KR20100119678A - Permeable reactive barriers containing waste foundry sands and method of remediation of contaminated groundwater with zinc using permeable reactive barriers - Google Patents

Abstract

PURPOSE: Permeable reactive barriers containing waste foundry sands and a method for treating zinc contaminated groundwater using the same are provided to efficiently eliminate zinc by easily absorbing zinc. CONSTITUTION: Permeable reactive barriers contain a reaction media. The reaction media includes clay 0.1-13.0 weight%, iron 0.1-11.5 weight%, organic carbon 0.1-4.0 weight%, and remained foundry sands. The reaction media is pH 2.5-7.0. The particle size of the clay is between 10.0-15.0% at P_200. If underwater is contaminated with zinc, the permeable reactive barriers with the reaction media are used.

Description

Permeable Reactive Barriers containing Waste Foundry Sands and Method of Remediation of Contaminated Groundwater with Zinc Using Permeable Reactive Barriers}

The present invention relates to a permeable reaction wall including waste foundry sand and a method for treating groundwater contaminated with zinc using the same, and more particularly, a permeable reaction wall for treating groundwater containing zinc using a permeable reaction wall and the same. It relates to a method of treating groundwater contaminated with zinc used.

Globally, the massive amount of waste generated by the accelerating industrial development and population growth has seriously contaminated ground and groundwater. In Korea, more than a thousand landfills without sanitary landfill systems, various chemical plants handling hazardous waste, underground oil storage tanks at gas stations scattered around the country, and overground areas such as pesticide overspread areas It is being polluted, which causes serious environmental pollution problems. In addition, the use of groundwater as industrial water, agricultural water, and drinking water is increasing, and interest in the groundwater quality is increasing, and various purification methods for improving the groundwater quality are being developed.

In developed countries, numerous studies on groundwater purification methods have been developed and put into practice, and these techniques include physical methods such as excavation removal, surface control, shielding, pumping, vacuum extraction, solidification and hydraulic fracturing; Chemical methods such as oxidation, neutralization, ion exchange, and surfactant addition; Thermal methods such as plasma, freezing, pyrolysis and vitrification; And biological methods such as nutrient injection and microbial use. Recently, electrokinetic methods using electroosmosis are also being developed.

Considering the ease of installation and economical efficiency among the various purification methods, the most practical method at present in the domestic situation can be seen as a shielding method of the physical method, the shielding material used in such a shielding method is largely impermeable wall (impermeable) barriers and permeable barriers, impermeable walls are mainly used to block contaminated water generated in the contaminated area, and permeable walls are mainly used to drain or adsorb debris. Impervious walls include slurry walls, sheet piles, grouting and other walls, and permeable walls include vertical drains and reaction media. reactive barriers).

The permeable reactive wall is installed in the flow path of contaminated groundwater to facilitate the purification of the groundwater, and in the prior art regarding the reaction medium used for the permeable reactive wall, a technique using iron and iron sulfide is disclosed in US Patent No. 5,575,927. In addition, US Pat. No. 5,543,059 discloses a technique for purifying contaminated groundwater using an iron wall or column having a layered structure by dividing iron particles into three regions by size.

Iron is mainly used as a reaction medium of the permeable reaction wall because iron is relatively harmless to the human body, is easy to purchase, and has an excellent treatment ability against various contaminants. To date, few cases have been applied to the domestic field of permeable reactive walls, but in the case of advanced countries in the United States, its use is expected to increase significantly.

Groundwater contaminants are largely classified into organic and inorganic materials. Among them, inorganic materials include anions and heavy metals. Heavy metals are not easily decomposed but are accumulated in the human body and are harmful to human health. The main causes of heavy metal pollution include abandoned mines, smelting plants, and plating factories. Especially, abandoned mines are located in areas separated from residential areas, and have not received special attention. In such an isolated area, it is not easy to invest a lot of money for groundwater restoration.

However, Youngga Iron can clean various kinds of contaminants. However, due to the rising cost of Youngga Iron, the use of permeable reaction walls is greatly limited and there is a problem that the restoration cost can not be drastically reduced.

In order to solve the above problems, it is an object of the present invention to provide a water-permeable reaction wall containing an inexpensive reaction medium that can be easily adsorbed to the water-permeable reaction wall, and can replace iron.

