CN1330969A - Decomposition treatment process for dioxine - Google Patents
Decomposition treatment process for dioxine Download PDFInfo
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- CN1330969A CN1330969A CN01123184A CN01123184A CN1330969A CN 1330969 A CN1330969 A CN 1330969A CN 01123184 A CN01123184 A CN 01123184A CN 01123184 A CN01123184 A CN 01123184A CN 1330969 A CN1330969 A CN 1330969A
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- dioxins
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- A—HUMAN NECESSITIES
- A62—LIFE-SAVING; FIRE-FIGHTING
- A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
- A62D3/00—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances
- A62D3/30—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances by reacting with chemical agents
- A62D3/37—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances by reacting with chemical agents by reduction, e.g. hydrogenation
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/08—Reclamation of contaminated soil chemically
Abstract
The present invention provides a method for simply performing the decomposition of dioxins contained in fly ash, soil or the like without forming toxic byproducts. The decomposition method decomposes or dechlrinates dioxins in an object to be treated by bringing dioxins contained in the object to be treated to a Grignard reagent state, its characteristic is based on that it consists of a dehydration process for removing moisture of the treated object containing dioxins, a mixing process for mixing a magnesium powder with the object to be treated obtained in the dehydration process, a heating process for heating the object to be treated at least at one point of time selected from points of time before, after and during the mixing process, and an acceleration liquid adding process for adding an acceleration liquid, which generates reducing reaction, to dioxins held to the Grignard reagent state in the object to be treated obtained after the mixing process and the heating process.
Description
The present invention relates to a method for performing a simple decomposition treatment of dioxins in solid materials such as fly ash, incineration ash, waste such as sludge or oil sludge, soil or the like (hereinafter referred to as "treated material") by effective decomposition or dechlorination without generating toxic by-products and without heating at high temperature by external heating means or combustion, and more preferably to a decomposition treatment method of dioxins for preventing heavy metals from being eluted from treated solid materials after treatment.
It is known that dioxins cause skin and internal organ diseases, and are teratogenic and carcinogenic, and are highly toxic substances unprecedented in addition to this. In particular, 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin, which is a narrow definition, is known as one of the most toxic substances acquired by humans. In addition, other dioxins are also harmful to the human body, and among them, the toxicity of polychlorinated biphenyl (PCB) is considered to be a problem to be studied, but especially coplanar PCB has a very toxic planar structure in PCB.
In recent years, various proposals have been made on the problem of contamination by such highly toxic dioxins. In particular, it has been found that dioxin is generated by burning refuse, and there has been a problem that dioxin is generated by burning refuse under the operating conditions of a refuse burning site, and the generated dioxin is mixed into fly ash discharged from the refuse burning site, or dioxin is contained in a chimney exhaust gas of the refuse burning site, and soil around the refuse burning site is contaminated.
Further, in agricultural chemicals used in the past such as herbicides, dioxins are contained as impurities, and there are cases where: by using such a pesticide, soil contaminated with dioxins remains until now.
Dioxins are mixed in the above waste, and further soil and river are contaminated.
In addition, after the treatment by the conventional method, harmful heavy metals such as cadmium and lead in the remaining solid are eluted to the outside, and there is a social problem such as environmental destruction.
In view of the above circumstances, as a decomposition treatment technique for dioxins absorbed and adsorbed in a treatment object, ① melting method, ② high temperature incineration method, ③ gas phase hydrogen reduction method, ④ reduction heating dechlorination method, ⑤ supercritical water oxidation decomposition method, ⑥ metallic sodium dispersion method, ⑦ photochemical decomposition method, ⑧ method in which dioxins are mixed in basic ethylene glycol or basic alcohol, heated to 150 ℃ and held for 90 minutes to decompose dioxins, and the like have been proposed.
These methods, except ⑥ and ⑦, require heating and require time for decomposition, but ⑥ is dangerous, and ⑦ has problems of low efficiency due to the inability of light to pass through the solid, high equipment and operating costs, and the like.
As another decomposition treatment technique, japanese patent application laid-open No. 57-52900 discloses the following method: the organic substances, which contain halogen and/or phosphorus and are particularly radioactively contaminated, are pyrolyzed, wherein the substances are mixed in stoichiometric excess with an alkaline substance and are introduced in the form of a suspension into a fixed-bed reactor filled with mechanically moving spherical ceramic shaped bodies. Since this method decomposes at high temperature, it requires energy, and has disadvantages that by-products which are environmentally undesirable are produced by the reaction, and that a special apparatus is required and the apparatus is damaged by the high-temperature reaction.
Further, Japanese patent application laid-open No. 6-61373 proposes a method for dehalogenating a halogenated hydrocarbon in the presence of a nucleophilic reaction partner, wherein the halogenated hydrocarbon is dispersed chemically, and the resulting finely dispersed reaction product is subjected to a chemical reaction with a nucleophilic reaction partner at a reaction temperature between ambient temperature and about 510 ℃. The following disadvantages apply when the process is carried out at temperatures below 250 ℃: in the case of dehalogenation by nucleophilic reaction, there is an increase in some of the polychlorinated furans, or the formation of new toxic by-products, and in addition, there is a disadvantage of poor dehalogenation efficiency.
As mentioned above, any solution of the prior art has the following problems: or the operation is difficult, or the energy cost is too high, or the decomposition treatment requires time, or the treatment is accompanied by danger, or a new toxic by-product or a by-product which can cause global warming is produced.
Under such circumstances, there is a strong demand for a decomposition treatment method for dioxins, which is a simple method capable of decomposing dioxins without requiring special treatment such as special equipment or high-temperature heating and without generating toxic by-products or some by-products that may cause global warming, and which is preferably capable of preventing harmful heavy metals such as cadmium or lead from being eluted to the outside.
