Part A

 Introductory
 Solvent and Bio-scouring
 Biopolishing

 Ammonia Mercerization
1. Introductory
1.1 Factors

Many factors exert significant influences upon the path

of technological developments in the wet processing and
many of the factors include :

❑comparable quality with existing processes with or

without value addition,
❑chemical compatibility to provide multi-functional
process,
❑ cost reduction.
 Introductory

How to achieve the goal?

 By minimizing the use of energy and water

 By increasing the levels of process control
 By monitoring and increasing automation
 By applying eco-friendly methods etc.
ECOLOGY & TEXTILES: Textile industry mostly produces 3
types of pollution 1) Air 2) Water 3) Sound

1) AIR POLLUTION:

a) Cotton dust and fluff from spinning/weaving department.

b) Boiler flue gases and smoke
c) Kerosene vapors from polymerizing machine.
d) Chemical vapors from finishing machine
e) Chlorine vapors.
ECO-FRIENDLY CHEMICAL PROCESSING OF TEXTILES & ENVIRONMENTAL MANAGEMENT
2) WATER POLLUTION:
a) Sizing: pH 8-9.5, BOD-1000mg/l
b) Desizing: pH Acid to Neutral, BOD 35% of total BOD
c) Scouring: 30% of water used in a process house, COD 35% of
total COD.
d) Mercerization: Most of caustic soda is recovered. pH of effluent
is 12-13.5, BOD & COD is low.
e) Dyeing: Colored effluent & Contains excess suspended/dissolved
solids. High COD
f) Printing: Unfixed dyes, starch, gums in effluent. High BOD due
to thickening.
g) Finishing: Less wastewater, Low BOD.

ECO-FRIENDLY CHEMICAL PROCESSING OF TEXTILES & ENVIRONMENTAL MANAGEMENT

3) SOUND POLLUTION:

Sound pollution is a major problem from

machines in Spinning and weaving
department.

ECO-FRIENDLY CHEMICAL PROCESSING OF TEXTILES & ENVIRONMENTAL MANAGEMENT

 Introductory

Wet preparatory processes

The uniformity of dyed materials mainly depends on

the efficiency of fabric preparatory processes. The
removal of natural and added impurities thoroughly
from the fabrics to achieve uniform whiteness
throughout the fabrics is most important for the
production concern.
 Introductory

Wet preparatory processes

Recent developments in fabric preparation process:

Attempts have been made, in the past few decades, to optimize the individual
unit operations involved in wet processing to derive the advantages in the
respective unit operations1–3. New methods involving low temperature, low
pH and eco-friendly chemicals are also explored for reducing the pollution and
effluents generated during various operations in industrial sectors. However, a
logical approach to conserve energy and materials in the preparatory
processes is to shorten the sequence by combining the three operations,
desizing, scouring, bleaching, commonly known as DSB process. Most of the
combined preparation processes have failed mainly due to inadequate
removal of seed coats/mote. Various combined processes have been
developed in the past using different chemicals and also using new
formulations for the process 1– 3.
 1.Solvent Scouring
Solvent Scouring:
Solvent scouring is the treatments of fabrics in
organic solvent medium to remove impurities such
as lubricating oils and spin finishes. Certain organic
solvents will readily dissolve oils fats and waxes
and these solvents can be used to purify textiles.
Removal of impurities by dissolution is called
Extraction.
Suitable Solvents:
It is found that waxes are removed by solvents like
chloroform, benzene, carbon tetra chloride etc. But
those are not used industries because of their high cost
and toxicity. Now a days widely used trichloro
ethylene, perchloro ethylene etc.
Solvent Properties:

Boiling Point: Temperature at which solvent is converted

from liquid to a gas.
Specific Heat: The amount of energy needed to raise one
gram of solvent by one degree centigrade
(Calories/gram/ C). For example, the specific heat
of water is 1 calorie (or 4.186 joules) per gram per Celsius
degree.
Latent Heat of Evaporation: The amount of energy
needed to vaporize one gram of solvent (Calories/gram).
Solvent Scouring Process:

There are commercial processes where textiles are

cleaned with organic solvents. Fabrics processed this
way are said to be "Dry Cleaned". Although not
widely used as a fabric preparation step, it is an
important way of removing certain difficult to
remove impurities, where a small amount of residuals
can cause downstream problems. Garment dry-
cleaning is more prevalent.
For fabrics that do not have to be desized, solvent
scouring is an effective way of removing fiber producer
finishes, coning and knitting oils. Knitted fabrics made
from nylon, polyester, acetate and acrylics, are
particularly amenable to this method of preparation. Wool
grease is effectively removed by solvent scouring.
Solvent Extractions are particularly useful in the
laboratory for determining the amount of processing oils
added to man-made fibers and the residual amounts of
oils and waxes left by aqueous scouring. Properly
controlled, fabrics can be produced with very little
residual matter.
 Advantages of Solvent Scouring:

Solvents dissolve almost all oils and waxes. They have

low liquid surface tensions and quickly and easily wet
out with waxes. They are much easier to evaporate than
water, requiring less time and energy.
 Disadvantages of Solvent Scouring:
On the negative side hydrocarbon solvents are flammable and
present explosion hazards.

Most chlorinated solvents are proven or suspect carcinogens and

some are known to contribute to atmospheric ozone depletion.
Chlorinated hydrocarbons thermally decompose to form phosgene
and hydrochloric acids. These decomposition by-products are
corrosive to metals and also damage cellulosic fibers. Solvents are
expensive so they must be recovered and purified by distillation
requiring special equipment. The distillation residue becomes a
solid waste disposal problem.

Solvents do not aid in the removal of motes, metal ions, starch and
other solvent.
 Role of Enzymes in
Textile Wet-Processing
Figure: Processing of cellulosic fibers.
 Table : Environmental impact of chemical and enzymatic processes.

Impact category Chemical Enzyme Change

Energy 5450 3810 1640
consumption (MJ
LHV)
Global warming (kg 382 281 101
CO2 eqv.)
Acidification (g 1100 792 308
SO2 eqv.)
Nutrient 3480 1200 2280
enrichment (g
PO4 eqv.)
Summer smog (g 331 238 93
ethylene eqv.)
 Enzymes used in textile processing
Enzymes are biological catalysts for specific chemical
reactions and require comparatively mild conditions. All
enzymes are proteins and biodegradable. The precise
reaction specificity of an enzyme can be used for specific
or targeted textile finishing without causing undesirable
effects. Enzymes are classified by the Enzyme
Commission of the International Union of Biochemistry
into six groups: oxidoreductases, transferases,
hydrolases, lyases, isomerases, and ligases (see Table
4.1).
Table 4.1. The Enzyme Commission’s system of classification of
enzymes and assigning code numbers (Palmer, 2001)

Group Enzyme class Type of reaction catalyzed

Oxidation/reduction
1 Oxidoreductases
reactions
Transfer of an atom or group
2 Transferases
between two molecules
3 Hydrolases Hydrolysis reactions
Removal of a group from
4 Lyases
substrate (not by hydrolysis)
5 Isomerases Isomerization reactions
The synthetic joining of two
molecules, coupled with the
6 Ligases breakdown of pyrophosphate
bond in a nucleoside
triphosphate
Most enzymes used in textile wet processing belong to
Group 3, hydrolases for catalyzing hydrolysis of
chemical bonds in substrates. This group includes
amylases, cellulases, pectinases, catalases, and
proteases, which are used for various textile
applications such as desizing, bioscouring, biopolishing,
bleach cleanup, and imparting wool shrink resistance.

One of most popular enzymes used in textiles is

cellulase.
 Properties of enzymes used in textiles
 Firstly, the enzyme accelerates the reaction by lowering the
activation energy and remains intact at the end of the reaction by
acting as a catalyst.
 Secondly, enzymes operate under a milder condition. Enzymes
can be used in catalytic concentrations at low temperatures and at
pH-values near to neutral.
 Thirdly, enzymes are the best alternative to toxic, hazardous, and
polluting chemicals.
 Fourthly, enzymes act only on specific substrates, for example,
enzymes used in desizing do not affect cellulose hence there is no
loss of strength of cotton.
 Fifthly, enzymes are easy to control because their activity
depends upon optimum condition.
 Sixthly, enzymes are biodegradable. At the end of the reaction in
which enzymes used we can simply drain the remaining solution
because enzymes are biodegradable and do not produce toxic
waste on degradation hence there is no pollution.
Enzymes used in textile processing

• Enzymatic desizing
Amylases are used to remove starch-based size for improved and
uniform wet processing in the textile industry. An amylase enzyme
can be used for desizing processes at low-temperature (30-60ºC)
and optimum pH is 5.5-6.5. The advantage of these enzymes is that
they are specific for starch, removing it without damaging to the
support fabric.

