JP2012219279A - Method and device for separating and recovering cadmium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for securely separating and recovering metallic cadmium from cadmium-containing waste.SOLUTION: The method for separating and recovering cadmium includes: a pretreatment step of subjecting cadmium-containing waste to prescribed pretreatment so as to form the waste into powdery shape; a mixing-stirring step of performing stirring-mixing while adding a starch suspension or nano-bubble water or after its addition to obtain kneaded matter in which fine bubbles are dispersed; a molding step of molding the kneaded matter to obtain a molded body having strength to a degree to hold its external shape; a vacuum heating step of heating the molded body in a vacuum atmosphere to volatilize a cadmium simple substance, and discharging the same; and a separating-recovering step of cooling the exhaust gas to precipitate metallic cadmium. The device is used for implementing the method.

Description

  The present invention relates to a technique for separating and recovering metal cadmium from waste containing heavy metal, particularly cadmium (hereinafter referred to as cadmium-containing waste).

  Heavy metals contained in solid waste and contaminated soil, especially cadmium, have become a social problem and need to be separated and removed. For example, processed residue of seafood such as scallops is usually stored in a processing facility, but it causes environmental problems such as the generation of malodors due to the generation of ammonia gas during storage and the withering phenomenon of surrounding plants. ing. In addition, such processing residues often contain cadmium, which gradually elutes, contaminates the soil around the storage facility, and may develop into groundwater veins and river water contamination. It is in place. Some other industrial wastes contain cadmium, and there is a situation in which cadmium flows out to the soil around treatment facilities and storage facilities. Also, cadmium contamination has occurred.

  Under these circumstances, various proposals have been made for the separation and removal of cadmium from cadmium-containing waste such as paddy fields and rivers, including industrial waste such as scallop and other seafood processing residues. (For example, refer to Patent Documents 1 and 2). In recent years, proposals for newly adsorbing and removing cadmium on other substances have been made and put into practical use. However, all of the techniques according to these proposals remove cadmium as a compound, and the present situation is that the substance adsorbed with cadmium is stored as it is.

JP 2001-137825 A JP-A-9-217131

  An object of this invention is to provide the method and apparatus which isolate | separate and collect | recover metal cadmium reliably from a cadmium containing waste material in view of the said situation.

  According to one aspect of the present invention, the object is to perform a predetermined pretreatment on the cadmium-containing waste to make the waste into a granular state, while adding a starch suspension or nanobubble water or Mixing and stirring step for obtaining a kneaded product having a structure in which fine bubbles are dispersed by stirring and mixing, and forming a kneaded product having a strength sufficient to maintain its outer shape Characterized in that it comprises a step, a vacuum heating step in which the molded article is heated in a vacuum atmosphere to volatilize cadmium alone, and this is exhausted; and a separation and recovery step in which the exhaust is cooled to deposit metal cadmium. This is achieved by a method for separating and recovering cadmium.

  In addition, according to another aspect of the present invention, the object is to add a pretreatment device for subjecting the cadmium-containing waste to a predetermined pretreatment so that the waste is granulated, and starch suspension or nanobubble water. A mixing and stirring device for obtaining a kneaded product having a structure in which fine bubbles are dispersed by stirring and mixing after or after the addition, and a molded body having a strength sufficient to form the kneaded product and maintain its outer shape A vacuum heating device for heating the molded product in a vacuum atmosphere to volatilize cadmium alone and exhausting it, and a cooling device for cooling the exhaust to deposit metal cadmium. This is achieved by the characteristic cadmium separation and recovery device.

  According to the present invention, a binder and water are added to a cadmium-containing waste powder that has been granulated by pretreatment to obtain a molded body having a predetermined porosity and a strength sufficient to maintain its outer shape, and this is vacuumed. Since the cadmium simple substance is volatilized by heating in the atmosphere, the metal cadmium can be more reliably separated and recovered by cooling the volatilized cadmium simple substance vapor. In addition, since heating is performed in a vacuum atmosphere, the heating temperature can be set relatively lower than in the case of heating under atmospheric pressure, which contributes to energy saving.

