Membrane-free electrodeionization for purification of wastewater containing low concentration of nickel ions

Electrodeionization (EDI) is widely used for removal and recovery of nickel from dilute wastewater due to its high efficiency and easy operation. However, the use of membranes in EDI causes problems such as membrane fouling, scaling and concentration polarization. In this work, the treatability of nickel containing wastewater by membrane-free electrodeionization (MFEDI) was experimentally investigated. The study concentrated on the effect of different resin bed configurations in MFEDI system in term of nickel removal, precipitation generation and water recovery, as well as energy consumption. The experiment results show that excellent purification and effective regeneration were achieved by MFEDI with a layered mixed bed. It was observed that, in the purification stage, with an inlet conductivity of 42.5 μS/cm and a nickel concentration of 10.0 mg/L, the effluent conductivity was 0.3-1.0 μS/cm and the nickel concentration of the effluent was below the detection limit; in the regeneration stage, the average nickel concentration of the concentrate was over 80.0 mg/L, the average pH of the concentrate was 7.4, thereby precipitation was prevented. The energy consumption and water recovery rate were 5.6 kWh/m3 and 88%, respectively.