CONTINUOUS FIXATION AND REMOVAL OF EXPLOSIVE WASTES
FROM PINK WATER USING SURFACTANT TECHNOLOGY
Donald J. Freeman, Chemical Engineer
Large Caliber Weapon Systems Laboratory
U.S. Army Armament Research and Development Center
Dover, New Jersey 07801
INTRODUCTION
Army Ammunition Plants (AAP's) performing load-assemble-pack (LAP) operations have, in the
past, discharged TNT and RDX contaminated process wastewaters, commonly known as "pink
water," into lagoons and nearby streams. Although the stream may actually be a dark orange color,
the term "pink water" is derived from the photolysis products of aqueous solutions of TNT, which
are aesthetically, as well as environmentally, undesirable. Both TNT and RDX are toxic and yield
positive Ames test results that are indicative of potential mutagenic-carcinogenic properties. This has
resulted in pollution of soil, ground water, rivers, and streams with toxic and possibly carcinogenic
substances.
Effluent guidelines of 40 ppb for TNT, 30 ppb for RDX/HMX, and 0.7 ppb for DNT have been
proposed by the US Army Medical Bioengineering R&D Laboratory to the Surgeon General even
though the methods to reliably measure these low concentrations are still being developed. Neither
TNT nor RDX are biodegraded under normal conditions in the environment or in biological waste
treatment facilities. There is some evidence that RDX is biodegraded slowly under anaerobic conditions while TNT is biotransformed into amine complexes which are even more toxic than the original explosive [1]. Although these substances may be removed from wastewaters using carbon
adsorption, the basic process is expensive, and there is an added expense for regeneration of spent
carbon or environmental problems associated with the incineration of the explosive-laden spent carbon. In addition there are serious unanswered questions as to the efficiency of overall removal of
explosives from a multi-component system such as one containing TNT, RDX, and other secondary
components.
A new technology for the removal of TNT and RDX from water with surfactants has been recently
developed. Two types of surfactants have been demonstrated to be effective in the precipitation of
TNT from solution. One is a surfactant in which the polar group is a primary amine while the other
is a quaternary amine. The precipitation of TNT from solution is the result of the reaction between
TNT and the surfactant in an alkaline medium to form an intermediate substance identified as the
Janovsky complex [2,3] that in turn reacts with the protonated surfactant and precipitates as a salt.
In the case of RDX, it has been demonstrated that the surfactant accelerates the rate of alkaline
hydrolysis of the RDX rather than the formation of a precipitate. The increased rate of hydrolysis
is probably due to the solubilization of the explosive by the surfactant micelles (oriented aggregation
of surfactant ions or molecules) which concentrate the explosive and make it more available to the
action of the alkali [3]. Thus, both TNT and RDX can be removed from a wastewater stream under
the same alkaline-surfactant conditions.
On the basis of these findings, bench-scale pilot studies were conducted at Hazards Research
Corporation, Rockaway, NJ, to develop the process and, if possible, obtain economic data. A preliminary investigation was performed with TNT solution alone. The results obtained showed that
TNT could indeed be readily removed. The surfactants found most effective were N-tallow 1, 3,
diaminopropane (Duomeen T) and trimethyl tallow ammonium chloride (Arquad T-50).
This work was then extended to the treatment of water containing dissolved Composition B (40%
TNT, 60% RDX), thus simulating wastewaters from the load-assemble-pack of Composition B and
related explosives into munitions at Army Ammunition Plants.
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