EPA/600/A-95/082
BENCH-SCALE TESTING OF SORBENT ADDITIVES
FOR TRACE METAL CAPTURE AND RETENTION
Shyam Venkatesh, Gregory J. Carroll* and Larry R. Waterlana
Acurex Environmental Corporation
Incineration Research Facility
Jefferson, Arkansas 72079
* - U.S. Environmental Protection Agency, RREL
Cincinnati, Ohio 45268
ABSTRACT
The suitability of six minerals; silica, diatomaceous earth, kaolin, bauxite, alumina and attapulgite clay,
as potential sorbents for the capture and immobilization of trace metals was evaluated. The behavior of
five trace metals; arsenic, cadmium, chromium, lead and nickel was tested. The minerals and metals
were chosen based on the past and ongoing work of a number of researchers in this area. The first five
minerals constitute a spectrum of alumino-silicate compounds ranging from pure silica (SiOJ to pure
alumina (A1203). The attapulgite clay is primarily a magnesium hydroxide/silicate compound with small
amounts of alumina. It has frequently been used in trace metal related test programs at the Incineration
Research Facility (IRF) as a carrier of metals and organics in synthetically blended waste streams.
The objective of the test program was to evaluate the candidate sorbents for their ability to limit
vaporization by retaining the trace metals in the mineral matrix, and the degree to which they retain the
trace metals as measured by TCLP extraction.
Bench-scale tests were conducted in the IRF's thermal treatability unit. The test matrix was defined by
varying the mineral-sorbent type, treatment temperature of 540°, 700° and 870°C, and chlorine
concentration of the feed from 0 to 4 percent by weight of chlorine.
The test results indicate that under specific conditions, varying for each mineral, all of the minerals limit
metal vaporization, and or TCLP leachability. Of these, kaolin and attapulgite clay were most successful,
over most of the test matrix, in limiting both metal vaporization and TCLP leachability.
INTRODUCTION
There has been considerable interest in the potential use of mineral-based additives as sorbents for
capturing and retaining hazardous constituent trace metals in incineration processes. Two approaches of
metal capture and retention are of interest. The first approach is the capture of vaporized metals in the
flue gas on sorbent particles injected into the flue gas stream. In such applications it is theorized that
vaporized metals will be captured by the sorbent particles at the high incineration temperatures and will
be immobilized, thus, reducing the potential for metal leaching. Metals bound to the relatively larger
sorbent particles are more effectively collected by air pollution control devices. The second approach
seeks to capture and bind metals in the incinerator bottom-ash, thereby preventing vaporization in the first
place. This test program was designed to further investigate the second approach by screening several
minerals for their suitability as sorbent-materials in the solid bed and preventing their release to the flue
gas. Further, the ideal sorbent would reduce the potential of metal leachability. Thus, the objective of
the test program was to evaluate several candidate sorbents with respect to: the degree to which they
facilitate retention of trace metals in the solid bed; and the degree to which they retain trace metals in the
solid bed when subjected to toxicity characteristic leachate procedure (TCLP) extraction.

