CN112280560B

CN112280560B - Composite eluting agent and method for eluting soil organic pollutants

Info

Publication number: CN112280560B
Application number: CN202011039417.0A
Authority: CN
Inventors: 周海燕; 邓一荣; 王琳玲; 姜利国; 李韦钰; 周健
Original assignee: GUANGDONG PROVINCIAL ACADEMY OF ENVIRONMENTAL SCIENCE
Current assignee: GUANGDONG PROVINCIAL ACADEMY OF ENVIRONMENTAL SCIENCE
Priority date: 2020-09-28
Filing date: 2020-09-28
Publication date: 2021-12-07
Anticipated expiration: 2040-09-28
Also published as: CN112280560A

Abstract

The invention discloses a composite eluting agent and a method for eluting soil organic pollutants. The composite eluting agent can be applied to repairing organic matter contaminated soil, the composite eluting agent is mixed with the organic matter contaminated soil, and gas is introduced to generate foam. According to the invention, the easily biodegradable green surfactant alkyl glycoside and the sodium dodecyl sulfate are compounded, so that secondary pollution to soil can be avoided, and organic pollutants in the soil can be efficiently removed. In the soil remediation process, gas is introduced into the mixture of the composite eluting agent and the organic matter-contaminated soil to generate foam, so that the organic matter is enriched in the foam, the foam can be separated by the foam separation device, and the amount of eluting waste liquid needing to be subjected to post-treatment can be effectively reduced.

Description

Composite eluting agent and method for eluting soil organic pollutants

Technical Field

The invention belongs to the technical field of environmental remediation, and particularly relates to a composite eluting agent and a method for eluting soil organic pollutants.

Background

The soil leaching remediation technology has the advantages of thorough pollutant removal, rapidness, high efficiency, large treatment capacity and low cost, is a rapid and efficient remediation technology for soil, and has related field engineering application cases. The key point of the soil leaching remediation technology is that a proper leaching agent and a leaching method are selected.

The surfactant has the characteristics of hydrophilicity and lipophilicity, can effectively reduce the interfacial tension of a solution and increase the solubility of pollutants, and is widely researched and applied to the leaching remediation of organic polluted soil. Most of common surfactants are chemical surfactants, such as nonionic surfactants TX-100, Tween 80 and the like, however, the chemical surfactants have certain toxicity, and have residues of different degrees when being applied to soil remediation, so that the leaching efficiency is influenced, secondary pollution is easily caused, and potential threats are brought to human health and ecological environment safety.

The existing eluting agent for soil organic matters is mainly a composite eluting agent, but most of the existing eluting agents adopt chemical surfactants or organic solvents, so that secondary pollution is easily caused. For example, CN110639943A adopts non-negative mixed surfactant aqueous solution as eluent to repair the soil polluted by organic matters, wherein the non-ionic surfactant is one or two of Triton X-100 and OP-10, and the total concentration is 10 g/L; the anion surfactant is SDS, the concentration is 10g/L, the leacheate can degrade organic pollutants under the action of ultraviolet irradiation and ozone. Wherein OP-10 has toxicity to organisms such as fish and the like, is difficult to degrade and causes secondary pollution to the environment. CN108817059A mixes water, organic solvent and oil according to a certain proportion to form a composite microemulsion as an eluent for repairing organic contaminated soil, wherein the organic solvent is one or a mixture of several of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, 1-pentanol, 2-pentanol, 3-pentanol and dimethyl sulfoxide in any proportion, the oil is one of trans-anethole, castor oil, rapeseed oil, mineral oil, cinnamon oil, anise oil, divinylbenzene and unsaturated fatty acid, the organic solvent can cause certain damage to human body when in use, certain danger exists, the removal rate of the eluent to organic matters is below 90%, and the removal efficiency to the organic matters is limited.

In addition, the existing soil leaching method generally mixes the leaching agent with the polluted soil, separates solid from liquid after leaching for a certain time, and then carries out post-treatment on the leaching agent. Generally, in order to obtain a better leaching effect, the liquid-solid ratio of the leaching agent to soil is often higher (10: 1-20: 1), so that the amount of the generated leaching solution is very large, and the treatment amount of the leaching waste solution is large and the cost is high.

Therefore, the existing soil leaching remediation technology has the problems of secondary pollution of the leaching agent to soil, limited organic matter removal efficiency, large treatment amount of the leaching agent and the like, so that the development and design of an efficient and environment-friendly leaching agent and a leaching method for reducing the amount of leaching waste liquid are urgently needed.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art.

Therefore, the first purpose of the invention is to provide a compound eluting agent, which can avoid secondary pollution to soil and can effectively remove organic pollutants in the soil.

The above object of the present invention is achieved by the following means.

A compound eluent comprises alkyl glycoside (APG) and Sodium Dodecyl Sulfate (SDS).