The present invention has been made in view of such social needs, and an object thereof is to provide a method for decomposition treatment of a dioxin-containing material to be treated (such as the fly ash) which is safe and simple, does not require excessive energy, does not require a special apparatus, decomposes dioxins without generating new toxic by-products or by-products having an adverse effect on the environment such as global warming, and preferably prevents elution of harmful heavy metals, and enables effective use of the treated material.
The present invention relates to a method for decomposition or dechlorination of dioxins in a material to be treated by bringing dioxins contained in the material to be treated into a grignard reagent state, the method comprising the steps of: the method for treating the dioxin-containing material comprises a dehydration step of removing water from the dioxin-containing material to be treated, a mixing step of adding mixed magnesium powder to the material to be treated obtained in the dehydration step, and a promoting liquid adding step of adding a promoting liquid for the reduction reaction of the dioxin in a Grignard reagent state in the material to be treated obtained in the mixing step.
The present invention relates to the method for decomposition treatment of dioxins according to the above invention, which is characterized by comprising a heating step of heating the object to be treated at least 1 time before, after and simultaneously with the mixing step.
The present invention relates to the method for decomposition treatment of dioxins according to any one of the above inventions, wherein the heating step is performed simultaneously with and/or after the accelerating solution adding step.
The present invention relates to the method for decomposition treatment of dioxins according to any one of the above inventions, wherein a heavy metal elution inhibitor is added in any one of the mixing step, the heating step and the accelerator addition step.
The present invention relates to the method for decomposition treatment of dioxins according to any one of the above inventions, wherein calcium oxide or calcium oxide coated with oil is used in the dehydration step and/or the heating step.
The present invention according to item 6 is the method for decomposition treatment of dioxins according to any one of the above inventions, wherein at least 1 of water, an aqueous solution of an alkali metal compound, hydrogen peroxide water, detergent water, an aqueous solution of a 1-membered or polyhydric alcohol, and an aqueous solution of an organic chelating agent is used in the acceleration liquid addition step.
The present invention relates to the method for decomposition treatment of dioxins according to any one of the above 4 to 6, wherein the heavy metal elution inhibitor is at least 1 selected from zeolite, a salt of a phosphorus compound, and an organic chelating agent.
The present invention relates to the decomposition treatment method for dioxins according to any one of the above inventions, wherein the object to be treated is at least 1 selected from the group consisting of fly ash contaminated with dioxins, incineration ash, waste such as sludge or oil sludge, and soil.
Modes for carrying out the invention
The following describes embodiments of the present invention.
In the present invention, the decomposition treatment of dioxins means that the dioxins are dechlorinated to become a non-toxic compound, and further, the dioxins are decomposed to become a non-toxic compound having a lower molecular weight to the extent that the skeleton itself of the compound is changed.
In the present invention, dioxins are used as a general expression of "dioxins" (so-called dioxins, also referred to as "narrow-sense dioxins" in the present specification) specified in article 2 and "coplanar PCBs" of "special measures for dioxins" of law No. 105, which is filed in the 11-year-old, in particular.
Among the dioxins in the narrow sense mentioned above, polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans are included.
Within the above-mentioned dioxins in the narrow sense, among polychlorinated dibenzo-p-dioxins, tetrachlorodibenzo-p-dioxins, pentachlorodibenzo-p-dioxins, hexachlorodibenzo-p-dioxins, heptachlorodibenzo-p-dioxins, and octachlorodibenzo-p-dioxins are included.
Further, among the dioxins in the narrow sense, polychlorinated dibenzofurans include tetrachlorodibenzofuran, pentachlorodibenzofuran, hexachlorodibenzofuran, heptachlorodibenzofuran, and octachlorodibenzofuran.
Coplanar PCB refers to isomers having the same toxicity as dioxins in polychlorinated biphenyl (PCB), which is specified among isomers having no substituent at the ortho position (2, 2 ', 6 and 6') (no ortho position), isomers having 1 substituted chlorine at the ortho position (mono ortho position), and isomers having 2 substituted chlorine at the ortho position (di ortho position), and has the same flat structure as dioxins. Examples of the nonadjacent isomer include 3, 4, 4 ', 5-tetrachlorobiphenyl, etc., examples of the monoadjacent isomer include 2, 3, 3', 4, 4 '-pentachlorodiphenyl, etc., and examples of the diadjacent isomer include 2, 2', 3, 3 ', 4, 4', 5-heptachlorobiphenyl, etc.
In the present invention, the measurement of the dioxin content (concentration) is carried out according to "a standard verification method for managing general waste and industrial waste in particular" and "a japanese industrial standard" of dioxin and co-planar PCB in exhaust gas "in the thick-life-saving bulletin No. 6 (1, 14, 12), which is based on the thick-life-saving directive No. 1 (1, 14, 12), and" a method for measuring dioxin and co-planar PCB ". JIS K0311, established on 11 years, 9 months, 20 days).
In the JIS standards, 2, 3, 7, 8-TeCDD toxicity equivalent coefficients (TEF) (see table 2) and 2, 3, 7, 8-TeCDD toxicity equivalent equivalents (TEQ) (see table 3) are defined as indexes indicating the toxicity of each compound described above, based on the toxicity of 2, 3, 7, 8-tetrachlorodibenzo to dioxin (TeCDD). In the specification, the method of indicating toxicity is defined in accordance with the standard.
Specifically, based on the measurement results, equivalent toxicity of dioxins is calculated from the following formula with reference to tables 1 and 2 corresponding to the respective toxicity equivalence coefficients (TEF) of dioxins.
