Environmental Remediation of Dense Non-Aqueous-Phase Liquids Using Multifunctional Iron-Carbon Nanocomposites

Dense non-aqueous phase liquids, such as trichloroethylene (TCE) and carbon tetrachloride (CCl₄), are widespread groundwater and soil contaminants which cause long-term environmental pollution. Extensive efforts have been carried out to develop the optimal remediation strategy. Here, we will introduce a composite with carbon submicrospheres serving as the supports and embedded nanoscale zero valent iron (NZVI) being the reactive agent to treat TCE and dechlorinate it to non-toxic products. This Fe-C composite unites the current prominent method of using NZVI with the hydrophobic nature of carbon, which enables the composites to target organic contaminants and facilitates the dehalogenation reaction by increasing the local concentration of TCE in the vicinity of iron particles through rapid TCE adsorption. Besides, hydrophobically modified chitosan (HMC) can be easily coated around the carbon supports to enhance the suspension stability of these submicrospheres in groundwater.  

This composite has been proven to be effective and has several conspicuous advantages: (a) the synthesize process is a simple one-step process with inexpensive precursors and can be scaled up to manufacturing level (b) the NZVI particles are well dispersed on the carbon support, preventing them from aggregation, which eliminates the major challenge of using NZVI (c) composite particles are of the optimal size for transport through sediments (d) toxic intermediates such as dichloroethane (C₂H₂Cl₂) and vinyl chloride (C₂H₃Cl) can be sequestered within the carbon supports until they reacted to final light gas products.

The presentation will focus on the detailed materials synthesizing and characterization, and the significant aspects of adsorption, transport and reaction of this composite in remediation of groundwater contaminants will be discussed.