KR20160091477A - Method for stabilization of heavy metals in contaminated marine sediment using bentonite - Google Patents

Abstract

Disclosed is a method for stabilizing heavy metals in contaminated marine sediment by using bentonite, which can fix and stabilize heavy metals included in contaminated marine sediment by using bentonite as a coating material of the contaminated marine sediment. The method for stabilizing heavy metals in contaminated marine sediment by using bentonite comprises the steps of: supplying bentonite onto contaminated marine sediment by using equipment capable of scattering bentonite in the water; and coating the contaminated marine sediment with the bentonite, and fixing and stabilizing heavy metals in the contaminated marine sediment. The fixing and stabilizing of the heavy metals are performed in such a manner that the bentonite sinks onto the contaminated marine sediment and forms a blocking layer to thus block diffusion and elusion of the heavy metals and hydrates of the heavy metals are formed and deposited inside the contaminated marine sediment due to an increase in pH inside the contaminated marine sediment resulting from the bentonite.

Description

METHODS FOR STABILIZING HEAVY METALS IN SALTED PLANTS WITH BENTONITE

The present invention relates to a method for stabilizing heavy metals in marine polluted sediments by bentonite, and more particularly, to a method for stabilizing heavy metals in marine contaminated sediments using bentonite as a covering material for marine polluted sediments, To a method for stabilizing heavy metals in marine polluted sediments.

Recently, interest in the coastal environment has been increasing due to the increase in leisure activity in the coastal area and the increase of production of inland water aquaculture and aquatic products. Due to industrial development and active human activity, various types of heavy metals have been released into the water system, These are ultimately imported into the coastal waters and submarine sediments, accumulating and accumulating pollutants in quantitative and qualitative terms. The pollution of heavy metals in the coastal area has the potential to be dangerous not only to the ecosystem environment that is formed but also to humans, and the necessity of treatment and elimination has been emphasized (EPA, US Environmental Protection Agency 2005), "Contaminated sediment remediation guidance for hazardous waste sites, http://www.epa.gov/superfund/health/conmedia/sediment/guidance.htm").

In Korea, as a method of disposal of coastal sediments, dredging and ocean dumping have been used until recently. However, with the enactment of the London Protocol in 2012, marine dumping of polluted sediments is virtually banned, and instead of disposing of marine dumping, coastal dump sites are being used, but there are problems such as difficulty in securing dump sites. In developed countries, in-situ capping is used as a solution to dredging, but there is little attempt in Korea. The field coating method is one of the active treatment methods of contaminated sediments. It is known as an environmentally friendly technique which has advantages of low cost and has less effect of secondary pollution.

In order to apply such a field coating method to domestic applications, it is necessary to solve some problems such as the absence of a covering material. In other words, in the past, sand has been used as a main covering material, and problems such as environmental destruction of a sand collection place due to abuse of sand have been pointed out. Therefore, research and application of a new reactive covering material have been actively conducted. In order to successfully realize the field coating method, development of a coating material having excellent economical efficiency along with the development of coating technique is urgently required.

Bentonite (mineralogical name: montmorillonite), which is used as a covering material, was first discovered in France, and mines are widely distributed in Gyeongbuk province in Korea. Since bentonite is a viscous mineral, it has properties such as high viscosity, broad specific surface area, swelling property, adsorptivity and ion exchange property (Grim, 1976), and it is used in waterproofing agent, cosmetics, paint, casting, And so on. Particularly, it has a relatively large specific surface area and has a high ion exchange capacity, and thus has been used as a waterproofing material for preventing contamination of heavy metals and organic matter, and for preventing pollution of soil or ground water around a landfill (Jaynes and Boy, 1991). (2000) reported that the adsorption of heavy metal on the surface of austenitic stainless steels has a negative effect on the adsorption of heavy metals. A study on the stabilization / immobilization of heavy metals using bentonite has been reported (Katsioti et al., 2008), which has been reported on the stabilization / immobilization of heavy metals in activated sludge contaminated with heavy metals (Katsioti et al., 2008) There are no studies that reflect the contaminated condition of heavy metals. Therefore, it is required to develop a method for effectively stabilizing heavy metals in polluted sediments using marine contaminated sediments contaminated with mixed heavy metals, using natural mineral bentonite.

