail vegetable reaches 8.46 g/L; the humic acid content of the pyrolysis liquid (T-L2) of the sweet potato vine tail vegetable is 6.75 g/L.

2) The liquid humic acid obtained by the method has obvious inhibition effect on pathogenic bacteria of Botrytis cinerea (Botrytis cinerea) and phytophthora capsici (Phytophthoracapsii). When the concentration of humic acid in the liquid phase is 100mg/L, the inhibition rates of Y-L7, X-L2 and T-L2 on botrytis cinerea are respectively as follows: 39.53%, 38.76% and 49.61%; the inhibition rates of Y-L7, X-L2 and T-L2 on phytophthora capsici are respectively as follows: 29.89%, 13.79% and 29.89%.

3) The invention selects the tailed vegetable as the raw material, is cheap and easy to obtain, reduces secondary pollution, realizes high-value utilization of the waste, improves the application effect and the utilization value of the tailed vegetable, and promotes the green and healthy development of the vegetable industry.

4) Adding KOH solution to break the connection between the cellulose and the lignin, removing the lignin in the cellulose, dissolving hemicellulose to obtain cellulose, and improving the conversion rate of humic acid; at the same time introduce K ⁺ And the content of the potassium fertilizer in the prepared humic acid is increased.

Drawings

FIG. 1 shows the characteristics of humic acid in different thermal decomposition liquids of the tail vegetables.

FIG. 2 shows the inhibition effect of different pyrolysis liquids of cabbage on Botrytis cinerea and Phytophthora capsici.

FIG. 3 shows the effect of different pyrolysis liquids of cabbage on promoting the growth and yield of cabbage.

Fig. 4 shows the effect of different pyrolysis liquids of cabbage on promoting the growth quality of cabbage.

Detailed Description

The present invention will be described more fully hereinafter with reference to the following examples, in which specific parameters are set forth to provide a thorough understanding of the features and advantages of the invention, and thus, it will be apparent to those skilled in the art that the invention may be embodied and practiced in a wide variety of ways without departing from the spirit and scope of the invention.

The invention is further illustrated by four examples.

Example 1

Taking a proper amount of Chinese cabbage tail, broccoli tail and sweet potato vine tail (shown in table 1), and crushing to 1-2 cm, wherein the physical and chemical properties of the Chinese cabbage tail, broccoli tail and sweet potato vine tail are shown in table 1; adding 50% (w/w) KOH solution, and uniformly mixing according to the addition amount of 5%, 15% and 25% (w: w) of the weight of the dried tailstocks, wherein the pH value of the materials is shown in Table 2. Placing the materials in a high-temperature high-pressure reaction kettle for hydrothermal reaction, wherein the filling degree of the reaction kettle is 60% (in specific application, the filling degree of the reaction kettle can be controlled within the range of 60% -70% according to actual conditions), the temperatures of the hydrothermal reaction are respectively 160 ℃, 190 ℃ and 220 ℃, the time of the hydrothermal reaction is respectively 1, 2 and 4 hours, and the heating rates are respectively 1-5 ℃ min ^-1 (ii) a In the reaction, the autogenous pressure in the reaction kettle is 5-10 MPa; and after the reaction is finished, collecting the hydrothermal product and carrying out solid-liquid separation to obtain a filtrate, namely the humic acid-containing pyrolysis liquid. The detection of humic acid in the Chinese cabbage tail pyrolysis liquid Y-L, the broccoli tail pyrolysis liquid X-L and the sweet potato vine tail pyrolysis liquid T-L is shown in tables 3-5.

TABLE 1 basic physicochemical Properties of the vegetable tails tested

Note: mean ± standard error (n ═ 3)

TABLE 2 pH of the hydrothermal reaction mass after addition of KOH solution

Note: mean ± sem (n ═ 3); the content of liquid Humic Acid (HA) obtained from three types of rape tails under different hydrothermal reaction conditions in terms of the addition amount of 50% (w/w) KOH solution based on the weight of the dried substances of the rape (w: w) is shown in tables 2 to 4: the assay is described in "Fan Yang, Shuaishuai Zhang, Kui Cheng, Markus Antonietti, A hydrothermal process to turn waste biological inter-organic fluidic fulvic and human acids for soil rededification".

