JP2003251104A - Inorganic flocculant for water treatment and usage therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flocculant capable of being manufactured in a short manufacturing time by a simplified manufacturing process, excellent in stability and working safety, having a high sedimentation speed because a floc forming speed is high and a final arriving floc particle size is large and capable of separating a supernatant liquid and sludge in a short time. <P>SOLUTION: The inorganic flocculant for water treatment comprises an aqueous alkali silicate solution (1), characterized in that (A) a molar ratio (SiO<SB>2</SB>/A<SB>2</SB>O) (A: alkali metal) of silicon and alkali is 4-30 and (B) the concentration of silicon in terms of an oxide (SiO<SB>2</SB>concentration) is 6.8-30 wt.%, and a solution (2) containing iron or titanium ions. Further, if necessary, after or before the inorganic flocculant for water treatment is added, at least one of swellable clay minerals, phosphorus compounds and cement is used. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inorganic flocculant used for chemical water treatment of various types of water or wastewater, and more specifically, construction sites, crushed stone factories, concrete product factories,
The present invention relates to an inorganic flocculant suitable for recovered sludge water containing cleaning wastewater and the like generated from concrete processing equipment such as a Ladymix factory.

The present invention also relates to a water treatment method using the above inorganic flocculant.

[0003]

2. Description of the Related Art Normally, muddy water treatment at concrete factories is
A natural sedimentation method or a coagulation sedimentation method using a polymer coagulant is generally used. When attempting to positively and effectively utilize concrete sludge water, the natural sedimentation method makes rapid treatment difficult, and suspended substances (SS components) tend to remain in the treated water. It is known that when a polymer coagulant is mixed into concrete or the like, breathing and strength decrease occur, and that when the polymer coagulant concentration is 30 ppm or more, it affects slump and slump flow.

When various kinds of water or waste water are treated by chemical means, a coagulant for coagulating and precipitating a colloidal substance existing in water is often used. In the precipitation method using a flocculant, a main agent for flocculation and an auxiliary agent are usually used in combination. So-called activated silicic acid is known as a coagulation aid. Activated silicic acid is usually prepared by adding an acid to silicic acid, but the activated silicic acid prepared in this way undergoes gelation in a short time, and the gelled substance can be used effectively as a coagulant anymore. I can't. Therefore, the active silicic acid can be used as a coagulation aid for about 1 day after the preparation, which has been a big problem in using the active silicic acid coagulation aid.

As a technique for prolonging gelation by active silicic acid, an example of adding water glass to an acidic liquid and immediately adding ferric salt to the "water treatment method and water treatment coagulant" of Patent Document 1 However, the polymerization of the monomer silica does not proceed, and only an aggregating agent having an inferior aggregating effect is obtained. Furthermore, unless polymerized to a predetermined intrinsic viscosity, a coagulant having a large coagulation effect cannot be obtained. Since silica polymerization rapidly progresses and gelation occurs, it is extremely difficult to set an appropriate range, which frequently causes gelling troubles, and there is a problem that it is very difficult to produce a coagulant.

On the other hand, it is also known to use iron salts of ferric sulfate and ferric chloride as the aggregating agent, but if the aggregating treatment is carried out using only these iron salts, a considerable aggregating effect can be obtained. Since it is not possible and slaked lime is often used together for the purpose of adjusting the pH, there is a defect that a large amount of sludge is generated. By the way, in an aqueous solution of alkali silicate called water glass, a relatively large amount of alkali ions is contained in order to maintain a solution state, so the molar ratio of silicon to alkali (SiO ₂ / A
₂ O) (A: alkali metal) is usually less than 4. Although the solution contains silicate ions and alkali ions, since the negative charge is small, the anion activity is also low, and the zeta potential, which is an indicator of anion activity, exceeds -40 MV and -14 M.
It is in the range of V or less.

On the other hand, primary particles called silicic acid sol and colloidal silica have no internal surface area or crystalline portion, and these are dispersed in an alkaline medium. Alkali reacts with the surface of silica to form a negative charge on the surface of the alkali, and the silica particles have a negative charge, which is stabilized by the repulsive force of the negative charges between the particles. However, basically there are many silanol groups (Si-OH) in addition to the silicic acid anion that forms a negative charge on the surface of the silica colloidal substance, so the negative charge is small and the zeta potential is in the range of -25 to -38 MV. It is in.

Although de-alkalization of water glass gives colloidal silica, a stable intermediate between water glass and colloidal silica has not been obtained. That is, as the dealkalization proceeds, the molar ratio becomes high, and the water glass cannot maintain the solution state. Generally, the molar ratio is 4.
When it is 2 or more, precipitation of silica occurs and the water glass cannot maintain a solution state.

On the other hand, it has a solution-like property like water glass, and has a molar ratio and S like colloidal silica.
If a high molar ratio aqueous solution of alkali silicate having a high iO ₂ concentration is used as a component of the above-mentioned inorganic coagulant for water treatment, there is a possibility that it can contribute to improvement in stability and work safety. That is, the high-molar-ratio alkali silicate aqueous solution has a longer life than activated silica and is less likely to undergo rapid gelation.

That is, the solution property of water glass is retained.
, Molar ratio, activity and SiO ₂Highly concentrated silicate
The use of aqueous Lucari solution should be considered. Shi
However, simply concentrating the water glass by evaporative concentration
Can not increase the molar ratio, for example in water glass
But the product with the highest molar ratio of 4.0 is SiO₂Concentration is 30% by weight
If it is concentrated to a point, it will completely gel.

On the other hand, colloidal silica is also concentrated by an ultrafiltration method (see, for example, Patent Documents 2 to 4). Although colloidal silica in which silica particles are in the state of particle growth can be sufficiently concentrated by the ultrafiltration method, water glass has many low molecular weight components such as ions and the yield by the ultrafiltration method is low. In addition, since many ions are lost, the anion activity originally possessed by water glass is also lost.

