United States
Environmental Protection
Agency
Municipal Environmental Research ~
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-83-091   Dec. 1983
Project  Summary
Bromination   Process  for
Disposal  of  Spilled  Hazardous
Materials
A.J. Darnell
  A novel process was tested for oxi-
 dizing organic materials, including so-
 called "refractory organics" and pesti-
 cides. Bromine and water were allowed
 to react with such materials at 250° to
 300°C to form carbon dioxide and
 aqueous  hydrobromic acid. The HBr
 solution can be electrolyzed at ambient
 conditions, using a membraneless
 electrolysis cell, to produce hydrogen
 and regenerate bromine for recycling.
 The byproduct hydrogen can be sold or
 used as fuel for the process.
  The bromination process has now
 been evaluated for the destruction of
 hazardous  waste spills on both a
 laboratory and a pilot-plant scale. Mala-
 thion,* the selected model compound,
 was successfully treated in an 8-liter,
 tantalum-lined autoclave at 300*C as
 part of a simulated spill mixture
 consisting of the malathion, soil, sand,
 humus, and  moisture. Essentially
 complete destruction of the malathion
 (>99.9999%) was achieved.
  The aqueous HBr solution resulting
 from the oxidation was electrolyzed in
 an  inclined membraneless cell with
 graphite electrodes to yield a solution
 containing about 20 wt % HBr and 18
 wt % dissolved bromine. Coulombic
 efficiency for the electrolysis was about
 96%.
  A conceptual design for a larger-scale
system was developed on the basis of
the laboratory and pilot-plant results.
This design consisted of batch oxidation
coupled with continuous electrolysis. It
could process hazardous wastes at an

•Mention of trade names or commercial products
does not constitute endorsement or recommendation
for use.
average rate of 7.5 kg/hr. The total
capital cost for such a system installed
at an available site was estimated at
$625.000 in January 1979.  Of this
total, $350,000  represented actual
costs for equipment.
  Laboratory-scale oxidations using
bromine were also carried out using
two chlorinated hydrocarbons, gamma-
lindane, and heptachlor. Under the
conditions employed, which were not
optimized, decomposition of  both of
these compounds was less efficient
than when trichloroethane was the
substrate.  The HBr yields for lindane
and  heptachlor were 56% and 71%,
respectively.
  This Project Summary was developed
by EPA's Municipal Environmental
Research Laboratory, Cincinnati,  OH,
to announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).

Introduction and Background
  The health and safety factors related to
hazardous materials mandate that a high
level  technology be used in their disposal
or destruction. Methods used to dispose
of hazardous wastes must also be able to
cope  with the nonhazardous materials
that  are often present, such  as dirt,
vegetation, and water. The variability in
hazardous wastes encountered and the
conditions under which cleanup must be
conducted create unique problems for
response and cleanup personnel.
  Rockwell International has developed a
novel process that uses oxidation with
bromine  and  water to  destroy organic

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materials. When allowed to react with
bromine and water at 250° to 300°C in a
closed system, organics (represented by
CH) are oxidized to carbon dioxide and
aqueous  hydrobromic acid according to
the general Equation 1:
                     COi (To Atmosphere)
                                                     H2 for Use
                                                      or Flare
        CH + 2.5 Br2 + 2 H20 -

        5HBr(aq. sol.) + CO2
(1)
The carbon dioxide can be released to the
atmosphere  after  the bromine  and
hydrogen bromine  vapors have been
stripped. The hydrobromic acid solution
can be electrolyzed,  as in Equation 2, to
produce hydrogen and bromine:


     SHBr (aq.) electrolytic cell
               •	>
     2.5H2 + 2.5Br2(indil.HBr)      (2)

