JPH10118660A - Treatment of deinking waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a deinking waste water treatment method subjecting waste water discharged from a deinking process to solid-liquid separation to reutilize water and a chemical agent dissolved in water, to enable the reduction of the generation of scale and the rationalization of a process and capable of producing deinked pulp of high quality. SOLUTION: A cationic charge adjusting agent having a quaternary ammonium salt of which the intrinsic viscosity measured at 25 deg.C using a 1N sodium nitrate aq. soln. as a solvent is 1dl/g is added to waste water discharged from a deinking process to perform primary flocculation treatment and a polymeric flocculant is added to secondary flocculation treatment to perform solid-liquid separation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for treating deinking wastewater. More specifically, the present invention provides a high-quality deinked pulp with reduced scale disturbance, solid-liquid separation of wastewater discharged from the deinking process, and reuse of water and chemicals dissolved in the water. The present invention relates to a method for treating deinking wastewater that can be manufactured.

[0002]

2. Description of the Related Art In recent years, reuse of waste paper has become a major issue from the standpoint of energy saving and resource saving. In order to collect and reuse waste paper, deinking pulp is produced by removing printing ink and the like in a deinking process. As an example of the deinking process, first, wastepaper fibers are dispersed in water by a pulp and pulped, then kneaded with a deinking agent in a kneader, and the ink is peeled off from the pulp in a tower. Next, the ink is floated and separated out of the system by a flotator, and the pulp and water are washed and separated by an extractor, and the water is further separated by a filter. The deinked pulp from which ink and dirt have been removed in this way is used as a raw material for newsprint, medium quality paper, household paper, and the like. In the deinking process, it is necessary to separate the ink and the fine SS from the wastewater discharged from the washing process and the filtrate discharged from the dehydration process, and reuse the water and the chemicals dissolved in the water. To this end, pressure flotation devices have been installed in the process of collecting water from the washing filtrate. In the pressure flotation device, an anionic polymer flocculant was used to remove ink and SS. However, only the anionic polymer coagulant does not sufficiently coagulate the ink and the SS, and the quality of the treated water is not sufficiently improved. Therefore, a sulfate band and an anionic polymer flocculant have been used in combination. However, in this combination, alkaline chemicals such as caustic soda and sodium silicate used for the purpose of deinking are depleted, and if the recovered water is used, the pH of the deinking step is lowered, and dewatering is caused by the mixed aluminum ions. The black effect is reduced. Further, troubles such as generation of a scale mainly composed of an aluminum compound are likely to occur. In addition, the recovered SS
There is a problem that the amount of waste when discarding is increased.
Therefore, a method of eliminating these adverse effects by using bentonite and a nonionic polymer flocculant in combination instead of the sulfate band has been adopted. According to the combination of the bentonite and the nonionic polymer flocculant, the SS component is effectively removed without lowering the pH of the treated water because the bentonite has a property of adsorbing the fine fibers, filler and ink in the washing filtrate. . However, the combination of bentonite and a nonionic polymer flocculant has a weak flocculence and has little effect on the filtrate of a dehydrator between a pulper and a kneader having a high pH. For this reason, in the deinking process, ink and fine SS are separated from the wastewater discharged from the washing process and the filtrate discharged from the dehydration process, and are dissolved in water and water without causing scale disturbance. There is a need for a deinking wastewater treatment method that enables the reuse of chemicals such as deinking agents, caustic soda, and sodium silicate, and that can produce high quality deinked pulp.

[0003]

SUMMARY OF THE INVENTION The present invention provides a solid-liquid separation of waste water discharged from a deinking process, reuses water and chemicals dissolved in the water, reduces the generation of scale, and streamlines the process. It is an object of the present invention to provide a method for treating deinked wastewater, which can produce high-quality deinked pulp. ☆☆

