JPH07328323A - High molecular coagulant - Google Patents

Abstract

PURPOSE:To obtain a coagulant which, when used for dewatering of sludge, has a good coagulation effect, gives a coagulated block with high strength and a low water content by mechanical dewatering, and is capable of stable dewatering of sludge by preparing it from a polymer which has benzyl vinylamine monomeric units of a specified structure in a specified ratio. CONSTITUTION:A coagulant is prepared from a polymer having 2-30 mole % of a benzyl vinylamine unit expressed by the formula as a monomeric unit. The polymer is a benzylated product of hydrolyzate of poly-N-vinylformamide or copolymer of N-vinylformamide and other vinyl monomer. The high molecular coagulant when used for dewatering of sludge, has a good coagulation effect, gives a coagulated block with high strength, a low water content by mechanical dewatering, and peelable dewatered cake, enabling stable dewatering of sludge.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a novel polymer flocculant,
More specifically, when used in the sludge dewatering treatment, it gives a flocculated floc with excellent cohesive strength and high strength, and it is possible to obtain a dehydrated cake with a low water content and good peelability by mechanical dehydration, and a stable sludge. The present invention relates to a polymer flocculant capable of being dehydrated.

[0002]

2. Description of the Related Art In recent years, activated sludge treatment such as municipal sewage treatment and sewage treatment and industrial wastewater has been widely performed. However, since the organic sludge generated has a high water content, it can be efficiently disposed of for disposal, incineration and fertilization. It is necessary to perform dehydration treatment. Conventionally, sludge is dehydrated mainly by using a high molecular weight cationic polymer as a dehydrating agent, for example, tertiary salts such as dimethylaminoethyl (meth) acrylate hydrochloride and sulfate, or quaternary salts such as methyl chloride quaternary. A homopolymer of an ammonium salt or a copolymer with acrylamide is used. However, in recent years, the amount of sludge generated has increased due to the development of sewer systems, the amount of organic matter in sludge has increased, and sludge properties have deteriorated due to decay, etc. When a conventional cationic polymer such as (1) is used, (1) the flocculation flocs are large, but the strength is weak, so (a) peeling of the cake from the filter cloth is poor, and operating problems of the dehydrator are likely to occur. (B) Due to poor filterability, the sludge treatment amount does not increase, (c) SS content in the sludge leaks into the separated liquid, (2) because the dehydrated cake has a high water content, (a) In the case of cake landfill disposal, the transportation cost is high, (b) In the case of incineration disposal, the fuel cost is high and troubles in the incinerator are likely to occur, (3) Sludge dewatering process is not stable, etc. The problem of Improvement of the method has been demanded.

[0003]

DISCLOSURE OF THE INVENTION The present invention overcomes the drawbacks of such conventional cationic polymers, and when used for sludge dewatering treatment, provides floc with excellent cohesive force and high strength. The purpose of the present invention is to provide a polymer flocculant capable of obtaining a dehydrated cake having a low water content and good peelability by mechanical dehydration and capable of performing stable dehydration treatment of sludge.

[0004]

Means for Solving the Problems As a result of intensive studies to develop a polymer flocculant having the above-mentioned preferable properties, the present inventors have found that a specific proportion of a benzylated vinylamine unit is contained as a constitutional unit. It has been found that a polymer flocculant composed of the above polymer can meet the purpose, and the present invention has been completed based on this finding. That is,
The present invention provides the following formula (1) as a constituent monomer unit:

[Chemical 2] 2-30 mol% of benzylated vinylamine unit represented by
And a polymer flocculant comprising a polymer containing (2) a polymer, a hydrolyzate of a homopolymer of N-vinylformamide or a copolymer of N-vinylformamide and another vinyl-based monomer. Benzylated one
The polymer coagulant according to the item (1) is provided.

The present invention will be described in detail below. The polymer flocculant of the present invention has the formula:

[Chemical 3] 2-30 mol% of benzylated vinylamine unit represented by
And a vinylamine unit and / or another copolymerizable vinyl-based monomer as a constituent monomer unit other than the benzylated vinylamine unit represented by the formula [1]. A unit etc. can be mentioned. In the polymer, when the content of benzylated vinylamine unit is less than 2 mol%, the effect of benzylation is difficult to be exhibited, and the object of the present invention cannot be sufficiently achieved.
If it exceeds 30 mol%, the hydrophobicity becomes too strong and the effect as a sludge dehydrating agent tends to be rather lowered. The method for producing the polymer flocculant of the present invention is not particularly limited, but the polymer flocculant can be preferably produced by, for example, the method described below. First, a homopolymer of N-vinylformamide or N-vinylacetamide, a copolymer of N-vinylformamide and N-vinylacetamide, or N-vinylformamide or N-
A copolymer of vinylacetamide and another vinyl monomer is produced. Examples of the copolymerizable vinyl monomer used at this time include acrylamide, methacrylamide, styrene, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, vinyl acetate, acrylonitrile, N-vinylpyrrolidone, etc. Nonionic monomers; acrylic acid, methacrylic acid or alkali metal salts thereof, vinyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, styrene sulfonic acid and other compounds having a sulfone group, or alkali metal salts thereof, etc. Anionic monomer of dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate,
Examples thereof include, but are not limited to, cationic monomers such as tertiary salts such as dimethylaminopropyl acrylamide and dimethylaminopropyl methacrylamide, or quaternary ammonium salts.
These copolymerizable vinyl monomers may be used alone or in combination of two or more.

The polymerization method is not particularly limited, and examples thereof include solution polymerization method, suspension polymerization method and emulsion polymerization method.
A commonly used method can be adopted. Then, to the base polymer thus obtained, an acidic substance such as hydrochloric acid or an alkaline substance such as sodium hydroxide is added in an amount according to the hydrolysis rate, and the temperature is usually 40 to 100 ° C.
By reacting at a moderate temperature, hydrolysis is performed to cationize, that is, a polymer having a primary amino group is obtained. At this time, the hydrolysis rate (cationization rate) is N-
The range of 20 to 95 mol% is preferable with respect to the vinylformamide unit or the N-vinylacetamide unit. Next, the primary amino group is benzylated by reacting the polymer having a primary amino group with a benzyl halide such as benzyl chloride or benzyl bromide at a temperature of about 40 to 100 ° C. under alkaline conditions. ,
A polymer containing 2 to 30 mol% benzylated vinylamine units is prepared. The reaction solution thus obtained may be used as a polymer flocculant as it is, or may be used as a polymer flocculant by adding an acid such as hydrochloric acid to convert the amine moiety into a hydrochloride or the like. Alternatively, the powdery polymer may be put into an appropriate solvent such as acetone or methanol and taken out to be used as a polymer flocculant. The molecular weight of the polymer used as the polymer flocculant of the present invention is appropriately selected depending on the properties of the object to be treated (sludge), the mechanical conditions for sludge dewatering, etc.
The intrinsic viscosity measured at a temperature of 30 ° C. in a 1N sodium chloride aqueous solution is preferably 8 dl / g or more. The structure of the polymer is qualitatively determined by infrared spectroscopic analysis (IR
Method), but it is preferable to use the nuclear magnetic resonance absorption method (NMR method) in order to know the benzylation rate accurately. The polymer flocculant of the present invention is particularly preferably used as a sludge dehydrating agent,
At this time, if necessary, an inorganic flocculant such as ferric chloride, polyferric sulfate, polyaluminum chloride, and a sulfuric acid band, or other organic polymer flocculant can be used in combination. When the polymer flocculant of the present invention is used as a sludge dehydrating agent, the target sludge may be an organic sludge, and the sludge species and sludge properties are not particularly limited, and for example, mixed raw sludge of sewage. , Sewage digested sludge, human waste treatment sludge,
Examples include surplus sludge generated by general industrial wastewater treatment.
Examples of the dehydrator used for dehydrating sludge include a belt press dehydrator, a centrifugal dehydrator, a filter press dehydrator, a screw press dehydrator, a vacuum dehydrator and the like.

[0007]