[1] Ahmaruzzaman, M. (2011), "Industrial wasts as low-cost potential adsorbents for the treatment of wastewater laden with heavy metals", Adv. Colloid Interface Sci., Vol. 166, pp. 36-59. [2] Bacon, J. R. and Davidson, C. M. (2008), "Is there a future for sequential chemical extraction?", Analyst, vol. 133, pp. 25-46. [3] Batjaral, T., Otgonjargal, E., Baek, K. and Yang, JS (2010), "Assessment of metals contamination of soils in Ulaanbaatar, Mongolia, J. Hazard. -876. [4] Benefield, L. D. and Morgan, J. M. (1990), Chemical precipitation, Water Quality and Treatment, Pontius, F.W. McGraw-Hill Inc., New York. [5] Bruell, R., Nikolaidis, N. P. and Long, R. P. (1999), "Evaluation of remedial alternatives of lead from shooting range soil ", Environ. Engin. Sci., Vol. 16, pp. 403-414. [6] Chen, G. Z. and Fray, D. J. (2001), "Cathodic refining in molten salts: Removal of oxygen, sulfur and selenium from static and flowing molten copper", J. Appl. Electrochem., Vol. 31, pp. 155-164. [7] Garcia, D. (1995), Modeling of Pb (II) absorption by activated carbon, MS thesis, Dept of Civ. and Environ. Eng., West virgina Univ., Morgontown. [8] Goh, E. O., Lee, J. O., Cho, W. J., Hyun, J. H., Kang, H. and Chun, K. S. (2000), "Adsorption characteristics of copper ion onto a bentonite", J. Kor. Soc. Environ. Eng., Vol. 22, pp. 83-89. [9] Goudie (1981), Geomophological techniques, Allen and Unwin, London. [10] Grim, R.E. (1976), Clay mineralogy, McGraw-Hill Book Company, pp. 79-195. [11] Hatje, V., Payne, TE, Hill, DM, McOrist, G., Birch, GF and Sztmczak, R. (2003), "Kinetics of trace element uptake and release in particles in estuarine waters: , salinity, and particle loading ", Environ. Inter., Vol. 29, pp. 619-629. [12] Jaynes, W. F. and Boyd, S. A. (1991), "Clay mineral type and organic compound sorption by hexadecyltrimethylammonium-exchanged clays", Soil. Sci. Soc. Am. J., Vol. 55, pp. 43-48. [13] Kang, H., Park, S. M., Jang, Y. D. and Kim, J. J. (2008), "Studies on adsorption of heavy metals with zeolite and bentonite", J. Miner. Soc. Korea, Vol. 21, pp. 45-56. [14] Katsioti, M., Katsiotis, N., Rouni, G., Bakirtzis, D. and Loizidou, M. (2008), "The effect of bentonite / cement mortar for the stabilization / solidification of sewage sludge containing heavy metals , Cem. Conc. Composites, Vol. 30, pp. 1013-1019. [15] Kim, J. D. (2008), "Extraction Characteristics of Heavy Metals for Soil Washing of Mine Tails According to Contaminated Soil", J. Kor. Ind. Eng. Chem., Vol. 19, pp. 98-104. [16] Korea Mineral Resources Information Service (2014), http://www.kores.net/main.do [17] Kumpiene, J., Lagerkvist, A. and Maurice, C. (2008), "Stabilization of As, Cr, Cu, Pb and Zn in soil using amendments A review," Waste Manage., Vol. 28, pp. 215-225. [18] Levy, D. B., Barbarich, K. A., Siemer, E. G. and Sommers, L. E. (1992), "Distribution and partitioning of trace metals in contaminated soils near leadville, Colorado", J. Environ. Qual., Vol. 21, pp. 185-195. "Adsorption of Co2 + and Zn2 + ions on hydrous Fe (III), Sn (IV), and Fe (III) / Sn (IV) oxides" J. Coll. Inter. Sci., Vol. 184, pp. 31-43. [20] Park, G. O. and Jun, S. H. (2008), "Chemical Forms and Release Potential of Heavy Metals from the Lime Sediments", Korean J. Limnol., Vol. 41, pp. 166-173. [21] Port and Airport Research Institute (PARI) (2010), "Management of hazardous chemicals in port and harbor sediment", Technical note of the Port and Airport Research Institute (No.1219). In-situ stabilization of Pb, Zn, Cu, Cd, and Ni in the multi-contaminated sediments with ferrihydrite and apatite (Kang, W., Lim, TT and Chui, composite additives, J. Hazard. Mater., Vol.170, pp. 1093-1100. [23] Shin, W. S. and Kim, Y. G. (2014), "Adsorption characteristics of synthetic heavy metals (Zn2 +, Ni2 +, Cd2 +, Cu2 +, and Pb2 +) by bentonite", J. KORRA, Vol. 22, pp. 17-25. [24] Spuller, C., Weigand, H. and Marb, C. (2007), "Trace metal stabilization in a shooting range of soil: Mobility and phytotoxicity," J. Hazard. Mater., Vol. 141, pp. 378-387. [25] Tessier, A., Camphell, P. G. C. and Bisson, M. (1979), "Sequential extraction procedure for the speciation of particulate trace metals", Anal. Chem., Vol. 51, pp. 844-851. [26] U.S. Environmental Protection Agency (1992), Toxicity characteristic leaching procedure (method 1311) in SW-846, Office of Solid Waste, Washington DC. [27] Weng, C. H. and Huang, C. P. (1994), "Treatment of metal industrial waste water by fly ash and cement fixation", J. Environ. Eng., Vol. 120, pp. 1470-1487. [28] Zhirong, L., Uddin M. A. and Zhanxue, S. (2011), "FT-IR and XRD analysis of natural Na-bentonite and Cu (II) -loaded Na-bentonite", Spectrochim. Acta, Part A, Vol. 79, pp. 1013-1016.

