JP2020037091A - Method for treating oil-containing wastewater using water-soluble polymer and inorganic porous body - Google Patents

Abstract

To provide a chemical formulation as an application for aggregating oil-containing wastewater using a water-soluble polymer superior in oil/water separation performance and capable of improving the quality of treated water, compared with the conventional chemical formulations.SOLUTION: A polyvinylamine-based water-soluble polymer with a reduced viscosity of 1.0-12.0 dL/g in a saline solution of 1 mol/L concentration at 25°C and amination degree in the range of 10 to 100 mol% is added to an oil-containing wastewater for stirring. After that, an inorganic porous body is added thereto for aggregation, so that it exhibits high aggregation performance, resulting in oil separation and improved quality of the treated water.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for coagulating oil-containing wastewater using a water-soluble polymer. More specifically, the present invention relates to an aggregation treatment method using a polyvinylamine-based water-soluble polymer having a specific structural unit and physical properties and an inorganic porous material.

Water generated in various factories such as automobile factories, machinery factories, food factories, printing factories, maintenance factories, and oil factories contains a large amount of oil such as mineral oil and vegetable oil. In addition, water that has been washed with a cleaning agent for machines and equipment also contains oil. In general, a method of adding a water-soluble polymer as a flocculant to these oil-containing wastewaters to flocculate and remove insoluble substances such as oil and SS other than oil, and releasing treated water to the outside of the system. Have been applied. As these flocculants, polyacrylamide (PAM) -based polymers are widely used, and various formulations have been proposed so far.
For example, Patent Document 1 discloses a treatment method in which a cationic polymer is added to oil-containing wastewater. As the cationic polymer, a homopolymer of dimethylaminoethyl methacrylate, or a copolymer with acrylamide, or a quaternized product thereof is used. Homopolymers or copolymers are mentioned.
Patent Literature 2 discloses that a combination of a water-soluble polymer such as polyacrylamide and polyacrylic acid and bentonite is preferable as a coagulant suitable for oil-containing wastewater.
Further, Patent Literature 3 describes that bentonite is used for oil-containing sludge wastewater and oil in the wastewater is adsorbed, suggesting that bentonite is effective for oil-containing wastewater.
However, even in these formulations, the treatment effect of the oil-containing wastewater may not always be satisfied, and there is a demand for the development of a more effective formulation.

JP-A-60-202787 JP 2007-167779 A JP 2014-124594 A

An object of the present invention relates to a method for treating oil-containing wastewater, and more particularly, to a method for separating oil and improving water quality by subjecting the oil-containing wastewater to coagulation treatment using a chemical formulation using a water-soluble polymer.

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, a polyvinylamine-based water-soluble polymer and an inorganic porous material having a specific composition and physical properties have an excellent coagulation effect on oil-containing wastewater. Then, the inventors have invented that the above problems can be solved, and have reached the present invention.

The formulation using the polyvinylamine-based water-soluble polymer and the inorganic porous material in the present invention is superior in the coagulation treatment performance as compared with the chemical formulation generally used for the treatment of oil-containing wastewater. The quality of treated water is improved.

  Wastewater discharged from various factories such as automobile factories, machinery factories, food factories, printing factories, maintenance factories, and oil factories contains oil (mineral oil, vegetable oil, etc.), and the dirt components containing these oils are processed. It is necessary to separate and treat oily dirt components and water from wastewater since they are present in a finely dispersed state by a surfactant used as a detergent or a detergent. The oil-containing wastewater to which the present invention is applied means water containing oil, and may contain suspended substances other than oil.

  The polyvinylamine-based water-soluble polymer of the present invention has a reduced viscosity of 1.0 to 12.0 dL / g at 25 ° C. in a 1 mol / L saline solution and a degree of amination of 10 to 100 mol%. Range. By adding the polyvinylamine-based water-soluble polymer in this range to the oil-containing wastewater, excellent coagulation performance is exhibited, the oil is separated, and the quality of the treated water is improved.

The polyvinylamine-based water-soluble polymer in the present invention can be produced by a conventional polyvinylamine production method.

