Characterization of dissolved wood organics in totally-chlorine-free bleaching kraft pulp mill effluents

Graduation date: 1999Six filtrate samples (liquid state) were obtained from selected stages in a totally-chlorine-\ud free (TCF) bleach pulp mill. The solids were recovered by evaporation on rotary\ud evaporators and by lyophilization with a freeze drier.\ud Chemical contents (inorganic and organic chemicals) of the six filtrates were\ud analyzed quantitatively according to TAPPI Test Methods, 1988. Results showed that\ud the #1BS filtrate had the largest amount of inorganic and organic chemicals, which\ud would influence the pulp mill systems the most.\ud Thin-layer chromatography (TLC) was utilized to qualitatively analyze\ud carbohydrates by using pre-coated cellulose plates. No free monosaccharides were\ud detected in the six filtrates as received. The solids were then acid hydrolyzed and the\ud monosaccharides, D-Glucose, D-Galactose, D-Mannose, D-Xylose, and L-Arabinose\ud were detected in the hydrolyzates of the solids recovered from the filtrates of the early\ud stages of bleaching. This showed that these samples contained both cellulose and\ud hemicelluloses. Wood extractives were also qualitatively determined by TLC using pre-coated\ud silica plates. The freeze-dried solids were extracted with methanol, with distilled water\ud and with ethyl acetate. Results revealed that dihydroquercetin, quercetin and catechin\ud existed in the filtrates from the early stages of bleaching. These catechol-type chemicals\ud will influence the problem of metallic accumulation severely.\ud The results of both carbohydrates and wood extractives were supported by Rf\ud values, Rs (relative resolution) and Rx (relative retention).\ud Pulsed Fourier Transform carbon-13 nuclear magnetic resonance (NMR)\ud spectroscopy was applied to study the functional groups, particularly hydroxyl groups, of\ud the filtrate lignin samples with a proton decoupling method. A commercial kraft\ud softwood lignin, Aldrich lignin, was used as a reference for the TCF mill filtrate lignins.\ud A newly emerged method of lignin acetylation with acetyl chloride enriched with\ud carbon-13 as reagent was introduced The conventional method of using acetic anhydride\ud to acetylate lignin was used as a reference method. NMR spectra showed that the\ud conventional method gave more functional group information, but the method of acetyl\ud chloride acetylation determined the hydroxyl groups with greater resolution and higher\ud speed. The TCF filtrate lignins were different from the commercial Aldrich lignin. Some\ud differences were also found among the TCF filtrate lignins. These may be important for\ud the future research of lignin modeling with metal complexity