Adsorption of radium and barium on goethite and ferrihydrite: A kinetic and surface complexation modelling study
Adsorption of radium and barium on goethite and ferrihydrite: A kinetic and surface complexation modelling study
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DOI：
10.1016/j.gca.2014.10.008
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发表时间：
2014-12-01
影响因子：
5
通讯作者：
Morris, K.
中科院分区：
文献类型：
--
作者：
Sajih, M.;Bryan, N. D.;Morris, K.
在1 nM至5 mM的浓度范围内，pH值为4至10，研究了水铁矿和针铁矿对镭和钡的吸收，以建立一个模型来预测遗留铀矿废物中的镭行为。对于水铁矿，在pH >7时，以nM浓度的Ra 2+的摄取是强的。在较高的浓度下，Ba 2+吸附到水铁矿略弱于Ra 2+。针铁矿的实验表明，在所有系统中，两种金属离子的结合力较弱。镭与水铁矿和针铁矿的相互作用是完全可逆的。镭在水铁矿转化为针铁矿过程中的行为进行了研究，没有发现针铁矿晶格内不可逆掺入的证据;针铁矿吸收镭是相同的，无论它是否存在于其形成过程中。只有在高钙浓度（>10 mM）时，钙才与镭竞争水铁矿吸附。钡是一个更有效的竞争者，1 mM的浓度减少镭的吸附。沉积物样品从一个遗留的铀矿开采现场进行了分析，并在原位的R-D值是一致的，由表面涂层的水铁矿或针铁矿样相的镭吸收。建立了水铁矿和针铁矿吸附镭的表面络合模型，成功地模拟了实验数据。在这两种情况下，基于单个表面官能团和四齿结合位点的方法成功地模拟了数据。这些数据可用于支持传统采矿场地的安全情况。(C)2014爱思唯尔有限公司版权所有。
Radium and barium uptake onto ferrihydrite and goethite have been studied in the concentration range 1 nM to 5 mM and from pH 4 to 10, to develop a model to predict radium behaviour in legacy uranium mining wastes. For ferrihydrite, uptake of Ra2+ at nM concentrations was strong at pH >7. At higher concentrations, Ba2+ sorption to ferrihydrite was slightly weaker than that of Ra2+. Experiments with goethite showed weaker binding for both metal ions in all systems. The interactions of radium with both ferrihydrite and goethite are fully reversible. The behaviour of radium during transformation of ferrihydrite to goethite has been studied, and no evidence for irreversible incorporation within the goethite lattice was found; radium uptake to goethite was the same, whether or not it was present during its formation. Calcium competed with radium for ferrihydrite sorption only at high calcium concentrations (>10 mM). Barium is a more effective competitor, and a concentration of 1 mM reduced radium sorption. Sediment samples from a legacy uranium mining site have been analysed, and the in situ R-d values are consistent with radium uptake by surface coatings of ferrihydrite or goethite like phases. Surface complexation models have been developed for radium sorption to ferrihydrite and goethite which simulate the experimental data successfully. In both cases, approaches based on a single surface functional group and tetradentate binding sites simulated the data successfully. These data could be used in underpinning the safety case for legacy mining sites. (C) 2014 Elsevier Ltd. All rights reserved.