JP6119300B2 - Nitrate nitrogen and nitrite nitrogen reducing agent and waste water treatment method using the same - Google Patents

Description

  The present invention relates to a nitrate nitrogen and a nitrite nitrogen reducing agent capable of easily reducing nitrate nitrogen and nitrite nitrogen in water.

  Nitrate nitrogen and nitrite nitrogen contained in domestic wastewater and factory wastewater are eutrophication substances in rivers, lakes, and oceans, and so in the wastewater treatment process to preserve and improve the water quality environment. There is a demand for efficient reduction and removal by processing. Known methods for reducing nitrate nitrogen and nitrite nitrogen include biological purification methods using microorganisms, membrane filtration methods, ion exchange methods, and catalytic denitrification methods. However, it is difficult to control the quality of the treated water in the biological purification method, and further time is required for the treatment, and the high initial cost and running cost are required in the physical purification method. ing.

As a method of solving the above-mentioned problems and efficiently reducing the nitrogen component in the wastewater at low cost, an agent in which a hydrophilic cationic polymer compound is fixed to the wool surface (Patent Document 1), and the particle surface is hydrophilic. Fine particle (Patent Document 2) having a cationic polymer chain and having a hydrophilic cationic polymer compound fixed to the surface of a hydrophobic polymer compound in the center is a nitrate nitrogen and nitrite nitrogen reducing agent As proposed.

JP 2008-260004 A JP 2010-214356 A

However, in the above prior art documents, the manufacturing process is complicated because it takes a complicated form in which wool, which is the core of nitrate nitrogen and nitrite nitrogen reducing agent, or a hydrophobic polymer compound and a hydrophilic cationic polymer compound are fixed. It becomes. Further, the described hydrophilic cationic polymer compound may not be able to sufficiently exhibit the performance as the reducing agent. In addition, the molecular weight of the hydrophilic cationic polymer compound is set to be relatively small in order to prevent a decrease in the adhesion rate to wool and hydrophobic polymer compounds, so that an ion complex with nitrate ions and nitrite ions is formed. The ability to do so is considered to be limited.

  This invention is made | formed in view of the said situation, The objective is to provide this reducing agent with a simple form and high nitrate nitrogen and nitrite nitrogen removal performance.

  As a result of diligent research to solve the above problems, it was found that amidine-based cationic polymer compounds, which are hydrophilic cationic polymer compounds, are effective in reducing nitrate nitrogen and nitrite nitrogen, resulting in the present invention. .

  That is, the first gist of the present invention is nitrate nitrogen and nitrous acid composed of an amidine-based cationic polymer compound containing a structural unit having an amidine ring represented by the structural formula (1) and / or (2). Exists in a natural nitrogen reducing agent.

式（１）、（２）中、Ｒ１〜Ｒ４は各々水素原子またはメチル基であり、Ｘ⁻は陰イオンである。

In the formulas (1) and (2), R1 to R4 are each a hydrogen atom or a methyl group, and X ⁻ is an anion.

  The second gist of the present invention resides in a wastewater treatment method using the nitrate nitrogen and the nitrite nitrogen reducing agent.

  Since the nitrate nitrogen and the nitrite nitrogen reducing agent of the present invention take a simple form composed only of amidine-based cationic polymer compounds, they can be easily produced. Moreover, compared with other hydrophilic cationic polymer compounds, the performance as the reducing agent is high. Therefore, it is possible to reduce nitrate nitrogen and nitrite nitrogen more efficiently in a short time than water containing nitrate nitrogen and nitrite nitrogen.

FIG. 1 is a graph showing nitrite ion removal rates in Examples and Comparative Examples.

  Hereinafter, the present invention will be described in detail.

<Nitrate nitrogen and nitrite nitrogen reducing agent>
The nitrate nitrogen and nitrite nitrogen reducing agent in the present invention is composed of an amidine cationic polymer containing a structural unit having an amidine ring represented by the following structural formula (1) and / or (2). The X ⁻ in the structural formula is an anion. Examples of the anion include Cl ⁻ , 1 / 2SO ₄ ^2−, etc., but considering general ion selectivity, SO ₄ ²⁻ > NO ₃ ⁻ > NO ₂ ⁻ > Cl ⁻ is satisfied. , Cl ⁻ is preferred.

