Engineering, 2013, 5, 314-320
http://dx.doi.org/10.4236/eng.2013.510B064 Published Online Octob er 2013 (http://www.scirp.org/journal/eng)
Bentonite Adsorption & Coagulation Treatment of
Recycled Fiber Pulping Wastewater
Tingzhi Liu , Kaiyang Zheng, Defa Wang, Shuai Li, Haoyu Wang
School of Material Sci ence& Technol ogy, Tianjin University of Sci ence & Technol ogy,
Tianjin Key Laborato ry of Pulp & Paper, Tianjin, China
Received July 2013
ABSTRACT
A bentonite & PAM particle floc culation system was employed in recycled fiber pulp wastewater treatment in t his pa-
per. The o ptimum cond itions of the adsorption & coagulation treatment was explored and optimized and effects of the
treatment were focused on, especially stickies substances removal. U nd er t he optimal conditions, the removal of MTBE
extract and cationic demand reached 91.26% and 86.93%, and the average particle size in the treated wastewater pollu-
tants is reduced from 40.95 μm to 0.5 μm. I n this treatment the removal of CODcr, turbidity, SS and color were 89.67%,
99.56%, 95.58% and 93.08%, respectively. The results showed that the particle flocculation system was effective for
the treatment of recycled fiber pulp wastewater, especially for controlling the stickies.
Keywords: Recycled Fibe r Pulp; Wastewater; Stickies, Bentonite; Coagulation
1. Introduction
Increased consumption of recycled fiber in paper indus-
try not only reduced the dep endence on for e s t resource
require ments, but also the pollution of environment. On
the ot her ha nd, the impurities from the waste paper bring
about more and more serious problems, and the accumu-
lation problems of stickies are especially paid attention.
The accumulation of stickies in waste paper stock and
follow-up white water system will make drainage in the
wet-end of the paper machine become uneven, resulting
in paper flaws such as paper hole and stain. Sorting of
waste paper, flocculation deinking, screening of pulp,
dispersion, process water treatment, chemical agent ap-
plication and b io-treatment, all these technologies can be
used to control the stickies troubles of recycle fiber pulp
[1-5]. All these mentioned technological measures aimed
at recycle fiber pulp and pulping process, but reducing
the stickies content of pulping wastewater is useful and
helpful to control the stickies troubles, too. In this artic le,
a bentonite & PAM particle flocculation system was em-
ployed in recycled fiber pulping wastewater treatment.
Bentonite, clay, coke, activated sludge and some other
materials were used as adsorption aids to improve floc-
culation efficiency [6, 7 ]. Bentonite, which is available in
large quantities, can be used as an adsorbent for the re-
moval of dissolved organic compounds from pulp & pa-
per mill effluent with appreciably lower cost [8].
2. Material and Methods
The wastewater was collected at a laboratory installation,
include wastewater from pulping, floatation deinking. It
was stor ed in a refri gerator until use. Its i nitial prope rties
were shown in Table 1. The bentonite (800 mesh,
Na-bentonite) and the PAM (medium cationic, MW
about 10 million daltons) were obtained from YaGuang
Development Co., Ltd, Ningbo, Zhejiang province of
China.
Put appropriate amount recycled fiber pulp wastewater
liquor into a beaker and the pH and temperature of the
wastewater sample were first adjusted. Then put into
Table 1. Index of routine analysis for original wastewater
and those after treatment.
wastewater Treated water Removal (%)
CODcr (mg/L) 3020 312 89.67
SS (mg/L) 860 38 95.58
Turbidity( NTU) 108.00 1.03 99.56
pH 6.4 7.9 -
color (C.U.) 867.4 58.2 93.08
MTBE extract ( mg/L) 236.8 20.7 91.26
CD (μmol/L) 1065.4 150.0 85.92
pa r t icle size(μm) 40.95 0.51 -

T. Z. LIU ET AL.
315
appropriate amount bentonite and Stiring at 150 rpm for
30 min for adsorption. After adsorption reaction, put
PAM int o beake r and stri ng for a few minute s, then con-
tent settle for 30 min, the supernatant in the b eaker was
taken out and used for the analyse s .
