Experimental study on remediation of chromium-contaminated mucky clay by electrokinetic soil flushing method considering temperature

A series of column tests on chromium-contaminated mucky clay are conducted in lab using the self-designed electrokinetic soil flushing apparatus considering temperature. The changes of the current and electrolyte solution pH, and the effects of the type of leaching agent, applied voltage and temperature on the removal behavior of chromium are analyzed. The results show that the chromium in soil can be removed effectively by the electrokinetic soil flushing method. When the voltage is 15 V, using sodium dodecylbenzene sulfonate (SDS) and oxalic acid (OA) as leaching agent, the removal ratio of Cr(VI) is 95.86% and 95.91% respectively, and the removal ratio of Cr (total) is 81.31% and 78.08% respectively. Raising temperature to 45℃ can promote complexation of oxalic acid and chromium leading to the migration of chromium, the removal ratio of Cr (VI) and Cr (total) reaches 99.65% and 82.50% respectively. However, raising temperature results in the removal ratio of Cr(total) by 10.99% when using SDS as leaching agent. Raising the voltage to 55 V, the chromium migration has slight effect on its migration. When using SDS and OA as leaching agents, the removal ratio of Cr(VI) can increase by 2.58% and 3.05% respectively, and that of Cr (total) can increase by 9.29% and 3.78% respectively. Lower voltage can be selected for the sake of saving energy. The water-soluble and weak acid-extracted chromium can be efficiently removed by the electrokinetic soil flushing method and the toxicity of contaminated soil can be reduced. After remediation, the soil structure is changed, and the pores between soil particles become smaller and the soil is more compacted.