Innovative amino acid-porphyrin decorated hyper-crosslinked polymers for efficient electrosorption of uranium (VI) in aqueous solution

The uranium extraction is of great importance for the development of the nuclear energy industry. In this study, a series of porous organic polymers were explored via crosslinking the amino acids and tetraphenyl-porphyrin by Friedel-Crafts alkylation reaction (HCP-TPP-AAs). The obtained polymer was loaded on carbon cloth to prepare the polymer electrode and was applied for the electrosorption of uranyl ions in an aqueous solution. The experimental parameters such as external voltage, pH value, adsorption time, and initial uranium concentration have also been systematically investigated to evaluate their influences on the adsorption performance. Owing to the abundant active sites such as the TPP unit, amino and carboxyl groups in the polymer skeleton, the HCP-TPP-AAs electrodes displayed an excellent uranium adsorption capacity and selectivity. Under the driving force of the electrode, the maximum U(VI) adsorption capacity reached up to 754.5 mg/g, which was six times higher than that of the static adsorption. Furthermore, the uranium removal efficiency by HCP-TPP-AAs electrodes was 81 % in the coexistence of competing metal ions and it can still maintain 85 % of its original adsorption capacity after seven cycles. The XPS analysis and DFT calculations indicate that the TPP unit, COOH and NH 2 groups in the polymer network display a strong inner sphere complexation with the uranyl ion. This strategy overcomes the long-standing drawbacks of conventional uranium extraction (e.g., low adsorption capacity, poor selectivity, and slow kinetics), offering innovative materials and technical solutions for the efficient capture of U(VI) from seawater and wastewater.