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have added a cationic charge control agent having a quaternary ammonium group to deinking wastewater to perform primary coagulation treatment. After that, it was found that by adding a polymer flocculant and performing secondary flocculation treatment, it was possible to effectively remove SS without depleting the alkaline agent in the deinking wastewater. The invention has been completed. That is, the present invention provides (1) a cationic charge control having a quaternary ammonium group having an intrinsic viscosity of 1 dl / g or less measured at 25 ° C. using a 1N aqueous solution of sodium nitrate as a solvent in the wastewater discharged from the deinking step. After the primary flocculation treatment by adding an agent, secondary flocculation treatment by adding a polymer flocculant,
A method for treating deinking wastewater, which is characterized by performing solid-liquid separation. Further, in a preferred embodiment of the present invention, (2) the cationic charge control agent having a quaternary ammonium group is a dimethylamine-epichlorohydrin condensate, polydimethyldiallylammonium chloride or methyldimethyltetrachloride of polydimethylaminoethyl acrylate. (1) The method for treating deinking wastewater according to the above (1), which is a graded product or a copolymer comprising a monomer constituting these and a nonionic monomer such as acrylamide; (4) The method for treating deinked wastewater according to (1), wherein the polymer flocculant is a cationic polymer flocculant; 5) The method for treating deinked wastewater according to item (1), wherein the method of solid-liquid separation is pressurized flotation.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the method of the present invention, deinking wastewater discharged from a deinking process for collecting used paper and reusing it as deinking pulp, for example, dewatered by a dewatering machine located between a pulper and a kneader. The present invention can be applied to treatment of filtrate, floss discharged from a flotator, and drainage discharged from a washing step after the flotator. In the method of the present invention, a primary charge treatment is first performed by adding a cationic charge control agent having a quaternary ammonium group to the deinking wastewater.
Examples of the cationic charge control agent having a quaternary ammonium group include condensates of amine and epichlorohydrin such as alkylamine-epichlorohydrin condensate, polyamidoamine-epichlorohydrin condensate, and dimethyldiallylammonium. Examples include halide polymers or copolymers, dimethylaminoalkyl acrylates, dimethylaminoalkyl methacrylate polymers or copolymers, and quaternized products. In the deinking wastewater, newspaper pulp, which is the main raw material, contains mechanical pulp containing a large amount of anionic substances such as lignin, and alkali agents such as caustic soda, sodium silicate, and sodium sulfite are added. Shows strong anionicity and is in a dispersed state. In general, a cationic polymer flocculant neutralizes the charge to generate flocs with respect to SS having such a strong anionic property, but a cationic charge having a quaternary ammonium group is used for deinking wastewater. Modifiers are particularly effective. The cationic charge control agent having a quaternary ammonium group used in the method of the present invention has an intrinsic viscosity of 1 dl / measured at 25 ° C. using a 1N aqueous solution of sodium nitrate as a solvent.
g or less, and more preferably 0.5 dl / g or less. In general, a polymer flocculant is said to have an excellent flocculating effect because the larger the molecular weight, the more the molecules are spread in water and cross-linking is likely to occur, but in the method of the present invention, contrary to expectation, the molecular weight is quite unexpected. When a cationic charge control agent having a quaternary ammonium group having a large value is used for primary aggregation, the aggregation effect is poor and the intrinsic viscosity is 1 dl.
/ G, the coagulation effect is sharply reduced. In the method of the present invention, the lower limit of the intrinsic viscosity required for the cationic charge control agent having a quaternary ammonium group to exhibit the aggregation effect differs depending on the type of the cationic charge control agent. Chlorohydrin condensate exhibits an aggregation effect up to an intrinsic viscosity of 0.002 dl / g, whereas polydimethyldiallylammonium chloride exhibits an aggregation effect when the intrinsic viscosity is less than 0.01 dl / g. The methyl quaternary chloride of ethyl acrylate has an intrinsic viscosity of 0.05 dl / g.
If it is less than this, the aggregation effect is reduced.

