A granular soil conditioner for modifying acidified aluminum and its preparation method

Abstract

The present invention discloses a granular soil conditioner for acid-modified and aluminum-passivated soil and a preparation method thereof, belonging to the technical field of soil improvement. The present invention provides a preparation method of a granular soil conditioner for acid-modified and aluminum-passivated soil, comprising the following steps: uniformly mixing alkaline phosphorous tailing powder, silicon-based yellow phosphorus slag powder, silicate minerals and a carbon source conditioner to obtain a mixed powder material; soaking the mixed powder material in an alkali solution for alkali modification treatment to obtain an alkali-modified conditioner; soaking the alkali-modified conditioner in a chitosan solution, and reacting to make the functional groups of chitosan attach to the surface of the alkali-modified conditioner to obtain a chitosan-modified conditioner; adding a binder to the chitosan-modified conditioner for granulation to obtain a granular soil conditioner for acid-modified and aluminum-passivated soil. The granular soil conditioner provided by the present invention can effectively improve acidic soil and has a high aluminum passivation ability.

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 preparation method of a granular soil conditioner for acid-modified and passivated aluminum, comprising the following steps:

[0006] Mix alkaline phosphorus tailing powder, silicon-based yellow phosphorus slag powder, silicate mineral and carbon source conditioner evenly to obtain a mixed powder material.

[0007] Soak the mixed powder material in an alkali solution for alkali modification treatment to obtain an alkali-modified conditioner.

[0008] Soak the alkali-modified conditioner in a chitosan solution, and react to make the functional groups of chitosan attach to the surface of the conditioner to obtain a chitosan-modified conditioner.

[0009] Add a binder to the chitosan-modified conditioner and granulate to obtain a granular soil conditioner for acid-modified and passivated aluminum.

[0010] In the preparation process of the present invention, after the mixed powder material is subjected to alkali modification treatment, in order to further improve the performance of the granular soil conditioner for acid-modified and passivated aluminum, it is dried by rotary evaporation after alkali modification treatment to ensure that part of the active nutrients are retained in the material to obtain an alkali-modified conditioner.

[0011] In the granulation process of the present invention, first put half of the conditioner powder into the granulation pan, weigh the binder powder according to the proportion of the conditioner addition amount, and evenly sprinkle the binder with the same proportion of conditioner content on the raw material mixture while the granulation pan is rotating to form small particles, and then synchronously add the remaining raw material mixture and the remaining binder to continue granulation until the predetermined particle size is reached to obtain conditioner particles. After sieving the prepared conditioner particles, place them in an oven to dry and then take them out to cool at room temperature to finally obtain a granular soil conditioner for acid-modified and passivated aluminum.

[0012] In a preferred embodiment of the present invention, the ratio of the alkali-modified conditioner to the chitosan solution is 0.4 kg: 1 L, and the addition amount of chitosan is 1% - 3% of the alkali-modified conditioner. For example, the addition amount of chitosan is 1%, 1.5%, 2%, 2.5%, 3%, etc. of the alkali-modified conditioner, but it is not limited to the listed values, and other unlisted values within the above numerical range are also applicable.

[0013] In a preferred embodiment of the present invention, when preparing the chitosan-modified conditioner, the reaction time is 24 h.

[0014] In a preferred embodiment of the present invention, the addition amount of the binder is 0.6% - 1% of the chitosan-modified conditioner.

[0015] In a preferred embodiment of the present invention, the ratio of the mixed powder material to the alkali solution is 0.4 kg: 2 L, and the concentration of the alkali solution is 1 mol / L.

[0016] In a preferred embodiment of the present invention, the reaction time of the alkali modification treatment is 24 h.

[0017] In a preferred embodiment of the present invention, the mixed powder material is composed of the following components by mass percentage: 60% of alkaline phosphate tailings powder, 10% of silicon-based yellow phosphorus slag powder, 15% of silicate mineral, and 15% of carbon source conditioner.

[0018] In a preferred embodiment of the present invention, the binder is sodium carboxymethyl cellulose.

