MOLECULAR-WEIGHT DISTRIBUTIONS OF ORGANIC HALOGENS IN BLEACHED KRAFT PULP-MILL EFFLUENTS

The molecular weight distribution of chlorinated compounds of bleached kraft mill effluent (BKME) was studied by aqueous and nonaqueous size exclusion chromatography (SEC) and by ultrafiltration. Ninety percent of the BKME halogenated organics dissolved into tetrahydrofuran used as a nonaqueous SEC eluent. The tetrahydrofuran-soluble component of the BKME had the same molecular weight distribution as the original BKME when both were analyzed by aqueous SEC. Over 85% of the chlorinated material of BKMEs studied by nonaqueous SEC was of low molecular mass (<1000 g/mol). This was confirmed by vapor pressure osmometry. The amount of BKME components retained on ultrafiltration MW >10000 decreased to one-fourth upon 100-fold dilution with distilled water, indicating that the halogenated components occurred as micellar aggregates. We conclude that the molecular weight distribution of the BMKE chlorinated material obtained by nonaqueous SEC is more accurate than that obtained in aqueous media unless high dilution is applied.