کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
593562 1453942 2013 11 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Water repellency enhances the deposition of negatively charged hydrophilic colloids in a water-saturated sand matrix
موضوعات مرتبط
مهندسی و علوم پایه مهندسی شیمی شیمی کلوئیدی و سطحی
پیش نمایش صفحه اول مقاله
Water repellency enhances the deposition of negatively charged hydrophilic colloids in a water-saturated sand matrix
چکیده انگلیسی


• Effect of wettability on colloid transport and deposition was studied.
• Colloid breakthrough could be described with attachment and detachment kinetics.
• High colloid deposition rates were found in hydrophobic porous media.
• Effects of wettability were most pronounced at higher ionic strength.
• High deposition rates were related to strongly attractive acid–base interactions.

The effect of grain water repellency on transport and deposition of hydrophilic colloids was studied by analyzing the breakthrough behavior of carboxylate-modified microspheres in water-saturated wettable and hydrophobic sand columns at different ionic strengths. Interaction free energies calculated from zeta (ζ)-potential and contact angle data were used to explain the specific colloid breakthrough behavior. Experimental breakthrough data could be well described with the finite-element code HYDRUS-1D using a one kinetic site model with attachment and detachment kinetics. Higher colloid deposition rates found for the hydrophobic sand could primarily be explained by its small electron-donor component of surface free energy (γs− = 1.6 × 10−2 mJ m−2, compared to γs− = 64.1 mJ m−2 for the wettable sand), leading to strongly attractive acid–base interactions at separation distances < 5 nm. Increasing ionic strength reduced the repulsive electrostatic interactions and generally increased colloid deposition with the effect being more pronounced in the hydrophobic sand. It can be concluded that grain water repellency tends to increase the deposition of negatively charged hydrophilic colloids, which can be ascribed to specific acid–base interactions. However, our results further revealed that the calculated interaction free energy profiles should be considered only as an approximation showing general trends because surface chemical heterogeneity as detected by atomic forces microscopy impeded the determination of the actual interaction energy conditions, resulting in an overestimation of electrostatic repulsion.

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ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Colloids and Surfaces A: Physicochemical and Engineering Aspects - Volume 431, 20 August 2013, Pages 150–160
نویسندگان
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