Sulfur Pollution from Coal Combustion. Effect of the Mineral Components of Coal on the Thermal Stabilities of Sulfated Ash and Calcium Sulfate Daniel C. Baker and Amir Attar’? Department of Chemical Engineering, University of Houston, Houston, Texas 77004 Previous literature on related topics, although somewhat contradictory, provides the following main observations: (1) Cas04 reacts with clays (12, 13) and quartz (14-17) in the temperature range of 800-1400 OC. (2) The reaction between Cas04 and Si02 is diffusion controlled below 1210 “C. Metal oxides enhance its rate (14, 18). (3) NaCl enhances the rate of the reaction (16,19,20)
The rates of decomposition of sulfated coal ashes, calcium sulfate, and calcium sulfate mixed with coal and with minerals were investigated in the temperature range of 700-1200 “C. Sulfated ashes lose sulfur oxides faster than puie calcium sulfate. The retention of sulfur in the ash depends on the composition of the ash. Calcium-rich ashes retain sulfur oxides while iron-rich ashes lose sulfur oxides. The decomposition of pure calcium sulfate in inert gas is slow and proceeds to calcium and sulfur oxides. However, in reducing environment, calcium sulfide is favored and the decomposition may stop. Minerals enhance the rate of decomposition of calcium sulfate to a limited extent. However, potassium-containing minerals are very effective catalysts for the decomposition.
NaCl
3CaS04 + C a s -+ 4Ca0
+ S02(g) H20,coz,
CBM-SO2
02
A
02
HzO COz
CBM-SO2
CBM
+ SOz(g)
retention
A1203 + Cas04
decomposition (2)
The rate and the mechanism of the decomposition reaction are the subject of this study. Four types of reactions were examined: (A) decomposition of “pure” calcium sulfate (CaSOd), (B) decomposition of Cas04 “contaminated” with coal, (C) decomposition of Cas04 mixed with different minerals, and (D) decomposition of sulfated ash.
288
Environmental Science & Technology
+C
-
-
CaO A1203
+ SO2 + COZ
(4)
Alumina and aluminates also enhance the rate of decomposition of Cas04 (21,22). (5) Moisture accelerates the rate of decomposition of Cas04 (16,23,24).(6) CaO and Cas04 lower the ash melting temperature (25,26).( 7 ) Cas04 is reduced to Cas by reducing gases like CO and Hz (27).Our observations on the stability of calcium sulfate and sulfated ashes are consistent with the available literature.
(1)
t Present address: Department of Chemical Engineering, North Carolina State University, Raleigh, North Carolina 27650.
(3)
(4) In the presence of carbon, A1203 reacts with Cas04 as follows (211:
Utilization of calcium-based minerals (CBM) for flue-gas desulfurization (FBG) and for trapping sulfur oxides during fluidized-bed combustion of coal (FBC) is emerging as one of the leading technologies to reduce sulfur oxide pollution. The effectiveness of the desulfurization process seems to be associated with one or more of the following variables: (1)the pore structure of the CBM used (1-4), (2) the time-temperature history of the CBM in the reactor (5, 6 ) , (3) mass-transport limitations for the desulfurization process during combustion, and (4)impurities in the solid CBM. Several madels were proposed to account for the rate of reaction of SO2 with CBM (7-9), and several models were proposed to correlate the kinetics of desulfurization in fluidized beds ( 1 0 , l l ) .However, no predictive theory is available which accounts for the variability of the mineral composition on the retention of sulfur on the CBM. The apparent retention of sulfur on solid CBM can be described as the result of two schematic reactions: CBM
+ 4Soz
