JP2013011562A - Processing method of waste liquid containing metal atom, and adsorbent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a processing method in which metal atoms can be efficiently removed from waste liquid by using an adsorbent having high adsorption capacity for the metal atoms, especially radioactive metal atoms and a coagulant capable of settling the adsorbent at high yield.SOLUTION: A processing method for removing and recovering metal atoms from waste liquid includes the steps of: adding and mixing diamond fine particles or carbon nano-tubes to the waste liquid; and adding a coagulant to the waste liquid obtained by adding and mixing the diamond fine particles or the carbon nano-tubes.

Description

  The present invention relates to a method for treating a waste liquid by adsorbing and removing the metal atoms from a waste liquid containing a radioactive element such as a metal atom, particularly cesium, strontium, plutonium, and the adsorbent used in the treatment method. The present invention also relates to a waste liquid treatment method comprising an adsorption step of the metal atoms by diamond fine particles and / or carbon nanotubes, and an aggregation step by an aggregating agent, and an adsorbent comprising the diamond fine particles and / or carbon nanotubes.

  In nuclear facilities such as nuclear power plants and spent nuclear fuel reprocessing plants, waste liquids containing various radioactive substances are generated. The radioactive liquid waste is separated into radioactive material and water by operations such as evaporation, ion exchange, and coagulation sedimentation. Water from which the radioactive material has been sufficiently removed is released, and the concentrated radioactive material is subjected to vitrification, asphalt solidification, etc. Fixed and stored by method.

  Among these methods, the evaporative concentration method is very efficient in separating water and radioactive materials, that is, decontamination efficiency, but the construction cost and operation cost of the evaporation equipment are high, and the material of the evaporator is corroded. There are disadvantages such as easy. On the other hand, the ion exchange resin method and the coagulation sedimentation method have the disadvantage that the decontamination efficiency is low, although the construction cost and operation cost of the equipment are small.

  The radioactive waste liquid usually contains sodium salt used to clean the nuclear fuel material extractant, so the evaporation concentration method has a problem that sodium salt such as sodium nitrate precipitates in the residue of the kettle and the concentration rate does not increase. In the ion exchange resin method, there is a problem that the adsorption amount of monovalent cations such as cesium decreases due to the high concentration of sodium nitrate and the decontamination efficiency decreases. There exists a problem that a decontamination coefficient falls by existence.

  Radioactive substances in the waste liquid include various elements such as ruthenium and zirconium, which have low solubility as hydroxides, alkali metals such as cesium and strontium, which have high solubility as hydroxides, and alkaline earth metals. ing. Of these, heavy metals such as ruthenium and zirconium are effective by the coagulation precipitation method, in which the liquidity is made alkaline and precipitated by coprecipitation with iron hydroxide and the like. In addition, it is very difficult to remove alkaline earth metals.

  As a method for removing alkali metals, alkaline earth metals and the like, an ion exchanger method has been widely studied. As an adsorbent for alkaline earth metals such as strontium and uranium, titanic acid is known. For example, the surface area of titanic acid as shown in JP-A-57-140644 (Patent Document 1) is extremely high. A composite adsorbent molded product of titanic acid and an acrylonitrile-based polymer, which improves the adsorbing capacity by improving the handleability and at the same time, is effective.

  Also, zeolites and ferrocyanide metal salts are known for adsorbing and removing alkali metals such as cesium. In particular, ferrocyanide metal salts have a higher adsorption capacity than zeolite, and have selectivity for cesium. The adsorbent is excellent in terms of high points. However, since the metal ferrocyanide salt becomes a colloid or a slime (mud) or very fine particles, it is very difficult to settle and has poor filterability. For this reason, after adsorbing cesium, it is difficult to separate the adsorbate, resulting in a decrease in removal efficiency.

In order to solve these problems, Japanese Patent Laid-Open No. 63-130137 (Patent Document 2) discloses a ferrocyanide metal salt / titanate composite adsorbent obtained by supporting a ferrocyanide metal salt on titanic acid. Japanese Patent Laid-Open No. 1-15134 (Patent Document 3) discloses an acrylic fiber having the general formula K ₂ M (II) [Fe (CN) ₆ ] [where M (II) represents a divalent metal. And a heavy metal trapping material such as a radionuclide comprising a combination of an adsorbent carrying a ferrocyanate compound and a granular or fibrous chelate resin, and further disclosed in Japanese Patent Application Laid-Open No. 2-207839 ( Patent Document 4) discloses a combustible cesium adsorbent in which a metal ferrocyanide compound hardly soluble in water is deposited in the pores of activated carbon.

  However, the composite adsorbents described in Patent Documents 2 to 4 have a problem that the supported amount of the metal ferrocyanide is not sufficient and the ability to remove cesium is low. For example, in order to increase the supported amount, As the amount of the adsorbent increases, the sedimentation property of the composite adsorbent after adsorption of metal atoms deteriorates, and improvement is particularly desired as an adsorbent used for the treatment of radioactive substances.

JP-A-57-140644 Japanese Unexamined Patent Publication No. 63-130137 Japanese Patent Laid-Open No. 1-15134 Japanese Patent Laid-Open No. 2-207839

  Therefore, an object of the present invention is to use an adsorbent having a high adsorption capacity for metal atoms, particularly radioactive metal atoms, and an aggregating agent capable of precipitating the adsorbent in a high yield, so that the metal atoms are removed from a waste liquid. It is an object of the present invention to provide a processing method that can efficiently remove the water.

