LABORATORY INVESTIGATION OF PCDD/Fs AND DIOXIN-LIKE COMPOUNDS FORMATION DURING CHLOR-ALKALI PROCESS

Abstract We examined polychlorinated dibenzo-p-dioxin, polychlorinated dibenzofuran (PCDD/Fs) and dioxin-like compounds formation during brine electrolysis with pitch used as the binding agent of graphite electrode. Graphite electrode was used in the past as an industrial process of chlorine production. The level of PCDFs was up to 1,800,000pg/L (28,000pg-TEQ/L) in brine electrolysis with pitch. This value corresponds approximately to 150μg/g-pitch ( 4.4μg-TEQ/g-pitch). It was obvious that specific homologue/congener patterns of PCDF from lower to higher components were apparently formed according to electrolytic conditions such as temperature, current density and also pitch form. Amounts of PCDF formation per unit concentration of pitch were 10,000-100,000ng/g-pitch. Additionally, high levels of chlorinated polycyclic aromatic hydrocarbons (Cl-PAHs), which were dioxin-like compounds, were also detected in the above anolyte samples of brine electrolysis. Furthermore, concentrations of Cl-PAHs and the ratio of Cl-PAHs to dioxins varied according to the electrolysis process performed. These results can support the assumption that brine electrolysis by graphite electrode abundantly contained pitch in the past might have been a significantly potential source of Cl-PAHs as well as PCDFs contamination.