TCF bleaching of eucalypt kraft pulp with oxone

Abstract

TCF delignification and bleaching of kraft eucalypt pulp using ozone and oxone under alkaline conditions has been investigated. The pulp samples were bleached in two stages of oxone (Ox) treatment using an AZOx1Ox2 sequence. Pulp brightness greater than 84% ISO was achieved. The effects of oxone charge, alkali charge, bleaching temperature and time on the bleaching response were studied. The colour removal was determined from the chromaticity coordinates (L*, a* and b*) and 98% colour removal was achieved. Accelerated ageing experiments showed excellent brightness stability with very little brightness reversion (or thermal degradation) of the oxone treated pulp. Improvements in pulp strengths compared to ozone and acid treatments were achieved along with significant HexA removal demonstrating the feasibility of oxone in TCF bleaching.