&EPA
United States
Environmental Protection
Agency
Municipal Environmental Research EPA-600/2-78-081
Laboratory June 1978
Cincinnati OH 45268
Research and Development
Summary Report
Detoxification of
Navy Red Dye by
Microwave Plasma
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-78-081
June 1978
Summary Report
DETOXIFICATION OF NAVY RED DYE
BY MICROWAVE PLASMA
by
L. J. Bailin
Lockheed Palo Alto Research Laboratory
LOCKHEED MISSILES & SPACE COMPANY, INC,
Palo Alto, California 94304
Contract No. 68-03-2190
Project Officer
Donald A. Oberacker
Solid and Hazardous Waste Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Municipal Environmental Research Labora-
tory, U.S. Environmental Protection Agency, and approved for publication. Approval
does not signify that the contents necessarily reflect the views and policies of the U.S.
Environmental Protection Agency, nor does mention of trade names or commercial
products constitute endorsement or recommendation for use.
ii
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FOREWORD
The Environmental Protection Agency was created because of increasing public
and government concern about the dangers of pollution to the health and welfare of the
American people. Noxious air, foul water, and spoiled land are tragic testimony to
the deterioration of our natural environment. The complexity of that environment and
the interplay between its components require a concentrated and integrated attack on
the problem.
Research and development is that necessary first step in problem solution, and it
involves defining the problem, measuring its impact, and searching for solutions. The
Municipal Environmental Research Laboratory develops new and improved technology
and systems for the prevention, treatment, and management of wastewater and solid
and hazardous waste pollutant discharges from municipal and community sources, for
the preservation and treatment of public drinking water supplies, and to minimize the
adverse economic, social, health, and aesthetic effects of pollution. This publication
is one of the products of that research; a most vital communications link between the
researcher and the user community.
This report describes a successful detoxification by microwave plasma of a parti-
cularly refractory U.S. Navy red dye mixture which is used in pyrotechnic smoke com-
positions. The reactions produced harmless gases, and no carcinogens or other toxic
materials in the process effluent. During the study, various unit operations and proc-
esses were evaluated to determine efficiency and the potential for future expansion.
Francis T. Mayo
Director
Municipal Environmental Research Laboratory
111
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PREFACE
Toxic organic substances, such as chlorinated hydrocarbons, and many organo-
nitrogen, organophosphorous, and organometallic compounds are components of pesti-
cides which have been withdrawn from use, are obsolete, or are constituents of haz-
ardous military or industrial wastes. These materials must be managed or disposed
of safely and effectively. A primary responsibility of the U.S. Environmental Protec-
tion Agency's Solid and Hazardous Waste Research Division (SHWRD) has been to en-
courage and support research and development efforts in the area of hazardous waste
disposal technology. For compounds of nominal toxicity, laudable achievements have
been accomplished in the technology of thermal destruction, chemical and biological
detoxification, and special landfill methods. However, with the exception of high-
cost incinerator processing, little or new technology has been developed for the dis-
posal of highly toxic or extremely persistent wastes. These materials are described
in the 1974 EPA Report to Congress, Disposal of Hazardous Wastes, SW-115.
As part of a continuing program to evaluate the newly developed microwave plasma
process on toxic materials of current interest, a U.S. Navy red dye pyrotechnic
smoke mixture was selected for detoxification because of the refractory, or difficult
to decompose, behavior of the two potentially carcinogenic dyes which constitute a
major portion of this mixture.
IV
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ABSTRACT
The process of microwave plasma detoxification has been applied successfully to
the destruction/disposal of a U.S. Navy red dye pyrotechnic smoke mixture. The
mixture was added as a powder, a solvent solution, and a water slurry.
Material balance for detoxification of the slurry indicated that less than 0.20 per-
cent solids were found beyond the reaction zone, or 99.8+ percent conversion to gas-
eous products. Analysis by spectrophotometry in the visible region indicated little or
no dye starting materials ( < 5 ppm) in the residue. Ultraviolet fluorescence, UV
spectrophotometry, and gas chromotography/mass spectrometry indicated the pres-
ence of less than 2 ppm carcinogenic polyaromatic hydrocarbons (PAH). Since PAH
has been found in air oxidation products derived from these materials, a significant
advantage would appear to derive from the plasma process.
During the study, several vacuum feed techniques were evaluated with a view to-
ward their utilization in forthcoming pilot equipment tests. Especially with high solids
slurries and solutions, where non-Newtonian flow can cause difficulties when gravity
feed methods are used, it will be necessary to use positive displacement methods to
obtain uniformity and reproducibility during the addition process.
Further work is suggested, using larger quantities of the mixture to optimize
throughput and to calculate process costs for economic comparisons with other de-
toxification methods.
This report was submitted in partial fulfillment of Phase II of Contract 68-03-2190
by the Lockheed Palo Alto Research Laboratory of Lockheed Missiles & Space Com-
pany, Inc., under the sponsorship of the U.S. Environmental Protection Agency. The
report covers the period August 1976 July 1977.
For work performed under Phase I, the report entitled, "Development of Micro-
wave Plasma Detoxification Process for Hazardous Wastes," EPA-600/2-77-030,
April 1977, may be consulted for additional details on the technique development.
