Particle type soil conditioner capable of improving acid and passivating aluminum and preparation method of particle type soil conditioner

Abstract

The invention discloses a granular soil conditioner capable of improving acid and passivating aluminum and a preparation method of the granular soil conditioner, and belongs to the technical field of soil improvement. The invention provides a preparation method of a granular soil conditioner for modifying acid and passivating aluminum. The preparation method comprises the following steps: uniformly mixing alkaline phosphate tailing powder, silicon-based yellow phosphorus slag powder, silicate minerals and a carbon source conditioner to obtain a mixed powder material; the mixed powder material is soaked in an alkali solution for alkali modification treatment, and an alkali modified conditioner is obtained; soaking the alkali modified conditioner in a chitosan solution, and reacting to enable functional groups of chitosan to be attached to the surface of the alkali modified conditioner, so as to obtain a chitosan modified conditioner; and adding a binder into the chitosan modified conditioner, and granulating to obtain the acid-modified aluminum-blunt granular soil conditioner. The granular soil conditioner provided by the invention can be used for effectively improving acid soil and has relatively high capability of passivating aluminum.

Description

Technical Field

[0001] The present invention relates to the technical field of soil improvement, and more specifically to a granular soil conditioner for modifying acid-passivated aluminum and a preparation method thereof. Background Art

[0002] Soil acidification is one of the most serious and common soil degradation problems in agriculture. The high-intensity use of cultivated soil has exacerbated the process of soil acidification. Soil acidification is not only manifested as a decrease in soil pH, but also accompanied by the loss of nutrients such as calcium and magnesium in the soil; in severe cases, it will increase Al toxicity in the soil and increase the risk of heavy metal pollution such as lead and cadmium in the soil. 3+ It will cause serious damage to the plant root system, reduce root elongation by 40%, lead to poor root development, and also reduce the photosynthetic efficiency and pigment of the leaves. In addition, excessive aluminum content in acidic soil will accelerate the loss of soil calcium and magnesium, and aluminum-poisoned crops will have corresponding mineral nutrient deficiencies, thus affecting the production performance of crops. Therefore, carrying out soil acidification control and inhibiting Al activity in the soil is an important measure to improve soil quality, soil fertility and crop yields, which is of great significance for improving agricultural productivity and achieving sustainable soil utilization.

[0003] Phosphorus tailings, as a byproduct in the phosphorus chemical industry, have always had the problem of difficulty in utilization. Although current researchers are actively exploring the resource recycling of phosphorus tailings in the fields of industry, construction, environmental protection and agriculture, they lack practical applications due to the immaturity of cost and technology. In contrast, the production technology and cost required for using phosphorus tailings as acidic soil conditioners are relatively low, and in recent years there have been some cases of using them as compost materials and conditioner raw materials. For example, in CN117568046A, phosphorus tailings are combined with materials such as algae nutrients and bacterial agents to form a composite soil conditioner, which promotes the dissolution of soluble mineral nutrients and improves soil structure. In CN116948654A, phosphorus tailings are used to develop acidic soil conditioners supplied with calcium and magnesium. On the whole, phosphorus tailings have abundant calcium and magnesium and certain alkalinity, and have great potential as a raw material for improving acidic soils. However, in acidic soils, especially in strongly acidic soils, Al poisoning is the main factor that harms crop growth, so these acidic soil conditioners need to pay more attention to the passivation of Al. For acidic soils with severe aluminum toxicity, there is an urgent need for targeted acid-modifying Al-type soil conditioners that can reduce costs while achieving the desired effect. Summary of the invention

[0004] In view of the above problems, the present invention provides a granular soil conditioner for improving the passivation of Al in acidic soil and a preparation method thereof. The granular soil conditioner provided by the present invention can effectively improve acidic soil and enhance the passivation of Al in the soil.

[0005] The first object of the present invention is to provide a method for preparing a granular soil conditioner with acid-passivated aluminum, comprising the following steps: The alkaline phosphorus tailings powder, silicon-based yellow phosphorus slag powder, silicate mineral and carbon source conditioner are uniformly mixed to obtain a mixed powder material.

[0006] The mixed powder material is immersed in an alkali solution for alkali modification treatment to obtain an alkali modified conditioner.

