Formation and leachability of hexavalent chromium in the Al2O3-CaO-MgO-Cr2O3 system

Research paper by Yingjiang Wu, Shengqiang Song; Andrie M. Garbers-Craig; Zhengliang Xue

Indexed on: 02 Mar '18Published on: 26 Feb '18Published in: Journal of the European Ceramic Society


Publication date: June 2018 Source:Journal of the European Ceramic Society, Volume 38, Issue 6 Author(s): Yingjiang Wu, Shengqiang Song, Andrie M. Garbers-Craig, Zhengliang Xue The Al2O3-CaO-MgO-Cr2O3 system has immense potential for refractory castables applications. However, Cr(III) can potentially be oxidized to carcinogenic Cr(VI) during the usage, which can cause subsequent problems with disposal. Equilibrium experiments on the Al2O3-CaO-MgO-4wt%Cr2O3 system were performed at 1500 °C in air. The effect of MgO addition (0 and 20 wt%) on the formation and leachability of hexavalent chromium was investigated using XPS, XRD, SEM-EDS, the TRGS 613 standard Cr(VI) leaching test and multiple leaching tests. A Cr(VI)-containing phase Ca4Al6CrO16 predominantly formed in the samples with 0 and 5 wt% MgO, while the Cr(III)-containing Mg(Al, Cr)2O4 spinel phase formed in the samples with 10 and 20 wt% MgO. Addition of MgO suppressed the formation of Cr(VI) while favored the formation of spinel phase. Concentrations of Cr(VI) in the leachates from TRGS 613 tests exceeded the European limit of 0.0002 wt% in all samples, although decreased significantly with 20 wt% MgO addition. Graphical abstract