JP7527587B2 - Flocculant composition - Google Patents

Description

The present invention relates to a flocculant composition for treating muddy water.

In muddy water shield construction using shield machines, the generated soil and sand is in the form of muddy water, so solid-liquid separation is carried out to reduce the amount of soil and sand disposed of. Specifically, the soil and sand (muddy water) generated underground is pumped to the ground, and after classification (primary treatment) is performed to remove coarse particles in the muddy water using a cyclone or similar device, the muddy water containing fine particles (excess muddy water) is stored in a storage tank. Next, the fine particles contained in the excess muddy water are coagulated and settled in the storage tank, and further passed through a dehydrator such as a filter press for advanced dehydration (secondary treatment). The cake generated after dehydration is either discarded as waste or reused.

In general, inorganic coagulants and organic polymer coagulants are used to perform the coagulation and settling treatment of muddy water. For example, there is a muddy water treatment device used in muddy water shield construction that adds an inorganic coagulant to muddy water and introduces it into a mixer, and then injects an organic polymer coagulant into the mixture of muddy water and inorganic coagulant discharged from the mixer (see, for example, Patent Document 1). The muddy water treatment device in Patent Document 1 adds inorganic coagulant and organic polymer coagulant separately to the front and back stages to treat muddy water with high concentrations of SS that can cause blockages, etc. Patent Document 1 also describes the use of polyaluminum chloride (PAC) as an inorganic coagulant (paragraph [0007] of the same document).

A dehydration method is also known in which a polymer coagulant is added to the highly water-containing excavated soil (mud) generated during slurry shield construction to produce primary coagulated soil, an inorganic coagulant is added to this primary coagulated soil, and the mixture is mixed to produce secondary coagulated soil, which is then passed through a dehydrator to separate solid and liquid (see, for example, Patent Document 2). Patent Document 2 describes the use of polyacrylamide, polyvinyl alcohol, maleic anhydride polymers, etc. as polymer coagulants, and the use of polyaluminum chloride, ferric chloride, aluminum sulfate, etc. as inorganic polymer coagulants (paragraph [0032] of the same document).

Japanese Patent Application Publication No. 11-244611 JP 2005-36517 A

When carrying out slurry shield construction, it has traditionally been necessary to treat the slurry without imposing a large burden or cost. However, when the time required for dewatering exceeds the time required for shield tunneling, or when the dewatering rate of the dewatered cake is insufficient, it has been necessary to deal with this by adding an excess of chemicals to improve the dewatering performance. In these cases, it is also desirable to achieve the desired improvement in dewatering performance without causing corrosion of machinery and equipment, and without adversely affecting the surrounding environment.

In this regard, the muddy water treatment device of Patent Document 1 uses highly acidic polyaluminum chloride as an inorganic coagulant, and so increasing the amount of inorganic coagulant added is likely to accelerate corrosion of machinery and equipment. In order to prevent corrosion of such machinery and equipment, measures such as using corrosion-resistant materials or applying corrosion-resistant coatings to the inorganic coagulant itself or to areas that may come into contact with the treated muddy water are necessary. Also, in order to dispose of waste without putting a burden on the environment, it is necessary to adjust the pH (neutralization work) of the dehydrated cake and treated water, which is time-consuming and costly.

The dehydration treatment method of Patent Document 2 also has the same inherent problems as Patent Document 1 because it uses inorganic coagulants that are moderately to strongly acidic, such as polyaluminum chloride, ferric chloride, and aluminum sulfate.

The present invention was made in consideration of the above problems, and aims to provide a flocculant composition that does not impose a large burden or cost on the treatment of muddy water, has little risk of causing corrosion of machinery and equipment even when the amount of chemical added is increased to improve dewatering performance, and is also environmentally friendly.

（Ｒ_１～Ｒ_４は、共に又は独立して、メチル基、エチル基、プロピル基、イソプロピル基、ブチル基、イソブチル基、及びターシャリーブチル基からなる群から選択されるアルキル基である。）
を有する第４級アンモニウムカチオンと他のアニオンとの塩（第４級アンモニウム塩）を含む凝集剤と、
（ｂ）二価のカチオンの金属塩を含む凝集脱水助剤と、
を含有することにある。 The characteristic configuration of the flocculant composition according to the present invention for solving the above problems is as follows:
A flocculant composition for treating muddy water, comprising:
(a) a compound having the following structural formula (I):