Equal amount of toxicity (sum of toxicity of dioxins contained in the object to be treated: ng-TEQ/g-dry) ═ Sigma (concentration of each dioxin ng/g-dry X TEF of each dioxin)
In order to clarify the meaning of the terms relating to the state of the Grignard reagent used in the present invention, the Grignard reagent itself will be described, and the dechlorination function of the Grignard reagent will be described.
Grignard reagents are represented by the general formula RMgX, which is commonly known as alkylmagnesium halides. Grignard reagents are obtained by reacting alkyl halides with magnesium metal in anhydrous ethers, which are well known. Grignard reagents are highly reactive with other compounds and therefore used as such in ether solutions in various organic synthesis reactions.
Dehalogenation by reduction via a Grignard reagent is well known among halogenated aryl groups, but at best is aimed at compounds of the fluorobenzene degree. Further, since the Grignard reagent cannot be prepared in the presence of water, the reduction reaction is carried out in an ether under extremely strict control. Further, since the grignard reagent has high reactivity, the dehalogenation by the reduction reaction is limited to a case where a purified substance (i.e., a single substance) is used as an object, and is merely carried out at a laboratory level.
In other words, since these methods lose their functions immediately when only an extremely small amount of a substance is present in a medium, they cannot be practically used in the field of environmental protection because the mixture often has a problem of containing a component which makes the necessary catalyst ineffective after a short time.
In particular, it is not known that such a reaction occurs in a very stable compound such as dioxin. Further, since the solid contains water, it is difficult to form the Grignard reagent, and therefore, it has not been thought to utilize the Grignard reagent for dechlorination of a chlorine-containing compound in the solid.
The present inventors have made studies and developments on a method for dechlorinating and decomposing dioxins without being bound to these conventional findings, and have surprisingly found that dioxins in a solid state can be efficiently dechlorinated and decomposed by a grignard reagent, and have completed the present invention.
The grignard reagent according to the present invention is in the form of a grignard reagent formed by reacting a dioxin and magnesium powder contained in a material to be treated.
The Grignard reagent is a very unstable compound as described above, and therefore, the presence thereof in the treatment object is not easily confirmed, but when a reaction promoting liquid containing water is added, the occurrence of the following reaction can be understood by judging from the compound which is dechlorinated and analyzed from the reaction result.
The mechanism of this reaction is now described in comparison with the dehalogenation mechanism of the conventionally known nucleophilic substitution reaction of halogenated aryl groups.
It is generally believed that the halogenated aryl group is para-OH-、OR-、NH3And CN-Such nucleophiles are very inefficient in reactivity (Morrison, 6 th edition of organic chemistry, Mitsu Tanshi, 4.1.1998, carried out by Tokyo chemists), and high-temperature and high-pressure reaction conditions are required for the reaction.
Specifically, chlorobenzene was reacted in 6 to 8% NaOH aqueous solution at 350 ℃ under 300 atm under the following reaction conditions (see chemical formula 1)
Chemical formula 1
Due to such a background, when this nucleophilic reaction is used for decomposition (or dechlorination) of dioxins, the efficiency is low, and reduction of the cost is not expected.
On the other hand, when the dechlorination reaction by the halogenated aryl dechlorination of the present invention is carried out, the reduction reaction by the Grignard reagent is as follows, and the chlorobenzene is exemplified and explained.
Chemical formula 2
The Grignard reagent is formed when magnesium is added to chlorobenzene in the case of anhydrous ether. When water is subsequently added, the Grignard reagent reacts with water immediately to form benzene, and the reduction reaction is terminated (see chemical formula 2)
The above mechanism was studied with respect to dioxins.
2g of magnesium powder was added to 100g of fly ash containing dioxins (dioxins concentration: 7.0ng-TEQ/g-dry, moisture content: 0.01% or less) at 25 ℃ and uniformly stirred. Then, 60ml of water was added thereto, followed by thorough stirring. The reactant is then assayed for dioxin concentration. The concentration of dioxins in the reaction mixture was 5.5 ng-TEQ/g-dry.
This mechanism will be explained by taking an example of 2, 3, 7, 8-tetrachlorodioxin in dioxin. Further, since the intermediate organometallic compound (aryl magnesium halide) reacts with water immediately, the intermediate grignard reagent cannot be detected, but the following reduction reaction is presumed to proceed by judging from the reaction product (see chemical formula 3 and chemical formula 4). In addition, it is also judged from the reaction product that the skeleton portion is also decomposed at the same time.
Chemical formula 3
Chemical formula 4Etc. of
As a proof of this reaction, it can be judged that the nucleophilic substitution reaction of the halogenated aryl compound such as dioxin does not occur even when the data is almost unchanged from the OH substituent generated in the nucleophilic substitution reaction result shown by the following formula (see chemical formula 5) in which the nucleophilic substitution reaction product is not detected and the result of heating to 200 ℃ and holding for 6 hours.
As can be seen from the above, in the present invention, dioxins are dechlorinated and decomposed by a reduction reaction in a grignard reagent state.
Chemical formula 5
Etc. of
The water content of the object to be treated dried in the dehydration step can be determined by the method described in the above-mentioned journal of general public health and economic notice No. 6. That is, as described in "adjustment of sample at 2) ゥ (ァ)" in table 1 (relationship No. 1) "in the above report, about 40g of the object to be treated was taken and accurately measured (taken as the initial weight of the object to be treated). The object was dried at 105 ℃ to 110 ℃ for 2 hours, and then left to cool in a dryer for 30 minutes, and the weight of the residue (taken as the residual weight of the object) was determined. The water content in the object to be treated was determined by the following equation.
Water content (%) in the object to be treated [ { (initial weight of object to be treated) - (residual weight of object to be treated) } ÷ (initial weight of object to be treated)]× 100
The water content in the object to be treated dehydrated in the dehydration step of the present invention is 1% or less, preferably 0.1% or less, particularly preferably 0.01% or less, which is a general object to put dioxins in a grignard reagent state.
