Influence of surfactant on the penetration time of hydrophilic microparticles impacting into the gas–liquid interface at low impact velocities

Abstract

The micro-mechanics of particle-interface collision is fundamental for revealing the separation mechanism of gas-borne particles in the bubble column. This study further investigates the particle penetration time under different concentrations of anionic and nonionic surfactant solutions at low impact velocities (up0 ≤ 0.5 m/s) utilizing high-speed imaging technique. The results show that the penetration time exhibits a power function to the particle size, which remains constant with increasing the concentration of surfactants. The variation of interfacial deformation width wi and three-phase contact line dTPCL controls the cavity shape and capillary force exerted on the particle, further influencing the penetration time. The increased concentration of surfactant slightly improves the particle surface wettability, while the interfacial deformation width wi exhibits quite different features before and after reaching the critical micelle concentration (CMC). When csurfactant < CMC, the impact cavity will cause the uneven distribution of interfacial concentration and induce the Marangoni effect. When csurfactant> CMC, the disintegration of micelles can supply the monomers and eliminate the Marangoni effect. The model of penetration time has been extended to include the variation of surfactant at pre- and post- CMC.