ABSTRACT

Solvent extracts of samples of waste cooking liquor (WBL, weak black liquor) from several Canadian kraft pulp mills were analyzed by gas chromatography/atomic emission detection (GC/AED). Of particular interest were the sulfur-containing compounds that might be useful chemical markers of WBL in final effluent. The WBL samples were extracted under four conditions: air excluded, moderate aeration, after oxidation by hydrogen peroxide (H2O2) and after treatment by alkaline zinc oxide (ZnO2−2) solutions. The types and amounts of compounds present in the extracts were dependent on the degree of oxidation of the black liquor prior to sampling, the treatment after sampling and the degree of oxidation during the extraction phase, and prior to extraction. One WBL was fractionated using silica gel and the chromatograms of the fractions were compared to chromatograms of similar fractions derived from treated final effluent from the same mill. One S-containing compound was found in both the black liquor and the effluent. The major sulfur compounds observed in the slightly oxidized black liquors were elemental sulfur (S8), dimethyltrisulfide and dimethyltetrasulfide. The occurrence of these compounds in the extracts discussed.