The slide contains advances (recent developments) in textile pretreatment called desizing, scouring, and bleaching. Different advances such as an enzyme, ozone, and plasma treatments are included for each pretreatment process.

1. Presentation
On
“RECENT ADVANCES IN DESIZING,
SCOURING AND BLEACHING”
UNDER THE GUIDANCE OF
Prof. (Dr.) K.MURUGESH
BY
NATINAEL KOKEB

2. A good preparatory process has several objectives
•Removal of loose hairy protruding fibres from the surface of the
fabric to give a smooth, even and clean looking face.
•Removal of natural impurities like oils, fats, waxes,
greases, natural matter, lignin and sizing material
like starches.
•To obtain an absorbent fabric,this is ready
for dyeing or printing process.
•To obtain softer and proper white fabric,
depending on its application.

3. Singeing Desizing Scouring and Bleaching
Merserization
Dyeing
Finishing

4. Eco friendly pre-treatment
 Enzymes are
 Class of proteins, biocatalysts andbiodegradable
 produced from fungi or bacteria.
 Enzymes are complex organic, soluble bio-catalysts, formed by
living organisms that catalyze chemical reaction in biological
processes.
 Enzymes are quite specific in their action on a
particular substance and used in small quantities.
Enzymatic process

5. E + S → E S → P + E
(Enzyme) (Substrate) (Enzyme-Substrate) (Product) (Enzyme)
Substrate entering
In active side of
enzyme
Enzyme
substrate
complex
Enzyme/substrate
complex
Prodcut release from
enzyme

6. The removing of size material which incorporated in pre-weaving process is known
as desizing.

7. There are three main advanced desizing method are
1. Enzymatic desizing
2. Solvant desizing
3. Atmospheric plasma desizing
4. Ultrasonic desizing

8. •Amylases are the enzyme that hydrolyses and reduces the molecular
weight of cellulose.
 hydrolyze starch molecules to give diverse products.
 specific for starch, removing it without damaging to the
support fabric.
 optimum temperature is 30-60°C, optimum pH is 5.5-6.5.

9. Cont…
Enzymatic desizing and utilisation of desizing liquor for H2O2
 To utilize desizing baths for bleaching in which glucose oxidase
enzymes generate hydrogen peroxide and gluconic acid using
glucose as a substrate.
 Amyloglucosidases areenzymes used in desizing to degrade
starch until it becomes glucose.
 Optimum conditions are 0.75% (o.w.f.) enzyme, pH 4.1, 62 °C
and a process time of 45 minutes.
Advantages:
 reducing the use of peroxide stabilizing agents with the help of gluconic acid
 saving water and energy by using desizing liquor for bleach.

10. • Some solvent are used for desizing of textile substrate.
• Sonafab 1000). It is a unique Desizing Agent, having
excellent solvent and emulsifying action on all types of
stain. (Sonal Dye-ChemPvt. Ltd)
Perchloroethylene -- desizing solvent

11. Effect of organic solvents on fiber

12. •It is a very clean operation with no disposal problem, the
pollution effect is negligible.
•The time of desizing and floor area for the machinery is far less
than for conventional system.
•Due to quick and even solvent penetration the size removal is
more uniform.
•The solvents are recoverable and have less or no effluent load.
•This method is useful since energy consumption is low, time of
desizing is low.
•Acrylic and wool fabrics develop a lustrous, soft hand in solvent
without any felting.
•When solvent desizing is followed by bleaching, the caustic
scouring is omitted since pectin and wax

13. DISADVANTAGE OF SOLVENT DESIZING
•Although solvent desizing ranges are available
commercially, the price of the equipment is high.
• The majority of size systems used in aqueous process is
not readily applicable in solvent desizing.
•Cost of processing is higher than for water base process.

14. • attractive water-free process Here material having
in ionized condition
• Plasma is produce by applying electric field on a gas
• Plasma is etching the fabric surface
• Etching is depend upon the voltage, type of
gas, time
Desizing of PVA sized cotton fabric can be done only by using
cold water washing after plasma treatment using air + helium
+ oxygen plasma.

15. Mechanism of plasma treatment
 Plasma generates electrons, -ve and +ve ions, radicals, and
atoms when it absorbs energy; consequently, plasma changes to
electricity from electrical conductivity.
 so, the fabric surface gets modified due to physiochemical
changes depending on the nature of gaseous matter, type of
fabric, current, pressure, and temperature.
 for textiles it is employs electrical discharge techniques.