In order to solve the above problems, the present invention is a method for treating groundwater contaminated with zinc using a permeable reaction wall containing an inexpensive reaction medium in which zinc can be easily adsorbed to the permeable reaction wall and replaces iron. The purpose is to provide.

In order to achieve the above object, the present invention

In the permeable reaction wall for groundwater purification contaminated with zinc,

From 0.1 to 13.0 weight percent clay,

Iron from 0.1 to 11.5% by weight,

0.1 to 4.0 weight percent of organic carbon, and

Provided is a permeable reaction wall for treating groundwater contaminated with zinc including a reaction medium containing a residual amount of waste foundry sand.

In order to achieve the above another object, the present invention

In the method of treating groundwater contaminated with zinc,

A method of treating groundwater contaminated with zinc using a permeable reaction wall comprising a reaction medium containing 0.1 to 13.0% by weight of clay, 0.1 to 11.5% by weight of iron, 0.1 to 4.0% by weight of organic carbon, and a residual waste sand. To provide.

According to the present invention, since the waste foundry sand exhibits a very good effect on the removal and movement of zinc, the waste foundry sand can be used as a reaction medium for a permeable reactive barrier, and using a permeable reactive wall including the waste foundry sand. Groundwater contaminated with zinc can be purified.

According to one embodiment of the present invention, in the permeable reaction wall for purification of groundwater contaminated with zinc, containing 0.1 to 13.0% by weight of clay, 0.1 to 11.5% by weight of iron, 0.1 to 4.0% by weight of organic carbon, and residual waste sand It provides a permeable reaction wall for treating groundwater contaminated with zinc containing a reaction medium.

The clay component in the reaction medium used in the permeable reaction wall increases the pH of the reaction medium and is responsible for adsorbing heavy metals because the surface is negative. The content of clay included in the reaction medium is preferably 0.1 to 13.0% by weight. When the content of clay is less than 0.1% by weight, it is not preferable because the content of clay is too small, so that a predetermined effect cannot be obtained, and when the content of clay is more than 13.0% by weight, the flowability of water may be reduced.

The particle size of the clay is preferably 10.0 to 15.0% at P ₂₀₀ . P ₂₀₀ means the percentage of particles passed by the 200 sieve. Higher values of P ₂₀₀ mean that more particles pass through the sieve, which means that the clay particles are smaller. If the P ₂₀₀ is less than 10.0% is not preferable since the effect of including a clay in the reaction medium control particles are too seonggeul reduced, if the P ₂₀₀ exceeds 15%, since the particles are too small, the passage of underground water reaction medium, and This is undesirable because it can inhibit the flow.

Iron (Fe) is relatively harmless to the human body, is easy to purchase and has excellent treatment capacity for various pollutants. The content of iron used in the present invention is preferably 0.1 to 11.5% by weight. If the iron content is less than 0.1% by weight, the iron content is insignificant, and the effect of adding iron to the reaction medium cannot be obtained. If the iron content is more than 11.5% by weight, the permeability of the permeable wall is increased due to the increase in the cost of iron. There may be restrictions on use.

The organic carbon serves to improve the flowability of groundwater and to adsorb heavy metals, and the content of the organic carbon used in the present invention is preferably 0.1 to 4.0% by weight. If the content of the organic carbon is less than 0.1% by weight, the effect is insignificant and undesirable. If the content of the organic carbon exceeds 4.0% by weight, the flowability of the groundwater may be impaired.

According to the present invention, since zinc can be easily adsorbed to the waste foundry sand, a method of treating groundwater contaminated with zinc by replacing the iron content with a predetermined amount of iron and a permeable reactive wall including the waste foundry sand as a reaction medium. Can be provided. The content of waste foundry sand is composed of the residual amount except the content of clay, iron and organic carbon in the reaction medium.

The adsorption and removal ability of zinc on foundry sands depends on the initial pH of the zinc solution used. The higher the pH, the better the adsorption and removal ability of zinc. The reaction medium used in the conventional permeable reaction wall did not properly handle contaminants when the pH is low. However, even in the present invention, even when the pH is 2.5 to 7.0, excellent contaminant treatment results can be obtained.