[0019] In a preferred embodiment of the present invention, the alkaline phosphate tailings are the tailings of collophanite flotation; the available nutrients of the collophanite flotation tailings are: P 2 O 5 5% - 10%, CaO 30% - 35%, MgO 12% - 18%, SiO 2 5% - 7%. The silicon-based yellow phosphorus slag powder is a by-product of the production of yellow phosphorus by the electric furnace method; the available nutrients of the silicon-based yellow phosphorus slag powder are: SiO 2 30% - 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%.

[0020] The second object of the present invention is to provide a granular soil conditioner for acid-modified and passivated aluminum prepared by the above preparation method.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) Based on phosphate tailings, the present invention forms a granular soil conditioner mainly composed of acid-modified and passivated aluminum, which solves problems such as acidic soil and Al toxicity, and provides an effective measure for the disposal of a large amount of accumulated industrial by-products of phosphate tailings. The granular soil conditioner prepared by the present invention, as a compound acidic soil conditioner, the phosphate tailings and the silicon-based yellow phosphorus slag material supplement the calcium, magnesium and silicon elements in the soil, and the addition of the silicate mineral and the carbon source conditioner provides a more abundant surface charge amount and surface activity. At the same time, the nutrient activity of the phosphate tailings is improved through surface modification, so as to improve its utilization efficiency in the soil. And after modification, there are more abundant functional groups and surface adsorption capabilities among the overall materials, so that the conditioner can adsorb and passivate more Al, and can adjust the Al form in the soil by surface adsorption and passivation, so as to achieve a better acid-modifying and Al-passivating effect.

[0023] (2) The present invention realizes granulation of an acidic soil conditioner formed by compounding sand-type materials such as phosphorus tailings. The granular soil conditioner obtained after granulation meets the requirements of current conditioner technical standards, and the nutrient release of the granular soil conditioner in the soil is slower. Therefore, it can better meet the crop's demand for calcium and magnesium elements and continuously improve the acidity of the soil and passivate Al. Compared with most current conditioner products and phosphorus tailings-based products, the granular soil conditioner of the present invention is granulated, making it easier to transport and use in the field. Description of the Drawings

[0024] Figure 1 are infrared spectra of different conditioners.

[0025] Figure 2 are bar graphs of the effects of different forms of conditioners on the biomass of nut crops.

[0026] Figure 3 are bar graphs of the particle strength of conditioners prepared with different binders.

[0027] Figure 4 are bar graphs of the particle strength of different treatment groups. Specific Embodiments

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0029] In the present invention, the flotation tailings of collophanite are used as the main raw material, aiming to promote the resource reuse of by-products in the phosphorus chemical industry. The conditioner is formed by compounding multiple materials, ensuring the main functional materials of the conditioner and the improvement effect on acidic soil. Among them, alkaline phosphorus tailings powder and silicon-based yellow phosphorus slag materials mainly provide sufficient alkalinity for the conditioner to ensure the effect of soil acidification improvement. At the same time, these two materials, alkaline phosphorus tailings powder and silicon-based yellow phosphorus slag materials, are rich in calcium, magnesium, and silicon elements to supplement the nutrient deficiency in the soil. Compared with alkaline phosphorus tailings powder, the nutrient activity of silicon-based yellow phosphorus slag powder is higher and the alkalinity is stronger, which can quickly and efficiently improve the soil. Secondly, silicate minerals such as sepiolite ensure that the conditioner has a higher specific surface area and surface charge amount while supplying nutrients, providing a basis for subsequent modification. Finally, in addition to ensuring that the conditioner has a certain biological regulation effect, most carbon source conditioners are rich in charge amounts and functional groups, which also provide a necessary basis for subsequent improvement. Moreover, the main raw materials are sufficient in quantity and low in price, making it easy to realize industrial production.

