Integrated environmental management of pyrrhotite tailings at Raglan Mine: Part 1 challenges of desulphurization process and reactivity prediction

The aim of this project is to assess the efficiency of pyrrhotite rich tailings desulfurization and its capacity to make mine operations more sustainable and respectful to the environment. The Raglan mine ore concentrator produces acid-generating tailings, which contain pyrrhotite, that need to be properly managed. Partial desulphurization of the total tailings produced at the end-circuit was investigated to assess the option of using desulphurized material as a component of a cover to control acid mine drainage (AMD) generation. The weathering and contaminant generation potential was investigated through kinetic testing. The objective of Part 1 of this study is to present results in terms of: i) physical, chemical, and mineralogical characterization of the Raglan Mine tailings; ii) optimization of the pyrrhotite flotation process; and iii) kinetic testing on the desulphurized tailings to predict their acid generating potential, as well as their contaminant (particularly Ni) release rates. Desulphurization succeeded in reducing the sulphur content in the tailings to less than 0.4 wt% (mainly as pyrrhotite-lizardite intergrowths). Contaminant releases complied all with Quebec environmental regulations. The tailings were proven to be non-acid generating based on quantitative evaluation of mineralogy by scanning electron microscopy (QEMSCAN) results and the calculation of absolute reactivity.