CN106001093B

CN106001093B - Remediation method for heavy metal pollution of alkaline soil

Info

Publication number: CN106001093B
Application number: CN201610564380.0A
Authority: CN
Inventors: 何曦; 刘胜强
Original assignee: Aerospace Kaitian Environmental Technology Co Ltd
Current assignee: Aerospace Kaitian Environmental Technology Co Ltd
Priority date: 2016-07-18
Filing date: 2016-07-18
Publication date: 2020-03-27
Anticipated expiration: 2036-07-18
Also published as: CN106001093A

Abstract

The invention discloses a method for remedying heavy metal pollution of alkaline soil, which adopts a structural formula of Si (OR)₄Dissolving the siloxane substances in an acid solution of alcohol or ether to be used as a remediation reagent, mixing the remediation reagent with alkaline soil, reacting, and then adding water for further reaction; it is composed ofWherein R represents one or more of methyl, ethyl or propyl. The remediation method disclosed by the invention is low in cost, simple, convenient and efficient in heavy metal pollution of alkaline soil, and the remediated heavy metal can be stably trapped in the soil for a long time.

Description

Remediation method for heavy metal pollution of alkaline soil

Technical Field

The invention belongs to the field of soil heavy metal pollution remediation, and particularly relates to a method for remediating alkaline soil heavy metal pollution.

Background

In 17 th 4 th month in 2014, the ministry of environmental protection and the ministry of national soil resources jointly published the survey bulletin on the soil pollution status in China, and the society draws wide attention to the soil pollution status in China. According to survey bulletin, the total exceeding rate of national soil is 16.1%, wherein the proportion of slightly, moderately and severely polluted sites is 11.2%, 2.3%, 1.5% and 1.1%, respectively. From the pollution distribution condition, the soil pollution in south is heavier than that in north, and the overproof range of heavy metals in soil in southwest and southwest areas is larger. Generally, the national soil environment condition is not optimistic, the soil pollution in some regions is very serious, and the soil remediation work is not slow at all.

Common soil heavy metal pollution remediation methods include a leaching method, a phytoremediation method, a microbial remediation method, a chemical extraction method, a chemical oxidation method, a stabilization method and the like. The method can obtain a certain repairing effect and is a mode aiming at the characteristics of the heavy metal. Heavy metal ions are stripped from the surface of basic particles of the soil and then enriched, removed or fixed, but the methods have the problems of large repairing workload, high cost, non-lasting repairing effect and the like on the whole.

Disclosure of Invention

In practice of treating a large amount of soil, the inventor makes a large number of attempts to stabilize and solidify heavy metals in the soil according to the characteristics of different heavy metals, uses a large number of different heavy metal stabilizing and solidifying agents and combinations, but the effect is not satisfactory, and on the premise that the inventor changes the idea, and after a large number of deep researches are made on the soil property and the like, the method for repairing the heavy metal pollution of the alkaline soil is provided, wherein the method is low in cost, simple, and capable of efficiently coating and fixing the heavy metals for a long time.

The purpose of the invention can be realized by the following technical scheme: a method for remedying heavy metal pollution of alkaline soil, which is a method for remedying heavy metal pollution of alkaline soil and takes the structural formula as Si (OR)₄Dissolving the siloxane substances in an acid solution of alcohol or ether to be used as a repair reagent, mixing the repair reagent with alkaline soil, reacting, and then adding water for further reaction;

wherein, R represents one or more of methyl, ethyl or propyl.

The invention further comprises the following preferred technical scheme:

in a preferred embodiment, the siloxane is tetraethoxysilane or tetramethoxysilane.

In a preferred scheme, the mass ratio of the remediation agent to the alkaline soil is 1:20-1: 200.

In a preferable scheme, the water is one or more of rainwater, tap water, well water, lake water, pond water or underground water with the pH of 6-8.

In a preferred scheme, the mass ratio of the water to the alkaline soil is 1:20-1: 200.

