Acid mine drainage
Acid mine drainage (AMD) is generated when sulphide minerals, usually exposed by mining, are exposed to the atmosphere and oxidise, releasing acidity and dissolved heavy metals. AMD must be neutralised before it can leave a site, and this process generates a sludge which has to be disposed of. Research at La Trobe University on AMD has concentrated on two aspects:
Increasing the chemical stability (resistance to leaching) of neutralisation sludges
Danny McDonald's PhD project (2006) showed that the sludges are readily leached by acid waters, no matter which chemical is used to neutralise the acidity, and should not be disposed of in pit lakes. He also demonstrated that if the iron minerals in the sludge are crystalline, they are much more resistant to acid attack. This project has proceeded in cooperation with several environmental consulting companies, particularly Earth Systems and URS, and has also received financial support from the Australian Synchrotron Research Program.
Neutralisation using limestone, particularly anoxic and open limestone drains
Our studies have looked at natural remediation of AMD in limestone terrains, and Silvana Santomartino's PhD project (2005) investigated ways of minimising the problem of ferrihydrite armouring of the limestone, and made substantial progress in this regard. She developed predictors for the lifetime of the drains, and also determining the role of carbon dioxide exsolution in drain performance. This work has been carried out in collaboration with Charles Cravotta, Water Resources Division of the US Geological Survey, Pennsylvania.