Stabilization and Solidification of Sulphide-Arsenic Tailings in Cemented Paste Piles

Symposium Rouyn-Noranda 2002
Philippe Marion, Isabelle Picquet, Bruno Bussière,
Abstract Cemented paste backfilling is used more and more in underground mines. Another alternative to using paste for backfilling is to pump it onto the surface and to stock it in piles. In addition to physical stability advantages, the cemented paste on surface would also stabilize the contaminants in the matrix through the solidification and stabilization process.

In this study, various paste piles made of sulphide mine tailings containing much arsenic and various binders were tested to evaluate the stability of the contaminants in the matrix. The Soxhlet extractor leach test was used to evaluate the stabilization and solidification of the contaminants. The geochemical results from these tests and the chemical and mineralogical characteristics of the leached piles were analyzed to understand the chemical phenomena present during curing. The results show that the sulphides present in the piles studied (Pyrite FeS2 and arsenopyrite FeAsS) oxidize and cause the dissolution of the more vulnerable hydrates (dissolution of the portlandite Ca(OH)2 and/or the decalcification of CSH gels). The calcium produced precipitates the sulphates (mainly as more or less hydrated gypsum) and the arsenic as stable calcium arsenates. The various binders tested resulted in varying stabilization and solidification, which will be discussed in the present article.
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