Visualizing oxygen transfer and wake dynamics around single bubbles in Frother-modified systems

Understanding how frothers influence bubble-wake structure, oxygen transfer and particle entrainment remains a central challenge in the field of flotation. This study introduces a high-resolution, non-intrusive visualization framework that examines wake structure and interfacial renewal around single rising bubbles under controlled conditions in frother-modified systems. The motivation for this work lies in the strong coupling between bubble-scale hydrodynamics and metallurgical performance. The rise of bubbles from the collection zone inevitably transports water in their wakes into the froth zone. The amount of water recovered in the froth directly governs both recovery and grade such that, a higher water flux enhances the mobility of bubble-particle aggregates into the launder and promotes particle recovery yet simultaneously increases the entrainment of fine hydrophilic gangue leading to concentrate grade dilution. To probe the mechanisms underlying this trade-off, an oxygen-sensitive dye, resazurin, is employed in a thin-gap (4 mm) quasi-two-dimensional vessel to map spatial and temporal wake activity through image derived oxygen transfer fields. This approach converts otherwise invisible wake induced transport into observable grayscale intensity patterns, enabling direct comparison of wake morphology across frother types and concentration. Processed wake fields show systematic attenuation of wake structures with increasing frother concentration, consistent with progressive interfacial immobilization and reduced convective renewal. Distinct wake morphologies are further observed between alcohol-based and polyglycol frothers, specifically methyl isobutyl carbinol (MIBC) and polypropylene glycol (PPG 425) at comparable concentrations, highlighting chemistry specific modification of interfacial behaviour. The visualization results offer insights into how frothers regulate bubble induced water transport and a physical basis for understanding entrainment related trade-offs in flotation. This study establishes a foundation for subsequent quantitative studies linking wake structure to water transfer and entrainment under flotation-relevant conditions.