KR20030062988A - Remediation and dewatering of dredged slurry and mine tailing with the vacuum method and electrokinetic phenomenon(Vacuum-electrokinetic dewatering and remediatin method) - Google Patents

Abstract

PURPOSE: A remediation and dewatering of dredged slurry and mine tailing with vacuum method and electrokinetic phenomenon(vacuum-electrokinetic dewatering and remediation method) is provided, which can remove heavy metal contained in river bed sediment and highly moisturized mine tailing by desorbing heavy metal by electrokinetic phenomenon and by removing the desorbed heavy metal by electrophoresis and mud flow caused by electro-osmosis and vacuum-dehydration at water discharge material served also as a cathode. The system can also facilitate dewatering by smoothly removing pore water by vacuum-dehydration and electro-osmosis. CONSTITUTION: In the purifying and dewatering treatment method of river bed sediment and highly moisturized mine tailing contaminated with heavy metal within a shortened time by a vacuum-dehydration and electrokinetic phenomenon, hydrogen ion generated by electrolysis at anode(3) migrates toward the soil sample by electrophoresis caused by electrostatic force and mud flow caused by electro-osmosis and vacuum-dehydration to separate heavy metal adsorbed onto the surface of soil particle, and the desorbed heavy metal ions migrate toward water draining material(4) served also as a cathode by electrophoresis caused by electrostatic force and mud flow caused by electro-osmosis and vacuum-dehydration to remove heavy metal and at the same time smoothly remove pore water by vacuum-dehydration and electro-osmosis.

Description

(Remediation and dewatering of dredged slurry and mine tailing with the vacuum method and electrokinetic phenomenon (Vacuum-) by the combined technique of vacuum drainage technique and electrokinetic phenomena electrokinetic dewatering and remediatin method)}

The present invention combines vacuum drainage techniques and electrokinetic phenomena to reduce heavy metal content and volume during recycling and landfill treatment of dredged soils and tailings contaminated with heavy metals.

Currently, dredged soil treatment is reclaimed at land reclamation site, landfill site, waste landfill site after purification of landfills, recycling, recycling, or when the pollution is severe, after purifying pollutants through closed water disposal site and closed disposal site. However, in general, there are many known techniques for the purification of contaminated soil, but only some of the organic contaminants have been commercialized for contaminated dredged soils, and almost no dredged soils contaminated with heavy metals. In addition, since most dredged soils are highly functional, containing many fine particles such as clay, much time and effort are required to reduce water content.

Currently, the dewatering treatment of dredged soils uses coagulant or flocculant in the lagoon or presses or centrifuges, and the purification treatments include physical separation, thermal processes and biological processes. Biological decontamination is used. However, the use of flocculants requires a lot of secondary contamination and time, and compression and centrifugation are limited in treating large amounts of dredged soil.

The tailings, which are produced as a by-product after recovering the useful metals by beneficiation, contain heavy metals and various harmful substances, and are formed in the form of dams between the valleys and the valleys, or are disposed of in landfills. Currently, some landfills are being recycled to cover materials and concrete blocks, but most of them are left untouched, and heavy metals are eluted by acid rain or snow, acting as a contaminant for nearby groundwater, river water, and soil. It requires a lot of time and money to reduce the volume.

Therefore, new techniques are needed for the purification and dehydration of heavy dredged soils and tailings contaminated with heavy metals.

Representative prior art associated with the present invention is as follows.

Deal's 1986 patent (US Patent: 4608179) is a 'continuous method for dehydration of phosphate slime'. This invention relates to the use of close loop systems with electrokinetic phenomena and adequate continuous drainage of supernatant for the dewatering of mill residues, slime and slurries and to plant development. The main claim includes the development and operation of a plant for the continuous processing of slime.

A patent registered in 1988 by Fremont et al. (US Pat. No. 4755305) is a sequential dewatering technique of sludge. This is the application of the electrokinetic purification technique used in contaminated soil to the sludge. The electrode is inserted vertically to form an electric field, and the dehydration treatment and the device in the sludge by the anode and cathode (-) electrode parts contacting the sludge are described. to be. The charged particles in the sludge are moved to the condensed electrode part by electrophoresis and condensed, and the filter material in the electrode part allows only the drainage of water from the sludge. It also uses direct current, alternating current, and half-wave rectification for economical dewatering. Key claims include electrokinetic methods for separating liquid phases from solid phases, such as emulsions and slurries, minimizing volume, applied current and voltage gradients, and electrode placement.