In the method of the present invention, the amount of the cationic charge control agent having a quaternary ammonium group is not particularly limited, and the amount can be appropriately selected according to the properties of the deinking wastewater. For example, a cationic charge having a relatively large amount of quaternary ammonium groups such as 100 to 500 mg / liter for wastewater having a high pH, such as a filtrate of a dehydrator between a pulper and a kneader in a deinking process. Preferably, a regulator is added. For wastewater having a relatively low pH, such as a filtrate in a washing step after a flotator, cationic charge control having a relatively small amount of quaternary ammonium groups such as 0.5 to 5 mg / liter. By adding the agent, the coagulation effect can be sufficiently exhibited. In the method of the present invention, after adding a cationic charge control agent having a quaternary ammonium group to the deinking wastewater and performing a primary aggregation treatment,
A secondary flocculation treatment is performed by adding a polymer flocculant. The polymer flocculant to be used is not particularly limited, and for example, an anionic polymer flocculant, a nonionic polymer flocculant, a cationic polymer flocculant and the like can be used. Examples of the anionic polymer coagulant include sodium polyacrylate, a partially hydrolyzed polyacrylamide, a copolymer of acrylamide and acrylic acid, and 2-acrylamide-2.
A polymer or copolymer of -methylpropanesulfonic acid; Examples of the nonionic polymer flocculant include polyacrylamide, polyethylene oxide, and a urea-formalin condensate. Examples of the cationic polymer flocculant include polyaminoalkyl methacrylate or its methyl chloride quaternary, aminoalkyl methacrylate or its methyl chloride quaternary and acrylamide copolymer, polyethyleneimine, chitosan and the like. In the method of the present invention, the polymer flocculant used for the secondary flocculation treatment is preferably an anionic polymer flocculant such as a hydrolyzate of polyacrylamide when the pH of the deinking wastewater exceeds 9. When the pH of black ink wastewater is 9 or less, polydimethylaminoethyl acrylate or its methyl chloride quaternary, polydimethylaminoethyl methacrylate or its methyl quaternary, dimethylaminoethyl acrylate or its methyl quaternary chloride It is preferably a cationic polymer flocculant such as a copolymer of acrylamide, dimethylaminoethyl methacrylate or a copolymer of acrylamide with methyl chloride quaternary.

In the method of the present invention, the polymer flocculant used for the secondary flocculation treatment is preferably high in molecular weight, unlike the cationic charge control agent having a quaternary ammonium group used for the primary flocculation treatment. The anionic polymer coagulant and the nonionic polymer coagulant preferably have an intrinsic viscosity of 5 dl / g or more measured at 25 ° C. using a 1N aqueous solution of sodium chloride as a solvent.
The intrinsic viscosity measured at 25 ° C. using an N sodium nitrate aqueous solution as a solvent is preferably 5 dl / g or more. In the method of the present invention, the amount of the polymer flocculant to be added is not particularly limited, but is usually 0 to the deinking wastewater after the primary flocculation treatment with a cationic charge control agent having a quaternary ammonium group. The secondary aggregation treatment can be sufficiently performed by adding 0.5 to 5 mg / liter. In the method of the present invention, the waste water subjected to the secondary coagulation treatment by adding a polymer coagulant is then subjected to solid-liquid separation. There is no particular limitation on the solid-liquid separation method.For example, solid-liquid separation can be performed by sedimentation treatment, pressure flotation, filtration, and the like. Among these methods, pressure flotation is particularly preferably used. it can. In the method of the present invention,
The deinking wastewater discharged from the deinking process can be mixed with wastewater generated in other processes, for example, machine surplus white water, surplus white water treatment water, raw wastewater, and the like. According to the method of the present invention, unlike the conventional combination of a sulfuric acid band and a polymer flocculant, SS is efficiently removed from high pH wastewater without depleting the alkaline agent in the deinking wastewater, and used. Water and chemicals dissolved in water can be reused to economically produce high quality deinked pulp. In addition, compared to the conventional sulfuric acid band, the amount of scale generated is small, and the number of times of cleaning the device can be reduced,
The process can be streamlined.

