JP2011110476A - Cleaning material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a cleaning material which enables the clean-up of complex pollution by insolubilizing and adsorbing a wide range of heavy metals, and is excellent in workability. <P>SOLUTION: The cleaning material is obtained by granulating metallic iron powder and/or iron oxide powder, magnesium hydroxide and/or magnesium oxide, and a pH adjusting agent with a binder. The pH adjusting agent adjusts the pH value of polluted water to be treated to 4-10. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a purification material that adsorbs and purifies heavy metals contained in contaminated soil or waste.

Metallic iron powder, iron oxide powder, cerium oxide, magnesium oxide, etc. are used as a heavy metal insolubilizer (purifier) for the treatment of contaminated soil containing heavy metals such as fluorine, boron, arsenic, chromium, lead, and selenium. Yes. When such a purification material is used in the form of powder, there is a problem that it is easy to scatter and the workability is poor.
Thus, for example, there is a purification material disclosed in Patent Document 1 as a solution to such a problem.
The purification material disclosed in Patent Document 1 is a purification material that is mixed with soil and installed at a thickness of 5 cm or more below or on the side of the contaminated soil or waste, or both. Iron, iron hydroxide, iron oxide or hydrate thereof, magnesium hydroxide, magnesium oxide or hydrate thereof, cerium carbonate fluoride, cerium hydroxide, cerium oxide or hydrate thereof, or these Characterized in that a powder material containing one or more of the above is mixed with a fibrous material having an average diameter of 1 to less than 1000 μm and a ratio of fibrous material / powder material = 0.33 to 3 ” It is.

Japanese Patent No. 4187223

Generally, the type of purification material is selected according to the pollutant in the target contaminated soil. For example, when arsenic, lead, chromium, etc. are pollutants, metallic iron powder is used. When cadmium, cyan, etc. are pollutants, magnesium oxide or the like is used.
However, the metal iron powder has a weak purification action against fluorine and boron, and the magnesium oxide has a weak purification action against arsenic, etc., so that the contaminated soil is contaminated with, for example, both fluorine and arsenic. However, it is difficult to obtain a sufficient purification effect with a conventional purification material using metallic iron powder or magnesium oxide alone.
In addition, complex pollution means that the soil to be purified is contaminated with a plurality of contaminants that cannot be purified with a single purification material.

In this regard, in Patent Document 1, “iron hydroxide, iron oxide or a hydrate thereof, magnesium hydroxide, magnesium oxide or a hydrate thereof, or a powder material containing one or more of these” and There is a description which includes what mixes both iron powder and magnesium oxide.
However, as can be seen by referring to “Best Mode for Carrying Out the Invention” in Patent Document 1, the purifying action is studied in Patent Document 1 when the powder materials are used alone. Only.
Thus, the conventional purification material is not known to be effective against complex contamination.

  The present invention has been made to solve such problems, and it is intended to obtain a purification material that can purify complex contamination by insolubilizing and adsorbing a wide range of heavy metals and that is excellent in workability. Yes.

In order to solve the above-mentioned problems, the inventor, as an example of complex contamination, as a purification material for contaminated soil contaminated with both fluorine and arsenic substances, metallic iron having a purification action against each contaminant. The use of a mixture of powder and magnesium oxide was considered.
However, since specific gravity differs greatly between metallic iron powder and magnesium oxide, it is difficult to uniformly mix even if the powder is mixed as it is. Therefore, if it is intended to construct the powder as it is, it must be constructed in two stages, which causes a problem that the operation becomes complicated.

Further, when magnesium hydroxide is formed on the surface by hydration reaction, magnesium oxide insolubilizes and adsorbs heavy metals, and the pH value of contaminated water rises to 10-11. On the other hand, if the pH value is high, the surface valence of metallic iron powder becomes negative, so the mechanism of insolubilization of anions such as arsenic that metallic iron powder is subject to purification does not work, and the purification effect cannot be exhibited. There is also.
Thus, when metal iron powder and magnesium oxide are mixed and used for complex contamination, there is a particular problem.
However, although such problems have not been studied at all in the past, the inventor has paid attention to such problems and has intensively studied to solve these problems and completed the present invention. Is.