An object of the present invention is to provide a method for stabilizing heavy metals in marine polluted sediments by bentonite which can fix and stabilize heavy metals contained in contaminated sediments using bentonite as a coating material for marine polluted sediments.

In order to achieve the above object, the present invention provides a method for producing bentonite, comprising the steps of: supplying the bentonite on a marine fouling sediment using equipment capable of underwater spraying of bentonite; And a step of stabilizing and stabilizing heavy metals in the marine polluted sediment by coating the marine polluted sediment with the bentonite, wherein the stabilization and stabilization of the heavy metal is performed by immersing the bentonite in the marine polluted sediment, Which is formed by the formation of bentonite and the precipitation of heavy metals in the marine polluted sediments due to the increase of the pH in the marine polluted sediment caused by the bentonite to thereby prevent the diffusion and elution of heavy metals, Thereby providing a stabilization method.

The method of stabilizing heavy metals in marine polluted sediments by bentonite according to the present invention can fix and stabilize heavy metals contained in contaminated sediments by using bentonite as a covering material for marine polluted sediments.

1 is a view showing FT-IR spectrum of bentonite used in a method of stabilizing heavy metals in marine polluted sediments according to an embodiment of the present invention.
FIG. 2 is a view illustrating the pH change of contaminated sediments for 150 days after adding bentonite to contaminated sediments in a method of stabilizing heavy metals in marine polluted sediments according to an embodiment of the present invention. FIG.
FIG. 3 is a view illustrating a change in heavy metal form of contaminated sediment for 150 days after adding bentonite to a contaminated sediment in the method for stabilizing heavy metals in marine polluted sediments according to an embodiment of the present invention. FIG.

Hereinafter, the present invention will be described in detail.

According to the present invention, in order to fix and stabilize heavy metals contained in marine polluted sediments using bentonite as a covering material for marine contaminated sediments, first, by using equipment capable of spraying bentonite in water, The bentonite is supplied on a marine polluted sediment

The bentonite is an additive which acts as a stabilizer to stabilize and stabilize the heavy metals of marine polluted sediments and must be excellent in expandability and water tightness as it is to be sprayed in water and should be placed on the top of the contaminated sediments, do. As such bentonite, natural bentonite which can be collected from natural mining such as sodium-bentonite and calcium-bentonite can be used without limitation. Since all of these are eco-friendly substances produced naturally, Even if it is sprayed in water, the problem of secondary pollution does not occur. On the other hand, a processed bentonite such as activated sodium-bentonite obtained by replacing calcium of natural calcium bentonite with sodium by sodium bentonitization can also be used (however, in this case, bentonite produced by processing , It must be an environmentally friendly material that does not cause water pollution).

The amount of the bentonite to be added is 1 to 8 parts by weight, preferably 3 to 7 parts by weight, more preferably 4 to 6 parts by weight, relative to 100 parts by weight of the marine fouling sediment, If the amount of the bentonite is less than 1 part by weight with respect to 100 parts by weight of the marine polluted sediment, the contaminated deposit may not be sufficiently coated with the bentonite so that the contaminated sediment may not be fixed and stabilized. When the amount exceeds 8 parts by weight, Bentonite is excessively coated on the contaminated sediments. In this case, there is no particular advantage, and there is a risk that the cost efficiency is very low.

The marine polluted sediments are heavy metal contaminated sediments in the marine waters and include marine (abyssal sea and shallow sea) containing heavy metals such as nickel (Ni), lead (Pb), zinc (Zn) (including shallow sea), coastal, harbor, river, dam, reservoir, reservoir, lake, pond and stream.

Examples of facilities that enable the underwater spraying of bentonite include barges, backhoes, conveyor belts, clamshells, and aircrafts, but allow for underwater spraying of the bentonites, So long as it can supply bentonite on the surface of the steel sheet.