  The method for producing the amidine-based cationic polymer is not particularly limited, and examples thereof include N-vinylcarboxylic amides exemplified by N-vinylformamide or N-vinylacetamide, acrylonitrile, methacrylonitrile and the like. To produce a copolymer with nitriles, which are modified (hydrolyzed) with an acid to make the vinylamide group a primary amino group, and then heated to react the nitrile group with the primary amino group in the copolymer. A method of amidinating is mentioned.

  The ratio (A) :( B) of (A) N-vinylcarboxylic acid amide and (B) nitriles to be copolymerized is usually 20:80 to 95: 5 in terms of molar ratio, and the reaction rate of amidation is It is preferably 40:60 to 80:20 from the viewpoint of increasing. For the copolymer modification reaction, the acid modifier is usually used in an amount of 0.1 to 2 mol, preferably 0.2 to 1.5 mol per mol of the desired formyl group in the copolymer. The temperature is 30 to 130 ° C, preferably 40 to 110 ° C. The modified copolymer is usually heated at 70 to 130 ° C., preferably 80 to 110 ° C., to form a polymer having an amidine ring.

  The nitrate nitrogen and nitrite nitrogen reducing agent comprising an amidine-based cationic polymer compound used in the present invention is most typically a copolymer of N-vinylformamide and acrylonitrile as described above. The produced copolymer is preferably produced by heating in the presence of hydrochloric acid to form an amidine structural unit from a nitrile group adjacent to the amino group produced by hydrolysis. The amidine-based cationic polymer compound may be selected from commercially available products.

In the nitrate nitrogen and nitrite nitrogen reducing agent of the present invention, the content of the amidine ring-containing structural unit is preferably 20 to 95 mol%, more preferably 35 to 80 mol%, based on all the structural units. preferable. When the content of the amidine ring-containing structural unit is in the range of 20 to 95 mol%, the effect of adsorbing nitrate nitrogen and nitrite nitrogen is enhanced.

  The viscosity of the aqueous solution of the amidine-based cationic polymer compound obtained as described above is usually 1 to 20 mPa · s. As the nitrate nitrogen and nitrite nitrogen reducing agent in the present invention, nitrate ions and nitrite are used. 3-8 mPa · s is preferable from the viewpoint of reactivity for forming an ion complex with ions and handling. This value is a value measured as a 0.5% by mass aqueous solution of the reducing agent in a 4% by mass sodium chloride aqueous solution at 25 ° C., and is an aqueous solution of another polymer compound described below (including examples). The same applies to the viscosity.

  One reason why amidine-based cationic polymer compounds are preferable as nitrate-nitrogen and nitrite-nitrogen reducing agents is that the molecular weight per structural unit is lower than that of conventional acrylic-based cationic polymer compounds. The charge density is high and the negative charges of nitrate ions and nitrite ions can be adsorbed efficiently. Secondly, particularly in the middle to weak alkali range, the amidine group is more dissociated than the amino group, and an ion complex with nitrate ion and nitrite ion in a wider pH range. It is thought that it becomes easy to form. In addition, since the structural unit includes a cyclic structure, molecules due to the rigidization of the main chain are likely to spread, and as a result, more nitrate ions and nitrite ions can be adsorbed and collected.

<Usage method of nitrate nitrogen and nitrite nitrogen reducing agent>
The method of using the nitrate nitrogen and nitrite nitrogen reducing agent of the present invention is not particularly limited. For example, nitrate nitrogen and nitrite nitrogen reducing agent are directly added to nitrate nitrogen or nitrite nitrogen-containing water. After stirring and mixing and dispersing sufficiently, adjust the pH, add inorganic flocculant and / or anionic flocculant, stir and mix again to adsorb nitrate nitrogen or nitrite nitrogen And a method of forming a floc with the agent to separate the solid and liquid. The nitrate nitrogen and nitrite nitrogen reducing agent of the present invention can be widely applied to wastewater containing nitrate nitrogen or nitrite nitrogen.

  As addition amount of a nitrate nitrogen reducing agent and a nitrite nitrogen reducing agent, 50 ppm or more is preferable with respect to nitrate nitrogen or nitrite nitrogen containing water. If the amount added is too small, sufficient adsorption cannot be performed. Moreover, 500 ppm or less is preferable with respect to nitrate nitrogen or nitrite nitrogen containing water. If the amount is too large, no further effect can be obtained.

  Examples of the inorganic flocculant include sulfate band, PAC, polyiron, ferric chloride, slaked lime, and the like, and these may be used alone or in combination, and are not particularly limited.

