JP5682809B2 - Method for producing heavy metal or fluorine elution reducing material - Google Patents

Description

  The present invention relates to an elution reducing material that suppresses the elution of harmful heavy metals mainly from contaminated soil and the like, and its manufacturing method, and more particularly to an elution reducing material suitable for contaminated soil containing harmful chemical substances and its manufacturing method. .

  In recent years, soil contamination at the site of factories and soil contamination due to illegal dumping of industrial waste, etc. have been pointed out as social problems, and various attempts have been made to prevent chemical substances from eluting from such contaminated soil. It has been.

  For example, it has been proposed that a heavy metal contained in the contaminated soil be subjected to an elution reduction treatment using magnesium oxide, light burned dolomite, cement, zeolite, iron salt, blast furnace slag, or the like. Among them, dolomite is a mineral that is produced in large quantities in Japan, such as the Kuzuu region in Tochigi Prefecture, and can be obtained at a relatively low cost. It is attracting attention (see Patent Document 1 below).

By the way, this light-fired dolomite is said to suppress elution of heavy metals by causing calcium ions and magnesium ions derived from CaCO ₃ and MgCO ₃ which are the main components of dolomite to cause a pozzolanic reaction or gelation reaction. However, in the conventional light burned dolomite, when lightly burned dolomite is prepared by lightly burning the produced dolomite, the dissolution reduction effect of the light burned dolomite may vary greatly depending on the preparation conditions. There was a problem that it was difficult to set the preparation conditions.

  In addition, the use of conventional light burned dolomite alone is not sufficient to suppress elution of heavy metals and the like, and there is a problem that other elution reducing means must be used in combination to enhance the elution reduction effect. .

JP 2006-289306 A

In view of the above problems of such prior art, and an object thereof is to provide a production method excellent heavy metal or fluorine elution reducing material of elution inhibition of the heavy metals.

  As a result of diligent research by the present inventors, when a magnesium carbonate-containing mineral such as dolomite is fired at a relatively low temperature (also referred to as “light calcining” in the present invention) to produce a composition containing calcium and magnesium, It has been found that an elution reducing material having an excellent elution inhibitory effect can be prepared by using certain light firing conditions. Furthermore, it has been found that by adding magnesium oxide to the elution reducing material, the action of reducing the elution of heavy metals can be further enhanced. That is, the present inventors have a remarkable effect of reducing elution of heavy metals by coexisting a magnesium oxide and a composition containing calcium and magnesium produced by treating a magnesium carbonate-containing mineral under a specific light baking condition. Thus, the present invention has been conceived.

In the present invention, dolomite is lightly burned under the condition of 650 to 1000 ° C., and when the weight reduction rate due to the light burn becomes 9 to 20%, the light burn is terminated , so that the BET specific surface area is 5 ~10m a ² / g, and a peak radius of the pore size distribution and light burned product is in the range of: 10 to 20 nm, elution reducing material added to the said light sintered product with magnesium oxide and ferrous sulfate A method for producing a heavy metal or fluorine elution reducing material is provided.

In addition, the method for producing a heavy metal or fluorine elution reducing material according to the present invention is a method in which dolomite is lightly burned under a condition of 650 to 1000 ° C., and the weight reduction rate due to the light baking becomes 9 to 20%. By ending the light baking, it becomes possible to obtain a light baking product having a BET specific surface area of 5 to 10 m ² / g and a peak radius of the pore size distribution in the range of 10 to 20 nm. . Therefore, the elution reducing material which can exhibit the outstanding elution inhibitory effect can be manufactured by adding the light-burning product obtained through such a process and preparing an elution reducing material. In addition, by combining the lightly burned product, magnesium oxide, and ferrous sulfate, it is possible to produce an elution reducing material for heavy metals or fluorine that can exhibit a more excellent elution suppressing effect for heavy metals and the like. .

As described above, according to the present invention, it is possible to provide a manufacturing method excellent heavy metal or fluorine elution reducing material of elution inhibition of the heavy metals.

