Environ. Sci. Technol. 1988, 22, 1166-1 170
Vanadium Release from Stabilized Oil Ash Waste in Seawater Vincent T. Bresiin"? and Iver W. Duedalit
Marine Sclences Research Center, State University of New York at Stony Brook, Stony Brook, New York 11794, and Department of Oceanography and Ocean Engineering, Florida Institute of Technology, Melbourne, Florida 3290 1 Laboratory investigations were conducted to measure the release of vanadium from five different stabilized oil ash waste mixes as a first step toward evaluating the environmental acceptability of stabilized oil ash waste for the purpose of artificial reef construction in the ocean. Vanadium content of the stabilized oil ash mixes ranged from 1.84% to 4.08%. Seawater tank leaching studies showed that vanadium release from stabilized oil ash blocks was continuous. However, the rate of vanadium release decreased with time. Calculated effective diffusion coefficients for vanadium, ranging from 29 X to 0.24 X cm2 s-l for the five stabilized oil ash waste mixes, were found to be lowest in the mixes with the highest cement content. Calculations describing the dispersion distance of vanadium away from a hypothetical artificial reef, depending on the mix type used for reef construction, showed that vanadium is diluted to natural seawater levels within 0.04-0.4 m of the reef.
Introduction Oil ash is the residue remaining after the combustion of oil in oil-fired power generating utilities. Present usage of oil as a fuel for electric power generation requires utilities with ash collection devices to dispose of the collected oil ash in an environmentally acceptable manner. Vanadium is often a major component of the oil ash produced by the combustion of oil (1). Some of the generated oil ash waste with a high vanadium content has been sold to steel companies for recovery of vanadium. At present, recovery of vanadium from the oil ash waste is not a viable economic alternative. As a result, landfill or containment of oil ash waste in on-site storage facilities are the current methods for disposal of oil ash waste materials (2). The presence of potentially toxic elements, such as vanadium, associated with oil ash waste poses a threat to ground water, rendering a landfill containing oil ash waste environmentally tenuous. Leaching studies performed on oil ash waste with a high vanadium content indicate that large quantities of vanadium may be released into solution (3). Thus, alternatives to landfill must be sought for the disposal of oil ash waste. Research has shown that coal waste (fly ash and FGD residue) can be successfully stabilized into blocks and disposed of in the marine environment (4-8).The success of these coal waste projects led to the present project on stabilization of oil ash wastes for the purpose of marine disposal of oil ash blocks for artificial reef construction (9, IO). Oil ash waste, unlike coal fly ash, possesses no pozzolanic properties; thus, a cementitious matrix containing cement, coal fly ash, lime, and sodium carbonate was used to achieve an effective stabilization. These additives were combined with the oil ash waste to produce a series of stabilized mixes for testing. Engineering studies conducted on the stabilized mixes have shown that the blocks possess properties which will allow them to be fabricated, stored, handled, and transported. Additional engineering studies performed on the stabilized oil ash blocks indicated that 'State University of New York at Stony Brook. f Florida Institute of Technology. 1166
Environ. Sci. Technol., Vol. 22, No. 10, 1988
Table I. Mix Designs for Stabilized Oil Ash Wastea
mix 1
8 10 11 13
ash ratio (dry wt) oikcoal
additives, based lime
cementb
NazCOs
water
3070 5050 1000 5050 3070
10 6 0 10 10
3 20 50 3 0
0.5 0.5 0 0.5 0
40 40 40 40 35
on total dry ash wt, %
aRef 9 and 10. *Portland type I cement.
the blocks should meet the minimum requirements for ocean disposal as reef material (9, 10). Prolonged seawater exposure of the various stabilized oil ash mixes show that the blocks gain compressive strength with time. Results of this research led to the permitting and placement of an artificial reef constructed with stabilized oil ash waste in coastal Florida waters (11). The objective of the present research was to determine the rate of release of vanadium from stabilized oil ash waste blocks to seawater. Tank leaching studies were performed, with the leachate waters periodically analyzed for vanadium to determine the leaching behavior of stabilized oil ash waste in seawater. Prior to the tank leaching studies, the total vanadium concentration, estimated pore water pH, and the maximum leachable fraction of vanadium were measured for each of the stabilized oil ash mixes. From the tank leaching results, effective diffusion coefficients for vanadium were calculated. By studying the leaching behavior of vanadium from several oil ash waste mixes, it was possible to determine which compositional factors control vanadium dissolution. Knowledge of dissolution processes have been useful in predicting the diffusion coefficients for elements in stabilized coal waste (12-14) and will provide a way to predict the physical and chemical behavior of stabilized oil ash waste in the sea.
