Molecular Scale Assessment of Methylarsenic Sorption on Aluminum Oxide
Molecular Scale Assessment of Methylarsenic Sorption on Aluminum Oxide
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DOI：
10.1021/es9027502
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发表时间：
2010-01-15
影响因子：
11.4
通讯作者：
Sparks, Donald L.
中科院分区：
文献类型：
--
作者：
Shimizu, Masayuki;Ginder-Vogel, Matthew;Sparks, Donald L.
砷的甲基化形式，单甲基胂酸盐（MMA）和二甲基胂酸盐（DMA），历史上被用作除草剂和杀虫剂。由于甲基化砷在农业上的广泛应用以及甲基丙烯酸甲酯和二甲基丙烯酸甲酯的毒性，甲基化砷在土壤组分上的吸附需要研究。采用宏观批量吸附动力学、扩展X射线吸收精细结构（EXAFS）和傅里叶变换红外（FTIR）光谱技术研究了MMA和DMA在无定形氧化铝（AAO）上的吸附。吸附等温线的研究表明，吸附最大值为0.183，0.145，和0.056毫摩尔砷/毫摩尔铝砷酸盐（砷-V），MMA，DMA，分别。在吸附动力学研究中，100%的添加的As-V在5分钟内被吸附，而78%和15%的添加的MMA和DMA被吸附，分别。解吸实验，使用磷酸盐作为解吸剂，导致吸附的As-V释放30%，而吸附的MMA和DMA分别释放48%和62%。FTIR和EXAFS研究表明，MMA和DMA与AAO主要形成双齿双核配合物。在此基础上，提出了甲基取代度的增加会导致AAO对As的吸附量减少，而As的解吸量增加。
Methylated forms of arsenic (As), monomethylarsenate (MMA) and dimethylarsenate (DMA), have historically been used as herbicides and pesticides. Because of their large application to agriculture fields and the toxicity of MMA and DMA, the sorption of methylated As to soil constituents requires investigation. MMA and DMA sorption on amorphous aluminum oxide (AAO) was investigated using both macroscopic batch sorption kinetics and molecular scale extended X-ray absorption fine structure (EXAFS) and Fourier transform infrared (FTIR) spectroscopic techniques. Sorption isotherm studies revealed sorption maxima of 0.183, 0.145, and 0.056 mmol As/mmol Al for arsenate (As-V), MMA, and DMA, respectively. In the sorption kinetics studies, 100% of added As-V was sorbed within 5 min, while 78% and 15% of added MMA and DMA were sorbed, respectively. Desorption experiments, using phosphate as a desorbing agent., resulted in 30% release of absorbed As-V, while 48% and 62% of absorbed MMA and DMA, respectively, were released. FTIR and EXAFS studies revealed that MMA and DMA formed mainly bidentate binuclear complexes with AAO. On the basis of these results, it is proposed that increasing methyl group substitution results in decreased As sorption and increased As desorption on AAO.