Question

Bleaching by hydrogen peroxide occurs at ____ °C for _____h.

(a) 40°C, 2 h

(b) 60°C, 2.5 h

(c) 40°C, 3 h

(d) 10°C, 4 h

The question was posed to me during an interview for a job.

Question is taken from Pulping, Digestion and Bleaching in section Paper and Paper Based Packaging Materials of Food Packaging Technology

Answer 1

Right option is (c) 40°C, 3 h

To explain I would say: Bleaching by hydrogen peroxide occurs at 40°C for 3 h. It is followed by neutralization and destruction of excess peroxide with SO2. These pulps may be improved in color to only a limited extent since they contain virtually all the lignin from the original wood. Peroxide bleaching allows brightness to be increased by nearly 20%.