The effect of the borate/boric acid buffer on the transfer of potassium counter-ion through a cation-exchange membrane: current-voltage characteristics

Abstract

In this study, we compare the current–voltage (I–V) curves of the same counter-ion with and without buffer coions. We compare the polarization curves of the counter-ion K⁺ without and with borate coions which results from boric acid dissociation. The boric acid was added progressively from 0.005 to 0.1 N. The role of the mixture (borate coions/boric acid) is to buffer the solution at pH = 9.23, the protons, whatever their origin, do not contribute to the over-limiting current transport. We have a later onset of the over-limiting current and an increase in the plateau length of the membrane’s polarization curves. On the other hand, the addition of boric acid to a potassium sulfate solution does not affect the limiting current density, also the plateau length decreases and its slop increase with increasing boric acid concentration, this unexpected results helps us to better understand the classical electrochemical concentration polarization phenomena in electrodialysis process.

Keywords:

• Cation-exchange membrane
• Limiting current density
• Boric acid
• Concentration polarization
• Plateau length
• Over-limiting current
• Water dissociation

Notes

Presented at The Fifth Desalination Workshop (IDW 2012), October 28–31, 2012, Jeju, Korea