Faculty of Mathematics and Natural Sciences, Dep. of Geosciences, Institute of Geography, Univ. of Cologne, Albertus-Magnus-Platz, Köln, D-50923, Germany.
ZEuUS, THM Univ. of Applied Sciences, Wiesenstr. 14, Gießen, D-35390, Germany.
J Environ Qual. 2020 May;49(3):712-722. doi: 10.1002/jeq2.20071. Epub 2020 Apr 22.
Chromite ore processing residue (COPR) is a waste derived from the chromate extraction from roasted ores and is deposited in some countries in landfills. The objective of this study was to investigate the leaching characteristics of hexavalent Cr [Cr(VI)] from two COPR samples obtained from unlined landfills in the Kanpur area of northern India. Column experiments were conducted under water-saturated conditions to simulate Cr release from the wastes caused by tropical heavy-rain events. Leached Cr(VI) decreased from 1,800 to 300 mg L (Rania site) and 1,200 to 163 mg L (Chhiwali site) during exchange of 12 pore volumes, which approximately corresponds to 2 yr of monsoon precipitation. Flow interruptions for 10, 100, and 1,000 h had little effect on Cr(VI) concentrations in the leachate, suggesting that Cr(VI) leaching was not limited by slow release kinetics. Calcium aluminum chromium oxide hydrates (CAC), and highly soluble phases such as Na CrO may play a role in controlling Cr(VI) concentration in the leachates. The amount of Cr(VI) leached from the columns accounted for 16% of the total Cr(VI) present in both COPR samples. A decrease in the solid-phase Cr(VI)/Cr ratio along the column was identified by X-ray absorption near edge structure (XANES) spectroscopy. Consistently, the smallest Cr(VI)/Cr ratios were found in the lower column section closest to the inflow. Our results suggest that Cr(VI) leaching from the unlined COPR landfills will continue for centuries, highlighting the urgent need to remediate these dumpsites.
铬铁矿加工残渣（COPR）是从焙烧矿石中提取铬酸盐后产生的废物，在一些国家被存放在垃圾填埋场中。本研究的目的是研究从印度北部坎普尔地区未衬砌垃圾填埋场获得的两个 COPR 样品中六价铬[Cr(VI)]的浸出特性。在水饱和条件下进行柱实验，以模拟热带暴雨事件导致废物中 Cr 的释放。在交换 12 个孔隙体积时，浸出的 Cr(VI)从 1800 降至 300mg/L（Rania 点）和 1200 降至 163mg/L（Chhiwali 点），这大约相当于 2 年的季风降水。中断 10、100 和 1000 小时的流动对浸出液中 Cr(VI)浓度几乎没有影响，表明 Cr(VI)浸出不受缓慢释放动力学的限制。钙铝铬氧化物水合物（CAC）和高溶解度相，如 Na CrO，可能在控制浸出液中 Cr(VI)浓度方面发挥作用。从柱中浸出的 Cr(VI)量占两个 COPR 样品中总 Cr(VI)的 16%。X 射线吸收近边结构（XANES）光谱表明，沿柱固相 Cr(VI)/Cr 比下降。一致地，在最接近入口的下部柱段发现了最小的 Cr(VI)/Cr 比。我们的研究结果表明，未衬砌 COPR 垃圾填埋场中的 Cr(VI)浸出将持续几个世纪，这突显了急需修复这些垃圾填埋场的迫切需要。
