It was difficult for mature technologies to manage the low-level heavy metal wastewater due to low efficiency, secondary pollution and difficult enrichment. In this study, a novel capacitive deionization-electrodeionization (CDI-EDI) technology was developed through coordination mechanism of electromigration, electro-adsorption and ion exchange. Based on this technique, the low-content heavy metal ions in high-salinity wastewater could be removed efficiently. Moreover, a higher electro-adsorption CDI electrode was applied in the CDI-EDI stack. EDI device was optimized by decreasing ion exchange membranes from 4 to 2, thus reduced the stack cost. Based on the CDI-EDI stack, the simulated Cu(II) wastewater (C0 = 42.9 mg/L) was treated, and its average removal rate in 1st cycle cathode- and anode-effluent was 95.7% and 87.6%, respectively, under optimal direct current (DC) of 1.5 mA for 1.5 min, followed by electroregeneration of resin and electrode. Besides, the actual electroplating wastewater containing Ni(II) (389.4 mg/L) was treated via this device after precipitation to verify its feasibility. The results indicated that Ni(II) in the anode- and cathode-compartments were removed by 1.61 mg/L and 2.01 mg/L, respectively, only via one-stage CDI-EDI device under the operating voltage (0.10-0.20 V) and direct current (2.0-4.0 mA). It was possible to improve desalination efficiency of low-concentration heavy metal using tandem-type multistage devices. The CDI-EDI technique could not only ensure stable effluent and lower regenerations cost, but also enrich heavy metal from regeneration fluid to achieve resource recovery. This study would have obvious implications in treatment of low-content and salt-containing heavy metal wastewater with high efficiency and low energy consumption.
Keywords: Capacitive deionization; Copper wastewater; Electrodeionization; Heavy metal; Ion exchange.
Copyright © 2018 Elsevier Ltd. All rights reserved.