ANRCP-1998-2 Treatment of HMX and RDX Contamination Robert E. Card, Jr. Robin Autenrieth Texas A&M University College Station, Texas Texas A&M University College Station, Texas Submitted for publication to Amarillo National Resource Center for Plutonium March 1998
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ANRCP-1998-2
Treatment of HMX and RDX Contamination
Robert E. Card, Jr. Robin Autenrieth
Texas A&M University College Station, Texas
Texas A&M University College Station, Texas
Submitted for publication to
Amarillo National Resource Center for Plutonium
March 1998
DISCLAIMER
This report was prepared as an acEOunt of work sponsored by an agency of the United States Government. Neither the United States Government nor aay agency thereof, nor any of thdr employees, makes any warranty, exprrss or implied. or assumes any legal liability or responsibility for the accuracy, completeness, or use- fulness of any infomation, apparatus. product, or process diioscd, or represents that its use would not infringe privately owned rights. Reference hmin to any spe- cific comm&al product, proau, or 3crvjcc by trade name, trademark, manufac- mrcr, or otherwise does not n d I y constitute or imply its endorsement, recom- mendation, or favoring by the United Statcs Government or any agency thenof. The views and opinions of authors e x p d herein do not ntowarily state or reflect those of the United States Government or any agency thereof.
c
DISCLAIMER
Portions of this document may be illegible electronic image products. Images are produced from the best available original document.
Abstract
Treatment of HMX and RDX Contamination Robert E. Card, Jr. and Robin L. Autenrieth
Texas A&M University, College Station, Texas
HMX and RDX are often found in the soil, groundwater, and surface waters at facilities
where they are manufactured as the result of negligent disposal methods. The toxicity of these
compounds and their degradation products has led to concern about their fate in the environment
and the potential for human exposure. HMX and RDX are recalcitrant in the environment, with
low rates of biodegradation and photolysis.
Several methods of treating contaminated soils and waters have been developed and
studied. Many of these technologies (ie., carbon adsorption, oxidation, and chemical treatment)
have been developed to treat munition plant wastewaters that are contaminated with explosives.
These methods need to be adapted to remediate contaminated water. Other technologies such as
bioremediation and composting are being developed as methods of remediating HMX and RDX
contamination in a solid matrix. This report describes and evaluates each of these technologies.
This report also describes the processes which affect HMX and RDX in the environment.
The major transformation processes of RDX and HMX in the environment are biodegradation and
photolysis. A major factor affecting the transport and treatment of RDX and HMX in soil-water
environments is their sorption and desorption to soil particles. Finally, this report draws
conclusions as to which treatment methods are currently most suitable for the remediation of
Pounds of reactants for a 100 lb . batch ..................................... 4
Chemical and physical properties of HMX and RDX .......................... 7
Health advisory standards for HMX and RDX ............................... 9
Comparison of the toxicity and carcinogenicity
values of RDX. HMX. and their degradation products ........................ 10
14
19
20
21
Photolytic degradation rates for HMX and RDX in Holston River water . . . . . . . . . . Photolysis of RDX in a laminar flow tray .................................. Mixed zero and first order rate parameters for RDX and HMX decomposition . . . . . UV.H.0. treatment first-order degradation rates for RDX and HMX . . . . . . . . . . . . . Initial concentrations and first-order rate
constants of HMX and RDX in corona oxidation study ....................... Summary of biodegradation studies ......................................
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35
V
List of Figures
Figure Page
1.1 Flow diagram of the RDX and HMX manufacturing process at Holston AAP . . . . . . . . 5
1.2 Chemical structure of RDX ............................................... 6
1.3 Chemical structure of HMX ............................................... 6
3.1 Proposed pathway for the anaerobic degradation of RDX ........................ 26
3.2 Proposed pathway for the formation of mono- and dinitroso derivatives of HMX . . . . . 27
3.3 Block flow diagram of proposed bioreactor/activated
carbon system for the treatment of pink water ................................. 31
The manufacture and use of HMX and RDX in the United States has led to the
contamination of soil and water at a large number government installations. The toxicity and
potential carcinogenicity of these compounds has led to concern about their fate in the
environment and the potential for human exposure.