  As a result of intensive studies in view of the above object, the present inventors have found that diamond fine particles and / or carbon nanotubes are excellent in adsorption ability for metal atoms, particularly cesium, strontium, etc., inorganic flocculants and / or organic high The present inventors have found that a molecular flocculant significantly accelerates the precipitation of the diamond fine particles and / or carbon nanotubes, and arrived at the present invention.

  That is, the waste liquid treatment method of the present invention is a method for removing and recovering metal atoms from the waste liquid, the step of adding diamond fine particles and / or carbon nanotubes to the waste liquid, and the diamond fine particles and / or carbon. It has the process of adding a flocculant to the waste liquid which added and mixed the nanotube, It is characterized by the above-mentioned.

  The flocculant is preferably an inorganic flocculant and / or an organic polymer flocculant.

  The inorganic flocculant is preferably at least one selected from the group consisting of aluminum sulfate, aluminum chloride, polyaluminum chloride, ferric chloride, and polyferric sulfate.

  The organic polymer flocculant is at least one selected from the group consisting of cationic organic polymer flocculants, anionic organic polymer flocculants, nonionic organic polymer flocculants, and amphoteric organic polymer flocculants. Preferably there is.

  The step of adding the flocculant preferably comprises a step of adding and mixing the polymer flocculant after adding and mixing the inorganic flocculant and / or the polymer flocculant.

  The diamond fine particles are preferably obtained by an explosion method.

  The diamond fine particles are preferably those obtained by hydrophilizing the surface by oxidation treatment.

The diamond fine particles preferably have a specific gravity of 2.55 to 3.48 g / cm ³ .

  The carbon nanotube is preferably a cup stack type.

  The adsorbent of the present invention comprises diamond fine particles and / or carbon nanotubes.

  The waste liquid treatment method of the present invention can selectively remove metal atoms, particularly alkali metals such as cesium and strontium and alkaline earth metals in the waste liquid, so that radioactive cesium, strontium, etc. from the waste liquid containing radioactive substances It is suitable for removing.

  Since the adsorbent composed of diamond fine particles and / or carbon nanotubes has a large surface area and has many functional groups, metal atoms in the waste liquid can be efficiently removed and recovered.

It is a schematic diagram which shows an example of the container of the ice used when synthesize | combining a diamond microparticle by an explosion method.

[1] Waste liquid treatment method The waste liquid treatment method of the present invention removes and recovers metal atoms in the waste liquid, and adsorbs metal atoms in the waste liquid using diamond fine particles and / or carbon nanotubes as an adsorbent. After that, by adding a flocculant to the waste liquid, the diamond fine particles and / or carbon nanotubes adsorbed with the metal atoms are settled, and the sediment is recovered.

  Since the diamond fine particles and / or carbon nanotubes can selectively adsorb metal atoms, particularly alkali metals such as cesium and strontium and alkaline earth metals, the waste liquid treatment method of the present invention contains, for example, a radioactive substance. It is effective for removing and recovering radioactive cesium and radioactive strontium from waste liquids.

  The amount of diamond fine particles and / or carbon nanotubes added to the waste liquid containing metal atoms depends on the amount of metal atoms such as cesium and strontium contained in the waste liquid, but is preferably 0.01 g or more per liter of the waste liquid. More preferably, it is 0.1 g or more, and most preferably 1 g or more. The upper limit is not particularly required, but practically it is about 50 g per liter of waste liquid. After the addition of the diamond fine particles and / or carbon nanotubes, it is preferably sufficiently stirred and allowed to stand for 1 hour or longer, more preferably 5 hours or longer, and most preferably 24 hours or longer.

  The diamond fine particles and / or carbon nanotubes adsorbed with the metal atoms can be removed from the waste liquid by a method such as filtration or decantation, but can be rapidly aggregated and solidified by adding a flocculant. .

  The amount of the flocculant added is not particularly limited as long as the metal atom in the waste liquid can be sufficiently aggregated and precipitated. In addition, sufficient aggregation precipitation means that 99% or more of the added diamond fine particles and / or carbon nanotubes are precipitated. Therefore, in practice, the amount of flocculant added may be adjusted as appropriate to achieve such removal efficiency. For example, when an anionic flocculant is used, the amount of diamond fine particles and / or carbon nanotubes added to the waste liquid is reduced. On the other hand, if about 0.1 to 10% of a flocculant is added, sufficient aggregation and precipitation can be achieved.

  As a method for efficiently separating the aggregate from the waste liquid to which the flocculant has been added, there are filtration, decantation, centrifugation, a method of adsorbing to a non-woven fabric, etc., but filtration or decantation is easy for handling. preferable. By allowing the flocculant to stand for a certain period of time after adding the flocculant, the flocculent precipitates on the bottom of the treatment tank, so the supernatant is filtered or removed by decantation. For decantation, methods such as extraction from a drain valve, suction or suction by a pump, use of a siphon, etc., or tilting the treatment tank itself and discharging from the upper end of the wall surface are used. Furthermore, natural filtration using a nonwoven fabric as a filter is more preferable because it is excellent in handling after filtration. The nonwoven fabric is preferably made of rayon, polyester, polypropylene or the like, but is not limited thereto.

