Functionalization of biomass carbonaceous aerogels and their application as electrode materials for electro-enhanced recovery of metal ions

Capacitive deionization (CDI) is a promising water desalination technology in which a pair of porous electrodes is electrically charged to remove ionic species from water. Rational design of electrode materials and device structure opens new possibilities in removing heavy metals from wastewater by the CDI process. Herein, a bench-scale CDI device based on 3D functionalized flexible carbonaceous aerogels (CAs) derived from natural and renewable biomass was designed for water decontamination. We put forward a new and promising fabrication method, which utilized only low valence metal precursors to fabricate high valence metal oxides (MO) and CA hybrids (denoted CAs/MO). The resultant CAs/MO hybrids exhibited a hierarchical porous structure with a specific surface area of 262.6 m² g^-1 and an excellent specific capacity of 120.4 F g^-1. Enhanced electrochemical capacity and low inner resistance endowed the CAs/MO hybrid electrodes with an outstanding decontamination capacity of 57.13 mg g^-1 for Cu(ii) at a low applied voltage of 1.2 V, which was nearly 3 times higher than that of 19.28 mg g^-1 at an open circuit and highlighted the advantages of the CDI process in decontamination technology. The CAs/MO electrodes had good cycling stability for CDI decontamination applications. This study certifies the feasibility of decontamination and recovery of aqueous toxic heavy metals using the CDI process in pollution cleanup.