Suspended particles behavior in aqueous [Bmim]BF4 solution by novel on-line electrical sensing zone method

•A novel on-line electrical sensing zone (ESZ) method is developed.•The solids suspension curves in aqueous [Bmim]BF4 solutions are measured.•The aqueous [Bmim]BF4 solution stirred by radial flow impeller is better for solids suspension.•The mechanism of solids suspension is dominated by the mean flow in unbaffled tanks. Ionic liquids (ILs) and aqueous ionic liquid solutions have been investigated as excellent solvents or catalysts in a few multiphase systems. To optimize the reactor design and operation conditions, it is significant to study the suspended particles behaviors in ILs involved solid–liquid mixing processes. A novel on-line electrical sensing zone (ESZ) method is developed to achieve the measurement of local solids concentration in aqueous [Bmim]BF4 conductive solutions. The suspension degrees of solid particles stirred by different impellers at varied agitation speeds have been obtained. The mean fluid velocities and turbulent fluctuating velocities close to the bottom of the unbaffled tanks have been determined by stereoscopic particle image velocimetry (SPIV). The results showed that the aqueous [Bmim]BF4 solutions are more efficient on solids than normal saline solution. Radical flow impeller with wider blades at C/T = 0.2 presents its better performance on solids suspension. The variations of solids suspension curves are more consistent with that of mean radial velocities at axial height of z/H = 0.99. It indicated that the solids suspension in unbaffled stirred tanks is mainly related to the mean flow rather than to turbulent fluctuations.