Efficient removal of uranium using a melamine/trimesic acid-modified hydrothermal carbon-based supramolecular organic framework

In this study, we prepared a hydrothermal carbon-based supramolecular organic framework (HTC-MA-TMA) by grafting melamine and trimesic acid on hydrothermal carbon (HTC) for efficient removal of U (VI) from aqueous solutions. The nano-sized supramolecular organic framework (SOF) particles consisted of N-donor-containing melamine and O-donor-containing trimesic acid self-assembled through hydrogen bonds. Their large number of specific active sites acted as the immobilization center for capturing U (VI). Chemical modification facilitated the dispersion of the SOF particles on HTC, which was synthesized using a novel covalent/non-covalent bond strategy. The HTC-MA-TMA adsorbent exhibited exceptional U (VI) adsorption capacity (271.83 mg/g) because of the coordination interaction between UO22+ and its ligands (amino, carboxyl and amide groups). The adsorption equilibrium was achieved within 30 min and followed a pseudo-second-order equation, suggesting the occurrence of a chemical adsorption process. Furthermore, the U (VI) ions adsorbed onto the HTC-MA-TMA adsorbent could be easily desorbed using 0.1 M HNO3 solution. This regeneration caused no significant decrease in the sorption capacity of the adsorbent. These results suggest that advanced HTC-MA-TMA adsorbent can be applied in the nuclear-fuel industry for extracting U (VI) from radioactive wastewater.