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Six minerals were chosen for evaluation. They were silica, diatomaceous earth, kaolin, bauxite, alumina
and attapulgite clay. The first five were chosen based on the most promising results from past and
ongoing studies by various researchers. The attapulgite clay is commonly used at the IRF as a carrier
in synthetic waste mixtures prepared for various test programs. The former five minerals constitute a
spectrum ranging from pure silica (SiCy to pure alumina (A1203) with diatomaceous earth, kaolin and
bauxite having varying degrees of both silica and alumina. The attapulgite clay is a crystalline hydrated
magnesium silicate with a typical composition such as [QH2]4 [OH]2 Mg,Si, 0?ji.4H30. Typical chemical
composition and some relevant physical properties are listed in Table I.
PLACE TABLE I HERE
FACILITY DESCRIPTION
The tests were conducted in the thermal treatability unit (TTU) at the IRF. The TTU is illustrated in
Fig. 1. The combustor portion of the TTU consists of three chambers, the charge chamber, the retention
chamber, and the breeching chamber. The charge chamber is designed to accept the ITU's solid material
feed stream and corresponds to the primary combustion chamber of a waste incinerator. The inner cross
section is 0.66 sq.m and is 1.9 m high, and has a chamber volume of 0.82 m\ The retention and
breeching chambers correspond to the secondary combustor in a waste incinerator. All chambers are
lined with 13 cm thick refractory. The burners installed in the charge and retention chambers are natural
gas-fired, with 350 kW capacities and 5-to-l turndowns. Modulating burner controls allow variable firing
rates to control temperatures in each chamber at preset levels between 260° and 1090°C with variable
air-to-fuel ratio. The breeching chamber has a manually adjustable 220 kW burner. Test material was
manually fed to the charge chamber in quartz trays 18.5 cm long by 8 cm wide by 4 cm deep.
PLACE FIGURE 1 HERE
TEST MATRIX AND TEST FEED DESCRIPTION
The test variables were mineral material type, solid bed temperature and feed chlorine content. Three
solid bed temperatures were tested, 540°, 700° and 870°C. Two feed chlorine contents, 0 and 4 percent
by weight, were tested. One test condition was performed in triplicate. The test matrix comprised of
38 tests to include all the test variables. The desired chlorine content was provided by adding
polyvinylchloride (PVC) powder to the mineral feed. Five metals; arsenic, cadmium, chromium, lead
and nickel were tested. The metals were added as their respective aqueous nitrates, except arsenic, which
was added as an oxide. Target feed metal concentrations were constant for all tests, and were as follows:
arsenic, 200 mg/kg; cadmium, 50 mg/kg; chromium, 150 mg/kg; lead, 250 mg/kg; and nickel, 150
mg/kg.
The approximate particle size distributions of the various minerals are reported in Table I. The effect
of particle size was not a test program parameter. Therefore, it was important that all of the minerals
had similar size distributions. The factor limiting the particle size selection was kaolinite. Kaolinite is
naturally mined as a fine clay with a typical particle size of 5-10 ^m. The kaolin obtained for this test
series had a size distribution where 88 percent of the particles were less than 49 pun. Therefore, the rest
of the minerals were obtained to match the kaolin size distribution as closely as possible.
Feed mixtures were prepared by adding the correct proportions of mineral material, PVC powder and
the metals spike to a 2 liter container, after which the container was sealed and tumbled for 8-12 hours
in a tumbler unit to obtain a homogeneously dispersed mixture. Each feed tray was nominally charged
to a depth of 2 cm corresponding to a charge volume in the tray of 315 cm3. The charge weights ranged
from 50 g for diatomaceous earth to 320 g for alumina. The "tray bulk densities" are listed in Table I.

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The TI'U was allowed to reach steady state conditions for each temperature condition of the test matrix.
Just before each test the requisite amount of material was added to the tray and the feed tray was fitted
with two chromel-alumel ("K-type") thermocouples that monitored temperatures close to the top and
bottom of the material bed. After the thermocouples were imbedded in the bed, the tray was manually
introduced into the charge chamber. Each tray was held at the target bed temperature for at least 20
minutes. Based on past research work in this area it was assumed that this time length was sufficient for
potential mineral metal reactions to go to completion. All data were recorded using a computerized
electronic data acquisition system. A schematic of the bed thermocouple arrangement and graphical
presentation of a typical test run are shown in Fig. 2. Table II is a summary of operating conditions.
PLACE FIGURE 2 HERE
PLACE TABLE II HERE
SAMPLING AND ANALYSIS
Samples of unspiked sorbent, metal spiking solution, TTU feed and treated material were collected for
metals analysis. One TTU feed sample from each sorbent/metal formulation combination and the treated
material from each test were subject to TCLP extraction, and the resulting leachates analyzed for trace
metals. Quality assurance samples were prepared as well1,2.
Aqueous liquid samples were digested using EPA Method 30103. Solid samples were digested using a
microwave-assisted HF/HN03 procedure4. Analyses of each of the latter digestates for arsenic were by
Method 70603 (GFAA). All other digestates were analyzed by Method 60103 (ICAP).
RESULTS AND DISCUSSION
Feed Samples
Despite the use of the rigorous microwave assisted HF/HN03 digestion procedure4, analyses of feed
samples often yielded concentrations below those expected (based on prepared metal spike solutions).
The measured metal concentrations in the feed samples are reported in Table III. Of the five metals, on
an average, cadmium and lead exhibited the largest difference between target and measured
concentrations. Overall, metal concentrations in attapulgite clay and kaolinite were below the expected
more than the other matrices. Since the same preparation and analysis methods were applied to both feed
and treated material samples, it was assumed that sampling bias should manifest itself in the analysis of
all solid matrices. Therefore, comparisons between the feed samples and treated material were based on
measured (as opposed to prepared) feed concentrations.
PLACE TABLE III HERE.
Retention of Metals in Treated Mineral
The concentration of the metals in each of the treated material matrix are reported in Table IV. Metal
volatility was judged by examining the treated material metal concentration relative to the feed
concentration (adjusted for material losses); the greater the reduction in concentration, the greater the
volatility.
PLACE TABLE IV HERE.
The trace metal fraction (of that fed) in each of the treated material matrix is listed in Table V. On
average, there was little difference among the sorbents for limiting the volatility of chromium and nickel.

