%0 Generic
%A Lammertink, Rob
%A Wood, Jeffery A.
%A Paul, Arputha
%D 2023
%T Data underlying the research of Enhancing Electrodialysis using Spacer Electrokinetic Effects: The Influence of Bivalent Ions on Spacer Performance
%U 
%R 10.4121/a7bea874-4fd6-4a32-bfd6-d5d6658d0983.v1
%K Bivalent cation
%K electrodialysis
%K ion transport
%K Mono-bivalent mixture feed
%X <p>Concentration polarization in electrodialysis (ED) stacks can significantly reduce the process efficiency in the separation of ions. We previously investigated an innovative way of reducing the concentration polarization by inducing electro-osmotic mixing through the use of surface-modified spacers and tested this approach using single monovalent salt streams.&nbsp;Typically, more complex mixtures containing multivalent ionic species occur in practical settings which may lead to divalent ion adsorption on spacers and a reduction in electro-osmotic mixing, therefore reducing the improvement in efficiency observed for the monovalent-only case. To further test the effectiveness of using surface-modified spacers for enhancing electrodialytic transport, we have studied the influence of bivalent cations on the resulting ED process using polyelectrolyte-coated spacers. For this, we compared the monovalent feed solutions with feeds containing either bivalent ions or a mixture of monovalent and bivalent salts. The results showed that when using surface-modified spacers in ED with a mixture of bivalent and monovalent salts (MgCl$_2$ + NaCl) in the feed, a similar enhancement to the monovalent ion only case was obtained whereas when using a feed consisting of only a bivalent salt (MgCl$_2$) there was a negligible difference between the performance of surface-modified and conventional spacers. We show that the loss in performance of surface-modified spacers can be plausibly attributed to a reduction in the zeta potential (surface charge) in the presence of divalent cations leading to a reduction in the electro-osmotic remixing of the boundary layer, obtaining the behaviour of an ED process using uncoated spacers. Our findings also indicate that this performance loss in using surface-coated spacers&nbsp;can be mitigated or avoided if there is an additional monovalent cation in the mixture at similar concentrations. This work highlights that the use of surface-modified spacers can be a viable option for enhancing electrodialysis for realistic feed sources consisting of mixtures of mono and higher valence ions.</p>
%I 4TU.ResearchData