Universidad Autónoma Metropolitana, Unidad Cuajimalpa, Mexico.
J Hazard Mater. 2010 Jun 15;178(1-3):450-4. doi: 10.1016/j.jhazmat.2010.01.102. Epub 2010 Jan 28.
This paper reports arsenic methylation in betaine-nontronite clay-water suspensions under environmental conditions. Two nontronites (<0.05 mm), NAu-1 (green color, Al-enriched) and NAu-2 (brown color, Al-poor, contains tetrahedral Fe) from Uley Mine - South Australia were selected for this study. Betaine (pK(a)=1.83) was selected as methyl donor. The reaction between 5 g L(-1) clay, 20 ppm As(III), and 0.4M betaine at 7< or =pH(0)< or =9 under anoxic conditions was studied. The presence of nontronite clays were found to favor As(III) conversion to monomethylarsenic (MMA). Arsenic conversion was found to be as high as 50.2 ng MMA/ng As(III)(0). Conversion of As was found to be more quantitative in the presence of NAu-2 ((Na(0.72)) [Si(7.55) Al(0.16)Fe(0.29)][Al(0.34) Fe(3.54) Mg(0.05)] O(20)(OH)(4)) than NAu-1 ((Na(1.05)) [Si(6.98) Al(0.95)Fe(0.07)][Al(0.36) Fe(3.61) Mg(0.04)] O(20)(OH)(4)). The inherent negative charge at the nontronite tetrahedral layer stabilizes positively charged organic intermediate-reaction species, thereby leading to decreases in the overall methylation activation energy. The outcome of this work shows that nontronite clays catalyze As methylation to MMA via non-enzymatic pathway(s) under environmental conditions.
本文报道了在环境条件下甜菜碱-钠蒙脱石粘土-水悬浮液中的砷甲基化作用。选择了来自南澳大利亚乌利矿的两种非绿脱石（<0.05 毫米），NAu-1（绿色，富铝）和 NAu-2（棕色，贫铝，含有四面体 Fe）进行此项研究。选择甜菜碱（pK(a)=1.83）作为甲基供体。在缺氧条件下，研究了 5 g L(-1)粘土、20 ppm As(III)和 0.4M 甜菜碱在 7<或=pH(0)<或=9 下的反应。发现非绿脱石粘土的存在有利于 As(III)转化为单甲基砷（MMA）。砷的转化率高达 50.2 ng MMA/ng As(III)(0)。在 NAu-2（((Na(0.72)) [Si(7.55) Al(0.16)Fe(0.29)][Al(0.34) Fe(3.54) Mg(0.05)] O(20)(OH)(4))的存在下，As 的转化率比在 NAu-1（((Na(1.05)) [Si(6.98) Al(0.95)Fe(0.07)][Al(0.36) Fe(3.61) Mg(0.04)] O(20)(OH)(4))的存在下更具定量性。非绿脱石四面体层的固有负电荷稳定带正电荷的有机中间体反应物种，从而导致整体甲基化活化能降低。这项工作的结果表明，在环境条件下，非绿脱石粘土通过非酶途径催化 As 向 MMA 的甲基化。