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Cadmium volatility also appeared limited for all sorbents in the absence of feed chlorine. With 4 percent
chlorine present in the feed, cadmium appeared to be less volatile from kaolinite, relative to other
sorbents. Overall, for all matrices (with and without chlorine), arsenic appeared to be less volatile from
attapulgite clay and lead less volatile from kaolinite, compared to other sorbents.
PLACE TABLE V HERE.
Temperature effects were observed in several of the sorbents when chlorine was present in the feed.
Arsenic volatility in the silica, diatomaceous earth and alumina matrices increased with increasing
temperature, while the reverse was observed in attapulgite clay. Cadmium volatility in diatomaceous
earth, alumina and bauxite increased with increasing temperature. Chromium volatility was relatively
constant across the temperature range. Lead volatility increased with increasing temperature for the
alumina and bauxite matrices. Nickel volatility in the attapulgite clay decreased with increasing
temperature.
In cases where chlorine appeared to impact metal behavior (independent of temperature), it consistently
increased metal volatility. Such increases were seen for arsenic in bauxite; cadmium in silica and
attapulgite clay; and lead in silica. Chromium and nickel volatility did not appear to be impacted by
chlorine in any of the matrices.
Resistance to Leaching bv TCLP
Table VI presents the concentration of the metals in the TCLP leachate of the feed matrix. Nearly all
of the TCLP regulated metals were above their respective regulatory levels with the following exceptions:
arsenic in the no feed chlorine matrix of attapulgite clay and both feed matrices of bauxite; cadmium in
the no feed chlorine matrices of attapulgite clay and bauxite.
PLACE TABLE VI HERE
In general, as can be seen from Table VII, the concentration of the metals in the TCLP leachate of each
of the treated materials were less than the corresponding feed. Silica and diatomaceous earth were
relatively less effective in limiting arsenic leachability. The concentrations of the metals in the leachate
of each treated matrix were below their respective regulatory limits with the following exceptions: arsenic
in silica under conditions of no feed chlorine and nominal treatment temperatures of 540° and 870°C;
cadmium in alumina for 4 percent feed chlorine and nominal treatment temperature of 540°C; chromium
in attapulgite clay for no feed chlorine and nominal treatment temperatures of 700° and 870°C; and lead
in bauxite for no feed chlorine and nominal treatment temperature of 700°C. Nickel is not TCLP
regulated.
PLACE TABLE VII HERE
"Fractional leachability" represents the ratio of TCLP-extracted metal to the total metal measured in the
sample. Feed metals fractional leachability data are presented in Table VI. Table VIII presents the
fractional leachability of each metal in each treated material matrix. Attapulgite clay, bauxite, kaolinite,
and alumina were better for limiting arsenic leachability during tests with and without chlorine in the
feed. With no chlorine in the feed, all of the sorbents had similar leachabilities for cadmium and lead.
With feed chlorine, attapulgite clay, kaolinite, and diatomaceous earth were better for limiting cadmium
and lead leachability, as was bauxite for cadmium leachability. With one exception, all of the sorbents
had similar chromium leachability; chromium was very easily leached from the treated attapulgite clay
with no feed chlorine. Nickel in general was relatively less leachable. Nickel leachability did not differ
significantly among the sorbents for the tests with chlorine in the feed. With no chlorine in the feed,
alumina, attapulgite clay, bauxite, and kaolinite were better at limiting nickel leachability.

