Résumé - Abstract
More than 237,000 metric tons of arsenic trioxide roaster waste dusts have been stored underground in the abandoned Giant Mine (Yellowknife, NWT). This arsenic trioxide dust has a high arsenic content (60 wt.%), which is hazardous to both people and the environment. Long-term management of this waste is complex due to its large quantity, physical characteristics, and the current storage conditions. Currently, the frozen block method was selected for the stabilization of the arsenic. However, because of the current toxic form of the dusts, climate change, and the decline in natural permafrost, there are some critical concerns about the performance of this technology. Therefore, more permanent arsenic stabilization methodologies must be considered. Among these methodologies, cemented paste backfill (CPB) technology as a high-density paste mixture of binding materials, dewatered tailings, and water can be considered as an arsenic trioxide dust stabilization method. The most significant benefit of the CPB includes alleviating the environmental impacts of the hazardous mine wastes through placing them safely into underground openings. Previous researchers have discussed the potential applicability of this method for the stabilization of different arsenic species, mostly arsenopyrite. In this research, the effectiveness of arsenic trioxide dust stabilization through incorporation within the cemented paste backfill will be investigated. At the first stage, the physical, chemical, and mineralogical characterization of the dusts and tailings sample were studied, and based on their results, the paste backfill samples will be prepared using different arsenic trioxide dust content, old mine tailings and binder mixtures. To study the stabilization mechanisms of arsenic within the cementitious matrices, preliminary CPB samples were prepared using pure silica to mimic the tailings, different types of binders, and pure arsenic trioxide. Rheological tests will be done on the mixes, then mechanical tests will be carried out on the cured samples to define the optimal CPB formulations. Leaching protocols will be done on the optimal samples to evaluate the extent of arsenic stabilization. Mineralogical characterization of the hydrated species occurring within the cured CPB will be performed to study the speciation of the arsenic compounds and their long-term stability in conditions similar to those encountered at the Giant Mine.