Extraction methods of Dyes from plants, Natural and Synthetic dyes, Sources of dyes

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Dyes are the water-soluble plant extract that can be obtained from leaves, stem, root and flower. Dyes gives characteristic color to an object.


Difference between dyes and Pigments

Dyes are water soluble plant extract, while Pigments are insoluble in water.

CLASSIFICATION OF DYES.

Dyes can be classified into Natural and Synthetic.

Natural dyes are the plant extracts.

Synthetic dyes are obtained from Coal Tar example: Aniline dye.

HOW DYES COLOR THE FABRICS?

Fibres contains charged particles, these particles bounded with dyes by Hydrogen and Hydrophobic interactions which is necessary for adsorption of dye on fabric.

Fabric contains cellulose which act as binding site for dyes, the number of binding sites can be changed by altering the structural configuration of cellulose polymer.

WHAT ARE MORDANTS? 

There are some substances that increase the adhesion of dyes to fibres thus act as holdfast on fabrics for dyes knowns as Mordants.

Mordants are usually salts of metals.

Examples: Copper sulphate, Ferrous sulphate, Potassium chromate etc.

SOURCE OF NATURAL DYES

Natural dyes can be obtained from various plants such as:

Rubia tinctorum: Red dye from the root extracts can be prepared from this plant.

Indigofera tinctoria : Indico blue dye can be extracted from the leaves.

Lawsonia intermis: Leaves of Henna plant can be used as natural dyes.

Crocus sativus: The red stigma of saffron flower can be used ion dye making.

Haematoxylon compechianum: This logwood tree is source of black dye Hematoxylin used for staining purposes in labs.  

EXTRACTION METHODS FOR OBTAINING DYES

Some of the steps for extraction of dyes are as follows:

1.Fermentation: 

* In this method microorganisms are used for extracting dyes. Indigo from Indigofera       tinctoria is extracted by this method by following steps:

* Leaves and branches once harvested from plant are covered with water in a tub this     promotes fermentation.

* The partially rotted plant matter is then collected.

* The material get pressed into cakes.

* Upon drying these cakes grounded to fine powder that produces colored solution in water after exposure to air.

* The process of indigo dye production was originated in India.

* The Indigo dye is of exceptional quality and color fast in nature.

2.Aqueous extraction: 

* In this method the raw material is first dried and then grinded.

* The grinded material then soaked in water (Aqueous)

* The soaked material then boiled and filtered; the filtered material obtained can be used in  dyeing purposes. 

3.Microwave extraction:

*This method is used for faster rate of extraction of dyes from plant like Bixa orellena 

*In this method the plant material like flower passed through microwaves so that high   temperature fastens the rate of extraction. The powder is the prepared and used as dye.


4.Alkaline extraction:

* In this method acids or alkali are used for extracting dye from plant material.

* The plant material kept in acidic medium containing dilute acid that attacks on glycosides  of plant material and hence hydrolyze it. This releases the dye from plant into the medium.

Watch the complete video with simple explanation:





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