The chemical oxygen demand (CODcr) of the water
sample was determined by colorimetric methods. The
turbidity of the water sample was measured by an ASN
2000 turbidity meter [9]. The MBTE extract of effluent
was determined according to the method described in an
article [10]. And the Cationic demand (CD), mean di-
ameter of particles of wastewater were measured by
PCD-03 particle charge analyzer (Mütek). The color of
wastewater was determined by spectrophotometer at 465
nm and convert s to Pt -Co C.U.
3. Results and Discussion
The op timal conditions of recycled fiber pulp wastewater
treatment were studied. This article was focused on ef-
fects of bentonite, PAM dosages, pH, temperature of
wastewater and the stir speed and time on removal of
pollutions. The CD, SS, turbidity and OD of 465 nm
were determined to optimize the treatment conditio ns.
Table 1 offered an index of routine analysis for original
wastewater and those after treatment under the optimal
conditions. As shown in Table 1, the results of routine
tested of recycled fiber pulp wastewater were: The
CODcr was 3020 mg/L, pH was 6.4. The average particle
size was 40.95 μm and the turb idity was 108.0NTU. The
contents of SS and MTBE extract were 860 mg/L and
236.8 mg/L, respectively. The CD of the wastewater was
as high as 1065.4 μmol/L. These anionic constituents
were related to the content of stickies i n wa st e wate r [11].
3.1. Effect o f the Bentonite Dosage
As sho wn i n Figure 1, the tur bidity and SS of t he treated
wastewater were reduced with the increase of bentonite
dosage, and reached the minimum at the same dosage
which was about 250 mg/L. It is because that the SS of
the treated water was devoted by fines concentration. The
light beam will be scattered and reflected by the small
particles. This is exactly corresponds with the determina-
tion theory of turbidity. So the turbidity of the water in
this stud y was linear with the content o f SS. T he CD and
465 nm OD of the treated water were decreased with the
increase of bentonite dosage, and reached the minimum
at about 150 mg/L dosage, but increased at the dosage of
250 mg/L, then drop again while the dosage reached at
400 mg/L. This was most likely caused by that the re-
moval of CD and color substances due to the two ways:
adsorption and coagulation mechanism.
Figure 1 further showed that the removal of the four
index were significant only when the dosage from 50
mg/L to 150 mg/L, and the maximum color and CD re-
movals were observed at about 150 mg/L. So the 150
mg/L was the optimal bentonite dosage.
3.2. Effect o f the PAM Dosage
The Figure 2 showed that the curve trends of turbidity
and SS of the treated wastewater were similar with the
increase of PAM dosage. The SS and turbidity of treated
water reached the minimum points at the same dosage
which was about 50 mg/L PAM, and then increased
while the PAM dosage increased to 100 mg/L, the max-
imum dosage of this study. The similar result of SS and
Turbidity removal with the increase of PAM dosage was
also reported by Angela C.R while they used a Fe- culant
to treated pulp effluent [12]. The CD of the treated water
reduced sharply with the increase of PAM dosage while
the dosage lower than 10 mg/L, then increased slightly
with the dosage from 20 mg/L increased to 100 mg/L.
The changes of color of the treated water with the
150
200
250
300
350
400
0
10
20
30
40
50
050100 150 200 250 300 350 400
200
250
300
350
400
SS(mg·L
-1
)
CD
SS
OD of 465nm
Turbidity
Dosage of bentonite(mg.L
-1
)
CD(umol
·
L
-1
)
0. 0
0. 1
0. 2
0. 3
0. 4
0. 5
0. 6
0. 7
0. 8
0. 9
1. 0
Turbidity( NTU)
465nm O D
Figure 1. Effect of the bentoni te dosage on adsorption & coag ulation t r e atment .

