KR20110076240A - Method for removing heavy metal and color from landfill leachates - Google Patents

Abstract

PURPOSE: A method for eliminating heavy metal ions and color from landfill leachates is provided to effectively control organic materials and chromaticity of the landfill leachates. CONSTITUTION: Landfill leachates passes through a column filled with steel manufacturing slag in order to absorb and eliminate heavy metal ions from the landfill leachates. The pH of the landfill leachates is neutralized. The pH of the landfill leachates is controlled by carbon dioxide containing exhaust gas. The color of the landfill leachates is eliminated by passing the landfill leachates through a column filled with activated charcoal.

Description

Method for removing heavy metal and color from landfill leachates

The present invention relates to a method for removing heavy metal ions and colors in leachate, and more particularly, to a method for treating leachate using steelmaking slag, carbon dioxide-containing flue gas, and activated carbon.

Leachate from landfills is a malignant wastewater containing various organic substances, heavy metal ions, and other inorganic substances, which is difficult to treat.

The best known landfill leachate treatment to date is collected through a porous layer and then treated by a biological method, but heavy metal ion removal is mainly used for chemical precipitation.

Recently, however, by adsorbing contaminants in leachate from landfills using clay or cover soil, which are used as landfill structures, methods for fundamentally reducing environmental risks and stabilizing landfills by recycling leachate are actively carried out. Is being studied.

However, the conventional methods as described above have many problems in terms of technical aspects, and chemical precipitation methods using chemicals require a lot of chemical costs, a large amount of sludge generation, and additional treatment of the resulting sludge. There is a problem.

Accordingly, one aspect of the present invention is to provide a method for economically and efficiently controlling heavy metal ions and chromaticity in leachate.

According to one aspect of the invention, the first step of the landfill leachate is passed through a column filled with steelmaking slag adsorption and removal of heavy metal ions and neutralized by adjusting the pH, the second step of adjusting the pH using carbon dioxide-containing flue gas and Provided is a method for removing heavy metal ions and chromaticity in a landfill leachate, comprising a third step of passing the activated carbon through a packed column to remove chromaticity of the leachate.

The residence time of the leachate passing through the column filled with the steelmaking slag is 1.5 to 5 hours, the flow rate is preferably 4 to 6 S.V.

In the first step, the pH is preferably adjusted to greater than 8.

In the second step, the pH is preferably adjusted to 6 to 8.

The heavy metal ion is preferably at least one selected from the group consisting of chromium, zinc and lead.

The exhaust gas preferably contains 10 to 30% by volume of carbon dioxide.

The present invention is to treat the leachate generated in the landfill using steelmaking slag, carbon dioxide-containing flue gas and activated carbon, in particular, a method that can economically and efficiently remove heavy metal ions such as chromium, zinc, lead, etc. It is about.

Hereinafter, the present invention will be described in more detail, but embodiments of the present invention can be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. In addition, the embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

According to the present invention, the landfill leachate is passed through a column filled with steelmaking slag in a first step to desorb and neutralize heavy metal ions, and neutralize by adjusting pH. In a second step, pH is adjusted using a carbon dioxide-containing exhaust gas. Provided is a method of treating landfill leachate, which passes through a column filled with activated carbon in three steps to remove leachate's chromaticity and organic matter.

1 is a process diagram schematically showing an example of a leachate treatment method according to the present invention. Referring to Figure 1, the method of the present invention is a collection tank for collecting landfill leachate containing heavy metal ions, steelmaking slag packed column for first neutralizing the leachate and adsorption of heavy metal ions, the treated leachate It can be carried out through a process consisting of a pH adjusting tank for adjusting the pH to a carbon dioxide-containing flue gas, and an activated carbon packed column for removing organic matter and color.

Referring to the heavy metal treatment method of the present invention divided by stages as follows.

In the first step, landfill leachate containing heavy metal ions is first contacted through a steelmaking slag packed column for a certain time. As a result, as listed in Table 1, steelmaking slag containing about 50 wt% of CaO generally acts as a neutralizing agent because the CaO shows alkalinity, and the pH is adjusted to exceed 8.

On the other hand, as can be seen in Table 2 of the following examples, each pollutant concentration eluted from the steelmaking slag is very low, there is no problem in using the steelmaking slag as a neutralizer and heavy metal ion adsorption removing agent.

The residence time of the landfill leachate passing through the column filled with the steelmaking slag is preferably 1.5 to 5 hours, and the flow rate is preferably 4 to 6 S.V (space velocity). When the residence time is 1.5 hours or more, it can be seen that the heavy metal ions as shown in FIG. 2 are almost completely removed at about 90% or more. When the leachate flows through the column filled with the steelmaking slag, if the residence time in the column is less than 1.5 hours, the treatment flow rate increases, but the treatment efficiency decreases, and the effect is difficult to be expected. There is a tendency to be too small.

Preferably, the packed density of the column is 0.8 to 0.9 kg / L, and when the packed density is less than 0.8 kg / L, the contact efficiency of the wastewater and the steelmaking slag decreases due to the channeling effect, and the particle size exceeds 0.9 kg / L. The size is so small that the water resistance is large.

On the other hand, the specific surface area of the steelmaking slag particles has the greatest influence on the adsorption capacity of heavy metal ions, and as shown in Table 3 of the Examples, the smaller the steelmaking slag particles are, the more the surface area increases, and thus the adsorption area increases, thereby increasing the adsorption capacity. Is improved.