The soil other than the sludge usually contains 5 to 80% by weight of water, and the sludge contains 80% by weight or more of water. On the other hand, the moisture content of fly ash and incineration ash is approximately 10 wt% or less.
Therefore, in the present invention, the moisture content must be dried to the target or less before adding and mixing the magnesium powder to the object.
The water content of fly ash is 0.1 wt% or less, and in this case, the sequence may be advanced to the mixing step without performing the dehydration step.
The moisture in the object to be treated does not have to be completely removed from the object to be treated to the outside, and the dioxin and magnesium powder may be in a grignard reagent state and remain in the object to be treated.
As a means therefor, a method of adding a dehydrating agent or a drying agent to substantially remove moisture from the periphery of dioxins is considered.
The dehydration rate is only a rough target, and finally, it is necessary to secure the state of grignard reagent, and as a method for making this exact, a sample is taken from a treated object, the content of dioxin contained therein is grasped, the treated object is subjected to dehydration, optionally heating, magnesium powder is mixed, a treatment accelerator is added, the finally obtained treated object is analyzed to grasp the dechlorination or decomposition state of dioxin, and various conditions are experimentally determined by grasping data with the dehydration conditions, heating conditions, the amount of magnesium added, and the addition ratio of the treatment accelerator as parameters.
The specific decomposition treatment method will be further clarified by the examples described later, but the present invention is not limited thereto.
As the dehydration means in the dehydration step, there are a heating method, a vacuum suction method, and a method of adding a dehydrating agent. In the heating and vacuum suction method, care must be taken not to scatter dioxins in the object to be treated.
Examples of the dehydrating agent or the drying agent used as the dehydrating means include calcium oxide, magnesium oxide, silica gel, and water-absorbing polymer. One or more of them may be combined. For example, when the treated soil is used as agricultural soil, civil engineering soil or the like, the selection of the dehydrating agent or the drying agent is not detrimental.
Among the above-mentioned dehydrating agents and drying agents, calcium oxide is preferable because calcium oxide generates heat by reaction with water as in the following formula and has a heating action, and can be used without any particular trouble in addition to the problem of being alkaline in the subsequent reuse.
The calcium oxide used for dehydrating or drying the object containing water is preferably added in an amount of about 3 times the water content (calcium oxide equivalent to the water content).
The magnesium powder to be added in the mixing step may be commercially available. The particle size of the powder is preferably 40 mesh or more, more preferably 100 mesh or more. The amount of magnesium powder to be mixed is an amount necessary to form a grignard reagent state between dioxins and magnesium, and the content of dioxins contained in the material to be treated is determined by sampling and is set to be at least equivalent to dioxins.
In short, the concentration of dioxin in the object to be treated is at most several hundred ng-TEQ/g-dry (several tens mg/g-dry in terms of total concentration), and the equivalent thereof is several tens ng per 1g of the object to be treated. Expressed as equivalent magnesium powder, this amount is several tens ng. Even if ten times equivalent, it is 1mg or less. It is difficult to uniformly mix 1mg of the magnesium powder in 1g of the object to be treated (the apparatus must be designed), and a large excess of the magnesium powder is usually added. Namely, the amount of the surfactant is in the range of 0.01 to 10 wt% based on the object to be treated. However, if the amount is too small, uniform mixing becomes difficult, and the decomposition rate decreases. For this, it is preferably 0.1 to 5% by weight.
In addition, various conventionally known means can be used for the mixing method. Mechanical mixing, air-flow mixing, etc., and among them, a screw mixer, an eccentric mixer (ヘンシェルミキサ —), a ball mill, a rotary mixer, etc. can be used as the mechanical mixing. As the air flow mixing method, there is a method of mixing heated air (N)2) A method of blowing the treatment object which falls together with the magnesium powder. It is recommended to perform heating in combination with mixing.
The method of simultaneously dehydrating and heating and then mixing includes a method of simultaneously dehydrating and heating and mixing, a method of heating before or after mixing, a method of combining these methods, and the like, and can be appropriately selected depending on the object to be treated.
The heating condition is not particularly limited, but from the viewpoint of energy consumption, it is preferably 250 ℃ or lower, more preferably 200 ℃ or higher.
When the dehydration step and the heating step are performed using calcium oxide, the treatment time is within 30 minutes, and is usually about 3 to 30 minutes.
In addition, since calcium oxide has a function of generating heat while absorbing water, calcium oxide or oil-coated calcium oxide is preferably used in the dehydration step and the heating step. In addition, the added magnesium powder itself is an effective component for plant growth. Therefore, the mixing ratio may be added in a multi-purpose manner.
The oil-coated calcium oxide can be dehydrated in the dehydration step, and when added to a dehydrated object, it does not react with heat, but when added with a promoting liquid described below, it can react and heat.
In the acceleration liquid addition step of adding the acceleration liquid for the reduction reaction of dioxins in the Grignard reagent state, the added acceleration liquid is substantially aqueous, and the dioxins in the Grignard reagent state (see chemical formula 3) and water are subjected to the reduction reaction, converted into various compounds in a dechlorinated state (see chemical formula 4), and dechlorinated. It was also confirmed that during this reaction, the polycyclic structure of the basic skeleton portion of dioxin-like compounds was itself decomposed and converted into lower molecular compounds having low toxicity or extremely low toxicity.
The present invention is characterized by carrying out the reduction reaction. It has not been confirmed that dioxins contained in a material to be treated such as soil can undergo such a reduction reaction, and the present invention makes it possible to realize the reduction reaction. It has been newly confirmed that such a reduction reaction does not produce dioxins having higher toxicity, that is, dioxins to which a hydroxyl group is added, than dioxins produced in the nucleophilic substitution reaction of the dioxin dechlorination method (see chemical formula 5).
