Electrodialysis of solutions containing Mn (II) ions

Electrodialysis of manganese (II) containing solutions has been studied. It was shown that Mn (II) cations themselves do not render any negative impact on the ion-exchange membranes. These ions are highly movable within the cationite membrane phase and may be easily removed during the electrodialysis desalination up to the maximum permissible concentration allowed for the potable water. The reason of possible impairment of the electrochemical characteristics of membranes during the electrodialysis of the Mn (II) containing solutions is scaling on the surface of the anion-exchange membranes in brine side. This is observed under severe concentration polarization conditions. The techniques to avoid deposition of the poorly soluble manganese compounds on the surface of the anionic membranes in brine side are proposed.

Thus, it has been shown that Mn (II) cations themselves do not render any negative impact on the ion-exchange membranes. They are highly movable within the cationite membrane phase and may be easily removed during the electrodialysis desalination up to the MPC allowed for the potable water. A reason for a possible impairment in the electrochemical characteristics of membranes during the electrodialysis of the Mn (II) containing solutions are the same factors causing CaCO3 and Mg(OH)2 deposition on the surface of anion-exchange membranes in brine side. This effect is observed under severe concentration polarization conditions. It is shown that both brine acidification and addition of sulphite ions in the brine reduces amount of deposits on the anion-exchange membrane. Increase in sulphate ions concentration in the water under electrodialysis treatment also facilitates decrease in formation on membranes of poorly soluble manganese compounds.