(R ₁ to R ₄ are each independently or together an alkyl group selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, isobutyl, and tertiary butyl groups.)
and a flocculant comprising a salt of a quaternary ammonium cation having the formula:
(b) a flocculating dewatering aid comprising a metal salt of a divalent cation;
The point is that it contains:

According to the flocculant composition of this configuration, by combining a quaternary ammonium salt as a flocculant and a metal salt of a divalent cation as a flocculant and dehydration aid, when the flocculant composition is used for the flocculation and settling treatment and advanced dehydration treatment (secondary treatment) of muddy water generated in muddy water shield construction, it is possible to achieve both high floc forming ability (flocculation) and strong cake forming ability (dehydration). Therefore, for example, even in a situation where a large amount of muddy water is generated, it is possible to efficiently proceed with muddy water treatment, which contributes to reducing the burden on workers and the treatment cost. In addition, since the quaternary ammonium salt and the metal salt of a divalent cation are neutral or weakly basic substances, there is little risk of causing corrosion of machines and equipment even if the amount of the flocculant composition added is increased to improve dehydration performance. And, since the dehydrated cake and treated water generated after treatment can maintain neutral or weak acidity, the pH adjustment (neutralization work) that was previously required can be unnecessary or can be reduced, and as a result, the burden on the environment is also small.

In the flocculant composition according to the present invention,
The flocculant and the flocculating dewatering aid are preferably in the form of a solution or suspension.

According to the flocculant composition of this configuration, the flocculant and flocculation dehydration aid are applied in the form of a solution or suspension, which suppresses heat generation when a quaternary ammonium salt and a metal salt of a divalent cation are mixed, or when a metal salt of a divalent cation comes into contact with water, improving the safety of the working environment.

In the flocculant composition according to the present invention,
It is preferable that the content of the quaternary ammonium salt in the flocculant is 30 to 50% by weight, and the content of the metal salt of the divalent cation in the flocculating dewatering aid is 25 to 45% by weight.

The flocculant composition of this configuration has an appropriate range of quaternary ammonium salt content in the flocculant and divalent cation metal salt content in the flocculant dehydration aid, making it easy to use and capable of exhibiting excellent flocculation and dehydration properties.

In the flocculant composition according to the present invention,
It is preferable that the blending ratio (a:b) of the flocculant and the flocculating dewatering aid is set to 1:0.5 to 1:7 by volume.

The flocculant composition of this configuration has an appropriate blend ratio of the flocculant and the flocculation and dewatering aid, resulting in an excellent balance between flocculation and dewatering properties.

In the flocculant composition according to the present invention,
It is preferably diluted with water to 3 to 5 times its volume.

The flocculant composition of this configuration is diluted with water at an appropriate ratio, so it maintains excellent flocculation and dewatering properties while improving ease of use as a liquid agent and improving workability.

In the flocculant composition according to the present invention,
It is preferable that the concentration of the divalent cation metal salt is set to 2.5% by weight or more.

The flocculant composition of this configuration ensures that the concentration of the divalent cation metal salt is at a certain level or higher, making it possible to achieve excellent dewatering properties.

In the flocculant composition according to the present invention,
It is preferable that the concentration of the quaternary ammonium salt is set to 3% by weight or more.

The flocculant composition of this configuration ensures that the concentration of the quaternary ammonium salt is at a certain level or higher, making it possible to achieve excellent flocculation properties.

In the flocculant composition according to the present invention,
The metal salt of a divalent cation is preferably at least one selected from the group consisting of calcium salts, magnesium salts, barium salts, nickel salts, zinc salts, and cobalt salts.

The flocculant composition of this configuration contains an appropriate metal salt as a metal salt of a divalent cation, so it has excellent flocculation and dewaterability, and can be provided in the form of an easy-to-use liquid formulation such as a solution or suspension.

In the flocculant composition according to the present invention,
The metal salt of a divalent cation is preferably at least one selected from the group consisting of calcium chloride, calcium sulfate, and calcium phosphate.

The flocculant composition of this configuration contains an appropriate inorganic calcium salt as a metal salt of a divalent cation, which provides better flocculation and dewaterability, and further improves usability as a liquid agent.

In the flocculant composition according to the present invention,
It is preferred that the composition does not contain any inorganic flocculants.

The flocculant composition of this configuration does not contain an inorganic flocculant, and therefore it is possible to simultaneously solve the various problems that have been desired to be solved with conventional flocculants or flocculant compositions, such as corrosivity, workability, cost, and environmental impact.

FIG. 1 is a graph showing the results of the dehydration tests of Examples 4 to 7, Comparative Example 2, and Reference Examples 2 and 3.

