Improved water recovery: A review of clay-rich tailings and saline water interactions

The presence of clays can make dewatering of tailings from mineral processing challenging. This review focuses on the interaction of clays in tailings under different conditions, including the impact of high salinity. The surface chemistry and aggregation behaviour of clays in suspension are first discussed, and this is then extended to clay aggregation responses during polymer-induced flocculation, with a view to developing an understanding of how flocculant properties and applied shear can be optimised to enhance dewatering processes. There is increasing interest in polymer dosing to high solids tailings streams to enhance dewatering on deposition, and the demands for this process are contrasted against those for conventional flocculation at lower feed solid concentrations. The review concludes by highlighting a number of research challenges, which include that: (i) aggregate structures from polymer-assisted flocculation that are optimal for settling cannot also be assumed to be so for sediment consolidation; (ii) there is scope for reducing longer-term tailings impacts by choosing novel processing routes in the flowsheet design phase, but this requires insights on how tailings may behave after such processing at a much earlier stage; and (iii) most flocculation studies suffer from inconsistent, ill-defined or inappropriate conditions during the preparative stages, which prevent definitive conclusions being drawn on how high salinity impacts upon tailings flocculation, despite evidence that it can change aggregate density. (C) 2020 Elsevier B.V. All rights reserved.