3.1.1 test samples totaling 100 g, were prepared

3.1.1
Study AreaObuasi located between latitude 5.35 and 5.65N and longitude
6.35 and 6.90N covers a land area of about 162.4 km2 (Obuasi Municipality, 2009). AngloGold
Ashanti, AGA, is located about 79.98 km from Ashanti Regional Capital, Kumasi,
Ghana. There has been continuous underground mining in this town since 1890s,
posing a potential source of heavy metal contamination in the Obuasi Municipal
and its environs. Tailings from the mine is disposed off at Sansu Tailings
facility (TSF) and Pampora TSF which were commissioned in 1992 (AngloGold Ashanti, 2006). The TSF serves both the sulphide treatment and oxide
treatment plants. It has an area of about 63 km2 and about 40 m high
(Sansu Tailings Storage Facility
Operations manual, 2008). 3.1.2
SamplingSolid tailings samples from the Sansu tailings dam were
collected from a demarcated area (30m x 30m) on the north-eastern portion of
the dam. The demarcated area was further divided into six equal zones of 10m x
15m area. Solid samples each of about 1 kg were taken from five locations in
the demarcation at a depth of 50 cm within each zone. A total of 5 kg sample
was collected, put together and mixed thoroughly to ensure a uniform mixture.
The sample was transported to the Department of Mineral Engineering, University
of Mines and Technology, UMaT, for test analysis. 3.2
Methodology3.2.1
Sample preparationFourteen (14) test samples totaling 100 g, were prepared by
cone and quartering from the already mixed collected solid tailings sample
(5kg). Beakers labeled A1, A2, A3, A4, A5 and A6, with solution, 300 cm3
each, of pH 2, 4, 6, 8, 10, 13 respectively were prepared in duplicates. Acidic
pH was adjusted using sulphuric acid whiles the alkaline pH was adjusted using
sodium hydroxide solution. A total of twelve samples were contacted with the
solutions in A1 to A6. The two remaining samples were left in tap water (300 cm3,
pH 6.8). All samples were left to stand for 10 weeks with periodic shaking and
sampling heavy metal analysis in two-weeks intervals up to the tenth week. The
pH and conductivity of each sample was taken during these time intervals. 3.2.2
Head grade analysisThe total concentrations of As, Fe,
Cu, Zn, Cd and Pb in the BIOX mine tailings were determined. Samples were dried
in oven at temperature of 40oC for 3-4 days and homogenized by
thorough mixing. The homogenized samples were then sieved through a 0.2 mm
sieve and then acid digested using aqua regia. The concentrations of the metals
mentioned were determined using atomic absorption spectrometer. 3.2.3
Chemical analysis

About 10 cm3
solution samples from A1, A2, A3, A4, A5, A6 and Aw were digested with 14.5 cm3
of aqua regia solution. The volume of filtrate was adjusted to 50 cm3
with deionized water in volumetric flask. The concentrations of As, Fe, Cu, Pb,
Zn and Cd in the solution were determined using atomic absorption spectrometer
(AAS).    

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