The recalcitrance and toxicity of RDX makes the remediation and monitoring of
contaminated sites a necessity. The two major transformation processes of HMX and RDX in
the environment, biodegradation and photolysis, occur at very slow rates, making these
chemicals persistent in the environment. Many of the degradation products are more toxic than
HMX and RDX making it undesirable to allow them to decompose in soils and water.
A variety of methods have been developed for the treatment of waters contaminated with
HMX and RDX including: carbon adsorption, oxidation, biodegradation, composting, and
chemical treatment. Many of these technologies were developed to treat explosives-
contaminated waters generated from munitions manufacture and handling, and have not yet been
adapted to the remediation of contaminated waters. This paper describes and evaluates each of
these remediation technologies.
1.1 Background
The use of HMX and RDX as explosives became common during World War II when
their use became widespread due to their relative stability, which is only slightly less than TNT;
and their explosive power, much greater than TNT. Since then, HMX and RDX have been used
in detonators, primers, mines, rocket boosters, and plastic explosives (Yinon. 1990).
During their early manufacture, wastewaters generated at the munitions plant were often
dumped into unlined pits. While this practice has ended, it had already led to the contamination
of soil, surface water, and groundwater at approximately 28 sites in the United States (Griest, et
al. 1990). The following is a list of all the sites that are potentially contaminated with RDX
and/or HMX, identified during the course of this study.
Cornhusker AAP - Grand Island, Nebraska Iowa AAP - Middletown, Iowa Joilet AAP - Joilet, Illinois Kansas AAP - Parsons, Kansas Lonestar AAP - Texarkana, Texas Milan AAP - Milan Tennessee Louisiana AAP - Shreveport, Louisiana Holston AAP - Kingsport, Tennessee US Navy - Crane, Indiana US Navy - Hawthorne, Nevada US Navy - McAlster, Oklahoma US Navy - Yorktown, Virginia US Army - Umatilla, Oregon Pantex Plant - Amarillo, Texas Los Alamos National Laboratory Bangor Naval Submarine Base - Bangor, Washington Savanna Army Depot - Savanna, Illinois
(Doyle and Kitchens. 1993; Kitts, et al. 1994; Sullivan, et al. 1979; US 1991, 1992)
Now that the US is disassembling many of its nuclear weapons, the explosives in the
detonation devices needs to be destroyed.
2
1.2 Manufacture
The most common methods of manufacturing RDX are the Woolwich and Bachmann
processes. In the Woolwich process hexamine (C,H,,N,) is nitrated directly as shown in
Equation 1.1.
C6H,,N, + 4HN0, -+ RDX + 3C0, + 2N, + 6H,O
In the Bachmann process, hexamine is nitrated indirectly by an ammonium nitratehitric
acid mixture in the presence of acetic acid and acetic anhydride at 75 "C, as summarized in
Dewatering and Grinding L--r' TNT, Wax, etc. Incorporation
Figure 1.1: Flow Diagram of RDX and HMX Manufacturing Process at Holston AAP (Kitchens, et al. 1978)
5
1.3 Physical and Chemical Properties
RDX (Figure 1.2) is a colorless polycrystalline high-explosive that was developed for use
during World War II. RDX is short for Research Department explosive or Royal Demolition
explosive. It is also known as cyclonite, cyclotrimethylenetrinitramine, hexogen, and hexahydro-
1,3,5-trinitr0-1,3,5-triazine (Gibbs and Popolato. 1980). Physical and chemical properties of
RDX are presented in Table 1.1.
Figure 1.2: Chemical Structure of RDX.
HMX (Figure 1.3) is a colorless polycrystalline high explosive similar to RDX. HMX
has a higher melting point than RDX and was thus named HMX for High Melting explosive. It
is also known as octogen, octahydro- 1,3,5,7,-tetranitro- 1,3,5,7-tetrazocine, and
cyclotetramethylene-tetranitramine (Gibbs and Popolato. 1980).
