Composite passivator for repairing heavy metal pollution of soil and preparation method of composite passivator

Abstract

The invention discloses a preparation method of a composite passivator for soil heavy metal pollution remediation, and the preparation method comprises the following steps: (1) preparing biochar from corn straws, and treating with a hydrochloric acid solution to obtain pretreated biochar powder; (2) performing modification treatment to obtain modified charcoal powder; (3) carrying out amination and carboxylation treatment to obtain functionalized charcoal powder; and (4) carrying out phosphoryl acetic acid treatment to obtain the composite passivator. The soil passivator prepared by the method has a good passivation effect on lead in soil, can convert available lead in the soil into passivated lead which cannot be assimilated by animals and plants, and reduces the harm of heavy metals to the soil. This may be the effect caused by the adsorption passivation of the passivating agent on lead.

Description

Technical Field

[0001] The present invention relates to the technical field of soil remediation, and in particular to a composite passivating agent for remediating soil heavy metal pollution and a preparation method thereof. Background Art

[0002] Heavy metal pollution in soil is mainly caused by human factors. The metal content exceeds the normal level, resulting in the decline of soil quality and the deterioration of the environment. At present, the soil in some parts of my country has been seriously polluted by heavy metals, which has had a serious impact on food production, so that heavy metals often exceed the standard in agricultural production. Therefore, various regions are actively looking for effective ways to repair heavy metals. Among them, physical remediation, chemical remediation, biological remediation, agronomic remediation, etc. are the remediation technologies commonly used by scholars at home and abroad. Biochar is a solid material obtained by thermal cracking of biomass under oxygen-limited conditions. Studies have shown that the application of biochar can improve soil structure, soil water holding capacity, increase soil organic matter content, promote soil nutrient circulation and increase crop yields. At the same time, biochar has attracted widespread attention in the environmental remediation community as a remediation material for heavy metal-contaminated soil due to its high pH, ​​high specific surface area, rich pores and surface functional groups. Summary of the invention

[0003] To this end, the present invention provides a method for preparing a composite passivating agent for remediation of soil heavy metal pollution, the preparation steps comprising:

[0004] (1) Wash the corn stalks with clean water to remove dirt, then cut them into sections, soak them in an aqueous solution of sodium glycerophosphate, heat them in a water bath to 80±5°C and keep them warm for more than 60 minutes, then separate the solid and liquid, dry the solid phase at 100°C for more than 30 minutes, then heat and keep them warm in a muffle furnace at 600°C for more than 1 hour, then take them out and air cool them to room temperature, grind them to obtain biochar, prepare a hydrochloric acid solution, add the biochar to the hydrochloric acid solution and soak it for more than 60 hours, remove the soluble phase, then separate the solid and liquid, wash the solid phase with deionized water until the washed liquid is neutral, and dry them at 100°C for more than 5 hours to obtain pretreated biochar powder;

[0005] (2) A composite aqueous solution of cerium chloride and ferric chloride is prepared in a reactor, the pretreated biochar powder is added to the composite aqueous solution of cerium chloride and ferric chloride, and stirred for more than 10 minutes, and then urea and sodium citrate are added to the solution under stirring. After the addition is completed, stirring is continued for more than 10 minutes under an ultrasonic environment, and then the reactor is sealed, heated to 140-145° C. and kept warm for 4-5 hours, and then cooled to room temperature, the reactor is opened, the solid-liquid separation is carried out, the solid phase is washed with deionized water for more than 3 times, and dried at 80° C. for more than 8 hours to obtain modified biochar powder;

[0006] (3) preparing an ethanol solution of polyetheramine, adding the modified biochar powder to the ethanol solution of the polyetheramine, stirring the solution for more than 20 minutes under an ultrasonic environment after the addition is completed, then separating the solid and the liquid, drying the solid phase at 100° C. for more than 6 hours, adding the dried solid phase to ethanol, stirring and dispersing with ultrasonic waves to obtain a dispersion, and then adding glutaric anhydride to the dispersion under stirring. After the addition is completed, heating the dispersion to 40±2° C. in a water bath, stirring at this temperature for more than 3 hours, then separating the solid and the liquid, washing the solid phase with ethanol for more than 3 times, and drying at 80° C. for more than 8 hours to obtain functionalized biochar powder;

[0007] (4) preparing a composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine, stirring the solution, and then adding the functionalized biochar powder to the solution under stirring, and after the addition is completed, ultrasonic stirring is performed for more than 10 minutes to obtain a suspension, and then 1-propylphosphonic anhydride is added to the suspension under stirring, and after the addition is completed, the suspension is continued to be stirred for more than 10 hours, and then the solid-liquid is separated, the solid phase is washed with N,N-dimethylformamide for more than 2 times, and then washed with deionized water for more than 3 times, and dried at 80° C. for more than 8 hours to obtain the composite passivator.

[0008] Furthermore, in the step (1), the concentration of sodium glycerophosphate in the aqueous solution of sodium glycerophosphate is 4-5g / 100mL, and the solvent is water; the mass ratio of corn stalk segments soaked in the aqueous solution of sodium glycerophosphate is stalk segments: aqueous solution of sodium glycerophosphate = 1:50.

[0009] Furthermore, in the step (1), the mass percentage of the solute in the hydrochloric acid is 3%; the mass ratio of the biochar added to the hydrochloric acid solution for soaking is biochar: hydrochloric acid solution = 1:80.

[0010] Furthermore, in the step (2), in the composite aqueous solution of cerium chloride and ferric chloride, the concentration of cerium chloride is 20-25 g / L, the concentration of ferric chloride is 6-8 g / L, and the solvent is water; the mass ratio of the pretreated biochar powder, the composite aqueous solution of cerium chloride and ferric chloride, and the urea and sodium citrate is pretreated biochar powder: composite aqueous solution of cerium chloride and ferric chloride: urea: sodium citrate = 1:100:3-4:0.4-0.5.

