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Rheological behavior of sepiolite suspensions homogenized by ultra-turrax high-speed homogenizer

Tonkur Hatice, Can Muhammed Fatih, Sabah Eyüp

Physicochemical Problems of Mineral Processing

2022

Vol. 58, iss. 5

art. no. 153415

The ability to disperse sepiolite suspensions is of great interest in various fields such as the production of cosmetics, pharmaceuticals, colors, etc., and in preparing the sample material for analytical purposes. In this study, the flow curves and time-dependent rheological behavior of sepiolite aqueous suspensions homogenized by Ultra-Turrax high-speed rotor-stator homogenizer were investigated under operating conditions. Forward and backward flow curves for homogenized sepiolite suspensions at different homogenization times and solid concentrations were plotted, and the amount of existing hysteresis loop was measured to determine the best conditions for the obtention of a suitable product having gel-forming properties for industrial and/or analytical applications. The results showed that the dispersed sepiolite suspensions exhibited a substantial increase in the viscosity values owing to gel formation, and thixotropic behavior that was rapidly improved by the increasing the solid content of suspension/ homogenization time, and their apparent viscosity decreased by the increasing the time of shearing, and flow characteristic was time-dependent. However, changing the distance between dispersing tool/bottom showed no favorable effect on preserving the rheological behavior of sepiolite suspensions, although the apparent viscosity decreased marginally due to increased distance between dispersing tool/bottom. Also, two time-dependent/independent models, namely the Power-law model and the Weltman model, were used to describe the thixotropy behavior, and different parameters of these models were analyzed. The Weltman model was found to be appropriate to fit the timedependency behavior of sepiolite suspensions and the most obtained value for model parameters A and B belonged to sepiolite suspension with 6 wt% at 25 min, which was considered as the optimized sample in the applied experiments, its final viscosity level increased from 0.82 to 12.55 Pas.