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PLACE TABLE VIII HERE
Increases in temperature consistently resulted in decreased leachability of cadmium from each of the
sorbents and of arsenic, chromium, lead and nickel from diatomaceous earth. Arsenic leachability from
the other sorbents was not affected by temperature. When chlorine was not present in the feed,
chromium leachability from silica and alumina decreased with increasing temperature, as did lead
leachability from kaolinite and nickel leachability from silica. With chlorine in the feed, lead leachability
from silica, and nickel leachability from silica, alumina and bauxite decreased as temperature rose.
Chromium leachability increased with increases in temperature with and without chlorine in the feed. This
behaviour was observed in earlier tests in the IRF's rotary kiln system6.
CONCLUSIONS
Given the screening nature of the tests and considering the probable analytical problems encountered
regarding metal recovery from solid samples, the quantitative aspect of the results must be viewed with
caution. Nevertheless, a number of preliminary conclusions may be drawn. In general, with a few
exceptions, the sorbents showed comparable performance over the entire test matrix. Combining the dual
criteria of limiting metal volatilization and TCLP leaching, kaolinite and attapulgite clay appear to be the
most promising sorbents for arsenic; kaolinite for cadmium, kaolinite, diatomaceous earth, and attapulgite
clay for lead. Chromium fractional leachability appeared to increase in the attapulgite clay matrix with
increased temperature.
REFERENCES
1.	ACUREX ENVIRONMENTAL CORP., "Quality Assurance Project Plan for Evaluating the
Effectiveness of Additives as Sorbents for Metal Capture Using the Thermal Treatability Unit," EPA
Contract 68-C9-0038, WA 4-1 (December 1993).
2.	ACUREX ENVIRONMENTAL CORP., "Evaluation of the Effectiveness of Additives as Sorbents for
Metal Capture Using the Thermal Treatability Unit," Draft Report, EPA Contract 68-C9-0038, WA 4-1
(November 1994).
3.	EPA SW846, "Test Methods for Evaluating Solid Waste: Physical/Chemical Methods," 3rd Ed.,
Revision 1, U.S. EPA (1992).
4.	40 CFR Part 261, Appendix II, "Method 1311 Toxicity Characteristic Leaching Procedure (TCLP).*
5.	40 CFR Part 266, Appendix IX, "Methodology for the Determination of Metals Emissions in Exhaust
Gases from Hazardous Waste Incineration and Similar Combustion Processes."
6.	ACUREX ENVIRONMENTAL CORP., "Evaluation of Rotary Kiln Operation at Low to Moderate
Temperature Conditions," Draft Report, EPA Contract 68-C9-0038 (Sept. 1994).
FIGURE CAPTIONS:
Fig. 1. Schematic of the Thermal Treatability Unit.
Fig. 2. (a) Schematic of the Bed Thermocouple Arrangement and (b) Graphical Presentation of a Typical
Test Run.

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Table I. Approximate Chemical Composition and Physical Properties of Minerals

Silica
Diatomaceous
Earth
Kaolin
Alumina
Bauxite
Atupulgite Clay
Chemical Composition. %






SiO,
99.8
90.4
45.4
—
6.2
—
ai2o3
0.07
6.5
38.5
> 99.9
88.5
—
CaO
0.04
0.2
0.08
—
—
—
MgO
< 0.01
0.3
0.008
—
—
—
Fe2°3
0.023
2.3
0.8
—
1.3
—
Physical Properties






Particle size
95% < 40
88% < 44 /xm
88% <49 ftm
85% < 75 /im
85% < 75 fim
88% < 40 iim
Typical surface area, m2/g
Cry. < 3
Amorph. —200
>3
125
—
—
125-200
Specific gravity
2.7
2.3
2.2
3.9
3.2
2.4
Bulk density, g/cm3
0.5
0.2
0.4
1.0
0.9
0.3

