XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1799
2018). Wang et al.(Wang et al., 2014) studied vanadium
extraction from shale ore using CaO as an additive. An
85.50% leaching efficiency was obtained under the follow-
ing conditions: roasting temperature of 950 °C, roasting
time of 4 h, leaching acid dosage of 40%, and leaching
time of 6 h. Yang et al.(Yang et al., 2017) studied the
roasting process using NaCl-Na2CO3-Na2SO4 as an addi-
tive. The results indicated that the higher the content of
NaCl in the composite additive, the higher the vanadium
leaching efficiency. During the roasting process, NaCl and
Na2CO3 had a cooperative effect and the leaching rate was
higher than other combinations. Na ion replaced K ion in
melt and promoted the growth of albite. The presence of
Na2CO3-activated quartz promoted the reaction of albite
with activated quartz and melt. It accelerated the formation
of vanadate. In general, the additive roasting process could
significantly improve the reactivity of vanadium-bearing
minerals and the leaching efficiency of vanadium. However,
there are still problems such as a large number of additives
(about 10 wt.%), waste gas pollution (Eqs.1 and 2), and
low economic benefits(Wang et al., 2015).
K(Al, V)2(AlSi3O10)(OH)2+SiO2+NaCl+O2→
(K, Na)AlSiO8+V2O5+HCl (1)
2V2O5+4NaCl+O2=4NaVO3+2Cl2 (2)
CaF2+2H++[SO4]2+=2HF(aq)+CaSO4↓ (3)
(Ca, Mg)(CO3)2+4H+=
CaSO4↓+MgSO4+2CO2↑+2H2O (4)
Mg5Al2Si3O10(OH)8+HF(aq)+H+→
SiO2↓+Mg2++[SiF
6 ]2–+[AlF
5 ]2–+Al3++H
2 O (5)
KMg3(Al,V)Si3O10(OH)2+HF(aq)+H++O2→
SiO2↓+VO2++K++Mg2++[SiF6]2–
+[AlF5]2–+Al3++H2O (6)
Fluoride-enhanced direct leaching process was pro-
posed to solve the above problems(Li et al., 2017 Li et al.,
2010 Lin et al., 2017). CaF2 is the common aid-leaching
agent. Wang et.al (Wang et al., 2015) studied the mecha-
nism of CaF2-enhanced vanadium leaching from black
shale. Compared to direct acid leaching without CaF2,
leaching with CaF2 can increase the vanadium leaching
rate by more than 40%. CaF2-enhanced leaching process
can be described as Eqs.3–6. CaF2 promoted the combina-
tion of F, Al, and Si in the vanadium-bearing phlogopite.
The formation of [SiF6]2–, [AlF5]2– reduced the apparent
activation energy of the reaction process and improved the
vanadium leaching efficiency(Zhang et al., 2022). Zheng
et al.(Zheng et al., 2021) investigated the mechanism of
CaF2-enhanced vanadium extraction by leaching kinetics
and DFT simulation. The results indicated that the direct
acid leaching process was controlled by chemical reactions.
The V-O octahedron was destroyed by the synergism of H+
with F–. The structural oxygen and the central vanadium
were destroyed by H+ and F–, respectively. and released
from the mica lattice structure as a six-coordinated [VF6].
To sum up, direct acid leaching with CaF2 is an efficient
vanadium extraction method. However, the corrosion of
leaching equipment and the treatment of F-containing
wastewater in production has become a problem that can-
not be ignored. In addition, the evaporation of HF during
the high-temperature leaching process seriously endangered
the health of on-site production personnel. Meanwhile, the
rise in the price of fluorite (CaF2) also increases the pro-
duction cost. In general, the current vanadium extraction
process needs to be improved.
In recent years, fluidized oxidation roasting-acid leach-
ing without an aid-leaching agent process was proposed to
realize the highly efficient utilization of low-grade vana-
dium-bearing shale. Compared with traditional tunnel
kiln roasting and rotary kiln roasting, fluidized roasting
has the advantages of higher heat transfer efficiency, higher
mass transfer efficiency, and better-roasted products. Bai
et al(Bai et al., 2023 Bai et al., 2022) used a novel two-
step fluidized roasting process to treat a black shale. After
decarburization at low temperature followed by roasting
at high temperature to destroy vanadium-bearing miner-
als lattices, compared with direct acid leaching with CaF2
and original NaCl roasting process, the vanadium leach-
ing rate increased 38.28% and 13.54%, respectively. Zhu
et al.(Zhu et al., 2023) pretreated the shale ore by suspen-
sion oxidation without additive roasting. Under the condi-
tion that no aid-leaching agent and the amount of leaching
acid was reduced by 20%, the vanadium leaching rate was
increased by nearly 8%. The results indicated that fluid-
ized oxidation roasting provides an economically feasible,
environmentally friendly, and high-efficiency method for
the broader utilization of vanadium-bearing shale(Yuan et
al., 2022 Yuan et al., 2022 Zeng et al., 2015). However, at
present, most research focuses on the change of shale ores in
the roasting process, but there are few studies on the opti-
mization of the leaching process and the leaching behavior
of the roasting products.
