Modeling of the linen fabric dyeing after previous preparation

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68
Advanced technologies
MODELING OF THE LINEN FABRIC DYEING AFTER PREVIOUS
PREPARATION
Nemanja Vučković*, Marija Kodrić, Milena Nikodijević, Dragan Đordjević
University of Niš, Faculty of Technology Leskovac, Serbia
The study deals with modeling of linen fabric dyeing after previous scouring and
bleaching. The results reveal the process of the direct dye adsorption on the fabric,
as well as the capacity and energy of adsorption based on which the optimization
of the dyeing process with maximum performance and minimal costs can be done.
With the increase of the dye concentration during dyeing, the degree of exhaustion
decreases while the longer dyeing time gives a higher degree of dye exhaustion.
Variation in the adsorbed amount of adsorbate increases with the increased initial
concentration and time, i.e. a bigger amount of the dye or a longer time period of
dyeing causes a bigger quantity of the adsorbed dye per mass unit of the linen fabric.
The advantage in results processing is given to Freundlich-s model since the maxi-
mal value of the determination coecient can be obtained.
Keywords: dyeing, linen fabric, direct dye,
modeling, Langmuir's model, Freundlich's
model.
Introduction
Because of good mechanical characteristics, thermo-
stability, raw material renewability and biodegradability, nat-
ural bers become more interesting for use in textile and
can evenly replace articial materials [1, 2].
Parameters that are decisive for using natural-cellulose
bers are [3]:
- Lower price compared to higher property bers.
- High elasticity module and low elongation at break.
- They origin from natural resources.
Flax bers have similar mechanical properties as glass
bers and some carbon bers. Because of micro-morpho-
logical characteristics, they have smaller density, a rough
surface, a specic layered structure, they are air permeable
and absorptive and therefore cannot cause some allergic
reactions [4].
On the other hand, various chemical modications of
cellulose bers are possible (acetylation, cyanoethylation,
treatment with alkaline) for both natural and articial bers.
The advantage of these modications is that bers, espe-
cially natural ones possess the structure with good physi-
cal-mechanical properties [5].
Considering its chemical composition and morphology,
ax is a very demanding substrate for the preparation pro-
cess. Many bers impurities, like lignin, pectin etc., require the
preparation that is long lasting and divided in many individual
processes, and they are related to high costs. Flax contains
almost 20% more impurities compared to cotton [6, 7].
Demands in terms of a degree in the whiteness of ax
became greater in time, and a dierent quality of harvest
very often causes changes in the initial whiteness of ax.
A new technological approach has replaced these two
bulky processes with another two important ones: cold
chlorite bleaching and hot peroxide bleaching. The combi-
nation of optimizing cold chlorite bleaching with hot perox-
ide bleaching enables making shorter operations in a very
simple and eective way [8].
The modeling of linen fabric dyeing after preparation
processes, scouring and bleaching was studied in this work.
The results are satisfying considering the way of direct dye
adsorption on a fabric, as well as the capacity and energy
of adsorption, based on what we can optimize the process
of dyeing with maximum performance and minimal costs.
Experimental
In the study, 100% of raw linen fabric in plain weave
was used. Basic characteristics are as follows: warp and
weft count, 73 and 63 tex (unit for neness), respectively;
surface mass 238 g·m-2, setting of warp and weft, 17 and
16 cm-1, respectively, thickness 0.53 mm.
Dyeing of linen fabric was performed with the direct dye
Solophenyl green 5BL (Huntsman, USA).
The pretreatment of linen fabric includes processes of
scouring and bleaching. Scouring of linen was carried out
within 6 minutes at the temperature of 95 °C, in the ratio of
the solution 1:80 and with the addition of sodiumcarbonate
Na2CO3 (Tehnohemija, Serbia).
The complete bleaching was done in two steps. The
rst step includes a treatment in the solution with the ration
1:100, for 30 minutes at the temperature of 40-50 °C, in the
presence of 0.5 g·dm-3 potassiumpermanganate KMnO4
(Centrohem, Serbia), after which the abundant was rinsed
with cold and hot water.
(ORIGINAL SCIENTIFIC PAPER)
UDC 677.027:677.074:677.11
*Author address: Nemanja Vučković, Faculty of Technology,
16000 Leskovac, Bulevar oslobodjenja 124, Serbia
E-mail: vucko989@gmail.com
The manuscript received: November, 15, 2018.
Paper accepted: December, 10, 2018
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The second step of the sample bleaching was performed
in the solution with ratio of 1:100. The reaction lasted for 30
minutes, at the temperature of 40-50 °C, with the addition
of 3 g·dm-3 ascorbic acid, C6HO6 (Oleohemija, Serbia). At
the end, the samples were abundantly rinsed with hot and
cold water and sent to dry.
