Method for treating dye-containing wastewater

Abstract

To provide an organic coagulant with higher performance which is used as wastewater treatment in treating dye-containing wastewater, and a treatment method using the same.SOLUTION: After adding an inorganic porous material, an organic coagulant made of a polymer obtained by polymerizing a specific cationic monomer component can be added to improve a treatment performance of dye-containing wastewater. An organic coagulant consisting of a polymer obtained by polymerizing a monomer component containing 50 to 100 mol% of a specific cationic monomer based on the total monomer is preferred. Moreover, it is preferable to use one or more kinds selected from bentonite, kaolin, talc, silica gel, and diatomaceous earth as the inorganic porous material.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for treating dye-containing wastewater, and more particularly to a method for treating dye-containing wastewater using an inorganic porous material and an organic coagulant. [Background technology]

[0002] Chemical wastewater treatment methods generally involve the addition of inorganic flocculants and / or organic coagulants, or the addition of inorganic flocculants and / or organic coagulants followed by polymer flocculants. Organic coagulants are effective for dye wastewater, and various treatment methods have been proposed. For example, Patent Document 1 discloses a treatment method in which an inorganic flocculant, a dicyandiamide-based cationic decolorizing agent, and a polymer flocculant are added to colored wastewater containing reactive dyes. Patent Document 2 discloses a method for treating dye wastewater in which an inorganic flocculant, an organic coagulant, and a polymer flocculant are added to wastewater containing organic dye compounds, and describes the use of polyamine condensates, dicyandiamide condensates, or dialkylamine-epichlorohydrin condensates as the organic coagulants. However, the use of inorganic coagulants increases the amount of sludge generated, and the use of dicyandiamide / formalin condensate as a dicyandiamide-based polymer raises concerns about the environmental and health effects of formaldehyde, while the use of dialkylamine-epichlorohydrin condensate raises concerns about the health effects of epihalohydrins. Furthermore, various compositions effective for treating colored wastewater have been investigated. For example, Patent Document 3 discloses a treatment method in which a polymer compound containing at least 75 to 100 mol % of (meth)acryloyloxyethyl dimethyl benzyl ammonium chloride units and having a viscosity of 10 to 150 mPa·s as a 10% aqueous solution is added to colored wastewater. However, even these methods do not always provide satisfactory results in decolorizing dyes and treating wastewater, and there is a demand for more effective methods for treating dye wastewater.

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-343976 [Patent Document 2] Japanese Patent Application Publication No. 2018-61923 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-98042 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention relates to a method for treating dye-containing wastewater using an organic coagulant, and an object of the present invention is to provide a method for treating dye wastewater using an organic coagulant with higher performance. [Means for solving the problem]

[0005] As a result of intensive research to solve the above problems, the present inventors have found that the use of an organic coagulant consisting of an inorganic porous material and a polymer having a specific composition can improve the performance of treating wastewater containing dyes, which led to the present invention. [Effects of the Invention]

[0006] By using the inorganic porous material and organic coagulant of the present invention, it is possible to achieve decolorization of dyes in dye-containing wastewater and improve wastewater treatment performance. DETAILED DESCRIPTION OF THE INVENTION

[0007] The organic coagulant in the present invention is made of a water-soluble polymer having a cationic monomer represented by the following general formula (1) as a constituent unit. TIFF0007806997000001.tif2684 General formula (1) R1 is hydrogen or a methyl group, R2 and R3 are alkyl groups or alkoxy groups having 1 to 3 carbon atoms, and may be the same or different. A is oxygen or NH, B is an alkylene group or alkoxy group having 2 to 4 carbon atoms, and X1 ― represents an anion, respectively.

[0008] The cationic monomer represented by general formula (1) is a hydrophobic monomer, specifically a quaternized product of dimethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylamide, or the like, with benzyl chloride. Examples include (meth)acryloyloxyethyl dimethylbenzyl ammonium chloride, (meth)acryloyloxy-2-hydroxypropyl dimethylbenzyl ammonium chloride, (meth)acryloylaminopropyl dimethylbenzyl ammonium chloride, (meth)acryloyloxyethyl diethylbenzyl ammonium chloride, (meth)acryloyloxy-2-hydroxypropyl diethylbenzyl ammonium chloride, and (meth)acryloylaminopropyl diethylbenzyl ammonium chloride. Two or more of these can also be used in combination. The molar amount of the cationic monomer represented by general formula (1) is preferably 50 to 100 mol%, more preferably 70 to 100 mol%.

