1 research outputs found
Probing Silica–Kaolinite Interactions with Sum Frequency Generation Spectroscopy
Treating the oil sands tailings ponds is a major challenge
because
of the vast amounts of tailings and the need for a reliable treatment
technique for releasing water and generating the highly consolidated
material required for land reclamation. Treatment with chemicals such
as lime (calcium (hydr)oxide) is a promising technology for tailings
dewatering and consolidation, particularly at higher pH. Given that
kaolinite and silica minerals are the main constituents of many oil
sands, we have investigated the influence of lime and NaOH addition
on the silica/aqueous kaolinite interface over the pH range 7.4–12.4
using vibrational sum frequency generation spectroscopy (SFG). With
lime addition, at pH 12.0 and above we observe a complete disappearance
of the vibrational features of the interfacial water molecules for
planar silica in contact with an aqueous dispersion of kaolinite particles.
A concurrent increase in the amount of adsorbed kaolinite on the silica
surface at pH 12.0 and above is observed, shown in the increased intensity
of the kaolinite SFG peak at 3694 cm–1. This suggests
that the absence of water features in the SFG spectra is associated
with conditions that facilitate dewatering. With NaOH addition, however,
the interfacial water SF intensity is still significant even under
highly alkaline conditions despite the increase in adsorbed kaolinite
at high pH. To better understand the SFG observations and get a deeper
insight into the chemistry of the silica/aqueous kaolinite interface,
we measure the ζ-potential on the planar silica/aqueous interface
and kaolinite aqueous dispersions under the same pH conditions with
NaOH and lime addition