JP2005097431A - Iron sulfide composition, its production method, heavy metals-treatment agent and treatment method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new iron sulfide composition excellent in durability and treatment capability of heavy metals, to provide a method which produces the new iron sulfide composition, further to provide a heavy metals-treatment agent containing the iron sulfide composition as an active principle, and to provide a method which treats heavy metals contained in ashes, soil, waste water and so on to render those metals harmless by using the treatment agent. <P>SOLUTION: The method comprises treating wastes containing heavy metals using an iron sulfide composition as a heavy metals-treatment agent, wherein the iron sulfide composition is comprised of an iron sulfide having a maquinawate structure shown by FeM<SB>x</SB>N<SB>y</SB>S<SB>z</SB>as an essential component of constituting element (in the formula, M shows an alkaline earth metal, N shows an alkali metal, x, y and z show mol ratio, wherein 0.01<x≤0.5, 0<y≤0.2, 0.7≤z≤1.4) and at least one kind selected from the group consisting of organic acids, salts of organic acids other than alkali metal salts, ketones, water-soluble polymer compounds, weak inorganic acids, and salts of weak inorganic acids other than alkali metal salts. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a novel iron sulfide composition excellent in durability, a method for producing the same, a heavy metal treating agent containing the novel iron sulfide composition as an active ingredient, and various heavy metals using the heavy metal treating agent. The present invention relates to a method for detoxification of wastes contained.

  Generally known industrial iron sulfide or iron sulfide made by melting iron powder and sulfur has a pyrotite structure, and a solution containing iron (II) ions and a solution containing sulfur ions are mixed. It is disclosed that the iron sulfide generated by this has a makinawite structure (see, for example, Non-Patent Documents 1 and 2).

  It is widely known that the waste containing various heavy metals is detoxified using iron sulfide (see, for example, Patent Documents 1, 2, 3, 4, 5, and 6), and industrial iron sulfide. A method of treating harmful heavy metals such as Pb, Cd, Cr, Hg and As in an aqueous solution using (pilotite structure) or the like is disclosed.

  In addition, it is also known to treat heavy metals using a makinawite-structured iron sulfide prepared by mixing a solution containing iron (II) ions and a solution containing sulfur ions. The sulfide obtained by this method is also known. Iron is known to have a higher ability to treat heavy metals than iron sulfide with a pyrotite structure, and a solution containing iron (II) ions and a solution containing sulfur ions, or a mixture of these solutions A method for treating harmful heavy metals using the obtained iron sulfide has been disclosed (see, for example, Patent Documents 7, 8, 9, 10, 11, and 12).

  However, the iron sulfide having a makinawite structure is very easily oxidized, reacts with moisture and oxygen in the air, decomposes into sulfur and iron (III) hydroxide, and easily reduces the ability to treat heavy metals. Therefore, conventionally, a solution containing iron (II) ions and a solution containing sulfur ions are mixed to prepare a slurry containing iron sulfide, and the slurry is immediately mixed with an object to be treated such as waste water. It was customary. Usually, a solution containing sulfur ions uses sodium sulfide or aqueous sodium hydrosulfide solution because of its price and industrial availability. However, a skilled person who has knowledge of chemistry due to its harmfulness, corrosiveness, bad odor, etc. However, it was necessary to perform operation, and general handling was difficult. Furthermore, when used in a slurry, it is difficult to increase the concentration of iron sulfide in order to have a certain fluidity. For example, when iron sulfide slurry is produced in a factory, the transportation cost becomes large, and wastewater When used for treatment, etc., no problem occurs, but for example when adding a large amount of iron sulfide to treat fly ash or soil containing high concentrations of heavy metals, the water content of the treated material becomes too high, There were problems such as subsequent handling becoming difficult.

  On the other hand, when preparing the makinawite-structured iron sulfide powder by filtering and drying the slurry, it was necessary to operate in an inert atmosphere or add an antioxidant to prevent oxidation. It was necessary to store the obtained iron sulfide powder in a container that does not allow oxygen and moisture to permeate, or to add a reducing agent for preventing oxidation so as not to cause oxidative deterioration. Even when a reducing agent is added, the ease of oxidative degradation has not been fundamentally solved, and since the oxidation of iron sulfide starts when the reducing agent is consumed, the storage stability is extremely low.

As a method for improving the disadvantage that the heavy metal treatment activity of the iron sulfide having a makinawite structure is high but inferior in durability, the present inventors have incorporated a certain amount of alkaline earth metal into the iron sulfide, and are essential components of the constituent elements. Fe · M _x · N _y · S _z (wherein M is an alkaline earth metal, N is an alkali metal, x, y and z are molar ratios, 0.01 <x ≦ 0.5, y ≦ 0.2, 0.7 ≦ z ≦ 1.4)), and as a method for preparing such iron sulfide, a divalent iron salt It has been proposed to mix an aqueous solution, an aqueous solution containing sulfur ions, and an alkaline earth component, and to set the slurry pH after mixing to 7.0 or higher (see Patent Document 13).