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CONTENTS
Foreword iii
Preface iv
Abstract v
Figures and Tables viii
Acknowledgment ix
1. Introduction 1
2. Conclusions and Recommendations 2
3. Materials 3
4. Microwave Plasma System 4
4.1 Microwave Plasma Characteristics 4
4.2 Chemistry of Microwave Plasma Reactions 5
4.3 Apparatus 5
4.4 Analytical Procedures 8
4.5 Experimental Procedures 8
5. Results 9
References 14
Appendix 15
Chronological Development of Feed Techniques 15
A. 1 Methanol-Water Dispersions 15
A. 2 Powdered Solids 15
A. 2.1 Laboratory Model Continuous Solids Feeder 15
A. 2.2 Pressed-Cake Batch Process 19
A. 3 Methyl Ethyl Ketone Solutions 20
A. 4 Aqueous Dispersions 20
VII
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FIGURES
Number Page
1 Block diagram of microwave plasma system and related
components. 6
2 Schematic of expanded scale microwave plasma system. 7
3 Red dye slurry feed system. 10
4 Infrared scan of solid residue from oxygen plasma reactor. i2
Al Schematic of solids feed system. lg
A2 Solids feed system, close up. 17
A3 Solids feed system, front view. 18
TABLES
1 Composition of Smoke Component of the MK 13 Mod O Marine 3
Smoke and Illumination Signal
o
2 Polyaromatic Compounds and Their 2537 A Ultraviolet 13
Fluorescent Response and Absorption Maxima
A-l Surfactants Tested for Preparation of Aqueous Red Dye 21
Dispersions
viii
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ACKNOWLEDGMENT
This report was prepared by the Lockheed Palo Alto Research Laboratory, Lock-
heed Missiles & Space Company, Inc., under U.S. Environmental Protection Agency
Contract 68-03-2190. The work was performed in the Department of Chemistry,
Dr. Ernest L. Littauer, Manager. Dr. Lionel Bailin was principal investigator.
Major contributions to the program were made by Dr. Barry L. Hertzler, plasma
chemistry and mass spectroscopy, and Dr. Gerald B. McCauley, infrared, visible,
and ultraviolet spectroscopy.
Appreciation is expressed to Dr. Carl E. Dinerman and Mr. James Short, Naval
Weapons Support Center, Crane, Indiana, who foresaw the applicability of the micro-
wave plasma process to detoxification of Navy dye compositions, supplied the dyes,
and advised on pertinent analytical and handling procedures.
The Project Officer for the Environmental Protection Agency was Mr. Donald A.
Oberacker, whose advice and guidance are sincerely acknowledged.
ix
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SECTION 1
INTRODUCTION
During 1975 1976, based on an EPA supported study, the process of microwave
plasma decomposition of organic and organometallic compounds was applied success-
fully to the detoxification/destruction of highly toxic wastes.^' The effectiveness of
an expanded scale plasma was evaluated using hazardous organic materials of current
interest. The products of these reactions were identified in order to estimate their
toxicity and to determine the potential for recycling or recovery of useful by-products.
The program resulted in an expansion of the state-of-the-art in microwave plasma
detoxification from 1 to 5 g/hr in the original laboratory apparatus to 3 kg/hr (7 IbAr)
in the larger system. This scale-up changed the perspective from one of academic
interest to that of a realistic or practical level.
As a result of successful detoxification, more complex, real-world mixtures were
suggested for continued process testing and evaluation. Such a material was obtained
from the Naval Weapons Support Center (NWSC), Crane, Indiana. As a colored
smoke, these materials were considered important for disposal because of the pres-
ence of carcinogenic or suspected carcinogenic dyes in the smoke mixture. (2) The
results of a study of the detoxification of this mixture are presented in the sections
which follow.
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SECTION 2
CONCLUSIONS AND RECOMMENDATIONS
The process of microwave plasma decomposition was used successfully to detoxify
a U.S. Navy dye mixture to harmless gases and solids. The rate of addition in this
initial study was 500 g/hr of aqueous slurry which contained 15 percent solids. The
process, in its current state of development, required drop-feed (gravity) addition to
the plasma zone. Decomposition was complete; very little or no starting material
was found in a small amount of solid product and no significant quantities of poly-
aromatic hydrocarbons were detected, according to UV absorption, UV fluorescence,
IR spectroscopy, and GC/MS.
Further work is recommended to improve the methods of addition to maximize
material throughput, and should include testing of total smoke mixtures containing
the potassium chlorate oxidizer component. It is also recommended that detoxifica-
tion be carried out in the 15-kW plasma system now under construction, whereby
positive feed techniques would be used for solids as well as aqueous slurries.
Work on other toxic waste materials of interest to the Navy is also suggested.
These include shipboard hazardous chemicals, outdated disinfectants, organometallic
compounds from munitions, and certain pesticides originally used to clear bird-
attracting insects from airfields. The use of portable microwave plasma detoxifica-
tion equipment would, in addition, result in a significant diminution in time and labor
now required for the transportation of these materials to incinerators, where permit-
ted, or to regulated toxic waste disposal sites when necessary.
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SECTION 3
MATERIALS
The smoke composition selected is contained in a Navy inventory material known as
MK 13 Mod O Marine Smoke and Illumination Signal. This material accounted for
approximately 70 percent of the 9300 kg excess to be disposed of by the Navy. The
composition contained 1-methylanthraquinone and xylene-azo-/?-napthol dyes, which
appear red in powder form. The components, excluding the potassium chlorate oxi-
dant, are listed in Table 1. The KCIO^ was omitted since it can be removed from
mixtures by water extraction.(3) in addition, its inclusion, initially, would result in
the formation of nonuniform, and therefore, detrimental gas expansions in the reactor,
which would confound the initial data. The KClOs component should, however, be
investigated later as part of the mixture, pending approval of the need for further
study.
