Chlorine-Free Bleaching of Kraft Pulp from Oil Palm Empty Fruit Bunches

Abstract

Chlorine-free bleaching was carried out on kraft pulp from oil palm empty fruit bunches (EFB) with an oxygen (O₂) - acid (H₂SO₄) - ozone (O₃) - hydrogen peroxide (H₂O₂) bleaching sequence. The κ-number (= an indicator of lignin content) of the pulp was reduced considerably after these processes indicating that most of the lignin present in the pulp can be removed using this chlorine-free sequence. Handsheets of both bleached and unbleached EFB pulp were prepared and their paper properties were determined. Brightness, a measure of the whiteness of paper, was achieved to ca. 75% for the bleached EFB pulp, showing a possibility of achieving 80% of brightness by chlorine-free bleaching. Paper strengths as indicated by tensile, tear and burst indices as well as stretch did not show significant differences between before and after bleaching. It is notable that these results were obtained despite a large decrease in viscosity by the bleaching process. Moreover, the EFB bleached pulp showed comparable strengths to hardwood pulps, indicating that EFB has the potential as a raw material for chemical pulp production using chlorine-free bleaching sequences.