The flocculant composition of the present invention will be described. However, the present invention is not limited to the configurations described in the embodiments and examples described below.

The flocculant composition of the present invention contains a flocculant and a flocculation dewatering aid.

<Flocculant>
Flocculants are chemicals used to flocculate and settle soil particles suspended in the muddy water generated during muddy water shield construction, and their main component is quaternary ammonium salt. Quaternary ammonium salts are salts of quaternary ammonium cations and other anions, and are classified as cationic flocculants.

Quaternary ammonium cations have the following structural formula (I):

を有する。ここで、Ｒ_１～Ｒ_４は、共に又は独立して、メチル基、エチル基、プロピル基、イソプロピル基、ブチル基、イソブチル基、及びターシャリーブチル基からなる群から選択されるアルキル基である。すなわち、構造式（Ｉ）に示される第４級アンモニウムカチオンと他のアニオンとの塩は、テトラアルキルアンモニウム塩である。

Here, R ₁ to R ₄ are each or independently an alkyl group selected from the group consisting of a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, and a tertiary butyl group. That is, the salt of the quaternary ammonium cation and another anion shown in structural formula (I) is a tetraalkylammonium salt.

The quaternary ammonium cation is represented by the following structural formula (II) in which _R3 and _R4 in the above structural formula (I) are both methyl groups:

を有するものが好ましい。ここで、Ｒ_１及びＲ_２は、共に又は独立して、メチル基、エチル基、プロピル基、イソプロピル基、ブチル基、イソブチル基、及びターシャリーブチル基からなる群から選択されるアルキル基である。すなわち、構造式（ＩＩ）に示される第４級アンモニウムカチオンと他のアニオンとの塩は、ジメチルジアルキルアンモニウム塩である。

Here, _R1 and _R2 are, either together or independently, alkyl groups selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, isobutyl, and tertiary butyl. That is, the salt of the quaternary ammonium cation and other anion shown in structural formula (II) is a dimethyldialkylammonium salt.

Preferred dimethylalkylammonium salts are tetramethylammonium salt in which R ₁ and R ₂ are both methyl groups, trimethylethylammonium salt in which one of R ₁ and R ₂ is a methyl group and the other is an ethyl group, dimethyldiethylammonium salt in which R ₁ and R ₂ are both ethyl groups, trimethylpropylammonium salt in which one of R ₁ and R ₂ is a methyl group and the other is a propyl group, dimethylethylpropylammonium salt in which one of R ₁ and R ₂ is an ethyl group and the other is a propyl group, dimethyldipropylammonium salt in which R ₁ and R ₂ are both propyl groups, dimethyldibutylammonium salt in which R ₁ and R ₂ are both butyl groups, trimethylbutylammonium salt in which one of R ₁ and R ₂ is a methyl group and the other is a butyl group, dimethylethylbutylammonium salt in which one of R ₁ and R ₂ is an ethyl group and the other is a butyl group, and dimethylpropylbutylammonium salt in which one of R ₁ and R ₂ is a propyl group and the other is a butyl group.

Other anions that can be combined with the quaternary ammonium cation include monoatomic ions such as halide ions, such as chloride ion (Cl ^- ), bromide ion (Br ^- ), fluoride ion (F ^- ), and iodide ion (I ^- ), polyatomic ions, such as hypochlorite ion (ClO ^- ), hydroxide ion (OH ^- ), nitrate ion (NO ₃ ^- ), sulfate ion (SO ₄ ^- ), phosphate ion (PO ₄ ^- ), acetate ion (CH ₃ COO ^- ), and bicarbonate ion (HCO ₃ ^- ), and complex ions, such as tetrahydroxide aluminate ion ([Al(OH) ₄ ] ^- ). Of these, preferred anions are halide ions, and more preferred anion is chloride ion (Cl ^- ).

The quaternary ammonium salt, which is a combination of the quaternary ammonium cation shown in the above structural formula (I) or structural formula (II) and another anion, may be a single substance consisting of only the same type of quaternary ammonium salt having the same structural formula, or it may be a mixture of quaternary ammonium salts having two or more different structural formulas.

The formulation of the flocculant containing the above-mentioned quaternary ammonium salt is preferably a solution or suspension in terms of heat generation issues and ease of use, which will be described later. If the quaternary ammonium salt is water-soluble, the flocculant is prepared as an aqueous solution, and if the quaternary ammonium salt is poorly water-soluble, the flocculant is prepared as a suspension.

