Plasma-enhanced vanadium-based hybrid capacitive deionization for high selective removal of Pb2+

Lead ion is one of the toxic metal ions contaminants in wastewater, and its efficient removal is a critical challenge in wastewater treatment. Therefore, developing a low-cost hybrid capacitive-deionization (HCDI) technology with high adsorption capacity is imminent. Herein, we fabricated (NH4)2V10O25·8H2O (NVO) micro flowers with large layer spacing and achieved enhanced hydrophilicity and rich oxygen vacancies by Ar plasma treatment. The plasma-treated (NH4)2V10O25·8H2O (P-NVO) electrode exhibits high electrochemical performance (204.6 F/g at 1 A/g). Additionally, the P-NVO//active carbon (AC) cell displays a superior adsorption capacity (49.56 mg/g) than that of the NVO//AC cell in Pb(NO3)2) solution. The enhanced adsorption capacity can be attributed to the increased oxygen vacancies, improved hydrophilicity and ion-insertion mechanism induced by plasma treatment. More importantly, the P-NVO//AC cell holds a superior regeneration performance and excellent ion selectivity, as confirmed by experimental results and DFT calculations. Interestingly, we display the concept of aqueous lead-ion batteries based on this cell, demonstrating the potential of combining Pb2+ energy storage and removal. Overall, this work highlights the significance of developing high-performance technology for removing lead ions from wastewater.