A method for removing white phosphorus from soil

Abstract

This invention discloses a method for removing white phosphorus from soil. First, contaminated soil is mixed evenly with water, stirred, and then nitric acid solution is added. After stirring, a phosphorus removal agent is added, and stirring continues. The mixture is then filtered, freeze-dried, and the phosphorus removal agent is removed using a magnetic sieve to obtain treated soil. The phosphorus removal agent contains nano-ferric oxide, allowing it to separate from the soil via magnetic attraction after treating the white phosphorus, reducing the difficulty of separation and enabling reuse. The soil is treated with nitric acid, causing the white phosphorus to react with the nitric acid to produce phosphate ions. The addition of the phosphorus removal agent releases lanthanum carbonate from the surface. Lanthanum has strong Lewis acidity and can form strong ligands with phosphate, which has Lewis basicity, to adsorb phosphate ions from the soil, thus forming a complex. Simultaneously, the free amino groups on the chitosan surface can adsorb metals, further completing the adsorption of the complex.

Description

TECHNICAL FIELD

[0001] The application relates to the field of contaminated soil recovery, in particular to a method for removing white phosphorus in soil. BACKGROUND

[0002] White phosphorus is an important basic industrial raw material and is mainly used in the fields of chemical industry, pesticides and the like. White phosphorus is difficult to be biodegraded in soil and can cause long-term harm and risk to the environment. The main component of bentonite is montmorillonite, which has good cation exchange performance, hydrophilicity, swelling property, good adsorption performance and high specific surface area and the like, and is therefore often used as an adsorbent matrix. SUMMARY

[0003] The application aims to provide a method for removing white phosphorus in soil, and solve the problems that white phosphorus pollution in soil is difficult to be treated and the treatment effect is poor at the present stage.

[0004] The purpose of the application can be achieved by the following technical scheme.

[0005] A method for removing white phosphorus in soil, specifically comprising the following steps.

[0006] The contaminated soil is uniformly mixed with water, and under the condition that the rotating speed is 200-300 r / min and the temperature is 25-30 DEG C, the mixture is stirred and nitric acid solution is added, after stirring for 20-30 min, a phosphorus removal agent is added, and under the condition that the rotating speed is 120-150 r / min, the mixture is stirred for 2-3 h, then the mixture is filtered and freeze-dried, and the phosphorus removal agent is removed by magnetic attraction screening, to obtain treated soil.

[0007] Further, the mass ratio of the contaminated soil, water and nitric acid solution is 10:7-9:3, the mass fraction of the nitric acid solution is 25-30%, and the amount of the phosphorus removal agent is 1-3% of the mass of the contaminated soil.

[0008] Further, the phosphorus removal agent is prepared by the following steps.

[0009] Step A1: iron sulfate heptahydrate is dissolved in deionized water, bentonite is added, and under the condition that the rotating speed is 200-300 r / min and the temperature is 20-25 DEG C, the mixture is stirred for 1-1.5 h, then the temperature is raised to 80-85 DEG C, sodium hydroxide solution is added, and the mixture is continuously stirred for 1-1.5 h, then the mixture is filtered and dried, to obtain pretreated bentonite;

[0010] Step A2: the pretreated bentonite, acrylic acid, methyl methacrylate, butyl acrylate and deionized water are uniformly mixed, and under the condition that the rotating speed is 200-300 r / min and the temperature is 75-80 DEG C, the mixture is stirred and potassium persulfate is added, and the mixture is reacted for 2-3 h, then the mixture is filtered and dried, to obtain modified bentonite;

[0011] Step A3: the modified bentonite, chitosan, 1-hydroxybenzotriazole and acetic acid solution were mixed, stirred at 200-300 r / min and 20-25℃ for 3-5h to prepare a pretreated matrix, the modified matrix was dispersed in acetic acid solution, chitosan was added, and glutaraldehyde was added at 150-200 r / min and 35-40℃ for 3-5h, then the filtrate was removed by filtration to prepare a modified matrix;

[0012] Step A4: the modified matrix was dispersed in deionized water, lanthanum chloride heptahydrate was added, and ultrasonic treatment was carried out at 30-40 kHz for 30-40 min, sodium carbonate was added to pH 10-11, and ultrasonic treatment was continued for 30-40 min, then the filtrate was removed by filtration and dried to prepare a phosphorus removal agent.

