ENHANCED PHOTODEGRADATION OF PERSISTENT
HALOGENATED ORGANIC MATERIALS
D. C. Christensen, Research Engineer
W. C. Weimer, Senior Research Scientist
Battelle-Northwest Laboratories
Richland,Washington 99352
INTRODUCTION
At the present time the Environmental Protection Agency is proposing the basic elements
of a national hazardous waste control program to manage wastes from their generation to
their final disposition. This program, as directed by congress, is the Resource Conservation
and Recovery Act (RCRA). A major area of emphasis of RCRA is treatment of hazardous
wastes. Treatment is defined to include "any process designed to change the physical,
chemical, or biological character or composition of any hazardous waste so as to neutralize
the waste, render it nonhazardous, safer for transport, amenable for recovery or storage, or
reduced in volume" [ 1 ]. The EPA prefers treatment over the various disposal techniques
such as landfilling or land spreading because of the potential for detoxification and destruction.  In this vein, treatment protocol for hazardous wastes should be as follows: (a) reuse,
(b) reprocess, (c) detoxify, and (d) destroy.  This protocol suggests the various stages of
treatment in decreasing order of desirability.
The first two stages in the protocol (reuse and reprocess) will generally apply only to processing stream wastes and concentrated wastes where there are few impurities to interfere
with reprocessing. The second two stages (detoxify and destroy), although applicable to
processing stream wastes, are more commonly applied to the low concentration wastes such
as blended waste streams or soil spills.
This report describes a process developed to detoxify various low concentration hazardous wastes by utilizing natural solar radiation in conjunction with a chemical promoter.
Various chemicals have been tested to promote detoxification of two test materials (Kepone
and polybrominated biphenyls). These chemical promoters are primary and tertiary amines.
In pure amine-Kepone solutions, Kepone degradation of up to 99% was measured after only
one day of UV exposure. In contaiminated soil tests destruction of up to 78% was measured
after ten days of sunlight exposure. Similar tests with PBB contaminated soils showed up to
49% degradation after only four days of sunlight exposure.
LITERATURE SURVEY
The first reported incident of photolytic decomposition of a halogenated organic contaminant was measured by Gibson, et al. [2] and involved the contaminant mirex. Mirex was
exposed to direct sunlight for three months with only a 5% degradation occurring. Carlson,
et al. [3] found that mirex in the 0.3 to 1.0 mg/1 range degraded over a 12 year period as a
result of photodecomposition. Degradation ranged from 20 to 35% on a variety of different
samples. Alley, er al, [4] showed that degradation of mirex by sunlight was significantly
enhanced via its interaction with aliphatic amines (triethylamine). The photodecomposition
of mirex in aliphatic amines was different from the decomposition observed in hydrocarbon
solvents in both the decomposition product analysis and the wavelength of light absorbed.
The enhanced degradation is attributed to an intermediate charge transfer complex formed
between the amine and mirex.
Botre, et al. [ 5 ] found that photodecomposition of 2,3, 7, 8 tetrachlorodibenzoparadioxin
(TCDD) took place in contaminated soils exposed to the sunlight. A solubilizing agent, 1-
hexadecylpyridinium chloride (HPC) enhanced the solubilizing properties and the photochemical degradation of TCDD in micellar solutions when exposed to sunlight or UV irradiation. Under experimental conditions the time required for total TCDD decomposition of
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