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Textile Research Conference, 16 August 2014, Dhaka, Bangladesh
AN ECO FRIENDLY TEXTILE TECHNIQUE: POLLUTION REDUCTION
AND WATER SAVING BY REUSING MERCERIZATION EFFLUENT
Arun Kanti Guha* and Md. Obaidur Rahman
Department of Textile Engineering, Southeast University,
Tejgaon, Dhaka 1208, Bangladesh.
(E-mail of presenting and corresponding author: arunguha70@yahoo.com)
Abstract: It is well known that a large quantity of water is
required for wet processing Textiles, such as pretreatment, dyeing,
washing, denim and garment industries. After appropriate
treatment of effluent the reuse of treated effluent leads to zero-
waste discharge in Textile industries. Reuse of mercerization
effluent can be a good solution for implementation of zero-waste
concept in Textiles. In this work the effluent obtained after
mercerization collected from woven dyeing unit of Zaber & Zubair
Fabrics Ltd., Tongi, Gazipur, Bangladesh. Excess NaOH was
recovered by distillation process as well as the distilled water was
collected in a receiver. After that, distilled water was reused for
dyeing knit fabric with reactive dye. After dyeing, rubbing fastness
of dyed fabric was checked at Quality Control Lab of National
Institute of Textile Engineering & Research (NITER), Savar,
Dhaka, Bangladesh. We obtained very close values of rubbing
fastness under both the dry and wet conditions indicative of novel
possibility of reuse of mercerized effluent after recovery of NaOH.
There are double benefits in this process, one is recovery of NaOH
and the other one is reuse of water.
Keywords: Reuse, Mercerization, Recovery, Dyeing , Zero
waste.
1. Introduction
1.1 General Interpretation
Water is essential to sustain life on the biosphere. However;
with the increasing population and industrial growth, its
resources are becoming limited and/or contaminated [1].
Due to growing demand globally more than a billion people
lack access to sufficient water of good quality. Studies
reported that one third of the world’s population will
experience severe water scarcity within the next 20 years [1].
Water reuse continues to rise as demand for fresh water
supplies increases worldwide. By recycling and reusing
treated wastewater, communities and industries can save on
the costs of clean water, ensure adequate supplies and help
to preserve a diminishing natural resource.
A zero waste or discharge concept, in principle, should
reduce the pollution completely. Textile effluents are being
directly discharged into the surrounding channel in many
cases, agricultural fields, irrigation channels, surface water
and these finally enter into Burigonga, Turag, Shitalakkhya
and Balu rivers surrounding Dhaka City.
1.2 Mercerization
Mercerization is a process in which fabric (typically cotton
made) is treated with a caustic soda (NaOH) solution to
improve properties such as fiber strength, shrinkage
resistance, luster, and dye affinity. The caustic soda actually
rearranges the cellulose molecules in the fiber to produce
these changes.
Literature reports described reuse of dyeing effluents of
various dyestuffs on different fabrics. For example,
Vandevivere et al. [2] , Lamas et al. [3] and Erdumlu et al.
[4] reported reuses of textile dyeing and finishing
wastewaters. But reuse of mercerization effluent was not
found as per our literature survey. This paper includes reuse
of mercerization effluent in dyeing as well as recovery of
excess sodium hydroxide from mercerization effluent.
In this work, the effluent obtained after mercerization
collected from woven dyeing unit of Zaber & Zubair
Fabrics Ltd., Tongi, Gazipur, Bangladesh and it was
distilled to collect distilled effluent with recovery of caustic
soda. After that distilled water was reused for dyeing knit
fabric with reactive dye. Another piece of the same knit
fabric was also dyed by same reactive dye using normal tap
water following the same dyeing procedure to compare with
dyed fabric where the distilled water was used. Finally
quality was checked at the Quality Control Lab of National
Institute of Textile Engineering & Research (NITER), Savar,
Dhaka, Bangladesh.
2. Material and Methods
2.1. Mercerization Effluent and Equipment
The mercerization effluent used in this work was collected
in fresh plastic bottle from a textile industry “Zaber &
Zubair Fabrics Ltd.” located at Pagar, Tongi, Gazipur,
Bangladesh. The authority of Zaber & Zubair Fabrics Ltd.
used aqueous NaOH solution (270-300 g/L) for
mercerization at room temperature. The pH was measured
by pocket sized pH meter.
