Note: Descriptions are shown in the official language in which they were submitted.
10672Z~
Thi5 invention relates to a method for treating waste waters which
can exhibit an excellent treating effect on the clarification of not only
solid-containing ~spended waste liquids such as pulp spent liquors from paper
mills or waste waters discharged from sand and gravel extracting places, but
also waste effluents in the form of solutions or emulsions such as emulsion
wastes and rubber latices discharged from textile finishing plants, aqueous
solutions of acid dyes discharged from dyeing factories, or oil-containing
emulsion wastes from machine-building factories.
More specifically, this invention relates to a method for treating
waste liquids, which comprises adding to a solution or suspension to be clari-
fied a water-soluble melamine resin containing in the molecule a unit ex-
pressed by the following formula
NH+2X-
11
N l (I)
N - C~ /C-N~ICH2
CH2 N
OH
wherein X represents an anion derived from an inorganic or organic acid,
wherein the amino group to which a methylol group is not attached is cationic.
Clarification of waste liquids discharged in various chemical and
other industries has been an i~lportant problem in controlling environmental
pollution.
It has already been proposed (Japanese Patent Publication No.
12517/63 published on July 18, 1963) to clarify waste liquids by removing
hydrophobic or nearly hydrophobic inorganic or organic fine solid particles
suspended therein. This Japanese Patent discloses a wide variety of chemicals
for use in such a method, which include:
(A) Polycondensates formed between urea, thiourea or melamine and
formaldehyde;
(B) Copolycondensates prepared from a combination of urea, thiourea
and formaldehyde, a combination of urea, melamine and formaldehyde, and a
combination of thiourea, melamine and formaldehyde;
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(C) Copolycondensates prepared from the polymers (A) or (B) above and
other compounds copolymerizable with them to an extent that their properties
as a flocculating agent are not lost; and
(D) Neutral, anionic, cationic or amphoteric modified products ob-
tained by reacting the methylol group of the above polymers (A), (B) or (C)
with an alcohol such as methyl alcohol, ethyl alcohol, ethylene glycol,
glycerine or sucrose, an acid such as acetic acid, succinic acid, malic acid,
tartaric acid, maleic acid or glutamic acid, or an amine such as ethanolamine,
ethylene diamine or lysine capable of reacting with the methylol group; or
salts of these modified products.
It is described in this Patent that the base of the condensation
polymers (A) to (D) consists of a combination of a urea, thiourea or melamine
group shown below ~1)
0 S N
Il 11 l
/ \ / C // \ N (1)
=N-C C-N=
~N
urea groupthiourea group melamine group
with a monovalent or divalent hydrocarbon group or other group having a re-
latively low molecular weight shown below (2-1) and (2-2).
~2-1) In the case of the polymers (A), (B) and (C):-
-H, -CH20H, -CH2-, -CH20CH2-
(2-2) In the case or the polymer (D):-
-H, -CH20H, -CH2-, -CH20CH2-; -CH20CH3, -CH20CH2-CH20H
(when the methylol group is reacted with an alcohol);
-CH200CCH3, -CH200C CH2-CH2-COOH
(when the methylol group is reacted with an acid);
2 2 CH2 NH3-Cl , -CH20-CH2-CH~-NH+-Cl-
(when the methylol group is reacted with an amine).
We made extensive investigations with a view to developing a
treating agent which would be able to flocculate and sediment not only solid
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particles suspended in waste liquors but also solutes in waste liquors in
the form of solutions or emulsions. These investigations finally led to the
discovery that a water-soluble melamine resin containing in the molecule a
unit expressed by the following formula (I)
NH X
/c \
HN N
CH ~N / (I)
0}1
wherein X represents an anion derived from an inorganic or organic acidJ
which can be distinguished from the melamine resins disclosed in the above
patent in that the amino group to which a methylol group is not attached is
cationic, can be used as a very effective treating agent for waste liquids.