In the accelerating solution addition step (so-called reduction reaction accelerating step) of the present invention, at least 1 of water, an aqueous solution of an alkali metal compound, detergent water, an aqueous solution of a 1-membered or polyhydric alcohol, and an aqueous solution of an organic chelating agent can be used as the reduction reaction accelerating solution.
The amount of the reduction reaction promoting liquid is 2 times or more equivalent to that of dioxins in the form of grignard reagents contained in the object to be treated, but a large excess amount of water is usually added from the viewpoint that dioxins are very trace and magnesium powder is added in a large excess amount. That is, the amount of the magnesium powder is in the range of 1 to 10 wt% based on the treated material.
In the present invention, when the heating step is performed using calcium oxide and oil-coated calcium oxide, it is necessary to add an amount of water corresponding to 1 to 20 times equivalent (if the weight is 0.3 to 6 times the weight) of the amount of calcium oxide added to react with water. More preferably 2 to 10 times equivalent.
The invention also features: the reaction is carried out at normal temperature, normal pressure or a condition close thereto without requiring a special heating apparatus and pressurizing apparatus. As a result, according to the present invention, dechlorination and decomposition of dioxins are possible without excessive energy.
When the accelerating liquid is an aqueous solution of an alkali metal compound, the accelerating liquid can serve to remove oil coated on calcium oxide in terms of improvement in handling. The same effect can be obtained by using detergent and other promoter.
Further, the oil used for oil coating is not particularly limited, and if a vegetable oil is used, it is used for soil treatment after treatment, and is directly used for farming after treatment, and thus it can be effectively used. Preferred vegetable oils may be exemplified by corn oil, rapeseed oil, coconut oil, palm oil, soybean oil, castor oil, and the like.
Preferable examples of the alkali metal compound include alkali metal salts of inorganic acids such as carbonic acid, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, and silicic acid, alkali metal hydroxides, and alkali metal compounds of organic chelating agents. Examples of the alkali metal include sodium and potassium in view of price. In particular, potassium salts of plant micronutrients are desirable for soil applications, and alkali metal salts of phosphoric acid, phosphorous acid, hypophosphorous acid, and organic chelating agents, which form insoluble materials by binding to heavy metals, are more desirable for fly ash and other heavy metals. That is, potassium carbonate, sodium silicate, sodium chloride, sodium nitrate, potassium phosphate, sodium phosphate, potassium phosphite, sodium phosphite, potassium hypophosphite, sodium nitrate, and the like can be preferably exemplified.
The detergent may be any one of those used, and examples thereof include a neutral detergent, an acidic detergent, and an alkaline detergent.
As the alcohol, various alcohols can be used, and isopropyl alcohol can be exemplified as the 1-membered alcohol, and ethylene glycol can be exemplified as the polyhydric alcohol. It is preferable to add at least one of the aqueous solutions to the object to be treated.
This addition and mixing has the following effects that the decomposition rate of dioxins is improved, and the treated material after the decomposition treatment can be reused for landfill or the like.
The object to be treated by the method of the present invention, for example, fly ash, may contain harmful heavy metals such as cadmium and lead, and when such fly ash is disposed outdoors, a new pollution problem is caused.
In the present invention, it is preferable to use a heavy metal elution preventing agent in order to adsorb and trap these harmful metals so as not to elute them to the outside. As such a heavy metal elution inhibitor, zeolite, an organic chelating agent, and an alkali metal salt (salt of a phosphorus compound) of phosphoric acid, phosphorous acid, or hypophosphorous acid can be used.
The zeolite used as such a heavy metal elution inhibitor is generally a hydrous silicate, but in the present invention, an artificial zeolite is preferably used instead of a natural zeolite or a synthetic zeolite. This artificial zeolite is a zeolite synthesized from coal ash or the like as a raw material, and is different from a synthetic zeolite which requires a raw material (silicic acid, aluminum hydroxide or the like) of a certain degree of purity. In addition, such artificial zeolite contains intermediate products and unburned carbon components which do not completely constitute zeolite, and the purity of zeolite is in a position intermediate between synthetic zeolite and natural zeolite. Therefore, the artificial zeolite has useful characteristics such as adsorption performance and ion exchange performance due to impurities (intermediate products and unburned carbon components) contained therein. The cation exchange capacity is about the same as or 3 times as that of natural zeolite. Further, although sodium type, iron type, calcium type, lead type, silver type, magnesium type, and the like are preferable as the method for producing such artificial zeolite, calcium type artificial zeolite is most preferable from the viewpoint of safety and price.
Among the above zeolites, iron-type zeolites are particularly preferable because they can not only prevent elution of heavy metals but also promote decomposition ability of dioxins.
As an organic chelating agent used as such a heavy metal elution inhibitor, ethylenediaminetetraacetic acid, dithiocarbamic acid, or the like is used, and a chelate compound is formed with a heavy metal such as cadmium or lead to prevent elution of the heavy metal.
The object to be treated in the present invention may be a waste such as fly ash, incineration ash, sludge, or soil contaminated with dioxins, each of which is independent of the other, or may be a combination of a plurality of appropriate objects to be treated. For example, since incineration ash contains alkali metal components, if it is combined with a treatment object such as sludge, the addition of a promoting liquid can be omitted or reduced.
When the fly ash or the like obtained after decomposition of dioxins is alkaline, it may not be suitable for direct landfill, and therefore it is preferable to add an acid to the fly ash or the like for neutralization. Examples of the acid for neutralization include inorganic acids such as carbonated water and sulfuric acid water, and organic acids such as citric acid.
