Post-bleaching of colored office paper with formamidine sulphinic acid and hydrogen peroxide

Colored office paper cause significant problems during recycling. Even if a small amount of colored waste paper fibers are mixed with colorless fibers, the dyestuff separated from the colored paper fiber will also stain other fibers. Therefore this dyestuff should be reduced or stripped for effective recycling. In this study, to enhance the color removal, the color stripping effects of formamidine sulfinic acid (FAS) and hydrogen peroxide (P) at the post-bleaching stage of recycling process were examined. In the study pre-bleached blue, green, red and yellow colored office paper fibers and the mixture of these colored office paper fibers were used. FAS and hydrogen peroxide charges were varied as 0 %, 0,25 %, 0,50 %, 0,75 %, 1,00 %, 1,50 % 2,00 % and 3,00 % during post-bleaching. As a result of the study, FAS has been determined to be a more effective color stripper than peroxide. The CIE a* and b* value of mixed colored office paper fibers were decreased from -12,1 to -1,3 and from 5,5 to 4,0 respectively with 1,5 % FAS usage. This means that FAS was more effective on green than yellow color. On the other hand, hydrogen peroxide was determined more effective on yellow color than others. According to this result, It should be considered to use FAS and peroxide together as (FAS) P or P (FAS) sequence to obtain colorless fibers. FAS and peroxide charges were not affect the tensile and tear index of samples significantly.