Fan Q H, Tan X L, Li J X, Wang X K, Wu W S, Montavon G
Key Laboratory of Novel Thin Film Solar Cells, Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei 230031, PR China.
Environ Sci Technol. 2009 Aug 1;43(15):5776-82. doi: 10.1021/es901241f.
The effects of pH, ionic strength, and temperature on sorption of Eu(III) on attapulgite were investigated in the presence and absence of fulvic acid (FA) and humic acid (HA). The results indicated that the sorption of Eu(III) on attapulgite was strongly dependent on pH and ionic strength, and independent of temperature. In the presence of FA/HA, Eu(III) sorption was enhanced at pH < 4, decreased at pH range of 4-6, and then increased again at pH > 7. The X-ray photoelectron spectroscopy (XPS) analysis suggested that the sorption of Eu(III) might be expressed as is identical to X3Eu0, is identical to S(w)OHEu3+, and is identical to SOEu-OOC-/HA in the ternary Eu/HN/attapulgite system. The extended X-ray absorption fine structure (EXAFS) analysis of Eu-HA complexes indicated that the distances of d(Eu-O) decreased from 2.415 to 2.360 angstroms with increasing pH from 1.76 to 9.50, whereas the coordination number (N) decreased from approximately 9.94 to approximately 8.56. Different complexation species were also found for the different addition sequences of HA and Eu(III) to attapulgite suspension. The results are important to understand the influence of humic substances on Eu(III) behavior in the natural environment.
在有和没有富里酸（FA）和腐殖酸（HA）存在的情况下，研究了pH值、离子强度和温度对凹凸棒石吸附Eu(III)的影响。结果表明，Eu(III)在凹凸棒石上的吸附强烈依赖于pH值和离子强度，而与温度无关。在存在FA/HA的情况下，Eu(III)的吸附在pH < 4时增强，在pH范围为4 - 6时降低，然后在pH > 7时再次增加。X射线光电子能谱（XPS）分析表明，在三元Eu/HN/凹凸棒石体系中，Eu(III)的吸附可能表示为与X3Eu0相同、与S(w)OHEu3+相同以及与SOEu - OOC-/HA相同。Eu - HA配合物的扩展X射线吸收精细结构（EXAFS）分析表明，随着pH值从1.76增加到9.50，d(Eu - O)的距离从2.415埃减小到2.360埃，而配位数（N）从约9.94减小到约8.56。对于HA和Eu(III)添加到凹凸棒石悬浮液的不同顺序，也发现了不同的络合物种。这些结果对于理解腐殖物质对Eu(III)在自然环境中行为的影响具有重要意义。
