Effect of environmental conditions on the adsorption behavior of Sr(II) by Na-rectorite

The adsorption behavior of Sr(II) by Na-rectorite was investigated as a function of various environmental parameters such as pH, ionic strength, humic acid (HA) and temperature under ambient conditions. The results indicated that the adsorption of Sr(II) on Na-rectorite was strongly dependent on pH and ionic strength. The presence of HA enhanced the adsorption of Sr(II) on Na-rectorite at low pH, whereas suppressed Sr(II) adsorption on Na-rectorite at high pH. The Langmuir model simulated the adsorption isotherms of Sr(II) better than the Freundlich model at three different temperatures of 293, 313 and 333 K. The thermodynamic parameters (Delta H-0, Delta S-0 and Delta G(0)) calculated from the temperature dependent adsorption isotherms indicated that the adsorption process of Sr(II) on Na-rectorite was spontaneous and endothermic. The adsorption of Sr(II) was dominated by outer-sphere surface complexation and ion exchange at low pH, whereas inner-sphere surface complexation was the main adsorption mechanism at high pH. The results indicate that Na-rectorite may be a promising candidate for the treatment of radionuclides from large volume solution. (C) 2013 Elsevier B.V. All rights reserved.

在环境条件下，研究了钠累托石对锶（II）的吸附行为随各种环境参数（如pH值、离子强度、腐殖酸（HA）和温度）的变化情况。结果表明，钠累托石对锶（II）的吸附强烈依赖于pH值和离子强度。在低pH值时，腐殖酸的存在增强了钠累托石对锶（II）的吸附，而在高pH值时则抑制了锶（II）在钠累托石上的吸附。在293 K、313 K和333 K三个不同温度下，朗缪尔模型比弗罗因德利希模型更好地模拟了锶（II）的吸附等温线。由温度相关的吸附等温线计算得到的热力学参数（ΔH⁰、ΔS⁰和ΔG⁰）表明，锶（II）在钠累托石上的吸附过程是自发的且吸热的。在低pH值时，锶（II）的吸附以外层表面络合和离子交换为主，而在高pH值时，内层表面络合是主要的吸附机制。结果表明，钠累托石可能是处理大量溶液中放射性核素的一种有前景的材料。（C）2013爱思唯尔公司。保留所有权利。