Mineralogically-Based Determinations of Neutralization and Acid Potential Using Automated Mineralogy

摘要

The determination of the neutralization potential (NP) and acid potential (AP) of environmentally reactive material is a crucial step in the characterization and prediction of acid rock drainage (ARD) and metal leaching (ML) in mine waste for environmental planning. The calculations performed from laboratory tests (static testing) make assumptions regarding acidification and neutralization potential without mineralogical information. The role of mineralogy in ML/ARD is significant and mineralogical characterization can be used to check assumptions or enhance the prediction of water quality.Mineral Liberation Analyzer (MLA), a scanning electron microscopy-based software program, can provide highly detailed information regarding the abundance, variability, chemistry, and physical characteristics of various acid producing and acid neutralizing minerals. Mineralogical information was determined for several mining projects in Canada using MLA and AP and NP were calculated from modal mineralogy. These results were compared to the results of static testing. Automated mineral analysis is suitable for mining projects with unusual circumstances, such as cases where detailed characterization of acid-neutralizing and acid-generating phases is called for or where concentrations of key mineral phases are below detection limits of other mineralogical characterization techniques such as XRD. Notably, the energy dispersive X-ray spectroscopy associated with MLA is ideal for the identification and quantification of iron and manganese bearing carbonates such as siderite and ankerite, which are measured as carbonates in static tests of NP but can contribute acidity from iron and manganese when dissolved. In addition, there are many other factors that control ML/ARD that can be analysed using automated mineral analysis, including mineral associations, exposure of minerals, and grain size.