[0011] Furthermore, in the step (3), the concentration of polyetheramine in the ethanol solution of polyetheramine is 0.6-0.7 g / 100 mL, the solvent is ethanol, and the mass ratio of the modified biochar powder added to the ethanol solution of polyetheramine is ethanol solution of polyetheramine:modified biochar powder=100:1.

[0012] Furthermore, in step (3), the mass ratio of the dried solid phase added to ethanol to form a dispersion is 1:80; the mass ratio of the added mass of glutaric anhydride to the solid phase in the dispersion is 2-3:1.

[0013] Furthermore, in the step (4), in the composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine, the concentration of phosphoacetic acid is 1.5-1.6 g / 100 mL, the concentration of 4-dimethylaminopyridine is 1.8-2.0 g / 100 mL, and the solvent is N,N-dimethylformamide; the mass ratio of the composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine, the functionalized biochar powder, and 1-propylphosphonic anhydride is the composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine: functionalized biochar powder: 1-propylphosphonic anhydride = 100:1:4-5.

[0014] The beneficial effect of the present invention is that the soil passivator prepared by the method of the present invention has a good passivation effect on lead in the soil, and can convert the effective lead in the soil into a passivated lead that cannot be assimilated by animals and plants, thereby reducing the harm of heavy metals to the soil. This may be due to the effect caused by the passivation of lead by the passivator. The present invention first introduces sodium glycerophosphate in the preparation process of biochar, so that the surface of the biochar is rich in highly electronegative PO4 3- or P2O7 4- Functional groups such as cerium chloride and ferric chloride are added to improve the adsorption of heavy metals by the passivator, and at the same time, points are provided for subsequent biochar surface modification, and the specific surface area of ​​biochar is significantly increased, and the pore structure is richer. Then, by adding a composite aqueous solution of cerium chloride and ferric chloride for modification, cerium and iron are precipitated and modified on the surface of biochar using the hydroxide ions and carbonate ions produced by urea hydrolysis, the stability of lead on the surface after the passivator adsorbs lead is improved, the re-dissolution of adsorbed lead is reduced, and the lead is converted from a biologically effective state to a stable residual state. Subsequently, it is treated with amination, carboxylation and phosphoacetic acid to significantly increase the number of oxygen-containing functional groups on the surface of the passivator, which is conducive to the formation of complexes with money and improves adsorption. DETAILED DESCRIPTION

[0015] The present invention will be further described below in conjunction with the embodiments.

[0016] Example 1

[0017] A method for preparing a composite passivating agent for repairing soil heavy metal pollution, the preparation steps comprising:

[0018] (1) Wash corn stalks with clean water to remove dirt, cut them into segments, and soak them in an aqueous solution of sodium glycerophosphate, wherein the concentration of sodium glycerophosphate in the aqueous solution is 4 g / 100 mL and the solvent is water; the mass ratio of corn stalk segments soaked in the aqueous solution of sodium glycerophosphate is 1:50; heat in a water bath to 80±5° C., keep warm and stir for 60 min, then separate the solid and liquid, dry the solid phase at 100° C. for 30 min, and then The biochar was heated and kept in a muffle furnace at 600°C for 1 hour, then taken out and air-cooled to room temperature, ground to obtain biochar, and a hydrochloric acid solution was prepared. The biochar was added to the hydrochloric acid solution and soaked for 60 hours to remove the soluble phase. The mass percentage of the solute in the hydrochloric acid was 3%. The mass ratio of the biochar added to the hydrochloric acid solution for soaking was biochar: hydrochloric acid solution = 1:80. The solid-liquid separation was then performed, and the solid phase was washed with deionized water until the washed liquid was neutral, and dried at 100°C for 5 hours to obtain pretreated biochar powder.

[0019] (2) A composite aqueous solution of cerium chloride and ferric chloride is prepared in a reactor, wherein the concentration of cerium chloride in the composite aqueous solution of cerium chloride and ferric chloride is 20 g / L, the concentration of ferric chloride is 6 g / L, and the solvent is water; the pretreated biochar powder is added to the composite aqueous solution of cerium chloride and ferric chloride, stirred for 10 min, and then urea and sodium citrate are added to the solution under stirring, wherein the mass ratio of the pretreated biochar powder, the composite aqueous solution of cerium chloride and ferric chloride, and the urea and sodium citrate is pretreated biochar powder: composite aqueous solution of cerium chloride and ferric chloride: urea: sodium citrate = 1:100:3:0.4; after the addition is completed, stirring is continued for 10 min under an ultrasonic environment, and then the reactor is sealed, heated to 140°C and kept warm for 5 h, and then cooled to room temperature, the reactor is opened, the solid-liquid separation is carried out, the solid phase is washed 3 times with deionized water, and dried at 80°C for 8 h to obtain modified biochar powder;

[0020] (3) preparing an ethanol solution of polyetheramine (D-230), adding the modified biochar powder to the ethanol solution of the polyetheramine, wherein the concentration of the polyetheramine in the ethanol solution of the polyetheramine is 0.6 g / 100 mL, the solvent is ethanol, and the mass ratio of adding the modified biochar powder to the ethanol solution of the polyetheramine is the ethanol solution of the polyetheramine: the modified biochar powder = 100:1; after the addition is completed, stirring the solution under an ultrasonic environment for 20 minutes, then separating the solid and the liquid, and drying the solid phase at 100° C. for 6 hours. The dried solid phase is added to ethanol, and the mass ratio of the dried solid phase to ethanol to form a dispersion is 1:80; ultrasonic stirring and dispersion is performed to obtain a dispersion, and then glutaric anhydride is added to the dispersion under stirring, and the mass ratio of the added glutaric anhydride to the solid phase in the dispersion is 2:1; after the addition is completed, the water bath is heated to 40±2°C, and the mixture is stirred for 3 hours, and then the solid and liquid are separated, the solid phase is washed with ethanol 3 times, and dried at 80°C for 8 hours to obtain functionalized biochar powder;