Further, in order to grow plants, it is necessary to prevent the damage caused by excessive calcium in agricultural soil, i.e., to prevent magnesium deficiency, and it is desirable to contain magnesium oxide or magnesium peroxide. Further, in order to prevent magnesium deficiency, a mixture of oil-coated calcium oxide and oil-coated magnesium oxide is preferable, and in this case, the amount of magnesium oxide is preferably 5 to 50% relative to calcium oxide.
Next, the form of the decomposition treatment method of the present invention will be described by way of examples.
[ examples]
The present invention will be described below by way of examples, which are illustrative and do not limit the scope of the present invention in any way.
[ example 1]
100g of fly ash containing dioxins and having a water content of 2.3% (dioxins concentration: 7ng-TEQ/g-dry) was put into a beaker, and the beaker was placed in a large-sized dryer containing a desiccant (silica gel) and stored for about 2 weeks. The moisture content in the fly ash after drying was 0.15%. 2g of magnesium powder was added thereto at room temperature, and the mixture was uniformly stirred. Then, 60ml of water was added thereto and the mixture was sufficiently stirred. The reactant is then assayed for dioxin concentration. The concentration of dioxins in the reaction mixture was 5.8 ng-TEQ/g-dry. The residual rate was 80% (residual rate (%) (equivalent amount of dioxin toxicity per dry weight in the reaction product)/(equivalent amount of dioxin toxicity per dry weight in the initial fly ash) × 100).
[ example 2]
100g of fly ash containing dioxins (dioxins concentration: 7ng-TEQ/g-dry) having a water content of 2.3% was put into an SUS flat container, and then the SUS container was placed in a sealed container having 2 relatively small holes. The fly ash was dried by passing dry air through the holes of the closed container for about 1 week. The water content in the fly ash after drying is below 0.01%. 2g of magnesium powder was added thereto at room temperature, and the mixture was uniformly stirred. Then, 60ml of water was added thereto and the mixture was sufficiently stirred. The reactant is then assayed for dioxin concentration. The concentration of dioxins in the reaction mixture was 5.5 ng-TEQ/g-dry. The survival rate was 79%.
[ example 3]
100g of fly ash containing dioxins and having a water content of 2.3% (dioxin concentration: 7ng-TEQ/g-dry) was put into an SUS flat container, the SUS flat container to which the fly ash was put was placed on an electric heating plate set to 90 ℃ in a sealed container, the plate was put into a sealed container having two opposite holes, and N was introduced from one hole of the sealed container2While the SUS vessel containing the fly ash was kept at 90 ℃ for about 1 day and night, the vessel was dried. The water content in the fly ash after drying is below 0.01%. The mixture was kept on a hot plate, and 2g of magnesium powder was added thereto, and the mixture was uniformly stirred. Then, water heated to 90 ℃ was added thereto, and the mixture was sufficiently stirred. The reactant is then assayed for dioxin concentration. The concentration of dioxins in the reaction mixture was 2.5 ng-TEQ/g-dry. The survival rate was 36%.
[ example 4]
100g of dioxin-containing fly ash (dioxin concentration: 7ng-TEQ/g-dry) having a water content of 0.01% or less was dried and held on a hot plate set at 90 ℃ for about 1 hour in the same manner as in example 1, and then 2g of magnesium powder was added thereto and uniformly stirred. Then, 60ml of water was added thereto and the mixture was sufficiently stirred. The reactant is then assayed for dioxin concentration. The concentration of dioxins in the reaction mixture was 3.1 ng-TEQ/g-dry. The survival rate was 44%.
[ example 5]
In the same manner as in example 2, the dried fly ash at 90 ℃ was charged into a ball mill container previously warmed to 150 ℃ in a closed container, and 2g of magnesium powder was added thereto and uniformly stirred. Then, 60ml of water was added thereto and the mixture was sufficiently stirred. The reactant is then assayed for dioxin concentration. The concentration of dioxins in the reaction mixture was 2.2 ng-TEQ/g-dry. The survival rate was 31%.
[ example 6]
In example 2, when 2g of magnesium powder was added, calcium type artificial zeolite as a heavy metal elution inhibitor was further added. The others are the same. Then, a heavy metal dissolution test was performed. The results are shown in Table 1.
[ example 7]
In example 2, the accelerating solution was changed to a 2% aqueous solution of sodium phosphite as a heavy metal elution inhibitor. The others are the same. Then, a heavy metal dissolution test was performed. The results are shown in Table 1.
[ example 8]
In example 2, the accelerating solution was changed to a 2% aqueoussolution of sodium thiocarbamate as the heavy metal elution inhibitor. The others are the same. Then, a heavy metal dissolution test was performed. The results are shown in Table 1.
TABLE 1 heavy metal dissolution test results (mg/l except content)
| Reference value mg/l | Object to be treated Middle and early stage of the disease Amount ppm of | Example 3 mg/l | Example 6 mg/l | Example 7 mg/l | Example 8 mg/l | |
| Cadmium or compounds thereof | ＜0.3 | 61 | ＜0.001 | ＜0.001 | ＜0.001 | ＜0.001 |
| Lead or compounds thereof | ＜0.3 | 1180 | 0.85 | 0.15 | 0.10 | ＜0.03 |
| 6-valent chromium compound | ＜1.5 | 120 | ＜0.05 | ＜0.05 | ＜0.05 | ＜0.05 |
| Arsenic or compounds thereof | ＜0.3 | 7.9 | ＜0.03 | ＜0.03 | ＜0.03 | ＜0.03 |
| Mercury or compounds thereof | ＜0.005 | 4.3 | ＜0.0005 | ＜0.0005 | ＜0.0005 | ＜0.0005 |
| Selenium or compounds thereof | ＜0.3 | ＜0.03 | ＜0.03 | ＜0.03 | ＜0.03 | |
| Heavy metal dissolution inhibitor | Zeolite | Phosphorous acid salts | Organic chelating agents |
[ example 9]
100g of fly ash containing dioxins (dioxins concentration: 7ng-TEQ/g-dry) having a water content of 2.3% was charged into a beaker using a heat insulating material on the outer side, and 8g of calcium oxide was added as a drying agent and sufficiently stirred. The temperature of the fly ash rose to 50 ℃. The water content in the fly ash after drying is below 0.01%. Immediately, 2g of magnesium powder was added thereto, and the mixture was uniformly stirred. Then, 60ml of water was added thereto, followed by thorough stirring. The reactant is then assayed for dioxin concentration. The concentration of dioxins in the reaction mixture was 2.8 ng-TEQ/g-dry. The survival rate was 40%.
