JP5235276B2 - Purification equipment for contaminated materials including heavy metals - Google Patents

Description

  The present invention relates to a technology for purifying environmental pollutants by heavy metals, and in particular, lead (Pb), cadmium (Cd), chromium (Cr), tin (Sn), mercury (Hg), uranium (U), plutonium (Pu), Including heavy metals such as arsenic (As), soil, sludge, sediment, waste, incinerated ash, sludge, extracts of these, industrial water containing these, wastewater, surface water, groundwater, seawater and other heavy metals The present invention relates to a purification method and apparatus for separating and removing solid or fluid-like contaminants.

  As a method for purifying and repairing soil contaminated with heavy metals, a method using an electrochemical method has been proposed (Patent Document 1). According to this method, the contaminated soil is mixed with an acidic solvent to form a slurry, and after heavy metal ions are extracted from the contaminated soil into the slurry (pore water), the slurry containing heavy metal ions is filtered through the filter medium. A DC voltage is applied to transfer heavy metal ions filtered from the slurry to the cathode part that is separated and formed by the filter medium, thereby separating heavy metals from the contaminated soil.

  However, in this method, since the cathode part and the slurry are separated by the filter medium, the pore water flows from the anode side through the filter medium to the cathode side, and the slurry is reduced by the reduction potential of the cathode. On the contrary, there is a high possibility of being maintained in an oxidative atmosphere by the oxidation potential of the anode. For this reason, among solid deposits such as lead, cadmium, and mercury, it is not possible to efficiently extract fractions that have poorly soluble deposits called ferromanganese adsorption and organic binding, and the concentration of heavy metals in the soil is sufficient. There is a problem that it cannot be lowered.

  As a method for removing heavy metals from the incineration ash, adjust the pH of the contaminated incineration ash to a uniform slurry, then introduce it into a separation and recovery tank equipped with a stirrer, cathode, and anode and apply a DC voltage. Has proposed a method of attaching heavy metal to an electrode (Patent Document 2).

  However, in this method, since the slurry directly contacts the cathode and anode provided in the separation and recovery tank, the slurry cannot be maintained in a reducing atmosphere due to the influence of chlorine, oxygen gas, etc. generated from the anode. Therefore, there is a problem that it is not possible to efficiently extract the fraction having the poorly soluble adhesion form called the above-described ferromanganese adsorption state and organic matter binding state, and the concentration of heavy metals in the incineration ash cannot be sufficiently reduced. is there.

  Furthermore, as a method for removing heavy metals from the incineration ash, the contaminated incineration ash is subjected to solid-liquid separation after acid extraction, and by performing electrolysis by lowering the cathode potential stepwise to the obtained extract, A method of recovering heavy metals by depositing a plurality of types of metals in stages has been proposed (Patent Document 3).

  However, even in this method, since the reduction potential is not applied during the acid extraction, it is not possible to efficiently extract the fraction having the above-mentioned poorly soluble adhesion form, and the concentration of heavy metals in the incineration fly ash is sufficiently reduced. I can't.

  Further, in this method, the extraction of heavy metals into an aqueous solution and the separation from the aqueous solution are not performed at the same time, but are performed in two stages, so that the concentration of heavy metals in the aqueous solution is increased in the extraction stage, There is a problem that small heavy metal salts cannot be completely dissolved. Furthermore, since solid-liquid separation is performed in a state where high-concentration heavy metals are dissolved in the pore water, it is impossible to remove heavy metals contained in the pore water (sludge) remaining after the solid-liquid separation from the incinerated ash. There is also.

  These conventional methods use a reaction in which heavy metals are eluted using an acid, and then the eluted heavy metals are moved and / or precipitated by an electrode potential difference. In any of the above methods, the idea of maintaining the contaminated material in a reducing atmosphere by the reduction potential of the cathode to promote the elution of heavy metals is not disclosed or suggested.

  Furthermore, in these methods, in order to sufficiently elute heavy metals, it is necessary to increase the volume of the liquid phase as a solvent in order to be restricted by the solubility product as a hardly soluble substance. There is a problem that the entire volume becomes large and it is difficult to reduce the size of the apparatus.

  As a means to solve these problems, the inventors separated the cathode compartment and the anode compartment with a diaphragm, and introduced contaminated materials contaminated with heavy metals into the cathode compartment, thereby reducing the atmosphere and strongly acidic or strong. A method has been proposed in which heavy metals contained in a contaminated material are eluted by being maintained in the presence of an alkaline atmosphere and further deposited on the cathode surface (Patent Document 4). According to this method, the contaminants are maintained in a reducing atmosphere and separated from the oxidizing atmosphere formed by the anode, so that the elution of heavy metals is promoted, and the eluted heavy metals are deposited on the cathode surface. Since the liquid-phase heavy metal ion concentration is kept low, even heavy metals with low solubility products can be eluted in a relatively small amount of solvent in sequence, ensuring reliable coverage of the above-mentioned contaminants to the insoluble fraction of heavy metals. Can be removed.

However, especially when copper was used as the electrode, it could be used repeatedly without any problem in a small device, but in a large device with a cathode compartment capacity of 100L or more, the electrolytic treatment was stopped while the electrolytic treatment and electrolytic stop were repeated. The copper electrode corroded, patina was produced, the electrode was worn out, and a problem was required that it took a long time to lower the cathode potential to the desired potential during the electrolytic treatment.
Japanese Patent Laid-Open No. 11-253924 JP 2002-126692 JP JP 2002-173790 A International Patent Publication WO2005 / 035149 Pamphlet

  The object of the present invention is to reliably remove even the hardly soluble fraction of heavy metals from contaminated materials such as soil, sludge, sediment, waste, incinerated ash, etc., and reduce the concentration of heavy metals in the contaminated materials themselves It is another object of the present invention to provide a method and an apparatus for cleaning a contaminated object that can eliminate the risk of contamination in the future. In particular, it is an object of the present invention to provide a purification method and apparatus that can avoid the problem of electrode corrosion and can treat a large volume of contaminated substances.

  As a result of diligent research, the present inventors have conducted electrolysis by using a conductive material having corrosion resistance such as lead, tin, nickel, chromium and an alloy containing at least one of these in the wetted part of the electrode. Corrosion of the cathode surface can be suppressed in both the state of time and no power supply, the electrode potential is not worn, and the cathode potential can be quickly lowered to the target reduction potential during electrolysis. The present invention has been made based on the knowledge that heavy metals can be stably removed from contaminated materials containing heavy metals even in an electrolysis apparatus.

  Specifically, according to the present invention, the liquid contact part of the cathode is composed of a conductive material having corrosion resistance under a condition where a reduction potential is not applied in a strongly acidic or strongly alkaline atmosphere. Provided is a cathode for use in an apparatus for removing heavy metals from contaminants containing heavy metals.

  The cathode of the present invention is electrically conductive, well electrodeposits contaminated heavy metals, and has corrosion resistance against the acidity (or alkalinity) of the catholyte in a reducing and oxidizing atmosphere (air presence conditions). It is preferable that For this reason, the cathode of the present invention only needs to have at least the liquid contact portion made of the above-described conductive material, or the entire surface of the cathode which is made of the above-mentioned conductive material, or the surface that becomes the liquid contact portion of the cathode. You may coat | cover with the said electroconductive substance. In the case where only the surface of the wetted part of the cathode is coated with a conductive material, the base material constituting the cathode (hereinafter referred to as “cathode base material”) is a conductive base material such as copper, stainless steel or steel. Is preferable, and copper is particularly preferable. Moreover, in order to coat | cover a conductive material with a cathode base material, it can coat | cover using well-known techniques, such as plating or fusion | melting immersion.

  The conductive material constituting the wetted part of the cathode of the present invention is at least one metal selected from lead, nickel, chromium and tin or an alloy containing at least one metal selected from these metals For example, lead, lead alloys (lead-tin, lead-zinc, etc.), nickel, nickel alloys (nickel-copper, nickel-zinc, nickel-iron, etc.), chromium, chromium alloys (chromium-nickel, chromium- Nickel-iron, chromium-nickel-copper, etc.).

  Thus, the cathode wetted part is formed by using a conductive material having corrosion resistance to the acidity (or alkalinity) of the catholyte in a reducing atmosphere and an oxidizing atmosphere (air existence condition). Can be protected from oxidative corrosion even when no current is applied, and cathode wear can be prevented. Further, when the cathode corrodes and the metal oxide accumulates on the surface, a reduction reaction of the metal oxide occurs at the time of electrolysis, so that there is a problem that the electrolysis current is wasted. In particular, when the metal composing the metal oxide that accumulates on the cathode surface is a metal having a higher potential than the contaminated heavy metal to be removed (for example, copper oxide is generated due to contamination of lead, chromium, etc.) In this case, since the reduction precipitation of the metal occurs prior to the precipitation of the contaminated heavy metal, it is impossible to selectively deposit only the heavy metal even if the potential is controlled. In addition, since a reduction precipitation reaction of the metal first occurs during electrolysis, the cathode potential does not drop moderately, and there is a problem that it takes a long time to realize a low cathode potential capable of depositing the target heavy metal. Furthermore, once the oxide of the metal is generated, it is always deposited on the cathode surface at the end of electrolysis, so it is not discharged out of the system, and is repeatedly oxidized on the cathode surface to be reduced during electrolysis. There is a problem of significantly reducing the processing speed. By using the corrosion-resistant cathode of the present invention, these problems can be avoided.

  In addition, the corrosion-resistant cathode of the present invention preferably has a large surface area for electrolytic deposition of the intended heavy metals. For example, it has a fibrous shape, a mesh shape, an expanded metal shape, a punching metal shape, a honeycomb shape, etc. It is preferable to have a structure. In particular, from the viewpoint of equipment cost and workability, after forming a cathode base material such as copper or stainless steel into a shape such as expanded metal, a structure in which a conductive material such as a lead-tin alloy is coated by plating or melt dipping, etc. It is preferable that

  Moreover, according to this invention, the purification apparatus of the to-be-contaminated object containing the heavy metals which comprise the above-mentioned corrosion-resistant cathode of this invention is provided. Specifically, an anode including a pollutant supply means for supplying a pollutant containing heavy metals, a corrosion-resistant cathode that provides the above-described reducing atmosphere, a diaphragm, and an anode. The zone and the cathode zone including the cathode and the contaminant supply means are formed by a diaphragm, and the cathode zone is maintained in a reducing atmosphere and a strong acidic or strong alkaline atmosphere to elute and elute heavy metal ions from the contaminated substance. There is provided a pollutant purification apparatus including a reaction tank for separating heavy metal ions from a contaminated substance and pore water in parallel.

  The cathode used in the purification apparatus of the present invention is the above-described corrosion-resistant cathode of the present invention, and is selected from at least one metal selected from lead, nickel, tin, and chromium on a copper cathode base material, or from these. It is preferable to have one of a net shape, an expanded metal shape, a punching metal shape, and a honeycomb shape in which the liquid contact surface is coated with an alloy containing at least one metal.

  In the contaminated material purification apparatus of the present invention, a plurality of cathodes can be arranged in the reaction tank. In this embodiment, at least one of the plurality of cathodes is an elution cathode mainly having an action of eluting heavy metal ions, and at least one of the other cathodes is used for precipitation mainly having an action of precipitating heavy metal ions. Functions as a cathode. For this reason, a substance having a relatively high standard electrode potential is used as the deposition cathode, and a substance having a relatively low standard electrode potential is used as the elution cathode. The deposition cathode is preferably made of a material that deposits heavy metals more easily than the elution cathode, and has a shape that maximizes the specific surface area. It is a structure that is easy to remove when redissolving heavy metals deposited on the electrode surface by applying a high potential, and the surface is uneven, mesh-like, etc. so that the deposited heavy metals do not peel again in the reduction reaction tank The shape is preferred. The corrosion-resistant cathode of the present invention is used as a deposition cathode. The elution cathode is required to have friction resistance, acid resistance, and alkali resistance. Specifically, carbon or a surface-treated metal is used as a cathode base material, and heavy metals are hardly deposited on the surface. It is desirable that it be finished as smooth and curved as possible so that it can be easily removed even if heavy metals are deposited. Examples of the shape include a rectangular plate shape, a disk shape, a dish shape, a bowl shape, A shape such as a spherical shape that is less likely to be worn away by the slurry is preferable. Further, the deposition cathode is preferably disposed at a position closer to the anode than the elution cathode, and heavy metals are deposited on the deposition cathode at a position where precipitation is likely to occur, and is relatively far from the anode than the position. It is possible to elute heavy metals from the hardly soluble fraction of the contaminated material using the elution cathode at a position, that is, a position where it is relatively difficult to deposit. As a result, the proton concentration around the folding cathode is higher than that around the elution cathode, so that the current density proportional to the proton concentration also increases. Since the deposition rate of the metal on the electrode increases as the current density increases, heavy metals are more likely to be deposited on the deposition cathode. The provision of a reducing atmosphere by adjusting the elution cathode and the deposition cathode potential is achieved by controlling the distance between the anode and the deposition cathode and the deposition cathode and the elution cathode in the combination of the anode, reference electrode, elution cathode and deposition cathode. It can be adjusted by controlling the distance between the cathodes and the flow in the apparatus. For example, lead (standard electrode potential -0.126V) and cadmium (standard electrode potential -0.40V) can be obtained by adjusting the deposition cathode potential to -0.16V or less, preferably -0.25V or less with respect to the hydrogen standard electrode. It can be deposited on the cathode surface for deposition. On the other hand, it is desirable to control the elution cathode at the same or higher potential than the deposition cathode in order to avoid deposition of heavy metals as much as possible. Also, when the elution cathode is operated at the same potential as the deposition cathode, it is desirable to protect the electrode from deposition of heavy metals by using a different conductive material or adopting a shape that is difficult to deposit. . For example, the carbon electrode does not bond to the metal, so even if heavy metal is deposited on the surface of the carbon electrode by applying a low potential, if there is agitation or flow, the deposited heavy metal solid will move away from the electrode and redissolve in a reducing atmosphere. Finally, it is deposited on the deposition cathode. Also, care must be taken because both cathodes may cause the cathode to melt and generate a reverse current depending on the material. Therefore, it is desirable to control the potential of both cathodes to −0.16 V or less using a constant potential power supply.

