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

Bleaching of paper involves the removal of lignin from wood pulp to achieve brightness and whiteness [3]. Historically and industrially, chlorine and its derivatives are the primary agents used for this purpose [3]. Chlorine gas is used to manufacture bleaching powder, which is specifically applied for bleaching wood pulp in paper factories [2]. Modern industrial processes often utilize chlorine dioxide (ClO2) in a method known as Elemental Chlorine Free (ECF) bleaching, which is currently the global technological standard for sustainable paper manufacturing [3]. While the options list 'Chloride', in the context of general chemistry and competitive exams, it refers to chlorine-based bleaching agents (like chlorine gas or bleaching powder) derived from chloride sources [3]. Other options like chlorobenzene, ammonium chloride, and hydrochloric acid are not standard bleaching agents in the paper industry [3].

Sources

1. [2] Science , class X (NCERT 2025 ed.) > Chapter 2: Acids, Bases and Salts > Bleaching powder is used – > p. 31
2. [3] Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 11: Industries > PAPER INDUSTRY > p. 56
3. [1] Science , class X (NCERT 2025 ed.) > Chapter 2: Acids, Bases and Salts > Bleaching powder > p. 30