[0030] 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 chitosan material is used for modification after alkali modification to improve the surface activity and the content of surface functional groups of the conditioner, so that more soil active Al can be passivated in the soil through surface adsorption. At the same time, the silicon element in the conditioner forms a complex or hydroxyaluminum with Al, improving the passivation effect on Al; calcium, magnesium, silicon, organic additives, etc. in the components can improve the nutrient utilization rate and meet the nutrient requirements during the growth and development of crops through reasonable proportioning, thereby increasing the yield and quality of crops. 3+ forms a complex or hydroxyaluminum with Al to improve the passivation effect on Al 3+ ; calcium, magnesium, silicon, organic additives, etc. in the components can improve the nutrient utilization rate and meet the nutrient requirements during the growth and development of crops through reasonable proportioning, thereby increasing the yield and quality of crops.

[0031] Finally, in order to further improve the utilization convenience of the conditioner, the soil conditioner mainly composed of sandy material alkaline phosphorous tailing powder is granulated, and sodium carboxymethylcellulose with relatively low cost and high viscosity is used. The conditioner has good particle strength and granulation rate, and can be quickly disintegrated and released in the soil, facilitating the field use of the conditioner.

[0032] The alkaline phosphorous tailing powder used in the present invention is the tailing powder of collophanite flotation, and its nutrient indexes are: P 2 O 5 5 - 10%, CaO 30% - 35%, MgO 12% - 18%, SiO 2 5% - 7%. After the collophanite flotation tailings are pressure-filtered and then crushed and sieved in a crusher, the fineness of the material is 60 mesh and the water content is about 15%.

[0033] The silicon-based yellow phosphorus slag powder is a by-product of yellow phosphorus production by the electric furnace method and is obtained after being crushed. The fineness of the material is 60 mesh. The available nutrients are: SiO 2 30% - 38%, CaO 29% - 35%, MgO 1% - 4%.

[0034] The sepiolite powder is a directly purchased product, which is the product of direct processing of sepiolite ore, with CaO 20% - 25% and MgO 12% - 16%, and the fineness of the material is 100 mesh.

[0035] The humic acid is the purchased mineral source humic acid, with the organic matter content ≥ 30%, and the fineness of the material is 100 mesh.

[0036] The montmorillonite powder is a directly purchased product, with an effective CaO of about 10%, a BET specific surface area of 55.9 m 2 / g, and a CEC of 40 cmol / kg, and the fineness of the material is 100 mesh.

[0037] Example 1

[0038] 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.

[0039] 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.

[0040] 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.

[0041] Step (3), soak 400g of the alkali-modified conditioner in 1L of CH 3 In COOH, chitosan material with a weight of 2% of the alkali-modified conditioning agent was added, ultrasonic homogenized for 30 minutes, magnetically stirred for 24 hours, centrifuged, and rotary evaporated at 60°C to remove water to obtain a black precipitate. The formed black precipitate was placed in an oven at 80°C for 12 hours to obtain a chitosan-modified conditioning agent, and the obtained material was ground through a 100-mesh sieve.

[0042] 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.

[0043] 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.

[0044] Example 2

[0045] 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.

[0046] Step (1): Put 240 g of alkaline phosphorus tailings powder, 40 g of silicon-based yellow phosphorus slag powder, 60 g of mineral source humic acid, and 60 g of sepiolite powder into a blender and stir and mix to obtain a mixed powder material.

[0047] Step (2): Pass 400 g of the mixed powder material through a 100-mesh sieve, mix it with 2 L of a NaOH solution with a concentration of 1 mol / L, then stir magnetically for 24 h, and rotary evaporate at a temperature of 60 °C until most of the water is evaporated, ensuring that some active nutrients are retained in the material to obtain an alkali-modified conditioner.

[0048] Step (3): Immerse 400 g of the alkali-modified conditioner in 1 L of CH 3 COOH with 3% by weight of chitosan material based on the weight of the alkali-modified conditioner, ultrasonically homogenize for 30 min, stir magnetically for 24 h, centrifuge, and then rotary evaporate at a temperature of 60 °C to remove water to obtain a black precipitate. Place the formed black precipitate in an oven at 80 °C for 12 h to obtain a chitosan-modified conditioner, and grind the obtained material through a 100-mesh sieve.

