Eco friendly in textile processing

Supercritical Carbon Dioxide... What is supercritical carbon dioxide?.  A supercritical fluid is a substance above its critical temperature and critical pressure.. Above 31.10C and 73 a

Eco Friendly In Textile Wet

Processing

By

Supercritical

Carbon Dioxide

What is supercritical carbon

dioxide?

 A supercritical fluid is a substance above its

critical temperature and critical pressure Under these conditions the distinction between gases and liquids does not apply and the substance can only be described as

a fluid.

Supercritical Fluid of CO 2

Above 31.10C and 73 atm carbon dioxide behaves as a supercritical fluid and shows properties of both a liquid and a gas

It fills the container, like a gas, and dissolves substances like a liquid.

Supercritical fluid of CO 2

 With an increase in

temperature the meniscus begins to diminish.

 The liquid density falls due

to expansion and the gas density rises as more of the substance evaporates.

Supercritical fluid of CO 2

 Once the critical

temperature and pressure have been reached the two distinct phases of liquid and gas are no longer visible The meniscus can no longer

be seen One homogenous phase called the

"supercritical fluid" phase occurs.

Industrial extraction with

supercritical CO 2

 Decaffeinating coffee and tea

 Extracting bitterness to make beer

 Defatting cocoa powder

 Extracting spices and aromatic plants

Significant properties of

supercritical fluids

Diffusivity gas > supercritical fluid > liquid Viscosity gas < supercritical fluid < liquid Surface tension gas = supercritical fluid < liquid Density gas < supercritical fluid < or =

liquid

Benefits of using supercritical CO 2 for

extraction

 It is having the penetration power of a gas

and the extraction power of a liquid.

 It acts as a solvent to extract organic

compounds with a low molecular weight.

 It leaves no residual trace on treated

material

 It respects the environment.

Supercritical CO 2 as solvent

 Purification of specialty chemicals and

useful natural products

 An alternative solvent in coatings industry

(replacing 40 - 90% of volatile solvents)

 Degreasing and dry cleaning applications

 Increasingly applied as a solvents in

synthetic industrial processes

Use of supercritical CO2 in dyeing processes

Use of supercritical CO2 in dyeing processes

Enzymes

Electron-ray treatment

Microwaves are electromagnetic waves whose frequency ranges from 1000MHz to10,00,000 MHz.

Microwave dyeing takes into account only the dielectric and the thermal properties.

The dielectric property refers to the intrinsic electrical properties that affect the dyeing by dipolar rotation of the dye and influences the microwave field upon the dipoles.

 The aqueous solution of dye has two components

which are polar, in the high frequency microwave field oscillating at 2450MHz It influences the vibrational energy in the water molecules and the dye molecules.

 The heating mechanism is through ionic

conduction, which is a type of resistance heating Depending on the acceleration of the ions through the dye solution, it results in collision of dye molecules with the molecules of the fiber.

 This helps and affects the penetration of the dye

and also the depth to which the penetration takes place in the fabric This makes microwave superior

to conventional dyeing techniques

Ultrasonic Treatments

Electrochemical dyeing

Vat and sulphur dyeing involves both a reducing and an oxidising step, which are carried out with chemical oxidants and reducing agents The environmental concerns associated with the use of these chemicals are many An attractive alternative technique is to reduce and oxidise the dye by means of electrochemical methods.

With direct electrolysis the dye itself is reduced at the surface

of the cathode In indirect electrolysis the reducing power of the cathode is transferred to the solution by a soluble reversible redox system (e.g based on antraquinone chemistry

or iron complexes) With this reversible redox system the reducing agent is continuously regenerated at the cathode, which thus allows full recycling of the dye bath and the reducing agent.

Plasma Treatment

4 th State of Matter

+ve, -ve Charges,

Radicals, Electrons, Excited molecules, atoms.

Electrically neutral

Lightening bolt

Sun

Fire

Hydrogen Bomb

RT to Over 50,000°C

Thermal Plasma Cold Plasma Hybrid Plasma

Thermal Plasma

Thermal Equilibrium Between

Neutral Particles and

the Charged Particles

Potential Difference > Dielectric Strength