The content of quaternary ammonium salt in the flocculant is preferably 30 to 50% by weight, and more preferably 35 to 45% by weight. If the content of quaternary ammonium salt in the flocculant is within the above range, it will be easy to use as a flocculant and will be able to exhibit excellent flocculation properties.

<Flocculating dehydration aid>
The flocculating dewatering aid is an agent for improving the flocculating performance of a flocculant and for improving the dewatering effect of a cake when flocs of soil particles flocculated and settled by the flocculant are passed through a dehydrator such as a filter press to produce a cake, and its main component is a metal salt of a divalent cation. Metal salts of divalent cations have conventionally been known for applications such as antifreezing agents, dehumidifying agents, drying agents, wastewater treatment agents, and fertilizers, but the present inventors have discovered an unexpected new effect that the coagulation of soil particles in muddy water and the dewatering of flocs are improved when a metal salt of a divalent cation is used in combination as an auxiliary in muddy water treatment using a quaternary ammonium salt as a flocculant, and have thus completed the present invention.

Examples of metal salts of divalent cations include calcium salts, magnesium salts, barium salts, nickel salts, zinc salts, and cobalt salts. These metal salts of divalent cations may be used as a single substance consisting of only the metal salt of the same kind of divalent cation, or may be used as a mixture of metal salts of two or more different kinds of divalent cations. A particularly preferred metal salt of a divalent cation is a calcium salt. As the calcium salt, either a water-soluble calcium salt such as calcium chloride or a poorly water-soluble calcium salt such as calcium sulfate or calcium phosphate can be used, but calcium chloride, which is a water-soluble calcium salt, is more preferably used.

The formulation of the flocculating dehydration aid containing the metal salt of the divalent cation is preferably a solution or suspension, like the flocculating agent, in order to suppress the heat generated when the quaternary ammonium salt and the metal salt of the divalent cation are mixed (heat generated during preparation of the flocculating composition) or when the metal salt of the divalent cation comes into contact with water (heat generated during preparation of the flocculating dehydration aid). By suppressing the heat generated during preparation of the flocculating composition or the flocculating dehydration aid, the safety of the working environment is improved. When a water-soluble calcium salt such as calcium chloride is used as the metal salt of the divalent cation, the flocculating dehydration aid is prepared as an aqueous solution, and when a poorly water-soluble calcium salt such as calcium sulfate is used, the flocculating dehydration aid is prepared as a suspension.

The content of the metal salt of a divalent cation in the flocculating dehydration aid is preferably 25 to 45% by weight, and more preferably 30 to 40% by weight. If the content of the metal salt of a divalent cation in the flocculating dehydration aid is within the above range, it will be easy to use as a flocculating dehydration aid and will be able to exhibit excellent flocculation and dehydration properties.

<Flocculant Composition>
The flocculant composition according to the present invention is a combination of the flocculant and the flocculating and dehydrating aid, and when the flocculant composition is used for the flocculating and settling treatment and advanced dehydration treatment (secondary treatment) of muddy water generated in muddy water shield construction, it is possible to achieve both high floc forming ability (flocculation) and strong cake forming ability (dehydration). Therefore, for example, even in a situation where a large amount of muddy water is generated, it is possible to efficiently proceed with the muddy water treatment, which contributes to reducing the burden on workers and the treatment cost. In addition, since the quaternary ammonium salt contained in the flocculant and the metal salt of the divalent cation contained in the flocculating and dehydrating aid are neutral or weakly basic substances, there is little risk of causing corrosion of machines and equipment even when the amount of the flocculant composition added is increased to improve the dehydration performance. And, since the dehydrated cake and treated water generated after the treatment can maintain neutral or weak acidity, the pH adjustment (neutralization work) that was previously required can be unnecessary or can be reduced, and as a result, the burden on the environment is also small.

In the flocculant composition of the present invention, in order to simultaneously enhance (achieve both) the flocculant (coagulation) and cake-forming (drainage) abilities, it is preferable that the flocculant and the flocculant dehydration aid are each mixed in appropriate amounts. Specifically, if the amount of flocculant mixed in the flocculant composition is a and the amount of flocculant dehydration aid mixed in the flocculant composition is b, the mixing ratio (a:b) of the flocculant and the flocculant dehydration aid is preferably set to 1:0.5 to 1:7 by volume, and more preferably set to 1:1 to 1:7. If the mixing ratio (a:b) of the flocculant and the flocculant dehydration aid is within the above range, when the flocculant composition is used for muddy water treatment, it can exhibit excellent coagulation and dehydration, and the balance between coagulation and dehydration is also excellent.