[0049] Step (4): Granulate the chitosan-modified conditioner, using sodium carboxymethyl cellulose as a binder for granulation, and the dosage of the binder is 0.6% of the mass of the chitosan-modified conditioner.

[0050] The specific operation steps are as follows: First, put 50% of the total amount of the chitosan-modified conditioner powder into the granulation tray, weigh the binder powder according to 0.6% of the dosage of the chitosan-modified conditioner, and while the granulation tray is rotating, evenly sprinkle 50% of the total amount of the binder on the chitosan-modified conditioner to form small particles, and then synchronously add the remaining chitosan-modified conditioner and the remaining binder to continue granulation until the predetermined particle size is reached to obtain conditioner particles. After passing the prepared conditioner particles through a sieve with a size of 1 mm - 4.75 mm, place them in an oven at 60 °C and dry for 4 h, and then take them out and cool at room temperature to finally obtain a granular soil conditioner.

[0051] Example 3

[0052] This example provides a granular soil conditioner for acid-modifying and passivating aluminum, comprising the following raw materials in weight percentages: 60% of alkaline phosphorus tailings powder, 10% of silicon-based yellow phosphorus slag powder, 15% of mineral source humic acid, and 15% of montmorillonite powder.

[0053] Step (1): Put 240 g of alkaline phosphorus tailings powder, 40 g of silicon-based yellow phosphorus slag powder, 60 g of mineral source humic acid, and 60 g of montmorillonite powder into a blender and stir and mix to obtain a mixed powder material.

[0054] Step (2): Pass 400 g of the mixed powder material through a 100-mesh sieve, mix it with 2 L of a NaOH solution with a concentration of 1 mol / L, then stir magnetically for 24 h, and rotary evaporate at a temperature of 60 °C until most of the water is evaporated, ensuring that some active nutrients are retained in the material to obtain an alkali-modified conditioner.

[0055] Step (3): Immerse 400 g of the alkali-modified conditioner in 1 L of 2% CH 3 COOH, and add 3% by weight of the chitosan material based on the weight of the alkali-modified conditioner. Homogenize by ultrasonic for 30 min, stir magnetically for 24 h, and after centrifugation, rotary evaporate at a temperature of 60 °C to remove water to obtain a black precipitate. Place the formed black precipitate in an oven at 80 °C for 12 h to obtain a chitosan-modified conditioner, and grind the obtained material through a 100-mesh sieve.

[0056] Step (4): Granulate the chitosan-modified conditioner, using sodium carboxymethylcellulose as a binder for granulation, and the dosage of the binder is 0.6% of the mass of the chitosan-modified conditioner.

[0057] The specific operation steps are as follows: First, put 50% of the total amount of the chitosan-modified conditioner powder into the granulation pan, weigh the binder powder according to 0.6% of the dosage of the chitosan-modified conditioner. With the granulation pan rotating, evenly sprinkle 50% of the total amount of the binder on the chitosan-modified conditioner to form small particles, and then synchronously add the remaining chitosan-modified conditioner and the remaining binder to continue granulation until the predetermined particle size is reached to obtain conditioner particles. After passing the prepared conditioner particles through a 1 mm - 4.75 mm sieve, place them in an oven at 60 °C and dry for 4 h, then take them out and cool at room temperature to finally obtain granular soil conditioner.

[0058] Comparative Example 1

[0059] This comparative example provides a granular soil conditioner, which includes the following raw materials in weight percentages: 60% of alkaline phosphorous tailings powder, 10% of silicon-based yellow phosphorus slag powder, 15% of mineral source humic acid, and 15% of sepiolite powder.

[0060] Step (1): Put 240 g of alkaline phosphorous tailings powder, 40 g of silicon-based yellow phosphorus slag powder, 60 g of mineral source humic acid, and 60 g of sepiolite powder into a blender and stir and mix to obtain a mixed powder material.