  As a method for using the flocculant, a method in which an inorganic flocculant and an organic polymer flocculant are used in combination is preferable. Only with the inorganic flocculant, the mechanical strength of the colloidal particles generated by the aggregation is not so large, and there is a limit to the size and settling speed of the particles. By using the organic polymer flocculant in combination, coarse particles (floc) having a large particle size and a high sedimentation speed can be obtained.

  Examples of inorganic flocculants include sodium chloride, potassium chloride, sodium bromide, calcium chloride, sodium sulfate, aluminum sulfate (sulfate band), aluminum chloride, polyaluminum chloride, ferric chloride, ferrous sulfate, and polysulfate Iron and other polyvalent metal salts used in general water treatment can be used, and among them, aluminum sulfate, aluminum chloride, polyaluminum chloride, ferric chloride and polyferric sulfate are preferable. These inorganic flocculants are used alone or in combination.

  The organic polymer flocculant is preferably selected from cationic organic polymer flocculants, anionic organic polymer flocculants, nonionic organic polymer flocculants, and amphoteric organic polymer flocculants. In particular, a combination of a cationic organic polymer flocculant and an anionic organic polymer flocculant, or an amphoteric organic polymer flocculant is preferred.

  Examples of cationic organic polymer flocculants include polyethyleneimine, halogenated polydiallylammonium, water-soluble aniline resin, polythiourea, polyacrylamide cation-modified products modified with formalin and amines, and cationic vinyl lactams. Acrylamide copolymer, cyclized polymer of diallylammonium halide, copolymer obtained by reacting diamine with copolymer of isobutylene and maleic anhydride, vinyl imidazoline polymer, polymer of dialkylaminoethyl acrylate, alkylene dichloride Condensation product of olefin and alkylenepolyamine, polycondensation product of dicyandiamide and formalin, polycondensation product of aniline and formalin, copolymer of amines and epichlorohydrin, copolymer of ammonia and epichlorohydrin Copolymers of amines with aspartic acid, acrylic polymers, and the like having a quaternary ammonium salt in the side chain.

  Examples of the amines include methylamine, ethylamine, n-propylamine, isopropylamine, methoxypropylamine, butylamine, amylamine, allylamine, hexylamine, caprylamine, laurylamine, stearylamine, oleylamine, monomethylaminopropylamine, and benzylamine. Alkylamines and cyclic amines such as piperidine and pyrrolidine, polyethylenepolyamines, aminopropylethanolamine, methyliminobispropylamine, monomethylaminopropylamine, dialkylaminopropylamine, hydroxyethylaminopropylamine, diethylaminoethylamine, tetramethylenediamine, Examples include hexamethylene diamine.

  Examples of the anionic organic polymer flocculant include sodium polyacrylate, maleic acid copolymer, partially hydrolyzed polyacrylamide, polyacrylamide-acrylic acid copolymer, and partially sulfomethylated polyacrylamide.

  Nonionic organic polymer flocculants include polyacrylamide, polyethylene oxide, urea-formalin resin, polyaminoalkyl methacrylate, chitosan, and the like.

  The amphoteric organic polymer flocculant is a polymer flocculant having a cationic group and an anionic group in one molecule. Examples of cationic groups include tertiary amines, neutralized salts thereof, and quaternary salts. Examples of anionic groups include carboxyl groups, sulfone groups, and salts thereof. In particular, amphoteric polymer flocculants having a carboxyl group are preferred. In addition to these ionic components, a nonionic component may be contained. More specifically, examples of the anionic monomer unit include acrylic acid, methacrylic acid, and alkali metal salts thereof. Cationic monomer units include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide, diethylaminopropyl (meth) acrylamide, allyl dimethylamine or neutralized salts thereof, quaternary Examples include salts. Nonionic monomer units include (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide and the like.

  Zwitterionic organic polymer flocculants include dimethylaminoethyl acrylate / acrylic acid / acrylamide copolymer, dimethylaminoethyl methacrylate / acrylic acid / acrylamide copolymer, dimethylaminopropylacrylamide hydrochloride / acrylic acid / acrylamide copolymer Preferred are a polymer, a Mannich modified product of dimethylaminoethyl acrylate / acrylic acid copolymer, sodium acrylate / acrylamide copolymer, and the like.

  The order of addition and the addition method of the flocculant are not particularly limited, but in order to strengthen the bond between diamond fine particles and / or carbon nanotubes and coarsen the floc, (a) an inorganic flocculant and a cationic organic polymer flocculant And then stirring and mixing, then adding an anionic organic polymer flocculant and stirring and mixing, (b) adding inorganic flocculant, cationic organic polymer flocculant and anionic organic polymer flocculant and stirring and mixing After that, a method of further adding an anionic organic polymer flocculant and stirring and mixing, (c) adding an inorganic flocculant and stirring and mixing, then adding a cationic organic polymer flocculant and an anionic organic polymer flocculant and stirring Method of mixing, (d) After adding inorganic flocculant and stirring and mixing, adding amphoteric organic polymer flocculant and stirring and mixing, (e) Adding inorganic flocculant and amphoteric organic polymer flocculant Stirring and mixing After the method and the like are preferably used for further mixing and stirring were added both ionic organic polymer flocculant. The method for adding the flocculant is not limited to the above-described method, and various combinations are conceivable, and it is preferable to select the method appropriately depending on the type of waste liquid.

