3004 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
syringe-driven membrane filter, and the filtrate was imme-
diately analyzed using ICP-AES to measure the concentra-
tion of dissolved Pb. Meanwhile, the residue was washed
thoroughly with distilled water, dried in a vacuum drying
oven at 40 °C. The experiments were done in triplicate to
ascertain that the differences observed were statistically sig-
nificant. The Pb recovery (R
Pb )was calculated using the
following equation
R 100
Pb@
Pb
I F #=
-6Pb
6Pb@I
where [Pb]i and [PB]F are the initial and final concentra-
tions of Pb (mM) in the leachate, respectively.
Coupled Extraction-Cementation Experiments
Coupled extraction-cementation (CEC, described in the
section of results and discussion) experiments were con-
ducted in 50 mL Erlenmeyer flasks. A 10 mL of NaCl-HCl
was added to the flask, and N2 was introduced for 15 min
to remove DO. Then, 0.5 g of PbSO4 and 0.5 g of ZVI was
added to the flask, and N2 was further introduced for 5 min.
The flask was tightly capped with a silicon rubber plug and
parafilm, and shaken in a thermostat water bath shaker at a
shaking speed of 120 rpm and amplitude of 40 mm at 25
°C. After this, magnetic Pb-loaded ZVI was recovered from
the pulp using a handheld 0.6 T magnet. The magnetic
fractions were then thoroughly washed with distilled water
and dried in a vacuum drying oven at 40 °C for 24 h. After
drying, the magnetic fractions were digested using aqua
regia in a microwave-assisted acid digester (Ethos Advanced
Microwave Lab station, Milestone Inc., USA) and the
leachates were analyzed for Pb by ICP-AES. Meanwhile,
the leachate was filtered using a 0.2 μm syringe-driven
membrane filter, and the filtrate was immediately analyzed
using ICP-AES to measure the concentration of dissolved
Pb. Distribution of Pb to magnetic fraction (Rmag), solu-
tion (Rsol), and residue (Rres) after treatment was calculated
according to following equations
R M
M W
100
mag
total
mag mag #
#=
R Mtotal
C V
100
sol
sol sol #
#=
R R R 100
res mag sol =--
where Mtotal is the mass of total Pb (g), Mmag is the mass of
magnetic fraction (g) and Wmag is the ratio of Pb in mag-
netic fraction, Csol is the Pb concentration in solution (g/L)
and Vsol is the volume of the solution (L).
Flotation Experiments
Flotation experiments were carried out using an agita-
tor-type flotation machine (ASH-F30H, Kankyo-kanri
Engineering, Akita, Japan) equipped with a 400 mL flota-
tion cell under the following conditions: pH, 6.5 tempera-
ture, 25 °C pulp density, 5% impeller speed, 1000 rpm
air flow rate, 1 L/min. In a 500 mL beaker, a model sam-
ple containing 15 g of ZnS and 5 g of PbSO4 was sus-
pended in 300 mL of distilled water, and the supernatant
was decanted to remove fine particles (38 µm). After des-
liming, a model sample was repulped to 400 mL with dis-
tilled water in the flotation cell and conditioned for 3 min
after adding the following reagents in sequence: ~5 kg/t of
ZnSO4 (100 ppm Zn2+), 1 kg/t of Na2SO3, 20 g/t of KAX,
and 20 μL/L of MIBC. Afterwards, air was introduced at
a flowrate of 1 L/min, and froth was recovered for 3 min.
The recovered froth/tailing products were dried at 105 °C
for 24 h and analyzed by XRF to determine the recovery of
Zn. The experiments were performed in duplicate to ascer-
tain that the differences observed were statistically signifi-
cant. An aliquot of the pulp of about 5 mL was collected 3
min after adding the depressant, filtered through a 0.2 μm
syringe-driven membrane filter, and immediately analyzed
using ICP-AES to check the extent of lead activation of
ZnS. In addition, flotation experiments of ZnS/PbSO4
mixture after pretreatment were conducted to check how
effective the removal of PbSO4 was on the depression of
ZnS floatability. A mixture of 15 g ZnS and 5 g PbSO4 was
pretreated with extraction using CH3COONH4 or CEC
using NaCl-HCl and Fe0, following the same procedures
as described in the previous sections. After the pretreat-
ment, flotation experiments were conducted as described
previously.
RESULTS AND DISCUSSION
Extraction of PbSO4 Using CH3COONH4 and
Recovery of Extracted Pb2+ as Zero-Valent Pb by
Cementation Using Zero-Valent Fe
The extraction experiments of PbSO4 were conducted using
CH3COONH4 at solid-liquid (S/L) ratio of 0.5 g/10 mL.
First, effects of CH3COONH4 concentration and time on
extraction of PbSO4 for 24 h were investigated (Figure 1).