[0061] Step (2): Pass 400 g of the mixed powder material through a 100-mesh sieve, mix it with 2 L of a NaOH solution with a concentration of 1 mol / L, then stir magnetically for 24 h, and use rotary evaporation to ensure that some active nutrients are retained in the material to obtain an alkali-modified conditioner.

[0062] Step (3): Soak 400 g of the alkali-modified conditioner in 1 L of 2% CH 3 COOH, and add 5% by weight of chitosan material to the alkali-modified conditioner. Homogenize it by ultrasonic treatment for 30 min, stir it magnetically for 24 h, and after centrifugation, rotate and evaporate to dryness at 60 °C to remove water to obtain a black precipitate. Place the formed black precipitate in an oven at 80 °C for 12 h to obtain the chitosan-modified conditioner, and grind the obtained material through a 100-mesh sieve.

[0063] Step (4): Granulate the chitosan-modified conditioner, using sodium carboxymethyl cellulose as a binder for granulation, and the dosage of the binder is 0.6% of the mass of the chitosan-modified conditioner.

[0064] The specific operation steps are as follows: First, put 50% of the total amount of the chitosan-modified conditioner powder into the granulation pan, weigh the binder powder according to 0.6% of the dosage of the chitosan-modified conditioner, and while the granulation pan is rotating, evenly sprinkle 50% of the total amount of the binder on the chitosan-modified conditioner to form small particles, and then synchronously 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 passing the prepared conditioner particles through a 1 mm - 4.75 mm sieve, place them in an oven at 60 °C and dry for 4 h, then take them out and cool at room temperature to finally obtain the granular soil conditioner.

[0065] Compared with Example 1 and Example 2, since too much chitosan was added during the preparation of this comparative example, it was difficult for chitosan to dissolve during the experiment, resulting in chitosan residue. At the same time, when the modification treatment was carried out according to the method of step (3), the viscosity of the overall solution increased. No good effect was formed after granulation.

[0066] In order to further prove the effect of the granular soil conditioner for acid-modified and passivated aluminum prepared by the present invention, the granular soil conditioner prepared in Example 1 was used to set up a pot experiment treatment to verify the effect, and the treatment included the following groups of experiments:

[0067] CK: No conditioner is added.

[0068] T1: The conditioner is directly mixed from the following components by mass percentage: 60% tailings, 20% yellow phosphorus slag, and 20% sepiolite.

[0069] T2: The conditioner is directly mixed from the following components by mass percentage: 60% tailings, 10% yellow phosphorus slag, 15% sepiolite, and 15% humic acid.

[0070] T3: The granular soil conditioner prepared in Example 1.

[0071] The application rate of the conditioner for T1 to T3 is 0.2% of the test soil mass. The crop planted is broad bean, and the tested soil is acidic red soil with pH values of 4.7 and 5.2 respectively.

[0072] Table 1 Effects of different conditioners on improving acidic soil with a pH value of 4.7

[0073]

[0074] The experimental results in Table 1 show that: in the strongly acidic soil with an initial acidity of 4.7, the modified phosphate tailing-based conditioner can increase the soil pH by 0.24 units, which is better than the T1 and T2 treatments; all three conditioners can significantly supplement the exchangeable calcium and magnesium in the soil. Among them, the T2 treatment mainly supplying calcium and magnesium has the best supply of exchangeable calcium and magnesium in the soil, but the T3 treatment has a stronger ability to increase the soil pH value and passivate the soil Al toxicity.

[0075] The three conditioners can significantly reduce the soil active Al pool. Compared with the T1 and T2 treatments, the modified phosphate tailing-based conditioner has the best effect, and the active Al is reduced by 12.3%. This is because in addition to the aluminum passivation caused by simple acid modification, after the chitosan modification treatment, the surface activity and the types and quantities of functional groups of the conditioner are significantly increased.

[0076] From Figure 1 the infrared spectrogram, it can be seen that after the modification treatment, the quantities of functional groups such as hydroxyl, carboxyl, and amino groups on the conditioner surface are significantly increased. The increase of these active functional groups makes the particle surface have higher surface activity and adsorption capacity, thus forming surface adsorption passivation on the content of active Al in the soil.