The above water-soluble melamine resin may contain minor amounts,
for e~ample, less than 1 mol, preferably less than 0.7 mol, more preferably
less than 0.5 mol, per mol of the triazine nucleus of the above formula, of
another unit derived from an amino compound such as urea, dicyandiamide or
acetoguanamine.
The above water-soluble melamine resins which contains the above
unit in the molecule and in which the amino group to which a methylol is not
attached is cationic are known (H.P. Wohnsiedler: I.E.C., 44, 2679, 1952),
and it is known to use resins of this type for improving the wet strength of
paper (United States Patent specification No. 2,345,543). However, it has
been completely unknown that these resins would exhibit superior activities
in the clarification of waste liquids in the form of solutions or emulsions
as well as suspensions. According to this invention, it was unexpectedly
found that these melamine resins exhibit superior clarifying activities in
fields where the effect and the time of addition are quite different from
those for incrcasing the wet strength of paper, especially in the field of
waste water treatment.
This invention seeks to provide a met~od
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for treating waste liquids in the form of solutions or e~ulsions as well as
suspensions with a superior clarifying effect.
m us, this invention provides for a method for treating a waste
aqueous liquid which comprises adding to an aqeuous solution or suspension
to be clarified an effective amount of a water-soluble melamine-based resin
containing in the lecule from about 5 to about 20 units of the formula I
N ~3 H2X ~3
C \ (I)
HN ~NH
- CH2H C / - NH - CH2
wherein X ~3 represents an anion derived from an organic or inorganic acid,
which resin has been prepared by reacting 1 mol of melamine with from 2 to 3
mols of formaldehyde, and adding to the resulting methylol melamine solution
an organic or inorganic acid in an amount of from about 0.5 to about 3.5 mols
per mol of melamine present.
m e solutions or suspensions which are to be treated in accordance
with the method of this invention include, for example, pulp spent liquors
from paper mills, waste waters from sand and gravel extracting places, emul-
sions and rubber latices from textile finishing plants, aqueous solutions of
acid dyes discharged from dyeing factories, and oil-containing emulsions from
machine-building factories. m e resins used in this invention are especially
useful for removing the matter dissolved or suspended in wastes of the solu-
tion or emulsion type.
Melamine resins containing about 5 to 20, preferably 10 to 20,units of the above formula (I) are preferably used. Examples of anion ex-
pressed by X in the formula (I) are those derived from inorganic acids such
as hydrochloric acid or phosphoric acid, or those derived from organic acids
such as formic acid or acetic acid.
The water-soluble melamine resin containing the unit of formula (I)
can be prepared, for example, by reacting 1 mol of melamine with about 2 to 3
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` 1(~67Z21
mole of formaldehyde in a custo~ary manner, cldding a relatively large amount
of an acid to the resulting methylol melamine solution to adjust the resin
concentration properly, for example, to an extent of providing about 6-20%
aqueous solution, and aging the solution at room temperature for more than
about one day. The amount of the acid can be varied properly according to
the type of the acid used, and the preferred amount is, for example, 0.7
to 1.3 mols for hydrochloric acid, 2 to 3 mols for phosphoric acid, and about
1.6 to 2~5 mols for formic acid, all per mol of the melamine. ~enerally, the
amount of the acid is about 0.5 to 3.5 mols per mole of the melamine.
In the method of this invention, the above melamine resin can be
used conjointly with an inorganic metal salt such as aluminum s~lfate, ferrous
chloride or poly(aluminum chloride) or an organic polymeric flocculant such
as polyacrylamide. The amount of the ir.organic salt and/or the organic poly-
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meric flocculant can be varied properly according to such ~actors as the type
of the ~aste liquid to be treated, or the type of the suspended, dissolved or
dispersed matter to be flocculated and removed. For example, the amount of
the inorganic metal salt is not more than about 500% by weight of the matter
to be removed, and the amount of the organic polymeric flocculant is equal to,
or lower than, the amount of the water-soluble melamine resin used in accord-
ance with this method.
