Thermal stabilization of chromium(VI) in kaolin

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Please use this identifier to cite or link to this item: http://140.128.103.80:8080/handle/310901/21688

Title:	Thermal stabilization of chromium(VI) in kaolin
Authors:	Wei, Y.-L., Chiu, S.-Y., Tsai, H.-N., Yang, Y.-W., Lee, J.-F.
Contributors:	Department of Environmental Science and Engineering, Tunghai University
Keywords:	Absorption spectroscopy;Chromium;Detoxification;Fourier transforms;Leaching;Mixing;Reduction;Thermodynamic stability;Toxicity
Date:	2002-11-01
Issue Date:	2013-05-15T09:04:21Z (UTC)
Abstract:	Reduction of Cr(VI) by heating may be a useful detoxification mechanism for thermal immobilization. Using X-ray absorption spectroscopy, the change of speciation of chromium in 105?C dried 3.7% Cr(VI)-sorbed kaolin further heated at 500, 900, or 1100?C was studied. The 105?C dried 3.7% Cr(VI)-sorbed kaolin sample was prepared by mixing 1.5 L of 0.257 M CrO 3 solution (pH 0.71) with 0.5 kg of kaolin powder for 48 h, and then the slurry was heated (dried) at 105?C until a constant weight was reached. The toxicity characteristic leaching procedure method was used to determine the percentage of leached chromium from all heated samples. In all 500-900?C heated Cr(VI)-sorbed kaolin samples, Cr 2O 3 transformed from the hydrated Cr(VI) by a 4-h heat application was identified by the X-ray absorption near edge structure and extended X-ray absorption fine structure (EXAFS) spectroscopy as the key species that is leaching-resistant due to its low solubility. For the 1100?C heated Cr(VI)-sorbed kaolin sample, the Fourier transform of its EXAFS spectrum indicates that the intensity of the peaks at 2.45 (Cr-Cr shell of Cr203) and 5.00 A (Cr-Cr and Cr-O shells of Cr 2O 3) without phase shift correction is either relatively smaller or disappearing, compared with that of the 500-900?C heated Cr(VI)-sorbed kaolin samples. It is suggested that chromium octahedra were bridged to silica tetrahedra and incorporated in minerals formed at 1100?C, such as mullite or sillimanite, since these phases were detected by XRD. Cr of this form is not easily leached.
Relation:	Environmental Science and Technology 36 (21) , pp. 4633-4641
Appears in Collections:	[環境科學與工程學系所] 期刊論文

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