This dissertation characterised geochemically waste from a copper mine in the
Bushveld Igneous Complex, coupled with hydrochemical interpretations. In the
first part of the dissertation, the methods involved in the quantification and
qualification of mine acidic drainage were discussed. This included paste and
rinse pH, Acid and Base potentials, net neutralisation potentials and
neutralisation potential ratio. These methods form what is known as Acid-Base
Accounting, (ABA). In the second part of this dissertation, the sampling methods
and representativeness of the samples were discussed. All these methods are
scientifically justifiable as they are in agreement with methods used
internationally. In the third and most important part of this dissertation, results
where discussed and proven to correlate with visual estimates from the field.
In sulphides-containing waste material, Acid Mine Drainage (AMD) is produced
due to the ingress of oxygen and water mainly from rainfall, and thus subsequent
oxidation of sulphide-bearing minerals with the help of bacteria. However, in the
presence of sufficient neutralisation potential, alkaline drainage is favoured as
carbonated minerals (mainly dolomite and calcite) buffer the acidity. For this
study, copper sulphide is recovered from foskorite ore imbedded with carbonatite
which helped at the non acidification of the mine site.
In the dissertation, the geochemical software PHREEQC was used and it
confirmed that many silicates and alumino-silicates minerals are dissolved in the
groundwater. This is an important finding as the presence of silica is an indication
that substantial amount of acidity could have been released. This also constitutes
reasonable evidence for the fact that chalcocite and covellite which are the main
sulphides of copper mined on site can be considered as âweakâ sulphides unlike
pyrite which can be more severe to the environment. The software PHREEQC
also confirmed that dolomite and calcite control the pH of the water, thus only
fairly alkaline values in the range of pH 8 to pH 9.5 are expected on site. With visual investigations, it has been noticed that natural vegetation is taking
place around the site even on the most hostile tailings like the magnetite. This is
a very important aspect as positive outcome is expected for the fauna after mine
closure.
The following serve as recommendations:
- The neutralisation processes release sulphate into the groundwater, and it
is recommended that tracer tests methods be conducted to estimate the
travelling time of the salts.
- It is also recommended that the mine speed up the re-vegetation process
as many animals cross the Kruger National Park to feed themselves within
the mine.
- It is recommended that more regular monitoring on boreholes be
conducted as many dataless. Also it is suggested that anomalous
boreholes be investigated, geochemically logged and re-sampled to verify
or determine likely origins and interactions.
- For further research, standard values of salt loads should be implemented
so as to compare acceptable values with abnormal values.
- The study of ABA using static tests should always be coupled with the
humidity cells methods. While the former provides with the probability of
acid formation, the latter provides with the reaction rates.
- Additional studies should be conducted exclusively outside the mine to
corroborate with the results from inside the mine.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-03112010-100041 |
| Date | 11 March 2010 |
| Creators | Moukodi, Georges Pascal |
| Contributors | Dr BH Usher |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-03112010-100041/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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