First, regarding the difference in specific gravity between metal iron powder and magnesium oxide, we thought that by granulating these, even if there is a difference in specific gravity between them, it can be applied uniformly in one operation.
Moreover, about the problem of the pH value increase by magnesium oxide, it considered adding the pH adjuster and granulating including a pH adjuster. By granulating with a pH adjuster, in addition to being able to apply metal iron powder and magnesium oxide uniformly, the surrounding environment of the metal iron powder can always be maintained at the optimum pH value that can exert the purification action of the metal iron powder. It is.
The present invention is based on the discovery of such a problem and the above knowledge of solving the discovered problem, and specifically comprises the following configuration.

(1) The purification material according to the present invention is a purification material obtained by granulating metal iron powder and / or iron oxide powder, magnesium hydroxide and / or magnesium oxide, and a pH adjuster with a binder, The said pH adjuster adjusts the pH value of the contaminated water used as a process target to 4-10.

(2) Further, in the above (1), it is characterized by being granulated containing cerium oxide and / or cerium hydroxide.

(3) Further, in the above (1) or (2), the pH adjuster contains 10 to 100 parts by weight with respect to 100 parts by weight of magnesium hydroxide and / or magnesium oxide. To do.

(4) Moreover, in the thing in any one of said (1)-(3), the said pH adjuster is 1 type selected from aluminum sulfate, iron sulfate, iron chloride, acidic clay, and a citric acid, or It is characterized by being of multiple types.

  In the present invention, it is a purification material obtained by granulating metal iron powder and / or iron oxide powder, magnesium hydroxide and / or magnesium oxide, and a pH adjuster with a binder, and the pH adjuster is treated. Since the pH value of the target contaminated water is adjusted to 4 to 10, it is possible to put different kinds of specific gravity into one particle by granulation, and the complex target to be treated Uniform spraying is possible with a single installation on contaminated soil. And since it granulates including a pH adjuster, the pH value of the vicinity of metal iron powder can always be made into the optimal value for metal iron powder, and a purification effect can be performed effectively.

It is explanatory drawing of the apparatus of the Example which confirms the effect of this invention.

The purification material of the present embodiment is a purification material obtained by granulating metallic iron powder and / or iron oxide powder, magnesium hydroxide and / or magnesium oxide, and a pH adjuster with a binder, and the pH The adjusting agent adjusts the pH value of the contaminated water to be treated to 4-10.
Details will be described below.

<Metal iron powder>
In addition to heavy metal insolubilized metal iron powder, fine metal metal powder, crushed alloy iron powder, iron powder for powder metallurgy and the like can be used as the metal iron powder.
As fine metal iron powder, atomized iron powder, sponge iron powder, reduced iron powder, and electrolytic iron powder can be used.
Moreover, as a metal iron powder particle diameter, the average particle diameter of 50-200 micrometers is preferable.
<Iron oxide powder>
As the iron oxide, heavy metal insolubilized iron oxide, titanium refining residue iron oxide, iron ore, iron hydroxide and the like can be used. The average particle size is preferably about 5 to 100 μm.

  Iron and iron oxide have a high adsorption effect on arsenic, lead, chromium, and selenium.

<Magnesium oxide powder>
Magnesium oxide powder adsorbs and insolubilizes fluorine, boron, cadmium, lead, cyan, and chromium. The average particle size of the magnesium oxide powder is preferably about 3 to 100 μm.

<PH adjuster>
As the pH adjuster, aluminum sulfate, iron sulfate, iron chloride, acidic clay, citric acid or the like is used.
The pH adjuster is contained in an amount of 10 to 100 parts by weight with respect to 100 parts by weight of magnesium hydroxide and / or magnesium oxide.
As described above, when magnesium hydroxide is formed on the surface by hydration reaction, magnesium oxide insolubilizes and adsorbs heavy metals and raises the pH value of contaminated water to 10-11. Therefore, in order to set the pH value of contaminated water to pH 4 to 10, more preferably pH 5 to 9.5, which is a pH range in which iron can exert a purification action, it is necessary to add the above amount of pH adjusting agent. is there.

<Binder>
As a binder used as a powder binder, polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), starch, gelatin, vinyl acetate and the like are used as an aqueous binder.

<Granulation>
Granulation is processed into granules using a granulator.
The average powder diameter is 100 to 1000 microns.

<Mixing ratio>
The mixing ratio of metallic iron powder and / or iron oxide powder and magnesium hydroxide and / or magnesium oxide is changed according to the ratio of soil pollutants to be purified, etc., and optimized. .
The binder is added in an amount of 0 to 20% by mass.

