Insights into the enhanced electrokinetic remediation of lead and cadmium contaminated soil with the composite electrolyte of citric acid and calcium chloride

Electrolyte is one of the critical factors for the efficient and green implementation of electrokinetic remediation (EK). Modelling of enhanced EK in the complex heavy metal contaminated soils was designed. Enhanced electrokinetic remediation experiments with composite electrolyte (citric acid + calcium chloride) were conducted to investigate their influence on the removal of cadmium (Cd) and lead (Pb), depletion of soil cations, and electric energy consumption. The results indicated that the removal efficiency of lead and cadmium rose from 10.8% and 14% to 15.1% and 22.5%, at the same time, the power consumption increased from 140.4 to 402 Wh since calcium chloride was added to citric acid. With the extension of time, the highest removal of Pb and Cd were 58% and 99.2%, respectively, in the section of S1 where soil pH was 2.5. The dominant cations (detected) in the pore water of the soil were Ca2+, Mg2+, and Mn2+, which was more evident with the extension of time. Lead-cadmium transmission efficiency under the electric field was lowered because the ratio of the heavy metal ions to the total amount of cations was very low, especially with the addition of calcium chloride.