[0008]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. In Examples and Comparative Examples, the intrinsic viscosities of the cationic charge control agent and the cationic polymer flocculant are values measured at 25 ° C. using a 1N aqueous solution of sodium nitrate as a solvent. The intrinsic viscosity of the water-soluble polymer flocculant is a value measured at 25 ° C. using a 1N aqueous solution of sodium chloride as a solvent.
The filtrate used in Examples and Comparative Examples was generated from the deinking step by the flotation method shown in FIG. In this step, the used paper is dissociated into pulp in water in the pulper 1, squeezed in the dehydrator 2, and sent to the kneader 3. In the dehydrator, a highly alkaline filtrate having a high pH is generated. The pulp and the deinking agent are kneaded by a kneader, and the printing ink and the like are separated from the pulp in the tower 4. The printing ink and the like are floated and separated by the floater 5 and removed outside the system. Next, pulp and water are washed and separated by the extractor 6, and water is further separated by the valveless filter 7. Extractors and valveless filters produce a relatively weak alkaline filtrate. Example 1 Cationic Charge Modifier Having Quaternary Ammonium Group (A)
Using a dimethylamine-epichlorohydrin condensate having an intrinsic viscosity of 0.2 dl / g as a polymer flocculant (B)
Has a hydrolysis rate of 70% and an intrinsic viscosity of 15 dl /
g of the polyacrylamide hydrolyzate was used to treat the filtrate of the dehydrator between the pulper and the kneader in the deinking step. The filtrate was SS 715 mg / liter, pH 1
0.8, the zeta potential was -31.2 mV. To 0.5 liter of the filtrate, 300 mg / l of the charge control agent (A) was added, and the mixture was stirred at 150 rpm for 30 seconds to perform a primary coagulation treatment. Then, 2 mg / l of the polymer coagulant (B) was added. Fifteen
The mixture was stirred at 0 rpm for 30 seconds, and further stirred at 50 rpm for 60 seconds to perform a secondary aggregation treatment. SS of the supernatant water after treatment is 3
It was 0 mg / l and the pH was 10.8. Comparative Example 1 The same filtrate as in Example 1 was treated using only the polymer flocculant (B). To 0.5 liter of the filtrate, 2 mg / liter of the polymer flocculant (B) was added, and the mixture was stirred at 150 rpm for 30 seconds.
Further, the mixture was stirred at 50 rpm for 60 seconds to perform an aggregation treatment.
The SS of the supernatant water after the treatment is 500 mg / liter,
Was 10.8. Comparative Example 2 The same filtrate as in Example 1 was mixed with a sulfate band and a polymer flocculant (B).
The treatment was performed using To 0.5 liter of the filtrate, 5,000 mg / l of a sulfuric acid band was added, and the mixture was stirred at 150 rpm for 30 seconds. Then, 2 mg / l of a polymer flocculant (B) was added, and the mixture was stirred at 150 rpm for 30 seconds, and further added at 50 rpm. At 60
The mixture was stirred for 2 seconds to perform an aggregation treatment. SS of treated supernatant water
Was 20 mg / l and the pH was 7.0. Comparative Example 3 The same filtrate as in Example 1 was used except that bentonite and a polymer flocculant were used.
As (C), it processed using the polyacrylamide whose intrinsic viscosity is 15 dl / g. To 0.5 liter of the filtrate, 1500 mg / liter of bentonite was added, and the mixture was added at 150 rpm for 3 hours.
After stirring for 0 seconds, 2 mg / liter of the polymer flocculant (C) was added, and the mixture was stirred at 150 rpm for 30 seconds, and further stirred at 50 rpm.
For 60 seconds to perform an aggregation treatment. The SS of the supernatant water after the treatment was 450 mg / liter, and the pH was 10.8. Example 2 Cationic Charge Modifier Having Quaternary Ammonium Group (A)
Extractor filtrate and valveless filter in a washing step after a flotator, using a methyl quaternary chloride-acrylamide copolymer of dimethylaminoethyl acrylate having an intrinsic viscosity of 15 dl / g as a polymer flocculant (D). The mixture of the filtrate was treated. The mixture of the filtrates had SS of 695 mg / liter, pH of 8.7 and zeta potential of −20.9 mV. To 0.5 liter of the mixed solution of the filtrate, 2 mg / liter of the charge control agent (A) was added and 150 rp.
After stirring at 30 m for 30 seconds to perform a primary flocculation treatment, 1 mg / liter of a polymer flocculant (D) was added,
The mixture was stirred for 0 second, and further stirred at 50 rpm for 60 seconds to perform a secondary aggregation treatment. The SS of the supernatant water after the treatment was 5 mg / liter, and the pH was 8.7. Comparative Example 4 The same mixture of the filtrates as in Example 2 was treated using only the polymer flocculant (D). To 0.5 liter of the mixed solution of the filtrate, 1 mg / liter of the polymer flocculant (D) was added, and the mixture was stirred at 150 rpm for 30 seconds to perform a flocculation treatment. The SS of the supernatant water after the treatment was 350 mg / liter, and the pH was 8.7. Comparative Example 5 The same mixture of filtrates as in Example 2 was treated with a sulfuric acid band and a polymer flocculant (D). To 0.5 liter of the mixture of the filtrate, 2,000 mg / liter of a sulfuric acid band was added, and 1
Stir at 50 rpm for 30 seconds, then add 1 mg / L of polymer flocculant (D), stir at 150 rpm for 30 seconds,
Further, the mixture was stirred at 50 rpm for 60 seconds to perform an aggregation treatment.
The SS of the supernatant water after the treatment was 5 mg / liter, and the pH was 6.8. Comparative Example 6 The same mixture of the filtrates as in Example 2 was treated with bentonite and a polymer flocculant (C). To 0.5 liter of the filtrate, 500 mg / liter of bentonite was added, and the mixture was stirred at 150 rpm for 30 seconds. Then, the polymer flocculant (C) was added.
Was added at 1 mg / liter, and the mixture was stirred at 150 rpm for 30 seconds, and further stirred at 50 rpm for 60 seconds to perform an aggregation treatment. The SS of the supernatant water after the treatment is 25 mg / liter,
pH was 8.7. Table 1 shows the results of Examples 1 and 2 and Comparative Examples 1 to 6.