Experimental Section Experimental System. The relationship of the various units in the experimental system and the dimensions of the major noncommercial units are shown in Figure 1. The reactor consisted of a 10-mm i.d., 12-mm 0.d. quartz tube. The tube was wrapped with a high-temperature heating element and surrounded by high-temperature insulation; both items were obtained from Houston Atlas Inc. The quartz tube and insulations were encased in a Schedule 40 aluminum pipe. The initial section of the reactor was used as a preheating zone. The last section of the reactor was used to connect a ball-joint fitting to an absorption cell. A second quartz tube (7-mm i.d., 9-mm 0.d.) was used to inject samples into the reactor. One end of the quartz tube was fashioned into a boat sampler. Operation Procedure. The procedure for the determination of the rate of decomposition of pure Cas04 and of sulfated ashes consisted of grinding a sample to the mesh size 100-120, placing a thin layer in the boat sampler, and inserting the sampler into the heated reactor. The procedure for the determination of the mineral effect on Cas04 decomposition consisted of grinding 0.2 g of Cas04 and 0.05 g of mineral to the mesh size 100-120, mixing the sample, and loading into the boat sampler for testing. Nitrogen at a flow rate of 200 cm3/min was used as a sweep gas. An absorption cell was used to absorb the product gas; BaC12 solution was used to absorb the SO,. The acidity of the
0013-936X/81/0915-0288$01.25/0 @ 1981 American Chemical Society
x Il30*c
5.0
14-4
SYSYEM-
!-
I
I
I
HIGH TEMPERATURE REACTOR
I
% SO, FROM CaS04
STABILITY OF CaSO, BETWEEN 950T-l130°C
I
-5.0IN-12.0
N-I
r----
I I
METER
MIXER
Figure 1. Experimental system.
solution was used as a measure of the SO, absorbed. Material balance on the sulfur was performed to test the analytical method. The loss of sulfur from the solid Cas04 sample was equivalent to the gain in sulfates as calculated from the concentration in the absorbing solution. A Chemtrix millivolt meter equipped with electrodes was used to measure the change in potential of the absorption cell. The temperature was measured by using a Pt vs. 87%Pt-13% Rh thermocouple and an Omega digital thermometer. The temperature and the absorption cell potential were recorded on a double pen strip chart recorder. Detection of sulfide ions on the surface of the solid CBM was done by ESCA (electron spectroscopy for chemical analysis) or by reacting the solid in a solution containing mercuric chloride and HC1. In the presence of sulfide ions an orange-red color is formed due to mercuric sulfide (28). Materials. MCB reagent-grade Cas04 anhydrous powder was used in all of the experimental runs. The ashes were prepared according to ASTM D2795 and then sulfated in a mixture of 5 vol % of SO2 in air for 10 min in a fluidized bed at 800 OC.
MINUTES
Figure 2. Stability of CaS04 between 950 and 1130 O C .
%SOx FROM Cos04
STABILITY OF Cos04 AT 10201:
0 2 gm Cos04 001 gm COAL WST
10.0 -
PARTICLE SIZE -100 MESH +I20 MESH
1
5.0
X
Results The results of four types of experiments are described: the decomposition of pure CaS04; the decomposition of Cas04 contaminated with coal; the decomposition of CaS04-mineral mixtures; and the decomposition of sulfated ashes. Figure 2 shows the percent of SO, released from pure Cas04 in a nitrogen atmosphere between the temperatures of 950 and 1130 "C. After an initial induction period, Cas04 decomposition commenced and the evolution of SO, was detected. No sulfide precipitate was observed when the solid decomposition product was dissolved in aqueous HC1-HgC12. This indicated that little or no C a s was formed due to the decomposition reaction:
-
+
Cas04 C a s 2 0 2 (5) The solid product, when removed from the reactor, was observed to have fused. SEM (scanning electron microscope) photographs of Cas04 and Cas04 which was heated a t 1000 "C under nitrogen for 2 h confirmed that the particles had fused and that all of the rough surfaces had become smooth. The initial BET surface area of Cas04 was 4.78 m2/g, while the heated sample had a surface area of 0.34 m2/g. The evolution of SO, a t 1020 OC from Cas04 in reducing environment is shown in Figure 3. The reducing environment was created by mixing small amounts of coal particles of equal mesh size with the Cas04 particles. Sulfide precipitate was observed when the solid decomposition product was dissolved
0.2 am Cos01 CONTAMINATED WITH COAL DUST
MINUTES
Figure 3. Stability of CaS04 at 1020 O C in a reducing environment.