[0007] The alkali-modified conditioning agent is immersed in a chitosan solution, and the chitosan functional groups are attached to the surface of the conditioning agent by reaction, thereby obtaining a chitosan-modified conditioning agent.

[0008] A binder is added to the chitosan modified conditioner, and granulation is performed to obtain an acid-modified aluminum-passivated granular soil conditioner.

[0009] In the preparation process of the present invention, the mixed powder material is subjected to alkali modification treatment. In order to further improve the performance of the acid-passivated aluminum granular soil conditioner, the alkali-modified material is dried by rotary evaporation to ensure that part of the active nutrients are retained in the material, thereby obtaining the alkali-modified conditioner.

[0010] In the granulation process of the present invention, half of the conditioner powder is first put into the granulation disk, and the binder powder is weighed according to the proportion of the conditioner addition amount. When the granulation disk rotates, the binder with the same proportion as the conditioner content is evenly sprinkled on the raw material mixture to form small particles, and then the remaining raw material mixture and the remaining binder are added synchronously to continue granulation until the predetermined particle size is reached to obtain the conditioner particles. After the prepared conditioner particles are sieved, they are placed in an oven for drying and then taken out and cooled at room temperature to finally obtain the granular soil conditioner with acid passivation aluminum.

[0011] In a preferred embodiment of the present invention, the ratio of the alkali-modified conditioning agent to the chitosan solution is 0.4 kg: 1 L, and the amount of chitosan added is 1% to 3% of the alkali-modified conditioning agent. For example, the amount of chitosan added is 1%, 1.5%, 2%, 2.5%, 3%, etc. of the alkali-modified conditioning agent, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0012] In a preferred embodiment of the present invention, when preparing the chitosan modified conditioning agent, the reaction time is 24 hours.

[0013] In a preferred embodiment of the present invention, the added amount of the binder is 0.6% to 1% of the chitosan modified conditioning agent.

[0014] In a preferred embodiment of the present invention, the ratio of the mixed powder material to the alkaline solution is 0.4 kg:2 L, and the concentration of the alkaline solution is 1 mol / L.

[0015] In a preferred embodiment of the present invention, the reaction time of the alkali modification treatment is 24 hours.

[0016] In a preferred embodiment of the present invention, the mixed powder material is composed of the following components in percentage by mass: 60% alkaline phosphorus tailings powder, 10% silicon-based yellow phosphorus slag powder, 15% silicate mineral, and 15% carbon source conditioner.

[0017] In a preferred embodiment of the present invention, the binder is sodium carboxymethyl cellulose.

[0018] In a preferred embodiment of the present invention, the alkaline phosphorus tailings are collophanite flotation tailings; the effective nutrients of the collophanite flotation tailings are: P2O55%~10%, CaO 30%~35%, MgO 12%~18%, SiO25%~7%. The silicon-based yellow phosphorus slag powder is a by-product of the electric furnace process for producing yellow phosphorus; the effective nutrients of the silicon-based yellow phosphorus slag powder are: SiO230%~38%, CaO 29%~35%, MgO 1%~4%. The silicate mineral is sepiolite or montmorillonite. The carbon source conditioner is humic acid, and the organic matter content in the humic acid is ≥30%.

[0019] The second object of the present invention is to provide a granular soil conditioner with acid-modified aluminum passivation prepared by the above preparation method.

[0020] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention is based on phosphate tailings to form a granular soil conditioner mainly composed of acid-modified aluminum, which solves the problems of acidic soil and Al toxicity, and provides an effective disposal measure for the large-scale accumulation of phosphate tailings, an industrial by-product. The granular soil conditioner prepared by the present invention is a composite acidic soil conditioner. The phosphate tailings and silicon-based yellow phosphorus slag materials supplement the calcium, magnesium and silicon elements in the soil. The addition of silicate minerals and carbon source conditioners provides more abundant surface charge and surface activity. At the same time, the nutrient activity of the phosphate tailings is improved by surface modification, thereby improving its utilization efficiency in the soil. After modification, the overall material has more abundant functional groups and surface adsorption capacity, so that the conditioner can adsorb and passivate more Al, and the soil Al morphology can be adjusted by surface adsorption and passivation, thereby achieving a better effect of acid-modified Al.

