Molecular simulation of bulk carbon disulphide and salt-water solutions in bulk and in silica pores

Prathiraja, P 2011, Molecular simulation of bulk carbon disulphide and salt-water solutions in bulk and in silica pores, Doctor of Philosophy (PhD), Applied Sciences, RMIT University.


Document type: Thesis
Collection: Theses

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Title Molecular simulation of bulk carbon disulphide and salt-water solutions in bulk and in silica pores
Author(s) Prathiraja, P
Year 2011
Abstract Membranes for water purification are used in many applications and different types of membranes are being developed at the moment. No membrane can filter and purify water entirely, but improvements using novel kinds of membranes are still being made. Applications to desalination will continue to generate interest in membrane research at both fundamental and applied levels. The main challenge at the moment is to make membranes applicable to industrial processes which are more energy efficient and potentially much less expensive.

Recently many researchers are doing simulations of silica nano-pores using molecular dynamics to determine the macroscopic thermodynamic properties of porous systems. The realistic pore structures of membranes are not cylindrical and therefore the characteristics of the membrane may differ from pore shape to pore shape. Hence, it is worth while to examine the characteristics of the silica pore when the pore shape is not cylindrical. This study examines the salt solution behaviour in an equilibrated inhomogeneous silica pore system.

We used a simple model of linear triatomic molecule (CS2) to improve our simulation program to include a constraint algorithm that was later used to simulate water molecules. Within this study, we computed the transport properties of CS2 more accurately than previous studies. We were also able to describe the shear rate dependence of the internal energy and the pressure by a simple three parameter function.

Then we extended our program to calculate the viscosity of bulk water. Even though many papers have been published relating to liquid water models and properties, not many were able to calculate the viscosity accurately. After computing the temperature dependence of the viscosity of bulk water, we also performed molecular simulations to calculate the viscosity of salt solutions which had not been reported previously. Our results for these two systems agreed with existing experimental and simulation results. Here we were able to define a simpler and more accurate formula to predict the temperature dependence of the viscosity and the concentration dependence of the viscosity of salt solutions using existing experimental data.

Finally, we examined salt solutions in silica pores. Many applications of silica materials depend on their surface properties, which are largely determined by the functional groups on surfaces through various modification methods. Hydrophilic and hydrophobic functional group concentrations on the silica surfaces are the most important factor when liquid flows through the silica channel. Therefore we change the surface silanol groups and get comparatively hydrophilic and hydrophobic surfaces to examine the characteristics of the equilibrium state. We introduce a new method to generate silica pores with varying pore shape characteristics.
Degree Doctor of Philosophy (PhD)
Institution RMIT University
School, Department or Centre Applied Sciences
Keyword(s) silica
nanopore
viscosity
SPC/E
salt solution
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