Preparation method of charcoal-based soil conditioner

Abstract

The invention relates to the technical field of soil conditioners, and discloses a biochar-based soil conditioner preparation method, which comprises: adding acetone, an acidified straw biochar material, N, N-dicyclohexylcarbodiimide, and N-hydroxysuccinimide into a reaction container, stirring, adding 5-aminoisophthalaldehyde bis-thiosemicarbazone, stirring, and carrying out a reaction to obtain the biochar-based soil conditioner. The biochar-based soil conditioner is obtained. The biochar-based soil conditioner contains a plurality of thiosemicarbazide, amido bonds and other groups which can coordinate with heavy metal cadmium and lead ions in soil, so that the cadmium and lead ions in the soil are adsorbed, the activity of the heavy metal is effectively reduced, the toxicity to soil microorganisms is reduced, and the soil quality is improved. The adsorption performance of the biochar-based soil conditioner on lead and cadmium ions in polluted soil is improved.

Description

Technical Field

[0001] The invention relates to the technical field of soil conditioners, and in particular to a method for preparing a biochar-based soil conditioner. Background Art

[0002] The accumulation of heavy metals such as cadmium and lead in the soil poses a threat to the soil ecosystem and the quality and safety of crops. The high activity of cadmium and lead ions in the soil will poison the diversity and function of soil microorganisms, thereby destroying the ecological balance of the soil. Moreover, these heavy metals are easily absorbed by crops and then passed through the food chain, ultimately endangering human health.

[0003] At present, traditional soil remediation methods have certain limitations when dealing with heavy metal contaminated soil. For example, physical remediation methods are costly, and chemical remediation methods may introduce new pollutants. In addition, the addition of soil conditioners has a higher adsorption selectivity for metal ions. Therefore, it is urgent to develop an efficient and environmentally friendly soil conditioner to solve the problem of soil cadmium and lead pollution. Chinese patent CN110743494B discloses a corn cob modified activated carbon soil heavy metal adsorption material and a preparation method thereof. The obtained porous carbon material will not cause secondary pollution to the soil and can also enhance soil fertility. However, the activated carbon adsorption material of this patent does not show good adsorption performance for metal ions such as cadmium and lead. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a method for preparing a biochar-based soil conditioner, which contains a thiourea functional group, has a high adsorption capacity and adsorption performance, and can adsorb metal ions in the soil.

[0005] Step 1: Add the straw bio-based carbon material and a mixed solution of nitric acid and sulfuric acid in a volume ratio of 1: (0.8-1.2) into a reaction container, heat to 80-85°C, react for 6-8h, filter, wash with water, and dry to obtain an acidified straw bio-based carbon material; Step 2: Add acetone, acidified straw bio-based charcoal material, N,N-dicyclohexylcarbodiimide, and N-hydroxysuccinimide into a reaction container, stir, add 5-aminoisophthalaldehyde dithiosemicarbazone, stir evenly, react at 75-90°C for 6-12h, filter after the reaction, wash with water, and dry to obtain a biochar-based soil conditioner.

[0006] Preferably, in step 2, the mass ratio of the acidified straw bio-based carbon material, N,N-dicyclohexylcarbodiimide, N-hydroxysuccinimide, and 5-aminoisophthalaldehyde dithiosemicarbazone is 100:(1.5-2.8):(0.7-1.3):(50-80).

[0007] Preferably, the preparation method of 5-aminoisophthalaldehyde dithiosemicarbazone is: Step (1), add ethanol solvent and 5-nitroisophthalaldehyde, thiosemicarbazide and water into a reaction vessel, stir and mix, then dropwise add glacial acetic acid, heat to 50-60°C, react for 2-4h, cool and filter, and recrystallize the filter cake with ethanol to obtain 5-nitroisophthalaldehyde bis(thiosemicarbazide) .

[0008] Step (2), adding ethanol solvent and water in a volume ratio of 1: (0.8-1.2) and 5-nitroisophthalaldehyde bis(thiosemicarbazone) and sodium dithionite in a mass ratio of 1: (2.8-3.4) into a reaction container, heating to 50-60° C., reacting for 4-6 hours, cooling and filtering, heating the filtrate to evaporate, cooling and crystallizing, to obtain 5-aminoisophthalaldehyde bis(thiosemicarbazone).

