A soil conditioner composition doped with nano-active minerals and its preparation method

Abstract

This invention relates to a soil conditioner composition doped with nano-active minerals and its preparation method, belonging to the field of soil conditioner technology. The invention first protects the thiol group of 2-chloro-3-mercaptopyridine and then reacts it with diethyl (4-bromobutyl)phosphonate to generate a quaternary ammonium salt. The resulting quaternary ammonium salt is then used to modify nano-sodium montmorillonite. The phosphonate is then hydrolyzed to phosphonic acid, and the thiol protecting group is removed to obtain quaternary ammonium salt-modified nano-sodium montmorillonite. This is then mixed with biochar to obtain the soil conditioner composition doped with nano-active minerals. The soil conditioner composition obtained by this invention contains both phosphate and thiol groups, which, combined, can more broadly treat soil heavy metal pollution. Simultaneously, the presence of the quaternary ammonium salt enables it to improve soil structure and retain fertilizer.

Description

Technical Field

[0001] This invention belongs to the field of soil conditioner technology, specifically, it relates to a soil conditioner composition doped with nano-active minerals and its preparation method. Background Technology

[0002] Currently, heavy metal pollution in soil has become a key issue restricting ecological and environmental security and sustainable agricultural development. Furthermore, pollution has shifted from single-metal pollution to complex pollution, with multiple heavy metals acting synergistically in the soil, exacerbating the damage to soil ecosystems. These heavy metals are absorbed into plants through crop roots and accumulate there. Once ingested, they can cause heavy metal poisoning, posing a serious threat to human health. Moreover, heavy metals are persistent and bioaccumulative; once they enter the soil, they remain for extended periods, affecting the decomposition of soil organic matter and nutrient cycling, leading to soil fertility decline, compaction, and the gradual loss of normal soil productivity.

[0003] Traditional chemical remediation techniques, such as adding amendments like lime and phosphates, while simple to operate and low in cost, have limited effectiveness in treating complex pollution and cannot meet practical remediation needs. Currently, there is an urgent need for a soil conditioning composition that can broadly treat heavy metal pollution and address soil fertility decline and compaction. Summary of the Invention

[0004] The purpose of this invention is to provide a soil conditioning composition doped with nano-active minerals and its preparation method, in order to solve the problems mentioned in the background art.

[0005] The objective of this invention can be achieved through the following technical solutions: A method for preparing a soil conditioner composition doped with nano-active minerals includes the following steps: Step 1: Under a nitrogen atmosphere, 2-chloro-3-mercaptopyridine was dissolved in anhydrous dichloromethane, and then triphenylmethyl chloride was added. The reaction was carried out at room temperature for 2-4 hours. After the reaction was completed, the reaction solution was washed with saturated sodium bicarbonate solution and deionized water in turn. The organic phase was separated and dried, and then the solvent was removed by rotary evaporation to obtain the protected mercaptopyridine.

[0006] The second step involves dissolving the protected mercaptopyridine and diethyl (4-bromobutyl)phosphonate in toluene and reacting them at 80-90°C for 4-6 hours. After the reaction is complete, the mixture is cooled to room temperature, filtered, and the precipitated solid is collected. Finally, the solid is washed with petroleum ether and dried to obtain a pyridine quaternary ammonium salt.

[0007] Step 3: Place nano-sodium montmorillonite in distilled water, add pyridine quaternary ammonium salt, react at 80-90℃ for 2-3 hours, cool to room temperature, centrifuge to remove solvent, wash the precipitate with distilled water and dry, then under nitrogen protection, soak in a mixed solution of trimethylbromosilane and dichloromethane for 6-8 hours, filter to separate the solid, wash with ether and dry, then soak in a mixed solution of dichloromethane and trifluoroacetic acid for 1-3 hours, filter to separate the solid, wash with ether and dry, finally obtain quaternary ammonium salt modified nano-sodium montmorillonite.

[0008] Step 4: Mix quaternary ammonium salt modified nano-sodium montmorillonite with biochar and grind it to obtain a soil conditioner composition doped with nano-active minerals.

[0009] Furthermore, in the first step, the mass ratio of 2-chloro-3-mercaptopyridine to triphenylmethyl chloride is 32-40:60-80.

[0010] Furthermore, in the second step, the mass ratio of the protected mercaptopyridine to diethyl (4-bromobutyl)phosphonate is 25-32:18-23.