Japanese Patent Publication No.49-43472

JP 47-31806 A Japanese Patent Laid-Open No. 50-13294 Japanese Patent Laid-Open No. 50-96053 Japanese Patent Laid-Open No. 52-126665 JP 60-227881 A Japanese Patent Laid-Open No. 48-11291 Japanese Patent Laid-Open No. 48-59005 JP 49-31152 A Japanese Patent Laid-Open No. 52-113559 JP 52-148473 A Japanese Patent Laid-Open No. 53-112273 JP 2002-326819 A Reviews of Pure and Applied Chemistry, (Australia), 1970, 20, 175-206 JCPDS Card (Powder Diffraction File) 15-37

  An object of the present invention is to provide a novel iron sulfide composition which is excellent in durability and excellent in processing characteristics of heavy metals and a method for synthesizing the novel iron sulfide composition in the background described above. Furthermore, the present invention also provides a method for treating and detoxifying heavy metals contained in ash, soil, wastewater, etc., using the treatment agent for heavy metals containing the iron sulfide composition as an active ingredient, and this treatment agent. The purpose.

The present inventors have made conducted studies in order to further improve the properties of iron sulfide shown in Patent Document 13, as an essential component of the constituting _{elements, Fe · M x · N y} · S z ( wherein, M Is an alkaline earth metal, N is an alkali metal, x, y and z are molar ratios, 0.01 <x ≦ 0.5, 0 ≦ y ≦ 0.2, 0.7 ≦ z ≦ 1.4 And iron sulfide having a makinawite structure represented by: and organic acid, salts of organic acids other than alkali metal salts, ketones, water-soluble polymer compounds, inorganic weak acids, and salts of inorganic weak acids other than alkali metal salts It has been found that the durability can be further improved by using an iron sulfide composition comprising at least one selected from the group consisting of an aqueous solution of a divalent iron salt and sulfur. After mixing the aqueous solution containing ions and the alkaline earth metal component, and after mixing In the process of producing iron sulfide by performing filtration, washing and drying after the slurry pH of 7.0 is not less than, organic acids, salts of organic acids other than alkali metal salts, ketones, water-soluble polymer compounds, inorganic It has been found that it can be obtained by adding one or more selected from the group of inorganic weak acid salts other than weak acids and alkali metal salts, and the present invention has been completed.

  Hereinafter, the present invention will be described in detail.

Iron sulfide for use in the iron sulfide composition of the present invention, shown in Patent Document 13, as an essential component of the constituting _{elements, Fe · M x · N y} · S z ( wherein, M is alkaline earth metal, N Is an alkali metal, x, y, and z are molar ratios, and 0.01 <x ≦ 0.5, 0 ≦ y ≦ 0.2, and 0.7 ≦ z ≦ 1.4.) It is essential that the iron sulfide has.

  The iron sulfide used in the present invention has a non-stoichiometric ratio of iron and sulfur in the same manner as that of the conventional makinawite-structured iron sulfide, and the molar ratio of sulfur to iron is 0.7 or more and 1.4 or less. It is characterized by containing an alkaline earth metal such as calcium, and the content of the alkaline earth metal is more than 0.01 and less than or equal to 0.5 in terms of molar ratio to iron. The content of the alkali metal derived from the raw material is much less than that of iron sulfide having a normal makinawite structure, and the molar ratio to iron is 0.2 or less.

  The makinawite structure is described in Non-Patent Documents 1 and 2, and according to Non-Patent Document 1, the structure is a layered compound structure having two layers of sulfur atoms with an iron atom layer in between. It is formed of repeating units of atomic layer-sulfur atomic layer-sulfur atomic layer-iron atomic layer. The XRD diffraction pattern is shown in Non-Patent Document 2 and is shown in Table 1 below.

本発明に用いる硫化鉄は、表１で示されるマキナワイト構造の硫化鉄にアルカリ土類金属が取り込まれている。アルカリ土類金属は硫化鉄中の鉄と置換して取り込まれるのではなく、アルカリ土類金属の水酸化物、または酸化物の形で、主としてマキナワイト構造中のイオウ原子層−イオウ原子層間に取り込まれているものと推定される。

In the iron sulfide used in the present invention, an alkaline earth metal is incorporated into iron sulfide having a makinawite structure shown in Table 1. Alkaline earth metal is not incorporated by replacing iron in iron sulfide, but in the form of hydroxide or oxide of alkaline earth metal, mainly incorporated between the sulfur atom layer and the sulfur atom layer in the makinawite structure. It is estimated that

  Furthermore, in the present invention, in the XRD diffraction pattern of the makinawite structure shown in Table 1 above, the surface spacing of the 001 plane is 5.03 angstroms or more and 5.53 angstroms or less and extends in the c-axis direction. When the peak intensity of 100 is 100, it is more preferable to use iron sulfide having a “modified makinawite structure” characterized by the fact that the intensity ratios of diffraction peaks from other hkl planes are all 20 or less.

