Bleaching study of kenaf mechanical pulps

Optimization studies of hydrogen peroxide bleaching were carried out on two kinds of kenaf mechanical pulps. One was composed of whole kenaf with 65% core fiber ("kenaf"), and the other was made up of kenaf bark with 22% core fibers ("bark-22"). The kenaf and bark-22 pulps reached brightnesses of 62.0% and 64.0%, respectively, with only 1.0% H2O2 and 1.0% NaOH. With <LF>higher H2O2 and NaOH dosages, both pulps can be bleached to 75.0% ISO brightness. Results showed that peroxide consumption is higher for whole kenaf than for bark-22, probably because core fibers are higher in extractiveness and lignin. For each combination of H2O2 and NaOH dosages tested, the bleaching efficiency was better for bark-22 than for kenaf.