BLEACHING EFFICIENCY OF FORMAMIDINE SULFINIC ACID (FAS) IN COMPARISONTO HYDROSULFITE, BOROHYDRIDE, AND PEROXIDE IN ONE AND 2 STAGES

This study evaluates the potential of a reducing agent formamidine sul finic acid (FAS), for bleaching a spruce-balsam thermomechanical pulp. We review the main conclusions of the previous study that we conducte d on optimizing bleaching results with FAS and conventional bleaching with hydrosulfite, borohydride, and peroxide. Results of mixing FAS wi th the other bleaching agents in one stage or two sequential stages ar e compared. We also report the effect of these reducing agents when ap plied in sequence with an oxidizing stage using peroxide. The effect o f a chelating agent, such as DTPA, on FAS bleaching in one stage is sh own. We discuss two interstage treatments, simple washing and neutrali zation of peroxide, for sequential two-stage bleaching with peroxide a nd FAS. These results are discussed in terms of brightness and CIE col or coordinates. Blenching costs are compared to evaluate the feasibili ty of FAS bleaching.