Electrokinetic remediation using surfactant-coated ceramic casings

Electrokinetic remediation is an emerging technique that can be used to rem ove metals from saturated or unsaturated soils. In unsaturated soils, contr ol of the medium's water content is essential. Previously used electrode de signs have caused detrimental soil wetting due to excess electroosmotic how out of ceramic-encased anodes. We tested a method to reverse the electroos motic flow at the anode by treating the ceramic casing with the cationic su rfactant hexadecyltrimethylammonium (HDTMA). Laboratory tests showed the un treated ceramic had an electroosmotic permeability of 2.4 x 10(-5) cm(2) V- 1 s(-1). Ceramic treated with HDTMA had an electroosmotic permeability of - 1.3 x 10(-5) cm(2) V-1 S-1. Under an applied electric potential, electroosm otic flow was reversed in the HDTMA-treated ceramic, indicating a reversed zeta potential due to formation of an HDTMA bilayer on the ceramic surface. Field tests conducted over a 6-month period showed negligible water loss f rom HDTMA-treated ceramic (0.03 L b(-1)) compared to untreated ceramics (up to 6 L h(-1)). The results indicated that a surfactant treatment to the an ode ceramic casing can greatly improve the application of electrokinetics i n unsaturated environments.