JPH1119688A - Ferrous ion chelating agent and chelating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent the deposition of a ferrous ion by preparing a ferrous ion chelating agent for preventing the ferrous ion from being oxidized to a ferric ion and deposited from the charged silicon dioxide colloidal soln. obtained by passing a silicon dioxide colloidal soln. through a magnetic field region. SOLUTION: When a charged silicon dioxide colloidal soln. is prepared, a mixing vessel 10 is filled with pure water, the pure water is circulated by a pump 25 through a circulating pipeline 20, passed through a magnetic field region and a nonmagnetic field region and returned to the mixing vessel 10 and the process is performed for several minutes. The mixture liq. of a 3-4 N NaOH aq. soln. and a silica colloidal soln. is then added as an SiO2 concn. This treated soln. to be charged is circulated and passed through the magnetic region and the nonmagnetic region. The molar amt. of citric acid or its salt equivalent to the NaOH is gradually added in the process of the circulation. Then the pH of the soln. is regulated and the regulated soln. is further circulated. The soln. obtained is diluted with pure water to prepare a desired charged silica colloidal soln.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blocking agent and a blocking method for blocking ferrous ions in water, and more particularly, to oxidizing ferrous ions contained in pumped ground water and the like to ferric ions. The present invention relates to a ferrous ion sequestering agent and a sequestering method for preventing the ferrous ions from being precipitated.

[0002]

2. Description of the Related Art Pumping equipment for groundwater contaminated with volatile contaminants such as volatile organic chlorine compounds is provided with an aeration device for removing the volatile contaminants contained therein.
Water is discharged after removing volatile pollutants by aeration treatment. In this case, since ferrous ions are contained in the groundwater in a reduced state, the ferrous ions are oxidized to ferric ions by aeration treatment and are precipitated to form a precipitate, such as an aeration apparatus or a subsequent facility. It accumulates in pipes, drainage channels, etc., and causes obstacles such as blocking these facilities.

For this reason, an iron removing device for oxidizing ferrous ions in groundwater to ferric ions to perform coagulation treatment and separating the precipitate into solid and liquid forms is provided in front of the aeration device, or periodically or as necessary. In order to prevent the above-mentioned trouble, the inside of the aeration device is washed in accordance with the situation.

[0004] Such a problem due to the precipitation of iron can also occur in a cooling water system using groundwater as makeup water.

[0005] For these reasons, there is a demand for the development of a technique for preventing the formation of iron precipitates due to the oxidation of ferrous ions to ferric ions without requiring any special equipment or operation. .

Japanese Patent Application Laid-Open No. 7-508886 describes a taste enhancer composed of charged silica colloid, but there is no technical idea to block ferrous ions with the charged silica colloid.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional circumstances. By blocking ferrous ions in water, ferrous ions are oxidized to ferric ions. It is an object of the present invention to submit a ferrous ion blocking agent and a blocking method for preventing precipitation.

[0008]

The ferrous ion sequestering agent according to the present invention comprises a charged silicon dioxide colloid obtained by passing a silicon dioxide colloid through a magnetic field region. The sequestering agent may include citric acid and / or citrate.

The method for blocking ferrous ions of the present invention is characterized in that a blocking agent for ferrous ions is added to water containing ferrous ions.

In a silicon dioxide (silica: SiO ₂ ) colloidal liquid, silica particles exist as colloidal particles having a three-dimensional network structure entangled with each other by Si—O—Si bonds. When the silica colloid is passed through the magnetic field region, the silica particles are negatively charged. The silica colloid particles negatively charged as described above attract ferrous ions as positive ions.

As described above, the ferrous ions are adsorbed by the negatively charged silica colloid particles having a three-dimensional network structure, whereby the ferrous ions are blocked (that is, oxygen or oxygen ions are converted to ferrous ions). To prevent the ferrous ion from being oxidized to ferric ion and being deposited as a precipitate.

The silica colloid particles are further aggregated with each other due to a decrease in pH, grow and gel, and the gelled particles have a very small surface on which ferrous ions are to be adsorbed. No effect can be obtained. When the silica colloid liquid is passed through the magnetic field region, the silica colloid particles are negatively charged and repel each other, so that gelation due to particle aggregation is suppressed and an excellent sealing effect can be obtained.

