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A field demonstration was performed in which nanoscale bimetallic (Fe/Pd) particles were gravity-fed into groundwater contaminated bytrichloroethene and other chlorinated aliphatic hydrocarbons at a manufacturing site. With diameters on the order of 100-200 nm, the nanoparticles are uniquely suited to rapidly degrade redox-amenable contaminants and for optimal subsurface delivery and dispersion. Approximately 1.7 kg of the nanoparticles was fed into the test area over a 2-day period, resulting in minimal clogging of the injection well. The test area was located within a well-characterized region of the contaminant plume and included an injection well and three piezometer couplets spaced 1.5 m apart. Despite the low nanoparticle dosage, trichloroethene reduction efficiencies of up to 96% were observed over a 4-week monitoring period with the highest values observed at the injection well and adjacent piezometers. Data from the field assessment were consistent with the results of pre-injection laboratory studies, which showed rapid dechlorination of target chlorinated compounds accompanied by a sharp decrease of standard oxidation potential and an increase in pH.

Iron nanoparticles are increasingly being applied in site remediation and hazardous waste treatment. Nearly a decade after it was first proposed in 1996, the iron nanoparticle technology is at a critical stage of its developmental process. Significant research innovations have been made in terms of synthetic methods, surface property modification, and enhancement for field delivery and reactions. Extensive laboratory studies have demonstrated that nanoscale iron particles are effective for the treatment of a wide array of common groundwater contaminants such as chlorinated organic solvents, organochlorine pesticides, polychlorinated biphenyls (PCBs), organic dyes, and various inorganic compounds. Several field tests have also demonstrated the promising prospective for in situ remediation. Nonetheless, there are still considerable knowledge gaps on many fundamental scientific issues (e.g., fate, transport, and environmental impact) and economic hurdles, which could determine the acceptance of the technology within the academic community as well as by regulators and the private sector. An overview of the iron nanoparticle technology is provided in this article, beginning with a description of the process fundamentals. This is followed by a discussion of the synthetic schemes for the nanoparticle types developed at Lehigh University. Next, a summary of the major research findings is provided, highlighting the key characteristics and remediation-related advantages of the iron nanoparticle technology versus the granular/microscale iron technology. A discussion of challenges related to its future directions and environmental impact is presented.

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Nano zerovalent iron (nZVI) is a promising remediation technology utilizing in situ chemical reduction (ISCR) to clean up contaminated groundwater at hazardous waste sites. The small particle size and large surface area of nZVI result in high reactivity and rapid destruction of contaminants. Over the past 20 years, a great deal of research has advanced the nZVI technology from bench‐scale tests to field‐scale applications. However, to date, the overall number of well‐characterized nZVI field deployments is still small compared to other alternative remedies that are more widely applied. Apart from the relatively high material cost of nZVI and questions regarding possible nanotoxicological side effects, one of the major obstacles to the widespread utilization of nZVI in the field is its short persistence in the environment due to natural reductant demand (NRD). The NRD for nZVI is predominantly due to reduction of water, but other reactions with naturally present oxidants (e.g., oxygen) occur, resulting in situ conditions that are reducing (high in ferrous iron phases and H2) but with little or no Fe(0). This article reviews the main biogeochemical processes that determine the selectivity and longevity of nZVI, summarizes data from prior (laboratory and field) studies on the longevity of various common types of nZVI, and describes modifications of nZVI that could improve its selectivity and longevity for full‐scale applications of ISCR. © 2016 Wiley Periodicals, Inc.