  The cause of the modified makinawite structure is not clear, but the alkaline earth metal incorporated between the sulfur atomic layer and the sulfur value atomic layer in the iron sulfide increases the c-axis interval, and the a-axis and b-axis. That is, it is presumed to cause disorder of the arrangement of iron atoms and sulfur atoms.

  The reason why the durability of the iron sulfide used in the present invention is improved is not clear, but an oxidative decomposition in which a layer that prevents oxidative decomposition is formed on the surface of the iron sulfide by the alkaline earth metal incorporated in the iron sulfide. This is presumed to be because the progress of oxidization is hindered, the oxidative decomposition mechanism is changed, and the oxidative decomposition rate is lowered.

  In the present invention, when iron sulfide having a pyrotite structure is used, although the durability is excellent, the heavy metal treatment activity is low, and it is not possible to obtain an iron sulfide composition excellent in heavy metal treatment characteristics, which is the gist of the present invention. Further, when iron sulfide having a conventional makinawite structure is used, it is difficult to obtain an iron sulfide composition having poor durability and excellent durability as the gist of the present invention.

In the present invention, shown in Patent Document 13, as an essential component of the constituting elements in _{Fe · M x · N y ·} S z ( wherein, M is alkaline earth metal, N represents an alkali metal, x, y and z is The molar ratio is 0.01 <x ≦ 0.5, 0 ≦ y ≦ 0.2, 0.7 ≦ z ≦ 1.4.) The iron sulfide having a makinawite structure has an organic acid, By adding at least one selected from the group consisting of organic acid salts other than alkali metal salts, ketones, water-soluble polymer compounds, inorganic weak acids, and inorganic weak acid salts other than alkali metal salts, it becomes more durable. It is characterized by obtaining an excellent iron sulfide composition.

  The organic acid used is a carboxylic acid other than formic acid, acetic acid, propionic acid, stearic acid, oxalic acid, malonic acid, succinic acid, polyacrylic acid, glycolic acid, lactic acid, citric acid, tartaric acid, salicylic acid, and carboxylic acid Examples thereof include ascorbic acid, which is an organic acid, phenol, cresol, and alanine which is an amino acid. Among these, acetic acid, succinic acid, lactic acid, citric acid, and ascorbic acid can be exemplified as organic acids more preferable for obtaining an iron sulfide composition having excellent durability, which is the object of the present invention. In addition, examples of the salt include alkaline earth metal salts, ammonium salts, iron salts, and the like of the acids described above. However, when an alkali metal salt such as sodium or potassium is added, the cause is unknown, but the durability of iron sulfide. On the contrary, the properties are greatly reduced, so it is not preferred for the purpose of the present invention, and the most preferred salts include alkaline earth metal salts, especially calcium salts and magnesium salts.

  Examples of the ketone used include acetone, methyl ethyl ketone, and acetylacetone.

  Examples of the water-soluble polymer compound used include polyethylene glycol and polyvinyl alcohol.

  Examples of the inorganic weak acid used include boric acid, phosphoric acid, and silicic acid. Examples of inorganic weak acid salts other than alkali metal salts include the alkaline earth metal salts, ammonium salts, iron salts, and the like of the weak acids described above, but the cause of the alkali metal salts such as sodium and potassium is unknown. On the contrary, the durability of iron sulfide is greatly reduced, which is not preferable for the purpose of the present invention. The most preferable salts include alkaline earth metal salts, particularly calcium salts and magnesium salts.

  In the iron sulfide composition of the present invention, the mixing ratio of iron sulfide and these substances is not particularly limited, but if the mixing ratio of these substances relative to iron sulfide is too small, the durability improvement effect becomes insufficient. On the other hand, when the amount is too large, the content of iron sulfide is decreased, and the treatment characteristics when this composition is used as a heavy metal treating agent is deteriorated. Accordingly, although the optimum amount varies depending on the substance to be used, it can be exemplified by 0.1 to 50% by weight, preferably 0.2 to 40% by weight, more preferably 0.5 to 30% by weight based on iron sulfide. It can be illustrated.

  The reason why the durability of iron sulfide is further improved by using the iron sulfide composition of the present invention is not clear, but the coating of the iron sulfide surface hinders the progress of oxidation, or iron sulfide as a reducing component. It is presumed to prevent the progress of oxidation.