[0021] (4) preparing a composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine, wherein the concentration of phosphoacetic acid is 1.5 g / 100 mL, the concentration of 4-dimethylaminopyridine is 1.8 g / 100 mL, and the solvent is N,N-dimethylformamide; stirring the solution, and then adding the functionalized biochar powder to the solution under stirring, and after the addition is completed, ultrasonically stirring for 10 minutes to obtain a suspension, and then adding the suspension to the suspension under stirring. 1-propylphosphonic anhydride is added, and the mass ratio of the composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine, the functionalized biochar powder, and 1-propylphosphonic anhydride is the composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine: functionalized biochar powder: 1-propylphosphonic anhydride = 100:1:4; after the addition is completed, the suspension is continued to be stirred for 10 hours, and then the solid-liquid is separated, the solid phase is washed twice with N,N-dimethylformamide, and then washed three times with deionized water, and dried at 80°C for 8 hours to obtain the composite passivator.

[0022] Example 2

[0023] A method for preparing a composite passivating agent for repairing soil heavy metal pollution, the preparation steps comprising:

[0024] (1) Wash corn stalks with clean water to remove dirt, cut them into segments, and soak them in an aqueous solution of sodium glycerophosphate, wherein the concentration of sodium glycerophosphate in the aqueous solution is 4 g / 100 mL and the solvent is water; the mass ratio of corn stalk segments soaked in the aqueous solution of sodium glycerophosphate is 1:50; heat in a water bath to 80±5° C., keep warm and stir for 60 min, then separate the solid and liquid, dry the solid phase at 100° C. for 30 min, and then The biochar was heated and kept in a muffle furnace at 600°C for 1 hour, then taken out and air-cooled to room temperature, ground to obtain biochar, and a hydrochloric acid solution was prepared. The biochar was added to the hydrochloric acid solution and soaked for 60 hours to remove the soluble phase. The mass percentage of the solute in the hydrochloric acid was 3%. The mass ratio of the biochar added to the hydrochloric acid solution for soaking was biochar: hydrochloric acid solution = 1:80. The solid-liquid separation was then performed, and the solid phase was washed with deionized water until the washed liquid was neutral, and dried at 100°C for 5 hours to obtain pretreated biochar powder.

[0025] (2) A composite aqueous solution of cerium chloride and ferric chloride is prepared in a reactor, wherein the concentration of cerium chloride in the composite aqueous solution of cerium chloride and ferric chloride is 22 g / L, the concentration of ferric chloride is 7 g / L, and the solvent is water; the pretreated biochar powder is added to the composite aqueous solution of cerium chloride and ferric chloride, stirred for 10 min, and then urea and sodium citrate are added to the solution under stirring, wherein the mass ratio of the pretreated biochar powder, the composite aqueous solution of cerium chloride and ferric chloride, and the urea and sodium citrate is pretreated biochar powder: composite aqueous solution of cerium chloride and ferric chloride: urea: sodium citrate = 1:100:3:0.4; after the addition is completed, stirring is continued for 10 min under an ultrasonic environment, and then the reactor is sealed, heated to 140°C and kept warm for 5 h, and then cooled to room temperature, the reactor is opened, the solid-liquid separation is carried out, the solid phase is washed 3 times with deionized water, and dried at 80°C for 8 h to obtain modified biochar powder;

[0026] (3) preparing an ethanol solution of polyetheramine (D-230), adding the modified biochar powder to the ethanol solution of the polyetheramine, wherein the concentration of the polyetheramine in the ethanol solution of the polyetheramine is 0.6 g / 100 mL, the solvent is ethanol, and the mass ratio of adding the modified biochar powder to the ethanol solution of the polyetheramine is the ethanol solution of the polyetheramine: the modified biochar powder = 100:1; after the addition is completed, stirring the solution under an ultrasonic environment for 20 minutes, then separating the solid and the liquid, and drying the solid phase at 100° C. for 6 hours. The dried solid phase is added to ethanol, and the mass ratio of the dried solid phase to ethanol to form a dispersion is 1:80; ultrasonic stirring and dispersion is performed to obtain a dispersion, and then glutaric anhydride is added to the dispersion under stirring, and the mass ratio of the added glutaric anhydride to the solid phase in the dispersion is 2:1; after the addition is completed, the water bath is heated to 40±2°C, and the mixture is stirred for 3 hours, and then the solid and liquid are separated, the solid phase is washed with ethanol 3 times, and dried at 80°C for 8 hours to obtain functionalized biochar powder;

[0027] (4) preparing a composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine, wherein the concentration of phosphoacetic acid is 1.5 g / 100 mL, the concentration of 4-dimethylaminopyridine is 1.9 g / 100 mL, and the solvent is N,N-dimethylformamide; stirring the solution, and then adding the functionalized biochar powder to the solution under stirring, and after the addition is completed, ultrasonically stirring for 10 minutes to obtain a suspension, and then adding the suspension to the suspension under stirring. 1-propylphosphonic anhydride is added, and the mass ratio of the composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine, the functionalized biochar powder, and 1-propylphosphonic anhydride is the composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine: functionalized biochar powder: 1-propylphosphonic anhydride = 100:1:4; after the addition is completed, the suspension is continued to be stirred for 10 hours, and then the solid-liquid is separated, the solid phase is washed twice with N,N-dimethylformamide, and then washed three times with deionized water, and dried at 80°C for 8 hours to obtain the composite passivator.

