Question

The Kraft process of chemical pulping involves a mixture of two chemicals in water which are?

• A. NaOH, and Na$_2$S
• B. NaOH, and NaCl
• C. NaCl, and Na$_2$S
• D. NaOH, and K$_2$S

Hint:

Remember: The Kraft process uses a "white liquor" made of NaOH and Na$_2$S to efficiently remove lignin and separate cellulose fibers for paper production.

Answer 1

The Correct Option is A

The Kraft process, also known as the sulfate process, is one of the most widely used chemical pulping methods in the paper industry.
Its primary function is to separate lignin from cellulose fibers in wood. Lignin is a complex organic polymer that binds cellulose fibers together.
In this process, wood chips are cooked in a solution called "white liquor", which is an aqueous mixture of two primary chemicals:
- Sodium hydroxide (NaOH)
- Sodium sulfide (Na$_2$S)
These two chemicals play distinct roles:
- NaOH: Acts as a strong base to break down lignin and hemicellulose, making cellulose accessible.
- Na$_2$S: Enhances the delignification efficiency by aiding in the cleavage of certain chemical bonds in lignin that NaOH alone cannot efficiently break.
Other options like NaCl and K$_2$S are not used in the Kraft process. NaCl is a neutral salt and has no active role in delignification. K$_2$S is not commonly used because sodium-based reagents are more cost-effective and efficient.
Therefore, the correct chemicals used in the Kraft process are NaOH and Na$_2$S.