[0021] (2) The present invention realizes the granulation of the acidic soil conditioner formed by the composite of sand materials such as phosphate tailings. The granular soil conditioner obtained after granulation meets the requirements of the current technical standards for conditioners, and the granular soil conditioner releases nutrients in the soil slowly, so it can better meet the needs of crops for calcium and magnesium elements, and continuously improve the acidification and passivation of Al in the soil. Compared with most current conditioner products and phosphate tailings-based products, the granular soil conditioner of the present invention can be granulated and is easier to transport and use in the field. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Infrared spectra of different conditioning agents.

[0023] Figure 2 Bar graph showing the effects of different forms of conditioning agents on nut crop biomass.

[0024] Figure 3 Particle strength bar graph of conditioners prepared for different binders.

[0025] Figure 4 It is a bar graph of particle intensity of different treatment groups. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments 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 creative work are within the scope of protection of the present invention.

[0027] In the present invention, the flotation tailings of collophanite are used as the main raw material, aiming to promote the resource recycling of by-products of the phosphorus chemical industry. The conditioning agent is formed by compounding multiple materials, which ensures the main functional materials of the conditioning agent and the improvement effect on acidic soil. Among them, the alkaline phosphorus tailings powder and the silicon-based yellow phosphorus slag material mainly provide the conditioning agent with sufficient alkalinity to ensure the effect of soil acidification. At the same time, the two materials of alkaline phosphorus tailings powder and silicon-based yellow phosphorus slag material have extremely high calcium, magnesium and silicon elements to supplement the nutrient deficiency in the soil. Relative to the alkaline phosphorus tailings powder, the nutrient activity of silicon-based yellow phosphorus slag powder is higher, the alkalinity is stronger, and the soil can be improved quickly and efficiently. Secondly, silicate minerals such as sepiolite ensure that the conditioning agent has a higher specific surface area and surface charge while supplying nutrients, providing a basis for subsequent modification. Finally, the carbon source conditioning agent ensures that the conditioning agent has a certain biological regulation effect, and most of the carbon source conditioning agents have abundant charge and functional groups, which also provides a necessary basis for subsequent improvement. Moreover, the main raw materials are in sufficient quantity and low in price, making it easy to realize industrial production.

[0028] In the present invention, in order to further improve the passivation ability of active Al in the soil and reduce the toxicity of Al to crops, the surface activity and surface functional group content of the conditioner are increased by alkali modification and chitosan material modification, so that it can passivate more active Al in the soil through surface adsorption. At the same time, the silicon element in the conditioner and Al 3+ Forming complexes or hydroxyaluminum to improve Al 3+The calcium, magnesium, silicon, organic additives and other components in the plant can improve nutrient utilization, meet the nutrient needs of crops during growth and development, and improve crop yield and quality through reasonable proportions.

[0029] Finally, in order to further improve the convenience of the conditioner, the soil conditioner mainly composed of sandy alkaline phosphorus tailings powder was granulated with sodium carboxymethyl cellulose, which has a lower cost and higher viscosity. This makes the conditioner have better particle strength and granulation rate, and can be quickly disintegrated and released in the soil, making it easier to use the conditioner in the field.

[0030] The alkaline phosphorus tailing powder used in the present invention is collophanite flotation tailing powder, and its nutrient index is: P2O55-10%, CaO30%-35%, MgO 12%-18%, SiO25%-7%. The collophanite flotation tailing is subjected to filter pressing treatment and then crushed and sieved in a crusher. The fineness of the material is 60 meshes and the water content is about 15%.

[0031] Silicon-based yellow phosphorus slag powder is a by-product of yellow phosphorus production by electric furnace method. It is obtained after crushing, and the material fineness is 60 mesh. The effective nutrients are: SiO2 30%~38%, CaO 29%~35%, MgO 1%~4%.

[0032] Sepiolite powder is a directly purchased product, which is the product of direct processing of sepiolite ore, with CaO 20%~25%, MgO 12%~16%, and material fineness of 100 mesh.

[0033] Humic acid is purchased mineral humic acid, with an organic matter content of ≥30% and a material fineness of 100 mesh.

[0034] Montmorillonite powder is a directly purchased product, with an effective CaO of about 10% and a BET specific surface area of ​​55.9m 2 / g, CEC 40cmol / kg, material fineness is 100 mesh.

