Department of Hydrology, University of Bayreuth, 95440 Bayreuth, Germany.
Chemosphere. 2012 Feb;86(6):557-64. doi: 10.1016/j.chemosphere.2011.07.055. Epub 2011 Dec 3.
High As(III) enrichment in schwertmannite precipitated acid mine impacted areas is a major concern considering its acute toxicity and mobility where the current knowledge of their interaction, redox conditions and schwertmannite metastability is inadequate. In this study we have investigated such aspects through batch isotherm, microscopic and spectroscopic techniques. Schwertmannite produced by biotic process with 14.7 m(2)g(-1) surface area demonstrated a rapid As(III) uptake followed by slow retention possibly into the internal absorbing sites through multilayer and heterogeneous sorption processes. Chemical, X-ray diffraction, infrared and microscopic examinations revealed that ionic exchange between schwertmannite SO(4)(2-) and As(III) and surface precipitation governed the total As(III) uptake where lower dissolved SO(4)(2-) and high sorbent mass enhanced As(III) retention. Redox instability of sorbed As(III) was evidenced from the near-edge spectroscopic analysis at extremely high Fe(III):As(III) ratio (5.5×10(5)) leading to surface oxidation to As(V), while As(III) was found as the predominant redox species at high As(III):Fe(III) ratios. Only 0.83% of sorbed As(III) was released which was subsequently re-adsorbed into schwertmannite during 4 months stabilization without any evidence of mineralogical transformation.
在考虑到砷（III）的高富集和急性毒性及移动性的情况下，在受酸性矿山影响的地区，水铁矿的砷（III）的高富集是一个主要关注点，而目前对于它们之间的相互作用、氧化还原条件和水铁矿亚稳性的了解还不够充分。在这项研究中，我们通过批量平衡实验、微观和光谱技术研究了这些方面。通过生物过程产生的比表面积为 14.7 m(2)g(-1)的水铁矿表现出快速的砷（III）摄取，随后是缓慢的保留，可能是通过多层和非均相吸附过程进入内部吸收位点。化学、X 射线衍射、红外和微观检查表明，水铁矿 SO(4)(2-)与砷（III）之间的离子交换和表面沉淀控制了总砷（III）的摄取，其中较低的溶解 SO(4)(2-)和较高的吸附剂质量增强了砷（III）的保留。在高 Fe(III):As(III)比（5.5×10(5)）下，吸附的砷（III）的氧化还原不稳定性从近边缘光谱分析中得到证实，导致表面氧化为砷（V），而在高 As(III):Fe(III)比下发现砷（III）是主要的氧化还原物种。只有 0.83%的吸附砷（III）被释放出来，随后在 4 个月的稳定期内重新被水铁矿吸附，没有任何矿物转化的迹象。
