Preparation method for preparing plant growth substrate with high water and fertilizer retention performance based on construction waste soil

Abstract

The preparation method comprises the following steps: putting a sodium lignin sulfonate solution into a reactor, adjusting the pH value of the sodium lignin sulfonate solution, carrying out sedimentation treatment, and then carrying out freeze drying to obtain purified lignin; dissolving the purified lignin in DMF, adding pyridine and palmitoyl chloride under a water bath condition, stirring to react, pouring a reaction solution into an icy hydrochloric acid solution after the reaction is finished, stirring to precipitate, filtering, and drying the precipitate to obtain modified lignin; uniformly mixing and stirring the modified lignin solution and the polylactic acid solution, and adding the active charcoal to prepare a cladding material; adding an inorganic fertilizer and a trace element fertilizer into the cladding material for dipping treatment, filtering and quickly drying to obtain a slow-release fertilizer; the soil conditioner is prepared by stirring and mixing turfy soil, vermiculite, bagasse, polyacrylamide, kaolin, muck, slow-release fertilizer and citric acid. The plant growth substrate provided by the invention not only has excellent water and fertilizer retention performance, but also is low in preparation cost.

Description

Technical Field

[0001] The present invention relates to the field of agricultural technology, and in particular to a method for preparing a high-water- and fertilizer-retaining plant growth matrix based on construction waste. Background Art

[0002] Plant growth substrates are the material foundation for plant growth, providing nutrients and support. Current plant growth substrates primarily include the following components: Leaf mold: formed by microbial decomposition and fermentation of plant branches and leaves in the soil. It has excellent water and air permeability and is rich in organic matter. Garden soil: Soil from fields or vegetable gardens, which, after years of cultivation and fertilization, has become loose and nutrient-rich. Mountain soil: Humus soil from the mountains, containing a certain amount of organic matter and minerals, has good drainage and air permeability. River sand: While lacking in fertility, it is pure, pathogen-free, neutral in nature, and has excellent air and water permeability. It can improve soil structure. In addition to these components, materials such as ceramsite, perlite, and vermiculite can also serve as plant growth substrates. Current plant growth substrates are not only expensive to prepare, but their water and fertilizer retention capabilities require further improvement.

[0003] Construction waste primarily includes bricks, stones, concrete blocks, bentonite, organic matter, composite fibers, soil stabilizers, granulating agents, fertilizers, and acidic substances. These materials come from the demolition of old buildings and waste materials from new construction. Directly discarding construction waste not only wastes resources but also pollutes the environment. Therefore, the application of construction waste in the preparation of high-performance plant growth substrates has become a hot topic of research. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: in view of the shortcomings of the existing technology, a preparation method of a high water- and fertilizer-retaining plant growth matrix based on construction waste is provided. The plant growth matrix prepared by this method has good water- and fertilizer-retaining properties and low preparation cost.

[0005] In order to solve the above technical problems, the technical solution of the present invention is:

[0006] A method for preparing a high-water- and fertilizer-retaining plant growth substrate based on construction waste soil comprises the following steps:

[0007] S1: placing a sodium lignin sulfonate solution in a reactor, adjusting its pH to 2-3, and performing sedimentation treatment. The filter residue is washed and freeze-dried to obtain purified lignin; the purified lignin is dissolved in DMF in a reactor, pyridine and palmitoyl chloride are added to the reactor under water bath conditions, and stirred for reaction. After the reaction is completed, the reaction solution is poured into a glacial hydrochloric acid solution, stirred for precipitation, and finally filtered. The filter residue is washed and freeze-dried to obtain modified lignin;

[0008] S2: The modified lignin solution and the polylactic acid solution are mixed and stirred evenly, and then activated biochar is added to prepare a coating material; inorganic fertilizers and trace element fertilizers are added to the coating material for impregnation treatment, and then filtered and quickly dried to prepare a slow-release fertilizer;

[0009] S3: stir and mix peat soil, vermiculite, bagasse, polyacrylamide, kaolin, slag soil, slow-release fertilizer and citric acid until evenly mixed.

[0010] As a preferred embodiment of the above technical solution, in step S1, the concentration of the sodium lignin sulfonate solution is 0.03-0.05 g / ml, and the concentration of the glacial hydrochloric acid solution is 3-5 wt %.