[0035] Example 1 The present embodiment provides a granular soil conditioner for modifying acid-passivated aluminum, comprising the following raw materials in weight percentage: 60% alkaline phosphorus tailings powder, 10% silicon-based yellow phosphorus slag powder, 15% mineral humic acid, and 15% sepiolite powder.

[0036] Step (1), 240g of alkaline phosphorus tailings powder, 40g of silicon-based yellow phosphorus slag powder, 60g of mineral humic acid, and 60g of sepiolite powder are put into a blender for mixing to obtain a mixed powder material.

[0037] Step (2), pass 400 g of the mixed powder material through a 100-mesh sieve, mix with 2 L of a 1 mol / L NaOH solution, and then stir magnetically for 24 h, and rotary evaporate to dryness at 60° C. until most of the water is evaporated to ensure that some active nutrients are retained in the material, thereby obtaining an alkali-modified conditioner.

[0038] Step (3), soak 400g of the alkali-modified conditioning agent in 1L of CH3COOH with a mass concentration of 2%, wherein chitosan material of 2% by weight of the alkali-modified conditioning agent is added, ultrasonic homogenization for 30min, magnetic stirring for 24h, centrifugation, rotary evaporation at 60°C to remove water to obtain a black precipitate. The formed black precipitate is placed in an oven at 80°C for 12h to obtain a chitosan-modified conditioning agent, and the obtained material is ground through a 100-mesh sieve.

[0039] Step (4), granulating the chitosan modified conditioning agent, using sodium carboxymethyl cellulose as a binder for granulation, and the amount of the binder is 1% of the mass of the chitosan modified conditioning agent.

[0040] The specific operation steps are as follows: first, put 50% of the total amount of chitosan modified conditioner powder into the granulation disk, weigh the binder powder according to 1% of the amount of chitosan modified conditioner, and evenly sprinkle 50% of the total amount of binder on the chitosan modified conditioner while the granulation disk is rotating to form small particles, and then simultaneously add the remaining chitosan modified conditioner and the remaining binder to continue granulation until the predetermined particle size is reached to obtain the conditioner particles. After the prepared conditioner particles are sieved through a 1mm~4.75mm sieve, they are placed in an oven at 60℃ for 4h, and then taken out and cooled at room temperature to finally obtain a granular soil conditioner.

[0041] Example 2 The present embodiment provides a granular soil conditioner for modifying acid-passivated aluminum, comprising the following raw materials in weight percentage: 60% alkaline phosphorus tailings powder, 10% silicon-based yellow phosphorus slag powder, 15% mineral humic acid, and 15% sepiolite powder.

[0042] Step (1), 240g of alkaline phosphorus tailings powder, 40g of silicon-based yellow phosphorus slag powder, 60g of mineral humic acid, and 60g of sepiolite powder are put into a blender for mixing to obtain a mixed powder material.

[0043] Step (2), pass 400 g of the mixed powder material through a 100-mesh sieve, mix with 2 L of a 1 mol / L NaOH solution, and then stir magnetically for 24 h, and rotary evaporate to dryness at 60° C. until most of the water is evaporated to ensure that some active nutrients are retained in the material, thereby obtaining an alkali-modified conditioner.

[0044] Step (3), soak 400g of the alkali-modified conditioning agent in 1L of CH3COOH with a mass concentration of 2%, wherein 3% of the weight of the alkali-modified conditioning agent is added to the chitosan material, ultrasonic homogenization for 30 minutes, magnetic stirring for 24 hours, centrifugation, rotary evaporation at a temperature of 60°C to remove water to obtain a black precipitate. The formed black precipitate is placed in an oven at 80°C for 12 hours to obtain a chitosan-modified conditioning agent, and the obtained material is ground through a 100-mesh sieve.

[0045] Step (4), granulating the chitosan modified conditioning agent, using sodium carboxymethyl cellulose as a binder for granulation, and the amount of the binder is 0.6% of the mass of the chitosan modified conditioning agent.

