Gallium sorption on montmorillonite and illite colloids: Experimental study and modelling by ionic exchange and surface complexation
Gallium sorption on montmorillonite and illite colloids: Experimental study and modelling by ionic exchange and surface complexation
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DOI：
10.1016/j.apgeochem.2013.10.015
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发表时间：
2014-01-01
影响因子：
3.4
通讯作者：
Missana, Tiziana
中科院分区：
文献类型：
--
作者：
Benedicto, Ana;Degueldre, Claude;Missana, Tiziana
镓（Ga）等金属在环境中的迁移受粘土矿物（如蒙脱石和伊利石）的吸附影响很大。由于镓在工业和医学中的使用量增加，与镓相关的废物可能导致环境问题。在较宽的pH值、离子强度和镓浓度范围内，对蒙脱石和伊利石胶体进行了镓吸附实验。Ga吸附模型结合离子交换和表面络合的边缘网站（硅醇和铝样）的粘土片。利用线性自由能关系（LFER）尽可能地从Ga水解常数估算络合常数，从而减少模型中自由参数的数量。Ga在伊利石和蒙脱石上的吸附行为非常相似：实验数据模拟表明，Ga的吸附反应避免了Ga的吸附，沉淀，这是预测在没有粘土胶体之间的pH 3.5和5.5。假设这一假设，粘土胶体会影响镓水溶液的形态，防止有利于吸附沉淀。Ga在蒙脱石和伊利石上的吸附可以用三个主要反应来解释：在酸性条件下的Ga 3+交换（pH <类似于3.8）;在酸性-中性条件下，Ga（OH）（4）（-）在质子化弱中心上络合（在pH类似于5.2和pH类似于7.9之间）;和Ga（OH）（3）在碱性条件（pH >类似于7.9）下在强位点上的络合。(c)2013爱思唯尔有限公司保留所有权利。
The migration of metals as gallium (Ga) in the environment is highly influenced by their sorption on clay minerals, as montmorillonite and illite. Given the increased usage of gallium in the industry and the medicine, the Ga-associated waste may result in environmental problems. Ga sorption experiments were carried out on montmorillonite and illite colloids in a wide range of pH, ionic strength and Ga concentration. A Ga sorption model was developed combining ionic exchange and surface complexation on the edge sites (silanol and aluminol-like) of the clay sheets. The complexation constants were estimated as far as possible from the Ga hydrolysis constants applying the linear free energy relationship (LFER), which allowed to reduce the number of free parameters in the model.The Ga sorption behaviour was very similar on illite and montmorillonite: decreasing tendency with pH and dependency on ionic strength at very acidic conditions.The experimental data modelling suggests that the Ga sorption reactions avoid the Ga precipitation, which is predicted in absence of clay colloids between pH 3.5 and 5.5. Assuming this hypothesis, clay colloids would affect Ga aqueous speciation, preventing precipitation in favour of sorption. Ga sorption on montmorillonite and illite can be explained on the basis of three main reactions: Ga3+ exchange at very acidic conditions (pH < similar to 3.8); Ga(OH)(4)(-) complexation on protonated weak sites in acidic-neutral conditions (between pH similar to 5.2 and pH similar to 7.9); and Ga(OH)(3) complexation on strong sites at basic conditions (pH > similar to 7.9). (c) 2013 Elsevier Ltd. All rights reserved.