Coagulant for minute mineral particles in suspension and method for coagulating thereof

Disclosed herein are a coagulant for minute mineral particles in suspension, comprising a copolymer of 0.5 to 10 mol % of 2-acrylamido-2-methylpropanesulfonic acid or a salt thereof, 40 to 99.5 mol % of N-hydroxymethylacrylamide and 0 to 59.5 mol % of acrylamide and showing a reduced viscosity of 10 to 30 dl/g in an aqueous 1N solution of sodium chloride at a temperature of 25.degree. C. and a concentration of the copolymer of 0.1 g/dl therein, and a method for coagulating the minute mineral particles in a suspension, comprising adding the coagulant a neutral waste water.

FIELD OF THE INVENTION 
The present invention relates to a coagulant suitable for treating waste 
water which contains minute mineral particles in a suspended state 
therein, and a method for coagulating the minute mineral particles 
contained in waste water in a suspended state therein. 
More in detail, the present invention relates to (1) a coagulant for the 
minute mineral particles in suspension, comprising a copolymer of 0.5 to 
10 mol % of 2-acrylamido-2-methylpropanesulfonic acid or a salt thereof, 
40 to 99.5 mol % of N-hydroxymethylacrylamide and 0 to 59.5 mol % of 
acrylamide and showing a reduced viscosity of 10 to 30 dl/g in an aqueous 
1N solution of sodium chloride at a temperature of 25.degree. C. and a 
concentration of the copolymer of 0.1 g/dl therein and (2) a method for 
coagulating minute mineral particles, which method comprises adding a 
coagulant to neutral waste water containing the minute mineral particles 
in a suspended state therein, the coagulant comprising a copolymer of 0.5 
to 10 mol % of 2-acrylamido-2-methylpropanesulfonic acid or a salt 
thereof, 40 to 99.5 mol % of N-hydroxymethylacrylamide and 0 to 59.5 mol % 
of acrylamide and showing a reduced viscosity of from 10 to 30 dl/g in an 
aqueous 1N solution of sodium chloride at a temperature of 25.degree. C. 
and a concentration of the copolymer of 0.1 g/dl therein. 
As a coagulant used for removing from waste water minute solid particles 
suspending in the waste water, an anionic coagulant comprising a partially 
hydrolyzed polyacrylamide or a copolymer of acrylamide and acrylic acid 
has been broadly used in various fields. On the other hand, as another 
coagulants which are different from the hitherto-used coagulants of 
acrylamide/acrylic acids and exhibit favorable results over a broad range 
of pH of the waste water, such as those anionic coagulants containing 
sulfonate group(s) have come to be gradually used in specified fields. 
Since the waste water containing minute mineral particles, particularly the 
muddy water being discharged in the treatment of ore, is a waste water 
which is extremely difficultly subjected to the treatment of precipitating 
the particles contained therein and condensing thereof, and the 
conventional partially hydrolyzed polyacrylamide or the conventional 
copolymer of acrylamide and acrylic acid do not give a sufficient result 
of treatment, various specific coagulants have been proposed for that 
purpose. 
For example, a copolymer comprising 40 to 99 mol % of acrylamide, 1 to 35 
mol % of 2-acrylamido-2-methylpropanesulfonic acid (hereinafter referred 
to as AMPS) and 0 to 25 mol % of acrylic acid is disclosed in U.S. Pat. 
No. 4,342,653, and in European Pat. Nos. 74,660-74,662, it is disclosed 
that a copolymer of a hydrophilic monomer such as acrylamide and a 
hydrophobic monomer is suitable for that purpose. Furthermore, Japanese 
Patent Applications Laid-Open (KOKAI) No. 59-17013 (1984) and No. 
59-196309 (1984) disclose a copolymer comprising a monomer containing 
sulfonate group(s), N-substituted or not-substituted acrylamide or 
methacrylamide, a hydrophobic monomer and an unsaturated carboxylic acid 
monomer, and Japanese Patent Application Laid-Open (KOKAI) No. 59-156499 
(1984) also discloses the use of calcium sulfate in addition to the 
above-mentioned high polymeric coagulants for solidifying the waste water 
from phosphorous ore treating. 
