The direct observation and distribution regularity of contact angle for spherical particle attached to air bubble in static three-phase system

Abstract

Contact angle is a typical parameter to indicate the hydrophobicity of solid surface, and it is usually used to evaluate the wettability and floatability of mineral particles. Directly measurement on contact angle of particles is critical for laboratory research and industrial practice in flotation. By combining the image processing analysis and force balance calculation, a composite method to directly measure contact angle of particle was proposed. The good agreement between observed contact angle and calculated contact angle during lots of experiments proved the accuracy and convenience of this measurement method. The fundamental effects of particle size, hydrophobized time, and bubble size on contact angle distribution of particle were investigated using hydrophobized glass beads with different particle size. For glass beads with same surface hydrophobicity, the contact angle showed a nearly constant trend with varying particle size and bubble size. The essence of distribution regularity of contact angle was uncovered through force calculation analysis. Besides, the central angle is always larger than half of contact angle if a smooth spherical particle successfully attached to an air bubble and achieved equilibrium state.