Compared with the prior art, the invention adopts the easily biodegradable green surfactant alkyl glycoside and the sodium dodecyl sulfate for compounding, can avoid secondary pollution to soil and can efficiently remove organic pollutants in the soil. The mass concentration of the alkyl glycoside in the composite eluting agent is 0.1-1.5%, and the mass concentration of the sodium dodecyl sulfate in the composite eluting agent is 0.2-2%.

The number of carbon chains of the alkyl glycoside is 8-16.

The second purpose of the invention is to provide a preparation method of the compound eluting agent, which comprises the following steps: and (3) dissolving alkyl glycoside and lauryl sodium sulfate in water to obtain the composite eluting agent.

The third purpose of the invention is to provide the application of the compound eluting agent in the process of eluting soil organic pollutants.

Specifically, the method for leaching the organic pollutants in the soil comprises the following steps: and (3) leaching the organic pollutant-contaminated soil by using the compound eluting agent, introducing gas to generate foam, enriching the organic pollutants into the foam, and separating the foam enriched with the organic pollutants.

According to the invention, the composite eluent and the organic matter contaminated soil are mixed, stirred and leached, and gas is introduced into the mixture to generate foam, so that the organic matter is enriched in the foam, and the foam can be separated by the foam separation device, so that the separation process of the organic pollutant and the eluent in the eluent is greatly simplified, and compared with the eluent, the foam rich in the organic matter can effectively reduce the amount of the eluent waste liquid needing to be post-treated, and effectively reduce the treatment cost.

The liquid-solid ratio of the composite eluting agent to the organic matter contaminated soil is 2.5: 1-20: 1, and the liquid-solid ratio is a mass ratio.

The organic pollutants are hydrophobic organic matters, including polycyclic aromatic hydrocarbons, organochlorines and other hydrophobic organic matters, such as phenanthrene and Hexachlorobenzene (HCB).

The leaching time is 30 min-24 h.

The gas flow rate is 100-5000 mL/min. At this flow rate, a rich foam can be generated.

The gas is introduced for 10min to 4 h.

The invention can adopt a common method to introduce gas into the mixture of the compound eluting agent and the organic matter contaminated soil to generate foam, for example, the mixture of the compound eluting agent and the organic matter contaminated soil is mixed in a stirring tank, after stirring and leaching for a certain time, an aeration pipe is inserted into the mixture, and air is introduced into the stirring tank by an air compressor.

Compared with the prior art, the invention has the following beneficial effects:

(1) the composite eluting agent of the invention is easy to biodegrade, and avoids secondary pollution.

(2) The composite eluting agent has good separation effect on organic matters.

(3) Gas is introduced to generate bubbles in the leaching process, so that the amount of leaching waste liquid can be reduced while organic pollutants are effectively separated, and the separation process of pollutants and the leaching agent in the leaching solution is simplified.

Drawings

Fig. 1 is a schematic view of an apparatus for washing organic contaminants in soil according to the present invention.

Detailed Description

The composite eluting agent provided by the invention comprises alkyl glycoside and lauryl sodium sulfate and is used for eluting soil organic pollutants. The repairing method comprises the steps of preparing a compound eluent of alkyl glycoside with a certain concentration and a carbon chain number of 8-16 and sodium dodecyl sulfate; respectively adding the organic matter (polycyclic aromatic hydrocarbons, organic chlorine and other hydrophobic organic pollutants) polluted soil and the eluting agent into an eluting stirring tank, starting stirring, and carrying out eluting treatment for 30 min-24 h; an aeration pipe is inserted, air is introduced into the stirring tank by an air compressor (10 min-4 h), the flow rate is controlled by a rotameter to be 100-5000 mL/min, and the upper layer of the system can continuously generate foam. The foam is separated by a foam separating device and then enters a foam collector. The washing process is carried out using the apparatus shown in FIG. 1. In fig. 1, 1 denotes a leaching agitation tank; 2, an aeration pipe through which air compressed by an air compressor (not shown) is introduced into the mixture; 3 denotes a foam collector; 4 denotes a foam separating device; 5 is a sample injection hopper used for adding the organic matter contaminated soil into the leaching agitator tank; and 6, a dosing port for adding the composite eluting agent into the eluting stirring tank. The lower right corner of fig. 1 shows the longitudinal section of the leaching agitator tank, showing that the aeration pipes are evenly distributed on the inner wall of the leaching agitator tank.

The pollutant foam with higher concentration is collected for post-treatment, so that the amount of the washing waste liquid needing post-treatment can be greatly reduced, and the residual soil slurry can be repeatedly washed for multiple times according to actual needs. And when the leaching is repeated, adding the compound leaching agent into the stirring tank according to the foam collection amount, and repeating the operation for 2-3 times.

The technical solution of the present invention is further described below with reference to specific examples.