[ example 10]
100g of fly ash containing dioxins (dioxins concentration: 7ng-TEQ/g-dry) having a water content of 2.3% was charged into a beaker using a heat insulating material on the outer side, 8g of calcium oxide was added as a drying agent, and the mixture was sufficiently stirred. The temperature of the fly ash rose to 50 ℃. The water content in the fly ash after drying is below 0.01%. 2g of magnesium powder and 25g of calcium oxide as a heat generating agent for heating were immediately added thereto, and the mixture was uniformly stirred. Then, 60ml of water was added thereto, followed by thorough stirring. The temperature of the mixture rose to 100 ℃. The reactant is then assayed for dioxin concentration. The concentration of dioxins in the reaction mixture was 1.8 ng-TEQ/g-dry. The survival rate was 26%.
[ example 11]
100g of fly ash containing dioxins (dioxins concentration: 7ng-TEQ/g-dry) having a water content of 2.3% was charged into a beaker using a heat insulating material on the outer side, and 8g of calcium oxide was added as a drying agent and sufficiently stirred. The temperature of the fly ash rose to 50 ℃. The water content in the fly ash after drying is below 0.01%. 2g of magnesium powder and 25g of calcium oxide as a heat generating agent for heating, the surface of which was coated with vegetable oil, were immediately added and uniformly stirred. Then, 60ml of 2% alkaline washing water was added thereto, and the mixture was sufficiently stirred. The temperature of the mixture rose to 100 ℃. The reactant is then assayed for dioxin concentration. The concentration of dioxins in the reaction mixture was 1.6 ng-TEQ/g-dry. The survival rate was 23%.
As described above, the present invention can provide a method for decomposition treatment of dioxins in a solid material such as fly ash, incineration ash, waste such as sludge or oil sludge containing dioxins, and soil (object to be treated). The decomposition treatment method according to the present invention is safe and simple, does not require excessive energy, does not require a special apparatus, does not generate a new toxic by-product or a by-product having an adverse effect on the environment such as global warming, and can decompose dioxins, preferably prevent elution of harmful heavy metals, and effectively utilize the treated material after the treatment.
TABLE 2 toxicity equivalence coefficients for dioxins
1 "TEF (1988)", proposed by WHO/IPCS in 1988. 2 "TEF (1997)" which was proposed by WHO/IPCS in 1997.
| Isomers | TEF(1988)*1 | TEF(1997)*2 | |
| PCDD： | 2，3，7，8-TeCDD | 1 | 1 |
| 1，2，3，7，8-PeCDD | O.5 | 1 | |
| 1，2，3，4，7，8-HxCDD 1，2，3，6，7，8-HxCDD 1，2，3，7，8，9-HxCDD | O.1 0.1 0.1 | 0.1 0.1 0.1 | |
| 1，2，3，4，6，7，8-HpCDD | 0.01 | 0.01 | |
| 1，2，3，4，6，7，8，9-OCDD | 0.001 | 0.0001 | |
| Others | 0 | 0 | |
| PCDF： | 2，3，7，8-TeCDF | 0.1 | 0.1 |
| 1，2，3，7，8-PeCDF 2，3，4，7，8-PeCDF | 0.05 0.5 | 0.05 0.5 | |
| 1，2，3，4，7，8-HxCDF 1，2，3，6，7，8-HxCDF 1，2，3，7，8，9-HxCDF 2，3，4，6，7，8-HxCDF | 0.1 0.1 0.1 0.1 | 0.1 0.1 0.1 0.1 | |
| 1，2，3，4，6，7，8-HpCDF 1，2，3，4，7，8，9-HpCDF | 0.01 0.01 | 0.01 0.01 | |
| 1，2，3，4，6，7，8，9-OCDF | 0.001 | 0.0001 | |
| Others | 0 | 0 | |
TABLE 3 toxicity equivalence factor of coplanar PCBs
3 "TEF (1993)" which was proposed by WHO/IPCS in 1993. 4 "TEF (1997)" which was proposed by WHO/IPCS in 1997.
| Isomers | TEF(1993)*3 | TEF(1997)*4 | |
| No ortho-position body | 3，4，4′，5-TeCB(#81) 3，3′，4，4′-TeCB(#77) 3，3′，4，4′，5-PeCB(#126) 3，3′，4，4′，5，5′-HxCB(#169) | - 0.0005 0.1 0.01 | 0.0001 0.0001 0.1 0.01 |
| A ortho-isomer | 2′，3，4，4′，5-PeCB(#123) 2，3′，4，4′，5-PeCB(#118) 2，3，3′，4，4′-PeCB(#105) 2，3，4，4′，5-PeCB(#114) 2，3′，4，4′，5，5′-HxCB(#167) 2，3，3′，4，4′，5-HxCB(#156) 2，3，3′，4，4′，5′-HxCB(#157) 2，3，3′，4，4′，5，5′-HpCB(#189) | 0.0001 0.0001 0.0001 0.0005 0.00001 0.0005 0.0005 0.0001 | 0.0001 0.0001 0.0001 0.0005 0.00001 0.0005 0.0005 0.0001 |
| Two ortho-isomer | 2，2′，3，4，4′，5，5′-HpCB(#180) 2，2′，3，3′，4，4′，5-HpCB(#170) | 0.00001 0.0001 | - - |
Claims (8)
1. A method for decomposition treatment of dioxins, which decomposes or dechlorinates dioxins in an object to be treated by bringing the dioxins contained in the object to be treated into a Grignard reagent state, the method comprising the steps of: the method for treating the dioxin-containing material comprises a dehydration step of removing water from the dioxin-containing material to be treated, a mixing step of mixing magnesium powder with the material to be treated obtained in the dehydration step, and a promoting liquid adding step of adding a promoting liquid for the reduction reaction of the dioxin in a Grignard reagent state in the material to be treated obtained in the mixing step.
