Abstract：The leaching characteristics of cement solidified/stabilized Pb-contaminated kaolin under different pH of leachant are investigated via a series of semi-dynamic leaching tests as well as quantitative evaluation of the effectiveness of solidification/stabilization treatment in remediating Pb-contaminated kaolin. The designed initial pH of leachant is 2, 4, and 7. The results show that the accumulated leached Pb mass at leachant pH of 2 is 47 to 106 times that at leachant pH of 4 and 7. Nevertheless, the difference of the accumulated leached Pb mass between leachant pH of 4 and 7 is marginal. When cement content increases from 12% to 18%, accumulated leached Pb mass decreases by 28% to 68%, indicating that the increasing cement content will enhance the immobilization of Pb. The diffusion coefficient (De) of Pb is back-calculated by conducting a theoretical analysis of the relationship between the leaching time and the leached mass ratio. It is found that the values of De of Pb at leachant pH of 4 and 7 are very close; and those of Pb at leachant pH of 2 are 3 or 4 orders of magnitude greater than those at the leachant pH of 4 or 7. In addition, an increase of the cement content from 12% to 18% results in a decrease of De by 17% to 99%. The present results indicate that the strong acidic leachant (pH<4) and the increase in cement content have significant influence on the leached mass as well as diffusion coefficient of Pb for the cement-stabilized soils.
[1] YUKSELEN M A, ALPASLAN B. Leaching of metals from soil contaminated by mining activities[J]. Journal of Hazardous Materials, 2001, 87(1-3): 289-300. [2] 杜延军, 金 飞, 刘松玉, 等. 重金属工业污染场地固化/稳定处理研究进展[J]. 岩土力学, 2011, 32(1): 116-124. (DU Yan-Jun, JIN Fei, LIU Song-Yu, et al. Review of stabilization/solidification technique for remediation of heavy metals contaminated lands[J]. Rock and Soil Mechanics, 2011, 32(1): 116-124. (in Chinese)) [3] DU Y J, JIANG N J, SHEN S L, et al. Experimental investigation of influence of acid rain on leaching and hydraulic characteristics of cement-based solidified/stabilized lead contaminated clay[J]. Journal of Hazardous Materials, 2012, 225-226: 195-201. [4] 南京市环境保护局. 2011 年南京市环境状况公报[R]. 南京:南京市环境保护局, 2012. (Nanjing Environment Protection Administration. Report on the state of environment in Nanjing (2011)[R]. Nanjing: Nanjing Environment Protection Administration, 2012. (in Chinese)) [5] DE GROOT G J, VAN DER SLOOT H A. Determination of leaching characteristics of waste materials leading to environmental product certification[C]// GILLIAM T M, WILES C C, ed. Stabilization and Solidification of Hazardous, Radioactive and Mixed Wastes. Philadelphia: American Society for Testing Materials, 1992, 2: 149-170. [6] MOON D H, DERMATAS D. An evaluation of lead leachability from stabilized/solidified soils under modified semi-dynamic leaching conditions[J]. Engineering Geology, 2006, 85(1/2): 67-74. [7] MOON D H, DERMATAS D, GRUBB D G. Release of arsenic (As) and lead (Pb) from quicklime-sulfate stabilized/ solidified soils under diffusion-controlled conditions[J]. Environmental Monitoring and Assessment, 2010, 169(1/2/3/4): 259-265. [8] CUISINIER O, BORGNE T L, DENEELE D, et al. Quantification of the effects of nitrates, phosphates and chlorides on soil stabilization[J]. Engineering Geology, 2011, 117(3/4): 229-235. [9] 廖晓勇, 崇忠义, 阎秀兰, 等. 城市工业污染场地:中国环境修复领域的新课题[J]. 环境科学, 2011, 32(2): 784-794. (LIAO Xiao-Yong, CHONG Zhong-Yi, YAN Xiu-Lan, et al. Urban industrial contaminated sites: a new issue in the field of environmental remediation in China[J]. Environmental Science, 2011, 32(2): 784-794. (in Chinese)) [10] 杜延军, 蒋宁俊, 王 乐, 等. 