  The anode used in the purification apparatus of the present invention is electrically conductive, has resistance in a strongly acidic (preferably pH 3 or less) or strongly alkaline (preferably pH 12 or more) aqueous solution, and preferably has resistance to anodic corrosion, For example, furnace black, graphite, titanium, diamond electrode (conductive material surface-treated with conductive diamond film), platinum group metal coated metal (for example, ruthenium oxide coated titanium), titanium coated metal, lead-tin alloy, lead dioxide, etc. Can be mentioned. Further, it is preferable that the anode has a configuration in which it can be energized without being in direct contact with the contaminated material so that the contaminated material is not exposed to an oxidizing atmosphere. It is preferable to be isolated.

  The diaphragm used in the purification apparatus of the present invention is positioned between the cathode and the anode, and isolates the cathode section including the cathode and the anode section including the anode. In another embodiment, the diaphragm may be positioned so as to surround the anode, the anode section may be formed inside the diaphragm, and the cathode section may be formed outside the diaphragm. Alternatively, using a diaphragm alone or a reinforcing material such as a frame material that increases the strength of the diaphragm, a cylindrical, box-shaped or bag-shaped diaphragm unit with at least one end closed, and an anode positioned within the diaphragm unit as an anode region The cathode section may be formed by positioning the cathode outside the diaphragm unit. Since the distance between the anode and the diaphragm surface is preferably as short as possible in order to efficiently supply hydrogen ions generated at the anode to the diaphragm surface (but contact as described later should be avoided), the shape of the anode is It is desirable to correspond to the shape of the diaphragm unit. For example, if the diaphragm unit is cylindrical, the anode is also preferably cylindrical. Further, since the anode is stored in the diaphragm unit, the surface area tends to be relatively small with respect to the cathode. In order to prevent the anode reaction from becoming a rate-determining step depending on the surface area of the anode, it is preferable to increase the surface area of the anode by making it uneven, porous, net-like, or fibrous. Since the oxidation reaction proceeds on the anode surface by electrolysis, it is desirable that the anode surface and the diaphragm surface are not in contact with each other in order to protect the diaphragm surface from oxidative corrosion. It is desirable to insert some non-conductive spacer between them or fix the anode in some way so as not to contact the diaphragm. The diaphragm unit can be produced by forming a flat membrane material into an arbitrary container shape and bonding, welding, or sewing (FIG. 8). In order to avoid deformation and wear of the diaphragm, the surface is reinforced with a net-like or punched plate-like resin, and protective parts such as resin molds, plates, pipes, etc. are used, especially at the corners, bottom and top of the diaphragm. It is desirable to form and protect (FIG. 9). In this case, the unit may be formed by bonding or welding to the protective material even if the bottom or side of the diaphragm itself is not closed. Since the commercially available Astom ED-CORE membrane is already formed into a cylindrical shape, it can be preferably used to form a cylindrical diaphragm unit. Ceramic can be used as a diaphragm unit by making it into the shape of a container before firing or by fixing it to a polyhedral mold even if it is a flat plate (FIG. 10). However, the diaphragm-electrode unit does not necessarily need to be a closed type, and it is sufficient that the diaphragm surrounds the anode so that particles of contaminants including heavy metals do not directly contact the anode.

  In this embodiment, the cathode is disposed around the diaphragm unit, but has a surface area as large as possible to increase the electrodeposition efficiency of heavy metals, and as much as possible to efficiently use hydrogen ions supplied from the anode section. It is desirable to have a structure that is arranged in the vicinity of the unit and does not hinder the movement of hydrogen ions that permeate and diffuse through the diaphragm unit so that electrodeposition can be performed on the entire cathode surface. Here, the movement of hydrogen ions from the anode zone to the cathode zone is not only necessary for maintaining the charge balance of both zones during the electrolytic reaction and closing the circuit, but also impedes heavy metal electrodeposition on the cathode surface. It also plays a role in reducing the hydroxide ion concentration. As a method of arranging the cathode and the diaphragm-electrode unit satisfying these conditions, the cathode is arranged in a star shape so as to surround the diaphragm-electrode unit arranged so as to surround the central anode as shown in FIG. Alternatively, as shown in FIG. 12, it is desirable to arrange the cathodes radially around the diaphragm-electrode unit. The radially arranged cathodes may be in a single row form as shown in FIG. 12 (a) or in a multiple row form as shown in FIG. 12 (b). In the illustrated embodiment, the star-shaped corner is an acute angle, but may be curved. The number of star arrangements and the number of radial arrangements of radiation are not particularly limited. The size of the apparatus, the nature of the contaminated material (particularly the particle size in the case of the contaminated material), the method of stirring the reaction solution or slurry It should be changed as appropriate according to the stirring intensity. Alternatively, the cathode may be disposed between a plurality of diaphragm-electrode units in a partition plate shape as shown in FIGS. 13 (a) and 13 (b). At this time, in order to increase the area of the partition plate, the cathode may be formed into a wire mesh or expanded metal partition plate shape, and the plate may be curved into a corrugated plate shape as shown in FIG. As shown in FIG. 13D, it may be folded into a pleated shape. When the partition plate-like cathode is arranged in this way, there is an advantage that the arrangement of the jig for energization becomes regular and the cathode unit can be easily attached and detached. In addition, when the supply of hydrogen ions is sufficiently performed and the supply rate of hydrogen ions does not become the rate-determining step for the precipitation reaction of heavy metals, there is no need to take such an arrangement. You may arrange | position a cathode so that it may overlap by seeing.

  Heavy metals in the contaminated material undergo elution and electrolytic deposition in a reducing atmosphere by the cathode, and are separated and removed from the contaminated material. As described above, the cathode is arranged in a star shape, a radial shape, or a partition plate around the diaphragm-electrode unit, and the elution and electrolytic deposition reactions proceed using hydrogen ions that permeate the diaphragm. When the cathode is arranged in a stacked form with respect to the diaphragm, heavy metals are concentrated on the cathode closer to the diaphragm, and heavy metals accumulate especially in an arrangement where the cathode covers the diaphragm. As a result, the flow of hydrogen ions from the diaphragm to the cathode is blocked or blocked, and the contact efficiency between the hydrogen ions and the heavy metal ions in the reaction solution decreases, resulting in a decrease in electrolytic deposition efficiency. . This problem can be avoided by arranging the cathodes in a star shape, radial shape or partition shape around the diaphragm-electrode unit as described above.

When the reaction tank is enlarged, a plurality of the diaphragm-electrode units are arranged in the reaction tank, and a cathode is arranged around each diaphragm-electrode unit. The distance between the reaction liquids (or slurries) can be reduced, and the reaction rate and contaminant removal efficiency can be maintained. Further, when the diaphragm or the diaphragm unit is deteriorated due to fouling, reduced ion exchange ability, crack generation, etc., it can be easily repaired or replaced by pulling up the diaphragm-electrode unit from the inside of the reaction vessel. When a device that actually purifies contaminated materials such as soil is constructed, the volume of the reaction tank must be increased to complete the treatment within a realistic purification period. Generally, a volume of 10 m ³ or more is required. When a flat membrane type diaphragm is applied to such a large reaction tank, the distance between the electrode and the membrane and / or the distance between the electrode and the reaction liquid (or slurry) increases, and the reaction rate and the removal efficiency decrease. . In order to avoid this problem, it is possible to shorten the distance by making the reaction tank vertically flat and laminating it horizontally through the diaphragm, but it is possible to use several large flat membranes. It is not realistic because it increases the risk of leakage due to membrane swelling and it is difficult to repair or replace the membrane. The distance between the electrode and the diaphragm even in a large-scale actual apparatus by arranging the anode inside the closed cylindrical, box-shaped or bag-like diaphragm placed in the reaction tank and arranging the cathode outside the diaphragm. In addition, the distance between the electrode and the reaction solution (or slurry) can be kept sufficiently small, so that preferable contaminant removal efficiency can be obtained and the repair and replacement of the diaphragm can be facilitated.

  In the present invention, the diaphragm that can be used to separate the cathode and the anode is a diaphragm having a function of controlling movement of a substance other than specific ions in the aqueous solution, and performs ion exchange between the anode and the cathode. There may be mentioned a diaphragm having a function of closing the circuit, and a function of preventing the permeation of chlorine gas, oxygen gas, dissolved chlorine, dissolved oxygen, etc. and maintaining a reducing atmosphere in the cathode region. Specifically, a fluororesin ion exchange membrane (cation exchange membrane) having a sulfonic acid group can be preferably mentioned. The sulfonic acid group is hydrophilic and has a high cation exchange capacity. Further, as a cheaper diaphragm, a fluororesin ion exchange membrane in which only the main chain portion is fluorinated, or an aromatic hydrocarbon ion exchange membrane can also be used. As such an ion exchange membrane, for example, commercially available products such as NEPTON CR61AZL-389 manufactured by IONICS, NEOSEPTA CM-1 manufactured by Tokuyama or CMB, and Selemion CSV manufactured by Asahi Glass can be preferably used. Moreover, an anion exchange membrane can also be used as the diaphragm used for isolating the anode and the contaminant. Specifically, a hydroxide ion exchange membrane having an ammonium hydroxide group can be preferably exemplified. As such an anion exchange membrane, for example, commercially available products such as NEPTON AR103PZL-389 manufactured by IONICS, NEOSEPTA AHA manufactured by Tokuyama, and Shelemion ASV manufactured by Asahi Glass can be preferably used. Furthermore, as the diaphragm that can be used in the present invention, MF (microfilter) having no functional group, UF (ultrafilter) membrane, porous filter medium such as ceramic, nylon, polyethylene, polypropylene woven fabric, or the like is used. be able to. These diaphragms having no functional group preferably have a pore diameter of 5 μm or less and do not allow gas permeation under non-pressurized conditions. For example, PE-10 membrane manufactured by Schweiz Seidengazefabrik, NY1-HD membrane manufactured by Flon Industry, etc. Commercial products can be preferably used.

  In a preferred embodiment, the reaction vessel is a slurry formation vessel that makes a mixture containing a contaminated substance and an acidic substance or an alkaline substance and water into a slurry state. What is comprised so that external air may be interrupted | blocked so that the inside of a slurry formation tank may be reduced atmosphere is also preferable. Contaminated substances are supplied into the slurry forming tank, and the reducing atmosphere is maintained by the reduction potential of the elution cathode. At this time, for example, the distance between the cathode and the anode is increased, or a water flow from the cathode side to the anode side is present so that the reducing atmosphere on the cathode side is not impaired by the oxidizing atmosphere generated on the anode side. It is desirable to provide a porous wall or a diaphragm.

  In the present invention, it is preferable to deposit the heavy metal on the cathode surface by adjusting the cathode electrode potential to maintain the contaminated material containing the heavy metal in a reducing atmosphere. For this reason, it is necessary to maintain the slurry containing heavy metals in contact with the cathode to cause the electrolytic deposition reaction.

The rate K ₀ at which heavy metals precipitate on the cathode surface is determined by the diffusion material transfer rate K _{D of} heavy metal ions and the cathode surface deposition rate K _R as shown in the following relational expression.

