WASTE MANAGEMENT IN WATER-BASED PRINTING INK INDUSTRY
S. KUČAR-DRAGIČEVIĆ1, N. KOPRIVANAC2, D. VUJEVIĆ2
1
Croatian Environemnt Agency, Trg Maršala Tita 8, HR-10000 Zagreb, Croatia
2
University of Zagreb, Faculty of Chemical Engineering and Technology, Marulićev trg 19,
HR-10000 Zagreb, Croatia
ABSTRACT
Industrial production of the water-based printing inks, although initiated for strictly
environmental reasons, raised some new problems, especially regarding new waste stream
treatment. Due to the intensive colouration and loading with organic material conventional
treatment methods are not adequate. In this work the possibilities of final treatment of
residues after wastewater treatment with bentonites as a natural and cheap treatment material
has been studied. The extensive research has been performed to determine optimal pretreatment system parameters, bentonite types and its concentrations, pH of the system, as well
as influence of the ink composition and complexity, and the influence of the filter media. For
the
parameters
where
the
maximal
decolourization
extents
were
achieved,
precipitates/residues were analysed for heavy metal, water and ash content. The behaviour of
residues itself and their mixtures with natural clay during the thermal treatment was studied.
Temperature profile was varied from room temperature up to 1000 ºC because it corresponds
to heating profile used in brick production. The behaviour of samples were analysed by
differential scanning calorimetry (DSC) and thermal gravimetry (TG). The possibility of
adding residues into raw material for brick production have been investigated by preparing
1
model samples with 0.5% to 3.0% of residues in natural clay. Using this approach the highly
problematic waste could be managed without any further loading of the environment.
Keywords: water-based printing inks, bentonites, brick production, waste treatment
INTRODUCTION
The printing ink industry is under a strong pressure to produce new, upgraded, higher quality
types of printing inks. Besides a higher quality product and lower production costs, one of the
main demands is aimed on production of more environmental friendly products, by changing
the solvent-based to the water-based printing inks. However, the production of the waterbased printing inks, although initiated for strictly environmental reasons, has brought some
new problems, especially regarding the waste sludge treatment. Distillation, a very successful
technique for the treatment of the solvent- based wastes, has shown to be quite inadequate for
the water-based or mixed printing ink wastes. As this waste type is highly loaded with organic
materials, and highly coloured, it cannot be discharged into the sewage system without prior
colour removal, or to a natural recipient without prior organic load reduction. The most
widely performed investigations for colour removal were performed in decolourisation of
wastewater from textile industry and coagulation as a treatment method is just one of the
technique available. More researches in the field of coloured wastewater treatment were done
using biodegradation [1], photo-catalytic processes [2], adsorption [3] as well as combination
of those methods. A possible solution for the treatment of water-based or mixed printing ink
wastes may be application of flocculation/coagulation process using organic or inorganic
flocculants/coagulants such as aluminium or iron(III) salts or organic polielectrolites [4].
Disadvantage of this treatment process is formation of huge amounts of sludge which is
2
actually secondary waste and also demands adequate treatment procedure prior discharging to
the environment. So, in this work bentonites as flocculant/coagulant compounds have been
used [5]. Bentonites are cheap, and natural material. They are clays, usually montmorilonite
type, with general structural formulae Al2(OH)2Si4O10 [6-8]. Bentonites have the possibility
of ion exchange where the new neutral species are formed and agglomerate and precipitate
from water solutions. Residues separated after flocculation/coagulation with bentonites as a
process for the treatment of water-based or mixed printing ink wastes can be add into raw
material in brick production and in that way further pollution of effluents and environment
with the waste from printing ink industry is avoided. The basic raw material for brick
production is composed from clay, water and series of inorganic additives. Since the
temperature range applied during brick production has been from 120 ˚C up to 960 ˚C a
temperature profile used for the investigation of the behaviour of residues in this work were in
the range from room temperature up 1000 ˚C. This paper examines the possibilities of using
residues from the printing ink industry wastewater treatment, incorporating it into raw
material for brick production therefore avoiding burdening of the environment.
ELABORATION
Materials and methods
Preparation of samples
Four samples of precipitates have been prepared by adding two different bentonite types, B1
and B4, into the different model wastewaters M1 and M2 (Table 1). All samples were prepared
at optimal conditions of coagulation and precipitation for the each studied case (Table 1).