Materials and Methods Mix Designs. Oil ash waste used for the stabilization studies was obtained from the oil ash sludge drying area of the Florida Power and Light Co. Cape Canaveral Power Plant, Tittusville, FL; the coal fly ash was obtained from the ash collection hoppers at the Tampa Electric Co. Power Plant, Tampa, FL. The chemical and physical characteristics of the coal fly ash and the oil ash are described elsewhere (3,9). Oil ash waste was combined with additives including coal fly ash, Portland type I cement, lime, and sodium carbonate to form a stabilized block (9, IO). Portland cement type 11, due to its long-term resistance to sulfate attack, was substituted for Portland cement type I in oil ash waste mixes eventually placed in the sea (11). Five oil ash waste mixes with favorable engineering properties were chosen for this study (Table I). Fabrication processes and engineering properties of the stabilized oil ash waste mixes have been described elsewhere (9,10).
Acid Digestions. Vanadium anglysis of the stabilized oil ash waste blocks was performed according to the HFH3B03digestion technique (15). Prior to the actual acid 0013-936X/,88/0922-1166$01.50/0
0 1988 American Chemical Society
1
Table 11. Total Matrix Vanadium Concentration of the Stabilized Oil Ash Blocks
I
mix vanadium concn, % 1 8 10
i o - - -
*
0.07 2.09 f 0.09 4.08 f 0.1
1.84
mix vanadium concn, % 11 13
2.09 i 0.07 2.21 i 0.14
7
I 8
Figure 1. Tank canfiguration: (1) 0.45-pm Nuclepore membrane filter; (2) cover; (3) plastic tank; (4) filtered seawater; (5) monofiiiment line; (6) stabilized oil ash waste block; (7) magnetic stirring bar; (8) magnetic stirrer.
digestion, the stabilized oil ash waste blocks were ground by mortar and pestle to a powder that passed through a 0.5-mm sieve. Three replicate samples of each of the stabilized oil ash waste mixes were analyzed for vanadium. NBS SRM 1633-a coal fly ash was also digested to check the accuracy and precision of the method. The HF-H3B03 digests were analyzed for vanadium by flame atomic absorption spectrophotometry with a Perkin-Elmer Model 4000 spectrophotometer using a nitrous oxide acetylene flame. Experimental Design. Cylindrical stabilized oil ash waste blocks, with a geometrical surface area of 96.2 cm2, of each mix type were suspended with monofilament line in separate acid-washed plastic tanks containing 1.5 L of filtered (0.40 pm) coastal seawater (salinity 35 ppt) (Figure 1). Lids covered the tanks to prevent outside contamination; however, each lid had an opening covered by a membrane filter to allow free gas exchange between tank waters and atmosphere. The tanks were stirred continuously by magnetic stirrers. The experiments were conducted at room temperature (20-25 OC). The tank waters were sampled at 1, 2, 3, 6, 9, and 12 days during the initial 12-day period to determine the dissolution rate of vanadium over the short term. After the initial 3-day period, the water in each tank was replaced with fresh seawater. For the remainder of the leaching period, the sampling of the water was performed at approximately 5-day intervals, and the tank water was changed at 2-week intervals. The tank leaching studies were carried out for at least 100 days. Leachate Analysis. A seawater sample (20 mL) for vanadium analysis was withdrawn from the tanks, filtered through a 0.40-pm Nuclepore polycarbonate filter, acidified with "OB, and stored in a sealed vial. Vanadium analyses were performed by flameless atomic absorption spectrophotometry with a Perkin-Elmer Model 4000 spectrophotometer equipped with an HGA-400 graphite atomizer and an AS-40 autosampler. Leachable Fraction Analysis. Knowledge of the maximum leachable fraction of vanadium in the stabilized oil ash is required for the application of a mathematical model to the tank leaching results (14). The maximum
0
Figure 2. Cumulative release of vanadium from oil ash blocks in seawater. Mix designations in parentheses, by parts, are given as oil ash/coal ash/iime/cement/sodium carbonate: (+) mix 1 (30/70/ 10/3/0.5); ( 0 )mix 8 (50/50/6-20/0.5); (W) mix 10 (100/0/0/50/0); (0) mix 11 (50/50/10/3/0.5); (A)mix 13 (30/70/10/0/0).
