Pilot-scale separation of lead and sulfate ions from aqueous solutions using electrodialysis: Application and parameter optimization for the battery industry

Electrodialysis is receiving increased attention for the separation of important ions from industrial effluents. Insights on the simultaneous removal of lead and sulfate ions remain largely elusive in published work, while the works that address only lead removal consider concentrations higher than 100 mg/L. Effluents that contain lead and sulfate ions at industrially relevant concentrations (5 mg/L and 500-2000 mg/L, respectively, based on battery manufacturing characteristics) are investigated in this work. A pilot-scale electrodialysis setup is used that comprises 66 cell pairs of cation- and anion-exchange membranes of 5 m2 effective membrane area/stack, operated in batch mode. The setup is initially optimized according to key process parameters (applied voltage, product-to-concentrate ratio, and initial feed concentration) for sulfate ion removal, with the optimized conditions applied for simultaneous removal of lead and sulfate ions. Tests showed the negative effect of the high concentration ratio of sulfate-to-lead ions on the removal of lead. In order to improve the combined removal of lead ions, the operating conditions were changed and the optimal values corresponding to superficial velocity of 2 cm/s and applied voltage of 0.6 V/cell pair, resulted in 91% and 75% removal of sulfate and lead ions after 4 h of electrolysis, with energy consumption of 7 kWh/m3.