Highly selective and ultrafast uptake of uranium from seawater by layered double hydroxide co-intercalated with acetamidoxime and carboxylic anions

Abstract

Through the swelling/restoration reaction, acetamidoxime (ACAO) and the hydrolysates of carboxylic anions are co-intercalated into MgAl-LDH interlayers to generate a new material ACAO-AC-LDH. The as-formed ACAO-AC-LDH displays outstanding adsorption performance for uranium (U(VI)) both at high (ppm) and low (ppb) concentrations. The enormous maximum U sorption capacity (q^U_m) of 339 mg g⁻¹, exceptionally rapid uptake (k₂ = 3.06 g mg⁻¹ min⁻¹), and ultrahigh % removals (>90% at C^U₀ = 1–100 ppm) are among the best reported for U sorbents. For natural seawater with a trace amount of U (∼3.65 ppb) but highly concentrated concomitant cations of Ca²⁺ (∼400 ppm), Mg²⁺ (∼1300 ppm), K⁺ (∼500 ppm) and Na⁺ (∼11 000 ppm), the ACAO-AC-LDH can trap ≥99.99% U (reduced to ≤0.001 ppb), exhibiting extremely high selectivity (K^U_d ∼ 10⁶ mL g⁻¹) and capture ability for U. All these demonstrate that ACAO-AC-LDH is a first-class uranium sorbent, which is suitable for removing U from nuclear waste and extracting U from seawater.