Modified palygorskite-containing saline-alkali soil conditioner capable of avoiding drip irrigation blockage and application thereof

Abstract

The invention relates to a modified palygorskite-containing saline-alkali soil conditioner capable of avoiding drip irrigation blockage and application thereof. The conditioner is prepared from the following components in parts by weight: 1-3 parts of acid heat modified palygorskite, 1-10 parts of polyvinyl alcohol, 0.1-0.3 part of a dispersing agent, 0.05-0.2 part of a stabilizer and 90-97 parts of deionized water. The conditioner is suitable for a modern agricultural drip irrigation system, can continuously release active ingredients in soil for 30-56 days, effectively reduces the salinity and alkalinity, improves the soil structure, reduces the production cost and remarkably improves the crop yield. Field tests show that after the conditioner is applied, the wheat yield is increased, and the cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of agricultural ecological management, and in particular to a saline-alkali soil conditioner containing modified palygorskite for avoiding drip irrigation blockage. Background Art

[0002] Salt-alkali land, or salinized soil, is a global land degradation problem that poses a major threat to sustainable agricultural development and food security. The area of ​​salt-alkali land in my country has exceeded 150 million mu, mainly distributed in the northwest, North China Plain, Northeast China and Huanghuaihai Plain. High salinity and strong alkalinity are not only toxic to plant growth, but also destroy soil structure and reduce soil fertility, leading to crop yield reduction or even crop failure, and may further cause a series of problems such as land desertification and ecosystem degradation. Therefore, the management of salt-alkali land is of great significance to ensuring national food security, improving the ecological environment and promoting regional sustainable development.

[0003] At present, the following methods are mainly used for saline-alkali land treatment:

[0004] (1) Physical improvement, such as deep plowing, drainage and salt washing, and soil improvement. These methods can improve soil physical properties to a certain extent, but they have problems such as large investment, long treatment cycle, poor long-term effects, and waste of water resources. They are difficult to meet the needs of rapid and efficient treatment of saline-alkali soils on a large scale.

[0005] (2) Chemical improvement, such as applying chemical conditioners such as gypsum and sulfuric acid to neutralize soil alkalinity and reduce salinity. Although this method is effective, it also brings some problems: some chemical conditioners may cause secondary pollution risks such as soil acidification or heavy metal pollution, and are costly, require large doses, are difficult to accurately control, and are difficult to effectively combine with modern agricultural drip irrigation technology, thus affecting the overall governance effect.

[0006] (3) Biological improvement, such as planting salt-tolerant plants or applying microbial agents. This method is relatively eco-friendly, but the improvement cycle is long and the effect is slow, which is not easy to meet the needs of rapid treatment of saline-alkali land.

[0007] In addition to the above traditional methods, existing saline-alkali land treatment agents also face the following main problems:

[0008] Poor dispersibility and stability: Conventional conditioners tend to aggregate and settle in water, making it difficult to achieve uniform application in modern drip irrigation systems, resulting in a significant reduction in utilization efficiency.

[0009] Insufficient persistence: Conditioners are often released too quickly and have a short action period, requiring frequent application, which increases management costs and labor burden.

[0010] Low technical integration: There is a lack of composite materials with multiple functions such as adsorption, conditioning, and improvement, which makes it difficult to meet the needs of precise irrigation and efficient management.

[0011] Lack of environmental friendliness: Some traditional chemical conditioners may cause new pollution to the soil or surrounding environment, which is contrary to the concept of green agriculture and sustainable development.

[0012] Natural palygorskite is a porous structure with a specific surface area of ​​about 90-100m 2 / g, the mineral cation exchange capacity (abbreviated as 'mineral CEC') is about 30-35mmol / 100g, and its basic structure diagram is as follows Figure 1 As shown in Figure 2, it is expected to be used in soil conditioners. However, due to the limited number of active sites of natural palygorskite, poor dispersion performance, and difficulty in forming a stable suspension system, its application in modern drip irrigation systems is limited. Summary of the invention

[0013] The purpose of the present invention is to develop a nano-conditioner based on natural palygorskite, which has high specific surface area, high sodium ion adsorption capacity, high cation exchange capacity, and can be stably dispersed and is suitable for drip irrigation management of saline-alkali land. The conditioner is based on natural mineral palygorskite, and its interlayer spacing and specific surface area are greatly increased through acid-heat modification, thereby exposing more active sites, improving the selective adsorption capacity for Na+, and the selective adsorption capacity for Ca 2 +, Mg2+ release efficiency. The modified palygorskite not only has a higher cation exchange capacity (CEC), but also can cooperate with the network structure formed by PVA to significantly improve the physical and chemical properties of the soil, and ultimately achieve sustainable and effective improvement of saline-alkali land. The conditioner also has excellent long-term slow release and good water solubility, and can achieve precise application and efficient management through modern agricultural drip irrigation systems, and promote the green and sustainable use of saline-alkali land.