水泥固化锌污染高岭土强度及微观特性研究[J]. 岩土工程学报, 2012, 34(11): 2114-2120. (DU Yan-Jun, JIANG Ning-Jun, WANG Le, et al. Strength and microstructure characteristics of cement-based solidified/stabilized zinc-contaminated kaolin[J]. Chinese Journal of Geotechnical Engineering, 2012, 34(11): 2114-2120. (in Chinese)) [11] ASTM C1308#x02014;08 Standard method for accelerated leach test for diffusive release from solidified waste and a computer program to model diffusive, fractional leaching from cylindrical waste forms[S]. 2009. [12] 陈蕾. 水泥固化稳定重金属污染土机理与工程特性研究[D]. 南京: 东南大学, 2010. (CHEN Lei. Research of mechanism and properties of cement stabilized/solidified heavy metal contaminated soils[D]. Nanjing: Southeast University, 2010. (in Chinese)) [13] BONEN D, SARKER S L. The present state of the art of immobilization of hazardous heavy metals in cement-based materials[M]// GRUTZECK M W, SARKER S L, eds. Advances in Cement and Concrete. New York: American Society of Civil Engineers, 1994: 481-498. [14] LI X D, POON C S, SUN H, et al. Heavy metal speciation and leaching behaviors in cement based solidified/stabilized waste materials[J]. Journal of Hazardous Materials, 2001, 82(3): 215-230. [15] KNOP A, VANGULCK J, HEINECK K S, et al. Compacted artificially cemented soil-acid leachate contaminant interactions: Breakthrough curves and transport parameters[J]. Journal of Hazardous Materials, 2008, 155(1/2): 269-276. [16] RICOU-HOEFFER P, LECUYER I, LE C P. Experimental design methodology applied to adsorption of metallic ions onto fly ash[J]. Water Research, 2001, 35(4): 965-976. [17] DUTR#x000c9; V, VANDECASTEELE C. An evaluation of the solidification/stabilisation of industrial arsenic containing waste using extraction and semi-dynamic leach tests[J]. Waste Management, 1996, 16(7): 625-631. [18] ROWE R K, QUIGLEY R M, BRACHMAN R W I, et al. Barrier systems for waste disposal facilities[M]. London: Spon Press, 2004. [19] DELL#x02019;ORSO M, MANGIALARDI T, PAOLINI A E, et al. Evaluation of the leachability of heavy metals from cement-based materials[J]. Journal of Hazardous Materials, 2012, 227: 1-8. [20] SOPHIA A C, SWAMINATHAN K. Assessment of the mechanical stability and chemical leachability of immobilized electroplating waste[J]. Chemosphere, 2005, 58(1): 75-82. [21] SINGH T S, PANT K K. Solidification/stabilization of arsenic containing solid wastes using portland cement, fly ash and polymeric materials[J]. Journal of Hazardous Materials, 2006, 131(1): 29-36. [22] VANDECASTEELE C, BROECK K V D, DUTR#x000c9; V. ICP-MS, hydride generation-ICP-MS, and CZE for the study (analysis and speciation) of solidification/stabilisation of industrial waste containing arsenic[J]. Waste Management, 2000, 20(2): 211-216. [23] MOON D H. Lead leachability from quicklime treated soils in a diffusion controlled environment[J]. Environmental Engineering Research, 2005, 10(3): 112-121. [24] MOON D H, DERMATAS D. Arsenic and lead release from fly ash stabilized/solidified soils under modified semi-dynamic leaching conditions[J]. Journal of Hazardous Materials, 2007, 141(2): 388-394. [25] SONG F Y, GU L, ZHU N W, et al. Leaching behavior of heavy metals from sewage sludge solidified by cement-based binders[J]. Chemosphere, 2013, 92(4): 344-350. [26] MALVIYA R, CHAUDHRY R. Leaching behavior and immobilization of heavy metals in solidified/stabilized products[J]. Journal of Hazardous Materials, 2006, 137(1): 207-217.