[0011] Furthermore, in the third step, the mass ratio of pyridine quaternary ammonium salt to nano-sodium montmorillonite is 20-25:40-50.

[0012] Furthermore, in the fourth step, the mass ratio of quaternary ammonium salt modified nano-sodium montmorillonite to biochar is 30-40:60-70.

[0013] Furthermore, in the fourth step, the biochar is at least one of straw biochar, sawdust biochar, or livestock and poultry manure biochar.

[0014] A soil conditioner composition doped with nano-active minerals is prepared by any of the above preparation steps.

[0015] The beneficial effects of this invention are: 1) In this invention, the thiol group of 2-chloro-3-mercaptopyridine is protected and then reacted with diethyl (4-bromobutyl)phosphonate to generate a quaternary ammonium salt. The obtained quaternary ammonium salt is then used to modify nano-sodium montmorillonite. The protecting group is then removed to obtain quaternary ammonium salt-modified nano-sodium montmorillonite, which is then mixed with biochar to obtain a soil conditioning composition doped with nano-active minerals.

[0016] 2) By integrating phosphate groups and mercapto groups into the same system, this invention utilizes their synergistic effect to broaden the spectrum of heavy metal remediation in soil, achieving broad-spectrum, stable and long-term fixation of various heavy metal ions, thereby significantly inhibiting their migration in the soil environment and effectively curbing heavy metal pollution.

[0017] 3) This invention anchors the quaternary ammonium salt structure in nano-sodium montmorillonite. The quaternary ammonium cations are not only large in size but also carry a strong positive charge, which allows them to be more firmly adsorbed between montmorillonite layers and increases the interlayer spacing of montmorillonite. This provides more space for the subsequent exchange of other cations, giving montmorillonite excellent cation exchange capacity and thus playing a long-lasting fertilizer retention role. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to examples. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments in this application specification, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection claimed in this application.

[0019] The raw materials used in this invention are not particularly restricted in terms of their source; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0020] Example 1 A method for preparing a soil conditioner composition doped with nano-active minerals includes the following steps: Step 1: Under a nitrogen atmosphere, 32 parts by mass of 2-chloro-3-mercaptopyridine were dissolved in 100 parts of anhydrous dichloromethane, and then 80 parts of triphenylmethyl chloride were added. The reaction was carried out at room temperature for 2 hours. After the reaction was completed, the reaction solution was washed with saturated sodium bicarbonate solution and deionized water in turn. The organic phase was separated and dried. Then the solvent was removed by rotary evaporation to obtain the protected mercaptopyridine.

[0021] The second step involves dissolving 25 parts of protected mercaptopyridine and 23 parts of diethyl (4-bromobutyl)phosphonate in 80 parts of toluene by mass fraction, reacting at 80°C for 6 hours, cooling to room temperature after the reaction is complete, filtering to collect the precipitated solid, and finally washing with petroleum ether and drying to obtain pyridine quaternary ammonium salts.

[0022] Step 3: By mass fraction, 40 parts of nano-sodium montmorillonite were placed in 150 parts of distilled water, and 25 parts of pyridine quaternary ammonium salt were added. The mixture was reacted at 80°C for 3 hours. After cooling to room temperature, the solvent was removed by centrifugation. The precipitate was washed with distilled water and dried. Then, under nitrogen protection, the mixture was first soaked in a mixed solution of 20 parts of trimethylbromosilane and 100 parts of dichloromethane for 6 hours. The solid was separated by filtration, washed with ether and dried. Then, the mixture was soaked in a mixed solution of 114 parts of dichloromethane and 6 parts of trifluoroacetic acid for 3 hours. The solid was separated by filtration, washed with ether and dried. Finally, quaternary ammonium salt modified nano-sodium montmorillonite was obtained.

[0023] Step 4: Mix 30 parts by weight of quaternary ammonium salt modified nano-sodium montmorillonite and 70 parts by weight of straw biochar, grind them, and obtain a soil conditioner composition doped with nano-active minerals.

[0024] Example 2 A method for preparing a soil conditioner composition doped with nano-active minerals includes the following steps: Step 1: Under a nitrogen atmosphere, 40 parts by mass of 2-chloro-3-mercaptopyridine were dissolved in 150 parts of anhydrous dichloromethane, and then 60 parts of triphenylmethyl chloride were added. The reaction was carried out at room temperature for 4 hours. After the reaction was completed, the reaction solution was washed with saturated sodium bicarbonate solution and deionized water in turn. The organic phase was separated and dried. Then the solvent was removed by rotary evaporation to obtain the protected mercaptopyridine.