The amount of the water-soluble melamine resin to be used in this
invention can be varied properly according to the characteristics of the solu-
tion, emulsion or suspension to be treated, or the type or characteristics of
the matter contained therein. ~sually, the amount of the melamine resin used
is about 1/1000 to 2 parts by weight, and in most cases, about 1/500 to 1.5
parts by weight, per part by weight of the total amount of the matter in the
waste solution, emulsion or suspension. For example, in the case of an acid
dye solution, the melamine resin is used in an amount of about 200 to about
1500 g per kilogram of the solute; in the case of an emulsified solution, the
melamine resin is used in an amount of about 50 to about 200 g per kilogram
of the solute; and in the case of a suspension such as a pulp spent liquor,
the amount of the melamine resin is about 2 to about 300 g per kilogram of
the suspended matter.
When other chemicals are conjointly used, the amount of the melamine
resin used can be properly increased or decreased according to the types and
amounts of the other chemicals.
; In the practice of the method of this invention, the pH of the
waste liquid to be clarified can be easily determined experimentally accord-
ing to the type of the matter to be removed from the waste liquid and other
conditions. Specific examples of pH adjustment are shown in the Examples to
be given hereinbelow.
One specific procedure of performing the method of this invention
comprises adding the water-soluble melamine resin having the unit of formula
(I) in the molecule, to a liquid to be treated which has been adjusted to the
desired pH during its transfer to a precipitating or filtering device, stir-
Z21
ring the mixture rapidly so as not to cause non-uniformity in concentration,
and to form a flocculated mass, and if desired, rather slowly stirring the
liquid using the abovementioned other chemicals to grow the resulting floc-
culated mass to coarser particles to facilitate precipitation or filtration,
and then precipitating or filtering the solute or suspended matter in the
waste liquid.
The sequence of adding the water-soluble melamine resin and the
chemicals can be chosen as desired.
According to this invention, it is possible to rapidly precipitate
and flocculate not only the suspended matter in suspensions, but also in
particular the solute in a solution of an acid dye having a hydrophilic group
thereby rendering it extremely easy to clarify the waste water to be treated.
The following Examples and Comparative Examples illustrate the
present invention specifically. In these Examples, the following resins were
used.
Resin A
A reactor equipped with a condenser tube and a stirrer was charged
with 126 g ~1 mol) of melamine and 240 g (3 mols) of 37% formaldehyde whose
pH had been adjusted to 8 with sodium hydroxide, and at a reaction temperature
85 to 90C., the reaction mixture was stirred. After the melamine dissolved,
the reaction was further performed at this temperature for about 30 minutes.
The reaction product was cooled to room temperature to form a transparent
resin solution.
Resin B (invention)
2 Mols of formic acid, per 126 g (1 mol) of melamine in the resin
solution, of formic acid and water were added to the same resin solution as
resin solution A to adjust the solids content to 10%. The solution was aged
at room temperature for more than one day to form a slightly bluish resin
solution.
Re _ n C (invention)
A resin solution prepared in accordance with the same recipe as
resin A was dried by means of a spray dryer to form a dry solid powdery resin.
6 -
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216 G of this powdery resin was added to dilute hydrochloric acid obtained by
mixing 100 g of HCQ having a concentration of 36.3% and 3300 g of water. The
mixture was stirred to form a resin solution having a concentration of about
6%. Prior to use, the solution was aged at room temperature for more than 24
hours.
For comparison, the following resins D tc I were prepared.