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Table II. Test Matrix and Operating Conditions Summary
Target Bed Temperature Achieved Average Bed Achieved Average Charge
Mineral
Feed Chlorine
%
for 20 Minutes
~c
Temperature for Target
20 Minutes, °C
Chamber Temperature
°C
Silica
0
540
537
522
Silica
0
700
700
689
Silica
0
870
865
904
Silica
4
540
537
549
Silica
4
700
696
687
Silica
4
870
860
865
Clay
0
540
536
540
Clay
0
700
717
693
Clay
0
870
868
875
Clay
4
540
539
511
Clay
4
700
697
681
Clay
4
870
866
850
Earth
0
540
538
565
Earth
0
700
692
649
Earth
0
870
863
942
Earth
4
540
539
561
Earth
4
700
703
704
Earth
4
870
868
887
Kaolin
0
540
529
544
Kaolin
0
700
689
671
Kaolin
0
870
860
901
Kaolin
4
540
533
553
Kaolin
4
700
695
712
Kaolin
4
870
861
855
Kaolin
4
870
872
882
Kaolin
4
870
864
845
Bauxite
0
540
537
575
Bauxite
0
700
689
889
Bauxite
0
870
864
923
Bauxite
4
540
540
512
Bauxite
4
700
693
676
Bauxite
4
870
856
868
Alumina
0
540
543
579
Alumina
0
700
684
717
Alumina
0
870
858
931
Alumina
4
540
539
535
Alumina
4
700
693
711
Alumina
4
870
860
895

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Table III. Feed Metal Concentration
Feed, mg/kg
Feed Chlorine
Mineral
%
Arsenic
Cadmium
Chromium
Lead
Nickel
Silica
0
213.1
39.3
135.3
222.3
118.1
Silica
4
192.2
16.7
128.0
199.5
106.8
Clay
0
100.5
22.1
119.0
48.8
94.5
Clay
4
93.8
16.5
98.0
22.4
90.8
Earth
0
159.2
40.6
185.9
200,9
160.1
Earth
4
188.6
39.5
178.2
194.9
152.7
Kaolin
0
139.8
21.1
154.6
67.0
103.4
Kaolin
4
147.3
16.7
152.4
73.7
91.0
Alumina
0
162.7
34.5
118.2
139.8
94.9
Alumina
4
211.6
50.6
127.0
158.3
137.0
Bauxite
0
185.7
22.3
152.0
184.7
104.3
Bauxite
4
171.9
35.3
143.9
175.7
98.1
Target

200
50
150
250
150

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Table IV. Treated Material Metal Concentration
Treated Material, mg/kg
Mineral
Bed Temp
•c
Feed Chlorine
%
Arsenic
Cadmium
Chromium
Lead
Nickel
Silica
537
0
187,3
39.2
127.5
181.8
109.3
Silica
700
0
213.9
36.4
114.8
213.3
108.1
Silica
865
0
196.0
36.9
120.1
198.9
126.1
Silica
537
4
176.4
25.8
134.1
97.4
110.5
Silica
696
4
117.2
13.5
125.8
148.5
111.7
Silica
860
4
119.8
5.4
118.6
105.0
138,4
Clay
536
0
236.6
33.0
136.4
41.8
144.0
Clay
717
0
288.0
44.3
217.1
46.7
180.8
Clay
868
0
234.1
30.2
145.9
43.4
160.2
Clay
539
4
143.5
27.7
120.1
32.1
105.4
Clay
697
4
212.7
19.0
126.8
23.5
158.6
Clay
866
4
251.9
3.2
149.6
21.3
295.4
Earth
538
0
192,4
42.4
182.2
185.5
152.6
Earth
692
0
167.1
38.8
164,5
156.6
145.6
Earth
863
0
193.8
44.0
177.7
173.0
158.4
Earth
539
4
192.5
31.2
171.9
143.3
156.2
Earth
703
4
166.3
21.8
167.1
110.8
151.7
Earth
868
4
160.1
25.5
185.2
135.4
193.2
Kaolin
529
0
169.4
36.2
158.0
113.2
95.9
Kaolin
689
0
228.4
46.4
196.4
146.0
137.0
Kaolin
860
0
165.7
44,4
173.6
116.2
128.1
Kaolin
533
4
174.4
23.3
153.1
114.0
99.6
Kaolin
695
4
221.7
39.9
192.3
133.7
140.1
Kaolin
866
4
180.1
36.7
157.9
113.9
131.5
Alumina
543
0
195.2
36.4
133.4
128.4
90.6
Alumina
684
0
225.4
42.9
148.9
168.7
102.9
Alumina
858
0
209.8
39.2
128.4 '
134.4
104.8
Alumina
539
4
191.3
34.3
125.4
108.7
92.0
Alumina
693
4
168.1
19.4
117.9
97.1
108.3
Alumina
860
4
158.0
8.2
116.3
58.4
88.8
Bauxite
539
0
184.4
35.7
152.3
146.6
91.5
Bauxite
689
0
189.4
25.8
120.4
48.4
51,2
Bauxite
864
0
185.2
37.2
143.3
170.6
97.5
Bauxite
540
4
135.2
26.0
152.4
101.8
76.7
Bauxite
693
4
154.6
18.5
146.4
108.7
101.6
Bauxite
856
4
118.8
12.5
140.2
63.5
96.4

