A Study of Collision Characteristics in differential sedimentation according to variation of Ionic Strength, Zeta Potential and Particle Size

이온화세기, 제타전위, 입자크기에 따른 속도차 침전에서의 입자간 충돌특성에 관한 연구

  • 한무영 (경희대학교 토목공학과) ;
  • 독고석 (서울대학교 대학원 도시공학과) ;
  • 박중현 (서울대학교 도시공학과)
  • Published : 1998.01.15

Abstract

The possibility of collision of two particles slowly settling one after another in water can be described using the collision efficiency factor in differential sedimentation (${\alpha}_{DS}$). ${\alpha}_{DS}$ was found to be a function of several parameters particle size, particle size ratio, Hamaker constant, density of liquid and particle, gravity acceleration. Previous researches were limited to the case when there is no electric repulsion assuming that the suspension is destabilized. In this paper, ${\alpha}_{DS}$ is calculated for the stabilized condition. The relative trajectory of two particles are calculated including hydrodynamics, attraction and repulsion forces. Ionic strength and surface potential significantly affect the collision possibility of two settling particles. Depending on the surface potential and ionic strength, ${\alpha}_{DS}$ value is divided into three regions; stable, unstable and transition zone. ${\alpha}_{DS}$ increases as the ionic strength increases, and as the surface charge decreases. This result can be used to model both destabilized and stabilized suspension incorporating the collision efficiency factors of the other coagulant mechanisms such as fluid shear and Browian motion.

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