KR100712657B1 - Method for washing soils contaminated by heavy metals - Google Patents

Abstract

The present invention is a method for washing heavy metal contaminated soil, at least one step of washing the heavy metal contaminated soil using a 0.2 ~ 1M sodium hydroxide or 0.2 ~ 1M hydrochloric acid or 0.01 ~ 1M concentration of citric acid as a washing solution. It provides a method for washing heavy metal contaminated soil, characterized in that performed. In addition, the washing step may be such that the pH of the washing effluent is 4 to 13 after washing so that heavy metals are aggregated or adsorbed in the flocks with respect to the soil in which the flocks are formed, and in this case, the washing is performed so that the arsenic aggregates or adsorbs More preferably, the pH of the effluent is set to 5-6. In addition, the washing step is preferably removed after washing the floc formed in each washing step once or two or more times with respect to the soil in which the floc is formed during washing. In addition, the method may be, for example, diatomaceous earth in which pores attached to the pores or surfaces of ions such as iron, aluminum, lanthanum, or noble metals, which serve as a functional group for the washing effluent, which have undergone the flocculation or adsorption, precipitation and removal, are nano-sized It is preferable to adsorb using a porous medium such as, and further comprising the step of adsorbing the groundwater in the vicinity of heavy metal contaminated soil with the porous medium together with or separately from the soil washing.

According to the method for cleaning heavy metal contaminated soil according to the present invention, the removal effect of heavy metals such as arsenic, copper and lead, especially contained in the soil, is excellent, and further satisfies the economics. In addition, in the present invention, particularly by using a nano-porous medium, heavy metal contaminated soil and heavy metals in heavy metal contaminated groundwater surrounding heavy metal contaminated soil can be treated with excellent efficiency.

Heavy metal contaminated soil, flushing effluent, sodium hydroxide, citric acid, washing concentration, time, shaking ratio, continuous washing, coprecipitation, pH, flocculation

Description

Method for washing soils contaminated by heavy metals}

1 is a graph showing the amount of arsenic contained in the effluent after washing while changing the concentration of sodium hydroxide in the arsenic contaminated soil according to the experimental example of the present invention.

Figure 2a is a graph showing the arsenic elution history with time when using sodium hydroxide, citric acid, hydrochloric acid as a cleaning agent for the tailings soil according to the experimental example of the present invention, A is using 0.05M sodium hydroxide Represents a case where 0.1 M sodium hydroxide is used.

Figure 2b is a graph showing the arsenic elution history with time when using sodium hydroxide, citric acid, hydrochloric acid as a cleaning agent for the field soil according to the experimental example of the present invention, when A is using 0.05M sodium hydroxide Represents a case where 0.1 M sodium hydroxide is used.

Figure 2c is a graph showing the arsenic dissolution history with time when using sodium hydroxide, citric acid, hydrochloric acid as a cleaning agent for the river sedimentation soil according to the experimental example of the present invention, A using 0.05M sodium hydroxide A case is shown and B represents a case where 0.1 M sodium hydroxide is used.

3 is a graph showing the amount of arsenic eluted under each pH condition that is changed after the injection of varying the amount of sodium hydroxide according to the experimental example of the present invention.

Figure 4a is a graph showing the amount of arsenic contained in the washing effluent after washing with different shaking ratio using 0.2M sodium hydroxide for the tailings soil according to the experimental example of the present invention.

Figure 4b is a graph showing the amount of arsenic contained in the washing effluent after washing with different shaking ratio using 0.2M sodium hydroxide for the field soil according to the experimental example of the present invention.

Figure 4c is a graph showing the amount of arsenic contained in the washing effluent after washing with different shaking ratio using 0.2M sodium hydroxide for the river sedimentation soil according to the experimental example of the present invention.

Figure 5a is a graph showing the removal rate after washing with varying the acid concentration (range of pH 1 ~ 4) and shaking ratio for copper in the heavy metal according to the experimental example of the present invention.

Figure 5b is a graph showing the removal rate after washing with varying the acid concentration (range of pH 1 ~ 4) and shaking ratio for the lead in the heavy metal according to the experimental example of the present invention.

6 is a graph showing the amount of arsenic remaining in the soil after the continuous washing with 0.2M sodium hydroxide according to the experimental example of the present invention.

7 is a graph showing the amount of arsenic remaining according to the presence or absence of flocs after continuous washing with 1M hydrochloric acid for the floc-forming heavy metal contaminated soil according to the experimental example of the present invention.

8 is a graph showing the concentration of arsenic removed under each pH condition after 1: 1 mixing of effluent water generated when washing with acid and base in parallel according to the experimental example of the present invention.

FIG. 9 is a diagram illustrating the coagulation and precipitation (coprecipitation) of different heavy metal ions contained in the washing effluent of a river sediment soil (left graph) or a field sediment soil (right graph) according to the experimental example of the present invention. After removal, it is a graph showing the concentration of each ion remaining in the wash effluent.

10 is a graph showing the mass ratio of iron injected to remove arsenic present in the washing effluent at a relatively high concentration according to the experimental example of the present invention.

11 is a schematic view showing a concept of a process for treating a nanoporous porous medium according to the present invention.

12 is a graph showing the results of the adsorption experiment of the nanoporous porous medium according to the present experimental example.

The present invention relates to a method for cleaning heavy metal contaminated soil, and more particularly, to a method for cleaning heavy metal contaminated soil excellent in the removal effect of toxic substances such as arsenic, copper, lead and the like contained in the soil.

The waste-rock, waste tailings, and surrounding soils of the mines or waste mines contain large amounts of harmful heavy metals such as arsenic, cadmium, copper, lead, mercury, and chromium.

Among them, arsenic is a highly toxic carcinogenic substance that greatly contaminates the surrounding environment, and is introduced through various routes such as ingestion of soil- or water-based foods containing arsenic pollutants, direct inhalation of arsenic mixtures, and skin exposure. It is toxic to various organs such as human skin, respiratory system, digestive system and nervous system.

On the other hand, arsenic exists in the state of inorganic and organic in nature, the inorganic arsenate [Arsenate, As (V)] in the oxidation state and reduced arsenite [Arsenite 25 to 60 times more toxic than the arsenate] , As (III)], and organic arsenic compounds (As-C-) and the like.

As described above, various heavy metals, including arsenic with lethal toxicity, have emerged as serious environmental pollutants. Therefore, there is an urgent need for a technology capable of effectively treating them.

Conventional treatment techniques are generally known as solidification / stabilization, landfilling, soil cover, vitrification, plant purification, soil washing, and the like.

Among them, soil washing is a method of physicochemical purification of soil contaminated with heavy metals, nonvolatile materials, and biodegradable substances using water or special solutions. It is a purification technique that is easy to restore when there are few substances. This soil washing method has advantages such as the removal of various types of contaminants and the low cost.

However, the removal efficiency of heavy metals, especially arsenic, has been excellent so far, and economical soil cleaning methods have not been developed.

On the other hand, in particular, the technology applied to the removal of heavy metals in groundwater or soil wash runoff contaminated with heavy metals, there is a source leakage shielding technology or immobilization technology.

