Entropy generation analysis of electrodialysis desalination using multi-component groundwater

Abstract

Electrodialysis (ED) desalination is best-suited for groundwater. The groundwater comprises divalent and monovalent ions and radicals, such as Na+, Cl−, Mg2+, SO42−, Ca2+, K+, and HCO3−. Therefore, it is vital to conduct entropy generation analysis using a multi-component instead of a conventional binary NaCl solution. The current study evaluates and compares entropy generation in various zones of ED cell pairs using groundwater (multi-component) and NaCl solution with equivalent concentration by mass. Multi-component saltwater samples of the North Florida Peninsula region and Southeastern Tunisia are selected to represent groundwater. The results show that the divalent ions have contributed 78.78% and 60.89% to the total charge flux for the investigated groundwater. Besides, the divalent ions require half energy per unit charge flux compared to monovalent ions under the same activity ratio. The investigated groundwaters predict lower entropy generation rates than NaCl solution (e.g., by 39% at an applied potential of 90 mV). Moreover, a significant decrease in the entropy generation rates from 18% to 50% is observed for groundwater when compared with the case of NaCl solution due to the concentrate salinity variation from 1.25 to 1.75 times of diluate stream salinity.