Cathode surface deposition rate K _R are determined by the type and temperature of the heavy metal ions, for example, a temperature in the range of 25 to 80 ° C. in heavy metals other than the temperature in the range of 30 to 40 ° C., lead in the case of lead It is preferable to do. In general, the higher the temperature, the higher the ion diffusion rate, and heavy metals can be deposited on the cathode surface until a high current density (eg, 11.48 A / m ² ) is reached, but the precipitated grains tend to grow excessively. Since the hydrogen overvoltage is reduced and hydroxide is easily generated, it is advantageous to set the temperature within the above range. Diffusion mass transfer rate _the K _D is proportional to the stirring conditions and the temperature in the slurry formation tank, it is necessary to sufficiently stirred slurry. However, when the slurry is stirred, a shearing force acts on the cathode surface, and heavy metals deposited on the cathode surface may be peeled off. If the deposited heavy metals are peeled off from the cathode surface, the separation and removal efficiency of the heavy metals is lowered. Therefore, it is necessary to eliminate or suppress the influence of the shearing force due to such slurry. In this embodiment, suppression of shearing force by the slurry applied to the cathode surface is achieved by positioning the cathode at an upper position in the slurry forming tank, so that the solid particle size distribution in the slurry is small in the upper part of the slurry. It is preferably done by controlling the presence of large solids at the bottom in the slurry or by rectifying the slurry stream.

For controlling the solid particle size distribution of the slurry, a method of giving an upward flow to the slurry can be preferably used. The slurry upward flow providing means includes a slurry extraction port provided at the upper part in the reaction tank, a slurry introduction port provided at the bottom of the reaction tank, and a circulation pump for circulating the slurry from the slurry extraction port to the slurry introduction port. It is preferable that the slurry is raised from the bottom of the tank at a desired rate in the reaction tank. Or you may provide the air inlet which introduces air from a slurry formation tank bottom part. By making the slurry containing solids with various particle sizes into the upward flow, the solids with a large particle size can resist the upward flow and remain at the bottom of the slurry forming layer, and the solids with a small particle size can rise preferentially. As a result, the solid particle size distribution in the slurry is finer in the upper layer and larger in the lower layer. The solid particle size distribution can be controlled by controlling the flow rate of the upward flow of the slurry. If the terminal velocity of the upward flow is known, the solid particle size distribution can be estimated. For example, when the contaminated material is soil, solids with a particle size of 2 mm or less are often targeted for purification, and among them, the clay fraction containing hardly decomposable heavy metals has a particle size of 0.02 mm, It contains a lot of clay particles with a density of about 2.7 × 10 ³ kg / m ³ . Assuming that the density of the slurry containing such contaminants is 1.0 to 1.2 × 10 ³ kg / m ³ and the viscosity of the slurry is 1 × 10 ⁻³ N · s / m ² , the terminal velocity of the viscous particles is as follows: Stokes formula:

Therefore, it can be calculated as about 3.3 to 3.7 × 10 ⁻⁴ m / s. The particle Reynolds number Re at this time is expressed by the following formula:

Therefore, it is appropriate to use the Stokes equation.

  In addition, when the contaminated material contains a large amount of fine-grained fractions and viscous particles, the fine-grained fractions and viscous particles are charged and repel each other, making it more difficult to settle, that is, the terminal velocity Therefore, the desired solid particle size distribution can be obtained even if the upward flow rate is reduced.

  In addition, if the contaminated material contains a particle fraction with a Reynolds number greater than 1, instead of the Stokes equation, the Allen equation:

Can be used to calculate the terminal velocity.

  The desired particle size distribution of the solid in the slurry can be obtained by setting the terminal velocity of the upward flow using the chemical engineering profiling as described above. Thus, by controlling the solid particle size distribution of the slurry so that a solid having a smaller particle size is present in the upper layer portion of the slurry and a solid having a larger particle size is present in the lower layer portion of the slurry, the slurry is positioned at an upper position in the slurry forming tank. It is possible to avoid a shearing force due to a solid having a large particle size from acting on the cathode surface, and as a result, the shearing force applied to the cathode surface can be reduced.

  Moreover, it is preferable that the slurry forming tank includes a shearing force suppressing unit that controls the shearing force of the slurry acting on the surface of the cathode to be reduced and to maintain the contact state between the cathode and the slurry. The shear force suppressing means is a rectifying mechanism that rectifies the slurry flow so as to reduce the shear force of the slurry flow acting on the cathode surface, and is one kind selected from a plate material, a porous material, a lattice material, and a mesh material. A rectifying member made of the above materials may be used. For example, there is a form in which the cathode protection member is disposed at a lower position than the cathode positioned at the upper position in the slurry forming tank. The cathode protection member may be disposed so as to surround the cathode, or may be disposed as a partition wall in a slurry flow path toward the cathode surface. However, when the cathode protection member is used, the shearing force of the slurry acting on the cathode surface is reduced, but it is necessary to provide the cathode surface and the slurry so as to maintain the contact state. Therefore, when the cathode protection member is disposed so as to surround the cathode, it is preferable to use a material capable of circulating a slurry, such as a porous material, a lattice-like material, and a mesh-like material, as the cathode protection member. When the cathode protection member is arranged as a partition using a plate material or the like, it is preferable to appropriately adjust the distance between the cathode surface and the partition, the inflow angle of the slurry flow, and the like. As a material constituting the cathode protective member, a material that is resistant to friction and is made of a strong acid-resistant and strongly alkaline-resistant material can be preferably used. Specifically, tempered glass, quartz, reinforced plastic, fluorine-based resin, etc. Preferred examples include synthetic resins, fiber reinforced composite materials such as FRP, and those obtained by subjecting metal surfaces such as graphite, glassy carbon, concrete, ceramics, titanium, and iron to corrosion resistance.

  In a preferred embodiment, the reaction vessel is a stirring vessel in which a solid or liquid contaminated material, a mixture containing acid or alkali, and water is mixed by gas stirring or mechanical stirring and is brought into contact with the cathode. The gas used for gas stirring is preferably a gas containing an inert gas as a main component, and nitrogen gas is preferably used. It is also preferable to circulate and use the gas. Further, when the gas is circulated, it is also preferable that a small amount of gas is additionally supplied over time to bring the circulation system into a pressurized state, and the gas is gradually updated using a back pressure valve. What is comprised so that external air may be interrupted | blocked so that the inside of an apparatus may be reduced atmosphere is also preferable.

  In the purification apparatus of the present invention, the reaction tank is provided with a contaminant supply means. The contamination supply means is preferably selected from a belt feeder, a slurry pump or the like depending on the properties of the contamination. When the reaction tank is a slurry formation tank, the contamination to be introduced into the reaction tank is preliminarily provided with a dry or wet sieve such as a blade washer, a trommel or a vibrating screen in order to facilitate the formation of a slurry in the reaction tank. It is desirable to use fine particles of several millimeters or less. In addition, when it is desired to reduce the amount of contaminants input to the reaction tank, it is desirable to further reduce the fine particle fraction to 1 mm or less using a cyclone or the like. When using a slurry forming tank, by adjusting the cathode electrode potential to a range of, for example, -0.3 V or less -1.3 V or more, an electrolytic deposition reaction such as lead or cadmium can be efficiently generated, Since precipitation of iron contained in the slurry and generation of hydrogen due to electrolysis of water are suppressed, the electrolytic deposition reaction of heavy metals can be caused to be specific to a certain extent.

  Moreover, it is preferable that the contaminated material purification apparatus of the present invention includes means for supplying an acidic or alkaline substance to the reaction tank (or slurry forming tank). Supplying acidic or alkaline substances to the contaminated materials in order to maintain the contaminated materials in a strongly acidic or strongly alkaline atmosphere, except when the contaminated materials to be treated contain alkaline substances or acidic substances such as incineration ash Is preferred. In the strongly acidic atmosphere used in the present invention, the pH of the pore water of the contaminated material is preferably 3 or less, and more preferably 2 or less. By setting it as such a strong acidic atmosphere, the influence of iron sulfide etc. which exist in soil can be excluded. The strongly acidic atmosphere in the present invention can be formed by adding an acid to the contaminated material. Preferable examples of the acid that can be added include hydrochloric acid and organic acids such as methanesulfonic acid, formic acid, acetic acid, citric acid, oxalic acid, and terephthalic acid. On the other hand, the strongly alkaline atmosphere used in the present invention preferably has a pore water pH of 12 or more, more preferably 13 or more. The strong alkaline atmosphere in the present invention can be formed by adding an alkaline substance to a contaminated object. Preferred examples of the alkaline substance that can be added include hydroxide salts such as sodium hydroxide and potassium hydroxide.

  In the present invention, the cathode section of the reaction vessel is maintained in a reducing atmosphere. The reducing atmosphere can be formed by adjusting the cathode electrode potential. It is preferable to adjust the cathode electrode potential so that the cathode electrode potential is −0.16 V or less, more preferably −0.25 V or less with respect to the hydrogen standard electrode. Providing a reducing atmosphere by adjusting the cathode electrode potential can be accomplished by placing the diaphragm between the anode and cathode in a combination of anode, diaphragm, reference electrode and cathode. In this case, since the acid is supplied from the anode side through the diaphragm, there is an advantage that the necessity of supplying a large amount of acid can be eliminated.

  In order to apply the necessary reduction potential to the cathode, it is preferable to use a constant potential power source. In particular, when the heavy metals to be removed are lead or cadmium, by controlling the cathode potential to an appropriate potential using a constant potential power source, the negative current value generated by the precipitation reaction of heavy metals is precipitated. Since it decreases simultaneously with the end of the reaction, it is possible to know the completion of the precipitation reaction of heavy metals by measuring the current value, and it is advantageous that electricity is not wasted by causing an unnecessary electrolytic reaction. For example, if the cathode potential is controlled within the range of -0.3V or lower and -1.3V or higher, the electrolytic deposition reaction of lead and cadmium is efficiently generated. However, hydrogen generated by the precipitation of iron contained in the slurry or the electrolysis of water is used. Since generation | occurrence | production is suppressed, the electrolytic deposition reaction of heavy metals can be produced specifically, and it is advantageous. However, if the processing conditions are constant and the relationship between the current value and the electrolytic reaction is known, it is not always necessary to use a constant-potential power supply. Use a constant-current power supply and reduce the set current amount according to the reaction time. Thus, a preferable cathode electrode potential can be maintained.

  Contaminated substances containing heavy metals that can be purified by this embodiment include solid or liquid contaminated substances containing heavy metals such as soil, sludge, sediment, waste, incineration ash, sludge, and the above solids Preferred examples include liquid contaminated substances containing heavy metals such as extracts from industrial contaminants, industrial water, wastewater, surface water, groundwater, seawater and the like. The heavy metals separated and removed by the present invention include lead (Pb), cadmium (Cd), mercury (Hg), tin (Sn), chromium (Cr), arsenic (As), uranium (U), and plutonium. Preferred examples include (Pr).

  In the present invention, the slurry containing the contaminated material containing heavy metals is accommodated in the container, the slurry is maintained in a strong acidity or strong alkalinity, and the potential of the cathode disposed in the container is adjusted. Is placed in a reducing atmosphere to elute heavy metals into the slurry. Then, a step of separating the separated heavy metal ions from the slurry in the container is performed in parallel with the elution step. Here, since a plurality of cathodes are arranged in a container (reaction tank), it is possible to continue the operation of the apparatus even when different roles are shared, or when one of the functions is malfunctioning or replacement or maintenance is performed. it can.

  In general, heavy metals are present in a contaminated material in a form such as an ion exchange state, a carbonate bond state, an iron manganese adsorption state, or an organic matter bond state. Among these forms, heavy metals existing in an ion exchange state enter a corrosive zone under a strongly acidic or strongly alkaline atmosphere, and the water elution concentration is increased. On the other hand, heavy metals existing in a form such as a carbonate-bonded state, an iron-manganese adsorbed state, and an organic substance-bound state have low solubility and are difficult to elute even in a strongly acidic or strongly alkaline atmosphere. By subjecting these heavy metals present in a hardly soluble form to a reductive atmosphere, the heavy metals can be transferred to a corrosive zone and the solubility in water can be increased. When the contaminated heavy metal is mercury, volatile zero-valent mercury generated by reducing mercury ions by supplying hydrogen gas and / or nitrogen gas generated from the cathode surface into the tank and aeration. Is easily transferred to the gas phase along with hydrogen gas and / or nitrogen gas, and can be separated from the pore water.

  In the present invention, a diaphragm is positioned between the corrosion-resistant cathode that supplies the reduction potential and the anode, and is separated into a cathode area that includes the corrosion-resistant cathode and an anode area that includes the anode. By adding a contaminated material containing heavy metals, which is the object to be treated, and an acidic or alkaline substance, the pH is set to 3 or less, or 12 or more, and a reducing atmosphere is created to effectively remove heavy metals. And separate from pore water. In this method, at the cathode (reduction electrode), a reaction for reducing and eluting heavy metals contained in the contaminated material and a reaction for electrolytically depositing heavy metals on the surface of the corrosion-resistant cathode are performed in parallel. The contamination potential is maintained in a reducing atmosphere by the reduction potential of the cathode to promote the elution of heavy metals, so that even the insoluble fractions of heavy metals that do not elute even under strongly acidic or strongly alkaline conditions are eluted. And can effectively separate heavy metals from contaminants and interstitial water.