The reactant gas was 99.5 percent minimum purity industrial grade oxygen, Fed-
eral Spec. BB-0-925(a), Type I, in which the 0.5 percent nonoxygen components were
approximately 0.05 percent nitrogen, the remainder being argon and other gases in
trace amounts. Other specific one-time use materials are listed in the sections in
which they are applied.
TABLE 1. COMPOSITION OF SMOKE COMPONENT OF THE MK 13 MOD O
MARINE SMOKE AND ILLUMINATION SIGNAL
Components in Powder Mixture* Amount (%)
Xylene -azo-/3-naphthol 55.4
1-Methylaminoanthraquinone 18.9
Sucrose 18.0
Graphite 1.8
Silica Binder 5.9
100.0
*Excluding 18.9 percent KC1O3 oxidant. To convert to KC1O3
composition, multiply by the factor 0. 811.
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SECTION 4
MICROWAVE PLASMA SYSTEMS
4.1 MICROWAVE PLASMA CHARACTERISTICS
The characteristics associated with the microwave plasma detoxification process
are detailed in Ref. 1 and, therefore, are presented in abbreviated form as follows.
A plasma or discharge is a partially ionized gaseous mixture consisting of free
electrons, ions, and various neutral species. The free electrons are the principal
initiators of the plasma reactions. When the electrons undergo inelastic collisions
with the reactants, they cause either ionization, which produces more electrons and
ions, or dissociation of the reactants into free radicals. These fragments, with
their unpaired electrons, can then undergo a series of rapid reactions to the final
products.
The free electrons are energized by the oscillating electric field produced by the
microwave energy (2450 MHz) applied to the plasma. In this way, the electrons
couple the electrical energy into the reactants and force them to undergo the desired
reactions. The oscillating electric field produced by the microwaves changes polarity
so rapidly that the charged species in the plasma reverse their direction of accelera-
tion before they are swept to the walls of the container where they are likely to be
destroyed. Therefore, the plasma can be maintained without the use of internal elec-
trodes, which are usually required for plasmas operating at lower frequencies. Con-
sequently, there are no difficulties with internal electrode decomposition from corro-
sive species in the plasma, which is a known problem with DC or arc discharges.
The plasma used in this investigation is operated at reduced pressure on the order
of one to a few hundred torr. This permits the free electrons to be energized to
achieve temperatures much higher than those of the neutral gases, since there are
significantly fewer inelastic collisions occurring to cool the reactive electrons. The
electrons simulate "temperatures" on the order of 10,000°K and higher, while the
temperature of the neutral gas is less than 1,000°K. By operating under these
nonequilibrium conditions, it is possible to maintain the free electrons at high tem-
peratures without heating the bulk neutral gas, thereby conserving electrical energy.
Since the plasma decomposition mechanism is principally electronic, rather than
thermal, the microwave applicator-power coupling equipment can be maintained at
relatively low temperatures. Thus, the materials of construction associated with
furnaces or incinerator equipment are generally unnecessary, and maintenance ex-
penses will be low. In addition, the systems are leak tight, and, therefore, safe,
which is a result of the requirement for working at reduced pressures.
-------
4. 2 CHEMISTRY OF MICROWAVE PLASMA REACTIONS
In general, the decomposition of organic materials, including dyes, saccharides,
etc., will encompass a large number of complex reactions. The primary step proba-
bly involves collisions between the compound and either free electrons or reactive
species produced by the action of the discharge on the reactant gas. Through the ac-
tion of electron collisions with other species, free radicals and atoms are produced
from the organic compounds. These species then react further to form secondary
products.
When oxygen is used as the reactant gas in the plasma, atomic oxygen becomes
the primary reactive species which rapidly oxidizes the organic compounds introduced
into the discharge. In addition, the large numbers of energetic free electrons contin-
ually bombard the compounds, and any remaining organic components will be broken
up into smaller free radical fragments, which rapidly react with the oxygen present.
The free electrons may also collide with the CO£ produced, resulting in dissociation
to CO and oxygen atoms. W Thus, an equilibrium concentration of CO and CO2 may
be present in the product effluent under conditions of complete oxidative conversion.
4.3 APPARATUS
The plasma system, designed and built according to Lockheed Palo Alto Research
Laboratory (LPARL) specifications, consists of feed hardware, an oxygen supply, a
plasma reactor tube, and an effluent-product sampling receiver and traps. A block
diagram of the system and related components is shown in Fig. 1. A schematic dia-
gram is detailed in Fig. 2. The microwave hardware was supplied by Gerling Moore,
Inc., Palo Alto, CA. In Ref. 1, numerous photographs of the system can be seen, plus
the identification of all components. Additional engineering and design detail are also
provided for the reader interested in further information.
The applicator used was a dual trough waveguide in which each trough was fed by
a 2. 5-kW, 2450-MHz power source. The length of the applicator, exclusive of two
20.3-cm end-mounted radiation cutoff sections, was 41 cm. The reactor tubes were
fabricated from transparent quartz with a 1. 5-mm wall thickness, and an outside
diameter of 48- to 50-mm liter. Quartz Raschig rings were used in order to increase
the residence time of liquid and solid materials within the plasma zone. (Ring dimen-
sions were 8 mm o.d. by 4 mm length and 8 mm by 8 mm.) The volume of the reactor
was approximately 0.6 liter.
