Total chlorine free bleaching of old corrugated containers pulp

Abstract

Old corrugated container (OCC) pulp was upgraded to bleached pulp through a total chlorine-free (TCF) bleaching sequence consisting of formic acid (FA) delignification, followed by peroxyformic acid (PFA) treatment and two-stage alkaline hydrogen peroxide bleaching. In the FA delignification, the kappa number decreased from 51.5 to 42.9 after 2 h with minimal mass loss which shows selective lignin removal. The subsequent PFA treatment further reduced the kappa number to approximately 31 and increased the ISO brightness to about 24%. Two-stage alkaline peroxide bleaching resulted in a pulp brightness of 70–77% ISO and a yield of 49–52%. The bleached pulp exhibited a viscosity of 2.02–2.34 mPa·s, a holocellulose content of approximately 93%, and α-cellulose content of up to 84%. The pulp exhibited a tensile index of 38.1 N·m/g, a burst index of 1.09 kPa·m²/g, and a tear index of 2.03 mN·m²/g at a pulp freeness of 280 CSF. The FA/PFA-based TCF bleaching produced a moderate-strength, high-brightness pulp from OCC, which was suitable for paper and board applications.

Bangladesh J. Sci. Ind. Res. 61(2), 85-94, 2026