  By using the purification apparatus of the present invention, the elution step of heavy metal ions from the contaminated material and the separation step of separating the eluted heavy metal ions from the contaminated material and pore water are performed in the same container. The contaminated material containing heavy metals, wherein the contaminated material is maintained in the coexistence of a reducing atmosphere and a strong acidic or strong alkaline atmosphere until elution and separation of the heavy metal ions are completed. A purification method is provided.

  More specifically, the reducing atmosphere provided by the corrosion-resistant cathode is used for the heavy metals present in the contaminated material in a form such as an ion exchange state, a carbonate bond state, an ferromanganese adsorption state, or an organic matter bond state. Under deionization by contact with a sufficient amount of acidic or alkaline aqueous solution, and elution into the aqueous solution, electrolytic deposition on the corrosion-resistant cathode surface, or aeration removal in the case of mercury Thus, heavy metals are removed from the contaminated material. Since elution and separation of heavy metals from contaminated substances are completed in a single tank, it is not necessary to maintain the slurry in a reducing atmosphere in the solid-liquid separation step of the post-treatment. In addition, heavy metals are deposited on the surface of the corrosion-resistant cathode and removed from the pore water, so that heavy metals having a low solubility product are also dissolved sequentially, and the extraction efficiency can be further improved.

  In general, heavy metals are more easily eluted in a strongly acidic atmosphere than in a strongly alkaline atmosphere. However, depending on the nature of the contamination to be purified, a strong alkaline atmosphere may be preferable to a strong acidic atmosphere. For example, if the contaminated material is a soil containing a large amount of iron, the iron may elute in a strongly acidic atmosphere to cover the electrode or cause problems such as clogging. It is preferable. Furthermore, depending on the state of the contaminated material, it may not be necessary to add an acidic substance or an alkaline substance. When the contaminated material is incinerated ash, the incinerated ash is strongly alkaline, so a strong alkaline atmosphere can be formed without adding an alkaline substance.

  In the purification apparatus of the present invention, a surfactant and a complex ion forming agent that contribute to the elution of heavy metals and stabilization in an aqueous solution to the contaminated material according to the conditions of the field such as the soil to be purified. In addition, a substance selected from chelating agents, buffering agents that suppress pH fluctuations of contaminated substances, electron donors and reducing agents that maintain a reducing atmosphere, and combinations thereof can also be added. Examples of these additives include SDS (sodium dodecyl sulfate) and cationic surfactants as surfactants, citric acid, oxalic acid, and lactic acid as complex ion forming agents, EDTA (ethylenediaminetetraacetic acid) and NTA as chelating agents. (Nitrilotriacetic acid), phosphate buffer, Tris buffer and hydrochloric acid-potassium chloride buffer as buffers, hydrogen, sugar, organic acid (salt) as an electron donor, alcohol, various organic wastewater, ascorbic acid, DTT ( Dithiothreitol), titanium citrate, iron powder, granular iron and the like can be preferably mentioned. When complex ion forming agents and chelating agents are added, the potential at which heavy metals are electrolytically deposited on the surface of the corrosion-resistant cathode may decrease, so a preliminary test may be performed to set an appropriate potential. is necessary.

  Separation of heavy metal ions includes electrolytic deposition of heavy metals on the surface of the corrosion-resistant cathode, and in this case, an electric analysis of heavy metals by a shearing force acting on the surface of the corrosion-resistant cathode by a slurry containing at least contaminated substances. The heavy metals can be deposited on the cathode surface under conditions that rectify or suppress the flow of the slurry to reduce the shear forces acting on the cathode surface so that outflow is not hindered. In this embodiment, the slurry formed from the contaminated material containing heavy metals is maintained in a condition in which the precipitation of heavy metals on the corrosion resistant cathode surface is not hindered by the shearing force acting on the corrosion resistant cathode surface. Peeling of heavy metals deposited on the corrosive cathode surface and wear of the corrosion resistant cathode are prevented.

  The contaminated material containing heavy metals is preferably treated as a slurry so that the contained heavy metals are eluted as ions. This slurry contains at least an acidic or alkaline substance in order to maintain the contaminated material in a strong acidic or strong alkaline atmosphere. It is preferable to add an acidic substance or an alkaline substance when forming a slurry, except when an contaminated substance is incinerated ash or the like and contains an alkaline substance or an acidic substance. Preferred examples of the acidic substance that can be used in this embodiment include hydrochloric acid and organic acids such as formic acid, acetic acid, citric acid, oxalic acid, and terephthalic acid. The slurry containing these acidic substances is preferably maintained in a strongly acidic atmosphere in which the pH of pore water of the contaminated material is 3 or less, more preferably 2 or less. By setting it as such a strong acidic atmosphere, the influence of iron sulfide etc. which exist in soil can be excluded. Preferred examples of the alkaline substance include hydroxide salts such as sodium hydroxide and potassium hydroxide. The slurry containing these alkaline substances is preferably maintained in a strongly alkaline atmosphere in which the pH of the pore water of the contaminated material is 12 or more, more preferably 13 or more.

[Preferred embodiment]
Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. In the drawings, the same components are denoted by the same reference numerals.

  FIG. 1 is a schematic explanatory view showing a first preferred embodiment of the present invention for removing and recovering lead, cadmium, chromium, arsenic, tin, uranium, plutonium and the like by using an electrolytic deposition reaction.

  The purification apparatus 1 shown in FIG. 1 provides a contaminated substance supply means 22 for supplying a contaminated substance containing heavy metals, an acidic substance or alkaline substance supply means 24 for supplying an acidic substance or an alkaline substance, and a reducing atmosphere. A corrosive resistant cathode C, a diaphragm M, and an anode A, the anode section 10 including the anode A by the diaphragm M, the corrosive resistant cathode C, the contaminant supply means 22, and an acidic substance or an alkaline substance. A cathode zone 20 including a supply means 24, and the cathode zone 20 is maintained in a reducing atmosphere and a strong acidic or strong alkaline atmosphere to elute heavy metal ions from contaminated substances and to cover the eluted heavy metal ions. It is a purification apparatus for contaminated substances including a reaction tank 2 that performs separation from contaminants and pore water in parallel.

  The reaction vessel 2 further includes a water supply means 26 for supplying water to the cathode section 20 of the reaction vessel 2, a pH meter 28 for measuring the pH of the mixture in the reaction vessel 2, and a mixture formed in the reaction vessel 2. A slurry extraction port 30 is provided for extracting the slurry. A slurry transfer line 32 and a slurry pump 34 provided on the slurry transfer line 32 are connected to the slurry extraction port 30. The slurry transfer line 32 is connected to the solid-liquid separator 3. Connected to the solid-liquid separator 3 are a solid extraction line 36 for extracting separated solids and a liquid extraction line 38 for extracting separated liquids. A liquid circulation line 40 is branched from the liquid extraction line 38 to return a part of the liquid to the reaction tank 2 as a circulating liquid.

  A description will be given of an aspect in which the purification apparatus 1 is used to purify contaminated substances that are contaminated with heavy metals. First, the contaminated material contaminated with heavy metals such as soil, sludge, sludge, incineration ash, and deposits is supplied to the reaction tank (slurry forming tank) 2 through the contaminated material supply means 22. At this time, if the contaminated material is not saturated, that is, if the void of the contaminated material is not saturated with water, supply an appropriate amount of water via the water supply means 26 or the liquid circulation line 40, and the saturated state And In the slurry forming tank 2, the supplied contaminants and, in some cases, water are stirred and mixed to form a slurry. While measuring the pH of the slurry using the pH meter 28, the acidic substance or alkaline substance is added via the acidic substance or alkaline substance supply means 24 to adjust the pH of the slurry to 3 or less or 12 or more. . While measuring the oxidation-reduction potential of the slurry, the oxidation-reduction potential of the cathode electrode C is adjusted to be −0.16 V or less with respect to the hydrogen standard electrode. In this state, in the slurry, heavy metals are eluted from the contaminated material and then electrolytically deposited on the surface of the corrosion-resistant cathode C. At this time, the electrodeposition reaction rate increases as the electrode potential of the corrosion-resistant cathode C is lower, but if the electrode potential is too low (for example, about -0.6 V or less in the case of lead), heavy metals are deposited during the electrodeposition. However, a dense film is not formed, and the film once formed is easily peeled off by the shearing force of stirring. Therefore, an appropriate electrode potential is selected according to the contaminants and the conditions of the apparatus.

  Next, the slurry pump 34 is operated, and the slurry is pumped to the solid-liquid separator 3, and the liquid and the purified dehydrated solid (soil, sludge, sludge, incinerated ash, sediment-derived solid dehydrate, etc.) To separate. The separated solid component is extracted through a solid extraction line 36 and can be treated as soil, sludge, sludge, incinerated ash, or the like that is not contaminated with heavy metals. The separated liquid is extracted via the liquid extraction line 38 and recirculated to the slurry forming tank 2 via the liquid circulation line 40 or drained as excess drainage.

  Heavy metals electrolytically deposited on the surface of the corrosion-resistant cathode C are taken out of the system when the electrode is replaced, or the cathode is regenerated, for example, the cathode is temporarily taken out and washed with acid, or the electrode potential is changed. By temporarily raising the voltage to about −0.1 V, it can be eluted from the electrode surface and recovered as a heavy metal concentrate, discarded as a heavy metal contaminant, or reused as a heavy metal raw material. If a too high potential is applied during electrode regeneration (for example, about 0.0 V in the case of a copper electrode), the electrode components will dissolve, so the electrode potential should be set to a range where the electrode components do not dissolve, Alternatively, it is desirable to manage the time for applying a high potential in a short time.

  FIG. 2 is a schematic view of a second embodiment of the present invention suitable for the case where mercury or arsenic is included as heavy metals. The purification device 1A shown in FIG. 2 has substantially the same configuration as the purification device shown in FIG. 1, but an inert gas supply means 27 for supplying an inert gas such as nitrogen gas to the reaction tank 2, and a heavy metal vapor-containing gas A heavy metal trap 5 for collecting heavy metals therein is further provided. The heavy metal trap 5 is provided with an exhaust line 51 so that the gas after the heavy metal is collected and removed by the heavy metal trap 5 is discharged. As the heavy metal trap 5, for example, a gas cleaning bottle containing a sulfuric acid-acid potassium permanganate aqueous solution or a gas treatment carrier carrying an oxidizing agent such as sulfur powder can be used.

  Since the purification mode of the contaminated object using the purification device 1A is substantially the same as the mode described in the purification device 1 shown in FIG. 1 except for the operation of the heavy metal trap 5, only the operation of the heavy metal trap 5 will be described here. .

  This purification apparatus 1A is particularly suitable for the purification of contaminated substances including mercury and arsenic.

  In the case of contaminated substances containing mercury, the contaminated substances are supplied into the slurry forming tank 2 and maintained in a reducing atmosphere and a strong acidic or strong alkaline atmosphere, so that heavy metals containing mercury or mercury are contained in the contaminated substances. Elutes, and then mercury is reduced and vaporizes. The vaporized mercury is accompanied by an inert gas such as hydrogen gas generated at the cathode electrode and / or nitrogen gas supplied from the inert gas supply means 27 into the slurry formation tank 2, and moves from the slurry to the gas phase. , Collected in heavy metal trap 5. The collected heavy metals such as mercury can be discarded as heavy metal contaminants or recycled as heavy metal raw materials.

In the case of a contaminated substance containing arsenic, the contaminated substance is supplied into the slurry forming tank 2 and maintained in a reducing atmosphere and a strong acidic or strong alkaline atmosphere, whereby the heavy metal containing arsenic or arsenic from the contaminated substance Then, arsenic is reduced and hydrogenated, and vaporizes in the form of arsine (AsH ₃ ), for example. The vaporized arsenic is accompanied by an inert gas such as hydrogen gas generated at the cathode electrode and / or nitrogen gas supplied from the inert gas supply means 27 into the slurry formation tank 2, and moves from the slurry to the gas phase. , Collected in heavy metal trap 5. The collected heavy metal such as arsenic can be discarded as a heavy metal contaminant or reused as a heavy metal raw material.

  FIG. 3 shows a third preferred embodiment of the present invention that removes and recovers lead, cadmium, chromium, tin, arsenic, uranium, plutonium, and the like using an electrolytic deposition reaction (a mode including a shearing force suppressing unit). It is a schematic explanatory drawing shown.

  In FIG. 3, the purification apparatus 1B includes a contaminated material supply means 22 for supplying a contaminated material containing heavy metals, an acid or alkaline material supply means 24 for supplying an acid or an alkaline material, and a contaminated material with an acidic or alkaline property. Corrosion-resistant cathode C that provides a reducing atmosphere to a slurry containing at least a substance, and reducing the shear force due to the slurry acting on the surface of the corrosion-resistant cathode and maintaining the contact state between the corrosion-resistant cathode and the slurry And a slurry forming tank 2 having a shearing force suppressing means for controlling the shearing force.