leachable fraction (f') was previously defined as the fraction of the total concentration of an ion that can be leached from a crushed stabilized product at high dilution (1:200 w/v) (14). To prevent the influence of high pH, a stepwise extraction with renewal of the contact solution was used. Thus, portions of unreacted oil ash blocks were ground and sieved to achieve a powder size of less than 0.5 mm. Approximately 1.25 g of each powder was placed into acidwashed LPE bottles and mixed with 125 mL of filtered (0.40 pm) seawater (salinity 35 ppt). The bottles were then placed on a wrist action shaker for a period of 36 h. After the bottles were shaken, the samples were filtered through a 0.4-pm Nuclepore filter and solutions acidified to pH 2.0 with HN03. The residues were reextracted with 125 mL of fresh seawater for an additional 36 h and filtered, and the leachates were acidified to pH 2.0. The leachate solutions for each mix were combined and then analyzed for vanadium in the same manner as the tank leaching samples. Estimation of Pore Water pH. The pH of pore waters of each stabilized oil ash waste mix was estimated by determining the pH of a seawater-powdered stabilized oil ash slurry (14). The stabilized oil ash mixes were ground by mortar and pestle to a powdere whose particle size was less than 0.5 mm. The powder was then shaken in seawater at a 1:4 ratio (w/v) for 24 h on a wrist action shaker. After the 24-h period, the pH of the solution was recorded with an Orion Research Ionalyzer Model 407A MV/pH meter.
Results Vanadium in Oil Ash Blocks. The vanadium content of the oil ash mixes ranged from 1.84 f 0.07% for mix 1 to 4.08 f 0.10% for mix 10 (Table 11). These results are based on the HF-H3B03 acid digest which recovered 100% of the vanadium in NBS SRM coal fly ash. Vanadium Dissolution. Figure 2 shows the cumulative release of vanadium for the various stabilized oil ash mixes. The release of vanadium from the stabilized oil ash mixes persisted throughout the experiment. Mixes 1 and 11 released the greatest amount of vanadium during the study; 4810 pmol in 124 days and 3810 pmol of 103 days, Environ. Sci. Technol., Vol. 22, No. 10, 1988 1167
Table 111. Variables Used To Determine Effective Diffusion Coefficients for Vanadium
mix 1 8 10 11 13 loo
IOOC
TIME ( d i
Flgure 3. Vanadium flux versus time for stabilized oil ash blocks in seawater. Mix designations in parentheses, by parts, are given as oil ash/coal/ash/lime/cement/sodlum carbonate: (+) mix 1 (30/70/ 10/3/0.5); (0)mix 8 (50/50/6/20/0.5): (M) mix 10 (100/0/0/50/0): (0) mix 11 (50/50/10/3/0.5): (A)mix 13 (30/70/10/0/0).
