title: Interactions of Al(III), La(III), Gd(III), and Lu(III) with the fused silica/water interface studied by second harmonic generation.
abstract: 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.
authors.affiliation: Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA.
authors.forename: David S
authors.initials: DS
authors.lastname: Jordan
authors.forename: Jessica N
authors.initials: JN
authors.lastname: Malin
authors.forename: Franz M
authors.initials: FM
authors.lastname: Geiger
mesh_terms: D000535:Aluminum / Q000737:chemistry*; D002412:Cations / Q000737:chemistry; D055598:Chemical Phenomena; D004785:Environmental Pollutants / Q000737:chemistry*; D005682:Gadolinium / Q000737:chemistry*; D007811:Lanthanum / Q000737:chemistry*; D008187:Lutetium / Q000737:chemistry*; D008956:Models, Chemical; D012822:Silicon Dioxide / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D002412:Cations; D004785:Environmental Pollutants; D014867:Water; D008187:Lutetium; D007811:Lanthanum; D012822:Silicon Dioxide; D005682:Gadolinium; D000535:Aluminum