CHAPTER 2: COPPER METALLURGICLA SLAGS- CURRENT KNOWLEDGE AND FATE:
A REVIEW
38
Cu slag
USA
Cu: up to 1.35%
(13500 mg/kg)
Zn: up to 1.02%
(10200 mg/kg)
Pb: up to 0.047%
(47 mg/kg)
As: up to
0.0002%
(2 mg/kg)
FS: <2 mm
L/S: 20 (50g/1L)
LT: 1 min
shaking→ settling
24 h
Eastern synthetic
precipitation:
Leaching solution
composed of mixture
(ESP): H
2
SO
4
and HNO
3
with deionized water
adjusted to pH of 4.2
Deionized water (DW)
ESP leaching
Cu: up to 1800 µg/L (0.06-0.53%)
Pb: up to 0.3 µg/L (0.002-0.04%)
Zn: up to 470 µg/L (0.02-0.11%)
As: up to 0.3 µg/L (0.2-0.8%)
DW leaching:
Cu: up to 1100 µg/L (0.02-0.34%)
Pb up to 0.62 µg/L (0.003-0.04%)
Zn: up to 420 µg/L (0.02-0.11%)
As: up to 0.3 µg/L (0.2-1.20%)
Observations:
For most
of the samples final pH is
higher than pH of original solution.
Leaching is greater in the solution with
lower pH (4.2) compared to deionized
water (5.0)
Piatak et al.
(2004)
Cu/Pb slags and
Cu granulated
slag
NAMIBIA
Tsumeb area
Cu: up to 12.2%
(121850 mg/kg)
Pb: up to 18.4%
(183800 mg/kg)
Zn: up to 12.1%
(120850 mg/kg)
Cu/Pb slags:
FS:
<4 mm (EN)
<9.5 mm (TCLP)
Cu gran. slag:
FS <0.2mm
EN:
L/S: 10
LT: 24 h
AS: 60 rpm
TCLP:
LS ratio: 20
LT: 18 h
AS: 30 rpm
European Norm 12457
(EN): deionized water
Toxicity Characteristic
Leaching Procedure
(TCLP): deionized
water + acetic acid + 1M
NaOH
pH = 4.93
EN Historical slag - Modern slag
Cu: 0.08 mg/L (0.001%) –
0.04 mg/L (0.001%)
Pb: <0.03 mg/L (<0.0003%)
Zn: 0.01 mg/L (0.0003%) –
0.005 mg/L (0.0002%)
As: 0.4 mg/L (0.014%) –
4 mg/L (0.17%)
TCLP
Cu: 150 mg/L (2.8%) –
20 mg/L (1.5%)
Pb: 50 mg/L (0.5%) – 2 mg/L (0.04%)
Zn: 150 mg/L (9.1%) - 6 mg/L (0.4%)
As: 7 mg/L (0.5%) – 5 mg/L (0.4%)
Ettler et al.
(2009)
Cu slag
POLAND
The Rudawy
Janowickie
Mountains
Cu: up to 1.34%
(13400 mg/kg)
Pb: up to 0.07%
(738 mg/kg)
Zn: up to 0.94%
(9360 mg/kg)
As: 0.03%
315 mg/kg
FS: <4 mm
L/S: 10
LT: 24 h
AS: 200 rpm
Neutral conditions:
Deionized water
Stream water
Organic rich soil
conditions: 20 mM
citric acid
Neutral conditions/Stream water
conditions: metals leaching reach the
values below 0.1%
Citric acid solution
Cu: up to 2.6% (347 mg/L)
Zn: up to 2.2% (5 mg/L)
Pb: up to 1.9% (5.1 mg/L)
As: up to 1.1% (1.5 mg/L)
Fe: up to 0.8% (378 mg/L)
Kierczak et
al. (2013)
FS: Fraction size, L/S: liquid to solid ratio, LT: leaching time, AS: agitation speed,
n.i.: none information provided
CHAPTER 2: COPPER METALLURGICLA SLAGS- CURRENT KNOWLEDGE AND FATE:
A REVIEW
39
Two general types of leaching tests were carried out for Cu-slags: (1) experiments under
conditions corresponding to the natural environment, where slags are disposed and (2)
experiments following the protocols of standardised method (Table 2.2). Experimental
conditions referring to the environment cover simulation of rainfalls, peat water, calcareous
soil, extremely aggressive conditions such as highly acidic (Manz & Castro, 1997) and
organic matter rich (Ettler et al., 2009; Kierczak et al., 2013) soil. Standardised methods
include the Eastern synthetic precipitation procedure (Piatak et al., 2004), European Norm
and the Toxicity Characteristic Leaching Procedure (Ettler et al., 2009).
Generally, in most experiments that followed standardized procedures, copper showed
irrelevant mobilization not exceeding 0.53% (1.8 mg/L) (Piatak et al., 2004) and reaching a
maximum mobilization of 2.8% (150 mg/L) (Ettler et al., 2009). In the case of experimental
designs that simulate the natural environment, the mobilization of copper was slightly higher.
Although, relative values of leached metals seem to be comparable, their concentrations in the
solution are variable. The quantity of leached copper was in the range of 0.16% and 2.6% for
experiments representing aggressive conditions and organic matter-rich conditions,
respectively (Manz & Castro, 1997; Kierczak et al., 2013). The highest extraction efficiency
of 6.36-8.51% was achieved by leaching with NH
4
NO
3
(Manz & Castro, 1997). However, it
has also to be noticed that the quantity of solubilized copper was different due to the different
chemical and mineral phase compositions of slags. Apart from copper, metals such as lead,
zinc, nickel and arsenic were also measured. Zinc and lead revealed comparable leachability
usually not exceeding 0.4%, except under aggressive conditions that reached an extraction
level of 9.55% for zinc (Manz & Castro, 1997) and citric acid solution which leached up to
1.9% of lead (Kierczak et al., 2013). Arsenic showed a limited mobility achieving values not
exceeding 1.2% (Piatak et al., 2004; Ettler et al., 2009; Kierczak et al., 2013).
The results obtained for particular leaching solutions showed that acidified inorganic
solutions and organic acids have definitely a greater influence on the slags stability than
deionised water where metals showed concentrations at least one order of magnitude lower
(Piatak et al., 2004; Ettler et al., 2009; Kierczak et al., 2013). Therefore, despite the fact that
the pH is an important parameter driving metal mobility, bulk solution chemistry (
e.g. the
presence of organic compounds) should also be considered as it might strongly influence the
leaching process.
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