  Polyvinylamine is a primary amino group-containing vinyl polymer having the simplest structure, and its production method is a method of hydrolyzing a polymer of N-vinylcarboxylic acid amide with an acid or a base, N-vinyl-Ot A method of hydrolyzing a polymer of -butyl carbamate, or a method of subjecting polyacrylamide to a Hoffman reaction in the presence of hypohalous acid and an alkali metal hydroxide.

For example, it is disclosed in JP-A-6-65329. The polyvinylamine-based water-soluble polymer in the present invention can be easily obtained by modifying an N-vinylformamide polymer or copolymer by modifying the formyl group in the polymer. That is, the molar ratio of N-vinylformamide to another copolymerizable monomer is usually a mixture of 20:80 to 100: 0, preferably a mixture of 40:60 to 100: 0, and a radical polymerization initiator. It is produced by polymerization in the presence.

Since the formyl group is hydrolyzed by an acid or an alkali, a part of the monomer to be copolymerized is also hydrolyzed to form a carboxyl group in many cases. Therefore, when copolymerizing, it is convenient when acrylonitrile or the like is copolymerized. Other acrylamide, methyl acrylate, ethyl acrylate, n-propyl acrylate, 2-hydroxyethyl acrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, methacryl Sec-butyl acid, 2-hydroxyethyl methacrylate and the like. Since these monomers generate anionic groups, the molar ratio in the copolymer is preferably less than 20 mol%.

As a polymerization method for producing the N-vinylformamide copolymer, any of bulk polymerization, solution polymerization using water and various organic solvents, and precipitation polymerization can be used. Preferred polymerization solvents include water, an organic solvent having a boiling point of 60 to 110 ° C, and a mixture of water and a hydrophilic organic solvent having a boiling point of 60 to 110 ° C. When polymerizing the monomer in a solution, the molecular weight of the target polymer, the concentration of the monomer in consideration of the heat generated by the polymerization, the polymerization method, and the shape of the polymerization reactor are appropriately selected. The polymerization is carried out according to the method. That is, the polymerization is started in a solution having a monomer concentration of 5 to 20% by mass, a method of obtaining a polymer in a solution or as a precipitate, and the polymerization is started under the condition of a monomer concentration of 20 to 60% by mass, Examples of the method include a method of obtaining a gel or a precipitate containing a polymer and a solvent, and a method of polymerizing a solution having a monomer concentration of 20 to 60% by mass in a solvent in which the monomer is not dissolved in an emulsified or dispersed state. You.

As the radical polymerization initiator, any of the general initiators usually used for the polymerization of water-soluble or hydrophilic monomers is used, but in order to obtain a polymer with high yield, an azo compound is used. preferable. When water is used as the polymerization solvent, a water-soluble azo compound is preferable. Examples thereof include hydrochloride and acetate of 2,2′-azobis-2-amidinopropane, and 4,4′-azobis-4-cyano. Sodium salt of valeric acid; hydrochloride and sulfate of azobis-N, N'-dimethyleneisobutylamidine. The amount of these polymerization initiators is usually in the range of 0.01 to 1% by mass based on the mass of the monomer. The polymerization reaction is generally carried out at a temperature of 30 to 100 ° C. under a stream of inert gas.

The obtained N-vinylformamide copolymer may be used in the form of a solution or dispersion as it is, or may be diluted, or dehydrated or dried by a known method to form a powder, and then modified to obtain a polyvinylamine-based aqueous solution. It can be a conductive polymer. As the modification method used at this time, any method of modifying the N-vinylformamide copolymer under basic and acidic conditions can be used. When the basic hydrolysis is carried out in water, the ester group in the polymer is changed to a carboxyl group, which tends to produce an amphoteric copolymer containing a large amount of anionic group, which is an excellent method for producing an amphoteric polymer having good water solubility. . However, in order to produce a polyvinylamine imparted with hydrophobicity, it is preferable that the polyvinylamine be denatured under acidic conditions. Preferred modification methods of the N-vinylformamide copolymer include a method of performing acidic hydrolysis in water, a method of performing acidic hydrolysis in a hydrophilic solvent such as water-containing alcohol, and an alcoholysis under acidic conditions to formyl. Examples include a method of modifying the group while separating the group as a formate, and particularly preferred is alcoholysis under acidic conditions. According to this method, a polyvinylamine-based water-soluble polymer substantially containing no carboxyl group can be obtained.