2. The method of decomposition treatment of dioxins according to claim 1, wherein a heating step of heating the object to be treated is provided before, after and at least 1 time simultaneously with the mixing step.
3. The method of decomposition treatment of dioxins according to claim 1 or 2, wherein the heating step is performed simultaneously with and/or after the accelerating solution adding step.
4. The method of decomposition treatment of dioxins according to any one of claims 1 to 3, wherein a heavy metal elution inhibitor is added in any one of the mixing step, the heating step and the acceleration liquid adding step.
5. The method of decomposition treating dioxins according to any one of claims 1 to 4, wherein calcium oxide or calcium oxide coated with oil is used in the dehydration step and/or the heating step.
6. The method of decomposition treating dioxins according to any one of claims 1 to 5, wherein at least 1 of water, an aqueous solution of an alkali metal compound, hydrogen peroxide water, detergent water, an aqueous solution of a 1-membered or polyhydric alcohol, and an aqueous solution of an organic chelating agent is used in the acceleration liquid addition step.
7. The method of decomposition treating dioxins according to any one of claims 4 to 6, wherein the heavy metal elution inhibitor is at least 1 selected from zeolite, a salt of a phosphorus compound, and an organic chelating agent.
8. The method of decomposition treating dioxins according to any one of claims 1 to 7, wherein the material to be treated is at least 1 selected from the group consisting of fly ash contaminated with dioxins, incineration ash, waste such as sludge or oil sludge, and soil.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP166525/00 | 2000-05-31 | ||
| JP2000166525 | 2000-05-31 | ||
| JP166525/2000 | 2000-05-31 | ||
| JP177545/00 | 2000-06-13 | ||
| JP2000177545A JP2002052373A (en) | 2000-05-31 | 2000-06-13 | Method for decomposition of dioxins |
| JP177545/2000 | 2000-06-13 |
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| Publication Number | Publication Date |
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| CN1330969A true CN1330969A (en) | 2002-01-16 |
| CN1238074C CN1238074C (en) | 2006-01-25 |
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| CNB01123184XA Expired - Fee Related CN1238074C (en) | 2000-05-31 | 2001-05-31 | Decomposition treatment process for dioxine |
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| JP (1) | JP2002052373A (en) |
| KR (1) | KR20010109480A (en) |
| CN (1) | CN1238074C (en) |
| TW (1) | TW583143B (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102266712A (en) * | 2010-03-01 | 2011-12-07 | 中国科学院生态环境研究中心 | Method for inhibiting generation of dioxins |
| CN105290077A (en) * | 2014-06-16 | 2016-02-03 | 北京精诚博桑科技有限公司 | Method for coprocessing fly ash and landfill leachate |
| CN106824983A (en) * | 2017-01-10 | 2017-06-13 | 北京科技大学 | A kind of detoxification of incineration of refuse flyash Zhong bioxin and heavy metal |
| CN113633921A (en) * | 2021-09-08 | 2021-11-12 | 宜辰荣(浙江宁波)环境工程技术有限公司 | Fly ash dechlorination method |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4901268B2 (en) * | 2006-03-31 | 2012-03-21 | 中国電力株式会社 | Method for suppressing elution of harmful trace elements and elution inhibitor for coal addition used therefor |
| JP2012030198A (en) * | 2010-08-03 | 2012-02-16 | Omega:Kk | Reattachment prevention mechanism to soil, such as heavy metal |
| CN108101336B (en) * | 2016-11-25 | 2020-09-11 | 中国石油化工股份有限公司 | Drying treatment process for residual activated sludge |
-
2000
- 2000-06-13 JP JP2000177545A patent/JP2002052373A/en active Pending
-
2001
- 2001-05-16 TW TW090111688A patent/TW583143B/en not_active IP Right Cessation
- 2001-05-21 KR KR1020010027758A patent/KR20010109480A/en not_active Application Discontinuation
- 2001-05-31 CN CNB01123184XA patent/CN1238074C/en not_active Expired - Fee Related
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102266712A (en) * | 2010-03-01 | 2011-12-07 | 中国科学院生态环境研究中心 | Method for inhibiting generation of dioxins |
| CN105290077A (en) * | 2014-06-16 | 2016-02-03 | 北京精诚博桑科技有限公司 | Method for coprocessing fly ash and landfill leachate |
| CN106824983A (en) * | 2017-01-10 | 2017-06-13 | 北京科技大学 | A kind of detoxification of incineration of refuse flyash Zhong bioxin and heavy metal |
| CN113633921A (en) * | 2021-09-08 | 2021-11-12 | 宜辰荣(浙江宁波)环境工程技术有限公司 | Fly ash dechlorination method |
Also Published As
| Publication number | Publication date |
|---|---|
| KR20010109480A (en) | 2001-12-10 |
| JP2002052373A (en) | 2002-02-19 |
| CN1238074C (en) | 2006-01-25 |
| TW583143B (en) | 2004-04-11 |
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