respectively. Mixes 8 and 10 retained the vanadium most effectively, releasing only 400 and 326 pmol, respectively, after 104 days. Calculation of Vanadium Fluxes. The results of the dissolution studies were used to calculate the rate of loss of metal ions per unit geometric surface area of the stabilized oil ash blocks to the seawater medium. Thus, each flux is a normalized value taking into account the leaching period and the surface area of the block. The equation used to calculate the metal flux J (mol mm-2 day-l) was
where Ct is the ion concentration (mol L-l) in the test tank at time t, Co is the initial ion concentration (mol L-I) in the test tank, V, is the volume (L) of water in the test tank at time t, A is the geometric surface area (mm2) of the blocks, and t is the time (in days) since the water was last replaced. The calculated fluxes are not instantaneous rates but were averaged over a finite period of time. Vanadium Fluxes. Figure 3 is a log-log plot of the flux of vanadium versus time for the five stabilized oil ash mixes. Vanadium fluxes were highest initially and ranged mol mm-2 day-l for mix 1to 5.4 X mol from 3.4 X mm-2 day-l for mix 10. The vanadium fluxes for all mixes decreased with increasing time. After block submersion for 40 days, the vanadium flux for mix 1decreased to 5.5 X mol mm-2 dag1. The vanadium fluxes for mixed mol mmm2day-l, and 2.0 X 10 and 11were 2.3 X respectively, after 104 days. Application of Results to a Diffusion Model. A mathematical model was developed to describe the diffusion of Ca2+and SO>- from stabilized coal waste blocks into seawater (12). The model, one dimensional for the behavior of ions in coal waste blocks situated in well-stirred aqueous systems, assumes a uniform distribution of elements within the block and a one dimensional diffusion (a flux) of ions across the block-water boundary that is proportional to the concentration at that interface. This model was later revised to account for the fact that only a fraction of the ion may be in a form available for leaching and led to the development of eq 2 (24). Equation 2 incorporates a maximum leachable fraction term 0, defined as the total concentration of vanadium leached from crushed block at a liquid to solid ratio (w/v) of 200. For this study, the revised model provided a method for the calculation of effective diffusion coefficients for vanadium utilizing the calculated fluxes for the various stabilized oil ash mixes. The diffusion coefficients for vanadium were then used to calculate effective depths of vanadium diffusion (X,) from within each block. 1188
Environ. Sci. Technol., Vol. 22, No. 10, 1988
J," lo4 mmol
So,c
cm-2 day-'
mmol g-l
1.9 0.34 0.20 2.3 0.80
0.11 0.09 0.06 0.13 0.13
density: g ern"
0.36 0.41 0.80 0.41 0.43
1.9 1.8 1.7 1.8 1.8
D', cm2 s-l 29 0.67 0.24 22 14
"Vanadium fluxes, J , were obtained a t t = 100 days from experimental results in seawater (Figure 3). * Represents the leachable fraction obtained at high dilution (1:200w/v) and long contact time (72 h) (n = 3) (14). cSois the total vanadium concentration in the stabilized oil ash waste block as determined by a HF-H3B03 digested method (n = 3). Wet densitv (10). Table IV. Effective Distance ( X c ,om) of the Vanadium Diffusion"
time days years 100 200 365 1095 3650 10950
1 3 10 30
Mix 1
Mix 8
0.71 0.99 1.4 2.3 4.3 7.4
0.11 0.15 0.21 0.36 0.65 1.1
Mix 10 Mix 11 0.06 0.09 0.12 0.21 0.39 0.67
0.62 0.87 1.2 2.1 3.7 6.5
Mix 13 0.50 0.71 0.96 1.7 3.0 5.2
Values for X , were calculated by using eq 4.
The expression used for the calculation of the effective diffusion coefficients [D' (cm-2s-l)] for vanadium is given as D' = ?rt(J/fSo)2
(2)
where t = time of exposure (s), J = vanadium flux (mmol cm-2 d),So = vanadium concentration in the block (mmol cmW3), and f = maximum leachable fraction. The value of So is obtained from So = C d P M
(3)
where M = molecular weight (mg mmol-l) of vanadium, p = wet density of the block (g ~ m - ~and ) , C, = concentration of vanadium in the product (mg g-l). The effective depth of diffusion, X,(cm), defined as the depth within the stabilized block where a change in vanadium concentration due to diffusion can be observed (12), is given by
x,= &E
(4)
Vanadium Diffusion Coefficients. Effective diffusion coefficients (eq 2) for vanadium and the variables used to calculate these coefficients are shown in Table 111. D$ ranged from 0.24 X lo4 cm2s-l for mix 10 to 29 X lo* cm2 for mix 1. The diffusion coefficients were then substituted into eq 4 to calculate effective depths of diffusion for vanadium in the stabilized oil ash waste mixes (Table IV). The predicted depth of vanadium diffusion from within the stabilized oil ash blocks exposed to seawater, which is a function of time and mix design, ranged from a low of 0.67 cm to a high of 7.4 cm for mixes 10 and 1, respectively, after 30-year exposure. Discussion Factors Affecting Vanadium Dissolution. In order to understand the differences in the rate of vanadium leaching from the five stabilized oil ash mixes, several factors were investigated to determine what controls the 0;. These factors include pore water pH, cement content
Table V. Factors Affecting 0%
factors oil ash:coal Ob,X10-9 pore cement: total mix ash ratio cm2 s-l water pH % vanadium, % 1 8 10 11
13
30:70 5050 1oo:o 50:50 30:70
29 0.67 0.24 22 14
10.60 10.69 11.50 9.60 9.30
2.6 16 33 2.6 0
1.84 2.09 4.08 2.09 2.19
loo^^
"Cement content in the mix is based on weight percent.