[0012]

[Patent Document 1] Japanese Patent No. 2732067

[Patent Document 2] US Pat. No. 3,969,266

[Patent Document 3] British Patent No. 1,148,950

[Patent Document 4] JP-A-58-15022

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems and has an intermediate property between water glass and colloidal silica and has a molar ratio (SiO ₂ / A ₂ O) (A : Alkali metal) and silicon content is high, and by using an alkaline silicate aqueous solution having a high anion activation degree as a component of the coagulant for water treatment, the coagulant manufacturing process can be simplified and the manufacturing time can be shortened. Moreover, it is an object to provide an inorganic coagulant having excellent stability and work safety.

[0014]

SUMMARY OF THE INVENTION The inorganic coagulant for water treatment according to the present invention comprises:
(1) (A) Molar ratio of silicon to alkali (SiO ₂ / A ₂ O) (A:
Alkali metal) is 4 to 30, and (B) silicon oxide conversion concentration (SiO ₂ concentration) is 6.8 to 30% by weight, and (2) iron ion and / or It is characterized by comprising a titanium ion-containing solution.

In the inorganic coagulant for water treatment according to the present invention, the alkali silicate aqueous solution (1): 100 parts by weight (solid content) and the iron ion and / or titanium ion-containing solution (2): 0.1 ~ 250 parts by weight (iron [Fe] and /
Alternatively, it is preferably composed of titanium [Ti] (as solid). Further, the iron ion and / or titanium ion-containing solution (2) is preferably a solution containing trivalent iron ions or tetravalent titanium ions.

Further, the alkaline silicate aqueous solution (1) used in the present invention preferably satisfies at least one of the following characteristics (C) to (F) in addition to the characteristics (A) and (B). (C) The zeta potential is −40 MV to −80 MV, and (D) ²⁹ Si-NMR measurement shows a chemical shift of −100.
The peak area at --120 ppm is ²⁹ Si-N under the same conditions.
Chemical shift of water glass measured by MR −100 to −120 ppm
In not less than 1.35 times the peak area, and not less than 1.20 times the peak area at the chemical shift of -100 to-120 ppm of ²⁹ Si-NMR measurements were colloidal silica under the same conditions.

(E) Wavelength region 1000 in absorptiometry
The transmittance at 200 nm is 90 to 100%. (F) The electric conductivity is 2.1 to 35 mS / cm. According to the present invention, an inorganic coagulant that simplifies the process of manufacturing a coagulant, shortens the manufacturing time, and is excellent in stability and work safety is provided.

Further, the water treatment method according to the present invention is a method for treating recovered sludge water containing cleaning wastewater generated from concrete treatment facilities such as a construction site, a crushed stone factory, a concrete product factory, and a Lady Mix factory with the above-mentioned inorganic material for water treatment. It is characterized by adding a coagulant and performing solid-liquid separation into supernatant water and sludge. Further, if necessary, one or more of swelling clay minerals, phosphorus compounds and cements are added as a flocculant after or before the addition of the inorganic flocculant for water treatment.

According to the water treatment method of the present invention, since the floc formation rate is high and the final reached floc particle size is large, the sedimentation rate is high and the separation of the supernatant liquid and the sludge can be carried out in a short time. .

[0020]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in more detail below. The inorganic coagulant for water treatment according to the present invention,
As described above, the specific alkali silicate aqueous solution (1),
The solution contains the iron ion and / or titanium ion-containing solution (2) as an essential component and, if necessary, an optional component. Further, one or more of swelling clay minerals, phosphorus compounds and cements are used as a flocculant after or before the addition of the inorganic flocculant for water treatment.

Hereinafter, each component will be described in detail. Alkaline silicate aqueous solution (1) The alkaline silicate aqueous solution used in the present invention has an intermediate property between water glass and colloidal silica, and has a molar ratio (SiO ₂ / A
_It has a high content of ₂ O) (A: alkali metal) and silicon and has a high degree of anion activation.

That is, the aqueous solution of alkali silicate used in the present invention is characterized in that the content of silicon with respect to the alkali is higher than that of ordinary water glass. Here, as the alkali, lithium, sodium, potassium and the like are used, but most commonly it is sodium. In the alkali silicate aqueous solution used in the present invention, the molar ratio of silicon to alkali (A) (SiO ₂ / A ₂ O) (A: alkali metal) is 4
-30, preferably 9-26, more preferably 12-
21. When the alkali is lithium, sodium, potassium or the like, the molar ratio is a value calculated in terms of oxide (A ₂ O, where A is an alkali metal). Hereinafter, in this specification, (SiO ₂ / A ₂ O) (A: alkali metal) may be simply abbreviated as “molar ratio”.

In ordinary water glass, when dealkalization proceeds and the molar ratio (SiO ₂ / A ₂ O) (A: alkali metal) increases, silica precipitates and the solution state cannot be maintained.
In the present invention, it can exist stably as a solution. It is considered that the presence of the above-mentioned anions largely contributes. When the anion activity is high, the silicate anion actively contributes even when desalting Na, which is a polymerization stopper in water glass,
It keeps stable because it creates an electrical double layer.

In the alkali silicate aqueous solution used in the present invention, the silicon concentration in terms of oxide and the SiO ₂ concentration (B) are
It is 6.8 to 30% by weight, preferably 8 to 26% by weight, and more preferably 14 to 22% by weight. Such an alkali silicate aqueous solution used in the present invention has a silicon concentration similar to that of silicic acid sol or colloidal silica.

In addition to the above characteristics (A) and (B), the aqueous alkali silicate solution of the present invention preferably satisfies at least one of the following characteristics (C) to (F). That is,
The degree of anion activation is evaluated by the zeta potential, and in the alkaline silicate aqueous solution of the present invention, the zeta potential (C) is
Is preferably −40 MV to −80 MV, more preferably −
50 MV to -80 MV, particularly preferably -58 MV to -80 MV
Is in the range.

The zeta potential is a parameter involved in dispersion and aggregation of particles. When many particles of the same type are dispersed in the liquid, each particle has the same charge. And, the higher the charge is, the more repulsive each other is, and the longer time the stability is maintained without aggregation. On the contrary, when the particles do not have an electric charge, or when substances of opposite signs are mixed, the particles immediately aggregate and precipitate. The charge of this particle is the pH of the solution
Also depends on.