16. Ultrasonic energy are the high frequency waves rangeing from 20Khz to
50Mhz which is nnot audiable by human
• In liquids, longitudinal vibrations of molecules generate compression and rarefaction,
• The latter gives rise to cavities or bubbles, which expand and finally duringthe
compression phase, collapse violently generating shock waves.
• The phenomena of bubble formation and collapse (known as cavitation) is generally
considered responsible for most of ultrasonic physical and chemical effects observed in
solid/liquid or, liquid/liquid systems.

17. Use of ultrasonic energy in
desizing
Amylase
wetting agent
Temperature
Time
- 0.75 g/l
- o.5 g/l
- 55°C
- 20 min.
Desizing efficiency 7 when US is
used.
Desizing efficiency 2.5 when US is
not used.
Limitation
•Energy savings resulting from lower
process temperatures and shorter cycle
times
• Reduced consumption of dyes and
chemicals, which allows for a 20 -30%
reduction in the amount of effluent
• Water savings of around 20%
• Improvement in product quality
• Increased productivity because of shorter
cycle times
•This process requires some assistance from temperature. This process
does not involve in complete elimination of temperature.
Recipe Advantage

18. Conventional method: Alkaliscouring.
Where 3-4% caustic soda is used at high temperature (90-95oC) forlong
duration (2-3hours)
Disadvantages of alkali scouring:
1) Damage to fibre.
2) Requirement of large quantity of water for washing.
3) Heavy effluent load (Salts of neutralization)

19. Enzyme scouring
Scouring with cellulases and pectinases for cotton.
improvements in absorbency of water and water
retention on cotton.
The bio-scouring process does not
remove pectin rather it breaks.
Advantages
 lower Biological Oxygen Demand (BOD) and
 Chemical Oxygen Demand (COD) is low,
 Total Dissolved Solid (TDS), and
 positive effect on extent of the cotton weight loss b/c
specific to pectin and
waxes and not cellulose

20. Enzymatic Scouring or Bio-Scouring can simply be defined as the
application of living organisms and their components to remove the natural
and added impurities.
 Enzymes used for Bio scouring
Pectinase – (Pectins removal)
Protease – (Removal of proteins)
Combination of 2 or 3 enzymes
may be used to get synergistic effect.
Conventional scouring requires high temperatures and high
consumption of chemicals.

21. Parameter Bio Scouring Alkaline Scouring
pH 7-8 12-13
Temperature 50-600C 950C
Residual Pectin 20-25% 10-11%
Weight loss <1.5% 4-6%
Handle Very soft Harsh and papery
Rinse Water
Consumption
30-40% of Alkalinescouring
TDS 50% of AlkalineScouring
BOD 50% of AlkalineScouring
COD 50% of AlkalineScouring

23. Advantages of bio-scouring
 (BOD) and (COD) of enzymatic scouring process are 50 % as compared
to alkaline scouring (100 %). Total Dissolved Solid (TDS) of enzymatic
scouring process is 50% as compared to alkaline scouring(100%).
 Handle is very soft in enzymaticscouring.
 It also minimises health risks of operators as they are not exposed to
hazardous chemicals.
 reduced water and wastewater costs, reduced treatment time and
lower energy consumption because of lower treatment temperature
(the optimal temperature is from 40 to 60°C) .

24. •The enzymes used for scouring are costly and they require
temperature for their action.
•The increase in temperature or pH may deactivate the
enzyme which may alter the process efficiency.

25. BLEACHING
Bleaching is to decolourise to confer a pure white appearance to the
fibres. The common bleaching agent is hydrogen peroxide, applied at
alkaline pH and temperatures close to boiling.

26. BIO BLEACHING
Glucose oxidase
 Glucose oxidases (GODs) are flavoproteins with a Flavin-adenine-
dinucleotide (FAD) active site.
 The enzyme is highly specific for B-D-glucose and catalyses the following
reaction for hydrogen peroxide generation.
• Ph- 4.5-7
• temperatures-40°C
The actual bleaching process involves 2 steps:
1.Peroxide generation by GODs at the enzyme optimum conditions.
2.PH adjustment to 7.5-8 and bleaching process at 85-90°C for 60-120
minutes with the enzymatically hydrogen peroxide.