Next, when bentonite is supplied onto the marine polluted sediment, the bentonite is coated on the marine polluted sediment to fix and stabilize heavy metals in the marine polluted sediments.

When the high density bentonite is supplied (or sprayed) on the marine polluted sediment, the bentonite is settled on the contaminated sediment to form a barrier layer, which completely separates the contaminated sediment and the surrounding water. Unlike the conventional dredging method, this method can prevent contamination (diffusion of heavy metals and the like) from the source, thereby completely preventing diffusion and dissolution of contaminants during construction.

The process of supplying (or spraying) the bentonite to fix and stabilize the heavy metals in the marine polluted sediment is carried out by the following mechanism. First, the addition of bentonite results in an increase in the pH in marine contaminated sediments (see Examples and Fig. 2 below) (usually the pH of the bentonite is about 9.0 to 10.5 and the pH of the marine fouled sediment is about 8 to 8.5) hydrate formation within a result, marine pollution deposits of heavy metals _{(e.g., PbCO 3, Pb 3 (CO} 3) 2 (OH) 2, Pb (OH) 2) by inducing, wherein the heavy metal hydrates are precipitated (Garcia, 1995 ; Hatje et al., 2003; Misak et al., 1996). Further, the bentonite is formed on the surface of the heavy metal by the main functional group (functional group composed of Al, Si, O, etc., for example Si-O, Si-O-Si and Al- (Chen and Fray, 2001). In this study, we have investigated the effects of heavy metals on marine polluted sediments. In addition to this action, the complex action of the bentonite due to the specific surface area property and the heavy metal immobilization by the organic component also makes it possible to stabilize heavy metals in marine polluted sediments.

Meanwhile, in order to test the stabilization effect of heavy metals in marine polluted sediments by bentonite according to the present invention, an experiment can be carried out by the following process. First, the marine polluted sediments collected are air-dried, the foreign substances in the contaminated sediments are removed, bentonite is added, and the mixture is stirred and mixed to cover the bentonite in the marine polluted sediments, To moist cure.

The marine contaminated sediments are collected from marine water and contain marine (abyssal sea and / or sea water) containing heavy metals such as nickel (Ni), lead (Pb), zinc (Zn) All sediments such as shallow sea, coast, harbor, river, dam, reservoir, reservoir, lake, pond, and stream can be used. The marine polluted sediments collected in this manner should be used within a predetermined period of time, preferably within about one week, more preferably within about 3 days, and most preferably within about 1 day after being stored in an enclosed environment such as a sealed vessel do. The air drying process (wind drying) can be carried out at a room temperature, that is, at a temperature of about 20 ± 5 ° C., and the foreign substances (for example, various vinyl debris, wood debris, iron debris Can be removed by using a tool capable of removing a foreign substance to be removed due to the presence of a large number of fine holes, for example, various kinds of bodies having a large number of holes.

The addition amount of the bentonite is made equal to the amount applied to the water. After the addition of the bentonite, stirring of the contaminated sediments and bentonite should be sufficiently performed until the contaminated sediments and bentonite are homogeneously mixed. The agitation time may vary depending on the content of contaminated sediments and bentonite used, but is preferably 1 to 15 minutes, more preferably 3 to 10 minutes, more preferably 3 to 10 minutes when 100 g of the contaminated sediment is used as a standard Lt; / RTI > for 5 to 7 minutes.

Once the contaminated sediments and bentonite are homogeneously mixed, moisture must be added to the contaminated sediment and the bentonite to cure the mixture of contaminated sediment and bentonite in wet conditions (i.e., to prevent the mixture from drying). The supply of the water is desirably using ordinary water, and besides, a water supply source capable of wet-curing the contaminated sediment and the mixture of bentonite can be used without limitation. The amount of water added to the mixture of the contaminated sediments and bentonite is 60 to 150 parts by weight, preferably 80 to 120 parts by weight, more preferably 90 to 110 parts by weight based on 100 parts by weight of the mixture of the contaminated sediments and bentonite When the amount of water is less than 60 parts by weight based on 100 parts by weight of the mixture, the moisture is not sufficiently contained in the mixture of the contaminated sediments and bentonite, so that the wet curing of the mixture may be incomplete. If the amount exceeds 150 parts by weight, the moisture is excessively contained in the mixture, and the contaminated sediment and the bentonite are not mixed well, which may hinder the physicochemical reaction for removing contaminants. On the other hand, by using the masses of the water and the mixture,

,%) Is obtained, it becomes about 40 to 60%.

