Electrokinetically enhanced removal and degradation of nitrate in the subsurface using nanosized Pd/Fe slurry

Abstract

The aim of this work was to evaluate the effectiveness of transporting the slurry of Pd/Fe bimetallic nanoparticles under an electric field in the subsurface for in situ removal and degradation of nitrate. To mimic the subsurface environment, a bench-scale horizontal column packed with nitrate-contaminated soil was treated by electrokinetic (EK) remediation coupled with the injection of nanosized Pd/Fe slurry. The estimated transport distance of Pd/Fe nanoparticles in soil based on the calculated sticking coefficient was about 9 meters by the enhancement of electrokinetics, primarily by electroosmotic (EO) flow. By injecting the nanosized Pd/Fe slurry into the anode reservoir coupled with the application of an electric field (i.e., Test 2) would result in the greatest overall removal efficiency of nitrate in soil and reservoir fluids as compared with other injection positions, the cathode reservoir being the worst injection spot. In Test 2, over 99% of nitrate in the whole system was removed and degraded even only 0.05 wt% of nanoscale Pd/Fe bimetal was injected.

Keywords:

• Electrokinetic
• removal and degradation
• nitrate
• nanosized Pd/Fe slurry
• injection
• transport
• subsurface environment

Acknowledgments

The authors are grateful for the financial supports from National Science Council of Taiwan (NSC 94-2211-E-110-014) and Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung, Taiwan.