27. Cont….
Gluconic acid acts as bleach stabilizer
• it would allow for the reuse of sugar contaminated effluent from
other wet processing steps (desizing bath containing glucose)
Laccases are non-specific enzymes but capable to catalyze the
breakdown of the chromophore of colored components.
Rapid bleaching with laccase–hydrogen peroxide enhances the
whiteness of cotton fabrics.
Catalase enzyme catalyzes the decomposition of hydrogen peroxide to
water and oxygen.One catalase molecule can convert millions of
molecules of hydrogen peroxide to water and oxygen each second
reduce the temp and volume of the 2nd wash after bleaching from 80-95 oC to
30-40 oC, 9-14% saving of energy, a 17-18% saving of water and an overall
cost saving of 9%

28. OZONE BLEACHING
 Industrial production of ozone can be accomplished by
applying a plasma discharge to oxygen in air.
 Ozone is a natural substance and it is a strong oxidising
agent and it decomposes rapidly.
Process
Fabric having 24% moisture content is placed in application
chamber and exposed to 100 g/m of concentration of ozone
oxygen gas mixture.
pH – 5 with acetic acid
Time – 1-7 min
Temperature- 30°C

29. OZONE BLEACHING
Advantages
Have significant effect on
quality of processed fabric.
Grey preparation with ozone
can be with in 1 or 2 minute.
There is savings in thermal
energy, water and chemicals
Limitations
 The yield of ozone generator is
low (6-12% from oxygen and 4-
6% from air), and ozone
concentration is low as well.
 Ozone has to be generated on-
site because its problems to be
stored and transported.
 Energy consumption for
production of O3: Based on pure
oxygen, the costs will be 6 to 15
kWh/kg O3.

30. PER ACETIC ACID BLEACHING
• Per acetic acid is also known as peroxyaceticacid.
• It is colorless in nature.
• It is miscible with water and most of organic solvents.
• It is very powerful oxidizing agent.
• It is also used as germicide for protecting fruits/vegetables against spoilage.
• General formula is C2H4O3.
• It corresponds to acetic acid with additional oxygen atom permolecule.
i.e. CH3COOOH (peracetic acid)
• It is highly unstable at pH 5-5.5. But stable at lower pH of1.5-2.
• A concentration of 35% to 40% is dangerously explosive.
CH3CO3H

31. Preparation of Peracetic Acid
 Continuously feeding CH3COOH and H2O2 into an aqueous
reaction medium containing a H2SO4 catalyst.
 The equilibrium constant is 0.37 at room T
 High yields can be achieved with up to 10 days
31

32. Mechanism of oxidation with peracetic acid, it gives extra
oxygen atom and acetic acid is formed as co-product.
CH3COOOH CH3COOH + [O]
Procedure for bleaching with peracetic acid:
1) Peracetic acid being unstable has to be prepared before bleachingbeing
carried out as per above procedure.
2) Bleaching is carried out with
MECHANISM OF PERACETIC ACID

33. How Chemical Bleaches Work
 An oxidizing bleach
 Works by breaking the chemical bonds that make up the
chromophore.
 This changes the molecule into a different substance that either
does not contain a chromophore, or contains a chromophore
that does not absorb visible light.
 A reducing bleach
 Works by converting sites of unsaturation in the chromophore
into single bonds with a reducing agent.
 This eliminates the ability of the chromophore to absorb visible
light.

34.  Togo towards the eco friendly and sustainable textile
processing, New technology has to be incorporated in
the textile processing
 All over the world, the environmental regulations
are becoming more and more stringent and are
forcing the shift of technology towards less polluting
or non-polluting areas of technological development.
 Rapid changes in technology a dire need to
conserve water and energy have forced the textile
industry to give up the old conventional processes
and try out new methods
CONCLUSION

35. References
Aly AS, Sayed SM, & MK, Z. (2010). One-step process for enzymatic desizing
and bioscouring of cotton fabrics. Journa;l of natural fibers, 7, 71–92.
doi:10.1080/15440478.2010
Fiber2Fashio. (2006). Latest methods of Cotton Bleaching. World of Garment-
textile-fashio. Retrieved from https://www.fibre2fashion.com/industry-
article/79/latest-methods-of-cotton-bleaching
G.Buschle-Diller, Y.El Mogahzy, MK.Inglesby, & SH.Zeronian. (1998). Effects of
scouring with enzymes, organic solvents, and caustic soda on the properties of
hydrogen peroxide bleached cotton yarn. Textile Research Journal, 68(12), 920-
929. doi:https://doi.org/10.1177%2F004051759806801207
Gupta D, & S, N. (2017). Cleaner process for shrink proofing of wool using
ultraviolet radiation and sericin. Journal of textile institute, 108, 147–153.
doi:https://doi.org/10.1080/00405000.2016.1160757
Hasin, S. ( 2020). Solvent Scouring. Retrieved from
https://www.textileproperty.com/solvent-scouring/
Hoque, S. A., & Azim, A. (2016). Using enzymes as an aid of better and eco-
friendly scouring processing. Am J Eng Res, 5(6), 167-182.