[0009]

[Table 1]

A primary aggregation treatment is performed using a dimethylamine-epichlorohydrin condensate having a quaternary ammonium salt, and a polyacrylamide hydrolyzate or a dimethylaminoethyl acrylate methyl chloride quaternized-acrylamide copolymer is used. Example 1 in which secondary aggregation treatment was performed by using
In the treated water of Example 2, the amount of SS was sufficiently reduced, and the pH value was not different from that of the raw water, indicating that the alkaline agent was not consumed. On the other hand, Comparative Example 1 in which only the treatment using the polyacrylamide hydrolyzate was performed
In Comparative Example 4 in which only the treatment using methyl quaternary chloride of dimethylaminoethyl acrylate and acrylamide copolymer was performed, the pH value of the treated water was not different from that of the raw water, but the treated water still contained a large amount of SS. In. In Comparative Example 2 using a sulfuric acid band and a polyacrylamide hydrolyzate in combination and Comparative Example 5 using a sulfuric acid band and a methyl quaternary chloride-acrylamide copolymer of dimethylaminoethyl acrylate, SS in treated water was used. Although the amount of has decreased, the pH of the treated water has dropped,
Alkaline agent is depleted. The combination of bentonite and polyacrylamide is effective for the mixture of the extractor filtrate and the valveless filter filtrate of Comparative Example 6, but the filter of the dehydrator between the high pH pulper and the kneader of Comparative Example 3 is effective. The SS removal ability is insufficient for the liquid. Example 3 In the combination of the charge adjusting agent (A) and the polymer flocculant (B), the amount of the charge adjusting agent (A) was changed to change the amount between the pulper and the kneader in the deinking process used in Example 1. The filtrate of the dehydrator was treated. One of the four beakers containing 0.5 liter of the filtrate did not contain the charge control agent (A), and the other 3
100 mg / L each of the charge control agent (A)
Add 200mg / L and 300mg / L and add 1
After stirring at 50 rpm for 30 seconds to perform a primary flocculation treatment, 2 mg / L of a polymer flocculant (B) was added to each beaker, and the mixture was stirred at 150 rpm for 30 seconds, and further stirred for 5 seconds.
The mixture was stirred at 0 rpm for 60 seconds to perform a secondary aggregation treatment. The SS amount of the supernatant water after the treatment was 500 mg / L without the charge control agent (A), 194 mg / L with the addition of 100 mg / L, 48 mg / L and 300 mg / L with the addition of 200 mg / L. The amount added was 28 mg / liter. Example 4 Instead of the charge control agent (A), a cationic charge control agent (E) having a quaternary ammonium group was used.
The same operation as in Example 3 was repeated except that l / g of polydimethyldiallylammonium chloride was used. The SS amount of the supernatant water after the treatment was 10% for the charge control agent (E).
298 mg / liter added with 0 mg / liter, 2
194 mg / liter added with 00 mg / liter,
The addition of 300 mg / liter resulted in 116 mg / liter. Example 5 Instead of the charge control agent (A), a cationic charge control agent (F) having a quaternary ammonium group was used, which had an intrinsic viscosity of 0.2 d.
The same procedure as in Example 3 was repeated, except that a l / g polydimethylaminoethyl acrylate methyl quaternary chloride was used. The SS amount of the supernatant water after the treatment was 396 mg / L when the charge control agent (F) was added at 100 mg / L.
Liter, 200mg / liter added 241mg
Per liter and 300 mg / liter added to 151
mg / liter. Comparative Example 7 The same operation as in Example 3 was repeated except that polyethyleneimine having an intrinsic viscosity of 0.2 dl / g was used as the charge adjusting agent (G) instead of the charge adjusting agent (A). The SS amount of the supernatant water after the treatment was 475 mg / L when the charge adjusting agent (G) was added at 100 mg / L, 512 mg / L when the 200 mg / L was added, and 485 mg / L when the 300 mg / L was added. there were. Comparative Example 8 The same operation as in Example 3 was repeated except that polyvinylamine having an intrinsic viscosity of 0.2 dl / g was used as the charge adjusting agent (H) instead of the charge adjusting agent (A). The SS amount of the supernatant water after the treatment was 496 mg / L when the charge control agent (H) was added at 100 mg / L, 515 mg / L when the 200 mg / L was added, and 475 mg / L when the 300 mg / L was added. there were. Comparative Example 9 The same operation as in Example 3 was repeated, except that a dicyandiamide-formalin condensate having an intrinsic viscosity of 0.2 dl / g was used as the charge adjusting agent (I) instead of the charge adjusting agent (A). Was. The SS amount of the supernatant water after the treatment was 465 mg / L when the charge adjusting agent (I) was added at 100 mg / L, 483 mg / L when the 200 mg / L was added, and 496 mg / L when the 300 mg / L was added. there were. Table 2 shows the results of Examples 3 to 5 and Comparative Examples 7 to 9.