  Anionic polymer compounds include poly (meth) acrylate sodium, hydrolyzate of poly (meth) acrylamide, (meth) acrylamide / sodium (meth) acrylate copolymer, (meth) acrylamide / (meth) acrylic And sodium 2-acrylamido-2-methyl-propane-1-sulfonic acid sodium copolymer, (meth) acrylamide-sodium 2-acrylamido-2-methyl-propane-1-sulfonic acid sodium copolymer, and the like. There is no particular limitation. Natural polymer compounds such as sodium alginate may also be used.

  Although it does not restrict | limit especially as process temperature, 10-40 degreeC is preferable from the point of a normal waste water treatment. The processing time can be appropriately set depending on the processing temperature and the like. The treatment pH is not particularly limited, but is preferably 5 to 8 from the viewpoint of the structural stability of the amidine ring. The pH value is adjusted by adding an acid or an alkali. Examples of the acid include mineral acids such as sulfuric acid, hydrochloric acid and nitric acid, and organic acids such as formic acid, acetic acid and sulfamic acid. Examples of the alkali include sodium hydroxide, potassium hydroxide, magnesium hydroxide, aqueous ammonia, and amine compounds.

  It should be noted that the nitrate nitrogen and the nitrite nitrogen reducing agent that are flocated and separated by solid-liquid separation after the treatment can be incinerated.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated in detail, this invention is not limited by the following description, unless the summary is exceeded. Note that “%” in this example represents “% by mass” unless otherwise specified.

Production Example <Production Example 1>
[Amidine Cationic Polymer Compound (Treatment Agent 1)]
A mixture of 6 g of a mixture of acrylonitrile and N-vinylformamide (molar ratio 55:45) and 34 g of demineralized water was placed in a 50 ml four-necked flask equipped with a stirrer, a nitrogen inlet tube, and a condenser tube. While stirring in nitrogen gas, the temperature was raised to 60 ° C., 10% 2,2′-azobis (2-amidinopropane) dihydrochloride aqueous solution 0.12 g was added, and further maintained for 3 hours. A suspension was obtained. 20 g of water was added to the suspension, and 2 equivalents of concentrated hydrochloric acid was added to the formyl group of the polymer, and kept at 100 ° C. for 4 hours to obtain a yellow high-viscosity liquid. This was added to a large amount of acetone, the polymer was precipitated, chopped, dried at 60 ° C. for 1 night and pulverized to obtain an amidine-based cationic polymer compound (aqueous solution viscosity: 6.3 mPa · s). . This was designated Treatment Agent 1.

<Production Example 2>
[Amidine-based cationic polymer compound (treatment agent 2)]
A 2000 ml separable flask equipped with a reflux condenser and a stirrer was charged with 473 g of demineralized water and 22.5 g of polyethylene glycol (molecular weight 20000), and sufficiently deoxygenated by circulating nitrogen gas. Separately, an aqueous monomer solution consisting of 172 g of N-vinylformamide, 128 g of acrylonitrile, 181.5 g of demineralized water, and 1.5 g of sodium hypophosphite monohydrate was prepared. Nitrogen gas was circulated to sufficiently deoxygenate, the temperature was raised to 70 ° C., and 4.5 g of 2,2-azobis (2-amidinopropane) hydrochloride was added. Immediately thereafter, the monomer solution was continuously fed over 3 hours. As the polymerization progressed, the polymer precipitated and the content became a slurry. After completion of the monomer solution supply, the polymerization reaction was continued for another 3 hours to obtain an aqueous dispersion slurry of poly (N-vinylformamide-acrylonitrile) copolymer.

  A 100 ml separable flask equipped with a reflux condenser and a stirrer was charged with 50 g of the above poly (N-vinylformamide-acrylonitrile) copolymer slurry and heated to 70 ° C. Thereto was added 8.2 g of 35% HCl aqueous solution, and hydrolysis was carried out by heating at 70 ° C. for 1 hour and then at 80 ° C. for 10 hours to obtain an aqueous solution of amidine-based cationic polymer compound (aqueous solution viscosity: 1. 6 mPa · s). This was designated Treatment Agent 2.

<Production Example 3>
Production was conducted in the same manner as in Production Example 1 except that the addition amount of 10% 2,2′-azobis (2-amidinopropane) dihydrochloride aqueous solution was changed to 0.08 g. This was designated Treatment Agent 3.