The flocculant composition of the present invention can be used as is as a stock solution containing the above flocculant and the above flocculant dewatering aid, but in order to improve usability and workability as a liquid, it is usually diluted with water to 3 to 5 times its volume, preferably 3.5 to 4.5 times its volume, and more preferably 4 times its volume. In this case, in the flocculant composition diluted with water, the concentration of the metal salt of the divalent cation is preferably set to 2.5% by weight or more, and the concentration of the quaternary ammonium salt is preferably set to 3% by weight or more. Even in the flocculant composition diluted with water in this way, excellent flocculation properties and dewaterability can be maintained as long as the dilution ratio is appropriate.

The flocculant composition of the present invention exhibits excellent flocculation and dewatering properties by combining the above flocculant with the above flocculation and dewatering aid, and can be prepared without containing inorganic flocculants such as polyaluminum chloride (PAC), liquid aluminum chloride (LAC), aluminium sulfate (aluminum sulfate), ferric chloride, and polyferric sulfate that have been used in the past. This reduces the risk of the flocculant composition of the present invention causing corrosion of machinery and equipment. In addition, since there is no need to adjust the pH (neutralization work) of the dehydrated cake and treated water generated after treatment, the labor and cost of workers is significantly reduced, and the composition is also environmentally friendly.

The flocculant composition of the present invention may contain other components as necessary. Examples of other components include defoamers, pH adjusters, solvents, thickeners, stabilizers, colorants, deodorants, and rust inhibitors.

The flocculant compositions included in the present invention (Examples 1 to 3) and the flocculant composition not included in the present invention (Comparative Example 1) were prepared as follows. For reference, polyaluminum chloride (PAC), a representative inorganic flocculant, was also prepared (Reference Example 1).

Example 1
As the flocculant, dialkyldimethylammonium chloride (product name: TG Squall, dosage form: 40% by weight aqueous solution, manufactured by Technica Godo Co., Ltd.), which is a quaternary ammonium salt, was used, and as the flocculation and dehydration aid, calcium chloride (dosage form: 35% by weight aqueous solution, manufactured by Tokuyama Co., Ltd.) was used. Dialkyldimethylammonium chloride and calcium chloride were mixed in a volume ratio of 1:0.57, and water was added to this mixture to dilute it to 4 times its volume, to obtain the flocculant composition of Example 1 (dialkyldimethylammonium chloride concentration: 5% by weight, calcium chloride concentration: 2.5% by weight).

Example 2
As the flocculant, dialkyldimethylammonium chloride (product name: TG Squall, dosage form: 40% by weight aqueous solution, manufactured by Technica Godo Co., Ltd.), which is a quaternary ammonium salt, was used, and as the flocculation and dehydration aid, calcium chloride (dosage form: 35% by weight aqueous solution, manufactured by Tokuyama Co., Ltd.) was used. Dialkyldimethylammonium chloride and calcium chloride were mixed in a volume ratio of 1:1, and water was added to this mixture to dilute it to 4 times its volume, to obtain the flocculant composition of Example 2 (dialkyldimethylammonium chloride concentration: 5% by weight, calcium chloride concentration: 4.4% by weight).

Example 3
As the flocculant, dialkyldimethylammonium chloride (product name: TG Squall, dosage form: 40% by weight aqueous solution, manufactured by Technica Godo Co., Ltd.), which is a quaternary ammonium salt, was used, and as the flocculation and dehydration aid, calcium chloride (dosage form: 35% by weight aqueous solution, manufactured by Tokuyama Co., Ltd.) was used. Dialkyldimethylammonium chloride and calcium chloride were mixed in a volume ratio of 1:7, and water was added to this mixture to dilute it to 4 times its volume, to obtain the flocculant composition of Example 3 (dialkyldimethylammonium chloride concentration: 5% by weight, calcium chloride concentration: 30.6% by weight).

<Comparative Example 1>
As the flocculant, dialkyldimethylammonium chloride, which is a quaternary ammonium salt (product name: TG Squall, formulation: 40 wt% aqueous solution, manufactured by Technica Godo Co., Ltd.) was used. Water was added to the dialkyldimethylammonium chloride to dilute it to 8 times its volume, and a flocculant composition of Comparative Example 1 (dialkyldimethylammonium chloride concentration: 5 wt%, calcium chloride concentration: 0 wt%) was obtained.

