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Materials 2018, 11(1), 11; https://doi.org/10.3390/ma11010011

Removal of Hexavalent Chromium in Portland Cement Using Ground Granulated Blast-Furnace Slag Powder

1
Department of Architectural Engineering, Hanyang University, Seoul 04763, Korea
2
Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
3
Research Institute of Science and Technology, Nihon University College of Science and Technology, Chiyoda, Tokyo 101-8308, Japan
4
Department of Architecture, Graduate school of Engineering, The University of Tokyo, Bunkyo, Tokyo 113-8654, Japan
5
Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
6
School of Environmental and Sustainability Sciences, Kean University, Union County, NJ 07083, USA
*
Author to whom correspondence should be addressed.
Received: 23 October 2017 / Revised: 11 December 2017 / Accepted: 20 December 2017 / Published: 22 December 2017
(This article belongs to the Section Structure Analysis and Characterization)
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Abstract

Using ground granulated blast-furnace slag (GGBS) under different alkaline conditions, we studied the mechanisms and extents of Cr(VI) reduction and sorption and compared them to reactions with Portland cement (PC). We also investigated the effects of mixing PC/GGBS ratios on Cr(VI) dissolution after carbonating the substrates. We observed a complete sorption and reduction of Cr(VI) to Cr(III) in a GGBS-in-Ca(OH)2 solution (pH > ~12.5) after 10 h, whereas in distilled water (pH = ~11.5) GGBS exhibited only marginal sorption and reduction (20%). Cr reactions with dissolved ions in supernatants derived from GGBS indicated that the anions dissolved from GGBS act as a reducing agent for Cr(VI) in a Ca(OH)2 solution. Soft X-ray absorption microscopy identified a partial reduction of Cr(VI) to Cr(III) on the GGBS surface. The carbonation of pure PC paste substantially increased the amount of dissolved Cr(VI) in a solution phase whereas a 5 wt % replacement of PC with GGBS significantly reduced the amount of dissolved Cr(VI). We concluded that in the mixed paste during the early curing stage GGBS reduced a significant fraction of Cr(VI) to Cr(III) and that the Cr(III) adsorbed in the GGBS-PC mixture’s hydration products does not readily dissolve, even under carbonation conditions. View Full-Text
Keywords: hexavalent chromium; reduction; immobilization; slag; Portland cement hexavalent chromium; reduction; immobilization; slag; Portland cement
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Bae, S.; Hikaru, F.; Kanematsu, M.; Yoshizawa, C.; Noguchi, T.; Yu, Y.; Ha, J. Removal of Hexavalent Chromium in Portland Cement Using Ground Granulated Blast-Furnace Slag Powder. Materials 2018, 11, 11.

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