Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/32680
Title: Heavy metal speciation and leaching behaviors in cement based solidified/stabilized waste materials
Authors: Li, XD 
Poon, CS 
Sun, H
Lo, IMC
Kirk, DW
Keywords: Heavy metals
Leaching
MINTEQA2
Sequential extraction
Stabilization/solidification
TCLP
Issue Date: 2001
Publisher: Elsevier
Source: Journal of hazardous materials, 2001, v. 82, no. 3, p. 215-230 How to cite?
Journal: Journal of hazardous materials 
Abstract: A circuit board printing factory sludge containing high concentrations of copper, zinc and lead was stabilized and solidified (S/S) with different portions of ordinary Portland cement (OPC) and pulverized fly ash (PFA). The chemical speciation and leaching behavior of heavy metals in these cement-based waste materials were studied by different sequential extraction procedures, standard toxicity characteristic leaching procedure (TCLP) and progressive TCLP tests. The sequential extraction results showed that more than 80% of Cu, Pb and Zn were associated with Fraction 2 (weak acid soluble, extracted with 1M NaOAc at pH 5.0 with a solid to liquid ratio of 1:60). This indicated that the heavy metals could exist in the S/S matrix as metal hydrated phases or metal hydroxides precipitating on the surface of calcium silicate hydrates (C=S=H), PFA and sludge particles. The progressive TCLP test results and MINTEQA2 calculation also showed the importance of Cu and Zn oxides during the leaching process. The leaching behaviors of these metals in the S/S waste materials were mainly controlled by the alkaline nature and acid buffering capacity of the S/S matrix. During the progressive TCLP tests, the alkaline conditions and acid buffering capacity of the matrix decreased with the dissolution of calcium hydroxide and C=S=H, therefore, the leaching of heavy metals in the S/S waste materials increased. The leaching of heavy metals in the S/S materials can be considered as a pH dependent and corresponding metal hydroxide solubility controlled process.
URI: http://hdl.handle.net/10397/32680
ISSN: 0304-3894
EISSN: 1873-3336
DOI: 10.1016/S0304-3894(00)00360-5
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