  When using a cationic organic polymer flocculant or an anionic polymer flocculant, in order to make the polymer flocculant work effectively, the waste liquid is added to the pH according to each polymer flocculant before adding them. It is preferable to adjust. When a cationic organic polymer flocculant is used, it is weakly acidic. When an anionic polymer flocculant is used, it is weakly alkaline. The amount can also be reduced. Moreover, when using together a cationic organic polymer flocculant and an anionic polymer flocculant, when using an amphoteric organic polymer flocculant, it is preferable to adjust to pH near neutrality. In particular, after adding the inorganic flocculant, the pH is large and may be on the acidic side or the alkaline side. Therefore, it is preferable to adjust the pH in order to increase the aggregation efficiency of the organic polymer flocculant.

  When an inorganic flocculant and an organic polymer flocculant are used in combination, the amount of flocculant added is 10 to 1000 mg / L, preferably 20 to 500 mg, of inorganic flocculant (anhydrous basis) based on the amount of waste liquid. / L, cationic organic polymer flocculant 5-100 mg / L, preferably 10-50 mg / L, anionic organic polymer flocculant 2-50 mg / L, preferably 5-30 mg / L, both The ionic organic polymer flocculant is added in an amount of 5 to 100 mg / L, preferably 10 to 50 mg / L.

  Diamond fine particles and / or carbon nanotubes are excellent in the removal ability of radioactive cesium, radioactive strontium, etc., so when removing radioactive substances from waste liquid using this, they are treated with existing adsorbents such as zeolite in advance. After removing the substance to some extent, the radioactive substance remaining in a trace amount is preferably removed with diamond fine particles and / or carbon nanotubes. By treating the waste liquid in two stages in this way, radioactive substances can be removed more efficiently.

[2] Diamond fine particles and / or carbon nanotubes In the method of the present invention, diamond fine particles and / or carbon nanotubes are used as an adsorbent for metal atoms. Diamond fine particles and / or carbon nanotubes have a high specific surface area and a functional group such as a carboxyl group, a sulfonic acid group, and a hydroxyl group on the surface thereof, and thus have an excellent ability to adsorb metal elements. Thus, for example, radioactive cesium from the waste water (radioactive waste) containing the radioactive material ⁽¹³⁴ Cs, ¹³⁷ Cs, etc.), can be more efficiently adsorbing and removing radioactive strontium.

(1) Diamond fine particles and carbon nanotubes Since metal elements are adsorbed to functional groups such as carboxyl groups, sulfonic acid groups, and hydroxyl groups on the surfaces of diamond fine particles and carbon nanotubes, more metal elements are adsorbed on the surfaces of diamond fine particles and carbon nanotubes. In order to adsorb, it is preferable to use diamond fine particles and carbon nanotubes whose surfaces are modified (hydrophilized) with more functional groups such as carboxyl groups, sulfonic acid groups, and hydroxyl groups by a method such as oxidation treatment.

  Diamond fine particles and carbon nanotubes may be used alone or in combination. Moreover, you may mix and use with another adsorbent. Any other adsorbent used by mixing diamond fine particles and carbon nanotubes may be used as long as it does not impair the adsorption and removal performance of diamond fine particles and / or carbon nanotubes. When diamond fine particles and carbon nanotubes are used in combination, their mixing ratio may be any value, but it is preferable to make diamond fine particles excessive.

(a) Diamond fine particles The diamond fine particles have a large surface area, a relatively large number of functional groups such as carboxyl groups, sulfonic acid groups, and hydroxyl groups are present on the particle surface, and are easy to perform the chemical modification. It is preferable to use the nanodiamond obtained in (1). The unpurified nanodiamond obtained by the blasting method has a core / shell structure in which the surface of nanosized diamond fine particles is covered with graphite-based carbon, and it can be used as it is. It is preferable to remove a portion of the graphite on the particle surface by applying and to modify the surface with a functional group such as a carboxyl group, a sulfonic acid group, or a hydroxyl group.

Unpurified nanodiamond has a specific gravity of about 2.55 g / cm ³ and a median diameter (dynamic light scattering method) of about 200 to 250 nm. By oxidizing this unpurified nanodiamond, the graphite-based carbon on the particle surface is removed, and diamond fine particles having a high diamond content can be obtained. The fine diamond particles purified by the oxidation treatment are secondary particles having a median diameter of about 150 to 250 nm made of primary particles of diamond of about 2 to 10 nm. In order to increase the surface area of the diamond fine particles used in the present invention, it is preferable that the diamond fine particles are further used by deaggregating as much as possible by a method such as media dispersion, and the median diameter is preferably 10 to 200 nm, preferably 20 to More preferably, it is 150 nm.