In particular, citric acid and / or
Alternatively, when a salt thereof is added, the silica colloid particles having a three-dimensional network structure are stabilized and aggregation is prevented, and a very good sealing effect can be obtained.

[0014]

Embodiments of the present invention will be described below in detail.

In order to prepare the charged silica colloid solution of the ferrous ion sequestering agent of the present invention, for example, a solution obtained by mixing a 1 to 5N, particularly 3 to 4N aqueous NaOH solution and a 10 to 40% by weight silica colloid solution is used. (Hereinafter, may be referred to as a “liquid to be charged”) in a magnetic field region. Before or during the passage of the treatment liquid to be charged through the magnetic field region, if necessary, Na may be used to stabilize the colloid particles.
Add approximately equimolar amounts of citric acid and / or citrate to OH. Then, if necessary, acetic acid, hydrochloric acid, etc.
H is adjusted to 7.6 to 8.2, and then diluted with water such as pure water to a predetermined silica concentration.

Here, citric acid 3
Potassium, trisodium citrate and the like.

If the silica concentration of the finally obtained charged silica colloid solution is too high, the silica colloid may be gelled. If the concentration is too low, the silica colloid may be used as a blocking agent. Since it is necessary to add a large amount of a blocking agent, the amount is preferably about 100 to 10000 mg / L. At this silica concentration, the silica colloid particles in the charged silica colloid liquid generally contain 1
The particles have a negatively charged three-dimensional network structure having a size of about 0 to 100 °.

It is preferable that the charging treatment is performed so that the silica colloid liquid passes alternately through a magnetic field region and a non-magnetic field region. As described above, when the magnetic field region and the non-magnetic field region are alternately passed, the silica colloid particles charged by passing through the magnetic field region remove external magnetic force factors on the particles while passing through the non-magnetic field region. As a result, the colloidal particles come to take a form according to the charge and the internal particle bonding state, and the colloid particles are stabilized. This stable state is maintained when the colloid particles exit the non-magnetic field region and pass through the magnetic field region again.

Such a charged silica colloid liquid is preferably produced using an apparatus described in Japanese Patent Publication No. Hei 7-508886.

Hereinafter, the method for producing a charged silica colloid liquid according to the present invention will be described in more detail with reference to FIGS. 1 and 2 showing an apparatus described in JP-T-7-508886.

FIG. 1 is a perspective view of a charging apparatus suitable for producing a charged silica colloid liquid according to the present invention, and FIG. 2 is a cross-sectional view taken along the line-in FIG.

The mixing vessel 10 is fixed to the support legs 12 by screws 13 and is fixed above the base 11. The upper plate 14 is mounted on the support legs 12 and supports the motor 15 at a position above the mixing container 10. The shaft 16 extends downward from the motor 15 and holds a mixing blade 17 in the mixing container 10. The lower portion of the mixing vessel 10 has a conical shape whose diameter is reduced downward. The mixing container 10 and the support legs 12 are preferably made of a non-magnetic material such as plastic or wood.

Below the mixing vessel 10, electromagnets 30A,
The support tables 18 of 30B, 30C, and 30D are installed.

From the lower end of the lower conical portion 10a of the mixing vessel 10, a circulating pipe 20 (20A) made of a non-magnetic material extends above the conical section 10a. (It should be noted that the spiral portion 20B has a spiraling direction when the liquid is normally drained from the liquid container through the drain port, that is, the spiral direction is counterclockwise in the northern hemisphere, and is in the southern hemisphere. Is desirably designed to circulate clockwise.) The circulation pipe 20 extends from the lower part of the spiral part 20B to the opening 18A at the center of the upper plate of the support base 18.
, And extends to the pump 25, and further extends from the pump 25 to the upper opening of the mixing vessel 10 via the mounting portion 22 of the branch pipe 21. Reference numeral 23 denotes a flow control valve of the branch pipe 21, and reference numerals 15A and 25A denote cords for supplying drive power to the motor 15 and the pump 25, respectively. Also, 31
Is a DC power supply for supplying power to the electromagnets 30A to 30D, and 31A and 31B are cords.

