Chloroethene dehalogenation with ultrasonically produced air-stable nano iron.

Zerovalent iron (ZVI) has been demonstrated to be suitable for the dehalogenation of environmental pollutants such as chloroethenes. The construction of ZVI reactive barriers by conventional engineering measures is expensive and limited to shallow aquifers. The use of nanosized ZVI particles opens new opportunities to construct ZVI barriers with less invasive techniques. However, nanosized particles of pure ZVI are pyrophoric and react spontaneously with atmospheric oxygen. In this study, nanosized air-stable ZVI particles were produced by applying ultrasound to a solution of Fe(CO)(5) in edible oil. The resulting iron nanoparticles were dispersed in a carbon matrix, and coated with a non-crystalline carbon layer of approx. 2.5nm. Although, these nanoparticles are non-pyrophoric and stable in air, dechlorination of tetrachloroethene was demonstrated in synthetic aqueous medium and in polluted groundwater. Additionally, hydrogen was formed. Due to the larger surface area, significantly higher mass-normalized reaction rates of the novel carbon-coated nanoparticles were obtained as compared to conventional bulk ZVI material. Surface normalized pseudo-first-order-reaction rates of k(SA)=3.49x10(-3)Lh(-1)m(-2) and 2.33x10(-2)Lh(-1)m(-2) were calculated for the nano-ZVI and the bulk ZVI, respectively. Dechlorination reaction products of the novel nano-ZVI were trichloroethene, cis-dichloroethene, vinyl chloride, ethene, and ethane.