The diamond fine particles preferably have a specific gravity of 2.55 to 3.48 g / cm ³ . Since the specific gravity of diamond fine particles increases with the degree of purification of nanodiamond (removal rate of graphite-based carbon), the diamond content (the amount of graphite-based carbon present on the particle surface) in the particle can be obtained from the specific gravity. it can. That is, when the specific gravity is 2.55 g / cm ³ , the diamond content is 24% by volume, and when the specific gravity is 3.48 g / cm ³ , the diamond content is 98% by volume.

Even if the specific gravity of diamond fine particles is less than 2.55 g / cm ³ , that is, when oxidation treatment is not performed, the surface has functional groups such as carboxyl groups, sulfonic acid groups, hydroxyl groups, etc. By applying, the number of them can be increased. In addition, when excessive oxidation treatment is performed, graphite-based carbon in the shell portion of the nanodiamond is almost removed, and on the contrary, functional groups such as a carboxyl group, a sulfonic acid group, and a hydroxyl group are reduced. As a result, the ability to adsorb metal atoms such as cesium becomes insufficient. Therefore, the specific gravity is preferably not more than 3.48 g / cm ³ . The specific gravity is more preferably 3.0 g / cm ³ (diamond 84 vol%) or more and 3.46 g / cm ³ (diamond 97 vol%) or less, 3.38 g / cm ³ (diamond 90 vol%) or more and 3.45 g / Most preferably, it is not more than cm ³ (96% by volume of diamond). The volume percentage of diamond in the nanodiamond is a value calculated from the specific gravity of the nanodiamond using the specific gravity of diamond of 3.50 g / cm ³ and the specific gravity of graphite of 2.25 g / cm ³ .

(b) Carbon nanotube The carbon nanotube is a carbon material having a diameter of 1 to 1500 nm and a length of several nm to 1 mm in a shape in which graphite is wound in a cylindrical shape. The shape of the carbon nanotube used in the present invention is not particularly limited, but the diameter is preferably 1 to 1000 nm, more preferably 5 to 500 nm, most preferably 10 to 300 nm, and the length is preferably 10 nm to 5 μm, 20 nm to 1 μm is more preferable. Carbon nanotubes include single-walled ones, multi-layered ones, cup-stacked ones, etc., but the carbon nanotubes used in the present invention have a large surface area, such as carboxyl groups, sulfonic acid groups, hydroxyl groups, etc. It is preferable to use a cup stack type because of the relatively large number of functional groups present on the particle surface and the ease of the chemical modification.

  The cup-stacked carbon nanotube is a carbon fiber in which several to several hundred carbon network layers having a cup shape with no bottom are stacked, and has a structure in which the end face of the carbon network layer is exposed on the inner and outer walls of the fiber. . Since the end face of the carbon network layer has many functional groups such as a carboxyl group, a sulfonic acid group, and a hydroxyl group and is considered to have high activity, the cup-stacked carbon nanotube can adsorb many metal atoms.

(2) Diamond fine particle manufacturing method
(a) Explosive method Diamond fine particles can be produced by a known method. In particular, diamond fine particles obtained by an explosion method are preferred for the purposes of the present invention. Synthesis of diamond fine particles by the explosion method includes a wet method in which an explosive is exploded in the presence of water and / or ice, and a dry method in which air is cooled without using water and / or ice. A method may be adopted.

  As the wet method, for example, an explosive filled in a container made of ice [for example, TNT (trinitrotoluene) / HMX (cyclotetramethylenetetranitramine) = 50/50] is arranged in the almost central part of the pressure vessel. In addition, there may be mentioned a method of causing explosion while flowing water on the wall surface of the pressure vessel. In this method, unpurified diamond as a reaction product is recovered from water in a container. In the wet method, it is preferable to perform explosion by adding a water-soluble reducing agent (antioxidant) in advance in water and / or ice. Examples of the water-soluble reducing agent include hydrazines, hexamethylenetetraamine, urea, ammonia, acetonitrile, ascorbic acid, sodium sulfite, hydroquinone, sodium erythorbate, catechin, hydrazine, oxalic acid, formic acid and the like.

  As the explosive, a known organic explosive can be used. Organic explosives include trinitrotoluene (TNT), trinitrobenzene (TNB), cyclotrimethylenetrinitramine (RDX), cyclotetramethylenetetranitramine (HMX), tetranitromethylaniline (tetril), triaminotrinitrobenzene (TATB), diaminotrinitrobenzene (DATB), hexanitrostilbene (HNS), hexanitroazobenzene (HNAB), hexanitrodiphenylamine (HNDP), picric acid, ammonium picrate, benzotriazole (TACOT), ethylene dinitramine ( EDNA), nitroguanidine (NQ), pentaerythritol tetranitrate (pen slit), benzotrifluoroxane (BTF) and the like, and these are used alone or in combination. In particular, it is preferable to use Composition B, which is known as a mixed explosive of RDX (60%) and TNT (40%).

  These organic explosives have a carbon atom content of 15% by mass or more, preferably 20 to 35% by mass, a density of 1.5 g / cc or more, preferably 1.6 g / cc or more, and an explosion speed of 7000 m / s or more, preferably Is 7500 m / s or more, oxygen balance is negative, preferably -0.2 to -0.6, explosive pressure is 18 GPa or more, preferably 20 to 30 GPa, explosive temperature is 3000 K or more, preferably 3000 ~ 4000K. Therefore, carbon atoms in the explosive can be efficiently converted to diamond, and since the oxygen balance is negative, diamond is not oxidized during the explosion and the yield is not reduced.