[0014] The present invention first provides a modified palygorskite saline-alkali soil conditioner for preventing drip irrigation blockage, wherein the conditioner is composed of the following components in parts by weight:

[0015] Acid-heat modified palygorskite: 1-3 parts;

[0016] Polyvinyl alcohol: 1-10 parts, preferably 2-5 parts;

[0017] Dispersant: 0.1-0.3 parts;

[0018] Stabilizer: 0.05-0.2 parts;

[0019] Deionized water: 90-97 parts;

[0020] The number average molecular weight of the polyvinyl alcohol is 30,000-50,000.

[0021] Preferably, the specific surface area of ​​the acid-heat-modified palygorskite reaches 110 m 2 / g or more, the mineral cation exchange capacity (CEC) ≥ 40mmol / 100g, and the absolute value of Zeta potential ≥ 30mV. More preferably, the specific surface area of ​​the acid-heat modified palygorskite can reach 115-125m 2 / g; the mineral cation exchange capacity (CEC) is 40-50mmol / 100g.

[0022] Preferably, the dispersant is sodium polyacrylate, and the stabilizer can be hexadecyltrimethylammonium bromide and / or polyacrylate. More preferably, the stabilizer can be a combination of hexadecyltrimethylammonium bromide and polyacrylate in a weight ratio of 1-3:1 to achieve a better balance between dispersion stability and sustained release effect.

[0023] Preferably, the preparation method of the conditioner comprises the following steps:

[0024] (1) Adding the acid-heat-modified palygorskite into a polyvinyl alcohol aqueous solution; the concentration of the polyvinyl alcohol aqueous solution is, for example, 5 wt %.

[0025] (2) Adding dispersants and stabilizers;

[0026] (3) performing ultrasonic treatment to uniformly distribute the obtained particle size within the range of 100-200 nm, thereby forming a stable nanosuspension;

[0027] (4) centrifuging, washing and drying the nanosuspension, and drying at 60-75° C. for 20-30 hours to finally obtain the conditioner.

[0028] Preferably, the method for preparing the acid-thermal modified palygorskite comprises the following steps:

[0029] (1) Selecting palygorskite ore with a particle size of less than 20 μm;

[0030] (2) Add 1-2 mol / L hydrochloric acid solution, liquid-to-solid ratio 20:1-5, and stir and reflux at 95-100°C

[0031] 20-30 hours;

[0032] (3) washing with deionized water until the pH value of the filtrate is 6-7;

[0033] (4) drying at 60°C for 24 hours and passing the dried product through a 200-mesh sieve;

[0034] (5) Calcination at 280-320°C for 3-5 hours.

[0035] The present invention also provides a specific application method of the above-mentioned conditioner in the treatment of saline-alkali land, including: diluting the conditioner with water at a ratio of 1:80-150, and applying it through a drip irrigation system, with an amount of 15-30L per mu; the conditioner can act continuously in the soil for 30-56 days, can effectively reduce soil salinity and pH value and increase cation exchange capacity, thereby achieving comprehensive treatment of saline-alkali land.

[0036] The innovative features of the present invention are as follows:

[0037] 1. Efficient acid-heat modification strategy: Through acid treatment, combined with precisely controlled calcination temperature and duration, the specific surface area of ​​palygorskite can be greatly increased (from the original level of 90-100m 2 / g increased to 110m 2 / g or more), and at the same time increase its mineral CEC (for example, from 30-35mmol / 100g to about 40mmol / 100g or more, for example 45

[0038] mmol / 100g), thereby significantly enhancing the material's adsorption capacity for saline and alkali ions. It should be noted that the 'mineral CEC' referred to here is different from the 'soil CEC' test object mentioned later. In this process, acid-heat treatment is used to remove impurities in palygorskite and activate its surface active sites, achieving efficient adsorption and exchange of harmful salts such as sodium ions in the soil.

[0039] 2. PVA composite enhances dispersion stability: By selecting polyvinyl alcohol (PVA) with a number average molecular weight in the range of 30,000-50,000, synergistic stabilizers and dispersants, and compounding with acid-heat-modified palygorskite, and supplemented with ultrasonic dispersion technology (for example, ultrasonic power 200W, ultrasonic time 30 minutes), a nano suspension with uniform particle size (about 100-200nm) and excellent stability can be prepared. This nano-scale suspension has good fluidity and adaptability in the drip irrigation system, and is not prone to particle agglomeration or pipe clogging, thereby achieving precise and efficient application.