In a preferable scheme, the siloxane substances are dissolved in an acid solution of alcohol or ether, stirred for 5-240min, and then uniformly mixed with alkaline soil for reaction.

In a preferred scheme, the mass ratio of the siloxane substances to the alcohol or ether is 1:1-1: 10.

In a preferred embodiment, the mass ratio of the alcohol or ether to the acid solution is 1:1 to 1: 20.

In a preferred embodiment, the acid solution is selected from one of aqueous solutions of hydrochloric acid, nitric acid or sulfuric acid, wherein the mass ratio of acid to water in the acid solution is 1:10-1: 40.

In a preferred embodiment, the alcohol is ethanol or methanol, and the ether is diethyl ether.

The soil mainly comprises four major parts, namely basic particles (sand grains and soil colloidal particles), organic matters, microorganisms and water, wherein the basic particles account for more than 95% of the dry weight of the soil. The surface of the soil basic particle is enriched with a large amount of ions (hydrogen ions are enriched in an acidic environment, hydroxide ions are enriched in an alkaline environment), and the soil basic particle has strong adsorption and fixation effects (exchange adsorption in the acidic environment and electrostatic adsorption in the alkaline environment) on heavy metal ions in a water solution. Moreover, the ions on the surface of the elementary particles can provide conditions for forming a 'cage' for fixing heavy metal ions for a long time.

The repair reagent of the invention is subjected to acid catalysis reaction under the action of acid, because of the supply of alkylUnder the action of electrons (namely acting on O of Si-O-R), hydrogen ions can selectively attack oxygen (-O-) rich in electrons, and siloxane can undergo hydrolysis reaction under the catalysis of the hydrogen ions to obtain Si (OH)₄A monomer. The main component of the soil basic particle is SiO₂，Si(OH)₄To SiO₂Having affinity to Si (OH) under the action of hydroxide ion₄Monomers and monomers, Si (OH)₄Monomer and SiO₂Polycondensation reaction occurs and a cross-linked network structure is formed, so that heavy metal ions are trapped in soil. The method disclosed by the invention makes full use of the soil characteristics, provides a method for remediating heavy metal pollution of alkaline soil, which is lower in cost, simple, convenient and efficient than the traditional remediation method, and the remediated heavy metal can be stably trapped in the soil for a long time.

The invention is essentially different from the landfill method, the cement curing method and the glass curing method:

1. the landfill method is to transfer the polluted soil to a structure with anti-seepage performance for sealing, and the sealed soil cannot be utilized.

2. The cement solidification method is to mix the polluted soil with cement, and form a stable block structure after drying, so as to fix heavy metals in the block structure, and the solidified soil cannot be utilized.

3. The glass solidification method is to utilize high temperature to remove SiO in soil₂The heavy metals are fixed in the glass phase formed by melting, and the solidified soil cannot be utilized.

The method provided by the invention aims at the surface treatment of soil basic particles, and achieves the purpose of stably fixing heavy metals for a long time by forming a cage structure on the surface of the soil basic particles, and most importantly, the method hardly influences organic matters and microorganisms in the soil and does not influence the utilization of the soil.

The invention breaks through the thought restriction of the current soil remediation technology, explores the treatment method from the soil characteristics, provides a low-cost, simple, convenient and efficient remediation method for heavy metal pollution of alkaline soil, and the remediated heavy metal can be stably trapped in the soil for a long time.

The method can reduce the mobility and bioavailability of heavy metals in the soil, effectively repair the polluted soil, and is a safe, harmless and effective method for repairing the heavy metal polluted soil.

The invention provides a brand-new and efficient path for soil heavy metal treatment.

Detailed Description

The following are specific examples of the present invention, but the present invention is not limited to these examples.