  The above-mentioned explosion method is described in Science, Vol. 133, No. 3467 (1961), pp 1821-1822, JP-A No. 1-234311, JP-A No. 21-14414, Bull. Soc. Chem. Fr. Vol. 134 (1997). ), pp. 875-890, Diamond and Related materials Vol. 9 (2000), pp861-865, Chemical Physics Letters, 222 (1994), pp. 343-346, Carbon, Vol. 33, No. 12 (1995) , pp. 1663-1671, Physics of the Solid State, Vol. 42, No. 8 (2000), pp. 1575-1578, K. Xu. Z. Jin, F. Wei and T. Jiang, Energetic Materials, 1 , 19 (1993), JP-A-63-303806, JP-A-56-26711, British Patent No. 1154633, JP-A-3-271109, JP-A-6-505694 (WO93 / 13016), Carbon , Vol. 22, No. 2, 189-191 (1984), Van Thiei. M. & Rec., FH, J. Appl. Phys. 62, pp. 1761-1767 (1987), 7-1-1 No. 505831 (WO94 / 18123), US Pat. No. 5,861,349, JP-A-2006-239511, JP-A-2003-146637 and the like can be used.

(b) Oxidation treatment Oxidation treatment of unrefined diamond includes (i) high-temperature and high-pressure treatment in the presence of oxidants such as perchloric acid, dichromic acid, and nitric acid (oxidation treatment A), and (ii) water. And / or a method of treatment in a supercritical fluid comprising alcohol (oxidation treatment B), (iii) coexisting oxygen in a solvent comprising water and / or alcohol, and a temperature not lower than the normal boiling point of the solvent and 0.1 MPa ( A method of treating at a pressure equal to or higher than the gauge pressure (oxidation treatment C), or (iv) a method of treatment with a gas containing oxygen at 375 to 630 ° C. (oxidation treatment D). These oxidation treatments may be performed alone or in combination. When combining the oxidation treatment, it is preferable to first subject the unpurified diamond obtained by the explosion method to oxidation treatment A, and then to any one of oxidation treatments B to C.

  By applying oxidation treatment A to the unpurified diamond obtained by the explosion method, nano diamond (graphite-diamond fine particles) from which a part of the graphite phase has been removed is obtained. The graphite phase can be further removed by performing any of the treatments of C. In order to modify the particle surface with a functional group such as a carboxyl group, a sulfonic acid group, and a hydroxyl group, the oxidizing agent used in the oxidation treatment A preferably has a high oxidizing power. Specifically, perchloric acid, dichromic acid or nitric acid is preferable.

(c) Media dispersion treatment The median diameter of the unpurified diamond obtained by the blasting method and the nano diamond subjected to the oxidation treatment determined by the dynamic light scattering method is 150 to 250 nm. As described above, these particles are aggregates in which diamond primary particles having a median diameter of about 2 to 10 nm are strongly aggregated. In order to obtain diamond particles with less agglomeration, it is preferable to pulverize unpurified or oxidized diamond particles by a known media dispersion method such as a bead mill. For dispersion by a bead mill, zirconia beads are preferably used. The median diameter is preferably 100 nm or less, more preferably 50 nm or less, and most preferably 30 nm or less by dispersing the unpurified or oxidized diamond fine particles in a medium.

  Dispersion by a bead mill can be performed using a commercially available apparatus. It is preferable to use an apparatus that can grind with beads while continuously supplying the dispersion. For example, 0.1 mm diameter zirconia beads are filled in a 0.15 L vessel, and the peripheral speed is about 10 m / s. While rotating the rotor, the aqueous dispersion of diamond fine particles of about 5% is supplied at 0.12 L / min and pulverized. For further fine dispersion, 0.05 mm diameter zirconia beads may be used.

(3) Production method of carbon nanotubes Cup-stacked carbon nanotubes are commercially available, International Publication No. 2008/004347, JP 2003-147644, Qingfeng Liu et al. “Synthesis, Purification and Opening of Short Cup-Stacked Carbon Nanotubes ”, Journal of Nanoscience and Nanotechnology, vol. 9, 4554-4560, 2009, etc. can be used. Although an example of the manufacturing method of a cup stack type carbon nanotube is explained below, the present invention is not limited to this method.

Cup-stacked carbon nanotubes can be synthesized using the CoO-A1 ₂ 0 ₃ based catalyst. CoO-A1 ₂ 0 ₃ based catalysts, by heating the cobalt nitrate and aluminum nitrate is thermally decomposed to produce by grinding the reaction product obtained. The composition of the synthesis catalyst is preferably CoO: A1 ₂ 0 ₃ = 80: 20 to 40:60 (mass ratio). The cup-stacked carbon nanotube can be synthesized by placing the synthesis catalyst in a copper container and flowing a propane / butane mixed gas toward the catalyst at about 650 ° C. The obtained cup-stacked carbon nanotube is preferably obtained by dissolving and removing amorphous carbon and the synthetic catalyst by treatment with hydrochloric acid, and further subjecting to oxidation treatment in the same manner as the above-mentioned diamond fine particles to modify the hydrophilic group on the surface.