[0028] Example 3

[0029] A method for preparing a composite passivating agent for repairing soil heavy metal pollution, the preparation steps comprising:

[0030] (1) Wash corn stalks with clean water to remove dirt, cut them into segments, and soak them in an aqueous solution of sodium glycerophosphate, wherein the concentration of sodium glycerophosphate in the aqueous solution is 5 g / 100 mL and the solvent is water; the mass ratio of corn stalk segments soaked in the aqueous solution of sodium glycerophosphate is 1:50; heat in a water bath to 80±5° C., keep warm and stir for 60 min, then separate the solid and liquid, dry the solid phase at 100° C. for 30 min, and then The biochar was heated and kept in a muffle furnace at 600°C for 1 hour, then taken out and air-cooled to room temperature, ground to obtain biochar, and a hydrochloric acid solution was prepared. The biochar was added to the hydrochloric acid solution and soaked for 60 hours to remove the soluble phase. The mass percentage of the solute in the hydrochloric acid was 3%. The mass ratio of the biochar added to the hydrochloric acid solution for soaking was biochar: hydrochloric acid solution = 1:80. The solid-liquid separation was then performed, and the solid phase was washed with deionized water until the washed liquid was neutral, and dried at 100°C for 5 hours to obtain pretreated biochar powder.

[0031] (2) A composite aqueous solution of cerium chloride and ferric chloride is prepared in a reactor, wherein the concentration of cerium chloride in the composite aqueous solution of cerium chloride and ferric chloride is 24 g / L, the concentration of ferric chloride is 7 g / L, and the solvent is water; the pretreated biochar powder is added to the composite aqueous solution of cerium chloride and ferric chloride, stirred for 10 min, and then urea and sodium citrate are added to the solution under stirring, wherein the mass ratio of the pretreated biochar powder, the composite aqueous solution of cerium chloride and ferric chloride, and the urea and sodium citrate is pretreated biochar powder: composite aqueous solution of cerium chloride and ferric chloride: urea: sodium citrate = 1:100:4:0.5; after the addition is completed, stirring is continued for 10 min under an ultrasonic environment, and then the reactor is sealed, heated to 140°C and kept warm for 5 h, and then cooled to room temperature, the reactor is opened, the solid-liquid separation is carried out, the solid phase is washed 3 times with deionized water, and dried at 80°C for 8 h to obtain modified biochar powder;

[0032] (3) preparing an ethanol solution of polyetheramine (D-230), adding the modified biochar powder to the ethanol solution of the polyetheramine, wherein the concentration of the polyetheramine in the ethanol solution of the polyetheramine is 0.7 g / 100 mL, the solvent is ethanol, and the mass ratio of the modified biochar powder added to the ethanol solution of the polyetheramine is the ethanol solution of the polyetheramine: the modified biochar powder = 100:1; after the addition is completed, stirring the solution under an ultrasonic environment for 20 minutes, then separating the solid and the liquid, and drying the solid phase at 100° C. for 6 hours. The dried solid phase is added to ethanol, and the mass ratio of the dried solid phase to ethanol to form a dispersion is 1:80; the dispersion is obtained by ultrasonic stirring and dispersion, and then glutaric anhydride is added to the dispersion under stirring, and the mass ratio of the added mass of glutaric anhydride to the solid phase in the dispersion is 3:1; after the addition is completed, the water bath is heated to 40±2°C, stirred for 3 hours, and then the solid and liquid are separated, the solid phase is washed with ethanol 3 times, and dried at 80°C for 8 hours to obtain functionalized biochar powder;

[0033] (4) preparing a composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine, wherein the concentration of phosphoacetic acid is 1.6 g / 100 mL, the concentration of 4-dimethylaminopyridine is 1.9 g / 100 mL, and the solvent is N,N-dimethylformamide; stirring the solution, and then adding the functionalized biochar powder to the solution under stirring, and after the addition is completed, ultrasonically stirring for 10 minutes to obtain a suspension, and then adding the suspension to the suspension under stirring. 1-propylphosphonic anhydride is added, and the mass ratio of the composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine, the functionalized biochar powder, and 1-propylphosphonic anhydride is the composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine: functionalized biochar powder: 1-propylphosphonic anhydride = 100:1:5; after the addition is completed, the suspension is continued to be stirred for 10 hours, and then the solid-liquid is separated, the solid phase is washed twice with N,N-dimethylformamide, and then washed three times with deionized water, and dried at 80°C for 8 hours to obtain the composite passivator.

[0034] Example 4

[0035] A method for preparing a composite passivating agent for repairing soil heavy metal pollution, the preparation steps comprising:

[0036] (1) Wash corn stalks with clean water to remove dirt, cut them into segments, and soak them in an aqueous solution of sodium glycerophosphate, wherein the concentration of sodium glycerophosphate in the aqueous solution is 5 g / 100 mL and the solvent is water; the mass ratio of corn stalk segments soaked in the aqueous solution of sodium glycerophosphate is 1:50; heat in a water bath to 80±5° C., keep warm and stir for 60 min, then separate the solid and liquid, dry the solid phase at 100° C. for 30 min, and then The biochar was heated and kept in a muffle furnace at 600°C for 1 hour, then taken out and air-cooled to room temperature, ground to obtain biochar, and a hydrochloric acid solution was prepared. The biochar was added to the hydrochloric acid solution and soaked for 60 hours to remove the soluble phase. The mass percentage of the solute in the hydrochloric acid was 3%. The mass ratio of the biochar added to the hydrochloric acid solution for soaking was biochar: hydrochloric acid solution = 1:80. The solid-liquid separation was then performed, and the solid phase was washed with deionized water until the washed liquid was neutral, and dried at 100°C for 5 hours to obtain pretreated biochar powder.

