948 PCBs AND ASSOCIATED AROMATICS
TABLE 56Developer Technology Applicable wasteIn development Electrochemical PCBs, PCDFs, PCDDs, volatile & semivolatile
organics, PAHs, PCPs, petroleum by-products,
metals, synthetic organics
American Toxic Disposal Inc. Vapor extraction Volatile & semivolatile organics, PCBs, petroleum by-
products
CF Systems Corp./ENSCO Solvent extraction with liquified hydrocarbon gases PCBs, volatile & semivolatile organics, petroleum by-
products
Ozonics Recycling Corp. Soil washing, catalytic ozone oxidation Semivolatiles, pesticides, PCBs, PCP, PCDDs
Harmon Environmental Services Soil washing Heavy organic compounds
Western Research Institute Contained Recovery of oily wastes Coal tar derivatives, petroleum by-products
Resources Conservation Co. Solvent extraction with triethylamine High molecular weight organics
Chemical Waste Management Low temperature thermal desorption Volatile & semivolatile organics, PCBs
International Waste Technologies In situ solidification/stabilization PCBs
MoTec Inc. Liquid/solid contact digestion Halogenated & non-halogenated organics, pesticides
USEPA KPEG process PCBs
J.M. Huber Mobile incineration PCBs, organics
Penberthy Electromelt Infra red vitrification PCBs, organics
Westinghouse Plasma pyrolysis PCBs, organics
Battelle Memorial Institute Radiofrequency heating PCBs, organicsreagents. Step-wise reduction is observed with biphenyl as
an end product. The results of a research program to dem-
onstrate the effectiveness of an electrochemical process are
described in detail in this section. Data are presented for
the dechlorination of monochloro-benzene, hexachloro-
benzene and PCBs.
Chlorobenzenes and PCBs are very insoluble in water
and the initial solutions of these compounds were so concen-
trated that they entered the process as emulsions. The system
broke the emulsion in five to ten minutes and produced a
98% reduction of contamination in the same time. Reactions
were essentially complete in 30 minutes. PCBs, as Aroclor
1260, were reduced from an emulsion of 3,300 ppm PCB
down to 0.2 ppm PCB in 30 minutes at room temperature in
a safe, totally enclosed system.
Table 57 illustrates some of the results obtained with the
process.
A solution of monochlorobenzene (MCBz) in methanol
was added to water containing a supporting electrolyte. The
resulting solution contained 39,400 ppb MCBz.
A low D.C. current was passed through the mixture at
an initial pH of 7.4 and an ambient temperature of 24°C. As
the reaction progressed the pH decreased to a plateau value
of about 3.0 after 15 minutes and the temperature increased
to a stable value of 47°C in the same time. Samples were
withdrawn at regular intervals to be analysed by GC/ECD
to determine residual chlorobenzene and GC/MS to identify
reaction products. The final concentration of MCBz was
0.54 ppb.The initial concentration of benzene in solution was 32
ppb. After 15 minutes this had decreased to less than 1 ppb.
No other chlorinated species were found in the reacted
mixture.
A similar experiment was conducted with hexachloro-
benzene (HCBz) at a starting concentration of 11,500 ppb.
The mixture was at first an emulsion of HCBz in water. The
emulsion had completely disappeared within 5 minutes and
the pH decreased from an initial 7.4 to about 4.0 in the same
time. The temperature of the reaction mixture was controlled
by a circulating water jacket which maintained the tempera-
ture at about 50°C.
The first sample analysed was taken after 30 minutes
reaction. The HCBz concentration had decreased by a factor
of 1000 from 11,500 ppb to 11.3 ppb.
A comparison of the chromatograms obtained after
different reaction times clearly shows the formation of inter-
mediate chlorobenzene congeners.
After 30 minutes reaction time there is a dramatic change
in the concentration of HCBz while the concentrations of
penta-, and tetra- and tri-chlorobenzenes were greater than
in the starting solution, albeit at only 4–5 ppb or less. The
concentration of lower chlorinated congeners decreased
below the analytical detection limit with increasing reaction
time. The treated solution after 90 minutes contained 10.1
ppb HCBz and sub-ppb levels of the tetra- and lower chlori-
nated congeners.
A trace of unquantitated Aroclor 1260 is evident in the
starting solution. The chromatogram showed all of the charac-C016_003_r03.indd 948C016_003_r03.indd 948 11/18/2005 1:12:46 PM11/18/2005 1:12:46 PM