MSc(Eng) Project title Predicting the time-related generation of acid rock drainage from mine waste
(Supervisors: Dr J Broadhurst, A/Prof J Petersen) Graduated: 2014
The extraction and processing of sulphide ores generates large volumes of waste. The disposal of these wastes in dumps and/or impoundments has the potential to cause prolonged pollution of local water resources through the generation of acid rock drainage (ARD) over the long-term. A number of laboratory-scale tests, both static and kinetic, have been developed to characterise the acid generating potential of sulphide-bearing mine wastes. The extrapolation of empirical test results to full-scale waste deposit scenarios requires the subsequent use of mathematical models which take into account the governing chemical reaction and physical transport mechanisms. Current leachate generation models are, however, both complicated and resource intensive, and only warranted in the case of detailed site-specific predictive studies. This study entailed the development and application of a geochemical mass transport model for estimating the time-related leach behaviour of a copper sulphide waste rock sample in a flow-through column scenario. The results of this study showed that it is possible to accurately simulate the leachate concentration profiles using a combination of key geochemical reaction and simple mass transport equations. The model, which uses PHREEQ software, is particularly suitable for the early or screening evaluation of the potential long-term ARD risks associated with the disposal of sulphide wastes and forms an essential and integral component of a systematic protocol for predicting the life cycle impacts of such wastes. Model outputs can, furthermore, be used to identify the key reaction mechanisms controlling pore water chemistry, thus facilitating understanding and, ultimately, management of mineral waste behaviour in a disposal scenario.
Simunika, N., Broadhurst, J.L., Petersen, J., Harrison, S.T.L. and Franzidis, J.-P. 2013. Predicting the time-related generation of acid rock drainage from mine waste: a copper case study. In S. Winchester, F. Valenzuela and D. Mulligan (eds), Proceedings of the 3rdInternational Seminar on Environmental Issues in Mining (Enviromine 2013), 4-6 December 2013, Santiago, Chile. Santiago, Chile: Gecamin. ISBN 9789569393044.