As described above, this aqueous alkali silicate solution has a negative zeta potential and contains a large number of anionic molecules, and thus has a high anionic activity. The anionic molecules contained in this aqueous solution of alkali silicate are extremely small and smaller than colloids such as colloidal silica. Therefore, in the present invention, even if the anionic particles are present, a sol-like behavior is not observed, and the particles can be handled substantially as a solution. This is supported by the transmittance described below.

[0028] The present form of the anionic particles, SiO on the surface ^-
Existing as ultrafine particles having an average particle size of 3 to 15 nanometers. The structure of silicate anion is
Although various are known as described below, in the aqueous solution of alkali silicate used in the present invention, there are few compounds having 1 to 2 functionality and belonging to a linear polymer or polycyclic silicate anion, and trifunctional Q3x,
It is considered that a large amount of trifunctional Q3y and tetrafunctional Q4 is contained.

[0029]

[Chemical 1]

In ordinary colloidal silica, the presence of anions as described above is small, and the zeta potential is -25 MV to
It is about -38 MV. Further, although water glass contains anions, the zeta potential is about −14 MV to −40 MV because it has few highly functional anion parts. (D) ²⁹ Si-NMR
At the time of measurement, the peak area at chemical shift −100 to −120 ppm is preferably 1.35 times or more, more preferably 1.35 to the peak area at chemical shift −100 to −120 ppm of water glass measured under ²⁹ Si-NMR under the same conditions. It is 2.5 times, and 1.20 times or more, more preferably 1.20 to 1.33 times the peak area at chemical shift −100 to −120 ppm of colloidal silica measured by ²⁹ Si-NMR under the same conditions. From this result, the alkali silicate solution of the present invention,
1 to 2 functional, few belonging to linear polymers and polycyclic silicate anions, trifunctional Q3x, trifunctional Q3y, tetrafunctional
You can see that it contains a lot of Q4.

The peak area is calculated by the area enclosed by the vertical axis at -100 ppm, the vertical axis at -120 ppm, and the spectrum curve after baseline correction. The aqueous solution of alkali silicate used in the present invention has a transmittance (E) in the wavelength region of 1000 to 200 nm in the absorptiometry of preferably 90 to 100%, more preferably 95 to 100%.
%.

The transmittance of ordinary water glass is similar to the above, but the transmittance of colloidal silica is extremely low at 200 to less than 380 nm and is 10 to 0%. As a result, it is found that this aqueous solution of alkali silicate has characteristics close to those of water glass.
Further, the alkali silicate aqueous solution used in the present invention has an electric conductivity (F) of preferably 2.1 to 35 mS / cm, more preferably 2.1 to 16 mS / cm, and particularly preferably 5.0 to 1
It is 1.0 mS / cm. Since this alkaline silicate aqueous solution has high electric conductivity, it is a highly desalted solution, and is a solution that does not aggregate due to silicate anions and maintains stability.

The aqueous alkali silicate solution used in the present invention has an intermediate property between water glass and colloidal silica, has a high molar ratio and a high silicon content, and has a high degree of anion activation. The method for producing the aqueous alkali silicate solution as described above is not particularly limited, but the present inventors can efficiently and stably produce a novel aqueous alkali silicate solution by the first and second production methods described below. Is finding.

First of the aqueous alkali silicate solution used in the present invention
The production method of is the molar ratio (SiO ₂ / A ₂ O) (A: alkali metal) 4
Is less than the silicon oxide concentration (SiO ₂ concentration)
Is treated with an electrodialyzer to deal with 2.0 to 12% by weight of raw material alkali silicate aqueous solution. The silicic acid and the alkali (alkali has the same meaning as above) in the raw material alkali silicate aqueous solution have a molar ratio (SiO ₂ / A ₂ O) (A: alkali metal) of less than 4, preferably 1.5 to less than 4.0, more preferably 2.8 to 3.5 is suitable. The silicon oxide concentration (SiO ₂ concentration) is 2.0 to 12.0% by weight, preferably 3.0 to 12.0% by weight, and more preferably 4.5 to 12.0% by weight.
The degree is appropriate.

As shown in FIG. 1, the electrodialyzer has a cation exchange membrane 1 and an anion exchange membrane 2 between an anode and a cathode.
Are alternately arranged, and the desalting chambers 3 and the concentrating chambers 4 are alternately formed. As such an electrodialysis device,
Conventionally known materials can be used without particular limitation. That is, as the electrodes, ion exchange membranes, and other necessary members constituting such an electrodialysis device, known ones are used without particular limitation. For example, as the ion exchange membrane, generally, the cation exchange group is a sulfonic acid group,
The anion-exchange group is a quaternary ammonium group, and a hydrocarbon-based cation-exchange membrane and anion-exchange membrane made of a styrene-divinylbenzene copolymer material using a reinforcing base material are industrially used. Further, a fluorine-containing ion exchange membrane in which the material of the ion exchange membrane is a fluoropolymer can also be used. In the electrodialysis device, it is desirable to use an alkali-resistant ion exchange membrane because the raw material aqueous solution of alkali silicate to be subjected to electrodialysis is alkaline and condenses (generates) caustic alkali.

During electrodialysis, the desalting chamber 3 of the electrodialysis device
Then, the raw material alkali silicate aqueous solution is supplied, and water or a dilute caustic alkaline aqueous solution is supplied to the concentrating chamber 4 to perform electrodialysis. In the desalting chamber 3, alkali metal ions (for example, Na
⁺ ) Moves to the concentration chamber 4 side through the cation exchange membrane 1,
Further, hydroxide ions (OH ⁻ ) are transferred to the concentration chamber side 4 through the anion exchange membrane 2 for desalting. On the other hand, in the concentrating chamber 4, the alkali metal ions and hydroxide ions transferred from the desalting chamber 3 are concentrated to obtain a caustic alkaline aqueous solution.

