Correlation between Computed Ion Hydration Properties and Experimental Values of Sugar Transfer through Nanofiltration and Ion Exchange Membranes in Presence of Electrolyte

Alessio Fuoco,Sylvain Galier,Giorgio De Luca,Hélène Roux-De Balmann

doi:10.3390/computation6030042

Abstract

The widespread use of nanofiltration and electrodialysis membrane processes is slowed down by the difficulties in predicting the membrane performances for treating streams of variable ionic compositions. Correlations between ion hydration properties and solute transfer can help to overcome this drawback. This research aims to investigate the correlation between theoretically evaluated hydration properties of major ions in solution and experimental values of neutral organic solute fluxes. In particular, ion hydration energies, coordination and hydration number and the average ion-water distance of Na+, Ca2+, Mg2+, Cl− and SO42− were calculated at a high quantum mechanics level and compared with experimental sugar fluxes previously reported. The properties computed by simple and not computationally expensive models were validated with information from the literature. This work discusses the correlation between the hydration energies of ions and fluxes of three saccharides, measured through nanofiltration and ionic-exchange membranes. In nanofiltration, the sugar flux increases with the presence of ions of increasing hydration energy. Instead, inverse linear correlations were found between the hydration energy and the sugar fluxes through ion exchange membranes. Finally, an empirical model is proposed for a rough evaluation of the variation in sugar fluxes as function of hydration energy for the ion exchange membranes in diffusion experiments.

Highlights

Membrane technology is used in a number of civil and industrial applications such as the food industry, biological and chemical fields, pharmaceutical productions, water treatment, complex fluid treatment, gas separation and more [1,2,3]
coordination number (CN), NH, ion-water average distance and the hydration energies of Na+, Ca2+, Cl− and SO4 2− were evaluated by an accurate quantum mechanics computational approach
The sugar flux increases with the presence of ions of increasing hydration energy in the bulk solution, i.e., ions having a stronger interaction with the water clusters constituting their hydration shell

Summary

Introduction

Membrane technology is used in a number of civil and industrial applications such as the food industry, biological and chemical fields, pharmaceutical productions, water treatment, complex fluid treatment, gas separation and more [1,2,3]. The treatment of complex fluids is an active field in industrial applications for both economic reasons and sustainability. In this frame, nanofiltration (NF) plays a fundamental role, while electrodialysis (ED) has found a second life [4]. Salty environments are very common in applications where nanofiltration and electrodialysis are used and previous studies have shown that the nature and concentration of ions affects the transfer of neutral organic solutes through these kinds of membranes [5,6,7,8].

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