[0025] The second step involves dissolving 32 parts of protected mercaptopyridine and 18 parts of diethyl (4-bromobutyl)phosphonate in 120 parts of toluene by mass fraction, reacting at 90°C for 4 hours, cooling to room temperature after the reaction is complete, filtering to collect the precipitated solid, and finally washing with petroleum ether and drying to obtain pyridine quaternary ammonium salts.

[0026] Step 3: By mass fraction, 50 parts of nano-sodium montmorillonite were placed in 200 parts of distilled water, and 20 parts of pyridine quaternary ammonium salt were added. The mixture was reacted at 90°C for 2 hours. After cooling to room temperature, the solvent was removed by centrifugation. The precipitate was washed with distilled water and dried. Then, under nitrogen protection, the mixture was first soaked in a mixed solution of 30 parts of trimethylbromosilane and 150 parts of dichloromethane for 8 hours. The solid was separated by filtration, washed with ether and dried. Then, the mixture was soaked in a mixed solution of 164 parts of dichloromethane and 16 parts of trifluoroacetic acid for 1 hour. The solid was separated by filtration, washed with ether and dried. Finally, quaternary ammonium salt modified nano-sodium montmorillonite was obtained.

[0027] Step 4: Mix 40 parts by weight of quaternary ammonium salt modified nano-sodium montmorillonite with 60 parts by weight of sawdust biochar, grind them, and obtain a soil conditioner composition doped with nano-active minerals.

[0028] Example 3 A method for preparing a soil conditioner composition doped with nano-active minerals includes the following steps: Step 1: Under a nitrogen atmosphere, 38 parts by mass of 2-chloro-3-mercaptopyridine were dissolved in 130 parts of anhydrous dichloromethane, and then 75 parts of triphenylmethyl chloride were added. The reaction was carried out at room temperature for 3 hours. After the reaction was completed, the reaction solution was washed with saturated sodium bicarbonate solution and deionized water in turn. The organic phase was separated and dried. Then the solvent was removed by rotary evaporation to obtain the protected mercaptopyridine.

[0029] Step 2: Dissolve 28 parts of protected mercaptopyridine and 20 parts of diethyl (4-bromobutyl)phosphonate in 100 parts of toluene by mass, react at 85°C for 5 hours, cool to room temperature after the reaction is complete, filter and collect the precipitated solid, and finally wash with petroleum ether and dry to obtain pyridine quaternary ammonium salt.

[0030] Step 3: By mass fraction, 45 parts of nano-sodium montmorillonite were placed in 170 parts of distilled water, and 23 parts of pyridine quaternary ammonium salt were added. The mixture was reacted at 85°C for 3 hours. After cooling to room temperature, the solvent was removed by centrifugation. The precipitate was washed with distilled water and dried. Then, under nitrogen protection, the mixture was first soaked in a mixed solution of 25 parts of trimethylbromosilane and 125 parts of dichloromethane for 7 hours. The solid was separated by filtration, washed with ether and dried. Then, the mixture was soaked in a mixed solution of 150 parts of dichloromethane and 10 parts of trifluoroacetic acid for 2 hours. The solid was separated by filtration, washed with ether and dried. Finally, quaternary ammonium salt modified nano-sodium montmorillonite was obtained.

[0031] Step 4: Mix 38 parts by weight of quaternary ammonium salt modified nano-sodium montmorillonite and 62 parts by weight of livestock and poultry manure biochar, grind them, and obtain a soil conditioner composition doped with nano-active minerals.

[0032] Comparative Example 1 Step 1: Under a nitrogen atmosphere, 32 parts by mass of 2-chloro-3-mercaptopyridine were dissolved in 100 parts of anhydrous dichloromethane, and then 80 parts of triphenylmethyl chloride were added. The reaction was carried out at room temperature for 2 hours. After the reaction was completed, the reaction solution was washed with saturated sodium bicarbonate solution and deionized water in turn. The organic phase was separated and dried. Then the solvent was removed by rotary evaporation to obtain the protected mercaptopyridine.