<Reference Example 1>
Polyaluminum chloride (product name: PAC250A, concentration: 10% by weight (Al ₂ O ₃ equivalent), manufactured by Taki Chemical Industry Co., Ltd.), which is commercially available as an inorganic flocculant, was used as the flocculant in Reference Example 1 as it was.

To compare the performance of the flocculant compositions of Examples 1 to 3, the flocculant composition of Comparative Example 1, and the flocculant of Reference Example 1, the following tests were conducted using muddy water generated during muddy water shield construction.

[CST Test]
The Capillary Suction Time (CST) test measures the time it takes for a liquid to spread over a certain area due to capillary action, and this allows the freeness of muddy water to be evaluated. In the CST test, if the muddy water contains a lot of viscous substances, the measured value (CST value) will be large, and the muddy water will be evaluated as having poor dewatering properties.

The flocculant compositions of Examples 1 to 3, the flocculant composition of Comparative Example 1, and the flocculant of Reference Example 1 were added to the muddy water at a rate of 0 kg/m ³ , 2 kg/m ³ , and 4 kg/m ³ , respectively, and mixed thoroughly, and then the CST value of the muddy water was measured using a sludge evaluation CST measurement device (product name: Type 304M, manufactured by Triton Electronics). Note that the physical properties (initial values) of the muddy water before the addition of the flocculant composition were a specific gravity of 1.14, a funnel viscosity of 21.5 (seconds), suspended soil particles of 0.22 (sst/m ³ ), a pH of 10.3, and a sand content of 3 wt %. The funnel viscosity of the muddy water was measured using a funnel viscometer (product name: S-251, manufactured by Nishinippon Test Instruments Co., Ltd.). The measurement results of the CST value are shown in Table 1 below.

The flocculant composition of Example 1 showed a CST value equivalent to that of polyaluminum chloride (Reference Example 1), which has traditionally been used for muddy water treatment, suggesting that it can exhibit dewatering properties that are acceptable for practical use. The flocculant compositions of Examples 2 and 3 showed CST values superior to polyaluminum chloride (Reference Example 1), and were capable of exhibiting excellent dewatering properties. In contrast, the flocculant composition of Comparative Example 1, which does not contain calcium chloride, had a CST value inferior to polyaluminum chloride (Reference Example 1), and was considered to have insufficient dewatering properties.

The above CST test results show that if the concentration of calcium chloride contained in the flocculant composition is 2.5% by weight or more, it can exhibit excellent dewatering properties equal to or better than those of polyaluminum chloride, a conventional flocculant.

[Dehydration test]
The effect of improving the dewaterability of the muddy water used in the CST test by adding the flocculant composition included in the present invention was confirmed using a filter press tester (manufactured by Sano Co., Ltd.) (Examples 4 to 7). For comparison, the dewaterability of muddy water by adding a flocculant composition not included in the present invention (Comparative Example 2) and, for reference, the dewaterability of muddy water by adding polyaluminum chloride (PAC), a representative inorganic flocculant (Reference Example 3), were also confirmed using the same filter press tester.

Example 4
The flocculant composition of Example 2 (dialkyldimethylammonium chloride concentration: 5 wt%, calcium chloride concentration: 4.4 wt%) was added to 10 L of muddy water at a rate of 3.7 kg/ ^m3 , and the muddy water was stirred for 3 minutes. The stirred muddy water was then introduced into a filter press tester at a driving pressure of 0.5 MPa, and pressing was continued until the amount of filtrate reached 5000 g, during which the amount of filtrate was measured every minute. The dewatering time in Example 4 was 55 minutes. The characteristics of the dewatered cake collected after pressing were a weight of 3.01 (kg), a cone index of 60 (kN/ ^m2 ), and a moisture content of 49.3 (wt%). The characteristics of the filtrate were a pH of 10.1 and an electrical conductivity of 2.11 (ms/cm).

Example 5
The flocculant composition of Example 2 (dialkyldimethylammonium chloride concentration: 5 wt%, calcium chloride concentration: 4.4 wt%) was added to 10 L of muddy water at a rate of 7.4 kg/ ^m3 , and the muddy water was stirred for 3 minutes. The stirred muddy water was then introduced into a filter press tester at a driving pressure of 0.5 MPa, and pressing was continued until the amount of filtrate reached 5000 g, during which the amount of filtrate was measured every minute. The dewatering time in Example 5 was 37 minutes. The characteristics of the dewatered cake collected after pressing were a weight of 3.06 (kg), a cone index of 71 (kN/ ^m2 ), and a moisture content of 50.3 (wt%). The characteristics of the filtrate were a pH of 9.9 and an electrical conductivity of 1.88 (ms/cm).

