Heavy metals leaching in bricks made from lead and zinc mine tailings with varied chemical components
Abstract The stabilization/solidification approach has received considerable attentions for the disposal of hazardous metal-bearing mine tailings. A poor understanding of the immobilization mechanism of heavy metals in final products always restricts its practical applications. We reported that, the stabilization of toxic heavy metals (Zn, Pb, Cd and Cu) in bricks made from the lead and zinc mine tailings (LZMT) was highly dependent on the relative contents of SiO 2 , Al 2 O 3 , Fe 2 O 3 , CaO and MgO in LZMT. As the (SiO 2 +Al 2 O 3 )/(Fe 2 O 3 +CaO+MgO) ratios (SA/FCM ratios) increased, the C Pb , C Cd , or C Cu in leachates slightly decreased first and then increased. Much differently, C Zn firstly increased and then decreased, having highest C Zn (3.92mg/L at 30th day) at the SA/FCM ratios of 0.80. Compared with C Zn and C Pb , a much small C Cd and C Cu can be found. Notably, the C Zn and C Pb are also impacted by the change of SiO 2 :Al 2 O 3 ratios (and Fe 2 O 3 :CaO:MgO ratios as well). The C Pb decreased as the SiO 2 :Al 2 O 3 ratios increased from 1:0.046 to 1:1.354, while the C Zn reached a highest value at SiO 2 :Al 2 O 3 ratio of 1:0.084. The XRD analysis suggests that, the Al and Si can interact with Pb to form PbAl 2 Si 2 O 8 , which facilitates the immobilization of Pb 2+ . Excessive amount of SiO 2 and Al 2 O 3 bring the difficulties to forming stabile skeletons, resulting in the leaching of Pb readily. As for Zn, higher C Zn is generally owing to the occurrence of acid-soluble Zn 2 SiO 4 in bricks. The stabilization of Zn was achieved once Al 3+ was introduced as host to be substituted by Zn 2+ in the aluminate or aluminosilicate matrix. The findings could enrich the mechanistic understanding and pathway of heavy metals immobilization in eco-environmental products from LZMT. Highlights Impacts of SiO 2 :Al 2 O 3 and Fe 2 O 3 :CaO:MgO on metals leaching were examined. Leaching of Zn, Pb are highly depended on the chemical compositions in bricks. Presence of PbAl 2 Si 2 O 8 could facilitate the immobilization of Pb 2+ in bricks. Higher C Zn could be attributed to the formation of Zn 2 SiO 4 in bricks. Concentrations of Cd, Cu, Pb, Zn in leachate are all below the standard. Graphical abstract [DISPLAY OMISSION]
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- DOI : http://dx.doi.org/10.1016/j.conbuildmat.2016.12.076
- Elsevier : 저널> 권호 > 논문
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