Example 1

The repair comprises the following steps:

1. dissolving tetraethoxysilane in a nitric acid solution of ethanol and stirring for 30min to obtain a repairing reagent, wherein the mass ratio of tetraethoxysilane to ethanol is 1:5, the mass ratio of ethanol to nitric acid is 1:5, and the mass ratio of nitric acid to water is 1: 20;

2. uniformly mixing a remediation reagent with alkaline soil (the alkaline soil is dispersed in ultrapure water according to a solid-to-liquid ratio of 1:1, and the pH is measured to be 8.9) to ensure that the remediation reagent is fully contacted with basic particles of the soil, wherein the mass ratio of the remediation reagent to the soil is 1: 40;

3. uniformly mixing lake water with the pH value of 7 with the soil treated by the remediation reagent to ensure that the lake water is fully contacted with the remediation reagent and the remediation of heavy metal pollution is completed, wherein the mass ratio of the lake water to the soil is 1: 30;

the result shows that the total Cd content in the soil after the remediation is consistent with that in the soil without the remediation, and the exchange state Cd in the soil after the remediation is reduced from 1.2mg/kg to 0.1 mg/kg;

comparative example 1

When step 3 of example 1 is omitted and only steps 1 and 2 of example 1 are carried out, the total Cd in the soil is unchanged, but the state of exchange Cd is reduced from 1.2mg/kg to 0.6 mg/kg.

Example 2

1. Dissolving tetramethoxysilane in a hydrochloric acid solution of diethyl ether and stirring for 60min to form a repair reagent, wherein the mass ratio of the tetramethoxysilane to the diethyl ether is 1:5, the mass ratio of the diethyl ether to the hydrochloric acid solution is 1:5, and the mass ratio of the hydrochloric acid to water is 1: 20;

3. uniformly mixing lake water with the pH value of 7 with the soil treated by the remediation reagent to ensure that the lake water is fully contacted with the remediation reagent and the remediation of heavy metal pollution is completed, wherein the mass ratio of the lake water to the soil is 1: 50;

the result shows that the total Cd content in the soil after the remediation is consistent with that in the soil without the remediation, and the exchange state Cd in the soil after the remediation is reduced from 1.2mg/kg to 0.12 mg/kg;

comparative example 2

When step 3 of example 2 is omitted and only step 1 and step 2 of example 2 are carried out, the total Cd in the soil is unchanged, but the exchange state Cd is reduced from 1.2mg/kg to 0.55 mg/kg.

The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or scope of the invention as defined in the appended claims.

Claims

1. A method for remedying heavy metal pollution of alkaline soil is characterized in that siloxane substances with the structural formula of Si (OR) 4 are dissolved in an acid solution of alcohol or ether to be used as a remediation reagent, mixed with the alkaline soil for reaction, and then added with water for further reaction; forming a cross-linked network structure, and further trapping heavy metal ions in the soil; wherein R represents one or more of methyl, ethyl or propyl, the mass ratio of the alcohol or ether to the acid solution is 1:1-1:20, the alcohol is ethanol or methanol, and the ether is diethyl ether; the siloxane substance is tetraethoxysilane or tetramethoxysilane.

2. The remediation method of claim 1, wherein the mass ratio of remediation agent to alkaline soil is from 1:20 to 1: 200.

3. The method of remediating as defined in claim 1, wherein the water is one or more of rainwater, tap water, lake water, pond water, or groundwater having a pH of 6-8.

4. The remediation method of claim 1 or 3, wherein the water to alkaline soil mass ratio is from 1:20 to 1: 200.

5. The remediation method of claim 1 wherein the siloxane-based material is dissolved in an alcohol or ether acid solution, stirred for 5-240min, and then mixed uniformly with the alkaline soil for reaction.

6. The repair method according to claim 5, wherein the mass ratio of the siloxane-based substance to the alcohol or ether is 1:1 to 1: 10.

7. The repair method according to claim 5 or 6, wherein the acid solution is one selected from aqueous solutions of hydrochloric acid, nitric acid or sulfuric acid, and a mass ratio of acid to water in the acid solution is 1:10 to 1: 40.