[0046] The specific operation steps are as follows: first, put 50% of the total amount of chitosan modified conditioner powder into the granulation disk, weigh the binder powder according to 0.6% of the amount of chitosan modified conditioner, and evenly sprinkle 50% of the total amount of binder on the chitosan modified conditioner while the granulation disk is rotating to form small particles, and then simultaneously add the remaining chitosan modified conditioner and the remaining binder to continue granulation until the predetermined particle size is reached to obtain the conditioner particles. After the prepared conditioner particles are sieved through a 1mm~4.75mm sieve, they are placed in an oven at 60°C for 4h, and then taken out and cooled at room temperature to finally obtain a granular soil conditioner.

[0047] Example 3 The present embodiment provides a granular soil conditioner for modifying acid-passivated aluminum, comprising the following raw materials in weight percentage: 60% alkaline phosphorus tailings powder, 10% silicon-based yellow phosphorus slag powder, 15% mineral humic acid, and 15% montmorillonite powder.

[0048] Step (1), 240g of alkaline phosphorus tailings powder, 40g of silicon-based yellow phosphorus slag powder, 60g of mineral humic acid, and 60g of montmorillonite powder are put into a blender for mixing to obtain a mixed powder material.

[0049] Step (2), pass 400 g of the mixed powder material through a 100-mesh sieve, mix with 2 L of a 1 mol / L NaOH solution, and then stir magnetically for 24 h, and rotary evaporate to dryness at 60° C. until most of the water is evaporated to ensure that some active nutrients are retained in the material, thereby obtaining an alkali-modified conditioner.

[0050] Step (3), soak 400g of the alkali-modified conditioning agent in 1L of 2% CH3COOH, wherein 3% of the weight of the alkali-modified conditioning agent is added to the chitosan material, ultrasonic homogenization for 30 minutes, magnetic stirring for 24 hours, centrifugation, rotary evaporation at 60°C to remove water to obtain a black precipitate. The formed black precipitate is placed in an oven at 80°C for 12 hours to obtain a chitosan-modified conditioning agent, and the obtained material is ground through a 100-mesh sieve.

[0051] Step (4), granulating the chitosan modified conditioning agent, using sodium carboxymethyl cellulose as a binder for granulation, and the amount of the binder is 0.6% of the mass of the chitosan modified conditioning agent.

[0052] The specific operation steps are as follows: first, 50% of the total amount of chitosan modified conditioner powder is put into the granulation disk, and the binder powder is weighed according to 0.6% of the amount of chitosan modified conditioner. When the granulation disk is rotating, 50% of the total amount of binder is evenly sprinkled on the chitosan modified conditioner to form small particles, and then the remaining chitosan modified conditioner and the remaining binder are added simultaneously to continue granulation until the predetermined particle size is reached to obtain the conditioner particles. After the prepared conditioner particles are sieved through a 1mm~4.75mm sieve, they are placed in an oven at 60°C for 4h, and then taken out and cooled at room temperature to finally obtain a granular soil conditioner.

[0053] Comparative Example 1 This comparative example provides a granular soil conditioner, comprising the following raw materials in percentage by weight: 60% alkaline phosphorus tailings powder, 10% silicon-based yellow phosphorus slag powder, 15% mineral humic acid, and 15% sepiolite powder.

[0054] Step (1), 240g of alkaline phosphorus tailings powder, 40g of silicon-based yellow phosphorus slag powder, 60g of mineral humic acid, and 60g of sepiolite powder are put into a blender for mixing to obtain a mixed powder material.

[0055] Step (2), pass 400 g of the mixed powder material through a 100-mesh sieve, mix with 2 L of a 1 mol / L NaOH solution, and then stir magnetically for 24 h, use rotary evaporation to ensure that some active nutrients are retained in the material, and obtain an alkali-modified conditioner.

[0056] Step (3), soak 400g of the alkali-modified conditioning agent in 1L of 2% CH3COOH, wherein 5% of the weight of the alkali-modified conditioning agent is added to the chitosan material, ultrasonic homogenization for 30 minutes, magnetic stirring for 24 hours, centrifugation, rotary evaporation at 60°C to remove water to obtain a black precipitate. The formed black precipitate is placed in an oven at 80°C for 12 hours to obtain a chitosan-modified conditioning agent, and the obtained material is ground through a 100-mesh sieve.

[0057] Step (4), granulating the chitosan modified conditioning agent, using sodium carboxymethyl cellulose as a binder for granulation, and the amount of the binder is 0.6% of the mass of the chitosan modified conditioning agent.

