Environ. Sci. Technol. 2008, 42, 6116–6123
Anion Leaching from Refinery Oily Sludge and Ash from Incineration of Oily Sludge Stabilized/Solidified with Cement. Part I. Experimental Results ATHANASIOS K. KARAMALIDIS* AND EVANGELOS A. VOUDRIAS Department of Environmental Engineering, Democritus University of Thrace, GR 671 00 Xanthi, Greece
Received December 7, 2007. Revised manuscript received May 28, 2008. Accepted May 29, 2008.
This paper presents the leaching behavior of anions (SO42and CrO42-) from refinery oily sludge and ash produced by incineration of oily sludge, stabilized/solidified (s/s) with two types of cement, I42.5 and II42.5. Anion leaching was examined using a 5-step sequential toxicity characteristic leaching procedure (TCLP) test. A single TCLP extraction resulted in limited sulfate release ( 10.8 (Figure 3). This sulfate leaching behavior is indicative of reactions taken place at the waste mixture with the cement. As a result, when these cement-based structures (e.g., ettringite, monosulfate) are subject to variable pH, they could be substituted, dissociated, or dissolved and leach sulfate. Similar behavior of SO42leaching was also observed for solidified specimens with II42.5 cement (Figure 3B). The maximum leached amounts of sulfate from solidified ash samples with II42.5 cement at the pH range from 8.6 to 9.8 was from 800 to 980 mg/L (Figure 3B). In the presence of the pozzolanic cement (II42.5), the treated waste leached higher amounts of sulfate compared to solidified ash samples with I42.5 cement, as also was observed for the solidified oily sludge samples, as previously discussed. The effect of increasing cement content in the treated ash samples on sulfate leaching with increasing L/S ratio is presented in Figure 4. The results showed that as the L/S ratio increased, the effect of higher cement content in solidified specimens was more pronounced, contrary to what was observed for solidified oily sludge samples. This difference in leaching behavior between the two wastes was attributed to the presence of hydrocarbons in the case of the treated oily sludge, which retarded many of the reactions occurring in the hydrocarbon-free conditions of the solidified ash specimens. As the buffering capacity of the treated ash was higher than this of the treated oily sludge, the stability of sulfate-related solids was favored and the cumulative sulfate leaching was maintained low ( 11.5) (Figure 4). In the long term (at L/S ) 100) solidified specimens with 50-60% cement exhibited maximum cumulative leachability of >25 g SO42-/kg specimen, whereas solidified ash samples with 10-20% cement >34 g SO42-/kg specimen, again more than the ash and cement alone (Figure 4A).
cement, after five TCLP extractions against pH: (A) I42.5 cement The solidified ash samples with II42.5 cement resulted in sulfate leaching behavior similar to that observed for the solidified ash with I42.5 cement (Figure 4B). Addition of II42.5 cement favored sulfate leaching at L/S ratios >40 (Figure 4B) more than addition of I42.5. The increasing cement content in solidified ash samples with II42.5 cement had less pronounced effect, compared to that of solidified ash with I42.5 cement, in preventing sulfate leaching as the L/S ratio increased. All specimens solidified with II42.5 cement leached sulfate in the range of 38-44 g/kg specimen at L/S ) 100. Ash and cement alone leached lower amount of sulfate than solidified ash even at high L/S ratios. As also observed for solidified oily sludge samples (maximum cumulative leaching 20%), in none of the solidified ash samples did sulfate cumulative leaching surpass 21% of the initial sulfate content of the waste. See the Supporting Information for percent cumulative anion leaching. In addition, treated ash solidified with both additives, I42.5 and II42.5 cement, exhibited very low leaching (50% with II42.5), exhibited cumulative leaching of chromate lower than that of the untreated ash. At L/S ) 100, most of the solidified ash specimens exhibited lower leaching than ash, except for samples with 10-20 and 40% I42.5 cement addition (Figure 6A) and 10 and 30% II42.5 cement addition (Figure 6B), respectively. The maximum cumulative chromate leaching observed was 506 and 495 mg/kg for solidified ash with I42.5 and II42.5 cement, respectively. Solidified ash with II42.5 cement performed better with respect to the chromate retention in the matrix, which resulted in minimum cumulative leaching of 216 mg/kg for solidified ash sample with 70% cement (Figure 6B), whereas solidified specimens with 70% I42.5 cement leached 299 mg/kg, respectively (Figure 6A). Many mechanisms have been proposed for chromate immobilization in cement matrices, including reduction of Cr(VI) to Cr(III), which is considered difficult to occur at alkaline pH but have been reported (32), substitution of sulfate for chromate in ettringite (10, 33, 34), formation of CaCrO4(s) (35) and encapsulation. Some of these mechanisms imply that chromate is not well-retained in the cement matrix. Pera et al. (33) showed that ordinary Portland cement was the most efficient binder. The current experimental data indicate that in none of the solidified ash samples chromate cumulative leaching surpassed 0.9% of the initial chromate content in the waste and that pozzolanic cement (II42.5) was more efficient in chromate retention than Portland type cement (I42.5), only at high cement additions (>50%). See Supporting Information for percent cumulative anion leaching. Comparison of s/s Wastes. In Figure 7, a comparison between s/s oily sludge and ash samples with both types of cement is presented. A qualitatively similar leaching behavior for SO42- even for radically different wastes, such as oily sludge and ash (see Table S-1, Supporting Information), solidified with two different types of cement was observed. In addition, a similar behavior for CrO42- leaching from ash stabilized with two different types of cement was observed. It appears that pH is the controlling parameter in all cases. Similar results have been reported (29). The similarity in leaching behavior implies the same controlling phases in all cases, which was also confirmed with geochemical modeling (18). A qualitative comparison of anion leaching considering different parameters is presented in Table S-2 of the Supporting Information. Application of a two-sample t test showed that none of the differences in the mean concentrations between any of the results were found statistically significant (see details in the Supporting Information).
