KR20150112576A - Effective and eco-friendly Washing Method for metal-contaminated Soil Using Ferric - Google Patents

Effective and eco-friendly Washing Method for metal-contaminated Soil Using Ferric Download PDF

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KR20150112576A
KR20150112576A KR1020140037050A KR20140037050A KR20150112576A KR 20150112576 A KR20150112576 A KR 20150112576A KR 1020140037050 A KR1020140037050 A KR 1020140037050A KR 20140037050 A KR20140037050 A KR 20140037050A KR 20150112576 A KR20150112576 A KR 20150112576A
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South Korea
Prior art keywords
soil
lead
contaminated
heavy metals
washing
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KR1020140037050A
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Korean (ko)
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백기태
유종찬
박상민
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전북대학교산학협력단
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B09DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09CRECLAMATION OF CONTAMINATED SOIL
    • B09C1/00Reclamation of contaminated soil
    • B09C1/02Extraction using liquids, e.g. washing, leaching, flotation
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B09DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09CRECLAMATION OF CONTAMINATED SOIL
    • B09C1/00Reclamation of contaminated soil
    • B09C1/06Reclamation of contaminated soil thermally
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B09DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09CRECLAMATION OF CONTAMINATED SOIL
    • B09C1/00Reclamation of contaminated soil
    • B09C1/08Reclamation of contaminated soil chemically

Abstract

The present invention relates to a method for cleaning soil contaminated with heavy metals using trivalent iron. Conventionally, the soil contaminated with heavy metals is washed with inorganic acid, resulting in dissolution of soil minerals and acidification of the treated soil. The present invention is to provide an effective and environmentally friendly cleaning method of soils contaminated with heavy metals such as lead, copper, cadmium and zinc using less harmful and relatively safe trivalent soils.

Description

[0001] The present invention relates to an effective and eco-friendly washing method for soils contaminated with heavy metals by using ferrous metals,

The present invention relates to an effective and environmentally friendly cleaning method for soil contaminated with heavy metals using trivalent iron. Conventionally, the method of washing soil contaminated with heavy metals including heavy metals with inorganic acid has a problem of causing dissolution of soil minerals and acidification of treated soil. In order to solve this problem, the present invention provides a method for cleaning soil contaminated with heavy metals such as lead by using less harmful and relatively safe trivalent iron in the soil.

The cause of land pollution is the accumulation of organic matter, inorganic salts and heavy metals in the soil more than necessary. Organic and inorganic salts are decomposed by the plants and microorganisms in the soil. However, heavy metals remain in the soil for a long time, And the animal remains and accumulates in the livestock and the body that have consumed the crop as a food, resulting in a serious disease. In addition, since heavy metals are contaminated with surrounding ponds and rivers and can not be used as drinking water, the main cause of soil contamination is heavy metals remaining in the soil.

Many in-situ and ex-situ methods have been applied to purify soil contaminated with heavy metals including lead. In the United States, in situ solidification / stabilization treatment is the most commonly used (G. Dermont et al., Practice Period. Hazard. Toxic Radioact Waste Manage., 12 (3), 2008) , The soil washing process is used more than the solidification / stabilization process because the analysis of heavy metals is based on the extraction of the entire water content,

Soil cleansing technology is composed of physical selection and chemical extraction, and has the advantage of achieving high pollutant removal efficiency in a short time and reducing the volume of the soil (G. Dermont et al., J. Hazard Mater., 152, 1-31, 2008). However, it is difficult to reuse the wastewater treatment cost due to uniformly high concentration of pickling without taking into account the characteristics of heavy metals and soils, and the disadvantage of soil degradation due to major elements constituting soil or dissolution of soil minerals. .

In the case of divalent cationic heavy metals such as lead, copper and zinc except for heavy metals which are bonded with oxygen such as arsenic, chromium and selenium, heavy metals such as hydrochloric acid (HCl) and sulfuric acid (H 2 SO 4 ) When extracted, the soil is acidified by ion exchange with heavy metals (H + ), which are bound to the soil.