  Next, the manufacturing method of the iron sulfide composition of this invention is demonstrated in detail.

  The iron sulfide composition of the present invention comprises mixing an aqueous solution of a divalent iron salt, an aqueous solution containing sulfur ions, and an alkaline earth metal component, and setting the slurry pH after mixing to 7.0 or higher, In the process of producing iron sulfide by washing and drying, a group of organic acids, salts of organic acids other than alkali metal salts, ketones, water-soluble polymer compounds, inorganic weak acids and salts of inorganic weak acids other than alkali metal salts It prepares by adding 1 or more types chosen from these.

  "Addition of one or more selected from the group consisting of organic acids, salts of organic acids other than alkali metal salts, ketones, water-soluble polymer compounds, inorganic weak acids, and salts of inorganic weak acids other than alkali metal salts" Abbreviated as “component”.

  In the present invention, first, an aqueous solution of a divalent iron salt, an aqueous solution containing sulfur ions, and an alkaline earth metal component are mixed, and the slurry pH after mixing is 7.0 or more, so that the durability is excellent. A slurry containing iron sulphide having a machina wite structure is prepared.

  The mixing order of the above three components at this time can be selected as appropriate, and the alkaline earth metal component may be mixed after mixing the aqueous solution of the divalent iron salt and the aqueous solution containing sulfur ions. An aqueous solution of a divalent iron salt and an alkaline earth metal component may be mixed, and then mixed with an aqueous solution containing a sulfur ion, or an aqueous solution containing a sulfur ion and an alkaline earth metal component may be mixed and mixed. An aqueous solution of an iron salt may be mixed, and an optimum method for the production process can be selected. In addition, in the mixing method at this time, when an alkaline earth metal is present when an aqueous solution containing a divalent iron salt and an aqueous solution containing sulfur ions are mixed to produce iron sulfide, This method is more preferable as a mixing method because it has a modified makinawite structure.

  The aqueous solution of the divalent iron salt used in the present invention is not particularly limited as long as it is a water-soluble divalent iron salt, and specifically, iron (II) chloride, iron (II) nitrate, iron (II) sulfate. Examples thereof include iron (II) acetate. Further, the concentration of the aqueous solution of the iron salt is not particularly limited, but when considering productivity and handling, the concentration of the specific divalent iron salt is 1 to 25 wt%, more preferably 3 to 20 wt% as Fe. A range can be illustrated.

  The solution containing sulfur ions used in the present invention is not particularly limited as long as it contains sulfur ions. Alkali metal salt sulfides and hydrosulfides, ammonium salt sulfides and hydrosulfides, alkaline earth metal solutions Any sulfide or hydrosulfide dissolved in water can be suitably used. In addition, the concentration of the solution containing sulfur ions is not particularly limited. However, when considering productivity and handling, the specific sulfur ion concentration is in the range of 1 to 15 wt%, more preferably 2 to 10 wt% as S. Can be illustrated.

  The alkaline earth metal component is not particularly limited as long as it is water-soluble, and even if it does not show water solubility such as carbonate, it can be used that dissolves in an acidic solution. Specific examples of the alkaline earth metal component include alkaline earth metal chlorides, carboxylates, nitrates, hydroxides, and sulfides.

  The mixing ratio of the aqueous solution of the divalent iron salt and the aqueous solution containing sulfur ions is not particularly limited, but considering the productivity and characteristics, the molar ratio of Fe and S is 1: 0.7 to 1.8, More preferably, mixing is performed so as to be in a range of 1: 0.8 to 1.5.

  The mixing ratio of the divalent iron salt aqueous solution and the alkaline earth metal component varies depending on the type of alkaline earth metal, but if the amount of alkaline earth metal is small, iron sulfide having a makinawite structure with excellent durability can be obtained. Absent. Therefore, when the alkaline earth metal component is magnesium (Mg), it is preferable to mix so that the molar ratio of Fe and Mg is 1: 0.04 or more. When the alkaline earth metal component is calcium (Ca) It is preferable to mix so that the molar ratio of Fe and Ca is 1: 0.03 or more. When the alkaline earth metal component is strontium (Sr), the molar ratio of Fe and Sr is 1: 0.02 or more. It is preferable to mix so that the molar ratio of Fe to Ba is 1: 0.01 or more when the alkaline earth metal component is barium (Ba).

  The mixing operation is not particularly limited, and a semi-batch method or a continuous method known in chemical engineering can be used.

  The temperature at the time of mixing is not specifically limited, It is not necessary to cool and heat, For example, the temperature of 10-60 degreeC can be illustrated.

  Stirring at the time of mixing is not particularly limited, and there is no particular problem as long as the stirring strength does not cause retention of the slurry containing iron sulfide to be generated.