[0009] Preferably, in step (1), the mass ratio of 5-nitroisophthalaldehyde, thiosemicarbazide and glacial acetic acid is 1:(1.02-1.08):(1.1-1.3).

[0010] Preferably, the volume ratio of ethanol solvent to water in step (1) is 1:(1-1.4).

[0011] Preferably, the method for preparing the straw bio-based carbon material is: Step 1, washing the straw with water and ethanol for 3-4 times, drying it in an oven at 95-110°C, and pre-carbonizing the dried straw in a furnace at 290-320°C to obtain pre-carbonized straw; Step 2, add pre-carbonized straw and ZnCl2 in a mass ratio of 1: (2-8) into water, stir and mix, and then put it into an oven at 100-120°C for drying. The dried sample is placed in a tubular furnace in a nitrogen atmosphere at 580-620°C for calcination and carbonization for 4-6 hours, and then stirred with dilute hydrochloric acid for 4-6 hours, washed with water to neutrality, and dried to obtain straw bio-based carbon material.

[0012] (III) Beneficial technical effects: The present invention carbonizes straw to obtain straw bio-based carbon material; reacts 5-nitroisophthalaldehyde and semicarbazide under the condition of glacial acetic acid as a catalyst, and then undergoes a reduction reaction with sodium dithionite to generate 5-aminoisophthalaldehyde dithiosemicarbazide; then acidifies the straw bio-based carbon material to introduce carboxyl groups on the surface, and under the action of N,N-dicyclohexylcarbodiimide and N-hydroxysuccinimide catalysts, the surface carboxyl groups undergo an amidation reaction with the amino groups of 5-aminoisophthalaldehyde dithiosemicarbazide to generate a biochar-based soil conditioner, thereby introducing a large number of active groups such as semicarbazide and amide bonds on the surface of the biochar.

[0013] The biochar-based soil conditioner of the present invention contains multiple groups such as thiosemicarbazide and amide bonds, which can coordinate with heavy metal cadmium and lead ions in the soil, thereby adsorbing cadmium and lead ions in the soil, effectively reducing the activity of heavy metals, reducing toxicity to soil microorganisms, and improving the adsorption performance of the biochar-based soil conditioner for lead and cadmium ions in contaminated soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is the reaction formula for the preparation of 5-nitroisophthalaldehyde dithiosemicarbazone.

[0015] Figure 2 It is the reaction formula for the preparation of 5-aminoisophthalaldehyde dithiosemicarbazone. DETAILED DESCRIPTION

[0016] Example 1 Step 1: Wash the straw with water and ethanol three times, dry it in an oven at 100°C, place the dried straw in a Ma Fei furnace at 320°C for pre-carbonization to obtain pre-carbonized straw, add 1g of pre-carbonized straw and 2g of ZnCl2 into 40mL of water, stir to mix, and then place it in an oven at 120°C for drying. The dried sample is placed in a tubular furnace in a nitrogen atmosphere at 620°C for roasting and carbonization for 5h, then stirred with dilute hydrochloric acid for 6h, washed with water until neutral, and dried to obtain straw bio-based carbon material.

[0017] Step 2: add 100 mL of ethanol solvent and 3 g of 5-nitroisophthalaldehyde, 3.1 g of thiosemicarbazide, and 140 mL of water into a reaction vessel, stir and mix, then dropwise add 3.3 g of glacial acetic acid, heat to 50° C., react for 2 h, cool and filter, and recrystallize the filter cake with ethanol to obtain 5-nitroisophthalaldehyde bis(thiosemicarbazide); Add 300 mL of ethanol solvent and 360 mL of water, 3 g of 5-nitroisophthalaldehyde bis(thiosemicarbazone), and 8.4 g of sodium dithionite to a reaction container, heat to 50°C, react for 5 hours, cool and filter, heat the filtrate to evaporate, cool and crystallize, and obtain 5-aminoisophthalaldehyde bis(thiosemicarbazone).