Dyeing was performed with a direct green dye solution
(ratio 1:50) at 95 °C. The concentrations of the dye Solo-
phenyl green 5BL were 10, 20, 40, 60 mg·dm-3. The dura-
tion time of the dyeing process was 5, 10, 20, 40 and 60
minutes.
At the end of dyeing, the fabric sample was taken out of
the solution. The rest of the solution was cooled down, and
the adsorption was measured on spectrophotometer (Cary
100 Conc UV-VIS, Varian), with the maximum adsorption
for a direct green dye λmax=680 nm (obtained by measure-
ment).
A degree of dye exhaustion (%) was calculated accord-
ing to equation [9]:
......................................(1)
where: Co and Ct – (mg·dm-3) initial and the concentration
of the dye in time t.
The quantity of the absorbed dye per unit of the linen
mass was measured with the equation [9]:
.................................(2)
where: qt – (mg·g-1) mass of the absorbed dye per linin
mass unit at the time of dyeing t; qe – (mg·g-1) mass of the
absorbed dye per unit of the linen mass in balance, Co –
(mg·dm-3) the initial concentration of the dye, Ct – (mg·g-1)
the concentration of the dye in a the solution at the time of
dyeing t, Ce – (mg·dm-3) the equilibrium concentration of the
dye in the solution, w – (g) the sample mass of linen and
V – (dm3) the volume of the dyeing solution.
For modeling of dyeing of linen two adsorption models
are used, Langmuir's and Freundlich's.
Langmuir's adsorption isotherm describes the adsorp-
tion on the homogenic surface of adsorbents that contains
the limited number of identical adsorption sites and the ab-
sence of interaction between adsorbed molecules.
Langmuir's adsorption model is represented with the
equation [10]:
.........................................................(3)
where: qe – (mg·g-1) is the quantity of adsorbed adsorbate
per mass unit of adsorbent – linen, Qo – (mg·g-1) adsorp-
tion capacity, b – (dm3·mg-1) adsorption energy and Ce –
(mg·dm-3) equilibrium concentration of adsorbate – dye in
the solution.
Freundlich's adsorption isotherm has the empirical
character and describes the adsorption on an energetically
heterogenic surface on which adsorbed molecules interact.
Multilayer adsorption is well described with this model.
Freundlich's model is presented with the following equa-
tion [10]:
........................................................(4)
where: KF – (mg·g-1)·(dm3·mg-1)(n-1) and n – characteristic
constants for the predicted system: adsorbent, adsorbate
and the solution.
Results and discussion
The inuence of the initial dye concentration on adsorp-
tion – exhaustion, as well as the inuence on the quantity
of the adsorbed dye on ber while dyeing for dierent times
is presented in the diagram in Figure 1. With the increase
of the concentration of the dye, a degree of exhaustion is
reducing depending on the time of adsorption – dyeing. At
the beginning, with lower concentrations of the dye, there is
a bit bigger decrease in the percentage of the dye exhaus-
tion, but at the end, a decrease is something slighter.
The shortest time of dyeing (5 minutes) causes the
smallest exhaustion degree values, while the longest dye-
ing time (60 minutes) generates the highest values of the
exhaustion degree.
With the increase of the initial concentration of the dye,
the adsorption of the dye per mass unit of linin ber grows
rapidly, continuously during time.
Figure 2 shows the impact of time or the length of the
contact between adsorbate (dye) and adsorbent (linen fab-
ric) on adsorption – exhaustion of the dye during dyeing on
dierent initial concentrations of a direct dye. At the begin-
ning, with every initial concentration there is a rapid growth
of dye exhaustion, and after about 10 minutes of dyeing,
this trend is weaker until the end of dyeing.
Figure 1. The impact of the initial concentration of the dye on
the exhaustion degree and the quantity of the adsorbed dye on
the ax ber during dyeing (Dye exhaustion – black symbols,
full line; qt – white symbols, interrupted line)
10 20 30 40 50 60
30
40
50
60
70
80
90
100
60 min
40 min
20 min
10 min
5 min
Dye exhaustion (%)
C
0
(mgdm
-3
)
5
10
15
20
25
30
35
40
45
60 min
40 min
20 min
10 min
5 min
q
t
(mgg
-1
)
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Figure 2. The impact of time on the exhaustion degree of direct
green dye during the dyeing of the ax ber
Figure 3 presents the changes in the concentration
and quantity of the adsorbed dye on linen fabric during
dyeing for dierent initial concentrations. A relatively
slight change in the concentration of the dye as the dye-
ing time increases can be noticed. The change is intense
at the beginning and, after 20 minutes, it is quite slower.
