CHARACTERIZATION OF EFFLUENT FRACTIONS FROM CLO2 AND CL-2 BLEACHING OF UNBLEACHED AND O-2-BLEACHED SOFTWOOD KRAFT PULPS

Effluents from OC(EO), OD(EO), and D(EO) laboratory bleaching of softw ood kraft pulp were characterized by fractionation and analysis of the fractions. Each fraction was characterized by size and ratio of chlor ine to carbon. Replacement of chlorine with chlorine dioxide after oxy gen bleaching sharply reduced the adsorbable organic halide (AOX), tot al organic carbon (TOC), and chlorine-to-carbon ratio of the whole eff luents. Larger AOX, TOC, and Cl/C-100 reductions were seen in the ethe r-soluble fraction and in the phenolic subfraction of the ether-solubl e material. Oxygen delignification prior to a 100% chlorine dioxide st age reduced whole effluent AOX and TOC in rough proportion to the amou nt of lignin removed in the oxygen stage, but did not affect the overa ll Cl/C-100. There was a significant reduction in the Cl/C-100 of both the phenolic and neutral subfractions of the ether extract. Oxygen de lignification, like chlorine dioxide substitution, may therefore be mo re beneficial than the overall AOX reduction suggests.