However, in any of the above-mentioned methods, (1) a special monomer is 
used in a large aount for obtaining its effect as is seen, for instance, 
in the case of using the coagulant disclosed in U.S. Pat. No. 4,342,653 
wherein although the coagulant is effective in treating the 
above-mentioned waste water, it is necessary for that purpose that the 
coagulant contains the expensive monomer, AMPS, more than about 15 mol % 
therein and (2) it is difficult to obtain the copolymer of a high 
molecular weight. These facts result in the high cost of producing the 
copolymer and in the disadvantage of increasing the cost of treating the 
waste water. 
The object of the present invention is to solve the above-mentioned 
technical problem and to treat the waste water containing minute mineral 
particles, particularly the waste water from the mineral ore treating, 
advantageously in an industrial scale. 
The above-mentioned object of the present invention is attained by adding, 
to the neutral waste water containing the minute mineral particles in a 
suspended state, a coagulant comprising a copolymer of 0.5 to 10 mol % of 
AMPS or a salt thereof, 40 to 99.5 mol % of N-hydroxymethylacrylamide and 
0 to 59.5 mol % of acrylamide and showing a reduced viscosity of from 10 
to 30 dl/g in an aqueous 1N solution of sodium chloride at a temperature 
of 25.degree. C. and a concentration of the copolymer of 0.1 g/dl therein. 
SUMMARY OF THE INVENTION 
In a first aspect of the present invention, there is provided a coagulant 
for minute mineral particles in suspension, comprising a copolymer of 0.5 
to 10 mol % of AMPS or a salt thereof, 40 to 99.5 mol % of 
N-hydroxymethylacrylamide and 0 to 59.5 mol % of acrylamide and showing a 
reduced viscosity of 10 to 30 dl/g in an aqueous 1N solution of sodium 
chloride at a temperature of 25.degree. C. and a concentration of 0.1 g/dl 
therein. 
In a second aspect of the present invention, there is provided a method for 
coagulating minute mineral particles in suspension, which comprises adding 
a coagulant into a neutral waste water containing the minute mineral 
particles in suspension therein, said coagulant comprising a copolymer of 
0.5 to 10 mol % of 2-acrylamido-2-methylpropanesulfonic acid or a salt 
thereof, 40 to 99.5 mol % of N-hydroxymethylacrylamide and 0 to 59.5 mol % 
of acrylamide and showing a reduced viscosity of 10 to 30 dl/g in an 
aqueous 1N solution of sodium chloride at a temperature of 25.degree. C. 
and a concentration of the copolymer of 0.1 g/dl therein.

DETAILED DESCRIPTION OF THE INVENTION 
The waste water containing minute mineral particles in the present 
invention, particularly, the waste water in the course of treating the 
mineral ore is the waste water after clashing, sifting, classifying, 
floataton, etc. of the mined raw phosphorous ore, and, the waste water is 
almost neutral, namely, the pH of such a waste water is in general around 
7. As a waste water mentioned above, the wasste water from phosphorous ore 
treating, the tailing waste water from copper ore treating and the waste 
water from aggregates washing may be exemplified. These waste waters 
usually contain solid matter in an extent of 1 to 10% by weight. The 
suspended solid matter contained in such a waste water is hardly 
sedimented, and it is extremely important for the preservation of 
environment and the improvement of economic efficiency of the production 
of concentrate to rapidly sediment the solid matter by using thickeners, 
thereby reducing the amount of the muddy solid matter to be discharged and 
in the same time, reusing the supernatant water obtained by sedimentation 
of the solid matter in a pretreatment step. 
The copolymer composition exhibiting the performances as the object of the 
present invention comprises 0.5 to 10 mol % of AMPS or a salt thereof, 40 
to 99.5 mol % of N-hydroxymethylacrylamide and 0 to 59.5 mol % of 
acrylamide, preferably comprises 0.5 to 10 mol % of AMPS or a salt 
thereof, 45 to 99.5 mol % of N-hydroxymethylacrylamide and 0 to 54.5 mol % 
of acrylamide. Even if the content of AMPS is over 10 mol %, the 
improvement of the sedimentation rate of the solid matter is not observed 
and accordingly, such a large amount of AMPS only gives a negative result 
of impairing the economic efficiency. 