As described above, the leachate from the landfill is passed through a packed column of steelmaking slag, which is a by-product from the steelmaking process of the steelworks, to effectively adjust the pH before discharging it into the water, while adsorbing heavy metal ions in the pores of the steelmaking slag. By its capacity, heavy metal ions can be desorbed.

The steelmaking slag used in the present invention may use a conventional steelmaking slag, and a steelmaking slag having a composition as shown in Table 1 may be used as a representative example thereof.

ingredient CaO SiO ₂ Al ₂ O ₃ T-Fe MnO Composition (unit: wt%) 44.8 ~ 52.3 13.2-18.8 0.9-2.8 14.8 ~ 19.2 2.8 ~ 9.6

In a second step, the pH is adjusted to 6-8, preferably to about 7, using carbon dioxide containing flue gas for final pH control of the landfill leachate. The exhaust gas preferably contains 10 to 30% by volume, preferably 20% by volume, of carbon dioxide. As can be seen in FIG. 3, a 20 vol% carbon dioxide-containing exhaust gas may be added at 1 L / min to adjust the pH from 8.5 to 5.5 within 2 minutes, and the pH may be adjusted to 6 to 8 within 1 minute.

The heavy metal ions in the landfill leachate which can be removed by the present invention may be at least one selected from the group consisting of chromium, zinc and lead.

Finally, when the leachate is passed through the activated carbon packed column, the leachate has a transparent color, and organic matter is removed by adsorption from the pores of the activated carbon to satisfy the requirements of the final treated water.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

<Examples>

Experimental Example 1: Confirmation of Secondary Contamination by Steelmaking Slag

In order to determine the secondary contamination by steelmaking slag, the concentration of contaminants in the permeated water by the steelmaking slag dissolution test was analyzed, and the results are shown in Table 2 below.

ingredient F CD Pb Mn Cr Emission allowance standard (unit: mg / L) 2 or less 0.02 or less 0.1 or less 2 or less 0.5 or less Content (unit: mg / L) 0 ~ 0.1 0 0-0.01 0 0-0.02

As can be seen in Table 2, the concentration of each pollutant eluted from the steelmaking slag is very low, indicating that there is no problem in using the steelmaking slag as a pH regulator and an adsorption remover of the landfill leachate.

Experimental Example 2 Analysis of Specific Surface Area According to Particle Size of Steelmaking Slag

The most influential factor on the adsorption capacity of heavy metal ions is the specific surface area of the steelmaking slag particles. The smaller the steelmaking slag particles are, the more the surface area increases, and thus the adsorption area also increases, thereby improving the adsorption capacity. Table 3 below shows the results of the specific surface area analysis according to the particle size of steelmaking slag.

Particle size (mesh) 7-12 12-20 20-70 Specific surface area (m &lt; 2 &gt; / g) 20.27 23.61 41.43 Pore Volume (cc / g) 0.0072 0.0084 0.0147

Experimental Example 3: pH Control by Carbon Dioxide-Containing Flue Gas

For final pH control of the leachate, carbon dioxide-containing flue-gas can be introduced into the leachate of pH> 8 passing through a column filled with steelmaking slag to treat the pH stably near 7.

As can be seen in FIG. 3, 20 vol% carbon dioxide-containing flue gas may be added at 1 L / min to adjust the pH to 6 to 8 within 1 minute.

Thereafter, when the leachate is passed through the activated carbon packed column, the leachate may have a transparent color to satisfy the requirements of the final treated water.

Example 1

In order to experiment with heavy metal ion and chromaticity removal effect of landfill leachate according to the present invention, a heavy metal ion-containing leachate synthesized in place of the landfill leachate was filled with a 20-70 mesh steel slag 322g and 470mm in a column having an internal diameter of 26 mm and a height of 600 mm. In one column, it was contacted upflow for 5 hours at a flow rate of 4-6 SV.

As a result, it was confirmed that heavy metal ions including chromium, zinc, and lead ions were precipitated and removed by hydroxide, and that heavy metal ions were adsorbed and removed by the adsorption capacity of the steel-making slag pores.

Figure 2 is a graph showing the effect of removing heavy metal ions with respect to time, it can be seen that the heavy metal ions are almost completely removed to about 90% over 1.5 hours.

The present invention is not limited by the above-described embodiments and the accompanying drawings, but is intended to be limited only by the appended claims. It will be apparent to those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. something to do.

1 shows a process chart of the leachate according to an embodiment of the present invention.

2 is a graph showing the heavy metal ion removal efficiency with respect to the time change when the treatment according to an embodiment of the present invention.

Figure 3 is a graph showing the pH change over time after the addition of carbon dioxide-containing exhaust gas.

Claims (6)

A first step of allowing the landfill leachate to pass through a column filled with steelmaking slag to desorb heavy metal ions and to neutralize the pH by adjusting pH; A second step of adjusting pH using carbon dioxide-containing flue gas and Third step of removing chromaticity of the leachate by passing it through a column filled with activated carbon Method for removing heavy metal ions and chromaticity in landfill leachate comprising a. The method of claim 1, wherein the leachate passes through a column packed with steelmaking slag and has a residence time of 1.5 to 5 hours and a flow rate of 4 to 6 S.V (space velocity). The method of claim 1, wherein the pH is adjusted to greater than 8 in the first step. The method of claim 1, wherein the pH is adjusted to 6 to 8 in the second step. The method of claim 1, wherein the heavy metal ion is at least one selected from the group consisting of chromium, zinc, and lead. The method of claim 1, wherein the exhaust gas contains 10 to 30% by volume of carbon dioxide.

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