T. Z. LIU ET AL.
316
increase of PAM dosage were far more complicated than
the other three indexes. The 465 nm OD of the treated
water decreased sharply with the increase of the PAM
dosage from 2 to 10 mg/L, and then increased from 10
mg/L to 100 mg/ L. The OD had a minimum at the PAM
dosage about 10 mg/L and a maximum at about 100
mg/L. This confused c urve tre nd can be explained through
understanding ho w t he objects of PAM flocculation. As a
kind o f macromolecular flocculant, the function of P AM
in the waste water treatment is mainly due to the reaction
of adsorption bridging mechanism. This can be explained
the sharply decreasing with the increase of the PAM do-
sage from 2 to 10 mg/L. When the dosage of PAM was
too big, the positive electricity charges of the excessive
PAM (medium cationic PAM) will adsorb and coagulate
the fines concentration by compression of double
charged. It was very difficult to precipitate and demix,
because there was so much substantial macromolecular
floc in the treated water. It was also explained why the
SS, CD, turbidity and 465 nm OD of treated water in-
creased with the PAM from 50 mg/L to 100 mg/L. Con-
clusions as a result, the 10 mg/L was the choice dosage
of PAM.
3.3. Effect o f the Initial pH
Figure 3 Showed the effects of initial pH on the bento-
nite treatment of recycled fiber pulp wastewater. As a
whole, all of CD, SS, 465 nm OD and turbidity of the
treated water were increased with the initial pH value
increased. The color and CD of the treated water in-
creased slightly with the increased of pH, the acidic
property of water becomes stronger, the CD and color of
treated water will become smaller. It is different that the
color of the treated water altered little with the pH from 2
to 6 to that of raw material puling ef fluen t. The color of
raw material puling effluent will change very signifi-
cantly because the acidic precip itation of lignin that con-
tributes to the color of these effluents. The SS of the
treated water increased slightly with the pH from 2.0 to
6.0, and from 8.0 to 12.0, but decreased at the pH8.0.
The turbidity of the treated water shows two inflection
points at pH value 4.0 and 8.0. The turbidity decreased
with the pH from 2.0 to 4.0, and then increased fro m pH
4.0 to 8.0, after pH 8.0, with the increase of pH value, the
turbidit y increased significantly. It was ma ybe due t o the
good dispersion of bentonite at alkaline environment.
The dispersion of absorbed water and expanded bentonite
in water caused the increasing of turbidity.
The above mentioned factors should be under consid-
eration choice of pH value. Except for the SS of the
treated water, the other three indexes are good enough
for the treatment at pH6.0. Choose the pH 6.0 as the op-
timal value was under consideration not only the treated
efficiency but also the cost of the treatment, because the
pH value of the origin water was about 6.0.
3.4. Effect of the Wastewater Temperature
The temperature of wastewater will affect the adsorption
and coagulation efficiency of bentonite. As shown in
Figure 4, the CD, 465 nm OD, SS and turbidity of the
treated water decreased with the increase of the tempera-
ture from 30˚C to 60˚C, and reached a desired treated
effect at 60˚C. The n the C D, 4 65 nm OD, SS and turbid-
ity of the treated water increased with the increase of the
temperature from 60˚C to 80˚C. Figure 4 also shows that
the temperature affects the index of SS and turbidity
more weakly than those of CD and 465 nm OD. The CD
value of the water was to indicate the negative electric
charge. Another perspective reflects the content of nega-
tive substances. These substances are mainly composed
120
130
140
150
160
170
180
190
200
0
1
2
3
4
5
6
7
8
9
10
010 20 30 40 50 60 70 80 90100110
150
160
170
180
190
200
210
220
230
240
250
SS(mg
·
L-1)
CD
SS
O D of 465nm
Turbi dity
Dosage of PAM(mg.L-1)
CD(umol
·
L-1)
0. 10
0. 12
0. 14
0. 16
0. 18
0. 20
Turbidi ty( NTU)
465nm O D
Figure 2. Effect of the PAM dosage on bentonite adsorption & coagulat ion tr e a tme nt.

T. Z. LIU ET AL.
317
0
100
200
300
400
0
2
4
6
8
10
12
14
16
2 4 6 810 12
0
100
200
300
400
SS (mg·L
-1
)
CD
SS
O D of 465nm
Turbidity
pH
CD(umol·L
-1
)
0. 0
0. 2
0. 4
0. 6
0. 8
1. 0
Turbidi ty( NTU)
465nm O D
Figure 3. Effect of the initial pH on bentonite adsorption & coagulation treatment.