[0009] The polymer of the present invention may contain a nonionic monomer as a polymerization component. Examples of nonionic monomers include acrylamide, dimethylacrylamide, diethylacrylamide, isopropylacrylamide, hydroxyethylacrylamide, vinylpyrrolidone, vinylformamide, glycerol (meth)acrylate, and hydroxyethyl (meth)acrylate. Two or more of these may be used in combination. The nonionic monomer is preferably 0 to 50 mol %, more preferably 0 to 30 mol %, based on the total monomers.

[0010] The polymer of the present invention may contain, as a polymerization component, a cationic monomer other than the cationic monomer represented by general formula (1). Examples of the cationic monomer include tertiary amino group-containing cationic monomers such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylamide, diethylaminopropyl (meth)acrylamide, and salts thereof. Further examples include cationic monomers containing a quaternary ammonium base, such as (meth)acryloyloxyethyltrimethylammonium chloride, (meth)acryloylaminopropyltrimethylammonium chloride, (meth)acryloyloxy-2-hydroxypropyltrimethylammonium chloride, etc. Two or more of these may be used in combination.

[0011] Furthermore, an anionic monomer may be contained to the extent that the effect is not impaired. Examples of anionic monomers include (meth)acrylic acid, itaconic acid, maleic acid, styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and salts thereof. Two or more of these may also be used in combination.

[0012] Furthermore, the polymer of the present invention may contain a hydrophobic monomer as a polymerization component. However, in order to maximize the effect of the cationic monomer represented by general formula (1), it is preferable to minimize the addition rate of the hydrophobic monomer, and it is even more preferable to not contain the hydrophobic monomer. In the present invention, the hydrophobic monomer refers to a monomer having a solubility of 2% by mass or less in water at 20°C. Examples of hydrophobic monomers include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, octyl (meth)acrylate, stearyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, dodecyl (meth)acrylate, octadecyl (meth)acrylate, styrene, α-methylstyrene, hydroxystyrene, acetoxystyrene, and ethylstyrene.

[0013] The polymer product form of the present invention is not particularly limited and can be produced by known methods. That is, it can be produced by copolymerizing a monomer mixture containing a cationic monomer represented by general formula (1). Polymerization is carried out by preparing an aqueous solution of the monomers, followed by polymerization by, for example, aqueous solution polymerization, water-in-oil emulsion polymerization, water-in-oil dispersion polymerization, or dispersion polymerization in saltwater. Any product form, such as an aqueous solution, water-in-oil emulsion, saltwater dispersion, or powder, can be used.

[0014] Examples of polymerization initiators include azo-based polymerization initiators such as 2,2'-azobis[2-(5-methyl-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, and 2,2'-azobis-2-amidinopropane dihydrochloride. Other examples include persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate, and peroxides such as hydrogen peroxide and benzoyl peroxide. These initiators can be used alone or in combination with reducing agents such as sulfites and bisulfites to form redox-based polymerization initiators. The polymerization initiator is added in an amount of 0.01% to 2% by mass, preferably 0.1% to 1% by mass, based on the total monomer content. For example, the polymerization initiator is added under a nitrogen atmosphere, and radical polymerization is carried out with or without stirring.

[0015] Furthermore, a structural modifier, i.e., a crosslinkable monomer that structurally modifies the polymer, may be used during polymerization. The crosslinkable monomer is present in a range of 0.5 to 200 ppm by mass relative to the total amount of monomers. Examples of crosslinkable monomers include N,N'-methylenebis(meth)acrylamide and triallylamine. The combined use of a chain transfer agent such as sodium formate, isopropyl alcohol, or sodium methallyl sulfonate is also effective as a method for adjusting crosslinkability. The addition rate is 0.001 to 1.0% by mass relative to the total amount of monomers.