  The mixing speed of the raw materials is not particularly limited, but if the mixing is too slow, the productivity may be reduced, and if it is too fast, local stagnation and increase in viscosity may occur. Therefore, for example, in the case of a semi-batch type, the addition rate should be selected such that all the raw materials are mixed in 1 to 240 minutes, more preferably 3 to 120 minutes. The time may be 10 to 240 minutes, more preferably 15 to 120 minutes.

  As described above, the slurry containing the iron sulfide of the present invention is obtained when the mixing operation is completed. At this time, it is essential that the slurry pH at the end of the mixing operation is 7.0 or more. is there. An alkali source may be added after mixing to make the slurry pH 7.0 or more, but it is more preferable to add the alkali source to the aqueous solution containing sulfur ions in advance. The alkali source is not particularly limited, and examples thereof include alkali metal hydroxides and alkaline earth metal hydroxides. Specific examples include sodium hydroxide, potassium hydroxide, calcium hydroxide, and barium hydroxide. it can. When the slurry pH is less than 7.0, the alkaline earth metal is not taken into the iron sulfide and the iron sulfide of the present invention cannot be obtained. The slurry pH is preferably as high as possible, and is preferably 8.0 or more, more preferably 10.0 or more, and still more preferably around 12.0.

  Further, after the mixing of the raw materials is completed, in order to make the entire slurry generated uniform, stirring may be continued as it is and aging may be performed. The aging time is not particularly limited, and for example, a time of 0 to 300 minutes can be exemplified.

  In the present invention, it is necessary to use iron sulfide prepared by the above method. This is because it is difficult to prepare iron sulfide having excellent durability when this condition is exceeded, and an iron sulfide composition containing iron sulfide obtained by such a method is an object of the present invention. This is because the properties as a heavy metal treating agent are poor.

  In the present invention, an “additional component” may be added to the slurry containing iron sulfide obtained in this way to obtain an iron sulfide composition-containing slurry, which may be used as it is for the treatment of heavy metals. The addition method of the “addition component” at this time is not particularly limited, and the “addition component” may be added during the synthesis of iron sulfide, or the “addition component” may be added after preparing the slurry containing iron sulfide. It may be added.

  However, when such a slurry-like iron sulfide composition is used as it is for heavy metal treatment, the transportation cost becomes enormous, and in order to treat fly ash and soil containing high concentrations of heavy metals, a large amount is required. When the addition is performed, the water content of the object to be processed becomes too high, and the subsequent handling may be difficult. Therefore, it is aged as necessary, filtered and washed, and then dried to obtain an iron sulfide composition powder.

  In the present invention, as described above, an iron sulfide composition-containing slurry is prepared, followed by filtration, washing and drying to prepare an iron sulfide composition. In this case, in the filtration and washing step, Part of the “additive component” may be lost. Therefore, it is more preferable to add the “addition component” in the steps after filtration and washing of iron sulfide.

  Specific preferred methods include a method of adding “additional components” after filtration and washing of iron sulfide and then drying, or a method of adding “additional components” after drying of iron sulfide, and then mixing. The method of performing can be illustrated.

  The method of adding “additional components” after filtration and washing of iron sulfide is not particularly limited, and the method of adding “additional components” at the final stage of the filtration and washing process, or repulping the iron sulfide cake after filtration and washing A method of forming a slurry, adding an “addition component”, kneading, and subsequently drying can be exemplified.

  The method of adding the “addition component” after the iron sulfide is dried is not particularly limited, and the “addition component” may be added to the iron sulfide after drying and mixed, or may be pulverized as necessary.

  The iron sulfide composition of the present invention can be obtained by the above method.

  The iron sulfide composition of the present invention is extremely excellent in durability and exhibits extremely high performance when used as a “heavy metal treating agent” containing this as an active ingredient. The sulfide composition of the present invention alone can be used very suitably as a “heavy metal treating agent”, but it can also be used in combination with a chemical used for treating other heavy metals of alkaline or neutral type, For example, it may be used by mixing with cement or the like, or may be used in combination with an organic chelate heavy metal treating agent.

  Hereinafter, the details of the treatment agent for heavy metals of the present invention will be described.

  In the heavy metal treating agent of the present invention, the heavy metals that can be treated can include Pb, Cd, Hg, Zn, Cu, Ni, Cr, As, Se, Sb, and Mo as specific elements. . Of course, the treatment agent of the present invention can treat not only each of the above-mentioned heavy metals, but also treatment of those containing any of these elements.

