CN111420981A

CN111420981A - Method for removing heavy metals in polluted soil for ecological garden treatment

Info

Publication number: CN111420981A
Application number: CN202010272231.3A
Authority: CN
Inventors: 张勇伟; 毛正平; 李婷婷; 洪隽琰; 刘蕾
Original assignee: Shanghai Landscape Group Co ltd
Current assignee: Shanghai Landscape Group Co ltd
Priority date: 2020-04-09
Filing date: 2020-04-09
Publication date: 2020-07-17
Anticipated expiration: 2040-04-09
Also published as: CN111420981B

Abstract

The invention provides a method for removing heavy metals in polluted soil for ecological garden treatment, which uses leacheate containing 2-oxo-1, 3-imidazoline bisdithioformic acid as an active ingredient and is treated by microwaves. The leacheate disclosed by the invention can remove heavy metals in polluted soil and can avoid the loss of soil nutrient elements. The 1, 3-bis (sodium dithioformate) -2-oxo-imidazoline is selected as an eluent, has strong adsorption capacity on heavy metals, but has weak combination on metals such as Mg, Ca and the like.

Description

Method for removing heavy metals in polluted soil for ecological garden treatment

Technical Field

The invention belongs to the technical field of treatment of heavy metals in garden soil, and particularly relates to a method for removing heavy metals in polluted soil for ecological garden treatment.

Background

The current statistical data show that national soil pollution is serious, while the soil pollution is mainly inorganic pollution, wherein the heavy metal pollution accounts for more than 80%. The overproof rates of cadmium, mercury, arsenic and copper in the soil are respectively 7.0%, 1.6%, 2.7% and 2.1%. In ecological garden construction, in order to ensure normal growth of plants and human health, contaminated soil needs to be treated to remove heavy metals and other pollutants in the contaminated soil.

The physical remediation comprises the traditional methods of soil dressing, soil discharging, soil replacement and the like, an electrokinetic method, an electrothermal remediation technology, a vitrification technology, a frozen soil technology and the like. The chemical remediation is to select a proper chemical remediation agent according to the soil property and the heavy metal type and remove the heavy metal in the soil by utilizing the actions of desorption activation, oxidation reduction, chelation dissolution and the like. Bioremediation is the absorption, fixation, extraction and other actions of heavy metals by plants or microorganisms. The leaching method has high efficiency, can fundamentally remove heavy metals, and is the key to the selection of the leaching agent.

The eluting agent mainly comprises inorganic acid, inorganic salt, surfactant, chelating agent and the like, wherein the chelating agent can be well combined with heavy metal so as to effectively remove the heavy metal. Common chelating agents are ethylenediaminetetraacetic acid (EDTA), ethylenediamine disuccinic acid (EDDS), and the like. However, the chelating agent used at present can remove heavy metal ions and chelate other nutrients in the soil, such as Mg, Ca, etc., which results in nutrient loss. Therefore, there is a need to develop new eluting agents of chelating agents to minimize the loss of nutrients while removing heavy metals.

Through a large number of experiments, the known chelating agent is screened and modified, and the 2-oxo-1, 3-imidazoline bisdithioformic acid is found to be capable of acting with various heavy metal ions, but is weaker in combination with metals such as Mg, Ca and the like, and can be used as an eluent for soil heavy metals. So far, no research report of the 2-oxo-1, 3-imidazoline bisdithioformic acid for treating the soil heavy metal is found. In addition, the existing leaching method mostly adopts a mode of stirring the leacheate and the polluted soil, but the action of the leacheate and the heavy metal in the mode is not enough, and a new leaching method needs to be developed.

Disclosure of Invention

The invention aims to provide a method for removing heavy metals in polluted soil for ecological garden treatment and an improved leaching method.

The invention is realized by the following technical scheme:

a soil heavy metal leacheate comprises 2-oxo-1, 3-imidazoline bisdithioformic acid, alkali metal hydroxide and water, wherein the proportions of the 2-oxo-1, 3-imidazoline bisdithioformic acid and the alkali metal hydroxide are respectively 4-15% and 1-3% in parts by weight.

Preferably, the leacheate is added with 0.5 to 2 mass percent of reducing substances, such as sodium ascorbate, citric acid and the like, which can be used for reducing high-valence heavy metals possibly existing into low-valence easy-chelating forms, such as reducing hexavalent Cr into tetravalent Cr.