[0058] The specific operation steps are as follows: first, put 50% of the total amount of chitosan modified conditioner powder into the granulation disk, weigh the binder powder according to 0.6% of the amount of chitosan modified conditioner, and evenly sprinkle 50% of the total amount of binder on the chitosan modified conditioner while the granulation disk is rotating to form small particles, and then simultaneously add the remaining chitosan modified conditioner and the remaining binder to continue granulation until the predetermined particle size is reached to obtain the conditioner particles. After the prepared conditioner particles are sieved through a 1mm~4.75mm sieve, they are placed in an oven at 60°C for 4h, and then taken out and cooled at room temperature to finally obtain a granular soil conditioner.

[0059] Compared with Example 1 and Example 2, since too much chitosan was added during the preparation of this comparative example, chitosan was difficult to dissolve during the experiment, resulting in chitosan residue. At the same time, when the modification treatment was performed according to the method of step (3), the viscosity of the overall solution was enhanced. No good effect was formed after granulation.

[0060] In order to further demonstrate the effect of the granular soil conditioner prepared by the present invention, the granular soil conditioner prepared in Example 1 was used to set up a potted plant test to verify the effect, and the treatment included the following groups of tests: CK: No conditioners added.

[0061] T1: The conditioner is obtained by directly mixing the following components in percentage by mass: 60% tailings, 20% yellow phosphorus slag and 20% sepiolite.

[0062] T2: The conditioning agent is obtained by directly mixing the following components in percentage by mass: 60% tailings, 10% yellow phosphorus slag, 15% sepiolite and 15% humic acid.

[0063] T3: Granular soil conditioner prepared in Example 1.

[0064] The application rate of conditioners for T1~T3 was 0.2% of the test soil mass. The crop was broad bean, and the test soil was acidic red soil with pH values ​​of 4.7 and 5.2 respectively.

[0065] Table 1 Effects of different conditioners on improving acidic soil with a pH value of 4.7

[0066] The experimental results in Table 1 show that: in the strongly acidic soil with an initial acidity of 4.7, the modified phosphate tailings-based conditioner can increase the soil pH by 0.24 units, which is better than the T1 and T2 treatments; the three conditioners can significantly supplement the exchangeable calcium and magnesium in the soil, among which the T2 treatment, which mainly supplies calcium and magnesium, has the best supply of exchangeable calcium and magnesium in the soil, but the T3 treatment has a stronger ability to improve the soil pH and passivate soil Al toxicity.

[0067] The three conditioners can significantly reduce the active Al pool in the soil. Compared with T1 and T2 treatments, the modified phosphate tailings-based conditioner has the best effect, reducing the active Al by 12.3%. This is because in addition to the aluminum passivation caused by simple acid treatment, the surface activity and the types and quantities of functional groups of the conditioner are significantly increased after chitosan modification.

[0068] from Figure 1 It can be seen from the infrared spectrum that after the modification treatment, the number of functional groups such as hydroxyl, carboxyl and amino groups on the surface of the conditioner increased significantly. The increase of these active functional groups makes the particle surface have higher surface activity and adsorption capacity, thereby forming surface adsorption passivation for the active Al content in the soil.

[0069] Table 2 Effects of different conditioners on improving acidic soil with a pH value of 5.2

[0070] Similar results can be obtained from the exchangeable aluminum content of the soil in Table 1 and Table 2. Compared with simple phosphate tailings-based inorganic compound conditioners and organic compound conditioners, the modified phosphate tailings-based conditioner can convert more active exchangeable Al into solid-phase adsorbed hydroxyaluminum. In Table 1, the exchangeable aluminum decreased by 29% and the solid-phase organic-bound aluminum decreased by 12.2%. These results all illustrate the passivation ability of the modified conditioner on Al. In addition to adjusting the acidity, the modified conditioner product also has an adsorption and passivation effect on soil Al.