It is a flowchart which shows an example of the cadmium separation-and-recovery method of this invention. It is a figure which shows an example of the pre-processing apparatus in this invention. It is a figure which shows an example of the vacuum heating apparatus in this invention.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG. Examples of the cadmium-containing waste in the present invention include, for example, processing residues of seafood such as scallops and squid mainly containing cadmium, contaminated soil contaminated with heavy metals such as cadmium, metal waste containing cadmium, and cadmium compounds. Industrial waste such as collection materials such as filters attached. Hereinafter, the term “cadmium-containing waste” may be simply referred to as “waste”.

[Preprocessing]
In the present invention, first, cadmium-containing waste is pretreated (S01). For this pretreatment, the following method is adopted.
(1) Crushing and classification If there is a lump in the cadmium-containing waste, it is pulverized and pulverized, the particle size of the whole waste is reduced to increase its surface area, and classification further than the predetermined particle size. Extracts finely pulverized products. The pulverizer used for pulverization can be appropriately selected from conventionally known pulverizers in consideration of the appearance and properties of the cadmium-containing waste, the pulverization ability, the pulverization amount, and the like. In addition, for the classification, a conventionally known dry classifier or wet classifier can be used, but in the case of a small amount, a sieve can also be used. For example, in the case of a sieve, the predetermined particle size can be determined based on whether the mesh is under a 12 mesh sieve.

(2) Volume reduction by decomposition of organic matter When cadmium-containing waste is composed mainly of organic matter, it is decomposed in the presence of aerobic microorganisms and removed as carbon dioxide or water to obtain residue. Therefore, the volume is reduced. A known apparatus suitable for the decomposition of the organic substance can be used. As such an apparatus, for example, a garbage disposal apparatus described in Japanese Patent No. 35475731 can be suitably used. FIG. 2 shows the appearance and configuration of the garbage processing apparatus, where (a) is a side view and (b) is a front view. In this garbage disposal apparatus, two blenders 21 of a predetermined shape each having a stirring blade attached to a rotating rod are disposed in a treatment tank 11 (only one of which is shown, and the remaining one is omitted). It has a configuration in which it can rotate in the opposite direction. In addition, the treatment tank 11 is provided with an exhaust port 14 for supplying air through the air supply port 13 and exhausting the gas in the tank, and a rubber heater 17 capable of heating the contents in the tank is provided. Is provided.

  A predetermined amount of an aerobic microorganism-implanting auxiliary material and an aerobic microorganism-supporting body are introduced into the treatment tank 11 together with the cadmium-containing waste. Here, for example, a chip or the like can be used as the auxiliary material. Further, the input amounts of waste and auxiliary materials can be determined by the size of the processing tank 11, and the input ratio (weight basis) of both can be appropriately set within the range of the latter 1 to 5 with respect to the former 1. Moreover, the input amount of the aerobic microorganism carrier may be a small amount of about 100 to 300 g, for example.

In the pretreatment by this apparatus, the moisture content of the contents increases due to moisture generated by the decomposition reaction of the organic matter in the presence of aerobic microorganisms, and the generated carbon dioxide and nitrogen are discharged into the atmosphere through the exhaust port 14 to reduce the volume. Progresses. In particular, in the case of proteins among organic substances, amino groups are decomposed through the following microorganism decomposition process under the supply of air (oxygen), and the resulting water increases the moisture content of the contents, while nitrogen is exhausted. It will be discharged through the mouth 14.
(1) NH ₄ ⁺ + 3 / 2O ₂ → NO ₂ ⁻ + 2H ⁺ + H ₂ O (ammonia oxidizing bacteria)
(2) NO ₂ ⁻ + 1 / 2O ₂ → NO ₃ ⁻ (nitrite oxidizing bacteria)
(3) 2NO ₃ ⁻ + 10e ⁻ + 12H ⁺ → N ₂ ↑ + 6H ₂ O (denitrifying bacteria)
Depending on the type of cadmium-containing waste, volume reduction using this garbage processing device usually involves a powder with a water content of about 20%, which contains heavy metals such as cadmium, minerals and other trace substances. -Like residue is obtained. In this way, by using the garbage disposal device, the organic matter in the cadmium-containing waste is decomposed to reduce the volume, handling in the subsequent process is improved, and cadmium is separated and recovered efficiently and reliably. Is possible.