95
% CEMENT
Figure 4. -log D'" versus percent cement for stabilized oll ash waste in seawater. Mix designations in parentheses, by parts, are given as oil ash/coal ash/iime/cement/sodium carbonate; (+) mix 1 (30/70/ (B) mix 10 (100/0/0/50/0); (0) 101W0.5);(0)mix 8 (50/50/6/20/0.5); mix 1 1 (50/50/10/3/0.5); (A)mix 13 (30/70/10/0/0).
of the mix, and the total vanadium content of the mix (Table V). (A) Cement. Vanadium release decreased as the percentage of cement in the stabilized oil ash mix increased. Figure 2 shows the cumulative release of vanadium from stabilized oil ash mixes in seawater and highlights the differences in vanadium leaching for mixes 8 and 11,with 15.8% and 2.6% cement, respectively. Mix 8 was found to leach a total of 400 Mmol of vanadium, whereas mix 11 leached 3810 pmol of vanadium during the course of the tank leaching studies. In addition, Figure 3 shows the flux of vanadium as a function of time for mixes 8 and 11. Mix 11,which contained 2.6% cement and 2.1% vanadium, had an initial vanadium leaching rate of 3.4 X mol mm-2 day-l. Mix 8, which contained 15.8% cement and 2.0% vanadium, had a significantly lower initial rate of 8.8 X mol mm-2 day-l. After a period of 46 days, the rate of vanadium leaching decreased in each mix reaching 4.1 X lo4 mol mm-2 day-l for mix 11and 3.9 X lo4 mol mm-2 day-l for mix 8. Effective diffusion coefficients for vanadium decreased as the percentage of cement in the stabilized mix increased (Figure 4). As cement content increased there is an exponential decrease in vanadium leaching. Cement, therefore, is very important in controlling the release of vanadium in the stabilized oil ash mixes. Cement is also an important additive for the strength development of the oil ash mixes (9, 10). Conceptually, with increasing cement content, a larger percentage of the vanadium-rich oil ash particles may become more effectively encapsulated within the cementitous matrix of the stabilized mix. With the addition of water to the mix, cement particles beging to hydrate and form a calcium-silicate-hydrate gel. Crystalline hydration products form in the interstices of the cement matrix. During the final stages of hydration the gel swells to the point where particle overlap occurs and silica fibrils develop. The interlocking of the fibrils and the formation
of various hydration products binds the cement along with other components in the mix into a rigid mass (16). (B) pH. In general, as the estimated pore water pH of the stabilized mix increases, D$ decreases (Table V). Mix 10, with a pore water pH of 11.5, had a D$ of 0.24 X cm s-l, while mix 11, with a pore water pH of 9.6, had a cm s-l. D $ of 22.0 X Studies conducted to determine the release of vanadium from particulate oil ash in seawater show that vanadium is readily released (3). Vanadium oxyanion release from stabilized coal ash products is highest at pH 8-10; at higher or lower pH the release of vanadium was observed to decrease (14). stabilized oil ash mixes showing the highest vanadium diffusion coefficients have estimated pore water pH 8-10 (Table V). The pattern of decreasing D$ with increasing pH is also related to the cement content of the stabilized mixes. Cement, coal fly ash, and lime content of the mix contribute to the alkalinity of the stabilized oil ash mixes. As a result, the estimated pore water pH of the stabilized mixes is a function of the ratios of these ingredients in the stabilized mix. As shown in Table V, as the cement content of the stabilized mix increases, the estimated pore water pH of the mix also increases. (C) Total Vanadium. D$ appears to be independent of the initial vanadium concentration of the stabilized oil ash mix (Table V). Stabilized mixes 8 and 11 each contained 2.09% vanadium but had differing D$ values of 0.67 X lo4 and 22.0 X cm2 s-l, respectively. Mix 10, with the largest vanadium content (4.08%), had the lowest D$ of the mixes tested. Model for Ocean Disposal of Stabilized Oil