As the denaturing agent used for the acid denaturation, any compound that acts strongly acidic can be used. For example, hydrochloric acid, bromic acid, hydrofluoric acid, sulfuric acid, nitric acid, phosphoric acid, sulfamine Acids, alkanesulfonic acids and the like. The amount of the modifier used is appropriately selected usually from the range of 0.1 to 2 moles per formyl group in the polymer according to the desired modification rate. The denaturation reaction is usually carried out at 40 to 100 ° C.

According to the method disclosed in JP-A-2012-153747, a high-molecular-weight polyvinylamine-based water-soluble polymer having excellent storage stability can be produced. First, an N-vinylcarboxylic acid amide monomer is mixed with water, an oil composed of a water-immiscible hydrocarbon, an effective amount for forming a water-in-oil emulsion, and a surfactant having HLB. After vigorous stirring to form a water-in-oil emulsion, polymerization is carried out to synthesize an N-vinylcarboxylic acid amide polymer.

Thereafter, the water-in-oil emulsion of the N-vinyl carboxylic acid amide polymer can be hydrolyzed with an acid or a base. It can be appropriately selected according to the purpose, and when it is necessary to use it in the presence of an acid, it is preferable to carry out hydrolysis with an acid. In the hydrolysis with an acid, formic acid is generated as a by-product and corrodes a production tank or a storage tank. Therefore, it is preferable to carry out hydrolysis with a base. The acid amide group is converted into an amino group by hydrolysis to cationize, and the hydrolysis rate is appropriately set according to the purpose of use.

The hydrolysis is preferably performed in the presence of a polyoxyethylene alkyl ether. Examples of such polyoxyethylene alkyl ethers include polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene cetyl ether, and polyoxyethylene oleyl ether. Any HLB of the polyoxyethylene alkyl ether can be used depending on the polymerization conditions. These polyoxyethylene alkyl ethers can be added at the time of polymerization of N-vinylcarboxylic acid amide, or can be added after the polymerization and before the hydrolysis. preferable.

The ratio of the polyvinylamine-based water-soluble polymer in the present invention to the total constitution of the vinylamine structural units in the water-soluble polymer is in the range of 10 to 100 mol%, preferably 20 to 100 mol%. When the degree of amination is smaller than 10 mol%, the coagulation performance is poor when used in combination with the inorganic porous material, and a large improvement in water quality cannot be obtained.

The molecular weight of the polyvinylamine-based water-soluble polymer in the present invention is represented by the reduced viscosity. The reduced viscosity follows a general measuring method, and is determined, for example, by the following measuring method.
(Method of measuring reduced viscosity)
A polyvinylamine-based water-soluble polymer is dissolved in a 1 mol / L NaCl aqueous solution to obtain a salt aqueous solution having a polymer concentration of 0.01 to 0.1% by mass. The reduced viscosity is calculated by measuring the time during which the aqueous solution and the solvent flow down a certain distance using a capillary viscometer (automatic viscosity meter SS-120 manufactured by Shibayama Scientific Instruments) in a thermostat at 25 ° C.

The reduced viscosity is determined by allowing a 0.01 to 0.1% by mass aqueous salt solution of the polymer to flow down a fixed distance in a capillary viscometer and measuring the flowing time. In the present invention, the measurement was performed using a 0.06% by mass aqueous salt solution. The reduced viscosity of the polyvinylamine-based water-soluble polymer greatly varies depending on the degree of amination, but in the present invention, the reduced viscosity is in the range of 1.0 to 12.0 dL / g, and 1.5 to 11.0 dL / g. Is preferable, and 1.5 to 10.0 dL / g is more preferable. If the reduced viscosity is less than 1.0 dL / g, the coagulation performance is poor and efficient treatment cannot be exhibited. If it is more than 12.0 dL / g, the cohesive force is too large to form an appropriate floc, so it is presumed that oil cannot be taken into the floc, and the effect of improving the treated water decreases.