Over time, at higher dye concentrations, a slightly steep-
er drop of curves at the beginning of coloring occurs,
which is associated with the rapid bonding of the dye on
the fabric, given a big dierence in the gradient of the
concentration.
The start of dyeing brings about quicker dyeing in the
rst 20 minutes, i.e. a larger amount of the adsorbed dye
appears per unit mass of the adsorbent, so that later,
with the prolongation of the dyeing time this binding is
somewhat slower. At the highest applied initial dye con-
centrations and the longest dyeing, the highest adsorp-
tion occurs.
Figure 3. The change of the concentration and quantity of the
adsorbed dye on the linen fabric during dyeing for dierent ini-
tial concentrations (Ct – black symbols, full line; qt – white sym-
bols, interrupted line)
Figure 4 shows the appearance of the linen fabric in
individual nishing phases and after dyeing. There is a
signicant dierence according to the processing types:
scouring, bleaching and dyeing.
Figure 4. Raw (A), scoured (B), bleached (C) and dyed
(D) samples of linen fabric
A similar study focused on the colors of dierent pre-
treated ax bers (alkaline, acidic and enzymatic), dyed
both conventionally and ultrasonically using two red di-
rect dyes with dierent molecular mass, in terms of the
exhaustion rate etc. Dyeing was accomplished accord-
ing to both a conventional dyeing procedure (without the
ultrasound power) and an ultrasonic technique, using
two direct dyestus: CI Direct Red 80 (dye 1) and CI
Direct Red 81 (dye 2) [6].
Exhaustion curves dene the time dependent distri-
bution of the dye between the dyebath and ax bers
throughout the dyeing process and indicate the dye ad-
sorption at the surface of the ber and diusion into the
ber as a function of time. The obtained results demon-
strate that dierent pretreatments of ax could inuence
the dyeing behavior depending on the time and, above
all, the type of the dyeing procedure. During convention-
al dyeing, the dyeing rate slightly increased in the rst
stage of the process (the rst 30 min), most likely on ac-
count of very strong repulsion forces between the large
dye molecule and the ber [6].
After raising the temperature of the dyebath up to 98
°C (after 50 min), the exhaustion rapidly increased, espe-
cially for enzymatic and acidic pretreated samples, im-
plying a shorter time required to reach the state of equi-
librium. Later (after 78 min), the dierences in the curve
between dierent scoured samples were minor. The -
nal exhausted dye 1 after 92 min of dyeing was 94% for
acidic and enzymatically pretreated bers, followed by
95% for alkali-scoured bers. Generally, nal amounts
of dyestu exhausted over ultrasound assistance were
higher, and the time attaining equilibrium was shorter [6].
Dyeing with dye 2 is based on dissimilar exhaustion
behavior than when using dye 1. Because of the smaller
dye molecule, and hence better diusion, the exhaustion
curves show greater slopes during the rst division of
the dyeing process than on the earlier graphs, although
stronger migration of the dye is presented. During the
ultrasonic-assisted dyeing of dierent pretreated sam-
ples, the degradation of dye 2 was observed after 60 min
after the processes had started, which is not evident [6].
A diagram (Figure 5) represents Langmuir's adsorp-
tion isotherms for dyeing of linen fabric at the tempera-
ture of 95 °C, showing the dependency of parameters
(1/qe) in relation to the equilibrium concentration of the
010 20 30 40 50 60
30
40
50
60
70
80
90
100
10 mgdm
-3
20 mgdm
-3
40 mgdm
-3
60 mgdm
-3
Dye exhaustion (%)
t (min)
010 20 30 40 50 60
0
5
10
15
20
25
30
35
40
10 mgdm
-3
20 mgdm
-3
40 mgdm
-3
60 mgdm
-3
C
t
(mgdm
-3
)
t (min)
5
10
15
20
25
30
35
40
45
10 mgdm
-3
20 mgdm
-3
40 mgdm
-3
60 mgdm
-3
q
t
(mgg
-1
)
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dye (1/Ce).
From the slopes and intercept of linear t, the values
of Langmuir's constants are determined, Q0=33.3 mg·g-1
and b=0.94 dm3·mg-1. They are related to the maximum
quantity of adsorbate that can be bounded on adsorbent
and the free adsorption energy, respectively. The ana-
lytical expression of Langmuir's isotherm is = 0,030
+ 0,032 , while the coecient of the determination is
R2=0.95. The model is more representable when the co-
ecient of determination is closer to one.
Figure 5. Langmuir's linear regression model for balanced
dyeing of the linen fabric
Langmuir's isotherm can also be expressed with non-
dimensional constant, parameter of equilibrium RL. The
value of RL predicts if the isotherm is unfavorable (RL>1),
linear (RL=1), favorable (0<RL>1) or irreversible (RL=0).