[0016] The polymer in the present invention preferably has a viscosity of 5 to 200 mPa·s in a 5% by mass aqueous solution of the polymer. It is more preferably 10 to 100 mPa·s. The viscosity is measured using a Brookfield viscometer at 60 rpm and 25°C. If the viscosity is lower than this range, the treatment effect will be insufficient. If the viscosity is higher than this range, the solubility will decrease and handling will be difficult. As the Brookfield viscometer, general-purpose models such as the B8M and TVB-10M models manufactured by Toki Sangyo Co., Ltd. are appropriately used. If the viscosity is 100 mPa·s or less, a No. 1 rotor is used.

[0017] Examples of inorganic porous materials in the present invention include bentonite, kaolin, talc, silica gel, and diatomaceous earth. It is believed that these inorganic porous materials have a high adsorption capacity for dyes due to their porous structure. Adding the inorganic porous material adsorbs the dye, and then adding the organic coagulant in the present invention neutralizes the charge of the suspended solids, causing a coagulation reaction. Furthermore, the presence of hydrophobic groups in the polymer, represented by general formula (1), forms fine flocs incorporating the inorganic porous material, resulting in a treatment effect. Among these inorganic porous materials, bentonite is preferred. The main component of bentonite is the clay mineral montmorillonite. The cations are mainly Na. + The one with Na-montmorillonite is Ca 2+ The one having the above structure is Ca-montmorillonite. Na-montmorillonite is preferred, but Ca-montmorillonite can also be used. Two or more of these inorganic porous materials can be used in combination. The surface area of ​​these porous materials is 50 to 1000 m 2 The specific surface area can be measured by the BET method.

[0018] In the treatment method of the present invention, a polymer flocculant can be added after adding the inorganic porous material and the organic coagulant. The addition of the polymer flocculant is effective because it promotes coarsening of the flocs by bridging adsorption between the fine flocs formed by adding the organic coagulant. As the polymer flocculant, those generally used in wastewater treatment can be applied, such as polyamidine-based polymer flocculants and polyacrylamide-based polymer flocculants. Polyacrylamide-based polymer flocculants are particularly preferred. The polyacrylamide-based polymer flocculant may be cationic, anionic, amphoteric, or nonionic, but anionic polyacrylamide-based polymer flocculants are preferred.

[0019] The cationic monomers used as polyacrylamide polymer flocculants are quaternized products of dimethylaminoethyl (meth)acrylate or dimethylaminopropyl acrylamide with halides of lower alkyl groups such as methyl chloride or ethyl chloride. Examples include (meth)acryloyloxyethyl trimethylammonium chloride, (meth)acryloyloxyethyl dimethylbenzylammonium chloride, (meth)acryloylaminopropyl trimethylammonium chloride, (meth)acryloylaminopropyl dimethylbenzylammonium chloride, and (meth)acryloyloxy-2-hydroxypropyl trimethylammonium chloride. Two or more of these may also be used in combination. Examples of anionic monomers include (meth)acrylic acid or its alkali metal salts such as sodium salt or ammonium salt, maleic acid or its alkali metal salt, and acrylamidoalkanesulfonic acid such as acrylamido-2-methylpropanesulfonic acid or its alkali metal salt or ammonium salt. Two or more of these may be used in combination.

[0020] In polyacrylamide polymer flocculants, (meth)acrylamide is used as the nonionic monomer, but other nonionic monomers such as N,N'-dimethylacrylamide, acrylonitrile, 2-hydroxyethyl (meth)acrylate, diacetone acrylamide, N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide, and acryloylmorpholine may also be used in combination.