TABLE 3 humic acid content in the pyrolysis liquid of Chinese cabbage under different hydrothermal treatment conditions

TABLE 4 humic acid content in the thermal decomposition liquid of broccoli tail under different hydrothermal treatment conditions

TABLE 5 humic acid content in the thermal hydrolysate of caulis et folium Brassicae Capitatae under different hydrothermal treatment conditions

As can be seen from tables 3 to 5, the highest humic acid content in the pyrolysis liquid after the hydrothermal treatment of the Chinese cabbage is 7 th group: 7.72g/L, the pH value is 6.82, and the optimal hydrothermal reaction conditions are as follows: KOH concentration is 25%, reaction time is 1h, reaction temperature is 220 ℃, and pyrolysis liquid obtained from the optimal group is named as Y-L7; after the hydrothermal treatment of the broccoli and the kombucus vegetable, the humic acid content in the hot hydrolysate is 8.46g/L (group 2) and 6.75g/L (group 2), the pH value is 6.55 and 8.34, and the optimal hydrothermal reaction conditions are as follows: KOH concentration of 15%, reaction time of 2h and reaction temperature of 160 ℃, and the pyrolysis liquids obtained from the optimal group are respectively named as X-L2 and T-L2.

In the specific implementation process, the KOH concentration is 10-30% (w/w), the hydrothermal reaction temperature is 160-220 ℃, the reaction time is 1-3 h, and the heating rate is 1-5 ℃/min, so that the purpose of the invention can be realized.

Example 2

The method for extracting humic acid from the tailed vegetable pyrolysis liquid refers to a method of determination of humic acid content of water-soluble fertilizer (NY/T1971-: selecting the pyrolysis liquid obtained under the optimal hydrothermal condition of the Chinese cabbage tail, the broccoli tail and the sweet potato vine tail in the embodiment 1, namely (Y-L7, X-L2 and T-L2), adding 6mol/L hydrochloric acid into the pyrolysis liquid to acidify the pyrolysis liquid to the pH value of 1-2, uniformly mixing, and standing overnight; and then placing the solution in a centrifuge, centrifuging the solution for 10min at the rotating speed of 4000r/min (if solid floating substances exist in the solution, the centrifugation time needs to be prolonged), pouring out supernate, leaving precipitate, and freeze-drying to obtain the freeze-dried humic acid powder. Wherein, freeze-dried powders of humic acid extracted from Y-L7, X-L2 and T-L2 are respectively marked as Y-HA, X-HA and T-HA. Meanwhile, a commercial humic acid water-soluble fertilizer (Ji nong humic acid-containing water-soluble fertilizer, Shanxi Dingtian Ji nong humic acid product Co., Ltd.) is purchased as a reference, and the freeze-dried humic acid powder extracted by the method is recorded as C-HA. The picture of the obtained freeze-dried powder of humic acid is shown in figure 1 a.

200mg of the freeze-dried powder of humic acid extracted by the method is weighed and analyzed by Fourier transform infrared spectroscopy (FTIR).

The FTIR spectrum is shown in fig. 1b, wherein: peak 1(3236.21 cm) ^-1 ) The stretching vibration of saccharide C-OH, and the compound sources mainly comprise polysaccharide and cellulose; peak 2 (2930-2840 cm) ^-1 ) Is methylene CH characterizing fat and lipid compounds ₂ Antisymmetric telescopic vibration; peak 3(1640 cm) ^-1 ) The vibration of C ═ C skeleton for characterizing aromatic ring, and the C ═ O stretching vibration in amide substancesThe compound is derived from benzene ring and aromatic compound; peak 4(1528 cm) ^-1 ) The amide carboxyl C ═ O stretching vibration is characterized; peak 5(1408 cm) ^-1 ) The stretching vibration of the phenolic hydroxyl C-O is characterized, and the phenolic hydroxyl C-O can be classified into phenolic compounds; peak 6(1207 cm) ^-1 ) The stretching vibration of the aromatic compound COOH was characterized. The number and the positions of characteristic absorption peaks of an FTIR spectrum of HA in three brassica chinensis liquid-phase products are similar to those of commercial humic acid, and all the peaks are rich in oxygen-containing functional groups, such as C-O, COOH.

