XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2383
Effect of Xanthate on Hessite and Calaverite Flotation
The use of the microflotation column enables observation
of mineral-froth interaction. The addition of PAX in this
test work resulted in the destabilisation of the froth layer
for both hessite and calaverite in all microflotation tests in
this series. The use of additional frother did not stabilise
the observed froth layer. The froth appearance was dry and
immobile consistent with the use of excessive collector. The
hydrophobic material was physically skimmed from the
top of the cell whilst maintaining cell level. Froth destabi-
lisation was not observed for other telluride studies using
microflotation cells as the cell types used did not produce
a froth layer (Padmanaban &Lawson, 1991 Shackleton et
al., 2007).
A stable froth is required to successfully transport min-
eralised froth from the pulp to the concentrate launder
(Schwarz &Grano, 2005). Particles with high hydropho-
bicity can cause the thin liquid film between bubbles to
rupture causing destabilisation of froths (Aveyard et al.,
1994). Particles with a contact angle greater than 80 degrees
are considered to have high hydrophobicity that destabilise
froths and reduces the froth carrying capacity (Dippenaar,
1982 Johansson &Pugh, 1992 Schwarz &Grano, 2005).
The measured contact angle for naturally occurring cala-
verite was 80 degrees (Jin, 2016) hence accounting for the
natural floatability observed in Table 1. No contact angle
data is available for hessite. The addition of PAX may result
in a change to the surface hydrophobicity thereby resulting
in the froth destabilisation observed in this study.
The addition of PAX had a slightly negative effect on
recovery for hessite however calaverite recovery was sig-
nificantly reduced when compared with frother alone for
xanthate additions below 10–5M. As shown in Table 2, if
higher PAX dosages are applied recovery increases. This
may be attributed to the aggregation of particles due to
the increase in zeta potential with increasing PAX addi-
tion (Figure 1). The material was required to be manually
skimmed from the microflotation cell operating with a very
shallow froth level.
The results obtained for flotation with PAX (Table 2)
may only be partly explained by the destabilisation of the
froth phase. The reduction in calaverite recovery (Table 2)
with the addition of 50g/t PAX is consistent with results
obtained by Yan &Hariyasa (1997) where the use of PAX
alone resulted in reduced recovery of tellurides. It is in
contrast with results for platinum and palladium tellurides
where the use of sodium isobutyl xanthate at a greater con-
centration (5×10–5M SIBX) increased the recovery from
40–75% to 99% in synthetic process water (Shackleton
et al., 2007).
It is clear from the conflicting results that further
work investigating the surface interaction and potential
Figure 2. Base of microflotation cell showing agglomerates
present during hessite flotation (dark particulate matter
around magnetic stirrer). For scale column diameter is 2.5cm
Table 2. Summary of hessite and calaverite recovery using PAX
Mineral Frother Type
Frother Dosage,
mg/L
PAX Dosage,
g/t
PAX Concentration,
mol·L–1
Recovery,
%
Hessite H57 10 0 0 63
H57 10 80 1 × 10–6 61
H57 10 160 2 × 10–6 60
Calaverite H57 20 0 0 65
H57 20 80 1 × 10–6 47
H57 20 160 2 × 10–6 53
Calaverite MIBC 13 0 0 59
MIBC 13 50 6 × 10–7 43
MIBC 13 800 1 × 10–5 65
MIBC 13 8000 1 × 10–4 72
Effect of Xanthate on Hessite and Calaverite Flotation
The use of the microflotation column enables observation
of mineral-froth interaction. The addition of PAX in this
test work resulted in the destabilisation of the froth layer
for both hessite and calaverite in all microflotation tests in
this series. The use of additional frother did not stabilise
the observed froth layer. The froth appearance was dry and
immobile consistent with the use of excessive collector. The
hydrophobic material was physically skimmed from the
top of the cell whilst maintaining cell level. Froth destabi-
lisation was not observed for other telluride studies using
microflotation cells as the cell types used did not produce
a froth layer (Padmanaban &Lawson, 1991 Shackleton et
al., 2007).
A stable froth is required to successfully transport min-
eralised froth from the pulp to the concentrate launder
(Schwarz &Grano, 2005). Particles with high hydropho-
bicity can cause the thin liquid film between bubbles to
rupture causing destabilisation of froths (Aveyard et al.,
1994). Particles with a contact angle greater than 80 degrees
are considered to have high hydrophobicity that destabilise
froths and reduces the froth carrying capacity (Dippenaar,
1982 Johansson &Pugh, 1992 Schwarz &Grano, 2005).
The measured contact angle for naturally occurring cala-
verite was 80 degrees (Jin, 2016) hence accounting for the
natural floatability observed in Table 1. No contact angle
data is available for hessite. The addition of PAX may result
in a change to the surface hydrophobicity thereby resulting
in the froth destabilisation observed in this study.
The addition of PAX had a slightly negative effect on
recovery for hessite however calaverite recovery was sig-
nificantly reduced when compared with frother alone for
xanthate additions below 10–5M. As shown in Table 2, if
higher PAX dosages are applied recovery increases. This
may be attributed to the aggregation of particles due to
the increase in zeta potential with increasing PAX addi-
tion (Figure 1). The material was required to be manually
skimmed from the microflotation cell operating with a very
shallow froth level.
The results obtained for flotation with PAX (Table 2)
may only be partly explained by the destabilisation of the
froth phase. The reduction in calaverite recovery (Table 2)
with the addition of 50g/t PAX is consistent with results
obtained by Yan &Hariyasa (1997) where the use of PAX
alone resulted in reduced recovery of tellurides. It is in
contrast with results for platinum and palladium tellurides
where the use of sodium isobutyl xanthate at a greater con-
centration (5×10–5M SIBX) increased the recovery from
40–75% to 99% in synthetic process water (Shackleton
et al., 2007).
It is clear from the conflicting results that further
work investigating the surface interaction and potential
Figure 2. Base of microflotation cell showing agglomerates
present during hessite flotation (dark particulate matter
around magnetic stirrer). For scale column diameter is 2.5cm
Table 2. Summary of hessite and calaverite recovery using PAX
Mineral Frother Type
Frother Dosage,
mg/L
PAX Dosage,
g/t
PAX Concentration,
mol·L–1
Recovery,
%
Hessite H57 10 0 0 63
H57 10 80 1 × 10–6 61
H57 10 160 2 × 10–6 60
Calaverite H57 20 0 0 65
H57 20 80 1 × 10–6 47
H57 20 160 2 × 10–6 53
Calaverite MIBC 13 0 0 59
MIBC 13 50 6 × 10–7 43
MIBC 13 800 1 × 10–5 65
MIBC 13 8000 1 × 10–4 72