3414 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
thereby increasing the pulp density and impairing its effi-
ciency in extracting Li. Additionally, an elevated ratio can
lead to overloading the leaching solution, curtailing the
exposure of solid particles to water, consequently diminish-
ing Li recovery (Figure 7). The increase in the S/L ratio can
introduce competing reactions and approach the solubility
limit of Li in water (Stubblefield and Bach, 1972), further
impeding its dissolution. Complications related to agita-
tion and mixing at higher S/L ratios can yield non-uniform
exposure of solid particles to water, ultimately hindering Li
dissolution. Thus, based on our findings, a 10% S/L ratio
was determined as the optimal condition for Li dissolution
in this study. It’s worth noting that this phenomenon of
decreased metal recovery with increasing S/L ratio aligns
with results reported in literature on the subject (Li et al.,
2010 Golmohammadzadeh et al., 2017 Li et al., 2019
Setiawan et al., 2019 Yang and Honaker, 2020).
Effect of Temperature
Leaching processes are subject to distinct effects based on
whether they are predominantly governed by chemical reac-
tion-controlled processes or diffusion-controlled processes,
a phenomenon well-documented in literature (Levenspiel
1999). In this context, our investigation focused on the
influence of temperature on Li recovery during the water
leaching of NaOH-roasted-α-spodumene, spanning tem-
peratures from 10 °C to 90 °C while maintaining a stir-
ring speed of 100 rpm and a fixed S/L ratio of 10% for a
duration of 30 minutes (Figure 8). The retrieval of samples
over shorter intervals was necessitated by the rapid kinet-
ics observed within the initial 60 seconds. As depicted
in Figure 8, the Li recovery demonstrated a noteworthy
decline with increasing leaching temperatures. For instance,
the transition from 10 °C to 90 °C led to a decrease in
Li recovery from 71.01% to 27 ± 2.34% after 15 seconds
of the dissolution reaction (Figure 8). Furthermore, the
remarkable sensitivity of Li dissolution to temperature
strongly implies that the overall prevailing leaching mecha-
nism is primarily exothermic, and that diffusion-controlled
kinetics could be governing the reaction (Abdel-Aal 2000
Free 2013 Brahim et al., 2020 Yang and Honaker, 2020).
Consequently, the reaction adheres to a rapid leaching pro-
cess characterized by swift kinetics within the first minute,
followed by a slow reaction indicating the approach of reac-
tion completion. Hence, it is evident that when NaOH-
roasted α-spodumene undergoes water leaching, multiple
reaction mechanisms may be at play, a phenomenon docu-
mented in similar studies concerning metal extraction from
various sources (Yang and Honaker, 2020 Hassas et al.,
2023).
In addition, based on the observations during the first
minute of reaction and previous theoretical calculations
(Han et al., 2022), the overall reaction is exothermic and
hence the increase of temperature reduces the dissolution
of ions into solution. This is because the backward reaction
is more favored than the forward dissolution reaction in
exothermic reactions (Langmuir 1997).
Figure 8. Effect of leaching reaction temperature on Li recovery at optimum roasting
conditions
thereby increasing the pulp density and impairing its effi-
ciency in extracting Li. Additionally, an elevated ratio can
lead to overloading the leaching solution, curtailing the
exposure of solid particles to water, consequently diminish-
ing Li recovery (Figure 7). The increase in the S/L ratio can
introduce competing reactions and approach the solubility
limit of Li in water (Stubblefield and Bach, 1972), further
impeding its dissolution. Complications related to agita-
tion and mixing at higher S/L ratios can yield non-uniform
exposure of solid particles to water, ultimately hindering Li
dissolution. Thus, based on our findings, a 10% S/L ratio
was determined as the optimal condition for Li dissolution
in this study. It’s worth noting that this phenomenon of
decreased metal recovery with increasing S/L ratio aligns
with results reported in literature on the subject (Li et al.,
2010 Golmohammadzadeh et al., 2017 Li et al., 2019
Setiawan et al., 2019 Yang and Honaker, 2020).
Effect of Temperature
Leaching processes are subject to distinct effects based on
whether they are predominantly governed by chemical reac-
tion-controlled processes or diffusion-controlled processes,
a phenomenon well-documented in literature (Levenspiel
1999). In this context, our investigation focused on the
influence of temperature on Li recovery during the water
leaching of NaOH-roasted-α-spodumene, spanning tem-
peratures from 10 °C to 90 °C while maintaining a stir-
ring speed of 100 rpm and a fixed S/L ratio of 10% for a
duration of 30 minutes (Figure 8). The retrieval of samples
over shorter intervals was necessitated by the rapid kinet-
ics observed within the initial 60 seconds. As depicted
in Figure 8, the Li recovery demonstrated a noteworthy
decline with increasing leaching temperatures. For instance,
the transition from 10 °C to 90 °C led to a decrease in
Li recovery from 71.01% to 27 ± 2.34% after 15 seconds
of the dissolution reaction (Figure 8). Furthermore, the
remarkable sensitivity of Li dissolution to temperature
strongly implies that the overall prevailing leaching mecha-
nism is primarily exothermic, and that diffusion-controlled
kinetics could be governing the reaction (Abdel-Aal 2000
Free 2013 Brahim et al., 2020 Yang and Honaker, 2020).
Consequently, the reaction adheres to a rapid leaching pro-
cess characterized by swift kinetics within the first minute,
followed by a slow reaction indicating the approach of reac-
tion completion. Hence, it is evident that when NaOH-
roasted α-spodumene undergoes water leaching, multiple
reaction mechanisms may be at play, a phenomenon docu-
mented in similar studies concerning metal extraction from
various sources (Yang and Honaker, 2020 Hassas et al.,
2023).
In addition, based on the observations during the first
minute of reaction and previous theoretical calculations
(Han et al., 2022), the overall reaction is exothermic and
hence the increase of temperature reduces the dissolution
of ions into solution. This is because the backward reaction
is more favored than the forward dissolution reaction in
exothermic reactions (Langmuir 1997).
Figure 8. Effect of leaching reaction temperature on Li recovery at optimum roasting
conditions