When the water is added to the contaminated sediments and the bentonite, the heavy metals contained in the marine polluted sediments are fixed and stabilized by being stored at a room temperature for a certain period of time, that is, by curing.

Hereinafter, the present invention will be described in more detail with reference to specific examples. The following examples illustrate the present invention and are not intended to limit the scope of the present invention.

Collection and physico-chemical characterization of marine contaminated sediment samples and bentonite

Sediments from marine contaminated sediments were collected at a depth of about 10 to 30 cm from the surface layer of the sea near Pusan. The sediment was transported to the laboratory within one day and air-dried at room temperature. A sieve was used to remove the foreign substance. Bentonite used as a stabilizer is a product manufactured by Korea Bentonite Co., Ltd. in the Chungnam Province, Korea. It is used as a stabilizer in 35th (0.5 mm) and 10th (2 mm ), And a particle size distribution of 1.0 to 2.0 mm in size was used.

Then, in order to analyze the physico-chemical characteristics of each of the above substances, the pH of the sediments was measured by taking 10.0 g of the sample by air drying, adding 50 ml of distilled water thereto, stirring with intermittent stirring, (Park et al., 2008). The sediment particle size analysis was performed using a particle size analyzer (Bluewave, Microtrac, USA). Organic carbon and total nitrogen were quantitatively analyzed with an elemental analyzer (EA-1110, Instruments, Italy). The main components of bentonite were analyzed by X-ray fluorescence spectrometry (XRF, XRF-1700, Shimadzu Co., Kyoto, Japan) and Fourier transform infrared spectroscopy (FT-IR, VERTEX 70; Bruker, Germany) Respectively. Also, the specific surface area of bentonite was analyzed using AUTOSORB iQ-Kr / MP surface area analyzer (Quantachrome, USA).

Evaluation of physico-chemical properties of marine polluted sediment samples and bentonite

The basic characteristics of the marine polluted sediments are shown in Table 1 below. The pH is 8.3 and the particle size is composed of silt clay (silt clay or silt clay) with a particle size of 90% or more. Organic carbon and total nitrogen 1.62% and 0.15%, respectively. The sediment particle size is influenced largely by the repair, topography and sedimentological characteristics of the sedimentation area (Goudie, 1981). It is generally known that the particle size distribution and organic matter concentration are highly correlated, (Kim et al., 2008; Therefore, the marine polluted sediments seem to have accumulated particulate matter that has flowed from the land for a long period of time, and it is highly likely that the heavy metals accumulated in the sediments are accumulated due to the continuous inflow of contaminants from the surrounding area. In particular, sediments are more likely to accumulate heavy metals in sediments than silty sediments (PARI, 2010).

Characteristics of sediments Values pH 8.3 ± 0.2 Sand (%) 10.0 ± 0.5 Silt-Clay (%) 90.0 ± 0.4 Organic Carbon (%) 1.62 + - 0.10 T-N (%) 0.15 + 0.02 Water Contents (%) 51.2 ± 0.25

Next, as shown in Table 2 below, from the XRF analysis results, most of the components of bentonite were found to contain 92.8% of oxides SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ and TiO ₂ , Was analyzed to be about 16.3 m ² / g. The physicochemical properties of bentonite are highly likely to have heavy metal adsorption and immobilization effects and show their potential for use as heavy metal stabilizers (Weng et al., 1994; Ahmaruzzaman, 2011). 1 is a view showing FT-IR spectrum of bentonite used in a method of stabilizing heavy metals in marine polluted sediments according to an embodiment of the present invention. As shown in FIG. 1, FT-IR (Fourier Transform Infrared Spectrometer) The results show that the bentonite is a major band with functional groups (Si-O) at 1049 cm ^-1 Wavenumber and functional groups (Si-O-Si and Al-Si-O) at 526 cm ^-1 wavenum (Zhirong et al., 2011). This result is closely related to the major constituents of bentonite, and the functional groups formed in bentonite directly or indirectly contribute to the stabilization of heavy metals in contaminated sediments. FIG. 2 is a graph showing changes in pH of contaminated sediments for 150 days after adding bentonite to a contaminated sediment in the method of stabilizing heavy metals in marine polluted sediments according to an embodiment of the present invention. The initial pH of sediments is 8.3, which indicates the general pH of the sediments. However, in the case of contaminated sediments after 30 days, the pH increases to 8.8 due to the effect of bentonite. (Goh et al., 2000), since the pH of the bentonite itself is 9.0 to 10.5, which is the initial rise in pH upon stirring with the contaminated sediments.

