A modified biochar-polyaluminum ferric sulfate amendment and a method of making the same

Abstract

The application belongs to the technical field of soil improvement, and relates to a modified biochar-polyaluminum ferric sulfate modifier and a preparation method thereof, and specifically comprises the following steps: step one, preparing biochar; step two, modifying the biochar; step three, preparing an aluminum-iron mixed solution; step four, preparing polyaluminum ferric sulfate; and step five, preparing a modified biochar composite polyaluminum ferric sulfate saline-alkali soil modifier; the application comprehensively solves the defects of existing saline-alkali soil modifiers in aspects of single effect, high cost, poor timeliness and environmental risks, etc., through multi-component compounding, nano modification, waste resource utilization and precise process control. The core innovation point lies in the combination of the functional modification of biochar and the chemical properties of polyaluminum ferric sulfate, and the introduction of a composite microbial agent to enhance biological activity, so that the efficiency, economy and environmental friendliness of saline-alkali soil improvement are realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of soil improvement, and relates to a modified biochar-polyaluminum ferric sulfate improver and a preparation method thereof. BACKGROUND

[0002] Salinization and sodization are typical types of soil degradation caused by the combined action of natural and human factors, which seriously affect the sustainable development of agriculture. The characteristics of sodic-alkali soil are that the salt in the soil is mainly sodium carbonate and sodium bicarbonate, and this type of soil has strong alkalinity. Due to the adsorption of a large amount of sodium ions on the soil colloids, the soil colloids are dispersed, the permeability is poor, the soil structure is poor, and the high salinity increases the soil pH and electrical conductivity, which accelerates soil degradation and inhibits the growth and development of crops. Although traditional technologies including physical, chemical and biological methods can improve the soil quality affected by salt to a certain extent and alleviate the salt stress of plants, physical improvement requires a large amount of manpower, material resources and financial resources, especially in large-scale improvement, the workload is particularly huge and the cost is high in the long run; biological improvement needs a long time to see the effect, and for saline-alkali land that needs to be improved urgently, it may not meet the time requirement. Chemical method is the most effective and practical method, and the commonly used soil improvers at present include desulfurized gypsum, phosphorite gypsum, superphosphate, humic acid, aluminum sulfate, ferric sulfate and various organic and inorganic fertilizers. However, the existing improvers have the following significant defects:

[0003] 1) The single nature and side effects of chemical improvers, traditional chemical improvers (such as desulfurized gypsum and aluminum sulfate) rely on single components, and the improvement effect is limited, and soil compaction or secondary salt accumulation is easy to occur. For example, aluminum sulfate can reduce pH in the short term, but excessive use will release aluminum ions to poison plant roots. 2) High cost and low efficiency of physical improvers, physical methods (such as turning soil and guest soil method) require a large amount of manpower and material resources, and are only suitable for small-area improvement. Organic materials (such as straw) are difficult to release effective components in the short term when directly applied due to slow decomposition. 3) Insufficient timeliness and stability of biological improvers, microbial agents (such as Bacillus subtilis) are easily inhibited by saline-alkali environment, and the activity is difficult to maintain for a long time; salt-tolerant plants need to be planted for a long time to see the effect, and cannot quickly improve the physical and chemical properties of soil. 4) Insufficient application of nanomaterials and modification technology, the existing technology rarely combines nanomaterials (such as nano-SiO2 and Fe3O4) to functionalize the improver, resulting in poor dispersibility and limited adsorption capacity of the material.

[0004] Therefore, it is an urgent problem to provide an alkali soil improver that can be quickly, efficiently, stably and multifunctionally improved. SUMMARY

[0005] In order to solve the above problems, the present application provides a modified biochar-polyaluminum ferric sulfate improver and a preparation method thereof, which specifically comprises the following steps:

[0006] Step one, the agricultural waste and organic acid solution mixed soak 45-50 hours, (-40)-(-50) ℃ freeze 1-1.5h, crushed to 60-70 mesh, then mixed with enzymatic hydrolysis solution, 50-60 ℃ soak 4-5h, after taking out the surface, 70-90 ℃ drying to constant weight, then mixed with nano-SiO2 particles, 600-800 rpm ball milling 30-40 min, then 200-700 ℃ carbonization 6-8h, carbonization immediately after the drop into liquid nitrogen 10-20 min, get biochar.

