Arsenic(III) oxidation by iron(VI) (ferrate) and subsequent removal of arsenic(V) by iron(III) coagulation
Arsenic(III) oxidation by iron(VI) (ferrate) and subsequent removal of arsenic(V) by iron(III) coagulation
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DOI：
10.1021/es034203
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发表时间：
2003-12-15
影响因子：
11.4
通讯作者：
Yoon, J
中科院分区：
文献类型：
--
作者：
Lee, Y;Um, IH;Yoon, J
我们研究的化学计量，动力学，和机制的亚砷酸盐[As（III）]氧化高铁酸盐[Fe（VI）]，并进行砷的去除试验，使用Fe（VI）作为氧化剂和混凝剂。As（III）被Fe（VI）氧化为As（V）（砷酸盐），化学计量比为3：2 [As（III）：Fe（VI）]。动力学研究表明，As（III）与Fe（VI）的反应对于两种反应物都是一级反应，在25 ℃时，随着pH值从8.4增加到12.9，观察到的二级反应速率常数从（3.54 +/- 0.24）x 10（5）非线性降低到（1.23 +/- 0.01）x 10（3）M-1 s（-1）。提出了Fe（VI）氧化As（III）的氧转移反应机理。用河水进行的砷去除试验表明，用最低2.0毫克L-1的Fe（VI），砷浓度可以从最初的517降低到50微克L-1以下，这是孟加拉国砷的规定水平。从这个结果，Fe（VI）被证明是非常有效的去除砷物种从水中在一个相对较低的剂量水平（2.0毫克L-1）。此外，结合使用少量的Fe（VI）（低于0.5 mg L-1）和Fe（III）作为主要的混凝剂被认为是一个实用和有效的方法去除砷。
We investigated the stoichiometry, kinetics, and mechanism of arsenite [As(III)] oxidation by ferrate [Fe(VI)] and performed arsenic removal tests using Fe(VI) as both an oxidant and a coagulant. As(III) was oxidized to As(V) (arsenate) by Fe(VI), with a stoichiometry of 3:2 [As(III):Fe(VI)]. Kinetic studies showed that the reaction of As(III) with Fe(VI) was first-order with respect to both reactants, and its observed second-order rate constant at 25 degreesC decreased nonlinearly from (3.54 +/- 0.24) x 10(5) to (1.23 +/- 0.01) x 10(3) M-1 s(-1) with an increase of pH from 8.4 to 12.9. A reaction mechanism by oxygen transfer has been proposed for the oxidation of As(III) by Fe(VI). Arsenic removal tests with river water showed that, with minimum 2.0 mg L-1 Fe(VI), the arsenic concentration can be lowered from an initial 517 to below 50 mug L-1, which is the regulation level for As in Bangladesh. From this result, Fe(VI) was demonstrated to be very effective in the removal of arsenic species from water at a relatively low dose level (2.0 mg L-1). In addition, the combined use of a small amount of Fe(VI) (below 0.5 mg L-1) and Fe(III) as a major coagulant was found to be a practical and effective method for arsenic removal.