The hydrogen can be sold or used as fuel
for the process, and the bromine can be
recycled  to the oxidation  process.  The
process sequence is shown schematically
in Figure 1.
  During the first portion of this program
(designated as Task 1), laboratory investi-
gations were conducted  on the bromine
plus water  oxidation of  three  typical
hazardous chemicals—copper acetate,
trichloroethane, and malathion.  At the
preferred reaction temperature of 300°C,
destruction of all three compounds was
essentially complete in  1, 3,  and 5 hr,
respectively. The  chlorine, phosphorus,
and sulfur  in  the compounds were
converted to hydrochloric, phosphoric,
and sulfuric acid, respectively.  The
project  demonstrated  that the  metallic
bromides formed from the copper  (and
from other inorganic  components  that
might be in an actual spilled waste) could
be treated with sulfuric acid to recover
the bromine and reduce the bromide
content of the residue (inorganic sulfates)
to 0.6 ppm.
   Task 1 was alsodevoted to developing a
suitable  process for the electrolysis  of
aqueous HBr solutions. With the constant
boiling,  47% HBr/water azeotrope, a
minimum no-load decomposition poten-
tial of 0.69 volts was measured at 25°C.
Though  lower decomposition voltages
can be obtained at higher temperatures,
the nature of hazardous waste disposal is
such that it seemed advisable to carry out
the HBr electrolysis at ambient tempera-
ture and pressure in spite of this penalty.
Decomposition voltage was also found to
depend on  HBr concentration,  with
higher  voltages required for 20% and
65% HBr than for 47% HBr.
Carbonaceous -^
Waste
    Water —
                                         Concentrated
                                       Hydrogen Bromide
                                          (Aqueous)
                                                                           Electric
                                                                           'Power
                    Ash or
                   Inorganic
                   Residue
                               Bromine + Dilute Hydrogen
                                  Bromide (Aqueous)
      Figure  1.
           Schematic flow diagram for disposal of carbonaceous wastes by the bromination
           process.
        The results of Task 1 of this program
      were reported in the Proceedings of the
      1978 National Conference on Control of
      Hazardous Material Spills, Miami Beach,
      Florida, 1978. p. 221. Hazardous Materials
      Control Research Institute, Rockville, MD
      (now in Silver Spring, MD).

      Experimental Procedures
      and Results

      Laboratory Oxidations  Using
      Bromine
        Parameters affecting the oxidation
      reaction were evaluated by carrying out a
      series  of  experiments, first with  pure
      malathion in water and  then with a
      simulated spill mixture containing 70 wt
      % malathion, 10 wt % sand, 10 wt %
      sand, 5 wt  %  humus,  and  5 wt %
      moisture. The bromine was supplied first
      as a solution of bromine and water and
      later as a solution in aqueous hydrobromic
      acid, as might  be produced from  the
      electrolysis. The test apparatus consisted
      of a 600-ml glass ampule that was sealed
      and placed  inside  a 2000-ml  steel
      autoclave. The  autoclave was heated to
      300°Cand maintained at that temperature
      for up to 5 hr. After the required time, the
      autoclave was chilled in liquid nitrogen to
      condense the  carbon dioxide in  the
      reaction  ampule, and the ampule seal
      was broken.
        Analyses for  malathion residues were
      carried out on the gas phase, the liquid
                                        phase, and (if present) the solid residue
                                        from the reaction using gas chromatogra-
                                        phy with a flame photometric analyzer
                                        sensitive to phosphorus. An  electron
                                        capture detector was later substituted to
                                        achieve increased sensitivity. Liquid
                                        samples were  extracted with petroleum
                                        ether before analysis.  Solid  residues
                                        obtained when the simulated spill mixture
                                        was used  were filtered  to separate the
                                        solids, which  were  then extracted by
                                        refluxing in aqueous hydrobromic acid at
                                        127°C for 30 min. The  liquid was then
                                        extracted with  petroleum ether to obtain
                                        a sample for analysis.
                                          The first three experiments were
                                        intended to demonstrate that changes
                                        from Task 1 conditions would not affect
                                        the results of  subsequent experiments.
                                        These experiments were as follows:
                                          1) A control experiment was conducted
                                        under the same conditions as in Task 1,
                                        except that reactant  quantities  were
                                        increased  about tenfold. The same size of
                                        ampule was used (600-ml), which meant
                                        that the pressure developed from carbon
                                        dioxide would be about 10 atm instead of
                                        1 atm.

