Structure of sodium sulphate aqueous solution/quartz interface: a molecular dynamics simulation

Abstract

The molecular dynamics simulation was used to investigate the aqueous sodium sulphate solutions within quartz nanopores. Simulation was conducted for 13 ns to obtain the equilibrium distribution of water molecules, sulphate and sodium ions (Na⁺ and ) within the pores. The results clearly show an adsorption of sodium sulphate solution onto the quartz surface. However, Na⁺ shows a stronger attachment to the fully hydroxylated surface than due to size effects. The majority of Na⁺ ions appear within the primary and secondary water adsorption sites from the quartz surface. A special orientation of water molecules has been found in these layers, where one of the O–H bonds was parallel to the normal direction of the quartz surface. These observations illustrate the effect of quartz surface on the diffusion and precipitation of aqueous salt solutions under confinement, thus providing the mechanism of salt destruction on mural paintings.

Keywords::

• molecular dynamics simulation
• quartz
• sodium sulphate
• TIP4P/2005
• adsorption

Acknowledgements

The authors gratefully acknowledge the National Basic Research Program of China (Project number: 2012CB720902) and Zhejiang Education Administration Project (N20120082) for support of this work.