[0011] As a preferred embodiment of the above technical solution, in step S1, the usage ratio of the purified lignin, pyridine and palmitoyl chloride is 0.5-1 g: 5 ml: 4-5 ml.

[0012] As a preferred embodiment of the above technical solution, in step S1, the stirring reaction is carried out at a speed of 500-800 rpm, a temperature of 40-50° C., and a time of 2-3 h.

[0013] As a preferred embodiment of the above technical solution, in step S2, the concentration of the modified lignin solution is 5-7wt%, the concentration of the polylactic acid solution is 20-30wt%, and the mass ratio of the modified lignin solution, polylactic acid solution, and activated biochar is 1:1-2:0.05-0.08.

[0014] As a preferred embodiment of the above technical solution, in step S2, the inorganic fertilizer is a mixture of urea, potassium dihydrogen phosphate, and ammonium phosphate, and the mass ratio of the three is 1:1:1; the trace element fertilizer is a mixture of cobalt nitrate, zinc nitrate, and manganese nitrate, and the mass ratio of the three is 1:1:1; the mass ratio of the inorganic fertilizer to the trace element fertilizer is 1:0.01-0.05.

[0015] As a preferred embodiment of the above technical solution, in step S2, the immersion treatment temperature is room temperature, and the immersion treatment time is 1-2 minutes.

[0016] As a preferred embodiment of the above technical solution, in step S2, the method for preparing the activated biochar is: crushing corn straw and then calcining it to obtain biochar, placing the biochar in a mixed aqueous solution of acrylic acid and acrylamide, adding potassium persulfate and N,N-methylenebisacrylamide to carry out polymerization reaction, filtering after the reaction is completed, and drying the precipitate to obtain activated biochar.

[0017] As a preferred embodiment of the above technical solution, the calcination temperature is 500° C., the time is 2-3 hours, and the atmosphere is nitrogen.

[0018] As a preferred embodiment of the above technical solution, the mass ratio of the biochar, acrylic acid, acrylamide, potassium persulfate, and N,N-methylenebisacrylamide is 1:0.2-0.5:0.01-0.08:0.001-0.002:0.005-0.01; the reaction temperature is 65-70°C, and the reaction time is 1-2h.

[0019] As a preferred embodiment of the above technical solution, in step S3, the amounts of each component used are, by weight, 5-10 parts of peat soil, 1-2 parts of vermiculite, 2-5 parts of bagasse, 1-2 parts of polyacrylamide, 1-2 parts of kaolin, 3-4 parts of slag, 3-6 parts of slow-release fertilizer, and 1-2 parts of citric acid.

[0020] Due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0021] (1) The plant growth matrix disclosed in the present invention includes peat soil, vermiculite, bagasse, polyacrylamide, kaolin, slag, slow-release fertilizer and citric acid. It has a porous structure, can accommodate a large amount of water, and has good air permeability, can regulate water evaporation, and is beneficial to the growth of plant roots. Among them, polyacrylamide can improve the water retention capacity of the matrix, and kaolin can absorb the nutrients required by plants, thereby enhancing the fertilizer retention performance of the matrix. Slag and slow-release fertilizer can also slowly release nutrients, providing a continuous source of nutrition for plants. In addition, the addition of bagasse can increase the biological activity of the matrix, which is beneficial to promoting plant growth and nutrient absorption. In short, this plant growth matrix achieves high water retention and fertilizer retention performance through the combination and interaction of multiple materials, providing a good growth environment for plants.

[0022] (2) The slow-release fertilizer provided by the present invention uses a compound of modified lignin and activated biochar as a coating material, which can wrap the fertilizer and slow down the release rate of the fertilizer, thereby improving the utilization rate of the fertilizer. At the same time, the coating material can also adsorb and fix moisture and nutrients in the soil, reduce water evaporation and nutrient loss, and improve the plant's absorption efficiency of moisture and nutrients. In addition, the addition of activated biochar can improve the air permeability and permeability of the soil, promote the reproduction and activity of soil microorganisms, and further promote the growth and development of plants. The superior hydrophobic properties of palmitoyl chloride grafted lignin and the hierarchical porous structure of activated biochar work together to have good water retention capacity. In short, the above-mentioned slow-release fertilizer can improve the water and fertilizer retention properties of the plant growth matrix through multiple effects such as modified lignin, polylactic acid, and activated biochar, which helps to improve the yield and quality of crops. DETAILED DESCRIPTION

[0023] The present invention will be further described below with reference to the following examples. It should be understood that these examples are only intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0024] The slag in the following examples is waste concrete powder slag, and its chemical index is pH=8.7 and electrical conductivity is 340μs / cm.

