The Effect of Various Bleaches on Lignin Content in Paper

Paper strength and longevity varies with the amount of lignin bound in the paper. Lignin is a fiber, the bonds it makes allows trees and plant to grow past where gravity would otherwise let them, but as it breaks down it releases acids. This acid breaks down the other fibers and dye in paper. The more lignin in paper, the weaker it is and the more likely that it will wear down more quickly than it should. To limit the amount of lignin in paper, bleaches are used. The most common bleaches are calcium carbonate (CaCO3), sodium hypochlorite (NaClO) and hydrogen peroxide (H2O2). Each bleach is rarely used alone, so little is known about their individual effects. The experiment described in this paper tested each of these bleaches, to investigate which bleach had the greatest effect on lignin in paper.

The process of recycling paper was performed using each bleach individually. Since there is no direct way to measure lignin it was tested indirectly by using the pH to measure the acid produced by it. Of the three bleaches used, hydrogen peroxide (H2O2) had the most significant effect on the lignin content because its pH levels were the highest. This signifies the biggest decrease in lignin.. In the second set of data the fading of the paper color was measured using a color scale. The hydrogen peroxide (H2O2) also had the least amount of fading and is most favorable.

Research Done By:

Josie-Lynn Patalon
Cousino High School

Kaitlin Soper
Fitzgerald High School