Acar, et al., Registered in 1992 (US Pat. No. 5137608) is 'electrochemical contamination purification in soil or slurry'. The present invention is characterized by electrochemically purifying pollution from soil or slurry using an inert electrode and supplying water to the anode area. Claims include comprehensive purification procedures using inert carbon electrodes.

Brodsky and Ho registered two similar patents (US Patents: 5398756, 5476992) in 1995 under the titles 'In-situ Purification of Contaminated Soil' and 'In-situ Purification of Inhomogeneous Soil'. First, in-situ purification of contaminated soil is to remove contaminants by electroosmosis by forming at least one liquid permeation zone between contaminated soil. The main claims are the formation of liquid permeable zones and the injection of various additives. 'In situ contamination purification of heterogeneous soil' suggests similar contents and methods as the previous ones, but the difference is that hydrophobic gradient is applied to anisotropic soil to induce hydrophobic flow. In addition, it is also possible to apply the hydraulic inclination by changing the direction periodically and combining the technology of reversing the direction of the electroosmotic flow. The claim includes the application of hydraulic gradients to anisotropic soils and the periodic exchange of hydraulic gradients and electroosmotic flows.The same applies under the heading 'Remedy of Contaminated Bicomponent Soils' (Registration No .: 10-0193917). Patent is registered.

Kim Hyo-Geun and others filed a patent application with the Korean Patent Office in 1999 for the method of removing harmful heavy metals from sludge by electric power (application number: 1019990014523). The present invention relates to a technology for recycling waste resources by composting sludge that has been disposed of by incineration or landfill by removing heavy metals contained in sludge generated in sewage and wastewater treatment plants. The main claims are the removal of harmful heavy metals from the sludge by providing cleaning solutions and electrolyte solutions in the positive reservoir, and good water permeability at the interface between the sludge cell, positive cleaning solution and negative electrolyte solution. The acid solution used as the electric power, positive electrode cleaning solution, characterized in that the heterogeneous membrane (Hterogeneous Membrane) with high physical strength is used, and the current supplied is direct current rectification or half-wave rectification. The concentration is 0.001N-0.05N. It is characterized in that any one selected from the range of sulfuric acid solution, acetic acid solution, hydrochloric acid solution or nitric acid solution.

As mentioned above, the existing research trend deals with the dehydration treatment and the purification treatment separately. In this case, there is a limitation in treating a large amount of dredged soil and tailings. In addition, when the dredged soil and tailings are used as landfills in the landfill site, the purification and dehydration treatment is used after being treated in a separate site or device. Therefore, the present invention can simultaneously perform dehydration and purification of dredged soil and tailings generated in large quantities in lagoon or pond, and when used as a landfill material in a site reclaimed land, it is possible to directly purify and dehydrate the landfill. Can be. At this time, the physical vacuum drainage and electrochemical electrokinetic phenomena complement each other to implement drainage and purification at the same time.

The biggest problem in the treatment of bed dredged soil and tailings is the contamination by various compounds and the high water content containing fines. In fact, the following problems have been shown in the treatment of bedriding soil and tailings on land.

Firstly, dredged soils in the riverbed are contaminated for a long time by more than a few decades by various compounds released from the land, causing secondary water pollution such as eutrophication. Eric Stern (1994) reported that sedimentary sediments in urban or highly industrialized Port of New York / New Jersey are contaminated with dioxins, furans, PCBs, heavy metals, and peroxyacetyl nitrate (PAN). Masan Bay's sedimentary soils are reported to be extremely polluted by the pollutants emitted from industrial facilities and urban life such as Masan Free Export Zone and Changwon Machinery Industrial Complex. However, at present, some commercialized techniques for the purification of organic pollutants have been proposed, but there is no purification treatment for heavy metals. The tailings remain heavy metals and other harmful substances, and have high pH buffering ability, making it difficult to perform traditional purification treatments such as acid treatment. Currently, some landfills are recycled to cover soils and concrete blocks, but most of them are made of dam-type landfills between valleys and valleys, and are deposited or disposed of, and heavy metals are eluted by acid rain or snow, causing contamination of nearby groundwater, river water and soil. It is working.

Second, river dredged soils generally have high water content of more than several hundred percent, which makes them difficult to landfill or dispose of. Conventional dewatering treatment method is to accelerate the consolidation by using deep treatment methods such as surface stabilization method and vertical drainage method using horizontal drainage method or progressive trenching method (PTM) after dredging sedimentation settling. However, the horizontal drainage method and PTM have a lot of room for improvement in terms of time and economics, and the vertical drainage method requires a large amount of labor. In addition, the tailings are transported to the slag dam or tailings storage in a high content ratio because the tailings are generated in the process of beneficiation to recover the concentrated effective metal. After this process, the volume is reduced by sedimentation or consolidation, which requires a lot of time and money due to the fines of the tailings.

