JP6953095B2 - Iron powder for contaminated water treatment and iron powder manufacturing method for contaminated water treatment - Google Patents

Description

The present invention relates to iron powder for treating contaminated water and a method for producing iron powder for treating contaminated water.

As a method for purifying water contaminated with heavy metals or the like, in addition to a method using a coagulant and a method using a porous adsorbent, for example, as described in Japanese Patent No. 4755159, iron powder (treatment agent) A method of depositing and removing heavy metals and the like on the surface has been proposed. The iron powder described in the above publication contains sulfur, and it is said that at least one heavy metal such as selenium, lead, cadmium and chromium can be deposited and removed on the surface of the iron powder.

According to the Waterworks Law, in addition to heavy metals such as selenium, lead, cadmium and chromium, which are removed by the method described in the above publication, the content of fluorine must be equal to or less than the standard value.

Japanese Patent No. 4755159

In view of the above circumstances, it is an object of the present invention to provide an iron powder for treating contaminated water and a method for producing iron powder for treating contaminated water, which can remove heavy metals and fluorine in the contaminated water.

The iron powder for treating contaminated water according to one aspect of the present invention, which has been made to solve the above problems, is an iron powder for treating contaminated water that removes heavy metals in contaminated water, and contains iron as a main component and silicon. It is characterized by having an iron-based precipitate containing at least one of manganese, phosphorus, sulfur and chromium in the particles.

The iron powder for treating contaminated water has an iron-based precipitate containing at least one of silicon, manganese, phosphorus, sulfur and chromium in the particles, so that the potential difference between the iron-based precipitate and the iron substrate The local battery action that occurs promotes the iron anode reaction and promotes the reduction reaction or insolubilization reaction of pollutant elements in the polluted water. Therefore, the iron powder for treating contaminated water can be removed by precipitating fluorine on the surface of the iron powder particles in addition to heavy metals in the contaminated water.

In the iron powder for treating contaminated water, the average area ratio of the iron-based precipitates in the particle cross section is preferably 0.8% or more and 50% or less. As described above, when the average area ratio of the iron-based precipitates in the particle cross section is within the above range, the iron powder for treating contaminated water effectively promotes the anode reaction of the iron base material, and in the contaminated water. Heavy metals and fluorine can be removed efficiently.

In the iron powder for treating contaminated water, the average porosity in the particles is preferably 5% or less. By setting the average porosity in the particles to be equal to or less than the above upper limit in this way, the iron powder for treating contaminated water can be produced by the atomizing method, so that the composition can be easily adjusted and the above iron system is used. Since the precipitate can be reliably formed, it can be efficiently produced.

The method for producing iron powder for treating contaminated water according to one aspect of the present invention is a method for producing iron powder for treating contaminated water that removes heavy metals in contaminated water, in which a step of preparing molten iron in a furnace and a pan are used. It is characterized by comprising a step of adding an auxiliary raw material containing at least one of silicon, manganese, phosphorus, sulfur and chromium to the molten iron, and a step of injecting water into the molten iron after the addition to pulverize the molten iron.

The method for producing iron powder for treating contaminated water includes the preparation step, the addition step, and the pulverization step. In the addition step, at least one of silicon, manganese, phosphorus, sulfur, and chromium is added to the molten iron in the pan. Since an auxiliary material containing seeds is added, the powdering step is performed before the auxiliary material is completely melted and alloyed with iron, and iron is the main component, and silicon, manganese, phosphorus, sulfur and chromium are used. An iron-based precipitate containing at least one type can be uniformly dispersed and formed in the iron powder particles. Therefore, since the iron powder for treating contaminated water obtained by the method for producing iron powder for treating contaminated water has the iron-based precipitate in the particles, the local battery action between the iron-based precipitate and the iron substrate In addition to the heavy metals in the contaminated water, fluorine can be deposited and removed on the surface of the iron powder particles.

