CATION-ENHANCED REMOVAL OF LEAD FROM KAOLINITE BY ELECTROKINETICS

Natural solutions containing clay extracts and synthetic solutions wit h varying concentrations of Al3+, Ca2+, and Na+ were used as anodic fl ushing solutions, and investigated for their enhanced in-situ removal of Pb from clay by electrokinetics (E-K). The experiments were conduct ed in a horizontal soil column apparatus with kaolin clay at an initia l concentration of 340-410 mu g Pb/g clay (dry) and 80-83% moisture co ntent. Natural flushing solutions were prepared by mixing water and cl ay in ratios varying from 2:1 to 40:1 by weight, and the supernatant w as used as an anodic hushing solution. The 7:1 natural solution was th e most effective in Pb removal. Synthetic solutions were prepared from the salts of Al3+, Ca2+, Na+, Mg2+, and K+ ions. Pb removal was highe st at a solution ionic strength of similar to 0.001 M for each element group, and with trivalent Al3+ and divalent Ca2+ ions at concentratio ns of similar to 6.4 x 10(-5) M and 3.1 x 10(-4) M, respectively. The 5.5 x Ca synthetic solution had the highest overall Pb removal efficie ncy. Energy expenditure/unit volume of soil for all experiments was 8- 31 kW.h/m(3).