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Table V. Treated Material Metal Fraction

Bed Temp
"C
Feed Chlorine
%

Fraction of Metal
Fed Measured in Ash, %

Mineral
Arsenic
Cadmium
Chromium
Lead
Nickel
Silica
537
0
82
93
88
76
87
Silica
700
0
97
90
82
93
89
Silica
865
0
89
91
86
86
103
Silica
537
4
83
139
95
44
93
Silica
696
4
59
78
95
72
101
Silica
860
4
56
29
84
47
117
Clay
536
0
193
122
94
70
125
Clay
717
0
234
164
149
78
156
Clay
868
0
169
99
89
64
123
Clay
539
4
125
137
100
117
95
Clay
697
4
165
84
94
76
127
Clay
866
4
195
14
111
69
237
Earth
538
0
111
96
90
85
87
Earth
692
0
96
87
81
71
83
Earth
863
0
111
99
87
79
91
Earth
539
4
93
72
88
67
94
Earth
703
4
73
46
78
47
83
Earth
868
4
78
59
95
64
116
Kaolin
529
0
100
142
84
140
77
Kaolin
689
0
135
182
105
180
110
Kaolin
860
0
98
174
93
143
102
Kaolin
533
4
98
235
115
143
90
Kaolin
695
4
114
134
79
100
117
Kaolin
866
4
97
170
75
123
115
Alumina
543
0
117
103
110
89
93
Alumina
684
0
135
121
122
117
105
Alumina
858
0
123
109
104
92
106
Alumina
539
4
82
61
89
62
61
Alumina
693
4
74
36
87
57
74
Alumina
860
4
71
15
87
35
61
Bauxite
539
0
96
155
97
77
85
Bauxite
689
0
99
112
77
25
48
Bauxite
864
0
96
162
91
89
91
Bauxite
540
4
71
65
93
51
69
Bauxite
693
4
81
46
90
54
91
Bauxite
856
4
64
32
88
33
89

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Table VI. Feed TCLP Leachate Metal Data
F«-d, nig/L
Feed Chlorine
Mineral
%
Arsenic
Cadmium
Chromium
Lead
Nickel
Silica
0
6.71
1.81
4.44
6.91
4.69
Silica
4
6.61
1.66
4.20
6.88
4.44
Clay
0
3.51
0.82
0.14
0.14
1.45
Clay
4
6.71
1.22
0.30
0.38
2.64
Earth
0
6.70
1.76
4.54
7.81
4.72
Earth
4
6,98
1.78
4.58
7.93
4.69
Kaolin
0
5.59
1.60
1.93
6.34
3.84
Kaolin
4
5.18
1.51
1.79
5.83
3.59
Alumina
0
6.33
1.81
3.99
6.79
4.58
Alumina
4
5.08
1.57
2.28
6.45
4.22
Bauxite
0
0.48
1.51
0.25
2.72
4.10
Bauxite
4
0.4!
1.59
0.20
2.96
4.27
Regulatory Limit

5
I
S
5
_
Fraction Leachable, %
Silica
0
63
92
66
62
79
Silica
4
69
199
66
69
83
Clay
0
70
75
2 •
6
31
Clay
4
143
148
6
34
58
Earth
0
84
87
49
78
59
Earth
4
74
90
51
81
61
Kaolin
0
80
152
25
189
74
Kaolin
4
70
181
24
158
79
Alumina
0
78
105
68
97
97
Alumina
4
48
62
36
82
62
Bauxite
0
5
136
3
30
79
Bauxite
4
20
32
< 1
19
3