Components SiO ₂ Al ₂ O ₃ TiO ₂ CaO Fe ₂ O ₃ MgO Na ₂ O P ₂ O ₅ MnO K ₂ O Surface
areas (m ² / g) Composition (%) 72.8 16.5 0.2 1.6 3.3 - 2.4 - - - 16.25

[Example 1] Stabilization of heavy metals in marine polluted sediments by bentonite

5% of bentonite is added to 100 g of the contaminated sediments from which the foreign matter has been removed, and then the bentonite is coated on the marine polluted sediments by stirring and mixing. Then, the water content of the contaminated sediments is measured An additional amount of moisture was added to maintain it at 50% and moist curing for 150 days.

[Example 1, Comparative Example 1] Analysis of marine polluted sediments and heavy metal stabilized untreated marine polluted sediments stabilized with heavy metals by bentonite

In order to analyze the presence of heavy metals such as nickel (Ni), lead (Pb), zinc (Zn) and copper (Cu) in polluted sediments, the continuous extraction method proposed by Tessier et al. Respectively. The continuous extraction method is classified as an extraction step in five steps. The first step is an exchangeable fraction, the second step is a carbonate fraction, and the third step is an oxidation step of iron and manganese. , An organic fraction in the fourth step, and a residual fraction in the fifth step, and the total amount of the heavy metals means the sum of the heavy metals in the first to fifth steps. The extraction solution was filtered with 0.45 ㎛ filter paper (PTFE syringe filter, Whatman), and the filtrate was filtered using ICP-MS (Agilent 7500 Series, USA).

[Comparative Example 1a] Evaluation of heavy metal stabilized untreated marine polluted sediments - Concentrations and ratios of the presence of heavy metals in untreated polluted sediments

Table 3 shows the results of analysis of the chemical content of heavy metals from the ion exchange form of Pb, Zn, Cu and Ni to marine contaminated sediments by the continuous extraction method. Generally, the ion exchange form, the carbonate form and the oxide form can be eluted into a slightly acidic solution, but the organic form and the residue form are difficult to elute as a weakly acidic solution (Bacon and Davidson, 2008). That is, the ion exchange, carbonate and oxide forms can be easily eluted into the surrounding water environment by changes in the external environment (temperature, pH, oxidation-reduction potential, and the like), and thus the eluted heavy metal is potentially inhabited (Bacon, 2008; Batjargal et al., 2010). In addition, the impact of ecosystems on climate change can be affected.

As shown in Table 3, heavy metal except for Pb (13.55 mg kg ^-1 ) had residual forms of 20.03 mg kg ^-1 (Ni), 92.14 mg kg ^-1 (Zn), 19.28 as mg kg ^-1 (Cu), it can be seen that the present in a higher concentration than the other existing types (ion exchange, a carbonate, an oxide, and organic type). On the other hand, the presence ratio of ion exchange, carbonate and oxide forms, which are present in large amounts in contaminated sediments, account for about 46% and 60% of Zn and Pb, respectively, There is concern about elution. The NOAA standards and the total amount of heavy metals in polluted sediments by the US National Oceanic and Atmospheric Administration show that Ni (37.93 mg kg ^-1 ), Zn (203.73 mg kg ^-1 ), except Pb (42.38 mg kg ^-1 ) ^-1 ) and Cu (67.28 mg kg ^-1 ) are higher than the Effects Range Low (ERL) but lower than the Criteria 2 (Effects Range Median, ERM). The presence of heavy metals in polluted sediments can vary greatly depending on the pollutant source and deposition conditions (PARK, 2010). Pb and Zn in the contaminated sediments used in one embodiment of the present invention are easily destroyed by external environmental changes There is a high possibility that heavy metals will be eluted into the surrounding water layer.

[Example 1a] Evaluation of marine polluted sediments treated with heavy metal stabilization - stabilization of heavy metals in polluted sediments by bentonite

The effect of bentonite on the stabilization of heavy metals in contaminated sediments was assessed by comparing bentonite to the contaminated sediment for 150 days and comparing the control untreated sediment (0 day). FIG. 3 is a graph showing changes in heavy metal form of contaminated sediments for 150 days after adding bentonite to contaminated sediments in a method for stabilizing heavy metals in marine polluted sediments according to an embodiment of the present invention. P is the ratio of content to shape change, B is the content ratio of zinc (Zn), C is the content ratio of copper (Cu), and D is the content ratio of nickel (Ni). In FIG. 3A, the ion exchange, carbonate and oxide type ratios in the presence of Pb were relatively high at 60% for untreated contaminated sediments (0 day) and decreased by 19.2% during the 150 day stabilization period And 40.8% respectively. In particular, the proportion of stable organics and residues in the presence of Pb in contaminated sediments increased slightly as compared to untreated sediment samples, as the proportion of ion exchange, carbonate and oxide forms decreased.