[0018] Step 3: Add 5 g of straw bio-based carbon material, 50 mL of nitric acid and 60 mL of sulfuric acid mixed solution into a reaction container, heat to 80° C., react for 8 h, filter, wash with water, and dry to obtain an acidified straw bio-based carbon material; Add 1L of acetone, 4g of acidified straw bio-based charcoal material, 0.06g of N,N-dicyclohexylcarbodiimide, and 0.052g of N-hydroxysuccinimide into the reaction container, stir, add 2g of 5-aminoisophthalaldehyde dithiocarbazone, stir evenly, react at 75°C for 10h, filter after the reaction, wash with water, and dry to obtain a biochar-based soil conditioner.

[0019] Example 2 Step 1: wash with water and ethanol 4 times, dry in an oven at 95°C, place the dried straw in a Ma Fei furnace at 290°C for pre-carbonization to obtain pre-carbonized straw, add 1g of pre-carbonized straw and 5gZnCl2 into 40mL of water, stir to mix, and then place in an oven at 100°C for drying, place the dried sample in a tubular furnace in a nitrogen atmosphere at 580°C for calcination and carbonization for 4h, then stir with dilute hydrochloric acid for 4h, wash with water to neutrality, and dry to obtain straw bio-based carbon material.

[0020] Step 2: add 100 mL of ethanol solvent and 3 g of 5-nitroisophthalaldehyde, 3.06 g of thiosemicarbazide, and 100 mL of water into a reaction vessel, stir and mix, then dropwise add 3.6 g of glacial acetic acid, heat to 60° C., react for 4 h, cool and filter, and recrystallize the filter cake with ethanol to obtain 5-nitroisophthalaldehyde bis(thiosemicarbazide); Add 300 mL of ethanol solvent and 250 mL of water, 3 g of 5-nitroisophthalaldehyde bis(thiosemicarbazone), and 10.2 g of sodium dithionite to a reaction container, heat to 55° C., react for 4 h, cool and filter, heat the filtrate to evaporate, cool and crystallize, and obtain 5-aminoisophthalaldehyde bis(thiosemicarbazone).

[0021] Step 3: Add 5 g of straw bio-based carbon material, 50 mL of nitric acid and 40 mL of sulfuric acid mixed solution into a reaction container, heat to 85° C., react for 7 h, filter, wash with water, and dry to obtain an acidified straw bio-based carbon material; Add 1L of acetone, 4g of acidified straw bio-based charcoal material, 0.112g of N,N-dicyclohexylcarbodiimide, and 0.028g of N-hydroxysuccinimide into the reaction container, stir, add 2.4g of 5-aminoisophthalaldehyde dithiocarbazone, stir evenly, react at 90°C for 6h, filter after the reaction, wash with water, and dry to obtain a biochar-based soil conditioner.

[0022] Example 3 Step 1: Wash the straw with water and ethanol three times, dry it in an oven at 100°C, place the dried straw in a 300°C Ma Fei furnace for pre-carbonization to obtain pre-carbonized straw, add 1g of pre-carbonized straw and 8g of ZnCl2 into 40mL of water, stir to mix, and then place it in an oven at 110°C for drying. The dried sample is placed in a tubular furnace in a nitrogen atmosphere at 600°C for calcination and carbonization for 6h, then stirred with dilute hydrochloric acid for 5h, washed with water until neutral, and dried to obtain straw bio-based carbon material.

[0023] Step 2: add 100 mL of ethanol solvent and 3 g of 5-nitroisophthalaldehyde, 3.24 g of thiosemicarbazide, and 130 mL of water into a reaction vessel, stir and mix, then dropwise add 3.7 g of glacial acetic acid, heat to 55° C., react for 3 h, cool and filter, and recrystallize the filter cake with ethanol to obtain 5-nitroisophthalaldehyde bis(thiosemicarbazide); Add 300 mL of ethanol solvent and 300 mL of water, 3 g of 5-nitroisophthalaldehyde bis(thiosemicarbazone) and 9 g of sodium dithionite to a reaction container, heat to 60°C, react for 6 hours, cool and filter, heat the filtrate to evaporate, cool and crystallize to obtain 5-aminoisophthalaldehyde bis(thiosemicarbazone).