[0007] Preferably, the agricultural waste is one or more of plant straw, plant residue, nut shell, seaweed residue and waste mushroom stick. 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 hull, corn cob and dry branches and leaves. Most preferably, the agricultural waste is rice straw, corn cob, walnut shell and waste mushroom stick, with a mass ratio of 6:3:2:3.

[0008] 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.

[0009] Preferably, the organic acid solution is a citric acid solution with a mass fraction of 3%-5%.

[0010] Preferably, the enzymatic hydrolysis solution includes 0.5 U / g of cellulase, 0.4 U / g of pectinase and 0.3 U / g of laccase based on water.

[0011] Preferably, during the carbonization process, the temperature is raised to 200 ℃ for 1h, raised to 450 ℃ at a rate of 5 ℃ / min for 2h, and raised to 750 ℃ at a rate of 5 ℃ / min for 2h.

[0012] Step two, mix the biochar with the composite microbial agent, 30-35 ℃, 120-150 rpm oscillation culture 45-48h, then mix with the modifier, 4-5 kHz ultrasonic treatment 1-1.5h, after taking out the surface water, mix with attapulgite, 400-500 rpm ball milling 1-2h, get modified biochar.

[0013] Preferably, the mass ratio of the biochar, composite microbial agent, modifier and attapulgite is 5:15:15:1.

[0014] Preferably, the composite microbial agent includes Bacillus subtilis powder, Trichoderma spores, lactic acid bacteria powder, glucose and water, with a mass ratio of 5:3:3:10:1000.

[0015] 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. Most preferably, the particle size of the nano Fe3O4 particles is 40-50 nm.

[0016] Step three, mixing the aluminum source and the alkali solution in a mass ratio of 1:1.5 to obtain an aluminate solution; mixing the iron source and ferrous sulfate in a molar ratio of 1:3 to obtain a composite iron source, mixing the aluminate solution and the composite iron source in an Al 3+ / Fe 2+ molar ratio (1.8-2.5):1 to obtain an aluminum-iron mixed solution.

[0017] Preferably, the aluminum source is one or more of bauxite, waste aluminum foil and waste pop can, and most preferably waste aluminum foil. Preferably, the iron source is one or more of waste iron wire, waste iron plate and iron ore, and most preferably iron oxide.

[0018] Preferably, the alkali solution is a 30% mass fraction sodium hydroxide solution.

[0019] Step four, mixing the aluminum-iron mixed solution and sulfuric acid and reacting at 60-70°C for 30-40 min, adding hydrogen peroxide three times during the reaction, the first time adding 30%, the second time adding 30%, and the third time adding 40%, after the reaction is completed, filtering to remove the filter residue, and spray drying the filtrate to obtain polyaluminum ferric sulfate.

[0020] Preferably, the molar ratio of SO4 2- :(Al 3+ +Fe 2+ ) is (1.3-1.6):1, and the molar ratio of hydrogen peroxide:Fe 2+ is (1.05-1.15):1.

[0021] Most preferably, the molar ratio of Al 3+ / Fe 2+ is 2.2:1, the molar ratio of SO4 2- / (Al 3+ +Fe 2+ ) is 1.45:1, and the molar ratio of hydrogen peroxide:Fe 2+ is 1.08:1.

[0022] Step five, mixing the modified biochar, polyaluminum ferric sulfate, humic acid, earthworm manure, sodium alginate and polyglutamic acid in a mass ratio of 1:2:0.5:1.5:2:0.1 and ball milling at 600-800 rpm for 50-60 min to obtain a modified biochar composite polyaluminum ferric sulfate saline-alkaline land conditioner.

[0023] The present application has the following advantages:

[0024] (1) The present application realizes the synergistic effect of acid-base adjustment, ion adsorption, microbial activation and organic matter supplement by compounding modified biochar, polymeric aluminum ferric sulfate, humic acid, earthworm manure and other components, solves the soil hardening problem caused by the single nature of chemical improver, and avoids the aluminum toxicity risk of aluminum sulfate.

[0025] (2) The present application uses organic acid soaking, enzymolysis, mixed nano-SiO2 particles, combined with ball milling and liquid nitrogen quenching process, significantly improves the specific surface area of biochar, significantly improves the adsorption efficiency of sodium ions, and overcomes the problems of low porosity and insufficient adsorption efficiency of traditional biochar.

