The formation, structure, and ageing of As-rich hydrous ferric oxide at the abandoned Sb deposit Pezinok (Slovakia)
The formation, structure, and ageing of As-rich hydrous ferric oxide at the abandoned Sb deposit Pezinok (Slovakia)
复制标题
DOI：
10.1016/j.gca.2007.06.053
复制
发表时间：
2007-09
影响因子：
5
通讯作者：
J. Majzlan;Bronislava Lalinská;M. Chovan;Ľubomír Jurkovič;S. Milovská;J. Göttlicher
中科院分区：
文献类型：
--
作者：
J. Majzlan;Bronislava Lalinská;M. Chovan;Ľubomír Jurkovič;S. Milovská;J. Göttlicher
斯洛伐克废弃的Sb存款Pezinok是As和Sb污染的重要来源，可以在下游数公里的土壤上层中追踪到。类金属的来源是两个尾矿库，其中储存了380，000m3采矿废物。尾矿和排出的水具有接近中性的pH值（7.0 ± 0.6），这是因为原生硫化物（黄铁矿，FeS2;毒砂，FeAsS;铍矿，FeSb2S4）分解产生的酸性被丰富的碳酸盐迅速中和。原生硫化物上的风化边缘是铁氧化物，它们是As和Sb的非常有效的清除剂（高达19.2wt% As和23.7wt% Sb）。原位μ-XANES实验表明，风化边中的As被完全氧化（As~（5+））。蓄水池体内的孔隙溶液含有高达81 ppm的As和2.5 ppm的Sb。这些溶液从蓄水池中排出后，会沉淀或沉积大量富含As的水合三氧化二铁（As-HFO），其中As 2 O 5含量高达28.3wt%，Sb含量高达2.7wt%。所有As-HFO样品对X射线来说都是无定形的。存款。它们含有Fe和As在其最高的氧化态和八面体和四面体的协调，分别建议由XANES和EXAFS研究Fe K和As K边缘。As-HFO中的铁八面体共享边以形成短单链，并且链通过与相邻单元共享边或角而相互连接。砷酸根离子以二齿-双核和单齿的方式附着在链上。此外，氢键配合物可能存在，以满足所有的氧原子在第一个配位领域的As5+的键合要求。在老化实验过程中，通过化学分析和Fe EXAFS光谱跟踪了As-HFO样品的结构变化。随着样品老化，As变得更容易沥滤。EXAFS谱显示出在3.3 - 3.5 μ m的距离处Fe-Fe对数量增加的明显趋势，即增加铁八面体的聚合以形成具有较少吸附位点的较大单元。因此，尽管水铁矿是捕获砷的优良材料，但必须非常谨慎地考虑将其用作长期储存As的介质，因为随着时间的推移，它往往会释放砷。
The abandoned Sb deposit Pezinok in Slovakia is a significant source of As and Sb pollution that can be traced in the upper horizons of soils kilometers downstream. The source of the metalloids are two tailing impoundments which hold ∼380,000m3of mining waste. The tailings and the discharged water have circumneutral pH values (7.0±0.6) because the acidity generated by the decomposition of the primary sulfides (pyrite, FeS2; arsenopyrite, FeAsS; berthierite, FeSb2S4) is rapidly neutralized by the abundant carbonates. The weathering rims on the primary sulfides are iron oxides which act as very efficient scavengers of As and Sb (with up to 19.2wt% As and 23.7wt% Sb). In-situ μ-XANES experiments indicate that As in the weathering rims is fully oxidized (As5+). The pore solutions in the impoundment body contain up to 81ppm As and 2.5ppm Sb. Once these solutions are discharged from the impoundments, they precipitate or deposit masses of As-rich hydrous ferric oxide (As-HFO) with up to 28.3wt% As2O5and 2.7wt% Sb. All As-HFO samples are amorphous to X-rays. They contain Fe and As in their highest oxidation state and in octahedral and tetrahedral coordination, respectively, as suggested by XANES and EXAFS studies on Fe K and As K edges. The iron octahedra in the As-HFO share edges to form short single chains and the chains polymerize by sharing edges or corners with the adjacent units. The arsenate ions attach to the chains in a bidentate–binuclear and monodentate fashion. In addition, hydrogen-bonded complexes may exist to satisfy the bonding requirements of all oxygen atoms in the first coordination sphere of As5+. Structural changes in the As-HFO samples were traced by chemical analyses and Fe EXAFS spectroscopy during an ageing experiment. As the samples age, As becomes more easily leachable. EXAFS spectra show a discernible trend of increasing number of Fe–Fe pairs at a distance of 3.3–3.5Å, that is, increasing polymerization of the iron octahedra to form larger units with fewer adsorption sites. Therefore, although ferrihydrite is an excellent material for capturing arsenic, its use as a medium for a long-term storage of As has to be considered with a great caution because it will tend to release arsenic as it ages.