Study of Ionic Migration in Sea Water through Directional Freezing

The six most abundant ions present in seawater are chloride (Cl⁻), sodium (Na⁺), sulfate (SO4^2-), magnesium (Mg²⁺), calcium (Ca²⁺), and potassium (K⁺). By weight these ions make up almost 99 percent of the salinity of sea water. Removal of these ions or desalination makes the sea water useable. In the present work migration of these common and abundantly found ions in sea water has been studied when the water samples were subjected to directional freezing vertically as well as horizontally. Water samples collected from Arabian Sea were frozen in two partially insulated devices under different modes. The samples were placed in a freezer at different temperature conditions and all the six ions present in sea water were estimated in different fractions of ice extracted from various locations of frozen mass obtained after freezing. The fractions collected from the top of vertical device and from the periphery of the horizontal device were found to be completely decontaminated and free from the ions. Most of the ions were found concentrated at the bottom of the vertical device and in the center of horizontal device. The directional freezing method was found simple, inexpensive and free of chemicals method which can be effectively employed for the desalination of sea water particularly in the regions where cold energy is naturally available.