in aqueous HC1-HgC12. This confirmed that sulfide sulfur is formed in the reducing environment. The evolution of SO, at 1020 OC from mixtures of 80% CaS04-20% mineral matter are shown in Figure 4. All of the minerals that were tested, except MgO, increased the rate of evolution of SO, and the total quantity of SO, evolved from CaS04. No sulfide was observed in any of the solid decomposition products. Montmorillonite is an inorganic ion exchanger found in nature often in conjunction with other clays. The most abundant form is that in which the cation is calcium. Two natural montmorillonite samples were tested, calcium montmorillonite and sodium montmorillonite. A third sample, potassium montmorillonite, was prepared by treating sodium montmorillonite with KC1. A mixture of potassium montmorillonite and Cas04 was heated, and the rate of evolution of SO, was followed as before. Figure 5 shows that the nature Volume 15, Number 3, March 1981
289
16.0 14.0
/ /
-
Table I. Composition of Sulfated Ashes EFFECT OF MINERAL MbTTER ON CoSO) sTABlLllY@OZO'C
*
-
llllnols
WRTICLE SIZE' 100 MESH +lZOMESH EXCEPT MUSCOVITE
-
12.0 -
I
Texas Ilgnlte
Ca, %
4
16
Mg, %
0.12
Fe, %
5
K, %
0.48
total sulfur immediately after sulfation, % stabilized at room temperature, % sulfate sulfur of stabilized samples, %
10.0 -
8.0-
No. 6
/ /
A
Figure 4. Effect of mineral matter on CaS04stability at
9.6
6.5
7.5
/
STABILITY OF SULFbTED ASH a 1020%
80 -
1020 "C.
9.6
8.7
so, FROM SULFATED ASH BASE0 ON SULFATE SULFUR ONLY
"1
120
60 90 MINUTES
30
100
12
2 3.5 0.25
70 60 -
"'O
SOr RELEbSEO FROM Caso4 bT 1O2o0c 90
K-MONTMORILLONITE
PART,CLE
mn r n w
6 5 11 9. SULFPTE
7 5 w t ./. SULFATE SULFUR
30 20
PbRTICLE SIZE -100 MESH +I20 MESH
x'
1
30
90
60
120
MINUTES
20
40
60
80
100
10 - 9.
SO, FROM SULFPTEO ASH BbSED ON SULFATE SULFUR ONLY
120
MINUTES
Figure 5. Effect of montmorillonites on CaS04 stability at
8-
of the cation tied to the montmorillonite had a dramatic effect on the rate of decomposition of Cas04 and that potassium montmorillonite had the strongest catalytic effect on the rate of decomposition of pure CaS04. Table I shows the concentrations of Ca, Mg, Fe, and K in lignite ash and ash from an Illinois No. 6 coal and their sulfur content immediately following sulfation and after 4 days of storage in open air. Because of the sulfation, the sulfur content of lignite ash increased from 7.9 to 9.6 wt %. The sulfur content of the ash from the Illinois No. 6 coal increased from 8.5 to 12.0 wt %; however, the Illinois No. 6 ash slowly released SO2 a t ambient temperature and appeared to stabilize at 8.7 wt % sulfur. This was attributed to SO2 adsorbed on the surface of the iron-rich Illinois No. 6 ash. Little or no SO2 was lost at ambient temperature from the lignite ash. Figure 6 shows the rate of decomposition of the sulfated ashes at 820 and 1020 "C. Sulfated ashes were less stable than pure Cas04 at 1020 "C; however, they were reasonably stable at 820 "C. Addition of 20% Si02 to sulfated lignite ash did not change its rate of decomposition a t 820 "C. Photoelectron spectroscopy (ESCA) results of the surface composition of the products of the decomposition of lignite ash, pure CaS04, and 80%CaSO4--20%Si02 are given in Table 111. The data indicate that the mineral matter enhances the loss of sulfur from the surface layer of pure Cas04 and of sulfated ash. 290
Environmental Science & Technology
/
9-
1020 OC.
STPBILITY OF SULFATED I S H Q B20.C
5l /
4
3l /
ILLINOIS #6 8.7 11 Y. SULFUR 6 5 w t % SULFPTE SULFUR
2
Figure 6. Thermal stability of sulfated ash (A) at 820 OC and (B) at 1020 OC.
