Subcritical (hot/liquid) water dechlorination of PCBs (Aroclor 1254) with metal additives and in waste paint.
No disposal option exists for "mixed wastes" such as paint scrapings that are co-contaminated with polychlorinated biphenyls (PCBs) and radioactive metals. Either removal or destruction of the PCBs is required prior to disposal. Comparison of subcritical water dechlorination (350 degrees C, 1 h) of Aroclor 1254 in paint scrapings (180 ppm) and of standard Aroclor 1254 showed significantly enhanced dechlorination in the presence of paint. While no significant degradation was observed for standard Aroclor (no paint), the dechlorination of PCBs in paint was 99, 99, and 80% for the hepta-, hexa-, and pentachlorinated congeners, respectively, indicating that metals in the paint enhanced the dechlorination reactions. Adding metals to the standard Aroclor (no paint) reactions enhanced PCB dechlorination in subcritical water in descending order of activity: Pb approximately = Cu > Al > Zn > Fe. In the presence of both zerovalent and divalent lead and zerovalent copper in subcritical water (350 degrees C, 1 h), 99% of the Aroclor 1254 mixture (tetra- to heptachlorinated biphenyls) was dechlorinated. High dechlorination (ca. 95%) was also achieved with zerovalent aluminum. In contrast to other metals, lead retained its degradation ability at a lower temperature of 250 degrees C after 18 h. The high degradation efficiency achieved using metal additives in water at reasonable temperatures and pressures demonstrates the potential for subcritical water dechlorination of PCBs in paint scrapings and, potentially, in other solid and liquid wastes.
Kubátová
Alena
A
Energy and Environmental Research Center, Campus Box 9018, University of North Dakota, Grand Forks, North Dakota 58202, USA. akubatova@undeerc.org
Herman
Jamie
J
Steckler
Tamara S
TS
de Veij
Marleen
M
Miller
David J
DJ
Klunder
Edgar B
EB
Wai
Chien M
CM
Hawthorne
Steven B
SB
D020111:Chlorodiphenyl (54% Chlorine) / Q000737:chemistry / Q000302:isolation & purification*; D019216:Metals, Heavy / Q000737:chemistry / Q000302:isolation & purification*; D010150:Paint; D011078:Polychlorinated Biphenyls / Q000737:chemistry / Q000302:isolation & purification*; D011312:Pressure; D013696:Temperature; D014865:Waste Disposal, Fluid / Q000379:methods*
D019216:Metals, Heavy; D020111:Chlorodiphenyl (54% Chlorine); D011078:Polychlorinated Biphenyls