In the present invention In order to solve the above problems, the purpose is to simultaneously implement the purification and smooth dewatering treatment of the sediment and tailings.

First, when applying the electrokinetic phenomena, the heavy metal adsorbed on the sedimentary soil or tailings can be desorbed by the effect of H ⁺ ions generated from the anode. It can be collected by the negative electrode (-) in the advection by the drainage and removed from the sump.

Second, by using the negative electrode (-) combined drainage material combining the negative electrode (-) electrode and the drainage material can be smoothly drained by the electroosmotic and vacuum drainage of the electrokinetic phenomenon can promote dehydration.

Third, if the present method is applied in the sedimentation step, it can achieve rapid sedimentation by electrophoresis of the electrokinetic phenomenon.

Fourth, since OH ^- ions generated by electrolysis in the negative electrode drainage are forced out of the sample by the vacuum drainage technique to suppress the inflow into the sample, it is caused by hydroxide precipitation near the negative electrode portion. The reduction of the purification efficiency can be suppressed.

Fifth, it is possible to treat a large amount of dredged soil and tailings by multi-stage dumping of bed sediment and tailings and layered arrangement of anode (+) and cathode (-), and increase the efficiency thereof.

1 is a representative view of the present invention

Figure 2 is a conceptual diagram of the field multi-stage dumping to increase the applicability in the present invention

Figure 3 is a schematic diagram of the electrode combined vacuum drainage and the connection clamp for applying the present invention

4 is a block diagram of a tester for the embodiment

5 is a particle size distribution graph of a sample used in Examples

6 is a graph of settlement distribution according to the distance from the vacuum tube during the experiment in the vacuum-coupling drainage purification method in the embodiment

7 is a graph comparing the settling distribution in the simple gravity sedimentation and vacuum-electrical drainage purification techniques in the examples.

Figure 8 is a graph comparing the water content distribution in the sample at the third quarter point 30cm away from the vacuum tube after the end of the experiment in Example

Figure 9 is a graph comparing the sample pH distribution at three quarters away from the vacuum connection tube after the experiment is finished in the Example

Figure 10 is a graph comparing the lead concentration in the sample at the third quarter point 30cm away from the vacuum tube after the end of the experiment in Example

Figure 11 is a graph comparing the cadmium concentration in the sample at the third quarter point 30cm away from the vacuum tube after the end of the experiment in Example

12 is a graph comparing the chromium concentration in the sample at the third quarter point 30 cm away from the vacuum tube after the experiment in the Example

Figure 13 is a graph of the removal efficiency of each heavy metal in the simple gravity sedimentation and vacuum-electric drainage purification technique after the experiment is finished in the Example

It will be described in detail with reference to Figure 1 which is a representative of the system presented in the present invention.

Combined with the vacuum drainage technique and the electrokinetic phenomena, the vacuum-electrical drainage purification technique dumps the sedimented soil and tailings with the anode (+) (3) pre-installed at the bottom of the lagoon (8), and the dumping After completion, it begins with the installation of the negative (-) combined drain in the center of the sample and the installation of the positive (+) in the upper part. Installation of the negative electrode (-) combined drainage (4) can be installed after the end of the dumping, such as a horizontal vacuum drainage method, it can be installed by installing a negative (-) combined drainage (4) during the dumping. Connect the positive (+) (3) and negative (-) combined drain (4) from the power supply (2) outside the lagoon (8), and connect the negative (-) combined drain to the vacuum pump (1) (4) is connected to a power source and a vacuum at the same time to achieve rapid dewatering and purification of the dredged soil and tailings in the lagoon (8). In addition, the present invention, when the dredged sedimentary soil and tailings in addition to the lagoon (8) as landfill material of the site landfill, the positive (+) (3) and negative (-) combined drainage material (4) directly from the landfill Can be installed and applied.