The vacuum pump was a Welch "Duo-Seal" Model 1397 oil-sealed two-stage mechan-
ical pump with a free-air displacement of 425 liters/min. Dry ice-acetone and liquid
nitrogen traps were installed between the reactor output and the pump for product
collection, and to maintain cleanliness of the pump oil. The output from the pump was
passed through a stack exhaust to the exit port on the roof of the building.
During operation of the microwave units, a Holaday Model HI 1500-3 microwave
radiation monitor (Holaday Industries, Inc., .Edina, Minnesota) and a Narda Model
B86B3 radiation monitor (Narda Microwave Corp., Plainview, N. Y.) were used to
monitor power leakage. Levels were less than 1 mW/cm in the immediate vicinity
of the apparatus, including the plasma discharge tube.
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MATERIAL TO
BE DETOXIFIED
AND REACTANT
GAS (OXYGEN)
MICROWAVE
PLASMA
REACTOR
TUNING
CIRCUITRY
MICROWAVE
POWER SOURCE
2450 MHz
I c
GASES
PRODUCT
RECEPTOR
TRAPS
LIQUIDS, SOLIDS
ANALYTICAL
INSTRUMENTATION
FOR CHEMICAL
ANALYSIS
VACUUM
PUMP
Figure 1. Block diagram of microwave plasma system and related components.
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DYE SLURRY
DROP-FEED
BURET
CH
MICROWAVE \
POWER SOURCE
MICROWAVE
APPLICATOR
Qi
MICROWAVE \ "I"1
POWER SOURCE ^
PLASMA
REACTOR
TUBEy
RECEIVER
U
ION
PUMP
I
MASS
SPECTROMETER
I
FLOWMETER
GAS SUPPLY
i-WAY STOPCOCK
-VARIABLE-LEAK
VALVE
VACUUM
PUMP
'THROTTLE
VALVE
MANOMETER
COLD TRAP
[fi
THROTTLE
VALVE
MAIN
VACUUM
PUMP
COLD TRAP
Figure 2. Schematic of expanded scale microwave plasma system.
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4.4 ANALYTICAL PROCEDURES
Mass spectrometric (MS) analysis of the gases leaving the reactor were performed
on a Varian Associates Model 974-0002 residual gas analyzer (quadrupole mass spec-
trometer) with a range of 250 atomic mass units. A small quantity of the gas was
continuously pumped past a variable-leak sampling valve. The gases bled into the
mass spectrometer by the sampling valve were pumped from the sys tern by an ion
pump. The sampling system is included in Fig. 2.
Infrared spectra of solid and liquid effluents collected from the product receiver
and traps were determined on a Perkin-Elmer 621 infrared spectrophotometer with a
range of 4000 to 400 cm"1 (2. 5 to 25 jum). Materials to be analyzed were ground with
KBr and compressed into pellets for scanning over the prescribed spectrum.
Visible and ultraviolet spectra from 200 to 700 nm on solid and liquid effluents
were obtained on a Gary Model 14 Recording Spectrophotometer using conventional
procedures.
A Finnegan Model 4021 GC/MS data system was used toward completion of the
study for analysis of the polyaromatic dye decomposition products.
4. 5 EXPERIMENTAL PROCEDURE
In general, the procedure was the same as that used in previous expanded-scale
plasma reactions. (1) Certain modifications were required, however, as the result of
differences in feed technique, and several are detailed in the Appendix.
Initially, the entire system was evacuated to about 1 torr. The pressure was
then adjusted to about 10 torr by the addition of oxygen. The microwave power was
then turned on to initiate the plasma. Additional oxygen was introduced to obtain the
desired pressure and flow rate in combination with regulation by the main throttle
valve. At this point, the tuning controls were adjusted to give minimum reflected
power. After obtaining a background MS scan (reactant gas flowing minus material
to be detoxified), a needle valve at the bottom of the dropping funnel in the case of
liquids was opened to begin introduction of the dye mixture. The gaseous effluent
from the plasma was sampled and analyzed by mass spectrometry several times
during the course of a run.
8
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SECTION 5
RESULTS
The experimental approach was to obtain maximum throughput, with the objective
of achieving the lowest process costs. Generally, the total microwave power avail-
able was applied to the discharge. This allowed the plasma to operate at maximum
pressure, thereby permitting a maximum amount of oxygen to be used as the plasma
gas for reaction with the dye mixture.
The dye mixture was fed into the plasma system in several forms: as a methanol-
water mixture, a methyl ethyl ketone solution, an aqueous slurry, and a powdered
solid. Each of these materials was tested, but only the water slurry could be intro-
duced uniformly and reproducibly to obtain reliable analytical data. This work is
described from a chronological standpoint in the Appendix, and elucidates the prob-
lems as they developed and the solutions that were applied. The development of the
successful water slurry feed technique and subsequent detoxification is described in
the following subsections.
Of the several feed systems that were tested for the introduction of the dye mixture
into the plasma zone, the aqueous dispersion technique was the most successful. The
apparatus constructed for this application (Fig. 3) used the technology described in the
Appendix, section A. 4, with regard to development of dye dispersions in a water
medium. Experimental results using this technique are described in the following
paragraphs.