  The heavy metal treatment agent of the present invention is extremely effective for the treatment of refuse incineration ash, fly ash or molten fly ash containing heavy metals. Heavy metals contained in various types of garbage are concentrated in the waste incineration ash, fly ash and molten fly ash. This is particularly noticeable in fly ash and molten fly ash, and many of the molten fly ash contain heavy metals such as lead in a percent order, and thus a detoxification treatment is required. Fly ash and molten fly ash are classified into alkaline fly ash, neutral fly ash, alkaline molten fly ash, neutral molten fly ash, etc., depending on the structure and operation method of the incinerator, and the type of garbage to be incinerated. Although it is known that the kind and content of heavy metals contained greatly differ depending on each other, the heavy metal treating agent of the present invention can be used for any kind of fly ash. The heavy metal treating agent of the present invention and water are added to and kneaded with these waste incineration ash, fly ash and molten fly ash.

  The amount of the heavy metal treating agent of the present invention varies depending on the type and total amount of heavy metals contained in waste incineration ash, fly ash and molten fly ash, and therefore cannot be specified unconditionally. 0.1 to 50 wt%, preferably 0.5 to 30 wt%, and in addition, the incineration ash, fly ash and molten fly ash are sampled in advance and the minimum addition amount is obtained by a laboratory test. It is preferable to obtain the optimum addition amount in consideration of fluctuations in the amount of heavy metals contained in the incinerated ash, fly ash and molten fly ash. Further, even if excessive addition is performed, for example, a phenomenon that mercury (Hg) becomes polysulfide and becomes soluble does not occur, and there is no problem.

  The amount of water added varies depending on the properties of the waste incineration ash, fly ash, and molten fly ash, but usually, 10 to 40 wt% can be exemplified with respect to the amount of the waste incineration ash, fly ash, and molten fly ash. The kneading method and time are not particularly limited, and a conventionally known method can be used. The soluble heavy metals are converted into insoluble sulfides or iron salts, and the treatment is performed.

  The heavy metal treatment agent of the present invention is also effective for treating soil containing heavy metals. A heavy metal treatment agent is further added to the soil containing heavy metals, if necessary, and kneaded.

  The addition amount of the heavy metal treatment agent of the present invention cannot be defined unconditionally because it varies depending on the total amount of heavy metals contained in the soil, and can be exemplified by 0.1 to 20 wt% with respect to the amount of soil to be treated. Furthermore, it is preferable to sample the soil in advance and obtain the minimum addition amount by a laboratory test, and add a slight excess amount in anticipation of safety. When the amount of water contained in the soil is small, although depending on the type of soil, water is added as necessary so that the amount of water contained in the soil is usually 10 to 60 wt%. The kneading method and time are not particularly limited, and a conventionally known method can be used. The soluble heavy metals are converted into insoluble sulfides or iron salts, and the treatment is performed.

  Furthermore, wastewater containing heavy metals can be treated using the heavy metal treatment agent of the present invention. A heavy metal treatment agent is added to and mixed with wastewater containing heavy metals. The amount of heavy metal treatment agent added depends on the total amount of heavy metals contained in the wastewater, so it cannot be specified unconditionally. The wastewater is sampled in advance and the minimum amount is obtained by a laboratory test. It is preferable. At this time, if the pH of the wastewater is low, iron sulfide may decompose and hydrogen sulfide may be generated. Therefore, it is preferable to adjust the pH of the wastewater in advance, in which case the pH of the wastewater is 3.0 or more. More preferably, it should be 6.0 or more. The mixing method and time are not particularly limited, and a conventionally known method can be used, and the heavy metals in the wastewater are treated as insoluble sulfides or iron salts. Ordinarily, inorganic coagulant precipitants used in the coagulation precipitation process, for example, ferric chloride, polyaluminum chloride, sulfuric acid band, etc. are used in combination, or polymer coagulants that increase the coagulation rate are used in combination. Is also possible.

The present invention has the following effects.
1) The iron sulfide composition of the present invention has excellent processing characteristics for heavy metals and also has excellent durability.
2) The production method of the present invention can easily produce this excellent iron sulfide composition.
3) The heavy metal treatment agent of the present invention contains this excellent iron sulfide as an active ingredient, and by using this treatment agent, heavy metals contained in ash, soil, waste water, etc. can be treated and rendered harmless. .

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples. In addition, each measuring method in an Example is as follows.

(1) Measuring method of chemical composition Fe, S, and Ca were measured using a fluorescent X-ray analyzer (manufactured by JEOL Ltd., model JSX-3200). Na and Fe were measured using an ICP emission spectrometer (model: optima 3000, manufactured by Perkin Elmer) after dissolving the sample with hydrochloric acid. After the measurement, the molar ratio of alkaline earth metal element, alkali metal element, and sulfur was determined based on iron.

(2) Measuring method of crystal structure The crystal structure was measured using an X-ray diffractometer (manufactured by Mac Science, model: MXP-3, Cu target).

