XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3349
the proton dynamics within the samples with two individ-
ual components, as usually made for bulk water. Instead,
the Cole-Cole distribution was used as the sole function
to describe the QENS signal, and both slow unlocalized
motions, and fast localized dynamics contribute to the
result. Indeed, fast diffusion of liquids under confinement
has been extensively reported in experiments performed at
BASIS and has been associated with coating layers on the
matrix’s inner surfaces due to the immobilization of chemi-
cal species from the fluid. Here, however, it does not seem
to be the case since, as shown in Figure 8(a), Al(OH)3 –
LDH seemingly has the lower elastic fraction at 300K
among the three samples, in agreement with previously
published DSC-TGA analysis.20
While comparing the diffusivities of Al(OH)3 – LDH
around room temperature with those from Al2O3 – LDH
and Fe-LDH, the first sample is the one with the larger
mobility. Based on the previous discussions and as shown
in Figure 2(b)(d), such an effect is not necessarily related to
a larger amount of water molecules immobilized in the sur-
faces of the material. As the experiments were conducted at
higher temperatures, the dynamics from strongly confined
populations of water tend to play bigger roles in the QENS
signals either because the weakly bounded populations may
escape from the sample or because their dynamics become
too fast for the dynamic range of the instrument. As previ-
ously mentioned, Al(OH)3 – LDH experiences successive
escapes of water, and no clear temperature dependence can
be drawn for the diffusion coefficients. Here, the escape of
the weakly bounded populations of water is somewhat con-
sistent with their higher mobility at lower temperatures. In
Figure 8(b), note that, at 400K, the elastic fraction from
Table 1. Values of D and t0 as obtained by fitting the broadening of the QENS spectra with eq. 3
Sample Temperature, K D, ×10–10 m2/s t
0 ,ps
Al(OH)3 250 5.9 ± 1.2 64 ± 4
300 29.9 ± 3.5 26 ± 2
350 67.2 ± 8.0 23 ± 1
400 18.2 ± 2.9 8 ± 2
500 11.3 ± 0.8 4 ± 1
550 23.0 ± 0.6 0 ± -
600 9.0 ± 0.8 9 ± 1
Al
2 O
3 – LDH 300 15.1 ± 1.3 59 ± 1
350 35.4 ± 3.2 34 ± 1
400 10.5 ± 0.5 6 ± 0.4
450 13.9 ± 1.6 7 ± 1
500 19.9 ± 3.2 7 ± 1
550 22.1 ± 3.1 8 ± 1
600 24.8 ± 4.6 9 ± 1
Fe-LDH 300 19.3 ± 1.9 20 ± 1
400 20.2 ± 2.3 20 ± 2
Figure 8. Elastic fraction, A
0 (Q), (a) for the three samples at 300K and (b) at 400K and (c) for Al(OH)
3 – LDH, Al
2 O
3 – LDH,
and Fe-LDH at 600K
the proton dynamics within the samples with two individ-
ual components, as usually made for bulk water. Instead,
the Cole-Cole distribution was used as the sole function
to describe the QENS signal, and both slow unlocalized
motions, and fast localized dynamics contribute to the
result. Indeed, fast diffusion of liquids under confinement
has been extensively reported in experiments performed at
BASIS and has been associated with coating layers on the
matrix’s inner surfaces due to the immobilization of chemi-
cal species from the fluid. Here, however, it does not seem
to be the case since, as shown in Figure 8(a), Al(OH)3 –
LDH seemingly has the lower elastic fraction at 300K
among the three samples, in agreement with previously
published DSC-TGA analysis.20
While comparing the diffusivities of Al(OH)3 – LDH
around room temperature with those from Al2O3 – LDH
and Fe-LDH, the first sample is the one with the larger
mobility. Based on the previous discussions and as shown
in Figure 2(b)(d), such an effect is not necessarily related to
a larger amount of water molecules immobilized in the sur-
faces of the material. As the experiments were conducted at
higher temperatures, the dynamics from strongly confined
populations of water tend to play bigger roles in the QENS
signals either because the weakly bounded populations may
escape from the sample or because their dynamics become
too fast for the dynamic range of the instrument. As previ-
ously mentioned, Al(OH)3 – LDH experiences successive
escapes of water, and no clear temperature dependence can
be drawn for the diffusion coefficients. Here, the escape of
the weakly bounded populations of water is somewhat con-
sistent with their higher mobility at lower temperatures. In
Figure 8(b), note that, at 400K, the elastic fraction from
Table 1. Values of D and t0 as obtained by fitting the broadening of the QENS spectra with eq. 3
Sample Temperature, K D, ×10–10 m2/s t
0 ,ps
Al(OH)3 250 5.9 ± 1.2 64 ± 4
300 29.9 ± 3.5 26 ± 2
350 67.2 ± 8.0 23 ± 1
400 18.2 ± 2.9 8 ± 2
500 11.3 ± 0.8 4 ± 1
550 23.0 ± 0.6 0 ± -
600 9.0 ± 0.8 9 ± 1
Al
2 O
3 – LDH 300 15.1 ± 1.3 59 ± 1
350 35.4 ± 3.2 34 ± 1
400 10.5 ± 0.5 6 ± 0.4
450 13.9 ± 1.6 7 ± 1
500 19.9 ± 3.2 7 ± 1
550 22.1 ± 3.1 8 ± 1
600 24.8 ± 4.6 9 ± 1
Fe-LDH 300 19.3 ± 1.9 20 ± 1
400 20.2 ± 2.3 20 ± 2
Figure 8. Elastic fraction, A
0 (Q), (a) for the three samples at 300K and (b) at 400K and (c) for Al(OH)
3 – LDH, Al
2 O
3 – LDH,
and Fe-LDH at 600K