The operating conditions of the electrodialysis apparatus vary depending on the size of the apparatus, the concentration of the raw material alkaline silicate aqueous solution, etc., but the voltage is adjusted so as to be constant at 0.6 V / pair, and the desalination of the raw material alkaline silicate aqueous solution is performed. A supply rate of about 3.1 liters / minute to the chamber is suitable. In addition, water or a dilute caustic aqueous solution is supplied to the concentrating chamber at a rate of about 3.1 liters / minute.

From the desalting chamber 3, alkali silicate aqueous solution (dealkaline solution) having a reduced alkali concentration is obtained by dealkalization. The molar ratio of the alkali silicate aqueous solution obtained from the desalting chamber 3 is preferably 4.0 to 3 in order to suppress the precipitation of silica solids while increasing the molar ratio (SiO ₂ / A ₂ O).
It is desirable to adjust it to 0, more preferably 9 to 26, and particularly preferably 12 to 21.

By appropriately selecting the electrodialysis conditions, particularly the electrical conductivity, the molar balance (Si
O ₂ / A ₂ O) can be adjusted. Generally, when electric conductivity is high, SiO ₂ / A ₂ O tends to be low, and when electric conductivity is low, SiO ₂ / A ₂ O tends to be high. Further, in this first manufacturing method, since the raw material alkali silicate aqueous solution having a relatively high silicon content concentration is used, the silicon content concentration of the obtained alkali silicate aqueous solution is
It is preferably 6.8 to 12% by weight, and more preferably about 6.8 to 9% by weight in terms of SiO ₂ .

Conventionally, in electrodialysis of an aqueous alkali silicate solution, a relatively low concentration raw material aqueous alkali silicate solution has been used from the viewpoint of preventing clogging of the ion exchange membrane and performing continuous operation. The SiO ₂ conversion was at most about 6.0% by weight, and the resulting dealkalized solution also had a SiO ₂ conversion concentration of at most about 6.2% by weight.
On the other hand, in the first production method, since the raw material alkali silicate aqueous solution having a relatively high SiO ₂ conversion concentration is used as described above, a dealkalized solution (alkali silicate aqueous solution) having a high SiO ₂ conversion concentration is obtained. To be As a result, it is possible to obtain an active alkali silicate aqueous solution having a high molar ratio, which also satisfies the characteristics (A) and (B) described above, and more preferably (C) to (F).

In electrodialysis, a caustic aqueous solution is obtained from the concentrating chamber 4. In this caustic aqueous solution, silicic acid migrates through the ion exchange membrane in the course of dialysis, and a small amount of 0.1 to 1% by weight of silicic acid may be mixed in, but mixing of a small amount of silicic acid does not pose a problem. Application,
For example, when it is used as an alkali source for preparing an aqueous alkali silicate solution which is a starting material in the production of silicic acid sol, it can be recycled as it is. Also SiO ₂ /
It can also be used for the production of JIS No. 1 and No. 2 alkali silicates, sodium metasilicate and sodium orthosilicate having a low A ₂ O ratio.

The alkali concentration can be reduced by allowing the solution in the concentration chamber 4 to remain during the electrodialysis.
In the first manufacturing method, a reverse osmosis membrane method may be used to further concentrate the dealkalized solution (alkali silicate aqueous solution) obtained from the desalting chamber. Since the dealkalized solution contains a small amount of alkali, it is desirable to use an alkali resistant composite membrane as the reverse osmosis membrane. The reverse osmosis membrane has a molecular weight cutoff of preferably 100 to 20000, more preferably 100 to 1000, and particularly preferably 100 to 800. As a feature of the reverse osmosis method, it is possible to remove water in a form that consumes less energy without evaporating water, and to recover valuable resources (here, alkali silicate) stably and efficiently in a solution state. Points are given. For example, in the conventional method, which is a method of concentrating colloidal silica, such as an evaporative concentration method performed by raising the boiling point of water to 100 ° C. or a vacuum distillation method performed by lowering the boiling point of water under reduced pressure, the heating conditions are intentionally changed. Since the particles of colloidal silica are grown below, the silicate anion is slightly present on the surface of the particles, and the activity is easily lost.

On the other hand, pressure is applied to polysulfone, polyacrylonitrile, cellulose acetate, nitrocellulose,
An ultrafiltration membrane method, in which water is removed using an organic thin film such as cellulose, is generally used in terms of energy and easy control of conditions (US Pat. No. 3,969,
No. 266, British Patent No. 1,148,950, and JP-A-58-15.
See No. 022).

However, the ultrafiltration membrane method has a drawback that it removes effective and highly active silicate anions that are developed by electrodialysis. In contrast, the reverse osmosis membrane method, in which a stable organic thin film in a strong alkaline aqueous solution is three-dimensionally configured as a module with excellent volume efficiency, is an energy-saving, compact, easy-to-control condition and transforms valuable materials without applying heat. It is a method that can be concentrated and recovered without using.

The pressure during reverse osmosis is preferably 4.0 MPa.
It is the following (reverse osmosis module inlet), and more preferably, it is desirable to adjust the pressure to about 3.2 to 3.8 MPa. The solution temperature is preferably adjusted to about 35-40 ° C. By using such a reverse osmosis membrane method in combination, the alkaline silicate aqueous solution obtained through electrodialysis can be further concentrated, and the silicon content concentration can be changed to SiO ₂
Converted to preferably 3.0 to 30.0% by weight, more preferably
It can be concentrated to 6.5 to 30% by weight.

When the reverse osmosis membrane method is also used, it is not always necessary to use the above-mentioned solution having a high silicon concentration as the alkali silicate aqueous solution. That is, the second method for producing an alkali silicate aqueous solution used in the present invention is
It is characterized in that a raw material alkaline silicate aqueous solution having a molar ratio (SiO ₂ / A ₂ O) of less than 4 is dealkalized by using an electrodialyzer and the dealkalized solution is concentrated by a reverse osmosis membrane method.

The silicic acid and the alkali (alkali has the same meaning as above) in the raw material alkali silicate aqueous solution have a molar ratio (SiO ₂ / A
₂ O) is less than 4, preferably 1.5 to less than 4.0, and more preferably about 2.8 to 3.5. The concentration of silicon converted to oxide (SiO ₂ concentration) is not particularly limited, but is 2.0
-12.0 wt%, preferably 3.0-12.0 wt%, more preferably 4.5-12.0 wt% is suitable.