The purpose of this research is to reveal the mechanism
of enhanced vanadium leaching efficiency by suspension
2018). Wang et al.(Wang et al., 2014) studied vanadium
extraction from shale ore using CaO as an additive. An
85.50% leaching efficiency was obtained under the follow-
ing conditions: roasting temperature of 950 °C, roasting
time of 4 h, leaching acid dosage of 40%, and leaching
time of 6 h. Yang et al.(Yang et al., 2017) studied the
roasting process using NaCl-Na2CO3-Na2SO4 as an addi-
tive. The results indicated that the higher the content of
NaCl in the composite additive, the higher the vanadium
leaching efficiency. During the roasting process, NaCl and
Na2CO3 had a cooperative effect and the leaching rate was
higher than other combinations. Na ion replaced K ion in
melt and promoted the growth of albite. The presence of
Na2CO3-activated quartz promoted the reaction of albite
with activated quartz and melt. It accelerated the formation
of vanadate. In general, the additive roasting process could
significantly improve the reactivity of vanadium-bearing
minerals and the leaching efficiency of vanadium. However,
there are still problems such as a large number of additives
(about 10 wt.%), waste gas pollution (Eqs.1 and 2), and
low economic benefits(Wang et al., 2015).
K(Al, V)2(AlSi3O10)(OH)2+SiO2+NaCl+O2→
(K, Na)AlSiO8+V2O5+HCl (1)
2V2O5+4NaCl+O2=4NaVO3+2Cl2 (2)
CaF2+2H++[SO4]2+=2HF(aq)+CaSO4↓ (3)
(Ca, Mg)(CO3)2+4H+=
CaSO4↓+MgSO4+2CO2↑+2H2O (4)
Mg5Al2Si3O10(OH)8+HF(aq)+H+→
SiO2↓+Mg2++[SiF
6 ]2–+[AlF
5 ]2–+Al3++H
2 O (5)
KMg3(Al,V)Si3O10(OH)2+HF(aq)+H++O2→
SiO2↓+VO2++K++Mg2++[SiF6]2–
+[AlF5]2–+Al3++H2O (6)
Fluoride-enhanced direct leaching process was pro-
posed to solve the above problems(Li et al., 2017 Li et al.,
2010 Lin et al., 2017). CaF2 is the common aid-leaching
agent. Wang et.al (Wang et al., 2015) studied the mecha-
nism of CaF2-enhanced vanadium leaching from black
shale. Compared to direct acid leaching without CaF2,
leaching with CaF2 can increase the vanadium leaching
rate by more than 40%. CaF2-enhanced leaching process
can be described as Eqs.3–6. CaF2 promoted the combina-
tion of F, Al, and Si in the vanadium-bearing phlogopite.
The formation of [SiF6]2–, [AlF5]2– reduced the apparent
activation energy of the reaction process and improved the
vanadium leaching efficiency(Zhang et al., 2022). Zheng
et al.(Zheng et al., 2021) investigated the mechanism of
CaF2-enhanced vanadium extraction by leaching kinetics
and DFT simulation. The results indicated that the direct
acid leaching process was controlled by chemical reactions.
The V-O octahedron was destroyed by the synergism of H+
with F–. The structural oxygen and the central vanadium
were destroyed by H+ and F–, respectively. and released
from the mica lattice structure as a six-coordinated [VF6].
To sum up, direct acid leaching with CaF2 is an efficient
vanadium extraction method. However, the corrosion of
leaching equipment and the treatment of F-containing
wastewater in production has become a problem that can-
not be ignored. In addition, the evaporation of HF during
the high-temperature leaching process seriously endangered
the health of on-site production personnel. Meanwhile, the
rise in the price of fluorite (CaF2) also increases the pro-
duction cost. In general, the current vanadium extraction
process needs to be improved.
In recent years, fluidized oxidation roasting-acid leach-
ing without an aid-leaching agent process was proposed to
realize the highly efficient utilization of low-grade vana-
dium-bearing shale. Compared with traditional tunnel
kiln roasting and rotary kiln roasting, fluidized roasting
has the advantages of higher heat transfer efficiency, higher
mass transfer efficiency, and better-roasted products. Bai
et al(Bai et al., 2023 Bai et al., 2022) used a novel two-
step fluidized roasting process to treat a black shale. After
decarburization at low temperature followed by roasting
at high temperature to destroy vanadium-bearing miner-
als lattices, compared with direct acid leaching with CaF2
and original NaCl roasting process, the vanadium leach-
ing rate increased 38.28% and 13.54%, respectively. Zhu
et al.(Zhu et al., 2023) pretreated the shale ore by suspen-
sion oxidation without additive roasting. Under the condi-
tion that no aid-leaching agent and the amount of leaching
acid was reduced by 20%, the vanadium leaching rate was
increased by nearly 8%. The results indicated that fluid-
ized oxidation roasting provides an economically feasible,
environmentally friendly, and high-efficiency method for
the broader utilization of vanadium-bearing shale(Yuan et
al., 2022 Yuan et al., 2022 Zeng et al., 2015). However, at
present, most research focuses on the change of shale ores in
the roasting process, but there are few studies on the opti-
mization of the leaching process and the leaching behavior
of the roasting products.
The purpose of this research is to reveal the mechanism
of enhanced vanadium leaching efficiency by suspension