After the polyvinylamine-based water-soluble polymer in the present invention is added to the oil-containing wastewater and stirred, the inorganic porous material is added. Examples of the inorganic porous material include bentonite, kaolin, talc, silica gel, and diatomaceous earth. These inorganic porous materials have a high adsorptivity to oil and water due to their porous structure, and the addition of polyvinylamine-based water-soluble polymer allows the inorganic porous material It is presumed that the addition of the oil adsorbs the oil component spilled from the floc and promotes the oil-water separation effect. Among these inorganic porous bodies, bentonite, kaolin and talc are preferred. The main component of bentonite is montmorillonite, a clay mineral. Those whose cations are mainly Na ⁺ are Na-montmorillonite, and those whose Ca2 ⁺ is Ca2 ⁺ are montmorillonite. Na-montmorillonite is preferred, but Ca-montmorillonite can also be used. Further, two or more of these inorganic porous materials can be used in combination. The surface area of these porous bodies is preferably 50 to 1000 m ² / g. The specific surface area can be measured by the BET method.

  After adding the inorganic porous material in the present invention, a general polymer flocculant can be used. Among them, anionic polymer flocculants are preferred. This is because the addition of the anionic polymer flocculant allows the floc that has been flocculated by the polyvinylamine-based water-soluble polymer and the inorganic porous material to be more firmly adsorbed to promote the oil-water separation effect. As the anionic polymer flocculant, a polymer produced by polymerizing an anionic monomer alone or a polymer produced by copolymerizing an anionic monomer and a nonionic monomer can be used. Examples of the anionic monomer used include vinyl sulfonic acid, vinyl benzene sulfonic acid or 2-acrylamido-2-methylpropane sulfonic acid, methacrylic acid, acrylic acid, itaconic acid, maleic acid, phthalic acid and p-carboxy. Styrene acid and the like can be mentioned. These may be used in combination of two or more. Examples of the water-soluble nonionic monomer used include (meth) acrylamide, N, N′-dimethylacrylamide, vinyl acetate, acrylonitrile, 2-hydroxyethyl (meth) acrylate, diacetone acrylamide, and N-vinyl. Examples include pyrrolidone, N-vinylformamide, N-vinylacetamide, acryloylmorpholine, acryloylpiperazine and the like. These may be used alone or in combination of two or more. The anionic monomer in the anionic polymer is in the range of 1 to 100 mol%. 5-100 mol% is preferable, and 10-100 mol% is more preferable. If it is more than 30 mol%, it becomes difficult to produce high molecular weight ones. The weight average molecular weight is in the range of 1,000,000 to 20,000,000, preferably in the range of 3,000,000 to 20,000,000.

Further, the anionic polymer flocculant in the present invention may contain a cationic monomer within a range that does not inhibit the effect of 10 mol% or less of all the constituent units. Examples of the cationic monomer used include quaternized products of methyl chloride and benzyl chloride such as dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide, and methyldiallylamine. Examples thereof include (meth) acryloyloxyethyltrimethylammonium chloride, (meth) acryloyloxy-2-hydroxypropyltrimethylammonium chloride, (meth) acryloylaminopropyltrimethylammonium chloride, and (meth) acryloyloxyethyldimethylbenzylammonium. Chloride, (meth) acryloyloxy-2-hydroxypropyldimethylbenzylammonium chloride, (meth) acryloylaminopropyldimethylbenzylammonium chloride, diallyldimethylammonium chloride and the like. These may be used in combination of two or more.

  As the product form, any product form such as aqueous solution, dispersion, emulsion or powder after polymerization by aqueous solution polymerization, water-in-oil emulsion polymerization, water-in-oil dispersion polymerization, dispersion polymerization in salt water and the like can be used. . A preferred embodiment is a water-in-oil emulsion polymerization in which a polymer having a high molecular weight is easily obtained.