[0037] (2) A composite aqueous solution of cerium chloride and ferric chloride is prepared in a reactor, wherein the concentration of cerium chloride in the composite aqueous solution of cerium chloride and ferric chloride is 25 g / L, the concentration of ferric chloride is 8 g / L, and the solvent is water; the pretreated biochar powder is added to the composite aqueous solution of cerium chloride and ferric chloride, stirred for 10 minutes, and then urea and sodium citrate are added to the solution under stirring, wherein the mass ratio of the pretreated biochar powder, the composite aqueous solution of cerium chloride and ferric chloride, and the urea and sodium citrate is pretreated biochar powder: composite aqueous solution of cerium chloride and ferric chloride: urea: sodium citrate = 1:100:4:0.5; after the addition is completed, stirring is continued for 10 minutes under an ultrasonic environment, and then the reactor is sealed, heated to 140°C and kept warm for 5 hours, and then cooled to room temperature, the reactor is opened, the solid-liquid separation is carried out, the solid phase is washed 3 times with deionized water, and dried at 80°C for 8 hours to obtain modified biochar powder;

[0038] (3) preparing an ethanol solution of polyetheramine (D-230), adding the modified biochar powder to the ethanol solution of the polyetheramine, wherein the concentration of the polyetheramine in the ethanol solution of the polyetheramine is 0.7 g / 100 mL, the solvent is ethanol, and the mass ratio of the modified biochar powder added to the ethanol solution of the polyetheramine is the ethanol solution of the polyetheramine: the modified biochar powder = 100:1; after the addition is completed, stirring the solution under an ultrasonic environment for 20 minutes, then separating the solid and the liquid, and drying the solid phase at 100° C. for 6 hours. The dried solid phase is added to ethanol, and the mass ratio of the dried solid phase to ethanol to form a dispersion is 1:80; the dispersion is obtained by ultrasonic stirring and dispersion, and then glutaric anhydride is added to the dispersion under stirring, and the mass ratio of the added mass of glutaric anhydride to the solid phase in the dispersion is 3:1; after the addition is completed, the water bath is heated to 40±2°C, stirred for 3 hours, and then the solid and liquid are separated, the solid phase is washed with ethanol 3 times, and dried at 80°C for 8 hours to obtain functionalized biochar powder;

[0039] (4) preparing a composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine, wherein the concentration of phosphoacetic acid is 1.6 g / 100 mL, the concentration of 4-dimethylaminopyridine is 2.0 g / 100 mL, and the solvent is N,N-dimethylformamide; stirring the solution, and then adding the functionalized biochar powder to the solution under stirring, and after the addition is completed, ultrasonically stirring for 10 minutes to obtain a suspension, and then adding the suspension to the suspension under stirring. 1-propylphosphonic anhydride is added, and the mass ratio of the composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine, the functionalized biochar powder, and 1-propylphosphonic anhydride is the composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine: functionalized biochar powder: 1-propylphosphonic anhydride = 100:1:5; after the addition is completed, the suspension is continued to be stirred for 10 hours, and then the solid-liquid is separated, the solid phase is washed twice with N,N-dimethylformamide, and then washed three times with deionized water, and dried at 80°C for 8 hours to obtain the composite passivator.

[0040] Comparative Example 1

[0041] A method for preparing a passivating agent for comparison, the preparation steps comprising:

[0042] (1) Wash the corn stalks with clean water to remove dirt, then cut them into sections, dry them at 100°C for 30 minutes, then heat and keep them in a muffle furnace at 600°C for 1 hour, then take them out and air cool them to room temperature, grind them into powder, obtain biochar, prepare a hydrochloric acid solution, add the biochar into the hydrochloric acid solution and soak it for 60 hours to remove the soluble phase, the mass percentage of the solute in the hydrochloric acid is 3%; the mass ratio of the biochar added to the hydrochloric acid solution for soaking is biochar: hydrochloric acid solution = 1:80; then separate the solid and liquid, wash the solid phase with deionized water until the washed liquid is neutral, and dry it at 100°C for 5 hours to obtain pretreated biochar powder;

[0043] (2) A composite aqueous solution of cerium chloride and ferric chloride is prepared in a reactor, wherein the concentration of cerium chloride in the composite aqueous solution of cerium chloride and ferric chloride is 24 g / L, the concentration of ferric chloride is 7 g / L, and the solvent is water; the pretreated biochar powder is added to the composite aqueous solution of cerium chloride and ferric chloride, stirred for 10 min, and then urea and sodium citrate are added to the solution under stirring, wherein the mass ratio of the pretreated biochar powder, the composite aqueous solution of cerium chloride and ferric chloride, and the urea and sodium citrate is pretreated biochar powder: composite aqueous solution of cerium chloride and ferric chloride: urea: sodium citrate = 1:100:4:0.5; after the addition is completed, stirring is continued for 10 min under an ultrasonic environment, and then the reactor is sealed, heated to 140°C and kept warm for 5 h, and then cooled to room temperature, the reactor is opened, the solid-liquid separation is carried out, the solid phase is washed 3 times with deionized water, and dried at 80°C for 8 h to obtain modified biochar powder;

[0044] (3) preparing an ethanol solution of polyetheramine (D-230), adding the modified biochar powder to the ethanol solution of the polyetheramine, wherein the concentration of the polyetheramine in the ethanol solution of the polyetheramine is 0.7 g / 100 mL, the solvent is ethanol, and the mass ratio of the modified biochar powder added to the ethanol solution of the polyetheramine is the ethanol solution of the polyetheramine: the modified biochar powder = 100:1; after the addition is completed, stirring the solution under an ultrasonic environment for 20 minutes, then separating the solid and the liquid, and drying the solid phase at 100° C. for 6 hours. The dried solid phase is added to ethanol, and the mass ratio of the dried solid phase to ethanol to form a dispersion is 1:80; the dispersion is obtained by ultrasonic stirring and dispersion, and then glutaric anhydride is added to the dispersion under stirring, and the mass ratio of the added mass of glutaric anhydride to the solid phase in the dispersion is 3:1; after the addition is completed, the water bath is heated to 40±2°C, stirred for 3 hours, and then the solid and liquid are separated, the solid phase is washed with ethanol 3 times, and dried at 80°C for 8 hours to obtain functionalized biochar powder;

