Understanding the Mechanism of Arsenic Mobilisation and Behaviour in Tailings Dams

This study was carried out on leaching of tailings at 30 ？C and 40 ？C. The mineralogical and chemical composition of the tailings material were determined by Quantitative X-Ray Diffractometry (QXRD) and Scanning Electron Microscopy combined with Energy Dispersive Spectroscopy (SEM-EDAX). The study revealed that the tailings contain sulphides (arsenopyrite and pyrite) which can leach to produce arsenic (As) and other ions in solution. The acid released during leaching depends on the temperature of leaching. More acid was produced at higher temperature (40 ？C) than lower temperature (30 ？C). It was established that arsenic precipitation from solution was higher at higher temperature (40 ？C) than lower temperature (30 ？C). Mimicking the study in a typical tailings environment, it could be proposed that As mobilisation will be enhanced at lower temperature (30 ？C) than at higher temperature (40 ？C).