Formation, leachability and encapsulation of hexavalent chromium in the Al2O3–CaO–Fe2O3–Cr2O3 system
Formation, leachability and encapsulation of hexavalent chromium in the Al2O3–CaO–Fe2O3–Cr2O3 system
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DOI：
10.1016/j.jeurceramsoc.2015.12.036
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发表时间：
2016-05
影响因子：
5.7
通讯作者：
Sheng-qiang Song;A. Garbers-Craig
中科院分区：
文献类型：
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作者：
Sheng-qiang Song;A. Garbers-Craig
耐火浇注料可以含有Cr2 O3，作为特定的添加物或作为原材料中的杂质元素。当铝酸钙水泥用作这种浇注料中的粘合剂时，Cr（III）在使用过程中可转化为Cr（VI），这可导致后续的用过的耐火衬里的处理问题。研究了Al_2O_3-CaO-Fe_2 O_3 - 4wt%Cr_2O_3混合耐火浇注料中Cr（VI）的形成及其可熔性。样品由试剂级化学品制备，在1300 °C下在空气中平衡并在液氮中淬灭。在所有被检查的样品中形成含Cr（VI）的相Ca 4Al 6CrO 16（hauyne）。在ASTM D3987-85浸出试验期间，共存的C3 A、C12 A7、Ca 2（Al，Fe）2 O 5和CA相通过形成Cr（VI）类似物相3CaO·Al 2 O3·CaCO 4·nH 2 O包覆Cr（VI）。这些相将Cr（VI）的溶解性降低至低于EPA限值5 mg/l。然而，降低pH和升高温度可以使Cr（VI）再活化。
Refractory castables can contain Cr2O3, either as a specific addition or as a impurity element in the raw materials. When calcium aluminate cement is used as a binder in such castables, Cr(III) can transform to Cr(VI) during use, which can cause subsequent problems with the disposal of the used refractory lining. The formation of Cr(VI) in Al2O3–CaO–Fe2O3–4wt% Cr2O3mixtures, representing a simplified refractory castable system, was investigated as well as its leachability. Samples were prepared from reagent grade chemicals, equilibrated at 1300 °C in air and quenched in liquid nitrogen. A Cr(VI)-containing phase Ca4Al6CrO16(hauyne) formed in all the examined samples. During the ASTM D3987-85 leach test the co-existing C3A, C12A7, Ca2(Al,Fe)2O5and CA phases encapsulated the Cr(VI) by forming Cr(VI) analogue phases 3CaO·Al2O3·CaCO4·nH2O. These phases decreased the leachability of Cr(VI) to below the EPA limit of 5 mg/l. Decreasing the pH and increasing the temperature can however remobilise the Cr(VI).