CN111961473A

CN111961473A - Fixing agent for repairing arsenic-antimony composite polluted soil and preparation method and application thereof

Info

Publication number: CN111961473A
Application number: CN202010788317.1A
Authority: CN
Inventors: 杨志辉; 高世康; 黄培成; 杨卫春; 廖骐; 石岩; 曾盖
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2020-08-07
Filing date: 2020-08-07
Publication date: 2020-11-20

Abstract

The invention discloses a preparation method and application of a fixing agent for repairing arsenic-antimony composite polluted soil. The preparation of the fixing agent comprises the following steps: 1) adding straw powder into a ferric salt solution serving as a modifier, adjusting the pH value, and filling the mixture into a high-pressure reaction kettle; 2) placing the reaction kettle in a muffle furnace for heating; 3) and washing and filtering the reaction product, and drying to obtain the chemical fixing agent. After the prepared fixing agent is mixed with soil according to a certain proportion, the effective As (III) and As (V) in the polluted soil are respectively reduced by 42.06% and 50.67%, and the effective Sb (III) and Sb (V) are respectively reduced by 21.57% and 59.66%. The non-specific adsorption state arsenic and the specific adsorption state arsenic in the soil are respectively reduced by 10 percent and 11 percent; the non-specific adsorption state antimony and the specific adsorption state antimony are respectively reduced by 8% and 16%, and the fixing agent disclosed by the invention is simple in preparation process and low in cost, and can effectively reduce the mobility and bioavailability of arsenic and antimony in soil.

Description

Fixing agent for repairing arsenic-antimony composite polluted soil and preparation method and application thereof

Technical Field

The invention belongs to the field of arsenic and antimony polluted soil treatment, and particularly relates to a fixing agent for repairing arsenic and antimony polluted soil, and a preparation method and application thereof.

Background

At present, physical and chemical methods such as soil leaching, soil turning and soil dressing, chemical fixation, electric restoration and the like are common in methods for treating heavy metal pollution in soil, and the methods have quick and efficient decontamination effects, but because the methods are complex in equipment, high in input cost and large in soil disturbance, the methods are not suitable for large-scale application to large-area polluted soil, and the soil structure is often damaged, so that the biological activity of the soil is reduced and the fertility of the soil is degraded, and the chemical fixation method becomes a feasible choice. The biochar has strong adsorption performance, wide applicability and low cost, and is small in soil disturbance and commonly used for repairing heavy metal pollution of soil.

The biochar is mainly prepared by two methods of high-temperature carbonization and hydrothermal carbonization. The hydrothermal carbonization is a hydrothermal reaction which is carried out by mixing biomass and water according to a certain proportion and putting the mixture into a reactor at a certain temperature (180-. Although the single biochar has a certain adsorption and passivation effect on arsenic and antimony, the effect is not obvious.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a chemical fixing agent which is environment-friendly and low in price, does not destroy the physicochemical property of soil, and can effectively repair arsenic-antimony composite polluted soil, and a preparation method and application thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention relates to a preparation method of a fixing agent for repairing arsenic-antimony composite polluted soil, which comprises the following steps:

adding biomass powder into an iron salt solution to obtain slurry, adjusting the pH value of the slurry to 1-1.8, then carrying out hydrothermal reaction, and carrying out solid-liquid separation to obtain a fixing agent;

in the ferric salt solution, the concentration of ferric ions is 0.1-1.0 mol/L;

the temperature of the hydrothermal reaction is 180-260 ℃.

Preferably, the biomass is selected from straw.

Preferably, the method for obtaining the biomass powder comprises the following steps: adding the biomass into a chlorine-containing solution, stirring for 2-3 hours, filtering, drying the obtained filter residue at 105-115 ℃ for 12-24 hours, crushing, sieving with a 60-mesh sieve, and taking undersize products.

Further preferably, the chlorine-containing solution is selected to have an available chlorine content of 5 to 6%.

Still more preferably, the chlorine-containing solution is a sodium chlorate solution.

Further preferably, the solid-liquid mass volume ratio of the biomass to the chlorine-containing solution is 10-20g:100-200 mL.

