WASTE MANAGEMENT IN WATER-BASED PRINTING INK INDUSTRY

S. KUČAR-DRAGIČEVIĆ1, N. KOPRIVANAC2, D. VUJEVIĆ2

1Croatian Environemnt Agency, Trg Maršala Tita 8, HR-10000 Zagreb, Croatia

2University 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 pre-

treatment 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

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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 water-

based 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

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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

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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 B 1

and B4 added in the model mixtures M1 and M2

Precipitate label

Model Wastewater

Bentonite type Concentration of bentonite, kg m-3

T1 M1 B1 16T2 M1 B4 6T3 M2 B1 20T4 M2 B4 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.

Δm = m(T) – m0 (1)

Δm = m(t) – m (2)

where: 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 E473-

85). Measured signal (heat flow as differential of heat per time) is measured as follows:

Φr = dqr/dt = – K(T)×ΔTPR(T) (3)

where: 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 (5)

where: 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

ResidueHeavy metal, mg kg-1 Humidity

lost, %Ash

content, %Cd Cr Ni Pb HgT1 <0.0001 77.05 <0.0001 91.58 <0.0001 39.60 85.06T2 <0.0001 63.59 201.1 178.48 <0.0001 5.96 68.65T3 0 87.51 85.23 177.98 0 5.19 86.72T4 0 40.69 151.28 118.28 0 25.60 82.18

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 T1 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

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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

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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

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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 materialObserved property B1 T1 T3 B4 T2 T4

Total weight loss, % 13.14 19.55 20.01 17.05 28.17 22.20Difference in comparison with bentonites -45.46 -48.88   -65.22 -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, K-kaoline, Il-Ilite, Mo-montmorilonite

Figure 5. X-ray diffraction analyse for the system B4/T4(M2+B4), Q-quartz, F-feldspat, K-kaoline, 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 B1 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

Sample #5 Sample #8 Sample #13 Sample #16Observed property Clay 0.59 % T2 2.99 % T2 0.78 % T4 3.00 % T4

Total weight loss, % 9.71 9.47 9.91 9.56 11.19Difference in comparison

with the clay 

-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.

REFERENCES

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[3] Deo, N., Ali, M.; American Dyestuff Reporter, 85(10), (1996) 28.

[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.

[6] La Grega, M.D., Buchingham, P.L., Evans, J.C.; Hazardous Waste Management,

McGraw-Hill, Inc. & ERM, New York, 1994.

[7] Manahan, S.E.; Environmental Chemistry, 6th Edition, Lewis Publishers, 1994.

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[8] Parker, S.P.; Concise Encyclopaedia of Science and Technology, 3rd Edition, McGraw-

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