The graph which plotted the relationship between light baking time (minutes), a BET specific surface area (m < ² > / g), and a brain value (cm < ² > / g) about the elution reduction material of an Example and a comparative example. The graph which showed the pore size distribution measured about the elution reduction material of an Example and a comparative example. The graph which plotted the relationship between the light baking time (min) measured about each light baking product used by the Example and the comparative example, and weight reduction rate (%).

Hereinafter, it is assumed that a method for manufacturing the engagement Ru heavy metal or fluorine elution reducing material in the present invention.

As described above, the method for producing an elution reducing material according to the present invention lightly burns dolomite under the condition of 650 to 1000 ° C., and when the weight reduction rate due to the light burning becomes 9 to 20%, By finishing the calcination , a light baked product having a BET specific surface area of 5 to 10 m ² / g and a peak radius of the pore diameter distribution in the range of 10 to 20 nm is obtained. And a ferrous sulfate are added to prepare an elution reducing material.

Dolomite is not particularly limited as long as it contains magnesium carbonate as a main component and contains calcium carbonate. In addition to naturally occurring dolomite (white dolomite), magnesium hydroxide slurry and lime milk Synthetic dolomite obtained by firing the mixture can also be used.
In addition, the dolomite produced in nature generally has a molar ratio of a double salt represented by CaO / MgO in the range of 0.70 to 1.63, CaCO ₃ is approximately 9 to 40% by weight in terms of CaO, MgCO ₃ Is approximately 10 to 38% by weight in terms of MgO.

These minerals are preferably used in the form of lumps of several mm to 100 mm, or preferably pulverized into particles before light burning, and the brain value is in the range of 2000 to 3000 (cm ² / g). More preferably, it is in the form of particles.

  As temperature conditions at the time of light baking, it is set as the range of 650-1000 degreeC, Preferably it is 700-900 degreeC, More preferably, you may be 750-850 degreeC. Moreover, in order to complete | finish light baking when the weight reduction rate by this light baking becomes 9 to 20%, although light baking time changes also with temperature conditions, it is 10 to 60 minutes normally.

  Moreover, although the weight reduction rate by light baking shall be 9-20%, Preferably it is 10-17%, More preferably, you may be 16-17%. By setting the rate of weight reduction due to light firing within such a numerical range, a composition containing calcium and magnesium can be sufficiently produced by decarboxylation from magnesium carbonate or the like, and carbonation by the decarboxylation reaction. It is considered that a lightly burned product is obtained in a state where relatively small pores formed by transient gas escape are left, that is, in a state where the BET specific surface area is large.

  In addition, about other baking conditions, such as baking atmosphere, and the baking apparatus used for baking, a conventionally well-known baking condition and baking apparatus are employable.

  On the other hand, as the magnesium oxide, generally, a fired product obtained by firing magnesium carbonate or magnesium hydroxide is used. In this case, the properties of these fired products vary depending on the firing temperature, the type of raw material, the type and amount of impurities contained in the raw material, and various properties can be used in the present invention. Among these, a fired product containing 70% by weight or more of magnesium oxide can be suitably used.

  The blending ratio of the elution reducing material is preferably 5 to 25 parts by weight of magnesium oxide, more preferably 10 to 20 parts by weight with respect to 100 parts by weight of the total amount of the light baking product and magnesium oxide. .

In the case of an elution reducing material to which water-soluble sulfate is added , the total amount of magnesium oxide and ferrous sulfate is 5 to 30 parts by weight with respect to 100 parts by weight of the elution reducing material including ferrous sulfate. It is preferable to be 10 to 20 parts by weight.
Further, for each component, the light-burned product is preferably 60 to 95 parts by weight, more preferably 80 to 90 parts by weight, and magnesium oxide is 5 to 100 parts by weight in 100 parts by weight of the elution reducing material. It is preferably 25 parts by weight, more preferably 10 to 15 parts by weight, ferrous sulfate is preferably 5 to 15 parts by weight, and more preferably 9 to 12 parts by weight.

