Laboratory monitoring approaches for tailings settling and evaluation of flocculant and coagulant treatments

Abstract

X-ray computer tomography (CT), magnetic resonance imaging (MRI), and nuclear magnetic resonance (NMR) are applied for laboratory monitoring of the settling behaviour in tailings suspensions. It is shown that the developed monitoring techniques are consistent with each other and provide different levels of information from 2D density cross-sections obtained using X-ray CT to 1D and bulk water content using MRI and NMR. Analysis of coagulant and flocculant treatments based on obtained measurement information is conducted using linear and nonlinear kinetic modelling approaches. The linear Roberts' kinetic model describes the settling of original tailings suspensions very well, but it is not adequate for the suspensions treated with additives. A modified nonlinear Roberts' model is developed and successfully applied to analyze the suspension with additives. The analysis of combined flocculants and coagulants treatments reveals that flocculants significantly affect the settling rate; however, they decrease the efficiency of settling with respect to the residual water content. Coagulants affect mostly the residual water content in samples, but do not change the settling rate significantly. The trade-off between concentrations of coagulants and flocculants needs to be achieved for optimal settling treatments.