CN109013689B

CN109013689B - Remediation method for arsenic-contaminated soil

Info

Publication number: CN109013689B
Application number: CN201810669690.8A
Authority: CN
Inventors: 吕正勇; 冯国杰; 徐剑锋; 范吉强; 李淑彩; 苗竹; 宋登慧; 朱湖地
Original assignee: Beijing Geoenviron Engineering and Technology Inc
Current assignee: Beijing Geoenviron Engineering and Technology Inc
Priority date: 2018-06-26
Filing date: 2018-06-26
Publication date: 2021-06-01
Anticipated expiration: 2038-06-26
Also published as: CN109013689A

Abstract

The invention belongs to the field of soil remediation, and discloses a remediation method of arsenic-contaminated soil. The method comprises the following steps: mixing the arsenic-polluted soil, water and the complex, and stirring into slurry; electrolyzing the slurry in a neutral air-exposed environment; switching the polarity of the electrode, and electrolyzing the slurry again in an anoxic environment; wherein the complex is at least one of ethylenediamine tetraacetic acid, N' -ethylenediamine disuccinic acid, nitrilotriacetic acid, sodium or potassium polyphosphate, sodium silicate and potassium silicate. The method realizes the thorough mineralization and stabilization of organic arsenic in the soil based on electrochemical catalytic oxidation, so that the leaching amount of heavy metal arsenic in the repaired soil is low, and the bioavailability of arsenic and plants are obviously weakened.

Description

Remediation method for arsenic-contaminated soil

Technical Field

The invention belongs to the field of soil remediation, and particularly relates to a remediation method of arsenic-contaminated soil.

Background

Aromatic organic arsenics such as phenylarsinic acid and 3-nitro-4-hydroxyphenylarsonic acid have the effects of broad-spectrum sterilization, livestock and poultry growth promotion, laying rate improvement and the like, and are widely used in livestock and poultry breeding industry in China. However, the aromatic organic arsenic is difficult to be metabolized and decomposed in animals, and most of the aromatic organic arsenic is excreted out of the bodies along with feces by drug prototypes. The organic arsenic has high water solubility and is easy to migrate and diffuse into soil, and is converted into inorganic arsenic with stronger migration capability and higher toxicity in the soil due to biological and non-biological effects. As the largest livestock and poultry meat producing country in China, the annual consumption of feed additives such as amino phenylarsonic acid and the like exceeds 1000 tons, so that a large amount of soil is polluted in the breeding industry. In addition, soil problems still exist in the field after the industry for producing the organic arsenic is moved. Meanwhile, most of the organic arsenic-polluted soil is accompanied with the problem of inorganic arsenic pollution. Therefore, the research and development of the related technology for remedying and treating the organic arsenic and inorganic arsenic composite polluted soil are urgently needed.

At present, the effective treatment method of the organic matter and heavy metal combined polluted soil mainly comprises a chemical oxidation method and solidification/stabilization treatment. The chemical oxidation method for treating the organic arsenic-containing polluted soil mainly comprises Fenton reaction, pyrolysis desorption, ozone oxidation and the like, while the aromatic organic arsenic is quickly degraded under the oxidation condition to generate inorganic arsenic with higher toxicity and still exists in the soil; the solidification/stabilization technique is generally applicable to heavy metal soil treatment. The method for stabilizing the composite pollution of organic arsenic and inorganic arsenic containing benzene rings is not mature at present. Therefore, the development of a low-cost and secondary-pollution-free organic arsenic wastewater treatment and disposal technology is needed.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide the method for restoring the soil of the livestock and poultry breeding polluted soil and the chemical and pesticide relocation site containing the organic arsenic/arsenic.

In order to achieve the above object, the present invention provides a method for remediating arsenic-contaminated soil, comprising the steps of:

(1) mixing the arsenic-polluted soil, water and the complex, and stirring into slurry;

(2) electrolyzing the slurry in a neutral air-exposed environment;

(3) switching the polarity of the electrode, and electrolyzing the slurry again in an anoxic environment;

wherein the complex is at least one of ethylenediamine tetraacetic acid, N' -ethylenediamine disuccinic acid, nitrilotriacetic acid, sodium or potassium polyphosphate, sodium silicate and potassium silicate.

Specifically, the polluted soil is added into a reactor containing a certain amount of water and a complex, and is stirred to form slurry; electrolyzing in neutral air-exposed environment to degrade organic arsenic in the system; after the oxidation process is finished, the polarity of the electrode is switched, and electrolysis is carried out again in an anoxic environment, so that stable balance is realized for a certain time, and mud-water separation is realized.