I I 1 I
C-H2 H, -C
Figure 1.3: Chemical Structure of HMX.
6
HMX exists in four polymorphic forms, a, p, 'y, and 6. The a, p, and 7, are all stable at
room temperature, while the 6 readily transforms. The p form of HMX is most desirable because
it is the least sensitive and most stable to impact (Yinon and Zitrin. 1993). Physical and
chemical properties for the p form of HMX are given in Table 1.2.
Table 1.2: Chemical and Physical Properties of HMX and RDX (Rosenblatt, et al. 1991).
As an explosive, HMX is superior to RDX. Because of its higher density, HMX is used
where high energy and lower volume are important. HMX is more resistant to degradation and
chemical substitution than RDX (Urbanski. 1963). HMX is used in binary explosives, solid-fuel
rocket propellants, as a burster charge for artillery shells, and to implode fissionable material in
nuclear devices (Gibbs and Popolato. 1980; Yinon. 1990).
HMX and RDX can be analyzed by several methods. High-pressure liquid
chromatography (HPLC) has been widely used to separate munitions mixtures. Coupled with a
mass spectrometer, an HPLC can be used to analyze HMX and RDX in low nanogram to
7
picogram quantities. RDX and HMX have been well characterized by gas chromatography
(Rosenblatt, et al. 1991).
1.4 Toxicity
One of the primary objectives of hazardous waste remediation is to reduce or eliminate
the threat to human health and the environment. The toxicity of the contaminants is often used to
quantify the threat. To the impact of treatment methods, the toxicity of the parent chemicals and
the degradation products must be compared.
The data available on the effects of RDX poisoning on humans results from inhalation
studies on munitions plant workers. The effects of RDX poisoning usually develop within half
an hour to several hours after exposure. Symptoms include confusion, dizziness, convulsions,
loss of consciousness, vomiting, headaches, and nausea. Full recovery may require several days
to two months. The majority of RDX poisoning cases were munitions plants workers exposed
during World War I1 (Yinon. 1990).
When orally administered in rats and mice RDX is completely absorbed and rapidly
distributed. The highest concentrations of RDX are found in the kidneys, followed by the liver,
brain, and heart. Long-term effects of RDX exposure in rats and mice are increased liver weight
and testicular degeneration (McLellan, et al. 1988a).
No toxic effects have been observed in munitions plant workers potentially exposed to
HMX. In feeding studies conducted on rats and mice, toxic effects included hyperkinesia,
anataxia, and convulsions. Unlike RDX, when orally administered the majority of HMX is
excreted in the feces (70% in mice, 85% in rats). It is postulated that the poor absorption of
HMX is due to its low water solubility (Mchllan, et al. 1988b).
8
Health advisory standards for RDX and HMX have been developed by the Environmental
Protection Agency, Office of Drinking Water. Health advisories are the concentrations of
drinking water contaminants at which adverse health effects are not expected to occur over the
duration of the exposure. These standards are not legally enforceable and are subject to change
as new data becomes available. Longer-term standards are based on an exposure duration of
approximately 7 years, or 10% of an individual’s lifetime RDX (McLellan, et al. 1988a, 1988b).
Health advisory standards for RDX and HMX are given in Table 1.3.
Table 1.3: Health Advisory Standards for HMX and RDX (McLellan, et al. 1988a, 1988b).
Exposure Duration Exposure Concentration (mgL) I RDX HMX
I
9
One day Ten Day
Longer-term child Longer-term adult
Lifetime
0.1 0.1 0.1 0.35 0.002
5 5 5 20 0.4
The primary route of exposure of RDX and HMX released to the environment is the
ingestion of contaminated surface and groundwaters that have migrated offsite. The toxicity of
HMX and RDX through the ingestion of contaminated water is limited by their low solubilities.
Due to the restricted access to sites where RDX and HMX contamination has occurred, exposure
to contaminated soil is not likely. However, because of the high concentrations, over 10,000
ppm at some locations, the inhalation and ingestion of airborne particulates is a concern for
workers.
