Question

The end bleaching agent used to remove last traces of colour bodies from the pulp is

• A. \(ClO_2\)
• B. \(MgO\)
• C. \(SO_2\) gas
• D. Mercaptans

Hint:

Chlorine dioxide \((ClO_2)\) is an important pulp bleaching agent used to improve final brightness.

Answer 1

The Correct Option is A

In pulp and paper industry, bleaching is done to remove coloured impurities from pulp. The colour in pulp is mainly due to lignin and other colouring bodies. Bleaching is usually done in stages. The final or end bleaching stage requires a strong and selective bleaching agent. Chlorine dioxide: \[ ClO_2 \] is widely used as a bleaching agent in pulp bleaching. It is effective in removing the last traces of colour bodies. It improves brightness of pulp without excessive degradation of cellulose. Magnesium oxide is not a bleaching agent for this purpose. Sulphur dioxide gas is a reducing agent but not the standard end bleaching agent here. Mercaptans are sulphur compounds and are not used for pulp bleaching. Therefore, the end bleaching agent is: \[ ClO_2. \]