Porous carbonized N-doped MOF-199 modified with MWCNTs for the deionization of uranium(VI)

When applying Capacitive Deionization (CDI) for water desalination, discovering effective techniques to attract more salt ions poses significant challenges. Herein, a 3D porous carbonized MOF-199@PVP/MWCNTs (CMPC) composite for enhanced electrosorption of U(VI) in water had been developed. Further investigation revealed that the incorporation of polyvinylpyrrolidone (PVP) enabled the CMPC composite to maintain its distinctive octahedral porous structure and rich N-doping to reduce particle size, providing more active sites. Additionally, the interpenetrating of multi-walled carbon nanotubes (MWCNTs) had formed a localized conductive network, further enhancing its properties. As a result, the CMPC electrode had been demonstrated a remarkable removal ratio of 95.2% with the uptake electroadsorption capacity of 410.3 mg g-1 for UO22+ aqueous solution (1.2 V). The exceptional CDI efficiency achieved by the CMPC electrode is attributed to the collaborative influence of electrochemical double layers (EDLs) and pseudocapacitance derived from the unique assembly of MOF-199, PVP, and MWCNTs. Besides, the results of the experiments on the effect of ionic strength showed that the electrosorption ratio still remained at 80.1% when 60 mg L−1 NaNO3 was added to the UO22+ solution. And the removal performance of U(VI) remained over 85.7% even after five CDI cycles. Overall, CMPC is a highly prospective electrode material in CDI for efficient extraction of uranium from water.