Remediation of lead (II)-contaminated soil using electrokinetics assisted by permeable reactive barrier with different filling materials

Abstract Removal of lead (II) (Pb2+) from contaminated soil was investigated using a new-type switchable-array-electrode electrokinetics assisted by permeable reactive barrier (SAE/EK-PRB). The soil pH after treatments with SAE/EK-PRB ranged from 3.5 to 4.8, and the peak values of current density was highest with 3.01 mA/cm2 at voltage gradient 2.5 V/cm. Both voltage gradient and moisture content promoted the removal of Pb2+. Moisture content 35% and 2.5 V/cm were considered as the optional operating conditions. Different PRB filling materials including zeolite, fly ash, active carbon alone and the combination of fly ash and graphene oxide were, therefore, investigated under the optional operating conditions. The highest removal reached 92.6% with the combination of fly ash and graphene oxide. Pb2+ forms in the soil with different PRB filling materials showed the percentages of weak bindings, such as exchangeable and carbonate forms decreased. However, strong binding, residual form increased largely, indicating the SAE/EK-PRB could effectively reduce the environmental risk of Pb2+ to a great extent. Fly ash and the combination of zeolite and fly ash as PRB filling materials demonstrated to be highly promising for the effective EK remediation of Pb2+-contaminated soil, taking the economic and environmental principles and remediation efficiency into consideration.