                                          2) An experiment was done  in which
                                        bromine dissolved in 22 wt % hydrobromic
                                        acid was substituted for the bromine/wa-
                                        ter  reagent. This  test  was necessary,
                                        since the plan was to reuse the recovered
                                        solutions  from the electrolysis as the
                                        source of  bromine in  the bromination
                                        reaction.

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  3) An experiment was conducted
using  the simulated spill mixture of
malathion with soil, sand,  humus,  and
moisture and bromine dissolved in 22 wt
% hydrobromic acid.
  The change did not adversely affect the
results  in any of the three experiments.
After reaction at  300°C for  5  hr, no
organo-phosphorus residue was detected
in the gaseous, liquid, or solid phases of
the  reaction mixture. Based on  the
sensitivity of the  analytical procedures,
the  bromination  reaction effectively
destroyed more than 99.9998% of the
malathion.
  An experiment was then carried out to
assess the effect of agitation on reaction
time. Agitation, which was accomplished
by  rocking  the autoclave and furnace
assembly at 3 cycles/min, had a clearly
beneficial effect on the destruction  rate
(Table  1).
  Reaction of the  simulated spill mixture
with bromine and water for 5 hr required
more  bromine than malathion  alone
required, since  each of the  added
materials (particularly the humus) also
consumed some bromine. Table 2 summa-
rizes some of the data on  bromine
consumption by the other constituents in
the mixture.
Table 1.    Effect of Agitation on Reaction of
       Malathion with Bromine and Water!*)

            Amount of Malathion Used
Reaction
Time
Ihr)
1
2
2
5
Without
Agitation
1%)
85ft)
89ft)
>99 999ft)
With
Agitation
ss
(*IReaction with an initial Br2/H£)/malathion mole
 ratio of 40/600/1

ftlFrom analyses of HBr. HiSOt. and Hz POt formed

ft)From analysis  of malathion residuals by gas
  chromatography

Table 2.   Amount of Bromine that Reacted with
         Debris in 5 hr at 300°C
Component
Sand
So/I
Humus
Bromine Reacted*
Ig Bromine/ g of
Debris Component)
004
0 11
4.74
"For comparison, the reaction used IS.Sg of bromine
 for each gram of malathion consumed

  Tests were  also carried out  in the
laboratory apparatus at 300°C for  1  hr
using  lindane (gamma-CeHeCU) and
heptachlor (CioHsCI?). With the production
of HBr as a measure of oxidation, it was
clear that both of these cyclic chlorinated
compounds were considerably more
resistant to bromine oxidation than was
trichloroethane. The yields of HBr were
56% for li ndane and 71 % for the heptachlor,
but reaction  conditions  had  not been
optimized.
Pilot-Plant Bromine Oxidation
  The pilot-plant apparatus  consisted
of an 8-liter,  tantalum-lined autoclave
plus all the  auxiliary  equipment for
stirring, heating,  and temperature and
pressure monitoring.  A simulated spill
mixture composed of 35  g malathion, 5
g sand,  5 g soil, 2.5 g humus, and 2.5 g
moisture was  allowed to react with a 5
wt % excess of bromine  at 300°C for 2
hr. When the reaction was complete and
the autoclave was cool, the residual
pressure from carbon dioxide was 1208
kPa. Since the calculated carbon dioxide
pressure for complete reaction was 1159
kPa, the reaction of the  malathion plus
debris mixture was essentially complete.
No malathion residue was detected in the
gaseous, liquid, or solid products.