[0040] 3. Long-term sustained-release mechanism: Through the coating effect of PVA and the optimized design of the pore structure of palygorskite itself, the active components in the conditioner can be gradually released and maintain a continuous action period of 30-56 days in the soil environment.

[0041] This slow-release mechanism effectively improves the physical and chemical properties of saline-alkali soil, reduces application frequency and management costs, helps to ensure a stable growth environment and balanced nutrient supply for crops over a longer period of time, and correspondingly improves crop yield and quality.

[0042] Technical effects and application advantages

[0043] 1. Significant soil improvement: The conditioner of the present invention can significantly improve the physical and chemical properties of saline-alkali soil, efficiently absorb harmful ions, release beneficial ions, and reduce the degree of soil salinization. Relevant test data show that after 56 days of application of the conditioner of the present invention, the soil pH value can be reduced by about 0.8-1.2 units, the salt content can be reduced by 30%-55%, and the soil CEC

[0044] (Compared to untreated soil) it increases by 20%-45%, effectively improving the physical and chemical properties of the soil and providing a good environment for the healthy growth of crops.

[0045] 2. Precise application and efficient utilization: By preparing the conditioner into a nano-scale suspension and combining it with a drip irrigation system, the uniformity and pertinence of application can be greatly improved, thereby reducing the waste of the conditioner and significantly improving the effective utilization rate. Crops can obtain nutritional ions and improvement effects in a more balanced manner, further ensuring the stability of yield and quality.

[0046] 3. Environmental protection and economy: The acid-heat modified palygorskite matrix used in the present invention is mainly derived from natural mineral resources, and the polyvinyl alcohol compounded therewith is a degradable polymer material. Both are relatively simple in formula and process and can achieve stable production under large-scale conditions, so they can effectively avoid the risk of chemical pollution and have obvious advantages in reducing the cost of governance, which is in line with the sustainable development direction of green agriculture.

[0047] 4. Long-term sustained-release effect: The conditioner can maintain a continuous improvement effect for 30-56 days in the soil environment. The long-term sustained-release effect can significantly reduce the frequency of repeated application, so that agricultural production can maintain high and stable yields while effectively reducing labor input and comprehensive costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a schematic diagram of the basic structure of natural palygorskite;

[0049] Figure 2 The infrared spectra of unmodified palygorskite, the acid-heat-modified palygorskite of Preparation Example 1, and the acid-heat-modified palygorskite and PVA composite material of Example 1;

[0050] Figure 3 TEM photos of the uncalcined palygorskite powder obtained in step (3) of Preparation Example 1, the acid-thermal modified palygorskite obtained in Preparation Example 1, and the acid-thermal modified palygorskite obtained in Preparation Example 3. DETAILED DESCRIPTION

[0051] Preparation Example 1 Preparation method of acid-heat modified palygorskite-1

[0052] (1) Raw material pretreatment:

[0053] The raw palygorskite ore from Mingguang, Anhui Province is selected, and its specific surface area is about 90-100m2 / g, CEC is about 30-35mmol / 100g, and the absolute value of Zeta potential is about 20-25mV. After being crushed by a ball mill and passed through a 200-mesh sieve, the palygorskite powder with a particle size of less than 20μm was collected for subsequent treatment.

[0054] (2) Acidification treatment:

[0055] Weigh 20g of palygorskite powder, place it in a 500mL three-necked flask, add 200mL of 2mol / L hydrochloric acid solution (liquid-to-solid ratio 10:1). After equipping with a condensation reflux device, place the reaction system in a 100℃ oil bath and stir the reaction for 24 hours (stirring speed is about 160rpm).

[0056] (3) Washing and drying:

[0057] After the reaction is completed, the mixture is cooled to room temperature naturally. The mixture is filtered by vacuum filtration, and the filter cake is repeatedly washed with deionized water until the pH value of the filtrate is 6-7. Subsequently, the washed filter cake is placed in an oven at 110°C and dried for 24 hours, and ground through a 200-mesh sieve to obtain a pre-treated powder.

[0058] (4) Calcination:

[0059] The pretreated powder was placed in a crucible and calcined in a muffle furnace at 300°C for 4 hours. After calcination, it was naturally cooled to room temperature to obtain acid-heat-modified palygorskite, which was sealed and stored. The test results show that the specific surface area of ​​the obtained acid-heat-modified palygorskite is about 120m 2 / g, and the cation exchange capacity (CEC) is 45mmol / 100g.