Here, the "main component" means the component having the highest mass content. Further, "molten iron" is a concept that includes molten iron and steel in general regardless of the carbon content.

As described above, the contaminated water treatment iron powder and the contaminated water treatment iron powder produced by the method for producing contaminated water treatment iron powder of the present invention can remove heavy metals and fluorine in the contaminated water.

It is an electron microscope image of the particle cross section of the iron powder for treatment of contaminated water of one Embodiment of this invention. It is a graph which shows the removal rate of the contaminated element in the contaminated water treatment test using the prototype example of iron powder for contaminated water treatment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

[Iron powder for treating contaminated water]
The iron powder for treating contaminated water according to the present invention is used for removing heavy metals including arsenic, selenium, lead, cadmium and chromium in the contaminated water. Further, the iron powder for treating contaminated water can remove fluorine in addition to heavy metals.

The iron powder for treating contaminated water contains iron as a main component and iron-based precipitates containing at least one of silicon, manganese, phosphorus, sulfur and chromium (hereinafter, may be collectively referred to as specific elements) in the particles. Have in. That is, the iron powder for treating contaminated water has the iron-based precipitate in the particles of the iron base material made of iron or an iron alloy.

The iron powder for treating contaminated water may be, for example, atomized iron powder, cast iron powder, reduced iron powder, etc. It is preferably atomized iron powder.

Examples of elements other than iron contained in the iron powder for treating contaminated water and the above-mentioned specific elements include carbon, oxygen, copper, nickel, molybdenum, zinc, aluminum and cobalt. In addition, the iron powder for treating contaminated water may contain unavoidable impurities other than elements that are intentionally added. In the present invention, the unavoidable impurities are not the target of the specific element contained in the iron-based precipitate. That is, even if silicon, manganese, phosphorus, sulfur or chromium is inevitably contained, the iron-based precipitate is not considered to "contain at least one of silicon, manganese, phosphorus, sulfur and chromium". The content of the unavoidable impurities is usually less than 1% by mass, preferably less than 0.01% by mass in terms of the content of a single element.

FIG. 1 illustrates an example of an image obtained by taking a cross section of the particles of the iron powder for treating contaminated water using a scanning electron microscope. In the figure, the black spots are iron-based precipitates. As described above, it is preferable that the iron powder for treating contaminated water has a plurality of iron-based precipitates dispersed in the particles.

The iron-based precipitate of the iron powder for treating contaminated water is formed with the above-mentioned specific element as a nucleus, contains iron as a main component, and usually contains oxygen.

The lower limit of the average particle size of the iron powder for treating contaminated water is preferably 1 μm, more preferably 10 μm. On the other hand, the upper limit of the average particle size of the iron powder for treating contaminated water is preferably 1000 μm, more preferably 500 μm, and even more preferably 100 μm. If the average particle size of the contaminated water treatment iron powder is less than the above lower limit, the production efficiency and handleability of the contaminated water treatment iron powder may be insufficient. On the contrary, when the average particle size of the iron powder for treating contaminated water exceeds the above upper limit, heavy metals and fluorine in the contaminated water may not be sufficiently removed due to the small surface area. The "average particle size" refers to a particle size in which the particle size distribution is determined by a dry sieving test using a sieve specified in JIS-Z8801 (2006) and the cumulative mass is 50% in this particle size distribution. ..

The lower limit of the total content of the specific elements in the iron powder for treating contaminated water is preferably 0.3% by mass, more preferably 0.5% by mass, and even more preferably 1% by mass. On the other hand, as the upper limit of the total content of the specific element in the iron powder for treating contaminated water, 5% by mass is preferable, 3% by mass is more preferable, and 2% by mass is further preferable. If the total content of the specific elements in the iron powder for treating contaminated water is less than the above lower limit, it may be difficult to form a sufficient amount of iron-based precipitates. On the contrary, when the total content of the specific elements in the iron powder for treating contaminated water exceeds the above upper limit, the production cost of the iron powder for treating contaminated water may increase unnecessarily.