Acknowledgments We thank Mitchell Small, who provided suggestions regarding statistical methods and interpretation, as well as the anonymous reviewers for their helpful input. 6122
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 42, NO. 16, 2008
Supporting Information Available Further information about experimental design, sulfate and chromate leaching as a function of the 5-step sequential TCLP extractions, as a function of binder addition, percent cumulative leaching, qualitative leaching trends, and statistical methods (PDF). This information is available free of charge via the Internet at http://pubs.acs.org.
Literature Cited (1) Gougar, M. L. D.; Scheetz, B. E.; Roy, D. M. Ettringite and C-S-H Portland cement phases for waste ion immobilization: A review. Waste Manage. 1996, 16 (4), 295–303. (2) Myneni, S. C. B.; Traina, S. J.; Logan, T. J.; Waychunas, G. A. Oxyanion Behavior in Alkaline Environments: Sorption and Desorption of Arsenate in Ettringite. Environ. Sci. Technol. 1997, 31, 1761–1768. (3) Skanly, J.; Marchand, J.; Odler, I. Sulfate Attack on Concrete; Spon Press: New York, 2002. (4) Perkins, R. B.; Palmer, C. D. Solubility of ettringite (Ca6[Al(OH)6]2(SO4)3 · 26H2O) at 5-75°C. Geochim. Cosmochim. Acta 1999, 63 (13/14), 1969–1980. (5) Baur, I.; Keller, P.; Mavrocordatos, D.; Wehrli, B.; Johnson, C. A. Dissolution-precipitation behavior of ettringite, monosulfate, and calsium silicate hydrate. Cem. Concr. Res. 2004, 34, 341– 348. (6) Omotoso, O. E.; Ivey, D. G.; Mikula, R. Hexavalent chromium in tricalcium silicate: Part I Quantitative X-ray diffraction analysis of crystalline hydration products. J. Mater. Sci. 1998, 33, 507– 513. (7) Perkins, R. B.; Palmer, C. D. Solubility of Ca6[Al(OH)6]2(CrO4)3 · 26H2O, the chromate analog of ettringite; 5-75°C. Appl. Geochem. 2000, 15, 1203–1218. (8) Albino, V.; Cioffi, R.; Marroccoli, M.; Santoro, L. Potential application of ettringite generating systems for hazardous waste stabilization. J. Hazard. Mater. 1996, 51 (1-3), 241–252. (9) Berardi, R.; Cioffi, R.; Santoro, L. Matrix stability and leaching behaviour in ettringite-based stabilization systems doped with heavy metals. Waste Manage. 1997, 17 (8), 535–540. (10) Poellmann, H.; Auer, St.; Kuzel, H.-J.; Wenda, R. Solid solution of ettringites part II: incorporation of B(OH)4- and CrO42- in 3CaO · Al2O3 · 3CaSO4 · 32H2O. Cem. Concr. Res. 1993, 23, 422– 430. (11) Halim, C. E.; Amala, R.; Beydoun, D.; Scott, J. A.; Low, G. Evaluating the applicability of a modified toxicity characteristic leaching procedure (TCLP) for the classification of cementitious wastes containing lead and cadmium. J. Hazard. Mater. 2003, B103, 125–140. (12) Hooper, K.; Iskander, M.; Silvia, G.; Hussein, F.; Hsu, J.; De Guzman, M.; Odion, Z.; Ilejay, Z.; Sy, F.; Petreas, M.; Simmons, B. Toxicity Characteristic Leaching Procedure fails to extract oxoanion-forming elements that are extracted by Municipal Solid Waste leachates. Environ. Sci. Technol. 1998, 32, 3825– 3830. (13) Poon, C. S.; Lio, K. W. The limitation of the toxicity characteristic leaching procedure for evaluating cement-based stabilized/ solidified waste forms. Waste Manage. 1997, 17 (1), 15–23. (14) Kosson, D. S.; van der Sloot, H. A.; Sanchez, F.; Garrabrants, A. C. An Integrated Framework for Evaluating Leaching in Waste Management and Utilization of Secondary Materials. Environ. Eng. Sci. 2002, 19 (3), 159–204. (15) Li, X. D.; Poon, C. S.; Sun, H.; Lo, I. M. C.; Kirk, D. W. Heavy metal speciation and leaching behaviors in cement based solidified/stabilized waste materials. J. Hazard. Mater. 