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TABLE 6.2 Leaching rates calculated based on concentration of elements in the leachates.
(GMB total: growth medium with bacteria digested, GMB: growth medium with bacteria filtered <0.22 µm, GM: growth medium, UPW: ultrapure water)
Crystalline slag
Si [mg/kg/day]
Fe [mg/kg/day]
Cu [mg/kg/day]
Zn [mg/kg/day]
Pb [mg/kg/day]
Time
[days]
GMB
tot.
GMB
GM
UPW
GMB
tot.
GMB GM
UPW
GMB
tot.
GMB GM
UPW
GMB
tot.
GMB GM
UPW
GMB
tot.
GMB GM
UPW
14
9.40 8.47
6.75 5.02
3.26 1.38
0.20 0.05
15.84 14.72 1.87 1.30
0.87 0.54
0.07 0.25
0.019 0.010 0.004 0.010
28
4.35 3.52
2.06 1.31
1.63 1.40
0.08 0.03
4.59 4.84
5.30 0.88
0.79 0.22
0.03 0.16
0.011 0.010 0.004 0.003
42
5.45 5.18
2.20 1.25
1.46 1.21
0.08 0.02
3.32 3.28
4.10 1.04
2.03 0.61
0.00 0.07
0.017 0.010 0.003 0.003
56
2.79 2.45
2.21 1.12
1.85 1.31
0.08 0.01
3.57 3.36
3.07 1.84
0.86 0.59
0.01 0.04
0.016 0.010 0.003 0.002
70
3.57 2.24
2.53 1.16
3.37 2.85
0.08 0.02
2.77 2.66
2.54 1.32
2.33 0.89
0.00 0.07
0.017 0.013 0.002 0.002
84
3.70 3.10
2.70 1.02
3.09 2.92
0.09 0.01
2.30 2.31
2.06 1.63
1.03 0.62
0.01 0.03
0.016 0.012 0.003 0.002
98
3.70 2.93
2.95 1.13
2.96 2.93
0.06 0.01
2.33 2.37
1.82 1.42
1.15 0.94
0.00 0.02
0.014 0.012 0.002 0.002
112
3.42 3.13
3.30 0.84
3.29 2.95
0.07 0.01
2.23 2.40
1.66 1.95
1.60 0.63
0.00 0.03
0.014 0.013 0.003 0.003
Granulated slag
Si [mg/kg/day]
Fe [mg/kg/day]
Cu [mg/kg/day]
Zn [mg/kg/day]
Pb [mg/kg/day]
Time
[days]
GMB
tot.
GMB GM
UPW
GMB
tot.
GMB GM
UPW
GMB
tot.
GMB GM
UPW
GMB
tot.
GMB GM
UPW
GMB
tot.
GMB GM
UPW
14
8.37 7.41
3.96 2.44
2.74 2.55
0.32 0.05
6.08 5.74
0.64 0.44
0.37 0.39
0.00 0.00
0.59 0.51
0.27
0.09
28
4.85 3.85
1.84 0.61
2.82 2.51
0.20 0.00
0.84 0.69
1.50 0.62
1.49 0.21
0.05 0.02
0.59 0.48
0.14
0.10
42
5.02 3.69
2.07 0.91
2.85 2.84
0.22 0.02
0.61 0.55
0.57 0.38
0.93 0.14
0.03 0.04
0.58 0.50
0.14
0.07
56
5.75 4.32
2.46 0.88
3.34 2.54
0.19 0.00
0.60 0.47
0.25 0.39
0.80 0.41
0.02 0.06
0.59 0.44
0.12
0.07
70
4.78 3.79
2.42 1.13
5.19 4.41
0.22 0.00
0.61 0.51
0.22 0.19
0.90 0.13
0.38 0.07
0.58 0.43
0.12
0.05
84
5.20 4.51
2.76 1.20
4.78 4.30
0.17 0.09
0.50 0.41
0.13 0.58
1.11 0.33
0.01 0.10
0.55 0.47
0.09
0.07
98
4.50 3.79
3.06 1.41
4.36 4.07
0.13 0.01
0.41 0.31
0.11 0.19
1.32 0.23
0.01 0.08
0.47 0.38
0.07
0.08
112
5.65 4.42
3.17 1.55
4.76 4.12
0.12 0.02
0.44 0.35
0.09 0.70
1.77 0.14
0.03 0.17
0.51 0.40
0.07
0.37
CHAPTER 6: BACTERIALLY MEDIATED WEATHERING OF CRYSTALLINE AND AMORPHOUS Cu-SLAGS
178
6.3.5 Bacterial related organic products
The fluorescence matrixes for GS and CS incubations in the presence of Pseudomonas
aeruginosa as well as the abiotic medium control are presented in Figure 6.5. Four specific
organic fluorophore peaks were recorded in biotic incubations. According to the literature, the
peaks recorded at Ex/Em 220-240/325-350 nm, 270-290/337-350 nm, 270-300/450-475 nm
and 370-390/450-475 nm correspond to proteins-like molecules (according to the
fluorescence properties of 2 aromatic amino acid; tyrosine, tryptophan), microbial by-product-
like, humic-like substances (humic-like and fulvic-like) (Bourven et al., 2012; Bhatia et al.,
2013; Bourven et al., 2014) and siderophore-like (pyoverdine) (Dumas et al., 2013; Dartnell et
al., 2013), respectively. The maximum intensities of the identified fluorophores are presented
in Table 6.3.
