What are the cationic dyes?

What are the cationic dyes?

Cationic dyes are also known as basic dyes, and when dissolved in water cationic dyes acts like base. Cationic dyes forms bright shades with high tinctorial values, on fabric and textile materials. Cationic dyes are mainly used on acrylic fibers.

What are cationic and anionic dyes?

Dyes contain three kinds of anionic, cationic, and nonionic dyes. Anionic dyes are divided into direct, acid, and reactive dyes while the cationic dyes are basic dyes. 3 Methylene blue (MB) is a well-known cationic dye for wood, paper, leather, and silk.

Is acid dye cationic or anionic?

Acid dyes are anionic, soluble in water and are essentially applied from acidic bath. These dyes possess acidic groups, such as SO3H and COOH and are applied on wool, silk and nylon when ionic bond is established between protonated –NH2 group of fibre and acid group of dye.

Is basic dye cationic or anionic?

cationic colorants
Specifically, basic dyes are positively charged, cationic colorants. At the molecular level, basic dyes have amino groups, which are responsible for the molecule’s positive charge. Because of their positive charge, basic dyes react with negatively charged compounds.

Is methylene blue a cationic dye?

The Methylene Blue (MB) is a cationic dye, having a molecular formula of C16H18N3SCl and the corresponding molecular weight of 319.85 g/mol. The MB solutions at a concentration of 10 mg/L were prepared in distilled water.

What are non ionic dyes?

Disperse dyes are developed with the aim of solving the problems related to fiber irregularities during dyeing of polymers. Such dyes are non-ionic, carry reactive groups, and are intended to combine the favorable characteristics of disperse and reactive dyes of nylon.

What are examples of anionic dye?

Two anionic dyes were used in this study: namely, Remazol Black and Remazol Red supplied from Bayer, Frankfurt, Germany. Reactive Dyes, of which these are an example, represent about 20–30% of the dyes used worldwide (12).

Is reactive dye anionic or cationic?

Reactive dyes are anionic in character and cotton fibers also adopt anionic surface charge in water causing limited exhaustion of dye due to charge repulsion.

What is endothermic adsorption?

Physical adsorption is essentially exothermic. The reaction of gases with the surface layer of solids may, however, lead to the formation of endothermic compounds. Chemisorption, therefore, may have an endothermic character.

What are disperse dyes made of?

Disperse dyes are suspensions of finely divided insoluble, organic pigments used to dye such hydrophobic fibres as polyesters, nylon, and cellulose acetates.

What is a cationic stain?

Basic stain (Cationic stain) Chromogen or coloured part of basic stain is positively charged. so, it is also known as cationic stain. Basic stain are used to stain negatively charged components such as bacterial cell. Examples: methylene blue, safranin, malachite green,basic fuschin, crystal violet.

Why are basic dyes cationic?

Basic dyes are called cationic dyes because the chromophore in basic dye molecules contains a positive charge. The basic dyes react on the basic side of the isoelectric points. Basic dyes are salts, usually chlorides, in which the dyestuff is the basic or positive radical. Basic dyes are powerful coloring agents.

Which is irreversible adsorption?

Physical adsorption is reversible in nature (due to presence of weak van der waals forces) and chemical adsorption is irreversible in nature (due to presence of strong chemical bonds).

Why adsorption is always exothermic?

Adsorption is an exothermic process since surface particles of the adsorbent are unstable and when the adsorbate is adsorbed on the surface, the energy of adsorbent decreases, and this results in the evolution of heat. Therefore, adsorption is always exothermic.

What is an anionic dye?

Anionic dyes are dyes having components that can make the dye molecule dissociate into negatively charged ions in an aqueous solution. In other words, anionic dyes separate into ions and form anions when added to water. Usually, anionic dyes are acidic dyes.

What ionic nature is disperse dye?

Disperse dyes are non-ionic in nature and partially soluble in water. The interaction of dye molecule and polymer takes place with Van der Waals and dipole forces. Disperse dyes have better diffusion at boiling to a higher temperature.

Is hematoxylin cationic or anionic?

Haematoxylin in complex with aluminium salts is cationic and acts as a basic dye. It is positively charged and can react with negatively charged, basophilic cell components, such as nucleic acids in the nucleus. These stain blue as a result. Eosin is anionic and acts as an acidic dye.

What dyes are positively charged?

Direct, cationic, basic or positive dyes: contain positively charged groups. Examples include methylene blue, basic fuchsin, and crystal violet. These dyes directly bind to and stain the negatively charged surface of bacterial cells.

What is reversible adsorption?

If the gas accumulation on the surface of solid takes place due to weak van der waal forces then it is termed as physisorption or physical adsorption. Here in physisorption the amount of adsorption decreases with increase of temperature and increases with increase of pressure. It is a reversible process.