Specifications of the pH meter: Pocket-Sized pH meter,
Model: HI 96107, Manufacturing Company: Hanna
Instruments, Country of Origin: Italy.
2.2 Distillation of Mercerization Effluent
The experimental set up included a condenser with two
flasks, one flak was used for distillation and another one
was used for receiving the distilled water came through the
condenser. Both the flasks were clamped by stand and two
rubber tubes were used for water in let and outlet. The
condenser and flasks were connected by glass tubes with
corks. The mercerization effluent was heated in a 250 mL
flask by gas burner for distillation. The duration of
distillation was 1-2 hour.
2.3 Dyeing Procedure
After getting distilled water from mercerized effluent it was
used it in manual cotton knit fabric dyeing with reactive dye
(Kiractive, Red ME3BL, Hot brand).
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Textile Research Conference, 16 August 2014, Dhaka, Bangladesh
Dyeing Recipe:
Liquor ratio : 1:40, Dyes: 3%, Salt : 70 g/L, Soda: 20 g/L,
Wetting Agent: 1 g/L, Sequestering Agent : 1 g/L, Leveling
Agent : 1 g/L, Temperature: 80 oC and Time : 50 min.
Neutralization Recipe:
Acetic Acid: 1 g/L, Temperature: 60 oC and Time: 10 min.
Soaping Recipe:
Detergent: 1 g/L, Temperature: 90 oC and Time: 10 min.
After dyeing the dyed fabric was dried in a dryer (Digioven,
MAG) in the dyeing lab.
2.4 Quality Test of Dyed Fabric
The dyed fabrics were tested at National Institute of Textile
Engineering & Research (NITER), a public-private
partnership education and training institute, located at Savar,
Dhaka, Bangladesh. We measured the rubbing fastness
under both the dry and wet conditions. We used an Auto
Rubbing Tester or Crock Meter (James H. Heal, UK) to
measure the rubbing fastness of dyed fabrics.
We used a grey scale to test the rubbing fastness of our dyed
fabric. Grey scale is the tool by which the fastness of a dyed
fabric can be evaluated in a numerical value. This Grey
Scale is for assessing the degree of staining caused by a
dyed fabric in color fastness tests. The scale consists of nine
pairs of gray color chips each representing a visual
difference and contrast. The fastness rating goes step-wise
from: note 5 = no visual change (best rating) to note 1 = a
large visual change (worst rating). The grey scale has the 9
possible values: 5, 4-5, 4, 3-4, 3, 2-3, 2, 1-2 and 1.
3. Results and Discussion
Efficiency of this work was checked by decreasing pH,
recovery of NaOH and quality of dyed fabric.
3.1. Characteristics of Mercerized Water
The key characteristic of mercerized water is pH which was
not highly variable and was comparable shown in Table 1.
TABLE 1: THE CHANGE OF THE pH VALUE BY THE
DISTILLATION PROCESS OF MERCERIZATION EFFLUENT
After distillation process it was shown that the key
characteristic pH was decreased slightly which was useful
to reuse the water in conventional dyeing process.
3.2 Recovery of Caustic soda
The recovery of NaOH is one of the major achievement of
this work. In textile sector a huge amount of NaOH is used,
in this sense it is necessary to know that how to minimize
the use of NaOH or how to recover the used NaOH. In this
work we recovered 78% caustic soda. Main environmental
benefits are reduction of alkaline load of wastewater and
minimization of acid requirement for wastewater
neutralization. It also minimizes the process manufacturing
cost by minimizing the usage of NaOH.
3.3 Quality of Dyed fabric
The quality of rubbing fastness, one of the most important
quality parameter of a dyed fabric,depends on buyer
requirements. The rubbing fastness result of dyed fabric
with distilled mercerized water was not so differ from
normal results.
TABLE 2: STANDARD RUBBING FASTNESS AT
VARIOUS CONDITIONS.
Shades
Rating
At Dry
At Wet
Dark shade
3-4
2-2/3
Medium shade
4
3
Light shade
4-5
3/4 - 4
TABLE 3: OBTAINED RUBBING FASTNESS IN THIS
WORK.
