Alternative waste residue materials for passive in situ prevention of sulfide-mine tailings oxidation: A field evaluation

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• 作者：Peter Nason ; Raymond H. Johnson ; Clara Neusch眉tz ; Lena Alakangas ; Bj枚rn 脰hl ; er
• 关键词：Sewage sludge ; Biosolid ; Fly ash ; Acid rock drainage
• 刊名：Journal of Hazardous Materials
• 出版年：28 February, 2014
• 年：2014
• 卷：267
• 期：Complete
• 页码：245-254
• 全文大小：1485 K

文摘

Novel solutions for sulfide-mine tailings remediation were evaluated in field-scale experiments on a former tailings repository in northern Sweden. Uncovered sulfide-tailings were compared to sewage-sludge biosolid amended tailings over 2 years. An application of a 0.2 m single-layer sewage-sludge amendment was unsuccessful at preventing oxygen ingress to underlying tailings. It merely slowed the sulfide-oxidation rate by 20%. In addition, sludge-derived metals (Cu, Ni, Fe, and Zn) migrated and precipitated at the tailings-to-sludge interface. By using an additional 0.6 m thick fly-ash sealing layer underlying the sewage sludge layer, a solution to mitigate oxygen transport to the underlying tailings and minimize sulfide-oxidation was found. The fly-ash acted as a hardened physical barrier that prevented oxygen diffusion and provided a trap for sludge-borne metals. Nevertheless, the biosolid application hampered the application, despite the advances in the effectiveness of the fly-ash layer, as sludge-borne nitrate leached through the cover system into the underlying tailings, oxidizing pyrite. This created a 0.3 m deep oxidized zone in 6-years. This study highlights that using sewage sludge in unconventional cover systems is not always a practical solution for the remediation of sulfide-bearing mine tailings to mitigate against sulfide weathering and acid rock drainage formation.