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Effects of Shear Stress on Phosphorus Adsorption Kinetics onto Air-Dried Sediments

Author(s): Qingxia Li; Hongwu Tang; Saiyu Yuan

Linked Author(s): Hongwu Tang, Saiyu Yuan

Keywords: Shear rate; Adsorption kinetic; Sediment drying

Abstract: Sediment aggregated with compaction in the process of air-drying, and the particle association could affect the contaminant ions adsorption. The change of aggregate size was often associated with shear stress, and thus experiments were designed to investigate the effects of shear stress on phosphorus adsorption kinetics in air-dried sediments. Shear flow was simulated at a stirred tank, and samples from a plain river were air-dried. Two different conditions were applied to the samples: variable shear rates in the process of an experiment; constant shear rates in an experiment, and applying different shear rates in each experiment. Sediments aggregated significantly during sediment air-drying, showing a quite different particle size distribution. Shear stress had a strong effect on P adsorption kinetics in sediments with aggregation, and made it more difficult to reach the dynamic pseudo-equilibrium. Sediments with fast shear rates variation showed a steeper slope at initial fast adsorption step than slow shear rates variation, and continued to show a higher adsorption amounts at the following slower adsorption stage. Shear rates affected P adsorption mainly through slow adsorption stage, and have little effect on the P adsorption at fast adsorption step, which likely resulted from the increase in surface area for diffusion and penetration by the breakdown of aggregation.


Year: 2016

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