  In the illustrated embodiment, the slurry forming tank 2 further includes water supply means 26 for supplying water to the slurry forming tank 2. The lower part of the slurry forming tank 2 is formed in a funnel shape, and a slurry extraction port 30 is provided at the funnel-shaped tip. A slurry transfer line 32 and a slurry pump 34 provided on the slurry transfer line 32 are connected to the slurry extraction port 30. A solid-liquid separator 3 is connected to the slurry transfer line 32, and the slurry is separated into a solid content and a liquid content. A circulation pump 39 and a liquid circulation line 40 are connected to the solid-liquid separation device 3, and the liquid component separated in the solid-liquid separation device 3 is provided as a circulating liquid at the upper part of the funnel shape at the bottom of the slurry formation tank 2. It is reintroduced into the circulating fluid inlet 42. The solid-liquid separator 3 includes a solid extraction line 36 for extracting separated solids (clean dehydrated soil, sludge, sludge, incineration ash, sediment, etc.), and a liquid extraction line (drain) 38 for extracting the separated liquid as surplus drainage. And are connected.

  In the slurry forming tank 2, a corrosion-resistant cathode C, an anode A, and a reference electrode B that provide a reducing atmosphere to the slurry are positioned in the upper position in the slurry forming tank 2, and a pH meter that measures the pH of the slurry. 28 is provided. The corrosion-resistant cathode C, the anode A, and the reference electrode B are connected to a power supply device outside the slurry forming tank 2, and a controlled applied potential is provided. A cathode protection member 50 is attached to the corrosion-resistant cathode C so that a solid having a large particle size in the slurry does not exist near the cathode surface. The protective member 50 is made of nylon mesh (eye size: 1.5 mm).

  Next, an aspect of purifying a contaminated object contaminated with heavy metals using the purification device 1B will be described.

  First, the contaminated material contaminated with heavy metals such as soil, sludge, sludge, incineration ash, and deposits is supplied to the slurry forming tank 2 through the contaminated material supplying means 22. At this time, if the contaminated material is not saturated, that is, if the void of the contaminated material is not saturated with water, supply an appropriate amount of water via the water supply means 26 or the liquid circulation line 40, and the saturated state And In the slurry forming tank 2, the supplied contaminants and, in some cases, water are stirred and mixed to form a slurry. While measuring the pH of the slurry using the pH meter 28, the acidic substance or alkaline substance is added via the acidic substance or alkaline substance supply means 24 to adjust the pH of the slurry to 3 or less or 12 or more. . While measuring the oxidation-reduction potential of the slurry, the oxidation-reduction potential of the corrosion-resistant cathode C is adjusted to be −0.16 V or less with respect to the hydrogen standard electrode. In this state, in the slurry, heavy metals are eluted from the contaminated material and then electrolytically deposited on the surface of the corrosion-resistant cathode C. At this time, the electrodeposition reaction rate increases as the electrode potential of the corrosion-resistant cathode C is lower, but if the electrode potential is too low (for example, about -0.6 V or less in the case of lead), heavy metals are deposited during the electrodeposition. However, a dense film is not formed, and the film once formed is easily peeled off by the shearing force of stirring. Therefore, an appropriate electrode potential is selected according to the contaminants and the conditions of the apparatus.

  The slurry descends to the funnel-shaped portion at the bottom of the slurry forming tank 2 while receiving the stirring action by the stirring device. Since the corrosion-resistant cathode C at the upper position in the slurry forming tank 2 is protected by the cathode protection member 50, the shearing force applied to the surface of the corrosion-resistant cathode C by the slurry flow can be suppressed low.

  After confirming that the treatment in the slurry forming tank 2 has been completed due to a decrease in the current value in the negative direction after a certain period of time or by observation of the current value, the slurry is pumped to the solid-liquid separator 3 and the liquid And purified dehydrated solids (soil, sludge, sludge, incineration ash, sediment-derived solid dehydrates, etc.). The separated solid component is extracted through a solid extraction line 36 and can be treated as soil, sludge, sludge, incinerated ash, or the like that is not contaminated with heavy metals. The separated liquid is recirculated to the slurry forming tank 2 via the liquid circulation line 40, or extracted via the liquid extraction line 38 and drained as excess drainage.

  Heavy metals electrolytically deposited on the surface of the corrosion-resistant cathode C may be taken out of the system by exchanging electrodes. Alternatively, as a method of regenerating the electrode, the electrode is taken out and washed with acid, or the electrode potential is temporarily increased to about −0.1 V, for example, and eluted from the surface of the corrosion-resistant cathode C to form a heavy metal concentrate. It may be recovered. If the potential applied during electrode regeneration is too high (for example, about 0.0 V in the case of a copper electrode), the material constituting the electrode itself will be dissolved. shorten. The recovered heavy metals may be disposed of as heavy metal contaminants or reused as heavy metal raw materials.

  FIG. 4 is a schematic explanatory view showing another aspect of the shear force suppressing means. The purifying apparatus 100 shown in FIG. 4 includes a contaminated material supply unit 111 that supplies a contaminated material containing heavy metals, an acid or alkaline material supply unit 112 that supplies an acid or an alkaline material, the contaminated material and the acid. Alternatively, the corrosion resistant cathode 113C that provides a reducing atmosphere to the slurry containing at least an alkaline substance, and the shearing force caused by the slurry acting on the surface of the corrosion resistant cathode is reduced, and the contact state between the corrosion resistant cathode and the slurry is maintained. And a slurry forming tank 110 having a shearing force suppressing means for controlling as described above.

  In the present purification apparatus 100, the reducing atmosphere includes a corrosion-resistant cathode 113C disposed in the slurry forming tank 110, an anode 113A, a cathode control reference electrode (hydrogen standard electrode) 113B, a corrosion-resistant cathode 113C, The slurry is provided to the slurry by an external power supply for controlling the applied voltage of the anode 113A and the reference electrode 113B. The reference electrode 113B is disposed in the vicinity of the electrode (cathode) to be controlled. In the illustrated embodiment, an electrolytic membrane (diaphragm) M is positioned between the corrosion resistant cathode 113C and the anode 113A, and the contact between the anode 113A and the slurry is dilute. . The corrosion-resistant cathode 113C, the anode 113A, the electrolytic membrane M, and the reference electrode 113B are positioned at an upper position in the slurry forming tank 110.

  The slurry forming tank 110 is equipped with a pH meter 116 for monitoring that the slurry is maintained in a strong acidic atmosphere or a strong alkaline atmosphere. In addition, the illustrated slurry forming tank 110 includes water supply means 115 for supplying water that is necessary in some cases to form a slurry. Further, a treated slurry extraction port 122 for extracting the processed slurry is provided at the bottom of the slurry forming tank 110. A slurry pump 123 for extracting processed slurry and a solid-liquid separator 120 are connected to the processed slurry extraction port 122. Connected to the solid-liquid separator 120 is a circulating liquid supply means (not shown) for recirculating the treated water obtained by the solid-liquid separation to the slurry forming tank 110.

  In the illustrated embodiment, the shear force suppressing means includes a slurry extraction port 117 provided at the top of the slurry forming tank, a slurry introduction port 118 provided at the bottom of the tank, and a slurry from the slurry extraction port 117 to the slurry introduction port 118. A circulation pump 119 that circulates, and is configured to raise the slurry from the bottom of the vessel at a desired rate to provide the desired slurry solids particle size distribution within the slurry forming vessel 110.

  In addition, a stirring device 121 is provided at the lower part of the slurry forming tank 110, and the slurry introduced into the slurry forming tank 110 from the slurry inlet 118 is sufficiently stirred so that the slurry at the horizontal level of the slurry forming tank 110 The heavy metal ions concentration is made constant.

  Next, a preferred embodiment for purifying a contaminated object contaminated with heavy metals using the purification device 110 will be described.

  First, the contaminated material contaminated with heavy metals such as soil, sludge, sludge, incineration ash, and deposits is supplied to the slurry forming tank 110 through the contaminated material supplying means 111. At this time, if the contaminated material is not saturated, that is, the void of the contaminated material is not saturated with water, an appropriate amount of water is supplied via the water supply means 115 and / or the circulating fluid supply means (not shown). Supply water to saturation. The contaminated material supplied into the slurry forming tank 110 and, in some cases, water and / or circulating liquid are stirred and mixed to form a slurry. While measuring the pH of the slurry by the pH meter 116, an acidic substance or alkaline substance is supplied via the acid or alkaline substance supply means 112, and the pH of the slurry is adjusted to 3 or less or 12 or more. While measuring the oxidation-reduction potential of the slurry, the oxidation-reduction potential of the corrosion-resistant cathode 113C is adjusted to be −0.16 V or less with respect to the hydrogen standard electrode 113B.

  The obtained slurry flows as an upward flow in the slurry formation tank 110 by the operation of the circulation pump 119, is extracted through the slurry extraction port 117 above the slurry formation tank 110, and is again slurried through the slurry introduction port 118. It is introduced into the forming tank 110 and flows again as an upward flow. The speed of the upward flow of the slurry is adjusted by adjusting the circulation pump 119.

  In the slurry flowing in the slurry forming tank 110 as an upward flow, a reducing atmosphere and a strong acidic or strong alkaline atmosphere are maintained, and heavy metals are eluted from the contaminated substances and electrolytically deposited on the surface of the corrosion-resistant cathode 113C. It becomes like this. At this time, the electrodeposition reaction rate increases as the cathode electrode potential is lower. However, if it is too low (for example, -0.6 V or less in the case of lead), the heavy metals that are electrodeposited cannot form a dense film. Since the coating is easily peeled off, the cathode electrode potential is adjusted to an appropriate range.

  By causing the slurry to flow in the slurry forming tank 110 as an upward flow, a solid having a large particle size exists in the lower part of the slurry forming tank 110 and a solid having a small particle diameter flows in the upper part. Thus, the slurry containing the solid having a small particle size flows in the vicinity of the corrosion-resistant cathode 113C positioned at the upper position in the slurry forming tank 110, and the shearing force due to the solid having a large particle size on the cathode surface 113C is eliminated. Therefore, the heavy metals electrolytically deposited on the surface of the cathode 113C can be deposited well without being affected by the shearing force due to the slurry, particularly the large particle size solid in the slurry.

  When it is confirmed by the observation of the current value that the processing in the slurry forming tank 110 has been completed due to the decrease in the current value in the negative direction, the slurry pump 123 is operated, and the treated slurry is extracted from the treated slurry extraction port 122. The slurry is extracted and pumped to the solid-liquid separator 120. The treated slurry is separated into an aqueous solution and purified dehydrated solids (soil, sludge, sludge, incineration ash, sediment-derived solid dehydrates, etc.) by the solid-liquid separator 120. You may process the isolate | separated solid content as soil, sludge, sludge, or incineration ash which is not polluted with heavy metals. The separated aqueous solution may be recycled to the slurry forming tank 110 as a circulating liquid and reused, or may be discharged out of the system as a surplus liquid.

  The post-treatment of heavy metals electrolytically deposited on the surface of the cathode 113C can be performed as described for the apparatus of FIG.

  FIG. 5 is a schematic explanatory diagram showing a fifth preferred embodiment of the present invention in which lead, cadmium, and the like are removed and recovered using electrolytic elution and electrolytic deposition reaction. A purification apparatus 100A shown in FIG. 5 includes a contaminated material supply means 22 for supplying a contaminated material containing heavy metals, an acid or alkali supply means 24 for supplying an acid or an alkali, and a reducing atmosphere that provides a reducing atmosphere. And a purification reaction tank 2 comprising a providing means. In this example, the purification reaction tank 2 is composed of an upstream slurry forming part 2a and a downstream separating part 2b.In this example, the slurry forming part 2a is a tank having a circular cross section, and the separating part 2b is A narrow rectangular tank. The reducing atmosphere providing means includes a first anode A-1 and a second anode A-2 arranged in the separation unit 2b, an elution cathode control reference electrode B-1 arranged in the slurry forming unit 2a, and A pair of elution cathodes C-1a and C-1b, a deposition cathode control reference electrode B-2 and a deposition disposed between the first anode A-1 and the elution cathodes C-1a and C-1b Cathode C-2. A first power supply device for applying an elution potential between the elution cathodes C-1a, C-1b and the second anode A-2, and between the deposition cathode C-2 and the first anode A-1. A second power supply device for applying a deposition potential is provided.

  Reference electrodes B-1 and B-2 are arranged in the vicinity of the electrodes to be controlled. The slurry forming unit 2a is preferably provided with, for example, a stirrer as a device for making the slurry inside the slurry uniform. Furthermore, a water supply means 26 for supplying water and a circulating liquid supply means 40a for reusing the treated water after solid-liquid separation may be provided. A pH meter electrode 28 for measuring the pH of the slurry is inserted into the purification reaction tank 2. A solid-liquid separation device 3 for solid-liquid separation of the slurry formed in the purification reaction tank 2 and a slurry pump 34 for slurry conveyance may be provided. In order not to impair the cathode-side reducing atmosphere due to the oxidative atmosphere generated on the anode side, for example, the cathode and the anode are separated from each other, the water flow from the cathode side to the anode side is present, or the porous wall Alternatively, a diaphragm M may be provided. In this example, a circulation pump for returning the liquid from the separation unit 2b to the slurry formation unit 2a is provided.