-------
Table VII. Treated Material TCLP Leaehate Metal Concentration
Treated Material, mg/L
Mineral
Bed Temp
•c
Feed Chlorine
%
Arsenic
Cadmium
Chromium
Lead
Nickel
Silica
537
0
6.10
0.90
3.22
0.37
1.62
Silica
700
0
3.90
0.56
0.60
0.69
0.61
Silica
865
0
6.80
0.42
0.12
1.66
0.19
Silica
537
4
0.36
0.50
0.53
1.36
0.54
Silica
696
4
3.07
0.19
0.97
0.92
0.17
Silica
860
4
3.58
0.08
0.54
0.89
0.09
Clay
536
0
0.73
0.17
4.78
< 0.10
0.60
Clay
717
0
1.47
0.06
7,91
< 0.10
0.40
Clay
868
0
1.03
0.06
7.61
< 0.10
0.13
Clay
539
4
0.63
0.31
2.88
< 0.10
0.38
Clay
697
4
0.60
0.21
3.35
< 0.10
0,67
Clay
866
4
1.92
0.09
0,29
< 0.10
0.10
Earth
538
0
4.42
0.41
2.91
0.31
1.63
Earth
692
0
4.54
0.23
1.46
0.32
0.92
Earth
863
0
3.31
0.04
0.03
< 0.10
0.06
Earth
539
4
4.41
0.16
1.39
0.29
0.52
Earth
703
4
3.66
0.03
0.63
< 0.10
0.06
Earth
868
4
3.72
0.01
0.06
< 0.10
0.09
Kaolin
529
0
0.36
0.12
0.32
0.88
0.24
Kaolin
689
0
0.85
0.03
1.75
0.62
0.12
Kaolin
860
0
0.50
0.02
0.11
< 0.10
0.06
Kaolin
533
4
0.74
0.39
0.53
0.12
0.18
Kaolin
695
4
1.14
0.03
1.72
< 0.10
0.11
Kaolin
866
4
0.47
0.01
0.16
0.13
0.23
Alumina
543
0
0.39
0.61
2.09
0.27
0.35
Alumina
684
0
0.48
0.46
2.18
0.15
0.19
Alumina
858
0
1.47
0.41
1.16
0.40
0.04
Alumina
539
4
0,30
1.23
0.23
1.72
0,58
Alumina
693
4
0.98
0.54
0.49
1.38
0.10
Alumina
860
4
1.85
0.01
0.52
0.54
0.03
Bauxite
539
0
0.32
0.63
1.95
0.31
0.59
Bauxite
689
0
0.22
0.11
0.30
5.60
0.21
Bauxite
864
0
2.24
0.10
0.05
0.18
0.04
Bauxite
540
4
1.38
0.42
< 0.03
0.94
0.12
Bauxite
693
4
0.07
0.05
0.03
0.89
0.04
Bauxite
856
4
1.84
0.02
< 0.03
< 0.10
0 02
Regulatory
Limit

