δ-MnO2 nanoplates@N-doped hollow carbon spheres for efficient uranium extraction via coordination-electrostatic synergy

To meet the pressing demands of sustainable nuclear energy development and radioactive pollution mitigation, the development of high-efficiency adsorbents for uranium extraction from real wastewater is paramount. In this study, a MNP@NHCS adsorbent was engineered through a carrier-supported strategy involving in-situ growth of δ-MnO 2 nanoplates (MNP) on N-doped hollow carbon spheres (NHCS). Material characterization confirmed that NHCS suppresses δ-MnO 2 agglomeration and enhances the specific surface area to 218.22 m 2 /g (3.5-fold higher than pristine δ-MnO 2 62.28 m 2 /g). Batch experiments demonstrated exceptional performance: excellent U(VI) adsorption capacity (423.61 mg/g), outstanding selectivity ( K d  = 1.9 × 10 5  mL/g), robust recyclability (>95 % removal over 8 adsorption-desorption cycles), and real wastewater breakthrough (95 % uranium recovery rate: 0.21 mg U(VI) / 100 mg ads.). Comprehensive characterization, multi-model fit analysis and in-situ zeta potential monitoring revealed that U(VI) capture follows a spontaneous, endothermic monolayer process driven by coordination-electrostatic synergy between Lewis acid-base sites (Mn-O, -OH, and -NH 2 ) and electrostatic attraction. This work provides an efficient, stable, and eco-friendly adsorbent for real wastewater treatment in the nuclear industry, advancing uranium resource recovery and sustainable nuclear energy development.