[0013] Further, the amount ratio of the ferric sulfate heptahydrate, deionized water, bentonite and sodium hydroxide solution in step A1 is 1.25 mmol: 50 mL: 1 g: 5 mL, and the mass fraction of the sodium hydroxide solution is 3%.

[0014] Further, the amount ratio of the pretreated bentonite, acrylic acid, methyl methacrylate and butyl acrylate in step A2 is 1:3:8:6, and the amount of potassium persulfate is 3-5% of the mass sum of the acrylic acid, methyl methacrylate and butyl acrylate.

[0015] Further, the mass ratio of the modified bentonite, chitosan and 1-hydroxybenzotriazole in step A3 is 1:1.5:1, and the mass ratio of the modified matrix, chitosan and glutaraldehyde is 1:3:0.3.

[0016] Further, the mass ratio of the modified matrix and lanthanum chloride heptahydrate in step A4 is 1:1.2.

[0017] The beneficial effects of this invention: This invention discloses a method for removing white phosphorus from soil. First, contaminated soil is mixed evenly with water, stirred, and nitric acid solution is added. After stirring, a phosphorus removal agent is added, and stirring continues. The mixture is then filtered and freeze-dried, and the phosphorus removal agent is removed using a magnetic sieve to obtain treated soil. The phosphorus removal agent is made from ferric sulfate heptahydrate and bentonite. Nano-ferric oxide is introduced into the interlayer of intercalated bentonite through co-precipitation to obtain pretreated bentonite. Acrylic acid, methyl methacrylate, and butyl acrylate are polymerized and added to the pretreated bentonite, resulting in a polyacrylate coating on the surface of the pretreated bentonite, thus obtaining modified bentonite. The modified bentonite is then dehydrated and condensed with chitosan, causing the carboxyl groups on the modified bentonite to react with some of the amino groups on the chitosan, resulting in a pretreated matrix. The pretreated matrix is ​​mixed with chitosan, and glutaraldehyde is added to the surface of the pretreated matrix. The chitosan on the surface is cross-linked with the added chitosan, forming microspheres on the surface to obtain a modified matrix. The modified matrix is ​​mixed with lanthanum chloride heptahydrate, and lanthanum carbonate is loaded on the surface of the modified matrix through the action of sodium carbonate to obtain a treatment agent. The phosphorus removal agent contains nano-iron oxide, which allows the phosphorus removal agent to separate from the soil by magnetic adsorption after treating white phosphorus in the soil, reducing the difficulty of separation and enabling reuse. The soil is treated with nitric acid, which causes the white phosphorus in the soil to react with nitric acid to produce phosphate ions. Then, the phosphorus removal agent is added, and the lanthanum carbonate on the surface is released. Lanthanum has strong Lewis acidity and can form strong ligand adsorption with phosphate, which has Lewis basicity, to form a complex and adsorb phosphate ions in the soil. At the same time, the free amino groups on the chitosan on the surface can adsorb metals, thus completing the treatment by adsorbing the complex. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1

[0020] A method for removing white phosphorus from soil, specifically including the following steps:

[0021] The contaminated soil was mixed evenly with water, stirred at 200 r / min and 25℃, and nitric acid solution was added. After stirring for 20 min, a phosphorus removal agent was added, and the mixture was stirred at 120 r / min for 2 h. The mixture was then filtered, freeze-dried, and the phosphorus removal agent was removed by magnetic sieve to obtain the treated soil.

[0022] The mass ratio of the contaminated soil, water, and nitric acid solution is 10:7:3, the mass fraction of the nitric acid solution is 25%, and the amount of phosphorus removal agent used is 1% of the mass of the contaminated soil.

[0023] The phosphorus removal agent is prepared by the following steps:

[0024] Step A1: Dissolve ferric sulfate heptahydrate in deionized water, add bentonite, stir for 1 hour at 200 r / min and 20℃, then raise the temperature to 80℃, add sodium hydroxide solution, continue stirring for 1 hour, filter and dry to obtain pretreated bentonite.