Since the red dye components, as a mixture, are essentially hydrophobic, TEC
1216E nonionic surfactant (TEC Chemical Co., Monterey Park, CA) ethylene oxide
nonylphenol, was used to produce the required dispersions. The slurry was prepared
from a 20 percent red-dye mixture dispersed in 2 percent aqueous surfactant, using
a V-7 "Lightnin" mixer for 20 min at maximum shear, in a 250-ml stainless steel
beaker. The slurry was filtered through a 100-mesh stainless steel screen. The
resultant solids content was 15.5 percent. Density was 1.03 g/cm3. No attempt
was made to recover or wash the remaining solids through the screen at this point
in the development process. The addition of the dye slurry occurred uniformly and
predictably. The dispersion settled slowly and showed a low shear-dependency rela-
tive to higher concentration thixotropic slurries that were also prepared. Rates of
addition were varied from 2 to 8 cnvVmin. The total quantity of slurry introduced
over an 18-min period was 58 cm3. This time period resulted from material limita-
tions, since only 10 g of dye powder remained in reserve when the series was run.
Consequently, no attempts to optimize the process were possible. Experimental
details are given below:
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PRESSURE EQUALIZING LINE
r ^»jo
^ v «-*s-JBBf
T * ^D*
I I
MM ORIFICE STOPCOCK
OXYGEN DISTRIBUTION RING
SLURRY FEED TUBE
' HI
QUARTZ REACTOR TUBE
COOLING AIR DUCTS'
MICROWAVE CUT-OFF TUB
MICROWAVE APPLICATOR
Figure 3. Red dye slurry feed system.
10
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Run No.: 68-58
Applicator: Series C, 0.6-liter reactor volume
Microwave Power: 4.6kW
Maximum Feed Rate (not optimized): 494 g/hr slurry, 87 g/hr
equivalent solids
Pressure Range: 35-60 torr
Oxygen Flow: 300 liters/hr
Packing: Quartz Raschig rings: 25% 0.4 by 0. 8 mm, top zone;
75% 0. 8 by 0. 8 mm, bottom zone
Conversion: 99.99%, based on starting material, which reacted to form
a mixture of gases and a solid residue
The principal effluent gases were CO2, CO, and H2O. The nitrogen oxides which
were expected were not observed because of a 2 to 3 part per thousand limit of sensi-
tivity in the mass spectrometer.
Samples were collected at three trap positions downstream from the plasma.
Methylene dichloride was used to dissolve the residues. A blank or control run was
performed preliminary to the detoxification sequence. Based on the weight of start-
ing material, the unknown solid residue, which was detected in the receiver, meas -
ured less than 0.2 percent.
Spectrophotometric comparisons in the visible region of a methylene dichloride
solution of the unknown solid, and known concentrations of the initial dye mixture in
the same solvent indicated that not more than 5 ppm of the starting dyes had passed
through the plasma. Polyaromatic hydrocarbons were not detected above 2 ppm,
using an automatic GC/MS data system. The less than 0.2 percent reddish-brown
residue showed via IR and GC/MS the additional presence of dioctyl phthalate, sili-
cone materials, and benzene traces, which probably entered the analytical samples
during the CH2C12 washing of the traps and connective tubing.
In Fig. 4, an infrared scan of the residue on a Perkin Elmer 621 spectrophoto-
meter is shown. A Finnegan Model 4021 was used for the GC/MS data system analysis
of the same residue.
UV fluorescence from the residue was negative, using a 2537 A Pen Ray quartz
lamp source, whereas 10 of 12 PAH compounds suggested by NWSC, Crane, Indiana,
as possible oxidation products of the dye mixture luminesced brightly. Two of the
12 compounds did not fluoresce and, subsequently, were scanned in the ultraviolet
after dissolving in methylene dichloride solution. Their reported spectral peaks
differed significantly from that of the residue in the same solvent. Table 2, Part I,
is a list of these compounds and their ultraviolet response to 2537 A UV exposure.
Ultraviolet Spectrophotometric scanning of the residue dissolved in methylene
dichloride showed no absorption peaks that could be attributed to PAH compounds
with known maxima. A listing of additional PAHs in Table 2, Part n was obtained
11
-------
WAVELENGTH (MICRONS)
6 7
Aromatic double bond region,
Probably water
4000
3500
3000
600
Figure 4. Infrared scan of solid residue from oxygen plasma reactor.
-------
from Ref. 5. Since PAHs have been found in air oxidation products derived from these
materials, (6) a significant advantage would appear to derive from the plasma process.
TABLE 2. POLYAROMATIC COMPOUNDS AND THEIR 2537 A ULTRAVIOLET
FLUORESCENT RESPONSE AND ABSORPTION MAXIMA
Compound
Visible
Fluorescent
Response
to 2537 A UV
UV Absorption
Maximum
(/on)
Parti
Anthracene
Benzo-a-phenanthrene
Benzo-d, e, f-phenanthrene
Benzo-a-pyrene
Chrysene
Decacyclene
1,2,3,4 - Dibenzanthracene
1,2,5,6 - Dibenzanthracene
9,10 - Dimethylanthracene
7,12 - Dimethylbenz-a-anthracene
9,10 - Dimethylbenz-a-anthracene
1-Methylnaphthalene
+ (yes)
- (no)
254
297
270
299
258
280
Part II
Phenanthrene
Pyrene
Fluoranthene
1,2 - Benzanthracene
3,4 - Benzopyrene
Perylene
Anthanthrene
1,12 - Benzoprylene
Coronene
295
338
289
290
270
334
441
435
388
13
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REFERENCES
1. Municipal Environmental Research Laboratory, Development of Microwave
Plasma Detoxification Process for Hazardous Wastes Phase I, Final Report
EPA-600/2-77-030, EPA Contract 68-03-2190, Cincinnati, Ohio 45268, Apr 1977.