[0060] The test results show that after acid-heat modification, the specific surface area of ​​the palygorskite obtained is about 120m 2 / g, the cation exchange capacity (CEC) is about 45mmol / 100g, and the absolute value of Zeta potential is increased to about 30mV, indicating that the modification process significantly improves the specific surface area and ion exchange capacity.

[0061] Preparation Example 2 Preparation method of acid-heat modified palygorskite-2

[0062] Except for the calcination temperature, the remaining steps are the same as those in Preparation Example 1. The difference is that the calcination temperature is adjusted to 320°C in step (4). The test results show that the specific surface area of ​​the obtained acid-heat-modified palygorskite is about 125 m 2 / g, and the cation exchange capacity (CEC) is 46mmol / 100g.

[0063] Preparation Example 3 Preparation method of acid-heat modified palygorskite-3

[0064] Except for the calcination temperature, the other operations are basically the same as those in Preparation Example 1. In this embodiment, the calcination temperature of step (4) is 350°C. The test results show that the specific surface area of ​​the obtained acid-heat-modified palygorskite is about 115 m 2 / g, and the cation exchange capacity (CEC) is 40mmol / 100g.

[0065] From the comparison between Preparation Examples 1-3, it can be seen that when the calcination temperature is below 320°C, the specific surface area and cation exchange capacity of the acid-heat-modified palygorskite are improved by increasing the temperature. However, when the temperature is too high, the specific surface area and cation exchange capacity are reduced. The reason may be that too high a temperature may destroy part of the layered structure and pore characteristics of the palygorskite.

[0066] SEM analysis of the preparation example: Figure 3 a and 3b, Figure 3 c and 3d, Figure 3 e and 3f are the microscopic morphologies of the uncalcined palygorskite powder obtained in step (3) of Preparation Example 1, the acid-heat-modified palygorskite obtained in Preparation Example 1, and the acid-heat-modified palygorskite obtained in Preparation Example 3, respectively, which more intuitively verify their layered structures and pore characteristics.

[0067] Depend on Figure 3 As can be seen from Figures 3a and 3b, the uncalcined palygorskite powder obtained in step (3) of Preparation Example 1 has a relatively complete layered or needle-like (fibrous) structure; the pores and surface roughness are close to the original mineral morphology, and impurities or crystal water have not been fully removed.

[0068] Depend on Figure 3 c and 3d show that the layered and pore structures of the acid-thermal modified palygorskite calcined at 300°C obtained in Preparation Example 1 are generally well maintained, and impurities and part of the crystal water are removed; the specific surface area and cation exchange capacity are high, which can provide excellent active sites for subsequent acid-thermal modification and composite.

[0069] Depend on Figure 3 As can be seen from Figures e and 3f, the layered or pore structure of the acid-heat-modified palygorskite calcined at 350°C obtained in Preparation Example 3 collapsed and destroyed to a certain extent, the surface roughness increased and even local accumulation occurred, resulting in a decrease in specific surface area and porosity.

[0070] Preparation of Control Conditioner-1

[0071] The other conditions were the same as those in Example 1, except that the pretreated powder obtained in step (3) of Preparation Example 1 was used instead of the acid-heat-modified palygorskite-1 described in Example 1.

[0072] Example 1: Preparation of alkaline soil conditioner containing modified palygorskite salt

[0073] 1. Preparation of PVA solution:

[0074] Weigh 5 g of polyvinyl alcohol (PVA, molecular weight 30,000-50,000, alcoholysis degree>99%) and add it to 100 mL of deionized water. Heat it in an oil bath at 80° C. and continue stirring until a clear and transparent 5% PVA aqueous solution is formed.

[0075] 2. Composite material preparation:

[0076] 2 g of acid-heat-modified palygorskite-1 was slowly added to the above PVA aqueous solution, and 0.2 g of sodium polyacrylate (dispersant) and 0.1 g of hexadecyltrimethylammonium bromide (stabilizer) were added while stirring.

[0077] After stirring at 410 rpm for 48 hours, the mixture was ultrasonically treated at 200 W for 30 minutes to make the particle size of the obtained nanoparticles uniformly distributed in the range of 100-200 nm, thereby obtaining a relatively stable nanosuspension.