  In the two methods, as described above, it is possible to determine which one of these is adopted according to the magnitude of the organic matter content in the cadmium-containing waste. In some cases, both may be combined and the organic matter in the waste may be decomposed before further pulverization and classification.

  In the above pretreatment, the cadmium-containing waste may be washed with water in advance. In particular, when the cadmium-containing waste is mainly composed of processed seafood residues, it is preferable to wash off the surface dirt by washing with water and remove the salt from the seawater. Washing with water can be performed by a conventionally known method. In the present invention, there is no problem even if the water content in the waste is increased by this water washing.

[Mixing and stirring process]
While adding the starch suspension or nanobubble water to the waste or the mixture of the pre-treated waste and the residue, or the mixture of both in this way (in the case of adding in multiple times at a predetermined time interval) Or a mixture with stirring and mixing to obtain a kneaded product having a structure in which fine bubbles are dispersed (S02). The starch suspension used is prepared by dissolving or suspending starch in water so that the starch concentration is in the range of 1 to 30% by weight, preferably 2 to 25% by weight, more preferably 3 to 20% by weight. Is. When the concentration of the starch suspension exceeds the above range, the viscosity of the aqueous solution becomes too high, and uniform mixing with the cadmium-containing residue becomes difficult. Even if a stirrer is used, a kneaded product having a structure in which fine bubbles are uniformly distributed cannot be obtained. In addition, although starch can use a commercial item irrespective of the kind of plant used as a raw material, the low molecular weight raw material which functions as an organic binder by dissolving or suspending in water other than starch can also be used.

  Nanobubble water is water in which fine bubbles of nanometer order (200 nm or less) are stably dispersed. For example, water produced by patent inventions of Patent Nos. 4144669 and 4080440 is preferably used. it can. The amount of nanobubble water added can be set substantially the same as that of the starch suspension.

  The water content of the final kneaded product is in the range of about 20 to 60% by weight, preferably about 30 to 50% by weight, more preferably about 30 to 40% by weight, by adjusting the amount of starch suspension added. It is good to fit in. When this range is exceeded, it becomes difficult to mold the molded body due to excessive moisture, and when it is less than the above range, molding becomes difficult due to insufficient moisture.

  As the mixing stirrer used in the present invention, it is preferable to use an apparatus suitable for obtaining a kneaded material having a structure in which minute bubbles are uniformly dispersed by this kneading. Specific examples of such a mixing stirrer include a shear type stirrer (trade name: Cornell Despa) manufactured by Asada Iron Works, a planetary mixer (stir kneader, trade name: Planetary Despa), and the like. In this way, an aqueous starch solution is added to the cadmium-containing waste, and the waste is mixed and stirred using the predetermined stirrer described above to obtain a kneaded product having a structure in which fine bubbles are uniformly distributed. be able to.

[Molding process]
Subsequently, the obtained kneaded material is poured into a predetermined mold and pressure-molded (S03). At the time of molding, it is preferable to adjust the press pressure so that the molded body has a strength that can maintain its outer shape without damaging the fine bubbles inside the molded body as much as possible. The guideline for the press pressure is usually the route in which the cadmium vapor that volatilizes inside is diffused to the outside by shaping the granular material such as waste with the starch suspension loosely bound as a binder. There is an advantage that is easily formed.