In addition, as shown in Table 3 and FIG. 3B, the total amount of zinc (Zn) in the contaminated sediments (203.73 mg kg ^-1 ) was higher than that of other heavy metals. In the samples of untreated contaminated sediments, The ratio of ion exchange, carbonate and oxide forms was about 46%. However, after 150 days of addition of bentonite, the presence of ion exchange, carbonate and oxide forms decreased to 20.5%. In other words, the addition of bentonite greatly reduced the oxide form in the contaminated sediment, while the presence of organic and residual forms increased. Previous studies have shown that Zn is present in the form of iron / manganese oxides (Levy et al., 1992) and is influenced by the rise of pH (8 or more) (Benefield and Morgan, 1990), as well as precipitation by the formation of zinc hydrates, such as ZnCO ₃ and Zn (OH) ₂ , to stabilize zinc.

In addition, as shown in Table 3 and as shown in Fig. 3C, the ion exchange, carbonate and oxide type ratio of copper (Cu) in the untreated contaminated sediment samples was relatively low, about 10.7%, and the stabilizer bentonite After 150 days of addition, it decreased to less than 5%. Compared with other heavy metals, the ratio of heavy metals in the form of ion exchange, carbonate, and oxide is very low and the possibility of easy dissolution into the surrounding environment is low. However, when the environmental change to the aerobic state occurs due to the high organic binding of Cu in untreated sediment samples , There is a possibility that the heavy metal which has been bound to the organic matter moves to the water layer due to decomposition of the organic matter or the like. In addition, the soil stabilization process contaminated with complex heavy metals may result in increased mobility of Cu in a basic environment with a pH of 8 or higher, thereby lowering the stabilization efficiency (Kumpiene et al., 2008; Spuller et al., 2007) . This can be explained by the relation between Cu and organic matter, especially Dissolved Organic Carbon (DOC), and it is known that Cu-DOC compound having high mobility can be formed in a high organic matter content (Spuller et al., 2007; Bruell et al., 1999).

Finally, as shown in Table 3 and shown in Figure 3 D, the presence of nickel (Ni) ion exchange, carbonate and oxide forms in untreated contaminated sediments represents 28%, but the addition of bentonite After 150 days, it decreased to 19.5%, which was 8.5%. Thus, it can be seen that the ratio of the organic matter and the residue type increased relatively slightly.

That is, the pH is increased contaminated sediment in accordance with the addition of the bentonite (see increase, Figure 2 at 8.2 to 8.8) that is, Therefore, the monohydrate form of the stain deposits of heavy metals (in the case of lead, PbCO _3, Pb ₃ (CO _{3) 2} (OH) _2, by inducing Pb (OH) _2), wherein the heavy metal hydrate precipitated, also, by a functional group consisting of a main functional group (Al formed on the surface of the bentonite, Si, O and the like), wherein the bentonite The heavy metal in the contaminated sediments is effectively stabilized. In addition to this action, the complex action by the specific surface area property of bentonite and the heavy metal immobilization action by the organic component, Stabilizing heavy metals in sediments.

[Example 1b] Evaluation of Marine Contaminated Sediments Stabilized with Heavy Metals - Extraction of heavy metals by TCLP

The toxicity characteristic leaching procedure (TCLP) was applied to the experiment based on USEPA Method 1311 (1992) as a dissolution test method for toxic substances. The extraction solvent (acetic acid) was added until the pH of the marine contaminated sediment was 2.88 ± 0.05, and the mixture was shaken at a constant temperature (23 ± 2 ° C.) for 18 hours while maintaining the stirring at 30 ± 2 rpm. After elution, the supernatant was filtered through a 0.45 μm filter paper (PTFE syringe filter, Whatman). The filtrate was stored under 1N HNO ₃ at pH 2 or lower, and then ICP-MS (Agilent 7500 Series, USA) Concentration analysis was performed.

