Understanding the Reduction Kinetics of Aqueous Vanadium(V) and Transformation Products Using Rotating Ring-Disk Electrodes
Understanding the Reduction Kinetics of Aqueous Vanadium(V) and Transformation Products Using Rotating Ring-Disk Electrodes
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DOI：
10.1021/acs.est.7b02021
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发表时间：
2017-10-17
影响因子：
11.4
通讯作者：
Liu, Haizhou
中科院分区：
文献类型：
--
作者：
Chen, Gongde;Liu, Haizhou
钒(V)是最新的环境保护署候选污染物清单（CCL4）中的一种新兴污染物。钒的氧化还原化学控制着其在水生环境中的发生，但钒(V)形态对氧化还原性质的影响在很大程度上仍是未知的。本研究利用旋转环盘电极技术研究了在存在和不存在磷酸盐的情况下，四种pH和浓度依赖的钒酸盐(V)的还原动力学。结果表明，VO2+、HxV4O12+x(4+x)- (V-4)和HVO42-的还原是通过单电子转移进行的，而NaxHyV10O28(6-x-Y)- (V-10)的还原是通过双电子转移进行的。Koutecky-Levich和Tafel分析表明，本质还原速率常数依次为V-10 > VO2+ > V-4 > HVO42-。环电极收集效率表明，V-10的还原产物稳定，而VO2+、HVO42-和V-4的半衰期较短，从毫秒到秒不等。当磷酸盐与钒(V)的摩尔比在0 ~ 1范围内变化时，磷酸盐加速了V-10和V-4的还原动力学，增强了VO2+、V-4和HVO42-还原产物的稳定性。研究表明，磷酸盐络合可以增强水处理中钒的还原脱除，抑制其还原产物的再氧化。
Vanadium(V) is an emerging contaminant in the most recent Environmental Protection Agency's candidate contaminant list (CCL4). The redox chemistry of vanadium controls its occurrence in the aquatic environment, but the impact of vanadium(V) speciation on the redox properties remains largely unknown. This study utilized the rotating ring-disk electrode technique to examine the reduction kinetics of four pH- and concentration-dependent vanadiurn(V) species in the presence and the absence of phosphate. Results showed that the reduction of VO2+, HxV4O12+x(4+x)- (V-4), and HVO42- proceeded via a one-electron transfer, while that of NaxHyV10O28(6-x-Y)- (V-10) underwent a two-electron transfer. Koutecky-Levich and Tafel analyses showed that the intrinsic reduction rate constants followed the order of V-10 > VO2+ > V-4 > HVO42-. Ring-electrode collection efficiency indicated that the reduction product of V-10 was stable, while those of VO2+, HVO42-, and V-4 had short half-lives that ranged from milliseconds to seconds. With molar ratios of phosphate to vanadium(V) varying from 0 to 1, phosphate accelerated the reduction kinetics of V-10 and V-4 and enhanced the stability of the reduction products of VO2+, V-4, and HVO42-. This study suggests that phosphate complexation could enhance the reductive removal of vanadium(V) and inhibit the reoxidation of its reduction product in water treatment.