Department of Renewable Resources, 4-42 Earth Sciences Building, University of Alberta, Edmonton, AB T6G 2E3, Canada.
Department of Biological Sciences, CW 405, Biological Sciences Building, University of Alberta, Edmonton, AB T6G 2E9, Canada.
Sci Total Environ. 2015 Feb 1;505:1-10. doi: 10.1016/j.scitotenv.2014.09.093. Epub 2014 Oct 10.
Bitumen extraction from oil sands ores after surface mining produces different tailings waste streams: 'froth treatment tailings' are enriched in pyrite relative to other streams. Tailings treatment can include addition of organic polymers to produce thickened tailings (TT). TT may be further de-watered by deposition into geotechnical cells for evaporative drying to increase shear strength prior to reclamation. To examine the acid rock drainage (ARD) potential of TT, we performed predictive analyses and laboratory experiments on material from field trials of two types of thickened froth treatment tailings (TT1 and TT2). Acid-base accounting (ABA) of initial samples showed that both TT1 and TT2 initially had net acid-producing potential, with ABA values of -141 and -230 t CaCO₃ equiv. 1000 t(-1) of TT, respectively. In long-term kinetic experiments, duplicate 2-kg samples of TT were incubated in shallow trays and intermittently irrigated under air flow for 459 days to simulate evaporative field drying. Leachates collected from both TT samples initially had pH6.8 that began decreasing after 50 days (TT2) or ~250 days (TT1), stabilizing at pH2. Correspondingly, the redox potential of leachates increased from 100-200 mV to 500-580 mV and electrical conductivity increased from 2-5 dS m(-1) to 26 dS m(-1), indicating dissolution of minerals during ARD. The rapid onset and prolonged ARD observed with TT2 is attributed to its greater pyrite (13.4%) and lower carbonate (1.4%) contents versus the slower onset of ARD in TT1 (initially 6.0% pyrite and 2.5% carbonates). 16S rRNA gene pyrosequencing analysis revealed rapid shift in microbial community when conditions became strongly acidic (pH~2) favoring the enrichment of Acidithiobacillus and Sulfobacillus bacteria in TT. This is the first report showing ARD potential of TT and the results have significant implications for effective management of pyrite-enriched oil sands tailings streams/deposits.
“泡沫处理尾矿”相对于其他流而言富含黄铁矿。尾矿处理可能包括添加有机聚合物以产生增稠尾矿（TT）。TT 可以通过沉积到土工细胞中进一步脱水，以进行蒸发干燥，从而在回用时增加剪切强度。为了研究 TT 的酸性矿山排水（ARD）潜力，我们对来自两种类型的增稠泡沫处理尾矿（TT1 和 TT2）现场试验的材料进行了预测分析和实验室实验。初始样品的酸碱会计（ABA）表明，TT1 和 TT2 最初都具有净产酸潜力，ABA 值分别为-141 和-230 t CaCO₃equiv. 1000 t(-1)的 TT。在长期动力学实验中，将约 2-kg 的 TT 重复样品在浅盘中孵育，并在空气流下间歇性灌溉 459 天，以模拟蒸发现场干燥。从两个 TT 样品收集的浸出液最初的 pH 值约为 6.8，在约 50 天（TT2）或约 250 天（TT1）后开始下降，稳定在 pH 值约为 2。相应地，浸出液的氧化还原电位从 100-200 mV 增加到 500-580 mV，电导率从 2-5 dS m(-1)增加到 26 dS m(-1)，表明 ARD 过程中矿物的溶解。与 TT1 相比，TT2 中快速出现且持续时间长的 ARD 归因于其较高的黄铁矿（13.4%）和较低的碳酸盐（1.4%）含量，而 TT1 中 ARD 的起始时间较长（最初为 6.0%黄铁矿和 2.5%碳酸盐）。16S rRNA 基因焦磷酸测序分析表明，当条件变得极强酸性（pH 值约为 2）时，微生物群落迅速发生变化，有利于 TT 中嗜酸菌和硫杆菌的富集。这是第一个报道 TT 具有 ARD 潜力的报告，研究结果对有效管理富含黄铁矿的油砂尾矿流/矿床具有重要意义。