The apparatus and conditions used for electrodialysis are the same as those in the first production method. The dilute alkali silicate aqueous solution (dealkaline solution) with a reduced alkali concentration obtained from the desalting chamber 3 increases the molar ratio (SiO ₂ / A ₂ O) and suppresses the precipitation of silica solids. (SiO ₂ / A ₂ O) is
It is desirable to adjust it to preferably 4.0 to 30, more preferably 9 to 26, and particularly preferably 12 to 21.

Further, the deallocation in the second manufacturing method is performed.
The concentration of silicon in the potassium solution is SiO ₂Converted preferably
3.0 to 10.0% by weight, more preferably 4.0 to 8.0% by weight
It is desirable to adjust it every time. Next, the second manufacturing method
In the method, reverse the dealkalized solution obtained from the desalting chamber.
Concentrate by permeation membrane method.

Reverse osmosis is performed as described above. By such a reverse osmosis membrane method, water in the dealkalized solution is removed and the dealkalized solution (alkali silicate aqueous solution) is concentrated. As a result, it is possible to obtain an active alkali silicate aqueous solution having a high molar ratio, which also satisfies the characteristics (A) and (B) described above, and more preferably (C) to (F).

The alkali concentration (calculated as oxide) of the high molar ratio active alkali silicate aqueous solution obtained by the above method is
Although it is reduced to 0.4% by weight or less, the alkali concentration can be further reduced by performing a contact treatment with a cation exchange resin, if necessary. As an ion exchange resin, R-SO ₃
H-type, R-COOH-type, and R-OH-type cation exchange resins are used without particular limitation. The contact treatment with the ion exchange resin may be performed either after electrodialysis or after reverse osmosis.

Desalination in an alkaline solution is carried out by direct contact treatment of a high molar ratio active aqueous solution of alkali silicate obtained by electrodialysis or further by electrodialysis and reverse osmosis. And the molar ratio (SiO ₂ / A ₂ O) can be adjusted to a high level. Contact with the cation exchange resin can, for example, in a column tower 200～1000Cm ^3, packed with a cation exchange resin of 240～530Cm ^3,
After washing with water, it is carried out by passing an aqueous alkali silicate solution at pH 5.0 to 6.0 and a flow rate of 4 to 25 ml / sec.

Containing iron ions and / or titanium ions
Solution (2) The iron-ion and / or titanium-ion-containing solution used in the present invention may be, for example, a solution of iron salts or titanium salts (preferably an aqueous solution), or such as titanium tetrachloride. It may be a liquid compound, and may be a compound that can be handled substantially like an ion-containing solution.

It is preferable that iron ions are contained in a trivalent state and titanium ions are contained in a tetravalent state. In particular, the ion-containing solution (2) used in the present invention is preferably an aqueous solution containing trivalent iron ions. The concentration of iron ions or titanium ions in the ion-containing solution is appropriately selected within a range that does not impair the object of the present invention, but is preferably 0.10 to 40.0 w / v%, more preferably 0.5 to 38 w. / V%, particularly preferably 1.0 to 35w
/ V%.

Examples of such a solution containing iron ions and / or titanium ions include ferric chloride,
Ferric sulfate or ferric polysulfate, titanium tetrachloride or an aqueous solution of titanyl sulfate, or a mixed solution thereof is preferably used. In the inorganic coagulant for water treatment of the present invention, the iron ion and / or titanium ion-containing solution (2) is converted into iron or titanium based on 100 parts by weight of the solid content of the alkali silicate aqueous solution (1). ,
It is preferably used in an amount of 0.1 to 250 parts by weight, more preferably 5.0 to 210 parts by weight.

Other Components In the inorganic coagulant for water treatment of the present invention, in addition to the above components, silicon dioxide such as colloidal silica, siloxane compounds such as silicone and organopolysiloxane, and water may be added, if necessary. You may add glass etc. In order to accelerate and complement the aggregating action, an aluminum-based aggregating agent such as a sulfuric acid band or polyaluminum chloride (PAC), or a very small amount of a polymer aggregating agent may be mixed in the production process.

These components are optionally used within a range that does not impair the object of the present invention, and the amount used varies depending on the nature of the components and the purpose of use, but in general, alkali silicate is used. It is preferably used in a proportion of 0.01 to 9000 parts by weight, more preferably 0.5 to 4500 parts by weight, based on 100 parts by weight of the solid content of the aqueous solution (1).

Inorganic Flocculant for Water Treatment The inorganic flocculant for water treatment of the present invention can be obtained by mixing the above components (1) and (2) and, if necessary, other components in a mixer. In addition, a diluent such as water may be used in mixing. The resulting inorganic coagulant for water treatment depends on the mixing ratio of the above components,
It preferably has the following composition.

That is, the inorganic coagulant for water treatment preferably contains silicon at an oxide conversion concentration (SiO ₂ concentration),
0.05 to 16.0% by weight, more preferably 0.10
.About.14.5% by weight, more preferably 1 to 11% by weight, particularly preferably 2 to 9% by weight, and the iron ion and / or titanium ion-containing solution is converted into iron or titanium in an amount of 0.01 to 25. 0% by weight, more preferably 0.05 to 21.0% by weight, still more preferably 0.1.
0-20.0% by weight, particularly preferably 0.30-18.
It is contained at 0% by weight, and the molar ratio of silicon and alkali (SiO ₂
/ A ₂ O) (A: alkali metal) is 4 to 30, preferably 15 to
30, more preferably 20 to 30, and particularly preferably about 25 to 30.

When an iron ion-containing solution is used as the ion-containing solution, the Fe / Si molar ratio is 0.01 or more, preferably about 0.05 or more. When a titanium ion-containing solution is used as the ion-containing solution, Ti
/ Si molar ratio is 0.005 or more, preferably 0.01
That's about it. The swelling clay minerals, phosphorus compounds, and cements used in combination with the above-mentioned water treatment inorganic coagulant are shown below.

