Selective Removal and Recovery of Cu²⁺ From Complex Water via Asymmetric Electrochemical Separation System

Industrial wastewater pollution and resource shortage are major issues affecting environmental sustainability today. Copper, a critical metal, is also a prevalent heavy metal contaminant in aquatic environment. Selective extraction/recovery of low-concentration Cu²⁺ from wastewater remains a hurdle. Herein, we develop an asymmetric electrochemical separation system to selectively capture Cu²⁺ from complicated water with the composite of covalent organic frameworks (COFs) and hollow mesoporous carbon spheres (HMCS) serving as cathode. By taking advantage of their synergistic effects, the HMCS@COF with suitable component proportion enables good electrical conductivity, fast ion movement, and full exposure of Cu²⁺ capture sites, achieving 97% Cu²⁺ removal and a Cu²⁺/Na⁺ selectivity of 10.54 at 1.2 V in 20 mg L^-1 Cu²⁺ and 100 mg L^-1 Na⁺ with additional involvement of minor electrodeposition route. Even in mixed solutions containing various metal ions (Na⁺, K⁺, Ca²⁺, Mg²⁺, Zn²⁺, Ni²⁺, Fe³⁺), it maintains high removal efficiency and selectivity for Cu²⁺. Moreover, satisfactory regenerability and stability are displayed over continuous operational cycles. The remarkable preferential removal of Cu²⁺ is also demonstrated by theoretical calculations. This work provides a new route for the selective removal of Cu²⁺ and offers the potential for copper recovery from wastewater containing multiple metals.