The lower limit of the total content of the specific elements in the iron-based precipitate of the iron powder for treating contaminated water is preferably 1% by mass, more preferably 2% by mass. If the total content of the specific elements is less than the above lower limit, the efficiency of removing heavy metals and fluorine in the contaminated water may be insufficient. On the other hand, the total content of the specific elements is not particularly limited and is appropriately determined depending on the components of the contaminated water to be removed, and can be, for example, 50% by mass.

The upper limit of the average porosity in the particles of the iron powder for treating contaminated water is preferably 5%, more preferably 3%. On the other hand, the upper limit of the average porosity in the particles of the iron powder for treating contaminated water is not particularly limited, and the physical limit value is 0%. When the average porosity in the particles of the iron powder for treating contaminated water exceeds the above upper limit, it is difficult to produce by the water atomization method, so that it is difficult to adjust the overall composition and the content of iron-based precipitates. There is a risk of becoming. That is, the iron powder for treating contaminated water can be produced relatively efficiently by the water atomization method by setting the average porosity to the above upper limit or less. The porosity is measured as the area ratio of the voids in the electron microscope observation image of the particle cross section.

The lower limit of the average area ratio of iron-based precipitates in the particle cross section of the iron powder for treating contaminated water is preferably 0.8%, more preferably 1.0%. On the other hand, the upper limit of the average area ratio of iron-based precipitates in the particle cross section of the iron powder for treating contaminated water is preferably 50%, more preferably 30%. If the average area ratio of iron-based precipitates in the particle cross section of the contaminated water treatment iron powder is less than the above lower limit, heavy metals and fluorine cannot be efficiently precipitated due to insufficient local battery action. , Heavy metals and fluorine in contaminated water may not be sufficiently removed. On the contrary, when the average area ratio of iron-based precipitates in the particle cross section of the iron powder for treating contaminated water exceeds the above upper limit, the area of the iron base material serving as the anode in the local battery operation becomes relatively small. Heavy metals and fluorine in contaminated water may not be sufficiently removed. The average area ratio of iron-based precipitates in the particle cross section of the iron powder for treating contaminated water is determined by using image analysis software to obtain an electron microscope observation image of the particle cross section in the iron-based precipitate portion and the iron substrate portion. It can be measured by digitizing. In this case, the threshold value for binarization is appropriately set, but since the contrast between the iron-based precipitate and the iron substrate in the electron microscope observation image is large, as long as the threshold value is set within an appropriate range according to common general knowledge. , The measurement error due to binarization is sufficiently small.

The lower limit of the average diameter (circular equivalent diameter) of the iron-based precipitate in the particle cross section of the contaminated water treatment iron powder is preferably 0.1 μm, more preferably 0.15 μm. On the other hand, the upper limit of the average diameter of the iron-based precipitate in the particle cross section of the iron powder for treating contaminated water is preferably 10 μm, more preferably 1 μm. If the average diameter of iron-based precipitates in the particle cross section of the iron powder for treating contaminated water is less than the above lower limit, the local battery operation may be insufficient. On the contrary, when the average diameter of iron-based precipitates in the particle cross section of the contaminated water treatment iron powder exceeds the above upper limit, the ability of each particle of the contaminated water treatment iron powder to remove heavy metals and fluorine varies. As a result, the ability of the iron powder for treating contaminated water as a whole to remove heavy metals and fluorine may be insufficient.

<Advantage>
The iron powder for treating contaminated water has the above-mentioned iron-based precipitate in the particles, so that a potential difference is generated between the iron-based precipitate and the iron base material, and the anode reaction of the iron base material is caused by the local battery action. By promoting the above, fluorine can be deposited on the particle surface in addition to heavy metals and can be removed relatively efficiently.