Preferably, the ferric salt solution is selected from one of ferric chloride solution, ferric sulfate solution or ferric citrate solution.

In a preferable scheme, the concentration of iron ions in the iron salt solution is 0.4-0.6 mol/L.

In a preferred scheme, the solid-liquid mass volume ratio of the biomass powder to the ferric salt solution is 3-10 g: 30-100 mL.

In a preferred embodiment, the pH is adjusted by adding a sodium hydroxide solution having a concentration of 8 to 10mol/L to the slurry until the pH of the slurry is 1.0 to 1.8.

In a preferred embodiment, the temperature of the reaction is 220-260 ℃.

In a preferred scheme, the time of the hydrothermal reaction is 2-4 h.

In a preferable scheme, the heating rate is 5-10 ℃/min;

in the actual operation process, the slurry with the pH value adjusted is put into a high-pressure reaction kettle and placed in a muffle furnace for hydrothermal reaction.

In the preferred scheme, the solid-liquid separation method comprises the steps of filtering, washing a solid phase obtained by filtering, drying for 12-24 hours at the temperature of 60-105 ℃, grinding and sieving by a 60-mesh sieve, taking undersize products to obtain the fixing agent,

the fixing agent for repairing arsenic and antimony polluted soil prepared by the preparation method.

The application of the fixing agent for repairing arsenic and antimony polluted soil prepared by the preparation method is to use the fixing agent for repairing arsenic and antimony polluted soil.

Preferably, the repairing method comprises the following steps: adding the fixing agent into arsenic-antimony composite polluted soil, adding deionized water, stirring uniformly, and treating for 7-14 days; the mass ratio of the arsenic-antimony composite polluted soil to the fixing agent is 100: 1-5; the solid-liquid mass volume ratio of the arsenic-antimony composite polluted soil to water is 100 g: 30-200 ml.

The invention has the following advantages:

1. the main raw material of the fixing agent is rice straw, the raw material source is wide, the recycling of waste resources is realized, and the green purpose of treating wastes with processes of wastes against one another is achieved.

2. The matrix used in the preparation process of the fixing agent is ferric salt solution, contains chemical elements such as iron, oxygen, hydrogen, sulfur and the like, and the elements are all contained in the soil, so that secondary pollution to the soil can not be caused.

3. According to the invention, a hydrothermal carbonization method is adopted for preparing and modifying the biochar, the biochar preparation and modification are combined into a whole, the hydrothermal method avoids the influence of water in raw materials on the fixing agent, meanwhile, the temperature required by the hydrothermal method is lower, energy is saved, the method is simple, the iron-based material on the surface of the prepared fixing agent is uniformly and stably distributed, and the agglomeration phenomenon of the iron-based material is effectively prevented. The fixing agent has a large specific surface area, iron loaded on the surface of the fixing agent has an adsorption effect on arsenic and antimony, and arsenic and antimony pollution in soil can be effectively repaired.

4. Compared with many common soil fixatives, the fixative prepared by the invention can better repair and fix arsenic-antimony composite pollution in soil on one hand, and can not cause serious soil acidification problem in the application process and influence the stability of soil structure on the other hand, and the addition of the biochar can increase fertility and is more beneficial to later-stage crop cultivation.

Drawings

FIG. 1 is a Scanning Electron Microscope (SEM) image of the fixing agent prepared in example 1 of the present invention;

FIG. 2 is an XRD pattern of the fixative prepared in example 1 of the present invention;

FIG. 3 shows FT-IR spectrum of the fixative prepared in example 1 of the present invention

FIG. 4 is a graph showing the effect of the fixing agent prepared in example 1 of the present invention on the fixing of As and Sb in As-Sb contaminated soil at different addition levels in application example 1;

FIG. 5 is a graph showing the effect of the fixative prepared in example 1 of the present invention on the fixation of As and Sb in As and Sb contaminated soil with different concentrations in application example 2;

FIG. 6 shows the morphological changes of As and Sb before and after fixation with the fixative prepared in example 1 of the present invention in application example 3; wherein in FIG. 6: a is non-specific adsorption state; b, specific adsorption state; c, amorphous or low-crystallinity iron and aluminum oxide combination state; d, the combination state of crystalline iron and aluminum oxide; e, residue state.

