Advanced remediation using nanosized zero-valent iron and electrical current in situ − A comparison with conventional remediation using nanosized zero-valent iron alone

Abstract

This study presents an advance on the standard in situ reductive remediation technique using nanosized zero valent iron (NZVI). The initial process used a conventional form of NZVI, NANOFER 25S (NANO IRON, s.r.o.), at a site contaminated with chlorinated hydrocarbons (CHC) in 2014. In 2018, levels of contamination at the site were still too high; hence, a second remediation intervention was performed using a cheaper form of NZVI, NANOFER STAR DC (NANO IRON, s.r.o.), accompanied with application of an electrical current (DC). The physical-chemical parameters at the site showed moderate reductive conditions for both techniques. While remediation with NANOFER 25S showed a continuous decrease in NZVI activity over time, application of NANOFER STAR DC + DC resulted in a long-term reductive effect, observable as a persistent decrease in CHC concentration and evolution of ethene and ethane dechlorination products. NZVI in the STAR DC + DC was still active after around 200 days. Final efficiency of the STAR DC + DC method was calculated at 3.7 times higher than the conventional technique using NANOFER 25S only. Laboratory-scale experiments confirmed the field observations, indicating the significantly elevated effectivity of STAR DC + DC.