In addition, it is possible to obtain and use the pluralistic copolymer by 
adding inert and copolymerizable component(s) to the ternary monomeric 
system consisting of AMPS, N-hydroxymethylacrylamide and acrylamide. 
It is desirable that the coagulant according to the present invention shows 
a reduced viscosity of 10 to 30 dl/g measured in an aqueous 1N solution of 
sodium chloride at a concentration of 0.1 g/dl and at a temperature of 
25.degree. C. 
The coagulant (anionic coagulant) according to the present invention can be 
produced by subjecting AMPS or a salt thereof, N-hydroxymethylacrylamide 
and acrylamide to known copolymerization in an aqueous solution or known 
water-in-oil suspension polymerization in the presence of a radical 
initiator. Since the thus formed copolymer is apt to be cross-linked and 
insolubilized by drying, it is reasonable to dilute the thus formed 
solution or suspension of copolymer without separating the copolymer and 
thereafter to use the thus diluted copolymer in treating the waste water. 
The coagulant according to the present invention can be also produced by a 
more economically advantageous method of N-hydroxymethylation of a 
copolymer of AMPS and acrylamide by inexpensive formaldehyde or 
paraformaldehyde. In such a case, into an aqueous solution of the 
copolymer of AMPS and acrylamide of a low concentration of 1 to 3% by 
weight, a basic substance is added as a catalyst, thereby adjusting the pH 
of the aqueous solution to not lower than 10 and then formaldehyde or 
paraformaldehyde is added to the mixture. The above-mentioned 
N-hydroxymethylation proceeds quite rapidly and accordingly, the reaction 
is carried out easily in the actual field of treating the waste water by 
admixing an N-hydroxymethylation agent with an aqueous solution of the 
copolymer of AMPS and acrylamide. 
On the other hand, a copolymer comprising 2 to 40 mol % of AMPS and 60 to 
98 mol % of N-hydroxymethylacrylamide and acrylamide has been known by 
U.S. Pat. No. 3,975,496 to be suitable for treating a strongly alkaline 
red mud generating in the production of alumina from bauxite. 
However, it is an unexpected fact that the coagulant according to the 
present invention comprising a specified copolymer containing the AMPS 
units in an amount of as low as 10 mol % exhibits an extremely remarkable 
effects also to the waste water around neutrality. 
As a catalyst for N-hydroxymethylation, those which can adjust the pH of 
the reaction system to not lower than 10 can be used without any 
restriction, however, the agent which can adjust the pH of the reaction 
system to not ower than 10 by use of 5 to 10 mol % thereof to the 
constituting acrylamide units, such as sodium hydroxide, potassium 
hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, 
potassium phosphate and triethylamine is particularly suitable. 
The amount of formaldehyde or paraformaldehyde necessary for the 
above-mentioned reaction (N-hydroxymethylation) is selected in the range 
of 75 to 100 mol % as formaldehyde to the amount of acrylamide units in 
the copolymer of AMPS and acrylamide. In the case of using an excess 
amount of formaldehyde, although the reaction rate of N-hydroxymethylation 
is higher than in the above-mentioned case, it is not favorable because 
the large amount of unreacted formaldehyde remain in the product. 
The mixing of an aqueous solution of the copolymer of AMPS and acrylamide 
with formaldehyde or paraformaldehyde is carried out by a known operation 
such as mixing in a vessel equipped with a stirrer, impregnation in a gel 
state or mixing in a tube. 
The above-mentioned N-hydroxymethylation proceeds extremely rapidly, and 
under the condition of a room temperature of 25.degree. to 30.degree. C., 
the reaction attains to 90% of the conversion at equilibrium within 3 to 5 
hours, and after a long time for the reaction, it reaches to the 
conversion at equilibrium. The N-hydroxymethylation is accelerated by 
raising the reaction temperature, however, the hydrolysis of acrylamide by 
the alkali added as a catalyst is also accelerated thereby. 