[0011]

[Table 2]

Example 3 in which primary aggregation was performed using dimethylamine-epichlorohydrin condensate, Example 4 in which primary aggregation was performed using polydimethyldiallylammonium chloride, and chlorination of polydimethylaminoethyl acrylate In Example 5 in which the primary aggregation treatment was performed using methyl quaternary product, the SS in the treated water after performing the secondary aggregation treatment using the polyacrylamide hydrolyzate was used.
Has been effectively reduced. On the other hand, in Comparative Example 7 in which primary aggregation was performed using polyethyleneimine, in Comparative Example 8, in which primary aggregation was performed using polyvinylamine, and in Comparative Example 9, in which primary aggregation was performed using dicyandiamide-formalin condensate. Is that the amount of SS in the treated water after performing the secondary flocculation treatment using the polyacrylamide hydrolyzate is almost reduced compared to the amount of SS when the treatment is performed using only the polyacrylamide hydrolyzate. Absent. Example 6 In the combination of the charge control agent (A) and the polymer flocculant (D), the amount of the charge control agent (A) was changed, and the extractor filter in the washing step after the floatator used in Example 2 was used. The mixture of the liquid and the filtrate of the valveless filter was treated. The charge adjusting agent (A) was not added to one of the four beakers each containing 0.5 liter of the mixed solution of the filtrate, and the other three were charged with the charge adjusting agent (A) at 5 mg / liter each. , 10mg /
Liter and 15 mg / liter and 150 rpm 3
After stirring for 0 second and performing primary aggregation treatment, 1 mg / L of a polymer flocculant (D) was added to each beaker, stirred at 150 rpm for 30 seconds, and further stirred at 50 rpm for 60 seconds to perform secondary aggregation treatment. Was done. SS of treated supernatant water
The amount was 350 mg / liter without the charge control agent (A), 68 mg / l with the charge control agent (A) added at 5 mg / l, 6 mg / l and 15 mg / l with the charge control agent (A) added at 10 mg / l. 5mg added
/ Liter. Example 7 The same operation as in Example 6 was repeated, except that the charge adjusting agent (E) was used instead of the charge adjusting agent (A). The SS amount of the supernatant water after the treatment was 147 mg / L when the charge control agent (E) was added at 5 mg / L, 99 mg / L when 10 mg / L was added, and 79 mg / L when 15 mg / L was added. there were. Example 8 The same operation as in Example 6 was repeated except that the charge adjusting agent (F) was used instead of the charge adjusting agent (A). The SS amount of the supernatant water after the treatment was 194 mg / L when the charge control agent (F) was added at 5 mg / L, 48 mg / L when 10 mg / L was added, and 13 mg / L when 15 mg / L was added. there were. Comparative Example 10 The same operation as in Example 6 was repeated, except that the charge adjusting agent (G) was used instead of the charge adjusting agent (A). The SS amount of the supernatant water after the treatment was 344 mg / L when the charge adjusting agent (G) was added at 5 mg / L, 338 mg / L when the 10 mg / L was added, and 331 mg / L when the 15 mg / L was added. there were. Comparative Example 11 The same operation as in Example 6 was repeated, except that the charge adjusting agent (H) was used instead of the charge adjusting agent (A). The SS amount of the supernatant water after the treatment was 326 mg / L when the charge control agent (H) was added at 5 mg / L, 341 mg / L when the 10 mg / L was added, and 326 mg / L when the 15 mg / L was added. there were. Comparative Example 12 The same operation as in Example 6 was repeated except that the charge adjusting agent (I) was used instead of the charge adjusting agent (A). The SS amount of the supernatant water after the treatment was 356 mg / L when the charge control agent (I) was added at 5 mg / L, 324 mg / L when the 10 mg / L was added, and 336 mg / L when the 15 mg / L was added. there were. Table 3 shows the results of Examples 6 to 8 and Comparative Examples 10 to 12.