• Enzymatic Scouring
Scouring is the removal of non-cellulosic material present on the
surface of the cotton. In generally cellulase and pectinase are
combined and used for Bioscouring. In this pectinase destroy the
cotton cuticle structure by digesting the pectin and removing the
connection between the cuticle and the body of cotton fiber whereas
cellulase can destroy cuticle structure by digesting the primary wall
cellulose immediately under the cuticle of cotton.
• Enzymatic Bleaching
The purpose of cotton bleaching is to decolorize natural pigments
and to confer a pure white appearance to the fibers. Mainly
flavonoids are responsible for the color of cotton. The most common
industrial bleaching agent is hydrogen peroxide. Conventional
preparation of cotton requires high amounts of alkaline chemicals
and consequently, huge quantities of rinse water are generated.
However, radical reactions of bleaching agents with the fiber can
lead to a decrease in the degree of polymerization and, thus, to
severe damage. Therefore, replacement of hydrogen peroxide by an
enzymatic bleaching system would not only lead to better product
quality due to less fiber damage but also to substantial savings on
washing water needed for the removal of hydrogen peroxide. An
alternative to this process is to use a combination of suitable enzyme
systems. Amyloglucosidases, pectinases, and glucose oxidases are
selected that are compatible concerning their active pH and
temperature range.
• Biopolishing
Biopolishing is a finishing process that improves
fabric quality by mainly reducing fuzziness and
pilling property of cellulosic fiber. The objective of
the process is the elimination of micro fibrils of
cotton through the action of cellulase enzyme.
Biopolishing treatment brings the fabric a cleaner
surface, a cooler feel, lustre, and softer feel.
 Bio-Scouring (enzymatic process) :

Bio-scouring with pectinases (enzyme) have shown promise in

replacing the traditional alkakine scouring treatment.

The new bio-scouring process operates at low pH conditions over a

broad temperature range and can be applied using equipment such as
jet machines.
The enzymatic process called bio-scouring allows cotton to
be treated under very mild conditions. Due to use of less
rinse water, bioscouring process reduces both effluent as
well as water consumption. In bioscouring alkaline
pectinase enzyme is used for natural cellulosic fibers such
as cotton, linen, hemp and blends. It removes pectin and
other impurities from the primary cell wall of the cotton
fibers without degradation of cellulose and thus has no
negative effect on strength properties of the fabric.
Several types of enzymes, including pectinases, cellulases,
proteases (Karapinar and Sariisik, 2004; Ibrahim et al.,
2004), and lipases/cutinases (Deganil et al., 2002;
Sangwatanaroj and Choonukulpong, 2003), have been
studied for cotton bioscouring. The most common fungal
sources of these enzymes include Aspergillus niger, A.
fumigatus, Penicillium notatum, Fusarium spp., Rhizopus
stolonifera, and P. frequetans (Rajendran et al., 2011).
Pectinases produced from Sclerotium rolfsii (del Valle et
al., 2007), Paecilomyces variotii (Nisha, 2016), Fusarium
solanipisi (Agrawal et al., 2008), Coniotryrium diplodiella,
Sclerotinia libertiana, and A. niger (Maleki et al., 2011)
have been reported for their use in bioscouring of cotton
fabrics.
Bio-Scouring
Bioscouring can also be combined with other wet
processes such as follows:

• Desizing and bioscouring

• Bioscouring and dyeing
• Bioscouring and biopolishing
• Bioscouring, biopolishing and dyeing

Combining these processes offer considerable time,

water and energy savings.
 Recipe Formulation:
Enzymatic scouring was carried out by the following recipe-

Enzyme: ………………………………………3 g/L or 0.5%

Sequestering agent : ………………………1 g/L
Wetting agent : ……………………………..2 g/L
Emulsifier……………………………………..0.5-1 g/l
Buffer………………………………………as required to maintain PH
Temperature : ……………………………….50-60 C
Time : …………………………………………30 min
M: L : …………………………………………1:10
pH : ……………………………………………8 -9

Scourzyme L (Novozymes) : 0.4-0.6% at pH 7.5 -8.5

The important parameters of the scouring
process are as follows:

 Concentration of Enzyme.
 Type and concentration of auxiliaries.
 Treatment temperature.
 Reaction time.
 PH
Figure: Process curve of Bioscouring
Comparison of Bioscouring and Conventional Scouring:
Conventional
Parameters Bioscouring
scouring
pH value of
7.5-8.5 13–14
process

Temperature 50–60 95–100

Residual pectin 10–15 10–15

Weight loss % <2.5 3–8

Hydrophilicity
<2 s <2 s
(TEGEWA)

Fibre damage (DP

<0.05 <0.05
component)

Degree of 5–10 points 1–2 points

whiteness improved improved
Handle Very soft Harsh
Dyeability Good Good
Water saving 20–50%
Bioscouring has following advantages:
 Over 50% reduction of TDS, COD and BOD in the effluent.
 Can be combined with enzymatic desizing.
 Core alkali migration no longer a problem in further processes.
 Overall savings in utilities up to 30% (less water and energy required).
 Improved strength when compared to conventional scouring.
 Lower weight loss, up to 1–2% compared to 4% of conventional alkaline
scouring.
 Better softness.
 No cellulosic/fibre damage.
 Less chemicals used.
 Mild conditions allow treatment of linen and blends.
 No oxy-cellulose formation and less strength loss because of absence
of heavy alkali in bath.
 Uniform removal of waxes results in better levelness in dyeing.
 Highly suitable for scouring of blends like silk, wool, viscose, modal,
lyocel, and Lycra etc.
 Low Total Dissolved Solids (TDS) in discharge waste water.
 Fabric is softer and fluffier than conventional scouring, ideal for terry
towel/knitted goods.
 Milder conditions of processing, low consumption of utilities,
excellent absorbency in goods.
 .
Bio-Scouring (enzymatic process) :

Advantage:

1. There is no need for the use of caustic soda in enzymatic

scouring. So this process reduced pollution loads, high TDS,
BOD and COD in the effluent

2. It is claimed that, due to a better bleachability of enzyme-

scoured textiles, bleaching can be carried out with reduced
amounts of bleaching chemicals and auxiliaries.

3. The process is economical.

 Bio-Scouring (enzymatic process) :

Disadvantage:

Bio-scouring enzymes actually make the substrate more

hydrophilic (which could explain better bleach ability), but they
are not able to destroy wax and seeds which are therefore removed
in the subsequent bleaching process.
Estimation or Scouring Effect:

The scouring effect can be estimated by carrying

out one of the following tests-
· Measurement of weight loss.
· Test of (absorbency):
Immersion test.
Drop test.
Wicking or column test.
Assessment of Scouring:/Absorbency Test: Drop/Spot Test:

In a pipette a solution of 0.1% direct red or Congo red is taken

and droplet of solution put on the different places of the fabric.
Then the absorption time of the fabric is observed. The standard
time for the absorption of one drop of solution is 0.5-0.8 sec up
to 1 sec.
Table : Commercial Cellulases Used for Biostoning

Trade name Company Acid/neutral cellulase

Biotouch OSB7® Neutral

Ecostone F7® AB enzymes Neutral

Ecostone L900® Acid

IndiAge®SuperL Neutral
DuPont (Genencor)
Primafast® GOLD Neutral

Cellusoft® CR Novozymes Neutral

 Difference Between Scouring and Souring:

Scouring Souring

To remove oil, waxes gum Not to remove any soluble

impurities, only for alkali
neutralization

Scouring is done in alkali Souring is done dilute solution.

HCl or H2SO4
Required heat to boiling No need of heat

Need of definite time No need of definite time

Biological Oxygen Demand Chemical Oxygen Demand
Definition
It is the amount of oxygen the microbes It is the total amount of oxygen
require to decompose the organic required to break down the
matter under aerobic conditions. organic/inorganic matter by chemical
oxidation.
Test
It can be determined by putting a sealed It can be determined by placing a water
water sample under specific sample with a strong oxidizing agent
temperature conditions for five days. under specific temperature conditions
for a short period.

Value
Lower than COD. Higher than BOD.
Use
•It is used to waste loadings in •To quantify the amount of oxidisable
treatment plants. pollutants found in water bodies.
•Evaluation of BOD removal efficiency of •It provides a measurement on how an
the waste plants. effluent will affect the water body.