  Next, specific oil-containing wastewater will be described. The polyvinylamine-based water-soluble polymer in the present invention can be applied to various oil-containing wastewaters generated in various factories. For example, many oils (mineral oils, vegetable oils, etc.) used in various factories such as automobile factories, machinery factories, food factories, printing factories, maintenance factories, and oil factories, and many components and machinery and equipment that have been washed with detergents are used. It is suitable because it is included. As an index of the amount of oil contained in the oil-containing wastewater, the amount of the n-hexane extract can be used. The amount of the n-hexane extract ranges from 1000 to 100,000 mg / L, preferably from 2000 to 100,000 mg / L. When the amount is less than 1000 mg / L or more than 100,000 mg / L, the aggregation effect of the polyvinylamine-based water-soluble polymer and the inorganic porous material in the present invention cannot be maximized. The pH of the oil-containing wastewater can be used in a wide range, but it is preferable to adjust the pH to less than 9 when the pH is high. In that case, adjustment is made by adding sulfuric acid, hydrochloric acid, polyaluminum chloride or the like. It is preferably in the range of pH 3 or more and less than 9.

  For the aggregation treatment, a known treatment method is applied. That is, the polyvinylamine-based water-soluble polymer of the present invention is added to the target oil-containing wastewater, mixed and coagulated, and then subjected to solid-liquid separation. Alternatively, coagulation flotation treatment is possible. It is preferable that the SS concentration (suspended matter concentration) of the wastewater is 3000 ppm or less, because the wastewater can be treated more efficiently. If the SS concentration is lower than 200 ppm, the agglomeration effect is reduced. These analytical values were measured according to JIS K0102.

The polyvinylamine-based water-soluble polymer of the present invention may be added as it is, or may be dissolved and diluted with water to an arbitrary concentration and added to wastewater. When dissolving, generally, a dissolution concentration of 0.05 to 0.3% by mass is applied. Further, the addition ratio to wastewater is usually 10 to 1000 ppm, preferably 50 to 500 ppm. The inorganic porous material is optionally used as an aqueous solution, and a 0.1 to 10% by mass solution is a preferable range. The addition rate is 50 to 10000 ppm, preferably 100 to 5000 ppm, based on the wastewater. When adding an anionic polymer flocculant, a dissolution concentration of 0.05 to 0.3% by mass is applied, and an addition ratio to wastewater is in a range of 1 to 100 ppm. Further, it may be used in combination with an inorganic coagulant such as ferric chloride, ferric sulfate, and sulfate band.

Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

  In the present invention, polyvinylamine-based water-soluble polymer samples A to F having a degree of amination of 10 to 100 mol% and a reduced viscosity of 1.0 to 12.0 dL / g were prepared and prepared by an ordinary method. Table 1 shows their compositions and physical properties. Bentonite (a product of Volclay Japan, Na-montmorillonite) and kaolin (a product of Kanto Chemical Co., Ltd.) were prepared as inorganic porous materials. In addition, water-soluble polymer samples 1 to 7 for general wastewater treatment and sample 8 for a polymer flocculant were prepared. Table 2 shows the composition and physical properties.

(Table 1)

(Table 2)

(Example of preliminary test)
First, as a preliminary test, a jar test test was carried out using automobile part manufacturing wastewater (pH 6.4, SS content 718 mg / L, COD 1020 mg / L, n-hexane extract amount 1540 mg / L, turbidity 1900 NTU, hue: gray). did. A wastewater (200 mL) was collected in a beaker, set in a jar tester, and a 0.2% by mass solution of the polyvinylamine-based water-soluble polymer sample D of the present invention in Table 1 was added to the wastewater (120 ppm), agitated at 100 rpm for 60 seconds, and flocculated. The diameter was measured, and the hue of the treated water was measured visually. The same operation was performed for the polyvinylamine-based water-soluble polymer samples E and F of the present invention in Table 1 and the water-soluble polymer sample in Table 2 of the present invention. Table 3 shows the results. The hue of the raw water is gray, the oil is removed by the coagulation treatment, and the color changes from gray to white to yellow.

(Table 3)

  When the polyvinylamine-based water-soluble polymer of the present invention was added, the hue of the wastewater changed from gray to yellow, indicating that oil was removed. Even if other polymer flocculants were added, the oil could not be removed, and no improvement in the treated water was obtained. No floc was formed when Samples 1 to 3 were added. When Samples 4, 6 and 7 were added, the floc diameter was relatively large, and it appeared that oil was removed in the flocculated flocs. However, in practice, the treated water was white and the oil was not removed. Do you get it. It was found that the polyvinylamine-based water-soluble polymer in the present invention is more effective in oil-containing wastewater than a general water-soluble polymer sample.

