EFFECT OF SALT COMPOSITION ON THE SEPARATION PROFILE OF CONTAMINATED GROUNDWATER IONS BY ELECTRODIALYSIS

Abstract

Chloride, nitrate, sulfate, and fluoride ions are sometimes available in groundwater at an elevated
level, which is harmful to humans and the environment. The membrane separation technique has been widely
explored for controlling the level of those ions in drinking water, particularly the electrodialysis method. In the
present study, divalent (AMX) and monovalent ion selective (ACS) anion exchange membranes were used to
remove the high concentrations of chloride and other co-existent ions from groundwater samples. The study focuses
on the effect of the composition of the salt in the groundwater on the reducing profile of ions, the number of
deionized ions, and the rate of ion removal in the diluting compartment. To achieve these experimental objectives,
two series of ion samples composed of sodium and calcium were designed. The compositions of the ions were
NaCl, Na2NO3, Na2SO4 for the Na-compound, and CaCl2, Ca(NO3)2.4H2O, CaSO4∙2H2O, and CaF2 for the Cacompound. The electrodialysis experiment was run at a constant applied voltage (8 volts), using sodium nitrate as
the electrode solution. In summary, the ED performance for all the investigated parameters was better in the case
of ions composed of sodium. Furthermore, a change in the applied current against the electrodialysis operation time
was also observed. The results indicated that the current requirement by ED to separate ions composed of calcium
needed to be slightly higher than that for ions composed of sodium.