Discussion The overall rate of release of SO2 or SO3 from solid Cas04 in the temperature range of 700-1150 OC appeared to be controlled strictly by the structure of the surface layer of the solid. When pure solid CaS04 was decomposed, CaO was formed; however, it did not seem to restrict the diffusion of SO,, at least up to -5% decomposition. For Cas04 with an
initial specific surface area of 4.8 m2/g, it corresponded to -80 molecular layers of product. CaO and Cas are both face-centered cubic crystals, and one could have expected that a layer of C a s on the surface of Cas04 would also be permeable to SO,. However, when a mixture of Cas04 and coal was decomposed, the reaction proceeded initially very fast, but after -30 min it stopped altogether. The fraction that decomposed seemed to depend on the level of contamination of the solid by the coal. However, no clear way has been found to quantify solid-solid contact, such as in the reaction between Cas04 and coal. Mixtures of Cas04 with silica and aluminosilicates released SO, faster than pure CaS04. While most of the silicates had approximately the same effect on the rate of decomposition of CaS04, potassium-containing minerals accelerate the decomposition significantly. The exact role of potassium is not clear; however, the large “mobility” of potassium at high temperatures could be one explanation. The rate of decomposition of mixtures of KC1 and Cas04 was substantially larger than that of pure CaS04. Decomposition of Pure Cas04 under Nitrogen. Decomposition of Cas04 in a nitrogen atmosphere proceeded according to the reaction CaS04(s)
-
CaO(s) + S02(g) + l/202(g)
(6)
Figure 2 shows that the rate of decomposition depended on the temperature and the heating time for the range of variables investigated. An increase of the product layer of CaO did not appear to restrict the diffusion of SO2 from the unreacted solid, at least up to 5% decomposition. Lau et al. (29) found that, while the initial step in Cas04 decomposition may be the release of an SO3 molecule from the surface of the Cas04 lattice due to thermal vibrations of S042ions, rapid surface conversion of SO3 to SO2 and 0 2 can preclude the direct desorption of SO3. At 1193 OC, calcium sulfate undergoes a phase transition from orthorhombic to monoclinic. Rotation of so42-ions during the crystalline transition may enhance the evolution of so3 molecules from the interior of the Cas04 particle. Decomposition of Cas04 above 1193 “C may be significantly different from decomposition below this phase-transition temperature. Reductive Decomposition. The mechanism of Cas04 decomposition changes in a reducing atmosphere. Besides reaction 5 , additional reactions can occur (30):
-
+ CO(g) CaO(s) + S02(g) + COz(g) CaS04(s) + 4C(s) CaS(s]+ 4CO(g)
CaSOe(s)
CaS04(s) t 4CO(g)
-
CaS(s)
+ 4co2(g)
(7)
(9)
Figure 3 shows that the initial rate of decomposition of Cas04 in a reducing atmosphere was very large, but after -30 min the decomposition stopped. The absence of SO, evolution after 30 min may be due to insufficient coal particles to maintain a reducing environment or to formation of a layer