[0077] Table 2 Effects of different conditioners on improving acidic soil with a pH value of 5.2

[0078]

[0079] Similar results can be obtained from the exchangeable aluminum content in the soil in Table 1 and Table 2. Compared with the simple phosphate tailing-based inorganic compound conditioner and organic compound conditioner, the modified phosphate tailing-based conditioner can convert the more active exchangeable Al into solid-phase adsorbed hydroxyaluminum. In Table 1, the exchangeable aluminum is reduced by 29%, and the solid-phase organically bound aluminum is reduced by 12.2%. These results all illustrate the passivation ability of the modified conditioner to Al. In addition to adjusting the acidity, the modified conditioner product also has an adsorption passivation effect on soil Al.

[0080] Table 3 Effects of different conditioners on crop Al toxicity in acidic soil with a pH value of 4.7

[0081]

[0082] Table 4 Effects of Different Conditioners on Al Toxicity in Crops in Acidic Soil with a pH of 5.2

[0083]

[0084] Meanwhile, as shown in Table 3 and Table 4, the modified conditioners showed higher improvement in plant biomass and inhibition of Al in crop root tips, which was consistent with the change in Al forms in the soil, indicating that they could significantly exhibit their effects on soil Al, thereby improving the yield and quality of crops. To illustrate the improvement effect of granulation and modification on soil conditioners and the enhancement effect on Al passivation ability, the verification effects on nut crops were set up, and the treatments included the following groups of experiments:

[0085] CK1: No conditioner was applied.

[0086] CK2: No conditioner was applied, but calcium and magnesium fertilizers were added. The calcium and magnesium fertilizers were calcium sulfate and magnesium sulfate, and the mass ratio of calcium to soil was 100 mg / kg, and the mass ratio of magnesium to soil was 100 mg / kg.

[0087] T1: The conditioner was directly mixed from the following components by mass percentage: 60% tailings, 20% yellow phosphorus slag, and 20% sepiolite.

[0088] T2: The conditioner was directly mixed from the following components by mass percentage: 60% tailings, 10% yellow phosphorus slag, 15% sepiolite, and 15% humic acid.

[0089] T3: The chitosan-modified conditioner prepared in step (3) of Example 1.

[0090] The conditioners of T1, T2, and T3 were in two forms, granular form and powder form. The granular form was obtained by granulation according to the steps of Example 1 (4). The application rate of the conditioner was 0.2%.

[0091] Figure 2The results show that, compared with CK1, the three conditioners T1 - T3 increased the nut biomass by 6.57 - 89.1%. Among them, the granular products of the three conditioners T1 - T3 increased by 68.4 - 89.1%, and the conditioner T3 had the best effect, with the nut biomass increasing by 89.1% compared with CK1. The powder products of the three conditioners T1 - T3 increased by 6.57 - 66.8%. Still, the conditioner T3 showed the best improvement in biomass. This is because the T3 conditioner prepared in Example 1 had a better improvement effect on acidic soil compared with T1 and T2 treatments. After modification, the surface activity of the conditioner granules was higher, and the surface functional groups were more abundant, which made it have a higher passivation effect on Al in the soil. At the same time, the higher surface activity could increase the cation exchange capacity of the soil, adsorb nutrients in the soil, maintain the effectiveness of nutrients, and reduce nutrient loss. Therefore, the comprehensive effect of the T3 treatment was the best.

[0092] From the comparison of the effects of powder products and granular products, it can be seen that in addition to being more convenient to use, granulation of the conditioner is more beneficial to the growth of nut crops and shows a better promotion effect. This is because, compared with the powder - shaped conditioner, the granular conditioner releases nutrients in the soil more slowly. Therefore, it can better meet the nut crops' demand for calcium and magnesium elements. At the same time, its effect of improving acidity and passivating Al can take effect continuously, making the conditioner effective during a longer growth period. Of course, it should be noted that when obvious crop poisoning occurs in the soil, rapid acid improvement is extremely necessary, and powder - shaped conditioners can be used or the dosage of granular conditioners can be increased.