[0078] 3. Purification treatment:

[0079] The nanosuspension was divided into 50 mL centrifuge tubes and centrifuged at 3,500 rpm for 5 minutes. After discarding the supernatant, deionized water was added and oscillated on a vortex oscillator for about 3 minutes. The operation was repeated 8 times to fully remove residual impurities. Finally, the purified product was placed in a 70 ° C oven and dried for 24 hours. After grinding and passing through a 60-mesh sieve, a stable powder of "acid-heat modified palygorskite and PVA composite material" (that is, the modified palygorskite salt-alkali soil conditioner described in the present invention) was obtained. When the FTIR, SEM and other tests were performed in the subsequent embodiment, the samples were taken in the form of this powder.

[0080] Material Characterization:

[0081] Particle size distribution and Zeta potential: measured by dynamic light scattering (DLS), the particle size of the nanoparticles prepared in this example is mainly concentrated in the range of 100-200 nm, and the absolute value of the Zeta potential is about 33 mV.

[0082] Specific surface area and porosity: measured by nitrogen adsorption-desorption method, the specific surface area is about 120m 2 / g, and the porosity also meets the requirements of nano-scale composite materials.

[0083] FTIR: Figure 2 As shown, Figure 2 The differences in the main infrared absorption peaks (such as the -OH stretching vibration peak near 3,400cm-1, the Si-O bond characteristic peak around 1,000cm-1, etc.) of unmodified palygorskite, acid-heat modified palygorskite, and the acid-heat modified palygorskite and PVA composites were compared to illustrate the influence and success of acid-heat modification and PVA composite on the material structure. Specifically:

[0084] Unmodified palygorskite has a more obvious -OH stretching vibration peak near 3,400 cm-1, which corresponds to the hydroxyl water molecules contained in the interlayers and pores of palygorskite; the Si–O bond absorption peak appears near 1,000 cm-1, reflecting the silicon-oxygen tetrahedral skeleton structure.

[0085] After acid-heat treatment, the -OH absorption peak of acid-heat-modified palygorskite near 3,400 cm-1 changed, indicating that some interlayer and pore water molecules or surface hydroxyl groups were removed or redistributed; around 1,000 cm-1, the position or intensity of the Si–O characteristic peak may also shift or increase or decrease to a certain extent, indicating that the acid treatment has an impact on the palygorskite skeleton and surface active sites; the enhancement / weakening of the absorption peak near 1,400 cm-1 is usually related to the residual carbonate or newly formed surface functional groups, which also indirectly confirms the effect of acid-heat modification.

[0086] In the acid-heat-modified palygorskite and PVA composite materials, -OH and C–H stretching vibration peaks that appear or are enhanced due to the introduction of PVA can be observed near 3,400cm-1 and 2,900cm-1; as shown in the figure, the C–H bond absorption unique to PVA may appear around 2,900cm-1; the Si–O bond peak at 1,000cm-1 and the peak shape near 1,400cm-1 also differ in position or intensity with the PVA coating, indicating that the PVA molecules interact with the active sites on the palygorskite surface; the weak peaks at 1,600cm-1~1,650cm-1 may be caused by local vibration of the PVA molecular chain or carbonyl absorption, which further confirms the successful composite of organic polymers and inorganic modified minerals.

[0087] Soil improvement performance test:

[0088] Simulated laboratory soil column elution: Under simulated drip irrigation conditions, the conditioner obtained in this example was applied to saline-alkali soil, and the change trends of soil pH, salt content, electrical conductivity and CEC were detected at 7 days, 14 days, 21 days, 28 days, 35 days, 49 days, and 56 days to evaluate the improvement effect.

[0089] The prepared COF modifier aqueous solution was added at a concentration of 2g / L.

[0090] Field test: Select saline-alkali soil with pH = 9.2 and salt content of 1.5g / kg to plant wheat, and apply the conditioner (water solution concentration is 2g / L) by drip irrigation, once a week through the drip irrigation system, and each application amount is 200mL per wheat seedling. After 56 days of continuous observation, the soil pH dropped to 7.5, the salt content decreased by about 48%, and the CEC increased by about 29%.

[0091] Drip irrigation system suitability test:

[0092] oDrip head clogging experiment: The obtained nanosuspension was diluted and continuously run through a drip head with a pore size of 0.2 mm for 48 hours, and no obvious clogging was observed.

[0093] oDroplet uniformity: The actual measurement of the distribution error of the conditioner solution in the drip irrigation system is small and the adaptability is excellent.