Ash Blocks. A conceptual model was used to portray the release of vanadium from a hypothetical oil ash artificial reef placed in shallow coastal ocean waters. A relationship was developed on the basis of measurements of turbulent and dispersive processes to describe the dispersion and dilution of a leached constituent from a stationary source near the seabed (17). This model has been applied in previous studies to calculate dispersion plumes for metals from stabilized wastes in seawater (18,19). By using the vanadium release rates measured in the tank leaching studies, the length of a vanadium dispersion plume from a hypothetical stabilized oil ash waste reef can be calculated. Dispersion distances for vanadium were determined for each of the stabilized oil ash mixes by
where L = downstream distance (m) of diffusion, q = source strength (pg) and is obtained by multipyling the vanadium concentration in the block (pg g-l) by the total weight of the reef (g), h = vanadium leaching rate (s-l) and is expressed as the fraction of vanadium leached per time (determined in the tank leaching studies), W = net flow velocity (cm s-l), Co = ambient vanadium concentration in seawater (g ~ m - ~and ) , H = mixing height from the bottom (cm). In the study, h was taken as the vanadium flux for 1and 100 days after placement of the oil ash blocks in seawater (Figure 3). The hypothetical reef was composed of 1000 tons of stabilized oil ash reef blocks and would contain approximately 40000 oil ash blocks (20 X 20 X 40 cm). Assuming 35% pore space within the reef, the reef would have a volume of 877 m3. The net flow velocity of the water in or near the reef is assumed to be 1 cm s-l, and the mixing height from the bottom is estimated to be 5 m. The Environ. Sci. Technoi., Voi. 22, No. IO, 1988 1169
Lazarus, A. G.; Palesh, C. M. Power Eng. (Barrington,Ill.)
Table VI. Calculated Dispersive Distance for Vanadium mix 1 8
10 11
13
mix typea
1 day, m
100 day, m
30/70/10/3/0.5 50/50/6/20/0.5 100/0/0/50/0 50/50/10/3/0.5 30/70/10/0/0
6.4 1.7
0.36 0.07 0.04 0.44 0.15
1.1
6.6 3.4
1981, 85.
Breslin, V. T. Ph.D. Dissertation, Florida Institute of Technology, 1986. Benson, R. E.; Chandler, H. M.; Chacey, K. A. J. Environ. Eng. (N. Y.) 1985, 111, 3. Parker, J. H.; Woodhead, P. M. J.; Duedall, I. W. Coal Waste Artificial Reef Program, Phase 3; EPRI Report CS-2009; Electric Power Research Institute: Palo Alto, CA, 1981; Vol. 2, 404 pp. Seligman, J. D.; Duedall, I. W. Enuiron. Sei. Tethnol. 1979, 13, 1082-1087. Roethel, F. J. Ph.D. Dissertation, State University of New York at Stony Brook, 1981. Suzuki, T. In Ocean Space Utilization '85; Kato, W., Ed.; Nihon University: Tokyo, Japan, 1985; pp 611-618. Mazurek, D. F. M.S. Thesis, Florida Institute of Technology, 1984. Teimouri, V. M.S. Thesis, Florida Institute of Technology, 1985. Kalajian, E. H.; Duedall, I. W.; Shieh, C. S.; Wilcox, J. R. In Proceedings of the Fourth International Conference on ArtificialHabitats for Fisheries, Miami, FL, Nov 2-6,1987. Duedall, I. W.; Buyer, J. S.; Heaton, M. G.; Oakley, S. A.; Okubo, A.; Dayal, R.; Tatro, M.; Roethel, F.; Wilke, R. J.; Hershey, J. P. In Industrial and Sewage Wastes in the Ocean;Duedall, I. W., Ketchum, B. H., Park, P. K., Kester, D. R., Eds.; Wiley-Interscience: New York, 1983. Edwards, T.; Duedall, I. W. In Wastes in the Ocean; Duedall, I. W., Kester, D. R., Park, P. K., Ketchum, B. H., Eds.; Wiley-Interscience: New York, 1985; Vol. 4. van der Sloot, H. A.; Wijkstra, J.; van Stigt, C. A.; Hoede, D. In Wastes in the Ocean;Duedall, I. W., Kester, D. R., Park, P. K., Ketchum, B. H., Eds.; Wiley-Interscience: New York, 1985; Vol. 4, pp 467-498. Parker, J. H.; Woodhead, P. M. J.; Duedall, I. W.; Colussi, J.; Hilton, R. G.; Pfeiffenberger, L. E. In Wastes in the Ocean;Duedall, I. W., Kester, D. R., Park, P. K., Ketchum, B. H., Eds.; Wiley-Interscience: New York, 1985; Vol. pp
Oil ash/coal ash/lime/Portland type I cement/sodium carbonate. Refer to Table I.