Examples of the swelling clay mineral include, but are not limited to, bentonite, montmorillonite, saponite, and hectorite, which are the main components of bentonite. Bentonite can be used without being affected by the production area and brane value. The bentonite may be used as a powder as it is, but in order to perform solid-liquid separation quickly, it is preferable to use water after swelling by adding water.

The phosphorus compound is not particularly limited, and examples thereof include sodium tripolyphosphate, sodium pyrophosphate, sodium hexametaphosphate, aluminum biphosphate,
Examples include magnesium biphosphate, acidic sodium metaphosphate, sodium polyphosphate and potassium salts thereof. Of these, sodium hexametaphosphate is preferably used because it has a high aggregating effect on hexametaphosphoric acid, which is a polymer, and is particularly easily available and inexpensive. These phosphorus compounds can be used without particular limitation such as powder, crystal, and solution type, but in view of ease of handling and reactivity, solution type, or powder or crystal dissolved in water is preferable. The concentration of the solution is not particularly limited, and the solution may be diluted before use.

The cement is a Portland cement type (ordinary Portland cement, early strength Portland cement, etc.) specified by JIS standard, a mixed cement type (fly ash cement, blast furnace cement, etc.), and other special cement type (ultrafine particle cement). Etc.) can be used without particular limitation. Above all, ultrafine particle cement having fine particles that can serve as nuclei in aggregation is preferable, and among them, ultrafine particle cement having a small slag content that becomes an impurity is particularly preferably used.

The inorganic coagulant for water treatment of the present invention may be appropriately diluted before use before use. Such an inorganic coagulant for water treatment according to the present invention is added to recovered sludge water including cleaning wastewater generated from a concrete treatment facility such as a construction site, a crushed stone factory, a concrete product factory, and a Lady Mix factory, and a supernatant water is added. And sludge are preferably used for solid-liquid separation.

When the flocculant of the present invention is added to the recovered sludge water and stirred in the flocculation stirring tank, very large flocs are quickly formed, and solid-liquid separation can be performed at high speed in the precipitation tank and the filtration tank. Since the coagulant of the present invention coexists with the high molar ratio alkali silicate aqueous solution as described above and iron ions and / or titanium ions, when added to the recovered sludge water, iron ions and / or titanium ions are recovered. Strongly neutralizes the negative charge in sludge water, hydrolyzes iron ions and titanium ions to form iron hydroxide and titanium hydroxide composite flocs, and a high molar ratio alkali silicate is iron hydroxide and titanium hydroxide composite. The particle size of flocs is significantly increased by the cross-linking action of polymerized silica. That is, according to the coagulant of the present invention, the floc formation rate is high, and the final reached floc particle size is large, so the sedimentation rate is high,
The supernatant and sludge can be separated in a short time.

The amount of the flocculant added varies depending on the composition of the recovered sludge water, but generally, the recovered sludge water 10
With respect to 0 parts by weight, the aggregating agent is 0.0 in terms of solid content.
It is preferably about 05 to 15.0 parts by weight. Further, when the swelling clay mineral, the phosphorus compound, and the cement are used, the addition amount thereof is preferably about 0.0001 to 1.0 part by weight in terms of the solid content based on 100 parts by weight of the recovered sludge water.

The supernatant liquid recovered by the above method can be used as a kneading liquid when preparing cement or concrete, for example.

[0068]

According to the present invention as described above, an inorganic flocculant which can simplify the process for producing the flocculant, shorten the production time, and is excellent in stability and work safety is provided. Further, according to the coagulant of the present invention, since the floc formation rate is high and the final reached floc particle size is large, the sedimentation rate is high, and the supernatant liquid and the sludge can be separated in a short time.

[0069]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited to these examples. The specifications of the electrodialyzer and reverse osmosis equipment used are as follows. Electrodialyzer (manufactured by Tokuyama Corp.) Anion exchange membrane (10 sheets): AHA (trade name), Ltd.
Tokuyama cation exchange membrane (12 sheets): CMB (trade name), Co., Ltd.
Tokuyama electrode material: Ni plate Distance between electrodes: 26.2 mm Distance between anion exchange membrane and cation exchange membrane: 0.7 mm Area of ion exchange membrane: ² dm ² / sheet Reverse osmosis equipment (Toray Engineering) Reverse osmosis Membrane: Mini spiral membrane (alkali-resistant synthetic composite membrane: molecular weight cutoff 200, membrane area 1.6m ² , φ2.0 × 40L) High-pressure circulation pump (SUS316L / NBR) Regular use: 5 to 12.5L / min, 40kgf / cm ² Pressure resistance: 10 L / min, 70 kgf / cm ² Spiral vessel: for φ2.0 x 40 L, FRP pressure resistance 70 kgf / cm
² Accumulator: bladder type, 100cc, maximum working pressure 70kgf / c
m ²

[0070]

[Production Example 1] The specific gravity and composition of the aqueous alkali silicate solution used as a raw material were as follows. Specific gravity (15 ° C): 1.404 SiO ₂ (%): 28.12 Na ₂ O (%): 9.21 SiO ₂ / Na ₂ O (molar ratio): 3.15 This was further diluted with water to obtain a silicic acid concentration. (Converted to SiO ₂ ) 6
A wt% alkali silicate aqueous solution was obtained.

The raw material aqueous solution of alkali silicate thus obtained was supplied to the desalting chamber of the electrodialyzer having the above-mentioned specifications, and the dilute caustic soda solution was supplied to the concentration chamber. In constant voltage operation
When electrodialysis was started at a cell voltage of 9 to 10 V including the electrode chamber at 0.6 V / pair (stack voltage 6 V / 10 pair), the initial electrical conductivity was 24 mS / cm. After starting electrodialysis,
It was operated until the electrical conductivity fell below 4.5 mS / cm. The average dialysis time until the electrical conductivity dropped to less than 4.5 mΩ / cm was 80 minutes. The dealkalized solution obtained from the desalting compartment had a silica content (SiO ₂ ) of 6.4% by weight and an alkali content (Na ₂ O) of 0.35% by weight.