However, these technologies are not a purification technology for separating and removing heavy metals, which are pollutants. Especially, groundwater contaminated with heavy metals is likely to leak due to fluidization due to fluctuations in on-site conditions such as water level, structure type, and pH. There is a limit to the application.

In addition to the disadvantage that the restoration method requires a long restoration period, it is difficult to achieve expectations due to the long-term low temperature phenomenon in the high mountains where the abandoned mines exist.

Therefore, the present invention has been made to solve the above problems,

An object of the present invention is to remove heavy metals contained in soil, in particular, to remove toxic substances such as arsenic, copper, lead, etc., and to be economical, and to wash heavy metal contaminated soil which is also excellent for removing heavy metals from soil washing effluent or groundwater around the soil. To provide a way.

An object of the present invention as described above, in the method of washing heavy metal contaminated soil, heavy metal contaminated soil using a 0.2-1 M sodium hydroxide or 0.2-1 M hydrochloric acid or 0.01-1 M concentration citric acid as a washing solution. The washing step is performed at least once, and at least two times are achieved by the method of washing heavy metal contaminated soil, wherein the washing solution of each washing step is the same or different.

And, the washing step is to use the sodium hydroxide as a washing solution, and to adjust the concentration of the sodium hydroxide corresponding to the pH of the soil to be washed so that the pH of the washing effluent is 10 or more, wherein the soil is washed It is preferable that the soil does not form a floc.

In addition, the washing step may be such that the pH of the washing effluent is 13 or more.

In addition, the shaking ratio of the washing solution to the soil weight in the washing step is preferably 1: 5 or less.

In addition, the washing step may be such that the pH of the washing effluent is 4 to 13 after washing so that heavy metals are aggregated or adsorbed in the flocks with respect to the soil in which the flocks are formed.

In addition, the washing step may be such that the pH of the washing effluent after washing so that arsenic is aggregated or adsorbed in the floc is 5-6.

In the washing step, it is preferable to remove and remove the floc formed in each washing step once or two or more times with respect to the soil in which the floc is formed during washing.

And, the washing step further comprises the step of flocculating or adsorbing the heavy metal in the wash effluent to precipitate and remove, it is preferable to adjust the pH to increase the amount of heavy metal removal.

And, the washing step is preferably to adjust the pH of the washing effluent in the range of 4-7.

And, it is preferable to adjust the pH of the washing effluent in the washing step to 5.

In addition, the washing step is a continuous washing method performed two or more times, by mixing any two or more of each washing effluent generated from each washing step to aggregate or adsorb heavy metals from the mixed washing effluent, to precipitate and remove Further comprising, it is preferable to adjust the pH so that the removal amount of the heavy metal increases.

And, the washing step, the first washing step of washing the soil by 0.2M hydrochloric acid; A second washing step of washing the soil washed by the first step with 1 M hydrochloric acid; And a third washing step of washing the soil washed by the second step with 1 M sodium hydroxide, and mixing the washing effluent of the second step and the washing effluent of the third step with 1: 1, followed by For flocculation or adsorption, precipitation and removal, the pH of the wash effluent is preferably adjusted to 6 or 8-9.

In addition, the method is preferably added to the iron chloride for the aggregation or adsorption, precipitation and removal.

In the above method, it is preferable to add iron chloride so that the weight ratio of iron to arsenic is 1:13 or less.

And, in the washing step, the pH of the washing effluent is adjusted to 5, and for the aggregation or adsorption, precipitation and removal, it is preferable to add iron chloride so that the weight ratio of arsenic and iron is 1:11.

In the washing step, it is preferable to use 0.2 M sodium hydroxide or 0.2 M hydrochloric acid or 0.5 M citric acid.

The method further includes the step of adsorbing the washing effluent through the flocculation or adsorption, precipitation, and removal using a porous medium having nano-sized pores attached to the pores or surfaces of the metal ions serving as a functional group. It is preferable.

The method further includes adsorption treatment of groundwater near heavy metal contaminated soil with or separately from the soil washing using a porous medium having nano-sized pores in which metal ions serving as functional groups or pores attached to the surface are nanosized. It is preferable to include.

First, in performing the soil washing method, the present invention provides a soil washing method which is remarkably excellent in the removal efficiency of heavy metals, especially arsenic, and also in terms of economy. To this end, first, in the present invention, a cleaning solution and a concentration capable of removing the heavy metal with high efficiency from soil contaminated with heavy metals such as arsenic were devised.

As the washing solution, sodium hydroxide at a concentration of 0.2 to 1 M or hydrochloric acid at a concentration of 0.2 to 1 M or citric acid at a concentration of 0.01 to 1 M is used. In particular, as can be seen from the following experimental example, the sodium hydroxide is particularly used at a concentration of 0.2 M. In particular, the effect is excellent in the leaching of arsenic, hydrochloric acid is particularly excellent at 0.2M, citric acid is 0.5M in the removal of heavy metals such as arsenic, copper, lead, respectively.

Furthermore, in the case of soil where no floc is formed, the sodium hydroxide is used as a washing solution, and the hydroxide is washed against various soils to be washed so that the pH of the washing effluent after washing the soil is 10 or more, preferably 13 or more. Adjusting the concentration (or pH) of sodium can maximize the dissolution of heavy metals, especially arsenic, for heavy metals, especially arsenic-contaminated soils.

In addition, as the shaking ratio, which is the volume ratio of the washing solution to the soil weight at this time, as can be seen from the following experimental example, for example, 1: 10 or less is preferable for the field soil, but it is eluted when considering all other soil such as river sedimentation soil. It is preferable to set it as 1: 5 or less (for example, 1: 4, 1: 3 etc., but there is a possibility that a washing machine may wear out in 1: 3 or less) from a efficiency and economical viewpoint.

Meanwhile, the washing step of washing the soil with the washing solution may be performed one or more times. That is, it is possible to wash the soil once, as well as to repeat the washing step using the hydrochloric acid or sodium hydroxide two or more times (that is, continuous washing).

At this time, as can be seen in the following experimental example, it is preferable to perform a continuous washing in parallel with hydrochloric acid or sodium hydroxide, especially in the case of continuous washing in combination with a predetermined concentration of hydrochloric acid and sodium hydroxide in terms of arsenic dissolution and natural neutralization conditions Do.

On the other hand, the present invention provides a soil washing method excellent in the treatment effect as follows, especially in the soil in which the floc is formed.

That is, in the present invention, a condition in which a floc including heavy metals such as arsenic is formed to a maximum with respect to the soil in which the floc is formed during washing (the larger the surface area of the floc, the greater the aggregation or adsorption of heavy metals, such as arsenic, and the aggregation or adsorption thereof. The pH is preferably adjusted to be washed under this maximum condition, and the floc thus formed is removed as much as possible after washing in each washing step during the first washing or the continuous washing.

Here, the pH of the washing effluent is set to 4 to 13 with respect to the target soil, and as shown in the following experimental example, the pH of the washing effluent is set to 5 to 6, in particular for flocculation or adsorption of arsenic.

In addition, in the present invention, the heavy metal in the washing effluent is aggregated or adsorbed, precipitated and removed (that is, co-precipitation) in each washing step, wherein the pH is adjusted to increase the amount of aggregation or adsorption, settling and removal of the heavy metal, and streams. In the case of various target soils including sedimentary soil or field soil, which is a typical general soil, its pH should be controlled in the range of 4 to 7, and in particular, the pH is adjusted to 5.