In a case where the content of the thus formed acrylic salt units of the 
copolymer is larger than 10 mol % of the content of the acrylamide units 
before subjecting the copolymer to the N-hydroxymethylation, the 
performance of the product of compressing the sedimented particles is 
reduced and accordingly, it is necessary to stop the N-hydroxymethylation, 
thereby keeping the content of the acrylic salt units not more than 10 mol 
%, preferably not more than 5 mol %. For that purpose, it is preferable to 
use the basic catalyst for the N-hydroxymethylation in an amount of not 
more than 10 mol % of the content of acrylamide unit in the copolymer 
before subjecting the copolymer to the N-hydroxymethylation and, in 
addition, to effect the reaction at a temperature of lower than about 
70.degree. C. 
The preferred method of coagulating the suspended minute mineral particles 
according to the present invention is a method using a thickener. In such 
a case, the aqueous solution of the coagulant is obtained by dissolving 
the copolymer into water at a concentration of 0.1 to 0.3% by weight and 
is supplied into the feed well of the thickener directly or after further 
dilution. The preferred amount of addition of the coagulant is 5 to 500 
g/ton of the minute mineral particles in the waste water. Although the 
addition of the coagulant may be carried out at one-point, it is 
preferable to carry out at multiple-points for better mixing of the 
coagulant with the waste water. 
In addition, it may be possible to mix the waste water with the aqueous 
solution of the coagulant in a mixing vessel in advance of supplying the 
waste water to the thickener. 
According to the present invention, a coagulant which can advantageously 
treat, in an industrial scale, the waste water containing minute mineral 
particles in a suspended state is provided, and the coagulant according to 
the present invention is favorably suitable for treating the waste water 
from the phosphorous ore which has been difficult hitherto. 
The present invention will be explained more in detail while referring to 
the non-limitative examples as follows. 
EXAMPLE 1 
Into a three-necked 50 ml-flask equipped with a stirrer, an aqueous 
solution consisting of 41.5 g of deionized water and 0.27 g of Na.sub.3 
PO.sub.4.12H.sub.2 O was introduced, and under stirring, 1.0 g of a 
powdery copolymer consisting of 1.0 mol % of AMPS and 99.0 mol % of 
acrylamide was added to the solution in the flask, and after dissolving 
uniformly, an aqueous 5% by weight solution of formaldehyde, which 
solution contains an equimolar amount of formaldehyde to the amount of 
acrylamide units in the copolymer was admixed with the mixture in the 
flask, and the N-hydroxymethylation of the copolymer was carried out while 
stirring and heating the mixture in the flask to 50.degree. C. for 3 
hours. The thus obtained N-hydroxymethylated copolymer was dissolved in an 
aqueous 1N solution of sodium chloride at a concentration of 0.1 g/dl. The 
reduced viscosity (.eta.sp/C) was obtained according to the following 
formula, wherein C(g/dl) is a concentration of N-hydroxymethylated 
copolymer in aqueous 1N solution of sodium chloride and t.sub. 0 (60.2 
sec) and t are flowing times (sec.) of aqueous 1N solution of sodium 
chloride and the N-hydroxymethylated copolymer solution, respectively, 
measured with Ostwald's viscometer at a temperature of 25.degree. C.: 
##EQU1## 
and is shown in Table 3. 
In the next place, after adding 5 parts of deionized water to 1 part of a 
waste water from the Florida phosphorous ore treating, the thus diluted 
waste water was introduced into a 100 ml-graduated colorimetric tube, and 
an aqueous 0.01% by weight solution of the thus prepared 
N-hydroxymethylated copolymer was added thereto. After mixing the two 
aqueous liquids by turning the tube upside down 10 times, the tube was 
kept for standing vertically to see the sedimentation velocity of the 
interface between dispersing layer and clarifying layer and the 
sedimentation volume after keeping the tube for one hour, thereby carrying 
out the test for evaluating the performance of the coagulant on the 
sedimentation and compressability of the solid particles. The results of 
the test are shown in Table 3. 
EXAMPLES 2 TO 8 
In the same manner as in Example 1 except for adding 1.0 g of each of the 
powdery copolymers shown below instead of adding 1.0 g of the copolymer 
consisting of 1.0 mol % of AMPS and 99.0 mol % of acrylamide, each of the 
N-hydroxymethylated copolymers according to the present invention was 
obtained. 