2001, A82, 215–230. (16) European Waste Catalogue (2002). Commission Decision 2001/ 118/EC of 16 January 2001, amending Decision 2000/532/EC as regards the list of wastes, L47/1. (17) Means, J. C.; Smith, L. A.; Nehring, K. W.; Brauning, S. E.; Gavaskar, A. R.; Sass, S. M.; Wile, C. C.; Mashni, C. I. The Application of Solidification/Stabilization to Waste Materials; CRC Press: Boca Raton, FL, 1994. (18) Karamalidis, A. K.; Voudrias, E. A. Anion Leaching from Refinery Oily Sludge and Ash from Incineration of Oily Sludge Stabilized/ Solidified with Cement. Part II. Modeling. Environ. Sci. Technol. 2008, 6124–6130. (19) Determination of Inorganic Anion by Ion Chromatography Method 9056. In Test Methods for Evaluating Solid Waste, Physical/Chemical Methods, EPA Publication SW-846, July 1992; U.S. Environmental Protection Agency: Washington, D.C., 1992.
(20) APHA, AWWA, and WEF. Standard Methods for the Examination of Water and Wastewater, 20th ed.; Clesceri, L. S., Greenberg, A. E., Eaton, A. D., Eds.; American Public Health Association: Washington, D.C., 1999. (21) Miller, J. C. and Miller J. N. Statistics for Analytical Chemistry, 3rd ed.; Ellis Horwood PTR Prentice Hall: New York, 1993. (22) Toxicity Characteristic Leaching Procedure (TCLP) Method 1311. In Test Methods for Evaluating Solid Waste, Physical/Chemical Methods;EPA Publication SW-846, July 1992; U.S. Environmental Protection Agency: Washington, D.C., 1992. (23) Glasser, F. P. Fundamental aspects of cement solidification and stabilization. J. Hazard. Mater. 1997, 52, 151–170. (24) Damidot, D.; Glasser, F. P. Thermodynamic investigation of the CaO-Al2O3-CaSO4H2O system at 50°C and 85°C. Cem. Concr. Res. 1992, 22, 1179–1191. (25) Giampaolo, C.; Mastro, S.Lo.; Polettini, A.; Pomi, R.; Sirini, P. Acid neutralisation capacity and hydration behaviour of incineration bottom ash-Portland cement mixtures. Cem. Concr. Res. 2002, 32, 769–775. (26) Myneni, S. C. B.; Traina, S. J.; Logan, T. J. Ettringite solubility and geochemistry of the Ca(OH)2-Al2(SO4)3-H2O system at 1 atm pressure and 298 K. Chem. Geol. 1998, 148, 1–19. (27) Council Directive 98/83/EC of 3 November 1998 on the quality of water intended for human consumption. (28) 40 Code of Federal Regulations vol. 19, part 141, 2002.
(29) Park, J.-Y.; Kang, W.-H.; Hwang, I. Hexavalent Chromium Uptake and Release in Cement Pastes. Environ. Eng. Sci. 2006, 23 (1), 133–140. (30) 40 Code of Federal Regulations 261, “Hazardous Waste Management System; Identification and Listing of Hazardous Waste; Toxicity Characteristics Revisions; Final Rule”, Part 261.24, USA, revised as of July 1, 2003. (31) Anderson, W. C., Ed. Innovative Site Remediation Technology; Stabilization/Solidification; American Academy for Environmental Engineers: Annapolis, MD, 1994. (32) Allan, M. L.; Kukacka, L. E. Blast furnace slag-modified grouts for in situ stabilization of chromium-contaminated soil. Waste Manage. 1995, 15 (3), 193–202. (33) Pera, J.; Thevenin, G.; Chabannet, M. Design of a novel system allowing the selection of an adequate binder for solidification/ stabilization of wastes. Cem. Concr. Res. 1997, 27 (10), 1533– 1542. (34) Kindness, A.; Macias, A.; Glasser, F. P. Immobilization of chromium in cement matrices. Waste Manage. 1994, 14 (1), 3–f11. (35) Wang, S.; Vipulanandan, C. Solidification/stabilization of Cr(VI) with cement. Leachability and XRD analyses. Cem. Concr. Res. 2000, 30, 385–389.
ES703063B
VOL. 42, NO. 16, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
6123