Furthermore, a coagulant such as iron chloride is further added for the purpose of satisfying the criteria suitable for drinking water. When the flocculant is added, a flocculant such as iron chloride is added such that the weight ratio of arsenic and iron is 1:13 or less, preferably 1:11, especially for various target soils including river sedimentation soil or representative soil soil.

Furthermore, the soil washing method of the present invention mixes any two or more of each washing effluent from each washing step, especially when performing a continuous washing, and aggregates and precipitates and removes heavy metals from the mixed washing effluent. The pH is adjusted to increase the amount of heavy metal removed.

On the other hand, the present invention is applied to the process of adsorption (including oxidation or reduction adsorption) to the porous medium having pores of nano-sized pores in order to further remove heavy metals in the washing effluent washed in the washing step, and also subjected to the flocculation, precipitation and removal process. do.

In detail, in the present invention, the material can be manufactured or synthesized at a lower price, can be reused by easy desorption, and the non-toxic material capable of biodegradation can be evenly applied to the soil-contaminated groundwater as described below. It is possible).

The porous medium is a porous medium having a nano-sized pore (hereinafter referred to as a nanoporous porous medium) in which metal ions serving as functional groups are attached to pores or surfaces, specifically, ions such as iron, aluminum, and lanthanum. It is a porous medium in which pores have nano-sized pores in which precious metal ions (so-called novel ions) such as gold, platinum, ruthenium, rhodium, osmium and iridium are attached to pores or surfaces. For example, diatomaceous earth is used as the medium.

In addition, the nano-porous medium may be synthesized using a nonionic surfactant, and an excellent adsorption efficiency may be obtained by controlling the synthesis conditions of factors such as surfactant type, temperature, pH, and related ions.

In addition, nanoporous media having a high adsorption area can be produced in a very uniform form with control of pore size depending on the synthesis conditions.

An example of the treatment process of the nano-porous medium is described in detail (see FIG. 11). Figure 11 consists of three processes (phases 1, 2, 3), for example, firstly, as-contaminated tailings and soils contaminated with contaminants, such as arsenic, together with sodium hydroxide. It is put into Cyclone, which performs the Separation & Extraction process. At this time, some of the solids are floatable and large-size soil compartments are formed at the bottom, which are reused (phase 1).

The treated soil is then subjected to neutralization, coagulation and precipitation (phase 2), and some are filtered and some are adsorbed through the adsorbents of the nanoporous porous medium. (Oxidation or reduction and adsorption are also possible) (Adsorption process) (phase 3).

Through the use of such nanoporous media, the heavy metals in the wash effluent (preferably installed at the end of the treatment process after flocculation or adsorption, sedimentation and removal) are lower than the previous treatment level (i.e. below baseline) Or nearly zero).

Furthermore, flocculation, sedimentation and removal of the effluents removes almost all of the fine soil and impurity suspended solids, which is almost identical to heavy metal contaminated groundwater. Therefore, the adsorption process using the nano-porous medium according to the present invention can be similarly applied to the heavy metal contaminated groundwater near the site where the heavy metal contaminated soil is located.

According to the present invention as described above, the removal efficiency of heavy metals, in particular arsenic, is remarkably excellent and further economically.

Hereinafter, the present invention will be described in more detail by explaining preferred examples and experimental examples of the present invention. However, the present invention is not limited to the specific embodiments, and various forms of embodiments can be implemented within the scope of the appended claims, and the following examples are only common in the art while making the disclosure of the present invention complete. It is intended to facilitate the implementation of the invention to those with knowledge.

<Sample to be tested>

In order to simulate heavy metal contaminated soils with copper and lead as samples, non-contaminated soils were collected from N-san, Seoul, and artificial contaminated soils (copper 500mg / kg dry soil, lead 1,000mg / kg dry soil) were used. In particular, only soil passing # 4 (4.75 mm) was used for the experiment. This was named Target Sample 1.

In the case of arsenic-contaminated soil, actual contaminated soil was used, and tailings soil, field soil, river sediment soil, and floc forming heavy metal contaminated soil were selected. The respective arsenic concentrations were 984 ± 16, 141 ± 4, 17 ± 1, 321 ± 32mg / kg dry soil.

The tailings soils, field soils, river sedimentary soils, and floc-forming heavy metal contaminated soils were used only for soils of # 20 (0.85 mm) or less. The floc-forming heavy metal contaminated soil was used for the experiment between # 10 (2mm) and # 100 (0.15mm) soils.

The tailings soils, field soils, river sedimentary soils, and floc-forming heavy metal contaminated soils were named as target samples 2, 3, 4, and 5, respectively.

Table 1 shows pH, particle density, effective size (effective size d ₁₀ ), uniformity coefficient (Cu), organic content, and cation exchange capacity of the target samples 1-5. , CEC).

Item Sample 1 (artificially contaminated soil) Target Sample 2 (Tailed Soil) Sample 3 (field soil) Target sample 4 (river sedimentation soil) Sample 5 (Floated Soil) pH 4.4 2.50 6.18 6.7 8.4 Particle Density (g / cm ³ ) 2.48 1.82 1.67 2.24 2.38 Effective diameter, d ₁₀ (mm) 0.18 0.33 0.34 0.22 0.15 Uniformity Factor, Cu 8.89 6.96 2.65 2.3 5.5 Organic matter content (%) 1.6 3.3 1.0 1.0 5.4 Divorce Divorce Capacity (meq / 100g) 4.08 21.3 8.2 6.1 15.4 Copper (mg / kg dry soil) 500 - - - - Lead (mg / kg dry soil) 1,000 3 21 9 - Arsenic (mg / kg dry soil) - 984 141 17 321

Based on the target sample prepared as shown in Table 1, the following experiment was performed. Hereinafter, each experimental example will be described in detail with reference to the drawings.

Experimental Example 1 Measurement of Concentration Effect When Sodium Hydroxide was Used as Wash Solution

The sample was extracted for each of the sample 2 (the tailings soil), the sample 3 (the field soil), and the sample 4 (the river sedimented soil), and the sodium hydroxide concentration was 0.05M, 0.2M, 0.3M, 0.5M, 0.75M, 1M was selected to carry out a washing experiment, the arsenic remaining after washing was measured by the soil pollution process test method.

Specifically, 10 g of soil and 200 ml of sodium hydroxide solution were mixed in a 250 ml Erlenmeyer flask, and the temperature was maintained at 20 ± 0.5 ° C., which was shaken at 300 rpm for 6 hours. The supernatant was collected by 12 ml, filtered, and analyzed. It was.

1 is a graph showing the amount of arsenic contained in the effluent after washing while changing the concentration of sodium hydroxide in the arsenic contaminated soil according to the experimental example of the present invention.

As shown in FIG. 1, in the case of sample 2 (tailings soil), arsenic elution was high at 0.1 M, and arsenic elution rapidly increased as 0.2 M. Furthermore, it was found that the elution efficiency was similar at higher concentrations.