TABLE 1 
______________________________________ 
Copolymers used in Examples 2 to 8 
Constitution unit (mol %) 
Examples AMPS Acrylamide 
______________________________________ 
2 2.0 98.0 
3 3.0 97.0 
4 5.0 95.0 
5 10.0 90.0 
6 4.0 96.0 
7 4.0 96.0 
8 4.0 96.0 
______________________________________ 
The constitutional composition and the reduced viscosity of each of the 
N-hydroxymethylated copolymers thus obtained, and the results of 
evaluation of the performances of the N-hydroxymethylated copolymers as 
the coagulant on the sedimentation and compressability of the solid 
particles are also shown in Table 3. 
COMATIVE EXAMPLES 1 TO 20 
Of Comparative Examples 1 to 20, in Comparative Examples 1 to 4, 14 to 18, 
the copolymer and homopolymer shown below were N-hydroxymethylated in the 
same manner as in Example 1 and the results of the performances of the 
thus obtained N-hydroxymethylated copolymers and homopolymer as the 
coagulant are shown also in Table 3. In Comparative Examples 5 to 13, 19 
and 20, the copolymers and homopolymer shown below were not subjected to 
N-hydroxymethylation and their performances as the coagulant are also 
shown in Table 3. 
TABLE 2 
______________________________________ 
Copolymers used in Comparative Examples 1 to 20 
Comparative 
Constitution unit (mol %) 
Example Nos. 
AMPS Acrylamide 
Acrylic acid 
______________________________________ 
1 0.0 100.0 0.0 
2 15.0 85.0 0.0 
3 20.0 80.0 0.0 
4 25.0 75.0 0.0 
5 0.0 100.0 0.0 
6 5.0 95.0 0.0 
7 10.0 90.0 0.0 
8 15.0 85.0 0.0 
9 20.0 80.0 0.0 
10 0.0 95.0 5.0 
11 0.0 90.0 10.0 
12 0.0 80.0 20.0 
13 0.0 70.0 30.0 
14 0.0 95.0 5.0 
15 0.0 90.0 10.0 
16 0.0 80.0 20.0 
17 0.0 70.0 30.0 
18 4.0 96.0 0.0 
19 4.0 96.0 0.0 
20 0.0 90.0 10.0 
______________________________________ 
TABLE 3 
__________________________________________________________________________ 
Constitution Units and Performance of the Coagulants 
Constitution Unit (mol %) 
Reduced 
Sedimenta- 
Sedimentation 
Example or N--hydroxy- Viscosity, 
tion volume of 
Comparative 
acrylamide 
AMPS 
methylacryl- 
acrylic 
.eta.sp/c 
velocity 
settled, solids ml 
Example 
unit unit 
amide unit 
acid Unit 
(dl/g) 
(cm/min) 
(after 60 min.) 
__________________________________________________________________________ 
Example 
1 27.4 1.0 71.6 0 24.4 13.1 18.5 
2 27.1 2.0 70.9 0 21.1 16.5 17.5 
3 28.9 3.0 68.1 0 21.7 19.5 16.0 
4 27.3 5.0 67.7 0 21.9 21.4 16.5 
5 22.0 10.0 
68.0 0 24.3 22.5 17.5 
6 20.3 4.0 75.7 0 22.0 25.2 13.5 
7 40.4 4.0 55.6 0 24.1 24.6 14.5 
8 52.2 4.0 43.8 0 23.2 17.7 18.0 
Comparative 
Example 
1 28.4 0 71.6 0 24.5 4.4 24.5 
2 20.9 15.0 
64.1 0 21.0 20.8 18.0 
3 15.2 20.0 
64.8 0 20.7 14.9 18.0 
4 9.1 25.0 
65.9 0 16.3 9.5 20.5 
5 100 0 0 0 27.1 .ltoreq.1.0 
48.5 
6 95 5 0 0 27.7 6.9 23.0 
7 90 10 0 0 25.7 14.5 18.5 
8 85 15 0 0 24.2 20.6 17.5 
9 80 20 0 0 24.5 22.3 17.5 
10 95 0 0 5 25.7 5.6 41.0 
11 90 0 0 10 30.0 3.1 28.0 
12 80 0 0 20 31.6 2.6 29.5 
13 70 0 0 30 27.1 1.6 33.0 
14 42.3 0 52.7 5 21.9 15.6 22.0 
15 32.7 0 57.3 10 25.9 10.9 26.5 
16 25.4 0 54.6 20 28.8 3.1 28.0 
17 17.0 0 53.0 30 29.5 2.4 28.0 
18 65.5 4.0 30.5 0 23.4 10.1 20.5 
19 96.0 4.0 0 0 24.5 8.4 23.0 
20 90 0 0 10 30.0 3.2 29.5 
__________________________________________________________________________ 
TABLE 4 
______________________________________ 
Constitution Units 
A B C D 
______________________________________ 
##STR1## 
##STR2## 
##STR3## 
##STR4## 
______________________________________ 
A: Acrylamide Unit 
B: AMPS Unit (sodium salt) 
C: N--hydroxymethylacrylamide Unit 
D: Acrylic acid Unit (sodium salt). 
