RESIDENCE TIME EFFECTS ON ARSENATE SURFACE SPECIATION AT THE ALUMINUM OXIDE-WATER INTERFACE
RESIDENCE TIME EFFECTS ON ARSENATE SURFACE SPECIATION AT THE ALUMINUM OXIDE-WATER INTERFACE
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DOI：
10.1097/00010694-200205000-00001
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发表时间：
2002-05
期刊：
影响因子：
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通讯作者：
Y. Arai;Donald L. Sparks
中科院分区：
文献类型：
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作者：
Y. Arai;Donald L. Sparks
金属/类金属的生物利用度通常受到土壤和沉积物中接触时间（即停留时间）的限制，从而导致不可逆反应。污染物的命运和运输不仅要根据短期（<48小时）的吸附/解吸研究，而且要根据长期（数月-数年）的反应来预测/模拟。然而，关于土壤和土壤组分中金属/类金属分配反应的长期影响的资料很少。本研究采用间歇吸附/解吸实验，结合时间分辨扩展x射线吸收精细结构光谱（EXAFS），研究了停留时间（3天- 1年）对As(V)吸附/解吸反应和氧化铝-水界面As(V)表面形态的影响。在pH为4.5和7.8时观察到双相As(V)吸附动力学，而在pH为4.5时3天后反应几乎完成，在pH为7.8时1年后缓慢吸附继续。停留时间越长（3天~ 1年），两种ph值下As(V)的解吸下降幅度越大，说明存在非奇异反应。在两种pH值下，老化As(V)反应的氧化铝的EXAFS分析表明，在pH为4.5和7.8时，所有老化样品（3天至1年）的As- al原子间距离为3.11−3.14 Å（±0.13 Å），表明主要存在双牙双核键环境。x射线吸收近边结构光谱（XANES）特征表明，随着老化，吸附的As(V)的局部化学结构发生了一些变化。表面转变，如(i)表面配合物的重排和/或（ii）表面配合物向砷酸铝样沉淀的转化，可能是导致as (V)可逆性随时效降低的重要化学因素。
Bioavailability of metals/metalloids is often rate limited by contact time (i.e., residence time) in soils and sediments, resulting in irreversible reactions. The fate and transport of the contaminants must be predicted/modeled not only on short-term (<48 h) adsorption/desorption studies but also on long-term (months-years) reactions. However, there is very little information on the long-term effects of metal/metalloid partitioning reactions in soils and soil components. In this study, residence time effects (3 days–1 yr) on As(V) adsorption/desorption reactions and on As(V) surface speciation at the aluminum oxide-water interface were investigated using batch adsorption/desorption experiments coupled with time-resolved Extended X-ray Absorption Fine Structure spectroscopy (EXAFS). Biphasic As(V) adsorption kinetics were observed at pH 4.5 and 7.8, and whereas the reaction at pH 4.5 was nearly completed after 3 days, slow adsorption continued at pH 7.8 after 1 year. The longer the residence time (3 days–1 yr), the greater the decrease in As(V) desorption at both pHs, suggesting nonsingular reactions. EXAFS analyses on aged As(V) reacted aluminum oxide at both pHs showed that As-Al interatomic distances were 3.11 − 3.14 Å (±0.13 Å) in all of the aged samples (3 days to 1 yr) at pH 4.5 and 7.8, suggesting that predominantly bidentate binuclear bonding environments were present. As a point of interest, X-ray Absorption Near Edge Structure spectroscopy (XANES) features suggested some changes in the local chemical structure of adsorbed As(V) with aging. The surface transformations such as (i) a rearrangement of surface complexes and/or (ii) a conversion of surface complexes into aluminum arsenate-like precipitates might be important chemical factors responsible for the decrease in As(V) reversibility with aging.