[0021] Polyacrylamide polymer flocculants can be produced by known methods. They can be produced by copolymerizing a monomer or a monomer mixture. Copolymerization can be carried out by any polymerization method. For example, after polymerization by aqueous solution polymerization, water-in-oil emulsion polymerization, water-in-oil dispersion polymerization, or dispersion polymerization in saltwater, the product can be formed into any desired form, such as an aqueous solution, a saltwater dispersion, a water-in-oil emulsion, or powder. A crosslinkable monomer can be used as a structural modifier during or after polymerization when producing the polymer flocculant. When used, a crosslinkable monomer such as N,N'-methylenebis(meth)acrylamide or triallylamine is present in an amount ranging from 0.00005 to 0.050 mass% relative to the total amount of monomers. The weight-average molecular weight of the polymer flocculant is preferably 1,000,000 to 20,000,000.

[0022] The dye wastewater to which the treatment method of the present invention is applicable refers to colored wastewater containing dyes. The color is primarily due to the dye. Examples of dyes include direct dyes, reactive dyes, acid dyes, architectural dyes, and sulfide dyes. Among these, the treatment method of the present invention is more effective when targeting wastewater containing reactive dyes that chemically react with functional groups in fibers to form covalent bonds. Examples of reactive dyes include yellow (pyrazolone azo), blue (anthraquinone), black, and navy blue (H-acid disazo). Reactive groups used in reactive dyes include sulfones such as sulfatoethylsulfone, triazines such as monochlorotriazine, and pyrimidines such as trichloropyrimidine. These reactive dyes are preferably used.

[0023] The organic coagulant used in the present invention is diluted with water to a desired concentration before addition. The preferred range is 0.01 to 1.0% by mass. The addition rate to wastewater is 1 to 1,000 ppm relative to the amount of wastewater. The inorganic porous material is optionally used as an aqueous solution, with a 0.1 to 10% by mass solution being preferred. The addition rate is 50 to 10,000 ppm, preferably 100 to 5,000 ppm, relative to the amount of wastewater. It may also be used in combination with inorganic coagulants such as aluminum sulfate, aluminum chloride, polyaluminum chloride, polyferrous sulfate, polyferric sulfate, and ferric chloride. However, since this increases the amount of sludge, it is preferable to minimize the addition rate or not use them at all. [Example]

[0024] The method for treating dye wastewater according to the present invention will be specifically explained below, but the present invention is not limited to the following examples.

[0025] (organic coagulant sample) Organic coagulant samples A to C of the present invention were produced by a conventional method of aqueous solution polymerization. Their compositions and physical properties are shown in Table 1. Furthermore, organic coagulant samples D to F were produced as comparative samples by a conventional method of aqueous solution polymerization. Their compositions and physical properties are shown in Table 2. Furthermore, commercially available organic coagulant samples 1 to 4 were prepared. Their compositions and physical properties are shown in Table 3.

[0026] (Table 1) TIFF0007806997000002.tif2573 Monomer; DMABC: acryloyloxyethyl dimethylbenzylammonium chloride, AAM: acrylamide Form; AQ: Aqueous polymer Viscosity of 5% by mass aqueous solution: Viscosity (mPa·s) measured at 25°C when dissolved in water to a polymer concentration of 5% by mass.

[0027] (Table 2) TIFF0007806997000003.tif2891 Monomer; DADMAC: diallyldimethylammonium chloride, DMQ: acryloyloxyethyltrimethylammonium chloride, DMC: methacryloyloxyethyltrimethylammonium chloride Form; AQ: Aqueous polymer Viscosity of 5% by mass aqueous solution: Viscosity (mPa·s) measured at 25°C when dissolved in water to a polymer concentration of 5% by mass.