TABLE 6.3 The maximum intensities (average of 3 replicates) of fluorophores
identified in biotic filtered solution (<0.22 µm).
Fluorophores determined
Crystalline slag
Granulated slag
Maximum intensity recorded
RDS
RDS
14 days
Proteins-like
315.1
±228.2 464.1
±65.4
Microbial by-products like
196.1
±83.0 240.4
±30.9
Humic-like substances
157.3
±70.6 203.4
±7.20
Siderophore-like
122.6
±25.0 125.3
±2.80
28 days
Proteins-like
189.3
±83.1 368.5
±34.2
Microbial by-products like
122.2
±65.9 206.6
±28.6
Humic-like substances
607.3
±32.4 344.3
±56.9
Siderophore-like
366.5
±19.8 176.7
±24.7
56 days
Proteins-like
107.9
±0.5 525.9
±31.0
Microbial by-products like
119.7
±1.0 263.2
±18.7
Humic-like substances
127.4
±1.6 505.7
±24.6
Siderophore-like
126.7
±11.3 234.2
±11.4
72 days
Proteins-like
87.2
±5.3 546.8
±6.6
Microbial by-products like
264.1
±2.6 368.5
±9.3
Humic-like substances
87.7
±5.4 582.9
±16.5
Siderophore-like
86.4
±6.0 299.5
±5.9
CHAPTER 6: BACTERIALLY MEDIATED WEATHERING OF CRYSTALLINE AND AMORPHOUS Cu-SLAGS
179
FIGURE 6.5 Three-dimensional spectra presenting the fluorophores of metabolic products
excreted by Pseudomonas aeruginosa in the presence of GS and CS
after 14 and 28 days of experiment.
(Control: growth medium, AP: aromatic proteins, HL: humic-like substances, Pvd: pyoverdine,
MB: microbial by-products, d
14
: spectra recorded after 14 days of experiment, d
28
: spectra recorded
after 28 days of experiment). Color intensity indicates intensity of peaks.
CHAPTER 6: BACTERIALLY MEDIATED WEATHERING OF CRYSTALLINE AND AMORPHOUS Cu-SLAGS
180
6.3.6 SEM observations
According to the SEM observations, components of the CS slag such as glass and sulfides
(especially bornite: Cu
5
FeS
4
) are partially dissolved even under abiotic conditions (Figure
6.6). A higher degree of alteration was observed on grains placed in GM compared to those
treated with UPW. Partial dissolution of sulfides was visible on the edges when slag was
exposed to UPW (Figure 6.6 A1), while a larger weathering zone (approximately 10 µm in
diameter) resulted from the GM treatment (Figure 6.6 B1). Glass dissolution resulting from
the UPW experiment is present as irregular fractures that reach the size up to 42 nm (Figure
6.6 A2), whereas glass corrosion in the form of round-shaped zones approximate in size to 1
µm was observed on the grains immersed in GM (Figure 6.6 B2). An exposure of CS grains
to biotic conditions led to more extensive glass and sulfides weathering as shown in Figure
6.6 C1. Glass dissolution features were similar in shape and diameter to those resulting from
abiotic GM experiment (Figure 6.6 C3). However, these characteristics are more widespread
on the samples immersed in the GMB solution. Furthermore, the breakdown of fayalite
(Fe
2
SiO
4
) was solely observed for slag grains that experienced exposure to biotic conditions
(GMB). Its decomposition appears as round-shaped altered zones having a diameter
approximately up to 10 µm (Figure 6.6 C2).
The GS grains that experienced abiotic weathering conditions showed eroded zones in the
form of holes related to removal of Cu-droplets and altered glass (Figure 6.7). Elongated thin
glass fractures were observed on the grains resulting from UPW treatment (Figure 6.7 A1),
while round-shaped alteration zones similar to those observed on CS grains appeared after
GM treatment (Figure 6.7 B1). Glass alteration in biotic solution exhibited highly altered
edges of grains (Figure 6.7 C1). Removal of Cu-droplets occurred on the grains treated with
all solutions (Figures 6.7 A2-C3), however a higher degree of their depletion was observed on
grains which experienced biotic treatment (Figures 6.7 C2 and C3).
CHAPTER 6: BACTERIALLY MEDIATED WEATHERING OF CRYSTALLINE AND AMORPHOUS Cu-SLAGS
181
FIGURE 6.6 SEM images presenting weathering features of crystalline slag after exposure to
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