Modified charcoal-polyaluminum ferric sulfate modifier and preparation method thereof

Abstract

The invention belongs to the technical field of soil improvement, and relates to a modified charcoal-polyaluminum ferric sulfate modifier and a preparation method thereof, and the preparation method specifically comprises the following steps: step 1, preparing charcoal; step 2, modifying the biochar; 3, preparing an aluminum-iron mixed solution; step 4, preparing polyaluminum ferric sulfate; step 5, preparing the modified charcoal composite polyaluminum ferric sulfate saline-alkali soil modifier; through multi-component compounding, nano modification, waste recycling and precise process control, the defects of single effect, high cost, poor timeliness, environmental risk and the like of the existing saline-alkali soil improver are comprehensively overcome. The core innovation point is that functional modification of biochar is combined with chemical characteristics of polyaluminum ferric sulfate, and a complex microbial inoculant is introduced to enhance biological activity, so that high efficiency, economical efficiency and environmental friendliness of saline-alkali soil improvement are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of soil improvement and relates to a modified biochar-polyaluminum ferric sulfate improver and a preparation method thereof. Background Art

[0002] Salinization and sodification are typical types of soil degradation caused by both natural and human factors, seriously impacting the sustainable development of agriculture. Soda-alkali soils are characterized by a predominance of sodium carbonate and sodium bicarbonate in the soil's salt content. These soils are highly alkaline. Due to the large amount of sodium ions adsorbed on soil colloids, these colloids disperse, resulting in poor permeability and a poor soil structure. High salinity increases soil pH and conductivity, accelerating soil degradation and inhibiting crop growth and development. While traditional technologies, including physical, chemical, and biological methods, can improve the quality of salt-affected soils and alleviate salt stress in plants to a certain extent, physical improvements require significant human, material, and financial resources, especially on a large scale, resulting in significant workload and high long-term costs. Biological improvements also require a long time to show results, which may not be feasible for saline-alkali lands in urgent need of improvement. Chemical methods are the most effective and practical. Commonly used soil amendments include desulfurized gypsum, phosphogypsum, superphosphate, humic acid, aluminum sulfate, ferric sulfate, and various organic and inorganic fertilizers. However, existing amendments have the following significant drawbacks: 1) The single nature and side effects of chemical amendments. Traditional chemical amendments (such as desulfurized gypsum and aluminum sulfate) rely on a single ingredient, resulting in limited improvement effects and a tendency to cause soil compaction or secondary salt accumulation. For example, aluminum sulfate can lower pH in the short term, but excessive use can release aluminum ions that are toxic to plant roots. 2) Physical amendments are costly and inefficient. Physical methods (such as tillage and soil addition) require significant labor and resources and are only suitable for small-scale improvement. Organic materials (such as straw) decompose slowly when applied directly, making it difficult to release their active ingredients in the short term. 3) Biological amendments lack long-term effectiveness and stability. Microbial agents (such as Bacillus subtilis) are easily inhibited by saline-alkali environments, making their activity difficult to maintain over time. Salt-tolerant plants require long-term cultivation to be effective, making rapid improvements in soil physical and chemical properties impossible. 4) The application of nanomaterials and modification technologies is inadequate. Existing technologies rarely incorporate nanomaterials (such as nano-SiO2 and Fe3O4) to functionalize amendments, resulting in poor dispersion and limited adsorption capacity.

[0003] Therefore, providing a fast, efficient, stable and multifunctional alkaline soil improver has become an urgent problem to be solved. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a modified biochar-polyaluminum ferric sulfate modifier and a preparation method thereof, which specifically comprises the following steps: Step 1: After mixing agricultural waste with organic acid solution and soaking for 45-50 hours, freezing at (-40)-(-50)℃ for 1-1.5 hours, crushing to 60-70 mesh, then mixing with enzymatic hydrolyzate, soaking at 50-60℃ for 4-5 hours, taking out and cleaning the surface, drying at 70-90℃ to constant weight, then mixing with nano-SiO2 particles, ball milling at 600-800rpm for 30-40 minutes, and then carbonizing at 200-700℃ for 6-8 hours. After carbonization, immediately plunge into liquid nitrogen for quenching for 10-20 minutes to obtain biochar.

[0005] Preferably, the agricultural waste is one or more of plant straw, plant residues, nut shells, seaweed residues, and discarded mushroom sticks. Most preferably, the plant straw includes one or more of rice straw, corn straw, and wheat straw, and the plant residue includes one or more of rice husks, corn cobs, and dead branches and leaves. Most preferably, the agricultural waste includes rice straw, corn cobs, walnut shells, and discarded mushroom sticks in a mass ratio of 6:3:2:3.