Example 1

The alkyl glycoside (APG0814) and Sodium Dodecyl Sulfate (SDS) with the mass ratio of 4:1 are dissolved in water to prepare the compound eluent with the mass concentration of 1% (the total mass concentration of APG0814 and SDS).

And adding the composite eluting agent and the phenanthrene-polluted soil (the concentration of the phenanthrene is about 62.4mg/kg) into an eluting stirring tank according to the liquid-solid ratio of 20:1, starting stirring, and eluting for 4 hours. And after rinsing for 4h, inserting an aeration pipe, introducing air into the stirring tank by using an air compressor while stirring (for 2h), controlling the flow rate by using a rotameter to be 1000mL/min, and continuously generating foam in a mixed system. The foam is separated by a foam separating device and then enters a foam collector. And carrying out solid-liquid separation on the residual soil slurry through standing and precipitation to obtain leacheate and the repaired soil.

The content of phenanthrene (or phenanthrene removal rate) in the leacheate and the repaired soil is detected, and the results are shown in table 1.

Example 2

APG0814 and SDS in a mass ratio of 4:1 are dissolved in water to prepare the compound eluent with a mass concentration of 1% (the total mass concentration of the APG0814 and the SDS).

Adding the composite eluting agent and Hexachlorobenzene (HCB) polluted soil (HCB concentration is about 10mg/kg) into an eluting stirring tank according to the liquid-solid ratio of 20:1, starting stirring, and eluting for three times, wherein each time lasts for 1 h. After each time of leaching and stirring for 1h, an aeration pipe is inserted, and air is introduced into the system while stirring (the gas flow rate is 2000mL/min), so that a large amount of foam is generated. After being separated by a foam separation device, the mixture enters a foam collector. After aeration for 0.5h, the foam amount gradually decreased. The eluent was replenished and the elution was repeated three times. The whole operation process of the embodiment takes about 4.5 hours. And carrying out solid-liquid separation on the residual soil slurry through standing and precipitation to obtain leacheate and the repaired soil.

The contents of HCB (or HCB removal rates) in the leacheate and the soil after remediation were measured, and the results are shown in table 1.

Comparative example 1

This comparative example is similar to example 1, except that no air was passed to generate the foam.

Namely, the soil leaching remediation method of the comparative example is as follows: and adding the composite eluting agent and the phenanthrene polluted soil into an eluting stirring tank according to the liquid-solid ratio of 20:1, starting stirring, and eluting for 4 hours.

Comparative example 2

This comparative example is similar to example 1, with the only difference that: the surfactant in the eluent used included only APG0814, i.e., the eluent of this comparative example was APG0814 eluent at a mass concentration of 1%.

Comparative example 3

This comparative example is similar to example 1, with the only difference that: the surfactant in the eluting agent used included only SDS, that is, the eluting agent of the present comparative example was an SDS eluting agent having a mass concentration of 1%.

TABLE 1 removal rate of organic matter in soil and concentration of organic matter in leacheate

As can be seen from the detection results in table 1, in examples 1 and 2, the composite eluting agent compounded by APG0814 and SDS is used for eluting the organic matter contaminated soil, and air is introduced during the eluting process to generate foam, so that the hydrophobic organic matters phenanthrene and HCB in the soil can be effectively removed, and the removal rate can be as high as 86.9% and 93.3%; and the organic matter content in the leacheate is low, such that the phenanthrene content in the leacheate is reduced by 88.2% compared with that in comparative example 1 in example 1, which shows that the organic matter can be transferred to the foam by introducing air to generate the foam, so that the organic matter content in the leacheate is reduced. Moreover, if the single-component eluent of APG0814 or SDS is adopted independently, the removal rate of organic matters in soil is obviously reduced, which shows that the removal rate of the organic matters in the soil can be effectively improved by compounding the APG0814 and the SDS.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims

1. A method for leaching soil organic pollutants is characterized in that: the method comprises the following steps: leaching the organic matter contaminated soil by using the composite eluting agent, and introducing gas to generate foam so as to enrich the organic pollutants in the foam; then separating the foam enriched with organic pollutants;

the composite eluting agent comprises alkyl glycoside and lauryl sodium sulfate, wherein the mass concentration of the alkyl glycoside in the composite eluting agent is 0.1-1.5%, and the mass concentration of the lauryl sodium sulfate in the composite eluting agent is 0.2-2%;

the mass ratio of the composite eluting agent to the organic matter contaminated soil is 2.5: 1-20: 1;

the gas flow rate is 100-5000 mL/min, and the gas introduction time is 10 min-4 h.

2. The method of leaching organic contaminants from soil according to claim 1, wherein: the number of carbon chains of the alkyl glycoside is 8-16.

3. The method of leaching organic contaminants from soil according to claim 1, wherein: the organic pollutants are hydrophobic organic matters.