| dc.description.abstract | Acid Mine Drainage (AMD) is identified as one of the contributors to
environmental hazard in the gold mining region of South Africa, as caused by the
mining operational activities performed by mining industries in South Africa. This
effect motivates the development of AMD prediction techniques application and
geochemistry modelling using gold tailing dams located in West Rand area,
Witwatersrand Basin as a case study. Control strategies are devised to assess,
understand and measure the acidic potential generation of waste materials in
ensuring the right method required to analyse risks caused by AMD to environment.
The method encompasses mineralogical and geochemical analysis of 93 samples
collected, AMD prediction, test modification and geochemical modelling. This
method was appropriately applied to understand the basic mechanisms involved in
controlling acid generation, assessing prediction procedure and selecting the right
prediction tools.
Study objectives are attained by performing a series of experimental lab tests on the
samples collected from the two major tailing dams (Mogale and Gold One_1
tailings). Results derived from the lab experiments (XRD and SEM-EDS) show
presence of mineral phases characterised with the surface feature of samples, and
unknown substances of samples were identified. Geochemical characterisation was
performed by XRF and ICP-MS to determine the major oxides elements and trace
elements, respectively. Leco test generate total sulphur and total carbon. Multistatistical
analysis is used to interpret the data derived from geochemical
characterisation process to explicate the metal and trace elements distribution and
occurrence. Initial samples were screened and categorised based on paste pH and
EC using kinetic tests to determine acid-forming and neutralising minerals in
samples and static tests to determine acid generation potential in samples.
Net Acid Producing (NAPP) was mathematically calculated from Acid Neutralising
Capacity (ANC), Maximum Potential Acidity (MPA) and total Sulphur. Results obtained from the Paste pH demonstrate that samples collected from 1 meter
downward the holes to 10 meters, with a few meters samples in hole T003 at Gold
One_1 are non-acidic while the remaining tailing samples are acidic. ANC/MPA
ratio was applied to assess the risk of acid generation from mine waste materials.
Graphical illustrations of the Acid Base Account (ABA) are plotted to demonstrate
the net acidic generation potential trends of samples, which were classified into
non-acid forming, potential acid forming and uncertain categories. Results
integration between ANC, Single Addition Net Acid Generation (NAG) test and
NAPP were used to classify acid generation potential of the samples. Leachate
collected from leaching column test were analysed for pH, EC and chemical
element by ICP-MS. The leaching column test used to analyse samples (T004) and
(T001) collected from the two major tailings was set up for a 4-month experiment.
Study findings present environmental assessment report on the two investigated
gold tailing dams in Witwatersrand Basin area. Other findings are improved
understanding of the application and limitations of various existing AMD prediction
methods for assessment of gold mine waste and conceptual geochemical modelling
developed to test appropriate methodology for AMD potential at a given gold mine
site. | en_US |