2. Naval Weapons Support Center, Ecological Disposal/Reclaim of Navy Colored
Smoke Compositions. Interim Report NWSC/CR/RDTR-36, Crane, Indiana
47522, 1 Jun 1976, pp. 5, 22.
3. Ref. 2, p. 7.
4. Brown, L. C. and A. T. Bell, "Kinetics of the Oxidation of Carbon Monoxide
and the Decomposition of Carbon Dioxide in a Radiofrequency Electric Discharge,"
Ind. Eng. Chem. Fund, Vol. 13, Mar 1974, pp. 203 - 18.
5. Leithe, W., Hie Analysis of Air Pollutants. Trans R. Kondor, Ann-Arbor-
Humphrey Science Publishers, Ann Arbor, Michigan, 1970, p. 260.
6. Ref. 2, p. 12.
14
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Appendix
CHRONOLOGICAL DEVELOPMENT OF FEED TECHNIQUES
A.I METHANOL-WATER MIXTURE
The first mixtures that were prepared contained 15 to 20 percent solids in 50/50
wt% methanol-deionized water solutions. Introduction to the plasma zone was by way
of two feed methods a 1-liter pressure-equalized volumetric dropping funnel and a
250 cm3 volumetric dropping buret which was open to the atmosphere at the top.
Methanol was used, since it wetted and dissolved a large amount of dye, but would not
consume a disproportionately large amount of oxygen in the plasma reaction. Water
was used in combination with methanol in order to minimize the oxygen demand of
the solvent. The 50/50 proportion was, from a handling standpoint, an efficient com-
bination, because the solids settled extremely slowly while waiting for the feed step
to start after filling the reservoir of the buret or funnel.
During the addition of these mixtures, however, the dissolved dye components and
the slurry solids clogged the orifices of both feed devices. This was caused by rapid
evaporation of the methanol solvent component of the system as the liquid passed from
bulk form into droplets in the reduced-pressure environment. The contention that the
clogging was increased by the presence of agglomerated solids in the slurry indicated
that this combination would probably not be satisfactory under any conditions and,
thus, was removed from further serious consideration.
A.2 POWDERED SOLIDS
A.2.1 Laboratory Model Continuous Solids Feeder
A first generation solids feed method was constructed to introduce materials into
the plasma zone via gravity fall. Figure A-l is a schematic drawing of the unit.
Figures A-2 and A-3 are photographs that illustrate the device positioned above the
reactor. Not shown in the drawing are relief valves and pressure-equalizing con-
nections between the lower chamber and the belt-feed area.
Tests under vacuum, as well as atmospheric pressure, showed that for granular,
free flowing solids, the system worked very well. For non-free-flowing powders,
however, "bridging" and "ratting" occurred in the lower chamber. The use of a
"Vibro-Graver" vibrator (Burgess Vibrocrafters, Inc., Model V-73), in which the
side of the vibrator shaft was placed against the outside handle of the lower powder
transfer valve, produced an immediate improvement but did not solve the problem
completely. Powder feed rate was low, but acceptable on an interim basis. Through-
put was about 1/2 kg/hr (1 Ib/hr).
15
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BLEED
VALVE
VACUUM
VALVE
POWDER
TRANSFER
VALVE
VACUUM
OXYGEN IN
VACUUM
OXYGEN IN
TO PLASMA
Figure A-l. Schematic of solids feed system.
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Figure A-2. Solids feed system, close up.
17
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Figure A-3. Solids feed system, front view.
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To minimize "ratting" etc., in the test powder, which was a non-free-flowing
mixture, the powder was pressed into 7.6 cm (3 in.) diameter cakes at about 15,000
psi, then crushed and sieved through an 80-mesh screen. The particles smaller than
80 mesh now essentially free-flowing could be added via the endless belt technique.
Because of their large size as compressed agglomerates, however, a second problem
developed which appeared, initially, to be related to a nonhomogeneous addition rate.
However, it was later surmised that the larger particles upon contacting the plasma
zone, decomposed very rapidly in the usual manner, resulting in development of
significant pressure differentials between the vacuum feed chambers and the lower
plasma reactor. As a result, the powder particles, in the process of falling under
gravity or during decomposition, were also drawn upward toward the feed chamber,
producing a whirlwind phenomenon with attendant, unpredictable changes in the amount
of material falling onto the belt, and consequently, off the belt into the plasma. The
results of this method were readily apparent in the tarry products which had not even
"seen" the plasma decomposition zone. To solve this problem, it will be necessary
to install larger-diameter pressure-equalizing connections between the feed and the
reactor chambers, and increase the construction angles of the hopper chambers.
During another powder feed sequence in which the original noncompacted powder was
being drop fed into the plasma, some air leaks developed in the feed system. Although
the run was otherwise acceptable, the presence of air precluded the reaction products
from being considered as valid samples for analysis. Since air-plasma reactions
result in NO, and probably NC>2, these NOX products could react with the dye as it
passed through the plasma zone or with the plasma effluent gases further down stream.
These nitrogen-containing materials would be nonreproducible and, more importantly,
nonrepresentative of oxygen plasma reactions.