(Example 1)
A jar test test was performed on lubricating oil production wastewater (pH 9.2, SS content 1438 mg / L, COD 46300 mg / L, BOD 188000 mg / L, n-hexane extract amount 23205 mg / L, hue: gray). 200 mL of waste water was collected in a beaker, set in a jar tester, 5000 ppm of sulfuric acid was added to the waste water, 100 ppm of a 0.2% by weight solution of the sample A in Table 1 of the present invention was added to the waste water, and after stirring at 150 rpm for 60 seconds, 5 mass of bentonite was added. % Solution was added to 2,000 ppm of wastewater and stirred at 150 rpm for 60 seconds, and then a 0.2 mass% solution of the polymer coagulant sample 8 was added at 5 ppm to wastewater, and stirred at 150 rpm for 30 seconds, 80 rpm for 30 seconds, and 40 rpm for 30 seconds. After the stirring was stopped, COD (chemical oxygen demand), BOD (biochemical oxygen demand) and n-Hx extract amount (n-hexane extract amount) of the treated water were measured according to JIS K0102 method. Further, the hue of the treated water was measured visually. Table 4 shows the results. The hue of the raw water is gray, the oil is removed by the coagulation treatment, the color changes from gray to white, and when the oil-water separation further proceeds, the color becomes almost transparent to transparent.

(Examples 2 to 9)
A similar test was conducted on the same wastewater as in Example 1 by changing the types and amounts of the polyvinylamine-based water-soluble polymer and the inorganic porous material shown in Table 1. Table 4 shows the results.

(Comparative Examples 1 to 17) Similar tests were conducted on the same wastewater as in Example 1 except that the formulation shown in Table 1 was not used in combination with the polyvinylamine-based water-soluble polymer and the inorganic porous material. Table 4 shows the results.

(Table 4)
Both sulfuric acid for adjusting pH and PAC (polyaluminum chloride) were added to wastewater at 5000 ppm, pH 7.7 after addition of sulfuric acid, and pH 8.9 after addition of PAC.
Hue; ◎: transparent, ○: almost transparent, Δ: white, ×: gray

  In the examples of the present invention in which the polyvinylamine-based water-soluble polymer and the inorganic porous material are used in combination, it can be seen that the color of the raw water of the wastewater becomes almost transparent or transparent from gray, and the oil is removed. In addition, the COD and BOD values of the treated water decreased, and particularly, the amount of the n-Hx extract decreased. In the formulations other than the combination of the polyvinylamine-based water-soluble polymer and the inorganic porous material in the present invention, the wastewater is gray or white, and the treated water does not show much improvement as compared with the examples. It was found that the oil was not efficiently removed.

Treated water after the jar test described in (Table 4). From the left, Comparative Example 14, Example 4, and Example 3 are arranged in that order. Compared to Comparative Example 14, in Examples 4 and 3, oil-water separation proceeded, and the hue was almost transparent or transparent.

Claims (5)

Polyvinylamine-based water-soluble oil-containing wastewater having a reduced viscosity in a 1 mol / L saline solution at 25 ° C. of 1.0 to 12.0 dL / g and an amination degree of 10 to 100 mol%. A method for treating oil-containing wastewater, comprising adding a polymer, stirring, adding an inorganic porous material, and subjecting the mixture to coagulation treatment. The method for treating oil-containing wastewater according to claim 1, wherein the amount of n-hexane extract in the oil-containing wastewater is in the range of 1,000 to 100,000 mg / L. The method for treating oil-containing wastewater according to claim 1 or 2, wherein the SS concentration of the oil-containing wastewater is in the range of 200 to 3000 mg / L. The method for treating oil-containing wastewater according to claim 1, wherein the inorganic porous body is at least one selected from bentonite, kaolin, talc, silica gel, and diatomaceous earth. The method for treating oil-containing wastewater according to any one of claims 1 to 3, wherein the pH of the oil-containing wastewater is adjusted to less than 9.