Next, the heavy metal or fluorine elution reducing material in the present embodiment is obtained by lightly burning dolomite by the above-described method, for example, having a BET specific surface area of 5 to 10 m ² / g and a peak of pore size distribution. It contains a lightly burned product having a radius within a numerical range of 10 to 20 nm, magnesium oxide, and ferrous sulfate .

BET specific surface area of the light burned product is a 5 to 10 m ² / g, preferably from 7~10m ² / g.

Further, the light burned product is not particularly limited as long as it is a light burned product having the BET specific surface area and the pore size distribution as described above, but the brane specific surface area of the light burned product is not particularly limited. , About 3000 to 7000 cm ² / g, preferably 4000 to 6500 cm ² / g.
When the firing is advanced more than necessary, the mineral is disintegrated and becomes fine due to excessive decarboxylation, and as a result, the BET specific surface area tends to be small and the peak radius of the pore diameter distribution tends to be large.

  Hereinafter, the present invention will be described in more detail with reference to examples.

Preparation of Elution Reduction Materials (Examples and Comparative Examples) Seven samples were prepared from dolomite (Sumitomo Osaka Cement Co., Ltd., Karasawa Mining Co., Ltd.) produced in Kuzuu, Tochigi Prefecture. Not)) Lightly burned product was prepared by light baking for 5 minutes, 10 minutes, 15 minutes, 30 minutes, 60 minutes, 120 minutes.

Measurement of physical properties of light -fired products The BET specific surface area (m ² / g) of each powder was measured using a BET specific surface area measuring device (manufactured by Nippon Bell Co., Ltd., high-precision gas adsorption device “BELSORP-mini”). In addition, the brane value (cm ² / g) is measured using a brane measuring apparatus (manufactured by Maruhishi Kagaku Kikai Seisakusho Co., Ltd., “Blaine Air Permeability Fineness Measuring Device”), and after light burning relative to the weight before light burning Was measured (ie, weight loss rate (%)). The results are shown in Table 1 below.

Further, based on the above measurement results, a graph plotting the relationship between the light baking time [min], the BET specific surface area (m ² / g), and the brain value (cm ² / g) for the elution reducing material of each light baking product. Is shown in FIG.

  Furthermore, about each said light-burning product, pore diameter distribution was measured using the BET specific surface area measuring apparatus (The Nippon Bell company make, high-precision gas adsorption apparatus "BELSORP-mini"). The results are shown in FIG. Moreover, the graph which plotted the relationship between the light baking time (min) measured about each light baking product and weight reduction rate (%) is shown in FIG.

Evaluation of each light-burning product Each light-burning product was added at a rate of 1 g to 100 ml of a standard solution of 5, 100 mg / l of arsenic and lead, mixed with stirring for 4 hours, and then filtrated. The concentration of heavy metals was measured using an ICP analyzer (manufactured by Varian Technologies Japan Limited, apparatus name “VARIAN ICP emission spectroscopic analyzer 730-ES”). From the measurement results, the adsorption removal rate was determined using the following calculation formula.

Adsorption removal rate [%] = (initial concentration−concentration in filtrate) ÷ initial concentration × 100

Moreover, the pH of the filtrate was also measured with a pH meter (manufactured by Horiba Ltd.). These results are shown in Tables 2 and 3 below.

  From Tables 2 and 3, and FIG. 3, the product 4 in which the dolomite was lightly burned for 15 minutes and the weight reduction rate was 9.8%, and the dolomite was lightly burned for 30 minutes and the weight reduction rate was 16.5%. The light burn product of product 5 has a large BET specific surface area compared to other light burn products, and the pH of the filtrate is kept low to about 11 or less. It is recognized that lead can exhibit an excellent adsorption action even in the long term.

Preparation of elution-reducing material Each light-burning product obtained as described above, ferrous sulfate monohydrate (manufactured by Sakai Chemical Industry Co., Ltd.) and magnesium oxide-containing fired product (manufactured by Nikkei International Co., Ltd., magnesium oxide content) 79% by weight) was mixed to prepare an elution reducing material having the composition shown in Table 4 below.