Comparison Resin D (melamine resin)
A reactor equipped with a condenser tube and a stirrer was charged
with 126 g (1 mol) of melamine, 240 g (3 mols) of 37% formaldehyde whose pH
had been adjusted to 8 with sodium hydroxide, and 60 g of water, and they were
reacted at a reaction temperature of 85 to 90C. After the melamine dissolved,
the pH of the solution was reduced to about 7 with hydrochloric acid, and the
condensation reaction was performed until the turbidity point (the temperature
at which the resin solution becomes turbid when the resin concentration is
3% - Koeda, Kogyo Kagaku Zasshi 60, 1567, 1957) became 15C. The product was
then cooled to room temperature to form a resin solution.
Comparison Resin E (urea resin)
60 G of urea was reacted with 240 g of 37% formaldehyde whose pH
had been adjusted to 8 with sodium hydroxide at a temperature of 85 to 90C.
for 30 minutes. The pH of the solution was reduced to 4.2 with formic acid,
and the reaction was continued at 80C. for about 3 hours. Then, the reaction
product was rapidly cooled to room temperature to form a resin solution.
Comparison Resin F (melamine-urea cocondensed resin)
180 G of urea, 13 g of melamine, 450 g of 37% formaldehyde and 100 g
of water were mixed, and the pH of the mixture was adjusted to 8 with sodium
carbonate. The mixture was reacted at 80C. for 3 hours to form a resin solu-
tion.
Comparison Resin G (alcohol-modified melamine resin)
50 G of melamine and 114 g of 37% formaldehyde whose pH had been
adjusted to 8.5 were mixed, and stirred at 85C. After the melamine dissolved,
240 g of methanol containing 1.6 mQ. of formic acid (2N) was added, and the
mixture was reacted under reflux for about 2 hours. The pH of the solution
~'
1()67221
was returned to 8, and the reaction mixture l~as concentrated at reduced pres-
sure to form a resin solution having a concentration of about 80%.
Comparison Xesin H (acid-modified melamine resin)
126 G of melamine, 240 g of 37% formaldehyde whose pH had been ad-
justed to 8.0, and 140 g of water were reacted at 80C. for 30 minutes with
stirring, and then, 75 g of tartaric acid was gradually added dropwise. Dur-
ing this time, the pH of the reaction mixture was adjusted to 7-8 with sodium
hydroxide. The reaction was continued for 30 minutes, and the temperature was
lowered to room temperature to form a resin solution.
Comparison Resin I (amine-modified melamine resin)
126 G of melamine, 240 g of 37% formaldehyde whose pH had been ad-
justed to 8 and 80 g of water were mixed, and reacted at 80C. for 30 minutes
with stirring. Then, 75 g of triethanolamine neutralized with 6N HCQ was
added, and the mixture was further reacted for 60 minutes. The reaction pro-
duct was cooled to room temperature to form a resin solution.
Tests for flocculation wers performed as follows:
1) Sedimentation Test
(a) PLace lO0 mQ. of a waste water in a 100 mQ. Nessler's tube.
(b) Add a predetermined amount of the test resins of a suitable concen-
tration.
(c) Seal the tube with a stopcock, and tumble it 10 times.
(d) Allow the tube to stand, and measure the speed (cm/min.) of move-
ment of the interface between the supernatant liquid and the flocculated mass.
(e) Where there is no distinct interface between the supernatant liquid
and the flocculated mass, measure the time required for the flocculated mass
to deposit to a height of 2 cm from the bottom of the tube.
2) Jar Test
(a) Place 300 mQ. of a waste water in a 500 mQ. beaker.
~b) Add a predetermined amount of the test resin of a suitable concen-
tration (or other chemical).
(c) Stir the mixture for 5 minutes at 150 revolutions per minute using
a jar tester. (In the case of an oil-containing waste water, the speed of
-- 8 --
~,.,
.. .
~)67ZZl
rotation is adjusted to 100 rpm.)
(d) Add a predetermined amount of other chemical (or a resin of suitable
concentration), if desiredJ and further stir the mixture for 5 minutes at 50
revolutions per minute.
(e) Suction filter the mixture using a filter paper (No. 5C~.
(f) Measure the percent transmission of the filtrate at a suitable
wavelength.