The dealkalized solution obtained from the desalting chamber is treated with 30
The temperature is controlled to -40 ℃, supplied to the concentration tank of the reverse osmosis equipment, concentrated at an inlet flow rate of 10 L / min, average pressure 3.0 MPa, flux (30 ℃) 35-28 kg / m ² hr, and have the following composition A high molar sodium silicate aqueous solution having the above characteristics was obtained. (A) Molar ratio (SiO ₂ / Na ₂ O): 14.8 (B) SiO ₂ concentration: 16.3 wt% (C) Zeta potential: -58.6 MV (D) ²⁹ Si-NMR spectrum is shown in FIG. 2.

For comparison, the following measured under the same conditions:
Of water glass and colloidal silica ²⁹Si-NMR spectrum
Are shown together in FIG. Water glass: diluted No. 3 sodium silicate (manufactured by Toso Sangyo Co., Ltd.) Specific gravity (15 ℃): 1.064 SiO₂      (%): 5.80 Na₂O (%): 1.90 SiO₂/ Na₂O (molar ratio): 3.15 Zeta potential: -27.5MV Colloidal silica: DuPont SM Specific gravity (15 ℃): 1.216 SiO₂      (%): 30 Na₂O (%): 0.56 SiO₂/ Na₂O (molar ratio): 55.26 Zeta potential: -34.0 MV Of the sodium silicate aqueous solution of the present invention²⁹In Si-NMR spectrum
Chemical shift Peak area at −100 to −120 ppm
Is 2.28 times the peak area of water glass.
1.27 times that of Hidal Silica (SM made by DuPont)
It was. (E) Transmittance at wavelength of 1000 to 200 nm: 95 to 100% The result of UV-visible absorption spectrophotometry is shown in FIG. Comparison
Therefore, colloidal silica (Dupo
UV) and the following colloidal silica
The results of the photometric analysis are shown together in FIG.

Colloidal silica: DuPont HS-40 Specific gravity (15 ° C.): 1.305 SiO ₂ (%): 40 Na ₂ O (%): 0.41 SiO ₂ / Na ₂ O (molar ratio): 100.68 Zeta potential: -36.7 MV (F) Electric conductivity: 7.5 mS / cm The measuring method and measuring device for each physical property value are as follows. (A) Molar ratio (SiO ₂ / Na ₂ O): SiO ₂ and Na according to JIS K1408
₂ O was analyzed and calculated. (B) SiO ₂ concentration: SiO ₂ was analyzed according to JIS K1408. (C) Zeta potential: Beckman Coulter DELSA
It was measured by the electrophoretic light scattering method using 4403X. (D) ²⁹ Si-NMR measurement: JEOL ALPHA-500 type (500 MH
z) was used. (E) Transmittance: UV-550 type manufactured by JASCO Corporation was used. (F) Electric conductivity: ES-12 type manufactured by Horiba, Ltd. was used.

[0075]

Example 1 The aqueous solution of sodium silicate produced in the above Production Example 1 was adjusted to have a silica concentration of 9% by weight.
For 0 g, ferric chloride aqueous solution (ferric chloride concentration 30
%, PH 0) was gradually added into 50 g and mixed, and an inorganic coagulant for water treatment (composition FeCl ₃ 15%, SiO ₂ 4.5
%, PH 0.12) was obtained.

Using the aggregating agent thus obtained, under the following conditions:
Floc formation time (sec) and floc sedimentation velocity (mm /
Minutes). Floc formation time (sec) and floc sedimentation velocity (mm /
(Minute) measurement Kaolin was added to tap water to prepare an SS20 mg / liter suspension, and the obtained flocculant was added to perform a jar test. Jar test conditions are stirring speed 150r
It was pm 3 minutes and 50 rpm 10 minutes. The pH after coagulant injection was kept constant at 6. The water temperature was 24 ° C. The coagulant injection rate was 4 mg / liter as the total amount of Ti and Fe. The floc formation time (the time when the flocs could be observed with the naked eye after the start of stirring) and the sedimentation rate of the flocs after the jar test were measured.

The results are shown in Table 1. Further, also in Comparative Examples using ferric chloride or titanium tetrachloride alone, the floc sedimentation rate after completion of stirring during the jar test was measured. The results are shown in Table 1.

[0078]

Comparative Example 1 No. 3 water glass stock solution (silica concentration 30%) was diluted with tap water to prepare an aqueous sodium silicate solution having a silica concentration 9%. Ferric chloride aqueous solution (ferric chloride concentration 30%, p
50 g of this sodium silicate aqueous solution was gradually added to 50 g of H0), and a ferric iron-containing silicic acid aqueous solution (composition FeCl ₃ 15%,
SiO ₂ 4.5%, pH 0.24) was obtained.

The floc formation time (seconds) and the floc sedimentation rate (mm / min) were determined in the same manner as above. The results are shown in Table 1.

[0080]

Comparative Example 2 No. 3 water glass stock solution (silica concentration 30%) was diluted with tap water to prepare an aqueous sodium silicate solution having a silica concentration 9%. 50 g of this sodium silicate aqueous solution was added to and mixed with 50 g of titanium tetrachloride aqueous solution (TiO ₂ concentration 15%, pH minus value), and a tetravalent titanium-containing silicic acid aqueous solution (composition;
TiO ₂ 7.5% and SiO ₂ 4.5%) were obtained. In the same manner as above, the floc formation time (second) and the floc sedimentation rate (mm / min) were determined.

The results are shown in Table 1.

[0082]

[Table 1]

(Preparation of simulated recovered water) In a 10 L container, 9500 g of tap water at 25 ° C. and 500 g of ordinary Portland cement were added,
Stirring (400 rpm) for 24 hours with a three-one motor was used as simulated recovered water (cement concentration 5%).

[0084]

[Comparative Example 3] 300 g of the artificially collected water prepared above was placed in a 300 ml death cup, and a jar tester (JM, manufactured by RIKEN Miyamoto Co., Ltd.
Using D-4 type), stirring was carried out for 6 minutes (stirring speed 190 rpm), stirring was immediately stopped, and the sedimentation speed was visually confirmed.