Laboratory  Electrolysis
  Since the electrolyzed solution was to
be  reused  as the source of  bromine,
electrolysis was carried out with solutions
that would be produced from  copper
acetate, chlorinated organics and mala-
thion (copper  (II), chloride, sulfate and
phosphate). These tests were carried out
in a cell containing graphite  electrodes
(surface area - 14 cm ) and an aluminum
oxide, fibered-felt membrane separator.
  Electrolyzing the  hydrobromic  acid
solution from a copper acetate reaction
required a  lower  decomposition voltage
than when copper-free hydrobromic
acid was used, possibly because of the
increased  ion  concentration  in the
solution. At a voltage of 3.2V, copper was
also observed to plate out on the cathode.
  During electrolysis of  the 47% hydro-
bromic acid solution from the trichloroe-
thane  reaction (which  also  contained
hydrochloric  acid), the decomposition
voltage was about 10%  lower than with
the  control.  Note that no chlorine
evolution was detected, since the decom-
position voltage for hydrochloric acid is
about 0.5 V higher than that of hydrobro-
mic acid.
  When malathion was the organic being
oxidized, 2 moles of sulfuric acid and 1
mole of phosphoric acid were formed  for
each 64 moles  of hydrobromic acid.
Electrolysis of this  reaction solution
required a higher decomposition voltage
than the control. Several explanations
are offered for this observation.
Pilot-Scale Electrolysis
  The electrolysis apparatus used in the
laboratory experiments was first scaled
up  about tenfold in electrode surface
area. With this equipment  a noticeable
decrease in coulombic efficiency was
observed when  the hydrobromic  acid
solution contained  large  amounts of
dissolved bromine.  The efficiency of
electrolysis was also reduced,  and
diffusion of bromine through the membrane
increased significantly.  Since  the  plan
was to use an HBr solution that would be
rich in bromine, these observations were
quite serious.
  A search of the literature indicated that
a membraneless electrolysis cell such as
the mercury cell  used in salt electrolysis
could overcome these difficulties. Based
on this review, the design selectedf or the
pilot-scale electrolysis cell  consisted of
graphite electrodes separated by Teflon
spacers. The upper  electrode was the
cathode. When current is passed through
a cell of this design, the hydrogen formed
at the cathode rises and escapes from
ports at the upper surface. The bromine
formed at the anode combines with HBr
to form HBra, which is more dense than
HBr and flows out ports at the lower end
of the cell. Tilting the assembly so that the
gas exit at the cathode was only slightly
above  the horizontal (3°) improved the
coulombic efficiency significantly (Table
3).  These results may  reflect  reduced
turbulence and mixing of the denser HBra
  The  inclined, membraneless cell was
then  used as part  of  a regeneration
system.  Concentrated hydrobromic acid
electrolyte was pumped at 2  ml/min from
a reservoir to the upper end of the cell,
and the product solution of  bromine and
dilute  hydrobromic acid was removed at
the lower end. The hydrogen byproduct
gas was scrubbed with water and sodium
bromide solution to remove  bromine and
HBr vapors. The scrubbed  exit gas
contained less than 2 ppm  of combined
bromine and HBr. The bromine/bromide
content could be further reduced to 0.1
ppm by  the addition of a  10%  sodium
hydroxide scrubber to the train.
  Decomposition voltages for electrolysis
of the 38% HBr solution from a malathion
bromination essentially paralleled those
obtained in the 4-liter membrane cell, but
the  coulombic efficiency of the membrane-
less, flow-through cell was much higher.
The voltage (energy)  requirements were
also considered to be several-fold higher
than expected by comparison with other
electrolysis  processes.  In  an  effort to
reduce the needed voltage,  the graphite
cathode was coated with 5.5 mg/cm2 of

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Table 3.    Coulombic Efficiency of Membraneless Cell
Electrode Current
Density
Milliamps/crr?
50
100
50
100
Electrode Angle
(Degrees from Horizontal)
16
16
3
3
Coulombic
Efficiency
(Percent)
66
64
96
92
platinum by electrochemical deposition.
This modification resulted in a significant
(more than 50%) decrease in the decom-
position voltages at comparable current
densities. For example, at lOOmilliamps/
cm2,  the decomposition voltage was
reduced from 2.95 to 1.24 V. In addition,
this value did not deteriorate over the 4 hr
of the test, during which time coulombic
efficiency was about 97%.