of C a s on the surface of the Cas04 which controlled the decomposition, probably by reducing the rate of mass transport. Table I1 shows calculated equilibrium constants and heats of reaction for the relevant reactions. Reactions 8 and 9 are exothermic while reactions 6 and 7 are endothermic. Reactions 8 and 9 are thermodynamically favored at temperatures below 1300 K. Wheelock and Boylan (30)found that the percent Cas in the solid decomposition product increased sharply below 1170 “C for an atmosphere 4%CO, 10%C02,5% S02, and 81% N2. Montagna et al. (31)report that a temperature of 1040 OC or higher is required to avoid the formation of Cas which will prevent further decomposition of CaS04. Reactions 7 and 9 are alternative ways by which CO or coal can react with CaS04. It seems that below -1200 “C reaction 9 dominates. This observation is consistent with the data of Wheelock and Boylan (30). The solid-solid reaction did not proceed to completion as evident from the coexistence of Cas04 and C a s in the final product after 90 min of each experimental run (Figure 3). The Cas was detected by the HgC12-HC1 test (reaction 6). Decomposition of Cas04 in the Presence of Mineral Matters. Mineral impurities may change the mechanism of the decomposition of CaS04. Figure 4 shows that layered silicates and amorphous Si02 enhanced the rate of evolution of SO, and the total quantity of SO, released from CaS04. Figure 4 also shows that Fez03also enhanced the rate of SO, evolution and increased the total quantity of SO, released from CaS04 but that MgO did not have a significant effect on Cas04 decomposition. Two mechanisms of interaction could be responsible for the results. Mechanism 1 involves the reaction of the CaO layer with Si02 CaO(s)
+ SiOZ(s)
-
CaSiO&)
(11)
Such a reaction could expose a new surface of Cas04 and thus enhance the apparent rate of release of SO,. Mechanism 1 may account for the enhancement effect of amorphous Si02 on Cas04 decomposition. Mechanism 2 involves the diffusion of ions of different valence than Ca2+, such as Fe3+ and Kf. Diffusion of these cations will increase the number of holes in the Cas04 crystal by creation of either Frenkel or Schottky disorders (32)and thereby increase the number of sites where SO, can be released. Mechanism 2 may account for the enhancement effect of Fez03 on Cas04 decomposition, as well as the absence of effect from MgO. Both mechanisms can take place when layered silicates are mixed with Cas04 since layered silicates contain tetrehedral sheets of Si02 and cation planes and may also contain cations in the interlayer. The large enhancement effect of muscovite and illite on the decomposition of Cas04 may be due to the potassium content
Table II no.
-
6
CaS04(s)
7 8
CaS04(s)+ CO(g)CaS04(s) 4C(s)
9 10
1200 K
reaction
CaO(s)
+ So&) + %02(g)
--
CaO(s)+ SO2(g)+ COZ(g) CaS(s) 4CO(g) CaS04(s) 4CO(g) CaS(s) 4C02(g) 3CaS04(s) CaSW 4CaO(s) 4S02(g)
+
+ +
-
+ +
+
-7.42 0.31 14.83 7.92 -6.68
log K 1400 K
4.51 1.48 17.75 6.69 -0.77
AHR, a 1600 K
-2.38
caII moI
110 600
2.28 19.75
43 400 -110 100
5.66
-48 400
3.44
222 200
Heat of reaction, 1 atm, 1400 K.
Volume 15, Number 3, March 1981
291
Table 111. Summary of ESCA Data CaSOqIS102 1000 oc, re1 no.
Cas04 1000 OC, re1 no. atoms a
164
BEb
531.9
BEb
13
102.3
30
102.9
31
102.7
531.9
176c
531.9
121c
531.8
136c
374.4 168.9
atomsa
977.7 23 18
347.3 169.1
BEb
lignite ash calclned 1050 OC, re1 no.
atomsa
977.6 31 28
lignite ash calcined 710 OC, re1 no.
atoms a
978.5
BEb
978.5
4.1 4.1
348.1 160.4
3.4
347.5
0.3
169
6.3
710.9
4.4
711.4
4.6 0.4
1304.3
2.9
1303.7
28
0.4 17
0.6
0.6
0.4 1.2
0.2 0.7
Relative number of atoms detected on surface by using relative sensitivity factors (Wagner, D. D. Anal. Cbem. 1972, 44, 1050) and calculated on the basis of homogeneousdistribution. Adventitious carbon used for static charge correction, C 1s = 284.6 eV. Estimated accuracy 10.2eV. Oxygen can be high because of absorbed H20. Samples heated for 2 h.