According to the present invention, preferably, the arsenic in the arsenic-contaminated soil is at least one of nitrophenylarsonic acid, 3-nitro-4-hydroxyphenylarsonic acid, p-aminophenylarsonic acid, 3-amino-4-hydroxyphenylarsonic acid, methyl arsenic and inorganic arsenic.

According to the invention, the solid-liquid ratio of the slurry can be adjusted according to requirements, and preferably, the solid-liquid ratio in the slurry is 1:150-1: 300.

According to the invention, the molar concentration of the complex in the slurry is preferably 0.001-100 mol/L. The molar concentration of the complex is adjusted according to the content of the organic arsenic.

According to the invention, preferably, said neutral-aeration environment comprises: the pH value of the slurry is 5-10.

According to the invention, preferably, said neutral-aeration environment comprises: aerating micropores with the introduction speed of 1-100 mL/s; the anoxic environment is to stop aeration. The operation method of the micropore aeration is well known to the person skilled in the art.

According to the invention, preferably, the anode of the electrolysis in the step (2) is iron metal and/or iron alloy, the cathode is at least one of metal and alloy of aluminum, zinc and magnesium, and the current density is 1-100mA/cm²The electrolysis time is 0.1-3 h. The anode can be selected from iron metal or iron alloy or a mixture of iron metal and iron alloy, the cathode can be selected from aluminum metal or zinc metal or magnesium metal, also can be selected from aluminum alloy or zinc alloy or magnesium alloy, and also can be selected from any two or more of the above.

According to the invention, preferably, the anode of the electrolysis in the step (3) is at least one of metals and alloys of aluminum, zinc and magnesium, the cathode is ferrous metal and/or ferrous alloy, and the current density is 50-500mA/cm²The electrolysis time is 0.1-2 h. The anode can be selected from aluminum metal, zinc metal or magnesium metal, also can be selected from aluminum alloy, zinc alloy or magnesium alloy, also can be selected from any two or more of the above mixtures, and the cathode can be selected from iron metal, iron alloy or a mixture of gold and iron alloy.

According to the invention, the electrolysis is preferably controlled by means of a constant current or a constant voltage.

According to the present invention, preferably, the arsenic-contaminated soil has an arsenic content of 0.001 to 100g/kg, as arsenic.

According to the invention, transition metal ions are formed through electrode surface reaction and electrolysis and combined with a complex to generate active oxygen species, and the organic arsenic pollutants in the slurry are thoroughly oxidized and degraded by the active oxygen species formed in situ in an aerobic system; and then various hydroxyl complexes and hydroxides formed in the oxidation process are utilized to perform chemical coordination, condensation and coating reactions with heavy metal arsenic, so that the coating and stabilization treatment of arsenic is realized, and further the stabilization treatment of soil heavy metal is realized.

Compared with the prior art, the invention has the following advantages:

1. the invention can realize the mineralization of organic arsenic through the oxidation process of the electrode and the formation of active free radicals;

2. the specific coordination and encapsulation of various hydroxyl complexes and metal hydroxides formed by electrolysis on inorganic arsenic realize the stabilization treatment of arsenic;

3. the invention uses air as an oxygen source to provide an oxidant, uses cheap electrodes to electrolyze to provide metal ions, not only reduces the sewage treatment cost, but also is green and environment-friendly.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Detailed Description

Preferred embodiments of the present invention will be described in more detail below. While the following describes preferred embodiments of the present invention, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein.

Example 1

Test soil formulations are given in Table 1 below

TABLE 1

The test steps are as follows:

(1) stirring soil and water according to the proportion of 1:200 to prepare slurry, then adding a mixture of 1mol/L of sodium polyphosphate and sodium silicate, and uniformly stirring;

(2) adopting iron alloy material as anode and aluminium alloy material as cathode, constant current density is 50mA/cm². Aerating air into the slurry uniformly stirred in the step (1) at the speed of 50ml/s, and continuously stirring for electrolysis reaction for 2 hours;

(3) switching the electrodes to adjust the constant current density to 150mA/cm²And (3) stopping aeration, and continuously stirring the slurry obtained in the step (2) for electrolysis reaction for 1 hour.

