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.