Determination of surface potential of kaolinite for selection of optimal enhancement pattern for removal of heavy metal contaminant in electrokinetics remediation

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Document Type : Article

Authors

1 -Bu-Ali Sina University -University of Tehran

2 Civil Eng. Department, Faculty of Eng., Bu-Ali Sina University

3 Civil Eng. Department,, Faculty of Eng. Bu-Ali Sina University

4 Civil Eng. Department, Faculty of Eng. Bu Ali Sina University

Abstract

Buffering capacity measurement is one of the common methods to evaluate the contaminant retention by soil or the selection of enhancement method for contaminant removal. However, due to the limitations of this experiment the quantitative use of the results of this experiment involves noticeable errors. The main objective of this paper is to present theoretical and practical insights of zeta potential theory to optimize removal of heavy metal contaminants from clayey soils. To achieve this objective series of zeta potential experiments, buffering capacity measurement, SEM photograph, XRD experiments and batch equilibrium tests were performed on kaolinite, decarbonated kaolinite and washed kaolinite samples. The experiments were performed to align the direction of electro-osmosis flow with the ion migration phenomenon. Based on the results of this paper, with determination of variation of surface potential of clay at different geo-environmental conditions, the curve of zeta potential can be divided to three zones which are called retention, stable and desorption sections. As the carbonate content of sample increases the length of stable section in zeta potential curve increases which shows the resistance of soil to contaminant removal. Based on these three different areas, with selection of optimum enhancement pattern, one can align the direction of electro-osmosis flow with the ion migration phenomenon. Consequently, more uniform removal of heavy metals and an increase in efficiency of electrokinetics method will be achieved. Furthermore, according to the results of this paper as the concentration of heavy metal increases, due to the reduction of double layer thickness the zeta potential reduces which might cause a change in electro-osmosis direction at relatively high heavy metal concentration. Finally, it is shown that the use of fundamental aspect of surface potential of clays with the concept of different retention phases of contaminant in soil is an applicable and theoretical method for optimized contaminant removal from clayey soils.

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Sharif Journal of Civil Engineering

Articles in Press, Accepted Manuscript
Available Online from 20 December 2024

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