According to another embodiment of the present invention, in the method of treating groundwater contaminated with zinc, containing 0.1 to 13.0% by weight of clay, 0.1 to 11.5% by weight of iron, 0.1 to 4.0% by weight of organic carbon, and the remaining amount of waste foundry sand Provided is a method for treating groundwater contaminated with zinc using a permeable reaction wall comprising a reaction medium.

Adsorption and removal ability of the permeable reaction wall to zinc can be obtained by measuring the concentration of zinc after a certain time has elapsed, wherein the concentration of zinc can be represented by Equation 1.

Where C _aq (t) is the concentration of zinc at the time of measurement, C ₀ is the concentration of initial zinc, R is the low-constant constant of zinc adsorbed to the foundry sand at the beginning (within 1 minute of the beginning of the experiment), K _obs is the removal constant of zinc, t represents the elapsed time (hr) from the start of the experiment to measurement, exp is an exponential function.

_Larger C _aq (t) means that zinc is removed relatively slowly from groundwater contaminants, while smaller C _aq (t) means that the removal of zinc from groundwater contaminants proceeds relatively quickly.

The low constant R of zinc adsorbed to the foundry sand of Equation 1 may be represented by Equation 2.

Where ρ _d is the mass (g) of foundry sand used and n is the volume (mL) of the zinc solution. K _p represents the instantaneous distribution coefficient for the foundry sand of zinc adsorbed within 1 minute of the experiment. In the case of the reaction medium containing the foundry sand according to the present invention, the adsorption to the initial foundry sand increases rapidly as the initial pH is increased.

The instantaneous distribution coefficient (K _p ) and the removal ability of Equation 2 are affected by the pH of the component and the solution contained in the foundry sand, which can be represented by Equation 3.

Log K _p = -2.30 + 0.48 pH + 0.048 C

Here, C represents the content (wt%) of clay contained in the foundry sand. In other words, it can be seen that the instantaneous distribution coefficient is affected by clay content and pH, and more particularly by pH.

In addition, the removal ability (K _obs ) of zinc can be represented by the equation (4).

K _obs = -0.0852 + 0.00138 C + 0.00277 TOC + 0.00126 I + 0.0163 pH

Where C is the content of clay contained in the foundry sand, TOC is the content of organic carbon contained in the foundry sand (%), and I represents the content of iron (%) contained in the foundry sand. Therefore, it can be seen that the removal ability of zinc contained in groundwater contaminants is affected by clay content, organic carbon content, iron content, and pH, and among them, pH is most affected.

According to the present invention, by using the equation (4) according to the user's convenience, it is possible to constantly control and predict the removal rate of zinc by appropriately adjusting the clay, iron, organic carbon, pH.

On the other hand, PVE (pore volume of effluent) represents the pore size may be represented by the following equation (5).

Where Q is the flow rate (mL / hr), T is the time (hr), and V is the void volume (mL) of the foundry sand charged to the column. PVE indicates how much the movement of zinc is inhibited as compared with the conventional permeable reaction wall without foundry sand, which means that the larger the PVE value, the more the movement of zinc is inhibited.

According to the present invention, the permeable reaction wall is installed in a cross-sectional direction with respect to the flow path of the contaminated groundwater, and the zinc-contaminated groundwater is purified by passing the groundwater contaminated with zinc along the flow path. Provide a method for the purification of contaminated groundwater.

In the method of purifying groundwater contaminated with zinc using the permeable reaction wall according to the present invention, the permeable reaction wall may be subjected to a pretreatment process by an acid treatment or the like to facilitate the removal of organic pollutants or zinc. In addition, the passage speed of groundwater contaminated with zinc is not limited as long as it is suitable to obtain a predetermined purification efficiency.

Hereinafter, the present invention will be described in more detail with reference to the drawings and embodiments.

Example

In the present invention, adsorption phenomenon, adsorption capacity, and removal constant of zinc foundry sand were determined through batch experiments and column experiments. The zinc solution used here was completely removed by using nitrogen in consideration of the characteristics of groundwater, and then dissolved in zinc chloride to a desired concentration. In the column experiments, a zinc solution was injected into the column using a pump to simulate the phenomenon when applied to the actual site.

