In the search for more sustainable
alternatives to the chemical
reagents currently used in froth flotation, the present work offers
further insights into the behavior of functionalized cellulose nanocrystals
as mineral hydrophobization agents. The study corroborates that hexylamine
cellulose nanocrystals (HACs) are an efficient collector for the flotation
of quartz and also identifies some particular characteristics as a
result of their colloidal nature, as opposed to the water-soluble
reagents conventionally used. To investigate the individual and collective
effects of the frother and HACs on the attachment of particles and
air bubbles, an automated contact timer apparatus was used. This induction
timer measures particle-bubble attachment probabilities (
P
att
) without the influence of macroscopic factors present
in typical flotation experiments. This allowed the study of the combined
influence of nanocellulose and frother concentration on
P
att
for the first time. While HACs readily adsorb on quartz
modifying its wettability, the presence of a frother leads to a drastic
reduction in
P
att
up to 70%. The improved
recovery of quartz in flotation cells might thus be attributed to
froth stabilization by HACs, perhaps acting as a Pickering foam stabilizer.
Among the main findings, a tendency of HACs to form mineral agglomerates
was identified and further explained using the extended DLVO theory
in combination with measured adsorption rates in a quartz crystal
microbalance. Therefore, this study distinguishes for the first time
the antagonistic effect of frothers on
P
att
and their synergies with HACs on the stabilization of orthokinetic
froths through the hydrophobization mechanism unlike those of typical
water-soluble collectors.