Comparative Production Example <Comparative Production Example 1>
[Vinylamine Cationic Polymer Compound (Comparative Treatment Agent 1)]
N-vinylformamide homopolymer (aqueous solution viscosity: 25 mPa · s) is made into 5% aqueous solution, hydrochloric acid with respect to N-vinylformamide unit 40 mol% is added, and the mixture is stirred at 60 ° C. for 30 minutes, and the hydrolysis rate is 40 mol%. A vinylamine-based cationic polymer compound was obtained (aqueous solution viscosity: 7 mPa · s). This was designated as Comparative Treatment Agent 1.

[Acrylic cationic polymer compound (Comparative treatment agents 2, 3)]
As the acrylic cationic polymer compound, the following two were used as comparative treatment agents 2 and 3.

  Comparative treatment agent 2: Diafloc KP201G (trade name, manufactured by Daianitrix, aqueous solution viscosity: 16 mPa · s)

  Comparative treatment agent 3: Diafloc KP1205E (trade name, manufactured by Dianitricks, aqueous solution viscosity: 17 mPa · s)

  The treating agents 1 to 3 and the comparative treating agents 1 to 3 were all dissolved in demineralized water so as to have a concentration of 0.3% by weight, and a solution was used.

[Anionic polymer compound]
As an anionic flocculant, Diafloc AP825C (trade name, manufactured by Daianitrix Co., Ltd., aqueous solution viscosity: 465 mPa · s) was dissolved in demineralized water to a concentration of 0.1% by weight, and a solution was used.

<Example 1>
50 ml of an aqueous solution prepared so that nitrite nitrogen was 100 mg / L was placed in a beaker, treatment agent 1 was added to 200 ppm, and the mixture was stirred for 1 minute using a stir bar. Thereafter, the pH value was adjusted to 6.5, an anionic polymer compound was added to 40 ppm, and the mixture was further stirred for 1 minute. The treated water is filtered using a 0.45 μm syringe filter, and the nitrite ion concentration in the treated water is determined by ion chromatography (detector: CM-8020 manufactured by Tosoh Corp., pump: CCPS manufactured by Tosoh Corp., column used: TSKgel IC manufactured by Tosoh Corp. -Anion-PW _XL PEEK, column thermostatic chamber: TOYO SODA CO-8000, Degasser: Tosoh SD-8023, eluent: Tosoh TSKluent IC-Anion-A (including acetonitrile 10%)) The removal rate of nitrite nitrogen was calculated. In addition, the removal rate of nitrite nitrogen was calculated as (%), ((concentration of treated nitrite ion) / (concentration of nitrite ion before treatment)) × 100.

  In addition, sodium nitrite was used for preparation of the nitrite nitrogen-containing aqueous solution, and hydrochloric acid and sodium hydroxide were used for pH adjustment.

<Examples 2 and 3>
The same test as in Example 1 was performed except that the treating agents 2 and 3 were used.

<Comparative Examples 1-3>
The same test as in Example 1 was performed except that the comparative treatment agents 1 to 3 were used.

  The test results in Examples and Comparative Examples are shown in FIG. From Examples 1 to 3 and Comparative Examples 1 to 5, the treating agents 1 to 3 which are the nitrate nitrogen and nitrite nitrogen reducing agents of the present invention have a removal rate of nitrite compared to the comparative treating agents 1 to 5. It can be confirmed that it is expensive. In particular, it can be seen that the treating agent 1 is within the preferable range of the aqueous solution viscosity, and the removal rate is further improved as compared with Examples 2 and 3.

  The nitrate nitrogen and nitrite nitrogen reducing agent of the present invention can be easily manufactured without taking a complicated form, and can easily reduce nitrate nitrogen and nitrite nitrogen in a short time. it can. Therefore, it can be said that the industrial value of the present invention is remarkable.

Claims (2)

A nitrate nitrogen and nitrite nitrogen reducing agent comprising an amidine-based cationic polymer compound containing a structural unit having an amidine ring represented by structural formula (1) and / or (2).

In the formulas (1) and (2), R1 to R4 are each a hydrogen atom or a methyl group, and X ⁻ is an anion. A wastewater treatment method using the nitrate nitrogen and the nitrite nitrogen reducing agent according to claim 1 in an amount of 50 ppm to 500 ppm with respect to nitrate nitrogen or nitrite nitrogen-containing water .

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