Precipitates were dried and subjected to the thermal treatment under similar conditions as
during the brick production. For comparison, pure clay as well as two pure bentonites were
3
subjected to the same treatment. Bentonites used were commercial bentonites B1, commercial
name “PF” and B4 commercial name “ljevački”, with the 59.3% SiO2, 14.2% Al2O3, 4.0%
Fe2O3, 3.1% MgO, 0% As and Pb and activated with 4-4.5% of Na2CO3 with difference in
granulation. Model mixtures of highly diluted printing ink sludges, representing real printing
ink industry system wastewater types were based on two main types of printing inks: x1
printing ink type – polyacrilic binder based, solvent content of about 7% and x 2 printing ink
type – methylmetacrylate copolymer based ink, with negligible solvent content. Both model
mixtures were prepared as polychrome models consisting of three different colour solutions of
T1 ink type, prepared in a ratio 1:1:1 (M1) and M2 consisting of six different colour solutions
of the T2 type ink, prepared in the 1:1:1:1:1:1. Model samples of the mixtures of the clay and
residues have been prepared by mixing approximately 0.5%, 1.0%, 2.0% and 3.0% (wt%) of
residues T1, T2, T3 and T4 in the clay. All used materials have been subjected to the wide
characterization process.
Table 1. Residues samples for the thermal treatment with optimal amounts of bentonites B1
and B4 added in the model mixtures M1 and M2
Precipitate
label
T1
T2
T3
T4
Model
Wastewater
M1
M1
M2
M2
Bentonite
type
B1
B4
B1
B4
Concentration of bentonite, kg m-3
16
6
20
16
Characterization of samples
The pH values were measured by a pH-meter, Iskra MA 5735. Electrokinetic measurements
were made on automated electrophoretic instrument, type OTSUKA ELS-800. Structure of
bentonites and precipitates were determined by X-ray diffraction on PHILIPS PW 1010
diffractometer.
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Atomic absorption specrophotometry (AAS)
The heavy metals content in the samples was determined on the basis of AAS using atomic
apsorption spectrophotometer AA-5, Varian Techtron.
X-ray diffraction
Identification of structural changes of the bentonites and residues has been performed on the
basis of X-ray diffraction of powdered samples using diffractometer, PHILIPS PW 1010 with
perpendicular goniometer and proportional counter with the application of CuKα radiation and
graphite monochromator. Scanning conditions: voltage of roentgen tube 40 kV, anodic
current 20 mA, counter speed velocity 0.5˚ min-1, paper velocity 5 mm min-1, number of
impulses per second (CPS) 400, time constant (TC) 4, scanning area 2θ = 3  60˚.
Thermal gravimetry analysis (TGA)
Change in a weight of samples by application of temperature-controlled program has been
measured as a function of temperature and time by thermogravimetric method. TG analysis
has been done on a NETZCH DSC/TG STA 409 thermogravimetric analyser.
where:
Δm = m(T) – m0
(1)
Δm = m(t) – m
(2)
m – weight of sample
m0 – initial weight of sample
T – temperature
t – time
t0 – initial time
Analyses have been performed with constant heating gradient of 10 K min-1 in the air
atmosphere.
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Differential scanning calorimetry (DSC)
Measurements have been performed on the NETZCH DSC/TG STA 409 instrument.
Differential scanning calorimetry is a technique where the difference in energetic inputs in the
sample and reference material is measured as a function of temperature while the sample and
reference material have been subjected to controlled temperature conditions (ASTM E47385). Measured signal (heat flow as differential of heat per time) is measured as follows:
Φr = dqr/dt = – K(T)×ΔTPR(T)
where:
(3)
ΔTPR – temperature difference
Φr – heat flow
qr – heat
K – calibration coefficient
t – time
qr = – K/β×t∫ ΔTPR(T)dT
(4)
Calibration coefficient K(T) can be determined by measurement of reference sample:
K(T) = – ΔHF×m/ΔTPR(t)dt
where:
(5)
ΔHF – fusion heat of standard referent material (SRM)
m – SRM weight
β – heating speed.
Results and discussion
Characterization of residues
Four samples of residues, T1 – T4, were different by colour, from grey to black, consistency
and moisture content. The results of heavy metals, moisture and ash content after drying at the
same conditions are presented with Table 2.
