Beijing Key Laboratory of Water Resources and Environmental Engineering, China University of Geosciences, Beijing 100083, China.
Water Sci Technol. 2013;67(6):1254-9. doi: 10.2166/wst.2013.689.
Zero-valent iron (ZVI) application in groundwater remediation is limited by its vulnerability to passivation, which significantly decreases its surface reactivity. Both biological and chemical processes can potentially passivate ZVI, although the understanding of biological passivation is limited. This study was conducted in bench-scale reactors packed with fresh ZVI or ZVI pre-exposed to nitrate (NO3(-)) and in the presence or absence of a denitrifying bacterial enrichment (DNBE). The first-order rate coefficients (k) for NO3(-) reduction by ZVI in the presence and absence of DNBE were 0.20 and 0.09 s(-1), respectively, suggesting that both ZVI and microbes contribute to NO3(-) removal. Abiotic reduction of nitrate was observed in reactors with trichloroethene (TCE) if ZVI was present; however, it resulted in reduced rates of TCE reduction (k = 0.29 s(-1)) when compared to reactors with fresh ZVI and no nitrate (k = 0.55 s(-1)). The TCE reduction efficiency decreased by 49% (k = 0.15 s(-1)) in the presence of DNBE, suggesting that microbial growth on ZVI or catalyzed oxidation of ZVI surface can inhibit TCE reduction by ZVI. Contrary to the presumption that denitrification may decrease ZVI passivation by nitrate, results from this study suggest that denitrifying bacteria actually exacerbate ZVI passivation.
零价铁 (ZVI) 在地下水修复中的应用受到其易钝化的限制，这大大降低了其表面反应性。生物和化学过程都可能使 ZVI 钝化，但对生物钝化的理解有限。本研究在填充新鲜 ZVI 或预先暴露于硝酸盐 (NO3(-)) 的 ZVI 的台式反应器中进行，并在存在或不存在反硝化细菌富集 (DNBE) 的情况下进行。有和没有 DNBE 时 ZVI 还原硝酸盐的一级速率系数 (k) 分别为 0.20 和 0.09 s(-1)，这表明 ZVI 和微生物都有助于去除硝酸盐。如果存在 ZVI，则在含有三氯乙烯 (TCE) 的反应器中观察到硝酸盐的非生物还原；然而，与没有硝酸盐的新鲜 ZVI 相比，它导致 TCE 还原速率降低 (k = 0.29 s(-1))。当存在 DNBE 时，TCE 还原效率降低了 49%（k = 0.15 s(-1)），这表明 ZVI 上的微生物生长或 ZVI 表面的催化氧化可以抑制 ZVI 还原 TCE。与反硝化可能通过硝酸盐降低 ZVI 钝化的假设相反，本研究的结果表明，反硝化细菌实际上加剧了 ZVI 的钝化。