140
150
160
170
180
190
200
5. 0
5. 5
6. 0
6. 5
7. 0
7. 5
8. 0
8. 5
9. 0
30 40 50 60 70 80
80
90
100
110
120
130
140
150
160
SS(mg
·
L
-1
)
CD
SS
O D of 465nm
Turbidity
Temperature(℃)
CD(umol
·
L
-1
)
0. 06
0. 08
0. 10
0. 12
0. 14
Turbidity(NTU)
465nm O D
Figure 4. Effect of the w ast ewater temperature on bentonite adsorption & coagulati on treatme nt.
of soluble and collo idal constituents. The color is mainl y
contributed by these soluble and colloidal constituents
too. Except effect of adsorption & coagulation of the
bentonite, the temperature of water also affects the ener-
gy of motion of these soluble and colloidal constituents.
The energy of motion of the se soluble and co lloidal con-
stituents was up to the status in adsorption & coagulation
treatment. So the temperature of water affects the CD
and 465 nm OD strongly than those of SS and turbidity.
By contrast, the components that influence the detec tio n s
of SS and turbidity index were composed of colloidal and
dispersive constituents. The energy motion of these col-
loidal and dispersive constit uents will be affected slightly
by temperature change than it of soluble and colloidal
constituents. So tha t the force of gravity and volume fac-
tors of these colloidal and dispersive constituents affect
the status settlement and separation much more impor-
tantly. So 60˚C was the optimal temperature for adsorp-
tion & coagulat ion treatment.
3.5. Effec t of the Stir Speed
As Figure 5 shown, the CD and 465 nm OD of treated
water decreased and then increased with the increase of
stir speed, and they all reached the maximum color and
CD removals at 200 rpm speed. Figure 5 also s hows that
the curve trends of turbidity and SS of the treated waste-
water were similar to these of the CD and 465 nm OD
with the increase of stir speed. However, the lowest
points of the SS and turbidity of the treated water were
observed at the 150 rpm. The appearance of the maxi-
mum removal speed of CD and 465 nm OD different to
that of SS and turbidit y attribu tes to the d ifferent removal
mechanism of them. For the removal of CD and color

T. Z. LIU ET AL.
318
constituents, the fast Stir not only enhances the mass
transfer cap ability of the water but also gives those more
chance to come into contact with the others. So the
minimum points of the CD and color reached at more
fast s tirri ng spe ed tha n tho se of t he SS and tur bidi ty. Bu t
over—rapid stirring will broke up the floc and disperse
the co nstitue nts into the water again, t his ca n explain t he
increases of CD and 465 nm OD with the speed from 200
rpm to 300 rpm. Stir speed affects the turbidity and SS
not o nly o n ca pab ilit y o f ma ss tr ans fer, but also o n sta tus
of the floc. A sli ght over stirri ng will give t he floc app re-
ciable damage effects, so the ideal stir speed for turbidity
and SS removal was lower than it of CD and 465 nm OD,
it was 150 rpm. Figure 5 also sho ws that the turbidity
changed slightly with the speed from 50 rpm to 100 rpm,
but significantly when the speed is over 100 rpm, and
will increase while the speed is more than 150 rpm.
Many researchers had obtained the same rule on the
effect of speed on turbidity in their studies [12,15].
3.6. Effec t of the Stir Time
Figure 6 showed that a short time stirring could o btain a
very good effect of SS, turbidity and 465 nm OD remo-
val. From Figure 6, the SS, turbidity and 465 nm OD
decreased significantl y with the stirri ng time fo rm 0 pro-
long to 2min, and reached to the good removal point at 2
- 5 min, then increased with the stirring time extended
again. It was different to the other three inde xes, the CD
of the treated water increased stably with the stirring time
extended. Removal of the material that indicated CD of
the water mainly depends on the adsorption of the bento-
nite. Before the addition of PAM, t he bentonite has been
added into the water and adsorbed the material for 30min,
so the content of CD materials has reduced to a limited
status. When the stirring beginning, the materials of CD
resolved into the water, so the CD incre ased.