Example 6
The flocculant composition of Example 3 (dialkyldimethylammonium chloride concentration: 5 wt%, calcium chloride concentration: 30.6 wt%) was added to 10 L of muddy water at a rate of 3.7 kg/ ^m3 , and the muddy water was stirred for 3 minutes. The stirred muddy water was then introduced into a filter press tester at a driving pressure of 0.5 MPa, and pressing was continued until the amount of filtrate reached 5000 g, during which the amount of filtrate was measured every minute. The dewatering time in Example 6 was 51 minutes. The characteristics of the dewatered cake recovered after pressing were a weight of 2.98 (kg), a cone index of 73 (kN/ ^m2 ), and a moisture content of 43.3 (wt%). The characteristics of the filtrate were a pH of 9.8 and an electrical conductivity of 3.15 (ms/cm).

Example 7
The flocculant composition of Example 3 (dialkyldimethylammonium chloride concentration: 5 wt%, calcium chloride concentration: 30.6 wt%) was added to 10 L of muddy water at a rate of 7.4 kg/ ^m3 , and the muddy water was stirred for 3 minutes. The stirred muddy water was then introduced into a filter press tester at a driving pressure of 0.5 MPa, and pressing was continued until the amount of filtrate reached 5000 g, during which the amount of filtrate was measured every minute. The dewatering time in Example 7 was 44 minutes. The characteristics of the dewatered cake recovered after pressing were a weight of 3.00 (kg), a cone index of 62 (kN/ ^m2 ), and a moisture content of 51.3 (wt%). The characteristics of the filtrate were a pH of 9.9 and an electrical conductivity of 5.33 (ms/cm).

<Comparative Example 2>
The flocculant composition of Comparative Example 1 (dialkyldimethylammonium chloride concentration: 5 wt%, calcium chloride concentration: 0 wt%) was added to 10 L of muddy water at a rate of 3.7 kg/ ^m3 , and the muddy water was stirred for 3 minutes. The stirred muddy water was then introduced into a filter press tester at a driving pressure of 0.5 MPa, and pressing was continued until the amount of filtrate reached 5000 g, during which the amount of filtrate was measured every minute. The dewatering time in Comparative Example 1 was 56 minutes. The characteristics of the dewatered cake recovered after pressing were a weight of 3.24 (kg), a cone index of 41 (kN/ ^m2 ), and a moisture content of 47.6 (wt%). The characteristics of the filtrate were a pH of 10.1 and an electrical conductivity of 1.20 (ms/cm).

<Reference Example 2>
To 10 L of muddy water, 5.6 kg/ ^m3 of the coagulant ( _polyaluminum chloride, concentration: 10% by weight ( _Al2O3 equivalent)) of Reference Example 1 was added, and the muddy water was stirred for 3 minutes. The stirred muddy water was then introduced into a filter press tester at a driving pressure of 0.5 MPa, and pressing was continued until the amount of filtrate reached 5000 g, during which the amount of filtrate was measured every minute. The dewatering time in Reference Example 2 was 60 minutes. The characteristics of the dewatered cake recovered after pressing were a weight of 3.01 (kg), a cone index of 25 (kN/ ^m2 ), and a moisture content of 44.5 (wt%). The characteristics of the filtrate were a pH of 7.3 and an electrical conductivity of 2.78 (ms/cm).

<Reference Example 3>
The flocculant of Reference Example 1 ( _polyaluminum chloride, concentration: 10% by weight ( _Al2O3 equivalent)) was added to 10 L of muddy water at a rate of 11.2 kg/ ^m3 , and the muddy water was stirred for 3 minutes. The stirred muddy water was then introduced into a filter press tester at a driving pressure of 0.5 MPa, and pressing was continued until the amount of filtrate reached 5000 g, during which the amount of filtrate was measured every minute. The dewatering time in Reference Example 3 was 43 minutes. The characteristics of the dewatered cake recovered after pressing were a weight of 2.95 (kg), a cone index of 46 (kN/ ^m2 ), and a moisture content of 45.9 (wt%). The characteristics of the filtrate were a pH of 6.6 and an electrical conductivity of 4.44 (ms/cm).