The elution reducing materials of Examples and Comparative Examples prepared as described above were added at a rate of 1 g to 100 ml of standard solutions of 5 mg / l and 100 mg / l of arsenic and lead, respectively, and stirred and mixed for 4 hours. The heavy metal concentration in the filtrate when filtered was measured using an ICP analyzer (manufactured by Varian Technologies Japan Limited, device name “VARIAN ICP emission spectroscopic analyzer 730-ES”). From the measurement results, the adsorption removal rate was determined using the following calculation formula.

Adsorption removal rate [%] = (initial concentration−concentration in filtrate) ÷ initial concentration × 100

Moreover, the pH of the filtrate was also measured with a pH meter (manufactured by Horiba Ltd.). These results are shown in Tables 5 and 6 below and FIG.

  From Table 5 and Table 6, the elution reducing material according to the present invention is obtained by adding magnesium oxide to a dolomite light burned product, and particularly by adding both magnesium oxide and ferrous sulfate to a dolomite light burned product. It is recognized that it can exhibit an excellent adsorbing action as compared with the additive-free light-burning product, and particularly, regarding lead, it is recognized that it exhibits an extremely excellent adsorbing action. Moreover, pH is also suppressed to about 11 or less, and it is recognized that the elution reducing material according to the present invention can exhibit an excellent adsorbing action in the long term.

Evaluation by Simulated Contaminated Soil While preparing the simulated contaminated soil in the following procedure, some of the elution reducing materials in the examples and comparative examples were further evaluated using the simulated contaminated soil.

Preparation of cocoon pseudo-contaminated soil Lead type nitrate, potassium arsenite, and sodium fluoride were added to sandy soil (produced in Narita, Chiba) to prepare two types of quasi-poisoned soil A and B. Further, an elution test was performed on the simulated soil A and B according to Notification No. 46 of the Environment Agency, and the concentrations of lead, arsenic and fluorine in the eluate were measured using the following apparatus. The results are shown in Table 7 below.
Lead concentration Graphite furnace atomic absorption method (manufactured by Hitachi, Ltd., apparatus name “Z-5000 type polarized Zeeman atomic absorption photometer”)
Arsenic concentration hydride atomic absorption method (manufactured by Hitachi, Ltd., apparatus name “Z-5000 type polarized Zeeman atomic absorption photometer”)
Fluorine concentration Lanthanum-alizarin complexone spectrophotometric method (manufactured by LB Tech, "Continuous flow analyzer SWAAT")

Dissolution test using simulated fouling soils A and B Using a part of the dissolution reducing materials prepared as the above examples and comparative examples, the proportion of powder was 100 kg / m ³ for simulated fouling soils A and B, respectively. Added at. Then, the elution test was conducted on the pseudo-contaminated soil after stirring and mixing in accordance with Environment Agency Notification No. 46 after the lapse of 28 days, and the above apparatus was used for the concentration of lead, arsenic and fluorine in the eluate. Measured. The results are shown in Table 8 below.

  From Table 8, the elution reducing material according to the present invention is obtained by adding magnesium oxide to a dolomite lightly burned product and adding an additive-free lightly burned product, even when added to the pseudo-polluted soil using sandy soil. In comparison, it is recognized that an excellent adsorption effect can be exhibited with respect to arsenic, lead and fluorine.

Claims (2)

As well as light burned dolomite under conditions of 650 to 1000 ° C., at Rukoto terminate the said light ware when the weight reduction rate due wherein the light yaki became 9 to 20%, BET specific surface area of 5 to 10 m ² / G and a light-burning product having a pore radius distribution with a peak radius in the range of 10 to 20 nm, and adding the light-burning product, magnesium oxide, and ferrous sulfate to prepare an elution reducing material. A method for producing a heavy metal or fluorine elution-reducing material. The process according to claim 1, heavy metal according or fluorine elution reducing material, wherein the weight reduction rate by the light burned is from 10 to 17%.

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