[0033] The second step involves dissolving 25 parts of protected mercaptopyridine and 23 parts of 2-chloroethylphosphonic acid in 80 parts of toluene by mass fraction, reacting at 80°C for 6 hours, cooling to room temperature after the reaction is complete, filtering to collect the precipitated solid, and finally washing with petroleum ether and drying to obtain pyridine quaternary ammonium salts.

[0034] Third step: By mass fraction, 40 parts of nano-sodium montmorillonite were placed in 150 parts of distilled water, and 25 parts of pyridine quaternary ammonium salt were added. The mixture was reacted at 80℃ for 3 hours. After cooling to room temperature, the solvent was removed by centrifugation. The precipitate was washed with distilled water and dried to obtain quaternary ammonium salt modified nano-sodium montmorillonite.

[0035] Step 4: Mix 30 parts by weight of quaternary ammonium salt modified nano-sodium montmorillonite and 70 parts by weight of straw biochar, grind them, and obtain a soil conditioner composition doped with nano-active minerals.

[0036] Comparative Example 2 Step 1: Under a nitrogen atmosphere, 32 parts by mass of 2-chloro-3-mercaptopyridine were dissolved in 100 parts of anhydrous dichloromethane, and then 80 parts of triphenylmethyl chloride were added. The reaction was carried out at room temperature for 2 hours. After the reaction was completed, the reaction solution was washed with saturated sodium bicarbonate solution and deionized water in turn. The organic phase was separated and dried. Then the solvent was removed by rotary evaporation to obtain the protected mercaptopyridine.

[0037] The second step involves dissolving 25 parts of protected mercaptopyridine and 23 parts of diethyl (4-bromobutyl)phosphonate in 80 parts of toluene by mass fraction, reacting at 80°C for 6 hours, cooling to room temperature after the reaction is complete, filtering to collect the precipitated solid, and finally washing with petroleum ether and drying to obtain pyridine quaternary ammonium salts.

[0038] Third step: By mass fraction, 40 parts of nano-sodium montmorillonite were placed in 150 parts of distilled water, and 25 parts of pyridine quaternary ammonium salt were added. The mixture was reacted at 80℃ for 3 hours. After cooling to room temperature, the solvent was removed by centrifugation. The precipitate was washed with distilled water and dried. Then, it was soaked in a mixed solution of 114 parts of dichloromethane and 6 parts of trifluoroacetic acid for 3 hours. The solid was separated by filtration, washed with ether, and dried to obtain quaternary ammonium salt modified nano-sodium montmorillonite.

[0039] Step 4: Mix 30 parts by weight of quaternary ammonium salt modified nano-sodium montmorillonite and 70 parts by weight of straw biochar, grind them, and obtain a soil conditioner composition doped with nano-active minerals.

[0040] Comparative Example 3 No modification was made to the montmorillonite; the remaining steps were the same as in Example 1.

[0041] Experimental Example 1 The following performance tests were conducted on each embodiment and each comparative example, and the test results are shown in Table 1-2.

[0042] Select a paddy field soil sample with a pH of 6.5, collect 20cm of topsoil, remove gravel and plant debris, air dry naturally, pass through a 10-mesh sieve, and mix evenly.

[0043] 1. Adsorption capacity of heavy metals in soil: 1000g of original soil sample was weighed, and 20g of each example and comparative sample was added to each sample. The original soil sample was used as a blank control and no samples were added. The mixed soil samples were then incubated in a constant temperature and humidity incubator at 25℃ and 60% humidity for 7 days. During the incubation period, deionized water was added daily. After the incubation, the content of available heavy metals in the soil was extracted using the DTPA extraction method, and the reduction rate was calculated. The results are shown in Table 1.