  As a measure for determining the state of the structure inside the molded body, porosity can be used. In the present invention, the measured porosity is about 5 to 30%, preferably about 7 to 25. %, More preferably about 8-20%. When the porosity exceeds the above range, it becomes difficult to maintain the outer shape of the molded body, and when the porosity is less than the above range, the structure of the molded body becomes dense and it is difficult to form a diffusion route for the cadmium simple substance vapor. . Further, it is good to observe that a plurality of bubbles having a diameter of about 0.5 to 3 mm, preferably about 1 to 2 mm are dispersed on the surface of the molded body. It is preferable that an arbitrary cut surface is observed in the same manner. The plurality of bubbles are not required to be uniformly dispersed on the surface or cut surface of the molded body.

  Although there is no particular limitation on the outer shape of the molded body, the complexity of this shape increases the cost of mold production, and there is a high possibility that the molded body itself will be damaged during molding. It is preferable to use a disk shape or a square plate shape. Further, the size of the molded body can be appropriately set in consideration of the accommodation volume in the heating furnace in the heating step described later. Usually, the thickness is set in the range of about 30 to 200 mm, and the diameter or length of one side is set in the range of about 50 to 200 mm.

  In the present invention, the type and specifications of the molding machine used for pressure molding are not particularly limited, but a high press pressure is not required, so a known small press molding is considered in consideration of the size of the molded product to be obtained. A machine (for example, a small press machine equipped with an air cylinder) can be used.

  The molded body obtained in the molding process may be once dried at a temperature of about 120 ° C. to evaporate moisture in the molded body. Thus, by drying a molded object and reducing the moisture content, the strength of the molded object can be improved, so that there is an advantage that handling property is improved and workability is improved.

[Vacuum (reduced pressure) heating process]
First, the obtained plurality of molded bodies are accommodated in a vacuum chamber in a vacuum heating device (S04). The compact can be accommodated by an ordinary method according to the type of vacuum heating device or the equipment configuration. Next, the vacuum pump attached to the vacuum heating device is activated to depressurize the vacuum chamber, and the low vacuum to high vacuum category, preferably the medium vacuum to high vacuum category, defined in JIS Z8126. The degree of vacuum (the maximum value is on the order of about 10 ⁻² to 10 ⁻³ Pa). This degree of vacuum may be uniformly set to the degree of vacuum in the high vacuum or medium vacuum category, regardless of the porosity measured for the molded body accommodated in the retort, depending on the magnitude of this measurement result. The set value of the degree of vacuum may be changed. That is, in the latter case, when the measurement result of the porosity shows a large value close to the upper limit within the above range, the degree of vacuum in the low vacuum to medium vacuum category is set, and the low limit close to the lower limit within the above range. When the value is shown, the degree of vacuum in the medium vacuum or high vacuum category is set.

  Thereafter, heating of the compact in the vacuum chamber is started under this vacuum atmosphere (S04). Here, evaporation of moisture from the molded body, burning of starch (including evaporation of moisture remaining as hydroxyl groups) and volatilization of cadmium alone occur in different temperature ranges, so the heating temperature is set in three stages for each of these. It can be set and heated at different temperatures by gradually increasing the heating temperature of the compact. At this time, the heating temperature in each stage can generally be set lower according to the degree of vacuum of the atmosphere than that at atmospheric pressure. However, in the present invention, in consideration of the type, content, processing time, and the like of the evaporation (volatile) substance contained in the molded body, the set temperatures under atmospheric pressure for the three stages (see Table 1). And a set temperature (see Table 1) corresponding to the degree of vacuum in the atmosphere, it is preferable to be able to adjust appropriately.

  During heating at each stage, the degree of vacuum in the vacuum chamber changes slightly due to the generation of water vapor, etc., and this is monitored, and when it is stabilized, it is switched to the next set temperature. After reaching the third set temperature, the degree of vacuum slightly decreases with the volatilization of cadmium alone, and the degree of volatilization decreases, so the degree of vacuum is restored. Regardless of this, it is preferable to maintain the heating state at the set temperature for about 1 to 2 hours. Based on the passage of time, it is determined that the third stage of heating is completed. In addition, when the molded body is dried before being accommodated in the vacuum drying apparatus, the heating temperature setting for the evaporation of the water may be omitted, and the remaining two temperature settings may be performed.

