Interfacial Water Structure and Surface Charge of Selected Alkali Chloride Salt Crystals in Saturated Solutions: A Molecular Dynamics Modeling Study

An initial molecular dynamics simulation (MDS) study regarding interfacial phenomena at selected alkali chloride salt surfaces in saturated brine solutions is reported. Simulation results show that small surface cations (Li+ and Na+) with large local electric fields strongly interact with interfacial water molecules. Consequently, interfacial water molecules are stabilized at these salt surfaces with distinct orientations, which appear to inhibit the adsorption of surfactant molecules. On the other hand, the interaction between interfacial water and large surface cations (K+ and Rb+) is weak, which favors the surfactant adsorption despite the sign of the charge at the salt surface. The surface charge signs obtained for selected alkali chloride salts using MD simulation complement both the extended lattice ion hydration theory based on ion hydration energy calculations and the results from nonequilibrium laser-Doppler electrophoretic measurements. Due to their large hydration energy, Li+ ions are preferent...

[1]  T. Chalikian.  Structural Thermodynamics of Hydration , 2001 .

[2]  K. Higashitani,et al.  Molecular Dynamics Simulations of Water at NaCl(001) and NaCl(011) Surfaces , 1998 .

[3]  J. Rasaiah,et al.  Structural and dynamic properties of concentrated alkali halide solutions: a molecular dynamics simulation study. , 2007, The journal of physical chemistry. B.

[4]  David E. Smith,et al.  Computer simulations of NaCl association in polarizable water , 1994 .

[5]  L. Dang,et al.  Comment on ‘‘Mean force potential for the calcium–chloride ion pair in water’’ [J. Chem. Phys. 99, 4229 (1993)] , 1995 .

[6]  R. Alcubilla,et al.  Effects of symmetry reduction in two-dimensional square and triangular lattices , 2004 .

[7]  Jianwei Wang,et al.  Structure, energetics, and dynamics of water adsorbed on the muscovite (001) surface: a molecular dynamics simulation. , 2004, The journal of physical chemistry. B.

[8]  L. Dang,et al.  Mechanism and Thermodynamics of Ion Selectivity in Aqueous Solutions of 18-Crown-6 Ether: A Molecular Dynamics Study , 1995 .

[9]  Roger Impey,et al.  Hydration and mobility of ions in solution , 1983 .

[10]  D. Chandler,et al.  Hydrogen-bond kinetics in liquid water , 1996, Nature.

[11]  Jon J. Kellar,et al.  Adsorption of collector colloids in the flotation of alkali halide particles , 1993 .

[12]  P. Kollman,et al.  Free Energy of Association of the K+:18-Crown-6 Complex in Water: A New Molecular Dynamics Study , 1995 .

[13]  A. Pramanik,et al.  Adsorption of water on sodium chloride surfaces: electrostatics – guided ab initio studies , 2005 .

[14]  J. Rasaiah,et al.  Computer simulation studies of aqueous sodium chloride solutions at 298 K and 683 K , 2000 .

[15]  Yue-hua Hu,et al.  The surface charge of alkali halides : consideration of the partial hydration of surface lattice ions , 1997 .

[16]  Amalendu Chandra,et al.  Molecular dynamics simulations of aqueous NaCl and KCl solutions: Effects of ion concentration on the single-particle, pair, and collective dynamical properties of ions and water molecules , 2001 .

[17]  J. Wolfenden,et al.  The viscosity of strong electrolytes measured by a differential method , 1934 .

[18]  M. Çelik,et al.  The Significance of Interfacial Water Structure in Soluble Salt Flotation Systems. , 2001, Journal of Colloid and Interface Science.

[19]  D. Chandler.  Interfaces and the driving force of hydrophobic assembly , 2005, Nature.

[20]  Chandler,et al.  Effect of environment on hydrogen bond dynamics in liquid water. , 1996, Physical review letters.

[21]  J. Rasaiah,et al.  Solvent Structure, Dynamics, and Ion Mobility in Aqueous Solutions at 25 °C , 1998 .

[22]  W Smith,et al.  DL_POLY_2.0: a general-purpose parallel molecular dynamics simulation package. , 1996, Journal of molecular graphics.

[23]  G. Ciccotti,et al.  Hoover NPT dynamics for systems varying in shape and size , 1993 .

[24]  Peter J. Rossky,et al.  A comparison of the structure and dynamics of liquid water at hydrophobic and hydrophilic surfaces—a molecular dynamics simulation study , 1994 .

[25]  A. Stone,et al.  Adsorption of water on the NaCl(001) surface. III. Monte Carlo simulations at ambient temperatures , 2000 .

[26]  T. Straatsma,et al.  THE MISSING TERM IN EFFECTIVE PAIR POTENTIALS , 1987 .

[27]  Jan D. Miller,et al.  Surface charge of alkali halide particles as determined by laser-Doppler electrophoresis , 1992 .

[28]  L. Dang.  Free energies for association of Cs+ to 18-crown-6 in water. A molecular dynamics study including counter ions , 1994 .