[0006] Preferably, the mass ratio of the agricultural waste, organic acid solution, enzymatic hydrolysis solution, nano-SiO2 particles and liquid nitrogen is 2:8:8:1:3. Most preferably, the particle size of the nano-SiO2 particles is 20-50 nm.

[0007] Preferably, the organic acid solution is a citric acid solution with a mass fraction of 3%-5%.

[0008] Preferably, the enzymatic hydrolysis solution comprises 0.5 U / g of cellulase, 0.4 U / g of pectinase and 0.3 U / g of laccase based on water.

[0009] Preferably, during the carbonization process, the temperature is raised to 200° C. and kept for 1 hour, then raised to 450° C. at 5° C. / min and kept for 2 hours, and then raised to 750° C. at 5° C. / min and kept for 2 hours.

[0010] Step 2: The biochar is mixed with the composite bacterial agent, cultured at 30-35°C and 120-150 rpm for 45-48 hours, then mixed with the modifier, and ultrasonically treated at 4-5 kHz for 1-1.5 hours. After being taken out and dried on the surface, the biochar is mixed with attapulgite soil and ball milled at 400-500 rpm for 1-2 hours to obtain modified biochar.

[0011] Preferably, the mass ratio of the biochar, composite bacterial agent, modifier and attapulgite is 5:15:15:1.

[0012] Preferably, the composite bacterial agent includes Bacillus subtilis powder, Trichoderma powder, lactic acid bacteria powder, glucose and water in a mass ratio of 5:3:3:10:1000.

[0013] Preferably, the modifier comprises nano-Fe3O4 particles, sodium alginate, chitosan, acetic acid and ethanol in a ratio of 200 mg: 5 g: 2 g: 1 mL: 100 mL. The most preferred particle size of the nano-Fe3O4 particles is 40-50 nm.

[0014] Step 3: Mix the aluminum source and the alkaline solution in a mass ratio of 1:1.5 to obtain an aluminate solution; mix the iron source and ferrous sulfate in a molar ratio of 1:3 to obtain a composite iron source; 3+ / Fe 2+ Mix them in a molar ratio of (1.8-2.5):1 to obtain an aluminum-iron mixed solution.

[0015] Preferably, the aluminum source is one or more of bauxite, waste aluminum foil, and waste cans, with waste aluminum foil being most preferred. Preferably, the iron source is one or more of waste iron wire, waste iron plate, and iron ore, with iron oxide being most preferred.

[0016] Preferably, the alkaline solution is a sodium hydroxide solution with a mass fraction of 30%.

[0017] Step 4: Mix the aluminum-iron mixture and sulfuric acid, react at 60-70° C. for 30-40 minutes, add hydrogen peroxide three times during the reaction, 30% for the first time, 30% for the second time, and 40% for the third time. After the reaction is completed, filter, remove the filter residue, and spray-dry the filtrate to obtain polyaluminum-ferric sulfate.

[0018] Preferably, SO4 2- :(Al 3+ +Fe 2+ ) is (1.3-1.6):1, hydrogen peroxide:Fe 2+ The molar ratio is (1.05-1.15):1.

[0019] Most preferably, Al 3+ / Fe 2+ Molar ratio 2.2:1, SO4 2- / (Al 3+ +Fe 2+ ) molar ratio 1.45:1, hydrogen peroxide / Fe 2+ The molar ratio is 1.08:1.

[0020] Step 5: Mix the modified biochar, polyaluminum ferric sulfate, humic acid, earthworm castings, sodium alginate and polyglutamic acid in a mass ratio of 1:2:0.5:1.5:2:0.1 and ball-mill at 600-800 rpm for 50-60 minutes to obtain a modified biochar composite polyaluminum ferric sulfate alkaline land improver.

[0021] The present invention has the following advantages: (1) The present invention achieves the synergistic effects of acid-base regulation, ion adsorption, microbial activation and organic matter supplementation by composite modified biochar, polyaluminum ferric sulfate, humic acid, earthworm castings and other components, thereby solving the problem of soil compaction caused by the singleness of chemical modifiers and avoiding the risk of aluminum toxicity of aluminum sulfate.

[0022] (2) The present invention adopts organic acid soaking, enzymatic hydrolysis, and mixed nano-SiO2 particles, and combines ball milling and liquid nitrogen quenching processes to significantly increase the specific surface area of ​​biochar and significantly improve the sodium ion adsorption efficiency, overcoming the problems of low porosity and insufficient adsorption efficiency of traditional biochar.