100
110
120
130
140
150
160
170
180
190
200
5.0
7.5
10.0
12.5
15.0
17.5
20.0
50100 150 200 250 300
100
120
140
160
180
200
220
240
SS(mg
·
L
-1
)
CD
SS
O D of 465nm
Turbidity
Stir(rpm)
CD(umol
·
L
-1
)
0.0
0.1
0.2
0.3
0.4
0.5
Turbidi ty( NTU)
465nm O D
Figure 5. Effect of the stir speed on bentoni te adsorption & coagulati on treatment.
120
140
160
180
200
220
0
2
4
6
8
10
12
14
16
18
20
05 10 15 20
120
140
160
180
200
SS(mg·L-1)
CD
SS
OD of 465nm
Turbidity
S tir time( min )
CD(umol
·
L-1)
0. 10
0. 15
0. 20
0. 25
0. 30
Turbidi ty( NTU)
465nm O D
Figure 6. Effect of the stir time on bentonite adsorption & coa gulation treat ment

T. Z. LIU ET AL.
319
3.7. The Removal Efficiency of Bentonite
Adsorption & Coagulation Treatment
Through the studies of influence factors we draw up the
optimal conditions for recycled fiber pulp wastewater
treatment. The optimal co nditi ons were: bentonite dosage
was 150 mg/L, PAM dosage was 10 mg/L, the adsorption
reaction temperature was 60˚C, pH value was 6.4, the
original pH of the wastewater, after PAM additio n, stir-
ring at the speed of 150 rpm for 2 - 5 min. Table 1 shows
an index of routine analysis for original wastewater and
those after treatment under the optimal cond itions.
From Table 1, under these optimal conditions, the
COD of the wastewater from 3020 mg/L reduced to 312
mg/L, and the removal rate reached about 90%. The tur-
bidity and the SS of the waste water red uced from 108 .00
NTU and 860 mg/L to 1.03NTU and 38 mg/L, and the
removal of them were 99.56%, 95.58%, respectively.
The color of the wastewater from 867.4 C.U. reduces to
58.2 C.U., and the removal rate was 93.08%. All these
lead up to the conclusion that the particle flocculation
system was effective for the treatment of recycled fiber
pulp wastewater. Figure 6 also shows that the average
particle size in the treated wastewater pollutants is re-
duced from 40.95 μm to 0.5 μm. It shows that the ad-
sorption coagulation aid treatment which is mainly used
to remove larger particles and colloids suspended materi-
al. It is worthwhile noting that the removal of MTBE
extract reached 91.26%. The stickes materials are mainly
composed of these constituents that can be e xtracted by
orga nic so lve nts. T he removal of organi c sol vent s extract
always reached to about 90% [13-15]. But those studies
were almost though the biological treatment to reach the
removal rate. And the removal of CD of the waste water
was about 87% reflecting that the bento nite adsor ption &
coagulation T r eatment wa s a very good treatment and the
removal of stickies was very efficiently.
4. Conclusion
The bentonite, which is available in large quantities, can
be used as an adsorbent for the removal of dissolved or-
ganic compounds from pulp & paper mill effluent with
appreciably lower cost. Und er the optimal condition s, the
removal of MTBE extract and cationic demand reached
91.26% and 86.93%. The results show that the particle
flocculation system is effective for the treatment of re-
cycled fiber pulp wastewater, and the control of stickes
of recycle fiber pulp wastewater is very efficien t.
5. Acknowledgemen ts (Heading 5)
Financial support from National “Twelfth five-year”
Science & Technology Key Project of China
(2011BAC11B04) and Science & Technology Develop-
ment Grants Planning Projects for Tianjin High Educa-
tion Colleges (SW 20080001).
REFERENCES
[1] J. Chen, “Judgment of Microstickies Removability with
Minerals During Paper Recycling,” China pulp & paper,
Vol. 23, No. 3, 2004, pp. 50-52.
[2] J. Chen, “New Methods for Removal o f Wax and Stickies
from OCC,” China Pulp & Paper Industry, Vol. 25, No. 7,
2004, pp. 37-38.
