Enzymatic Biobleaching of Recalcitrant Paper Dyes

Bleachability;Decoloration;Dyes;Enzymes;Fungi;Laccase;Mixed waste papers;Stilbenes

Knutson, Kristina Parks ; Institute of Paper Science and Technology

University:Georgia Institute of Technology

Department:Institute of Paper Science and Technology

关键词: Bleachability;    Decoloration;    Dyes;    Enzymes;    Fungi;    Laccase;    Mixed waste papers;    Stilbenes;   

Others  :  https://smartech.gatech.edu/bitstream/1853/7959/1/Thesis%20Knutson.pdf

美国|英语

来源: SMARTech Repository

【 摘 要 】

Modern manufacturing processes assume efficient utilization and recycling ofnatural resources whenever possible. Over the past decade paper recycling has progressedfrom 33.5% in 1990 to just above 48% in 2002.1 Indeed, for certain select grades,(newspaper and old corrugated containers) greater than 70% is currently being recycled.In contrast, mixed office waste and colored directory papers are often underutilized. Amajor difficulty in recycling these grades of paper is the problems associated withdecolorizing the dyes present in the paper.2 Of the commonly used paper dyes, thestilbene dye Direct Yellow 113 and methine dye Basazol 46L are notorious4 for poorbleachability with the commonly used chemical bleaching agents including chlorinedioxide, oxygen, hydrogen peroxide and sodium dithionite.The ability of white-rot fungi to decolorize colored effluents containing textiledyes is currently the subject of intensive research efforts. The secreted enzymes involvedin dye decolorization include manganese peroxidase, lignin peroxidase and laccase.Laccase, a lignolytic enzyme, has also been studied for many years for the biobleachingof wood pulps. The ability of laccase to delignify pulp is greatly enhanced by the additionof small molecule mediators such as 2-2´ azinobis (3-ethylbenzthiazoline-6-sulfonate)(ABTS) and 1-hydroxybenzotriazole (HBT).This research project focused on applying laccase combined with a mediator todecolorize C.I. Direct Yellow 11 and Basazol 46L. Three mediators were tested: ABTS,HBT and violuric acid. Laccase/ABTS was most effective with 60% of the color beingremoved. The level of color removal was maintained at 60% even when ABTSconcentration was lowered from 5 mM to 0.01 mM. When laccase/1 mM ABTS wasapplied to Direct Yellow 11 in solution, the majority of color loss occurred within 60minutes.The ability of soybean (SBP) and horseradish (HRP) peroxidases and laccase todecolorize Direct Yellow 11 and Basazol 46L in solution was also examined. The resultsdemonstrated that these two recalcitrant dyes could be effectively decolorized byenzymatic treatments by horseradish peroxidase, soybean peroxidase, and laccase withABTS as mediator. SBP is effective from pH 4.5 to 8.5. The stilbene dye Direct Yellow11 responded to both SBP and laccase/ABTS. For the methine dye Basazol 46L, SBP wasa more effective treatment than HRP or laccase/ABTS. Basazol 46L responded quickly toSBP treatment with 74% reduction in signal intensity within 5 minutes.To evaluate the effectiveness of laccase/ABTS treatment, pulp dyed with DirectYellow 11 and three commercial colored pulps were subjected to seven differentbleaching treatments. These treatments consisted of 1)laccase/ABTS; 2)laccase/ABTSfollowed by alkaline extraction; 3)laccase/ABTS followed by bleaching with sodiumdithionite; 4)oxygen bleaching; 5)oxygen bleaching followed by dithionite treatment;6)alkaline hydrogen peroxide bleaching; and 7)alkaline peroxide bleaching followed bydithionite treatment. The best results were obtained by including reductive bleaching withsodium dithionite. For Direct Yellow 11 dyed pulp, laccase/ABTS followed by dithioniteyield comparable reduction in color to oxygen or peroxide followed by dithionite.