Effect of anions on dispersion of a kaolinitic soil clay: A combined study of dynamic light scattering and test tube experiments

Dispersion is an important issue for clay leaching in soils. In this study, effects of various anions (Cl-, SO4 2-, acetate, oxalate and citrate) on dispersion of a kaolinitic soil clay were determined at different pH values and ionic strengths by dynamic light scattering and test tube experiments. Adsorption of anions on clay samples was characterized by the zeta potential (ζ) in a pH range of 2 to 11. At a pH range between 2 and 6, the effects of different anions on decreasing ζ were obvious and followed the order oxalate>citrate>SO4 2->Cl->acetate, while fluctuated changes in ζ were observed at pH>6. Based on a comparison of hydrodynamic radii (rh) obtained from dynamic light scattering and of transmission of 50% (T50 values) from the test tube experiments, the ability of anions to facilitate the dispersion of the clay fraction followed the sequence of oxalate>citrate>acetate>SO4 2->Cl-. It implies that adsorption of anions on positively charged edge sites of kaolinite resulting in a decrease in ζ is a key factor for dispersion of the clay fraction. Also, the results suggested that the dynamic light scattering can be used in combination with the test tube experiments in order to evaluate the effect of anions on dispersion at broader ranges of pH, ionic strength and clay concentration.

Title:	Effect of anions on dispersion of a kaolinitic soil clay: A combined study of dynamic light scattering and test tube experiments
Authors:	Nguyen Bui, Anh Thi Kim Dultz, Stefan Tran, Thu Thi Tuyet
Keywords:	Anion effect, Test tube, Light scattering, Dispersion
Issue Date:	2013
Publisher:	H. : ĐHQGHN
Abstract:	Dispersion is an important issue for clay leaching in soils. In this study, effects of various anions (Cl-, SO4 2-, acetate, oxalate and citrate) on dispersion of a kaolinitic soil clay were determined at different pH values and ionic strengths by dynamic light scattering and test tube experiments. Adsorption of anions on clay samples was characterized by the zeta potential (ζ) in a pH range of 2 to 11. At a pH range between 2 and 6, the effects of different anions on decreasing ζ were obvious and followed the order oxalate>citrate>SO4 2->Cl->acetate, while fluctuated changes in ζ were observed at pH>6. Based on a comparison of hydrodynamic radii (rh) obtained from dynamic light scattering and of transmission of 50% (T50 values) from the test tube experiments, the ability of anions to facilitate the dispersion of the clay fraction followed the sequence of oxalate>citrate>acetate>SO4 2->Cl-. It implies that adsorption of anions on positively charged edge sites of kaolinite resulting in a decrease in ζ is a key factor for dispersion of the clay fraction. Also, the results suggested that the dynamic light scattering can be used in combination with the test tube experiments in order to evaluate the effect of anions on dispersion at broader ranges of pH, ionic strength and clay concentration. © 2013 The Authors
Description:	Geoderma 209-210, pp. 209-213
URI:	http://repository.vnu.edu.vn/handle/VNU_123/27637
Appears in Collections:	Bài báo của ĐHQGHN trong Scopus