XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2267
Compared to hematite, malachite is more floatable with
NaOl, ASL, and LSL in the pH range from 6 to 10, while
the floatability is less pH sensitive (Figure 4b). The highest
recovery of 98% is achieved by LSL at pH 8. With increas-
ing pH, the floatability with NaOl and ASL monotonically
increases from 85% and 75%, respectively, to 90%. The
higher floatability comparted to hematite suggests that the
surfactants are better packed on malachite, which is likely
to be due to their higher adsorption density. In contrast,
there is no difference in the floatability of malachite and
hematite with DDM in the pH range from 6 to 10, indi-
cating that DDM is not selective to these minerals. Taking
into account the XPS results (see below), the relatively low
floatability with DDM can be explained by its adsorption
in a hydrophilic form.
Finally, all the four collectors do not float quartz at pH
5 and 10 (Figure 4c), which is a pre-requisite of its rejection
in mixed-mineral flotation.
Since chelating ligands can act as lixiviants, we mea-
sured the effect of 50 µM LSL, ASL, DDM, and NaOl on
the solubility of ultrafine hematite and malachite. As shown
in Table 1, the strongest lixiviant of hematite is ASL at pH
9.7, while LSL is the strongest lixiviant of malachite at
pH 5.2. The former result suggests that ASL leaches Fe(II)
ions chelating them with both its headgroups as in the case
of Cu(II) [19]. This conclusion is supported by XPS (see
below). The finding that non-ionic LSL is stronger lixiviant
of malachite than anionic ASL is unexpected. Considering
that XPS does not detect any change in the oxidation state
of the malachite surface by LSL (see below), we attribute
this results it suggests that LSL reacts with malachite or its
hydrolysis products are stronger lixiviants than ASL.
XPS spectra were measured on –20 mm hematite and
malachite particles after their conditioning (4% w/v) in a
50 µM collector solution at pH 6.7–6.9 (hematite) and 6.4
(malachite) for 4 hours. As seen from Figure 5a, C 1s spec-
tra of solid ASL and LSL feature a strong peak at 286.8 eV
of the C-O(H) bonds of the sophorose headgroup. This
peak is hard to resolve in the C 1s spectra of ASL and LSL
adsorbed at hematite (Figure 6a). The same is true for the O
1s peak of sophorose at 533 eV (Figure 6b). The O 1s spec-
tra are dominated by the peaks at 530 and 531.5 eV due to
the oxide and hydroxide oxygen. It follows that both ASL
and LSL are coordinated to the hematite surface through
their sophorose groups, these groups being shielded by the
Table 1. Fe and Cu concentration after conditioning of –20 mm hematite and malachite (1% w/v) in the absence and presence
of 50 µM LSL, ASL, DDM, and NaOl at pH 5.2 and 9.7 for 3 h. The relative error of the concentrations does not exceed 10%
Solution
Hematite Fe, μg/L Malachite Cu, μg/L
pH 5.2 ± 0.2 pH 9.7 ± 0.2 pH 5.2 ± 0.2 pH 9.7 ± 0.2
H
2 O 11 20 800 6.4
LSL 11 57 1740 15.3
ASL 17 86 1070 8.6
NaOl 15 26 860 10.2
DDM 10 57 900 5.3
536 535 534 533 532 531 530
Binding Energy (eV)
292 290 288 286 284 282
Binding Energy (eV)
a b
C 1s O 1s
-CH2
C-O-C/
C-OH
-C=O
O-C-O
Figure 5. XPS (a) C 1s and (b) O 1s spectra of (blue) di-acetylated LSL, (red) di-acetylated ASL,
and (green) non-acetylated ASL. Spectra are normalized by maximum peak intensity
Compared to hematite, malachite is more floatable with
NaOl, ASL, and LSL in the pH range from 6 to 10, while
the floatability is less pH sensitive (Figure 4b). The highest
recovery of 98% is achieved by LSL at pH 8. With increas-
ing pH, the floatability with NaOl and ASL monotonically
increases from 85% and 75%, respectively, to 90%. The
higher floatability comparted to hematite suggests that the
surfactants are better packed on malachite, which is likely
to be due to their higher adsorption density. In contrast,
there is no difference in the floatability of malachite and
hematite with DDM in the pH range from 6 to 10, indi-
cating that DDM is not selective to these minerals. Taking
into account the XPS results (see below), the relatively low
floatability with DDM can be explained by its adsorption
in a hydrophilic form.
Finally, all the four collectors do not float quartz at pH
5 and 10 (Figure 4c), which is a pre-requisite of its rejection
in mixed-mineral flotation.
Since chelating ligands can act as lixiviants, we mea-
sured the effect of 50 µM LSL, ASL, DDM, and NaOl on
the solubility of ultrafine hematite and malachite. As shown
in Table 1, the strongest lixiviant of hematite is ASL at pH
9.7, while LSL is the strongest lixiviant of malachite at
pH 5.2. The former result suggests that ASL leaches Fe(II)
ions chelating them with both its headgroups as in the case
of Cu(II) [19]. This conclusion is supported by XPS (see
below). The finding that non-ionic LSL is stronger lixiviant
of malachite than anionic ASL is unexpected. Considering
that XPS does not detect any change in the oxidation state
of the malachite surface by LSL (see below), we attribute
this results it suggests that LSL reacts with malachite or its
hydrolysis products are stronger lixiviants than ASL.
XPS spectra were measured on –20 mm hematite and
malachite particles after their conditioning (4% w/v) in a
50 µM collector solution at pH 6.7–6.9 (hematite) and 6.4
(malachite) for 4 hours. As seen from Figure 5a, C 1s spec-
tra of solid ASL and LSL feature a strong peak at 286.8 eV
of the C-O(H) bonds of the sophorose headgroup. This
peak is hard to resolve in the C 1s spectra of ASL and LSL
adsorbed at hematite (Figure 6a). The same is true for the O
1s peak of sophorose at 533 eV (Figure 6b). The O 1s spec-
tra are dominated by the peaks at 530 and 531.5 eV due to
the oxide and hydroxide oxygen. It follows that both ASL
and LSL are coordinated to the hematite surface through
their sophorose groups, these groups being shielded by the
Table 1. Fe and Cu concentration after conditioning of –20 mm hematite and malachite (1% w/v) in the absence and presence
of 50 µM LSL, ASL, DDM, and NaOl at pH 5.2 and 9.7 for 3 h. The relative error of the concentrations does not exceed 10%
Solution
Hematite Fe, μg/L Malachite Cu, μg/L
pH 5.2 ± 0.2 pH 9.7 ± 0.2 pH 5.2 ± 0.2 pH 9.7 ± 0.2
H
2 O 11 20 800 6.4
LSL 11 57 1740 15.3
ASL 17 86 1070 8.6
NaOl 15 26 860 10.2
DDM 10 57 900 5.3
536 535 534 533 532 531 530
Binding Energy (eV)
292 290 288 286 284 282
Binding Energy (eV)
a b
C 1s O 1s
-CH2
C-O-C/
C-OH
-C=O
O-C-O
Figure 5. XPS (a) C 1s and (b) O 1s spectra of (blue) di-acetylated LSL, (red) di-acetylated ASL,
and (green) non-acetylated ASL. Spectra are normalized by maximum peak intensity