[0094] Test data

[0095] Table 1: Measurement results of soil physical and chemical properties and crop growth indicators at different time points (Example 1 and control group)

[0096]

[0097]

[0098] Note: “Before treatment” refers to the initial condition of the soil before the application of the conditioner;

[0099] "Experimental group": refers to the application of the conditioning agent of the present invention;

[0100] “Control group”: refers to the situation where only the same irrigation conditions as the experimental group were used, but the control group conditioner-1 was used;

[0101] “Soil CEC”: The CEC in this table is obtained by testing the entire soil, which is different from the “modified palygorskite mineral CEC” in the claims;

[0102] As can be seen from Table 1: the pH value gradually decreases, indicating that the sodium ion leaching and alkaline environment improvement effects are significant, and the improvement rate can still be observed to be further reduced within the range of 7-56 days, reflecting the continuity of the slow-release effect; the continuous decline in salt content and conductivity shows that the conditioner can still continuously promote salt leaching or passivation in the later stage, avoiding a one-time explosive release and causing local high-salt damage; the steady increase in CEC reflects that the acid-heat modified palygorskite can maintain its improvement effect for a long time while releasing beneficial cations, and has made a positive contribution to the stability of soil aggregate structure and the accumulation of organic matter.

[0103] The gradual increase in crop height and biomass indicates that in the improved soil environment, the crops as a whole grow vigorously, the root system develops well, and the nutrient absorption is more efficient, which also reflects that the conditioner of the present invention has a positive role in promoting the increase of crop yield.

[0104] Example 2

[0105] The other conditions were the same as those in Example 1, except that 0.1 g of polyacrylate was used as a stabilizer instead of 0.1 g of hexadecyltrimethylammonium bromide in Example 1.

[0106] Soil improvement performance test

[0107] Simulated laboratory soil column leaching: Soil column leaching and field test were carried out on the same saline-alkali soil in the same manner as in Example 1. pH, salinity, conductivity and CEC were tested at 7 days, 14 days, 21 days, 28 days, 35 days, 49 days and 56 days.

[0108] Compared with Example 1, the improvement effect of this example was similar to that of Example 1 before 30 days; however, during the period from 28 days to 56 days, the pH dropped and the salt leaching rate decreased slightly, and the CEC increased steadily but the magnitude was slightly lower than that of Example 1.

[0109] ·After 56 days of observation, it can be seen that the soil pH value and salt content still have room for improvement, but the overall effect is lower than that of Example 1. This shows that although using 0.1g of polyacrylate as a stabilizer can reduce costs, the sustained release ability in the later stage is slightly weakened.

[0110] Field test: Under the same conditions, drip irrigation was applied to saline-alkali soil with pH = 9.2 and salt content of 1.5g / kg. The pH value can be reduced to 7.8, the salt content is reduced by about 45% compared with the initial value, and the CEC is increased by about 23% compared with the initial value. This result is better than Example 1, showing a longer-lasting slow-release effect.

[0111] Test data

[0112] Table 2: Measurement results of soil physical and chemical properties and crop growth indicators at different time points (Example 2 and control group)

[0113]

[0114] Note: “Before treatment” refers to the initial condition of the soil before the application of the conditioner;

[0115] "Experimental group": refers to the application of the conditioning agent of the present invention;

[0116] “Control group”: refers to the situation where only the same irrigation conditions as the experimental group were used, but the control group conditioner-1 was used;

[0117] “Soil CEC”: The CEC in this table is obtained by testing the entire soil, which is different from the “CEC” in the claims.

[0118] The "CEC" of palygorskite minerals is different;

[0119] Drip irrigation system adaptability

[0120] It still meets the requirements for drip irrigation adaptability in Example 1. After dilution, the nanosuspension has no clogging phenomenon and can maintain a relatively uniform dripping state.

[0121] Example 3

[0122] Except for the amount of stabilizer, the rest of the operation is the same as in Example 1. Specifically:

[0123] 1. Preparation of PVA solution:

[0124] Weigh 5 g of polyvinyl alcohol (PVA, molecular weight 30,000-50,000, alcoholysis degree>99%) and add it to 100 mL of deionized water. Heat it in an oil bath at 80° C. and continue stirring until a clear and transparent 5% PVA aqueous solution is formed.

[0125] 2. Composite material preparation:

[0126] 2 g of acid-heat-modified palygorskite-1 was weighed and slowly added to the above PVA solution, and a composition of 0.2 g of sodium polyacrylate (dispersant) and 0.5 g of polyacrylate and 0.5 g of hexadecyltrimethylammonium bromide was added as a stabilizer while stirring.

