United States
Environmental Protection
Agency
Municipal Environmental Research 5
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-82-021 May 1982
Project Summary
Sodium Fluxing and In-Situ
Classification for Hazardous
Materials Disposal
J. S. Greer, G. H. Griwatz, S. S. Gross, and R. H. Hiltz
Toxic waste disposal has become a
prime consideration in the maintenance
of the ecosystem. Numerous materials
of commerce pose problems in dis-
posal, being unsuitable for landfill and
resistant to thermal degradation. A
project was instituted by the U.S.
Environmental Protection Agency
to evaluate new approaches to the
ultimate disposal of such materials.
This program, one segment of the
major project, was instituted to assess
two innovative techniques, in-situ
glassification and reactive degradation
using liquid sodium.
The glassification technique was
successful in the encapsulation of
toxic materials. Because of the need
for very high reaction temperatures.
however, small but significant quanti-
ties of the toxic material were vented
during reaction. This difficulty could
not be corrected within the limits of
this contract.
The use of a molten sodium medium
to thermally degrade toxic materials to
products acceptable for direct disposal
or recovery was successfully demon-
strated. Based upon the data derived
and the existing state-of-the-art, a
practical system to use this technique
for ultimate disposal appears feasible.
This Project Summary was devel-
opedby EPA's MunicipalEnvironmen-
tal Research Laboratory, Cincinnati,
OH, to announce key findings of the
research project that is fully document-
ed in a separate report of the same title
(see Project Report ordering informa-
tion at back).
Introduction
As technology for the control and
cleanup of hazardous material spills has
evolved, the volume and types of mate-
rials that must be disposed of has
increased commensurately. Difficulties
have arisen in the disposal of certain
hazardous material categories. The short-
comings of landfill disposal have been
quite evident. Incineration is more re-
liable, but it is not adaptable to all
hazardous chemicals.
The existing situation has led the
Environmental Protection Agency to
investigate alternate procedures for the
ultimate disposal of hazardous chem-
icals. As part of this general investiga-
tion, a contract was awarded to MSA
Research Corporation to conduct a
laboratory feasibility study of two pro-
cedures—sodium metal fluxing and
glassification—for ultimate disposal.
Both procedures had sufficient back-
ground information to justify the investi-
gation.
At temperatures above its melting
point, the ability of sodium to degrade
organic compounds into simple or ele-
mental substances is well known. The
process, however, has never been in-
vestigated as a disposal technique.
The encapsulation of materials in a
glass matrix has been under investiga-
tion for some time as a disposal tech-
nique. The approach to date has been to
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disperse the material to be disposed in a
molten glass phase. The process could
be considered reasonably successful,
except for the fact that the dispersed
material is not always totally encap-
sulated. Since dispersion cannot be
accomplished on a micro scale, networks
of the contained phase can persist to the
surface of the total mass.
A laboratory study was initiated to
evaluate molten sodium as a mechanism
for degrading a range of hazardous
materials to disposable products and to
investigate encapsulation using in-situ
glass formation. The sodium fluxing
process was successfully demonstrated
for several categories of materials. The
glassification study, although technically
successful, generated some side effects
that were undesirable.
Glassification Study
The use of glass to encapsulate toxic
or radioactive materials for safe dis-
posal has seen extensive development.
Although several procedures have
evolved, they all essentially blend the
chemical to be disposed into a molten
glass matrix. The basic drawback has
been the difficulty of entraining the
material for disposal as a discontinuous
phase. Gross segregations or semi-
continuous areas in the glass allow a
path to the surface to occur, thereby
enabling the encapsulated material to
be leached by long-term exposure to the
environment. This action is exaggerated
when cracking or other failures occur in,
the glass.
This difficulty could be minimized by
dispersion of the encapsulated phase on
a micro scale. One approach is to use a
large volume ratio of glass to material
for disposal. An alternate approach,
which would also result in a smaller
disposal volume, appears possible if the
glass phase could be pyrochemically
formed in-situ. This procedure would
blend glass-forming compounds with
the material for disposal. A thermal
reaction would fuse the mass into glass
and entrain the hazardous material as
discrete particles.
A test program was conducted in
three steps—definition of pyrochemical
compositions that would form a glass,
selection of an optimum system based
upon leaching resistance, and deline-
ation of acceptable glass/hazardous
chemical ratios.
The test phase was begun by evalu-
ating pyrochemical glass reactions pre-
viously reported.* The basic thermal
reaction is given in equation 1 :
10K02
(1)
B203, Si 02, and AI2Os are added as
glass-forming compounds. Glass was
formed by these reactions, but the off-
gasing of COz caused severe porosity
and impaired fusion.
Additional pyrochemical reactions
were evaluatedto develop an essentially
gasless reaction. The restrictions im-
posed by the need to stay within the
glass-forming compositions limited the
reactions that could be considered to
the alkali and alkaline earth metal
peroxides and superoxides and the
metals silicon, boron, and aluminum.
A large number of compositional vari-
ations were evaluated. Equation 2 gives
the composition finally selected as the
best glass former.