On the other hand, in case of the sample 3 (field soil) and the sample 4 (river sedimentary soil), arsenic elution showed the highest efficiency at 0.2M, but if the concentration of sodium hydroxide was increased to more than that, the arsenic elution efficiency was slightly increased. The trend was decreasing.

Furthermore, as can be seen from the continuous washing experiment of Experimental Example 6, the residual arsenic concentration of the soil after washing showed a minimum value (138 mg / kg) when applying 0.2 M sodium hydroxide in the target sample 2 (tailings soil). In the case of (field soil) and sample 4 (river sediment soil), the minimum value (0.2 mg / kg, 4 mg / kg) was shown at 0.2 M, and similar values were also observed at higher concentrations (see FIG. 6).

Therefore, when considering the arsenic concentration removal efficiency and at the same time considering the economical decrease according to the increase in the usage, it was found that the concentration of 0.2M sodium hydroxide was the best in all three soils. Further, when considering the formation of flocs to be described below, it is preferable to use at a concentration of 1 M or less in terms of efficiency and economy.

Experimental Example 2-Measurement of Influence of Cleaning Time

Experimental Example 2-1: When measured at a laboratory scale using only sodium hydroxide

Samples were extracted for each of the sample 2 (the tailings soil), the sample 3 (the field soil), and the sample 4 (the river sedimented soil) to determine the time for the arsenic leaching by sodium hydroxide to reach equilibrium.

On the other hand, hydrochloric acid and citric acid (citric acid) was applied to 0.05M and 0.1M, respectively, and the washing results were compared with sodium hydroxide, and the amount of arsenic eluted by distilled water was also confirmed.

10 ml of supernatant was collected for each hour (1, 2, 3, 6, 14, 24h). The experiment was performed by mixing 15 g of soil and 300 ml of washing solution in a 500 ml Erlenmeyer flask, and maintaining the temperature at 20 ± 0.5 ° C. Shaking was carried out using a shaker for 24 hours at a shaking speed of 300 rpm.

Figure 2a is a graph showing the arsenic elution history with time when using sodium hydroxide, citric acid, hydrochloric acid as a cleaning agent for the target sample 2 (tailings soil) according to the experimental example of the present invention, A is a hydroxide of 0.05M The case where sodium is used is shown and B shows the case where 0.1 M sodium hydroxide is used.

Figure 2b is a graph showing the arsenic elution history with time when using sodium hydroxide, citric acid, hydrochloric acid as a cleaning agent for the sample 3 (field soil) according to the experimental example of the present invention, A is a hydroxide of 0.05M The case where sodium is used is shown and B shows the case where 0.1 M sodium hydroxide is used.

Figure 2c is a graph showing the arsenic elution history with time when using sodium hydroxide, citric acid, hydrochloric acid as a cleaning agent for the sample 4 (river sediment soil) according to the experimental example of the present invention, A is 0.05M The case where sodium hydroxide is used is shown, B shows the case where 0.1 M sodium hydroxide is used.

As shown in Fig. 2a to 2c, in the case of the target sample 2 (tailings soil), sodium hydroxide is 10 to 20 times compared to citric acid or hydrochloric acid, and in the case of the target sample 3 (field soil), sodium hydroxide is about 1.2 times than citric acid Citric acid was comparable to or slightly superior to sodium hydroxide in sample 4 (river sedimentary soil). However, for sample 4 (river sedimentary soil), sodium hydroxide was considered more economical considering the price of citric acid and sodium hydroxide.

On the other hand, the amount of arsenic leached by distilled water was 12 mg / kg in sample 2 (tailings soil), 14 mg / kg in field soil of sample 3 and 6 mg / kg in river sediment soil in sample 4, respectively. It appeared to be insignificant.

Furthermore, comparing the arsenic elution patterns of sodium hydroxide concentrations of 0.05M and 0.1M for sample 2 (tailings soil) and sample 3 (field soil), the initial elution was greater at 0.1M than 0.05M. After about 6 hours, the amount of leaching of arsenic was almost constant and the dissolution effect was over 90%. Even in subject sample 4 (river sedimentary soil), the amount of arsenic leaching was almost constant after about 6 hours.

Experimental Example 2-2: Measurement at the pilot scale by continuous washing

This experiment is to measure the residual arsenic concentration according to the results of the field application experiment using the continuous soil washing equipment at the pilot scale.

Table 3 shows the type and concentration of the washing solution used, the shaking ratio, the rotational speed and the measurement result (* unit: mg / kg dry soil).

Wash Solution Composition Shaking ratio (g: mL) 1, 2 cleaning part rotation speed (rpm)                                              Phase 1: 24 2nd: 10 1st: 12 2nd: 5 1st: 6 2nd: 2.5 1M hydrochloric acid (second wash) + sodium hydroxide 1M (third wash)-the first wash is 0.2M hydrochloric acid 1: 3 1.99 ± 0.20 ^* 1.81 ± 0.20 ^* 1.81 ± 0.02 ^* Cleaning time 1 time: 6 minutes 2 times: 3 minutes 3 times: 3 minutes 1 time: 6 minutes 2 times: 4 minutes 3 times: 4 minutes 1 time: 7 minutes 2 times: 5 minutes 3 times: 5 minutes 1: 5 - - 1.33 ± 0.33 ^* Cleaning time Episode 1:-Episode 2:-Episode 3:- Episode 1:-Episode 2:-Episode 3:- 1 time: 6 minutes 2 times: 4 minutes 3 times: 4 minutes 0.2 M hydrochloric acid (second wash) + 1 M sodium hydroxide (third wash)-0.2 M hydrochloric acid for the first wash                                              1: 5 - - 3.54 ± 0.10 ^*

As shown in Table 2, as a result of analyzing the arsenic concentration in the soil after washing by dividing the first, second and third by the rotational speed (up, middle, down), all soils are discharged from the first time The results with each washing time were below the baseline concentration (6 mg / kg).

Experimental Example 3 Determination of the Effect of the Concentration (or pH) of the Detergent on Heavy Metal Elution According to the pH of the Washing Effluent with Sodium Hydroxide as the Washing Solution

In order to determine the concentration of heavy metal eluted after adjusting the concentration (or pH) of the cleaning agent for heavy metal contaminated soil, the experiment was carried out by the following experimental procedure.

(1) The soil and distilled water were added to a Erlenmeyer flask with a volume of 1,000 mL, followed by shaking.

(2) The pH and heavy metal concentration of the shaken effluent were measured.

(3) A small amount of sodium hydroxide was injected and shaken at 6 hour intervals.

(4) The pH and heavy metal concentration of the effluent were measured.

(5) The shaking ratio (soil [g]: distilled water [mL]) of sample 2 (tailings soil) was 1: 10 (80 g: 800 mL), and sample 3 (field soil) and sample 4 (river sediment soil). ) Was 1: 5 (150 g: 750 mL), respectively.

3 is a graph showing the amount of arsenic eluted under each pH condition that is changed after the injection of varying the amount of sodium hydroxide according to the experimental example of the present invention.

As shown in FIG. 3, all three of the sample samples increased arsenic elution at pH 10 or higher, and it was found that arsenic was continuously eluted at pH 13 or higher. Therefore, the pH of the cleaning agent for maximizing the dissolution of arsenic with respect to arsenic contaminated soil was found to be excellent in the range of 10 or more (more, 13 or more).