The present invention will be described in more detail by way of examples, which should not be construed as limiting the invention thereto. Production Example 1 (1) Production of Base Polymer 204.8 g of N-vinylformamide was dissolved in distilled water to 1000 ml, and the pH was adjusted to about 7. The monomer aqueous solution was transferred to a 1000 ml separable flask equipped with a nitrogen gas introduction tube and a Dimroth condenser tube, and after nitrogen bubbling for 30 minutes, 0.52 g of 2,2′-azobiscyanoamidinopropane · hydrochloride was added. 10 at 50 ° C
Polymerization was carried out for a time. Next, the produced hydrogel polymer was put into a large amount of acetone, dehydrated and pulverized to obtain white powder of poly (N-vinylformamide). Yield is 1
It was 0.1%. (2) Hydrolysis of poly (N-vinylformamide) Poly (N-vinylformamide) 4 obtained in (1) above
0.0 g was placed in a separable flask equipped with a stirrer and a condenser, and 800 ml of distilled water was further added and stirred to dissolve it. Then, 117.2 g of 35 wt% concentrated hydrochloric acid was added,
The temperature was raised to 60 ° C. and hydrolysis was performed for 24 hours with stirring. The reaction product was poured into a large amount of acetone, dehydrated and pulverized to obtain a hydrochloride of a partial hydrolyzate of poly (N-vinylformamide) as white powder. The yield was 100.2%, and the hydrolysis rate determined by colloid titration was 84 mol%. (3) Benzylation 5.0 g of the hydrochloride of the partial hydrolyzate of poly (N-vinylformamide) obtained in (2) above was placed in a separable flask equipped with a stirrer and a condenser, and 200 ml of water was added. Add a uniform solution to the solution, and add 15 wt% sodium hydroxide aqueous solution 25 ml.
Then, the temperature was raised to 50 ° C. and a predetermined amount of benzyl chloride was added to obtain 4 kinds of polymers A, B, C and D. Polymer type Amount of benzyl chloride A 0.41 g B 0.81 g C 2.0 g D 3.0 g After completion of the reaction, the product was purified with acetone and powdered in the same manner as in the above (1) and (2). The benzylation ratios of the obtained polymers A to D were measured by proton NMR, and were measured from the area ratio of the signal of the proton of the benzene ring at around 8 ppm and the signal of the proton of the main chain methylene at around 2 ppm. Table 1 shows the physical properties of the polymers A to D obtained in Production Example 1 and the other test polymers E, F and G.

[0008]

[Table 1]

1) Colloid equivalent value at pH 3. 2) Intrinsic viscosity at 30 ° C. using 0.1N-NaCl aqueous solution as a solvent, however, () shows intrinsic viscosity at 30 ° C. using 1N-NaCl aqueous solution as a solvent. 3) A methyl chloride quaternary homopolymer of dimethylaminoethyl methacrylate. 4) Methyl chloride quaternary / acrylamide copolymer of dimethylaminoethyl acrylate. Examples 1 to 3 and Comparative Examples 1 to 4 As sludge, sewage mixed raw sludge (pH 6.1, SS1.36)
%, VSS / SS78.7%, fiber content / SS18.6%,
The conductivity was 1420 μs / cm), and the evaluation was performed by the following method. 200 ml of sludge was placed in a 300 ml polybeaker, a predetermined amount of the polymer solution prepared to have a concentration of 0.2% by weight was added to the sludge by a predetermined amount using a syringe, and the mixture was stirred at 250 rpm for 30 seconds with a stirrer equipped with a turbine blade. After measuring the floc diameter at that time, place a polyvinyl chloride cylinder with an inner diameter of 50 mm on a Nutcheroth covered with a nylon filter cloth, pour the agglomerated sludge into it, and use a graduated cylinder to filter it after 10 seconds. The liquid volume was measured. Next, a certain amount of the coagulated sludge remaining on the filter cloth was put on a polyester filter cloth for belt press and squeezed at 1.0 kg / cm ² for 1 minute, and the cake on the filter cloth was scraped off with a spatula to obtain a water content. Was measured. The sludge adhering to the filter cloth was washed off with high-pressure water, and the amount of solid matter was measured to evaluate the filter cloth releasability. The results are shown in Table 2.

[0010]

[Table 2]

Examples 4 to 6 and Comparative Examples 5 to 8 As sludge, a mixed sludge (pH 7.0, SS 2.3%, VSS / SS 72.7%, fiber content / SS 3.) of human waste surplus sludge and tertiary treated sludge was used. 4%, conductivity 2160 μs / cm) was used and evaluated in the same manner as in the case of the sewage mixed raw sludge.
The results are shown in Table 3.

[0012]

[Table 3]

[0013]

Industrial Applicability The polymer flocculant of the present invention, when used for sludge dewatering treatment, gives a flocculating floc having excellent cohesive force and high strength, a low water content by mechanical dewatering, and a good delaminating cake. Is obtained, and stable dehydration treatment of sludge is possible.

Claims (2)

[Claims] 1. A constitutional monomer unit as a constituent monomer unit: 2-30 mol% of benzylated vinylamine unit represented by
A polymer flocculant comprising a polymer containing 2. The polymer according to claim 1, wherein the hydrolyzate of a homopolymer of N-vinylformamide or a copolymer of N-vinylformamide and another vinyl monomer is benzylated. Polymer flocculant.