Environmental Engineering Reference
In-Depth Information
The predominant particle content of the tailing is quartz sand ranging from
36-94%, the percentage of silt and clay is low, unless tailing heap has been
mixed with soil (Table 2). Ongley et al. (2001) also reported quartz (30-45%
volume) as a predominant mineral in solid samples collected from Zimapan.
They found other minerals such as calcite, pyrite, kaolinite, mica and clay
minerals. Mendoza-Amezquita et al. (2006) found quartz as the main mineral
component in tailings from Guanajuato, but with other minerals such as albite
and calcite. Once the tailings are deposited, a sort of reaction occurs in the
tailing including the formation of different minerals, for example Romero et
al. (2006) found secondary minerals, such as: gypsum, kjarosite, lepidocrocite,
goethite, beudantite and kaolinite in the tailing from Zimapan.
Oxidation of sphalerite to sulphate (Garcia et al., 1995)
2
ZnS
4
O
2
2
Zn
2
2
SO
4
2
Pyrite oxidation by
Acidithiobacillus
(Silverman, 1967)
7
Fe
(
SO
4
)
3
FeS
2
8
H
2
O
15
FeSO
4
8
H
2
SO
4
Arsenopyrite oxidation (Sanchez and Brent Hiskey, 1988)
2
4
FeAsS
9
H
O
FeOOH
H
AsO
SO
15
H
12
e
2
2
3
These processes are commonly observed in the slag, which increases the
availability of the trace elements such as Cd. The naked tailing heaps can be
dispersed by eolic and hydric erosion p. e. in the sediment from Toliman River
in Zimapan, Central Mexico (Espinosa et al., 2009).
M
ANAGEMENT OF THE
T
AILINGS
Building up the tailing heaps involves the removal of the topsoil and its
accumulation in a pile around the deposition sites; the tailing heaps are then
formed. Most of the tailings are usually a mixture of the crushed and ground
minerals with grave, rocks and even soil. These heaps have mechanic
instability, which causes the heap fall and crumble when the water content is
high. In order to improve the stability of the heaps, wooden bars are vertically
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