a) 40°C, 2 h
b) 60°C, 2.5 h
c) 40°C, 3 h
d) 10°C, 4 h
Answer: c
Explanation: 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%.
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