  As a method of using the purification material as described above, the purification material may be mixed with the contaminated soil to be treated, or the purification material is spread over a predetermined thickness and the contaminated soil is embanked thereon. It is also possible to use it, or alternatively, digging the ground, setting the purification material on the bottom and side surfaces of the excavated ground with a predetermined thickness, and putting the contaminated soil into the space surrounded by the purification material You may do.

  Experiments for confirming the effects of the present invention will be described in the following examples.

As shown in FIG. 1, the experimental apparatus passes simulated contaminated water stored in a tank through a column filled with a purification material by a pump, collects purified water from the column, and measures pH and heavy metal element concentration. Quantitative analysis was performed.
<Experimental equipment specifications>
The specifications of the apparatus used for the experiment are as follows.
Column: φ10mm × 100mm
Purifying material ・ Particle size: 300μm
·composition:
(i) Examples Metallic iron powder 44%, Magnesium 44%, Aluminum sulfate 9%, Binder 3%
(100 parts metal iron powder, 100 parts magnesium, 20 parts aluminum sulfate,
7 parts by weight of binder)
(ii) Comparative example
Metal iron powder 48.5%, Magnesium 48.5%, Binder 3%
(Metal iron powder 100 parts by weight, magnesium 100 parts by weight, binder 6 parts by weight)

<Experimental operation>
The column was filled with a purification material granulated to 300 μm, and simulated contaminated water was introduced from the bottom of the column at 40 ml / day. The amount of 40ml / day corresponds to the amount of annual rainfall per day. The grounds that 40ml / day is equivalent to the amount of annual rainfall per day are as follows. If the average precipitation is 1500 mm and the permeability to the soil is 30%, 1500 (annual precipitation mm) ÷ 10 (annual precipitation converted to cm) x 0.3 (permeability) x 0.785 (column cross-sectional area cm2) = 35.33 ml / year was calculated. Therefore, there is no problem at 40ml / day.
The passing water that passed through the column was collected from above the column, and the pH of the passing water was measured and the quantitative analysis of the heavy metal element concentration was performed.
Tables 1 and 2 show each heavy metal element and pH value at the beginning (initial) of the simulated contaminated water, and each heavy metal element and pH value after passing through the column. Table 1 is an example and Table 2 is a comparative example.

In the examples, as shown in Table 1, the initial amount of each heavy metal element exceeded the environmental standard value, but after passing through the column, all the heavy metal elements were significantly below the environmental standard value. From this, it was confirmed that the adsorption action of both metallic iron powder and magnesium was exhibited.
In addition, this purifying effect is exhibited even after 90 days. Since the amount of passing water per day is equivalent to the amount of precipitation per year, 90 days corresponds to 90 years, and it was confirmed that the purifying material of the present invention exerts a long-term effect.
In addition, the pH value of the initial value was pH 8.9 to pH 9.1, and the effect of lowering pH was confirmed.

On the other hand, in the comparative example, as shown in Table 2, with respect to fluorine and boron, after passing through the column, the environmental standard value is greatly lower than in the example. However, with regard to arsenic and lead, even after passing through the column, there is almost no change from the initial. This means that the pH value, which was initially 10 at pH, became pH 10.8 to 10.9 after passing through the column, and since the pH value increased, the metal iron powder adsorption effect could not be exhibited. This is presumed to be because of
In other words, in the example in which aluminum sulfate, which is a pH adjuster, is added, the effect of the pH adjuster exhibits both the adsorption action of both metal iron powder and magnesium, and is excellent as a purification material. It can be said that it has been demonstrated.

In the granulation, cerium oxide and / or cerium hydroxide may be added. Cerium oxide and cerium hydroxide have an adsorption action on fluorine, boron, arsenic, lead, chromium, selenium and the like.

Claims (4)

  A purification material obtained by granulating metallic iron powder and / or iron oxide powder, magnesium hydroxide and / or magnesium oxide, and a pH adjuster with a binder, wherein the pH adjuster is contaminated water to be treated. The purification material characterized by adjusting pH value of 4-10.   2. The purification material according to claim 1, wherein the purification material is granulated by containing cerium oxide and / or cerium hydroxide.   The said pH adjuster contains 10-100 weight part with respect to 100 weight part of magnesium hydroxide and / or magnesium oxide, The purification | cleaning material of Claim 1 or 2 characterized by the above-mentioned.   The pH adjuster is one or more selected from aluminum sulfate, iron sulfate, iron chloride, acidic clay, and citric acid, according to any one of claims 1 to 3. The purification material as described.

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