[0024] Step 3: Add 5 g of straw bio-based carbon material, 50 mL of nitric acid and 50 mL of sulfuric acid mixed solution into a reaction container, heat to 80° C., react for 6 h, filter, wash with water, and dry to obtain an acidified straw bio-based carbon material; Add 1L of acetone, 4g of acidified straw bio-based charcoal material, 0.1g of N,N-dicyclohexylcarbodiimide, and 0.04g of N-hydroxysuccinimide into the reaction container, stir, add 2.8g of 5-aminoisophthalaldehyde dithiocarbazone, stir evenly, react at 80°C for 12h, filter after the reaction, wash with water, and dry to obtain a biochar-based soil conditioner.

[0025] Example 4 Step 1: Wash the straw with water and ethanol for 4 times, dry it in an oven at 100°C, place the dried straw in a Ma Fei furnace at 300°C for pre-carbonization to obtain pre-carbonized straw, add 1g of pre-carbonized straw and 4g of ZnCl2 into 40mL of water, stir to mix, and then place it in an oven at 120°C for drying. The dried sample is placed in a tubular furnace in a nitrogen atmosphere at 610°C for calcination and carbonization for 4h, then stirred with dilute hydrochloric acid for 5h, washed with water until neutral, and dried to obtain straw bio-based carbon material.

[0026] Step 2: add 100 mL of ethanol solvent and 3 g of 5-nitroisophthalaldehyde, 3.2 g of thiosemicarbazide, and 120 mL of water into a reaction vessel, stir and mix, then dropwise add 3.9 g of glacial acetic acid, heat to 60° C., react for 4 h, cool and filter, and recrystallize the filter cake with ethanol to obtain 5-nitroisophthalaldehyde bis(thiosemicarbazide); Add 300 mL of ethanol solvent and 320 mL of water, 3 g of 5-nitroisophthalaldehyde bis(thiosemicarbazone), and 10.2 g of sodium dithionite to a reaction container, heat to 60°C, react for 4 hours, cool and filter, heat the filtrate to evaporate, cool and crystallize, and obtain 5-aminoisophthalaldehyde bis(thiosemicarbazone).

[0027] Step 3: Add 5 g of straw bio-based carbon material, 50 mL of nitric acid and 60 mL of sulfuric acid mixed solution into a reaction container, heat to 85° C., react for 8 h, filter, wash with water, and dry to obtain an acidified straw bio-based carbon material; Add 1L of acetone, 4g of acidified straw bio-based charcoal material, 0.09g of N,N-dicyclohexylcarbodiimide, and 0.05g of N-hydroxysuccinimide into the reaction container, stir, add 3.2g of 5-aminoisophthalaldehyde dithiocarbazone, stir evenly, react at 85°C for 8h, filter after the reaction, wash with water, and dry to obtain a biochar-based soil conditioner.

[0028] Comparative Example 1 Step 1: Wash the straw with water and ethanol three times, dry it in an oven at 100°C, place the dried straw in a Ma Fei furnace at 320°C for pre-carbonization to obtain pre-carbonized straw, add 1g of pre-carbonized straw and 2g of ZnCl2 into 40mL of water, stir to mix, and then place it in an oven at 120°C for drying. The dried sample is placed in a tubular furnace in a nitrogen atmosphere at 620°C for roasting and carbonization for 5h, then stirred with dilute hydrochloric acid for 6h, washed with water until neutral, and dried to obtain straw bio-based carbon material.

[0029] Comparative Example 2 Step 1: Wash the straw with water and ethanol three times, dry it in an oven at 100°C, place the dried straw in a Ma Fei furnace at 320°C for pre-carbonization to obtain pre-carbonized straw, add 1g of pre-carbonized straw and 2g of ZnCl2 into 40mL of water, stir to mix, and then place it in an oven at 120°C for drying. The dried sample is placed in a tubular furnace in a nitrogen atmosphere at 620°C for roasting and carbonization for 5h, then stirred with dilute hydrochloric acid for 6h, washed with water until neutral, and dried to obtain straw bio-based carbon material.

