Electrochemical extraction and stabilization of selected inorganic species in porous media

There are metal and alkaline earth species which tend to remain ionic under a large range of pH and redox potential values. Those substances are expected to electromigrate and separate even under high pH and variable redox conditions unless they become adsorbed onto soil surfaces and clay interstices. In this study, first near complete separation of Na and Cl was accomplished in samples of drilling mud sludge recovered from a settling pond. Na recovery was invariable with the quantity of water flow through the sludge specimens of various initial degrees of water saturation. High recovery of Na and Cl was demonstrated with less than 0.5 pore volume of electroosmotic water flow. In most field situations, the contaminants are often found adsorbed onto soil surfaces. Natural buffering capacity of soil may hinder desorption and dissolution or high pH generated at the cathode site may cause insoluble hydroxide precipitates of some metal contaminants. Under such circumstances, electrochemistry may still be useful to stabilize and contain certain groups of contaminants in the ground. In this study, use of electrochemical process to deliver Fe(II) to reduce soluble species Cr(TV) to a less toxic and less soluble species Cr(III) was demonstrated in the laboratory. (C) 1997 Elsevier Science B.V.