5
1
5
5

-------
Table VIII. TCLP Fractional Leachabilities

Bed Temp
°C


Fraction Leachable by TCLP, %

Mineral
Feed Chlorine
%
Arsenic
Cadmium
Chromium
Lead
Nickel
Silica
537
0
65
46
50
4
30
Silica
700
0
36
31
10
6
11
Silica
865
0
69
23
2
17
3
Silica
537
4
4
39
8
28
10
Silica
696
4
52
27
15
12
3
Silica
860
4
60
28
9
17
. 1
Clay
536
0
6
10
70
< 5
8
Clay
717
0
10
2
73
< 4
4
Clay
868
0
9
4
104
< 5
2
Clay
539
4
9
23
48
< 6
7
Clay
697
4
6
22
53
< 9
9
Clay
866
4
15
5
4
< 9
1
Earth
538
0
46
19
32
3
21
Earth
692
0
54
12
18
4
13
Earth
863
0
34
2
< 1
< 1
1
Earth
539
4
46
10
16
4
7
Earth
703
4
44
2
7
< 2
1
Earth
868
4
46
1
1
< 1
1
Kaolin
529
0
4
7
4
15
5
Kaolin
689
0
7
1
18
9
2
Kaolin
860
0
6
1
13
< 2
1
Kaolin
533
4
9
16
5
2
4
Kaolin
695
4
10
2
22
< 2
2
Kaolin
866
4
5
1
2
2
4
Alumina
543
0
4
34
31
4
8
Alumina
684
0
4
21
29
2
4
Alumina
858
0
14
21
18
6
1
Alumina
539
4
3
72
4
32
13
Alumina
693
4
12
55
8
28
2
Alumina
860
4
23
3
9
18
1
Bauxite
539
0
3
35
26
4
13
Bauxite
689
0
2
8
5
231
8
Bauxite
864
0
24
5
1
2
1
Bauxite
540
4
20
32
< 1
19
3
Bauxite
693
4
1
6
1
16
1
Bauxite
856
4
31
4
< 1
< 3
1

-------
STACK
TE
SAMPLING
PORTS
BREECHING
CHAMBER
TE
BURNER 3
TE
RETENTION
CHAMBER
TO MOV-2
TIC
BURNER 2
TEMP INDICATING
CONTROLLER
TE
CR-1
CHARGE
CHAMBER
TE
CHART
RECORDER
TO MOV-1
TIG
TEMP INDICATING
CONTROLLER
BURNER 1
FEED
CONVEYOR
ASH
TE
2A
TE
1A
TE
1A
TE
TE
TE
TEl-1
TEMP INDICATOR
TEi-2
TEMP INDICATOR
Fig. 1. Schematic of the Thermal Treatability Unit.

-------
Tray: 18.5 cm L X 8.5 cm W X 4 cm D
Bed Temperature TC
2 cm
(a)
TREATMENT OF ALUMINA @ 540°C
Target Temperature
Treatment Chamber Exit Gas
Treatment Chamber Gas Near Bed Surface
. 600

3 500
- Average
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before complel
1. REPORT NO. 2.
EP A/600/A-95/082
3.
4. TITLE AND SUBTITLE
Bench-Scale Testing of Sorbent Additives For Trace
Metal Capture and Retention
5. REPORT DATE
6. PERFORMING ORGANIZATION CODE
7. AUTHORIS)
Shyam Venkatesh 1 , Gregory J. Carroll 2 ,
Larry R. Waterland *
8, PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
1	Acurex Environmental Corporation
555 Clyde Avenue
Mountain View, CA 94039
2	U.S. EPA/RREL
Cincinnati, OH 45268
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-C4-0044
12. SPONSORING AGENCY NAME AND ADDRESS
Risk Reduction Engineering Laboratory- Cincinnati, OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Conf ProceedinasAlan 1994
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES
For Presentation at the 1995 Incineration Conference - Seattle, WA ; May 1995
16. ABSTRACT
The suitability of six minerals; silica, diatomaceous earth, kaolin, bauxite,
alumina and attapulgite clay, as potential sorbents for the capture and immobiliza-
tion of trace metals was evaluated. The behavior of five trace metals; arsenic,
cadmium, chromium, lead and nickel was tested. The objective of the test program
was to evaluate the candidate sorbents for their ability to limit vaporization by
retaining the trace metals in the mineral matrix, and the degree to which they
retain the trace metals as measured by TCLP extraction. Bench-scale tests were
conducted in the IRF's thermal treatability unit. The test matrix was defined by
varying the mineral-sorbent type, treatment temperature of 540°, 700°, and 870°C,
and chlorine concentration of the feed from 0 to 4 percent by weight of chlorine.
The test results indicate that under specific conditions, varying for each mineral,
all 9f the minerals limit metal vaporization, and/or TCLP leachabi1ity. Of these,
kaolin and attapulgite clay were most successful, over most of the test matrix, in
limiting both metal vaporization and TCLP leachabi1ity.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b. IDENTIFIE RS/OPEN ENDED TERMS
c. COSATI Field/Group
Incineration
Hazardous Wastes
Metals
Emissions
Sorbents


18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
16
20. SECURITY CLASS (This page)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (Re*. 4-77) previous edition is obsolete
-------