From the value of b and the biggest initial quantity of
green dye (60 mg·dm-3), RL is determined to be 0.15.
These results conrm that the Langmuir's model is con-
venient for description adsorption – dyeing in the case.
The diagram in Figure 6 represents Freundlich's iso-
therm for the adsorption of the dye on adsorbent for the
constant quantity of the linen fabric and the temperature
of 95 °C. From this diagram, very high functionality of
variables is noticeable, higher than registered at Lang-
muir's model. Based on this diagram, Freundlich's con-
stants are determined.
KF, one of the Freundlich's constants, is used as a rel-
ative measure of the adsorption capacity. A bigger value
(KF=13.3 in concrete case) indicates a bigger adsorption
capacity.
The second Freundlich's constant, n, is an empiri-
cal parameter that changes with the degree of hetero-
genic indication, the degree of non-linearity between
the capacity of the adsorbed dye and the concentration
of non-adsorbed dye. Generally, 1/n<1 shows that the
adsorbate is suciently adsorbed on the adsorbent, the
adsorption capacity rises, new positions appear for ad-
sorption, the value of n is greater, the intensity of the
adsorption is stronger. The results conrm that n>1, i.e.
2.6>1, or, 1/2.6<1, i.e. 0.38<1. The analytical expression
of Freundlich's model is lnqe = 2,59 + 0,39 ∙ lnCe.
A coecient of determination of Freundlich's isotherm
is bigger than the one of Langmuir's expression, reach-
ing the value very close to 1 (0.99), which represents
the excellent, almost absolute functionality. This means
that both models can be used to describe the adsorption
of a direct green dye on adsorbent but the advantage is
given to the Freundlich's model because of the bigger
maximum value R2.
Figure 6. Freundlich's linear regression model for balanced
dyeing of the linen fabric
Conclusion
With modeling the dyeing process, the data that con-
nect the dye concentration, the temperature, the pres-
ence of electrolytes and the eciency of achieved dye-
ing on the fabric, i.e. the quantity of the waste dye that is
left after dyeing were obtained.
Based on the obtained experimental results it can be
concluded:
• Dyeing of the linen fabric with a direct dye in labora-
tory conditions gives excellent results at the temperature
of 95 °C.
• With the increase of the dye concentration while dye-
ing, the degree of exhaustion reduces.
• The longer time of dyeing gives a higher degree of
dye exhaustion.
• The change of the adsorbed quantity of adsorbate on
adsorbent increases with the increase of the initial quan-
tity and time, i.e. a bigger quantity of the dye or longer
time of dyeing give a larger quantity of the adsorbed dye
per mass unit of the ax ber.
• Both models can be used to describe direct dye ad-
sorption on the linen fabric, but the advantage is given
to Freundlich's model due to the maximum value of the
coecient of determination.
References
0.0 0.5 1.0 1.5 2.0 2.5
0.02
0.04
0.06
0.08
0.10
0.12
1/q
e
1/C
e
-1 0 1 2 3
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
lnC
e
lnq
e
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MODELOVANJE BOJENJA LANENE TKANINE POSLE PRETHODNE
PRIPREME
Nemanja Vučković, Marija Kodrić, Milena Nikodijević, Dragan Đorđević
Univerzitet u Nišu, Tehnološki fakultet u Leskovcu, Srbija
Rad se bavi modelovanjem bojenja lanene tkanine posle iskuvavanja i beljenja.
Rezultati su zadovoljavajući s obzirom da otkrivaju način adsorpcije direktne boje
za vlakno kao i kapacitet i energiju adsorpcije, na osnovu čega se može optimizo-
vati proces bojenja uz maksimalni učinak i minimalne troškove. Porastom kon-
centracije boje pri bojenju smanjuje se stepen iscrpljenja dok duže vreme bojenje
daje i veći stepen iscrpljenja boje. Promena adsorbovane količine adsorbata na
adsorbentu, raste tokom povećanja početne koncentracije i vremena, tj. veća
količina boje ili duži vremenski period bojenja donose veću količinu adsorbovane
boje po jedini mase lanene tkanine.Oba modela, Freundlich i Langmuir, mogu se
upotrebiti za opis adsorpcije direktne boje na adsorbent, s tim da se prednost daje
Freundlich-ovom modelu zbog maksimalne vrednosti koecijenta determinacije.
Ključne reči: bojenje, lanena tkanina, di-
rektna boja, modelovanje, Langmuir-ov
model, Freundlich-ov model.
(ORIGINALNI NAUČNI RAD)
UDK 677.027:677.074:677.11
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