Electrolyte conditioning for electrokinetic remediation of As, Cu, and Pb-contaminated soil

We carried out electrokinetic remediation with electrolyte conditioning and pretreatment using acidic and basic solutions to remediate Cu-, As-, and Pb-contaminated soil on a laboratory scale. Under given conditions the soil pH was made more acidic or more basic, and the pH change influenced the strength of the binding of metals and metalloids onto the soil surface. Catholyte conditioning using an acidic solution increased the removal of Cu and Pb from the soil, and the maximum removal was 60.1% for Cu and 75.1% for Pb. Anolyte conditioning using a basic solution enhanced the transport of arsenic (As), which exists in an anionic form. Even though most of the As was strongly bound to the soil matrix in a residual form (≥95%), 43.1% was removed by electrokinetics under anolyte conditioning with a basic solution. Simultaneous removal was attempted via a change in the purging solution. However, blocking phenomena occurred because of the sudden pH change of the electrolyte from acidic to basic, and the electrokinetic transport of the ionic species was interrupted in the soil compartment. Thus, catholyte or anolyte conditioning removed cationic or anionic metals from the soil, but the simultaneous removal of both was not achieved, and a sudden change in the conditioning solution caused precipitation of metal hydroxides and blocking of the pores.

Figure optionsDownload as PowerPoint slideHighlights
► Pretreatment and catholyte conditioning with an acidic solution enhanced the desorption and migration of Cu and Pb in an electric field.
► Catholyte-conditioning electrokinetic remediation with NaOH increased the removal efficiency of arsenic because of anion exchange with hydroxide ions under basic conditions.
► A change in the electrolyte from acidic to basic was not effective for simultaneously remediating multi-metal-contaminated soil because a blocking phenomenon is introduced by the sudden pH change in the electrolyte.