In order to increase the field applicability of the present invention, which is a combination of a vacuum drainage technique and an electrokinetic phenomenon, a multistage dumping method shown in FIG. 2 is proposed. The multi-stage dumping method pre-installs the anode (+) (3) at the bottom of the lagoon (8) to treat the dredged soil which is dumped with time difference in the actual site, and dumps the dredged sediment and tailings only partially, Install negative (-) drain (4), connect positive (+) (3) and negative (-) drain (4) from power supply (2) outside lagoon (8) After connecting the negative (-) combined drainage material (4) to the vacuum pump (1), the power and vacuum are applied simultaneously to purify and dewater the dredged soil and tailings in the lagoon (8). After achieving the target of purification and dehydration, the additional dredged soil and tailings are dumped, and the electrode portion used as the negative electrode (-) drainage material 4 in the pretreatment is used as the positive electrode (+) (3), and the new negative electrode on the upper side. Pour the negative (-) combined drain (4). This process is repeated after dehydration with the desired purification treatment. In this method, the used positive electrode (+) 3 can be extinguished by corrosion by electrolysis.

Electrode combined drain material developed in the present invention is a clamp (8) for fixing the drain material on both sides as shown in Figure 3, a filter (9) for preventing the inflow of particulates, such as clay, the electric power uniformly It is composed of a wire (10) installed in the drain material to be transferred to the inside of the sample, a core (11) for maintaining the role and shape of the flow path inside the drain material, and a vacuum connection tube 12 for applying a vacuum into the drain material. . In addition, in addition to disposing an electric wire inside the core 11, the electric power can be transmitted using metals or carbon through which the core 11 is electrically connected.

It will be described in more detail through the following examples. However, the technical scope of the present invention is not limited by the following examples.

EXAMPLES Comparison of Simple Gravity Sedimentation and Vacuum-Powered Drainage Purification Techniques

In order to verify the effectiveness and applicability of the vacuum drainage method and the electrokinetic drainage purification method using the electrokinetic phenomena indoors, the embodiment was compared with the simple gravity precipitation experiment using the indoor device as shown in FIG. The samples were sieved using a 0.074mm sieve to remove impurities such as gravel and shells that were large enough to affect the experiment by collecting marine viscous soils from the southern coast of Jinhae. The basic properties were based on the Korean Industrial Standard KS F. Basic physical properties are shown in Table 1.

The particle size distribution of the sample was shown in FIG. 4.

Basic Properties of Target Sample Classification characteristic Classification characteristic Classification of soil CH Firing limit (%) 20.6 importance 2.67 Plasticity index (%) 36.7 Liquid limit (%) 56.3 Initial pH 7.77

In this example, a certain amount of lead nitrate, cadmium nitrate, and nitric acid are used to artificially contaminate lead, cadmium, and chromium, which are classified as hazardous heavy metals in soil pollution test method and waste process test method, among heavy metals detected in dredged soil. Chromium was dissolved in brine and stirred with the sample indoors for about 10 days. The initial dredged soil was set to near 300% considering the water content after the sedimentation in the lagoon.

The experimental conditions of the examples are shown in Table 2.

Experimental Conditions of Examples Initial function ratio Initial phase Vacuum Contaminants and Contamination Concentrations Uptime Voltage sample Simple gravity settling 290.3% 34 cm 0kgf / cm ² Lead 1045.267 mg / kg Cadmium 34.491 mg / kg Chromium 32.473 mg / kg 13.5 days 0 V Haesung Clay Vacuum-Drainage Purification 282.7% 34 cm 0.3kgf / cm ² Lead 1031.255 mg / kg Cadmium 36.485 mg / kg Chromium 30.453 mg / kg 8 days 7 V Haesung Clay

During the experiment, the amount of sedimentation was measured from the sedimentation meter 10 at each point 10, 20, 30, 40, 50 cm away from the vacuum connection tube 12, and the drainage amount was measured in the collecting tank 7. After the experiment was completed, the sample was divided into five parts from the vacuum connection tube 12 to measure the water content, pH change, and pollutant concentration distribution in the sample.

6 is a schematic diagram of the settled amount measured in each settler 10 in time in the vacuum-electric drainage purification technique. Initially, faster settlements were observed near the area under vacuum, but after about 100 hours uniform settlements were seen throughout the sample. Consolidation was seen more than 90% at all points after about 160 hours. As described above, the partial settlement occurred under the influence of vacuum pressure, but as the operation period increased, the effect of the electrokinetic phenomenon became larger, indicating that the settlement was uniform throughout the entire area.

Figure 7 compares the total settling of the simple gravitational sedimentation and vacuum-electrical drainage techniques over time. In simple gravity sedimentation, the density was more than 90% after about 324 hours, but the vacuum-coupling drainage technique showed more than 90% of the density in about 160 hours, facilitating consolidation more than twice. In addition, after the consolidation was completed, it was found that the amount of settlement was about 9.25 and 11.5 cm, and the settlement was further increased by about 1.24 times or more when using the improvement technique.