(3) Durability test of iron sulfide The iron sulfide composition powder is put into a constant temperature and humidity machine at 70 ° C. and a relative humidity of 70%, subjected to a one-day durability treatment, and the main peak of X-ray diffraction of iron sulfide before the durability treatment. The intensity is I1, and the main peak intensity of X-ray diffraction of iron sulfide after endurance treatment is I2.
Iron sulfide residual rate (%) = I2 / I1 * 100
And the durability of iron sulfide was evaluated.

Example 1
In a glass reaction vessel having an internal volume of 2 liters, 600 mmol of commercially available reagents, sodium hydrosulfide, 840 mmol of sodium hydroxide, and 1000 g of water were placed and kept at 25 ° C. using a water bath while stirring and dissolving. A solution prepared by dissolving 420 mmol of iron (II) chloride and 180 mmol of calcium chloride in 600 g of water was added to this solution over 30 minutes. The pH of the slurry after the addition was 12.9. In this state, stirring was continued for 30 minutes and aging was performed. The slurry obtained after aging was filtered and washed, and then dried to obtain iron sulfide. The structure of iron sulfide at this time was a modified makinawite structure as a result of X-ray diffraction, and as a result of composition analysis, the molar ratio of each component was Fe · Ca _0.37 · Na _0.016 · S _0.98 . . To the obtained iron sulfide, 20% by weight of calcium acetate monohydrate as a reagent was added and pulverized and mixed with a ball mill to obtain a powder of an iron sulfide composition composed of iron sulfide and calcium acetate. As a result of X-ray diffraction, this iron sulfide composition mainly has an iron sulfide peak with a makinawite structure, and the calcium acetate peak is weaker than the intensity expected from the added amount, and iron sulfide and calcium acetate have some interaction. It was presumed to be a powder of an iron sulfide composition consisting of iron sulfide and calcium acetate.

  Next, a part of the obtained iron sulfide composition powder was put into a constant temperature and humidity machine of 70 ° C. and a relative humidity of 70%, and subjected to a one-day durability treatment. Peaks of sulfur, which is a decomposition product of iron sulfide, and iron (III) oxide were not observed. As a result of calculating the residual ratio of iron sulfide based on the intensity ratio of the main peak before and after the durability treatment, it was 94%.

Example 2
The same procedure as in Example 1 was performed using calcium succinate trihydrate instead of calcium acetate monohydrate. At this time, the residual ratio of iron sulfide was 95%.

Example 3
The same operation as in Example 1 was performed using calcium citrate tetrahydrate as a reagent instead of calcium acetate monohydrate. At this time, the residual ratio of iron sulfide was 93%.

Example 4
The same operation as in Example 1 was performed using calcium ascorbate dihydrate as a reagent instead of calcium acetate monohydrate. At this time, the residual ratio of iron sulfide was 96%.

Example 5
The same operation as in Example 1 was performed, except that the reagent succinic acid was used in place of calcium acetate monohydrate and the addition amount was 5% by weight. The residual ratio of iron sulfide at this time was 95%.

Comparative Example 1
The same operation as in Example 1 was performed without adding calcium acetate (durability test of iron sulfide itself). The residual ratio of iron sulfide at this time was 91%.

Comparative Example 2
The same procedure as in Example 1 was performed using sodium acetate as a reagent instead of calcium acetate monohydrate. The residual ratio of iron sulfide at this time was 10% or less, and the S peak of the iron sulfide decomposition product was the main.

  From Examples 1 to 5 and Comparative Examples 1 and 2, it can be seen that the durability of iron sulfide is further improved by using the iron sulfide composition of the present invention. It can also be seen that alkali metal salts are unsuitable for the purposes of the present invention, and conversely have the effect of reducing durability.

Example 6
Until the ripening operation, the same operation as in Example 1 was performed to prepare a slurry containing iron sulfide. The slurry after aging was filtered and washed to obtain a filter cake. The obtained filter cake was transferred to a 1000 ml polyethylene beaker and kneaded with a spoonful to obtain a paste-like iron sulfide slurry. While continuing to knead the obtained iron sulfide slurry, an aqueous acetylacetone solution (dissolved in 2 g of acetylacetone in 50 g of water) was gradually added. After completion of the addition, the slurry was dried and pulverized to obtain an iron sulfide composition powder. The residual rate was calculated | required by operation similar to Example 1 with respect to the obtained iron sulfide composition powder. At this time, the residual ratio of iron sulfide was 94%.

Example 7
The same operation as in Example 6 was performed using a polyethylene glycol aqueous solution (4 g of polyethylene glycol (average molecular weight 2000) dissolved in 50 g of water) instead of the acetylacetone aqueous solution. At this time, the residual ratio of iron sulfide was 93%.