  A method for purifying a contaminated object contaminated with heavy metals using the purification device 100A will be described. First, the contaminated material contaminated with heavy metals such as soil, sludge, sludge, incineration ash, and deposits is supplied to the purification reaction tank 2 through the contaminated material supply means 22. At this time, if the contaminated material is in an unsaturated state, that is, if the void of the contaminated material is not saturated with water, an appropriate amount of water is supplied via the water supply means 26 or the circulating fluid supply means 40b and saturated. State.

  In the slurry forming section 2a of the purification reaction tank 2, the supplied contaminants and, in some cases, water and / or circulating liquid are stirred to form a slurry. While measuring the pH of the slurry using the pH meter electrode 28, acid or alkali is added via the acid or alkali supply means 24, and the pH of the slurry is adjusted to 3 or less or 12 or more. While measuring the oxidation-reduction potential of the slurry, the oxidation-reduction potentials of the elution cathodes C-1a, C-1b and the deposition cathode C-2 are adjusted to be −0.16 V or less with respect to the hydrogen standard electrode.

  In this state, in the slurry, heavy metals are eluted from the contaminated material and then electrolytically deposited on the surface of the deposition cathode C-2. At this time, the electrodeposition reaction rate increases as the electric potential becomes lower. However, if the electric potential is too low (for example, about -0.6 V or less in the case of lead), heavy metals form a dense film during the electrodeposition. First, since the coating once formed is easily peeled off, an appropriate potential should be selected according to the contaminants and the conditions of the apparatus.

  Next, the slurry is pumped to the solid-liquid separator 3 using the slurry pump 34, and separated into an aqueous solution and purified dehydrated solids (soil, sludge, sludge, incinerated ash, sediment-derived solid dehydrates, etc.). . The separated solid content can be treated as soil, sludge, sludge, incinerated ash, or the like that is not contaminated with heavy metals. The separated aqueous solution is reused as a circulating liquid or drained as an excess liquid.

  The heavy metals electrolytically deposited on the surface of the deposition cathode C-2 are usually taken out of the system by exchanging the electrodes or by temporarily taking out the electrodes and washing them with an acid. Also, as a method for regenerating the deposition cathode C-2, the cathode potential for deposition is temporarily raised to, for example, about -0.1 V, and eluted from the surface of the deposition cathode C-2 and recovered as a heavy metal concentrate. Is done. This can be discarded as heavy metal contaminants or reused as a heavy metal source. At this time, if an excessively high potential is applied to the deposition cathode C-2 (for example, about 0.0 V in the case of a copper electrode), the material of the deposition cathode C-2 itself dissolves, so that the deposition cathode material does not dissolve. It is desirable to set the potential for regeneration of the deposition cathode C-2 or to control the time for applying a high potential to be short. If a pair of deposition cathodes C-2 are provided and one of them is taken out alternately, the apparatus can be operated continuously.

  In the embodiment shown in FIG. 5, the reaction tank 2 is composed of a slurry forming layer 2a having a circular cross section and a slurry separating tank 2b having a rectangular cross section, and a stirrer is disposed in the center of the slurry forming layer 2a to cause contamination. The material supply means 22, the acid or alkali supply means 24, and the water supply means 26 are provided at positions facing the inlet to the slurry separation tank 2b in the radial direction. For this reason, the contaminated material, acid or alkaline substance, and water supplied into the slurry forming layer 2a are stirred and rotated in the circumferential direction and are pushed away in the direction of the slurry separation tank 2b. Therefore, if the flow rate of extrusion in part 2b is made slower than the rotational speed in the circumferential direction by controlling the circulation pump, contact with the elution cathode in part 2a, precipitation in part 2b is maintained while maintaining elution efficiency. The shearing force to the cathode can be suppressed.

  FIG. 7 is a schematic explanatory view showing a sixth preferred embodiment of the present invention in which heavy metals are removed and recovered using electrolytic elution and electrolytic deposition reaction. The reaction tank 2 shown in FIG. 7 includes a slurry or liquid contaminant supply means 22 for supplying solid or liquid contaminants containing heavy metals, and an acid or alkali supply means for supplying acid or alkali. 24, a corrosion-resistant cathode C that is in contact with the slurry or liquid in the reaction tank 2, and a closed cylindrical, box-shaped or bag-shaped diaphragm unit M disposed in the reaction tank 2, This is a solid or liquid contamination purification apparatus including an anode A disposed inside the diaphragm unit M and a reduction potential providing means for providing a reduction potential to the corrosion-resistant cathode C. The reaction tank 2 is desirably provided with a device such as a gas diffuser 8 as a device for uniformizing the reaction solution inside. Furthermore, a water supply means 26 for supplying water and a circulating liquid supply means for reusing the treated water after solid-liquid separation (slurry transport line 32, slurry pump 34, solid-liquid separation device 3, circulating liquid transport line 40) may be provided.

  A method for purifying a solid or liquid contaminated object contaminated with heavy metals using the reaction vessel 2 will be described. First, solids contaminated with heavy metals such as soil, sludge, sludge, incineration ash, sediment, industrial wastewater, surface water, groundwater, seawater, etc. A liquid or liquid contaminant is supplied to the reaction tank 2. At this time, when the solid or liquid contaminated object is in an unsaturated state, that is, when the void of the solid contaminated object is not saturated with water, the water supply means 26 or the circulating fluid supply means (32, 34) , 3,40) to supply an appropriate amount of water to achieve saturation. In the reaction tank 2, the supplied solid or liquid contaminated material, and, in some cases, water and / or circulating liquid are stirred to form a slurry or a solution. While measuring the pH of the slurry using a pH meter (not shown), acid or alkali is added via the acid or alkali supply means 24 to adjust the pH of the slurry to 3 or less or 12 or more. . Using the reduction potential providing means, the reduction potential is applied so that the potential of the cathode C is −0.16 V or less with respect to the hydrogen standard electrode, or the current density is +0.01 to +10 A / L reaction vessel. The optimum cathode potential or current density varies greatly depending on the concentration of contaminants, the electrode area, and the shape of the apparatus. Therefore, an appropriate applied potential is selected according to the conditions.

  After the completion of the electrolytic elution and precipitation reaction, the slurry is pumped to the solid-liquid separator 3 using the slurry pump 34, and the aqueous solution and the purified dehydrated solid (soil, sludge, sludge, incinerated ash, sediment-derived solid dehydrate, etc. And). When the contaminated material is a liquid, a solid-liquid separation step is not necessary. The separated solid content can be treated as soil, sludge, sludge, incinerated ash, or the like that is not contaminated with heavy metals. The separated aqueous solution is reused as a circulating liquid or drained as an excess liquid. Heavy metals electrolytically deposited on the surface of the deposition cathode C are taken out of the system by exchanging the electrodes, or as a method for regenerating the deposition cathode C, the deposition cathode potential is temporarily reduced to, for example, about -0.1V. By elevating it, it elutes from the surface of the cathode C for precipitation and is recovered as a heavy metal concentrate and can be discarded as a heavy metal contaminant or reused as a heavy metal raw material. At this time, if a too high potential is applied (for example, about 0.0 V in the case of a copper electrode), the deposition cathode material itself is dissolved, so that the potential for regeneration of the deposition cathode is set within a range where the deposition cathode material does not dissolve. It is desirable to set or manage the time for applying a high potential in a short time.

  The method for electrolytic deposition removal of uranium contaminated soil by the purification apparatus of the present invention will be specifically described as follows. As shown in FIG. 1, a cation exchange membrane (Tokuyama NEOSEPTA CMB) is installed in the center of a 2000 mL plexiglass reactor, and the reactor is divided into two parts to provide a cathode zone and an anode zone. 100 g of poorly water-soluble uranium-contaminated soil, 800 mL of tap water, and 90 mL of 20% hydrochloric acid are added to the cathode zone, and the mixture is stirred with a Teflon (registered trademark) stirring blade at a speed of 700 rpm. A nickel-copper alloy (Daido Incoalloy Monel 400) wire mesh corrosion-resistant cathode is inserted into the cathode section and connected to the anode via a potentiostat (constant potential power supply). In the anode zone, 810 mL of tap water and 90 mL of 47% sulfuric acid are added, and an anode made of ruthenium oxide-coated titanium is inserted. A reference electrode is inserted into the cathode section and the potentiostat is adjusted so that the cathode electrode potential is -1.5 V with respect to the hydrogen standard electrode potential. Metal uranium is recovered from uranium contaminated soil by operating for 60 minutes after the cathode potential reaches -1.5V. Since uranium has radioactivity, work should be done while paying attention to the amount of exposure using remote control or radiation protective clothing and protective walls.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples. The specimens used in the following examples are prepared by mixing heavy metals with soil collected from various factory sites to prepare heavy metal-containing soil with a predetermined concentration.

[Example 1] Electrolytic precipitation removal test of lead-contaminated soil As shown in Fig. 1, a cation exchange membrane (Tokuyama NEOSEPTA CMB) was installed in the center of a 2000 mL plexiglass reactor, and the reactor was divided into two parts. A cathode zone and an anode zone.

  In the cathode area, add 100 g of poorly water-soluble lead-contaminated soil (lead-containing concentration 300 mg / kg dry soil; sampling location: A machine factory), 800 mL of tap water, and 90 mL of 20% hydrochloric acid, and Teflon (registered trademark) ) The test system was stirred with a stirring blade made at a speed of 700 rpm.

  A corrosion-resistant cathode of a nickel-copper alloy (Daido Incoalloy Monel 400) wire mesh was inserted into the cathode section and connected to the anode via a potentiostat (constant potential power supply).

  In the anode area, 810 mL of tap water and 90 mL of 47% sulfuric acid were added, and an anode made of ruthenium oxide-coated titanium was inserted.

  A reference electrode was inserted into the cathode area and the potentiostat was adjusted so that the cathode electrode potential was -0.55 V with respect to the hydrogen standard electrode potential. After 20 minutes of operation after the cathode electrode potential reached −0.55 V, the slurry in the reactor was subjected to suction filtration using GF / B filter paper to perform solid-liquid separation. During the reaction time, the pH of the cathode zone slurry was maintained below 1.0. After suction filtration, the lead concentration in the filtrate and the lead-containing concentration in the soil after filtration were measured using an atomic absorption method. Using the same experimental apparatus, the suction system and solid-liquid separation were similarly performed on the control system in which the cathode electrode potential was set to 0.0 V with respect to the hydrogen standard electrode potential. The lead concentration of was measured. The results are shown in Table 1.

  From Table 1, by maintaining the slurry containing heavy metal solid contaminants in a strongly acidic atmosphere and a reducing atmosphere, 96% of the poorly soluble lead adhering to the soil adheres to the cathode electrode. It can be seen that the water was removed from the pore water.

[Example 2] Electrode reduction cleaning test of mercury-contaminated sediment As shown in FIG. 2, a cation exchange membrane (NEOSEPTA CMB made by Tokuyama) was installed in the center of a 2000 mL plexiglass reactor, and the reactor was separated for 2 minutes. And provided with a cathode zone and an anode zone.

  To the cathode area, add 100 g of poorly water-soluble mercury contaminated sediment (total mercury content concentration 130 mg / kg dry soil; sampling location: B Chemical Factory), 800 mL of tap water, and 90 mL of 20% hydrochloric acid, and add Teflon ( The mixture was agitated with a stirring blade manufactured by (registered trademark) at a speed of 700 rpm, a nitrogen gas diffusing tube was inserted, and the cathode area was aerated with nitrogen at a rate of 10 mL / min to prepare a test system.

  A copper wire mesh corrosion-resistant cathode plated to a thickness of 10 μm with a lead-tin alloy (lead / tin = 60/40) was inserted into the test system and connected to the anode via a potentiostat. In order to collect the gas discharged from the cathode section, a gas washing bottle containing 100 mL of 1: 4 sulfuric acid containing potassium permanganate (50 g / L) was connected to the reactor.

  In the anode area, 810 mL of tap water and 90 mL of 47% sulfuric acid were added, and an anode made of ruthenium oxide-coated titanium was inserted.

  The reference electrode was inserted into the cathode section, and the potentiostat was adjusted so that the cathode electrode potential was −0.66 V with respect to the standard hydrogen electrode potential. After the cathode potential reached −0.66 V, the operation was continued for 20 minutes, and the slurry in the reactor was suction filtered using GF / B filter paper to perform solid-liquid separation. The pH of the cathode zone was maintained below 1.0. The gas from the reactor was collected in a gas wash bottle as a heavy metal trap. After suction filtration, measure the total mercury concentration in the filtrate and the mercury-containing concentration in the sediment after filtration using the heated vaporization atomic absorption method, and the mercury concentration collected in the gas wash bottle using the atomic absorption method. It was measured.

