Biomimetic TCF Bleaching of Pulp by Simple Inorganic Complexes of Cupric/Cobalt Acetate

Oxygen delignified kraft pulp from eucalyptus (E. urophylla × E. grandis) was catalytically pretreated in aerobic condition using ammonium persulfate in present of catalists like cupric acetate and/or cobalt acetate in acetic acid-water solution, i. e. S2O82--Cu2+, S2O82--Co2+ and S2O82--(Cu2++Co2+). Final bleached pulp after pretreatment with the three catalytic systems showed higher delignification (23.45%, 21.85% and 19.63% respectively), better optical properties (82.93, 82.18 and 81.92% ISO brightness respectively) and pulp viscosity (787, 791 and 762 mL/g respectively; mL/g: intrinsic viscosity unit of pulp)than the control pulp (14.12% delignification, 77.33% ISO brightness and 746 mL/g viscosity). S2O82--Cu2+ and S2O82--Co2+ showed similar reduction in hydrogen peroxide consumption (61.91%, 62.48%), and S2O82--(Cu2++Co2+) showed a greater reduction in hydrogen peroxide consumption than the two treatments (83.05%). Some improvements in tensile and tear strength of the resulting pulp were observed. The new sequence also yields composite effluents with larger percentage of lignin aromatic compounds compared to the control.