[0045] (4) preparing a composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine, wherein the concentration of phosphoacetic acid is 1.6 g / 100 mL, the concentration of 4-dimethylaminopyridine is 1.9 g / 100 mL, and the solvent is N,N-dimethylformamide; stirring the solution, and then adding the functionalized biochar powder to the solution under stirring, and after the addition is completed, ultrasonically stirring for 10 minutes to obtain a suspension, and then adding the suspension to the suspension under stirring. 1-propylphosphonic anhydride was added, and the mass ratio of the composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine, the functionalized biochar powder, and 1-propylphosphonic anhydride was the composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine: functionalized biochar powder: 1-propylphosphonic anhydride = 100:1:5; after the addition was completed, the suspension was continued to be stirred for 10 hours, and then the solid-liquid was separated, the solid phase was washed twice with N,N-dimethylformamide, and then washed three times with deionized water, and dried at 80°C for 8 hours to obtain the passivator described in this comparative example.

[0046] Comparative Example 2

[0047] A method for preparing a passivating agent for comparison, the preparation steps comprising:

[0048] (1) Wash corn stalks with clean water to remove dirt, cut them into segments, and soak them in an aqueous solution of sodium glycerophosphate, wherein the concentration of sodium glycerophosphate in the aqueous solution is 5 g / 100 mL and the solvent is water; the mass ratio of corn stalk segments soaked in the aqueous solution of sodium glycerophosphate is 1:50; heat in a water bath to 80±5° C., keep warm and stir for 60 min, then separate the solid and liquid, dry the solid phase at 100° C. for 30 min, and then The biochar was heated and kept in a muffle furnace at 600°C for 1 hour, then taken out and air-cooled to room temperature, ground to obtain biochar, and a hydrochloric acid solution was prepared. The biochar was added to the hydrochloric acid solution and soaked for 60 hours to remove the soluble phase. The mass percentage of the solute in the hydrochloric acid was 3%. The mass ratio of the biochar added to the hydrochloric acid solution for soaking was biochar: hydrochloric acid solution = 1:80. The solid-liquid separation was then performed, and the solid phase was washed with deionized water until the washed liquid was neutral, and dried at 100°C for 5 hours to obtain pretreated biochar powder.

[0049] (2) preparing an aqueous solution of ferric chloride in a reactor, wherein the concentration of ferric chloride in the aqueous solution is 7 g / L, and the solvent is water; adding the pretreated biochar powder to the aqueous solution of ferric chloride, stirring for 10 min, and then adding urea and sodium citrate to the solution under stirring, wherein the mass ratio of the pretreated biochar powder, the aqueous solution of ferric chloride, the urea and the sodium citrate is pretreated biochar powder: aqueous solution of ferric chloride: urea: sodium citrate = 1:100:4:0.5; after the addition is completed, stirring is continued for 10 min under an ultrasonic environment, and then the reactor is sealed, heated to 140°C and kept warm for 5 h, and then cooled to room temperature, the reactor is opened, the solid-liquid separation is carried out, the solid phase is washed 3 times with deionized water, and dried at 80°C for 8 h to obtain modified biochar powder;

[0050] (3) preparing an ethanol solution of polyetheramine (D-230), adding the modified biochar powder to the ethanol solution of the polyetheramine, wherein the concentration of the polyetheramine in the ethanol solution of the polyetheramine is 0.7 g / 100 mL, the solvent is ethanol, and the mass ratio of the modified biochar powder added to the ethanol solution of the polyetheramine is the ethanol solution of the polyetheramine: the modified biochar powder = 100:1; after the addition is completed, stirring the solution under an ultrasonic environment for 20 minutes, then separating the solid and the liquid, and drying the solid phase at 100° C. for 6 hours. The dried solid phase is added to ethanol, and the mass ratio of the dried solid phase to ethanol to form a dispersion is 1:80; the dispersion is obtained by ultrasonic stirring and dispersion, and then glutaric anhydride is added to the dispersion under stirring, and the mass ratio of the added mass of glutaric anhydride to the solid phase in the dispersion is 3:1; after the addition is completed, the water bath is heated to 40±2°C, stirred for 3 hours, and then the solid and liquid are separated, the solid phase is washed with ethanol 3 times, and dried at 80°C for 8 hours to obtain functionalized biochar powder;

[0051] (4) preparing a composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine, wherein the concentration of phosphoacetic acid is 1.6 g / 100 mL, the concentration of 4-dimethylaminopyridine is 1.9 g / 100 mL, and the solvent is N,N-dimethylformamide; stirring the solution, and then adding the functionalized biochar powder to the solution under stirring, and after the addition is completed, ultrasonically stirring for 10 minutes to obtain a suspension, and then adding the suspension to the suspension under stirring. 1-propylphosphonic anhydride was added, and the mass ratio of the composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine, the functionalized biochar powder, and 1-propylphosphonic anhydride was the composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine: functionalized biochar powder: 1-propylphosphonic anhydride = 100:1:5; after the addition was completed, the suspension was continued to be stirred for 10 hours, and then the solid-liquid was separated, the solid phase was washed twice with N,N-dimethylformamide, and then washed three times with deionized water, and dried at 80°C for 8 hours to obtain the passivator described in this comparative example.