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

Example 1
(1) Fabrication of nano diamond
A 0.65 kg explosive 1 containing TNT (trinitrotoluene) and RDX (cyclotrimethylenetrinitramine) in a ratio of 40/60 is filled into an ice container 2a formed by freezing degassed water (Fig. 1). (a)) A lid was placed on an ice container 2b formed by freezing degassed water (FIG. 1 (b)). The explosive 1 was equipped with a detonation explosive and an electric detonator. The weight of ice was 15 kg for both containers 2a and 2b.

Ice containers 2a and 2b filled with explosive 1 were suspended in a 3 m ³ pressure-resistant container with a copper wire, and the air in the pressure-resistant container was replaced with nitrogen. The electric current to the electric detonator for initiating the explosive was supplied through the copper wire. The inside of the pressure resistant container was 1 atm, and the oxygen concentration was 4% by volume. Explosive 1 filled in ice containers 2a and 2b was exploded while water was poured over the entire inner wall from the top of the pressure-resistant container.

  After leaving still for 5 minutes, the explosive 1 filled in the ice containers 2a and 2b was installed again in the same manner, and a second explosion was performed without performing the nitrogen replacement operation in the pressure-resistant container. However, when the explosive 1 filled in the ice containers 2a and 2b was installed, the operation was performed quickly while supplying nitrogen to the pressure resistant container.

After the second explosion, open the top of the pressure-resistant container, collect the black liquid explosion product (unpurified nanodiamond) while washing the inner wall of the pressure-resistant container with water, heat dry, Nanodiamond powder was obtained. The yield of this unpurified nanodiamond was 11% by mass with respect to the amount of explosive used, the specific gravity was 2.55 g / cm ³ , and the median diameter (dynamic light scattering method) was 220 nm. This unpurified nanodiamond was estimated to be composed of 76% by volume of graphite-based carbon and 24% by volume of diamond, calculated from the specific gravity. Nanodiamonds this unpurified, a peak intensity I _a of 1,330 ± 10 cm ^-1 in the Raman spectrum, the ratio of the peak intensity I _b of 1,610 ± 100 cm ^-1 was 0.86.

The obtained unpurified nanodiamond is mixed with 60% by mass nitric acid aqueous solution and subjected to oxidative decomposition under conditions of 160 ° C, 14 atmospheres, 20 minutes, and then oxidative etching at 130 ° C, 13 atmospheres, 1 hour. Processed. Oxidative etching treatment yielded particles from which graphite was partially removed from unpurified nanodiamonds. The particles were refluxed with ammonia at 210 ° C., 20 atm for 20 minutes, neutralized, then naturally settled, washed with 35% by mass nitric acid by decantation, and further washed with water three times by decantation. Dehydrated by centrifugation, dried by heating at 120 ° C., and oxidized nanodiamond powder was obtained. The specific gravity of the oxidized nanodiamond powder was 3.38 g / cm ³ , and the median diameter was 130 nm (dynamic light scattering method). Calculated from the specific gravity, it was estimated to be composed of 90 vol% diamond and 10 vol% graphite carbon.

(2) Cesium adsorption removal 1
After adding 5.0 g of oxidized nanodiamond to 1.0 L of 100 ppm cesium chloride aqueous solution, adjusting the pH to 8 and stirring for 2 hours, 2 g of sulfuric acid band aqueous solution (10% by mass) and 0.5 g of After adding a polyethyleneimine aqueous solution (30% by mass) and stirring for 30 minutes, 3 g of sodium polyacrylate aqueous solution (0.3% by mass) was added and stirred for 30 minutes, and then allowed to stand for 3 hours. Separated into supernatant. The supernatant was filtered through a 100 μmφ membrane filter to remove the precipitate. When cesium contained in the filtered water was quantified by atomic absorption, 99% or more of cesium was removed.

Example 2
Cesium adsorption removal 2
After adding 5.0 g of the oxidized nanodiamond of Example 1 to 1.0 L of 100 ppm aqueous cesium chloride solution, adjusting the pH to 8.5 and stirring for 2 hours, 1.0 g of polyaluminum chloride aqueous solution (10% by mass) , 0.05 g of cationic polymer flocculant (Uniflocca UF-340, polymethacrylate molecular weight about 3.1 million, manufactured by Unitika Ltd.), 0.05 g of anionic polymer flocculant (Uniflocca UF-105, poly An acrylamide molecular weight of about 13 million, manufactured by Unitika Ltd.) was added, and the mixture was stirred for 30 minutes and then allowed to stand for 3 hours. The supernatant was filtered through a 100 μmφ membrane filter to remove the precipitate. When cesium contained in the filtered water was quantified by atomic absorption, 99% or more of cesium was removed.

Example 3
Strontium adsorption removal
To 1.0 L of 100 ppm strontium chloride aqueous solution, 5.0 g of the oxidized nanodiamond of Example 1 was added, adjusted to pH 8 and stirred for 2 hours, and then 2 g of sulfuric acid band aqueous solution (10% by mass), And 0.5 g of polyethyleneimine aqueous solution (30% by mass) was added and stirred for 30 minutes, then 3 g of sodium polyacrylate aqueous solution (0.3% by mass) was added and stirred for 30 minutes, and then allowed to stand for 3 hours. The precipitate was separated into a supernatant. The supernatant was filtered through a 100 μmφ membrane filter to remove the precipitate. When strontium contained in the filtered water was quantified by atomic absorption, 99% or more of strontium was removed.

