Exploring the application of amino functionalized Three-dimensional Macroscopic g-C3N4 sponge for enhanced uranium recovery

Uranium is the key fuel for nuclear power and there is 4.5 billion tons of uranium in the oceans. However, it is a significant challenge for the current adsorbent with powder form to extract uranium from seawater. In this study, we report a facile method for the synthesis of three-dimensional macroscopic g-C3N4 sponge from melamine-formaldehyde (MFCN) resin by thermal polymerization, which can easily be extracted from aqueous solution. Different organic amino (diethylenetriamine, triethylenetetramine and tetraethylenepentamine) modified g-C3N4 sponge composites (MFCN-DETA, MFCN-TETA and MFCN-TEPA) has been designed by schiff base reaction. The uranium adsorption performance of the products from aqueous solutions and simulated seawater was investigated. MFCN, MFCN-DETA and MFCN-TEPA achieved the maximum adsorption capacity at pH 6 and the optimum pH for MFCN-TETA was 5.0. The results showed that the maximum adsorption capacity of MFCN-DETA composites was 658.57 mg/g at pH 6. Furthermore, the MFCN-DETA composites was effectively regenerated using 0.1 N HNO3, which could be reused for enrichment of uranium (VI) and the adsorption efficiency could maintain 83% after 5 cycles of adsorption and desorption. The distribution coefficie(Kd) value of uranium was 9.1 × 104 mL g−1 for MFCN-DETA in simulating seawater. Thus, MFCN-DETA composites are believed to have promising potential applications in removal of uranium (VI) from seawater.