[Iron powder manufacturing method for contaminated water treatment]
The above-mentioned iron powder for treating contaminated water can be produced by the method for producing iron powder for treating contaminated water according to the embodiment of the present invention.

The iron powder production method for contaminated water treatment includes a step of preparing molten iron in a furnace <preparation step> and a step of adding an auxiliary raw material containing at least one of silicon, manganese, phosphorus, sulfur and chromium to the molten iron in a pan. It includes a <addition step> and a step of injecting water into the molten iron after adding an auxiliary raw material to pulverize it <a pulverization step>.

<Preparation process>
In the preparation step, molten iron is prepared in a furnace such as a converter or an electric furnace. In this preparation step, for example, a known refining treatment for removing impurities such as desiliconization, dephosphorization, decarburization, and deoxidation may be performed, or a raw material other than iron may be added to adjust the components of molten iron. ..

<Addition process>
In the addition step, an auxiliary raw material containing a specific element as a core for forming the iron-based precipitate is added in the ladle. In this way, by adding the auxiliary material in the ladle, the time from the addition of the auxiliary material to the next pulverization step is shortened, and the specific element in the auxiliary material is not completely alloyed with iron. It is considered that the molten iron can be pulverized in a state where clusters of specific elements are dispersed in the molten iron (specific elements are microscopically unevenly distributed). As a result, iron-based precipitates can be formed with clusters of specific elements dispersed in molten iron as nuclei.

In this addition step, the auxiliary raw material may be added later to the ladle that stores the molten iron extracted from the furnace, but by pouring the molten iron into the ladle in which the auxiliary material has been added in advance, efficiency can be achieved in a short time. Auxiliary raw materials can be added to molten iron well.

Further, the auxiliary raw material is incorporated into the iron base material of the iron powder for treating contaminated water obtained by partially alloying. Therefore, it is preferable to adjust the composition of the molten iron prepared in the previous preparation step in consideration of the auxiliary raw materials added in this addition step. On the contrary, even if the amount of the auxiliary raw material added is the same, the amount and composition of the iron-based precipitate formed by the composition of the molten iron prepared in the preparation step changes. Therefore, it is preferable to select the type and amount of the auxiliary raw material to be added to the molten iron in the addition step in consideration of the composition of the molten iron prepared in the preparation step.

(Auxiliary raw material)
As the auxiliary raw material, for example, a compound of a specific element such as ferrosilicon, ferromanganese, iron phosphorus, iron sulfide, and ferrochrome and iron is preferably used. These auxiliary raw materials may be partially or wholly the same as the treatment agent used for the refining treatment in the preparation step or the material added for adjusting the composition of the molten steel.

<Powdering process>
In the pulverization step, the molten iron is rapidly cooled and pulverized by the water atomization method while making the molten iron finer. At this time, it is considered that the iron powder for treating contaminated water can be obtained by forming iron-based precipitates in the powder particles with clusters of specific elements dispersed in the molten iron as nuclei.

In the water atomization method, molten iron flows down and water is sprayed onto the flowing molten iron to make the molten iron finer and rapidly cool it to obtain iron powder. By adjusting the amount and pressure of water sprayed on the molten iron, the particle size of the obtained iron powder can be adjusted.

<Advantage>
The method for producing iron powder for treating contaminated water includes the above preparation step, the above addition step, and the above pulverization step. In the addition step, an auxiliary raw material containing a specific element is added to the molten iron in a pan. The iron-based precipitate can be uniformly dispersed and formed in the iron powder particles by performing a pulverization step before the powder is completely dispersed. Therefore, in the contaminated water treatment iron powder obtained by the contaminated water treatment iron powder production method, heavy metals and fluorine in the contaminated water are precipitated on the surface of the iron powder by the local battery action of the iron-based precipitate and the iron base material. It can be removed efficiently.