of the two minerals, as well as their Si02 content. The importance of potassium is also demonstrated in Figure 5, which shows the effect of three montmorillonite prototypes on Cas04 decomposition. The potassium prototype of this mineral produced the largest effect on Cas04 decomposition, possibly due to the large "mobility" of potassium at high temperatures. The calcium prototype of montmorillonite produced the smallest effect on Cas04 decomposition since diffusion of the interlayer cations did not produce disorders in the Cas04 crystal. Intimacy of contact between two solids is important for the occurrence of mechanisms 1 and 2. For the layered silicates that were tested, the layered structure becomes disrupted between 800 and 1000 "C, and the formation of new phases begins above 1000 "C depending on composition (33).Disruption of the layered structure can provide intimate contact between Cas04 and the mineral matter in coal. In lignite ash, there was intimate solid contact which resulted in a large loss of surface sulfur a t 1050 OC, as shown in Table 111. The atomic ratio of Ca to S was 1:l at 710 "C and 'increased to 11:1 a t 1050 "C. Pure Cas04 and a prepared mixture of Cas04 and Si02 showed considerably less loss of surface sulfur. Decomposition of Sulfated Ashes. Figure 6 shows that the Illinois No. 6 ash lost sulfur much faster than the Texas lignite ash. This was attributed to the composition of the basic component of each ash. In the Illinois No. 6 ash the dominant basic component was iron which tied the sulfur as FeS04. In lignite it was calcium which tied the sulfur as CaS04. Calcium sulfate is much more stable than iron sulfate; therefore, Texas lignite ash retained sulfur better than Illinois No. 6 ash. Conclusion Relevant t o Flue-Gas Desulfurization
The mineral matter of coal can affect the stability of sulfated minerals. In particular, fewer sulfur oxides will be retained in the solid calcium-based minerals when the potassium content of the ash is large. Also fewer sulfur oxides will be retained if the solid calcium-based absorber becomes tied up with the silica content of the ash. Under actual combustion, low utilization of the calciumbased sulfur absorbent will be obtained if at some stage the absorbent was exposed to a reducing environment. Under such circumstances a layer of C a s is formed which could limit the rate of diffusion of SO, in the calcium-based mineral and thus reduce the utilization of the mineral as a desulfurization ab292
Environmental Science & Technology
sorbent. The main results support the following conclusions: (1)In the absence of reducing or acidic materials, the decomposition of pure Cas04 proceeds according to
This observation is consistent with ref 29. (2) In the presence of a reducing material, e.g., coal dust, the decomposition of Cas04 proceeds also according to reaction 7 , 8, or 9. This observation is consistent with the data of Wheelock and Boylan (30),who reduced Cas04 with CO, and with ref 27. (3) The release of SO, from Cas04 contaminated with coal stops after a very small portion of the Cas04 decomposes. (4). In the presence of silica (SiOz), kaolinite, sodium montmorillonite, calcium montmorillonite, and hematite, the rate of decomposition of Cas04 is somewhat larger than that of pure CaS04. Illite, potassium montmorillonite, and muscovite enhance dramatically the rate of decomposition of CaS04. ( 5 ) The rate of decomposition of Cas04 in the presence of potassium-containing mineral is much larger than that in the presence of analogous minerals which do not contain potassium. (6) Sulfated ashes are less stable than pure CaSOr; however, their rate of decomposition is less sensitive to added minerals than pure CaS04. ( 7 ) Sulfated ashes from low-rank coals, e.g., lignites, are more stable than sulfated ashes from high-rank coals, e.g., bituminous coals. This is attributed to the relatively high ratio of calcium to iron in the mineral matter of lignites. (8) Sulfated ashes from Illinois No. 6 coal lose SO2 gradually even a t room temperature. This indicates that disposal of sulfated ashes from such coal, e.g., by using them as land refill, may create sulfur pollution problems due to the slow release of absorbed S02. These conclusions are valid at temperatures below 1200 "C and a t atmospheric pressure. Acknowledgment
We thank the Texas Energy Advisory Council and Dow Chemical Co. for their generous support of this work. The ESCA runs were done by Dr. Laird H. Gale, Shell Oil Development Co., to whom the authors are obliged.
