Kinetics of Fe(III) precipitation in aqueous solutions at pH 6.0-9.5 and 25 °C
Kinetics of Fe(III) precipitation in aqueous solutions at pH 6.0-9.5 and 25 °C
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DOI：
10.1016/j.gca.2005.10.018
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发表时间：
2006-02-01
影响因子：
5
通讯作者：
Waite, TD
中科院分区：
文献类型：
--
作者：
Pham, AN;Rose, AL;Waite, TD
在pH 6.0-9.5的范围内，使用可见分光光度法，Fe-55辐射测定法结合螯合铁的离子对溶剂萃取和数值模拟的合成缓冲沃茨的Fe（III）沉淀的动力学进行了研究。沉淀速率（对于溶解的和总的无机铁物种而言是一级的）在pH约8.0时变化近两个数量级，最大速率常数为16 +/- 1.5 x 10（6）M-1 s（-1）。我们的研究结果支持溶解的中性物种Fe（OH）3的存在，计算了Fe（OH）3（0）沉淀的本征速率常数为k（Fe（OH）30）= 2.0 × 10（7）M-1 s（-1），从而预测了Fe（III）的沉淀速率在pH 6.0-9.5范围内沉淀。该速率常数的值，以及在所考虑的pH范围内的沉淀速率常数的变化，与铁沉淀的动力学由溶解的铁水解物种中的水交换速率控制的机制一致。(c)2005年爱思唯尔公司All rights reserved.
The kinetics of Fe(III) precipitation in synthetic buffered waters have been investigated over the pH range 6.0-9.5 using a combination of visible spectrophotometry, Fe-55 radiometry combined with ion-pair solvent extraction of chelated iron and numerical modeling. The rate of precipitation, which is first order with respect to both dissolved and total inorganic ferric species, varies by nearly two orders of magnitude with a maximum rate constant of 16 +/- 1.5 x 10(6) M-1 s(-1) at a pH of around 8.0. Our results support the existence of the dissolved neutral species, Fe(OH)3, and suggest that it is the dominant precursor in Fe(III) polymerization and subsequent precipitation at circumneutral pH. The intrinsic rate constant of precipitation of Fe(OH)(3)(0) was calculated to be k(Fe(OH)30) = 2.0 x 10(7) M-1 s(-1) allowing us to predict rates of Fe(III) precipitation in the pH range 6.0-9.5. The value of this rate constant, and the variation in the precipitation rate constant over the pH range considered, are consistent with a mechanism in which the kinetics of iron precipitation are controlled by rates of water exchange in dissolved iron hydrolysis species. (c) 2005 Elsevier Inc. All rights reserved.