[0028] (Table 3) TIFF0007806997000004.tif3291Form;AQ:Aqueous solution polymer

[0029] (Test Example 1) A simulated wastewater containing a yellow azo-based reactive dye (Drimaren Yellow CL-2R p, Archroma Japan Co., Ltd.) was prepared [pH 7.3, SS content 12 mg / L, absorbance 0.326 (measurement wavelength 390 nm)], and a cylinder test was performed. 200 mL of simulated wastewater was collected in a cylinder and a 5% by mass solution of bentonite (main component: sodium montmorillonite, manufactured by Volclay Japan Co., Ltd.) was added as an inorganic porous material at 1000 ppm relative to the wastewater volume. After five cycles of upside-down agitation, a 0.2% by mass solution of organic coagulant sample A (Table 1) was added at 50 ppm relative to the wastewater volume (pure polymer content). After five cycles of upside-down agitation, the settling velocity of the flocs, the sludge volume (SV) after 30 minutes of standing, and the absorbance of the supernatant (HACH DR-3000 spectrophotometer, measurement wavelength: 390 nm) were measured. Similar tests were conducted under similar conditions for the other samples listed in Table 1. After adding the organic coagulant sample, a 0.1% by mass solution of polymer flocculant (commercially available powdered anionic polyacrylamide (A-PAM), acrylamide / acrylic acid (90 / 10 mol%) copolymer, weight-average molecular weight 12 million) was added to the wastewater at 2.5 ppm (pure polymer content), and the mixture was stirred upside down five times. The results are shown in Table 4.

[0030] Comparative Test Example 1 Using the same wastewater as in Test Example 1, a similar test was carried out using the organic coagulant samples in Tables 2 and 3. The results are shown in Table 4.

[0031] (Table 4) TIFF0007806997000005.tif4891

[0032] In Example 1, in which bentonite and an organic coagulant were added as the inorganic porous material of the present invention, it was found that the absorbance was lower, the decolorization effect was excellent, and the settling rate was faster than in Comparative Example 1. When Sample 1 was added, the absorbance was low, but the settling rate and sludge volume were poor compared to the Example 1.

[0033] (Test Example 2) A simulated wastewater containing a blue anthraquinone reactive dye (Drimaren Blue CL-BR p, Archroma Japan Co., Ltd.) was prepared [pH 7.7, SS content 14 mg / L, absorbance 0.315 (measurement wavelength 592 nm)], and a cylinder test was performed. 200 mL of simulated wastewater was collected in a cylinder and a 5% by mass solution of inorganic porous bentonite (product of Volclay Japan Co., Ltd., main component: Na-montmorillonite) was added at 1000 ppm relative to the wastewater volume. After five cycles of upside-down agitation, a 0.2% by mass solution of organic coagulant sample A (Table 1) was added at 50 ppm relative to the wastewater volume (pure polymer content). After five cycles of upside-down agitation, the settling velocity of the flocs, the sludge volume (SV) after 30 minutes of standing, and the absorbance of the supernatant (HACH DR-3000 spectrophotometer, measurement wavelength: 592 nm) were measured. The results are shown in Table 5.

[0034] Comparative Test Example 2 Using the same wastewater as in Test Example 2, a similar test was carried out using the organic coagulant samples in Tables 2 and 3. The results are shown in Table 5.

[0035] (Table 5) TIFF0007806997000006.tif3290

[0036] In Example 2, in which bentonite and an organic coagulant were added as the inorganic porous material of the present invention, it was found that the settling rate was faster, the absorbance was lower, and the decolorization effect was superior compared to Comparative Example 2. When Sample 1 was added, the absorbance was low, but the settling rate and sludge volume were poor compared to the Example.

Claims

1. A method for treating dye wastewater, comprising adding an inorganic porous material to dye wastewater, and then adding an organic coagulant made of a polymer obtained by polymerizing a monomer component containing 50 to 100 mol % of a cationic monomer represented by the following general formula (1) and 0 to 50 mol % of a nonionic monomer: General formula (1) R １ is hydrogen or a methyl group, R ２ , R ３ are alkyl groups or alkoxy groups having 1 to 3 carbon atoms, and may be the same or different. A is oxygen or NH, B is an alkylene group or alkoxylene group having 2 to 4 carbon atoms, X １ ― represents an anion, respectively.

2. 2. The method for treating dye wastewater according to claim 1, wherein a 5% by mass aqueous solution of the polymer has a viscosity of 5 to 200 mPa·s at a rotation speed of 60 rpm and a temperature of 25° C. as measured by a Brookfield viscometer.

3. 2. The method for treating dye wastewater according to claim 1, wherein the inorganic porous material is one or more selected from the group consisting of bentonite, kaolin, talc, silica gel, and diatomaceous earth.

4. 2. The method for treating dye wastewater according to claim 1, wherein a polymer flocculant is added after the organic coagulant is added.

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