[0052] Comparative Example 3

[0053] A method for preparing a passivating agent for comparison, the preparation steps comprising:

[0054] (1) Wash corn stalks with clean water to remove dirt, cut them into segments, and soak them in an aqueous solution of sodium glycerophosphate, wherein the concentration of sodium glycerophosphate in the aqueous solution is 5 g / 100 mL and the solvent is water; the mass ratio of corn stalk segments soaked in the aqueous solution of sodium glycerophosphate is 1:50; heat in a water bath to 80±5° C., keep warm and stir for 60 min, then separate the solid and liquid, dry the solid phase at 100° C. for 30 min, and then The biochar was heated and kept in a muffle furnace at 600°C for 1 hour, then taken out and air-cooled to room temperature, ground to obtain biochar, and a hydrochloric acid solution was prepared. The biochar was added to the hydrochloric acid solution and soaked for 60 hours to remove the soluble phase. The mass percentage of the solute in the hydrochloric acid was 3%. The mass ratio of the biochar added to the hydrochloric acid solution for soaking was biochar: hydrochloric acid solution = 1:80. The solid-liquid separation was then performed, and the solid phase was washed with deionized water until the washed liquid was neutral, and dried at 100°C for 5 hours to obtain pretreated biochar powder.

[0055] (2) A composite aqueous solution of cerium chloride and ferric chloride is prepared in a reactor, wherein the concentration of cerium chloride in the composite aqueous solution of cerium chloride and ferric chloride is 24 g / L, the concentration of ferric chloride is 7 g / L, and the solvent is water; the pretreated biochar powder is added to the composite aqueous solution of cerium chloride and ferric chloride, stirred for 10 min, and then urea and sodium citrate are added to the solution under stirring, wherein the mass ratio of the pretreated biochar powder, the composite aqueous solution of cerium chloride and ferric chloride, and the urea and sodium citrate is pretreated biochar powder: composite aqueous solution of cerium chloride and ferric chloride: urea: sodium citrate = 1:100:4:0.5; after the addition is completed, stirring is continued for 10 min under an ultrasonic environment, and then the reactor is sealed, heated to 140°C and kept warm for 5 h, and then cooled to room temperature, the reactor is opened, the solid-liquid separation is carried out, the solid phase is washed 3 times with deionized water, and dried at 80°C for 8 h to obtain modified biochar powder;

[0056] (3) preparing an ethanol solution of polyetheramine (D-230), adding the modified biochar powder to the ethanol solution of the polyetheramine, wherein the concentration of the polyetheramine in the ethanol solution of the polyetheramine is 0.7 g / 100 mL, the solvent is ethanol, and the mass ratio of adding the modified biochar powder to the ethanol solution of the polyetheramine is the ethanol solution of the polyetheramine: the modified biochar powder = 100:1; after the addition is completed, stirring the solution under an ultrasonic environment for 20 minutes, then separating the solid and the liquid, and drying the solid phase at 100° C. for 6 hours. The solid phase after drying is added to ethanol, and the mass ratio of the dried solid phase added to ethanol to form a dispersion is the dried solid phase: ethanol = 1:80; ultrasonic stirring and dispersion is performed to obtain a dispersion, and then glutaric anhydride is added to the dispersion under stirring, and the mass ratio of glutaric anhydride added to the solid phase in the dispersion is glutaric anhydride: solid phase = 3:1; after the addition is completed, the water bath is heated to 40±2°C, and the mixture is stirred for 3 hours. Then, the solid and liquid are separated, the solid phase is washed with ethanol 3 times, and dried at 80°C for 8 hours to obtain the passivating agent described in this comparative example.

[0057] Example 5

[0058] Lead-contaminated soil was collected, and the soil composition is shown in Table 1, where effective lead refers to the part that can be assimilated by plants and animals, that is, the effective state of heavy metals. According to standard HJ804-2016, DTPA extraction-ICP-MS was used to determine the effective content of Pb in the soil. The lead-contaminated soil was divided into 7 groups on average, and the passivator prepared by the methods described in the above embodiments and comparative examples was added to each group, and the amount of passivator added was 5% of the weight of each group of soil. After adding the passivator, stir evenly, add deionized water to adjust the moisture content to 50wt%, 25±3℃, and 80% humidity, and culture statically in an incubator for 30 days, and replenish water regularly once a day to maintain the above moisture content of the soil. After the culture is completed, it is naturally air-dried for 2 days, and the effective content of Pb in the soil after culture is tested. The results are shown in Table 2.

[0059] As shown in Table 2, the soil passivator prepared by the method of the present invention has a good passivation effect on lead in the soil, and can convert the effective lead in the soil into a passivated lead that cannot be assimilated by animals and plants, thereby reducing the harm of heavy metals to the soil. This may be due to the effect of the passivator on the adsorption and passivation of lead. The present invention first introduces sodium glycerophosphate in the preparation process of biochar, so that the surface of the biochar is rich in highly electronegative PO4 3- or P2O7 4- Functional groups such as cerium chloride and ferric chloride are added to improve the adsorption of heavy metals by the passivator, and at the same time, points are provided for subsequent biochar surface modification, and the specific surface area of ​​biochar is significantly increased, and the pore structure is richer. Then, by adding a composite aqueous solution of cerium chloride and ferric chloride for modification, cerium and iron are precipitated and modified on the surface of biochar using the hydroxide ions and carbonate ions produced by urea hydrolysis, the stability of lead on the surface after the passivator adsorbs lead is improved, the re-dissolution of adsorbed lead is reduced, and the lead is converted from a biologically effective state to a stable residual state. Subsequently, it is treated with amination, carboxylation and phosphoacetic acid to significantly increase the number of oxygen-containing functional groups on the surface of the passivator, which is conducive to the formation of complexes with money and improves adsorption.

