title: Double-Barrier mechanism for chromium immobilization: A quantitative study of crystallization and leachability.
abstract: Glass-ceramics are well known for the excellent combination properties provided by their components, a glassy matrix and crystalline phases, and have promising applications in the immobilization and detoxification of solid waste containing toxic metals. Glass-ceramic products were successfully synthesized in CaO-MgO-SiO2-Al2O3 -Cr2O3 system. Two key measures--partitioning ratio of Cr in the spinel and Cr leaching ratio--were used to investigate the mechanism of Cr immobilization in the glass-ceramic products. The results of powder X-ray diffraction revealed that both spinel and diopside were major crystalline phases in the products. The value of x in the MgCr(x)Al(2-x)O4 spinel was highly related to the amount of Cr2O3 added to the glass-ceramic system. As Cr2O3 content increased, the proportion of spinel phase increased, while that of glass phase decreased. The partitioning ratio of Cr in spinel phase was about 70% for 2 wt.% Cr2O3, and increased to 90% when loaded with 10 wt.% of Cr2O3. According to the results of the prolonged toxicity characteristic leaching procedure, the Cr leaching ratio decreased with the increase of Cr partitioning ratio into the spinel phase. The findings of this study clearly indicate that glass-ceramic formed by spinel structure and residual glass successfully immobilized Cr.
authors.affiliation: Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou 510650, PR China; Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, PR China.
authors.forename: Changzhong
authors.initials: C
authors.lastname: Liao
authors.affiliation: School of Environmental Science and Engineering, South University of Science and Technology of China, Shenzhen 518055, PR China.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Tang
authors.affiliation: Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou 510650, PR China; State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550009, PR China. Electronic address: csliu@soil.gd.cn.
authors.forename: Chengshuai
authors.initials: C
authors.lastname: Liu
authors.affiliation: Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, PR China.
authors.forename: Kaimin
authors.initials: K
authors.lastname: Shih
authors.affiliation: Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou 510650, PR China.
authors.forename: Fangbai
authors.initials: F
authors.lastname: Li
keywords: Chromium immobilization; Glass-ceramic; Leaching performance; Rietveld quantitative XRD; Spinel