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Open AccessArticle

The Initial Deposition Behavior of Silica Colloid and Amino-Modified Silica Colloid in Unsaturated Sand Columns

1
Iron and Steel Division, JFE Mineral Company, Ltd., 1 Kokan-cho, Fukuyama, Hiroshima 721-0931, Japan
2
Faculty of Life & Environmental Sciences, University of Tsukuba,1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan
*
Author to whom correspondence should be addressed.
Water 2020, 12(10), 2892; https://doi.org/10.3390/w12102892
Received: 16 September 2020 / Revised: 13 October 2020 / Accepted: 14 October 2020 / Published: 16 October 2020
(This article belongs to the Section Wastewater Treatment and Reuse)
Colloid transport experiments focusing on the initial deposition stage in water-unsaturated sand columns were conducted. To examine the effect of electrostatic interaction in the unsaturated condition, negatively and positively charged silica colloids were used for column transport experiments under different salt concentrations. The results of the column experiments were analyzed based on the colloid filtration theory and the deposition rate constants, and the single collector efficiency was calculated. The deposition rate constants of both negatively and positively charged silica in a water-unsaturated condition are larger than those in a water-saturated condition at an equivalent salt concentration, because the interface between air and water acts as an additional deposition site. The negatively charged silica shows the salt concentration, above which electric double layer (EDL) repulsion can be neglected, and the salt concentration is called critical deposition concentration (CDC). The CDCs were almost the same values in water-saturated as well as unsaturated conditions. The deposition rate constants of the positively charged silica were slightly increased at 0.05 mM due to the EDL attractive forces in the saturated condition. However, we could not see the significant effects of the EDL attractive force in the unsaturated condition in this study. Also, the present results demonstrated that a correlation equation for calculating collector efficiency can be applied to the non-spherical collector particles. View Full-Text
Keywords: colloid transport; initial deposition conditions; unsaturated sand column; silica particles; amino-modified silica particles; critical deposition concentration colloid transport; initial deposition conditions; unsaturated sand column; silica particles; amino-modified silica particles; critical deposition concentration
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Fujita, Y.; Kobayashi, M. The Initial Deposition Behavior of Silica Colloid and Amino-Modified Silica Colloid in Unsaturated Sand Columns. Water 2020, 12, 2892.

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