The effect of nitrate on fluoride removal by batch electrodialysis

Fluoride and nitrate are common pollutants in drinking water and their presence deteriorates the quality of drinking water. According to WHO guidelines, the fluoride content in drinking water cannot be higher than 1.5 mg F^–/dm³. The purpose of this paper was to evaluate the efficiency of fluoride removal from model aqueous solutions under the presence of nitrate. The experiments were conducted with the use of laboratory installation PCCell BED-1 System at a constant current density (0.78, 1.72, and 2.34 mA/cm²) with the use of monovalent selective ion-exchange membranes. The influence of initial nitrate concentration (15, 30, 45 mg NO₃ ^– /dm³) and initial fluoride concentration (5, 10, 15 mg F^–/dm³) on the process performance was studied. The degree of desalination varied from 85 to 91.7% depending on the solution composition and the applied current density, whereas the fluoride removal was in the range of 70–90%. The presence of coexisting NO₃ ^–ions in fluoride solutions improved process efficiency in view of fluoride removal by batch electrodialysis.