Experimental Example 4-Measuring the Effect of Shaking Ratio with Sodium Hydroxide as the Washing Solution

Shaking ratio selection experiments were based on sodium hydroxide concentration of 0.2M for sample 3 (field soil) and sample 4 (river sedimentary soil) (this concentration is close to the effect of the following continuous washing method) and 6 hours of operation time. As a result, we found efficient and economic concussion costs.

In this experiment, the temperature was maintained at 20 ± 0.5 ℃, and the ratio of soil (g) and washing solution (ml) was changed to 1: 3, 1: 5, 1:10, 1:20, 1:30 at 300rpm. Applied.

Figure 4a is a graph showing the amount of arsenic contained in the washing effluent after washing with different shaking ratio using 0.2M sodium hydroxide for the target sample 2 (tailings soil) according to the experimental example of the present invention.

Figure 4b is a graph showing the amount of arsenic contained in the washing effluent after washing with different shaking ratio using 0.2M sodium hydroxide for the target sample 3 (field soil) according to the experimental example of the present invention.

Figure 4c is a graph showing the amount of arsenic contained in the washing effluent after washing with different shaking ratio using 0.2M sodium hydroxide for the sample 4 (river sediment soil) according to the experimental example of the present invention.

As shown in FIGS. 4A to 4C, the dissolution efficiency of arsenic in the sample 3 (field soil) increased from shaking ratio 1:10 to shaking ratio 1: 5, but the increase rate was not very large.

For sample 4 (river sedimentary soil), the maximum elution efficiency was shown at shaking ratio 1: 5, and the arsenic leaching efficiency decreased as the shaking ratio increased.

In conclusion, as a result of measuring the soils of the two target samples, it was found that 1: 5 was excellent due to the agitation ratio in consideration of the wear prevention, the efficient aspect, and the economical efficiency of the soil washing method. May wear out).

In addition, in this experiment, only two soils were used as samples, but in the case of soils other than river sedimentation or field soils, it was confirmed that the melting efficiency was excellent in the range of 1: 5 and below (also in this case 1: Below 3, the washing machine may be worn).

Experimental Example 5 Determination of the Effect of Concentration and Shake Ratio on Heavy Metal Contaminated Soil Containing Copper and Lead when Citric Acid was Used as Washing Solution

For the 500 mg / kg dry soil and 1,000 mg / kg dry soil, four concentrations of citric acid cleaners were applied: 10, 30, 50, and 100 mM with a maximum concentration of 100 mM. Four cases: 4, 1: 5, and 1: 6 were applied.

Experimental conditions were put 10gTlr of soil in a 100mL Erlenmeyer flask, a suitable amount of detergent was injected, and shaken at room temperature for 24 hours.

The Soil Environment Conservation Act sets 40% (60% purification level) of the pollutant concentration to be purged as the standard of concern. In this experiment, the target purification level is tentatively set to 70%, slightly higher than 60%. It was.

Figure 5a is a graph showing the removal rate after washing with varying the acid concentration (range of pH 1 ~ 4) and shaking ratio for copper in heavy metals according to the experimental example of the present invention, Figure 5b is an experimental example of the present invention Therefore, it is a graph showing the removal rate after washing with varying the acid concentration (range of pH 1-4) and shaking ratio with respect to the lead in heavy metals.

As shown in Figure 5a and 5b, for the same shaking ratio, the washing efficiency is improved as the concentration of the cleaning agent is increased, but when the target purification level is about 70%, in the case of lead, the shaking ratio 1: 5 to the citric acid 50mM 72% of cases and 76% of citric acid were found to be suitable for shaking ratio of 1: 4.

However, it is economical to use a little more water than doubling the amount of detergent, so the application of shaking ratio 1: 5 to 50mM citric acid is required for soil contaminated with lead 1,000mg / kg dry soil. It was found to be the best soil washing condition.

Furthermore, for the same reason, copper was found to be the best soil washing condition for soil contaminated with copper 500mg / kg dry soil when applying the shaking ratio 1: 5 to citric acid 50mM.

Experimental Example 6-Continuous Washing Experiment

Continuous soil washing experiments were conducted to find ways to further improve the washing efficiency of the three target soils.

In this experiment, we performed the continuous soil washing experiments with the most effective shaking ratio of 1: 10, 1: 5 and 1: 5 using sodium hydroxide 0.2M.

Continuous soil washing experiments were conducted five times at 6-hour intervals, and the amount of arsenic remaining after washing was extracted by soil contamination process test method and analyzed and compared according to each cycle. The temperature was kept at 20 ± 0.5 ° C. and stirred with a stirrer at 300 rpm for 6 hours.

6 is a graph showing the amount of arsenic remaining in the soil after the continuous washing with 0.2M sodium hydroxide according to the experimental example of the present invention.

As shown in FIG. 6, three target samples 2 (tailings soil), target sample 3 (field soil), and target sample 4 (river sedimentation soil) based on the initial arsenic contamination concentration using the soil contamination process test method were used. In the first washing of the soil of the sample, it decreased to 104, 29 and 3mg / kg, respectively, and showed removal efficiency of about 90, 80, 82%, and the sample 2 (tailings soil) was washed up to 5 times. The concentration of arsenic remaining was almost constant.

On the other hand, in the case of subject sample 3 (field soil), the concentration of arsenic after the third washing showed a concentration (18 mg / kg) that satisfies the Concern Standard of the Soil Environment Conservation Act (20 mg / kg). The subsequent concentration was 8 mg / kg and 94% was washed at a concentration (6 mg / kg) close to the baseline of concern (6 mg / kg).

The sample 4 (river sedimentary soil) was present at a concentration (approximately 3 mg / kg) suitable for the concentration of the branches after the first washing, and the concentration after the fifth washing was about 1 mg / kg, which was 94% washed. It became.

In summary, the sample 2 (tailings soil) showed 90 ~ 92% treatment efficiency after 5 consecutive soil washing, but did not meet the standard of soil environmental conservation method.

This is because most of the arsenic is the most arsenic, as shown in the effect of the large amount of arsenic because the sample 2 (the tailings soil) is present as fine soil and has a large specific surface area. It is presumed that this is because it exists in a part which is difficult to elute, that is, in a crystal.

In case of sample 3 (field soil), it was suitable for the area of concern criteria, and the concentration was close to the area of concern area after the fifth consecutive soil washing. Target sample 4 (river sedimented soil) can be seen that the soil is suitable for the area of concern in the first washing.

Experimental Example 7-Measurement of pH Effect on Formation of Flux

Cut-off size accounting for 94% of the total weight was set to # 100 (0.15mm) and washing experiments were performed using 0.2, 1M sodium hydroxide and 0.1, 0.2, 1M hydrochloric acid.

Experimental conditions were mixed 20g soil and 100mL washing solution in a 300mL Erlenmeyer flask, and the temperature was maintained at 20 ± 0.5 ℃ and shaken at 300rpm for 6 hours.

After washing, the pH of the supernatant was measured, and the formed floc was collected using a microfluidic pump.

In order to determine the arsenic concentration of the flocs were dried for 6 hours at 100 ± 5 ℃ and then pretreated according to the soil process test method and analyzed.