[0127] After stirring at 410 rpm for 48 hours, the mixture was ultrasonically treated at 200 W for 30 minutes to make the particle size of the obtained nanoparticles uniformly distributed in the range of 100-200 nm, thereby obtaining a relatively stable nanosuspension.

[0128] 3. Purification treatment:

[0129] The nanosuspension was divided into 50 mL centrifuge tubes and centrifuged at 3,500 rpm for 5 minutes. After discarding the supernatant, deionized water was added and vortexed on a vortex shaker for about 3 minutes. The operation was repeated 8 times to fully remove residual impurities. Finally, the purified product was placed in a 70°C oven and dried for 24 hours, and then ground and passed through a 60-mesh sieve to obtain a stable powdered alkaline soil conditioner containing modified palygorskite.

[0130] Soil improvement performance test

[0131] Simulated laboratory soil column elution: The conditioner of this example was applied to the initial saline-alkali soil in the same manner as in Example 1, and the physical and chemical indicators were continuously monitored at 7 days, 14 days, 21 days, 28 days, 35 days, 49 days, and 56 days. The results showed that the pH value, electrical conductivity, and salt content of the soil continued to decline during the 35-day, 49-day, and 56-day stages of the combined stabilizer, while the CEC continued to rise to a certain extent, and the amplitude was slightly higher than that of Example 1.

[0132] Field test: Under the same conditions, drip irrigation was applied to saline-alkali soil with pH = 9.2 and salt content of 1.5g / kg. The pH value can be reduced to 7.2, the salt content is reduced by about 55% compared with the initial value, and the CEC is increased by about 43% compared with the initial value. This result is better than Example 1 and Example 2, showing a longer-lasting slow-release effect.

[0133] Test data

[0134] Table 3: Measurement results of soil physical and chemical properties and crop growth indicators at different time points (Example 3 and control group)

[0135]

[0136] Note: “Before treatment” refers to the initial condition of the soil before the application of the conditioner;

[0137] "Experimental group": refers to the application of the conditioning agent of the present invention;

[0138] “Control group”: refers to the situation where only the same irrigation conditions as the experimental group were used, but the control group conditioner-1 was used;

[0139] “Soil CEC”: The CEC in this table is obtained by testing the entire piece of soil, which is different from the “modified palygorskite mineral CEC” in the claims.

[0140] Drip irrigation system adaptability

[0141] It still meets the requirements for drip irrigation adaptability in Example 1. After dilution, the nanosuspension has no clogging phenomenon and can maintain a relatively uniform dripping state.

[0142] Example 4

[0143] Other conditions were the same as those in Example 1, but the acid-heat-modified palygorskite-2 of Preparation Example 2 (calcined at 320°C) was used instead of the acid-heat-modified palygorskite-1. The overall performance was comparable to that of Example 1, indicating that a better modification effect could still be obtained at calcination at 320°C.

[0144] Test data

[0145] Table 4: Measurement results of soil physical and chemical properties and crop growth indicators at different time points (Example 4 and control group)

[0146]

[0147] Note: “Before treatment” refers to the initial condition of the soil before the application of the conditioner;

[0148] "Experimental group": refers to the application of the conditioning agent of the present invention;

[0149] “Control group”: refers to the situation where only the same irrigation conditions as the experimental group were used, but the control group conditioner-1 was used;

[0150] “Soil CEC”: The CEC in this table is obtained by testing the entire soil, which is different from the “modified palygorskite mineral CEC” in the claims;

[0151] Example 5

[0152] Other conditions were the same as those in Example 1, but the acid-heat-modified palygorskite-3 of Preparation Example 3 (calcined at 350° C.) was used instead of the acid-heat-modified palygorskite-1. Due to the excessively high temperature, part of the structure was destroyed, so the overall performance was lower than that of Example 1, but still better than that of the control group without PVC compounding.

[0153] Test data

[0154] Table 5: Measurement results of soil physical and chemical properties and crop growth indicators at different time points (Example 5 and control group)

[0155]

[0156] Note: “Before treatment” refers to the initial condition of the soil before the application of the conditioner;

[0157] "Experimental group": refers to the application of the conditioning agent of the present invention;

[0158] “Control group”: refers to the situation where only the same irrigation conditions as the experimental group were used, but the control group conditioner-1 was used;

[0159] “Soil CEC”: The CEC in this table is obtained by testing the entire piece of soil, which is different from the “modified palygorskite mineral CEC” in the claims.

[0160] Preparation of Control Conditioner-2

[0161] The other conditions are the same as those in Example 1, except that: the same Anhui Mingguang palygorskite ore as in the present invention is selected, and only physically crushed to 200 meshes without acidification and calcination, and the crushed palygorskite is used instead of the acid-heat-modified palygorskite-1 in Example 1.

