Electrokinetic-enhanced transport of lactate-modified nanoscale iron particles for degradation of dinitrotoluene in clayey soils

This study investigated the transport and reactivity of bare nanoscale iron particles (NIP) and lactate modified NIP (LM-NIP) in low permeability clayey soils contaminated with dinitrotoluene (DNT) under applied electric potential. Bench-scale electrokinetic experiments were performed at constant voltage gradient (1 VDC/cm) with DNT spiked kaolinite at a concentration of 920 mg/kg. A cylindrical Plexiglas cell (3.81 cm inner diameter, 13.5 cm length) specially designed for this study was used. NIP or LM-NIP at a concentration of 4 g/L was injected at location 3 cm from the anode. Aluminum lactate 10% (w/w) was used as modifier for LM-NIP. The results showed 41–65% of DNT degradation in the soil near the anode, while it was lower at 30–34% near the cathode. The highest DNT degradation was achieved using LM-NIP. The total degradation of DNT was attributed to both NIP and electrochemical process. Overall it was found that electrokinetic system can enhance the delivery of nanoscale iron particles in low permeability soils for the degradation of energetic organic contaminants such as DNT.

► Application of voltage gradient was able to produce electro-osmotic flow in the low permeability kaolin soil when bare nanoscale iron particles (NIP) or lactate-modified NIP (LM-NIP) were used.
► Better delivery of NIP into the soil was achieved when using LM-NIP.
► About 41 to 65% of dinitrotoluene (DNT) was degraded in the soil near the anode, while 30 to 34% was degraded near the cathode; with the highest DNT degradation achieved using LM-NIP.
► The DNT degradation was primarily due to the NIP reductive capacity within the soil and electrochemical reduction of any DNT migrated into the cathode.