[3] L. Wang, L. Luo and H. Xiao, “Controlling Pol ysaccha-
ride-Based Anionic Trashes Using Lo w-M olecular-wei-
ghted HCS,” China pulp & paper, Vol.28, No. 1, 2009,
pp. 25-29.
[4] L. Wang, Y. Yu and Y. Chen, “Boosting AKD Neutral
Sizing of APMP by Anionic Trash Catchers,” China pulp
& paper, Vol. 29, No. 3, 2009, pp. 10-13.
[5] T. Liu, D. Wang, H. Zhao and K. Zheng, “Stickies
Treatments of Recycled Fiber Pulping Wastewater by Li-
pases,” Ad vanced Mat erial s Research, Vo l. 534, 2012, p p.
225-229.
http://dx.doi.org/10.4028/www.scientific.net/AMR.534.2
25
[6] T. Liu and E Zheng, “Improving Flocculation Effect in
Pre-treating High Yield Pulping Effluents of Cotton Staff
by Using Active Sludge,” 2nd International Papermaking
and Environment Conference Proceeding books A and B,
Tianjin, 1-3 May 2008, pp. 1101-1105.
[7] T. Liu, X. Duan and E Zheng, “Adsorbent & Treatment
for High Yield Pulp Effluents of Cotton Staff by Coke,”
Progress in Environmental Science and Technology, In-
ternational Symposium on Environmental Science and
Technology, Vol. II, Beijing, 12-14 May 2009, pp. 2378-
2383.
[8] X . Dua n, T. Li u and W. Duan, “Adsorption and Coagula-
tion Tertiary Treatment of Pulp & Paper Mills Wastewa-
ter,” 4th International Conference on Bioinformatics and
Biomedical Engineering, Chengdu, 15-18 June 2010, pp.
1110-1114.
[9] E. Magnus, G. Carlberg andH. Hoel, “TMP Wastewater
Treatment , In clud ing Biol ogi cal High-efficien c y Co mpact
Biological Reactor Removal and Characterisation of Or-
ganic Components,” Nordic Pulp and Paper Research
Journal, Vol. 15, No. 1, 2000 , p. 29.
http://dx.doi.org/10.3183/NPPRJ-2000-15-01-p029-036
[10] T. Liu, Z. He, H. Hu and Y. Ni, “Treatment of APMP
Pulping Effluent based on Aerobic Fermentation with
Aspergillus Niger Fungi and Post-Coagulation/Floccula-
tion,” Bioresource Technology, Vol. 102, No. 7, 2011, pp.
4712-4717.
http://dx.doi.org/10.1016/j.biortech.2011.01.047
[11] T. Liao and H. He, “Research and Discuss about Anioni c
Trash in DIP,” Paper and Paper Making, Vo l . 30 No. 2,
2011, pp. 23-27.
[12] C. R. Angela and B. Marcela, “Treatment of Paper Pulp
and Paper Mill Wastewater by Coagulation-Flocculation
Followed by Heterogeneous Photocatalysis,” Journal of

T. Z. LIU ET AL.
320
Photochemistry and Photobiology, Vol. 194, No. 1, 2008 ,
pp. 1-10.
[13] S. N. Lo and H. W. Liu, “C haracterizati on of Pollutants at
Source and Biological Treatment of a CTMP Effluents,”
Appita Journal, Vol. 44, No. 2, 1991, p. 133.
http://dx.doi.org/10.1016/j.jphotochem.2007.07.007
[14] S. F. Liver and E. R. Hall, “Interactions of Resin Acids
with Aerobic and Anaerobic Biomass-1,” Wat er Resea rch ,
Vol. 30, No. 3, 1996, p. 663.
http://dx.doi.org/10.1016/0043-1354(95)00215-4
[15] L. LaFleur, E. Barton and D. Aret, “Pulp Mill Effluents
Characterization and Treatment: An Upd ate, Fate and Ef-
fects of Pulp and Paper Mill Effluent,” 3rd International
Conference on Environmental Pollution, Rotorua, 1997.