Design Study
  A review of the magnitude of  reported
spills suggested that  a  unit capable of
treating 22.7 kg of hazardous chemical
would be suitable for field use. This figure
was used as the basis for the design of a
field-scale system. Batch bromination
coupled with continuous electrolysis for
bromine  regeneration were selected  as
the least costly scenario. The  design
reflected the laboratory and pilot-plant
results indicating that 2 hr at 300° and
8500 kPa were the maximum conditions
needed. Also considered were the
reactivity of other debris and the need to
remove solids after reaction. The tantalum
lining of  the reactor was retained.
  The  electrolysis unit (to be operated
continuously once a reserve of hydrobro-
mic  acid  liquor was  generated) would
operate at 25°C and atmospheric pressu re
and  convert the  bromination reactor
effluent to a final recyclestream containing
22% HBr and 16% bromine.
  The completed design is shown sche-
matically in Figure 2. A total capital cost
of $299,800 was estimated from vendor
quotes and other sources. Piping, overhead,
construction costs, etc., resulted in a total
installed cost (1979) at an available site of
$625,000 (Table 4). The system is
capable of processing about 7.5 kg/hr of
hazardous chemicals.

Table 4.    Cost Summary for  7.5-kg/hr
        Disposal System*
Item
Major equipment
Minor equipment
Installation
Piping
Total
Cost
$299,800
50,000
150,000
125,000
$624,800
*1979 dollars.
                               CO2
    Makeup
    Water
  Nz Purge
Spill
Charge
                                                      Bromine Dissolved in Dilute HBr

                                    — — — — Dashed Lines Indicate Flow During Shutdown
Figure 2.    Block diagram of a conceptual disposal system.

                                    4

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Conclusions
  Pilot-plant testing demonstrated that
an organic hazardous chemical such as
malathion can be completely destroyed
(99.9999%) by an oxidation process usi ng
bromine, even  in a simulated spill
mixture.  Bromine  and/or hydrobromic
acid  also  react with other organic and
inorganic  components of such mixtures
to a  limited extent during the process.
Some inorganic materials form metallic
bromides that consume bromine, but the
bromine can be  recovered readily by
treating these residues with sulfuric acid.
  The concentrated, aqueous hydrobromic
acid effluent from the bromine oxidation
process can be electrolyzed to make the
bromine  available for  reuse.  Based on
pilot-plant studies, the electrolysis can be
carried out in a single pass at ambient
temperature and pressure using a mem-
braneless electrolysis cell. The addition of
small amounts of a platinum catalyst to
the graphite cathode reduces the electrical
power requirements by more than 50%.
  A full-scale system capable of treating
7.5 kg/hr of hazardous  waste  had an
estimated installed capital cost of about
$650,000 in January 1979.

Recommendations
  The oxidation of hazardous wastes by
bromine should be considered as an
option for the destruction of  hazardous
chemcials, even when these  are mixed
with nonhazardous debris.
  Further studies should  be done  to
include the  use of catalysts  and  to
accelerate the oxidation  reaction or
reduce the required temperature. Similar-
ly, techniques should be  explored  to
increase the reactivity with other chlorin-
ated hydrocarbons such as  lindane and
heptachlor, which may be encountered in
spill cleanup situations.
  The amount of platinum  required on
the graphite cathode  to catalyze the
electrolysis of aqueous hydrobromic acid
should  be better defined.  Alternative
methods of activating the electrodes and
catalyzing the electrolysis (such  as the
reported  use of nitric  acid) should be
investigated.
  A unit capable  of destroying 8 to 10
kg/hr of  hazardous wastes should be
constructed for larger-scale confirmation
of the pilot-plant results and for possible
field testing.
  The full report was submitted in partial
fulfillment of Contract No. 68-03-2493 by
Rockwell International under the sponsor-
ship of the U.S. Environmental Protection
Agency.
A. J. Darnell is with Rockwell International, Canoga Park, CA 91304.
John E. Brugger is the EPA Project Officer (see below).
The  complete report,  entitled "Bromination Process for Disposal  of Spilled
  Hazardous  Materials," (Order No. PB 83-263 806; Cost: $10.00.  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 and Hazardous Materials Spill Branch
        Municipal Environmental Research Laboratory-Cincinnati
        U.S. Environmental Protection Agency
        Edison, NJ 08837

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