[0025] Step A2: Mix pretreated bentonite, acrylic acid, methyl methacrylate, butyl acrylate and deionized water evenly. Stir and add potassium persulfate at a speed of 200 r / min and a temperature of 75°C, and react for 2 hours. Filter and dry to obtain modified bentonite.

[0026] Step A3: Mix modified bentonite, chitosan, 1-hydroxybenzotriazole and acetic acid solution, and stir for 3 hours at 200 r / min and 20℃ to obtain a pretreated matrix. Disperse the modified matrix in acetic acid solution, add chitosan, and add glutaraldehyde at 150 r / min and 35℃. After reacting for 3 hours, filter to remove the filtrate to obtain the modified matrix.

[0027] Step A4: Disperse the modified matrix in deionized water, add lanthanum chloride heptahydrate, sonicate at a frequency of 30 kHz for 30 min, add sodium carbonate to bring the pH to 10, continue sonication for 30 min, filter to remove the filtrate and dry to obtain the phosphorus removal agent.

[0028] The ratio of ferric sulfate heptahydrate, deionized water, bentonite, and sodium hydroxide solution in step A1 is 1.25 mmol: 50 mL: 1 g: 5 mL, and the mass fraction of sodium hydroxide solution is 3%.

[0029] In step A2, the ratio of the pretreated bentonite, acrylic acid, methyl methacrylate and butyl acrylate is 1:3:8:6, and the amount of potassium persulfate is 3% of the total mass of acrylic acid, methyl methacrylate and butyl acrylate.

[0030] The mass ratio of modified bentonite, chitosan, and 1-hydroxybenzotriazole in step A3 is 1:1.5:1, and the mass ratio of modified matrix, chitosan, and glutaraldehyde is 1:3:0.3.

[0031] The mass ratio of the modified matrix and lanthanum chloride heptahydrate described in step A4 is 1:1.2.

[0032] Example 2

[0033] A method for removing white phosphorus from soil, specifically including the following steps:

[0034] The contaminated soil was mixed evenly with water, stirred at 200 r / min and 28℃, and nitric acid solution was added. After stirring for 25 min, a phosphorus removal agent was added, and the mixture was stirred at 120 r / min for 2.5 h. The mixture was then filtered, freeze-dried, and the phosphorus removal agent was removed by magnetic sieve to obtain the treated soil.

[0035] The mass ratio of the contaminated soil, water, and nitric acid solution is 10:8:3, the mass fraction of the nitric acid solution is 28%, and the amount of phosphorus removal agent used is 2% of the mass of the contaminated soil.

[0036] The phosphorus removal agent is prepared by the following steps:

[0037] Step A1: Dissolve ferric sulfate heptahydrate in deionized water, add bentonite, stir for 1.5 h at 200 r / min and 23 ℃, then raise the temperature to 83 ℃, add sodium hydroxide solution, continue stirring for 1.3 h, filter and dry to obtain pretreated bentonite;

[0038] Step A2: Mix pretreated bentonite, acrylic acid, methyl methacrylate, butyl acrylate and deionized water evenly. Stir and add potassium persulfate at a speed of 200 r / min and a temperature of 78°C, and react for 2.5 h. Filter and dry to obtain modified bentonite.

[0039] Step A3: Mix modified bentonite, chitosan, 1-hydroxybenzotriazole and acetic acid solution, and stir for 4 hours at 200 r / min and 23℃ to obtain a pretreated matrix. Disperse the modified matrix in acetic acid solution, add chitosan, and add glutaraldehyde at 200 r / min and 38℃. After reacting for 4 hours, filter to remove the filtrate to obtain the modified matrix.

[0040] Step A4: Disperse the modified matrix in deionized water, add lanthanum chloride heptahydrate, sonicate at a frequency of 35 kHz for 35 min, add sodium carbonate to bring the pH to 10, continue sonication for 35 min, filter to remove the filtrate and dry to obtain the phosphorus removal agent.

