The formation of unsaturated zones within cemented paste backfill mixtures-effects on the release of copper, nickel, and zinc.

Environmental Science and Pollution Research International
Roger HambergLena Alakangas

Abstract

Flooding of cemented paste backfill (CPB) filled mine workings is, commonly, a slow process and could lead to the formation of unsaturated zones within the CPB fillings. This facilitates the oxidation of sulfide minerals and thereby increases the risk of trace metal leaching. Pyrrhotitic tailings from a gold mine (cyanidation tailing (CT)), containing elevated concentrations of nickel (Ni), copper (Cu), and zinc (Zn), were mixed with cement and/or fly ash (1-3 wt%) to form CT-CPB mixtures. Pyrrhotite oxidation progressed more extensively during unsaturated conditions, where acidity resulted in dissolution of the Ni, Cu, and Zn associated with amorphous Fe precipitates and/or cementitious phases. The establishment of acidic, unsaturated conditions in CT-CBP:s with low fractions (1 wt%) of binders increased the Cu release (to be higher than that from CT), owing to the dissolution of Cu-associated amorphous Fe precipitates. In CT-CPB:s with relatively high proportions of binder, acidity from pyrrhotite oxidation was buffered to a greater extent. At this stage, Zn leaching increased due the occurrence of fly ash-specific Zn species soluble in alkaline conditions. Irrespective of binder proportion and water saturation level, the Ni ...Continue Reading

References

Mar 1, 2006·Journal of Hazardous Materials·Rachana Malviya, Rubina Chaudhary
Feb 27, 2007·Waste Management·Jurate KumpieneChristian Maurice
Aug 30, 2008·Waste Management & Research : the Journal of the International Solid Wastes and Public Cleansing Association, ISWA·Hannu NurmesniemiJaakko Rämö
Nov 16, 2010·Journal of Hazardous Materials·Samuel CoussyBruno Bussière

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