Abstract: The study on transport and deposition of suspended particles in porous media is important to groundwater recharge, underground pollutant diffusion, nuclear waste disposal and oil exploitation. Most natural suspended particles are non-spherical. To study the effect of shape on particle migration, soil column tests with three-phases were carried out on spherical particles (10 ?m in median particle diameter) and rod-shaped particles (aspect ratios of 3:1 and 6:1). The breakthrough curves of different shape particles under different ionic intensities were obtained. The mechanism of the deposition and release of suspended particles was analyzed by DLVO theory, and the effect of shape on particle migration behavior was explained. When the ionic strength is low (6 mmol/L), the DLVO interaction energy profile shows higher energy barriers. So particles of various shapes is mainly retained in secondary minimum. When the ionic strength is high (150 mmol/L), the retention mechanism of spherical particles is the secondary minimum retention due to high energy barriers. The 6:1 rod-like particles are retained in the secondary minimum and the primary minimum, relating to the electrostatic properties and the preferential orientation of the rod-like particles. For rod-like particles, a side-on orientation provides a deeper attractive well and larger influential distance than an end-on orientation. A side-on configuration is a more stable deposition method and preferred orientation for particle deposition. The Derjaguin approximation method is used in the DLVO calculation. The results show that the theoretical prediction agrees well with the soil test results.

Key words: suspended particles, particle shape, DLVO theory, breakthrough curves, preferred orientation