  For the control system in which the cathode potential was set to +0.2 V with respect to the hydrogen standard electrode potential using the same experimental apparatus, suction filtration and solid-liquid separation were performed in the same manner, and then the filtrate and the filtered sediment And the mercury concentration in the gas washing bottle was measured. The results are shown in Table 2.

  From Table 2, it can be seen that 99% of the hardly soluble mercury adhering to the deposit is removed from the deposit and the pore water by applying a reduction potential under acidic conditions.

[Example 3] Electrodeposition removal test of lead in fly ash As shown in FIG. 1, a cation exchange membrane (Tokuyama NEOSEPTA CMB) was installed in the center of a 2000 mL plexiglass reactor. To provide a cathode zone and an anode zone. In the cathode area, 100 g of molten fly ash (lead-containing concentration: 36 g / kg; sampling location: D waste incineration melting furnace) that is generated when waste incineration fly ash is further melted with plasma, 640 mL of tap water, and 250 mL of 20% hydrochloric acid , And stirred with a Teflon (registered trademark) stirring blade at a speed of 700 rpm to prepare a test system. A copper expanded metal corrosion-resistant cathode melted and immersed to a thickness of 0.5 mm with a lead-tin alloy (lead / tin = 60/40) was inserted into the test system, and the anode was connected to the anode via a potentiostat (constant potential power supply). Connected. In the anode area, 810 mL of tap water and 90 mL of 47% sulfuric acid were added, and an anode made of ruthenium oxide-coated titanium was inserted.

  A reference electrode was inserted into the cathode area and the potentiostat was adjusted so that the cathode electrode potential was -0.55 V with respect to the hydrogen standard electrode potential. After the cathode potential reached −0.55 V, the operation was performed for 60 minutes, and then the slurry in the reactor was centrifuged to perform solid-liquid separation. During the reaction time, the pH of the cathode zone slurry was maintained below 1.0.

  After centrifugation, the lead concentration in the liquid phase and the lead-containing concentration in the soil were measured using the atomic absorption method.

  Using the same experimental apparatus, the control system in which the cathode electrode potential was set to −0.1 V with respect to the hydrogen standard electrode potential was also operated for 60 minutes, and centrifuged in the same manner in the liquid phase and in the soil. The lead concentration of was measured. The results are shown in Table 3.

  From Table 3, in the test system, the slurry containing heavy metal-contaminated fly ash is maintained in a strongly acidic atmosphere and a reducing atmosphere (-0.55 V with respect to the hydrogen standard electrode), so that 99 of the lead in the fly ash It can be seen that% was attached to the cathode electrode and removed from the solid phase and the liquid phase.

[Example 4] Electrolytic precipitation removal test of lead-contaminated soil Table 4 shows the results of the lead removal test when the cathode potential was set to -0.25 V and operated for 20 minutes under the same conditions as in Example 1.

[Example 5] Electrolytic precipitation removal test of lead-contaminated soil

  As shown in FIG. 3, a 2000 mL acrylic container was used as a slurry formation tank. A cation exchange membrane (Tokuyama NEOSEPTA CMB) was installed at approximately the center of the slurry forming tank, and the tank was divided into two parts, which were a cathode zone and an anode zone, respectively.

  In the cathode area, add 100 g of poorly water-soluble lead-contaminated soil (lead-containing concentration 5000 mg / kg dry soil; sampling location: E car factory), 800 mL of tap water, and 50 mL of 1: 1 hydrochloric acid, and add Teflon (registered) The mixture was stirred at a speed of 500 rpm with a stirring blade manufactured by Trademark) to obtain a test system.

  A corrosion-resistant cathode of a nickel-copper alloy (Daido Incoalloy Monel 400) wire mesh was inserted into the test system and connected to the anode via a potentiostat (constant potential power supply). In the vicinity of the cathode, a partition wall was formed with a protective member made of nylon mesh (mesh size 1.0 mm) to prevent the shearing force due to the large particle size solid in the slurry from acting on the corrosion-resistant cathode surface. .

  In the anode zone, 800 mL of tap water and 90 mL of 47% hydrochloric acid were added, and a graphite anode was inserted.

  A reference electrode was inserted into the cathode area and the potentiostat was adjusted so that the cathode electrode potential was -0.55 V with respect to the hydrogen standard electrode potential. After 20 minutes of operation after the cathode electrode potential reached -0.55 V, the slurry in the tank was suction filtered using GF / B filter paper to perform solid-liquid separation. During the reaction time, the pH of the cathode zone slurry was maintained below 1.0. After suction filtration, the lead concentration in the filtrate and the lead-containing concentration in the soil after filtration were measured using an atomic absorption method. For the control system constructed using the same experimental equipment as the test system except that the cathode protection member was not used, suction filtration and solid-liquid separation were performed in the same manner, and the lead concentration in the filtrate and in the soil after filtration was determined. It was measured. The results are shown in Table 5.

  From Table 5, it can be seen that the concentration of lead distributed to the electrode is increased by suppressing the shearing force due to the slurry applied to the cathode. Therefore, according to the present invention, it was confirmed that peeling and re-dissolution of heavy metals electrolytically deposited on the cathode surface can be prevented.

[Example 6] Electrodeposition removal test of lead-contaminated soil As shown in FIG. 4, a cation exchange membrane is used at the center of an acrylic reaction tank having a height of 0.4 m, a width of 0.1 m, and a depth of 0.05 m and an internal volume of 2000 mL (Tokuyama NEOSEPTA CMB) was used to divide into compartments having a height of 0.4 m, a width of 0.05 m, and a depth of 0.05 m, respectively, to form a cathode compartment and an anode compartment. To the cathode compartment, add 100 g of poorly water-soluble lead-contaminated soil (lead-containing concentration 5000 mg / kg dry soil; sampling location: E car factory), 800 mL of tap water, and 50 mL of 1: 1 hydrochloric acid, and Teflon (registered) The mixture was stirred at a speed of 500 rpm with a stirring blade manufactured by Trademark) to obtain a test system. A corrosion-resistant cathode made of nickel-copper alloy (Daido Incoalloy Monel 400) wire mesh was installed at a depth of 2 cm in the test system and connected to the anode via a potentiostat (constant potential power supply). In addition, a circulation system was constructed in which the supernatant was sucked from the top using a Tygon tube and a circulation pump and reinjected from the bottom of the apparatus. The circulating water flow was adjusted to a flow rate (in this example, 0.5 L / min) at which only the fine-grained fraction contained in the soil could reach the cathode and lead deposited on the cathode surface did not peel off.

  In the anode compartment, 800 mL of tap water, 90 mL of 47% sulfuric acid, and a graphite anode were inserted. A reference electrode was inserted into the cathode compartment and the potentiostat was adjusted so that the cathode potential was -0.55 V relative to the hydrogen standard electrode. After the cathode potential reached −0.55 V, the operation was continued for 20 minutes, and the slurry in the reaction tank was subjected to suction filtration using GF / B filter paper to perform solid-liquid separation. During the reaction time, the pH of the slurry in the cathode compartment was maintained below 1.0. After suction filtration, the lead concentration in the filtrate and the lead-containing concentration remaining in the filtered soil were measured by atomic absorption method, respectively.

  A control system without a slurry circulation system was prepared, and after suction filtration and solid-liquid separation under the same experimental conditions as the test system, the lead content remaining in the filtrate and the soil after filtration was determined by atomic absorption spectrometry. It was measured. The results are shown in Table 6 below.

[Example 7] Electrodeposition removal test of lead-contaminated soil As shown in FIG. 5, a cation exchange membrane (NAFION manufactured by DuPont) was used so that a purification reaction tank 2 made of 2400 ml acrylic was 1400 ml on the cathode side and 1000 ml on the anode side ) Divide the center with M. In the slurry forming portion 2a, a nickel-copper alloy (Daido Incoalloy Monel 400) electrode is used as the deposition cathode C-2 at the position closest to the membrane, and the elution cathodes C-1a and C-1b are located farthest from the membrane. A graphite electrode was installed respectively. Two glassy carbon electrodes (manufactured by Tokai Carbon Co., Ltd.) were installed as anodes A-1 and A-2 at a position 2 cm from the membrane in the separation part 2b. Both cathodes were wired in parallel and connected to the anode via a potentiostat (constant potential power supply).

  Add 100 g of poorly water-soluble lead-contaminated soil (lead-containing concentration 5000 mg / kg dry soil; sampling location: F Chemical Factory), 1300 mL of tap water, and 80 mL of 1: 1 hydrochloric acid to the slurry forming part 2a, and then add PTFE It is kept in a nearly uniform state by stirring with a stirring blade made of (tetrafluoroethylene polymer) at a speed of 500 rpm. For the separation part 2b, 90 mL of 1: 1 sulfuric acid was added to 800 ml of tap water to prepare a test system. The reference electrode B-1 was inserted into the cathode area, and the potentiostat was adjusted so that the cathode potential was -0.55 V with respect to the hydrogen standard electrode. After operation for 20 minutes after the cathode potential reached −0.55 V, the slurry in the purification reaction tank 2 was subjected to suction filtration using GF / B filter paper to perform solid-liquid separation. During the reaction time, the pH of the slurry in the cathode zone was maintained below 1.0. After suction filtration, the lead concentration in the filtrate and the lead-containing concentration in the soil after filtration were measured by atomic absorption method, respectively. For the control system, which was conducted under the same conditions except that the elution cathodes C-1a and C-1b were removed, the lead concentration in the concentrated liquid and the filtered soil was also measured after suction filtration and solid-liquid separation. did. The results are shown in Table 7.

  From Table 7, it is understood that the removal effect superior to the conventional technology was obtained for heavy metals contained in the contaminated material by using a plurality of cathodes for elution and deposition.

[Example 8] Electrodeposition removal test of lead-contaminated soil with multiple electrodes As shown in FIG. 6, a square 2400 mL transparent polyvinyl chloride purification reaction tank has a cation such that the cathode side is 1400 mL and the anode side is 1000 mL. Partition the center with an exchange membrane (NAFION manufactured by DuPont) M. In the cathode area, a copper electrode plated with a lead-tin alloy (lead / tin = 40/60) with a thickness of 20 μm as the deposition cathode C-2 is located closest to the membrane, and the elution cathode is located farthest from the membrane. Carbon electrodes were installed as C-1. In the anode area, a glassy carbon electrode (made by Tokai Carbon Co., Ltd.) was installed as anode A at a position 2 cm from the membrane. Both cathodes were wired in parallel and connected to the anode via a potentiostat (constant potential power supply).

  In the cathode area, 100 g of poorly water-soluble lead-contaminated soil (lead-containing concentration 5000 mg / kg dry soil; sampling location: F Chemical Factory), 1300 mL of tap water, and 80 mL of 1: 1 hydrochloric acid are added, and PTFE (tetra The mixture was mixed almost uniformly by stirring at a speed of 500 rpm with a stirring blade made of (fluoroethylene polymer). In the anode zone, 5 mL of 1: 1 sulfuric acid was added to 800 ml of tap water to prepare a test system. The reference electrode B-1 was inserted into the cathode area, and the potentiostat was adjusted so that the cathode potential was -0.55 V with respect to the hydrogen standard electrode. After operation for 20 minutes after the cathode potential reached −0.55 V, the slurry in the purification reaction tank 2 was subjected to suction filtration using GF / B filter paper to perform solid-liquid separation. During the reaction time, the pH of the slurry in the cathode zone was maintained below 1.0. After suction filtration, the lead concentration in the filtrate and the lead-containing concentration in the soil after filtration were measured by atomic absorption method, respectively. For the control system, which was conducted under the same conditions except that the elution cathode C-1 was removed, the lead concentration in the concentrated liquid and the filtered soil was similarly measured after suction filtration and solid-liquid separation. The results are shown in Table 8.

[Example 9] Electrolytic precipitation removal test of lead-contaminated soil Lead-contaminated soil (lead-containing concentration of 5000 mg / kg dry) was added to a 2000 L square reactor (width 2 m, depth 1 m, depth 1 m) shown in FIGS. Sat; Sampling location: E car factory) Add 200kg, 1500L of tap water and 200L of 20% hydrochloric acid, arrange 6 nitrogen gas diffuser pipes at the bottom of the reactor, and gas at a ventilation rate of 2m ³ / min. The test system was stirred. As shown in FIG. 14, 10 units of a cylindrical diaphragm unit (Astom ED-CORE) with a diameter of 60 mm are arranged (effective membrane area 1.5 m ² ), and lead-tin alloy (lead / tin = 60/40) 27 units of cathode made of copper wire mesh plated to 20μm thickness were installed. A 5% sulfuric acid solution was circulated through the diaphragm unit to prepare an anode reaction solution. The cathode was connected to the anode via a jig and a rectifier and operated at a constant current of 1000 A for 20 minutes. The cathode potential immediately after the start of operation was about 0.0 V, but decreased to about -0.3 V in a few minutes. During this time, it is considered that the oxidizing substance in the liquid was consumed by reduction. After that, it gradually decreased to -0.76V by 30 minutes after stopping the operation. During this time, lead precipitation progresses and the liquid phase lead concentration decreases, and it is considered that the potential has shifted to a lower potential in order to maintain a constant current.