  The vacuum heating apparatus in the present invention is not particularly limited with respect to the type and the equipment configuration as long as the above vacuum conditions are obtained and heating up to about 800 ° C. is possible. For example, the vacuum heating device may be of a type that includes a retort for accommodating a molded body, and heats the retort together after the inside is set to a predetermined vacuum condition. In the case of such an apparatus, the retort is required to withstand the vacuum conditions as described above, and the material thereof is preferably, for example, stainless steel or aluminum alloy.

  In the case of a vacuum heating apparatus of a type using a retort, a plurality of molded bodies may be directly accommodated therein, or may be temporarily placed on a tray and accommodated together with the tray. In any case, a plurality of molded bodies are arranged in the retort so that an appropriate interval is provided between two adjacent molded bodies so that each surface is exposed to a vacuum atmosphere as much as possible. It is preferable to do this. Moreover, also when using a tray, it is preferable that the said tray is formed with the metal net | network etc. for the same reason.

  The vacuum pump attached to the vacuum heating device is not particularly limited as long as it has the ability to achieve the above vacuum conditions. For example, a diaphragm vacuum pump, a dry pump, an oil rotary vacuum pump, an ejector pump, A conventionally well-known thing, such as a mechanical booster pump and an oil diffusion pump, can be used.

[Separation and recovery process]
During the third stage of heating, vapor of cadmium alone volatilized from the compact is exhausted out of the vacuum chamber by suction of a vacuum pump. By installing a cooling device in the middle of the exhaust path, the vapor of cadmium alone is deposited as metal cadmium on the wall surface of the exhaust path. The cooling device is not particularly limited with respect to the cooling method, and water cooling, air cooling and other known methods can be specified. After completion of the third stage of heating, the vacuum heating apparatus itself is cooled, and the metal cadmium deposited on the wall surface is taken out, whereby the cadmium simple substance can be separated and recovered (S05). The extracted metal cadmium can be cast by a known method.

  Next, the present invention will be described in more detail with reference to examples. In this embodiment, cadmium contained in a small amount in scallopuro is separated and recovered as metal cadmium.

The apparatus used in this example is as follows.
A. 2. Garbage Disposal Equipment As shown in FIG. 2, the used garbage disposal apparatus has two blenders 21 having a predetermined shape in which a stirring blade is attached to a rotating rod (only one of which is shown, and the rest). (The illustration of one of these is omitted.) A basic configuration is provided in parallel so as to be rotatable in opposite directions. Further, in the processing tank 11, air can be supplied through the air supply port 13, and an exhaust port 14 for exhausting the processing tank 11 is provided. Further, a rubber heater 17 capable of heating the contents is provided in the processing tank 11.
B. Vacuum heating apparatus The vacuum heating apparatus used in the present embodiment is, as shown in FIG. 3, a stainless steel retort 30 having a flange 31 at one end and closed at the other end, and a position covering the entire surface except for the flange 31. And a position remote from the retort 30, and comprises an electric furnace 34 having a built-in heater 36 for electric heating, a decompression hose 44, and a vacuum pump 45 for evacuating the retort 30. Has been. A water cooling type cooling cylinder 37 used for separating and recovering cadmium alone is connected to the flange 31 of the retort 30 via a flange 38, and a vacuum is connected to the other end of the cooling cylinder 37 via the pressure reducing hose 44. A pump 45 is connected. The cooling cylinder 37 is provided with a double structure in which an inlet 40 and an outlet 41 are provided outside a pipe substantially equivalent to the retort 30 and a jacket 39 through which cooling water can flow is provided.