[Example 1b] Evaluation of heavy metal stabilized marine contaminated sediments - Analysis of heavy metal leaching characteristics by TCLP

As a result of analyzing the heavy metal elution characteristics by TCLP, as shown in Table 4, the stabilized heavy metals of marine contaminated sediments had a leaching reduction effect of about 85 to 99% compared to untreated sediments (0 day) (Ni: 95.7%, Cu: 96.8%, Pb: 99.2%, Zn: 85.9%). That is, when stabilization of heavy metals in contaminated sediments proceeds using bentonite as a stabilizer, the possibility of elution of heavy metals is much lower than that of untreated polluted sediments, even when external environment changes occur. In addition, for bentonite treated Pb and Ni, the elution rate satisfies the EPA Standards (there is no EPA standard for Zn and Cu). This result is similar to the evaluation of the stabilization of contaminated sediments using ferrihydrite and apatite (Qian et al., 2009). In the case of heavy metals in marine polluted sediments by bentonite according to the present invention The stabilization method is very effective.

heavy metal 0 day
(mg / L) 30 day
(mg / L) 60 day
(mg / L) 150 day
(mg / L) EPA
Standards
(mg / L) Pb 43.7 1.7 1.3 0.4 5.0 Zn 66.2 24.9 24.4 9.3 - Cu 45.7 3.7 3.5 1.4 - Ni 13.7 0.8 0.8 0.6 7.0

As can be seen from the above examples, bentonite can serve as a coating material capable of stabilizing heavy metals contained in marine polluted sediments. However, the price of bentonite is about 50,000 to 350,000 won / ton, which is higher than that of sand (12,329 won / ton, 2010) (Korea Resource Information Service, 2014), which uses only bentonite as a covering material There is a lot of economic burden. Therefore, rather than using bentonite as a single material, it is considered economically feasible to mix it with other reactive coating materials. In addition, when mixed with such a material, the amount of sand used is reduced, By reducing the burden on the destruction of the environment in the estuaries, there are advantages in environmental and social aspects.

The above-described method for stabilizing heavy metals in marine polluted sediments by bentonite according to the present invention has the following characteristics and effects. First, the marine polluted sediment used in the present invention is a weakly alkaline pearl-like sediment containing a relatively high level of organic matter, and the distribution of fine particles has a close correlation with the concentration of the pollutant, And may affect the reactivity with bentonite to be used for the stabilization of heavy metals in contaminated sediments.

Second, in the analysis of the chemical form of heavy metals in the contaminated sediments, the samples of untreated polluted sediments without bentonite, which is a stabilizer, have a high possibility of elution of heavy metals due to the change of physico - Ni, Zn and Cu exceeded the NOAA standard (ERL) except for Pb, whereas bentonite, which is a stabilizer, was added to a contaminated sediment sample. After 150 days, And Cu, Zn, and Ni contents of the hydrolyzate form decreased by 19.2%, 5.6%, 25.5% and 8.5%, respectively. This phenomenon means that, due to the physicochemical properties of bentonite, it changed from the unstable heavy metal form of the contaminated sediment to the more stable heavy metal form.

Third, in the leaching test using TCLP, the amount of leaching of heavy metals in the contaminated sediments with bentonite was lower than that of untreated sediments (Ni: 95.7%, Cu: 96.8%, Pb: 99.2%, Zn: 85.9 %). From this, it can be seen that the stabilization efficiency by bentonite is excellent.

While the present invention has been described with reference to particular embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention. Should be interpreted to include both.

Claims (6)

Supplying the bentonite on a marine fouling sediment using equipment capable of underwater spraying of bentonite; And
Wherein the bentonite is coated on the marine polluted sediment to fix and stabilize heavy metals in the marine polluted sediments,
The stabilization and stabilization of the heavy metal is carried out in such a manner that the bentonite is precipitated in the marine polluted sediment and forms a blocking layer to thereby prevent the diffusion and elution of heavy metals and increase the pH in the marine polluted sediment by the bentonite, METHOD FOR STABILIZING HEAVY METALS IN MARINE CONTAMINATED SUBSTANTS BY BENTONITE, INCORPORATING AND DETACHING HYDROGEN HYDROGEN PARTICLES IN CONTAMINATED SEDIMENTS. The method according to claim 1, wherein, when the bentonite is coated on the marine fouling sediment, the functional group formed on the surface of the bentonite is adsorbed on the surface of the heavy metal in the marine fouled sediment, and the functional group formed on the surface of the bentonite is Si- -O-Si, and < RTI ID = 0.0 > Al-Si-O. ≪ / RTI > The method according to claim 1, wherein the bentonite is added in an amount of 1 to 8 parts by weight based on 100 parts by weight of the marine polluted sediments. The method according to claim 1, wherein the bentonite is a natural bentonite selected from the group consisting of sodium-bentonite and calcium-bentonite. The method according to claim 1, wherein the heavy metal is selected from the group consisting of nickel (Ni), lead (Pb), zinc (Zn), copper (Cu) . The system of claim 1, wherein the facility enabling underwater application of the bentonite is selected from the group consisting of a barge, a backhoe, a conveyor belt, a clamshell and an aircraft, Methods of stabilizing heavy metals.

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