A.2.2 Pressed-Cake Batch Process
In another series of exploratory runs, small 2.5 cm (1 in.) press cakes were
treated in the plasma. The discs were formed at 1,000 psi, and placed in the reactor
above the Raschig ring section. The resultant cake breakup and plasma reactions
were also uneven. It was postulated that a much more rapid decomposition of the easily
decomposed sugar component (20 percent of the mixture) occurred in comparison
with that of the aromatic dye components. Since the microwave plasma is routinely
started at 10-torr oxygen pressure, the physical breakup of the press cake, and con-
comitant rapid powder flash-through, could have occurred prematurely, i.e., before
addition of the oxygen could be made to increase pressure to the required levels ad-
equate for detoxification. These phenomena inadequate oxygen and nonuniform cake
breakup are related directly to batch processing and would not be expected to occur
in a continuous feed system.
In the above context, attention is called to the successful press-cake decomposition
described in the Special Report, Microwave Plasma Detoxification of Kepone Pesticide,
May 1976. In these tests, the press cakes (80% Kepone, 20% clay) decomposed uni-
formly and cleanly in the plasma environment. The relative simplicity in the number
of organic compounds of the Kepone mixture, relative to the Navy dyes, may have
contributed to this difference. In addition, Kepone, when treated, sublimes from a
solid powder directly to the vapor state, and would be expected to react very rapidly
in the gas phase. However, the organic dye mixture components (two aromatic dyes,
sugar, carbon) will melt, decompose, and/or carbonize before reacting in the plasma,
19
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and only slowly under these batch conditions because of the large particles present in
the mass of the charred material. It is probable, therefore, that sublimation was a
principal cause of the extremely rapid and, therefore, favorable reactions which are
noted above for the Kepone-oxygen plasma detoxification.
Further in-house development was not pursued for two reasons: (1) commercially
available feeders were scheduled for acquisition during Phase IE of the current program
and (2) development of a rotating or vibrating reactor, plus reactor-internals (packings),
will be necessary in order to develop the needed capability for variable residence time
in the reactor. This is also part of Phase IH.
A.3 METHYL ETHYL KETONE SOLUTIONS
In this system, MEK was used as solvent per recommendations from NWSC, Crane,
Indiana. Mixtures, typically 40-g red dye mixture and 80-g MEK, were prepared and
allowed to stand overnight, or mixed 1 to 2 hr. The resultant solutions were filtered
and used for the plasma reaction tests. In all cases, the tip of the dropping funnel
clogged before the dye could reach the plasma. Since it became obvious, after the
fact, that the clogging was related to deposits at the orifice which occurred when the
solutions evaporated, lower, 13 to 15 percent concentrations were prepared. These
solutions passed through the feeder with no difficulties, and were detoxified with no
red colorations or deposits visible below the reactor. The products detected by MS
were CO£, CO, and H2O. Nitrogen oxides were expected, but these were below
detectability because of a 2 to 3 parts per thousand sensitivity in the mass spectrometer.
However, each mole of MEK, which made up 85 to 87 percent of the solution consumed
110 to 130 liters of oxygen as it passed through the plasma. This was counter-productive
for both the solvent and the oxygen plasma gas, indicating that essentially any solvent
system that is added purposely will result in an uneconomic operation of the process.
This led subsequently to preparation of aqueous dispersions as a feed vehicle, which
led to the successful introduction and detoxification reaction for the dye mixture.
Details of this development are presented in the next section.
A.4 AQUEOUS DISPERSIONS
Since the red dye components as a mixture were essentially hydrophobic or non-
water wetting, the initial effort involved obtaining wetting agents/surfactants which
would yield hydrophilic or water-wettable dispersions. The silica gel and carbon black
were expected to wet reasonably well, whereas the two dye components, xylene azo-/3-
naphthol and 1-methyl-aminoanthraquinone, were the principal hydrophobic components.
The sugar, of course, dissolved on wetting, hi consultation with NWSC personnel,
several surfactants were suggested in addition to those on hand at LPARL. A series
of tests was then run by mixing tenth-gram samples with 2 percent solutions of the
surfactants and visually determining the results of enhanced wetting. The best agent
was used to prepare concentrated slurries using a V-7 "Lightnin" mixer as a medium-
to-high shear agitator. Stability in suspension was also evaluated on a visual basis.
A list of the agents tested is given in Table A-l.
A nonionic surfactant, TEC 1216 E, yielded the most readily wetting, stable sus-
pension at 25 to 30 wt% solids. This agent is reported by Rohm and Haas to be very
similar to their Triton N-101 nonionic surfactant, which is a water-soluble nonyl
phenoxy polyethoxy ethanol containing 9 to 10 moles of ethylene oxide.
20
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TABLE A-l.
SURFACTANTS TESTED FOR PREPARATION OF AQUEOUS
RED DYE DISPERSIONS
Trade Name
Source
Type
Chemical Identity
TEC 1216 E
Ethoquad C/12
Roccal 10%
Aerosol OS
Aerosol OT
Aerosol GPG
TEC Chemical Co.
Armour Industrial
Chemicals
Winthrop Labs
American Cyanamid
American Cyanamid
American Cyanamid
Matheson Coleman
and Bell
Nonionic
Cationic
Cationic
Anionic
Anionic
Anionic
Anionic
Ethylene oxide nonylphenol
Methylbis (2-hydroxy ethyl)
cocoammonium chloride
Alkyl (C18H17-C18H37)
dimethyl benzylammonium
chloride
Sodium isopropyl-naphthalene
sulfonate
Sodium dioctyl-sulfosuccinate
Sodium lauryl sulfate
Various formulations of the dye in the TEC 1216 solution were added through a
dropping funnel inserted above the plasma zone. The funnel was used at atmospheric
pressure above the slurry. In all instances, using different stopcocks, orifices,
valves, etc., the slurry flow was such that excessive amounts entered the reactor as
the result of plugging and deplugging of the orifices. These instantaneous plug break-
throughs were large, on the order of 5 to 10 cc/s (40 to 80 lb/hr), which obviously
exceeded the oxygen supply in the reactor, causing untoward, excessive contamination
in the quartz reactor. It was determined next that when the slurry was added with
reduced pressure above the feed that plugging was minimized. It was this modification
which, in combination with other variables, permitted successful feed of the dye dis-
persion. The investigative steps are described below listing the methods used for
solving the non-Newtonian (thixotropic) flow and other problems associated with feed
procedure. A photograph of the new feed system is shown in Fig. 3, Section 4.
