Dynamic behavior of bubble spreading based on highspeed camera

During foam flotation，the adhesion process includes liquid film thinning，liquid film rupture and threephase wetting periphery formation.Previous scholars have conducted indepth research on liquid film thinning and rupture.However，the evolution of threephase wetting periphery has not yet been fully concerned.In this work，the highspeed dynamic camera was used to record the spreading process of bubbles on homogeneous solid(Teflon，plexiglass，glass，stainless steel) and heterogeneous solid(lignite and anthracite) surfaces.The scanning electron microscope(SEM)，infrared spectrometer，and contact angle meter were adopted to analyze the physicochemical structures of solid surfaces.The MATLAB software was applied to investigate the spreading mechanism of threephase lines(TPL) and the morphological evolution of gasliquid interface on both homogeneous and heterogeneous solid surfaces.The experimental results of bubble spreading show that the threephase wetting periphery mainly undergoes two stages:rapid spreading and slow spreading.The TPL during the rapid spreading stage exhibits a general selfsimilar behavior with no independence on the initial conditions，while that during slow spreading stage is closely related to the solid surface properties.The powerlaw，L= at b，was utilized to analyze the spreading dynamics on homogeneous surfaces，and it demonstrated the 1/2(inertia regime) and 1/10(viscous regime) scaling exponents for rapid and slow spreading process，respectively.Also，the scaling exponent of 1/2 was obtained for the rapid spreading process of bubbles on coal surfaces.Based on the physicochemical structures of sloid surfaces，the better hydrophobic property of homogeneous or heterogeneous solid surfaces leads to the longer TPL length(L)，due to the greater attraction force.The surfaces with more irregularities，grooves or pores，the greater the influence on TPL length(L)，bubble maximum width(W) and corresponding position(H).Compared to the homogeneous surface，the heterogeneous physicochemical structure of lignite and anthracite leads to great difference on the motion dynamics of TPL and evolution of gasliquid interface，due to the pinning and fusion effect.Thus，the TPL spreading dynamics during particlebubble attachment are closely related to the surface physicochemical structures，as well as their homogeneity.