Table 3 shows the experimental results for maximizing the floc formation, and measured the arsenic concentration of the formed floc and the pH of the washed effluent during the injection of 0.2M and 1M sodium hydroxide and the injection of 0.1M, 0.2M and 1M hydrochloric acid, respectively. .

Sodium hydroxide                                              Hydrochloric acid                                              0.2M 1M 0.1M 0.2M 1M pH 12.9 13.3 6.2 5.9 0.6 As conc. [mg / kg dry soil] 418 147 990 1,806 245

As shown in Table 3, the arsenic concentrations of the flocs formed during the injection of 0.2M and 1M sodium hydroxide were about 418 and 147 mg / kg dry soil, respectively, and the pH of the effluent was about 12.9 and 13.3, respectively.

In the case of 1M hydrochloric acid, the concentration of about 245mg / kg dry soil (pH 0.6) was shown. For 0.1M and 0.2M hydrochloric acid, the concentrations of arsenic were 990 and 1,086 mg / kg dry soil, respectively, and the pH of the effluent was measured to be 6.2 and 5.9, respectively.

Thus, the floc produced during soil washing was found to exist in a relatively high concentration by agglomerating a large amount of arsenic in the pH range of 5 to 6, and the washing efficiency can be improved by efficiently removing and removing the floc formed during soil washing. And it was found.

Experimental Example 8-Continuous Cleaning Method of Contaminated Soil Contaminated Heavy Metals>

Experiments on the application of the continuous cleaning method to floc-forming heavy metal contaminated soils were conducted to find ways to improve the cleaning efficiency.

When the first soil washing method was applied to the soil, the formation of flocs in the effluent was observed visually.

Therefore, the experiment was conducted according to the presence or absence of floc, and the cut-off size of the soil was # 100 sieve size.

Continuous soil washing was carried out five times at intervals of six hours according to the presence or absence of the floc generated during soil washing. The residual arsenic concentration after washing was analyzed according to each round.

Shaking ratio 1: 5 using 1M hydrochloric acid, the temperature was maintained at 20 ± 0.5 ℃ and shaken for 6 hours at 300rpm.

Experiments performed without removing the flocs generated in each step are the same as the above experimental conditions, and in the case of the experiment performed by removing the flocs, the floc formed in each step was removed by washing with water.

7 is a graph showing the amount of arsenic remaining according to the presence or absence of flocs after continuous washing with 1M hydrochloric acid for the floc-forming heavy metal contaminated soil according to the experimental example of the present invention.

As shown in Figure 7, when the washing without removing the formed flocs, the concentration of arsenic remaining up to five consecutive washing step showed about 9mg / kg dry soil, but in the case of continuous washing to remove the floc 3 It is about 6.7 mg / kg dry soil when washed twice, and about 3.9 and 3.3 mg / kg dry soil when washed 4 times and 5 times, respectively. It could be known.

As a result, it was found that in order to remove arsenic present in the heavy metal contaminated soil that forms the flocs, floc removal is essential for improving the cleaning efficiency.

Experimental Example 8 Continuous Washing Method Concurrently Acid and Base

In this experiment, a one-step wash using 0.2M hydrochloric acid with the largest flocs was formed, followed by a two-step wash on the washed soil.

The cleaning agent used for the two-stage washing was 0.2M, 1M hydrochloric acid and 1M sodium hydroxide.

In the case of the three-stage washing, the soil washed in the two-stage washing was continuously washed in parallel with the washing agent used in the two-stage washing and the application concentration.

Experimental conditions were washed every 6 hours, the temperature was maintained at 20 ± 0.5 ℃ and shaken for 6 hours at 300rpm.

In addition, in order to coagulate and precipitate the arsenic contained in the washing effluent generated during continuous washing by combining acid and base, the washing effluent was mixed at a ratio of 1: 1. After adjusting the pH using acid, the effluent contained in the washing effluent Arsenic concentration was determined.

Table 4 shows the results of the continuous washing in combination with the acidic group cleaner. In addition, the results of measuring the pH of the final effluent to derive natural neutralization conditions using the effluent generated during the soil wash.

Experimental Example 8 1st step cleaning Two stage wash 3-step washing As conc. [mg / kg dry soil] pH Experimental Example 8-1 0.2M hydrochloric acid 1M sodium hydroxide 1M hydrochloric acid 4.0 0.45 ± 0.05 0.2M hydrochloric acid 11.1 3.52 ± 0.05 1M sodium hydroxide 8.7 13.52 ± 0.05 Experimental Example 8-2 1M hydrochloric acid 1M sodium hydroxide 1.5 13.25 ± 0.05 0.2M Sodium Hydroxide 2.1 12.77 ± 0.05 0.2M hydrochloric acid 6.2 0.93 ± 0.05 Experimental Example 8-3 0.2M hydrochloric acid 1M sodium hydroxide 5.5 13.45 ± 0.05 1M hydrochloric acid 5.1 0.30 ± 0.05 0.2M hydrochloric acid 9.6 0.86 ± 0.05

As can be seen from Table 4, the lowest residual arsenic in the experiment of Experimental Example 8-1 was a method of washing the sodium hydroxide 1M in parallel and 1M hydrochloric acid in the third step, the concentration of about 4.0mg / kg dry soil The final pH was determined to be 0.45 ± 0.05.

In the experiment of Experimental Example 8-2, the method of washing the sodium hydroxide 1M and 0.2M in parallel with the soil washed with 1M hydrochloric acid in the second step was about 1.5 and 2.1 mg / kg dry soil, respectively. Seemed. The pH at this time was measured to be 13.25 ± 0.05 and 12.77 ± 0.05, respectively.

In the experiment of Experimental Example 8-3, washing with 0.2M hydrochloric acid in step 2 and washing with sodium hydroxide 1M and hydrochloric acid in 1 step in parallel was about 5.5 (pH 13.45 ± 0.05) and 5.1 (pH 0.30 ± 0.05, respectively). The mg / kg dry soil showed almost the same concentration, but was excluded from the runoff mixing experiment in consideration of the natural neutralization condition by the wash runoff.

Meanwhile, in order to derive basic operating conditions for natural neutralization, the effluents generated by the washing steps of the 8-2 and 8-3 methods having low residual arsenic concentrations among the Experimental Examples 8-1, 8-2, and 8-3 methods were Mixing was carried out under conditions of 1: 1, 1: 2, 1: 3. The results of measuring the pH are shown in Table 5.

Washing solution                                              pH 1: 1 (acid: base) 1: 2 (acid: base) 1: 3 (acid: base) 1M hydrochloric acid 1M sodium hydroxide 9.53 ± 0.05 12.82 ± 0.05 12.84 ± 0.05 0.2M Sodium Hydroxide 0.76 ± 0.05 1.06 ± 0.05 1.43 ± 0.05 0.2M hydrochloric acid 1M sodium hydroxide 13.03 ± 0.05 13.14 ± 0.05 13.17 ± 0.05

As shown in Table 5, when the effluent of 1M hydrochloric acid and 1M sodium hydroxide in the method of Experimental Example 8-2 was mixed under the conditions of 1: 1, pH 9.53 ± 0.05 was the closest result to pH 7.

