Predicting why, how, and when mine
tailings disposal sites become prone to dust scattering events is often hampered
by our limited understanding of the factors that affect the drying rates from their
surface layers. As a case study, thermal
imaging is demonstrated here to be a valuable tool to study the evaporation
mechanisms and rates from bauxite residues as a function of their thickness and
physicochemical properties, as well as environmental conditions. These investigations reveal their that late
stage drying rates are limited by gas phase diffusion through the interstitial
air within their internal microporosity. The smallness of the effective
diffusion coefficient indicates that water adsorption on bauxite residues surfaces
is the dominant phenomenon responsible for their slow water vapour transport
kinetics, a phenomenon that ultimately controls their late stage drying rates,
that is when dust scattering is most likely to occur. As such, application of this
thermal imaging methodology in the field may also contribute to improve the accuracy
of risk assessment protocols, support intervention and mitigation strategies,
underpin optimization efforts for mining residues management, and improve
forecasting of fugitive dust emissions from mine tailings by enabling more
accurate predictions of the evolution in their surface drying state.</p