The four electromagnets 30A, 30B, 30C and 30D have their bottoms fitted into recesses provided in the upper plate on the support base 18 and are stably mounted on the support base 18. The electromagnets 30 </ b> A to 30 </ b> D are arranged such that each magnetic pole is on the same plane and forms a quadrangular vertex in the plane. Preferably, the square is a square as shown. Adjacent electromagnets have opposite magnetic poles, and such an arrangement allows the electromagnet 30
The two positive poles of B and 30D form a pair of square tops, and the two negative poles of electromagnets 30A and 30C form another pair of tops. Each pole is magnetically attracted by two adjacent poles of opposite magnetism and repels the same pole at the top. These four electromagnets 30A-30
D generate spherical magnetically affected areas, most of which extend above the electromagnet, form a magnetic field above a plane containing the poles of the electromagnet, and surround the helical portion 20B of the circulation pipe 20. Accordingly, in the charging process, the liquid to be charged crosses the magnetic field lines of the magnetic field when flowing through the spiral portion 20B of the circulation pipe 20. The colloidal particles in the liquid to be charged are negatively charged as a whole by traversing the lines of magnetic force.

It should be noted that at least a part of the central region 30 between the electromagnets 30A to 30D is a substantially magnetic field-free region. That is, the magnetic field is formed above and below the electromagnets 30A to 30D (however, when the support 18 is made of a magnetic material such as stainless steel, the lower magnetic field is absorbed by the support 18). However, these electromagnets 30A to 30D
The central portion 30 between them is isolated from substantially all magnetic fields (including the earth's magnetic field).

Therefore, when the liquid to be charged flows through the vertical portion 20 C extending downward from the spiral portion 20 B of the circulation pipe 20, immediately before passing through the opening 18 A of the support base 18,
The non-electric field region 30 at the center between the electromagnets 30A to 30D
Pass through.

In order to form a stable non-electric field region, it is desirable that the four electromagnets 30A to 30D have the same magnetic force, are coaxial with each other, and are arranged at equal intervals.

As described above, the silica colloid particles of the liquid to be charged are charged when passing through the spiral portion 20B of the circulation pipe 20, and the charged particles are charged in the vertical section 20C of the circulation pipe 20.
When passing through the no-magnetic-field region, the external magnetic force factor on the colloid particles is removed, and the particles take a form according to their charge and the internal particle bonding state, and become relatively stable. This stable state occurs even when the colloid particles come out of the non-magnetic field region (when a magnetic field is also formed below the electromagnets 30A to 30D, and also when the colloid particles pass below the magnetic field). Will be maintained. In particular, when the liquid to be charged contains citric acid or a salt thereof, the stable state of the colloid particles is further enhanced.

Each of the electromagnets 30A to 30D has about 2
An electromagnet having a magnetic force of 000 to 3000 Gauss can perform a sufficient charging process. Note that the number of electromagnets is not limited to four, and the number is arbitrary as long as it is arranged to form a stable non-magnetic field region. Further, a permanent magnet may be used instead of the electromagnet.

In order to produce a charged silica colloid liquid using such a charging apparatus, first, the mixing vessel 10 is filled with pure water. The pump 25 returns the pure water from the mixing vessel 10 through the circulation pipe 20 through the magnetic field region and the non-magnetic field region to return to the mixing vessel 10 by 10-2.
Perform for 00 minutes. Next, a mixed solution of a 3 to 4 N NaOH aqueous solution and a silica colloid solution was used as a SiO ₂ concentration of 100 to 100
Add so as to be 10,000 mg / L. The liquid to be charged is circulated for 1 to 5 hours to pass through the magnetic field region and the non-magnetic field region. During this circulation step, citric acid or a salt thereof equimolar to NaOH is gradually added. Next, the pH of this solution is adjusted to pH 7.6 to 8.2.
The conditioned solution is circulated for an additional 1-3 hours. The obtained solution is diluted with pure water to prepare a desired charged silica colloid solution.

The obtained charged silica colloid liquid is taken out from the branch pipe 21 with the valve 23 opened.

Next, a method for blocking ferrous ions of the present invention using a blocking agent comprising such a charged colloidal silica solution will be described with reference to FIG.

FIG. 3 is a system diagram showing an embodiment in which the sealing method of the present invention is applied to the treatment system of the contaminated groundwater. The contaminated groundwater pumped up by the pump is first supplied to the aeration tower 4.
At 1 the gas comes into countercurrent contact with the air, whereby volatile contaminants such as organochlorine compounds are volatilized. The gas containing the volatile contaminants is sent to the activated carbon adsorption tower 43 by the blower 42, and after the volatile contaminants are adsorbed and removed by the activated carbon,
The exhaust gas is discharged out of the system. The treated water from which the volatile contaminants have been removed is discharged from the lower part of the aeration tower 41.