8 is a graph showing the concentration of arsenic removed under each pH condition after 1: 1 mixing of the effluents generated when washing with acid and base in parallel according to the experimental example of the present invention.

As illustrated in FIG. 8, after adjusting the pH by injecting acid into the washing effluent mixed at a ratio of 1: 1, the concentration of arsenic remaining was analyzed. As a result, drinking water standards (50 ppb) were in the range of pH 6 and 8-9. It seemed to fit).

Therefore, the acid and base washes considering the residual arsenic (1.5 mg / kg dry soil) by the effluent and the natural neutralization basic operating conditions (final pH 9.53 ± 0.05) are performed by washing 1M hydrochloric acid and 1M sodium hydroxide in parallel. It was found that 6 is suitable as a pH condition for the generated washing effluent.

Experimental Example 9-Measurement of the Effect of pH and Coagulant Addition of Washing Effluent

First, as shown in the washing solution experiment, sodium hydroxide, a washing solution having an excellent dissolving power in arsenic-contaminated soil, was stirred at a concentration of 0.2 M, a shaking ratio of 1: 5, and a temperature of 300 rpm at a temperature of 20 ± 0.5 ° C. Shake for 6 hours at speed.

Here, the test target sample is the target sample 3 (field soil) and the target sample 4 (river sedimentation soil). The shaken effluent was filtered to 0.45 ㎛ for supernatant and then stored in a brown bottle refrigerated at 4 ℃, a jar test was carried out for the precipitation experiment.

The initial concentrations of arsenic and various metals contained in the washed effluents of the sample, that is, the sample 3 (field soil) and the sample 4 (river sedimentary soil), are shown in Table 6. The concentrations of arsenic and various metal components were analyzed using ICP-OES and AAS (Atomic Absorption Spectrometer, Model: AA-6402F, SHIMADZU), respectively.

Al Si Mn Fe As pH Sample 3 (field soil) 136.1 107.9 5.0 45.3 73.9 13.09 ± 0.05 Sample 4 (river sediment) 27.3 32.3 - 0.3 2.9 13.29 ± 0.05

Specifically, in this experiment, 250 ml of river sediment and field soil effluent were injected into a 300 ml beaker, and then the initial pH was set to 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12. By adjusting, the removal efficiency of arsenic due to precipitation was observed.

A pH meter (Model: DP-880) was used to adjust the pH of the effluent, and a small amount of nitric acid (65%) stock solution was injected into the micropipette to observe the change in pH. It was soon.

As such, after adjusting the pH, the mixture was allowed to stand for 30 minutes, and 20 ml of the sample was collected and analyzed for arsenic and various metal components of the filtrate using 0.45 μm of filtrate.

FIG. 9A (left graph) shows that other heavy metal ions contained in the washing effluent of the river sedimentation soil are removed by mutual coagulation and precipitation (coprecipitation) at respective pH conditions in accordance with the experimental example of the present invention. 9B (right graph) is a graph showing the concentration of each remaining ion, the other heavy metal ions contained in the washing effluent of the field sedimentation soil coagulation and precipitation (coprecipitation) at each pH condition according to the experimental example of the present invention After removal by the action, a graph showing the concentration of each ion remaining in the washing effluent.

As shown in FIG. 9, after alkali washing, aluminum shows relatively higher concentrations in iron than in iron in the effluents of sample 3 (field soil) and sample 4 (river sedimentary soil). It is presumed to be relatively high compared to iron at high pH conditions. The dissolved metal components thus induce sediment formation due to appropriate pH conditions.

On the other hand, the removal amount of aluminum and iron for Sample 4 (river sediment) and Sample 3 (field soil) were the highest at pH values of 5-7 and 4-7, respectively.

The highest precipitation of arsenic concentrations in the washed effluents of sample 4 (river sediment) and sample 3 (field soil) was 0.02 (about 99%) and 26.4 (about 66%) mg / L, respectively, at a pH of 5 Although removal efficiency was shown, the removal efficiency of silicon (Si), which causes adsorption competition with arsenic, was the highest at pH 7 conditions. Therefore, the pH 5 condition was determined to be the best pH for arsenic precipitation removal of the two soil wash effluents.

The effluent of subject sample 4 (river sedimented soil) was found to have a residual pH of arsenic just by adjusting the pH to meet the drinking water standard.

However, in the case of washing effluent of sample 3 (field soil) containing high concentration of arsenic, the arsenic removal amount of aluminum due to pH adjustment is about 8 times lower than that of sample 4 (river sediment soil). In addition to treatment by pH adjustment, precipitation treatment by addition of a flocculant is required.

Accordingly, experiments were carried out for the addition of a flocculant, for example iron chloride (FeCl ₃ ).

Based on the results of the pH selection experiment on the washed out effluent of Sample 3 (field soil), 300 ml of the filtrate passed through the filter paper (0.45 μm) was placed in a 500 ml beaker, and then adjusted to 5, which is an optimum pH condition for arsenic removal.

The mass ratios of arsenic (As) and iron (Fe) are 1: 1, 1: 3, 1: 5, 1: 8, 1: 10, 1: 12 and 1: 20 for selecting the optimal amount of FeCl ₃ FeCl ₃ was injected in the amount.

The experimental procedure of the Jar test was as follows.

(1) Different amounts of FeCl ₃ were injected into the washing effluent.

(2) Then, it stirred rapidly for 5 minutes, maintaining 100 rpm.

(3) Then, the mixture was stirred slowly at 40 rpm for 60 minutes while maintaining pH 5.

(4) Then, after 20 minutes of standing, a 20 ml sample was aliquoted and filtered using a 0.45 µm filter, followed by analysis of arsenic in the filtrate.

10 is a graph showing the mass ratio of iron injected to remove arsenic present in the washing effluent at a relatively high concentration according to the experimental example of the present invention.

As shown in FIG. 10, it was found that the concentration of arsenic at a ratio of 1: 11 (arsenic: iron) was suitable for drinking water standards.

Experimental Example 10 Application of Nanoporous Media

Method for preparing nano porous media

(1) Each metal precursor of iron and lanthanum was dissolved in distilled water at a given concentration: the final volume of the solution in which the metal was dissolved was 15 mL.

(2) 10 g of dried diatomite was placed in a 500 mL Teflon bottle.

(3) A 1 mL iron and lanthanum precursor solution was dropped onto diatomaceous earth using a 1 mL micro pipette.

(4) After the lid was closed, the Teflon bottle was placed in a vortex mixer, and stirred rapidly at 3000 rpm for 5 minutes at which the iron solution and the diatomaceous earth were uniformly mixed so that a red change in the media could be observed.

(5) Injection of 1 mL of metal precursor solution was repeated until the volume of metal solution and mass (g) of diatomaceous earth were 1.5: 1.

(6) The solids are dried at room temperature for one day. (7) Calcination was performed in an oven programmed to increase the temperature from room temperature to 1.0 ° C./min.

Thereafter, the solids were stored in a vacuum chamber. The solids were washed until the conductivity came close to distilled water. For conductance experiments, 0.02 g of each medium was placed in 5 mL of distilled water, stirred for 10 minutes, and filtered to 0.45 μm. The conductance of the filtrate was analyzed with a conductance meter (YSI model 32) to determine if iron and lanthanum ions leached.

