Enhanced electrokinetic remediation of heavy metals contaminated soil by biodegradable complexing agents.

ABSTRACT

In this study, an electrokinetic technique for remediation of Pb2+, Zn2+ and Cu2+ contaminated soil was explored using sodium alginate (SA) and chitosan (CTS) as promising biodegradable complexing agents. The highest Cu2+ (95.69%) and Zn2+ (95.05%) removal rates were obtained at a 2 wt% SA dosage, which demonstrated that SA significantly improved the Cu2+ and Zn2+ removal efficiency during electrokinetic process. The abundant functional groups of SA allowed metal ions desorption from soil via ion-exchange, complexation, and electrolysis. Pb2+ ions were difficult to remove from soil by SA due to the higher gelation affinity with Pb2+ than Cu2+ and Zn2+, despite the Pb2+ exchangeable fraction partially transforming to the reducible and oxidizable fractions. CTS could complex metal ions and migrate into the catholyte under the electric field to form crosslinked CTS gelations. Consequently, this study proved the suitability of biodegradable complexing agents for treating soil contaminated with heavy metals using electrokinetic remediation.