New polyoxometalate-laccase integrated system for kraft pulp delignification

New polyoxometalate-laccase integrated system (PLIDS) employing polyoxometalate [(SiW11VO40)-O-V](5-) and laccase of Trametes versicolor for the continuous delignification of eucalypt kraft pulp has been developed. Pulp was delignified in a batch reactor containing catalytic amounts of [(SiW11VO40)-O-V](5-) at about 90 degrees C under atmospheric pressure. Re-oxidation of reduced polyoxometalate (POM) with laccase was carried out at 45 degrees C in a separate aerated bioreactor coupled with an ultrafiltration tubular ceramic membrane. This allowed the separation of laccase from re-oxidized POM, which was supplied in turn continuously to the delignification reactor. Proposed PLIDS allowed sustainable pulp delignification with minimal degradation of polysaccharides. The implementation of PLIDS, instead the fist chlorine dioxide stage (D) in conventional DEDED bleaching sequence, showed almost 60% of chlorine dioxide savings with strength properties of the bleached pulp (90% ISO) similar to those obtained after the conventional bleaching. (c) 2006 Elsevier B.V. All rights reserved.