FIGS. 1 to 4 are the graphical representation of the sedimentation velocity 
and the sedimentation volume shown in Table 3. 
EXAMPLE 9 
In a 50 ml test tube 3.78 g of acrylamide, 6.40 g of 
N-hydroxymethylacrylamide, 9.28 g of an aqueous 25% by weight solution of 
sodium 2-acrylamido-2-methylpropanesulfonate and 26.79 g of deionized 
water were introduced, and the content of the test tube ws uniformly mixed 
to obtain a solution. 
After introducing 3.75 g of an aqueous 0.2% by weight solution of 
dihydrochloride of 2,2'-azobis-2-amidinopropane into the solution, the 
test tube was equipped with a three-way stopper having an inlet tube for 
introducing gaseous nitrogen and an outlet tube connected with a vacuum 
syste and the atmosphere in the test tube was replaced with gaseous 
nitrogen. Polymerization of the reactant was carried out at a temperature 
of 50.degree. C. for 4 hours. 
In the same manner as in Example 1 the reduced viscosity and the 
performances of the thus obtained copolymer as a coagulant according to 
the present invention were evaluated, the results being shown in Table 5. 
EXAMPLE 10 
In the same manner as in Example 9, a copolymer shown in Table 5 was 
obtained. THe reduced viscosity and the performance thereof are shown also 
in Table 5. 
COMATIVE EXAMPLES 21 TO 24 
In a similar manner as in Example 9, one homopolymer and three copolymers 
shown in Table 5 were produced. The reduced viscosity and the performance 
of the homopolymer and the copolymers as a coagulant were determined as in 
Example 1 and the results are shown also in Table 5. 
TABLE 5 
__________________________________________________________________________ 
Constitution Units and Performance of the Coagulants 
Constitution Unit (mol %) 
Reduced 
Sedimenta- 
Sedimentation 
Example or N--hydroxy- Viscosity, 
tion volume of 
Comparative 
acrylamide 
AMPS 
methylacryl- 
acrylic acid 
.eta.sp/c 
velocity 
settled, solids ml 
Example 
unit unit 
amide unit 
unit (dl/g) 
(cm/min) 
(after 60 min.) 
__________________________________________________________________________ 
Example 
9 42.0 8.0 50.0 0 18.6 15.7 16.0 
10 0 8.0 92.0 0 14.2 16.5 14.5 
Comparative 
Example 
21 0 0 100.0 0 16.7 3.7 23.0 
22 72 8 20 0 20.8 10.6 19.0 
23 92 8 0 0 18.4 8.8 20.5 
24 90 0 0 10 30.0 3.4 28.5 
__________________________________________________________________________ 
EXAMPLE 11 
Content of Minute Particles in Underflow 
Evaluation of the three copolymers shown in Table 6 as a coagulant of the 
minute mineral particles in suspension was carried out by using a 3.5 
inch-thickener (made by Enviro Clear Co.) as follows. 