Experiment method

The column experiments were conducted to determine the arsenic-contained effluent washing effluent and the arsenic removal efficiency by each adsorption medium for arsenic-contaminated soil.

The highest efficiency of arsenic removal in the precipitation step was obtained at pH 5.0, where the pH of the influent containing 50 ppb of arsenic in the column test was 5.0.

Three glass columns (1.5 cm inner diameter and 15 cm length) were carefully filled to uniformly distribute 1.5 g of Fe (25%), La (50%), and AAFS-50.

In the second column experimental phase, the test was performed at a typical pH of groundwater, 6.5, containing 500 ppb of arsenate or arsenite in the influent.

Through this experiment, the adsorption capacity of each medium in the general pH range of groundwater was also found.

In this experiment a high EBCT of 3 min was set. The apparent density of each adsorbent was measured at the same empty bed contact time (EBCT) as the other flow rates.

The column was flushed with distilled water prior to passing through the arsenic contaminated water. A peristaltic pump was used to feed the synthesized arsenic solution from 12L jar to the bottom of the column.

Experiment result

12 is a graph showing experimental results [Ar (50%)-, Fe (25%)-diatomaceous earth, and arsenic column experiments of AAFS-50 (conditions: pH = 6.5, concentration. = 500 ppb, media mass = 1.5 g) , EBCT = 3.3 min)], and arsenite experiments showed arsenic removal of each medium under the same conditions.

Referring to FIG. 12, in the experiment, AAFS-50 showed higher arsenate (350BV below 50 μg / L) removal ability than arsenite. However, metal oxides supported on diatomaceous earth showed better efficiency. About 1,100 and 2,100 BV were treated with Fe (25%)-diatomite to less than 10 and 50µg / L, while La (50%)-diatomite treated 1 ~ 100BV by treating ~ 300 BV with less than 10µg / L of effluent. Despite lower throughput than Fe (25%)-diatomite treated, it did not go above 50 μg / L concentration during 5,000 BV.

Based on these results, when calculating BV as treated effluent volume, Fe (25%)-diatomaceous earth was 25.7 times higher than AAFS-50. Although no flow data for La (50%)-diatomaceous earth was shown, it was reduced to 20% of the initial flow rate after 5,000 BV, indicating a pore blockage. This problem may be due to the major precipitation of LaAsO4 (lanthanum arsenate).

According to the method for cleaning heavy metal contaminated soil according to the present invention, the removal effect of heavy metals such as arsenic, copper and lead, especially contained in the soil, is excellent, and further satisfies the economics. In addition, in the present invention, particularly by using a nano-porous medium, heavy metal contaminated soil and heavy metals in heavy metal contaminated groundwater surrounding heavy metal contaminated soil can be treated with excellent efficiency.

Although the present invention has been described in connection with the above-mentioned preferred embodiments, it is possible to make various modifications or variations without departing from the spirit and scope of the invention. Accordingly, the appended claims will cover such modifications and variations as fall within the spirit of the invention.

Claims (18)

In the method of washing heavy metal contaminated soil, Continuous washing method for washing heavy metal contaminated soil in parallel with acid and base, A first washing step of acid washing the heavy metal contaminated soil using hydrochloric acid at a concentration of 0.2-1 M or citric acid at a concentration of 0.01-1 M as the washing solution; A second washing step of washing the soil washed in the first washing step using hydrochloric acid at a concentration of 0.2 to 1 M or citric acid at a concentration of 0.01 to 1 M; And And a third washing step of washing the soil washed in the second washing step with a 0.2-1 M sodium hydroxide base. Wherein each washing step is a method of washing heavy metal contaminated soil, characterized in that for removing the floc formed in the case of the soil is formed during washing. The method of claim 1, The third washing step is to adjust the concentration of the sodium hydroxide in response to the pH of the soil to be washed so that the pH of the washing effluent is 10 or more, wherein the soil is characterized in that the soil does not form a floc upon washing Method of cleaning heavy metal contaminated soil. The method of claim 2, Method for washing the heavy metal contaminated soil, characterized in that the pH of the washing effluent to 13 or more. The method of claim 1, The method of washing heavy metal contaminated soil, characterized in that the shaking ratio of the washing solution to the soil weight in each washing step is 1: 5 or less. The method of claim 1, The washing step is a method for washing heavy metal contaminated soil, characterized in that the pH of the washing effluent after washing to wash or aggregate the heavy metal in the floc with respect to the soil on which the floc is formed. The method of claim 5, The washing step is a method for washing heavy metal contaminated soil, characterized in that the pH of the washing effluent after washing to ensure that the arsenic is aggregated or adsorbed in the floc. delete The method of claim 1, Each washing step further comprises the step of flocculating or adsorbing the heavy metal in the washing effluent to precipitate and remove, and the pH is adjusted to increase the removal amount of the heavy metal. The method of claim 8, Each washing step is a method for washing heavy metal contaminated soil, characterized in that for adjusting the pH of the washing effluent in the range of 4-7. The method of claim 9, The washing method of the heavy metal contaminated soil, characterized in that to adjust the pH of the washing effluent in each washing step to 5. The method of claim 1, Mixing any two or more of each of the washing effluent from each washing step, and agglomerated or adsorbed by the heavy metal from the mixed washing effluent to precipitate and remove, adjusting the pH to increase the removal amount of the heavy metal Method for washing heavy metal contaminated soil. The method of claim 11, Washing with 0.2 M hydrochloric acid in the first washing step, washing with 1 M hydrochloric acid in the second washing step, washing with 1 M sodium hydroxide in the third washing step, washing effluent of the second step and the third step Method for washing heavy metal contaminated soil, characterized in that to adjust the pH of the washing effluent to 6 or 8 to 9 to mix or adsorb, precipitate and remove the heavy metal after mixing the effluent of 1: 1. The method according to claim 8 or 11, wherein The method further comprises the addition of iron chloride for the flocculation or adsorption, precipitation and removal. The method of claim 13, The method is a method for washing heavy metal contaminated soil, characterized in that the iron chloride is added so that the weight ratio of iron to arsenic is 1:13 or less. The method of claim 14, In each washing step, the pH of the washing effluent is adjusted to 5, and heavy chloride-contaminated soil is introduced such that iron chloride is added so that the weight ratio of arsenic and iron is 1:11 for the aggregation, adsorption, precipitation and removal. Method of washing. The method of claim 1, The first washing step and the second washing step each use 0.2 M hydrochloric acid or 0.5 M citric acid, and the third washing step uses 0.2 M sodium hydroxide. Method of washing. The method of claim 1, The method further comprises the step of adsorbing the washed effluent after the agglomeration or adsorption, precipitation and removal using a porous medium having nano-sized pores with metal ions serving as a functional group or pores attached to the surface. Method for cleaning heavy metal contaminated soil. The method of claim 1, The method further comprises adsorption treatment of groundwater in the vicinity of heavy metal contaminated soil with or separately from the soil washing using a porous medium having nano-sized pores with metal ions serving as functional groups or pores attached to the surface. Method for washing heavy metal contaminated soil, characterized in that.

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