Further, the results of elemental analysis (Table 4) revealed that T-HA had the highest degree of fatness and the lowest degree of aromaticity, Y-HA had the highest degree of aromaticity and the lowest degree of fatness, and X-HA was between these two types.

TABLE 4 element content of humic acid and commercial humic acid in the pyrolysis liquid

Note: ^a calculated by difference subtraction to obtain

Example 3

The test strains used in this example were tomato Botrytis cinerea (Botrytis cinerea) and Phytophthora capsici (Phytophtora capsici), respectively (both of which are common strains, as reported in the references Shiping Wei, Meng Wu, Guilong Li, Ming Liu, Chunyu Jiang, Zhongpei Li, fungal activity of multiple hunic acids in relationship to the chemical structure, Agricultural and Food Chemistry,2018,66: 7514-.

Firstly, the bacterial strain is activated, and the activation method is described in the literature (Yello, Pink Kogyuchi, Wu' e jiao, Zhuning, Lidong, Mongolian dream letter, Zhou Zhu Meng, and Maps Lepiti. Bacillus altissima XP synthesizes spherical nano-selenium and inhibits the biological activity of strawberry pathogenic fungi. the biological engineering newspaper, 2021, 37 (8): 1-11). A5 mm bacterial dish of activated Botrytis cinerea (Botrytis cinerea) and Phytophthora capsici (Phytophthora capsicii) is taken from the edge of a culture dish, inverted and transferred to the center of a PDA culture medium (3.0 g of potato extract powder, 20.0g of glucose, 14.0g of agar and 1000mL of deionized water; before use, high-pressure steam sterilization is carried out for 20min at the temperature of 121 ℃ and the air is cooled to room temperature for standby), and placed at the temperature of 25 ℃ for dark culture, and the transfer is carried out once every 3 d.

The pyrolysis liquid (namely Y-L7, X-L2 and T-L2) obtained under the optimal hydrothermal condition of the 3 types of brassica chinensis in the example 1 is added into a PDA culture medium, so that the final concentration of the pyrolysis liquid is 10 mg/L, 20 mg/L, 50mg/L and 100mg/L respectively. A5 mm dish was punched out from the edge of a fresh colony cultured for 3 days with a punch, inoculated in the center of a PDA medium containing humic acid, and cultured for 3 days at 25 ℃ with 3 replicates for each treatment set.

As a result, the concentration of humic acid in the 3 types of tailed vegetable pyrolysis liquid is 50mg/L and 100mg/L respectively, and the bacteriostatic effect on botrytis cinerea and phytophthora capsici is better (figure 2). Wherein, as shown in figure 2(a), when the concentration of humic acid is 50mg/L, the Inhibition Rates (IR) of Y-L7, X-L2 and T-L2 on Botrytis cinerea are 39.53%, 38.76% and 49.61%, respectively; as shown in FIG. 2(b), when the humic acid concentration was 100mg/L, the IR values of Y-L7, X-L2, and T-L2 for Phytophthora capsici were 29.89%, 13.79%, and 29.89%, respectively. Under the optimal application condition, the inhibition effect of the tailed vegetable pyrolysis liquid on botrytis cinerea and phytophthora capsici is generally higher than that of commercial humic acid on the market under the same condition.

Example 4

A pot experiment is adopted, and a cabbage pyrolysis solution is sprayed on the leaf surfaces of the green vegetables (Brassica chinensis). Experimental design a total of 5 treatment groups: blank Control (CK) without any fertilizer, conventional fertilizer treatment (CF), application of commercial humic acid fertilizer (C-L), application of broccoli tail pyrolysis liquid (X-L2), and application of sweet potato vine tail pyrolysis liquid (T-L2). Wherein X-L2 and T-L2 were obtained from the optimal hydrothermal conditions in example 1; the fertilizer consists of urea, calcium superphosphate and potassium chloride, and the addition amount of the fertilizer is N, P and K is 2, 1 and 1. Except CK, the same amount of nitrogen is applied to the base fertilizer in each treatment, and the application amount of urea in each pot of soil is 210mg/kg according to the fertilizer requirement characteristic of green vegetable growth. The method for spraying the foliage comprises the following steps: after the green vegetables grow seedlings, the humic acid is sprayed on the leaves every 7 days, the application amount is 200 g/mu, namely 9.4mg of humic acid is sprayed on each pot, and the humic acid is sprayed for 3 times in the whole growth period.