After operating for 30 minutes, the slurry in the reactor was collected, centrifuged, and suction filtered using GF / B filter paper to perform solid-liquid separation. After suction filtration, the lead concentration in the filtrate and the lead-containing concentration in the soil after filtration were measured using an atomic absorption method. As a control system, as shown in FIGS. 16 and 17, the wall surfaces at both ends of the apparatus of FIGS. 14 and 15 are removed, and a cation exchange flat membrane (Astom NEOSEPTA CMB) is used with an effective area of 1.44 m ² with a 10 cm square lattice frame. The anode section having a volume of 200 L was provided on the outside, and five of the same anode 10 used in the test system were immersed in each, and a 5% sulfuric acid solution was circulated as a reaction solution. The same cathode 27 unit used in the test system was placed in the reactor vessel. The other conditions were the same as in the test system, and the lead concentration was measured after 30 minutes of constant current operation. The results are shown in Table 9.

  From Table 9, by applying a diaphragm unit instead of a flat membrane and arranging a cathode around it, even in a large reactor, electrolytic deposition of lead progressed efficiently and adhered to the soil. It can be seen that 98% of the poorly soluble lead adhered to the electrode and could be removed from the soil and pore water.

[Example 10] Electrolytic precipitation removal test of tin-contaminated soil The 2000L square reactor shown in FIGS. 14 and 15 was used as a test system, and the modified 2000L square reactor shown in FIGS. 16 and 17 was used as a control system. The test was conducted as in Example 9. As the contaminated material, tin-contaminated soil (tin-containing concentration of 530 mg / kg dry soil; sampling location: F chemical factory) was used in place of lead-contaminated soil. The results are shown in Table 10.

  From Table 10, by applying a diaphragm unit instead of a flat membrane and arranging a cathode around it, even in a large reactor, electrolytic deposition of tin proceeded efficiently and adhered to the soil It can be seen that 95% or more of the hardly soluble tin adhered to the electrode and could be removed from the soil and pore water.

[Example 11] Electrodeposition removal test of lead-contaminated soil using various cathode electrodes Lead-tin alloy (lead / tin = 60/40) as a cathode using a 2000L square reactor shown in FIGS. Using a copper wire mesh plated to a thickness of 20 μm by the test system 1, a nickel-copper alloy (Daido Incoalloy Monel 400) wire mesh as the cathode, and a test system 2 using a copper wire mesh The test was performed in the same manner as in Example 9 as a control system. The test was conducted over 2 days, and after testing the three types of cathodes on the first day, the cathode unit was left overnight with a hydrochloric acid acidic slurry attached without being washed with water. On the second day, the same test was repeated using the same cathode unit again, and the influence of corrosion caused by standing overnight was evaluated. The results on the first day are shown in Table 11, and the results on the second day are shown in Table 12.

From Table 11 and Table 12, in the test on the first day, there was no significant difference in the lead removal performance by using various cathode electrodes, but 2 after the cathode was left overnight with hydrochloric acid acidic slurry attached. In the day test, test systems 1 and 2 were not significantly different from day 1, whereas in the control system using a copper electrode cathode, the cathode potential almost decreased during the 30-minute operation time. It can be seen that the removal of lead could not be achieved. The copper cathode (control system) on the second day is corroded by generating green patina (CuCO ₃ · Cu (OH) ₂ , CuCl and CuCl ₂ · 3Cu (OH) ₂ as main components) In addition, since the reaction in which these divalent and trivalent coppers are reduced to 0 valence during the electrolytic reaction occurs prior to the reductive precipitation of lead, the cathode potential is not sufficiently lowered within a predetermined operation time, It is thought that lead did not precipitate. That is, it was shown that the use of the cathode electrode having higher corrosion resistance than the conventional technique has an effect of stably performing the electrolytic reduction reaction of heavy metal during repeated electrolytic operation in a large apparatus.

Note that when this test was the cathode electrode and the partition plate shaped unit, due to the structure to be replaced by a jig, even 2m ³ scale large apparatus is easy replacement of the various electrodes, the cathode of the star-shaped diaphragm -It was advantageous in terms of workability compared to the conventional method of winding around the electrode unit.

  According to the present invention, for example, soils, sludges, sediments, wastes, incinerated ash and other contaminated substances contaminated with heavy metals are hardly soluble in heavy metals contained in the contaminated substances. The concentration of heavy metals in the contaminated material itself can be reduced, eliminating the risk of secondary contamination due to elution of heavy metals not only at the point of processing but also in the future. The effect that it becomes possible is acquired.

  In addition, according to the present invention, it is possible to reliably remove from the contaminated materials such as soil, sludge, sediment, waste, incinerated ash, etc., which are contaminated with heavy metals, to the insoluble fraction of heavy metals. It is possible to prevent the heavy metals contained in the contaminated material from being separated from the cathode surface and re-dissolved in the slurry after electrolytic deposition of the heavy metals on the cathode surface.

  In addition, according to the present invention, for example, soil, sludge, sediment, waste, incineration ash, industrial wastewater, surface water, groundwater, seawater, etc. The elution cathode is surely eluted from the sparingly soluble fraction of heavy metals contained in the solid or liquid contaminated material, and the heavy metals eluted in the aqueous solution are deposited on the deposition cathode. As a result, heavy metals can be removed more reliably than in the prior art. Even in a large apparatus required for actual environmental purification, the distance between the membrane and / or the distance between the electrode and the reaction liquid (or slurry) can be maintained by increasing the number of diaphragm-electrode units, so that the removal efficiency and reaction speed It is possible to perform processing without lowering.

  Furthermore, according to the present invention, by using a cathode electrode with high corrosion resistance, the electrode is not corroded even when repeated operation of potential application and current stop is performed, and stable treatment can be performed.

FIG. 1 is a schematic explanatory diagram showing a preferred embodiment of the present invention in which lead, cadmium, and the like are removed and recovered using an electrolytic deposition reaction. FIG. 2 is a schematic explanatory view showing another preferred embodiment of the present invention in which mercury or the like is removed and recovered using an electrode reaction. FIG. 3 is a schematic explanatory view showing a preferred embodiment of the present invention, and in particular, a cathode protection member is disposed in the vicinity of the cathode so that a shearing force due to a large particle size solid in the slurry does not act on the cathode surface. It is a schematic explanatory drawing which shows the comprised aspect. FIG. 4 is a schematic illustration showing another preferred embodiment of the present invention, in particular, using a slurry upflow to form a solid particle size distribution in the slurry and a large particle size in the slurry to the cathode surface. It is a schematic explanatory drawing which shows the aspect which suppresses the shear force by the solid of. FIG. 5 is a schematic explanatory view showing a contaminated object purifying apparatus according to a preferred embodiment of the present invention. FIG. 6 is a schematic explanatory view showing a contaminated object purifying apparatus according to a preferred embodiment of the present invention. FIG. 7 is a schematic explanatory view showing a preferred embodiment of the present invention in which lead, cadmium, and the like are eluted from a solid or liquid contaminated substance by electrolytic deposition using a cathode and recovered. FIG. 8 is a conceptual diagram showing a form of a diaphragm for separating an anode section and a cathode section used in the present invention. FIG. 9 is a diagram showing an example of reinforcement using a mold and a pipe for protecting the bottom and top of the diaphragm against deformation and wear of the diaphragm. FIG. 10 is a diagram showing an example of using as a diaphragm unit by fixing a flat plate made of porous ceramic or the like to a polyhedral mold. FIG. 11 is a diagram showing a preferred example of the arrangement of the cathode and the diaphragm-electrode unit that does not hinder the movement of hydrogen ions that permeate and diffuse through the diaphragm unit. FIG. 12 is a diagram showing another preferred example of the arrangement of the cathode and the diaphragm-electrode unit that does not hinder the movement of hydrogen ions that permeate and diffuse through the diaphragm unit. FIG. 12A shows a single row of cathodes arranged in a row. FIG. 12B shows a case where a plurality of cathodes are arranged. FIG. 13 is a diagram showing another preferred example of the arrangement of the cathode and the diaphragm-electrode unit that do not hinder the movement of hydrogen ions that permeate and diffuse through the diaphragm unit, and FIGS. 13A and 13B show the arrangement of the cathode. Examples are shown, and FIGS. 13C and 13D show examples of the shape of the cathode plate (viewed from above). FIG. 14 is a schematic diagram (side view) showing the 2000 L square reactor used in Examples 9-11. FIG. 15 is a schematic diagram (top view) showing the 2000 L square reactor used in Examples 9-11. FIG. 16 is a schematic view (side view) showing a 2000 L square reactor used as a control system in Examples 9 to 11. FIG. 17 is a schematic diagram (top view) showing a 2000 L square reactor used as a control system in Examples 9 to 11.

Explanation of symbols

1; 1A; 1B; 100: Purification device
2: Reaction tank (slurry formation tank)
2a: Slurry forming part
2b: Separation part
3; 120: Solid-liquid separator
5: Heavy metal trap (gas cleaning bottle)
A: Anode
A-1: First anode
A-2: Second anode
C: Cathode
C-1a, C-1b: Elution cathode
C-2: Cathode for deposition
M: Diaphragm
10: Anode area
20: Cathode area
22; 111: Contaminated material supply means
24; 112: Means for supplying acidic or alkaline substances
26; 115: Water supply means
27: Inert gas supply means (air diffuser)
28: pH meter electrode
34: Slurry pump
40: Liquid circulation line
50: Cathode protection member

Claims (9)

A contaminant supply means for supplying a contaminant including heavy metals, a corrosion-resistant cathode that provides a reducing atmosphere in which at least the liquid contact portion is composed of a lead-tin alloy or a nickel-copper alloy, and a diaphragm; And an anode,
The diaphragm forms an anode zone containing the anode and a cathode zone containing the corrosion-resistant cathode and the contaminant supply means, and the cathode zone is maintained in a reducing atmosphere and a strong acidic or strong alkaline atmosphere. A device for purifying contaminated substances containing heavy metals, comprising a reaction tank that performs elution of heavy metal ions from the contaminated substances and separation of the eluted heavy metal ions from the contaminated substances and pore water in parallel . Positioned the diaphragm so as to surround the anode, the anode zone formed on the inside of the membrane, including the heavy metals according to claim 1, characterized by forming the cathode zone outside the membrane Contaminant purification equipment. The anode is positioned inside a cylindrical, box-shaped, or bag-shaped diaphragm composed of a diaphragm alone or a combination of a diaphragm and another reinforcing material, and at least the liquid contact part outside the diaphragm is a lead-tin alloy or nickel- 3. The apparatus for purifying contaminated objects containing heavy metals according to claim 2 , further comprising an electrode-diaphragm unit having a corrosion-resistant cathode provided with a reducing atmosphere made of a copper alloy .
The said corrosion-resistant cathode is arrange | positioned at star shape, radial shape, or a partition plate shape so that the said diaphragm may be surrounded, Purification of the contaminated material containing the heavy metals of Claim 2 or Claim 3 characterized by the above-mentioned. apparatus. The contaminated material containing heavy metals according to any one of claims 1 to 4 , wherein the reducing atmosphere is provided by setting an electrode potential of a cathode to -0.16V or less with respect to a hydrogen standard electrode potential. Purification equipment.
Contaminated material supply means for supplying a contaminated material containing heavy metals, and a corrosion-resistant cathode that provides a reducing atmosphere in which at least the liquid contact portion is composed of a lead-tin alloy or a nickel-copper alloy. A deposition cathode, an elution cathode, a diaphragm, and an anode;
The diaphragm forms an anode area containing the anode and a cathode area containing the deposition cathode, the elution cathode and the contaminant supply means, wherein the cathode area is a reducing atmosphere and strongly acidic or strongly alkaline. Contamination containing heavy metals, including a reaction tank that is maintained in an atmosphere and includes a reaction vessel that performs elution of heavy metal ions from the contaminated material and separation of the eluted heavy metal ions from the contaminated material and pore water in parallel. Purification equipment. The apparatus for purifying contaminated substances including heavy metals according to claim 6 , wherein the reducing atmosphere is provided by setting the electrode potential of the deposition cathode to -0.16V or less with respect to the hydrogen standard electrode potential. The purification apparatus according to claim 1, wherein a base material of the corrosion-resistant cathode is copper. The purification device according to any one of claims 1 to 8, wherein a shape of the corrosion-resistant cathode is one of a net shape, an expanded metal shape, a punching metal shape, and a honeycomb shape.

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