JP3422223B2 - Ferrous ion blocking agent and blocking method - Google Patents

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 specifically, ferrous ions contained in pumped groundwater are oxidized to ferric ions. The present invention relates to a ferrous ion sequestering agent and a method for sequestering the ferrous ion.

[0002]

2. Description of the Related Art In a groundwater pumping facility contaminated with volatile pollutants such as volatile organic chlorine compounds, an aeration device is provided to remove the volatile pollutants contained therein.
After removing volatile pollutants by aeration treatment, water is discharged. In this case, since ferrous ions are contained in the groundwater in a reduced state, the ferrous ions are oxidized to ferric ions in the aeration process and become a precipitate, which causes the aeration device and the equipment in the subsequent stage to be exposed. It accumulates in pipes and drainage channels, and causes obstacles such as blocking these facilities.

For this reason, an iron removing device for oxidizing ferrous ions in groundwater into ferric ions for aggregating treatment and solid-liquid separation of precipitates is provided in front of the aeration device, or periodically or as necessary. Depending on the situation, the inside of the aeration device is washed to prevent the above-mentioned trouble.

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

Therefore, 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. .

In addition, Japanese Patent Publication No. 7-508886 discloses a taste enhancer composed of a charged silica colloid, but there is no technical idea of blocking 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, and by blocking the ferrous ion in water, the ferrous ion is oxidized to ferric ion. The purpose of the present invention is to provide a sequestering agent for ferrous ions and a sequestering method for preventing the precipitation thereof.

[0008]

The ferrous ion sequestering agent of the present invention is an aqueous solution of a charged silicon dioxide colloidal solution obtained by passing a silicon dioxide colloidal solution through a magnetic field region.
And a citric acid and / or citrate .

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

In the silicon dioxide (silica: SiO ₂ ) colloidal solution, the silica particles are present as colloidal particles having a three-dimensional network structure in which they are entangled with each other by Si--O--Si bonds. When the silica colloidal liquid is passed through the magnetic field region, the silica particles are negatively charged. Thus, the negatively charged silica colloidal particles attract the positive ferrous iron ions.

As described above, the adsorption of ferrous ions on the negatively charged silica colloidal particles having a three-dimensional network structure sequesters the ferrous ions (ie, oxygen or oxygen ions to ferrous ions). It is considered that the ferrous ion is prevented from being oxidized to ferric ion and deposited as a precipitate.

The silica colloidal particles further agglomerate and grow with each other due to a decrease in pH and grow into a gel, but the gelled particles have a very small surface on which ferrous ions should be adsorbed, which results in good blocking. You can't get the effect. When the silica colloid liquid passes 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 blocking effect can be obtained.

In particular, the silica colloidal solution is citric acid and / or
Alternatively, since it contains a salt thereof, the silica colloidal particles having a three-dimensional network structure are stabilized and agglomeration is prevented, and a very good blocking effect can be obtained.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below.

To prepare the charged silica colloidal solution of the ferrous ion sequestering agent of the present invention, for example, a solution prepared by mixing 1 to 5N, especially 3 to 4N NaOH aqueous solution and 10 to 40% by weight of silica colloidal solution. (Hereinafter, it may be referred to as a "charged liquid".) Is passed through the magnetic field region. Before or during passing through the magnetic field region, the liquid to be charged may be adjusted with Na to stabilize the colloidal particles, if necessary.
Approximately equimolar to OH is added citric acid and / or citrate. After that, add acetic acid, hydrochloric acid, etc. if necessary.
H is adjusted to 7.6 to 8.2, and then diluted with water such as pure water so as to have a predetermined silica concentration.

Here, the citric acid salt is citric acid 3
Examples thereof include potassium and trisodium citrate.

If the silica concentration of the finally obtained charged silica colloidal solution is excessively high, the silica colloid may gel, and if it is excessively low, it may be used as a blocking agent. Since it is necessary to add a large amount of the sequestering agent, it is preferably about 100 to 10,000 mg / L. At this silica concentration, the silica colloid particles in the charged silica colloid solution generally have a particle size of 1
The particles are negatively charged and have a three-dimensional mesh structure with a size of 0 to 100Å.

The above-mentioned charging treatment is preferably carried out so that the silica colloidal liquid passes through the magnetic field regions and the non-magnetic field regions alternately. As described above, when the magnetic field region and the non-magnetic field region are alternately passed, the silica colloidal particles charged by passing through the magnetic field region remove the external magnetic force factor on the particle while passing through the non-magnetic field region. , The colloidal particles are stabilized by taking a morphology according to the electric charge and the internal particle binding state. This stable state is maintained even when the colloidal particles leave the non-magnetic field region and again pass through the magnetic field region.

