The Role of Stereological Assumptions in Bubble Size Estimations and Their Implications for Assessing Critical Coalescence Concentrations

Abstract

Accurate measurement of bubble size is critical for assessing flotation performance. However, the 3D nature of bubbles, in contrast to the 2D nature of photographs obtained using a bubble viewer apparatus, may lead to distortions related to stereological assumptions. This study aimed to quantify the impact of these stereological effects on bubble size measurements in frother characterisations. Our results showed that different assumptions regarding bubble shape and volume resulted in variations in bubble size calculations of up to 10%. Furthermore, these stereological effects were propagated to the calculation of the critical coalescence concentration, leading to uncertainties of up to 14% depending on the type of frother. These findings emphasise the importance of considering stereological effects and selecting an appropriate calculation method when measuring bubble size for flotation and reagent assessments.

Editorial for Special Issue “Hydrodynamics and Gas Dispersion in Flotation”

“…There are four contributions on the development of online sensors, simulators, and models to define the machine designs and operating strategies: (i) a correlation between froth water content and water overflow rate [1], (ii) a correlation between gas holdup and flotation performance, which demonstrated that the former captured the combined effect of gas rate and frother concentration [2], (iii) a demonstration of a model reliability to predict bubble size from gas velocity and holdup measurements [3], and (iv) a simulation tool that incorporated gas dispersion, which proved the potential of changing the launder designs to improve flotation performances [4]. Bubble size measurement was another area with three contributions: the effect on interfacial area by considering stereological corrections in the bubble size estimation from 2D images [5], the increase in the automatically identified bubbles by modifying the sampling devices to reduce the presence of clusters [6], and the detection of abnormal hydrodynamic conditions (presence of cap-shaped bubbles) in industrial flotation machines [7]. An option for increasing the formation of bubble-particle aggregates is the use of micro and nanobubbles: a review on the generation, detection, and applications of nanobubbles in flotation was included in this volume [8], along with a study on the potential of bulk micro-nano-bubbles to improve quartz recovery [9].…”