Cation-Enhanced Removal of Lead from Kaolinite by Electrokinetics

Abstract

Natural solutions containing clay extracts and synthetic solutions with varying concentrations of Al3+, Ca2+, and Na+ were used as anodic flushing solutions, and investigated for their enhanced in-situ removal of Pb from clay by electrokinetics (E-K). The experiments were conducted in a horizontal soil column apparatus with kaolin clay at an initial concentration of 340–410 μg Pb/g clay (dry) and 80–83% moisture content. Natural flushing solutions were prepared by mixing water and clay in ratios varying from 2:1 to 40:1 by weight, and the supernatant was used as an anodic flushing solution. The 7:1 natural solution was the most effective in Pb removal. Synthetic solutions were prepared from the salts of Al3+, Ca2+, Na+, Mg2+, and K+ ions. Pb removal was highest at a solution ionic strength of ∼0.001 M for each element group, and with trivalent Al3+ and divalent Ca2+ ions at concentrations of ∼6.4 × 10−5 M and 3.1 × 10−4 M, respectively. The 5.5 × Ca synthetic solution had the highest overall Pb removal efficiency. Energy expenditure/unit volume of soil for all experiments was 8–31 kWs˙h/m3.