When CH3COONH4 concentration was higher than
3.5 M, the extraction efficiency of Pb was higher than
99%, and almost all PbSO4 was extracted within 30 min
using 3.5 M of CH3COONH4. Extraction of PbSO4 with
CH3COONH4 would occur as described by following
equation
PbSO 2CH COO Pb^CH COOh SO
4 3 3 2 4
2- +=+-^aqh
syringe-driven membrane filter, and the filtrate was imme-
diately analyzed using ICP-AES to measure the concentra-
tion of dissolved Pb. Meanwhile, the residue was washed
thoroughly with distilled water, dried in a vacuum drying
oven at 40 °C. The experiments were done in triplicate to
ascertain that the differences observed were statistically sig-
nificant. The Pb recovery (R
Pb )was calculated using the
following equation
R 100
Pb@
Pb
I F #=
-6Pb
6Pb@I
where [Pb]i and [PB]F are the initial and final concentra-
tions of Pb (mM) in the leachate, respectively.
Coupled Extraction-Cementation Experiments
Coupled extraction-cementation (CEC, described in the
section of results and discussion) experiments were con-
ducted in 50 mL Erlenmeyer flasks. A 10 mL of NaCl-HCl
was added to the flask, and N2 was introduced for 15 min
to remove DO. Then, 0.5 g of PbSO4 and 0.5 g of ZVI was
added to the flask, and N2 was further introduced for 5 min.
The flask was tightly capped with a silicon rubber plug and
parafilm, and shaken in a thermostat water bath shaker at a
shaking speed of 120 rpm and amplitude of 40 mm at 25
°C. After this, magnetic Pb-loaded ZVI was recovered from
the pulp using a handheld 0.6 T magnet. The magnetic
fractions were then thoroughly washed with distilled water
and dried in a vacuum drying oven at 40 °C for 24 h. After
drying, the magnetic fractions were digested using aqua
regia in a microwave-assisted acid digester (Ethos Advanced
Microwave Lab station, Milestone Inc., USA) and the
leachates were analyzed for Pb by ICP-AES. Meanwhile,
the leachate was filtered using a 0.2 μm syringe-driven
membrane filter, and the filtrate was immediately analyzed
using ICP-AES to measure the concentration of dissolved
Pb. Distribution of Pb to magnetic fraction (Rmag), solu-
tion (Rsol), and residue (Rres) after treatment was calculated
according to following equations
R M
M W
100
mag
total
mag mag #
#=
R Mtotal
C V
100
sol
sol sol #
#=
R R R 100
res mag sol =--
where Mtotal is the mass of total Pb (g), Mmag is the mass of
magnetic fraction (g) and Wmag is the ratio of Pb in mag-
netic fraction, Csol is the Pb concentration in solution (g/L)
and Vsol is the volume of the solution (L).
Flotation Experiments
Flotation experiments were carried out using an agita-
tor-type flotation machine (ASH-F30H, Kankyo-kanri
Engineering, Akita, Japan) equipped with a 400 mL flota-
tion cell under the following conditions: pH, 6.5 tempera-
ture, 25 °C pulp density, 5% impeller speed, 1000 rpm
air flow rate, 1 L/min. In a 500 mL beaker, a model sam-
ple containing 15 g of ZnS and 5 g of PbSO4 was sus-
pended in 300 mL of distilled water, and the supernatant
was decanted to remove fine particles (38 µm). After des-
liming, a model sample was repulped to 400 mL with dis-
tilled water in the flotation cell and conditioned for 3 min
after adding the following reagents in sequence: ~5 kg/t of
ZnSO4 (100 ppm Zn2+), 1 kg/t of Na2SO3, 20 g/t of KAX,
and 20 μL/L of MIBC. Afterwards, air was introduced at
a flowrate of 1 L/min, and froth was recovered for 3 min.
The recovered froth/tailing products were dried at 105 °C
for 24 h and analyzed by XRF to determine the recovery of
Zn. The experiments were performed in duplicate to ascer-
tain that the differences observed were statistically signifi-
cant. An aliquot of the pulp of about 5 mL was collected 3
min after adding the depressant, filtered through a 0.2 μm
syringe-driven membrane filter, and immediately analyzed
using ICP-AES to check the extent of lead activation of
ZnS. In addition, flotation experiments of ZnS/PbSO4
mixture after pretreatment were conducted to check how
effective the removal of PbSO4 was on the depression of
ZnS floatability. A mixture of 15 g ZnS and 5 g PbSO4 was
pretreated with extraction using CH3COONH4 or CEC
using NaCl-HCl and Fe0, following the same procedures
as described in the previous sections. After the pretreat-
ment, flotation experiments were conducted as described
previously.
RESULTS AND DISCUSSION
Extraction of PbSO4 Using CH3COONH4 and
Recovery of Extracted Pb2+ as Zero-Valent Pb by
Cementation Using Zero-Valent Fe
The extraction experiments of PbSO4 were conducted using
CH3COONH4 at solid-liquid (S/L) ratio of 0.5 g/10 mL.
First, effects of CH3COONH4 concentration and time on
extraction of PbSO4 for 24 h were investigated (Figure 1).
When CH3COONH4 concentration was higher than
3.5 M, the extraction efficiency of Pb was higher than
99%, and almost all PbSO4 was extracted within 30 min
using 3.5 M of CH3COONH4. Extraction of PbSO4 with
CH3COONH4 would occur as described by following
equation
PbSO 2CH COO Pb^CH COOh SO
4 3 3 2 4
2- +=+-^aqh