8 KOz + 3 Si + 4 Al
3SiO2+2AI2
(2)
To evaluate the glass-forming reaction
as a mechanism of encapsulation, five
nonvolatile test compounds were selec-
ted. These were copper arsenate, cad-
mium selenide, leaddihydroxydicarbon-
ate, antimony sulfide, and ammonium
dichromate. These represent toxic in-
organic compounds containing heavy
metal ions. They cover materials that
decompose below the temperature of
the pyrochemical reaction (white lead
and dichromate), an intermetallic(CdSe),
and compounds that could take part in
the glass reaction (arsenate and sulfide).
In each case, the selected compound
was added as 25-volume percent of the
glass-forming components.
With the exception of the cadmium
selenide system, all compacts formed a
glass. The cadmium selenide charge
resulted in a porous clinker.
All compacts were subjected to 48-
hour exposures to boiling water leaching
studies. The averaged results of these
tests are as follows:
Element
Arsenic
Antimony
Chromium
Lead
Selenium
Cadmium
Copper
Leachate
mg/100 ml
5.0
1.5
0.01
0.05
1.70
0.025
0.12
'Carbon Dioxide Generating Compositions, U.S.
Patent No. 3,477,955.
Although the leaching results wer
encouraging, all fusions had as a
undesirable side effect, the release c
paniculate matter during reaction. Anal
yses showed that between 1 and •
percent of the material being encap
sulated or of a product resulting from it
thermal decomposition was released.
The investigation established that <
glass phase can be developed througl
pyrochemical reaction of base compo
nents and that materials can be incor
porated into the glass matrix during it!
formation with good resistance to ex
traction by leaching.
The utility of the pyrochemical systerr
is compromised by the release of panic-
ulate matter containing the hazardous
compound during reaction. The amount
lost is small compared to the total
volume of reactants, but it does not
appear to be a tolerable situation. Pro-
cesses to alleviate the problem were
defined, but not investigated.
Liquid Sodium Reactions
The ability of liquid sodium to degrade
a broad range of chemicals is well
established. Data have been developed
on the fate of the basic decomposition
products. With the exception of hydro-
gen and nitrogen, which are released as
pure gases, all other elements that
would occur in toxic materials would be
retained by the sodium and would be
recoverable as innocuous materials.
Some occur as particulates and can be
filtered out. Others have temperature
sensitive solubilities and can be removed
through temperature control. In a few
cases, distillation or dissolution of the
sodium may be necessary.
Because liquid alkali metals are used
as heat transfer fluids, systems to
handle liquid sodium are items of com-
merce, and technology is available to
provide a liquid alkali metal system to
degrade toxic materials. Questions re-
main concerning the controllability of
exotherms that may result and the ability
to remove or otherwise recover the
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resultant degradation products in a
practical manner.
An experimental apparatus was de-
signed, based upon the current practice
for alkali metal handling systems, to
conduct a laboratory evaluation of liquid
sodium as a disposal system. Five
representative hazardous materials were
selected for the test program—antimony
trisulfide, mercuric chloride, sodium
fluorosilicate, 2-chloro-4-phenyl phenol,
and parathion. Kepone was added as a
test material later in the program.
The reactions of the six materials with
molten sodium showthatthis technique
can provide the basis for the disposal of
many otherwise unmanageable waste
materials. As expected, the materials
reacted with excess sodium to form
innocuous salts, carbon, and free metals,
with the release of gaseous hydrogen.
The simple salts, mercuric chloride and
antimony sulfide, degrade basically to
the metal and appropriate sodium salt.
The more complex compounds proceed
through a series of intermediate reaction
products but ultimately degrade to basic
elements or sodium salts. This was
observed in tests with 2-chloro-4-phenyl
phenol, kepone, and parathion. Nitrogen
was the only element that did not behave
as expected. Parathion, which has a
nitro substituent, should have released
nitrogen, but none was found.
The products of these reactions (salts,
heavy metals, and free carbon) can be
separated by combinations of filtering,
cold trapping, solvent extraction, and/or
vacuum distillation. They could be re-
moved as relatively pure materials for
recycling, or as innocuous waste prod-
ucts that could be handled by standard
disposal procedures.
The potential of the system for degrad-
ing essentially pure materials has been
established. It is reasonably certain that
using state-of-the-art technology and
equipment, a system of commercial size
could be developed.
The full report was submitted in ful-
fillment of Contract No. 68-03-2492 by
MSA Research Corporation under the
sponsorship of the U.S. Environmental
Protection Agency.
J. S. Greer. G. H. Griwatz. S. S. Gross, and R. H. Hiltz are with MSA Research
Corporation, Evans City, PA 16033.
John E. Brugger is the EPA Project Officer (see below).
The complete report, entitled "Sodium Fluxing and In-Situ Classification for
Hazardous Materials Disposal," (Order No. PB 82-196 155; Cost: $7.50,
s subject to change} will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Oil'& Hazardous Materials Spills Branch
Municipal Environmental Research Laboratory—Cincinnati
U.S. Environmental Protection Agency
Edison, NJ 08837
if U S GOVERNMENT PRINTING OFFICE, 1982 — 559-017/0720
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