[0023] (3) The present invention adopts composite bacterial agents (Bacillus subtilis, Trichoderma, etc.) coated with nano-Fe3O4 and chitosan, which significantly improves the survival rate of bacterial species in saline-alkali environments and accelerates the decomposition of organic matter, thus solving the bottleneck of low activity and short action period of existing bacterial agents in saline-alkali land.

[0024] (4) The present invention uses agricultural waste (straw, mushroom sticks) and industrial waste (waste aluminum foil, iron oxide) as raw materials, significantly reducing the preparation cost and solving the high cost problem of physical modifiers.

[0025] (5) The present invention controls SO4 2- / (Al 3+ +Fe 2+ ) molar ratio and the amount of hydrogen peroxide added to ensure the stability of polyaluminum ferric sulfate, avoid excessive release of iron and aluminum ions, and circumvent the risk of salt accumulation caused by imbalance in the proportions in traditional aluminum ferric sulfate preparation. DETAILED DESCRIPTION

[0026] The following is a clear and complete description of the technical solutions in the embodiments of the invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0027] Example 1 Step 1: Agricultural waste is mixed with a 5% citric acid solution and soaked for 48 hours. The mixture is then frozen at -40°C for 1.5 hours, crushed to 70 mesh, mixed with an enzymatic hydrolysate, soaked at 55°C for 4 hours, removed, surface cleaned, and dried at 80°C to constant weight. The mixture is then mixed with nano-SiO2 particles and ball-milled at 700 rpm for 30 minutes. The mixture is then placed in a carbonization furnace and carbonized at 200°C for 1 hour, then heated to 450°C at a rate of 5°C / min for 2 hours, and finally heated to 750°C at a rate of 5°C / min for 2 hours. After carbonization, the mixture is immediately quenched in liquid nitrogen for 15 minutes to produce biochar. The mass ratio of the agricultural waste, citric acid solution, enzymatic hydrolysate, nano-SiO2 particles, and liquid nitrogen is 2:8:8:1:3. The agricultural waste consists of rice straw, corn cobs, walnut shells, and discarded mushroom sticks in a mass ratio of 6:3:2:3. The nano-SiO2 particles have a particle size of 40 nm. The enzymatic hydrolysis solution comprises 0.5 U / g of cellulase, 0.4 U / g of pectinase and 0.3 U / g of laccase based on water.

[0028] Step 2: Mix the biochar with the composite bacterial agent, culture at 35°C and 120rpm for 48 hours, then mix with the modifier, ultrasonicate at 4kHz for 1 hour, remove and dry the surface moisture, mix with attapulgite, and ball mill at 500rpm for 1 hour to obtain modified biochar. The mass ratio of the biochar, composite bacterial agent, modifier, and attapulgite is 5:15:15:1. The composite bacterial agent includes Bacillus subtilis powder, Trichoderma powder, lactic acid bacteria powder, glucose, and water in a mass ratio of 5:3:3:10:1000. The modifier includes nano-Fe3O4 particles, sodium alginate, chitosan, acetic acid, and ethanol in a ratio of 200mg:5g:2g:1mL:100mL. The particle size of the nano-Fe3O4 particles is 40nm.

[0029] Step 3: Mix the aluminum source with a 30% sodium hydroxide solution in a mass ratio of 1:1.5 to obtain an aluminate solution; mix ferric oxide and ferrous sulfate in a molar ratio of 1:3 to obtain a composite iron source; 3+ / Fe 2+ The molar ratio is 2.2:1 to obtain an aluminum-iron mixed solution.

[0030] Step 4: Mix the aluminum-iron mixture with sulfuric acid and react at 65°C for 30 minutes. During the reaction, add hydrogen peroxide three times, 30% for the first time, 30% for the second time, and 40% for the third time. After the reaction is completed, filter, remove the filter residue, and spray dry the filtrate to obtain polyaluminum-ferric sulfate. 2- / (Al 3+ +Fe 2+ ) molar ratio 1.45:1, hydrogen peroxide / Fe 2+ The molar ratio is 1.08:1.

[0031] Step 5: Mix the modified biochar, polyaluminum ferric sulfate, humic acid, earthworm castings, sodium alginate and polyglutamic acid in a mass ratio of 1:2:0.5:1.5:2:0.1 and ball-mill at 700 rpm for 55 minutes to obtain a modified biochar composite polyaluminum ferric sulfate alkaline land improver.

[0032] Test Example 1 A local abandoned saline-alkali land was selected and divided into several plots. 10-20 cm soil samples were taken and sent to a local testing agency for testing. The results are shown in Table 1. Two treatments were set up in the field. Treatment 1 applied the soil conditioner prepared in Example 1, and Treatment 2 applied biochar powder produced by Zhengzhou Xingsen Activated Carbon Co., Ltd. The application rate for both treatments was 500 kg / mu. During application, the soil conditioner was spread on the surface, and mechanical rotary tillage was performed to 15 cm to fully mix the soil conditioner with the soil. The soil was then irrigated once to wash away the salt. The irrigation amount for both treatments was the same. After 45 days, 10-20 cm soil samples were taken and sent to a local testing agency for testing. The results are shown in Table 1.