Detailed Description

The following detailed description of the invention, taken in conjunction with the accompanying drawings and specific embodiments, is intended to illustrate, but not limit the invention.

Example 1

The preparation method of the fixing agent for repairing arsenic-antimony composite polluted soil comprises the following steps:

(1) preparation of Fe³⁺Ferric chloride solution with the concentration of 0.5mol/L,

(2) adjusting the pH value of the ferric chloride solution to 1.6 by using 8-10mol/L sodium hydroxide solution;

(3) adding 100mL of ferric chloride solution into 10.0g of straw powder treated by sodium hypochlorite, uniformly mixing, and placing into a high-pressure reaction kettle with the volume of 150 mL;

(4) placing the reaction kettle in a muffle furnace under the set conditions of 240 ℃ of temperature, 5 ℃/min of heating rate and 3h of heat preservation time;

(5) and after the reaction kettle is cooled to room temperature, performing suction filtration on the prepared biochar, repeatedly washing the biochar for 3 times by using deionized water, and drying at 60 ℃ to obtain the iron-based biochar which takes ferric chloride and straws as raw materials, namely the fixing agent.

Example 2

The preparation method of the fixing agent for repairing arsenic-antimony composite polluted soil comprises the following steps: other conditions were the same as in example 1 except that in the case of the step (1), Fe was prepared³⁺Ferric chloride solution with concentration of 0.1 mol/L.

Example 3

The preparation method of the fixing agent for repairing arsenic-antimony composite polluted soil comprises the following steps: the other conditions were the same as in example 1 except that in the step (1), the pH of the ferric chloride solution was adjusted to 1.0.

Example 4

The preparation method of the fixing agent for repairing arsenic-antimony composite polluted soil comprises the following steps: the other conditions were the same as in example 1 except that in the step (4), the temperature was set to 180 ℃, the temperature increase rate was 5 ℃/min, and the holding time was 3 hours.

Comparative example 1

Preparing a biochar fixing agent which is not modified by iron: adding 100mL of deionized water into 10.0g of straw powder treated by sodium hypochlorite, uniformly mixing, placing the mixture into a high-pressure reaction kettle with the volume of 150mL, placing the reaction kettle into a muffle furnace under the set conditions of the temperature of 240 ℃, the heating rate of 5 ℃/min and the heat preservation time of 3h, performing suction filtration on the prepared biochar after the reaction kettle is cooled to the room temperature, and drying at the temperature of 60 ℃ to obtain the original biochar taking the straws as a raw material.

The application process comprises the following steps:

the iron modified biochar prepared in the examples 1-4 and the comparative example 1 is used as an adsorbing material for adsorbing arsenic and antimony in an arsenic and antimony polluted water body:

(1) the arsenic and antimony polluted water body is an artificial contaminated water body and is prepared by potassium pyroantimonate and sodium arsenate. 0.2158g of potassium pyroantimonate and 0.2775g of sodium arsenate are dissolved in a small amount of deionized water, the solution is put into a 1L volumetric flask, and the solution is diluted to a scale mark by the deionized water, so that the arsenic-antimony polluted water body with the concentration of 100mg/L is obtained.

(2) The adsorption material is added into the arsenic and antimony polluted water body, and the arsenic and antimony polluted water body comprises the following components in percentage by weight: iron-based biochar 100 ml: 0.3g, shaking on a shaker for 24h at 25 ℃ and a rotation speed of 180 rpm.

(4) Through detection, the arsenic and antimony concentrations in the water body polluted by arsenic and antimony before and after treatment are shown in the following table 1.

TABLE 1 arsenic and antimony removal rates before and after arsenic and antimony solution treatment

Sample (I)	As removal Rate (%)	Sb removal Rate (%)
			Example 1	48.36	59.33
Example 2	17.37	12.66
			Example 3	42.16	51.33
Example 4	13.65	20.27
			Comparative example 1	5.35	3.47

Application example 1

The arsenic-antimony composite polluted soil which is prepared by using the soil in the application example 1 as the artificial 100mg/kg soil is prepared by air drying, impurity removal and grinding, and then sieving with a 20-mesh nylon sieve.