As a result, as shown in FIG. 3(a), the fresh weight of the vegetables in the C-L, X-L2 and T-L2 treatments was increased by 16.9%, 19% and 21.6%, respectively, as compared to the control; as shown in FIG. 3(b), the dry weight was increased by 6.6%, 15.1% and 15.1%, respectively. Wherein the fresh weight and dry weight of the vegetables in the X-L2 and T-L2 treatments are higher than those in the C-L treatment. The result shows that the additional application of humic acid in the growth process of the green vegetables is beneficial to improving the accumulation of dry matters in the green vegetables, and particularly the thermal decomposition liquid of the tail vegetables has a very positive effect on the yield increase of the green vegetables.

As shown in fig. 4(a), spraying the thermal decomposition liquid of the tail vegetables can significantly (P <0.05) increase the chlorophyll content in the green vegetables, and has important effects on improving plant photosynthesis and promoting nutrient absorption of crops; as shown in fig. 4(b), compared with CK, the content of vitamin C in the green vegetables after spraying the tail vegetable pyrolysis liquid is averagely increased by 29% and 44%, and the increase is higher than that of commercial humic acid; as shown in FIG. 4(C), the soluble sugar content was substantially consistent with the trend of vitamin C, with average increases of about 16.0% and 16.8%, higher than commercially available commercial humic acid (i.e., 12.2%).

As shown in fig. 4(d), spraying the broccoli tail pyrolysis liquid can reduce the nitrate content in the green vegetables, but spraying the sweet potato tail pyrolysis liquid can significantly (P <0.05) increase the nitrate content in the green vegetables, which can be up to 609mg/kg (fresh weight), but is far lower than the limit regulation of nitrate (namely less than or equal to 3000mg/kg fresh weight) in the agricultural product safety quality-pollution-free vegetable safety requirement (GB18406.1-2001), and the reason may be that the thermal decomposition liquid prepared from the tail vegetables has high nitrogen content.

The results are combined, and the spraying of the thermal decomposition liquid of the tail vegetables has the effects of yield increase, efficiency improvement and safety on the green vegetables, and has the effect equivalent to that of commercial humic acid water-soluble fertilizer.

Claims (3)

1. A method for preparing a thermal decomposition liquid containing humic acid by a rape hydrothermal method is characterized by comprising the following steps:

1) crushing the waste vegetables to the size of 1-2 cm to obtain a waste vegetable raw material; the tail vegetable is one of Chinese cabbage leaves, broccoli rhizome and sweet potato vine;

2) adding 50% KOH solution into the waste vegetable raw material obtained in the step 1), and after the reaction is finished, cooling the waste vegetable raw material in a water bath or naturally cooling the waste vegetable raw material to room temperature to obtain a waste vegetable hydrothermal product;

when the cabbage raw material is cabbage leaves, the addition amount of the KOH solution is 25% of the weight of the dry cabbage, the reaction time is 1h, the reaction temperature is 220 ℃, the heating rate is 1-5 ℃ per minute ^-1 ；

When the tail vegetable raw material is broccoli rhizome or sweet potato vine, the addition amount of KOH solution is 15 percent of the weight of the dry tail vegetable, the reaction time is 2 hours, the reaction temperature is 160 ℃, the temperature rise rate is 1-5 ℃ per minute ^-1 ；

3) And carrying out solid-liquid separation on the hydrothermal product of the rape to obtain a filtrate, namely the humic acid-containing pyrolysis liquid.

2. Use of a humic acid-containing pyrolysate obtained by the process according to claim 1 for inhibiting Botrytis cinerea and Phytophthora capsici.

3. Use of a humic acid containing pyrolysate obtained by the method of claim 1 for increasing the yield of green vegetables.

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