[0033] Table 1 As can be seen from Table 1, the saline-alkali land conditioner prepared by the present invention can significantly reduce soil pH, significantly increase soil porosity, improve soil physical and chemical properties, and significantly improve soil fertility compared to traditional biochar, thereby further providing a suitable growth environment for crops.

[0034] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a modified biochar-polyaluminum ferric sulfate modifier, characterized in that: The following steps are involved: Step 1: The agricultural waste is mixed with an organic acid solution and soaked, frozen, crushed, and then mixed with an enzymatic solution and soaked. After being taken out, the surface is cleaned, dried, mixed with nano-SiO2 particles, ball-milled, and carbonized. After carbonization, the waste is immediately quenched in liquid nitrogen to obtain biochar. Step 2: mixing the biochar with the composite bacterial agent, culturing with shaking, then mixing with the modifier, ultrasonically treating, drying the surface moisture, mixing with attapulgite, and ball milling to obtain modified biochar; Step 3: mixing an aluminum source with an alkaline solution to obtain an aluminate solution; mixing an iron source with ferrous sulfate to obtain a composite iron source; and mixing the aluminate solution and the composite iron source to obtain an aluminum-iron mixed solution; Step 4: mixing the aluminum-iron mixed solution with sulfuric acid, adding hydrogen peroxide three times during the reaction, filtering after the reaction is completed, removing the filter residue, and drying the filtrate to obtain polyaluminum-ferric sulfate; Step 5: The modified biochar, polyaluminum ferric sulfate, humic acid, earthworm castings, sodium alginate and polyglutamic acid are mixed and ball-milled according to a mass ratio to obtain a modified biochar composite polyaluminum ferric sulfate alkaline land improver.

2. The method for preparing a modified biochar-polyaluminum ferric sulfate modifier according to claim 1, characterized in that: The mass ratio of the agricultural waste, organic acid solution, enzymatic hydrolyzate, nano-SiO2 particles and liquid nitrogen in step 1 is 2:8:8:1:

3.

3. The method for preparing a modified biochar-polyaluminum ferric sulfate modifier according to claim 1, characterized in that: The organic acid solution in step 1 is a citric acid solution with a mass fraction of 3%-5%, and the enzymatic hydrolysis solution includes 0.5U / g cellulase, 0.4U / g pectinase and 0.3U / g laccase based on water.

4. The method for preparing a modified biochar-polyaluminum ferric sulfate modifier according to claim 1, characterized in that: The mass ratio of the biochar, composite bacterial agent, modifier and attapulgite described in step 2 is 5:15:15:

1.

5. The method for preparing a modified biochar-polyaluminum ferric sulfate modifier according to claim 1, characterized in that: The composite bacterial agent in step 2 includes Bacillus subtilis powder, Trichoderma powder, lactic acid bacteria powder, glucose and water in a mass ratio of 5:3:3:10:1000, and the modifier includes nano-Fe3O4 particles, sodium alginate, chitosan, acetic acid and ethanol in a ratio of 200 mg:5 g:2 g:1 mL:100 mL.

6. The method for preparing a modified biochar-polyaluminum ferric sulfate modifier according to claim 1, characterized in that: In step 3, the mass ratio of the aluminum source to the alkaline solution is 1:1.5, and the iron source and ferrous sulfate are mixed in a molar ratio of 1:

3.

7. The method for preparing a modified biochar-polyaluminum ferric sulfate modifier according to claim 1, characterized in that: The alkaline solution in step 3 is a sodium hydroxide solution with a mass fraction of 30%.

8. The method for preparing a modified biochar-polyaluminum ferric sulfate modifier according to claim 1, characterized in that: SO4 as described in step 4 2- :(Al 3+ +Fe 2+ ) is (1.3-1.6):1, hydrogen peroxide:Fe 2+ The molar ratio is (1.05-1.15):

1.

9. The method for preparing a modified biochar-polyaluminum ferric sulfate modifier according to claim 1, characterized in that: In step five, the mass ratio of modified biochar, polyaluminum ferric sulfate, humic acid, earthworm castings, sodium alginate and polyglutamic acid is 1:2:0.5:1.5:2:0.

1.

10. The modified biochar-polyaluminium ferric sulfate improver prepared by the method according to any one of claims 1 to 9.

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