3392 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
of 12%. Conditions at which the highest lithium concen-
trations were achieved are shown in Table 4. Maximum
lithium concentrations of 129 mg/L (93% dissolution) and
108 mg/L (68% dissolution) were achieved after 6 hours,
using sulphuric acid and organic acid A, respectively.
Table 4 shows that the concentration of both calcium
and magnesium in solution is more than nine times higher
for sulphuric acid leaching, compared to the concentrations
achieved using organic acid A. XRD of the solid residue after
leaching with organic acid A identified the major phases as
hydrates of CaX and MgX, where X is the anionic ligand
of organic acid A. Dolomite and calcite, major components
in the feed material, react with organic acid A (H2X) to
form CaX, MgX, water and carbon dioxide, as shown in
Equation 1 and 2. Both MgX and CaX have relatively low
solubilities, resulting in precipitate formation.
CaMg CO 2H X CaX MgX
2H O 2CO2
3 2 2
2
"++
++
^h
(1)
CaCO H X CaX H O CO
3 2 2 2 "+++(2)
0
20
40
60
80
100
0 1 2 3 4 5 6
Time (h)
(a) (b)
0
20
40
60
80
100
0 1 2 3 4 5 6
Time (h)
Figure 4. Lithium dissolution as a function of time, acid type and acid concentration, for leaching optimisation tests
performed at (a) 25°C (1.5 M and 2 M organic acid A tests were conducted at temperatures of 30°C and 40°C, respectively)
and (b) 60°C, using 8% solids
0
20
40
60
80
100
0 1 2 3 4 5 6
Time (h)
0
20
40
60
80
100
0 1 2 3 4 5 6
Time (h)
(a) (b)
Figure 5. Lithium dissolution as a function of time, acid type and acid concentration, for leaching optimisation tests
performed at (a) 25°C (1.5 M and 2 M organic acid A tests were conducted at temperatures of 30°C and 40°C, respectively)
and (b) 60°C, using 12% solids
Li
dissolug415on
(%)
Li
dissolug415on
(%)
Li
dissolug415on
(
Li
dissolug415on
(