In the present embodiment, a blocking agent is added to the contaminated groundwater supplied to the aeration tower 41 by a pump 45 from a blocking agent storage tank 44, and the precipitation of iron precipitates by oxidation of ferrous ions in the aeration tower 41 To prevent

In this case, the blocking agent has a ferrous ion concentration of 1
It is preferable to add silica in an amount of 0.1 to 20 mg / L with respect to mg / L.

As soon as the charged silica colloid liquid is added to the ferrous ion-containing water, the charged silica colloid liquid exerts a function of blocking ferrous ions and effectively prevents the precipitation of iron precipitates.

The ferrous ion-containing water to be treated in the present invention includes, in addition to the above-mentioned contaminated groundwater, ferrous ion-containing water such as groundwater as makeup water for a cooling water system.

According to the present invention, the precipitation of iron precipitates can be achieved without adding any special equipment or operation only by adding an appropriate amount of the charged silica colloid to such ferrous ion-containing water. Can be prevented.

[0040]

The present invention will be described more specifically below with reference to examples and comparative examples.

Examples 1 to 6, Comparative Examples 1 and 2 A charged silica colloid solution was prepared using the apparatus shown in FIGS.

First, 5 L of pure water is put into the mixing vessel 10, and the pure water is removed from the electromagnets 30 A to 30 A with gentle stirring.
A step of passing through the magnetic field region generated at 30D and the non-magnetic field region and returning the mixed container to the mixing container 10 again was performed for 30 minutes. Thereafter, 1 L of a silica solution obtained by mixing 27% by weight of silica in a 3 molar NaOH aqueous solution was added to the mixing vessel 10, and the mixture was circulated for about 4 hours in the same manner as described above.

During this circulation, tripotassium citrate was added to the mixing vessel 10 so as to have an equimolar concentration with NaOH. After this 4 hour circulation, the pH of the solution is 7.6.
Acetic acid was added so as to be 8, and then circulated for another 2 hours.

Thereafter, pure water was further added into the mixing vessel 10 to obtain a charged silica colloid liquid having a silica concentration of 500 mg / L.

The obtained charged silica colloid solution was added to contaminated groundwater having a ferrous ion concentration shown in Table 1 in an amount shown in Table 1 (however, in Comparative Examples 1 and 2, the charged silica colloid solution was not added. ), And then the contaminated groundwater was aerated in a 250 mL container.

The state of precipitation in the container was visually observed, and the results are shown in Table 1.

[0047]

[Table 1]

Table 1 shows that according to the present invention, ferrous ions can be blocked to prevent precipitation of iron precipitate.

[0049]

As described above in detail, according to the ferrous ion-sequestering agent and the method of the present invention, the ferrous ion-sequestering water is simply added to the ferrous ion-containing water. By blocking the ions, it is possible to prevent ferrous ions from being oxidized to ferric ions to form a precipitate.

Therefore, according to the present invention, it is possible to easily prevent an obstruction such as a blockage of a pipe due to an iron precipitate without requiring a special equipment for removing ferrous ions or a work for removing a precipitate. it can.

[Brief description of the drawings]

FIG. 1 is a perspective view of a charging apparatus suitable for producing a sealing agent of the present invention.

FIG. 2 is a cross-sectional view taken along line-of FIG.

FIG. 3 is a system diagram showing an embodiment of the method for blocking ferrous ions of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Mixing container 10a Conical part 15 Motor 20 Circulation pipe 20B Spiral part 25 Pump 30A, 30B, 30C, 30D Electromagnet 31 DC power supply 41 Aeration tower 43 Activated carbon adsorption tower 44 Sealant storage tank

Claims (3)

[Claims] 1. A sequestering agent for ferrous ions in water, comprising a charged silicon dioxide colloid solution obtained by passing a silicon dioxide colloid solution through a magnetic field region. 2. The sequestering agent for ferrous ions in water according to claim 1, further comprising citric acid and / or citrate. 3. A method for blocking ferrous ions, wherein the blocking agent according to claim 1 is added to water containing ferrous ions.