Into a 2inch-blending vessel equipped with a stirrer, a waste water from 
the Florida phosphorous ore treating, containing 3.29% by weight of the 
minute particles was supplied at a rate of 175 ml/min. Separately, an 
aqueous 0.1% by weight solution of each of the three copolymers was 
diluted by deionized water to be an aqueous 0.01% by weight solution of 
the copolymer, and the diluted copolymer solution was added into the 
vessel at a rate of addition shown in Table 7, and the mixture was stirred 
at 100 r.p.m. to form flocs of the mineral particles (mud). The thus 
formed flocs were continuously transferred to the thickener, thereby 
forming gradually a bed. The height of the bed was detected by a sensor 
and the sedimented underflow of the bed was pumped out from the bottom of 
the vessel by using an underflow pump so as to maintain the height of the 
bed in the vessel at 15 cm. The underflow thus pumped out was dried for 3 
hours at 120.degree. C. to find the content of minute particles therein, 
and the results are shown in Table 7. 
TABLE 6 
__________________________________________________________________________ 
Constitution Composition of Copolymer 
Constitution Unit (mol %) 
N--hydroxy- 
acrylic 
acrylamide 
AMPS 
methylacryl- 
acid 
Reduced viscosity 
Copolymer 
unit unit 
amide unit 
unit 
.eta.sp/c, (dl/g) 
Remarks 
__________________________________________________________________________ 
I 43.6 4 52.4 0 25.4 modified 
copolymer 
II 22.0 4 74.0 0 11.2 terpolymer 
III 78.2 0 0 27.2 
38.9 partially 
hydrolyzed 
copolymer 
__________________________________________________________________________ 
TABLE 7 
______________________________________ 
Content of Minute Particles in Underflow 
Unit: % by weight 
Rate of addition of the copolymer 
(g/ton of solid matter) 
Copolymer 110 230 340 560 680 
______________________________________ 
Copolymer I 
7.2 12.4 14.6 -- -- 
Copolymer II 
-- 7.5 13.1 -- -- 
Copolymer III 
-- -- -- 6.8 8.8 
______________________________________ 
EXAMPLE 12 
Content of Minute Particles in Underflow 
In the same manner as in Example 11 except for using the waste water from 
the aggregates washing, containing 4% by weight of minute particles and 
adding copolymers I to III at a rate shown in Table 8, the evaluation of 
the same three copolymers in Example 11 was carried out. The results are 
shown in Table 8. 
TABLE 8 
______________________________________ 
Content of Minute Particles in Underflow 
Unit: % by weight 
Rate of addition of copolymer 
(g/ton of minute particles) 
Copolymer 25 50 75 100 125 
______________________________________ 
Copolymer I 
18.8 21.4 23.5 -- -- 
Copolymer II 
-- 19.8 21.1 21.8 -- 
Copolymer III 
-- -- 11.5 17.0 18.8 
______________________________________ 
EXAMPLE 13 
Relationship Between the Amount of Addition of the Copolymer and Minute 
Particle Content of Underflow 
The performance of the copolymers I and III was evaluated by using a 3 foot 
Pilot Unit Thickener (made by Enviro Clear Co.) in the treatment of the 
tailing waste water from floatation as follows. 
After adjusting the pH of the copper tailing waste water from floatation to 
pH 7.5 by sulfuric acid, the thus adjusted waste water was supplied to the 
thickener at a rate of 1.3 m.sup.3 /hour, the content of minute particles 
in the waste water being 37% by weight. 
Separately, 0.1% by weight solution of each of the copolymers in deionized 
water was line-diluted by process water to 0.01% by weight and the thus 
diluted copolymer solution was supplied to the inlet of the waste water of 
the thickener. The underflow was pumped out by an underflow pump from the 
bottom of the thickener so as to maintain the height of the bed of the 
sedimented particles at a predetermined level, and minute particles 
content of the thus pumped out underflow was measured by the specific 
gravity of the underflow, the relationship between the amount of addition 
of the copolymer and minute particle content of the underflow being shown 
in Table 9. 
TABLE 9 
______________________________________ 
Content of minute particle in underflow 
Unit: % by weight 
Amount of addition of copolymer 
(g/ton of minute particles) 
Copolymer 12.5 15.0 17.5 20.0 22.5 
______________________________________ 
Copolymer I 
52.0 55.5 59.5 63.5 67.0 
Copolymer III 
50.5 53.0 56.0 58.5 61.5 
______________________________________