Structure of Electrical Double Layer at Mica/KI Solution Interface
DOI:
https://doi.org/10.6000/1929-5030.2012.01.01.1Keywords:
Surface X-ray scattering, Solid–liquid interface, Electron density, Potassium iodide, Molecular dynamicsAbstract
Solid/liquid interfaces control many physical and chemical processes such as electrokinetic phenomena, dispersion of colloidal particles, heteroepitaxial growth of alkali halide, removal of toxic elements in water. The atomic distribution at solid/liquid interfaces is strongly correlated with these properties, and understanding these atomic structures is necessary in order to establish the fundamental physics and chemistry of solid/liquid interfaces. In this study, we investigated the structure of interfaces of mica with aqueous KI solution using surface x-ray scattering. The sub-angstrom-scale electron density profile of the interface is revealed as a function of the distance normal to the interface. The electron density of the KI solution oscillates to remain 10 Å away from the surfaces. The oscillations are interpreted in terms of the adsorbed hydrated K+ ions, adsorbed water molecules, and water molecules surrounding the hydrated ions. The adsorbed K+ ions are present as inner sphere complexes and the number is enough to compensate the negatively charged mica surface. No significant difference appeared between the surface x-ray scattering profiles of the KCl and KI solution interfaces, indicating that their interfacial structures are similar.
References
[2] Butt H-J, Graf K, Kappl M. Physics and chemistry of interfaces. Weinheim: Wiley-Vch Verlag GmbH & Co. KGaA 2003.
[3] Butt H-J, Cappella B, Kappl M. Forces measurements with the atomic force microscope: Technique, interpretation and applications. Surf Sci Rep 2005; 59: 1-152. http://dx.doi.org/10.1016/j.surfrep.2005.08.003
[4] Sakuma H, Kawamura K. Structure and dynamics of water on Li+ -, Na+ -, K+ -, Cs+ -, H3O+ -exchanged muscovite surfaces: A molecular dynamics study. Geochim Cosmochim Acta 2011; 75: 63-81. http://dx.doi.org/10.1016/j.gca.2010.10.007
[5] Fenter P. X-ray reflectivity as a probe of mineral-fluid interfaces: A user guide. Rev Mineral Geochem 2002; 49: 149-20. http://dx.doi.org/10.2138/gsrmg.49.1.149
[6] Willmott P. An introduction to synchrotron radiation: Techniques and applications. John Wiley & Sons, Ltd. 2011. http://dx.doi.org/10.1002/9781119970958
[7] Cheng L, Fenter P, Nagy KL, Schlegel ML, Sturchio NC. Molecular-scale density oscillations in water adjacent to a mica surface. Phys Rev Lett 2001; 87: 156103. http://dx.doi.org/10.1103/PhysRevLett.87.156103
[8] Fenter P, McBride MT, Srajer G, Sturchio NC, Bosbach D. Structure of barite (001)- and (210)-water interfaces. J Phys Chem B 2001; 105: 8112-9. http://dx.doi.org/10.1021/jp0105600
[9] Schlegel ML, Nagy KL, Fenter P, Cheng L, Sturchio NC, Jacobsen SD. Cation sorption on the muscovite (001) surface in chloride solutions using high-resolution x-ray reflectivity. Geochim Cosmochim Acta 2006; 70: 3549-65. http://dx.doi.org/10.1016/j.gca.2006.04.011
[10] Park C, Fenter PA, Nagy KL, Sturchio NC. Hydration and distribution of ions at the mica-water interface. Phys Rev Lett 2006; 97: 016101. http://dx.doi.org/10.1103/PhysRevLett.97.016101
[11] Sakuma H, Kondo T, Nakao H, Shiraki K, Kawamura K. Structure of hydrated sodium ions and water molecules adsorbed on the mica/water interface. J Phys Chem C 2011; 115: 15959-64. http://dx.doi.org/10.1021/jp111936s
[12] Lee SS, Fenter P, Nagy KL, Sturchio NC. Monovalent ion adsorption at the muscovite (001)-solution interface: Relationships among ion coverage and speciation, interfacial water structure, and substrate relaxation. Langmuir 2012; 28: 8637-50. http://dx.doi.org/10.1021/la300032h
[13] Izumi F, Ikeda T. A rietveld-analysis program Rietan-98 and its applications to zeolites. Mater Sci Forum 2000; 321-324: 198-205. http://dx.doi.org/10.4028/www.scientific.net/MSF.321- 324.198
[14] Pashley RM. DLVO and hydration forces between mica surfaces in Li+,Na+,K+,and Cs+ electrolyte-solutions - a correlation of double-layer and hydration forces with surface cation-exchange properties. J Coll Interf Sci 1981; 83: 531- 46. http://dx.doi.org/10.1016/0021-9797(81)90348-9
[15] Bowers GM, Bish DL, Kirkpatrick RJ. Cation exchange at the mineral-water interface: H3O+ /K+ competition at the surface of nano-muscovite. Langmuir 2008; 24: 10240-4. http://dx.doi.org/10.1021/la8021112
[16] Vlieg E. Integrated intensities using a six-circle surface x-ray diffractometer. J Appl Crystallogr 1997; 30: 532-43. http://dx.doi.org/10.1107/S0021889897002537
[17] Chantler CT. Theoretical form factor, attenuation and scattering tabulation for z = 1-92 from e = 1-10 eV to e = 0.4- 1.0 meV. J Phys Chem Ref Data 1995; 24: 71-643. http://dx.doi.org/10.1063/1.555974
[18] Vlieg E. Rod: A program for surface x-ray crystallography. J Appl Crystallogr 2000; 33: 401-5. http://dx.doi.org/10.1107/S0021889899013655
[19] Bevington PR, Robinson DK. Data reduction and error analysis for the physical sciences. New York: McGraw-Hill 2003.
[20] Sakuma H, Kawamura K. Structure and dynamics of water on muscovite mica surfaces. Geochim Cosmochim Acta 2009; 73: 4100-10. http://dx.doi.org/10.1016/j.gca.2009.05.029
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