[0025] Example 1

[0026] A method for preparing a high-water- and fertilizer-retaining plant growth substrate based on construction waste soil comprises the following steps:

[0027] S1: placing a 0.03 g / ml sodium lignin sulfonate solution in a reactor, adjusting its pH to 2, and performing sedimentation treatment. After washing the filter residue, freeze-drying it at -10°C for 20 hours to obtain purified lignin; dissolving 0.5 g of purified lignin in 50 ml of DMF in a reactor, adding 5 ml of pyridine and 4 ml of palmitoyl chloride to the reactor under a 40°C water bath condition, stirring at 500 rpm for 3 hours, and after the reaction is completed, pouring the reaction solution into 200 ml of a 3 wt% glacial hydrochloric acid solution, stirring and precipitating, and finally filtering, washing the filter residue, and freeze-drying it to obtain modified lignin;

[0028] S2: Corn straw was crushed and calcined at 500°C in a nitrogen atmosphere for 2 hours to produce biochar. 5g of biochar was placed in a mixed aqueous solution containing 1g of acrylic acid and 0.05g of acrylamide. 0.005g of potassium persulfate and 0.025g of N,N-methylenebisacrylamide were added. The mixture was polymerized at 70°C for 1 hour. After the reaction, the mixture was filtered and the precipitate was dried to produce activated biochar.

[0029] S3: 20 g of a 5 wt% modified lignin solution and 20 g of a 20 wt% polylactic acid solution were mixed and stirred uniformly, and then 1 g of activated biochar was added to prepare a cladding material; 2 g of urea, 2 g of potassium dihydrogen phosphate, 2 g of ammonium phosphate, 0.1 g of cobalt nitrate, 0.1 g of zinc nitrate, and 0.1 g of manganese nitrate were mixed to prepare a mixed fertilizer, which was added to the cladding material and impregnated for 1 minute, then filtered and quickly dried to prepare a slow-release fertilizer;

[0030] S4: In parts by weight, 8 parts of peat soil, 2 parts of vermiculite, 2 parts of sugarcane bagasse, 1 part of polyacrylamide, 2 parts of kaolin, 3 parts of slag soil, 5 parts of slow-release fertilizer, and 1 part of citric acid are stirred and mixed evenly.

[0031] Example 2

[0032] A method for preparing a high-water- and fertilizer-retaining plant growth substrate based on construction waste soil comprises the following steps:

[0033] S1: placing a 0.05 g / ml sodium lignin sulfonate solution in a reactor, adjusting its pH to 2, and performing sedimentation treatment. After washing the filter residue, freeze-drying it at -15°C for 20 hours to obtain purified lignin; dissolving 1 g of purified lignin in 50 ml of DMF in a reactor, adding 5 ml of pyridine and 5 ml of palmitoyl chloride to the reactor under a 50°C water bath condition, stirring at 800 rpm for 2 hours, and after the reaction is completed, pouring the reaction solution into 200 ml of a 5 wt% glacial hydrochloric acid solution, stirring and precipitating, and finally filtering, washing the filter residue, and freeze-drying it to obtain modified lignin;

[0034] S2: Corn straw was crushed and calcined at 500°C in a nitrogen atmosphere for 2 hours to produce biochar. 5g of biochar was placed in a mixed aqueous solution containing 2.5g of acrylic acid and 0.4g of acrylamide, and 0.01g of potassium persulfate and 0.05g of N,N-methylenebisacrylamide were added. The mixture was polymerized at 70°C for 2 hours. After the reaction, the mixture was filtered and the precipitate was dried to produce activated biochar.

