Physico-chemical limitations during the electrokinetic treatment of a polluted soil

Abstract

a b s t r a c tThe influence of the ion-exchange solid/liquid reaction on electrokinetic transport phenomena was studied and modelled for a non-permeable porous medium composed of kaolin. Kaolin was selected to model a low-permeable medium, even though it is usually considered to have low ion-exchange capacity and weak selectivity. The influence of this reaction on the characteristic time of the process was demonstrated by studying the lithium (Li + ) electrokinetic transport on a sodium (Na + ) pre-saturated kaolin. Experimental results were obtained using apparatus developed specifically for the study of the electrokinetic transport and which has been well characterized in previous works. The tests were performed by introducing a solution containing Li + at the anode, and measuring the Na + and Li + concentrations at the cathode outlet. Under operating conditions, local equilibrium is assumed in the medium. The equilibrium isotherm of Li + /Na + exchange was determined by independent experiments on a laboratory column. Ion-exchange equilibrium can be satisfactorily described by a linear isotherm. A theoretical model based on the tanksin-series model was used for modeling the experimental results of the Li + electrokinetic transport. This model considers electro-migration and electro-osmosis as the only transport mechanisms, and takes into account the solid/liquid reaction by a retardation factor, as is usually the case for linear equilibrium models. The comparison between experimental and theoretical results shows that the chemical solid/liquid reaction at least doubles the characteristic time of the transport.

Migration of ions and organic matter during electro-dewatering of anaerobic sludge

“…5a). Similar fluctuation of Na + was also observed by Fernandez et al [40] who investigated electrokinetic transport of Na + in kaolin. Moreover, a decrease in the sludge loading rate resulted in the shorter time to achieve the highest concentrations of Na + in the removed water at the cathode.…”

“…According to Acar and Alshawabkeh [9] and Fernandez et al [40], the relation between electro-migration of ions and the electrical potential gradient can be explained by Eq. (2).…”

Influence of Filter Cell Configuration and Process Parameters on the Electro-Osmotic Dewatering of Sewage Sludge

“…The soluble organic matter migrates preferentially toward the anode where it is partly oxidized at the anode. Indeed, as observed by Fernandez et al (36), the dominant electrochemical reaction is usually the water electrolysis but other electrochemical reactions may also take place spontaneously.…”

Physicochemical sensitivities of tropical peat to electrokinetic environment

“…The technique has been employed for dewatering, consolidation, stabilization (Casagrande, 1949, Asavadorndeja andGlawe, 2005), and contaminant removal of crystalline mineral soils (Weng and Yuan, 2001;Han et al, 2004;Kim et al, 2005;Lee et al, 2007;Castillo et al, 2008;Fernandez et al, 2009). The literature reports that the application of EK to a soil results in changes in soil pH due to electrolysis reactions, water flow between the electrodes, and migration of ions towards the electrode of the opposite sign (Acar et al, 1990;Acar and Alshawabkeh, 1993;Mitchell and Soga, 2005;Asavadorndeja and Glawe, 2005).…”