concentration of vanadium in coastal seawater was given as 1.5 pg L-l (20). The downstream distance of diffusion (eq 6) for vanadium for each of the mixes tested is shown in Table VI. L initially varied from 1.1to 6.6 m and decreased to 0.04 and 0.44 m for mixes 10 and 11,respectively, after 100 days of exposure to seawater. The mixes with the highest cement contents, 10 and 8, had the lowest values for L , reflecting the importance of the cement additive in controlling the release of vanadium. The ultimate fate of the released vanadium will depend on its speciation and interaction with particles in seawater. In seawater the stable form of vanadium is the orthovanadate ion, H2V04-. Dissolved vanadium in seawater has a residence time of 8 X lo4years, although vanadium can be effectively adsorbed onto ferric hydroxide and manganese oxide surfaces (21,22),thus causing a reduction in the dissolved vanadium. The association of vanadium with organic particulate matter is unclear at present, although vanadium porphyrins are cited as an important carrier of vanadium in marine sediments (23). Summary
Calculation of the effective distance of vanadium diffusion within the stabilized oil ash blocks shows that vanadium would be effectively retained by the stabilized oil ash waste mixes. Furthermore, calculations of the vanadium dispersion distances for a series of stabilized oil ash mixes from a hypothetical artificial reef show that the distance of vanadium dispersion decreases with time and that the released vanadium is rapidly diluted to natural seawater levels. The model calculations, however, have limitations since the experimental results used in these calculations were obtained under controlled laboratory conditions. Biological and physical processes may impact the physical and chemical integrity of the oil ash blocks once placed in the sea.
537-556. _ _ _.-
1
(17) (18)
(19) (20) (21)
Acknowledgments
(22)
We thank J. Ross Wilcox, Edward H. Kalajian, and John H. Trefrey for their assistance.
(23)
Christensen, D. C.; Wakamiya, W. In New and Promising UltimateDisposal Options;Posjasek, R. B., Ed.; Ann Arbor Science: Ann Arbor, MI, 1979; pp 75-90. Okubo, A., State University of New York at Stony Brook, personal communication, 1983. Roethel, F. J.; Duedall, I. W.; Woodhead, P. M. J. Coal Waste Artificial Reef Program: Conscience Bay Studies; Electric Power Research Institute: Palo Alto, CA, 1983; p 304. Lechich, A. F. M.S. Thesis, State University of New York a t Stony Brook, 1984. Prange, A.; Kremling, K. Mar. Chem. 1985, 16, 259. Jeandel, C.; Caisso, M.; Minster, J. F. Mar. Chem. 1987, 21, 51-74. Shieh, C. S. Ph.D. Dissertation, Florida Institute of Technology, in preparation. Nissenbaum, A.; Swaine, D. J. Geochim. Cosmochim. Acta 1977, 40,809.
Registry No. Na2C03,497-19-8; V, 7440-62-2.
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14,450-456.
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Received for review February 20,1987. Accepted March 14,1988. Support for this research was provided by the Florida Power and Light Co.