Literature Cited (1) Potter, A. E.; Harrington, R. E.; Spaite, P. W. Air Eng. 1968,10, 12-26. (2) Potter, A. E. Am. Ceram. SOC.Bull. 1969,48, 855-8. (3) Borgwardt, R. H.; Harvey, R. D. Environ. Sci. Technol. 1972,6, 350-60. (4) Falkenberry, H. L.; Slack, A. V. Chem. Eng. Prog. 1969, 69, 62-6. (5) Coutant, R. W.; Barrett, R. E.; Lougher, E. H. Trans. ASME 1970, 113. (6) Siegel, S.; Fuchs, L. H.; Hubble, B. R.; Nelsen, E. L. Enuiron. Sci. Technol. 1978,12, 1411-6. (7) Kito. M.: Wen, C. Y. AIChE Symp. Ser. 1974, No. 147, 119-25. (8) Pigford, R. L.; Sliger, G. Ind. Eng. Chem. Process Des. Deu. 1973, 12, 85-91. (9) Hartman, M.; Pata, J.; C o u g h , R. W. Ind. Eng. Chem. Process Des. Deu. 1978,17, 411-9. (10) Chen, Tan-Ping; Saxena, S. C. Fuel 1977,56, 401-11. (11) Best, R. J.; Yates, J. G. Ind. Eng. Chem. Process Des. Dev. 1977, 16, 347-52. (12) Leyko, J. Przem. Chem: 1956,35, 257-64; Chem. Abstr. 1959, 53, 2571-h. (13) Simon, A.; Thummler, Fr.; Klugel, E., Silikattechnik 1955,4, 101-4; Chem. Abstr. 1954,48, 1128-e. (14) Cismaru, D. Reu. Chim., Acad. Repub. Pop. Roum. 1957, 2, 267-78. (15) Hedvall, J. A.; Nordengren, S.; Liljegren, B. Acta Polytech., Chem. Incl. Metall. Ser. 1955,4, 7; Chem. Abstr. 1956,50, 6238. (16) Hedvall, J. A.; Nordengren, S.; Liljegren, B. Chalmers Tek. Hoegsk. Handl. 1955, No. 158; Chem. Abstr. 1955,49, 8719. (17) Shargorodskii, S. D. Ukr. Khim. Zh. (Russ.Ed.) 1950,16, 310-9; Chem. Abstr. 1952,46, 5411-i.
