The confinement effect of layered double hydroxides on intercalated pyromellitic acidic anions and highly selective uranium extraction from simulated seawater.

Oxygen-rich pyromellitic acidic anions (PMA) have been intercalated into MgAl-layered double hydroxides to fabricate the MgAl-PMA-LDH (abbr. PMA-LDH) composite exhibiting excellent adsorption performance toward uranium (U(VI)). Benefiting from the large number of functional groups of -COO, the PMA-LDH displays an extremely large maximum U adsorption capacity (Um) of 352 mg g and an ultra-fast sorption rate, reaching uptakes of ∼97% within 30 min and >99% in 1 h at the initial U concentration (U0) of 113 ppm. Over a very wide pH range of 5-11, high U removals (>93%) are achieved at U0 = 105 ppm. Moreover, in the presence of highly concentrated competitive ions, ultra-high selectivity of UO is observed, giving a very large distribution coefficient () of ∼10 mL g. Moreover, the PMA-LDH exhibits effective capture of UO in contaminated simulated seawater, showing high uptakes of >93% at U0 ∼ 10 ppm and >98% at U0 ∼ 100 ppm. The dispersion effect of LDH layers may contribute to the increase of U adsorption capacity, and the confinement effect of LDH is conducive to the improvement of sorption selectivity toward U. The exploration of the interaction mechanism of UO with PMA confined within the LDH gallery offers an important basis for the fabrication of new kinds of organic/inorganic hybrid materials. The PMA-LDH is a highly effective adsorbent which can be applied to uranium extraction from seawater and uranium disposal in nuclear wastewater.