[0035] S3: 20 g of a 6 wt% modified lignin solution and 20 g of a 20 wt% polylactic acid solution were mixed and stirred uniformly, and then 1.5 g of activated biochar was added to prepare a cladding material; 3 g of urea, 3 g of potassium dihydrogen phosphate, 3 g of ammonium phosphate, 0.15 g of cobalt nitrate, 0.15 g of zinc nitrate, and 0.15 g of manganese nitrate were mixed to prepare a mixed fertilizer, which was added to the cladding material and impregnated for 2 minutes, then filtered and quickly dried to prepare a slow-release fertilizer;

[0036] S4: In parts by weight, 6 parts of peat soil, 1 part of vermiculite, 3 parts of sugarcane bagasse, 1 part of polyacrylamide, 2 parts of kaolin, 4 parts of slag soil, 6 parts of slow-release fertilizer, and 1 part of citric acid are stirred and mixed evenly.

[0037] Example 3

[0038] A method for preparing a high-water- and fertilizer-retaining plant growth substrate based on construction waste soil comprises the following steps:

[0039] S1: placing a 0.04 g / ml sodium lignin sulfonate solution in a reactor, adjusting its pH to 2, and performing sedimentation treatment. After washing the filter residue, freeze-drying it at -10°C for 20 hours to obtain purified lignin; dissolving 0.6 g of purified lignin in 50 ml of DMF in a reactor, adding 5 ml of pyridine and 5 ml of palmitoyl chloride to the reactor under a 40°C water bath condition, stirring at 600 rpm for 2 hours, and after the reaction is completed, pouring the reaction solution into 200 ml of a 4 wt% glacial hydrochloric acid solution, stirring and precipitating, and finally filtering, washing the filter residue, and freeze-drying it to obtain modified lignin;

[0040] S2: Corn straw was crushed and calcined at 500°C in a nitrogen atmosphere for 2 hours to produce biochar. 5g of biochar was placed in a mixed aqueous solution containing 2g of acrylic acid and 0.1g of acrylamide, and 0.005g of potassium persulfate and 0.03g of N,N-methylenebisacrylamide were added. The mixture was polymerized at 70°C for 1 hour. After the reaction, the mixture was filtered and the precipitate was dried to produce activated biochar.

[0041] S3: 20 g of a 6 wt% modified lignin solution and 30 g of a 20 wt% polylactic acid solution were mixed and stirred uniformly, and then 1.5 g of activated biochar was added to prepare a cladding material; 4 g of urea, 4 g of potassium dihydrogen phosphate, 4 g of ammonium phosphate, 0.2 g of cobalt nitrate, 0.2 g of zinc nitrate, and 0.2 g of manganese nitrate were mixed to prepare a mixed fertilizer, which was added to the cladding material and impregnated for 1 min, then filtered and quickly dried to prepare a slow-release fertilizer;

[0042] S4: In parts by weight, 8 parts of peat soil, 2 parts of vermiculite, 4 parts of bagasse, 2 parts of polyacrylamide, 2 parts of kaolin, 3 parts of slag, 5 parts of slow-release fertilizer, and 2 parts of citric acid are stirred and mixed evenly.

[0043] Example 4

[0044] A method for preparing a high-water- and fertilizer-retaining plant growth substrate based on construction waste soil comprises the following steps:

[0045] S1: placing a 0.05 g / ml sodium lignin sulfonate solution in a reactor, adjusting its pH to 2, and performing sedimentation treatment. After washing the filter residue, freeze-drying it at -10°C for 20 hours to obtain purified lignin; dissolving 0.8 g of purified lignin in 50 ml of DMF in a reactor, adding 5 ml of pyridine and 5 ml of palmitoyl chloride to the reactor under a 40°C water bath condition, stirring at 600 rpm for 2 hours, and after the reaction is completed, pouring the reaction solution into 200 ml of a 4 wt% glacial hydrochloric acid solution, stirring and precipitating, and finally filtering, washing the filter residue, and freeze-drying it to obtain modified lignin;

[0046] S2: Corn straw was crushed and calcined at 500°C in a nitrogen atmosphere for 2 hours to produce biochar. 5g of biochar was placed in a mixed aqueous solution containing 2g of acrylic acid and 0.2g of acrylamide, and 0.008g of potassium persulfate and 0.035g of N,N-methylenebisacrylamide were added. The mixture was polymerized at 70°C for 2 hours. After the reaction, the mixture was filtered and the precipitate was dried to produce activated biochar.

