Rheology applied to the environmental management of mineral tailings: focus on safer disposal and water reuse

Abstract

Mining activities worldwide are subject to serious geotechnical accidents involving tailings dams. Therefore, many studies have focused on tailings dewatering before their deposition. This article studies the rheological properties of flocculated and thickened nickel tailings in order to determine the effect of the initial solid concentration and type of rheology modifying agents (two anionic polymeric flocculants) on their stability for disposal in dams. The sediment was submitted to rheological tests, with the vane technique, and slump tests, to obtain information about static and dynamic yield stress and slump height, respectively. The results showed a strong influence of the initial solid concentration and the polymeric flocculant on the particle aggregation. Both particle cohesion and yield stress of the sediment increased, reaching static yield stress of around 1,400 Pa. Both flocculants were efficient in thickening by batch sedimentation, allowing water recycling in the range of 70-90% with turbidity less than 100 NTU and the production of sediment with static yield stress much higher than specified for mineral paste.

Rheological Properties of a Tailing Thickened in an Excavated Ground Channel

“…Rheology, including viscosity yield stress, and the angle of repose are correlating parameters that define and characterize the behavior of a mineral paste (Boger, 2013;Garcia et al, 2003). Understanding the deformation and flow of matter is the primary purpose of studying the rheological properties of a pulp (Barnes et al, 1989;Trampus and França, 2019). The determination of apparent viscosity and yield stress are fundamental parameters for understanding the rheology of suspensions.…”

“…Viscosity measures the resistance to the displacement of fluid molecules as a function of internal friction; the greater the friction, the higher the viscosity (Garcia et al, 2003). However, variations in temperature, pressure, and solids concentration, as well as particle shape and size, and changes in particle aggregation level (due to the presence of salts, dispersing agents, or pH changes) cause variations in the rheological properties of a pulp (Sofrá and Boger, 2002;Trampus and França, 2019).…”