Example 1

P with a particle size of ₂₀₀ of 10.7% and a particle size of P _{2 μ} 6.7% clay, 5.1% by weight, and iron 2.83 wt%, the organic carbon of 1.5 wt%, the molding sand a composition comprising 90.57% by weight of the water-permeable reaction of reactive barrier It was used as a medium, and the groundwater contaminated with zinc flowed into the permeable reaction wall, and then the pH of the reaction medium was changed to pH 2.6, pH 3.0 and pH 4.8, respectively, and the adsorption phenomenon and the adsorption capacity were measured through batch experiments and column experiments. It was.

Example 2

P particle size of 13.2% of ₂₀₀ and with a particle size of P _{2 μ} 9.3% clay 10.5 wt%, iron 0.29% by weight, the organic carbon of 0.5% by weight, the molding sand a composition comprising 88.71% by weight of the water-permeable reaction of reactive barrier As a medium, zinc-contaminated groundwater was flowed into the permeable reaction wall, and the pH of the reaction medium was changed to pH 2.6, pH 3.0, and pH 4.8, respectively, and the concentration of zinc adsorbed and removed was measured.

Example 3

P particle size of 10.0% of ₂₀₀ and with a particle size of P _{2 μ} 3.5% clay, 4.7% by weight, and iron 0.14 wt%, organic carbon 0.5% by weight, the molding sand a composition comprising 94.66% by weight of the water-permeable reaction of reactive barrier As a medium, zinc-contaminated groundwater was flowed into the permeable reaction wall, and the pH of the reaction medium was changed to pH 2.6, pH 3.0, and pH 4.8, respectively, and the concentration of zinc adsorbed and removed was measured.

Example 4

P particle size of 16.0% of ₂₀₀ and with a particle size of P _{2 μ} 13.2% Clay 13.0 weight%, iron 0.18% by weight of organic carbon 4.0% by weight, the molding sand a composition comprising 82.82% by weight of the water-permeable reaction of reactive barrier As a medium, zinc-contaminated groundwater was flowed into the permeable reaction wall, and the pH of the reaction medium was changed to pH 2.6, pH 3.0, and pH 4.8, respectively, and the concentration of zinc adsorbed and removed was measured.

Example 5

P particle size of 10.0% of ₂₀₀ and with a particle size of P _{2 μ} 3.5% clay, 4.7% by weight, iron 11.26 wt% organic carbon of 2.4 wt%, the molding sand a composition comprising 81.64% by weight of the water-permeable reaction of reactive barrier As a medium, zinc-contaminated groundwater was flowed into the permeable reaction wall, and the pH of the reaction medium was changed to pH 2.6, pH 3.0, and pH 4.8, respectively, and the concentration of zinc adsorbed and removed was measured.

Example 6

P particle size of 14.3% of ₂₀₀ and with a particle size of P _{2 μ} 9.2% clay, 7.0% by weight, and iron 0.15 wt%, organic carbon 2.6% by weight, the molding sand a composition comprising 90.25% by weight of the water-permeable reaction of reactive barrier As a medium, groundwater contaminated with zinc was flowed into the permeable reaction wall, and then the reaction medium was adjusted to pH 4.0 and the concentration of zinc adsorbed and removed was measured.

Example 7

Particle size of 12.4% of P _200, and the clay and 8.4% by weight has a particle size of P _{2 μ} 8.0%, iron 0.14% by weight, the organic carbon of 1.8 wt%, the molding sand a composition comprising 89.66% by weight of the water-permeable reaction of reactive barrier As a medium, groundwater contaminated with zinc was flowed into the permeable reaction wall, and then the reaction medium was adjusted to pH 4.0 and the concentration of zinc adsorbed and removed was measured.

The materials and contents used in Examples 1 to 7 are shown in Table 1.

Clay (% by weight) Iron (% by weight) Organic Carbon (wt%) Foundry sand (weight%) Example  One 5.1 2.83 1.5 90.57 Example  2 10.5 0.29 0.5 88.71 Example  3 4.7 0.14 2.5 94.66 Example  4 13 0.18 4.0 82.82 Example  5 4.7 11.26 2.4 81.64 Example  6 7.0 0.15 2.6 90.25 Example  7 8.4 0.14 1.8 89.66

Comparative Example 1

Without including any substance as a reaction medium in the permeable reaction wall, the groundwater contaminated with zinc flows into the permeable reaction wall, and then the pH of the reaction medium is changed to pH 2.6, pH 3.0 and pH 4.8, respectively. The concentration adsorbed and removed was measured.

