Cwiertny David M, Bransfield Stephen J, Roberts A Lynn
Department of Geography and Environmental Engineering, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA.
Environ Sci Technol. 2007 May 15;41(10):3734-40. doi: 10.1021/es062993s.
Anticipating which pollutants are amenable to treatment by iron-based bimetallic reductants requires an understanding of the mechanism(s) driving pollutant reduction. Here, batch studies with six bimetals (Au/Fe, Co/Fe, Cu/Fe, Ni/ Fe, Pd/Fe, and Pt/Fe) and four oxidants (alkyl polyhalides, vinyl polyhalides, alkynes, and water) explored the influence of the electron acceptor on reductant reactivity. Bimetals exhibited disparate reactivity toward some oxidant classes. For example, Pt/Fe enhanced rates of cis-dichloroethylene reduction, but it inhibited the reduction of several alkyl polyhalides. Moreover, the rate increase for vinyl polyhalide reduction by Ni/Fe (approximately 100-fold) and Pd/Fe (approximately 1000-fold) was far greater than that measured for alkyl polyhalides (approximately 10-fold), and reactivity toward vinyl polyhalides exhibited a more pronounced dependence on Ni and Pd loadings than did reactivity toward alkyl polyhalides. These results suggest that the reactions of alkyl and vinyl polyhalides with iron-based bimetals involve different active reductants. Neither rates of alkyl nor vinyl polyhalide reduction correlated with rates of iron corrosion by water, contrary to expectations if galvanic corrosion was primarily responsible for organohalide reduction. Trends observed for the hydrogenation of 2-butyne did mirror the sequence we identified for 1,1,1-trichloroethane reduction, consistent with a role for atomic hydrogen as the principal electron donor in these two systems.
要预测哪些污染物适合用铁基双金属还原剂处理，就需要了解驱动污染物还原的机制。在此，我们进行了一系列批量研究，使用六种双金属（金/铁、钴/铁、铜/铁、镍/铁、钯/铁和铂/铁）和四种氧化剂（烷基多卤化物、乙烯基多卤化物、炔烃和水），探讨了电子受体对还原剂反应活性的影响。双金属对某些氧化剂类别表现出不同的反应活性。例如，铂/铁提高了顺式二氯乙烯的还原速率，但抑制了几种烷基多卤化物的还原。此外，镍/铁（约100倍）和钯/铁（约1000倍）对乙烯基多卤化物还原速率的提高远大于对烷基多卤化物的提高（约10倍），并且与烷基多卤化物相比，对乙烯基多卤化物的反应活性对镍和钯负载量的依赖性更强。这些结果表明，烷基和乙烯基多卤化物与铁基双金属的反应涉及不同的活性还原剂。与电偶腐蚀主要负责有机卤化物还原的预期相反，烷基和乙烯基多卤化物的还原速率均与水对铁的腐蚀速率无关。在2-丁炔氢化反应中观察到的趋势确实反映了我们为1,1,1-三氯乙烷还原确定的顺序，这与原子氢在这两个系统中作为主要电子供体的作用一致。
