Reutilization of effluents from laccase-mediator treatments of kraft pulp for biobleaching

Several effluents from laccase-mediator treatments of kraft pulp were recovered and subsequently reused with fresh pulp in order to simulate recirculation of effluents during biobleaching. The effluents were used as a new bleaching stage without any modification except enzyme addition. Pulp treated with effluents were afterwards chemically bleached by using the simple sequence LQPo, where L represents the treatment with effluent and laccase addition, Q is a chelating stage and Po is an alkaline peroxide stage. This system showed a promising potential on delignification, with kappa number ranging from 5.5 to 6.6 after LQPo sequence, depending on the type of effluent employed in L stage. Improvements on pulp brightness were also reported compared with control experiment.