In order to solve these problems, researches to prevent the acidification of soil and increase the soil washing efficiency by using a chelating agent having a high binding force with heavy metals such as EDTA have been carried out to a great extent (Lei et al. , Commun. Soil, Sci. Plant Anal., 39 (13-14), 1963-1978, 2008). However, chelating agents differ significantly in their extraction depending on the presence of heavy metals (Alvarez et al., Geoderma, 132, 450-463, 2006), and the chelating agent remained on the treated soil from the soil washing process, . Also, in the case of soil containing a large amount of iron (Fe), since the binding force of Fe-EDTA is much higher than the binding force of heavy metal-EDTA, a large amount of detergent is required and the cost is also a problem. (Voglar and Lestan, Chemosphere, 91, 76-82, 2013) are currently underway.

The gist of the prior art related to the present invention is as follows.

Korean Patent Laid-Open No. 10-2006-0003168 (method for recovering soil contaminated with arsenic and lead) comprises the steps of: inputting an acidic solution containing iron ions into soil contaminated with arsenic and lead; Immobilizing the remaining arsenic and lead which are not immobilized by the above step with lead phosphate and lead phosphate, which are insoluble metal phosphates, and arsenic phosphate, respectively; And CaO to neutralize the pH of the soil treated in the above step.

Korean Patent Laid-Open No. 10-2006-0078779 (Cleaning Method of Heavy Metal Contaminated Soil) is a method of washing heavy metal contaminated soil using 0.2 to 1M NaOH or 0.2 to 1M HCl or 0.01 to 1M citric acid as a washing solution Is washed at least once and the pH of the washing effluent is adjusted to 4 to 13 so that the heavy metal is flocculated or adsorbed on the soil in which the flocs are formed. As a result of the soil washing experiment in which the concentration of citric acid and the shaking ratio were adjusted to remove the lead, the soil was washed with artificially contaminated lead in the non-contaminated soil, The best lead extraction efficiency was obtained when 1: 5 was applied and shaking ratio 1: 4 was applied at 100 mM. However, there is a problem that the possibility of industrial use can not be assessed because the soil is artificially contaminated with lead and only the removal efficiency of lead is considered. Further, there is a problem that the cleaning agent may cause secondary environmental pollution by using inorganic acid, strong base and organic acid. However, the present invention focuses on techniques for purifying soil contaminated with arsenic using Fe (III), both of which differ in technical composition.

Korean Patent Laid-Open No. 10-2011-0071339 (composition for stabilizing lead-contaminated soil or water treatment) is prepared by calcining shellfish shell powder and livestock bone powder having a particle size of 1 to 400 mesh obtained by firing at 800 to 1500 ° C for 1 to 4 hours To a lead-contaminated soil stabilization or water treatment composition.

Korean Patent Laid-Open Publication No. 10201200647807 A discloses a multi-stage soil washing apparatus in order to overcome the drawback that the removal efficiency of heavy metals from the soil is lowered in the soil washing process. In order to supplement the disadvantages of the removal efficiency of heavy metals in the soil washing process, the present invention may cause problems with the apparatus not considering the damage of the treated soil.

The above-described conventional techniques are different from the present invention in the technical structure.

Lead-contaminated soil due to shooting ranges, abandoned abandoned mines and metal smelting activities are becoming increasingly serious social problems in the world. When a soil contaminated with heavy metals of divalent cations such as lead, arsenic, copper and zinc is washed and extracted with an inorganic acid or strong alkaline solution such as hydrochloric acid (HCl) or sulfuric acid (H 2 SO 4 ) There is a problem that the heavy metals bound to soil are acidified or basicized by ion exchange with hydrogen ion (H +). In order to purify soil contaminated with heavy metals including lead, it is pointed out that the dissolution of soil minerals and the acidification of treated soil are major disadvantages among the most widely used soil washing methods in Korea.

Disclosure of Invention Technical Problem [6] The present invention provides a method for cleaning contaminated soil using trivalent iron, which is easier to handle and more environmentally friendly than high-concentration inorganic acid. Trivalent iron has a positive effect on plant growth with Fe (OH) 3 precipitation (Makino et al., Chemosphere, 70, 1035-1043, 2008).

FeCl 3 - > Fe 3 + + 3Cl -

Fe 3 + + 3H 2 O? Fe (OH) 3 (s) + 3H +

The present invention utilizes a soil washing method using a trivalent iron, which is relatively easy and safe to handle than inorganic acids, for purification of soil contaminated with heavy metals, so that it has novelty and inventiveness as compared with the prior art.