[0071] Table 3 Effects of different conditioners on Al toxicity of crops in acidic soil with pH 4.7

[0072] Table 4 Effects of different conditioners on Al toxicity of crops in acidic soil with pH 5.2

[0073] At the same time, as shown in Tables 3 and 4, the modified conditioner showed a higher increase in plant biomass and an inhibitory effect on Al at the root tip of crops, which is consistent with the change in Al morphology in the soil, indicating that it can significantly show its effect on soil Al, thereby improving crop yield and quality. In order to illustrate the improvement effect of granulation and modification on soil conditioners and the improvement effect on Al passivation ability, its verification effect on nut crops was set up, and the treatment included the following groups of experiments: CK1: No conditioning agent was applied.

[0074] CK2: No conditioner was applied, but calcium-magnesium fertilizer was added. The calcium-magnesium fertilizer was calcium sulfate and magnesium sulfate. The mass ratio of calcium to soil was 100 mg / kg, and the mass ratio of magnesium to soil was 100 mg / kg.

[0075] T1: The conditioner is obtained by directly mixing the following components in percentage by mass: 60% tailings, 20% yellow phosphorus slag and 20% sepiolite.

[0076] T2: The conditioning agent is obtained by directly mixing the following components in percentage by mass: 60% tailings, 10% yellow phosphorus slag, 15% sepiolite and 15% humic acid.

[0077] T3: chitosan modified conditioning agent prepared in step (3) of Example 1.

[0078] The conditioning agents of T1, T2 and T3 are divided into two forms, granular form and powder form. The granular form is obtained by granulation according to step (4) of Example 1. The application amount of the conditioning agent is 0.2%.

[0079] Figure 2 The results showed that compared with CK1, the three conditioning agents T1~T3 increased the nut biomass by 6.57~89.1%, among which the granular products of the three conditioning agents T1~T3 increased by 68.4~89.1%, and the use effect of T3 conditioning agent was the best, and the nut biomass increased by 89.1% compared with CK1. The powder products of the three conditioning agents T1~T3 increased by 6.57~66.8%. T3 conditioning agent still showed the best biomass improvement effect. This is because the T3 conditioning agent prepared in Example 1 has a better improvement effect on acidic soil than T1 and T2 treatments. After modification, the particle surface activity of the conditioning agent is higher and the surface functional groups are richer, which makes it have a higher passivation effect on Al in the soil; at the same time, higher surface activity can increase the cation exchange capacity of the soil, can adsorb nutrients in the soil, maintain the effectiveness of nutrients, and reduce nutrient loss. Therefore, the comprehensive effect of T3 treatment is the best.

[0080] Comparison of the effects of powder products and granular products shows that, in addition to being more convenient to use, the granulation of conditioners is more conducive to the growth of nut crops and shows a better promotion effect. This is because, compared with powdered conditioners, granular conditioners release nutrients more slowly in the soil, so they can better meet the needs of nut crops for calcium and magnesium. At the same time, the effect of acidification and passivation of Al can be sustained, making the conditioner effective over a longer growth period. Of course, it should be noted that when the soil produces obvious crop toxicity, rapid acidification is extremely necessary, and powdered conditioners can be used or the amount of granular conditioners can be increased.

[0081] At the same time, from Figure 2It can be seen that the effect of the T3 granular conditioner is comparable to the CK2 treatment with calcium and magnesium fertilizer added to increase crop yield. Nuts are a crop with a high demand for calcium and magnesium, so conventional fertilization usually requires additional calcium and magnesium fertilizers, resulting in additional investment. However, calcium and magnesium are difficult to preserve in acidic soils, and calcium and magnesium fertilizers require long-term and continuous investment to ensure crop growth. In contrast, the conditioner prepared by the present invention has a lower cost. In addition to supplying calcium and magnesium, applying it to the soil can also increase the exchangeable calcium and magnesium in the soil, ensuring its long-term effect.

[0082] In order to verify the granulation effect of the binder on the phosphate tailings-based conditioner, the present invention selects two binders, sodium carboxymethyl cellulose and sodium lignin sulfonate, for comparison.

[0083] The granulation material is phosphate tailings, and sodium carboxymethyl cellulose and sodium lignin sulfonate are used for comparison. Figure 3 The results show that the granulation effect of sodium carboxymethyl cellulose is significantly better than that of sodium lignin sulfonate, with an average particle strength of 25.3N, while the average particle strength of sodium lignin sulfonate is 14.2N, and many particles have a strength lower than 10N. Considering the comprehensive cost and granulation effect, carboxymethyl cellulose material is selected as the granulation binder.

