Ozone Propagation in Sterile Waste Piles From Uranium Mining: Modeling and Experimental Validation

Abstract

Acid mine drainage is generated when sulfide minerals are exposed to air and water through the porous subsurface, and it is significantly accelerated by the action of oxidizing autotrophic bacteria. This is a serious problem in the extraction of most minerals. The use of ozone, which has powerful antimicrobial properties, for microbiological inactivation of sterile waste is a possible solution to mitigate the generation of acid mine drainage. However, ozone generates oxygen as a by-product which can produce short-term oxidation of exposed minerals as well as the potentialization of the leaching of metals and sulfides. This would require early intervention strategies for removal of these substances. In this study, a propagation prediction model of ozone in sterile waste piles from uranium mining was developed on an experimental basis. Such piles can be considered as porous medium consisting of a porous matrix and a pure gas phase for the flow of ozone. A kinetic coefficient of interaction between ozone and sterile waste of the order of 10−3 s−1 was obtained through bench-scale experiments conducted using waste columns. Another pilot-scale experiment was conducted on the pile using experimental parameters of a waste column to evaluate the propagation of ozone in the pile. A three-dimensional axisymmetric numerical simulation showed that ozone tends to rise near the injection site. The propagation of ozone was observed at approximately 1 m from the injection tube, showing an ozone concentration of the order of 10−4 mol m−3 in the porous subsurface.