Further, in the method for producing iron powder for treating contaminated water, since the auxiliary material is added to the molten iron in the ladle in the addition process, it is possible to prevent the melting point of the refractory of the furnace in which the preparation process is performed from being lowered by the auxiliary material. can. Therefore, in the method for producing iron powder for treating contaminated water, the deterioration of the refractory of the furnace in which the smelting process is performed is relatively small, and the downtime for cooling and maintenance can be suppressed to improve the production efficiency.

[Other Embodiments]
The above embodiment does not limit the configuration of the present invention. Therefore, in the above-described embodiment, the components of each part of the above-described embodiment can be omitted, replaced or added based on the description of the present specification and common general technical knowledge, and all of them are construed as belonging to the scope of the present invention. Should be.

The iron powder for treating contaminated water according to the present invention is not limited to that produced by the above-mentioned method for producing iron powder for treating contaminated water.

Hereinafter, the present invention will be described in detail based on Examples, but the present invention is not limitedly interpreted based on the description of this Example.

<Prototype example 1>
The total amount of molten iron prepared by melting the iron raw material in an electric furnace and adding 0.1% by mass of ferromanganese to the iron raw material to remove impurities is added in advance with 0.1% by mass of ferromanganese to the iron raw material. After taking it out into the prepared pan, it was pulverized by the water atomization method to obtain Prototype Example 1 of iron powder for treating contaminated water having an average particle size of 90 μm. The "average particle size" was calculated by approximating the "particle size distribution" measured by a dry sieving test using a sieve specified in JIS-Z8801 (2006) with a rosin Ramler distribution.

<Prototype example 2>
The total amount of molten iron prepared by melting the iron raw material in an electric furnace and adding 0.2% by mass of ferromanganese to the iron raw material to remove impurities is preliminarily converted to 0.1% by mass of ferromanganese and iron. Prototype 2 of iron powder for treating contaminated water having an average particle size of 92 μm was obtained by taking it out into a pan containing 0.8% by mass of iron sulfide and then pulverizing it by the water atomization method. rice field.

<Prototype example 3>
The total amount of molten iron prepared by melting the iron raw material in an electric furnace and adding 3.5% by mass of iron sulfide to remove impurities is preliminarily made into ferromanganese and iron with a ratio of 0.1% by mass of the iron raw material. Prototype 3 of iron powder for treating contaminated water having an average particle size of 88 μm was obtained by taking it out into a pan containing 0.3% by mass of iron sulfide and then pulverizing it by the water atomization method. rice field.

The content of trace elements in Prototype Examples 1 to 3 of iron powder for treating contaminated water was measured. Specifically, the contents of C and S were measured by an infrared absorption method, and the contents of Si, Mn and P were measured by ICP (inductively coupled plasma) emission spectroscopy. The results are shown in Table 1 below.

Further, the particles of the iron powder for treating contaminated water were cut by polishing the sample obtained by solidifying the trial examples 1 to 3 of the iron powder for treating contaminated water with a resin by 1 μm with diamond abrasive grains. Then, this particle cross section was photographed using "Quanta200FEG" manufactured by FEI. The scanning electron microscope was set to a voltage of 15.0 kV, a working distance of 10 mm from the lens to the object surface, and a BSE (reflected electron image) was acquired. Further, when acquiring the electronic image, the contrast was set to about 90 and the brightness was set to about 40. Furthermore, using this electron microscope image with the image analysis software "WIN-ROOF ver 5.5.0" of Mitani Shoji Co., Ltd., pixels with a brightness range of 80 or more and 175 or less in 256 gradations (0 to 255) are iron-based precipitates. The binarization process for extracting as a region was performed, and the noise removal (set value 0.001) and the fill-in-the-blank process were performed to calculate the area ratio of the iron-based precipitate.