(18) Cismaru. D. Stud. Cercet. Chim. 1958,6, 539-46; Chem. Abstr. 1959,53, 17446. (19) Ginstling, A. M.; Volkov, A. D. Zh. Prikl. Khim. (Leningrad) 1960,33, 274-9; Chem. Abstr. 1960,54, 10618. (20) Weychert, S.; Milewshi, J. Przem. Chem. 1957,13, 690-6; Chem. Abstr. 1958,52, 8495. (21) Osmani. R.: Datar. D. S. J . Indian Chem. SOC.Ind. News Ed. 1957,20, 1-5; Chem. Abstr. 1958,52, 2629. (22) Akerman, K.; Zmudzinski, B.; Orman, Z.; Musieko, Z. Arch. Hutn. 1956,1, 319-39; Chem. Abstr. 1957,51, 12383. (23) Bischoff, F. V. Z. Anorg. Allg. Chem. 1942,250, 10-22. (24) Briner. E.: Knodel. Ch. Helu. Chim. Acta 1944, 27, 1406-14; Chem. Abstr.’ 1945,39, 2923-7. (25) Zinzen, A. Forsch. Geb. Ingenieurwes 1943,14B, 89-104; Chem. Abstr. 1945,39, 1746. (26) Zinzen. A. Z. Ver,Dtsch. Ing. 1944,88,171-8; Chem.Abstr. 1945, 39, 401. (27) Fuji, K. Gypsum 1952, I, 320-3; Chem. Abstr. 1953,47, 4778. 128) Feigl. F. “SDot Tests in Inorganic Analysis”; Elsevier: Amster‘ dam,f958. (29) Lau. K. H.: Cubicciotti, D.; Hildebrandt, D. L. J. Chem. Phys. 1977,66,4932-9. (30) Wheelock, T. D.; Boylan, D. R. Ind. Eng. Chem. 1960, 52, 215-8. (31) Montagna, J. C.; Lene, J. F.; Vogel, G. J.; Jonke, A. A. Ind. Eng. Chem. Process Des. Dev. 1977,16, 230-6. (32) Shewmon, P. G. “Diffusion in Solids”; McGraw-Hill: New York, 1963. (33) Deer, W. A.; Howie, R. A.; Zussman, J. “Rock-FormingMinerals”; Wiley: New York, 1964; Vol. 3. ~~
I
Received for review May 24, 1979. Accepted November 12,1980
Airborne Plume Study of Emissions from the Processing of Copper Ores in Southeastern Arizona Mark Small,+ Mark S. Germani,* Ann M. Small,t and William H. Zoller” Department of Chemistry, University of Maryland, College Park, Maryland 20742
Jarvis L. Moyers Department of Chemistry, University of Arizona, Tucson, Arizona 8572 1
Air-filter samples were collected with a light, twin-engine aircraft in the plumes of five copper smelters in southeastern Arizona and analyzed for 37 elements. Abundances of many volatile and chalcophilic elements are greatly enriched compared to the crustal abundance pattern for those elements. Comparisons of average results for each smelter showed marked differences in the abundance pattern of trace elements on particles released from different smelters. These unique abundance patterns could possibly be used as “fingerprints” to determine contributions of material from various plants at a specific impact point.
Introduction In recent years there has been increased public concern about the potential health effects caused by atmospheric particulate material released by anthropogenic activities. Before the impact of major emission sources on any region can be evaluated, the compositions of particles released from the sources must be known. Considerable work has been done on various industrial and fossil-fuel combustion processes. A t Present address: Midwest Research Institute, Kansas City, MO 64110. Present address: Chemistry Department, Arizona State University, Tempe, AZ 85281.
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major type of anthropogenic source that has received only limited attention is nonferrous metallurgy processes, particularly the processing of copper ores. Previous studies have shown increased concentrations of many chalcophilic elements in the vicinity of other types of nonferrous metal smelters. For example, Ragaini et al. ( I ) performed studies near a lead smelter complex in Kellogg, ID, and found elevated concentrations of chalcophilic trace elements in soil, grass, and ambient aerosols. Children living in that area have up to 20 times as much lead in their hair as their urban counterparts (2). In an extensive study of a lead smelter in southern Missouri, Jennett et al. ( 3 )found high concentrations of Pb, Zn, Cd, and Cu in the particulate emissions. Jacko et al. ( 4 ) observed high concentrations of Zn, Cd, Ni, Cu, As, and Hg in stack emissions from a zinc smelter. Unfortunately, both of these studies focused on only a few elements. However, they did show that several chalcophilic elements in addition to the major one being processed are released in high concentrations during the processing of nonferrous metal ores. Studies of copper smelters have generally concentrated on only sulfur and arsenic species (5, 6), although a study by Parungo et al. (7) showed that many trace elements emitted from copper smelters are borne by small particles which can be transported long distances and can be deposited efficiently in the lungs.
0013-936X/81/0915-0293$01.25/0 @ 1981 American Chemical Society
Volume 15, Number 3, March 1981
293