  About 250 kg of scallopuro to be disposed of was prepared, and the entire amount was washed with water to remove surface dirt, and at the same time, the salt content of seawater was washed away, and then divided into five portions of about 50 kg each. Next, about 50 kg of them, approximately the same amount of supplement (chip), and 100 g of BN bacteria (manufactured by Meiji Seika) as aerobic microorganisms are put into the garbage processing apparatus shown in FIG. Stirring mixing was started. On the 4th day from the next day, about 50 kg of the remaining scallops were put into the apparatus every day, and the stirring and mixing of the apparatus was stopped on the 5th day. In these 5 days, scallops are decomposed (the temperature inside the scallops during decomposition was 38 ± 2 ° C), and the generated carbon dioxide and nitrogen are scattered to the outside, and part of the generated water is evaporated and remains. However, the water content of the kneaded product was increased. The residue taken out from the garbage processing apparatus on the fifth day was in the form of a brown powder having a water content of about 20% by weight, and the weight thereof was substantially equal to the weight of the mixed auxiliary material (about 50 kg). From this, it was found that almost the entire amount of scallop charged in the garbage processing apparatus was decomposed.

  While adding a starch suspension prepared by mixing 5 kg of powdered starch / 10 L of water to about 50 kg of the residue, the residue was kneaded until a homogeneous mud-like kneaded product was obtained. This kneaded product was sampled several times and the surface thereof was visually observed. As a result, it was confirmed that bubbles having a diameter of about 1 to 2 mm were dispersed.

Next, this kneaded product is poured into a mold having a cylindrical space inside, and is subjected to pressure molding while adjusting the press pressure by an air cylinder type small press molding machine, and a plurality of molded bodies 5, 5, 5, I got ... The pressing pressure at this time was adjusted in the range of 0.5 to ² kg / cm ² so that the obtained molded body could be molded to such an extent that the outer shape could be maintained. The size and shape of each molded body 5, 5, 5,... Is a disk shape having a diameter of about 20 mm and a thickness of about 50 mm.

  A plurality of molded bodies 25, 25, 25,... Thus obtained are adjacent to each other on a boat-shaped tray 27 having a semicircular cross section formed of a stainless steel net, as shown in FIG. The two molded bodies 25 were arranged with a space between them. By providing an interval between the adjacent molded bodies 25, a volatile scattering route of cadmium alone from the entire surface of each molded body 25 is ensured in a vacuum heating step described later, and volatilization of the cadmium alone can be promoted.

  Then, this boat-shaped tray 27 was accommodated in the internal space 32 of the retort 30. The flange 38 was fixed to the flange 31 of the retort 30 with bolts and nuts (not shown), and the cooling cylinder 37 was attached and connected to the retort 30. Further, the other end of the cooling cylinder 37 and the vacuum pump 45 were connected in a sealed state by a decompression hose 44. Note that a vacuum gauge (not shown) is attached to the retort 30 so that the internal degree of vacuum can be measured at an appropriate position.

After these series of operations were completed, the vacuum pump 45 was started and the suction of air in the retort 30 was started. The target value of the degree of vacuum was set to 10 ⁻² Pa by the measurement result of the vacuum gauge.

  When the predetermined degree of vacuum was reached, the electric furnace 34 was moved to the retort 30 side and set to a position where almost the entire surface excluding the flange 31 of the retort 30 was hidden in the heating chamber 35. The electric furnace 34 can be moved by a known method such as running on a rail.

  After setting the electric furnace 34, the switch was turned on to energize this to start heating. The heating temperature was set so as to be switched stepwise, and first, water was completely evaporated and removed at about 120 ° C. (first step). Whether or not moisture removal was complete was judged by whether or not the instruction of the vacuum gauge was stable. Next, the set temperature was raised to about 220 to 240 ° C., and water remaining as starch and hydroxyl groups was completely burned away and removed (second stage). Whether starch or the like was completely removed was also judged by whether or not the indication of the vacuum gauge was stable.

Thereafter, when the reading of the vacuum gauge was stabilized at 10 ⁻² Pa, the temperature setting was switched so as to be in the range of 380 ± 10 ° C. so that the cadmium alone was volatilized (third stage). It was confirmed that when cadmium volatilization and scattering were started at this temperature setting, the degree of vacuum slightly decreased, and when cadmium was completely volatilized, it returned to the original value. Further, after maintaining this state for about 1 to 2 hours, it was determined that the heating was completed, the heating switch was turned off, the electric furnace 34 was moved away from the retort 30, and the retort 30 was allowed to cool naturally.