The following variables were studied in this connection.
The pressure head above the buret stopcock was minimized by decreasing
the height of the slurry. This included equalizing the pressure above the
slurry to approximately that of the reactor through the use of flexible tube
connections.
A precision oxygen feed-ring for uniform gas addition into the reactor was
designed, machined, and operated successfully.
21
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The feed stopcock orifice size was optimized at 1 mm diameter. Less than
1 mm resulted in clogging. Greater than 1 mm resulted in an excessive
introduction rate which was significantly more than 10 lb/hr. The stopcock
was constructed from Teflon in order to obviate the need for stopcock lubricant.
When grease was used for the 1-mm orifice stopcock, clogging occurred. It
was necessary that the stopcock also be vacuum tight (approximately 1 torr)
to avoid nonuniform bubbling and frothing within the slurry.
The glass feed-line tube between the stopcock and the reaction zone was con-
structed to have a diameter significantly greater than the buret tip internal
diameter. The tube was cleaned with laboratory glassware detergent
("Alconox") to produce a water break-free surface to avoid nonuniform drop
formations within the tube. The tube end was cut 45 deg to minimize the size
of the drops. The position of the feed tube within the microwave cutoff was
optimized to prevent spattering and/or overheating within this zone, which,
if not prevented, could result in excessive evaporation and clogging at the tip.
The optimum slurry was developed from a number of trial dispersions; A
20 percent red dye mixture was dispersed in a 2 percent TEC 1216E surfactant solu-
tion using a V-7 Lightnin mixer for 20 min, with maximum shear/agitation in a stain-
less steel beaker. The slurry was filtered through a 100-mesh stainless steel screen
(nominal 150 /An openings). The resultant solids content was 15.5 percent. Density
was 1.03 g/cm3. The dispersion settled slowly and showed minimum thixotropy
relative to 30 percent slurries also prepared.
The above techniques, concentrations, etc., were developed specifically for gravity-
flow feeding for the current plasma reactor. It is important to note, however, that
because of the complex design required for gravity-flow introduction, the forthcoming
Phase m methods will utilize positive displacement feed techniques for liquids, dis-
persions, and related materials to obviate the requirement for these time-consuming
engineering developments.
22
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
. REPORT NO.
EPA-600/2-78-081
3. RECIPIENT'S ACCESSIOf»NO.
4. TITLE AND SUBTITLE
Summary Report
DETOXIFICATION OF NAVY RED DYE BY MICROWAVE PLASMA
5. REPORT DATE
June 1978 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
. AUTHOR(S)
Lionel J. Bail in
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Lockheed Palo Alto Research Laboratory
Lockheed Missiles and Space Company, Inc.
Palo Alto, California 94304
10. PROGRAM ELEMENT NO.
1DC618
11. CONTRACT/GRANT NO.
Contract No. 68-03-2190
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory--Cin.,OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Partial for Phase II 8/76-6/7I7
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES
Project Officer: Donald A. Ob.eracker (513) 684-7881.
This contract is ongoing and currently Phase III is underway.
See also EPA-600/2-77-030 and EPA-60Q/2-78-Q8CL
16. ABSTRACT
he process of microwave plasma detoxification has been applied successfully to the
destruction/disposal of a U.S. Navy red dye pyrotechnic smoke mixture. The mixture
vas added as a powder, a solvent solution, and a water slurry.
Material balance for detoxification of the slurry indicated that less than 0.20 percent
solids were found beyond the reaction zone, or 99.8+ percent conversion to gaseous
)roducts. Analysis by spectrophotometry in the visible region indicated little or no
dye starting materials ( < 5 ppm) in the residue. Ultraviolet fluorescence, UV spectro
photometry, and gas chromotography/mass spectrometry indicated the presence of less
than 2 ppm carcinogenic polyaromatic hydrocarbons (PAH). Since PAH has been found in
ir oxidation products derived from these materials, a significant advantage would
appear to derive from the plasma process.
During the study, several vacuum feed techniques were evaluated with a view toward
their utilization in forthcoming pilot equipment tests. Especially with high solids
slurries and solutions, where non-Newtonian flow can cause difficulties when gravity
feed methods are used, it will be necessary to use positive displacement methods to
obtain uniformity and reproducibility during the addition process.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COS AT I Field/Group
detoxification, degradation, decomposition,
waste disposal, microwave equipment, organi
wastes, pesticides
new microwave technique,
microwave disposal proce
Navy Red Dye
5S,
13 B
18. DISTRIBUTION STATEMENT
Release to public
19. SECURITY CLASS (ThisReport)
unclassified
21. NO. OF PAGES
33
20. SECURITY CLASS (Thispage)
unclassified
22. PRICE
EPA Form 2220-1 (9-73)
23
* U.S. GOVERNMENTPHOTIHC OFFICE; 1978 757 -140 /1314
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