Figure 8 compares the water content distribution in the sample at the third quarter, 30cm from the vacuum connection tube 12 after each experiment is finished. The final average water content was about 133.16,100.99%, which was more than about 1.33 times, which is thought to be due to the movement of particles due to electrophoresis, smooth drainage by vacuum drainage, and electroosmotic oscillation.

Figure 9 compares the pH distribution in the sample at the third quarter, 30cm from the vacuum connection tube 12 after each experiment is finished. After the completion of the simple gravity precipitation experiment, the pH in the sample was little changed compared to the initial pH of 7.77, but in the vacuum-electromotive drainage technique, it was acidified near the positive and basic near the negative drain. . This is due to the influence of H ⁺ and OH ^- ions generated by electrolysis at the anode. However, in the general electrokinetic purification process, there was no strong base phenomena seen near the negative electrode, which is a forced drainage by vacuum pressure in the negative electrode drainage material, and OH ^- ions generated by electrolysis at the negative electrode (-). This is because the flow into the sample is suppressed.

10, 11, and 12 compare the concentration distribution of lead, cadmium, and chromium in the sample at three quarters, which are 30 cm from the vacuum connection tube 12 after each experiment is completed. Simple gravity settling experiments showed no significant reduction compared to the initial concentration, whereas the vacuum-coupling drainage technique showed a lower concentration distribution across all samples than the initial concentration. In addition, the largest concentration decrease near the negative-electrode drainage 4 showed no decrease in the purification efficiency due to hydroxide precipitation near the negative electrode in the general electrokinetic purification treatment.

FIG. 13 compares the heavy metal removal efficiencies in the simple gravity settling and vacuum-powered drainage purification techniques after the end of the experiment. Simple gravity precipitation experiments showed removal efficiency of about 28.52, 20.38, and 12.15% for each heavy metal, because heavy metal ions dissolved in the solution without being adsorbed to the particles were discharged to the top due to drainage during gravity precipitation. In the vacuum-electric drainage purification technique, the removal efficiencies of 80.57, 77.47, and 81.05%, respectively, were about 3 times higher than those of simple gravity precipitation. It desorbs heavy metal adsorbed in the sample by the inflow of H ⁺ ions generated by electrolysis at the positive electrode (+), and through the negative electrode (-) combined drainage in two kinds of flows such as electro ion transport, electroosmotic and vacuum drainage techniques. Because it was removed.

According to the present invention as described above, the problems appearing in the treatment of the sedimentary soil and tailings, which is a high water content contaminated with heavy metals, could be solved as follows.

1) purification of heavy metals

The heavy metal in the sample was desorbed by the electrokinetic phenomenon, and the heavy metal was removed by the negative ion (-) combined drainage material by the ion ion transport, the electroosmotic, and the advection by vacuum drainage.

2) dehydration

By electroosmotic and vacuum drainage due to the electrokinetic phenomenon, it was possible to smoothly drain the gap water, thereby promoting dehydration.

Claims (7)

Combined with the vacuum drainage technique and the electrokinetic phenomena, the vacuum-coil drainage purification technique is a method of quickly purifying and dehydrating heavy water-contaminated riverbed sediments and tailings, which are generated by electrolysis at the anode (+). H ⁺ ions are introduced into the sample by electrophoretic migration, electroosmotic and vacuum drainage to desorb heavy metals adsorbed on the surface of the particles, and desorbed heavy metal ions by electrostatic attraction It is to promote dehydration by smoothly draining the gap water by vacuum drainage and electric osmosis at the same time by removing heavy metal with negative electrode (-) combined drainage as the advection by over-osmotic and vacuum drainage. The method of claim 1, Development of the electrode (-) combined drainage and connecting clamp combining the electrode and the drainage for applying this method. The method of claim 1, Method of increasing applicability by performing multi-stage dumping at the intersection of electrodes in a lagoon or pond in consideration of time-filling in the field. The method of claim 1, This method is applied directly on site when the sedimentary soils and tailings are used as landfill material in landfills, in addition to lagoons or ponds. The method of claim 1, A method for preventing hydroxide precipitation by inhibiting the inflow of OH ^- ions generated by electrolysis by vacuum pressure in a negative electrode drainage material into a sample. The method of claim 1 Application of a combination of optimum vacuum pressure and voltage for each slurry condition. Combining this process with existing treatment methods for organic pollutants to purify organic pollutants.