Such a charged silica colloidal solution is preferably produced by using the apparatus described in JP-A-7-508886.

Hereinafter, the method for producing a charged silica colloidal solution according to the present invention will be described in more detail with reference to FIGS. 1 and 2 showing the apparatus described in Japanese Patent Publication No. 7-508886.

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

The mixing container 10 is fixed to the supporting legs 12 by screws 13 and fixed above the base 11. The upper plate 14 is mounted on the upper portion of the support leg 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 container 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 container 10, electromagnets 30A,
30B, 30C, 30D support stand 18 is installed.

Further, a circulation pipe 20 (20A) made of a non-magnetic material extends above the cone portion 10a from the lower end of the lower cone portion 10a of the mixing container 10, and this circulation pipe 20 further has an outer surface of the cone portion 10a. Is spirally wound from the upper side to the lower side (Note that the spiral portion 20B swirls in the direction in which the liquid is normally drained from the liquid container through the drain port, that is, counterclockwise in the northern hemisphere, and the southern hemisphere. In it is desirable to be designed to circulate clockwise). The circulation pipe 20 is provided with a hole 18A at the center of the upper plate of the support 18 from the lower part of the spiral portion 20B.
To the pump 25, and further extends from the pump 25 to the upper opening of the mixing container 10 via the attachment portion 22 of the branch pipe 21. Reference numeral 23 is a flow rate adjusting valve of the branch pipe 21, and 15A and 25A are codes for supplying drive power to the motor 15 and the pump 25, respectively. Also, 31
Is a DC power supply for supplying electric power to the electromagnets 30A to 30D, and 31A and 31B are cords.

The bottoms of the four electromagnets 30A, 30B, 30C and 30D are fitted in the recesses provided in the upper plate on the support 18 and are stably mounted on the support 18. The electromagnets 30A to 30D are arranged such that their magnetic poles are on the same plane and form a rectangular vertex in that plane. Preferably, this quadrilateral is a square as shown. The magnets of adjacent electromagnets have opposite magnetic poles, and by such an arrangement, for example, the electromagnets 30
The two positive poles of B and 30D form a pair of square-shaped apexes, and the two negative poles of electromagnets 30A and 30C form the other pair of apexes. Each of the poles is magnetically attracted by two adjacent poles of opposite magnetism and repels the same pole at the apex. These four electromagnets 30A to 30
D generate mutually spherical magnetically influential regions, but most of them spread above the electromagnet to form a magnetic field above the plane containing the poles of the electromagnet and surround the spiral portion 20B of the circulation pipe 20. Therefore, in the charging process, the liquid to be charged crosses the magnetic lines of force of the magnetic field when flowing through the spiral portion 20B of the circulation pipe 20. Then, by crossing the lines of magnetic force, the colloidal particles in the liquid to be charged are negatively charged as a whole.

At least a part of the central region 30 between the electromagnets 30A to 30D is substantially a 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 therebetween is shielded from substantially all magnetic fields (including the earth's magnetic field).

Therefore, when the liquid to be charged flows through the vertical portion 20C extending downward from the spiral portion 20B of the circulation pipe 20, immediately before passing through the opening 18A of the support base 18,
The electric field-free region 30 in the central portion 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 and are coaxially arranged at equal intervals.

As described above, the silica colloidal 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 vertical portions 20C of the circulation pipe 20.
When passing through the non-magnetic field of, the external magnetic force factor on the colloidal particles is removed, and the particles come to have a morphology according to the electric charge and the internal particle binding state, and are in a relatively stable state. This stable state is obtained even when colloidal particles come out of the non-magnetic field region (when a magnetic field is formed below the electromagnets 30A to 30D, and when the colloidal particles pass through the magnetic field below this). Maintained. In particular, when citric acid or its salt is contained in the liquid to be charged, the stable state of the colloidal particles is further enhanced.

The electromagnets 30A to 30D each have about 2
If the electromagnet has a magnetic force of 000 to 3000 Gauss, sufficient charging processing can be performed. The number of electromagnets is not limited to four, and any number may be used as long as it is arranged so as to form a stable non-magnetic field region. A permanent magnet may be used instead of the electromagnet.