[0026] (3) The present application uses composite microbial agent (Bacillus subtilis, Trichoderma sp.) coated with nano-Fe3O4 and chitosan, which significantly improves the survival rate of the strain in saline-alkali environment, accelerates the decomposition of organic matter, and solves the bottleneck of low activity and short action period of existing microbial agents in saline-alkali soil.

[0027] (4) The present application uses agricultural waste (straw, fungus stick) and industrial waste (waste aluminum foil, iron oxide) as raw materials, significantly reduces the preparation cost, and solves the high cost problem of physical improver.

[0028] (5) The present application controls the molar ratio of SO4 2- / (Al 3+ +Fe 2+ ) and the addition amount of hydrogen peroxide to ensure the stability of polymeric aluminum ferric sulfate, avoid excessive release of iron and aluminum ions, and avoid the salt accumulation risk caused by proportion imbalance in the preparation of traditional aluminum ferric sulfate. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0030] Example 1

[0031] Step one, the agricultural waste was mixed with a 5% citric acid solution and soaked for 48 hours, then frozen at -40℃ for 1.5 hours, crushed to 70 mesh, then mixed with an enzymatic solution, soaked at 55℃ for 4 hours, then washed and dried at 80℃ until constant weight, then mixed with nano-SiO2 particles, ball milled at 700 rpm for 30 minutes, then placed in a carbonization furnace, heated to 200℃ for 1 hour, then heated to 450℃ at 5℃ / min for 2 hours, then heated to 750℃ at 5℃ / min for 2 hours, then immediately quenched in liquid nitrogen for 15 minutes to obtain biochar. The mass ratio of the agricultural waste, citric acid solution, enzymatic solution, nano-SiO2 particles, and liquid nitrogen is 2:8:8:1:3. The agricultural waste is rice straw, corn cob, walnut shell, and waste mushroom stick, with a mass ratio of 6:3:2:3, and the nano-SiO2 particles have a particle size of 40 nm. The enzymatic solution includes 0.5 U / g of cellulase, 0.4 U / g of pectinase, and 0.3 U / g of laccase based on water.

[0032] Step two, the biochar was mixed with a composite microbial agent and cultured at 35℃ with 120 rpm shaking for 48 hours, then mixed with a modifier and treated with ultrasonic waves at 4 kHz for 1 hour, then dried to remove surface moisture, mixed with attapulgite, and ball milled at 500 rpm for 1 hour to obtain modified biochar. The mass ratio of the biochar, composite microbial agent, modifier, and attapulgite is 5:15:15:1. The composite microbial agent includes Bacillus subtilis powder, Trichoderma spore powder, lactic acid bacteria powder, glucose, and water, with a mass ratio of 5:3:3:10:1000. The modifier includes nano-Fe3O4 particles, sodium alginate, chitosan, acetic acid, and ethanol, with a ratio of 200 mg:5 g:2 g:1 mL:100 mL. The nano-Fe3O4 particles have a particle size of 40 nm.

[0033] Step three, an aluminum source was mixed with a 30% sodium hydroxide solution at a mass ratio of 1:1.5 to obtain an aluminate solution; iron oxide was mixed with ferrous sulfate at a molar ratio of 1:3 to obtain a composite iron source, and the aluminate solution and composite iron source were mixed at an Al 3+ / Fe 2+ molar ratio of 2.2:1 to obtain an aluminum-iron mixed solution.

[0034] Step four, the aluminum-iron mixed solution was mixed with sulfuric acid and reacted at 65℃ for 30 minutes, during which hydrogen peroxide was added three times, with the first addition being 30%, the second addition being 30%, and the third addition being 40%. After the reaction was complete, the filtrate was obtained by filtration, and the filter residue was removed. The filtrate was spray dried to obtain polyaluminum ferric sulfate. The molar ratio of Al 2- / (Al 3+ +Fe 2+ ) is 1.45:1, and the molar ratio of hydrogen peroxide / Fe 2+ is 1.08:1.

[0035] Step five, the modified biochar, polymeric aluminum ferric sulfate, humic acid, vermicompost, sodium alginate and polyglutamic acid are mixed in a mass ratio of 1:2:0.5:1.5:2:0.1, 700 rpm ball milling for 55 min, to obtain a modified biochar composite polymeric aluminum ferric salt alkaline land conditioner.

