Synergetic high selectively Uranium(VI) adsorption via molecularly engineered tetradentate Schiff base functionalized chitosan/carboxymethyl cellulose bio-composite: From molecular design to life cycle assessment

The extraction of uranium has been an important solution for resolving the radioactive contamination in water resources and the nuclear fuel shortage. Developing effective eco-friendly bio-adsorbents is urgently needed. A composite biomaterial was designed by combining chitosan (CS) and carboxymethyl cellulose (CMC) (CS/CMC), which is further functionalized by a novel unsymmetrical O-phenylenediamine tetradentate Schiff base ligand (LOph) (3-bromo-2-((E)-((2-(((E)-2-chloro-6-hydroxybenzylidene)amino)phenyl)-imino)-methyl)phenol) (CS/CMC-LOph). CS/CMC-LOph composite showed a strong binding affinity to U(VI) and was able to adsorb 782.4 mg/g of uranyl ions at pH 5, 318 K, and 300 ppm. From an environmental perspective (1 ppm), the CS/CMC-LOph achieved significant adsorption, with a removal rate of 99.6% and a uranium residual concentration of 3.1 ppb after 24 h, which is below the WHO standards (15 ppb). In simulated real seawater, the material removes 98.7% of uranium with a K_d of 378663.3 mL/g. The thermodynamic study confirms that the process is endothermic and spontaneous. DFT calculations demonstrate a binding energy of −54.75 kcal/mol for U(VI) with the LOph, which is significantly stronger than those of chitosan and CMC. The CS/CMC-LOph demonstrated good recyclability with a removal capacity of 81.6% after six cycles. An LCA study has been conducted to assess the environmental impact of manufacturing 1 kg of CS/CMC-LOph. The minimum total cost of reusability and use of sustainable technologies proved to be effective in water treatment, uranium separation, and recovery.