Influence of Ozone and Peracetic Acid on Pulp and Effluent Characteristics, 1997 Pulping Conference Proceedings

Pulp and effluent characteristics were compared for softwood (mixed pine and spruce) and hardwood (birch) pulps bleached in TCF sequences based on ozone and peracetic acid. The results show that ozone charge is clearly correlated with the formation of alkali-labile carbonyl groups and with the amounts of carbohydrates and oxalic acid dissolved in the effluents. Alkali lability proved to be connected with ozone bleaching, especially when high ozone charges are used to treat pulp of low kappa number.

The dissolution of hemicelluloses and formation of carbonyl groups in pulp at high ozone charges were both reflected in pulp strength characteristics. No indications of alkali-lability have so far been seen on bleaching with peracetic acid. Lower amounts of oxalic acid and carbohydrates are dissolved in the effluents from the peracetic acid stage than from the ozone stage. Lowering the ozone charge by combining it with chlorine dioxide, or reducing the carbonyl group content by borohydride reduction both resulted in lower dissolution of carbohydrates and improved strength properties.