After the electrolysis is finished, after the slurry is stabilized for 48 hours, the removal rates of 3-amino-4-hydroxy phenylarsonic acid and p-amino phenylarsonic acid in the soil are detected to reach 90% and 95% respectively, and the leachable amount of As in the soil after the remediation of the detection result of a toxic leaching experiment (TCLP) is 0.5 mg/L.

Example 2

Test soil formulations are given in Table 2 below

TABLE 2

The test steps are as follows:

(1) stirring soil and water according to the proportion of 1:180 to prepare slurry, then adding a mixture of 4mol/L ethylene diamine tetraacetic acid and sodium silicate, and uniformly stirring;

(2) the scrap iron material is used as an anode, the aluminum material is used as a cathode, and the constant current density is 80mA/cm². Aerating air into the slurry uniformly stirred in the step (1) at the speed of 50ml/s, and continuously stirring for electrolysis reaction for 2.5 h;

(3) switching the electrodes to adjust the constant current density to 200mA/cm²Stopping aeration, and continuously stirring the slurry obtained in the step (2) for electrolysis reaction for 1.5 h.

After the electrolysis is finished, after the slurry is stabilized for 48 hours, the removal rate of 3-nitro-4-hydroxy phenylarsonic acid in the soil is detected to reach 90 percent, the removal rate of sodium arsenate is detected to be 98 percent, and the leachable amount of As in the soil after the remediation is detected to be 0.8mg/L through a toxicity leaching experiment (TCLP).

Example 3

Test soil formulations are given in Table 3 below

TABLE 3

The test steps are as follows:

(1) stirring soil and water according to the proportion of 1:190 to prepare slurry, then adding a mixture of 2mol/L of ethylenediamine tetraacetic acid and sodium silicate, and uniformly stirring;

(2) pure iron is used as an anode, pure aluminum is used as a cathode, and the constant current density is 25mA/cm². Aerating air into the slurry uniformly stirred in the step (1) at the speed of 100ml/s, and continuously stirring for electrolysis reaction for 1 h;

(3) switching the electrodes to adjust the constant current density to 100mA/cm²Stopping aeration, and continuously stirring the slurry obtained in the step (2) for electrolysis reaction for 0.5 h.

After the electrolysis is finished, after the slurry is stabilized for 48 hours, the removal rate of the sodium dimethylarsinate in the soil is detected to reach 95 percent, the removal rate of the sodium arsenate is detected to be 99 percent, and the leachable amount of As in the soil after the remediation is detected to be 0.4mg/L through a toxicity leaching experiment (TCLP).

Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.

Claims

1. The method for restoring the arsenic-polluted soil is characterized by comprising the following steps of:

(2) electrolyzing the slurry in a neutral air-exposed environment;

wherein the complex is at least one of ethylenediamine tetraacetic acid, N' -ethylenediamine disuccinic acid, nitrilotriacetic acid, sodium polyphosphate, potassium polyphosphate, sodium silicate and potassium silicate;

in the step (2), the anode of the electrolysis is iron metal and/or iron alloy, the cathode is at least one of aluminum metal, zinc metal, magnesium metal, aluminum alloy, zinc alloy and magnesium alloy, and the current density is 1-100mA/cm²The electrolysis time is 0.1-3 h;

in the step (3), the anode of electrolysis is at least one of aluminum metal, zinc metal, magnesium metal, aluminum alloy, zinc alloy and magnesium alloy, the cathode is iron metal and/or iron alloy, and the current density is 50-500mA/cm²The electrolysis time is 0.1-2 h.

2. The remediation method of claim 1, wherein the arsenic in the arsenic-contaminated soil is at least one of nitrophenylarsonic acid, 3-nitro-4-hydroxyphenylarsonic acid, p-aminophenylarsonic acid, 3-amino-4-hydroxyphenylarsonic acid, methyl arsenic, and inorganic arsenic.

3. The method for repairing according to claim 1, wherein the molar concentration of the complex in the slurry is 0.001 to 100 mol/L.

4. The repair method of claim 1, wherein the neutral-aeration environment comprises: the pH value of the slurry is 5-10.

5. The repair method of claim 1, wherein the neutral-aeration environment comprises: aerating micropores with the introduction speed of 1-100 mL/s; the anoxic environment is to stop aeration.

6. The repair method according to claim 1, wherein the electrolysis is performed by controlling the electrodes in a constant current or constant voltage manner.

7. The remediation method of claim 1, wherein the arsenic-contaminated soil has an arsenic content of from 0.001 to 100g/kg as arsenic.