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Synergistic arsenic(v) and lead(ii) retention on synthetic jarosite. I. Simultaneous structural incorporation behaviour and mechanism†
Environmental Science: Processes & Impacts ( IF 5.5 ) Pub Date : 2017-11-27 00:00:00 , DOI: 10.1039/c7em00426e
J. Aguilar-Carrillo 1, 2, 3, 4, 5 , M. Villalobos 6, 7, 8, 9, 10 , T. Pi-Puig 6, 7, 8, 9, 10 , I. N. Escobar-Quiroz 6, 7, 8, 9, 10 , F. M. Romero 6, 7, 8, 9, 10
Affiliation  

Jarosite [KFe3(SO4)2(OH)6] minerals are effective scavengers of potentially toxic elements (PTEs) and are abundant, for example, in acid rock/mine drainage scenarios. The retention process is highly relevant for environmental attenuation of heavy metals and metalloids since these are usually highly soluble and thus mobile under acidic conditions. We investigated both macroscopically and at the molecular scale the extent and the effects of concomitant incorporation of As(V) and Pb(II) into synthetic jarosite at different As/Pb starting molar ratios, using XRD-Rietveld, SEM, ATR-FTIR spectroscopy and wet chemistry. The amount of arsenate substituted in the jarosite structure was larger when Pb(II) was also incorporated, the former filling up to approximately 33% of the tetrahedral sites normally occupied by SO42−, as compared to 21% when Pb(II) was absent. Similarly, the amount of Pb(II) incorporated in the structure was larger when As(V) was also taken up. The jarosite unit cell volume increased as higher amounts of As(V) incorporated into its structure, but simultaneous Pb(II) incorporation seemed to limit this increase due to its smaller size as compared to K+. The extent to which As and Pb can accommodate in the jarosite structure was found to be limited by concentration maxima under the imposed synthesis conditions. At As/Pb ratios up to 1, Pb–As-jarosites were the only crystalline products. Above this ratio, a mixture of Pb–As-jarosite, anglesite (PbSO4) and poorly-crystalline ferric arsenate (AFA) phases was observed. At the highest As/Pb ratio investigated of 1.80 Pb–As-jarosite was no longer formed. Infrared spectroscopy analysis was applied for the first time here to substituted jarosites with both cations and anions, showing spectral changes in the solids as the As/Pb ratio increased: a characteristic As–O doublet at ∼810 and ∼855 cm−1 was observed upon Pb incorporation, showing an indirect effect of Pb(II) on the As–O bonds in the jarosite structure. Thus, structural incorporation of Pb plays a pivotal role in the unit cell environment of jarosite to balance the distortion caused by AsO4-for-SO4 substitution. The retention processes found in this work have important environmental implications and impacts: through the synergistic incorporation encountered, remediation enhancement of cationic pollutants such as Pb(II) is possible in a concomitant fashion with As(V) attenuation in acidic mining and metallurgical environments.

中文翻译:

合成黄铁矿上的 协同砷(v)和铅(ii)保留。一,同时的结构结合行为和机理

Jarosite [KFe 3(SO 42(OH)6 ]矿物是潜在有毒元素(PTE)的有效清除剂,并且在例如酸性岩石/矿山排水场景中含量很高。保留过程与重金属和准金属的环境衰减高度相关,因为重金属和准金属通常是高度可溶的,因此可以在酸性条件下移动。我们从宏观和分子角度研究了As(V)和Pb(II)的掺入程度和影响),使用XRD-Rietveld,SEM,ATR-FTIR光谱和湿化学法,以不同的As / Pb起始摩尔比将其合成为合成的黄钾铁矾。当还掺入Pb(II)时,黄铁矿结构中砷酸盐的取代量更大,前者填充了通常由SO 4 2-占据的四面体位点的约33%,而当Pb(II)时占21%。缺席。类似地,当还吸收As(V)时,结构中掺入的Pb(II)的量较大。随着较高量的As(V)掺入其结构,黄铁矿晶胞体积增加,但同时存在Pb(II))掺入似乎限制了这种增加,因为与K +相比它的体积较小。发现在所施加的合成条件下,As和Pb可以容纳在黄铁矿结构中的程度受到浓度最大值的限制。在As / Pb比例高达1的情况下,Pb-As砷铁矿是唯一的结晶产物。高于该比例,观察到Pb-As-铁矾石,斜铁矿(PbSO 4)和低结晶砷酸铁(AFA)相的混合物。在最高的As / Pb比为1.80的情况下,不再形成Pb-As-铁矾石。首次将红外光谱分析应用于具有阳离子和阴离子的取代的黄钾铁矾,显示出随着As / Pb比的增加,固体的光谱变化:在〜810和〜855 cm处具有特征性的As-O双重峰掺入Pb时观察到-1,表明Pb( II)对黄铁矿结构中As–O键的间接作用。因此,铅的结构掺入起着黄钾铁矾的单元电池环境中的关键作用,以平衡由ASO失真4 -用于-SO 4取代。这项工作中发现的保留过程具有重要的环境影响和影响:通过遇到的协同结合,在酸性采矿和冶金环境中,伴随着As( V)衰减的同时,可以提高阳离子污染物(如Pb( II))的修复效果。
更新日期:2017-11-27
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