Article

Dechlorination of trichloroethylene in aqueous solution by noble metal-modified iron

Graduate Institute of Environmental Engineering, National Taiwan University, 71 Chou-Shan Road, Taipei 106, Taiwan.
Journal of Hazardous Materials (Impact Factor: 4.53). 12/2004; 116(3):219-28. DOI: 10.1016/j.jhazmat.2004.09.005
Source: PubMed

ABSTRACT

Bimetallic particles are extremely interesting in accelerating the dechlorination of chlorinated organics. Four noble metals (Pd, Pt, Ru and Au), separately deposited onto the iron surface through a spontaneous redox process, promoted the TCE dechlorination rate, and the catalytic activity of the noble metal followed the order of Pd>Ru>Pt>Au. This order was found to be dependent on the concentrations of adsorbed atomic hydrogen, indicating that the initial reaction was cathodically controlled. Little difference in the distribution of the chlorinated products for the four catalysts (cis-DCE: 51%; 1,1-DCE: 27%; trans-DCE: 15% and VC: 7%) was observed. The chlorinated by-products accumulated in both Pt/Fe and Au/Fe (10.3% and 2.5% of the transformed TCE, respectively), but did not accumulate in Pd/Fe and Ru/Fe. Ru/Fe was further examined as an economical alternative to Pd/Fe. The 1.5% Ru/Fe was found to completely degrade TCE within 80 min. Considering the expense, the yield of chlorinated products and the lifetime of a reductive material, Ru provides a potential alternative to Pd as a catalyst in practical applications.

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    • "Some authors suggest that catalysts like Pd and Ni could absorb the H 2 produced by iron corrosion into its lattice to form a transitional compound that can accelerate the reductive dechlorination of the COCs (Xu et al., 2005, Wang et al., 2013). On the other hand, other researchers have advanced that the removal mechanism by bimetallic NP is based on the attack of the hydrogen produced by ZVI corrosion to the contaminant that is adsorbed onto the surface of the metal acting as a catalyst, resulting in the dechlorination of the COC (the parent compound and its chlorinated degradation compounds) (Cwiertny et al., 2007; Schrick et al., 2002; Lin et al., 2004). However, the studies to elucidate the mechanism of bimetallic NP operation are still scarce or plainly lacking. "
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    • "permeable reactive barrier), high pH condition is typically developed in the reaction zone due to Fe(0) oxidation, but external pH control is not practically feasible once reaction is initiated . Some researchers have employed noble metals such as palladium , nickel, and platinum to promote rate of contaminants reduction by Fe(0) (Kim and Carraway, 2000; Lin et al., 2004; He and Zhao, 2008). Although contaminants can be reduced in bimetallic system more rapidly, high cost of noble metals limits its use in field-scale application. "
    Dataset: p2013i1

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    • "In 2004, the U.S. Environmental Protection Agency [6] reported that of the 976 National Priorities List (1982–2003), a large number of these sites contain both BTEX and chlorinated compounds. The most popular technologies used for BTEX and chlorinated solvents remediation are biodegradation (microbial oxidation, [1,7–11]) and zero-valent iron (ZVI, [12] [13] [14] [15] [16] [17]). These two technologies can be combined to treat the mixed plumes of BTEX and chlorinated compounds. "
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