[0013]

[Table 3]

Example 6 in which primary aggregation was performed using a dimethylamine-epichlorohydrin condensate, Example 7 in which primary aggregation was performed using polydimethyldiallylammonium chloride, and chlorination of polydimethylaminoethyl acrylate In Example 8 in which the primary aggregation treatment was performed using a methyl quaternary compound, the SS in the treated water after performing the secondary aggregation treatment using a methyl chloride quaternary compound of dimethylaminoethyl acrylate-acrylamide copolymer was used. Has been effectively reduced. On the other hand, in Comparative Example 10 in which primary aggregation was performed using polyethyleneimine, Comparative Example 11 in which primary aggregation was performed using polyvinylamine, and in Comparative Example 12, in which primary aggregation was performed using dicyandiamide-formalin condensate. Is the amount of SS in the treated water after performing the secondary flocculation treatment using a dimethylaminoethyl acrylate chloride quaternary-acrylamide copolymer, the amount of dimethylaminoethyl acrylate chloride methyl quaternary-acrylamide copolymer There is almost no decrease compared to the amount of SS when the treatment is performed using only the polymer. Example 9 Using the filtrate of the dehydrator between the pulper and the kneader in the deinking step of Example 1, the intrinsic viscosity of the dimethylamine-epichlorohydrin condensate and the ability to remove SS in the deinking wastewater. The relationship was investigated. In 10 beakers containing 0.5 liter of filtrate, 1 having an intrinsic viscosity of 0.001-1 dl / g.
300 mg / liter of each of the 0 kinds of dimethylamine-epichlorohydrin condensate was added, and the mixture was stirred at 150 rpm for 30 seconds to perform a primary aggregation treatment. Then, each beaker has a hydrolysis rate of 70% and an intrinsic viscosity of 1
5 dl / g polyacrylamide hydrolyzate 2 mg /
One liter was added, and the mixture was stirred at 150 rpm for 30 seconds, and further stirred at 50 rpm for 60 seconds to perform a secondary aggregation treatment. The SS amount of the supernatant water after the treatment is 3 when the intrinsic viscosity of the dimethylamine-epichlorohydrin condensate is 0.001 dl / g.
50 mg / liter, 17 at 0.002 dl / g
7 mg / liter, 36 mg / liter at 0.01 dl / g, 32 mg / liter at 0.05 dl / g, 0.1 dl / g
35 mg / liter for g, 69 mg for 0.5 dl / g
Per liter and 1 dl / g was 218 mg / liter. Example 10 The relationship between intrinsic viscosity and performance was examined in the same manner as in Example 9 except that polydimethyldiallylammonium chloride was used instead of the dimethylamine-epichlorohydrin condensate. The SS amount of the supernatant water after the treatment is such that the intrinsic viscosity of polydimethyldiallylammonium chloride is 0.005 dl /
g is 360 mg / l, 0.01 dl / g is 269 mg / l, and 0.05 dl / g is 108 m
g / l, 119mg / l at 0.1dl / g,
It was 149 mg / l at 0.5 dl / g and 328 mg / l at 1 dl / g. Example 11 The relationship between the intrinsic viscosity and the performance was examined in the same manner as in Example 9 except for using methyl quaternary chloride of polydimethylaminoethyl acrylate instead of the dimethylamine-epichlorohydrin condensate. The SS amount of the supernatant water after the treatment is 396 mg / L when the intrinsic viscosity of the methyl quaternary chloride of polydimethylaminoethyl acrylate is 0.02 dl / g, and 315 mg / L when the intrinsic viscosity is 0.05 dl / g. .
The amount was 198 mg / l at 1 dl / g, 149 mg / l at 0.5 dl / g, 153 mg / l at 1 dl / g, and 382 mg / l at 2 dl / g. Table 4 shows the results of Examples 9 to 11.