[0047] S3: 20 g of a 6.5 wt% modified lignin solution and 25 g of a 20 wt% polylactic acid solution were mixed and stirred uniformly, and then 1.5 g of activated biochar was added to prepare a cladding material; 4 g of urea, 4 g of potassium dihydrogen phosphate, 4 g of ammonium phosphate, 0.2 g of cobalt nitrate, 0.2 g of zinc nitrate, and 0.2 g of manganese nitrate were mixed to prepare a mixed fertilizer, which was added to the cladding material and impregnated for 2 minutes, then filtered and quickly dried to prepare a slow-release fertilizer;

[0048] S4: In parts by weight, 9 parts of peat soil, 2 parts of vermiculite, 5 parts of bagasse, 2 parts of polyacrylamide, 2 parts of kaolin, 4 parts of slag soil, 6 parts of slow-release fertilizer, and 2 parts of citric acid are stirred and mixed evenly.

[0049] Comparative Example 1

[0050] No activated biochar was added during the preparation of the slow-release fertilizer, and other conditions were the same as in Example 4.

[0051] Comparative Example 2

[0052] No modified lignin was added during the preparation of the slow-release fertilizer, and other conditions were the same as in Example 4.

[0053] The performance of the plant growth substrate prepared above was tested. The test method and test results are as follows.

[0054] 1. Water retention performance

[0055] The plant growth substrates prepared in the above examples and comparative examples with a mass of m1 were respectively placed in non-woven bags with a mass of n. The bags were then soaked in 50 ml of distilled water for 24 h, taken out, drained until no water dripped out, and weighed, which was m2. The bags were weighed again 1 day later, which was recorded as m3. The water absorption rate and water evaporation rate were calculated.

[0056] Water absorption rate (%) = (m2-n-m1) / m1;

[0057] Evaporation rate (g / h) = (m3-m2) / 24.

[0058] 2. Fertilizer retention performance

[0059] Nutrient solutions were prepared using a fertilization standard of 0.8 g of ammonium nitrate per bag and 0.35 g of potassium dihydrogen phosphate per bag. These solutions were then poured into the substrate bags containing the plant growth substrates prepared in the above examples and comparative examples. Water was then applied daily at 200 mL per bag. Permeate was collected from beneath the substrate bags for seven consecutive days. The volume and nutrient content of the permeate were measured to calculate the nitrogen, phosphorus, and potassium nutrient losses after leaching from the different substrates after seven days.

[0060] Table 1

[0061]

[0062]

[0063] From the above tests, it can be seen that the plant growth matrix prepared by the present invention has excellent water and fertilizer retention properties, and the synergistic effect of the palmitoyl chloride grafted modified lignin and activated biochar in the coating material of the slow-release fertilizer further improves the performance of the plant growth matrix. This is mainly because the palmitoyl chloride grafted modified lignin has good hydrophobicity, which can delay the water penetration of fertilizer nutrients, thereby prolonging the release rate of the fertilizer and achieving a slow-release effect. Activated biochar has excellent adsorption properties and can effectively adsorb nutrients in the fertilizer, further reducing the release rate of the fertilizer and enhancing the slow-release effect of the fertilizer. The synergistic effect of the palmitoyl chloride grafted modified lignin and activated biochar can further improve the water and fertilizer retention properties. On the one hand, lignin forms a protective film on the surface of the fertilizer, effectively preventing excessive evaporation of water, and also preventing the rapid penetration of fertilizer nutrients; on the other hand, the adsorption effect of activated biochar can further slow down the release rate of fertilizer nutrients, thereby improving the utilization rate of the fertilizer.