Respectively weighing 10g of soil sample into a 100mL plastic bottle, adding the fixing agent prepared in the embodiment 1 according to 1%, 2%, 3%, 4% and 5% of the soil mass, uniformly mixing, adding deionized water according to the water-soil ratio of 1:1, stirring, sealing the bottle mouth with a sealing film, standing for 14 days, and airing the soil sample in an air drying box. Sampling and determining the content of available As (dilute hydrochloric acid extracted state) and available Sb (EDTA extracted state) in the soil. The detection shows that the additive amount of the fixing agent is positively correlated with the fixing effect, and the fixing effect tends to be stable after the additive amount reaches 3 percent. At the moment, the fixing rate of the fixing agent to the effective state As (III) can reach 37.16 percent, and the fixing rate to the effective state As (V) can reach 40.35 percent; the fixation rate to the effective state Sb (III) is more than 15.35 percent, and the fixation rate to the effective state Sb (V) is more than 55.66 percent.

Application example 2

The arsenic-antimony composite polluted soil in the application example 2 is prepared by using 50mg/kg, 100mg/kg and 150mg/kg of artificially prepared arsenic-antimony composite polluted soil, air drying, removing impurities, grinding and sieving with a 20-mesh nylon sieve.

Respectively weighing 10g of soil samples with different arsenic and antimony concentrations in a 100mL plastic bottle, adding the fixing agent prepared in the embodiment 1 according to 3% of the soil mass, uniformly mixing, adding deionized water according to the water-soil ratio of 1:1, stirring, sealing the bottle mouth with a sealing film, standing for 14 days, and airing the soil samples in an air drying box. Sampling and determining the content of available As (dilute hydrochloric acid extracted state) and available Sb (EDTA extracted state) in the soil. Through detection, the fixing agent has a good fixing effect on the soil polluted by arsenic and antimony with higher concentration. For 150mg/kg arsenic-antimony polluted soil, the fixing rate of the fixing agent on the effective As (III) can reach 39.55%, and the fixing rate on the effective As (V) can reach 53.66%; the fixation rate of the active Sb (III) is more than 17.11 percent, and the fixation rate of the active Sb (V) is more than 52.33 percent.

Application example 3

The arsenic-antimony composite polluted soil which is prepared by using the soil in the application example 3 as the artificial 100mg/kg soil is prepared by air drying, impurity removal and grinding, and then sieving with a 20-mesh nylon sieve.

Accurately weighing 1.00g of each air-dried soil sample which is not added with the fixing agent and is treated by 5 percent of the fixing agent, putting the air-dried soil sample into a 50mL centrifuge tube, and adding 25mL of (NH) with 0.05mol/L₄)₂SO₄Oscillating at 20 ℃ for 4h, centrifuging at 8000r/min for 15min, filtering the supernatant with 0.45 μm filter membrane, and refrigerating for storage. To the first-stage residue was added 25mL of 0.05mol/L (NH)₄)H₂PO₄Oscillating at 20 ℃ for 4h, centrifuging at 8000r/min for 15min, filtering the supernatant with 0.45 μm filter membrane, and refrigerating for storage. To the first-stage residue was added 25mL of 0.2mol/L ammonium oxalate buffer solution (pH 3.25), the mixture was shaken at 20 ℃ in the dark for 4 hours, centrifuged at 8000r/min for 15min, and the supernatant was filtered through a 0.45 μm filter and then refrigerated. Adding 25mL of a buffer solution (pH is 3.25) of 0.2mol/L ammonium oxalate and 0.1mol/L ascorbic acid into the primary residue, heating in a water bath under light (96 +/-3 ℃) for 30min, cooling, centrifuging at 8000r/min for 15min, filtering the supernatant with a 0.45 mu m filter membrane, refrigerating, storing for testing, washing the residue with 12.5mL of 0.2mol/L ammonium oxalate buffer solution (pH is 3.25), shaking and washing in dark for 10min, centrifuging for 15min, and discarding the washing solution. Taking out the solid phase at the previous stage, oven drying, weighing 0.2g-0.5g (accurate to 0.0001g) in 50mL colorimetric tube, adding 10mL (1+1) aqua regia, boiling in water bath for 2h, shaking for several times, taking down, cooling, diluting to scale, shaking, and standing. And (3) sucking a certain test solution into a 50mL colorimetric tube, adding 3mL hydrochloric acid and 10mL sulfur antibody, diluting to a scale, and taking supernate to be tested. The detection proves that the fixing agent is beneficial to the conversion of arsenic and antimony from a non-specific adsorption state and a specific adsorption state which are easy to move to an amorphous or low-crystallinity iron-aluminum oxide binding state which is difficult to move. The non-specific adsorption state and the specific adsorption state arsenic are respectively reduced by 10 percent and 11 percent, and the non-specific adsorption state and the specific adsorption state antimony are respectively reduced by 8 percent and 16 percent.