In order to produce a charged silica colloidal liquid using such a charging apparatus, first, the mixing container 10 is filled with pure water. Then, the steps of circulating pure water by the pump 25 from the mixing container 10 through the circulation pipe 20 to pass through the magnetic field region and the non-magnetic field region and returning to the mixing container 10 are performed 10-2.
Do it for 00 minutes. Next, a mixture of a 3 to 4 N NaOH aqueous solution and a silica colloidal solution is used as a SiO ₂ concentration of 100 to
Add so that it becomes 10000 mg / L. Then, 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 its salt equimolar to NaOH is gradually added. The pH of this solution is then adjusted to pH 7.6-8.2.
The conditioned solution is circulated for another 1-3 hours. The obtained solution is diluted with pure water to prepare a desired charged silica colloidal solution.

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

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

FIG. 3 is a system diagram showing an embodiment in which the blocking method of the present invention is applied to a contaminated groundwater treatment system. Contaminated groundwater pumped up by a pump is first aerated tower 4
In the case of 1, countercurrent contact with air occurs, whereby volatile pollutants such as organic chlorine compounds contained therein are volatilized. The gas containing the volatile pollutants is sent to the activated carbon adsorption tower 43 by the blower 42, and after removing the volatile pollutants with the activated carbon,
Exhaust gas is discharged outside the system. The treated water from which the volatile pollutants have been removed is discharged from the lower part of the aeration tower 41.

In the present embodiment, a sequestering agent is added to the contaminated groundwater supplied to the aeration tower 41 by the pump 45 from the sequestering agent storage tank 44, and the precipitation of iron due to the oxidation of ferrous ions in the aeration tower 41 is precipitated. 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.

The charged silica colloidal liquid exerts a blocking action of ferrous ions immediately when added to ferrous ion-containing water, and effectively prevents the precipitation of iron precipitates.

Examples of the ferrous ion-containing water to be treated in the present invention include the above-mentioned contaminated groundwater, and ferrous ion-containing water such as groundwater as make-up water for the cooling water system.

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

[0040]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples below.

Examples 1 to 6 and Comparative Examples 1 and 2 Charged silica colloidal solutions were prepared using the apparatus shown in FIGS.

First, 5 L of pure water was placed in the mixing container 10 and the pure water was introduced from the mixing container 10 to the electromagnets 30A.about.
The step of passing through the magnetic field region and the non-magnetic field region generated at 30D and returning to the mixing container 10 again was performed for 30 minutes. Thereafter, 1 L of a silica solution prepared by mixing 27% by weight of silica in a 3 molar NaOH aqueous solution was added into the mixing container 10 and circulated for about 4 hours 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 was 7.6.
Acetic acid was added to 8 and then circulated for another 2 hours.

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

The obtained charged silica colloidal liquid was added to the contaminated groundwater having the ferrous ion concentration shown in Table 1 in the amount shown in Table 1 (however, in Comparative Examples 1 and 2, the charged silica colloidal liquid 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]

From Table 1, it can be seen that according to the present invention, the precipitation of iron precipitates can be prevented by sequestering ferrous ions.

[0049]

As described above in detail, according to the ferrous ion sequestering agent and the sequestering method of the present invention, the ferrous iron is simply added to the water containing ferrous ion. The ions can be sequestered to prevent ferrous ions from oxidizing to ferric ions to form a precipitate.

Therefore, according to the present invention, it is possible to easily prevent obstruction such as blockage of the pipe due to iron precipitation without requiring special ferrous ion removal equipment or precipitation removal work. it can.

[Brief description of drawings]

FIG. 1 is a perspective view of an electrification processing apparatus suitable for producing a blocking agent of the present invention.

FIG. 2 is a sectional view taken along the line − in FIG.

FIG. 3 is a system diagram showing an embodiment of a ferrous ion sequestering method of the present invention.

[Explanation of symbols]

10 mixing vessels 10a cone part 15 motor 20 circulation piping 20B spiral part 25 pumps 30A, 30B, 30C, 30D Electromagnet 31 DC power supply 41 aeration tower 43 Activated carbon adsorption tower 44 Blocking agent storage tank

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C23F 11/18 101 C23F 11/18 101 (58) Fields investigated (Int.Cl. ⁷ , DB name) C02F 5/00-5 / 14 C23F 11/00-11/18 C23F 14/00-17/00 B01F 17/00-17/56 C09K 3/00 C11D 1/00-19/00

Claims (2)

(57) [Claims] 1. A sequestering agent for ferrous ions in water, which comprises a charged silicon dioxide colloidal solution obtained by passing a silicon dioxide colloidal solution through a magnetic field region.
Or a first in water characterized by containing citrate
Sequestering agent for iron ions. To 2. A water containing ferrous ions, sequestering method of ferrous ions added sealing <br/> chain agent according to claim 1.