Which substance is used to bleach the pulp?

Alkaline hydrogen peroxide
Alkaline hydrogen peroxide is the most commonly used bleaching agent for mechanical pulp.

Why bleaching is done for pulp preparation?

Pulp bleaching processing plays an important role in paper making, it is mainly used to improve lightness of paper pulp and get quality pulp with certain whiteness, cleanliness, purity and excellent physical and chemical characteristics. Pulp bleaching processing increases its applications.

What are the main differences between bleaching of chemical pulps and bleaching of mechanical pulps?

As chemical pulps are dark to begin with, bleaching increases brightness up to 70% with a maximum brightness of about 92%. Unlike bleached mechanical pulps, the high brightness is stable as the lignin is removed.

Why are some pulps bleached?

Bleaching is the process of making pulp white to improve print- ing properties and its ability to absorb liquids. Bleaching also attacks some contaminants to reduce stray dark colored parti- cles in the final sheet of paper. Bleaching processes add significantly to the total cost of making pulp.

What is bleach chemical?

Household bleach is actually a mixture of chemicals, Its main constituent is a solution of ~3-6% sodium hypochlorite (NaOCl), which is mixed with small amounts of sodium hydroxide, hydrogen peroxide, and calcium hypochlorite.

Which chemical is used in alkali bleach stage?

Hydrogen peroxide is best known for its bleaching reactions at alkaline pH in mechanical and chemical pulp bleaching as well as deinking. Hydrogen peroxide can also be used as a starting chemical for the production of peroxy acids.

What is the main purpose of bleaching?

bleach, solid or liquid chemical used to whiten or remove the natural colour of fibres, yarns, other textiles, and paper. In textile finishing, the bleaching process is used to produce white cloth, to prepare fabrics for other finishes, or to remove discoloration that has occurred in other processes.

Why lignin is removed from pulp?

(Lignin, the natural “glue” that holds cellulose fibers together and stiffens plant stems, causes paper made of wood pulp to weaken and discolor rapidly if not removed in the pulp mill; but the removal processes are harsh, and shorten the fibers on which the paper’s strength depends.)

What is TCF paper?

Chlorine-free paper is categorized as either “totally chlorine-free” (TCF) or “elemental chlorine-free” (ECF). TCF paper is produced with pulp that has been bleached without any type of chlorine, or that has not been bleached at all.

What are the components of bleach?

What is bleach? Household bleach is actually a mixture of chemicals, Its main constituent is a solution of ~3-6% sodium hypochlorite (NaOCl), which is mixed with small amounts of sodium hydroxide, hydrogen peroxide, and calcium hypochlorite.

What are the properties of bleach?

Structure of Sodium Hypochlorite

• Its molar mass is 74.4 g. mol-1.
• Sodium hypochlorite pentahydrate is a greenish-yellow solid.
• It has chlorine-like and a sweetish odor.
• Its melting point is 18 ℃.
• Its boiling point is 101 ℃.
• It is soluble in water.
• Its density is 1.11 g.cm-3.
• It is corrosive.

What is the best bleaching agent?