Example 4
(1) Synthesis of carbon nanotubes
14.6 g of cobalt nitrate hexahydrate and 9.4 g of aluminum nitrate nonahydrate dissolved in 24 g of distilled water are heated in a muffle furnace maintained at 650 ° C. ± 10 ° C. for thermal decomposition for 1 hour, and air Then, the resulting dendritic product was pulverized to obtain a CoO-A1 ₂ 0 ₃ catalyst for synthesizing cup-stacked carbon nanotubes. The composition of the obtained catalyst was CoO: A1 ₂ 0 ₃ = 60: 40 (mass ratio).

  O.4 g of this synthetic catalyst was evenly placed on a copper dish with a diameter of 60 mm, and a mixed gas of propane: butane = 1: 1 was directed from the top toward the catalyst in a pilot furnace maintained at 650 ± 5 ° C. It was supplied at a flow rate of 120 L / hr and reacted for 30 minutes to obtain a graphite compound in a yield of 39%. From the observation with a scanning electron microscope, it was confirmed that the obtained graphite compound contained cup-stacked carbon nanotubes. X-ray diffraction revealed that the carbon nanotubes contained 74% crystallized carbon. The graphite compound containing cup-stacked carbon nanotubes thus prepared was treated with hydrochloric acid, and the amorphous carbon and the synthetic catalyst were dissolved and removed, then mixed with a 60% by mass nitric acid aqueous solution and subjected to oxidation treatment, and the particle surface was subjected to carboxyl groups, It was modified with a functional group such as a hydroxyl group.

(2) Cesium adsorption removal
After adding 5.0 g of oxidized carbon nanotubes to 1.0 L of 100 ppm aqueous cesium chloride solution, adjusting the pH to 8 and stirring for 2 hours, 2 g of sulfuric acid band aqueous solution (10% by mass) and 0.5 g of After adding a polyethyleneimine aqueous solution (30% by mass) and stirring for 30 minutes, 3 g of sodium polyacrylate aqueous solution (0.3% by mass) was added and stirred for 30 minutes, and then allowed to stand for 3 hours. Separated into supernatant. The supernatant was filtered through a 100 μmφ membrane filter to remove the precipitate. When cesium contained in the filtered water was quantified by atomic absorption, 99% or more of cesium was removed.

Example 5
Strontium adsorption removal
To 1.0 L of 100 ppm strontium chloride aqueous solution, 5.0 g of the oxidized carbon nanotube of Example 4 was added, and after adjusting the pH to 8 and stirring for 2 hours, 2 g of sulfuric acid band aqueous solution (10% by mass), And 0.5 g of polyethyleneimine aqueous solution (30% by mass) was added and stirred for 30 minutes, then 3 g of sodium polyacrylate aqueous solution (0.3% by mass) was added and stirred for 30 minutes, and then allowed to stand for 3 hours. The precipitate was separated into a supernatant. The supernatant was filtered through a 100 μmφ membrane filter to remove the precipitate. When strontium contained in the filtered water was quantified by atomic absorption, 99% or more of strontium was removed.

1 ... Explosive
2a, 2b ... containers

Claims (10)

  A processing method for removing and recovering metal atoms from a waste liquid, the step of adding and mixing diamond fine particles and / or carbon nanotubes to the waste liquid, and agglomeration in the waste liquid obtained by adding and mixing the diamond fine particles and / or carbon nanotubes A processing method comprising a step of adding an agent.   The waste liquid treatment method according to claim 1, wherein the flocculant is an inorganic flocculant and / or an organic polymer flocculant.   The waste liquid treatment method according to claim 1 or 2, wherein the inorganic flocculant is at least one selected from the group consisting of aluminum sulfate, aluminum chloride, polyaluminum chloride, ferric chloride, and polyferric sulfate. A processing method characterized by the above.   The waste liquid treatment method according to claim 1, wherein the organic polymer flocculant is a cationic organic polymer flocculant, an anionic organic polymer flocculant, a nonionic organic polymer flocculant, or both ions. A processing method characterized in that it is at least one selected from the group consisting of conductive organic polymer flocculants.   5. The waste liquid treatment method according to claim 1, wherein the step of adding the flocculant further adds the polymer flocculant after the inorganic flocculant and / or the polymer flocculant is added and mixed. A processing method comprising a step of adding and mixing.   6. The treatment method according to claim 1, wherein the diamond fine particles are obtained by an explosion method.   The waste liquid treatment method according to any one of claims 1 to 6, wherein the diamond fine particles have a surface hydrophilized by an oxidation treatment. The waste liquid treatment method according to any one of claims 1 to 7, wherein the diamond fine particles have a specific gravity of 2.55 to 3.48 g / cm ³ .   The waste liquid treatment method according to claim 1, wherein the carbon nanotube is a cup stack type.   The adsorbent which consists of a diamond fine particle and / or a carbon nanotube for removing and collect | recovering metal atoms from a waste liquid in any one of Claims 1-9.

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