Which one among the following is used in bleaching of paper?

The correct answer is  Chloride.

Key PointsBleaching of Paper

• Chloride is commonly used in the bleaching process of paper. It is highly effective in removing color from the pulp, resulting in a white and bright paper product.
• The bleaching process involves chemical reactions that break down the chromophores, which are the color-causing components in the pulp.
• There are various forms of chloride used in the bleaching process, including chlorine gas (Cl2), sodium hypochlorite (NaOCl), and calcium hypochlorite (Ca(OCl)2).
• While chlorine dioxide (ClO2) is also used, it is considered more environmentally friendly compared to chlorine gas due to its lower release of harmful by-products.
• Chloride bleaching agents are preferred because they are cost-effective and have been proven to be efficient in the paper bleaching industry.

Additional Information

• Environmental Impact:
  • The use of chlorine gas in bleaching can lead to the formation of toxic chlorinated compounds, such as dioxins and furans, which are harmful to the environment and human health.
  • To mitigate these effects, the paper industry is increasingly adopting Elemental Chlorine Free (ECF) and Total Chlorine Free (TCF) bleaching processes.
• Elemental Chlorine Free (ECF):
  • In ECF bleaching, chlorine dioxide (ClO2) is used instead of elemental chlorine (Cl2) to reduce the formation of toxic by-products.
  • This process is considered a more environmentally friendly alternative while still being effective in producing high-quality bleached paper.
• Total Chlorine Free (TCF):
  • TCF bleaching eliminates the use of all chlorine compounds, relying on oxygen-based chemicals such as ozone (O3) and hydrogen peroxide (H2O2).
  • Although TCF processes are even more environmentally friendly, they can be more expensive and less effective than ECF processes.
• Paper Bleaching Alternatives:
  • Research is ongoing to find alternative bleaching agents that are both effective and environmentally benign, such as enzymes and natural organic compounds.