[0041] The ratio of ferric sulfate heptahydrate, deionized water, bentonite, and sodium hydroxide solution in step A1 is 1.25 mmol: 50 mL: 1 g: 5 mL, and the mass fraction of sodium hydroxide solution is 3%.

[0042] In step A2, the ratio of the pretreated bentonite, acrylic acid, methyl methacrylate and butyl acrylate is 1:3:8:6, and the amount of potassium persulfate is 4% of the total mass of acrylic acid, methyl methacrylate and butyl acrylate.

[0043] The mass ratio of modified bentonite, chitosan, and 1-hydroxybenzotriazole in step A3 is 1:1.5:1, and the mass ratio of modified matrix, chitosan, and glutaraldehyde is 1:3:0.3.

[0044] The mass ratio of the modified matrix and lanthanum chloride heptahydrate described in step A4 is 1:1.2.

[0045] Example 3

[0046] A method for removing white phosphorus from soil, specifically including the following steps:

[0047] The contaminated soil was mixed evenly with water, stirred at 300 r / min and 30℃, and nitric acid solution was added. After stirring for 30 min, a phosphorus removal agent was added, and the mixture was stirred at 150 r / min for 3 h. The mixture was then filtered, freeze-dried, and the phosphorus removal agent was removed by magnetic sieve to obtain the treated soil.

[0048] The mass ratio of the contaminated soil, water, and nitric acid solution is 10:9:3, the mass fraction of the nitric acid solution is 30%, and the amount of phosphorus removal agent used is 3% of the mass of the contaminated soil.

[0049] The phosphorus removal agent is prepared by the following steps:

[0050] Step A1: Dissolve ferric sulfate heptahydrate in deionized water, add bentonite, stir for 1.5 h at 300 r / min and 25 ℃, then raise the temperature to 85 ℃, add sodium hydroxide solution, continue stirring for 1.5 h, filter and dry to obtain pretreated bentonite.

[0051] Step A2: Mix pretreated bentonite, acrylic acid, methyl methacrylate, butyl acrylate and deionized water evenly. Stir and add potassium persulfate at 300 r / min and 80℃, and react for 3 hours. Filter and dry to obtain modified bentonite.

[0052] Step A3: Mix modified bentonite, chitosan, 1-hydroxybenzotriazole and acetic acid solution, and stir for 5 hours at 300 r / min and 25℃ to obtain a pretreated matrix. Disperse the modified matrix in acetic acid solution, add chitosan, and add glutaraldehyde at 200 r / min and 40℃. After reacting for 5 hours, filter to remove the filtrate to obtain the modified matrix.

[0053] Step A4: Disperse the modified matrix in deionized water, add lanthanum chloride heptahydrate, sonicate at a frequency of 40 kHz for 40 min, add sodium carbonate to bring the pH to 11, continue sonication for 40 min, filter to remove the filtrate and dry to obtain the phosphorus removal agent.

[0054] The ratio of ferric sulfate heptahydrate, deionized water, bentonite, and sodium hydroxide solution in step A1 is 1.25 mmol: 50 mL: 1 g: 5 mL, and the mass fraction of sodium hydroxide solution is 3%.

[0055] In step A2, the ratio of the amount of pretreated bentonite, acrylic acid, methyl methacrylate and butyl acrylate is 1:3:8:6, and the amount of potassium persulfate is 5% of the total mass of acrylic acid, methyl methacrylate and butyl acrylate.

[0056] The mass ratio of modified bentonite, chitosan, and 1-hydroxybenzotriazole in step A3 is 1:1.5:1, and the mass ratio of modified matrix, chitosan, and glutaraldehyde is 1:3:0.3.

[0057] The mass ratio of the modified matrix and lanthanum chloride heptahydrate described in step A4 is 1:1.2.

[0058] Comparative Example 1

[0059] Compared with Example 1, this comparative example uses bentonite instead of pretreated bentonite, but the other steps are the same.

[0060] Comparative Example 2

[0061] Compared with Example 1, this comparative example uses modified bentonite instead of the modified matrix, but the other steps are the same.

[0062] Comparative Example 3

[0063] Compared with Example 1, this comparative example uses a modified matrix instead of a phosphorus removal agent, but the other steps are the same.

