To investigate the application of selective cation-separation ED to acidic WW from the wet sulfuricacid process for PA production, sets of experiments at pH ~1.5 and ~2.0 and at 12-30 V applied voltage were undertaken, comparing the evolution of species concentrations and pH. In most experiments, desalination degree of 50% (i.e., recovery ratio = 2) was chosen as the endpoint (based on EC reduction). Several cation-cation selectivity values (defined in Eq S2) were calculated to indicate the separation achievable with ED (Table ). Finally, concentration experiments were undertaken using a higher and more practical diluate recovery ratio (>80%) and the practicability of the process in view of its energy requirements was assessed.