[0064] In addition, it should be understood that after reading the contents of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A method for preparing a high water and fertilizer retention plant growth matrix based on construction waste, characterized in that: The following steps are involved: S1: placing a sodium lignin sulfonate solution in a reactor, adjusting its pH to 2-3, and performing sedimentation treatment. The filter residue is washed and freeze-dried to obtain purified lignin; the purified lignin is dissolved in DMF in a reactor, pyridine and palmitoyl chloride are added to the reactor under water bath conditions, and stirred for reaction. After the reaction is completed, the reaction solution is poured into a glacial hydrochloric acid solution, stirred for precipitation, and finally filtered. The filter residue is washed and freeze-dried to obtain modified lignin; S2: The modified lignin solution and the polylactic acid solution are mixed and stirred evenly, and then activated biochar is added to prepare a coating material; inorganic fertilizers and trace element fertilizers are added to the coating material for impregnation treatment, and then filtered and quickly dried to prepare a slow-release fertilizer; S3: stir and mix peat soil, vermiculite, bagasse, polyacrylamide, kaolin, slag soil, slow-release fertilizer and citric acid until evenly mixed.

2. The method for preparing a high water and fertilizer retention plant growth matrix based on construction waste according to claim 1, characterized in that: In step S1, the concentration of the sodium lignin sulfonate solution is 0.03-0.05 g / ml, and the concentration of the glacial hydrochloric acid solution is 3-5 wt%.

3. The method for preparing a high water and fertilizer retention plant growth matrix based on construction waste according to claim 1, characterized in that: In step S1, the usage ratio of the purified lignin, pyridine and palmitoyl chloride is 0.5-1 g: 5 ml: 4-5 ml.

4. The method for preparing a high water and fertilizer retention plant growth medium based on construction waste according to claim 1, characterized in that: In step S1, the stirring reaction is carried out at a rotation speed of 500-800 rpm, a temperature of 40-50° C., and a time of 2-3 h.

5. The method for preparing a high water and fertilizer retention plant growth matrix based on construction waste according to claim 1, characterized in that: In step S2, the concentration of the modified lignin solution is 5-7wt%, the concentration of the polylactic acid solution is 20-30wt%, and the mass ratio of the modified lignin solution, polylactic acid solution, and activated biochar is 1:1-2:0.05-0.

08.

6. The method for preparing a high water and fertilizer retention plant growth medium based on construction waste according to claim 1, characterized in that: In step S2, the inorganic fertilizer is a mixture of urea, potassium dihydrogen phosphate, and ammonium phosphate, and the mass ratio of the three is 1:1:1; the trace element fertilizer is a mixture of cobalt nitrate, zinc nitrate, and manganese nitrate, and the mass ratio of the three is 1:1:1; the mass ratio of the inorganic fertilizer to the trace element fertilizer is 1:0.01-0.

05.

7. The method for preparing a high water and fertilizer retention plant growth medium based on construction waste according to claim 1, characterized in that: In step S2, the immersion temperature is room temperature, and the immersion time is 1-2 minutes.

8. The method for preparing a high water and fertilizer retention plant growth medium based on construction waste according to claim 1, characterized in that: In step S2, the preparation method of the activated biochar is as follows: corn straw is crushed and then calcined to obtain biochar, the biochar is placed in a mixed aqueous solution of acrylic acid and acrylamide, potassium persulfate and N,N-methylenebisacrylamide are added to carry out polymerization reaction, after the reaction is completed, it is filtered, and the precipitate is dried to obtain activated biochar.

9. The method for preparing a high water and fertilizer retention plant growth medium based on construction waste according to claim 1, characterized in that: The calcination temperature is 500° C., the time is 2-3 hours, and the atmosphere is nitrogen; the mass ratio of the biochar, acrylic acid, acrylamide, potassium persulfate, and N,N-methylenebisacrylamide is 1:0.2-0.5:0.01-0.08:0.001-0.002:0.005-0.01; the reaction temperature is 65-70° C., and the time is 1-2 hours.

10. The method for preparing a high water and fertilizer retention plant growth medium based on construction waste according to claim 1, characterized in that: In step S3, the amounts of the components used are 5-10 parts of peat soil, 1-2 parts of vermiculite, 2-5 parts of bagasse, 1-2 parts of polyacrylamide, 1-2 parts of kaolin, 3-4 parts of slag, 3-6 parts of slow-release fertilizer, and 1-2 parts of citric acid, respectively, in parts by weight.

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