[0093] Meanwhile, from Figure 2 it can be seen that the effect of the granular conditioner of T3 is equivalent to that of the CK2 treatment with added calcium and magnesium fertilizers in increasing crop yield. Nuts are crops with a relatively high demand for calcium and magnesium. Therefore, additional calcium and magnesium fertilizers are usually required in conventional fertilization, resulting in additional input. However, in acidic soil, calcium and magnesium are difficult to preserve, and calcium and magnesium fertilizers need to be continuously input for a long time to ensure crop growth. In contrast, the conditioner prepared in the present invention has a lower cost. When applied to the soil, it can not only supply calcium and magnesium but also increase the exchangeable calcium and magnesium in the soil, ensuring its long - term effect.

[0094] To verify the granulation effect of the binder on the phosphorus tailings - based conditioner, the present invention selected two binders, sodium carboxymethyl cellulose and sodium lignosulfonate, for comparison.

[0095] The granulation material was phosphorus tailings, and sodium carboxymethyl cellulose and sodium lignosulfonate were compared. Figure 3The results show that the granulation effect of sodium carboxymethyl cellulose is significantly better than that of sodium lignosulfonate. The average particle strength is 25.3 N, while the average particle strength of sodium lignosulfonate is 14.2 N, and there are many cases where the particle strength is lower than 10 N. Considering the comprehensive cost and granulation effect, sodium carboxymethyl cellulose is selected as the granulation binder.

[0096] In order to verify the granulation effect of sodium carboxymethyl cellulose as a binder on different phosphorus tailings-based conditioner products, the particle strengths of Example 1 and Example 2 were tested, and the treatments included the following groups of experiments:

[0097] CK: The phosphorus tailings were granulated according to step (4) of Example 1, and the binder dosage was 1% of the mass of the phosphorus tailings.

[0098] T1: The conditioner was composed of the following components by mass percentage: 60% tailings + 10% yellow phosphorus slag + 15% sepiolite + 15% humic acid. The above components were mixed to obtain a mixture, and the mixture was granulated according to step (4) of Example 1, and the binder dosage was 1% of the mass of the mixture.

[0099] T2: Example 1.

[0100] T3: Example 2.

[0101] T4: Example 3.

[0102] Figure 4 The results show that the selection and dosage of sodium carboxymethyl cellulose can be applied to the granulation of acid soil conditioner products mainly composed of sandy materials such as phosphorus tailings, and the average particle strength is above 15 N. Among them, the modified treatment is easier to granulate because a certain amount of chitosan material is added and it has a certain viscosity itself. The addition of chitosan can reduce the proportion of the binder, and the particle strength is reduced from an average of 19.52 N to 18.43 N, which generally meets the current requirements for conditioners. It should be noted that most of the relevant standards for the particle products of current conditioners refer to the standards of 10 N for compound fertilizers or 15 N for calcium magnesium phosphate fertilizers.

[0103] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications once they know the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0104] 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 equivalent technologies, 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 tailing 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 composed of the following components in percentage by mass: 60% of alkaline phosphorus tailing powder, 10% of silicon-based yellow phosphorus slag powder, 15% of silicate mineral and 15% of carbon source conditioner; 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%; 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 reaction causes the functional groups of chitosan to attach to the surface of the alkali-modified conditioning agent, thereby obtaining the chitosan-modified conditioning agent; the ratio of the alkali-modified conditioning agent to the chitosan solution is 0.4 kg:1 L, the amount of chitosan added is 1% to 3% of the alkali-modified conditioning agent, and the reaction time is 24 hours; 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 amount of binder added is 0.6%~1% of the chitosan modified conditioning agent.

3. The method for preparing a granular soil conditioner with acid-passivated aluminum 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.

4. 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.

5. 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.

6. A granular soil conditioner with modified acid and inactivated aluminum prepared by the preparation method according to any one of claims 1 to 5.

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