Preparation of novel organic–inorganic hybrid titanium phosphate composites for high-efficiency U(VI) removal from aqueous solutions

Abstract

Abstract

The removal of uranium (U) from nuclear wastewater is essential for sustainable development of nuclear energy and environmental protection. Herein, two novel organic-inorganic hybrid titanium phosphate (TiP) composites, 18C6/K 2 CO 3 /TiP and CTAB/Talc/TiP, were systematically synthesized and evaluated for U(VI) removal via batch and dynamic column sorption. At pH 4.5, 50 mg/L U(VI), and 25 °C, the two composites (18C6/K 2 CO 3 /TiP and CTAB/Talc/TiP) exhibited U(VI) removal capacities ( qₑ ) of 114 ± 4 mg/g and 124 ± 4 mg/g, which were 115% and 134% higher than that of pure TiP. Over pH 1–6, the removal capacity of both composites initially increased and then decreased, reaching its maximum at pH 4.5. Meanwhile, qₑ increased with rising initial U(VI) concentration and temperature. Conversely, U(VI) removal was suppressed by lower column loading, higher flow rates, and competing anions (inorganic: F⁻, Cl⁻, SO 4 ²⁻; organic: acetate, C₂H₃O₂⁻; citrate, C₆H₅O₇ 3- ). Kinetic, isotherm and thermodynamic analyses confirmed spontaneous endothermic process controlled by monolayer chemisorption. Both composites showed superior selectivity and reusability toward U(VI), retaining 93 and 86 mg/g after five cycles. Notably, CTAB/Talc/TiP achieved faster equilibrium (within 25 min) and higher structural stability. The primary U(VI) removal mechanisms involve surface complexation via -OH groups, electrostatic interaction, surface dissolution-precipitation, and ion exchange. These findings highlight the hybrid TiP composites, especially CTAB/Talc/TiP, as promising candidates for practical U(VI) separation from nuclear wastewater.