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Table 2. Heavy metals, moisture and ash content after drying (105 oC, 1.5 hrs.) for the four
studied residues
Heavy metal, mg kg-1
Cd
Cr
Ni
Pb
Hg
Humidity
lost, %
T1
T2
T3
<0.0001
<0.0001
0
77.05
63.59
87.51
<0.0001
201.1
85.23
91.58
178.48
177.98
<0.0001
<0.0001
0
39.60
5.96
5.19
85.06
68.65
86.72
T4
0
40.69
151.28
118.28
0
25.60
82.18
Residue
Ash
content, %
Thermal treatment of residues
Behaviour of residues at thermal treatment, from room temperature up to 1000 ºC, has been
monitored by differential scanning calorimetry (Figure 1). The differences between T 1 and T3
behaviours should be a consequence of dye structure impact, as well as differences between
T2 and T4, while differences between T1 and T2 behaviour (and T3 and T4, respectively)
should be a consequence of the bentonite structure impact (the same dye type treated with
different bentonites).
Figure 1. DSC curves for residues T1, T2, T3 and T4
7
The impact of bentonite type on the behaviour at the thermal treatment
Observing the DSC curves of the residues T3 and T4 (Figure 1, EXO = exothermic reaction),
both DSC curves have similar shape, although there are discrepancies in the range of
temperatures whereas changes have been occurred as well as in the magnitude of these
changes. The first significant peak is at about 100 ºC, obviously due to the loss of adsorbed
water from the bentonites. Both residues showed significant endothermal reaction in the
temperature range from 360 ºC up to 470 ºC, although for the residues T3 these changes have
been appeared in much tighter temperature range (402 ºC  433 ºC) than for the residue T4 
in the range of almost 100 ºC (from 378 ºC up to 464 ºC). Slight differences in DSC curves
can be a consequence of different behaviour of bentonites at thermal treatment. On the other
hand the behaviour of the residues T1/T2 during thermal treatment, seen from the DSC curves
Figure 2. DSC curves for bentonites B1 and B4
8
residue T2 differ from the behaviour of other residues. The significant effect – peak at the
curve at approximately 370 ºC, imply on the strong exothermic reaction. By further heating
(from 400 ºC up to 600 ºC) a strong endothermic reaction appears with the maximum at the
587 ºC. At 675 ºC an endothermic reaction appeared followed by further endothermic effects.
In order to find a cause of these differences, behaviour of pure bentonites at the same
conditions have been monitored. DSC and TG curves for the both bentonites (Figures 2 and 3)
imply on the existence of structural differences between them, what is surprising due to the
data obtained from the manufacturer that is the same type of bentonite with just the difference
in particle size. For the bentonite B1 the significant peak in DSC curves at the temperature of
98.9 ºC imply on impulsive endothermic reaction and from TG curve, it can be seen that at
this temperature also fast loss of weight occurred. This suggest the loss of adsorb water from
the bentonite structure. By raising temperature in the temperature range from 150 ºC up to
700 ºC a slow continuous degradation of samples has been occurred. As that degradation,
seen from the DSC curves, have not been followed by weight loss it is likely that energetic
changes occur as a consequence of the cage break up.
Figures 3. TG curves for bentonites B1 and B4
9
For the bentonite B4 a loss of adsorb water has been shifted on 101.1 ºC. The weight loss in
this range was bigger (9.89% in comparison to 7.33% for bentonite B1) but a major difference
showed up after 485 ºC. Namely, in the range of 485 ºC up to 726 ºC degradation in two
significant steps appeared with the weight loss in this range of 5.49%. A first significant
change at the 486.5 ºC is not visible at the curve B1, while the second change is visible at 726
ºC for B1 as a slight break up at the 704 ºC. There was not a further weight loss, just
degradation at both types of bentonites above 750 ºC. Analysis of the results of the sample
behaviour show differences during thermal treatment in the range of approximately 485 ºC up
to 730 ºC. It can be assumed that at the temperature of approximately 500 ºC a separation of
bentonite layer occurred, while at the higher temperatures of thermal treatment splitting with
braking up of bonds between tetraedars inside layers appeared. Total weight losses during
thermal treatment of the residues and the bentonites have been presented in the Table 6.
Bigger weight losses for the residues observed in comparison with bentonites are expected
due to the break up and combustion of binders from the dye structure. The differences
between curves T1/T2 in comparison with similarity of the curves T3/T4 could be more
attributed to the specific behaviour of residues T2 than bentonite impact. The X-ray diffraction
analyses made for bentonites, B1 and B4, and precipitates T1  T4, showed changes in the peak
position and shape for precipitates in relation to pure bentonites.