Example 1 and Comparative Example 1
The jar test was conducted using a solution of a dye (Milling
Brilliant Red B: C.I. Acid Red 249) in a concentration of 100 ppm as the
waste water and the resin C.
The test results are shown in Table l. It was found that the dye
dissolved was removed by the resin C almost completely, and the filtrate was
much the same as water.
A similar effect was obtained with the case of using the resin C
and an inorganic salt, but when the inorganic salt was used alone, no effect
was obtained.
Table l
Flocculating effect on dye solutions
Amount of Chemicals used conjointly Percent
resin C transmission
Runs Nos. as solids A12(SO4) FeCQ FeS0 (%)
(ppm) 3 3 4(~ = 520 nm)
.
Example 11 80 0 0 0 97.5
2100 0 0 0 98.5
380 100 0 0 95.0
4100 0 100 0 92.5
5100 0 0 100 96.3
_ _. .
Comparative
Example 16 0 100 0 0 1.5
200 0 0 1.2
0 100 0 3.0
0 0 10~ 11.3
_ g _
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Example 2
The same test as in Example 1 was repeated except that resin B was
used instead of the resin C. It was found that the percent transmission of
the filtrate was 96 to 98% when the amount of the resin added was 80 to 100
ppm. This means that the dye dissolved was almost completely removed.
Example 3 and Comparative Example 2
The jar test was performed using a light brown kraft pulp spent
liquor (involatile content 500 ppm) as the waste water and the resin C. The
pH of the spent liquor had been adjusted to about 5 with hydrochloric acid.
The test results are shown in Table 2. It can be seen from thé table
that both the resin alone or the combination of the resin and aluminum sul-
fate exhibited marked flocculating actions on the waste water. The filtrate
after separation of the flocculated mass by filtration was trasparent.
The use of aluminum sulfate alone led to a percent transmission of
less than 86%.
Table 2
Flocculating effect on pulp spent liquors
Amount ofAmount of Percent
resin CA12~S04)3 transmission
Runs Nos. as solids (%) at
(ppm) (ppm) ~ = 380 nm
~ __ I
Example 3 1 90 0 97.0
2 100 0 98.0
3 120 0 98.8
4 5 300 94.0
300 98.0
Comparative _ - -
Example 2 6 0 50 79.8
7 0 100 79.2
8 0 200 82.2
9 1 0 300 85.1
Example 4
The jar test was performed using two types of commercially available
acrylic emulsion (1000 ppm, pH 7-8) and the resin C. It was found that when
the amount of the resin C was 110 to 130 ppm, the emulsion flocculated con-
~ -- 10
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1~1672Zi~
siderably. The filtrate was very much clarified with a percent transmissionof 96 to 100%.
Example 5
The jar test was performed using two types of commercially available
machine oils [JIS W-ll type (1000 ppm, pH 10) and JIS W-31 type (10000 ppm,
pH 9.6)] as waste water and resin C.
When the amount of the resin C was 300 to 350 ppm, the emulsion of
the JIS W-ll type machine oil was flocculated and the flocculated mass got
afloat. The filtrate became transparent. The starting waste water and the
filtrate were treated respectively with n-hexane to extract the oil, and the
rate of oil removal was measured. On the other hand, COD of both the starting
waste water and the filtrate was measured using potassium permanganate, and
the rate of COD reduction was determined. Both of these tests were performed
in accordance with JIS KO102, and the rate of oil removal and the rate of COD
reduction were both more than 90%.
In the case of JIS W-31 type machine oil, the filtrate became trans-
parent when the amount of the resin C was 1000 to 3000 ppm. The rate of oil
removal determined by the same method was more than 98%.
Example 6 and Comparative Example 3
The sedimentation test was performed to compare the flocculating
effect of the resin C of this invention with those of the resins D to I.
The results are shown in Table 3, from which it can be seen that
the comparison resins had extremely poor effects.
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