Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA.
Environ Sci Technol. 2010 Aug 1;44(15):5862-7. doi: 10.1021/es100665c.
The interactions of the trivalent metal cations Al(III), La(III), Gd(III), and Lu(III) with the silica/water interface were studied using the nonlinear optical technique of second harmonic generation (SHG). Specifically, the Eisenthal chi(3) technique was used to quantify the thermodynamics of trivalent ion adsorption to the bare fused silica surface. SHG adsorption isotherms were measured and fit with the triple layer surface complexation model to obtain adsorption free energies, binding constants, and interfacial charge densities. The adsorption free energy for Al(III) was found to be -37.2(5) kJ/mol, while the adsorption free energies for the three trivalent lanthanide cations ranged from -29.9(9) to -32.2(7) kJ/mol. Despite identical ionic charges, the metals under investigation displayed different affinities for the fused silica/water interface, and this finding is analyzed and interpreted in the context of size-dependent metal cation properties and metal ion speciation. The thermodynamic results from this work are valuable benchmarks for computer simulations of trivalent metal transport in the environment.
采用非线性光学技术二次谐波产生（SHG）研究了三价金属阳离子 Al(III)、La(III)、Gd(III)和 Lu(III)与二氧化硅/水界面的相互作用。具体而言，利用 Eisenthal chi(3)技术定量研究了三价离子在裸露熔融二氧化硅表面的吸附热力学。测量了 SHG 吸附等温线，并通过三层表面络合模型进行拟合，以获得吸附自由能、结合常数和界面电荷密度。发现 Al(III)的吸附自由能为-37.2(5)kJ/mol，而三种三价镧系元素阳离子的吸附自由能范围为-29.9(9)至-32.2(7)kJ/mol。尽管离子电荷相同，但研究中的金属对熔融二氧化硅/水界面表现出不同的亲和力，这一发现根据尺寸依赖性金属阳离子特性和金属离子形态分析进行了分析和解释。这项工作的热力学结果为环境中三价金属迁移的计算机模拟提供了有价值的基准。