Table 3. Weight losses at thermal treatment of residues and bentonites
Investigated material
Observed property
Total weight loss, %
Difference in comparison with bentonites
B1
13.14
T1
19.55
-45.46
T3
20.01
-48.88
B4
17.05
T2
28.17
-65.22
T4
22.20
-30.21
The shifts, shown in Figure 8 for the two examined systems B1/T3(M2+B1) and B4/T4(M2+B4),
indicate changes in the structure, confirming that something has been incorporated into the
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crystal lattice of bentonites. However, the analyses done so far have been insufficient to draw
a more precise conclusion about the nature and structure of the incorporated materials.
Figure 4. X-ray diffraction analyse for the system B1/T3(M2+B1), Q-quartz, F-feldspat, Kkaoline, Il-Ilite, Mo-montmorilonite
Figure 5. X-ray diffraction analyse for the system B4/T4(M2+B4), Q-quartz, F-feldspat, Kkaoline, Il-Ilite, Mo-montmorilonite
The investigation of added residues on the clay properties
The clay "Aluvićeva žuta" has been subjected to the thermal treatment at the same conditions
like other samples (blind probe) and behaviour of the clay has been followed by DSC and TG
curves (Figure 6). DSC and TG curves for the clay and used bentonites B 1 and B4 have been
shown at the Figures 7 and 8. As these results showed that the type of bentonite has not the
key role on the thermal behaviour, further experiments had been focused on the residues T2
and T4 obtained by the bentonite B4. Sixteen model samples prepared by mixing of 0.5% to
3% of residues T2 and T4 into the regular clay for brick production were subjected to thermal
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Figure 6. DSC, TG and DTG curves for clay
Figure 7. DSC curves for clay and bentonites B1 and B4
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treatment at the temperature range similar to those temperatures used in the brick industry.
The analysis of the behaviour of investigated model samples during thermal treatment, their
DSC curves in comparison to DSC curves of referent sample of the clay, have not shown any
significant differences. Also the analyses of the final weight loss for the model samples, in
comparison with clay have shown to be negligible. Final weight loss for the clay and
minimum and maximum percentage of added T2 and T4 samples are shown in the Table 4.
Differences in a weight loss in comparison to clay are inside 2.4% with the exception of the
sample of maximum percentage of T4 (sample # 16). For the sample # 16 the final weight loss
is 11.19% in accordance to 9.71% of pure clay.
Table 4. Total weight loss for the samples with different ratio of the mixed residues T2 and T4
Observed property
Total weight loss, %
Difference in comparison
with the clay
Clay
9.71
Sample #5
Sample #8
Sample #13
Sample #16
0.59 % T2
9.47
2.99 % T2
9.91
0.78 % T4
9.56
3.00 % T4
11.19
-0.24
0.20
-0.15
1.48
CONCLUSIONS
Model samples of residues, prepared by bentonite treatment of the water-based printing ink
wastewater, were subjected to the thermal treatment analogue to the process of brick
production. The analysis of the behaviour of the residues during a thermal treatment was
targeted at the potential influence of bentonite type, ink composition or binder type on the
process. As expected, all investigated samples showed a weight lost due to the water
evaporation up to 100 ºC. During the further thermal treatment it can be seen that the biggest
differences appeared in the medium temperature range, which is consequence of different
splitting of bentonite layers. That can be the consequence of the incorporation of the part of
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binder from the investigated dyes into bentonite layers during the treatment process. The
impact of bentonite type on the thermal behaviour of samples showed not to have a key role.
DSC curves of the model samples, in comparison to DSC curves of referent raw clay, have
not shown any significant differences. The X-ray diffraction analyses of pure bentonites in
accordance with participates T1 – T4, imply the changes in the crystal lattice of bentonites.
However, the analyses done so far have been insufficient to draw a more precise conclusion
about the nature and structure of the incorporated materials. Final weight lost for the model
samples (clay + residues), in comparison with the clay, have shown negligible differences, as
well as their DSC curves. These results shows that mixing up to 3% of waste residues into
clay as raw material for brick production will have no impact on the behaviour of the raw
material for brick during thermal process. Furthermore it implies that no substantial changes
in the final structure of the products/bricks had been made what allows using problematic
waste type as one of the additives to the brick raw material.
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[4] Black, A.P., Hannah, S.A.; JAWWA, 53, (1961) 438.
[5] Clarke, J.B.; Journal of the Oil and Colour Chemist’s Association, 73(7), (1990) 476.
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