Claims

1. The preparation method of the fixing agent for repairing arsenic and antimony polluted soil is characterized by comprising the following steps: adding biomass powder into an iron salt solution to obtain slurry, adjusting the pH value of the slurry to 1-1.8, then carrying out hydrothermal reaction, and carrying out solid-liquid separation to obtain a fixing agent;

in the ferric salt solution, the concentration of ferric ions is 0.1-1.0 mol/L; the temperature of the hydrothermal reaction is 180-260 ℃.

2. The preparation method of the fixing agent for remediating arsenic-antimony contaminated soil as claimed in claim 1, wherein the preparation method comprises the following steps: the biomass is selected from straw.

3. The preparation method of the fixing agent for remediating arsenic-antimony contaminated soil as claimed in claim 1, wherein the preparation method comprises the following steps: the method for obtaining the biomass powder comprises the following steps: adding the biomass into a chlorine-containing solution, stirring for 2-3 hours, filtering, drying the obtained filter residue at 105-115 ℃ for 12-24 hours, crushing, sieving with a 60-mesh sieve, and taking undersize products.

4. The preparation method of the fixing agent for remediating arsenic-antimony contaminated soil as claimed in claim 3, wherein the preparation method comprises the following steps: in the chlorine-containing solution, the content of available chlorine is 5-6%; the solid-liquid mass volume ratio of the biomass to the chlorine-containing solution is 10-20g:100-200 mL.

5. The preparation method of the fixing agent for remediating arsenic-antimony contaminated soil as claimed in claim 1, wherein the preparation method comprises the following steps: the ferric salt solution is selected from one of ferric chloride solution, ferric sulfate solution or ferric citrate solution; the solid-liquid mass volume ratio of the biomass powder to the ferric salt solution is 3-10 g: 30-100 mL.

6. The preparation method of the fixing agent for remediating arsenic-antimony contaminated soil as claimed in claim 1, wherein the preparation method comprises the following steps: the pH value is adjusted by adding a sodium hydroxide solution with the concentration of 8-10mol/L into the slurry until the pH value of the slurry is 1.0-1.8.

7. The preparation method of the fixing agent for remediating arsenic-antimony contaminated soil as claimed in claim 1, wherein the preparation method comprises the following steps: the time of the hydrothermal reaction is 2-4h, and the heating rate is 5-10 ℃/min.

8. The preparation method of the fixing agent for remediating arsenic-antimony contaminated soil as claimed in claim 1, wherein the preparation method comprises the following steps: the solid-liquid separation method comprises filtering, washing the obtained solid phase, drying at 60-105 deg.C for 12-24 hr, grinding, sieving with 60 mesh sieve, and collecting the undersize product to obtain the fixative.

9. The fixing agent for repairing arsenic-antimony contaminated soil prepared by the preparation method of any one of claims 1-8.

10. The application of the fixing agent for repairing arsenic-antimony contaminated soil prepared by the preparation method according to any one of claims 1-8 is characterized in that: the fixing agent is used for repairing arsenic and antimony polluted soil.