The role of dibenzo-p-dioxin and dibenzofuran precursors in the formation of tetrachlorinated dibenzo-p-dioxins/-furans during bleaching

The position of the theoretical line describing dioxins control technology is dependent upon the concentration of dioxins precursors in brownstock. The tolerance of the bleaching process to precursor contamination increases as chlorine dioxide substitution increases to the extent that when 100% substitution is used, at the highest levels of precursor contamination studied, 2378-tetrachlorodibenzo-p-dioxin is non-detectable in pulp, and 2378-tetrachlorodibenzofuran is detectable but only at background laboratory levels.