[0036] Test example 1

[0037] A piece of abandoned saline-alkali land is selected and evenly divided into several plots, and 10-20 cm soil layer samples are taken and sent to a local testing agency for testing. The results are shown in Table 1. Two groups of treatments are set up in the field, treatment 1 applies the soil conditioner prepared in Example 1, and treatment 2 applies the biochar powder produced by Zhengzhou Xingsen activated carbon Co., Ltd. The application amount of the two groups of treatments is 500 kg / mu, and the soil conditioner is applied on the ground when applying, and the soil conditioner is fully mixed with the soil by mechanical rotary tillage 15 cm, and is irrigated once to wash salt, the irrigation amount of the two groups of treatments is the same, 10-20 cm soil layer samples are taken after 45 days, and sent to a local testing agency for testing, the results are shown in Table 1.

[0038] Table 1

[0039]

[0040] As can be seen from Table 1, the saline-alkali land conditioner prepared by the present application can significantly reduce the soil pH, significantly improve the soil porosity, improve the soil physical and chemical properties, and obviously improve the soil fertility, thereby further providing a suitable growth environment for crops.

[0041] The above description of the disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will 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 amendment, characterized by, The method comprises the following steps: Step one, mixing and soaking the agricultural waste with the organic acid solution, freezing, crushing, then mixing and soaking with the enzymatic solution, washing the surface after taking out, drying, then mixing with nano-SiO2 particles, ball milling, carbonizing, immediately quenching in liquid nitrogen after carbonizing, obtaining biochar; Step two, mixing the biochar with the composite microbial agent, oscillating culture, then mixing with the modifier, drying after ultrasonic treatment, mixing with palygorskite, ball milling, obtaining modified biochar; Step three, mixing the aluminum source with the alkali solution, obtaining aluminate solution; mixing the iron source with ferrous sulfate, obtaining composite iron source, mixing the aluminate solution and the composite iron source, obtaining aluminum-iron mixed solution; Step four, mixing the aluminum-iron mixed solution with sulfuric acid, adding hydrogen peroxide three times during the reaction, after the reaction, filtering, removing the residue, drying the filtrate, obtaining polyaluminum ferric sulfate; Step five, mixing and ball milling the modified biochar, polyaluminum ferric sulfate, humic acid, earthworm manure, sodium alginate and polyglutamic acid according to the mass ratio, obtaining modified biochar-polyaluminum ferric sulfate composite salt-alkaline land improvement agent; The organic acid solution in step one is a citric acid solution with a mass fraction of 3%-5%, the enzymatic solution includes 0.5 U / g of cellulase, 0.4 U / g of pectinase and 0.3 U / g of laccase based on water; the agricultural waste is rice straw, corn cob, walnut shell and waste mushroom stick, with a mass ratio of 6:3:2:3; The composite microbial agent in step two includes Bacillus subtilis powder, Trichoderma sp. powder, lactic acid bacteria powder, glucose and water, with a mass ratio of 5:3:3:10:1000, the modifier includes nano-Fe3O4 particles, sodium alginate, chitosan, acetic acid and ethanol, with a ratio of 200 mg:5 g:2 g:1 mL:100 mL.

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

3.

3. The method for preparing a modified biochar-polyaluminum ferric sulfate amendment according to claim 1, characterized in that, The mass ratio of the biochar, the composite microbial agent, the modifier and the palygorskite in step two is 5:15:15:

1.

4. The method for preparing a modified biochar-polyaluminum ferric sulfate amendment according to claim 1, characterized in that, The mass ratio of the aluminum source and the alkali solution in step three is 1:1.5, the iron source is mixed with ferrous sulfate according to a molar ratio of 1:

3.

5. The method for preparing a modified biochar-polyaluminum ferric sulfate amendment according to claim 1, characterized in that, The alkali solution in step three is a sodium hydroxide solution with a mass fraction of 30%.

6. The method for preparing a modified biochar-polyaluminum ferric sulfate amendment according to claim 1, characterized in that, The SO4 2- : (Al 3+ + Fe 2+ ) is (1.3-1.6):1 and the molar ratio of hydrogen peroxide:Fe 2+ is (1.05-1.15):

1.

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

1.

8. The modified biochar-polyaluminum ferric sulfate improvement agent prepared by the method of any one of claims 1-7.

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