Comparative Example 2

100% by weight of iron was used as the reaction medium of the permeable reaction wall, and the groundwater contaminated with zinc flowed into the permeable reaction wall, and then the pH of the reaction medium was changed to pH 2.6, pH 3.0, pH 4.8 and zinc The concentration adsorbed and removed was measured.

Results and rating

The results of Examples 1 to 5, Comparative Example 1, and Comparative Example 2 are shown in Figs. 1 to 3, it can be seen that in the case of the initial pH 2.6 and 3.0, most of the foundry sands had an initial adsorption of zinc, and no adsorption occurred over time. However, in the case of pH 3.0 shown in Figure 2 it can be seen that the continuous adsorption occurs in Example 5. In the case of pH 4.8 shown in Figure 3 it can be seen that in Example 1 to Example 5, Comparative Example 2 and the continuous removal occurs with the initial adsorption. These experimental results indicate that even with the same composition, the higher the initial pH, the faster the continuous removal rate of zinc proceeds.

1 and 2 are no longer removed zinc after the initial adsorption, Figure 3 can be obtained by applying the equation (2) to obtain the instantaneous distribution coefficient and removal capacity. Example 5 was experimented by changing the pH and the result of applying Equation 1 is shown in FIG. Referring to FIG. 4, the first pH is 2.6, 3.0, and 4.8, respectively, and the slope is abrupt when the pH is 4.8, indicating a sharp decrease in the concentration of zinc. In FIG. 4, when the initial pH was 2.6 and 4.8, only 18 hours and 36 hours were measured, but the same result may be obtained even after measuring about 80 hours such as pH 3.0.

Results of column experiments for evaluating applicability to actual sites are shown in FIGS. 5 and 6. Referring to FIGS. 5 and 6, Example 3 began to detect zinc after 50 PVE in an aqueous solution, and the zinc concentration rapidly increased to show a value similar to the initial concentration. Here, the meaning of 50 PVE can be confirmed that the movement of zinc is inhibited about 50 times compared to the case without the foundry sand. However, in the general sand, zinc is detected after about 1 PVE.

1 is a graph showing the removal pattern of zinc at initial pH 2.6 according to the present invention.

2 is a graph showing the removal pattern of zinc at initial pH 3.0 according to the present invention.

3 is a graph showing the removal pattern of zinc at the initial pH 4.8 according to the present invention.

4 is a graph showing the zinc removal pattern and the result of model fitting at the initial pH of the waste foundry sand according to Example 5 of the present invention.

5 is a graph showing the field applicability evaluation (initial pH 3.0) of the waste foundry through a column experiment according to the present invention.

6 is a graph showing the field applicability evaluation (initial pH 4.0) of the waste foundry through the column experiment according to the present invention.

Claims (6)

In the permeable reaction wall for groundwater purification contaminated with zinc, From 0.1 to 13.0 weight percent clay, Iron from 0.1 to 11.5% by weight, 0.1 to 4.0 weight percent of organic carbon, and A permeable reaction wall for treating groundwater contaminated with zinc containing a reaction medium containing a residual amount of waste foundry sand. The permeable reaction wall for treating groundwater contaminated with zinc according to claim 1, wherein the pH of the reaction medium is 2.5 to 7.0. The permeable reaction wall for treating groundwater contaminated with zinc according to claim 1, wherein the particle size of the clay is 10.0 to 15.0% at P ₂₀₀ . In the method of treating groundwater contaminated with zinc, A method of treating groundwater contaminated with zinc using a permeable reaction wall comprising a reaction medium containing 0.1 to 13.0% by weight of clay, 0.1 to 11.5% by weight of iron, 0.1 to 4.0% by weight of organic carbon, and a residual waste sand. . The method of claim 4, wherein the pH of the reaction medium is 2.5 to 7.0, the method for treating groundwater contaminated with zinc using a permeable reaction wall. 5. The method of claim 4, wherein the particle size of the clay is 10.0 to 15.0% at P _{200. 5} .

Images