In order to solve the problems of the prior art, the present invention can clean contaminated soil using trivalent iron, which is easier to handle and more environmentally friendly than inorganic acid.

Figure 1 compares the removal efficiency of lead according to the concentration of the cleaning agent
Figure 2 shows the ion exchange difference between trivalent and lead ions.
Fig. 3 shows the degree of extraction of Si and Al in soil of hydrochloric acid and iron chloride.
Fig. 4 shows the degree of extraction of Cu, Zn and Cd in soil of hydrochloric acid and iron chloride.

In the present invention, the trivalent iron reacts with water to form Fe (OH) 3 and H + , and the generated H + allows the heavy metals to be extracted from the soil through ion exchange with the cationic heavy metals present in the soil. Fe (OH) 3 has a beneficial effect on plant growth with precipitation.

≪ Example 1 >

Prior to applying the method proposed in the present invention to actual soils contaminated with lead, a high concentration of lead was artificially contaminated with kaolin (kaolin, Al 2 Si 2 O 5 (OH) 4 ) Respectively. The trivalent iron proposed in the present invention was compared with strong inorganic acids such as hydrochloric acid (HCl) and sulfuric acid (H 2 SO 4 ). Pb (NO 3 ) 2 solution of about 10,000 mg / L, which was adjusted to pH 3 ± 0.1 with nitric acid (HNO 3 ) in 500 g of kaolin, was stirred for 24 hours at 100 rpm. After stirring, the mixture was washed with 1 L of distilled water for 24 hours at a rate of 100 rpm in order to minimize the portion that could be very weakly bound to kaolin and affect the extraction efficiency of lead. The mixed slurry was dried at 75 ° C after vacuum filtration and used as a sample for soil washing. Soil washing experiments were carried out with a washing time of 30 minutes and a fixed ratio of 10 g to 30 mL. To examine the effect of the type of cleaning agent, the concentration of the cleaning agent, and the pH of the cleaning agent directly affecting the extraction, .

Figure pat00001

The initial lead concentration was about 6478.8 mg / kg and decreased to about 3102.1 mg / kg after washing with distilled water. At the beginning, more than 80% of lead was present in the ion exchange state, but it was confirmed that the ion exchange state was reduced to about 30% after washing with distilled water. As a result, the extraction efficiency of lead was mainly influenced by pH, and it was confirmed that most of the lead bound to ion exchange was removed. In particular, when sulfuric acid was used, lead was found to precipitate with PbSO 4 (anglesite) minerals at acidic pH range, indicating that extraction efficiency was very low and could not be used as an appropriate detergent. On the other hand, high lead extraction efficiency was obtained in the experimental group using hydrochloric acid or iron (III) chloride, and lead chloride extraction efficiency similar to that of hydrochloric acid was obtained at a relatively low concentration of hydrochloric acid (III). In addition, in the experimental group using iron (III) chloride, it was confirmed that the extraction efficiency of lead was not greatly influenced by pH. 144, 2-10, 2006), the major extractor of cadmium is the chlorine ion (Cl), which is the main extractor of cadmium, in a study using various chlorides to purify paddy soils contaminated with cadmium (Cd) (Makino et al. -) to form a complex of cadmium and chlorine ions. However, the stability constant (Ksp) of the cation heavy metal-chloride ion complex is very low. In the third experiment using 50 mM FeCl 3 , the initial concentration of iron (Ⅲ) in solution (1), the theoretical amount of Fe (OH) 3 by solution pH (②) (③) and the relationship between the actual and theoretical concentration of iron (Ⅲ) ((①-②) -③ = ④) and the concentration of lead in solution after washing (⑤) : ⑤ = 1: 1.02, and it was confirmed that iron and lead were ion-exchanged at a ratio of almost 1: 1. Therefore, it can be said that the main eliminator of lead is due to ion exchange of iron (III) and lead, as well as the formation of complexes of small heavy metal - chloride ions.