The results of the dehydration tests for the above Examples 4 to 7, Comparative Example 2, and Reference Examples 2 to 3 are shown in Tables 2 and 3, as well as in Figure 1. Tables 2 and 3 show the filtered water amount values during the pressing period using a filter press tester, divided into 0 to 30 minutes (Table 2) and 31 to 60 minutes (Table 3), and Figure 1 is a graph plotting the filtered water amounts shown in Tables 2 and 3.

Considering Tables 2 and 3, as well as Figure 1, the following findings were obtained regarding the dewaterability of the flocculant composition of the present invention.

(1) Comparing Examples 4 to 7 with Comparative Example 2, it was confirmed that the use of calcium chloride in combination with dialkyldimethylammonium chloride improved dehydration compared to the use of dialkyldimethylammonium chloride alone.
(2) Comparing Example 4 with Example 5, it was confirmed that when the concentration of calcium chloride contained in the flocculant composition was low, increasing the amount of the flocculant composition added to the muddy water improved the dewaterability. This tendency was also observed when the concentration of calcium chloride contained in the flocculant composition was high (comparing Example 6 with Example 7).
(3) Comparison between Example 4 and Example 6 confirmed that when the amount of flocculant composition added to the muddy water was small, the dewaterability improved as the concentration of calcium chloride contained in the flocculant composition increased. On the other hand, comparison between Example 5 and Example 7 suggested that when the amount of flocculant composition added to the muddy water was large, the concentration of calcium chloride contained in the flocculant composition did not necessarily contribute to improving dewaterability.
(4) Comparing Examples 4 and 6 with Reference Example 2, it was confirmed that the flocculant composition according to the present invention, which contains dialkyldimethylammonium chloride and calcium chloride, can achieve excellent dewatering properties with a smaller amount of addition than conventionally used polyaluminum chloride. This tendency was also observed when the amount of addition to the muddy water was doubled (comparing Examples 5 and 7 with Reference Example 3).
(5) The pH of the muddy water before the addition of the flocculant composition was 10.3, while the pH of the filtrate obtained in the dehydration tests of Examples 4 to 7 was 9.8 to 10.1, and the pH of the filtrate obtained in the dehydration tests of Reference Examples 2 and 3 was 6.6 to 7.3. As described above, since the flocculant composition according to the present invention has a small pH fluctuation before and after use, even if the amount of the flocculant composition added is increased to improve dehydration performance, there is little risk of causing corrosion of machines and equipment, and further, the burden of pH adjustment (neutralization work) can be reduced.

The flocculant composition of the present invention is suitable for use in treating muddy water generated during muddy water shield construction, but can also be used for other purposes, such as treating domestic wastewater such as sewage and human waste, and treating various industrial wastewater from the chemical industry, food industry, paper and pulp industry, ceramics industry, dyeing industry, etc.

Claims (10)

A flocculant composition for treating muddy water, comprising:
(a) a compound having the following structural formula (I):

(R ₁ to R ₄ are each independently or together an alkyl group selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, isobutyl, and tertiary butyl groups.)
a flocculant comprising a salt of a quaternary ammonium cation and an anion (quaternary ammonium salt) having the formula:
(b) a flocculating dewatering aid comprising a metal salt of a divalent cation;
A flocculant composition comprising: The flocculant composition according to claim 1, wherein the flocculant and the flocculation dewatering aid are in the form of a solution or suspension. The flocculant composition according to claim 2, wherein the content of the quaternary ammonium salt in the flocculant is 30 to 50% by weight, and the content of the metal salt of the divalent cation in the flocculant dehydration aid is 25 to 45% by weight. The flocculant composition according to any one of claims 1 to 3, wherein the mixing ratio (a:b) of the flocculant and the flocculation and dehydration aid is set to 1:0.5 to 1:7 by volume. The flocculant composition according to any one of claims 1 to 4, which is diluted with water to 3 to 5 times its volume. The flocculant composition according to claim 5, wherein the concentration of the metal salt of the divalent cation is set to 2.5% by weight or more. The flocculant composition according to claim 5 or 6, wherein the concentration of the quaternary ammonium salt is set to 3% by weight or more. The flocculant composition according to any one of claims 1 to 7, wherein the metal salt of the divalent cation is at least one selected from the group consisting of calcium salts, magnesium salts, barium salts, nickel salts, zinc salts, and cobalt salts. The flocculant composition according to any one of claims 1 to 8, wherein the metal salt of the divalent cation is at least one selected from the group consisting of calcium chloride, calcium sulfate, and calcium phosphate. The flocculant composition according to any one of claims 1 to 9, which does not contain an inorganic flocculant.

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