  On the other hand, during the third stage of heating, the cadmium simple substance volatilized from the compact and exhausted from the retort 30 was cooled by the cooling cylinder 37 and deposited on the pipe wall surface. The deposited metal cadmium was taken out and cast.

  Casting was performed by heating at a temperature of 330 to 350 ° C. on a sand bath in a reducing atmosphere. The molten metal cadmium was poured into a predetermined mold and cooled to obtain a metal cadmium ingot. On the other hand, when the molded body 25 in the retort 30 was taken out and the cadmium content was measured, a result that it was not detectable was obtained. Therefore, it was confirmed that cadmium was reliably separated and recovered from the scallops.

11 treatment tank (garbage disposal equipment)
13 Air supply port 14 Exhaust port 21 Blender 25 Molded body 27 Boat type tray 30 Retort 31 Flange 34 Electric furnace 35 Heating chamber 36 Heating heater 37 Cooling cylinder 39 Jacket 40 Cooling water inlet 41 Cooling water outlet 44 Decompression hose 45 Vacuum pump

Claims (10)

  Pre-treatment process for cadmium-containing wastes and pre-treatment to make the wastes fine, and fine bubbles are dispersed by stirring and mixing with or after adding starch suspension or nanobubble water A mixing and stirring step for obtaining a kneaded product having a texture to form, a molding step for forming the kneaded product and obtaining a molded body having a strength capable of maintaining the outer shape, and heating the molded product in a vacuum atmosphere. A method of separating and recovering cadmium, comprising: a vacuum heating step for volatilizing and exhausting cadmium alone; and a separation and recovery step for cooling the exhaust and precipitating metal cadmium.   In the pretreatment step, the cadmium-containing waste is pulverized, a pulverized product finer than a predetermined particle size is extracted by classification, and / or organic matter in the cadmium-containing material waste is removed in the presence of aerobic microorganisms. The method for separating and recovering cadmium according to claim 1, wherein the method is to decompose and reduce the volume.   The method for separating and recovering cadmium according to claim 1 or 2, wherein the concentration of the aqueous starch solution is 1 to 30% by weight.   The method for separating and recovering cadmium according to any one of claims 1 to 3, wherein the molded body has a porosity of about 5 to 30%.   5. The cadmium according to any one of claims 1 to 4, wherein the vacuum heating step is configured to switch a set value step by step to different heating temperature ranges that respectively cause at least the burning of starch and the volatilization of cadmium alone. Separation and recovery method.   Pretreatment equipment that cadmium-containing waste is pre-treated to make the waste into powder, and fine bubbles are dispersed by mixing with or after adding starch suspension or nanobubble water. A mixing and agitating device for obtaining a kneaded product having a texture to form, a molding device for forming the kneaded product and obtaining a molded body having a strength capable of maintaining the outer shape, and heating the molded product in a vacuum atmosphere. A cadmium separation and recovery device, comprising: a vacuum heating device that volatilizes and discharges cadmium alone; and a cooling device that cools the exhaust and deposits metal cadmium.   The pretreatment device pulverizes the cadmium-containing waste, and pulverizes and classifies the pulverized product finer than a predetermined particle size by classification, or the organic matter in the cadmium-containing material waste in the presence of aerobic microorganisms. The method for separating and recovering cadmium according to claim 1, wherein decomposition or volume reduction is performed by decomposing and volume reduction, or both of them are performed.   The cadmium separation and recovery device according to claim 1 or 2, wherein the concentration of the aqueous starch solution is 1 to 30% by weight.   The cadmium separation and recovery apparatus according to any one of claims 6 to 8, wherein the molded body has a porosity of about 5 to 30%.   The cadmium according to any one of claims 6 to 9, wherein the vacuum heating device is configured to switch a set value stepwise to different heating temperature ranges in which at least starch burns and cadmium vaporization occurs. Separation and recovery equipment.

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