The use of phosphate (PO4
3-) and/or EDTA to enhance the removal of arsenate (As(V))
from gold mine tailings by electrokinetic remediation (EKR) was investigated. The eff ect of
diff erent concentrations of PO4
3- or EDTA on As (50 mg/L) movement was fi rst evaluated in a
two-layered agar matrix with EKR at 2 V/cm for 72 h. Subsequently, the assay was repeated
for As-contaminated mine tailings (60 mg/kg), by applying the EKR for 168 h and using
the additive concentrations that gave maximal levels of As at the anode. The upper 10-cm
layer of agar was uncontaminated, while the lower 10-cm layer was contaminated with As
with or without the added PO4
3- (P) and/or EDTA (E) at 25, 50, or 75 mg/L of agar. The As
was translocated and accumulated at the anode at higher levels in the presence of 50 mg/L of
PO4
3-(P50) or EDTA (E50) than in the control. With the addition of P50, the As level increased
in the upper layer, whereas with E50 the As mainly accumulated in the lower layer. The coaddition
of both P50 and E50 (P50/E50) led to As accumulation in both the upper and lower
layers at essentially the same level. The pH, Eh, and EC in the tailing under EKR changed
less in P50 and E50 than in the control, but diff ered between each other. P50 supplementation
caused As to accumulate at the anode by electromigration, whereas in the control As migrated
to accumulate at the cathode and also in-between the cathode and anode by electro-osmosis.
In contrast, E50 and the combined P50/E50 addition did not result in a signifi cant As
concentration in each zone, but showed a trend of a decreased concentration at the cathode.