Some RDX degradation products are known carcinogens or mutagens. 1,2-
dimethylhydrazine, an anaerobic degradation product of RDX, has been identified as a cancer-
causing agent in rats (Fiala. 1977). Other RDX degradation products of concern include: RDX
nitroso derivatives, 1,l -dimethylhydrazine, hydrazine, formaldehyde, and methanol (McCormick
et al. 198 1). Nitrate, nitrite, formaldehyde, and 1,1 -dimethylhydrazine have been identified as
HMX degradation products (Spanggord, et al. 1983a).
A comparison of the toxicity of RDX and HMX with some of their degradation products
is shown in Table 1.4. LD,, is the dose of a chemical which causes the death of 50% of the
animals in the experiment.
Table 1.4: Comparison of the toxicity and carcinogenicity values of RDX, HMX, and their degradation products (LaGrega, et al. 1994; Sweet. 1987; US. 1993).
Direct addition of lime or NaOH is not feasible. It would take 9.8M NaOH to reduce the
concentration of RDX from 45 to 4.5 ppm in 20 minutes. Lime water with a 12 pH would
require 14 days to achieve the same reduction in RDX concentration. This decrease can be
41
achieved much faster by the use of basic resin that adsorbs RDX and then chemically interacts
with O H ions on the resin.
The resin used was Amberlite 400 which had been converted from the chloride ion form
to the hydroxide ion form with a 1M NaOH solution. After the resin had been used it was
regenerated by using a 1M NaCl solution and then a 1M NaOH solution.
In laboratory and pilot-scale, test water contaminated with 45 ppm RDX was treated at a
flow rate of 0.79 to 2.0 gpm (0.067 to 0.17 resin volumes/minute). The concentration of the
RDX in the effluent was less than 0.5 ppm. A resin volume of 1 ft' could be used to treat 1300
gallons of water contaminated with RDX at a concentration of 45 ppm. In both the laboratory
and pilot-scale studies the resin was regenerated 8 times with no deterioration in performance.
Hoffsommer, et al, (1977) concluded that a basic resin could be used for water contaminated with
low levels of RDX which did not contain a large anion concentration. Also, it is likely HMX
could be removed.
This process is somewhat limited by the low flow rate of the process. At an average flow
rate of 0.12 resin volumes/minute, approximately 80 cubic feet of resin would be needed to treat
100,000 gallons of contaminated water in 24 hours at which time the resin must be regenerated.
Therefore, this method could not be used to treat the 10 MGD of pink water generated at the
Holston AAP (Burrows. 1982).
RDX and HMX can also be removed from water by coagulation (Sullivan, et al. 1979).
The use of lime, ferric chloride, and Cat-Floc-T, a cationic polymer to remove HMX and RDX
were studied. A 90% reduction in munition concentration was achieved using 500 mg/l of lime,
and the initial RDX and HMX concentrations were not reported. The use of Cat-Floc-T is
discouraged because it is not compatible with RDX in dry form.
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Chapter 4
Conclusions
The production and use of RDX and HMX in the US over the past 50 years has led to the
contamination of soil and water at numerous sites. The concentration and extent of
contamination is widely variable from site to site. The remediation of HMX and RDX is needed
to reduce the threat they pose to human health and the environment.
The nature of these compounds in the environment poses several problems. Their low
solubility and sorption onto soil is especially troublesome in treating ground waters. The low
solubility of the compounds also limits their availability to microorganisms for biodegradation.
The most promising method of treating contaminated water appears to be the use of
ultraviolet degradation in combination with ozone or hydrogen peroxide. Ultraviolet radiation
provides a means of destroying the contaminants in an efficient and economical manner.
Composting has been well-studied as a means of treating contaminated soil and sediment.
The concentrations of HMX and RDX in the environment can be rapidly degraded by the use of
composting. However, studies should be conducted at the site to determine the optimum soil
loading rate under specified conditions.
43
The use of bioremediation for the treatment of waters and soils is a promising technology.
The limiting factor in the use of bioremediation to treat contamination is the low solubility of the
compounds. Much works needs to be done to see if bioremediation can be used in the field both
in situ and ex situ.
44
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