[0064] Contaminated soil with a white phosphorus content of 10.29 g / kg was used as a sample and treated with the phosphorus removal agents prepared in Examples 1-3 and Comparative Examples 1-3, respectively. The white phosphorus content was then tested, and the results are shown in the table below.

[0065]

[0066] As shown in the table above, the white phosphorus content in the soil treated by the methods of Examples 1-3 was 0.61-0.68 g / kg, while the white phosphorus content in the soil treated by the methods of Comparative Examples 2 and 3 was 1.33 g / kg and 2.48 g / kg, respectively, indicating that the present invention has a very good white phosphorus treatment effect.

[0067] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for removing white phosphorus from soil, characterized in that: Specifically, the steps include the following: The contaminated soil is mixed evenly with water. Under the conditions of 200-300 r / min and 25-30℃, nitric acid solution is added while stirring. After stirring for 20-30 min, phosphorus removal agent is added. Then, under the conditions of 120-150 r / min, the mixture is stirred for 2-3 h. After filtration and freeze-drying, the phosphorus removal agent is removed by magnetic sieve to obtain the treated soil. The phosphorus removal agent is prepared by the following steps: Step A1: Dissolve ferric sulfate heptahydrate in deionized water, add bentonite, stir for 1-1.5 hours at a speed of 200-300 r / min and a temperature of 20-25℃, then raise the temperature to 80-85℃, add sodium hydroxide solution, continue stirring for 1-1.5 hours, filter and dry to obtain pretreated bentonite. Step A2: Mix pretreated bentonite, acrylic acid, methyl methacrylate, butyl acrylate and deionized water evenly. Stir and add potassium persulfate at a speed of 200-300 r / min and a temperature of 75-80℃, and react for 2-3 hours. Filter and dry to obtain modified bentonite. Step A3: Mix modified bentonite, chitosan, 1-hydroxybenzotriazole and acetic acid solution, and stir for 3-5 hours at a speed of 200-300 r / min and a temperature of 20-25℃ to obtain a pretreated matrix. Disperse the pretreated matrix in acetic acid solution, add chitosan, and add glutaraldehyde at a speed of 150-200 r / min and a temperature of 35-40℃. After reacting for 3-5 hours, filter to remove the filtrate to obtain the modified matrix. Step A4: Disperse the modified matrix in deionized water, add lanthanum chloride heptahydrate, and sonicate at a frequency of 30-40 kHz for 30-40 min. Add sodium carbonate to bring the pH to 10-11, continue sonicating for 30-40 min, filter to remove the filtrate and dry to obtain the phosphorus removal agent.

2. The method for removing white phosphorus from soil according to claim 1, characterized in that: The mass ratio of the contaminated soil, water, and nitric acid solution is 10:7-9:3, the mass fraction of the nitric acid solution is 25-30%, and the amount of phosphorus removal agent is 1-3% of the mass of the contaminated soil.

3. The method for removing white phosphorus from soil according to claim 1, characterized in that: The ratio of ferric sulfate heptahydrate, deionized water, bentonite, and sodium hydroxide solution in step A1 is 1.25 mmol: 50 mL: 1 g: 5 mL, and the mass fraction of sodium hydroxide solution is 3%.

4. The method for removing white phosphorus from soil according to claim 1, characterized in that: The ratio of the amount of pretreated bentonite, acrylic acid, methyl methacrylate and butyl acrylate used in step A2 is 1:3:8:6, and the amount of potassium persulfate used is 3-5% of the total mass of acrylic acid, methyl methacrylate and butyl acrylate.

5. The method for removing white phosphorus from soil according to claim 1, characterized in that: The mass ratio of modified bentonite, chitosan, and 1-hydroxybenzotriazole in step A3 is 1:1.5:1, and the mass ratio of pretreated matrix, chitosan, and glutaraldehyde is 1:3:0.

3.

6. The method for removing white phosphorus from soil according to claim 1, characterized in that: The mass ratio of the modified matrix and lanthanum chloride heptahydrate described in step A4 is 1:1.2.

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