The kappa number (K n) reduction of oil palm empty fruit bunch (EFB) soda-anthraquinone (AQ) pulp by oxygen delignification was limited to only 34% to avoid substantial cellulose degradation. Thus, a preliminary study of photo-pretreatment was performed to improve the bleaching selectivity, and its effect was compared with the AQ-aided H 2 O 2 reinforced O-stage (O p-stage). The results showed that both methods performed better selectivity than the ordinary O-stage. It was suggested that the

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... to-treatment improved selectivity by diminishing carbonyl-induced carbohydrate degradation. Conversely, the AQ-aided O p-stage delivered higher delignifying power with minimum cellulose degradation. For pulps with the K n above 6.0, the effectiveness of both methods was about the same, but to achieve lower K n (5.8 and below), the AQ aided O p pulps exhibited better selectivity.