[0030] Step 2: add 5 g of straw bio-based carbon material, 50 mL of nitric acid and 60 mL of sulfuric acid mixed solution into a reaction container, heat to 80° C., react for 8 hours, filter, wash with water, and dry to obtain acidified straw bio-based carbon material.

[0031] Comparative Example 3 Step 1: Wash the straw with water and ethanol three times, dry it in an oven at 100°C, place the dried straw in a Ma Fei furnace at 320°C for pre-carbonization to obtain pre-carbonized straw, add 1g of pre-carbonized straw and 2g of ZnCl2 into 40mL of water, stir to mix, and then place it in an oven at 120°C for drying. The dried sample is placed in a tubular furnace in a nitrogen atmosphere at 620°C for roasting and carbonization for 5h, then stirred with dilute hydrochloric acid for 6h, washed with water until neutral, and dried to obtain straw bio-based carbon material.

[0032] Step 2: Add 5 g of straw bio-based carbon material, 50 mL of nitric acid and 60 mL of sulfuric acid mixed solution into a reaction container, heat to 80° C., react for 8 h, filter, wash with water, and dry to obtain an acidified straw bio-based carbon material; Add 1L of acetone, 4g of acidified straw bio-based charcoal material, 0.06g of N,N-dicyclohexylcarbodiimide, and 0.052g of N-hydroxysuccinimide into the reaction container, stir, then add 2g of thiosemicarbazide, stir evenly, react at 75°C for 10h, filter after the reaction, wash with water, and dry to obtain a biochar-based soil conditioner.

[0033] Before the test, simulated soil was prepared by adding cadmium nitrate and lead nitrate to natural soil to obtain simulated contaminated soil; The simulated contaminated soil was set into 7 groups, and 500g of air-dried soil was taken from each group and sieved. The soil was evenly divided into three parts in three beakers as three level experiments. 2g of the biochar-based soil conditioner of Examples 1-4 and Comparative Examples 1-3 was taken out respectively and added to each group of soil. Water was added until the liquid level was 5 cm above the soil, stirred for 3min, and the upper clear liquid was taken. The concentrations of cadmium ions and lead ions C0 were determined by a high-resolution inductively coupled plasma mass spectrometer. Place for 1-7 days, stir for 5min every 6h, take the upper clear liquid, and determine the concentrations of cadmium ions and lead ions C1 by a high-resolution inductively coupled plasma mass spectrometer. Calculate the adsorption rate. Adsorption rate = (C0-C1) / C0×100%, the concentration of cadmium ions or lead ions in the solution before C0 adsorption. The concentration of cadmium ions or lead ions in the solution after C1 adsorption.

[0034] Table 1 Adsorption rate test of cadmium ions Table 2 Adsorption rate test of lead ions As shown in Table 1, in Examples 1-4, the adsorption rate of cadmium ions or lead ions in the simulated soil solution is significantly higher than that of Comparative Examples 1-3, indicating that the biochar-based soil conditioners in Examples 1-4 have better adsorption performance for lead and cadmium ions in simulated contaminated soil. The reason is that the biochar-based soil conditioners in the examples contain multiple groups such as thiosemicarbazide and amide bonds, which can coordinate with heavy metal cadmium and lead ions in the soil, thereby adsorbing cadmium and lead ions in the soil, thereby improving the adsorption performance of the biochar-based soil conditioners for lead and cadmium ions in contaminated soil.

[0035] Compared with Example 1, Comparative Example 1 adds straw bio-based carbon material, which has very few active functional groups on its surface, and has a very low adsorption rate for cadmium ions or lead ions in the simulated soil solution, and has poor adsorption performance.

[0036] Compared with Example 1, Comparative Example 2 adds acidified straw bio-based carbon material. The acidified straw bio-based carbon material contains carboxyl groups, which can react with lead and cadmium ions in the solution, and has only a certain adsorption performance for lead and cadmium ions in contaminated soil, but does not contain aminothiourea, amide bonds and other groups, resulting in an adsorption rate lower than that of the embodiments.