[0044] 2. Soil fertility retention experiment: Leaching experiment: An acrylic leaching column with an inner diameter of 5cm and a height of 30cm was used. A 2cm thick layer of quartz sand was laid at the bottom, followed by a 20cm thick layer of a mixed soil-conditioner sample (1000g soil + 20g conditioner, control group only 1000g soil). The soil layer thickness was 20cm. A 1cm thick layer of quartz sand was laid on top of the soil column, and 1.5g of ammonium nitrogen fertilizer (ammonium sulfate, nitrogen content 21%) and potassium fertilizer (potassium chloride, potassium content 60%) were evenly applied to the top of each soil column. 1.0g of fertilizer was added, followed by slow dripping of 50mL of deionized water to ensure complete dissolution and penetration into the soil. After standing for 24 hours, simulated rainwater leaching was initiated: deionized water (simulating annual rainfall, total leaching volume 500mL) was dripped onto the top of the soil column at a rate of 2mL / min. All leachate was collected and diluted to 500mL. The concentrations of ammonium and potassium ions in the leachate were then measured. Soil without conditioner was used as a blank control. The ammonium ion concentration in the blank control group was set to C. 铵空 The potassium ion concentration is C 钾空 , using (C 铵空 -C 铵 ) / C 铵空 The ammonium ion retention rate of each component of the soil conditioner composition was obtained by multiplying by 100%, and then used (C) 钾空 -C 钾 ) / C 钾空 The potassium ion retention rate of each component of the soil conditioner composition was obtained by multiplying by 100%. The results are shown in Table 2.

[0045] Table 1 Table 2 As shown in Table 1, compared with Comparative Examples 1-2, Examples 1-3 showed significantly higher reduction rates of available forms of mercury, arsenic, cadmium, and lead in the soil. This indicates that the synergistic effect of phosphate groups and thiol groups broadened the heavy metal adsorption spectrum, achieving broad-spectrum treatment of complex heavy metal pollution. As shown in Table 2, Comparative Examples 1-2 had weaker fertilizer retention effects than Examples 1-3. This shows that although modifying montmorillonite with a single functional group can slightly improve the soil's fertilizer retention capacity, the improvement is not significant due to the lack of quaternary ammonium salt structure. Comparative Example 3, without modified montmorillonite, relied solely on the soil's own adsorption capacity, and its fertilizer retention rate was close to that of the blank group, further verifying the key role of quaternary ammonium salt modification in improving soil fertilizer retention capacity.

[0046] The descriptions of the above embodiments are merely illustrative of the methods and core ideas of the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a soil conditioner composition doped with nano-active minerals, characterized in that, Includes the following steps: Step 1: 2-Chloro-3-mercaptopyridine undergoes a nucleophilic substitution reaction with triphenylmethyl chloride to yield protected mercaptopyridine; The second step involves quaternizing the protected mercaptopyridine with diethyl(4-bromobutyl)phosphonate to obtain pyridine quaternary ammonium salts. The third step involves reacting pyridine quaternary ammonium salts with nano-sodium montmorillonite to obtain quaternary ammonium salt-modified nano-sodium montmorillonite. Step 4: Mix quaternary ammonium salt modified nano-sodium montmorillonite with biochar and grind it to obtain a soil conditioner composition doped with nano-active minerals.

2. The method for preparing a soil conditioner composition doped with nano-active minerals according to claim 1, characterized in that, In the first step, the mass ratio of 2-chloro-3-mercaptopyridine to triphenylmethyl chloride is 32-40:60-80.

3. The method for preparing a soil conditioner composition doped with nano-active minerals according to claim 1, characterized in that, The reaction time in the first step is 2-4 hours.

4. The method for preparing a soil conditioner composition doped with nano-active minerals according to claim 1, characterized in that, In the second step, the mass ratio of the protected mercaptopyridine to diethyl (4-bromobutyl)phosphonate is 25-32:18-23.

5. The method for preparing a soil conditioner composition doped with nano-active minerals according to claim 1, characterized in that, The reaction temperature in the second step is 80-90℃, and the reaction time is 4-6 hours.

6. The method for preparing a soil conditioner composition doped with nano-active minerals according to claim 1, characterized in that, In the third step, the mass ratio of pyridine quaternary ammonium salt to nano-sodium montmorillonite is 20-25:40-50.

7. The method for preparing a soil conditioner composition doped with nano-active minerals according to claim 1, characterized in that, The reaction temperature in the third step is 80-90℃, and the reaction time is 2-3 hours.

8. The method for preparing a soil conditioner composition doped with nano-active minerals according to claim 1, characterized in that, In the fourth step, the mass ratio of quaternary ammonium salt modified nano-sodium montmorillonite to biochar is 30-40:60-70.

9. The method for preparing a soil conditioner composition doped with nano-active minerals according to claim 1, characterized in that, In the fourth step, the biochar is at least one of straw biochar, sawdust biochar, or livestock and poultry manure biochar.

10. A soil conditioner composition doped with nano-active minerals, characterized in that, A soil conditioning composition doped with nano-active minerals is prepared by the preparation method described in any one of claims 1-9.

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