[0060] Table 1

[0061] pH Organic matter (g / kg) Effective lead content 5.46 36.92 14.76mg / kg

[0062] Table 2

[0063]

[0064]

[0065] The technical solution provided by the present invention is introduced in detail above. For those skilled in the art, according to the concept of the embodiments of the present invention, there may be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for preparing a composite passivating agent for soil heavy metal pollution remediation, characterized in that: The preparation steps include: (1) Wash the corn stalks with clean water to remove dirt, then cut them into sections, soak them in an aqueous solution of sodium glycerophosphate, heat them in a water bath to 80±5°C and keep them warm for more than 60 minutes, then separate the solid and liquid, dry the solid phase at 100°C for more than 30 minutes, then heat and keep them warm in a muffle furnace at 600°C for more than 1 hour, then take them out and air cool them to room temperature, grind them to obtain biochar, prepare a hydrochloric acid solution, add the biochar to the hydrochloric acid solution and soak it for more than 60 hours, remove the soluble phase, then separate the solid and liquid, wash the solid phase with deionized water until the washed liquid is neutral, and dry them at 100°C for more than 5 hours to obtain pretreated biochar powder; (2) A composite aqueous solution of cerium chloride and ferric chloride is prepared in a reactor, the pretreated biochar powder is added to the composite aqueous solution of cerium chloride and ferric chloride, and stirred for more than 10 minutes, and then urea and sodium citrate are added to the solution under stirring. After the addition is completed, stirring is continued for more than 10 minutes under an ultrasonic environment, and then the reactor is sealed, heated to 140-145° C. and kept warm for 4-5 hours, and then cooled to room temperature, the reactor is opened, the solid-liquid separation is carried out, the solid phase is washed with deionized water for more than 3 times, and dried at 80° C. for more than 8 hours to obtain modified biochar powder; (3) preparing an ethanol solution of polyetheramine, adding the modified biochar powder to the ethanol solution of the polyetheramine, stirring the solution for more than 20 minutes under an ultrasonic environment after the addition is completed, then separating the solid and the liquid, drying the solid phase at 100° C. for more than 6 hours, adding the dried solid phase to ethanol, stirring and dispersing with ultrasonic waves to obtain a dispersion, and then adding glutaric anhydride to the dispersion under stirring. After the addition is completed, heating the dispersion to 40±2° C. in a water bath, stirring at this temperature for more than 3 hours, then separating the solid and the liquid, washing the solid phase with ethanol for more than 3 times, and drying at 80° C. for more than 8 hours to obtain functionalized biochar powder; (4) preparing a composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine, stirring the solution, and then adding the functionalized biochar powder to the solution under stirring, and after the addition is completed, ultrasonic stirring is performed for more than 10 minutes to obtain a suspension, and then 1-propylphosphonic anhydride is added to the suspension under stirring, and after the addition is completed, the suspension is continued to be stirred for more than 10 hours, and then the solid-liquid is separated, the solid phase is washed with N,N-dimethylformamide for more than 2 times, and then washed with deionized water for more than 3 times, and dried at 80° C. for more than 8 hours to obtain the composite passivator.

2. The method for preparing a composite passivating agent for soil heavy metal pollution remediation according to claim 1, characterized in that: In the step (1), the concentration of sodium glycerophosphate in the aqueous solution of sodium glycerophosphate is 4-5g / 100mL, and the solvent is water; the mass ratio of corn stalk segments soaked in the aqueous solution of sodium glycerophosphate is stalk segments: aqueous solution of sodium glycerophosphate = 1:

50.

3. The method for preparing a composite passivating agent for soil heavy metal pollution remediation according to claim 2, characterized in that: In the step (1), the mass percentage of the solute in the hydrochloric acid is 3%; the mass ratio of the biochar added to the hydrochloric acid solution for soaking is biochar: hydrochloric acid solution = 1:

80.

4. The method for preparing a composite passivating agent for soil heavy metal pollution remediation according to claim 1, characterized in that: In the step (2), in the composite aqueous solution of cerium chloride and ferric chloride, the concentration of cerium chloride is 20-25 g / L, the concentration of ferric chloride is 6-8 g / L, and the solvent is water; the mass ratio of the pretreated biochar powder, the composite aqueous solution of cerium chloride and ferric chloride, and the urea and sodium citrate is pretreated biochar powder: composite aqueous solution of cerium chloride and ferric chloride: urea: sodium citrate = 1:100:3-4:0.4-0.

5.

5. The method for preparing a composite passivating agent for soil heavy metal pollution remediation according to claim 1, characterized in that: In the step (3), the concentration of polyetheramine in the ethanol solution of polyetheramine is 0.6-0.7 g / 100 mL, the solvent is ethanol, and the mass ratio of the modified biochar powder added to the ethanol solution of polyetheramine is ethanol solution of polyetheramine:modified biochar powder=100:

1.

6. The method for preparing a composite passivating agent for soil heavy metal pollution remediation according to claim 5, characterized in that: In the step (3), the mass ratio of the dried solid phase added to ethanol to form a dispersion is 1:80; the mass ratio of the added mass of glutaric anhydride to the solid phase in the dispersion is 2-3:

1.

7. The method for preparing a composite passivating agent for soil heavy metal pollution remediation according to claim 1, characterized in that: In the step (4), in the composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine, the concentration of phosphoacetic acid is 1.5-1.6 g / 100 mL, the concentration of 4-dimethylaminopyridine is 1.8-2.0 g / 100 mL, and the solvent is N,N-dimethylformamide; the mass ratio of the composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine, the functionalized biochar powder, and 1-propylphosphonic anhydride is the composite N,N-dimethylformamide solution of phosphoacetic acid and 4-dimethylaminopyridine:functionalized biochar powder:1-propylphosphonic anhydride=100:1:4-5.

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