The active component of the leacheate adopted by the invention is 2-oxo-1, 3-imidazoline bisdithioformic acid, and the chemical structure is as follows:

wherein, a plurality of chelating sites such as thiocarbonyl, N atom, carbonyl and the like exist simultaneously, and a plurality of chelating modes are endowed to the chelating agent, so that the complexing effect on transition metal ions such as Pb, Cu and the like is increased, and the binding effect on alkaline earth metal is very weak. Therefore, the leacheate which takes the 2-oxo-1, 3-imidazoline bisdithioformic acid as the active component can leach heavy metals in the polluted soil and avoid the loss of soil nutrient elements.

A method for removing heavy metals in polluted soil for ecological garden improvement comprises the following steps:

an eluent containing 2-oxo-1, 3-imidazoline bisdithioformic acid as an active ingredient was used, and treated with microwave.

Preferably, the frequency of the microwave is 500-1000W, and the treatment time is 3-30 minutes.

The invention has the beneficial effects that:

the leacheate disclosed by the invention can remove heavy metals in polluted soil and can avoid the loss of soil nutrient elements. The 1, 3-bis (sodium dithioformate) -2-oxo-imidazoline is selected as an eluent, has strong adsorption capacity on heavy metals, but has weak combination on metals such as Mg, Ca and the like.

Detailed Description

The technical solutions in the present invention will be clearly and completely described below with reference to specific embodiments, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the scope of protection of the present patent.

Example 1: preparation of leacheate

Dissolving 8g of 2-oxo-1, 3-imidazoline bisdithioformic acid in 92g of NaOH solution with the mass concentration of 2%, stirring for 1.5 hours, and obtaining the eluent after complete dissolution.

Example 2: soil remediation

Selecting polluted soil near a chemical plant, drying the soil, crushing the soil, and analyzing the content of metal in the soil by an atomic absorption spectrophotometer to obtain the following result:

the heavy metal content is: pb 189.36Mg/Kg, Cu 316.24Mg/Kg, 6-valent Cr 72.38Mg/Kg, and the nutrient elements Mg 168.26Mg/Kg and Ca 76.24 Mg/Kg.

The dried soil is further ground into fine powder and sieved by a 40-mesh sieve, 20 g of the powder is weighed and placed into a reaction bottle, the leacheate 300m L of the embodiment 1 is respectively added, the mixture is slightly stirred and is subjected to 800W microwave treatment for 10 minutes, the mixture is transferred into a centrifuge tube and subjected to centrifugal treatment, the treated soil is separated from the leacheate, the supernatant liquid is discarded after centrifugation, the lower soil is dried, and the content of metal elements in the lower soil is tested, and the results are shown as follows:

the contents (mg/Kg) of metals in the soil after the leacheate is combined with the microwave treatment are as follows in sequence: 42.68, 92.38, 18.35, 147.52, 69.76.

Therefore, the leaching solution of the invention has high removal efficiency on heavy metals, and the leaching method combined with microwave treatment has high efficiency and improves removal efficiency.

Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that various changes in the embodiments and/or modifications of the invention can be made, and equivalents and modifications of some features of the invention can be made without departing from the spirit and scope of the invention.

Claims

1. A method for removing heavy metals in polluted soil for ecological garden management is characterized by comprising the following steps: an eluent containing 2-oxo-1, 3-imidazoline bisdithioformic acid as an active ingredient was used, and treated with microwave.

2. The method for removing heavy metals from contaminated soil for ecological landscape architecture improvement, according to claim 1, wherein: the rinse solution also contains an alkali metal hydroxide and water.

3. The method for removing heavy metals from contaminated soil for ecological landscape management as set forth in any one of claims 1 to 2, wherein: the leacheate also contains a reducing substance.

4. The method for removing heavy metals from contaminated soil for ecological landscape architecture improvement, according to claim 3, wherein: the reducing substance is sodium ascorbate, citric acid, etc.

5. The method for removing heavy metals from contaminated soil for ecological landscape management as set forth in any one of claims 1 to 4, wherein: the 2-oxo-1, 3-imidazoline bisdithioformic acid in the leacheate accounts for 4-15% of the total leacheate by weight.

6. The method for removing heavy metals from contaminated soil for ecological landscape management as set forth in any one of claims 1 to 5, wherein: the frequency of the microwave is 500-1000W, and the treatment time is 3-30 minutes.