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Article
Colloid Transport with Wetting Fronts: Interactive Effects of Solution Surface Tension and Ionic Strength
Water Research (2010)
  • Jie Zhuang, University of Tennessee - Knoxville
  • Nadine Goeppert
  • Ching Tu, University of Tennessee - Knoxville
  • John McCarthy, University of Tennessee - Knoxville
  • Edmund Perfect, University of Tennessee - Knoxville
  • Larry McKay, University of Tennessee - Knoxville
Abstract
Transport of colloids with transient wetting fronts represents an important mechanism of contaminant migration in the vadose zone. The work presented here used steady-state saturated and transient unsaturated flow columns to evaluate the transport of a fluorescent latex microsphere (980 nm in diameter) with capillary wetting fronts of different solution surface tensions and ionic strengths. The saturated transport experiments demonstrated that decreasing solution surface tension and ionic strength decreased colloid deposition at the solid-liquid interface and increased colloid recovery in the column effluent. The effect of solution surface tension on colloid transport and deposition was greater at lower ionic strength, suggesting an interaction between these two factors. Under transient unsaturated flow conditions, the number of colloids retained in sand decreased exponentially with travel distance through the porous media. However, lowering the solution surface tension and ionic strength resulted in a more even distribution of colloids along the column. The measured zeta potentials of colloids in different solutions suggest that both lowering surface tension and ionic strength would enhance the electrostatic repulsion between colloid and sand. The experimental results revealed that the effects are nonlinear, implying the possible existence of critical threshold values, beyond which the effects were not significant. In addition, colloid migration slowed down as solution surface tension decreased due to reduction of capillary forces that drove liquid movement.
Keywords
  • Colloid transport; Transient unsaturated flow; Surface tension; Ionic strength; Horizontal column; Capillary force
Disciplines
Publication Date
February, 2010
Citation Information
Jie Zhuang, Nadine Goeppert, Ching Tu, John McCarthy, et al.. "Colloid Transport with Wetting Fronts: Interactive Effects of Solution Surface Tension and Ionic Strength" Water Research Vol. 44 Iss. 4 (2010)
Available at: http://works.bepress.com/larry_mckay/3/