Effect of Mixed Anions (HCO3−−SO42−−ClO4−) on Granular Iron (Fe0) Reactivity
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- 作者：Erping Bi ; Ian Bowen ; J. F. Devlin
- 刊名：Environmental Science & Technology
- 出版年：2009
- 出版时间：August 1, 2009
- 年：2009
- 卷：43
- 期：15
- 页码：5975-5981
- 全文大小：176K
- 年卷期：v.43,no.15(August 1, 2009)
- ISSN：1520-5851
文摘
Batch experiments were conducted with granular iron (Fe0) in pH 10 solutions of 4-chloronitrobenzene (4ClNB) and mixed anions (ClO4−, SO42−, and HCO3−). In pure solutions, SO42− is known to enhance Fe0 reactivity, whereas HCO3− has been variously reported to depress Fe0 reactivity or enhance it. ClO4− has been found to be minimally reactive with Fe0. It was hypothesized that the effects of the anions on reactivity were mutually independent, and the combined effects could be predicted from simple mixing lines. In concentrated carbonate solutions (>25% of the bicarbonate salt content in 8 mM ionic strength solutions), the hypothesis was supported. In mixtures where the aqueous carbonate species concentrations were low (<25% of the salt content in 8 mM ionic strength solutions) an anomalous reactivity enhancement was noted. Geochemical modeling using PHREEQC suggested that precipitation of Fe(OH)2(a) in preference to FeCO3(s) in weak carbonate solutions freed CO32− to corrode the iron, causing the deviation from the mixing line prediction. SEM analysis confirmed higher carbon presence on iron that had contacted carbonate rich solutions compared to iron that had not.