Bahir Dar University

Institute of Technology Textile, Garment and Fashion Design(iOTEX)

Advanced Pretreatment process

Seminar on Bio-Scouring process

Prepared by: Bademaw Abate

BIO-SCOURING

Introduction• Cotton is the leading fibre in Textile Industry; it is still the "King" of

fibers because most of the world's apparel is made of Cotton andCotton must be properly prepared for Dyeing, printing and finishing.

• Scouring is an important pre-treatment operation in the processingof cotton and cotton blended materials.

• The main objective of scouring is to remove the non-cellulosicconstituents of cotton fibre which make the fibre non-absorbent.

• Conventionally, scouring is done in a hot aqueous solution of NaOHto remove hydrophobic components from the primary wall (e.g.pectin, protein and organic acids) and the cuticle (waxes and fats).

Cont…. Enzymes in textile wet processing has added a new line

research and likely eco-friendly substance to give a good solution to the problem of highly toxic chemicals causing environmental pollution.

Enzymes, generally, act in low temperature with excellent efficacy.

It saves high cost of energy consumption compared to conventional process. Moreover, it reduces Biological/Biochemical Oxygen Demand (BOD) and Chemical Oxygen Dmand (COD), and other waste water effluent load thus reduces ETP operational cost.

The fabrics treated with harsh chemicals are also unsafe for human health (may affect on human skin) but bio scoured fabrics are completely safe.

Cont….Bioscouring is a process by which alkaline stable

pectinase is used to remove pectin and waxes

selectively from the cotton fibre.

Pectinase, as the name suggests, hydrolyses pectins

present in cotton as a non-cellulosic impurity.

This process is substrate-specific and does not alter

the cellulose component.

It takes place at lower temperatures and does not

swell or remove the seed coat fragments called

motes, which can be beneficial when scouring for the

'natural look'.

Types of enzymes that are used for bio-

scouring process

• Pectinase:-Pectinases are used for the removal

pectic substances from cotton.

• Lipases :- They are used for the removal of

natural fatty substances from cotton

• proteases:- proteases are enzymes that catalyse

the hydrolysis of proteins.

Mechanism of bio-scouring To break the outer pectin layer of cotton fibre, Pectinase

enzymes can be used. In general, it can be said that the

pectinases or pectinolytic enzymes catalyze the random

hydrolysis 1, 4- alpha-D-galactosiduronic linkages in pectin

substance.

There are Four main types of enzymes are used to break down

pectin substances namely protopectinases, pectin esterases,

polygalacturonases and pectin lyases.

Protopectinases: These enzyme catalyze the solubilisation of

insoluble protopectin and give rise to highly polymerized soluble

pectin.

Protopectin (Insoluble) + H2O Protopectinases Pectin (

Soluble)

Cont…

• Pectin Esterases: These liberate pectin and

methanol by de-esterifying the methyl ester

linkages of pectin backbone.

They are active in the pH range of 4-8. Optimal temperature

range for maximum activity is 40- 50 degree C.

Cont…

• Pectin Lyases:Transeliminase or shortly lyase(depolymerase) catalyses the cleavage of α (1 4) bonds inpolygalacturonan chain without releasing water andcreating a double bond (producing an unsaturated product)between the C4 and C5 atoms. Endo and exo enzymeswork within or at the end of the chain, respectively,similar to the polygalacturonases.

Cont…

• In a much simplified way, the action of the abovementioned Pectinase enzymes can be summarizedpictorially in the figure given below:

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 ………………………………………. 0.5-1.5 g/l

Temperature : .....................................60oC

Time : ................................................30 min

M: L : ................................................1:10

PH : ...................................................6-9

Here, 1. Water,wetting agent, PH buffer and fabric; 2. Enzyme (pectinase); 3. Emulsifier. Figure: Bioscouring processing curve

Comparison of Bio-Scouring and

Alkali Scouring

Bio-scouring

Blend of Enzymes-

Pectinase + Protease

Removes Pectin,

protein, Wax, Oil etc

Alkaline-scouring

Sodium Hydroxide

Remove Pectin, Protein, Wax, Oil, Cellulose

Results of Bio and Alkaline scouring

Bio-scouring

Soft Handle

cellulose with complete removal of Impurities

No core Alkali neutralization, thus less washing cycle

Less TDS, COD, BOD

Alkaline-scouring

Harshness

cellulose with complete removal of Impurities and partial Callulose

Required core alkali neutralization, thus more washing cycle

More TDS, COD, BOD

Cont……

Cost

Bio-scouring

Direct cost is more

but Overall cost is less

(Grey to finished)

Alkaline-scouring

Direct cost is less

but Overall cost is more

(Grey to finished)

CONT…

. Examples of Bio-Scouring and Alkaline Scouring

Advantages of Bio-scouring

• Save energy

• Save cost

• Water saving

• Temperature saving

• Time saving

• Smoother surface profile(Fully retain cellulose structure)

• Lesser weight loss

• Lesser costs of auxiliaries

• Mild application condition

• Environmental benefits

• Reduces effluent treatment process/ ETP cost

Disadvantage of bio-scouring

• Inability of removing of cotton fiber waxes.

• Enzyme activity can, however, be reduced or even

completely destroyed (denatured) by high temperatures,

extremes of pH and high concentrations of electrolytes

that destroy their three-dimensional structures. Heavy

metal ions and oxidizing and reducing agents also

deactivate the enzymes.

• The degree of whiteness is often less and the process is

not suitable for removing seed-coat fragments and mote

adequately.

Summary

Though the conventional scouring process is extremely using now-a-days, it has great bad effect on environment.

Many of the developed countries are avoiding the convention-al scouring process replacing enzymatic, ecofriendly, scouring processes.

Bioscouring is an eco-friendly scouring process it has great future.

The new enzymatic procedure is corresponding with a significant role in minimising the de-mandof energy, water, chemicals, time and costs.

Thank you