Influence of the water structuring on the adsorption energy of Na in sulfo cation exchanger at low degrees of hydration

Abstract

Influence of the water structuring on the adsorption energy of Na in sulfo cation exchanger at low
degrees of hydration was studied in this paper. The aim of the research was to carry out quantum-chemical
calculations of the effect of two water molecules in different configurations on the binding energy of the ion
sodium with adsorption center in sulfo cation exchanger. Computer calculations (HF/6-311G(d,p)) of the
total energies and the molecular orbitals of sulfo cation exchanger fragments with the contact ion pair in the
absence of and with the participation of one, two water molecules, and water dimer were held to achieve this
goal. The interaction energy of the sodium ion with sulfo cation exchanger in the absence and in the presence
of water molecules were obtained using the calculated values of total energies. It has been shown that the
addition of two unbound molecules of water, as compared with water dimer, increases the binding energy of
Na+ to oxygen atoms in the SO3̄ group. We have also studied the allocation of the electron density and the
electric charge and as a result, it was concluded that this effect has the quantum nature and is associated with
a decrease of electron states energy due to increasing of bonding orbitals uniformity. These results can be
used in the development of optimization process techniques of purification the aqueous solutions of metal
ions.