[0162] The experimental results show that in order to complete the long-term observation of the control group, multiple / frequent stirring is required in actual operation to avoid large-scale sedimentation; but it is still difficult to meet the continuous application requirements of real drip irrigation. Due to the serious agglomeration of particles in the control group, it is not suitable to be suspended in the drip irrigation system for a long time; if it is not stirred frequently or additional measures are taken, it is easy to settle and create a risk of local blockage. Based on this, we adopted manual operation (timed stirring, batch addition, etc.) in the laboratory environment to barely maintain an observation period of 56 days, but all performances were inferior to the embodiments of the present invention. Moreover, in large-scale drip irrigation applications, palygorskite that lacks acid-heat modification is difficult to maintain stable suspension and requires frequent maintenance, which is obviously not as good as the dispersion / stability of the acid-heat modified product shown in the embodiments of the present invention.

Claims

1. A modified palygorskite saline-alkali soil conditioner for preventing drip irrigation blockage, characterized in that: Contains the following components by weight: Acid-heat modified palygorskite: 1-3 parts; Polyvinyl alcohol: 1-10 parts; preferably 2-5 parts; the number average molecular weight of the polyvinyl alcohol is 30,000-50,000; Dispersant: 0.1-0.3 parts; Stabilizer: 0.05-0.2 parts; Deionized water: 90-97 parts.

2. The conditioning agent according to claim 1, characterized in that The acid-heat modified palygorskite has a mineral cation exchange capacity (CEC) of ≥40 mmol / 100 g and a specific surface area of ​​≥110 m 2 / g, Zeta potential absolute value ≥30mV.

3. The conditioning agent according to claim 2, characterized in that The specific surface area of ​​the acid-heat modified palygorskite is 115-125m 2 / g, and the mineral cation exchange capacity (CEC) is 40-50mmol / 100g.

4. The conditioning agent according to claim 1, characterized in that The amount of the polyvinyl alcohol is 2-5 parts.

5. The conditioning agent according to claim 1, characterized in that The dispersant is sodium polyacrylate, and the stabilizer is hexadecyltrimethylammonium bromide and / or polyacrylate.

6. The conditioning agent according to claim 5, characterized in that The stabilizer is a combination of hexadecyltrimethylammonium bromide and polyacrylate in a weight ratio of 1-3:

1.

7. The conditioning agent according to any one of claims 1 to 6, characterized in that The preparation method of the conditioning agent comprises the following steps: (1) adding the acid-heat-modified palygorskite into a polyvinyl alcohol aqueous solution; (2) Adding dispersants and stabilizers; (3) Ultrasonic treatment to make the particle size uniformly distributed in the range of 100-200 nm to form a stable nanosuspension; (4) centrifuging, washing and drying the nanosuspension at 60-75° C. for 20-30 hours to obtain the conditioner.

8. The conditioning agent according to claims 1 to 6, characterized in that The preparation method of the acid-heat modified palygorskite comprises the following steps: (1) Selecting palygorskite ore with a particle size of less than 20 μm; (2) adding 1-2 mol / L hydrochloric acid solution with a liquid-to-solid ratio of 20:1-5, stirring and refluxing at 95-100° C. for 20-30 hours; (3) washing with deionized water until the pH value of the filtrate is 6-7; (4) drying at 60°C for 24 hours and passing the dried product through a 200-mesh sieve; (5) Calcinate at 280°C-320°C for 3-5 hours.

9. The conditioning agent according to claim 7, characterized in that The preparation method of the acid-heat modified palygorskite comprises the following steps: (1) Selecting palygorskite ore with a particle size of less than 20 μm; (2) adding 1-2 mol / L hydrochloric acid solution, wherein the liquid-to-solid ratio of the hydrochloric acid solution to palygorskite is 20:1-5, and stirring and refluxing at 95-100° C. for 20-30 hours; (3) washing with deionized water until the pH value of the filtrate is 6-7; (4) drying at 110° C. for 24 hours, and passing the dried product through a 200-mesh sieve; (5) Calcinate at 280°C-320°C for 3-5 hours.

10. Use of the conditioning agent according to any one of claims 1 to 7 in the treatment of saline-alkali land, characterized in that: The conditioner is diluted with water at a ratio of 1:80-150 and applied through a drip irrigation system, with a dosage of 15-30L per mu. The conditioner lasts in the soil for 30-56 days, significantly reducing soil pH and salt content and increasing cation exchange capacity.

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