<Example 2>: Evaluation of removal efficiency of lead in washing test according to the concentration of cleaning agent in a soil contaminated with actual lead

In Example 1, the efficacy of iron (III) chloride in the extraction of lead from artificially contaminated kaolin was verified and the applicability to actual soils contaminated with lead was evaluated. The initial lead concentration was about 5700 mg / kg and exceeded the limit of 700 mg / kg, which is the criterion for soil contamination in 3 areas. About 60% of the lead in the soil below 75 μm was present in the ion exchange state and about 30% was present in the iron - manganese oxide form. In addition, Quartz, Muscovite, and Anglesite were identified as major minerals by XRD (X-ray Diffraction) analysis. First, the cleaning agent was determined with hydrochloric acid and iron (III) chloride, and the removal efficiency of lead according to the concentration of the cleaning agent was compared.

Figure pat00002

The removal efficiency of lead was significantly lower than that of hydrochloric acid at 50 mM and lead removal efficiency similar to that of 10 mM ferric chloride was obtained. Similar removal efficiencies were obtained when 100 mM of hydrochloric acid and 25 mM of iron (III) chloride were used. The initial pH of 100 mM hydrochloric acid was about 1.24, which was very strong acid, and 25 mM of iron (III) chloride was about 2.07, which was slightly higher than that of hydrochloric acid.

Example 3: Evaluation of removal efficiency of soil contaminated with other heavy metals (cadmium, copper, zinc)

To evaluate the applicability of iron (Ⅲ) to other heavy metals except lead, a separate soil washing experiment was conducted on soils contaminated with heavy metals such as cadmium, copper and zinc by waste landfill. The concentrations of cadmium, copper and zinc in the initial soil were 4.2, 368.6 and 335.4 mg / kg, respectively. Soil washing experiments were carried out according to the concentration of the cleaning agent at constant liquid ratio and time, and the removal efficiency of heavy metals was evaluated according to the type of cleaning agent after the washing experiment.

Figure pat00003

When the extracted heavy metals were compared with the concentration of hydrogen ions (H + ) using hydrochloric acid and iron (III) chloride, the difference could be regarded as a difference by ion exchange of iron (Ⅲ) ion and heavy metal ion. Therefore, as in the preliminary experiment, iron (III) and heavy metal ion exchange can be regarded as the main eliminator of heavy metals using iron (III) chloride rather than small pH.

Additionally, the extracted amounts of the major elements (Si, Al) in the soil were compared by a detergent. In the case of hydrochloric acid, a relatively large amount of Si and Al were extracted at a concentration of 50 mM or more. On the other hand, in the case of iron (III) chloride, the increase of the solution concentration and the extraction of Si and Al were relatively linear I could see what was visible.

In the above example, sulfuric acid can not be a suitable detergent for treating soil contaminated with lead by the washing method, and heavier metals than FeCl 3 can be removed from the soil than HCl. It also shows that FeCl 3 can reduce the degradation of soil quality by reducing the dissolution of minerals constituting the soil rather than HCl.

INDUSTRIAL APPLICABILITY The present invention is industrially applicable because it cleans the contaminated soil by using trivalent iron which is easy to handle and eco-friendly to solve soil pollution.

Claims (3)

  1. 3 How to clean soil contaminated with heavy metals using ferrous metals
  2. The method according to claim 1, wherein the heavy metal is any one selected from the group consisting of Pb, Cu, Zn, and Cd.
  3. The method according to claim 1, wherein the trivalent iron is any one selected from FeCl 3 , Fe (OH) 3 , Fe 2 (SO 4 ) 3 and Fe (NO 3 ) 3 . How to clean
KR1020140037050A 2014-03-28 2014-03-28 Effective and eco-friendly Washing Method for metal-contaminated Soil Using Ferric KR20150112576A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3492187A1 (en) * 2017-12-04 2019-06-05 ENVIT, Environmental Technologies and Engineering Ltd. Curbing toxic emissions from remediated substrate
KR101989536B1 (en) 2018-02-05 2019-06-14 한국광해관리공단 A heavy metal contaminated soil washing method using a washing solution composed of a strongly reducing agent or combination of strongly reducing agent and another agent

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3492187A1 (en) * 2017-12-04 2019-06-05 ENVIT, Environmental Technologies and Engineering Ltd. Curbing toxic emissions from remediated substrate
KR101989536B1 (en) 2018-02-05 2019-06-14 한국광해관리공단 A heavy metal contaminated soil washing method using a washing solution composed of a strongly reducing agent or combination of strongly reducing agent and another agent

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