[Remediation of chromate contaminated soils by combined technology of electrokinetic and iron PRB].

Remediation efficiency on artificial chromate [Cr (VI)] contaminated soil and a field Cr (VI) contaminated soil around industrial Cr residue (Tianjin Tongsheng Chemical and Industrial Factory) by using electrokinetic method was studied. Moreover, the electrokinetic method was combined with iron permeable reactive barrier (PRB) and a better combination mode was found. The remediation efficiency of the combined method was compared with electrokinetic method. The results showed that Cr (VI) contaminated soil can be remedied effectively by electrokinetic method. For artificial contaminated soil, the removal ratio of Cr (VI) reached 98%-100%, while the total Cr was removed about 80% near the anode, and more than 90% near the cathode, where the content of Cr came back to soil background. The reduction of Cr (VI) to Cr (III) occurred during the soil remediation, and more than 90% of the residual Cr was Cr (III) at the end of remediation. More than 98% Cr (VI) were removed, whereas only 75%-77% of total Cr were removed from the heavily contaminated field soil as the soil contained 28% Cr (III) initially. Soil pH increased near the cathode and decreased near the anode, while the change of soil pH was insignificant in the middle. In situ combination mode of electrokinetic and PRB is a better method that could take the full advantages of the two technologies. The removal efficiency of total Cr was about 90% at the end of the remediation, which is better than electrokinetic method especially near the anode, and had less effect on soil pH.