Characterisation Leaching Tests and Associated Geochemical Speciation Modelling to Assess Long Term Release Behaviour from Extractive Wastes

A pH dependent leaching test (CEN/TS 14429) and a percolation leaching test (CEN/TS 14405) developed in CEN/TC 292 have been used for the first time to characterise the release behaviour of different sulphidic mining wastes. Geochemical speciation modeling using LeachXS Orchestra provides another type of partitioning between mineral and sorptive phases than is currently practised in the mining industry. Comparing new leaching test data for seven tailings and two waste rock samples with model predictions gives new insights into release behaviour. In leaching, mineral transformations on the surface of waste rock or tailings particles, rather than bulk mineral composition, dictate release, which implies that mineralogical examinations are not necessarily relevant from a leaching perspective. Kinetic aspects of release from sulphidic waste can be addressed by testing material in different stages of oxidation or exposure to atmospheric conditions.