  Next, the result of having processed heavy metals using the iron sulfide composition of the present invention is shown.

Example 8
Using alkaline fly ash containing 2400 ppm of lead, 160 ppm of chromium and 2.1 ppm of mercury, the processing characteristics of heavy metals were examined. To 100 parts by weight of alkaline fly ash, 30 parts by weight of water and the iron sulfide prepared in Examples and Comparative Examples were added and kneaded to carry out heavy metal treatment. The obtained treated fly ash was subjected to Environmental Agency Notification No. 13 dissolution test (1973), and the results are shown in Table 2.

表２の結果から明らかなように、実施例１で調製した硫化鉄組成物は良好な重金属処理特性を有しており、また、比較例１で調製した硫化鉄よりも７０℃、相対湿度７０％で１日耐久処理を行なったあとの重金属処理特性の低下がより小さく、本発明の硫化鉄組成物とすることにより、硫化鉄の耐久性がより向上することがわかる。

As is apparent from the results in Table 2, the iron sulfide composition prepared in Example 1 has good heavy metal treatment characteristics, and is 70 ° C. and relative humidity 70 than the iron sulfide prepared in Comparative Example 1. It can be seen that the durability of the iron sulfide is further improved by using the iron sulfide composition of the present invention, since the deterioration of the heavy metal treatment characteristics after the one-day durability treatment at% is smaller.

Claims (14)

As an essential component of the constituent element, Fe · M _x · N _y · S _z (wherein M is an alkaline earth metal, N is an alkali metal, x, y and z are molar ratios, and 0.01 <x ≦ 0.5, 0 ≦ y ≦ 0.2, 0.7 ≦ z ≦ 1.4.) Iron sulfide having a makinawite structure represented by: a salt of an organic acid other than an organic acid or an alkali metal salt, An iron sulfide composition comprising at least one selected from the group consisting of ketones, water-soluble polymer compounds, inorganic weak acids, and salts of inorganic weak acids other than alkali metal salts. In the case of iron sulfide, when the plane spacing of the 001 plane is 5.03 angstroms or more and 5.53 angstroms or less and the XRD peak intensity of the 001 plane is 100, the intensity ratios of the diffraction peaks of other hkl planes are all 20 or less. The iron sulfide composition according to claim 1, which has a modified makinawite structure. The iron sulfide composition according to claim 1 or 2, wherein the organic acid is a carboxylic acid. The iron sulfide composition according to claim 3, wherein the carboxylic acid is at least one selected from the group consisting of acetic acid, succinic acid, lactic acid and citric acid. The iron sulfide composition according to claim 1 or 2, wherein the organic acid is ascorbic acid. The iron sulfide composition according to claim 1 or 2, wherein the weak inorganic acid is at least one selected from the group consisting of boric acid, phosphoric acid and silicic acid. Mixing an aqueous solution of a divalent iron salt, an aqueous solution containing sulfur ions, and an alkaline earth metal component, and setting the slurry pH after mixing to 7.0 or higher, followed by filtration, washing, and drying to produce iron sulfide One or more selected from the group consisting of organic acids, organic acid salts, ketones, water-soluble polymer compounds, inorganic weak acids and salts of inorganic weak acids other than alkali metal salts after filtration and washing of iron sulfide The method for producing an iron sulfide composition according to any one of claims 1 to 6, wherein the iron sulfide is added and then dried. Mixing an aqueous solution of a divalent iron salt, an aqueous solution containing sulfur ions, and an alkaline earth metal component, and setting the slurry pH after mixing to 7.0 or higher, followed by filtration, washing, and drying to produce iron sulfide In the process, after the iron sulfide is dried, it is selected from the group of organic acids, salts of organic acids other than alkali metal salts, ketones, water-soluble polymer compounds, inorganic weak acids and salts of inorganic weak acids other than alkali metal salts The method for producing an iron sulfide composition according to any one of claims 1 to 6, wherein one or more kinds are added and then mixed. The heavy metal processing agent which uses the iron sulfide composition in any one of Claims 1 thru | or 6 as an active ingredient. A detoxification treatment method comprising adding the heavy metal treatment agent according to claim 9 and water to any one of incineration ash, fly ash, and molten fly ash containing heavy metals, and kneading. A detoxification treatment method comprising adding the heavy metal treatment agent according to claim 9 to a soil containing heavy metals and kneading. The detoxification treatment method according to claim 11, further comprising adding water in addition to the heavy metal treatment agent. A detoxification treatment method comprising adding and mixing the heavy metal treating agent according to claim 9 to wastewater containing heavy metals. The heavy metal is one or more elements selected from the group consisting of Pb, Cd, Hg, Zn, Cu, Ni, Cr, As, Se, Sb, and Mo. Detoxification processing method of description.