XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2281
presented in Figures 3–8. Results clearly show that SHA
concentrations deplete to equilibrium over time depending
on the pH. In most cases, the best results were obtained at
pH 9, a behavior attributed to SHA being an anionic col-
lector adsorbing at a surface that is less negatively charged
compared to pH 10 and 11. However, because SHA
adsorption occurs even though the collector and surface are
similarly charged, it is not attributed to physisorption but
rather to chemisorption and possibly surface precipitation
depending on the initial concentration (Trant et al. 2018).
Based on these findings, SHA appears to adsorb on RES in
the following order: Ln2Si2O7 Ln4.67(SiO4)3O, where Ln
is La, Nd or Dy.
Adsorption Density
Adsorption density plots were generated from the solution
depletion plots in Figures 3–8 to better represent adsorption
kinetics on RES surfaces in conventional units of mol/cm2.
Results are shown in Figures 9–14. This standardizes the
plots according to the initial concentration but also allows
the quantity of adsorbed SHA to be compared to results
obtained for REOs, REPs and RECs by Trant et al. 2018.
To determine adsorption densities per Equation 3, it was
necessary to use the BET apparatus and measure surface
areas. Table 2 displays the BET surface areas in cm2/g of
the six RESs used in this study, taken as the average of three
measurements.
To make the comparisons easy, the adsorption density
plots in Figures 9–14 also show two horizontal lines which
represent different levels of adsorption at equilibrium (Sime
2018). Maximum adsorption density for a monolayer of
vertically-oriented SHA molecules is shown in orange
representing a Langmuir Blodgett (LB) adsorption den-
sity of approximately 1.25×10–10 mol/cm2. Likewise, the
0
0.0001
0.0002
0.0003
0.0004
0.0005
0 50 100 150
Time (min)
pH 9 pH 10 pH 11
Figure 5. SHA solution depletion via Nd
4.67 (SiO
4 )
3 O
0
0.0001
0.0002
0.0003
0.0004
0.0005
0 50 100 150
Time (min)
pH 9 pH 10 pH 11
Figure 6. SHA solution depletion via Nd
2 Si
2 O
7
0
0.0001
0.0002
0.0003
0.0004
0.0005
0 50 100 150
Time (min)
pH 9 pH 10 pH 11
Figure 7. SHA solution depletion via Dy
4.67 (SiO
4 )
3 O
0
0.0001
0.0002
0.0003
0.0004
0.0005
0 50 100 150
Time (min)
pH 9 pH 10 pH 11
Figure 8. SHA solution depletion via Dy
2 Si
2 O
7
Conc.
moles/L
Conc.
moles/L
Conc.
moles/L
Conc.
moles/L
presented in Figures 3–8. Results clearly show that SHA
concentrations deplete to equilibrium over time depending
on the pH. In most cases, the best results were obtained at
pH 9, a behavior attributed to SHA being an anionic col-
lector adsorbing at a surface that is less negatively charged
compared to pH 10 and 11. However, because SHA
adsorption occurs even though the collector and surface are
similarly charged, it is not attributed to physisorption but
rather to chemisorption and possibly surface precipitation
depending on the initial concentration (Trant et al. 2018).
Based on these findings, SHA appears to adsorb on RES in
the following order: Ln2Si2O7 Ln4.67(SiO4)3O, where Ln
is La, Nd or Dy.
Adsorption Density
Adsorption density plots were generated from the solution
depletion plots in Figures 3–8 to better represent adsorption
kinetics on RES surfaces in conventional units of mol/cm2.
Results are shown in Figures 9–14. This standardizes the
plots according to the initial concentration but also allows
the quantity of adsorbed SHA to be compared to results
obtained for REOs, REPs and RECs by Trant et al. 2018.
To determine adsorption densities per Equation 3, it was
necessary to use the BET apparatus and measure surface
areas. Table 2 displays the BET surface areas in cm2/g of
the six RESs used in this study, taken as the average of three
measurements.
To make the comparisons easy, the adsorption density
plots in Figures 9–14 also show two horizontal lines which
represent different levels of adsorption at equilibrium (Sime
2018). Maximum adsorption density for a monolayer of
vertically-oriented SHA molecules is shown in orange
representing a Langmuir Blodgett (LB) adsorption den-
sity of approximately 1.25×10–10 mol/cm2. Likewise, the
0
0.0001
0.0002
0.0003
0.0004
0.0005
0 50 100 150
Time (min)
pH 9 pH 10 pH 11
Figure 5. SHA solution depletion via Nd
4.67 (SiO
4 )
3 O
0
0.0001
0.0002
0.0003
0.0004
0.0005
0 50 100 150
Time (min)
pH 9 pH 10 pH 11
Figure 6. SHA solution depletion via Nd
2 Si
2 O
7
0
0.0001
0.0002
0.0003
0.0004
0.0005
0 50 100 150
Time (min)
pH 9 pH 10 pH 11
Figure 7. SHA solution depletion via Dy
4.67 (SiO
4 )
3 O
0
0.0001
0.0002
0.0003
0.0004
0.0005
0 50 100 150
Time (min)
pH 9 pH 10 pH 11
Figure 8. SHA solution depletion via Dy
2 Si
2 O
7
Conc.
moles/L
Conc.
moles/L
Conc.
moles/L
Conc.
moles/L