[0037] Compared with Example 1, the biochar-based soil conditioner in Comparative Example 3 is formed by condensation of semicarbazide and acidified straw biochar material, and contains semicarbazide groups, which can coordinate with heavy metal cadmium and lead ions in the solution, but the number of semicarbazide groups is relatively small, resulting in lower adsorption performance and adsorption rate than those in the embodiments.

Claims

1. A method for preparing a biochar-based soil conditioner, characterized in that: The preparation method comprises: Step 1: Add the straw bio-based carbon material and a mixed solution of nitric acid and sulfuric acid in a volume ratio of 1: (0.8-1.2) into a reaction container, heat to 80-85°C, react for 6-8h, filter, wash with water, and dry to obtain an acidified straw bio-based carbon material; Step 2: Add acetone, acidified straw bio-based charcoal material, N,N-dicyclohexylcarbodiimide, and N-hydroxysuccinimide into a reaction container, stir, add 5-aminoisophthalaldehyde dithiosemicarbazone, stir evenly, filter after reaction, wash with water, and dry to obtain a biochar-based soil conditioner.

2. The method for preparing the biochar-based soil conditioner according to claim 1, characterized in that: The reaction temperature in step 2 is 75-90° C. and the reaction time is 6-12 h.

3. The method for preparing the biochar-based soil conditioner according to claim 1, characterized in that: In the step 2, the mass ratio of the acidified straw bio-based carbon material, N,N-dicyclohexylcarbodiimide, N-hydroxysuccinimide, and 5-aminoisophthalaldehyde dithiosemicarbazone is 100:(1.5-2.8):(0.7-1.3):(50-80).

4. The method for preparing the biochar-based soil conditioner according to claim 3, characterized in that: The preparation method of the 5-aminoisophthalaldehyde bis(thiosemicarbazone) is as follows: Step (1), adding ethanol solvent and 5-nitroisophthalaldehyde, thiosemicarbazide, and water into a reaction vessel, stirring and mixing, then dropping glacial acetic acid, heating to 50-60° C., reacting for 2-4 hours, cooling and filtering, and recrystallizing the filter cake with ethanol to obtain 5-nitroisophthalaldehyde bis(thiosemicarbazide); Step (2), adding ethanol solvent, water, 5-nitroisophthalaldehyde bis(thiosemicarbazone) and sodium dithionite to a reaction vessel, heating to 50-60° C., reacting for 4-6 hours, cooling and filtering, heating the filtrate to evaporate, cooling and crystallizing, to obtain 5-aminoisophthalaldehyde bis(thiosemicarbazone).

5. The method for preparing the biochar-based soil conditioner according to claim 4, characterized in that: In the step (1), the mass ratio of 5-nitroisophthalaldehyde, thiosemicarbazide and glacial acetic acid is 1:(1.02-1.08):(1.1-1.3).

6. The method for preparing the biochar-based soil conditioner according to claim 4, characterized in that: The volume ratio of the ethanol solvent to water in the step (1) is 1:(1-1.4).

7. The method for preparing the biochar-based soil conditioner according to claim 4, characterized in that: In the step (2), the mass ratio of 5-nitroisophthalaldehyde dithiosemicarbazone to sodium dithionite is 1:(2.8-3.4).

8. The method for preparing the biochar-based soil conditioner according to claim 4, characterized in that: The volume ratio of the ethanol solvent to water in the step (2) is 1:(0.8-1.2).

9. The method for preparing the biochar-based soil conditioner according to claim 4, characterized in that: The preparation method of the straw bio-based carbon material is: Step 1, washing the straw with water and ethanol for 3-4 times, drying it in an oven at 90-100° C., and pre-carbonizing the dried straw in a furnace at 290-320° C. to obtain pre-carbonized straw; Step 2, add pre-carbonized straw and ZnCl2 in a mass ratio of 1: (2-8) into water, stir and mix, and then put it into an oven at 100-120°C for drying. The dried sample is placed in a tubular furnace in a nitrogen atmosphere at 580-620°C for calcination and carbonization for 4-6 hours, and then stirred with dilute hydrochloric acid solution, washed with deionized water until neutral, and dried to obtain straw bio-based carbon material.

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