Effects of Molecular Composition of Natural Organic Matter on Ferric Iron Complexation at Circumneutral pH
Effects of Molecular Composition of Natural Organic Matter on Ferric Iron Complexation at Circumneutral pH
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DOI：
10.1021/es405496b
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发表时间：
2014-04-15
影响因子：
11.4
通讯作者：
Waite, T. D.
中科院分区：
文献类型：
--
作者：
Fujii, Manabu;Imaoka, Akira;Waite, T. D.
采用5-磺基水杨酸竞争配体法，在pH值为6.0-8.0、离子强度为0.06M的条件下，测定了不同来源的腐殖酸（HS）与三价铁（Fe[III]）络合的热力学和动力学参数。测得的铁结合性能，包括条件稳定常数和络合能力的范围超过2个数量级，这取决于原产地和特定的操作定义的分数HS检查。络合参数的HS的化学性质的范围内的统计比较表明铁（III）络合能力和芳香族碳含量在HS在所有pH值检查之间的强正相关性。相比之下，络合能力被确定为比存在的羧基和酚基的浓度小几个数量级。因此，特定的官能团，包括那些居民在附近的芳香族结构内的HS可能是优选的Fe（III）的协调条件下检查。总体而言，我们的研究结果表明，在自然沃茨中溶解的Fe（III）络合物的浓度是在很大程度上影响HS特性的变化，除了其他众所周知的因素，如HS浓度和性质和浓度的竞争阳离子存在。
Thermodynamic and kinetic parameters for ferric iron (Fe[III]) complexation by well-characterized humic substances (HS) from various origins were determined by a competitive ligand method with 5-sulfosalicylic acid at circumneutral pH (6.0-8.0) and an ionic strength of similar to 0.06 M. The measured Fe binding properties including conditional stability constants and complexation capacities ranged over more than 2 orders of magnitude, depending on the origin and the particular operationally defined fraction of HS examined. Statistical comparison of the complexation parameters to a range of chemical properties of the HS indicated a strong positive correlation between Fe(III) complexation capacity and aromatic carbon content in the HS at all pHs examined. In contrast, the complexation capacity was determined to be up to a few orders of magnitude smaller than the concentration of carboxylic and phenolic groups present. Therefore, specific functional groups including those resident in the proximity of aromatic structures within the HS are likely preferable for Fe(III) coordination under the conditions examined. Overall, our results suggest that the concentration of dissolved Fe(III) complexes in natural waters is substantially influenced by variation in HS characteristics in addition to other well-known factors such as HS concentration and nature and concentration of competing cations present.