Shade
Rating
At Dry
At Wet
Red (dyeing with normal tap
water in our lab)
4/5
3/4
Red ( dyeing with distilled
mercerized water)
3
2/3
It was shown that our experimental values of rubbing
fastness (Table 4) were close to normal conditions (Table 3).
More over our obtained rubbing fastness values were
similar to requirement of a famous buyer of Textile
Products, H & M [5]. On the other hand DIN EN ISO 105-
X12 requirement was very similar to our obtained results [6].
In a previous paper, Molla et al. [7] reported very similar
rubbing fastness values for cationized cotton fabrics printed
by using C.I. Acid Blue 113 under exhaustion method. They
Characteristics
Value
Percentage
of change
Before
distillation
After
distillation
pH of industrial
mercerized water
13.1
12.5
4.58%
decreased
pH of lab made
mercerized water
12.4
11.8
4.84%
decreased
Fig. 1. Dyed fabric with distilled
mercerization effluent.
Fig. 2. Dyed fabric with normal tap
water
TRC 2014 www.clothinginstitute.org 27
Textile Research Conference, 16 August 2014, Dhaka, Bangladesh
reported several rubbing fastness values such as, 2-3, 3-4, 4
and 4-5 at both the dry and wet conditions. These values are
similar to our values. We obtained 2/3, 3, 3/4 and 4/5 at dry
and wet conditions. Molla et al. [7] also interpreted that,
cotton is one of the most important fibers in the textile
industry among other fibres and its coloration can be
achieved, by dyeing, printing in aqueous solution, or with
pigments using a printing paste. Printed cellulosic fabrics
are considered for more than 70% of all printed substrates
and pigment printing is a major method [8, 9]. They also
concluded that anionic dyes other than reactive dyes (such
as acid and direct dyes) for cotton printing are not generally
used, because of the repulsion between the negative surface
and charge of cellulosic part and the solubilising sulphonic
groups in the dye stuff. The above problems can be
overcome by modifying the surface of the cotton fiber to
carry positive charge that lead to ionic bond formation with
the anionic dyes used [ 10, 11].
Khalifa et al. [12] reported new azo heterocyclic disperse
dyes with thiophene moiety for dyeing polyester fibers.
They analyzed dyeing performance from aqueous
dispersions by color fastness evaluation. They reported
rubbing fastness, 2-3, 3-4, 4 and 5 in both the dry and wet
conditions. These values are similar to our results in this
work. Authors reported that the fastness to rubbing (dry and
wet) may be attributed to inadequate diffusion of dye
molecule into the fibers.
In another previous report, El-Halwagy et al. [13] concluded
that pollution can be reduced in cotton printing with
reactive dyeing. We also explained that pollution load can
be reduced by recovery of sodium hydroxide as well as
using the same wastewater in dying of knit cotton fabric by
reactive dye.
4. Conclusion
Reclaimed water is a treated effluent that is considered to be
of appropriate quality for an intended water reuse
application. Water reclamation and reuse can enable
communities to strategically link the distribution and use of
locally available water resources with specific water quality
and quantity goals, particularly in areas where there are
concerns about water supply sustainability. This paper
includes most effective methods to recover excess caustic
soda and reuse of distilled mercerization effluent. We
recovered caustic soda (78%) and reused distilled
mercerization effluent to dye cotton knit fabric by reactive
dye using conventional manual method. The quality of dyed
fabric was checked by testing rubbing fastness in National
Institute of Textile Engineering & Research (NITER),
Bangladesh. Further studies should be carried out to find
out suitable industrial process for recovery of sodium
hydroxide and reuse of mercerization effluent in Textiles.
Acknowledgements
Authors are grateful to Mr. Sahadeb Malo (AGM, Zaber & Zubair
Fabrics Ltd.) for kind help to collect effluent samples and
providing important information. Authors are also grateful to Mr.
Md. Jahangir Hossain (Lecturer, NITER) for helpful discussion
and instrumental support. Finally authors express gratitude to Prof.
Syed Fakhrul Hassan, Dean (Acting) of School of Science and
Engineering and Dr. ANM Ahmedullah, Assistant Professor, Dept.
of Textile Engineering, Southeast University for their moral
support during this work.
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