[0015]

[Table 4]

From the results in Table 4, it can be seen that among the three cationic charge control agents having quaternary ammonium groups tested,
It can be seen that the dimethylamine-epichlorohydrin condensate is the best in reducing the SS content, followed by methyl quaternary chloride of polydimethyldiallylammonium chloride and polydimethylaminoethyl acrylate in this order. In addition, it can be seen that the performance of any of the cationic charge control agents decreases as the intrinsic viscosity increases, and that the one in the low molecular weight region of 1 dl / g or less has excellent performance. Comparative Example 13 The deinking process by the flotation method shown in FIG.
Conventionally, it was operated under the following conditions. That is, the filtrate of the dehydrator between the pulper and the kneader was used as it was as the water for charging the pulper without treatment. Further, the mixture of the extractor filtrate and the valveless filter filtrate in the washing step after the flotator was subjected to primary aggregation by adding 2,000 mg / l of a sulfuric acid band, and then subjected to dimethyl with an intrinsic viscosity of 15 dl / g. Aminoethyl acrylate-acrylamide copolymer was added at 1 mg / liter to perform secondary aggregation treatment, and the treated water after floating under pressure was used as washing water after the flotator. In this deinking process, it was necessary to wash the extractor every three days. In addition, JIS P80 of the obtained deinked pulp
The ash content measured according to J.03 was 7% by weight and
Hunter whiteness measured according to SP 8123 was 55.5%. Example 12 The method of the present invention was applied to the deinking process of Comparative Example 13. That is, 300 mg / L of a dimethylamine-epichlorohydrin condensate having an intrinsic viscosity of 0.2 dl / g was added to the filtrate of the dehydrator between the pulper and the kneader, and the mixture was subjected to primary aggregation treatment. Is 70% and 2 mg of polyacrylamide hydrolyzate having an intrinsic viscosity of 15 dl / g.
/ Liter was added for secondary coagulation treatment, and the treated water after pressure flotation was used as the pulper charging water. Also, the mixture of the extractor filtrate and the valveless filter filtrate in the washing step after the floatator has an intrinsic viscosity of 0.2 dl.
/ G of dimethylamine-epichlorohydrin condensate is added at 10 mg / l to perform primary aggregation, and then dimethylaminoethyl acrylate methyl chloride quaternary-acrylamide copolymer having an intrinsic viscosity of 15 dl / g Was added to form a secondary flocculation treatment, and the treated water after floating under pressure was used as washing water after the flotator.
As a result, the generation of scale in the washing process has been reduced, and the extractor has to be washed twice a month. The ash content of the deinked pulp measured in the same manner as in Comparative Example 13 was 2% by weight, and the Hunter whiteness was 56.9%. Table 5 shows the results of Comparative Example 13 and Example 12.

[0017]

[Table 5]

As can be seen from the results in Table 5, by applying the method of the present invention to the wastewater treatment in the deinking step, the number of times of cleaning of the extractor is reduced to one-fifth of the conventional one, and the step is greatly streamlined. Was. In addition, the ash content of the deinked pulp produced was reduced to about one third, the hunter whiteness was improved, and the quality of the deinked pulp was improved.

[0019]

According to the method of the present invention, SS is efficiently removed from high pH wastewater without depleting the alkaline agent in the deinking wastewater, and the water used and the chemicals dissolved in the water are removed. It can be reused to produce high quality deinked pulp economically. In addition, the amount of generated scale is small, and the number of times of cleaning of the apparatus can be reduced, so that the process can be rationalized.

[Brief description of the drawings]

FIG. 1 is a system diagram of a deinking process by a flotation method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pulper 2 Dehydrator 3 Kneader 4 Tower 5 Floater 6 Extractor 7 Valveless filter

Claims (1)

[Claims] 1. A cationic charge control agent having a quaternary ammonium group having an intrinsic viscosity of 1 dl / g or less measured at 25 ° C. using a 1N aqueous solution of sodium nitrate as a solvent is added to waste water discharged from the deinking step. After primary coagulation treatment,
A method for treating deinking wastewater, comprising adding a polymer flocculant, performing a secondary flocculation treatment, and performing solid-liquid separation.