[0085]

[Example 2] 300 g of the pseudo-recovered water prepared above was put in a 300 ml death cup and stirred using a jar tester (190 rp).
m) while adding 0.3 g of a solution of the sodium silicate aqueous solution obtained in Production Example 1 adjusted to a silica concentration of 13.5% by weight (0.1 part by weight to 100 parts by weight of simulated recovered water) at the same rotation speed.
After stirring for a minute, the stirring was stopped immediately and the sedimentation speed was visually confirmed.

[0086]

Example 3 In the same manner as in Example 2, 0.3 g of an aqueous sodium silicate solution (silica concentration: 13.5% by weight) was added, followed by stirring for 1 minute (190
rpm), and 0.9 g of fine particle cement (simulated recovered water 1
After adding 0.3 part by weight to 00 parts by weight), the mixture was stirred for 6 minutes at the same number of revolutions, immediately after which the stirring was stopped and the sedimentation rate was visually confirmed.

[0087]

Example 4 In the same manner as in Example 2, 0.3 g of an aqueous sodium silicate solution (silica concentration: 13.5% by weight) was added, and the mixture was stirred at 190 rpm for 1 minute, followed by 0.9 g of bentonite (adding 7.5 g of bentonite to 100 g of water at room temperature). After stirring for 1 hour underneath), the mixture was stirred for 6 minutes at the same number of revolutions, then immediately stopped stirring, and the sedimentation rate was visually confirmed.

[0088]

[Example 5] In the same manner as in Example 2, 0.3 g of an aqueous sodium silicate solution (silica concentration: 13.5% by weight) was added, followed by stirring at 190 rpm for 1 minute, followed by addition of 0.3 g of a sodium hexametaphosphate 3% solution. After stirring for 6 minutes at the rotation speed, the stirring was immediately stopped and the sedimentation speed was visually confirmed. The experimental results of Comparative Example 3 and Examples 2 to 5 are shown in Table 2.

[0089]

[Table 2]

[Brief description of drawings]

FIG. 1 is a schematic view of an electrodialysis device used in a production example.

[FIG. 2] ²⁹ Si of sodium silicate aqueous solution, water glass and colloidal silica (SM produced by DuPont) produced in Production Example
-Indicates an NMR spectrum.

FIG. 3 shows the results of ultraviolet-visible absorptiometry of the aqueous sodium silicate solution, colloidal silica (SM manufactured by DuPont) and colloidal silica (HS-40 manufactured by DuPont) manufactured in Preparation Examples.

[Explanation of symbols]

1 ... Cation exchange membrane 2 ... Anion exchange membrane 3 ... Desalination chamber 4 ... Concentration room

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yuuji Miyahara             1-40 Oshima, Koto-ku, Tokyo Tosoh Product             Business in Tokyo factory (72) Inventor Takayoshi Nagano             9-57 Tsuboi-cho, Kumamoto-shi, Kumamoto Co., Ltd.             Nagano Industry (72) Inventor Junichiro Sahara             5-10 Daimoncho, Moriguchi City, Osaka Prefecture Tomi Co., Ltd.             Shishikai (72) Inventor Kim Tetsu Next             1-40 Oshima, Koto-ku, Tokyo Tosoh Product             Business in Tokyo factory F-term (reference) 4D015 BA03 BA08 BA11 BA12 BA19                       BB05 BB09 BB16 CA10 CA20                       DA13 DA30 DA32 DA36 DC02                       DC03 EA32

Claims (9)

[Claims] (1) (A) The molar ratio of (A) silicon to alkali (SiO ₂ / A ₂ O) (A: alkali metal) is 4 to 30, and (B) the oxide conversion concentration (SiO ₂ ) of silicon. Density) is 6.8
An inorganic flocculant for water treatment, comprising 30% by weight of an alkali silicate aqueous solution and (2) a solution containing iron ions and / or titanium ions. 2. The alkali silicate aqueous solution (1): 100
Parts by weight (solid content) and the solution containing iron ions and / or titanium ions (2): 0.1 to 250 parts by weight (iron [F
e] and / or titanium [Ti] solid conversion), The inorganic flocculant for water treatment according to claim 1, characterized in that 3. The water treatment according to claim 1, wherein the iron ion and / or titanium ion-containing solution (2) is a solution containing trivalent iron ions or tetravalent titanium ions. Inorganic coagulant. 4. The inorganic coagulant for water treatment according to claim 1, wherein the aqueous solution of alkali silicate (1) has a zeta potential (C) of −40 MV to −80 MV. 5. The ²⁹ Si—N of the alkali silicate aqueous solution (1)
At the time of MR measurement, the peak area (D) at chemical shift −100 to −120 ppm is 1.35 times or more of the peak area at chemical shift −100 to −120 ppm of water glass measured by ²⁹ Si-NMR under the same conditions, and ²⁹ Si-NMR under the same conditions
Measured chemical shift of colloidal silica -100 to -1
The inorganic coagulant for water treatment according to any one of claims 1 to 4, which has a peak area of 1.20 times or more at 20 ppm. 6. The transmittance (E) in the wavelength region of 1000 to 200 nm of the alkali silicate aqueous solution (1) in the absorptiometry is 9
It is 0-100%, The inorganic coagulant for water treatment in any one of Claims 1-5 characterized by the above-mentioned. 7. The inorganic coagulant for water treatment according to claim 1, wherein the alkali silicate aqueous solution (1) has an electric conductivity (F) of 2.1 to 35 mS / cm. 8. The treated sludge water containing cleaning wastewater, etc. generated from concrete treatment equipment such as a construction site, a crushed stone factory, a concrete product factory, and a Lady Mix factory, for water treatment according to claim 1. A water treatment method comprising adding an inorganic coagulant and performing solid-liquid separation into supernatant water and sludge. 9. The one or more of swelling clay minerals, phosphorus compounds and cements are added after or before the addition of the alkali silicate aqueous solution to the recovered sludge water. 8. The water treatment method according to item 8.