[0084] In order to verify the granulation effect of sodium carboxymethyl cellulose as a binder on different phosphate tailings-based conditioning agent products, the particle strength of Example 1 and Example 2 was tested, and the treatment included the following groups of tests: CK: The phosphate tailings were granulated according to step (4) of Example 1, and the amount of binder used was 1% of the mass of the phosphate tailings.

[0085] T1: The conditioning agent is composed of the following components in percentage by mass: 60% tailings + 10% yellow phosphorus slag + 15% sepiolite + 15% humic acid. The above components are mixed to obtain a mixture, and the mixture is granulated according to step (4) of Example 1. The amount of binder used is 1% of the mass of the mixture.

[0086] T2: Example 1.

[0087] T3: Example 2.

[0088] T4: Example 3.

[0089] Figure 4The results show that the selection and dosage of sodium carboxymethyl cellulose can be applied to the granulation of acidic soil conditioner products based on sandy materials such as phosphate tailings, and the average particle strength is above 15N. Among them, the modified treatment is easier to granulate because it has a certain viscosity after adding a certain amount of chitosan material. The addition of chitosan can reduce the proportion of binder, and the particle strength is reduced from an average of 19.52N to 18.43N, which generally meets the current requirements for conditioners. It should be noted that most of the current standards for granular products of conditioners refer to the 10N standard of compound fertilizers or the 15N standard of calcium magnesium phosphate fertilizers.

[0090] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0091] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing a granular soil conditioner with modified acid passivation aluminum, characterized in that: The following steps are involved: The alkaline phosphorus tailings powder, silicon-based yellow phosphorus slag powder, silicate mineral and carbon source conditioner are uniformly mixed to obtain a mixed powder material; The mixed powder material is immersed in an alkali solution for alkali modification to obtain an alkali-modified conditioning agent; The alkali-modified conditioning agent is immersed in a chitosan solution, and the chitosan functional groups are attached to the surface of the alkali-modified conditioning agent by reaction, thereby obtaining a chitosan-modified conditioning agent; A binder is added to the chitosan modified conditioner, and granulation is performed to obtain an acid-modified aluminum-passivated granular soil conditioner.

2. The method for preparing a granular soil conditioner with acid-passivated aluminum according to claim 1, characterized in that: The ratio of the alkali-modified conditioning agent to the chitosan solution is 0.4 kg:1 L, and the amount of chitosan added is 1% to 3% of the alkali-modified conditioning agent.

3. The method for preparing a granular soil conditioner with acid-passivated aluminum according to claim 1, characterized in that: When preparing chitosan modified conditioning agent, the reaction time is 24h.

4. The method for preparing a granular soil conditioner with modified acid and aluminum passivation according to claim 1, characterized in that: The amount of binder added is 0.6%~1% of the chitosan modified conditioning agent.

5. The method for preparing a granular soil conditioner with modified acid and aluminum passivation according to claim 1, characterized in that: The ratio of the mixed powder material to the alkaline solution is 0.4 kg:2 L, and the concentration of the alkaline solution is 1 mol / L.

6. The method for preparing a granular soil conditioner with modified acid and aluminum passivation according to claim 1, characterized in that: The reaction time of the alkali modification treatment is 24 h.

7. The method for preparing a granular soil conditioner with modified acid and aluminum passivation according to claim 1, characterized in that: The mixed powder material consists of the following components in percentage by mass: 60% of alkaline phosphorus tailings powder, 10% of silicon-based yellow phosphorus slag powder, 15% of silicate minerals, and 15% of a carbon source conditioner.

8. The method for preparing a granular soil conditioner with modified acid and aluminum passivation according to claim 1, characterized in that: The binder is sodium carboxymethyl cellulose.

9. The method for preparing a granular soil conditioner with modified acid and aluminum passivation according to claim 1, characterized in that: Alkaline phosphate tailings are the flotation tailings of collophanite; Silicon-based yellow phosphorus slag powder is a by-product of yellow phosphorus production by electric furnace method; The silicate minerals are sepiolite or montmorillonite; The carbon source conditioner is humic acid, and the organic matter content in the humic acid is ≥30%.

10. A granular soil conditioner with modified acid and inactivated aluminum prepared by the preparation method according to any one of claims 1 to 9.

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