In addition, the composition of the iron-based precipitate portion of the cross section of the sample was analyzed by energy dispersive X-ray analysis (EDX). Specifically, three particles having different particle sizes are selected from each sample, energy dispersive X-ray analysis is performed on the three iron-based precipitates in each particle, and the iron powder for treating contaminated water is subjected to energy dispersive X-ray analysis. The composition of the iron-based precipitate was calculated by weighted averaging based on the particle size distribution of the prototype.

Table 2 below shows the area ratio of the iron-based precipitates of Prototype Examples 1 to 3 of the iron powder for treating contaminated water and the composition of the iron-based precipitates. In addition, "-" in the table means that the element was not detected.

As the test contaminated water, an aqueous solution of disodium hydrogen arsenide heptahydrate having an As concentration adjusted to 1 mg / L, an aqueous solution of sodium selenate having an Se concentration adjusted to 1 mg / L, and a Cr concentration adjusted to 1 mg / L. An aqueous solution of potassium dichromate, an aqueous solution of lead nitrate with a Pb concentration adjusted to 1 mg / L, an aqueous solution of cadmium nitrate with a Cd concentration adjusted to 1 mg / L, and an aqueous solution of sodium fluoride with an F concentration adjusted to 1 mg / L. I prepared.

0.1% by mass of Prototype Examples 1 to 3 of iron powder for treating contaminated water was added to the above contaminated water for testing, and the mixture was continuously shaken at room temperature for 24 hours (200 rpm, shaking width was 3 to 5 cm), and then the opening was 0. After filtering with a .45 μm filter, a contaminated water treatment test was conducted to measure the concentration of contaminated elements (heavy metals or fluorine to be removed) in the solution. The concentration of pollutant elements was measured according to JIS-K0102 (2016).

Table 3 below shows the measurement results of the concentration of residual contaminated elements in each test contaminated water after treatment by Prototype Examples 1 to 3 of iron powder for contaminated water treatment.

From the measurement results of the concentration of the residual contaminated elements, the removal rates of the contaminated elements according to the trial examples 1 to 3 of the iron powder for treating contaminated water were calculated, and these are summarized in FIG.

As described above, the prototype examples 1 to 3 of the iron powder for treating contaminated water having iron-based precipitates were able to remove heavy metals and fluorine in the contaminated water for testing. Among them, Prototype Examples 2 and 3 of iron powder for treating contaminated water having a relatively large area ratio of iron-based precipitates in the particle cross section obtain a sufficiently large removal rate for chromium, cadmium and fluorine, which are relatively difficult to remove. Was done.

The iron powder for treating contaminated water according to the present invention and the iron powder for treating contaminated water obtained by the method for producing iron powder for treating contaminated water according to the present invention can be widely used for purifying contaminated water.

Claims (4)

Iron powder for treating contaminated water that removes heavy metals in contaminated water.
Iron as a main component, possess the balance silicon, manganese, phosphorus, iron precipitates composed of at least one and inevitable impurities sulfur and chromium in the particles,
An iron powder for treating contaminated water, wherein the total content of silicon, manganese, phosphorus, sulfur and chromium in the iron powder for treating contaminated water is 0.3% by mass or more and 5% by mass or less . The iron powder for treating contaminated water according to claim 1, wherein the average area ratio of the iron-based precipitate in the particle cross section is 0.8% or more and 50% or less. The iron powder for treating contaminated water according to claim 1 or 2, wherein the average porosity in the particles is 5% or less. A method for producing iron powder for treating contaminated water that removes heavy metals in contaminated water.
The process of preparing molten iron in the furnace and
A step of adding an auxiliary raw material composed of silicon, manganese, phosphorus, sulfur , chromium and at least one compound of these irons and unavoidable impurities to the molten iron in a ladle.
It is provided with a step of injecting water into the molten iron after the addition to pulverize it.
A method for producing iron powder for contaminated water treatment, wherein the total content of silicon, manganese, phosphorus, sulfur and chromium in the iron powder for contaminated water treatment is 0.3% by mass or more and 5% by mass or less .

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